GB1595992A - Process for the production of powdered polyethylenes - Google Patents

Description

(54) A PROCESS FOR THE PRODUCTION OF POWDERED POLYETHYLENES (71) We, VEBA-CHEMIE Aktiengesellschaft, a German Body Corporate, of Pawikerstrafe 30, 4660 Gelsenkirchen-Buer. Germany, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The process relates to the production of a powdered ethylene polymer by the polymerisation of ethylene or the copolymerisation thereof with other 1-olefins using the ZIEGLER process. The polyolefin powder produced according to the process of the invention is especially suitable for processing into mouldings using conventional machines for plastics processing such as extruders or injection moulding machines.

It is known that ethylene and 1-olefins can be polymerised with ZIEGLER catalysts consisting of compounds of the transition metals of the IVth to VIth sub-groups of the Periodic Table and aluminium-organic compounds to form high-molecular products. It is also known that for the production of high-molecular of high-molecular polyethylenes by the polymerisation of ethylene it is possible to use mixed catalysts consisting of aluminium-organic compounds and compounds of the metals titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, thorium and uranium, the heavy metal compounds formed by reduction from the catalyst mixtures being separated from the other reaction products and the separated compounds, if necessary after further purification, can be used in any combination with organometallic compounds of aluminium for the polymerisation of ethylene. It is also known that catalysts consisting of vanadium compounds - such as for example vanadium oxytrichloride, vanadium tetrachloride, vanadium trichloride, vanadium dichloride or vanadate esters - and aluminium-organic compounds only possess a short working life and display low productivity. As further disadvantages of these catalysts one may mention the formation of wall coatings and lumps in the reactor during the polymerisation and also a quality of the polymerisate powder which is completely inadequate for processing to form mouldings without prior granulation.

The latter disadvantages may be caused as a result of the fact that during the moulding of the catalyst by known processes to some extent soluble complexes are formed from vanadium and aluminium alkyl compounds.

In known methods polyolefins are processed to form mouldings such as hollow bodies, tubes, plates or foils quite predominantly in the form of granulates. For this purpose the powdered polyolefins produced by the ZIEGLER process are melted in double screw extruders, plasticised, homogenised with the usual packing media and granulated according to known processes. There has been no lack of attempts to avoid this cumbersome and costly stage in the process: nevertheless it has not been possible to achieve any satisfactory results. The cause of this is to be found in the fact that the powdered polyolefins as compared with the granulate usually possess considerably lower bulk densities, considerably greater specific surface areas of the powder grains and frequently also dust fractions.

These undesirable properties of the powders are the cause of the known disadvantages during their processing. As a consequence of the low bulk densities and the moderate to poor pouring capacity of the powders one obtains during the extrusion as compared with the granulate a reduction in the output, which can amount to 50% and over. The strongly fissured surface of the powder grains causes during the melting the inclusion of air bubbles in the melt. This leads to faulty or even unusable finished parts. A melt containing bubbles can also result from moisture, which can be taken up by the powder because of its high specific surface area considerably more in quantity than with the granulates. The dust fraction in powders leads to difficulties during pneumatic conveyance. Thus it may for example be necessary instead of air to use an inert gas such as nitrogen in order to exclude the risk of dust explosions caused by electrostatic charge.

As compared with this, it has now surprisingly been found that it is possible to produce powdered polyolefins which possess valuable technical properties by using catalysts consisting of vanadium compounds and aluminium-organic compounds which have a high productivity and a long working life.

The Invention therefore relates to a process for the production of powdered polyolefins with high bulk densities, good pouring capacity, mean grain diameters of up to 1000 ,um and practically without any extremely fine grains as a result of the polymerisation of ethylene, possibly mixed with other 1-olefins and also in the presence of hydrogen, in inert liquid hydrocarbons at temperatures between 50"C and 95"C and at pressures of 10 to 100 bar, preferably 20 to 60 bar, using discontinuous or continuous processes by means of ZIEGLER catalysts, produced in inert liquid hydrocarbons by reacting vanadyl (V) compounds containing chlorine and alkoxy with aluminium-organic compounds, separating the insoluble reaction product and activating it with any aluminium-organic compounds, which is characterised by the fact that 1. as vanadyl (V) compound one uses a reaction product of vanadyl (V) chloride and a vanadyl (V) alcoholate in molar proportions of 1: 2 to 2 : 1 or directly the reaction product of vanadyl (V) chloride with an alcohol, preferably ethyl alcohol, propyl (1) alcohol, butyl (1) alcohol in molar proportions of 1 : 2 to 1 : 1 and 2. one uses as aluminium-organic compounds for the reduction ethyl aluminium dichloride and/or diethyl aluminium chloride or isobutyl aluminium dichloride and/or diisobutyl aluminium chloride in molar proportions of aluminium to vanadium compound of 1 : 1 to 3 : 1, 3. the reaction of the vanadium compounds with the aluminium-organic compounds being carried out whilst stirring with specific stirring capacities of 0.1 to 20,000 watt/m3, preferably 1 to 5,000 watt/m3 and 4. the activation is carried out with aluminium alkyl compounds of the formula AIR3, in which R signifies hydrocarbon radicals with 2 to 8 carbon atoms, or with alkyl aluminium sesquichloride and/or alkyl aluminium dichloride, especially ethyl alumi nium sesquichloride and/or ethyl aluminium dichloride.

As vanadyl (V) alcoholates one can use both those with straight-chained alkyl radicals and those with branched alkyl radicals. Alcoholates with 2 to 4 carbon atoms per alkyl radical, such as are usual on the market, are preferred. The reaction of the vanadyl (V) chloride with the vanadyl (V) alcoholate is generally carried out in an inert liquid hydrocarbon at room temperature or even at elevated temperature.

In the same way it is also possible instead of the reaction product of vanadyl (V) chloride and vanadyl (V) alcoholate to use directly the reaction product of vanadyl (V) chloride with an alcohol, preferably ethyl alcohol, propanol-(1) or butanol-(1) in molar ratios of vanadyl (V) chloride to alcohol of 1 : 2 to 1 1, preferably 1: 1.5 in a hydrocarbon.

In the production of the catalyst according to the invention both the molar- ratio of vanadyl-(V) chloride to vanadyl (V) alcoholate and also the molar ratio of aluminium to vanadium compound are critical. If one maintains the molar ratios according to the invention the formation of soluble aluminium vanadium complexes is avoided and surprisingly a catalyst is produced with such a compact uniform granulation as makes possible the production according to the invention of powdered polyolefins with outstanding properties. It is desirable to adjust a coarse powder granule with at the same time a high bulk density of the powder. The mean particle size of the polymerisate powder depends upon the mean particle size of the catalyst granule. According to the process of the invention the latter can be controlled by the agitation power during the reaction of the vanadium compound with the aluminium-organic compound. Higher specific agitation powers lead to a finer catalyst grain than lower powers and therefore under the same polymerisation conditions to a smaller mean particle diameter of the polymerisates.

It was completely surprising and in no way foreseeable that the use of the process according to the invention in the production of the catalyst would make possible such a technical advance as it has been possible to achieve with regard to the production of powdered polyolefins. The use of the new catalysts according to the process of the Invention is carried out in a known manner under the conditions which are usual for ZIEGLER's low-pressure polymerisation, such as have- already been given above. Because of the high productivity of the catalysts according to the invention measures for the removal of the catalysts from the polymerisates are not necessary.

When one uses the direct reaction product of vanadyl (V) chloride and alcohols one also has the special advantage that one can dispense with the cumbersome production of chlorine-free vanadyl (V) alcoholates and instead of a reaction product of vanadyl (V) alcoholate with vanadyl (V) chloride can use a reaction mixture containing chlorine which can be obtained in a simple way from vanadyl (V) chloride and an alcohol. The reaction of the vanadyl (V) chloride with the alcohol is advantageously carried out in an inert liquid hydrocarbon at room temperature or at elevated temperature, more or less hydrogen chloride being given off according to the reaction conditions. Thus, for example, when using a liquid inert hydrocarbon with a boiling range from about 60 to 80"C when heating for several hours under a reflux the hydrogen chloride liberated during the reaction of the vanadyl (V) chloride with the alcohol is almost quantitatively driven off. However for the process according to the Invention the proportion of hydrogen chloride remaining in the reaction mixture is not of great importance. As alcohols one can generally use monohydric alcohols with straight-chained or branched alkyl radicals. The best results with regard to as high as possible a catalyst activity are achieved with primary monohydric straight-chined alcohols. As regards high bulk densities, freedom from dust and good pouring capacity of the polymerisate powder one obtains particularly good results when one uses ethanol, propanol-(1) and butanol-(1). If the number of carbon atoms in the alcohols is more than 4, one obtains with increasing chain length increasingly finer powders which are less desirable for processing to form plastic parts.

The catalyst component containing vanadium produced according to the Invention and insoluble in liquid hydrocarbons can be activated both with halogen-free aluminium-organic compounds and also with those containing halogen. In all cases one obtains during the polymerisation of ethylene under the conditions stated above polymerisate powders of outstanding quality in regard to pouring capacity, bulk density and freedom from dust.

When one uses halogen-free aluminium-organic compounds such as trialkyl aluminium for the activation of the catalyst component containing vanadium according to the Invention one obtains polymerisate with a wide distribution of molecular weight, which are particularly suitable especially for processing according to the extrusion process to form foils, plates, hollow bodies, tubes and sections. When one uses aluminium-organic compounds containing halogen, such as ethyl aluminium sesquichloride and/or ethyl aluminium dichloride, one obtains on the other hand polymerisates with a narrow molecular weight distribution such as are particularly advantageous for the production of injection moulded articles.

As is known, injection moulded articles from low-pressure polyethylene with a narrow molecular weight distribution of the polymer display a number of advantages as compared with those polymers with a wide molecular weight distribution, such as for example a lower tendency to distort, a high loading capacity when stacked and good suitability for use even at very low temperatures.

For the activation it is possible to use both ethyl aluminium dichloride and/or diethyl aluminiumchloride as well as isobutyl aluminium dichloride and/or diisobutyl aluminium chloride.

Isobutyl aluminium dichloride is characterised as compared with the corresponding ethyl aluminium compound in the technical execution of the process according to the Invention in that it shows a lower melting or solidification point and a better solubility in liquid hydrocarbons at low temperatures. Isobutyl aluminium dichloride has a melting point of -30"C, whilst ethyl aluminium dichloride already solidifies at +32"C (Ullmans Encyklop - die der technischen Chemise, 4th Edition, Vol. 7, page 344, Verlag Chemie GmbH, 1973).

Unlike the case of ethyl aluminium dichloride, therefore, a heating of the storage tanks and pipes is not necessary.

The powdered polyethylenes or copolymerisates of ethylene and propylene and/or butylene-(1) or other olefins which are copolymerisable with ZIEGLER catalysts when produced by the process according to the Invention are suitable according to their molecular weight adjustment and the composition of the catalyst according to the Invention used in their production for use in injection moulding or extrusion. The powders produced according to the Invention have high bulk densities of about 0.420 to 0.550 g/ml (DIN 53 468) and are practically free from very fine grain sections which give rise to dust. They have an outstanding pouring capacity. The pouring speeds according to DIN Draft 53 492 when using an outlet aperture with a diameter of 10 mm are 6 to 10 mm3 per second. With the powders produced according to the Invention it is possible when processing them as plastics to achieve greater throughput or extrusion yields, the greater the mean particle diameter, as is shown in the following table. The determination of the mean particle size d' is carried out from the RRSB distribution function (DIN 66 145). d' is therefore defined in such a way that 36.8 per cent by weight of the powder has a greater particle size diameter than d'.

Mean particle size d' Throughput in the processing to form 10-litre hollow bodies kg/hr 480 87.0 680 98.5 820 103.0 Naturally the figures given in the table for the throughput or extrusion performances are comparative figures determined under the same conditions, and whose absolute values and possibly also their relationships are dependent to a large extent on the processing machines.

The polyolefin powders produced according to the Invention can be processed according to their molecular weight distribution without trouble into mouldings, such as injection moulded articles or extruded articles, such as for example tubes, plates, sections, hollow bodies and foils. As a result of the compact granular structure, the melt is practically free from bubbles. Preferably the coarser of the powders according to the Invention are used, because they are the most similar to the granulate in their total behaviour during plastic processing.

The process according to the present Invention is illustrated by the following Examples: Example 1: a) Production of catalyst 122.3 g (705.7 m moles) of vanadyl (V) chloride and 172.3 g (705.7 m moles) of vanadyl (V) n-propylate were heated together in 1.7 litres of a hexane cut 63/80"C under nitrogen for 2 hours at 55"C. After cooling the mixture a solution of 340.3 g (2,822.6 m moles) of diethyl aluminium chloride in 1.43 litres of the hexane cut 63/80"C were added at 20 to 250C over a period of 2 hours, with a blade stirrer and a specific stirring performance of 126 watts/m3. The suspension obtained was then stirred for a further 2 hours at 550C with the same specific stirring performance. After cooling, the solid was separated and was washed 5 times, each time with 5 litres of the hexane cut.

b) Polymerisation of ethylene In a 2-litre steel autoclave there were placed under nitrogen 1 litre of a hexane cut 63/80"C and 0.4 g of triisobutyl aluminium. To this there were added 30 mg of the catalyst produced according to Example la, suspended in a few ml of the hexane cut.

After the displacement of the nitrogen by ethylene, 6.3 bar of hydrogen were forced in and then ethylene up to a total pressure of 31.4 bar. At the same time the reactor content was heated to 75"C. The polymerisation was carried out for 1 hour whilst stirring with a stirrer speed of 1000 r.p.m. at 75"C, the total pressure being maintained by forcing in additional ethylene. Then the pressure of the reactor was released. and after cooling the reactor contents the polyethylene formed was filtered off and dried.

The yield of polyethylene amounted to 356 g, corresponding to 11.9 kg per g of catalyst. The particle size d' was 610 Fm, the bulk density according to DIN 53 468 was 0.460 g/ml, the trickling time according to DIN Draft 53 492 for an outlet aperture with a diameter of 10 mm was 16.6 seconds, corresponding to a trickling speed VR to of 9.41 cm3/sec.

Example 2: a) Production of catalyst The procedure was carried out as in Example la, but instead of the diethyl aluminium chloride solution one used as a solution of 535.7 g (4.220 moles) of ethyl aluminium dichloride in 2.27 litres of the hexane cut 63/800C for reaction with a mixture of 182.8g (1.055 moles) of vanadyl (V) chloride and 257.6 g (1.055 moles) of vanadyl (V) n-propylate in 1.77 litres of the hexane cut.

b) Polymerisation of ethylene The procedure was as in Example lb, except that one used 20 mg of the catalyst produced according to 2a instead of the catalyst produced according to la. The yield of polyethylene was 221 g, corresponding to 11.1 kg per g of catalyst. The particle size d' was 480 llm, the bulk density according to DIN 53 468 was 0.430 g/ml, the trickling time according to DIN Draft 53 492 for an outlet aperture with a diameter of 10 mm was 19.4 seconds, corresponding to a pouring speed VR 10 of 8.05 cm3/sec.

Comparative Example 1: a) Production of catalyst In the manner described in Example la a mixture of 274.3 g (1.583 moles) of vanadyl (V) chloride and 128.9 g (0.528 moles) of vanadyl (V) n-propylate (molar proportion of chloride to alkoxide = 3 1) in 1.84 litres of the hexane cut 63/800C was reacted with 535.7 g (4.220 moles) of ethyl aluminium dichloride in 2.25 litres of the hexane cut.

b) Polymerisation of ethylene With 15 mg of this catalyst an ethylene polymerisation was carried out as described in Example lb. The yield of polyethylene amounted to 173 g, corresponding to 11.5 kg per g of catalyst. The particle size d' only amounted to 140 llm, the bulk density according to DIN 53 468 only amounted to 0.200 g/ml, the trickling time according to DIN Draft 53 492 for an outlet aperture with a diameter of 10 mm was 106.6 seconds, corresponding to a pouring speed Van 10 of 1.47 cm3/sec.

Comparative Example 2: a) Production of catalyst 8.67 g (50 m moles) of vanadyl (V) chloride and 12.21 g (50 m moles) of vanadyl (V) n-propylate were heated together in 85 ml of a hexane cut 63/80"C under nitrogen for 2 hours under a reflux. After cooling the mixture, there was added at 250C a solution of 76.17 g (600 m moles) of ethyl aluminium dichloride (molar ratio Al/V compounds = 6 : 1) in 352 ml of the hexane cut 63/80"C in the course of 2 hours whilst stirring with a specific stirring performance of 400 watt/m3. The suspension obtained was then heated for a further 2 hours under reflux and while doing this it was stirred with the same specific stirring performance, when the precipitate which first resulted dissolved again.

b) Polymerisation of ethylene With 5 ml of this catalyst solution (containing 1 m mole of V compound) and 2 g of triisobutyl aluminium an ethylene polymerisation was carried out as described in Example lb. The yield of polyethylene was 41 g. There occurred very marked incrustations of polymerisate on the wall of the autoclave and on the stirrer. The polymerisate had no granular structure and had caked together into lumps. The bulk density according to DIN 53 468 was only 0.110 g/ml.

Example 3: a) Production of catalyst 8.67 g (50 m moles) of vanadyl (V) chloride and 14.32 g (50 m moles) of vanadyl (V) isobutvlate were heated together in 85 ml of a hexane cut 63/80"C under nitrogen for 2 hours under a reflux. After cooling the mixture, there was added at 250C a solution of 25.4 g (200 m moles) of ethyl aluminium dichloride in 180 ml of hexane cut 63/800C over a period of 2 hours whilst stirring with a blade stirrer and a specific stirring performance of 400 watt/m3. The suspension obtained was then heated for a further 2 hours under a reflux and the stirring was carried out at the same specific stirring performance. After cooling, the solid was separated and was washed 5 times, each time with 500 ml of the hexane cut.

b) Polymerisation of ethylene With 10 mg of this catalyst an ethylene polymerisation was carried out as described in Example ib, but with a hydrogen partial pressure of 1.6 bar. The yield of polyethylene was 184 g, corresponding to 18.4 kg per g of catalyst. The particle size d' was 460 ijm, the bulk density according to DIN 53 468 was 0.475 g/ml, the trickling time according to DIN Draft 53 492 for a outlet aperture with a diameter of 10 mm was 19.8 seconds, corresponding to a pouring speed VR I() of 7.89 cm3/sec.

Example 4: In a 750-litre stirrer reactor the vanadium catalyst described in Example la was used for the continuous polymerisation of ethylene. The polymerisation was carried out in suspension; as suspension medium one used a hexane cut in the boiling range between 63"C and 80"C. The quantity filled into the polymerisation reactor was 300 litres, the mean residence time chosen for the catalyst in the reactor was 4 hours. The maintenance of the level was carried out via a Co-60 radiation barrier, connected with a double ball cock section.

The polymerisation was carried out at a temperature of 75"C. The ethylene partial pressure in the gas chamber of the reactor amounted to 31.8 bar. For controlling the molecular weight, hydrogen was used; the hydrogen partial pressure in the gas chamber of the reactor was 3.2 bar. As co-catalyst one used triisobutyl aluminium. The catalyst and co-catalyst were diluted in hexane 63/80"C in a stirrer contained and fed continuously to the reactor with a membrane pump. The concentration of the catalyst in the polymerisation vessel was 9.33 mg/litre of suspension medium and that of the co-catalyst was 100 mg/litre of suspension medium. The rotation speed of the stirrer in the polymerisation reactor was set at 150 r.p.m. The powdered polymerisate resulting in the reactor was separated from the suspension medium in a centrifuge and dried in a partially evacuated container at about 80"C. Under these experimental conditions a polymerisate was obtained with the catalyst described in Example la) which possessed the following properties: Melt index MFI 190/5 according to DIN 53 735 29 g/10 min.

Relative viscosity change I on basis of concentration according to DIN 53 728 150 cm3/g Mean molecular weight 55,000 Density at 23"C according to DIN 53 479 0.969 g/cm3 Total ash 60 ppm Ash analysis 26 ppm Al203 17 ppm V2Os 10 ppm chlorine In this mode of operation the calculated catalyst consumption was 57.7 mg vanadium catalyst/kg polyethylene and 620 mg triisobutyl aluminium/kg polyethylene. The polymeri sate powder produced in this way had an extraordinarily high bulk density according to DIN 53 468 of 0.550 g/ml. The mean particle size d' was 750 ijm; the powder during the determination of the pouring capacity according to DIN Draft 53 492 had an outlet time tR !( of only 15.6 seconds. This corresponds to a pouring speed VR 10 of 10.02 cm3/sec.

Example 5: The catalyst described in Example la was used in the same apparatus for the continuous polymerisation of ethylene mixed with propylene. The addition of 10 per cent by weight of propylene, reckoned on the quantity of ethylene offered per hour, brought about as compared with homopolymerisation a distinct lowering of the mean molecular weight. As a result of this it was possible to adjust the mean molecular weight as desired with a hydrogen partial pressure of only 1.2 bar in the gas chamber of the reactor. The ethylene partial pressure was 33.8 bar. The mean residence time of the catalyst in the reactor was 2 hours.

The catalyst concentration was adjusted at 2.7 mg vanadium catalyst/litre suspension medium and 100 mg triisobutyl aluminium per litre. With this mode of operation a polymerisate was obtained with the following properties: Melt index MFI 190/5 according to DIN 53 735 31 g/10 min.

Relative viscosity change I on basis of concentration according to DIN 53 728 150 cm3/g Mean molecular weight 55,000 Density at 230C according to DIN 53 479 0.953 g/cm3 Total ash 50 ppm Ash analysis 22 ppm Al2O3 10 ppm V2O5 10 ppm chlorine The calculated catalyst consumption was 29.8 mg vanadium catalyst per kg of polyethylene and 530 mg triisobutyl aluminium per kg of polyethylene. The bulk density according to DIN 53 468 of the polymerisate powder was 0.501 g/ml. The mean particle size d' was 570 Fm; the powder during the determination of the pouring capacity had an outlet time Rlo of 22.2 seconds, corresponding to a pouring speed VR 10 of 7.04 cm3/sec.

Example 6: With the catalyst described in Example 2a) ethylene was continuously polymerised in the apparatus already described. The hydrogen partial pressure in the gas chamber of the reactor was set at 2.5 bar; the ethylene partial pressure was 32.5 bar. The catalyst concentration in the polymerisation reactor was 4 mg vanadium catalyst/litre suspension medium and 100 mg triisobutyl aluminium/litre suspension medium. The mean residence time chose for the catalyst in the reactor was 2 hours. In this way one obtained polyethylene with the following properties: Melt index MFI 190/5 according to DIN 53 735 0.41 g/10 min.

Relative viscosity change I on basis of concentration according to DIN 53 728 400 cm32/g Mean molecular weight 178,000 Density at 23"C according to DIN 53 479 0.959 g/cm3 Total ash 40 ppm Ash analysis 22 ppm Al203 14 ppm V2O5 10 ppm chlorine The calculated catalyst consumption was 50.7 mg vanadium catalyst/kg polyethylene and 1,230 mg triisobutyl aluminium/kg polyethylene. The bulk density of the polymerisate powder was 0.485 g/ml. The mean particle size d' was 660 ,um; the polymerisate powder when determining the pouring capacity had an outlet time tR lo of 18.2 seconds, corresponding to a pouring speed VR 10 of 8.59 cm3/sec.

Example 7: In the semi-technical polymerisation apparatus of Example 4 the catalyst of Example 2a) was used for the polymerisation of ethylene mixed with propylene. The ethylene partial pressure in the gas chamber of the reactor was 34.1 bar; the hydrogen partial pressure was 0.9 bar; propylene was offered in relation to ethylene in the proportion by weight of 6 to 100. The catalyst concentration was 3.3 mg vanadium catalyst per litre of suspension medium. The mean residence time of the catalyst in the reactor was 2 hours. Under these experimental conditions polyethylene was obtained with the following properties: Melt index MFI 190/5 according to DIN 53 735 0.30 g/10 min.

Relative viscosity change I on basis of concentration according to DIN 53 728 410 cm3/g Mean molecular weight 183,000 Density at 200C according to DIN 53 479 0.949 g/cm3 Total ash 40 ppm Ash analysis 18 ppm Al203 11 ppm V2O5 10 ppm chlorine The calculated consumption of catalyst amounted in this Example to 37.4 mg vanadium catalyst per kg of polyethylene and 1,120 mg of triisobutyl aluminium per kg of polyethylene. The polymerisate powder had a bulk density of 0.475 g/ml, the mean particle size d' was 640 Fm. On the determination of the pouring capacity according to DIN Draft 53 492 an outlet time tor 10 of 18.9 seconds was measured. This corresponds to a pouring speed VR 10 of 8.27 cm/sec.

Example 8: In the same manner as described in Example 7 ethylene was polymerised in admixture with 6 per cent by weight of butene-1. The polymerisate so obtained had the following properties: Melt index MFI 190/5 according to DIN 53 735 0.40 g/10 min.

Relative viscosity change I on basis of concentration according to DIN 53 728 410 cm3/g Mean molecular weight 183,000 Density at 20"C according to DIN 53 479 0.950 g/cm3 Total ash 50 ppm 23 ppm Al203 12 ppm V205 10 ppm chlorine The calculated catalyst consumption was 33.8 mg vanadium catalyst per kg of polyethylene and 1,020 mg triisobutyl aluminium per kg of polyethylene. The powder had a bulk density of 0.482 g/ml, the mean particle size d' was 6601lem. The outlet time tR 1(1 of the powder when determining the pouring capacity was 18.2 secs., corresponding to a pouring speed VR 10 of 8.59 cm3/sec.

Example 9: a) Production of catalyst The procedure was carried out as described in Example 2a, but the stirring was carried out with a specific stirring performance of 3,400 watt/m3.

b) Copolymerisation of ethylene and butene-1 The catalyst described in Example 9a) was used in the semi-technical apparatus for the continuous polymerisation of ethylene mixed with 3 per cent by weight of butene-l.

The reactor temperature, mean residence time in the reactor and also the hydrogen and ethylene partial pressures were the same as those stated in Example 7. The concentration of the vanadium catalyst in the reaction vessel was 4 mg/litre; the concentration of triisobutyl aluminium was the same as in Example 7. The polymerisate prepared in this way had the following properties: Melt index MFI 190/5 according to DIN 53 735 0.50 g/10 min.

Relative viscosity change I on basis of concentration according to DIN 53 728 390 cm3/g Mean molecular weight 172,000 Density at 20"C according to DIN 53 479 0.956 g/cm3 Total ash 40 ppm Ash analysis 21 ppm Altos 11 ppm V2O5 10 ppm chlorine The calculated catalyst consumption was 49.5 mg of vanadium catalyst per kg of polyethylene and 1,230 mg of triisobutyl aluminium per kg of polyethylene. The polymerisate powder had a bulk density of 0.492 g/ml; the mean particle size d' was 430 clam.

When determining the pouring capacity an outlet time tR 10 of 24.7 seconds was measured.

This corresponds to a pouring speed VR 10 Of 6.33 cm3/sec.

Example 10: a) Catalyst production The procedure was the same as described in Example 2a), but one operated with a specific stirring performance of 5 watt/m3.

b) Copolymerisation of ethylene and butene-1 With the vanadium catalyst described in Example 10a) ethylene was continuously polymerised mixed with 3 per cent by weight of butene-1. The hydrogen partial pressure was 0.7 bar; the ethylene partial pressure in the gas chamber of the reactor was 34.3 bar. The vanadium catalyst was offered in a concentration of 2.7 mg/litre of suspension medium. The concentration of the co-catalyst triisobutyl aluminium was the same as in Example 7. A polymerisate prepared in this way had the following properties: Melt index MFI 190/5 according to DIN 53 735 0.35 g/10 min.

Relative viscosity change I on basis of concentration according to DIN 53 728 390 cm3/g Mean molecular weight 172,000 Density at 20"C according to DIN 53 479 0.952 g/cm3 Total ash 70 ppm Ash analysis 35 ppm Awl203 8 ppm V2O5 < 10 ppm chlorine The calculated catalyst consumption was 28.7 mg of vanadium catalyst per kg of polyethylene and 1,080 mg of triisobutyl aluminum per kg of polyethylene. The polymerisate powder had a bulk density of 0.423 g/ml; the mean particle size d' was 960 Fm.

When determining the pouring capacity according to DIN Draft 53 492 the outlet time tR 10 was 24.7 seconds; this corresponds to a pouring speed VR 10 of 6.33 cm3/sec.

Example 11: a) Production of the catalyst component containing vanadium 182.8 g (1.055 moles) of vanadyl (V) chloride and257.6 g (1.055 moles) of vanadyl (V) n-propylate were heated together in 1.77 litres of a hexane cut 63/800C under nitrogen for 2 hours at 55"C. After cooling the mixture, a solution of 535.7 g (4.220 moles) of ethyl aluminium dichloride in 2.27 litres of hexane cut 63/80"C were added over a period of 2 hours at 20 to 250C whilst stirring with a blade stirrer and a specific stirring performance of 126 watts/m3. The suspension obtained was then stirred for a further 2 hours at 55"C with the same specific stirring performance. After cooling, the solid was separated and was washed 5 times, on each occasion with 5 litres of the hexane cut.

b) Polymerisation of ethylene In a 2-litre steel autoclave there were placed under nitrogen 1 litre of a hexane cut 63/80"C, 254 mg (2 m moles) of ethyl aluminium dichloride and 15 mg of the catalyst component prepared according to Example lia and suspended in a few ml of the hexane cut. This mixture was stirred for 30 minutes at room temperature. Then, after the displacement of the nitrogen by ethylene, 1.6 bar of hydrogen was forced in and then ethylene was forced in up to a total pressure of 31.4 bar. At that same time the reactor contents were heated to 75"C. The polymerisation was carried out for 1 hour whilst stirring with a stirrer rotation speed of 1,000 r.p.m. at 750C, the total pressure being maintained by forcing in ethylene. Then the pressure in the reactor was released.

after the reactor content had been cooled the polyethylene formed was filtered off and dried. The yield of polyethylene was 292 g, corresponding to 19.5 kg per g of catalyst.

The mean particle size d' was 590 Fm, the bulk density according to DIN 53 468 was 0.445 g/ml, the pouring speed VRIO was 8.68 cm3/sec. (DIN Draft 53 492). The viscosity index according to DIN 53 728 was 400 cm3/g. The molecular non-uniformity (M/Mn1) was determined gel-chromatographically as being 4.6, and the proportion < Mw/S was found to be 25.4%.

Example 12: a) Production of the catalyst component containing vanadium 182.8 g (1.055 moles) of vanadyl (V) chloride and 257.6 g (1.055 moles) of vanadyl (V) n-propylate were stirred together in 1.66 litres of a hexane cut 63/800C for 1 hour at room temperature. This mixture and a solution of 535.7 g (4.22 moles) of ethyl aluminium dichloride in 2.30 litres of hexane cut 63/800C were fed synchronously over a period of 2 hours at 25"C to 2 litres of the hexane cut whilst stirring with a blade stirrer and a specific stirring performance of 1,000 watt/m3. The suspension obtained was then heated for a further 2 hours under a reflux and stirred with the same specific stirring performance. After cooling, the solid was separated and washed 5 times, each time with 5 litres of the hexane cut.

b) Polymerisation of ethylene The catalyst component containing vanadium described under 12a was used with ethyl aluminium sesquichloride in a 750-litre stirrer reactor for the continuous polymerisa tion of ethylene. The polymerisation was carried out in suspension; as suspension medium one used a hexane cut of the boiling range between 63"C and 80"C. The filling level in the polymerisation reactor was 300 litres, the mean residence time of the catalyst in the reactor was 2 hours. The maintenance of the level in the polymerisation reactor was carried out via a Co-60 radiation barrier, connected with a double ball cock section.

The polymerisation was carried out at a temperature of 75"C. The ethylene partial pressure in the gas chamber of the polymerisation reactor was 30.6 bar. For regulating the molecular weight of the polymerisate one used hydrogen; the hydrogen partial pressure in the gas chamber of the reactor was 4.4 bar. The catalyst component containing vanadium and ethyl aluminium sesquichloride were diluted in hexane 63/80"coin a stirrer vessel and after a mean residence time of 0.5 hours were continuously fed to the reactor with a membrane pump. The concentration of the catalyst component containing vanadium in the polymerisation vessel was 7.33 mg/litre of suspension medium and that of the ethyl aluminium sesquichloride was 100 mg/litre suspension medium. The rotation speed of the stirrer in the polymerisation reactor was set at 150 r.p.m. The powdered polymerisate resulting in the reactor was separated from the suspension medium in a centrifuge and dried in a partially evacuated vessel at about 80"C. Under these experimental conditions one obtained a polymerisate which possessed the following properties: Melt index MFI 190/5 according to DIN 53 735 1.7 g/10 mins.

Viscosity index I according to DIN 53 728 300 cm3/g Mean molecular weight 126.000 Density at 23"C according to DIN 53 479 0.959 g/cm3 Molecular non-uniformity U (U = Mw/Mn1) 4.3 Proportion of molecular weight < Mw/5 25.6% The consumption of catalyst component containing vanadium with this mode of operation amounted to 72.2 mg/kg polyethylene and that of ethyl aluminium sesquichloride amounted to 985 mg/kg polyethylene. The polymerisate powder produced in this way had a bulk density determined according to DIN 53 468 of 0.435 g/ml. The mean particle size d' was 300 llm; the powder had a pouring speed VR 10 = 7.2 cm3/sec. determined according to DIN Draft 53 492.

Example 13: a) Production of the catalyst component containing vanadium The process was carried out as described in Example 12a, but with a specific stirring performance of 126 watt/m3.

b) Polymerisation of ethylene In the polymerisation apparatus described in Example 12b a catalyst component containing vanadium produced according to 13a was used together with ethyl aluminium sesquichloride for the continuous polymerisation of ethylene.

In the gas chamber of the polymerisation reactor an ethylene partial pressure of 31 bar was adjusted; the hydrogen partial pressure there was 4 bar. The concentration of the catalyst component containing vanadium in the polymerisation reactor was 6.7 mg/litre suspension medium; the concentration of the ethyl aluminium sesquichloride was unchanged as compared with Example 12b. With this mode of operation one obtained a polymerisate with the following properties: Melt index MFI 190/5 according to DIN 53 735 2.8 g/10 min.

Viscosity index I according to DIN 53 728 240 cm3/g Mean molecular weight 97,000 Density at 230C according to DIN 53 479 0.960 g/cm3 Molecular non-uniformity U (U = M,/Mn1) 6.5 Proportion of molecular weight < Mw/S 30.4% Under the experimental conditions described, the consumption of catalyst component containing vanadium was 68.7 mg/kg polyethylene and that of ethyl aluminium sesquichloride was 1,030 mg/kg polyethylene. The polymerisate powder had a bulk density according to DIN 53 468 of 0.425 g/ml. The mean particle size d' was 560 llm; the polymerisate powder when determining the pouring capacity according to DIN Draft 53 492 had a pouring speed VR 10 of 8.4 cm3/sec.

Example 14: a) Production of the catalyst component containing vanadium The procedure was carried out as in Example Ila, but instead of the ethyl aluminium dichloride solution one used a solution of 340.3 g 2,822.6 m moles) of diethyl aluminium chloride in 1.43 litres of the hexane cut 63/800C for reaction with a mixture of 122.3 g (705.7 m moles) of vanadyl (V) chloride and 172.3 g (705.7 m moles) of vanadyl (V) n-propylate in 1.7 litres of the hexane cut 63/80"C.

b) Polymerisation of ethylene The catalyst component containing vanadium described under 14a was used in the apparatus described in Example 12b for the continuous polymerisation of ethylene.

With a filling level in the polymerisation reactor of 300 litres, a mean residence time of the catalyst in the reactor was selcted as 4 hours. The catalyst component containing vanadium was. as described in Example 12b, diluted in a stirrer vessel in hexane 63/80"C, before it was fed into the reaction vessel; the concentration in the polymerisation reactor was 16 mg/litre suspension medium. Ethyl aluminium sesquich chloride was pumped out of a storage vessel direct into the polymerisation reactor, where a concentration of 100 mg/litre suspension medium was maintained.

The ethylene partial pressure in the gas chamber of the reactor was 32.7 bar. For regulating the molecular weight one forced hydrogen into the gas chamber of the reactor up to a partial pressure of 2.3 bar. With the mode of operation described here a polymerisate was obtained with the following properties: Melt index MFI 190/5 according to DIN 53 735 1.9 g/10 min.

Viscosity index I according to DIN 53 728 250 cm3/g Mean molecular weight 102,000 Density at 23"C according to DIN 53 479 0.95.6 g/cm3 Molecular non-uniformity U (U = M,/M,-1) 5.4 proportion of molecular weight < Mw/5 25.8% The consumption of catalyst component containing vanadium was 97.4 mg/kg polyethylene and that of ethyl aluminium sesquichloride was 620 mg/kg polyethylene. The bulk density of the polymerisate was 0.440 g/ml. The powder had a mean particle size d' = 790 Fm and when determining the pouring capacity it had a pouring speed VR I() of 8.2 cm3/sec.

Example 15: With 10 mg of the catalyst component produced according to Example lia an ethylene polymerisation was carried out as described in Example lib, but with the addition of 310 mg (2 m moles) of isobutyl aluminium dichloride instead of ethyl aluminium dichloride and doing away with the previous reaction of 30 minutes between the catalyst component containing vanadium and the aluminium-organic compound. The yield of polyethylene was 164 g, corresponding to 16.4 kg per g of catalyst. The molecular non-uniformitv was determined gel-chromatographically as being 4.6 and the proportion < Mw/5 as being 26.7%.

Example 16: a) Production of catalyst 346.6 g (2 moles) of vanadyl (V) chloride and 180.3 g (3 moles) of propanol-(1) were heated together in 1.59 litres of a hexane cut 63/800C for 2 hours under a reflux. when hydrogen chloride was given off. After this, this mixture and a solution of 507.8 g (4 moles) of ethyl aluminium dichloride in 2.25 litres of the hexane cut 63/800C were fed synchronously over a period of 2 hours into 2 litres of the hexane cut at 280C under nitrogen and whilst stirring with a blade stirrer and a specific stirring performance of 95 watt/m3. The suspension obtained was then heated for a further 1 hour under a reflux and this was done whilst stirring with the same specific stirring performance. After cooling, the solid was separated and washed 5 times, each time with 5 litres of the hexane cut.

b) Polymerisation of ethylene The vanadium catalyst described in Example 16a was used in a 750-litre stirrer vessel for the continuous polymerisation of ethylene. The polymerisation of the ethylene was carried out in a suspension of a hexane cut of the boiling range between 63"C and 8() C and powdered polyethylene and also catalyst. The filling level in the polymerisation vessel was adjusted at 300 litres; the mean residence time chosen for the catalyst in the polymerisation vessel was 2 hours.

The polymerisation was carried out at a temperature of 75"C. The ethylene partial pressure in the gas chamber of the polymerisation vessel was 34.1 bar. In order to regulate the mean molecular weight hydrogen was used: the hydrogen partial pressure in the gas chamber of the polymerisation reactor was 0.9 bar. As co-catalvst for activation one used triisobutyl aluminium. The catalyst and co-catalyst were diluted in a stirrer vessel in hexane 63/80"C and fed continuously into the polymerisation vessel with a dosing pump. The concentration of the catalyst in the polymerisation vessel was 3.33 mg/litre of suspension medium and that of the co-catalyst was 100 mg/litre of suspension medium. The rotation speed of the stirrer in the polymerisation vessel was 150 r.p.m. The powdered polymerisate resulting in the reactor was separated from the suspension medium in a centrifuge and dried in a partially evacuated vessel at approximately 80"C. Under these conditions one obtained a polymerisate with the following properties: Mean molecular weight 178,000 Melt index MFI 190/5 according to DIN 53 735 0.46 g/10 min.

Viscosity index I according to DIN 53 728 400 cm3/g Density at 23"C according to DIN 53 479 0.956 g/cm3 Molecular non-uniformity U (U = Mw/Mn1) 22.2 Proportion of molecular weight ( < Mw/5) 48.5% Total ash 40 ppm The calculated catalyst consumption with this mode of operation was 45.9 mg vanadium catalyst/kg polyethylene and 1,380 mg of triisobutyl aluminium per kg of polyethylene. The polymerisate powder had according to DIN 53 468 a bulk density of 0.509 g/ml. The mean particle size d' was 595 llm; the powder when determining the pouring capacity according to DIN Draft 53 492 had a pouring speed VR I() of 9.8 cm3/sec.

Example 17: In the same apparatus as that described in Example 16b, the catalyst of Example 16a was used for the continuous polymerisation of ethylene with the addition of small quantities of butene-(1). The ethylene partial pressure in the gas chamber of the polymerisation vessel was 34.3 bar; the hydrogen partial pressure there was 0.7 bar. Butene-(1) was offered in relation to ethylene in a proportion by weight of 2 to 100. The catalyst concentration in the reactor, the co-catalyst and also the co-catalyst concentration in the polymerisation reactor, the reactor temperature, the mean residence time of the catalyst in the polymerisation reactor and the rotation speed of the stirrer were unchanged as compared with Example 16b. Under these conditions a copolymerisate was produced which had the following properties: Mean molecular weight 168,000 Melt index MFI 190/5 0.48 g/10 min.

according to DIN 53 735 Viscosity index I according to DIN 53 728 380 cm3/g Density at 23"C according to DIN 53 479 0.954 g/cm3 Molecular non-uniformity U (U = Mw/Mn1) 27.9 Proportion of molecular weight < Mw/5 50.6% Total ash 50 ppm Ash analysis 14 ppm Al2O3 10 ppm V2OS < 10 ppm chlorine The calculated catalyst consumption was 48.6 mg vanadium catalyst/kg polyethylene and 1,430 mg triisobutyl aluminium/kg polyethylene. The bulk density of the polymerisate according to DIN 53 468 was 0.496 g/ml; the mean powder particle size d' was found to be 540 llm. On determining the pouring capacity according to DIN Draft 53 492 one obtained a pouring speed VR 10 for the polymerisate powder of 9.0 cm3/sec.

Example 18: a) Catalyst production 17.33 g (0.10 moles) of vanadyl (V) chloride and 11.12 g (0.15 moles) of butanol-(1) were stirred together in 80 ml of a hexane cut 63/800C for 2 hours at room temperature.

Then this mixture and a solution of 25.39 g (0.20 moles) of ethyl aluminium dichloride in 112 ml of the hexane cut 63/80or were fed synchronously over a period of 2 hours at 25 to 30"C into 100 ml of the hexane cut under nitrogen and whilst stirring with a blade stirrer and a specific stirring performance of 300 watt/m3. The suspension obtained was then heated for a further 2 hours under a reflux and the stirring continued with the same specific stirring performance. After cooling, the solid was separated and washed with a total of 2 litres of the hexane cut.

b) Polymerisation of ethylene In a 2-litre steel autoclave there were placed under nitrogen 1 litre of a hexane cut 63/80"C and 0.4 g of triisobutyl aluminium. To this there were added 15 mg of the catalyst produced according to Example 18a, suspended in a few ml of the hexane cut.

After displacing the nitrogen with ethylene. 6.3 bar of hydrogen were forced in and then ethylene was forced in up to a total pressure of 31.4 bar. At the same time the reactor contents were heated to 75"C. The polymerisation was carried out over a period of 1 hour whilst stirring with a stirrer rotation speed of 1000 r.p.m. at 75"C, the total pressure being maintained by forcing in ethylene. Then the pressure of the reactor was released, after the reactor contents had been cooled the polyethylene formed was filtered off and dried. The yield of polyethylene amounted to 326 g; corresponding to 21.7 kg per g of catalyst. The mean particle size d' was 560 Mm, the bulk density according to DIN 53 468 was 0.420 gimp, the pouring speed VR It} was 7.4 cm3/sec (DIN Draft 53 492). The viscositv index according to DIN 53 728 was 180 cm3/g. The molecular non-uniformity (M,.IM,-1) was determined gel-chromatographicallv to be 13 and the proportion < M v/5 was determined as being 49coo Example 19: With 10 mg of the catalyst produced according to Example 16a one carried out an ethylene polymerisation as described in Example 18b, but with the addition of 127 mg of ethyl aluminium dichloride instead of the triisobutyl aluminium, and forcing in only 1.6 bar of hydrogen. The yield of polyethylene was 232 g. corresponding to 23.2 kg per g of catalyst. The mean particle size d' was 480 Ltm. the pouring speed VR 1() was 4.9 cm isec (DIN Draft 53 492). The viscosity index according to DIN 53 728 was 520 cm3/g. The molecular non-uniformity (M,/M,-I) was determined gel-chromatographically to be 5.5 and the proportion < M,/5 was determined as being 30.8%.

Example 20: a) Production of catalyst 9.14 g (52.7 m moles) of vanadyl (V) chloride and 12.88 g (52.7 m moles) of vanadyl (V) n-propylate were heated together in 89 ml of a hexane cut 63/8 C under nitrogen for 2 houdrs under a reflux. After cooling the mixture, a solution of 32.7 g (211 m moles) of isobutyl aluminium dichloride in 114 ml of the hexane cut 63/80"C were added over a period of 2 hours at 25"C whilst stirring with a blade stirrer and a specific stirring performance of 400 watt/m3. The suspension obtained was then heated under a reflux for a further 2 hours and when so doing it was stirred with the same specific stirring performance. After cooling the solid was separated and washed 5 times. each time with 500 ml of the hexane cut.

b) Polymerisation of ethylene In a 2-litre steel autoclave there were placed under nitrogen 1 litre of a hexane cut 63i80"C and 0.4 g of triisobutyl aluminium. To this there were added 10 mg of the catalyst produced according to Example 20a suspended in a few ml of the hexane cut.

After displacement of the nitrogen with ethylene one forced in 1.6 bar of hydrogen and then ethylene up to a total pressure of 31.4 bar. At the same time the reactor contents were heated to 75"C. The polymerisation was carried out for 1 hour whilst stirring with a stirrer rotation speed of 1000 r.p.m. at 75"C. the total pressure being maintained by forcing in ethylene. Then the pressure of the reactor was released. after the reactor contents had been cooled the polyethylene formed was filtered off and dried. The yield of polyethylene amounted to 183 g. corresponding to 18.3 kg per g of catalyst. The mean particle size d' was 370 Ftm. the bulk density according to DIN 53 468 was 0.425 g/ml, the pouring speed VR 10 was 8.2 cm3/sec (DIN Draft 53 492). The molecular non-uniformit(Mw/M,lI) was determined gel-chromatographically to be 23 and the proportion < MEv/5 was determined as being 45%.

Example 21: a) Production of catalyst 183 g (1.06 moles) of vanadyl (V) chloride and 258 g (1.06 moles) of vanadyl (V) n-propylate were stirred together in 1.77 litres of a hexane cut 63/800C for 1 hour at room temperature. This mixture and a solution of 620 g (4 moles) of isobutyl aluminium dichloride in 3.45 litres of the hexane cut 63/800C were fed synchronously over a period of 2 hours into 2 litres of the hexane cut at 32 to 36"C whilst stirring with a blade stirrer and a specific stirring performance of 78 watt/m3. The suspension obtained was then heated for a further 2 hours under a reflux and the stirring was continued with the same specific stirring performance. After cooling, the solid was separated and washed 5 times, each time with 5 litres of the hexane cut.

b) Copolymerisation of ethylene and butene-(1) The vanadium catalyst described under 21a was used with triisobutyl aluminium as co-catalyst for the continuous polymerisation of ethylene with the addition of small quantities of butene-(1). As polymerisation reactor one used a 750-litre stirrer vessel.

The polymerisation of the ethylene mixed with butene-(1) was carried out in a suspension of a hexane cut of the boiling range between 63"C and 80"C and powdered polyethylene and also catalyst. The filling level in the polymerisation vessel was 300 litres; as mean residence time for the catalyst in the polymerisation vessel one chose 2 hours.

The copolymerisation of ethylene and butene-(1) was carried out at a temperature of 75"C. In the gas chamber of the polymerisation reactor an ethylene partial pressure of 34.1 bar and a hydrogen partial pressure of 0.9 bar were maintained by continuously dosing in ethylene and hydrogen which was used for regulating the mean molecular weight. The co-monomer, butene-(1), was offered in relation to ethylene in the proportion by weight of 2 to 100. The catalyst and the co-catalyst were diluted in a stirrer vessel in hexane 63/80"C and after this were fed continuously to the polymerisation vessel by a dosing pump. The concentration of the catalyst in the polymerisation reactor was 3.33 mg/litre of suspension medium and that of the cocatalyst was 100 mg/litre of suspension medium. The rotation speed of the stirrer in the polymerisation vessel was 150 r.p.m. The copolymerisate resulting in the reactor was separated from the suspension medium in a centrifuge and dried in a partially evacuated vessel at about 80"C. The copolymerisate produced in this way had the following properties: Mean molecular weight 168,000 Melt index MFI 190/5 according to DIN 53 735 0.46 g/10 min Viscosity index I according to DIN 53 728 380 cm3/g Density at 23"C according to DIN 53 479 0.956 g/cm3 Molecular non-uniformity U (U = Mw/Mn1) 20.1 proportion of molecular weight < Mw/5 46.6% Total ash 50 ppm Ash analysis 30 ppm Al203 9 pp

Claims (24)

WHAT WE CLAIM IS:

1. A process for the production of a powdered ethylene polymer which process comprises polymerising ethylene, optionally mixed with other l-olefins and also in the presence of hydrogen, in an inert liquid hydrocarbon at a temperature of from 50"C to 95"C and a pressure of from 10 to 100 bar, by means of a discontinuous or continuous process using a ZIEGLER catalyst, the catalyst being one which is produced in an inert liquid hydrocarbon by reacting a vanadyl (V) compound containing chlorine and alkoxy groups with a first organo-aluminium compound, separating the insoluble reaction product and activating it with a second organo-aluminium compound, the vanadyl (V) compound being a reaction product of vanadyl (V) chloride and a vanadyl (V) alcoholate in molar proportions of 1:2 to 2:1 or directly the reaction product of vanadyl (V) chloride with an alcohol in molar proportions of 1:2 to 1:1, the first organo-aluminium compound being ethyl aluminium dichloride and/or diethyl aluminium chloride or isobutyl aluminium dichloride and/or diisobutyl aluminium chloride in molar proportions of aluminium compound to vanadium compound of 1:1 to 3:1, the reaction of the vanadium compound with the first organo-aluminium compound being carried out whilst stirring with specific stirring capacities of 0.1 to 20,000 watt/m3 and the second organo-aluminium compound used for the activation of the resultant reaction product being selected from an aluminum alkyl compound of the formula AIR3, in which R represents a hydrocarbon radical with 2 to 8 carbon atoms, an alkyl aluminium sesquichloride, an alkyl aluminium dichloride and a dialkyl-aluminium monochloride.

2. A process according to Claim 1, wherein the alcohol used to prepare the vanadyl (V) compound is ethyl alcohol, propan-1-ol or butan-1-ol.

3. A process according to Claim 1 or Claim 2, wherein the stirring capacity used when reacting the vanadium compound with the aluminium-organic compound is from 1 to 5,000 wattle .

4. A process according to any one of the preceding claims, wherein the alkyl aluminium sesquichloride is ethyl aluminium sesquichloride.

5. A process according to any one of the preceding claims, wherein the alkyl aluminium dichloride is ethyl aluminium dichloride.

6. A process according to any one of the preceding claims, wherein the dialkyl aluminium monochloride is diethyl aluminium chloride or diisobutyl aluminium chloride.

7. A process according to any one of the preceding claims, wherein the polymerisation is performed at a pressure of from 20 to 60 bar.

8. A process according to any one of the preceding claims, wherein the molar ratio of vanadyl (V) chloride to alcohol is 1:1.5.

9. A process for the production of a powdered ethylene polymer according to Claim 1, which process comprises polymerising ethylene, optionally mixed with other 1-olefins and also in the presence of hydrogen, in an inert liquid hydrocarbon at a temperature of from 50"C to 95 C and a pressure of from 10 to 100 bar, by means of a discontinuous or continuous process using a ZIEGLER catalyst, the catalyst being one which is produced in an inert liquid hydrocarbon by reacting a vanadyl (V) compound containing chlorine and alkoxy grouts with a first organo-aluminium compound, separating the insoluble reaction product and activating it with a second organo-aluminium compound, the vanadyl (V) compound being a reaction product of vanadyl (V) chloride and a vanadyl (V) alcoholate in molar proportions of 1:2 to 2:1, the first organo-aluminium compound being ethyl aluminium dichloride and/or diethyl aluminium chloride in molar proportions of aluminium compound to vanadium compound of 1:1 to 3;1, the reaction of the vanadium compound with the first organo-aluminium compound being carried out whilst stirring with specific stirring capacities of 0.1 to 20,000 watt/m3 and the second organo-aluminium compound used for the activation of the resultant reaction product being an aluminium alkyl compound of the formula AIR3, in which R represents a hydrocarbon radical with 2 to 8 carbon atoms.

10. A process according to Claim 9, wherein the stirring capacity used when reacting the vanadium compound with the aluminium-organic compound is from 1 to 5,000 watt/m'.

11. A process according to Claim 9 or 10, wherein the polymerisation is performed at a pressure of from 20 to 60 bar.

12. A process according to Claim 9 substantially as described in any one of the foregoing Examples 1 to 10.

13. A process for the production of a powdered ethylene polymer according to Claim 1, which process comprises polymerising ethylene, optionally mixed with other 1-olefins and also in the presence of hydrogen, in an inert liquid hydrocarbon at a temperature of from 50"C to 95"C and a pressure of from 10 to 100 bar. by means of a discontinuous or continuous process using a ZIEGLER catalyst, the catalyst being one which is produced in an inert liquid hydrocarbon by reacting a vanadyl (V) compound containing chlorine and alkoxy groups with a first organo-aluminium compound, separating the insoluble reaction product and activating it with a second organo-aluminium compound, the vanadyl (V) compound being a reaction product of vanadyl (V) chloride and a vanadyl (V) alcoholate in molar proportions of 1:2 to 2:1, the first organo-aluminium compound being ethyl aluminium dichloride and/or diethyl aluminium chloride in molar proportions of aluminium compound to vanadium compound of 1:1 to 3:1, the reaction of the vanadium compound with the first organo-aluminium compound being carried out whilst stirring with specific stirring capacities of 0.1 to 20,000 watt/m3 and the second organo-aluminium compound used for the activation of the resultant reaction product being selected from an alkyl aluminium sesquichloride, and an alkyl aluminium dichloride.

14. A process according to Claim 13, wherein the alkyl aluminium sesquichloride is ethyl aluminium sesquichloride.

15. A process according to Claim 13 or 14, wherein the alkyl aluminium dichloride is ethyl aluminium dichloride.

16. A process according to Claim 13, substantially as described in any one of the foregoing Examples 11 to 15.

17. A process for the production of a powdered ethylene polymer according to Claim 1, which process comprises polymerising ethylene, optionally mixed with other 1-olefins and also in the presence of hydrogen, in an inert liquid hydrocarbon at a temperature of from 50"C to 95"C and a pressure of from 10 to 100 bar, by means of a discontinuous or continuous process using a ZIEGLER catalyst, the catalyst being one which is produced in an inert liquid hydrocarbon by reacting a vanadyl (V) compound containing chlorine and alkoxy groups with a first organo-aluminium compound, separating the insoluble reaction product and activating it with a second organo-aluminium compound, the vanadyl (V) compound being directly the reaction product of vanadyl (V) chloride with an alcohol in molar proportions of 1:2 to 1:1, the first organo-aluminium compound being ethyl aluminium dichloride and/or diethyl aluminium chloride in molar proportions of aluminium compound to vanadium compound of 1:1 to 3:1, the reaction of the vanadium compound with the first organo-aluminium compound being carried out whilst stirring with specific stirring capacities of 0.1 to 20,000 watt/m3 and the second organo-aluminium compound used for the activation of the resultant reaction product being selected from an aluminium alkyl compound of the formula AIRS, in which R represents a hydrocarbon radical with 2 to 8 carbon atoms, an alkyl aluminium sesquichloride, and an alkyl aluminium dichloride.

18. A process according to Claim 17, wherein the alcohol used to prepare the vanadyl (V) compound is ethyl alcohol, propan-1-ol or butan-l-ol.

19. A process according to Claim 17 or 18, wherein the molar ratio of vanadyl (V) chloride to alcohol is 1:1.5.

20. A process according to Claim 17 substantially as described in any one of the foregoing Examples 16 to 19.

21. A process for the production of a powdered ethylene polymer according to Claim 1, which process comprises polymerising ethylene, optionally mixed with other 1-olefins and also in the presence of hydrogen, in an inert liquid hydrocarbon at a temperature of from 50"C to 95"C and a pressure of from 10 to 100 bar, by means of a discontinuous or continuous process using a ZIEGLER catalyst, the catalyst being one which is produced in an inert liquid hydrocarbon by reacting a vanadyl (V) compound containing chlorine and alkoxy groups with a first organo-aluminium compound, separating the insoluble reaction product and activating it with a second organo-aluminium compound, the vanadyl (V) compound being a reaction product of vanadyl (V) chloride and a vanadyl (V) alcoholate in molar proportions of 1:2 to 2:1 or directly the reaction product of vanadyl (V) chloride with an alcohol in molar proportions of 1:2 to 1:1. the first organo-aluminium compound being isobutyl aluminium dichloride and/or diisobutyl aluminium chloride in molar proportions of aluminium compound to vanadium compound of 1:1 to 3:1, the reaction of the vanadium compound with the first organo-aluminium compound being carried out whilst stirring with specific stirring capacities of 0.1 to 20,000 watt/m3 and the second organo-aluminium compound used for the activation of the resultant reaction product being selected from an aluminium alkyl compound of the formula AIR3, in which R represents a hydrocarbon radical with 2 to 8 carbon atoms, an alkyl aluminium sesquichloride. and an alkyl aluminium dichloride.

22. A process according to Claim 21 substantially as described in the foregoing Example 20 or 21.

23. An ethylene polymer when prepared by a process as claimed in any one of the preceding claims.

24. A moulded article when prepared from an ethylene polymer as claimed in Claim 23.