Control and optimization for vinyl chloride/N-phenylmaleimide copolymer composition

N-phenylmaleimide (PMI) is used to copolymerize with vinyl chloride (VC) for improving the heat resistance of PVC. The variations of instantaneous and integral copolymer compositions with conversion for VC/PMI copolymerization system were investigated quantitatively by use of the recurrence method. The copolymer composition variation could be controlled and optimized by means of selecting a third monomer and its content. For VC/PMI suspension copolymerization, acrylonitrile (AN) and methyl methacrylate (MMA) are preferably selected to improve copolymer composition homogeneity and heat resistance. There were different effects of control parameters on the selectable monomer feed fraction ranges. The influences of the third monomer on the ranges of monomer feed fraction with integral terpolymer composition error were studied in detail. Subsequently, on the basis of prediction, control and optimization for variation of copolymer composition with conversion and the suspension terpolymerization technology feature, the optimum regions of monomer feed fraction for VC/PMI/AN and VC/PMI/MMA terpolymerizations are obtained.