| 摘要 |
PROBLEM TO BE SOLVED: To provide both a readily handleable paper strengthening agent having quick solubility and a method for strengthening the paper using the same agent. SOLUTION: This method for strengthening the paper is characterized by dissolving a dispersion produced by the coexistence of a cationic polymer dispersing agent in an amount of 0.5-3.0 times based on ionic equivalent of an anionic water-soluble polymer in water, producing a polyionic complex and then adding the resultant polyionic complex into a papermaking raw material before forming into the sheet of paper when a monomer mixture comprising 5-30 mol% of an anionic monomer represented by the following general formula (1) (R1 is hydrogen, methyl group or carboxymethyl group; R2 is hydrogen or carboxy group; A is SO3 , C6 H4 SO3 , CONHC(CH3 )2 CH2 SO3 or COO; and Y is hydrogen or a cation), 70-95 mol% of (meth)acrylamide and 0-20 mol% of other copolymerizable nonionic monomers is polymerized in the coexistence of the dispersing agent composed of a cationic polymer in an aqueous solution of a salt according to a dispersion polymerization method.
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