Association-type water-soluble ternary block copolymer

PROBLEM TO BE SOLVED: To obtain an association-type water-sol. thickening polymer which can well control the flow characteristics of a water-base compsn. contg. a filler, a pigment, etc., by forming a triblock copolymer comprising a central hydrophilic block formed by the free-radical polymn. of a specific water-sol. unsatd. monomer and two terminal hydrophobic blocks. SOLUTION: This copolymer comprises a central hydrophilic block formed by the free-radical polymn. of a water-sol. unsatd. monomer and the same or different two terminal hydrophobic blocks and has a mol.wt. of 5,000-300,000, pref. 20,000-150,000. The central block is formed by the polymn. of a hydrophilic ethylenic monomer selected from among acrylamide, its N-substd. driv. (e.g. 2-acrylamido-2-methylpropanesulfonic acid), acrylic acid, its salt, etc. The hydrophobic blocks are formed by the decomposition of an initiator for the above polymn. into two primary free radicals having a hydrophobic chain. COPYRIGHT: (C)1997,JPO