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. At least one decorative layer, in particular as a printed decoration, is provided on the top side. The method 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. The first resin layer on the top side of the wood-based panel provided with the abrasion-resistant particles is not dried after application. The method also includes 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, and 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. A method for producing an abrasion-resistant wood-based panel with a top side and a bottom side, wherein at least one decorative layer is provided on the top side in the form of a printed decoration, and wherein a protective layer of a not yet fully cured resin is applied to the decorative layer, comprising the steps of: applying at least one first resin layer to the at least one decorative layer on the upper surface 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 provided with the abrasion-resistant particles on the upper surface of the wood-based panel is not dried after application; applying at least a second resin layer to the first wet resin layer provided with the abrasion-resistant particles on the upper surface of the wood-based panel; subsequent drying of the assembly of first resin layer and second resin layer on the upper surface of the wood-based panel in at least one drying device; applying at least one further resin layer to the dried first and second resin layers provided with the abrasion-resistant particles on the upper surface of the wood-based panel and then drying after the respective application; and, pressing the layer structure following the last drying step in a short-cycle press.

2. The method according to claim 1, wherein the resin layers are based on aqueous formaldehyde-containing resins, such as melamine-formaldehyde resin, urea-formaldehyde resin or melamine-urea-formaldehyde resin.

3. The method according to claim 1, wherein the first resin layer is applied in an amount between 10 to 100 g/m.sup.2.

4. The method according to claim 1, wherein the first resin layer is applied in an amount between 40 to 80 g/m.sup.2.

5. The method according to claim 1, wherein the first resin layer is applied in amount between 45 to 60 g/m.sup.2.

6. The method according to claim 1, wherein the amount of scattered abrasion-resistant particles is 10 to 50 g/m.sup.2.

7. The method according to claim 1, wherein the amount of scattered abrasion-resistant particles is 10 to 30 g/m.sup.2.

8. The method according to claim 1, wherein the amount of scattered abrasion-resistant particles is 15 to 25 g/m.sup.2.

9. The method according claim 1, wherein the second resin layer applied to the upper surface of the wood-based panel is applied in an amount between 10 to 50 g/m.sup.2.

10. The method according to claim 1, wherein the second resin layer applied to the upper surface of the wood-based panel is applied in an amount between 20 to 30 g/m.sup.2.

11. The method according to claim 1, wherein the second resin layer applied to the upper surface of the wood-based panel is applied in an amount between 20 to 25 g/m.sup.2.

12. The method according to claim 1, wherein 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 upper surface of the wood-based panel, and each is dried after application.

13. The method according to claim 12, wherein the at least one of the third, fourth, fifth and sixth resin layer comprises glass beads or fibers.

14. The method according to claim 13, wherein the glass beads or fibers comprise wood fibers or cellulose fibers.

15. The method according to claim 1, wherein an at least one resin layer is applied to the bottom surface of the wood-based panel together with the second resin layer to be applied to the top surface of the wood-based panel.

16. The method according to claim 1, wherein the at least one wood-based panel is a medium density fiber (MDF), high density fiber (HDF) or rough chipboard (OSB) or plywood panel and/or a wood-plastic panel.

17. A production line for carrying out a process according to claim 1, comprising: at least one first applicator device for applying a first resin layer to the upper surface of the wood-based panel, wherein no active drying device is provided upstream of the first applicator device; and wherein the at least one first applicator is designed as a single-sided applicator with a grooved roller; at least one device for scattering a predetermined quantity of abrasion-resistant particles, arranged downstream of the first applicator device in the processing direction; at least one second applicator device arranged downstream of the first applicator device and spreader device for applying a second resin layer to the upper surface of the wood-based panel, wherein no drying device is provided between the spreading 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 layer 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 upper side and/or lower side of the carrier plate and subsequent drying device for drying the further upper and/or lower resin layer; and, a short-cycle press (KT press) arranged downstream of the last drying device.

18. The production line according to claim 17, wherein the second applicator for applying the second resin layer is formed as a double applicator, so that a resin layer is applied to the underside of the wood-based panel simultaneously with the second resin layer on the upper side.

19. A method of producing a panel, the method comprising: providing a panel comprising wood and having a top side and a bottom side, wherein at least one decorative layer is provided on the top side, and wherein a protective layer of a partially but not yet completely cured resin is applied to the decorative layer; applying a first resin layer to the protective layer on the top side of the panel, wherein the provided panel including the decorative layer and the protective layer is not heated in a dryer before the application of the first resin layer; scattering abrasion-resistant particles on the first resin layer on the top side of the panel, wherein the first resin layer on the top side of the panel provided with the abrasion-resistant particles is not dried after application; applying a second layer of resin to the first resin layer on the top side of the panel; and subsequently drying the structure consisting of the first resin layer and the second resin layer on the top side of the panel in at least one drying device, wherein the abrasion-resistant particles comprise one or more of corundum, boron carbide, silicon dioxide, and silicon carbide, and wherein the second resin layer is applied using a roller applicator and at least a portion of the abrasion-resistant particles scattered on the first resin layer and not fixed to or penetrated into the first resin layer are taken up by the roller applicator and entrained in the resin applied as the second resin layer such that, after drying, both the first and second resin layers contain the abrasion-resistant particles, applying at least one further resin layer to the dried first and second resin layers provided with the abrasion-resistant particles on the upper surface of the wood-based panel and then drying after the respective application; and, pressing of the layer structure following the last drying step in a short-cycle press.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[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. 2 is a schematic diagram of a production line of a wood-based panel using the process according to the invention.

DESCRIPTION OF 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 μm 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.