Patent ID: 7589160

Claim:
A process for preparing 1-butene polymers optionally containing up to 30% by mol of derived units of ethylene, propylene or an alpha olefin of formula CH 2 =CHZ, wherein Z is a C 3 –C 10 alkyl group, comprising polymerizing 1-butene and optionally ethylene, propylene or said alpha olefin, in the presence of a catalyst system obtained by contacting: a) at least a metallocene compound of formula (I): wherein: M is an atom of a transition metal selected from those belonging to group 4; p is 2, being equal to the formal oxidation state of the metal M minus 2; X, equal to different from each other, are hydrogen atoms, halogen atoms, R, OR, OSO 2 CF 3 , OCOR, SR, NR 2 or PR 2 groups, wherein R is a linear or branched, C 1 –C 20 alkyl, C 3 –C 20 cycloalkyl, C 6 –C 20 aryl, C 7 –C 20 alkylaryl or C 7 –C 20 arylalkyl radical, optionally containing heteroatoms belonging to groups 13–17 of the Periodic Table of the Elements; R 1 , equal to or different from each other, are linear or branched, C 1 –C 20 -alkyl, C 3 –C 20 -cycloalkyl, C 6 –C 20 -aryl, C 7 –C 20 -alkylaryl or C 7 –C 20 -arylalkyl radicals, optionally containing at least one heteroatom belonging to groups 13–17 of the Periodic Table of the Elements; R 2 , R 3 and R 6 , equal to or different from each other, are hydrogen atoms or linear or branched, C 1 –C 20 -alkyl, C 3 –C 20 -cycloalkyl, C 6 –C 20 -aryl, C 7 –C 20 -alkylaryl or C 7 –C 20 -arylalkyl radicals, optionally containing at least one heteroatom belonging to groups 13–17 of the Periodic Table of the Elements; R 4 and R 5 , form together a condensed saturated or unsaturated C 3 –C 7 membered ring optionally containing heteroatoms belonging to groups 13–16 of the Periodic Table of the Elements; every atom forming said ring being substituted with R 7 radicals wherein R 7 , equal to or different from each other, are hydrogen atoms or linear or branched, C 1 –C 20 -alkyl, C 3 –C 20 -cycloalkyl, C 6 –C 20 -aryl, C 7 –C 20 -alkylaryl or C 7 –C 20 -arylalkyl radicals, optionally containing at least one heteroatom belonging to groups 13–17 of the Periodic Table of the Elements; L is Si(R 8 ) 2 wherein R 8 is a linear or branched, C 1 –C 20 alkyl, C 3 –C 20 cycloalkyl, C 6 –C 20 aryl, C 7 –C 20 alkylaryl, or C 7 –C 20 arylalkyl radical; and b) an alumoxane or a compound that forms an alkylmetallocene cation.