INFLUENCE OF METALLOCENE STRUCTURES ON ETHENE COPOLYMERIZATION WITH 1-BUTENE AND 1-OCTENE

Ethene/1-octene and ethene/1-butene copolymerization using various met hylaluminoxane-activated metallocene catalysts, e.g. silylene-bridged substituted bisindenyl zirconocene systems and halfsandwich titanocene , was performed at 40 degrees C in toluene. The influence of the ligan d substitution on comonomer incorporation, catalyst activity, molar ma ss, molar mass distribution, degree of polymerization and copolymeriza tion parameters was investigated in ethene/1-octene copolymerization a t constant comonomer ratio and in ethene/1-butene copolymerization as a function of varying ethene/1-butene feed mass ratios. In ethene/1-oc tene copolymerization the highest comonomer incorporation was achieved with MAO-activated Me2Si(Me4Cp)(N-tert-butyl)TiCl2 catalyst. Best per formance in terms of comonomer incorporation combined with high cataly st activity and molar mass was found for silylene-bridged bisindenylzi rconocenes, where 2-methyl substitution promoted high degree of polyme rization and benzannelation accounted for improved catalyst activity, comonomer incorporation and randomness of comonomer incorporation. In ethene/1-butene copolymerization at high 1-butene feed content silylen e-bridged substituted bisindenyl systems showed polymerization charact eristics similar to that of ethene/1-octene copolymerization. The infl uence of 2-methyl substitution on activity and comonomer incorporation was significant only at low 1-butene feed content. Storage moduli and glass transition temperature of the poly(ethene-co-1-butene) copolyme rs decreased with increasing 1-butene content. (C) 1998 Elsevier Scien ce B.V.