A polymer mixture in solid or aqueous form, comprising, based on the polymer fraction, 5 to 95% by weight of a water-soluble or water-dispersible polymer having a weight-average molecular weight of 1000 to 20 000 g/mol, determined by means of gel-permeation chromatography in comparison with polyacrylic acid standards, of 20 to 80% by weight of at least one monomer selected from the group consisting of C 2 to C 8 olefins, allyl alcohol, isoprenol, C 1 to C 4 alkyl vinyl ethers and vinyl esters of C 1 to C 4 monocarboxylic acids, 20 to 80% by weight of at least one monoethylenically unsaturated C 3 to C 8 carboxylic acid, an anhydride or salt of same, 0 to 50% by weight of one or more monomers comprising sulfonic acid groups, 5 to 95% by weight of a water-soluble or water-dispersible polymer having a weightaverage molecular weight of 1000 to 50 000 g/mol, determined by means of gel-permeation chromatography in comparison with polyacrylic acid standards, of 30 to 100% by weight of at least one monoethylenically unsaturated C 3 to C 8 carboxylic acid, an anhydride or salt of same, 0 to 70% by weight of one or more monomers comprising sulfonic acid groups, 0 to 70% by weight of one or more nonionic monomers of the formula H 2 C=C(R 1) (CH 2) x O[R 2 O] o -R 3, where R 1 is hydrogen or methyl, R 2 is identical or different, linear or branched, C 2 -C 6 alkylene radicals, which can be arranged in blocks or randomly, and R 3 is hydrogen or a straight-chain or branched C 1 -C 4 alkyl radical, x is 0, 1 or 2, and o is a number from 3 to 50. 5 to 95% by weight of a water-soluble or water-dispersible polymer having a weight-average molecular weight of 1000 to 20 000 g/mol, determined by means of gel-permeation chromatography in comparison with polyacrylic acid standards, of 20 to 80% by weight of at least one monomer selected from the group consisting of C 2 to C 8 olefins, allyl alcohol, isoprenol, C 1 to C 4 alkyl vinyl ethers and vinyl esters of C 1 to C 4 monocarboxylic acids, 20 to 80% by weight of at least one monoethylenically unsaturated C 3 to C 8 carboxylic acid, an anhydride or salt of same, 0 to 50% by weight of one or more monomers comprising sulfonic acid groups, 20 to 80% by weight of at least one monomer selected from the group consisting of C 2 to C 8 olefins, allyl alcohol, isoprenol, C 1 to C 4 alkyl vinyl ethers and vinyl esters of C 1 to C 4 monocarboxylic acids, 20 to 80% by weight of at least one monoethylenically unsaturated C 3 to C 8 carboxylic acid, an anhydride or salt of same, 0 to 50% by weight of one or more monomers comprising sulfonic acid groups, 5 to 95% by weight of a water-soluble or water-dispersible polymer having a weightaverage molecular weight of 1000 to 50 000 g/mol, determined by means of gel-permeation chromatography in comparison with polyacrylic acid standards, of 30 to 100% by weight of at least one monoethylenically unsaturated C 3 to C 8 carboxylic acid, an anhydride or salt of same, 0 to 70% by weight of one or more monomers comprising sulfonic acid groups, 0 to 70% by weight of one or more nonionic monomers of the formula H 2 C=C(R 1) (CH 2) x O[R 2 O] o -R 3, where R 1 is hydrogen or methyl, R 2 is identical or different, linear or branched, C 2 -C 6 alkylene radicals, which can be arranged in blocks or randomly, and R 3 is hydrogen or a straight-chain or branched C 1 -C 4 alkyl radical, x is 0, 1 or 2, and o is a number from 3 to 50. 30 to 100% by weight of at least one monoethylenically unsaturated C 3 to C 8 carboxylic acid, an anhydride or salt of same, 0 to 70% by weight of one or more monomers comprising sulfonic acid groups, 0 to 70% by weight of one or more nonionic monomers of the formula H 2 C=C(R 1) (CH 2) x O[R 2 O] o -R 3, where R 1 is hydrogen or methyl, R 2 is identical or different, linear or branched, C 2 -C 6 alkylene radicals, which can be arranged in blocks or randomly, and R 3 is hydrogen or a straight-chain or branched C 1 -C 4 alkyl radical, x is 0, 1 or 2, and o is a number from 3 to 50.