Patent ID: 7390865

Claim:
A process for preparing a water-soluble carboxyl group-containing polymer of which monomer composition consists essentially of an α,β-unsaturated carboxylic acid and a compound having at least two ethylenically unsaturated groups, said process comprising reacting the α,β-unsaturated carboxylic acid with the compound having at least two ethylenically unsaturated groups in an inert solvent in the presence of a radical polymerization initiator, said process for preparing a water-soluble carboxyl group-containing polymer being characterized in that the α,β-unsaturated carboxylic acid is further added to a reaction mixture in which 20 to 70% by mol of an unreacted α,β-unsaturated carboxylic acid remains, and the α,β-unsaturated carboxylic acid is reacted with the compound having at least two ethylenically unsaturated groups, wherein the α,β-unsaturated carboxylic acid is acrylic acid, or a mixture of acrylic acid and lauryl methacrylate, and wherein the compound having at least two ethylenically unsaturated groups is pentaerythritol tetraallyl ether, diethylene glycol diallyl ether or polyallyl saccharose.