| 摘要 |
<p>Disclosed is a process for preparing high molecular weight ethylene- alpha -olefin elastomers, preferably an ethylene-propylene elastomer, by liquid phase polymerization of the requisite monomers in the presence of a metallocene/alumoxane catalyst system. Preferably, the process is carried out as a slurry polymerization utilizing the metallocene/alumoxane catalyst in supported form on a silica gel support with the alpha -olefin monomer maintained in liquid state and used in excess to serve as a polymerization diluent. The metallocene component of the catalyst by which the process is practiced is of the formul: <CHEM> wherein M is zirconium, titanium or hafnium; each R<1> independently is a C1-C20 linear, branched or cyclic alkyl group or a C2-C4 cyclic alkylene group which forms a fused ring system group; R<2> is a C1-C6 linear, branched or cyclic alkylene, a Si1-Si2 alkyl substituted silanylene group or an alkyl substituted silaalkylene group; each X independently is an alkyl, aryl, halide, hydride or oxygen bridge of a zirconocene dimer; "y" is a number 2, 3 or 4, and "b" is a number 0 or 1. M is preferably zirconium. Most preferably, the supported zirconocene/alumoxane catalyst is prepolymerized with ethylene or another olefin to provide spherical, free-flowing catalyst particles which give free-flowing particulate elastomer product from the slurry polymerization.</p> |
