CA1312985C - Coating agents based on soluble acrylate copolymers containing carboxyl groups - Google Patents

Abstract

ABSTRACT

The invention relates to a coating agent contain-ing, as essential binder, (A) an acrylate copolymer having an acid number ranging from about 15 to about 200 and (B) a compound containing at least two epoxide groups per molecule, the ratio of (A) to (B) being chosen so that the ratio of the acid groups of (A) to the epoxide groups of (B) is in the range of 0.5:3 to 2:0.5. The coatings obtained with the coating agent according to the invention have outstanding properties in respect of stability towards long-term exposure to chemicals and solvents, and in respect of stability towards gasoline, elasticity, gloss, corrosion resist-ance and stability towards water and steam.

Description

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This application is a division of Canadian ap-plication No. 519,320, filed September 29, 1986, which relates to a soluble acrylate copolymer which can be obtained by copolymerization of monomers with at least two polymerizable, olefinically unsaturated double bonds, monomers which carry functional groups and other polymerizable monomers with an olefinically unsaturated double bond, the acrylate copolymer containing carboxyl groups.
An acrylate copolymer which has been obtained by copolymerization of 10 to 95% by weight of t-butyl acrylate, 0.1 to 3% by weight of polyfunctional mono-mers, such as, for example, trimethylolpropane tri-acrylate, 1 to 30% by weight of comonomers with func-tional crosslinkable groups and 0 to 80% by weight of other polymerizable, ethylenically unsaturated monomers is known from the genus-determining European Patent A-103,199. Monomers containing carboxyl groups, such as acrylic acid and methacrylic acid, are mentioned, inter alia, as comonomers with a functional crosslinkable group.
A coating composition which contains an acrylate copolymer containing carboxyl groups and branched by copolymerization of monomers with several ethylenically unsaturated bonds and a polyepoxide as a crosslinking agent is furthermore known from European Patent A-103,199. The branched acrylate copolymers described lead to coatings with a high resistance to weathering, in particular a good resistance to humidity, which is to be attributed to the content of copolymerized t-butyl acrylate on the one hand and to the content of co-polymerized monomers with several olefinically unsatu-rated bonds.
A reactive hardenable binder mixture on the basis of particular polycarboxylic acid units based on poly-merization and/or condensation products, carboxyl groups ' :
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being formed, for example, by addition of cyclic car-bo~ylic acid anhydrides onto OH-acrylates, and on the basis of aliphatic or cycloaliphatic epoxide compounds is known from European Patent B-51,275. The advantage of the hardenable binder mixture is that, in addition to the binder, a catalyst for the carboxyl-epoxy cross-linking is present in the form of metal salts, so that an external catalyst can be dispensed with.
A composition which hardens even at room temper-ature and consists of polyepoxides and polymers which contain carboxyl groups and tertiary amino groups and are formed by reaction of vinyl polymers containing acid anhydride groups and carboxyl groups with compounds which contain at least one active hydrogen capable of 1~ reactioll with acid anhydrides and at least one tertiary amino group, such as, for example, tertiary amino-alcohols, is known from European Patent A-123,793. The compositions described have the advantage that they harden even at room temperature and have a high stabil-~0 ity towards gasoline, water and alkalis, and that noundesirable discoloration attributable to tertiary amino compounds arise.
Japanese Preliminary Published Specification 53,145/79 describes compositions based on copolymers ~5 with tertiary amino groups, carboxyl groups and phos-phoric acid groups and on aliphatic polyepoxides. The compositions harden at relatively low temperatures and lead to films with a good stability towards solvents and resistance to weathering.
3~ Compositions of acrylate resins and di- and polyepoxides are known from German Offenlegungsschrift ~,635,177. ~,~-Ethylenically unsaturated carboxylic aci~s are copolymerized into the acrylate resins, and the resins have an acid number of 70 to 250. The com-positions have a high solids content and show good results in respect of mechanical properties, stability . ~.

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towards chemicals and solvents and corrosion resistance.
A coating composition which is obtainable by mixing acrylate copolymers of acrylic acid esters, mono-mers containing carboxyl groups and acrylic monomers containing tertiary nitrogen, such as, for example, diethylaminoethyl acrylate, with polyepoxides is known from Japanese Preliminary Published Specification 76,338/77. The coating compositions can harden at low temperatures and have a high solids content.
A process for the production of a coating in which an acrylate copolymer formed by copolymerization of acrylic monomers with a tertiary amino group, acrylic or methacrylic acid esters and, if appropriate, other monomers, a polyepoxide component and a carboxylic acid activated by double bonds and/or hydroxyl groups are mixed and the mixture is applied to the substrate is known from Japanese Preliminary Published Specification 219,267/83. The mixtures harden at room temperature or somewhat elevated temperature, and the film formed has good physical properties, a good stability towards gasoline and good resistance to weathering. An advan-tage of the process described in Japanese Preliminary Published Specification 219,267~83 is that no brown coloration of the acrylate solution due to the tertiary ~5 amino groups occurs on prolonged storage, this being achieved by addition of the activated carboxylic acid.
The preparation of a tertiary amino group in an acrylate copolymer is known from European Patent B-13,439. The tertiary amino group is obtained by reac-3a tion of glycidyl groups incorporated into the acrylatecopolymer with amines which have a secondary amino group and at least one secondary hydroxyl group.
The object of the present invention was to im-prove the properties of coating agents and coatings based on epoxy-carboxyl crosslinking in respect of stability towards long-term exposure to chemicals and -~, - 4 - 1 3 ~2 ~ ~r~

solvents, in respect of stability -towards gasoline and elasticity of the coatings obtained on the basis of the coating agent, the gloss and the corrosion resistance and in respect of stability towards water and steam. A
further requirement imposed on the compositions is that, if appropriate, they harden at room temperature or at slightly elevated temperatures and can therefore be used, for e~ample, in automobile refinishing. It should furthermore be possible, for economic reasons, to achieve a high solids content of the hardenable coating agents at a relatively low viscosity.
This object is achieved, surprisingly, by a soluble acrylate copolymer which has a higher content of copolymerized monomers with several ethylenically un-saturated bonds than the acrylate resins described in~,uropean Patent A-103,199. In comparison with linear acrylate resins and the acrylate resins from European Patent A-103,199, a lower viscosity can be achieved at a relatively high solids content with the acrylate co-polymers according to the invention. Only by the reac-tion condltions according to the invention during co-polymerization can amounts of more than 3% by weight of polyunsaturated monomers be incorporated into the acrylate resin. The functional groups of the acrylate resin become more reactive due to the highly crosslinked structure of the copolymer, which provides a great ad-vantage.
The object on which the invention is based is achieved by the above-mentioned soluble acrylate co-3~ polymer, which is characterized in that more than 3 to30~ by weight, based on the total weight of the mono-m~rs, of a monomer with at least two polymerizable, olef.inically unsaturated double bonds are copolymerized into the acrylate copolymer and the acid number of the - . .
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_ 5 _ ~ 3 1 2 ~ ~rj acrylate copolymer is 15 to 200, preferably 30 to 120.
According to the invention, the acid groups can be realized in the acrylate copolymer in various ways.
The invention relates to a soluble acrylate co-polymer which is characterized in that it can be ob-tained from al) more than 3 to 30% by weight, preferably 5 to 25~ by weight, of a monomer with at least two polymer-izable, olefinically unsaturated double bonds, a2) 3 to 30% by weight, preferably 5 to 20~ by weight, of a monomer containing carboxyl groups and a3) 40 to 93~ by weight of other monomers with a poly-merizable, olefinically unsaturated double bond, the sum of al, a2 and a3 being 100% by weight.
Compounds of the general formula R O O R
l 11 11 1 CH2 C C X (C 2)n 2 in which: R = H or CH3, X = O, NR' or S, where R' = H, alkyl or aryl, and n = 2 to 8, can advantageously be used as component al.
Examples of such compounds are hexanediol di-acrylate, hexanediol dimethacrylate, glycol diacrylate, glycol dimethacrylate, butanediol diacrylate, butanediol dimethacrylate, hexamethylenebismethacrylamide, tri-methylolpropane triacrylate, trimethylolpropane tri-methacrylate and similar compounds.
It is of course also possible to use combinations of the polyunsaturated monomers.
Other possible components al are reaction prod-ucts o~ a carboxylic acid with a polymerizable, olefini-cally unsa-turated double bond and glycidyl acrylate and~or glycidyl methacrylate. It is also possible to use a polycarboxylic acid or unsaturated monocarboxylic acid esterified with an unsaturated alcohol containing a polymerizable double bond as component al. Diolefins, - 6 - ~3~8~
such as divinylbenzene, can furthermore be employed.
Reaction products of a polyisocyanate with alcohols or amines containing unsaturated, polymerizable double bonds are also employed as monomers with at least two polymerizable, olefinically unsaturated double bonds.
An example which may be mentioned here is the reaction product of one mole of hexamethylene diisocyanate with 2 moles of allyl alcohol. The monomers containing several ethylenically unsaturated bonds can advantageously be diesters of polyethylene glycol and/or polypropylene glycol with an average molecular weight of less than 1,500, preferably less than 1,000, and acrylic acid and/or methacrylic acid.
~ -Carboxyethyl acrylate is particularly suitable as component a2), and acrylic acid, methacrylic acid, itaconic acid, crotonic acid, aconitic acid, maleic acid and fumaric acid or half-esters thereof are furthermore suitable.
The choice of component a3) depends largely on the desired properties of the acrylate copolymer in respect of elasticity, hardness, compatibility and polarity. These properties can in part be controlled with the aid of the known glass transition temperatures of the monomers. The monomers can be chosen from the group comprising styrene, vinyltoluene, alkyl esters of acrylic acid and of methacrylic acid, alkoxyethyl acrylates and aryloxyethylacrylates and the correspond-ing methacrylates and esters of maleic and fumaric acid.
Monomers which may be mentioned are methyl acrylate, ethyl acrylate, propyl acrylate, butyl ~ acrylate, isopropyl acrylate, isobutyl acryla-te, pentyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, 3,5,5-trimethylhexyl acrylate, decyl acrylate, dodecyl acrylate, hexadecyl acrylate, octadecyl acrylate, octadecenyl acrylate, pentyl metha-crylate, isoamyl methacrylate, hexyl methacrylate, - ~ .

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2-ethylbutyl methacrylate, octyl methacrylate, 3,5,5-trimethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, hexadecyl methacrylate, octadecyl metha-crylate, butoxyethyl acrylate, butoxyethyl methacrylate, methyl methacrylate, ethyl methacrylate, propyl metha-crylate, isopropyl methacrylate, butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, acrylo-nitrile, methacrylonitrile, vinyl acetate, vinyl chlo-ride and phenoxyethyl acrylate. Other monomers can be used as long as they do not lead to undesirable proper-ties in the copolymer.
Monomers containing hydroxyl groups, for example hydroxyalkyl esters of acrylic and/or methacrylic acid, can also be employed as component a3). It is possible to employ 0.1 to 5% by weight, based on the total weight of all the monomers, of monomers with phosphoric acid groups, that is to say, for example, phosphoric acid esters with polymerizabie double bonds, as other mono-mers with a polymerizable olefinically unsaturated ~0 double bond.
It is particularly advantageous if the acrylate copolymer with an acid number of 15 to 200, preferably 30 to 120, has built into it monomers which contain groups which catalyze subsequent crosslinking of the ~5 acrylate copolymer containing carboxyl groups with epoxide groups, tha-t is to say, for example, tertiary amino groups.
The invention also relates to a soluble acrylate copolymer, which is characterized in that it can be obtained from al) more than 3 to 30% by weight, preferably 5 to 25% by weight, of a monomer with at least two polymer-izable, olefinically unsaturated double bonds, di-and polyesters of di- and polyols with acrylic acid being excluded, .

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a2) 3 to 30% by weigh~, preferably 5 to 20% by weight, of a monomer containing carboxyl groups, a3) 0.1 to 20% by weight, preferably 1 to 14% by weight, of a tertiary amine with a polymerizable, olefini-cally unsaturated double bond, ad) 0 to 40% by weight, preferably 5 to 25% by weight, of a monomer containing hydroxyl groups and a5) 0 to 80% by weight of other monomers with a polymer-izable, olefinically unsaturated double bond, 10 the sum of components al, a2, a3, a4 and a5 being 100 by weight.
Compounds of the general formula fH3 ~ fH3 CH2 = C - C - X - (CH2)n - X - C - C = CH2 in which: X = O, NR or S, where R = H, alkyl or aryl, and n - 2 to 8, can advantageously be used as component al.
Component al can be a reaction product of a car-70 boxylic acid with a polymerizable, olefinically unsatu-rated double bond, excluding acrylic acid, and glycidyl methacrylate. Polycarboxylic acids or unsaturated mono-carboxylic acids esterified with an unsaturated alcohol containing a polymerizable double bond are furthermore ~5 suitable, derivatives of acrylic acid being excluded.
The use of polyolefins, such as, for example, divinyl-benzene, is also advantageous. Components al are advan-tageously selected from products which are prepared from polyisocyanates with alcohols or amines containing un-saturated, poiymerizable double bonds. Diesters ofpolyethylene glycol and/or polypropylene glycol with an avcrage molecular weight of less than 1,500, preferably oE less than 1,000, and methacrylic acid are furthermore s~litable.

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~ xamples of ethylenically unsaturated compounds with a tertiary amino group, that is to say of component a3, are N,N'-dimethylaminoethyl methacrylate, N,N'-diethylaminoethyl methacrylate, 2-vinylpyridine and 4-vinylpyridine, vinylpyrroline, vinylquinoline, vinyl-isoquinoline, N,N'-dimethylaminoethyl vinyl ether and 2-methyl-5-vinylpyridine.
If appropriate, monomers containing hydroxyl groups can be employed. Examples which may be mentioned are hydroxyalkyl esters of acrylic and methacrylic acid, such as, for example, hydroxyethyl acrylate, hydroxy-propyl acrylate, hydroxybutyl acrylate, hydroxyamyl acrylate, hydroxyhexyl acrylate, hydroxyoctyl acrylate and the corresponding methacrylates. The other monomers with a polymerizable, olefinically unsaturated double bond are chosen from the group already mentioned above.
In this case also, if appropriate, it is advantageous for 0.1 to 5% by weight, based on the total weight of all the monomers, of monomers with phosphoric acid groups to be employed as other monomers with a polymer-izable double bond.
According to the invention, the soluble acrylate copolymer with an acid number of 15 to 200, preferably 30 to 120, can be obtained from 25 al) more than 3 -to 30% by weight, preferably 5 to 25% by weight, of a monomer with at least two polymer-izable, olefinically unsaturated double bonds, di-and polyesters of di- and polyols with acrylic acid being excluded, 30 a2) 0.1 to 20% by weight, preferably 1 to 14% by weight, oE a tertiary amine with a polymerizable, olefini-cally unsaturated double bond, a3) 5 to 40% by weight, preferably 10 to 30% by weight, of monomers containing hydroxyl groups, a4) 0 to 80% by weight of other polymerizable monomers with an olef~nically unsaturated double bond and }

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a5) cyelic carboxylic acid anhydrides, the sum of al, a2, a3 and a4 being 100% by weight.
Compounds of the general formula CH O O CH
1 3 ~ 3 CH2 C C X (CH2)n 2 in which: X = O, NR' or S, where R' = H, alkyl or aryl, and n = 2 to ~3, can advantageously be used as eomponent al.
Examples of eompounds with several ethylenically unsaturated bonds are hexanediol dimethacrylate, glycol dimethacrylate, butanediol dimethacrylate, trimethyl-olpropane trimethacrylate, divinylbenzene and similar eompounds. The ethylenically unsaturated compounds whieh have already been mentioned can also advantage-ously be used, provided that they are not di- or poly-~sters of di- andpolyols with acrylic aeid.
Possible polymerizable tertiary amines are those already mentioned above.
~0 Hydroxyalkyl esters of acrylic and/or methacrylie aeid with a primary hydroxyl group, for example hydroxy-ethyl aerylate, hydroxypropyl aerylate, hydroxybutyl aerylate, hydroxyamyl aerylate, hydroxyhexyl aerylate, hydroxyoetyl aerylate and the corresponding methaeryl-2~ ates, and hydroxyalkyl esters with a seeondary OH group, sueh as 2-hydroxypropyl aerylate, 2-hydroxybutyl aerylate, 3-hydroxybutyl aerylate and the eorresponding methacrylates, are suitable as eomponent a3.
Reaetion products of acrylic acid and/or metha-erylie aeid with the glycidyl ester of a earboxylie aeidwith a tertiary a-earbon atom are also possible as com-`ponent a3.

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, The choice of component a4 is not particularly critical and depends on -the desired properties of the acrylate copolymer. It should be mentioned that mono-mers containing carboxyl groups can also be employed as component a4.
Examples of component a5 are phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhy-dride, succinic anhydride and halogenated derivatives thereof. Maleic anhydride can also be used as component a5, but it should be ensured that no solvents which react with maleic anhydride under catalysis by the ter-tiary nitrogen groups are employed. Examples of sol-vents which cannot be used are acetone, methyl ethyl ketone, butyl acetate and other acetylating solvents.
Solvents which can be used are hydrocarbons and polar solvents, such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone etc.
The present invention also relates to a soluble acrylate copolymer with an acid number of 15 to 200, which can be obtained from al) more than 3 to 30% by weight, preferably 5 to 25% by weight, of monomers with at least two polymerizable, olefinically unsaturated double bonds, a2) 1 to 25% by weight, preferably 3 to 15~ by weight, of monomers with cyclic carboxylic acid anhydride groups, a3) 45 to 80% by weight of other polymerizable monomers with an olefinically unsaturated double bond, the sum of al, a2 and a3 being 100% by weight, and a4) compounds which contain both at least one hydrogen which can react with acid anhydride groups and at least one tertiary amino group, it also being possible for some of the carboxylic acid anhydride groups to be reacted with a monofunctional compound with active hydrogen.

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The monomers containing several ethylenically unsaturated bonds which have been mentioned above, in-cluding the di- and polyesters of di- and polyols with acrylic acid, are suitable as component al.
Examples of monomers with cyclic carboxylic acid anhydride groups are maleic anhydride and itaconic anhydride.
The choice of component a3 depends on the desired properties of the acrylate copolymer. I-t should be mentioned that in the present case monomers containinq carboxyl groups, that is to say, for example, acrylic acid or methacrylic acid, are also suitable.
Alcohols which contain a tertiary amino group and primary or secondary amines with a tertiary amino group are advantageously employed as component a4. The reac-tive hydrogen of component a4 can originate from a hydroxyl group, a primary or secondary amino group or a thiol group.
Examples of alcohols with tertiary amino groups 2~ are adducts of secondary amines and epoxide compounds.
Examples of secondary amines are dimethylamine, diethyl-amine, dipropylamine, dibutylamine, morpholine and pyrrolidine.
Examples of suitable epoxide compounds are ethylene oxide, propylene oxide, butylene oxide, styrene oxide and cyclohexane oxide.
Suitable alcohols with tertiary amino groups which are obtained by reaction of secondary amines with epoxide compounds are dimethylaminoethanol, diethyl-3n aminoethanol, di-n-propylaminoethanol, diisopropylamino-~thanol, di-n-butylaminoe-thanol, N-(2-hydroxyethyl) morpholine, N-t2-hydroxyethyl)piperidine, N-(2-hydroxy-ethyl)pyrrolidone, N-(2-hydroxyethyl)azeridine (sic), N,N'-dimethyl-2-hydroxypropylamine, N,N'-diethyl-2-hydroxypropylamine, triethanolamine and tripropanol-amine.

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- 13 - ~ ~ ~ 2 ~ ~r~j Other examples of alcohols containing tertiary amino groups are vinyl polymers which have both a ter-tiary amino group and a hydroxyl group in the side chain and can be obtained by copolymerization of the above-mentioned (meth)acrylate monomers containing tertiaryamino groups with monomers containing OH groups, such as, for e~ample, ~-hydroxyethyl (meth)acrylate.
Examples of the primary or secondary amines which contain a tertiary amino group are N,N'-dialkyl-1,3-propylenediamines, such as, for example, N,N'-dimethyl-1,3-propylenediamine and N,N'-diethyl-1,3-propylene-diamine, and N,N'-dialkyl-1,4-tetramethylenediamines, such as, for example, N,N'-dimethyl-1,4-tetramethylene-diamine and N,N'-diethyl-1,4-tetramethylenediamine.
N,N'-Dialkyl-1,6-hexamethylenediamines and N-alkyl-piperazines as well as 2-aminopyridine, 4-aminopyridine and N-alkylaminopyridine (sic) are furthermore suitable.
It should be mentioned that some of the car-boxylic acid anhydride groups can also be reacted with a monofunctional compound with active hydrogen, such as, for example, alcohols.
The present invention furthermore relates to an acrylate copolymer which has an acid number of 15 to 200, preferably 30 to 120, and can be obtained from 25 al) more than 3 to 30% by weight, preferably 5 to 25% by weight, of monomers with at least two polymerizable, olefinically unsaturated double bonds, a2) 1 to 30~ by weight of glycidyl esters of ethyleni-cally unsaturated carboxylic acids and/or glycidyl ethers of olefinically unsaturated compounds, a3) 40 to 95% by weight of other polymerizable monomers with an olefinically unsaturated double bond, -the sum of all the monomers being 100% by weight, and a~) amines with a secondary amino group or dl- or poly-amines with at least one tertiary amino group and one primary or secondary amino group and/or .. : . , ~. , ':

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a5) carboxylic acids which contain a tertiary nitrogen atom and a6) cyclic carboxylic acid anhydrides.
The monomers with several ethylenically unsatu-rated bonds which have already been mentioned are suit-able as component al.
Examples of component a2) are glycidyl esters of acrylic acid or of methacrylic acid and allyl and vinyl glycidyl ethers, glycidyl-vinyl esters or glycidyl-allyl esters, such as glycidyl vinyl phthalate and glycidyl allyl phthalate.
The choice of component a3 depends on the desired properties of the acrylate copolymer and can be made from the group already mentioned above. However, no monomers containing carboxyl groups or amino groups should be used as component a3, since these react with the oxirane group of component a2. The content of mono-mers containing hydroxyl groups should be as low as possible. If hydroxyl groups are necessary to achieve a ~0 certain polarity in the copolymer, monomers with second-ary OH groups should be preferred.
Examples of component a4 are imidazole, amino-pyridine, N-alkylaminopyridines, ethylpiperazine and dibutylamine.
Examples of component a5 are 3- and 4-dime-thylaminobenzoic acid, picolinic acid and dimethylamino-salicylic acid.
Examples which may be mentioned of component a6 are phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, succinic anhydride and halogenated derivatives thereof.
The invention also relates to processes for the preparation of soluble acrylate copolymers as defined above, which are characterized in that, for preparation of the copolymers, the monomers are copoly-merized in an organic solvent at 70C to 130C, prefer-, . , . , : .
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ably at 80C to 120C, using at least 0.5~ by weight, preferably at least 2.5~ by weight, based on the -total weight of the monomers, of a polymerization regulator and using polymerization initiators to give a pre-cross-linked, non-gelled product.
According to a preferred embodiment, the mono-mers are first copolymerized in an organic solvent at 70C to 130C, preferably at 80C to 120C, using at least 0.5% by weight, preferably at least 2.5% by weight, based on the total weight of the monomers, of a polymerization regulator and using polymerization initi-ators, to give a pre-crosslinked, non-gelled product which, when the copolymerization has ended, is further reacted with a cyclic acid anhydride.
According to another preferred embodiment, the monomers are first copolymerized in an organic solvent at 70C to 130C, preferably at 80C to 120C, using at least 0.5~ by weight, preferably at least 2.5~ by weight, based on the total weight of the monomers, of a 70 polymerization regulator and using polymerization initiators, to give a pre-crosslinked, non-gelled pro-duct which, when the copolymerization reaction has ended, is further reacted with a compound which contains both at least one hydrogen capable of reaction with acid ~5 anhydride groups and at least one tertiary amino group and, if appropriate, with a monofunctional compound with active hydrogen.
According to still another preferred embodi-ment, the monomers are first copolymerized in an organic solvent at 70 C to 130 C, preferably at 80C to 120C, using at least 0.5~ by weight, preferably at least 2.5~
by weiyht, based on the total weight of the monomers, of a polymerization regulator and using polymerization initiators, to give a pre-crosslinked, non-gelled pro-duct which, when the copolymerization reaction has ended, is further reacted with a di- or polyamine which : ` :

contains at least one tertiary amino group and at least one primary or secondary amino group and/or with a carboxylic acid which contains a tertiary nitrogen and with a cyclic carboxylic acid anhydride.
It should be remembered that a pre-crosslinked but non-gelled copolymer is obtained. Surprisingly a clear, transparent, non-gelled solution of a branched copolymer can be prepared under suitable polymerization conditions. Pre-crosslinking of the copolymer molecules which, because of the particular reaction conditions according to the invention, nevertheless does not lead to gelled products can be brought about by using mono-mers with at least two ethylenically unsaturated groups.
The polymerization is carried out so that a solutlon of the polymer with a solids content of 40 to 65~ by weight results. The solids content depends on the content of copolymerized monomers containing several ethylenically unsaturated bonds. If this content is low, polymerization can be càrried out at higher solids contents.
It is furthermore necessary to use suitable initiators, and, depending on the content of polyfunc-tional monomer, at least 0.5~ by weight, but preferably at least 2.5~ by weight, of a polymerization regulator.
~5 The choice of initiator depends on the content of poly-unctional monomers employed. If the content is low, the initiators customary for such temperatures, such as, for example, peroxyesters, can be used. At a higher content of polyfunctional monomers, initiators such as, or example, azo compounds are preferably employed.
~;Eter the polymerization, the polymer solution is con-celltrated to the desired solids content, preferably to solids contents of 60% by weight, by distilling off the solvent. The clear copolymer solutions thus obtained have a viscosity of 0.4 to 10 dPa.s when adjusted to a solids content of 50~ by weight.

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The polymerization is carried out in the pres-ence of an organic solvent. Examples are ethanol, iso-propanol, n-propanol, n-butanol, isobutanol, t-butanol, methyl, ethyl, propyl and butyl acetate, acetone, methyl ethyl ketone, xylene and toluene.
The polymerization can also be carried out in the presence of a chlorinated polyolefin, -the ratio of acrylate to polyolefin ranging from 98:2 to 30:70.
Acrylate resin solutions which, after crosslinking according to the invention, guarantee good adhesion to non-metallic substrates, such as, for example, plastics, result.
Compounds containing mercapto groups are pre-ferably suitable as polymerization regulators, mercap-to-ethanol being particularly preferably employed. Other possible regulators are, for example, t-dodecylmercap-tan, phenylmercaptan, octyldecylmercaptan, butylmercap-tan and thio-carboxylic acids, such as, for example, thiolactic acid.
It should be ensured that no hydroxymercaptans or mercaptans with primary SH groups are employed as the polymerization regulator in the preparation of the acrylate copolymer obtained from monomers with at least two polymerizable, olefinically unsaturated double bonds, monomers with cyclic carboxylic acid anhydride groups, other polymerizable monomers with an olefinical-ly unsaturated double bond, compounds which contain both at least one hydrogen capable of reaction with acid anhydride groups and at least one tertiary amino group and, if desired, monofunctional compounds with active hydrogen. When choosing the polymerization regulator for the preparation of the acrylate obtained from mono-mers with at least two polymerizable, olefinically unsa-turated double bonds, glycidyl esters of ethylenically unsaturated carboxylic acids and/or glycidyl ethers of olefinically unsaturated compounds, other polymerizable '' - ' ' .
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monomers with an olefinically unsaturated double bond, amines with a secondary amino group or di- or polyamines which contain at least one tertiary amino group and at least one primary or secondary amino group and/or car-boxylic acids which contain a tertiary nitrogen andcyclic carboxylic acid anhydrides, it should be ensured that no thiocarboxylic acids are used.
The invention also relates to a coating agent containing, as the essential binder, A) an acrylate copolymer as defined above, and B) a compound containing at least two epoxide groups per molecule, the ratio of (A) to (B) being chosen so that the ratio of the acid groups of (A) to the epoxide groups of (B) is in the range from 0.5 : 3 to 2 : 0.5, and optionally further containing a crosslinking catalyst.
Examples of compounds with at least two epoxide groups per molecule are condensation products of epichlorohydrin and bisphenol A, cycloaliphatic bis-~0 epoxides which correspond to the formulae (I) and (II):
o C - O - CH (I) < ~ ~ >

O O
~ 2 0 - e - (CH2)~ - C - O - CH (II) 3~ R R = H,CH3 R
and epoxidized polybutadienes which are formed by reac-tion of commercially available polybutadiene oils with peracids or organic acid/H202 mixtures, novolaks con-taining epoxide groups, glycidyl.ethers of a polyhydric alcohol, for example ethylene glycol diglycidyl ether, :; , ~ ~ - ; ' ' , '-~ ~ .

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glycerol polyglycidyl e-ther, sorbitol polyglycidyl ether, trimethylolpropane polyglycidyl ether and penta-erythritol polyglycidyl ether, and low molecular weight acrylate resins with lateral oxirane groups.
If appropriate, a crosslinking catalyst can be used. Tertiary amines, quaternary ammonium compounds, such as, for example, benzyltrimethylammonium hydroxide and benzyltrimethylammonium chloride, particular chro-mium compounds and tin compounds are especially suitable here. The use of a crosslinking catalyst is of course unnecessary in most cases where tertiary amino groups are already incorporated into the acrylate copolymer.
Lower stoving temperatures and shorter stoving times are achieved by using an internal or external crosslinking catalyst. The crosslinking catalyst is preferably used in an amount of 0.5 to 10% by weight, based on the weight of the di- or polyepoxide component.
The invention also relates to a process for the preparation of a coating agent as defined above, ~0 which is characterized in that, for preparation of the coating agent, an acrylate copolymer (A) as defined above is processed with (B), a compound which contains at least two epoxide groups per molecule, if appropriate also using a crosslinking catalyst, and with organic 2~ solvents, if appropriate pigments and customary auxilia-ries and additives, by mixing and if appropriate dis-persing, to give a coating composition, the ratio of (A) to (~) being chosen so that the ratio of the acid groups of (A) to the epoxide groups of (~) is in the range from 30 0.5 : 3 to 2 : 0~5.
The coating agents according to the invention can be hardened at low temperatures, for example at temperatures of 20 to 80 C, and are therefore employed, in particular, in repair lacquering on motor vehicles.
3~ The coating agents can of course also be stoved at tem-peratures higher than 80C.

- 20 - ~3~2~

The invention also relates to a process for the production of a coating, in which a coating agent as defined above is applied in the form of a film by spraying, flooding, dipping, rolling, knife-coating or brushing to a substrate, and the film is hardened to a firmly adhering coating. The invention also relates to substrates coated by the process according to the inven-tion.
The coatings according to the invention have outstanding properties in respect of stability towards long-term exposure to chemicals and solvents, and in respect of stability towards gasoline, elasticity, gloss, corrosion resistance and stability towards water and steam. If appropriate, the coating agents harden at low temperatures and can therefore be used, for example, in car repair lacquering. It is furthermore possible to achieve a high solids content of the hardenable coating agents at a relatively low viscosity, compared with linear acrylate copolymers and with acrylate resins with a lower content of copolymerized monomers with several ethylenically unsaturated bonds.
The invention is illustrated below in more detail with the aid of embodiment examples:
A) Preparation of copolymers according to the invention (binder A) In the following examples, unless indicated otherwise, all percentage data relate to percentages by weight and all the parts quoted relate to parts by weight. The solids contents were determined in a circu-lating air oven after 1 hour at 130 C. The viscosities were determined on a ball/plate viscometer.
Acrylate resin I
The following are taken in a 3 1 stainless steel kettle 212 parts of SOLVENON PM* (l-methoxypropan-2-ol) 212 parts of butyl acetate 98/100 * Trade mark .- . . . ,-: .- - :- . - . .

' -'.

- 21 - ~ ~ ~2~

0.16 part of hyperphosphorous acid (50% in H2O) The mixture is heated to 110C and the following components are metered in uniformly from 2 feed vessels in the course of 3 hours:
Feed 1:
160 parts of styrene 160 parts of hexanediol dimethacrylate 80 parts of ~-carboxyethyl acrylate 120 parts of n-butyl acrylate 200 parts of t-butyl acrylate 52 parts of thiolactic acid Feed 2:
80 parts of 4-vinylpyridine The following components are metered in uniformly from feed vessel 3 in the course of 4 hours Feed 3:
32 parts of azobisisobutyronitrile 230 parts of SOLVENON PM (l-methoxypropan-2-ol) 230 par-ts of butyl acetate 98/100 All 3 feeds are started at the same time. When the initiator feed has ended, after-polymerization is carried out for a further 2 hours.
Acrylate resin solution I has a solids content (2 hours at 100C) of 50.7~, a viscosity (23C, original) of 6.1 dPa.s and an acid number of 67 (mg of KOH/g of solid resin).
Acrylate resin II
The process and feed times are as for acrylate resin I, Initial mixture: 197.0 parts of butyl acetate 98/100 197.0 parts of 1-methoxyprop-2-yl acetate Feed 1: 140 parts of styrene 140 parts of butanediol dimeth-acrylate 105 parts of n butyl acrylate ,.,~

~3~2~

175 parts of t-butyl acrylate 70 parts of 4-hydroxybutyl acrylate 31.5 parts of mercaptoethanol Feed 2: 70 parts of 4-vinylpyridine 5 Feed 3: 25.2 par-ts of azobisisobutyronitrile 181.3 parts of butyl acetate 98/100 181.3 parts of 1-methoxyprop-2-yl acetate Feed 1 ~ 2 3 hours, Feed 3 4 hours, followed by after-polymerization at 110C for 3 hours.
90.8 parts of succinic anhydride are added to the acrylate resin solution and the mixture is kept at 120C
for 6 hours, with stirring. The solution of the addi-tion product of succinic anhydride on the OH-acrylate has an acid number of 71, a viscosity of 6 dPa.s and a solids content of 52.2%.
Acrylate resin solution III
The foIlowing are taken in a 3 1 stainless steel kettle:
195 parts of butyl acetate 9~/100 195 parts of 1-methoxyprop-2-yl acetate The mixture is heated up to 112 C and feeds 1 and 2 are metered in uniformly in the course of 3 hours:
Feed 1: 140 parts of styrene 140 parts of hexanediol dimethacrylate 70 parts of butanediol monoacrylate 105 parts of n-butyl acrylate 175 parts of t-butyl acrylate 31.5 parts of mercaptoethanol Feed 2: 70 parts of 4-vinylpyridine Feed 3 is metered in uniformly in the course of 4.25 hours, Eeeds 1, 2 and 3 being started simulta-neously.
Feed 3: 181.6 parts of butyl acetate 98/100 181.6 parts of 1-methoxyprop-2-yl acetate 25.2 parts of azobisisobutyronitrile .

-~ - 23 - 13~2~

After the end of feed 3, after-polymerization is carried out at 112C for a further 2 hours, 81.4 parts of succinic anhydride are then added and the mixture is kept at 120C for 6 hours, with stirring. The resulting clear acrylate resin solution has a solids content of 52.5%, an acid number of 68 and a viscosity of 6.8 dPa.s.
Acrylate resin solution IV
The following components are taken and heated up to 110C in a 3 1 stainless steel kettle:
Initial mixture: 235 parts of SOLVENON PM
235 parts of butyl acetate 98/100 0.16 part of hyperphosphorous acid ` The following components are metered in uniformly in the course of 3 hours:
Feed 1: 140 parts of styrene 182 parts of butanediol dimethacrylate 133 parts of n-butyl acrylate 175 parts of t-butyl acrylate 2~ 70 parts of thiolactic acid Feed 2: 70 parts of 4-vinylpyridine The following components are metered in uni.formly in the course of 4 hours:
Feed 3: 161.2 parts of SOLVENON PM
161.2 parts of butyl acetate 98/100 22.4 parts of azobisisobutyronitrile Feeds 1, 2 and 3 are started uniformly, the tem-perature is kept at 110 C during the polymerization and, when feed 3 has ended, after-polymerization is carried out for 2 hours. The resulting clear acrylate resin solution has a viscosity of 2.1 dPa.s , a solids content of ~8.5~ and an acid number of 52.
Acrylate resin solution V
The following components are taken in a 3 1 .
stainless steel kettle:
Initial mixture: 266 parts of butyl acetate 98/100 . . . - , , . . .. ~
~.

: . :
.~, .~ ~

~3~2~

266 parts of xylene The initial mixture is heated up to 112C and feeds 1 and 2 are metered in uniformly at 112C in the course of 3 hours.
5 Feed 1: 70 parts of butyl methacrylate 105 parts of butanediol diacrylate 175 parts of styrene 210 par-ts of t-butyl acrylate 70 parts of 2-ethylhexyl acrylate 42 parts of tert.-dodecylmercaptan Feed 2: 70 parts of maleic anhydride 70 parts of butyl acetate 98/100 70 parts of xylene Feed 3 is metered in uniformly in the course of 3.5 hours, all feeds being started simultaneously.
Feed 3: 23.8 parts of 2,2'bis-azo(2-methyl-butyronitrile) 47.6 parts of butyl acetate 98/100 47.6 parts of xylene When feed 3 has ended, after-polymerization is carried out at 114C for 2 hours. The acrylate`resin solution has a solids content of 49% and a viscosity of 3.1 dPa.s.
~5 To this acrylate resin solution, 53.6 parts of 2-aminopyridine 109 parts of 2-methoxyprop-2-yl acetate are added and an addition reaction is carried out with the maleic anhydride copolymer at 80C. The reaction has ended after 3.5 hours at 80 C and the clear and colorless acrylate resin solution has a viscosity of 9.5 dPa.s , an acid number of 57, an amine equivalent weight of 1400 ~ 20 and a solids content of 49.4%.
Acrylate resin solution VI
The following are taken in a 3 l stainless steel kettle:

- 25 - ~3~2~ 3 Initial mixture: 197 parts of 1-methoxyprop-2-yl acetate 197 parts of butyl acetate The initial mixture is heated up to 110C and feeds 1 and 2 are metered in uniformly in the course of 3 hours.
Feed 1: 140 parts of styrene 140 parts of butanediol dimeth-acrylate 10 70 parts of butanediol monoacrylate 105 parts of n-butyl acrylate 175 parts of t-butyl acrylate 31.5 parts of mercaptoethanol Feed 2: 70 parts of imidazoylethyl 15 methacrylate Feed 3: 25.2 parts of 2,2'bisazobutyronitrile 181.3 parts of butyl acetate 98/100 181.3 parts of 1-methoxyprop-2-yl acetate 20 Feed 3 is metered in uniformly in the course of 4 hours. Feeds 1, 2 and 3 are started simultaneously, and the temperature is kept at 110C during the polymeriza-tion. When feed 3 has ended, after-polymerization is carried out at 110C for a further 3 hours. The clear, colorless acrylate resin solution thus obtained is then reacted with 81 parts of succinic anhydride at 120C to ~ive the COOH-acrylate. The resulting acrylate resin solution has a viscosity of 7.2 dPa.s , a solids content o 52.3~ and an acid number of 68.
Acrylate resin solution VII
The following are taken in a 3 1 stainless steel kettle:
286 parts of xylene 286 parts of butyl acetate 98/100 143 parts o butan-2-ol .

.
.

- 26 ~ ~ 3 ~ 2 ~ ~t~

The initial mixture is heated up to 110C and feeds 1 and 2 are metered in uniformly in -the course of 3 hours.
Feed 1:
183 parts of methyl methacrylate 144 parts of ~-carboxyethyl acrylate 136 parts of tert.-butyl acrylate 97 parts of divinylbenzene (isomer mixture, 62~ in ethylstyrene) 80 parts of hydroxyethyl methacrylate 80 parts of n-butyl acrylate 44 parts of mercaptoethanol Feed 2:
80 parts of vinylpyridine Feed 3 is metered in over a period of 4 hours, all the feeds being started simultaneously and the tem-perature being kept at 110C during the polymerization.
Feed 3:
27.2 parts of 2,2'-bisazo(2-methylbutyronitrile) ~0 62 parts of xylene 62 parts of butyl acetate 98/100 31 parts of butan-2-ol When feed 3 has ended, after-polymerization is carried oùt at 110C for a further 2 hours. The clear acrylate resin solution thus obtained has a solids con-tent of 50.5%, an acid number of 64.2 and a viscosity of 12.0 dPa.s.
~crylate resin solution VIII
The following are taken in a 3 1 stainless steel kettle:
479 parts of xylene ~39 parts of dimethylformamide The initial mixture is heated up to 110C and feeds 1 and 2 are metered i.n uniformly in the course of 3 hours.

.:

.

~ - 27 - ~3~2~

Feed 1:
80 parts of dimethylaminoethyl methacrylate Feed 2:
183 parts of methyl methacrylate 80 parts of hydroxybutyl acrylate 47 parts of divinylbenzene (isomer mixture, 61~ in ethylstyrene) 200 parts of tert.-butyl acrylate 80 parts of hydroxyethyl methacrylate 80 parts of n-butyl acrylate 44 parts of mercaptoethanol 0.24 part of hypophosphorous acid Feed 3 is metered in over a period of 4 hours.
Feeds 1, 2 and 3 are started simultaneously.
Feed 3:
27.2 parts of 2,2'-bisazo(2-methylbutyronitrile) 103 parts of xylene 51 parts of dimethylformamide The temperature is kept at 110C during the poly-meriæation and, when feed 3 has ended, after-polymeriza-tion is carried out at 110C for a further 2 hours.
Thereafter, 101 parts of maleic anhydride are added and an addition reaction with the hydroxyl groups of the copolymer is carried out at 100 C until the acid number ~5 of 71 and a viscosity (original, 23C) of 8.2 dPa.s are reached. 340 parts of the solvent mixture are then distilled off and the residue is partly dissolved with 270 parts of butyl acetate 98/100. The resulting solu-tion of a branched acrylate has a solids content of 3~ 56.6~, a viscosity of 13.5 dPa.s and an acid number of 70.S.
Acrylate resin IX
The following are taken in a 3 1 stainless steel kettle:
480 parts of xylene 240 parts of dimethyl;ormamide ~ . . ~ . -- . I
- :

- 28 - ~3~

The initial mixture is heated up to 110C and feed 1 is metered in over a period of 3 hours:
160 parts of me-thyl methacrylate 80 parts of dimethylaminoethyl methacrylate 120 parts of n-butyl acrylate 200 parts of styrene 100 parts of 1,4-butanediol monoacrylate 80 parts of hydroxyethyl methacrylate 60 parts of hexamethylenebismethacrylamide 28 parts of mercaptoethanol (feed 1) Feed 2 is metered in over a period of 4 hours.
Feeds 1 and 2 are started simultaneously.
Feed 2:
36 parts of tert.-butyl peretylhexanoate 96 parts of xylene 48 parts of dimethylformamide The temperature is kept at 110C during the poly-merization. When feed 2 has ended, after-polymerization is carried out at 110C for a further 3 hours. 101 parts of maleic anhydride are then added at 100C and an addition reaction with the OH-acrylate is carried out until the acid number of 70 is reached. Thereafter, 227 parts of the solvent mixture are distilled off and 320 parts of n-butanol are added. The resulting solution of ~5 a branched acrylate resin has a solids content of 49.5~, an acid number of 68.3 and a viscosity of 18 dPa.s (original).
B) Preparation of toning pastes The pigment pastes were dispersed in a laboratory sand mill for 40 minutes in accordance with the follow-ing recipes (particle fineness 10 ,um).
Paste 25/2 Acrylate resin II 36.0 Anti-sedimentation agent l.S
35 Layered silicate 1.0 Lead molybdate pigment 50.0 . ~ ~ . . . . .

,- ~
.' ' ','~, ' ' ' ' :`

- 29 - ~31 Methoxypropyl acetate13.0 Paste 25/3 Acrylate resin I 37.0 Anti-sedimentation agent1.5 Titanium dioxide rutile pigment 53.0 ~lethoxypropyl acetate8.5 Paste 25/4 ~crylate resin I 90.0 Copper phthalocyanine green 10 pigment 8.0 Methoxypropyl acetate2.0 C) Preparation and testing of lacquers Covering lacquers are prepared in accordance with the following recipes and are applied to glass plates by means of a doctor blade (dry coating thickness 40 ,um), dried at room temperature or under forced conditions at 60C for 30 minutes, stored at room temperature for 6 days and then tested.
Pendulum hardness: According to Konig 0 Stability towards gasoline (FAM test fuel according to DIN 51604) and xylene: exposure for 5 minutes to a sheet of felt impregnated with the particular solvent, covered.
Example 1 25 Acrylate resin I 43.9 Paste 25/3 43,9 Silicone solution 1.0 Epoxy resin based on bisphenol A with an epoxide equivalent 30 weight of 190 6.5 ~letho~ypropyl acetate4.7 Results:
Drying: 30 minutes at 60 C Room temperature Pendulum hardness 35 after 6 days: 137 seconds 101 seconds ,:

: 1 ' ~ 30 -~3 Stability towards xylene after 6 days O.K. O.K.
Stability towards gasoline after 6 daysO.K. O.K.
5 Example 2 Acrylate resin I 44.8 Paste 25/3 44.8 Silicone solution 1.0 3,4-Epoxy-cyclohexylmethyl-10 3,4-epo~ycyclohexane carboxylate 4.4 Methoxypropyl acetate 5.0 Results:
Drying: 30 minutes at 60 C Room temperature 15 Pendulum hardness after 6 days 147 seconds 109 seconds Stability towards xylene after 6 days O.K. O.K.
Stability towards ~0 gasoline aEter 6 days O.K. O.K.
Example 3 Acrylate resin I 31.5 Paste 25/4 52.5 Silicone solution 1.3 Epoxy resin based on bisphenol A with an epoxide equivalent weight of 190 8.6 Methoxypropyl acetate 6.1 Results:
30Drying: 30 minutes at 60 C Room temperature Pen~ulum hardness ater 6 days 167 seconds 111 seconds Stability towards xylene a~ter 6 days O.K. O.K.
35 Stability towards gasoline after 6 days O.K. O.K.

~. , ::

- 31 ~ ~3~2~

Example ~
Acrylate resin II43.7 Paste 25/3 43.7 Silicone solution 1.0 Epoxy resin based on blsphenol A with an epoxide equivalent weight of 190 6.9 l~lethoxypropyl acetate 4.7 Results:
10 Drying: 30 minutes at 60 C Room temperature Pendulum hardness after 6 days 67 seconds 72 seconds Stability towards xylene after 6 days O.K. slight marking Stability towarcls gasoline after 6 days O.K. slight marking Example 5 Acrylate resin VII is mixed with a polyglycidyl ether based on sorbitol (epoxide equivalent weight 180) in a ratio of 82/18`(solid to solid) and the mixture is diluted with butyl acetate to 25'' DIN ~ and knife-coated onto glass sheets (wet film thickness 200 jum).
Drying: 30 minutes at 60 C Room temperature Pendulum hardness 25 after 3 days 98'' 81'' Crosslinking test with methyl ethyl ketone (double wipe) 200 double 200 double wipes wipes Example 6 Acrylate resin VIII is mixed with a novolak poly-~lycidyl ether (epoxide equivalent weight 178) in a ratio of 82/18 (solid to solid) and the mixture is diluted with xylene and knife-coated onto glass sheets ~5 ~200 ~um wet film thickness). After drying at room tem-- : .
.
. . ,. ~ .

:i ' - - 32 - 1 3 ~ r~

perature ior 6 days, a pendulum hardness of 70'' is achieved. The result of the crosslinking test with ~ethyl ethyl ketone is 155 double wipes.

. .

~ .

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Coating agent containing, as essential binder, A) an acrylate copolymer having an acid number of about 15 to about 200 and obtained from a1) more than 3 to 30% by weight of a monomer with at least two polymerizable, olefinically unsatu-rated double bonds, a2) 3 to 30% by weight of a monomer containing carboxyl groups, and a3) 40 to 93% by weight of other monomers with a polymerizable, olefinically unsaturated double bond, the sum of a1), a2) and a3) being 100% by weight; and B) a compound containing at least two epoxide groups per molecule, the ratio of (A) to (B) being chosen so that the ratio of the acid groups of (A) to the epoxide groups of (B) is in the range of 0.5:3 to 2:0.5.

2. Coating agent as claimed in claim 1, further eon-taining a crosslinking catalyst.

3. Coating agent containing, as essential binder, A) an acrylate copolymer having an acid number of about 15 to about 200 and obtained from a1) more than 3 to 30% by weight of a monomer with at least two polymerizable, olefinically unsatu-rated double bonds, di- and polyesters of di- and polyols with acrylic acid being excluded, a2) 3 to 30% by weight of a monomer containing carboxyl groups, a3) 0.1 to 20% by weight of a tertiary amine with a polymerizable, olefinically unsaturated double bond, a4) 0 to 40% by weight of a monomer containing hydroxyl groups, and a5) 0 to 80% by weight of other monomers with a polymerizable, olefinically unsaturated double bond, the sum of components a1), a2), a3), a4) and a5) being 100%
by weight; and B) a compound containing at least two epoxide groups per molecule, the ratio of (A) to (B) being chosen so that the ratio of the acid groups of (A) to the epoxide groups of (B) is in the range of 0.5:3 to 2:0.5.

4. Coating agent as claimed in claim 3, further con-taining a crosslinking catalyst.

5. Coating agent containing, as essential binder, A) an acrylate copolymer having an acid number of about 15 to about 200 and obtained from a1) more than 3 to 30% by weight of a monomer with at least two polymerizable, olefinically unsatu-rated double bonds, di- and polyesters of di- and polyols with acrylic acid being excluded, a2) 0.1 to 20% by weight of a tertiary amine with a polymerizable, olefinically unsaturated double bond, a3) 5 to 40% by weight of monomers containing hydroxyl groups, a4) 0 to 80% by weight of other polymerizable monomers with an olefinically unsaturated double bond and a5) cyclic carboxylic acid anhydrides, the sum of a1), a2), a3) and a4) being 100% by weight; and B) a compound containing at least two epoxide groups per molecule, the ratio of (A) to (B) being chosen so that the ratio of the acid groups of (A) to the epoxide groups of (B) is in the range of 0.5:3 to 2:0.5.

6. Coating agent as claimed in claim 5, further con-taining a crosslinking catalyst.

7. Coating agent containing, as essential binder, A) an acrylate copolymer having an acid number of about 15 to about 200 and obtained from a1) more than 3 to 30% by weight of monomers with at least two polymerizable, olefinically unsatu-rated double bonds, a2) 1 to 25% by weight of monomers with cyclic carboxylic acid anhydride groups, a3) 45 to 80% by weight of other polymerizable monomers with an olefinically unsaturated double bond, the sum of a1), a2) and a3) being 100% by weight, and a4) compounds which contain both at least one hydrogen which can react with acid anhydride groups and at least one tertiary amino group; and B) a compound containing at least two epoxide groups per molecule, the ratio of (A) to (B) being chosen so that the ratio of the acid groups of (A) to the epoxide groups of (B) is in the range of 0.5:3 to 2:0.5.

8. Coating agent as claimed in claim 7, further con-taining a crosslinking agent.

9. Coating agent containing, as essential binder, A) an acrylate copolymer having an acid number of about 15 to about 200 and obtained from a1) more than 3 to 30% by weight of monomers with at least two polymerizable, olefinically unsatu-rated double bonds, a2) 1 to 30% by weight of glycidyl esters of ethylenically unsaturated carboxylic acids and/or glycidyl ethers of olefinically unsaturated compounds, a3) 40 to 95% by weight of other polymerizable monomers with an olefinically unsaturated double bond, the sum of all the monomers being 100% by weight, and a4) amines with a secondary amino group or di-or polyamines with at least one tertiary amino group and one primary or secondary amino group and/or a5) carboxylic acids which contain a tertiary nitrogen atom and a6) cyclic carboxylic acid anhydrides; and B) a compound containing at least two epoxide groups per molecule, the ration of (A) to (B) being chosen so that the ratio of the acid groups of (A) to the epoxide groups of (B) is in the range of 0.5:3 to 2:0.5.

10. Coating agent as claimed in claim 9, further con-taining a crosslinking catalyst.

11. Coating agent as claimed in claim 2 or 4, wherein the crosslinking catalyst is present in an amount of 0.5 to 10% by weight, based on the weight of the di- or polyepoxide component.

12. Coating agent as claimed in claim 6, 8 or 10, wherein the crosslinking catalyst is present in an amount of 0.5 to 10% by weight, based on the weight of the di- or polyepoxide component.

13. Process for the preparation of a coating agent as defined in claim 1 or 3, wherein the acrylate copolymer (A) is mixed with the compound (B) which contains at least two epoxide groups per molecule, in the presence of organic solvents, the ratio of (A) to (B) being chosen so that the ratio of the acid groups of (A) to the epoxide groups of (B) is in the range of 0.5:3 to 2:0.5.

14. Process for the preparation of a coating agent as defined in claim 5, 7 or 9, wherein the acrylate copolymer (A) is mixed with the compound (B) which con-tains at least two epoxide groups per molecule, in the presence of organic solvents the ratio of (A) to (B) being chosen so that the ratio of the acid groups of (A) to the epoxide groups of (B) is in the range of 0.5:3 to 2:0.5.

15. Process for the production of a coating, wherein a coating agent as defined in claim 1 is applied in the form of a film by spraying, flooding, dipping, rolling, knife-coating or brushing onto a substrate, and the film is hardened to a firmly adhering coating.

16. Process for the production of a coating, wherein a coating agent as defined in claim 3 is applied in the form of a film by spraying, flooding, dipping, rolling, knife-coating or brushing onto a substrate, and the film is hardened to a firmly adhering coating.

17. Process for the production of a coating, wherein a coating agent as defined in claim 5 is applied in the form of a film by spraying, flooding, dipping, rolling, knife-coating or brushing onto a substrate, and the film is hardened to a firmly adhering coating.

18. Process for the production of a coating, wherein a coating agent as defined in claim 7 is applied in the form of a film by spraying, flooding, dipping, rolling, knife-coating or brushing onto a substrate, and the film is hardened to a firmly adhering coating.

19. Process for the production of a coating, wherein a coating agent as defined in claim 9 is applied in the form of a film by spraying, flooding, dipping, rolling, knife-coating or brushing onto a substrate, and the film is hardened to a firmly adhering coating.

20. Coated substrate obtained by a process as defined in claim 15 or 16.

21. Coated substrate obtained by a process as defined in claim 17, 18 or 19.