Patent ID: 8088874

Claim:
A crosslinked (meth)acrylic acid-type copolymer obtained by the steps of: polymerization of a (meth)acrylic acid imino compound represented by the general formula (1): wherein in the formula (1), R represents a hydrogen atom or a methyl group, and a (meth)acrylic acid ester in the presence of a crosslinking agent, and nitroxidation, wherein said (meth)acrylic acid ester is at least one ester selected from the group consisting of hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate.