Patent ID: 8536252

Claim:
A process for preparing a copolymer in a semicontinuous mode of operation in a polymerization apparatus containing a polymerization reactor connected to a metering device, the process comprising: (a) initially introducing acid monomer into the metering device and initially introducing polyether macromonomer and water into the polymerization reactor, (b) metering the acid monomer from the metering device into the polymerization reactor, (c) passing free radical polymerization initiator into the polymerization reactor before and/or during the metering of the acid monomer into the polymerization reactor, thereby forming an aqueous medium in the polymerization reactor, and reacting the acid monomer and the polyether macromonomer in the aqueous medium by free radical polymerization, forming the copolymer, wherein the molar ratio of all the acid monomer used to all the polyether macromonomer used is 20:1 to 1:1, the molar ratio of the acid monomer initially introduced into the polymerization reactor to the acid monomer metered into the polymerization reactor is from 10:1 to 1:10, and wherein the metering of the acid monomer is effected with the proviso that at least 70 mol % of all the acid monomer is introduced and metered in during the course of 5 to 19 minutes at a metering rate that is constant or varies such that the maximum rate of addition is at most a factor of 3 higher than the minimum rate of addition.