CATALYST SYSTEM AND PROCESS FOR PRODUCING ALPHA-OLEFIN POLYMER

Abstract: A process for producing an α-olefin polymer which comprises polymerizing an α-olefin in the presence of a catalyst system comprising (A) a solid catalyst component containing at least titanium, magnesium, halogen, and an electron donor and (B) a sterically hindered aluminum amide compound represented by the general formula wherein, R¹ through R⁵ denote each a hydrocarbon group of to 20 carbon atoms, L denotes an alkoxy group of 1 to 20 carbon atoms and/or halogen, ℓ is 2 or 3, x is defined by 0 < x < 1, y is defined by 0 ≦ y < 3, and z is defined by 0 < z < 3 with the proviso that x + y + z = 3.

Description: The present invention relates to a catalyst system and a process for producing an α-olefin polymer and more particularly to a process for producing an α-olefin polymer in the presence of a novel catalyst system having a very high catalytic activity per unit weight of solid catalyst component as well as per unit gram atom of titanium. The produced α-olefin polymer contains extremely decreased amounts of catalyst residue and of amorphous polymer and is superior in mechanical properties and processability. It is well known to use generally the so-called Ziegler-Natta catalyst that comprises a transition metal compound, said metal being selected from the metals belonging to the group IV-VI of the periodic table, and an organometallic compound, said metal being selected from the metals belonging to the group I-III of the periodic table, in processes for producing polymers of α-olefins including propylene and butene-1. In particular, titanium trichloride catalysts are used extensively for the industrial productions of α-olefin polymers. However, any of these processes produces incidentally an amorphous polymer besides a high-stereoregular α-olefin polymer of high industrial utility value. The amorphous polymer is limited in industrial utility value and has adverse effects on mechanical properties of the films, fibers, and other processed articles of the α-olefin polymer when contained therein. In addition, the formation of the amorphous polymer causes a loss of raw material monomer and simultaneously makes a facility indispensable which is necessary to remove the amorphous polymer, thus bringing about very great disadvantages from the industrial point of view. Accordingly, if such an amorphous polymer is not formed at all or is formed in a slightest amount, it will be a very great benefit. On the other hand, the α-olefin polymer obtained from such a polymerization process as stated above contains a catalyst residue, which raises problems in various respects such as the stability and processability of the α-olefin polymer and hence necessitates a facility for removing the catalyst residue and for stabilizing the polymer. This drawback can be offset by increasing the catalytic activity represented by the weight of α-olefin polymer produced per a unit weight of catalyst. If this catalytic activity can be increased sufficiently, the facility to remove the catalyst residue will become unnecessary and the cost required for producing the α-olefin polymer will be reduced. The present inventors previously proposed a process for producing an α-olefin polymer in the presence of a catalyst system comprising a solid catalyst component which contains at least titanium, magnesium, halogen, and an electron donor, that is, a process employing a catalyst system consisting of (i) a solid obtained by reducing a titanium compound represented by the general formula Ti(OR⁶) n X 4-n , with an organomagnesium compound and treating the resulting solid with an ester compound and then with a mixture of an ether compound and titanium tetrachloride, (ii) an organoaluminum compound, and (iii) a silicic ester compound (JP-A-61-218606). This process provides a highly stereoregular α-olefin polymer but has drawbacks in that the catalytic activity during polymerization lowers to a large extent and that the polymerization process is complicated since the catalyst system is composed of three components. For the purpose of improving the stereoregularity of α-olefin polymers, there are disclosed processes employing each a catalyst system which comprises a third component in addition to a solid catalyst component containing titanium, magnesium, halogen, an electron donor and an organoaluminum co-catalyst, said third component comprising a sterically hindered amine having very weak reactivity on the organoaluminum (JP-A-55-127408, JP-A-58-138707, and JP-A-59-206407). According to these processes, however, the α-olefin polymer obtained still does not have a stereoregularity adequate to give satisfaction and also the catalytic activity is not sufficient to omit the operation step of removing the catalyst residue. Moreover, these processes have the drawback of being complicated in polymerization process since the catalyst system comprises three components. On the other hand, processes for α-olefin polymerization are disclosed wherein two-component catalyst systems are used which consist each of an aluminum amide compound co-catalyst and a solid catalyst component containing titanium, magnesium, halogen, and an electron donor. According to an example of these processes, an α-olefin is polymerized in the presence of a two-component catalyst system comprising (i) a solid catalyst component composed of a transition metal halide such as TiCl₄ · TiCl₃ supported by stratified crystals of MgCl₂ or the like and (ii) a metal amide compound represented by R′₂YNR″₂ wherein, R′ is a C₁-C₂₀ alkyl group, R″ is a bulky C₅-C₂₀ alkyl group or forms, jointly with the neighboring nitrogen atom, a sterically hindered cyclic amino group, and Y is Al, In, or Ga (JP-A-55-127406). According to these processes, however, the catalyst system does not have such a high activity as to permit omitting the step of removing the catalyst residue, though a high-stereoregularity α-olefin polymer can be obtained. Under such circumstances as stated above, the problems to solve according to the present invention, in other words, an object of the present invention is to provide a process for producing an α-olefin polymer in the presence of a catalyst system which exhibits such a high activity and a stereospecificity that the removal of catalyst residue and amorphous polymer may be unnecessary. The present invention involves a process for producing an α-olefin polymer in the presence of a catalyst system which comprises (A) a solid catalyst component containing at least titanium, magnesium, halogen, and an electron donor, which is obtained by (i) reducing a titanium compound represented by the general formula Ti(OR⁶) n X 4-n wherein R⁶ denotes a hydrocarbon group of 1 to 20 carbon atoms, X denotes halogen, and n is a number defined by 0 < n ≦ 4, with an organomagnesium compound in the presence of an organosilicone compound having one or more Si-O bonds, and (ii) treating the resulting solid product with an ester compoud and a mixture of an ether compound and titanium tetrachloride, and (B) a sterically hindered aluminum amide compound represented by the general formula wherein, R¹ through R⁵ denote each a hydrocarbyl group of 1 to 20 carbon atoms, L denotes an alkoxy group of 1 to 20 carbon atoms and/or halogen, ℓ is 2 or 3, x is defined by 0 < x < 1, y is defined by 0 ≦ y < 3, and z is defined by 0 < z < 3 with the proviso that x + y + z = 3. The above and other objects can be achieved by using the present catalyst system. Fig. 1 is a flow chart for facilitating the understanding of the present invention. This flow chart shows a typical embodiment of the invention without implying any restriction on the invention. Hereinfafer the present invention is described in detail. (A) Solid catalyst component Description is given below on the solid catalyst component, used in the present invention, which contains at least titanium, magnesium, halogen, and an electron donor. (a) Titanium compound The titanium compound used in the present invention is represented by the general formula Ti(OR⁶) n X 4-n (R⁶ is a hydrocarbon group of 1 to 20 carbon atoms, X is halogen, and n is a number defined by 0 < n ≦ 4). Examples of R⁶ include alkyl groups such as methyl, ethyl, isopropyl, and heptyl and aryl groups such as phenyl, xylyl, and naphthyl. Of these groups, preferred are linear alkyl groups of 2 to 18 carbon atoms. Of halogen atoms represented by X, chlorine gives favorable results in particular. The value of n is defined by 0 < n ≦ 4, preferably 2 ≦ n ≦ 4, particularly preferably n = 4. (b) Organic silicon compound having an Si-O bond The organic silicon compound having an Si-O bond used in the present invention is represented by the general formula Si(OR⁹) m R¹⁰ 4-m , R¹¹(R¹²₂SiO) p SiR¹³₃, or (R¹⁴₂SiO) q wherein, R⁹ is a hydrocarbon group of 1 to 20 carbon atoms, R¹⁰, R¹¹, R¹², R¹³, and R¹⁴ are each a hydrocarbon group of 1 to 20 carbon atoms or hydrogen, m is a number defined by 0 < m ≦ 4, p is an integer of 1 to 1000, and q is an integer of 2 to 1000. Examples of the organic silicon compound are tetramethoxysilane, dimethyldimethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dibutoxydibutylsilane, hexamethyldisiloxane, diphenylpolysiloxane and methylhydropolysiloxane. Of these compounds, preferred are alkoxysilane compounds represented by the general formula Si(OR⁹) m R¹⁰ 4-m , wherein 1 ≦ m ≦ 4 is preferred and m = 4 is particularly preferred. (c) Organomagnesium compound Preferred organomagnesium compounds for use in the present invention are Grignard compounds represented by the general formula R¹⁵MgX (R¹⁵ is a hydrocarbon group of 1 to 20 carbon atoms and X is halogen) and dialkylmagnesium compounds or diarylmagnesium compounds represented by the general formula R¹⁶R¹⁷Mg (R¹⁶ and R¹⁷ are each a hydrocarbon group of 1 to 20 carbon atoms). More specifically, the above R¹⁵, R¹⁶, and R¹⁷ are the same or different and may denote each alkyl, aryl, aralkyl, or alkenyl of 1 to 20 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, amyl, isoamyl, hexyl octyl, 2-ethylhexyl, phenyl, or benzyl. Examples of the Grignard compounds include methylmagnesium chloride, ethylmagnesium chloride, ethylmagnesium bromide, isoamylmangesium chloride, phenylmagnesium chloride, and phenylmagnesium bromide. Examples of the compounds represented by R¹⁶R¹⁷Mg include diethylmagnesium, dipropylmagnesium, diisopropylmagnesium, diamylmagnesium and diphenylmagnesium. Suitable solvents for use in the preparation of the above organomagnesium compound include ethers such as diethyl ether and dipropyl ether. It is also possible to use a hydrocarbon such as hexane, heptane, cyclohexane, toluene, or xylene or a mixture of the above ether and hydrocarbon. In view of the catalyst efficiency, it is favorable in particular to use the Grignard compound represented by R¹⁵MgCl in the form of ether solution. (d) Ester compound Suitable ester compounds for use in the preparation of solid catalyst component (A) are monovalent or multivalent carboxylic esters including aliphatic carboxylic esters, olefincarboxylic esters, alicyclic carboxylic esters, and aromatic carboxylic esters. Examples of the suitable ester compounds are methyl acetate, ethyl acetate, phenyl acetate, ethyl benzoate, ethyl anisate, diethyl malonate, dimethyl maleate, methyl methacrylate, diisobutyl phthalate, octyl phthalate, and diphenyl phthalate. Of these ester compounds, preferred are olefincarboxylic esters such as methacrylic esters, maleic esters and aromatic carboxylic esters such as benzoic esters and particularly preferred are phthalic esters. (e) Ether compound Suitable ethers for use in the preparation of the solid catalyst component (A) are dialkyl ethers including diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, diamyl ether, and diisoamyl ether. Of these ethers, preferred are dibutyl ether and diisoamyl ether. (f) Preparation of solid catalyst component (A) The solid catalyst component (A) of the present invention is prepared by reducing a titanium compound with an organomagnesium compound in the presence of an organic silicon compound, and treating the solid product obtained by reduction with an ester compound and a mixture of the ether compound and titanium tetrachloride. Preferably, the solid product obtained by reduction is treated with the ester compound and thereafter with a mixture of the ether compound and titanium tetrachloride. The method of reduction of the titanium compound with the organomagnesium may be conducted either by adding the organomagnesium compound to a mixture of the titanium compound and the organic silicon compound or on the contrary by adding a mixture of the titanium compound and the organic silicon compound to a solution of the organomagnesium compound. The former order of addition is preferably from the viewpoint of catalytic activity. It is preferable to use the titanium compound and the organic silicon compound with them dissolved or diluted with a suitable solvent. Such solvents include; aliphatic hydrocarbons, e.g. hexane, heptane, octane, and decane; aromatic hydrocarbons, e.g. toluene and xylene; alicyclic hydrocarbons, e.g. cyclohexane, methylcyclohexane, and decalin; and ethers, e.g. diethyl ether, dibutyl ether, diisoamyl ether, and tetrahydrofuran. The reduction temperature ranges from -50 to 70°C, preferably from -30 to 50°C, particularly preferably from -25 to 35°C. When the reduction temperature is too high, the catalytic activity will be low. There is no particular restriction on the period of adding the organomagnesium compound dropwise. Generally, this period is from about 30 minutes to about 6 hours. After completion of the reduction, after-reaction may be conducted at a temperature of 20 to 120°C. As to the amount of organic silicon compound to be used, the atomic ratio of Si atoms therein to Ti atoms in the titanium compound used, that is, the Si/Ti ratio, is from 1 to 50, preferably from 3 to 30, particularly preferably from 5 to 25. As to the amount of organomagnesium compound to be used, the atomic ratio of the sum of titanium atoms and silicon atoms to magnesium atoms in the reaction system, that is, the Ti + Si/Mg ratio, is from 0.1 to 10, preferably from 0.2 to 5.0, particularly preferably from 0.5 to 2.0. The solid product produced by the reduction is separated from the liquid and washed several times with an inert liquid hydrocarbon such as hexane or heptane. The thus obtained solid product contains trivalent titanium, magnesium, and a hydrocarbyloxy group and is generally noncrystalline or shows a very weak crystalinity. In particularly, the noncrystalline structure is preferable in view of the catalyst efficiency. The reduction of the titanium compound with the organomagnesium compound can also be carried out in the presence of a porous polymer or a porous oxide. Such porous polymers or oxides include, for example, a styrene polymer, acrylonitrile polymer, vinyl chloride polymer, propylene polymer, acrylonitriledivinylbenzene copolymer, styrene-divinylbenzene copolymer, aluminum oxide, magnesium oxide, silicon oxide, aluminum oxide-silicon oxide compound, and niobium oxide. Of these materials, preferred are a styrene-divinylbenzene copolymer and silicon oxide. In the next place, the solid product obtained as stated above is treated with the ester compound. The ester compound is used in an amount of 0.1 to 50 moles, preferably 0.3 to 20 moles, particularly preferably 0.1 to 10 moles, per mole of titanium atoms in the solid product. On the other hand, the amount of the ester compound to be used per mole of magnesium atoms contained in the solid product is from 0.01 to 1.0 mole, preferably from 0.03 to 0.5 mole. Excessive use of the ester compound tends to collapse the particles of the solid product. The treatment of the solid product with the ester compound can be carried out by any of the known methods such as a slurry method, ball milling and other mechanical means of size reduction which contact both materials with each other. Preferably, this contact is conducted in the presence of a diluent. Diluents usable in this case include; aliphatic hydrocarbons such as pentane, hexane, heptane, and octane; aromatic hydrocarbons such as benzene, toluene, and xylene; alicyclic hydrocarbons such as cyclohexane and cyclopentane; and halogenated hydrocarbons such as 1,2-dichloroethane and monochlorobenzene. Of these diluents, preferred are aromatic hydrocarbons and halogenated hydrocarbons. The diluent is used in an amount of 0.1 to 1000 ml, preferably 1 to 100 ml, per 1 g of the solid product. The treatment temperature is from -50 to 150°C, preferably from 0 to 120°C. The treatment period is at least 10 minutes, preferably from 30 minutes to 3 hours. The treated solid is separated from the liquid, and washed several times with an inert liquid hydrocarbon. Thus, an ester-treated solid is obtained. The next treatment of the ester-treated solid with a mixture of the ether compound and titanium tetrachloride is preferably carried out in a slurry state. Suitable media for this slurrying include the above-mentioned aliphatic hydrocarbons, aromatic hydrocarbons, alicyclic hydrocarbons, and halogenated hydrocarbons. In particular, the above aromatic hydrocarbons and halogenated hydrocarbons are preferable. The solid concentration in the slurry is from 0.05 to 0.5 g, preferably from 0.1 to 0.3 g, per ml of the medium. The reaction temperature is from 30 to 150°C, preferably from 45 to 120°C, particularly preferably from 60 to 100°C. While there is no particular restriction on the reaction period, generally preferred periods are from 30 minutes to 6 hours. As to the manner of adding the ether compound and titanium chloride to the ester-treated solid, it is preferable to add a mixture of an ether compound and titanium tetrachloride prepared previously or to add these compounds at the same time. The reaction with a mixture of an ether compound and titanium tetrachloride is desirably conducted at least twice from the viewpoint of the catalytic activity and stereospecificity of the catalyst system. The ether compound is used in an amount of 0.1 to 100 moles, preferably 0.5 to 50 moles, particularly preferably 1 to 20 moles, per mole of titanium atoms contained in the solid product. Titanium tetrachloride is used in an amount of 1 to 1000 moles, preferably 3 to 500 moles, particularly preferably 10 to 300 moles, per mole of titanium atoms contained in the solid product. The amount of titanium tetrachloride to be added per mole of the ether compound is from 1 to 100 moles, preferably from 1.5 to 75 moles, particularly preferably from 2 to 50 moles. The solid catalyst component containing a trivalent titanium compound, obtained in the above described manner, is separated from the liquid, and washed several times with an inner liquid hydrocarbon such as hexane or heptane, thereafter being used in polymerization. It is preferable in view of the catalytic activity and stereospecificity of the catalyst system that the solid separated from the liquid be washed at least once with an aromatic hydrocarbon such as toluene or xylene or with a halogenated hydrocarbon such as monochlorobenzene at a temperature of 50 to 120°C and further washed several times with an aliphatic hydrocarbon such as hexane, thereafter being used in polymerization. (B) Preparation of sterically hindered aluminum amide Alkylaluminum amide compounds are generally synthesized from alkylaluminum compounds and primary or secondary amine compounds by the following reaction: AlR₃ + RNH₂ → RNHAlR₂ + RH↑ or AlR₃ + R₂NH → R₂NAlR₂ + RH↑ [Peone Gazz/ Chim. Ital. 55 , 306 (1925), Weiss and C.J. Marsel Aeronautical Research Laboratory Report, ARL, 124, December (1961)] The sterically hindered aluminum amide compound used in the present invention, that is, component (B) represented by the general formula wherein, R¹ through R⁵ are each a hydrocarbon group of 1 to 20 carbon atoms, L is an alkoxy group of 1 to 20 carbon atoms or halogen, ℓ is 2 or 3, x is defined by 0 < x < 1, y is defined by 0 ≦ y < 3, and z is defined by 0 < z < 3, with the proviso that x + y + z = 3, is synthesized from the corresponding amine compound and alkylaluminum. Examples of the amine compound used to synthesize the sterically hindered aluminum amide include 2,5-diisopropylpyrrolidine, 2,5-di-tert-butylpyrrolidine, 2,6-diisopropylpiperidine, 2,6-di-tert-butylpiperidine, 2,2,5,5-tetramethylpyrrolidine, and 2,2,6,6-tetramethylpiperidine. Of these compounds, preferred are 2,2,5,5-tetramethylpyrrolidine and 2,2,6,6-tetramethylpiperidine. The alkylaluminum compound used for synthesizing the sterically hindered aluminum amide is a trialkylaluminum and/or a dialkylaluminum hydride represented by the general formulae R¹⁹₃Al and/or R²⁰₂ AlH, respectively, wherein R¹⁹ and R²⁰ are each a hydrocarbon group of 1 to 20 carbon atoms. Such alkylaluminum compounds include, for example, trimethylaluminum, triethylaluminum, triisobutyl aluminum, trihexylaluminum, trioctylaluminum, tripropylaluminum, tributylaluminum, tri(2-methylpentyl)aluminum, diethylaluminum hydride, and diisobutylaluminum hydride. Of these compounds, preferred are triisobutylaluminum and diethylaluminum hydride and particularly preferred is triethylaluminum. To react the organoaluminum compound with the amine compound, there are the order of adding the former compound to the latter and the order of adding the latter compound to the former. Either order is acceptable. The amine compound and the organoaluminum compound are used preferably with themselves dissolved or diluted with a suitable solvent. Such solvents include; aliphatic hydrocarbons, e.g. hexane, heptane, octane, and decane; aromatic hydrocarbons, e.g. toluene and xylene; and alicyclic hydrocarbons, e.g. cyclohexane and methylcyclohexane. There is no particular restriction on the reaction temperature or period, that is to say, the synthesis can be carried out under any of customary reaction conditions, provided that these conditions result in the complete disappearance of the infrared absorption assigned to the stretching vibration of the N-H bond of the amine compound used. Generally, the synthesis can be accomplished at temperatures of 0 to 90°C for periods of 30 minutes to 4 hours. The aluminum amide compound having the intended average composition can be obtained by mixing an aluminum amide of optional composition with trialkylaluminum, alkylaluminum halide, or alkylaluminum alkoxide. Aluminum amide compounds represented by the general formula synthesized by the above stated methods have x values in the range of 0 < x < 1, preferably 0.0001 ≦ x ≦ 0.9, particularly preferably 0.001 ≦ x ≦ 0.7. The amount of component (B) to be used can be chosen from the wide range of 1 to 100,000 moles per mole of titanium atoms contained in component (A), though that amount ranges preferably from 5 to 10,000 moles, particularly preferably from 10 to 1,000 moles. (C) Polymerization of α-olefin There is no particular restriction on the manner of charging the catalyst components into the polymerization reactor except that the components should be charged in the moisture-free state under an atmosphere of inert gas such as nitrogen or argon. While the polymerization can be carried out at temperatures ranging from -30 to 200°C, polymerization temperatures lower than 0°C decrease the rate of polymerization and temperatures above 100°C give no polymer having high streoregularity. Hence, the polymerization is normally conducted in the range of 0 to 100°C. There is no particular restriction on the polymerization pressure, but 3,03 g × 10⁵ to 101,3 × 10⁵ Pa (3- to 100-atm.) polymerization pressures are preferable in the industrial and economical aspects. The polymerization can be operated either continuously or batchwise according to any of the techniques of slurry polymerization employing an inert hydrocarbon medium such as propane, butane, pentane, hexane, heptane, or octane, liquid-phase polymerization using no solvent and gas-phase polymerization. α-Olefins polymerizable advantageously according to the present invention are those of at least 3 carbon atoms including, for example, propylene, butene-1, pentene-1, hexene-1, 3-methyl-pentene-1, 4-methyl-pentene-1, and decene-1, though not limited to these compounds. According to the present invention, either homopolymerization or copolymerization (including copolymerization with ethylene) is possible. In the copolymerization, a copolymer can be obtained by contacting two or more olefins in mixed form with the present catalyst system. A chain transfer agent such as hydrogen can be added for the purpose of controlling the molecular weight of polymer. The present invention is illustrated in more detail with reference to the following examples, which, however, put no restriction on the scope of the invention The valences of titanium compounds in the example were determined from measuring polarograms thereof. Conditions of polarogram measurement Example 1 (A) Preparation of organomagnesium compound A 1-liter flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer was flushed with argon, and 32.0 g metallic magnesium in the form of thin turnings was put into the flask. In the dropping funnel were fed 120 g of butyl chloride and 500 ml of dibutyl ether, and 30 ml of this mixture was dropped on the magnesium in the flask to initiate reaction. Thereafter the remainder of the butyl chloride-dibutyl ether mixture was dropped over 4 hours at 50°C, and the reaction was continued further for 1 hour at 60°C. Then the reaction product solution was cooled to room temperature, and the solid matter was filtered off. The concentration of butylmagnesium chloride in the filtrate (the solvent: dibutyl ether) was determined by hydrolyzing a sample of the filtrate with 1-N sulfuric acid, followed by back titration with 1-N aqueous sodium hydroxide (phenolphthalein was used as an indicator). The found concentration of butylmagnesium chloride was 2.2 moles/ℓ. (B) Preparation of solid product A 500-ml flask equipped with a stirrer and a dropping funnel was flushed with argon, and 300 ml of hepatane, 4.1 g (12.1 mmoles) of tetrabutoxytitanium, and 42.9 g (206 mmoles) of tetraethoxysilane were put into the flask and formed into a uniform solution. Then, 100 ml of the organomagnesium compound prepared in (A) was added dropwise from the dropping funnel over 2 hours while keeping the temperature of the flask contents at 5°C. The resulting mixture was further stirred for 1 hour at room temperature, and the formed precipitate was separated from the liquid at room temperature, washed three times with 300-ml portions of heptane, and dried under reduced pressure, giving 32.0 g of a brown solid product. Titanium atoms contained in the solid product were found by polarography to have a valence of 3. The solid product was found to contain 1.7 wt.% of trivalent titanium atoms, 18.2 wt.% of magnesium atoms, 2.2 wt.% of silicon atoms, 0.8 wt.% of dibutyl ether, 33.5 wt.% of ethoxy groups, and 2.4 wt.% of butoxy groups. This solid product showed no distinct diffraction in the wide-angle X-ray (Cu-Kα ray) diffraction pattern, hence being noncrystalline. (C) Preparation of ester-treated solid A 200-ml flask was flushed with argon, and 15 g of the solid product prepared in (B) and 90 ml toluene were charged in the flask and 2.7 ml of diisobutyl phthalate was added and reacted with the solid product at 80°C for 1 hour. The resulting solid was separated from the liquid, and washed three times with 120-ml portions of heptane. The ester-treated solid obtained was found to contain 6.2 wt.% of phthalate. (D) Preparation of solid catalyst component After the washing in above (C) had been finished, 5.6 ml (32.6 mmoles) of dibutyl ether and 49.3 ml (450 mmoles) of titanium tetrachloride with 90 ml of toluene were added to the flask contents and reacted with the solid at 80°C for 1 hour. Thereafter the resulting solid was separated from the liquid at 80°C, washed twice with 90-ml of toluene at the same temperature, and further washed four times with 120-ml of heptane at room temperature. The above treatment with the mixture of dibutyl ether and titanium tetrachloride was repeated once more under the same conditions, yielding 13.0 g of a solid catalyst component having a yellow-soil color. Titanium atoms contained in this solid catalyst component were found by polarography to have a valence of 3. The solid catalyst component was found to contain 1.8 wt.% of titanium atoms, 21.1 wt.% of magnesium atoms, 0.2 wt.% of silicon atoms, 0.3 wt.% of butoxy groups, 1.1 wt.% of ethoxy groups, 6.2 wt.% of phthalate, 0.2 wt.% of diisoamylether, and 66.7 wt.% of chlorine. (E) Preparation of aluminum amide compound A 300-ml of flask equipped with a stirrer and a dropping funnel was flushed with argon, and 100 ml of a solution consisting of 76.6 ml of toluene and 23.4 ml (171 mmoles) of triethylaluminum was charged into the flask. Then, 100 ml of a solution consisting of 91.3 ml of toluene and 8.7 ml (51.3 mmoles) of 2,2,6,6-tetramethylpiperidine was added dropwise from the dropping funnel in 10 minutes while keeping the temperature of the flask contents at 80°C. The resulting mixture was further stirred for 4 hours at 80°C, yielding an aluminum amide compound having an average composition represented by Infrared spectrographic analysis confirmed that the absorption at 3310 cm⁻¹ assigned to the NH stretching vibration disappeared after completion of the reaction and GC-MS analysis confirmed that the gas evolving during the reaction was ethane. (F) Polymerization of propylene A 3-liter autoclave of the mechanical agitation type was flushed with argon, and charged with 10.8 mg of the solid catalyst component prepared in above (D), 26.3 mmoles of the aluminum amide prepared in above (E) having the average compositon: and 780 g of liquefied propylene. The temperature of the autoclave contents was kept at 80°C for 2 hours while stirring to finish the polymerization. Then the excess propylene was discharged, and the product was dried for one day, to yield 356 g of polypropylene. Accordingly, the yield (g) of polypropylene per 1 g of the solid catalyst component (PP/cat) (hereinafter this abbreviation applies) was 33,000. The content of atactic polymer (hereinafter abbreviated as CXS) in the obtained polypropylene was 2.5 wt.%. The CXS is defined as the content of polymer soluble in xylene at 20°C. Example 2 Propylene was polymerized according to the procedure of (F) of Example 1 but using 11.4 mg of the solid catalyst component prepared in (D) of Example 1 and 26.3 mmoles of an aluminum amide compound having the average composition yielding 345 g of polypropylene. PP/cat = 30,300 accordingly and CXS = 2.6 wt.%. Example 3 Propylene was polymerized according to the procedure of (F) of Example 1 but using 5.1 mg of the solid catalyst component prepared in (D) of Example 1 and 26.3 mmoles of an aluminum amide having the average composition. yielding 176 g of polypropylene. PP/cat = 35,000 accordingly and CXS = 2.8 wt.%. Example 4 Propylene was polymerized according to the procedure of (F) of Example 1 but using 6.4 mg of the solid catalyst component prepared in (D) of Example 1 and 26.3 mmoles of an aluminum amide compound having the average composition yielding 274 g of polypropylene. PP/cat = 42,800 accordingly and CXS = 2.9 wt.%. Example 5 Propylene was polymerized according to the procedure of (F) of Example 1 but using 5.6 mg of the solid catalyst component prepared in (D) of Example 1 and 7.8 mmoles of an aluminum amide compound having the average composition yielding 258 g of polypropylene. PP/cat = 46,000 accordingly and CXS = 3.1 wt.%. Example 6 Propylene was polymerized according to the procedure of (F) of Example 1 but using 5.1 mg of the solid catalyst component prepared in (D) of Example 1 and 7.8 mmoles of an aluminum amide compound having the average composition yielding 215 g of polypropylene. PP/cat = 42,300 accordingly and CXS = 2.8 wt.%. Example 7 Propylene was polymerized according to the procedure of (F) of Example 1 but using 6.3 mg of the solid catalyst component prepared in (D) of Example 1 and 26.8 mmoles of an aluminum amide having the average composition yielding 176 g of polypropylene. PP/cat = 28,000 accordingly and CXS = 3.2 wt.%. Comparative Example 1 Propylene was polymerized according to the procedure of (F) of Example 1 but using 10.2 mg of the solid catalyst component prepared in Example 1 and 26.3 mmoles of an aluminum amide compound having the average composition to yield 197 g of polypropylene. PP/cat = 19,300 accordingly and CXS = 2.8 wt.%. Comparative Example 2 Propylene was polymerized according to the procedure of (F) of Example 1 except that no aluminum amide compound was used and 26.8 mmoles of triethylaluminum, 0.78 mmole of 2,2,6,6-tetramethylpiperidine, and 6.6 mg of the solid catalyst component prepared in Example 1 were charged in that order in the autoclave, thereby yielding 152 g of polypropylene. PP/cat = 23,000 accordingly and CXS = 3.5 wt.%. Comparative Example 3 Propylene was polymerized according to the procedure of (F) of Example 1 but using 6.6 mg of the solid catalyst component prepared in Example 1 and 26.3 mmoles of an aluminum amide having the average composition to yield 66 g of polypropylene. PP/cat = 11,000 accordingly and CXS = 21.6 wt.%. Comparative Example 4 Propylene was polymerized according to the procedure of (F) of Example 1 but using 14.6 mg of the solid catalyst component prepared in Example 1 and 26.3 mmoles of an aluminum amide compound having the average composition Et 2.7 Al ( (NPh₂) 0.3 , yielding 141 g of polypropylene. PP/cat = 9,660 accordingly and CXS = 23.0 wt.%. Comparative Example 5 Propylene was polymerized according to the procedure of (F) of Example 1 except that 5.1 mg of the solid catalyst component prepared in Example 1 and 7.8 mmoles of 2,2,6,6-tetramethylpiperidine were previously brought into contact with each other and then charged into the autoclave and 26.3 mmoles of triethylaluminum was then added, thereby yielding 59 g of polypropylene. PP/cat = 11,600 accordingly and CXS = 4.1 wt.%. Example 8 Polymerization of 4-methyl-1-pentene A 3-liter autoclave of the mechanical agitation type was flushed with argon, and charged with 15.6 mg of the solid catalyst component prepared in Example 1-(D), 2.2 mmoles of the aluminum amide compound prepared in Example 1-(E) having the average composition: and 1000 ml of 4-methyl-1-pentene. The temperature of the autoclave contents was kept at 70°C for 1 hour while stiring, and then 50 ml of isobutylalcohol was added to finish the polymerization. Then the slurry formed was filtered by glass-filter (G-3) to separate the polymer formed, and the polymer was washed with 1000 ml of dry n-heptane and dried at 80°C for 4 hours under reduced pressure to yield 229.7 g of poly-4-methyl-pentene-1 powder. The filtrate and washing liquid were subjected to evaporation to yield 11.5 g of heptane-soluble polymer. The ratio of heptane-insoluble portion [(hereinafter abbreviated to HIP(wt.%))] contained in the whole polymer was 95.2 wt.%, and polymer yield per 1 g of solid catalyst component (hereinafter abbreviated to PMP/cat) was 15,460 g/g. Comparative Example 6 4-Methyl-1-pentene was polymerized according to the procedure of Example 8 except that there was used aluminum amide compound having the average composition There were obtained HIP(%) = 83.5 and PMP/cat = 2113 g/g. Example 9 Copolymerization of 4-methyl-1-pentene and 1-decene A 3-liter autoclave of the mechanical agitation type was flushed with argon, and charged with 15.3 mg of the solid catalyst component prepared in Example 1-(D), 2.2 mmoles of the aluminum amide prepared in Example 1-(E) having the average composition: 1000 ml of 4-methyl-1-pentene and 25 ml of 1-decene. The temperature of the autoclave contents was raised to 60°C to initiate polymerization and polymerization was carried out while supplying 1-decene in a rate of 5 ml/hour over 2.5 hours while stiring, and then 50 ml of i-butylalcohol was added to finish the polymerization. Then the slurry formed was filtered by glass-filter (G-3) to separate the polymer formed, and the polymer was washed with 1000 ml of dry n-heptane and dried for 4 hours under reduced pressure to yield 286.3 g of copolymer powder of 4-methylpentene-1 and 1-decene. The filtrate and washing liquid were subjected to evaporation to yield 16.6 g of solvent-soluble polymer. HIP(%) = 94.5 and PMP/cat = 19,800 g/g. As described hereinbefore, the use of the catalyst system of the present invention achieves the following effects: (1) Since the catalytic activity is very high per one gram of the solid catalyst component and per one gram atom of titanium atoms contained therein, the contents of halogen and titanium atoms, which relate intimately to the coloration, stability and corrosiveness of the parent α-olefin polymer, in the product polymer can be reduced extremely without removing the catalyst residue particularly. That is, any facility for catalyst residue removal becomes unnecessary and production costs for α-olefin polymers can be reduced. (2) α-olefin polymers having very high streoregularity can be produced. That is, since the amount of amorphous polymer formed incidentally is extremely limited, α-olefin polymers excellent in mechanical properties are producible without removing the amorphous polymer. (3) Since the low-stereoregular polymer soluble in the polymerization medium forms a very little, none of such process problems arise as the adhesion of polymer to reactors, pipes, flask hoppers, etc. and in addition the raw material monomer can be utilized effectively.

Claims: 1. A catalyst system for producing an α-olefin polymer which comprises (A) a solid catalyst component containing at least titanium, magnesium, halogen, and an electron donor, which is obtained by (i) reducing a titanium compound represented by the general formula Ti(OR⁶) n X 4-n wherein R⁶ denotes a hydrocarbon group of 1 to 20 carbon atoms, X denotes halogen, and n is a number defined by 0 < n ≦ 4, with an organomagnesium compound in the presence of an organosilicone compound having one or more Si-O bonds, and (ii) treating the resulting solid product with an ester compound and a mixture of an ether compound and titanium tetrachloride, and (B) a sterically hindered aluminum amide compound represented by the general formula wherein R¹ through R⁵ denote each a hydrocarbon group of 1 to 20 carbon atoms, L denotes an alkoxy group of 1 to 20 carbon atoms and/or halogen, ℓ is 2 or 3, x is defined by 0 < x < 1, y is defined by 0 ≦ y < 3, and z is defined by 0 < z < 3 with the proviso that x + y + z = 3. 2. A catalyst system according to Claim 1, wherein in the titanium compound represented by the general formula Ti(OR⁶) n X 4-n , R⁶ is a straight chain alkyl group having 2 to 18 carbon atoms. 3. A catalyst system according to Claims 1 or 2, wherein in the titanium compound represented by the general formula Ti(OR⁶) n X 4-n , X is chlorine. 4. A catalyst system according to any one of Claims 1 to 3, wherein in the titanium compound represented by the general formula Ti(OR⁶) n X 4-n , n is 2 ≦ n ≦ 4. 5. A catalyst system according to any one of Claims 1 to 4, wherein the organomagnesium compound is a Grignard compound represented by the general formula R¹⁵ MgX (wherein R¹⁵ represents a hydrocarbon group of 1 to 20 carbon atoms and X is halogen) or a dialkylmagnesium compound or diarylmagnesium compound represented by the general formula R¹⁶R¹⁷ Mg (wherein R¹⁶ and R¹⁷ each denotes a hydrocarbon group of 1 to 20 carbon atoms), R¹⁵, R¹⁶ and R¹⁷ being the same or different. 6. A catalyst system according to Claim 5, wherein R¹⁵, R¹⁶ and R¹⁷ each represents an alkyl group, aryl group, aralkyl group or alkenyl group of 1 to 20 carbon atoms. 7. A catalyst system according to any one of Claims 1 to 6, wherein the organosilicone compound is one represented by the general formula Si(OR⁹) m R¹⁰ 4-m , R¹¹(R¹²₂SiO) p SiR¹³₃, or (R¹⁴₂SiO) q wherein R⁹ denotes a hydrocarbon group of 1 to 20 carbon atoms, R¹⁰, R¹¹, R¹², R¹³ and R¹⁴ each denotes a hydrocarbon group of 1 to 20 carbon atoms or hydrogen, m is defined by 0 < m ≦ 4, p is an integer of 1 to 1000 and q is an integer of 2 to 1000. 8. A catalyst system according to any one of Claims 1 to 7, wherein the ester compound is a mono- or multi-valent carboxylic acid ester. 9. A catalyst system according to Claim 8, wherein the carboxylic acid ester is aliphatic carboxylic ester, olefinic carboxylic ester, alicyclic carboxylic ester or aromatic carboxylic ester. 10. A catalyst system according to any one of Claims 1 to 9, wherein the ether compound is a dialkyl ether. 11. A catalyst system according to Claim 10, wherein the dialkyl ether is diethyl ether, dipropyl ether, diisopropyl ether, diisoamyl ether or dibutyl ether. 12. A catalyst system according to any one of Claims 1 to 11, wherein the sterically hindered aluminum compound is 2,5-diisopropylpyrolidine, 2,5-di-tert-butylpyrolidine, 2,6-diisopropylpiperidine, 2,6-di-tert-butylpiperidine, 2,2,5,5-tetramethylpyrolidine, or 2,2,6,6-tetramethylpiperidine. 13. A catalyst system according to any one of Claims 1 to 12, wherein the organosilicone compound is used in term of the ratio of the sum of titanium atoms and silicone atoms to magnesium atoms from 0.1 to 10. 14. A catalyst system according to any one of Claims 1 to 13, wherein the organosilicone compound is used in terms of the ratio of silicone atoms therein to titanium atoms in the titanium compound from 1 to 50. 15. A catalyst system according to any one of Claims 1 to 14, wherein the ester compound is used in an amount of 0.1 to 50 moles per mole of titanium atoms in the solid product, and from 0.01 to 1.0 mole per mole of magnesium atoms contained in the solid product. 16. A catalyst system according to any one of Claims 1 to 15, wherein the ether compound is used in an amount of 0.1 to 100 moles per mole of titanium atoms contained in the solid product. 17. A catalyst system according to any one of Claims 1 to 16, wherein the titanium tetrachloride compound is used in an amount of 1 to 1000 moles per mole of titanium atoms contained in the solid product. 18. A catalyst system according to any one of Claims 1 to 17, wherein the sterically hindered aluminum amide is used in an amount of from 1 to 100,000 moles per mole of titanium atoms contained in component (A). 19. A catalyst system according to any one of Claims 1 to 18, wherein the treatment of ester-treated product with an ether compound and titaniumtetrachloride is carried out in a slurry state. 20. A catalyst system according to any one of Claims 1 to 19, wherein the reduction of titanium compound with magnesium compound is carried out in the copresence of porous polymer or porous oxides. 21. A process for producing an α-olefin polymer which comprises polymerizing an α-olefin in the presence of a catalyst system comprising A) a solid catalyst component containing at least titanium, magnesium, halogen, and an electron donor, obtained by (i) reducing a titanium compound represented by the general formula Ti(OR⁶) n X 4-n wherein R⁶ denotes a hydrocarbon group of 1 to 20 carbon atoms, X denotes halogen, and n is a number defined by 0 < n ≦ 4, with an organomagnesium compound in the presence of an organosilicone compound having one or more Si-O bonds and, (ii) treating the resulting solid product with an ester compound and a mixture of an ether compound and titanium tetrachloride, and (B) a sterically hindered aluminum amide compound represented by the general formula wherein R¹ through R⁵ denote each a hydrocarbon group of 1 to 20 carbon atoms, L denotes an alkoxy group of 1 to 20 carbon atoms and/or halogen, ℓ is 2 or 3, x is defined by 0 < x < 1, y is defined by 0 ≦ y ≦ 3, and z is defined by 0 < z < 3 with the proviso that x + y + z = 3 at a temperature of 0 to 100°C under a pressure of 3,03 g × 10⁵ to 101,3 × 10⁵ Pa (3 to 100 atm).

Inventors: EBARA, TAKESHI, JYOHOUJI, HIROFUMI, KAWAI, KIYOSHI, SASAKI, TOSHIO
Applicants: SUMITOMO CHEMICAL COMPANY, LIMITED
Application year: 1988
Main classification: C08F4
IPC codes: C08F4, C08F10