Title of Invention	A PROCESS FOR PRODUCING A CATALYST SYSTEM AND A PROCESS FOR PREPARING POLYMERS OF POLYPROPYLENE IN THE PRESENCE OF THE SAID CATALYST SYSTEM
Abstract	"A process for producing a catalyst system and a process for preparing polymers of polypropylene in the presence of the said catalyst system" The invention relates to a process for producing a catalyst system of the Ziegler-Natta type, comprising as active constituents (a) a titanium-containing solid component comprising a compound of titanium, a compound of magnesium, a halogen, silica gel as support and a carboxylic ester as electron donor compound, and also, as cocatalyst, (b) an aluminum compound and (c) if desired, a further electron donor compound, wherein the silica gel used has a mean particle diameter of from 5 to 200 µm, a mean particle diameter of the primary particles of from 1 to 10 µm and voids or channels having a mean diameter of from 1 to 10 µm whose macroscopic proportion by volume in the total particle is in the range from 5 to 20% wherein said titanium containing solid component and said cocatalyst and if desired said further electron donor are reacted together at from 0 to 150°C and at a pressure of from 1 to 100 bar to obtain said catalyst system. The invention also relates to a process for preparing polymers of propylene by polymerization of propylene in the presence of a Ziegier-Natta catalyst system.

Title of Invention

A PROCESS FOR PRODUCING A CATALYST SYSTEM AND A PROCESS FOR PREPARING POLYMERS OF POLYPROPYLENE IN THE PRESENCE OF THE SAID CATALYST SYSTEM

Abstract

"A process for producing a catalyst system and a process for preparing polymers of polypropylene in the presence of the said catalyst system" The invention relates to a process for producing a catalyst system of the Ziegler-Natta type, comprising as active constituents (a) a titanium-containing solid component comprising a compound of titanium, a compound of magnesium, a halogen, silica gel as support and a carboxylic ester as electron donor compound, and also, as cocatalyst, (b) an aluminum compound and (c) if desired, a further electron donor compound, wherein the silica gel used has a mean particle diameter of from 5 to 200 µm, a mean particle diameter of the primary particles of from 1 to 10 µm and voids or channels having a mean diameter of from 1 to 10 µm whose macroscopic proportion by volume in the total particle is in the range from 5 to 20% wherein said titanium containing solid component and said cocatalyst and if desired said further electron donor are reacted together at from 0 to 150°C and at a pressure of from 1 to 100 bar to obtain said catalyst system. The invention also relates to a process for preparing polymers of propylene by polymerization of propylene in the presence of a Ziegier-Natta catalyst system.

Full Text	The present invention relates to catalyst systems of the Ziegler-Natta type comprising as active constituents a) a titanium-containing solid component comprising a compound of titanium, a compound of magnesium, a halogen, silica gel as support and a carboxylic ester as electron donor compound, and also, as cocatalyst, b) an aluminum compound and c) if desired, a further electron donor compound, wherein the silica gel used has a mean particle diameter of from 5 to 200 µm, a mean particle diameter of the primary particles of from 1 to 10 µm and voids or channels having a mean diameter of from 1 to 10 µm whose macroscopic proportion by volume in the total particle is in the range from 5 to j 20%. In addition, the invention provides a process for producing such Ziegler-Natta catalyst systems, a process for preparing polymers of propylene using these catalyst systems, the polymers obtainable in this way and also films, fibers and moldings comprising these polymers. Catalyst systems of the Ziegler-Natta type are known, inter alia, from EP-B 014523, EP-A 023425, EP-A 045975 and EP-A 195497. These systems are used, in particular, for the polymerization of C2-C10-alk-l-enes and comprise, inter alia, compounds of polyvalent titanium, aluminum halides and/or aluminum alkyls, and also electron donor compounds, particularly silicon compounds, ethers,, carboxylic esters, ketones and lactones which are used, on the one hand, in connection with the titanium component and, on the other hand, as cocatalyst. The Ziegler-Natta catalysts are usually produced in two steps. The titanium-containing solid component is produced first and subsequently reacted with the cocatalyst. The polymerization is subsequently carried out using the catalysts thus obtained. Furthermore, US-A 48 57 613 and US-A 52 88 824 describe catalyst systems of the Ziegler-Natta type which comprise a titanium-containing solid component and aluminum compound plus organic silane compounds as external electron donor compounds. The catalyst systems obtained in this way have, inter alia, a good productivity and give polymers of propylene having a high stereospecificity, ie. a high isotacticity, a low chlorine I content and a good morphology, viz. a low proportion of fines. If films are produced from polymers obtained by means of the catalyst systems described in US-A 48 57 613 and US-A 52 88 824, the increased occurrence of microspecks, ie. small irregularities on the surface of the films, is frequently observed. If such microspecks occur to a great extent, they impair the optical quality of the film. It is an object of the present invention, starting from the catalyst systems described in US-A 48 57 613 and US-A 52 88 824, to develop an improved catalyst system of the Ziegler-Natta type which does not have the abovementioned disadvantages in respect of the formation of microspecks and additionally gives a high productivity and stereospecificity of the polymers thus obtained. We have found that this object is achieved by means of the catalyst systems of the Ziegler-Natta type defined in the introduction. The catalyst systems of the present invention contain, inter alia, a cocatalyst in addition to a titanium-containing solid component a). The cocatalyst may here be the aluminum compound b). Preferably, an additional electron donor compound c) is used as a further constituent of the cocatalyst together with this aluminum compound b). To produce the titanium-containing solid component a), titanium compounds used are generally halides or alkoxides of trivalent or tetravalent titanium, with the chlorides of titanium, in particular titanium tetrachloride, being preferred. The titanium-containing solid component also contains silica gel as support. In addition, compounds of magnesium are used, inter alia, in the production of the titanium-containing solid component. Suitable magnesium compounds are, in particular, magnesium halides, magnesium alkyls and magnesium aryls, and also magnesium alkoxy and magnesium aryloxy compounds, with preference being given to using magnesium dichloride, magnesium dibromide and di(C1-C10-alkyl)magnesium compounds. The titanium-containing solid component can additionally contain halogen, preferably chlorine or bromine. The titanium-containing solid component a) also contains electron donor compounds, for example monofunctional or polyfunctional carboxylic acids, carboxylic anhydrides and carboxylic esters, also ketones, ethers, alcohols, lactones, and organophosphorus and organosilicon compounds. As electron donor compounds within the titanium-containing solid component, preference is given to using phthalic acid derivatives of the general formula (II) where X and Y are each a chlorine atom or a C1-C10-alkoxy radical or together are oxygen. Particularly preferred electron donor compounds are phthalic esters in which X and Y are each a C1-C8-alkoxy radical, for example a methoxy, ethoxy, propyloxy or a butyloxy radical. Further preferred electron donor compounds within the titanium-containing solid components are, inter alia, diesters of 3- or 4-membered, substituted or unsubstituted cycloalkyl-l,2-dicarboxylic acids, and also monoesters of substituted or unsubstituted ben2ophenone-2-carboxylic acids. The hydroxy compounds used for these esters are the alcohols customary in esterification reactions, for example C1-C15-alkanols and C5-C7-cycloalkanols which may in turn bear C1-C10-alkyl groups, also C8-C10-phenols. The titanium-containing solid component can be produced by methods known per se. Examples of such methods are described, inter alia, in EP-A 45 975, EP-A 45 977, EP-A 86 473, EP-A 171 200, GB-A 2 111 066, US-A 48 57 613 and US-A 52 88 824. For producing the titanium-containing solid component a), the following two-stage process is preferably employed: In the first stage, silica gel (Si02) generally having a mean particle diameter of from 5 to 200 um, in particular from 20 to 70 um, a pore volume of from 0.1 to 10 cm2/g, in particular from 1.0 to 4.0 cm3/g, and a specific surface area of from 10 to 1000 m2/g, in particular from 100 to 500 m2/g, as finely divided support is first admixed with a solution of the magnesium-containing compound in a liquid alkane, after which this mixture is stirred for from 0.5 to 5 hours at from 10 to 120"C. Preference is given to using from 0.1 to 1 mol of the magnesium compound per mol of the support. Subsequently, while stirring continuously, a halogen or a hydrogen halide, in particular chlorine or hydrogen chloride, is added in an at least two-fold, preferably at least five-fold, molar excess, based on the magnesium-containing compound. After from about 30 to 120 ninutes, this reaction product is, at from 10 to 150C, admixed with a C1-C8-alkanol, in particular ethanol, a halide or an alkoxide of trivalent or tetravalent titanium, in particular titanium tetrachloride, and also an electron donor compound. In this procedure, from 1 to 5 mol of the trivalent or tetravalent titanium and from 0.01 to 1 mol, in particular from 0.1 to 0.5 mol, of the electron donor compound are used per mol of magnesium in the solid obtained from the first stage. This mixture is stirred for at least 1 hour at from 10 to 150c, the solid thus obtained is subsequently filtered off and washed with a C7-C10-alkylbenzene, preferably with ethylbenzene. In the second stage, the solid obtained from the first stage is extracted for a few hours at from 100 to 150°C with excess titanium tetrachloride or an excess of a solution of titanium tetrachloride in an inert solvent, preferably an alkylbenzene, with the solvent containing at least 5% by weight of titanium tetrachloride. The product is then washed with a liquid alkane until the washings contain less than 2% by weight of titanium tetrachloride. The titanium-containing solid component obtainable in this way is used together with a cocatalyst as Ziegler-Natta catalyst system. A suitable cocatalyst is here, inter alia, an aluminum compound b). Aluminum compounds b) suitable as cocatalysts are trialkylaluminums and also those compounds in which an alkyl group is replaced by an alkoxy group or by a halogen atom, for example by chlorine or bromine. Preference is given to using trialkylaluminum compounds whose alkyl groups each have from 1 to 8 carbon atoms, for example trimethylaluminum, triethylaluminum or methyldiethylaluminum. Preference is given to using not only the aluminum compound b) but also electron donor compounds c) as further cocatalyst, for i example monofunctional or polyfunctional carboxylic acids, carboxylic anhydrides and carboxylic esters, also ketones, ethers, alkohols, lactones, and organophosphorus and organosilicon compounds. Preferred electron donor compounds are here organosilicon compounds of the general formula (I) where R1 are identical or different and are each a C1-C2o-alkyl group, a 5- to 7-membered cycloalkyl group which in turn can bear a C1-C10-alkyl group, or a C6-C2o-aryl or aralkyl group, R2 are identical or different and are each a C1-C2o-alkyl group and n is 1, 2 or 3. Particular preference is here given to those compounds in which R1 is a C1-C8-alkyl group or a 5- to 7-membered cycloalkyl group, and R2 is a C1-C4-alkyl group and n is 1 or 2. Among these compounds, particular emphasis is given to dimethoxydiisopropylsilane, dimethoxyisobutylisopropylsilane, dimethoxydiisobutylsilane, dimethoxydicyclopentylsilane, dimethoxyisobutyl-sec-butylsilane, dimethoxyisopropyl-sec-butylsilane, diethoxydicyclopentylsilane and diethoxyisobutylisopropylsilane. The individual compounds b) and, if desired, c) can be used as cocatalyst in any order, either individually or as a mixture of two components. According to the present invention, the silica gel used in the titanium-containing solid component a) is a finely divided silica gel which has a mean particle diameter of from 5 to 200 µm, in particular from 20 to 70 µm, and a mean particle diameter of the primary particles of from 1 to 10 µm, in particular from 1 to 5 µm. For the purposes of the present invention, the primary particles are porous, granular silica gel particles which are obtained from an Si02 hydrogel by milling, if desired after appropriate sieving. Furthermore, the finely divided silica gel to be used according to the present invention also has voids or channels having a mean diameter of from 1 to 10 µm, in particular from 1 to 5 µm, whose macroscopic proportion by volume in the total particle is in the range from 5 to 20%, in particular in the range from 5 to 15%. The finely divided silica gel additionally has, in particular, a pore volume of from 0.1 to 10 cm2/g, preferably from 1.0 to 4.0 cm2/g, and a specific surface area of from 10 to 1000 m2/g, preferably from 100 to 500 m2/g. Owing to the voids or channels present in the finely divided silica gel, there is a significantly improved distribution of the catalytically active components in the support material. Furthermore, a material pervaded in this way by voids and channels has a positive effect on the diffusion-controlled supply of monomers and cocatalysts and thus also on the polymerization kinetics. Such a finely divided silica gel is, inter alia, obtainable by spray drying milled, appropriately sieved Si02 hydrogel, which for this purpose is slurried with water or an aliphatic alcohol. However, such a finely divided silica gel is also commercially available. The silica gel is present within the titanium-containing solid component a) in such amounts that from 0.1 to 1.0 mol, in particular from 0.2 to 0.5 mol, of the magnesium compound is present per 1 mol of the silica gel. The cocatalytically active compounds b) and, if desired, c) can be allowed to act either successively or together on the titanium-containing solid component a). This is usually carried out at from 0 to 150°C, in particular from 20 to 90°C, and at pressures of from 1 to 100 bar, in particular from 1 to 40 bar. The cocatalysts b) and, if used, c) are preferably used in such an amount that the atomic ratio between aluminum from the aluminum compound and titanium from the titanium-containing solid component a) is from 10:1 to 800:1, in particular from 20:1 to 200:1, and the molar ratio between the aluminum compound and the electron donor compound c) used as cocatalyst is from 1:1 to 250:1, in particular from 10:1 to 80:1. The catalyst systems of the present invention are particularly suitable for preparing polymers of propylene, ie. homopolymers of propylene and copolymers of propylene together with other C2-C10-alk-l-enes. The description C2-C10-alk-l-enes here refers to, inter alia, ethylene, but-1-ene, pent-1-ene, hex-1-ene, hept-1-ene or oct-1-ene, with the comonomers ethylene and but-1-ene being particularly preferred. However, the catalyst systems of the present invention can also be used for preparing polymers of other C2-C10-alk-l-enes, for example for preparing homopolymers or copolymers of ethylene, but-1-ene, pent-1-ene, hex-1-ene, hept-1-ene or oct-1-ene. The preparation of such polymers of C2-C10-alk-l-enes can be carried out in the customary reactors used for the polymerization of C2-C10-alk-l-enes, either batchwise or preferably continuously, for example as suspension polymerization or preferably as gas-phase polymerization. Suitable reactors include continuously operated stirred reactors containing a fixed bed of finely divided polymer which is usually kept in motion by means of suitable agitators. Of course, the reaction can also be carried out in a plurality of reactors connected in series. The reaction time, ie. the mean residence time, is determined by the reaction conditions selected in each case. It is usually from 0.2 to 20 hours, mostly from 0.5 to 10 hours. The polymerization reaction is advantageously carried out at from 20 to 150C and at pressures of from 1 to 100 bar. Preference is given to temperatures of from 40 to 100°C and pressures of from 10 to 50 bar. Specifically for the preparation of propylene homopolymers, the polymerization reaction is preferably carried out at from 50 to 100c, in particular from 60 to 90°C, at pressures of from 15 to 40 bar, in particular from 20 to 35 bar, and at mean residence times of from 0.5 to 5 hours, in particular from 0.5 to 3 hours. The molecular weight of the polyalk-1-enes formed can be controlled by addition of regulators customary in polymerization technology, for example hydrogen, and adjusted over a wide range. It is also possible to make concomitant use of inert solvents such as toluene or hexane, inert gas such as nitrogen or argon and relatively small amounts of polypropylene powder. The propylene homopolymers and copolymers obtained by means of the catalyst system of the present invention are obtainable in the molecular weights usual for polyalk-1-enes, with preference being given to polymers having molecular weights (weight average) of from 20,000 to 500,000. Their melt flow indices at 230°C and under a load of 2.16 kg, in accordance with DIN 53 7 35, are in the range from 0.1 to 100 g/10 min, in particular in the range from 0.5 to 50 g/10 min. The catalyst system of the present invention has, compared with the catalyst systems known hitherto, a higher productivity and an improved stereospecificity, in particular in gas-phase polymerization. The polymers obtainable in this way also have a high bulk density and a low residual chlorine content. Furthermore, the catalyst system of the present invention has the advantage of significantly reducing the microspeck formation in the polymers obtained therefrom. Owing to their good mechanical properties, the propylene polymers prepared using the catalyst system of the present invention are especially suitable for producing films, fibers and moldings. Examples Example 1 a) Production of the titanium-containing solid component (1) In a first stage, finely divided silica gel (SiO2) having a particle diameter of from 20 to 45 pun, a pore volume of 1.5 cm2/g and a specific surface area of 260 m2/g was admixed with a solution of n-butyloctylmagnesium in n-heptane, with 0.3 mol of the magnesium compound being used per mol of Si02. The finely divided silica gel was additionally characterized by a mean particle size of the primary particles of 3-5 µm and by voids and channels having a diameter of 3-5 µm with the macroscopic proportion by volume of the voids and channels in the total particle being about 15%. The solution was stirred for 45 minutes at 95°C, then cooled to 20c, after which the 10-fold molar eunount, based on the organomagnesium compound, of hydrogen chloride was passed in. After 60 minutes, the reaction product was admixed while stirring continuously with 3 mol of ethanol per mol of magnesium. This mixture was stirred for 0.5 hour at 80°C and subsequently admixed with 7.2 mol of titanium tetrachloride and 0.3 mol of di-n-butyl phthalate, in each case based on 1 mol of magnesium. The mixture was subsequently stirred for 1 hour at 100c, the solid thus obtained was filtered off and washed a number of times with ethylbenzene. The solid product thus obtained was extracted for 3 hours at 125°C with a 10% strength by volume solution of titanium tetrachloride in ethylbenzene. The solid product was then separated from the extractant by filtration and washed with n-heptane until the extractant contained only 0.3% by weight of titanium tetrachloride. The titanium-containing solid component contained The particle diameter was determined by Coulter Counter analysis (particle size distribution of the silica gel particles), the pore volume and the specific surface area were determined by nitrogen adsorption in accordance with DIN 66131 or by mercury porosimetry in accordance with DIN 66133. The mean particle size of the primary particles, the diameter of the voids and channels and their macroscopic proportion by volume were determined by means of scanning electron microscopy or electron probe microanalysis, in each case on particle surfaces and on particle cross sections of the silica gel. b) Polymerization of propylene The polymerization was carried out in a vertically stirred gas-phase reactor having a utilizable capacity of 800 1 in the presence of hydrogen as molecular weight regulator. The reactor contained an agitated fixed bed of finely divided polymer. The reactor output of polymer was 152 kg of polypropylene per hour. Gaseous propylene was passed into the gas-phase reactor at 80°C and at a pressure of 32 bar. Polymerization was carried out continuously at a mean residence time of 1.5 hours with the aid of the titanium-containing solid component a) described in Example 1 a, with 6.6 g/h of the titanium-containing solid component a), 1384 mmol/h of triethylaluminum and 40 mmol/h of dimethoxyisobutylisopropylsilane being used as cocatalyst. After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 12.2 g/10 min at 230°C and 2.16 kg (in accordance with DIN 53 735) was obtained. comparative Example A Propylene was polymerized using a method similar to the example according to the present invention with the scune catalyst system and under the same conditions, but using a titanium-containing solid component a) containing a granular silica gel having the following properties: After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 12.5 g/10 min at 230C and 2.16 kg (in accordance with DIN 53 735) was obtained. Table I below shows, both for Example 1 according to the present invention and for Comparative Example A, the productivity of the catalyst system used and also the following properties of the propylene homopolymers obtained in each case: xylene-soluble proportion (measure of the stereospecificity of the polymer), heptane-soluble proportion (measure of the stereospecificity of the polymer), chlorine content, bulk density, shear modulus (G modulus), viscosity and number of microspecks. Comparison of Example 1 according to the present invention with Comparative Example A makes it clear that the catalyst system of the present invention has a higher productivity and leads to polymers of propylene having an increased stereospecificity (lower xylene- and heptane-soluble proportions), a reduced chlorine content and an increased bulk density. Furthermore, the polymers of propylene obtained with the aid of the catalyst system of the present invention also have a higher stiffness (higher G modulus) and a significantly reduced number of nicrospecks. Example 2 i) Preparation of the titanium-containing solid components (1) In a first stage, finely divided silica gel (Si02) having a particle diameter of from 20 to 45 µm, a pore volume of 1.5 cm2/g and a specific surface area of 260 m2/g was admixed with a solution of n-butyloctylmagnesium in n-heptane, with 0.3 mol of the magnesium compound being used per mole of Si02. The finely divided silica gel also had a mean particle size of the primary particles of 3-5 µm and had voids and channels having a diameter of 3-5 µm, with the macroscopic proportion by volume of the voids and channels in the total particle being about 15%. The solution was stirred for 45 minutes at 95°C, then cooled to 20°C, after which the 10-fold molar amount, based on the organomagnesium compound, of hydrogen chloride was passed in. After 60 minutes, the reaction product was admixed while stirring continuously with 3 mol of ethanol per mole of magnesium. This mixture was stirred for 0.5 hour at 80C and subsequently admixed with 7.2 mol of titanium tetrachloride and 0.5 mol of di-n-butyl phthalate, in each case based on 1 mol of magnesium. The mixture was subsequently stirred for 1 hour at 100°C, the solid thus obtained was filtered off and washed a number of times with ethylbenzene. The solid product thus obtained was extracted for 3 hours at 125°C with a 10% strength by volume solution of titanium tetrachloride in ethylbenzene. The solid product was then separated from the extractant by filtration and washed with n-heptane until the extractant contained only 0.5% by weight of titanium tetrachloride. The titanium-containing solid component contained The particle diameter was determined by Coulter Counter analysis (particle size distribution of the silica gel particles), the pore volume and the specific surface area were determined by nitrogen adsorption in accordance with DIN 66131 or by mercury porosimetry in accordance with DIN 66133. The mean particle size of the primary particles, the diameter of the voids and channels and their macroscopic proportion by volume were determined by means of scanning electron microscopy or electron probe microanalysis, in each case on particle surfaces and on particle cross sections of the silica gel. b) Polymerization of propylene The polymerization was carried out in a vertically stirred gas-phase reactor having a utilizable capacity of 800 1 in the presence of hydrogen as molecular weight regulator. The reactor contained an agitated fixed bed of finely divided polymer. Gaseous propylene was passed into the gas-phase reactor at 80°C and at a pressure of 32 bar. Polymerization was carried out continuously at a mean residence time of 1.5 hours with the aid of the titanium-containing solid component a) described in Example 2 a, with 7.4 g/h of the titanium-containing solid component a), 450 mmol/h of triethylaluminum and 45 mmol/h of dimethoxyisobutylisopropyl-silane being used as cocatalyst. After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 11.9 g/10 min at 230C and 2.16 kg (in accordance with DIN 53 735) was obtained. Comparative Example B Propylene was polymerized using a method similar to Example 2 according to the present invention with the same catalyst system and under the same conditions, but using a titanium-containing solid component a) containing a granular silica gel having the following properties: Proportion of voids and channels in the total particle: After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 12.4 g/10 min at 230'c and 2.16 kg (in accordance with DIN 53 735) was obtained. Example 3 The procedure of Example 2 according to the present invention was repeated. Propylene was passed into a vertically stirred 800 1 gas-phase reactor at a mean residence time of 1.5 hours. Polymerization was carried out continuously at a mean residence time of 1.5 hours, with 6.6 g/h of the titanium-containing solid component described, 450 mmol/h of the aluminum component and 15 mmol/h of dimethoxyisobutylisopropylsilane being used as catalyst constituents. After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 12.3 g/10 min at 230°C and 2.16 kg (in accordance with DIN 53 735) was obtained. Comparative Example C Propylene was polymerized using a method similar to Example 3 according to the present invention with the same catalyst system and under the same conditions, but using a titanium-containing solid component a) containing a granular silica gel having the following properties: After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 13.0 g/10 min at 230°C and 2.16 kg (in accordance with DIN 53 735) was obtained. Example 4 The procedure of Example 2 according to the present invention was repeated. Propylene was passed into a vertically stirred 800 1 gas-phase reactor at a mean residence time of 1.5 hours. Polymerization was carried out continuously at a mean residence time of 1.5 hours, with 5.9 g/h of the titanium-containing solid component described/ 450 mmol/h of the aluminum component and 9 mmol/h of dimethoxyisobutylisopropylsilane being used as catalyst constituents. After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 12.8 g/10 min at 230*C and 2.16 kg (in accordance with DIN 53 735) was obtained. Comparative Example D Propylene was polymerized using a method similar to Example 4 according to the present invention with the Seune catalyst system and under the same conditions, but using a titanium-containing solid component a) containing a granular silica gel having the following properties: After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 12.1 g/10 min at 230°C and 2.16 kg (in accordance with DIN 53 735) was obtained. Table II below shows, both for Examples 2 to 4 according to the present invention and for Comparative Exeunples A to C, the productivity of the catalyst system used and also the following properties of the propylene homopolymers obtained in each case: xylene-soluble proportion (measure of the stereospecificty of the polymer), chlorine content and stiffness (G modulus). Comparison of Examples 2 to 4 according to the present invention with Comparative Examples B to D makes it clear that the process of the present invention has a higher productivity and leads to polymers of propylene having an increased stereospecificity (lower xylene-soluble proportions), a reduced chlorine content and an increased stiffness (higher G modulus). WE CLAIM: 1. A process for producing a catalyst system of the Ziegler-Natta type, comprising as active constituents (a) a titanium-containing solid component comprising a compound of titanium, a compound of magnesium, a halogen, silica gel as support and a carboxylic ester as electron donor compound, and also, as cocatalyst, (b) an aluminum compound and (c) if desired, a further electron donor compound, wherein the silica gel used has a mean particle diameter of from 5 to 200 µm, a mean particle diameter of the primary particles of from 1 to 10 µm and voids or channels having a mean diameter of from 1 to 10 µm whose macroscopic proportion by volume in the total particle is in the range from 5 to 20% wherein said titanium containing solid component and said cocatalyst and if desired said further electron donor are reacted together at from 0 to 150oC and at a pressure of from 1 to 100 bar to obtain said catalyst system. 2. The process as claimed in claim 1, wherein the silica gel used has voids and channels having an average diameter of from 1 to 5 µm whose macroscopic proportion by volume in the total particle is in the range from 5 to 15%. 3. The process as claimed in claim 1 or 2, wherein the silica gel used is spray dried. 4. The process as claimed in any of claims 1 to 3, wherein the further electron donor compound c) used in an organosilicon compound of the general formula (I) R1nSi(0R2)4-n (I), where R1 are identical or different and are each a C1-C20-alkyl group, a 5- to 7-membered cycloalkyl group which in tum can bear a C1-C10-alkyl group, or a C6-C20-aryl or arylalkyl group, R2 are identical or different and are each a C1-C20-alkyl group and n is 1, 2 or 3. 5. The process as claimed in any of claims 1 to 4, wherein the aluminum compound b) used is a trialkylaluminum compound whose alkyl groups each have from 1 to 8 carbon atoms. 6. A process for preparing polymers of propylene by polymerization of propylene and, if desired, added comonomers at from 20 to 150°C and at pressures of from 1 to 100 bar in the presence of a Ziegler-Natta catalyst system, wherein said catalyst system being produced by the process as claimed in any of claims 1 to 5. 7. The process as claimed in claim 6, wherein the propylene is polymerized at from 20 to 100°C, at pressures of from 15 to 40 bar and at mean residence times of from 0.5 to 5 hours, 8. A film, fiber or molding comprising a polymer as prepared by the process of claim 6 or 7. 9. A process for producing a catalyst system substantially as hereinbefore described. 10. A process for preparing polymers of propylene by polymerization of propylene substantially as hereinbefore described. 11. A film, fiber or molding made from the polymers of propylene substantially as hereinbefore described.

Full Text

The present invention relates to catalyst systems of the Ziegler-Natta type comprising as active constituents
a) a titanium-containing solid component comprising a compound
of titanium, a compound of magnesium, a halogen, silica gel
as support and a carboxylic ester as electron donor compound,
and also, as cocatalyst,
b) an aluminum compound and
c) if desired, a further electron donor compound,
wherein the silica gel used has a mean particle diameter of
from 5 to 200 µm, a mean particle diameter of the primary
particles of from 1 to 10 µm and voids or channels having a
mean diameter of from 1 to 10 µm whose macroscopic proportion
by volume in the total particle is in the range from 5 to j
20%.
In addition, the invention provides a process for producing such Ziegler-Natta catalyst systems, a process for preparing polymers of propylene using these catalyst systems, the polymers obtainable in this way and also films, fibers and moldings comprising these polymers.
Catalyst systems of the Ziegler-Natta type are known, inter alia, from EP-B 014523, EP-A 023425, EP-A 045975 and EP-A 195497. These systems are used, in particular, for the polymerization of C2-C10-alk-l-enes and comprise, inter alia, compounds of polyvalent titanium, aluminum halides and/or aluminum alkyls, and also electron donor compounds, particularly silicon compounds, ethers,, carboxylic esters, ketones and lactones which are used, on the one hand, in connection with the titanium component and, on the other hand, as cocatalyst.
The Ziegler-Natta catalysts are usually produced in two steps. The titanium-containing solid component is produced first and subsequently reacted with the cocatalyst. The polymerization is subsequently carried out using the catalysts thus obtained.
Furthermore, US-A 48 57 613 and US-A 52 88 824 describe catalyst systems of the Ziegler-Natta type which comprise a titanium-containing solid component and aluminum compound plus

organic silane compounds as external electron donor compounds. The catalyst systems obtained in this way have, inter alia, a good productivity and give polymers of propylene having a high stereospecificity, ie. a high isotacticity, a low chlorine I content and a good morphology, viz. a low proportion of fines.
If films are produced from polymers obtained by means of the catalyst systems described in US-A 48 57 613 and US-A 52 88 824, the increased occurrence of microspecks, ie. small irregularities on the surface of the films, is frequently observed. If such microspecks occur to a great extent, they impair the optical quality of the film.
It is an object of the present invention, starting from the catalyst systems described in US-A 48 57 613 and US-A 52 88 824, to develop an improved catalyst system of the Ziegler-Natta type which does not have the abovementioned disadvantages in respect of the formation of microspecks and additionally gives a high productivity and stereospecificity of the polymers thus obtained.
We have found that this object is achieved by means of the catalyst systems of the Ziegler-Natta type defined in the introduction.
The catalyst systems of the present invention contain, inter alia, a cocatalyst in addition to a titanium-containing solid component a). The cocatalyst may here be the aluminum compound b). Preferably, an additional electron donor compound c) is used as a further constituent of the cocatalyst together with this aluminum compound b).
To produce the titanium-containing solid component a), titanium compounds used are generally halides or alkoxides of trivalent or tetravalent titanium, with the chlorides of titanium, in particular titanium tetrachloride, being preferred. The titanium-containing solid component also contains silica gel as support.
In addition, compounds of magnesium are used, inter alia, in the production of the titanium-containing solid component. Suitable magnesium compounds are, in particular, magnesium halides, magnesium alkyls and magnesium aryls, and also magnesium alkoxy and magnesium aryloxy compounds, with preference being given to using magnesium dichloride, magnesium dibromide and di(C1-C10-alkyl)magnesium compounds. The titanium-containing solid

component can additionally contain halogen, preferably chlorine or bromine.
The titanium-containing solid component a) also contains electron donor compounds, for example monofunctional or polyfunctional carboxylic acids, carboxylic anhydrides and carboxylic esters, also ketones, ethers, alcohols, lactones, and organophosphorus and organosilicon compounds. As electron donor compounds within the titanium-containing solid component, preference is given to using phthalic acid derivatives of the general formula (II)

where X and Y are each a chlorine atom or a C1-C10-alkoxy radical or together are oxygen. Particularly preferred electron donor compounds are phthalic esters in which X and Y are each a C1-C8-alkoxy radical, for example a methoxy, ethoxy, propyloxy or a butyloxy radical.
Further preferred electron donor compounds within the titanium-containing solid components are, inter alia, diesters of 3- or 4-membered, substituted or unsubstituted cycloalkyl-l,2-dicarboxylic acids, and also monoesters of substituted or unsubstituted ben2ophenone-2-carboxylic acids. The hydroxy compounds used for these esters are the alcohols customary in esterification reactions, for example C1-C15-alkanols and C5-C7-cycloalkanols which may in turn bear C1-C10-alkyl groups, also C8-C10-phenols.
The titanium-containing solid component can be produced by methods known per se. Examples of such methods are described, inter alia, in EP-A 45 975, EP-A 45 977, EP-A 86 473, EP-A 171 200, GB-A 2 111 066, US-A 48 57 613 and US-A 52 88 824.
For producing the titanium-containing solid component a), the following two-stage process is preferably employed:
In the first stage, silica gel (Si02) generally having a mean particle diameter of from 5 to 200 um, in particular from 20 to 70 um, a pore volume of from 0.1 to 10 cm2/g, in particular from 1.0 to 4.0 cm3/g, and a specific surface area of from 10 to 1000 m2/g, in particular from 100 to 500 m2/g, as finely divided support is first admixed with a solution of the

magnesium-containing compound in a liquid alkane, after which this mixture is stirred for from 0.5 to 5 hours at from 10 to 120"C. Preference is given to using from 0.1 to 1 mol of the magnesium compound per mol of the support. Subsequently, while stirring continuously, a halogen or a hydrogen halide, in particular chlorine or hydrogen chloride, is added in an at least two-fold, preferably at least five-fold, molar excess, based on the magnesium-containing compound. After from about 30 to 120 ninutes, this reaction product is, at from 10 to 150C, admixed with a C1-C8-alkanol, in particular ethanol, a halide or an alkoxide of trivalent or tetravalent titanium, in particular titanium tetrachloride, and also an electron donor compound. In this procedure, from 1 to 5 mol of the trivalent or tetravalent titanium and from 0.01 to 1 mol, in particular from 0.1 to 0.5 mol, of the electron donor compound are used per mol of magnesium in the solid obtained from the first stage. This mixture is stirred for at least 1 hour at from 10 to 150c, the solid thus obtained is subsequently filtered off and washed with a C7-C10-alkylbenzene, preferably with ethylbenzene.
In the second stage, the solid obtained from the first stage is extracted for a few hours at from 100 to 150°C with excess titanium tetrachloride or an excess of a solution of titanium tetrachloride in an inert solvent, preferably an alkylbenzene, with the solvent containing at least 5% by weight of titanium tetrachloride. The product is then washed with a liquid alkane until the washings contain less than 2% by weight of titanium tetrachloride.
The titanium-containing solid component obtainable in this way is used together with a cocatalyst as Ziegler-Natta catalyst system. A suitable cocatalyst is here, inter alia, an aluminum compound b).
Aluminum compounds b) suitable as cocatalysts are trialkylaluminums and also those compounds in which an alkyl group is replaced by an alkoxy group or by a halogen atom, for example by chlorine or bromine. Preference is given to using trialkylaluminum compounds whose alkyl groups each have from 1 to 8 carbon atoms, for example trimethylaluminum, triethylaluminum or methyldiethylaluminum.
Preference is given to using not only the aluminum compound b) but also electron donor compounds c) as further cocatalyst, for i example monofunctional or polyfunctional carboxylic acids, carboxylic anhydrides and carboxylic esters, also ketones, ethers, alkohols, lactones, and organophosphorus and

organosilicon compounds. Preferred electron donor compounds are here organosilicon compounds of the general formula (I)
where
R1 are identical or different and are each a C1-C2o-alkyl group, a 5- to 7-membered cycloalkyl group which in turn can bear a C1-C10-alkyl group, or a C6-C2o-aryl or aralkyl group, R2 are identical or different and are each a C1-C2o-alkyl group and n is 1, 2 or 3. Particular preference is here given to those compounds in which R1 is a C1-C8-alkyl group or a 5- to 7-membered cycloalkyl group, and R2 is a C1-C4-alkyl group and n is 1 or 2.
Among these compounds, particular emphasis is given to dimethoxydiisopropylsilane, dimethoxyisobutylisopropylsilane, dimethoxydiisobutylsilane, dimethoxydicyclopentylsilane, dimethoxyisobutyl-sec-butylsilane, dimethoxyisopropyl-sec-butylsilane, diethoxydicyclopentylsilane and diethoxyisobutylisopropylsilane.
The individual compounds b) and, if desired, c) can be used as cocatalyst in any order, either individually or as a mixture of two components.
According to the present invention, the silica gel used in the titanium-containing solid component a) is a finely divided silica gel which has a mean particle diameter of from 5 to 200 µm, in particular from 20 to 70 µm, and a mean particle diameter of the primary particles of from 1 to 10 µm, in particular from 1 to 5 µm. For the purposes of the present invention, the primary particles are porous, granular silica gel particles which are obtained from an Si02 hydrogel by milling, if desired after appropriate sieving.
Furthermore, the finely divided silica gel to be used according to the present invention also has voids or channels having a mean diameter of from 1 to 10 µm, in particular from 1 to 5 µm, whose macroscopic proportion by volume in the total particle is in the range from 5 to 20%, in particular in the range from 5 to 15%. The finely divided silica gel additionally has, in particular, a pore volume of from 0.1 to 10 cm2/g, preferably from 1.0 to 4.0 cm2/g, and a specific surface area of from 10 to 1000 m2/g, preferably from 100 to 500 m2/g.

Owing to the voids or channels present in the finely divided silica gel, there is a significantly improved distribution of the catalytically active components in the support material. Furthermore, a material pervaded in this way by voids and channels has a positive effect on the diffusion-controlled supply of monomers and cocatalysts and thus also on the polymerization kinetics. Such a finely divided silica gel is, inter alia, obtainable by spray drying milled, appropriately sieved Si02 hydrogel, which for this purpose is slurried with water or an aliphatic alcohol. However, such a finely divided silica gel is also commercially available.
The silica gel is present within the titanium-containing solid component a) in such amounts that from 0.1 to 1.0 mol, in particular from 0.2 to 0.5 mol, of the magnesium compound is present per 1 mol of the silica gel.
The cocatalytically active compounds b) and, if desired, c) can be allowed to act either successively or together on the titanium-containing solid component a). This is usually carried out at from 0 to 150°C, in particular from 20 to 90°C, and at pressures of from 1 to 100 bar, in particular from 1 to 40 bar.
The cocatalysts b) and, if used, c) are preferably used in such an amount that the atomic ratio between aluminum from the aluminum compound and titanium from the titanium-containing solid component a) is from 10:1 to 800:1, in particular from 20:1 to 200:1, and the molar ratio between the aluminum compound and the electron donor compound c) used as cocatalyst is from 1:1 to 250:1, in particular from 10:1 to 80:1.
The catalyst systems of the present invention are particularly suitable for preparing polymers of propylene, ie. homopolymers of propylene and copolymers of propylene together with other C2-C10-alk-l-enes.
The description C2-C10-alk-l-enes here refers to, inter alia, ethylene, but-1-ene, pent-1-ene, hex-1-ene, hept-1-ene or oct-1-ene, with the comonomers ethylene and but-1-ene being particularly preferred.
However, the catalyst systems of the present invention can also be used for preparing polymers of other C2-C10-alk-l-enes, for example for preparing homopolymers or copolymers of ethylene, but-1-ene, pent-1-ene, hex-1-ene, hept-1-ene or oct-1-ene.

The preparation of such polymers of C2-C10-alk-l-enes can be carried out in the customary reactors used for the polymerization of C2-C10-alk-l-enes, either batchwise or preferably continuously, for example as suspension polymerization or preferably as gas-phase polymerization. Suitable reactors include continuously operated stirred reactors containing a fixed bed of finely divided polymer which is usually kept in motion by means of suitable agitators. Of course, the reaction can also be carried out in a plurality of reactors connected in series. The reaction time, ie. the mean residence time, is determined by the reaction conditions selected in each case. It is usually from 0.2 to 20 hours, mostly from 0.5 to 10 hours.
The polymerization reaction is advantageously carried out at from 20 to 150C and at pressures of from 1 to 100 bar. Preference is given to temperatures of from 40 to 100°C and pressures of from 10 to 50 bar. Specifically for the preparation of propylene homopolymers, the polymerization reaction is preferably carried out at from 50 to 100c, in particular from 60 to 90°C, at pressures of from 15 to 40 bar, in particular from 20 to 35 bar, and at mean residence times of from 0.5 to 5 hours, in particular from 0.5 to 3 hours. The molecular weight of the polyalk-1-enes formed can be controlled by addition of regulators customary in polymerization technology, for example hydrogen, and adjusted over a wide range. It is also possible to make concomitant use of inert solvents such as toluene or hexane, inert gas such as nitrogen or argon and relatively small amounts of polypropylene powder.
The propylene homopolymers and copolymers obtained by means of the catalyst system of the present invention are obtainable in the molecular weights usual for polyalk-1-enes, with preference being given to polymers having molecular weights (weight average) of from 20,000 to 500,000. Their melt flow indices at 230°C and under a load of 2.16 kg, in accordance with DIN 53 7 35, are in the range from 0.1 to 100 g/10 min, in particular in the range from 0.5 to 50 g/10 min.
The catalyst system of the present invention has, compared with the catalyst systems known hitherto, a higher productivity and an improved stereospecificity, in particular in gas-phase polymerization. The polymers obtainable in this way also have a high bulk density and a low residual chlorine content. Furthermore, the catalyst system of the present invention has the advantage of significantly reducing the microspeck formation in the polymers obtained therefrom.

Owing to their good mechanical properties, the propylene polymers prepared using the catalyst system of the present invention are especially suitable for producing films, fibers and moldings.
Examples
Example 1
a) Production of the titanium-containing solid component (1)
In a first stage, finely divided silica gel (SiO2) having a particle diameter of from 20 to 45 pun, a pore volume of 1.5 cm2/g and a specific surface area of 260 m2/g was admixed with a solution of n-butyloctylmagnesium in n-heptane, with 0.3 mol of the magnesium compound being used per mol of Si02. The finely divided silica gel was additionally characterized by a mean particle size of the primary particles of 3-5 µm and by voids and channels having a diameter of 3-5 µm with the macroscopic proportion by volume of the voids and channels in the total particle being about 15%. The solution was stirred for 45 minutes at 95°C, then cooled to 20c, after which the 10-fold molar eunount, based on the organomagnesium compound, of hydrogen chloride was passed in. After 60 minutes, the reaction product was admixed while stirring continuously with 3 mol of ethanol per mol of magnesium. This mixture was stirred for 0.5 hour at 80°C and subsequently admixed with 7.2 mol of titanium tetrachloride and 0.3 mol of di-n-butyl phthalate, in each case based on 1 mol of magnesium. The mixture was subsequently stirred for 1 hour at 100c, the solid thus obtained was filtered off and washed a number of times with ethylbenzene.
The solid product thus obtained was extracted for 3 hours at 125°C with a 10% strength by volume solution of titanium tetrachloride in ethylbenzene. The solid product was then separated from the extractant by filtration and washed with n-heptane until the extractant contained only 0.3% by weight of titanium tetrachloride.
The titanium-containing solid component contained

The particle diameter was determined by Coulter Counter analysis (particle size distribution of the silica gel particles), the pore volume and the specific surface area were determined by nitrogen adsorption in accordance with DIN 66131 or by mercury porosimetry in accordance with DIN 66133. The mean particle size of the primary particles, the diameter of the voids and channels and their macroscopic proportion by volume were determined by means of scanning electron microscopy or electron probe microanalysis, in each case on particle surfaces and on particle cross sections of the silica gel.
b) Polymerization of propylene
The polymerization was carried out in a vertically stirred gas-phase reactor having a utilizable capacity of 800 1 in the presence of hydrogen as molecular weight regulator. The reactor contained an agitated fixed bed of finely divided polymer. The reactor output of polymer was 152 kg of polypropylene per hour.
Gaseous propylene was passed into the gas-phase reactor at 80°C and at a pressure of 32 bar. Polymerization was carried out continuously at a mean residence time of 1.5 hours with the aid of the titanium-containing solid component a) described in Example 1 a, with 6.6 g/h of the titanium-containing solid component a), 1384 mmol/h of triethylaluminum and 40 mmol/h of dimethoxyisobutylisopropylsilane being used as cocatalyst.
After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 12.2 g/10 min at 230°C and 2.16 kg (in accordance with DIN 53 735) was obtained.
comparative Example A
Propylene was polymerized using a method similar to the example according to the present invention with the scune catalyst system and under the same conditions, but using a titanium-containing solid component a) containing a granular silica gel having the following properties:

After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 12.5 g/10 min at 230C and 2.16 kg (in accordance with DIN 53 735) was obtained.
Table I below shows, both for Example 1 according to the present invention and for Comparative Example A, the productivity of the catalyst system used and also the following properties of the propylene homopolymers obtained in each case: xylene-soluble proportion (measure of the stereospecificity of the polymer), heptane-soluble proportion (measure of the stereospecificity of the polymer), chlorine content, bulk density, shear modulus (G modulus), viscosity and number of microspecks.

Comparison of Example 1 according to the present invention with Comparative Example A makes it clear that the catalyst system of the present invention has a higher productivity and leads to polymers of propylene having an increased stereospecificity (lower xylene- and heptane-soluble proportions), a reduced chlorine content and an increased bulk density. Furthermore, the polymers of propylene obtained with the aid of the catalyst system of the present invention also have a higher stiffness (higher G modulus) and a significantly reduced number of nicrospecks.
Example 2
i) Preparation of the titanium-containing solid components (1)
In a first stage, finely divided silica gel (Si02) having a particle diameter of from 20 to 45 µm, a pore volume of 1.5 cm2/g and a specific surface area of 260 m2/g was admixed with a solution of n-butyloctylmagnesium in n-heptane, with 0.3 mol of the magnesium compound being used per mole of Si02. The finely divided silica gel also had a mean particle size of the primary particles of 3-5 µm and had voids and channels having a diameter of 3-5 µm, with the macroscopic proportion by volume of the voids and channels in the total particle being about 15%. The solution was stirred for 45 minutes at 95°C, then cooled to 20°C, after which the 10-fold molar amount, based on the organomagnesium compound, of hydrogen chloride was passed in. After 60 minutes, the reaction product was admixed while stirring continuously with 3 mol of ethanol per mole of magnesium. This mixture was stirred for 0.5 hour at 80C and subsequently admixed with 7.2 mol of titanium tetrachloride and 0.5 mol of di-n-butyl phthalate, in each case based on 1 mol of magnesium. The mixture was subsequently stirred for 1 hour at 100°C, the solid thus obtained was filtered off and washed a number of times with ethylbenzene.
The solid product thus obtained was extracted for 3 hours at 125°C with a 10% strength by volume solution of titanium tetrachloride in ethylbenzene. The solid product was then separated from the extractant by filtration and washed with n-heptane until the extractant contained only 0.5% by weight of titanium tetrachloride.
The titanium-containing solid component contained

The particle diameter was determined by Coulter Counter analysis (particle size distribution of the silica gel particles), the pore volume and the specific surface area were determined by nitrogen adsorption in accordance with DIN 66131 or by mercury porosimetry in accordance with DIN 66133. The mean particle size of the primary particles, the diameter of the voids and channels and their macroscopic proportion by volume were determined by means of scanning electron microscopy or electron probe microanalysis, in each case on particle surfaces and on particle cross sections of the silica gel.
b) Polymerization of propylene
The polymerization was carried out in a vertically stirred gas-phase reactor having a utilizable capacity of 800 1 in the presence of hydrogen as molecular weight regulator. The reactor contained an agitated fixed bed of finely divided polymer.
Gaseous propylene was passed into the gas-phase reactor at 80°C and at a pressure of 32 bar. Polymerization was carried out continuously at a mean residence time of 1.5 hours with the aid of the titanium-containing solid component a) described in Example 2 a, with 7.4 g/h of the titanium-containing solid component a), 450 mmol/h of triethylaluminum and 45 mmol/h of dimethoxyisobutylisopropyl-silane being used as cocatalyst.
After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 11.9 g/10 min at 230C and 2.16 kg (in accordance with DIN 53 735) was obtained.
Comparative Example B
Propylene was polymerized using a method similar to Example 2 according to the present invention with the same catalyst system and under the same conditions, but using a titanium-containing solid component a) containing a granular silica gel having the following properties:

Proportion of voids and channels in
the total particle: After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 12.4 g/10 min at 230'c and 2.16 kg (in accordance with DIN 53 735) was obtained.
Example 3
The procedure of Example 2 according to the present invention was repeated. Propylene was passed into a vertically stirred 800 1 gas-phase reactor at a mean residence time of 1.5 hours. Polymerization was carried out continuously at a mean residence time of 1.5 hours, with 6.6 g/h of the titanium-containing solid component described, 450 mmol/h of the aluminum component and 15 mmol/h of dimethoxyisobutylisopropylsilane being used as catalyst constituents.
After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 12.3 g/10 min at 230°C and 2.16 kg (in accordance with DIN 53 735) was obtained.
Comparative Example C
Propylene was polymerized using a method similar to Example 3 according to the present invention with the same catalyst system and under the same conditions, but using a titanium-containing solid component a) containing a granular silica gel having the following properties:

After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 13.0 g/10 min at 230°C and 2.16 kg (in accordance with DIN 53 735) was obtained.
Example 4
The procedure of Example 2 according to the present invention was repeated. Propylene was passed into a vertically stirred 800 1 gas-phase reactor at a mean residence time of 1.5 hours. Polymerization was carried out continuously at a mean residence time of 1.5 hours, with 5.9 g/h of the titanium-containing solid

component described/ 450 mmol/h of the aluminum component and 9 mmol/h of dimethoxyisobutylisopropylsilane being used as catalyst constituents.
After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 12.8 g/10 min at 230*C and 2.16 kg (in accordance with DIN 53 735) was obtained.
Comparative Example D
Propylene was polymerized using a method similar to Example 4 according to the present invention with the Seune catalyst system and under the same conditions, but using a titanium-containing solid component a) containing a granular silica gel having the following properties:

After completion of the gas-phase polymerization, a propylene homopolymer having a melt flow index of 12.1 g/10 min at 230°C and 2.16 kg (in accordance with DIN 53 735) was obtained.
Table II below shows, both for Examples 2 to 4 according to the present invention and for Comparative Exeunples A to C, the productivity of the catalyst system used and also the following properties of the propylene homopolymers obtained in each case: xylene-soluble proportion (measure of the stereospecificty of the polymer), chlorine content and stiffness (G modulus).

Comparison of Examples 2 to 4 according to the present invention with Comparative Examples B to D makes it clear that the process of the present invention has a higher productivity and leads to polymers of propylene having an increased stereospecificity (lower xylene-soluble proportions), a reduced chlorine content and an increased stiffness (higher G modulus).

WE CLAIM:
1. A process for producing a catalyst system of the Ziegler-Natta type, comprising
as active constituents
(a) a titanium-containing solid component comprising a compound of titanium, a compound of magnesium, a halogen, silica gel as support and a carboxylic ester as electron donor compound, and also, as cocatalyst,
(b) an aluminum compound and
(c) if desired, a further electron donor compound, wherein the silica gel used has a mean particle diameter of from 5 to 200 µm, a mean particle diameter of the primary particles of from 1 to 10 µm and voids or channels having a mean diameter of from 1 to 10 µm whose macroscopic proportion by volume in the total particle is in the range from 5 to 20% wherein said titanium containing solid component and said cocatalyst and if desired said further electron donor are reacted together at from 0 to 150oC and at a pressure of from 1 to 100 bar to obtain said catalyst system.

2. The process as claimed in claim 1, wherein the silica gel used has voids and channels having an average diameter of from 1 to 5 µm whose macroscopic proportion by volume in the total particle is in the range from 5 to 15%.
3. The process as claimed in claim 1 or 2, wherein the silica gel used is spray dried.

4. The process as claimed in any of claims 1 to 3, wherein the further electron
donor compound c) used in an organosilicon compound of the general formula
(I)
R1nSi(0R2)4-n (I),
where R1 are identical or different and are each a C1-C20-alkyl group, a 5- to 7-membered cycloalkyl group which in tum can bear a C1-C10-alkyl group, or a C6-C20-aryl or arylalkyl group, R2 are identical or different and are each a C1-C20-alkyl group and n is 1, 2 or 3.
5. The process as claimed in any of claims 1 to 4, wherein the aluminum compound b) used is a trialkylaluminum compound whose alkyl groups each have from 1 to 8 carbon atoms.
6. A process for preparing polymers of propylene by polymerization of propylene and, if desired, added comonomers at from 20 to 150°C and at pressures of from 1 to 100 bar in the presence of a Ziegler-Natta catalyst system, wherein said catalyst system being produced by the process as claimed in any of claims 1 to 5.
7. The process as claimed in claim 6, wherein the propylene is polymerized at from 20 to 100°C, at pressures of from 15 to 40 bar and at mean residence times of from 0.5 to 5 hours,
8. A film, fiber or molding comprising a polymer as prepared by the process of claim 6 or 7.

9. A process for producing a catalyst system substantially as hereinbefore
described.
10. A process for preparing polymers of propylene by polymerization of propylene
substantially as hereinbefore described.
11. A film, fiber or molding made from the polymers of propylene substantially as
hereinbefore described.

Documents:

1380-mas-96 abstract(duplicate).pdf

1380-mas-96 abstract.pdf

1380-mas-96 claims(duplicate).pdf

1380-mas-96 claims.pdf

1380-mas-96 correspondance po.pdf

1380-mas-96 description(complete).pdf

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Patent Number

198067

Indian Patent Application Number

1380/MAS/1996

PG Journal Number

30/2009

Publication Date

24-Jul-2009

Grant Date

Date of Filing

05-Aug-1996

Name of Patentee

NOVOLEN TECHNOLOGY HOLDINGS C.V

Applicant Address

OOSTDUINLAAN 75, 2596 JJ, THE HAGUE

Inventors:

#	Inventor's Name	Inventor's Address
1	STEPHEN HUFFER	WEIMARER STR. 50, 67071 LUDWIGSHAFEN
2	JURGEN KERTH	WATTENHEIMER STR. 15, 67316 CARLSBERG
3	PETER KOLLE	AUF DEM KOPPEL 2/11, 67098 BAD DURKHEIM
4	PATRIK MULLER	JOHANNISKREUZER STR. 67, 67661 KAISERSLAUTERNM
5	RAINER HEMMERICH	LINDENWEG 10, 67269 GRUNSTADT, MEINOLF KERSTING, IN DER ACHEN 26, 67435, NEUSTADT
6	RAINER ALEXANDER WERNER	WELLSRING 33, 67098 BAD DURKHEIM
7	GUNTER SCHERER	MANDELBERGSTR.36, 67455 NEUSTADT
8	STEFAN SEELERT	MATTHAUS-MERIAN RING 24A, 67227 FRANKENTHAL

PCT International Classification Number

C08F4/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA