Process for the preparation of a polyolefin

Claim 1

A process for the preparation of a polyolefin by polymerizing an olefin of the formula R 11 --CH═CH--R 12 in which R 11 and R 12 are identical or different and are a hydrogen atom or a C 1 -C 14 -alkyl radical or R 11 and R 12 , together with the carbon atom connecting them, form a ring having 4 to 28 carbon atoms, at a temperature of from 0° C. to 150° C., at a pressure of from 0.5 to 100 bar, in solution, in suspension or in the gas phase, in the presence of a catalyst which comprises a metallocene and an aluminoxane of the formula (II) ##STR9## for the linear type and/or of the formula (III) ##STR10## for the cyclic type, where, in the formulae (II) and (III), the radicals R 10 are identical or different and are hydrogen, a C 1 -C 6 -alkyl group, phenyl or benzyl, and n is an integer from 2 to 50, wherein the metallocene is a compound of the formula (I) ##STR11## in which M is zirconium or hafnium, R 1 and R 2 are identical or different and are a hydrogen atom, a C 1 -C 10 -alkyl group, a C 1 -C 10 -alkoxy group, a C 6 -C 10 -aryl group, a C 6 -C 10 -aryloxy group, a C 2 -C 10 -alkenyl group, a C 7 -C 40 -arylalkyl group, a C 7 -C 40 -alkylaryl group, a C 8 -C 40 -arylalkenyl group or a halogen atom, R 3 and R 4 are identical or different and are a hydrogen atom, a halogen atom or a C 1 -C 10 -alkyl group, or any two adjacent radicals R 3 and R 4 , together with the carbon atoms connecting the, for a ring, a radical from the group consisting of R 5 , R 6 , R 7 and R 8 is a --CH 2 --SiMe 3 group and each of the other radicals of the group is a hydrogen atom, and the compound of the formula I is in the form of at least two of its stereo-isomers originating from the metallocene preparation.