Toagosei Company, Ltd.

Koichi Adachi

Yoshio Mori

Tetsuya Tsuzuki

Ken Takeda

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&#xb7;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. From the standpoint of attaining excellent formation, the component (B) preferably has a molar proportion of the cationic radical-polymerizable monomer unit to the anionic radical-polymerizable monomer unit (hereinafter referred to as Ca/An) satisfying Ca/An&#x3c;1.2.

Retention improving composition

A composition is provided which comprises amphoteric polymers comprising, as constituent monomer units, a cationic monomer unit, an anionic monomer unit, and optionally a nonionic monomer unit and having a 0.5% salted viscosity of 10 to 120 mPa&#xb7;s, wherein said amphoteric polymers comprise a first amphoteric polymer satisfying the following expression (1) and a second amphoteric polymer satisfying the following expression (2) or a third amphoteric polymer satisfying the following expressions (3) and (4):Ca/An&#x2267;1&#x2003;&#x2003;(1)Ca/An&#x3c;1&#x2003;&#x2003;(2)Ca/An&#x2267;1&#x2003;&#x2003;(3)|(Ca&#x2212;An)&#x2212;(Ca&#x2212;An)|&#x2267;1.5&#x2003;&#x2003;(4)wherein Caand Anrespectively represent the total mole number of the cationic monomer units and the total mole number of the anionic monomer units in the first amphoteric polymer on a condition that the total mole number of all the constituent monomer units in the first amphoteric polymer is converted to be 100 mol; on a condition similar to the above, Caand An, and Caand An, respectively represent the total mole number of the cationic monomer units and the total mole number of the anionic monomer units in the second and third amphoteric polymers. The composition is excellent in various flocculation and dewatering performances for various types of sludge, in particular, for sludge high in ratio of excess sludge, and can be used for process yield improvement in papermaking process.

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Nagoya, Japan

Koichi Adachi