Ethylene polymerization with siloxane modified catalyst

Claim 1

In a process for polymerizing a monomer charge comprising ethylene by contacting said charge with activated inorganic oxide supported bis(cyclopentadienyl) chromium [II] catalyst wherein said inorganic oxide is selected from the group consisting of silica, alumina, thoria, zirconia and mixtures thereof, and the bis(cyclopentadienyl) chromium [II] compound has the structure ##STR6## wherein n' and n" are each integers of 0 to 5, inclusive, and R' and R" are each C 1 to C 20 , inclusive, hydrocarbon radicals, the improvement which comprises modifying said catalyst prior to said contact with said monomer charge by contacting said catalyst with, per mol of the organo-chromium compound, 0.01 to 20 mols of at least one modifying compound having in its structure at least one moiety of the formula ##STR7## said modifying compound being devoid of OH, SH, NH 2 , COOH, halogen, alkoxy and aryloxy radicals in such amounts as would poison the polymerization system under the prevailing reaction conditions, and said modifying with said modifying compound providing a modified catalyst with which, in comparison to the use of the unmodified catalyst in said polymerization process, polymers of improved impact strength are prepared.