WO2003014167A1

WO2003014167A1 - Polymerization process using a specific organosilane as external donor

Info

Publication number: WO2003014167A1
Application number: PCT/NL2002/000531
Authority: WO
Inventors: Geerling Willem Wijsman; Lieven K. Van Looveren; Henricus Johannes Arts
Original assignee: Dsm N.V.; Bp Corporation North America Inc.
Priority date: 2001-08-10
Filing date: 2002-08-06
Publication date: 2003-02-20

Abstract

The invention deals with a process for the polymerization of one or more α-olefins in the presence of a specific catalyst system. The gist is in using a specific organosilane compound as an external electron donor; the silicon is embedded in a ring system, wherein only one hetero-atom is present.

Description

POLYMERIZATION PROCESS USING A SPECIFIC ORGANOSILANE AS EXTERNAL DONOR

The present invention relates to a process for the polymerization of one or more α-olefins in the presence of a catalyst system comprising a transition metal compound, an organo-metal compound as co-catalyst, and, as an external electron donor, at least one organosilane compound in which the silicon atom has at least one hetero atom containing substituent. Such a process is known from EP-A-250,229. In this publication the polymerization of one ore more α-olefins is described under the use of specific aliphatic organosilane compounds as external electron donors to modify the catalytic performance of the catalyst system.

The disadvantage of the use of such an organosilane compound is the fact that the control of the melt flow rate (MFR) of the polyolef in prepared in the polymerization process necessitates a high consumption of hydrogen. This is especially the case for obtaining products with a high MFR (above 10 dg/min).

The present invention offers an improved process for the polymerization of one ore more α-olefins in which the above disadvantage is reduced.

The process according to the present invention is characterized in that the organosilane compound has the formula:

(R₄)s

in which R^ R₂ and R₃ are hydrocarbon-based substituents, R₄ is a substituent to Q_t and s = 0 -3, depending on the valency state of Q_L and Q_T (embedded in a ring with the silicon atom and R^ is a hetero-atom, selected from the group of nitrogen, phosphorus, oxygen and sulphur, and one, and only one hetero-atom Q is present in the ring and directly attached to the silicon-atom, and in which 1 ,1- dimethoxy-3,4-benzo-1 ,2 siloxacyclohexane is disclaimed. The elements of the catalyst system will be described in more detail below.

a) Transition metal compound: The transition metal in this compound has been chosen from groups 4-6 of the Periodic Table of the Elements (Newest IUPAC notation); more preferably, the transition metal has been chosen from group 4; the greatest preference is given to titanium (Ti) as transition metal.

Although different transition metals are applicable, the following is focused on the most preferred one: titanium. Titanium containing compounds useful in the present invention as catalyst generally are supported on hydrocarbon-insoluble, magnesium or silicon containing supports, generally in combination with an internal electron donor compound. Such supported titanium- containing α-olefin polymerization catalyst compound is formed typically by reacting a titanium (IV) compound, an organic internal electron donor compound and a magnesium or silicon containing support. Optionally, such supported titanium-containing reaction product may be further treated or modified with an additional electron donor or Lewis acid species.

Suitable magnesium-containing supports include magnesium halides; a reaction product of a magnesium halide such as magnesium chloride or magnesium bromide with an organic compound, such as an alcohol or an organic acid ester, or with an organometallic compound of metals of groups 1-3; magnesium alcoholates; or magnesium alkyls.

One possible magnesium-containing support, described in U.S. Patent 4,612,299, (incorporated by reference herein) is based on at least one magnesium carboxylate prepared in a reaction between a hydrocarbyl magnesium (halide) compound with carbon dioxide.

Another possible transition metal compound is described in US patent 4,581,342. The compound described therein is prepared by complexing a magnesium alkyl composition with a specific class of hindered aromatic esters such as ethyl 2,6-dimethylbenzoate followed by reaction with a compatible precipitation agent such as silicon tetrachloride and a suitable titanium(IV) compound in combination with an organic internal electron donor compound in a suitable diluent. The possible solid catalyst components listed above only are illustrative of many possible solid, magnesium-containing, titanium halide-based, hydrocarbon-insoluble catalyst compounds useful in the process of the present invention and known to the art. This invention is not limited to a specific supported catalyst compound.

Titanium (IV) compounds useful in preparing the solid, titanium- containing catalyst compound of invention preferably are titanium halides and haloalcoholates having 1 to about 20 carbon atoms per alcoholate group. Mixtures of titanium compounds can be employed if desired. Preferred titanium compounds are the halides and haloalcoholates having 1 to about 8 carbon atoms per alcoholate group. Examples of such compounds include TiCI₄, TiBr₄, Ti(OCH₃)CI₃, Ti(OC₂H₅)CI₃, Ti(OC₄H₉)CI₃, Ti(OC₆H₅)CI₃, Ti(OC_βH₁₃)Br₃, Ti(OC₈H₁₇)CI₃, Ti(OCH₃)₂Br₂, Ti(OC₂H₅)₂CI₂, Ti(OC₆H₁₃)₂CI₂, Ti(OC₈H₁₇)₂Br₂, Ti(OCH₃)₃Br, Ti(OC₂H₅)₃CI, Ti(OC₄H₉)₃CI, Ti(OC₆H₁₃)₃Br and Ti(OC₈H₁₇)₃CI. Titanium tetrahalides, particularly titanium tetrachloride (TiCI₄), are most preferred.

Internal electron donors useful in the preparation of a stereospecific supported titanium-containing catalyst compound can be organic compounds containing one or more atoms of oxygen, nitrogen, sulphur and phosphorus. Such compounds include organic acids, organic acid esters, alcohols, ethers, aldehydes, ketones, amines, amine oxides, amides, thiols and various phosphorous acid esters and amides, and the like. Mixtures of internal electron donors can be used if desired. Specific examples of useful oxygen- containing internal electron donor compounds include organic acids and esters. Useful organic acids contain from 1 to about 20 carbon atoms and 1 to about 4 carboxyl groups.

Preferred internal electron donor compounds include esters of aromatic acids. Preferred internal electron donors are

alkyl esters or aromatic mono- and dicarboxylic acids, and halogen, hydroxyl-, oxo-, alkyl-, alkoxy-, aryl-, and aryloxy-substituted aromatic mono- and dicarboxylic acids. Among these, the alkyl esters of benzoic and halobenzoic acids wherein the alkyl group contains 1 to about 6 carbon atoms, such as methyl benzoate, methyl bromobenzoate, ethyl benzoate, ethyl chlorobenzoate, ethyl bromobenzoate, butyl benzoate, isobutyl benzoate, hexyl benzoate, and cyclohexyl benzoate, are preferred. Other preferable esters include ethyl p-anisate and methyl-p-toluate. An especially preferred aromatic ester is a dialkylphthalate ester in which the alkyl group contains from about two to about ten carbon atoms. Examples of preferred phthalate esters are diisobutylphthalate, ethylbutylphthalate, diethylphthalate, and di-n-butylphthalate.

The internal electron donor component is used in an amount ranging from about 0.001 to about 1.0 mol per gram atom of the transition metal and preferably from about 0.005 to about 0.8 mol per gram atom. Best results are achieved when this ratio ranges from about 0.01 to about 0.6 mol per gram atom of the transition metal.

Although not required, the solid reaction product prepared as described herein may be contacted with at least one Lewis acid prior to polymerization. Such Lewis acids are generally liquids at treatment temperatures and have a Lewis acidity high enough to remove impurities such as un-reacted starting materials and poorly affixed compounds from the surface of the above- described solid reaction product. Preferred Lewis acids include halides of group 4, 5, 13-15 metals which are in the liquid state at temperatures up to about 170°C. Specific examples of such materials include BCI₃, AIBr₃, TiCI₄, TiBr , SiCI , GeCI₄, SnCI₄, PCI₃ and SbCI₅. Preferable Lewis acids are TiCI and SiCI₄. Mixtures of Lewis acids can be employed if desired. Such Lewis acid may be used in a compatible diluent. Although not required, the above-described solid reaction product may be washed with an inert liquid hydrocarbon or halogenated hydrocarbon before the contact with the Lewis acid. If such a wash is conducted it is preferred to substantially remove the inert liquid prior to contacting the washed solid with the Lewis acid. Due to the sensitivity of the catalyst to poisons such as water, oxygen, and carbon oxides, the catalyst preferably is prepared in the substantial absence of such materials. Catalyst poisons can be excluded by carrying out the preparation under an atmosphere of an inert gas such as nitrogen or argon, or an atmosphere of an α-olefin, or any other method known in the art. As noted above, purification of any diluent to be employed also aids in removing poisons from the preparative system.

As a result of the above-described preparation there is obtained a solid reaction product suitable for use as a catalyst. Prior to such use, it is desirable to remove incompletely reacted starting materials from the solid reaction product. This is conveniently accomplished by washing the solid, after separation from any preparative diluent, with a suitable solvent, such as a liquid hydrocarbon or halo(hydro)carbon, preferably within a short time after completion of the preparative reaction, because prolonged contact between the catalyst compound and un-reacted starting materials may adversely affect the performance of the catalyst.

The catalyst preferably contains from about 1 to about 6 wt.% transition metal, from about 10 to about 25 wt.% magnesium, and from about 45 to about 65 wt.% halogen. Preferred catalysts for use in this invention contain from about 1.0 to about 5 wt.% transition metal, from about 15 to about 21 wt.% magnesium, and from about 55 to about 65 wt.% chlorine. Most preferred is titanium as transition metal.

The transition metal compound used in this invention may be prepolymehzed with an α-olefin before use as a polymerization catalyst. In the prepolymerization the transition metal compound and an organometal compound as a cocatalyst (such as triethylaluminum) are contacted with an α-olefin (such as propylene) under polymerization conditions, preferably in the presence of an external electron donor (such as a silane and preferably an organosilane as used in the process of the present invention), and in an inert hydrocarbon (such as hexane). Typically, the polymer/catalyst weight ratio of the resulting prepolymerized component is about 0.1 :1 to about 20:1. Prepolymerization forms a coat of polymer around the catalyst particles which in many instances improves the particle morphology, activity, stereospecificity, and attrition resistance. A particularly useful prepolymerization procedure is described in U.S. Patent 4,579,836.

b) The organo-metal compound:

In the catalyst system used in the process of the present invention an organo-metal hydride and/or a metal alkyl compound is used as a co- catalyst. The metal in this compound is chosen from groups 1-3 and 12-13 of the Periodic Table of Elements. Preferred is a metal alkyl and, more preferably, an alkyl aluminum compound.

Preferred metal alkyls are compounds of the formula MR_m wherein M is chosen from groups 2, 12 or 13, each R is independently an alkyl radical of 1 to about 20 carbon atoms, and m corresponds to the valence of M. Examples of useful metals, M, include magnesium, calcium, zinc, cadmium, aluminum, and gallium. Examples of suitable alkyl radicals, R, include methyl, ethyl, butyl, hexyl, decyl, tetradecyl, and eicosyl. From the standpoint of polymerization performance, preferred metal alkyls are those of magnesium, zinc, and aluminum wherein the alkyl radicals contain 1 to about 12 carbon atoms. Specific examples of such compounds include Mg(CH₃)₂, Mg(C₂H₅)₂, Mg(C₂H₅)(C₄H₉), Mg(C₄H₉)₂, Mg(C₆H₁₃)₂, Mg(C₁₂H₂₅)₂, Zn(CH₃)₂, Zn(C₂H₅)_2> Zn(C₄H₉)₂, Zn(C₄H_θ)(C₈H₁₇), Zn(C₆H₁₃)₂, Zn(C₁₂H₂₅)₂, AI(CH₃)₃, AI(C₂H₅)₃, AI(C₃H₇)_3> AI(C₄H₉)₃, AI(C₆H₁₃)₃, and AI(Cι₂H₂₅)₃. More preferably a magnesium, zinc, or aluminum alkyl containing 1 to about 6 carbon atoms per alkyl radical is used. Alkyl aluminum compounds are most preferred. Best results are achieved through the use of trialkylaluminums containing 1 to about 6 carbon atoms per alkyl radical, and particularly thethylaluminum and triisobutylaluminum or a combination thereof.

If desired, metal alkyls having one or more halogen or hydride groups can be employed, such as ethylaluminum dichloride, diethylaluminum chloride, ethylaluminum sesquichlohde or diisobutylaluminum hydride.

In a catalyst system used in a process according to the present invention, typically, useful organo-metal compound to transition metal atomic ratios in such catalyst system are about 10 to about 500 and preferably about 30 to about 300.

c) The organosilane compound: The organosilane compound is present in the catalyst system as an external electron donor, meaning that this compound is added to the reaction system, and not used in the preparation of the transition metal compound (vide a) supra). The organosilane compound used in the process of the present invention has the formula:

in which R^ R₂ and R₃ are hydrocarbon-based substituents, R4 is a substituent to Q_T and s = 0 - 3, depending on the valency state of Q_1f and Q (embedded in a ring with the silicon atom and R1) is a hetero-atom, selected from the group of nitrogen, phosphorus, oxygen and sulphur, and one, and only one hetero-atom Qi is present in the ring and directly attached to the silicon-atom, and in which 1,1-dimethoxy-3,4-benzo-1 ,2 siloxacyclohexane is disclaimed. The respective groups in this organosilane compound will be dealt with below:

c1) The Q₁ - group: Qι is a hetero-atom, selected from the group of nitrogen, phosphorus, oxygen and sulphur, having an electro-negative character. Because of its good electron-donating capacity, there is a preference for Q being oxygen. c2) R»is a possibly present substituent to Q_1t depending on the valency state of

Q For example, in the case of Q₁ being nitrogen, the number of s = 1, and Rjcan be H, or an optionally substituted hydrocarbon group; in the case of Q₁ being oxygen, R₄ is absent. c3) R₂and R₃are hydrocarbon-based substituents, meaning that R₂and R₃can be a substituent containing only carbon and hydrogen atoms, but also that R₂ and R₃can be a substituent that, next to carbon and hydrogen atoms also contains one or more hetero-atoms, also selected from the group of nitrogen, phosphorus, oxygen and sulphur, either in the backbone or in pendant groups.

In one preference R₂and /or R₃are an alkoxy group; in more preference a methoxy or ethoxy group. M. Harkonen et.al. disclose in Macromol. Chem. 192, 2857-63 (1991) that 1,1-dimethoxy-3,4-benzo-1 ,2 siloxacyclohexane has been tested on its performance as external electron donor and found not suitable. Therefore, this specific organosilane compound has been disclaimed from use in the present invention. According to the present invention it has been found that when R₂and R₃are not. simultaneously a methoxy group, such organosilane compound can successfully be used as an external donor.

More preferred, R₂is a cycloalkyl (preferably a cyclohexyl) group and R₃ is an alkoxy group (preferably a methoxy or ethoxy group; most preferred an ethoxygroup). In another preferred embodiment R₂and R₃form a second ring structure, preferably a ring structure in which a second hetero-atom Q₂, also selected from the group of nitrogen, phosphorus, oxygen and sulphur, is present. In that case R₂and R₃ form an analogous structure as the group, and as a result, everything noted herein above with respect to the R_{1 t} Qi and R» groups holds mutatis mutandis also for the second ring structure. c4) Ri is also a hydrocarbon-based substituent (the term being as defined above). It forms, together with the Qι (R₄)_s group a ring attached to the silicon atom. In one preferred embodiment R^ has the following structure:

wherein: n = 0 - 6 m = 0 - 6

Re. R7, Re. Rg, Rio. Rn. R12 and R₁₃, each individually, are hydrogen or a hydrocarbon-based substituent.

Preferred in this embodiment is that for this type of external electron donor, R₂ is a cycloalkyl (preferably cyclohexyl) group, R₃ is an alkoxy (preferably ethoxy) group, R_βand R₇ are hydrogen and n = 2 and m = 0. Another preference in this embodiment is that R₂ is an alkyl

(preferably methyl or ethyl, most preferred a methyl) group, R₃ is an alkoxy

(preferably a methoxy or ethoxy, most preferred a methoxy) group, R_eand R₇ are hydrogen and n = 1-3 and m = 0.

In another embodiment of the present invention R, is a (CReR )_p -group, with

3 < p < 8; more preferred in this embodiment Re = R₇= H and p = 4.

In the process of the present invention preference is given to the use of an organosilane compound selected from the group comprising: ^* 1 -cyclohexyl-1 -ethoxy-5,6-benzo-1 ,2-siloxacyclohexane ^* 1-methoxy-1-methyl-3,4-benzo-1 ,2-siloxacycloheptane

^* 1-cyclohexyl-1-ethoxy-1 ,2-siloxacyclohexane.

The external organosilane electron donor is usually added to the other catalyst system components or added separately to the polymerization reactor, preferably in a molar ratio relative to the transition metal of from 0.1 :1 to 250:1.

The above-described catalyst system is useful in the polymerization of α-olefins such as ethylene and propylene, and are most useful in stereospecific polymerization of one of more α-olefins containing 3 or more carbon atoms such as propylene, 1-butene, 1-pentene-1, 4-methyl-1-pentene and 1-hexene, as well as mixtures thereof and mixtures thereof with ethylene. The catalyst system is particularly effective in the stereospecific polymerization of propylene or mixtures thereof with up to about 15 mol % ethylene or a higher α-olefin. Such polymerization is known to a person skilled in the art. According to the present invention, highly crystalline poly-α-olefins are prepared by contacting at least one α-olefin with the above- described catalyst system under polymerizing conditions. Such conditions include polymerization temperature and time, monomer pressure, avoidance of contamination of catalyst, choice of polymerization medium in slurry processes, the use of ingredients (like hydrogen) to control polymer molecular weights, and other conditions well known to persons of skill in the art. Slurry-, bulk-, and gas- phase polymerization processes are contemplated herein.

The amount of catalyst to be employed varies depending on choice of polymerization technique, reactor size, monomer to be polymerized, and other factors known to persons skilled in the art, and can also be determined on the basis of the Examples appearing hereinafter. Typically, in this invention catalysts are used in amounts ranging from about 0.2 to 0.02 milligrams of catalyst to gram of polymer produced.

Irrespective of the polymerization process employed, polymerization should be carried out at temperatures sufficiently high to ensure reasonable polymerization rates and avoid unduly long reactor residence times, but not so high as to result in the production of unreasonably high levels of stereorandom products. Generally, temperatures range from about 40°C to about 150°C with about 40°C to about 95°C being preferred from the standpoint of attaining good catalyst performance and high production rates. More preferably, the polymerization process according to this invention is carried out at temperatures ranging from about 50°C to about 80°C. α-Olefin polymerization according to this invention is carried out at monomer pressures of about atmospheric or above. Generally, monomer pressures range from about 0,1 to 5 MPa although in gas phase polymerizations, monomer pressures should not be below the vapor pressure at the polymerization temperature of the α-olefin(s) to be polymerized.

The polymerization time will generally range from about V_ to several hours in batch processes with corresponding average residence times in continuous processes. Polymerization times ranging from about 1 to about 4 hours are typical in autoclave-type reactions. In slurry processes, the polymerization time can be regulated as desired. Polymerization times ranging from about V_ to several hours are generally sufficient in continuous slurry processes.

Diluents suitable for use in slurry polymerization processes include alkanes and cycloalkanes (such as pentane, hexane, heptane, n-octane, isooctane, cyclohexane, and methylcyclohexane); alkylaromatics (such as toluene, xylene, ethylbenzene; isopropylbenzene, ethyl toluene, n-propyl- benzene, diethylbenzenes, and mono- and dialkylnaphthalenes); halogenated and hydrogenated aromatics (such as chlorobenzene, chloronaphthalene, orthodichlorobenzene, tetrahydronaphthalene, decahydronaphthalene); high molecular weight liquid paraffins or mixtures thereof, and other well-known diluents. It often is desirable to purify the polymerization medium prior to use, such as by distillation, percolation through molecular sieves, contacting with a compound such as an alkylaluminum compound capable of removing trace impurities, or by other suitable means.

Examples of gas-phase polymerization processes, which are the preferred mode, include both stirred bed reactors and fluidized bed reactor systems; they are described in U.S. Patents 3,957,448; 3,965,083; 3,971 ,768; 3,970,611; 4,129,701; 4,101 ,289; 3,652,527; and 4,003,712, all incorporated by reference herein. Typical gas phase α-olefin polymerization reactor systems comprise a reactor vessel to which α-olefin monomer(s) and a catalyst system can be added and which contain an agitated bed of forming polymer particles. Typically, the components of the catalyst system are added together or separately through one or more valve-controlled ports in the reactor vessel. α-Olefin monomer, typically, is provided to the reactor through a recycle gas system in which un-reacted monomer removed as off-gas and fresh feed monomer are mixed and injected into the reactor vessel. A quench liquid which can be liquid monomer, can be added to the polymerizing α-olefin through the recycle gas system in order to control temperature. Preferably, the reactor is a stirred, essential horizontal sub-fluidized bed reaction.

It is well known that α-olefin polymers can be exothermically produced as powders in fluidized bed reactors wherein the fluidization is provided by a circulating mixture of gases that includes the monomer(s). The fluidizing gases leaving the reactor can be re-circulated with cooling before reintroduction to the reactor in order to remove the heat of reaction and keep the fluidized bed temperature at the desired temperature. Preferably (a portion of) the re-circulating stream (the off gas) is cooled to condense a portion of said gas to liquid, after which the condensed and cooled products are (at least partially) recycled to the reactor. It is advantageous to remove the latent heat of vaporization, in addition to the sensible heat accumulated in the gas, since the latent heat of vaporization is much larger per degree of cooling than the sensible heat of the uncondensed stream.

A variety of methods can be used for reintroduction of the cooled recycle gas and liquids to the reactor. Often, most of the cooled recycle gas is injected into the reactor through a distributor plate below the fluid bed. The condensed recycle liquids may be entrained in the recycle gas or injected directly into the bed through some sort of nozzle assembly. Examples of the above technologies are shown in U.S. Pat. Nos. 3,595,840; 4,543,399; 4,588,790 and 5,352,749, all incorporated by reference herein.

Irrespective of polymerization technique, polymerization is carried out under conditions that exclude oxygen, water, and other materials that act as catalyst poisons.

Although not usually required, upon completion of polymerization, or when it is desired to terminate polymerization or deactivate the catalyst system in the process of the present invention, the polymer can be contacted with water, alcohols, acetone, or other suitable catalyst deactivators in a manner known to persons skilled in the art.

The products produced in accordance with the process of this invention are normally solid, predominantly isotactic poly-α-olefins. Polymer yields are sufficiently high relative to the amount of catalyst employed so that useful products can be obtained without removal of catalyst residues. Further, levels of stereorandom by-products are sufficiently low so that useful products can be obtained without removal thereof. The polymeric products produced in the presence of the mentioned catalyst system can be fabricated into useful articles by extrusion, injection molding, and other common techniques. The invention described herein is illustrated, but not limited, by the following Examples and comparative experiments.

I. Synthesis of organosilane compounds according to the invention

EXAMPLES A - H

Example A: Synthesis of 1-cyclohexyl-1-ethoxy-5,6-benzo-1,2-siloxacyclohexane

a. Synthesis of cyclohexyltriethoxysilane

To 1500 ml of diethyl ether and 97.0 g of Mg (4.0 mol) was added 2 ml of 1 ,2-dibromoethane. The mixture was stirred for 14 hour. While cooling with a water bath, 357 g of cyclohexylchloride (3.0 mol) was added drop wise over a period of 3 4 hour. Initially 15 g of cyclohexylchloride was added at once, the remainder of the cyclohexylchloride was added drop wise upon cooling. After the addition was complete, stirring was continued overnight at room temperature. Subsequently, the reaction mixture was cooled to -60 °C with acetone/CO₂ and became a slurry.

In a second flask 635 g of tetraethoxysilane (3.05 mol) was dissolved in 500 ml of diethyl ether and was cooled to -60 °C. The abovementioned slurry was added. Thereafter, the mixture was allowed to warm to room temperature. As soon as room temperature was reached atmospheric distillation of the diethyl ether was started. The product was purified by redistilling under reduced pressure. Boiling point was 94 - 96 °C (490 Pa). Yield 434 g (59 %) of a colourless liquid.

b. Synthesis of (2-(2-bromophenyl)ethoxy)diethoxycyclohexylsilane

40.5 g of 2-bromophenethyl alcohol (0.20 mol) was dissolved in 1000 ml of toluene. To the solution was added 96.0 g of cyclohexyltriethoxysilane (0.39 mol) and 1 drop of concentrated sulphuric acid. The mixture was warmed to reflux and toluene and ethanol were distilled off slowly. Approximately half of the toluene was distilled off over a period of 5 hours, the remainder of the toluene was distilled off faster. First the product was distilled crude and fast, under reduced pressure, to remove the acid and side products. The product was further purified by vacuum distillation. Boiling point 160 - 166 °C (11 Pa). Yield 42.8 g (53 %) of a colour less oil.

c. Synthesis of 1-cyclohexyl-1-ethoxy-5,6-benzo-1,2-siloxacyclohexane 0.5 ml of 1 ,2-dibromoethane was added to 5.0 g of Mg (0.2 mol) in 50 ml of tetrahydrofuran (THF). The resulting mixture was stirred for V_ hour. The THF was removed and 500 ml of fresh THF was added to the Mg. 41.0 g of (2-(2-bromophenyl)ethoxy)diethoxycyclohexylsilane (0.1 mol) was added over a period of 30 minutes. No exotherm was observed. Stirring was continued overnight. The solution was separated from the excess Mg and the THF was removed under reduced pressure. The boiling point of the resulting product was 130 - 137 °C (11 Pa). Yield 25.3 g (90 %) of a colourless liquid, which was characterised by ¹H- and ¹³C-NMR (Nuclear Magnetic Resonance). Purity was higher than 98 %, the main impurity was (2-phenylethoxy)diethoxycyclo- hexylsilane (1.6 %) as determined by GC-MS (gaschromatografy, combined with mass-spectroscopy).

Example B: Synthesis of spiro-[4,4]-3,4,8,9-dibenzo-2,2,7,7-tetramethyl-1,6- dioxa-5-sila-nonane

In 125 ml of petroleum ether 30 ml of TMEDA (tetramethylenediamine) was dissolved. To this 13.6 g of α.α-dimethylbenzyl- alcohol (0.10 mol) was added. While cooling with ice, 125 ml of n-butyllithium (1.6 M in hexane, 0,20 mol) was added drop wise. The mixture was warmed to reflux and was maintained refluxing overnight. The red mixture was cooled to -60 °C and 8.3 g of siliciumtetrachloride (49 mmol) was added. The reaction mixture was stirred overnight at room temperature. To the light pink suspension was added 100 ml of water. The water and organic layers were separated and the water layer was extracted 3 times with 50 ml of diethyl ether. The combined organic layers were dried over Na₂SO₄. The Na₂SO₄ was filtered off and the solvent was evaporated from the filtrate. The residue, an oily liquid, was distilled under reduced pressure using a Kugelrohr, yielding a colourless oil which crystallised upon standing. The product was characterised by ¹H- and ¹³C-NMR, purity was higher than 99 % as detected by GC-MS. The yield was 2.3 g (16%).

Example C: Synthesis of spiro-[4,4]-2,3,7,8-dibenzo-5-sila-1 ,6-dioxanonane

a. Synthesis of bis(2-methoxybenzyl)diphenylsilane 5.9 g 2-methoxybenzylchloride (38 mmol) was added drop wise to 1.7 g Mg (71 mmol) and 50 ml THF over a period of 20 minutes. The reaction mixture was cooled with a water bath to maintain a temperature between 20 and 25 °C. After dosing, the reaction mixture was stirred for another hour at room temperature. 4.2 g of diphenyldichlorosilane (17 mmol) was added at once. Stirring was continued overnight. 50 ml water was added. The THF was evaporated and the residue was extracted 3 times with 50 ml of dichloromethane. The combined organic layers were dried over Na₂SO₄. The Na₂SO was filtered off and the solvent was removed from the filtrate. The residue was purified over silica. Yield was 6.3 g (90%) of a white powder.

b. Synthesis ofbis(2-hydroxybenzyl)diphenylsilane

4.35 g bis(2-methoxybenzyl)diphenylsilane (10.3 mmol) was dissolved in 50 ml dichloromethane. The solution was cooled to -60 °C. 30 ml of a solution of borontribromide (1.0 M in dichloromethane, 30 mmol) was added. The temperature was allowed to rise to room temperature and the reaction mixture was stirred for another V. hour. 50 ml water was added and the mixture was stirred vigorously for 1 hour. Another 50 ml water was added and the organic and water layers were separated. The water layer was extracted two more times with 50 ml dichloromethane. The combined organic layers were washed once with 50 ml water. The organic solution was dried over Na₂SO . The Na₂SO₄ was filtered off and the filtrate was freed from solvent. The residue, 3.9 of a brown sticky solid, was further purified over silica yielding 2.25 g (55%) of a white solid.

c. Synthesis ofspiro-[4,4]-2,3,7,8-dibenzo-5-sila-1,6-dioxanonane

1.0 g of bis(2-hydroxybenzyl)diphenylsilane (2.5 mmol) was dissolved in 40 ml of dichloromethane. Through this solution was bubbled a flow of HBr over a period of 2 hours. (The HBr was made by dropping bromine to tetrahydronaphtalene during the mentioned period). The reaction mixture was warmed to reflux and the solvent was evaporated by a small flow of nitrogen. The residue, a dark brown oil, was distilled by means of a Kugelrohr (50 Pa, 150°C). The product solidified upon condensation in nice crystals. Yield 0.5 g (80%). ¹H-NMR (CDCI₃) showed two sets of signals, in the aromatic region (6.2 - 7.5) and in the benzylic region (1.5 - 2.9).

Example D: Synthesis of 1-ethoxy-1-methyl-1,2-siloxacyclopentane

a. Hydrosilylation between ally! acetate and dichloromethylsilane

Under an atmosphere of nitrogen, 100 g allyl acetate, 80 g toluene, and 4.5 g of a 0.25 w% solution of H PtCI₆ in acetone were placed into a 1000 ml four-neck stirring vessel equipped with thermometer, mechanical stirrer, dropping funnel and reflux condenser. The mixture is heated to 90 °C, and 125 g dichloromethylsilane were slowly added, keeping the temperature below 100 °C. After the addition was complete, the mixture is stirred for an additional hour at 90 °C. Distillation of the crude product at 1 kPa over a 30 cm distillation column gave 172 g (80 %) 3-acetoxypropyl(dichloro)methylsilane (boiling point 98°C at 1 kPa).

b. Ethoxylation of3-acetoxypropyl(dichloro)methylsilane and ring closure 85 g ethanol and 112 g urea were placed into a four-neck stirring vessel with thermometer, mechanical stirrer, and a dropping funnel charged with the raw product from synthesis step a. While stirring, the product was added drop wise, keeping the temperature below 60 °C. After the addition, the reaction mixture was kept at 60 °C for another hour to complete the reaction. The lower (urea hydrochloride) phase was separated and discharged. To the organic phase, 40 g of a 20% solution of sodium ethylate in ethanol was added, and the resulting mixture was heated to 100 ^CC for three hours. Distillation of the resulting raw reaction mixture under reduced pressure (16 kPa) gave 74 g 1- ethoxy-1-methyl-1 ,2-siloxacyclopentane (boiling point 70 °C at 16 kPa).

Example E: Synthesis of a mixture of silane compounds, composed mainly of 1 -methoxy-1 -methyl-3,4-benzo-1 ,2-siloxacycloheptane

a. Hydrosilylation and ring closure

180 g trichloroethylene and 0.038 ml of a 0.25 wt% solution of H₂PtCI₆ in acetone were placed into a four-neck stirring vessel equipped with stirrer, two dropping funnels and a 40 cm distillation column. The mixture was heated to 85 °C under an inert gas atmosphere followed by simultaneous separate addition of 134.2 g allyl phenol and 287.5 g dichloromethylsilane from the two dropping funnels within two hours. During the addition, excess of dichloromethylsilane was recovered by distillation. After the addition, the mixture was heated for an additional hour under reflux to complete the reaction and to remove the trichloroethylene from the reaction mixture. Thus, 266.3 g raw product mixture was formed.

b. Methoxylation

80 g methanol and 140 g urea were placed into a four-neck stirring vessel with thermometer, mechanical stirrer, and a dropping funnel charged with the raw product from synthesis step a. While stirring, the raw product was added drop wise, keeping the temperature below 60 °C. After the addition, the reaction mixture was kept at 60 °C for another hour to complete the reaction.

The lower (urea hydrochloride) phase was separated and the organic phase was purified by distillation under reduced pressure (200 Pa) to give 85 g of a product isomer mixture (boiling point 85 °C at 200 Pa) consisting of at least 70 %

1 -methoxy-1 -methyl-3,4-benzo-1 ,2-siloxacycloheptane.

Example F: Synthesis of a mixture of silane compounds, composed mainly of spiro-[6,6]-dibenzo-[2,3:9,10]-5-sila-1 ,8-dioxa-undodecane a. Reaction between o-allylphenol and dichlorosilane

Under an atmosphere of nitrogen, 275 g toluene, 107 g urea, and 200 g 2-allylphenol were placed into a 2000 ml three-neck stirring vessel equipped with a mechanical stirrer, a reflux condenser, and a gas inlet tube. After cooling the mixture down to -2 °C, 75 g dichlorosilane was slowly added from a bottle via the gas inlet tube within 1 hour while stirring. Then the mixture was slowly heated to 30 °C and kept at this temperature for one hour. After cooling to room temperature, the formed solid urea hydrochloride was separated from the raw reaction mixture by filtration.

b. Hydrosilylation reaction

Under a nitrogen atmosphere, 400 g of the solution resulting from the former synthesis step a, 300 g toluene, and 0.05 g of a 0.25 w% solution of H₂PtCI₆ in acetone were placed into a 1000 ml three-neck stirring vessel equipped with a mechanical stirrer, a reflux condenser and a thermometer. The mixture was slowly heated and kept at reflux for 2 hours. After cooling down and removing the toluene using a rotation evaporator, the raw reaction mixture was distilled under reduced pressure (200 Pa) giving 87 g of an isomer mixture of cis- frans-spiro-[5.5]-dibenzo-[2,3:8,9]-5,11-dimethyl-1 ,7-dioxa-6-sila-undecane and spiro-[6.6]-dibenzo-[2,3:9,10]-1,8-dioxa-7-sila-undodecane.

Example G: Synthesis of 1-cyclohexyl-1-ethoxy-1,2-siloxacyclohexane

a. Synthesis of 4-bromo-1-butanol 600 ml of THF was warmed to reflux. Over a period of 4 hours

500 g HBr (48 % in water, (3.0 mol)) was added drop wise. After the addition reflux was maintained for another hour. The excess of THF was evaporated at a rotary evaporator. The residue was extracted 3 times with 200 ml diethyl ether. The combined ether layers were washed once with 250 ml of water. The ether layer was dried over Na₂SO₄. The Na₂SO was filtered off and the filtrate was freed from solvent. The residue, 141.9 g of a pale yellow liquid, was the desired product (yield 31 %).

b. Synthesis of (4-bromobutoxy)diethoxycyclohexylsilane 74 g 4-bromo-1-butanol (0.46 mol) was dissolved in 1000 ml of toluene. 172 g cyclohexyltriethoxysilane (0.7 mol) and a few drops of concentrated sulphuric acid were added. The mixture was warmed to reflux, toluene and ethanol were distilled off slowly (half of the toluene was distilled off over a period of 5 hours, the remainder of the toluene was distilled off faster). First the product was distilled crude and fast, under reduced pressure, to remove the acid and side products. The product was further purified by vacuum distillation. Yields 76.5 g of the desired product (47 %) and 77.0 g of un-reacted cyclohexyltriethoxysilane (45 %). Boiling point of the desired product was 122 - 124 °C (16 Pa). The synthesis was performed in duplicate to have enough starting material for synthesis step c.

c. Synthesis of 1-cyclohexyl-1-ethoxy-1,2-siloxacyclohexane

To 50 ml THF was added 10.0 g Mg (0.42 mol) and 1 ml of 1 ,2- dibromoethane. The resulting mixture was stirred for V_ hour. The THF solution was removed from the Mg and 1500 ml of fresh THF was added. While cooling with a water bath 99.0 g of (4-bromobutoxy)diethoxycyclohexylsilane (0.28 mol) was added drop wise over a period of 3 hours. After the addition, stirring was continued overnight. THF was removed under reduced pressure (rotary evaporator) and the crude product was distilled at a Kugelrohr (125 °C, 110 Pa). The yield of the crude product was 50.6 g (79 %). The product was purified (96 %) by distillation and characterised by H- and ¹³C-NMR; main impurities were cyclohexytriethoxysilane (1.3 %) and cyclohexylbutoxydiethoxysilane (2.7 %) as analysed by GC-MS.

Example H: Synthesis of spiro-[5,5]-4,5,10,11-dibenzo-6-sila-1 ,7-dioxa-nonane

5.0 g 2-bromophenethyl alcohol (24.9 mmol) was dissolved in 200 ml toluene. 5.2 g of tetraethoxysilane (25.0 mmol) and 1 drop of n-butyllithium (1.6 M in hexane) were added. The reaction mixture was heated to reflux and toluene/ethanol was distilled off slowly. Approximately half of the toluene was distilled off over a period of 4 hours. The remainder of the toluene was removed under reduced pressure.

0.7 g Mg in 150 ml THF were activated with 0.25 ml 1 ,2-dibromoethane. To the mixture was added the residue of the first step. The reaction mixture was stirred for 3 days at room temperature. Solids were removed by filtration. The THF was evaporated from the filtrate and the residue was distilled under reduced pressure with a Kugelrohr. The yield was 0.73 g of a colourless liquid (22 %). The compound was analysed by ¹H- and ¹³C-NMR; no impurities were detected by GC-MS.

II. Slurry Polymerization results

Examples I - VIII and comparative experiment A

To demonstrate the usefulness of the organosilane compounds of this invention propylene polymerizations were performed in a typical bench scale slurry reactor using a supported high activity catalyst produced in accordance with US Patent 4,886,022. Triethylaluminum (TEAI) was used as the cocatalyst in a typical Al/Ti molar ratio of 180; the Si/Ti molar ratio was 8. The polymerizations were performed in a 12 L stainless steel reactor with a typical amount of 110 mg of a titanium-containing solid catalyst. In starting the polymerization, nitrogen (0.18 MPa) was vented off by opening the outlet valve. 4500 ml of purified heptane from a vessel which was continuously purged with nitrogen was dosed to the reactor. Consequently, a mixture of the TEAI cocatalyst and the organosilane compound was dosed in a typical concentration range of 0.20 - 0.25 mol/l. The mixture was prepared in a nitrogen atmosphere dry-box kept free from oxygen and water. The TEAI/organosilane compound solution was adjusted to the reactor under nitrogen atmosphere with a glass pipette. The weighted amount of catalyst was dosed to the reactor with nitrogen and small amounts of purified heptane, afterwards filling up the reactor with purified heptane to a final amount of 5500 ml. The reactor was purged with a mixture of propylene (dosed by a dip tube) and hydrogen (dosed in the gas-phase) with a constant flow of 1000 Nl/hour and 10 Nl/hour respectively during 2 min. The reactor vent valve was closed and the temperature increased to 45 °C, starting a prepolymerization of the catalyst system. Meanwhile, the pressure increased to around 0.14 MPa depending on the activity of the catalyst system. After an additional 2 minutes at 45 °C, the pressure was increased to 0.7 MPa, meanwhile increasing the temperature to 70 °C dosing 1000 Nl/hour propylene and a constant concentration of hydrogen of 1.5 % measured by gaschromatography and a H₂-sensor. Depending on the activity of the catalyst system, the temperature and pressure increase took about 20 to 25 minutes. After 120 minutes of polymerization at constant pressure, temperature and H₂-concentration, the reactor was vented off in around 20 minutes to 0.11 MPa, while cooling to room temperature. During the polymerization, the reactor settings were controlled by an operating system and the data are recorded automatically. The collected polymer slurry was centrifuged and the resulting homopolymer powder was dried in a vacuum oven at 60 °C. The amount of atactic polymer (aPP) was determined by drying a specified amount of the heptane solution after reaction.

Data from the polymerization experiments are summarized in Table I. Catalyst yields in kg polymer/amount of catalyst were determined based on the dried amount of polymer; the isotacticity index (I.I.) was determined via an extraction with hexane. The MFR of the polymer (in dg/min) was determined according to ISO-1133 with a weight of 2.16 kg at 230 °C.

Examples IX - XVI and comparative experiments B - D

In order to determine the H₂/MFR correlation, a comparison was made for the H₂-sensitivity of organosilane compounds A and G compared to di-isobutyldimethoxysilane (DIBDMS). For the selected organosilane compounds of the invention, 4 different H₂-settings were determined. The polymerization results are given in Table 2 and graphically illustrated in Figure 1.

III. Gas-phase polymerization results

Gas-phase polymerizations were performed in a set of two horizontal, cylindrical reactors in series, wherein a homopolymer was formed in the first reactor and optionally a typical ethylene - propylene copolymer rubber in the second one to prepare an impact copolymer. The first reactor was operated in a continuous way, the second one in a batch manner. In the synthesis of the homopolymer, the polymer was charged into the secondary reactor blanketed with nitrogen. The first reactor was equipped with an off-gas port for recycling reactor gas through a condenser and back through a recycle line to the nozzles in the reactor. Both reactors had a volume of one gallon (3.8-liter) measuring 10 cm in diameter and 30 cm in length. In the first reactor liquid propylene was used as the quench liquid; for the synthesis of copolymers the temperature in the second reactor was kept constant by a cooling jacket. The catalyst was introduced into the first reactor as a 5 - 7 wt.% slurry in hexane through a liquid propylene-flushed catalyst addition nozzle. A mixture of the organosilane compound and TEAI in hexane at an Al/Ti ratio of 180 and Si/Ti ratio of 8 were fed separately to the first reactor through a different liquid propylene flushed addition nozzle. For the synthesis of impact copolymers an Al/Mg ratio of 10 and an Al/Si ratio of 6 was used.

During operation, polypropylene powder produced in the first reactor passed over a weir and was discharged through a powder discharge system into the second reactor. The polymer bed in each reactor was agitated by paddles attached to a longitudinal shaft within the reactor that was rotated at about 50 rpm in the first and at about 75 rpm in the second reactor. The reactor temperature and pressure were maintained at 71 °C and 2.2 MPa in the first and for the copolymer synthesis at 66 °C and 2.2 MPa in the second reactor. By varying the amount of hydrogen in the first reactor, homopolymers with different melt flow rates were obtained. For the copolymer synthesis, hydrogen was fed independently to both reactors to obtain a melt flow rate of 4-5 dg/min for the homopolymer product and a total melt flow rate of the final polymer of 1-2 dg/min. The production rate was about 200 - 250 g/h in the first reactor in order to obtain a stable process.

Molecular weight distributions (MWD) of the homopolymer resins, represented by M M_n (= ratio between weight average molecular weight and number average molecular weight), were measured on a Waters M150C GPC using a Polymer Labs PLgel 10 μm column using 1 ,2,4-trichlorobenzene as the solvent.

The polypropylene products, made by a catalyst system according to this invention, were compounded on a PM-20 extruder under standard conditions. The polymers were stabilized by adding typically 0.3 wt.% Irganox^® B225 and 0.05 wt.% calcium stearate. Injection moulding parts were produced typically on a Arburg Injection Moulder. The stiffness of the material was measured by a standard procedure described in ASTM D790. A notched Izod measurement at room temperature was performed according to ISO 180/4A. The tensile test was performed based on ISO R37/2.

The crystallization properties of the polymers were determined on a PERKIN ELMER DSC-7 calorimeter which was connected by an interface TAC/7DX instrument controller using the standard procedure described in ASTM D3417/3418 E793/794. A sample weight in between 4 and 6 mg was used. At 40 °C an isotherm waiting time of 5 minutes was applied, after which the temperature was increasing with a scan speed of 10°C/min to 200°C. This is the so-called first heating curve. After again an isotherm waiting time of 5 minutes the temperature was decreased with a scan speed of 10°C/min to 40°C. This is the so-called cooling curve. After again an isotherm waiting time of 5 minutes the temperature was increasing again to 200°C with a scan speed of 10°C/min. This is the second heating curve. By using the second heating curve it is possible to compare different samples because in the second heating curve the samples all have the same thermal history. The melting temperature (T_m) was determined from the second heating curve; the crystallization temperature (T_c) and the heat of fusion (ΔH_f) were determined from the cooling curve. The results are given in Table 5.

Examples XVII - XXV and comparative experiments E - 1

Typical homopolymers were prepared using the in Table 3 indicated organosilane compounds.

A H₂/MFR relationship was determined for selected organosilane compounds E and G and compared with reference compound DIBDMS. A higher hydrogen response was found for organosilane compound G compared to the reference as illustrated by a higher resulting MFR at comparable ^-concentrations in the feed as illustrated in Figure 2. Broadening of the MWD was observed for organosilane E with respect to the DIBDMS reference.

Examples XXVI - XXVIII and comparative experiment J Data from the polymerization results are summarized in Table 4. The stereoselective control of the organosilane compounds of the invention at comparable Al/Mg and Al/Si ratio's was the best for organosilane compound G. Organosilane compound E resulted in a broadening of the MWD. The mechanical properties, displayed in Table 5, showed a comparable impact - stiffness balance for organosilane compound G with the DIPDMS reference. In this respect, TC₂ is the amount of ethylene incorporated in the impact copolymer (wt%). RCC₂ is the amount of ethylene incorporated in the rubber fraction (wt.%), both determined by Fourier Transform Infrared spectroscopy (FTIR).

Table 1

Summary of slurry polymerization results with selected organosilane compounds

Table 2

H₂/MFR correlation in slurry-polymerization

Table 3

H₂/MFR relationship in gas-phase for selected organosilane compounds

^la| Catalyst yield based on the determination of the Mg concentration in the polymer by Inductively Coupled Plasma measurements (ICP) ^lbl Isotacticity Index, based on an extraction with hexane ^[cl Batch based yield numbers ^[d] CXS (Cold Xylene Solubles) numbers

Table 4

Summary of the gas-phase copolymehzation results performed with selected organosilane compounds

Based on an average catalyst yield of different batches in the first reactor ^[bl Bulk density of the product of the first reactor

^[cl MFR of the impact copolymer (between brackets MFR of the homopolymer) ^[dl II and CXS numbers of the homopolymer product ^[el Total ethylene content, determined via FTIR ^[f] Ethylene content of the rubber phase, determined via FTIR Table 5

DSC results of gas-phase homopolymers and mechanical properties of impact copolymers

Claims

1. Process for the polymerization of one or more α-olefins in the presence of a catalyst system comprising a transition metal compound, an organo- metal compound as co-catalyst, and, as an external electron donor, at least one organosilane compound in which the silicon atom has at least one hetero-atom containing substituent, wherein the organosilane compound has the formula:

(R₄)s

in which R^ R₂ and R₃ are hydrocarbon-based substituents, R is a substituent to Qi and s = 0 - 3, depending on the valency state of Q_L and Q (embedded in a ring with the silicon atom and R,) is a hetero-atom, selected from the group of nitrogen, phosphorus, oxygen and sulphur, and one, and only one hetero-atom Qi is present in the ring and directly attached to the siliconatom, and in which 1 ,1-dimethoxy-3,4-benzo-1 ,2 siloxacyclohexane is disclaimed.

2. Process according to claim 1 , wherein Qi is oxygen.

3. Process according to anyone of claims 1-2, wherein R₂ and/or R₃ are an alkoxy group.

4. Process according to anyone of claims 1-3, wherein R₂ and R₃ together form a second ring structure.

5. Process according to claim 4, wherein in the second ring structure a second hetero-atom Q₂, selected from the group of nitrogen, phosphorus, oxygen and sulphur, is directly attached to the silicon atom.

6. Process according to claim 5, wherein the second hetero-atom Q₂ is oxygen.

7. Process according to anyone of claims 1-6, wherein R, has the following structure:

wherein:

n = 0 - 6 m = 0 - 6 R₆, R_7> Re, R₉, Rio, Rn , Rι₂ and Rι₃, each individually, are hydrogen or a hydrocarbon-based substituent.

8. Process according to anyone of claims 1-3, wherein R₂ is a cycloalkyl group and R₃ is an alkoxy group.

9. Process according to claim 8, wherein R₂ is a cyclohexyl group. 10. Process according to claim 3 or claim 8, wherein R₃ is an ethoxy group.

11. Process according to anyone of claims 1-6, wherein Ri is a (CR_eR₇)_p group, and 3 < p < 8.

12. Process according to claim 11 , wherein R₆ and R₇ are hydrogen and p = 4.

13. Process according to claim 7, wherein R₂ is a cycloalkyl group, R₃ is an alkoxy group, R₆ and R₇ are hydrogen, n = 2 and m = 0.

14. Process according to claim 13, wherein R₂ is a cyclohexylgroup and R₃ is an ethoxygroup.

15. Process according to claim 7, wherein R₂ is a methyl or ethyl group, R₃ is a methoxy- or ethoxy-group, R₆ and R₇ are hydrogen, n = 1 - 3 and m = 0.

16. Process according to claim 15, wherein R₂ is a methyl group and R₃ is a methoxy group.

17. Process according to any one of claims 1-16, wherein the transition metal is selected from group 4 of the Periodic Table of Elements. 18. Process according to claim 17, wherein the transition metal is titanium.

19. Process according to anyone of claims 1-18, wherein the polymerization is carried out in the gas-phase.

20. Process according to claim 19, wherein the process is carried out in a stirred or fluidized bed reactor.

21. Process according to claim 20, wherein the stirred bed reactor is an essentially horizontal sub-fluidized bed reactor.

22. Process according to anyone of claims 1-21 , wherein the polymerization is performed at a temperature of between 40 and 150°C. 23. Process according to anyone of claims 1-22, wherein the α-olefin comprises ethylene, propylene, 1-butene or a mixture thereof. 24. Process according to claim 20, wherein the off gas of the reactor is cooled to condense a portion of said gas to liquid, after which the condensed and cooled products are (at least partially) recycled to the reactor. 25. Process according to anyone of claims 1-24, wherein the organosilane compound is present in the catalyst system relative to the transition metal in a molar ratio of from 0.1 :1 to 250:1. 26. Process according to anyone of claims 1-25, wherein the transition metal compound is prepolymerized with an α-olefin. 27. Catalyst system comprising a transition metal compound, an organo-metal compound as co-catalyst, and, as an external electron donor, at least one organosilane compound in which the silicon atom has at least one hetero- atom containing substituent, wherein the organosilane compound has the formula:

in which R_1f R₂ and R₃ are hydrocarbon-based substituents, R is a substituent to Qi and s = 0 - 3, depending on the valency state of Qi, and Q (embedded in a ring with the silicon atom and R^ is a hetero-atom, selected from the group of nitrogen, phosphorus, oxygen and sulphur, and one, and only one hetero-atom Qi is present in the ring and directly attached to the siliconatom, and in which 1 ,1-dimethoxy-3,4-benzo-1 ,2 siloxacyclohexane is disclaimed.

8. Catalyst system according to claim 27, wherein the organosilane compound is selected from the group comprising:

* 1 -cyclohexyl-1 -ethoxy-5,6-benzo-1 ,2-siloxacyclohexane

* 1 -methoxy-1 -methyl-3,4-benzo-1 ,2-siloxacycloheptane

* 1 -cyclohexyl-1 -ethoxy- 1 ,2-siloxacyclohexane.