Uv-active binding agent

ES 2 285 263 T3

DESCRIPTION

UV-active binding agent.

The invention relates to a process for the preparation of radiation-curable and / or dual cure poly (meth) acrylates, to the poly (meth) acrylates themselves, to their use as components in the production of dispersions or as components in lacquer formulations, to lacquer formulations containing the poly (meth) acrylates according to the invention and to a process for the production of the formulations and their use.

Dual cure and UV curable poly (meth) acrylates are especially interesting for use in top coatings. In general, poly (meth) acrylates have excellent stability against outdoor exposure. In combination with a UV curing technique additional benefits can be achieved. For example, the scratch resistance of the coating can be significantly increased and thereby improved coating results. However, especially important improvements are achieved in the application of the coating materials, in particular very fast drying. This property is decisive for a fast processing technique.

According to the current state of the art, UV-curable polyacrylates are subjected to a polymerization reaction with glycidyl methacrylate and subsequent thermal reaction with acrylic acid in the presence of a catalyst (DEA 2 436 186, EP-A- 0 650 978) . A disadvantage of this state-of-the-art preparation method is due to the side reactions and color deterioration that occurs during it. Due to the conditions under which the reaction is carried out, in particular high temperatures, it is absolutely necessary to use stabilizers to avoid radical polymerization of the acrylic acid used.

Poly (meth) acrylates having hydroxy functional side chains cannot be subjected to conventional acid esterification with acrylic acid because the ester linkages of the poly (meth) acrylate are dissociated in this process.

In the current state of the art, the functionalization of polymeric compounds with (meth) acrylic acid and / or its esters is known.

Documents EP-A 0 999 230 and EP-A 0 999 229 relate to processes for the preparation of (meth) acrylic acid esters of hydroxy functional siloxanes and / or of polyalkylene ('230) modified siloxanes and also of polyoxyalkylenes ('229), by esterification or transesterification of siloxanes or polyoxyalkylenes with (meth) acrylic acid and / or its esters in the presence of enzymes. However, according to EP-A 0 999 230 and EP-A 0 999 229, only said special polymers react with (meth) acrylic acid and / or its esters. No reaction is mentioned for poly (meth) acrylates.

E. Marechal et al., Polymer Bulletin 26, 55-62 (1991), refers to the transesterification of oligo (methacrylates) presenting end ester groups with allyl alcohol in the presence of lipase. Transesterification only occurs at the end groups.

H. Ritter et al., Polymer Bulletin 21, 535-540 (1989), refers to lipase-catalyzed acetylation of OH group-containing methacrylic acid polymers. Acetylation takes place in the presence of vinyl acetate. An excellent leaving group is obtained by reaction with vinyl acetate and the formed aldehyde can be easily separated from the reaction mixture. However, the reaction takes 2 to 15 days.

H. Ritter et al., Makromol. Chem. 193, 323 to 328 (1992), refers to the enzymatic catalyzed acylation of comb-like methacrylic acid polymers containing OH groups with active esters, such as vinyl acetate, phenyl acetate, 4-fluorophenyl acetate and phenyl stearate. The esterification of polymers with acrylates is not mentioned. The reaction according to Ritter et al. it has a long duration (2, 4 and 6 days).

The aim of the present invention is to present a careful and selective process for the preparation of poly (meth) acrylates functionalized with (meth) acrylic acid or with (meth) acrylates which, compared to the known preparation process that starts from methacrylate glycidyl, can be based on cheaper starting substances and is more variable, and has a more careful preparation, so that new poly (meth) acrylates substituted with (meth) acryl groups can be accessed.

This objective is solved by a process for the preparation of poly (meth) acrylates curable by UV and / or dual cure that includes the following steps:

a) Preparation of poly (meth) acrylates having hydroxy functional side chains by polymerization of

ES 2 285 263 T3 aa) at least one (meth) acrylate of general formula (I), as component A

R¹

Λ⁰'.

Or where

R¹ means H, CH₃ or CH₂Oh, and

R² is an alkyl or cycloalkyl group, optionally substituted with functional groups such as acryl, ether, amino, epoxy, halogen or sulfonic acid groups, preferably an alkyl group (C₁C₁₈), especially an alkyl group (C₁-C₈), most preferably an alkyl group (C₁C₈) unsubstituted with functional groups, in particular a methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, 2-ethylhexyl, tert-butyl, cyclohexyl, tert-butylcyclohexyl, isobornyl or trimethylcyclohexyl group; and ab) at least one hydroxyalkyl (meth) acrylate of general formula (II), as component B r 'or

where

R¹ means H, CH₃ or CH₂Oh, and

R³ means - (CH₂) _n-, -CH₂-CH (CH₃) -CH₂- or -CH₂CH (CH₃) - or -CH (CH₃) CH₂- or - CHj— ©) -CHj— • where n is at least 2, preferably 2 to 8, especially 2 to 6, most preferably 2 to 4, the hydroxyalkyl (meth) acrylate of the general formula being selected (II), in particular, from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate or hydroxybutyl (meth) acrylate; and ac) where appropriate other comonomers copolymerizable with the (meth) acrylates of general formulas (I) and (II), as component C, preferably selected from the group consisting of styrene, acrylonitrile, vinyl acetate, nitrile propionate, vinyl chloride, vinylidene chloride, butadiene and glycidyl group addition products of Versatic acid and unsaturated acids, in particular (meth) acrylic acid; and ad) optionally auxiliary monomers as components D, preferably selected from the group consisting of (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and the amides of said acids;

^Y

b) transesterification or esterification of poly (meth) acrylates having hydroxy functional side chains with a (meth) acrylate or with (meth) acrylic acid, preferably with methyl, ethyl, 2-ethylhexyl or butyl (meth) acrylate, given the case in the presence of stabilizers selected from the group consisting of 2,6-dibutylphenols such as di-tert-butylphenol, p-cresol, hydroquinone, dimethylhydroquinone, phenothiazines and phosphorous acid esters, and in the presence of a transesterification or esterification catalyst enzyme.

As an abbreviation for "methacrylic acid or methacrylic acid" is used "(meth) acrylic acid". Correspondingly, "(meth) acrylate" is used as an abbreviation for "methacrylate or acrylate".

With the aid of the process according to the invention, a careful incorporation of functional groups, in particular (meth) acryl groups, into the poly (meth) acrylates can be carried out without taking into account a disodium.

ES 2 285 263 T3 tion of the ester groups of the poly (meth) acrylate. It is also possible to prepare the functionalized polymers from poly (meth) acrylates having hydroxy functional side chains, which are considerably cheaper than the glycidyl functional poly (meth) acrylates used hitherto in the state of the art.

Step a)

In a preferred embodiment of the process according to the invention, step a) uses

- between 10 and 80% by weight, preferably between 20 and 80% by weight, especially preferably between 30 and 70% by weight, of component A, and

- between 10 and 80% by weight, preferably between 20 and 70% by weight, especially preferably between 20 and 60% by weight, of component B, and

- between 0 and 50% by weight, preferably between 0 and 40% by weight, especially preferably between 5 and 25% by weight, of component C and

- between 0 and 15% by weight, preferably between 0 and 10% by weight, especially preferably between 0.5 and 5% by weight, of component D.

The poly (meth) acrylates having hydroxy functional side chains used according to the invention can be prepared by different processes known to those skilled in the art. In this context, preparation by radical polymerization is preferred.

The polymerization is generally carried out by emulsion, solution or bulk polymerization, with emulsion or solution polymerization being preferred.

In one embodiment, poly (meth) acrylates having hydroxy functional side chains are prepared by emulsion polymerization. In emulsion polymerization, components A, B, and optionally C and optionally D are reacted with one another in the presence of water, emulsifiers, initiators and, if appropriate, regulators.

In general, anionic, nonionic, cationic or amphoteric emulsifiers are used as emulsifiers, with anionic or nonionic emulsifiers being preferred. Suitable anionic emulsifiers are: sodium, potassium or ammonium salts of long-chain aliphatic carboxylic acids and of sulfonic acids, alkyl (Ci2-i6) -alkali sulfates, ethoxylated and sulfated or sulfonated long-chain aliphatic alcohols or alkylphenols and esters of sulfodicarboxylic acids. Suitable nonionic emulsifiers are: fatty alcohols and ethoxylated alkylphenols, the ethylene oxide units being able to represent between 2 and 50 mol / mol. As suitable cationic emulsifiers there are mentioned: ammonium, phosphonium and sulfonium compounds containing at least one long aliphatic hydrocarbon chain as hydrophobic molecular part. It is also possible to use a combination of different emulsifiers, for example ionic and non-ionic emulsifiers.

Preferably, the water used is distilled or desalinated water, since salts can negatively influence the stability of the emulsion. The polymerization process is generally carried out under nitrogen, since oxygen inhibits polymerization.

The molecular weight of poly (meth) acrylates having hydroxy functional side chains can be reduced by the addition of regulators. Suitable regulators are, for example, halogen-containing compounds such as carbon tetrachloride, carbon tetrabromide, bromal, benzyl bromide and trichlorobromomethane or mercaptans such as butyl mercaptan or dodecyl mercaptan or Rongalit^® C.

Generally, all initiators known to those skilled in the art for the polymerization of (meth) acrylates are suitable as initiators. In general, water-soluble peroxo compounds such as alkali persulfates or ammonium persulfate, hydrogen peroxide or tert-butylperoxyethyl hexanoate are used. Redox systems such as H₂OR₂-ascorbic acid, H₂OR₂-Fe (II) / Fe (III), F₂OR₂-Ce (IV), persulfites-Fe, metabisulfitesFe or metal salts of hydroperoxides. The initiators are generally used in an amount between 0.05 and 8% by weight, preferably between 0.2 and 2% by weight, relative to the amount of monomers used.

The initiator, if any, still present after the polymerization can be deactivated in order to avoid a possible polymerization of the poly (meth) acrylates prepared according to the invention in step b). Generally, deactivation is carried out by the addition of a reducing agent, for example ascorbic acid.

In general, the polymerization is carried out at a temperature of 30 to 120 ° C, preferably 40 to 110 ° C, especially 50 to 90 ° C. The polymerization is generally carried out at a pressure of 1 to 20, preferably 1 to 15, and especially 1 to 5 bar.

ES 2 285 263 T3

In general, the emulsifiers are used in an amount of 0.5 to 15% by weight, preferably 0.5 to 10% by weight, especially 0.5 to 5% by weight, relative to the amount of the Components A, B, possibly C and optionally D, used.

The particle diameter of poly (meth) acrylates having hydroxy functional side chains obtained after polymerization generally ranges between 20 and 1000 nm, preferably between 20 and 500 nm, especially between 50 and 400 nm, calculated by dispersion of light.

Generally, the pH value during the emulsion polymerization ranges between 1 and 6, preferably between 2 and 6. Hydroxyl numbers generally range between at least 20 and 180, preferably at least between 40 and 120. The solids content of the dispersions in general it ranges between 10 and 50, preferably between 20 and 40, and the glass transition temperature of the polymers obtained generally ranges between -40 and + 80 ° C.

The poly (meth) acrylates having hydroxy functional side chains obtained generally have an average molecular weight of 1,000 to 2,000,000, preferably 1,000 to 1,000,000, especially 50,000 to 500,000. The average molecular weight has been calculated by gel filtration chromatography (GPC). This is the number average molecular weight.

Poly (meth) acrylates having hydroxy functional side chains can be prepared by single pot processes or by batch processes, feed processes, and continuous processes. The performance of such procedures is known to specialists.

The poly (meth) acrylate having hydroxy functional side chains obtained in step a) can be isolated by methods known to those skilled in the art. For example, in EP-A 0 029 637 an embodiment is described, but in the process according to the present application solvents free of hydroxyl groups are used, or in a second step a solvent containing hydroxyl groups is replaced by a solvent free of hydroxyl groups. For use in step b) of the process according to the invention, the poly (meth) acrylate having hydroxy functional side chains is used in a water-free form after isolation.

In another preferred embodiment, poly (meth) acrylates having hydroxy functional side chains are prepared by solution polymerization. In solution polymerization, components A, B, and optionally C and optionally D are reacted with one another in the presence of a solvent, an initiator and optionally regulators.

Some suitable initiators for solution polymerization are peroxides such as dialkyl peroxides, for example di-tert-butyl peroxide or di-tert-amyl peroxide; peroxyesters such as tert-butylperoxy-2-ethyl hexanoate and tert-amylperoxy-2-ethyl hexanoate; diacyl peroxides such as benzoyl peroxide, lauroyl peroxide, and decanoyl peroxide; percarbonates such as tert-butyl-peroxyisopropyl carbonate, di-2-ethylhexyl peroxydicarbonate; percetals and ketoperoxides; and also azo initiators such as 2,2'-azo-bis (2,4-dimethylpentanitrile), 2,2'azo-bis (2-methylpropanenitrile), 2,2'-azo-bis (2-methylbutanonitrile), 1, 1'-azo-bis (cyclohexanecarbonitrile), 2,2'-azo-bis (2,4,4-trimethylpentane) and 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile.

Those solvents that do not interfere with an enzymatic reaction according to step b) are preferred, so that it is not necessary to remove the solvent before carrying out said step b). Solvents selected from methyl isobutyl ketone, acetone, xylene, N-methylpyrrolidone, methyl ethyl ketone, methyl propyl ketone, methyl amyl ketone and solvent naphtha are particularly preferably used.

Step b)

In step b) the transesterification or esterification of the poly (meth) acrylates having hydroxy functional side chains is carried out with at least one (meth) acrylate or (meth) acrylic acid or a stabilizer, in the presence of a catalytic enzyme of transesterification or esterification. Preferably a transesterification is carried out with methyl, ethyl, 2-ethylhexyl or butyl (meth) acrylate.

In general, enzymatic transesterification or esterification with a (meth) acrylate or with (meth) acrylic acid takes place at low temperatures, preferably between 10 and 100 ° C, especially between 20 and 80 ° C. The transesterification or enzymatic esterification reaction conditions are mild. Thanks to the low temperatures and the other mild conditions, in step b) the formation of secondary products is avoided, which could otherwise come from, for example, chemical catalysts or an unwanted radical polymerization of the (meth) acrylate or the (meth) acrylic acid used, which in that case could only be avoided by adding stabilizers.

In general, the product from step a) can be used directly for the enzymatic reaction (step b)) without any additional pre-treatment. If necessary, the product can be freed from volatile substances (eg solvents) or additional substances (eg solvents) can be added. In particular, it should, if possible, be free of radical initiators or be poor in radical initiators.

Hydrolases are preferably used as enzymes, in particular hydrolases selected from the group consisting of lipases, esterases and proteases. Enzymes can be used in their free form or immobilized on a

ES 2 285 263 T3 support to which they are attached chemically or physically. The amount of enzyme catalyst preferably ranges from 0.1 to 20% by weight, especially from 1 to 10% by weight, based on the poly (meth) acrylate having hydroxy functional side chains used.

The reaction time depends, among other things, on the amount used and the activity of the enzyme catalyst and the degree of reaction desired, and also on the hydroxy functional side chain of the poly (meth) acrylate.

The (meth) acrylate used for transesterification or (meth) acrylic acid used for esterification are generally used in equimolar amounts or in excess relative to the amount of hydroxy functional side chains of the poly (meth) acrylate. Preferably, a molar ratio between the (meth) acrylate or (meth) acrylic acid and the hydroxyl groups of the side chains of the poly (meth) acrylate of 1: 1 to 10: 2 is used. A greater excess does not influence negatively.

In general, in step b), 20-100%, preferably 40-100%, especially 60-100%, of all hydroxy functional side chains contained in the poly (meth) acrylate are reacted with a (meth) acrylate or with (meth) acrylic acid.

Suitable stabilizers to be used if necessary are selected from the group consisting of 2,6-dibutylphenols such as di-tert-butylphenol, p-cresol, hydroquinone, dimethylhydroquinone, phenothiazines and phosphorous acid esters. However, step b) can also be carried out without using stabilizers.

The reaction can be carried out in any suitable reactor for reactions of this type. These reactors are known to specialists. Preferably, the reaction is carried out in a stirred tank reactor, in a fixed bed reactor or in a Taylor reactor.

The reaction water formed during the transesterification or esterification, or the corresponding alcohol, can be removed by methods known to those skilled in the art, for example by absorption (for example with a molecular sieve), distillation or pervaporation.

The reaction progresses to the desired conversion, generally 5 to 100%. If the reaction is carried out while removing the alcohol or water formed during the reaction, higher conversions can be achieved in shorter reaction times due to the shift in reaction equilibrium.

The enzyme catalyst can then be separated from the reaction by suitable measures, for example filtration or decantation, and can be used several times if necessary.

Another object of the present application consists of poly (meth) acrylates curable by UV and / or dual cure which can be prepared according to the process according to the invention. Thanks to the mild reaction conditions applied in the process according to the invention, new poly (meth) acrylates with (meth) acryl functionality can be obtained, without the risk of dissociation of the ester bonds of the poly (meth) acrylates by acid catalysis or high temperatures.

These poly (meth) acrylates with (meth) acryl functionality according to the invention are suitable as binders in radiation-curable or dual-cure coating materials, for example in topcoats such as clearcoats, or also in basecoats, primers and fillers. . Poly (meth) acrylates with (meth) acryl functionality exhibit excellent stability against exposure to the elements. In combination with a curing technique (radiation hardening or dual cure) other advantages can be achieved, for example an increase in the scratch resistance of a coating. However, a particularly decisive advantage lies in the improvement in the application by using the poly (meth) acrylates with (meth) acryl functionality according to the invention, since these make quick drying possible.

Consequently, another object of the present application is the use of the poly (meth) acrylates with (meth) acryl functionality according to the invention or prepared according to the process according to the invention as binders in radiation-curable or dual coating materials. cure, preferably in top coatings, especially clear lacquers.

By the term "dual cure" it is to be understood that the materials are thermally curable and with actinic radiation. Within the framework of the present invention, actinic radiation is understood to be electromagnetic radiation such as visible light, UV radiation or X radiation, mainly UV radiation; and corpuscular radiation as an electron beam.

Radiation curable binders are those that are curable by actinic radiation as described above, mainly by UV radiation.

Another object of the present application consists of lacquer formulations containing the poly (meth) acrylates with (meth) acryl functionality according to the invention or which are prepared according to the process according to the invention. Poly (meth) acrylates with (meth) acryl functionality or stabilizer-functionalized poly (meth) acrylates can be used in both basecoats and clearcoats. It is preferable to use them in covering coatings

ES 2 285 263 T3 due to its special properties, such as increased scratch resistance combined with high UV stability in a coating.

Generally, the composition of the topcoat is chosen such that the cured topcoat has a memory modulus E 'elastic rubber of at least 10⁷'⁶ Pa, preferably at least 10⁸'⁰ Pa, especially at least 10⁸'³ Pa, and a loss factor at 20 ° C of a maximum of 1.10, preferably of a maximum of 0.06, the memory modulus E 'and the loss factor tand being measured by means of dynamic-mechanical thermonalysis in homogeneous free films with a thickness of 40 ± 10 pm layer. The loss factor tand is defined as the quotient between the loss module E "and the memory module E '.

Dynamic-mechanical thermonanalysis is a general measurement method to determine the viscoelastic properties of coatings and is described for example in Murayama T., Dynamic Mechanical Analyze of Polymeric Material, Elsevier, New York, 1978 and Loren W. Hill, Journal of Coatings Technology, vol. 64, n ° 808, May 1992, pp. 31 to 33. The measurements can be carried out, for example, with the MKII, MKIII or MKIV apparatus from Rheometrics Scientific.

Preferably, radiation-curable or dual cure topcoats have a viscosity at 23 ° C <100 s pouring time in DIN4 cup, especially <80 s pouring time in DIN4 cup. Viscosity can also be higher for a pour or roll application.

In addition to the methacryl-functional poly (meth) acrylates according to the invention, the top coatings according to the invention optionally contain one or more photoinitiators and optionally auxiliary substances and the usual additives. Suitable photoinitiators are those commonly used in radiation curable or dual cure coating materials, for example benzophenones, benzoins or benzoin ethers, preferably hydroxyacryloketones and bis (acyl) phosphine oxides. It is also possible to use, for example, the photoinitiators that are commercially available under the names Irgacure® 184, Irgacure® 1800 and Irgacure® 500 from Ciba Geigy, Genocure® MBF from Rahn and Lucirin® TPO from Ciba Geigy. signed BASF AG.

Other suitable auxiliary substances and additives are, for example, photoresists (for example HALS compounds, benzotriazoles, oxalanilide and others), slip additives (slip), polymerization inhibitors, matting agents, defoamers, leveling aids and film-forming auxiliary agents. , for example cellulose derivatives and others. Rheology control components such as organic urea compounds, urethane urea compounds and / or SiO can also be used.₂.

Topcoats according to the invention are mainly used as clearcoats, so that they usually do not contain fillers or only contain transparent fillers and do not contain any topcoat pigments. However, they can also be used in the form of pigmented topcoats. In this case, the top coatings additionally contain pigments. Furthermore, in this case, the top coatings can also contain one or more fillers.

Consequently, another object of the present application consists of covering coatings containing between 5 and 80% by weight, preferably between 10 and 60% by weight, especially between 20 and 50% by weight, such as at least one poly (meth) acrylate with (meth) acryl functionality according to the invention or prepared according to the process according to the invention;

between 0.5 and 15% by weight, preferably between 1 and 10% by weight, especially between 1 and 5% by weight, of at least one photoinitiator;

between 0.5 and 8% by weight, preferably between 1 and 6% by weight, especially between 1 and 4% by weight, of other auxiliary substances and additives;

between 0 and 40% by weight, preferably between 0 and 36% by weight, especially between 0 and 25% by weight, of pigments;

and between 0 and 40% by weight, preferably between 0 and 30% by weight, especially between 0 and 25% by weight, of at least one filler, such as a transparent metal oxide, BaSO₄ and waxes.

Poly (meth) acrylates with (meth) acryl functionality, photoinitiators, auxiliaries and additives, and preferred fillers and pigments have already been mentioned above.

The production of the top coatings according to the invention takes place by mixing the individual components according to procedures known to those skilled in also known devices.

Consequently, another object of the present application consists of a process for the production of the covering coating according to the invention, in which the poly (meth) acrylate with (meth) acryl functionality, the photoinitiator, optionally other are mixed together. auxiliaries and additives, and if necessary fillers and pigments.

ES 2 285 263 T3

Topcoats according to the invention are generally applied on substrates coated with a basecoat. They can be applied to substrates by means of the so-called coil coating or by injection molding. Said substrates consist, for example, of metal sheets or metal and plastic tapes of any type, for example car bodies and motorcycle parts.

After the topcoat is applied, it is subjected to radiation curing or dual cure. The facilities and conditions for these curing methods are disclosed in the literature and do not require a more detailed description (for radiation curing see e.g. R. Homes, UV and EB Curing Formulations for Printing Inks, Coatings and Paints, SITA Technology, Academic Press, London, UK 1984).

The following examples explain the invention in more detail.

Examples

1. Production of a binder with hydroxy functionality

Formulation

<td>Load initial</td><td>Methyl isobutyl ketone</td><td colspan="2">540.0 g</td>

<td>Monomers</td><td>Styrene</td><td>10.00% by weight ¹⁾</td><td>123.6 g</td>

<td></td><td>EHA (2-ethylhexyl acrylate)</td><td>46.50% by weight ¹⁾</td><td>574.4 g</td>

<td></td><td>HEMA (ethylhexyl methacrylate)</td><td>27.00% by weight ¹⁾</td><td>336.6 g</td>

<td></td><td>HBA (hydroxybutyl acrylate)</td><td>15.00% by weight ¹⁾</td><td>185.2 g</td>

<td></td><td>AS (acrylic acid)</td><td>1.50% by weight ¹⁾</td><td>18.6 g</td>

<td>washed</td><td>Methyl isobutyl ketone</td><td></td><td>5.0 g</td>

<td>Initiator</td><td>Tert-Butylperoxy-2- hexanoate ethyl</td><td>8% by weight ²⁾</td><td>98.8 g</td>

<td></td><td>Methyl isobutyl ketone</td><td></td><td>74.2 g</td>

<td>washed</td><td>Methyl isobutyl ketone</td><td></td><td>46.6 g</td>

Final 2,000.0 g ¹⁾Regarding the sum of the following components: styrene, EHA, HEMA, HBA, AS ²⁾Regarding the sum of the following components: styrene, EHA, HEMA,

HBA, AS

Process

The initial charge is introduced and heated to 110 ° C. At a constant temperature, monomers and initiator are added to the reactor in a uniform and metered manner. The monomer feed ends after 4 hours. The initiator feed ends after 4.5 hours. After the initiator dosing has ended, the mixture is polymerized for 1 hour and then cooled. The reaction mixture obtained is then collected.

* Final values:

Solid content (1 h, 130 ° C): 66.3% total OH number (theoretical): 174.8 mg / g (calculated according to DIN

43402) OH number (in practice): 165 mg / g (calculated according to DIN

53246)

ES 2 285 263 T3

GC (residual monomer content)³': EHA 0.3%; AS &lt;0.3%, all others &lt;0.1%

GPC⁴'Mn⁵’ 5.829

M_w⁶⁾ 20.722

Mw / Mn⁷’ 3,55 ³⁾ GC = Gas Chromatography ⁴⁾ GPC = Gel Filtration Chromatography (with polystyrene standard) ⁵⁾ M_n= Number average molecular weight ⁶⁾ M_w= Weight average molecular weight ⁷⁾ Mw / M_n= Polydispersity

2. Production of a UV-active polyacrylate

Basic charge: 300 ml of polymer solution in methyl isobutyl ketone from Example 1

300 ml of methyl acrylate (MA)

150 mg methoxyphenol

150 g of molecular sieve 5 A g Novozym® 435 (immobilized lipase from Candida antarctica from Novozymes).

The mentioned components are stirred for 72 hours at 40 ° C. The reaction mixture is then filtered and the polyacrylate obtained is washed with methyl isobutyl ketone (MIK). The excess MA and MIK are removed under vacuum at a temperature of 60 ° C to 70 ° C on a rotary evaporator. 227 g of product are obtained. The proportion of acrylated hydroxyl groups determined according to the OH number is approximately 34%.

The determination of the OH number is carried out according to a method known in the state of the art (DIN 53240, part 2).

3. Production of a UV lacquer formulation a) Mother lacquer

UV polyacrylate according to the invention

Sartomer® 399

Thixharz® SCA (base; benzylamine / hexamethylene diisocyanate)

Irgacure® 184 (photolitiator)

Lucirin® TPO (photolinitiator)

Byk® 358 (leveling aid)

Tinuvin® 292 (radical scavenger)

Tinuvin® 400 (UV absorber)

Acetate of butilo

32.5

30.6 11,5

0,8

0,4

0,2

1,0

1,0

22,0

ES 2 285 263 T3

b) Hardener mix

Add a curing mixture consisting of 72.7 parts of Roskydal® UA VP LS 2337 (unsaturated isophorone diisocyanate), 18.2 parts of Roskydal® UA VP FWO 3003 77 and 9.1 parts of butyl acetate (the parts are parts by weight).

The components are mixed in a dissolver (dissolution vessel).

Four. The lacquer formulation is applied by spraying.

5. Variation of hydroxy functional units

As the following examples show, different hydroxy functional units can be used. However, the examples mentioned do not constitute any limitation. The polymer solutions were prepared according to the procedure according to Example 1.

g of polymer solution, 10 g of methyl acrylate, 5 g of molecular sieve (5 A) and 1 g of immobilized lipase (Novozym 435) were stirred for 72 hours at 40 ° C. After filtration and concentration, the conversion level was determined by means of the OH number.

<td>Polymer solution</td><td>Esterified unit</td><td>Conversion [%]</td>

<td> 2</td><td>Hydroxyethyl acrylate</td><td> 34</td>

<td> 3</td><td>Hydroxyethyl acrylate</td><td> 41</td>

<td> 4</td><td>Hydroxyethyl methacrylate</td><td> 12</td>

<td> 5</td><td>Hydroxyethyl methacrylate</td><td> 22</td>

<td> 6</td><td>Hydroxyethyl methacrylate</td><td> 47</td>

<td> 7</td><td>Hydroxybutyl acrylate</td><td> 67</td>

<td> 8</td><td>Hydroxybutyl acrylate</td><td> 80</td>

6. Reaction optimization

The reaction conditions could be optimized by varying the reaction time, the amount of methyl acrylate added and the molecular sieve. The polymer solutions listed in the table of Example 5 were reacted under the following optimized conditions:

g of polymer solution, 2 g of methyl acrylate, 2 g of molecular sieve and 1 g of Novozym® 435 were stirred for 24 hours at 40 ° C. After filtration and concentration, the conversion level was determined by means of the OH number.

Polymer solution

Conversion [%] 23

6 17

46