Ethylene/α-Olefin Copolymerization with Dimethylsilyl-bis(2-methyl-4-phenyl-indenyl) zirconium dichloride and Methylaluminoxane: Influences on Polymerization Activity and Molecular Weight
The copolymerizations of ethylene with 1-hexene and of ethylene with 1-octene have been investigated using rac-Me2Si [2-Me-4-Ph-Ind]2 ZrCl2 and methylaluminoxane as cocatalyst. This metallocene catalyst readily incorporates α-olefin, and at the same time the polymerization activities remain relatively high. Interestingly no comonomer effect can be observed with this catalyst in contrast to other metallocene catalysts, e. g. Cp2ZrCl2 or Me2Si-[Ind]2ZrCl2. Also the mode of addition of catalyst components influences the polymerization rate. The separate addition of the metallocene from the MAO is accompanied by longer induction periods, whereas the combined addition induces copolymerization almost instantaneously. The activities obtained with 1-octene are slightly lower than those obtained with 1-hexene. The molecular weight drops with increasing α-olefin concentration, however it is relatively high compared to copolymers produced with other metallocene catalysts. With a highly racemic mixture of the title catalyst unprecedented activities were obtained of 1,170,000 kg polyethylene/(mol Zr x h x [mon]) at 40 °C, and 477,000 kg ethylene/1-hexene copolymer/(mol Zr x h x [mon]) at 45 °C and a monomer ratio of unity in the reaction.
KeywordsRacemic Mixture Polymerization Rate Metallocene Catalyst Molar Feed Ratio Catalyst Component
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