GB2114581A

GB2114581A - Ziegler catalyst for producing propylene

Info

Publication number: GB2114581A
Application number: GB08235201A
Authority: GB
Inventors: Hiromasa Chiba; Katsumi Kumahara; Takakiyo Harada; Takahiro Oka; Akihiro Sato
Original assignee: Chisso Corp
Current assignee: JNC Corp
Priority date: 1981-12-17
Filing date: 1982-12-09
Publication date: 1983-08-24
Also published as: DE3246447C2; CA1193398A; GB2114581B; DE3246447A1

Abstract

A polypropylene capable of producing high-rigidity molded products is obtained by polymerizing propylene in the presence of a catalyst prepared by reacting an organoaluminum compound or a reaction product of an organoaluminum compound with an electron donor, with TiCl4, further reacting the resulting solid product (II) with an electron donor and an electron acceptor, and then combining the resulting solid product (III) with an organoaluminum compound and an aromatic carboxylic acid ester (V), the molar ratio of (V) to (III) being 0.2 to 10.0, and the polypropylene having an isotactic pentad ratio P relative to MFR in the range of 1.00>/=P>/=0.015 log MFR + 0.955.

Description

SPECIFICATION Polypropylene capable of producing high-rigidity molded products BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a polypropylene capable of producing high-rigidity molded products, a process for producing the same, and high-rigidity injection molded products and high-rigidity films shaped from the same. More particularly it relates to a polypropylene from which highrigidity molded products and films are produced without adding any particular additive, a process for producing the same, and high-rigidity injection molded products and high-rigidity films shaped from the same.

Description of the Prior Art Polypropylene is superior in heat resistance, resistance to chemicals and electric properties, and also good in rigidity, tensile strength, optical characteristics and processability. Thus it has been broadly used for injection molding, film- or sheet-extrusion molding, blow molding, etc.

However, these properties have not been always satisfactory depending on its application fields, and its usage has been restricted.

Particularly the rigidity of polypropylene is lower than those of polystyrene and ABS resin and this has been a serious bottleneck in broadening its application fields. If its rigidity is improved, it is possible to reduce the thickness of the resulting molded product as much. This is not only effective for resource-saving, but also for increasing cooling velocity at the time of molding.

Thus it is possible to make the molding velocity per unit time faster and improve the productivity. Particularly as to rigidity, since biaxially stretched films of polypropylene are inferior to those of cellophane, polyester films, etc., automatic packagings as in overlapping packaging, twisted packaging are difficult. Further, as to electric articles, the use of films has such disadvantages that they are liable to form wrincles due to their inferior rigidity, and attempt to avoid such wrincle formation results in inferior processability. Furthermore, as to tensile strength, if it can be improved together with rigidity, it is possible to further reduce the thickness.

The present invention is directed to a process for producing polypropylene having an extremely high stereoregularity, by polymerizing propylene by the use of a specified catalyst and under specified use conditions; a polypropylene for high-rigidity molded products obtained according to the process; and high-rigidity injection molded products and high-rigidity films produced from such polypropylene, and it has been found that high-rigidity molded products of polypropylene which have never been produced are obtained by using the above-mentioned polypropylene.

As a known art for improving the rigidity of crystalline polypropylene, for example, there is a process of adding an organic neucleus-creating agent such as aluminum para-t-butylbenzoate, 1,3- or 2,4-dibenzylidenesorbitol, etc. to polypropylene and molding the mixture, but the process has such drawbacks that the cost is high and hence uneconomical, and moreover, the luster, impact strength, tensile elongation, etc. are greatly reduced. As another means for rigidity improvement, there is a process of using various inorganic fillers such as talc, calcium carbonate, mica, barium sulfate, asbestos, calcium silicate, etc., but this process has such drawbacks that properties such as light weight and transparency specific of polypropylene are not only damaged, but also the impact strength, luster, tensile strength, additive property, etc.

are lowered. As a technique of using polypropylene having a higher isotacticity for obtaining high-rigidity molded products (Japanese patent application laid-open No. Sho 55-81125), but polypropylene used therein has an isotacticity in the range of those according to conventional art; hence the effectiveness of improving the rigidity of molded products is still yet insufficient.

In view of the present status of the above-mentioned known art, the present inventors have made strenuous studies on a process for producing a polypropylene capable of high-rigidity molded products without adding any particular additive, and as a result, have found that highrigidity molded products are obtained for the first time by using a polypropylene produced under definite conditions accordings to the present invention, hereinafter described, and have completed the present invention.

As apparent from the above description, the object of the present invention is to provide a polypropylene capable of producing high-rigidity molded products by molding, a process for producing the same, and high-rigidity molded products and films of polypropylene, produced from the above-mentioned polypropylene.

SUMMARY OF THE INVENTION The present invention is directed to: in a first aspect, (1) a polypropylene capable of producing high-rigidity molded products obtained by polymerizing propylene in the presence of a catalyst prepared by reacting an organo-aluminum compound (I) or a reaction product (VI) of an organoaluminum compound (I) with an electron donor (A), with TiC14 (C), further reacting the resulting solid product (II) with an electron donor (A) and an electron acceptor (B), and then combining the resulting solid product (III) with an organoaluminum compound (IV) and an aromatic carboxylic acid ester (V), the molar ratio of said aromatic carboxylic acid ester to said solid product (III) being in the range of 0.2 to 10.0;; (2) a polypropylene according to the above item (1) wherein said organoaluminum compound is a dialkylaluminum monohalide; (3) a process for producing a polypropylene according to the above item (1) wherein said catalyst is further preactivated by reacting an a-olefin with a combination of said solid product (Ill) with an organoaluminum compound; and (4) a polypropylene according to the above item (1), which has an isotactic pentad ratio (P) relative to MFR in the range of 1.002P20.015 log MFR + 0.955; in a second aspect, (5) a process for producing a polypropylene which comprises polymerizing propylene in the presence of a catalyst prepared by reacting an organoaluminum compound (I) or a reaction product (VI) of an organoaluminum compound (I) with an electron donor (A), with TiCI4 (C), further reacting the resulting solid product (II) with an electron donor (A) and an electron acceptor (B), and then combining the resulting solid product (III) with an organoaluminum compound (IV) and an aromatic carboxylic acid ester (V), the molar ratio of said aromatic carboxylic acid ester to said solid product (Ill) being in the range of 0.2 to 10.0;; (6) a process for producing a polypropylene according to the above item (5), wherein said organoaluminum compound (IV) is a dialkylaluminum monohalide; (7) a process for producing a polypropylene according to the above item (5), wherein said catalyst is further preactivated by reacting an a-olefin with a combination of said solid product (III) with an organoaluminum compound; and (8) a process for producing a polypropylene according to the above item (5), which has an isotactic pentad ratio (P) relative to MFR in the range of 1.002P20.015 log MFR + 0.955; in a third aspect, (9) a high-rigidity injection molded product of polypropylene obtained by using a crystalline polypropylene which has an isotactic pentad ratio (P) relative to MFR in the range of 1.002P20.015 log MFR + 0.955, and those successive extracts with boiling n-hexane and boiling n-heptane, have an isotactic pentad ratio (P) in the range of 0.450 to 0.700 and that in the range of 0.750 to 0.930, respectively; and in a fourth aspect, (10) a high-rigidity film of polypropylene obtained by using a crystalline polypropylene which has an isotactic pentad ratio (P) relative to MFR in the range of 1.002P20.015 log MFR + 0.955, and whose successive extracts with boiling n-hexane and boiling n-heptane, have an isotactic pentad ratio (P) in the range of 0.450 to 0.650 and that in the range of 0.750 to 0.900, respectively, the total amount of said extracts being in the range of 3 to 6% by weight based on said polypropylene.

DETAILED DESCRIPTION OF THE INVENTION Even if the above-mentioned solid product (III) as a catalyst component used in the present invention is replaced by various kinds of titanium trichloride such as products obtained by reacting TiCI4 with metallic aluminum or hydrogen or milling them for activation, that is, the socalled A type, H type, AA type or HA type, further a product obtained by having TiCI4 supported on a carrier such as magnesium chloride or a product obtained by reducing TiCI4 with an organoaluminum compound, followed by a mere heat-treatment, it is impossible to achieve the object of the present invention.

The solid product (III) is prepared as follows: First, (a) an organoaluminum compound (I) is reacted with TiCI4 (C), or (b) a reaction product (Vl) of the former with an electron donor (A) is reacted with the latter, to obtain a solid product (II). The latter process (b) can yield finally a more preferable titanium catalyst component. The process (b) is disclosed in Japanese patent application No. Sho 55-12875/1980 (Japanese patent application laid-open No. Sho 56-110707/1981), and is as follows: The reaction of an organoaluminum (I) with an electron donor (A) 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 (I), (A) and (D) has no particular limitation, and as to the proportions of their amounts used, the amount of the election donor is suitably in the range of 0.1 to 8 mols, preferably, 1 to 4 mols, and the amount of the solvent is suitably in the range of 0.5 to 51, preferably 0.5 to 21, each based on one mol of the organoaluminum. Aliphatic hydrocarbons are preferable as the solvent. Thus a reaction product (VI) is obtained.It is possible to subject this reaction product (VI) to the succeeding reaction without being separated, that is, in a liquid state after completion of the reaction (such a liquid hereinafter being often referred to as reaction liquid (Vl)): The reaction of the solid product (VI) with TiCI4 (C) is carried out at 0, to 200"C, preferably 10 to 90"C, for 5 minutes to 8 hours. It is preferred not to use solvent, but it is also possible to use aliphatic or aromatic hydrocarbons.Mixing of (VI), (C) and solvent may be carried out in any order; it is preferred to complete mixing of the total amount within 5 hours; and after this mixing of the total amount, it is preferred to further continue the reaction at 1 0, to 90"C within 8 hours. As to the respective amounts used, the solvent is used in an amount of O to 3,000 ml based on one mol of TiCI4 and the reaction product (VI) is used in a ratio of the number of Al atoms in the product (Vl) to the number of Ti atoms in TiCI4 (Al/Ti) of 0.05 to 10, preferably 0.06 to 0.2.After the reaction, the resulting material is subjected to filtration or decantation to separate off a liquid portion, followed by repeated washings with a solvent to obtain a solid product (II), which may be used in the succeeding step in a state suspended in the solvent as it is, or may be further dried, taken out in the form of solids and used.

The solid product (II) is then reacted with an electron donor (A) and an electron acceptor (B).

This reaction may be carried out without using any solvent, but use of aliphatic hydrocarbons affords preferable results. The respective amounts used based on 100 g of the solid product (II) are as follows: (A), 10 to 1,000 g, preferably 50 to 200 g; (B), 10 to 1,000 g, preferably 20 to 500 g; and solvent, 0 to 3,000 ml, preferably 100 to 1 ,000 ml. It is preferred to mix these three or four substances at - 1 0'C to + 40"C over 30 seconds to 60 minutes and react them at 40 to 200"C, preferably 50 to 100"C, for 30 seconds to 5 hours.The mixing oder of the solid product (II), (A), (B) and solvent has no particular limitation. (A) and (B) may be reacted together in advance of mixing them with the solid product (II), and in this case, (A) is reacted with (B) at 10 to 100"C for 30 minutes to 2 hours, and the resulting material is cooled down to 40"C or lower and used.After the reaction of the solid product (II) with (A) and (B), the reaction mixture is subjected to filtration or decantation to separate off a liquid portion, followed by repeated washings with a solvent to remove unreacted liquid raw materials to thereby obtain a solid product (III), which is dried, taken out in the form of solids and used in the succeeding step, or used in a state suspended in the solvent, as it is.

The thus obtained solid product (III) is combined with 0.1 to 500 g of an organoaluminum compound and a definite amount of an aromatic ester mentioned below to obtain a catalyst, or preferably this catalyst is further preactivated by reacting an a-olefin therewith, followed by adding the ester to obtain a catalyst of the present invention.

The organoaluminum compounds (IV) used in this invention are expressed by the general formula AIR,R1,,X3 - (n + n') (wherein R and R' each represent hydrocarbon groups such as alkyl group, aryl group, alkaryl group, cycloalkyl group, etc. or alkoxy groups, X represents a halogen atom such as F, Cl, Br and I, and n and n' each represent an optional number satisfying a condition of O < n + n''3).

As for concrete examples, trialkylaluminums such as trimethylaluminum, triethylaluminum, tri-npropylaluminum, tri-n-butylaluminum, tri-i-butyialuminum, tri-n-hexylaluminum, tri-i-hexylaluminum, tri-2-methylpentylaluminum, tri-n-octylaluminum, tri-n-decylaluminum, etc., dialkylaluminum monohydrides such as diethylaluminum monochloride, di-n-propylaluminum monochloride, di-i-butylaluminum monochloride, diethylaluminum monofluoride, diethylaluminum monobromide, diethylaluminum monoiodide, etc., alkylaluminum hydrides such as diethylaluminum hydride, alkylaluminum halides such as methylaluminum sesquichloride, ethylaluminum sesquichloride, ethylaluminum dichloride, i-butylaluminum, etc. are mentioned, and besides, alkoxyalkylaluminums such as monoethoxydiethylaluminum, diethoxymonoethylaluminum, etc. can be also employed.These organoaluminum compounds may be used in admixture of two or more kinds. The organoaluminum compound (I) for obtaining the solid product (VI) may be the same as or different from the organoaluminum compound (IV) to be combined with the solid product (III).

As the electron donor (A) used in the present invention, various compounds mentioned below are illustrated, but it is preferred to use mainly ethers and use other electron donors together with ethers. Compounds used as the electron donor are organic compounds containing at least one atom selected from oxygen, nitrogen, sulfur and phosphorus, such as ethers, alcohols, esters, aldehydes, carboxylic acids, ketones, nitriles, amines, amides, ureas, thioureas, isocyanates, azo compounds, phosphines, phosphites, phosphinites, thioethers, thioalcohols, etc.As for concrete examples, ethers such as diethyl ether, di-n-propyl ether, di-n-butyl ether, di-i-amyl ether, di-n-pentyl ether, di-n-hexyl ether, di-i-hexyl ether, di-n-octyl ether, di-i-octyl ether, di-ndodecyl ether, diphenyl ether, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, etc., alcohols such as methanol, ethanol, propanol, butanol, pentanol, hexanol, octanol, etc., phenols such as phenol, cresol, xylenol, ethyl phenol, naphthol, etc., 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 naphtoate, ethyl naphthoate, propyl naphthoate, butyl naphthoate, 2-ethylhexyl naphthoate, ethyl phenylacetate, etc., aldehydes such as acetaldehyde, benzaldehyde, etc., carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, succinic acid, acrylic acid, maleic acid, benzoic acid, etc., ketones such as methyl ethyl ketone, methyl isobutyl ketone, benzophenone, etc., nitriles such as acetonitrile, etc., amines such as methylamine, diethylamine, tributylamine, triethanolamine, fl(N,N-dimethy- lamino)ethanol, pyridine, quinoline, a-picoline, N, N, N', N'-tetramethylhexaethylenediamine, aniline, dimethylaniline, etc., amides such as formamide, hexamethylphosphoric acid triamide, N,N,N',N',N"-pentamethyl-N'-ss-dimethylaminomethylphosphoric acid triamide, octamethylpyrophosphoroamide, etc., ureas such as N,N,N',N'-tetramethylurea, etc., isocyanates such as phenylisocyanate, toluylisocyanate, etc., azo compounds such as azobenzene, etc., phosphines such as ethylphosphine, triethylphosphine, tri-n-butylphosphine, tri-n-octylphosphine, triphenylphosphine, triphenylphosphine oxide, etc., phosphites such as dimethylphosphite, di-n-octylphosphite, tri-n-butylphosphite, triphenylphosphite, etc., phosphinites such as ethyldiethylphosphinite, ethyldibutylphosphinite, phenyldiphenylphosphinite, etc., thioethers such as diethyl thioether, diphenyl thioether, methyl phenyl thioether, ethylene sulfide, propylene sulfide, etc., thioalcohols such as ethyl thioalcohol, n-propyl thioalcohol, thiophenol, etc., and the like can be illustrated.

The electron acceptor (B) used in the present invention is represented by halides of elements of groups IlI-VI of the Periodic Table. concrete examples are anhydrous AICI3, SiCI4, SnCl2, SnC14, TiCI4, ZrCl4, PCI3, PCl5, VCl4, SbCl5. They may also be used in admixture. The most preferably compound is TiCI4.

As the solvent, the following are used: as aliphatic hydrocarbons, n-heptane, n-octane, i-octane, etc. are illustrated, and in place of or together with aliphatic hydrocarbons, halogenated hydrocarbons such as carbon tetrachloride, chloroform, dichloroethane, trichloroethylene, tetrachloroethylene, etc. may also be used. Aromatic compounds such as aromatic hydrocarbons e.g. naphthalene, alkyl- -substitutes as their derivatives such as mesitylene, durene, ethylbenzene, isopropylbenzene, 2-ethylnaphthalene, 1-phenylnaphthalene, etc., halides e.g. monochlorobenzene, o-dichlorobenzene, etc. are illustrated.

The thus obtained solid product (III) is then combined with an organoaluminum compound (IV) and the above-mentioned aromatic ester to obtain a catalyst, which is used for propylene polymerization in a conventional manner, or preferably further reacted with an a-olefin and used as a preactivated catalyst. As the organoaluminum compound (IV), dialkylaluminum monohalides expressed by the formula AIR'R2X are preferable. In the formula, R, and R2 each represent hydrocarbons such as alkyl group, aryl group, alkaryl group, cycloalkyl group, etc. and alkoxy group, and X represents a halogen of F, Cl, Br or I. Concrete examples are diethylaluminum monochloride, di-n-butylaluminum monochloride and diethylaluminum iodide.In the case of slurry polymerization or bulk polymerization, even a catalyst obtained by combining the solid product (III) with an organoaluminum compound, sufficiently exhibits its effectiveness, but in the case of gas phase polymerization, it is preferred to further react the catalyst with an a-olefin and use the resulting preactivated catalyst having a higher activity. In the case of slurry or bulk polymerization followed by gas phase polymerization, even if the catalyst initially used is the former catalyst, the catalyst used in the gas phase polymerization is the same as the latter catalyst since the catalyst initially used has already reacted with propylene; thus the catalyst exhibits a superior effectiveness.

For the preactivation it is preferred to use 0.1 to 500 g of an organoaluminum, 0 to 501 of a solvent, 0 to 1,000 ml of hydrogen and 0.05 to 5,000 g, preferably 0.05 to 3,000 g of an aolefin, each based on 1 g of the solid product (Ill), and react the a-olefin at 0 to 100"C for one minute to 20 hours to thereby yield 0.01 to 2,000 g, preferably 0.05 to 200 g, of reacted aolefin based on 1 g of the solid product (Ill).

The reaction of an a-olefin for the preactivation can be carried out either in an aliphatic or aromatic hydrocarbon solvent or in a liquefied a-olefin such as liquefied propylene, liquefied butene-1, etc. without using any solvent, and it is also possible to react ethylene, propylene or the like in gas phase. Further it is also possible to carry out the reaction in the coexistence of an a-olefin polymer prepared in advance or hydrogen.

The preactivation process includes various embodiments such as (1) a process wherein an aolefin is contacted with a catalyst consisting of a combination of the solid product (III) with an organoaluminum to carry out slurry, bulk or gas phase reaction; (2) a process wherein the solid product (III) is combined with an organoaluminum in the presence of an a-olefin; (3) a process wherein an a-olefin polymer is made coexistent in the above process (1) or (2); and (4) a process wherein hydrogen is made coexistent in the above process (1), (2) or (3). In the preactivation, it is also possible to add an aromatic ester (V) in advance.

The a-olefin used for the preactivation includes straight chain monoolefins such as ethylene, propylene, butene-1, hexene-1, heptene-1, etc., branched chain monoolefins such as 4-methyl pentene-1 ,2-methyl-pentene-1, 3-methyl-butene-1, etc. Styrene can also be used. These olefins may be same as or different from a-olefins as the objective of polymerization, and also may be used in admixture.

After completion of the preactivation, solvent, organoaluminum compound and unreacted aolefin may be removed by distilling off under reduced pressure or the like means, to use the resulting product for polymerization in the form of dry powder; or the product may be used in a suspended state in a solvent within a range of amount which does not exceed 801 per g of the solid product (III); or solvent, unreacted olefin and organoaluminum compound may be removed by filtering off and decantation or further dried, and used in the form of powder. Further it is also possible to add an organoaluminum compound in advance of polymerization.

Using the thus obtained preactivated catalyst, propylene polymerization can be carried out according to slurry polymerization carried out in a hydrocarbon solvent such as n-hexane-nheptane, n-octane, benzene, toluene, etc., slurry polymerization carried out in liquefied propylene or gas phase polymerization, and for elevating the isotacticity of the resulting propylene polymer, it is necessary to add an aromatic acid ester (V) (hereinafter abbreviated to aromatic ester) to the solid product (III) in a molar ration (V/Ill) of 0.1 to 10.0. If the amount of an aromatic ester added is less, improvement in the isotacticity is insufficient, while if it is too large, the catalyst activity lowers; hence such outside ratios are not practical.Examples of aromatic esters 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, 2ethylhexyl naphthoate, ethyl phenylacetate, etc. The ratio by mol of an organoaluminum compound (IV) to the solid product (III) used (Al/Ti) is in the range of 0.1 to 100, preferably 1 to 20. In this case, the number of mols of the solid product (III) refers to substantially the number of Ti g atoms in (III). As the crystallinity of polymer which enables the present invention to exhibit its effectiveness, the isotactic pentad ratio P (defined later) relative to MFR, of the polymer is in the range of 12P20.015 log MFR + 0.955.There is a tendency that the higher the MFR value, the higher the P value, and practical MFR values are in the range of usually 0.05 to 100, preferably about 0.1 to 50. The polymerization temperature is in the range of usually 20 to 1 00 C, preferably 40 to 85"C. Too low temperatures are not practical due to lower catalyst activity. Higher temperatures make elevation of the isotacticity difficult. As to the polymerization pressure, polymerization is carried out under a pressure in the range of the atmospheric one to 50 Kg/cm2G, usually for about 30 minutes to 1 5 hours. Addition of a suitable amount of hydrogen for adjusting the molecular weight and the like means at the time of polymerization, are the same as those in conventional polymerization processes.

The extract portion with boiling n-hexane, of polypropylene used in the above-mentioned third aspect of the present invention must have a P value in the range of 0.45 to 0.700. If the value is less than 0.450, it is possible to improve the rigidity of injection molded products of the present invention (which will often be hereinafter referred to as products of the present invention), but the effectiveness of improvement in other physical properties of products of the present ivnention such as hardness, heat deformation temperature, etc. is insufficient.Further, the isotactic pentad ratio P of an extract portion by successive extractions with boiling n-hexane and boiling n-heptane is the ratio of an extract portion obtained by extracting polypropylene used in the present invention with boiling n-hexane and then further extracting the resulting extraction residue with boiling n-heptane. This extract portion must have a P value in the range of 0.750 to 0.930. If it is less than 0.75, the rigidity of products of the present invention is improved, but as to other physical properties of products of the present invention, similar drawbacks to those in the case of the above-mentioned extract with boiling n-hexane occur.The total amount of extracts by successive extractions with boiling n-hexane and boiling n-heptane has no particular limitation, but in reality the total amount of extracts in raw material polypropylene is mostly in the range of 1.0 to 10.0% by weight, and polypropylene within this range yields better results than that outside this range. The above-mentioned successive extractions are carried out as described later.

The extract portion in polypropylene used in the above-mentioned fourth aspect of the present invention must have a P value in the range of 0.450 to 0.650. Even if the P value is less than 0.45, it is possible to improve the rigidity of products of the present invention, but the effectiveness of improvement in other physical properties such as hardness, heat deformation temperature, etc. is insufficient. Further, the ratio P of an extract with boiling n-heptane is that of an extract portion obtained by extracting polypropylene used in the present invention with boiling n-hexane, and further extracting the resulting extraction residue with boiling n-heptane.

This extract portion in polypropylene used in the present invention must have a P value in the range of 0.75 to 0.850. Even if it is less than 0.75, it is possible to improve the rigidity of products of the present invention, but as to other physical properties of products of the present invention, similar drawbacks to those in the case of the above-mentioned extract with boiling nheptane occur. If the P value exceeds the upper limit of the above range, punching impact strength and transparency lower together with the decrease in the amount of the extract. The total amount of extracts by successive extractions with boiling n-hexane and boiling n-heptane must be in the range of 3.0 to 6.0% by weight based on the weight of raw material polypropylene.If the total amount is less than 3.0% by weight, transparency, punching impact strength and stretchability lower, and if it exceeds 6.0% by weight, the effectiveness of improvement in the rigidity of products of the present invention is insufficient. The proportion of the amount of the extract with boiling n-hexane in the total amount of extracts has no particular limitation. However, when polypropylene produced according to the above-mentioned process of Japanese patent application No. Sho 56-204066 is successively extracted with boiling nhexane and then boiling n-heptane, the amount of the former extract portion is in the range of 0.5 to 4.0% by the weight based on the weight of the polypropylene and that of the latter extract portion is in the range of 2 to 4% by weight. The successive extractions are carried out as described later.

Polypropylene for high-rigid molded products of the present invention is broadly applicable to various molding fields and can exhibit its effectiveness.

For example, in the injection molding field, the following effectiveness is exhibited: an effectiveness of expanding the field where polypropylene has been used, as far as the fields of high-rigidity polymers such as polystyrene, ABS resin, etc., where propylene has heretofore been impossible to use; an effectiveness of quality improvement due to creation of high-rigidity molded products; and an effectiveness of making molded products thinner than conventional products, due to creation of high-rigidity molded products. Thus, it is possible to expect an effectiveness of resources saving, cost down due to improvement in the molding rate, etc.

Further, when a nucleus-creating agent or an inorganic filler is used at the same time, it is possible to achieve a high rigidity which conventional products could have never achieved, and in the case where it is sufficient to maintain a resin on a similar rigidity level to those of conventional products, it is possible to save the amount of the resin used. Similarly, in the field of films, it is possible to exhibit an effectiveness of improving operability at the time of automatic packaging, etc. by rigidity improvement, and effecting cost reduction by making molded products thinner.

The present invention will be further concretely described by way of Examples, but it is not limited thereby. In addition, the methods of measuring various physical properties described in Examples and Comparative examples are as follows: Methods of measuring physical properties of injection molded products: Bending modulus: according to JIS K 6758 (kgf/cm2) Bending strength: according to JIS K 6758 (Kgf/cm2) Tensile strength: according to JIS K 6758 (Kgf/cm2) Hardness (Rockwell): according to JIS K 6758 (R-scale) Heat deformation temperature (HDT): according to JIS K 7202 ("C) Method of measuring physical properties of films: Young's modulus: according to ASTM D 888 (Kgf/mm2) Tensile yield strength: according to ASTM D 882 (Kgf/mm2) (In Examples, the above Young's modulus and tensile yield strength are shown in terms of the average value of TD and MD.) Haze: according to ASTM D 1003 (%) Punching impact strength: according to ASTM D 781 (Kgf/cm2) MFR: according to ASTM D 1238 (g/10 min.), 230"C, 2.16 Kg Isotactic pentad ratio (P): This is measured based on Macromolecules 8 687 (1975), and refers to an isotactic ratio in terms of pentad units in polypropylene molecule chain, measured using '3C-NMR.

Successive extractions: This is carried out by adding a small amount of a heat stabilizer (e.g. 0.1 part of 2,6-di-tbutyl-p-cresol) to 100 parts of polypropylene powder, granulating them by means of an extruder, milling by means of a mill, sieving by means of 20 mesh sieve, and extracting 3 g of the resulting 20 mesh pass with boiling n-hexane (100 ml) for 6 hours and successively with boiling n-heptane (100 ml). for 6 hours, by means of a Soxhlet extractor.

Example 1 (1) Preparation of catalyst n-Hexane (600 ml), diethylaluminum monochloride (DEAC) (0.50 mol), diisoamyl ether (1.20 mol) were mixed together at 25"C for one minute and reacted at the same temperature for 5 minutes to obtain a reaction liquid (Vl) (molar ratio of diisoamyl ether/DEAC: 2.4).TiCI4 (4.0 mols) was placed in a nitrogen gas-purged reactor and heated to 35"C, followed by dropwise adding the total amount of the reaction liquid (Vl) over 1 80 minutes, keeping the temperature at the same temperature for 30 minutes, raising the temperature up to 75"C, reacting them for one hour, cooling the resulting reaction material down to room temperature, removing the supernatant, and 4 times repeating a procedure of adding n-hexane (4,000 ml) and removing the supernatant by decantation, to obtain a solid product (11) (190 g).The total amount of this product (II) was suspended in n-hexane (3,000 ml), and to the resulting suspension were added diisoamyl ether (160 g) and TiCI4 (350 g) at room temperature (20"C) over about one minute, followed by reacting them at 65"C for one hour, cooling the resulting reaction material down to room temperature (20 C), removing the supernatant by decantation, 5 times repeating a procedure of adding n-hexane (4,000 ml), stirring for 10 minutes, allowing to still stand and removing the supernatant and drying under reduced pressure, to obtain a solid product (III).

(2) Preparation of preactivated catalyst Into a 20 1 capacity stainless steel reactor equipped with slant blades, after purged by nitrogen gas, were added at room temperature, n-hexane (151), diethylaluminum monochloride (42 g), and the above solid product (Ill) (30 g), followed by introducing hydrogen (15 NI), reacting them under a propylene partial pressure of 5 Kg/cm2G for 5 minutes, and removing unreacted propylene, hydrogen and n-hexane under reduced pressure, to obtain a preactivated catalyst (VII) in the form of powder (reacted propylene per g of the solid product (Ill): 82.0 g).

(3) Propylene polymerization Into a 250 I capacity stainless steel polymerization vessel equipped with turbine type agitating blades, after purged with nitrogen gas, were fed n-hexane (100 I) and then diethylaluminum monochloride (10 g), the above preactivated catalyst (VII) (10 g) and methyl p-toluylate (11.0 g), and further hydrogen (100 NI) was added, followed by raising the temperature up to 70"C, feeding propylene to raise the total pressure up to 10 Kg/cm2G, continuously carrying out polymerization at 70"C under 10 Kg/cm2G for 4 hours, feeding methanol (25 I), raising the temperature up to 80"C, after 30 minutes, adding an aqueous solution of 20% NaOH (100 g), stirring for 20 minutes, adding purified water (50 I), discharging remaining propylene, withdrawing the aqueous layer, further adding purified water (50 1), washing with water with stirring for 10 minutes, discharging the aqueous layer, further withdrawing polypropylene-nhexane slurry, filtering and drying, to obtain polypropylene powder.

(4) Production of injection molded product To the polypropylene powder (4.0 g) obtained in the above polymerization (3) were added a phenolic heat stabilizer (0.004 Kg) and calcium stearate (0.004 g), and they were mixed together at room temperature for 10 minutes by means of a high speed agitation type mixer (Henschel mixer, trade name), followed by granulating the resulting mixture by means of an extrusion granulator having a screw bore diameter of 40 mm.The resulting granulated material was injection-molded at a molten resin temperature of 230"C and a die temperature of 50"C by means of an injection molding machine to prepare a test piece of JIS type, which was then conditioned in a room at a humidity of 50% and room temperature (23"C) for 72 hours, followed by measuring the values of its physical properties as shown in Table 1 mentioned later.

Examples 2 and 3 Example 1 was repeated except that 100 NI of hydrogen in Example 1 was replaced by 200 NI in Example 2 and 410 NI in Example 3. The results are shown in Table 1.

Comparative examples 1, 2 and 3 Examples 1, 2 and 3 were respectively repeated except that the preactivated catalysts (VII) in Examples 1, 2 and 3 were replaced by a commercially available catalyst (AA type) (40 g) obtained by reducing TiCI4 with metallic aluminum, followed by milling activation, and methyl toluylate (22 g). The results are shown in Table 1. As apparent from the Table, in the case of usual AA type catalyst, even if an aromatic ester is added at the time of propylene polymerization, it is impossible to obtain high rigidity as an effectiveness of the present invention.

Comparative example 4 Anhydrous magnesium chloride (20 g), ethyl benzoate (10.0 ml) and methylpolysiloxane (6.0 ml) were milled in a ball mill for 100 hours. The resulting solid product (15 g) was suspended in TiCI4 (200 ml), followed by stirring at 80"C for 2 hours, removing the liquid by filtration, washing with n-hexane till no TiCI4 was detected in the filtrate, and drying to obtain a solid catalyst. Example 1 was then repeated except that this solid catalyst (10 g) was used in place of the preactivated catalyst of Example 1 and TEA (10 g) was used in place of DEAC. The results are shown in Table 1. As apparent from the Table, according to the supported type catalyst of this Comparative example, it was impossible to obtain high rigidity as an effectiveness of the present invention.

Comparative exmple 5 In the reaction of obtaining the solid product (II) in Example 1, DEAC (0.5 mol) was used in place of the reaction liquid (VI) and dropwise addition was carried out as in Example 1 but at 0 C in place of 35"C, followed by raising the temperature up to 75"C, reacting them with stirring for one hour, refluxing at a boiling temperature of TiCI4 (about 136"C) for 4 hours to allow the reaction material to transform to a violet one, cooling, washing with n-hexane, filtering and drying as in Example 1, to obtain a solid catalyst. Comparative example 2 was repeated except that the solid product was used in place of the catalyst (AA) of Comparative example 2.

The results are shown in Table 1. This case also was inferior to Examples 1, 2 and 3 in overall rigidity.

Table 1 Polymerization conditions and results and physical properties of injection molded products (I)

Example Comparative example 1 2 3 1 2 3 4 5 Mol ratio of aromatic * 1.0 1.0 1.0 0.5 0.5 0.0 - 1.0 ester/solid product Kind of catalyst For present invention AA Type Supported Org. Altype reduced type Polypropylene yield (Kg) 45.5 46.5 44.0 41.5 40.5 39.5 42.5 43.5 MFR 2.5 10.6 34.0 2.7 9.8 36.5 4.3 9.4 Amount of C6+C7 extracts 2.8 3.2 3.5 4.2 4.5 5.1 8.0 4.1 (%) Isotactic pentad ratio Total 0.972 0.981 0.990 0.922 0.935 0.948 0.915 0.955 P # n-C6 extract 0.516 0.587 0.654 0.286 0.244 0.297 0.152 0.312 n-C7 extract ** 0.775 0.846 0.893 0.577 0.598 0.681 0.547 0.693 Bending modulus 17,200 18,300 19,200 12,100 13,600 15,000 11,700 15,600 Bending strength 465 488 510 350 383 410 338 425 Tensile strength 370 378 385 325 337 348 320 355 Hardness 111 115 117 100 103 104 99 104 H D T 118 121 123 101 105 110 100 110 NOTE: * Methyl toluylate was used.

** n-C6 extract was successively extracted.

As apparent from Table 1, in the case of Comparative examples 1, 2 and 3 where titanium trichloride AA was used in place of the solid product (Ill) of the present invention, various strengths, hardness and HDT of molded products obtained by subjecting the respective polypropylenes prepared in these Comparative examples to injection molding were far inferior to those in Examples 1, 2 and 3, irrespective of whether or not the titanium trichloride AA was combined with an aromatic ester. Since polypropylenes of Comparative examples 1, 2 and 3 are similar products to those which are currently commercially available, it is apparent that the highrigid molded product of the present invention cannot be obtained from such commercially available products.

Similar results are also obtained in Comparative example 4 where a supported type TiCI4 was used in place of the solid product (III) and no aromatic ester was used, and also in Comparative example 5 where a titanium trichloride obtained by reduction with an organoaluminum (note: this correspondes to the solid product (Il) of the present invention) was used in place of the solid product (III), and in the case of Comparative example 5, the values of various physical properties excluding hardness were intermediate values between those of Example 2 and those of Comparative example 2.

Examples 4-6 and Comparative examples 6-8 The ratio of methyl p-toluylate to solid product in Example 2 was varied as listed in Table 2, but in Example 4 and Comparative examples 6 and 7, the preactivated catalyst in an amount of 5 g in each case was used. The results are shown in Table 2.

Table 2 Polymerization conditions and results and physical properties of injection molded products (II)

Example Comparative example # 4 5 6 6 7 8 Mol ratio of aromatic ester/ solid product * 0.5 2.0 5.2 0.0 0.05 15 Kind of catalyst component For present invention Polypropylene yield (Kg) 28.5 26.0 9.0 34.5 32.5 2.5 MFR 18.2 8.7 6.2 37 26 10.4 Amount of C6+C7 extracts (%) 4.7 2.5 2.1 9.2 6.6 4.2 Isotactic pentad ratio Total 0.972 0.981 0.985 0.955 0.960 0.981 P # n-C6 extract 0.516 0.587 0.614 0.291 0.345 0.574 n-C7 extract ** 0.775 0.846 0.860 0.710 0.712 0.835 Bending modulus 17,800 19,100 18,800 15,300 16,100 Bending strength 470 502 498 425 435 Tensile strength 376 383 380 350 355 Hardness 112 116 115 103 104 H D T 118 120 118 109 110 Note: *: Methyl toluylate was used. **: n-C6 extract was successively extracted.

#: Mol ratios of aromatic ester to solid product are outside the range of the present invention.

In the case of Comparative examples 6-8, a combination of the solid product (III) with an organoaluminum compound was used as in the process of the present invention, but no aromatic ester was used or the mol ratios of an aromatic ester to the solid product were outside the range of the present invention; hence the resulting polypropylene molded products could not have any required high rigidity. In addition, in the case of Example 8, no measurement of physical properties was carried out since the yield was too low.

Example 7 Example 2 was repeated except that the solid product (III) was used in place of the preactivated catalyst (VII). The results are shown in Table 3.

Example 8 A solution of DEAC (340 ml) in n-hexane (900 ml) was added to n-hexane (1,200 ml) and TiCI4 (300 ml) with stirring at 1 C over 4.5 hours. After the addition, the mixture was further agitated for 1 5 minutes, followed by warming it to 23"C over one hour, further heating to 65"C over 30 minutes, further stirring for one hour, filtering the resulting solid catalyst, dispersing it in n-hexane (1 ,000 ml), 5 times repeating an operation of washing by decantation, dispersing the solid product in hexane (3,000 ml), adding diisoamyl ether (480 ml), heating them with stirring at 35"C for one hour, separating the resulting treated solid from the liquid, dispersing this treated solid in a mixed liquid of n-hexane (1,000 ml) and TiCI4 (700 ml), agitating the dispersion at 65'C for 2 hours, separating the resulting solid catalyst by filtration, 4 times dispersing in and washing with n-hexane (1,000 ml), further washing with n-hexane (1,000 ml) heated to 65"C, filtering and drying to obtain a solid product. Example 2 was repeated except that this solid product was used in place of the preactivated catalyst (VII). The results are shown in Table 3.

Examples 9-11 Example 3 was repeated except that DEAC was replaced by di-n-propylaluminum monochloride, di-i-butylaluminum monochloride or diethylaluminum monoiodide. The results are shown in Table 3.

Examples 12-17 Example 2 was repeated except that methyl p-toluylate was replaced by ethyl p-toluylate (12.0 g) (Example 12), butyl p-toluylate (14.0 g) (Example 13), methyl benzoate (10.0 g) (Example 14), ethyl benzoate (11.0 g) (Example 15), methyl p-anisate (12.0 g) (Example 16) and ethyl p-anisate (13.0 g) (Example 17).

The results are shown in Table 3.

Table 3 Polymerization conditions and results and physical properties of injection molded products (III)

Example No. 7 8 9 10 11 12 Kind of aromatic ester* a a a a a b Kind of organoaluminium compound** i i ii iii iv i Polypropylene yield (Kg) 45.1 37.5 42.0 47.3 40.5 42.4 M F R 11.0 12.6 30.6 26.2 28.3 13.5 amount of C6+C7 extracts (%) 3.4 4.1 4.0 3.6 2.1 2.3 Isotactic pentad ratio Total 0.977 0.973 0.985 0.986 0.993 0.983 P # n-C6 extract 0.564 0.512 0.610 0.604 0.651 0.615 n-C7 extract ** 0.819 0.783 0.855 0.862 0.893 0.837 Bending modulus 17,900 17,100 18,800 18,600 19,400 18,200 Bending strength 483 472 494 492 516 492 Tensile strength 377 370 382 381 389 378 Hardness 114 111 116 115 118 115 H D T 120 117 120 121 123 119 Table 3 (continued)

Example No. 13 14 15 16 17 Kind of aromatic ester* c d e f g Kind of organoaluminium compound** i i i i i Polypropylene yield (Kg) 39.8 32.2 31.9 44.0 44.3 M F R 14.9 17.5 18.4 15.1 17.6 amount of C6+C7 extracts (%) 3.6 4.1 4.4 3.7 3.5 Isotactic pentad ratio Total 0.977 0.975 0.373 0.979 0.980 P # n-C6 extract 0.550 0.522 0.487 0.579 0.583 n-C7 extract ** 0.821 0.818 0.792 0.830 0.825 Bending modulus 17,900 17,600 17,500 18,000 18,100 Bending strength 484 480 477 486 490 Tensile strength 373 372 365 374 381 Hardness 114 114 113 114 115 H D T 119 118 117 119 120 Note: * a, b and c represent methyl, ethyl and butyl p-toluylate, respectively; d and e, methyl and ethyl benzoate, respectively; and f and g,methyl and ethyl p-anisate, respectively.

** i, ii and iii represent diethyl-, di-n-propyl- and di-i-butylaluminum monochloride, respectively, and iv represents diethylaluminium monoiodide.

Examples 18 and 19 Example 2 was repeated except that the proportion of the amount of methyl p-toluylate used (molar ratio) was varied as in Table 4, to obtain polypropylene powders. To the respective polypropylene powders (each 5.0 Kg) were added a phenolic heat stabilizer (0.005 Kg), calcium stearate (0.005 Kg) and fine powder of silica (0.01 Kg), followed by mixing them at room temperature for 10 minutes by means of a high speed agitation type mixer as mentioned above and then granulating the mixture by means of an extrusion granulator having a screw bore diameter of 40 mm.From the granulated material was prepared an inflation film having a flattened width of 1 50 mm and a thickness of 30 ju, by means of a film-making machine (CYT, trade name of machine manufactured by Yamaguchi Seisakusho Co., Japan), at a die temperature of 215"C and a cooling water temperature of 20"C. The film was then conditioned by allowing it to stand in a room at a constant temperature and a constant humidity (room temperature (23"C) and a humidity of 50%), followed by measuring the values of their physical properties as in Table 4.

Comparative examples 9, 9-2-9-5 Example 1 8 was repeated except that the granulated material used in Example 1 8 was replaced by commercially available polypropylene (F 1088, trade name of pellet manufactured by Chisso Corporation). The results are shown in Table 4.

Table 4 Polymerization conditions and results and physical properties of inflation film

Example Comparative example 18 19 9*** 9-2 9-3 9-4 9-5 Mol ratio of aromatic 1.0 0.7 - - - - ester/solid product * Polypropylene yield (Kg) 45.1 51.4 - - - - M F R 10.5 10.2 10.1 9.7 10.2 10.6 10.1 amount of C6+C7 extracts 3.1 3.8 5.4 4.2 9.6 2.3 4.5 (%) Isotactic pentad ratio Total 0.982 0.975 0.938 0.950 0.923 0.981 0.976 P # n-C6 extract 0.591 0.524 0.159 0.295 0.237 0.583 0.388 n-C7 extract ** 0.862 0.791 0.624 0.637 0.581 0.854 0.659 Young's modulus 98 94 72 75 64 95 83 Tensile yield strength 2.9 2.8 2.1 2.2 2.0 2.7 2.4 Haze 2.3 1.9 1.8 1.7 1.4 4.8 1.9 Punching impact strength 5.3 6.2 5.2 6.3 6.5 2.1 5.9 Note: * Methyl p-toluylate was used. ** n-C6 extract was successively extracted.

*** Commercially available polypropylene (F1088, manufactured by Chisso Corp.) was used.

As apparent from Table 4, inflation films of Examples 18 and 1 9 produced by using each polypropylene which itself has and whose respective extracts have isotactic pentad ratio P in the range of those of the present invention, respectively and the total amount of extracts of which are also in the range of that of the present invention, are superior in any of the four kinds of physical properties in the Table i.e. Young's modulus and the succeeding three, and also have various strengths and transparency which are sufficient for high-rigid polypropylene films.

Whereas, in the above Comparative examples wherein either one or more of the isotactic pentad ratios (three kinds) or the total amount of extracts (%) is outside the range of those of the present invention, either one or more of the physical properties of the films are evidently inferior to those of products of the present invention. Particularly, in the case of Comparative example 9-4 wherein even if the isotactic pentad ratios P of the polymer itself and the respective extracts are in the range of those of the present invention, the total amount of extracts is insufficient, haze and punching impact strength are far inferior to those of products of the present invention, although Young's modulus and tensile yield strength are good.From this fact, it is apparent that isotactic pentad ratios in specified ranges and n-C6- and n-C7- extracts in specified ranges of extracted amounts (%) are necessary to be coexistent. In the case of Comparative example 9-5, in contrast to Comparative example 9-4, the total amount of extracts is in the range of that of the present invention, but the isotactic pentad ratios P of n-C6- and n-C7- extracts are outside the range of those of the present invention. As a result, the Young's modulus and tensile yield strength are inferior to those of the respective Examples. On the other hand, the haze and punching impact strength are good, contrary to the case of Comparative example 9-4.

Examples 20 and 21 Example 4 and Example 5 were repeated except that the amount of hydrogen used was changed to 40 NI (Example 20) or 55 NI (Example 21), to obtain two kinds of polypropylene powder. To each thereof (5.0 Kg) were added a phenolic heat stabilizer (0.005 Kg), calcium stearate (0.005 Kg) and ultrafine particles of silica (average particle size: 0.1 it) (0.0025 Kg), followed by mixing them by means of a high-speed agitation type mixer at room temperature for 10 minutes, and then granulating the mixture by means of an extrusion type granulator having a bore diameter of 40 mm.The resulting granulated material was extruded by means of a T-die type film-making machine, at a resin temperature of 250"C and made into a sheet of 1 mm thick by means of a roll cooled to 20"C. The sheet was heated by hot air at 150"C for 70 seconds and stretched in both the longitudinal and lateral directions at the same time, each at a rate of 5 m/min. and to 7 times the original lengths, by means of a biaxially stretching machine, to obtain a biaxially stretched film of 20 IL thick. The values of physical properties of films thus obtained are shown in Table 5.

Comparative example 10 Comparative example 1 was repeated except that 80 NI of hydrogen was used, to obtain polypropylene powder. This powder was subjected to the same granulation and film-making as in Example 20. The values of physical properties of the film are shown in Table 5.

Comparative example 11 Example 20 was repeated except that no methyl p-toluylate was used. The results are shown in Table 5.

Comparative example 11-2 Example 20 was repeated except that the polymerization temperature was 50"C, the amount of hydrogen was 85 Ml, and 8 g of the preactivated catalyst (VII) was used. The yield of polypropylene was 28.7 Kg. The results are shown in Table 5.

Table 5 Polymerization conditions and physical properties of biaxially stretched films

Example Comparative example 20 21 10 11 11-2 Mol ratio of aromatic ester/ 0.5 2.0 0.5 - 0.5 solid product * Polypropylene yield (Kg) 31.2 24.8 42.9 36.1 28.7 M F R 1.8 1.6 1.8 1.7 1.9 Amount of C6+C7 extracts (%) 4.8 3.2 6.7 4.5 1.8 Isotactic pentad ratio Total 0.965 0.974 0.916 0.939 0.972 P # n-C6 extract 0.472 0.513 0.169 0.251 0.498 n-C7 extract ** 0.783 0.814 0.537 0.591 0.786 Stretchability Good Good Good Good Bad Young's modulus 320 370 185 200 280 Tensile yield strength 230 250 140 160 195 Haze 0.8 1.1 0.6 0.8 1.5 Punching impact strength 9 10 8 9 3 Note: * Methyl p-toluylate was used.

** n-C6 extract was successively extracted.

As apparent from Table 5, the above films produced by using polypropylene prepared by polymerizing propylene by the use of a catalyst wherein titanium trichloride AA was used in place of the solid product (III) are good in stretchability, but far inferior in Young's modulus, tensile yield strength and haze to those of Examples 20 and 21 (Comparative example 10). On the other hand, in the case where the solid product (III) was combined with an organoaluminum compound but no aromatic ester was used, similar stretchability, Young's modulus, tensile strength and haze to those of Comparative example 10 were exhibited (Comparative example 11). On the other hand, punching impact strength of Comparative example 10 is somewhat inferior, but that of Comparative example 11 is similar to that of Example 20.Particularly in the case of Comparative example 11-2 where the total amount of extracts is insufficient, the stretchability and all the physical properties are insufficient; from this fact, it is evident that it is necessary that polypropylene used for products of the present invention contain specified amounts of n-C6- and n-C7- extracts.

Examples 22 and 23 and Comparative examples 12-15 Examples 1-3 were repeated except that various kinds of polypropylene powder having MFRs and isotactic pentad ratios shown in Table 6 were used. The quality of polypropylene used and the physical properties of the resulting injection molded products are shown in Table 6. Table 6 Injection molding test (I)

Example Comparative example 22 23 12 13 14 15 Physical properties of polypropylene M F R (g/10 min.) 8.3 8.7 8.6 9.4 10.3 11.2 Polymer itself 0.971 0.987 0.915 0.955 0.978 0.983 P # n-C6 extract 0.473 0.669 0.152 0.312 0.380 0.477 n-C7 succesive extract 0.780 0.885 0.547 0.693 0.674 0.641 Physical properties of molded products (i) Bending modulus 17,100 19,100 11,700 15,600 17,400 17,700 (ii) Bending strength 465 502 338 425 465 478 (iii) Tensile strength 380 383 320 355 374 378 (iv) Hardness 113 116 99 104 107 108 (v) H D T 117 120 100 110 113 115 As apparent from Table 6, products of the present invention obtained by using polypropylene having isotactic pentad ratios P in the range of those of the present invention, have values of various physical properties (i)-(v) in the Table, on the same levels as in Examples 1-3.

Whereas, in the case of Comparative examples 1 2 and 1 3 wherein neither of the three kinds of isotactic pentad ratios P satisfies the requirements of the present invention, neither of values of the physcial properties (i)-(v) amounts to the levels of the values of Examples 1-3, 22 and 23, as in the case of Comparative examples 1-3. On the other hand, in the case of Comparative examples 14 and 15, the effectiveness is somewhat different.Namely, in the case of these Comparative examples, values of physical properties (i)-(iii) i.e. bending modulus, bending strength and tensile strength, among those of Table 6 can be maintained on the levels of the present invention, possibly due to the fact that the isotactic pentad ratio P of polymer itself satisfies the requirements of the present invention, but in the case of Comparative examples 14 and 15, the values of physical properties (iv) and (v) i.e. hardness and HDT cannot be maintained on the levels of the present invention.

Example 24 Comparative example 16 Examples 1-3 were repeated except that the same polypropylene as in Example 2 was used in Example 24 and the same polypropylene as in Comparative example 2 was used in Comparative example 16, and fine powder of talc having an averagr particle size of 2 to 3 y (0.04 Kg) was added per 4 Kg of polypropylene. The results are shown in Table 7.

As apparent from thins Table, addition of a small amount of talc notably improves various kinds of strengths of injection molded products, as compared with the respective corresponding cases of non-addition (Example 2 and Comparative example 2); hence this fact shows that the simultaneous use of inorganic filler is effective in the presen invention. However, any of the values of physical properties of Comparative example 1 6 does not amount to the corresponding values of Example 24; this shows that the requirements of the present invention relative to polypropylene used (three kinds of isotactic pentad ratios P) are indispensable.

Example 25 and Comparative example 17 Example 24 and Comparative example 1 6 were repeated except that talc was replaced by an aluminum salt of t-butylbenzoic acid (0.016 Kg). (The former: Example 25, the latter: Comparative example 17). The results are shown in Table 7.

Table 7 Injection molding test (Il) Comp. Comp.

Ex. Ex. Ex. Ex.

24 16 25 17 Physical properties of polypropylene M F R (g/10 min.) 10.6 9.8 10.6 9.8 Physical properties of molded products (i) Bending modulus 20,500 16,100 21,000 16,500 (ii) Bending strength 537 445 545 457 (iii) Tensile strength 370 331 365 325 (iv) Hardness 121 109 120 109 As apparent from Table 7, addition of a small amount of an aluminum salt of t-butylbenzoic acid notably improves various strengths of injection molded products as compared with the corresponding cases of non-addition (Example 2 and Comparative example 2); hence this shows that the simultaneous use of an organic nucleus-creating agent is effective in the present invention. However, any of the values of physical properties of Comparative example 1 7 does not amount to those of the corresponding Example; this shows that it is indispensable that the requirements of the present invention relative to polypropylene used (three kinds of isotactic pentad ratios P) be in specified ranges.

Claims

1. A polypropylene capable of producing high-rigidity molded products obtained by polymerizing propylene in the presence of a catalyst prepared by reacting an organoaluminum compound (I) or a reaction product (VI) of an organoaluminum compound (I) with an electron donor (A), with TiCI4 (C), futher reacting the resulting solid product (II) with an electron donor (A) and an electron acceptor (B), and then combining the resulting solid product (III) with an organoaluminum compound (lV) and an aromatic carboxylic acid ester (V), the molar ratio of said aromatic carboxylic acid ester to said solid product (III) being in the range of 0.2 to 10.0.

2. A polypropylene according to claim 1 wherein said organoaluminum compound is a dialkylaluminum monohalide.

3. A process for producing a polypropylene according to claim 1 wherein said catalyst is further preactivated by reacting an a-olefin with a combination of said solid product (III) with an organoaluminum compound.

4. A polypropylene according to claim 1, which has an isotactic pentad ration (P) relative to MFR in the range of 1.002P20.015 log MFR + 0.955.

5. A process for producing a polypropylene which comprises polymerizing propylene in the presence of a catalyst prepared by reacting an organoaluminum compound (I) or a reaction product (VI) of an organoaluminum compound (I) with an electron donor (A), with TiCI4 (C), further reacting the resulting solid product (II) with an electron donor (A) and an electron acceptor (B), and then combining the resulting solid product (Ill) with an organoaluminum compound (IV) and an aromatic carboxylic acid ester (V), the molar ratio of said aromatic carboxylic acid ester to said solid product (III) being in the range of 0.2 to 10.0.

6. A process for producing a polypropylene according to claim 5, wherein said organoaluminum compound (IV) is a dialkylaluminum monohalide.

7. A process for producing a polypropylene according to claim 5, wherein said catalyst is further preactivated by reacting an a-olefin with a combination of said solid product (III) with an organoaluminum compound.

8. A process for producing a polypropylene according to claim 5, which has an isotactic pentad ratio (P) relative to MFR in the range of 1.002P20.015 log MFR + 0.955.

9. A high-rigidity injection molded product of polypropylene obtained by using a crystalline polypropylene which has an isotactic pentad ration (P) relative to MFR in the range of 1.002P20.015 log MFR + 0.955, and whose successive extracts with boiling n-hexane and boiling n-heptane, have-an isotactic pentad ratio (P) in the range of 0.450 to 0.700 and that in the range of 0.750 to 0.930, respectively.

10. A high-rigidity film of polypropylene obtained by using a crystalline polypropylene which has an isotactic pentad ration (P) relative to MFR in the range of 1.002P20.015 log MFR + 0.955, and whose successive extracts with boiling n-hexane and boiling n-heptane, have an isotactic pentad ratio (P) in the range of 0.450 to 0.650 and that in the range of 0.750 to 0.900, respectively, the total amount of said extracts being in the range of 3 to 6% by weight based on said polypropylene.