Process for producing stereospecific polymers

Abstract

Stereospecific catalysts and processes for the stereotactic polymerization of ethylenically unsaturated monomers, specifically C3-C4 alpha olefins involving a molecular sieve supported metallocene catalyst comprising a stereospecific metallocene catalyst component and a co-catalyst component. The metallocene catalyst component incorporates a metallocene ligand structure having two sterically dissimilar cyclopentadienyl ring structures coordinated with the central transition metal atom. Both the metallocene catalyst component and the co-catalyst component are supported on a molecular sieve having an average effective pore size which is less than the kinetic diameter of at least one of said ring structures. This supported catalyst is contacted in a polymerization reaction zone with an ethylenically unsaturated monomer which contains 3 or more carbon atoms or which is a substituted vinyl compound under polymerization conditions to produce stereospecific polymerization of the monomer. The supported catalyst incorporates a molecular sieve support having an average effective pore size within the range of 5-10 angstroms. The metallocene component can be an unbalanced metallocene having a ligand structure in which stereorigidity is imparted by means of a structural bridge extending between dissimilar cyclopentadienyl groups, for example, a fluorenyl group, a cyclopentadienyl group, of a ligand which exhibits bilateral symmetry. The specific zeolite supports are zeolite Y, zeolite X, mordenite, and zeolite beta . Others include various zeolites of the ZSM substitutional series, including ZSM-5, ZSM-11, and ZSM-12.

Description

technical field [0001] The present invention relates to supported stereorigid metallocene catalysts for the production of stereoregular polymers from ethylenically unsaturated compounds, and more particularly to molecular sieve supports incorporating the catalysts and uses thereof. Background technique [0002] Syndiotactic and isotactic are stereoregular structural relationships that are associated with the formation of stereoregular polymers from various monomers. Stereotactic growth (propagation) can be used to polymerize ethylenically unsaturated monomers such as C 3 + Alpha-olefins, 1-dienes such as 1,3-butadiene, substituted vinyl compounds such as vinyl aromatic compounds such as styrene or vinyl chloride, vinyl chloride, vinyl ethers such as alkyl vinyl ethers such as isobutyl aryl vinyl ethers, or even aryl vinyl ethers. Stereotactic polymer growth is probably most important in the production of isotactic or syndiotactic polypropylene. [0003] Syndiotactic polym...

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Problems solved by technology

[0016] Despite the semi-ordered structure, hemi-isotactic polypropylene is essentially amorphous because of the disorder of the alternating methylene (methene) units

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