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

• US 4,935,474 A
• Filed: 04/26/1985
• Issued: 06/19/1990
• 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): Smith, Edward J.
• Application Number:
  US06/727,969
• Time in Patent Office: 1,880 Days
• Field of Search: 526/114, 526/116, 526/119
• US Class Current: 526/114
• 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 process for producing polyethylene having a multimodal molecular weight distribution comprising polymerizing ethylene in the presence of a homogeneous catalyst system comprising (a) at least two different metallocenes selected from mono, di or tricyclopentadienyls and their derivatives of a Group 4b, 5b and 6b transition metal each metallocene having different propagation and termination rate constants for ethylene polymerization and (b) and alumoxane.

2. The process in accordance with claim 1 wherein the transition metals are selected from titanium and zirconium.

3. A process for producing polyethylene having a multimodal molecular weight distribution comprising polymerizing ethylene in the presence of a homogeneous catalyst system comprising:

(a) at least two or more metallocenes represented by the general formula

space="preserve" listing-type="equation">(C.sub.5 R'"'"'.sub.m).sub.p R".sub.s (C.sub.5 R'"'"'.sub.m)MeQ.sub.3-p or

space="preserve" listing-type="equation">R".sub.s (C.sub.5 R'"'"'.sub.m).sub.2 MeQ'"'"',

each having a different propagation and termination rate constant, 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, each Q which can be the same or different 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, s is 0 when p is 0, m is 4 when s is 1, m is 5 when s is 0.

4. The process in accordance with claim 3 comprising two zirconocenes.

5. The process in accordance with claim 3 comprising two titanocenes.

6. The process in accordance with claim 4 comprising at least 2 zirconocenes and 1 titanocene.

7. The process in accordance with claim 5 comprising at least 2 titanocenes and 1 zirconocene.