| 摘要 |
The invention provides a metallocene catalyst for use in preparing polyolefins having low molecular weight. The catalyst comprises a bridged metallocene in which one of the cyclopentadienyl rings is substituted in a substantially different manner from the other ring. The catalyst comprises a metallocene compound generally described by the formula R''(C5R4)(R'2C5C4R'4)MeQp wherein (C5R4) is a substituted cyclopentadienyl ring; (R'2C5C4R'4n) is an indenyl ring or substituted indenyl ring; each R and R' is hydrogen or hydrocarbyl radical having from 1-20 carbon atoms, a halogen, an alkoxy, and alkoxy alkyl or an alkylamino radical, each R and R' may be the same or different; (C5R4) has one R substituent in a distal position which is at least as bulky as a t-butyl radical; R'' is a structural bridge between the (C5R4) and (R'2C5C4R'4) rings to impart stereorigidity; Q is a hydrocarbyl radical, such as an alkyl, aryl, alkenyl, alkylaryl or arylalkyl radical having 1-20 carbon atoms or is a halogen; Me is a Group IIIB, IVB, VB, or VIB metal as positioned in the Periodic Table of Elements; and p is the valence of Me minus 2.
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