Water-soluble polymer and additive for paper manufacture

摘要

The present invention provides a method for preparing a water soluble polymer, which comprises:
a first step of polymerizing:(a) 60 to 99.5 mol % of at least one selected from acrylamide and methacrylamide,(b) 0.5 to 20 mol % of at least one selected from α,β-unsaturated monocarboxylic acid, α,β-unsaturated dicarboxylic acid and salts thereof, and (c) 1 to 20 mol % of at least one selected from a water soluble cationic monomer and a salt thereof,(d) 0.01 to 1 mol % of a chain transfer agent, and(e) 0.005 to 5 mol % of a crosslinkable monomer,

in the presence of a persulfate-based catalyst to obtain a prepolymer; and
a second step of further adding the persulfate-based catalyst to the prepolymer obtained in the first step and the residual monomer, followed by the polymerization and termination of the polymerization. Consequently, it is made possible to suppress a rapid increase in viscosity during the polymerization thereby to obtain a water soluble branched polymer having high molecular weight and low viscosity.

主权项

1. A method for preparing a water soluble polymer, which comprises:
a first step of polymerizing: (a) 60 to 99.5 mol % of at least one monomer selected from the group consisting of acrylamide and methacrylamide, (b) 0.5 to 20 mol % of at least one monomer selected from the group consisting of α,β-unsaturated monocarboxylic acid, α,β-unsaturated dicarboxylic acid and salts thereof, and (c) 1 to 20 mol % of at least one monomer selected from the group consisting of a water soluble cationic monomer and a salt thereof, (d) 0.01 to 1 mol % of a chain transfer agent, and (e) 0.005 to 5 mol % of a crosslinkable monomer, in the presence of a persulfate-based catalyst to obtain a prepolymer, and a second step of further adding 6-40 mol % copolymerizable monomers and the persulfate-based catalyst after the polymerization of the first step, followed by the polymerization and termination of the polymerization; wherein the amount of the persulfate-based catalyst to be added in the first step is from 0.01 to 0.08% by weight based on the total amount of all the monomers; the amount of the persulfate-based catalyst added in the second step is from 0.01 to 0.1 by weight based on the total amount of all the monomers and the persulfate-based catalyst in the second stage is charged after 20 minutes or more have passed since the addition of the copolymerizable monomers; and the molecular weight distribution (Mw/Mn) of the water soluable polymer is 3.3 or less.