| abstract |
A water-soluble polymer sensitive to salts is a copolymer of (A) 10 to 90% of acrylic acid and/or methacrylic acid; and (B) 90 to 10% of a vinyl monomer of Formula (I): <IMAGE> (I) (wherein R represents a hydrogen atom or a methyl group; and R1 represents an aryl group or a cycloalkyl group); or the foregoing component (A); (B) 2 to 70% of a vinyl monomer of Formula (II): <IMAGE> (II) (wherein R2 represents an alkyl group, an aryl group or a cycloalkyl group); and (C) 2 to 40% of a vinyl monomer of Formula (III): <IMAGE> (III) (wherein R3 represents an aryl group), 2 to 70 mole % of the repeating units derived from the acrylic acid and/or methacrylic acid being in the form of a salt. It is soluble in tap water, but insoluble in an aqueous solution containing not less than 0.5% of an inorganic salt of a monovalent ion. |