Title of Invention	A PROCESS FOR PREPARING SUPPORTED TITANIZED CHROMIUM CATALYST AND A CHROMIUM CATALYST PREPARED THERBY
Abstract	Process for preparing supported, titanized chromium catalysts, which comprises the following steps: A) bringing a support material into contact with a protic medium comprising a titanium compound and a chromium compound, B) optionally removing the solvent, C) optionally calcining the precatalyst obtained after step B) and D) optionally activating the precatalyst obtained after step B) or C) in an oxygen-containing atmosphere at from 400°C to 1100°C.

Title of Invention

A PROCESS FOR PREPARING SUPPORTED TITANIZED CHROMIUM CATALYST AND A CHROMIUM CATALYST PREPARED THERBY

Abstract

Process for preparing supported, titanized chromium catalysts, which comprises the following steps: A) bringing a support material into contact with a protic medium comprising a titanium compound and a chromium compound, B) optionally removing the solvent, C) optionally calcining the precatalyst obtained after step B) and D) optionally activating the precatalyst obtained after step B) or C) in an oxygen-containing atmosphere at from 400°C to 1100°C.

Full Text	Supported chromium catalyst and its use for preparing homopoiymers and copolymers of ethylene The present invention relates to novel supported, titanized chromium catalysts for the homopoly-merization of ethylene and the copolymerizanon of ethylene with a-oiefins, a process for preparing them and their use for the polymerization of olefins. Ethylene homopoiymers and copolymers of ethylene with higher a-oiefins such as 1-butene. 1-pentene, 1-hexene or 1-octene can be prepared, for example, by polymerization using supported titanium compouncs. known as Ziegier-Natta catalysts, or else using supported chromium compounds, known as Phillips catalysts. When the homopoiymers and copolymers of ethylene are used, for example, for biown film extrusion, it is important that the polymers have a good balance between mechanical properties and processability. It is known that supported chromium catalysts are very suitable for producing ethylene copolymers having good mechanical properties. The properties of the polymers obtained in the polymerization are dependent on the way in which the chromium catalyst used has been prepared, in particular on the type of support material, e.g. its chemical structure, composition, surface area or pore volume, the type of chromium compound used, the presence of further compounds, e.g. titanium compounds, aluminum alkyls or carbon monoxide, the order in which the various components are applied or the manner of calcination and activation. It is a combination of the starting materials used together with the procedure for application to a support which then gives the desired chromium catalyst for the preparation of polymers having the property profile required for the specific application. The supported chromium catalysts are often titanized, i.e. they comprise not only the chromium compound but also variable proportions of a titanium compound by means of which the molar mass distribution and the HLM! (high load melt index), for example, can be influenced. The application of the titanium compound to the support is usually carried out during the preparation of the hydrogel, giving an Si02-Ti02 cogel. In this, the titanium dioxide is uniformly distributed throughout the support material. A disadvantage is that only a fraction of the total titanium oxide is available for polymerization at the pore surface of the catalyst. For this reason, numerous embodiments of titanized chromium catalysts in which the titanium compound is applied in a targeted manner to the pore surface, usually in a step separate from the doping of the chromium compound, have been developed. Thus, for example, EP-A-882740 describes a process for preparing a supported chromium catalyst, in which the support material has a specific surface area of from 450 to 500 m2/g and the chromium component is applied to the support first and the titanium compound is applied subsequently, with ;he titanization being carried out at temperatures of at least 300°C. EP-A-882741 teaches that poiyethylenes having favourable ultimate tensile strengtns are obtained when using a supported chromium catalyst whose support material has a specific surface area of at least 400 m2/g and has been dehydrated before use and in the preparation of which the chromium component is applied to the support first and the titanium compound is acoiied subsequently. The application of a mixture of a chromium compound and a titanium compound in an aprotic solvent to a support under aprotic conditions is described in JP 54141893 and JP 57049605. However the preparation and handling of organometallic compounds under aprotic conditions is complicated and costly, since the solvents have to be dried before use. In acdition: only few chromium compounds are soluble in aprotic media. An increase in the solubility of cnromium compounds in aprotic solvents can often oniy be achieved by means of a complicated synthesis. It is an object of the present invention to provide a novel, less complicated process for preparing supported, titanized chromium catalysts. We have found that this object is achieved by a process for preparing supported, titanized chromium catalysts, which comprises the following steps: A) bringing a support material into contact with a protic medium comprising a titanium compound and a chromium compound, B) optionally removing the solvent, C) optionally calcining the precatalyst obtained after step B) and D) optionally activating the precatalyst obtained after step B) or C) in an oxygen-containing atmosphere at from 400°C to 1100°C. The invention further provides novel supported, titanized chromium catalysts which are suitable for the polymerization of ethylene and, if desired, further comonomers and are obtainable by the process of the present invention. This novel supported, titanized chromium catalyst for the ho-mopolymerization of ethylene and the copoiymerization of ethylene with a-c.efins will in the interests of brevity hereinafter be referred to as "chromium catalyst of the present rnvention". The invention also provides a process for preparing homopolymers of ethy ene and copolymers of ethylene with ct-olefins by polymerization of ethylene or mixtures of ethylene and a-olefins using at least one chromium catalyst according to :ne present invention, the horrcoolymers and copolymers of ethylene obtainable therefrom and their use for producing films Accordingly. ,t has now been found that homopolymers and especially copolymers of ethylene are obtained in particularly good yields when using the chromium catalysts of the present invention. The film prccucts oc:ained therefrom also have a very high puncture resistance. In view of the onor a, it was not to be expected that this novel process would ma; One constituent of me chromium catalyst of the present invention is the support material, in particular an incganic solid, which is usually porous. Preference is given to oxidic support materials which may s:u\ contain hydroxy groups. The inorganic metal oxide can be spherical or granular. Examples c" such sciids, which are known to those skilled in the art, are aluminum oxide, silicon dioxide (silica gel), titanium dioxide and their mixed oxides or cogels, and aluminum phosphate. Further suitaoie support materials can be obtained by modification of the pore surface, e.g. by means of compounds of the elements boron (BE-A-861,275), aluminum (US 4,284,527), silicon (EP-A-0 16c '57) or phosphorus (DE-A 36 35 715). Preference is given to using a silica gel. Preference is given to spnerical or granular silica gels, which in the case of the former may be spray dried. Preferred support materials are finely divided silica xerogels which can be prepared, for example, as describee n DE-A 25 40 279. The finely divided silica xerogels are preferably prepared by: a) use z: a particulate silica hydrogel which has a solids content of from 10 to 25% by weight (calculated as Si02) and is largely spherical, has a particle diameter of from 1 to 8 mm and 's obtained by a1) introducing a sodium or potassium water glass solution into a swirling stream of an aqueous mineral acid, both longitudinally and tangentially to the main direction of flow, a2) spraying the resulting silica hydrosol into a gaseous medium so as to form droplets, a3) allowing the sprayed hydrosol to solidify in the gaseous medium, a4) freeing the resulting largely spherical particles of the hydrogel of salts without prior aging by washing, b) extraction of at least 60% of the water present in the hydrogel by means of an organic iiquc c) dryi-g of the resulting gel at up to 180°C and a reduced pressure cf 13 mbar for 30 minutes -n til no further weight loss occurs (xerogel formation) and d) adjustment of the particle diameter of the xerogel obtained to from 20 to 2000 urn. In the first step a) of the preparation of the support material, it is important tc use a silica hydrogel which has a -eiatively high solids content of from 10 to 25% by weight (calculated as Si02). preferably from '2 to 20% by weight, particularly preferably from 14 to 20% by //eight, and is largely spnencai. This silica -ydrogel has been prepared in a specific manner as described in steps a1) to a&). The steos al :o a3) are described in more detail in DE-A 21 03 243. Step a4',. viz. washing of the hycroce:. can be carried out in any desired manner for example by the ccuntercurrent principle using wate* .vnicn contains a small amount of ammonia (prl up to aoout 1C; and is at up :c 3C^C. Tne extraction c: re .vater from the hydroget (step b)) is preferably carried out using an organic iiquic. which is panic arly preferably miscibe with water, from the group consisting of d-C4-aicohols anc.or C:-Crotones. Particularly creferred alcohols are tert-butancL i-procanol, ethanol and methane Amc~g the ketones, preference is given to acetone. The organic liquid can also consist of mixtures ;' the abevementioned organic liquids; in any case, the organic liquid contains less than 5% oy weignt, preferably iess than 3% by weight, of water prior tc the extraction. The extraction can be C3":ed out in customary extraction apparatuses, e.g. column extractors. Drying (step c;.) is ore'erably carried out at rom 30 to 140°C, particularly preferably from 80 to 110CC. and pressures of preferably from 1.3 mbar to atmospheric pressure. For reasons of the vapor pressu-e. a rise in temperature shoulc be accompanied by a rise in pressure and vice versa. The adjustment of the particle diameter of the resulting xerogel (step d)) car be carried out in any desired manner, e g. oy milling and sieving. A further preferred support material is produced, for example, by spray drying milled, appropriately sieved nydrogeis which are for this puroose mixed with water or an aliphatic alcohol. The primary particles are porous granular particies of the appropriately milled ana sieved hydrogei which have a mean particle diameter of from 1 to 20 um, preferably from 1 tc 5 um. Preference is given to using milled and sieved Si02 hydrogels. In general, the mean particle diameter of the support particles is in the range from 1 to 1000 um, preferably in tne range from 10 to 500 um and particularly preferably in the range from 30 to 150 um. The mean average pore volume of the support material used is in the range from 0.1 to 10 ml/g, in particular frc~ 0.3 to 4.0 ml/g and particularly preferably from 1 to 25 ml/g. In general, re suooort particles have a specific surface area of from 10 tc '300 m2/g, in particular from 100 tc 530 m2/g. in particular from 20C to 550 m2/g. The specific surface area and the mean pore volume are determined by nitrogen adsorption in accordance with the BET method, as described, for example by S. Brunauer. P. Emmett and E. Teller in Journal of the American Chemical Society, 60, (1939). cages 209-319. In addition, the support particles used according to the present 'nver.ticn nave a mean core diameter of from 80 to 250 A, preferably from 90 to 210 A anc particularly prer'eraoiy from 95 to 200 A. The mean pore diameter in A is calculated by dividing the numerical value of the mean pore volume (in cm"7g) by the numerical value of the specific surface area (in m". g) and multiplying the result by 40 000. Suitable support materials are also commercially avaiiacie. The support material can also have been partially or fully modified before use in the process of the present invention. The support material can, for example, oe treated under oxidizing or non-oxidizing conditions at from 200 to 1000CC, in the presence or acsence of'iuorinating agents such as ammonium hexaflucrosilicate. In this way. it is possible, for example, to vary the water and/or OH group content. The support material is preferably dried uncer reducec pressure at from 100 to 200CC for from 1 to 10 hours before use in the process of the present invention. In step A), the support material is brought into contact with a protic medium comprising, preferably consisting of. a titanium compound and a chromium compounc. The "titanium compound and the chromium compound can be dissolved or suspended in the protic solvent ard are preferably both dissolved. The titanium compound and the chromium compound can be brought into contact with the solvent in any order, simultaneously or as a premixed mixture. The titanium compound and the chromium compound are preferably mixed separately, in any order, with the solvent. The reaction time is usually in the range from 10 seconds to 24 hours, preferably from 1 minute to 10 hours and particularly preferably from 10 minutes to 5 hours, before the protic medium is brought into contact with the support material. As titanium compound, preference is given to using a tetravalent compounc of the formula (RO)nX4-nTi, where the radicals R are identical or different and are each an organosilicon or car-boorganic substituent having from 1 to 20 carbon atoms, e.g. a linear, brancned or cyclic C1-C20-alkyf group such as methyl, ethyl, n-propyl, isopropyl, n-butyl. sec-butyl, isccutyl. tert-butyi, n-pentyl, sec-pentyl, isopentyl, n-hexyi, cyclohexyl, n-heptyl or n-octyl. a C=-C-3-aryl group such as phenyl, 1-naphthyl, 2-napthyl, 1-anthryl. 2-anthryl, 9-anthry! and l-penanthr/l or a trialkylsilyl group such as trimethylsilyl or tnethylsilyi. R is preferably a linear or brancred C:-Cs-aikyi group such as methyl, ethyl, n-pjopyl, isopropyl. n-butyl, sec-butyf: isobutyi. tert-cutyl. n-pentyl or n-hexyi. X car, be a halogen such as fluorine, chlorine, bromine or iodine., pre'srably chlorine, n is from 0 to 4 and is preferably 4. Mixtures of various titanium compounds ca-~ also be used. The titanium compound is preferably soluble in the protic solvent anc preference is therefore given to using titanium tetralkoxides because they have good solubilities in very ma~y solvents. Apart from compounds of titanium with simple aliphatic alkoxides. it is alsc possible fc Afunctional ligands such as bisalkoxices or ethoxyaminates to be present. Particularly useful compounds are bis(triethanolamine) bis(isopropyl)titanate or ammonium salts of lactic acid-titanium complexes which are soluble in water. The chromium compounds can contain inorganic or organic groups. Preference is given to inorganic chromium compounds. Examples of chromium compounds include chromium trioxide and chromium hydroxide and also salts of trivaler: chromium with organic and inorganic acids, e.g. chromium acetate, chromium oxalate, chromium sulfate and chromium nitrate, and chelates of trivalent chromium, e.g. chromium acetylacetcnate. Among these, very particular preference is given to using chromium(lll) nitrate 9-hydrate and chromium acetyiacetonate. In preferred chromium compounds the oxidation state of the cnromium is lower than 5 and preferentially chromium is in the oxidation state 2, 3 or 4. The protic medium is a solvent or solvent mixture comprising from 1 to 100% by weight, prefera-. bly from 50 to 100% by weight and particularly preferably 100% by weight, of a protic solvent or a mixture of protic solvents and from 99 to 0% by weight, preferably from 50 to 0% by weight and particularly preferably 0% by weight, of an aprotic solvent or a mixture of aprctic solvents, in each case based on the protic medium. Protic solvents are, for example, alcohols R'-OH, amines NRYxHx-i, CT-Cs-carboxylic acids and inorganic aqueous acids such as dilute hydrochloric acid or sulfuric acid, water, aqueous ammonia or mixtures thereof, preferably alcohols R -OH, where R1 are each, independently of one another, C1-C2:-alkyl, C2-C2o-alkenyl, C5-C20-aryl, alkyiaryl having from 1 to 10 carbon atoms in the alkyl part and 6-20 carbon atoms in the aryl part or SiR23l where R2 are each, independently of one another. CrC20-alkyi, C2-C20~alkenyl, C6-C20-aryl, alkyiaryl having from 1 to 10 carbon atoms in the alkyl part and 6-20 carbon atoms in the aryl part, and x is 1 or 2. Examples of possible radicals R1 or R are: Ci-C20-alkyl which may be linear or branched, e.g. methyl, ethyl, n-propyl, iso-propyl, n-butyl. isobutyi, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl. n-decyl or n-dodecyl, 5- to 7-membered cyloalkyl which may in turn bear a C6-CT0-aryl group as substituent, e.g. cycloprcpyl, cyclobutyl, cyclopentyl, cyciohexyl. cycloheptyl, cyclooctyl. cyclononyl orcyclo-dodecyl, C2-C2c-alkenyl which may be linear, cyclic or branched and in whicn the double bond may be internal or terminal, e.g. vinyl, 1-allyl. 2-allyl, 3-aliyl, butenyl, pentenyl. hexenyl, cyclopen-tenyl, cyclohexenyl, cyclooctenyi or cyciooctadienyl. C5-C20-ary! which may bear further alkyl groups as sucstituents, e.g. phenyl, naphthyl. biphenyl, anthranyl. o-; m-: p-methylphenyl, 2,3-, * "2.4-1 2,5- or 2.6-dimethylphenyl, 2,3,4-, 2,3.5-, 2,3,6-. 2,4,5-, 2,4,6- or 3:4.5-:-:methylphenyl, or aryialkyl whicn may bear further alkyl groups as substituents, e.g. benzyl, c- rn-, p-methylbenzyl, 1- or 2-ethy.cnenyl, where two R1 or two R2 may in each case also be joinec :o form a 5- or 6-membered ring and the organic radicals R1 and R2 may also be substituted c/ halogens such as fluorine, chicnne or bromine. Preferred carboxylic acids are C1-C3-carboxyii': acids such as formic acid or ace:: acid. Preferred alcohols R1-OH are methanol, ethanol. 1-prcc=~ol, 2-propanol, 1- butanol, 2-butanol. 1-pentanol, 2-pentanol, 1-hexanol, 2-ethylhexanol, 2,2-dimethyiethanol or2,2-dimethylpropanol. in particular methanol, ethanol, 1-propanol, 1-butanoi, 1-pentanoL 1-hexanol or 2-ethyihexanoi. The water content of the protic medium is preferably less than 20°: by weight. Examples of aprotic solvents are aliphatic and aromatic hydrocarbons such as pentane, hexane, heptane, octane, isooctane, nonane, aodecane, cyclohexane, benzene and C7-C-:-alkylbenzenes such as toluene, xyiene or ethylbenzene. The support material can be brought into contact with the protic medium comprising the titanium compound and the chromium compound in any desired way. Thus, the mixture of erotic medium, titanium compound and chromium compound can be added to the support material or the support material can be introduced into the mixture. The support material can aiso be slurried in a suspension medium beforehand. The mixture of suspension medium used and protic medium comprises from 1 to 100% by weight preferably from 50 to 100% by weight and particularly preferably 100% by weight, of a protic solvent or a mixture of protic solvents and from 99 to 0% by weight, preferably from 50 to 0% by weight and particularly preferably 0% by weight, of an aprotic solvent or a mixture of aprotic solvents, in each case based on the mixture of the suspension medium used and the protic medium. This suspension medium is preferably likewise the protic medium used according to the present invention. The chromium compound is usually present in a concentration of from 0.05 to 20% by weight, preferably from 0.1 to 15% by weight and particularly preferably from 0.5 to 10% by weight, based on the protic medium. The titanium compound is usually present in a concentration of from 0.05 to 30% by weight, preferably from 0.1 to 20% by weight and particularly preferably from 0.5 to 15% by weight, based on the protic medium. The molar ratio of chromium compound to titanium compound is usually in the range from 10:1 to 1:10, preferably from 5:1 to 1:7 and particularly preferably from 4:1 to 1:5. The support material is generally loaded in a weight ratio of supported gel particies:Ti in the titanium compound of from 100:0.1 to 100:12, in particular from 100:1 to 100:5 and a weight ratio of support gel particles:chromium in the chromium compound of from 100:0.1 :o 100:10, in particular from 100:0.3 to 100:3. Reaction step A) can be carried out at from 0 to 150°C. For cost reasons, preference is given to room temperature. . . The solvent can optionally be removed in a subsequent step B); preferably at from 20 to 150CC and pressures of from 10 mbar to 1 mbar. Preference is given to removing cart or all of the solvent. The precatalyst obtained in this way can be completely dry or can co-tain some residual moisture. The volatile constituents still present are preferably presentjn ar amount of not more than 20% by weight, in particular not more tn3n 10% by weight, based on the not yet activated chromium-containing precatalyst. The precatalyst obtained from reaction step 3) can immediately be subjected to step D) or can be calcined beforehand at above 280°C in a water-free inert gas atmosphere in step C). The calcination is preferably carried out at from 230 to 5J0°C in a fluidized bed for from 10 to 1000 minutes. The intermediate obtained in this way from step B) or C) is then activated in step D) under oxidizing conditions, for example in an oxygen-containing atmosphere at from 400 to 1000°C. The intermediate obtained in step B) or C) is preferably activated directly in the fiuidized bed by replacing the iner gas by an oxygen-containing gas and increasing the temperature to the activation temperature. The intermediate is advantageously heated at from 400 to 1100CC, in particular from 500 to 300'C. in a water-free gas stream in 'which oxygen is present in a concentration of above 10% by volume for from 10 to 1000 minutes. ;n particular from 150 to 750 minutes, and then cooled to room temperature, resulting in the Phillips catalyst to be used according to the present invention. The maximum temperature of the activation is below, preferably at least 20-100°C below, the sintering temperature of the intermediate from step B) or C). This oxidation can also be carried out in the presence of suitable fluorinating agents such as ammonium hexafluorosilicate. A preferred orocess for preparing the supported, titanized chromium catalysts comprises the fallowings steos: A) bringing a support material into contact with a protic medium comprising a titanium compound and a chromium compound. B) removing the solvent, C) calcining the precatalyst obtained after step B) and D) activating the precatalyst obtained after step C) in an oxygen-containing atmosphere at from 400CC to 1100°C. Particular preference is given to a process consisting of the steps A) to D). The chromium catalyst of the present invention advantageously has a chromium content of from 0.1 to 5% o/ weight, in particular from 0.3 to 2% by weight, and a titanium content of from 0.5 to 10% by weight, in particular from 1 to 5% by weight. The catalyst systems of the present invention have a short induction perioc in the polymerization of 1-aikenes The resulting chromium catalyst to be used according to the present invention can also be reduced, for example by means cf ethylene ar.c/or a-olefins, carbon monoxide or triethyfborane. in suspension or in the gas phase before use c- :t can be modified by siiylation. The molar ratio of reducing agent tc cnromium (cf tne chromium catalyst according to the present invention to ce reduced) is usually in the range from 0.05:1 :c 500:1. preferably from 0.1:1 to 50:1. in particular from 0.5:1 to 5.0:1. In suspension, the reduction temperature is generally in the range from 10 to 200CC. preferacly in the range from 10 to 100°C, and the pressure is in the range from 0.1 to 500 bar preferably the range from 1 to 200 bar. The reduction temperature in fluidized-bed processes is usually in the range from 10 to 100CCC; ■ preferably from 10 to 800°C, in particular from 10 to 600°C. In general, the gas-phase reduction is carried out in the pressure range from 0.1 to 500 bar. preferably in the range from 1 to 100 bar and in particular in the range from 5 to 20 bar. In the gas-phase reduction, the chromium catalyst to be reduced is generally fluidized by means of an inert carrier gas stream, for example nitrogen or argon, in a fiuidized-oed reactor. The carrier gas stream is usually laden with the reducing agent, with liquid reducing agents preferably having a vapor pressure of at least 1 mbar under normal conditions. The chromium catalyst of the present invention is very useful for the preparation of homopolymers of ethylene and copolymers of ethylene with a-olefins in the customary processes known for the polymerization of olefins at temperatures in the range from 20 to 300°C and pressures of from 5 to 400 bar, for example solution processes, suspension processes in stirring autoclaves or in a loop reactor, stirred gas phases or gas-phase fiuidized-bed processes, which may be carried out continuously or batchwise. The advantageous pressure and temperature ranges for carrying out the process accordingly depend greatly on the polymerization method. In particular, temperatures of from 50 to 150°C, preferably from 70 to 120'C, and pressures which are generally in the range from 1 to 400 bar are set in these polymerization processes. As solvent or suspension medium, it is possible to use inert hydrocarbons such as iscoutane or else the monomers themselves, for example higher olefins such as propene, butere or hexene in a liquefied or liquid state. The solids content of the suspension is generally in the -ange from 10 to 80% by weight. The polymerization can be carried out either batchwise, e.g. in stirring autoclaves, or continuously, e.g. in tube reactors, preferably in loop reactors. In particula' it can be carried out using the Phillips PF process as described in US-3 242 150 and US-3 2^6 179. Among the polymerization processes mentioned, gas-phase polymehzation. in particular in gas-phase fluidized-bed -eactors. is preferred according to the present invention. It has been found that despite the variety of processing steps and the spray-dried succort materials, no fine dust is formed during tne gas-phase polymerization In general, it is carriec out at a temperature wr.ich is at least a few degrees under the softening temperature of the polymer. The gas-phase polymerization can also be carried out in the condensed, supercondensed c supercritical mode. The different polymerization processes, or even the same polymerization process, can, if desired. be connected in seres so as to form a polymerization cascade. However, the special catalyst composition makes it possible for the polymers accorcmg to the present invention to be reaaiiy obtained from a single reactor. Examples of suitable a-olefins which can be :opolymer;zed with ethylene are monoolefins and dioiefins having from three to 15 carbon atcms in the molecule. We:.-suited ^-olefins of this type are propene. 1-butene, 1-pentene, 1-hexene, 1-octene. 1-decene. %dodecene and 1-pentadecene and also the conjugated and ncnconjugated dioiefins butadiene, penta-1,3-diene. 2,3-dimethylbutadiene, penta-1,4-diene. hexa-1,5-diene and vinylcyciohexene. Mixtures of these comonomers can also be used. Preference is given to using 1-butene. 1-hexene or 1-octene, in particular 1-hexene. To control the molar mass, hydrogen can advantageously be used as regulator in the polymerization. It has been found to be advantageous to carry out the polymerization of the 1-alkenes by means of the catalysts of the present invention in the presence of organometallic compounds of elements of the first, second, third or fourth main group or of the second transition group of the Periodic Table of the Elements. Well-suited compounds of this type are homcieptic C--C1c-alkyls of lithium, boron, aluminum or zinc, e.g. n-butyllithium, triethylboron. trimethylaiuminum. triethylaluminum, triisobutylaluminum, tributylaluminum, trihexylaluminum, trioctyiaiuminum and diethylzinc. Furthermore, C'-C^-dialkyialuminum alkoxides such as diethylaluminum methcxide are also well suited. It is aiso possible to use dimethylaiuminum chloride, methylaiuminum dichloride, methyl-aluminum sesquichlonde or diethylaluminum chloride. n-Butyllithium and trihexyialuminum are particularly preferred as organometallic compound. Mixtures of the aoove-described organometal-iic compouncs are generally also well suited. The molar ratio of organometallic compound:chromium is usually in tne range from 0.1:1 to 5G: 1, preferably m the range from 1:1 to 50:1. However, since many of the activators, e.g. aluminum alkyis, can a:so be used at the same time for removing catalyst poisons (known as scavengers), the amount used is dependent on the impurities present in the other starting materials. However, a person ski ed in the art can determine the optimum amount by means of simple tests. The chromium catalysts of the present invention can also be used together with another catalyst suitable for the polymerization of a-olefins in the above polymerization processes The chromium catalyst of the present invention is preferably used together with another suopcrtec chromium catalyst customary for the polymerization of ^-olefins. The use of two different succorted chrc-mium catalysts is described, for example, in WO 92/17511. The polymerization ca~ also be carried out using two or more of the chromium catalysts of the present invent,on simultaneously. The polymerization is particuiariy preferably carried out using a chromium catalyst acceding to the present invention together with a supported, nontitanized chromium catalyst. Mixtures of titanized and nontitanized supported chromium catalysts are described, for exampie. in US-2 798 202. but in that case the titamzation is carried out oniy after the chromium component has ceen applied to a support. The two different Phillips cataiysts can be mixed before they come into contact w:t~ the monomers and can then be introduced together into the reactor, or they can be introduced into the reactor separately from one another, for example at a plurality of points. The homopolymers and copolymers of ethylene prepared according to the oresent invention usually have a density, measured in accordance with DIN 53479. in the range "rom 0.9 to 0.97 g/cm3, preferably in the range from 0.92 to 0.96 g/cm3 and particularly preferably .r, the range from 0.925 to 0.945 g/cm3, and a melt flow index (Ml (190°C/2.16 kg) or HLMI (190°C 21.6 kg);, measured in accordance with DIN 53735 under different loads (in brackets), in the range from G to 10 g/10 min, preferably in the range from 0.01 to 1 g/10 min and particularly preferably :- the range from 0.05 to 0.6 g/10 min, in the case of Ml and in the range from 1 to 50 g/10 min. preferably in the range from 3 to 30 g/10 min and particularly preferably in the range from 5 to 25 g/10 min. In the case of the HLMI. The weight average molar mass Mw is generally in the range from 10 000 tc 7 000 000 g/moL preferably in the range from 100 000 to 500 000 g/mol. The molar mass distribution M;v/Mn, measured by GPC (gel permeation chromatography) at 135°C in 1,2,4-trichlorccenzene using polyethylene standards, is usually in the range from 3 to 50, preferably in the range from S to 30 and particularly preferably in the range from 15 to 30. In general, the ethylene polymers produced in the reactor are melted and -omogenized in an extruder. The melt flow index and the density of the extrudate can then drer from the corresponding parameters for the crude polymer, but are also in the range specified according to the present invention. In the olefin polymerization in which the catalyst prepared according to the cresent invention is used, it is possible to prepare homopolymers of ethylene or copolymers c ethylene with a co- monomer having from 3 to 12 carbon atoms in an amount of up to 10 moi% of comonomer in the copolymer. Preferred copolymers contain from 0.3 to 1,5 mol% of hexene. based on the polymer, particularly preferably from 0.5 to 1 mo!% c* nexene. The ethylene copolymer prepared according :o the present invention can also form mixtures with other olefin polymers, in particular homopolymers and copolymers of ethylene. These mixtures can, on the one hanc, be prepared by tne acove-described simultaneous polymerization of a plurality of chromium catalysts. On the other hand, these mixtures car also be obtained simply by suosequent blending of the polymers prepared according to the present invention with other ho-mopolymers or copolymers of ethylene. MF! HLMI. density, comonomer content, Mw and Mw/Mn of these mixtures are preferably likewise in tne same ranges as these for the polymers which have been prepared using only a titanium-ccntaining chromium catalyst accorcing to the present invention. In addition, the ethylene copoiymers, polymer mixtures and blends can further comprise auxiliaries and/or additives known per se, e.g. processing stabilizers, stabilizers against the action of light and heat, customary additives such as .upricants, antioxidants, antiblocking agents and antistatics, and also, if desired, cciorants. The tyoe and amounts of these additives are well known to these skilled in the art. The polymers prepared according to the present invention can also be modified subsequently by grafting, crosslinking. hydrogenation or other functionalization reactions which are known to those skilled in the art. The polymers prepared according to the present invention are very useful for, for example, producing fiims on blown film plants at high outputs. Films comprising tne polymers prepared according to the present invention have good mechanical properties. The nigh puncture resistance of the films produced therefrom is also worthy of note. The films obtained in this way are suitable, in particular, for the packaging sector and for large, heavy duty sacks and also for the food sector. Furthermore, the films have only a low blocking tendency anc can therefore be passed through machines without use of lubricants and antiblocking additives or with use of only small amounts thereof. The Phillips catalyst prepared according to the present invention has particular unexpected advantages. It is very useful for the homopolymerization and copolymerization of ethylene by the customany arc known particle form processes in a gas-phase fluidlzed-bec polymerization. Here, it gives, at a nigh productivity, (co)polymers having excellent morphology and good processability. In particular, tne catalyst of the present invention displays a good comonomer incorporation behavior and gves high productivities even at iow activation temperat^es. The (copolymers pre- pared by means of the Phillips catalyst of the present invention are therefore particularly useful for processing by the blown film process and the blow molding process. The following examples illustrate the invention. The productivity of the catalyst is reported as the amount of polymer isolated per amount of Phillips catalyst used in g. The melt flow index was determined in accordance with ISO 1133 at 190CC under a load of 21.6 kg (190°C/21.6 kg, HLMI) and under a load of 2.16 kg (190°C/2.16 kg, Ml). The density [g/cm3] was determined in accordance with ISO 1183. The bulk density (BD) [g/l] was determined in accordance with DIN 53468. The environmental stress cracking resistance (ESCR) was determined in Basell's round disk in-dentor test (Rl). Test conditions: round disks (produced from a pressed plate, diameter: 38 mm, thickness: 1 mm, scored on one side by means of a scratch having a length of 20 mm and a depth of 200 urn) are dipped at 50 or 80°C into a 5% strength aqueous solution of Lutensol® FSA and loaded by means of a gas pressure of 3 bar. The time to occurrence of stress cracks which produce a pressure drop in the measuring apparatus is measured (in h). The measurement of the dart drop impact strength was carried out on 20 urn films in accordance with ASTM 1709 A. The Staudinger index (n)[dl/g] was determined at 130°C on an automatic Ubbelohde viscometer (Lauda PVS 1) using decalin as solvent (ISO 1628 at 130°C, 0.001 g/ml of decalin). The determination of the molar mass distributions and the means Mn, Mw and Mw/Mn derived therefrom was carried out by means of high-temperature gel permeation chromatography using a method based on DIN 55672 under the following conditions: solvent: 1,2,4-trichlorobenzene, flow: 1 ml/min, temperature: 140°C, calibration using PE standards. Abbreviations in the following tables: Tp0iy Temperature during the polymerization Mw Weight average of the molar mass Mn Number average of the molar mass Density Polymer density DDl Dart drop impact - - ESCR Environmental stress cracking resistance % by volume Percentage by volume of the respective component during the polymerization Prod. Proc-ctivity of the catalyst in g of polymer obtained per g of catalyst used HLMI Mel: "ow index at a loading weight of 21.6 kg THA Amc^nt of trihexylaluminum used TI StaLc'nger index mg cat. mg c:* the catalyst used in the polymerisation Vinyl Viny groups in the polymer oer (1000 C) Examples and Comparative Experiments Example 1 The support material was prepared as described in DE 2 540 279. Preparation of the silica xerogel A mixing nozzle as shown in the figure in DE-A 2 103 243 and having the following data was utilized: the diameter of :ne cylindrical mixing chamber formed by a plastic tube is 14 mm, the length of the mixing zone (including after-mixing section) is 350 mm. The end of the mixing chamber nearest the inlet is cicsed off and near this end there is a tangential inlet hole having a diameter of 4 mm for the mineral acid." Four further holes likewise having a diameter of 4 mm and the same inflow direction for the water glass solution follow, with the spacing of the holes^ measured in the longitudinal direction of the mixing chamber, being 30 mm. Accordingly, the ratio of length to diameter of the primary mixing zone is about 10:1. For the subsequent secondary mixing zone, this ratio is 15. As spraying nozzle, a flattened, slightly kidney shaped piece of tube was pushed over the outlet end of the plastic tube. This mixing apparatus was supplied with 325 l/h of 33 percent strength by weight sulfuric acid at 20°C and an operating pressure of about 3 bar and also 1100 l/h of water glass solution (prepared from technical-grade water glass containing 27% by weight of Si02 and 8% by weight of Na20 by dilution with water) having a density of 1.20 kg/I and a temperature of likewise 20°C and a pressure of likewise about 3 bar. Progressive neutralization in the mixing chamber lined with the plastic tube resulted in formation of an unstable hydrosol which had a pH of 7-3 and remained in the after-mixing zone for about 0.1 s until completely homogenized before it was sprayed through the nozzle attachment inic the atmosphere as a fan-shaped liquid jet. During its flight through the air, the jet broke ,o into individual droplets which, as a result of the surface tension, took on a largely spherical shace and solidified to form hydrogel spheres within about one second while still in flight. The spheres had a smooth surface, were clear as glass, contained aoout 17% by weight of Si02 and hac the following particle size distribution: > 8 mm 10% by weight 5-8 mm 45% by weight 4-6 mm 34% by weight (The particle s;ze distributer can be varied a; will by use of other nozzle attachments.) The ny-drogel spheres were collectec at the end of ;-e;r flight In a scrubbing tower whic~ ,vas filled almost completely with hydrcgei spheres and ,r. which the spneres were washed free of salts immediately without aging by means of water containing a little ammonia and having a temperature of about 50°C ;n a continuous countercurrer: process. The spheres wnich had a ciameier in tne range from 2 to 5 mm were isc;ated by sieving and 112 kg of these spneres were c.aced in an extraction vessel which had an in;et at the top. a sieve bottom and swan-neck shaced overflow whicn is connected to the bottom of the drum and keeps the liquid level in the arum sufficiently high for the hydrogel spheres to be completely covered with liquid. The hycrogel was extracted by means of methanol. The spheres obtained in this way were then dried (12 hours at 120~C under a pressure of 20 mbar) until no further weight loss occurred a: 180°C under a pressure of 13 mbar over a period of 30 minutes. The spheres which had been dried in this way were subsequently milled and the xerogel particles which have a diameter of from 40 to 300 urn were isolated by sieving. The pore volume was 1.9 ml/g. 39 ml of titanium tetraisopropoxide were added to a solution of 11.6 g of cnromium(lll) nitrate nonahydrate (Cr(N03)3x9H20) in 700 ml of methanol. The solution of chrcmium(ill) nitrate nona-hydrate and titanium tetraisopropoxide in methanol was clear and displayed no turbidity. The solution obtained in this way was added to 150 g of the above-described silica gel support. The suspension was stirred for 1 hour and then evaporated to dryness on a rotary evaporator at 80°C with application of a vacuum. The precatalyst obtained in this way contains 1 % by weight of chromium and 4% by weight of titanium, based on the weight of the precatalyst. Comparative Example C1 Example 1 was repeated without addition of titanium tetraisopropoxide. Tne precatalyst obtained in this way contains 1% by weight of chromium, based on the weight of re precatalyst. Example 2 * ' 400 g of chromium(lli) nitrate nonanyarate were dissolved in 6.5 I of methanol while stirring in a dissolution reactor. After stirring for one hour. 0.97 I of titanium tetraisop'cooxide were added and the mixture was stirred for another 5 minutes. This solution was subsequently pumped over a period of 1 hour onto 5 kg of the silica gel support Sylopol SG332 5N (commercially available from Grace) in a double cone drier. The dissolution reactor was then rinsed v. t~ 1.5 I or m-ethano! which was then likewise added to the supper:. The suspension was then stirred for A- hour and subsequently heated to 95°C and the methanol was distilled off at 900 mbar. After aoout 3 hours, the pressure was reduced to 300 moar and the product was driec under rese conditions for a further 2 hours, "he precatalyst obtained in this way contains 1% by weight z: znrom^n and 3% by weight of titanium, based on the weignt of the pecataiyst. Comparative Example C2 The procedure of Example 2 was repeated ;-sing 5 kg c the silica gel supper: Sylcccl SG332 5N and 120 g of chromium(lll) nitrate nonahydrate but without adaiticn of titanium tetracropoxide. The precatalyst obtained in this way contains 0.3% by weignt of chromium, based on the weight of the precatalyst. Example 3 1000 g of chrcmium(ill) nitrate nonahydrate and 21 I of methanol were mixed with s::rr;ng in a dissolution reactor. After stirring for one hour, 2.3 I of titanium tetraisopropoxide were added to this solution and the mixture was stirred for 5 minutes. This solution was suosequentiy pumped over a period of 1 hour onto 18 kg of the siiica gel support XP021C7 (commercially available from Grace) (which had been dried beforehand at 130°C and 10 mbar for 7 hours in this couble cone drier) in a double cone drier which was rotated uniformly. After the addition, the dissolution reactor was rinsed with 5 i of methanol and this rinsing solution was likewise added to the silica gel support. The suspension was stirred for a further 1 hour and was then dried at 903C witn application of a vacuum until a pressure of 10 mbar at a temperature of 100°C was reached after a period of 1 hour. The precatalyst obtained in this way contains 0.7% by weight of chromium and 2% by weight of titanium, based on the weight of the precatalyst. Comparative Example C3 3.5 I of titanium tetraisopropoxide were mixed with 20 I of heptane wnile stirring in a dissolution reactor. After stirring for 10 minutes, the solution was pumped over a period of one hour onto 18 kg of the siiica gel support XPO2107 (which had been dried beforehand at 30°C and 10 mbar for 7 hours in this double cone drier) in a double cone drier which was rotated uniformly. The dissolution reactor was rinsed with 5 I of heptane and this rinsing solution was likewise transferred into the double cone drier. The suspension was then stirred for 1 hour. It was suosequentiy dried at 90°C with abdication of a vacuum until a pressure of 10 mbar at a temperature of 100GC was reached after 1 hour. 1000 g of chromium(lll) nitrate nonahydrate and 23 ! of methanol were sub-sequently mixed white stirring in the dissolution reactor. After stirring 'or 1 .TOUT, this solution was pumped over a period of 1 hour onto the supported titanium compound in the rotating double cone drier. After the addition, the dissolution reactor was rinsed with 5 i of methane; and the rinsing solution //as likewise transferred to the double cone drier. The suspension was stirred for a further 1 he and then dried at 90°C with application of a vacuum until a pressure of 10 mbar at a > > temperature of 100°C was reached after 1 nour. The precatalyst obtained in this way contains 0.7% by weight of chromium and 3% by weight of titanium, based on the weight of the precataiyst. Activation Activation was carried out at 500 or 65CCC cy means of air in a fluidized-oed activatcr. To ac: vate the precatalyst, it was heated to 300CC ove- a period of 1 hour, kept at th:s temperature for1 hour, subsequently heated to the desired activation temperature, kept at :nis temperature fcr 2 (Examples 1 and C1) or 5 hours (Examoles 2. 3, C2 and C3) and subsecuently codec. Cocl^g below 300CC was carried out under nitrogen. The precatalysts from Exar.cies 1. CI and C2 'were heated to an activation temperature of 75C:C. the precatalyst from Examoie 2 was heated tc an activation temperature of 600-C and the precatalysts from Examples 3 ana C3 were heated :c an activation temperature of 520CC. Polymerization The polymerization experiments in Table 1 were carried out under the ccrcitions specified ir. Table 1 at a total pressure of 40 bar and an output of 25 kg/h in a 180 I PF cop reactor (= particle-forming loop reactor) (suspension medium: :sobutane). The catalysts described in Examples 1 and C1 served as catalyst. The polymerization experiments in Table 2 were carried out in a continues gas-phase fluidized-bed reactor (Lupotech G as described in W099/29736 A1) under the conations specified in tne tables at a total pressure of 20 bar and an output of 50 kg/h. The products prepared in the gas-phase process were granulated at 20C:C under protective gas on a ZSK 40. Processing to produce films was carried out on a blown film oiant from W&H provided with a 60/25D extruder. The catalysts described in Examples 2, C2 3 and C3 served as catalyst. The results of the polymerizations and product tests are summarized in re tables. Example 4 1430 g of chromium(lll) nitrate nonahycrate and 26 I of methanol were mixed with stirring in a dissolution reactor. After stirring for one hour. 2.3 i of titanium tetraisopropoxide were added to this solution and the mixture was stirred for 5 minutes. This solution was subsequently pumped over a period of 1 hour onto 18 kg of the silica gel support XP02107 (commercially available from Grace). After the addition, the dissolution reactor was rinsed with 4 I of methanol and this rinsing solution was likewise added to the silica ge, support. The suspension was stirred for a further 1 hour and was then dried at 95°C with application of a. The precatalyst obtained in this way contains 1 % by weight of chromium and 2% by weight of titanium, based on the weight of the precatalyst. Comparative Example C4 Di-tert.butylchromate was prepared by adcing to a suspension of 4.86 g CrCK and 10 g MgS04 in 300 ml of hexane a solution of 9.45 ml of tert.-butanol in 50 ml hexane. After stirring for 15 min the solution was filtered to give a hexane solution of di-tert.butylchromate. 31.5 ml of titanium tetraisopropoxide and the di-tert.butylchromate solution were added together onto 250 g of the silica gel support XP02107 (commercially available from Grace). The suspension was then stirred for 1 hour. The hexane was distilled off and the resulting solid was subsequently dried at 80°C with application of a vacuum. The precatalyst obtained in this way contains 1 % by weight of chromium and 2% by weight of titanium, based on the weight of the precatalyst. Activation Activation was carried out at 520°C by means of air in a fluidized-bed activator as described above. Polymerization The polymerization experiments in Table 3 were carried out at a total pressure of 40 bar, 100°C for 90min in a 1 I autoclave reactor (suspension medium: isobutane 400ml, 10ml hexene). The catalysts described in Examples 4 and C4 served as catalyst. Both showed a productivity of about 6000 g of polymer per g catalyst. The new catalyst gave ethylene copolymers with a higher molecular weight (Mw and Mn) and a broader molecular weight distribution (Mw/Mn) with about the same density than the catalyst prepared in an aprotic medium (comparative example C4). We claim: 1. A process fcr preparing supported, :::anized chromium catalysts, which comprises the following steos: A) bringing a support material in:c contact with a protic medium comprising a titanium compound and a chromium compound. B) optionally removing the soive,":. C) optionally calcining the precataiyst obtained after step B) and D) optionally activating the preca:aiyst obtained after step B) or C) in an oxygen- containing atmosphere at from 400°C to 1100QC. 2. A process as claimed in claim 1, wherein the support material is a silica gel. 3. A process as claimed in claim 1 or 2. wherein the chromium compound is an inorganic chromium compound. 4. A process as claimed in claim 3, wherein the inorganic chromium compound is chrcmium(lll) nitrate nonahydrate. 5. A process as claimed in any of claims 1 to 4, wherein the titanium compound is titanium tetraisopropoxide, titanium tetra-n-butoxide or a mixture of these two titanium compounds. 6. A process as claimed in any of claims 1 to 5, wherein the protic medium is methanol. 7. A catalyst system obtainable by a process as claimed in any of claims 1 to 6. 8. A process for preparing polyolefins by polymerization or copolymerization of olefins in the presence of a catalyst system as claimed in claim 7. 9. A process as claimed in claim 8, wherein ethylene or a monomer mixture of ethylene and/or C3-C-2-1-alkenes containing at least 50 mol% of ethylene is used as monomer(s) in the Supported chromium catalyst and its use "'or preparing homopolymers and copolymers of ethylene Abstract Process for preparing supported, titanizec chromium catalysts, which comprises the following steps: A) bringing a support material into ccr:act wit" a prctic medium comprising a titanium compound and a chromium compounc B) optionally removing the solvent. C) optionally calcining the precatalyst cotainec after step B) and D) optionally activating the precatalyst obtained after step B) or C) in an oxygen-containing atmosphere at from 400°C to 110QzC.

Full Text

Supported chromium catalyst and its use for preparing homopoiymers and copolymers of ethylene
The present invention relates to novel supported, titanized chromium catalysts for the homopoly-merization of ethylene and the copolymerizanon of ethylene with a-oiefins, a process for preparing them and their use for the polymerization of olefins.
Ethylene homopoiymers and copolymers of ethylene with higher a-oiefins such as 1-butene. 1-pentene, 1-hexene or 1-octene can be prepared, for example, by polymerization using supported titanium compouncs. known as Ziegier-Natta catalysts, or else using supported chromium compounds, known as Phillips catalysts. When the homopoiymers and copolymers of ethylene are used, for example, for biown film extrusion, it is important that the polymers have a good balance between mechanical properties and processability.
It is known that supported chromium catalysts are very suitable for producing ethylene copolymers having good mechanical properties. The properties of the polymers obtained in the polymerization are dependent on the way in which the chromium catalyst used has been prepared, in particular on the type of support material, e.g. its chemical structure, composition, surface area or pore volume, the type of chromium compound used, the presence of further compounds, e.g. titanium compounds, aluminum alkyls or carbon monoxide, the order in which the various components are applied or the manner of calcination and activation. It is a combination of the starting materials used together with the procedure for application to a support which then gives the desired chromium catalyst for the preparation of polymers having the property profile required for the specific application.
The supported chromium catalysts are often titanized, i.e. they comprise not only the chromium compound but also variable proportions of a titanium compound by means of which the molar mass distribution and the HLM! (high load melt index), for example, can be influenced. The application of the titanium compound to the support is usually carried out during the preparation of the hydrogel, giving an Si02-Ti02 cogel. In this, the titanium dioxide is uniformly distributed throughout the support material. A disadvantage is that only a fraction of the total titanium oxide is available for polymerization at the pore surface of the catalyst. For this reason, numerous embodiments of titanized chromium catalysts in which the titanium compound is applied in a targeted manner to the pore surface, usually in a step separate from the doping of the chromium compound, have been developed.
Thus, for example, EP-A-882740 describes a process for preparing a supported chromium catalyst, in which the support material has a specific surface area of from 450 to 500 m2/g and the chromium component is applied to the support first and the titanium compound is applied subsequently, with ;he titanization being carried out at temperatures of at least 300°C.

EP-A-882741 teaches that poiyethylenes having favourable ultimate tensile strengtns are obtained when using a supported chromium catalyst whose support material has a specific surface area of at least 400 m2/g and has been dehydrated before use and in the preparation of which the chromium component is applied to the support first and the titanium compound is acoiied subsequently.
The application of a mixture of a chromium compound and a titanium compound in an aprotic solvent to a support under aprotic conditions is described in JP 54141893 and JP 57049605.
However the preparation and handling of organometallic compounds under aprotic conditions is complicated and costly, since the solvents have to be dried before use. In acdition: only few chromium compounds are soluble in aprotic media. An increase in the solubility of cnromium compounds in aprotic solvents can often oniy be achieved by means of a complicated synthesis.
It is an object of the present invention to provide a novel, less complicated process for preparing supported, titanized chromium catalysts.
We have found that this object is achieved by a process for preparing supported, titanized chromium catalysts, which comprises the following steps:
A) bringing a support material into contact with a protic medium comprising a titanium compound and a chromium compound,
B) optionally removing the solvent,
C) optionally calcining the precatalyst obtained after step B) and
D) optionally activating the precatalyst obtained after step B) or C) in an oxygen-containing atmosphere at from 400°C to 1100°C.
The invention further provides novel supported, titanized chromium catalysts which are suitable for the polymerization of ethylene and, if desired, further comonomers and are obtainable by the process of the present invention. This novel supported, titanized chromium catalyst for the ho-mopolymerization of ethylene and the copoiymerization of ethylene with a-c.efins will in the interests of brevity hereinafter be referred to as "chromium catalyst of the present rnvention".
The invention also provides a process for preparing homopolymers of ethy ene and copolymers of ethylene with ct-olefins by polymerization of ethylene or mixtures of ethylene and a-olefins using at least one chromium catalyst according to :ne present invention, the horrcoolymers and copolymers of ethylene obtainable therefrom and their use for producing films

Accordingly. ,t has now been found that homopolymers and especially copolymers of ethylene are obtained in particularly good yields when using the chromium catalysts of the present invention. The film prccucts oc:ained therefrom also have a very high puncture resistance.
In view of the onor a*, it was not to be expected that this novel process would ma; One constituent of me chromium catalyst of the present invention is the support material, in particular an incganic solid, which is usually porous. Preference is given to oxidic support materials which may s:u\ contain hydroxy groups. The inorganic metal oxide can be spherical or granular. Examples c" such sciids, which are known to those skilled in the art, are aluminum oxide, silicon dioxide (silica gel), titanium dioxide and their mixed oxides or cogels, and aluminum phosphate. Further suitaoie support materials can be obtained by modification of the pore surface, e.g. by means of compounds of the elements boron (BE-A-861,275), aluminum (US 4,284,527), silicon (EP-A-0 16c '57) or phosphorus (DE-A 36 35 715). Preference is given to using a silica gel. Preference is given to spnerical or granular silica gels, which in the case of the former may be spray dried.
Preferred support materials are finely divided silica xerogels which can be prepared, for example, as describee n DE-A 25 40 279. The finely divided silica xerogels are preferably prepared by:
a) use z: a particulate silica hydrogel which has a solids content of from 10 to 25% by weight
(calculated as Si02) and is largely spherical, has a particle diameter of from 1 to 8 mm
and 's obtained by
a1) introducing a sodium or potassium water glass solution into a swirling stream of an aqueous mineral acid, both longitudinally and tangentially to the main direction of flow, a2) spraying the resulting silica hydrosol into a gaseous medium so as to form droplets, a3) allowing the sprayed hydrosol to solidify in the gaseous medium, a4) freeing the resulting largely spherical particles of the hydrogel of salts without prior aging by washing,
b) extraction of at least 60% of the water present in the hydrogel by means of an organic iiquc
c) dryi-g of the resulting gel at up to 180°C and a reduced pressure cf 13 mbar for 30 minutes *-n til no further weight loss occurs (xerogel formation) and
d) adjustment of the particle diameter of the xerogel obtained to from 20 to 2000 urn.
In the first step a) of the preparation of the support material, it is important tc use a silica hydrogel which has a -eiatively high solids content of from 10 to 25% by weight (calculated as Si02). preferably from '2 to 20% by weight, particularly preferably from 14 to 20% by //eight, and is largely

spnencai. This silica -ydrogel has been prepared in a specific manner as described in steps a1) to a&). The steos al :o a3) are described in more detail in DE-A 21 03 243. Step a4',. viz. washing of the hycroce:. can be carried out in any desired manner for example by the ccuntercurrent principle using wate* .vnicn contains a small amount of ammonia (prl up to aoout 1C; and is at up :c 3C^C.
Tne extraction c: re .vater from the hydroget (step b)) is preferably carried out using an organic iiquic. which is panic arly preferably miscibe with water, from the group consisting of d-C4-aicohols anc.or C:-Crotones. Particularly creferred alcohols are tert-butancL i-procanol, ethanol and methane Amc~g the ketones, preference is given to acetone. The organic liquid can also consist of mixtures ;*' the abevementioned organic liquids; in any case, the organic liquid contains less than 5% oy weignt, preferably iess than 3% by weight, of water prior tc the extraction. The extraction can be C3":ed out in customary extraction apparatuses, e.g. column extractors.
Drying (step c;.) is ore'erably carried out at rom 30 to 140°C, particularly preferably from 80 to 110CC. and pressures of preferably from 1.3 mbar to atmospheric pressure. For reasons of the vapor pressu-e. a rise in temperature shoulc be accompanied by a rise in pressure and vice versa.
The adjustment of the particle diameter of the resulting xerogel (step d)) car be carried out in any desired manner, e g. oy milling and sieving.
A further preferred support material is produced, for example, by spray drying milled, appropriately sieved nydrogeis which are for this puroose mixed with water or an aliphatic alcohol. The primary particles are porous granular particies of the appropriately milled ana sieved hydrogei which have a mean particle diameter of from 1 to 20 um, preferably from 1 tc 5 um. Preference is given to using milled and sieved Si02 hydrogels.
In general, the mean particle diameter of the support particles is in the range from 1 to 1000 um, preferably in tne range from 10 to 500 um and particularly preferably in the range from 30 to 150
um.
The mean average pore volume of the support material used is in the range from 0.1 to 10 ml/g, in particular frc~ 0.3 to 4.0 ml/g and particularly preferably from 1 to 25 ml/g.
In general, re suooort particles have a specific surface area of from 10 tc '300 m2/g, in particular from 100 tc 530 m2/g. in particular from 20C to 550 m2/g.

The specific surface area and the mean pore volume are determined by nitrogen adsorption in accordance with the BET method, as described, for example by S. Brunauer. P. Emmett and E. Teller in Journal of the American Chemical Society, 60, (1939). cages 209-319.
In addition, the support particles used according to the present 'nver.ticn nave a mean core diameter of from 80 to 250 A, preferably from 90 to 210 A anc particularly prer'eraoiy from 95 to 200 A. The mean pore diameter in A is calculated by dividing the numerical value of the mean pore volume (in cm"7g) by the numerical value of the specific surface area (in m". g) and multiplying the result by 40 000. Suitable support materials are also commercially avaiiacie.
The support material can also have been partially or fully modified before use in the process of the present invention. The support material can, for example, oe treated under oxidizing or non-oxidizing conditions at from 200 to 1000CC, in the presence or acsence of'iuorinating agents such as ammonium hexaflucrosilicate. In this way. it is possible, for example, to vary the water and/or OH group content. The support material is preferably dried uncer reducec pressure at from 100 to 200CC for from 1 to 10 hours before use in the process of the present invention.
In step A), the support material is brought into contact with a protic medium comprising, preferably consisting of. a titanium compound and a chromium compounc. The "titanium compound and the chromium compound can be dissolved or suspended in the protic solvent ard are preferably both dissolved. The titanium compound and the chromium compound can be brought into contact with the solvent in any order, simultaneously or as a premixed mixture. The titanium compound and the chromium compound are preferably mixed separately, in any order, with the solvent. The reaction time is usually in the range from 10 seconds to 24 hours, preferably from 1 minute to 10 hours and particularly preferably from 10 minutes to 5 hours, before the protic medium is brought into contact with the support material.
As titanium compound, preference is given to using a tetravalent compounc of the formula (RO)nX4-nTi, where the radicals R are identical or different and are each an organosilicon or car-boorganic substituent having from 1 to 20 carbon atoms, e.g. a linear, brancned or cyclic C1-C20-alkyf group such as methyl, ethyl, n-propyl, isopropyl, n-butyl. sec-butyl, isccutyl. tert-butyi, n-pentyl, sec-pentyl, isopentyl, n-hexyi, cyclohexyl, n-heptyl or n-octyl. a C=-C-3-aryl group such as phenyl, 1-naphthyl, 2-napthyl, 1-anthryl. 2-anthryl, 9-anthry! and l-penanthr/l or a trialkylsilyl group such as trimethylsilyl or tnethylsilyi. R is preferably a linear or brancred C:-Cs-aikyi group such as methyl, ethyl, n-pjopyl, isopropyl. n-butyl, sec-butyf: isobutyi. tert-cutyl. n-pentyl or n-hexyi. X car, be a halogen such as fluorine, chlorine, bromine or iodine., pre'srably chlorine, n is from 0 to 4 and is preferably 4. Mixtures of various titanium compounds ca-~ also be used. The titanium compound is preferably soluble in the protic solvent anc preference is therefore given to using titanium tetralkoxides because they have good solubilities in very ma~y solvents. Apart from compounds of titanium with simple aliphatic alkoxides. it is alsc possible fc Afunctional ligands

such as bisalkoxices or ethoxyaminates to be present. Particularly useful compounds are bis(triethanolamine) bis(isopropyl)titanate or ammonium salts of lactic acid-titanium complexes which are soluble in water.
The chromium compounds can contain inorganic or organic groups. Preference is given to inorganic chromium compounds. Examples of chromium compounds include chromium trioxide and chromium hydroxide and also salts of trivaler: chromium with organic and inorganic acids, e.g. chromium acetate, chromium oxalate, chromium sulfate and chromium nitrate, and chelates of trivalent chromium, e.g. chromium acetylacetcnate. Among these, very particular preference is given to using chromium(lll) nitrate 9-hydrate and chromium acetyiacetonate. In preferred chromium compounds the oxidation state of the cnromium is lower than 5 and preferentially chromium is in the oxidation state 2, 3 or 4.
The protic medium is a solvent or solvent mixture comprising from 1 to 100% by weight, prefera-. bly from 50 to 100% by weight and particularly preferably 100% by weight, of a protic solvent or a mixture of protic solvents and from 99 to 0% by weight, preferably from 50 to 0% by weight and particularly preferably 0% by weight, of an aprotic solvent or a mixture of aprctic solvents, in each case based on the protic medium.
Protic solvents are, for example, alcohols R'-OH, amines NRYxHx-i, CT-Cs-carboxylic acids and inorganic aqueous acids such as dilute hydrochloric acid or sulfuric acid, water, aqueous ammonia or mixtures thereof, preferably alcohols R -OH, where R1 are each, independently of one another, C1-C2:-alkyl, C2-C2o-alkenyl, C5-C20-aryl, alkyiaryl having from 1 to 10 carbon atoms in the alkyl part and 6-20 carbon atoms in the aryl part or SiR23l where R2 are each, independently of one another. CrC20-alkyi, C2-C20~alkenyl, C6-C20-aryl, alkyiaryl having from 1 to 10 carbon atoms in the alkyl part and 6-20 carbon atoms in the aryl part, and x is 1 or 2. Examples of possible radicals R1 or R* are: Ci-C20-alkyl which may be linear or branched, e.g. methyl, ethyl, n-propyl, iso-propyl, n-butyl. isobutyi, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl. n-decyl or n-dodecyl, 5- to 7-membered cyloalkyl which may in turn bear a C6-CT0-aryl group as substituent, e.g. cycloprcpyl, cyclobutyl, cyclopentyl, cyciohexyl. cycloheptyl, cyclooctyl. cyclononyl orcyclo-dodecyl, C2-C2c-alkenyl which may be linear, cyclic or branched and in whicn the double bond may be internal or terminal, e.g. vinyl, 1-allyl. 2-allyl, 3-aliyl, butenyl, pentenyl. hexenyl, cyclopen-tenyl, cyclohexenyl, cyclooctenyi or cyciooctadienyl. C5-C20-ary! which may bear further alkyl groups as sucstituents, e.g. phenyl, naphthyl. biphenyl, anthranyl. o-; m-: p-methylphenyl, 2,3-, * "2.4-1 2,5- or 2.6-dimethylphenyl, 2,3,4-, 2,3.5-, 2,3,6-. 2,4,5-, 2,4,6- or 3:4.5-:-:methylphenyl, or aryialkyl whicn may bear further alkyl groups as substituents, e.g. benzyl, c- rn-, p-methylbenzyl, 1- or 2-ethy.cnenyl, where two R1 or two R2 may in each case also be joinec :o form a 5- or 6-membered ring and the organic radicals R1 and R2 may also be substituted c/ halogens such as fluorine, chicnne or bromine. Preferred carboxylic acids are C1-C3-carboxyii': acids such as formic acid or ace:: acid. Preferred alcohols R1-OH are methanol, ethanol. 1-prcc=~ol, 2-propanol, 1-

butanol, 2-butanol. 1-pentanol, 2-pentanol, 1-hexanol, 2-ethylhexanol, 2,2-dimethyiethanol or2,2-dimethylpropanol. in particular methanol, ethanol, 1-propanol, 1-butanoi, 1-pentanoL 1-hexanol or 2-ethyihexanoi. The water content of the protic medium is preferably less than 20°: by weight.
Examples of aprotic solvents are aliphatic and aromatic hydrocarbons such as pentane, hexane, heptane, octane, isooctane, nonane, aodecane, cyclohexane, benzene and C7-C-:-alkylbenzenes such as toluene, xyiene or ethylbenzene.
The support material can be brought into contact with the protic medium comprising the titanium compound and the chromium compound in any desired way. Thus, the mixture of erotic medium, titanium compound and chromium compound can be added to the support material or the support material can be introduced into the mixture. The support material can aiso be slurried in a suspension medium beforehand. The mixture of suspension medium used and protic medium comprises from 1 to 100% by weight preferably from 50 to 100% by weight and particularly preferably 100% by weight, of a protic solvent or a mixture of protic solvents and from 99 to 0% by weight, preferably from 50 to 0% by weight and particularly preferably 0% by weight, of an aprotic solvent or a mixture of aprotic solvents, in each case based on the mixture of the suspension medium used and the protic medium. This suspension medium is preferably likewise the protic medium used according to the present invention.
The chromium compound is usually present in a concentration of from 0.05 to 20% by weight, preferably from 0.1 to 15% by weight and particularly preferably from 0.5 to 10% by weight, based on the protic medium. The titanium compound is usually present in a concentration of from 0.05 to 30% by weight, preferably from 0.1 to 20% by weight and particularly preferably from 0.5 to 15% by weight, based on the protic medium. The molar ratio of chromium compound to titanium compound is usually in the range from 10:1 to 1:10, preferably from 5:1 to 1:7 and particularly preferably from 4:1 to 1:5.
The support material is generally loaded in a weight ratio of supported gel particies:Ti in the titanium compound of from 100:0.1 to 100:12, in particular from 100:1 to 100:5 and a weight ratio of support gel particles:chromium in the chromium compound of from 100:0.1 :o 100:10, in particular from 100:0.3 to 100:3.
Reaction step A) can be carried out at from 0 to 150°C. For cost reasons, preference is given to
room temperature. . .
The solvent can optionally be removed in a subsequent step B); preferably at from 20 to 150CC and pressures of from 10 mbar to 1 mbar. Preference is given to removing cart or all of the solvent. The precatalyst obtained in this way can be completely dry or can co-tain some residual moisture. The volatile constituents still present are preferably presentjn ar amount of not more

than 20% by weight, in particular not more tn3n 10% by weight, based on the not yet activated
chromium-containing precatalyst.
The precatalyst obtained from reaction step 3) can immediately be subjected to step D) or can be calcined beforehand at above 280°C in a water-free inert gas atmosphere in step C). The calcination is preferably carried out at from 230 to 5J0°C in a fluidized bed for from 10 to 1000 minutes.
The intermediate obtained in this way from step B) or C) is then activated in step D) under oxidizing conditions, for example in an oxygen-containing atmosphere at from 400 to 1000°C. The intermediate obtained in step B) or C) is preferably activated directly in the fiuidized bed by replacing the iner gas by an oxygen-containing gas and increasing the temperature to the activation temperature. The intermediate is advantageously heated at from 400 to 1100CC, in particular from 500 to 300'C. in a water-free gas stream in 'which oxygen is present in a concentration of above 10% by volume for from 10 to 1000 minutes. ;n particular from 150 to 750 minutes, and then cooled to room temperature, resulting in the Phillips catalyst to be used according to the present invention. The maximum temperature of the activation is below, preferably at least 20-100°C below, the sintering temperature of the intermediate from step B) or C). This oxidation can also be carried out in the presence of suitable fluorinating agents such as ammonium hexafluorosilicate.
A preferred orocess for preparing the supported, titanized chromium catalysts comprises the fallowings steos:
A) bringing a support material into contact with a protic medium comprising a titanium compound and a chromium compound.
B) removing the solvent,
C) calcining the precatalyst obtained after step B) and
D) activating the precatalyst obtained after step C) in an oxygen-containing atmosphere at from 400CC to 1100°C.
Particular preference is given to a process consisting of the steps A) to D).
The chromium catalyst of the present invention advantageously has a chromium content of from 0.1 to 5% o/ weight, in particular from 0.3 to 2% by weight, and a titanium content of from 0.5 to 10% by weight, in particular from 1 to 5% by weight.
The catalyst systems of the present invention have a short induction perioc in the polymerization of 1-aikenes

The resulting chromium catalyst to be used according to the present invention can also be reduced, for example by means cf ethylene ar.c/or a-olefins, carbon monoxide or triethyfborane. in suspension or in the gas phase before use c- :t can be modified by siiylation. The molar ratio of reducing agent tc cnromium (cf tne chromium catalyst according to the present invention to ce reduced) is usually in the range from 0.05:1 :c 500:1. preferably from 0.1:1 to 50:1. in particular from 0.5:1 to 5.0:1.
In suspension, the reduction temperature is generally in the range from 10 to 200CC. preferacly in the range from 10 to 100°C, and the pressure is in the range from 0.1 to 500 bar preferably the range from 1 to 200 bar.
The reduction temperature in fluidized-bed processes is usually in the range from 10 to 100CCC; ■ preferably from 10 to 800°C, in particular from 10 to 600°C. In general, the gas-phase reduction is carried out in the pressure range from 0.1 to 500 bar. preferably in the range from 1 to 100 bar and in particular in the range from 5 to 20 bar.
In the gas-phase reduction, the chromium catalyst to be reduced is generally fluidized by means of an inert carrier gas stream, for example nitrogen or argon, in a fiuidized-oed reactor. The carrier gas stream is usually laden with the reducing agent, with liquid reducing agents preferably having a vapor pressure of at least 1 mbar under normal conditions.
The chromium catalyst of the present invention is very useful for the preparation of homopolymers of ethylene and copolymers of ethylene with a-olefins in the customary processes known for the polymerization of olefins at temperatures in the range from 20 to 300°C and pressures of from 5 to 400 bar, for example solution processes, suspension processes in stirring autoclaves or in a loop reactor, stirred gas phases or gas-phase fiuidized-bed processes, which may be carried out continuously or batchwise. The advantageous pressure and temperature ranges for carrying out the process accordingly depend greatly on the polymerization method.
In particular, temperatures of from 50 to 150°C, preferably from 70 to 120'C, and pressures which are generally in the range from 1 to 400 bar are set in these polymerization processes. As solvent or suspension medium, it is possible to use inert hydrocarbons such as iscoutane or else the monomers themselves, for example higher olefins such as propene, butere or hexene in a liquefied or liquid state. The solids content of the suspension is generally in the -ange from 10 to 80% by weight. The polymerization can be carried out either batchwise, e.g. in stirring autoclaves, or continuously, e.g. in tube reactors, preferably in loop reactors. In particula' it can be carried out using the Phillips PF process as described in US-3 242 150 and US-3 2^6 179.

Among the polymerization processes mentioned, gas-phase polymehzation. in particular in gas-phase fluidized-bed -eactors. is preferred according to the present invention. It has been found that despite the variety of processing steps and the spray-dried succort materials, no fine dust is formed during tne gas-phase polymerization In general, it is carriec out at a temperature wr.ich is at least a few degrees under the softening temperature of the polymer. The gas-phase polymerization can also be carried out in the condensed, supercondensed c supercritical mode.
The different polymerization processes, or even the same polymerization process, can, if desired. be connected in seres so as to form a polymerization cascade. However, the special catalyst composition makes it possible for the polymers accorcmg to the present invention to be reaaiiy obtained from a single reactor.
Examples of suitable a-olefins which can be :opolymer;zed with ethylene are monoolefins and dioiefins having from three to 15 carbon atcms in the molecule. We:.-suited ^-olefins of this type are propene. 1-butene, 1-pentene, 1-hexene, 1-octene. 1-decene. %dodecene and 1-pentadecene and also the conjugated and ncnconjugated dioiefins butadiene, penta-1,3-diene. 2,3-dimethylbutadiene, penta-1,4-diene. hexa-1,5-diene and vinylcyciohexene. Mixtures of these comonomers can also be used. Preference is given to using 1-butene. 1-hexene or 1-octene, in particular 1-hexene.
To control the molar mass, hydrogen can advantageously be used as regulator in the polymerization.
It has been found to be advantageous to carry out the polymerization of the 1-alkenes by means of the catalysts of the present invention in the presence of organometallic compounds of elements of the first, second, third or fourth main group or of the second transition group of the Periodic Table of the Elements. Well-suited compounds of this type are homcieptic C--C1c-alkyls of lithium, boron, aluminum or zinc, e.g. n-butyllithium, triethylboron. trimethylaiuminum. triethylaluminum, triisobutylaluminum, tributylaluminum, trihexylaluminum, trioctyiaiuminum and diethylzinc. Furthermore, C'-C^-dialkyialuminum alkoxides such as diethylaluminum methcxide are also well suited. It is aiso possible to use dimethylaiuminum chloride, methylaiuminum dichloride, methyl-aluminum sesquichlonde or diethylaluminum chloride. n-Butyllithium and trihexyialuminum are particularly preferred as organometallic compound. Mixtures of the aoove-described organometal-iic compouncs are generally also well suited.
The molar ratio of organometallic compound:chromium is usually in tne range from 0.1:1 to 5G: 1, preferably m the range from 1:1 to 50:1. However, since many of the activators, e.g. aluminum alkyis, can a:so be used at the same time for removing catalyst poisons (known as scavengers), the amount used is dependent on the impurities present in the other starting materials. However, a person ski ed in the art can determine the optimum amount by means of simple tests.

The chromium catalysts of the present invention can also be used together with another catalyst suitable for the polymerization of a-olefins in the above polymerization processes The chromium catalyst of the present invention is preferably used together with another suopcrtec chromium catalyst customary for the polymerization of ^-olefins. The use of two different succorted chrc-mium catalysts is described, for example, in WO 92/17511. The polymerization ca~ also be carried out using two or more of the chromium catalysts of the present invent,on simultaneously. The polymerization is particuiariy preferably carried out using a chromium catalyst acceding to the present invention together with a supported, nontitanized chromium catalyst. Mixtures of titanized and nontitanized supported chromium catalysts are described, for exampie. in US-2 798 202. but in that case the titamzation is carried out oniy after the chromium component has ceen applied to a support.
The two different Phillips cataiysts can be mixed before they come into contact w:t~ the monomers and can then be introduced together into the reactor, or they can be introduced into the reactor separately from one another, for example at a plurality of points.
The homopolymers and copolymers of ethylene prepared according to the oresent invention usually have a density, measured in accordance with DIN 53479. in the range "*rom 0.9 to 0.97 g/cm3, preferably in the range from 0.92 to 0.96 g/cm3 and particularly preferably .r, the range from 0.925 to 0.945 g/cm3, and a melt flow index (Ml (190°C/2.16 kg) or HLMI (190°C 21.6 kg);, measured in accordance with DIN 53735 under different loads (in brackets), in the range from G to 10 g/10 min, preferably in the range from 0.01 to 1 g/10 min and particularly preferably :- the range from 0.05 to 0.6 g/10 min, in the case of Ml and in the range from 1 to 50 g/10 min. preferably in the range from 3 to 30 g/10 min and particularly preferably in the range from 5 to 25 g/10 min. In the case of the HLMI.
The weight average molar mass Mw is generally in the range from 10 000 tc 7 000 000 g/moL preferably in the range from 100 000 to 500 000 g/mol. The molar mass distribution M;v/Mn, measured by GPC (gel permeation chromatography) at 135°C in 1,2,4-trichlorccenzene using polyethylene standards, is usually in the range from 3 to 50, preferably in the range from S to 30 and particularly preferably in the range from 15 to 30.
In general, the ethylene polymers produced in the reactor are melted and -omogenized in an extruder. The melt flow index and the density of the extrudate can then drer from the corresponding parameters for the crude polymer, but are also in the range specified according to the present invention.
In the olefin polymerization in which the catalyst prepared according to the cresent invention is used, it is possible to prepare homopolymers of ethylene or copolymers c* ethylene with a co-

monomer having from 3 to 12 carbon atoms in an amount of up to 10 moi% of comonomer in the copolymer. Preferred copolymers contain from 0.3 to 1,5 mol% of hexene. based on the polymer, particularly preferably from 0.5 to 1 mo!% c* nexene.
The ethylene copolymer prepared according :o the present invention can also form mixtures with other olefin polymers, in particular homopolymers and copolymers of ethylene. These mixtures can, on the one hanc, be prepared by tne acove-described simultaneous polymerization of a plurality of chromium catalysts. On the other hand, these mixtures car also be obtained simply by suosequent blending of the polymers prepared according to the present invention with other ho-mopolymers or copolymers of ethylene. MF! HLMI. density, comonomer content, Mw and Mw/Mn of these mixtures are preferably likewise in tne same ranges as these for the polymers which have been prepared using only a titanium-ccntaining chromium catalyst accorcing to the present invention.
In addition, the ethylene copoiymers, polymer mixtures and blends can further comprise auxiliaries and/or additives known per se, e.g. processing stabilizers, stabilizers against the action of light and heat, customary additives such as .upricants, antioxidants, antiblocking agents and antistatics, and also, if desired, cciorants. The tyoe and amounts of these additives are well known to these skilled in the art.
The polymers prepared according to the present invention can also be modified subsequently by grafting, crosslinking. hydrogenation or other functionalization reactions which are known to those skilled in the art.
The polymers prepared according to the present invention are very useful for, for example, producing fiims on blown film plants at high outputs. Films comprising tne polymers prepared according to the present invention have good mechanical properties. The nigh puncture resistance of the films produced therefrom is also worthy of note.
The films obtained in this way are suitable, in particular, for the packaging sector and for large, heavy duty sacks and also for the food sector. Furthermore, the films have only a low blocking tendency anc can therefore be passed through machines without use of lubricants and antiblocking additives or with use of only small amounts thereof.
The Phillips catalyst prepared according to the present invention has particular unexpected advantages. It is very useful for the homopolymerization and copolymerization of ethylene by the customany arc known particle form processes in a gas-phase fluidlzed-bec polymerization. Here, it gives, at a nigh productivity, (co)polymers having excellent morphology and good processability. In particular, tne catalyst of the present invention displays a good comonomer incorporation behavior and gves high productivities even at iow activation temperat^es. The (copolymers pre-

pared by means of the Phillips catalyst of the present invention are therefore particularly useful for processing by the blown film process and the blow molding process.
The following examples illustrate the invention.
The productivity of the catalyst is reported as the amount of polymer isolated per amount of Phillips catalyst used in g.
The melt flow index was determined in accordance with ISO 1133 at 190CC under a load of 21.6 kg (190°C/21.6 kg, HLMI) and under a load of 2.16 kg (190°C/2.16 kg, Ml).
The density [g/cm3] was determined in accordance with ISO 1183.
The bulk density (BD) [g/l] was determined in accordance with DIN 53468.
The environmental stress cracking resistance (ESCR) was determined in Basell's round disk in-dentor test (Rl). Test conditions: round disks (produced from a pressed plate, diameter: 38 mm, thickness: 1 mm, scored on one side by means of a scratch having a length of 20 mm and a depth of 200 urn) are dipped at 50 or 80°C into a 5% strength aqueous solution of Lutensol® FSA and loaded by means of a gas pressure of 3 bar. The time to occurrence of stress cracks which produce a pressure drop in the measuring apparatus is measured (in h).
The measurement of the dart drop impact strength was carried out on 20 urn films in accordance with ASTM 1709 A.
The Staudinger index (*n)[dl/g] was determined at 130°C on an automatic Ubbelohde viscometer (Lauda PVS 1) using decalin as solvent (ISO 1628 at 130°C, 0.001 g/ml of decalin).
The determination of the molar mass distributions and the means Mn, Mw and Mw/Mn derived therefrom was carried out by means of high-temperature gel permeation chromatography using a method based on DIN 55672 under the following conditions: solvent: 1,2,4-trichlorobenzene, flow: 1 ml/min, temperature: 140°C, calibration using PE standards.
Abbreviations in the following tables:
Tp0iy Temperature during the polymerization
Mw Weight average of the molar mass
Mn Number average of the molar mass
Density Polymer density
DDl Dart drop impact - -

ESCR Environmental stress cracking resistance
% by volume Percentage by volume of the respective component during the polymerization
Prod. Proc-ctivity of the catalyst in g of polymer obtained per g of catalyst used
HLMI Mel: *"ow index at a loading weight of 21.6 kg
THA Amc^nt of trihexylaluminum used
TI StaLc'nger index
mg cat. mg c:* the catalyst used in the polymerisation
Vinyl Viny groups in the polymer oer (1000 C)
Examples and Comparative Experiments
Example 1
The support material was prepared as described in DE 2 540 279.
Preparation of the silica xerogel
A mixing nozzle as shown in the figure in DE-A 2 103 243 and having the following data was utilized: the diameter of :ne cylindrical mixing chamber formed by a plastic tube is 14 mm, the length of the mixing zone (including after-mixing section) is 350 mm. The end of the mixing chamber nearest the inlet is cicsed off and near this end there is a tangential inlet hole having a diameter of 4 mm for the mineral acid." Four further holes likewise having a diameter of 4 mm and the same inflow direction for the water glass solution follow, with the spacing of the holes^ measured in the longitudinal direction of the mixing chamber, being 30 mm. Accordingly, the ratio of length to diameter of the primary mixing zone is about 10:1. For the subsequent secondary mixing zone, this ratio is 15. As spraying nozzle, a flattened, slightly kidney shaped piece of tube was pushed over the outlet end of the plastic tube.
This mixing apparatus was supplied with 325 l/h of 33 percent strength by weight sulfuric acid at 20°C and an operating pressure of about 3 bar and also 1100 l/h of water glass solution (prepared from technical-grade water glass containing 27% by weight of Si02 and 8% by weight of Na20 by dilution with water) having a density of 1.20 kg/I and a temperature of likewise 20°C and a pressure of likewise about 3 bar. Progressive neutralization in the mixing chamber lined with the plastic tube resulted in formation of an unstable hydrosol which had a pH of 7-3 and remained in the after-mixing zone for about 0.1 s until completely homogenized before it was sprayed through the nozzle attachment inic the atmosphere as a fan-shaped liquid jet. During its flight through the air, the jet broke ,o into individual droplets which, as a result of the surface tension, took on a largely spherical shace and solidified to form hydrogel spheres within about one second while still in flight. The spheres had a smooth surface, were clear as glass, contained aoout 17% by weight of Si02 and hac the following particle size distribution:
> 8 mm 10% by weight
5-8 mm 45% by weight

4-6 mm 34% by weight
(The particle s;ze distributer can be varied a; will by use of other nozzle attachments.) The ny-drogel spheres were collectec at the end of ;-e;r flight In a scrubbing tower whic~ ,vas filled almost completely with hydrcgei spheres and ,r. which the spneres were washed free of salts immediately without aging by means of water containing a little ammonia and having a temperature of about 50°C ;n a continuous countercurrer: process.
The spheres wnich had a ciameier in tne range from 2 to 5 mm were isc;ated by sieving and 112 kg of these spneres were c.aced in an extraction vessel which had an in;et at the top. a sieve bottom and swan-neck shaced overflow whicn is connected to the bottom of the drum and keeps the liquid level in the arum sufficiently high for the hydrogel spheres to be completely covered with liquid. The hycrogel was extracted by means of methanol.
The spheres obtained in this way were then dried (12 hours at 120~C under a pressure of 20 mbar) until no further weight loss occurred a: 180°C under a pressure of 13 mbar over a period of 30 minutes.
The spheres which had been dried in this way were subsequently milled and the xerogel particles which have a diameter of from 40 to 300 urn were isolated by sieving. The pore volume was 1.9 ml/g.
39 ml of titanium tetraisopropoxide were added to a solution of 11.6 g of cnromium(lll) nitrate nonahydrate (Cr(N03)3x9H20) in 700 ml of methanol. The solution of chrcmium(ill) nitrate nona-hydrate and titanium tetraisopropoxide in methanol was clear and displayed no turbidity. The solution obtained in this way was added to 150 g of the above-described silica gel support. The suspension was stirred for 1 hour and then evaporated to dryness on a rotary evaporator at 80°C with application of a vacuum. The precatalyst obtained in this way contains 1 % by weight of chromium and 4% by weight of titanium, based on the weight of the precatalyst.
Comparative Example C1
Example 1 was repeated without addition of titanium tetraisopropoxide. Tne precatalyst obtained
in this way contains 1% by weight of chromium, based on the weight of re precatalyst.
Example 2 * '
400 g of chromium(lli) nitrate nonanyarate were dissolved in 6.5 I of methanol while stirring in a dissolution reactor. After stirring for one hour. 0.97 I of titanium tetraisop'cooxide were added and the mixture was stirred for another 5 minutes. This solution was subsequently pumped over a period of 1 hour onto 5 kg of the silica gel support Sylopol SG332 5N (commercially available from Grace) in a double cone drier. The dissolution reactor was then rinsed v. t~ 1.5 I or m-ethano!

which was then likewise added to the supper:. The suspension was then stirred for A- hour and subsequently heated to 95°C and the methanol was distilled off at 900 mbar. After aoout 3 hours, the pressure was reduced to 300 moar and the product was driec under rese conditions for a further 2 hours, "he precatalyst obtained in this way contains 1% by weight z: znrom^n and 3% by weight of titanium, based on the weignt of the p*ecataiyst.
Comparative Example C2
The procedure of Example 2 was repeated ;-sing 5 kg c* the silica gel supper: Sylcccl SG332 5N
and 120 g of chromium(lll) nitrate nonahydrate but without adaiticn of titanium tetracropoxide. The
precatalyst obtained in this way contains 0.3% by weignt of chromium, based on the weight of the
precatalyst.
Example 3
1000 g of chrcmium(ill) nitrate nonahydrate and 21 I of methanol were mixed with s::rr;ng in a dissolution reactor. After stirring for one hour, 2.3 I of titanium tetraisopropoxide were added to this solution and the mixture was stirred for 5 minutes. This solution was suosequentiy pumped over a period of 1 hour onto 18 kg of the siiica gel support XP021C7 (commercially available from Grace) (which had been dried beforehand at 130°C and 10 mbar for 7 hours in this couble cone drier) in a double cone drier which was rotated uniformly. After the addition, the dissolution reactor was rinsed with 5 i of methanol and this rinsing solution was likewise added to the silica gel support. The suspension was stirred for a further 1 hour and was then dried at 903C witn application of a vacuum until a pressure of 10 mbar at a temperature of 100°C was reached after a period of 1 hour. The precatalyst obtained in this way contains 0.7% by weight of chromium and 2% by weight of titanium, based on the weight of the precatalyst.
Comparative Example C3
3.5 I of titanium tetraisopropoxide were mixed with 20 I of heptane wnile stirring in a dissolution reactor. After stirring for 10 minutes, the solution was pumped over a period of one hour onto 18 kg of the siiica gel support XPO2107 (which had been dried beforehand at *30°C and 10 mbar for 7 hours in this double cone drier) in a double cone drier which was rotated uniformly. The dissolution reactor was rinsed with 5 I of heptane and this rinsing solution was likewise transferred into the double cone drier. The suspension was then stirred for 1 hour. It was suosequentiy dried at 90°C with abdication of a vacuum until a pressure of 10 mbar at a temperature of 100GC was reached after 1 hour. 1000 g of chromium(lll) nitrate nonahydrate and 23 ! of methanol were sub-sequently mixed white stirring in the dissolution reactor. After stirring *'or 1 .TOUT, this solution was pumped over a period of 1 hour onto the supported titanium compound in the rotating double cone drier. After the addition, the dissolution reactor was rinsed with 5 i of methane; and the rinsing solution //as likewise transferred to the double cone drier. The suspension was stirred for a
further 1 he and then dried at 90°C with application of a vacuum until a pressure of 10 mbar at a
>
>

temperature of 100°C was reached after 1 nour. The precatalyst obtained in this way contains 0.7% by weight of chromium and 3% by weight of titanium, based on the weight of the precataiyst.
Activation
Activation was carried out at 500 or 65CCC cy means of air in a fluidized-oed activatcr. To ac: vate the precatalyst, it was heated to 300CC ove- a period of 1 hour, kept at th:s temperature for1 hour, subsequently heated to the desired activation temperature, kept at :nis temperature fcr 2 (Examples 1 and C1) or 5 hours (Examoles 2. 3, C2 and C3) and subsecuently codec. Cocl^g below 300CC was carried out under nitrogen. The precatalysts from Exar.cies 1. CI and C2 'were heated to an activation temperature of 75C:C. the precatalyst from Examoie 2 was heated tc an activation temperature of 600-C and the precatalysts from Examples 3 ana C3 were heated :c an activation temperature of 520CC.
Polymerization
The polymerization experiments in Table 1 were carried out under the ccrcitions specified ir. Table 1 at a total pressure of 40 bar and an output of 25 kg/h in a 180 I PF cop reactor (= particle-forming loop reactor) (suspension medium: :sobutane). The catalysts described in Examples 1 and C1 served as catalyst.
The polymerization experiments in Table 2 were carried out in a continues gas-phase fluidized-bed reactor (Lupotech G as described in W099/29736 A1) under the conations specified in tne tables at a total pressure of 20 bar and an output of 50 kg/h.
The products prepared in the gas-phase process were granulated at 20C:C under protective gas on a ZSK 40. Processing to produce films was carried out on a blown film oiant from W&H provided with a 60/25D extruder. The catalysts described in Examples 2, C2 3 and C3 served as catalyst.
The results of the polymerizations and product tests are summarized in re tables.

Example 4
1430 g of chromium(lll) nitrate nonahycrate and 26 I of methanol were mixed with stirring in a dissolution reactor. After stirring for one hour. 2.3 i of titanium tetraisopropoxide were added to this solution and the mixture was stirred for 5 minutes. This solution was subsequently pumped over a period of 1 hour onto 18 kg of the silica gel support XP02107 (commercially available from Grace). After the addition, the dissolution reactor was rinsed with 4 I of methanol and this rinsing solution was likewise added to the silica ge, support. The suspension was stirred for a further 1 hour and was then dried at 95°C with application of a. The precatalyst obtained in this way contains 1 % by weight of chromium and 2% by weight of titanium, based on the weight of the precatalyst.
Comparative Example C4
Di-tert.butylchromate was prepared by adcing to a suspension of 4.86 g CrCK and 10 g MgS04 in 300 ml of hexane a solution of 9.45 ml of tert.-butanol in 50 ml hexane. After stirring for 15 min the solution was filtered to give a hexane solution of di-tert.butylchromate.
31.5 ml of titanium tetraisopropoxide and the di-tert.butylchromate solution were added together onto 250 g of the silica gel support XP02107 (commercially available from Grace). The suspension was then stirred for 1 hour. The hexane was distilled off and the resulting solid was subsequently dried at 80°C with application of a vacuum. The precatalyst obtained in this way contains 1 % by weight of chromium and 2% by weight of titanium, based on the weight of the precatalyst.
Activation
Activation was carried out at 520°C by means of air in a fluidized-bed activator as described
above.
Polymerization
The polymerization experiments in Table 3 were carried out at a total pressure of 40 bar, 100°C for 90min in a 1 I autoclave reactor (suspension medium: isobutane 400ml, 10ml hexene). The catalysts described in Examples 4 and C4 served as catalyst. Both showed a productivity of about 6000 g of polymer per g catalyst. The new catalyst gave ethylene copolymers with a higher molecular weight (Mw and Mn) and a broader molecular weight distribution (Mw/Mn) with about the same density than the catalyst prepared in an aprotic medium (comparative example C4).

We claim:
1. A process fcr preparing supported, :::anized chromium catalysts, which comprises the
following steos:
A) bringing a support material in:c contact with a protic medium comprising a titanium compound and a chromium compound.
B) optionally removing the soive,":.
C) optionally calcining the precataiyst obtained after step B) and
D) optionally activating the preca:aiyst obtained after step B) or C) in an oxygen-
containing atmosphere at from 400°C to 1100QC.
2. A process as claimed in claim 1, wherein the support material is a silica gel.
3. A process as claimed in claim 1 or 2. wherein the chromium compound is an inorganic
chromium compound.
4. A process as claimed in claim 3, wherein the inorganic chromium compound is
chrcmium(lll) nitrate nonahydrate.
5. A process as claimed in any of claims 1 to 4, wherein the titanium compound is titanium
tetraisopropoxide, titanium tetra-n-butoxide or a mixture of these two titanium compounds.
6. A process as claimed in any of claims 1 to 5, wherein the protic medium is methanol.
7. A catalyst system obtainable by a process as claimed in any of claims 1 to 6.
8. A process for preparing polyolefins by polymerization or copolymerization of olefins in the
presence of a catalyst system as claimed in claim 7.
9. A process as claimed in claim 8, wherein ethylene or a monomer mixture of ethylene and/or
C3-C-2-1-alkenes containing at least 50 mol% of ethylene is used as monomer(s) in the

Supported chromium catalyst and its use "'or preparing homopolymers and copolymers of ethylene
Abstract
Process for preparing supported, titanizec chromium catalysts, which comprises the following steps:
A) bringing a support material into ccr:act wit" a prctic medium comprising a titanium compound and a chromium compounc
B) optionally removing the solvent.
C) optionally calcining the precatalyst cotainec after step B) and
D) optionally activating the precatalyst obtained after step B) or C) in an oxygen-containing atmosphere at from 400°C to 110QzC.

Documents:

1195-chenp-2005-claims.pdf

1195-chenp-2005-correspondnece-others.pdf

1195-chenp-2005-correspondnece-po.pdf

1195-chenp-2005-description(complete).pdf

1195-chenp-2005-form 1.pdf

1195-chenp-2005-form 26.pdf

1195-chenp-2005-form 3.pdf

1195-chenp-2005-form 5.pdf

1195-chenp-2005-form18.pdf

1195-chenp-2005-pct.pdf

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Patent Number

228159

Indian Patent Application Number

1195/CHENP/2005

PG Journal Number

10/2009

Publication Date

06-Mar-2009

Grant Date

28-Jan-2009

Date of Filing

10-Jun-2005

Name of Patentee

BASELL POLYOLEFINE GMBH

Applicant Address

BRUHLER STRASSE 60, 50389 WESSELING,

Inventors:

#	Inventor's Name	Inventor's Address
1	ROHDE, WOLFGANG	HEERSTRASSE 43, 41542 DORMAGEN,
2	FUNK, GUIDO	DURERSTRASSE 5, 67549 WORMS,
3	HAUFE, ANDREAS	HORST-SCHORK-STRASSE 178, 67069 LUDWIGSHAFEN,
4	BOLD, ANKE	STAHLBERGER STRASSE 7, 67246 DIRMSTEIN,
5	NADALIN, NEIL	IM HERLENSTUECK 2, 65779 KELKHEIM-RUPPERTSHAIN,

PCT International Classification Number

C08F10/00

PCT International Application Number

PCT/EP03/13914

PCT International Filing date

2003-12-09

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/446,936	2003-02-12	Germany
2	102 57 740.4	2002-12-10	Germany
3	60/467,633	2003-05-02	Germany