Title of Invention

PROCESS FOR THE POLYMERIZATION OF OLEFINS

Abstract

A multistep process comprising the following steps: step a) polymerizing propylene and optionally one or more monomers selected from ethylene or alpha olefins of formula CH2=CHTl, wherein T1' is a C2-Cio alkyl radical in the presence of a catalyst system supported on an inert carrier, comprising: ii) one or more metallocene compounds of formula (I); ii) an alumoxane or a compound capable of forming an alkyl metallocene cation; and optionally iii) an organo aluminum compound; step b) contacting, under polymerization conditions, in a gas phase, propylene or ethylene with one or more alpha olefins of formula CH2=CHT, wherein T is hydrogen or a C1-C10 alkyl radical, and optionally a non-conjugated diene, in the presence of the polymer obtained in step a) and optionally in the presence of an additional organo aluminum compound; provided that an homopolymer is not produced; wherein: the compound of formula (I) is described in the application.

Full Text

Title: Process for the polymerization of olefins The present invention relates to a multistep process for preparing heterophasic propylene copolymers, by using a particular class of metallocene compounds. Multistep processes for the polymerization of olefins, carried out in two or more reactors, are known from the patent literature and are of particular interest in industrial practice. The possibility of independently varying, in any reactors, process parameters such as temperature, pressure, type and concentration of monomers, concentration of hydrogen or other molecular weight regulator, provides much greater flexibility in controlling the composition and properties of the end product compared to single-step processes. Multistep processes are generally carried out using the same catalyst in the various steps/reactors. The product obtained in one reactor is discharged and sent directly to the next step/reactor without altering the nature of the catalyst. WO 01/48034 describes a class of bis indenyl metallocene compounds wherein the indenyl moieties are substituted in position 4 with a substituted aryl radical. This document exemplifies the use of this class of metallocene compounds in a multistage process. WO 05/058916 relates to a class of bis indenyl metallocene compounds wherein at least one indenyl moiety is substituted in position 5 and 6 with a condensed ring. This documents describes in a generical way a process for preparing an heterophasic polymer. It describes only the polymers that can be prepared in each stage without explaining how each step has to be carried out. The applicant now surprisingly found that when a particular class of bis indenyl metallocene compounds is used for the preparation of an heterophasic polymer in particular process conditions it is possible to achieve in high yield a polymer having an high molecular weight. In particular the rubber phase of the heterophasic polymer results to have a very high molecular weight. Therefore an object of the present invention is a multistep process comprising the following steps: step a) polymerizing propylene and optionally one or more monomers selected from ethylene or alpha olefins of formula CH-CHT1, wherein T1 is a C2-C10 alkyl radical in the presence of a catalyst system supported on an inert carrier, comprising: i) one or more metallocene compounds of formula (I): ii) an alumoxane or a compound capable of forming an alkyl metallocene cation; and optionally iii) an organo aluminum compound; step b) contacting, under polymerization conditions, in a gas phase, propylene or ethylene with one or more alpha olefins of formula CH2=CHT, wherein T is hydrogen or a C1-C10 alkyl radical, and optionally a non-conjugated diene, in the presence of the polymer obtained in step a) and optionally in the presence of an additional organo aluminum compound; provided that an homopolymer is not produced; wherein the amount of the polymer obtained in step a) ranges from 5% by weight to 90% by weight of the polymer obtained in the whole process and the amount of polymer obtained in step b) ranges from 10% by weight to 95% by weight of the polymer obtained in the whole process; 4 wherein: in the compound of formula (I): tr. M is an atom of a transition metal Selected from those belonging to group 4 of the Periodic Table of the Elements; preferably M ii zirconium, titanium or hafnium; X, equal to or different from £ach other, is a hydrogen atom, a halogen atom, a R, OR, OR'O, OSO2CF3, OCOR, SR, NR2 of .PR2 group wherein R is a linear or branched, cyclic or acyclic, C3-C4o-alkyl, C2-C40 alkenyl, C2-C40 alkynyl, C1-C16-aryl, C7-C4o-alkylaiyl or C7-C4o~arylalkyl radical; optionally containing ^heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; and R' is a G-C2o-alkylidene, C6-C2o-arylidene, C7-C2o-alkylarylidene, or C7-C2o-arylalkylidene radical; preferably X is a hydrogen atom, a halogen atom, a OR'O or R group; more preferably X is chlorine or a methyl radical; L is a divalent bridging group selected from C1-C20 alkylidene, C3-C20 cycloalkylidene, C6-C20 arylidene, C7-C20 alkylarylidene, or a C7-C20 arylalkylidene radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, or it is a silylidene radical containing up to 5 silicon atoms; preferably L is Si(R11)2 wherein R11 is a linear or branched, cyclic or acyclic, C1-C4o-alkyl, C2-C40 alkenyl, C2-C40 alkynyl, C6-C40-aryl, C7-C4o-alkylaryl or C7-C4o-atylalkyl radical; more preferably L is Si(CH3)2 or SiPh2; R1 and R19 are different from each other and are a Z1 or Z2 group wherein Z1 is an alpha branched G-C20 hydrocarbon radical optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, and Z is a linear C1-C40 hydrocarbon radical optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; with the proviso that if R1 or R19 are Z1 ithen R19 or R1 are Z2; preferably Z1 is a compound of formula (II) or an alpha branched aryl or arylalkyl radical containing from 2 to 20 carbon atoms optionally containing O, N, S, P and Se atoms, in particular O, N and S atoms such as 2(5-Me-thiophenyl) or 2(5-Me-furanyl) radicals; wherein in the compound of formula (II) R and R , equal to or different from each other, are C1-C40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably C1-C10 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; more preferably R23 and R24 are C1-C20-alkyl, C2-C40 alkenyl, C2-C40 alkynyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; more preferably R23 and R are linear or branched C1-C10-alkyl radical such as methyl, or ethyl radicals; R is an hydrogen atom or it has the same meaning of R and R ; more preferably R is a hydrogen atom; preferably Z2 is a linear C1-C20-alkyl, C2-C40 alkenyl, C2-C40 alkynyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably Z is a linear C1-C10-alkyl radical; more preferably Z is a methyl, or ethyl radical; R and R , are part of 4-7 membered ring condensed to the benzene ring of the indenyl moiety; preferably a 5 or 6 membered ring; said ring optionally containing heteroatoms belonging to groups 13-16 of the Periodic Table of the Elements preferably groups 15-16 of the Periodic Table of the Elements; the valence of each atom forming said ring being substituted with R radicals; that means that is filled with R18 groups, wherein R18, equal to or different from each other, are hydrogen atoms or a C1-C40 hydrocarbon radical; preferably R18 is a hydrogen atom or a linear or branched, cyclic or acyclic, Ci-C4o-alkyl, C2-C40 alkenyl, C2-C40 alkynyl, C6-C4o-aryl, C7-C4o-alkylaryl or C7-C4o-arylalkyl radical, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; more preferably R is a hydrogen atom or a linear or 1R branched, C1-C20-alkyl radical; more preferably R is a hydrogen atom or a methyl or ethyl radical; said ring can be saturated or it can contain double bonds; preferably R2 and R3, form together a condensed saturated 3-7 membered ring; R4 is a hydrogen atom or a C1-C40 hydrocarbon radical optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R4 is a hydrogen atom or a linear or branched, cyclic or acyclic, Ci-C4o-alkyl, C2-C40 alkenyl, C2-C40 alkynyl, C6-C40-aiyl, C7-C4o-alkylaryl or C7-C4o-arylalkyl radical optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R4 is a hydrogen atom a CrCio-alkyl or a C6-C40-aryl radical; W is an aromatic 5 or 6 membered ring that can contain heteroatoms belonging to groups 15-16 of the Periodic Table of the Elements; the valence of each atom of said ring is substituted with hydrogen atom or it can optionally be substituted with R5 groups, wherein R5, equal to or different from each other, are C1-C40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R5, are linear or branched, cyclic or acyclic, C1-C40-alkyl, C2-C40 alkenyl, C2-C40 alkynyl, C6-C4o-aiyl, C7-C4o-alkylaryl or C7-C40-arylalkyl radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; Preferably W is selected from the group comprising the following moieties of formula (Wa), (Wb) and (Wc): wherein the * represents the point in which the moiety bounds the indenyl moiety of the compound of formula (I); R,R,R, R and R , equal to or different from each other, are hydrogen atoms or C1-C40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R6, R7, R8, R9 and R10, are hydrogen atoms or linear or branched, cyclic or acyclic, C1-C40-alkyl, C2-C40 alkenyl, C2-C40 alkynyl, C6-C4o-aryl, C7-C4o-alkylaryl or C7-C4o-arylalkyl radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; Z is a nitrogen atom or a CR group; Z is a nitrogen atom or a CR group; Z is a nitrogen atom or a CR group; Z is a nitrogen atom or a CR group; Z is a nitrogen atom or a CR group; provided 1 1 "i A £ that not more that 2 groups among Z , Z , Z , Z and Z are nitrogen atoms, preferably not more that one group among Z , Z , Z , Z and Z is a nitrogen atom; Z6 is an oxygen atom, a sulfur atom, a NR13 group or a CR13 group; Z7is an oxygen atom, a sulfur atom, a NR14 group or a CR14 group; Z8is an oxygen atom, a sulfur atom, a NR15 group or a CR15group; Z9 is an oxygen atom, a sulfur atom, a NR16 group or a CR16 group; Z10 is a nitrogen atom or a carbon atom that bonds the indenyl moiety of the structure of formula (I); with the proviso that not more than 1 group among Z6, Z7, Z8, Z9 or Z10 is a sulfur atom, an oxygen atom or a nitrogen-containing group atom selected from NR13, NR14, NR15, NR16, and a nitrogen atom; R13, R14, R15 and R16, equal to or different from each other, are hydrogen atoms or C1-C40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R6, R7, R8, R9 and R10, are hydrogen atoms or linear or branched, cyclic or acyclic, CrC4o-alkyl, C2-C40 alkenyl, C2-C40 alkynyl, Ce-Gw-aryl, C7-C4o-alkylaryl or C7-C4o-arylalkyl radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of Ihe Elements; more preferably R6, R7, R8, R9 and R10 are hydrogen atoms, C1-C40-alkyl or C6-C40-aryl radicals; In the moiety of formula (Wa), in a preferred embodiment, R is a C1-C40-alky] radical, preferably a branched C1-C40-alkyl radical such as a tertbutyl radical, more preferably R7 is a branched CrC4o-alkyl radical wherein the carbon atom in position alpha is a tertiary carbon atom and R6, R8, R9andR10 are hydrogen atoms; In a further preferred embodiment R 10 and R are C1-C4o-alkyl radicals, preferably they are linear O-C40 alkyl radicals such as methyl radicals and R , R and R are hydrogen radicals: In a ftirther preferred embodiment R6, R7 and R8 are linear or branched Ci-C4o-alkyl radicals such as methyl or tertbutyl radicals and R30 and R9 are hydrogen atoms. In a tether preferred embodiment R6, R7, R8, R9 and R10 are hydrogen atoms; In the moiety of formula (Wb), in a preferred embodiment, Z1 is a nitrogen atom and Z2, Z3, Z4 and Z5 are respectively CR6, CR7, CR8 and CR9 wherein the meaning of R6, R7, R8, and R9 is described above; in a further preferred embodiment Z is a nitrogen atom and Z , Z , Z and Z are respectively CR10, CR6, CR8 and CR9 wherein the meaning of R10, R6, R8, and R9 is described above; in a further preferred embodiment Z is a nitrogen atom arid Z,Z,Z and Z are respectively. CR10, CR7, CR8 and CR9 wherein the meaning of R10, R7, R8, and R9 is described above; In the moiety of formula (Wc) in a preferred embodiment Z6 is an oxygen atom, a sulfur atom, a NR16 group; preferably it is a sulfur atom or a NR16; wherein R16 is preferably a Ci-C4o-alkyl radical; more preferably Z6 is a sulfur atom; and Z7, Z8, Z9 and Z10 are respectively a CR14, CR15, CR16 and a carbon atom, wherein R14 is a hydrogen atom or a Ci-Qo-alkyl radical such as methyl or ethyl; and R15 and R16 are hydrogen atoms or Q-Qo-alkyl radicals; R , R and R , equal to or different from each other, are hydrogen atoms or CT-CAO hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R20 and R21 are hydrogen atoms or C1-C10 alkyl radicals, with the proviso that they are not both or C1 -C10 alkyl radicals; preferably R22 is an hydrogen atom; referred class of compounds of formula (I) have formula (HI) (in) Wherein M, L, X, R1, R4, R14, R15, R16, R19, R20, R21, R22 and W have the meaning reported above and R1 1 and R12, equal to or different from each other, are hydrogen atoms or d-C4o hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R11 and R12 are hydrogen atoms or linear or branched, cyclic or acyclic, C1-C40-alkyl, C2-C40 alkenyl, C2-C40 alkynyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; more preferably Rn and R12 are hydrogen atoms or C1-C10-alkyl radicals such as methyl or ethyl radicals. A further preferred class of compounds of formula (I) have formula (IV) |. (IV) Wherein M, L, X, R1, R4, R6, R7[ R8, R9, R10, R19, R20, R21, R22 and W have the meaning reported above and R and R , equal to OT different from each other, are hydrogen atoms or C1-C40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R11 and R12 are hydrogen atoms or linear or branched, cyclic or acyclic, C1-C4o-alkyl5 C2-C40 alkenyl, C2-C40 alkynyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; more preferably R and R are hydrogen atoms or d-C1-C10-alkylradicals such as methyl or ethyl radicals; Preferably W is a moiety of formula (Wa) as described above. Compounds of formula (I) can be prepared according to PCT/EP2004/013827. Alumoxanes used as component ii) in the catalyst system according to the present invention can be obtained by reacting water with an organo-aluminium compound of formula HjAlU3-1 or HjAhU6-j, where the U substituents, same or different, are hydrogen atoms, halogen atoms, CrC2o-alkyl, C3- C20-cyclalkyl, C6-C20-aryl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radicals, optionally containing silicon or germanium atoms, with the proviso that at least one U is different from halogen, and j ranges from 0 to 1, being also a non-integer number. In this reaction the molar ratio of Al/water is preferably comprised between 1:1 and 100:1. The alumoxanes used in the catalyst system according to the invention are considered to be linear, branched or cyclic compounds containing at least one group of the type: can be used in the case of cyclic compounds, wherein n2 is an integer from 2 to 40 and the U substituents are defined as above. Examples of alumoxanes suitable for use according to the present invention are methylalumoxane (MAO), tetra-(isobutyl)alumoxane (TIBAO), tetra-(2,4,44rimethyl~pentyl)alumoxane (TIOAO), tetra-(2,3"dimethylbutyl)alumoxane (TDMBAO) and tetra»(2,3,3-trime1hylbutyl)alumoxane (TTMBAO). Particularly interesting cocatalysts are those described in WO 99/21899 and in WOO 1/21674 in which the alkyl and aryl groups have specific branched patterns. Non-limiting examples of aluminium compounds that can be reacted with water to give suitable alumoxanes (b), described in WO 99/21899 and WO01/21674, are: 1ris(2,33-trimethyl-butyl)aluminiums tris(2,3-dimethyl-hexyl)aluminium, tris(2,3-dimethyl- butyl)aluminium, tris(2,3-dimethyl-pentyl)aluminium, tris(2,3-dimethyl-heptyl)aluminium, tris(2-methyl-3-ethyl-pentyl)aluminium, tris(2-methyl-3-ethyl-hexyl)aluminium3 tris(2-methyl-3- ethyl-heptyl)aluminium, tris(2-methyl"3-propyl-hexyl)aluminium, tris(2-ethyl-3-methyl- butyl)aluminium, tris(2-ethyl-3-methyl-pentyl)aluminium, tris(2,3-diethyl-pentyl)aluminium, tris(2-propyl-3-methyl-butyl)aluminium, tris(2-isopropyl-3-methyl-butyl)aluminium, tris(2-isobutyl- 3-methyl-pentyl)aluminium, tris(2,3,3-trimethyl-pentyl)aliiminiiun, tris(2,3,3-trimethyl- hexyl)aluminium, tris(2-ethyU3,3-dimethyl-butyl)aluminium, tris(2-ethyl-3,3-dimethyl- pentyl)aluminium, tris(2-isopropyl-3,3-dimethyl-butyl)aluminium, tris(2-trimethylsilyl- propyl)aluminium, tris(2-methyl-3-phenyl-butyl)aluminium, tris(2-ethyl-3-pheny]-bu1yl)aluminium, tris(2,3-dimethyl-3-phenyl-butyl)aluminium, tris(2-phenyl-propyl)aluminium, tris[2-(4-fluoro-phenyl)-propyl]aluminium, tris[2-(4-chloro-phenyl)-propyl]aluminium, tris[2-(3-isopropyl-phenyl)-propyl]aluminium, lris(2-pheny]-butyl)aluininiiim, tris(3-melhyl-2-phenyl-butyl)aluminiuin, tris(2~ phenyl-pentyl)aluminium, tris[2-(pentafluorophenyl)-propyl]aluminium, tris[2,2-diphenyl-ethyl]aluminium and tris[2-pheny]-2-methyl-propyl]aluminium, as well as the corresponding compounds wherein one of the hydrocarbyl groups is replaced with a hydrogen atom, and those wherein one or two of the hydrocarbyl groups are replaced with an isobutyl group. Amongst the above aluminium compounds, trimethylaluminium (TMA), triisobutylaluminium (TIBA), tris(2,4,4-trimethyl-pentyl)a]uminium (TTOA), tris(2,3-dimethylbutyl)aluminium (TDMBA) and tris(2,3,3-trimethylbutyl)aluminium (TTMBA) are preferred. Non-limiting examples of compounds able to form an alkylmetallocene cation are compounds of formula D+E", wherein D+ is a Bnerosted acid, able to donate a proton and to react irreversibly with a substituent X of the metallocene of formula (I) and E" is a compatible anion, which is able to stabilize the active catalytic species originating from the reaction of the two compounds, and which is sufficiently labile to be removed by an olefinic monomer. Preferably, the anion E" comprises one or more boron atoms. More preferably, the anion E" is an anion of the formula BAr4("), wherein the substituents Ar which can be identical or different are aiyl radicals such as phenyl, pentafluorophenyl or bis(trifluoromethyl)phenyl. Tetrakis-pentafluorophenyl borate is particularly preferred compound, as described in WO 91/02012. Moreover, compounds of formula BAr3 can be conveniently used. Compounds of this type are described, for example, in the International patent application WO 92/00333. Other examples of compounds able to form an alkylmetallocene cation are compounds of formula BA^P wherein P is a substituted or unsubstituted pyrrol radical. These compounds are described in WOO 1/62764. Compounds containing boron atoms can be conveniently supported according to the description of DE-A-19962814 and DE-A-19962910. All these compounds containing boron atoms can be used in a molar ratio between boron and the metal of the metallocene comprised between about 1:1 and about 10:1; preferably 1:1 and 2.1; more preferably about 1:1. Non limiting examples of compounds of formula D'E" are: Tributylammoniumtetra(pentafluorophenyl)aluminate, Tributylammoniumtetra(trifluoromethylphenyl)borate, Tributylammoniumtetra(4-fluorophenyl)borate, N5N-Dimethylbenzylammonium-tetrakispentafluorophenylborate, N,N-Dimethylhexylamonium-tetrakispentafluorophenylborate, N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)borates N,N-DimethylaniliniuTntetrakis(pentafluorophenyl)aluminate5 N,N-Dimethylbenzylammoniiim-tetrakispentafluorophenylborate5 N,N-Dimethylhexylamonium-tetrakispentafluorophenylborate, Di(propyl)ammoniumtetrakis(pentafluorophenyl)borate, Di(cyclohexyl)aTnmoniumtetrakis(pentafluorophenyl)borate, Triphenylcarbeniumtetrakis^entafluorophenyljborate, Triphenylcarbeniumtetrakis(pentafluorophenyl)aluminate, Ferroceniumtetrakis(pentafluorophenyl)borate, Fenoceniumtetrakis(pentafluorophenyl)aluminate. Triphenylcarbeniumtetrakis(pentafluorophenyl)borate, and N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)borate. Organic aluminum compounds used as compound in) are those of formula HJA1U3.J or HjA^Ue-j as described above. The catalysts system to be used in the process of the present invention is supported on an inert carrier. This is achieved by depositing the metallocene compound i) or the product of the reaction thereof with the component ii), or the component ii) and then the metallocene compound i) on an inert support. The support can be a porous solid such as talc, a sheet silicate, an inorganic oxide or a finely divided polymer powder (e.g. polyolefin). Suitable inorganic oxides may be found among the oxides of elements of groups 2, 3, 4, 5, 13, 14, 15 and 16 of the Periodic Table of the Elements. Examples of oxides preferred as supports include silicon dioxide, aluminum oxide, and also mixed oxides of the elements calcium, aluminum, silicon, magnesium or titanium and also corresponding oxide mixtures, magnesium halides, styrene/divinylbenzene copolymers, polyethylene or polypropylene. Other inorganic oxides which can be used alone or in combination with the abovementioned preferred oxidic supports are, for example, MgO, Z1O2, Ti02 or B2O3. A suitable class of supports which can be used is that constituted by porous organic supports functionalized with groups having active hydrogen atoms. Particularly suitable are those in which the organic support is a partially crosslinked styrene polymer. Supports of this type are described in European application EP-633 272. Another class of inert supports particularly suitable for use according to the invention is that of polyolefin porous prepolymers, particularly polyethylene. A further suitable class of inert supports for use according to the invention is that of porous magnesium halides such as those described in International application WO 95/32995. The support materials used preferably have a specific surface area in the range from 10 to 1 000 m /g, a pore volume in the range from 0.1 to 5 ml/g and a mean particle size of from 1 to 500 [im. Preference is given to supports having a specific surface area in the range from 50 to 500 m2/g, a pore volume in the range from 0.5 to 3.5 ml/g and a mean particle size in the range from 5 to 350 |im. Particular preference is given to supports having a specific surface area in the range from 200 to 400 m2/g, a pore volume in the range from 0.8 to 3.0 ml/g and a mean particle size of from 10 to 300 µm. The inorganic support can be subjected to a thermal treatment, e.g. to remove adsorbed water. Such a drying treatment is generally carried out at from 80 to 300°C, preferably from 100 to 200°C, with drying at from 100 to 200°C preferably being carried out under reduced pressure and/or a blanket of inert gas (e.g. nitrogen), or the inorganic support can be calcined at from 200 to 1 000°C to produce the desired structure of the solid and/or set the desired OH concentration on the surface. The support can also be treated chemically using customary desiccants such as metal alkyls, preferably aluminum alkyls, chlorosilanes or SiCl4, or else methylaluminoxane. Appropriate treatment methods are described, for example, in WO 00/31090. The inorganic support material can also be chemically modified For example, treatment of silica gel with (NH4)2SiF6 leads to fluorination of the silica gel surface, or treatment of silica gels with silanes containing nitrogen-, fluorine- or sulfiir-containing groups leads to correspondingly modified silica gel surfaces. Organic support materials such as finely divided polyolefin powders (e.g. polyethylene, polypropylene or polystyrene) can also be used and are preferably likewise freed of adhering moisture, solvent residues or other impurities by means of appropriate purification and drying operations before use. It is also possible to use functionalized polymer supports, e.g. supports based on polystyrene, via whose functional groups, for example ammonium or hydroxy groups, at least one of the catalyst components can be immobilized. The solid compound obtained by supporting the catalyst system object of the present invention on a carrier in combination with the further addition of the alkylaluminium compound either as such or prereacted with water if necessary, can be usefully. Preferably step a) further comprises a prepolymerization step a-1). The prepolymerization step a-1) can be carried out by contacting the catalyst system with ethylene propylene or one or more alpha olefins of formula CH2NDHT1, wherein T1 is a C2-C20 alkyl radical. Preferably said alpha olefins are propylene or ethylene, at a temperature ranging from - 20°C to 70°C, in order to obtain a prepolymerized catalyst system preferably containing from 5 to 500 g of polymer per gram of catalyst system. Thus preferably step a) comprises a-1) contacting the catalyst system described above with ethylene and/or propylene and/or one ore more alpha olefins of formula CH2-CHT1, wherein T1 is a C2-C20 alkyl radical; preferably propylene or ethylene, in order to obtain a prepolymerized catalyst system preferably containing from 5 to 500 g of polymer per gram of catalyst system; preferably from 5 to 100 g of polymer per gram of catalyst system; a-2) polymerizing propylene and optionally one or more monomers selected from ethylene and alpha olefins of formula CH2=CHT1, wherein T1 is a C2-C20 alkyl radical in the presence of the prepolymerized catalyst system obtained in step a-1). Step a) of the present invention can be carried out in liquid phase, in which the polymerization medium can be an inert hydrocarbon solvent or the polymerization medium can be liquid propylene optionally in the presence of an inert hydrocarbon solvent, and of ethylene or one or more comonomer of formula CH2=CHT1, or step a) can be carried out in a gas phase. Said hydrocarbon solvent can be either aromatic (such as toluene) or aliphatic (such as propane, hexane, heptane, isobutane, cyclohexane and 2,2,4-trimethylpentane). Preferably the polymerization medium is liquid propylene. It can optionally contain minor amounts (up to 40% by weight, preferably up to 20% by weight, more preferably up to 5% by weight) of an inert hydrocarbon solvent or of one or more comonomer such as ethylene or alpha- olefins of formula CH2=CHT1. Mixtures of both comonomers and inert hydrocarbon solvent can be also present. Step a) can be carried out in the presence of hydrogen. The ratio hydrogen/propylene present during the polymerization reaction is preferably higher than 1 ppm; more preferably it ranges from 5 to 2000 ppm; even more preferably from 6 to 500 ppm with respect to the propylene present in the reactor. Hydrogen can be added either at the beginning of the polymerization reaction or it can also be added at a later stage after a prepolymerization step has been carried out. The propylene polymer obtained in step a) is a propylene homopolymer or a propylene copolymer containing up to 20% by mol preferably from 0.1 to 10% by mol, more preferably from 1% to 5% by mol of derived units of ethylene or one or more alpha olefins of formula CH2=CHT\ Non-limiting examples of alpha olefins of formula CH2=CHT1 which can be used in the process of the invention are 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 4,6-dimethyl-l-heptene, 1-decene, 1-dodecene, 1-tetradecene, 1 -hexadecene, 1-octadecene and 1-eicosene. Preferred comonomers are ethylene or 1-butene. The amount of polymer obtained in step a) ranges from 5% to 90% by weight of the total polymer produced in the whole process, preferably it ranges from 10% to 70% by weight of the total polymer produced in the whole process; more preferably from 30% to 60% by weight of the total polymer produced in the whole process. Preferably in step a) a propylene homopolymer or a propylene/ethylene copolymer having an ethylene content lower than 10% by weight is prepared. Step b) is carried out in a gas phase, preferably in a fluidized bed reactor or in a continuous stirrer tank reactor. The polymerization temperature is generally comprised between -100°C and +200°C, and, preferably, between 10°C and n-100°C. The polymerization pressure is generally comprised between 0,5 and 100 bar. The amount of polymer obtained in step b) ranges from 10% to 95% by weight of the polymer produced in the whole process, preferably it ranges from 30% to 90% by weight of the polymer produced in the whole process, more preferably it ranges from 70% to 40% by weight of the polymer produced in the whole process; another useful range is from 61% to 80% by weight of the polymer produced in the whole process. Step b) can be carried out in the presence of hydrogen. The ratio hydrogen/hethylene present during the polymerization reaction is preferably higher than 1 ppm with respect to the ethylene or propylene, depending on what is the prevalent monomer, present in the reactor; more preferably it ranges from 5 to 2000 ppm; even more preferably from 6 to 500 ppm. In step b) an ethylene or propylene copolymer having from 4% by mol to 90% by mol, preferably from 15% by mol to 60% by mol of derived units of comonomers of formula CH2=CHT and optionally up to 20% of derived units of non conjugated diene, is produced. Examples of comonomer of formula CH2=CHT that can be used in step b) of the present invention other then propylene and ethylene are: 1-butene, 1-pentene, 4-methyl-l-pentene, 1-hexene, 1-octene, 4,6-dimethyl-1 -heptene, 1 -decene, 1 -dodecene, 1 -tetradecene, 1 -hexadecene, 1 -octadecene and 1-eicosene. In step b) of the present invention a propylene copolymer or an ethylene copolymer can be produced. In case a propylene copolymer is produced, propylene is copolymerized with an alpha olefins of formula CH2=CHT, wherein T is hydrogen or a Ci-Cio alkyl radical, and optionally a non-conjugated diene, in the presence of the polymer obtained in step a) and optionally in the presence of an additional organo aluminum compound; provided that an homopolymer is not produced; examples of suitable comonomers of formual CH2=CHT are reported above; preferred comonomer to be used with propylene are ethylene, 1-butene and 1 -hexene. In case an ethylene copolymer is produced ethylene is copolymerized with an alpha olefins of formula CH2=CHT, wherein T is hydrogen or a Ci-Cio alkyl radical, and optionally a non-conjugated diene, in the presence of the polymer obtained in step a) and optionally in the presence of an additional organo aluminum compound; provided that an homopolymer is not produced; examples of suitable comonomers of formula CH2=CHT are reported above; preferred comonomer to be used with ethylene are 1 -butene and 1 -hexene. The polymer obtained in step b) can optionally contains up to 20% by mol of a non conjugated diene. Non conjugated dienes can be a straight chain, branched chain or cyclic hydrocarbon diene having from 6 to 20 carbon atoms. Examples of suitable non-conjugated dienes are: - straight chain acyclic dienes, such as 1,4-hexadiene and 1,6-octadiene; - branched chain acyclic dienes, such as 5-methyl-l,4-hexadiene, 3,7-dimethyl-l,6-octadiene, 3,7-dimethyl-l,7-octadiene and mixed isomers of dihydro myricene and dihydroocinene; - single ring alicyclic dienes, such as 1,3-cyclopentadiene, 1,4-cyclohexadiene, 1,5-cyclooctadiene and 1,5-cyclododecadiene; - multi-ring alicyclic fused and bridged ring dienes, such as tetrahydroindene, methyl tetrahydroindene, dicyclopentadiene, bicyclo-(2,2,l)-hepta-2, 5-diene; and - alkenyl, alkylidene, cycloalkenyl and cycloalkylidene norbornenes, such as.5-methylene-2-norbornene (MNB), 5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene,5-(4-cyclopentenyl)-2-norbornene, 5-cyclohexylidene-2-norbornene, 5-vinyl-2-norbornene and norbornadiene. Preferred dienes are 1,4-hexadiene (HD), 5-ethylidene-2-norbornene (ENB), 5-vinylidene-2- norbornene (VNB), 5-methylene-2-norbornene (MNB) and dicyclopentadiene (DCPD). Particularly preferred dienes are 5-ethylidene-2-norbornene (ENB) and 1,4-hexadiene (HD). When present the non-conjugated dienes are generally incorporated into the polymer in an amount from 0.1% to about 20% by mol; preferably from 1% to 15% by mol, and more preferably from 2% to 7% by; mol. If desired, more than one diene may be incorporated simultaneously, for example HD and ENB, with total diene incorporation within the limits specified above. , The process of the present invention can be carried out in one reactor or in two or more reactor in series. The following examples have an illustrative a non limiting purpose Examples General characterization Intrinsic viscosity (IV) in decahydronaphthalene The intrinsic viscosity in Decahydronaphthalene (DHN) was determined on an Ubbelohde viscometer PVS 1 with an S 5 measuring head (both from Lauda) in decalin at 135°C. To prepare the sample, 20 mg of polymer were dissolved in 20 ml of decalin at 135°C over a period of 2 hours. 15 ml of the solution were placed in the viscometer; the instrument carried out a minimum of three running-out time measurements until a consistent result had been, obtained. The IV was calculated from the running-out times according to IV = (t/t0~l)*l/c where t: mean of the running-out time of the solution, tO: mean of the running-out time of the solvent, c: concentration of the solution in g/ml. Intrinsic viscosity (IV) in tetrahydronaphthalene The measurement for examples 1-5 were done in tetrahydronaphthalene (THN) solution obtained by dissolving the polymer at 135°C for 1 hour. Xylene soluble fraction at 25°C 2.5g of polymer were dissolved in 250 ml of o-xylene under stirring at 135°C for 30 minutes, then the solution was cooled to 25°C and after 30 minutes the insoluble polymer was filtered. The resulting solution was evaporated in nitrogen flow and the residue was dried and weighed to determine the percentage of soluble polymer. Melting Temperature Tm Calorimetric measurements were performed by using a differential scanning calorimeter DSC Mettler. The instrument is calibrated with indium and tin standards. The weighted sample (5-10 mg), was sealed into aluminum pans, heated to 200°C and kept at that temperature for a time long enough (5 minutes) to allow a complete melting of all the crystallites. Successively, after cooling at 20°C/min to -20°C. After standing 5 minutes at 0°C, the sample was heated to 200°C at a rate of 20°C/min. In this second heating run, the peak temperature was assumed as melting temperature (Tm) and the area as the global melting hentalpy (AH). Gel permeation chromatography Gel permeation chromatography (GPC) was carried out at 145°C in 1,2,4-trichlorobenzene using a GPC apparatus 150C from Waters. The data were evaluated using the software Win-GPC from HS-Entwicklungsgesellschaft furwissenschaftliche Hard- und Software mbH, Ober- Hilbersheim. The calibration of the columns was carried out by means of polypropylene standards having molar masses of from 100 to 107 g/mol. Mass average molar masses (Mw) and number average molar masses (Mn) of the polymers were determined. The Q value is the ratio of mass average (Mw) to number average (Mn). Chemicals and characterization. All chemicals were handled using standard Schlenk techniques. Methylalumoxane (MAO) was received from Albemarle as a 30% wt/wt toluene solution and used as such and the silica was received from 1NEOS ( ES70Y, 100 microns). Pscudo rac DimcthylsilancdiyI-(6-mcthyl-4-(4,-tcrt-butylphcnyl)-l,2^,5-tctrahydro-s- indaccn-7-yI)(2-isopropyl-4-(4'-tcrt-butylphcnyI)-l-indenyl)-zirconium dichloridc (C-l) was synthesized according to PCT/EP2004/013827. was prepared according to the procedure described in WO 01/48034. Preparation of supported catalyst system 6,3 g SiC>2 are placed in a round flask equipped with a KPG stirrer and suspended at 0 °C in 30 ml toluene. Via a dropping funnel 15.1 ml MAO are slowly added at 0 °C. After addition, the suspension is allowed to come to room temperature (RT), and is then stirred for 2 h. The reaction mixture is placed in a stirred glass flask equipped with filter (size P3), where the solvent is filtered off. The residual is suspended in 20 ml toluene, stirred for 15 min at room temperature, and filtered. The support is suspended in 20 ml toluene, then brought to 80°C, and stirred for 30 min at this temperature before hot filtration. Again, the support is suspended in 20 ml toluene, then brought to 80°C, and stirred for 30 min at this temperature before hot filtration. The MAO/silica is suspended at 15 °C in 20 ml toluene. Under stirring, a solution of 0.25 mmol (207 mg, 40|imol/g carrier) of the metallocene indicated in table 1 in 2 ml MAO and 2 ml toluene is slowly added. The reaction mixture is stirred for 1 h at 15 °C, and after raising the temperature to 40 °C, again stirred for 2 h. Then, it is filtered. The residual solid is washed 3 times at 60 °C with 20 ml toluene each (stirring: 3 x 30 min). After the last filtration, the reaction product is transferred with some toluene into a glass ftit (size P3), and filtered again. The catalyst is transfer after drying at RT in high vacuum until weight constant. Polymerization examples 1-3 (multistep polymerization) Step a) A 2.5 L autoclave, previously kept overnight under nitrogen purge, is added with 2 mmol Triethylaluminum (TEA) (as 10% w/v hexane solution) as reactor scavenger. Also 0.5 bar-g of propylene are fed to prevent air insertion in the reactor. Prepolymerization: 252 g propylene are fed in the autoclave at 0°C. The catalytic system is injected in the reactor and propylene is prepolymerized at 30°C for 5 minutes. At the end of this step the reactor temperature was raised from 30 to 70°C (in 10 minutes). During the temperature increase also 59 cc H2 are fed, corresponding to 2.63 mmol H2. Propylene polymerization in bulk this step is carried out at 30 bar-g pressure and 70°C until the liquid propylene is totally consumed, and the pressure inside the reactor starts to decrease. When this step is completed, the PP matrix polymerization time is recorded and the pressure is released down to 0.1 bar-g propylene; at the same time the temperature decreases to 30°C. Stepb) Ethylene and propylene at a molar ratio ethylene(C2)/propylene(C3)+ethylene(C2) of 0.5 are fed in the reactor to reach the pressure of 21 bar-g then the temperature is raised to 60°C and the ethylene/propylene mixture is fed at constant pressure until 232g of monomers are consumed. Then the reactor is vented and cooled down to room temperature; thus, the reaction is stopped. The polymer is collected and dried at reduced pressure and 60°C. The resulting polymer has been subjected to xylene extraction at 25°C according to the procedure described above. The fraction of polymer soluble in xylene at 25°C has been taken as the amount of ethylene propylene copolymers produced in the process. The polymerization data are reported in table 1. A 2.5 L autoclave, previously kept overnight under nitrogen purge, is added with 2 mmol Triethylaluminum (TEA) (as 10% w/v hexane solution) as reactor scavenger. Also 0.5 bar-g of propylene are fed to prevent air insertion in the reactor. Prepolymerization: 134 g propylene are fed in the autoclave at 0°C. The catalytic system is injected in the reactor and propylene is prepolymerized at 30°C for 5 minutes. At the end of this step the reactor temperature was raised from 30 to 80°C (in 10 minutes). Propylene polymerization in gas phase: this step is carried out at 24 bar-g pressure and 80°C until 70 grams of propylene are consumed and the pressure inside the reactor starts to decrease. When this step is completed, the PP matrix polymerization time is recorded and the pressure is released down to 0.1 bar-g propylene; at the same time the temperature decreases to 30°C. Step b) Ethylene and propylene are fed in the reactor at a molar ratio (ethylene (propylene + ethylene)) of 0.3 and the temperature is raised to reach the pressure of 21 bar-g and the temperature of 70°C. Then the ethylene/propylene mixture is fed at constant pressure until 23 2g of monomers are consumed. Then the reactor is vented and cooled down to room temperature; thus, the reaction is stopped. The polymer is collected and dried at reduced pressure and temperature. The results are reported in table 2 Claims 1. A multistep process comprising the following steps: step a) polymerizing propylene and optionally one or more monomers selected from ethylene or alpha olefins of formula CH2=CHT1, wherein T1 is a C2-C10 alkyl radical in the presence of a catalyst system supported on an inert carrier, comprising: i) one or more metallocene compounds of formula (I): ii) an alumoxane or a compound capable of forming an alkyl metallocene cation; and optionally iii) an organo aluminum compound; step b) contacting, under polymerization conditions, in a gas phase, propylene or ethylene with one or more alpha olefins of formula CH2=CHT, wherein T is hydrogen oraCi-C10 alkyl radical, and optionally a non-conjugated diene, in the presence of the polymer obtained in step a) and optionally in the presence of an additional organo aluminum compound; provided that an homopolymer is not produced; wherein the amount of the polymer obtained in step a) ranges from 5% by weight to 90% by weight of the polymer obtained in the whole process and the amount of polymer obtained in step b) ranges from 10% by weight to 95% by weight of the polymer obtained in the whole process; wherein: in the compound of formula (I): M is an atom of a transition metal selected from those belonging to group 4of 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, OSO2CF3, OCOR, SR, NR2 or PR2 group wherein R is a linear or branched, cyclic or acyclic, C1-C40-alkyl, C2-C40 alkenyl, C2-C40 alkynyl, C6-C40-aryl, C7-C4o-alkylaryl or C7-C40-arylalkyl radical; optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; and R' is a CrC2o-alkylidene, C6-C2o-arylidene, C7-C2o-alkylarylidene, or C7-C20-arylalkylidene radical; L is a divalent bridging group selected from Q-C20 alkylidene, C3-C20 cycloalkylidene, C6-C20 arylidene, C7-C20 alkylarylidene, or a C7-C20 arylalkylidene radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, or it is a silylidene radical containing up to 5 silicon atoms; R1 and R19 are different from each other and are a Z1 or Z2 group wherein Z1 is an alpha branched C1-C20 hydrocarbon radical optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, and Z is a linear C1-C40 hydrocarbon radical optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; with the proviso that if R1 or R19 are Z1 then R19 or R1 are Z2; R and R , are part of 4-7 membered ring condensed to the benzene ring of the indenyl moiety; preferably a 5 or 6 membered ring; said ring optionally containing heteroatoms belonging to groups 13-16 of the Periodic Table of the Elements; the valence of each atom forming said ring is filled with R18 groups, wherein R18, equal to or different from each other, are hydrogen atoms or a C1-C40 hydrocarbon radical; said ring can be saturated or it can contain double bonds; R4 is a hydrogen atom or, a C1-C40 hydrocarbon radical optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; W is an aromatic 5 or 6 membered ring that can contain heteroatoms belonging to groups 15-16 of the Periodic Table of the Elements; the valence of each atom of said ring is substituted with hydrogen atom or it can optionally be substituted with R5 groups, wherein R5, equal to or different from each other, are C1-C40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; 20t 21 22 _ — R , R and R , equal to or different from each other, are hydrogen atoms or C1-C40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements. 2. The multistep process according to claim 1 wherein in the compound of formula (I) X is a hydrogen atom, a halogen atom, a OR'O or R group; L is Si(R11)2 wherein R11 is a linear or branched, cyclic or acyclic, C1-C40-alkyl, C2-C40 alkenyl, C2-C40 alkynyl, C6-C40-aryl, C7-C40-alkylaryl or C7-C4o-arylalkyl radical; R4 is a hydrogen atom a C1-C10-alkyl or a C6-C40-aryl radical; R is a hydrogen atom or a linear or branched, C1-C20-aIkyl radical; R and R3, form together a condensed saturated 3-7 membered ring optionally containing heteroatoms belonging to groups 13-16 of the Periodic Table of the Elements; R20 and R21 are hydrogen atoms or C1-C10 alkyl radicals, with the proviso that they are not both or C1-C10 alkyl radicals. 3. The multistep process according to claims 1 or 2 wherein W is selected from the group comprising the following moieties of formula (Wa), (Wb) and (Wc): wherein the * represents the point in which the moiety bounds the indenyl moiety of the compound of formula (I); R6, R7, R8, R9 and R10, equal to or different from each other, are hydrogen atoms or C1-C40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; Z1 is a nitrogen atom or a CR10 group; Z2 is a nitrogen atom or a CR6 group; Z3 is a nitrogen atom or a CR7 group; Z4 is a nitrogen atom or a CR8 group; Z5 is a nitrogen atom or a CR9 group; provided that not more that 2 groups among Z1, Z2, Z3, Z4 and Z5 are nitrogen atoms, Z6 is an oxygen atom, a sulfur atom, a NR13 group or a CR13 group; Z7 is an oxygen atom, a sulfur atom, a NR14 group or a CR14 group; Z8is an oxygen atom, a sulfur atom, a NR15 group or a CR15group; Z9 is an oxygen atom, a sulfur atom, a NR16 group or a CR16group; Z10 is a nitrogen atom or a carbon atom that bonds the indenyl moiety of the structure of formula (I); with the proviso that not more than 1 group among Z6, Z7, Z8, Z9 or Z10 is a sulftir atom, an oxygen atom or a nitrogen-containing group atom selected from NR13, NR14, NR15, NR16, and a nitrogen atom; R13, R14, R15 and R16, equal to or different from each other, are hydrogen atoms or C1-C40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; 4. The multistep process according to anyone of claims 1-3 wherein, in the moiety of formula (Wa), R7 is a C1-C40-alkyl radical, and R6, R8, R9 and R10 are hydrogen atoms. 5. The multistep process according to anyone of claims 1-3 wherein, in the moiety of formula (Wa), R10 and R8 are C1-C40-alkyl radicals and R7, R8 and R9 are hydrogen radicals. 6. The multistep process according to anyone of claims 1-3 wherein, in the moiety of formula (Wa), R6, R7 and R8 are linear or branched C1-C40-alkyl radicals and R10 and R9 are hydrogen atoms. 7. The multistep process according to anyone of claims 1-3 wherein, in the moiety of formula (Wa), R6, R7, R8, R9 and R10 are hydrogen atoms. 8. The multistep process according to anyone of claims 1-3 wherein in the moiety of formula (Wb), Z1 is a nitrogen atom and Z2, Z3, Z4 and Z5 are respectively CR6, CR7, CR8 and CR9 wherein the meaning of R6, R7, R8, and R9 is described in claim 3; otherwise Z3 is a nitrogen atom and Z], Z2, Z4 and Z5 are respectively CR10, CR6, CR8 and CR9 wherein the meaning of R!0, R6, R8, and R9 is described in claim 3; otherwise Z2 is a nitrogen atom and Z1, Z3, Z4 and Z5 are respectively CR10, CR7, CR8 and CR9 wherein the meaning of R10, R7, R8, and R9 is described in claim 3. 9. The multistep process according to anyone of claims 1-3 wherein in the moiety of formula (Wc), Z6 is an oxygen atom, a sulfur atom or a NR16 group; wherein R16 is a Ci-C4o-alkyl radical. 10. The multistep process according to anyone of claims 1-9 wherein Z1 is a compound of formula of formula (II) or an alpha branched aryl or aiylalkyl radical containing from 2 to 20 carbon atoms optionally containing O, N, S, P and Se atoms, in particular O, N and S atoms; wherein in the compound of formula (II) R and R , equal to or different from each other, are C1-C40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; R25 is an hydrogen atom or it has the same meaning of R and R ; Z is a linear Ci-C2o-a]kyl, C2-C40 alkenyl, C2-C40 alkynyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements. 11. The multistep process according to claim 10 wherein R23 and R24 are Ci-C2o-alkyl, C2-C40 alkenyl, C2-C40 alkynyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; R25 is a hydrogen atom; and Z2 is a linear Ci-Cio-alkyl radical. C1-C40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements. 13. The multistep process according to anyone of claims 1-11 claim wherein the compounds of formula (I) have formula (IV) (IV) wherein M, L, X, R1, R4, R6, R7, R8, R9, R10, R19, R20, R21, R22 and W have the meaning described in claim 1-11 and R and R , equal to or different from each other, are hydrogen atoms or C1-C40 hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements. 14. The multistep process according to claim 13 wherein W is a moiety of formula (Wa). 15. The multistep process according to anyone of claims 1-14 wherein step a) further comprises a prepolymerization step a-1). 16. The multistep process according to anyone of claims 1-15 wherein step a) is carried out in liquid phase, in which the polymerization medium can be an inert hydrocarbon solvent or the polymerization medium can be liquid propylene optionally in the presence of an inert hydrocarbon solvent, and of ethylene or one or more comonomer of formula CH2=CHTI, or step a) can be carried out in a gas phase. 17. The multistep process according to anyone of claims 1-16 wherein step a) is carried out in the presence of hydrogen. 18. The multistep process according to anyone of claims 1-17 wherein the propylene polymer obtained in step a) is a propylene homopolymer or a propylene copolymer containing up to 20% by mol of derived units of ethylene or one or more alpha olefins of formula CH2=CHT1. 19. The multistep process according to claim 18 wherein in step a) a propylene homopolymer or a propylene/ethylene copolymer having an ethylene content lower than 10% by weight is prepared. 20. The multistep process according to anyone of claims 1-19 wherein step b) is carried out in the presence of hydrogen. 21 The multistep process according to anyone of claims 1-20 wherein in step b) an ethylene or propylene copolymer having from 4% by mol to 90% by mol, of derived units of comonomers of formula CH2=CHT and optionally up to 20% of derived units of non conjugated diene, is produced 22. The multistep process according to anyone of claims 1-21 wherein in step b) propylene is copolymerized with an alpha olefins of formula CH2=CHT3 wherein T is hydrogen or a d- Cio'alkyl radical, and optionally a non-conjugated diene, in the presence of the polymer obtained in step a) and optionally in the presence of an additional organo aluminum compound; provided that an homopolymer is not produced. 23. The multistep process according to anyone of claims 1-21 wherein in step b) ethylene is copolymerized with an alpha olefins of formula CH2=CHT, wherein T is hydrogen or a Ci- C10 alkyl radical, and optionally a non-conjugated diene, in the presence of the polymer obtained in step a) and optionally in the presence of an additional organo aluminum compound; provided that an homopolymer is not produced.

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