Patent No. U.S. 7,026,392 B2
Kansai Paint Co., Ltd. has received a patent for a water-based pigment dispersion comprised of a pigment dispersing resin, pigment and aqueous medium. The resin is a copolymer of polymerizable unsaturated monomer containing at least one quaternary ammonium salt group; nonionic polymerizable unsaturated monomer having polyoxyethylene chain; and other ethylenically unsaturated monomer, wherein the copolymer is produced by the copolymerization of one to 15% by weight of quaternary ammonium salt group-containing polymerizable unsaturated monomer, five to 40% by weight of nonionic polymerizable unsaturated monomer and 45 to 94% by weight of other ethylenically unsaturated monomer on the basis of the total weight of monomers.