WATER-SOLUBLE COPOLYMER HAVING ALKYL-MODIFIED CARBOXYL GROUP

摘要

Disclosed is a water-soluble copolymer having an alkyl-modified carboxyl group, which shows an extremely low viscosity in the absence of an electrolyte but shows a significantly increased viscosity in the presence of an electrolyte, and can form a viscous nutralizing solution having a high viscosity, a high transmittance, no greasy feeling and a fresh texture even in the presence of a relatively high concentration of an electrolyte. Also disclosed is a thickening agent comprising the water-soluble copolymer. The water-soluble copolymer can be produced by polymerization of 100 parts by weight of (meth)acrylic acid, 0.5 to 5 parts by weight of a (meth)acrylic acid alkyl ester having 18 to 24 carbon atoms in the alkyl group and 0 to 0.1 part by weight of a compound having two or more ethylenically unsaturated groups. The water-soluble copolymer shows a viscosity of 1500 mPa·s or lower and a transmittance of 90% or higher when prepared into a viscous neutralizing solution containing 1% by weight of the water-soluble copolymer, and shows a maximum viscosity of 15000 to 40000 mPa·s and a transmittance of 90% or higher when 0.25 to 5 parts by weight of sodium chloride is added to 100 parts by weight of the viscous neutralizing solution.