ES2717176T3 - Catalyst system for the polymerization of olefins - Google Patents

Description

DESCRIPTION

Catalyst system for the polymerization of olefins.

The present invention relates to a catalyst system capable of showing, in the polymerization of propylene, high activity, stereospecificity and greater response to hydrogen.

Catalyst systems for the stereospecific polymerization of olefins are widely known in the art. The most common type of catalyst system belongs to the Ziegler-Natta family and comprises a solid catalyst component, constituted by magnesium dihalide where a titanium compound and an internal electron donor compound are supported, used in combination with an Al-alkyl compound . However, conventionally, when higher polymer crystallinity is required, an external donor, usually an alkoxysilane, is also needed to obtain greater isotacticity. In fact, when an external donor is absent, the isotactic index of the resulting polymer is not high enough, even if a 1,3-diether is used as an internal donor.

In some applications, particularly in thin-wall injection molding (TWIM), it is necessary to use polymers with a relatively high fluidity, that is, with a relatively low molecular weight for high quality molding.

Low molecular weight polymers are commonly obtained by increasing the content of the chain transfer agent (molecular weight regulator), in particular hydrogen, which is commonly used industrially.

In the case of TWIM applications, both a high crystallinity and a low molecular weight are required and, therefore, the catalyst system must also incorporate an external donor. However, the use of the most common external donors, such as alkylalkoxysilane, leads to a worsening of the hydrogen response, that is, the ability to produce shorter and shorter polymer chains with respect to the increasing concentration of hydrogen.

This means that it is necessary to increase the hydrogen content in the polymerization mixture, thus increasing the pressure of the reaction system which, in turn, would imply the use of equipment specially designed to withstand high pressure and, therefore, more expensive. A possible solution, in particular for the liquid phase polymerization, would be to operate the plant at a lower temperature that allows to have a reduced pressure, but this negatively affects the efficiency of the heat exchanger and the relative productivity of the plant. Therefore, it would be necessary to have a catalyst system that shows an improved hydrogen response, ie, the ability to produce polymers with a lower molecular weight in the presence of small amounts of hydrogen.

Examples of catalysts that have a high response to hydrogen are the Ziegler-Natta catalysts containing 1,3-diethers described, for example, in EP622380. Said catalyst components are generally capable of producing propylene polymers with high melt flow rates. When an external donor of the alkylalkoxysilane type is added to increase its stereospecificity, the hydrogen response of the catalyst decreases.

The applicant has found that the selection of a specific type of catalyst system is capable of solving the problem mentioned above. Therefore, an object of the present invention is a catalyst system comprising the product obtained by contacting (a) a solid catalyst component containing Mg, Ti, halogen and at least one electron donor compound selected from 1.3- diethers;

(b) an alkylaluminum cocatalyst; Y

(c) an ester of the formula ROOC- (CH2) n-COOR in which n is an integer from 2 to 8 and the R groups, equal or different from each other, are C1-C10 alkyl groups.

Preferably, the solid catalyst component comprises Mg, Ti, halogen and an electron donor selected from 1,3-diethers of formula (I):

where RI and R "are the same or different and are hydrogen or C1-C18 linear or branched hydrocarbon groups which can also form one or more cyclic structures, the Rm groups, equal or different from each other, are hydrogen or C ¹ -C ¹⁸ hydrocarbon groups; RIV groups, equal or different from each other, have the same meaning of Rm, except that they can not be hydrogen; each of the groups RI to RIV may contain heteroatoms selected from halogens, N, O, S and Si.

In the electron donor of formula (I), preferably, RIV is an alkyl radical of 1-6 carbon atoms and, more particularly, a methyl, while the radicals Rm are preferably hydrogen. In addition, when RI is methyl, ethyl, propyl or isopropyl, R "can be ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, isopentyl, 2-ethylhexyl, cyclopentyl, cyclohexyl, methylcyclohexyl, phenyl or benzyl, when RI is hydrogen, R "can be ethyl, butyl, sec-butyl, tert-butyl, 2-ethylhexyl, cyclohexylethyl, diphenylmethyl, p-chlorophenyl, 1-naphthyl, 1-decahydronaphthyl; RI and R "may be the same and may be ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, neopentyl, phenyl, benzyl, cyclohexyl, cyclopentyl.

Specific examples of ethers that can be used advantageously include: 2- (2-ethylhexyl) -1,3-dimethoxypropane, 2-isopropyl-1,3-dimethoxypropane, 2-butyl-1,3-dimethoxypropane, 2-sec-butyl -1,3-dimethoxypropane, 2-cyclohexyl-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-di-n -butyl-1,3-dimethoxypropane, 2,2-1,3-diethoxypropane, 2,2-dicyclopentyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3-diethoxypropane, 2,2-di-n- Butyl-1,3-diethoxypropane, 2,2-ethyl-1,3-dimethoxypropane, 2-methyl-2-propyl-1,3-dimethoxypropane, 2-methyl-2-benzyl -1,3-dimethoxypropane, 2-methyl-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-dimethoxypropane, 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-dineopentyl-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.

In addition, the 1,3-diethers of formula (II) are particularly preferred.

wherein the RIV radicals have the same meaning as explained above and the Rm and RV radicals, equal or different from each other, are selected from the group consisting of hydrogen; halogens, preferably Cl and F; C1-C20 alkyl radicals, linear or branched; C3-C20 cycloalkyl, C6-C20 aryl, C7-C20 alkylaryl and C7-C20 arylalkyl and two or more of the RV radicals can be joined together to form condensed, saturated or unsaturated cyclic structures, optionally substituted with RVI radicals selected from the group consists of halogens, preferably Cl and F; C1-C20 alkyl radicals, linear or branched; C3-C20 cycloalkyl, C6-C20 aryl, C7-C20 arylalkyl and C7-C20 arylalkyl; said RV and RVI radicals optionally containing one or more heteroatoms as substitutes for carbon or hydrogen atoms, or both.

Preferably, in the 1,3-diethers of formulas (I) and (II), all the radicals Rm are hydrogen and all the radicals RIV are methyl. In addition, the 1,3-diethers of formula (II) are particularly preferred, where two or more of the radicals RV are linked together to form one or more condensed cyclic structures, preferably benzene, optionally substituted by RVI radicals. Especially preferred are compounds of formula (III):

where the RVI radicals, equal or different, are hydrogen; halogens, preferably Cl and F; Ci-C20 alkyl radicals, linear or branched; C3-C20 cycloalkyl, C6-C20 aryl, C7-C20 alkylaryl and C7-C20 arylalkyl 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; the radicals Rm and RIV are as defined above for formula (II).

Specific examples of compounds comprised in formulas (I) and (II) include:

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-dicyclopentylcyclopentadiene;

1,1-bis (methoxymethyl) indene; 1,1-bis (methoxymethyl) -2,3-dimethylindene;

1,1-bis (methoxymethyl) -4,5,6,7-tetrahydroindene;

1,1-bis (methoxymethyl) -2,3,6,7-tetrafluoroindene;

1,1-bis (methoxymethyl) -4,7-dimethylindene;

1,1-bis (methoxymethyl) -3,6-dimethylindene;

1,1-bis (methoxymethyl) -4-phenyl-indene;

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) -7-trimethylsilyldedene;

1,1-bis (methoxymethyl) -7-trifluoromethylindene;

1,1-bis (methoxymethyl) -4,7-dimethyl-4,5,6,7-tetrahydroindene;

1,1-bis (methoxymethyl) -7-methylindene;

1,1-bis (methoxymethyl) -7-cyclopentyldene;

1,1-bis (methoxymethyl) -7-isopropylindene;

1,1-bis (methoxymethyl) -7-cyclohexylindene;

1,1-bis (methoxymethyl) -7-tert-butylindene;

1,1-bis (methoxymethyl) -7-tert-butyl-2-methylindene;

1,1-bis (methoxymethyl) -7-phenylindene;

1,1-bis (methoxymethyl) -2-phenyl-indene;

1,1-bis (methoxymethyl) -1H-benz [e] indene;

1,1-bis (methoxymethyl) -1H-2-methylbenz [e] indene;

9.9-bis (methoxymethyl) fluorene;

9,9-bis (methoxymethyl) -2,3,6,7-tetramethyl fluororen;

9.9-bis (methoxymethyl) -2,3,4,5,6,7-hexafluorofluorene;

9.9-bis (methoxymethyl) -2,3-benzofluorene;

9.9-bis (methoxymethyl) -2,3,6,7-dibenzofluorene;

9.9-bis (methoxymethyl) -2,7-diisopropyl fluorene;

9.9-bis (methoxymethyl) -1,8-didorofluorene;

9.9-bis (methoxymethyl) -2,7-dicidopentyl fluorene;

9.9-bis (methoxymethyl) -1,8-difluorofluorene;

9.9-bis (methoxymethyl) -1,2,3,4-tetrahydrofluorene;

9.9-bis (methoxymethyl) -1,2,3,4,5,6,7,8-octahydrofluorene;

9.9-bis (methoxymethyl) -4-tert-butyl fluorene.

In addition to the 1,3-diethers described above, the solid catalyst component (a) may also contain additional electron donors belonging to ethers, esters of aromatic or aliphatic mono or dicarboxylic acids, ketones or alkoxyesters. Among them, esters of succinic acids according to formula (I) of EP1088009 are particularly preferred.

Additional donors may be present in an amount such that the 1,3-diether / other donor molar ratio ranges from 0.1 to 10, preferably from 0.2 to 8.

As explained above, the catalyst components of the invention comprise, in addition to the above electron donors, Ti, Mg and halogen. In particular, the catalyst components comprise a titanium compound having at least one Ti-halogen bond and the electron donor compounds mentioned above supported on an Mg halide. Magnesium halide is preferably MgCU in active form, which is widely known in the patent literature as support for Ziegler-Natta catalysts. USP 4,298,718 and USP 4,495,338 were the first to describe the use of these compounds in the Ziegler-Natta catalysis. It is known, thanks to these patents, that magnesium dihalides in active form, used as a support or co-carrier in catalyst components for the polymerization of olefins, are characterized by X-ray spectra in which the most intense diffraction line appears in the spectrum of the non-active halide sees its intensity diminished and is replaced by a halo whose maximum intensity moves towards the lower angles, compared with those of the most intense line.

The preferred titanium compounds used in the catalyst component of the present invention are TiCU and TiCb; in addition, Ti-haloalcoholates of the formula Ti (OR) n-yXy can also be used, where n is the valence of titanium and is a number between 1 and n-1, X is halogen and R is a hydrocarbon radical having 1 to 10 carbon atoms.

The preparation of the solid catalyst component can be carried out according to various methods. According to one of these methods, the magnesium dichloride in an anhydrous state, the titanium compound and the electron donor compounds are milled together under conditions in which activation of the magnesium dichloride occurs. The product obtained can be treated one or more times with an excess of TiCU at a temperature between 80 and 135 ° C. This treatment is followed by washes with hydrocarbon solvents until the chloride ions disappear. According to another method, the product obtained by the co-trituration of the magnesium chloride in an anhydrous state, the titanium compound and the electron donor compounds are treated with halogenated hydrocarbons such as 1,2-dichloroethane, chlorobenzene, dichloromethane, etc. The treatment is carried out for 1 to 4 hours and at a temperature between 40 ° C and the boiling point of the halogenated hydrocarbon. The product obtained is generally washed with inert hydrocarbon solvents, such as hexane.

According to another method, the magnesium dichloride is preactivated according to well-known methods and then treated with an excess of TiCU at a temperature of about 80 to 135 ° C in the presence of the electron donor compounds. The treatment with TiCU is repeated and the solid is washed with hexane to remove unreacted TiCU. A further method described in WO2005 / 095472 comprises reacting, in the presence of a 1,3-diether, a titanium compound having at least one Ti-Cl bond with a precursor of formula MgCln (OR) 2-nLBp wherein n is from 0.1 to 1.9, p is greater than 0.4 and R is a C1-C15 hydrocarbon group. Preferably, the reaction is carried out in an excess of TiCU at a temperature of about 80 to 120 ° C.

According to a preferred method, the solid catalyst component can be prepared by the reaction of a titanium compound of the formula Ti (OR) n-yXy, where n is the valence of titanium and y is a number between 1 and n, preferably TiCU, with a magnesium chloride derived from an adduct of formula MgCUpROH, where p is a number between 0.1 and 6, preferably between 2 and 3.5, and R is a hydrocarbon radical having between 1 and 18 carbon atoms. The adduct can be suitably prepared in spherical form by mixing alcohol and magnesium chloride in the presence of an inert hydrocarbon immiscible with the adduct, working under stirring conditions at the adduct melting temperature (100-130 ° C). Then, the emulsion is rapidly inactivated, which causes the solidification of the adduct in the form of spherical particles. Examples of spherical adducts prepared according to this method are described in USP 4,399,054 and USP 4,469,648. The adduct thus obtained can be reacted directly with a Ti compound or can be previously subjected to a thermally controlled dealcoholization (80-130 ° C) in order to obtain an adduct in which the amount of moles of alcohol is generally lower to 3, preferably between 0.1 and 2.5. The reaction with the Ti compound can be carried out by the suspension of the adduct (dealcoholated or as such) in cold TiCU (generally at 0 ° C); The mixture is heated to 80-130 ° C and maintained at this temperature for 0.5-2 hours. The treatment with TiCU can be carried out one or more times. Electron donor compounds can be added during the treatment with TiCU. They can be added together in the same treatment with TiCU or separately in two or more treatments.

The preparation of spherical catalyst components is described, for example, in European Patent Applications EP-A-395083, EP-A-553805, EP-A-553806, EPA601525 and WO98 / 44001.

The solid catalyst components obtained according to the above method show a surface area (by BET method), generally between 20 and 500 m2 / g and preferably between 50 and 400 m2 / g, and a total porosity (by BET method) greater than 0.2 cm3 / g, preferably between 0.2 and 0.6 cm3 / g. The porosity (Hg method) due to the pores with a radius of up to 10,000A in general ranges between 0.3 and 1.5 cm3 / g, preferably between 0.45 and 1 cm3 / g.

The solid catalyst component has an average particle size ranging from 5 to 120 μm and more preferably from 10 to 100 μm.

The Al-alkyl compound (b) is preferably selected from trialkylaluminum compounds, such as for example triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum. It is also possible to use mixtures of trialkylaluminum compounds with alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesquichlorides, such as AlEt2Cl and AbEfeCk. Ester (c) is used as an external electron donor and is preferably selected from compounds in which R is a straight or branched C1-C6 alkyl, preferably ethyl or isobutyl.

In the esters (c), n is preferably from 2 to 7, more preferably from 4 to 6 and especially from 4 to 5.

Non-limiting examples of esters (c) are diethyl succinate, diethyl glutarate, diethyl adipate, diethyl suberate, diethyl pimelate and the corresponding esters that derive from the substitution of ethyl with methyl, isobutyl or 2-ethylhexyl.

The catalyst of the invention is capable of polymerizing any type of olefins CH2 = CHR in which R is hydrogen or a C1-C10 hydrocarbon group or mixtures of said olefins. However, as mentioned above, it is particularly suitable for the preparation of polymers of propylene due to the fact that it shows a greater response to hydrogen with respect to the alkylalkoxysilane most commonly used, maintaining at the same time a high stereospecificity expressed as a percentage of insolubility. in xylene at 25 ° C, generally 97% or higher. The molecular weight distribution (expressed as a polydispersity index determined as described hereinafter) remains narrow, generally less than 4 and preferably less than or equal to 3.5. Another important advantage is that the response to hydrogen and high stereospecificity are retained, while maintaining a very good level of polymerization activity.

Any type of polymerization process can be used with the catalysts of the invention, which are very versatile. The polymerization can be carried out, for example, in suspension using a diluent as a liquid or bulk inert hydrocarbon using a liquid monomer (propylene) as a reaction medium or in solution using monomers or inert hydrocarbons as the solvent for the new polymer. In addition, it is possible to carry out the gas phase polymerization process, working in one or more fluidized bed reactors or mechanically agitated.

The process of the present invention is particularly advantageous for producing said isotactic propylene polymers with high fluidity in liquid phase because in this type of process the pressure problems related to the use of higher amounts of hydrogen are more evident. As mentioned, the liquid phase process can be in suspension, in solution or in bulk (liquid monomer). This latter technology is the most preferred and can be used in various types of reactors, such as continuous stirred tank reactors, loop reactors or plug-flow reactors. The polymerization is generally carried out at a temperature between 20 and 120 ° C, preferably between 40 and 85 ° C. When the polymerization takes place in the gas phase, the operating pressure generally ranges 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.

The catalyst of the present invention can be used as such in the polymerization process by introducing it directly into the reactor. In the alternative, the catalyst can be prepolymerized before being introduced into the first polymerization reactor. The term "prepolymerized," as used in the art, means a catalyst that has been subjected to a polymerization step at a low conversion rate. In accordance with the present invention, a catalyst is considered to be prepolymerized when the amount of the polymer produced is from about 0.1 to about 1000 g per gram of solid catalyst component.

The prepolymerization can be carried out with the α-olefins selected from the same group of olefins disclosed above. In particular, it is especially preferred to prepolymerize ethylene or mixtures thereof with one or more aolefins in an amount of up to 20 mol%. Preferably, the conversion of the prepolymerized catalyst component is from about 0.2 g to about 500 g per gram of solid catalyst component.

The pre-polymerization step can be carried out at temperatures from 0 to 80 ° C, preferably from 5 to 70 ° C, in the liquid phase or in the gas phase. The prepolymerization step can be carried out online, as part of a continuous polymerization process, or separately in a batch process. Batch prepolymerization of the catalyst of the invention with ethylene is particularly preferred in order to produce an amount of polymer ranging from 0.5 to 20 g per gram of catalyst component.

The following examples are provided to better illustrate the invention without limiting it.

Characterization

Determination of X.I.

2.5 g of polymer and 250 ml of o-xylene were placed in a round bottom flask equipped with a cooler and a reflux condenser and this was kept under nitrogen. The obtained mixture was heated to 135 ° C and kept stirring for about 60 minutes. The final solution was allowed to cool to 25 ° C under continuous stirring and then the insoluble polymer was filtered. Then, the filtrate was evaporated in a stream of nitrogen at 140 ° C to reach a constant weight. The content of said xylene-soluble fraction is expressed as a percentage of the original 2.5 grams and then, by difference, the X.I. %.

Melt Flow Rate (MFR)

Determined in accordance with ISO 1133 (230 ° C, 2.16 Kg)

Polydispersity index (P.I.)

Determined at a temperature of 200 ° C with the use of a parallel plate rheometer model RMS-800, marketed by RHEOMETRICS (USA), which operates at an oscillation frequency that increases from 0.1 rad / sec to 100 rad / sec The value of the polydispersity index is derived from the crossing module by means of the equation:

P.I. = 105 / Gc

where Gc is the crossing module that is defined as the value (expressed in Pa) in which G '= G ", where G' is the storage module and G" is the loss module.

Examples

General procedure for the preparation of spherical adducts

An initial quantity of microspherical MgCb-2,8C2H5OH was prepared according to the method described in ex. 2 of WO98 / 44009 but operating on a larger scale. The solid adduct thus obtained was subsequently subjected to thermal dealcoholation at increasing temperatures of 30 to 130 ° C and operating in nitrogen flow to an alcohol content of 2.1 moles per mole of MgCb.

General procedure A for the preparation of the solid catalyst component (Examples 1-17, Comp.1-3)

250 ml of TiCU were introduced at room temperature under a nitrogen atmosphere into a 500 ml round bottom flask equipped with a mechanical stirrer, cooler and thermometer. After cooling to 0 ° C, while stirring, the internal donor 9,9-bis (methoxymethyl) fluorene and 10.0 g of the microspherical MgCb-2 ^ 1C2H5OH (prepared as described above) were sequentially added to the flask. .

The amount of 9,9-bis (methoxymethyl) fluorene was specifically loaded to have a molar Mg / donor ratio of 6. The temperature was increased to 100 ° C and maintained for 1 hour. Subsequently the stirring was stopped, the solid product was allowed to settle and the supernatant liquid was siphoned off maintaining the temperature at 100 ° C.

After removing the supernatant, an additional 250 ml of new TiCl4 was added. The mixture was then heated to 110 ° C and maintained at this temperature for 60 minutes. Once again the stirring was interrupted, the solid product was allowed to settle and the supernatant liquid was siphoned off maintaining the temperature at 110 ° C. A third aliquot of fresh TiCU (250 ml) was added, the mixture was kept under stirring at 110 ° C for 30 minutes and then the supernatant liquid was removed with siphon. The solid was washed with anhydrous hexane six times (6 x 100 ml) in a descending temperature gradient up to 60 ° C and once (100 ml) at room temperature. The solid obtained was finally dried under vacuum and analyzed. The amount of Ti bound to the catalyst resulted in 3.9% p., While the amount of bound internal donor resulted in 12% p.

General procedure B for the preparation of the solid catalyst component (Examples 18-21, Comp.4)

250 ml of TiCl 4 were introduced at room temperature under a nitrogen atmosphere into a 500 ml round bottom flask equipped with a mechanical stirrer, cooler and thermometer. After cooling to 0 ° C, while stirring, the internal donors 9,9-bis (methoxymethyl) fluorene and 2,3-diisopropylsuccinate diethyl and 10.0 g of MgCb-2,1C2H5OH microspheroidal were sequentially added to the flask. (prepared as described above). The amount of 9,9-bis (methoxymethyl) fluorene and diethyl 2,3-diisopropylsuccinate was specifically charged to have a total molar Mg / donor ratio of 8. The temperature was increased to 100 ° C and maintained for 1 hour. Subsequently the stirring was stopped, the solid product was allowed to settle and the supernatant liquid was siphoned off maintaining the temperature at 100 ° C. After removing the supernatant, 250 ml of fresh TiCU was added. The mixture was then heated to 110 ° C and maintained at this temperature for 60 minutes. Once again the stirring was interrupted, the solid product was allowed to settle and the supernatant liquid was siphoned off maintaining the temperature at 110 ° C. A third aliquot of fresh TiCU (250 ml) was added, the mixture was kept under stirring at 110 ° C for 30 minutes and then the supernatant liquid was removed with siphon. The solid was washed with anhydrous hexane six times (6 x 100 ml) in a descending temperature gradient up to 60 ° C and once (100 ml) at room temperature. The solid obtained was finally dried under vacuum and analyzed. The amount of Ti bound to the catalyst resulted in 3.7% p., While the amount of bound internal donors resulted in 2.8% p. for 9,9-bis (methoxymethyl) fluorene and 8.7% p. for diethyl 2,3-diisopropylsuccinate.

Examples 1-21 and comparative examples 1-4

A 4 liter steel autoclave equipped with a stirrer, pressure gauge, thermometer, catalyst feed system, monomer feed lines and thermostatic jacket was purged with a stream of nitrogen at 70 ° C for one hour. Subsequently, at 30 ° C in propylene flow, 75 ml of anhydrous hexane, 0.76 g of AlEt3, the ester (c) indicated in Table 1 (molar ratio AlEt3 / ester of 20) were charged in sequence. mg of the solid catalyst component indicated in Table 1. The autoclave was closed and subsequently the amount of hydrogen indicated in Table 1 was added. Then, under stirring, 1.2 kg of liquid propylene was introduced. The temperature was raised to 70 ° C in five minutes and the polymerization was carried out at this temperature for two hours. At the end of the polymerization, the unreacted propylene was removed; the polymer was recovered and dried at 70 ° C under vacuum for three hours. Then, the polymer was weighed, analyzed and fractionated with o-xylene to determine the amount of insoluble xylene fraction (X.I.). The polymer analyzes, as well as the activity of the catalyst, are indicated in Table 1.

TABLE 1

DES = Diethyl Succinate

DIPS = 2,3-Diethyl Diisopropylsuccinate DEG = Diethyl Glutarate

DEA = Diethyl Adipate

DAY = Diisobutyl Adipate

DEP = Diethyl pimelate

DMP = dimethyl pimelate

DESB = Diethyl Subetrate

DEM = Diethyl malonate

C = Cyclohexylmethyldimethoxy silane

n.d. = not determined

Claims (10)

A catalyst system comprising the product obtained by contacting (a) a solid catalyst component containing Mg, Ti, halogen and at least one electron-donor compound selected from 1,3-diethers; (b) an alkylaluminum cocatalyst; Y (c) an ester of the formula ROOC- (CH2) n-COOR in which n is an integer from 2 to 8 and the R groups, equal or different from each other, are C1-C10 alkyl groups. 2. The catalyst system of claim 1 wherein, in said solid catalyst component (a), the electron donor is selected from 1,3-diethers of formula (I):

where RI and R "are the same or different and are hydrogen or linear or branched C ¹ -C ¹⁸ hydrocarbon groups, which may also form one or more cyclic structures, the Rm groups, equal or different from each other, are hydrogen or hydrocarbon C groups ¹ -C ¹⁸ , the RIV groups, equal or different from each other, have the same meaning of Rm, except that they can not be hydrogen, each of the groups RI to RIV can contain heteroatoms selected from halogens, N, O, S and Yes. 3. The catalyst according to claim 1 wherein the ester (c) is selected from the compounds wherein R is a linear or branched C ¹ -C ²⁰ alkyl. 4. The catalyst according to claim 3 wherein R is ethyl or isobutyl. 5. The catalyst according to claim 1 wherein, in the ester (c), n is from 4 to 7. 6. The catalyst according to claim 1 wherein, in the ester (c), n is from 4 to 6. The catalyst according to claim 1 wherein, in the solid catalyst component, (a) the electron donor is selected from 1,3-diethers of formula (III):

wherein the radicals Rm and RIV have the same meaning defined in claim 2 and the RVI radicals, equal or different from each other, are hydrogen; halogen, C1-C20 alkyl, C3-C20 cycloalkyl, C6-C20 aryl, C7-C20 alkylaryl and C7-C20 arylalkyl optionally containing one or more heteroatoms selected from the group consisting of N, O, S, P, Si and halogens. The catalyst according to claim 1 wherein the solid catalyst component (a) further comprises electron donors belonging to ethers, esters of aromatic or aliphatic mono or dicarboxylic acids, ketones or alkoxyesters. 9. Process for the polymerization of olefins carried out in the presence of hydrogen and a catalyst system according to claim 1. 10. The process according to claim 9 wherein the olefin is propylene.