Patent ID: 8143332

Claim:
A dispersant for a hydraulic composition, comprising a polymer obtained by copolymerizing monomer 1 represented by the following formula (1), monomer 2 represented by the following formula (2), monomer 3 represented by the following formula (3) and monomer 4 represented by the following formula (4), at pH 7 or less, wherein the ratio (Mw/Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the polymer is from 1.0 to 2.6: wherein R 1 and R 2 each represent a hydrogen atom or a methyl group, R 3 represents a hydrogen atom or —(CH 2 ) q (CO) p O(AO) r R 4 wherein AO represents an oxyalkylene group having 2 to 4 carbon atoms or an oxystyrene group, p denotes a number of 0 or 1, q denotes a number of 0 to 2, p and q are not simultaneously 0, r denotes the mole number of AO units added on the average per molecule and denotes a number of 3 to 300, and R 4 represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms; wherein R 11 represents a hydrogen atom or a methyl group, R 12 represents an alkylene group having 2 to 12 carbon atoms, m1 denotes a number of 1 to 30, and M 3 and M 4 each represent a hydrogen atom, an alkali metal or an alkaline earth metal; wherein R 13 and R 15 each represent a hydrogen atom or a methyl group, R 14 and R 16 each represent an alkylene group having 2 to 12 carbon atoms, m2 and m3 each denote a number of 1 to 30, and M 5 represents a hydrogen atom, an alkali metal or an alkaline earth metal; and wherein R 17 to R 19 each represent a hydrogen atom a methyl group, or (CH 2 ) 5 COOM 7 , (CH 2 ) 5 COOM 7 being optionally combined with COOM 6 or another (CH 2 ) 5 COOM 7 to form an anhydride without M 6 and M 7 in the groups, s denotes a number of 0 to 2, and M 6 and M 7 each represent a hydrogen atom, an alkali metal, an alkaline earth metal, an ammonium group, an alkylammonium group, a substituted alkylammonium group, an alkyl group, a hydroxyalkyl group or an alkenyl group.