CZ471799A3 - Prepolymerized components of olefin polymerization catalyst - Google Patents

Abstract

New prepolymerized (co) polymerization catalyst components olefins of the formula CH2 = CHR, wherein R is hydrogen or an alkyl group having from 1 to 12 carbon atoms, which is C 1 -C 12 they are characterized by the fact that they contain a solid component a catalyst comprising titanium, magnesium, halogen, and the like an electrodonor compound and being capable of standard polymerization conditions produce propylene a homopolymer whose insolubility in xylene at 25 ° C is more than 90% prepolymerized with ethylene to the extent that the amount of ethylene polymer it reaches up to 100 grams / gram of said solid component catalyst. These catalyst components make it possible to obtain them catalysts with high activity, high isotactic the indexem is not affected by the effects of aging.

Description

Pre-polymerized olefin polymerization catalyst components

Technical field

The invention relates to components of an olefin polymerization catalyst of the formula CH-CHR, wherein R is a hydrogen atom or a hydrocarbon radical having 1 to 12 carbon atoms, catalysts obtained from these components and their use in the polymerization of said olefins. The catalyst components of the invention are particularly suitable for the preparation of crystalline (co) polymers of propylene (co) polymerization in gas phase, slurry or bulk (co) polymerization.

BACKGROUND OF THE INVENTION

Catalyst components for the polymerization of olefins, especially propylene, in high yield are known and are usually obtained by depositing a titanium compound together with an electron donor compound as a selectivity-affecting agent on a magnesium halide carrier. Said catalyst components are then used together with an aluminum alkyl and optionally another (external) electron donor compound in the stereospecific polymerization of propylene. Depending on the type of electron donor used, the stereoregularity of the polymer may vary. However, stereospecific catalysts of interest should be capable of providing polypropylene (co) polymers whose isotactic index expressed as xylene insolubility is greater than 90%.

Said catalyst components and catalysts prepared therefrom are widely used in plants for the (co) polymerization of propylene operating both in the liquid phase ((co) polymerization in suspension, bulk (co) polymerization) and in the gas phase. However, the use of catalyst components such as these is not entirely satisfactory. Indeed, when using such catalyst components, problems such as the formation of polymers with irregular morphology and in particular the formation of too fine particles, low bulk density polymers and low catalyst activity are observed.

4

9 I

These problems can be solved by including in the process an additional prepolymerization step in which the catalyst is prepolymerized under controlled conditions so that the obtained catalyst has a good morphology. After prepolymerization, the catalyst also increases its resistance so much that the tendency to disintegrate under polymerization conditions is reduced. As a result, the formation of fine particles is also reduced. . Further, the activity of the catalyst and the bulk density of the resulting polymer are increased. However, the use of this additional stage is reflected in the greater complexity of the design of the whole operation and higher costs, which makes it desirable in some cases to avoid this stage.

One alternative solution is a prepolymerized catalyst, in another device. This is a supply that may require a process to be prepared to prepare a prepolymerized catalyst that meets several requirements such as readiness and handling, easy shelf life, no or minimal loss of activity with time (aging) best associated with high baseline activity.

U.S. Pat. No. 5,641,721 describes a process for preparing a prepolymerized catalyst comprising (i) preparing a procatalyst composition by depositing a transition metal compound on a suitable carrier, (ii) mixing said procatalyst composition with a viscous substance and prepolymerizing said procatalyst composition with a monomer in the presence of the viscous substance. The viscous substance has a viscosity of from 1000 to 15000 cP, while the monomer used is propylene. Although it is reported that the activity of the catalyst remains unchanged after 5 months, the selectivity of the catalyst appears to be reduced. In addition, prepolymerization in such a viscous material makes the preparation of the prepolymerized catalyst complex and further leads to low catalyst activity.

SUMMARY OF THE INVENTION

Recently, it has surprisingly been found that by performing prepolymerization with a specific monomer, it is possible to obtain an olefin polymerization catalyst with a high activity, high isotactic index, which does not exhibit the effects of aging. Accordingly, the present invention provides a pre-polymerized olefin polymerization catalyst component of the formula CH ₂ = CHR, wherein R is a hydrogen atom or an alkyl group containing 1 to 12 carbon atoms, characterized in that it comprises a solid catalyst component containing titanium, magnesium, a halogen and an electron donor compound and capable of producing, under standard polymerization conditions, a propylene homopolymer whose xylene insolubility at 25 ° C is greater than 90% which is prepolymerized with ethylene to such an extent that the amount of ethylene polymer reaches up to 100 grams / gram said solid catalyst components. The amount of ethylene polymer is preferably less than 15 grams, preferably 5 grams / gram of solid catalyst component.

The catalyst components include, in particular, a titanium compound containing at least one Ti-halogen bond and the aforementioned electron donor compound supported by a magnesium halide. Active forms of magnesium halides, preferably magnesium chloride, are used as carriers for Ziegler-Natta catalysts and are widely known in the patent literature. U.S. Pat. Nos. 4,298,718 and 4,495,338 disclose the use of these compounds for the first time in Ziegler-Natta catalysis. It is known from these patents that magnesium halides in active form, which are used as carriers or carrier components in olefin polymerization catalyst components, are characterized by their X-ray spectra in which the intensity of the most intense diffraction observed in the inactive halide spectrum is minimized and replaced halogen, whose maximum intensity is displaced towards smaller angles relative to the angles of the more intense line.

Preferred titanium compounds used in the catalyst component of the present invention are titanium tetrachloride and titanium tetrachloride; titanium haloalcoholates of the general formula Ti (OR) _{n - y} X _y , where n is the valence of the titanium and y is the number between lan.

The internal electron donor compound may be selected from the group consisting of esters, ethers, amines, and ketones. Preferably, it is selected from the group consisting of alkyl, cycloalkyl or aryl esters of monocarboxylic acids such as benzoic acid or polycarboxylic acids such as phthalic or malonic acid, said alkyl, cycloalkyl or aryl group having 1 to 18 carbon atoms. Further, the substance may be selected from the group of 1,3-diethers of formula I:

wherein R ¹ , R ¹ , R ¹¹¹ , R ^IV , R ^v and R ^VI are the same or each other and are hydrogen atoms or hydrocarbon radicals containing 1 to 18 carbon atoms and R ^vn and R ^{VI 11} are the same or each other and have same meaning as R @ ^{1 71,} except that they can not be hydrogen; one or more of the groups Pt-R ⁷¹¹¹ may be joined together to form a ring. Particularly preferred are 1,3-diethers in which the groups R ⁷¹¹ and R ^{1111 are} C 1 -C 4 alkyl radicals. Examples of preferred electron donor compounds are methyl benzoate, ethyl benzoate, diisobutyl phthalate and 9,9-bis (methoxymethyl) fluorene. However, as explained above, the internal electron donor compound must be selected in such a way that the resulting solid catalyst component is capable of producing a propylene homopolymer whose insolubility in xylene at 25 ° C is greater than 90% in the standard polymerization test described below. .

• · • ·

The solid catalyst component can be prepared in several ways. In one method, anhydrous magnesium chloride, a titanium compound, and an electron donor compound of formula I are milled together under conditions where the magnesium chloride is activated. The product thus obtained may be exposed one or more times to an excess of titanium tetrachloride at a temperature between 80 and 135 ° C. This step is followed by washing with hydrocarbon solvents until the chloride ions completely disappear. In another method, the product obtained by co-grinding anhydrous magnesium chloride, titanium compound and electron donor compound is exposed to halogenated hydrocarbons such as 1,2-dichloroethane, chlorobenzene, dichloromethane and the like. The product is thus treated for 1 to 4 hours at 40 ° C to the boiling point of the halogenated hydrocarbon. The product thus obtained is completely washed with an inert hydrocarbon solvent such as hexane.

In another method, magnesium chloride is pre-activated by known methods and then exposed to an excess of titanium tetrachloride at a temperature of about 80-135 ° C in the presence of an electron donor compound. The treatment with titanium tetrachloride is repeated and the solid is washed with hexane to remove any unreacted titanium tetrachloride. Another method involves the reaction between magnesium alcoholates or magnesium chloroalcoholates (especially chloroalcoholates prepared according to U.S. Patent No. 4,220,554) and an excess of titanium tetrachloride in the presence of an electron donor compound of formula (I) at a temperature of about 80 to 120 ° C.

Particularly preferred are the solid catalyst components prepared by reacting a titanium compound of the formula Ti (OR) _n - _y Xy, wherein n is a titanium valence and y is a number between ropes, preferably TiCl ₄ with an adduct of MgCl ₂ .pROH where p is a number between 0 , 1 and 6 and R is a hydrocarbon radical having 1 to 18 carbon atoms. The adduct can be conveniently prepared in spherical form by mixing the alcohol and magnesium chloride in the presence of an inert immiscible hydrocarbon with the adduct with continuous mixing at the melting point of the adduct (100 to 130 ° C). Thereafter, the emulsion is rapidly cooled, causing the adduct to solidify in the form of spherical particles. Examples of spherical adducts prepared by the process are described in U.S. Pat. No. 4,3990,554. The adducts thus obtained may react directly with the titanium compound or may be first subjected to thermally controlled dealcoholation (at a temperature of 80 to 130 ° C) to obtain an adduct with a number of moles of alcohol of less than three, preferably between 0, 1 and 2,5. The dealcoholated adduct is then suspended in cold titanium tetrachloride (generally at 0 ° C), the resulting mixture heated to a temperature of 80 to 130 ° C and maintained at this temperature for 0.5 to 2 hours. The reaction with titanium tetrachloride can be carried out one or more times. An internal electron donor compound may be added during the reaction with titanium tetrachloride. Also, the reaction with the internal electron donor compound can be performed one or more times.

The preparation of spherical catalyst components is described, for example, in European patent application EP 395083 A.

The solid catalyst components obtained according to the above process generally have a surface area (according to the method E. E. T) of between 20 and 500 m ² / g and most preferably between 50 and 400 m ² / g, more preferably between 100 and 400 m ² / g; a total porosity (according to the method E. E. T) of greater than 0.2 cm @ 7, preferably between 0.2 and 0.6 cm @ ³ / gram, more preferably between 0.3 and 0.5 cm @ ³ / gram. The porosist (according to the mercury method) generally has values of from 0.3 to 1.5 cm ³ / gram, preferably from 0.45 to 1 cm ³ / gram, thanks to pores of up to 10,000 A.

Another method of preparing the solid catalyst component of the present invention comprises halogenating a compound of formula (RO) ₂ Mg wherein R is a hydrocarbon radical such as magnesium dialkoxide or diaryloxide with titanium tetrachloride in an aromatic hydrocarbon (such as toluene, xylene etc.) at 80-130 ° C. The reaction with titanium tetrachloride in the aromatic hydrocarbon may be repeated one or more times and an internal electron donor compound is added during one or more of these reactions. According to all these methods of preparation, the required internal electron donor may be required. The compound added as such or, as an alternative method, can be obtained in situ using a suitable precursor which is capable of being converted to the desired electron donor compound by, for example, known chemical reactions such as esterification, transesterification, etc. In general, the internal electron donor compound is used in a molar ratio based on magnesium chloride of from 0.01 to 1, preferably from 0.05 to 5.

As explained above, the prepolymerized catalyst component can be obtained by prepolymerizing the solid catalyst component together with ethylene. This prepolymerization normally proceeds in the presence of an alkyl-aluminum compound. The alkyl aluminum compound (B) is preferably selected from the group consisting of trialkyl aluminum compounds such as triethyl aluminum, triisobutyl aluminum, tri-n-butyl aluminum, tri-n-hexyl aluminum, tri-n-octyl aluminum. It is also possible to use mixtures of trialkylaluminums with alkylaluminium halides, alkylaluminium hydrides or aluminum sesquichlorides such as AlEt-Cl and

Al ₂ Et ₃ Cl ₃ .

It has been found to be particularly advantageous to carry out said prepolymerization with a small amount of alkyl aluminum compounds. In particular, said amounts may be in an Al / Ti ratio of from 0.0001 to 50, preferably from 0.001 to 10, and most preferably from 0.01 to 1.

Furthermore, it has been found advantageous to carry out said prepolymerization in the absence of an external electron donor compound.

The prepolymerization can be carried out in the liquid phase (slurry or bulk polymerization) or in the gas phase generally at a temperature of less than 80 ° C, preferably at a temperature of from -20 to 50 ° C. It is further preferably carried out in a liquid diluent selected from the group consisting of liquid hydrocarbons, among which pentane, hexane and heptane are preferred.

As explained above, the prepolymerized catalyst components thus obtained can be used in the polymerization of olefins, especially propylene polymerization, whereby it is possible to obtain highly active catalysts and polymers with high stereoregularity, high bulk density and very good morphology, thereby providing catalyst components for suspension. or by volume is shown in the examples, the particular suitability of these processes in both liquid (polymerization in polymerization) and gas phase has been demonstrated. Furthermore, how the aging problems of the catalyst have been solved, since the activity of the catalyst has remained unchanged for several months and even increased in some cases. Accordingly, the catalyst components of the present invention are particularly suitable for use in liquid or gas phase olefin polymerization plants operating without a prepolymerization step.

In particular, it is possible to carry out said polymerization in the presence of a catalyst comprising (A) a prepolymerized catalyst component; (B) an alkyl aluminum compound of the type described above and optionally (C) one or more external electron donor compounds. These electron donor compounds may be the same or different from the internal donor described above. Suitable external electron donor compounds include silicon compounds, ethers, esters, amines, heterocyclic compounds - particularly the 2,2,6,6-tetramethylpiperidine, ketones and 1,3-diethers of the above general formula (I).

Another group of preferred external electron donor compounds are silicon compounds of formula R _and ⁵ Rb ^with Si (OR ⁷ ) c, wherein a and b are integers from 0 to 2, c is an integer from 1 to 3, and the sum of (a + b + c) is equal to four; R ⁵ , R ⁶ and R ⁷ are alkyl, cycloalkyl or aryl of 1 to 18 carbon atoms, optionally containing heteroatoms. Particularly preferred are those 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 the group consisting of a branched alkyl group, a cycloalkyl group or an aryl group containing from 3 to 10 optionally containing heteroatoms and R ⁷ is an alkyl group having 1 to 10 carbon atoms, especially methyl. Examples of such preferred silicon compounds are methylcyclohexyldimethoxysilane, diphenyldimethoxysilane, methyl tert. butyldimethoxysilane, dicyclopentyldimethoxy • 9 * · · ·

Silane, 2-ethylpiperidyl-2-tert. butyldimethoxysilane and 1,1,1-trifluoropropyl-2-ethylpiperidinyldimethoxysilane. Also preferred are silicon compounds in which a is 0, c is 3, R ⁶ is selected from the group consisting of a branched alkyl or cycloalkyl group optionally containing heteroatoms, and R 'is a methyl group. Examples of such preferred silicon compounds are cyclohexyltrimethoxysilane, tert. butyltrimethoxysilane and thexyltrimethoxysilane.

If, in a particular case, monocarboxylic acid esters such as benzoates are used as internal electron donor compounds, the external donor compound is also selected from this group. In this case, the most preferred substance is p-ethoxyethyl benzoate. It is further possible to use a mixture of this donor with another donor, in particular a donor selected from the group consisting of silicon compounds. In this case, methylcyclohexyldimethoxysilane and dicyclopentyldimethoxysilane are most preferred. The electron donor compound (C) is used in an amount such that the molar ratio between the organoaluminum compound and the donor is from 0.1 to 500, preferably from 1 to 300, more preferably from 3 to 100.

The polymerization described above may be carried out under generally known polymerization conditions. Accordingly, the polymerization is generally carried out at temperatures of from 20 to 120 ° C, preferably at from 40 to 80 ° C. If the polymerization is carried out in the gas phase, the working pressure is usually from 0.5 to 10 bar

MPa, preferably from 1 to 5 MPa. In bulk polymerization, the working pressure is usually from 1 to 6 MPa, preferably from 1.5 to 4 MPa. In all polymerization processes (in both liquid and gaseous phases), the components (A), (Β) or (C) forming the catalyst may be precontacted before being added to the polymerization reactor. This pre-contacting step can be carried out in the absence of polymerizable olefins or optionally in the presence of such olefins in an amount of up to 3 grams / gram of solid catalyst component. The catalyst-forming constituents may be contacted with an inert hydrocarbon solvent such as propane, n-hexane or 0 · 0.

I 0

00

n-heptane at a temperature of less than about 60 ° C, and preferably at a temperature of about 0 to 30 ° C for 10 seconds to 60 minutes. The gas phase polymerization can be carried out according to known procedures in one or more reactors having a fluidized bed or a mechanically supported bed. Inert fluidized gases such as nitrogen or low hydrocarbons such as propane can be used to fluidize and improve heat exchange within the reactor. Further, it is possible to use processes increasing the removal of the heat of reaction comprising adding liquids or liquids mixed with the gas to the reactor. The liquids are preferably fresh or modified monomers. Such processes are described, for example, in EP 89691 A, EP 241947 A, US 5 352 749, WO94 / 28032 and

EP 695313 A.

DETAILED DESCRIPTION OF THE INVENTION

The following examples are provided to better illustrate the present invention and do not limit it in any way.

Characterization

Determination of insolubility index (I.N.)

2.5 grams of the polymer were dissolved in 250 ml of o-xylene for 30 minutes with stirring at 135 ° C. The solution was then cooled to 25 ° C and after 30 minutes the insoluble polymer was filtered off. The remaining solution was evaporated under a stream of nitrogen, the residue was dried and weighed to determine the percentage of soluble polymer, and the percent insolubility index was then determined from the difference.

General Procedure for Standard Propylene Polymerization Test

A 4 liter steel autoclave equipped with a stirrer, manometer, thermometer, catalyst loading system, monomer feed line, and a constant temperature jacket was charged with 0.01 grams of solid catalyst, triethyl aluminum (TEAL) and cyclohexylmethyldimethoxysilane in amounts such that the Al / The donor was 20. Next, 3.2 liters of propylene and 1.5 liters of hydrogen were added. The system was heated to 70 ° C with stirring for ten minutes and these conditions were maintained for 120 minutes. At the end of the polymerization, the polymer was isolated by removing all unreacted monomers and dried under vacuum.

Determination of melting index

The melting index was determined according to ASTM D 1238, condition L

Examples 1-2 and Comparative Example 3

Preparation of the solid catalyst component

To a 500 ml 4-necked flask previously flushed with nitrogen was added 250 ml TiCl ₄ at 0 ° C. 10 grams of microspheric MgCl ₂ were added under continuous stirring. % C ₂ H ₅ OH, which contained 54 wt. alcohol, and 6 mmol of diisobutyl phthalate. The temperature was raised to 100 ° C and held at that temperature for two hours. Stirring was then stopped, the solid product was allowed to settle and the supernatant was decanted.

The reaction with titanium tetrachloride was repeated and the solid obtained was washed six times with anhydrous hexane (6 x 100 ml) at 60 ° C and dried in vacuo. The characteristics of the catalyst components and the propylene polymerization results are shown in Table 1.

0

0

5 «** ·«

• · • 0

Pre-polymerization of ethylene

The catalyst components prepared as described above were prepolymerized with ethylene under the conditions given in Table 2. In Comparative Example 3, prepolymerization was not carried out.

Polymerization of propylene

The prepolymerized catalyst obtained was further used in the bulk polymerization of propylene under the following conditions:

Al / catalyst (mass ratio):

Al / donor (weight ratio): 6

Donor / catalyst (mass ratio): 1.3

Duration (minutes): 80

Temperature (° C)

The results are shown in Table 3

Examples 4-5 and Comparative Example 6

Preparation of the solid catalyst component

The catalyst components were prepared according to Example 1 with the only difference that ethyl benzoate was used instead of diisobutyl phthalate. The characteristics of the catalyst components and the propylene polymerization results are shown in Table 1.

Pre-polymerization of ethylene

The catalyst components prepared as described above were prepolymerized with ethylene under the conditions given in Table 2. In Comparative Example 6, prepolymerization was not carried out.

Polymerization of propylene

The prepolymerized catalyst obtained was further used in the bulk polymerization of propylene under the following conditions:

9 i

999

· 9 99 9

9 9 9 9 9

9

9 · 99

Al / catalyst (weight ratio): Al / donor (weight ratio):

Donor / catalyst (weight ratio) Duration (minutes):

Temperature (° C)

4, 6

1/4

3.2

P-Ethoxyethylbenzoate was used as an external electron donor. The results are shown in Table 3

Example 7 and Comparative Example 8

The catalyst components were prepared according to Example 4 with the only difference that 9.9-bis (methoxymethyl) -fluorene was used instead of ethyl benzoate. The characteristics of the catalyst components and the propylene polymerization results are shown in Table 1.

Pre-polymerization of ethylene

The catalyst components prepared as described above were prepolymerized with ethylene under the conditions given in Table 2. In Comparative Example 8, prepolymerization was not carried out.

Polymerization of propylene

The prepolymerized catalyst obtained was further used in the bulk polymerization of propylene under the following conditions:

Al / catalyst (mass ratio): 13.7

Duration (minutes): 80

Temperature (° C)

No external electron donor. The results are shown in Table 3

9 ·

::

Evaluation of property changes over time

The catalyst components prepared according to Examples 4 and 5 were tested in propylene polymerization to determine the effect of time on their properties. The first test was performed after prepolymerization and the second one after 120 days. All assays were performed according to general standard procedures using p-ethoxyethylbenzoate as an external electron donor in an amount such that the Al / electron donor molar ratio was 1.8. The results are shown in Table 4.

ί:

• ♦ · · ···

9

99 9 9 <· ·· ♦ 9 »··· ► ·« ··

Table 1

Solid catalyst components Example Ti (%) Mg (%) Donor (%) I. N. (%) 1 3 18.8 9, 6 98.1 2 3, 1 18.9 9.5 97.9 comparative 3 3 18, 9 9.4 98, 1 4 4.3 17 13, 5 95, 9 5 3.4 17, 5 13, 8 95, 6 comparative 6 4, 1 17.1 13.3 96 7 4.1 15, 5 17.2 97 comparative 8 _ rr _ _ H _ _ H _ _ π _

· ♦ «99 · · 9 · φ · · · · 9

989 99 9

9 9 9 • 999 · 9 99 ♦ · 99 9 9 »· · (9 9 4 ► 9 9 4 ··

Table 2

Solid catalyst components Pre-polymerization conditions Example Al / cataly- tor (mass) Catalyst/ C2- Duration (minutes) Temperature (° C) 1 0.004 1 300 20 May 2 0, 004 1 300 20 May comparative 3 - - - - 4 0.005 1 300 20 May 5 0, 01 1 300 20 May comparative 6 - - - 7 0, 005 1 300 20 May comparative 8 - - - -

44 «3 4 • 4 ·

444

4

4444 44

4

44 • 4 4 • · · · · · · · · · · · · · · · · · ·

Table 3

Polymerization results with prepolymerized catalyst components

Example Yield I. N. Obj emová density MIL 1 23 96 0, 47 1.3 2 24 96 0, 48 1,2 comparative 3 16 95 0, 32 1.4 4 28 95, 5 0.43 1, 6 5 30 95 0.42 2 comparative 6 20 May 94 0.3 3 7 78 96, 3 0, 43 1 comparative 8 55 95 0.32 1

Table 4

Example Aging (days) Yield (kg / g) I. N. (%) Obj emová density 4 0 38, 6 94, 4 0, 38 4 120 41.4 94, 6 0, 41 5 0 35, 3 94, 3 0, 385 5 120 36, 1 95 0, 40

• Φ

Claims (26)

PATENT CLAIMS ·· φ φ φ φ 999 · · · 999 999 999 ΦΦ ΦΦ .. .. • φφφ '• φ φ φ • φ φ φ • φ φ φ • φ φφ A prepolymerized olefin polymerization catalyst component of the formula CH ₂ = CHR, wherein R is a hydrogen atom or an alkyl group containing 1 to 12 carbon atoms, characterized in that it comprises a solid catalyst component comprising magnesium, titanium, halogen and an electron donor compound and is capable of under standard propylene polymerization conditions to provide a propylene homopolymer whose xylene insolubility at 25 ° C is greater than 90% and is prepolymerized with ethylene to such an extent that the amount of ethylene prepolymer is up to 100 grams per gram of solid catalyst component. 2. The catalyst component of claim 1 comprising less than 15 grams of ethylene polymer per gram of solid catalyst component. 3. Catalyst component according to claim 2 characterized by that contains less than 5 grams ethylene per 1 gram solid components of the catalyst. 4. Catalyst component according to claim 1 characterized by that the solid catalyst component comprises a titanium compound containing at least a Ti-halogen bond and an electron donor compound deposited on the magnesium halide in active form. A prepolymerized catalyst component according to any one of claims 1 to 4, characterized in that the solid catalyst component is obtained by reacting a titanium compound of the formula Ti (OR) _n - _y X _y / where n is the valence of titanium and y is a number from 1 to n, s. an adduct of formula MgCl ₂ .pROH, where p is a number between 0, 1 and 6 and R is a hydrocarbon radical containing 1 to 18 carbon atoms. • φ # # # # # # # # # # # # # Φ φ φ φ φ φ φ φ φ φ φ φ # φ φ Φφφφ 6. A catalyst component as claimed in any one of the preceding claims wherein the titanium compound. 7. The catalyst component of claim 1 wherein the internal electron donor compound is selected from the group consisting of esters, ethers, amines, and ketones. from claims 1 to 5 titanium is chloride The catalyst component of claim 6, wherein said internal electron donor compound is an alkyl, cycloalkyl or monocarboxylic acid group, wherein said cycloalkyl or aryl group contains 1 carbon. is selected from aryl alkyl esters of up to 18 atoms The catalyst component of claim 6, wherein the internal electron donor compound is selected from the group consisting of ethyl benzoate and diisopropyl phthalate. 10. The catalyst component of claim 6 wherein the internal electron donor compound is selected from the group consisting of 1,3-diethers of Formula I: wherein ^{R ',} R ^11, R ^111, R ^IV, R ^V and R ^VI are equal or each other and are hydrogen or hydrocarbon radicals having 1 to 18 carbon atoms and R ^vu and R ^VUI are the same or each other and have the same as R ^T -R ^VI , except that they cannot be hydrogen; one or more of the R ^I -R ^VIIX may be joined together to form a ring. • 0 0 · ♦ 0 • 0 0 0 0 0 ♦ 0 4 45 4 A catalyst component as claimed in claim 9, wherein the groups R ^VI1 and R ^VI11 are selected from the group consisting of alkyl radicals containing one to four carbon atoms and the groups R ¹¹¹ and R ^IV are joined to form a ring. A process for preparing a prepolymerized catalyst component according to any one of claims 1 to 11, characterized in that it is carried out by prepolymerizing ethylene in the presence of a solid catalyst component comprising a magnesium, titanium, halogen and electron donor compound and an alkyl aluminum compound. 13. The method of claim 12 wherein the alkyl aluminum compound is selected from the group consisting of trialkyl aluminum compounds and alkyl aluminum halides. 14. The process of claim 13 wherein the alkyl aluminum compound is selected from the group consisting of triethyl aluminum, triisobutyl aluminum, tri-n-butyl aluminum, tri-n-hexyl aluminum, trinoctyl aluminum. Process according to any one of claims 12 to 14, characterized in that the prepolymerization is carried out using an amount of an alkyl-aluminum compound such that the Al / Ti molar ratio is from 0.0001 to 50. The method of claim 15, wherein the Al / Ti molar ratio is from 0.001 to 10. 17. The process of claim 16 wherein the Al / Ti molar ratio is from 0.01 to 1. 18. The process of claim 12 wherein the prepolymerization is carried out in a liquid diluent selected from the group consisting of liquid hydrocarbons. ** · · 9 9 9 9 a 9 a 9 a 9 9 9 9 9 9 9 9 9 9 ea ea ea 9 9 9 9 9 9 99 99 An olefin polymerization catalyst of the formula CH ₂ = CHR, wherein R is a hydrogen atom or a C 1 -C 12 hydrocarbon radical, characterized in that it comprises a prepolymerized catalyst component according to any one of claims 1 to 11, an alkyl aluminum compound and optionally one or more electron donor compounds. 20. The catalyst of claim 19 wherein the internal and external electron donor compound is a benzoic acid derivative. 21. The catalyst of claim 20 wherein the external electron donor is a mixture of a benzoic acid derivative and a silicon compound. 22. The catalyst of claim 20 wherein the internal electron donor is ethylbenzoate and the external electron donor is p-ethoxyethylbenzoate. 23. The catalyst of claim 21 wherein the internal electron donor is ethylbenzoate and the external electron donor comprises a mixture of p-ethoxyethylbenzoate and dicyclopentyldimethoxysilane. A process for the polymerization of olefins of the formula CH ₂ = CHR, wherein R is a hydrogen atom or a hydrocarbon radical containing 1 to 12 carbon atoms, characterized in that it is carried out in the presence of a catalyst comprising (A) a prepolymerized catalyst component according to one of claims 1 to 11 ; (B) an alkyl-aluminum compound and optionally (C) an external electron donor. The process according to claim 24, characterized in that the components (A), (Β) or (C) forming the catalyst are precontacted prior to their addition to the polymerization reactor. * 9 • 9 ΦΦ ♦ 9 9 9 9 ΦΦΦΦ • · ···· • ΦΦ Φ 9 9 · Φ Φ Φ 9 9 9 • Φ Φ · ΦΦ 99 ® Φ Φ Φ Φ « ΦΦ ΦΦ 26. The process of claim 24 wherein the olefin is propylene. 27. The method of claim 24 wherein the external electron donor compound is selected from the group consisting of silicon compounds, ethers, esters, amines, heterocyclic compounds, ketones, and 1,3-diethers of Formula I. 28. The method of claim 27 wherein the compound used as the external electron donor is selected from the group consisting of silicon compounds of formula R _a ⁵ R b ⁶ Si (OR ⁷⁾ 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; R ⁵ , R ⁶ and R ⁷ are selected from the group consisting of an alkyl, cycloalkyl or aryl radical of 1 to 18 carbon atoms optionally containing heteroatoms. The method of claim 21 wherein a is 1, b is 1, c is 2, at least one of R ⁵ and R ⁶ is selected from the group consisting of a branched alkyl group, a cycloalkyl group or an aryl group containing 3 to 10 and R 'is an alkyl group having 1 to 10 carbon atoms.