Abstract: There is disclosed a process for the continuous polymerization of methyl methacrylate with a lesser cost, thermally polymerizable comonomer such as styrene, in the presence of a large quantity of solvent by introducing the monomers into a continuos loop of recycled solvent and removing the polymerized product therefrom. The polymerization is practiced in a plurality of stages, preferably two stages wherein the bulk of the polymerization is performed in the first stage and the final stage is operated to deplete the initiator and any thermally polymerizable comonomer, and polymerization modifiers from the crude polymerizate, thereby forming a crude polymerizate suitable for devolatilization. The crude polymerizate is preheated and devolatilized in a flash zone. Sufficient pressure is maintained on the crude polymerizate in the devolatilizer preheater to avoid the formation of foam encrustations on the heat exchange surfaces of the devolatilizer preheater and on the surfaces of the transfer lines.