FI104080B - Stereospecific catalyst system for olefin polymerization and multiphase polymerization processes employing this system - Google Patents

Description

104080

Stereospecific catalytic system for the polymerization of olefins and multiphase polymerization processes employing this system Fol olefin polymerization avsett stereospecific catalysis system and flerstegsprocesser color detta system används 5

The present invention relates to a catalyst system for olefin polymerization comprising at least one titanium compound based procatalyst, an organoaluminum cocatalyst and at least two silane compounds, at least one of which has a high stereospecificity but a low stereospecificity and at least one has a correspondingly low hydrogen sensitivity. The invention also relates to multi-step polymerization processes using this catalyst system.

The olefins are generally polymerized using the Ziegler-Natta catalyst system which contains, as essential components, a procatalyst and a cocatalyst. The procatalyst is composed of a transition metal compound of subgroups 4-8 of the Periodic Table of the Elements (Hubbard, IUPAC 1970). The cocatalyst is an organic compound of a metal belonging to major groups 1 to 3 of the aforementioned periodic rigid system of elements.

As the transition metal, compounds of titanium, zirconium or vanadium, preferably titanium compounds, are usually used, and in particular titanium has been found to be the preferred transition metal. The compounds are usually halides or oxyhalides, or alternatively j '·,. organic compounds, usually alkoxides, alcoholates or haloalkoxides. Others: Organic compounds are rarer, but they are also presented. The transition metal compound can be represented by the following general formula: (M): (RO) nR "mMXpn.m (1) where M is the transition metal of subgroups 4-8, preferably Ti, Zr or V, wherein R 'and R "• 30 30 are en or the same organic group having a predominantly carbon atom containing from 1 to 20, I t ′ M is a transition metal and X is halogen, preferably chlorine. It is preferred and common for R 'and R "to be solely a hydrocarbon group, preferably an alkyl group. P is an oxidation number of the metal M, usually p is 4 or 5. n and m are integers from 0 to p.

2 104080

Most preferred are titanium alkoxides, halides or haloalkoxides, especially if the halogen is chlorine. Suitable compounds are thus Ti-tetramethoxide, -tetraethoxide, -tetra-propoxides, -tetrabutoxides and the like, further corresponding Ti-alkoxide halides in which 1-3 alkoxide groups are replaced by halogen, especially chlorine, and Ti-halides, of which in particular TiBr4 and TiCl4. The most common compound is TiCL. Naturally, two or more transition metal compounds can be used as different mixtures.

The cocatalyst, in its most common form, is an organic compound of the metal of main groups 1-3. Usually it is an aluminum compound, although for example compounds of boron, zinc and alkali metals have been used. The aluminum compound can be defined by the following formula (2): wherein R is an organic hydrocarbon group, preferably C 1 -C 20 alkyl, X is halogen and n is an integer from 1 to 3. Different cocatalysts can be used in several different mixtures at the same time.

The catalyst system further comprises components that improve and modify the catalytic properties. The procatalyst may be placed on a more or less inert support, whereby the procatalyst may become solid even if the transition metal compound as such is not solid. The procatalyst may be complexed with a stereospecific catalyst system. electron donating, so-called syphilis and / or activity enhancer internal donor group. ' ': Distillate. An additive may be used in the preparation of the procatalyst, which may be a soluble or additive additive, some of which may be complexed with the procatalyst composition. This compound can also act as an electron donor. Also, a cocatalyst, which is generally only fed to the polymerization reaction separately from the procatalyst composition, can also be fed with so-called. electron donor, which is intended primarily to improve the stereospecificity of the end product. This is when we talk about an external donor.

In order to obtain a heterogeneous solid procatalyst composition, a separate: V: carrier compound is required if the procatalyst transition metal compound is not itself. This is the case with the transition metal compounds described above. The carrier can be a variety of 3,104,080 inorganic or organic solid compounds. Common are mixtures of silicon, aluminum, titanium, magnesium, chromium, thorium or zirconium or their oxides, salts of various inorganic acids, for example salts of the above metals or alkaline earth or earth metals such as Mg silicate, Ca silicate, chloride , sulfate, etc. (see e.g.

5 FI 85 710). Magnesium compounds, for example alkoxides, hydroxides, hydroxy halides, and halides of which the latter, in particular magnesium chloride, is a very important carrier of procatalyst compounds, have proved to be important carriers. The carriers are characterized by various treatments prior to use, they can be heat-treated, for example, by calcination, and can be chemically removed from so-called. surface hydroxyl groups, they may be mechanically treated, for example, milled in a ball mill or a jet mill (see, for example, FI 83 330). An important group of carriers are Mg halides, especially MgCl2, which can be preferably complexed with alcohols, whereby this complexed carrier can be converted into a morphologically advantageous form by crystallization and / or solidification from the emulsion by spray drying or molten spray crystallization (see e.g. FI 15 80 055). Organic carriers are, above all, different polymers, either as such or modified. Such carriers include various polyolefins (polymers of ethylene, propylene and other olefins) and various polymers of aromatic olefinic compounds (PS, ABS, etc.).

20 If the polymerizable olefin monomers can settle at different spaced positions upon attachment to the resulting polymer molecule, this alignment is required to control: '. in general, a specific compound that complexes with a procatalyst such that the new monomer unit attached to the polymer chain can predominantly position only at a particular position.

* «:" ': Because of their mode of attachment to the procatalyst, such compounds are called "electron donors," or "donors." The donor may also have effects other than the aforementioned stereospecificity, for example, it may improve the activity of the catalyst by accelerating the incorporation of a new mono-mer unit into the polymer molecule. A donor that complexes with a procatalyst during its preparation is called an intimal or internal donor. These include many alcohols, ketones, aldehydes, carboxylic acids, derivatives of carboxylic acids. Esters, anhydrides, halides, and various ethers, silanes, siloxanes,: V, etc. Several donors can be used simultaneously. : for example, mono- and diesters of aromatic carboxylic acids and aliphatic alcohols, • 104080 4 liters, the simultaneous use of which makes possible the transesterification of the donor compound (see EN 86 866).

Only the compound controlling the stereospecificity introduced into the polymerization reactor with the cocatalyst 5 is termed an extrema or external donor. They are often the same compounds as internal donors, but it is often preferable that the external donor in the same polymerization reaction is not the same compound as the internal donor, since different properties of different compounds can be exploited, especially if different donor combinations are enhanced and synergistic. interactions. Finding the optimal synergies is the goal of selecting different donors. Preferred external donors include, for example, various silane and ether compounds, especially alkoxysilanes (see, e.g., EP 231 878 and EP 261 961).

EP 385 765 and EP 601 496 teach that, if desired, to broaden the molecular weight distribution of a product while maintaining a high process yield, two alkoxysilane compounds can be used: [I] R 2 Si (OR 2) 2 wherein R 1 is alkyl, cycloalkyl or aryl wherein the carbon atom adjacent to the Si atom is a secondary or tertiary carbon atom and R2 is a hydrocarbon group, and pi] R1 "Si (OR2) 4.n wherein n is an integer from 0 <n <4, R2 is a hydrocarbon group, and when n = 2, one R 1-20 group is an alkyl or alkenyl group having a carbon atom adjacent to the Si atom and a primary carbon atom and the other R 1 group being an arylalkyl group wherein the carbon atom adjacent to the Si atom is a primary atom, and when n is 0 <n <2 or 2 <n <4 satisfying · 'j1: integer, R1 is an alkyl or alkenyl group In the following examples, · ·: a mixture of silane [I] with dicyclopentyldimethoxysilane and silane 25 [II] was used in particular. is propyl or vinyltriethoxysilane.

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• • I

: Pat. hak. WO 95/21303 teaches the use of tetraethoxysilane and dicyclopentyldimethoxysilane together as external donors to provide a relatively high melt flow rate! \ I .; and a reasonably wide molecular weight distribution.

«« · • · · V '30 | : A: When polymerizing a single polymer molecule, there may be a few monomer units up to millions of units. Typically a commercially available solid; · · · ·

MM

104080 5 polyolefin has a molecular weight of 10,000-1,000,000 g / mol. If the degree of polymerization is lower, the product is a soft and plastic wax or paste, even a viscous liquid, which is used in special cases. More than one million higher degrees of polymerization are difficult to achieve and, moreover, often the polymer is too hard for most applications or the processing of the polymer is difficult. Thus, the regulation of the molecular weight of the polymer becomes important and can be done by so-called. with chain adjusters. Usually, the chain regulator added to the polymerization reaction is hydrogen and, when used, does not leave any foreign molecular group in the molecule. If the molecular weight of the polymer formed can be controlled by the amount of hydrogen added, the polymerization catalyst is said to be hydrogen sensitive. Different catalyst systems have different sensitivity to hydrogen, requiring different amounts of hydrogen to produce the same melt flow. On the other hand, the addition of hydrogen increases the polymerization activity of the catalyst.

The polymerization can be carried out in the gas phase, whereby either the gaseous monomer or the inert gas or a mixture thereof is introduced into the reactor so that the gas to be conducted keeps the polymer formed as particles on the surface of which the polymer molecules grow. The reaction temperature is so high that one or more of the liquid monomers under normal conditions evaporate. During the continuous polymerization process, polymer particles are continuously removed from the reactor, and additional monomer or monomer mixture is continuously fed. Removal and feeding can also be intermittent. The layer of polymer particles, which is preferably in a fluidized state, can be mixed by mechanical mixing. A large number of yesterday's mixers and mixing systems are available.

Y; Gaseous phase polymerization is often carried out in a circulating fluidized bed reactor having: ** [: a fluidized bed of solid particles maintained by a gaseous medium with an upward flow of ·: / ·· 25 fluidized bed. The turbulent fluidized bed may be formed by a wide variety of inert solid particles of inorganic and organic compounds.

»» ·. If a liquid phase polymerization is to be used, a liquid medium, which may be one or more monomers * · · ·, must be present at the polymerization temperature. v (which may be referred to as bulk polymerization), a separate solvent or diluent, 1 ... '· which dissolves or slides the monomer and / or the polymer. If the slurry can be called * 104080 6 suspension or slurry, the corresponding polymerization process is referred to. The medium is then a hydrocarbon solvent, especially alkanes and cycloalkanes such as propane, butane, isobutane, pentane, hexane, heptane, cyclohexane, etc. are common. The formation and preservation of the slurry can be enhanced by mechanical mixing; suspensions and colloidal preservatives. The polymerization reactor can be a conventional mixing tank reactor with many different types or features. loop-type, or annular tubular reactor, in which the polymer slurry is circulated through various feed, discharge and mixing arrangements. When polymerization is carried out in a medium while producing a polymer having a high MFR, poorly hydrogen-sensitive catalyst systems may have the problem of increasing the amount of hydrogen required since only a certain maximum concentration of hydrogen can be dissolved in the medium.

The polymerization may be carried out in a multi-step process in which two or more polymerization reactors are connected in series. The reactors may be either gas or liquid phase reactors or combinations thereof. Preferably a combination of loop type and gas phase reactors is used.

The advantage of multi-step processes is a narrower residence time distribution, whereby a more uniform distribution of particle size and polymer composition is achieved. Another goal of multi-stage processes is to be able to run reactors under different polymerization conditions, which provides new opportunities for modifying product properties. For example, using different concentrations of hydrogen in each step results in a broader molecular weight distribution (MWD) for the final: Y product. The polymerization can be carried out: in at least two reactors, and then a higher hydrogen sensitivity donor may be fed first, and then only the inferior, even very poorer, feed; man hydrogen donor to one or more of the other reactors.

• · · i:

One method of adjusting end product properties in multi-step processes 9 is to supply different external donors to each reactor step. Such a method is described in EP 601 496 and WO 95/21303. For example, the MWD mole-: Y: weight distribution can be broadened by adding a highly hydrogen-sensitive external <· · 1 ... * donor to the first reactor, and then significantly less hydrogen-sensitive external »« * «a ·; ·: 104080 7 donor to the second reactor in fact, the aforementioned donor mix. In conventional methods, when external hydrogen-sensitive donors are used, further poor isotacticity of the final product is a further consequence of propylene homopolymer production.

5

The molecular weight distribution (MWD) typically remains relatively narrow in the production of polyolefins using high yield Ziegler-Natta catalyst systems consisting of a titanium compound-containing procatalyst and an organoaluminum cocatalyst. Using the above catalyst system in a continuous polymerization reaction 10, the polypropylene typically gives a polydispersity (Mw / Mn) of about 4-5.

By increasing the MWD molecular weight distribution, for example by increasing the polydispersity to 6-8, the stiffness of the polypropylene can be increased. At the same time, however, its impact strength is reduced. The width of the MWD affects not only the mechanical properties but also the workability of the polymer. By providing greater rigidity and improved workability in the production process using compound-extrusion technology, the yield of the final products can be significantly increased, while at least maintaining the rigidity of the product.

The MWD width of the molecular weight distribution is most often measured by gel permeation chromatography (GPC), which gives polydispersity (Mw / Mn). Another fairly commonly used method is based on the effect of MWD on the theological properties of the polymer. Measuring the shear thinning or elasticity of molten polymer samples, for example as a Shear Thinning Index (SHI1) or an Elastic :: index, provides valuable information on the MWD width. Wider MWD generally increases the elasticity and shear thinning of the molten polymer at the same time.

l '\ l 25 • · »_«. • .s The most widely used method in the industry for widening the MWD of the molecular weight distribution of polyolefins in continuous polymerization reactors is to prepare the polymer in an apparatus of two series-connected reactors, *. whereby the polymer fractions produced in each reactor should have distinct molecular weights. However, it is not always possible or practical to connect two reactors to Saija to expand MWD. According to patent application EP 452916, the molecular weight distribution MWD of polypropylene can be extended by using a? 8104080 of a particular type of alkoxysilane as an external donor. As mentioned above, in EP 385765, the MWD of a polypropylene is made wider by using a catalyst system having two different alkoxysilanes in a 1: 1 ratio as an external donor.

It has now surprisingly been found that when polymerizing olefins using a Ziegler-Natta catalyst system having a titanium compound containing procatalyst and an organoaluminum cocatalyst, addition of monomers, procatalyst and cocatalyst, to the resulting polymer, may be added to the polymerization reaction to improve the resulting polymer. The mixture containing these compounds has A) at least one silane compound having low hydrogen sensitivity but very high stereospecificity, having the structural formula (3):

Ri (MeO) 2 Si (3) wherein R 'is an aliphatic cyclic or branched hydrocarbon group having at least four carbon atoms and Me is a methyl group, and B) at least one silane compound having very high hydrogen sensitivity but possibly lower stereospecificity than compound A) (4): R "(EtO) 3 Si (4)". Wherein R "is either a branched or cyclic alkyl group containing at least 3 carbon atoms, a linear alkyl group containing at least 6 carbon atoms or an aryl group having 6 to 12 carbon atoms and Et ethyl group, and the melt flow ratio of the polyolefins produced by this catalyst system is: ≤ 1.0 MFR (B) / MFR (A) ≤ 30 V 4 · · · f where MFR (B ) and MFR (A) are melt flow rates for polyolefins measured according to ISO 1133,

• I

: ** prepared with the aid of a catalyst system containing external donor B or external donor A, as appropriate, 1 ii 104080 9, and the isotactic ratios of the polyolefins thus prepared are: XS (B) / XS (A) <4, preferably <25 where XS (B) and XS (A) are isotacticities (determined by solubility in xylene at 25 ° C) of polyolefin prepared by a catalyst system containing external donor B or external donor A, respectively. The molar ratio of donor B to A may be in the range of 0.5 to 0.95.

10

The solubility of the product in xylene is determined as follows: A sample (about 2 g) of propylene as a homo- or copolymer is circulated for 1 hour at 135 ° C in a two-neck reflux distillation apparatus containing 250 ml of xylene with continuous stirring under nitrogen. The mixture is then allowed to cool to 25 ° C, the insoluble polymer separating as a precipitate is filtered off. The filtrate is evaporated under nitrogen and dried under vacuum at 90 ° C, after which the cooled residue is weighed. XS is calculated from the formula: XS = 100% x B x D / (A x C) 20 where A is the mass of the sample (g), B is the volume of xylene (ml), C is the volume of filtrate (ml) and D is the evaporation residue (g) .

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• V

In addition to serving as the stereospecific regulatory compound, this donor combination makes the polymerization reaction highly hydrogen-sensitive, i.e., the molecular weight of the resulting polymer *, ·, * can be better controlled by the amount of hydrogen added to the reaction than before and especially to produce a polymer having low molecular weight or high digestible MFR.

f • «·> i t; ti · * 1 * '.' A very advantageous feature of the present invention is the high-MFR, 1! the unexpectedly high isotacticity of the propylene homopolymer to be achieved

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specifically when using the donor combination of the invention in the polymerization reaction.

»« «F * * 104080 10

It is likely that the branched, cyclic or long linear structure of the hydrocarbon group R "in donor 6 will give this very advantageous result.

The catalyst system of the invention can be used in multi-step polymerization processes. The donor mixture as such may be fed to the first reaction step or alternatively the higher hydrogen sensitivity donor B may be fed to the first reactor and the lower hydrogen sensitive donor A will then be fed to the second reactor, which in practice means that the donor mixture of the invention is used only in the second step.

10

For the purposes of this invention, olefin means a hydrocarbon contained in one or more carbon-carbon double bonds. Such olefins are in particular various alkenes, for example linear monoalkenes such as ethylene, propylene, butenes, pentenes, etc. They may also be hydrocarbon-branched compounds, a simple example of which is 4-methyl-1-pentene.

In the polymerization of olefins, one or more of the above compounds may be present in the reaction. In particular, homo- and copolymers of propylene are important.

Almost all asymmetric unsaturated hydrocarbons (out of the usual mono-olefins only ethylene is symmetric) are spatially isomeric polymer: Y: molecules. For mono-olefins, stereospecificity is defined as the tacticity of the polymer such that if the new units of the growing polymer chain are always aligned in the same double-bond, it is an isotactic polymer, and if the new V .. 25 units are always opposite to the previous unit, it is syndiotactic. • I »V · polymer, and if units are randomly positioned anyway, it is an atactic polymer. Of these, any shape may be most suitable for a particular application, i.e., the properties of the polymer will also depend on tact. For conventional purposes, the isotactic shape is most desirable. It crystallizes most strongly, is mechanically • and v 30 most durable and non-sticky. If desired, to reduce the crystallinity of the polypropylene, the propylene may be copolymerized with ethylene, whereby the resulting polymer can be used in applications where transparency, good impact resistance or sealability are required.

Applications for both gay and copolymers include films, sheets, tubes and various injection molded parts for a variety of applications, particularly in the automotive industry and in households.

To illustrate the invention, reference will now be made to the invention and comparative examples.

10

Example 1

Propylene was polymerized for 1 hour at 70 ° C in the propylene liquid phase using a high yield catalyst.

15

Weighed 20 mg of titanium catalyst as carrier MgCl 2 (prepared according to FI 86 866) with a titanium content of 2.5% by weight. A mixture of triethoxyisobutylsilane (IBTEO) and dicyclopentyldimethoxysilane (DCPDMS) in molar ratio IBTEO / DCPDMS = 95/5 was used as the external donor. Cocalytes (triethylaluminum 20 = TEA) and external donors were so fed, the calculated molar ratios were Al / Ti = 250; and Al / donor = 10. TEA was initially mixed with about 35 mL of dried heptane and an external donor was then added to this solution. The solution was allowed to react for 5 minutes with stirring. Half of the solution was fed to a volume of 5 dm 3 of the polymerization autoclave (at a temperature of about 18 ° C) and the other half of the solution was mixed with catalyst 25. After about 10 minutes of exposure, the catalyst · t · · V ′ thus suspended was also introduced into the polymerization autoclave. 220 mmol of hydrogen from a pressure vessel and 1400 g of liquid propylene were also fed in the same volume. The temperature was slowly raised to 70 ° C over a period of 20 minutes. Propylene was polymerized for 60 minutes at 70 ° C.

After polymerization, MFR, isotacticity by both the IR method, and ≤ 30% solubility in xylene (XS) at 25 ° C and polymerization activity were determined. The results of the polymerization are shown in Table 1.

f f · · 1 · · 12 104080

Example 2

The polymer was prepared as in Example 1 except that the molar ratio was IBTEO / DCPDMS = 90/10. The results of the polymerization are shown in Table 1.

5

Example 3

The polymer was prepared as in Example 1 except that the molar ratio was IBTEO / DCPDMS = 80/20. The results of the polymerization are shown in Table 1.

10

Example 4

The polymer was prepared as in Example 1 except that the molar ratio was IBTEO / DCPDMS = 50/50. The results of the polymerization are shown in Table 1.

15

Example 5

The polymer was prepared as in Example 1 except that the combination of triethoxyoctylsilane (OCTEO) and dicyclopentyldimethoxysilane (DCPDMS) in a 50/50 molar ratio was used as the external donor. The results of the polymerization are shown in Table 1.

; :; Example 6 The polymer was prepared as in Example 5 except that the molar ratio was 25 OCTEO / DCPDMS = 90/10. The results of the polymerization are shown in Table 1.

• · · • · · · ·

Example 7 Polymerization was carried out using a donor mixture, the donors being fed in two steps.

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104080 13

The polymerization was carried out as in Example 1 except that in the first step triethoxyisobutylsilane (IBTEO) was used as the external donor and after half of the feedstock was polymerized, dicyclopentyldimethoxysilane (DCPDMS) diluted with pentane was introduced into the polymerization autoclave. Hydrogen was fed at 500 mmol instead of 220 mmol. The polymerization results are shown below.

Donor Ratio Hydrogen Activity MFR XS MWD

[mol%% / mol%] feed [kg PP / g cat.] [mmol] IB-TEO / DCPDMS = 5- 500 28.6 95 3.4 5.5 10 0/50 _

Example 8 The polymerization was carried out in a continuous biphasic reaction using a donor mixture.

The propylene copolymers were fed to a test equipment formed by a series-connected loop-type reactor and a gas-phase fluidized bed reactor. The catalyst, cocatalyst and donor were fed to the loop reactor. The reaction medium used in the loop reactor was evaporated before the active catalyst containing the solid polymer was subsequently fed to the 20 gas phase reactors. The polymerization used a prepolymerized Ti catalyst as the support

MgCl 2 (prepared according to FI 86 866). The cocatalyst was triethylaluminium (TEA) and the external donor was a mixture of IBTEO and DCPDMS in a 70/30 molar ratio.

;,; The Al / Ti molar ratio was 150 and the Al / Donor molar ratio was 5. In the first step (loop reactor), a high molecular weight propylene homopolymer was prepared and the polymer was continued in the second step (gas phase reactor) where a low i · · • a molecular weight propylene homopolymer. The polymerization temperature in both steps was 70 ° C. The ratio of production volumes between the first and second stages was 45/55. The MFR was adjusted in both reactors to change the hydrogen supply • · · • · · rack. The MFR of the final product was 8.1 g / 10 min. The XS of the final product was 2.3 wt%.

30 l ":« »» IMI • · 104080 14

Comparative Example 1

The polymer was prepared as in Example 1 except that the isobutyltrimethoxysilane (IBTMO) alone and not the IBTEO / DCPDMS mixture was the external donor. Hydrogen was fed at 5 70 mmol instead of 220 mmol. The results of the polymerization are shown in Table 2.

Comparative Example 2

The polymer was prepared as in Comparative Example 1 except that the external donor was triethoxyisobutylsilane (IBTEO) and not IBTMO. The results of the polymerization are shown in Table 2.

Comparative Example 3 The polymer was prepared as in Comparative Example 1 except that the external donor was triethoxyoctylsilane (OCTEO) and not IBTMO. The results of the polymerization are shown in Table 2.

Comparative Example 4 20

The polymer was prepared as in Comparative Example 1 except that the external donor was dicyclopentyldimethoxysilane (DCPDMS) and not IBTMO. The results of the polymerisation are shown in Table 2.

25 Comparative Example 5 ιί:

The polymerization was carried out in a continuous reaction using one external donor. The polymer · · · V · * 'was prepared as in Example 8 except that the external donor was only dicyclo ♦ · · * · * pentyldimethoxysilane (DCPDMS) and the hydrogen supply to both reactors was as before. 30: 8. The final product had an MFR of 3.6 g / 10 min. The XS of the final product was 2.3 wt%.

<<· A - i ·: ··; ] 15 104080

Table 1. Polymerization results using mixtures of silane compounds as external donors.

Eg Donor ratio Hydrogen Activity MFR Π XS MWD

[mol / mol-%] feed [kg / g cat.] (F- [mmol] TIR) [%] _____ [%] ___ 5 1 IBTEO / D 220 30.3 19.4 - 3.1 __95 / 5 ________ 2 IBTEO / D 220 28.7 13.6 98.6 2.9 6.1 __90 / 10 _______ 3 IBTEO / D 220 27.5 10.7 98.6 2.2 5.9 __80 / 20_ ____ 4 IBTEO / D 220 31.7 6.8 - 2.2 __50 / 50 _______ 5 OCTEO / D 220 32.7 7.5 - 2.1 __50 / 50 _______ 10 6 OCTEO / D 220 29.1 13.3 - 2.9 90 / 10 __

Table 2. Polymerization Results Using Single Silane Compounds Mixtures 15 as External Donors.

Benchmark Donor Activity MFR II XS MWD

', e.g. [kg / g cat.] (FTIR). [%] [%], t I 1 —— "1" "1 1" 1 IBTMO 20.4 6.1 92.3 • · '"1 1 1' 20 2 IBTEO 20.8 15.9 95.2 4.3 6 • · »1 - - -" ~ ——— ^ "" "- 1 11 - '3 OCTEO 19.2 24.5 93.6 5.4 5.2t: ----- - 4 DCPDMS 26.6 1.4 - 2.2 i:: - —J - • »· • · • · t:

Claims (12)

Catalyst system for the polymerization of olefins, comprising a titanium compound-based procatalyst and an organoaluminum cocatalyst and at least two external electron donors, characterized in that said electron donors consist of a mixture of at least two silane compounds A) and B), wherein: and has the structural formula (3): R; (MeO) 2 Si (3) wherein R 'is an aliphatic cyclic or branched hydrocarbon group having at least four carbon atoms and Me is a methyl group, and B) has a very high hydrogen sensitivity and has the structural formula (4): R "(EtO) 3 Si (4) wherein R" is either a branched or cyclic alkyl group containing at least 3 carbon atoms, a linear alkyl group containing at least 6 carbon atoms or an aryl group containing 6 to 12 carbon atoms and a ethyl olefin prepared by this catalyst system: , 0 <MFR (B) / MFR (A) <30 I II: '; '; wherein MFR (B) and MFR (A) are melt flows for the polyolefins prepared by a catalyst system containing external donor B: *** or external donor A, respectively, and the polyolefins thus prepared have an isotactic ratio: • I * «· · · · · O : XS (B) / XS (A) <4, preferably <2 • ·: * · · where XS (B) and XS (A) are isotacticities as determined by solubility in xylene at 25 ° C. for phials prepared with external donor B or external donor A, respectively. ·; catalyst system. f · »« • S '; 18 i VI Ί u 4 O 8 O Catalyst system according to claim 1, characterized in that R 'is a cycloalkyl group. Catalyst system according to claim 2, characterized in that R 'is a cyclo-5-pentyl group. Catalyst system according to claim 1, characterized in that R "is an isobutyl, n-octyl or phenyl group. Catalyst system according to one of Claims 1 to 4, characterized in that the procatalyst contains a magnesium dihalide in active form on which is deposited a titanium halide or oxalide, preferably TiCl 4, and an electron donor compound. Catalyst system according to any one of claims 1 to 5, characterized in that the above organoaluminum compound is trialkylaluminium, preferably triethylaluminum or triisobutylaluminum. Catalyst system according to one of Claims 1 to 6, characterized in that the molar ratio of the above compounds B) and A) is 0.5-0.95. 20 Use of a catalyst system according to any one of claims 1 to 7 for the polymerization of propylene, alone or with at least one other different α-olefin and / or ethylene. * * «<* • · · *. * ·: 9. Multi-step process for the polymerization of olefins in the presence of a« 25 catalyst system according to any one of claims 1-7. • · ««:: A process according to claim 9, characterized in that the propylene is polymerized stepwise in at least one loop reactor and in at least one gas phase reactor, preferably a fluidized bed reactor. 30 i: «· · •« · t „104080 Process according to claim 10, characterized in that the polymerization is carried out in at least two reactors and that the donor of formula (4) is fed to the first polymerization reactor and that the donor of formula (3) is supplied to one or more of the following reactors. The process of claim 10, characterized in that the donor fed to the first polymerization reactor is isobutyltriethoxysilane and that the donor fed to the second polymerization reactor is dicyclopentyldimethoxysilane. ('I II • · · • Ψ * * · • · f *::: II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II 4 4 II II II II II II II II II II II II II II II II II II II II II II II II II II II ft · I · | i: • «• · ·« «I *» tn «m 104080