Dual Catalyst Systems for Producing Polymers with a Broad Molecular Weight Distribution and a Uniform Short Chain Branch Distribution (Chevron Phillips)

CATEGORY: CATALYSIS: POLYMERS
Dual Catalyst Systems for Producing Polymers with a Broad Molecular Weight Distribution and a Uniform Short Chain Branch Distribution (Chevron Phillips)
United States Patent Application 20160068625
Yang; Qing ;   et al.   March 10, 2016
Assignee: Chevron Phillips Chemical Company LP
Abstract
Disclosed herein are ethylene-based polymers having a melt index less than 50 g/10 min, a ratio of Mw/Mn from 4 to 20, a density from 0.90 to 0.945 g/cm.sup.3, and a substantially constant short chain branch distribution. These polymers can be produced using a dual catalyst system containing a boron bridged metallocene compound with a cyclopentadienyl group and an indenyl group, and a single atom bridged metallocene compound with a fluorenyl group.
BACKGROUND OF THE INVENTION
[0002] Polyolefins such as high density polyethylene (HDPE) homopolymer and linear low density polyethylene (LLDPE) copolymer can be produced using various combinations of catalyst systems and polymerization processes. In some end-use applications, it can be beneficial to use a dual metallocene catalyst system to produce copolymers having broad and/or bimodal molecular weight distributions. Moreover, it can be beneficial for such copolymers to also have a flat or uniform comonomer distribution. Accordingly, it is to these ends that the present invention is directed.
SUMMARY OF THE INVENTION
[0003] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify required or essential features of the claimed subject matter. Nor is this summary intended to be used to limit the scope of the claimed subject matter.
[0004] The present invention generally relates to new catalyst compositions, methods for preparing catalyst compositions, methods for using the catalyst compositions to polymerize olefins, the polymer resins produced using such catalyst compositions, and articles produced using these polymer resins. In particular, aspects of the present invention are directed to catalyst compositions employing two metallocene catalyst components. The first catalyst component can comprise a boron bridged metallocene compound with a cyclopentadienyl group and an indenyl group. The second catalyst component can comprise a single atom bridged metallocene compound with a fluorenyl group. Such catalyst compositions can be used to produce, for example, ethylene-based copolymers for variety of end-use applications.
[0005] The present invention also contemplates and encompasses olefin polymerization processes. Such processes can comprise contacting a catalyst composition with an olefin monomer and optionally an olefin comonomer under polymerization conditions to produce an olefin polymer. Generally, the catalyst composition employed can comprise any of the catalyst component I (boron bridged) cyclopentadienyl-indenyl metallocene compounds, any of the catalyst component II (single atom bridged) metallocene compounds with a fluorenyl group, and any of the activators and optional co-catalysts disclosed herein. For example, organoaluminum compounds can be utilized in the catalyst compositions and/or polymerization processes.
[0006] Polymers produced from the polymerization of olefins, resulting in homopolymers, copolymers, terpolymers, etc., can be used to produce various articles of manufacture. A representative and non-limiting example of an olefin polymer (e.g., an ethylene copolymer) consistent with aspects of this invention can be characterized as having the following properties: a melt index of less than or equal to about 50 g/10 min, a ratio of Mw/Mn in a range from about 4 to about 20, a density in a range from about 0.90 g/cm.sup.3 to about 0.945 g/cm.sup.3, and a substantially constant short chain branch distribution (SCBD). Another representative and non-limiting ethylene-based polymer described herein can have a melt index of less than or equal to about 10 g/10 min, a ratio of Mw/Mn in a range from about 4.1 to about 8, a density in a range from about 0.915 g/cm.sup.3 to about 0.945 g/cm.sup.3, and a substantially constant short chain branch distribution (SCBD). These polymers, in further aspects, can be characterized by low levels of long chain branches (LCB) and/or by a bimodal molecular weight distribution.
[0007] Both the foregoing summary and the following detailed description provide examples and are explanatory only. Accordingly, the foregoing summary and the following detailed description should not be considered to be restrictive. Further, features or variations may be provided in addition to those set forth herein. For example, certain aspects and embodiments may be directed to various feature combinations and sub-combinations described in the detailed description.
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