Olefin copolymerization with metallocene catalysts. II. Kinetics, cocatalyst, and additives

The kinetics of ethylene/propylene copolymerization catalyzed by (ethylene bis (indeyl)‐ZrCI2/methylaluminoxane) has been investigated. Radiolabeling found about 80% of the Zr to be catalytically active. The estimates for rate constants at 50°C are k11 = 1104 (Ms)−1, k12 = 430 (Ms)−1, k22 = 396 (Ms)−1,k21 = 1020 (Ms)−1, and kAtr,1 + kAtr.2 = 1.9 × 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 loweing 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°C resulted in a doubling of molecular weight but suffered 10‐fold reduction in polymerization activity and increase of ethylene in copolymer.