MXPA00003277A - Pre-polymerized catalyst components for the polymerization of olefins - Google Patents

Abstract

Components of catalysts for the polymerization of olefins are ob tained by contacting a Ti compound of formula Ti(OR)n-yXy, where n is the valence of titanium and y is a number between 1 and n, with a pre-polymer having a porosity higher than 0.3 cc/g and containing from 0.5 to 100 g of polymer per g of solid catalyst component, the pre-polymer being obtained by (co)polymerizing an olefin or a diolefin in the presence of a catalyst comprising a Ti, V, Zr of Hf compound supported on an Mg dihalide having a mean crystallite dimension lower than 30 nm.

Description

PREPOLIMERIZED CATALYST COMPONENTS FOR THE POLYMERIZATION OF OLEFINS DESCRIPTIVE MEMORY The present invention relates to catalyst components for the polymerization of olefins CH2 = CHR, wherein R is hydrogen or a hydrocarbon radical having 1-12 carbon atoms, to the catalysts obtained therefrom and to their use in the polymerization of said olefins. In particular, the catalyst components of the present invention are very suitable for the preparation of crystalline propylene copolymers using gas, suspension or bulk phase copolymerization processes. High-performance catalyst components for the polymerization of olefins, and in particular propylene, are known in the art. They are generally obtained by supporting, on a magnesium dihalide, a titanium compound and an electron donor compound as a selectivity controlling agent. Said catalyst components are then used together with an aluminum alkyl and, optionally, another electron donor compound (external) in the stereospecific polymerization of propylene. Depending on the type of electron donor used, the stereoregularity of the polymer may vary. However, the stereospecific catalysts of interest must be capable of giving polypropylene copolymers having an isotactic index, expressed in terms of insolubility in xylene, of more than 90%. Said catalyst components, and the catalysts obtained therefrom, are widely used in the plants for the copolymerization of propylene both operating in the liquid phase (suspension or bulk) and in the gas phase. However, the use of the catalyst components themselves is not completely satisfactory. In fact, problems such as formation of polymers with irregular morphology and in particular of fine particles and low global density are experienced when the plants work with catalyst components such as these. To solve these problems, the catalyst components are commonly prepolymerized under controlled conditions, so that prepolymerized catalysts having an appropriate morphology are obtained. After the prepolymerization, the catalysts also increase their strength in such a way that the tendency to rupture under polymerization conditions is decreased. As a consequence, the formation of fine particles is reduced and the main polymerization process, either in suspension or gas phase, can be carried out smoothly and with the production of final polymers having high overall density. However, one of the possible disadvantages associated with this method is the decrease in activity expressed as the amount of polymer obtained per gram of fed catalyst. In other words, even if activity of the catalyst itself (expressed with respect to the magnesium chloride contained in the catalyst) could remain at the same level, the activity with respect to the prepolymer / catalyst system is lower due to the effect of the dilution of the catalyst. catalyst inside the prepolymer. Depending on the degree of prepolymerization, the loss of activity can also be substantial. This means that a large amount of prepolymer / catalyst system must be fed to the reactor to obtain acceptable yields. Therefore, it would be important to have a prepolymerized catalyst component in which this disadvantage is absent or minimized. In the international patent application WO95 / 26369 the prepolymer obtained by the prepolymerization of a catalyst component comprising a Ti compound supported on magnesium dihalide, is contacted with a metallocene compound selected in particular from the class of zirconocenes . The resulting catalyst shows an adequate activity with respect to the magnesium chloride contained therein, but the performance is quite low if reference is made to the prepolymer / catalyst system. In any case, the catalyst obtained after the treatment with the metallocene compound is different in nature from the original conventional Ziegler-Natta catalyst, so that also the polymers obtained show the typical characteristics associated with the use of metallocene catalysts such as a very narrow molecular weight distribution. As a result, the polymerization results shown in the above-mentioned patent application do not provide any useful teaching about the possible activity of the original catalyst system contained in the prepolymer. European patent application EP-A-604401 proposes the solution of prepolymerizing a catalyst component, comprising a titanium compound and an electron-donor compound supported on a magnesium dihalide, first with a linear olefin and then with an olefin not linear to produce a linear olefin / non-linear olefin copolymer as a prepolymer. The prepolymer / catalyst system obtained in this way is further contacted with a Ti compound, in particular TiCl, and optionally also with an electron donor compound to obtain a final catalyst component. However, the obtained prepolymer / catalyst system does not solve the problem because the decrease in activity observed in the polymerization examples if the activity is calculated as Kg of polymer produced per g of prepolymer feed / catalyst, is always proportional to the dilution of the catalyst component in the prepolymer. In other words, when the amount of prepolymer is about 50% of the total prepolymer / catalyst system (see Table 2 of EP604401), the activity in the polymerization test is about half the activity of the non-prepolymerized catalyst. This means that, according to the description of EP604401, the prepolymerization step and the additional titanation treatment did not improve the activity of the catalyst itself. A catalyst component having improved activity and which is the product obtained by contacting a Ti compound of the formula Ti (OR) n-yXy, where R is an alkyl, isoalkyl radical, has now been found unexpectedly. cycloalkyl or aryl having from 1 to 18 carbon atoms, preferably an alkyl, isoalkyl or cycloalkyl radical having from 1 to 8 carbon atoms, most preferably n-butyl or isopropyl, X is a halogen atom, preferably an chlorine or bromine, n is the valence of titanium and (y) is a number of 1 an, with a prepolymer having a porosity (measured with the Hg method) of more than 0.3 cc / g and containing 0.5 to 100 g of polymer per gram of solid catalyst component, said prepolymer being obtained by copolymerizing an olefin or diolefin which is copolymerizable in the presence of a catalyst comprising a solid component comprising a transition metal compound selected from the group consisting of The compound consisting of Ti compounds of the above formula Ti (OR) n-yXy, vanadium, halides, halogenoalcoholates and vanadyl halides, Ti, Zr and Hf compounds containing at least one metal p-bond, said compound transition metal being supported on a Mg dihalogenide having an average crystallite size of less than 30 nm. The porosity of the prepolymer is preferably higher than 0.4 cc / g and still more preferably higher than 0.5 cc / g. In the present invention, the term porosity (Hg) referred to the prepolymer means the porosity measured by the mercury porosimetry method described below and due to pores with a radius of up to 75,000A. The amount of prepolymer preferably varies from 1 to 50 and most preferably from 2 to 30 g of polymer per gram of solid catalyst component used to prepare it. The term "prepolymer" used hereinbefore and hereinafter means a polymer prepared under conditions such that a polymer weight ratio / solid catalyst component equal to, or less than 100; the catalyst used to prepare the prepolymer being able to give, under the general polymerization conditions of propylene or ethylene given below, a yield of more than 1 Kg / g of solid catalyst component. The magnesium halides, preferably MgCl 2, in active form used as a support for Ziegler-Natta catalysts are well known. Active magnesium halides are those having an average crystallite size, determined by X-ray diffractometry, of less than 30 nm, and those in which the average crystallite size is less than 15 nm are particularly preferred. Particularly preferred magnesium chlorides are those characterized by X-ray spectra in which the most intense diffraction line appearing in the non-active chloride spectrum is decreased in intensity and replaced by a halogen whose maximum intensity is shifted towards angles lower in relation to the one of the most intense line. The preparation of the solid catalyst component used to prepare the prepolymer can be carried out according to various methods. The preferred methods are those that produce catalyst components which, because of their particular physical properties, are capable of directly producing porous prepolymers during the prepolymerization step. In one of the preferred methods the solid catalyst component is prepared by reacting a titanium compound of the general formula Ti (OR) x-yXy as mentioned above, preferably TiCl 4, with an adduct of the formula MgCl 2 * pROH, wherein p is a number from 0.1 to 6 and R is a hydrocarbon radial, suitably an alkyl, isoalkyl or cycloalkyl radical having from 1 to 18, preferably from 1 to 8, most preferably from 1 to 4 carbon atoms. The adduct can be suitably prepared in spherical form by mixing an alcohol of the above formula ROH and magnesium chloride in the presence of an inert hydrocarbon not miscible with the adduct, operating under stirring conditions at the melting temperature of the adduct. Then, the emulsion is rapidly quenched, thereby causing the solidification of the adduct in the form of spherical particles. Examples of spherical adducts prepared according to this procedure are described in USP 4,399,054 and USP 4,469,648. The adduct obtained in this way can be reacted directly with the Ti compound or can be previously subjected to controlled thermal dealcoholization (80-130 ° C) to obtain an adduct in which the number of moles of alcohol is generally less than 3, preferably between 0.1 and 2.5. The reaction with the Ti compound can be carried out for example by suspending the adduct (dealcoholated or as such) in TiC. cold (usually at 0 ° C); The mixture is heated to 80-130 ° C and maintained at this temperature for 0.5-2 hours. The treatment with TiCl4 can be carried out one or more times. When a stereospecific catalyst is to be prepared, an internal electron donor compound is added during the TiCU treatment. The treatment with the electron donor compound can be repeated one or more times. The preparation of catalyst components in spherical form according to the above general procedure is described for example in USP 4,399,054, EP-A-395083, EP-A-553805, WO98 / 44001. According to another embodiment, the MgCl 2 * pROH adduct is thermally dealcoholized first according to the procedure described above and contacted successively with reactive compounds capable of removing the alcohol. Suitable reactive compounds are, for example, Al-alkyl or SiCl compounds. The adduct obtained in this way is then reacted with a titanium compound to obtain the final solid catalyst component. The preparation of catalyst components in spherical form according to this process is described for example in EP-A-553806, and EP-A-601525.

In general, the solid catalyst components obtained according to the methods described above show a surface area (by the BET method) of between 20 and 500 m2 / g, preferably between 50 and 400 m2 / g, most preferably between 100 and 400 m2 / g; a total porosity (by the method B.E.T.) of more than 0.2 cm3 / g, preferably between 0.2 and 0.6 cm3 / g and most preferably from 0.3 to 0.5 cm3 / g. The porosity (Hg method) due to pores with a radius of up to 10,000A generally varies from 0.3 to 1.5 cm3 / g, preferably from 0.45 to 1 cm3 / g. As explained above, when a stereospecific catalyst is desired, an electron donor compound is used in the preparation of the solid catalyst component. The so-called internal electron donor compound can be selected from esters, ethers, amines and ketones. It is preferably selected from alkyl, cycloalkyl or aryl esters of monocarboxylic acids, for example benzoic acid, or polycarboxylic acids, for example phthalic or malonic acid, said alkyl, cycloalkyl or aryl groups having from 1 to 18 carbon atoms. Examples of electron donor compounds that are preferred are methyl benzoate, ethyl benzoate, diisobutyl phthalate, di-n-hexyl phthalate, di-octyl phthalate, di-neopentyl phthalate. In addition, the electron-donor compound can be suitably selected from 1,3-diethers of the formula O): wherein R 1 and R "are the same or different and are hydrogen or straight or branched C.sub.C.sub.s. or hydrocarbon groups which they can also form one or more cyclic structures, the R1"groups, equal or different from each other, are hydrogen or C-C18 hydrocarbon groups; the R? v groups, equal or different from each other, have the same meaning of R1"except that they can not be hydrogen, each of the groups R1 to R? v can contain heteroatoms selected from halogens, N, O, S and Si Preferably, R v is an alkyl radical of 1-6 carbon atoms, and very particularly a methyl, while the radicals R 1"are preferably hydrogen. Also, when R1 is methyl, ethyl, propyl or isopropyl, R "can be ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, isopentyl, 2-ethylhexyl, cyclopentyl, ciciohexilo, methylcyclohexyl, phenyl or benzyl; when R1 is hydrogen, R "can be ethyl, butyl, sec-butyl, tert-butyl, 2-ethylhexyl, cyclohexylethyl, diphenylmethyl, p-chlorophenyl, 1-naphthyl, 1-decahydronaphthyl, R1 and R" may also be the same and can be ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, neopentyl, phenyl, benzyl, ciciohexilo, cyclopentyl specific examples of ethers that can be advantageously used include:. 2- (2-ethylhexyl) 1, 3-dimethoxypropane, 2-isopropiI -1, 3-dimethoxypropane, 2-butyl-1, 3-dimethoxypropane, 2-sec-butyl-1, 3-dimethoxypropane, 2-cicIohexil-1, 3-dimethoxypropane, 2-phenyl-1, 3-dimethoxypropane, 2 -tert-butyl-1, 3-dimethoxypropane, 2-cumyl-1, 3-dimethoxypropane, 2- (2-phenylethyl) -1, 3-dimethoxypropane, 2- (2-cyclohexylethyl) -1, 3-dimethoxypropane, 2- (p-chlorophenyl) -1,3-dimethoxypropane, 2- (diphenylmethyl) -1,3-dimethoxypropane, 2- (1 -naphthyl) -1,3-dimethoxypropane 2- (p-fluorophenyl) -1 , 3-dimethoxypropane, 2- (1 -decahydronaphthyl) -1, 3-dimethoxypropane, 2- (p-tert-butylphenyl) -1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane, 2,2-diethyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3 -dimethoxypropane, 2,2-dibutyl-1,3-dimethoxypropane, 2,2-diethyl-1,3-diethoxypropane, 2,2-dicyclopentyl-1,3-dimethoxypropane, 2,2-dipropyl-1, 3- diethoxypropane, 2,2-dibutyl-1,3-diethoxypropane, 2-methyl-2-ethyl-1,3-dimethoxypropane, 2-methyl-2-propyl-1,3-dimethoxypropane, 2-methyl- 2-benciI-1, 3-dimethoxypropane, 2-MetII-2-phenyl-1, 3-dimethoxypropane, 2-methyl-2-cyclohexyl-1, 3-dimethoxypropane, 2-methyl-2-methylcyclohexyl-1, 3- dimethoxypropane, 2,2-bis (p-chlorophenyl) -1,3-dimethoxypropane, 2,2-bis (2-phenylethyl) -1,3-dimethoxypropane, 2,2-bis (2-cyclohexylethyl) -1,3 -methoxypropane, 2-methyl-2-isobutyl-1,3-dimethoxypropane, 2-methyl-2- (2-ethylhexyl) -1,3-dimethoxypropane, 2,2-bis (2-ethylhexyl) -1,3-dimethoxypropane, 2,2-bis (p-methylphenyl) -1,3-dimethoxypropane, 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2,2-diphenyl- 1,3-dimethoxypropane, 2,2-dibenzyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl-1,3-dimethoxypropane, 2,2-bis (cyclohexylmethyl) -1,3-dimethoxypropane, 2,2-diisobutyl-1,3-diethoxypropane, 2,2-diisobutyl-1,3-dibutoxypropane, 2-isobutyl-2-isopropyl-1,3-dimethoxypropane, 2,2-di-sec-butyl-1 , 3-dimethoxypropane, 2,2-di-tert-butyl-1,3-dimethoxypropane, 2,2-dineopentyI-1,3-dimethoxypropane, 2-iso-propyl-2-isopentyl-1,3-dimethoxypropane, 2 phenyl-2-benzyl-1,3-dimethoxypropane, 2-cyclohexyl-2-cyclohexylmethyl-1,3-dimethoxypropane. Particularly preferred are 1,3-diethers of the formula (II) (II) wherein the radicals Rm and R? V have the same meaning as explained above, and the radicals Rv, equal or different from each other, are selected from the group consisting of hydrogen; halogens, preferably Cl and F; linear or branched C.sub.2 -C.sub.60 alkyl radicals, C3-C20 cycloalkyl radicals, C6-C2o aryl, C7-C2alkaryl and C7-C20 aralkyl, and two or more of the Rv radicals can be linked together for form condensed, saturated or unsaturated cyclic structures, optionally substituted with radicals Rv? selected from the group consisting of halogens, preferably Cl and F; linear or branched C-C20 alkyl radicals, C3-C20 cycloalkyl radicals, C6-C20 aryl, C7-C2 alkaryl and C-C20 aralkyl; said radicals Rv and Rv? optionally contain one or more heteroatoms as substituents for carbon or hydrogen atoms, or both. Preferably, in the 1,3-diethers of the formulas (I) and (II) all the radicals Rm are hydrogen, and all the radicals R? V are methyl. In addition, the 1,3-diethers of the formula (II) are particularly preferred in which two or more of the radicals Rv are joined to one another to form one or more condensed cyclic structures, preferably benzene, optionally substituted by radicals Rv ?. Especially preferred are the compounds of the formula (III): where the radicals Rv? the same or different are hydrogen; halogens, preferably Cl and F; linear or branched C? -C2o alkyl radicals; C3-C20 cycloalkyl radicals, C6-C20 aryl. alkylaryl of C -C2o and aralkyl of C7-C2o, optionally containing one or more heteroatoms selected from the group consisting of N, O, S, P, Si and halogens, in particular Cl and F, as substituents for carbon atoms or hydrogen, or both; the radicals R1"and R? v are as defined above for formula (II). Specific examples of the compounds comprised in formulas (II) and (III) are: 1,1-bis (methoxymethyl) -cyclopentadiene; 1,1-bis (methoxymethyl) -2,3,4,5-tetramethylcyclopentadiene; 1,1-bis (methoxymethyl) -2,3,4,5-tetraphenylcyclopentadiene; 1,1-bis (methoxymethyl) -2,3,4,5-tetrafluorocyclopentadiene; 1,1-bis (methoxymethyl) -3,4-dicyclopentyl-cyclopentadiene; 1,1-bis (methoxymethyl) indene; 1,1-bis (methoxymethyl) -2,3 -dimethylidene, 1,1-bis (methoxymethyl) -4,5,6,7-tetrahydroindene, 1,1-bis (methoxymethyl) -2,3,6,7-tetrafluoroindene, 1,1-bis (methoxymethyl) l) -4,7-dimethylindene, 1,1-bis (methoxymethyl) -3,6-dimethylindene, 1,1-bis (methoxymethyl) -4-phenylindene, 1,1-bis (methoxymethyl) -4 phenyl-2-methylindene; 1,1-bis (methoxymethyl) -4-cyclohexylindene; 1,1-bis (methoxymethyl) -7- (3,3,3-trifluoropropyl) indene; 1,1-bis ( methoxymethyl l) -7-trimethylsilylidene; 1,1-bis (methoxymethyl) l-7-trifluoromethylindene; 1,1-bis (methoxymethyl) -4,7-dimethyl-4,5,6,7-tetrahydroindene; 1,1-bis (methoxymethyl) -7-methylindene; 1,1-bis (methoxymethyl I) -7-cyclopentyldene; 1,1-bis (methoxymethyl) -7-isopropylindene; , 1-bis (methoxymethi 7-cyclohexylindene;, 1-bis (methoxymethi-7-tert-butylindene;, 1-bis (methoxymethi 7-tert-butyl-2-methylindene;; , 1-bis (methoxymethi 7-phenylindene;, 1-bis (methoxymethi 2-phenyl-indene;, 1-bis (methoxymethi 1 H-benz [e] indene;, 1-bis (methoxymethi 1 H-2-methylbenz [e] indene; 9,9-bis (methoxymethiifluorene; 9,9-bis (methoxymethyl-2,3,6,7-tetramethyl-fluorene; 9,9-bis (methoxymethyl-2,3,4,5,6,7-hexafluorofluorene; , 9-bis (methoxymethyl-2,3-benzofluorene; 9,9-bis (methoxymethi-2,3,6,7-dibenzofluorene; 9,9-bis (methoxymethi-2,7-diisopropyl-fluorene; 9,9-bis ( methoxymethi? -1,8-dichlorofluorene; 9,9-bis (methoxymethi 2,7-dicyclopentyl-fluorene; 9,9-bis (methoxymethi 1,8-difluorofluorene; 9,9-bis (methoxymethi 1, 2,3,4- tetrahydrofluorene; 9,9-bis (methoxymethi 1, 2,3,4,5,6,7,8-octahydrofluorene; 9,9-bis (methoxymethyl) -4-tert-butylfluorene; (methoxymethyl) fluorene The internal constituents that are most preferred to be used in the preparation of the catalyst components of the present invention are the phthalic acid esters and the 1,3-diethers described above. Above, the internal electron donor compound can be added as such, or alternatively, it can be obtained in situ using a suitable precursor capable of being transformed into the desired electron donor compound by, for example, known chemical reactions such as as esterification or transesterification. Generally, the internal electron donor compound is added in a molar ratio to MgCl2 of 0.01 to 1, preferably 0.05 to 0.5. The solid catalyst components used to prepare the prepolymer can also be prepared according to the disclosure of WO 95/32995 wherein a metallocene compound of Ti, Zr or Hf is supported on an MgCl 2 having a surface area of more than 100m2. / g and porosity (BET) of more than 0.2 cm3 / g. As explained above, the original solid catalyst component is then prepolymerized with one or more olefins or diolefins to obtain the porous prepolymer. Generally, the prepolymer has the same nature as the final polymer that will be produced but, if it is considered advisable, the prepolymer may also have a different nature with respect to the final polymer. This may be the case for the example in which the polymer has to work as a nucleating agent that disperses homogeneously within the final product. Suitable olefins that can be prepolymerized are those of the formula CH 2 = CHR, wherein R is hydrogen or a C 1 -C 12 alkyl group or an aryl radical. Preferably, the olefin is selected from ethylene, propylene, butene-1, hexene-1 and 4-methyl-1-pentene. Ethylene and propylene are especially preferred. Preferably, the prepolymer is prepared under such conditions to obtain a crystalline polymer, and in particular polymers having a high crystallinity content. In the case of the propylene prepolymerization for example, the preferred polypropylenes are those having a crystallinity such that the melting enthalpy, measured by the DSC method, is more than 70 J / g. The prepolymerization is generally carried out in the presence of an alkyl-aluminum compound. The alkyl-Al (B) compound is preferably chosen from trialkylaluminum compounds such as for example triethylaluminum (TEAL), triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum. It is also possible to use mixtures of trialkylaluminums with alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesquichlorides such as AIEt2CI and AI2Et3Cl3. It is also possible to use a metallo-alkyl compound different from the alkyl-Al compound, such as a di-alkyl zinc compound capable of promoting the polymerization of olefins when used together with a Ti compound containing Ti-halogen bonds. When the catalyst components comprise a metallocene compound supported on magnesium dihalide, the Al-alkyl is suitably selected from alumoxanes containing the repeating unit - (R 1) -AI-O- in which R 1, equal or different from one another are hydrocarbon groups having from 1 to 20 carbon atoms. The amount of Al-alkyl compound generally used is such that an Al / Ti molar ratio of 1 to 50 is obtained. In the present invention it has been found particularly advantageous to carry out said prepolymerization using lower amounts of alkyl-Al compound. In particular, said amount can be so low that there is a Al / Ti molar ratio of 0.01 to 10 and most preferably 0.05 to 5. During the prepolymerization step, the presence of an external donor is not strictly necessary. However, it can be used in such amounts as to give molar Al / donor ratios ranging from 0.1 to 300 and preferably from 1 to 50. The external electron donor compound can be the same as, or different from, the internal donor described above. Suitable external electron donor compounds include silicon compounds, ethers, esters, amines, heterocyclic compounds and particularly 2,2,6,6-tetramethylpiperidine, ketones and the 1,3-diethers of the general formula (I) given above. One class of external donor compounds that will be used in particular when the internal donor is phthalate, is that of silicon compounds of the formula Ra5Rb6Si (OR7) c, where a and b are integers from 0 to 2, c is an integer from 1 to 3 and the sum (a + b + c) is 4; R5, R6 and R7 are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms. Particularly preferred are the silicon compounds in which a is 1, b is 1, c is 2, at least one of R 5 and R 6 is selected from branched alkyl, cycloalkyl or aryl groups with 3-10 carbon atoms optionally containing heteroatoms, and R7 is an alkyl group of C.-C .o, in particular methyl. Examples of such silicon compounds which are preferred are methylcyclohexyldimethoxysilane, diphenyldimethoxysilane, methyl-t-butyldimethoxysilane, dicyclopentyldimethoxysilane, 2-ethylpiperidinyl-2-t-butyldimethoxysilane and 1,1-trifluoropropyl-2-ethylpiperidinium-dimethoxysilane. In addition, silicon compounds in which a is 0, c is 3, R6 is a branched alkyl or cycloalkyl group, which optionally contains heteroatoms, and R7 is methyl are also preferred. Examples of said silicon compounds which are preferred are cyclohexyltrimethoxysilane, t-butyltrimethoxysilane and trihexyltrimethoxysilane. In particular, when esters of monocarboxylic acids, for example benzoates, are used as internal donors, also the external donor compound is selected from this class, with more p-ethoxy-ethyl benzoate being preferred. In addition, a mixture of this donor with another, in particular one selected from the class of silicon compounds, can be used. In this case, more ethylcyclohexydimethoxysilane and dicyclopentyldimethoxysilane are preferred. The prepolymerization can be carried out in liquid phase (suspension or solution) or gas phase at temperatures generally of less than 80 ° C, preferably in the range of -20 to 60 ° C. In addition, it is preferably carried out in a liquid diluent selected in particular from liquid hydrocarbons. Among these, pentane, hexane and heptane are preferred. The catalyst component of the present invention is then obtained by contacting the prepolymer prepared according to the above process with the Ti compound as previously defined. The Ti compound is preferably liquid under normal conditions, i.e. room temperature and atmospheric pressure. When the Ti compound is a solid, it is used in solution in a suitable solvent which is inert towards the prepolymer and towards the catalyst components contained therein and which can be removed from the Ti compound by heating and / or chemical reaction with compounds such as SiCl 4 or Al-alkyl compounds. Preferably, the Ti compound is selected from the group consisting of halides and, among these, the use of TICI4. The contact of the prepolymer with the Ti compound is carried out under suitable conditions to fix at least 0.05% of the Ti compound, expressed as Ti, on the prepolymerized catalyst component. A Ti compound is considered fixed on the prepolymerized catalyst component when it is not extractable to a higher degree of 50% with heptane at 80 ° C for 2 hours. The amount of Ti compound fixed on the prepolymerized catalyst by the effect of the contacting step is generally higher than 0.05%, preferably higher than 0.2%, expressed as Ti. In particular, when a Ti-based catalyst component is used to prepare the prepolymer, the total amount of Ti compound (expressed as Ti) after the contacting step is from 0.1 to 5%, preferably from 0.15 to 3% and most preferably 0.2 to 2.5%. In this case, catalyst components containing magnesium dichloride in an amount of 50 to 50,000 ppm, expressed as Mg, and in which the total amount of Ti compound fixed on the prepolymerized catalyst component are such as to be particularly advantageous. have a Ti / Mg weight ratio of 0.01 to 3, preferably from 0.1 to 2.5. According to one of the preferred methods the prepolymer is reacted with an excess of concentrated TiCl 4 at a temperature of between 40 and 120 °, preferably 60 and 90 ° C for a period of time ranging from 0.2 to 2 hours. At the end of the treatment, excess TiCU is removed by siphoning or filtering the solid component. Preferably, the reaction with TiCU is carried out two or more times. In addition, it is especially preferred to carry out said reaction in the presence of an electron donor compound dissolved in the TiCU. Preferably, the electron donor compound is selected from the groups described above as suitable internal electron donor compounds.

According to another method the reaction is carried out with TiCl 4 diluted in a suitable hydrocarbon compound such as pentane, hexane, heptane, toluene. Also in this case the use of an internal electron donor compound is preferred. After the contact step with the Ti compound is completed the prepolymerized catalyst component is suitably washed with solvents, to remove compounds not fixed thereon. The washings are generally carried out at temperatures ranging from room temperature to the boiling point of the solvent used. Suitable solvents for use include liquid hydrocarbons such as hexane, heptane, toluene and halogenated hydrocarbons such as CH 2 Cl 2. The prepolymerized catalyst components obtained in this way make it possible to obtain highly active catalysts. In particular, when they are used in the polymerization of propylene, they allow to obtain polymers with high esterregularity, high global density and very good morphology, thus showing their particular suitability for liquid (bulk or suspension) and gas phase processes. In particular, the prepolymerized catalyst components of the invention show Mg-related activities that are markedly improved over those of the original solid component used to prepare the prepolymer. Likewise, the yields referred to the prepolymer / catalyst system are higher than the yields of the prepolymer / catalyst system not treated with the Ti compound. In view of these peculiarities, the catalyst components of the invention are particularly suitable for use in liquid olefin or gas phase polymerization plants operating without a prepolymerization line. In particular, said olefin polymerization processes can be carried out in the presence of a catalyst comprising (A) the prepolymerized catalyst component described above; (B) a suitable co-catalyst, particularly an Al-alkyl compound, and optionally (C) one or more electron donor (external) compounds. The latter can be selected from the groups of compounds described above as suitable external electron donor compounds and in accordance with the guidance already described. In the main polymerization step the electron donor compound (C) is used in such an amount as to give a molar ratio between the organoaluminum compound and said electron donor compound from 0.1 to 500, preferably from 1 to 300 and most preferably from 2 to 100. The Al / Ti ratio is preferably higher than 10. The Al-alkyl compounds are preferably selected from those of the formula R2AIX3_Z wherein R is a Ci-C2o hydrocarbon group, particularly an alkyl, isoalkyl radical, cycloalkyl or aryl, z is 2 or 3 and X is a halogen atom, preferably chlorine. Particularly preferred is the use of trialkylaluminum compounds such as, for example, triethylaluminum (TEAL), triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum and trs (2,4,4-trimethyl). -pentiI) aluminum. It is also possible to use mixtures of trialkylaluminum compounds with alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesquichlorides.; such as AIEt2CI and AI2Et3CI. Another class of compounds suitable as catalyst components for preparing the prepolymer is that of the metallocene compounds having at least one M-R bond in which M is Ti, Zr or Hf and R is an alkyl radical. The mentioned metallocene compounds are used in amounts such that they are in an equimolar or excess ratio to the metal compound present in the catalyst component. Preferably, said ratio varies from 2: 1 to 30: 1. In case of using an equimolar amount of co-catalyst, it is preferred to add a scavenger compound to the selected system of Al, Mg or alkyl Zn compounds that are not capable of promoting olefin polymerization when used together with compounds containing Ti bonds. -halogen. Examples of these compounds are Zn diethyl, Mg diethyl and AIEt3 complexed with ethers or electron donor compounds that do not contain active hydrogen atoms. Suitable metallocene compounds having at least one M-R bond are generally those comprising two cyclopentadienyl rings, coordinated with the metal, which can be substituted and / or bridged and possibly condensed with other rings. Representative compounds are specifically mentioned and are described in WO95 / 26369, the relevant part of which is incorporated herein by reference. In the case of catalyst components comprising a metallocene compound, it is advisable to use, alone or in combination with another Al-alkyl compound, an alumoxane selected from those containing the repeating unit - (R1) -AI-O- in where R1, which are the same or different from one another are hydrocarbon groups having from 1 to 20 carbon atoms. The use of methyl alumoxane is preferred. In addition, it is also possible to use compounds of the formula Y + Z "wherein Y + is a Brónsted acid capable of donating a proton and reacting irreversibly with a substituent of the metallocene compound, and 77 is a non-coordinating compatible anion which is capable of stabilizing the active catalytic species resulting from the reaction of the two compounds and which is sufficiently labile to be displaced by an olefinic substrate Preferably, the anion Z "consists of one or more boron atoms. Most preferably, the anion Z "is an anion of the formula BAr4, wherein the Ar substituents which may be identical or different are aryl radicals such as phenyl, pentafluorophenyl or bis (trifluoromethyl) phenyl. pentafluorophenyl In addition, the compounds of the formula BAf3 can be used conveniently Compounds of this type are described for example in International patent application WO92 / 00333 The polymerization process described above can be carried out under the generally known polymerization conditions. In the art, the polymerization is generally carried out at a temperature of 20 to 120 ° C, preferably 40 to 80 ° C. When the polymerization is carried out in gas phase the operating pressure is generally between 0.5 and 10 MPa, preferably between 1 and 5 MPa In the bulk polymerization the operating pressure is generally between 1 and 6 MPa, preferably between 1.5 and 4 MPa. In any of the polymerization processes used (liquid polymerization or gas phase), the catalyst-forming components (A), (B) and optionally (C) can be contacted before being added to the polymerization reactor. Said precontact step can be carried out in the absence of a polymerizable olefin or optionally in the presence of said olefin in an amount of up to 3 g per g of solid catalyst component. The catalyst formation components can be contacted with an inert liquid hydrocarbon solvent such as propane, n-hexane or n-heptane at a temperature below about 60 ° C, and preferably around 0 ° C to 30 ° C. for a period of time from 10 seconds to 60 minutes. When a gas phase polarization procedure is used, this can be carried out according to known techniques operating in one or more reactors having a fluidized or mechanically agitated bed. Inert fluids such as nitrogen or low hydrocarbons such as propane can be used, both as a fluidized aid and to improve heat exchange within the reactors. In addition, techniques can also be used that increase the removal of heat of reaction comprising the introduction of liquids, optionally mixed with gas, into the reactors. Preferably, the liquids are fresh monomers or constituents. Such techniques are described, for example, in EP-A-89691, EP-A-241947, USP 5,352,749, WO94 / 28032 and EPA-695313. Among the olefin polymers obtainable by the process of the invention, particularly interesting are the propylene copolymers having a heat of fusion (ΔHf) of more than 70 J / g as measured by the D.S.C method. The following examples are given to better illustrate the invention without limiting it.

EXAMPLES Characterization and dimension of crystallites Determined by measuring the expansion at an average height of (1 10) reflection that appears in the magnesium halide spectrum by applying Sherrer's equation D (1 10) = (K-1.542-57.3) / (B-b) cos? where: K = constant (1.83 in the case of magnesium chloride) B = expansion at medium height; B = instrumental widening; cos? = Bragg angle. The X-ray diffraction spectrum of the catalyst component is carried out with a diffractometer using CuKa radiation (? = 1.5418Á), established with a 0.2 mm receiving groove and recording conditions such that a number of counts is given associated with reflection (1 10) of 1000 or more; said spectrum taking place and without adding any standard to the sample.

Determination of X.l. 2.5 g of polymer were dissolved in 250 ml of o-xylene under stirring at 135 EC 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 and then, by difference, X.l.%.

General procedure for the standard propylene polymerization test A 4 liter steel autoclave equipped with a stirrer, pressure gauge, thermometer, catalyst feed system, monomer feed lines and heat seal cover was used. The reactor was charged with 0.01 g of solid catalyst component and with TEAL, and cyclohexylmethyldimethoxysilane in amounts such that they gave an Al / donor molar ratio of 20. In addition, 3.2 I of propylene and 1 L of hydrogen were added. The system was heated at 70 ° C for 10 minutes under agitation, and kept under these conditions for 120 minutes. At the end of the polymerization, the polymer was recovered by removing any unreacted monomers and dried under vacuum.

General procedure for the standard polymerization of ethylene (HDPE) In a 4 liter stainless steel autoclave degassed under a stream of N2 at 70 ° C, 1600 cc of anhydrous hexane, 0.02 g of a spherical component and 0.3 g of triisobutylaluminum ( Tiba). Everything was stirred, heated to 75 ° C and then 4 bars of H2 and 7 bars of ethylene were fed. The polymerization lasted 2 hours, during which time ethylene was fed to maintain constant pressure. At the end of the polymerization, the polymer was recovered by removing any unreacted monomer and dried under vacuum.

Porosity (due to pores with a radius of up to 75,000A): The measurement was carried using a "Porosimeter 2000" by Cario Erba The porosity is determined by absorption of mercury under pressure. For this determination, a calibrated dilatometer is used (diameter 3 mm) CD3 (Cario Erba) connected to a mercury deposit and to a high vacuum pump (1-10"2 mbar) A heavy amount of sample is placed in the dilatometer, the device is then placed under high vacuum (<0.1 mm Hg) and kept under these conditions for 10 minutes.The dilatometer is then connected to the mercury reservoir and the mercury is allowed to flow slowly into the interior until it reaches the level marked on the dilatometer at a height of 10 cm The valve that connects the dilatometer to the vacuum pump closes and then the mercury pressure increases gradually with nitrogen up to 140 kg / cm2 Under the effect of the pressure the mercury enters the pores and the low level of According to the porosity of the material, the porosity (cm3 / g) and the pore distribution is calculated directly from the integral pore distribution curve, which is a function of the volume reduction of the mercury and the pressure values. ion applied (all these data are provided and elaborated by the computer associated with the porosimeter that is equipped with a "MILESTONE 200 / 2.04" program by C. Erba).

Determination of melt index ASTM D 1238 condition "L" EXAMPLES EXAMPLE 1 Preparation of solid catalyst component (example 1 A) . 0 mg of MgCl2- microspheroidal »2.8C2H5? H (prepared according to the method described in example 2 of USP 4,399,054 but operating at 3,000 rpm instead of 10,000) were subjected to thermal dealcoholization carried out at increasingly high temperatures from 30 to 95 ° C and operating in a stream of nitrogen until a molar ratio EtOH / MgC ^ of about 1 was obtained. The adduct obtained in this manner was poured into a 500 ml four-necked round flask purged with nitrogen, which contained 250 ml of TiCl4 introduced at 0 ° C. The flask was heated to 40 ° C and after adding 6 mmoles of diisobutyl phthalate (DIBP). The temperature was raised to 100 ° C and maintained for two hours, then the stirring was discontinued, the solid product was allowed to settle and the liquid supernatant was siphoned. The treatment with TiCU was repeated and the solid obtained was washed six times with anhydrous hexane (6 X 100 ml) at 60 ° C and then dried under vacuum. A catalyst component having a surface area (measured by BET) of 130 m2 / g and a porosity (Hg due to pores with a radius of up to 10,000 A) of 0.72 was obtained. The chemical characteristics of the solid, the results of the propylene polymerization test and those of the ethylene polymerization test are reported in table 1.

Propylene prepolymerization (example 1 B) The catalyst component prepared according to the above procedure was prepolymerized with propylene to give a weight ratio prepolymer / solid catalyst component of 10 g / g. The prepolymerization was carried out in hexene in the presence of TEAL (TEAL weight ratio / solid catalyst component = 0.05) and cyclohexylmethyl-dimethoxysilane as external donor (TEAL molar / donor ratio of 20). The prepolymer catalyst system obtained in this way, which had a porosity (Hg due to pores with a radius of up to 75,000A) of 0.56 cm3 / g, was subjected to the propylene polymerization process, the results of which are reported in Table 1.

Step of treatment with the Ti compound The prepolymer prepared above was suspended in TiCU using amounts of reagents to give a suspension of 50 g / l. The temperature was then raised to 80 ° C and the system was maintained under these conditions, with stirring, for 1 hour. After that time the stirring was discontinued, the liquid was siphoned and the solid obtained was washed with hexane. The chemical characteristics of the solid, the results of the propylene polymerization test and those of the ethylene polymerization test are reported in table 1.

EXAMPLE 2 The prepolymer prepared according to the procedure of Example 1 was suspended in liquid TiCU also containing DIBP. The amounts of reagents were such that a TiCU prepolymer concentration of 50 g / l and a DIBP / prepolymer weight ratio of 12% was given. The temperature was then raised to 80 ° C and the system was maintained under these conditions, with stirring, for 1 hour. After that time the agitation was discontinued and the liquid siphoned. An additional step of contacting with TiCU, without DIBP, was carried out under the same conditions, at the end of which the solid was washed with hexane at 60 ° C. The chemical characteristics of the solid, the results of the propylene polymerization test and those of the ethylene polymerization test are reported in table 1.

EXAMPLE 3 The prepolymer prepared according to the procedure of Example 1 was suspended in a liquid medium containing heptane and TiCU in a 1: 1 volume ratio and also containing 9,9-bis (methoxymethyl) fluorene.

The amounts of reagents were such that a concentration of prepolymer in the liquid phase of 50 g / l, and a weight ratio of 9,9-bis (methoxymethyl) fluorene / prepolymer of 5% were given. The temperature was then raised to 80 ° C and the system was maintained under these conditions, with agitation, for 1 hour. After that time the agitation was discontinued and the liquid was siphoned. An additional step of contacting pure TiCU without 9,9-bis (methoxymethyl) fluorene, under the same conditions as those described in example 1 was carried out at the end of the solid having been washed with hexane. The chemical characteristics of the solid, the results of the propylene polymerization test and those of the ethylene polymerization test are reported in table 1.

EXAMPLE 4 The same prepolymerization procedure described in Example 1 was repeated, with the only difference that the prepolymerization was prolonged until a final weight ratio prepolymer / catalyst of 15 g / g was obtained.

Stage of treatment with the Ti compound The treatment was Snowed out according to the procedure described in example 1. The chemical characteristics of the solid, the results of the propylene polymerization test and those of the ethylene polymerization test were they also report table 1.

EXAMPLE 5 Ethylene prepolymerization The catalyst component prepared according to the procedure described in Example 1 was prepolymerized with ethylene to give a prepolymer / catalyst weight ratio of 11.6 g / g. The prepolymerization was carried out in hexane using TEAL as co-catalyst (TEAL weight ratio / solid catalyst component = 0.05). The prepolymer catalyst system obtained in this manner, having a porosity (Hg due to pores with a radius of up to 75,000A) of 0.6 cm3 / g, was subjected to the propylene polymerization process and the ethylene polymerization process whose results were report in table 1.

Step of treatment with the Ti compound The obtained ethylene prepolymer was suspended in a liquid medium containing heptane and TiCU in a 1: 1 volume. The amounts of reagents were such that a prepolymer concentration in the liquid phase of 50 g / l was given. The temperature was then raised to 80 ° C and the system was maintained under these conditions with stirring for 1 hour. After that time the stirring was discontinued, the liquid was siphoned and the solid was washed with hexane at 60 ° C. The chemical characteristics of the solid and the results of the propylene polymerization test are reported in table 1.

EXAMPLE 6 Treatment step with the Ti compound The ethylene prepolymer according to example 5 was suspended in a liquid medium containing heptane / TiCU in a 1: 1 volume ratio, and also containing 9,9-bis (methoxymethyl) fluorene. The amounts of reagents were such that a concentration of prepolymer in the liquid phase of 50 g / l and a weight ratio of 9,9-bis (methoxymethyl) fluorene / prepolymer of 5% was given. The temperature was then raised to 80 ° C and the system was maintained under these conditions, with stirring, for 1 hour. After that time the stirring was discontinued, the liquid was siphoned and an additional treatment with TiCU without 9,9-bis (methoxymethyl) fluorene was carried out. At the end the solid was washed with hexane and then dried. The chemical characteristics of the solid, the results of the propylene polymerization test and those of the ethylene polymerization test are reported in table 1.

EXAMPLE 7 Ethylene prepolymerization The catalyst component prepared according to the procedure described above in Example 1 was prepolymerized with ethylene to give a prepolymer / catalyst weight ratio of 30 g / g. The prepolymerization was carried out in hexane using TEAL as co-catalyst (TEAL weight ratio / solid catalyst component = 0.5). The prepolymer catalyst system obtained in this way having a porosity (Hg due to pores with a radius of up to 75,000A) of 0.6 cm3 / g was subjected to the propylene polymerization process whose results are reported in Table 1.

Step of treatment with the Ti compound The ethylene prepolymer according to example 5 was suspended in a liquid medium containing heptane / TiCU in a 1: 1 volume ratio, and also containing DIBP. The amounts of reagents were such that a prepolymer concentration in the liquid phase of 50 g / l and a DIBP / prepolymer weight ratio of 5% was given. The temperature was then raised to 80 ° C and the system was maintained under these conditions, with stirring, for 1 hour. After that time the stirring was discontinued, the liquid was siphoned and an additional TiCU treatment without DIBP was carried out. At the end the solid was washed with hexane and then dried. The chemical characteristics of the solid and whose results of the propylene polymerization test are reported in table 1.

TABLE 1 OR Activity (a): activity expressed in terms of Kg of polymer per g of prepolymer fed. Activity (b): activity expressed in terms of Kg of polymer per g of comp. of cat. content in the prepolymer (*): polymerization carried out in the absence of external donor (+): polymerization carried out with a dicyclopentyl dimethoxysilane as external donor with a TEAL / donor ratio of 60 Et: 9,9-bis (methoxymethyl) fluorene nd = not determined

Claims (31)

NOVELTY OF THE INVENTION CLAIMS

1. - Catalyst components for the polymerization of olefins CH2 = CHR, wherein R is hydrogen or a hydrocarbon radical having 1-12 carbon atoms, comprising the product obtained by contacting a Ti compound of the formula Ti (OR) n-yXy, wherein R is an alkyl, isoalkyl, cycloalkyl or aryl radical having from 1 to 18 carbon atoms, X is a halogen atom, n is the valence of titanium and (y) is a number of 1 an , with a prepolymer having a porosity (measured with Hg method) of more than 0.3 cc / g and containing 0.5 to 100 g of polymer per g of solid catalyst component, said prepolymer being obtained by copolymerizing an olefin or a diolefin is copolymerizable in the presence of a catalyst comprising a solid component comprising a transition metal compound selected from the group consisting of Ti compounds of the above formula Ti (OR) n-yXy, vanadium halides, halogen haloalcohol Atoms and vanadyl halides, composed of Ti, Zr and Hf containing at least one metal bond p, said transition metal compound being supported on an Mg dihalide having an average crystallite size of less than 30 nm.

2. - Catalyst components according to claim 1, in which the contact of the prepolymer with the Ti compound is carried out under suitable conditions to fix at least 0.05% Ti compound, expressed as Ti.

3. Catalyst component according to claim 2, wherein the Ti compound fixed on the prepolymerized catalyst component is higher than 0.2%, expressed as Ti.

4. Catalyst components according to claim 1, wherein the Mg dihalogenide has an average crystallite size of less than 15 nm.

5. Catalyst component according to claim 1, in which the porosity of the prepolymer is higher than 0.4 cm3 / g.

6. Catalyst component according to claim 5, in which the porosity of the prepolymer is higher than 0.5 cm3 / g.

7. Catalyst component according to claim 1, wherein the amount of prepolymer varies from 1 to 50 of polymer per g of solid catalyst component used to prepare it.

8. Catalyst component according to claim 7, wherein the amount of prepolymer varies from 2 to 30 g of polymer per g of solid catalyst component.

9. - Catalyst components according to claim 1, wherein the solid catalyst component used to prepare the prepolymer is obtained by reacting a titanium compound of the formula Ti (OR) n-yXy, wherein R is an alkyl radical , isoalkyl, cycloalkyl or aryl having 1 to 18 carbon atoms, X is a halogen atom, n is the titanium valence and (y) is a number of 1 an, with an adduct of the formula MgCl2 «pROH, in where p is a number from 0.1 to 6 and R is an alkyl, isoalkyl or cycloalkyl radical having 1-18 carbon atoms.

10. Catalyst components according to claim 9, wherein the Ti compound is TiCI4.

11. Catalyst components according to claim 1, wherein the solid catalyst component used to prepare the prepolymer has a surface area (by the method of B.E.T.) between 20 and 500 m2 / g and a porosity (Hg method) due to pores with a radius of up to 10,000A, from 0.3 to 1.5 cm3 / g.

12. Catalyst components according to claim 1, wherein the solid catalyst component used to prepare the prepolymer contains an internal electron donor compound selected from esters, ethers, amines and ketones.

13. Catalyst components according to claim 12, in which the internal donor is selected from alkyl, cycloalkyl or aryl esters of monocarboxylic or polycarboxylic acids.

14. - Catalyst components according to claim 13, wherein the internal donor is selected from methyl benzoate, ethyl benzoate, diisobutyl phthalate, di-n-hexyl phthalate, di-octyl phthalate and di-octyl phthalate. neopentyl.

15. Catalyst components according to claim 12, in which the internal donor is selected from 1,3-diethers of the formula (I) wherein R1 and R11 are the same or different and are hydrogen or straight or branched C.sub.C.sub.s.C.sub.hydrocarbon groups which may also form one or more cyclic structures; the groups R1", equal or different from each other, are hydrogen or hydrocarbon groups of C-C? 8, the R? v groups, equal or different from one another, have the same meaning of RMI except that they can not be hydrogen each of the groups R1 to R? v may contain heteroatoms selected from halogens, N, O, S and Si. 16.- Catalyst components according to claim 15, in which the internal electron donor compound is selected of 1, 3-diethers of the formula (II) (II) wherein the Rlv radicals have the same meaning as explained above, and the radicals R 1"and Rv, equal or different from one another, are selected from the group consisting of hydrogen; halogens, preferably Cl and F; C-C20 alkyl radicals linear or branched; C3-C20 cycloalkyl radicals, C6-C20 aryl. C7-C2al alkaryl and C7-C20 aralkyl, and two or more of the radicals R can be linked to each other to form condensed, saturated or unsaturated cyclic structures, optionally substituted with radicals Rv? selected from the group consisting of halogens, preferably Cl and F; C-C20 alkyl radicals linear or branched; C3-C2o cycloalkyl radicals, C6-C20 aryl, C7-C2 alkaryl and C7-C2al aralkyl; said radicals Rv and Rv? optionally containing one or more heteroatoms as substitutes for carbon or hydrogen atoms, or both. 17. Catalyst components according to claim 16, in which the internal electron donor compound is selected from the compounds of the formula (III): wherein the radicals R v ?, the same or different, are hydrogen; halogens, preferably Cl and F; C-C20 alkyl radicals linear or branched; C3-C20 cycloalkyl radicals, C6-C20 aryl, C-C20 alkylaryl and C7-C2al aralkyl. optionally containing one or more heteroatoms selected from the group consisting of N, O, S, P, Si and halogens, in particular Cl and F, as substitutes for carbon or hydrogen atoms, or both; radicals R1"and R? V are as defined above for formula (II). 18. Catalyst components according to claim 17, in which the electron donor compound is 9,9-bis (methoxymethyl) fluorene. 19. Catalyst components according to claim 1, in which the prepolymer is obtained by prepolymerizing ethylene or propylene. 20. Catalyst components according to claim 1, wherein the prepolymer is a crystalline prepolymer. 21. Catalyst components according to claim 10, wherein the catalyst used to prepare the prepolymer further comprises an Al-alkyl compound used in such an amount as to give an Al / Ti ratio of 0.01 to 10. 22. - Catalyst components according to claim 21, in which the Al / Ti ratio is 0.05 to 5. 23. Catalyst components according to any of the preceding claims, in which the Ti compound contacted with the prepolymer is TÍCI4. 24.- Catalyst components for the polymerization of olefins CH2 = CHR, wherein R is hydrogen or a hydrocarbon radical having 1-12 carbon atoms, comprising a Ti compound of the formula Ti (OR) n-yXy, where n is the valence in titanium and (y) is a number of 1 an, fixed on a prepolymerized catalyst component containing Mg dichloride in an amount of 50 to 50, 000 ppm, expressed as Mg, said Ti compound being present in a Ti / Mg weight ratio of 0.01 to 3. 25.- Catalysts for the polymerization of olefins comprising (A) a catalyst component in accordance with any of claims 1 to 24, (B) a suitable co-catalyst and, optionally, (C) one or more (external) electron donor compounds. 26. A catalyst according to claim 25, wherein the co-catalyst (B) is selected from Al-alkyl compounds of the formula RzAIX3-z wherein R is an alkyl, isoalkyl, cycloalkyl or aryl radical of C1-C20, z is an integer from 2 to 3 and X is halogen. 27. A catalyst according to claim 26, wherein the co-catalyst is selected from triethylaluminum (TEAL), triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum and tris (2). , 4,4-trimethylpentyl) aluminum. 28. A catalyst according to claim 25, wherein the external electron donor compound is selected from silicon compounds of the formula Ra5Rb6Si (OR7) c, wherein a and b are integers from 0 to 2, c is an integer from 1 to 3 and the sum (a + b + c) is 4; R5, R6 and R7 are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms. 29. A process for the co-polymerization of olefins CH2 = CHR, wherein R is hydrogen or a hydrocarbon radical having 1-12 carbon atoms, which is carried out in the presence of a catalyst in accordance with any of claims 21-24. 30.- Olefin polymers obtainable by the process according to claim 29. 31.- Propylene co-polymers having a heat of fusion (ΔHf) of more than 70 J / g measured by the DSC method. , which can be obtained by the method according to claim 29.