Solid component of a catalyst for the homo- and co-polymerization of ethylene

Abstract: A solid component of a catalyst for the (co)polymerization of ethylene which includes magnesium, halogen and titanium is obtainable by (i) dissolving a dialkyl magnesium compound, a silicon halide and, optionally, an alkyl halide in an inert organic solvent and maintaining contact until a granular solid precipitates; (ii) reacting the granular solid with a titanium halide, alkoxide or halogen-alkoxide, to produce a solid catalyst component; and (iii) activating this solid component by contacting it with alkyl aluminium halide if a titanium alkoxide or halogen-alkoxide has been used in step (ii).

Description: The present invention relates to a solid catalyst component which, combined with metal alkyl compounds or metal alkyl halides, affords a catalytic system suitable for the homo-polymerization of ethylene and the co-polymerization of ethylene with, e.g., alpha-olefins such as propylene, butene-1, hexene-1, 4-methyl-pentene-1, octene-1 and similar monomers. Catalytic systems of the Ziegler-Natta type for the polymerization of alpha-olefins are already known in the art and are generally composed of a combination of an organometallic compound of elements of groups I to III of the periodic table and a compound of a transition metal belonging to groups IV to VI of the periodic table (Boor Jr., "Ziegler-Natta Catalysts and Polymerization", Academic Press, New York, 1979). Generally, the organometallic compound used is an aluminium alkyl and the transition metal compound is a titanium halide. The possibility of binding or supporting this titanium halide on a solid, granular carrier is also known (Karol F.J., Catal. Rev. - Sci.Eng., 26 , 384, 557-595, 1984). Also known is the activation of magnesium chloride and its use in the preparation of catalysts based on highly active titanium salts for the polymerization of olefins, as described in DE-A-2 153 520 (CA 77 , 62505, 1972); DE-A-2 638 429 (CA 83 , 59870, 1972); DE-A-2 638 429 (CA 86 , 140706, 1975); BE-A-848 427 (CA 87 , 68839, 1977); and JP-A-79-118,484 (CA 92 , 59450, 1979). Finally, it is known that heterogeneous catalysts for the polymerization of alpha-olefins are capable of reproducing their morphology in an equivalent polymeric morphology; this is made possible by applying technological conditions of catalyst synthesis which can be both complicated and onerous (Karol F.J., supra, and McDaniel M.P., J.Polym.Chem. Ed., 19 , 1967-1976, 1981). The polyolefin market increasingly demands products which are able to satisfy the most varied requirements of application whereas, on the other hand, there is also the need to simplify the production processes of polyolefins and to reduce investments and production costs. There is a particular need to have available catalysts which are not only simple and economical, but are also able to afford, if possible in a single polymerization step, olefinic homo- and copolymers which are suitable for both extrusion and moulding processes. Eaborn, C.E. in "Organo Silicon Compounds", Butterworths Scientific Publications, London 1960; Rochow, E.G. in "The Chemistry of Silicon", New York, 1975; and Voorhoeve, R.J.H. in "Organosilanes", Elsevier, New York, 1967, describe an alkylation reaction between a dialkyl magnesium compound (MgR₂) or an alkyl magnesium halide (MgRX) and silicon tetrachloride (SiCl₄), which results in a solid non-crystalline compound, according to the reaction: SiCl₄ + MgRX (or MgR₂)→MgXCl + R n SiCl (4-n) It has now been found, according to the present invention, that this precipitate can be obtained by using a particle size which is specifically controlled in relation to the ratio of the reagents. It has also been found that the precipitate thus obtained is able to react with a titanium compound to afford a solid catalyst component which is extremely active in the (co)polymerization of ethylene, and in which the ratio of titanium in its tetravalent state to titanium in its trivalent state is related to the ratio of silicon to magnesium in the solid. It has finally been found that the addition of a metal compound selected from vanadium, zirconium and hafnium compounds in the precipitation phase of the solid, allows to obtain solid catalyst components which can yield polyethylenes with a broader molecular weight distribution in a single polymerization stage. According to the present invention it is, therefore, possible to obtain in an easy and convenient way catalysts which are capable of producing polyethylenes with various characteristics, using simplified polymerization processes, thus eliminating, or at least reducing, the disadvantages involved in the known techniques described above. In accordance with this, one aspect of the present invention relates to a solid component of a catalyst for the (co)-polymerization of ethylene which includes magnesium, halogen and titanium and is obtainable by (i) dissolution, in an inert, organic solvent, of a dialkyl magnesium compound, a silicon halide and, optionally, an alkyl halide, the atomic ratio of silicon in the silicon halide to magnesium in the dialkyl magnesium compound ranging from 0.5/l to 15/l and the molar ratio of alkyl halide to silicon halide ranging from 0/l to 10/l, and maintenance of the contact between the components until a granular solid precipitates from the solution; (ii) contact and reaction of the above granular solid with a titanium halide, alkoxide and/or halogen-alkoxide, the atomic ratio of magnesium in the granular solid to titanium in the titanium compound(s) ranging from 1/l to 60/l, to prepare a solid catalyst component; and, in case a titanium alkoxide and/or halogen-alkoxide has been used in step (ii), (iii) activation of the solid catalyst component by contact thereof with an alkyl aluminium halide. In a preferred method, predetermined quantities of at least one compound of a metal M selected from vanadium, zirconium and hafnium are additionally added to the solution in step (i), to obtain solid catalyst components which are particularly suitable for the production of polymers and copolymers of ethylene having a broad molecular weight distribution. In step (i) according to the present invention, a granular solid of a dialkyl magnesium compound, a silicon chloride and optionally also an alkyl halide is precipitated from a solution in an inert organic solvent. Examples of silicon halides suitable for this purpose are silicon chlorides and bromides and chloro and bromo silanes. Specific examples of these compounds are silicon tetrachloride, silicon tetrabromide, trichlorosilane, vinyl trichlorosilane, trichloroethoxy silane and chloroethyl trichlorosilane. It is particularly preferred to use silicon tetrachloride. The alkyl halides which are suitable for the above purpose are, e.g., alkyl chlorides and bromides, either primary, secondary or tertiary, the alkyl group whereof contains from 1 to 20 (e.g. 1 to 10) carbon atoms. Specific examples of suitable alkyl halides are ethyl bromide, butyl chloride, hexyl chloride, octyl chloride and cyclohexyl chloride. Dialkyl magnesium compounds suitable for the present purpose are, e.g., compounds which can be defined by the formula MgR'R'', where R' and R'', the same or different from each other, stand for an alkyl group, either linear or branched which contains from 1 to 10 (e.g. 2 to 8) carbon atoms. Specific examples thereof are diethyl magnesium, ethyl butyl magnesium, dihexyl magnesium, butyl octyl magnesium, and dioctyl magnesium. The solvents to be used for dissolving the above-mentioned compounds are organic solvents which are liquid under the operating conditions and are also inert (non-reactive) with respect to the other components. Examples of suitable solvents are hydrocarbons, particularly aliphatic hydrocarbons, such as pentane, isopentane, hexane, heptane and octane. Step (i) may be carried out by preparing a solution of dialkyl magnesium compound, silicon halide and possibly alkyl halide in the organic solvent chosen, operating at or about room temperature (about 20 to 25°C), with such amounts of the above compounds as to result in an atomic ratio of silicon to magnesium of from 0.5/l to 15/l and a molar ratio of alkyl halide to silicon halide of from 0/l to 10/l. The solution thus obtained may then be heated to a temperature of from 40 to 100°C, causing the precipitation of a granular solid. In practice, when operating under the conditions specified above, an almost complete precipitation has taken place after 0.5 to 5 hours. Preferred operating conditions are an atomic ratio Si/Mg in the initial solution of from 1/l to 9/l and a molar ratio of alkyl halide to silicon halide of from 0/1 to 5/l, the solution being preferably heated to a temperature of from 70 to 95°C for 1 to 2 hours. The solid thus obtained is in granular form with a controlled particle size. More specifically, it has been found that more than 95% of the solid have a particle size of from 1 to 50 µm, and more than 90% have a granulometry ranging from 2 to 40 µm. It has also been found that, in the above-mentioned range, the obtained value of the apparent density of the polymers depends on the ratio Si/Mg in the starting solution, higher ratios corresponding to a higher apparent density. The alkyl halide, an optional component in step (i), basically has the effect of facilitating the chlorination of the dialkyl magnesium compound. The granular solid precipitated in step (i) may be separated from the liquid phase and preferably is thoroughly washed with an inert liquid solvent, particularly a hydrocarbon solvent, such as hexane or heptane. In step (ii), the solid obtained as described above is contacted and made to react with a titanium compound selected from titanium halides, alkoxides, halogen-alkoxides and mixtures thereof. Specific examples of these compounds are titanium tetrachloride, titanium tetrabromide, titanium tetra-n-propylate, titanium tetra-n-butylate, titanium tetra-i-propylate, titanium tetra-i-butylate and the corresponding titanium mono- and di-chloro alkoxides and mono- and di-bromo alkoxides. Mixtures of two or more of the above-mentioned titanium compounds may also be used. Step (ii) may be carried out by suspending the granular solid in an inert organic solvent, for example a hydrocarbon solvent, of the aliphatic type, such as hexane, heptane, octane etc., and adding the titanium compound, possibly dissolved in the same or a similar solvent, to the suspension. In particular, the quantity of the titanium compound should be such as to result in an atomic ratio of magnesium in the granular solid to titanium in the titanium compound of from 1/1 to 60/1, preferably of from 4/1 to 20/1. The suspension thus obtained usually is kept at a temperature of from 50 to 100°C, preferably from 60 to 90°C over a period of from 0.5 to 5 hours, preferably 1 to 2 hours. A solid catalyst component is thus obtained, which can be recovered from the corresponding suspension, e.g., by evaporating the organic solvent at atmospheric or reduced pressure. When a titanium alkoxide and/or halogen-alkoxide is used in step (ii), the solid catalyst component should undergo an activation treatment. This activation is carried out, in a further step (iii), by contacting the component at the end of step (ii) with an alkyl aluminium halide. Alkyl aluminium halides suitable for this purpose are, e.g., alkyl aluminium chlorides and bromides, such as diethyl aluminium chloride and bromide, ethyl aluminium sesquichloride and sesquibromide, and diisobutyl aluminium chloride and bromide. More specifically, in a preferred embodiment the solid catalyst component, suspended in an inert organic solvent such as a hydrocarbon solvent of the aliphatic type, for example hexane or heptane, is contacted with an alkyl aluminium halide, the ratio of halogen atoms in the alkyl aluminium halide to alkoxy groups in the titanium alkoxide and/or halogen-alkoxide preferably ranging from 0.1/l to 10/l, and the suspension is kept at a temperature preferably ranging from 10 to 100°C for 10 minutes to 5 hours. At the end of the treatment, the solid catalyst component can be recovered from the suspension, for example by filtration, washed with a hydrocarbon solvent and, if desired, dried. When a titanium tetrahalide is used in step (ii), the catalyst component obtained at the end of this step generally contains 0.5 to 10% by weight of titanium, 10 to 30% by weight of magnesium and 50 to 75% by weight of halogen. When a titanium alkoxide and/or halogen-alkoxide is used in step (ii), the solid catalyst component obtained at the end if step (iii) may additionally contain small quantities of aluminium and alkoxide groups. The mechanism of interaction between the titanium compound and the granular solid in step (ii) of the present process is not very clear, and in particular it is not known whether the interaction is of physical or chemical nature or both. Whatever the case may be, if the operating conditions described above are applied, there is obtained a catalyst component in the form of a granular solid with a particle size similar to that of the solid obtained in the precipitation step (i), capable of affording polymers having an apparent density which, depending on the specific conditions used, ranges from 0.25 to 0.40 g/ml, normally from about 0.30 to 0.35 g/ml. This granular solid has a pour rate which is lower than 30 sec(ASTM-D 1895). Moreover, the titanium in the solid catalyst component obtained at the end of step (ii) can be in a substantially tetravalent form, or partially in a trivalent form and partially in a tetravalent form depending, in particular, on the ratio Mg/Si in the solid obtained at the end of step (i). More specifically, with higher values of this ratio, the formation of trivalent titanium is more likely, whereas lower values favour the formation of tetravalent titanium. The degree of oxidation of the titanium can be further varied in the method which includes step (iii). In fact, in this step there is a reduction to the lower state of oxidation, together with an increase in the halogen content and an either partial or total elimination of the alkoxy groups present in the solid catalyst component. It is therefore possible, according to the present invention, to obtain solid catalyst components with the desired degree of oxidation of the titanium, suitable for the production of polyethylenes having a molecular weight distribution from narrow to average. When polyethylenes having a relatively broad molecular weight distribution are required, at least one compound of a metal M selected from vanadium, zirconium and hafnium is added to the solution in step (i). Examples of suitable compounds for this purpose are the halides, oxyhalides, alkoxides and halogen-alkoxides, preference being given to halides, such as vanadium trichloride and tribromide, zirconium tetrachloride and tetrabromide and hafnium tetrachloride and tetrabromide. In this method, the atomic ratio of magnesium in the dialkyl magnesium compound to the sum of titanium and metal or metals M usually ranges from 1/l to 30/l and the atomic ratio of titanium to metal or metals M usually is from 0.1/l to 2/l. In a preferred method, the atomic ratio Mg/(Ti+M) is kept at a value of from 1/l to 9/l and the atomic ratio Ti/M is from 0.5/l to 1/l. The mechanism with which the compound(s) of the metal(s) M interact(s) with the other components in step (i) of the present procedure is not entirely clear. It is assumed, however, that the interaction involves a reduction of the metal M by the dialkyl magnesium compound. For example, the solid catalyst component obtained in example 6 below, when subjected to X-ray analysis (the spectrum is shown in Figure 1), shows its characteristic peak of HfCl at about 10° and that of HfCl₄ at about 15 to 20°. This proves that the solid catalyst component contains a mixture of mono- and tetravalent Hf, with tri- and tetravalent Ti, in the presence of MgCl₂ in the delta form. In any case, at the end of step (i) there is obtained a granular solid with a particle size of the granules which is very similar to that obtained without the compound(s) of metal(s) M, which is suitable for the reaction with the titanium compound in the following step (ii). It is also assumed that in step (ii) redox reactions occur between the titanium and the metal(s) M, thus allowing a further diversification of the active catalytic centres present in the solid catalyst component. This diversification can be further increased by using more metals M and/or in the optional carrying out of step (iii), as specified previously. In any case, solid catalyst components are obtained which are highly active in the (co)polymerization of ethylene and which are capable of yielding polyethylene having a broader distribution of molecular weights, operating in a single polymerization process. It should be pointed out that polymers having a broad molecular weight distribution have a monomodal distribution which makes them easier to mould and extrude as compared to those having a bimodal distribution. Figure 2 shows the molecular weight distribution of the polymer prepared in example 6 below. In addition, in the copolymerization of ethylene with alpha-olefin(s), copolymers with a homogenous distribution of the comonomer in the polymer chain may be obtained. The present invention also provides catalysts for the (co)polymerization of ethylene, comprising the solid catalyst component described above combined with an organometallic compound of aluminium (co-catalyst) which preferably is selected from aluminium trialkyls and alkyl aluminium halides (particularly chlorides) having from 1 to 6 carbon atoms in the alkyl groups. Among these, aluminium trialkyls such as triethyl aluminium, tributyl aluminium, triisobutyl aluminium and trihexyl aluminium are particularly preferred. In the catalysts of the present invention, the atomic ratio of aluminium (in the co-catalyst) to titanium (in the solid catalyst component) generally ranges from 0.5:1 to 1,000:1, preferably from 50:1 to 200:1. These catalysts are extremely active in processes for the polymerization of ethylene and the copolymerization of ethylene with alpha-olefins and can be used in polymerization processes carried out by means of the suspension technique in an inert diluent or by using the gas phase method in a fluidized or stirred bed. The alpha-olefins which can be copolymerized with ethylene generally are those containing from 3 to 15 carbon atoms, such as butene-1, hexene-1, 4-methyl-pentene-1, octene-1, undecene-1, 1,4-hexadiene and ethylidene norbornene. The general polymerization conditions are: temperature of from 50 to 100°C, total pressure of from 5 to 40 bar, the partial pressure ratio of hydrogen to ethylene ranging from 0:1 to 10:1. The catalysts of the present invention are sensitive to the polymerization temperature and the kind of co-catalyst used. For example, it is possible to obtain a marked increase in the MFR (melt flow ratio) value of the polyethylenes when, under the same operating conditions, the polymerization temperature is lowered. It has also been found that an alkyl aluminium co-catalyst with a higher alkyl group (for example trihexyl aluminium) affords more constant polymerization kinetics and an increase in the MFR value of the polyethylenes produced than an aluminium alkyl co-catalyst with a lower alkyl group (such as triisobutyl aluminium). These observations allow the polymerization to be regulated according to the final products desired. In any event, there is a high yield of olefinic polymer, and the polymer thus obtained has excellent rheological properties and, in particular, is in the form of non-friable granules of which more than 95% by weight have a size distribution ranging from 250 to 1000 µm and are without fines. The following examples are to further illustrate the present invention without limiting it in any way. EXAMPLE 1 200 ml of a 20% solution by weight of butyl octyl magnesium (Mg₁Bu 1.5 Oct 0.5 ; 29.16 g, 175 mmoles) and 202 ml of silicon tetrachloride (297 g, 1750 mmoles) in n-heptane are charged, in a nitrogen atmosphere, into a 500 ml flask equipped with reflux cooler, mechanical stirrer and thermometer. The mixture is heated at 77°C for 1 hour. The resulting solid precipitate in the form of granules of from 1 to 50 µm is separated by filtration and thoroughly washed with n-heptane. The washed solid is suspended in 150 ml of n-heptane and 1.43 g (7.5 mmoles) of titanium tetrachloride are added to the suspension. Contact is maintained for 1 hour at 90°C and the suspension is then dried by evaporating the solvent at atmospheric pressure. 17 g of a solid catalyst component are thus obtained in the form of granules whose size is similar to that of the solid precipitate, containing 0.9% by weight of titanium (in the form of tetravalent titanium), 24.3% by weight of magnesium and 66.8% by weight of chlorine. The solid catalyst component prepared in the above way is used in a test for the polymerization of ethylene. More specifically, the polymerization is carried out in a 5 litre autoclave containing 2 litres of n-hexane, using 50 mg of the solid component and 4 mmoles of triethyl aluminium as cocatalyst. The solid component is charged into the reaction vessel, under hydrogen at atmospheric pressure and at a temperature of 30°C. The reaction vessel is brought to the required operating conditions, within 30 minutes, by feeding ethylene and hydrogen up to a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 0.47/l) and raising the temperature to 90°C. Polymerization is continued under these conditions for 60 minutes. A yield equal to 9.0 kg of polyethylene per gram of solid catalyst component is thus obtained and the polyethylene has the following characteristics: - density: (ASTM D-1505) 0.9570 g/ml - MFI (2.16 kg): (Melt Flow Index - ASTM D-1238) 0.38 g/10' - apparent density: (ASTM D-1895) 0.36 g/ml - MFR: (MFR = Melt Flow Index Ratio, defined as ratio MFI (21.6 kg)/MFI (2.16 kg). 33.8 The polyethylene is in granular form with the following size distribution in µm: ≧ 2000 0.0% by weight < 2000 to ≧ 1000 0.5% by weight < 1000 to ≧ 500 62.7% by weight < 500 to ≧ 125 35.7% by weight < 125 1.1% by weight . EXAMPLE 2 The procedure described in example 1 is followed, with the exception that 20.2 ml (29.66 g, 175 mmoles) of silicon tetrachloride are used. 17 g of a solid catalyst component in granular form, containing 1.4% by weight of titanium (42% in trivalent form), 22.6% by weight of magnesium and 62.5% by weight of chlorine, are thus obtained. The solid catalyst component prepared in the above way is used in a test for the polymerization of ethylene carried out as described in example 1. A yield of 6.2 kg of polyethylene per gram of solid component is obtained and the polyethylene has the following characteristics: EXAMPLE 3 100 ml of n-heptane, 48 ml of a 20% by weight solution of butyl octyl magnesium (Mg₁Bu 1.5 Oct 0.5 ; 7.0 g, 42 mmoles) and 17 ml of silicon tetrachloride (25 g, 147 mmoles) in n-heptane are charged, in a nitrogen atmosphere, into a 250 ml flask equipped with reflux cooler, mechanical stirrer and thermometer. The contents of the flask are heated at 90°C for 1 hour. The resulting solid precipitate in the form of granules of from 1 to 50 µm is separated by filtration and thoroughly washed with n-hexane. The washed solid is suspended in 100 ml of n-hexane and 1.22 g (3.6 mmoles) of titanium tetra-n-butylate are added. Contact is maintained for 1 hour at 65°C and the suspension is then dried by evaporating the solvent at a pressure of 10 mm Hg. Obtained are 4.5 g of a solid which is suspended in 50 ml of n-hexane, and 3.9 ml of a 40% by weight solution of ethyl aluminium sesquichloride (1.31 g, 5.3 mmoles) in decane are added to the suspension. Contact is maintained for 15 minutes at 25°C whereafter the solid is recovered by filtration, washed with n-hexane and dried by evaporating the solvent. The solid catalyst component thus obtained has a particle size similar to that of the solid precipitate and contains 3.2% by weight of titanium, 19.4% by weight of magnesium, 58.1% by weight of chlorine, 8.9% by weight of butanol and 0.6% by weight of aluminium. A test for the polymerization of ethylene is carried out as described in example 1, using 40 mg of the solid catalyst component and 5.0 mmoles of triethyl aluminium as cocatalyst. A yield of 11.4 kg of polyethylene per gram of solid catalyst component is obtained and the polyethylene has the following characteristics: EXAMPLE 4 The same procedure as in example 3 is carried out, the only difference being that 6 ml (5.32 g, 67.8 mmoles) of butyl chloride are added together with the silicon tetrachloride. A solid catalyst component is obtained, containing 2.6% by weight of titanium, 20.0% by weight of magnesium, 58.1% by weight of chlorine, 8.0% by weight of butanol and 1.3% by weight of aluminium. A test for the polymerization of ethylene is carried out as described in example 1, using 50 mg of the solid catalyst component and 6 mmoles of triethyl aluminium as cocatalyst. A yield of 13.1 kg of polyethylene per gram of solid catalyst component is thus obtained and the polyethylene has the following characteristics: EXAMPLE 5 100 ml of n-heptane, 10.2 ml of a 20% by weight solution of butyl octyl magnesium (Mg₁Bu 1.5 Oct 0.5 ; 1.49 g, 8.9 mmoles), 6.8 ml of silicon tetrachloride (9.98 g, 58.8 mmoles) and 4.6 ml (4.08 g, 44.0 mmoles) of butyl chloride in n-heptane are charged, in a nitrogen atmosphere, into a 250 ml flask equipped with reflux cooler, mechanical stirrer and thermometer. The contents of the flask are heated for 2 hours at a temperature of 90°C whereafter 6.8 ml (9.98 g, 58.8 mmoles) of silicon tetrachloride and 4.6 ml (4.08 g, 44.0 mmoles) of butyl chloride are again added and the mixture is kept for 2 hours at a temperature of 90°C. The solid precipitate in the form of granules of from 1 to 50 µm is separated by filtration and thoroughly washed with n-hexane. The washed solid is suspended in 50 ml of n-hexane and 2.55 g (5.7 mmoles) of titanium tetra-n-butylate are added to the suspension. Contact is maintained for 1 hour at 65°C and the suspension is then dried by evaporating the solvent at a pressure of 10 mm Hg. Thereby 2.1 g of a solid are obtained, which are suspended in 20 ml of n-hexane, and 3.4 ml of a 40% by weight solution of ethyl aluminium sesquichloride (0.99 g, 4.0 mmoles) in decane are added to the resulting suspension. Contact is maintained for 14 minutes at 25°C and the solid is then recovered by filtration, washed with n-hexane and dried by evaporating the solvent. A catalyst component is obtained in the form of granules whose size is similar to that of the solid precipitate, and is used in a test for the polymerization of ethylene with the procedure described in example 4. A yield of 12.1 kg of polyethylene per gram of solid catalyst component is obtained and the polyethylene has the following characteristics: EXAMPLE 6 114 ml of a 20% by weight solution of butyl octyl magnesium (Mg₁Bu 1.5 Oct 0.5 ) and 8.0 g (25.0 mmoles) of hafnium tetrachloride in n-heptane are charged, in a nitrogen atmosphere, into a 500 ml flask equipped with reflux cooler, mechanical stirrer and thermometer. The contents of the flask are heated for 15 minutes at 40°C, whereafter 100 ml (147 g, 864 mmoles) of silicon tetrachloride are added and the mixture is heated at 77°C for 1 hour. The solid precipitate in the form of granules of from 1 to 50 µm is separated by filtration and thoroughly washed with n-heptane. The washed solid is suspended in 150 ml of n-heptane and 2.8 ml (4.84 g, 25.5 mmoles) of titanium tetrachloride are added to the suspension. Contact is maintained for 1 hour at 90°C and the suspension is then dried by evaporating the solvent at atmospheric pressure. 20 g of a solid catalyst component are thus obtained in the form of granules whose size distribution is similar to that of the solid precipitate, and containing, in addition to the hafnium, 5.0% by weight of titanium (93% in the form of trivalent titanium), 11.1% by weight of magnesium and 57.1% by weight of chlorine. The solid catalyst component prepared in the above way is used in a test for the polymerization of ethylene. More specifically, the polymerization is carried out in a 5 litre autoclave containing 2 litres of n-hexane, using 50 mg of the solid catalyst component and 5 mmoles of triisobutyl aluminium as cocatalyst, operating with a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 1.2/l), at a temperature of 85°C and for 1.5 hours. A yield equal to 8.1 kg of polyethylene per gram of solid catalyst component is obtained and the polyethylene has the following characteristics: EXAMPLE 7 The solid catalyst component obtained according to the procedure described in example 6 is used in a further test for the polymerization of ethylene in a 5 litre autoclave, containing 2 litres of n-hexane, using 50 mg of said solid component and 5 mmoles of triisobutyl aluminium as cocatalyst, operating with a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 0.94/l), at a temperature of 80°C, over a period of 4 hours. A yield equal to 12.1 kg of polyethylene per gram of solid catalyst component is obtained and the polyethylene has the following characteristics: EXAMPLE 8 The solid catalyst component obtained according to the procedure described in example 6 is used in a further test for the polymerization of ethylene in a 5 litre autoclave, containing 2 litres of n-hexane, using 50 mg of said solid component and 4 mmoles of trihexyl aluminium as cocatalyst, operating with a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 1.17/l), at a temperature of 85°C, over a period of 2 hours. A yield equal to 9.0 kg of polyethylene per gram of solid catalyst component is obtained and the polyethylene has the following characteristics: EXAMPLE 9 The solid catalyst component obtained according to the procedure described in example 6 is used in a further test for the polymerization of ethylene in a 5 litre autoclave, containing 2 litres of n-hexane, using 50 mg of said solid component and 4 mmoles of trihexyl aluminium as cocatalyst, operating with a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 1/l), at a temperature of 85°C, over a period of 2 hours. A yield equal to 10.5 kg of polyethylene per gram of solid catalyst component is obtained and the polyethylene has the following characteristics: EXAMPLE 10 The solid catalyst component obtained according to the procedure described in example 6 is used in a further test for the polymerization of ethylene in a 5 litre autoclave, containing 2 litres of n-hexane, using 50 mg of said solid component and 5 mmoles of triisobutyl aluminium as cocatalyst, operating with a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 1.8/l), at a temperature of 75°C, over a period of 4 hours. A yield equal to 9.0 kg of polyethylene per gram of solid catalyst component is obtained and the polyethylene has the following characteristics: EXAMPLE 11 A solid catalyst component is prepared according to the procedure described in example 6, with the difference that 4.0 g (12.5 mmoles) of hafnium tetrachloride and 1.4 ml (2.42 g, 12.8 mmoles) of titanium tetrachloride are used. 15.5 g of a solid catalyst component are thus obtained, containing, in addition to the hafnium, 3.6% by weight of titanium (88% in the form of trivalent titanium), 14.6% by weight of magnesium and 56.9% by weight of chlorine. The solid catalyst component prepared in the above way is used in a test for the co-polymerization of ethylene. More specifically, the co-polymerization is carried out in a 5 litre autoclave containing 2 litres of n-hexane and 10 g of butene-1 as comonomer, using 60 mg of the solid catalyst component and 4 mmoles of triisobutyl aluminium as cocatalyst, operating with a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 1.35/l), at a temperature of 85°C, over a period of 1.5 hours. A yield equal to 8.3 kg of ethylene-butene-1 copolymer per gram of solid catalyst component is obtained and the copolymer thus obtained has the following characteristics: EXAMPLE 12 The solid catalyst component obtained according to the procedure described in example 11 is used in a further test for the copolymerization of ethylene in a 5 litre autoclave containing 2 litres of n-hexane and 10 g of butene-1 as comonomer, using 30 mg of said solid component and 4 mmoles of triisobutyl aluminium as cocatalyst, operating with a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 1.54/l), at a temperature of 85°C, over a period of 4 hours. A yield equal to 6.2 kg of ethylene-butene-1 copolymer per gram of solid catalyst component is obtained and the copolymer thus obtained has the following characteristics: EXAMPLE 13 A solid catalyst component is prepared according to the procedure described in example 6, but with the difference that 4.0 g (12.5 mmoles) of hafnium tetrachlorid are used. Thereby 16 g of a solid catalyst component are obtained, containing, in addition to the hafnium, 4.7% by weight of titanium (74.5% in the form of trivalent titanium), 13.7% by weight of magnesium and 56.9% by weight of chlorine. The solid catalyst component prepared in the above way is used in a test for the polymerization of ethylene. More specifically, the polymerization is carried out in a 5 litre autoclave, containing 2 litres of n-hexane, using 50 mg of the solid catalyst component and 5 mmoles of triisobutyl aluminium as cocatalyst, operating with a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 1.26/l), at a temperature of 85°C, over a period of 1.5 hours. A yield equal to 7.4 kg of polyethylene per gram of solid catalyst component is obtained and the polyethylene has the following characteristics: EXAMPLE 14 A solid catalyst component is prepared according to the procedure described in example 6, but with the difference that 16.0 g (50 mmoles) of hafnium tetrachloride are used. 27 g of a solid catalyst component are obtained, containing, in addition to the hafnium, 3.9% by weight of titanium (93.5% in the form of trivalent titanium), 7.8% by weight of magnesium and 50.9% by weight of chlorine. The solid catalyst component prepared in the above way is used in a test for the polymerization of ethylene. More specifically, the polymerization is carried out in a 5 litre autoclave, containing 2 litres of n-hexane, using 50 mg of the solid catalyst component and 4 mmoles of triisobutyl aluminium as cocatalyst, operating with a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 1.11/l), at a temperature of 85°C, over a period of 1.5 hours. A yield equal to 2.7 kg of polyethylene per gram of solid catalyst component is obtained and the polyethylene has the following characteristics: EXAMPLE 15 A solid catalyst component is prepared according to the procedure described in example 6, but with the difference that zirconium tetrachloride (5.8 g, 25 mmoles) is used instead of hafnium tetrachloride. Thereby 19 g of a solid catalyst component are obtained, containing, in addition to the zirconium, 4.9% by weight of titanium (93.0% in the form of trivalent titanium), 11.5% by weight of magnesium and 66.4% by weight of chlorine. The solid catalyst component prepared in the above way is used in a test for the polymerization of ethylene. More specifically, the polymerization is carried out in a 5 litre autoclave, containing 2 litres of n-hexane, using 50 mg of the solid catalyst component and 4 mmoles of triisobutyl aluminium as cocatalyst, operating with a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 1.10/l), at a temperature of 85°C, over a period of 1.5 hours. A yield equal to 8.4 kg of polyethylene per gram of solid catalyst component is obtained and the polyethylene has the following characteristics: EXAMPLE 16 A solid catalyst component is prepared according to the procedure described in example 6, but with the difference that 3.93 g (25 mmoles) of vanadium trichloride are used instead of hafnium tetrachloride. Thereby 23.6 g of a solid catalyst component are obtained, containing 2.8% by weight of titanium, 5.8% by weight of vanadium, 11.1% by weight of magnesium and 47.1% by weight of chlorine. The solid catalyst component prepared in the above way is used in a test for the polymerization of ethylene. More specifically, the polymerization is carried out in a 5 litre autoclave, containing 2 litres of n-hexane, using 50 mg of the solid catalyst component and 5 mmoles of triisobutyl aluminium as cocatalyst, operating with a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 1.46/l), at a temperature of 85°C, over a period of 2 hours. A yield equal to 6.2 kg of polyethylene per gram of solid catalyst component is obtained and the polyethylene has the following characteristics: EXAMPLE 17 114 ml of a 20% by weight solution of butyl octyl magnesium (Mg₁Bu 1.5 Oct 0.5 ) and 6.0 g of a mixture of vanadium trichloride and hafnium tetrachloride (atomic ratio V/Hf equal to 1/l) in n-heptane are charged, in a nitrogen atmosphere, into a 500 ml flask equipped with reflux cooler, mechanical stirrer and thermometer. The mixture of chlorides was previously ground for 4 hours in an argon atmosphere. The resulting suspension is heated to 40°C for 15 minutes and 100 ml (147 g, 864 mmoles) of silicon tetrachloride are then added. The contents of the flask are heated for 1 hour at 77°C. The solid granular precipitate is separated by filtration and thoroughly washed with n-hexane. The washed solid is suspended in 150 ml of n-hexane,and 2.8 ml (4.84 g, 25.5 mmoles) of titanium tetrachloride are added to the suspension. Contact is maintained for 1 hour at 90°C and the suspension is dried by evaporating the solvent at atmospheric pressure. 21 g of a solid catalyst component are thus obtained, containing 3.0% by weight of titanium, 3.1% by weight of vanadium, 12.5% by weight of magnesium and 52.5% by weight of chlorine. The solid catalyst component prepared in the above way is used in a test for the polymerization of ethylene. More specifically, the polymerization is carried out in a 5 litre autoclave, containing 2 litres of n-hexane, using 50 mg of the solid catalyst component and 5 mmoles of trihexyl aluminium as cocatalyst, operating with a total pressure of 15 bar (ratio of hydrogen pressure to ethylene pressure of 1.35/l), at a temperature of 75°C, over a period of 4 hours. A yield equal to 8.4 kg of polyethylene per gram of solid catalyst component is obtained and the polyethylene has the following characteristics: EXAMPLE 18 The solid catalyst component prepared according to the procedure described in example 6 is used in a fluidized bed polymerization reactor. The reactor consists of an 80 cm long steel tube having a diameter of 5 cm and containing a porous metal disk on the bottom to allow the gas to gurgle upwards, through the bed. 5 g of solid catalyst component are suspended in 100 ml of isobutane and 1 ml of this suspension is charged into the reaction vessel. A solution of 50 mmoles of triisobutyl aluminium in 100 ml of isobutane is also prepared, and 10 ml thereof are introduced into the reaction vessel. A 1:1 mixture of ethylene and hydrogen is distributed in the reaction vessel with a calibrated rotameter. An automatic pressure release valve discharges part of the unreacted mixture, which leaves the reaction vessel, in such a way as to keep the pressure of the system constant at 20 bar. The mixture is recycled in the reactor by means of a compressor and is mixed with the fresh feed. The recycling rate is regulated with a flow control valve to obtain an adequate fluidifying and mixing level. The temperature of the reaction vessel is fixed by passing the recycled and fresh flows through both a cooler and a heater, in order to set the temperature at the entrance to the reaction vessel. The cocatalyst solution is pumped by means of a calibrated pump through a coil in a heated bath to allow the complete evaporation of the solution. The vapour flow is then injected into the recycled ethylene-hydrogen mixture. At the beginning of the test, 1 ml of solid catalyst component is injected into the suspension and the flow of the ethylene-hydrogen mixture is started. When the system has become stationary, the cocatalyst is introduced and the polymerization process begins. The duration of the test is 1.5 hours and the polymerization temperature is 75°C. A yield of 10.5 kg of polymer per gram of solid catalyst component is obtained and the polyethylene thus obtained has the following characteristics:

Claims: Claims for the following Contracting States : AT, BE, CH, LI, DE, DK, FR, GB, GR, IT, LU, NL, SE Solid component of a catalyst for the (co)polymerization of ethylene, comprising magnesium, halogen and titanium and obtainable by the steps of (i) dissolving, in an inert, organic solvent, a dialkyl magnesium compound, a silicon halide and, optionally, an alkyl halide, the atomic ratio of silicon to magnesium ranging from 0.5/l to 15/l, and the molar ratio of alkyl halide to silicon halide ranging from 0/l to 10/l, and maintaining the contact between the above compounds until a granular solid precipitates from the solution; (ii) contacting and reacting the above granular solid with a titanium halide, alkoxide and/or halogen-alkoxide, the atomic ratio of magnesium to titanium ranging from 1/1 to 60/l, to prepare a solid catalyst component; and, in case a titanium alkoxide or halogen-alkoxide has been used in step (ii), (iii) activating the solid of step (ii) with alkyl aluminium halide. Catalyst component according to claim 1, wherein in step (i) the silicon halide is selected from silicon chlorides, silicon bromides, chloro silanes, bromo silanes and mixtures thereof, e.g. from silicon tetrachloride, silicon tetrabromide, trichlorosilane, vinyl trichlorosilane, trichloroethoxy silane and chloroethyl trichlorosilane, and preferably is silicon tetrachloride. Catalyst component according to any one of claims 1 and 2, wherein in step (i) the alkyl halide is selected from primary, secondary and/or tertiary C₁-C₂₀ alkyl chlorides and bromides, particularly from ethyl bromide, butyl chloride, hexyl chloride, octyl chloride, cyclohexyl chloride and mixtures thereof. Catalyst component according to any one of claims 1 to 3, wherein in step (i) the dialkyl magnesium compound is selected from those of formula MgR'R'', wherein R' and R'', the same or different, represent linear or branched C₁-C₁₀ alkyl groups, and particularly from diethyl magnesium, ethyl butyl magnesium, dihexyl magnesium, butyl octyl magnesium, dioctyl magnesium and mixtures thereof. Catalyst component according to any one of claims 1 to 4, wherein in step (i) the solvent is selected from hydrocarbons, preferably aliphatic hydrocarbons. Catalyst component according to any one of claims 1 to 5, wherein in step (i) the solution is heated to a temperature of from 40 to 100°C over a period of 0.5 to 5 hours. Catalyst component according to any one of claims 1 to 6, wherein in step (i) the atomic ratio Si/Mg ranges from 1/1 to 9/1 and/or the molar ratio of alkyl halide to silicon halide ranges from 0/1 to 5/1, the solution being heated to a temperature of from 70 to 95°C for 1 to 2 hours. Catalyst component according to any one of claims 1 to 7, wherein in step (i) the solid precipitate is separated from the liquid and is thoroughly washed with an inert liquid solvent, preferably a hydrocarbon solvent. Catalyst component according to any one of claims 1 to 8, wherein in step (ii) the titanium compound is selected from titanium tetrachloride, titanium tetrabromide, titanium tetra-n-propylate, titanium tetra-n-butylate, titanium tetra-i-propylate, titanium tetra-i-butylate, the corresponding titanium mono- and di-chloro alkoxides and mono- and di-bromo alkoxides, and mixtures thereof. Catalyst component according to any one of claims 1 to 9, wherein in step (ii) the granular solid is suspended in an inert organic solvent, at a temperature of from 50 to 100°C over a period of 0.5 to 5 hours. Catalyst component according to any one of claims 1 to 10, wherein in step (ii) the atomic ratio Mg/Ti ranges from 4/1 to 20/1 and the operating temperature ranges from 60 to 90°C for 1 to 2 hours. Catalyst component according to any one of claims 1 to 11, wherein the component obtained at the end of step (ii) is recovered from the corresponding suspension by evaporating the organic solvent at atmospheric or reduced pressure. Catalyst component according to any one of claims 1 to 12, wherein in step (iii) the alkyl aluminium halide is selected from alkyl aluminium chlorides and bromides, particularly from diethyl aluminium chloride and bromide, ethyl aluminium sesquichloride, diisobutyl aluminium chloride and bromide and mixtures thereof, and the activation is carried out with the component suspended in an inert organic solvent, the ratio of halogen atoms in the alkyl aluminium halide to alkoxy groups in the titanium alkoxide and/or halogen alkoxide ranging from 0.1/1 to 10/1, at a temperature ranging from 10 to 100°C, over a period of from 10 minutes to 5 hours. Catalyst component according to any one of claims 1 to 13, wherein at the end of step (iii) the component is recovered from the corresponding suspension by filtration, is washed with hydrocarbon solvent and dried. Catalyst component according to any one of claims 1 to 14, additionally containing at least one metal M selected from vanadium, zirconium and hafnium, the corresponding metal compound(s) having preferably been added to the solution of step (i). Catalyst component according to claim 15, wherein the compound(s) of vanadium, zirconium and hafnium is (are) selected from the corresponding halides, oxyhalides, alkoxides and halogen-alkoxides, particularly from vanadium trichloride and tribromide, zirconium tetrachloride and tetrabromide and hafnium tetrachloride and tetrabromide, as well as mixtures thereof. Catalyst component according to any one of claims 15 and 16, wherein in step (ii) the atomic ratio of magnesium to the sum of titanium and metal(s) M ranges from 1/1 to 30/1, particularly from 1/1 to 9/1, the atomic ratio Ti/M being from 0.1/1 to 2/1, particularly from 0.5/1 to 1/1. Catalyst for the (co)polymerization of ethylene, comprising the solid catalyst component according to any one of claims 1 to 17 and an organometallic compound of aluminium. Process for the (co)polymerization of ethylene, wherein the catalyst according to claim 18 or the solid catalyst component of any one of claims 1 to 17 is employed. Claims for the following Contracting State : ES Process for the (co)polymerization of ethylene, wherein a solid component of a catalyst for the (co)polymerization of ethylene is employed which comprises magnesium, halogen and titanium and obtainable by the steps of (i) dissolving, in an inert, organic solvent, a dialkyl magnesium-compound, a silicon halide and, optionally, an alkyl halide, the atomic ratio of silicon to magnesium ranging from 0.5/1 to 15/1, and the molar ratio of alkyl halide to silicon halide ranging from 0/1 to 10/1, and maintaining the contact between the above compounds until a granular solid precipitates from the solution; (ii) contacting and reacting the above granular solid with a titanium halide, alkoxide and/or halogenalkoxide, the atomic ratio of magnesium to titanium ranging from 1/1 to 60/1, to prepare a solid catalyst component; and, in case a titanium alkoxide or halogenalkoxide has been used in step (ii), (iii) activating the solid of step (ii) with alkyl aluminium halide. Process according to claim 1, wherein in step (i) the silicon halide is selected from silicon chlorides, silicon bromides, chloro silanes, bromo silanes and mixtures thereof, e.g. from silicon tetrachloride, silicon tetrabromide, trichlorosilane, vinyl trichlorosilane, trichloroethoxy silane and chloroethyl trichlorosilane, and preferably is silicon tetrachloride. Process according to any one of claims 1 and 2, wherein in step (i) the alkyl halide is selected from primary, secondary and/or tertiary C₁-C₂₀ alkyl chlorides and bromides, particularly from ethyl bromide, butyl chloride, hexyl chloride, octyl chloride, cyclohexyl chloride and mixtures thereof. Process according to any one of claims 1 to 3, wherein in step (i) the dialkyl magnesium compound is selected from those of formula MgR'R'', wherein R' and R'', the same or different, represent linear or branched C₁-C₁₀ alkyl groups, and particularly from diethyl magnesium, ethyl butyl magnesium, dihexyl magnesium, butyl octyl magnesium, dioctyl magnesium and mixtures thereof. Process according to any one of claims 1 to 4, wherein in step (i) the solvent is selected from hydrocarbons, preferably aliphatic hydrocarbons. Process according to any one of claims 1 to 5, wherein in step (i) the solution is heated to a temperature of from 40 to 100°C over a period of 0.5 to 5 hours. Process according to any one of claims 1 to 6, wherein in step (i) the atomic ratio Si/Mg ranges from 1/1 to 9/1 and/or the molar ratio of alkyl halide to silicon halide ranges from 0/1 to 5/1, the solution being heated to a temperature of from 70 to 95°C for 1 to 2 hours. Prcoess according to any one of claims 1 to 7, wherein in step (i) the solid precipitate is separated from the liquid and is thoroughly washed with an inert liquid solvent, preferably a hydrocarbon solvent. Process according to any one of claims 1 to 8, wherein in step (ii) the titanium compound is selected from titanium tetrachloride, titanium tetrabromide, titanium tetra-n-propylate, titanium tetra-n-butylate, titanium tetra-i-propylate, titanium tetra-i-butylate, the corresponding titanium mono- and di-chloro alkoxides and mono- and di-bromo alkoxides, and mixtures thereof. Process according to any one of claims 1 to 9, wherein in step (ii) the granular solid is suspended in an inert organic solvent, at a temperature of from 50 to 100°C over a period of 0.5 to 5 hours. Process according to any one of claims 1 to 10, wherein in step (ii) the atomic ratio Mg/Ti ranges from 4/1 to 20/1 and the operating temperature ranges from 60 to 90°C for 1 to 2 hours. Process according to any one of claims 1 to 11, wherein the component obtained at the end of step (ii) is recovered from the corresponding suspension by evaporating the organic solvent at atmospheric or reduced pressure. Process according to any one of claims 1 to 12, wherein in step (iii) the alkyl aluminium halide is selected from alkyl aluminium chlorides and bromides, particularly from diethyl aluminium chloride and bromide, ethyl aluminium sesquichloride, diisobutyl aluminium chloride and bromide and mixtures thereof, and the activation is carried out with the component suspended in an inert organic solvent, the ratio of halogen atoms in the alkyl aluminium halide to alkoxy groups in the titanium alkoxide and/or halogen alkoxide ranging from 0.1/1 to 10/1, at a temperature ranging from 10 to 100°C, over a period of from 10 minutes to 5 hours. Process according to any one of claims 1 to 13, wherein at the end of step (iii) the component is recovered from the corresponding suspension by filtration, is washed with hydrocarbon solvent and dried. Process according to any one of claims 1 to 14, additionally containing at least one metal M selected from vanadium, zirconium and hafnium, the corresponding metal compound(s) having preferably been added to the solution of step (i). Process according to claim 15, wherein the compound(s) of vanadium, zirconium and hafnium is (are) selected from the corresponding halides, oxyhalides, alkoxides and halogen-alkoxides, particularly from vanadium trichloride and tribromide, zirconium tetrachloride and tetrabromide and hafnium tetrachloride and tetrabromide, as well as mixtures thereof. Process according to any one of claims 15 and 16, wherein in step (ii) the atomic ratio of magnesium to the sum of titanium and metal(s) M ranges from 1/1 to 30/1, particularly from 1/1 to 9/1, the atomic ratio Ti/M being from 0.1/1 to 2/1, particularly form 0.5/1 to 1/1. Process for the (co)polymerization of ethylene, wherein a catalyst for the (co)polymerization of ethylene is employed comprising the solid catalyst component according to any one of claims 1 to 17 and an organometallic compound of aluminium. Solid component of a catalyst for the (co)polymerization of ethylene according to any one of claims 1 - 17. Catalyst for the (co)polymerization of ethylene comprising the solid catalyst component according to claim 19 and an organometallic compound of aluminium.

Inventors: BORGHI ITALO, INVERNIZZI RENZO, LUCIANI LUCIANO, MILANI FEDERICO, PONDRELLI MADDALENA, BORGHI, ITALO, INVERNIZZI, RENZO, LUCIANI, LUCIANO, MILANI, FEDERICO, PONDRELLI, MADDALENA
Applicants: ENICHEM SPA, ENICHEM S.P.A.
Application year: 1991
Main classification: C08F10
IPC codes: C08F10, C08F4, B01J31