| abstract |
(57) [Summary] [PROBLEMS] Even if the molecular weight of a paper strength enhancer is increased, it is possible to form a product with a high concentration, and the paper strength enhancing effect is high. Moreover, it is an object of the present invention to provide a paper strength enhancer which is easy to handle and has high solubility, and to provide a paper strength enhancer method. A tertiary amino group-containing cationic monomer, a quaternary amino group-containing cationic monomer, a monomer having a specific molar ratio of each of the following anionic monomers and (meth) acrylamide monomers: The mixture can be achieved by a paper strength enhancer comprising a polymer dispersion prepared by a dispersion polymerization method in the presence of a dispersant comprising an ionic polymer soluble in the aqueous salt solution in the aqueous salt solution. |