Reivindicaciones
1. A process for obtaining homopolymers of alpha-olefins containing from 2 to 20 carbon atoms and copolymers of different alpha-olefins containing from 2 to 20 carbon atoms with wide bimodal or multimodal molecular weight distributions, characterised by use of catalytic systems consisting of two subsystems a) and b): (a) a single supported or unsupported metallocene catalyst, being mono, di and tricyclopentadienyl and their derivatives of transition metals in groups 4b, 5b, 6b of the Periodic Table of elements, represented by the general formulae: (C 5 R' m ) p R" s (C 5 R' m )MeQ 3-p or R" s (C 5 R' m ) 2 MeQ' <img class="EMIRef" id="429842254-ib0003" /> where (C<5> R'<m> ) is cyclopentadienyl or substituted cyclopentadienyl, each R' may be the same or different, and may be hydrogen, monohydrocarbon radicals such as alkyl, alkenyl, aryl, alkylaryl or arylalkyl containing from 1 to 20 carbon atoms, or two adjacent carbon atoms joined to form a C4-C6 ring, or various condensed rings, R" is an alkylene radical containing from 1 to 4 carbon atoms, a dialkyl germanium or silicon radical, or an alkylphosphine or amino radical joining two (C<5> R'<m> ) rings, Q is a hydrocarbon radical such as aryl, alkyl, alkenyl, alkylaryl, arylalkyl containing from 1 to 20 carbon atoms, or halogen, and each one may be the same or different, Q' is an alkylidine radical containing from 1 to 20 carbon atoms, Me is a transition metal in groups 4b, 5b or 6b of the Periodic Table of elements, s is 0 or 1, p is 0.1 or 2; when p is 0, s is 0; m is 4 if s is 1 and m is 5 if s is 0. (b) a mixture of two or more co-catalysts selected from the following groups i), ii) and iii): 1) Aluminium compounds having the general formula: AlR'"<3> where the R'" groups, which may be the same or different, may be alkyls or aryls containing from 1 to 20 carbon atoms, or halogens, and Al is aluminium, ii) Aluminium compounds having Al-O bonds (aluminoxanes) corresponding to the general formulae: (RAlO) n or R(R-Al-O) n AlR 2 <img class="EMIRef" id="429842254-ib0004" /> where R is an alkyl or aryl group containing from 1 to 20 carbon atoms, and n is a number from 1 to 20, iii) Boron compounds corresponding to the general formulae: BX 1 X 2 X 3 OR [Y] [BX 1 X 2 X 3 X 4 ] <img class="EMIRef" id="429842254-ib0005" /> where B is boron, X<1> , X<2> , X<3> , X<4> , which are the same or different, may be hydride, halide, alkyl containing from 1 to 20 carbon atoms, substituted alkyls containing from 1 to 20 carbon atoms, in which one or more hydrogens are substituted by halogens, metal hydrocarbon radicals (organometalloids) in which each substitution contains from 1 to 20 carbon atoms and the metal is selected from group 4a of the Periodic Table of elements, aryl, substituted aryls containing from 6 to 20 carbon atoms. The aryl groups can be substituted by other groups such as alkoxy and alkylamido or fluoro radicals or halogen-substituted hydrocarbon groups, and may be a Bronsted acid, such as H<+> , ammonium or substituted ammonium cations in which up to 3 of the hydrogen atoms may be replaced by hydrocarbon radicals containing from 1 to 20 carbon atoms or by substituted hydrocarbon radicals in which one or more of the hydrogen atoms are substituted by halogens, phosphonium radicals or substituted phosphonium radicals in which up to 3 hydrogens can be substituted by hydrocarbon radicals containing from 1 to 20 carbon atoms, or by substituted hydrocarbon radicals in which one or more of the hydrogens may be substituted by halogens, or carbene radicals in which up to 3 of the hydrogens may be substituted by hydrocarbon radicals containing from 1 to 20 carbon atoms, or substituted hydrocarbon radicals in which one or more of the hydrogens may be substituted by halogens. 2. A process for the preparation of homopolymers in accordance with claim 1, characterised in that the olefin is ethylene. 3. A process for preparing copolymers in accordance with claim 2, characterised in that the co-monomer is 1-butene, 1-hexene or 1-octene and is incorporated at random. 4. A process for the preparation of homopolymers and copolymers in accordance with claim 1, characterised by the use of hydrocarbon solvents under inert conditions for the catalyst system and reaction temperatures between -60°C and 280°C, preferably between 40°C and 160°C, reactor pressures between 1 and 500 atmospheres, in the presence or absence of H<2> as a regulator of the molecular weight of the polymer. 5. A process according to claim 1, characterised in that the metallocene is supported or unsupported bis(cyclopentadienyl) zirconium dichloride, in which the aluminium compound is an aluminium alkyl, preferably trimethyl aluminium, triethyl aluminium or triisobutyl aluminium, in which the aluminoxane is methyl aluminoxane, and in which the boron compound is tris(pentafluorophenyl) borane. 6. A process according to claim 1, characterised in that the catalyst composition has molar ratios of aluminium compound to metallocene catalyst metal from 1.0:1.0 to 10<8> :1.0, preferably from 5.0:1.0 to 10<5> :1.0 and molar ratios of aluminium compound and/or aluminoxane to boron from 0.01:1 to 10<4> :1, preferably from 0.1:1 to 10<3> : 1.0. 7. The product prepared according to claims 1, 2, 3, 4, 5 and 6.
