| 摘要 |
PROBLEM TO BE SOLVED: To obtain a water-soluble acrylic copolymer having a specific constitution, capable of increasing the flowability of cement slurry and retaining the viscosity for a long time, and capable of being added in a lower concentration than conventional. SOLUTION: This water-soluble acrylic copolymer has 5,000-80,000 weight average molecular weight, includes structural units of formulae I and II [RA to RC RI and RII are each H or CH3; M+ is H+, a cation from groups I A and II A, or the like; (n) is 0-2; A0 is COO (RT is a 2-4C alkyl; (m) is 7-50; RZ is H or a 1-4C saturated alkyl); RIII is H or COOH] in a molar ratio (I/II) of (1/1)-(50/1) and has silanol on the chain end. The copolymer optionally includes structural units from a monomer such as an aliphatic 3-5C monounsaturated sulfonic acid in a content of 0-20% based on the total weight of all monomers. The copolymer is obtained by copolymerizing monomers in the presence of a chain transfer agent of a mixture between (A) a compound of formula III (RIA is H or a saturated 1-3C alkyl; RIB is a 1-3C alkyl; NB is 0 or 1; NA is 2 or 3; NA+NB=3) and (B) an inorganic acid from phosphorus (I)-(III) or its salt. |
