Copolymerization of ethylene and 1-hexene catalyzed by the zirconocene/AI(i-Bu)3/B(C6F5)3 catalytic system

Copolymerizations of ethylene/1-hexene were conducted using different zirconocene/AIR(3)/B(C6F5)(3) catalytic systems at 50 degrees C. When AIEt(3) was used as alkylate agent, very low copolymerization activity was observed with both bridged catalyst Et[Ind](2)ZrCI2 and unbridged zirconocene Cp2ZrCI2 in-situ activated with B(C6F5)(3). In appropriate AI/Zr mole ratio using AI(i-Bu)(3), the catalytic activities of both zirconocene catalytic systems were similar to those of sophisticated zirconocene/methylaluminoxane(MAO) catalytic system. The catalytic activities, comonomer incorporation and molecular weight of the copolymer synthesized with Et[Ind](2)ZrCI2/AI(i-Bu)(3)/B(C6F5)(3) were higher than those obtained with Cp2ZrCI2/AI(i-Bu)(3)/B(C6F5)(3). The effect of the concentration of 1-hexene on catalytic activity, copolymer molecular weight, and comonomer incorporation was investigated. The complicated "co-monomer effect", together with an increase in comonomer incorporation, a decrease in the copolymer molecular weight, was found when the comonomer concentration was increased.