US Patent 7141527 Catalyst system and process for the polymerization of olefins

A catalyst system for the polymerization of olefins comprising the product obtained by contacting:(A) a metallocene complex;(B) an organometallic aluminium compound of formula (II):Al[CH2—C(Ar)R4R5]xHy  (II)wherein Ar is a substituted or unsubstituted aryl group having from 6 to 20 carbon atoms; R4 is a linear or branched, saturated or unsaturated, C1–C10 alkyl, C6–C20 aryl, C7–C20 arylalkyl or C7–C20 alkylaryl; R5 is hydrogen or a linear or branched, saturated or unsaturated, C1–C10 alkyl, C6–C20 aryl, C7–C20 arylalkyl or C7–C13 alkylaryl group;x=2 or 3; y=3-x; andwater;the molar ratio (B)/(C) being between 1:1 and 100:1. These catalysts show an improved activity with respect to known catalysts, wherein different aluminium compounds are used.