Patent ID: 7534841

Claim:
A process for preparing 1-butene polymers comprising the properties: a) a distribution of molecular weight (Mw/Mn) lower than 3; b) a melt flow rate (MFR) measured according to ISO 1133 (190° C., 2.16 kg) ranging from 200 to 1000; c) an intrinsic viscosity (IV) measured in tetrahydronaphthalene (THN) at 135° C. lower than 0.8 dl/g; d) a melting point higher than 90° C.; e) isotactic pentads (mmmm) measured with 13 C-NMR operating at 100.61 MHz higher than 90% corresponding to the total units derived from butene and copolymerized alpha olefins; f) 4,1 insertions not detectable at a C 13 -NMR operating at 100.61 MHz; g) a yellowness index lower than 0; and h) an aluminum content ranging from 2 ppm by weight to 40 ppm by weight, the process comprising polymerizing 1-butene or copolymerizing 1-butene with ethylene, propylene or an alpha-olefin of formula CH 2 ═CHZ wherein Z is a C 3 -C 10 alkyl group, in the presence of hydrogen at a concentration higher than 1000 ppm by mole and a catalyst system obtained by contacting: (A) a metallocene compound represented by formula (I): wherein: M is an atom of a transition metal selected from those belonging to group 3, 4, or to the lanthanide or actinide groups in the Periodic Table of the Elements; X, equal to or different from each other, is a hydrogen atom, a halogen atom, a R, OR, OR′O, OSO 2 CF 3 , OCOR, SR, NR 2 or PR 2 group wherein R is a linear or branched, cyclic or acyclic, C 1 -C 40 -alkyl, C 2 -C 40 alkenyl, C 2 -C 40 alkynyl, C 6 -C 40 -aryl, C 7 -C 40 -alkylaryl or C 7 -C 40 -arylalkyl radical; optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; and R′ is a C 1 -C 20 -alkylidene, C 6 -C 20 -arylidene, C 7 -C 20 -alkylarylidene, or C 7 -C 20 -arylalkylidene radical; R 1 , R 2 , R 5 , R 6 , R 7 , R 8 and R 9 , equal to or different from each other, are hydrogen atoms, or C 1 -C 40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or R 5 and R 6 , and/or R 8 and R 9 can optionally form a saturated or unsaturated, 5 or 6 membered rings, said ring can bear C 1 -C 20 alkyl radicals as substituents; with the proviso that at least one of R 6 or R 7 is a linear or branched, cyclic or acyclic, C 1 -C 40 -alkyl, C 2 -C 40 alkenyl, C 2 -C 40 alkynyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; R 3 and R 4 , equal to or different from each other, are linear or branched, cyclic or acyclic, C 1 -C 40 -alkyl, C 2 -C 40 alkenyl, C 2 -C 40 alkynyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; (B) an alumoxane or a compound that forms an alkyl metallocene cation; and optionally (C) an organo aluminum compound.