PURPOSE: To provide a paper strength-reinforcing agent containing a specific water-soluble copolymer as an effective component, excellent in adsorption, paper strength-improving effect and folding endurance and useful for the re- generation of waste paper, etc.
CONSTITUTION: The objective paper strength-reinforcing agent contains as an effective component a water-soluble copolymer comprising (A) 0.01-15mol% of a hydrocarbon group-containing cationic monomer having a 4-28C hydrocarbon group and a polymerizable functional group and represented by formula I, II or III (R1 is H, methyl; R2, R3 are 1-3C lower alkyl; R4 is 4-28C hydrocarbon; Y is O, NH-; Z, Z' are 2-4C hydroxyalkylene; X is halide or acid residue), (B) 0.01-15mol% of a copolymerizable anionic monomer having an anionic group selected from a carboxylic acid group, a sulfonic acid group and a phosphoric ester group and their salts, and (C) 70-99.98mol% of a copolymerizable hydrophilic monomer such as (meth) acrylamide or N-vinyl-2- pyrrolidone as constituting monomers.
MORIWAKI HISAKAZU
KONDO JUNJI
