Enhancement of poly(vinyl chloride) productivity by continuous initiator injection

Abstract

Polymerization of vinyl chloride monomer with continuous initiator dosage at constant temperature was modeled. Initiators with a half‐life shorter than 0.4 hour at the reaction temperature are suitable for continuous injection. Using a suitable initiator dosage regime, it is possible to keep the reaction rate at its maximum permissible value until critical conversion. It is found that a suitable dosage regime allows the total polymerization time to be reduced by as much as 38.6%, while the final conversion remains unchanged from standard isothermal polymerization. Also, addition of initiators with a half‐life greater than 0.47 hour, preferably from 0.47 hour to the time needed to reach the critical conversion, at the polymerization temperature at the beginning of the reaction are required to achieve a high conversion. The injection of initiators during polymerization into the reactor causes the weight‐averaged molecular weight and corresponding K value of the product to decrease. The drop in K value can be compensated by a decrease in reaction temperature. Initiator dosage shows no significant effect on the structural chemical defects in the PVC chains. Dispersibility and persistent gels (fisheyes) were not measured. J. VINYL ADDIT. TECHNOL., 23:248–258, 2017. © 2015 Society of Plastics Engineers