Process and catalyst for producing polyolefins having low molecu

Details Process and catalyst for producing polyolefins having low molecu Process and catalyst for producing polyolefins having low molecu

1996-04-19

2000-09-05

Wu, David W.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

526127, 526170, 526943, 502152, C08F 464

Patent

active

061144800

ABSTRACT:
The invention provides a metallocene catalyst for use in preparing polyolefins having low molecular weight. The catalyst comprises a metallocene compound generally described by the formula R"(C.sub.5 R.sub.4) (H.sub.2 C.sub.5 C.sub.4 H.sub.4)MeQ.sub.p wherein (C.sub.5 R.sub.4) is a substituted cyclopentadienyl ring; (H.sub.2 C.sub.5 C.sub.4 H.sub.4) is an indenyl ring; (C.sub.5 R.sub.4) 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 (C.sub.5 R.sub.4) and (H.sub.2 C.sub.5 C.sub.4 H.sub.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. This catalyst produces a crystalline or atactic polymer with a low molecular weight and narrow or broad molecular weight distribution depending upon the isomer(s) used in polymerization. A single threo-isomer produces isotactic polypropylene and a single erythro-isomer produces atactic polypropylene, both polymers having narrow molecular weight distribution. When the bridge between the substituted cyclopentadienyl and the indenyl rings is substituted such that four diastereomers are possible, the threo-isomers produce isotactic polypropylene with broad molecular weight distribution.

REFERENCES:
patent: 5321107 (1994-06-01), Tsutsui et al.
patent: 5329031 (1994-07-01), Miyake et al.
patent: 5741868 (1998-04-01), Winter et al.
"Highly Isospecific Polymerization of Propylene with Unsymmetrical Metallocene Catalysts", S. Miyake et al., Macromolecules, vol. 28, No. 9 (Apr. 24, 1995).

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