JP2010275443A - Polypropylene film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene film having excellent transparency and excellent balance between slipperiness and impact resistance at low temperature. <P>SOLUTION: The film comprises a polypropylene-based copolymer including 50-95 wt.% of a polymer component (component A) having a structural unit derived from propylene as a principal component and 5-50 wt.% of a polymer component (component B) of propylene, ethylene, and a 4C or more α-olefin. In morphology obtained when the film is observed with a transmission electron microscope, a volume-average equivalent circle diameter of dispersed particles of the polymer component (component B) of propylene, ethylene, and a 4C or more α-olefin is 1.5 μm or less. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a polypropylene film. More specifically, the present invention relates to a polypropylene film suitable as a material for a retort food packaging film having an excellent balance of transparency, slipperiness and low temperature impact property.

Polypropylene is widely used in the field of packaging materials such as food packaging and fiber packaging because it is excellent in rigidity, heat resistance and packaging suitability. The packaging material is required to have rigidity, heat resistance, impact resistance at low temperatures, heat sealability, blocking resistance, and the like, and it is required to have less fish eyes and excellent appearance. In addition, large packaging bags are beginning to spread in retort food packaging and the like, and excellent impact resistance is required so that they can be used at low temperatures. In this case, it is known as a prior art to contain a large amount of an elastomer component. However, in that case, it is difficult to achieve both impact resistance and slipperiness.

Japanese Patent Application Laid-Open No. 11-10698 describes that a film obtained by extruding crystalline polypropylene has a specific morphology and is excellent in impact resistance at low temperatures.

Japanese Patent Laid-Open No. 2003-55479 discloses a polypropylene film obtained by molding a propylene-α-olefin block copolymer having a specific property and having an elastomer block having a specific dispersed state, which is a heat seal layer of a packaging material. When used as, it is described that the decrease in heat seal strength due to heat sterilization such as retort sterilization treatment is small, the low-temperature impact strength is excellent, and there is no generation of crushed skin.

Japanese Patent Laid-Open No. 11-10698

JP 2003-55479 A

However, the above composition may be insufficient particularly in impact resistance at low temperatures, and it is not satisfactory in balance between transparency, slipperiness and impact resistance at low temperatures.
An object of the present invention is to provide a polypropylene film having an excellent balance of transparency, slipperiness and impact resistance at low temperatures.

As a result of intensive studies, the present inventors have found that the present invention can solve the above problems, and have completed the present invention.

That is, the present invention relates to a polymer component (component) of 50 to 95% by weight of a polymer component (component A) whose main component is a structural unit derived from propylene and propylene, ethylene and an α-olefin having 4 or more carbon atoms. B) A film made of a polypropylene-based copolymer containing 5 to 50% by weight, wherein the weight of propylene, ethylene, and α-olefin having 4 or more carbon atoms in the morphology of the film observed with a transmission electron microscope. The volume average equivalent-circle particle diameter of the dispersed particles of the combined component (component B) is 1.5 μm or less.

The film of the present invention is excellent in balance between transparency, slipperiness and impact property at low temperature. And the film of this invention can be used suitably as a material of the film for retort food packaging.

The film of the present invention comprises a polymer component (component A) whose main component is a structural unit derived from propylene, and a polymer component (component B) of propylene, ethylene and an α-olefin having 4 or more carbon atoms. It consists of a polypropylene copolymer.

Here, the proportion of component A and component B in the polypropylene copolymer is in the range of 50 to 95% by weight of component A and 5 to 50% by weight of component B, preferably 60 to 95% by weight of component A. %, Component B is 5 to 40% by weight, more preferably component A is 60 to 90% by weight, and component B is 10 to 40% by weight. When the component B is less than 5% by weight, the impact resistance at low temperatures is poor, and when the component B exceeds 50% by weight, the slipping property may be deteriorated.

Component A is a polymer whose main component is a structural unit derived from propylene. From the viewpoint of rigidity, the melting point preferably exceeds 155 ° C, more preferably 160 ° C or higher. Component A may be copolymerized with an α-olefin such as ethylene or 1-butene within a range where the melting point does not become 155 ° C. or less, but is preferably a propylene homopolymer. When an α-olefin such as ethylene or 1-butene is copolymerized, the content of the structural unit derived from the α-olefin in the polymer component (component A) whose main component is the structural unit derived from propylene is 5% by weight or less, preferably 3% by weight or less (the polymer component mainly composed of propylene is 100% by weight). Although there is no restriction | limiting in particular about the intrinsic viscosity of the component A, the range of 1.5-3.0 dL / g is preferable, and the range of 1.5-2.5 dL / g is further more preferable.

The content (Y) of the structural unit derived from ethylene contained in Component B is not particularly limited, but is preferably 50 <Y ≦ 70 wt%, more preferably 52 ≦ Y ≦ 70 wt% (provided that Component B Content of structural unit derived from propylene contained in (X), content of structural unit derived from ethylene (Y), and content of structural unit derived from α-olefin having 4 or more carbon atoms (Z) Is 100% by weight). When the content of the structural unit derived from ethylene is 50% by weight or less, or exceeds 70% by weight, impact resistance at low temperatures may be lowered.

The content (Z) of the structural unit derived from the α-olefin contained in Component B is not particularly limited, but is preferably 0 <Z ≦ 20% by weight, more preferably 1 ≦ Z ≦ 16% by weight (provided that Content of structural unit derived from propylene contained in component B (X), content of structural unit derived from ethylene (Y), and content of structural unit derived from α-olefin having 4 or more carbon atoms ( Z) is defined as 100% by weight). When the content of the structural unit derived from α-olefin exceeds 0% by weight or 20% by weight, the impact resistance at low temperature may be lowered.

Examples of the α-olefin having 4 or more carbon atoms contained in Component B include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, vinylcyclohexane, vinylnorbornane. 1-butene is preferable. Although there is no restriction | limiting in particular about the intrinsic viscosity of the component B, the range of 2.0-5.0 dL / g is preferable from a viewpoint of fish-eye generation | occurrence | production, and the range of 2.5-4.5 dL / g is further more preferable.

As a method for producing a polypropylene-based copolymer, after polymerizing a polymer component (component A) whose main component is a structural unit derived from propylene, propylene, ethylene, and an α-olefin having 4 or more carbon atoms are continuously produced. The polymer component (component B) is polymerized and produced, and can be produced by various polymerization methods using a normal stereoregular catalyst.

Examples of the stereoregular catalyst include a catalyst comprising a solid titanium catalyst component, an organometallic compound catalyst component, and an electron donor used as necessary, and a transition of group IVB of the periodic table having a cyclopentadienyl ring. Examples include a catalyst system composed of a metal compound and an alkylaluminoxane, or a compound composed of a group IVB transition metal compound having a cyclopentadienyl ring and a compound which reacts with it to form an ionic complex and an organoaluminum compound. .

A method for producing a polypropylene copolymer by the following steps may be mentioned.
Polymerization step 1: Propylene is homopolymerized to produce a polypropylene homopolymer component (component A), or propylene and an olefin selected from the group consisting of ethylene and an α-olefin having 4 to 10 carbon atoms. A step of copolymerization to produce a polymer component (component A) whose main component is a structural unit derived from propylene. Polymerization step 2: Mainly the structural unit derived from the polypropylene homopolymer component or propylene obtained in step 1 above. In the presence of a copolymer component as a component, propylene, ethylene and an α-olefin having 4 or more carbon atoms are copolymerized to form a polymer component (component) of propylene, ethylene and an α-olefin having 4 or more carbon atoms. B) generating step

A time for polymerizing a polymer component (component A) whose main component is a structural unit derived from propylene, and a time for polymerizing a polymer component (component B) of propylene, ethylene and an α-olefin having 4 or more carbon atoms; , The ratio of component A and component B can be changed.
In addition, by polymerizing a polymer component (component B) of propylene, ethylene and an α-olefin having 4 or more carbon atoms, by changing the gas composition in the mixed gas of propylene, ethylene and α-olefin, the component The composition of B can be changed.

The morphology obtained by observing a film obtained by extrusion-molding a polypropylene copolymer with a transmission electron microscope is a polymer component (component A) whose main component is a structural unit derived from propylene, and propylene and ethylene. And a dispersed phase of a polymer component (component B) of α-olefin having 4 or more carbon atoms is dispersed in the continuous phase.
In the morphology of the film of the present invention observed with a transmission electron microscope, the volume average equivalent-circle particle diameter (Dv) of dispersed particles of a polymer component (component B) of propylene, ethylene, and α-olefin having 4 or more carbon atoms is It is 1.5 μm or less, preferably 1.4 μm or less. When Dv exceeds 1.5 μm, the impact resistance at low temperatures may be inferior.

The volume average equivalent-circle particle diameter (Dv) of a polymer component (component B) of propylene, ethylene, and an α-olefin having 4 or more carbon atoms is prepared by preparing a test piece from an extruded film, and cutting the piece, for example, ruthenium. After dyeing with an acid, a photograph is taken with a transmission electron microscope, and the photograph is obtained by image analysis.

（上記式中、ｉは１〜ｎの整数であり、Ｄｉは各粒子の円相当粒子径である。） In the image analysis process, a photograph obtained from a transmission electron microscope is taken into a computer and binarized with high-precision image analysis software or the like to obtain an analysis area. Next, since the shape of the dispersed particles corresponding to the polymer component (component B) of propylene, ethylene, and α-olefin having 4 or more carbon atoms is indefinite, propylene, ethylene, and α-olefin having 4 or more carbon atoms. The diameter of a circle having the same area as the polymer component (circle equivalent particle diameter: Di, unit: μm) can be obtained, and the volume average circle equivalent particle diameter (Dv) can be obtained from the following formula.

(In the above formula, i is an integer of 1 to n, and Di is the circle equivalent particle diameter of each particle.)

The film of the present invention is formed by subjecting a polypropylene-based copolymer to a melt-kneading process and an extrusion process by ordinary methods.
Examples of the melt-kneading step include a method in which a polypropylene copolymer is heated and melt-kneaded using a single-screw or biaxial or more multi-screw extruder, a Banbury mixer, a roll kneader, or the like. The melt kneading temperature is preferably 180 ° C to 350 ° C. Examples of the extrusion step include a method of forming a film from a melted polypropylene copolymer by an extrusion molding method such as a T-die molding method or a tubular molding method.

The thickness of the film of the present invention is preferably 10 to 500 μm, more preferably 10 to 100 μm. The film may be subjected to a surface treatment such as a corona discharge treatment, a flame treatment, a plasma treatment, an ozone treatment, etc. by a method that is usually employed industrially.

When producing the film of the present invention, from the viewpoint of improving processability and reducing fish eyes, one to a plurality of filters composed of sintered fibers having a filtration accuracy of 10 to 150 μm are provided at the tip of the extruder. May be repeated.

You may add an additive and another resin to the film of this invention as needed. Examples of the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, an adhesive, an antifogging agent, an antiblocking agent, and an organic peroxide. Examples of other resins include high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and elastomers that are copolymers of ethylene and α-olefin, which are manufactured using heterogeneous catalysts. Alternatively, it may be produced with a homogeneous catalyst (for example, a metallocene catalyst). Further, an elastomer such as a styrene copolymer rubber obtained by hydrogenating a styrene-butadiene-styrene copolymer or a styrene-isoprene-styrene copolymer may be added.

The film of the present invention is preferably a film for retort food packaging that is subjected to heat treatment at a high temperature. The film is also preferably used as a single layer of a composite film. The composite film is a film composed of the film of the present invention and other films. Examples of the other films include a polypropylene biaxially stretched film, an unstretched nylon film, a stretched polyterephthalate film, and an aluminum foil. Examples of the method for producing the composite film include a dry laminating method and an extrusion laminating method.

Hereinafter, although the present invention is explained using an example and a comparative example, the range of the present invention is not limited only to an example. The detailed description of the invention and the measured values of each item in the examples and comparative examples were measured by the following methods.

(1) Melting point (unit: ° C)
Using a differential scanning calorimeter (DS Instruments Q100, manufactured by TA Instruments), about 10 mg of a test piece was melted at 200 ° C. under a nitrogen atmosphere, held at 200 ° C. for 5 minutes, and then the temperature decreasing rate was 10 ° C./min. After the temperature was lowered to -90 ° C, the temperature was raised at 10 ° C / min, and the temperature of the maximum peak of the obtained melting endotherm curve was defined as the melting point (Tm).

(2) MFR (unit: g / 10 minutes)
According to JIS K7210, the temperature was 230 ° C. and the load was 2.16 kgf.

(3) Intrinsic viscosity ([η], unit: dL / g)
The measurement was performed in 135 ° C. tetralin using an Ubbelohde viscometer.

(4) Intrinsic viscosity of component A [η] A ([η], unit: dL / g)
Intrinsic viscosity of polymer component (component A) of monomer mainly composed of propylene: [η] A is measured by the method of (3) above after extracting the polymer powder from the polymerization tank after polymerization of component A. Asked.

(5) Intrinsic viscosity of component B [η] B ([η], unit: dL / g)
Intrinsic viscosity of polymer component (component B) of propylene, ethylene, and α-olefin having 4 or more carbon atoms: [η] B is the limit of the polymer component (component A) of a monomer whose main component is propylene. Viscosity: [η] A, intrinsic viscosity of the entire polypropylene copolymer containing component A and component B: [η] T was measured by the method of (3) above, and the entire polypropylene copolymer of component B was measured. The polymerization ratio was calculated from the following formula using χ (the polymerization ratio of component B with respect to the entire polypropylene copolymer: χ was obtained by the method described in (6) below).
[Η] B = [η] T / χ− (1 / χ−1) [η] A
[Η] A: Intrinsic viscosity (dL / g) of the polymer part of the monomer whose main component is propylene
[Η] T: Intrinsic viscosity (dL / g) of the entire polypropylene-based copolymer containing component A and component B
χ: Polymerization ratio of component B to the entire polypropylene copolymer

(6) Polymerization ratio of component B to the entire polypropylene copolymer: χ (unit:% by weight)
Regarding Examples 1 to 3, the polymerization ratio of the polymer component (component B) of propylene, ethylene, and α-olefin having 4 or more carbon atoms to the entire polypropylene copolymer containing component A and component B: χ is It was calculated by the following method.
χ = 1−Mg (T) / Mg (P)
Mg (P): Magnesium content of polymer taken out from polymerization tank after polymerization of polymer component (component A) of monomer mainly composed of propylene Mg (T): polypropylene system containing component A and component B Magnesium content of the entire copolymer The magnesium content of the polymer was determined by ICP emission spectrometry for the liquid part obtained after the sample was poured into a sulfuric acid aqueous solution (1 mol / liter) and the metal component was extracted by applying ultrasonic waves. Quantified.
In Comparative Examples 1 and 2, calculation was performed by the following method.
χ = 1−ΔH _B / ΔH _A
ΔH _A : Polymer component (component A) whose structural unit derived from propylene is the main component (component A) Heat of fusion of polymer after polymerization (J / g)
ΔH _B : Polymer component of propylene, ethylene and α-olefin having 4 or more carbon atoms (component B) Heat of fusion of polymer after polymerization (J / g)

(7) Content of structural unit derived from ethylene of component B (Y) and content of structural unit derived from 1-butene (Z) (unit:% by weight)
About Examples 1-3, content (C2 '(T)) of the structural unit derived from ethylene in the polypropylene-type copolymer containing the component A and the component B, and content of the structural unit derived from 1-butene The quantity (C4 ′ (T)) was determined based on the description of J of Polymer Science; Part A; Polymer Chemistry, 28, 1237-1254, 1990. In Comparative Examples 1-2, the content of structural units derived from ethylene (C2 ′ (T)) in the polypropylene-based copolymer containing component A and component B, and structural units derived from 1-butene. Content (C4 ′ (T)) was determined by the method described in pages 616 to 619 of the Polymer Handbook (1995, published by Kinokuniya Shoten).
Next, C2 ′ (T), C4 ′ (T) and χ described in the above (6) are derived from the content (Y) of structural unit derived from ethylene of component B and 1-butene by the following method. The content (Z) of the structural unit was calculated.
Y = C2 ′ (T) / χ × 100
Z = C4 ′ (T) / χ × 100

(8) Transparency (haze, unit:%)
It measured according to JIS K7105.

(9) Coefficient of static friction (unit: μs) and coefficient of dynamic friction (unit: μk)
At the room temperature of 23 ° C and humidity of 50%, the measurement surfaces of two film samples of MD100mm x 50mm are superposed on each other, using a weight of 79.4g with an installation area of 40mm x 40mm, a friction measuring machine manufactured by Toyo Seiki (TR -2 type) at a moving speed of 15 cm / min.

(10) Impact resistance (unit: kJ / m)
The film was placed in a thermostat set at a predetermined temperature (−15 ° C.), and the impact strength of the film was measured using a Toyo Seiki film impact tester using a hemispherical impact head having a diameter of 15 mm.

（上記式中、ｉは１〜ｎの整数であり、Ｄｉは各粒子の円相当粒子径である。） (11) Volume average equivalent-circle particle diameter (Dv) (unit: μm) of dispersed particles of a polymer component (component B) of propylene, ethylene, and an α-olefin having 4 or more carbon atoms
Test pieces were cut out from the films produced in Examples 1 to 3 and Comparative Examples 1 and 2 (2 mm × 10 mm strips) and embedded and fixed with an epoxy resin (60 ° C., 24 hours). Next, after dyeing with ruthenic acid vapor (60 ° C., 3 hours), an ultrathin section having a thickness of about 1000 mm was prepared using a cryoultra microtome (cutting temperature—70 ° C.). The ultrathin section was observed at an observation magnification of 5000 times using a transmission electron microscope (Hitachi H-7650 type). Here, the black dyed portion corresponds to a polymer component (component B) of propylene, ethylene and an α-olefin having 4 or more carbon atoms. From the photograph taken using the transmission electron microscope, the image analysis processing shown below is performed using high-accuracy image analysis software “IP-1000” manufactured by Asahi Engineering Co., Ltd. The volume average circle equivalent particle diameter (Dv) of the dispersed particles of the polymer component (component B) with α-olefin was determined.
(Image analysis processing) A photograph obtained from a transmission electron microscope with a scanner GT-X970 manufactured by EPSON is loaded into a computer (96 dpi, 24 bits), and binarized with high-accuracy image analysis software "IP-1000" manufactured by Asahi Engineering did. The analysis area was 309 μm ² . Since the shape of the dispersed particles corresponding to the polymer component (component B) of propylene, ethylene, and α-olefin having 4 or more carbon atoms is indefinite, the weight of propylene, ethylene, and α-olefin having 4 or more carbon atoms is The diameter (circle equivalent particle diameter: Di, unit: μm) of the circle having the same area as the combined component (component B) was obtained, and the volume average equivalent circle particle diameter (Dv) was obtained from the following formula.

(In the above formula, i is an integer of 1 to n, and Di is the circle equivalent particle diameter of each particle.)

Example 1
(1) Production of polypropylene copolymer (BCPP1) Propylene homopolymer component (component A) having an intrinsic viscosity of 1.84 dL / g was produced in the first step using a Ziegler-Natta type catalyst, and then the second In the process, ethylene / propylene / ethylene having an intrinsic viscosity of 3.96 dL / g, an ethylene content (Y) of 56% by weight, a propylene content (X) of 40% by weight, and a 1-butene content (Z) of 4% by weight. A 1-butene polymer component (component B) was produced to obtain a polypropylene copolymer (BCPP1). The polymerization ratio of the ethylene / propylene / 1-butene polymer component (component B) was 36% by weight.

(2) Film production and its physical properties As a stabilizer against 199.8 g of polypropylene copolymer (BCPP1), [η] = 1.57, Tm = 162.1 ° C. propylene homopolymer 250.2 g 0.25 g of calcium stearate, 0.9 g of Irganox 1010 (manufactured by Ciba Specialty Chemicals) and 0.225 g of Irgaphos 168 (manufactured by Ciba Specialty Chemicals) were added, and a 20 mm single screw extruder (VS20-14 type). , Manufactured by Tanabe Plastics Machine Co., Ltd., with L / D = 12.6 full flight type screw) at 250 ° C. to obtain a polypropylene resin composition having MFR = 3.8 (g / 10 min). Obtained.
The obtained polypropylene resin composition was melt-extruded at a resin temperature of 280 ° C. using a 20 mmT die film forming apparatus (VS20-14 type, manufactured by Tanabe Plastics Machine Co., Ltd., with a 100 mm width T die). The melt-extruded product was cooled with a cooling roll through which cooling water of 30 ° C. was passed to obtain a film having a thickness of 30 μm. The properties of the obtained film are shown in Table 2.

Example 2
(1) Production of polypropylene copolymer (BCPP2) A propylene homopolymer component (component A) having an intrinsic viscosity of 1.78 dL / g was produced in the first step using a Ziegler-Natta type catalyst, and then the second Ethylene / propylene / ethylene having an intrinsic viscosity of 4.29 dL / g, an ethylene content (Y) of 65% by weight, a propylene content (X) of 19% by weight and a 1-butene content (Z) of 16% by weight in the process. A 1-butene polymer component (component B) was produced to obtain a polypropylene copolymer (BCPP2). The polymerization ratio of the ethylene / propylene / 1-butene polymer component (component B) was 28% by weight.

(2) Film production and its physical properties As a stabilizer against 171.3 g of polypropylene copolymer (BCPP2) and 128.7 g of propylene homopolymer with [η] = 1.57 and Tm = 162.1 ° C. 0.15 g of calcium stearate, 0.6 g of Irganox 1010 (manufactured by Ciba Specialty Chemicals) and 0.15 g of Irgaphos 168 (manufactured by Ciba Specialty Chemicals) were added, and a 20 mm single screw extruder (VS20-14 type). , Manufactured by Tanabe Plastics Machine Co., Ltd., with L / D = 12.6 full flight type screw) at 250 ° C. to obtain a polypropylene resin composition having MFR = 3.8 (g / 10 min). Obtained.
The obtained polypropylene resin composition was extruded in the same manner as in Example 1 to obtain a film. The properties of the obtained film are shown in Table 2.

Example 3
(1) Production of polypropylene copolymer (BCPP3) A propylene homopolymer component (component A) having an intrinsic viscosity of 1.65 dL / g was produced in the first step using a Ziegler-Natta type catalyst, and then the second Ethylene / propylene / ethylene having an intrinsic viscosity of 3.59 dL / g, an ethylene content (Y) of 54 wt%, a propylene content (X) of 45 wt%, and a 1-butene content (Z) of 1 wt% in the process. A 1-butene polymer component (component B) was produced to obtain a polypropylene copolymer (BCPP3). The polymerization ratio of the ethylene / propylene / 1-butene polymer component (component B) was 38% by weight.

(2) Film production and its physical properties As a stabilizer against 168.4 g of polypropylene copolymer (BCPP3) and 231.6 g of propylene homopolymer with [η] = 1.57 and Tm = 162.1 ° C. 0.2 g of calcium stearate, 0.8 g of Irganox 1010 (manufactured by Ciba Specialty Chemicals) and 0.2 g of Irgafos 168 (manufactured by Ciba Specialty Chemicals) were added, and a 20 mm single screw extruder (VS20-14 type). , Manufactured by Tanabe Plastics Machine Co., Ltd., with L / D = 12.6 full flight type screw) at 250 ° C. to obtain a polypropylene resin composition having MFR = 4.6 (g / 10 min). Obtained.
The obtained polypropylene resin composition was extruded in the same manner as in Example 1 to obtain a film. The properties of the obtained film are shown in Table 2.

Comparative Example 1
(1) Production of polypropylene copolymer (BCPP4) A propylene homopolymer component (component A) having an intrinsic viscosity of 1.80 dL / g was produced in the first step using a Ziegler-Natta type catalyst, and then the second In the process, an ethylene / propylene polymer component (component B) having an intrinsic viscosity of 3.01 dL / g, an ethylene content (Y) of 65% by weight, and a propylene content (X) of 35% by weight is produced. A copolymer (BCPP4) was obtained. The polymerization ratio of the ethylene / propylene polymer component (component B) was 24% by weight.

(2) Film production and physical properties thereof 335 g of polypropylene copolymer (BCPP4) and [η] = 1.84, Tm = 161.9 ° C. of propylene homopolymer 165 g of calcium stearate as stabilizer. 25 g, Irganox 1010 (Ciba Specialty Chemicals) 1 g, Irgafos 168 (Ciba Specialty Chemicals) 0.25 g were added, and a 20 mm single screw extruder (VS20-14 type, Tanabe Plastics Machinery Co., Ltd.) A polypropylene resin composition having MFR = 2.9 (g / 10 min) was obtained by melt-kneading at 250 ° C. using a company-made L / D = 12.6 full-flight screw).
The obtained polypropylene resin composition was extruded in the same manner as in Example 1 to obtain a film. The properties of the obtained film are shown in Table 2.

Comparative Example 2
(1) Production of polypropylene copolymer (BCPP5) Propylene homopolymer component (component A) having an intrinsic viscosity of 1.80 dL / g was produced in the first step using a Ziegler-Natta type catalyst, and then the second In the process, an ethylene / propylene polymer component (component B) having an intrinsic viscosity of 3.01 dL / g, an ethylene content (Y) of 55% by weight, and a propylene content (X) of 45% by weight is produced. A copolymer (BCPP5) was obtained. The polymerization ratio of the ethylene / propylene polymer component (component B) was 20% by weight.

(2) Film production and physical properties thereof Polypropylene copolymer (BCPP5) 400 g, [η] = 1.84, Tm = 161.9 ° C. propylene homopolymer 100 g as a stabilizer, calcium stearate 0. 25 g, Irganox 1010 (Ciba Specialty Chemicals) 1 g, Irgafos 168 (Ciba Specialty Chemicals) 0.25 g were added, and a 20 mm single screw extruder (VS20-14 type, Tanabe Plastics Machinery Co., Ltd.) A polypropylene resin composition having MFR = 2.5 (g / 10 min) was obtained by melt-kneading at 250 ° C. using a company-made L / D = 12.6 full-flight screw).
The obtained polypropylene resin composition was extruded in the same manner as in Example 1 to obtain a film. The properties of the obtained film are shown in Table 2.

Table 1

Table 2

Claims (2)

Polymer component (component A) of 50 to 95% by weight having a structural unit derived from propylene as a main component, and polymer component (component B) of 50 to 50% by weight of propylene, ethylene and an α-olefin having 4 or more carbon atoms. And a polymer component of propylene, ethylene, and an α-olefin having 4 or more carbon atoms (component B) in a morphology obtained by observing the film with a transmission electron microscope. The above-mentioned film, wherein the dispersed particles have a volume average equivalent-circle particle diameter of 1.5 μm or less. The film according to claim 1, wherein the α-olefin having 4 or more carbon atoms is 1-butene.