POLYMERIZATION IN A TWIN SCREW EXTRUDER - EFFECT OF SCREW CONFIGURATION ON MWD AND COPOLYMER CONTENT

摘要

A counter-rotating nonintermeshing twin screw extruder specifically designed to provide extensive backmixing was used to investigate the molecular weight distribution (MWD) occurring in the polymerization of Butyl Acrylate and the MWD and drift of copolymer content occurring in the copolymerizations of Butyl Acrylate/Styrene and Butyl Acrylate/Butyl Methacrylate. In contrast to almost plug flow characteristics observed in conventional single screw and twin screw extruders, this backmixed extruder has a residence time distribution comparable to a continuous stirred tank reactor, yet provides a positive drag flow regime for high viscosity fluids not available in stirred pots. The polydispersity (M_w/M_n) of chain addition polymerizations carried out in the backmixed extruder was cut in half when compared to those obtained in a conventional (plug flow) extruder, thus producing a more monodisperse polymer, and approached the theoretical value for a micromixed CSTR. The copolymer content of chain addition copolymerizations carried out in the backmixed extruder was demonstrated to be constant as a function of position in the reactor, whereas drift was observed in the conventional (plug flow) extruder.