BUILDING PANEL WITH A MECHANICAL LOCKING DEVICE AND A METHOD OF PRODUCING SUCH BUILDING PANEL

Abstract

A building panel, such as a floor panel, or wall panel, having a multi-layered substrate including a back side layer comprising lignocellulosic particles and a binder, an intermediate layer comprising lignocellulosic particles and a binder which is arranged on the back side layer, and a front side layer comprising lignocellulosic particles and a binder, and which is arranged on the intermediate layer. The back side layer was formed from a first mixture, the intermediate layer was formed from a second mixture and the front side layer was formed from a third mixture. The building panel further has a mechanical locking device arranged along at least one edge portion of the building panel where the mechanical locking device is configured for horizontal and/or vertical locking of similar or essentially identical building panels in an assembled position.

Claims

1. A set of building panels, each building panel comprising: a multi-layered substrate comprising a back side layer comprising lignocellulosic particles and a binder, an intermediate layer comprising lignocellulosic particles and a binder, arranged on the back side layer, and a front side layer comprising lignocellulosic particles and a binder, arranged on the intermediate layer, wherein the back side layer is formed from a first mixture, the intermediate layer is formed from a second mixture and the front side layer is formed from a third mixture, each building panel further comprising: a first mechanical locking device arranged along at least one edge portion of the building panel, wherein the first mechanical locking device is configured for horizontal and/or vertical locking of similar or essentially identical building panels in an assembled position, the first mechanical locking device comprising at least along a first edge portion a locking strip with a locking element, which is arranged in a back side area of the at least one edge portion and which extends in an essentially parallel direction to a back surface, along at least one edge portion of the building panel, the first mechanical locking device further comprising at least along a second edge portion, opposing the first edge portion, a locking groove arranged in a lower edge area of the first edge portion and extending in a direction upwards into and away from the bottom surface of the building panel, wherein the locking element comprises a front locking surface configured to, in the assembled position, cooperate with a locking surface of the locking groove, wherein the front locking surface of the locking element at least partly is arranged in the back side layer.

2. The set of building panels according to claim 1, wherein an average particle size of the lignocellulosic particles in the second mixture is greater than an average particle size of the lignocellulosic particles in the first and/or third mixture.

3. The set of building panels according to claim 1, wherein a portion of the front locking surface of the locking element is configured to, in the assembled position and when a force is applied on a horizontal direction, form a contact surface with the locking surface of the locking groove, wherein the contact surface of the locking element is arranged in the back side layer.

4. The set of building panels according to claim 1, wherein the front locking surface of the locking element is entirely arranged in the back side layer.

5. The set of building panels according to claim 1, wherein the locking surface of the locking groove at least partially is arranged in the back side layer.

6. The set of building panels according to claim 1, wherein a portion of the locking surface of the locking groove is configured to, in the assembled position and when a force is applied on a horizontal direction, form a contact surface with the front locking surface of the locking element, wherein the contact surface of the locking groove is arranged in the back side layer.

7. The set of building panels according to claim 5, wherein the locking surface of the locking groove is entirely arranged in the back side layer.

8. The set of building panels according to claim 1, wherein an upper surface of the locking groove, having a least a portion extending in a direction substantially parallel to the bottom surface, is at least partially arranged in the back side layer.

9. The set of building panels according to claim 8, wherein the upper surface of the locking groove is entirely arranged in the back side layer.

10. The set of building panels according to claim 1, wherein the first mechanical locking system further comprises an upper surface, which is arranged in a front side area of at least the first edge portion and which extends in a direction essentially parallel to a top surface, along at least the first edge portion, of the building panel, displaced from said top surface, wherein the upper surface is arranged in the intermediate layer.

11. The set of building panels according to claim 1, wherein the first mechanical locking system further comprises an upper surface, which is arranged in a front side area of the at least one edge portion and which extends in an essentially parallel direction to a top surface, along at least one edge portion, of the building panel, displaced from said top surface, wherein the upper surface is arranged in the front side layer.

12. The set of building panels according to claim 1, further comprising a second mechanical locking device at least along a third edge portion, the second mechanical locking device comprising: a locking strip with a locking element, which is arranged in a back side area of the at least one edge portion and which extends in an essentially parallel direction to a back surface, along at least one edge portion of the building panel, the second mechanical locking device further comprising at least along a fourth edge portion, opposing the third edge portion, a locking groove arranged in a lower edge area of the first edge portion and extending in a direction upwards into and away from the bottom surface of the building panel, wherein the locking element comprises a front locking surface configured to, in the assembled position, cooperate the locking surface of the locking groove, wherein the front locking surface of the locking element at least partly is arranged in the back side layer.

13. The set of building panels according to claim 1, wherein a ratio between an amount of the applied third mixture and an amount of the applied first mixture is between 40:60 and 60:40.

14. The set of building panels according to claim 1, wherein a ratio between an amount of the applied second mixture and a total amount of the applied first and third mixture is between 70:30 and 30:70.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Embodiments of the disclosure will be described in the following: reference being made to the appended drawings which illustrate non-limiting embodiments of how the disclosure can be reduced into practice.

[0037] FIG. 1 is a schematic illustration of a method to produce a building panel according to an embodiment of the present disclosure,

[0038] FIG. 2 is a schematic illustration of a method to produce a building panel according to another embodiment of the present disclosure,

[0039] FIG. 3A is a schematic illustration of a continuation of the methods illustrated in FIGS. 1 and 2, according to an embodiment of the present disclosure,

[0040] FIG. 3B is a schematic illustration of another continuation of the methods illustrated in FIGS. 1 and 2, according to an embodiment of the present disclosure,

[0041] FIG. 4 is a schematic illustration of a method to produce a building panel according to an embodiment of the present disclosure,

[0042] FIG. 5 is a schematic illustration of a method to produce a building panel according to an embodiment of the present disclosure,

[0043] FIG. 6 is a schematic illustration of a method to produce a building panel according to another embodiment of the present disclosure,

[0044] FIG. 7 is an illustration of a cross section through layers in a building panel, according to an embodiment of the present disclosure,

[0045] FIG. 8 is an illustration of a cross section through layers in a building panel, according to another embodiment of the present disclosure,

[0046] FIG. 9A is an illustration of a cross section through layers in a building panel, according to yet another embodiment of the present disclosure,

[0047] FIG. 9B is a photo of the cross section through layers in the building panel as illustrated in FIG. 9A,

[0048] FIG. 10 is an illustration of a cross section through a building panel with open features, according to an embodiment of the present disclosure,

[0049] FIG. 11 is an illustration of a top view of a building panel with a mechanical locking device, according to an embodiment of the present disclosure,

[0050] FIG. 12A is an illustration of an assembly of three substantially identical building panels, according to an embodiment of the present disclosure,

[0051] FIG. 12B is an illustration of the three building panels in FIG. 12A in an assembled state,

[0052] FIG. 13A is an illustration of a cross section of a mechanical locking device according to an embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0053] FIG. 13B is an illustration of a cross section of a mechanical locking device according to an embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0054] FIG. 13C is an illustration of a cross section of a mechanical locking device according to another embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0055] FIG. 13D is an illustration of a cross section of a mechanical locking device according to another embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0056] FIG. 13E is an illustration of a cross section of a mechanical locking device according to another embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0057] FIG. 14 is an illustration of a top view of a displaceable locking tongue according to an embodiment of the present disclosure, for a mechanical locking device,

[0058] FIG. 15A is an illustration of a cross section of a building panel according to another embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent panels,

[0059] FIG. 15B is an illustration of a cross section of a building panel according to yet another embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent panels,

[0060] FIG. 16A is an illustration of a cross section of a mechanical locking device according to an embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0061] FIG. 16B is an illustration of a cross section of a mechanical locking device according to an embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0062] FIG. 16C is an illustration of a cross section of a mechanical locking device according to another embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0063] FIG. 16D is an illustration of a cross section of a mechanical locking device according to another embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0064] FIG. 17 is an illustration of a cross section of a mechanical locking device according to another embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0065] FIG. 18 is an illustration of a cross section of a mechanical locking device according to another embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0066] FIG. 19 is an illustration of a cross section of a mechanical locking device according to another embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0067] FIG. 20 is an illustration of a cross section of a mechanical locking device according to another embodiment of the present disclosure, in an assembled state arranged along opposite edges of two adjacent building panels,

[0068] FIG. 21 is a diagram showing the results of Example 3, and

[0069] FIGS. 22-26 show density profiles of different types of building panels and particle boards and fibre boards.

DETAILED DESCRIPTION OF EMBODIMENTS

[0070] Specific embodiments of the disclosure will now be described with reference to the accompanying drawings. The present disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the present disclosure. In the drawings, like numbers refer to like elements.

[0071] Generally, in this disclosure, terms like below or lower typically implies closer to the back surface of the panel or a plane thereof, whereas above or upper implies closer to the front surface or a plane thereof. Further, the thickness direction of the panel is defined as the vertical direction when the panel lays flat on a surface. The horizontal and vertical direction are applicable definition when the building panel lays flat on e.g. a floor. Instead of horizontal and vertical directions, the description will also refer to a direction parallel with extension of the decorative surface and a direction perpendicular to the extension of the decorative surface. When a building panel lays flat on e.g. a floor, the horizontal direction is the same as the direction parallel with the extension of the decorative surface and the vertical direction is the same as the direction perpendicular to the extension of the decorative surface.

[0072] FIGS. 1-6 illustrate different setup possibilities and methods for producing a building panel in accordance with the present disclosure. Several features in the production setups are the same. For example, each setup has three applicator devices 2a, 2b, 2c which are configured to respectively apply a mixture 13a, 13b, 13c. The applicator devices 2a, 2b, 2c may scatter the mixtures or roll on the mixtures, i.e. may work either at a distance from where the mixtures are applied or be in contact with where the mixtures are applied. The applicator devices 2a, 2b, 2c may further be configured to handle mixtures of any form, i.e. mixtures in e.g. dry form or wet form.

[0073] Each setup further has at least one building panel forming device 4a, 4b which is configured to apply both heat and pressure to form a building panel. In the illustrated example there is illustrated two opposite building panel forming devices 4a, 4b where one is arranged on the front side and the other is arranged on the back side. Both may be configured to apply both pressure and heat, but it is also possible that there is a difference between the two building panel forming devices 4a, 4b, e.g. one may be configured to apply both heat and pressure while the other is only configured to apply pressure. In the illustrated example the building panel forming devices 4a, 4b are continuous devices working in the feeding direction F. In another embodiment (not illustrated) the building panel forming devices may be discontinuous devices, such as a static device.

[0074] The first applicator device 2a is configured to apply a first mixture 13a to form a back side layer 15 of a building panel 10. In FIGS. 1-2 and 4-5 the first mixture 13a is applied onto a carrier 6, such as a carrier belt or conveyor belt or the like, whereas in FIG. 6 the first mixture 13a is applied onto a back side element 11.

[0075] The first mixture 13a may be applied in dry form or wet form and may in an embodiment be a powder. For example, the mixture(s) may be in dry form, such as in powder form. For example, the mixture(s) may be in wet form, such as in a mixture with water or other liquid.

[0076] The resulting back side layer 15 of the applied and subsequently pressed first mixture 13a preferably has a thickness in the direction perpendicular to the longitudinal extension of a top surface 24 of the building panel 10 which may be between 2 mm and 3 mm of a building panel 10 with the total thickness of about 10 mm. The resulting back side layer 15 of the applied and subsequently pressed first mixture 13a preferably has a thickness in the direction perpendicular to the longitudinal extension of a top surface 24 of the building panel 10 which is between 20% and 30% of the total thickness of the building panel 10.

[0077] The first mixture 13a includes at least lignocellulosic particles and a binder.

[0078] The lignocellulosic particles in the first mixture 13a may be wood particles, e.g. made of pine, oak, eucalyptus or other wood species, straws from grain products, sisal, coconut, bamboo, hemp, flax, jute, curaua, ramie, or any combination of such particles. The lignocellulosic particles make up between 70 wt. % and 99 wt. %, above 75 wt. % or above 85 wt. % of the first mixture 13a.

[0079] The majority, i.e. at least 50 wt. %, of the lignocellulosic particles in the first mixture 13a has a particle size of between 0.3 mm and 0.6 mm. Preferably at least 60 wt. %, at least 70 wt. % or at least 80 wt. % of the lignocellulosic particles in the first mixture 13a have a particle size of between 0.3 mm and 0.6 mm. In an alternative embodiment, the majority, i.e. at least 50 wt. %, of the lignocellulosic particles in the first mixture 13a has a particle size of between 0.3 mm and 1.25 mm. Preferably at least 60 wt. %, at least 70 wt. % or at least 80 wt. % of the lignocellulosic particles in the first mixture 13a have a particle size of between 0.3 mm and 1.25 mm.

[0080] In an embodiment, the average particle size of the lignocellulosic particles in the first mixture 13a is between 0.3 mm and 1.25 mm, such as between 0.3 and 0.6 mm. Average particle size and particle size may be determined by conventional vibratory sieving analysis, using a vibratory sieve shaker. A method referring to sieving analysis is described in DIN 66165. In the present disclosure, average particle size and particle size have been determined by a Fritsch Analysette 3 Pro. Average particle size may be determined as the median value of the particle size interval of the size class with the highest weight proportion in a sieving analysis. A size class in a sieving analysis may be the size interval ranging from the aperture size of the sieving net that the particles did not fall through until the aperture size of the sieving net that the particles fell through. A size class may for example be from 0.5 mm to 1 mm, or from 0.3 mm to 0.4 mm.

[0081] The lignocellulosic particles in the first mixture 13a can also be measured by an aspect ratio, i.e. the ratio between the length of the particle and its width. The aspect ratio of the majority, i.e. at least 50%, of the lignocellulosic particles in the first mixture 13a is below 30. Preferably at least 60%, at least 70% or at least 80% of the lignocellulosic particles in the first mixture 13a have an aspect ratio below 30. The aspect ratio of the majority, i.e. at least 50%, of the lignocellulosic particles in the first mixture 13a is between 1:1 and 30:1, between 1:1 and 20:1 or between 1:1 and 10:1. Preferably the aspect ratio of at least 60%, at least 70% or at least 75% of the lignocellulosic particles in the first mixture 13a is between 1:1 and 30:1, between 1:1 and 20:1 or between 1:1 and 10:1. In an embodiment the particle size of the lignocellulosic particles in the first mixture 13a is between 0.3 mm and 1.25 mm, or between 0.3 mm and 0.6 mm and with an aspect ratio less than 20 or less than 10.

[0082] Establishing the aspect ratio may for the embodiments in this disclosure be made by, e.g., optical means, by photographing the fibres and digitally measure them. Other suitable means and methods may be used to establish the aspect ratio.

[0083] The percentage of lignocellulosic particles when referring to aspect ratio in the present disclosure is calculated by calculating the number of particles having the specified aspect ratio.

[0084] The binder in the first mixture 13a may be a thermoset resin. Examples of suitable thermoset resins are amino resins such as melamine formaldehyde, urea formaldehyde, phenol formaldehyde resins, or combinations thereof, or no-added formaldehyde resins such as epoxy resins, acrylic resins, polyurethane resins, polymeric diphenylmethane diisocyanate resin, polyester resins, or combinations thereof.

[0085] The binder makes up between 5 wt. % and 35 wt. %, or between 10 and 25 wt. % of the first mixture 13a. As common in wood industry and described above, the amounts are calculated on dry weight, with the amount of bone-dry wood=100 wt. % as base. The amount of binder in the first mixture 13a, or in any of the mixtures 13b, 13c in this disclosure, may affect the water resistant or water repellent properties of the layers 15, 17, 19 of the building panel 10 which are formed from respective mixture 13a, 13b, 13c. Having more binder in the mixture 13a, 13b, 13c will increase the water resistant or water repellent properties in the building panel 10. However, the binder is also the more expensive component of the mixture, thus, an amount as defined above gives a beneficial balance between effect and cost.

[0086] The first mixture 13a may further include a hydrophobing agent, such as wax. The first mixture 13a may comprise 1-3 wt. % or 1-2 wt. % of the hydrophobing agent. Preferred hydrophobing agents are paraffin emulsions. An advantage with having a hydrophobing agent in the first mixture 13a, and in any of the mixtures 13b, 13c in this disclosure, is that it provides the layers 15, 17, 19 of the building panel 10 which are formed from respective mixture 13a, 13b, 13c with improved water repellent properties, in turn creating a more water resistant building panel 10. It may thus be beneficial to add a hydrophobing agent in the mixture 13a, 13b, 13c forming a layer 15, 17, 19 in which features for increasing the water resistant properties of the building panel 10 are created. Examples of this will be described later on.

[0087] The first mixture 13a may further comprise different types of additives, such as colorant, catalyst (e.g. ammonium sulphate), formaldehyde scavenger (e.g. urea), or buffer solution.

[0088] The second applicator device 2b is configured to apply a second mixture 13b to form an intermediate layer 17 of the building panel 10. In FIGS. 1-6 the second mixture 13b is applied onto the first mixture 13a. As the second mixture 13b is applied onto the first mixture 13a, particles, in particular lignocellulosic particles, from each of the back side layer 15 and the intermediate layer 17 will mix, at least in a border area between the back side layer 15 and the intermediate layer 17.

[0089] The second mixture 13b may be applied in dry form or wet form and may in an embodiment be a powder. For example, the mixture(s) may be in dry form, such as in powder form. For example, the mixture(s) may be in wet form, such as in a mixture with water or other liquid.

[0090] The resulting intermediate layer 17 of the applied and subsequently pressed second mixture 13b preferably has a thickness in the direction perpendicular to the extension of the top surface 24 of the building panel 10 which is between 0.9 mm and 19.6 mm of a building panel 10, resulting in a panel with the total thickness of between 4 mm and 28 mm. In an embodiment, the resulting intermediate layer 17 of the applied and subsequently pressed second mixture 13b preferably has a thickness in the direction perpendicular to the extension of a top surface 24 of the panel 10 which is between 3 mm and 7 mm of a building panel 10, resulting in a panel with the total thickness of about 10 mm. The resulting intermediate layer 17 of the applied and subsequently pressed second mixture 13b preferably has a thickness in the direction perpendicular to the longitudinal extension of the top surface 24 of the building panel 10 which is between 30% and 70% of the total thickness of the building panel 10.

[0091] The second mixture 13b includes at least lignocellulosic particles and a binder.

[0092] The lignocellulosic particles in the second mixture 13b may be wood particles, e.g. made of pine, oak, eucalyptus or other wood species, straws from grain products, sisal, coconut, bamboo, hemp, flax, jute, curaua, ramie, or any combination of such particles. The lignocellulosic particles make up between 70 wt. % and 99 wt. %, above 75 wt. % or above 85 wt. % of the second mixture 13b.

[0093] The majority, i.e. at least 50 wt. %, of the lignocellulosic particles in the second mixture 13b has a particle size of between 0.5 mm and 4 mm, or between 0.5 mm and 2.5 mm, or between 0.5 mm and 1.5 mm, or between 0.6 mm and 1.3 mm. Preferably at least 60 wt. %, at least 70 wt. % or at least 80 wt. % of the lignocellulosic particles in the second mixture 13b have a particle size of between 0.5 mm and 4 mm, or between 0.5 mm and 4 mm, or between 0.5 mm and 2.5 mm, or between 0.5 mm and 1.5 mm, or between 0.6 mm and 1.3 mm.

[0094] In an embodiment, the average particle size of the lignocellulosic particles in the second mixture 13b is between 0.5 and 4 mm, such as between 0.5 and 2.5 mm, such as between 0.5 and 1.5 mm or such as between 0.6 and 1.3 mm.

[0095] The lignocellulosic particles in the second mixture 13b can, like explained for the first mixture, also be measured by an aspect ratio, i.e. the ratio between the length of the particle and its width. The aspect ratio of the majority, i.e. at least 50%, of the lignocellulosic particles in the second mixture 13b is below 30. Preferably at least 60%, at least 70% or at least 80% of the lignocellulosic particles in the second mixture 13b have an aspect ratio below 30. The aspect ratio of the majority, i.e. at least 50%, of the lignocellulosic particles in the second mixture 13b is between 1:1 and 30:1, between 1:1 and 20:1 or between 1:1 and 10:1. Preferably the aspect ratio of at least 60%, at least 70% or at least 75% of the lignocellulosic particles in the second mixture 13b is between 1:1 and 30:1, between 1:1 and 20:1 or between 1:1 and 10:1. In an embodiment the particle size of the lignocellulosic particles in the second mixture 13b is between 0.6 mm and 1.3 mm and with an aspect ratio less than 10. In another embodiment the particle size of the lignocellulosic particles in the second mixture 13b is between 0.6 mm and 4 mm and with an aspect ratio less than 10.

[0096] The binder in the second mixture 13b may be a thermoset resin. Examples of suitable thermoset resins are amino resins such as melamine formaldehyde, urea formaldehyde, phenol formaldehyde resins, or combinations thereof, or no-added formaldehyde resins such as epoxy resins, acrylic resins, polyurethane resins, polymeric diphenylmethane diisocyanate resin, polyester resins, or combinations thereof. The binder in the second mixture 13b may be the same binder as in the first mixture 13a.

[0097] The binder may make up between 3 wt. % and 20 wt. %, or between 5 wt. % and 10 wt. % of the second mixture 13b. The amount of binder in the second mixture 13b, or in any of the mixtures 13a, 13c in this disclosure, may affect the water resistant or water repellent properties of the layers 15, 17, 19 of the building panel 10 which are formed from respective mixture 13a, 13b, 13c. Having more binder in the mixture 13a, 13b, 13c will increase the water resistant or water repellent properties in the building panel 10. However, the binder is also the more expensive component of the mixture, thus, an amount as defined above gives a beneficial balance between effect and cost.

[0098] The second mixture 13b may further include a hydrophobing agent, such as wax. The second mixture 13b may comprise 1-3 wt. % or 1-2 wt. % of the hydrophobing agent. Preferred hydrophobing agents are paraffin emulsions. An advantage with having a hydrophobing agent in the second mixture 13b, and in any of the mixtures 13a, 13c in this disclosure, is that it provides the layers 15, 17, 19 of the building panel 10 which are formed from respective mixture 13a, 13b, 13c with improved water repellent properties, in turn creating a more water resistant building panel 10. It may thus be beneficial to add a hydrophobing agent in the mixture 13a, 13b, 13c forming a layer 15, 17, 19 in which features for increasing the water resistant properties of the building panel 10 are created. Examples of this will be described later on.

[0099] The second mixture 13b may further comprise different types of additives, such as colorant, catalyst (e.g. ammonium sulphate), formaldehyde scavenger (e.g. urea), or buffer solution.

[0100] The third applicator device 2c is configured to apply a third mixture 13c to form a front side layer 19 of the building panel 10. In FIGS. 1-6 the third mixture 13c is applied onto the second mixture 13b. As the third mixture 13c is applied onto the second mixture 13b, particles, in particular lignocellulosic particles, from each of the intermediate layer 17 and the front side layer 19 will mix, at least in a border area between the front side layer 19 and the intermediate layer 17.

[0101] The third mixture 13c may be applied in dry form or wet form and may in an embodiment be a powder. For example, the mixture(s) may be in dry form, such as in powder form. For example, the mixture(s) may be in wet form, such as in a mixture with water or other liquid.

[0102] The resulting front side layer 19 of the applied and subsequently pressed third mixture 13c preferably has a thickness in the direction perpendicular to the extension of a top surface 24 of the building panel 10 which is between 2 mm and 3 mm of a building panel 10 with the total thickness of about 10 mm. The resulting front side layer 19 of the applied and subsequently pressed third mixture 13c preferably has a thickness in the direction perpendicular to the longitudinal extension of the top surface 24 of the building panel 10 which is between 20% and 30% of the total thickness of the building panel 10.

[0103] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a is between 40:60 and 60:40, or between 45:55 and 55:45. The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be about 50:50.

[0104] The ratio between the amount of the applied second mixture 13b and the total amount of the applied first and third mixture 13a, 13c may be between 70:30 and 30:70, or between 60:40 and 40:60. The ratio between the amount of the applied first mixture 13a, the applied second mixture 13b and the applied third mixture 13c may be 20-60-20 wt. %, or 25-50-25 wt. % or 30-40-30 wt. %. The sum of the first mixture 13a, the second mixture 13b, and the third mixture 13c form the total amount of applied mixtures, i.e. 100 wt. %. This may advantageously reduce and/or provide more controlled swelling of the building panel 10. This may lower the amount of added binder when producing the building panel 10, compared to known building panels, while still keeping good water resistant or water repellent properties in the building panel.

[0105] Correspondingly, in the pressed building panel 10, the ratio between the thickness of the front side layer 19 and the thickness of the back side layer 15 may be between 40:60 and 60:40, or between 45:55 and 55:45, such as about 50:50.

[0106] In the pressed building panel 10, the ratio between the thickness of the intermediate layer 17 and the thickness of the back side layer 15 may be between 70:30 and 30:70, or between 60:40 and 40:60. The ratio between the thickness of the front side layer 19, the intermediate layer 17 and the back side layer 15 may be 20-60-20%, or 25-50-25%, or 30-40-30%, such as in a range from 20-60-20% to 10-50-40%.

[0107] The third mixture 13c includes at least lignocellulosic particles and a binder.

[0108] The lignocellulosic particles in the third mixture 13c may be wood particles, e.g. made of pine, oak, eucalyptus or other wood species, straws from grain products, sisal, coconut, bamboo, hemp, flax, jute, curaua, ramie, or any combination of such particles. The lignocellulosic particles make up between 70 wt. % and 99 wt. %, or above 75 wt. %, or above 85 wt. % of the third mixture 13c.

[0109] The majority, i.e. at least 50 wt. %, of the lignocellulosic particles in the third mixture 13c has a particle size of between 0.3 mm and 0.6 mm. Preferably at least 60 wt. %, at least 70 wt. % or at least 80 wt. % of the lignocellulosic particles in the third mixture 13c have a particle size of between 0.3 mm and 0.6 mm. In an alternative embodiment, the majority, i.e. at least 50 wt. %, of the lignocellulosic particles in the first mixture 13a has a particle size of between 0.3 mm and 1.25 mm. Preferably at least 60 wt. %, at least 70 wt. % or at least 80 wt. % of the lignocellulosic particles in the first mixture 13a have a particle size of between 0.3 mm and 1.25 mm.

[0110] In an embodiment, an average particle size of the lignocellulosic particles in the third mixture 13c is between 0.3 mm and 1.25 mm, such as between 0.3 and 0.6 mm.

[0111] The lignocellulosic particles in the third mixture 13c can, as explained above, also be measured by an aspect ratio, i.e. the ratio between the length of the particle and its width. The aspect ratio of the majority, i.e. at least 50%, of the lignocellulosic particles in the third mixture 13c is below 30. Preferably at least 60%, at least 70% or at least 80% of the lignocellulosic particles in the third mixture 13c have an aspect ratio below 30. The aspect ratio of the majority, i.e. at least 50%, of the lignocellulosic particles in the third mixture 13c is between 1:1 and 30:1, between 1:1 and 20:1 or between 1:1 and 10:1. Preferably the aspect ratio of at least 60%, at least 70% or at least 75% of the lignocellulosic particles in the third mixture 13c is between 1:1 and 30:1, between 1:1 and 20:1 or between 1:1 and 10:1. In an embodiment the particle size of the lignocellulosic particles in the third mixture 13c is between 0.3 mm and 1.25 mm or between 0.3 mm and 0.6 mm and with an aspect ratio less than 20 or less than 10.

[0112] The binder in the third mixture 13c may be a thermoset resin. Examples of suitable thermoset resins are amino resins such as melamine formaldehyde, urea formaldehyde, phenol formaldehyde resins, or combinations thereof, or no-added formaldehyde resins such as epoxy resins, acrylic resins, polyurethane resins, polymeric diphenylmethane diisocyanate resin, polyester resins, or combinations thereof. The binder in the third mixture 13c may be the same binder as in the first mixture 13a and/or the second mixture 13b.

[0113] The binder may make up between 5 wt. % and 35 wt. %, or between 10 wt. % and 25 wt. % of the third mixture 13c. The amount of binder in the third mixture 13c, or in any of the mixtures 13a, 13b in this disclosure, may affect the water resistant or water repellent properties of the layers 15, 17, 19 of the building panel 10 which are formed from respective mixture 13a, 13b, 13c. Having more binder in the mixture 13a, 13b, 13c will increase the water resistant or water repellent properties in the building panel 10. However, the binder is also the more expensive component of the mixture, thus, an amount as defined above gives a beneficial balance between effect and cost.

[0114] The third mixture 13c may further include a hydrophobing agent, such as wax. The third mixture 13c may comprise 1-3 wt. % or 1-2 wt. % of the hydrophobing agent. Preferred hydrophobing agents are paraffin emulsions. An advantage with having a hydrophobing agent in the third mixture 13c, and in any of the mixtures 13a, 13b in this disclosure, is that it provides the layers 15, 17, 19 of the building panel 10 which are formed from respective mixture 13a, 13b, 13c with improved water repellent properties, in turn creating a more water resistant building panel 10. It may thus be beneficial to add a hydrophobing agent in the mixture 13a, 13b, 13c forming a layer 15, 17, 19 in which features for increasing the water resistant properties of the building panel 10 are created. Examples of this will be described later on.

[0115] The third mixture 13c may further include colorant. The colorant may be a pigment, dye, or a chemical staining agent. An example of a chemical staining agent is iron vitriol. By having a colorant in the third mixture 13c it is possible to control and adapt appearance features of the building panel 10. For example if a front side element 21, such as a front side wood veneer element, or top surface, has open features 22 (see FIG. 10), such as cracks, holes or the like, the colorant of the third mixture 13c is configured to colour the open features 22 as the third mixture 13c penetrates into the open features 22 and at least partly fills such open features 22 when pressure is subsequently applied. This can advantageously provide additional water resistance.

[0116] The third mixture 13c may yet further comprise other types of additives, such as catalyst (e.g. ammonium sulphate), formaldehyde scavenger (e.g. urea), or buffer solution.

[0117] In an embodiment the third mixture 13c may comprise wear resistant particles, such as aluminium oxide particles, or scratch resistant particles. This may be preferred if the front side layer 19, formed from the third mixture 13c, is the top layer of the building panel 10.

[0118] In order to even further increase the water resistant properties of the building panel 10 the density of each layer 15, 17, 19, formed by the mixtures 13a, 13b, 13c, may be adapted to different water resistant properties designed within the layers 15, 17, 19 of the building panel 10. For example, it may be desirable to, in the front side layer 19, design water resistant features of a mechanical locking device, which will be described in more detail below, and thus, desirable to increase the density of the front side layer 19 in order to even further improve the water resistant features of such a mechanical locking device. Whereas the intermediate layer 17 may be designed to have no additional water resistant features and therefore does not need an increased density. By adapting the density of each layer, the back side layer 15, the intermediate layer 17 and the front side layer 19 it is possible to both increase the water resistant properties of the building panel 10 where it is desirable to do so and decrease the risk of the building panel 10 becoming too heavy. The weight of the building panel 10 will also depend on the thickness of each of the components of the building panel 10 but by being able to control and adapt the thickness, the density, the lignocellulosic particle sizes, the amount of binder, etc. in each of the back side layer 15, the intermediate layer 17 and the front side layer 19 the weight of the building panel 10 also becomes controllable.

[0119] A preferred density of the intermediate layer 17 is less than the density of the front side layer 19 and/or the back side layer 15. A preferred density of the intermediate layer 17 may be between 700-900 kg/m.sup.3, or about 800 kg/m.sup.3. A preferred density of the front side layer 19 may be between 800-1200 kg/m.sup.3, or between 900-1100 kg/m.sup.3. In an embodiment the density of the intermediate layer 17 may be between 900-950 kg/m.sup.3 where the total thickness of the building panel is about 10 mm.

[0120] In order to balance the building panel 10, it is preferred that the back side layer 15, even if it does not have any additional water resistant features designed in it, has the same density as the front side layer 19. Thus, the density of the back side layer 15 is substantially the same as the density of the front side layer 19. Thus, the density of the back side layer 15 may be between 800-1200 kg/m.sup.3, or between 900-1100 kg/m.sup.3.

[0121] In further embodiments of the present disclosure, there may be yet further layers (not illustrated) applied before applying the heat and pressure to form the building panel. Such layers may comprise a mixture in accordance with any mixture described above with at least lignocellulosic particles and a binder. If the additional layer/s further include(s) a decorative layer the mixture may comprise colorant. The mixture may be applied in dry form or wet form and may in an embodiment be a powder. The mixture may be applied with any of the above described amounts. In an embodiment a yet further layer may be a coating layer. In another embodiment a yet further layer may comprise wear resistant particles, such as aluminium oxide particles, or scratch resistant particles. This may be preferred if the yet further layer is a top layer of the building panel.

[0122] There are however some differences in the setups between the production methods as illustrated in FIGS. 1-6. Each method is however possible in order to achieve a building panel 10 according to the present disclosure.

[0123] In FIG. 1 the first mixture 13a is applied onto a carrier 6, in the illustrated example a conveyor belt. Once the first mixture 13a, the second mixture 13b and the third mixture 13c have been applied the layers 15, 17, 19 of mixtures 13a, 13b, 13c are transferred into the building panel forming devices 4a, 4b where pressure and heat are applied to form the building panel 10. Pressure and heat are applied preferably by a combined heat and pressure device as the building panel forming device 4a, 4b. In the illustrated examples of FIGS. 1-6 there is one combined heat and pressure device 4a, 4b on each opposite sides of the building panel 10. The heat and pressure devices 4a, 4b are also illustrated as continuous heat and pressure devices feeding the building panel 10 in the feeding direction F.

[0124] In alternative setups the heat and pressure devices may be discontinuous devices. It is further possible to only have one single heat and pressure device instead of a double as illustrated. Also, it is possible to have a combined heat and pressure device operating from one side of the building panel and a pressure device, with no added heat, operating from the opposite side of the building panel.

[0125] When forming the building panel 10 in a continuous pressing device a pressure of between 20-80 bar, between 40-80 bar, between 50-70 bar, about 50 bar, or about 60 bar is applied, which is applied at a press factor of between 6-16 s/mm, between 7-14 s/mm or between 8-12 s/mm. Further, a temperature in the press board of between 120-250 C., between 130-200 C. or about 160-180 C. is applied.

[0126] In an embodiment the method of forming the building panel 10 may further include creating a pattern in the top surface of the front side layer 19 simultaneously with applying pressure and heat to form the building panel 10. This may be achieved e.g. by a structured press plate (not shown) in the heat and pressing device 4a, or with a displaceable pressing sheet (not shown) which can be arranged in between the front surface of the front side layer 19 and the heat and pressure device 4a. By having such a feature in the method, it is possible to achieve a desirable and attractive structure or different gloss levels in the top surface.

[0127] After the building panel 10 has been formed by the heat and pressure devices 4a, 4b the back side layer 15, the intermediate layer 17 and the front side layer 19, more specifically the binder of each layer 15, 17, 19, are cured.

[0128] After the building panel 10 has been heated and pressed the method may further comprise a cooling device (not shown). The cooling device is configured to control the cooling process of the formed building panel and to prevent the building panel to change shape and created unwanted forces within and between the layers of the building panel.

[0129] In FIG. 2 the method in FIG. 1 is illustrated but with an addition of a pre-pressure method step. Everything that has been described above with reference to FIG. 1 also applies for the method as illustrated in FIG. 2.

[0130] If yet further layer/s is/are applied, as described above, the pre-pressing step may be achieved either before or after such further layer/s is/are applied.

[0131] In an embodiment there may be more than one pre-pressing steps.

[0132] The addition of the pre-pressure method step is arranged before the layers 15, 17, 19 formed by the mixtures 13a, 13b, 13c enter the building panel forming devices 4a, 4b. The pre-pressure method step is achieved by a pressure device 8, in the illustrated example a continuous pressing device. The pressure device 8 is configured to press out unwanted air from the first mixture 13a, the second mixture 13b and the third mixture 13c such that unwanted air is not contained and trapped within the back side layer 15, the intermediate layer 17 and the front side layer 19 when the mixtures 13a, 13b, 13c, more specifically the binders of the mixtures 13a, 13b, 13c, are cured. The pressing device 8 is not configured to cure the binders of the mixtures 13a, 13b, 13c, or at least not configured to completely cure the binders of the mixtures 13a, 13b, 13c. The pressing device 8 is arranged after the third mixture 13c has been applied to the second mixture 13b.

[0133] FIG. 3A illustrates a possible continued process of the building panel 10 after the front side layer 15, the intermediate layer 17 and the back side layer 19 have been formed in the heat and pressure devices 4a, 4b as illustrated in FIGS. 1 and 2. The method may further include applying a front side element 21 after the step of applying heat and pressure. Before the front side element 21 is applied it is preferred to add e.g. an adhesive 7a such as glue or the like, onto the top surface of the front side layer 19. The adhesive 7a may be applied by means of a second applicator device 7 which is arranged before the front side element 21 is applied onto the front side layer 19. The front side element 21 may be chosen from a group of a wood veneer element, a paper sheet, a resin impregnated paper sheet or an unimpregnated paper sheet, a cork element, a polymer-based sheet, a prefabricated powder-based sheet, a powder layer comprising wood fibres and binder, a foil, such as a thermoplastic foil, or a coating layer, such as a lacquer. In an embodiment, such front side element 21 is configured to receive a print, such as a digital print and/or an analog print.

[0134] The front side element 21 of the building panel may comprise a thermoset resin, for example an amino resin such as melamine formaldehyde, urea formaldehyde, phenol formaldehyde resins, or combinations thereof, or no-added formaldehyde resins such as epoxy resins, acrylic resins, polyurethane resins, polymeric diphenylmethane diisocyanate resin, polyester resins, or combinations thereof.

[0135] The front side element 21 of the building panel may comprise thermoplastic materials, such as polyvinyl chloride (PVC), polyvinyl butyral (PVB), polyethylene (PE), polypropylene (PP), thermoplastic polyurethane (TPU), acrylonitrile butadiene styrene (ABS), polystyrene (PS), polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), polyethersulfone (PES), or combinations thereof.

[0136] Any of the mentioned front side elements may further be combined with a suitable wear layer, such as a lacquer, an overlay sheet, or any other layer comprising e.g. wear resistant particles, such as aluminium oxide particles, and/or scratch resistant particles.

[0137] FIG. 3B illustrates another possible continued process of the building panel 10 after the front side layer 15, the intermediate layer 17 and the back side layer 19 have been formed and the binders of the layers 15, 17, 19 have been cured in the heat and pressure devices 4a, 4b as illustrated in FIGS. 1 and 2. The method may further include applying a top layer 7b which can be decorative, functional and/or protective. E.g. a decorative surface, such as a painted surface which is able to receive a print, a coating layer such as a lacquered layer, or a combination of such layers, after the step of applying heat and pressure. The top layer 7b may be applied by means of a second applicator device 7.

[0138] In FIG. 4 the first mixture 13a is applied onto a carrier 6, in the illustrated example a conveyor belt. Once the first mixture 13a, the second mixture 13b and the third mixture 13c have been applied a back side element 11 and a front side element 21 are being introduced. The first mixture 13a, the second mixture 13b and the third mixture 13c are transferred onto the back side element 11 such that the first mixture 13a is applied onto to back side element 11. The front side element 21 may be chosen from a group of a wood veneer element, a paper sheet, a resin impregnated paper sheet, or an unimpregnated paper sheet, a cork element, a polymer-based sheet, a prefabricated powder-based sheet, a powder layer comprising wood fibres and binder, a foil, such as a thermoplastic foil, or a coating layer, such as a lacquer. In an embodiment, such front side element 21 is configured to receive a print.

[0139] The front side element 21 of the building panel may comprise a thermoset resin, for example an amino resin such as melamine formaldehyde, urea formaldehyde, phenol formaldehyde resins, or combinations thereof, or no-added formaldehyde resins such as epoxy resins, acrylic resins, polyurethane resins, polymeric diphenylmethane diisocyanate resin, polyester resins, or combinations thereof.

[0140] The front side element 21 of the building panel may comprise thermoplastic materials, such as polyvinyl chloride (PVC), polyvinyl butyral (PVB), polyethylene (PE), polypropylene (PP), thermoplastic polyurethane (TPU), acrylonitrile butadiene styrene (ABS), polystyrene (PS), polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), polyethersulfone (PES), or combinations thereof.

[0141] Any of the mentioned front side elements may further be combined with a suitable wear layer, such as a lacquer, an overlay sheet, or any other layer comprising e.g. wear resistant particles, such as aluminium oxide particles, and/or scratch resistant particles.

[0142] The back side element 11 may be a balancing layer. The back side element 11 may be a balancing layer which is chosen to correspond to the front side element 21, i.e. if the front side element 21 is a wood veneer element the back side layer 11 may be a wood veneer element in order to create a symmetry in the building panel 10, or if the front side element 21 is a paper sheet the back side layer 11 may be the same type of paper sheet for the same reason. However, it may be possible to choose a back side element 11 not corresponding to the front side element 21.

[0143] Further, the front side element 21 is applied onto the third mixture 13c.

[0144] After the front side element 21 and the back side element 11 are in place pressure and heat are applied to form the building panel 10. Pressure and heat are applied preferably by a combined heat and pressure device as the building panel forming device 4a, 4b. In the illustrated examples of FIGS. 1-6 there is one combined heat and pressure device 4a, 4b on each opposite sides of the building panel 10. The heat and pressure devices 4a, 4b are also illustrated as continuous heat and pressure devices feeding the building panel 10 in the feeding direction F.

[0145] In alternative setups the heat and pressure devices may be discontinuous devices. It is further possible to only have one single heat and pressure device instead of a double as illustrated. Also, it is possible to have a combined heat and pressure device operating from one side of the building panel and a pressure device, with no added heat, operating from the opposite side of the building panel.

[0146] As has been previously described, when forming the building panel 10 in a continuous pressing device a pressure of between 20-80 bar, between 40-80 bar, between 50-70 bar, or about 50 bar, or about 60 bar is applied, at a press factor of between 6-16 s/mm, between 7-14 s/mm, or between 8-12 s/mm. Further, a temperature in the press board of between 120-250 C., between 130-200 C., or about 160-180 C. is applied.

[0147] In an embodiment the method of forming the building panel 10 may further include creating a pattern in the top surface of the front side element 21 simultaneously with applying pressure and heat to form the building panel 10. This may be achieved e.g. by a structured press plate (not shown) in the heat and pressing device 4a, or with a displaceable pressing sheet (not shown) which can be arranged in between the front surface of the front side element 21 and the heat and pressure device 4a. By having such a feature in the method, it is possible to achieve a desirable and attractive structure, or different gloss levels in the top surface.

[0148] After the building panel 10 has been formed by the heat and pressure devices 4a, 4b the back side layer 15, the intermediate layer 17 and the front side layer 19, more specifically the binders of the layers 15, 15, 19, are cured.

[0149] Further, the front side layer 19 is attached to the front side element 21 and the back side layer 15 is attached to the back side element 11. Yet further, the front side layer 19 has penetrated into open features 22, if such are present, of the front side element 21. Open features 22 may be cracks, holes, pores, etc. The front side layer 19 penetrates and at least party fills such open features 22 when heat and pressure is applied. It may be preferred that the front side layer 19 completely fills the open features 22 of the front side element 21 (see FIG. 10). This can advantageously provide water resistance. The front side layer 19 partly or completely filling the open features 22, when pressure is applied, may eliminate the need of a further production step for filling the open features 22. This may in turn decrease the production time and increase the production efficiency of producing the building panel 10.

[0150] After the building panel 10 has been heated and pressed the method may further comprise a cooling device (not shown). The cooling device is configured to control the cooling process of the formed building panel and to prevent the building panel to change shape and created unwanted forces within and between the layers of the building panel.

[0151] In FIG. 5 the method in FIG. 4 is illustrated but with an addition of a pre-pressure method step. Everything that has been described above with reference to FIG. 4 also applies for the method as illustrated in FIG. 5.

[0152] The addition of the pre-pressure method step is preferably arranged before the front side element 21 and the back side element 11 is applied. The pre-pressure method step is achieved by a pressure device 8, in the illustrated example a continuous pressing device. The pressure device 8 is configured to press out unwanted air from the first mixture 13a, the second mixture 13b and the third mixture 13c such that unwanted air is not contained and trapped within the back side layer 15, the intermediate layer 17 and the front side layer 19 when the mixtures 13a, 13b, 13c, more specifically the binders of the mixtures 13a, 13b, 13c, are cured. The pressing device 8 is not configured to cure the binders of the mixtures 13a, 13b, 13c, or at least not configured to completely cure the binders of the mixtures 13a, 13b, 13c. The pressing device 8 is arranged after the third mixture 13c has been applied to the second mixture 13b. A further advantage with the pre-pressing method step, besides of removing unwanted air from the mixtures 13a, 13b, 13c, is that the mixtures after the pre-pressing method step may be easier to handle and easier to transfer from the carrier 6 to the back side element 11 before the building panel is formed.

[0153] In FIG. 6 the first mixture 13a is, unlike what is illustrated in FIGS. 4 and 5, applied directly onto the back side element 11. The back side element 11 is then transported on the carrier 6, i.e. the conveyor belt in the illustrated example, together with the applied first mixture 13a, second mixture 13b and third mixture 13c before the front side element 21 is applied to the third mixture 13c and transferred into the combined heat and pressure devices 4a, 4b for forming the building panel 10.

[0154] Just like in FIG. 4, after the front side element 21 is in place, pressure and heat are applied to form the building panel 10. Pressure and heat are applied preferably by the combined heat and pressure devices 4a, 4b.

[0155] In alternative setups the heat and pressure devices may be discontinuous devices. It is further possible to only have one single heat and pressure device instead of a double as illustrated. Also, it is possible to have a combined heat and pressure device operating from one side of the building panel and a pressure device, with no added heat, operating from the opposite side of the building panel.

[0156] When forming the building panel 10 in a continuous pressing device a pressure of between 20-80 bar, between 40-80 bar, between 50-70 bar, or about 50 bar, or about 60 bar is applied, which is applied at a press factor of between 6-16 s/mm, between 7-14 s/mm, or between 8-12 s/mm. Further, a temperature in the press board of between 120-250 C., between 130-200 C., or about 160-180 C. is applied.

[0157] In an embodiment the method of forming the building panel 10 may further include creating a pattern in the top surface of the front side element 21 simultaneously with applying pressure and heat to form the building panel 10. This may be achieved e.g. by a structured press plate (not shown) in the heat and pressing device 4a, or with a displaceable pressing sheet (not shown) which can be arranged in between the front surface of the front side element 21 and the heat and pressure device 4a. By having such a feature in the method, it is possible to achieve a desirable and attractive structure, or different gloss levels in the top surface.

[0158] After the building panel 10 has been formed by the heat and pressure devices 4a, 4b, as the building panel forming device, the back side layer 15, the intermediate layer 17 and the front side layer 19, more specifically the binders of the layers 15, 17, 19, are cured. Further, the front side layer 19 is attached to the front side element 21 and the back side layer 15 is attached to the back side element 11. Yet further, the front side layer 19 has penetrated into open features 22, if such are present, of the front side element 21. Open features 22 may be cracks, holes, pores, etc. The front side layer 19 penetrates and at least party fills such open features 22 when heat and pressure is applied. It may be preferred that the front side layer 19 completely fills the open features 22 of the front side element 21. This can advantageously provide water resistance. The front side layer 19 partly or completely filling the open features 22, when heat and pressure is applied, may eliminate the need of a further production step for filling the open features. This may in turn decrease the production time and increase the production efficiency of producing the building panel 10.

[0159] After the building panel 10 has been heated and pressed the method may further comprise a cooling device (not shown). The cooling device is configured to control the cooling process of the formed building panel and to prevent the building panel to change shape and created unwanted forces within and between the layers of the building panel.

[0160] For the embodiment illustrated in FIG. 6 it may also be possible and preferred to add the pre-pressing method step as described with reference to FIG. 5 above, in order to remove unwanted air from the mixtures 13a, 13b, 13c. The pressure device (not shown in this embodiment) may then be arranged after the third mixture 13c has been applied and before the front side element 21 has been applied to the third mixture 13c.

[0161] In an embodiment (not illustrated), additional scattering devices may be used to apply a powder layer as either the back side element, or the front side element, or both. Such powder layer may comprise at least wood-based particles and a binder, preferably also a decorative feature such as a colouring.

[0162] FIG. 7 is a schematic illustration of a cross section of a building panel 10 formed by any of the methods illustrated in FIGS. 1 and 2.

[0163] FIG. 8 is a schematic illustration of a cross section of a building panel 10 formed by any of the methods illustrated in FIGS. 1 and 2 with any of the additional method steps illustrated in FIGS. 3A and 3B.

[0164] FIG. 9A is a schematic illustration of a cross section of a building panel 10 formed by any of the methods illustrated in FIGS. 4-6, and FIG. 9B is a photo showing the cross section as described.

[0165] FIG. 10 is a schematic illustration of a building panel 10 formed by any of the methods illustrated in FIGS. 4-6 where there are open features 22 in the front side element 21 of the building panel 10.

[0166] The differences between the building panels 10 in FIGS. 7-10 are the presence of a front side element 21 and/or a back side element 11 and the way such front side element 21 and/or back side element 11 is attached to the front side layer 19 and/or back side layer 15.

[0167] However, much other is the same in all building panel 10, such as the multi-layered substrate 14 with the back side layer 15, the intermediate layer 17, the front side layer 19 and the two boarder areas 18a, 18b.

[0168] As explained above, the back side layer 15 was formed from the first mixture 13a and includes at least lignocellulosic particles 15a and a binder 15b. The intermediate layer 17 was formed from the second mixture 13b and includes at least lignocellulosic particles 17a and a binder 17b. The front side layer 19 was formed from the third mixture 13c and includes at least lignocellulosic particles 19a and a binder 19b.

[0169] In between the back side layer 15 and the intermediate layer 17, respective between the intermediate layer 17 and the front side layer 19, there is a border area 18a, 18b between the layers in which lignocellulosic particles 15a, 17a, 19a and occasionally also binder 15b, 17b, 19b from respective layer 15, 17, 19 have been mixed. I.e. in a lower boarder area 18a, which can also be called a lower transition area, at least lignocellulosic particles 15a, 17a from the back side layer 15 and the intermediate layer 17 are mixed, and in an upper boarder area 18b, which can also be called an upper transition area, at least lignocellulosic particles 17a, 19a from the intermediate layer 17 and the front side layer 19 are mixed.

[0170] As described above, the back side layer 15 is made from the first mixture 13a, thus the back side layer 15 includes at least the lignocellulosic particles 15a and the binder 15b. The lignocellulosic particles 15a may be wood particles, e.g. made of pine, oak, eucalyptus, or other wood species, straws from grain products, sisal, coconut, bamboo, hemp, flax, jute, curaua, ramie, or any combination of such particles. The lignocellulosic particles 15a make up between 70 wt. % and 99 wt. %, above 75 wt. %, or above 85 wt. % of the back side layer 15.

[0171] The majority, i.e. at least 50 wt. %, of the lignocellulosic particles 15a in the back side layer 15 has a particle size of between 0.3 mm and 0.6 mm. Preferably at least 60 wt. %, at least 70 wt. %, or at least 80 wt. % of the lignocellulosic particles 15a in the back side layer 15 have a particle size of between 0.3 mm and 0.6 mm. In an alternative embodiment, the majority, i.e. at least 50 wt. %, of the lignocellulosic particles in the first mixture 13a has a particle size of between 0.3 mm and 1.25 mm. Preferably at least 60 wt. %, at least 70 wt. %, or at least 80 wt. % of the lignocellulosic particles in the first mixture 13a have a particle size of between 0.3 mm and 1.25 mm.

[0172] The lignocellulosic particles 15a in the back side layer 15 can also be measured by an aspect ratio, i.e. the ratio between the length of the particle and its width. The aspect ratio of the majority, i.e. at least 50%, of the lignocellulosic particles 15a is below 30. Preferably at least 60%, at least 70%, or at least 80% of the lignocellulosic particles 15a have an aspect ratio below 30, or below 10. The aspect ratio of the majority, i.e. at least 50%, of the lignocellulosic particles 15a in the back side layer 15 is between 1:1 and 30:1, between 1:1 and 20:1, or between 1:1 and 10:1. Preferably the aspect ratio of at least 60%, at least 70%, or at least 75% of the lignocellulosic particles 15a is between 1:1 and 30:1, between 1:1 and 20:1, or between 1:1 and 10:1. At least 50%, of the lignocellulosic particles 15a in the back side layer 15 has a particle size of between 0.3 mm and 1.5 mm, or between 0.3 mm and 0.6 mm and an aspect ratio less than 30, or less than 20. In an embodiment the particle size of the lignocellulosic particles 15a in the back side layer 15 is between 0.3 mm and 1.25 mm, or between 0.3 mm and 0.6 mm and with an aspect ratio less than 10.

[0173] The binder 15b in the back side layer 15 may be a thermoset resin. Examples of suitable thermoset resins are amino resins such as melamine formaldehyde, urea formaldehyde, phenol formaldehyde resins, or combinations thereof, or no-added formaldehyde resins such as epoxy resins, acrylic resins, polyurethane resins, polymeric diphenylmethane diisocyanate resin, polyester resins, or combinations thereof.

[0174] The binder 15b makes up between 5 wt. % and 35 wt. %, or between 10 wt. % and 25 wt. % of the back side layer 15. The amount of binder 15b in the back side layer 15, or in any of the layers 17, 19 in this disclosure, may affect the water resistant, or water repellent properties of the layers 15, 17, 19 of the building panel 10. Having more binder in the layers 15, 17, 19 will increase the water resistant, or water repellent properties in the building panel 10. However, the binder is also the more expensive component of the mixture, thus, an amount as defined above gives a beneficial balance between effect and cost.

[0175] The back side layer 15 may further include a hydrophobing agent, such as wax. The back side layer 15 may comprise 1-3 wt. %, or 1-2 wt. % of the hydrophobing agent. Preferred hydrophobing agents are paraffin emulsions. An advantage with having a hydrophobing agent in the layers 15, 17, 19 of the building panel 10 is that it provides the layers 15, 17, 19 with improved water repellent properties, in turn creating a more water resistant building panel 10. It may thus be beneficial to have a hydrophobing agent in the layer 15, 17, 19 in which features for increasing the water resistant properties of the building panel 10 are created. Examples of this will be described later on.

[0176] The back side layer 15 may further comprise different types of additives, such as colorant, catalyst (e.g. ammonium sulphate), formaldehyde scavenger (e.g. urea), or buffer solution.

[0177] As described above, the intermediate layer 17 is made from the second mixture 13b, thus, the intermediate layer 17 includes at least lignocellulosic particles 17a and the binder 17b.

[0178] The lignocellulosic particles 17a in the intermediate layer 17 may be wood particles, e.g. made of pine, oak, eucalyptus, or other wood species, straws from grain products, sisal, coconut, bamboo, hemp, flax, jute, curaua, ramie, or any combination of such particles. The lignocellulosic particles 17a make up between 70 wt. % and 99 wt. %, above 75 wt. %, or above 85 wt. % of the intermediate layer 17.

[0179] The majority, i.e. at least 50 wt. %, of the lignocellulosic particles 17a in the intermediate layer 17 has a particle size of between 0.5 mm and 4 mm, or between 0.5 mm and 2.5 mm, or between 0.5 mm and 1.5 mm, or between 0.6 mm and 1.3 mm. Preferably at least 60 wt. %, at least 70 wt. %, or at least 80 wt. % of the lignocellulosic particles 17a in the intermediate layer 17 have a particle size of between 0.5 mm and 4 mm, or between 0.5 mm and 2.5 mm, or between 0.5 mm and 1.5 mm, or between 0.6 mm and 1.3 mm. The lignocellulosic particles 17a in the intermediate layer 17 can, like explained for the back side layer 15, also be measured by an aspect ratio, i.e. the ratio between the length of the particle and its width. The aspect ratio of the majority, i.e. at least 50 wt. %, of the lignocellulosic particles 17a in the intermediate layer 17 is below 30, or below 10. Preferably at least 60 wt. %, at least 70 wt. %, or at least 80 wt. % of the lignocellulosic particles 17a in the intermediate layer 17 have an aspect ratio below 30. The aspect ratio of the majority, i.e. at least 50%, of the lignocellulosic particles 17a in the intermediate layer 17 is between 1:1 and 30:1, between 1:1 and 20:1, or between 1:1 and 10:1. Preferably the aspect ratio of at least 60%, at least 70%, or at least 75% of the lignocellulosic particles 17a in the intermediate layer 17 is between 1:1 and 30:1, between 1:1 and 20:1, or between 1:1 and 10:1. At least 50%, of the lignocellulosic particles 17a in the intermediate layer 17 has a particle size of between 0.6 mm and 1.3 mm and an aspect ratio less than 30, or less than 20. In an embodiment the particle size of the lignocellulosic particles 17a in the intermediate layer 17 is between 0.6 mm and 1.3 mm and with an aspect ratio less than 10. In another embodiment the particle size of the lignocellulosic particles in the second mixture 13b is between 0.6 mm and 4 mm and with an aspect ratio less than 20, or less than 10.

[0180] The binder 17b in the intermediate layer 17 may be a thermoset resin. Examples of suitable thermoset resins are amino resins such as melamine formaldehyde, urea formaldehyde, phenol formaldehyde resins, or combinations thereof, or no-added formaldehyde resins such as epoxy resins, acrylic resins, polyurethane resins, polymeric diphenylmethane diisocyanate resin, polyester resins, or combinations thereof. The binder 17b in the intermediate layer 17 may be the same binder as in the back side layer 15.

[0181] The binder 17b makes up between 3% and 20 wt. %, between 3 wt. % and 12 wt. %, or between 5 wt. % and 10 wt. % of the intermediate layer 17. The amount of binder 17b in the intermediate layer 17, or in any of the layers 15, 19 in this disclosure, may affect the water resistant, or water repellent properties of the layers 15, 17, 19 of the building panel. Having more binder in the layers 15, 17, 19 will increase the water resistant, or water repellent properties in the building panel 10. However, the binder is also the more expensive component of the mixture, thus, an amount as defined above gives a beneficial balance between effect and cost. In an embodiment the binder content in the intermediate layer 17 is lower than the binder content in the front side layer 19 and/or the back side layer 15.

[0182] The intermediate layer 17 may further include a hydrophobing agent, such as wax. The intermediate layer 17 may comprise 1-3 wt. %, or 1-2 wt. % of the hydrophobing agent. Preferred hydrophobing agents are paraffin emulsions. An advantage with having a hydrophobing agent in the layers 15, 17, 19 of the building panel 10, is that it provides the layers 15, 17, 19 with improved water repellent properties, in turn creating a more water resistant building panel 10. It may thus be beneficial to have a hydrophobing agent in the layer 15, 17, 19 in which features for increasing the water resistant properties of the building panel 10 are created. Examples of this will be described later on.

[0183] The intermediate layer 17 may further comprise different types of additives, such as colorant, catalyst (e.g. ammonium sulphate), formaldehyde scavenger (e.g. urea), or buffer solution.

[0184] The front side layer 19 includes at least lignocellulosic particles 19a and the binder 19b. The lignocellulosic particles 19a in the front side layer 19 may be wood particles, e.g. made of pine, oak, eucalyptus, or other wood species, straws from grain products, sisal, coconut, bamboo, hemp, flax, jute, curaua, ramie, or any combination of such particles. The lignocellulosic particles 19a make up between 70 wt. % and 99 wt. %, above 75 wt. %, or above 85 wt. % of the front side layer 19.

[0185] The majority, i.e. at least 50 wt. %, of the lignocellulosic particles 19a in the front side layer 19 has a particle length of between 0.3 mm and 0.6 mm. Preferably at least 60 wt. %, at least 70 wt. %, or at least 80 wt. % of the lignocellulosic particles in the front side layer 19 have a particle length of between 0.3 mm and 0.6 mm. In an alternative embodiment, the majority, i.e. at least 50 wt. %, of the lignocellulosic particles in the first mixture 13a has a particle size of between 0.3 mm and 1.25 mm. Preferably at least 60 wt. %, at least 70 wt. %, or at least 80 wt. % of the lignocellulosic particles in the first mixture 13a have a particle size of between 0.3 mm and 1.25 mm.

[0186] The lignocellulosic particles 19a in the front side layer 19 can, as explained above, also be measured by an aspect ratio, i.e. the ratio between the length of the particle and its width. The aspect ratio of the majority, i.e. at least 50%, of the lignocellulosic particles 19a in the front side layer 19 is below 30. Preferably at least 60%, at least 70%, or at least 80% of the lignocellulosic particles 19a in the front side layer 19 have an aspect ratio below 30. The aspect ratio of the majority, i.e. at least 50%, of the lignocellulosic particles 19a in the front side layer 19 is between 1:1 and 30:1, between 1:1 and 20:1, or between 1:1 and 10:1. Preferably the aspect ratio of at least 60%, at least 70%, or at least 75% of the lignocellulosic particles 19a in the front side layer 19 is between 1:1 and 30:1, between 1:1 and 20:1, or between 1:1 and 10:1. At least 50 wt. %, of the lignocellulosic particles 19a in the front side layer 19 has a particle size of between 0.3 mm and 1.25 mm, or between 0.3 mm and 0.6 mm and an aspect ratio less than 30, or less than 20. In an embodiment the particle size of the lignocellulosic particles 19a in the front side layer 19 is between 0.3 mm and 1.25 mm, or between 0.3 mm and 0.6 mm and with an aspect ratio less than 10.

[0187] The binder 19b in the front side layer 19 may be a thermoset resin. Examples of suitable thermoset resins are amino resins such as melamine formaldehyde, urea formaldehyde, phenol formaldehyde resins, or combinations thereof, or no-added formaldehyde resins such as epoxy resins, acrylic resins, polyurethane resins, polymeric diphenylmethane diisocyanate resin, polyester resins, or combinations thereof. The binder 19b in the front side layer 19 may be the same binder as in the first back side layer 15 and/or the intermediate layer 17.

[0188] The binder 19b makes up between 3 wt. % and 35 wt. %, or between 10 wt. % and 25 wt. % of the front side layer 19. The amount of binder 19b in the front side layer 19, or in any of the layers 15, 17 in this disclosure, may affect the water resistant, or water repellent properties of the layers 15, 17, 19. Having more binder in the layers 15, 17, 19 will increase the water resistant, or water repellent properties in the building panel 10. However, the binder is also the more expensive component of the mixture, thus, an amount as defined above gives a beneficial balance between effect and cost.

[0189] The front side layer 19 may further include a hydrophobing agent, such as wax. The front side layer 19 may comprise 1-3 wt. %, or 1-2 wt. % of the hydrophobing agent. Preferred hydrophobing agents are paraffin emulsions. An advantage with having a hydrophobing agent in layers 15, 17, 19 of the building panel 10 is that it provides the layers 15, 17, 19 with improved water repellent properties, in turn creating a more water resistant building panel 10. It may thus be beneficial to have a hydrophobing agent in the layer 15, 17, 19 in which features for increasing the water resistant properties of the building panel 10 are created. Examples of this will be described later on.

[0190] The front side layer 19 may further include colorant 19c. The colorant 19c may be a pigment, dye, or a chemical staining agent. An example of a chemical staining agent is iron vitriol. By having a colorant 19c in the third mixture 13c it is possible to control and adapt appearance features of the building panel 10. For example, if the front side layer 19 is the top surface of the building panel 10 as illustrated in FIG. 7, or if a front side element 21, such as a front side wood veneer element, or top surface, has open features 22 as illustrated in FIG. 10 and explained in more detail both above and below.

[0191] The front side layer 19 may yet further comprise other types of additives, such as catalyst (e.g. ammonium sulphate), formaldehyde scavenger (e.g. urea), or buffer solution.

[0192] In an embodiment the front side layer 19 may comprise wear resistant particles, such as aluminium oxide particles, or scratch resistant particles. This may be preferred if the front side layer 19 is the top layer of the building panel 10.

[0193] In order to even further increase the water resistant properties of the building panel 10 the density of each layer 15, 17, 19, may be adapted to different water resistant properties designed within the layers 15, 17, 19 of the building panel 10. For example, it may be desirable to, in the front side layer 19, to design water resistant features of a mechanical locking device, which will be described in more detail below, and thus, desirable to increase the density of the front side layer 19 in order to even further improve the water resistant features of such a mechanical locking device. Whereas the intermediate layer 17 may be designed to have no additional water resistant features and therefore does not need an increased density. By adapting the density of each layer, the back side layer 15, the intermediate layer 17 and the front side layer 19 it is possible to both increase the water resistant properties of the building panel 10 where it is desirable to do so and decrease the risk of the building panel 10 becoming too heavy. The weight of the building panel 10 will also depend on the thickness of each of the components of the building panel 10 but by being able to control and adapt the thickness, the density, the lignocellulosic particle sizes, the amount of binder, etc. in each of the back side layer 15, the intermediate layer 17 and the front side layer 19 the weight of the building panel 10 also becomes controllable.

[0194] A preferred density of the intermediate layer 17 is less than the density of the front side layer 19 and/or the back side layer 15. A preferred density of the intermediate layer 17 may be between 700-900 kg/m.sup.3, or about 800 kg/m.sup.3. A preferred density of the front side layer 19 may be between 800-1200 kg/m.sup.3, or between 900-1100 kg/m.sup.3. In order to balance the building panel 10, it is preferred that the back side layer 15, even if it does not have any additional water resistant features designed in it, has the same density as the front side layer 19. Thus, the density of the back side layer 15 is substantially the same as the density of the front side layer 19. Thus, the density of the back side layer 15 may be between 800-1200 kg/m.sup.3, or between 900-1100 kg/m.sup.3.

[0195] In further embodiments of the present disclosure, there may be yet further layers (not illustrated) of the building panel. Such layers may comprise a mixture in accordance with any mixture described above with at least lignocellulosic particles and a binder. If the additional layer/s further include(s) a decorative layer the mixture may comprise colorant. The mixture may have been applied in dry form or wet form and may in an embodiment be a powder. The mixture may have been applied with any of the above described amounts. In an embodiment a yet further layer may be a coating layer. In another embodiment a yet further layer may comprise wear resistant particles, such as aluminium oxide particles, or scratch resistant particles. This may be preferred if the yet further layer is a top layer of the building panel.

[0196] The building panel 10 may have a thickness in the direction perpendicular to the extension of the top surface 24 of between 4 mm and 15 mm, preferably about 10 mm.

[0197] The ratio between the thickness of the intermediate layer 17 and the total thickness of the back side layer 15 and the front side layer 19 is between 70:30 and 30:70, or between 60:40 and 40:60.

[0198] The ratio between the thickness of the front side layer 19 and the thickness of the back side layer 15 is between 40:60 and 60:40, or between 45:55 and 55:45. The ratio between the thickness of the front side layer 19 and the thickness of the back side layer 15 may be about 50:50.

[0199] As explained above the building panel 10 may further include a pattern (not shown) in the top surface of the front side layer 15, or in the front side element 21 if such is present which has been created simultaneously with applying pressure and heat to form the building panel 10. The pattern may be a desirable and attractive structure, or different gloss levels in the top surface 24.

[0200] The differences between the building panel illustrated in FIG. 7 and the building panels illustrated in FIGS. 8-10 is now discussed.

[0201] In FIG. 8 the building panel 10 further has a front side element 21 which has been applied to the front side layer 19 after the step of applying heat and pressure, i.e. after the binder of the front side layer 19 has been cured. The front side element 21 may have been applied by means of e.g. an adhesive, such as glue, or the like. The front side element 21 may be chosen from a group of a wood veneer element, a paper sheet, a resin impregnated paper sheet, or an unimpregnated paper sheet, a cork element, a polymer-based sheet, a prefabricated powder-based sheet, a powder layer comprising wood fibres and binder, a foil, such as a thermoplastic foil, or a coating layer, such as a lacquer. In an embodiment, such front side element 21 is configured to receive a print, such as a digital print and/or an analog print.

[0202] The front side element 21 of the building panel may comprise a thermoset resin, for example an amino resin such as melamine formaldehyde, urea formaldehyde, phenol formaldehyde resins, or combinations thereof, or no-added formaldehyde resins such as epoxy resins, acrylic resins, polyurethane resins, polymeric diphenylmethane diisocyanate resin, polyester resins, or combinations thereof.

[0203] The front side element 21 of the building panel may comprise thermoplastic materials, such as polyvinyl chloride (PVC), polyvinyl butyral (PVB), polyethylene (PE), polypropylene (PP), thermoplastic polyurethane (TPU), acrylonitrile butadiene styrene (ABS), polystyrene (PS), polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), polyethersulfone (PES), or combinations thereof.

[0204] Any of the mentioned front side elements may further be combined with a suitable wear layer, such as a lacquer, an overlay sheet, or any other layer comprising e.g. wear resistant particles, such as aluminium oxide particles, and/or scratch resistant particles.

[0205] In FIG. 9A the building panel 10 include, on the bottom, a back side element 11 and, on the top, a front side element 21. The front side element 21 may be chosen from the same group as the front side elements described above.

[0206] The back side element 11 may be a balancing layer. The back side element 11 may be a balancing layer which is chosen to correspond to the front side element 21, i.e. if the front side element 21 is a wood veneer element the back side layer 11 may be a wood veneer element in order to create a symmetry in the building panel 10, or if the front side element 21 is a paper sheet the back side layer 11 may be the same type of paper sheet for the same reason. However, it may be possible to choose a back side element 11 not corresponding to the front side element 21.

[0207] The back side element 11 of the building panel may comprise a thermoset resin, for example an amino resin such as melamine formaldehyde, urea formaldehyde, phenol formaldehyde resins, or combinations thereof, or no-added formaldehyde resins such as epoxy resins, acrylic resins, polyurethane resins, polymeric diphenylmethane diisocyanate resin, polyester resins, or combinations thereof.

[0208] The back side element 11 of the building panel may comprise thermoplastic materials, such as polyvinyl chloride (PVC), polyvinyl butyral (PVB), polyethylene (PE), polypropylene (PP), thermoplastic polyurethane (TPU), acrylonitrile butadiene styrene (ABS), polystyrene (PS), polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), polyethersulfone (PES), or combinations thereof.

[0209] In between the back side layer 11 and the front side element 21 there is the multi-layered substrate 14 including the back side layer 15, the intermediate layer 17 and the front side layer 19. The back side layer 15 of the multi-layered substrate 14 is arranged on and attached, by means of the binder 15b in the back side layer 15, to the back side layer 11. The intermediate layer 17 is arranged in between the back side layer 15 and the front side layer 19. The front side layer 19 of the multi-layered substrate 14 is arranged on and attached, by means of the binder 19b in the front side layer 19, to the front side element 21.

[0210] The back side layer 15 attaches to the back side element 11 by means of the binder 15b, which has, during the production of the building panel 10, penetrated into the back side element 11, as illustrated in FIG. 9A. The same applies to the opposite side of the building panel 10 where the front side layer 19 attaches to the front side element 21 by means of the binder 19b, which has, during the production of the building panel 10, penetrated into the front side element 21, as illustrated in FIG. 9A. FIG. 9B is a photo of a building panel illustrated in FIG. 9A. This can advantageously provide water resistance.

[0211] Further, as illustrated in FIG. 10, the front side layer 19 is adapted to penetrate open features 22, if such are present in the front side element 21, in the front side element 21, such that the front side layer 19 at least partly fills the open features 22. Open features may be cracks, holes, pores, or the like. Therefore, it is preferred that the front side layer 19 further includes colorant 19c. The colorant may be a pigment, dye, or a chemical staining agent. An example of a chemical staining agent is iron vitriol. By having a colorant in the front side layer 19 is possible to control and adapt appearance features of the top surface 24 of the building panel 10. For example if the front side element 21, has open features 22, such as cracks, holes, or the like, the colorant of the front side layer 19 is configured to colour the open features 22 as the front side layer 19, or the third mixture 13c from which the front side layer 19 is made of, penetrates into the open features 22 and at least partly fills such open features 22 when pressure is subsequently applied. Preferably, the front side layer 19 substantially completely fills such open features 22, as illustrated in FIGS. 5 and 6. This can advantageously provide water resistance. The front side layer 19 partly or completely filling the open features 22, when pressure is applied, may eliminate the need of a further production step for filling the open features 22. This may in turn decrease the production time and increase the production efficiency of producing the building panel 10.

[0212] Thus, the front side layer 19, is configured to achieve at least three tasks, to mix with the intermediate layer 17, at least in the border area 18b, to attach to the front side element 21 and to at least partly fill open features 22 if such are present in the front side element 21 of the building panel 10. This can advantageously reduce the need to provide multiple features for achieving these objectives, and thus can help reduce manufacturing cost.

[0213] FIG. 11 illustrates a top view of a building panel 10 which may for example be a floor panel, a wall panel, a ceiling panel, or similar. The building panel 10 has a top surface 24, which preferably is the visible surface of the building panel in an assembled state, and a bottom surface 29, which preferably is arranged parallel to and spaced apart from, by the thickness of the building panel 10, the top surface 24. The bottom surface 29 further faces away from the top surface 24. Either the back side layer 15 or the back side element 11 may comprise the bottom surface 29. The top surface 24 may preferably be a decorative top surface and either the front side layer 19 or the front side element 21 may comprise the top surface 24.

[0214] When installed in the room as a floor panel, the bottom surface 29 is intended to face a sub-floor. The top surface 24 is intended to face the interior of the room.

[0215] The building panel further has a first edge portion 25, a second edge portion 26, a third edge portion 27 and a fourth edge portion 28. The second edge portion 26 is arranged opposite the first edge portion 25 and extends in a parallel direction to the first edge portion 25. The fourth edge portion 28 is arranged opposite the third edge portion 27 and extends in a parallel direction to the third edge portion 27. In the illustrated examples the first and second edge portions 25, 26 are the long edge portions of the building panel 10 and the third and fourth edges 27, 28 are the short edge portions of the building panel 10. The building panel 10 is designed to be assembled with similar or substantially identical building panels 10, 10 as illustrated in FIGS. 12A and 12B.

[0216] In order to assemble similar or essentially identical building panels 10, 10, 10 the first edge portion 25 and the second edge portion 26 of the building panel 10 are provided with a first mechanical locking device 30a, configured such that the first edge portion 25 of a building panel 10 is able to mechanically lock to a second edge portion 26 of an adjacent building panel 10 and vice versa, i.e. the opposite first and second edge portions 25, 26 are designed to be compatible with each other. The first mechanical locking device 30a extends preferably along the entire length of the first and second edge portion 25, 26, respectively. Further, the third edge portion 27 and the fourth edge portion 28 of the building panel 10 are provided with a second mechanical locking device 30b, configured such that the third edge portion 27 of a building panel 20 is able to mechanically lock to a fourth edge portion 28 of an adjacent building panel 20 and vice versa, i.e. the opposite third and fourth edge portions 27, 27 are designed to be compatible with each other. The second mechanical locking device 30b extends preferably along the entire length of the third and fourth edge portion 25, 26, respectively. Each mechanical locking device 30a, 30b is configured to lock adjacent building panels 10, 10, 10 in a horizontal and/or vertical direction, preferably in a horizontal and vertical direction, by means of a folding and/or vertical displacement. To be even more specific, the first mechanical locking device 30a, which is arranged in the first and second edge portion 25, 26 of the building panel is configured to lock adjacent building panels 10, 10, 10 in a direction parallel to the longitudinal extension of the third and fourth edge portions 27, 28 and in the direction perpendicular to the longitudinal extension of the third and fourth edge portion 27, 28. The other way around, the second mechanical locking device 30b, which is arranged in the third and fourth edge portion 27, 28 of the building panel is configured to lock adjacent building panels 10, 10, 10 in a direction parallel to the longitudinal extension of the first and second edge portion 25, 26 and in the direction perpendicular to the longitudinal extension of the first and second edge portions 25, 26. If such building panels 10, 10, 10 are assembled as floor panels, the parallel directions correspond to the horizontal direction and the perpendicular directions correspond to the vertical direction.

[0217] A first building panel 10 is assembled to a second building panel 10 by means of the first mechanical locking device 30a provided along respective first and second edge portions 25, 26 of respective building panel 10, 10. The first mechanical locking device 30a may be configured to assemble and lock adjacent building panels 10, 10 in a horizontal and vertical direction by means of a pivoting motion P, see FIG. 12A. The first building panel 10 may pivot about an upper portion of the second edge portion 26 of the second building panel 10.

[0218] When the first building panel 10 is assembled with the second building panel 10 the first building panel 10 may preferably be displaceable in the horizontal direction such that the first building panel 10 is placed in the right location for being assembled to the third building panel 10

[0219] The first building panel 10 is then assembled to a third building panel 10 by means of the second mechanical locking device 30b provided along respective third and fourth edge portions 27, 28 of respective building panel 10, 10. The second mechanical locking device 30b may be configured to assemble and lock adjacent building panels 10, 10 in a horizontal and vertical direction by means of a vertical displacement, such as vertical folding.

[0220] In an alternative installation (not shown) the first building panel may firstly be assembled with the third building panel, along the short side edge, and then assembled to the second building panel, along the long side edge.

[0221] In the assembled position, as is illustrated in FIG. 12B, an upper edge area 25b of the first edge portion 25 of the first building panel 10 and an upper edge area 26b of the second edge portion 26 of the second panel 10 are juxtaposed to form a joint seal JS1 between the first and second building panel 10, 10. Further, in the assembled position, an upper edge area 27b of the third edge portion 27 of the first building panel 10 and an upper edge area 28b of the fourth edge portion 28 of the third building panel 10 are juxtaposed to form a joint seal JS2 between the first and third building panel 10, 10. These two join seals JS1, JS2 are illustrated in more detail in FIGS. 13A and 13B.

[0222] The detailed description of embodiments below is based on the assembling illustrated in FIG. 12B, i.e., with a first, a second and a third building panel 10, 10, 10. Since all building panels 10, 10, 10 are similar or essentially identical, all features of the mechanical locking device are present on each building panel 10, 10, 10.

[0223] FIG. 13A illustrates the first mechanical locking device 30a in the assembled state of two adjacent building panels 10, 10. Preferably, all features of the first mechanical locking device 30a are integrally formed in the first and second edge portion 25, 26, respectively.

[0224] The first mechanical locking device 30a comprises along the second edge portion 26 a locking strip 32. The locking strip 32 is arranged at a lower edge area 26a of the edge portion 26, projecting outwards from the lower edge are 26a. The locking strip 32 may be configured to be angularly displaced during the folding displacement.

[0225] The locking strip 32 includes, at the outermost end of the locking strip 32, a locking element 34. The outermost end of the locking strip may be the most distal end of the locking strip 32 in view of the joint seal JS1. The locking element 34 is configured to be received in a locking groove 44 arranged in a lower edge area 25a of the first edge portion 25 of an adjacent building panel, by means of the folding displacement.

[0226] The locking strip 32 has an elongated shape with the locking element 34 arranged at the outermost end. Between the innermost end of the locking strip 32 and the locking element 34 the locking strip 32 has an elongated body 33. The elongated body 33 has a lower surface 33a facing the bottom surface 29 of the building panel and an upper surface 33b facing in the opposite direction, i.e. towards the top surface 24 of the building panel. The upper surface 33b is preferably plane. The lower surface 33a may be flush with the bottom surface 29 of the building panel.

[0227] The upper surface 33b, in the assembled position, extends preferably in the same direction as a lower surface 46a of a locking tongue 46 in the first edge portion 25 of an adjacent building panel, pushing on the upper surface 33b. The upper surface 33b and the lower surface 46a are preferably planar. The upper surface 33b of the elongated body 33 of the locking strip 32 is configured to, in the assembled state, cooperate and preferably at least partly be in contact with the lower surface 46a of the locking tongue 46.

[0228] The locking element 34 of the locking strip 32 includes a front locking surface 34a. The front locking surface 34a is arranged at the innermost end of the locking element 34. The upper surface 33b of the elongated body 33 merges into the front locking surface 34a of the locking element 34. The front locking surface 34a of the locking element 34 is configured to, in the assembled state, cooperate and preferably at least partly be in contact with a front wall 44a of a locking groove 44 in the first edge portion 25. The front locking surface 34a of the locking element 34 and the front wall 44a of the locking groove 44 are configured to lock two adjacent building panels in at least a direction parallel to the longitudinal extension of the third and fourth edge portion 27, 28.

[0229] The elongated body 33 may be configured to be bendable, to the extent that a portion of the elongated body 33 during installation of two building panels 10, 10, 10 may be pushed and displaced downwards.

[0230] In order to reduce the risk of affecting the properties of the locking strip 32, e.g. that the elongated body 33 is supposed to flex to a degree during the assembling process it is preferred to control and adapt in which layer 15, 17, 19 of the multi-layered substrate 14 the locking strip 32 is located.

[0231] In the embodiment illustrated in FIGS. 13A and 13B, the front locking surface 34a of the locking element 34 is at least partially arranged in the back side element 15. The front locking surface 34a of the locking element 34 may be arranged in the back side element 15 entirely or partially. This may provide a stronger mechanical locking device, for example at least in a horizontal direction.

[0232] At least a portion of the front locking surface 34a is configured, in the assembled position and when a force is applied in a horizontal direction away from the joint seal JS1, form a contact surface with the locking surface 44a of the locking groove 44. The contact surface of the locking element 34 is arranged in the back side layer 15, as illustrated in FIGS. 13A and 13B.

[0233] The first mechanical locking device 30a, in the second edge portion 26, further includes a tongue groove 38. The tongue groove 38 is arranged above the locking strip 32 at the innermost end of the locking strip 32 and extends inwards into the second edge portion 26. The tongue groove 38 is configured and shaped to receive a locking tongue 46 in the first edge portion 25 of the adjacent building panel. In the assembled position, the tongue groove 38 and the locking tongue 46 are configured to cooperate and lock two adjacent building panels in at least a direction perpendicular to the longitudinal extension of the third and fourth edge portion 27, 28. The tongue groove 38 and the locking tongue 46 may further be configured to lock two adjacent building panels in the direction parallel to the longitudinal extension of the third and fourth edge portion 27, 28.

[0234] An upper wall 38a of the tongue groove 38 may be configured to cooperate and preferably be in contact with an upper surface 46b of the locking tongue 46 in the first edge portion 25 of an adjacent building panel. The upper wall 38a may be configured to lock the locking tongue 38 in the direction perpendicular to the longitudinal extension of the third and fourth edge portion 27, 28.

[0235] The first mechanical locking device 30a, in the second edge portion 26, further includes a front side tongue 40. The front side tongue 40 is arranged in an upper edge area 26b of the second edge portion 26 and extends outwards away from the second edge portion 26. The front side tongue 40 is arranged above the tongue groove 38.

[0236] The front side tongue 40 is configured and shaped to be received in a front side tongue groove 48 in the first edge portion 25 of the adjacent building panel. In the assembled position, the front side tongue 28 and the front side tongue groove 48 are configured to lock two adjacent building panels in the direction perpendicular, and preferably also parallel, to the longitudinal extension of the third and fourth edge portion 27, 28.

[0237] An upper surface 40a, extending in the direction parallel to the longitudinal extension of the third and fourth edge portion 27, 28, of the front side tongue 40 is configured to cooperate and preferably be in contact with an upper wall 48a of the front side tongue groove 48. The upper wall 48a of the front side tongue groove 48 is configured to lock the front side tongue 40 in the direction perpendicular to the longitudinal extension of the third and fourth edge portion 27, 28.

[0238] It may be preferred to have a height h1 of the front side tongue 40 of between 0.5 and 2.5 mm. It is preferred for the height h1 of the front side tongue 40 to be greater than the height h2 of the front side tongue groove 48. The difference between the height h1 of the front side tongue 40 and the height h2 of the front side tongue groove 48 is in the range of 0.01 to 0.5 mm, preferably 0.01 to 0.25 mm, more preferably 0.01 to 0.15 mm.

[0239] When the front side tongue 40 is arranged in the front side tongue groove 48, in the assembled position, the front side tongue 40 and the front side tongue groove 48 create a tight seal. This is advantageous since the tight seal can obstruct e.g. water, or other fluids, to penetrate further down into the mechanical locking device 30a. It is especially beneficial if the upper surface 40a of the front side tongue 40 creates a tight seal against the upper wall 48a of the front side tongue groove 48 since it is where the fluids are prone to spread out into the rest of the mechanical locking device 30a and the rest of the building panel.

[0240] In order to increase the water resistant properties even further it may be desirable to design and position at least the upper surface 40a of the front side tongue 40 in the above described front side layer 19, see the upper dotted lines in FIG. 13A. The features of the front side layer 19, as described above, are controlled such that they contribute to the increased water resistant properties of the mechanical locking device 30a and the building panel 10. This is achieved for example by having a higher density, lignocellulosic particles with a smaller size than for example in the intermediate layer 17, a higher binder content or adding a hydrophobing agent in the front side layer 19. Of course, the position of the upper surface 40a of the front side tongue 40 may be adjusted and adapted to the front side layer 19, e.g. due to a preferred thickness of the front side layer 19. Vice versa, the thickness of the front side layer 19 may be adjusted and adapted to the position of the upper surface 40a of the front side tongue 40.

[0241] In the embodiment illustrated in FIG. 13A, the thickness of the front side layer 19 substantially corresponds to the thickness of the back side layer 15. The thickness of the intermediate layer 17 may exceed the thickness of the front side layer 19 and/or the thickness of the back side layer 15.

[0242] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 40:60 and 60:40, or between 45:55 and 55:45, such as 50:50.

[0243] The ratio between the amount of the applied second mixture 13b and the amount of the applied first mixture 13a may be between 60:40 and 40:60. The ratio between the amount of the applied third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be 20-60-20 wt. %, or 25-50-25 wt. % or 30-40-30 wt. %. In the embodiment illustrated in FIG. 13A, the ratio between the amount of the applied first mixture 13a, the applied second mixture 13b and the applied third mixture 13c may be about 30-40-30 wt. %.

[0244] Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17, and the back side layer 15 may be 20-60-20%, or 25-50-25% or 30-40-30%. In the embodiment illustrated in FIG. 13A, a ratio between the thickness of the front side layer 19, the intermediate layer 17, and the back side layer 15 may be about 30-40-30%.

[0245] Alternatively, in order to increase the water resistant properties even further it may be desirable to design and position the front side tongue 40 in the intermediate layer 17, see the upper dotted line in FIG. 15A, in order to be able to achieve a controlled swelling of at least the upper surface 40a of the front side tongue 40, when fluid penetrates into the building panel. A controlled swelling of at least the upper surface 40a can provide a tight seal when the front side tongue 40 is arranged in the front side tongue groove 48 and in turn provide increased water resistant properties and prevent fluid from penetrate further into the building panel. In all other aspects, the disclosure in FIG. 15A corresponds to embodiment described with reference to FIG. 13A.

[0246] In the embodiment illustrated in FIG. 15A, the thickness of the front side layer 19 may be about of the thickness of the back side layer 15. The thickness of the intermediate layer 17 may exceed the thickness of the front side layer 19 and/or the thickness of the back side layer 15, such as having a thickness being about twice the thickness of the back side layer 15.

[0247] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 1:5 to 1:2, such as 1:4 to 1:3, for example about 1:3.

[0248] The ratio between the amount of the applied second mixture 13b and the amount of the applied first mixture 13a may be between 2:1 and 3:1. In the embodiment illustrated in FIG. 15A, the ratio between the amount of the third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be about 10-60-30 wt. %.

[0249] Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17, and the back side layer 15 may be about 10-60-30%.

[0250] One of the main advantages of the present disclosure is to be able to adapt and control all features of the building panel without any addition preprocessing of the components of the building panel.

[0251] At the upper edge area 26b of the second edge portion 26, above the front side tongue 40 there is provided a locking surface 42 extending perpendicular to the upper surface 40a of the front side tongue 40, i.e. extending in the direction perpendicular to the longitudinal extension of the third and fourth edge portion 27, 28. At the upper edge area 25b of the opposite first edge portion 25 there is provided an opposite locking surface 50, extending parallel to the locking surface 42 of the second edge portion 26, i.e. extending in the direction perpendicular to the longitudinal extension of the third and fourth edge portion 27, 28. The locking surface 42 of the second edge portion 26 is configured to cooperate, and preferably be in contact with the locking surface 50 of the first edge portion 25, in the assembled position, as illustrated in FIG. 13A. Together, the locking surface 42 of the second edge portion 26 and the locking surface 50 of the first edge portion 25 form the joint seal JS1. The seal between the two locking surfaces 42, 50 may preferably have a pretension, such that there is a force between the two locking surfaces 42, 50 working towards each other. This pretension may decrease the risk of fluids entering into the mechanical locking device 30a ever further.

[0252] Although many of the features of the first mechanical locking device 30a in the first edge portion 25 has been described above, additional features are now described in more detail.

[0253] The first mechanical locking device 30a in the first edge portion 25 includes the locking groove 44. The locking groove 44 is arranged in the lower edge area 25a of the first edge portion 25 and extends in a direction upwards into and away from the bottom surface 29 of the building panel.

[0254] The locking groove 44 is configured and shaped to receive the locking element 34 of the locking strip 32 of the adjacent building panel. In the assembled position, the locking groove 44 and the locking element 34 are configured to lock two adjacent building panels in at least the direction parallel to the longitudinal extension of the third and fourth edge portion 27, 28. In order to do so the locking groove 44, in the illustrated embodiments, includes a front wall 44a. The front wall 44a is configured to, in the assembled position, cooperate and preferably at least partly be in contact with the front locking surface 34a of the locking element 34 of the adjacent building panel.

[0255] A portion of the front wall 44a may be referred to a locking surface 44a of the locking groove 44. The locking surface 44a of the locking groove 44 is configured to, in the assembled position and when a force is applied in a horizontal direction and away from the joint seal JS1, cooperate with the front locking surface 34a of the locking element 34 of the adjacent building panel.

[0256] At least a portion of the locking surface 44a of the locking groove 44 may be positioned in the back side layer 15.

At least a portion of the locking surface 44a of the locking groove 44 is configured to, in the assembled position and when a force is applied in a horizontal direction and away from the joint seal JS1, form a contact surface with the front locking surface 34a of the locking element 34. The contact surface of the locking groove 44 is arranged in the back side layer 15, as illustrated in FIGS. 13A and 13B.

[0257] Further, the first mechanical locking device 30a in the first edge portion 25 includes a locking tongue 46. The locking tongue 46 extends outwards, in a direction parallel to the longitudinal extension of the third and fourth edge portion 27, 28, away from the first edge portion 25.

[0258] The locking tongue 46 is at least partly configured and shaped to be received in the tongue groove 38 in the second edge portion 26 of the adjacent building panel, as explained above.

[0259] The locking tongue 46 preferably has an elongated shape where at least an outermost portion 46c is received in the tongue groove 38, in the assembled position. The locking tongue 46 and the outermost portion 46c have an upper surface 46b which is configured to cooperate and preferably be in contact with the upper wall 38a of the tongue groove 38 of the adjacent building panel. The upper wall 38a and the upper surface 46b are configured to lock two adjacent building panels in the direction perpendicular to the longitudinal extension of the third and fourth edge portion 27, 28.

[0260] As briefly described above, the locking tongue 46 further has a lower surface 46a. The lower surface 46a may be configured to cooperate and even be in contact with the upper surface 33a of the elongated body 33 of the locking strip 32, in the assembled state. For example, during installation, the lower surface 46a may be configured to displace, and preferably push on, the upper surface 33a of the elongated body 33 of the locking strip 32. As explained above, the locking strip may be flexible allowing the lower surface 46a of the locking tongue 46 to push the locking strip 32 downwards. This movement may increase the preferred pretension in the two parallel locking surfaces 42, 50 in the upper edge area 25b, 26b of respective first and second edge portion 25, 26 of adjacent building panels.

[0261] The lower surface 46a of the locking tongue 46 may be arranged in the back side layer 15.

[0262] The first mechanical locking device 30a in the first edge portion 25 may also include a front side tongue groove 48. The front side tongue groove 48 is arranged above the locking tongue 46 and extends inwards, into the building panel.

[0263] The front side tongue groove 48 is configured and shaped to receive the front side tongue 40 in the second edge portion 26 of the adjacent building panel. In the assembled position, the front side tongue groove 48 and the front side tongue 40 are configured to lock two adjacent building panels in the direction perpendicular to the longitudinal extension of the third and fourth edge portion 27, 28.

[0264] As explained above, in order to cause a tight seal, it may be preferred to have a height h1 of the front side tongue 40 of between 0.5 and 2.5 mm. It is preferred for the height h1 of the front side tongue 40 to be greater than the height h2 of the front side tongue groove 48. Thus, as the front side tongue 40 is arranged in the front side tongue groove 48, in the assembled position, the front side tongue 40 and the front side tongue groove 48 create a tight seal. This is advantageous since the tight seal can obstruct e.g., water, or other fluids, to penetrate further down into the mechanical locking device 30a.

[0265] Thus, when the front side tongue 40 is arranged in the front side tongue groove 48, in the assembled position, the front side tongue 40 and the front side tongue groove 48 create a tight seal. This is advantageous since the tight seal can obstruct e.g. water, or other fluids, to penetrate further down into the mechanical locking device 30a. It is especially beneficial if the upper surface 40a of the front side tongue 40 creates a tight seal against the upper wall 48a of the front side tongue groove 48 since it is where the fluids are prone to spread out into the rest of the mechanical locking device 30a and the rest of the building panel.

[0266] At the upper edge area 25b of the first edge portion 25, above the front side tongue groove 48 there is provided a locking surface 50 extending perpendicular to the upper wall 48a of the front side tongue groove 48, i.e. extending in the direction perpendicular to the longitudinal extension of the third and fourth edge portion 27, 28. At the upper edge area 26b of the opposite second edge portion 26 there is provided the opposite locking surface 42, extending parallel to the locking surface 50 of the first edge portion 25, i.e. extending in the direction perpendicular to the longitudinal extension of the third and fourth edge portion 27, 28. The locking surface 50 of the first edge portion 25 is configured to cooperate, and preferably be in contact with the locking surface 42 of the second edge portion 26, in the assembled position, as illustrated in FIG. 13A. Together, the locking surface 50 of the first edge portion 25 and the locking surface 42 of the second edge portion 26 form the joint seal JS1. The seal between the two locking surfaces 42, 50 may preferably have a pretension, such that there is a force between the two locking surfaces 42, 50 working towards each other. This pretension may decrease the risk of fluids entering into the mechanical locking device 30a ever further. Such a pretension between the two locking surfaces 42, 50 may, in an environment with normal humidity of two building panels each being 100 mm long, be between 2-100N, or between 5-80N.

[0267] FIG. 13B illustrates an embodiment of the first mechanical locking device 30a essentially corresponding to the first mechanical locking device 30a described above with reference to FIG. 13A. However, the embodiment of first mechanical locking device 30a illustrated in FIG. 13B does not include the front side tongue 40 and the front side tongue groove 48. In the embodiment illustrated in FIG. 13B, the locking surface 42 of the second edge portion 26 extends from the top surface 24 to the tongue groove 38 in the second edge portion 26. The opposite locking surface 50 of the opposite first edge portion 25 extends from the top surface 24 to the locking tongue 46. Together, the locking surface 50 of the first edge portion 25 and the locking surface 42 of the second edge portion 26 form the joint seal JS1. The locking surface 42 and the locking surface 50 may at least partly extend in the front side layer 19, or may completely extend in the front side layer 19. In one embodiment, the locking surface 42 and the locking surface 50 may extend both in the front side layer 9 and in the intermediate layer 17.

[0268] In the embodiment illustrated in FIG. 13B, the thickness of the front side layer 19 may be about of the thickness of the back side layer 15. The thickness of the intermediate layer 17 may exceed the thickness of the front side layer 19 and/or the thickness of the back side layer 15.

[0269] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 1:5 to 1:2, such as 1:4 to 1:3, for example about 1:3.

[0270] The ratio between the amount of the applied second mixture 13b and the amount of the applied first mixture 13a may be between 1:1 and 3:2. In the embodiment illustrated in FIG. 13B, the ratio between the amount of the applied third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be about 15-50-35 wt. %.

[0271] Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17, and the back side layer 15 may about 15-50-35%.

[0272] In all other aspects, the description of the embodiment in FIG. 13A is applicable for the embodiment in FIG. 13B as well.

[0273] FIG. 13C illustrates the second mechanical locking device 30b in the assembled state. Preferably, all features, with the exception of a displaceable locking tongue 72, of the second mechanical locking device 30b are integrally formed in the third and fourth edge portion 27, 28, respectively. Much is similar to the first mechanical locking device 30a and its embodiments. The second mechanical locking device 30b is configured to assemble and lock adjacent building panels 10, 10, 10 in a direction parallel and perpendicular to the longitudinal extension of the first and second edge portion 25, 26 of the building panel, by means of the vertical displacement.

[0274] The second mechanical locking device 30b includes along the fourth edge portion 28 a locking strip 52, preferably integrally formed in the fourth edge portion 28. The locking strip 52 is arranged at a lower edge area 28a of the fourth edge portion 28, projecting outwards from the lower edge area 28a. The locking strip 52 may be configured to be angularly displaced during the vertical displacement.

[0275] The locking strip 52 includes, at the outmost end of the locking strip 52, a locking element 54. The locking element 54 is configured to be received in a locking groove 64 arranged in a lower edge area 27a of the third edge portion 27 of an adjacent building panel, by means of the vertical displacement.

[0276] The locking strip 52 has an elongated shape with the locking element 54 arranged at the outermost end. Between the innermost end of the locking strip 52 and the locking element 54 the locking strip 52 has an elongated body 53. The elongated body 53 has a lower surface 53a facing the bottom surface 29 of the building panel and an upper surface 53b facing in the opposite direction, i.e. towards the top surface 24 of the building panel.

[0277] The upper surface 53b, in the assembled position, extends preferably in the same direction as a lower surface 66 in the lower edge area 27a of the third edge portion 27 of an adjacent building panel, pushing on the upper surface 53b. The upper surface 53b and the lower surface 66 are preferably planar. The upper surface 53b of the elongated body 53 of the locking strip 52 is configured to, in the assembled state, cooperate and preferably at least partly be in contact with the lower surface 66 in the lower edge area 27a of the third edge portion 27.

[0278] The locking element 54 of the locking strip 52 includes a front locking surface 54a. The front locking surface 54a is arranged at the innermost end of the locking element 54. The upper surface 53b of the elongated body 53 merges into the front locking surface 54a of the locking element 54. The front locking surface 56 of the locking element 54 is configured to, in the assembled state, cooperate and preferably at least partly be in contact with a front wall 64a of a locking groove 64 in the third edge portion 27. The front locking surface 54a of the locking element 54 and the front wall 64a of the locking groove 64 are configured to lock two adjacent building panels in at least a direction parallel to the longitudinal extension of the first and second edge portion 25, 26.

[0279] The elongated body 53 may be configured to be bendable, to the extent that a portion of the elongated body 53 during installation of two building panels 10, 10 may be pushed and displaced downwards.

[0280] In order to reduce the risk of affecting the properties of the locking strip 52, e.g. that the elongated body 53 is supposed to flex to a degree during the assembling process it is preferred to control and adapt in which layer 15, 17, 19 of the multi-layered substrate 14 the locking strip 52 is located.

[0281] In the embodiment illustrated in FIGS. 13C and 13D, the front locking surface 54a of the locking element 54 is at least partially arranged in the back side element 15. The front locking surface 54a of the locking element 54 may be arranged in the back side element 15 entirely or partially.

[0282] At least a portion of the front locking surface 54a is configured, in the assembled position and when a force is applied in a horizontal direction away from the joint seal JS2, form a contact surface with the locking surface 64a of the locking groove 64. The contact surface of the locking element 54 is arranged in the back side layer 15, as illustrated in FIGS. 13C and 13D.

[0283] The second mechanical locking device 30b, in the fourth edge portion 28, further includes a displaceable tongue groove 58. The displaceable tongue groove 58 is arranged above the locking strip 52 at the innermost end of the locking strip 52, and extends inwards, preferably angled, into the fourth edge portion 27.

[0284] The displaceable tongue groove 58 is configured and shaped to receive a displaceable locking tongue 72. The displaceable locking tongue 72, when arranged in the displaceable tongue groove 58, is configured to lock two adjacent building panels in at least a direction perpendicular to the longitudinal extension of the first and second edge portion 25, 26, when engaged with a displaceable tongue groove 68 in the third edge portion 27 of the adjacent building panel.

[0285] The displaceable locking tongue 72 may be a separate member and comprise the same or a different material than the building panel. The displaceable locking tongue 72 may be made of a polymer-based material. The displaceable locking tongue 72 is described in more detail below with reference to FIG. 14.

[0286] The first mechanical locking device 30b, in the fourth edge portion 28, further includes a front side tongue 60. The front side tongue 60 is arranged in the upper edge area 28b of the fourth edge portion 28 and extends outwards away from the fourth edge portion 28. The front side tongue 60 is arranged above the displaceable tongue groove 58.

[0287] The front side tongue 60 has an upper surface 60a which is configured to cooperate and preferably be in contact with a lower surface 67 arranged in the upper edge area 27b of the third edge portion 27 of the adjacent building panel. The lower surface 67 of the third edge portion 27 is configured to lock the upper surface 60a of the front side tongue 60 in the direction perpendicular to the longitudinal extension of the first and second edge portion 25, 26.

[0288] When the upper surface 60a of the front side tongue 60 is locked against the lower surface 67 of the third edge portion 27 of the adjacent building panel, the upper surface 60a and the lower surface 67 create a tight seal. This is advantageous since the tight seal can obstruct e.g. water, or other fluids, to penetrate further down into the mechanical locking device 30a.

[0289] In order to increase the water resistant properties even further it may be desirable to design and position at least the upper surface 60a of the front side tongue 60 in the above described front side layer 19, see the upper dotted line in FIG. 13C. The features of the front side layer 19, as described above, are controlled such that they contribute to the increased water resistant properties of the mechanical locking device 30b and the building panel 10. This is achieved for example by having a higher density, lignocellulosic particles with a smaller size than for example in the intermediate layer 17, a higher binder content or adding a hydrophobing agent in the front side layer 19. Of course, the position of the upper surface 60a of the front side tongue 60 may be adjusted and adapted to the front side layer 19, e.g. due to a preferred thickness of the front side layer 19. Vice versa, the thickness of the front side layer 19 may be adjusted and adapted to the position of the upper surface 60a of the front side tongue 60.

[0290] Alternatively, in order to increase the water resistant properties further it may be desirable to design and position the front side tongue 60 in the intermediate layer 17, see the upper dotted lines in FIG. 15B, in order to be able to achieve a controlled swelling of at least the upper surface 60a of the front side tongue 60, when fluid penetrates into the building panel. A controlled swelling of at least the upper surface 60a can provide a tight seal of the front side tongue 60 against the lower surface 67 and in turn provide increased water resistant properties and prevent fluid from penetrate further into the building panel.

[0291] In the embodiment illustrated in FIG. 15B, the thickness of the front side layer 19 may be about of the thickness of the back side layer 15. The thickness of the intermediate layer 17 may exceed the thickness of the front side layer 19 and/or the thickness of the back side layer 15, such as having a thickness being about twice the thickness of the back side layer 15.

[0292] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 1:5 to 1:2, such as 1:4 to 1:3, for example about 1:3.

[0293] The ratio between the amount of the applied second mixture 13b and the amount of the applied first mixture 13a may be between 2:1 and 3:1. In the embodiment illustrated in FIG. 15B, the ratio between the amount of the applied third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be about 10-60-30 wt. %.

[0294] Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17 and the back side layer 15 may be about 10-60-30%.

[0295] In all other aspects, the embodiment illustrated in FIG. 15B corresponds to the embodiment described above with reference to FIG. 13C.

[0296] One of the main advantages of the present disclosure is to be able to adapt and control all features of the building panel without any additional preprocessing of the components of the building panel.

[0297] At the upper edge area 28b of the fourth edge portion 28 above the upper surface 60a of the front side tongue 60 there is provided a locking surface 62 extending perpendicular to the upper surface 60a of the front side tongue 60, i.e. extending in the direction perpendicular to the longitudinal extension of the first and second edge portion 25, 26. At the upper edge area 27b of the opposite third edge portion 27 of the adjacent building panel 1 there is provided an opposite locking surface 70 extending parallel to the locking surface 62 of the fourth edge portion 28, i.e. extending in the direction perpendicular to the longitudinal extension of the first and second edge portion 25, 26. The locking surface 62 of the fourth edge portion 28 is configured to cooperate, and preferably be in contact with the locking surface 70 of the third edge portion 27, in the assembled position, as illustrated in FIG. 13C. Together, the locking surface 62 of the fourth edge portion 28 and the locking surface 70 of the third edge portion 27 form the joint seal JS2. The seal between the two locking surfaces 62, 70 may preferably have a pretension, such that there is a force between the two locking surfaces 62, 70 working towards each other. This pretension may decrease the risk of fluids entering into the mechanical locking device 30b ever further.

[0298] Although many of the features of the second mechanical locking device 30b in the third edge portion 27 has been described above, additional features are now described in more detail.

[0299] The second mechanical locking device 30b in the third edge portion 27 includes the locking groove 64. The locking groove 64 is arranged in the lower edge area 27a of the third edge portion 27 and extends in a direction upwards into and away from the bottom surface 29 of the building panel.

[0300] The locking groove 64 is configured and shaped to receive the locking element 54 of the locking strip 52 of the adjacent building panel. In the assembled position, the locking groove 64 and the locking element 54 are configured to lock two adjacent building panels in at least the direction parallel to the longitudinal extension of the first and second edge portion 25, 26. In order to do so the locking groove 64, in the illustrated embodiments, includes a front wall 64a. The front wall 64a is configured to, in the assembled position, cooperate and preferably at least partly be in contact with the front locking surface 54a of the locking element 54 of the adjacent building panel.

[0301] A portion of the front wall 64a may be referred to a locking surface 64a of the locking groove 64. The locking surface 64a of the locking groove 64 is configured to, in the assembled position and when a force is applied in a horizontal direction and away from the joint seal JS2, cooperate with the front locking surface 54a of the locking element 54 of the adjacent building panel.

[0302] At least a portion of the locking surface 64a of the locking groove 64 may be positioned in the back side layer 15.

[0303] At least a portion of the locking surface 64a of the locking groove 64 is configured to, in the assembled position and when a force is applied in a horizontal direction and away from the joint seal JS2, form a contact surface with the front locking surface 54a of the locking element 54. The contact surface of the locking groove 64 is arranged in the back side layer 15, as illustrated in FIGS. 13C and 13D. The second mechanical locking device 30b in the third edge portion 27 further preferably has the lower surface 66 as mentioned above. The lower surface 66 is arranged in the lower edge area 27a of the third edge portion 27 of the building panel. The lower surface 66 may be configured to cooperate and even be in contact with the upper surface 53b of the elongated body 53 of the locking strip 52, in the assembled state. For example, during installation, the lower surface 66 may be configured to displace, and preferably push on, the upper surface 53a of the elongated body 53. As explained above, the locking strip may be flexible allowing the lower surface 66 to push the locking strip 52 downwards. This movement may increase the preferred pretension in the two parallel locking surfaces 62, 70 in the upper edge area 27b, 28b of respective third and fourth edge portion 27, 28 of adjacent building panels.

[0304] The second mechanical locking device 30b in the third edge portion 27 there is also provided a displaceable tongue groove 68. The displaceable tongue groove 68 is arranged below the lower surface 67 of the upper edge area 27b and above the lower surface 66 of the lower edge area 27a. The displaceable tongue groove 68 is shaped and configured to receive the displaceable locking tongue 72, explained in more detail below. The displaceable tongue groove 68 extends along the longitudinal extension of the third edge portion 27 of the building panel.

[0305] The displaceable tongue groove 68 is configured to, together with the displaceable locking tongue 72, lock two adjacent building panels in the direction perpendicular to the longitudinal extension of the first and second edge portion 25, 26.

[0306] Above the displaceable tongue groove 68 there is provided the lower surface 67 of the upper edge area 27b of the third edge portion 27. The lower surface 67 extends in a direction parallel to the longitudinal extension of the first and second edge portion 25, 26. The lower surface 67 faces down towards the bottom surface 29 of the building panel. The lower surface 67 is configured to, in the direction perpendicular to the longitudinal extension of the first and second edge portion 25, 26, lock the upper surface 60a of the front side tongue 60 in the assembled position. The lower surface 67 is configured to cooperate and preferably be in contact with the upper surface 60a of the front side tongue 60 in the assembled position.

[0307] At the upper edge area 27b of the third edge portion 27, above the lower surface 67 there is provided a locking surface 70 extending perpendicular to the lower surface 67, i.e. extending in the direction perpendicular to the longitudinal extension of the first and second edge portion 25, 26. At the upper edge area 28b of the opposite fourth edge portion 28 there is provided the opposite locking surface 62, extending parallel to the locking surface 70 of the third edge portion 27, i.e. extending in the direction perpendicular to the longitudinal extension of the first and second edge portion 25, 26. The locking surface 70 of the third edge portion 27 is configured to cooperate, and preferably be in contact with the locking surface 62 of the fourth edge portion 28, in the assembled position, as illustrated in FIG. 13C. Together, the locking surface 70 of the third edge portion 27 and the locking surface 62 of the fourth edge portion 28 form the joint seal JS2. The seal between the two locking surfaces 62, 70 may preferably have a pretension, such that there is a force between the two locking surfaces 62, 70 working towards each other. This pretension may decrease the risk of fluids entering into the mechanical locking device 30b ever further. Such a pretension between the two locking surfaces 62, 70 may, in an environment with normal humidity of two building panels each being 100 mm long, be between 2-100N, or between 5-80N.

[0308] In the embodiment illustrated in FIG. 13C, the thickness of the front side layer 19 may substantially correspond to the thickness of the back side layer 15. The thickness of the intermediate layer 17 may substantially correspond to the thickness of the front side layer 19 and/or the thickness of the back side layer 15.

[0309] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 4:5 to 5:4, such as about 1:1.

[0310] The ratio between the amount of the applied second mixture 13b and the amount of the applied first mixture 13a may be between 4:5 and 5:4, such as about 1:1. In the embodiment illustrated in FIG. 13C, the ratio between the amount of the applied third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be about 30-35-35 wt. %, or about 33-33-33 wt. %.

[0311] Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17 and the back side layer 15 may be about 30-35-35%, or about 33-33-33%.

[0312] FIG. 13D illustrates an embodiment of the second mechanical locking device 30b essentially corresponding to the second mechanical locking device 30b described above with reference to FIG. 13C. However, the embodiment of the second mechanical locking device 30b illustrated in FIG. 13D does not include the front side tongue 60 and the front side tongue groove 48. In the embodiment illustrated in FIG. 13D, the locking surface 62 of the fourth edge portion 28 extends from the top surface 24 to the displaceable tongue groove 58 in the fourth edge portion 28. The opposite locking surface 70 of the opposite third edge portion 27 extends from the top surface 24 to the displaceable tongue groove 68. Together, the locking surface 62 of the fourth edge portion 28 and the locking surface 70 of the third edge portion 27 form the joint seal JS2. The locking surface 62 and the locking surface 70 may at least partly extend in the front side layer 19, or may completely extend in the front side layer 19. In one embodiment, the locking surface 62 and the locking surface 70 may extend both in the front side layer 9 and in the intermediate layer 17.

[0313] In the embodiment illustrated in FIG. 13D, the thickness of the front side layer 19 may substantially correspond to the thickness of the back side layer 15. The thickness of the intermediate layer 17 may substantially correspond to the thickness of the front side layer 19 and/or the thickness of the back side layer 15.

[0314] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 4:5 to 5:4, such as about 1:1.

[0315] The ratio between the amount of the applied second mixture 13b and the amount of the applied first mixture 13a may be between 4:5 and 5:4, such as about 1:1. In the embodiment illustrated in FIG. 13D, the ratio between the amount of the applied third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be about 30-35-35 wt. %, or about 33-33-33 wt. %.

[0316] Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17 and the back side layer 15 may be about 30-35-35%, or about 33-33-33%.

[0317] In all other aspects, the description of the embodiment in FIG. 13C is applicable for the embodiment in FIG. 13D as well.

[0318] FIG. 13E illustration an embodiment wherein the second mechanical locking device 30b is configured to be assembled by means of the vertical assembly but without having any displaceable locking tongue. Alternatively, the embodiment may illustrate the second mechanical locking device 30a configured to be assembled by means of the vertical assembly but without having any displaceable locking tongue.

[0319] Instead of an arrangement with a displaceable locking tongue, as illustrated in FIGS. 13c-13D and explained above, the second mechanical locking device 10 is provided with cooperating locking chamfers 58b, 70b for locking the two adjacent building panels 10, 10 in at least the vertical direction. The locking chamfers 58b, 70b each is provided with a tilted surface.

[0320] The first chamfer 58b is arranged in an outer surface, preferably an outermost surface, of the upper edge portion 28b of the edge 28. The tilted surface of the first locking chamfer 58b is preferably tilted down and in towards the rest of the building panel 10.

[0321] The second chamfer 70b is arranged in an outer surface, preferably and outermost surface, of the upper edge portion 27b of the edge The tilted surface of the second locking chamfer 70b is preferably tilted down and out from the rest of the building panel 10.

[0322] The two locking chamfers 58b, 70b are configured to cooperate in the assembled position between the two adjacent building panels 1, 10, and preferably also be in contact with each other during the assembled position in order to create a tight locking of the two adjacent building panels 10, 10.

[0323] In the embodiment illustrated in FIG. 13E, the upper locking surfaces 62, 70 arranged in the uppermost part of the upper edge portion 28b, 27b of each edge 28, 27 are not completely vertical, as mostly illustrated and described above, but may be arranged at an angle in relation to the horizontal plane. The angle may be between 90 and 110, or between 90 and 100. The two corresponding upper locking surfaces 62, 70 are preferably substantially parallel to each other.

[0324] In the embodiment illustrated in FIG. 13E are portions of the upper locking surfaces 62, 70 arranged at an angle in relation to the horizontal plane arranged in the front side layer 19.

[0325] The two front locking surfaces 54a, 64a are together configured to lock the adjacent building panels 1, 1 in at least the horizontal direction.

[0326] In order to facilitate the assembly of such mechanical locking device 10 it may be preferred that the elongated part 53 of the locking strip 52 is able to flex in a direction perpendicular to the extension of the elongated part 53, or in the vertical direction. A flexible locking strip 52 facilitates the assembly as the building panel 10 is pushed down in the vertical direction once the building panel 10 being assembled reaches the position illustrated in FIG. 13E. The flexible locking strip 52 may further be configured to create a pretension in the front locking surfaces 54a, 64a of the second mechanical locking device 30b such that the edges 28b, 27b of two adjacent building panels 10, 10 are in contact with each other, in the assembled position. The pretension may be created by the two locking surfaces 54a, 64a of respective locking element 54 and locking groove 64, which are in the assembled position in contact with each other.

[0327] In the embodiment illustrated in FIG. 13E, the front locking surface 54a of the locking element 54 is at least partially arranged in the back side element 15. The front locking surface 54a of the locking element 54 may be arranged in the back side element 15 entirely or partially. This may provide a stronger mechanical locking device, for example at least in a horizontal and/or vertical direction.

[0328] At least a portion of the front locking surface 54a is configured, in the assembled position and when a force is applied in a horizontal direction away from the joint seal JS2, form a contact surface with the locking surface 64a of the locking groove 64. The contact surface of the locking element 54 is arranged in the back side layer 15, as illustrated in FIG. 13E.

[0329] Correspondingly, at least the contact surface of the locking surface 64a of the locking groove 64 is arranged in the back side layer 15.

[0330] In the embodiment illustrated in FIG. 13E, the thickness of the front side layer 19 may be about of the thickness of the back side layer 15. The thickness of the back side layer 15 may exceed the thickness of the front side layer 19 and/or the thickness of the intermediate layer 17.

[0331] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 1:5 to 1:2, such as 1:4 to 1:3, for example about 1:3.

[0332] The ratio between the amount of the applied second mixture 13b and the total amount of the applied first mixture 13a may be between 1:1 and :12. In the embodiment illustrated in FIG. 153E, the ratio between the amount of the applied third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be about 10-40-50 wt. %.

[0333] Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17 and the back side layer 15 may be about 10-40-50%.

[0334] Illustrated in FIG. 14 the displaceable locking tongue 72 has a longitudinal base portion 74 which continuously extends along the length of the displaceable locking tongue 72. Along the base portion 74 several elongated flexible or bendable parts 76 are provided. The elongated bendable parts 76 are integrally formed with the base portion 74 at a first end 77a. The opposite second end 77b of the bendable part 76 is configured to move freely between a resting position and an assembled position.

[0335] In the resting position, as illustrated in FIG. 14, the elongated bendable parts 76 extend away from the base portion 74, with the second end 77b farthest away from the base portion 74. Between the elongated bendable part 76 and the base portion 74 there is provided a slot, or a gap 78, in the resting position. The bendable part 76 may bend downwards in the slot 78 towards the base portion 74. In an assembled position the bendable parts 76 are bent into the slot 78.

[0336] The displaceable locking tongue 72 is configured to be received in the displaceable tongue groove 58 in the fourth edge portion 28 and in the displaceable tongue groove 68 in the third edge portion 27, as illustrated in FIGS. 13C-D and 15B.

[0337] Before assembling the adjacent building panels 10, 10 the displaceable locking tongue 72 is arranged in the displaceable tongue groove 58 in the fourth edge portion 28, with the bendable parts 76 facing into the displaceable tongue groove 58 and the longitudinal base portion 74 arranged just outside the displaceable tongue groove 58, facing the building panel to be assembled.

[0338] During installation, the building panel 10 is vertically pushed down into the adjacent building panel 10, where the building panel 10 pushes on the base portion 74, forcing the bendable parts 76 to be displaced into the slot 78 towards the base portion 74, allowing the building panel 10 to continue down. When the building panel 10 is in the assembled position the longitudinal base portion 74 of the displaceable locking tongue 72 snaps into the displaceable tongue groove 68 of the third edge portion 27, locking the two building panels 10, 10 in the horizontal and vertical direction.

[0339] FIGS. 16A-16D illustrates embodiments essentially corresponding to embodiments of FIGS. 13A-13D. The first mechanical locking device 30a illustrated in FIG. 13A essentially corresponds to the first mechanical locking device 30a illustrated in FIG. 16A. The first mechanical locking device 30a illustrated in FIG. 13B essentially corresponds to the first mechanical locking device 30a illustrated in FIG. 16B. The second mechanical locking device 30b illustrated in FIG. 13C essentially corresponds to the second mechanical locking device 30b illustrated in FIG. 16C. The second mechanical locking device 30b illustrated in FIG. 13D essentially corresponds to the second mechanical locking device 30b illustrated in FIG. 16D. The embodiments illustrated in FIGS. 16A-16D differ from the embodiments described above with reference to FIGS. 13A-13D in the arrangement of the back side layer 15, which will be described below.

[0340] In the embodiments illustrated in FIGS. 16A and 16B, the entire locking element 34 may be arranged in the back side layer 15. The locking element 34 may be defined as any portion extending above the lower surface 33b of the elongated body 33 of the locking strip 32 in a direction towards the top surface 24 of the building panel.

[0341] The locking element 34 has an upper surface 34b, having at least a portion extending in a direction substantially parallel to the bottom surface 29. In the example illustrated in 16A and 16B, the upper surface 34b extends a direction substantially parallel to the bottom surface 29. The upper surface 34b of the locking element 34 may be arranged in the back side element 15. The upper surface 34b of the locking element 34 may be arranged in the back side element 15, completely as illustrated in FIGS. 16A and 16B, or at least partially.

[0342] The locking groove 44 has an upper surface 44b, having at least a portion extending in a direction substantially parallel to the bottom surface 29. In the example illustrated in 16A and 16B, the upper surface 44b extends a direction substantially parallel to the bottom surface 29. The upper surface 44b of the locking groove 44 may be arranged in the back side element 15. The upper surface 44b of the locking groove 44 may be arranged in the back side element 15, completely as illustrated in FIGS. 16A and 16B, or at least partially.

[0343] In the embodiments illustrated in FIGS. 16C and 16D, the entire locking element 54 may be arranged in the back side layer 15. The locking element 54 may be defined as any portion extending above the lower surface 53b of the elongated body 53 of the locking strip 52 in a direction towards the top surface 24 of the building panel.

[0344] The locking element 54 has an upper surface 54b, having at least a portion extending in a direction substantially parallel to the bottom surface 29. In the example illustrated in 16C and 16D, the upper surface 54b extends a direction substantially parallel to the bottom surface 29. The upper surface 54b of the locking element 54 may be arranged in the back side element 15. The upper surface 54b of the locking element 54 may be arranged in the back side element 15, completely as illustrated in FIGS. 16C and 16D, or at least partially.

[0345] The locking groove 64 has an upper surface 64b, having at least a portion extending in a direction substantially parallel to the bottom surface 29. In the example illustrated in 16C and 16D, the upper surface 64b extends a direction substantially parallel to the bottom surface 29. The upper surface 64b of the locking groove 64 may be arranged in the back side element 15. The upper surface 64b of the locking tongue 64 may be arranged in the back side element 15, completely as illustrated in FIGS. 16C and 16D, or at least partially.

[0346] In the embodiment illustrated in FIG. 16A, the thickness of the front side layer 19 substantially corresponds to the thickness of the back side layer 15. The thickness of the intermediate layer 17 may exceed the thickness of the front side layer 19 and/or the thickness of the back side layer 15. Alternatively, the thickness of the back side layer 15 may exceed the thickness of the intermediate layer 17 and/or the thickness of the front side layer 19.

[0347] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 40:60 and 60:40, or between 45:55 and 55:45, such as 50:50.

[0348] The ratio between the amount of the applied second mixture 13b and the amount of the applied first mixture 13a may be between 60:40 and 40:60, or between 45:55 and 55:45, such as 50:50. In the embodiment illustrated in FIG. 16A, the ratio between the amount of the applied third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be about 30-40-30 wt. % or 30-30-40 wt. %.

[0349] Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17 and the back side layer 15 may be about 30-40-30%, or about 30-30-40%.

[0350] In the embodiment illustrated in FIG. 16B, the thickness of the front side layer 19 may be about of the thickness of the back side layer 15. The thickness of the intermediate layer 17 may exceed the thickness of the front side layer 19 and/or the thickness of the back side layer 15.

[0351] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 1:5 to 1:2, such as 1:4 to 1:3, for example about 1:3.

[0352] The ratio between the amount of the applied second mixture 13b and the amount of the applied first mixture 13a may be between 4:5 and 5:4. In the embodiment illustrated in FIG. 16B, the ratio between the amount of the applied third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be about 15-40-45 wt. %. Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17 and the back side layer 15 may be about 15-40-45%.

[0353] In the embodiment illustrated in FIG. 16C, the thickness of the front side layer 19 substantially corresponds to the thickness of the back side layer 15. The thickness of the intermediate layer 17 may exceed the thickness of the front side layer 19 and/or the thickness of the back side layer 15. Alternatively, the thickness of the back side layer 15 may exceed the thickness of the intermediate layer 17 and/or the thickness of the front side layer 19.

[0354] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 40:60 and 60:40, or between 45:55 and 55:45, such as 50:50.

[0355] The ratio between the amount of the applied second mixture 13b and the amount of the applied first mixture 13a may be between 60:40 and 40:60, or between 45:55 and 55:45, such as 50:50. In the embodiment illustrated in FIG. 16C, the ratio between the amount of the applied third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be about 30-40-30 wt. % or 30-30-40 wt. %.

[0356] Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17 and the back side layer 15 may be about 30-40-30%, or about 30-30-40%.

[0357] In the embodiment illustrated in FIG. 16D, the thickness of the front side layer 19 may be about of the thickness of the back side layer 15. The thickness of the intermediate layer 17 may exceed the thickness of the front side layer 19 and/or the thickness of the back side layer 15.

[0358] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 1:5 to 1:2, such as 1:4 to 1:3, for example about 1:3.

[0359] The ratio between the amount of the applied second mixture 13b and the amount of the applied first mixture 13a may be between 4:5 and 5:4. In the embodiment illustrated in FIG. 16D the ratio between the amount of the applied third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be about 15-40-45 wt. %.

[0360] Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17 and the back side layer 15 may be about 15-40-45%.

[0361] FIG. 17 illustrates an embodiment of the first mechanical locking device 30a and/or the second mechanical locking device 30b in the assembled state of two adjacent building panels 10, 10. Preferably, all features of the first mechanical locking device 30a are integrally formed in the first and second edge portion 25, 26, respectively.

[0362] The mechanical locking device 30a, 30b of FIG. 17 is configured being assembling by vertical displacement.

[0363] The mechanical locking device 30a, 30b comprises along at least one edge portion 26 a locking strip 92. The locking strip 92 is arranged at a lower edge area 26a of the edge portion 26, projecting outwards from the lower edge are 26a.

[0364] The locking strip 92 includes, at the outermost end of the locking strip 92, a locking element 94. The outermost end of the locking strip may be the most distal end of the locking strip 92 in view of the joint seal JS1, JS2. The locking element 94 is configured to be received in a locking groove 44 arranged in a lower edge area 25a of the first edge portion 25 of an adjacent building panel, by means of the vertical displacement.

[0365] The locking strip 92 has an elongated shape with the locking element 94 arranged at the outermost end. Between the innermost end of the locking strip 92 and the locking element 92 the locking strip 92 has an elongated body 73. The elongated body 73 has a lower surface 73a facing the bottom surface 29 of the building panel and an upper surface 73b facing in the opposite direction, i.e. towards the top surface 24 of the building panel. The upper surface 73b may be plane. The lower surface 33a may be flush with the bottom surface 29 of the building panel.

[0366] The upper surface 73b, in the assembled position, extends preferably in the same direction as a lower surface 86a of a locking tongue 86 in the first edge portion 25 of an adjacent building panel, pushing on the upper surface 73b. The upper surface 73b and the lower surface 86a are preferably planar. The upper surface 73b of the elongated body 3 of the locking strip 92 is configured to, in the assembled state, cooperate and preferably at least partly be in contact with the lower surface 86a of the locking tongue 86.

[0367] The locking element 94 is provided with a locking protrusion 94a. The locking protrusion 94a extends from a distal end of the locking element 94, as seen from the joint seal JS1, JS2. The locking protrusion 94a may extend from the locking element 94 in a direction substantially parallel to the top surface 24 of the building panel 10, 10, 10. The locking protrusion 94a is configured to cooperate with a locking recess 84a of the locking groove 84 for locking the building panels 10, 10, 10 in a vertical direction. The locking recess 84a may have a shape corresponding to the shape of the locking protrusion 94a. The locking protrusion 94a may be divided into an upper locking surface and a lower locking surface. Similarly, the locking recess 84a may be divided into an upper locking surface and a lower locking surface.

[0368] As illustrated in FIG. 13B, the locking protrusion 94a may be arranged in the back side layer 15. The locking protrusion 94a may be arranged in the back side layer 15, partially or completely.

[0369] Similarly, the locking recess 84a may be arranged in the back side layer 15. The locking recess 84a may be arranged in the back side layer 15, partially or completely.

[0370] Thereby, the strength of the vertical locking may be improved.

[0371] The locking element 94 of the locking strip 92 includes a front locking surface. The front locking surface is arranged at the innermost end of the locking element 94. The upper surface 73b of the elongated body 73 merges into the front locking surface of the locking element 94. The front locking surface of the locking element 34 is configured to, in the assembled state, cooperate and preferably at least partly be in contact with a front wall of a locking groove 44 in the edge portion 27. The front locking surface of the locking element 94 and the front wall of the locking groove 94 are configured to lock two adjacent building panels in at least a direction parallel to the longitudinal extension of the third and fourth edge portion 27, 28.

[0372] At an upper edge area 28b of the edge portion 28 there is provided a locking surface 62 extending perpendicular to the planar extension of the top surface 24. Similarly, at an upper edge area 27b of the edge portion 27 there is provided a locking surface 70 extending perpendicular to the planar extension of the top surface 24. The locking surfaces 62, 70 are preferably in contact in the assembled position.

[0373] The embodiment differs from the embodiment illustrated among other in FIG. 13B in that the embodiment in FIG. 17 comprises no front side tongue and no front side tongue groove.

[0374] In the embodiment illustrated in FIG. 17, the thickness of the front side layer 19 may be about of the thickness of the back side layer 15. The thickness of the intermediate layer 17 may exceed the thickness of the front side layer 19 and/or the thickness of the back side layer 15.

[0375] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 1:5 to 1:2, such as 1:4 to 1:3, for example about 1:3.

[0376] The ratio between the amount of the applied second mixture 13b and the amount of the applied first mixture 13a may be between 4:5 and 5:4. In the embodiment illustrated in FIG. 17 the ratio between the amount of the applied third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be about 15-45-40 wt. %.

[0377] Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17 and the back side layer 15 may be about 15-45-40%.

[0378] FIGS. 18-20 illustrate various embodiments of the second mechanical locking device 30b. The embodiments in FIGS. 18-20 corresponds to the second mechanical locking device 30b described above with reference to FIGS. 13D and 16D. The design and shape of the displaceable locking tongue differ from the embodiments of FIGS. 13D, 14 and 16D.

[0379] In the embodiments of FIGS. 18-20 the displaceable locking tongue 172, 272, 372 is of a different material than the building panel 10, 10, 10. At least a portion of the displaceable locking tongue 172, 272, 372 may be flexible and/or resilient. An inner portion 172a, 272a, 272a of the displaceable locking tongue 172, 272, 372 is inserted in an inner portion 158a, 258a, 358a of the displaceable tongue groove 158, 258, 358. An outer portion 172b, 272b, 372b of the displaceable locking tongue 172, 272, 372 is configured to pivot in an unlocking direction to an unlocking position in response to a vertical displacement of a lower edge portion 27 of an adjacent panel 10. The outer portion 172b, 272b, 272b of the displaceable locking tongue 172, 272, 372 is further configured to pivot in an opposite locking direction to cooperate with a wedge groove 168, 268, 368 of the adjacent panel 10 to obtain a vertically locking position, for example, by resilient flexing of the outer portion 172b, 272b, 372b of the displaceable locking tongue 172, 272, 372.

[0380] The wedge groove 168, 268, 368 may also be referred to as the displaceable tongue groove in the third edge portion 27.

[0381] In other embodiments (not shown), the inner portion 172a, 272a, 272a of the displaceable locking tongue 172, 272, 372 may be arranged in the third edge portion 27, and the outer portion 172b, 272b, 372b of the displaceable locking tongue 172, 272, 372 may be configured to be displaced into lockingly engagement with the wedge groove 158, 258, 358 of the fourth edge portion 28.

[0382] As previously described with reference to FIGS. 13C-13D, a portion of the front wall 64a may be referred to a locking surface 64a of the locking groove 64. The locking surface 64a of the locking groove 64 is configured to, in the assembled position and when a force is applied in a horizontal direction and away from the joint seal JS2, cooperate with the front locking surface 54a of the locking element 54 of the adjacent building panel.

[0383] At least a portion of the locking surface 64a of the locking groove 64 may be positioned in the back side layer 15.

[0384] At least a portion of the locking surface 64a of the locking groove 64 is configured to, in the assembled position and when a force is applied in a horizontal direction and away from the joint seal JS2, form a contact surface with the front locking surface 54a of the locking element 54. The contact surface of the locking groove 64 is arranged in the back side layer 15, as illustrated in FIGS. 18-20.

[0385] In an alternative embodiment (not shown) of the second mechanical locking device illustrated in FIGS. 18-20, the entire locking element 54 may be arranged in the back side layer 15. The locking element 54 may be defined as any portion extending above the lower surface 53b of the elongated body 53 of the locking strip 52 in a direction towards the top surface 24 of the building panel.

[0386] The locking element 54 has an upper surface 54b, having at least a portion extending in a direction substantially parallel to the bottom surface 29, The upper surface 54b may extends a direction substantially parallel to the bottom surface 29. The upper surface 54b of the locking element 54 may be arranged in the back side element 15. The upper surface 54b of the locking element 54 may be arranged in the back side element 15, completely, or at least partially.

[0387] The locking groove 64 has an upper surface 64b, having at least a portion extending in a direction substantially parallel to the bottom surface 29. The upper surface 64b may extends a direction substantially parallel to the bottom surface 29. The upper surface 64b of the locking groove 64 may be arranged in the back side element 15. The upper surface 64b of the locking tongue 64 may be arranged in the back side element 15, completely, or at least partially.

[0388] In the embodiment illustrated in FIG. 18 is a space provided between the upper surface 54b of the locking element 54 and the upper surface 64b of the looking groove 64. The upper surface 54b of the locking element 54 may be spaced apart from the upper surface 64b of the looking groove 64.

[0389] In the embodiments illustrated in FIGS. 18-20, the thickness of the front side layer 19 may be about of the thickness of the back side layer 15. The thickness of the intermediate layer 17 may exceed the thickness of the front side layer 19 and/or the thickness of the back side layer 15.

[0390] The ratio between the amount of the applied third mixture 13c and the amount of the applied first mixture 13a may be between 1:5 to 1:2, such as 1:4 to 1:3, for example about 1:3.

[0391] The ratio between the amount of the applied second mixture 13b and the amount of the applied first mixture 13a may be between 4:5 and 5:4. In the embodiments illustrated in FIGS. 18-20 the ratio between the amount of the applied third mixture 13c, the applied second mixture 13b and the applied first mixture 13a may be about 15-45-40 wt. %, or 15-40-45 wt. %.

[0392] Correspondingly, a ratio between the thickness of the front side layer 19, the intermediate layer 17 and the back side layer 15 may be about 15-45-40%, or 15-40-45%.

EXAMPLES

Example 1:10 mm Building Panel

[0393] In Example 1, a 10 mm three-layered building panel was pressed in a single-opening lab press (500500 mm) at 180 C. with a pressing time factor of 12 s/mm The building panel was manufactured by applying 20 wt. % of the first mixture, or about 1.9 kg/m.sup.2, forming the back side layer, 60 wt. % of the second mixture, or about 5.6 kg/m.sup.2, forming the intermediate layer, and 20 wt. % of the third mixture, forming the front side layer, or about 1.9 kg/m.sup.2. The second mixture comprised wood particles (mixture of 70 wt. % oak and 30 wt. % spruce in the size of 0.6-1.25 mm) which were mixed with 10 wt. % MUF-resin and 1.5 wt. % hydrophobing agent (paraffin emulsion). The first mixture and the third mixture both comprised wood particles (mixture of 70 wt. % oak and 30 wt. % spruce in the size of 0.315-0.6 mm) which were mixed with 20 wt. % MUF-resin and 1.5 wt. % hydrophobing agent (paraffin emulsion). Note: as common in wood industry, the amounts are calculated on dry weight, with the amount of bone-dry wood=100 wt. % as base.

[0394] The resulting building panel had a density of 940 kg/m.sup.3 (EN 323), compared with a standard particle board of type P5 (according to EN 312) with a density of 655 kg/m.sup.3 and an HDF-board in flooring quality with a density of 940 kg/m.sup.3. A building panel produced according to Example 1 has a density profile (FIG. 22) closer to a standard HDF-board (FIG. 26) than to a moisture-resistant, load bearing standard particle board of type P5 (FIG. 25).

[0395] The resulting building panel had an internal bond of 2.34 N/mm.sup.2 (EN 319) and showed a thickness swelling of 2.2% (EN 317). Internal bond of the shop-bought type P5 particle board was 0.55 N/mm.sup.2 and its thickness swelling 7.6%. For the HDF-board, internal bond was 1.95 N/mm.sup.2 and thickness swelling 10.2%. After thickness swelling test, all samples were dried until bone dry, and thickness measured on the dry samples. The thickness of the building panel from this sample was thinner than initially (1.88%), whereas the HDF board remained thicker than initially (+0.79%), and the type P5 standard particle board in between (0.62%). This indicates irreversible damage on HDF caused by soaking with water, whereas the building panel and the particle board were not irreversibly damaged. This also can be seen visually with raised edges, whereas no raised edges could be seen on the building panel from this example.

Example 2: Different Particle Sizes

[0396] In Example 2, a 10 mm three-layered building panel were pressed in a single-opening lab press (500500 mm) at 160 C. with a pressing time factor of 12 s/mm. The building panel was manufactured by applying 20 wt. % of the first mixture, or about 1.9 kg/m.sup.2, forming the back side layer, 60 wt. % of the second mixture, or about 5.6 kg/m.sup.2, forming the intermediate layer, and 20 wt. %, or about 1.9 kg/m.sup.2. of the third mixture, forming the front side layer. For the second mixture, wood particles were mixed with 12 wt. % MUF-resin and 2.0 wt. % hydrophobing agent (paraffin emulsion). For both first mixture and the third mixture, wood particles were mixed with 20 wt. % MUF-resin and 1.5 wt. % hydrophobing agent (paraffin emulsion). The wood particles used were a mixture of 70 wt. % oak, 20 wt. % spruce and 10 wt. % of a pulpwood graded mixture of species. In a first series, the particle size in the second mixture was 2.5-4.0 mm and in the first and third mixture 0.3-1.25 mm, resulting in a building panel with a density of 916 kg/m.sup.3. In a second series, the particle size in the second layer was 0.6-1.25 mm and in the first and third mixture 0.3-0.6 mm, resulting in a building panel with a density of 967 kg/m.sup.3.

[0397] This trial showed that fine particles are preferred to reach high technological requirements. The building panel with fine particles, i.e. the second series, performed better than the building panel with relatively coarse particles, i.e. the first series. Internal bond (EN 319) for the building panel with fine particles was 3.60 N/mm.sup.2 and surface soundness (EN 311) 2.80 N/mm.sup.2. For the building panel with coarse particles, internal bond was 2.74 N/mm.sup.2 and surface soundness 2.46 N/mm.sup.2.

Example 3: Effect of Hydrophobing Agent

[0398] In Example 3, a 10 mm three-layered building panel were pressed in a single-opening lab press (300300 mm) at 180 C. with a pressing time factor of 12 s/mm in three different density levels (800 kg/m.sup.3, 900 kg/m.sup.3 and 1000 kg/m.sup.3) and five levels of paraffin emulsion (1.0 wt. %, 1.3 wt. %, 1.5 wt. %, 1.7 wt. % and 2.0 wt. %). The building panel was manufactured by applying 20 wt. % of the first mixture, or about 1.60, 1.80, 2.00 kg/m.sup.2 for each density level, forming the back side layer, 60 wt. % of the second mixture, or about 4.80, 5.40, 6.00 kg/m.sup.2 for each density level, forming the intermediate layer, and 20 wt. % of the third mixture, or about 1.60, 1.80, 2.00 kg/m.sup.2 for each density level, forming the front side layer. For the second mixture, wood particles (mixture of 70 wt. % oak and 30 wt. % spruce in the size of 0.6-1.25 mm) were mixed with 10 wt. % MUF-resin and afore mentioned levels of hydrophobing agent (paraffin emulsion). For both the first and the third mixture, wood particles (mixture of 70 wt. % oak and 30 wt. % spruce in the size of 0.2-0.6 mm) were mixed with 20 wt. % MUF-resin and afore mentioned levels of hydrophobing agent (paraffin emulsion), i.e. 1.0 wt. %, 1.3 wt. %, 1.5 wt. %, 1.7 wt. % and 2.0 wt. %. The resulting building panels clearly showed a reduction in thickness swelling (EN 317) between 1.0 wt. % and 1.3 wt. % hydrophobing agent, see FIG. 21. Increased hydrophobing agent content above 1.3 wt. % showed no or just marginal improvement in thickness swelling.

Example 4: High Performance Building Panel

[0399] In Example 4, a 10 mm three-layered building panel was pressed in a single-opening lab press (500500 mm) at 160 C. with a pressing time factor of 12 s/mm. The building panel was manufactured by applying 20 wt. % of the first mixture, or about 2.0 kg/m.sup.2, forming the back side layer, 60 wt. % of the second mixture, or about 5.5 kg/m.sup.2, forming the intermediate layer, and 20 wt. % of the third mixture, or about 2.0 kg/m.sup.2, forming the front side layer. For the second mixture, wood particles (mixture of 70 wt. % oak and 30 wt. % spruce in the size of 0.6-1.25 mm) were mixed with 12 wt. % MUF-resin and 3.0 wt. % hydrophobing agent (paraffin emulsion). For both first and third mixture, wood particles (mixture of 70 wt. % oak and 30 wt. % spruce in the size of 0.315-0.6 mm) were mixed with 20 wt. % MUF-resin and 2.5 wt. % hydrophobing agent (paraffin emulsion). The resulting building panel had a density of 990 kg/m.sup.3 (EN 323). The resulting building panel had an internal bond of 3.61 N/mm.sup.2 (EN 319) and showed a thickness swelling of 2.1% (EN 317). Modulus of elasticity (EN 310) of this building panel was 5212 MPa and bending strength (EN 310) 34.4 N/mm.sup.2, which is far above what EN 312 requires for heavy-duty load-bearing particle boards of type P7.

Example 5:11 mm Building Panel with a Wood Veneer as Front Side Element, Preferably Used as a Floor Panel

[0400] In Example 5, a 11 mm building panel was pressed in a single-opening lab press (500500 mm) at 170 C. with a pressing time factor of 12 s/mm. The five-layered building panel was manufactured by providing a balancing layer of birch veneer, applying 20 wt. % of the first mixture, or about 1.7 kg/m.sup.2, forming the back side layer, 60 wt. % of the second mixture, or about 4.9 kg/m.sup.2, forming the intermediate layer, 20 wt. % of the third mixture, or about 1.7 kg/m.sup.2, forming the front side layer, and a decorative layer of oak veneer. For the second mixture, wood particles (mixture of 70 wt. % oak, 20 wt. % spruce and 10 wt. % unknown mixture in the size of 0.6-1.25 mm) were mixed with 12 wt. % MUF-resin and 2.0 wt. % hydrophobing agent (paraffin emulsion). For both the first and the third mixture, wood particles (mixture of 70 wt. % oak, 20 wt. % spruce and 10 wt. % unknown mixture in the size of 0.3-0.6 mm) were mixed with 25 wt. % MUF-resin and 1.0 wt. % hydrophobing agent (paraffin emulsion). The resulting building panel had a density of 824 kg/m.sup.3 (EN 323), and a typical density profile is shown in FIG. 24. The resulting building panel had a surface soundness (EN 311) of 2.25 N/mm.sup.2.

Example 6:6 mm Building Panel

[0401] In Example 6, a 6 mm three-layered building panel was pressed in a single-opening lab press (500500 mm) at 130 C. with a pressing time factor of 20 s/mm. The building panel was manufactured by applying about 4 kg/m.sup.2 of the first mixture, forming the back side layer, about 4 kg/m.sup.2 of the second mixture, forming the intermediate layer, and about 4 kg/m.sup.2 of the third mixture, forming the front side layer. The second mixture comprised wood particles (mixture of 70 wt. % oak and 20 wt. % spruce and 10 wt. % unknown mixture in the size of 0.315-0.6 mm) which were mixed with 20 wt. % MUF-resin and 2.0 wt. % hydrophobing agent (paraffin emulsion). The first mixture and the third mixture both comprised wood particles (unknown mixture in the size of 0.05-0.3 mm) which were mixed with 145 wt. % MF-resin, 15 wt. % pigments and 30 wt. % corundum particles. The resulting building panel had a density of 1150 kg/m.sup.3 (EN323). A typical density profile of the 6 mm building panel is shown in FIG. 23. The actual maximum density is higher than depicted, but since the actual density is out of the measuring range of the machine, the tops are cut at about 1350 kg/m.sup.3.

Example 7

[0402] In Example 7, a 10 mm three-layered building panel was pressed in a single-opening lab press (450450 mm) at 180 C. with a pressing time factor of 12 s/mm (total 120 s). The building panel was manufactured by applying 27 wt. % of the first mixture, forming the back side layer, 60 wt. % of the second mixture, forming the intermediate layer, and 13 wt. % of the third mixture, forming the front side layer. The sum of the layers forms 100 wt. %. The second mixture comprised wood particles (mixture of 70 wt. % oak and 30 wt. % spruce in the size of 0.6-1.25 mm) which were mixed with 10% MUF-resin and 1.5% hydrophobing agent. The first mixture and the third mixture both comprised wood particles (mixture of 70 wt. % oak and 30 wt. % spruce in the size of 0.315-0.6 mm) which were mixed with 20 wt. % MUF-resin and 1.5 wt. % hydrophobing agent. Note: as common in wood industry, the amounts are calculated on dry weight, with the amount of bone-dry wood=100 wt. % as base.

[0403] Finally, although the present disclosure has been described above with reference to specific embodiments, it is not intended to be limited to the specific form set forth herein. Other embodiments than the specific above are equally possible, and all embodiments may be used separately or in combinations. Angles, dimensions, rounded parts, spaces between surfaces, etc. are only examples and may be adjusted within the basic principles of the invention.

Items

[0404] 1. A method of producing a building panel (10), such as a floor panel or wall panel, comprising: [0405] providing a back side layer (15) comprising a first mixture of at least lignocellulosic particles and a binder, [0406] applying an intermediate layer (17) comprising a second mixture of at least lignocellulosic particles and a binder, on the back side layer (15), [0407] applying a front side layer (19) comprising a third mixture of at least lignocellulosic particles and a binder, on the intermediate layer (17), [0408] wherein, preferably, an average particle size in the second mixture is greater than an average particle size in the first and/or third mixture, [0409] applying pressure and heat to form said building panel (10), [0410] creating a first mechanical locking device (30a; 30b) along at least one edge (25, 26, 27, 28) of the building panel (10), wherein the mechanical locking device (30a; 30b) is configured for horizontal and/or vertical locking of similar or essentially identical building panels (10, 10, 10) in an assembled position, the first mechanical locking device (30a; 30b) comprising [0411] a locking strip (32; 52) with a locking element (34; 54), which is arranged in a back side area (26a; 28a) of the at least one edge portion (25, 26, 27, 28) and which extends in an essentially parallel direction to a back surface (29), along at least one edge portion (25, 26, 27, 28) of the building panel (10), [0412] the first mechanical locking device (30a; 30b) further comprising at least along a second edge portion (25, 26, 27, 28), opposing the first edge portion, [0413] a locking groove (44; 64) arranged in a lower edge area (25a) of the first edge portion (25) and extending in a direction upwards into and away from the bottom surface (29) of the building panel, [0414] wherein the locking element (34; 54) comprises a front locking surface (34a; 54a) configured to, in the assembled position, cooperate with a locking surface (44a; 64a) of the locking groove (44; 64), [0415] wherein the front locking surface (34a; 54a) of the locking element (34; 54) at least partly is arranged in the back side layer (15). [0416] 2. The method according to item 1, wherein a portion of the front locking surface (34a; 54a) of the locking element (34; 54) is configured to, in the assembled position and when a force is applied on a horizontal direction, form a contact surface with the locking surface (44a; 64a) of the locking groove (44; 64), wherein the contact surface of the locking element (34; 54) is arranged in the back side layer (15). [0417] 3. The method according to item 1 or 2, wherein the front locking surface (34a; 54a) of the locking element (34; 54) is entirely arranged in the back side layer (15). [0418] 4. The method according to any one of the preceding items, wherein the locking surface (44a; 64a) of the locking groove (44; 64) at least partially is arranged in the back side layer (15). [0419] 5. The method according to any one of the preceding items, wherein a portion of the locking surface (44a; 64a) of the locking groove (44; 64) is configured to, in the assembled position and when a force is applied on a horizontal direction, form a contact surface with the front locking surface (34a; 54a) of the locking element (34; 54), wherein the contact surface of the locking groove (44; 64) is arranged in the back side layer (15). [0420] 6. The method according to item 4 or 5, wherein the locking surface (44a; 64a) of the locking groove (44; 64) is entirely arranged in the back side layer (15). [0421] 7. The method according to any one of the preceding items, wherein an upper surface (44b; 64b) of the locking groove (44; 64), having a least a portion extending in a direction substantially parallel to the bottom surface (29), is at least partially arranged in the back side layer (15). [0422] 8. The method according to item 7, wherein the upper surface (44b; 64b) of the locking groove (44; 64) is entirely arranged in the back side layer (15). [0423] 9. The method according to any one of the preceding items, wherein the first mechanical locking system further comprises an upper surface (40a; 60a), which is arranged in a front side area (26b; 28b) of at least the first edge portion (25, 26, 27, 28) and which extends in a direction essentially parallel to a top surface (24), along at least the first edge portion (25, 26, 27, 28), of the building panel (10), displaced from said top surface (24), wherein the upper surface (40a; 60a) is arranged in the intermediate layer (17). [0424] 10. The method according to any one of items 1-8, wherein the first mechanical locking system further comprises an upper surface (40a; 60a), which is arranged in a front side area (26b; 28b) of the at least one edge portion (25, 26, 27, 28) and which extends in an essentially parallel direction to a top surface (24), along at least one edge portion (25, 26, 27, 28), of the building panel, displaced from said top surface (24), wherein the upper surface (40a; 60a) is arranged in the front side layer (19). [0425] 11. The method according to any one of the preceding items, further comprising creating a second mechanical locking device (30b) at least along a third edge portion (25, 26, 27, 28), the second mechanical locking device (30b) comprising: [0426] a locking strip (52) with a locking element (54), which is arranged in a back side area (28a) of the at least one edge portion (25, 26, 27, 28) and which extends in an essentially parallel direction to a back surface (29), along at least one edge portion (25, 26, 27, 28) of the building panel (10), [0427] the second mechanical locking device (30b) further comprising at least along a fourth edge portion (25, 26, 27, 28), opposing the third edge portion, [0428] a locking groove (64) arranged in a lower edge area (25a) of the first edge portion (25) and extending in a direction upwards into and away from the bottom surface (29) of the building panel, [0429] wherein the locking element (54) comprises a front locking surface (54a) configured to, in the assembled position, cooperate the locking surface (64a) of the locking groove (64), [0430] wherein the front locking surface (54a) of the locking element (54) at least partly is arranged in the back side layer (15). [0431] 12. The method according to any one of the preceding items, wherein the front side layer (19) is the top layer comprising said top surface (24) of the building panel (10). [0432] 13. The method according to item 12, wherein the method further comprising: [0433] creating a pattern in the top surface (24) of the front side layer (19) simultaneously with applying pressure and heat to form the building panel (10). [0434] 14. The method according to any one of the items 1-12, wherein a front side element (21) is applied to the front side layer (19) subsequent of applying pressure and heat to form said building panel (10). [0435] 15. The method according to any one of the items 1-12, wherein the method further comprises, prior to applying pressure and heat to form the building panel: [0436] providing a back side element (11) on which the first mixture is applied creating the back side layer (15), and/or [0437] applying a front side element (21) on the front side layer (19), wherein [0438] the front side layer (19) attaches to the front side element (21) and the back side layer (15) attaches to the back side layer (11), when pressure and heat are applied. [0439] 16. The method according to item 15, wherein the back side element (11) and/or the front side element (21) is a wood veneer element. [0440] 17. The method according to item 15, wherein the back side element (11) and/or the front side element (21) is a paper sheet, an unimpregnated paper sheet or an impregnated paper sheet. [0441] 18. The method according to any one of the items 15-17, wherein the method further comprising: [0442] creating a pattern in a top surface (24) of the front side element (21) simultaneously with applying pressure and heat to form the building panel. [0443] 19. The method according to any one of the preceding items, wherein the third mixture further comprises colorant, such as pigment, dye, or chemical staining agent. [0444] 20. The method according to any one of the preceding items, wherein at least 50% of the lignocellulosic particles in the second mixture has an aspect ratio of between 1:1 and 30:1. [0445] 21. The method according to any one of the preceding items, wherein lignocellulosic particles from the second mixture and lignocellulosic particles from the third mixture are mixed, at least in a border area (18b) between the intermediate layer (17) and the front side layer (19). [0446] 22. A set of building panels, such as floor panels or wall panels, each building panel comprising [0447] a multi-layered substrate (14) comprising [0448] a back side layer (15) comprising lignocellulosic particles and a binder, [0449] an intermediate layer (17) comprising lignocellulosic particles and a binder, arranged on the back side layer (15), and [0450] a front side layer (19) comprising lignocellulosic particles and a binder, arranged on the intermediate layer (17), wherein [0451] the back side layer (15) is formed from a first mixture, the intermediate layer (17) is formed from a second mixture and the front side layer (19) is formed from a third mixture, wherein, preferably, an average particle size in the second mixture is greater than an average particle size in the first and/or third mixture, [0452] each building panel further comprising: [0453] a first mechanical locking device (30a; 30b) arranged along at least one edge portion (25, 26, 27, 28) of the building panel, wherein the first mechanical locking device (30a; 30b) is configured for horizontal and/or vertical locking of similar or essentially identical building panels (10, 10, 10) in an assembled position, [0454] the first mechanical locking device (30a; 30b) comprising at least along a first edge portion (25, 26, 27, 28) [0455] a locking strip (32; 52) with a locking element (34; 54), which is arranged in a back side area (26a; 28a) of the at least one edge portion (25, 26, 27, 28) and which extends in an essentially parallel direction to a back surface (29), along at least one edge portion (25, 26, 27, 28) of the building panel (10), [0456] the first mechanical locking device (30a; 30b) further comprising at least along a second edge portion (25, 26, 27, 28), opposing the first edge portion, [0457] a locking groove (44; 64) arranged in a lower edge area (25a) of the first edge portion (25) and extending in a direction upwards into and away from the bottom surface (29) of the building panel, [0458] wherein the locking element (34; 54) comprises a front locking surface (34a; 54a) configured to, in the assembled position, cooperate with a locking surface (44a; 64a) of the locking groove (44; 64), [0459] wherein the front locking surface (34a; 54a) of the locking element (34; 54) at least partly is arranged in the back side layer (15). [0460] 23. The set of building panels according to item 22, wherein a portion of the front locking surface (34a; 54a) of the locking element (34; 54) is configured to, in the assembled position and when a force is applied on a horizontal direction, form a contact surface with the locking surface (44a; 64a) of the locking groove (44; 64), wherein the contact surface of the locking element (34; 54) is arranged in the back side layer (15). [0461] 24. The set of building panels according to item 22 or 23, wherein the front locking surface (34a; 54a) of the locking element (34; 54) is entirely arranged in the back side layer (15). [0462] 25. The set of building panels according to any one of the preceding items 22-24, wherein the locking surface (44a; 64a) of the locking groove (44; 64) at least partially is arranged in the back side layer (15). [0463] 26. The set of building panels according to any one of the preceding items 22-25, wherein a portion of the locking surface (44a; 64a) of the locking groove (44; 64) is configured to, in the assembled position and when a force is applied on a horizontal direction, form a contact surface with the front locking surface (34a; 54a) of the locking element (34; 54), wherein the contact surface of the locking groove (44; 64) is arranged in the back side layer (15). [0464] 27. The set of building panels according to item 25 or 26, wherein the locking surface (44a; 64a) of the locking groove (44; 64) is entirely arranged in the back side layer (15). [0465] 28. The set of building panels according to any one of the preceding items 22-27, wherein an upper surface (44b; 64b) of the locking groove (44; 64), having a least a portion extending in a direction substantially parallel to the bottom surface (29), is at least partially arranged in the back side layer (15). [0466] 29. The set of building panels according to item 28, wherein the upper surface (44b; 64b) of the locking groove (44; 64) is entirely arranged in the back side layer (15). [0467] 30. The set of building panels according to any one of the preceding items 22-29, wherein the first mechanical locking system further comprises an upper surface (40a; 60a), which is arranged in a front side area (26b; 28b) of at least the first edge portion (25, 26, 27, 28) and which extends in a direction essentially parallel to a top surface (24), along at least the first edge portion (25, 26, 27, 28), of the building panel (10), displaced from said top surface (24), wherein the upper surface (40a; 60a) is arranged in the intermediate layer (17). [0468] 31. The set of building panels according to any one of items 22-29, wherein the first mechanical locking system further comprises an upper surface (40a; 60a), which is arranged in a front side area (26b; 28b) of the at least one edge portion (25, 26, 27, 28) and which extends in an essentially parallel direction to a top surface (24), along at least one edge portion (25, 26, 27, 28), of the building panel, displaced from said top surface (24), wherein the upper surface (40a; 60a) is arranged in the front side layer (19). [0469] 32. The set of building panels according to any one of the preceding items 22-31, further comprising a second mechanical locking device (30b) at least along a third edge portion (25, 26, 27, 28), the second mechanical locking device (30b) comprising: [0470] a locking strip (52) with a locking element (54), which is arranged in a back side area (28a) of the at least one edge portion (25, 26, 27, 28) and which extends in an essentially parallel direction to a back surface (29), along at least one edge portion (25, 26, 27, 28) of the building panel (10), [0471] the second mechanical locking device (30b) further comprising at least along a fourth edge portion (25, 26, 27, 28), opposing the third edge portion, [0472] a locking groove (64) arranged in a lower edge area (25a) of the first edge portion (25) and extending in a direction upwards into and away from the bottom surface (29) of the building panel, [0473] wherein the locking element (54) comprises a front locking surface (54a) configured to, in the assembled position, cooperate the locking surface (64a) of the locking groove (64), [0474] wherein the front locking surface (54a) of the locking element (54) at least partly is arranged in the back side layer (15). [0475] 33. The set of building panels according to any one of the items 22-32, wherein the front side layer (19) is the top layer comprising said top surface (24) of the building panel. [0476] 34. The set of building panels according to any one of the items 22-32, wherein the building panel further comprises: [0477] a back side element (11) to which the back side layer (15) is attached to, and/or [0478] a front side element (21) to which the front side layer (19) is attached to. [0479] 19. The set of building panels according to item 18, wherein the back side element (11) and/or the front side element (21) is a wood veneer. [0480] 35. The set of building panels according to item 34, wherein the back side element (11) and/or the front side element (21) is a paper sheet, an unimpregnated paper sheet or an impregnated paper sheet. [0481] 36. The set of building panels according to any one of the preceding items 22-35, where lignocellulosic particles from the second mixture and lignocellulosic particles from the third mixture are mixed, at least in a border area (18b) between the intermediate layer (17) and the front side layer (19). [0482] 37. The method according to any one of the items 1-21, wherein a ratio between an amount of the applied third mixture (13c) and an amount of the applied first mixture (13a) is between 40:60 and 60:40, or between 45:55 and 55:45, or about 50:50. [0483] 38. The method according to any one of the items 1-21 or 37, wherein a ratio between an amount of the applied second mixture (13b) and a total amount of the applied first (13a) and third (13c) mixture is between 70:30 and 30:70, or between 60:40 and 40:60. [0484] 38. The set of building panels according to any one of the items 22-36, wherein a ratio between an amount of the applied third mixture (13c) and an amount of the applied first mixture (13a) is between 40:60 and 60:40, or between 45:55 and 55:45, or about 50:50. [0485] 39. The set of building panels according to any one of the items 22-36 or 38, wherein a ratio between an amount of the applied third mixture (13c) and an amount of the applied first mixture (13a) is between 40:60 and 60:40, or between 45:55 and 55:45, or about 50:50.