ONLINE CALORIMETRIC CONTROL OF EMULSION POLYMERIZATION REACTORS

Reaction calorimetery was used to monitor and control unseeded semi-ba tch emulsion copolymerization of VAc and BuA. An external PC, using th e information derived from a commercial reaction calorimeter, calculat ed on-line the thermal and material balances of the calorimetric react or, and thus the monomer conversions. For a desired copolymer composit ion profile, previously calculated conversion-dependent monomer feed p rofiles were used to determine the rates of monomer addition every 20 seconds. Gas chromatography and gravimetry confirmed that copolymers h aving the desired variable composition profiles were successfully obta ined. The control strategy devised lends itself to polymer quality con trol and safe operation, since variable monomer inhibitor levels or su dden inhibition during the reaction do not lead either to the formatio n of off-composition polymer nor to monomer accumulation in the reacto r. Furthermore, the rate of polymerization can be reduced by fixing up per limits for monomer concentrations in the polymer particles, useful in cases where the minimum-time optimal feed profile, which correspon ds to maximum swelling, might lead to thermal runaway.