Retention improving composition

A method for improving retention of a stuff as a raw material in papermaking, which comprises adding to said stuff a retention improving composition which is of one-pack type, wherein said composition consists of (A) a cationic water-soluble polymer and (B) an amphoteric water-soluble polymer,

• in which said cationic water-soluble polymer (A) comprises 0.5 to 55.0 mole percent of a cationic radical-polymerizable monomer unit consisting essentially of a quaternary salt of a dialkylaminoalkyl (meth)acrylate,
• said amphoteric water-soluble polymer (B) comprises a cationic radical-polymerizable monomer unit consisting essentially of a quaternary salt of a dialkylaminoalkyl (meth)acrylate, an anionic radical-polymerizable monomer unit consisting essentially of a (meth)acrylic acid or a salt thereof, and a nonionic radical-polymerizable monomer unit consisting essentially of a (meth) acrylamide, and
• said component (B) has a molar proportion of the cationic radical-polymerizable monomer unit to the anionic radical-polymerizable monomer unit (hereinafter referred to as Ca/An) which satisfies a Ca/An of 5 to 15, and having a 0.5% salted viscosity of 10 to 80 mPa·s.

A method of papermaking, which comprises adding a composition for improving retention to a stuff as a raw material for papermaking, and then carrying out papermaking using said stuff to which said composition was added, wherein said composition consists of (A) a cationic water-soluble polymer and (B) an amphoteric water-soluble polymer,

• in which said cationic water-soluble polymer (A) comprises 0.5 to 55.0 mole percent of a cationic radical-polymerizable monomer unit consisting essentially of a quaternary salt of a dialkylaminoalkyl (meth)acrylate, and
• said amphoteric water-soluble polymer (B) comprises a cationic radical-polymerizable monomer unit consisting essentially of a quaternary salt of a dialkylaminoalkyl (meth)acrylate, a anionic radical-polymerizable monomer unit consisting essentially of a (meth)acrylic acid or a salt thereof, and a nonionic radical-polymerizable monomer unit consisting essentially of a (meth) acrylamide,
• said component (B) having a molar proportion of the cationic radical-polymerizable monomer unit to the anionic radical-polymerizable monomer unit (hereinafter referred to as Ca/An) which satisfies a Ca/An of 0.5 to 0.9, and having a 0.5% salted viscosity of 10 to 50 mPa·s.