Patent ID: 7459513

Claim:
A process for preparing (meth)acrylic acid copolymers, which comprises the steps: (1) free-radically polymerizating (meth)acrylic acid, thereby resulting in a polymer I; and (2) amidating polymer I resulting from process step (1) by reaction with at least one aminoalkanesulfonic acid to form a sulfonated polymer, wherein the molar ratio of monomers in polymer I to aminoalkanesulfonic acid ranges from 15:1 to 4:1 and the (meth)acrylic acid copolymer comprises: (a) from 30 to 95% by weight of a poly(meth)acrylic acid basic framework, (b) from 5 to 70% by weight of amide units based on aminoalkylsulfonic acids, the total weight of the units in the sulfonated polymer being 100% by weight and all weights being based on the sulfonated polymer.