JPH0643095B2 - Method for producing polypropylene biaxially stretched film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a polypropylene biaxially stretched film having excellent mechanical properties, particularly rigidity and stretchability.

[Prior art]

Polypropylene biaxially stretched film is excellent in optical properties such as transparency and gloss, heat resistance, chemical resistance and electrical properties, and also has good mechanical properties such as tensile strength and rigidity. It is widely used for electric appliances such as capacitors and electric cables. However, depending on the application, it may not be said that these properties are sufficiently satisfied, which limits expansion of specific applications. Especially in terms of rigidity (so-called stiffness), biaxially stretched polypropylene film is inferior to cellophane and polyester film, so that it is difficult to perform automatic wrapping or twist wrapping. Also,
Even in the use of electric articles, since the rigidity is insufficient, wrinkles are likely to occur during processing into a capacitor or the like, and workability is deteriorated.

The rigidity of polypropylene is greatly affected by the draw ratio and its structure. Polypropylene has a homopolymer consisting of a propylene homopolymer and a random copolymer in which a small amount of ethylene is copolymerized.Since the homopolymer is excellent in rigidity, the homopolymer is usually used for applications requiring rigidity. It is stretched before use. Then, as a method for further improving the rigidity, a method using an isotactic index (II) of 98.0% or more (Japanese Patent Laid-Open Publication No. 5 (1999) -512058).
7-103819) has been proposed. Further, as a method for improving the stretchability of the homopolymer, a method using a random copolymer, for example, titanium tetrachloride is reduced with an organoaluminum compound, and propylene is produced using a catalyst composed of activated titanium trichloride and an organoaluminum compound. A method has been proposed in which a small amount of ethylene is supplied at the time of polymerization to use polypropylene having an ethylene content of 0.1 to 1.0% by weight (JP-A-56-32512).

[Problems to be solved by the invention]

However, in the above method, no matter how much I.V. Even if I is increased, the rigidity is improved, but on the other hand, the drawability is further decreased, making it difficult to draw at a high draw ratio, and as a result, a stretched film that is more rigid toward the left cannot be obtained.

Further, in the above-mentioned method, even if a random copolymer is produced by using such a conventional catalyst, the stretchability is improved to some extent, but the I.V. I is low, the rigidity is low, and only a stretched film having a weak elasticity can be obtained. As described above, although methods for improving the rigidity or drawability of polypropylene have been proposed, polypropylene having excellent rigidity and drawability has not yet been developed.

[Means for solving problems]

In view of the above-mentioned conventional techniques, the present inventors have made diligent studies in order to improve the rigidity and stretchability of polypropylene, and as a result, the rigidity of the polypropylene was maintained by adding a small amount of a specific hydrocarbon polymer to the specific polypropylene. As it was, they found that the stretchability was significantly improved, and completed the present invention.

That is, the gist of the present invention is that the stereoregularity of the boiling heptane-insoluble part is 100 parts by weight of a polypropylene homopolymer having an isotactic pentad fraction of 0.960 or more as determined by ¹³ C-NMR, and at least one end of the homopolymer is used. A composition obtained by blending 0.01 to 2 parts by weight of a saturated or partially saturated hydrocarbon polymer having a hydroxyl group is formed into a film or a sheet, and the composition is formed at a temperature of 150 to 200 ° C in the longitudinal and transverse directions. And a polypropylene biaxially stretched film, each of which is stretched 2 to 10 times.

Hereinafter, the present invention will be described in more detail.

The polypropylene used in the present invention is a homopolymer of propylene homopolymer, and the stereoregularity of the boiling heptane-insoluble portion is 0.960 or more, preferably 0.970 or more, in the isotactic pentad fraction determined by ¹³ C-NMR.
Or more, more preferably 0.975 or more. Such polypropylene can be produced by the method described in JP-A-56-59285 and JP-A-59-13630. If the isotactic pentad fraction of the polypropylene is less than 0.960, the effect of improving the rigidity of the stretched film is reduced, which is not preferable.

In the present invention, the isotactic pentad fraction of the boiling heptane-insoluble part of the polypropylene is determined as follows.

After completely dissolving 5 g of polypropylene in 500 ml of boiling xylene, the mixture is allowed to cool to 20 ° C. Then separate 20
℃ Separated into xylene soluble part and insoluble part. Then 20 ℃
The xylene-insoluble part is further separated into Soxhlet extract residue and extract with boiling heptane for 6 hours. This extraction residue is used as a boiling heptane-insoluble portion.

The isotactic pentad fraction is an isotactic fraction in pentad units in a polypropylene molecular chain, which is measured by using ¹³ C-NMR.
It is measured based on the method described in les 8 687 (1975). Specifically, the isotactic pentad fraction is measured as the area fraction of the mmmm peak in all the absorption peaks in the methyl carbon region of the ¹³ C-NMR spectrum.

The polypropylene melt-fluorate index (abbreviated as MFi) used in the present invention may be any of those used in the field of stretched film, but according to the method of JIS K-7210, the value measured at 230 ° C. and a load of 2160 g is 0.2. ~ 1
It is preferably in the range of 0, more preferably 0.5 to 7
It is in the range of.

On the other hand, the saturated or partially saturated hydrocarbon polymer of the main chain having at least one hydroxyl group at the terminal used by being blended with the polypropylene specifically means, for example, the following.

This polymer has at least one hydroxyl group at the end,
It includes a polymer having a saturated main chain and having a molecular weight of 500 to 200,000, which is liquid, semi-solid or solid at room temperature. The average number of hydroxyl groups per molecule is preferably 1.5 to 8.0. Further, a saturated or partially saturated hydrocarbon polymer having a main chain having at least one hydroxyl group at the terminal used in the present invention (hereinafter, simply referred to as "saturation of a main chain having at least one hydroxyl group at the terminal"). Abbreviated as "hydrocarbon-based polymer") is a polymer in which main chain hydrocarbons are completely or partially saturated. With respect to 1,4-polybutadiene, the proportion of hydrogenation is at least 20%, preferably 50%.
% Or more, more preferably 80% or more.

The main chain saturated hydrocarbon polymer having at least one hydroxyl group at these terminals is a diene polymer and / or produced by a known method using a diene as a raw material, for example, a radical polymerization method or an anionic polymerization method. Alternatively, the diene-based copolymer is usually obtained by hydrogenation.
However, in the case of anionic polymerization, a hydrocarbon-based polymer having a main chain saturated with a main amount of, for example, 50% or more, particularly 70% or more of vinyl groups on alternating carbon atoms of a polydiene skeleton depending on conditions, That is, 1,2-polybutadiene is obtained, which does not require further hydrogenation.

In the case of radical polymerization, the method for producing a diene polymer having at least one hydroxyl group at the terminal can be easily obtained by polymerizing a diene monomer using hydrogen peroxide as a polymerization initiator. In order to obtain a polymer having a hydroxyl group at the terminal by an anionic polymerization method, the living polymer may be reacted with, for example, a monoepoxy compound, formaldehyde, acetaldehyde or acetone, or halogenoalkylene oxide or polyepoxide.

The living polymer here is produced by polymerizing a conjugated diene alone or a conjugated diene and a vinyl monomer with an anionic polymerization catalyst, for example, an alkali metal or an organic alkali metal compound according to a well-known method. A polymer having a structure in which an alkali metal is bonded to at least one of both ends of the polymer.

At least one conjugated diene monomer is used as a raw material monomer for these polymers. Examples of the conjugated diene monomer include butadiene-1,3, isoprene, chloroprene, pentadiene-1,3,2,3-dimethylbutadiene-1,3, 1-phenylbutadiene1,3 and the like. On the other hand, as a copolymerization component of the conjugated diene-based copolymer, one or more vinyl monomers are used depending on the purpose. As these vinyl monomers, vinyl aromatic compounds such as styrene, α-methylstyrene and vinyltoluene; (meth) acrylic acid derivatives such as methyl acrylate, butyl acrylate and methyl methacrylate; nitrile compounds such as acrylonitrile and methacrylonitrile;
Vinyl pyridine such as 2-vinyl pyridine and 4-vinyl pyridine; vinyl ether such as methyl vinyl ether and 2-chloroethyl vinyl ether; halogenated vinyl such as vinyl chloride and vinyl bromide; vinyl ester such as vinyl acetate. Further, vinyl monomers having active hydrogen such as 2-hydroxyethyl methacrylate, acrylic acid and acrylamide can also be used. When used in combination with a conjugated diene-based monomer, the amount of vinyl monomer used is 5 based on the total amount of monomers when the physical properties of the final product are taken into consideration.
It is preferably 0% by weight or less.

The unsaturated double bonds in the main chain of these diene-based polymers and / or diene-based copolymers are used after being wholly or partially hydrogenated. However, in the case of 1,2-bond polybutadiene and 3,4-bond polyisoprene polymer which do not substantially contain unsaturated bonds in the main chain, they are used as they are. The above hydrogenation may be complete hydrogenation saturation or partial hydrogenation. However, for 1,4-polybutadiene, the proportion of hydrogenation is at least 20%,
It is preferably 30% or more. If the hydrogenation rate is less than 20%, the adhesiveness is insufficient, and even if there is some adhesive force, the adhesive surface is uneven, which is not preferable. Since 50% of carbon atoms involved in double bonds are present in the main chain of 1,4 polybutadiene, it is necessary in the present invention to reduce this to 40% or less. Also, as already mentioned above, for example 1,2
Since 1,2 polybutadiene having a bond of 50% has only 33% of carbon atoms involved in a double bond in the main chain, it can be directly used as the polymer (2) of the present invention without hydrogenation. Can be used.

For the hydrogenation, generally used catalytic hydrotreating means can be adopted. That is, as the hydrogenation catalyst, a Nickel catalyst (for example, Raney-Nickel) which has been used for a long time, cobalt, platinum, palladium, ruthenium, rhodium catalyst, a mixture thereof or an alloy catalyst can be used. These catalysts can be used alone, as a solid or soluble homogeneous complex, or supported on carbon, silica, diatomaceous earth or the like. Further, hydrogenation may be carried out using a metal complex obtained by reducing a compound containing nickel, titanium, cobalt or the like with an organometallic compound (eg, trialkylaluminum, alkylallithium, etc.).
As the hydrogen used, molecular hydrogen is usually used,
A hydrogen-containing gas can also be used as long as it does not contain a substance that becomes a catalyst poison. The hydrogen pressure may be either atmospheric blow or pressurized system. The temperature is room temperature to 200 ° C, preferably 180 ° C or lower. The diene-based polymer and / or diene-based copolymer can be used alone or as a solvent solution. As such a solvent, aliphatic hydrocarbons, aliphatic hydrocarbons, aromatic hydrocarbons, alcohols, aliphatic carboxylic acids and the like can be used alone or in a mixed system.

As another method for producing the saturated hydrocarbon polymer used in preparing the composition of the present invention, a method of oxidizing and decomposing a copolymer of α-olefin and another monomer, and then reducing it Is mentioned. For example, a butyl rubber-based polymer obtained by cationically polymerizing isobutylene and butadiene or 1,3-pentadiene is subjected to ozone decomposition treatment, and then reduced with lithium aluminum hydride to obtain polyhydroxypolyisobutylene. Also,
Poly-α having an unsaturated bond obtained by copolymerizing with ethylene alone or with a diene in the presence of propylene.
-Polyhydroxypolyolefins are obtained by ozonolysis of olefins and subsequent reduction.

In the present invention, the blending amount of the main chain saturated hydrocarbon polymer having at least one hydroxyl group at the terminal, which is added to improve the stretchability of the polypropylene, is usually 0.01 to 100 parts by weight of the polypropylene. 2, preferably 0.1 to 2 parts by weight, more preferably 0.3 to 1.2 parts by weight. If the amount of the main chain saturated hydrocarbon polymer having at least one hydroxyl group at the terminal is less than the above range, the effect of improving the drawability of polypropylene is small, and if it exceeds the above range, the drawability is improved. The effect is not further increased, and the solvent resistance is decreased, which is not preferable.

The polypropylene resin composition used in the present invention may be prepared by dry blending the above-mentioned polypropylene and a hydrocarbon polymer having a saturated main chain having at least one hydroxyl group at the end with a blender, or by dry blending and then performing a normal melting. A kneading method, for example, a Banbury mixer, a continuous mixer, a mixing roll, an extruder, etc., melt-mixes at the temperature of 190-300 degreeC, and it is obtained by pelletizing.

The polypropylene resin composition of the present invention, if necessary, various known additives used for polypropylene such as heat stabilizers, antioxidants, ultraviolet absorbers, anti-blocking agents, lubricants and other additives. May be added.

In the present invention, an unstretched film or sheet is molded using the polypropylene resin composition obtained above,
Then, the unstretched film or sheet is biaxially stretched under specific conditions to produce a biaxially stretched film.

The unstretched film or sheet is formed by using a usual film or sheet forming apparatus and forming method, for example, an inflation forming method using a circular die, a T die forming method using a T die, or the like, and applying the above composition to a resin temperature of 190. ~ 300
The molding is carried out under the molding conditions of a temperature range of 1 ° C and a draft rate of 1 to 50.

When molding with inflation, set the blow up ratio to 1.
5 to 4.0, draft rate 1 to 50, resin temperature 200 to 27
It is desirable to carry out under conditions of 0 ° C. and a cooling rate index (τ) of 7 or less.

In the present invention, the draft rate is obtained as follows.

In the formula, the symbols are as follows In the case of T-die molding, it is expressed as BUR = 1.

If the draft ratio is less than 1, the optical properties of the film-forming film will be poor, and if it is greater than 100, longitudinal tearing will tend to occur during stretching, such being undesirable.

The cooling rate index (τ) indicates the residence time (second) until the molten resin is extruded from the die and reaches the frost line, and is represented by the following formula (I).

In the method of the present invention, the cooling rate index (τ) is set in the range of 7 or less. The cooling rate index (τ) may be controlled to a predetermined value by changing each requirement in the above formula (I), and for example, the frost line height (FL
If you want to change (H), you can change the cooling degree of the cooling device such as the air ring, and to change V ₀ and V _1, you can control by changing the extrusion amount of the extruder and the take-up speed of the take-up device. Often, each of these elements is combined to set a predetermined cooling rate index (τ).

When the cooling rate index (τ) exceeds the above range, the cooling becomes insufficient and the bubbles become unstable, or the generated molecular orientation relaxes, and the film strength decreases.

Further, in the case of T die molding, the draft rate is 1 to 10,
It is desirable to carry out under conditions of a resin temperature of 190 to 300 ° C. and a cooling rate index of 7 or less (cooling roll temperature of 40 to 120 ° C.).

The unstretched film obtained as described above is then biaxially stretched. The biaxial stretching treatment is carried out by directly biaxially stretching or simultaneously biaxially stretching an unstretched film obtained by the T-die method or the inflation method as it is or by slitting it into a predetermined width. Sequential biaxial stretching is carried out either in the longitudinal direction (film take-up direction) and then in the transverse direction (direction orthogonal to the film take-up direction), or vice versa. Further, in the simultaneous biaxial stretching, the time distribution of the stretching in the machine direction and the transverse direction is arbitrary, and for example, the stretching is gradually continued in the machine direction until the stretching in the machine direction is completed, or the stretching is started in the machine direction. And the horizontal direction at the same time, but the vertical direction is completed first.

In the present invention, it is possible to employ a tenter sequential biaxial stretching method, a tubular simultaneous biaxial stretching method, or the like, but particularly when the tenter sequential biaxial stretching method is adopted, the transparency is remarkably improved. It is preferable because

The biaxial stretching treatment in the present invention is performed under the following conditions of stretching temperature, stretching speed and stretching ratio.

The stretching temperature is 150 ° C to 200 ° C, preferably 155 ° C to
It is in the range of 175 ° C. If the stretching temperature is less than 150 ° C., the mobility of the molecular chain is poor, so that the film is easily cut during stretching, and even if it can be stretched, the stretching ratio does not increase and a stretched film having excellent physical properties cannot be obtained. Further, at a temperature higher than 200 ° C., the resin composition is partially melted and cannot be stretched and oriented, and even if it is stretched, uneven stretch is severe and transparency is impaired. Does not mean

The stretching speed is in the range of 2 to 300% / sec, preferably 10 to
It is in the range of 150% / sec. If the stretching speed is slower than 2% / sec, the stretchability is likely to be hindered by oriented crystallization during stretching, and if it is faster than 50% / sec, the deformation of the polymer cannot keep up with the stretching speed and the stretch breaks. become.

The stretching ratio is 2 in the machine direction of the film in terms of the operability (stretchability) and the physical properties of the obtained biaxially stretched film.
It is a range of 10 to 10 times, preferably 4 to 9 times, and a range of 2 to 10 times in the lateral direction, preferably a range of 4 to 9 times.

When the stretching ratio in the machine direction is less than 2 times, the thickness unevenness of the obtained stretched film becomes large and a uniform stretched film cannot be obtained, and when it is more than 10 times, the stretching operability deteriorates.
It is not preferable because a satisfactory stretched film cannot be obtained.

Further, if the stretching ratio in the transverse direction is less than 2 times, the thickness unevenness of the obtained stretched film becomes large and a uniform stretched film cannot be obtained. If it is more than 10 times, the stretch operability is deteriorated and a satisfactory stretched film is obtained. It is not preferable because it cannot be done.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples without departing from the gist thereof.

(1) Method for measuring isotactic pentad fraction The PP5g of the sample was reflipped with 500 cc of p-xylene for 5 minutes.
The insoluble matter was subjected to ux treatment, and after being left to cool, the deposited matter was subjected to a reflux treatment with 200 cc of n-heptane for 6 hours, and the insoluble matter was subjected to C-13 NMR measurement.

C-13 NMR measurement method and spectrum analysis
cromolecules 8 687 (1975).

(2) Evaluation of Stretchability of Biaxially Stretched Film For the evaluation of stretchability, the mechanical stress at each lengthwise and horizontal stretching during the production of the biaxially stretched film was recorded. The smaller the stress, the better the stretchability.

(3) Measurement of Rigidity of Biaxially Stretched Film Using a 25 mm × 140 mm strip-shaped test piece, the tensile initial elastic modulus was determined by a tensile tester at a crosshead speed of 10 mm / min.

Examples 1 to 5 (1) Production of saturated hydrocarbon-based polymer having hydroxyl group at the end Polyhydroxypolybutadiene (R-45HT, Arco Chem., [-OH] = 0.
82meq / g, cis 1,4: 15%, trans-1,4: 58
%, Vinyl: 27%), cyclohexane 3 kg, and carbon-supporting ruthenium (5%) catalyst [manufactured by Nippon Engelhardt Co., Ltd.] 300 g, and the system was replaced with purified argon gas, and then high-purity hydrogen gas was autoclaved. Then, the heating is started at the same time. Approximately 30 minutes are required and the autoclave is operated under steady conditions (internal temperature 100 ° C, internal pressure 15
0 kg / cm ² ) has been reached. After 15 hours had passed under these conditions, the hydrogenation reaction was stopped, and the polymer was purified and dried according to a conventional method.

As a result of analysis by infrared absorption spectrum, the obtained polymer was a hydrocarbon polymer containing almost no double bonds. The —OH group of the hydrogenated product was 0.81 meq / g, and the molecular weight measured by the vapor pressure method was 3,000.

(2) Manufacture of polypropylene resin composition and manufacture of biaxially stretched film Obtained by the above (1) in 100 g of polypropylene homopolymer having a melt florate index of 2.5 g / 10 min and an isotactic pentad fraction of 0.980. The saturated hydrocarbon polymer having a hydroxyl group at the end is added in a blending amount shown in Table 1, dry blended, and then melt-kneaded at a temperature of 190 ° C. with a single-screw extruder having a cylinder diameter of 40 mmφ and extruded. Pelletized.

Obtained polypropylene resin composition (melting point: 162 ° C)
Using a T-die molding machine at a resin temperature of 260 ° C., a cooling roll temperature of 90 ° C., a winding speed of 0.5 m / min, and a draft rate of 1.5.
A sheet having a thickness of 2 mm was extruded under the conditions of 1. Using a batch type biaxial stretching machine, this sheet was
It was stretched 5 times in the machine direction at 0 ° C. and then stretched 9 times in the transverse direction at 165 ° C. (sequential drawing) to produce a biaxially stretched film having a thickness of about 45 μ. At this time, the stretchability and the rigidity were measured by the above method. The results are shown in Table 1.

Comparative Example 1 Example 1 was repeated except that the saturated hydrocarbon polymer having a hydroxyl group at the terminal was not added at all in Example 1.
I went as well.

The results are shown in Table 1.

Comparative Example 2 The procedure of Example 1 was repeated, except that the amount of the saturated hydrocarbon polymer having a hydroxyl group at the terminal was changed to 3 parts by weight.

The results are shown in Table 1.

Comparative Example 3 In Example 1, polypropylene had MFi of 2.0 g /
The procedure was the same as in Example 1 except that the polypropylene homopolymer having an isotactic pentad fraction of 0.955 was replaced with the polypropylene homopolymer after 10 minutes, and that the saturated hydrocarbon polymer having a hydroxyl group at the end was not added at all.

The results are shown in Table 1.

As is clear from Table 1, polypropylene having a high stereoregularity has a high stress required for stretching, but the blending of the "polymer having a hydroxyl group at the terminal" described in the present invention reduces the stretching stress, and It can be seen that the rigidity of the axially stretched film can be maintained.

In order to stably produce a biaxially stretched film with an industrial scale device, the stretching stress obtained by this experiment is 1
It is preferably 5 kg / cm ² or less and the lateral weight is 12 kg / cm ² or less. Outside the above range, troubles such as tearing of the film at the time of stretching and tearing off on a tenter are likely to occur.

Examples 6 to 9 100 wt% of polypropylene homopolymer having a melt florate index of 2.5 g / 10 min and an isotactic pentad fraction of 0.980 has a hydroxyl group at the end obtained in (1) of Example 1 above. Saturated hydrocarbon polymers were added in the blending amounts shown in Table 2, dry blended, and then melt kneaded at a temperature of 190 ° C. in a single screw extruder having a cylinder diameter of 40 mmφ to form extrusion pellets.

Obtained polypropylene resin composition (melting point: 162 ° C)
Using a T-die type molding machine, the resin temperature was 260 ° C., the cooling roll temperature was 90 ° C., the winding speed was 0.5 m / min, and the draft rate was 1.5.
A sheet having a thickness of 2 mm was extruded under the conditions of 1. Using a tenter method sequential biaxial stretching device, this sheet was first stretched by roll stretching at 160 ° C. in the longitudinal direction by 7 times, and then by tenter stretching at 165 ° C. in the transverse direction by 7 times, and the thickness was about 40 μm. A biaxially stretched film was manufactured. At this time, the rigidity was measured by the above method, and the stretch molding stability was evaluated by the following method. The results are shown in Table 2.

The stretching speed was 100% / sec.

Evaluation Method of Stretch Molding Stability The stretch molding stability during production of the biaxially stretched film was evaluated according to the following ranks.

C: Checking at the tenter part is disengaged and continuous operation is not possible.

B: Checking does not occur at the tenter portion, but the stretching load is large and uniform stretching cannot be performed.

C: Stretch molding can be performed without any problem.

Example 10 In Example 9, the isotactic pentad fraction was 0.
Example 9 was repeated except that 975 polypropylene homopolymer was used. The results are shown in Table 2.

Comparative Example 4 Example 6 was repeated except that the saturated hydrocarbon polymer having a hydroxyl group at the terminal was not added at all in Example 6.
I went as well.

The results are shown in Table 2.

Comparative Example 5 The procedure of Example 6 was repeated except that the amount of the saturated hydrocarbon polymer having a hydroxyl group at the terminal was changed to 3 parts by weight.

The results are shown in Table 2.

Comparative Example 6 In Example 6, polypropylene has MFi of 2.0 g /
The procedure was the same as in Example 1 except that the polypropylene homopolymer having an isotactic pentad fraction of 0.955 was replaced with the polypropylene homopolymer after 10 minutes, and that the saturated hydrocarbon polymer having a hydroxyl group at the end was not added at all.

The results are shown in Table 2.

Comparative Example 7 In Example 6, polypropylene had MFi of 2.0 g /
The procedure was the same as in Example 6 except that the polypropylene homopolymer having an isotactic pentad fraction of 0.955 was replaced with the polypropylene homopolymer in 10 minutes and the compounding amount of the saturated hydrocarbon polymer having a hydroxyl group at the terminal was changed to 2 parts by weight. . The results are shown in Table 2.

EFFECTS OF THE INVENTION According to the present invention, a specific polypropylene is blended with a specific amount of a hydrocarbon polymer having a saturated main chain having at least one hydroxyl group at the end, and the high rigidity of the polypropylene is maintained. A polypropylene biaxially stretched film having remarkably improved stretchability can be obtained.

Therefore, since the polypropylene biaxially stretched film obtained by the present invention has high rigidity, it can be suitably used for the above-mentioned applications requiring high rigidity such as packaging and electric articles.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihisa Shinohara, 3-10 Shiodori, Kurashiki City, Okayama Prefecture, Mizushima Plant, Mitsubishi Kasei (72) Inventor Kiyoshi Fukuda 3-10, Shidori, Kurashiki, Okayama Prefecture Mitsubishi Chemical Industry Co., Ltd. Mizushima factory

Claims (1)

[Claims] 1. The stereoregularity of the boiling heptane-insoluble part is ¹³ C.
-Polypropylene homopolymer 100 having an isotactic pentad fraction of 0.960 or more determined by NMR
Main chain saturated or partially saturated hydrocarbon polymer having at least one hydroxyl group at the end, based on parts by weight.
Biaxially stretched polypropylene characterized in that a composition containing 01 to 2 parts by weight is molded into a film or a sheet and stretched at a temperature of 150 to 200 ° C. in the machine direction and the transverse direction by 2 to 10 times, respectively. Film manufacturing method.