Control of the Copolymer Composition in Suspension Copolymerization Reactions

A new strategy for control of the copolymer composition is proposed for suspension copolymerizations. The control strategy assumes that one of the monomers is soluble in the continuous (aqueous) phase, as in the case of vinyl acetate (VAc)/acrylic acid (AA) copolymerizations. First, a hypothetical suspension copolymerization reaction is studied through simulation in order to illustrate the main features of the proposed control scheme. Then, the control strategy is implemented experimentally for actual control of the copolymer composition during VAc/AA suspension copolymerizations. The strategy is based on a detailed model developed to describe the process behavior and the AA partitioning between the organic phase and the aqueous phase, which is a fundamental point for the successful description of both conversion and copolymer composition. The proposed model was used to design monomer feed rate profiles in order to keep the copolymer composition constant throughout the batch. It is shown that the proposed control procedure is indeed able to keep the copolymer composition constant throughout the batch, despite the huge differences of reactivity between the monomer species.