Maleic-anhydride-grafted polycarboxylic acid plasticity-maintaining agent and preparation method thereof

The invention discloses a maleic-anhydride-grafted polycarboxylic acid plasticity-maintaining agent and a preparation method thereof. The method comprises the following steps: synthesizing an intermediate polyester from maleic anhydride, cellulose hydroxypropyl methyl ether and phosphorous acid at 60-100 DEG C by a metal salt catalytic process; and carrying out water solution polymerization on the polyester, unsaturated acid monomer, unsaturated polyoxyethylene large monomer, acrylamide monomer, initiator and other raw materials at 40-70 DEG C, and neutralizing to obtain the maleic-anhydride-grafted polycarboxylic acid plasticity-maintaining agent. The intermediate polyester has the effect of increasing the plasticity stability of the freshly mixed mortar; and the end product maleic-anhydride-grafted polycarboxylic acid plasticity-maintaining agent has the comprehensive effects of favorable dispersity, plasticity maintaining property and thickening property on the freshly mixed mortar. The maleic-anhydride-gr