EP0824560A1 - Process for producing an ornamental, weather-resistant moulding section - Google Patents

Abstract

The invention relates to a coating process by urethanization allowing 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 radiation hardening.

Description

 Process for producing a weatherproof, decorative molded part

Technical field

The invention relates to a method for producing a decorative molded part comprising a core layer and weather-resistant decorative layer (s) surrounding it on one or both sides.

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 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 with a longer reaction time with the condensation agent, which is usually formaldehyde, do these intermediates react to form highly crosslinked end products (so-called “duroplasts”). Despite high crosslinking, the triazine system of the melamine resin component tends to hydrolysis during weathering

Hydrolysis end product of cyanuric acid. 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 (Foliei phase boundary

(Layer boundary)

/ NH-CH ₂ OCH2

C = abbreviated: Layer 1 = Aminoplast NN -NHCH 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 (known as a 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 chemical composition of the two layers is uniform throughout, namely on the one hand the aminoplast or phenoplast impregnating 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 aminoplast resins as coating mixtures for producing an outermost radiation-curable layer. This creates a single-layer coating system consisting of two or more resins, which is shown in a sketch as follows:

1 zone

Mix of:

a) - (CH ₂ -CH-) _n b)

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

Particle phase boundary ( ^~ Substance 2)

However, since cured aminoplast resins and polymerized acrylic resins are not miscible with one another, the coating under the microscope shows a uniform layer which consists of two phases in which one polymer is more or less finely dispersed in the other polymer, but with clear, sharp phase boundaries on its particle surfaces are delimited from the matrix polymer in which it is embedded. Such mixtures, however, do not add up the desired properties of the mixture components, so that the finished products essentially only the bad ones

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 crosslinks the acrylate oligomer layer, while the aminoplast layer, which is separated by a sharp phase boundary, condenses into a thermosetting plastic after pressing. In a preferred embodiment of this process, any pigmentation or decoration is already indicated in the amino-plast undercoat, while only an unpigmented and thus easily non-porous clearcoat is used as the acrylate topcoat. Such a system - as explained in more detail by the following sketch - shows weathering, in particular with slight irregularities in the topcoat layer, an undermining at the only physically connected boundary layer between the aminoplast base and the topcoat. 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 ₂ -CH

COOR

0

0 = C and or -R'-CH = CH ₂

Mandatory free from:

-NHCH, OCH NH crosslinker residue

Phase boundary

(Layer boundary)

Aminoplast or. Phenolic layer

Layer 1

Respectively. the crosslinking products resulting therefrom by radiation curing.

Due to the pressing process, depending on the local elasticities and deformability of the two layers lying on top of one another, 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 (i.e. the two separate ones) Phases mesh with each other like gears). Satisfactory weather properties and also significantly improved scratch resistance of up to 7 N are achieved with the above-mentioned processes.

But this method also has the disadvantage that only a physical cover film adhering physically to the phenolic or aminoplast-impregnated backing paper underlayer is applied, 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.

The object of the invention is now to provide a method of the type mentioned at the outset, in which the technical advantages of the individual resin systems such as the aminoplasts or phenoplasts for decorative paper impregnation and those of the acrylates for the outermost protective layer are retained and, in contrast to those Conventional processes between aminoplast or phenol plastic and the acrylate or polyester form an intimate chemical bond in the form of a reaction product of the two.

Presentation of the invention

According to the invention, a process of the type mentioned is proposed, which is characterized in that in a 1st step onto the backing layer consisting of backing materials impregnated with isocyanate group-reactive aminoplast or phenoplast, a hydroxyl group-containing polyacrylate containing incorporated unsaturated comonomers in the polymer chain, with the exception of those with free or unblocked acrylic and / or methacrylic double bonds (abbreviated UPA) or an unsaturated hydroxyl-containing polyester (abbreviated UPE) with a di- and / or poly-isocyanate, with the boundary layer between aminoplast or phenoplast and hydroxyl group-containing polyacrylate or polyester, a clear mixing and mutual diffusion occurs and a stoichiometric excess of isocyanate component in the form of an NCO group overshoot relative to the existing NCO-reactive groups from the hydroxyl group-containing polyacrylate or polyester and possible 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 Aminoplasts or phenoplasts are formed by the formation of urethane groups); that the free radical, radiation-induced post-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 in the weatherproof decorative layers thus obtained Film shape is pressed onto the core layer to be coated at a temperature and pressure, as is usually set for the pressing of carrier materials with aminoplast or phenoplast-impregnated decorative films.

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

In addition, in the process according to the invention, a system is built up which, in addition to the carrier material, consists of the following substances: 1 = first not cured aminoplast or phenoplast (also called "B-state resin"), which has isocyanate-reactive methylol groups (abbreviated below) plus substance 2 = isocyanate-crosslinkable UPA or UPE and substance 3 = reaction product of aminoplast or phenoplast-methylol groups and excess isocyanate groups from the UPA or UPE-isocyanate crosslinker addition product, which - after basically only at least di-functional isocyanates and these in a stoichiometric excess to the OH groups present from the UPA or UPE are already chemically anchored to the UPA or UPE resin residue, and which 3 substances are used among each other Reaction brings, so that at least in the middle mixing and inter-diffusion layer also a new substance, of the type of a urethane aminop loads, or urethane phenoplasts.

Sketch to illustrate the Svstem principle:

Zone 1 urethane acrylate

Transition 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, this method uses a new, third component as a chemical Connection component brought into play, namely substance 3, a urethane aminoplast or a urethane phenoplast, namely the reaction product mentioned from 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 fluid transition in the former composition from the pure aminoplast or phenoplast to the pure urethane acrylate is achieved. The three zones mentioned mesh with one another like gearwheels, but are welded together.

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

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

| | | unsaturated hydroxy polyesters) COOR COORi-O * ⁾ R ² -CH = CH ₂

\

C = 0 or their radical / crosslinking products

HN * ⁾ hydroxyacrylate residue

\ ** ⁾ rest of d. Crosslinker

R ^ ** ⁾ -Di or. Polyisocyanate

/ ***) rest of the aminoplast B-HN state methylol groups

\

/ -NH-CH ₂ 0 *** ⁾ 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, analogously to conventional aminoplast or phenoplast-impregnated decorative papers, which is chemically only a single coating Outer layer can be defined. 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 μm 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 radical radiation-induced crosslinking products (all 3 areas a, b, c = zone 2), up to the outer zone - but none represents a separate layer - one that is also radically networked UPA or UPE (= Zone 3).

By means of 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 matter, which can only be determined spectroscopically on the basis of their gradually varying former composition, naturally do 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 before 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.

Such products therefore differ fundamentally from the products of the prior art, in which only ever different the substances are 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 also other substances, such as the radical-induced crosslinked urethane aminoplasts or Urethane phenoplasts are present. Accordingly, such products show even when the surface is sanded to such an extent that the outermost zone has partially been completely removed, and the underlying urethane aminoplast-urethane or urethane phenolic, or even partially except for the purely lowest aminoplast or phenoplastic. Removed layer, surprising weathering properties: In those places where sanding was made except for the pure urethane aminoplast or urethane phenoplast zone, the weathering properties were still significantly improved than with normal aminoplast surfaces, and even in those places where too the urethane aminoplast or urethane phenolic zone was ground away, although the usual susceptibility to weathering of the aminoplastic or phenolic surfaces, but no undermining at the limits where urethane aminoplast UPA or urethane phenolic 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 mixed with isocyanate groups are reactive and are still flowable at temperatures above 80 ° C., preferably above 100 ° C.

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 pre-condense the aminoplast resin, preferably a melamine-formaldehyde resin, before applying the UPA or UPE lacquer system to a total residual water content of 5 to 25% by weight, preferably 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 precondense the aminoplasts or phenoplasts with which the

Carrier material has been impregnated 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.

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 stoichiometric requirement of the UPA or UPE system for (with isocyanate groups) reactive groups, preferably whose hydroxyl groups, expressed in mol% OH, plus b) the isocyanate loss to be calculated in and determined in a preliminary test (see below) by side reactions such as hydrolysis among the

Reaction conditions and c) the "significant NCO excess" according to the invention, i.e. the excess of - after the aforementioned reactions with the UPA or UPE system and possible 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 process, brought to the process reaction temperature and then the remaining isocyanate excess is added, for example titrated back using the di-n-butylamine method. The NCO loss results from the difference between the NCO consumption on the shock-dried sample and an undried sample due to 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 time.

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 mixture as provided later on the applicator roller / trough, the isocyanate loss is determined by side reactions in the coating system.

Basically, the total amount of isocyanate to be used according to the invention then results from a) the stoichiometric 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 be used which can release or form isocyanate groups at or just below the curing temperature. 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, customary urethanization catalysts can be added, preferably immediately before applying UPA or UPE lacquer, such as triethylenediamine (TÄDA), dimethalaminoethyl morpholine (XDM) - so-called DABLOs - or dibutyltin dilaurate, etc. .

The UPA to be used according to the invention are hydroxyl group-containing polyacrylates containing unsaturated comonomers, with the exception of those with free or unblocked acrylic and / or methacrylic double bonds. Branched and unbranched alkyl acrylates and / or come as monomers for the polyacrylate

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-containing acrylates such as 2-hydroxyethyl acrylate (2 HEA) in an amount of 5 up to 40 mol% of OH groups, preferably 15 to 35 mol% of OH groups, based on the average monomer unit, are copolymerized, and moreover - to provide radiation-curable double bonds - with mono- or polyunsaturated monomers of the so-called "after-curable" type -double-bounds "comonomers (ACDB comonomers) copolymer are based. 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 proportions 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, 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 the methacrylates, in particular the MMA, in the acrylic components cause glassier topcoat films and thereby lead to a certain embrittlement, they are particularly preferred in rather minor amounts, in particular only in the range from 0 to 10 mol% used in the range of 1-5 mol%. The longer the longer-chain alkyl radicals are, the more flexible or elasticizing the alkyl acrylates are. The appropriate mechanical property of the coating can thus be adjusted or the embrittlement or stress crack formation avoided by appropriate combination of the monomers 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 Incorporate 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 and having a similar radiation-induced 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 safely available for radiation-induced 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 chosen.

When using comonomers to provide post-curable double bonds of the type of mono- or polyunsaturated compounds with double bonds of similar reactivity as To avoid undesirable premature crosslinking, TMPDAs tend to have low proportions, that is to say in the range from 0.1 to 5 mol%, preferably 1 to 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 radically or by radiation, such as trimethylolpropane mono- or dialyl ether (TMPMAE or TMPDAE), and 0 to 15 mol%, preferably 2 up to 10 mol% of polyacrylates with one or more hydroxyl group (s) such as trimethylolpropane monoacrylate (TMPMA) and / or trimethylolpropane diacrylate (TMPDA) as the alcohol component and optionally also small amounts of crosslinking agents such as trimethylolpropane (TMP) and / or pentaerythritol ( PER) can 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-centered OH groups for example from condensed TMP in comparison to the acid components used, so 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 is 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 TMPDA, TMPMA and TMPDAE and TMPMAE are preferred for the UPE systems, and TMPDAE is particularly preferred.

It is also possible that unsaturated analog, i.e. As far as the content of reactive OH groups and double bonds is concerned, polyester acrylates are used.

Both the UPA and the UPE are particularly preferred resins in which the copolymerization or the condensation of the comonomer, which is intended to provide the radiation-curable double bonds, is carried out 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 60% 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 20-40% 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 usual stabilizers, dispersants, surface tension regulators and defoamers, viscosity regulators and flow control 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 central monomer unit of the coating resin polymer, acrylic monomers such as, in particular, butyl acrylate, or 2-ethylhexyl acrylate, or methyl methacrylate or their

Mixtures can be used as the total acrylic component 1 of the lacquer.

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 post-cured at temperatures above the light-off 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 are converted as quickly and completely as possible with the isocyanate groups.

The urethanized UPA or UPE system on the aminoplast or phenoplast-impregnated carrier material, hereinafter referred to as the primary film, is / are radically crosslinked. This crosslinking can also take place during the urethanizing lacquer hardening, in that the lacquer is hardened by blasting. For example, UV rays can be used as the radiation source in a manner known per se so-called UV sensitizers such as IRGACURE, ESACURE or DAROCURE from CIBA-GEIGY are added to the varnish for UV curing. The curing reaction in the coating system can also be triggered by an electron beam.

The decorative films obtained in this way are aminoplast / urethanaminoplast or phenoplast / urethanphenoplast impregnated carrier materials. They are easy to store and stack and can be used immediately

Production or can only be further processed after long 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 coating system thus prefabricated as the only film 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 to say at temperatures of at least 80 ° C. , preferably at temperatures between 110 and 200 ° C. and at pressures of at least 5 bar, preferably of at least 10 bar, in particular of 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 mintp results ⁱⁿ seconds after: a mintp ^{= 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 backing paper of 100 g / m ² (bleached 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 back titration method) of 14 milliequivalents NCO / m ² .

A 2-component acrylate varnish (UPA varnish) in the form of premixed component A (consisting of: UPA varnish resin + pigments + additives) in total is immediately applied to the belt coming out of the dryer in a next station of the impregnation / coating machine all in 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 dispersing agents and additives)) plus component B, which is added to component 1 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.

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. 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 mol% 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 lacquer component A.

The average molecular weight of the monomer unit of the polyacrylate is thus: PA ^M M _OΠ ⁼ 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 Eq ^M NCO ⁼ 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. 45/50, namely 2.25 kg, of UPA correspond to 1000x2.25 / pA ^M Mon ⁼ 2250 / 112.3 = 20.04 medium monomer units or 6.01 moles hydroxyl groups according to the 30 mol% OH-containing monomer part . 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 NCO ⁼ 6/01 ^x l ⁵ * 168 = 1.161 kg plus ( from the determination of the expected isocyanate losses through side reactions known SUIV = 1.3 g / m2), that is a total of 1161 + 1.3 g / m ² χ (H300g / 150g / m ² ) = 1161 + 97 g, 1 26 kg isocyanate (component B).

The stacked film is subjected to electron beam curing at 200 kV in a separate process step.

In a final step, the film, hardened by means of electron beams, is pressed in a short-cycle press onto a 10mm thick laminate made of phenolic resin-impregnated papers at a temperature of 150oC and a pressure of 30 bar for 5 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, starting from these points, no undermining of the neighboring zones in the lacquer layer was detectable.

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 varnish is a mixture of 2 parts by weight of a UPE resin of the type "UPE-LV" in addition to one part by weight of a UPE resin of the type "UPE-M".

UPE-LV is characterized in that it is a polycondensate composed of 51 mol FS (M = 116.07; n _Sr = 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 component after elimination of condensate water is Kond ^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 (Kond ^M MonEinh) is 103.9.

The OH surplus balance and the resulting number of end groups thus result in Kond ^M Sr + Korid ^M Gly ⁽ⁿ Gly ⁿ Sr ⁾ nGly * ^ ^or - ⁿ Sr

LV ^M n ⁼ the moles ⁿ _G lγ / ⁿ Sr ~ 1 acid used

(or also anhydride) or glycols 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 (P ittel ^{= 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 .

Thus the average molecular weight of the acid fraction after elimination of condensate water, which in this case does not take place due to the use of pure acid anhydrides, is: κond ^M _S r ⁼ 118.3.

The average molecular weight of the "glycol" fraction after elimination of condensate water is Kond ^ Gly ⁼ 79 ⁿ⁷ -

Thus the average molecular weight per monomer unit after elimination of condensate water _is : κon _d ^M _M onEin _h ⁼ 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. 3500 _(m edium P = approx. 35). That means for every 3,500 g there are 2 mol of OH groups from the end groups plus the 5 / (51 + 53.9) = 4.77 mol% of 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, i.e. 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 paint resin mixture has (2 * 0, 15 + 1 * 1.05) / 3 = 0.45 mol OH groups per 1000 g and is used as the resin base (binder) for the UPE paint with a total solids content of the paint of 50% by weight, half of which is resin, the rest being pigments, dispersants and additives; the rest on 100% paint component A is water.

For 10 kg UPE paint component A, which thus contains 2.5 kg UPE resin, corresponding to 1.13 moles OH, component B is isophorone diisocyanate (IPDI; M = 222.28, that is ⁱ ) 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 share of component-B.

1.5% by weight of Irgacure 651 solid and 1% by weight of Irgacure 184 from CIBA-GEIGY are added to the coating preparation as UV sensitizers.

Immediately after the lacquer has been applied, the film is subjected to UV radiation with 6 pieces of 200 W lamps at a throughput speed of 6 m / min.

In a last step, the cured film was pressed in a short-cycle press onto a 10 mm thick laminate consisting of phenol 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.

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 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.

Commercial usability

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:

A process for the production of a decorative molded part comprising a core layer and weather-resistant decorative layer (s) surrounding it on one or both sides, characterized in that in a first step onto the carrier film consisting of carrier materials impregnated with isocyanate group-reactive aminoplast or phenoplast, containing a hydroxyl group-containing polyacrylate incorporated in the polymer chain unsaturated comonomers, with the exception of those with free or unblocked acrylic and / or methacrylic double bonds or an unsaturated hydroxyl group-containing polyester with a di- and / or poly-isocyanate, with the boundary layer between aminoplast or phenoplast and Hydroxyl group-containing polyacrylate or polyester a significant mixing and mutual diffusion occurs and a stoichiometric excess of isocyanate component in the form of an NCO

Excess group relative to the existing NCO-reactive groups from the hydroxyl-containing polyacrylate or polyester and possible NCO consumption by side reactions is used so that a chemical compound from the hydroxyl-containing polyacrylate or polyester is used the di- or polyfunctional-NCO component on the methylol groups of the aminoplast or phenoplast is formed by the formation of urethane groups; that the free radical, radiation-induced post-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 Foil form on the core layer to be coated at a temperature and a pressure, as is customary for the pressing of carrier materials with aminoplast or

Phenoplast-impregnated decorative films are set, pressed on.

Claim 2:

Coating process according to claim 1, characterized in that an aminoplast is used which preferably is a reactive with isocyanate groups at temperatures above 80 ° C above 100 ° C. is still flowable melamine resin, 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.

Claim 4:

Coating process according to claim 1, characterized in that a phenoplast is used which is a phenolic resin which is still reactive with isocyanate groups and which 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:

Urethane aminoplast, characterized in that an only partially fully reacted aminoplast, preferably one according to claims 5 and 6, is reacted with di- and / or polyfunctional isocyanates in the presence of a hydroxyl-containing UPA or UPE resin, a stoichiometric excess of isocyanate is used according to claim 7 and the double bonds of the UPA or UPE resin are induced by free radical polymerization.

Claim 9:

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 10:

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 11: Coating process according to one of Claims 1-7, characterized in that in the hydroxyl-containing polyacrylate monomers consisting of Cl to C8 alkyl acrylates and / or methacrylates, 5 to 40 mol%, preferably 15 to 35 mol% Hydroxyalkyl acrylates and 0.1 to 20 mol%, preferably 2 to 10 mol% unsaturated conomers (ACDB comonomers) are excluded those with free or unblocked acrylic and / or methacrylic double bonds are present.

Claim 12:

Coating method according to claim 11, characterized in that the hydroxyl group-containing polyacrylate is water-dispersible by incorporating suitable comonomers, it preferably containing 5 to 10 mol%, in particular 2 to 6 mol%, acrylic acid and / or methacrylic acid.

Claim 13:

Coating method according to claim 11 or 12, characterized in that the hydroxyl group-containing polyacrylate contains 0.1 to 20 mol% of radically crosslinkable comonomers.

Claim 14:

Coating process according to claims 11 to 13, characterized in that the hydroxyl-containing polyacrylate contains up to 30 mol%, preferably up to 10 mol%, of copolymerizable comonomers, preferably styrene, or tripropylene glycol diallyl ether (TPGDA).

Claim 15:

Coating method according to one of Claims 1-7, characterized in that the unsaturated polyester containing hydroxyl groups is a polyester consisting of free-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-containing unsaturated polyester up to 15 Mol%, preferably 2 to 10 mol% contains two or more hydroxyl-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% condensed radicals or radiation-induced post-reactable alcohols.

Claim 18:

Coating process according to one of Claims 15 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 7 or 9 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 process according to one of Claims 1 to 7 or 9 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 preparation which is as immediate as possible the mixture prepared from the application 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 formers, 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 total paint preparation from hydroxyl groups -containing polyacrylates or hydroxyl groups-containing unsaturated polyester resins as well as the additives and medium and high-quality additives commonly used in coating technology hsiedern contains. Claim 2 1:

Coating method according to one of claims 1 to 7 or 9 to 20, characterized in that the hydroxyl-containing polyacrylate or the hydroxyl-containing unsaturated polyester in solution or in a mixture with 1 to 50 mol%, preferably 1 - 30 mol% unsaturated monomers based on the average monomer unit of the hydroxyl-containing polyacrylate is used.

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.

Claim 23:

Coating process according to one of Claims 1 to 7 or 9 to 11 or 14 to 22, characterized in that unsaturated polyesters containing hydroxyl groups are used whose unsaturated comonomer content (ACDB comonomers) is preferably only from 20 to 60% can only be condensed in from 20 to 40% of the reaction time necessary to achieve the desired final molecular weight.

Claim 24:

Coating method according to one of claims 1 to 7 or 9 to 23, characterized in that the radical post-crosslinking is triggered by UV radiation, customary UV sensitizers being added to the paint preparation.

Claim 25:

Coating method according to one of Claims 1 to 7 or 9 to 23, characterized in that the radical post-crosslinking by electron beam curing at conventional accelerator voltages appropriate to the coating thickness to be cured, preferably from 100 to 300 kV, in particular from 150 to 250 kV takes place. Claim 26:

Coating method according to one of Claims 1 to 7 or 9 to 25, 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 of at least 15 bar, and that a pressing time is set which is from the applied pressing temperature T in degrees Celsius according to the formula a mintp = m + seconds b + T

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