COPOLYMER ADMIXTURE SYSTEM FOR WORKABILITY RETENTION OF CEMENTITIOUS COMPOSITIONS

摘要

Preparing a non-ionic copolymer having a hydrolysable monomer residue and a polyether macromonomer residue in a semicontinuous mode in a polymerization reactor associated with a metering device, including introducing polyether macromonomer and water into the reactor, wherein hydrolysable monomer which is added thereto forms a polymerization reaction mixture; introducing hydrolysable monomer into the metering device; adding hydrolysable monomer into the reactor from the metering device; passing a free radical polymerization initiator into the reactor before and/or during the addition of the hydrolysable monomer, the hydrolysable monomer and the polyether macromonomer reacting by free radical polymerization to form the non-ionic copolymer; and, subjecting the reaction mixture to polymerization while an addition rate of the hydrolysable monomer and/or at least a component of the polymerization initiator is varied stepwise or continuously. No monomer is introduced to incorporate ionic cement binding sites into the non-ionic copolymer.