| 摘要 |
Syndiospecific catalysts and processes for the syn- diotactic propagation of a polymer chain derived from an ethyle- nically unsaturated monomer which contains 3 or more carbon atoms or is a substituted vinyl compound. The catalysts comprise unba- lanced 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 vir- tue 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 syn- diotactic polymer.
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