JPH07286008A - Propylene polymer for biaxially oriented film and its production - Google Patents

Abstract

PURPOSE:To obtain a propylene polymer for biaxially oriented film excellent in optical properties and fabricability and having a low content of solid matter. CONSTITUTION:This polymer is one containing at most 20 solid foreign matter particles having a maximum diameter of 10mum or above and not melting at 150 deg.C per (g) of the polymer, and containing at most 1 solid foreign matter particle having a maximum diameter of 100mum or above per (g) of the polymer. This is produced by a deashing-free process after forming a propylene polymer in an amount of 3X10<5> (g) per (g,) of the titanium atoms of the catalyst component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a propylene polymer suitable for producing a biaxially stretched film having excellent properties such as optical properties and secondary processability, and a process for producing the same.

[0002]

2. Description of the Related Art Biaxially stretched propylene polymer films are excellent in optical properties such as transparency and gloss, and mechanical properties such as rigidity and tensile strength are also good, so that various packaging films are available. Widely used for etc.

However, since the biaxially stretched propylene polymer film has voids (voids) generated around the residue of the catalyst used for the polymerization of propylene, when used as a material for print lamination, the voids are conspicuous. However, it had a drawback of deteriorating the appearance. In particular,
Lamination on dark-colored prints significantly reduced the commercial value. Further, when the biaxially stretched film is printed or subjected to aluminum vapor deposition treatment, it also causes pinholes in printing and vapor deposition. Therefore, development of a void-free biaxially stretched film is desired.

Conventionally, voids generated around antiblocking agents such as silicon dioxide, calcium carbonate, magnesium oxide and kaolin having a particle size of about 2 μm, which are added to an olefin polymer in order to prevent blocking between films, are formed. A method of suppressing has been proposed. However, although it is effective in suppressing the small voids caused by the antiblocking agent, it is not effective in improving the voids of a size that can be easily visually confirmed, and no proposal has been made to eliminate the large voids. .

The present inventors have conducted extensive studies to solve the problems of the prior art, and as a result, by using a propylene polymer produced by a specific method, a void of a size that can be easily visually confirmed It was found that a small stretched film was obtained, and the present invention was completed.

[0006]

The present invention has the following configuration. (1) 20 or less solid foreign matter having a maximum diameter of 10 μm or more and 1 solid foreign matter having a maximum diameter of 100 μm or more which does not melt at a temperature of 150 ° C. contained in 1 g of a propylene polymer.
A propylene polymer for a biaxially stretched film, characterized in that the number is not more than the number. (2) The propylene polymer is a propylene homopolymer and a copolymer of propylene having a propylene content of 98.0 mol% or more with ethylene and an α-olefin other than propylene. Propylene polymer for axially stretched film. (3) 3 × 1 per gram of titanium atom in the catalyst component
0 After producing ⁵ grams or more of the propylene polymer, the preparation of biaxially oriented film for propylene polymer, characterized in that to produce a process omitting the step of removing the propylene polymerization catalyst component (no demineralization process) . (4) The method for producing a propylene polymer for a biaxially stretched film according to claim 3, wherein a supported catalyst having a titanium compound supported on a carrier is used.

The structure of the present invention will be described in detail below. The propylene polymer used in the present invention is a propylene homopolymer, or one or two of propylene and ethylene, an α-olefin other than propylene, for example, butene-1, 4-methyl-pentene-1, hexene-1. It is a random copolymer or block copolymer with one or more species. Two or more kinds of propylene-based polymers may be used as long as they have the above composition. Especially heat resistance,
A propylene homopolymer having good physical properties such as rigidity, tensile strength and chemical resistance, and a copolymer of propylene having a propylene component content of 98 mol% or more with ethylene and an α-olefin other than propylene are preferable. Further, considering the film-forming property, the melt flow rate (MFR) of the propylene polymer at 230 ° C. is preferably 0.2 to 20 g / 10 min.

The solid foreign matter referred to in the present invention is a compound other than a propylene polymer which does not melt at a temperature of 150 ° C. Specifically, catalyst residues, heat stabilizers added after the reaction, neutralizing agents, antistatic agents, nucleating agents, antiblocking agents such as silicon dioxide, polymer additives such as petroleum resins, propylene weight generated during melting It is a heat deterioration product (carbide) of coalescence, or dust mixed from the outside. Examples of these are titanium oxide, titanium hydroxide, aluminum oxide, aluminum hydroxide, sodium chloride, calcium carbonate, silicon dioxide, magnesium chloride, magnesium oxide, kaolin, iron, 4-fluoroethylene polymer, nylon, polyester, Examples thereof include 4-methyl-pentene-1 polymer, epoxy resin, and cellulose.

What is important in the present invention is the size of the solid foreign matter. When solid foreign matter is present in the propylene polymer, voids are generated around the foreign matter when it is formed into a biaxially stretched film. The size of this void is about 10 times the size of the solid foreign matter. Therefore, when a solid foreign matter having a maximum diameter of 10 μm or more is present in the propylene polymer, a void having a size that can be easily visually confirmed is generated in the biaxially stretched film. The maximum diameter is 100 μm
When the above solid foreign matter is present, the resulting biaxially stretched film not only has a significantly deteriorated film appearance due to voids, but also has a portion where solid foreign matter is a protrusion on the film surface, so the film is printed, and aluminum vapor deposition is performed. In this case, it may cause pinholes. Voids are generated in the biaxially stretched film even when solid foreign matter having a maximum diameter smaller than 10 μm is present, but the commercial value of the film is hardly impaired because the voids are small.

In the propylene polymer for a biaxially stretched film of the present invention, 20 g or less of solid foreign matter having a maximum diameter of 10 μm or more contained in 1 g of the propylene polymer and a maximum diameter of 10 are contained.
One or less solid foreign matter of 0 μm or more. When the number of solid foreign matters having a maximum diameter of 10 μm or more exceeds 20, voids generated in the obtained biaxially stretched film are easily noticeable and the appearance of the film deteriorates. In particular, it is particularly preferable that 1 g of the propylene polymer has 5 or less solid foreign matters of 10 μ or more, and voids in the obtained biaxially stretched film are hardly visually observed. When the solid foreign matter having a maximum diameter of 100 μm or more exceeds one, when the obtained biaxially stretched film is printed or vapor-deposited with aluminum, pinholes are conspicuous and the commercial value is significantly reduced. Especially 100
Most preferably, the number of solid foreign matters having a size of μm or more is zero.

As a method for preventing the generation of such solid foreign matter, in the granulation step of melt-mixing an additive such as a heat stabilizer with the propylene polymer powder obtained by polymerization to produce pellets, sand, paper, Preventing foreign matter such as threads from being mixed, and heat deterioration products (carbides) of propylene polymer during melting
It is necessary to prevent such occurrence. As specific measures, prevent the inclusion of sand, paper, threads, etc. from the outside by performing all processes from propylene polymerization to granulation in a closed system, increase the amount of heat stabilizer, and add organic acid metal salts. It is possible to prevent the thermal deterioration of the molten propylene polymer in the granulator due to such reasons.

Further, in the transportation of pellets, it is preferable that the air used in an air flow conveyor which is usually used is a filter or the like to remove solid foreign matters such as sand.

When a heat stabilizer, a neutralizing agent, an antistatic agent, a nucleating agent, an antiblocking agent such as silicon dioxide, or a polymer additive such as petroleum resin is added to the propylene polymer for a biaxially stretched film of the present invention. It is necessary to use an additive having no particle size of 10 μm or more and sufficiently disperse so as not to form an aggregate of 10 μm or more.

However, even if the above-mentioned treatment is carried out, the propylene polymer for a biaxially stretched film of the present invention cannot be obtained if solid foreign matter is already generated in the propylene polymer immediately after the production. Therefore, it is most important to suppress the generation of solid foreign matter in the polymer manufacturing process.

The method for producing the propylene polymer for a biaxially stretched film of the present invention is not particularly limited as long as it satisfies the requirements of the present invention. Generally, in the propylene polymer production step, a deashing step for removing the catalyst is generally performed after the propylene polymerization step. In the deashing step, alcohols for solubilizing the catalyst, neutralizing agents such as basic compounds for neutralizing, water for washing and the like are added. It has been found by the present inventors that in this step, the catalyst residue that partially remains aggregates to form solid foreign matter of 10 μm or more. However, generally, a biaxially stretched film obtained from a polypropylene polymer produced by omitting the deashing step is not preferable because it is colored and its commercial value is reduced. The present invention makes it possible to provide a film with less solid foreign matter without such coloring, and can be produced by the following method.

The production method of the present invention is a method for producing 3 × 10 ⁵ grams or more of propylene polymer per 1 gram of titanium atom in the catalyst component, and a non-decalcification process. A preferred embodiment is to use a supported catalyst having high polymer productivity per titanium atom as the catalyst. As the supported catalyst, a known catalyst in which a titanium compound is supported on a carrier whose main component is magnesium compound such as magnesium chloride can be used.

The propylene polymer for a biaxially stretched film is
It can be formed into a film by a known biaxially stretched film manufacturing method.

[0018]

EXAMPLES The following examples are given to specifically describe the present invention, but the present invention is not limited thereto. The properties of the propylene polymer for a biaxially stretched film used in Examples and the properties of the obtained stretched film were measured by the following methods. Characteristics of each component forming the olefin polymer for stretched film (1) Melt flow rate of propylene polymer (MF
R) Measured by a method according to JIS K6758. (2) Copolymerization ratio of propylene polymer [Method] Calculated from the area of each peak measured by ¹³ C-NMR method. [Apparatus] (trade name) FT-NMR spectrometer
(GX-270) (manufactured by JEOL Ltd.) [Conditions] Observation width: 12000 Hz; Pulse angle: 35 °;
Pulse interval: 4.5 seconds; measurement temperature: 130 ° C .; solvent: mixed solution of orthodichlorobenzene and deuterated bromobenzene (bromobenzene-d5); cumulative number of times: 1
0000 times or more (3) Number of solid foreign substances [Device] Optical microscope with camera, heating stage [Method] 5 g of propylene polymer molded into a biaxially stretched film is observed with a microscope, and solid foreign substances with a maximum diameter of 10 μm or more are heated. Is heated at a temperature of 150 ° C., the number of foreign matters that do not melt is counted, and the average value is converted per 1 g. (4) Number of voids in biaxially stretched film [Apparatus] Optical microscope with camera [Method] Observe 5 g of biaxially stretched film with a microscope, count the number of voids having a maximum diameter of 100 μm or more, and calculate the average value per 1 g. Convert to.

(Example 1) (1) Production of solid catalyst component for propylene polymerization In a stainless reactor equipped with a stirrer, decane 3 was added.
L, anhydrous magnesium chloride 480 g, orthotitanic acid n
-Butyl 1700 g and 2-ethyl-1-hexanol 1950 g were mixed and heated at a temperature of 130 ° C for 1 hour with stirring to form a uniform solution. Add the homogeneous solution to 70
180 g of diisobutyl phthalate while stirring
After 1 hour, 5200 g of silicon tetrachloride was added dropwise over 2.5 hours to precipitate a solid, and the mixture was further heated at 70 ° C. for 1 hour. The solid was separated from the solution and washed with hexane to obtain a solid component (II). The total amount of the solid component (II) was mixed with a mixed liquid of 15 L of toluene and 15 L of titanium tetrachloride, 380 g of diisobutyl phthalate was added, and the mixture was reacted at 130 ° C. for 2 hours while stirring. The liquid phase part was removed by decantation, and toluene 15 was added again.
L and 15 L of titanium tetrachloride were added, and the mixture was stirred at 130 ° C. for 2 hours, the liquid phase portion was removed by decantation at the same temperature, washed with hexane and dried to obtain a solid catalyst component. (2) Preparation of pre-activated solid catalyst component After replacing a stainless steel reactor with an agitator with an internal volume of 30 L with nitrogen gas, 18 L of hexane, 17 g of triethylaluminum, and 180 g of the solid catalyst component obtained in (1)
After adding, 600 g of ethylene was continuously fed,
A preliminary activation treatment was performed at 16 ° C. for 16 hours to obtain a preactivated solid catalyst component in a slurry state (per 1 g of the solid catalyst component,
Ethylene 3.1 g reaction). (3) Polymerization of Propylene L / D = equipped with a stirrer with an internal volume of 80 L replaced with nitrogen
Propylene polymer powder 2 with MFR = 3.0 in the polymerization vessel of 3
After the addition of 0 kg, the slurry of the preactivated solid catalyst component obtained in (2) was 0.26 mg atom / hr in terms of titanium atom and 1.2 g / triethylaluminum.
hr, and 0.25 g of diisobutyldimethoxysilane
/ Hr was continuously supplied from different supply ports. Further, hydrogen was supplied so that the concentration in the polymerization vessel was kept at 0.45% by volume, and propylene was supplied so that the total pressure was kept at 23 kg / cm ² G. It went on continuously for hours. During the polymerization, the polymer was continuously withdrawn at 10.0 kg / hr so that the retained level of the polymer in the polymerization vessel was 60% by volume. The polymer extracted was subsequently subjected to contact treatment with nitrogen gas containing 5.0% by volume of steam at 95 ° C. for 30 minutes, and MFR =
3.5 g / 10 min of propylene polymer powder was obtained.
The propylene polymer powder was sealed and stored in a 30 L container. The polymer production amount per gram of titanium atom was 8.03 × 10 ⁵ gram. (4) Granulation of propylene polymer In 100 parts by weight of the propylene polymer powder obtained in (3), 0.2 part by weight of 2,6-di-t-butyl-p-cresol and tetrakis [methylene (3,5 -Di-t-butyl-4-hydroxyhydrocinnamate)] methane 0.0
5 parts by weight and 0.07 parts by weight of calcium stearate were charged into a Henschel mixer (trade name), and dry blended for 3 minutes, and then a single-screw extruder (cylinder diameter 40 m
m) was melt-kneaded (temperature: 220 ° C.) and pelletized. (5) Production of biaxially stretched film The propylene polymer pellets obtained in (4) are melt-extruded (temperature 250 ° C) with an extruder equipped with a T-die, and wound around a cooling drum (temperature 40 ° C) to be cooled and solidified, An unstretched sheet (thickness 1.0 mm) was formed. Then, the obtained unstretched sheet is heated at a temperature of 158 using a batch type biaxial stretching machine.
Biaxial stretching at ℃ (5.0 times in the extrusion direction, 8.0 in the transverse direction)
To obtain a biaxially stretched film (thickness: 25 μm). (6) Evaluation results Table 1 shows the evaluation results.

[Table 1]

Example 2 (1) Polymerization of Propylene Using the preactivated solid catalyst component used in Example 1,
Subsequent to the polymerization of propylene of Example 1, the following conditions were changed to carry out the polymerization. The same procedure as in Example 1 was carried out except for the following conditions. -Supply of catalyst component Pre-activated solid catalyst slurry: 0.24 mg atom / hr Triethylaluminum: 1.1 g / hr Diisobutyldimethoxysilane: 0.23 g / hr-Gas concentration in the polymerization vessel Hydrogen concentration in the polymerization vessel: 0.55% by volume of ethylene was continuously supplied, and the ethylene concentration in the polymerization vessel was:
0.50% by volume-Polymerization time: 50 hours The obtained propylene polymer had an MFR of 3.2 g / 10.
min, propylene component content = 98.7 mol%, ethylene component content = 1.3 mol%. The propylene polymer powder was sealed and stored in a 30 L container as in Example 1. The polymer production amount per gram of titanium atom was 8,70 × 10 ⁵ gram. (2) Granulation of propylene polymer The same as in Example 1. (3) Production of biaxially stretched film The same procedure as in Example 1 was performed. (4) Evaluation results Table 1 shows the evaluation results.

Example 3 (1) Production of Solid Catalyst Component for Propylene Polymerization The same procedure as in Example 1 was carried out. (2) Preparation of pre-activated solid catalyst component After replacing a stainless reactor equipped with a stirrer with an internal volume of 5 L with nitrogen gas, 3 L of hexane, 0.6 g of triethylaluminum, 0.2 g of diisobutyldimethoxysilane,
After adding 50 g of the solid catalyst component, 60 g of propylene was continuously supplied, and preactivation treatment was performed at 30 ° C. for 5 hours to obtain a preactivated solid catalyst component in a slurry state (1. 1 g reaction). (3) Polymerization of Propylene 250 L of hexane, 60 g of triethylaluminum, 17 g of diisobutyldimethoxysilane, and the preactivated solid catalyst component slurry obtained in (2) were added to a titanium atom in a polymerization vessel equipped with a stirrer having an internal volume of 500 L and purged with nitrogen. After supplying 2.6 mg atom in terms of conversion, 2.5 mol of hydrogen was added, and propylene was continuously supplied so as to keep the total pressure at 7.0 kg / cm ^2, thereby carrying out slurry polymerization of propylene to 7
It was carried out at 0 ° C. for 2 hours. After the polymerization, the temperature was lowered to 40 ° C., the residual propylene in the polymerization vessel was purged, and the total amount of the obtained propylene polymer powder and hexane slurry was transferred to a reactor equipped with a stirrer having an internal volume of 600 L, After adding 1.0 L of methanol and stirring at 80 ° C. for 30 minutes, the slurry of propylene polymer powder and hexane in the reactor was centrifuged to remove hexane with a dryer, and M
50 kg of propylene polymer powder with FR = 2.4 g / 10 min was obtained. The polymer production amount per gram of titanium atom was 4.01 × 10 ⁵ gram. The propylene polymer powder was sealed and stored in a 30 L container. (4) Granulation of propylene polymer The same as in Example 1. (5) Production of biaxially stretched film The same procedure as in Example 1 was carried out. (6) Evaluation results Table 1 shows the evaluation results.

Comparative Example 1 (1) Polymerization of Propylene Using the preactivated solid catalyst prepared in Example 3, slurry polymerization of propylene was carried out for 2 hours in the same manner as in Example 3. After the polymerization, the temperature was lowered to 40 ° C., the residual propylene in the polymerization vessel was purged, and the total amount of the obtained propylene polymer powder and hexane slurry was transferred to a reactor equipped with a stirrer having an internal volume of 600 L, Add 25 L of methanol to 80
Stir at 30 ° C for 30 min, add 0.4 L of 20 wt% caustic soda water, stir at 85 ° C for 30 min, and add pure water 50
L was added and the mixture was stirred at 85 ° C. for 20 minutes. After the temperature was lowered to 40 ° C., the slurry was left standing and the water tank was taken out. Furthermore,
After adding 300 L of pure water and stirring for 20 minutes, the mixture was left standing and the water tank was taken out. The slurry of propylene polymer powder and hexane in the reactor was centrifuged to remove hexane, and 48 kg of propylene polymer powder with MFR = 2.5 g / 10 min was obtained. The polymer production amount per gram of titanium atom was 3.85 × 10 ⁵ gram. The propylene polymer powder was sealed and stored in a 30 L container. (2) Granulation of propylene polymer The same as in Example 1. (3) Production of biaxially stretched film The same procedure as in Example 1 was performed. (4) Evaluation results Table 1 shows the evaluation results.

Comparative Example 2 (1) Production of Solid Catalyst Component for Propylene Polymerization 6 L of hexane, 5.0 mol of diethylaluminum monochloride, and 12.0 mol of diisoamyl ether were added to 25 parts.
A reaction solution (I) was obtained by reacting at 10 ° C. for 10 minutes. 40 mol of titanium tetrachloride was placed in a nitrogen-substituted reactor equipped with a stirrer, heated to 35 ° C., and the whole amount of the reaction solution (I) was added dropwise to this in 30 minutes, then kept at the same temperature for 30 minutes and heated to 75 ° C. The mixture was warmed to react for 1 hr, cooled to room temperature, the liquid phase part was removed by decantation, and washed with hexane to obtain a solid product (II). This solid product (I
The whole amount of I) was suspended in 30 L of hexane, 1.0 mol of diethylaluminum monochloride was added, 400 g of propylene was added at 30 ° C. for 1 hr reaction, the liquid phase part was removed by decantation, and further washed with hexane. Then, a solid product (II-A) subjected to a polymerization treatment was obtained (propylene reaction amount 240 g). This solid product (II-A)
Was suspended in 30 L of hexane, 13.3 mol of titanium tetrachloride was added at room temperature for 10 min, and the mixture was mixed at 80 ° C. for 3 minutes.
After reacting for 0 min, 4.0 mol of diisoamyl ether was further added, and the mixture was reacted at 80 ° C. for 1 hr. After completion of the reaction, the liquid phase portion was removed by decantation, washed with hexane, and dried to obtain a solid catalyst component. (2) Polymerization of Propylene 230 L of hexane, 120 g of diethylaluminum monochloride, and 54 mg of the solid catalyst component obtained in (1) in terms of titanium atom were supplied to a polymerization vessel equipped with a stirrer having an internal volume of 500 L and purged with nitrogen. Thereafter, 4.4 mol of hydrogen was added, and propylene was continuously supplied so that the total pressure was kept at 10.0 kg / cm ^2, and slurry polymerization of propylene was carried out at 70 ° C. for 4 hours. After the polymerization, the temperature was lowered to 40 ° C., the residual propylene in the polymerization vessel was purged, and the total amount of the obtained propylene polymer powder and hexane slurry was transferred to a reactor equipped with a stirrer having an internal volume of 600 L, Add 50 L of methanol and heat at 80 ° C for 30 min
Stir and add 0.7 L of 20 wt% caustic soda water and stir at 85 ° C. for 30 minutes, add 100 L of pure water to 85 ° C.
And stirred for 20 min. After the temperature was lowered to 40 ° C., the slurry was left standing and the water tank was taken out. Furthermore, 300 L of pure water
In addition, after stirring for 20 minutes, the mixture was left standing and the water tank was taken out. The propylene polymer powder and the hexane slurry in the reactor were centrifuged to remove hexane with a dryer, and M
52 kg of propylene polymer powder having FR = 2.8 g / 10 min was obtained. The polymer production amount per gram of titanium atom was 2.01 × 10 ⁴ gram. The propylene polymer powder was sealed and stored in a 30 L container. (3) Granulation of propylene polymer The same as in Example 1. (4) Production of Biaxially Stretched Film The same procedure as in Example 1 was carried out. (5) Evaluation results The evaluation results are shown in Table 1.

Example 4 (1) Granulation of Polypropylene Polymer Propylene polymer powder 10 obtained in (3) of Example 3
0.2 parts by weight of 2,6-di-t-butyl-p-cresol and tetrakis [methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate)] in 0 parts by weight.
Methane 0.05 part by weight, calcium stearate 0.0
7 parts by weight, and further synthetic silicon dioxide (average particle size: 1.8 μ
m, maximum particle size: 5.0 μm or less) 0.20 part by weight, acid-modified polyethylene wax [Mitsui Petrochemical Co., Ltd. Mitsui High Wax 2203A (trade name)] 0.5 part by weight, N, N
-0.5 parts by weight of stearic acid ester of bis (2-hydroxyethyl) stearylamine was charged into a Henschel mixer (trade name) and dry-blended for 3 minutes, and then melt-kneaded with a single screw extruder (cylinder diameter 40 mm) (temperature). 220 ° C.) and pelletized. (2) Production of biaxially stretched film The same procedure as in Example 1 was carried out. (3) Evaluation results The evaluation results are shown in Table 1.

Comparative Example 3 (1) Granulation of Propylene Polymer One propylene polymer powder obtained in (1) of Comparative Example 1 was used.
The same procedure as in Example 4 was carried out except that 100 parts by weight was used. (2) Production of biaxially stretched film The same procedure as in Example 1 was carried out. (3) Evaluation results The evaluation results are shown in Table 1.

(Comparative Example 4) The propylene polymer powder obtained in (3) of Example 1 was not stored in a container in a closed manner, but was left to stand in the atmosphere for 10 days to obtain 100 propylene polymer powder.
Granulation of the propylene polymer and production of the biaxially stretched film were performed in the same manner as in Example 1 except that the parts by weight were used. The evaluation results are shown in Table 1.

[0027]

The biaxially stretched film molded from the propylene polymer for a biaxially stretched film of the present invention has no visually observed voids and has an extremely good appearance.
Since there are few irregularities on the film surface, there are no pinholes due to printing, vapor deposition, etc., and it is suitable as a material in the field of packaging and the field of print lamination on printed matter.

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Claims (4)

[Claims] 1. A propylene polymer contained in 1 g of 15
A propylene polymer for a biaxially stretched film, comprising 20 or less solid foreign matters having a maximum diameter of 10 µm or more and not more than 1 solid foreign matter having a maximum diameter of 100 µm or more, which do not melt at a temperature of 0 ° C. 2. The propylene polymer is a propylene homopolymer and a copolymer of propylene having a propylene content of 98.0 mol% or more with ethylene and an α-olefin other than propylene. The propylene polymer for biaxially stretched film. 3. A propylene polymer of 3 × 10 ⁵ g or more per 1 gram of titanium atoms in the catalyst component is produced, and then the propylene polymerization catalyst component is removed by a process (decalcification-free process). A method for producing a propylene polymer for a biaxially stretched film, comprising: 4. The method for producing a propylene polymer for a biaxially stretched film according to claim 3, wherein a supported catalyst having a titanium compound supported on a carrier is used.