Patent Application
20190016008
The present invention relates to a method for producing wood-based materials having a smooth surface by applying surfactants to the surface.
Methods for producing single-layer and multilayer wood-based materials are known in principle and described for example in M. Dunky, P. Niemz, Holzwerkstoffe and Leime, Springer 2002, pages 91 to 150. A firm component of the production operation is the inconvenient and costly sanding of the wood-based material immediately after the hot press. According to page 129, paragraph 3, the purpose of sanding is to remove the press skin. The press skin, which is attributable to the plastication of the wood in the hot press, has to be removed by sanding, again, because it seals the wood-based material in such a way as to prevent direct coating with decorative papers.
The coating of wood-based materials with decorative papers is typically accomplished using decorative papers impregnated with amino resin. A distinction is to be drawn here between decorative papers impregnated with melamine resin, and decorative papers containing urea resin.
Melamine-resin-impregnated decorative papers are heated together with the wood-based material board in the hot press under pressure (up to 60 bar) to around 200° C. In order to produce a durable bond between board and paper, the sanding of the wood-based material board is necessary.
Urea-resin-impregnated decorative papers are typically applied to a wood-based material board with the aid of what is called a curative primer and what is called a surface glue or laminating glue. Here again, in order to produce a durable bond between board and paper, the sanding of the wood-based material board is necessary.
The sanding of wood-based material boards is a component operation which consumes time and materials and is liable for improvement.
It was an object of the present invention, therefore, to remedy the disadvantages identified above, and in particular to develop a simpler and cost-effective technique allowing wood-based materials to be coated with decorative papers.
Found accordingly has been a new and improved method for coating wood-based material, which comprises treating the surface of a wood-based material with 0.05 to 50 g/m2, preferably 0.1 to 20 g/m2, more preferably 0.3 to 10 g/m2 of a surface-active substance, preferably as 0.1 to 60 wt %, preferably 0.5 to 50 wt %, more preferably 1 to 40 wt %, more particularly 2.5 to 30 wt % solutions, more particularly a solution of a surfactant. The coating according to the invention is carried out preferably in place of, in other words without, partial abrading of the wood-based materials. The present invention further relates to coated wood-based materials produced according to the aforesaid method.
Suitable surfactants are anionic, cationic, nonionic, amphoteric surfactants or mixtures thereof.
Suitable anionic surfactants are
Suitable nonionic surfactants are
The nonionic surfactants may be alkyl alcohol alkoxylates with an unbranched or branched, primary or secondary alkyl chain, or aryl alkoxylates. Preferred are alkyl or aryl alkoxylates of the formula (I)
where
R1=linear or branched, primary or secondary C7 to C24 alkylphenyl and naphthyl,
R2=linear or branched C1 to C16 alkyl,
R3═H, benzyl, linear or branched C1 to C18 alkyl,
n=1 to 200,
m=0 to 80,
where the alkylene oxide units may be arranged randomly or in blocks in any order.
Preferred nonionic surfactants are branched or unbranched C8 to C15 alkyl ethoxylates having 3 to 20 ethylene oxide units.
Preferred nonionic surfactants are branched or unbranched C8 to C15 alkyl ethoxylates having 3 to 20 ethylene oxide units.
The nonionic surfactants may be PO/EO block copolymers.
The nonionic surfactants may be alkylpolyglucosides or mixtures thereof, based on C5 sugars or C6 sugars, and preferably of the general formula (IIa) or (IIb)
R1O(R2O)b(Z)a (IIa)
R1O(Z)a(R2O)bH (IIb)
where
R1=linear or branched C4 to C30 alkyl,
R2═C2 to C4 alkylene,
Z=independently at each occurrence a sugar residue, preferably glucose or xylose,
b=0 to 12,
a=1 to 15, including the possibility of fractional numbers.
In preferred alkylpolyglycosides, R1 is a linear or branched C8 to C16 alkyl radical, b=0, and a=1.1 to 4.
Suitable cationic surfactants are
Suitable amphoteric surfactants are alkyl betaines and imidazolines.
Other suitable surfactants are known from McCutcheon's, vol. 1: Emulsifiers & Detergents, McCutcheon's Directories, Glen Rock, USA, 2008 (International Ed. or North American Ed.).
The solutions are composed of solvents and the surface-active substance. Examples of suitable solvents include alcohols, glycols, organic solvents or water, preferably methanol, ethanol or water, more preferably water.
In another preferred embodiment, the surface-active substance (e.g., the surfactant) may be applied together with the curative primer in proportions by mass of 0.001:1 to 1:1, preferably of 0.005:1 to 0.5:1, more preferably 0.01:1 to 0.02:1, separately or mixed, to the surface of the wood-based material.
The surface-active substances may be applied by usual techniques such as rolling, spraying, knifecoating, spreading, preferably rolling or spraying, more preferably spraying. In this operation the temperatures are 10 to 50° C., preferably 15 to 40° C., more preferably 20 to 25° C.
Wood-based materials, particularly in the form of boards, consist of edges and faces. In this invention the faces are referred to as surfaces.
The wood-based materials coated in accordance with the invention are suitable for use as decorative wood-based material boards, more particularly for the production of furniture boards.
Commercial unsanded 19 mm P2 chipboard (emission class E1) [examples 1 to 8] were used.
Surfactants:
The results can be seen in table 1.
Commercial unsanded 19 mm P2 chipboard (emission class E1) were used.
The results can be seen in table 1.
Testing of coatability by droplet holdout time:
As a measure of the coatability, the holdout time of a water droplet or the curative droplet was employed: Using a pipette, a liquid droplet of defined volume was applied to the surface of the wood-based material and a determination was made of the time taken for the liquid to be taken completely into the WBM surface. The longer the droplet holdout time, the poorer the coatability.
Coating materials:
The wood-based material boards were coated as follows with decorative papers.
Materials testing of the coating:
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 215 215 096.8 | Aug 2015 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/066881 | 7/15/2016 | WO | 00 |
