Abstract: What is described herein is a process for making a copolymer of high specific viscosity by polymerization of maleic anhydride and a C.sub.1 -C.sub.4 alkyl vinyl ether monomer. The invention involves polymerizing said monomers to form a slurry of said copolymer in excess alkyl vinyl ether and toluene and is characterized by the steps of: (a) precharging a reactor with C.sub.1 -C.sub.4 alkyl vinyl ether as solvent at a reaction temperature, (b) feeding a mixture of maleic anhydride and a C.sub.1 -C.sub.4 alkyl vinyl ether in substantially stoichiometric amounts, preferably with a slight excess of the alkyl vinyl there, and at a selected rate, into said precharged reactor, and (c) simultaneously feeding a predetermined mixture of toluene and a polymerization initiator continuously over substantially the entire period of polymerization.

Abstract: What is described herein is a process for making copolymers of maleic anhydride and C.sub.1 -C.sub.4 alkyl vinyl ethers of predetermined specific viscosities extending over a wide viscosity range. The invention is characterized by (a) precharging a reactor with a C.sub.1 -C.sub.4 alkyl vinyl ether as solvent and a polymerization initiator at a reaction temperature, (b) feeding a mixture of maleic anhydride and a C.sub.1 -C.sub.4 alkyl vinyl ether in substantially stoichiometric amounts, preferably with a slight excess of alkyl ether, and at a selected rate, into said precharged reactor, (c) polymerizing said reactants to form a slurry of said copolymer in said escess alkyl vinyl ether solvent, and (d) introducing toluene into said reactor during the polymerization to control the specific viscosity of the copolymer product being produced.