ELASTOMERIC PROPERTIES OF ETHYLENE PROPYLENE COPOLYMERS PREPARED BY ZIRCONOCENE/METHYLALUMINOXANE CATALYSTS/

Ethylene/propylene copolymers (EPM) have been prepared by a liquid pro pylene suspension process, using homogeneous catalysts based on nonbri dged zirconocenes and methylaluminoxane (MAO). When bis(eta(5)-cyclope ntadienyl)zirconium dichloride (Cp(2)ZrCl(2)), bis(eta(5)-cyclopentadi enyl) dimethyl zirconium (Cp(2)ZrMe(2)) and bis(eta(5)-cyclopentadieny l), dibenzyl zirconium (Cp(2)ZrBz(2)) were used as catalyst components , EPM having low average molecular weight (MW) were in general obtaine d in low yield. On the contrary, a very large improvement of productiv ity and MW was observed when bis(eta(5)-indenyl)zirconium dichloride ( Ind(2)ZrCl(2)) and bis(eta(5)-indenyl) dimethyl zirconium (Ind(2)ZrMe( 2)) as well as bis(eta(5)-tetrahydroindenyl)zirconium dichloride [(Ind H(4))(2)ZrCl2] were employed in combination with MAO. In particular, t his last catalytic system allowed one to obtain EPM with a narrower di stribution of MW in addition to the above characteristics. Better perf ormances, in terms of theological and elastomeric properties, were als o found for the crude and vulcanized samples prepared by (IndH(4))ZrCl 2/MAO catalyst.