JP7637550B2 - Film and method for producing film - Google Patents

Description

The present invention relates to a film and a method for producing the film.

Films containing at least two types of olefin polymers are used in a variety of applications. For example, such films are sometimes used as a sealant layer of a multilayer film used as a packaging material. A multilayer film having such a sealant layer can be formed into a packaging bag by heat sealing the multilayer film with the sealant layer facing inward to form a storage space. Then, a package can be formed by storing an item in such a packaging bag and sealing it.

The above-mentioned packaging bags are required to be easy to tear by hand when removing an item from the package (easy to cut), and to form a package that is not easily broken when dropped (bag rupture resistance). For this reason, the film used as the sealant layer is also required to be easy to cut and rupture-resistant. As a film that can impart such easy-to-cut and rupture-resistant properties to packaging bags, Patent Document 1 discloses a film that contains two types of propylene-based polymers, an ethylene-based polymer, and a specified crystal nucleating agent in a specified ratio.

JP 2019-172780 A

However, even with the above-mentioned films, there is still room for improvement in terms of ease of cutting, and there is a demand for films with even better ease of cutting.

Therefore, the objective of the present invention is to provide a film that is resistant to bag breakage and relatively easy to cut, and to provide a method for producing such a film.

The film according to the present invention is
A film containing at least two kinds of olefin polymers,
the at least two kinds of olefin polymers form an islands-in-a-sea type phase-separated structure consisting of a continuous phase and a discontinuous phase,
The degree of orientation in the MD direction of the film determined by wide-angle X-ray scattering measurement is 76% or more.

The method for producing a film according to the present invention comprises the steps of:
A method for producing the above film, comprising the steps of:
A melt-kneading step of melt-kneading a mixture containing at least two kinds of propylene-based polymers, an ethylene-based polymer, and a phosphate metal salt-based nucleating agent;
an extrusion step of extruding the kneaded material obtained in the melt kneading step into a sheet shape;
a cooling step in which the sheet-like kneaded material obtained in the extrusion step is pressed against a cooling roll by gas blown out of an air chamber to cool it;
A film-forming process of forming a film by forming the sheet-like kneaded material into a film,
In the cooling process, the amount of gas blown out from the air chamber is adjusted so that the gas pressure in the air chamber is 50 Pa to 300 Pa.

The present invention provides a film that is resistant to bag breakage and relatively easy to cut, and a method for producing such a film.

The film according to this embodiment contains at least two types of olefin-based polymers. These at least two types of olefin-based polymers form an islands-in-the-sea type phase separation structure consisting of a continuous phase and a discontinuous phase in the film.

In addition, the film according to this embodiment has an orientation degree in the MD direction (the flow direction of the film during film production) of the film determined by wide-angle X-ray scattering measurement of 76% or more, preferably 76% to 98%, and more preferably 76% to 95%. The orientation degree in the MD direction can be determined by the method described in the Examples below. In addition, the orientation degree in the MD direction can be changed by adjusting the gas pressure in the air chamber and adjusting the force with which the sheet-like kneaded material is pressed against the cooling roll in the film production method described below. Specifically, the orientation degree in the MD direction can be increased by decreasing the gas pressure in the air chamber, and decreased by increasing the gas pressure.

Furthermore, the film according to the present embodiment preferably satisfies the following formulas (1) and (2). Nx, Ny, Nz, and θ in the following formulas (1) and (2) can be determined by the method described in the Examples below. In addition, Nx, Ny, Nz, and θ can be changed by adjusting the gas pressure in the air chamber and adjusting the force pressing the sheet-like kneaded material against the cooling roll in the film manufacturing method described below. Specifically, Nx can be increased and Ny and Nz can be decreased by decreasing the gas pressure in the air chamber, and Nx can be decreased and Ny and Nz can be increased by increasing the gas pressure.

(Nx×cosθ−Ny×cosθ)/d≧3.0×10 ^-8 ...(1)
(Nx-(Ny+Nz)/2)/d≧3.4×10 ^-8 ...(2)

(Wherein,
Nx represents the refractive index of the slow axis of the film determined by three-dimensional refractive index measurement.
Ny represents the refractive index of the fast axis of the film determined by three-dimensional refractive index measurement.
Nz indicates the refractive index in the thickness direction of the film determined by three-dimensional refractive index measurement.
θ represents the angle (°) between the MD direction of the film and the slow axis, which is determined by three-dimensional refractive index measurement.
d indicates the thickness of the film (nm).

As the olefin-based polymer, for example, a propylene-based polymer can be used. The propylene-based polymer is a polymer containing 50% by mass or more (preferably more than 50% by mass) of monomer units derived from propylene, and may be a propylene homopolymer or a propylene-based copolymer.

Such a propylene-based polymer may be a propylene-based polymer A-1 that contains preferably 95% by mass or more of monomer units derived from propylene. The propylene-based polymer A-1 may contain, more preferably, 97% by mass or more, and even more preferably, more than 99% by mass of monomer units derived from propylene. Such a propylene-based polymer A-1 may be a propylene homopolymer or a propylene-based copolymer.

When the propylene-based polymer A-1 is a propylene-based copolymer, the propylene-based polymer A-1 may contain, in addition to the monomer units derived from propylene, monomer units derived from ethylene and/or an α-olefin having 4 to 12 carbon atoms. In such a case, the content of the monomer units derived from ethylene and/or an α-olefin having 4 to 12 carbon atoms in the propylene-based polymer A-1 is preferably 5% by mass or less, more preferably from more than 0% by mass to 3% by mass, and even more preferably from more than 0% by mass to 1% by mass. Examples of the α-olefin having 4 to 12 carbon atoms include 1-butene, 1-hexene, 1-octene, etc., and preferably 1-butene.

The propylene-based polymer may be a propylene-based polymer A-2 that contains preferably 50% by mass to 90% by mass of monomer units derived from propylene. The propylene-based polymer A-2 may be one that contains more preferably 50% by mass to 80% by mass, and even more preferably 60% by mass to 80% by mass of monomer units derived from propylene.

The propylene-based polymer A-2 may be a propylene-ethylene copolymer A-21 containing a monomer unit derived from ethylene. The content of the monomer unit derived from ethylene in the propylene-ethylene copolymer A-21 is preferably 10% by mass to 50% by mass, and from the viewpoint of excellent blocking resistance and bag rupture resistance, is more preferably 20% by mass to 50% by mass, and even more preferably 20% by mass to 40% by mass.

When the film according to the present invention contains propylene polymer A-1 and propylene-ethylene copolymer A-21 as the olefin polymer, the mass ratio of the propylene polymer A-1 to the total mass of the propylene polymer A-1 and the propylene-ethylene copolymer A-21 is preferably 50% by mass to 90% by mass, more preferably 60% by mass to 90% by mass, and even more preferably 60% by mass to 80% by mass, from the viewpoint of an excellent balance between heat sealability and blocking resistance. The mass ratio of the propylene-ethylene copolymer A-21 to the total mass of the propylene polymer A-1 and the propylene-ethylene copolymer A-21 is preferably 10% by mass to 50% by mass, more preferably 10% by mass to 40% by mass, and even more preferably 20% by mass to 40% by mass, from the viewpoint of an excellent balance between heat sealability and blocking resistance.

The film according to the present embodiment may contain a propylene-based polymer composition containing at least two kinds of propylene-based polymers as described above. The combination of at least two kinds of propylene-based polymers contained in the propylene-based polymer composition may be, for example, a combination of propylene homopolymers (e.g., propylene homopolymers having different physical properties, molecular weights, molecular weight distributions, and/or stereoregularities), a combination of a propylene homopolymer and a propylene-based copolymer, or a combination of propylene-based copolymers. The at least two kinds of propylene-based polymers contained in the propylene-based polymer composition may be at least two kinds of propylene-based polymers constituting a multistage polymer formed by carrying out multiple polymerization steps in stages, or may be at least two kinds of propylene-based polymers polymerized separately. Preferably, the propylene-based polymer composition contains a propylene-based multistage polymer composed of at least two kinds of propylene-based polymers.

Examples of the propylene-based polymer composition include those having a cold xylene soluble portion content of 5% by mass to 25% by mass, a cold xylene soluble portion having an intrinsic viscosity [η] _CXS of 1.5 dL/g to 3.5 dL/g, a cold xylene insoluble portion content of 75% by mass to 95% by mass, and a cold xylene insoluble portion having an intrinsic viscosity [η] _CXIS of 1.0 dL/g to 2.5 dL/g (hereinafter also referred to as "propylene-based polymer composition (A)"). The propylene-based polymer composition (A) has a cold xylene soluble portion content of preferably 5% by mass to 20% by mass, more preferably 10% by mass to 20% by mass. The propylene-based polymer composition (A) has a cold xylene soluble portion having an intrinsic viscosity [η] _CXS of preferably 1.7 dL/g to 3.2 dL/g, more preferably 2.0 dL/g to 3.2 dL/g. The propylene polymer composition (A) has a cold xylene insoluble content of preferably 80% by mass to 95% by mass, more preferably 80% by mass to 90% by mass. The propylene polymer composition (A) has a cold xylene insoluble content of preferably 1.5 dL/g to 2.5 dL/g, more preferably 1.5 dL/ _g to 2.0 dL/g. The content of the propylene polymer composition (A) in the film according to this embodiment is preferably 75% by mass to 95% by mass, more preferably 80% by mass to 95% by mass, and even more preferably 80% by mass to 90% by mass.

The values of the cold xylene soluble portion content, the intrinsic viscosity [η] _CXS of the cold xylene soluble portion, the content of the cold xylene insoluble portion, and the intrinsic viscosity [η] _CXIS of the cold xylene insoluble portion can be changed by changing the type, content, composition distribution, and molecular weight of the monomer derived from ethylene and/or an α-olefin having 4 to 12 carbon atoms. The cold xylene soluble portion content, the intrinsic viscosity [η] _CXS of the cold xylene soluble portion, the content of the cold xylene insoluble portion, and the intrinsic viscosity [η] _CXIS of the cold xylene insoluble portion can be determined by the method described in the Examples below.

The propylene polymer composition contained in the film according to the present embodiment may, for example, satisfy the following formula (3) (hereinafter, also referred to as "propylene polymer composition (C)"). The content of the propylene polymer composition (C) in the film is preferably 5% by mass to 30% by mass, more preferably 5% by mass to 25% by mass, and even more preferably 5% by mass to 20% by mass.

MT ^C >70×MFR ^C-1.1 ...(3)

(Wherein,
^MTC indicates the melt tension (mN) measured at a temperature of 190° C. and a take-up speed of 15.7 m/min.
MFR ^C indicates the melt flow rate (g/10 min) measured at a temperature of 230° C. and a load of 2.16 kg.

The melt tension can be varied by changing the molecular weight, branching degree of molecular chains, or crosslinking degree between molecular chains of the propylene polymer contained in the propylene polymer composition. The MFR ^C can be varied by changing the molecular weight of the propylene polymer contained in the propylene polymer composition. The melt tension and MFR ^C can be determined by the methods described in the Examples below.

The method for producing the above propylene-based polymer is not particularly limited. For example, the method for producing the above propylene-based polymer A-1 and propylene-ethylene copolymer A-21 includes a method for polymerizing the raw materials propylene and ethylene using a Ziegler-Natta catalyst or a metallocene catalyst. In addition, the polymerization method for the propylene-based polymer A-1 and the propylene-ethylene copolymer A-21 includes a method for polymerizing in an inert solvent such as hexane, heptane, toluene, or xylene, a method for polymerizing in liquid propylene or ethylene, a method for adding a catalyst to gaseous propylene or ethylene and polymerizing in a gas phase state, or a combination of these methods.

From the viewpoint of productivity, a preferred method for producing the propylene polymer A-1 and the propylene-ethylene copolymer A-21 is a method in which a first step is carried out to produce the propylene polymer A-1 substantially in the absence of an inert solvent, and then a second step is carried out to produce the propylene-ethylene copolymer A-21 by polymerizing propylene and ethylene in a gas phase in the presence of the propylene polymer A-1. This allows the production of a propylene-based multistage polymer containing the propylene polymer A-1 and the propylene-ethylene copolymer A-21.
The method for adjusting the content of the monomer unit derived from ethylene in such a propylene-based multistage polymer includes a method of adding a molecular weight regulator such as hydrogen gas or a metal compound and ethylene in appropriate amounts in each step of polymerization, and a method of adjusting the temperature and pressure during polymerization. The production ratio of the propylene-based polymer A-1 and the propylene-ethylene copolymer A-21 can be controlled by the polymerization time in the first step and the second step, the size of the polymerization tank, the amount of the polymer held in the polymerization tank, the polymerization temperature, the polymerization pressure, and the like. If necessary, drying may be performed at a temperature below the melting temperature of polypropylene in order to remove the residual solvent of polypropylene and ultra-low molecular weight oligomers by-produced during production. Examples of the drying method include the methods described in JP-A-55-75410 and JP Patent No. 2565753.

The melt flow rate of the above-mentioned propylene-based polymer composition (A) measured at 230°C under a load of 2.16 kg is preferably 0.001 g/10 min to 10 g/10 min, more preferably 0.01 g/10 min to 10 g/10 min, and even more preferably 0.01 g/10 min to 5 g/10 min, from the viewpoint of improving the processability and hygienic properties of the film.

The melt flow rate can be varied by changing the molecular weight of the propylene polymer. The melt flow rate can be determined by the method described in the examples below.

In the film according to this embodiment, the at least two types of olefin-based polymers may include an ethylene-based polymer (B) in addition to the above-mentioned propylene-based polymer. The ethylene-based polymer (B) is a polymer containing more than 50% by mass of monomer units derived from ethylene, and may be an ethylene homopolymer or an ethylene-based copolymer.

In such a case, the content of the propylene-based polymer composition (A) is preferably 70% by mass to 98% by mass, more preferably 75% by mass to 95% by mass, and even more preferably 80% by mass to 95% by mass, based on 100% by mass of the total of the propylene-based polymer composition (A) and the ethylene-based polymer (B). Also, the content of the ethylene-based polymer (B) is preferably 2% by mass to 30% by mass, more preferably 5% by mass to 30% by mass, and even more preferably 5% by mass to 25% by mass, based on 100% by mass of the total of the propylene-based polymer composition (A) and the ethylene-based polymer (B).

Examples of the ethylene-based polymer (B) include ethylene-α-olefin copolymers. The ethylene-α-olefin copolymers contain monomer units derived from ethylene and monomer units derived from an α-olefin having 4 to 12 carbon atoms (preferably 4 to 8 carbon atoms). The content of monomer units derived from ethylene in the ethylene-α-olefin copolymer is preferably 70% by mass to 95% by mass, more preferably 75% by mass to 95% by mass, and even more preferably 80% by mass to 95% by mass. The content of monomer units derived from an α-olefin having 4 to 12 carbon atoms (preferably 4 to 8 carbon atoms) in the ethylene-α-olefin copolymer is preferably 5% by mass to 30% by mass, more preferably 5% by mass to 25% by mass, and even more preferably 5% by mass to 20% by mass. Examples of α-olefins having 4 to 12 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene, and 4-methyl-1-hexene. The monomer units derived from α-olefins having 4 to 12 carbon atoms may be monomer units derived from a single type of α-olefin or monomer units derived from two or more types of α-olefins. From the viewpoint of improving heat seal strength, the α-olefins having 4 to 12 carbon atoms are preferably 1-hexene.

The density of the ethylene-α-olefin copolymer is preferably 850 kg/m ³ to 950 kg/m ³ , more preferably 850 kg/m ³ to 930 kg/m ³ , and even more preferably 880 kg/m ³ to 930 kg/m ^3. When the density of the ethylene-α-olefin copolymer is 850 kg/m ³ or more, a film excellent in terms of rigidity can be obtained, and when the density is 950 kg/m ³ or less, a film excellent in bag rupture resistance can be obtained.

The melt flow rate of the ethylene-α-olefin copolymer measured at 190°C under a load of 2.16 kg is preferably 0.1 g/10 min to 50 g/10 min, more preferably 0.1 g/10 min to 10 g/10 min, and even more preferably 1 g/10 min to 5 g/10 min.

The melt flow rate can be varied by changing the molecular weight of the ethylene-α-olefin copolymer. The melt flow rate can be determined by the method described in the examples below.

The molecular weight distribution of the ethylene-α-olefin copolymer is preferably 1 or more and 5 or less, more preferably 1 or more and 4 or less, and even more preferably 2 or more and 4 or less. When the molecular weight distribution of the ethylene-α-olefin copolymer is 1 or more, the extrusion load is reduced and the processability is good. Furthermore, when the molecular weight distribution of the ethylene-α-olefin copolymer is 5 or less, a film with excellent resistance to rupture can be obtained. Here, the "molecular weight distribution" refers to the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured under the following conditions using gel permeation chromatography (hereinafter sometimes referred to as "GPC"). The baseline on the chromatogram was a straight line formed by connecting the points of a stable horizontal region where the retention time is sufficiently shorter than the appearance of the sample elution peak and the points of a stable horizontal region where the retention time is sufficiently longer than the observation of the solvent elution peak.

Apparatus: Waters 150C manufactured by Waters
Separation column: TOSOH TSK-GEL GMH6-HT
Measurement temperature: 140°C
Carrier: orthodichlorobenzene Flow rate: 1.0 mL/min Injection volume: 500 μL
Detector: Differential refractometry Molecular weight standard: Standard polystyrene

An example of a method for adjusting the molecular weight distribution of the ethylene-α-olefin copolymer to the above range is to copolymerize ethylene and an α-olefin using a metallocene catalyst to adjust the density of the ethylene-α-olefin copolymer to 850 kg/m ³ to 950 kg/m ³ .

Ethylene-α-olefin copolymers can be produced, for example, using a metallocene catalyst. The metallocene catalyst is, for example, an olefin polymerization catalyst that uses a transition metal compound having a group with a cyclopentadiene-type anion skeleton (hereinafter also referred to as a "metallocene-based transition metal compound").

Examples of the metallocene transition metal compound include compounds represented by the following formula (X).

MLaXn-a...(X)

(Wherein,
M is a transition metal atom of Group 4 or the Lanthanide series of the Periodic Table of the Elements.
L is a group having a cyclopentadiene anion skeleton or a group containing a hetero atom, and at least one of Ls is a group having a cyclopentadiene anion skeleton. A plurality of Ls may be crosslinked to each other.
X is a halogen atom, a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms.
n represents the valence of the transition metal atom.
a is an integer satisfying 0<a≦n)

Examples of metallocene transition metal compounds represented by the above formula include bis(1,3-n-butylmethylcyclopentadienyl)zirconium dichloride, bis(1,3-n-propylmethylcyclopentadienyl)zirconium dichloride, bis(n-butylcyclopentadienyl)zirconium dichloride, bis(1,3-dimethylcyclopentadienyl)zirconium dichloride, bis(1,3-diethylcyclopentadienyl)zirconium dichloride, ethylene bis(indenyl)zirconium dichloride, ethylene bis(4-methyl-1-indenyl)zirconium dichloride, and ethylene bis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride.

The metallocene transition metal compound is preferably used in contact with an activating cocatalyst. Examples of the activating cocatalyst include an alumoxane compound, and an organoaluminum compound and a boron compound such as trityl borate or anilinium borate. The metallocene transition metal compound may also be used in combination with a particulate carrier, such as _an inorganic carrier such as _{SiO2 or Al2O3} , or an organic carrier such as a polymer of ethylene or styrene.

When the film according to this embodiment contains the propylene polymer A-1 and the propylene-ethylene copolymer A-21, the film contains the propylene polymer A-1 in an amount of preferably 60% by mass to 95% by mass, more preferably 65% by mass to 95% by mass, and even more preferably 65% by mass to 90% by mass, relative to the total mass of all polymers in the film, and contains the propylene-ethylene copolymer A-21 in an amount of preferably 5% by mass to 40% by mass, more preferably 5% by mass to 35% by mass, and even more preferably 10% by mass to 35% by mass.

When the film according to this embodiment contains the propylene polymer A-1 and the propylene-ethylene copolymer A-21, and an ethylene-α-olefin copolymer as the ethylene polymer (B), the film contains the propylene polymer A-1 in an amount of preferably 40% by mass to 90% by mass, more preferably 40% by mass to 85% by mass, and even more preferably 45% by mass to 85% by mass, the propylene-ethylene copolymer A-21 in an amount of preferably 5% by mass to 40% by mass, more preferably 5% by mass to 35% by mass, and even more preferably 10% by mass to 35% by mass, and the ethylene-α-olefin copolymer in an amount of preferably 5% by mass to 30% by mass, more preferably 5% by mass to 25% by mass, and even more preferably 5% by mass to 20% by mass, based on the total mass of all polymers in the film.

In addition, when the film according to this embodiment contains the above propylene-based polymer A-1 and the above propylene-ethylene copolymer A-21, and an ethylene-α-olefin copolymer as the above ethylene-based polymer (B), the ratio of the total mass of the propylene-based polymer A-1 and the propylene-ethylene copolymer A-21 to the total mass of the propylene-based polymer A-1, the propylene-ethylene copolymer A-21, and the ethylene-α-olefin copolymer is preferably 70% by mass to 95% by mass, more preferably 75% by mass to 95% by mass, and even more preferably 75% by mass to 93% by mass. When the ratio of the total mass of the propylene-based polymer A-1 and the propylene-ethylene copolymer A-21 is in the above range, a film having good heat sealability can be obtained.

The film according to this embodiment may further contain a phosphate metal salt nucleating agent. The content of the phosphate metal salt nucleating agent in such a film is preferably 100 to 10,000 ppm, more preferably 100 ppm to 5,000 ppm, and even more preferably 500 ppm to 5,000 ppm.

Examples of phosphate metal salt-based nucleating agents include aromatic phosphate metal salts. Specific examples include sodium bis(4-t-butylphenyl) phosphate, sodium bis(4-methylphenyl) phosphate, sodium bis(4-ethylphenyl) phosphate, sodium bis(4-i-propylphenyl) phosphate, sodium bis(4-t-octylphenyl) phosphate, potassium bis(4-t-butylphenyl) phosphate, calcium bis(4-t-butylphenyl) phosphate, magnesium bis(4-t-butyl phenyl) phosphate, lithium bis(4-t-butylphenyl) phosphate, aluminum bis(4-t-butylphenyl) phosphate, sodium 2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate, sodium 2,2'-ethylidene-bis(4,6-di-t-butylphenyl) phosphate, lithium 2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate, lithium 2,2'-ethylidene-bis(4,6- di-t-butylphenyl) phosphate, sodium-2,2'-ethylidene-bis(4-i-propyl-6-t-butylphenyl) phosphate, lithium-2,2'-methylene-bis(4-methyl-6-t-butylphenyl) phosphate, lithium-2,2'-methylene-bis(4-ethyl-6-t-butylphenyl) phosphate, calcium-bis[2,2'-thiobis(4-methyl-6-t-butylphenyl) phosphate], calcium-bis[2,2'-thiobis(4 -ethyl-6-t-butylphenyl)phosphate], calcium bis[2,2'-thiobis-(4,6-di-t-butylphenyl)phosphate], magnesium bis[2,2'-thiobis(4,6-di-t-butylphenyl)phosphate], magnesium bis[2,2'-thiobis-(4-t-octylphenyl)phosphate], sodium 2,2'-butylidene-bis(4,6-di-methylphenyl)phosphate, sodium 2,2'-butylidene-bis(4,6 -di-t-butylphenyl) phosphate, sodium-2,2'-t-octylmethylene-bis(4,6-di-methylphenyl) phosphate, sodium-2,2'-t-octylmethylene-bis(4,6-di-t-butylphenyl) phosphate, calcium-bis[2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate], magnesium-bis[2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate], barium-bis[2,2 '-methylene-bis(4,6-di-t-butylphenyl)phosphate], sodium-2,2'-methylene-bis(4-methyl-6-t-butylphenyl)phosphate, sodium-2,2'-methylene-bis(4-ethyl-6-t-butylphenyl)phosphate, sodium-(4,4'-dimethyl-5,6'-di-t-butyl-2,2'-biphenyl)phosphate, calcium-bis[(4,4-dimethyl-6,6'-di-t-butyl-2,2'-biphenyl)phosphate phosphate], sodium 2,2'-ethylidene-bis(4-m-butyl-6-t-butylphenyl) phosphate, sodium 2,2'-methylene-bis(4,6-di-methylphenyl) phosphate, sodium 2,2'-methylene-bis(4,6-di-ethylphenyl) phosphate, potassium 2,2'-ethylidene-bis(4,6-di-t-butylphenyl) phosphate, calcium bis[2,2'-ethylidene-bis(4,6-di-t-butylphenyl) phosphate ], magnesium bis[2,2'-ethylidene-bis(4,6-di-t-butylphenyl)phosphate], barium bis[2,2'-ethylidene-bis(4,6-di-t-butylphenyl)phosphate], aluminum tris[2,2'-methylene-bis(4,6-di-t-butylphenyl)phosphate] and aluminum tris[2,2'-ethylidene-bis(4,6-di-t-butylphenyl)phosphate] and mixtures of two or more of these can be exemplified. Sodium 2,2'-methylene-bis(4,6-di-t-butylphenyl)phosphate is particularly preferred.

The film according to this embodiment may contain additives and other resins as necessary. Examples of additives include antioxidants, neutralizing agents, UV absorbers, antistatic agents, lubricants, nucleating agents, adhesives, antifogging agents, antiblocking agents, and melt flow rate regulators. Examples of antioxidants include phenolic antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. Composite antioxidants having units that combine a phenolic antioxidant mechanism and a phosphorus-based antioxidant mechanism in one molecule can also be used. Other resins include elastomers such as styrene-butadiene-styrene copolymers and styrene-isoprene-styrene copolymers hydrogenated styrene-based copolymer rubbers.

The method for producing a film configured as described above includes a melt-kneading step of melt-kneading a mixture containing at least two types of propylene-based polymers, an ethylene-based polymer, and a phosphate metal salt-based nucleating agent. The method for producing such a film also includes an extrusion step of extruding the kneaded material obtained in the melt-kneading step into a sheet, and a cooling step of pressing the sheet-like kneaded material obtained in the extrusion step against a cooling roll with gas blown out of an air chamber to cool it. The method for producing such a film also includes a film-forming step of forming a film by forming the sheet-like kneaded material into a film.

In the melt-kneading step, for example, the above propylene-based polymer composition (A) and the above ethylene-based polymer (B), and preferably the above propylene-based polymer composition (C), may be melt-kneaded. In addition, the melt-kneading step is preferably carried out by adding the various additives described above.

The melt-kneading step can be carried out using a conventional method and device. For example, the above materials (e.g., pellet-like materials) can be mixed using a mixing device such as a Henschel mixer, ribbon blender, or tumble mixer, and then melt-kneaded. Alternatively, the above materials can be continuously fed at a constant rate using a constant-volume feeder to obtain a homogeneous mixture, and then the mixture can be melt-kneaded using a single-screw or twin-screw or more extruder, a Banbury mixer, a roll kneader, or the like. The melt-kneading temperature is preferably 190°C to 320°C, and more preferably 210°C to 280°C.

The extrusion process can be carried out using a conventional method and apparatus. For example, the T-die method, the tubular method, etc. are mentioned, and the T-die method is preferable.

The air chamber used in the cooling process is installed close to the cooling roll. The air chamber is a box-structured device with an opening in the portion facing the cooling roll. Any conventional device can be used as the air chamber. The air chamber is configured to receive gas from a blower connected by a duct to increase the air pressure in the internal space, and to blow gas from the opening at an air volume and pressure corresponding to the air pressure. As a result, the sheet-like kneaded material extruded from the T-die is pressed against the cooling roll by the gas blown from the air chamber to make it adhere to the cooling roll. Examples of the gas introduced into the air chamber include air, nitrogen, and carbon dioxide gas. The temperature of the gas can be, for example, preferably 10°C to 50°C.

The cooling step is performed by adjusting the amount of gas blown out of the air chamber so that the gas pressure in the air chamber is 50 Pa to 300 Pa, preferably 50 Pa to 250 Pa, and more preferably 100 Pa to 250 Pa. In the cooling step, a sheet-like kneaded material is supplied between the air chamber and the cooling roll. Then, gas is blown from the air chamber onto the sheet-like kneaded material to bring the sheet-like kneaded material into close contact with the cooling roll.

The air chamber has an opening (gas outlet) for blowing gas in the horizontal direction, and the gas outlet is disposed to the side of the cooling roll at a distance from the cooling roll. The shortest distance between the gas outlet and the cooling roll in the horizontal direction is preferably 0.01 cm to 5 cm, more preferably 0.01 cm to 1 cm. The width of the air chamber opening (gas outlet) is preferably configured to be wider than the width of the sheet-like kneaded material (i.e., the width of the blown airflow is wider than the sheet-like kneaded material). This allows the sheet-like kneaded material to be pressed evenly against the cooling roll.

The surface temperature of the cooling roll is preferably 20°C to 80°C, and more preferably 20°C to 70°C.

The film-forming process may be performed by contacting the sheet-like kneaded material obtained in the extrusion process with a cooling roll (i.e., it may be performed simultaneously with the cooling process), or it may be performed after the cooling process. When the film-forming process is performed after the cooling process, for example, the sheet-like kneaded material after the cooling process may be sandwiched between nip rolls to form a film of a predetermined thickness.

The film according to this embodiment can be used as a sealant layer of a multilayer film. The film forming the other layer laminated on the sealant layer is not particularly limited. For example, it can be a barrier film such as a stretched nylon film, an aluminum foil, or a polyvinylidene chloride film, or a transferable film such as a nylon film, a biaxially stretched polypropylene film, or a polyethylene terephthalate film. Methods for bonding films together include, for example, a dry lamination method and an extrusion lamination method.

The thickness of the film according to this embodiment is preferably 5 to 500 μm, and more preferably 30 to 150 μm.

A multilayer film having the film according to this embodiment as a sealant can be used in packaging applications, for example, for packaging items such as food, textiles, and miscellaneous goods. For example, the multilayer film can be used as a material for forming a packaging bag, preferably a material for a packaging bag for retort foods.

The film according to this embodiment may be subjected to a surface treatment such as corona discharge treatment, flame treatment, plasma treatment, or ozone treatment by a method commonly used in industry.

As described above, this embodiment can provide a film that is resistant to bag breakage and has relatively excellent cuttability, and can also provide a method for producing such a film.

In other words, the film according to this embodiment has an islands-in-a-sea type phase separation structure consisting of a continuous phase and a discontinuous phase made of at least two types of olefin polymers, and the degree of orientation in the MD direction of the film determined by wide-angle X-ray scattering measurement is within the above range, so that the film has resistance to bag breakage and is relatively easy to cut.

In addition, by satisfying the above formulas (1) and (2), the film according to this embodiment has excellent resistance to bag breakage and is also easy to cut.

In addition, the film according to this embodiment contains the propylene-based polymer composition (A), which makes it possible to obtain a film with superior resistance to bag rupture.

In addition, the film according to this embodiment contains the propylene-based polymer composition (A) and the ethylene-based polymer (B) in the above ratio, so that a film with excellent resistance to bag rupture can be obtained.

In addition, by containing the phosphate metal salt nucleating agent in the above ratio, the film according to this embodiment can have excellent resistance to bag breakage and excellent ease of cutting.

In addition, the film according to this embodiment contains the propylene-based polymer composition (C) that satisfies the above formula (3) in the above ratio, so that a film having excellent resistance to bag breakage and excellent ease of cutting can be obtained.

In addition, the film manufacturing method according to this embodiment can produce a film that is resistant to bag breakage and relatively easy to cut by setting the gas pressure in the air chamber in the above range during the cooling process.

The film and the method for producing the film according to the present invention are not limited to the above-mentioned embodiment, and various modifications are possible without departing from the gist of the present invention. Furthermore, it goes without saying that the configurations and methods of the above and following embodiments may be arbitrarily adopted and combined (the configurations and methods of one embodiment may be applied to the configurations and methods of other embodiments).

The measurements for each item in the examples and comparative examples were measured using the following methods.

The contents of the propylene polymer and propylene-ethylene copolymer contained in the propylene polymer composition were obtained from the mass balance during the polymerization of each.

The content of the monomer units derived from ethylene contained in the propylene-ethylene copolymer contained in the propylene polymer composition was calculated by measuring the IR spectrum of the entire propylene polymer composition and calculating it according to the following formula (4) in accordance with "(ii) Method for block copolymers" described on page 616 of Polymer Analysis Handbook (published by Kinokuniya Shoten in 1995). Here, ET, EA and EB in the following formula (4) respectively represent the content of the monomer units derived from ethylene in the entire propylene polymer composition, the content of the monomer units derived from ethylene in the propylene polymer and the content of the monomer units derived from ethylene in the propylene-ethylene copolymer, and PA and PB respectively represent the content of the propylene polymer and the propylene-ethylene copolymer.

EB=(ET-EA×PA)/PB...(4)

(1) Melt flow rate (MFR, unit: g/10 min)
The melt flow rate of the propylene-based polymer composition was measured at a temperature of 230° C. and a load of 2.16 kg in accordance with the method specified in JIS K7210.
The melt flow rate of the ethylene polymer was measured at a temperature of 190° C. and a load of 2.16 kg in accordance with the method specified in JIS K7210.

(2) Cold xylene solubles content (CXS, unit: mass%)
0.5 g of the propylene-based polymer composition was dissolved in 100 mL of boiling xylene, and the resulting solution was cooled to 0° C. and allowed to stand at the same temperature for 0.5 hours. The xylene solution was then heated to 20° C. and stirred at the same temperature for 1 hour. The resulting mixture was filtered to separate the precipitate and the solution, and the propylene-based polymer in the solution was quantified by liquid chromatography to measure the amount of cold xylene solubles. The measurement conditions for the liquid chromatography were as follows:

Column: SHODEX GPC KF-801
Eluent: tetrahydrofuran Sample injection volume: 100 μL
Flow rate: 1.5 mL/min Detector: differential refractometer

(3) Intrinsic viscosity ([η], unit: dL/g)
The intrinsic viscosity of the propylene polymer composition was measured in tetralin (1,2,3,4-tetrahydronaphthalene) at 135° C. using an Ubbelohde viscometer.
The intrinsic viscosity [η] _CXIS of the cold xylene insoluble portion of the propylene-based polymer composition was calculated from the intrinsic viscosity [η] of the propylene-based polymer composition, the intrinsic viscosity [η] _CXS of the cold xylene soluble portion of the propylene-based polymer composition and the weight, using the following formula (5).

[η] _CXIS = ([η] x 100 - [η] _CXS x W _CXS )/W _CXIS ... (5)

(Wherein,
[η] _CXIS represents the intrinsic viscosity (dL/g) of the cold xylene insoluble portion of the propylene-based polymer composition.
[η] represents the intrinsic viscosity (dL/g) of the propylene polymer composition.
[η] _CXS represents the intrinsic viscosity (dL/g) of the cold xylene soluble portion of the propylene polymer composition.
W _CXS represents the cold xylene soluble content (mass%) of the propylene polymer composition.
W _CXIS indicates the cold xylene insoluble content (mass%) of the propylene polymer composition.

(4) Melt tension (MT, unit: mN)
The melt tension of the propylene polymer composition was measured under the following conditions using a melt tension measuring device manufactured by Toyo Seiki Seisakusho.

Specifically, an orifice with a length of 8.00 mm and an inner diameter of 2.10 mm was attached to a cylinder with an inner diameter of 9.55 mm. The cylinder was then filled with the propylene-based polymer composition, and a piston was inserted and preheated at 190°C for 5 minutes to fully melt the propylene-based polymer composition. The piston was then lowered at a speed of 5.7 mm/min, and the propylene-based polymer composition extruded in a molten state from the orifice at 0.32 g/min was withdrawn at 15.7 m/min, and the tension (mN) acting on the propylene-based polymer composition was measured with a tension detector and taken as the melt tension.

(5) Observation of sea-island type phase separation structure The observation of the sea-island phase separation structure in the monolayer film was performed using a transmission electron microscope. The film was embedded in a resin, then stained with an aqueous solution of ruthenium tetroxide, and a cross section determined by the MD and ND directions of the film was cut out with a cryomicrotome to prepare an ultra-thin sample having a thickness of 200 nm or less. However, the MD direction is the flow direction of the film during the film formation of the monolayer film, and the ND direction is the thickness direction of the film. After placing the ultra-thin sample on an observation mesh, a cross-sectional image was taken with a transmission electron microscope (Hitachi High-Tech Corporation, H-7650) under conditions of an accelerating voltage of 100 kV and an observation magnification of 5000 times.

(6) Three-dimensional refractive index measurement A test piece with a width of about 50 mm (TD direction) and a length of about 40 mm (MD direction) was cut out from the monolayer film. However, the TD direction is the width direction of the film when the monolayer film is formed, and the MD direction is the flow direction of the film when the monolayer film is formed. The obtained test piece was subjected to three-dimensional refractive index measurement using a measuring device KOBRA-WR (manufactured by Oji Scientific Instruments Co., Ltd.) and software KOBRA-RE. The test piece was set in the measuring device so that the MD direction and the 0 degree direction in the angle reference of the measuring device KOBRA-WR coincided. The retardation value R (0) (nm) was measured by irradiating light with a wavelength of 589.3 nm from the thickness direction of the film, and the retardation value R (30) (nm) was measured by irradiating light with a wavelength of 589.3 nm from a direction inclined by 30° with respect to the thickness direction of the film with the slow axis as the tilt axis. From the obtained R(0) and R(30) and the film thickness d(nm), the refractive index Nx of the slow axis, the refractive index Ny of the fast axis, and the refractive index Nz in the thickness direction of the film, which satisfy the following formulas (6) to (11), were calculated using the following formula (12) as a constraint condition. Here, N' is the refractive index in the incident plane when the incident angle is 30°, β1 is the refraction angle with respect to the refractive index N' when the incident angle is 30°, and β2 is the refraction angle with respect to the refractive index Nx when the incident angle is 30°. Furthermore, the angle θ(°) between the MD direction of the film and the slow axis was obtained.

Nx-Ny=R(0)/d...(6)
Nx-N'=R(30)×cosβ/d...(7)
N'=Ny×Nz/(Ny ² ×sin ² β1+Nz ² ×cos ² β1) ^1/2 ...(8)
however,
β=(β1+β2)/2...(9)
β1=sin ^-1 (sin30°/N')...(10)
β2=sin ^-1 (sin30°/Nx)...(11)
(Nx+Ny+Nz)/3=1.4915...(12)

(7) Wide-angle X-ray scattering measurement A plurality of test pieces each having a width of about 2 cm (TD direction) and a length of about 2 cm (MD direction) were cut out from the monolayer film. The TD direction is the width direction of the film when the monolayer film is formed, and the MD direction is the flow direction of the film when the monolayer film is formed. Six test pieces were stacked so that the MD directions of the test pieces were aligned to prepare a test piece for measurement. The obtained test piece for measurement was subjected to wide-angle X-ray scattering measurement under the following conditions.

- Model: Rigaku Nano Viewer
・Tube: Cu-Kα
Detector: PILATUS 100k
Exposure time: 300 seconds Tube voltage: 40 kV
Tube current: 20mA
Beam diameter: 0.25 mmφ

The camera length, which is the distance from the X-ray source to the camera, was kept constant, and the transmission intensity I ₀ and the scattering intensity I _Air were obtained without setting the test piece for measurement. The X-ray was set to be incident perpendicularly to the surface of the test piece for measurement, and the transmission intensity I _t and the scattered diffraction intensity I _s were measured. The ratio of _{I 0} to I _t was set as the correction ratio R, and air scattering correction was performed from the measured scattered diffraction intensity I _s using the following formulas (13) and (14). The corrected scattered diffraction intensity was set as I _c .

R=I _t /I ₀ (13)
I _c = I _s - R×I _Air ... (14)

From the X-ray diffraction image obtained by the measurement, the _Ic of the diffraction peak of the (040) plane of the polypropylene crystal was plotted every 0.2° in the circumferential direction to create an azimuth angle profile. Using the peak that appeared on the TD side of the test piece for measurement, the peak height was determined from the bottom to the top of the peak, and the half-width W, which is the peak width at which the peak height is half, was obtained. The sum of the half-widths of the peaks that appeared on the TD side was taken as ΣW, and the degree of orientation F (%) of the MD was calculated using the following formula (15).

F=(360-ΣW)×100/360...(15)

(8) Evaluation of Tear Strength Based on JIS K7128-2 (Elmendorf tear method), the tear strength of a monolayer film was measured under the following conditions.
A test piece with a width of 76 mm (TD direction) and a length of 63 mm (MD direction) was cut out from the monolayer film. The TD direction is the width direction of the film when the monolayer film is formed, and the MD direction is the flow direction of the film when the monolayer film is formed. The obtained test piece was placed in a constant temperature room at 23 ° C., and then a 20 mm cut was made in the length direction from the end of the center of the width. Next, the test piece was attached to the grip of a digital Elmendorf tear tester (manufactured by Toyo Seiki Co., Ltd.) to measure the tear strength. The value (N) obtained by tearing was divided by the thickness (mm) of the test piece and used as the tear strength (N / mm).

(9) Evaluation of Bag Drop Strength A composite film was used in which a monolayer film, an aluminum foil having a thickness of 7 μm, and a polyethylene terephthalate film having a thickness of 12 μm were laminated in the order described above by a dry lamination method. Then, the monolayer film surface was folded inward using a standing pouch bag making machine manufactured by Seibu Machinery Co., Ltd., and the three sides were heat-sealed three times at 240° C. for 0.5 seconds to produce a packaging bag. After filling the obtained packaging bag with 160 g of water, the remaining side that was not heat-sealed was heat-sealed with an impulse sealer for 1.0 seconds to produce a water-filled packaging bag having a length of 150 mm and a width of 130 mm. After conditioning the water-filled packaging bag for 24 hours at 5° C., a test was performed by dropping it repeatedly 20 times from a height of 16 cm. The test was performed on 12 bags each, and the drop strength was evaluated based on the total number of times that the bags did not break. If no bags broke at all, the score was 240, and if all bags broke in one try, the score was 0.

The components used in the examples and comparative examples are as follows:

[Propylene-based polymer composition (a-1)]
Using a Ziegler-Natta catalyst, propylene was polymerized in a gas phase in a first step, and then propylene and ethylene were copolymerized in a gas phase in a second step to obtain a propylene-based multistage polymer consisting of a propylene homopolymer (a-11) and a propylene-ethylene copolymer (a-12). The obtained propylene-based multistage polymer had a propylene homopolymer (a-11) content of 70 mass%, a propylene-ethylene copolymer (a-12) content of 30 mass%, and a monomer unit content derived from ethylene in the propylene-ethylene copolymer (a-12) of 30 mass%. 100 parts by mass of the obtained propylene-based multistage polymer were mixed with 0.005 parts by mass of calcium hydroxide, 0.075 parts by mass of Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.), and 0.03 parts by mass of Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.), and then melt-kneaded to obtain a propylene-based polymer composition (a-1). The propylene-based polymer composition (A-1) had a cold xylene insoluble content of 81% by mass, an intrinsic viscosity ([η] _CXIS ) of 1.82 dl/g, a cold xylene soluble content of 19% by mass, an intrinsic viscosity ([η] _CXS ) of 2.95 dl/g, and a melt flow rate of 3.1 g/10 min.

[Propylene-based polymer composition (a-2)]
Using a Ziegler-Natta catalyst, propylene was polymerized in a gas phase in the first step, and then propylene and ethylene were copolymerized in a gas phase in the second step to obtain a propylene-based multistage polymer consisting of a propylene homopolymer (a-21) and a propylene-ethylene copolymer (a-22). The obtained propylene-based multistage polymer had a propylene homopolymer (a-21) content of 84% by mass, a propylene-ethylene copolymer (a-22) content of 16% by mass, and a content of monomer units derived from ethylene in the propylene-ethylene copolymer (a-22) of 40% by mass. 0.005 parts by mass of calcium hydroxide, 0.075 parts by mass of Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.), and 0.03 parts by mass of Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.) were mixed with 100 parts by mass of the obtained propylene multistage polymer, and then melt-kneaded to obtain a propylene-based polymer composition (a-2). The propylene polymer composition (a-2) had a cold xylene insoluble content of 90% by mass, a limiting viscosity ([η] _CXIS ) of 1.56 dl/g, a cold xylene soluble content of 10% by mass, a limiting viscosity ([η] _CXS ) of 2.00 dl/g, and a melt flow rate of 7.0 g/10 min.

[Propylene-based polymer composition (a-3)]
Using a Ziegler-Natta catalyst, propylene was polymerized in a gas phase in a first step, and then propylene and ethylene were copolymerized in a gas phase in a second step to obtain a propylene-based multistage polymer consisting of a propylene homopolymer (a-31) and a propylene-ethylene copolymer (a-32). The obtained propylene-based multistage polymer had a propylene homopolymer (a-31) content of 77% by mass, a propylene-ethylene copolymer (a-32) content of 23% by mass, and a monomer unit content derived from ethylene in the propylene-ethylene copolymer (a-32) of 30% by mass. 100 parts by mass of the obtained propylene-based multistage polymer were mixed with 0.005 parts by mass of calcium hydroxide, 0.075 parts by mass of Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.), and 0.075 parts by mass of Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.), and then melt-kneaded to obtain a propylene-based polymer composition (a-3). The propylene-based polymer composition (a-3) had a cold xylene insoluble content of 84% by mass, an intrinsic viscosity ([η] _CXIS ) of 1.93 dl/g, a cold xylene soluble content of 16% by mass, an intrinsic viscosity ([η] _CXS ) of 3.03 dl/g, and a melt flow rate of 2.5 g/10 min.

[Ethylene-based polymer (b-1)]
An ethylene-butene copolymer (manufactured by Sumitomo Chemical Co., Ltd., product name: Sumikathene L GA401) was used. The melt flow rate was 3.0 g/10 min and the density was 935 kg/ ^m3 .

[Ethylene-based polymer (b-2)]
An ethylene-butene copolymer (manufactured by Mitsui Chemicals, Inc., product name: Tafmer A4085s) was used. The melt flow rate was 3.6 g/10 min and the density was 885 kg/m ³ .

[Propylene-based polymer composition (c-1)]
Using a Ziegler-Natta catalyst, a propylene homopolymer (c-11) having an intrinsic viscosity of 7.18 dl/g was produced in the first step, and a propylene homopolymer (c-12) having an intrinsic viscosity of 0.85 dl/g was produced in the second step to obtain a propylene-based multistage polymer. The obtained propylene-based multistage polymer had a content of 19% by mass of the propylene homopolymer (c-11) produced in the first step and a content of 81% by mass of the propylene homopolymer (c-12) produced in the second step. 0.050 parts by mass of calcium stearate, 0.2 parts by mass of Irganox 1010 (manufactured by BASF), and 0.025 parts by mass of Irgafos 168 (manufactured by BASF) were mixed with 100 parts by weight of this propylene-based multistage polymer, and then melt-kneaded to obtain a propylene-based polymer composition (c-1). The propylene polymer composition (c-1) had a melt flow rate of 8.9 g/10 min and a melt tension of 25.7 mN.

[Composition (d) containing one propylene polymer]
Propylene was polymerized using a Ziegler-Natta catalyst to obtain a propylene homopolymer. 100 parts by weight of the obtained propylene homopolymer were mixed with 0.002 parts by weight of calcium hydroxide and 0.15 parts by weight of Irganox 1010 (manufactured by BASF), and then melt-kneaded to obtain a composition (d) containing one type of propylene-based polymer. The melt flow rate of the obtained composition (d) was 8.0 g/10 min.

[Phosphate metal salt nucleating agent masterbatch (MB)]
Propylene was polymerized using a Ziegler-Natta catalyst to obtain a propylene homopolymer. 94% by mass of the obtained propylene homopolymer was mixed with 6% by mass of Adeka STAB NA-11 (sodium-2,2'-methylene-bis(4,6-di-tert-butylphenyl)phosphate, manufactured by ADEKA Corporation), which is a phosphate metal salt. 0.01 parts by mass of hydrotalcite, 0.1 parts by mass of Irganox 1010 (manufactured by BASF Corporation), and 0.05 parts by mass of Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.) were mixed with 100 parts by mass of the obtained mixture, and then melt-kneaded to obtain a phosphate metal salt nucleating agent master batch (MB).

[Example 1]
42% by mass of the propylene-based polymer composition (a-1), 45% by mass of the propylene-based polymer composition (a-2), 8% by mass of the ethylene-based polymer (b-1), and 5% by mass of the phosphate metal salt nucleating agent master batch (MB) were pellet-blended. The mixture obtained was melt-kneaded with three extruders, and then the resulting molten mixture was combined and introduced into a feed block type T-die (die width 1250 mm, lip opening 0.8 mm) and melt-extruded at a die temperature of 240°C. The extruded molten film was cooled and solidified with a chill roll (cooling roll) rotating at 50 m/min and having a cooling temperature of 50°C, to obtain a monolayer film having a thickness of 70 μm. The obtained monolayer film had a sea-island type phase separation structure. The components contained in the monolayer film are shown in Tables 1 and 2.

The obtained monolayer film was subjected to three-dimensional refractive index measurement, wide-angle X-ray scattering measurement, and tear strength evaluation. In addition, a composite film made using the obtained monolayer film was subjected to a bag drop strength evaluation. The results of each evaluation are shown in Table 3.

[Example 2]
A monolayer film was produced and evaluated in the same manner as in Example 1, except that a mixture obtained by pellet-blending 85% by mass of the propylene-based polymer composition (a-3), 10% by mass of the ethylene-based polymer (b-2), and 5% by mass of a phosphate metal salt nucleating agent master batch (MB) was used. The obtained monolayer film had an islands-in-a-sea type phase-separated structure. The components contained in the monolayer film are shown in Table 1. The evaluation results are also shown in Tables 2 and 3.

[Example 3]
A monolayer film was produced and evaluated in the same manner as in Example 1, except that a mixture obtained by pellet-blending 75% by mass of the propylene-based polymer composition (a-3), 10% by mass of the propylene-based polymer composition (c), 10% by mass of the ethylene-based polymer (b-2), and 5% by mass of a phosphate metal salt nucleating agent master batch (MB) was used. The obtained monolayer film had an islands-in-a-sea type phase-separated structure. The components contained in the monolayer film are shown in Table 1. The evaluation results are also shown in Tables 2 and 3.

[Comparative Example 1]
A monolayer film was produced and evaluated in the same manner as in Example 1, except that the air volume of the air chamber was adjusted so that the air pressure in the air chamber box was 500 Pa. The obtained monolayer film had a sea-island type phase separation structure. The components contained in the monolayer film are shown in Table 1. The evaluation results are also shown in Tables 2 and 3.

[Comparative Example 2]
A monolayer film was produced and evaluated in the same manner as in Example 1, except that 100% by mass of the propylene-based polymer composition (a-3) was used. The obtained monolayer film had an islands-in-a-sea type phase-separated structure. The components contained in the monolayer film are shown in Table 1. The evaluation results are shown in Tables 2 and 3.

[Comparative Example 3]
A monolayer film was produced and evaluated in the same manner as in Example 1, except that a mixture obtained by pellet-blending 90% by mass of the propylene-based polymer composition (a-3) and 10% by mass of the ethylene-based polymer (b-2) was used. The obtained monolayer film had an islands-in-a-sea type phase-separated structure. The components contained in the monolayer film are shown in Table 1. The evaluation results are shown in Tables 2 and 3.

[Comparative Example 4]
A monolayer film was produced and evaluated in the same manner as in Example 1, except that a mixture of 95% by weight of composition (d) containing one type of propylene-based polymer and 5% by weight of a phosphate metal salt nucleating agent master batch (MB) was used as a pellet blend. The obtained monolayer film did not have an islands-in-a-sea type phase separation structure. The components contained in the monolayer film are shown in Table 1. The evaluation results are also shown in Tables 2 and 3.

Claims (5)

A film containing at least two kinds of olefin polymers,
the at least two kinds of olefin polymers form an islands-in-a-sea type phase-separated structure consisting of a continuous phase and a discontinuous phase,
The degree of orientation in the MD direction of the film determined by wide-angle X-ray scattering measurement is 76% or more,
the at least two olefin-based polymers are at least two propylene-based polymers;
a propylene-based polymer composition (A) including a propylene-based multistage polymer composed of the at least two kinds of propylene-based polymers,
Further, the composition contains an ethylene-based polymer (B),
the content of the propylene-based polymer composition (A) is 70% by mass to 98% by mass, and the content of the ethylene-based polymer (B) is 2% by mass to 30% by mass, relative to 100% by mass of the total of the propylene-based polymer composition (A) and the ethylene-based polymer (B);
Further, it contains 100 ppm to 10,000 ppm of a phosphate metal salt-based nucleating agent .
film. Satisfying the following formulas (1) and (2):
The film of claim 1.

(Nx×cosθ-Ny×cosθ)/d≧3.0×10 ^-8 ...(1)
(Nx-(Ny+Nz)/2)/d≧3.4×10 ^-8 ...(2)
(Wherein,
Nx represents the refractive index of the slow axis of the film determined by three-dimensional refractive index measurement.
Ny represents the refractive index of the fast axis of the film determined by three-dimensional refractive index measurement.
Nz indicates the refractive index in the thickness direction of the film determined by three-dimensional refractive index measurement.
θ is the angle (°) between the MD direction of the film and the slow axis, determined by three-dimensional refractive index measurement.
Shows.
d indicates the thickness of the film (nm).
The propylene polymer composition (A) comprises
The content of the cold xylene soluble portion is 5 to 25 mass %, and the intrinsic viscosity [η] _CXS of the cold xylene soluble portion is 1.5 to 3.5 dL/g;
The content of the cold xylene insoluble portion is 75 to 95 mass%, and the intrinsic viscosity [η] _CXIS of the cold xylene insoluble portion is 1.0 to 2.5 dL/g.
The film according to claim 1 or 2. The composition (C) contains 5% by mass to 30% by mass of a propylene-based multistage polymer composed of the at least two kinds of propylene-based polymers,
The propylene polymer composition (C) satisfies the following formula (3):
The film according to any one of claims 1 to 3 .

MT ^C >70×MFR ^C-1.1 ...(3)
(Wherein,
^MTC indicates the melt tension (mN) measured at a temperature of 190° C. and a take-up speed of 15.7 m/min.
MFR ^C indicates the melt flow rate (g/10 min) measured at a temperature of 230° C. and a load of 2.16 kg.
A method for producing the film according to any one of claims 1 to 4 , comprising the steps of:
A melt-kneading step of melt-kneading a mixture containing at least two kinds of propylene-based polymers, an ethylene-based polymer, and a phosphate metal salt-based nucleating agent;
an extrusion step of extruding the kneaded material obtained in the melt kneading step into a sheet shape;
a cooling step in which the sheet-like kneaded material obtained in the extrusion step is pressed against a cooling roll by gas blown out of an air chamber to cool it;
A film-forming process of forming a film by forming the sheet-like kneaded material into a film,
In the cooling process, the amount of gas blown out of the air chamber is adjusted so that the gas pressure in the air chamber is 50 Pa to 300 Pa.
A method for manufacturing a film.