A process for producing a high-stiffness polypropylene

Abstract: A process for producing a highly transparent and highly stiff polypropylene, which process comprises using a catalyst by combining (1) a titanium trichloride composition (III) obtained by reacting TiCℓ₄ with an organoaluminum compound (A₁) or a reaction product (I) of (A₁) with an electron donor (B₁) to obtain a solid product (II), followed by subjecting the product (II) to a multi-stage polymerization treatment with a linear olefin and a non-linear olefin, each used one or more times, and further reacting the resulting linear olefin-non-linear olefin block copolymer with an electron donor (B₂) and an electron accceptor, (2) an organoaluminum compound (A₂); and as a third component, (3) an aromatic carboxylic acid ester (E) or an organosilicon compound (S) having a Si-O-C bond and/or a mercapto group.

Description: This invention relates to a process for producing a high-stiffness polypropylene. More particularly it relates to a process for producing a high-stiffness polypropylene having a far superior transparency. The inventors of Chisso Corporation have previously proposed a process for producing a high-stiffness polypropylene using a catalyst prepared by combining a titanium trichloride composition obtained according to a specified process with an organoaluminum compound an aromatic carboxylic acid ester, each in specified proportions (Japanese patent application laid-open No. Sho 58-104,907, hereinafter referred to as the prior application invention). According to the process of this prior application invention, it has become possible to produce a polypropylene affording a molded product having a far higher stiffness than that of polypropylene obtained according to conventional known processes, even without adding any particular additive. However, while the polypropylene obtained according to the prior application invention has the above-mentioned high stiffness, it is translucent and hence in the field of its use applications, the commodity value has often been damaged so that improvement in the transparency has been desired. On the other hand, as an attempt of improving the transparency of polypropylene or as another attempt of improving the stiffness, various processes have been proposed such as those of polymerizing propylene using a catalyst subjected to a preliminary activation treatment by polymerizing a small quantity of a non-linear olefin such as vinylcyclohexane, p-t-butylstyrene, allyltrimethylsilane, 4,4-dimethylpentene-1, etc., or a catalyst obtained by the preliminary activation treatment with a non-linear olefin, followed by a prelimiary activation treatment with propylene (Japanese patent application laid-open Nos. Sho 60-139,710, Sho 63-15,803, Sho 63-15,804, Sho 63-37,105, Sho 63-218,709). Thus, the present inventors have carried out polypropylene production according to these proposed processes. As a result, according to any of these processes, the polymerization activity of propylene not only lowers, but also operational problems occurred such as formation of massive polymer, adhesion of scales onto the wall of the polymerization vessel, inferior controllability of polymerization reaction; hence it was impossible to employ these processes in the case of commercial long term continuous polymerization processes, particularly in the case of gas phase polymerization process of carrying out propylene polymerization in gas phase. Further, the stiffness of the resulting polypropylene was lower and insufficient as compared with that of polypropylene obtained according to the process of the prior application invention. Further, when the polypropylene was processed into film, a definite improvement in the transparency was observed, but a number of voids occurred in the film to damage its commodity value. Further, as a similar technique, a process has been proposed wherein propylene is polymerized using a catalyst component obtained by adding a non-linear olefin polymer such as vinylcyclohexane polymer, allyltrimethylsilane, midway during the production of the transition metal component for propylene polymerization (Japanese patent application laid-open No. 63-69,809), but this proposed process requires a separate process of producing a non-linear olefin polymer so that the process has been not only accompanied with a commercial disadvantage, but also there have been raised problems of insufficient stiffness and occurrence of voids in the film as in the case of the above-mentioned prior art. The present inventors have made extensive research on a process for producing a high-stiffness polypropylene having solved various problems of the above-mentioned prior application invention and prior art and having an improved transparency, and as a result, have found a titanium trichloride composition having a linear olefin-non-linear olefin block copolymer contained therein, and further have found that when this titanium trichloride composition is combined with specified quantities of an organoaluminum compound and further an aromatic carboxylic acid ester and polypropylene is produced using the resulting catalyst, then the problems of the above-mentioned prior art in the aspect of production and quality are dissolved and also the polypropylene has not only a far superior transparency, but also a further improved stiffness as compared with the polypropylene obtained according to the process of the prior application invention, and thus have completed the present invention in a first aspect. As apparent from the foregoing, the object of the present invention is to provide a process for producing a high-stiffness polypropylene having very small occurrence of voids and a far superior transparency. The present invention has the following constitutions: (1) A process for producing a high-stiffness polypropylene having a flexual modulas of at least 1765 M.Pa (18000 Kgf/cm 2 ) which comprises polymerizing propylene using a catalyst obtained by combining 1 ○ a titanium trichloride composition (III) obtained by reacting TiCℓ 4 with an organoaluminum compound (A 1 ) or a reaction product (I) of an organoaluminum compound (A 1 ) with an electron donor (B 1 ) to obtain a solid product (II), followed by subjecting said solid product (II) to a multi-stage polymerization treatment with a linear olefin and a non-linear olefin, each once or more times used, to form a linear olefin-non-linear olefin block copolymer in a ratio by weight of a linear olefin polymer block therein to a non-linear olefin polymer block therein of 2/98 to 98/2, followed by further reacting said block copolymer with an electron donor (B 2 ) and an electron acceptor to obtain said titanium trichloride composition (III), which contains o.1 to 49.5% by weight of said linear olefin polymer block and 0.01 to 49.5% by weight of said non-linear olefin polymer block; 2 ○ an organoaluminum compound (A 2 ); and 3 ○ an aromatic carboxylic acid ester (E), the molar ratio of said aromatic carboxylic acid ester (E) to the gram atoms of Ti in said titanium trichloride composition (III), that is, (E)/(III) being made 0.1 to 10.0, and the molar ratio of said organoaluminum compound (A 2 ) to the gram atoms of Ti in said titanium trichloride composition (III), that is, (A 2 )/(III) being made 0.1 to 200. (2) A production process according to item (1) wherein said organoaluminum compound (A 1 ) is expressed by the formula AℓR 1 p R 2 p' X 3-(p+p') wherein R 1 and R 2 each represent a hydrocarbon radical selected from an alkyl group, a cycloalkyl group or an aryl group, X represents a halogen atom and p and p' each represent an optional number satisfying an expression of 0<p+p'≦3. (3) A production process according to item (1) wherein said non-linear olefin is a saturated ring-containing hydrocarbon monomer expressed by the formula CH 2 = CH - R 3 wherein R 3 represents a saturated ring-containing hydrocarbon radical of 3 to 18 carbon atoms having a saturated ring structure of a hydrocarbon, which radical may contain a silicon atom. (4) A production process according to item (1), wherein said non-linear olefin is a branched olefin expressed by the formula wherein R 4 represents a chain hydrocarbon radical of 1 to 3 carbon atoms which may contain silicon atom or silicon atom, R 5 , R 6 and R 7 each represent a chian hydrocarbon radical of 1 to 6 carbon atoms which may contain silicon atom, but any one of R 5 , R 6 and R 7 may be hydrogen atom. (5) A production process according to item (1), wherein said non-linear olefin is an aromatic monomer expressed by the formula wherein n represents 0 or 1, m represents 1 or 2, R 8 represents a chian hydrocarbon radical of 1 to 6 carbon atoms which may contain silicon atom and R 9 represents a hydrocarbon radical of 1 to 12 carbon atoms which may contain silicon atom, hydrogen atom or a halogen atom, and in the case of m=2, the respective R 9 s may be same or different. (6) A production process according to item (1), wherein said organoaluminum compound (A 2 ) is a dialkylaluminum monohalide. (7) A production process as described in Claim 1 according to item (1), wherein a preactivated catalyst component obtained by combining said titanium trichloride composition (III) with an organoaluminum compound, followed by reacting 0.05 to 3000 g of an olefin, per 1g of titanium trichloride composition, with the resulting combination is used in place of said titanium trichloride composition (III). (8) A production process according to item (1), wherein the relationship between the isotactic pentad ratio (P) and the melt flow rate (MFR) of the resulting polypropylene satisfies the following expression: 1.00≥ P ≥ 0.015 log MFR + 0.955 Figs. 1 shows a flow sheet illustrating the process for producing polypropylene of the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The constitution of the present invention will be described in more detail. The titanium trichloride composition (III) used in the present invention comprises a linear olefin-non-linear olefin block copolymer (hereinafter abbreviated to a specified block copolymer) having at least one linear olefin polymer block and at least one non-linear olefin polymer block. A process for producing the composition (III) will be described. The preparation of the titanium trichloride composition (III) is carried out as follows: Firstly, an organoaluminum compound (A 1 ) is reacted with an electron donor (B 1 ) to obtain a reaction product (I), followed by reacting the product (I) with TiCℓ 4 or with an organoaluminum compound (A 1 ) and TiCℓ 4 to obtain a solid product (II), subjecting this product (II) to a multi-stage polymerization treatment with 1 ○ a linear olefin and 2 ○ a non-linear olefin, each once or more times used, to form a linear olefin-non-linear olefin block copolymer, and further reacting this block copolymer with an electron donor (B 2 ) and an electron acceptor to obtain a final solid product (III) i.e. a titanium trichloride composition (III). In addition, "polymerization treatment" referred to in the present invention means that a linear olefin or a non-linear olefin is contacted with the solid product (II) under polymerizable conditions to thereby polymerize the linear olefin or the non-linear olefin. By this polymerization treatment, the solid product (II) forms a state coated with the polymers. The reaction of the organoaluminum compound (A 1 ) with the electron donor (B 1 ) is carried out in a solvent (D) at -20°C to +200°C, preferably -10°C to +100°C, for 30 seconds to 5 hours. The addition order of the organoaluminum compound (A 1 ), (B 1 ) and (D) has no particular limitation, and the respective proportions of quantities thereof used are 0.1 to 8 mols, preferably 1 to 4 mols of the electron donor (B 1 ), and 0.5 to 5 ℓ, preferably 0.5 to 2 ℓ of the solvent, each based on one mol of the organoaluminum compound (A 1 ). Thus, the reaction product (I) is obtained. The product (I) may be subjected to the subsequent reaction, without separating it, that is, in a liquid state after completion of the reaction (hereinafter referred to often as reaction liquid (I)), as it is. The process of subjecting the solid product (II) obtained by reacting the reaction product (I) with TiCℓ 4 or with an organoaluminum compound (A 1 ) and TiCℓ 4 , to a multi-stage polymerization treatment with a linear olefin and a non-linear olefin,includes 1 ○ a process of adding a linear olefin and a non-linear olefin at a multi-stage during an optional process of the reaction of the reaction product (I) or the organoaluminum compound (A 1 ) with TiCℓ 4 to thereby subject the solid product (II) to a multi-stage polymerization treatment; 2 ○ a process of adding a linear olefin and a non-linear olefin at a multi-stage after completion of the reaction of the reaction product (I) or an organoaluminum compound (A 1 ) with TiCℓ 4 to thereby subject the solid product(II) to a multi-stage polymerization treatment; and 3 ○ a process of separating and removing a liquid portion by filtering off or decantation after completion of the reaction of the reaction product (I) or an organoaluminum compound (A 1 ) with TiCℓ 4 , followed by suspending the resulting solid product (II) in a solvent and further adding an organoaluminum compound and thereafter adding a linear olefin and a non-linear olefin at a multi-stage to effect polymerization treatment. Further, as to the order of the polymerization treatment at a multi-stage with a linear olefin and a non-linear olefin, either of the linear olefin or the non-linear olefin may be used in advance, but in the aspects of the polymerization operability at the time of using the resulting final titanium trichloride composition (III) as well as the quality of the resulting polyolefin, it is preferred to 1 ○ first carry out the polymerization treatment with the linear olefin and 2 ○ successively carry out the polymerization treatment with the non-linear olefin. By this multi-stage polymerization treatment, the linear olefin-non-linear olefin block copolymer is formed, and the solid product (II) forms a state coated by the block copolymer. Still further, the multi-stage polymerization treatment is carried out using a linear olefin and a non-linear olefin each once or more times, as described, to obtain the titanium trichloride composition (III) for achieving the object of the present invention, but it is also possible to carry out the polymerization treatment twice or more, for example, by further adding 3 ○ a linear olefin after the polymerization treatment with the non-linear olefin to carry out an additional polymerization treatment. The reaction of the reaction product (I) or an organoaluminum compound (A 1 ) with TiCℓ 4 is carried out at -10°C to +200°C, preferably 0°C to 100°C for 5 minutes to 10 hours, irrespective of whether a linear olefin and a non-linear olefin are added or not added during an optional process of the reaction. While it is preferred to use no solvent, it is also possible to use an aliphatic or aromatic hydrocarbon. Mixing of the reaction product (I) or an organoaluminum compound (A 1 ), TiCℓ 4 and a solvent may be carried out in an optional order, and the addition of a linear olefin and a non-linear olefin may also be carried out at any stage. Mixing of the total quantity of the reaction product (I) or an organoaluminum compound (A 1 ), TiCℓ 4 and a solvent is preferred to be completed within 5 hours, and the reaction is carried out even during the mixing. After the mixing of the total quantity, the reaction is preferred to be continued further within 5 hours. As to the respective quantities of these materials used in the reaction, the quantity of the solvent is 0 to 3,000 mℓ based on one mol of TiCℓ 4 , and as to the quantities of the reaction product (I) or the organoaluminum compound (A 1 ), the ratio of the number of Aℓ atoms in the (I) or the (A 1 ) to the number of Ti atoms in TiCℓ 4 (Aℓ/Ti) is 0.05 to 10, preferably 0.06 to 0.3. As to the polymerization treatment with a linear olefin and a non-linear olefin, 1 ○ in the case where the linear olefin and the non-linear olefin are added during an optional process of the reaction of the reaction product (I) or an organoaluminum compound (A 1 ) with TiCℓ 4 , and 2 ○ in the case where a linear olefin and a non-linear olefin are added after completion of the reaction of the reaction product (I) or an organoaluminum compound (A 1 ) with TiCℓ 4 , a multi-stage polymerization is carried out in either of polymerization treatment with a linear olefin or a non-linear olefin, using 0.1 g to 100 Kg of a linear olefin and 0.01 g to 100 Kg of a non-linear olefin based on 100 g of the solid product (II), under conditions of a reaction temperature of 0° to 90°C, a reaction time of one minute to 10 hours and a reaction pressure of the atmospheric pressure [0.1 MPa (0 Kgf/cm 2 G)] to 1.08 MPa (10 Kgf/cm 2 G), so as to give a content of the linear olefin polymer block in the final solid product (III) i.e. the titanium trichloride composition (III) of 0.1 to 49.5% by weight, and a content of the non-linear olefin polymer block therein of 0.01 to 49.5% by weight and also so as to give a ratio by weight of the linear olefin polymer block to the non-linear olefin polymer block of 2/98 to 98/2. If the content of the linear olefin polymer block is lower than 0.1% by weight, improvement in the operating properties at the time of using the resulting titanium trichloride composition and the effect of inhibiting voids in the resulting polyolefin are insufficient, while even if the content exceeds 49.5% by weight, the improvement in the effect is not notable, resulting in operational and economical disadvantages. Further, the ratio by weight of the linear olefin polymer block to the non-linear olefin polymer block is preferred to be 2/98 to 98/2 in view of the balance among the effect of improving the operating properties, the voids-inhibiting effect and the effect of improving the transparency. In the case 3 ○ where the multi-stage polymerization treatment with a linear olefin and a non-linear olefin is carried out by separating and removing a liquid portion by filtering-off or decantation after completion of the reaction of the reaction product (I) or an organoaluminum compound (A 1 ) with TiCℓ 4 , followed by suspending the resulting solid product (II) in a solvent, the multi-stage polymerization is carried out in either polymerization treatment with a linear olefin or a non-linear olefin, in the presence of 100 to 5,000 mℓ of a solvent and 0.5 to 5,000 g of an organoaluminum compound based on 100 g of the solid product (II), under the conditions of a reaction temperature of 0° to 90°C, a reaction time of one minute to 10 hours and a reaction pressure of the atmospheric pressure [0.1 MPa (0 Kgf/cm 2 G)] to 1.08 MPa 10 Kgf/cm 2 G], using 0.1 g to 100 Kg of a linear olefin and 0.01 g to 100 Kg of a non-linear olefin based on 100 g of the solid product and so as to give a content of the linear olefin polymer block in the final solid product (III) i.e. the titanium trichloride composition (III) of 0.1 to 49.5% by weight,and a content of the non-linear olefin polymer block therein of 0.01 to 49.5% by weight and also so as to give a ratio by weight of the linear olefin polymer block to the non-linear olefin polymer block of 2/98 to 98/2. In the case of any of the above-mentioned multi-stage polymerization treatments, the reaction mixture after completion of the polymerization treatments at the respective stages may be used, as it is, for the polymerization treatment at the subsequent stage. Further, the coexisting solvent, unreacted linear olefin or non-linear olefin and an organoaluminum compound may be removed by filtering off, decantation, followed by again adding a solvent and an organoaluminum compound and using the resulting mixture for the subsequent stage polymerization treatment with a non-linear olefin or a linear olefin. The solvent used at the time of the polymerization treatment is preferred to be an aliphatic hydrocarbon, and the organoaluminum compound may be the same as or different from that used when the reaction product (I) is obtained, or that used directly for the reaction with TiCℓ 4 , without reacting with an electron donor (B 1 ). After completion of the reaction, a liquid portion is separated and removed by filtering-off or decantation, followed by further repeatedly washing with a solvent, and the resulting solid product subjected to polymerization treatment (hereinafter referred to often as solid product (II-A)) may be used for the subsequent process in a state suspended in the solvent as it is, or may be further dried, taken out in the form of a solid substance and used. The solid product (II-A) is then reacted with an electron donor (B 2 ) and an electron acceptor (F). This reaction may be carried out without using any solvent, but use of an aliphatic hydrocarbon solvent affords preferred results. The quantities of these materials used are 0.1 to 1,000 g, preferably 0.5 to 200 g of (B 2 ), 0.1 to 1,000 g, preferably 0.2 to 500 g of (F) and 0 to 3,000 mℓ, preferably 100 to 1,000 mℓ of the solvent, each based on 100 g of the solid product (II-A). The reaction method includes 1 ○ a process of simultaneously reacting an electron donor (B 2 ) and an electron acceptor (F) with the solid product (II-A), 2 ○ a method of reacting (F) with (II-A), followed by reacting (B 2 ), 3 ○ a method of reacting (B 2 ) with (II-A), followed by reacting (F) and 4 ○ a method of reacting (B 2 ) with (F), followed by reacting (II-A), but any of these methods may be employed. As to the reaction conditions, in the case of the above methods 1 ○ and 2 ○, 40° to 200°C, preferably 50° to 100°C and 30 seconds to 5 hours are preferred, and in the case of the method 3 ○, (II-A) is reacted with (B 2 ) at 0° to 50°C for one minute to 3 hours, followed by reacting with (F) under the same conditions as in the methods 1 ○ and 2 ○. Further, in the case of the method 4 ○, (B 2 ) is reacted with (F) at 10° to 100°C for 30 minutes to 2 hours, followed by cooling down to 40°C or lower, adding (II-A) and reacting under the same conditions as in the above methods 1 ○ and 2 ○. After completion of the reaction of the solid product (II-A), (B 2 ) and (F), a liquid portion is separated and removed by filtering-off or decantation, followed by further repeatedly washing with a solvent to obtain a final titanium trichloride composition (III) used in the present invention, containing a linear olefin-non-linear olefin block copolymer in a ratio by weight of a linear olefin polymer block to a non-linear olefin polymer block of 2/98 to 98/2, the content of the linear olefin polymer block therein being 0.1 to 49.5% by weight and the content of the non-linear olefin polymer block therein being 0.01 to 49.5% by weight. As the organoaluminum compound (A 1 ) used for preparing the titanium trichloride composition (III) used in the present invention in the first aspect, an organoaluminum compound expressed by the formula AℓR 1 p R 2 p' X 3-(p+p') wherein R 1 and R 2 each represent a hydrocarbon radical such as an alkyl group, a cycloalkyl group, an aryl group, etc. or an alkoxy group, X represents a halogen atom and p and p' each represent an optional number satisfying an expression of 0<p+p'≦3. Its concrete examples are trialkylaluminums such as trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, tri-i-butylaluminum, tri-n-hexylaluminum, tri-i-hexylaluminum, tri-2-methylpentylaluminum, tri-n-octylaluminum, tri-n-decylaluminum, dialkylaluminum monohalides such as diethylaluminum monochloride, di-n-propylaluminum monochloride, di-i-butylaluminum monochloride, diethylaluminum monofluoride, diethylaluminum monobromide, diethylaluminum monoiodide, dialkylaluminum hydrides such as diethylaluminum hydride, alkylaluminum sesquihalides such as methylaluminum sesquichloride, ethylaluminum sesquichloride, monoalkylaluminum dihalides such as ethylaluminum dichloride, i-butyl-aluminum dichloride, and besides, alkoxyalkylaluminums such as monoethoxydiethylaluminum, diethoxymonoethylaluminum. These organoaluminum compounds may be used in admixture of two or more kinds thereof. As the electron donor used in the present invention, various examples thereof are mentioned below, but it is preferred that ethers are mainly used as (B 1 ) and (B 2 ) and other electron donors are used together with ethers. Examples of the electron donor are organic compounds having any atom(s) of O, N, S and P i.e. ethers, alcohols, esters, aldehydes, aliphatic acids, ketones, nitriles, amines, amides, ureas, thioureas, isocyanates, azo compounds, phosphines, phosphites, phosphinites, H 2 S, thioethers, thio alcohols. Concrete examples are ethers such as diethyl ether, di-n-propyl ether, di-n-butyl ether, diisoamyl ether, di-n-pentyl ether, di-n-hexyl ether, di-i-hexyl ether, di-n-octyl ether, di-i-octyl ether, di-n-dodecyl ether, diphenyl ether, ethylene glycol monoethyl ether, tetra-hydrofuran, alcohols such as methanol, ethanol, propanol, butanol, pentanol, hexanol, octanol, phenol, cresol, xylenol, ethylphenol, naphthol, phenols, esters such as methyl methacrylate, ethyl acetate, butyl formate, amyl acetate, vinyl butyrate, vinyl acetate, ethyl benzoate, propyl benzoate, butyl benzoate, octyl benzoate, 2-ethylhexyl benzoate, methyl toluylate, ethyl toluylate, 2-ethylhexyl toluylate, methyl anisate, ethyl anisate, propyl anisate, ethyl cinnamate, methyl naphthoate, ethyl naphthoate, propyl naphthoate, butyl naphthoate, 2-ethylhexyl naphthoate, ethyl phenylacetate, aldehydes such as acetaldehyde, benzoaldehyde, aliphatic acids such as formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, succinic acid, acrylic acid, maleic acid, etc., aromatic acids such as benzoic acid, ketones such as methyl ethyl ketone, methyl isobutyl ketone, benzophenone, nitriles such as acetonitrile, amines such as methylamine, diethylamine, tributylamine, triethanolamine, β(N,N-dimethylamino)ethanol, pyridine, quinoline, α-picoline, 2,4,6-trimethylpyridine, N,N,N',N'-tetramethylethylenediamine, aniline, dimethylaniline, amides such as formamide, hexamethylphosphoric acid triamide, N,N,N',N',N"-pentamethyl-N'-β-dimethylaminomethylphosphoric acid triamide, octamethylpyrophosphoroamide, ureas such as N,N,N',N'-tetramethyl-urea, isocyanates such as phenyl isocyanate, toluyl isocyanate, azo compounds such as azobenzene, phosphines such as ethylphosphine, triethylphosphine, tri-n-butylphosphine, tri-n-octylphosphine, triphenylphosphine, triphenylphosphine oxide, phosphites such as dimethylphosphite, di-n-octylphosphite, triethylphosphite, tri-n-butylphosphite, triphenylphosphite, phosphinites such as ethyldiethylphosphinite, ethylbutylphosphinite, phenyldiphenylphosphinite, thioethers such as diethyl thioether, diphenyl thioether, methyl phenyl thioether, ethylene sulfide, propylene sulfide, thioalcohols such as ethyl thioalcohol, n-propyl thioalcohol, thiophenol. These electron donors may be used in admixture thereof. The electron donor (B 1 ) for obtaining the reaction product (I) and the electron donor (B 2 ) to be reacted with the solid product (II-A) may be same or different. The electron acceptor (F) used in the present invention in the first aspect is those represented by halides of elements belonging to Groups III to VI of the Periodic Table. Concrete examples thereof are anhydrous aluminum chloride, SiCℓ 4 , SnCℓ 2 , SnCℓ 4 , TiCℓ 4 , ZrCℓ 4 , PCℓ 3 , PCℓ 5 , VCℓ 4 , SbCℓ 5 . These may be used in admixture. TiCℓ 4 is most preferred. As the solvent, the following are used: aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, n-octane, i-octane, etc. are used, and in place of or together with aliphatic hydrocarbons, halogenated hydrocarbons may also be used such as CCℓ 4 , chloroform, dichloroethane, trichloroethylene, tetrachloroethylene, etc. Examples of the aromatic compounds are aromatic hydrocarbons e.g. naphthalene, their derivativatives such as alkyl derivatives e.g. mesitylene, durene, ethylbenzene, isopropylbenzene, 2-ethylnaphthalene, 1-phenylnaphthalene, halides such as monochlorobenzene, chlorotoluene, chloroxylene, chloroethylbenzene, dichlorobenzene, bromobenzene. As the linear olefin used for the polymerization treatment, linear olefins such as ethylene, propylene, butene-1, pentene-1, hexene-1 are used, and particularly, ethylene and propylene are preferably used. These linear olefins are used alone or in admixture thereof. The non-linear olefin used for the polymerization treatment includes 1 ○ a saturated ring-containing hydrocarbon monomer expressed by the formula CH 2 = CH - R 3 wherein R 3 represents a saturated ring-containing hydrocarbon radical of 3 to 18 carbon atoms which has a saturated ring structure of hydrocarbon, which structure may contain silicon atom and which radical may contain silicon atom; 2 ○ a branched olefin expressed by the formula wherein R 4 represents a chain hydrocarbon radical of 1 to 3 carbon atoms which may contain silicon atom or a silicon atom, and R 5 , R 6 and R 7 each represent a chain hydrocarbon radical of 1 to 6 carbon atoms which may contain silicon atom, but any one of R 5 , R 6 and R 7 may be hydrogen atom; and 3 ○ an aromatic monomer expressed by the formula wherein n represents 0 or 1, m represents 1 or 2, R 8 represents a chain hydrocarbon radical of 1 to 6 carbon atoms which may contain silicon atom and R 9 represents a hydrocarbon radical of 1 to 12 carbon atoms which may contain silicon atom, hydrogen atom or halogen atom, and in the case of m=2, the respective R 9 s may be same or different. Concrete examples of the saturated ring-containing hydrocarbon monomer 1 ○ are vinylcycloalkanes such as vinylcyclopropane, vinylcyclobutane, vinylcyclopentane, 3-methylvinylcyclopentane, vinylcyclohexane, 2-methylvinylcyclohexane, 3-methylvinylcyclohexane, 4-methylvinylcyclohexane, vinylcycloheptane, allylcycloalkanes such as allylcyclopentane, allylcyclohexane, and besides, saturated ring-containing hydrocarbon monomers having silicon atom in the saturated ring structure such as cyclotrimethylenevinylsilane, cyclotrimethylenemethylvinylsilane, cyclotetramethylenevinylsilane, cyclotetramethylenemethylvinylsilane, cyclopentamethylenevinylsilane, cyclopentamethylenemethylvinylsilane, cyclopentamethyleneethylvinylsilane, cyclohexamethylenevinylsilane, cyclohexamethylenemethylvinylsilane, cyclohexamethyleneethylvinylsilane, cyclotetramethyleneallylsilane, cyclotetramethylenemethylallylsilane, cyclopentamethyleneallylsilane, cyclopentamethylenemethylallylsilane, cyclopentamethyleneethylallylsilane, saturated ring-containing hydrocarbon monomers containing silicon atom outside the saturated ring structure such as cyclobutyldimethylvinylsilane, cyclopentyldimethylvinylsilane, cyclopentylethylmethylvinylsilane, cyclopentyldiethylvinylsilane, cyclohexylvinylsilane, cyclohexyldimethylvinylsilane, cyclohexylethylmethylvinylsilane, cyclobutyldimethylallylsilane, cyclopentyldimethylallylsilane, cyclohexylmethylallylsilane, cyclohexyldimethylallylsilane, cyclohexylethylmethylallylsilane, cyclohexyldiethylallylsilane, 4-trimethylsilylvinylcyclohexane, 4-trimethylsilylallylcyclohexane. Concrete examples of the branched olefin 2 ○ are branched olefins at 3-position such as 3-methylbutene-1, 3-methylpentene-1, 3-ethylpentene-1, branched olefins at 4-position such as 4-ethylhexene-1, 4,4-dimethylpentene-l, 4,4-dimethylhexene-1, alkenylsilanes such as vinyltrimethylsilane, vinyltriethylsilane, vinyltri-n-butylsilane, allyltrimethylsilane, allylethyldimethylsilane, allyldiethylmethylsilane, allyltriethylsilane, allyltri-n-propylsilane, 3-butenyltrimethylsilane, 3-butenyltriethylsilane, diallylsilanes such as dimethyldiallylsilane, ethylmethyldiallylsilane, diethyldiallylsilane. Further, concrete examples of the aromatic monomer 3 ○ are styrene, as derivatives of styrene, alkylstyrenes such as o-methylstyrene, p-t-butylene, dialkylstyrenes such as 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, halogen-substituted styrenes such as 2-methyl-4-fluorostyrene, 2-ethyl-4-chlorostyrene, o-fluorostyrene, p-fluoro-styrene, etc., trialkylsilylstyrenes such as p-trimethylsilylstyrene, m-triethylsilylstyrene, p-ethyldimethylsilylstyrene, allyltoluenes such as o-allyltoluene, p-allyltoluene, allylxylenes such as 2-allyl-p-xylene, 4-allyl-o-xylene, 5-allyl-m-xylene, alkenylphenylsilanes such as vinyldimethylphenylsilane, vinylethylmethylphenylsilane, vinyldiethylphenylsilane, allyldimethylphenylsilane, allylethylmethylphenylsilane, further, 4-(o-tolyl)-butene-1, 1-vinylnaphthalene. These non-linear olefins are used alone or in admixture. The thus obtained titanium trichloride composition (III) is combined with an organoaluminum (A 2 ) and an aromatic carboxylic acid ester (E) in definite quantities mentioned below to prepare the catalyst of the present invention, or preferably by further reacting an olefin with the combination obtained above to obtain a pre-activated catalyst. The polymerization form of the propylene polymerization using the above catalyst has no particular limitation, and not only liquid phase polymerization such as slurry polymerization and bulk polymerization, but also gas phase polymerization are adequately employed. In the case of slurry polymerization or bulk polymerization, even a catalyst obtained by combining the titanium trichloride composition (III) with an organoaluminum compound (A 2 ) and an aromatic carboxylic acid (E) exhibits a sufficient effect, but in the case of gas phase polymerization, it is preferred to use a preactivated catalyst component having a higher activity, obtained by combining the titanium trichloride composition (III) with an organoaluminum compound in place of the titanium trichloride composition (III), followed by reacting an olefin with the resulting combination. In the case where slurry polymerization or bulk polymerization is succeeded by gas phase polymerization, even when the initially used catalyst is the former catalyst, since the reaction of propylene has already been carried out at the time of gas phase polymerization, the same catalyst as the latter catalyst is formed to exhibit a superior effect. For the preactivation, it is preferred to polymerize an olefin using 0.005 to 500 g of an organoaluminum, 0 to 50 ℓ of a solvent, 0 to 1,000 mℓ of hydrogen and 0.01 to 5,000 g, preferably 0.05 to 3,000 g of an olefin, each based on 1 g of the titanium trichloride compositition (III), at 0° to 100°C and for one minute to 20 hours. The reaction of an olefin for the preactivation may be carried out either in an aliphatic or aromatic hydrocarbon solvent such as n-pentane, n-hexane, n-heptane, toluene or in a liquefied olefin such as liquefied propylene, liquefied butene-1, without using any solvent, or an olefin such as ethylene, propylene may be reacted in gas phase, or the reaction may be carried out making an olefin polymer or hydrogen coexistent in advance. Further, in the preactivation, it is also possible to add an aromatic carboxylic acid ester (E). Examples of the olefin used for the preactivation are linear olefins such as ethylene, propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, branched monoolefins such as 4-methyl-pentene-1, 2-methyl-pentene-1 and at least one kind of olefins may be used. Further, as the organoaluminum compound, the same as the above-mentioned (A 1 ) may be used, but preferably, the same dialkylaluminum monohalides as (A 2 ) mentioned later may be used. After completion of the preactivation reaction, a catalyst obtained by adding a definite quantity of an aromatic carboxylic acid ester (E) to the above preactivated catalyst component slurry may be used, as it is, for propylene polymerization, or a catalyst obtained by removing coexisting solvent, unreacted olefin and an organoaluminum compound by filtering-off or decantation, followed by drying, to obtain a powder material, or a material having a solvent added to the above powder material to prepare a suspension, followed by combining an aluminum compound (A 2 ) and an aromatic carboxylic acid ester (E) with the suspension to obtain a catalyst for propylene polymerization, may be used, or a catalyst obtained by removing coexisting solvent and unreacted olefin by vaporization by means of reduced distillation, passing of an inert gas flow, followed by adding an aluminum compound (A 2 ) to the resulting powder or a suspension obtained by adding a solvent to the powder, further adding an organoaluminum compound (A 2 ) to the mixture, if necessary, and still further combining the resulting mixture with an aromatic carboxylic acid ester (E), to obtain a catalyst for propylene polymerization, may be used. At the time of the propylene polymerization, as to the respective quantities of the above titanium trichloride composition (III), organoaluminum compound (A 2 ) and aromatic carboxylic acid ester (E) used, they are used so as to give a mol ratio of the aromatic carboxylic acid ester (E) to the titanium trichloride composition (III) (E)/(III) in the range of 0.1 to 10.0 and a molar ratio of the organoaluminum compound (A 2 ) to the titanium trichloride composition (III) (Aℓ 2 /(III)) in the range of 0.1 to 200, preferably 0.1 to 100. If the quantity of the aromatic acid ester (E) added is small, improvement in the isotacticity is insufficient so that no high stiffness is obtained, while if it is too large, the resulting polymerization activity lowers and hence such large quantity is unpractical. In addition, the number of mols of the titanium trichloride composition (III) substantially refers to the number of Ti gram atoms contained in (III). At the time of propylene polymerization, as the organoaluminum compound (A 2 ) to be combined with the titanium trichloride composition, dialkylaluminum monohalides expressed by the formula AℓR 10 R 11 X are preferred. In the formula, R 10 and R 11 each represent a hydrocarbon radical such as alkyl group, cycloalkyl group, aryl group, arkaryl group or alkoxy group and X represents a halogen. Its concrete examples are diethylaluminum monochloride, di-n-propylaluminum monochloride, di-i-butylaluminum monochloride, di-n-butylaluminum monochloride, diethylaluminum monoiodide, diethylaluminum monobromide. Concrete examples of the aromatic carboxylic acid ester (E) as one of the components constituting the catalyst are ethyl benzoate, propyl benzoate, butyl benzoate, octyl benzoate, 2-ethylhexyl benzoate, methyl toluylate, ethyl toluylate, 2-ethylhexyl toluylate,methyl anisate, ethyl anisate, propyl anisate, ethyl cinnamate, methyl naphthoate, propyl naphthoate, butyl naphthoate, 2-ethylhexyl naphthoate, ethyl phenylacetate. The thus obtained catalyst used in the present invention (in the first aspect) is used for propylene polymerization. As to the polymerization form of propylene polymerization, the polymerization may be carried out by sluury polymerization in a hydrocarbon solvent such as n-hexane, n-heptane, n-octane, benzene, toluene or by bulk polymerization carried out in liquefied propylene or by gas phase polymerization. As to the polymer crystallinity capable of exhibiting the effectiveness of the present invention with polypropylene obtained according to the above various polymerization forms, the isotactic pentad ratio (P) in relation to the melt flow rate (MFR) is in the range of 1≧P≧0.015.log MFR + 0.955. There is a tendency that the higher MFR, the higher P, and usually, practical MFR is 0.05 to 200, preferably about 0.1 to 100. The polymerization temperature is usually 20° to 100°C, preferably 40° to 85°C. If the temperature is too low, the polymerization activity becomes low so that such temperature is not practical, while if it is too high, it is difficult to raise the isotacticity. The polymerization pressure is in the range of the atmospheric pressure to 5MPa (50 Kg/cm 2 G), and the polymerization time is usually about 30 minutes to 15 hours. In the polymerization, addition of a suitable quantity of hydrogen for adjusting the molecular weight and the like means are the same as those in conventional polymerization processes. The polypropylene obtained according to the present invention is a high stiffness polypropylene having a notably high transparency and used as various molded products according to known injection molding, vacuum molding, extrusion molding, blow molding, etc. (Function) The high-stiffness polypropylene obtained according to the process of the present invention exhibits a high stiffness due to the high-stiffness polypropylene-producing performance of the catalyst consisting of a combination of definite quantities of the catalyst components used in the present invention although the detailed mechanism is unclear. Further, since the resulting polypropylene contains the highly stereoregular linear olefin-non-liner olefin block copolymer in a very highly dispersed state, the non-linear olefin polymer block in the specified block copolymer exhibitsa nucleus-creating function at the time of melt-molding to thereby promote crystallization of polypropylene so that the transparency and crystallinity of the whole polypropylene are enhanced. Still further, since the linear olefin polymer block in the linear olefin-non-linear olefin block copolymer has a high compatibility with polypropylene, voids geneated in the film prepared from the polypropylene are very few. On the other hand, since the specified block copolymer introduced into the polypropylene by way of the titanium trichloride composition (III) used in the present invention in the first aspect is a stereoregular high molecular weight polymer having a high compatibility with polypropylene, as described above, no bleed thereof onto the surface of polypropylene occurs. (Example) The present invention will be described in more detail by way of Examples. The definitions of the terms and the measurement methods employed in Examples and Comparative examples are as follows: (1) TY: polymerization activity i.e. polymer yield (unit: Kg/gram atom) per gram atom of Ti. (2) MFR: melt flow rate according to JIS K 7210, Table 1, condition 14 ( unit: g/10 min. ) (3) Isotactic pentad ratio (P): measured based upon Macromolecules 8 687 (1975), that is, isotactic ratio in terms of pentad units in polypropylene molecular chain, measured using 13 C-NMR. (4) Inside haze: a haze inside a film, having removed the effect of its surface; measured by making up a polypropylene into a film of 150 µm thick by means of a press under conditions of a temperature of 200°C and a pressure of 19.7 MPa (200 Kg/cm 2 G), followed by coating liquid paraffin onto both the surfaces of the film and measuring the haze according to JIS K 7105. (Unit: %) (5) Crystallization temperature: measured using a differential scanning calorimeter at a lowering rate of 10°C/min. (6) Stiffness, strength and heat resistance: Tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane (0.1 part by weight) and calcium stearate (0.1 part by weight) were mixed with polypropylene (100 parts by weight), followed by granulating the mixture by means of an extrusion-granulator having a screw of 40 mm in bore diameter, making up the resulting granules by means of an injection molding machine at a melt resin temperature of 230°C and at a mold temperature of 50°C, into a test piece of JIS type, allowing the test piece to stand for 72 hours in a room of a humidity of 50% and room temperature (25°C) and then measuring the stiffness, strength and heat resistance according to the following methods: 1 ○ Flexural elastic modulus: measured according to JIS K 7203, at 23°C. [Unit: MPa (Kgf/cm 2 )] 2 ○ Tensile strength: measured according to JIS K 7113, at 23°C. [Unit: MPa (Kgf/cm 2 )] 3 ○ Heat deformation temperature: measured according to JIS K 7202. (Unit: °C) (7) Void: Polypropylene was granulated in the same manner as in the above item (6), followed by extruding the resulting granules by means of a T-die type film-making machine at a molten resin temperature of 250°C, preparing a sheet of 1 mm thick by means of a cooling roll at 20°C, heating the sheet with a hot air at 150°C for 70 minutes, stretching it by means of a twinscrew stretching machine in the longitudinal and lateral directions, to 7 times the respective lengths in these directions to obtain a biaxially stretched film of 20 µm thick, and observing the film by means of an optical microscope to measure the number of voids of 10 µm or larger in diameter, 10 or less of the voids per cm 2 being designated as 0, 10 to 30 voids being designated as Δ and 30 or more voids being designated as ×. (8) Weight average molecular weight and weight average molecular weight/number average molecular weight (Q): measured according to gel permeation chromatography using a device of GPC-150 C type manufactured by Waters Co., Ltd. to seek the above values. (9) Melting point: measured by means of a differential scanning calorimeter of 1090 type manufactured by Dupont Co., Ltd., that is, under conditions of keeping a sample at 230°C for 10 minutes, lowering the temperature down to -60°C at a rate of -20°C/min., keeping it at the same temperature for 10 minutes and raising the temperature at a rate of 20°C/min. (Unit: °C). (10) Durability: A test piece was prepared in the same manner as in the above item (5), followed by subjecting it to tensile creep test [load: 24.3 MPa (248 Kgf/cm 2 )] according to JIS K 7115 and measuring the creep rupture time. (Unit: hour). Example 1 (1) Preparation of titanium trichloride composition (III) n-Hexane (6 ℓ), diethylaluminum monochloride (DEAC) (5.0 mols) and diisoamyl ether (12.0 mols) were mixed at 25°C for one minute, followed by reacting the mixture at the same temperature for 5 minutes to obtain a reaction solution (I) (molar ratio of diisoamyl ether/DEAC: 2.4). TiCℓ 4 (40 mols) was placed in a reactor purged with nitrogen gas, followed by heating it to 35°C, dropwise adding thereto the total quantity of the above reaction solution (I) over 180 minutes, keeping the mixture at the same temperature for 60 minutes, raising the temperature up to 80°C, further reacting for one hour, cooling down to room temperature, removing the supernatant and 4 times repeating a procedure of adding n-hexane (20 ℓ) and removing the supernatant by decantation to obtain a solid product (II). The total quantity of this (II) was suspended in n-hexane (30ℓ), followed by adding diethylaluminum monochloride (400 g), adding propylene (1.5 Kg) at 30°C, subjecting the mixture to polymerization treatment at the same temperature for one hour, thereafter removing the supernatant by decantation, twice washing the resulting solids with n-hexane (30 ℓ), successively adding n-hexane (30 ℓ) and diethylaluminum monochloride (400 g), making the temperature 40°C, adding vinylcyclohexane (1.9 Kg), subjecting the mixture to polymerization treatment at 40°C for 2 hours, thereafter removing the supernatant and 4 times repeating a procedure of adding n-hexane (30 ℓ) and removing the supernatant by decantation to obtain a solid product (II-A) subjected to a multi-stage polymerization treatment with propylene and vinylcyclohexane. The total quantity of this solid product was suspended in n-hexane (9 ℓ), followed by adding TiCℓ 4 (3.5 Kg) to the suspension at room temperature over about 10 minutes, reacting the mixture at 80°C for 30 minutes, further adding diisoamyl ether (1.6 Kg), reacting the mixture at 80°C for one hour, thereafter 5 times repeating a procedure of removing the supernatant and drying under reduced pressure to obtain a titanium trichloride composition (III). The content of the propylene polymer block in the resulting titanium trichloride composition (III) was 25.0% by weight, the content of the vinylcyclohexane polymer block therein was 25.0% by weight and the Ti content therein was 12.6% by weight. (2) Preparation of a preactivated catalyst component Into a 80 ℓ capacity stainless reactor provided with slant blades and purged with nitrogen gas were added n-hexane (40 ℓ), diethylaluminum monochloride (114 g) and the titanium trichloride composition (III) (1.8 Kg) obtained above in the item (1) at room temperature, followed by feeding ethylene (1.8 Nm 3 ) at 30°C for 2 hours, reacting it (quantity of ethylene reacted per g of the titanium trichloride composition (III): 1.0 g), removing unreacted ethylene, washing with n-hexane, filtering and drying to obtain a preactivated catalyst component. (3) Propylene polymerization Into a 150 ℓ capacity stainless polymerization vessel (L/D=4) provided with a stirrer and purged with nitrogen gas was fed a polypropylene powder having an MFR of 2.0 (3 0 Kg), followed by continuously feeding into the vessel through the same piping, a suspension obtained by adding n-hexane to the preactivated catalyst component obtained above in the item (2) so as to give a 4.0% by weight of n-hexane suspension, at a rate of 8.77 mg atom in terms of Ti atom per hour, and diethylaluminum monochloride and methyl p-toluylate so as to give a molar ratio of 7.0 and that of 1.0, respectively, each based on Ti atom. Further, feeding hydrogen gas so as to keep its concentration in the gas phase of the polymerization vessel at 2.7% by volume, and also feeding propylene so as to give a total pressure of 2.36 MPa (23 Kg/cm 2 G), gas phase polymerization of propylene was continuously carried out at 70°C over 120 hours. During the polymerization, the resulting polymer was continuously withdrawn at a rate of 13.5 Kg/hr. so as to give a level of the polymer retained in the polymerization vessel, 45% by volumem. The withdrawn polymer was successively subjected to contact treatment with nitrogen gas containing 0.2% by volume, at 100°C for 30 minutes, followed by contact treatment with steam at 100°C for 30 minutes and further drying with nitrogen gas at 100°C to obtain polypropylene. Examples 2 and 3 Example 1 was repeated except that, in Example 1 (3), the respective catalyst components were fed so as to give hydrogen concentrations in the gas phase of the polymerization vessel, of 4.0% by volume (Example 2) and 9.7% by volume (Example 3) and so as to give a total pressure in the polymerization vessel, of 2.36 MPa (23 Kg/cm 2 G), to obtain polypropylene. Comparative example 1 (1) A titanium trichloride composition was obtained in the same manner as in Example 1 (1) except that the multi-stage polymerization of the solid product (II) with propylene and vinylcyclohexane was omitted, to prepare a solid product (II-A) corresponding to the solid product (II). (2) A preactivated catalyst component was obtained in the same manner as in Example 1 (2) except that the titanium trichloride composition obtained above in the item (1) was used in place of the titanium trichloride composition (III). (3) Polypropylene was obtained in the same manner as in Example 1 (3) except that the preactivated catalyst component obtained above in the item (2) was used as a preactivated catalyst component and the respective catalyst components were fed so as to give a total pressure in the polymerization vessel, of 23.6 MPa (23 Kg/cm 2 G). Comparative examples 2 and 3 Polypropylene was obtained in the same manner as in Comparative example 1 except that, in Example 1 (3), the hydrogen concentration in the gas phase of the polymerization vessel was changed to 4.0% by volume (Comparative example 2) and 9.7% by volume (Comparative example 3). Comparative example 4 In Example 1 (1), the polymerization treatment with vinylcyclohexane at the second step was omitted and propylene alone was reacted to obtain a titanium trichloride composition, and using this titanium trichloride composition, a preactivated catalyst component was prepared in the same manner as in Example 1 (2). Successively, Example 1 (3) was repeated except that the above preactivated catalyst component was used and the respective catalyst components were fed so as to give a total pressure in the polymerization vessel, of 23.6 MPa (23 Kg/cm 2 G), to obtain polypropylene. Comparative example 5 (1) A titanium trichloride composition was obtained in the same manner as in Example 1 (1). (2) Into the reactor employed in Example 1 (2) were added n-hexane (20 ℓ), diethylaluminum monochloride (28.5 g) and the titanium trichloride composition (III) (225 g) obtained above in the item (1) at room temperature, followed by adding vinylcyclohexane (190 g), reacting the mixture at 40°C for 2 hours (the quantity of vinylcyclohexane reacted per g of the titanium trichloride composition: 0.5 g), thereafter removing the supernatant by decantation, twice washing the solids with n-hexane (20 ℓ), successively adding n-hexane (20 ℓ) and diethylaluminum monochloride (28.5 g), making the temperature 30°C, adding propylene (150 g), reacting it at 30°C for one hour (the quantity of propylene reacted per g of the titanium trichloride composition: 0.5 g), successively removing the supernatant, washing the solids with n-hexane, filtering and drying to obtain a pre-activated catalyst component. (3) Propylene polymerization was carried out in the same manner as in Example 1 (3) except that the pre-activated catalyst component obtained above in the item (2) was used as a preactivated catalyst component. As a result, the formed mass polymer clogged the withdrawing piping so that 6 hours after the start of the polymerization, propylene polymerization had to be stopped. Comparative example 6 (1) Comparative example 1 (1) was repeated except that when the reaction solution (I) was reacted with TiCℓ 4 , separately using a titanium trichloride composition (500 g) obtained in the same manner as in Comparative example 1 (1) and diethylaluminum monochloride (120 g) as catalyst, vinylcyclohexane (1.3 Kg) added into n-hexane (100 ℓ) was polymerized at 60°C for 2 hours, followed by washing with methanol, drying, milling the resulting vinylcyclohexane polymer (950 g) in a 10 ℓ capacity vibration mill at room temperature for 5 hours and suspending the resulting material in the above TiCℓ 4 , to obtain a titanium trichloride composition containing 33.3% by weight of the vinylcyclohexane polymer. (2) A preactivated catalyst component was obtained in the same manner as in Example 1 (2) except that the titanium trichloride composition obtained above in the item (1) was used in place of the titanium trichloride composition (III). (3) Propylene polymerization was carried out in the same manner as in Example 1 (3) except that the pre-activated catalyst component obtained above in the item (2) was used as a preactivated catalyst component, to obtain polypropylene. Comparative example 7 Into a reactor purged with nitrogen gas were n-hexane (4 ℓ) and TiCℓ 4 (10 mols), followed by keeping the mixture at 0°C, dropwise adding a n-hexane solution (4 ℓ) containing diethylaluminum monochloride (8 mols), raising the temperature up to 40°C, further reacting the mixture for one hour, adding vinylcyclohexane (1.9 Kg), subjecting the mixture to polymerization treatment at the same temperature for 2 hours, thereafter removing the supernatant, three times repeating a procedure of adding n-hexane (5 ℓ) and removing by decantation, suspending the resulting solid product subjected to the polymerization treatment in n-hexane (9 ℓ), successively adding TiCℓ 4 (3.5 Kg) at room temperature, reacting the mixture at 90°C for one hour and thereafter washing with n-hexane, to obtain a titanium trichloride composition. Propylene polymerization was carried out in the same manner as in Comparative exmaple 1 except that the titanium trichloride composition obtained above was used, to obtain polypropylene. Comparative example 8 Comparative example 1 was repeated except that, in Comparative example 1 (3), methyl p-toluylate as a catalyst component was not used. Comparative example 9 and Examples 4 and 5 In Example 1 (1), allyltrimethylsilane was used in place of vinylcyclohexane, and the quantities of propylene and allyltrimethylsilane used were varied to thereby obtain titanium trichloride compositions (III) having the polymer contents as shown in Table 1, followed by preparing preactivated catalyst components using the above titanium trichloride compositions in the same manner as in Example 1 (2). Successively, propylene polymerization was carried out in the same manner as in Example 1 (3) except that the above preactivated catalyst components were used and the respective catalyst components were fed so as to give a pressure inside the polymerization vessel, of 23.6 MPa (23 Kg/cm 2 G). Comparative examples 10 - 12 and Examples 6 and 7 Polypropylenes were obtained in the same manner as in Example 1 except that, in Example 1 (1), the quantity of propylene used was changed to 750 g, and 3-methylbutene-1 (2.7 Kg) was used in place of vinylcyclohexane to carry out a multi-stage polymerization treatment, and in Example 1 (3), the molar ratio of methyl p-toluylate to Ti atom was varied as shown in Table 1 and the respective catalyst components were fed so as to give a total pressures in the polymerization vessel, of 23.6 MPa (23 Kg/cm 2 G). Example 8 n-Heptane (4 ℓ), diethylaluminum monochloride (5.0 mols), diisoamyl ether (9.0 mols) and di-n-butyl ether (5.0 mols) were reacted at 18°C for 30 minutes, followed by dropwise dropping the resulting reaction solution into TiCℓ 4 (27.5 mols) at 40°C over 300 minutes, keeping the mixture at the same temperature for 1.5 hour to react it, raising the temperature up to 65°C, reacting for one hour, removing the supernatant, 6 times repeating a procedure of adding n-hexane (20 ℓ) and removing by decantation, suspending the resulting solid product (II) (1.8 Kg) in n-hexane (40 ℓ), adding diethylaluminum monochloride (500 g), adding propylene (1.5 Kg) at 30°C and reacting for one hour, to carry out the first step polymerization treatment. After lapse of the reaction time, the supernatant was removed, followed by twice repeating a procedure of adding n-hexane (20 ℓ) and removing by decantation, successively adding n-hexane (40 ℓ) and diethylaluminum monochloride (500 g), adding 4,4-dimethylpentene-1 (3.0 Kg), reacting the mixture at 40°C for 2 hours to carry out the second step polymerization treatment and thereby obtain a solid product (II-A) subjected to a multi-stage polymerization treatment with propylene and 4,4-dimethylpentene-1. After the reaction, the supernatant was removed, followed by twice repeating a procedure of adding n-hexane (20 ℓ) and removing by decantation, suspending the above solid product (II-A) subjected to polymerization treatment in n-hexane (7 ℓ), adding TiCℓ 4 (1.8 Kg) and n-butyl ether (1.8 Kg), reacting the mixture at 60°C for 3 hours, thereafter removing the supernatant, adding n-hexane (20 ℓ), agitating for 5 minutes, allowing the resulting material to stand still, 3 times repeating a procedure of removing the supernatant and drying under reduced pressure to obtain a titanium trichloride composition (III). Propylene polymerization was carried out in the same manner as in Example 1 (2) and (3) except that the above titanium trichloride composition (III) was used. Comparative example 13 Example 8 was repeated except that a titanium trichloride composition was obtained without the multi-stage polymerization treatment with propylene and 4,4-dimethylpentene-l and the composition was used in place of the titanium trichloride composition (III), to obtain polypropylene. Example 9 (1) Preparation of titanium trichloride composition (III) TiCℓ 4 (27.0 mols) was added to n-hexane (12 ℓ), followed by cooling the mixture down to 1°C, further dropwise adding n-hexane (12.5 ℓ) containing diethylaluminum monochloride (27.0 mols) at 1°C over 4 hours, thereafter keeping the mixture at the same temperature for 15 minutes to react it, successively raising the temperature up to 65°C over one hour and further reacting at the same temperature for one hour. Next, the supernatant was removed, followed by 5 times repeating a procedure of adding n-hexane (10 ℓ) and removing by decantation, suspending 1.8 Kg of the resulting solid product (II) (5.7 Kg) in n-hexane (50 ℓ), adding diethylaluminum monochloride (350 g), further adding propylene (0.6 Kg) at 30°C subjecting it to polymerization treatment at the same temperature for one hour, successively removing the supernatant by decantation, washing the resulting solids with n-hexane (50 ℓ), adding n-hexane (50 ℓ) and diethylaluminum monochloride (350 g), further adding p-trimethylsilylstyrene (6.9 Kg), subjecting the mixture to polymerization treatment at 40°C for 2 hours, thereafter removing the supernatant, twice repeating a procedure of adding n-hexane (30 ℓ) and removing by decantation, suspending the total quantity of the resulting solid product (II-A) subjected to polymerization treatment in n-hexane (11 ℓ), adding diisoamyl ether (1.2 ℓ) and ethyl benzoate (0.4 ℓ), agitating the resulting suspension at 35°C for one hour, 5 times washing with n-hexane (3 ℓ), suspending the resulting treated solids in a n-hexane solution (6 ℓ) of TiCℓ 4 (40% by volume) and SiCℓ 4 (10% by volume), raising the temperature of the resulting suspension up to 65°C, reacting it at the same temperature for 2 hours, thereafter three times washing the resulting solids each time with n-hexane (20 ℓ) and drying under reduced pressure to obtain a titanium trichloride composition (III). (2) Preparation of a preactivated catalyst component Example 1 (2) was repeated except that the titanium trichloride composition (III) (1.8 Kg) obtained above in the item (1) was used in place of the titanium trichloride composition (III) in Example 1 (2), and propylene (1.3 Kg) was used in place of ethylene, to obtain a preactivated catalyst component. (3) Propylene polymerization Into a 200 ℓ capacity polymerization vessel provided with a stirrer having two-stage turbine elements were continuously fed a 4.0% by weight n-hexane suspension of the preactivated catalyst component obtained above in the item (2), at a rate of 19.6 mg atom in terms of Ti atom/hr., and diethylaluminum monochloride and methyl p-toluylate in molar ratios of 3.0 and 1.0 relative to Ti atom, through the same piping, and separately n-hexane at a rate of 21 Kg/hr. through a separate piping. On the other hand, feeding hydrogen so as to keep its concentration in the gas phase of the polymerization vessel at 2.9% by volume and feeding propylene so as to keep a total pressure of 1.08 MPa (10 Kg/cm 2 G), slurry polymerization of propylene was continuously carried out for 120 hours. During the polymerization period, the resulting polymer slurry was continuously withdrawn from the polymerization vessel so as to keep the level of the slurry inside the polymerization vessel at 75% by volume, into a 50 ℓ capacity flash tank. The pressure was dropped in the flash tank and unreacted propylene and hydrogen were removed, while methanol was fed at a rate of 1 Kg/hr. and the catalyst was treated at 70°C, followed by neutralizing with a NaOH aqueous solution,washing the polymer with water, separating and drying to obtain polypropylene at a rate of 10 Kg/hr. Comparative example 14 Example 9 was repeated except that the multi-stage polymerization treatment with propylene and p-trimethylsilylstyrene was not carried out to obtain a titanium trichloride composition corresponding to the solid product (II-A). Using this composition, slurry polymerization of propylene was carried out in the same manner as in Example 9. Example 10 (1) Example 1 (1) was repeated except that di-n-butylaluminum monochloride (4.0 mols) was used in place of diethylaluminum monochloride to obtain a reaction solution (I), followed by dropwise adding the solution to TiCℓ 4 at 45°C, and the first stage polymerization treatment was carried out using ethylene (950 Nℓ) in place of propylene, followed by removing unreacted ethylene, and without washing the reaction mixture, carrying out the second stage polymerization treatment using 2-methyl-4-fluorostyrene (7.6 Kg) in place of vinylcyclohexane, to obtain a titanium trichloride composition (III). (2) Example 1 (2) was repeated except that the titanium trichloride composition (III) (1.8 Kg) obtained above in the item (1) was used as the titanium trichloride composition (III), to obtain a preactivated catalyst component. (3) Example 1 (3) was repeated except that the pre-activated catalyst component obtained above in the item (2) was used as the preactivated catalyst component, ethyl p-anisate was used as the aromatic carboxylic acid ester and an equimolecular mixture of diethylaluminum monoiodide with n-propylaluminum monochloride was used as the organoaluminum compound; the molar ratio of the organoaluminum compound to the titanium trichloride composition (III) was changed to 6.0; and the respective catalyst components were fed so as to keep the total pressure at 2.36 MPa (23 Kg/cm 2 G), to obtain polypropylene. Comparative example 15 Example 10 was repeated except that, in Example 10 (1), the multi-stage polymerization treatment with ethylene and 2-methyl-4-fluorostyrene was omitted, to obtain a titanium trichloride composition. Polypropylene was then obtained in the same manner as in Example 10. The catalyst systems of Examples 1-10 and Comparative examples 1-15, the polymerization results and the evaluation results of the resulting polypropylenes are shown in the Table listed below. (Effectiveness of the Invention The main effectiveness of the present invention in the first aspect consists in that a high-stiffness polypropylene, even when made up into film, having few occurrence of voids and a superior transparency is obtained stably without causing any operational problem. As apparent from the above Examples, according to the process of the present invention in the first aspect, there is no problem in the aspect of production and a long-term, stabilized production is possible. Further, the film produced using the resulting polypropylene has an inside haze of 1.4 to 3.0% and hence has a far higher transparency than films produced using conventional polypropylenes obtained using a titanium trichloride composition containing no specified block copolymer or the polypropylene prepared according to the process of the prior application invention,either having an inside haze of about 11% to about 12%. Further, the crystallization temperature, too, has been elevated by about 12°C to about 14°C as compared with conventional polypropylenes and by about 8°C to about 10°C as compared with the polypropylene obtained according to the process of the prior application invention, and as a result of such improved crystallinity, the flexural elastic modulus, too, has been improved (see Examples 1-10, Comparative examples 1-4, 8 and 13-15). Whereas, according to conventional technique of introducing a non-linear olefin polymer according to a process other than the present invention in the first aspect, operational problems have occurred, and further problems have been raised that when the resulting polypropylene is made into a film, many voids occur, and since the dispersibility is inferior, improvements in the transparency and stiffness are insufficient (see Comparative examples 5 and 6).

Claims: A process for producing a high-stiffness polypropylene having a flexual modulus of at least 1765 M.Pa (18000 kgf/cm 2 ) which comprises polymerizing propylene using a catalyst obtained by combining: (1) a titanium trichloride composition (III) obtained by reacting TiCℓ 4 with an organoaluminum compound (A 1 ) or a reaction product (I) of an organoaluminum compound (A 1 ) with an electron donor (B 1 ) to obtain a solid product (II), followed by subjecting the solid product (II) to a multi-stage polymerization treatment with a linear olefin and a non-linear olefin, each used one or more times, to form a linear olefin-non-linear olefin block copolymer in a weight ratio of linear olefin polymer block therein to non-linear olefin polymer block of 2/98 to 98/2, followed by further reacting the block copolymer with an electron donor (B 2 ) and an electron acceptor to obtain the titanium trichloride composition (III), which contains 0. 1 to 49. 5% by weight of the linear olefin polymer block and 0.01 to 49. 5% by weight of the non-linear olefin polymer block; (2) an organoaluminum compound (A 2 ); and (3) an aromatic carboxylic acid ester (E), the molar ratio of the aromatic carboxylic acid ester (E) to the gram atoms of Ti in the titanium trichloride composition (III), that is (E)/(III), being from 0.1 to 10.0, and the molar ratio of the organoaluminum compound (A 2 ) to the gram atoms of Ti in the titanium trichloride composition (III), that is, (A 2 ) / (III), being 0.1 to 200. A process according to Claim 1 wherein the organoaluminum compound (A 1 ) has the formula AℓR 1 / pR 2 / p, X 3-(p+p') wherein R 1 and R 2 are each an alkyl, cycloalkyl or aryl group; X is a halogen atom; and p and p' are each an optional number such that 0<p+p'≤3. A process according to Claim 1 or Claim 2 wherein the non-linear olefin is a saturated ring-containing hydrocarbon monomer of the formula CH 2 = CH - R 3 wherein R 3 represents a saturated ring-containing hydrocarbon radical of 3 to 18 carbon atoms having a saturated ring structure of a hydrocarbon, which radical may contain a silicon atom. A process according to Claim 1 or Claim 2, wherein said non-linear olefin is a branched olefin of the formula wherein R 4 represents a silicon atom or a chain hydrocarbon radical of 1 to 3 carbon atoms which may contain a silicon atom; R 5 , R 6 and R 7 each represent a chain hydrocarbon radical of 1 to 6 carbon atoms which may contain a silicon atom, and one of R 5 , R 6 and R 7 may be a hydrogen atom. A process according to Claim 1 or Claim 2, wherein the non-linear olefin is an aromatic monomer of the formula wherein n represents 0 or 1; m represents 1 or 2; R 8 represents a chain hydrocarbon radical of 1 to 6 carbon atoms which may contain a silicon atom; and R 9 represents a hydrogen atom or a halogen atom or a hydrocarbon radical of 1 to 12 carbon atoms which may contain a silicon atom, and when m=2, the groups R 9 s may be the same or different. A production process according to Claim 1, wherein the organoaluminum compound (A 2 ) is a dialkylaluminum monohalide. A process according to any one of the preceding claims wherein there is used, in place of the titanium trichloride composition (III) a preactivated catalyst component obtained by combining the titanium trichloride composition (III) with from 0.005 to 500 grams of an organoaluminium compound, per 1 gram of the titanium trichloride composition (III) and then polymerising 0.05 to 3,000 grams of an olefin using, per 1 gram of the titanium trichloride composition (III) 0 to 50 litres of a solvent and 0 to 1,000 ml of hydrogen, polymerization being carried out at 0-100°C and for 1 minute to 20 hours. A process according to Claim 1, wherein the relationship between the isotactic pentad ratio (P) and the melt flow rate (MFR) of the resulting polyproylene satisfies the expression: 1.00≥ P ≥ 0.015 log MFR + 0.955

Inventors: SAITO JUN, SANDPEI AKIHIKO, SAITO, JUN, SANDPEI, AKIHIKO
Applicants: CHISSO CORP, CHISSO CORPORATION
Application year: 1990
Main classification: C08F297
IPC codes: C08F4, C08F210, C08F297, C08F110