Syndiotactic polystyrene preparation in a rim process

Abstract

Very few polymeric systems are suitable for preparing engineering parts using reaction injection molding (RIM) processing. A new two-component metallocene catalyst, which is able to polymerize bulk styrene at high rates to the syndiotactic form, was studied. The catalyst used in this work was based on monocyclopentadienyl analogs of titanium (Cp*TiMe3), which was used in conjunction with a boron cocatalyst [B(C6F5)3]. When separate streams of the catalyst and cocatalyst, dissolved in either styrone or styrene/toluene solutions, met in a mixhead, the styrene polymerized rapidly to form crystalline, syndiotactic polystyrene (s-PS). Using a bench scale RIM device, the monomer conversion during polymerization was monitored through the quasi-adiabatic temperature rise, recorded by a rapid data acquisition system. The rate equation was found to be second order with respect to the monomer concentration and first order with respect to the catalyst concentration, given some assumptions. The s-PS was brittle and attempts were made to incorporate elastomer toughening into the reacting system. Several potential problems associated with using this system for RIM process discussed. © 1996 John Wiley & Sons, Inc.