Graft polymers of natural substances containing saccharide structures or derivatives thereof and ethylenically unsaturated compounds and their use

A polymer prepared by free radical polymerization of monomers selected from the group consisting of (A) and (B), wherein

• (A) monomers or a monomer mixture of
• (a) from 10-100% by weight of N-vinyl carboxamides of the formula ##STR13## wherein R.sup.1 and R.sup.2 are each H or C.sub.1 -C.sub.6 -alkyl (b) 0-90% by weight of other carboxyl-free monoethylenically unsaturated monomers which are copolymerizable with monomers (a), said carboxyl-free monoethylenically unsaturated monomers selected from the group consisting of vinyl esters of C.sub.1 -C.sub.6 -saturated carboxylic acids, esters of monoethylenically unsaturated C.sub.3 -C.sub.6 -carboxylic acids, amides of monoethylenically unsaturated C.sub.3 -C.sub.6 -carboxylic acids, nitriles of monoethylenically unsaturated C.sub.3 -C.sub.6 -carboxylic acids, N-vinylpyrrolidone, N-vinylcaprolactam, acrylonitrile, methacrylonitrile, N-vinylimidazole, substituted N-vinylimidazoles, N-vinylimidazolines, vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate and 2-acrylimido-2-methyl-propane sulfonic acid, and
• (c) 0-5% by weight of monomers containing two or more ethylenically unsaturated, non-conjugated double bond;
• wherein a+b+c=100%,
• are polymerized in the presence of
• (B) a compound selected from the group consisting of monosaccharides, oligosaccharides, polysaccharides, oxidatively, hydrolytically or enzymatically degraded polysaccharides, oxidized hydrolytically degraded or oxidized enzymatically degrade polysaccharides, chemically modified mono- oligo, or polysaccharides selected from the group consisting of phosphated starch, acetylated starch, starch alkyl ethers, starch hydroxyalkyl ethers, starch carboxyalkyl ethers, starch allyl ethers, cationically modified starches, hydrogenation products of starch hydrolysis products, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethyl-hydroxyethylcellulose, sulfoethylcellulose, carboxymethyl-sulfoethylcellulose, hydroxypropylsulfoethylcellulose, hydroxyethylsulfoethylcellulose, methylsulfoethylcellulose and ethylsulfoethylcellulose, and mixtures thereof;
• in a monomer weight ratio (A):(B) of from 95:5 to 20:80
• to form a polymer having a K-value of 8-250 measured in a 1% strength solution of said polymer at pH 7 and at 25.degree. C., said polymer containing 10% by weight or more of units of the formula ##STR14## wherein R.sup.1 and R.sup.2 are each H or C.sub.1 -C.sub.6 -alkyl, wherein said polymerization is followed by hydrolysis of 2 to 100% of the carboxamide groups of the graft polymer to form units of the formula ##STR15## wherein R.sup.2 is H or C.sub.1 -C.sub.6 -alkyl.