WOOD PARTICLE BOARD

Abstract

A wood particle board includes: a core layer formed of resin-covered wood particles with large particle size; at least one surface layer formed of resin-covered wood particles, wherein the at least one surface layer comprises wood particles with particle sizes smaller than the particle sizes of the core layer; and at least one interfoil disposed between a surface layer (1, 4) and the core layer, wherein the at least one interfoil has a surface weight in the range of 5 g/m.sup.2 to 600 g/m.sup.2 and a thickness in the range of 0.05 to 3 mm.

Claims

1. Wood particle board comprising: a core layer formed of resin-covered wood particles with large particle size; at least one surface layer formed of resin-covered wood particles, wherein the at least one surface layer comprises wood particles with particle sizes smaller than the particle sizes of the core layer; and at least one interfoil disposed between a surface layer and the core layer, wherein the at least one interfoil has a surface weight in the range of 5 g/m.sup.2 to 600 g/m.sup.2 and a thickness in the range of 0.05 to 3 mm.

2. Wood particle board according to claim 1, wherein the at least one interfoil is permeable to vapour.

3. Wood particle board according to claim 1, wherein the wood particle board comprises two surface layers and two interfoils arranged on opposite surfaces of the core layer.

4. Wood particle board according to claim 1, wherein the at least one interfoil is adhered to the core and surface layers by an adhesive agent provided in the core layer and/or in the surface layer.

5. Wood particle board according to claim 1, wherein the at least one interfoil is formed of paper, perforated plastic sheet material, textile material or a mesh.

6. Wood particle board according to claim 1, wherein the core layer has a density below 500 kg/m.sup.3 and the at least one surface layer has a density above 700 kg/m.sup.3.

7. Method for producing a wood particle board comprising: depositing wood particles with a small particle size and an adhesive agent to form a first surface layer; depositing wood particles with a particle size larger than that of the first surface layer and an adhesive agent to form a core layer; providing an interfoil on top of the core layer wherein the interfoil has a surface weight in the range of 5 g/m.sup.2 to 600 g/m.sup.2 and a thickness in the range of 0.05 to 3 mm; depositing wood particles with particle sizes smaller than the particle sizes of the core layer and an adhesive agent to form at least one second surface layer; and compressing the deposited layers to form a wood particle board.

8. Method for producing a wood particle board according to claim 7, further comprising: coating the wood particles with an adhesive agent before performing the steps of depositing the wood particles.

9. Method for producing a wood particle board according to claim 7, wherein the interfoil is adhered to the core and surface layers by the adhesive agent provided in the core and surface layers.

10. Method for producing a wood particle board according to claim 7, further comprising: before depositing the wood particles and adhesive agent of the core layer, depositing a first interfoil on the first surface layer, wherein the core layer is subsequently deposited on top of the first interfoil; providing a second interfoil on top of the core layer; and depositing a second surface layer on top of the second interfoil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows a schematic representation of a first embodiment of the present invention of a particle board.

[0026] FIG. 2 shows a schematic representation of a second embodiment of the present invention of a particle board.

[0027] FIG. 3 shows an example of a dual density wood particle board wherein an interfoil as shown in FIG. 1 or 2 may be used.

[0028] FIG. 4 is a schematic illustration of the application of adhesive onto interfoil layers during manufacture of a wood particle board according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] For manufacture of a particle board according to one of the embodiments described in detail below, layers of adhesive-coated wood particles are formed. Therein, different layers typically comprise wood particles with different properties, and the layers are deposited on top of each other. In the embodiments as described below, at least one interfoil is placed between two layers of deposited wood particles. Subsequent to the formation of the particle layers and the provision of the interfoil between two particle layers, at least one curing or pressing process takes place, which may include simultaneous heating and pressing. The heating and pressure activates the adhesive agent which seeks out any available moisture. The adhesive agent bonds throughout all layers, then sets to provide a strong bond between wood particles as well as wood particles and the interfoil. Moreover, pressing is applied to consolidate the layers and develop the internal structure of the wood particle board, including the final density profile of the wood particle board. The pressing may either be performed as a continuous process, wherein particle layers are continuously deposited and conveyed through a hot-press apparatus, or pressing may be performed as a batch process, wherein a layered particle structure of a predetermined size is placed in a hot press apparatus where it remains stationary during the pressing.

[0030] After pressing, the wood particle board may be cooled and trimmed to obtain the desired length and width. The wood particle boards can be formed into panels, but can also be formed into molded particleboard products such as furniture parts. Furthermore, the wood particle boards may be sanded or planed before further processing. Further layers, such as e.g. decorative outer layers or further supporting layers, may be applied to the wood particle boards after pressing and cooling.

[0031] FIG. 1 shows a schematic representation of a first embodiment of the present invention. The wood particle board 10 according to the present embodiment comprises multiple layers arranged from bottom to top as follows: a bottom surface layer 1, a core layer 2, an interfoil 3 and a top surface layer 4.

[0032] In the depicted embodiment, the surface layers 1 and 4 are formed of small wood particles in order to provide a smooth, high-quality surface. Therein, both surface layers 1 and 4 may consist of wood particles with substantially the same size and mechanical properties, in order to ensure a balanced structure of the wood particle board and to prevent distortion or mechanical stress within the board. The surface layers 1 and 4 of the finished wood particle board may have a density above 700 kg/m.sup.3 in order to ensure sufficient stability of the overall wood particle board.

[0033] In the depicted embodiment, the interfoil 3 is arranged between the core layer 2 and the top surface layer 4. The interfoil 3 may have a surface weight in the range of 5-600 g/m.sup.2, preferably 5-200 g/m.sup.2, most preferably 5-60 g/m.sup.2. The interfoil 3 may have a thickness in the range of 0.05-3 mm, preferably 0.05-2.0 mm, most preferably 0.05-2.0 mm. A key characteristic of the interfoil material may be that it has a certain vapour penetrability to ensure heat and steam transfer during the hot-pressing process. Gurley resistance may be used for determining the level of air resistance. For example the air resistance for the interfoil may be between 1.1-12 Gurley seconds. Preferably, the material may be mechanically stable up to about 240 C. to withstand the hot-pressing process undamaged. Alternatively, the interfoil may be designed to be destroyed or melted during pressing or curing once the position of the wood particles in the respective layers of the wood particle board is fixed.

[0034] Various materials can compose the interfoil 3, such as paper, in particular paper which has not been resin impregnated, a perforated plastic sheet, textile or mesh. In the first embodiment of FIG. 1, it is not necessary to provide additional adhesive agents on the interfoil 3. However, in another embodiment, the interfoil 3 could be treated with an adhesive agent to improve the bound of the interfoil 3 with the core layer 2 and the surface layer 4, as shown e.g. in FIG. 4 and described in detail below.

[0035] Due to the provision of the interfoil 3, the thickness of the surface layer 4 can be reduced compared to conventional wood particle boards, so that e.g. the thickness of each surface layer amounts to about 8% per side of the total board thickness, e.g. for an 11 mm board, each surface layer may be 0.7 mm thick or for a 40 mm board, the thickness of each surface layer may be 2 mm. Thus, the overall density and weight of the wood particle board can be reduced while ensuring a high surface quality.

[0036] The interfoil 3 is placed between the core layer 2 and the top surface layer 4 and thus prevents wood particles to move from the top surface layer 4 into the core layer 2, thereby providing a smooth and even surface of the surface layer 2. This embodiment can be used for various applications, e.g. providing a flawless exterior of furniture.

[0037] Due to the usage of an interfoil 3, the core layer 2 does not need to serve as a carrier of the fine surface particles. Hence, the core layer 2 can be produced with even lower density than in conventional wood particle boards, comprising even larger air pockets due to the use of larger wood particles in the core layer 2.

[0038] FIG. 2 shows a schematic representation of a second embodiment of the present invention. In comparison to the first preferred embodiment, the wood particle board 11 of the second embodiment comprises an additional interfoil 5 between the bottom surface layer 1 and the core layer 2.

[0039] The interfoils 3 and 5 are preferably provided with the same thickness, density and mechanical properties to ensure a balanced structure of the wood particle board 11 preventing distortion. Due to the symmetrical arrangement of all layers, interfoils 3 and 5 can be chosen which are thicker than the interfoil 3 in the first embodiment. Preferably, the thickness of each one of the interfoils 3 and 5 is in the range of 0.05-3 mm, preferably 0.05-2.5 mm, most preferably 0.05-2.0 mm.

[0040] The arrangement of two interfoils 3 and 5 provides two smooth and even surfaces of surface layers 1 and 4. This is needed only when the top interfoil is too thick, in order to keep the stability of board and in order to prevent the board bending due to the provision of a single, thick interfoil.

[0041] The present invention is not limited to the above described embodiments, but rather various modifications and/or additions may be incorporated in the described embodiments without departing from the scope of the present invention.

[0042] For example, it may also be possible to apply veneers or other materials on top of the surface layer 1 and/or surface layer 4 to provide a decorative surface. The wood particle boards may also be finished with lacquer or paint, or may be treated with fire-resistant chemicals. Moreover, other materials like agricultural residues may be incorporated into the layers of the wood particle board.

[0043] The wood particle boards according to the embodiments described above may be produced in a continuous process or in a batch process. According to an embodiment of a continuous manufacturing method, wood particles may be coated with an adhesive agent. Subsequently, adhesive-coated wood particles may be deposited on a conveyor belt or the like in order to form the first surface layer 1 and the core layer 2. A vapour-permeable interfoil 3 may then be placed in top of the core layer, wherein e.g. the interfoil 3 is continuously supplied from a roll. On top of the interfoil 3, a top surface layer 4 of smaller adhesive-coated wood particles may be deposited. The finished stack of adhesive-coated wood particles, with the interfoil 3 provided therebetween, may then be conveyed into a continuous hot-pressing apparatus for forming the finished wood particle board 10.

[0044] As a modification of the method as described above, additional wood particle layers, such as e.g. an additional surface layer 1, may be deposited before or after deposition of the core layer particles as described above. Therein, a second interfoil 5 may be provided after deposition of an additional bottom surface layer 1, onto which the particles that form the core layer 2 are then deposited.

[0045] In summary, the embodiments as described above provide a wood particle board, wherein a core layer may be formed from large wood particles in order to achieve a low density of the finished board, and wherein at least one surface layer may be formed from smaller wood particles in order to achieve at least one smooth surface. The quality of the surface is ensured by providing an interfoil between the core layer and the at least one surface layer, wherein the interfoil prevents any movement from particles of the surface layer into the core layer and vice versa. Since the interfoil may be vapour-permeable, it may not affect a hot-pressing process during manufacture of the wood particle board. During hot-pressing, the interfoil adheres to the particles of the core and surface layers using the adhesive agent attached to the wood particles, so that it is generally not necessary to provide a further adhesive coating on the interfoil.

[0046] For some applications, it can be advantageous to provide a wood particle board with two high-quality surfaces. In this case, two interfoils on either side of a core layer can be provided. Additionally, interfoils with desired mechanical properties can be used for e.g. reinforcing wood particle boards while keeping the overall density of the board low. In this case, two interfoils may be used in order to achieve a balanced construction of the reinforced wood particle board.

[0047] FIG. 3 shows an illustrative example of another type of wood particle board 12, wherein one or two interfoils as described above may be used. The dual density wood particle board 12 comprises a core layer 2 sandwiched between first and second surface layers 1, 4 as described above. In addition to the features described above for wood particle boards 10, 11, the dual density wood particle board 12 depicted in FIG. 4 has a plurality of different regions 6, 7, wherein high density regions 6 are arranged in an alternating fashion with low density regions 7, e.g. as lengthwise stripes of alternating low and high density. Similar as described above for the wood particle boards 10, 11 of FIGS. 1 and 2, one or two interfoil layers may be placed between the core layer 2 and respective surface layers 1, 4 of the dual density wood particle board 12 prior to hot pressing or curing. Thus, the interfoil as described above can be applied to a variety of different types of wood particles boards while still achieving the technical effects of ensuring a high surface quality and a lightweight construction of the wood particle board.

[0048] FIG. 4 is a schematic drawing for illustrating how additional adhesive can be applied to interfoil layers 3, 5 during deposition of the wood particle layers 1, 2, 4 of a wood particle board 11 as shown in FIG. 2.

[0049] Therein, the interfoil 3, 5 is supplied via respective rolls 21. A first interfoil layer 5 is provided on top of the deposited adhesive-coated wood particles of a first surface layer 1 as it is transported along a conveyor belt 22. An additional adhesive agent can be applied via respective spray nozzles 20 or the like to the top of the first surface layer 1 and to the top of the first interfoil layer 5. Thus, both surfaces of the first interfoil can be coated with a suitable adhesive in order to ensure a secure adhesion of the wood particle layers 1, 2 to the interfoil 5 while the adhesion of the wood particles within each surface or core layer is ensured by the adhesive that has been coated onto the respective wood particle prior to deposition of the layers. Similarly, for the second interfoil layer 3, spray nozzles 20 may be provided for coating the top of the deposited core layer 2 and the second interfoil layer 3 with adhesive before the wood particles of the second surface layer 4 are deposited on top of the second interfoil layer 3.

EXAMPLES

[0050] Example embodiments of wood particle board compositions are with over all board density of 530 kg/m3, having particles of thickness between 0.2 and 0.8 mm with surface dimensions from 2 to 120 mm in the width and having length of above 50 mm the core layer and finer particles passing mesh 1.61.6 mm in the surface layer. As adhesive for the core layer standard polymeric MDI may be used and the adhesive content may be 3.2%. For the surface layer a traditional MUF resin with MR 0.95 and melamine content of 2.5% and adhesive content may be 14%. As interfoil e.g. a 17 g/m2 paper may be used with air resistance of 2 Gurley seconds.