Development of batch emulsion polymerization processes

Although emulsion polymerization has been used for a long time, relatively little attention has been paid to the technological issues of this polymeri zation technique. This paper describes the research on chemical engineering aspects of emulsion polymerization in (semi-)batchwise operated stirred ta nks. The objective of this work was to improve the operation of current pro cesses and to allow for improvements in the development of novel emulsion p olymerization processes. For this purpose, different issues have shown to b e important, for which the work described in this paper has been focused on four topics: emulsification, colloidal stability, rheology in high solids polymerization and heat transfer. These topics have been studied using the polymerization of styrene and vinyl acetate as two representative model sys tems. Our results reveal that sufficient emulsification is essential for proper c ontrol of the polymerization process. For the emulsifier used in this study , the colloidal stability of the polymer particles is mainly governed by th e physico-chemical properties of the reaction mixture. During high solids e mulsion polymerization, the particle size distribution of the polymer parti cles considerably influences the rheological properties of the reaction mix ture and thereby the Row pattern in the reactor. Heat transfer to the react or wall depends strongly on reactor geometry, impeller type and diameter as well as stirrer speed. Additionally, the physical properties of the reacti on mixture, being related to solids content, conversion and monomer type, a re important for heat transfer.