METHOD FOR PRODUCING A VENEERED BOARD

Abstract

A method for producing a veneered board having a veneer and a carrier board, to provide a veneered board having improved use properties. The method includes: providing a veneer having an upper face and a lower face, applying an additive onto the lower face of the veneer, applying a binder onto the lower face of the veneer, heating the binder, producing a stack of materials to be pressed, having a carrier board and a veneer provided with an additive and a binder on its lower face, wherein the lower face of the veneer lies on the carrier board, pressing the stack of materials to be pressed in order to form a veneered board.

Claims

1. A method for producing a veneered board, comprising a veneer (4) and a carrier board (1), said method comprising the steps of: providing the veneer (4) having an upper face (6) and a lower face (5), applying an additive (7) onto the lower face (5) of the veneer (4), applying a particulate binder (8) onto the lower face (5) of the veneer (4), heating the particulate binder (8), after application onto the veneer (4) in order to soften the particulate binder (8), at least on the surface, optionally, storing the veneer (4), producing a stack of materials to be pressed, having the carrier board (1) and the veneer (4) provided with an additive (7) and the binder (8) on its lower face, wherein the particles of the binder (8) were heated at least on the surface and adhere to one another, and wherein the lower face (5) of the veneer (4) lies at the carrier board (1), pressing the stack of materials to be pressed in order to form a veneered board by liquefying and chemically curing the binder at an increased temperature and increased pressure, and by solidifying said binder during cooling.

2. The method according to claim 1, wherein one of the following substances or a mixture of two or more of the following substances is used as the additive (7): dye, pigment, effect pigment, flame retardant, ink, UV stabilizer, infrared absorber, agents for increasing the conductivity, antibacterial agents, hydrophobizing agents, bleaching agents, stain.

3. The method according to claim 1, wherein the additive (7) is applied as a particulate solid or in liquid form.

4. The method according to claim 1, wherein the additive (7) is insoluble in the binder (8) or is not homogeneously soluble in the binder (8).

5. The method according to claim 1, wherein the additive (7) after being applied is fixed onto the veneer (4).

6. The method according to claim 1, wherein the binder (8) is applied as a solid.

7. The method according to claim 1, wherein a first partial amount of the binder (8) is applied as a solid, and wherein a second partial amount of the binder is applied in liquid form.

8. The method according to claim 1, wherein the binder (8) is applied in the form of particles.

9. The method according to claim 1, wherein the binder (8) after being applied is fixed onto the veneer (4) or respectively additive (7).

10. The method according to claim 1, wherein the lower face (5) of the veneer (4) faces upward when the additive (7) and/or binder (8) is applied, such that the additive (7) and binder (8) are supported by the lower face (5) of the veneer (4).

11. A veneered board, composed of a carrier board (1) and a veneer (4) arranged above the carrier board (1), and optionally a backing, wherein the veneer (4) is impregnated with a binder (8) and wherein additives (7) are present on the upper face of the binder (8) in the veneer (4), wherein one of the substances or a mixture of two or more of the substances from the following group is used as the additive: UV stabilizer, infrared absorber, antibacterial agents, hydrophobizing agents, stain.

12. (canceled)

13. (canceled)

14. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Details of the invention are explained in greater detail below using exemplary embodiments. In the FIGURE:

[0034] FIG. 1 is a schematic representation of the layers of a carrier board according to the invention.

DETAILED DESCRIPTION

[0035] The components of the veneered board are a carrier board 1 having an upper face 2 and a lower face 3. Furthermore, a veneer 4 with a lower face 5 and an upper face 6 is a component of the veneered board. The veneer is prepared before a stack of materials to be pressed is built up in layers. This is done by arranging the lower face 5 of the veneer pointing up. Firstly, an additive 7 is applied onto the lower face of the veneer 4. Alternatively, a mixture of additives may be applied or multiple additives are applied in succession. Once the additive 7 has been applied, a layer of synthetic resin 8 is applied. In this case, the synthetic resin 8 is used as a solid, specifically a particulate solid. The synthetic resin 8 is sprayed on by means of Tribo pistols.

[0036] Following on the application of the synthetic resin 8, the veneer 4 with the additive 7 applied onto the lower face 5 of the veneer 4 and the synthetic resin 8 applied on the additive 7 is heated. In the process, at least the surface of the synthetic resin 8 softens such that the individual particles adhere to one another. Depending on the extent of the heating, the synthetic resin may also flow so as to form a layer. However, it does not cure due to heating, but rather remains reactive. Since synthetic resin particles 8 are also in contact with the additive 7 and the lower face 5 of the veneer, the additive 7 is also bonded to the lower face 5 of the veneer 4. After the synthetic resin 8 and additive 7 have bonded to the veneer 4 in this manner, the veneer 4 can be stored or immediately processed further.

[0037] The further production of the veneered board takes place in that the lower face 5 of the veneer 4 is laid on the upper face 2 of a carrier board, thus creating a stack of materials to be pressed. The stack of materials to be pressed is pressed into a veneered board. Optionally, the stack of materials to be pressed is supplemented by a backing, which is applied onto the lower face 3 of the carrier board 1 and which then forms the lower face of the veneered board 1. According to an advantageous embodiment, the backing is designed in the same manner as the veneer 4 coated with additive on the upper face of the carrier board. However, in principle, any layer on the lower face of the carrier board that absorbs at least some of the forces that are exerted by the veneer 4 arranged on the upper face 2 of the carrier board 1 is suitable as the backing.

Exemplary Embodiment 1—Applying Ink

[0038] Sheets of veneer made of oak (0.8 mm thickness) are placed on a transport belt with the lower face facing upward. In a first treatment station, liquid black digital printing ink (dilution 1:10) is sprayed on by means of a spraying bar in an amount of 5 g/m.sup.2 and dried with the aid of an IR radiator. Subsequently, in a second treatment station, 120 g/m.sup.2 of synthetic resin, in this case melamine resin, is applied as a solid to the digital printing ink by means of Tribo pistols. The resin is fixed by means of the electrostatic charging. The synthetic resin is surface-fused with the aid of an IR radiator, such that the resin does not come off or respectively trickle down when the sheet of veneer is handled. The sheet of veneer is then turned again such that the additive and synthetic resin on the lower face point downward.

[0039] A second sheet of veneer (birch, thickness 0.8 mm) as the backing is provided with the same amount of melamine resin as described above for the veneer that is applied onto the upper face of the carrier board, and the resin is in turn heated such that it flows and gels.

[0040] A high-density fiberboard (HDF board) with a thickness of 12 mm is used as the carrier board.

[0041] Subsequently, the following stack of materials to be pressed is built up in layers (listed in order from top to bottom): [0042] Oak veneer [0043] HDF 12 mm [0044] Birch veneer

[0045] The two veneers are each arranged such that the layer of synthetic resin faces the carrier board.

[0046] The stack of materials to be pressed is pressed into a veneered board in a short-cycle press (SC press) at a pressing temperature of 200° C. and a pressing pressure of 40 kg/cm.sup.2 with a pressing time of 45 seconds. Alternatively, the stack of materials to be pressed may be pressed in the short-cycle press into a veneered board at a pressing temperature of 180° C., a pressing pressure of 30 N/mm.sup.2 and a pressing duration of 30 seconds.

[0047] After the press is opened, a significant blackening can be seen in the pores of the oak veneer in the veneered board on account of the black ink that was transported through the veneer by the liquefied synthetic resin in spite of drying in the press. However, no melamine resin was visible on the surface of the veneer. The veneered board showed a dyed real wood surface.

[0048] According to an alternative of exemplary embodiment 1, part of the synthetic resin can be used in liquid form. A typical application sequence for the synthetic resin may, for example, provide that the additive is applied onto the veneer first. Subsequently, a first portion of the synthetic resin is applied in powder form onto the additive. A second portion of the synthetic resin is then applied in liquid form. Subsequently, the synthetic resin is dried but not cured. Curing takes place, as described above, in the press.

Exemplary Embodiment 2—Increasing the Conductivity

[0049]

TABLE-US-00001 Starting materials: Veneer for the Thickness: 0.8 mm upper face: Type: Oak Additive: Aquacyl AQ 0302 (3%) 30 g/m.sup.2 Applied by means of spraying (*1) (*2) Synthetic resin: Melamine resin Resin application: 600% or 120 g/m.sup.2 Carrier board: High-density fiberboard: HDF Thickness: 12 mm Backing: Type: Veneer, birch Thickness: 0.8 mm Resin application: 600% Synthetic resin: Melamine resin (*1) The product Aquacyl AQ 0302 is an aqueous dispersion of multi-wall carbon nanotubes. (*2) Figures given in “%” in this text without further explanation are percentages by weight.

[0050] The veneer is produced, with the application of an additive and synthetic resin, as described above for exemplary embodiment 1. However, an aqueous, 3% dispersion of multi-wall carbon nanotubes is sprayed on as the additive, for example by means of a nozzle arrangement that extends across the width of the carrier board. Fixation of the additive is dispensed with here.

[0051] The backing is also produced as described for exemplary embodiment 1. The carrier board and the oak veneer are layered onto the backing in order to form a stack of materials to be pressed. Said stack of materials to be pressed is pressed in an SC press at a temperature of 180° C. and a pressure of p=30 N/mm.sup.2 for a pressing time of 50 seconds. The veneered board produced in this manner shows a real wood surface; the synthetic resin is not visible on the surface.

[0052] For comparison, a board with otherwise the same structure and production was produced without the additive Aquacyl AQ0302 on the veneer impregnated with synthetic resin.

[0053] In this exemplary embodiment, a press plate with an embossed wood texture was also used to provide texture. The wood texture of the press plate was recognizable as a negative in the veneer. After the veneered board had cooled, in both specimens with and without additive, the surface resistance was determined in accordance with DIN EN 1081: 2018 following climatization (48 h, 23° C., 50% relative air humidity). A value of 3×10.sup.11Ω was determined for the sample without Aquacyl AQ 0302. For the sample with the additive, 5×10.sup.8Ω was measured.

[0054] Additionally, for the sample with the additive, approx. 0.2 mm of the veneer surface was additionally sanded off using a belt sander in another sample. A repeat measurement of the surface resistance produced 5.5×10.sup.8Ω. The surface resistance can therefore be reduced by approx. three powers of ten compared with the control sample by using Aquacyl AQ 0302 with carbon nanotubes. The conductivity of the veneered upper face of the veneered board is thus substantially improved, despite making sparing use of the additive. It has proven advantageous that the additive is conveyed in a targeted manner into the veneer and to the surface of the veneer by being applied onto the sticky surface of the synthetic resin and by being conveyed by means of the synthetic resin during the pressing.

Exemplary Embodiment 3—Improving the Light-Fastness

[0055]

TABLE-US-00002 Starting materials: Veneer for the Thickness: 0.8 mm upper face: Type: Oak Resin application: 600% or 120 g/m.sup.2 Synthetic resin: Melamine resin Additives: Lignostab 1198 (10% solution) 2 g/m.sup.2 Tinuvin 292 (10% solution) 2 g/m.sup.2 Applied one after the other by means of spraying Carrier board: High-density fiberboard: HDF Thickness: 12 mm Backing: Type: Veneer, birch Thickness: 0.8 mm Resin application: 600% Synthetic resin: Melamine resin

[0056] The veneer impregnated with synthetic resin and the backing were produced in the same manner as described for exemplary embodiment 1. Two additives were applied onto the veneer one after the other, i.e. a 10% solution of Lignostab and a 10% solution of Tinuvin, each in an amount of 2 g/m.sup.2. The amount applied is so small that fixation is dispensed with.

[0057] The stack of materials to be pressed, which, apart from the additives, has the same structure as in the previous exemplary embodiments, is pressed in an SC press at a temperature of 180° C., a pressure of p=30 N/mm.sup.2 and with a pressing time of 50 seconds. The resulting veneered board shows a real wood surface; the synthetic resin is not visible on the surface.

[0058] For comparison, an otherwise identical, veneered board without additives (Lignostab 1198 and Tinuvin 292) was produced on the overlay.

[0059] A press plate with a wood texture was used to provide texture. The wood texture of the press plate was visible in the veneer of the veneered board.

[0060] Subsequently, a light-fastness test according to DIN EN ISO4892-2, 2013-06 (600 h) was performed. The comparison board (control sample) without the two additives was also tested. In the case of the veneered board according to the invention with the additives resulted in ΔE<1.5, and the sample without agent resulted in an ΔE of 4. The veneered board according to the invention is therefore far more stable than a comparison board without additives. In this case, too, it was found that the additives lie on the surface of the liquefied synthetic resin and are conveyed into or through the veneer during the pressing.

Exemplary Embodiment 4—Veneer on Both Sides of the Carrier Board

[0061]

TABLE-US-00003 Veneer for the lower Thickness: 0.8 mm and upper face: Type: Oak Resin application: 600% or 120 g/m.sup.2 Synthetic resin: Melamine resin Carrier board: High-density fiberboard: HDF Thickness:   6 mm

[0062] In each case, a veneer made of oak for the upper face of the carrier board and a veneer made of oak for the lower face of the carrier board is provided with synthetic resin, as described for exemplary embodiment 1. An additive is placed on the synthetic resin. In this connection, a dye, a pigment, an effect pigment, e.g. metal pigments or reflective pigments, flame retardants such as boron compounds or water glass, ink, a UV stabilizer, an infrared absorber, agents for increasing the conductivity, antibacterial agents, hydrophobizing agents, bleaching agents or stain may be used as the additive.

[0063] The additive may be present as a solid, preferably as a particulate solid, e.g. as dust or powder, but also as granular material. Alternatively, a liquid or paste-like additive may be used. However, the additive may also be soluble in the binder; in this case, the additive may not be completely transported to the surface. It is a question of the dose of the additive. The amount to be used depends on the desired technical or aesthetic effect and can be determined within few experiments.

[0064] In this case, the carrier board is a HDF board that is thin compared with the previous exemplary embodiments, with a thickness of 6 mm. Thin carrier boards are particularly suitable for equipping vehicles, e.g. for the interior finishing of driver's cabs, camper vans, motor homes, airplanes or boats, in particular cruise ships.

[0065] In principle, other thin boards of sufficient strength may be used as an alternative, e.g. water-resistant boards with minimal swelling and shrinkage, which are also suitable for use in humid spaces such as swimming pools or saunas, but also bathrooms and kitchens, in particular water-resistant MDF boards or fiberboards with a high content of binder. The following exemplary embodiments demonstrate this possibility.

Exemplary Embodiment 5—Water-Resistant Board

[0066]

TABLE-US-00004 Starting materials: Veneer for the Thickness: 0.8 mm upper face: Type: Oak Synthetic resin: Synthetic resin application: 120 g/m.sup.2 Synthetic resin: Melamine resin Additive: Digital printing ink, liquid black, 5 g/m.sup.2 aqueous, applied by means of spraying: Carrier board: Board consisting of 55 wt. % melamine resin and 45 wt. % wood fibers Thickness: 5.8 mm Backing: Synthetic resin: 120 g/m.sup.2 Veneer as outer layer: Birch Thickness: 0.8 mm

[0067] Sheets of veneer made of oak with a thickness of 0.8 mm and made of birch with a thickness of 0.8 mm are prepared as described for exemplary embodiment 1, i.e. they are provided with an additive and with synthetic resin in solid, not liquid, form.

[0068] A water-resistant board with a thickness of 5.8 mm, in which the proportion of synthetic resin, in this case melamine resin, outweighs the proportion of wood fibers, is used as the carrier board.

Producing the Veneered Board

[0069] Backing A backing of birch veneer, a carrier board and an oak veneer are layered in order to form a stack of materials to be pressed. In this case, the veneers provided as described above with synthetic resin and, in the case of the oak veneer, also with the additive are used. The side of the veneer that is coated with synthetic resin faces the carrier board in each case.

[0070] The stack of materials to be pressed is introduced into an SC press (short-cycle press), where it is pressed at a temperature of 180° C. and a pressure of p=30 N/mm.sup.2 for a pressing time of 30 seconds. It can be pressed with a simple, smooth press plate. However, in this embodiment, textured press plates may also be used to provide texture. For example, a press plate with a wood texture may be used.

[0071] After the pressing, black color seepage could be observed in the pores of the veneer and in the veneer flaws (knotholes, etc.). The wood texture of the press plate was visible in the veneer. No visible layer of melamine resin had formed on the upper face of the veneer. Visible discoloration was solely produced by the additive, in this case the black ink. The black ink was therefore conveyed through larger openings in the veneer or between the fibers of the veneer to the surface of the veneer by means of the liquefying synthetic resin during the pressing process. Thereafter, the boards were finished with a UV varnish or UV oil in the surface. The amounts applied were based on the desired use class. The veneer surface has therefore been accentuated or respectively designed in a manner that was not possible previously. The method according to the invention offers better design properties and thus use properties for a veneered board.

Exemplary Embodiment 6

[0072] Water-Resistant Board with Digitally Printed Veneer

TABLE-US-00005 Starting materials: Veneer for the Thickness: 0.8 mm upper face: Type: Oak, natural, witout knotholes Synthetic resin: Synthetic resin: Melamine resin Resin application: 120 g/m.sup.2 Additive: Digital printing ink, liquid 5 g/m.sup.2 black, aqueous, applied by means of spraying: Carrier board: Board consisting of 55 wt. % melamine resin and 45 wt. % wood fibers Thickness: 5.8 mm Format: 2800 × 2060 mm Backing: Synthetic resin application: 120 g/m.sup.2 Veneer: Birch Thickness: 0.8 mm

[0073] The veneer is prepared as described for exemplary embodiment 1.

Producing the Veneered Board

[0074] A backing of birch veneer, a carrier board, and an oak veneer are layered into a stack of materials to be pressed.

[0075] The stack of materials to be pressed is introduced into an SC press (short-cycle press), where it is pressed at a temperature of 180° C. and a pressure of p=30 N/mm.sup.2 for a pressing time of 30 seconds. It can be pressed with a simple, smooth press plate. However, in this embodiment, textured press plates may also be used to provide texture. For example, a press plate with a wood texture may be used. The wood texture of the press plate was visible in the veneer. No visible layer of melamine resin had formed on the upper face of the veneer.

[0076] Subsequently, knotholes or veneer flaws (cracks, etc.) were printed on the veneer at random using a digital printer, wherein one imprint is present on at least each plank which later is cut from the large format (1400×195 mm). The boards were then finished with a UV varnish or UV oil in the surface. The amounts applied were based on the desired use class. The method according to the invention offers better design properties and thus use properties for a veneered board.

[0077] The four exemplary embodiments mentioned exhibit only a small selection of the possibilities offered by this method. To improve the properties of the veneers used, no intensive surface treatment and no “dip impregnation” is required. The melamine resin penetrating into the veneer serves as a substrate or respectively transport medium for the additives or respectively agents. At the same time, a distribution of the agent is achieved in the veneer cross-section.

[0078] Furthermore, the boards with the veneer surfaces may, of course, also be used to produce wall or ceiling paneling. It is also possible to use the boards for the production of furniture, interior elements such as partition walls, changing cubicles, etc., as well for vehicle fittings or outdoor furniture. In addition, this technology can also cover special applications in which product properties that were not achievable before with wood surfaces are required. These may be, for example, resistance to moisture, cleanability/disinfectability, scratch resistance, etc. By virtue of the method, a veneer/wood surface that has the properties of a melamine resin surface is obtained. Said surface is known for its good resistance to mechanical, chemical and thermal stresses. By controlling the flow of melamine resin, it is possible to achieve the properties of a melamine resin surface without it actually being visible. Specifically, when the melamine resin rises to the surface, the appearance of the veneer changes from wood-like, i.e. natural, to plastic-like. This effect is undesirable and is avoided here according to the invention. Some examples of possible applications include partition walls in sanitary/changing areas, the vehicle sector, payment counters, outdoor furniture, etc. Of course, this list is not exhaustive and illustrates only some possible applications.