METHOD FOR PRODUCING A VENEERED BOARD

Abstract

To provide a method which is intended for producing a veneered board with a simple structure that also makes it possible to improve the properties of the veneer in a simple manner, a method is proposed for producing a veneered board, wherein the veneered board comprises a veneer (4) having an upper face (6) and a lower face (5) and a carrier board (1) having an upper face (2) and a lower face (3), comprising the steps of providing a veneer (4), applying a binder (8) onto the upper face (2) of the carrier board (1) or the lower face (5) of the veneer (4), wherein a PU prepolymer is used as the binder, producing a stack of materials to be pressed comprising the carrier board (1) and the veneer (4) with the binder (8) arranged between the carrier board (1) and the veneer (4) and with the additive (7) arranged between the binder (8) and the veneer (4), pressing the stack of materials to be pressed in order to form a veneered board. The invention additionally relates to a veneered board.

Claims

1. A method for producing a veneered board, which comprises a veneer (4) having an upper face (6) and a lower face (5) and a carrier board (1) having an upper face (2) and a lower face (3), comprising the steps of: providing a veneer (4), applying an additive (7) between the binder (8) and veneer (4) applying a binder (8) onto the upper face (2) of the carrier board (1) or the lower face (5) of the veneer (4), wherein a PU prepolymer is used as the binder, producing a stack of materials to be pressed comprising the carrier board (1) and the veneer (4) with the binder (8) arranged between the carrier board (1) and the veneer (4) and with an additive (7) arranged between the binder (8) and the veneer (4), pressing the stack of materials to be pressed in order to form a veneered board wherein one of the following substances is used as the additive (7), either individually or in a mixture: dye, pigment, effect pigment, flame retardant, ink, UV stabilizer, infrared absorber, agents for increasing the conductivity, antibacterial agents, antifungal agents, antialgal agents, hydrophobizing agents, bleaching agents, stain.

2. The method according to claim 1, wherein an aliphatic and/or aromatic PU prepolymer is used as the binder (8).

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 binder (8) is applied as a liquid.

6. The method according to claim 1, wherein the pressing temperature is between 100° C. and 240° C.

7. The method according to claim 1, wherein the pressing time is between 20 seconds and 60 seconds.

8. The method according to claim 1, wherein the pressing pressure is between 25 N/mm.sup.2 and 50 N/mm.sup.2.

9. A veneered board consisting of a carrier board (1) and a veneer (4) arranged above the carrier board, wherein the veneer (4) is impregnated at least in sections with a polyurethane and wherein an additive (7) is present on the upper face of the polyurethane in the veneer (4).

10. The veneered board according to claim 9, wherein the carrier board (1) is a wood composite board.

11. (canceled)

12. (canceled)

13. The veneered board according to claim 9, further comprising a backing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In the drawings:

[0027] FIG. 1 is a schematic representation of a stack of materials to be pressed provided with the binder according to the invention.

DETAILED DESCRIPTION

[0028] 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 carrier board 1 or, alternatively, the veneer 4 is prepared before a stack of materials to be pressed is built up in layers. This is done either by arranging the lower face 5 of the veneer facing upside. Optionally, an additive 7 is firstly 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 or, alternatively, additives 7 have been applied, a layer of binder 8 is applied. A PU prepolymer is used here as the binder. The binder 8 is used in liquid form. The binder 8 is applied in liquid form by means of a roller or a pouring machine. Alternatively, the binder according to the invention is applied onto the upper face 2 of the carrier board 1.

[0029] The further production of a 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, preferably without intermediate drying, whereby a stack of materials to be pressed is layered in which the binder 8 according to the invention is arranged between the carrier board 1 and the veneer 4. The stack of materials to be pressed is pressed in a press in order to form 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 on the upper face of the carrier board. However, in principle, any coating on the lower face of the carrier board is suitable as the backing that at least partially absorbs the forces that are exerted by the veneer 4 arranged on the upper face 2 of the carrier board 1.

Exemplary Embodiment 1

Starting Materials:

[0030] Veneer: Thickness: 0.8 mm [0031] Type: Oak [0032] This veneer is used on the upper face 2 of the carrier board 1. [0033] Binder: Aliphatic PU prepolymer in liquid form [0034] This binder is used between the upper face 2 of the carrier board 1 and the oak veneer. The binder is exposed to light after the veneered carrier board has been produced. [0035] Carrier board: Thickness: 10 mm [0036] Type: HDF (high-density fiberboard) [0037] Binder: Aromatic PU prepolymer 678.05 (manufacturer: Jowat) in liquid form [0038] This binder is used between the lower face 3 of the carrier board 1 and the birch veneer used as the backing. [0039] Veneer: Thickness: 1.05 mm [0040] Type: Birch [0041] This veneer is used on the lower face 3 of the carrier board 1.

Production of the Veneered Carrier Board:

[0042] 100 g/m.sup.2 of PU prepolymer with the product name 678.05 from the company Jowat is applied onto the carrier board, in this case a HDF board (high-density fiberboard) with the format 2800×2070×10 mm (length×width×thickness). Said PU prepolymer was produced based on aromatic isocyanates and alcohol, which were reacted to form a prepolymer. The PU prepolymer is liquid. The solids content is approx. 90 wt. % relative to the total weight of the PU prepolymer. The viscosity is approximately 65 mPas (20° C., Brookfield). The PU prepolymer is applied by means of a pouring machine. Then, the PU prepolymer is applied onto the birch veneer. The birch veneer, which is to be fixed to the lower face 3 of the carrier board 1, is laid underneath the lower face 3 of the carrier board provided with binder and thus layered in order to form a stack of materials to be pressed. The stack of materials to be pressed is pressed in a short-cycle press (SC press). The pressing conditions of the SC press are set as follows: pressing temperature 180° C., pressure 40 kg/cm.sup.2 and pressing time 60 seconds. The pressing temperature ensures the curing of the binder during the pressing time and the pressing pressure causes compression of the veneer while the PU prepolymer simultaneously penetrates in.

[0043] Then, the SC press is opened and the HDF board covered on one side cools. The carrier board 1 covered on one side on the lower face 3 is turned and 200 g/m.sup.2 of prepolymer based on aliphatic isocyanates is applied onto the upper face 2 of the carrier board 1. Then, the oak veneer is laid on and this stack of materials to be pressed is in turn pressed with the above-mentioned parameters. In this case, too, curing of the binder under the action of heat, penetration of the binder into the veneer and as well as compression of the veneer under the action of the pressing pressure take place. The board, which is now veneered on both sides, is cooled. Subsequently, floor boards with a glue-free profile are milled from the carrier board 1 veneered on both sides. In this case, the oak veneer side serves as the usable surface. In order to apply the oak veneer on the usable surface, which is exposed to light, an aliphatic PU prepolymer, which does not react or hardly reacts under the influence of light, in particular it does not change color or rather turn yellow, has been applied.

[0044] On account of the pressing of the veneered carrier board under a high pressure, as described above, the veneer is compressed while the binder simultaneously penetrates the veneer. This creates a veneered board that has a veneer surface that is particularly capable of bearing mechanical loads, in particular a veneer surface with increased compressive strength. In addition, the polyurethane, which is formed during pressing, is a water-resistant binder, so that the veneer, which is not water-resistant per se, is also made water-resistant on account of the binder that has penetrated therein at least in sections.

Exemplary Embodiment 2

Starting Materials:

[0045] Veneer: Thickness: 0.8 mm [0046] Type: Oak [0047] This veneer is used on the upper face 2 of the carrier board 1. [0048] Binder: Aliphatic PU prepolymer in liquid form [0049] This binder is used between the upper face 2 of the carrier board 1 and the oak veneer. The binder is exposed to light after the veneered carrier board has been produced. [0050] Carrier board: Thickness: 10 mm [0051] Type: HDF (high-density fiberboard) [0052] Backing: Melamine resin-impregnated sheet of paper

Production of the Veneered Carrier Board:

[0053] 200 g/m.sup.2 of liquid PU prepolymer based on aliphatic isocyanates is applied onto the carrier board 1, in this case a HDF board (format: 2800×2070×10 mm) using a spraying device. Optionally, an additive is applied, e.g. a dye. Then, the oak veneer is laid onto the polymer with the optionally applied additive. A sheet of paper impregnated with melamine resin is positioned on the rear face as the backing. The sheet of paper impregnated with melamine resin has a paper weight of 80 g/m.sup.2 and a resin application of 120 wt. % relative to the paper weight. The stack of materials to be pressed consisting of the backing on the lower face 3 of the carrier board 1, the carrier board 1, and the veneer 4 on the upper face 2 of the carrier board 1 is pressed in an SC press. The pressing temperature is 180° C., the pressing pressure is set to 30 kg/cm.sup.2 and the pressing time is 60 seconds. Then, the veneered carrier board 1 is left to cool. During the pressing time, the prepolymer is pressed into the veneer and often also into the surface of the carrier board on account of the pressing pressure, such that the curing prepolymer is also mechanically anchored there. At the same time, the pressing pressure compresses the veneer and thus densifies it. In addition, restoring forces in the veneer are reduced or eliminated.

[0054] After the prepolymer has cured and cooled, floor boards with a glue-free profile are milled therefrom. In this case, the oak veneer side serves as the usable surface. The increased use of binder here causes that the veneer is penetrated by the binder and is thus completely water-resistant. The backing can advantageously be pressed with the carrier board in one pressing process, because melamine also cures under the conditions selected for the pressing. Therefore, in contrast to exemplary embodiment 1, one pressing process is omitted here.

[0055] Of course, an additive or a mixture of additives, which produce particular properties in the product, can also be added to the prepolymer. This may, for example, be dyes, agents for increasing the conductivity, etc. However, according to the invention, the additive may also be applied between the veneer 4 and the binder 8, such that the additive can act close to the surface, since additives are generally used to create surface effects.

[0056] According to the invention, the veneered carrier board can be used in any application where veneered surfaces were used previously. Furthermore, the boards with the veneer surfaces may, of course, also be used for the production of wall or ceiling panels in addition to the production of floor panels. They can also be used to produce furniture.

Exemplary Embodiment 3

Starting Materials:

[0057] Veneer: Thickness: 0.8 mm [0058] Type: Oak [0059] This veneer is used on the upper face 2 of the carrier board 1. [0060] Binder: Aliphatic PU prepolymer [0061] This binder is used between the upper face 2 of the carrier board 1 and the oak veneer. The binder is exposed to light after the veneered carrier board has been produced. [0062] Carrier board: Thickness: 10 mm [0063] Type: Fiberboard, comprising 48 wt. % wood fibers and 52 wt. % melamine resin, in each case relative to the total weight of the board. [0064] Binder: Aromatic PU prepolymer 678.05 Jowat [0065] The binder is applied between the lower face 3 of the carrier board and the birch veneer used as the backing. [0066] Veneer: Thickness: 1.05 mm [0067] Type: Birch

Production of the Veneered Carrier Board:

[0068] The carrier board (i) according to exemplary embodiment 3 is veneered in the same manner as the veneered carrier board according to exemplary embodiment 1.

[0069] Since the carrier board (i) used in exemplary embodiment 3 and also the binder are water-resistant, a water-resistant, veneered carrier board 1 is provided.