| 摘要 |
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 complex. 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 formula: <IMAGE> wherein M is zirconium, titanium or hafnium; R1 and R2 are independently a C1-C20 linear, branched or cyclic alkyl group; X an alkyl, aryl, halide, hydride or oxygen bridge of a zirconocene dimer; "y" and "z" are independently numbers 0, 1 or 2; and 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.
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