Patent ID: 7030178

Claim:
A method of dispersing a hydraulic composition, said method comprising: dispersing said hydraulic composition with a powdery dispersant, said powdery dispersant comprising at least one copolymer, wherein said copolymer is a powder and made by polymerizing at least one vinyl monomer (a) represented by the formula (1): wherein R 1 and R 2 represent a hydrogen atom or a methyl group, R 3 represents a hydrogen atom or —COO(AO) n X, m is a number of 0 to 2, p is a number of 0 or 1, AO represents a C 2-4 oxyalkylene group or an oxystyrene group, n is the average mole number of AO groups and is a number of 2 to 300, and X represents a hydrogen atom or a C 1-18 alkyl group; with at least one vinyl monomer (b) selected from the group consisting of acrylic acid, methacrylic acid, an alkaline earth metal salt of acrylic acid, an alkaline earth metal salt of methacrylic acid and maleic anhydride; wherein the average mole number of C 2-4 oxyalkylene groups or oxystyrene groups of said copolymer is 45 to 150; (a)/[(a)+(b)]×100 ranges from 15 to 45 (mole %); and at least part of the copolymer is an alkaline earth metal salt.