Method for Producing an Abrasion-Resistant Wood Composite Board, and Production Line Therefor

Abstract

A method for producing an abrasion-resistant wood-based panel with a top side and a bottom side, wherein at least one decorative layer, in particular as a printed decoration, is provided on the top side, includes applying at least one first resin layer to the at least one decorative layer on the top side of the wood-based panel, uniformly scattering abrasion-resistant particles onto the first resin layer on the top side of the wood-based panel; wherein the first resin layer on the top side of the wood-based panel provided with the abrasion-resistant particles is not dried after application, and applying at least one second resin layer to the first, moist resin layer provided with the abrasion-resistant particles on the top side of the wood-based panel, then drying the assembly of first resin layer and second resin layer on the top side of the wood-based panel in at least one drying apparatus.

Claims

1-15. (canceled)

16. A method of producing an abrasion-resistant wood-based panel having a top side and a bottom side, wherein at least one decorative layer, in particular as a print decoration, is provided on the top side, and wherein a protective layer of a not yet completely cured resin is applied to the decorative layer, comprising the steps: applying at least one first resin layer to the at least one decorative layer on the top side of the wood-based panel, wherein the wood-based panel provided with the protective layer and decorative layer is not heated in a dryer before the application of the first resin layer, even scattering of abrasion-resistant particles on the first resin layer on the top side of the wood-based panel wherein the first resin layer on the top side of the wood-based panel provided with the abrasion-resistant particles is not dried after application, applying at least a second layer of resin to the first, moist resin layer on the top side of the wood-based panel, which is provided with the abrasion-resistant particles, and subsequent drying of the structure consisting of the first resin layer and the second resin layer on the top side of the wood-based panel in at least one drying device.

17. The method according to claim 16, wherein the resin layers are based on aqueous formaldehyde-containing resins, in particular melamine-formaldehyde resin, urea-formaldehyde resin or melamine-urea-formaldehyde resin.

18. The method according to claim 16, wherein the first resin layer is applied in an amount between 10-100 g/m.sup.2, preferably 40-80 g/m.sup.2, in particular preferably 45-60 g/m.sup.2.

19. The method according to claim 16, wherein the amount of scattered abrasion-resistant particles is 10 to 50 g/m.sup.2, preferably 10 to 30 g/m.sup.2, in particular preferably 15 to 25 g/m.sup.2.

20. The method according to claim 16, wherein the second resin layer to be applied to the top side of the wood-based panel is applied in an amount between 10-50 g/m.sup.2, preferably 20-30 g/m.sup.2, in particular preferably 20-25 g/m.sup.2.

21. The method according to claim 16, wherein at least one further resin layer, preferably a third, fourth, fifth and sixth resin layer, is applied to the dried first and second resin layer provided with the abrasion-resistant particles on the top side of the wood-based panel and is dried after each application.

22. The method according to claim 21, wherein in that the at least one further resin layer comprises glass beads and/or fibres, in particular wood fibres or cellulose fibres.

23. The method according to claim 16, wherein at least one resin layer is applied to the bottom side of the wood-based panel together with the second resin layer to be applied to the top side of the wood-based panel.

24. The method according to claim 16, wherein the at least one wood-based panel is a medium density fibre (MDF), high density fibre (HDF) or coarse particle board (OSB) or plywood panel and/or a wood-plastic panel.

25. A production line for carrying out a method according to claim 16, the production line comprising: at least a first application device for applying a first resin layer to the top side of the wood-based panel, wherein no active drying device is provided in front of the first application device; at least one device arranged downstream of the first application device in a processing direction for scattering a predetermined quantity of abrasion-resistant particles; at least one second application device arranged behind the first application device and scattering device in the processing direction for applying a second resin layer to the top side of the wood-based panel, wherein no drying device is provided between the scattering device and the second application device; at least one first drying device arranged downstream of the second application device in the processing direction for drying the layered structure of first and second resin layers; at least one further application device arranged downstream of the first drying device in the processing direction for applying a further resin layer to the top and/or bottom side of the carrier board and subsequent drying device for drying the further top and/or bottom resin layer; and a short-cycle press (KT press) arranged downstream of the last drying device in the processing direction.

26. The production line according to claim 25, wherein the second application device for applying the second resin layer is designed as a double applicator, so that a resin layer is applied to the bottom side of the wood-based panel simultaneously with the second resin layer on the top side.

Description

[0101] The invention is explained in more detail below with reference to the figures in the drawings by means of an example of execution. Show it:

[0102] FIG. 1 is a schematic diagram of a wood-based panel production line using a conventional process; and

[0103] FIG. 2A schematic diagram of a production line of a wood-based panel using the process according to the invention.

[0104] The conventional production line shown schematically in FIG. 1 comprises an IR dryer 10, a single-sided applicator unit 1, and five double applicator units 2, 3, 4, 5, 6 for simultaneous application of the respective resin layer to the top and bottom sides of the separated printed material boards, e.g. of printed HDF boards, as well as four convection dryers 1a, 2a, 3a, 4a, 5a, 6a each arranged behind the applicator units in the processing direction.

[0105] Before the first resin application, the surface of the boards is preheated by the IR dryer 10 to a temperature of approx. 45 C. The resin is applied to the board surface via a rubberized roller in the applicator unit. The excess resin is pumped back into the application tank, from where it is transported back to the rollers.

[0106] After the first application roller 1, a first scattering device 20 is provided for evenly scattering the abrasion-resistant material such as corundum on the first resin layer on the top of the HDF board. The abrasion-resistant material used is corundum F200, which, according to the FEPA standard, measures approximately 53-75 m in diameter. The scattering device 20 essentially consists of a storage hopper, a rotating, structured spiked roller and a scraper. The application rate of the material is determined by the rotational speed of the scattering roller. Depending on the required abrasion class of the product, between 12-25 g/m.sup.2 corundum is scatter onto the resin-coated plate (AC4 (according to EN 13329)=20 g/m.sup.2). From the spiked roller, the corundum falls at a distance of 5 cm onto the melamine resin treated panel. Since the first resin layer is still liquid at the time of scattering, the abrasion-resistant particles can sink into the resin layer. Below the present scattering device, in front of the scattering roller, there is at least one hopper (not shown) for collecting excess abrasion-resistant particles (i.e. not scattered on the at least one wood-based panel, but rather, before the wood-based panel is moved by means of the transport device under the scattering roller, in front of the same falling abrasion-resistant particles).

[0107] The first resin layer is then dried in the first convection dryer 1a at 150-250 C. for 20-50 s.

[0108] This is followed by a second double applicator 2 for applying a second resin layer and a second convection dryer 2a for drying the second resin layer.

[0109] The third double coating unit 3 for the application of the third resin layer can be followed by another scattering device 20 for the application of glass beads on the third resin layer followed by a third convection dryer 3a for drying the third resin layer. The scattering device 20 for the glass beads is optional. The glass beads can also be applied together with the third resin layer.

[0110] After application of the fourth to sixth resin layer in a fourth to sixth double application unit 4, 5, 6 and drying in a convection dryer 4a, 5a, 6a each, the layer structure is cured in a short-cycle press 7 at a pressing temperature of 180-220 C. and a pressing time of 5 to 25 seconds under a specific pressure of 35-55 kg/cm.sup.2. The pressed sheets are cooled and stored.

[0111] In the invention-related production line shown schematically in FIG. 2, the IR dryer 10 is removed or switched off. Removal of the IR dryer from the production line avoids the electrostatic charging of the board surface that would otherwise occur in the IR dryer, thus enabling the formation of a homogeneous scattering curtain of the corundum.

[0112] Furthermore, an additional double-sided applicator 1-1 is installed behind the one-sided applicator 1 (grooved roller) and the scattering device 20 in the processing direction, in which the panel coated with melamine-formaldehyde resin and corundum is coated with melamine-formaldehyde resin (approx. 20 g/m.sup.2). At the same time, the unattached corundum is removed in small quantities and accumulates in the melamine resin liquor until saturation (about 10 wt. %). This lost portion of the corundum is now continuously re-applied to the board by the roller application of the coating unit 1-1. By the second application the corundum grains are covered with liquid resin or worked into the overlay layer. This prevents the corundum from being removed in the convection dryer due to the high air turbulence.

[0113] The coating unit 1-1 is followed by a convection dryer 1a followed by the other double coating units 2, 3, 4, 5, 6 for simultaneous application of the respective resin layer on the top and bottom side of the separated printed material sheets as well as the convection dryers 2a, 3a, 4a, 5a, 6a arranged behind the coating units in the processing direction.

[0114] The following advantages result from the conversion measures taken in the production line of FIG. 2: Homogeneous scattering pattern; no loss of corundum in the dryer; reduction of the corundum consumption for required abrasion class; reduction of the dust load of the environment and the obvious health burden of the employees; as well as corundum dust deposits on plant parts of the production line; reduction of the corundum deposit on the transport chains and thus saving of additional material costs by replacing the chains.