On-line control of molecular weight distribution in semibatch emulsion polymerization using CTA

摘要

Polystyrene latexes haveing a well defined molecular weight distribution (MWD) were prepared by means of an on-line control strategy that uses the measurements of both unreacted monomer and chain transfer agent (CTA). Based on a mathematical model for the prediction of the MWD and an off-line optimization algorithm, optimal trajectories of styrene and CTA (CCI_4 in this work) as a function of conversion that ensure the production of polystyrene of the desired MWD were obtained. The control strategy used a nonlinear model based controller to calculate the feed flow rates of styrene and CCI_4 to track the optimal conversion based trajectiories. The control strategy was first assessed by numerical simulation and then experimentally verified to produce polytyrene latexes of widely different MWDs.