Patent ID: 7790667

Claim:
A water-soluble copolymer which consists essentially of, in copolymerized form, (a) 60 to 99% by weight of at least one monoethylenically unsaturated polyalkylene oxide monomer of the formula I H 2 C═CR 1 —X—Y R 2 —O n R 3 I wherein the variables have the following meanings: X is —CH 2 — or —C(O)—, if Y is —O—; is —C(O)—, if Y is —NH—; is —O— or —O—(CH 2 ) 4 —, if Y is a chemical bond; Y is —O—, —NH— or a chemical bond; R 1 is hydrogen or methyl; R 2 is C 2 -C 4 -alkylene radicals, which may be identical or different and also linear or branched, but where at least 50% of the radicals R 2 are ethylene; R 3 is C 1 -C 4 -alkyl, phenyl, p-(C 1 -C 12 -alkyl)phenyl or hydrogen; n is an integer from 6 to 50; (b) 1 to 40% by weight of at least one nonquaternized dipolar monomer comprising at least one nitrogen atom and chosen from the group of N-vinylpyrrolidones, N-vinylimidazoles, N-vinylcaprolactams, vinylpyridines, N-vinylformamides, N-vinylacetamides, basic (meth)acrylic esters and (meth)acrylamides; (c) 0 to 39% by weight of other nonionic monoethylenically unsaturated monomers; and (d) 0 to 10% by weight of other anionic monoethylenically unsaturated monomers; has an average molecular weight M w of from 2000 to 500 000 D, and has a glass transition temperature of from −62° C. to −48° C.