Title of Invention

A PROCESS FOR PRODUCING ULTRA HIGH MOLECULAR WEIGHT POLYMERS OF OLEFINS

Abstract

This invention relates to a process for producing high molecule weight polymers of olefins. Ethylene and/or l-olefins are polymerised in the presence of a mixed catalyst system consisting of component A and component B. Component A is prepared by reacting a dialkylmagnesium compound with a .halogenating agent, a titanium compound and an electron donor which is fixed by reduction with an aluminium alkyl. This component A is used with an organoaluminium compound such as alkyl aluminium sesquichlorides to produce the olefin polymers.

Full Text

GOVERNMENT OF INDIA, THE PATENT OFFICE 2nd M.S.O. BUILDING, 234/4, ACHARYA JAGADISH CHANDRA BOSE ROAD KOLKATTA - 700 020. Complete specification No. 193264 dated: 13th Jun 2001 Application No471/MAS/2001 dated: 13th Jun 2001 Division to Patent Application No: 461 /MAS/1995Ante-dated toDated: 18th April 1995 Acceptance of the complete specification advertised on 17/07/2004 Index at acceptance —32 E International Classification 7 -C 08 F 10/00; C 08 F 4/64 Title : "A PROCESS FOR PRODUCING ULTRA HIGH MOLECULAR WEIGHT POLYMERS OF OLEFINS" Applicant: TICONA GMBH OF AN DERB43, 65451 KELSTERBACH A GERMAN COMPANY GERMANY Inventors: 1. DIETER BILDA 2. LUDWIG BOHM The following specification particularly describes and ascertains the natures of this invention and the manner in which it is to be preformed:- This invention relates to a process for producing/high molecular weight polymers having a molecular weight MW equal or greater than 1.106 g/mol. It is known that high molecular weight polyethylene can be synthesized in a low-pressure process using Ziegler catalysts, by employing catalysts which are prepared by reaction of compounds of the elements of transition groups IV to VI of the Periodic Table with organometallic compounds of the main groups I to (II of the Periodic Table. The effectiveness of these catalysts can be substantially increased by supporting the transition metal component. Support materials used are, inter alia, silica gels, organic soiids and inorganic salts. A particularly strong increase in the catalytic activity is achieved by fixing to MgCl2 supports, since the lattice structure of this salt allows optimum incorporation of the titanium compound. Here, the method of preparing the MgC2 can be used to influence its surface area, which should be > 60m2/g for highly active Ziegler catalysts. Ultrahigh molecular weight polyethylene is supplied as a fine powder to the processor, where it is processed mainly by pressure sintering and ram extrusion to give plates and rods. Therefore, a decisive role is played not only by the molecular properties such as molecular weight and molecular weight distribution, but also by morpho-logical properties of the high molecular weight products, for example particle size, particle size distribution and bulk density. A catalyst is known which is prepared by reaction of anhydrous MgCI2 with ethanol, diethylaluminum chloride and titanium tetrachloride and, at polymerization temperatures of below 50°C, produces ultrahigh molecular weight polyethylene having an intrinsic viscosity (IV) of >2700 cm3/g (cf. US 4 933 393). Furthermore, a catalyst has been described in which two different titanium compounds are applied to an organic support, and which can be used, at a temperature of 80°C, to prepare polyethylene having a molecular weight Mw of about 2-106 g/mol, which corresponds to an intrinsic viscosity (IV) of about 1500 cm3/g (cf. DD 282 013). Ultrahigh molecular weight polyethylene having a narrow particle size distribution can also be prepared using a catalyst based on oxygen-containing inorganic Mg compounds (cf. EP 349 146). At polymerization temperatures of from 55°C to 75°C, IV values in the range from 1000 to 2500 cm3/g are obtained. The mean particle sizes are between 190 and 240 fjm. A catalyst system has been described for preparing ultrahigh molecular weight polyethylene, which catalyst system leads, by means of the use of soluble titanium esters, to polymers having a narrow particle size distribution and a defined particle size (cf. EP 523 657). The IV values are in the range from 1000 to 2500 cm3/g. However, washing and drying steps are required in the course of the catalyst synthesis. Finally, a catalyst has been described for preparing ultrahigh molecular weight polyethylene, which catalyst can be prepared by reaction of MgCI2 with an alkoxytitanium compound and an aluminum trihalide (cf. EP 574 153). However, at a polymerization temperature of 65°C, only IV values of To overcome the disadvantage of the polymers often being formed with a particle size which is too large, complicated milling processes for the polyethylene have been proposed (cf. US 3 847 888). However, the milled products have an irregular shape and a relatively broad particle size distribution. It is an object of the invention to develop a highly active catalyst system which is able to prepare, at polymerization temperatures > 70°C, ultrahigh molecular weight ethylene polymers having a narrow particle size distribution and a mean particle diameter in the range from 100 to 200 //m. The catalyst synthesis should here be able to be carried out in a single-vessel reaction, i.e. without intermediate separation, washing and drying steps. This object is achieved according to the invention by synthesizing, in the first step of the catalyst preparation, a solid which is the reaction product of a dialkylmagnesium compound with a halogenating agent and which has a mean particle size Accordingly the present invention provides a process for producing ultra high molecular weight polymers having a molecular weight Mw equal or greater than 1.10* g/mol by polymerising ethylene and/or 1 - olefins either in suspension or in the gas phase comprising the steps of polymerising the same under known polymerization conditions in the presence of a mixed catalyst system consisting of component A and an organoaluminum compound such as herein described wherein said component A is prepared by reacting in a first reaction step (a) a magnesium compound of the formula I wherein R1 and R2 are identical or different, and are each a C1_ C20 alkyl radical, a C5 - C20 cycloalkyl radical, a C6-C20 - alkenyl radical with a halogenating agent of the formula II where X is a halogen atom, n is 3 and R3 is a hydrogen atom, a Ci - C20 alkyl radical, a C5 - C20 cyclo alkyl radical, a C6 - C20 aryl radical, or a C2 -C20 alkenyl radical to produce a catalyst support consisting predominantly of a compound of the formula III where X is a halogen atom, reacting said catalyst support in a second reaction step (b) with a hydrocarbon soluble titanium compound of the formula IV where R4 and R5 are identical and are each a halogen atom, a C1 - C6 alkoxy group, or C1 - C20 carbony radical, and m is a number from 0 to 4, in an inert hydrocarbon medium at a temperature from 0 to 100°C in a molar ratio of Ti:Mg of from 0.01 to 1; a known electron donor in an amount of from 0.01 to 1 mol per mol of said Magnesium compound of formula III being present in one of the reaction steps (a) or (b), reducing the dissolved titanium compound of formula IV with a known aluminum alkyl to precipitate the same on said catalyst support, said precipitate having a particle size of It is known that the viscosity number, which is employed for characterizing the degree of polymerization, is a reciprocal function of the polymerization temperature and reflects the quotient of the chain growth and chain termination rates. This rate ratio is specific to each catalyst system. In the achievement of this object it has been further assumed that one catalyst particle produces one polymer particle and that the growth proceeds spherically (multigrain model). It follows therefrom that the catalyst particle diameter is limited by the productivity (CA), which should be greater than 20 kg of PE/mmol of Ti, to values To prepare the catalyst component of the invention, a magnesium compound of the formula I R1-Mg-R2 (I), where R1 and R2 are identical or different and are each preferably a C2- r C8-alkyl rad ical, a C6-C8-cycloalkyl radical, a C6-C10aryl radical or a C2-C8-alkenyl radical, is used. This magnesium compound is reacted with a halogenating agent of the formula II Xn - C - R3 (ii), where X is preferably CI, n is 3 and R3 is a hydrogen atom, a halogen atom, preferably a C2-Ca-alkyl radical, a C6-C8-cycloalkyl radical, a C6-C10-aryl radical or a C2-C8-alkenyl radical. The reaction is carried out in a hydrocarbon having from 4 to 12 carbon atoms or in a mixture of such hydrocarbons. Suitable hydrocarbons are, for example, butanes, hexanes, octanes, decanes, cyclohexanes and petroleum fractions, containing these hydrocarbons. This gives a solid product consisting predominantly of a compound of the formula III, which serves as catalyst support: X - Mg - X (III) The specific surface area of the MgCI2 which is particularly suitable according to the invention was determined as 68 m2/g by the method of Brunauer, Emmett and Teller (BET method). The X-ray powder diffraction spectrum has the typical reflections for a MgCI2 which is obtained from reaction of a Grignard compound with a chlorinating agent. For the achievement of the object, the use of an electron donor compound has been found to be necessary. This compound has two functions. Firstly, it strengthens the fixing of the titanium to the support, secondly it lowers the electrophilicity of the transition metal and thus leads to higher molecular weights of the polymers. Suitable donor compounds are esters of carboxylic acids, ethers, ketones, amides, alcohols and also oxygen-containing phosphorus and sulfur compounds. Typical esters are, for example, alkyl benzoates, alkyl phthalates and alkyl anisates. The electron donor compound is preferably reacted with the catalyst support (III) prior to the fixing of the titanium compound. However, it is also possible to simultaneously react catalyst support, donor and titanium compound or to allow the titanium compound as adduct with the electron donor to react with the catalyst support. The content of donor component is from 0.01 to 1 mol, preferably from 0.05 to 0.5 mol, per mol of magnesium. The molar ratio between electron donor and titanium compound is in the range from 0.1 to 10, preferably from 0.5 to 1.5. The adduct of the catalyst support (III) with the electron donor is reacted with a hydrocarbon-soluble titanium compound of the formula IV R4m-Ti-R54.m (IV), where R4 and R5 are identical or different and are each preferably CI, a C1-C4-alkoxY group or a C6-C8carboxy radical and m is a number from 0 to 4. The reaction takes place in an inert hydrocarbon at a temperature of from 0 to 100°C. The molar ratio of fixed Ti:Mg is preferably in the range from 0.02 to 0.2. In the final reaction step, the unreacted, dissolved titanium compound is converted into a hydrocarbon-insoluble form by reduction with an aluminum alkyl compound of the formula AIR6nR73.n, where R6 can be identical or different alkyl or aryl radicals each having from 1 to 20 carbon atoms and R7 can be halogen and/or hydrogen, alkoxy and/or siloxy radicals having from 1 to 20 carbon atoms, where n is an integer from 0 to 3, and is thus fixed to the catalyst support. Examples of preferred compounds of this type are AI(C2H5)3, AI(C2H5)2H, AI{C3H7)3, AUC3H7)2H, AI(iC4H9)3, AI(iC4H9)2H, AI(C8H17)3, AI(C12H25)3, AI(C2H5)(C12H25)2, AI(iC4H9)(C12H25)2 and also (C2H5)2AICI, (iC4H9)2AICI, (C2H5)3AI2CI3. This gives the catalyst component A. The component A can be reacted as a suspension directly with the component B; however, it can also first be isolated as a solid, stored and resuspended for further use later. As component B, preference is given to using organoaluminum compounds. Suitable organoaluminum compounds are chlorine-containing organoaluminum compounds, the dialkylaluminum monochlorides of the formula R82AICI or alkylaluminum sesquichlorides of the formula R83AI2CI3, where R8 is an alkyl radical having from 1 to 16 carbon atoms. Examples which may be mentioned are (C2H5)2AICI, (iC4H9)2AICI, (C2H5)3AI2CI3. It is also possible to use mixtures of these compounds. Particular preference is given to using chlorine-free compounds as organoaluminum compounds. Suitable compounds for this purpose are, on the one hand, the reaction products of trialkylaluminum or diafkylaluminum hydrides containing hydrocarbon radicals having from 1 to 6 carbon atoms, preferably AI(iC4H9)3 or AI(iC4H9)2H, with diolefins containing from 4 to 20 carbon atoms, preferably isoprene. An example which may be mentioned is isoprenylaluminum. On the other hand, compounds which are suitable as such chlorine-free organoaluminum compounds are trialkylaluminums or dialkylaluminum hydrides of the formula AIR83 where R8 is as defined above. Examples are AI(C2H5)3, AI{C2H5)2H, AI(C3H7)3, AI(C3H7)2H, AI(iC4H9)3, A!(iC4H9}2H, AI(C8H17)3, AI(C12H25)3, AI(C2H5)(C12H2S)2. AI{iC4H9)(C12H25)2. It is also possible to use mixtures of organometallic compounds of metals of group I, II or III of the Periodic Table, in particular mixtures of various organoaluminum compounds. As examples, the following mixtures may be mentioned: AI{C2H5)3 and AI(iC4H9)3, AI(C2H5)2CI and AI(CaH17}3, AI(C2H5)3 and AKC8H17)3, AI(C4H9)2H and AI{C8H17)3, AI(iC4H9)3 and AI(C8H17)3, Ai(C2H5)3 and AI(C12H25)3, AI(iC4H9)3 and AI(C12H25)3, AI(C2H5)3 and AI(C16H33)3, AI(C3H7)3 and AI(C18H37)2(iC4H9), AI(C2H5)3 and isoprenylaluminum (reaction product of isoprene with AI(iC4Hg)3 or AI(iC4H9)2H), The component A and the component B can be mixed prior to polymerization in a stirred reactor at a temperature of from -30 to 150°C, preferably from -10 to 120°C. It is also possible to combine the two components directly in the polymerization reactor at a temperature of from 20 to 200°C. However, the addition of the component B can also be carried out in two steps, by preactivating the component A with a part of the component B at a temperature of from -30 to 150°C prior to the polymerization reaction and carrying out the further addition of the component B in the polymerization reactor at a temperature of from 20 to 200°C. The polymerization catalyst prepared according to the invention is used for the polymerization of 1-olefins of the formula R9-CH = CH2, where R9 is a hydrogen atom or an alkyl radical having from 1 to 10 carbon atoms, for example ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene. Preferably, ethylene is polymerized alone or as a mixture of at least 90 % by weight, in particular at least 95 % by weight, of ethylene and at most 10 % by weight, in particular at most 5 % by weight, of another 1-olefin of the above formula. The polymerization is carried out in a known manner in solution, in suspension or in the gas phase, continuously or batchwise, in one or more stages, at a temperature of from 20 to 200°C, preferably from 50 to 150°C. The pressure is from 0.5 to 50 bar. Preference is given to carrying out the polymerization in the pressure range of from 5 to 30 bar which is of particular importance in industry. The component A is here used in a concentration, based on transition metal, of from 0.0001 to 1 mmol, preferably from 0.0005 to 0,1 mmol of transition metal per dm3 of dispersion medium. The organometallic compound (component B) is used in a concentration of from 0.1 to 5 mmol, preferably from 0.5 to 4 mmol, per dm3 of dispersion medium. However, higher concentrations are also possible in principle. The suspension polymerization is carried out in an inert dispersion medium customary for the Ziegler low-pressure process, for example in an aliphatic or cycloaliphatic hydrocarbon; examples of such hydrocarbons which may be mentioned are butane, pentane, hexane, heptane, isooctane, cyclohexane, methylcyclohexane. It is also possible to use petroleum or hydrogenated diesel oil fractions which have been carefully freed of oxygen, sulfur compounds and moisture. The gas-phase polymerization can be carried out directly or after prepolymerization of the catalyst in a suspension process. The molecular weight of the polymer is regulated by temperature or by chain-termination reagents; hydrogen is preferably used for this purpose. An advantage of the process of the invention is that, by means of the catalyst component A prepared according to the invention, polymers having a mean particle diameter of from 50 to 200 //m can be prepared and that this mean particle diameter can be set by the catalyst particle r diameter and by the catalyst productivity Furthermore, ultrahigh molecular weight polyethylene having a viscosity number greater than 2000 cm3/g can be prepared. The following examples illustrate the invention. Definitions: CA Catalyst productivity [kg PE/mmol Ti] CTYred Reduced catalyst-time yield [kg PE/mmolTi-h-bar] d50 Mean particle size [um] BD Polymer bulk density [g/dm3] (measured in accordance with DIN 53 468) VN Viscosity number [cm3/g] (measured in accordance with DIN 53 728) Dm Mass average diameter Dn Number average diameter For the experiments, a petroleum fraction having a boiling range from 90 to 120°C was used. The mean particle size and the particle size distribution of the catalyst and polymer particles were determined by Malvern laser light scattering. The ratio Dm/Dn was determined in accordance with NF X 11-630 of June 1981: Example 1 a) Preparation of the catalyst component A 0.15 mol of tetrachloromethane in 50 cm3 of the petroleum fraction was added dropwise under inert conditions at 65°C over a period of one hour to a solution of 0.15 mol of n-butyl-n-octylmagnesium (BOMAG-A from WITCO; 20 % strength in heptane) in 100 cm3 of viscous paraffin (dynamic viscosity from 110 to 230 mPa-s). The stirring speed was 600 rpm. A brown, finely dispersed solid was formed. The mixture was stirred for a further half an hour at 85°C and the suspension A., was obtained. Subsequently, 0.05 mol of diisobutyl phthalate, dissolved in 20 cm3 of the petroleum fraction, was added dropwise as electron donor to the suspension A, and the mixture was stirred for half an hour at 80°C. This gave the suspension A2. Titanium tetrachloride (0.02 mol), dissolved in 50 cm3 of the petroleum fraction, was added dropwise over a period of one hour at a reaction temperature of 85°C to suspension A2 (suspension A3). The dark brown suspension was stirred for a further 2 hours at 80°C and then cooled to room temperature. While stirring, 0.020 mol of ethylaluminum sesquichloride, dissolved in 30 cm3 of the petroleum fraction, was metered in. The suspension was stirred for 1 hour at 70°C and subsequently washe'd 3 times with 0.5 dm3 of the petroleum fraction. The titanium content of the catalyst suspension was 41.5 mmol/dm3. The titanium/magnesium ratio was determined as 0.13. The catalyst particles had, according to measurements by optical microscopy, a mean diameter of 9.5 um. The quotient Dm/Dn was 1.16. b) Polymerization The polymerization of ethyJene was carried our in a 1.5 dm3 laboratory autoclave in 800 cm3 of the petroleum fraction at a stirrer speed of 750 rpm isobarically at an ethylene partial pressure of 4 bar over a period of 2 hours. The polymerization temperature was 80°C. 1.5 mmol of triisobutylalumrnum were used as cocatalyst. The suspension of the catalyst component A was diluted to a concentration of 1 mmol of Ti/dm3. 3 cm3 of this diluted suspension were used for the polymerization. The reaction was ended by venting and cooling and the polymer was separated off from the dispersion medium by filtration and drying. This gave 152 g of ethylene corresponding to a CA of 51 kg PE/mmol Ti and a CTYred of 6.3 kg PE/mmol Ti-h-bar. The VN was 2900 cm3/g, the product had a bulk density of 370 g/dm3 and a d50 value of 182 um. The quotient Dm/Dn was 1.16. Example 2 a) Preparation of the catalyst component A 0.3 mol of tetrachloromethane in 50 cm3 of the petroleum fraction was added dropwise under inert conditions at 65°C over a period of one hour to a solution of 0.3 mol of a 0.6 molar solution of n-Bu2Mg in octane, prepared by a Grignard reaction of n-BuCI and magnesium powder with subsequent separation of the solid. The stirring speed was 600 rpm. A brown, finely dispersed solid was formed. The mixture was stirred for a further half an hour at 85°C and the suspension A1 was obtained. Subsequently, 0.10 mol of n-butanol, dissolved in 20 cm3 of the petroleum fraction, was added dropwise as electron donor to the suspension A1 and the mixture was stirred for half an hour at 80°C. This gave the suspension A2. Titanium tetrachloride (0.05 mol), dissolved in 50 cm3 of the petroleum fraction, was added dropwise over a period of one hour at a reaction temperature of 85°C to suspension A2 (suspension A3). The dark brown suspension was stirred for a further 2 hours at 90°C and then cooled to room temperature. While stirring, 0.050 mol of triethylaluminum, dissolved in 30 cm3 of the petroleum fraction, was metered in. The suspension was stirred for 1 hour at 70°C and subsequently washed 3 times with 0.5 dm3 of the petroleum fraction. The titanium content of the catalyst suspension was 48.5 mmol/dm3. The catalyst particles had, according to measurements by optical microscopy, a mean diameter of 8.9 um. b) Polymerization The polymerization was carried out as in Example 1. This gave 197 g of polyethylene corresponding to a CA of 66 kg PE/mmol Ti and a CTYred of 8.2 kg PE/mmol Ti-hbar. The VN was 2700 cm3/g, the product had a bulk density of 360 g/dm3 and a d50 value of 184 um. The quotient Dm/Dn was 1.15. Example 3 a) Preparation of the catalyst component A The catalyst component A was prepared by a method similar to Example 2. b) Polymerization The polymerization was carried out as in Example 2. In place of triisobutylaluminum, 2 mmol of isoprenylaluminum were used as cocatalyst. This gave 143 g of polyethylene corresponding to a CA of 48 kg PE/mmol Ti and a CTYred of 6.0 kg PE/mmol Ti-h-bar. The VN was 3100 cm3/g, the product had a bulk density of 365 g/dm3 and a d50 value of 165 um. The quotient Dm/Dn was 1.18. Example 4 The preparation of the catalyst component A and also the polymerization were carried out by a method similar to Example 1, with the exception that the polymerization temperature was 70°C. This gave 108 g of polyethylene corresponding to a CA of 36 kg PE/mmol Ti and a CTYred of 4.5 kg PE/mmol Ti-h-bar. The VN was 3300 cm3/g, the product had a bulk density of 360 g/dm3 and a d50 value of 162 pm. The quotient Dm/Dn was 1.16. Example 5 a) Preparation of the catalyst component A The preparation of the catalyst component A was carried out by a method similar to Example 2. The titanium content of the catalyst suspension was 48.5 mmol/dm3. The catalyst panicles had, according to measurements by optical microscopy, a mean diameter of 9.0 um b) Polymerization The polymerization was carried out in a 150 dm3 reactor in 100 dm3 of the petroleum fraction using 7.0 cm3 of the abovementioned catalyst component A, corresponding to 0.34 mmol of titanium, and 0.05 mol of triisobutylaluminum as cocatalyst. The amount of ethylene introduced was 6.0 kg/h. The polymerization temperature was 80°C and the polymerization time was 4 hours. The reaction was ended by venting and cooling and the polymer was separated off from the dispersion medium by filtration and drying. This gave 23.8 kg of polyethylene corresponding to a CA of 70 kg PE/mmol Ti and a CTYred of 5.3 kg PE/mmol Ti-h-bar. The VN was 3250 cm3/g, the product had a bulk density of 405 g/dm3 and a d50 value of 191 um. The quotient Dm/Dn was 1.13. Example 6 a) Preparation of the catalyst component A The catalyst component A was prepared by a method similar to Example 3. b) Gas-phase polymerization of ethylene A gas-phase polymerization of ethylene was carried out in a 2 dm3 steel autoclave having polished walls. The fiuidized bed was produced mechanically by means of a double-helix stirrer going around the wall with an initial charge of 10 g of polyethylene powder as seed bed. First the cocatalyst (2 mmol of triisobutylaluminum in 2 cm3 of isopentane) and then 2 cm3 of the catalyst suspension (0.01 mmol of Ti) were metered into the autoclave via a pressure burette. After repeated pressurization with argon and evacuation to remove the suspension medium, the polymerization was carried out at an ethylene partial pressure of 8 bar at a temperature of 80°C over a period of 2 hours and was ended by venting the autoclave. This gave 207 g of polyethylene corresponding to a CA of 20.7 kg PE/mmol Ti and a CTYred of 1.3 kg PE/mmol Ti-h-bar. The VN was 3050 cm3/g, the product had a bulk density of 375 g/dm3 and a d50 value of 128 um. This application has been divided out of Indian patent application no.461/MAS/95 which relates to "A process for preparing a catalyst composition for the polymerization of ethylene and/or 1-olefins". Claim 1 of the above patent application reads as: "A process for preparing a catalyst composition for the polymerization of ethylene and/or 1-olefins for producing high molecular weight ethylene polymers having a molecular weight Mw equal or greater than 1.106 g/mol either in suspension or in the gas phase comprising reacting in a first reaction step (a) a magnesium compound of the formula I wherein R1 and R2 are identical or different, and are each aC1- C20 alkyt radical, a C5 - C20, cyclo alkyl radical, a C6 - Q>o aflcenyl radical with a halogenating agent of the formula II X„.- C-R3 01) where X is a halogen atom, n is 3 and R3 is a hydrogen atom, a Ct - C20 alkyl radical, a C5 - C20 cyclo alkyl radical, a C6 - C2o aryl radical, or a C^to C2o aflcenyl radical to produce a catalyst support consisting of a compound of the formula III X-Mg-X (m) where X is a halogen atom, reacting said catalyst support in a second reaction step (b) with a hydrocarbon soluble titanium compound of the formula IV R4m Ti-R54-m (IV) where R4 and R5 are identical and are each a halogen atom, a Ct to C6 alkoxy group, or Ci - C3o carbony radical, and m is a number from 0 to 4, in an inert hydrocarbon medium at a temperature from 0 to 100°C in a molar ratio of Ti:Mg of from 0.01 to 1; a known electron donor in an amount of from 0.01 to I mol per mol of said Magnesium compound of formula III being present in one of the reaction steps (a) or (b), reducing the dissolved titanium compound of formula IV with an aluminum alkyl to precipitate the same, on said catalyst support, said precipitate having a particle size of WE CLAIM: I. A process for producing ultra high molecular weight polymers having a molecular weight Mw equal or greater than 1.106 g/mol by polymerising ethylene and/or 1 - olefins either in suspension or in the gas phase comprising the steps of polymerising the same under known polymerization conditions in the presence of a mixed catalyst system consisting of component A and an organoaluminum compound such as herein described wherein said component A is prepared by reacting in a first reaction step (a) a magnesium compound of the formula I wherein R1 and R2 are identical or different, and are each a C1_ C20 alkyl radical, cycloalkyl radical, a C6-C20 - alkenyl radical with a halogenating agent of the formula II where X is a halogen atom, n is 3 and R3 is a hydrogen atom, aC1 - C20 alkyl radical, a C5 - C20 cyclo alkyl radical, a C6 - C20 aryl radical, or a C2 -C20 alkenyl radical to produce a catalyst support consisting predominantly of a compound of the formula III x-Mg-x (ni) where X is a halogen atom, reacting said catalyst support in a second reaction step (b) with a hydrocarbon soluble titanium compound of the formula IV RVTi-R54.m (IV) where R4 and Rs are identical and are each a halogen atom, a Ci - C6 alfcoxy group, or Ci - C20 carbony radical, and m is a number from 0 to 4, in an inert hydrocarbon medium at a temperature from 0 to 100°C in a molar ratio of Ti:Mg of from 0.01 to 1; a known electron donor in an amount of from 0.01 to 1 mot per mot of said Magnesium compound of formula III being present in one of the reaction steps (a) or (b), reducing the dissolved titanium compound of formula IV with a known aluminum alkyl to precipitate the same on said catalyst support, said precipitate having a particle size of 2. The process as claimed in claim 1, wherein said ultra high molecular weight polymer obtained has a mean particle size in the range of from 100 to 200 um. 3. The process as claimed in claim 1 and 2 wherein said ultra molecular weight olefin polymer has a viscosity number of > 2000 cm3/g. 4. A process for producing ultra high molecular weight polymers having a molecular weight Mw equal or greater than 1.106 g/mol substantially as herein described.

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