DEVELOPMENT OF BATCH EMULSION POLYMERIZATION PROCESSES

Abstract

Although emulsion polymerization has been used for a long time, relatively little attention has been paid to the technological issues of this polymerization technique. This paper describes the research on chemical engineering aspects of emulsion polymerization in (semi-)batchwise operated stirred tanks. The objective of this work was to improve the operation of current processes and to allow for improvements in the development of novel emulsion polymerization processes. For this purpose, different issues have shown to be 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 systems Our results reveal that sufficient emulsification is essential for proper control of the polymerization process. For the emulsifier used in this study, the colloidal stability of the polymer particles is mainly governed by the physico-chemical properties of the reaction mixture. During high solids emulsion polymerization, the particle size distribution of the polymer particles considerably influences the Theological properties of the reaction mixture and thereby the flow pattern in the reactor. Heat transfer to the reactor wall depends strongly on reactor geometry, impeller type and diameter as well as stirrer speed. Additionally, the physical properties of the reaction mixture, being related to solids content, conversion and monomer type, are important for heat transfer.