Water-soluble polymer sensitive to salt

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): ##STR1## (wherein R represents a hydrogen atom or a methyl group; and R.sup.1 represents an aryl group or a cycloalkyl group); or the foregoing component (A); (B) 2 to 70% of a vinyl monomer of Formula (II): ##STR2## (wherein R.sup.2 represents an alkyl group, an aryl group or a cycloalkyl group); and (C) 2 to 40% of a vinyl monomer of Formula (III): ##STR3## (wherein R.sup.3 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.

Dependencies are inferred from the claim text.