A polymer composition comprising a polymer material which is obtainable by reacting a) a polymer P1 of the formula where k is an integer from 0 to 4; n is 0 or 1 p is an integer from 1 to 10, the number average of p being from 1.5 to 10; Q is a divalent moiety selected from the group consisting of -O- and -NH-; P is a p-valent hydrophilic neutral polymer radical; R 1 is independently selected from the group consisting of halogen, COOCH 3, -N(C 1 -C 6 -alkyl) 2, -NO 2, -S(=O) 2 R 2, C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy, aryloxy, aryl, heteroaryl, where aryl, hetaryl and aryloxy are unsubstituted or substituted by 1,2, 3 or 4 radicals selected from the group consisting of-OH, -COOCH 3, -N(C 1 -C 6 -alkyl) 2, -NO 2, -S(=O) 2 R 2, C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy and halogen; R 2 is selected from the group consisting of -NH 2, -NH(C 1 -C 6 -alkyl), -N(C 1 -C 6 -alkyl) 2, C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy, aryl and heteroaryl, where aryl and hetaryl are unsubstituted or substituted by 1,2, 3 or 4 radicals selected from the group consisting of C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy and halogen; with b) a succinic anhydride of the formula where R is C 4 -C 24 -alkyl or C 4 -C 24 -alkenyl. a) a polymer P1 of the formula where k is an integer from 0 to 4; n is 0 or 1 p is an integer from 1 to 10, the number average of p being from 1.5 to 10; Q is a divalent moiety selected from the group consisting of -O- and -NH-; P is a p-valent hydrophilic neutral polymer radical; R 1 is independently selected from the group consisting of halogen, COOCH 3, -N(C 1 -C 6 -alkyl) 2, -NO 2, -S(=O) 2 R 2, C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy, aryloxy, aryl, heteroaryl, where aryl, hetaryl and aryloxy are unsubstituted or substituted by 1,2, 3 or 4 radicals selected from the group consisting of-OH, -COOCH 3, -N(C 1 -C 6 -alkyl) 2, -NO 2, -S(=O) 2 R 2, C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy and halogen; R 2 is selected from the group consisting of -NH 2, -NH(C 1 -C 6 -alkyl), -N(C 1 -C 6 -alkyl) 2, C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy, aryl and heteroaryl, where aryl and hetaryl are unsubstituted or substituted by 1,2, 3 or 4 radicals selected from the group consisting of C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy and halogen; with k is an integer from 0 to 4; n is 0 or 1 p is an integer from 1 to 10, the number average of p being from 1.5 to 10; Q is a divalent moiety selected from the group consisting of -O- and -NH-; P is a p-valent hydrophilic neutral polymer radical; R 1 is independently selected from the group consisting of halogen, COOCH 3, -N(C 1 -C 6 -alkyl) 2, -NO 2, -S(=O) 2 R 2, C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy, aryloxy, aryl, heteroaryl, where aryl, hetaryl and aryloxy are unsubstituted or substituted by 1,2, 3 or 4 radicals selected from the group consisting of-OH, -COOCH 3, -N(C 1 -C 6 -alkyl) 2, -NO 2, -S(=O) 2 R 2, C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy and halogen; R 2 is selected from the group consisting of -NH 2, -NH(C 1 -C 6 -alkyl), -N(C 1 -C 6 -alkyl) 2, C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy, aryl and heteroaryl, where aryl and hetaryl are unsubstituted or substituted by 1,2, 3 or 4 radicals selected from the group consisting of C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy and halogen; b) a succinic anhydride of the formula where R is C 4 -C 24 -alkyl or C 4 -C 24 -alkenyl.