WO1997033930A1

WO1997033930A1 - Urethanization coating process providing one layer and many zones

Info

Publication number: WO1997033930A1
Application number: PCT/AT1997/000050
Authority: WO
Inventors: Heinz Haschke
Original assignee: Constantia-Iso Holding Aktiengesellschaft
Priority date: 1996-03-12
Filing date: 1997-03-11
Publication date: 1997-09-18
Also published as: ATA46696A; EP0824559A1; AT405150B

Abstract

The invention relates to a coating process by urethanization to form a single-layer composite coating, having three materials and three zones, by combined polyaddition hardening/ polycondensation hardening with radical polymerisation, and pressing of the resultant films on the bodies to be coated, the radical polymerisation process being initiated by radical forming agents.

Description

Single-layer, multi-zone urethane coating process

Technical field

The invention relates to a coating process by urethanization to form a three-substance, three-zone, single-layer composite structure with combined polyaddition / polycondensation curing with free-radical polymerization and pressing films thus obtained onto the body to be coated.

State of the art

It is known that aminoplast resins such as urea-formaldehyde resins or better melamine-formaldehyde resins as the outermost surfaces of coating systems have good scratch resistance. In particular, melamine resin surfaces can bring scratch resistance of up to approx. 10 Newtons (abbreviated N; according to DIN 53799, part 10). The curing of aminoplast resins is chemically a polycondensation in which water is split off. The hardening process of ureas and melamines takes place via condensation intermediates which are still meltable and soluble in solvents such as dimethylformamide and which have a large number of free, yet reactive methylol groups (= so-called "B-phase" products). Only after a longer reaction time with the condensing agent, which is usually formaldehyde, do these intermediates react to form highly cross-linked end products (-> so-called "Duro-Plastics"). Despite the high degree of crosslinking, the triazine system of the melamine resin component tends to hydrolysis to the end hydrolysis product of cyanuric acid during weathering. This hydrolysis reaction leads to degradation, stress cracking and graying effects, so that coating systems based on melamine-formaldehyde resins are only very poorly weather-resistant. Coating systems based on urea resins have a similar poor weather resistance.

On the other hand, aminoplast resins have proven themselves well as impregnating resins for decorative papers, which, after lamination or compression with carrier materials such as laminated, chipboard or fiberboard, result in a good bond with the carrier material, so that apart from the poor weather resistance - satisfactory decorative parts and panels are created.

Analogous results can be achieved with phenolic resins as impregnation resins. However, even the outermost layers of phenolic resins are not weather-resistant, since they yellow when exposed to light and air, so that an undesirable discoloration of the decor is caused.

Furthermore, it is known that acrylic resins and also polyester resins and polymers made from ester acrylates, urethane acrylates, ether acrylates and epoxy acrylates generally have much better weathering properties, but such systems are in turn not nearly as suitable for impregnating decorative papers as the aforementioned ones Aminoplast or phenoplast resins. In addition, they give only relatively soft, not very scratch-resistant coatings.

In this respect, the conventional coating consisting of a single resin layer cannot achieve satisfactory results for the production of molded parts and plates for outdoor use.

On the basis of the results mentioned, it is also known to combine amino or phenolic resins with acrylic and polyester and polyester-acrylic resins in order to achieve satisfactory impregnation behavior and good weather properties in the surface layer.

The simplest method in this regard is the lamination of a finished, weather-resistant polyacrylate film as a top and protective layer on a carrier material which is already coated with an aminoplast or phenoplast-impregnated decorative paper. This combines the advantages of a decorative paper surface that adheres well to the carrier material and the good decorative paper properties known from amino and phenoplastic impregnations, with the advantages of weather-resistant synthetic resin layers, into which, if necessary - for example to protect the UV-sensitive phenolic nical impregnating resins - substances that absorb UV rays can also be incorporated.

The following sketch shows the coating system mentioned for a better explanation:

- (CH ₂ -CH-) _n

Layer 2 = polyacrylate

COOR (foil) phase boundary

(Layer boundary)

/ NH-CH ₂ OCH2

= abbreviated: Layer 1 = aminoplast

NN -NHCH ₂ OCH ₂ - (paper impregnate)

I I

-HN-C C-NH-CH ₂ OCH ₂ N

An advantageous embodiment of such a coating system is previously known from DE-OS 30 10 060, according to which an upper film (a so-called decorative film) coated with a lacquer hardened by electron beams is laminated together with a carrier film underneath between pairs of rolls.

This coating system now consists of two layers of resins with different chemical constitution, so that a sharp, straight dividing line between the two layers, namely the carrier film and the decorative film, is clearly visible under the microscope in cross section. The two layers are uniform throughout in their chemical constitution, namely on the one hand the aminoplast or phenoplast impregnation resin layer and on the other hand the cover layer based on the acrylic resin. Although this layer structure achieves a weather-resistant surface, it has the disadvantages that the layers can only be mutually bonded by physical adhesion. forces are connected. However, these adhesive forces only act on the respective layer. Accordingly, any mechanical damage to the outermost layer leads to infiltration starting from this point of injury, due to diffusion processes and thus also to large-scale weathering disturbances up to the detachment of the outermost laminate layer. In addition, the paint systems mentioned are much less scratch-resistant than aminoplast or phenoplast surfaces.

Furthermore, it is proposed in DE-AS 29 47 597 to combine the advantages of aminoplast resins as impregnating resins with the weathering properties of acrylic resins to the extent that mixtures of polymers made from acrylates, ester acrylates, epoxy acrylates, urethane acrylates, ether acrylates and unsaturated acrylic resins , optionally together with unsaturated acrylate monomers with amino resins as coating mixtures for the production of an outermost radiation-curable layer. The result is a single-layer coating system consisting of two or more resins, which is shown in a sketch as follows:

1 zone mixture of:

a) - (CH ₂ -CH-) _n b)

| - Particles embedded in: -NHCH OCH ₂ - COOR (= substance 1) matrix

Phase boundary at the particles ( ⁼ substance 2)

However, since cured aminoplast resins and polymerized acrylic resins are not miscible with one another, the coating under the microscope shows a self-contained layer, which consists of two phases, in which one polymer is more or less finely dispersed in the other polymer with clear, sharp phase boundaries on its particle surfaces from the matrix polymer in which it is embedded. However, the desired properties of the mixture components cannot be added up by such mixtures, so that the finished products essentially only have the poor weathering properties of the aminoplast resins combined with the poor scratch resistance of the acrylic resins.

According to EP-A-166 153 it is therefore proposed to apply aminoplast-free, unsaturated (meth) acrylate layers as the outermost layer on phenolic or aminoplast-impregnated decorative paper layers. This system of (oligomeric) prepolymers, consisting of two delimited layers, is first radiation-hardened after the impregnation process and then pressed at a pressure of at least 15 bar and at temperatures of at least 80 ° C. The result is an essentially physical bond between the outermost radiation-crosslinked aminoplast-free acrylate layer and the underlying aminoplast layer, which is chemically and physically delimited from the acrylate layer. Electron beam curing polymerizes and optionally cross-links the acrylate oligomer layer, while the aminoplast layer, which is separated by a sharp phase boundary, is condensed to a thermosetting plastic after pressing. In a preferred embodiment of this method, any pigmentation or decoration is also already indicated in the aminoplast underlayer, while only an unpigmented and thus easily non-porous clearcoat is used as the acrylate topcoat. A system of this type - as explained in more detail by the following sketch - shows weathering, especially minor irregularities in the top coat layer, undermining at the only physically connected boundary layer between the aminoplast base and the top coat. The top coat layer can therefore easily stand out from the aminoplast substrate or have undesirable shades of gray. Sketch to illustrate the system principle:

(CH ₂ -CH-) _n R can also be: Layer 2

I -CH-COOR \

O

0 = C and or -R'-CH = CH ₂

Mandatory free of: - HCH ₂ OCH ₂ - NH crosslinker residue

Phase boundary

(Layer boundary)

Aminoplast or phenoplast layer

Layer 1

Respectively. the crosslinking products that result from radiation curing.

Due to the pressing process, depending on the local elasticities and deformability of the two layers lying one on top of the other, the acrylate layer is pressed to different depths into the underlying amino or phenolic layer, so that a toothed phase boundary can be determined in the microscopic cross-sectional image (the two separate phases stand) to each other like gears meshing). With the methods mentioned, satisfactory weather properties and, in addition, significantly improved scratch resistance of up to 7 N are achieved.

But this method also has the disadvantage that only a physically adhering protective cover film is applied to the base paper layer, which is impregnated with phenolic or aminoplast, so that there is a risk of long-term weathering or surface damage for example by diffusion of water vapor through the outermost cover layer to infiltrate it and finally to attack the underlying support layer is coming. Separation effects can also occur between the outermost cover and protective layers.

In addition, the radiation-chemically curing processes require a separate operation with relatively complex apparatuses such as electron emitters or UV emitters. Furthermore, it is known that - in particular the systems produced by electron beam radiation tend to form stress cracks, especially if profile bodies are to be coated, especially if vertical surfaces are connected to a horizontal surface at an obtuse angle, so that the film is subjected to strong mechanical stress or shear . The paint on the outer paint layer of the film on partial areas can either be completely sheared off or shifted on the film. In addition, parts of the lacquer can flake off or microcracks can form in the lacquer. In any case, these effects lead to a weakening or even destruction of the protective effect of the lacquer.

The object of the invention is now to provide a method of the type mentioned, in which the technical advantages of the individual resin systems such as amine plastics or phenoplasts for decorative paper impregnation and those of the acrylates for the outermost protective layer are retained.

Presentation of the invention

According to the invention, a process of the type mentioned is proposed, which is characterized in that, in a first step, a hydroxyl group-containing polyacrylate, which also contains unsaturated comonomers in the polymer chain, is formed on the backing film consisting of backing materials impregnated with isocyanate group-reactive aminoplast or phenoplast after copolymerization still contains reactive double bonds, or an unsaturated hydroxyl group-containing polyester is applied with a di- and / or poly-isocyanate, whereby at the boundary layer between aminoplast or phenoplast and hydroxyl group-containing polyacrylate (abbreviated UPA) or polyester (abbreviated UPE) a clear mixing and mutual diffusion occurs and a stoichiometric excess of isocyanate component nente in the form of an excess of NCO groups relative to the existing NCO reactive groups from the hydroxyl group-containing polyacrylate or polyester and any NCO consumption by side reactions, so that a chemical compound from the hydroxyl group-containing polyacrylate or Polyester (via the di- or polyfunctional-NCO component to the methylol groups of the aminoplast or phenoplast by formation of urethane groups) is formed; that in a second step the radical post-crosslinking of the double bonds initiated by radical formers in the unsaturated comonomer units in the hydroxyl group-containing polyacrylate or in the unsaturated hydroxyl group-containing polyester is effected; and that, in a third step, the weather-resistant decorative layers in film form thus obtained are pressed onto the core layer to be coated at a temperature and pressure, as is customarily set for the pressing of carrier materials with decorative films impregnated with aminoplast or phenoplast.

This method ensures that, in contrast to the prior art, an intimate chemical bond is formed in the form of a reaction product between the aminoplast or phenoplast and the acrylate or polyester.

In the process according to the invention, in addition to the carrier material, this system is based on the following substances: 1 = first not hardened aminoplast or phenoplast (also called "B-state resin") that still has isocyanate-reactive methylol groups (hereinafter also abbreviated to "B-state resin"), plus substance 2 = isocyanate crosslinkable UPA or UPE and substance 3 = reaction product from aminoplast or phenoplast methylol groups and excess isocyanate groups from the UPA or UPE isocyanate crosslinker addition product, which - after basically only at least difunctional isocyanates and these are used in a stoichiometric excess of the OH groups present in the UPA or UPE - are already chemically anchored to the UPA or UPE resin residue, and which 3 substances are reacted with one another, so that at least in the middle mixture and Interdiffusion layer also a new substance, of the type of a urethane aminoplast or urethane phen oplasten is created. Sketch to illustrate the system principle:

Zone 1 urethane acrylate

Transitional urethane acrylate-URETHANAMINOPLAST mixed phase) URETHANAMINOPLAST-URETHANACRYLATE pure phase) Zone 3

Transitional-URETHANAMINOPLAST-aminoplast mixed phase)

Aminoplast Zone 2 only one layer in total

In contrast to the conventional methods, a new, third component is brought into play as chemical connecting component in this method, namely substance 3, a urethane aminoplast or a urethane phenoplast, namely the reaction product mentioned, which consists of only partially reacted aminoplast or Phenoplast and its methylol groups and the isocyanate crosslinker in the presence of a UPA or UPE which is also reactive with isocyanate using a stoichiometric excess of isocyanate. By mediating the phases with this urethane aminoplast or urethane phenoplast, it is no longer possible to have several layers which can be separated from one another, but instead a smooth transition in the former composition from the pure aminoplast or phenoplastic to the pure urethane acrylate is achieved. The three zones mentioned are in mesh with one another like gear wheels, but are welded to one another.

The method according to the invention is explained in more detail using a further sketch:

- (CH -CH-) _x - (CH2-CH-) y- (CH ₂ -CH-) _z (or corresponding ones

| | | unsaturated hydroxy polyesters)

COOR COOR ¹ -0 *) R ² -CH = CH ₂

\ C = 0 or their radical

/ Networking products

HN * ⁾ hydroxyacrylate residue

\ ** ⁾ rest of d. Crosslinker

R ³ - ** ⁾ -Di or. Polyisocyanate / *** ⁾ rest of the aminoplast-B-

HN state methylol groups

\

C = 0 / -NH-CH2O *** ⁾

Aminoplast residue

The process according to the invention thus gives a coating which adheres well to the boundary layer from the base material to the film, in a manner analogous to conventional aminoplast or phenoplast-impregnated decorative papers, which coating can only be chemically defined as a single outer layer. Under the microscope a cross-section shows a "multi-zone" layer, which is, however, without a sharp, clear phase boundary dividing line and with a gradual change in its chemical composition in a - in contrast to the conventional multi-layer systems relatively broad, ie in the area of several μ lying intermediate zone, of fully hardened pure aminoplast or phenoplast resin, which well envelops the fibers of the carrier paper, in addition to areas where carrier paper fibers are also encased by the acrylate varnish (both in total = zone 1) merges into an area in which (a) urethanized aminoplast or phenoplast is dissolved in normal aminoplast or phenoplast, further to an area which mainly consists of a new substance which is to be addressed chemically as (b) Urethane-aminoplast or urethane-phenoplast-urethane-UPA or -UPE (= "Substance 3") (connected on both sides by the polyfunctional isocyanate), above it a (c) solution of urethane-UPA or urethane-UPE in urethane -Aminoplast-UPA or -UPE, or urethane-phenoplast-urethane-UPA or -UPE and their free-radical crosslinking products (all 3 areas a, b, c = zone 2) to the outer zone - the but does not represent a separate layer - one that is also radically networked UPA or UPE (= Zone 3).

Using infrared microscope spectrometry, a gradual transition can be determined across this layer, but no sharp layer dividing line, so that the system is a single-layer system. However, the course of the individual, gradual chemical transitions (= zones) can be determined spectroscopically. The gradual changes in the composition of the substance, which can only be determined spectroscopically on the basis of their gradually varying former composition, do of course not follow the surface of the carrier material in parallel, but - depending on the different depths of penetration when mixing or diffusing substance 1 into substance 2 prior to urethanization - besides a) the chemical compound and b) the intermingling penetrating deeply into the individual zones also c) a course of the transitions of the chemical compositions.

Products of this type therefore fundamentally differ from the products of the prior art, in which only different substances are always physically combined with one another, while in the method according to the invention the coating materials are connected to one another by a real chemical reaction and only then are radically crosslinked and in the finished product The product thus also contains other substances, such as the radical-crosslinked urethane aminoplasts or urethane phenoplasts mentioned. Accordingly, such products show even when the

Surface is sanded so far that the outermost zone has been partially removed, and the underlying urethane aminoplast urethane or urethane phenolic, or even partially down to the pure lowest aminoplast or phenolic layer Surprising weathering properties: In those places where sanding was made except for the pure urethane aminoplast or urethane phenoplast zone, the weathering properties are still significantly improved than in normal aminoplast surfaces, and even in the places where the urethane aminoplast or urethane phenoplast zone was also sanded away, although the usual susceptibility to weathering of the aminoplast or phenoplastic surfaces, but no infiltration at the limits where urethane aminoplast UPA or urethane phenoplast UPE still remained.

Paper which can be impregnated with aminoplasts or phenoplasts is suitable as a carrier material. However, nonwovens based on natural or synthetic fibers or on the basis of mixtures thereof are also suitable. So-called decorative papers are particularly suitable.

The following can be considered as core layers according to the method according to the invention:

Laminated boards, chipboard, fiberboard such as medium or high density fiberboard (HDF, MDF), woodfibre materials or profile bodies made of such materials.

According to the coating method according to the invention, it is advantageous to use a phenolic resin for the impregnation of the carrier material, which is preferably present in an aqueous dispersion and is only precondensed to such an extent that it is still reactive with isocyanate groups and at temperatures above 80 ° C., before preferably above 100 ° C, is still flowable.

It is particularly preferred to use an aqueous melamine resin for impregnating the carrier material, which is only precondensed to such an extent that it is still capable of reacting with isocyanate groups and at temperatures above 80 ° C., preferably above 100 ° C., is still flowable.

It is particularly advantageous to apply the aminoplast resin, preferably a melamine-formaldehyde resin, before applying the UPA or UPE Pre-condensing paint systems to a total residual water content of 5 to 25% by weight, preferably to 10 to 15% by weight.

It has proven to be very particularly advantageous to precondense the precondensation of the aminoplasts or phenoplasts with which the carrier material has been impregnated before applying the UPA or UPE coating system to such an extent that they have an NCO titer of at least 3, preferably at least 6, in particular at least 7 milliequivalents of NCO per square meter.

It has also proven to be particularly advantageous to carry out the precondensation of the aminoplasts or phenoplasts with which the support material has been impregnated to such an extent that they have an NCO titer of at most 25, preferably at most 20, in particular at most 15 Milliequivalents of NCO per square meter.

The above-mentioned NCO titer of the aminoplasts or phenoplasts can be determined by pouring a solution of the isocyanate to be used in the process over a sample of 1 dm ^{2 of} the precondensed aminoplast - after shock drying as described below - and heating after heating Reaction temperature determined the isocyanate consumption based on this standard area by back titration with di-n-butylamine and then converted to 1 square meter.

The total amount of isocyanate to be used according to the invention results from a) the stochiometric requirement of the UPA or UPE system for groups which are reactive (with isocyanate groups), preferably its hydroxyl groups, expressed in mol% OH, plus b) that isocyanate loss to be calculated and determined in a preliminary test (see below) by side reactions such as hydrolysis under the reaction conditions and c) the “significant NCO excess” according to the invention, ie the excess of - after the aforementioned

Reactions with the UPA or UPE system and any side reactions - still "reactive" isocyanate, which is provided to react with the aminoplast or phenoplast. The significant excess of NCO depends on the hydroxyl number or the mol% of hydroxyl groups of the UPA or UPA system and should be according to the invention:

Mol% NCO excess = A / mol% OH, where A = 20 to 500, preferably A = 200 to 400.

To set the total excess of isocyanate required for the process according to the invention (= "gross excess"), the proportion of isocyanate which is consumed under process conditions by processes other than the desired main reactions or is lost as a result is determined in a preliminary test, certainly. This proportion is then added to the calculated net excess when using the method according to the invention in order to determine the gross isocyanate requirement required. One can proceed in such a preliminary test as follows, for example:

An aminoplast or phenoplast of the same type is produced and precondensed to the same extent as provided for the process according to the invention, with the only difference that the degree of condensation is shock-cooled and freeze-dried in vacuo immediately after the desired ("B state") degree of condensation has been reached.

Then the aminoplast or phenoplast B impregnate sample is poured over with an excess of the UPA or UPE isocyanate coating system to be used for the method, brought to the process reaction temperature and then, for example, the remaining isocyanate excess titrated back using the di-n-butylamine method. From the difference in NCO consumption on the shock-dried sample and an undried sample, the NCO loss results from the residual water content of the aminoplast or phenoplast substrate, which is accessible to the isocyanate in the mixing and boundary phase and is reactive during the curing period is.

Analogously, NCO titration on UPA or UPE lacquer samples, which is analogous to the process as a mixture of component A, that is the UPA or UPE pigments + additives + water lacquer system, and component B, namely isocyanate, is produced and the same long and at the same temperature under the same conditions, for example pumping around the Mixtures as later provided on the application roller / trough were exposed, the isocyanate loss is determined by side reactions in the coating system.

In principle, the total amount of isocyanate to be used according to the invention then results from a) the stochiometric requirement of the UPA or UPE system, based on its number of NCO-reactive groups, b) increased by the amount mentioned above. Formula determined significant NCO excess, plus c) the sum of the isocyanate losses determined by the above methods by side reactions ("SUIV").

To optimize the excess of isocyanate, unconverted isocyanate groups on the product can optionally be determined after drying by reaction with di-n-butylamine and back-titration of the unconverted amine against bromocresol green. Likewise, the optimal excess of isocyanate can be obtained by reaction of the aminoplast as in the precondensed state, i.e. after predrying with a large excess of isocyanate and then titrating back the unused isocyanate by the di-n-butylamine method.

Aliphatic and / or cycloaliphatic di- or polyisocyanates are preferably used as isocyanate components, ie the so-called "component B" of the coating system.

The following are preferred: hexamethylene diisocyanate, isophorone diisocyanate and their intermolecular addition products such as

Desmodur N or L from BAYER, but also so-called masked isocyanates such as "Desmodur AP stable" from BAYER, in particular those which remain stable for some time in aqueous systems at processing temperature but below the curing temperature. Such capped isocyanates preferably have a pot life at room temperature of at least 10 minutes, preferably of at least 1 hour, in particular of at least 3 hours.

In a further embodiment, instead of free isocyanates, compounds can also be used which release isocyanate groups at or just below the curing temperature can train. This in turn produces reactive di- or polyfunctional isocyanates, preferably those selected from the group of aliphatic and / or cycloaliphatic isocyanates.

To accelerate the urethanizing reaction of the isocyanate component, conventional urethanization catalysts can be added, preferably immediately before applying UPA or UPE lacquer, such as triethylenediamine (TÄDA), dimethylaminoethyl morpholine (XDM) - so-called DABLOs - or dibutyltin dilaurate, etc. .

The UPA to be used according to the invention are hydroxyl group-containing polyacrylates with unsaturated co-monomers built into the polymer chain, which contain reactive double bonds even after polymerization into the polyacrylate. When selecting the unsaturated comonomers, those which contain free or unblocked acrylic and / or methacrylic double bonds after polymerization into the polyacrylate are to be excluded.

Monomers for the polyacrylate are branched and unbranched alkyl acrylates and / or methacrylates such as methyl acrylate (MA), ethyl acrylate (EA), n-propyl and / or isopropyl acrylate (n / iPA), n-, iso- and / or tert. Butyl acrylate (n / i / tBA), 2-ethylhexyl acrylate (2EHA) or methyl methacrylate (MMA) in question, which with hydroxyl group-containing acrylates such as 2-hydroxyethyl acrylate (2 HEA) in an amount of 5 to 40 mol% OH groups, preferably 15 to 35 mol% OH groups, based on the average monomer unit, are copolymerized, and moreover - to provide double bonds which can be hardened with free radical formers - with mono- or polyunsaturated monomers of the so-called "after-curable-double" type -bounds "comonomers (ACDB comonomers) are copolymerized. The proportion of these ACDB comonomers is 0.1 to 20 mol%, preferably 2 to 10 mol%.

As ACDB comonomers, preference is given to comonomers such as allyl acrylate (AA), vinyl acrylate (VA), mono- and / or di-allyl maleate (MAM, DAM), mono- and / or di-allyl fumarate (MAF, DAF), mono- and / or di-allyl tetrahydrophthalate (MATHPH, DATHPH), 2,2-dimethylpropane diol (1,3) diacrylate (DMPDDA), tert-butyl-ethylene glycol diacrylate (tBuEGDA) or mixtures thereof. The proportions of acidic ACDB comonomers can be used to adjust the water dispersibility of the systems analogously or together with and in consideration of the acrylic acid and / or methacrylic acid components described in the systems, which may also be copolymerizable for this purpose, with preference being given to them Is allyl acrylate.

The UPAs can also contain small amounts, preferably 0.1-20 mol% of di- or polyfunctional, crosslinking components such as mono- or diethylene glycol diacrylate (DEGDA) and / or butanediol diacrylate (BDDA) and / or trimethylolpropane di- or triacrylate (TMPDA, TMPTA ) and / or tripropylene glycol diacrylate (TPGDA), whereby in order to avoid undesirable excessive crosslinking when selecting and dosing, the possibly partially pre-crosslinking effect of ACDB comonomers such as DMPDDA or tBuEGDA must also be taken into account, the ACDB behavior of which is not the same as for the allyl compounds is based on their lower reactivity due to the hyperconjugation of the TT electrons in the allyl group, but on the steric hindrance due to the respective substituents. If necessary, other comonomers such as styrene can also be used in the mixture. In this case, it is no longer pure UPA, but instead, for example, styrene acrylates. In these cases, the proportion of such comonomers should not be more than 30 mol%, preferably not more than 10 mol%.

Since in the acrylic components the methacrylates, in particular the MMA, cause glassy topcoat films and thereby lead to a certain degree of embrittlement, they are used in rather minor amounts, in particular only in the range from 0 to 10 mol%, particularly preferably in the range from 1 to 5 mol%.

The longer the longer-chain alkyl radicals are, the more flexible or elasticizing the alkyl acrylates are.

The desired mechanical property of the coating can thus be obtained by a suitable combination of the monomers adjusted or embrittlement or stress cracking are avoided if deformation over narrow radii is necessary to produce the molded part produced according to the invention.

Since it is also known that the water dispersibility of coating systems is improved by hydrophilic, polar groups, it is expedient to also add small amounts, preferably 2-10 mol%, based on the average monomer unit in the polymer used, in particular, to the UPA resins Install 2 to 6 mol% of acid units such as acrylic acid units and / or methacrylic acid units and / or MAM, MAF, MATHF or set a corresponding acid number in UPE systems.

Acrylic acid units are preferred.

When using compounds with more than one double bond as comonomers in the UPA, preference is given to those which, in addition to a double bond with a similar radical polymerization reactivity, are analogous to the other monomers used, ie to the acrylates preferably used, or have several double bonds of lower reactivity, so that these double bonds remain more securely available for radical post-curing. These double bonds are ACDB comonomers, preferably in the case of allyl acrylates. When using such comonomers with double bonds which can be reactivated particularly specifically, the proportion of these comonomers may also be at the upper limit, that is to say 5-20 mol%, preferably 5-10 mol%, based on the average total number of monomer units per UPA. Molecule can be selected.

When using comonomers to provide post-curable double bonds of the type of mono- or polyunsaturated compounds with double bonds of similar reactivity as TMPDA, rather low proportions are preferred to avoid undesired premature crosslinking, that is to say in the range from 0.1 to 5 mol%. , preferably 1 - 3 mol% based on the average total number of monomer units per UPA molecule. The UPE to be used according to the invention are also unsaturated polyesters, that is to say polycondensates from monomers such as fumaric acid (FS) and / or maleic acid (anhydride) (MSA) and / or tetrahydrophthalic acid (THP) which are usually used for the production of unsaturated polyesters, where optionally also phthalic acid (anhydride) (PSA) as acid components and ethylene glycol (EG) and / or diethylene glycol (DEG) and / or propylene glycol (PG) and / or dipropylene glycol (DPG) and / or butanediol (BD) and / or hexanediol (HD) are condensed.

In addition, small amounts, preferably 1-10 mol%, in particular 2-6 mol%, of products which can be reacted by free radicals such as trimethylolpropane mono- or diallyl ether (TMPMAE or TMPDAE) and 0 to 15 mol%, preferably 2 to 10 mol%, % Polyacrylates with one or more hydroxyl group (s) such as trimethylolpropane monoacrylate (TMPMA) and / or trimethylolpropane diacrylate (TMPDA) as an alcohol component and optionally also small amounts of crosslinking agents such as trimethylolpropane (TMP) and / or pentaerythritol (PER) be condensed. These hydroxyl group-containing polyacrylates can also be used in a mixture with the UPE lacquer system, the total hydroxyl group content of the UPE resins and their admixed crosslinking agents in the form of a) OH end groups together with b) the chain-middle-sized OH groups. Groups, for example from condensed TMP, are adjusted in comparison to the acid components used in such a way that UPE resins with OH end groups are formed in principle and also the content of reactive OH groups including these end groups) of the UPE system at 1 to 15 mol%, preferably 1 to 10 mol%, in particular 1 to 5 mol%.

When using condensable unsaturated compounds to provide the post-curable double bonds for the UPE systems, TMPDA, TMPMA and TMPDAE are preferred, as is TMPMAE, and TMPDAE is particularly preferred.

It is also possible to use unsaturated analogue polyester acrylates as UPE systems, ie as far as the content of reactive OH groups and double bonds is concerned. Both in the UPA and in the UPE, those resins are particularly preferred in which the copolymerization or the condensation of the comonomer, which is intended to provide the radically post-curable double bonds, takes place in such a way that these monomers are used in the preparation of the UPA or UPE resin are only added when oligomers of a certain chain length have already formed from the other comonomers, so that the ACDB comonomers are statistically uniformly distributed over the UPA or UPA molecule chains.

Products in which the ACDB comononomers in the production of the UPA or UPE resins using the kinetics in their production only after 20% to 40% of the total for the polymerization or polycondensation of the resin are particularly preferred the desired final molecular weight total reaction time required can be added. The addition of the ACDB comonomers after 20-50% of the total reaction time is particularly preferred.

UPA systems are preferred, in particular pure UPA systems.

The 2-component UPA or UPE lacquer which is based on these UPA or UPE resins and is suitable according to the invention is a lacquer preparation which consists of a mixture of isocyanate (= component B) and component A (the UPA or . UPE system) exists. Component A is preferably a water-based paint system consisting of 40 to 80% by weight of water, preferably 40 to 60% by weight of water, in addition to 60 to 20, preferably 60 to 40% by weight of solid-forming agents, of which 0 to 60% by weight (ds 0 to 60x0.6 = 36% by weight based on total paint component A preparation) color pigments and / or UV stabilizers, in addition to 95 to 45% by weight based on total paint component A preparation) UPA or UPE -Resin and the rest of the usual stabilizers, dispersants, surface tension regulators and defoamers, viscosity regulators and leveling agents, as well as medium and high boilers common in coating technology. As a rule, the two paint components are only combined using the so-called pot life before processing.

In a preferred embodiment, they are only brought together with intimate mixing when applied to the substrate to be coated.

In a further embodiment, it is also possible to use coating resins as described above in a mixture with 1-50 mol%, preferably 1-30 mol%, based on the average monomer unit of the coating resin polymer, acrylic monomers such as, in particular, butyl acrylate, or 2-ethylhexyl acrylate, DMPDDA, tBuEGDA or methyl methacrylate or mixtures thereof can be used as the total acrylic component 1 of the lacquer.

To initiate the radical polymerization of the UPA or UPE, free-radical formers are added in customary amounts, preferably immediately before mixing the paint component A with the paint component B. These radical formers are selected depending on the desired light-off temperature. If the radical crosslinking is therefore to take place already during the post-drying, the light-off temperature of the radical formers is matched to the post-drying temperature. However, the radical crosslinking is preferably carried out in the third process step, namely during the pressing-on process, so that the starting temperature of the radical formers is above the post-drying temperature, but below the temperature during the pressing process. However, radical formers which show no yellowing when exposed to light are particularly preferred, that is to say aliphatic or cycloaliphatic compounds.

If the free-radical crosslinking reaction is already to be started during post-drying, then bis-azo-isobutyronitrile and tert-butyl-peroxy-2-ethylhexoate are selected for low post-drying temperatures. Di-cumyl peroxide, for example, is suitable for medium post-drying temperatures, or di-tert-butyl peroxide if crosslinking is desired only during pressing. The temperature dependency the radical initiation by such initiators is tabulated in the literature.

After the coating has been applied, the urethanization reaction, that is the reaction between the isocyanate groups and the hydroxyl groups of the polyacrylate, is cured again at temperatures above the starting temperature. The temperature range is preferably between 100 and 180 ° C, in particular between 110 and 150 ° C.

The post-reaction and drying temperature set is advantageously chosen so that on the one hand the formation of vapor bubbles is avoided and on the other hand the methylol groups from the aminoplast and the isocyanate groups are converted as quickly and completely as possible.

The decorative films obtained in this way are aminoplast / urethanaminoplast or phenoplast / urethanphenoplast impregnated carrier materials.

They are readily storable and stackable and can be processed further immediately after manufacture or only after prolonged storage. Storage at room temperature is preferably not longer than 6 weeks, particularly preferably not longer than 14 days.

The air humidity during storage should preferably not be above 60% rel.LF for a long time, especially not above 50% rel.LF.

In the third process step, the single film of the prefabricated coating system is applied to the core layer to be coated, which can be, for example, a laminate, particle board or wood fiber board, in a manner known per se, that is at temperatures of at least 80 ° C., preferably at temperatures between 110 and 200 ° C and at pressures of at least 5 bar, preferably at least 10 bar, in particular at least 25 bar and a pressing time, which is preferably in the range of 30 seconds and 10 minutes. The minimum pressing time to be used should be observed using the following formula, depending on the selected pressing temperature: The minimum pressing time is mintp i ⁿ seconds after: a min ^ n - m + b + T

with the parameters: m = - 600 b = -70 a = - 67,500

The invention is illustrated by the following examples:

Example 1:

An impregnable carrier paper of 100 g / m ² (bleached with sodium kraft paper) is mixed with an aqueous (50% by weight solids content) melamine-formaldehyde resin (molar ratio HCHO: melamine = 2.5: 1) on a continuous impregnation system to a resin content of 100 g / m ² impregnated based on solid resin and in a suspension dryer at a temperature of 110 ° C (dryer section: 6 m; belt speed: 9 m / min) to a residual water content of 12% by weight (determined by drying: 2 hours in Vacuum drying cabinet pre-dried at 80 ° C) and pre-condensed. The precondensed impregnate has an NCO titer (determined by the n-butylamine in back titration method) of 14 milliequivalents NCO / m ² .

In a next station of the impregnation / varnishing machine, a 2-component acrylate varnish (UPA varnish) in the form of the premixed component A (consisting of UPA varnish resin + pigments + additives, everything in total) is immediately applied to the belt coming from the dryer in an aqueous dispersion with a total solids content of 50% by weight (including 20 parts by weight of pigments in addition to 5 parts by weight of dispersant and additives)) plus component B which is added to component A immediately before application (this is the isocyanate System).

The amount applied after urethanization is 75 g / m ² based on the content of the lacquer and solid. Since the radical crosslinking is only desired during the pressing process, the paint is applied immediately Mixing of components A and B 1% by weight di-tert-butyl peroxide based on the solids content (including paint resin content) added.

After applying the paint, the coated impregnate is fed into a dryer. This has the following temperature profile: 5m unheated exhaust zone + 6m floating dryer with 125 ° C + 6m floating dryer with 140 ° C. The throughput speed is 12m / min.

A residual water content of 5% by weight is set and the coated decorative film produced is then stacked.

A copolymer of 30 mol% 2HEA with 30 mol% EA + 15 mol% BA, 4 mol% HA, 5 mol% MMA and 5 ml% AS, and 1 mol% of DEGDA and 10 mol% AA is used as the coating resin. With a proportion of 45 parts by weight of paint resin in addition to 5 parts by weight of 2EHA monomer, a total of 25% by weight of acrylic component of the total solids content of paint component A is obtained.

The average molecular weight of the monomer unit of the polyacrylate is thus: pA ^M Mon ⁼ 112.3.

A trimeric hexamethylene diisocyanate with a molecular weight of M = 504.5 is used as component B, which has an NCO equivalent weight of equivalent ^M N _CO ⁼ 168.

1.26 kg of isocyanate are used as component B on 10 kg of lacquer component A.

The solids content of the paint component is 50% by weight, of which 20% by weight are pigments and a further 5% are additives. This results in 25% by weight - that is 2.5 kg of acrylic component. Of this, 45/50, namely 2.25 kg, account for UPA accordingly

1000x2.25 / _PA M _Mon = 2250 / 112.3 = 20.04 medium monomer units or according to the 30 mol% OH-containing monomer fraction 6.01 mols of hydroxyl groups. This paint component is now mixed with the isocyanate component directly on the paint application roller by means of a 2-component metering and a short turbo mixing section. With a choice of 15 (A = ^' 450; 15 = 450/30) mol% isocyanate excess (NIÜ) 6.01 x 1.15 x eq ^M NC _O ⁼ 6.01 ^{x 1} ' ^{15 x} l ⁶⁸ = 1/161 kg plus (SUIV = 1.3 g / m ² known from the determination of the expected isocyanate losses through side reactions), i.e. a total of 1161 + 1.3 g / m ² x (11300 g / 150 g / m ² ) = 1161 +97 g results in 1.26 kg isocyanate (component B).

In a final step, the hardened film is pressed in a short-cycle press onto a 10mm thick laminate consisting of phenolic resin-impregnated papers at a temperature of 150 ° C and a pressure of 30 bar for 6 minutes.

A decorative plate with a scratch resistance on the decorative side of 5 Newtons is obtained.

In the weathering test according to BAM (Federal Office for Materials Testing in Berlin), there were no visible surface or color changes even after 6 months.

On a section of the plate, the surface of which had first been sanded down 70 μm in steps, there were no visible changes after 1000 hours of the QUV test. On the partial surface where 80 μm had been sanded off, changes in color (graying) are only visible at individual points where the melamine resin substrate penetrated fully to the surface. However, based on these locations, no undermining of the neighboring zones in the lacquer layer could be demonstrated.

Example 2:

A procedure is carried out as in Example 1, except that a UPE lacquer is used instead of the UPA lacquer.

The resin base of this UPE lacquer is a mixture of 2 parts by weight of a UPE resin of the "UPE-LV" type in addition to a part by weight of a UPE resin of the "UPE-M" type. UPE-LV is characterized by the fact that it is a polycondensate composed of 51 mol FS (M = 116.07; ng _r = 51) with 30 mol DEG (M = 106.12) + 10 mol DPG (M = 134, 17) + 2.3 mol PG (M = 76.09) + 8 mol TMPDAE (M = 214.30) + 1 mol TMP (M = 134.17; n _Gly = 51.3 *)). The average molecular weight of the acid fraction after elimination of condensate water is κond ^M Sr ⁼ 116.07-18 = 98.07. The average molecular weight of the "glycol" fraction after elimination of condensate water is κond ^M Gly ⁼ 127.66-18 = 109.66.

Thus the average molecular weight per monomer unit after elimination of condensate water (κond ^M MonEinh) is 103.9.

The OH surplus balance and the resulting number of end groups thus result in

Kond ^M Sr ⁺ Kond ^M Gly ( ⁿ Gly / ⁿ Sr) r ^ Gly * ^or - ⁿ Sr

LV ^M n ⁼ the moles ⁿ Gly / ⁿ Sr - 1 acid (or anhydride) or glycols used

98.07 + 109.66. (51.3 / 51) (including TMP as

= 2-valent alcohol

(51,3 / 51) - 1 with a third free OH group

= approx.35,000 (Pmittel ^{= 337} )

an average (number average) molecular weight for this product of 35,000. That means for every 35,000 g there are 2 mol of OH groups from the end groups plus the 1 / (51 + 51.3) = 0.98 mol% of OH groups from the TMP, d.s. 0.98 OH groups per 100 * 103.9 g, i.e. per 10390 g, or 3.3 OH groups per 35000 g, i.e. a total of 5.3 mol OH groups per 35000 g, corresponding to 0.15 OH per 1000 g UPE-LV. That is 1.57 mol% OH based on average monomer units.

UPE-M is characterized in that it is a polycondensate composed of 31 mol of MSA (M = 98.06) + 12 mol of PSA (M = 148, II) + 8 mol of THPSA (M = 152.14), that is n _Sr = 51, with 28 mol DEG (M = 106.12) + 20.9 mol PG (M = 76.09) + 5 mol TMP (M = 134.17), i.e. n _G ι _y = 53.9 .

This is the average molecular weight of the acid fraction after elimination of condensate, which in this case is due to the Use of pure acid anhydrides does not take place: κond ^M Sr ⁼ 118.3. The average molecular weight of the "glycol" fraction after elimination of condensate water is κond ^M Gly ⁼ 79.07.

Thus the average molecular weight per monomer unit after elimination of condensate water is: Kond ^M MonEinh ⁼ 98.2.

An average (number average) molecular weight for this product thus results from the OH excess balance and the resulting number of end groups

_M M _n = d. 3,500 (P mean = around 35). This means that there are 2 moles of OH groups per 3,500 g from the end groups plus the 5 / (51 + 53.9) = 4.77 mole% OH groups from the TMP, that is 4.77 OH groups per 100 * 98.7 g, that is per 9870 g or 1.69 OH groups per 3500 g, that is a total of 3.69 mol OH groups per 3500 g, corresponding to 1.05 OH per 1000 g UPE-M, that is 10.4 mol% OH based on average monomer units.

The entire UPE resin system thus had an average OH content of 4.5 mol%.

This lacquer resin mixture has (2 * 0.15 + 1 * 1.05) / 3 = 0.45 mol OH groups per 1000 g. Furthermore, as a resin base (binder) for the UPE varnish, a solids content of 50% by weight, half of which are resin content, the rest are pigments, dispersants and additives.

For 10 kg UPE lacquer component A, which thus contains 2.5 kg UPE resin, corresponding to 1.13 moles OH, component 2 is isophorone diisocyanate (IPDI; M = 222.28, that is

⁴ ) used. An excess of isocyanate (NIÜ) of 44 (A = 200; 44.4 = 200 / 4.5) mol% is used (1.13 * 1.44 * 111.14 = 180.9 g) and one separately determined SUIV = 2 g / m ² with 2 x 10200/150 + 181 = 317 g gross portion of component B.

Since radical crosslinking can be desirable even during the after-drying, 2% by weight of bis-a <-zo-isobutyronitrile, based on the solids and resin content, are added to the lacquer when components A and B are mixed. In a final step, the cured film was pressed in a short-cycle press onto a 10 mm thick laminate consisting of phenolic resin-impregnated papers at a temperature of 140 ° C and a pressure of 10 bar for 7 minutes.

A decorative plate with a scratch resistance on the decorative side of 2 Newtons is obtained.

On a section of the plate, from the surface of which 70 µm had first been sanded in steps, there were no visible changes after a 1000-hour QUV test. On the partial surface on which 80 μm had been ground off, changes in color such as graying can only be found at individual points where the melamine resin substrate penetrated fully to the surface. However, based on these points, no infiltration of the neighboring zones in the paint system was found.

Industrial applicability

The composite materials produced by the coating method according to the invention are particularly suitable as facade panels for outdoor use.

Claims

Claims: Claim 1:

Coating process by urethanization to form a three-component, three-zone, single-layer composite structure, characterized in that, in a 1st step, a hydroxyl group-containing polyacrylate, which contains unsaturated comonomers in the polymer chain, is formed on the carrier film consisting of carrier materials impregnated with isocyanate group-reactive aminoplast or phenoplast contains reactive double bonds even after copolymerization, or an unsaturated hydroxyl group-containing polyester is applied with a di- and / or poly-isocyanate, with a clear reduction at the boundary layer between aminoplast or phenoplast and hydroxyl group-containing polyacrylate or polyester Schung and mutual diffusion occurs and a stoichiometric excess of isocyanate component in the form of an NCO group excess relative to the existing NCO-reactive groups from the hydroxyl group-containing polyacrylate or polyester and possibly NCO consumption by side reactions is used, so that a chemical compound from the hydroxyl group-containing polyacrylate or polyester via the di- or polyfunctional-NCO component to the methylol groups of the amino plastic or phenoplast by forming Urethane groups are formed; that the free radical crosslinking of the double bonds in the unsaturated comonomer units in the hydroxyl group-containing polyacrylate or in the unsaturated hydroxyl group-containing polyester is effected in a second step and that in a third step the weather-resistant decorative layers obtained in this way is pressed in film form onto the core layer to be coated at a temperature and a pressure, as is usually set for the pressing of carrier materials with aminoplast or phenoplast-impregnated decorative films.

Claim 2:

Coating method according to Claim 1, characterized in that an aminoplast is used which is a melamine resin which is reactive with isocyanate groups and is still flowable at temperatures above 80 ° C, preferably above 100 ° C, preferably in an aqueous dispersion. Claim 3:

Coating method according to Claim 2, characterized in that the aminoplast resin, preferably a melamine-formaldehyde resin, and before application of the UPA or UPE lacquer system to a total residual water content of 5 to 25% by weight, preferably 10 up to 15% by weight is pre-dried.

Claim 4:

Coating process according to Claims 1 to 3, characterized in that a phenoplast is used which is a phenolic resin which is still reactive with isocyanate groups and is still flowable at temperatures above 80 ° C, preferably above 100 ° C, preferably in aqueous dispersion.

Claim 5:

Coating method according to one of Claims 1-4, characterized in that the aminoplast or phenoplast is precondensed only so little until the UPA or UPE isocyanate system is applied that it has an NCO titer of at least 3, preferably at least 6, in particular of at least 7 milliequivalents of NCO per square meter.

Claim 6:

Coating method according to one of claims 1-5, characterized in that the aminoplast or phenoplast up to

Application of the UPA or UPE isocyanate system is in any case precondensed to such an extent that it has an NCO titer of at most 25, preferably at most 20, in particular at most 15 milliequivalents of NCO per square meter.

Claim 7:

Coating process according to one of Claims 1-6, characterized in that the excess of isocyanate used is in accordance with the formula: Mol% NCO excess = A / mol% OH

is set, where A is a number between 20 to 500, preferably between 200 and 400, and wherein mol% OH means the hydroxyl group-containing polyacrylate or polyester content of OH groups reactive with isocyanate groups.

Claim 8:

Coating method according to one of claims 1 to 7, characterized in that an aliphatic and / or a cycloaliphatic di- or polyisocyanate is used as the isocyanate component.

Claim 9:

Coating method according to one of claims 1 to 7, characterized in that a compound is used as the di- and / or polyisocyanate component which releases or forms isocyanate groups at or just below the curing temperature, preferably selected from the group of aliphatic and / or cycloaliphatic isocyanates .

Claim 10:

Coating process according to one of claims 1-9, characterized in that in the unsaturated hydroxyl-containing polyacrylate monomers consisting of unbranched and / or branched alkyl acrylates and / or methacrylates, 5 to 40 mol%, preferably 15 to 35 mol% % Of hydroxyalkyl acrylates and 0.1 to 20 mol%, preferably 2 to 10 mol%, of unsaturated conomers (ACDB comonomers) built into the polymer chain with double bonds which are still reactive even after polymerisation into the polyacrylate. Claim 11:

Coating method according to one of Claims 1 - 10, characterized in that the ACDB comonomers are those which, after incorporation into the polyacrylate, no longer have any free or unblocked acrylic and / or methacrylic double bonds.

Claim 12:

Coating method according to one of claims 1 to 11, characterized in that the hydroxyl group-containing polyacrylate is water-dispersible by incorporating suitable comonomers, it preferably containing 2 to 10 mol%, in particular 2 to 6 mol%, acrylic acid and / or methacrylic acid.

Claim 13:

Coating method according to one of Claims 1 to 12, characterized in that the polyacrylate containing hydroxyl groups contains 0.1 to 20 mol% of radically crosslinkable comonomers.

Claim 14:

Coating method according to one of claims 1 to 13, characterized in that the hydroxyl-containing polyacrylate contains up to 30 mol%, preferably up to 10 mol%, of copolymerizable comonomers, preferably styrene.

Claim 15:

Coating method according to one of claims 1 to 9, characterized in that the unsaturated polyester containing hydroxyl groups is a polyester consisting of radically polymerizable dicarboxylic acids and / or their anhydrides, in addition to portions of non-radically polymerizable dicarboxylic acids or their anhydrides and dihydric alcohols with one portion of hydroxyl groups (including the end groups) from 1 to 15 mol%, preferably from 1 to 10 mol%, in particular from 1 to 5 mol%, of OH groups reactive with isocyanate groups is used. Claim 16:

Coating method according to claim 15, characterized in that the hydroxyl group-containing unsaturated polyester contains up to 15 mol%, preferably 2 to 10 mol%, of two or more hydroxyl group-containing polyacrylates condensed.

Claim 17:

Coating method according to claim 15 or 16, characterized gekenn¬ characterized in that the hydroxyl-containing unsaturated polyester contains 1 to 10 mol%, preferably 2 to 6 mol% of free-radically post-reactive alcohols condensed.

Claim 18:

Coating process according to one of claims 14 to 17, characterized in that the hydroxyl-containing unsaturated polyester contains small amounts, preferably 0.1 to 2 mol%, of crosslinking agent.

Claim 19:

Coating method according to one of claims 1 to 18, characterized in that the aminoplast or phenoplast is present in the B state in the impregnated carrier material, which is preferably a decorative paper.

Claim 20:

Coating method according to one of claims 1 to 19, characterized in that the hydroxyl group-containing polyacrylate or the hydroxyl group-containing unsaturated polyester system is applied in the form of a lacquer preparation which consists of a mixture of isocyanate (= Component B) and component A of the hydroxyl group-containing polyacrylate or hydroxyl group-containing unsaturated polyester system, which consists of 40 to 80% by weight of water, preferably 40 to 60% by weight of water, in addition to 60 to 20% preferably 60 to 40% by weight of solids, of which 0 to 60 % By weight of color pigments and / or UV stabilizers are, in addition to 95 to 45% by weight, preferably 57 to 18% by weight, based on the overall paint preparation of hydroxyl-containing polyacrylates or hydroxyl-containing unsaturated polyester resins and those for Lacquer technology contains usual additives.

Claim 21:

Coating method according to one of Claims 1 to 20, characterized in that the hydroxyl-containing polyacrylate or the hydroxyl-containing unsaturated polyester is obtained in solution or in a mixture with 1 to 50 mol%, preferably 1 - 30 mol%, of unsaturated monomers is used on the middle monomer unit of the hydroxyl-containing polyacrylate.

Claim 22:

Coating method according to claim 21, characterized in that the unsaturated monomers are low molecular weight acrylates and / or methacrylates, preferably Cl to C8 alkyl acrylates, or styrene or TMPDA and / or DMPDAA.

Claim 23:

Coating process according to one of Claims 1 to 22, characterized in that unsaturated polyesters containing hydroxyl groups are used whose content of unsaturated comonomers (ACDB comonomers) is only from 20 to 60%, preferably only from 20 to 40%, of that required to achieve the desired reaction time required molecular weight.

Claim 24:

Coating process according to one of Claims 1 to 23, characterized in that the radical post-crosslinking is triggered by radical formers which are added to the coating preparation immediately before the isocyanate component is added. Claim 25:

Coating method according to one of claims 1 to 24, characterized in that the decorative layers are pressed onto the

Core layer at temperatures of over 80 ° C, preferably between 100 and 200 ° C and at pressures of at least 4 bar, preferably at least 10 bar, in particular at least 15 bar, and that a pressing time is set which is in degrees from the pressing temperature T used Celsius according to the formula

a mintp = ro + seconds b + T

depends, where m = - 600 a = - 26,500 and b = - 70.