Aqueous emulsion polymers, their preparation and use

1. An aqueous emulsion polymer, comprising units of:

(A) a monomer A,

(B) a monomer B, which is a (meth)acrylate having at least one olefinically unsaturated side group, and

(C) a photoinitiator,

wherein said monomer B comprises at least one member selected from the group consisting of methacryloyloxy-2-ethyloleamide, methacryloyloxy-2-ethyllinoleamide, methacryloyloxy-2-ethyllinolenamide, methacryloyloxy-2-hydroxypropyl-linoleic ester methacryloyloxy-2-hydroxypropyl-oleic ester, and a mixture thereof, and

said photoinitiator comprises a mixture of 4-methylbenzophenone and 2,4,6-trimethylbenzophenone.

2. The aqueous emulsion polymer according to claim 1 , wherein the glass transition temperature is ≦60° C.

3. The aqueous emulsion polymer according to claim 1 , wherein the glass transition temperature is ≧−50° C. and ≦30° C.

4. The aqueous emulsion polymer according to claim 1 , wherein the glass transition temperature is ≧−50° C. and ≦10° C.

5. The aqueous emulsion polymer according to claim 1 , wherein the glass transition temperature is ≧−40° C. and ≦0° C.

6. The aqueous emulsion polymer according to claim 1 , wherein the monomer A is at least one monomer selected from the group consisting of α,β-ethylenically unsaturated monomers.

7. The aqueous emulsion polymer according to claim 1 , wherein the monomer A is selected from the group consisting of esters of α,β-ethylenically unsaturated monocarboxylic and dicarboxylic acids with C 1 -C 20 alkanols, vinylaromatics, esters of vinyl alcohol with C 1 -C 30 monocarboxylic acids, ethylenically unsaturated nitriles, vinyl halides, vinylidene halides, monoethylenically unsaturated carboxylic and sulfonic acids, phosphorus-containing monomers, esters of α,β-ethylenically unsaturated monocarboxylic and dicarboxylic acids with C 2 -C 30 alkanediols, amides of α,β-ethylenically unsaturated monocarboxylic and dicarboxylic acids of C 2 -C 30 amino alcohols having a primary or secondary amino group, primary amides of α,β-ethylenically unsaturated monocarboxylic acids and the N-alkyl and N,N-dialkyl derivatives thereof, N-vinyllactams, open-chain N-vinylamide compounds, esters of allyl alcohol with C 1 -C 30 monocarboxylic acids, esters of α,β-ethylenically unsaturated monocarboxylic and dicarboxylic acids with amino alcohols, amides of α,β-ethylenically unsaturated monocarboxylic and dicarboxylic acids with diamines having at least one primary or secondary amino group, N,N-diallylamines, N,N-diallyl-N-alkylamines, vinyl- and allyl-substituted nitrogen heterocycles, vinyl esters, C 2 -C 8 monoolefins, nonaromatic hydrocarbons having at least two conjugated double bonds, polyether (meth)acrylates, monomers containing urea groups, and/or mixtures thereof.

8. The aqueous emulsion polymer according to claim 1 , wherein said monomer B is present in an amount of 0.1% to 30% by weight and component C in an amount of 0.01% to 5% by weight, in each based on the sum of the monomers.

9. The aqueous emulsion polymer according to claim 1 , wherein the monomer B has an iodine number in the range from 50 to 300 g iodine/100 g monomer.

10. The aqueous emulsion polymer according to claim 1 , wherein

said monomer B comprises methacryloyloxy-2-hydroxypropyl-oleic ester.

11. A coating material comprising a binder according to claim 1 .

12. An exterior architectural paint comprising a binder according to claim 1 .

13. An elastic coating composition comprising a binder according to claim 1 .

14. The aqueous emulsion polymer according to claim 1 , wherein the mixture of said photoinitiator further comprises at least one member selected from the group consisting of benzophenone; acetophenone; isopropylthioxanthone; (meth)acryloxyethoxybenzophenone; and 4-vinyloxybenzophenone.

15. The aqueous emulsion polymer according to claim 1 , wherein the mixture of said photoinitiator further comprises benzophenone.