Method for Producing a Laminate Consisting of a Backing Sheet and Decorative Paper

Abstract

The present invention relates to a method for producing a laminate having a backing sheet and a decorative paper arranged on the backing sheet, including the steps of: a) providing the backing sheet, b) scattering at least one layer of at least one powdered resin onto at least one side of the backing sheet, the surface of the side of the backing sheet that is to be scattered with the powdered resin being unsmoothed, c) placing at least one decorative paper onto the side of the backing sheet that is provided with the powdered resin, and d) pressing the layered structure including the backing sheet, the powdered resin and the decorative paper. The present invention likewise relates to a laminate that can be produced by this method.

Claims

1. A method for producing a laminate consisting of a wooden composite board and a decorative paper disposed on the wooden composite board, comprising the steps of: a) providing the wooden composite board, b) scattering at least one layer of at least one pulverulent resin onto at least one side of the wooden composite board, where the surface of that side of the wooden composite board on which the pulverulent resin is to be scattered is unsanded and bears a press skin or rotting layer; c) placing at least one decorative paper onto the side of the wooden composite board that bears the pulverulent resin, and d) compressing the layer system composed of wooden composite board, pulverulent resin and decorative paper.

2. (canceled)

3. The method according to claim 1, wherein the pulverulent resin is applied in an amount of 3 to 20 g/m.sup.2 to the wooden composite board.

4. The method according to claim 1, wherein the side of the wooden composite board on which the pulverulent resin is to be scattered is pretreated, before the scattering of the pulverulent resin, to improve the adhesion of the pulverulent resin.

5. The method according to claim 4, wherein the pretreatment of the side on which scattering is to take place comprises subjecting the wooden composite board to moisture or comprises electrostatically charging the wooden composite board.

6. The method according to claim 4, wherein the pretreatment of the side on which scattering is to take place comprises subjecting the wooden composite board to 0.5-5 g/m.sup.2 of water.

7. The method according to claim 1, wherein the pulverulent resin is a formaldehyde resin, a urea resin, a melamine resin, a phenolic resin, or a melamine-formaldehyde resin.

8. The method according to claim 1, wherein the pulverulent resin has a scatter density of 0.5 to 1.5 kg/l and an average particle size of 10 to 50 m.

9. The method according to claim 1, wherein the pulverulent resin is scattered onto at least one side of at least one backing paper, and the backing paper scattered with the resin powder is disposed with the resin in the direction of the side of the wooden composite board.

10. The method according to claim 9, wherein the side of the wooden composite board that is to be coated with the backing paper, and/or the side of the backing paper that is to be scattered with the pulverulent resin, is pretreated, before scattering of the pulverulent resin, to improve the adhesion of the pulverulent resin.

11. The method according to claim 1, wherein the pulverulent resin is applied using a scattering apparatus.

12. The method according to claim 1, wherein the at least one decorative paper and/or the at least one backing paper is an at least partially impregnated decorative paper and/or backing paper.

13. The method according to claim 1, wherein the wooden composite board consists of a wood-based material or a wood-based material/polymer mixture.

14. (canceled)

15. The method according to claim 6, wherein the pretreatment comprises subjecting the wooden composite board to 1 to 2 g/m.sup.2 of water.

16. The method according to claim 7, wherein the pulverulent resin is a melamine-formaldehyde resin or a urea resin.

17. The method according to claim 8, wherein the pulverulent resin has a scatter density of 0.8 to 1.0 kg/l and an average particle size of 20 to 30 m.

18. The method according to claim 10, wherein the side of the wooden composite board that is to be coated with the backing paper, and/or the side of the backing paper that is to be scattered with the pulverulent resin, is pretreated by being subjected to moisture or being electrostatically charged.

19. The method according to claim 13, wherein the wooden composite board is a particle board, medium density fibre (MDF) board, high-density fibre (HDF) board or oriented strand board (OSB) or plywood board.

20. The method according to claim 3, wherein the pulverulent resin is applied in an amount of 6 to 10 g/m.sup.2 to the wooden composite board.

Description

[0052] The present invention is elucidated below and described using a number of working examples, with reference to the figures, for better understanding. In the figures

[0053] FIG. 1 shows a detail of a densogram of a control sample of a laminate, and

[0054] FIG. 2 shows a detail of a densogram of an embodiment of the laminate of the invention.

WORKING EXAMPLE 1

[0055] A quantity of approximately 1 g water per/m.sup.2 was applied by a Rotorspray unit from Ahlbrandt to the top side of an unsanded HDF (fiber board with increased apparent density) in a thickness of 7 mm in continuous passage ahead of an SC press. Thereafter, likewise in continuous passage, 3 g melamine resin powder/m.sup.2 were applied to the top side, using a scattering apparatus. The HDF was then covered on the top side with a melamine-resin-impregnated decorative paper and with an overlay. On the bottom side, a backing paper was used which was likewise impregnated with melamine resin. The board was pressed in an SC press at 200 C./40 bar. The pressing time was 10 seconds. The board was cooled and provided for testing. In addition, a control sample (without application of resin on the top side) was co-produced.

WORKING EXAMPLE 2

[0056] The top side of an unsanded HDF (fiber board with increased apparent density) in a thickness of 7 mm was charged by means of a device for electrostatic charging (manufacturer: Eltex) in continuous passage ahead of an SC press. Thereafter, likewise in continuous passage, 6 g melamine resin powder/m.sup.2 were likewise applied to the top side, using a scattering apparatus. The HDF was then covered on the top side with a melamine-resin-impregnated decorative paper and with an overlay. On the bottom side, a backing paper was used which was likewise impregnated with melamine resin. The board was pressed in an SC press at 200 C./40 bar. The pressing time was 10 seconds. The board was cooled and provided for testing.

WORKING EXAMPLE 3

[0057] A quantity of approximately 1 g water per/m.sup.2 was applied by a Rotorspray unit from Ahlbrandt to the top side of an impregnated backing (100 g/m.sup.2 paper weight, resin application: 150%) in continuous passage ahead of an SC press. Thereafter, likewise in continuous passage, 6 g melamine resin powder/m.sup.2 were applied to the top side, using a scattering apparatus. An unsanded 7 mm HDF was placed onto this backing.

[0058] The HDF board was wetted on the top side with a quantity of approximately 1 g of water per/m.sup.2 by a second Rotorspray unit from Ahlbrandt. Thereafter, likewise in continuous passage, 6 g melamine resin powder/m.sup.2 were applied to the top side of the HDF board, using a scattering apparatus. Thereafter the board was covered on the top side with a melamine-resin-impregnated decorative paper and with an overlay. On the bottom side, a backing paper was used which was likewise impregnated with melamine resin. The board was pressed in an SC press at 200 C./40 bar. The pressing time was 10 seconds.

[0059] The samples from working examples 1, 2, a control sample produced using an unsanded HDF as per working example 1 but without pulverulent resin, and a comparative sample with sanded HDF board were subsequently subjected to testing.

[0060] In this testing, a modified cross-cut test was carried out with the aid of a cutter blade. Using the blade, cuts were made in the surface of the coated boards, leading to diamond patterns. The blade was then used to attempt to peel the diamonds from the surface. The expenditure of force was then assessed in comparison. Additionally, on the diamonds removed by peeling, the layer thickness made up of coating and adhering fibers was determined. The layer thickness of the coating (overlay and decoration) here was approximately 0.15 mm. Table 1 summarizes the results.

TABLE-US-00001 TABLE 1 Application rate of Layer melamine resin in Cross-cut thickness Sample g/m.sup.2 (expenditure of force) in mm Control sample 0 Low 0.29* Sample 1 3 Moderate 0.35** Sample 2 6 High 0.39** Comparative 0 High 0.42** sample, sanded *The decorative paper can still be seen through the fibers. **The reverse side of the diamond exhibits complete fiber occupation.

[0061] As the table shows, the expenditure of force required in order to peel off the diamonds increases as the amount of melamine resin goes up. There is also an increase in the layer thickness of the fibers also removed on peeling. For sample 2, this thickness is almost as great as that of the sanded board. The difference between the variant with 6 g of melamine resin powder/m.sup.2 and the control sample can be seen from a comparison of the corresponding densograms (see FIGS. 1 and 2).

[0062] Accordingly, in the case of the control sample (FIG. 1), a marked drop in the apparent density can be seen (from 1700 to less than 1000 kg/m.sup.3) beneath the coating (0.15 mm) and the fibers adhering to the coating. In the case of the sample with 6 g of melamine resin powder (FIG. 2), this drop is no longer apparent, or is apparent only to little extent. This zone is the cracked press skin. When it can no longer be perceived in the densogram, the weak zone is also no longer present.

[0063] Furthermore, the densogram for the control sample in FIG. 1 has a shoulder which suggests a defect. Such defects can lead to instances of delamination. This defect, on the other hand, no longer occurs at 6 g/m.sup.2 powder (FIG. 2), and so instances of delamination are prevented.

WORKING EXAMPLE 4

[0064] In a further series of experiments, different amounts of melamine-formaldehyde powder resins applied by scattering to unsanded HDF, with subsequent pressing in a laboratory press, were compared.

[0065] The pressing was carried out with an impregnated decorative paper and an overlay on the facing side and an impregnated backing on the reverse side. The pressing time was 10 seconds, the pressing pressure 400 N/cm.sup.2, and the temperature 200 C.

[0066] In order to assess the anchoring of the system on the top side, or the consolidation of the press skin, a cross-cut test was again carried out. In this test, the adhesion of the coating to the board was not tested by means of an adhesive strip, but instead by peeling off the incised surface using a cutter blade. The results are summarized in table 2.

TABLE-US-00002 TABLE 2 Application rate of MF Cross-cut result powder resin (g/m.sup.2) (DIN EN ISO 2409)*) 0 5 10 2 20 1 *)Assessment: Level 0 = coating removable in small area only with substantial expenditure of force Level 5 = coating removable in large area with little expenditure of force; coating undergoes partial detachment even when the surface is incised.

[0067] The results of the cross-cut test show an increase in the expenditure of force required as the application rate of MF resin powder goes up.