| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a polymer useful for cement additive having excellent storage stability, capable of improving productivity while keeping high water reducing performance by polymerizing a specific glycol-based monomer with an unsaturated carboxylic acid-based monomer while keeping concentration of water in a reactor during polymerization to a specific amount or below. SOLUTION: When polymerization is carried out by using at least (A) an unsaturated polyalkylene glycol-based monomer and (B) an unsaturated carboxylic acid-based monomer, the concentration of water in a reactor during the polymerization is kept to <=50 wt.% and at least a part of the monomers during the polymerization is previously initially charged into the reactor and residual monomers are charged into the reactor after initiation of the polymerization, and these monomers are polymerized to provide the objective polymer useful for cement additive without adding any antifoam agent. The component A is preferably a monomer of formula I [R1 is H or methyl; R2O is a 2-28C oxyalkylene or a mixture of two or more kinds of 2-28C oxyalkylenes; R3 is phenyl, or the like; (n) is 1-300] and the component B is preferably a monomer of formula II [R4 is H or methyl; M is a monovalent metal, or the like].
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