DISCONTINUOUS MINIMUM END-TIME TEMPERATURE INITIATOR POLICIES FOR BATCH EMULSION POLYMERIZATION OF VINYL-ACETATE

The reactions of batch emulsion polymerization systems can generally be separated into two stages. In stage one, there exists a separate monomer phase in the reactor, while, in stage two, the monomer phase disappears. The kinetics of the reaction is different in the above two stages. Previously, it was assumed that the optimal initiator policy for the operation of a batch vinyl acetate latex reactor could be approximated by a collocation polynomial and the problem solved using a nonlinear programming solver. In this work, a discontinuous solution was obtained using a finite-element collocation method. Since the physical and chemical properties of the latex system are different in the two stages, the discontinuous policies were found to be superior to continuous ones. In this work, the minimum end-time initiator and/or temperature policies were solved. Since the physical properties of polymer products depend on their molecular weight distribution or long-chain branching, in addition to the restrictions of the maximum reaction rate and the total amount of the initiator added to the reactor, the quality of the product, i.e. the number average of branches in each polymer species, was also considered as a constraint of the optimization problem. The simulation and the experimental results showed that substantial improvement of the operation of the batch reactor could be achieved.