Cement dispersant copolymer for cement dispersant and a cement composition

A novel copolymer which can exhibit excellent dispersion performance for a variety of cements including illiquid cement (Difficult cement), as well as cement dispersant and a cement composition containing the copolymer to provide things. A unsaturated (poly) alkylene glycol ether monomer (a), an unsaturated carboxylic acid monomer (b), and an unsaturated crosslinking monomer (c) or unsaturated crosslinkable monomer a copolymer obtained by polymerizing a polymer component containing mer (d). .BACKGROUND