Increasing PVC suspension polymerization productivity by using temperature‐programmed reactions

Vinyl chloride polymerizations are known to be autoaccelerating. The reaction rate increases with conversion. Because of this phenomenon, substantial reactor productivity at early conversion can be lost because the heat‐removal capacity of the reactor is not fully utilized until near the end of the polymerization. For this reason it is desirable to speed up the polymerization at the beginning and slow it down near the end. This rate adjustment can be achieved by running the polymerization hotter in the beginning and then cooling. We have written a scientifically based computer model of the polymerization designed specifically to simulate such temperature‐programmed reactions. The model does a complete heat balance on the polymerization, has a molecular weight predictor, and will be described and demonstrated for a polymerization at 50°C using sec ‐butyl peroxydicarbonate (SBP) as initiator. By using this single initiator and a very simple straight‐line temperature‐programmed reaction, the time to 80% conversion can be reduced from 335 minutes to 240 minutes. This is a substantial increase in productivity.