CATALYSTS FOR THE POLYMERIZATION OF OLEFINS

Abstract: Catalysts for the polymerization of alpha-olefins comprising the reaction product of: a) an Al-alkyl compound; b) a silicon compound containing at least one Si-OR¹ or Si-OCOR¹ or Si-NR bond, R being a hydrocarbyl radical); and c) a solid product consisting of as essential component at least an anhydrous Mg-dihalide in active form, said solid product being obtainable by reacting a Ti-halide with an aduct of Mg-dihalide with an alcohol.

Description: The present invention relates to catalysts for the polymerization of α-olefins. The supported highly active and highly stereospecific catalysts up to now known for the polymerization of propylene and higher olefins, are obtained by the reaction of an Al-alkyl compound partially complexed with an electron donor compound (outside donor) with a solid component comprising a Ti compound and an electron-donor compound (inside donor) supported on a Mg-halide in active form. Examples of such catalysts have been described in British Patent No. 1,559,194 and Belgian Patent No. 868,682. The above supported catalysts need the use of an inside donor in order to obtain polymers having a high isotactic index. If the inside donor is omitted polymers having low isotactic index are obtained. It has now unexpectedly been found that it is possible to obtain with high yield polymers of alpha olefins having a high isotactic index by using Ti-containing Mg dihalides-supported catalysts free from inside electron donor compounds obtained by a method comprising the reaction of a Ti-halide with an adduct of Mg dihalide with an alcohol, if an outside donor is used which is a silicon compound containing Si-OR, Si-OCOR or Si-NR₂ bonds. The above results are surprising if one considers that catalysts are known which are prepared by using both as inside and outside donor a silicon compound containing Si-O-C bonds and which do not offer a performance in terms of activity and stereospecificity better than the one obtainable with catalysts in which an ester of benzoic acid is used as inside and outside donor. The rather poor performance of the above prior art catalysts is due to the fact that the Si-containing inside donor is substantially removed from the Ti- containing supported component as result of the method of preparation of said component. The catalysts of this invention are obtainable by reacting a) an organoaluminium compound, b) an electron-donor compound and c) a solid component comprising a Ti-compound supported on a Mg-dihalide in active form, whereby a) the organo aluminium compound is an Al-trialkyl or an Al-alkyl compound containing 2 or more Al atoms linked together via an oxygen or nitrogen atom or via SO₄ or SO₃ groups; b) the electron-donor compound is a silicon compound containing one or more Si-OR¹, Si-OCOR¹ or Si-NR¹₂ (R¹ being a hydrocarbyl radical); and c) the solid component essentially consists of a Ti-compound which is obtainable by reaction of a Ti-halide with an adduct of a Mg-dihalide with an alcohol and which is supported on at least one anhydrous Mg dihalide in active form wherein the anhydrous Mg-dihalide in active form is a Mg-dihalide showing in the X-ray powder spectrum of component c) a broadening of at least 30 % of the most intense diffraction line which appears in the powder spectrum of the corresponding dihalide having 1 m²/g of surface area or a Mg-dihalide showing an X-ray powder spectrum in which said most intense diffraction line is replaced by a halo with the intensity peak shifted with respect to the interplanar distance of the most intense line, and/or a Mg-dihalide having a surface area, measured after treatment of component c) with boiling TiCl₄ for 2 hours, greater than 3 m²/g. The found value in the measurement of the surface area of the Mg dihalides made on component c) after treatment with boiling TiCl₄ for 2 hours is considered as surface area for the Mg dihalide. Very active forms of Mg dihalides are those showing a X-ray powder spectrum in which the most intense diffraction line appearing in the spectrum of the corresponding halide having 1 m²/g of surface area is decreased in relative intensity and broadened to form a halo or are those in which said most intense line is replaced by a halo having its intensity peak shifted with respect to the interplanar distance of the most intense line. Generally the surface area of the above forms is higher than 30-40 m²/g and is comprised in particular between 100-300 m²/g. Active forms are also those deriving from the above forms by heat-treatment in inert hydrocarbon solvents and showing in the X-ray spectrum sharp diffraction lines in place of the halos. The sharp, most intense line of these forms shows a broadening of at least 30% with respect to the corresponding line of the Mg dihalide having 1 m²/g of surface area. Preferred Mg dihalides are Mg dichloride and Mg dibromide. The content in water of the dihalides is generally less than 1% by weight. "Ti halides supported on the active Mg dihalide" means that the above compounds may be chemically or physically fixed on the support and are not extractable from component c) by treatment of the same with boiling 1,2-dichloroethane for 2 hours. Components a), b) and c) may be reacted with each other in any order; preferably, however, components a) and b) are premixed before being contacted with component c). The pre-mixing of a) and b) is conducted at temperatures comprised, usually, between room temperature and the temperature used in the polymerization process. The pre-reaction of c) and b) may be carried out also at higher temperatures. Compound b) may be also incorporated and made to react with component c) itself. Component b) is made to react in a molar ratio with respect to the halogenated Ti compound supported on component c) of at least 1 and in a molar ratio with respect the Al-alkyl compound used as component a) of less than 20 and preferably comprised between 0.05 to 0.3. In component c) the molar ratio between the Mg dihalide and the halogenated Ti compound supported thereon is comprised between 1 and 500 and the molar ratio between said halogenated Ti compound and the electron-donor supported on the Mg dihalide is comprised between 0.1 and 50. The silicon compounds set forth in b) include compounds of general formula: R m SiY n X p wherein: R is an alkyl, alkenyl, aryl, arylalkyl, cycloalkyl radical with from 1 to 20 carbon atoms; Y is a -OR', -OCOR', -NR₂' wherein R', either equal to or different from R, has the same meaning as R; X is either a halogen or hydrogen atom or a -OCOR", -NR₂" group wherein R", either equal to or different from R', has the same meaning as R'; m, n and p are numbers comprised respectively between: m between 0 and 3, n between 1 and 4 and p between 0 and 1; and m+n+p is equal to 4. Other silicon compounds that may be used are compounds in which two or more silicon atoms are bound to each other through oxygen or nitrogen atoms. Examples of these compounds are hexaethoxydisiloxane, symmetrical diphenyltetraethoxydisiloxane Preferred silicon compounds are: phenylalkoxysilanes as phenyltriethoxy or trimethoxysilane, diphenyldimethoxy and diethoxysilane, monochlorophenyldiethoxysilane; alkylalkoxysilanes as ethyltriethoxysilane, ethyltriisopropoxysilane. Examples of other suitable compounds are: chlorotriethoxysilane, acetoxytriethoxysilane, vinyltriethoxysilane, butyltriethoxysilane, triphenylmonoethoxysilane, phenyltricycloethoxysilane, phenyldiethoxydiethylaminosilane, tetraphenoxysilane or tetralkoxysilanes as tetramethoxysilane. The silicon compound can also be formed.. in situ by reaction for instance of a halogenated silicon compound as SiCl₄ with an alcohol or an alcoholate of Mg or Al. In the catalysts of the invention the silicon compound is present in a combined form in the solid product of the reaction between the various catalyst- forming components, in a molar ratio between the silicon compound and the halogenated Ti compound greater than 0.05 and generally comprised between 0.1 and 5. The Al-alkyl compounds forming component a) includes Al-trialkyls as for instance Al-triethyl, Al-triisobutyl, Al-triisopropyl and compounds containing two or more Al atoms linked to each other through etero-atoms as: As indicated Al-alkyl compounds in which Al atoms are linked through groups as SO₄ or SO₃ are also suitable. The Al-alkyl compounds may be used in mixture with Al-alkyl halides as AlEt₂Cl. Component c) free from inside donors is prepared by methods comprising the reaction of an adduct between a Mg dihalide and an alcohol with TiCl₄. The reactions are described in Belgian patent 868,682 and DE-A-3,022,738. In the above method the final product contains a Mg dihalide, present in the active form as set forth here above. Other known methods which lead to the formation of Mg dihalide in active form or to Ti- containing Mg dihalide supported components, in which the dihalide is present in active form, are based on the following reactions: reaction of a Grignard reagent or a Mg R₂ compound (R being a hydrocarbyl radical) or complexes of said Mg R₂ compounds with Al-trialkyls, with halogenating agents as AlX₃ or Al R m X n compounds (X is halogen, R is a hydrocarbyl m+n = 3), SiCl₄ or HSiCl₃; reaction of a Grignard reagent with a silanol or polysiloxane, H₂O or with an alcohol and further reaction with a halogenating agent or with TiCl₄; reaction of Mg with an alcohol and a hydrogen halide or of Mg with a hydrocarbyl halide and an alcohol; reaction of MgO with Cl₂ or AlCl₃; reaction of MgX₂.nH₂O (X = halogen) with a halogenating agent or TiCl₄; reaction of Mg mono or dialcoholates or Mg carboxylates with a halogenating agent. The Ti-halides include in particular the Ti-tetrahalides and Ti-trihalides. Preferred compounds are: TiCl₄ and TiBr₄. The Ti-trihalides are obtained according to known methods, for instance by reduction of TiCl₄ with Al or a metallorganic Al compound or with hydrogen. In case of the Ti-trihalides it may be convenient for the purpose of improving the performance of the catalysts to carry out an oxidization, even partial, of the titanium, either during or after the preparation of component c). To this purpose there may be used halogens, iodine halides. Component a) is preferably an Al-trialkyl, such as Al-triethyl or Al-triisobutyl. The catalysts according to the invention are used to polymerize alpha-olefins CH₂=CHR in which R is an alkyl radical with 1 to 4 carbon atoms or an aryl radical and mixtures of said olefins with ethylene. The polymerization is carried out according to known methods that is, in liquid phase, either in the presence or absence of an inert hydrocarbon solvent, or in gas phase or also by combining, for instance, a liquid phase polymerization step with a step in gas phase. In general the temperature is comprised between 40° and 160°C, but preferably between 60° and 90°C, operating either at atmospheric or at greater than atmospheric pressure. As a molecular weight regulator hydrogen or other regulators of a known type are used. The catalysts are particularly suitable for polymerizing propylene, butene-1, styrene, 4-methylpentene. The catalysts may also be used according known methods to polymerize mixtures of propylene and ethylene to form modified polypropylenes having better shock-resistance at low temperatures (the so called block copolymers of propylene and ethylene) or to obtain random crystalline copolymers of propylene with minor proportions of ethylene. The following examples are given for merely illustrative purpose and are not intended to be in any way limiting the scope of the invention. EXAMPLE 1 Into an inox steel autoclave of 2000 ml holding capacity, equipped with a magnetical stirrer and a thermometer, heat stabilized at 60°C and kept under pressure by a nitrogen atmosphere, there were introduced 5 m moles of triethylaluminum, 1.5 m mols of phenyltriethoxysilane, the solid catalytic component obtained by reacting TiCl₄ with MgCl₂.2,3 C₂H₅OH, operating under the same conditions as described in Example 1 of Belgian Pat. No. 868,682 and 700 ml of degassed and anhydrous n-heptane, while propylene was also fed in. The catalytic component thus prepared showed a X-ray powder spectrum in which the most intense diffraction line appearing in the spectrum of MgCl₂ having 1 m²/g of surface area was decreased in relative intensity and broadened to form a halo. Thereupon there was fed in 0.2 atm of hydrogen and then the whole was rapidly heated up to 70°C, while contemporaneously additional propylene was fed in to reach a total pressure of 7 atm. This latter pressure was maintained constant over the whole polymerization be feeding in the monomer. After 4 hours the polymerization was interrupted, the polymer was isolated by filtering and then was dried. The quantity of polymer dissolved in the filtrate was thereupon isolated, weighed and summed to the polymer soluble in boiling n-heptane, for the calculation of the isotacticity index. The quantity of the catalytic component used and the content of Ti in said component, the yield in polymer with respect to the introduced Ti, the isotacticity index (I.I.) and the inherent viscosity determined in tetralin at 35°C, are reported in Table I. Comparative EXAMPLE 1 Example 1 was repeated but using a solid catalytic component prepared as follows. Anhydrous MgCl₂, phenyltriethoxysilane in molar ratio Mg/Si of 6, and TiCl₄ in molar ratio of 1:1 with respect to the phenyltriethoxysilane were co-milled in a vibrating mill of the type VIBRATOM manufactured by N.V. TEMA'S, Gravenhage (Holland), having a total volume of one liter and containing 3 kg of stainless steel balls of 16 mm diameter. Grinding was effected employing a filling coefficient equal to 100 g/l of total volume (vacuum), at an interior temperature of the mill of 25°C, and with a grinding time of 72 hours. Charging of the mill with the materials to be ground, the grinding and discharging of the product from the mill occurred in a nitrogen atmosphere. 10 g of the co-ground product was contacted with 100 ml of 1,2-dichloroethane at 80°C for 2 hours. After this period, 1,2-dichloroethane was removed by filtration at 80°C and the residual solid product was repeatedly washed with n-heptane at room temperature till the disappearance of the chloride ions from the filtrate and then was kept in suspension in heptane. The catalytic components thus prepared showed a X-ray powder spectrum in which the most intense diffraction line appearing in the spectrum of MgCl₂ having 1 m²/g of surface area was decreased in relative intensity and broadened to form a halo. The characteristics of the solid catalytic component, and the results of polymerization test have been reported in Table I. Comparative EXAMPLE 2 62 g of MgCl₂ and 12.5 g of TiCl₄ were introduced in the mill described in Comparative Example 1 and co-milled for 60 hours at room temperature. The content of Titanium was of 3.9% by weight. 10 g of the co-ground product were contacted with 100 ml of 1,2 dichloroethane at 80°C for 2 hours. The solid was separated by filtering and then was washed with heptane at said temperature until the disappearance of the chloride ions from the filtrate. The X-ray powder spectrum was similar to that of catalytic component of Example 1. The solid catalytic component obtained was used in the polymerization of propylene under the same polymerization conditions described in Example 1. The results of the polymerization have been reported in Table I. Comparative EXAMPLE 3 40 g of MgCl₂ was milled in the mill described in Comparative Example 1 for 200 hours at room temperature. 10 g of the ground product were treated with 150 ml of TiCl₄ for 2 hours at 135°C. After hot filtering, the treatment with TiCl₄ was repeated. After washing with heptane at 80°C and drying, the dry solid was used under the same polymerization conditions described in Example 1. The solid catalytic component showed a X-ray powder spectrum similar to that of the catalytic component of Example 1. The results of the polymerization have been reported in Table I. Comparative EXAMPLE 4 200 mg of the solid catalytic component prepared according to Comparative Example 3 were used in the polymerization of propylene under the same conditions described in Example 1 but using ethyl p-toluate instead of PES. The result of the polymerization have been reported in Table I. Comparative EXAMPLE 5 Comparative Example 4 was repeated but using the solid catalytic component prepared according to Comparative Example 2. The results of the polymerization test have been recorded in Table I.

Claims: Claims for the following Contracting States : BE, CH, DE, FR, GB, IT, LI, NL, SE Catalysts for the polymerization of alpha-olefins obtainable by reacting a) an organoaluminium compound, b) an electron-donor compound and c) a solid component comprising a Ti-compound supported on a Mg-dihalide in active from, characterized in that a) the organo aluminium compound is an Al-trialkyl or an Al-alkyl compound containing 2 or more Al atoms linked together via an oxygen or nitrogen atom or via SO₄ or SO₃ groups; b) the electron-donor compound is a silicon compound containing one or more Si-OR¹, Si-OCOR¹ or Si-NR¹₂ (R¹ being a hydrocarbyl radical); and c) the solid component essentially consists of a Ti-compound which is obtainable by reaction of a Ti-halide with an adduct of a Mg-dihalide with an alcohol and which is supported on at least one anhydrous Mg dihalide in active form wherein the anhydrous Mg-dihalide in active form is a Mg-dihalide showing in the X-ray powder spectrum of component c) a broadening of at least 30 % of the most intense diffraction line which appears in the powder spectrum of the corresponding dihalide having 1 m²/g of surface area or a Mg-dihalide showing an X-ray powder spectrum in which said most intense diffraction line is replaced by a halo with the intensity peak shifted with respect to the interplanar distance of the most intense line, and/or a Mg-dihalide having a surface area, measured after treatment of component c) with boiling TiCl₄ for 2 hours, greater than 3 m²/g. Catalysts as defined in claim 1, characterized in that the anhydrous Mg-dihalide of the solid component c) is Mg-dichloride or Mg-dibromide. Catalysts as defined in claim 1 characterized in that the Ti-halide of the solid component c) is a Ti-tetrahalide. Catalyst as defined in one of claims 1 to 3 characterized in that the surface area of the active Mg-dihalide is between 100 and 300 m²/g. The use of a solid component c) as defined in one of claims 1 to 4 for the preparation of a catalyst according to claim 1. A process for the polymerization of alpha-olefins CH₂=CHR in which R is an alkyl radical with 1 to 4 carbon atoms or an aryl radical and mixtures of said olefins with ethylene, characterized in that the polymerization process is carried out in liquid phase in presence or not of an inert hydrocarbon solvent or in gas phase by employing a catalyst as defined in one of claims 1 to 4. Claim for the following Contracting State : AT A process for preparing catalysts for the polymerization of alpha-olefins by reacting a) an organoaluminium compound, b) an electron-donor compound and c) a solid component comprising a Ti-compound supported on a Mg-dihalide in active form, characterized in that a) the organo aluminium compound is an Al-trialkyl or an Al-alkyl compound containing 2 or more Al atoms linked together via an oxygen or nitrogen atom or via SO₄ or SO₃ groups; b) the electron-donor compound is a silicon compound containing one or more Si-OR¹, Si-OCOR¹ or Si-NR¹₂ (R¹ being a hydrocarbyl radical); and c) the solid component essentially consists of a Ti-compound which is obtainable by reaction of a Ti-halide with an adduct of a Mg-dihalide with an alcohol and which is supported on at least one anhydrous Mg dihalide in active form wherein the anhydrous Mg-dihalide in active form is a Mg-dihalide showing in the X-ray powder spectrum of component c) a broadening of at least 30 % of the most intense diffraction line which appears in the powder spectrum of the corresponding dihalide having 1 m²/g of surface area or a Mg-dihalide showing an X-ray powder spectrum in which said most intense diffraction line is replaced by a halo with the intensity peak shifted with respect to the interplanar distance of the most intense line, and/or a Mg-dihalide having a surface area, measured after treatment of component c) with boiling TiCl₄ for 2 hours, greater than 3 m²/g. The process of claim 1, characterized in that the anhydrous Mg-dihalide of the solid component c) is Mg-dichloride or Mg-dibromide. The process of claim 1 characterized in that the Ti-halide of the solid component c) is a Ti-tetrahalide. The process of any one of claims 1 to 3 characterized in that the surface area of the active Mg-dihalide is between 100 and 300 m²/g. The use of a solid component c) as defined in one of claims 1 to 4 for the preparation of a catalyst according to claim 1. A process for the polymerization of alpha-olefins CH₂=CHR in which R is an alkyl radical with 1 to 4 carbon atoms or an aryl radical and mixtures of said olefins with ethylene, characterized in that the polymerization process is carried out in liquid phase in presence or not of an inert hydrocarbon solvent or in gas phase by employing a catalyst prepared according to one of claims 1 to 4.

Inventors: BARBE, PIER CAMILLO, GIANNINI, UMBERTO, DR., NOCCI, ROBERTO, PARODI, SANDRO, SCATA, UMBERTO
Applicants: MONTEDISON S.P.A.
Application year: 1981
Main classification: C08F10
IPC codes: C08F4, B01J31, C08F110, C08F10