Methods for producing polyolefins with catalyst systems

Abstract

Described herein are methods comprising contacting one or more olefins with a catalyst system in a polymerization reactor at conditions sufficient to produce a polyolefin, wherein the catalyst system comprises a first metallocene catalyst compound comprising a first transition metal atom, two cyclopentadienyl ligands bound to the first transition metal atom, and two leaving groups bound to the first transition metal atom, wherein at least one leaving group is selected from the group consisting of a halo-phenoxy and a halo-alkoxy; wherein the first metallocene catalyst compound has a catalyst productivity that is at least 20% greater than a comparative metallocene catalyst compound used to produce the same polyolefin, wherein the comparative metallocene catalyst compound is the same as the first metallocene catalyst compound except neither leaving group is a halo-phenoxy or a halo-alkoxy.

Description

Background technique [0001] A number of catalyst compositions containing single-site catalysts have been used to prepare polyolefins to produce relatively uniform copolymers. In contrast to conventional multi-site Ziegler-Natta catalyst compositions, single-site catalysts, such as metallocene catalysts, are catalytic compounds that contain uniform polymerization sites. [0002] To achieve acceptable and commercially viable polymerization activity with metallocene catalyst compounds, large amounts of activators, such as methylaluminoxane ("MAO"), are often required. Unfortunately, these activators are expensive, and the amount of activator required to produce active polymerization catalysts has been a serious obstacle to commercializing metallocene catalysts for the production of polyolefins. Therefore, there is a need for catalysts with improved activity and productivity and thus requiring less activator. [0003] Mixed catalyst systems often include at least one metallocene...

AI Technical Summary

Problems solved by technology

Unfortunately, these activators are expensive, and the amount of activators required to produce active polymerization catalysts is a serious obstacle to commercializing metallocene catalysts for the production of polyolefins

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