Process for the polymerization of 1-butene

A process for polymerizing 1-butene carrier out in liquid monomer, wherein the liquid monomer comprises liquid 1-butene, the process comprising the step of contacting, under polymerization conditions, 1-butene and optionally from 0 to 20% by mol of ethylene, propylene and/or an alpha olefins of formula CH2═CHZ wherein Z is a C3-C10 alkyl group, with a catalyst system obtained by contacting:

• a) a racemic or racemic-like bridged metallocene compound of formula (I)
• wherein
• R1, same or different, is hydrogen, a linear or branched, saturated or unsaturated C1-C20-alkyl, C3-C20-cycloalkyl, C6-C20-aryl, C7-C20-alkylaryl, or C7-C20-arylalkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements;
• A, same or different, is a carbon atom, a germanium atom or a silicon atom;
• with the proviso that when m is 1, A is not a carbon atom;
• m is 1 or 2;
• R2, same or different, is hydrogen, a linear or branched saturated or unsaturated C1-C20-alkyl, C3-C20-cycloalkyl, C6-C20-aryl, C7-C20-alkylaryl, or C7-C20-arylalkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements;
• M is a transition metal atom selected from those belonging to group 4 of the Periodic Table of the Elements;
• X, same or different, is a hydrogen atom, a halogen atom, or a R, OR, OSO2CF3, OCOR, SR, NR2 or PR2 group, wherein R is a linear or branched, saturated or unsaturated C1-C20 alkyl, C3-C20 cycloalkyl, C6-C20 aryl, C7-C20 alkylaryl or C7-C20 arylalkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements;
• or two X can optionally form a substituted or unsubstituted butadienyl radical or a OR11O group wherein R11 is a divalent radical selected from C1-C20 alkylidene, C6-C40 arylidene, C7-C40 alkylarylidene or C7-C40 arylalkylidene radicals;
• L, same or different, is a moiety of formula (IIa)
• wherein
• in the moiety of formula (IIa), T bonds to the cyclopentadienyl group in position 5;
• T is an oxygen (O) atom, a sulphur (S) atom, or a CH2 group;
• R3 is hydrogen, linear or branched, saturated or unsaturated C1-C20-alkyl, C3-C20-cycloalkyl, C6-C20-aryl, C7-C20-alkylaryl, or C7-C20-arylalkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements;
• b) an alumoxane or a compound of formula D+E−, wherein D+ is a Brønsted acid that donates a proton and to react irreversibly with a substituent X of the metallocene of formula (I) and E− is a compatible anion which stabilizes the active catalytic species originating from the reaction of the two compounds, and which is sufficiently labile to be removed by an olefinic monomer;
• and
• c) optionally an organo aluminum compound, wherein the process produces a polymer comprising more isotactic triads (mm) than syndiotactic triads (rr) and having an intrinsic viscosity higher than 1.0 dL/g.