Method for producing polycarboxylic acid for cement dispersant and cement composition

A method for producing a polycarboxylic acid for a cement dispersion, wherein the polycarboxylic acid includes a polyalkylene glycol ester unit (III), a monocarboxylic acid unit (IV) and optionally, a repeating unit (VI),

• said polyalkylene glycol ester unit (III) being represented by the general formula (4) below:
• where:
• R9 represents hydrogen or methyl group;
• R10O represents one kind or a mixture of two or more kinds of oxyalkylene group having 2 to 4 carbon atoms, in the case of two or more kinds, those may be added in a block state or random state;
• R11 represents an alkyl group having 1 to 22 carbon atoms, phenyl group, or alkylphenyl group, with the alkyl group in the alkylphenyl group having 1 to 22 carbon atoms;
• and s is an integer of 5 to 100;
• said polyalkylene glycol ester unit (III) being given from a polyalkylene glycol ester monomer,
• said polyalkylene glycol ester monomer being obtained by esterification between a polyalkylene glycol (6) represented by the general formula (6) below and (meth)acrylic acid or ester interchange between the polyalkylene glycol (6) and alkyl(meth)acrylate, with the alkyl group in the alkyl(meth)acrylate having 1 to 22 carbon atoms,
• HO—(R10O)s—R11 (6)
• where:
• R10O represents one kind or a mixture of two or more kinds of oxyalkylene group having 2 to 4 carbon atoms, in the case of two or more, those may be added in a block state or random state;
• R11 represents an alkyl group having 1 to 22 carbon atoms, phenyl group, or alkylphenyl group, with the alkyl group in the alkylphenyl group having 1 to 22 carbon atoms;
• and s is an integer of 5 to 100;
• and
• said polyalkylene glycol (6) being obtained by an addition reaction of alkylene oxide having 2 to 4 carbon atoms in the range of 80 to 155° C.,
• said monocarboxylic acid unit (IV) represented by the general formula (5) below:
• where:
• R12 represents hydrogen or methyl group:
• and M3 represents hydrogen, monovalent metal, divalent metal, ammonium, or organic amine,
• said repeating unit (VI) being other than the polyalkylene glycol ester unit (III) and the monocarboxylic acid unit (IV), and
• the weight ratio of the polyalkylene glycol ester unit (III)/the monocarboxylic acid unit (IV)/the repeating unit (VI) being in the range of 60-95/40-5/0-30.