Ethylene polymers with α-olefins

A method for improving cold properties of middle distillates, comprising mixing said middle distillates with ethylene-octene co-polymers and terpolymers comprising ethylene, octene with at least an alpha-olefin of from 3 to 12 carbon atoms, and optionally, comonomers containing more than one ethylenic unsaturation,

• wherein the ethylene-octene co-polymers and terpolymers are obtainable by polymerization of monomers in the presence of catalysts comprising:
• 1) a bis-cyclopentadienyl derivative having the general formula:
• (Cp1Cp2)—M—(L2L3)
• containing groups with oxygen bound to the transition metal, wherein
• M is a metal from the IIIb group to the Vb group or of the lanthanide series of the Periodic Table of the Elements;
• Cp1 and Cp2, equal to or different from each other, represent the following groups bound to M with delocalized π bonds, wherein the groups are selected from cyclopentadiene, indene, fluorene, or derivatives thereof substituted in the case of indene and fluorene also with the hydrogenated phenil ring (rings) and with substituents both in the phenilic and cyclopentadienylic rings, also with heteroatoms;
• or with π bonds in the case of cyclooctatriene;
• or said Cp1Cp2 groups constrained with M by a bivalent linking bridge, —R— type, wherein R is an alkylene from 1 to 4 carbon atoms, —Si(R′)2— wherein R′ is an alkyl from 1 to 10 C atoms;
• or an aryl optionally containing heteroatoms, or an alkylaryl or an arylalkyl from 7 to 20 carbon atoms;
• L2 and L3, equal to or different from each other represent an ORa group wherein Ra is an aryl group, optionally the ring carbon atoms being substituted by heteroatoms, and optionally containing substituents of alkyl type from 1 to 10 carbon atoms, and
• 2) a co-catalyst comprising a compound of formula:
• (L1—H)+(A)−
• wherein (A)− is (B Qq)−,
• wherein L1 is a neutral Lewis base;
• (L1—H)+ is a Bronsted acid;
• B is boron with valence 3;
• Q, equal to or different from each other, are selected from the following group consisting of hydrides, halides, alkyls, aryls optionally substituted, with halogens, alkoxides, aryioxides, dialkylamido, or R0COO— wherein R0 has from 1 to 20 carbon atoms, with the proviso that Q can be equal to halide only once;
• and
• q is an integer equal to the valence of B plus 1.