Non-bridged syndiospecific metallocene catalysts and polymerization process
US5162278A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 10, 1989 |
| Grant date | Nov 10, 1992 |
| Priority date | — |
| Expiry date | Oct 10, 2009 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S526/943
- WIPO fieldMacromolecular chemistry, polymers
- WIPO sectorChemistry
Abstract
Syndiospecific catalysts and processes for the syndiotactic propagation of a polymer chain derived from an ethylenically unsaturated monomer which contains 3 or more carbon atoms or is substituted vinyl compound. The catalysts comprise unbalanced stereorigid metallocenes in which a structural bridge is not required for stereorigidity. The ring structures of the metallocene catalyst are substituted cyclopentadienyl rings, which are sterically different from one another. The substituent groups on the cyclopentadienyl rings impart stereorigidity to the catalyst by virtue of a sterically hindered relationship between the rings sufficient to prevent rotation of the rings, or by virtue of the cyclopentadienyl groups being at a low kinetic energy state induced by the substituents to prevent rotation of the rings about their coordination axes at the temperature of the catalyst. The catalyst is contacted with a C3+ alpha olefin or other ethylenically unsaturated compound in a polymerization reaction zone and maintained in contact with the catalyst in the reaction zone under polymerization conditions to produce a syndiotactic polymer.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.