PURPOSE:To prepare a nonionic copolymer useful as a dispersant which has flowability even in a high concn. and can provide a coal-water slurry less liable to bring about precipitation over a long period of time, by polymerizing a plurality of particular comonomers. CONSTITUTION:A nonionic copolymer useful as the title dispersant is prepd. by polymerizing 20-90wt.% polyalkylene glycol mono(meth)acrylate monomer (A) of formula I (wherein R1 is H or CH3; X is a divalent 2-4 C alkylene oxide residue; m is 1-100; and R2 is H, 1-3 C alkyl or a 2-3 C alkenyl), 10-80wt.% monomer (B) selected from among a methacrylate monomer (a) of formula II [wherein R3 is H or CH3; and R4 is a 1-30 C (substd.) alkyl or the like], a polyalkylene glycol mono(meth)acrylate monomer (b) of formula III [wherein R5 is H or CH3; Y has the same meaning as X; n is 1-30; and R6 is a 4-30 C (substd.) alkyl or the like] and a vinyl monomer (c) of formula IV (wherein R7 is H or CH3; and R8 has the same meaning as R4), and 0-30wt.% nonionic monomer (C) copolymerizable with comonomers A and B.
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