OLEFIN COPOLYMERIZATION WITH METALLOCENE CATALYSTS .2. KINETICS, COCATALYST, AND ADDITIVES

The kinetics of ethylene/propylene copolymerization catalyzed by (ethylene bis(indenyl)-ZrCl2/methylaluminoxane) has been investigated. Radiolabeling found about 80% of the Zr to be catalytically active. The estimates for rate constants at 50-degrees-C are k11 = 1104 (M s)-1, k12 = 430 (M s)-1, k22 = 396 (M s)-1, k21 = 1020 (M s)-1, and k(tr,2)A = 1.9 x 10(-3) s-1. Substitution of trimethylaluminum for methylaluminoxane resulted in proportionate decrease in polymerization rate. The molecular weight of the copolymer is slightly increased by lowering the [Al]/[Zr] ratio, or addition of Lewis base modifier but at the expense of lowered catalytic activity and increase in ethylene content in the copolymer. Lowering of the polymerization temperature to 0-degrees-C resulted in a doubling of molecular weight but suffered 10-fold reduction in polymerization activity and increase of ethylene in copolymer.