Method for finishing a wood board

Abstract

The disclosure relates to a method for finishing a wood board with an upper face and a lower face, having the following steps: a) applying a undercoat made of a liquid melamine resin onto the upper face, the melamine resin at least partly penetrating into the upper edge layer of the wood board, b) drying the undercoat into an undercoat layer, c) applying a base color onto the undercoat layer, d) drying the base color into a base color layer, e) applying a base color onto the base color layer in order to produce a decorative element, f) drying the decorative element into a decorative layer, g) applying a liquid melamine resin onto the dried decorative layer, h) drying the melamine resin into a melamine resin layer, and i) applying a liquid medium with a proportion of isocyanate.

Claims

1. A process for finishing of a wood-based board with an upper side and an underside, comprising: a) application of a basecoat made of a first liquid melamine resin to the upper side of the wood-based board, wherein the first liquid melamine resin penetrates at least to some extent into the upper side of the wood-based board, b) drying the basecoat to give a basecoat layer, c) application of a base color to the basecoat layer, d) drying the base color to give a base color layer, e) application of at least one printing ink to the base color layer to produce a decorative effect, wherein the decorative effect is based on the base color and the at least one printing ink, f) drying the at least one printing ink to give a decorative layer, g) application of a second liquid melamine resin to the decorative layer, h) drying the second liquid melamine resin to give a melamine resin layer, i) application of a liquid medium having a proportion of isocyanate groups to the melamine resin layer in a quantity from 50 to 200 g/m.sup.2, wherein the liquid medium is a dispersion which has a solid content and water as a solvent, wherein the liquid medium is applied in a plurality of individual layers, j) drying the liquid medium with a proportion of isocyanate groups to give a finished layer, and k) pressing layers under pressure and heat to form the finished wood-based board, wherein the isocyanate groups are reactive, and react with an NH group or a methylol group of the melamine resin layer when the liquid medium is applied to the melamine resin layer, leading to anchoring of the resulting layer of the liquid medium on the surface of the melamine resin layer; wherein a third liquid melamine resin is applied to the underside, and is dried to provide a counterbalancing material.

2. The process as claimed in claim 1, wherein the liquid medium having the proportion of isocyanate groups is applied to the counterbalancing material.

3. The process as claimed in claim 1, wherein the liquid medium includes the water, in addition to organic solvents or additions.

4. The process as claimed in claim 3, wherein the organic solvents or additions are dispersing agents, release agents, wetting agents, and/or antifoams.

5. The process as claimed in claim 1, wherein at least one protective covering layer is applied to a dried layer of the liquid medium.

6. The process as claimed in claim 5, wherein the at least one protective covering layer comprises nanoparticles in order to improve resistance to microscratching.

7. The process as claimed in claim 1, wherein the liquid medium comprises wear-inhibiting particles.

8. The process as claimed in claim 7, wherein the wear-inhibiting particles are corundum particles.

9. The process as claimed in claim 1, wherein at least one of the liquid medium, the first and second melamine resin layers, and protective covering layer comprise(s) glass beads and/or agents having antistatic and/or antibacterial effect.

10. The process as claimed in claim 9, wherein a diameter of the glass beads is less than 30 μm.

11. The process as claimed in claim 9, wherein a diameter of the glass beads is from 30 to 120 μm.

12. The process as claimed in claim 1, wherein the liquid medium is applied in a plurality of individual layers.

13. The process as claimed in claim 1, wherein during the pressing of the layered structure a structure is embossed into the layers applied on the upper side.

14. The process as claimed in claim 13, wherein the structure is formed synchronously with respect to the decorative effect.

15. The process as claimed in claim 1, wherein a short-cycle press is used for a pressing process.

16. The process as claimed in claim 1, wherein the decorative effect is a decorative wood effect, decorative stone effect, decorative tile effect, or imaginative decorative effect.

17. The process as claimed in claim 1, wherein the isocyanate groups are in a dried dispersion of the liquid medium, wherein the reaction between the NH group of the melamine resin layer and the dried dispersion provides a polyurethane, and wherein the reaction between the methylol group of the melamine resin layer and the dried dispersion provides a urea derivatives.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described in more detail below with the aid of a drawing.

(2) The single FIGURE shows a wood-based board of the invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

(3) The single FIGURE shows a wood-based board 1 made of HDF or MDF with an upper side O and an underside U. Liquid melamine resin is applied as basecoat to the upper side O, and penetrates at least to some extent into the upper peripheral layer of the wood-based board 1. The basecoat is then dried to give a basecoat layer 2. A base color is applied to the dried basecoat layer 2, and is dried to give a base color layer 3. A printing ink is applied to the base color layer 3 to produce a decorative effect, and said ink is then dried to give a decorative layer 4. A liquid melamine resin is applied to the dried decorative layer 4, and is dried to give a melamine resin layer 5. The melamine resin can comprise glass beads 12, in particular with diameter up to 30 μm, these being mixed into the liquid melamine resin.

(4) A liquid medium which comprises a proportion of isocyanate groups is applied to the upper side O of the melamine resin layer 5. The liquid medium preferably has from 50 to 60% solids content, with water as solvent. Other materials that can also be used alongside water are organic solvents or additions, for example dispersing agents, release agents, wetting agents, and/or antifoams. Drying of the liquid medium then forms a layer.

(5) It is also possible, instead of application of the liquid medium in the form of dispersion to the upper side O of the melamine resin layer 5, followed by active drying, to use a hotmelt (hotmelt adhesive) which has isocyanate groups. The hotmelt is heated before application and then, on cooling, spontaneously forms the layer 6. Formation of the layer can be accelerated by active cooling.

(6) Hotmelt used can by way of example be the product marketed as PUR HC 717.5 from Kleiberit. The isocyanate groups in the hotmelt or in the (dried) dispersion are reactive, and react with the methylol group of the melamine resin to give a polyurethane, and/or with the NH group to give a urea derivative. Another possibility is the reaction with water to give amine and further reaction with free isocyanate groups to give urea derivatives. This achieves anchoring of the dried dispersion or of the hotmelt on the melamine resin layer 5. A layer is thus formed which, in comparison with a pure melamine resin layer, is softer, but nevertheless more wear-resistant, has warmer haptic properties, and produces less noise.

(7) The medium 6 can comprise wear-inhibiting particles 8, in particular corundum particles, which can be mixed into the medium and/or scattered thereon, and also glass beads 12 with diameter from 30 to 120 μm which, during the subsequent pressing process, serve as spacers between the press plate and the wear-inhibiting particles 8, in order to reduce wear on the press plate.

(8) A protective covering layer 7 is applied to the upper side O of the solid layer 6 of medium, and can be composed of a UV lacquer which preferably comprises nanoparticles 11 based on silica in order to increase resistance to microscratching.

(9) The protective covering layer 7 can moreover comprise agents having antistatic and/or antibacterial effect. There can also be microglass material 12 with diameter up to 30 μm provided to improve surface properties.

(10) The resultant layer structure is finally—as is known—pressed with exposure to pressure and heat to give a laminate. It is possible here that a structure corresponding to the decorative effect is embossed into the layer structure, in particular into the layer 6. If a dispersion is applied as liquid medium, it is preferable that a short-cycle press is used for the pressing process of the layer structure. If a hotmelt is used, it is preferable that a calender roll is used to press the layer structure. In the case of the short-cycle press, the structure has been engraved into the press plate, and in the case of the calender roll, it has been engraved into the circumferential surface thereof.