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AssigneeAlbemarle Corporation
InventorSteven P. Diefenbach
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Described are solid olefin polymerization catalysts that have, inter alia, very high productivities (at least 18,000 grams of polyethylene per gram of catalyst in one hour) as shown by a standard test procedure for measuring this property or characteristic. Such particulate catalysts can be prepared by prepolymerizing vinylolefin with a Group 4 metallocene-aluminoxane solution, using proportions of vinylolefin (most preferably, ethylene) in the range of about 150 to about 1500, and preferably in the range of about 175 to about 1000, moles per mole of Group 4 metallocene used in forming the solution. The atom ratio of aluminum to Group 4 metal in the solution is in the range of about 150:1 to about 1500:1, and preferably in the range of about 175:1 to about 1000:1. In addition, the Group 4 metallocene ingredient used in forming these highly productive catalysts has in its molecular structure at least one polymerizable olefinic substituent. These particulate catalysts do not contain, and thus are not produced in the presence of, a preformed support such as an inorganic compound (silica or etc.) or a preformed particulate polymeric support.
A vinylolefin prepolymerized Group 4 metallocene-aluminoxane particulate catalyst composition devoid of a preformed support and having (i) a productivity, when fresh and if tested for productivity, of at least 18,000 grams of polyethylene per gram of catalyst in one hour, and (ii) a specific surface area of no more than about 20 m2/g, the metallocene having prior to prepolymerization at least one polymerizable olefinic substituent in the molecule.
A process which comprises:
A process which comprises:
Dependencies are inferred from the claim text.