Patent ID: 7405264

Claim:
A cement additive which comprises the polycarboxylic acid copolymer obtained by a method of producing a polycarboxylic acid copolymer comprising copolymerizing monomer components comprising a monomer (A) having an oxyalkylene group and an unsaturated carboxylic acid monomer (B) using a hydrophobic chain transfer agent, the monomer (A) having an oxyalkylene group is an unsaturated alcohol-polyalkylene glycol adduct represented by the following formula (2); wherein in the above formula (2), R 1 and R 3 are the same or different and each represents a hydrogen atom or a methyl group, R 2 represents a methyl group, R 4 represents a hydrogen atom or a hydrocarbon group containing 1 to 20 carbon atoms, R x may be the same or different and each represents an alkylene group containing 2 to 18 carbon atoms, and m represents the average number of moles of the oxyalkylene group represented by R X O as added and is a number of 1 to 300; X represents a divalent alkylene group containing 1 to 5 carbon atoms or a direct bond between the carbon atom and oxygen atom linked by X in the case where the group R 1 R 3 C═CR 2 X— is a vinyl group; and the hydrophobic chain transfer agent is a thiol compound having a hydrocarbon group containing not less than 3 carbon atoms.