Patent ID: 8809474

Claim:
A carboxyl group-containing polymer composition comprising a carboxyl group-containing polymer, wherein the carboxyl group-containing polymer consists of a structure unit (a) derived from an acrylic acid-based monomer (A) at a level of from 62 to 70% by mass and a structure unit (b) derived from a sulfonic acid group-containing monomer (B) at a level of from 30 to 38% by mass based on 100% by mass of all structure units derived from all monomers in the carboxyl group-containing polymer, the carboxyl group-containing polymer has a weight average molecular weight of 23,000 to 50,000, and wherein the carboxyl group-containing polymer composition further comprises an adduct of a hydrogen sulfite to the acrylic acid-based monomer (A), and the adduct is present at a level of 0.3 to 5% by mass based on 100% by mass of a solids content of the carboxyl group-containing polymer composition.