HIGH ACTIVITY CATALYST PREPARED WITH ALKOXYSILANES

摘要

An ethylene-alpha-olefin copolymerization catalyst is prepared by impregnating a silica calcined at elevated temperature sequentially with an organomagnesium compound such as dialkylmagnesium compound, a silane compound which is free of hydroxyl groups, such as tetraethyl orthosilicate. A transition metal component such as titanium tetrachloride is then incorporated into the support. Unexpectedly, the calcination temperature of the silica used to prepare the catalyst precursors has a strong influence on polymer product properties. By increasing the calcination temperature of the silica from 600° to 700° C. or higher temperatures, a catalyst precursor when activated produced ethylene/1-hexene copolymers with narrower molecular weight distributions (MWD) as manifested by a decrease of resin MFR values of ~3-4 units. Activation of this catalyst precursor with a trialkylaluminum compound results in a catalyst system which is effective for the production of ethylene copolymers.