Patent ID: 7259216

Claim:
A process for preparing highly branched ethylene polymers, which comprises polymerizing ethylene over a catalyst system comprising a compound of the formula I a or I b and an activator, where the variables in the formulae I a and I b are defined as follows: X 1 , X 2 are identical or different and are selected form the group consisting of halide, trifluoroacetate, BF 4 - , PF 6 - or SbF 6 - , C 1 -C 8 -alkyl, C 7 -C 13 -aralkyl, C 6 -C 14 -aryl, C 1 -C 6 -alkoxy and NR 9 R 10 , where R 9 and R 10 are selected independently from the group consisting of hydrogen, C 2 -C 12 -alkenyl and C 6 -C 14 -aryl, which may from a saturated or unsaturated 5- to 10-membered ring; R 1 -R 6 are identical or different and are selected from the group consisting of hydrogen, C 1 -C 8 -alkyl, substituted or unsubstituted, C 3 -C 12 -cycloalkyl, substituted or unsubstituted, C 2 -C 12 -alkenyl, C 7 -C 13 -aralkyl, C 6 -C 14 -aryl, unsubstituted or substituted by one or more identical or different substitutents selected from the group consisting of C 1 -C 8 -alkyl, substituted or unsubstituted, C 3 -C 12 -cycloalkyl, C 7 -C 13 -aralkyl, C 6 -C 14 -aryl, halogen, C 1 -C 6 -alkoxy, C 6 -C 14 -aryloxy, SiR 11 R 12 R 13 and O—SiR 11 R 12 R 13 , where R 11 to R 13 are selected from the group consisting of C 1 -C 8 -alkyl, C 3 -C 12 -cycloalkyl, C 7 -C 13 -aralkyl or C 6 -C 14 -aryl k is 0, 1, 2 or 3, Z 1 -Z 4 are identical or different and are selected from the group consisting of hydrogen, C 1 -C 8 -alkyl, substituted or unsubstituted, C 3 -C 12 -cycloalkyl, substituted or unsubstituted, C 2 -C 12 -alkenyl, halogen, NO 2 , C 7 -C 13 -aralkyl and C 6 -C 14 -aryl, and R 7 ,R 8 are identical or different and are selected from the group consisting of branched C 3 -C 8 -alkyl, C 3 -C 12 -cycloalkyl, and a-substituted C 3 -C 12 -alkenyl, and the process is carried out at from 50 to 110° C. and a pressure of from 10 to 100 bar.