Investigation of tubular reactors for the bulk polymerization of methyl methacrylate

The behaviour of tubular reactors in the bulk polymerization of methyl methacrylate has been investigated. Particular emphasis was placed on the study of reactor fouling (polymer deposition in the reactor), as this poorly understood phenomenon has presented a major obstacle to the use of tubular reactors in polymerization processes. Five reactor configurations, varying in spatial orientation and flow direction, were studied. It was found that the optimum configuration for delaying the onset of fouling was a vertical reactor with the feed flowing downward. Fouling was shown to exhibit criticality with respect to operating conditions; that is there are distinct boundaries separating fouling from non-fouling regimes. Using the vertical, feed downward configuration a feasible (non-fouling) operating region was mapped out as a function of conversion for a wide range of molecular weights. As the molecular weight increases the maximum conversion at which the reaction can be operated without fouling decreases. Experiments with solution polymerizations and copolymerizations of methyl methacrylate with styrene provided further insight into the role of autoacceleratory behaviour in reactor fouling.;In addition a pilot scale tubular polymerization reactor, which utilized an on-line densitometer, was constructed. This apparatus was used to investigate the production of low molecular weight PMMA at relatively low conversions (up to 40%). A comprehensive fluid dynamical model of the tubular polymerization reactor provided further insight into the reactor behaviour. In particular it was found that the assumption of zero slip at the tube wall may not be valid. A model allowing for slip at the wall proved capable of predicting reactor behaviour and predicting the onset of fouling, while a traditional rheokinetic model assuming zero slip was unable to predict either reactor behaviour or fouling criticality.