Increasing PVC suspension polymerization productivity by using temperature‐programmed reactions

Abstract

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.

Principles of Thermal Degradation

“…37 But this is always optimized with product quality in mind, including thermostability (application of different initiator results at different concentration of tertiary chlorines and chloroallyl groups). 37 But this is always optimized with product quality in mind, including thermostability (application of different initiator results at different concentration of tertiary chlorines and chloroallyl groups).…”

The Effects of Initiators Mixture on Suspension Polymerization of Vinyl Chloride and its Comparison with other Productivity-Enhancing Procedures

“…Among works performed on the enhanced productivity of PVC through temperature-trajectory [2][3][4][5][6][7][8], in earlier work [9][10][11] we suggested the most reduction in the polymerization time up to 33%. Bijanmanesh et al [13] reported that continuous dosing of a fast initiator during suspension polymerization of vinyl chloride enhanced productivity by 40%.…”

Free‐Radical Polymerization: Suspension

“…If the monomers are volatile at the working pressure of the reactor, then some heat can be removed relatively quickly by monomer vaporization (as discussed above for vinyl chloride polymerization; see Section 5.2.5). Longeway and Witenhafer [113] suggested that the reactor could be operated at a higher temperature in the early stages, to make full use of the cooling capacity. Pinto and Giudici [111] suggested that a mixture of initiators, with different half-lives and activation energies, could be used.…”