Process and catalyst for producing polyethylene having a broad molecular weight distribution

• US 4,530,914 A
• Filed: 06/06/1983
• Issued: 07/23/1985
• Est. Priority Date: 06/06/1983
• Status: Expired due to Term

• Current Assignee: Exxon Research and Engineering Company (Exxon Mobil Corporation)
• Original Assignee: Exxon Research and Engineering Company (Exxon Mobil Corporation)
• Inventors: Ewen, John A., Welborn, Howard C. Jr.
• Primary Examiner(s): GARVIN, PATRICK
• Application Number:
  US06/501,740
• Time in Patent Office: 778 Days
• Field of Search: 502/113, 502/117, 502/103
• US Class Current: 502/113
• CPC Class Codes: C08F 10/00 Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
• CPC Class Codes: C08F 4/65904 in combination with another component of C08F4/64
• CPC Class Codes: C08F 4/65912 in combination with an organoaluminium compound
• CPC Class Codes: C08F 4/6592 containing at least one cyclopentadienyl ring, condensed or not, e.g. an indenyl or a fluorenyl ring
• CPC Class Codes: Y10S 526/943 Polymerization with metallocene catalysts

Abstract

Polyolefins having a broad molecular weight distribution are obtained by polymerizing ethylene or higher alpha-olefins in the presence of a catalyst system comprising two or more metallocenes each having different propagation and termination rate constants and alumoxane.

Claims

1. A catalyst system for the (co)polymerization of ethylene to polyethylene having a broad molecular weight distribution, said catalyst comprising (a) at least two different metallocenes selected from mono, di or tricyclopentadienyls and substituted cyclopentadienyls of a Group 4b, 5b and 6b transition metal each having different propagation and termination rate constants of ethylene polymerizations and (b) an alumoxane.

2. The catalyst system of claim 1 wherein the transition metals are selected from titanium and zirconium.

3. A catalyst system for the (co)polymerization of ethylene to polyethylene having a broad and/or multimodal molecular weight distribution;

said catalyst comprising;

(a) at least two or more metallocenes represented by the general formula (C₅ R'"'"'_m)_p R"_s (C₅ R'"'"'_m)MeQ_3-p or R"_s (C₅ R'"'"'_m)₂ MeQ'"'"', each having a different propagation and termination rate constant for ethylene polymerization, and

(b) an alumoxane wherein (C₅ R'"'"'_m) is a cyclopentadienyl or substituted cyclopentadienyl, each R'"'"' which can be the same or different is hydrogen or a hydrocarbyl radical selected from alkyl, alkenyl, aryl, alkylaryl, or arylalkyl radicals having from 1 to 20 carbon atoms or two carbon atoms of the cyclopentadienyl ring are joined together to form a C₄ -C₆ ring, R" is a C₁ -C₄ alkylene radical, a dialkyl germanium or silicone or alkyl phosphine or amine radical bridging two (C₅ R'"'"'_m) rings, Q is a hydrocarbon radical selected from aryl, alkyl, alkenyl, alkylaryl, or arylalkyl radicals having from 1-20 carbon atoms or halogen and can be the same or different, Q'"'"' is an alkylidene radical having from 1 to about 20 carbon atoms, Me is a Group 4b, 5b or 6b metal, s is 0 or 1, p is 0, 1 or 2, when p is 0, s is 0;

m is 4 when s is 1 and m is 5 when s is 0.

4. The catalyst system of claim 3 comprising two zirconocenes.

5. The catalyst system of claim 3 comprising two titanocenes.

6. The catalyst system of claim 4 comprising at least 2 zirconocenes and 1 titanocene.

7. The homogeneous catalyst system of claim 5 comprising at least 2 titanocenes and 1 zirconocene.