Title of Invention

CATALYST SYSTEMS OF THE ZIEGLER-ZATTA TYPE AND A PROCESS FOR PRODUCING THE SAME

Abstract

Catalyst systems of the Ziegler-Natta type Abstract The catalyst systems comprise as active constituents a) a titanium-containing solid component comprising a compound of titanium, a compound of magnesium, a halogen, an inorganic oxide as support and a carboxylic ester as electron donor compound, and also, as cocatalyst, b) an aluminum compound and c) optionally a further electron donor compound, wherein the inorganic oxide used has a pB of from 1 to 6, an average particle diameter of from 5 to 200 urn, an average primary particle diameter of from 1 to 20 urn and voids or channels having an average diameter of from 0.1 to 20 um and a macroscopic share of the volume of the overall particle within the range from 5 to 30 s.

Full Text

The present invention relates to catalyst systems or 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, an inorganic oxide as support and a carboxylic ester as electron donor compound, and also, as cocatalyst, b) an aluminum compound and c) optionally a further electron donor compound, wherein the inorganic oxide used has a pH of from 1 to 6, an average particle diameter of from 5 to 200 µm, an average primary particle diameter of from 1 to 20 µm and voids or channels having an average diameter of from 0.1 to 20 µm and a macroscopic share of the volume of the overall particle within the range from 5 to 30 %. The present invention also relates to a process for produC1ng such Ziegler-Natta catalyst systems, to the production of polymers of propylene with the aid of these catalyst systems, to the polymers thus obtainable, and to films, fibers and moldings composed of these polymers. Catalyst systems of the Ziegler-Natta type are known inter 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 alkyls, and also electron donor compounds, espeC1ally silicon compounds, ethers, carboxylic esters, ketones and lactones, used on the one hand in conjunction with the titanium component and, on the other hand, as cocatalyst. Ziegler-Natta catalysts are usually produced in two steps. First the titanium-containing solid component is produced. It is then reacted with the cocatalyst. The thus-obtained catalyst is then used to carry out the polymerization. Furthermore, US-A 48 57 613 and US-A 52 88 824 describe catalyst systems of the Ziegler-Hatta type which, as well as a titanium-containing solid component and an aluminum compound, comprise organic silane compounds as external electron donor compounds. The catalyst systems in question are notable inter alia for good productivity and yield polymers of propylene having high stereospeC1fiC1ty, i.e. high isotactiC1ty, a low chlorine content and good morphology, viz. a low proportion of fines. Propylene polymers obtained with the aid of the catalyst systems described in US-A 48 57 613 and US-A 52 88 824 still have certain proportions of xylene and heptane solubles, which is disadvantageous for some applications, for example in the food sector or in the hygiene sector. It is an object of the present invention to develop, on the basis of the catalyst systems described in US-A 48 57 613 and US-A 52 88 824, an improved catalyst system of the Ziegler-Natta type which does not have the abovementioned disadvantages in respect of the presence of xylene and heptane solubles and which, what is more, shall be notable for the high production and stereospeC1fiC1ty of the polymers obtained. We have found that this object is achieved by the initially defined catalyst systems of the Ziegler-Natta type. The catalyst systems of this invention, as well as a titanium-containing solid component a), further comprise a cocatalyst. The cocatalyst may be an aluminum compound b). Preferably, the cocatalyst, as well as this aluminum compound b), additionally comprises an electron donor compound c) as further constituent. The titanium-containing solid component a) is typically produced using halides or alkoxides of ter- or tetravalent titanium, preferably the chlorides of titanium, espeC1ally titanium tetrachloride. The titanium-containing solid component further comprises a support. In addition, the titanium-containing solid component is produced using, inter alia, compounds of magnesium. Suitable magnesium compounds for this purpose include in particular magnesium halides, magnesium alkyls and magnesium aryls and also magnesium alkoxy and magnesium aryloxy compounds, of which magnesium i dichloride, magnesium dibromide and magnesium di{C1-Cl0-alkyl) compounds are preferred. In addition, the titanium-containing solid component can further contain halogen, preferably chlorine or bromine. Phe titanium-containing solid component a) further comprises alectron donor compounds, for example mono- or polyfunctional :arboxylic aC1ds, carboxylic anhydrides and carboxylic esters, also ketones, ethers, alcohols, lactones and also Drganophosphorus and organosilicon compounds. Preferred electron ionor compounds for inclusion in the titanium-containing solid component are phthalic aC1d derivatives of the general formula (ID where X and y each represent a chlorine atom or a Cj-C1o-alkoxy radical or together represent oxygen. Particularly preferred electron donor compounds are phthalic esters in which X and Y are each C1-Cg-alkoxy, for example methoxy, ethoxy, propyloxy or butyloxy. Further preferred electron donor compounds for inclusion in the titanium-containing solid component include diesters of 3- or 4-membered, substituted or unsubstituted cycloalkyl-1,2-dicarboxylie aC1ds and also monoesters of substituted or unsubstituted benzophenone-2-carboxylic aC1ds. The hydroxy compounds used for these esters are the alcohols vhich are customarily used in esterification reactions, for example C1~C15~alkanols, C5-C7-cycloalkanols which may in turn bear C1-C1o-alkyl groups, and also C^-C1o-phenols. The titanium-containing solid component can be produced by methods known per se. Examples thereof 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. The titanium-containing solid component a) is preferably produced using the following two-stage process: In the first stage, an inorganic oxide, which generally has a pH of from 1 to 6, an average particle diameter of from 5 to 200 urn, espeC1ally of from 20 to 70Cim, a pore volume of from 0.1 to 10 cm3/g, espeC1ally of from 1.0 to 4.0 cm3/g, and a speC1fic surface area of from 10 to 1000 m2/g, espeC1ally of from 100 to 500 m2/g, is admixed with a solution of the magnesium-containing compound in a liquid alkane, and the mixture is stirred at iiua 10 to 120°C for from 0.5 to 5 hours. From 0.1 to 1 mol of the magnesium compound is preferably used per mole of the support. Subsequently, while the mixture is stirred continuously, a halogen or a hydrogen halide, espeC1ally chlorine or hydrogen chloride, is added in an at least twofold, preferably at least fivefold, molar excess, based on the magnesium-containing compound. After from about 30 to 120 minutes, this reaction product is admixed at from 10 to 15Q°C with a C1-Cg-alkanol, espeC1ally ethanol, a halide or an alkoxide of the ter- or tetravalent titanium, espeC1ally titanium tetrachloride, and also with an electron donor compound. The amounts used are, per mole of magnesium in the solid obtained in the first step, from 1 to 5 mol of the ter- or tetravalent titanium and from 0.01 to 1 mol, espeC1ally from 0.1 to 0.5 mol, of the electron donor compound. This mixture is stirred at from 10 to 150°C for at least 30 minutes, and the resulting solid substance is subsequently filtered off and washed with a C7-C1o-alkylbenzene, preferably with ethylbenzene. In the second stage, the solid obtained from the first stage is extracted for some hours at from 100 to 150°C with excess titanium tetrachloride or an excess solution of titanium tetrachloride in an inert solvent, preferably an alkylbenzene, in which case the solvent comprises at least 5 % by weight of titanium tetrachloride. The product is then washed with a liquid alkane until the titanium tetrachloride content of the wash liquor is less than 2 % by weight. The titanium-containing solid component obtainable in this way is combined with a cocatalyst to form a Ziegler-Katta catalyst system. The cocatalyst used includes an aluminum compound b). Aluminum compounds b) suitable for use as cocatalysts are trialkylaluminums and trialkylaluminum compounds where one alkyl group has been 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 trimethy 1 aluminum, triethylaluminum or methyldiethylaluminum. As well as said aluminum compound b), the cocatalyst further comprises an electron donor compound c), for example mono- or polyfunctional carboxylic aC1ds, carboxylic anhydrides and carboxylic esters, also ketones, ethers, alcohols, lactones and also organophosphorus and organosilicon compounds, Preferred electron donor compounds are organosilicon compounds of the general formula (I) where R1 is identical or different and represents C1-Cjg-alkyl, 5-, 6-or 7-membered cycloalkyl with or without C1-C1o-alkyl attached to it, or Cg-C2o-a^yl or -arylalkyl, R2 is identical or different and represents C1-C20-alkyl.- and n is 1. 2 or 3. Particular preference is given in this context to those compounds in which R1 is C1-Ce-alkyl or 5-, 6- or 7-membered cycloalkyl, R2 is C1-C4-alkyl, and n is 1 or 2. Among these compounds, particular emphasis is given to dimethoxydiisopropylsilane, dimethoxyisobutylisopropylsilane, dimethoxydiisobutylsilane, dimethoxydicyclopentylsilane, dimethoxyisobutylsec.butylsilane, dimethoxyisopropylsec.butylsilane, diethoxydicyclopentylsilane and diethoxyisobutylisopropylsilane. The individual compounds b) and optionally c) can be used as cocatalyst in any order, either individually or as a mixture of two components. According to the present invention, the titanium-containing solid component a) comprises a finely divided inorganic oxide having a pH of from 1 to 6, an average particle diameter of from S to 200 um, espeC1ally of from 20 to 70 ym, and an average primary particle diameter of from X to 20 um, espeC1ally of from 1 to 5 um. Primary particles are porous, granular oxide particles obtained by grinding, with or without previous sieving, from a corresponding hydrogel. The hydrogel in question is produced within the aC1dic range, i.e. within a range having a pH within the range from 1 to 6, or else aftertreated with appropriately aC1dic wash liquors for the purpose of purification. Furthermore, the finely divided inorganic oxide to be used according to this invention also has voids or channels having an average diameter of from 0.1 to 20 Jim, in particular of from 1 to 15 um, and a macroscopic share of the volume of the overall particle within the range from 5 to 30 *, in particular within the range from 10 to 30 %. The finely divided inorganic oxide further has in particular a pore volume of from 0.1 to 10 cm3/g, i preferably of from 1.0 to 4.0 cmVg, and a speC1fic surface area of from 10 to 1000 m2/g, preferably of from 100 to 500 m2/g. The pH, i.e. the negative decadic logarithm of the proton concentration of the inorganic oxide, is within tne range now A to 6, espeC1ally within the range from 2 to 5. Preferred inorganic oxides are in particular oxides of silicon, of aluminum, of titanium or of a metal of main group 1 or II of the Periodic Table. Very particularly preferred oxides include not only aluminum oxide or magnesium oxide or a sheet-silicate but also silica gel (SiOa), espeC1ally silica gel obtainable by spray drying. It is also possible to use cogels, i.e. mixtures of two different inorganic oxides. Owing to the voids or channels present in the finely divided inorganic oxide, there is a significantly improved distribution of the catalytically active components in the support material. The aC1dic centers on the oxide surface additionally bring about a more homogeneous loading with the catalyst constituents, in particular with the magnesium compound. In addition, 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 inorganic oxide is obtainable inter alia by spray drying ground, appropriately sieved hydrogel, which for this purpose is slurried up with water or an aliphatic alcohol. During the spray drying, the requisite pH of from 1 to 6 can also be obtained by using appropriately aC1dic primary particle suspensions. Such a finely divided inorganic oxide, however, is also commerC1ally available. The inorganic oxide is preferably present within the titanium-containing solid component a) in such amounts that for every mole of the inorganic oxide there is from 0.1 to 1.0 mol, espeC1ally from 0.2 to 0.5 mol, of the compound of magnesium. The cocatalytically active compounds b) and optionally c) can be made to act on the titanium-containing solid component a) not only in succession but also together. This is usually done at from 0 to 150°C, espeC1ally at from 20 to 90°C, and from 1 to 100 bar, espeC1ally from 1 to 40 bar. The cocatalysts b) and optionally c) are preferably used in such an amount that the atomic ratio between aluminum in the aluminum compound and titanium in the titanium-containing solid component a) is within the range from 10:1 to 800:1, espeC1ally within the range from 20:1 to 200;2, and the molar ratio between the aluminum compound and the cocatalyst electron donor compound c) * is within the range from 1:1 to 250:1, espeC1ally within the range from 10:1 to 80:1. The catalyst systems of this invention are used for produC1ng polymers of Ca-C1o-alk-1-enes. They are particularly highly suitable for produC1ng polymers of propylene and of ethylene, i.e. ethylene homopolymers, propylene homopolymers, and copolymers of ethylene and propylene with other C2-Cjo-alk-l-enes. The propylene and/or ethylene monomer content of these copolymers shall be at least 50 mcl%. Herein the designation C2-C1o-alk-l-enes includes inter alia ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene, of which ethylene, propylene and 1-butene are particularly preferred. However, the catalyst systems of this invention can also be used for produC1ng polymers of other C2-C1o-alk-l-enes, for example for produC1ng homo- or copolymers of 1-butene, of 1-pentene, of 1-hexene, of 1-heptene or of 1-octene. The catalyst system of this invention is preferably used to produce polymers containing from 50 to 100 mol% of propylene, from 0 to 50 mol%, espeC1ally from 0 to 30 mol%, of ethylene and from 0 to 20 mol%, espeC1ally from 0 to 10 mol%, of C^-Cto-alk-l-enes. The molSages always add up to 100. The production of such polymers of C2-C1o-alk-l-enes can be carried out in the customary reactors used for the polymerization of C2-C1o-alk-l-enes, either batchwise or preferably continuously, for example as a suspension polymerization or preferably as a gas-phase polymerization. Suitable reactors include continuously stirred reactors which contain a solid bed of finely divided polymer which is customarily kept in agitation by suitable stirring means, of course, the reaction can also be carried out in a plurality of reactors connected in series (reactor cascade). The reaction time depends cruC1ally on the particular reaction conditions used. It is customarily within the range from 0.2 to 20 hours, typically within the range from 0.5 to 10 hours. The polymerization reaction is advantageously carried out at from 20 to 150°C and from 1 to 100 bar. Preference is given to temperatures of from 40 to 100°C and pressures of from 10 to 50 bar. The molar mass of the resulting polyalk-1-enes can be controlled, and adjusted over a wide range, by addition of regulators customary in polymerization technology, for example hydrogen. It is further possible to use inert solvents such as, for example, toluene or hexane, an inert gas such as nitrogen or argon and minor amounts of polypropylene powder. The propylene homopolynters and copolymers obtained by means of the catalyst system of this invention are obtainable in the molar masses customary for polyalk-1-enes, preference being given to polymers having weight average molar masses within the range from 20,000 to 500,000. Their melt flow indices, at 230DC and a load of 2.16 kg, in accordance with DIN 53 735 are within the range from 0.1 to 100 g/10 min, in particular within the range from 0.5 to 50 g/10 min. The catalyst system of this invention, compared with existing catalyst systems, is notable for very high productivity and improved stereospeC1fiC1ty, in particular in gas-phase polymerizations. The polymers obtainable in this way are also notable for a high bulk density, reduced xylene solubles and a low residual chlorine content. Furthermore, the heptane solubles content of the polymer is reduced. Owing to their good mechanical properties, the propylene polymers produced using the catalyst system of this invention are espeC1ally suitable for produC1ng films, fibers and moldings. Examples Comparative Example A a) Production of the titanium-containing solid component (1) In a first stage, finely divided silica gel (Si02) having a particle diameter of from 20 to 45 \unr a pore volume of 1.5 cmVg and a speC1fic surface area of 260 m2/g was admixed with a solution of n-butyloctylmagnesium in n-heptane in a proportion of 0.3 mol of the magnesium compound per mole of SiOj. The finely divided silica gel was additionally characterized by a pH of 7.0, an average primary-particle size of 3-5 \im and by voids and channels having a diameter of 3-5 pja and a macroscopic share of the volume of the overall particle of about 15 %, The solution was stirred at 95°C for 30 minutes and then cooled down to 20°C, at which point 10 times the molar amount, based on the organomagneaium compound, of hydrogen chloride was introduced. After 60 minutes, the reaction product was admixed with 3 mol of r ethanol per mole of magnesium under constant stirring. This mixture was stirred at 80°C for 0.5 hours and then admixed with 7.2 mol of titanium tetrachloride and 0.5 mol of di-n-butyl phthalate, each based on 1 mol of magnesium. The batch was subsequently stirred at 100°C for 1 hour, and the resulting solid was filtered off and repeatedly washed with ethylbenzene. The resulting solid product was extracted at 125°C with a 10 % strength by volume solution of titanium tetrachloride in ethylbenzene for 3 hours. The solid product was then filtered off the extractant and washed with n-heptane until the extractant had a titanium tetrachloride content of just 0.3 %. The titanium-containing solid component comprised 3.5 % by weight of Ti 7.4 % by weight of Mg 28.2 % by weight of C1. The particle diameter was determined by Coulter Counter analysis (particle size distribution of the silica gel particles), the pore volume and the speC1fic surface area by nitrogen adsorption in accordance with DIN 66131 or by mercury porosimetry in accordance with DIN 66133, The average size of the primary particles, the diameter of the voids and channels and their macroscopic share of the volume were determined with the aid of scanning electron microscopy or electron probe microanalysis, in each case on particle surfaces and on particle cross sections of the silica gel. The pH of the silica gel was determined by means of the method described in S.R. Morrison, The Chemical Physics of Surfaces, Plenum Press, New York [1977], pages 130 and 131. b) Polymerization of propylene The polymerization was carried out in the gas phase in a stirred autoclave reactor having a useful capaC1ty of 10 1 in the presence of hydrogen as molecular weight regulator. Gaseous propylene was passed into the gas phase reactor at 28 bar and 70°C in the presence of 8 liters of hydrogen. A polymerization was carried out by means of the titanium-containing solid component a) described in Example 1 a using a residence time of 1.5 hours and using 100 mg of the titanium-containing solid component a), 10 mmol of triethylaluminum and 1 mmol of dimethoxyisobutylisopropyl-silane as cocatalyst. After the gas-phase polymerization had ended, the propylene homopolymer obtained had a melt flow index of 12.2 g/10 min, at 230°C and 2.16 kg (in accordance with DIH 53 735). Representative Example 1 Comparative Example A was repeated, except that the titanium-containing solid component a) used had been obtained on the basis of an aC1dic silica gel having a pH of 3.5 and a 15 % macroscopic volume share for the voids and channels within the overall particle. The granular silica gel had the following properties: Primary particle size: 3 - 5 (mi Particle diameter: 20 - 45 fun Pore volume: 1.5 cmVg SpeC1fic surface area: 325 m2/g Proportion of voids and channels in overall particle: 15 % The titanium-containing solid component comprised: 3.4 % by weight of Ti 7.4 % by weight of Mg 28.0 % by weight of C1 Representative Example 2 Comparative Example A was repeated, except that the titanium-containing solid component a) used had been obtained on the basis of an aC1dic silica gel having a pfl of 3.5 and a 25 % macroscopic volume share for the voids and channels within the overall particle. The granular silica gel had the following properties: Primary particle size: 3 - 5 jim Particle diameter: 20 - 45 jun Pore volume: 1.6 cmVg SpeC1fic surface area; 320 m2/g Proportion of voids and channels in overall particle: 25 % The titanium-containing solid component comprised: 3.6 * by weight of Ti 7.4 % by weight of Hg 28.4 % by weight of Cl Comparative Example B Comparative Example A was repeated, except that the titanium-containing solid component a) used had been obtained on the basis of a neutral silica gel having a pH of 7.0 and & 1 % macroscopic volume share for the voids and channels within the overall particle. The granular silica gel had the following properties: Primary particle size: 3 - 5 jun Particle diameter: 20 - 45 fun Pare volume: 2.8 cmVg SpeC1fic surface area: 325 m2/g Proportion of voids and channels in overall particle: The titanium-containing solid component comprised: 3.5 % by weight of Ti 7.3 % by weight of Mg 28.0 % by weight of Cl The table below shows not only for Representative Examples 1 and 2 but also for Comparative Examples A and B the productivity of the catalyst system used as well as the following properties of the propylene homopolymers obtained in each case: xylene solubles {measure of the stereospeC1fiC1ty of the polymer), heptane solubles (measure of the stereospeC1fiC1ty of the polymer), chlorine content, bulk density, fines content ( A comparison between Representative Examples 1 and 2 and Comparative Examples A and B makes it clear that the catalyst system of this invention has a higher productivity and leads to propylene polymers having an increased stereospeC1fiC1ty (lower xylene and heptane solubles), a reduced chlorine content and an increased bulk density. WE CLAIM: 1. 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, an inorganic oxide selected from the group consisting of an oxide of silicon, of aluminum, of titanium or of a metal of main group I or II of the Periodic Table as support and a carboxylic ester as electron 'Honor compound, and also, as cocatalyst, b) a trialkyl aluminum compound the alkyl groups of which each have from 1 to 8 carbon atoms, and c) as a further electron donor compound, organosilicon compounds of the general formula (I) R\Si(OR2)4-n (I) where Rl is identical or different and represents C1-C20-alkyl, 5-, 6- or 7-membered cycloalkyl with or without C1-C10-alkyl attached to it, or C6-C20-aryl or -arylalkyl, R2 is identical orjdifferent.and represents C1-C20~ alkyl, and n is 1, 2 or 3, wherein the inorganic oxide used has a pH of from 1 to 6, an average particle diameter of from 5 to 200 um, an average primary particle diameter of from 1 to 20 urn and voids or channels having an average diameter of from 0.1 to 20 um and a macroscopic share of the volume of the overall particle within the range from 5 to 30%. 2. The catalyst systems as claimed in claim 1, wherein the inorganic oxide used has voids and channels having an average diameter of from 1 to 5 um and a macroscopic share of volume of the overall particle within the range from 10 to 30%. 3. The catalyst systems as claimed in claim 1 or 2, wherein said inorganic oxide used is spray-dried. 4. The catalyst systems as claimed in any of claims 1 to 3, wherein said inorganic oxide used has apH of from2 to 5. 5. The catalyst systems, as claimed in any of claims 1 to 4, wherein said inorganic oxide is silica gel (Si02). 6. A process for producing catalyst systems as claimed in any of claims 1 to 5, which comprises combining said titanium-containing solid component a) and said cocatalyst b) and c) at from 0 to 150°C and from 1 to 100 bar. 7. The process for producing polymers of C2-C10-alk-l-enes by homopolymerization or copolymerization of C2-C10-alk-l-enes at from 20 to 150°C and from 1 to 100 bar in the presence of Ziegler-Natta catalyst systems, as claimed in any of claims 1 to 5. 8. The process as claimed in claim 7, wherein the C1-C10-alk-l-ene used is propylene.

Documents:

1216-mas-1997 abstract.pdf

1216-mas-1997 assignemnt.pdf

1216-mas-1997 claims dublicate.pdf

1216-mas-1997 claims.pdf

1216-mas-1997 correspondence others.pdf

1216-mas-1997 correspondence po.pdf

1216-mas-1997 description (complete) dublicate.pdf

1216-mas-1997 description (complete).pdf

1216-mas-1997 form-19.pdf

1216-mas-1997 form-2.pdf

1216-mas-1997 form-26.pdf

1216-mas-1997 form-4.pdf

1216-mas-1997 form-6.pdf

1216-mas-1997 petition.pdf