Patent ID: 7589153

Claim:
A method for producing a glyoxalated inter-copolymer of high charge density useful for strengthening paper, comprising: (a) reacting a first portion of glyoxal with a blended composition comprising (1) a polyacrylamide having pendant amide groups and (2) a high charge density polymer having pendant glyoxal-reactive groups selected from the group consisting of (A) a polyamidoamine epichlorohydrin polymer; (B) a Michael addition adduct of a polyamidoamine epichlorohydrin polymer and an acrylamide; (C) an interchange reaction inter-copolymer of primary amine-terminated cationic polyamidoamine and neutral polyacrylamide; (D) a cationic polyamidoamine grafted polyacrylamide; and (E) mixtures thereof, to form a first mixture comprising a glyoxalated inter-copolymer of high charge density having separate segments of the polyacrylamide and the high charge density polymer.