Patent ID: 7964682

Claim:
A method for producing a phosphoric acid ester-based polymer, comprising a mixing step of preparing a mixed solution comprising a monomer 1 represented by the following formula (1), a monomer 2 represented by the following formula (2), and a monomer 3 represented by the following formula (3) and a copolymerizing step of copolymerizing monomer 1, monomer 2 and monomer 3, wherein the mixing step is mixing the monomers 1, 2 and 3 at a temperature of 10 to 50° C., the copolymerizing step is copolymerizing the monomers at pH 7 or lower, in a polymerization solvent having a dissolved oxygen concentration at 25° C. of 0.01 to 4.0 mg/kg, in the presence of a phosphonic acid chelating agent, the copolymerizing step is initiated within 72 hours after the mixing step and the temperature of the mixed solution is maintained in the range of 10 to 50° C. until the copolymerizing step is initiated: wherein R 1 and R 2 each represent a hydrogen atom or a methyl group; and R 3 represents a hydrogen atom or —COO(AO) n X [wherein AO represents an oxyalkylene group or oxystyrene group having 2 to 4 carbon atoms; n represents an average number of added moles of AO, and is a number from 3 to 200; and X represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms], wherein R 4 represents a hydrogen atom or a methyl group; R 5 represents an alkylene group having 2 to 12 carbon atoms; m1 represents a number from 1 to 30; and M represents a hydrogen atom, an alkali metal or an alkaline earth metal, and wherein R 6 and R 8 each represent a hydrogen atom or a methyl group; R 7 and R 9 each represent an alkylene group having 2 to 12 carbon atoms; m2 and m3 each represent a number from 1 to 30; and M represents a hydrogen atom, an alkali metal or an alkaline earth metal.