Patent ID: 8067517

Claim:
A water-soluble copolymer having alkyl-modified carboxyl groups obtained by polymerizing 100 parts by weight of (meth)acrylic acid, 5-10 parts by weight of lauryl(meth)acrylate, and 0.001-0.044 parts by weight of a compound having two or more of ethylenic unsaturated groups, wherein a liquid containing 1 weight % of said water-soluble copolymer having alkyl-modified carboxyl groups has a viscosity of 1000 mPa·s or lower and a transmittance of 95% or higher, and when 1-7 parts by weight of sodium chloride is added to 100 parts by weight of the liquid containing 1 weight % of said water-soluble copolymer having alkyl-modified carboxyl groups, a viscosity is 10000-30000 mPa·s and a transmittance is 95% or higher.