SYNDIOTACTIC POLYSTYRENE PREPARATION IN A RIM PROCESS

Very few polymeric systems are suitable for preparing engineering part s using reaction injection molding (RIM) processing. A new two-compone nt metallocene catalyst, which is able to polymerize bulk styrene at h igh rates to the syndiotactic form, was studied. The catalyst used in this work was based on monocyclopentadienyl analogs of titanium (CpTi Me(3)), which was used in conjunction with a boron cocatalyst [B(C6F5) (3)]. When separate streams of the catalyst and cocatalyst, dissolved in either styrene or styrene/toluene solutions, met in a mixhead, the styrene polymerized rapidly to form crystalline, syndiotactic polystyr ene (s-PS). Using a bench scale RIM device, the monomer conversion dur ing polymerization was monitored through the quasi-adiabatic temperatu re rise, recorded by a rapid data acquisition system. The rate equatio n was found to be second order with respect to the monomer concentrati on and first order with respect to the catalyst concentration, given s ome assumptions. The s-PS was brittle and attempts were made to incorp orate elastomer toughening into the reacting system. Several potential problems associated with using this system for RIM process are discus sed. (C) 1996 John Wiley & Sons, Inc.