Copolymer for cement admixtures and its production process and use

A copolymer for cement admixtures,

• wherein the copolymer has:
• a weight-average molecular weight of not less than 10,000;
• respective signals detected at the chemical shifts of 0.6 to 1.0 ppm, 1.2 to 1.8 ppm, 1.8 to 2.4 ppm and 3.2 to 3.8 ppm with 1H-NMR;
• respective signals detected at the chemical shifts of 20.0 to 30.0 ppm, 30.0 to 50.0 ppm, 58.0 to 62.0 ppm and 60.0 to 80.0 ppm with 13C-NMR;
• and a spin-spin relaxation time (T2) of 1 msec to 50 msec as to the signal observed at 1.2 to 1.8 ppm with 1H-NMR and/or a spin-spin relaxation time (T2) of 1 msec to 90 msec as to the signal observed at 1.8 to 2.4 ppm with 1H-NMR, and
• unsaturated polyalkylene glycol ether monomer (a) having an alkenyl group having 5 carbon atoms coexists.

A production process for a copolymer for cement admixtures, comprising:

• copolymerizing comonomers including unsaturated polyalkylene glycol ether monomer (a) and unsaturated monocarboxylic acid monomer (b) as essential components,
• with the process being characterized in that:
• unsaturated polyalkylene glycol ether monomer (a) as used is a compound having an alkenyl group having 5 carbon atoms and an oxyalkylene group having 2 to 18 carbon atoms with an average addition number of moles of the oxyalkyene groups to be in the range of 10 to 300;
• and
• a chain-transfer agent is used when copolymerizing the comonomers and/or pH of a resultant reaction mixture after copolymerizing the comonomers is adjusted to not less than 5.