Abstract: A novel retention aid is provided, which can realizes not only high retention but also excellent paper formation and is easy to use, in various papermaking processes. A composition for improving retention is provided, which comprises (A) a cationic water-soluble polymer and (B) an amphoteric water-soluble polymer. The component (A) preferably is a copolymer having a cation equivalent of 0.05 to 4.00 meq/g or one having a 0.5% salted viscosity of 30 to 200 mPa·s. The component (B) preferably is either a copolymer comprising a cationic radical-polymerizable monomer unit, an anionic radical-polymerizable monomer unit, and a nonionic radical-polymerizable monomer unit, or an amphoteric water-soluble polymer obtained by polymerizing a cationic radical-polymerizable monomer with an anionic radical-polymerizable monomer in the presence of a polysaccharide.

Abstract: An object of the present invention is to provide a composition excellent in various flocculation performances for various sludge and papermaking systems, especially excellent as a polymer flocculant, and provide a sludge-dewatering agent excellent in dewatering performances for various sludge, especially excellent in flocculationability, as well as a retention aid which can realize a high retention and ensure excellent formation of paper and which is easy to use. A composition is provided, which comprises two or more amphoteric water-soluble polymers in combination shown below, the polymers being obtained by polymerizing a cationic radical-polymerizable monomer and an anionic radical-polymerizable monomer in a presence of a polysaccharide. 1. A combination of a polymer satisfying the molar ratio of the cationic radical-polymerizable monomer to the anionic radical-polymerizable monomer (hereinafter referred to as Ca/An) of Ca/An?1, and a polymer satisfying Ca/An<1, or 2.

Abstract: A novel retention aid is provided, which can realizes not only high retention but also excellent paper formation and is easy to use, in various papermaking processes. A composition for improving retention is provided, which comprises (A) a cationic water-soluble polymer and (B) an amphoteric water-soluble polymer. The component (A) preferably is a copolymer having a cation equivalent of 0.05 to 4.00 meq/g or one having a 0.5% salted viscosity of 30 to 200 mPa·s. The component (B) preferably is either a copolymer comprising a cationic radical-polymerizable monomer unit, an anionic radical-polymerizable monomer unit, and a nonionic radical-polymerizable monomer unit, or an amphoteric water-soluble polymer obtained by polymerizing a cationic radical-polymerizable monomer with an anionic radical-polymerizable monomer in the presence of a polysaccharide.

Abstract: An object of the present invention is to provide a process for easily producing a water-soluble polymer which has a reduced residual monomer amount and has excellent various flocculating performances when used as a flocculant, the process being capable of grafting a high molecular weight polymer onto starch. A process for producing a water-soluble polymer is provided, which comprises polymerizing water-soluble radical-polymerizable monomers comprising a cationic radical-polymerizable monomer as an essential component in a presence of a polysaccharide, an azo polymerization initiator, and a hydrogen-abstracting agent. A polymer flocculant is also provided, which comprises a water-soluble polymer obtained by the production process.

Abstract: A process in which an aqueous solution of a vinyl monomer is subjected to photopolymerization to produce a water-soluble polymer which has a high molecular weight, is highly soluble in water, and reduced in unreacted monomer content is provided. The process comprises subjecting an aqueous solution of a vinyl monomer to photopolymerization with the aid of an azo compound having a 10-hour half-life decomposition temperature of 90° C. or lower as a photopolymerization initiator in such a manner that first-stage light irradiation is conducted at an irradiation intensity of 0.5 to 7 W/m2 and second-stage or subsequent light irradiation is conducted at an irradiation intensity higher than that in the first stage and in an integrated quantity of light of 70,000 J/m2 or larger.