Polypropylene film, gas barrier film, laminate, and packaging bag

Abstract

To provide a polypropylene film which, when used as a material for a gas barrier film, is excellent in stability of adhesion to another layer after heat sterilization treatment and hardly reduces the wettability of the other layer.SOLUTION: A polypropylene film which has a laminated structure including a core layer and a first skin layer and is subjected to a heat sterilization treatment, in which the first skin layer is one outermost surface layer of the polypropylene film, the first skin layer contains a copolymer of propylene and another monomer, and when a surface of the first skin layer is subjected to elemental quantitative analysis by X-ray photoelectron spectroscopy, an average value of a ratio (O / C) of the number of oxygen atoms to the number of carbon atoms is 0.010 to 0.050 and a standard deviation of the ratio (O / C) is 0.0010 to 0.0050.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a polypropylene film, a gas barrier film, a laminate, and a packaging bag. [Background technology]

[0002] Packaging bags used for packaging foods, medicines, etc. require gas barrier properties that block the intrusion of water vapor, oxygen, and other gases that can deteriorate the contents, in order to prevent deterioration and spoilage of the contents and to maintain their functions and properties. For this reason, gas barrier films have traditionally been used in packaging bags.

[0003] For example, Patent Document 1 discloses a gas barrier film that includes a substrate whose main component is polypropylene or polyethylene and a gas barrier layer formed on a first surface of the substrate, and in which the wet tension of a second surface opposite the first surface is 21 mN / m or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2022 / 168976 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, with growing awareness of environmental issues, there has been growing interest in packaging materials made from a single material, so-called mono-material packaging, in order to make packaging materials recyclable. Olefin-based films such as polypropylene are generally used as sealant films for packaging materials. Therefore, the present inventors selected polypropylene as the material for mono-material packaging. However, the inventors' investigations revealed that when polypropylene film is subjected to heat sterilization treatments such as retort treatment or boiling treatment, there is room for improvement in terms of the stability of adhesion with other layers, such as the sealant layer.

[0006] The gas barrier film of Patent Document 1 does not take into consideration the adhesion or stability of adhesion between the substrate and other layers after heat sterilization treatment such as retort treatment or boiling treatment.

[0007] Furthermore, the inventors' investigations have revealed that when a polypropylene film is used as a base material for a gas barrier film, there is room for improvement in the following respects. Specifically, the gas barrier film may be wound up as a raw web. When one surface of a gas barrier film is a polypropylene film, the polypropylene film comes into contact with the other surface (e.g., a vapor deposition layer) of the gas barrier film. Then, components on the surface of the polypropylene film migrate to the vapor deposition layer, reducing the wettability of the vapor deposition layer. When a gas barrier coating layer is formed on a vapor deposition layer with reduced wettability, the coatability of the gas barrier coating layer deteriorates, leading to a reduction in gas barrier properties. In other words, when used as a material for a gas barrier film, a polypropylene film is required to be less likely to reduce the wettability of other layers.

[0008] The present disclosure provides a polypropylene film that, when used as a material for a gas barrier film, exhibits excellent adhesion stability with other layers after heat sterilization treatment and is less likely to reduce the wettability of other layers. The present disclosure also provides a gas barrier film, a laminate, and a packaging bag that include such a polypropylene film. [Means for solving the problem]

[0009] The present disclosure provides the following polypropylene film, gas barrier film, laminate, and packaging bag. [1] The core layer, a first skin layer; a laminated structure comprising: A polypropylene film that is heat sterilized, the first skin layer is one outermost layer of the polypropylene film, the first skin layer comprises a copolymer of propylene and another monomer; A polypropylene film in which, when the surface of the first skin layer is subjected to elemental quantitative analysis by X-ray photoelectron spectroscopy, the average ratio of the number of oxygen atoms to the number of carbon atoms (O / C) is 0.010 to 0.050 and the standard deviation of the ratio (O / C) is 0.0010 to 0.0050. [2] The polypropylene film according to [1], wherein the other monomer comprises an α-olefin. [3] The polypropylene film according to [1] or [2], wherein the softening temperature of the first skin layer measured by local thermal analysis is 120°C or higher. [4] The polypropylene film according to any one of [1] to [3], a vapor-deposited layer containing an inorganic oxide located on the surface of the polypropylene film opposite to the first skin layer; A gas barrier film comprising: [5] The gas barrier film according to [4], wherein the polypropylene film has a laminated structure further comprising a second skin layer as the outermost layer on the side opposite to the first skin layer. [6] The gas barrier film according to [4] or [5], wherein the inorganic oxide comprises at least one selected from aluminum oxide and silicon oxide. [7] The gas barrier film according to any one of [4] to [6], further comprising a gas barrier coating layer between the polypropylene film and the vapor deposition layer, or on the surface of the vapor deposition layer opposite to the polypropylene film. [8] The gas barrier film according to any one of [4] to [7], further comprising an anchor coat layer located between the polypropylene film and the vapor deposition layer. [9] A gas barrier film according to any one of [4] to [8], a sealant layer comprising polypropylene; A laminate comprising:

[10] The laminate according to [9], further comprising a polypropylene film on the surface of the gas barrier film opposite to the sealant layer.

[11] A packaging bag made by producing the laminate according to [9] or

[10] . [Effects of the Invention]

[0010] According to the present disclosure, there is provided a polypropylene film that, when used as a material for a gas barrier film, exhibits excellent adhesion stability with other layers after heat sterilization treatment and is less likely to reduce the wettability of other layers. The present disclosure also provides a gas barrier film, a laminate, and a packaging bag that include such a polypropylene film. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a polypropylene film according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a film processing apparatus (plasma processing apparatus) used to produce a polypropylene film according to one embodiment of the present disclosure, and FIGS. 2(a) and (b) show the switching state. [Figure 3] FIG. 3 is a schematic cross-sectional view showing a gas barrier film according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a laminate according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail, with reference to the drawings as needed. However, the present disclosure is not limited to the following embodiments.

[0013] [Polypropylene film] Hereinafter, a polypropylene film according to an embodiment of the present disclosure will be described. FIG. 1 is a schematic cross-sectional view showing a polypropylene film according to an embodiment of the present disclosure. As shown in FIG. 1, a polypropylene film 10 according to an embodiment has a laminated structure including a first skin layer 10a, a core layer 10b, and a second skin layer 10c. One outermost layer of the polypropylene film 10 is the first skin layer 10a, and the other outermost layer is the second skin layer 10c. The core layer 10b contains a polypropylene resin. The first skin layer 10a contains a copolymer of propylene and another monomer. The polypropylene film 10 is used for packaging that undergoes thermal sterilization. When the surface of the first skin layer 10a is quantitatively analyzed by X-ray photoelectron spectroscopy, the average ratio of the number of oxygen atoms to the number of carbon atoms (hereinafter simply referred to as "O / C") is 0.010 to 0.050, and the standard deviation of O / C is 0.0010 to 0.0050.

[0014] The polypropylene film 10 exhibits excellent adhesion to other layers after heat sterilization, excellent adhesion stability, and little deterioration in the wettability of other layers. The inventors believe that the reason for these effects is as follows: Since polypropylene films are composed of carbon and hydrogen atoms, they have low wettability and poor adhesion to sealant layers. When the average O / C value is less than 0.01, the polypropylene film has low wettability and insufficient adhesion. When the average O / C value is greater than 0.05, when a polypropylene film is used as a base layer of a gas barrier film, as described below, components on the surface of the polypropylene film migrate to other layers (deposited layers), reducing the wettability of the deposited layers. When a gas barrier coating layer is formed on a deposited layer with reduced wettability, the coatability of the gas barrier coating layer deteriorates, leading to reduced gas barrier properties. The surface of the first skin layer 10a of the polypropylene film 10 has an average O / C value of 0.01 to 0.05 and a standard deviation of O / C of 0.0010 to 0.0050. Furthermore, the first skin layer 10a contains a copolymer of propylene and other monomers, which allows the polypropylene film 10 to have excellent adhesion to other layers after heat sterilization, excellent adhesion stability, and less deterioration in the wettability of other layers.

[0015] The polypropylene film 10 is a film containing a polypropylene resin. The polypropylene film 10 may be, for example, a film obtained by forming a polypropylene resin into a sheet, stretching it, and oriented it uniaxially or biaxially.

[0016] The polypropylene resin may be a crystalline polypropylene resin. From the viewpoint of improving heat resistance, the polypropylene resin may be a homopolypropylene resin, which is a homopolymer of propylene. The polypropylene resin may contain, for example, a random copolymer of propylene and an α-olefin.

[0017] The content of the polypropylene resin may be 90% by mass or more, 95% by mass or more, or 99% by mass or more, based on the total mass of the polypropylene film 10. The content of the polypropylene resin may be substantially 100% by mass (an embodiment in which the base layer is made of polypropylene resin), based on the total mass of the polypropylene film.

[0018] The polypropylene film 10 may contain organic additives such as antiblocking agents (AB agents), antioxidants, stabilizers, lubricants, and antistatic agents, or may contain inorganic additives such as silica, zeolite, hydrotalcite, silicon particles, and siloid.

[0019] The anti-blocking agent may be either organic or inorganic particles. Examples of organic particles include polymethyl methacrylate particles, polystyrene particles, and polyamide particles. Examples of inorganic particles include silica particles, zeolite, talc, kaolinite, and feldspar. These anti-blocking agents may be used alone or in combination of two or more.

[0020] In consideration of anti-blocking performance, it is preferable to use an AB agent with an average particle size of 0.1 to 5 μm, where the average particle size is the weight average diameter measured by the coal tar method.

[0021] The thickness (total thickness) of the polypropylene film 10 is not particularly limited, but may be, for example, 3 μm or more and 200 μm or less, 6 μm or more and 50 μm or less, or 10 μm or more and 30 μm or less.

[0022] The polypropylene used in the polypropylene film 10 may be a resin polymerized from fossil fuels, a recycled resin, or a resin obtained by polymerizing raw materials derived from biomass such as plants. When using these resins, they may be used alone or in combination with a resin polymerized from fossil fuels and a recycled resin or a resin obtained by polymerizing raw materials derived from biomass such as plants.

[0023] The polypropylene film 10 can be used as a substrate for a gas barrier film. It can also be used as each layer of a multi-layer laminate. For example, when used as a printing substrate, it improves the adhesion to ink.

[0024] Examples of heat sterilization treatments that can be performed on the polypropylene film 10 include retort treatment, boiling treatment, and autoclave treatment. The temperature for retort treatment may be, for example, 110 to 135°C, and the treatment time may be 5 to 120 minutes. The temperature for boiling treatment may be, for example, 80 to 100°C, and the treatment time may be 5 to 120 minutes.

[0025] The first skin layer 10a, the second skin layer 10c, and the core layer 10b of the polypropylene film 10 will be described below.

[0026] <First Skin Layer> The first skin layer 10a includes a copolymer of propylene and another monomer. The copolymer content may be 90% by mass or more, 95% by mass or more, or 99% by mass or more, based on the total mass of the first skin layer 10a. The copolymer content may be substantially 100% by mass, based on the total mass of the first skin layer 10a.

[0027] Other monomers used in the copolymer may include, for example, α-olefins such as ethylene, 1-butene, and 1-hexene. The first skin layer 10a may contain a copolymer of propylene and an α-olefin. The copolymer may be a random copolymer.

[0028] The content of propylene units in the copolymer may be 80 mol% or more, 90 mol% or more, 95 mol% or more, or 96 mol% or more, or may be 99.7 mol% or less, 99.5 mol% or less, 99 mol% or less, or 98 mol% or less, based on the total amount of monomer units.

[0029] The first skin layer 10a can be formed on the core layer 10b, for example, by co-extruding the polypropylene resin that forms the core layer 10b and a copolymer of propylene and another monomer that forms the first skin layer 10a.

[0030] The copolymer used in the first skin layer 10a may be a resin polymerized from fossil fuel, a recycled resin, or a resin obtained by polymerizing a raw material derived from biomass such as plants. When using these resins, they may be used alone or in combination with a resin polymerized from fossil fuel and a recycled resin or a resin obtained by polymerizing a raw material derived from biomass such as plants.

[0031] The softening temperature of the first skin layer 10a measured from a cross section of the film by local thermal analysis (LTA) is preferably 120°C or higher. This tends to suppress blocking with other layers (e.g., vapor-deposited layers) and further suppress a decrease in the wettability of other layers. The softening temperature of the first skin layer 10a measured from a cross section of the film by local thermal analysis is preferably 170°C or lower. This tends to ensure flexibility of the first skin layer 10a and ensure sufficient adhesive strength with the core layer 10b. The softening temperature may be a temperature measured at the center of the first skin layer 10a.

[0032] The thickness of the first skin layer 10a is 0.1 μm or more. A thickness of 0.1 μm or more allows for uniform lamination and reduces thickness variation. It is also believed that stress on the vapor deposition layer during heat sterilization can be sufficiently alleviated, thereby suppressing barrier degradation. From this perspective, the thickness of the first skin layer 10a is preferably 0.3 μm or more. On the other hand, there is no particular upper limit to the thickness of the first skin layer 10a, but from the perspective of ensuring sufficient heat resistance of the entire polypropylene film 10, it is preferably 2.0 μm or less, and more preferably 1.8 μm or less.

[0033] The ratio of the thickness of the first skin layer 10a to the thickness of the polypropylene film 10 (thickness of the first skin layer 10a / thickness of the polypropylene film) may be 1 / 100 to 1 / 5, or 1 / 70 to 1 / 10. When the thickness ratio is within the above range, the heat resistance of the entire polypropylene film can be more sufficiently ensured. Furthermore, when the polypropylene film 10 is used as a material for a gas barrier film or a laminate, the adhesion between these layers tends to be further increased, and the adhesion stability can be further improved.

[0034] (O / C) The O / C has an average value of 0.010 to 0.050 and a standard deviation of 0.0010 to 0.0050. The average O / C is 0.010 or more, and from the viewpoint of further improving adhesion and further improving adhesion stability, it is preferably 0.011 or more, more preferably 0.012 or more, and even more preferably 0.015 or more. The average O / C is 0.050 or less, and from the viewpoint of suppressing a decrease in the wettability of other layers, it is preferably 0.045 or less, more preferably 0.040 or less, and even more preferably 0.030 or less. The average O / C value may be 0.010 to 0.050, 0.010 to 0.045, 0.010 to 0.040, 0.010 to 0.030, 0.011 to 0.050, 0.011 to 0.045, 0.011 to 0.040, 0.011 to 0.030, 0.012 to 0.050, 0.012 to 0.045, 0.012 to 0.040, 0.012 to 0.030, 0.015 to 0.050, 0.015 to 0.045, 0.015 to 0.040, or 0.015 to 0.030.

[0035] The standard deviation of O / C is 0.0010 or more, and from the viewpoint of further improving adhesion and further improving adhesion stability, it is preferably 0.0012 or more, more preferably 0.0015 or more, and even more preferably 0.0020 or more. The standard deviation of O / C is 0.0050 or less, and since there is a tendency to obtain a stable surface treatment state with little variation, it is preferably 0.0045 or less, more preferably 0.0040 or less, and even more preferably 0.0035 or less. The standard deviation of O / C is 0.0010 to 0.0050, 0.0010 to 0.0045, 0.0010 to 0.0040, 0.0010 to 0.0035, 0.0012 to 0.0050, 0.0012 to 0.0045, 0.0012 to 0.0040, and 0.0012 to 0.0035. , 0.0015 or more and 0.0050 or less, 0.0015 or more and 0.0045 or less, 0.0015 or more and 0.0040 or less, 0.0015 or more and 0.0035 or less, 0.0020 or more and 0.0050 or less, 0.0020 or more and 0.0045 or less, 0.0020 or more and 0.0040 or less, or 0.0020 or more and 0.0035 or less.

[0036] The average value and standard deviation of O / C are determined as follows. That is, the surface of the first skin layer 10a is narrow-spectrum analyzed using the following measuring equipment under the following measurement conditions. As a result, narrow spectra of the O1s and C1s orbitals on the surface of the first skin layer 10a are obtained. For each of the O and C elements, elemental quantitative values ​​(atomic %) are determined from the respective peak areas using relative sensitivity coefficients of 1.00 eV for C1s and 2.28 eV for O1s. O / C is calculated using the determined elemental quantitative values. The ratio of oxygen atoms to oxygen atoms (O / C) is the atomic ratio. The locations where O / C is measured may be five locations randomly selected on the surface of the first skin layer 10a. The average value and standard deviation of O / C are calculated from the measurement results of the five locations.

[0037] {Measuring equipment} JEOL Ltd., JPS-9030 photoelectron spectrometer {Measurement conditions: Spectrum collection conditions} Incident X-ray: MgKα (hν=1253.6eV) X-ray output: 100W (10kV 10mA) Measurement area: 6mm diameter circular area Photoelectron capture angle: 15° Dwell Time: 100ms Measurement step: 0.2 eV Pass energy: 10 eV Accumulation count: 5 times

[0038] {Surface treatment method} The average value and standard deviation of the O / C ratio of the first skin layer 10a can be adjusted, for example, by performing a surface treatment on the surface of the first skin layer 10a. Any surface treatment method can be used as long as the above-mentioned ranges of the average value and standard deviation of O / C are satisfied. Examples of such surface treatment methods include corona treatment, plasma treatment, and flame treatment. Among these surface treatment methods, plasma treatment is preferred because it can be performed effectively at low temperature and in a short time, and the degree of treatment is stable over time. Plasma treatment can be performed, for example, under atmospheric pressure or in a vacuum. To achieve a stable and high degree of treatment, it is preferable to perform the treatment in a vacuum. Furthermore, when the polypropylene film 10 is used as a substrate for a gas barrier film, the plasma treatment in a vacuum can be performed simultaneously with the process of forming the inorganic oxide layer.

[0039] The apparatus used for the plasma treatment is not particularly limited, but an example is the plasma treatment apparatus shown in Fig. 2. By using such an apparatus, it is possible to suppress the occurrence of abnormal discharge such as arc discharge even when high power is input, and to perform stable plasma treatment for a long period of time.

[0040] FIG. 2 is a schematic cross-sectional view of a film processing apparatus (plasma processing apparatus) used for surface treatment of a polypropylene film according to one embodiment. As shown in FIG. 2, the film processing apparatus 1 used in this embodiment is a magnetron plasma processing apparatus arranged, for example, in a vacuum chamber. The magnetron plasma processing apparatus generates a mutual discharge by applying an AC voltage to two magnetron cathodes. The film processing apparatus 1 includes a box 2, a first discharge electrode unit 3 and a second discharge electrode unit 4 arranged in parallel within the box 2, and an AC power supply 5 electrically connected to the first discharge electrode unit 3 and the second discharge electrode unit 4. A film F to be processed is inserted into the film processing apparatus 1, and a predetermined surface treatment is performed using plasma P generated within the apparatus. The magnetron plasma processing apparatus forms a magnetic field G by arranging magnets (south pole, north pole) on the back side of the electrodes, generating high-density plasma to perform ion etching and other processes (including amorphization of the substrate surface and modification of functional groups). The electrodes of the first discharge electrode unit 3 and the second discharge electrode unit 4 are arranged in parallel in a direction (TD, referred to as the "film width direction", a direction perpendicular to the plane of the paper in FIG. 2) perpendicular to the flow direction (MD, the left-right direction in FIG. 2) of the film F. The electrode width in the film width direction is designed to be equal to or greater than the width of the film F, making it possible to perform uniform processing over the entire surface of the film.

[0041] As described above, the box 2 is a housing that is placed in the vacuum device and has a predetermined reduced pressure inside. The box 2 is provided with an entrance 2a and an exit 2b so that the film F to be surface-treated with the plasma P can be inserted and removed.

[0042] The first discharge electrode unit 3 and the second discharge electrode unit 4 are electrode units of a flat-plate (planar) magnetron plasma processing apparatus, each comprising a flat electrode 3a, 4a (flat electrode) and magnets 3b, 4b arranged on the backside of the flat electrodes 3a, 4a to form a magnetic field. The flat electrodes 3a, 4a may be made of, for example, stainless steel, but may also be made of metals such as aluminum (Al), titanium (Ti), niobium (Nb), tantalum (Ta), or zirconium (Zr). Each magnet 3b, 4b is composed of multiple permanent magnets (e.g., neodymium magnets) with pairs of south and north poles, with adjacent magnets having different magnetization directions. These magnets 3b, 4b form a magnetic field G in space, enabling the first discharge electrode unit 3 and the second discharge electrode unit 4 to generate high-density plasma. The first discharge electrode unit 3 and the second discharge electrode unit 4, each configured as described above, are electrically connected to both ends of an AC power supply 5. The magnetic field G formed by the magnets 3b and 4b is preferably formed in a ring shape (doughnut shape) in a plan view (when viewed from above in the drawing).

[0043] The first discharge electrode unit 3 and the second discharge electrode unit 4, which will be described in detail later, are configured so that when one functions as a cathode, the other functions as an anode, by switching using high-frequency power supplied from an AC power source 5. The first discharge electrode unit 3 and the second discharge electrode unit 4 configured in this way are electrically connected to the AC power source 5 with neither being grounded.

[0044] The AC power supply 5 is a plasma generation power supply for supplying a predetermined high-frequency power to the first discharge electrode unit 3 and the second discharge electrode unit 4. When the AC power supply 5 supplies AC high-frequency power to the first discharge electrode unit 3 and the second discharge electrode unit 4, one discharge electrode unit becomes a cathode and the other discharge electrode unit becomes an anode, creating a state in which charged particles travel back and forth between the first discharge electrode unit 3 and the second discharge electrode unit 4 (see FIGS. 2(a) and 2(b)). In other words, the high-frequency signal from the AC power supply 5 causes magnetron discharges to occur alternately in the first discharge electrode unit 3 and the second discharge electrode unit 4.

[0045] Furthermore, the frequency of the high-frequency power supplied from the AC power supply 5 is, for example, 1 kHz or more and 400 kHz or less, and more preferably 10 kHz or more and 100 kHz or less. A large voltage drop occurs on the surface side of the magnetron electrode and is smaller on the surface side (bottom surface in the figure) of the film F. However, with the film processing device 1, higher power can be supplied to each discharge electrode unit by switching the polarity using AC. Furthermore, the magnetic field G generated by the magnet generates plasma in a bridge shape that approaches the film F. As a result, the film processing device 1 can increase the intensity of the treatment on the surface of the film F.

[0046] Next, a description will be given of a method for surface processing of the film F using the above-described film processing device 1. First, in the processing method, the film processing device 1 having the above-described device configuration is prepared.

[0047] Next, gas is introduced into box 2 of the film processing apparatus 1. Examples of such gases include argon (Ar), helium (He), nitrogen (N), and oxygen (O). To ensure that the average and standard deviation of the O / C ratio on the surface of the first skin layer 10a satisfy the above-mentioned numerical ranges, oxygen atoms must be introduced into the surface of the first skin layer 10a. To effectively introduce oxygen atoms into the surface of the first skin layer 10a, the gas introduced into box 2 preferably contains oxygen. For example, when argon (Ar) gas is used, high power input is required to satisfy the O / C ratio. However, high power input can easily cause static electricity on the film surface, which may result in peel charging during subsequent processes. The gas introduced into box 2 is preferably a mixture of oxygen and argon to stabilize the plasma, perform uniform processing, and achieve more stable adhesion strength. The flow rate ratio of oxygen to argon (oxygen:argon (unit: sccm)) may be 5:95 to 99:1. The optimal EPD varies depending on the type of gas, so appropriate conditions must be determined.

[0048] Next, once the specified gas has been introduced, the pressure inside box 2 is reduced to, for example, 0.1 Pa or more and less than 50 Pa. If the pressure is 0.1 Pa or less, the discharge is unlikely to be stable, making it impossible to perform stable surface treatment. On the other hand, if the pressure is 50 Pa or more, the self-bias voltage will decrease, making it difficult to obtain a sufficient effect from plasma P. In the region where the pressure inside box 2 is 40 Pa or more, the effect of magnetic induction by magnets 3b, 4b of each electrode will be somewhat weak, so the pressure inside box 2 is preferably in the range of 1 Pa to 25 Pa.

[0049] Next, with a predetermined gas or the like introduced into the box 2 and the pressure adjusted to a predetermined level, a predetermined high-frequency power is supplied from the AC power supply 5, which functions as a plasma generation power supply, to the first discharge electrode unit 3 and the second discharge electrode unit 4. In other words, an AC voltage is applied to the first discharge electrode unit 3 and the second discharge electrode unit 4. This supply of high-frequency power causes discharges to occur alternately by the first discharge electrode unit 3 and the second discharge electrode unit 4 at a predetermined cycle (for example, 40 kHz). The frequency of this high-frequency power is preferably within a range of, for example, 1 kHz to 400 kHz, more preferably 10 kHz to 100 kHz.

[0050] Next, when plasma P is generated by the first discharge electrode unit 3, the second discharge electrode unit 4 and the AC power supply 5, the polarity is continuously switched and the film F to be treated is transported so that it passes above the first discharge electrode unit 3 and the second discharge electrode unit 4. At this time, the side to be surface treated is faced towards the first discharge electrode unit 3 and the second discharge electrode unit 4. The distance between the first discharge electrode unit 3 and the second discharge electrode unit 4 and the film F is preferably within a range of 5 mm to 100 mm, more preferably within a range of 10 mm to 50 mm, and the film F is transported within the box 2 so that it remains within this range.

[0051] The film F is then fed through the box 2 at a predetermined transport speed, and the treated surface of the film F is subjected to plasma treatment. The transport speed (per second) of the film F can be, for example, 2 m / s or more and 20 m / s or less, but is not limited thereto. This treatment, for example, can disrupt the crystalline structure of the surface of the film F to make it amorphous, allowing it to be used as a pretreatment (adhesion treatment) for vapor deposition or as a pretreatment (adhesion treatment) for lamination (including bonding) with other films. The above-described plasma treatment may be repeated on the film F (for example, the same treatment may be repeated two or three times). The above-described plasma treatment may also be performed on the corona-treated surface.

[0052] The high frequency power supplied from the AC power supply 5 is, for example, 3 kW or more. In addition, in this film processing device 1, the electrode width (electrode length in the flow direction) used in the plasma processing and the processing intensity Epd per processing speed are set to 105 to 800 [W·s / m 2 The AC power source 5 may supply a predetermined amount of power to the first discharge electrode unit 3 and the second discharge electrode unit 4 so that the processing power [W] is the power from the AC power source 5 and the electrode width [m] in the machine direction of the film F / electrode area [m 2 ] is the electrode width / electrode area of ​​the discharge electrode unit, and the processing speed [m / s] is the transport speed of the film being processed.

number

[0053] The electrode area in the above formulas (1) and (2) refers to the area of ​​the cathode electrode. Because the cathode electrodes in the film processing device 1 alternate between electrodes 3a and 4a due to the application of AC voltage, the electrode area in the above formulas (1) and (2) is equal to the sum of the areas of the two electrodes divided by 2, or equal to the area of ​​one electrode if they have the same shape. Epd can be set so that the average value and standard deviation of the O / C ratio on the surface of the first skin layer 10a fall within the above-mentioned numerical ranges. Furthermore, the optimal Epd varies depending on the plasma processing method, so the conditions must be determined appropriately depending on the surface processing method.

[0054] (Second skin layer) The second skin layer 10c may contain a copolymer of propylene and another monomer. The content of the copolymer of propylene and another monomer, the other monomers used in the copolymer, the content of propylene units in the copolymer, the method for forming the second skin layer 10c, the softening temperature, and the thickness of the second skin layer 10c may be similar to those of the first skin layer 10a. The ratio of the thickness of the second skin layer 10c to the thickness of the polypropylene film may be similar to the ratio of the thickness of the first skin layer 10a to the thickness of the polypropylene film.

[0055] (core layer) The core layer 10b contains polypropylene. The polypropylene used for the core layer 10b may be crystalline polypropylene to enhance the heat resistance of the polypropylene film 10, or may be homopolypropylene, which is a homopolymer of propylene, to further improve the heat resistance for thermal sterilization treatment. However, a random copolymer of propylene and an α-olefin, or a mixture of such a copolymer with homopolypropylene, may also be used as long as the effects of the present disclosure are not significantly impaired.

[0056] The polyolefin used in the core layer 10b may be a resin polymerized from fossil fuel, a recycled resin, or a resin obtained by polymerizing raw materials derived from biomass such as plants. When using these resins, they may be used alone or in combination with a resin polymerized from fossil fuel and a recycled resin or a resin obtained by polymerizing raw materials derived from biomass such as plants.

[0057] When the polypropylene film 10 includes a first skin layer 10a and a second skin layer 10c, the core layer 10b disposed between the first skin layer 10a and the second skin layer 10c may not contain an AB agent.

[0058] From the viewpoint of maintaining the processability and ease of handling of the polypropylene film 10, the thickness of the core layer 10b may be 10 to 200 μm, 12 to 50 μm, or 15 to 30 μm.

[0059] Although the polypropylene film according to one embodiment has been described above, the polypropylene film according to the present disclosure is not limited to the above embodiment. For example, the polypropylene film according to the present disclosure does not necessarily have to include a second skin layer.

[0060] [Gas barrier film] A gas barrier film according to an embodiment of the present disclosure will now be described. Fig. 3 is a schematic cross-sectional view showing a gas barrier film according to an embodiment of the present disclosure. The gas barrier film 20 shown in Fig. 3 has a laminated structure including, in this order, a base layer 21, an anchor coat layer 22, a vapor deposition layer 23, and a gas barrier coating layer 24. The base layer 21 is a polypropylene film 10. A first skin layer 10a of the polypropylene film 10 is one of the outermost layers of the gas barrier film 20, and a second skin layer 10c of the polypropylene film 10 is located on the anchor coat layer 22 side.

[0061] The polypropylene film is provided with the second skin layer 10c, which can reduce the stress on the vapor-deposited layer caused by shrinkage of the polypropylene film after heat sterilization, and tends to suppress damage to the vapor-deposited layer. The anchor coat layer 22, the vapor-deposited layer 23, and the gas barrier coating layer 24 will be described below.

[0062] <Anchor coat layer> The anchor coat layer 22 is a layer for further improving the adhesion between the substrate layer 21 and the vapor deposition layer 23, and is provided between the substrate layer 21 and the vapor deposition layer 23. The material constituting the anchor coat layer 22 is not particularly limited as long as it can improve the adhesion between the substrate layer 21 and the vapor deposition layer 23.

[0063] For example, a material containing a reaction product of a polyol compound containing a (meth)acrylic resin and an isocyanate compound can be used as the material for the anchor coat layer 22. Note that the term "(meth)acrylic resin" refers to at least one of "acrylic resin" and the corresponding "methacrylic resin."

[0064] Examples of (meth)acrylic resins include (meth)acrylic polymers obtained by polymerizing polymerizable monomers containing (meth)acrylic monomers. The (meth)acrylic polymer may be a homopolymer or a copolymer with a polymerizable monomer other than a (meth)acrylic monomer. The (meth)acrylic resin may be a resin capable of thermal crosslinking, such as urethane curing or epoxy curing. From the viewpoint of reactivity with an isocyanate compound used as a curing agent, which will be described later, the (meth)acrylic resin may be a polyol having two or more hydroxyl groups in one molecule, and in particular, a (meth)acrylic polyol.

[0065] The (meth)acrylic polyol may be a (meth)acrylic copolymer obtained by copolymerizing a hydrocarbon (meth)acrylate with a hydroxyl group-containing monomer, or a (meth)acrylic copolymer obtained by copolymerizing a hydrocarbon (meth)acrylate with a hydroxyl group-containing monomer and a monomer component other than these (other monomer components). By copolymerizing the above-mentioned monomers, a (meth)acrylic polyol containing multiple hydroxyl groups can be obtained.

[0066] The anchor coat layer may contain a curing agent, which may be an isocyanate compound having two or more NCO groups in the molecule, from the viewpoint of excellent reactivity with the (meth)acrylic resin.

[0067] The isocyanate compound may be a monomeric isocyanate. Examples of the monomeric isocyanate include aromatic or araliphatic isocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), xylene diisocyanate (XDI), and tetramethylxylylene diisocyanate (TMXDI); and aliphatic isocyanates such as hexamethylene diisocyanate (HDI), bisisocyanatemethylcyclohexane (H6XDI), isophorone diisocyanate (IPDI), and dicyclohexylmethane diisocyanate (H12MDI).

[0068] The isocyanate compound may be a polymer or derivative of the above-mentioned monomeric isocyanate. The isocyanate compound may be, for example, a trimer nurate type, an adduct type reacted with 1,1,1-trimethylolpropane, or a biuret type reacted with biuret. The isocyanate compound may be an isocyanate having an aromatic ring, from the viewpoint of excellent reactivity with the (meth)acrylic resin.

[0069] When the (meth)acrylic resin is a (meth)acrylic polyol, the content of the isocyanate compound may be an amount such that the number of OH groups in the acrylic polyol is equal to the number of NCO groups in the isocyanate compound.

[0070] The anchor coat layer may contain a silane coupling agent to further improve adhesion to the vapor deposition layer. Examples of silane coupling agents include epoxy-based silane coupling agents having an epoxy group such as 3-glycidoxypropyltrimethoxysilane; amino-based silane coupling agents having an amino group such as 3-aminopropyltrimethoxysilane; mercapto-based silane coupling agents having a mercapto group such as 3-mercaptopropyltrimethoxysilane; and isocyanate-based silane coupling agents having an NCO group such as 3-isocyanatepropyltriethoxysilane. These silane coupling agents can be used alone or in combination of two or more.

[0071] Alternatively, a polyurethane resin formed from an acid group-containing polyurethane and a polyamine can be used as a material for forming the anchor coat layer 22. The polyurethane resin is obtained by bonding the acid groups of the acid group-containing polyurethane with the amino groups of a polyamine used as a crosslinking agent. In other words, the polyurethane resin can be said to be a reaction product of the acid group-containing polyurethane and the polyamine, or to be formed by crosslinking the acid group-containing polyurethane with the polyamine. The bond between the acid group of the acid group-containing polyurethane and the amino group of the polyamine may be an ionic bond (e.g., an ionic bond between a carboxyl group and a tertiary amino group) or a covalent bond (e.g., an amide bond).

[0072] In addition, a silane coupling agent or a carbodiimide compound may be added to the polyurethane resin. By adding such a compound, a crosslinked structure is formed with the polyurethane resin, and the gas barrier property or the adhesion between the substrate layer and the inorganic oxide layer can be further improved. As the silane coupling agent, a commonly used one can be used, and for example, a compound in which an alkoxy group and an organic reactive group are bonded to a silicon atom can be mentioned.

[0073] The thickness of the anchor coat layer 22 is not particularly limited as long as it is a thickness that can improve the adhesion between the base layer 21 and the vapor deposition layer 23, but is preferably 30 nm or more. In this case, compared to when the thickness of the anchor coat layer 22 is less than 30 nm, the surface smoothness of the anchor coat layer 22 can be further improved, the thickness of the vapor deposition layer can be made more uniform, and the oxygen barrier property can also be further improved. This further improves the oxygen barrier property of the gas barrier film 20. The thickness of the anchor coat layer 22 is more preferably 40 nm or more, and even more preferably 50 nm or more. By increasing the thickness of the anchor coat layer 22, it is possible to further suppress the deterioration of the water vapor barrier property when an external force such as stretching is applied.

[0074] The thickness of the anchor coat layer 22 is preferably 2000 nm (2 μm) or less. In this case, the flexibility of the gas barrier film 20 is further improved, and the oxygen gas barrier properties of the gas barrier film 20 after abuse can be further improved, compared to when the thickness of the anchor coat layer 22 exceeds 2000 nm. The thickness of the anchor coat layer 22 is more preferably 1500 nm (1.5 μm) or less.

[0075] The anchor coat layer 22 can be formed, for example, by applying an anchor coat solution onto the resin layer by a method such as gravure coating, roll coating, or bar coating, and then drying it.

[0076] In order to improve the adhesion between the substrate layer and the vapor deposition layer, instead of forming an anchor coat layer, the surface of the substrate layer on which the vapor deposition layer is to be formed may be subjected to a surface treatment such as plasma treatment or corona treatment. Alternatively, the anchor coat layer may be formed on the surface that has been subjected to the surface treatment.

[0077] <Vapour-deposited layer> The vapor-deposited layer contains an inorganic oxide. From the viewpoint of improving gas barrier properties against water vapor, oxygen, etc., the vapor-deposited layer may be formed directly on the anchor coat layer. The vapor-deposited layer may be transparent.

[0078] Examples of inorganic oxides that can be used include aluminum oxide, silicon oxide, tin oxide, magnesium oxide, and mixtures thereof. From the viewpoint of excellent sterilization resistance, the inorganic oxide may be at least one selected from aluminum oxide and silicon oxide.

[0079] The thickness of the vapor-deposited layer may be 5 nm or more, 10 nm or more, or 15 nm or more from the viewpoints of achieving a uniform film thickness and excellent gas barrier properties, and may be 300 nm or less, 150 nm or less, or 100 nm or less from the viewpoint of making the vapor-deposited layer less susceptible to cracking even when an external force is applied after film formation. From these viewpoints, the thickness of the vapor-deposited layer may be 5 to 300 nm, 10 to 150 nm, or 15 to 100 nm.

[0080] The vapor deposition layer can be formed by, for example, a vacuum deposition method, a plasma-assisted method, an ion-beam-assisted method, a sputtering method, a reactive vapor deposition method, etc. The vapor deposition layer may be formed by a vacuum deposition method from the viewpoint of excellent productivity, or by a plasma-assisted method or an ion-beam-assisted method from the viewpoint of excellent adhesion between the vapor deposition layer and the resin layer and improving the density of the vapor deposition layer, or by a reactive vapor deposition method in which various gases such as oxygen are blown in from the viewpoint of excellent transparency of the vapor deposition film.

[0081] Examples of the heating means for the vacuum deposition method include an electron beam heating method, a resistance heating method, an induction heating method, etc. The heating means for the vacuum deposition method may be an electron beam heating method, from the viewpoint of an excellent range of selectivity for evaporation materials.

[0082] <Gas barrier coating layer> By providing the gas barrier film with a gas barrier coating layer, the vapor deposition layer can be protected, and the gas barrier properties can be further improved.

[0083] The gas barrier coating layer may contain a silicon compound or a hydrolyzate thereof, and a water-soluble polymer having a hydroxyl group.

[0084] Examples of silicon compounds include Si(OR 1 )4 and R 2 Si(OR 3 )3. OR 1 and OR 3 are each independently a hydrolyzable group, and R 2 is an organic functional group. 2 Examples of the alkyl group include vinyl, epoxy, methacryloxy, ureido, and isocyanate groups. 1 )4 may be tetraethoxysilane (Si(OC2H5)4) from the viewpoint that it is relatively stable in an aqueous solvent after hydrolysis.

[0085] Examples of water-soluble polymers having hydroxyl groups include polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, and sodium alginate. The water-soluble polymer having hydroxyl groups may be polyvinyl alcohol from the viewpoint of excellent gas barrier properties.

[0086] The gas barrier coating layer may further contain additives such as an isocyanate compound, a silane coupling agent, a dispersant, a stabilizer, a viscosity adjuster, and a colorant.

[0087] The thickness of the gas barrier coating layer may be 0.1 μm or more, or 0.3 μm or more, or 5 μm or less, or 1 μm or less. The thickness of the gas barrier coating layer may be 0.1 to 5 μm, or 0.3 to 1 μm.

[0088] The gas barrier coating layer can be formed, for example, by dissolving a water-soluble polymer in water or a water / alcohol mixed solvent, mixing in a silicon compound or a hydrolyzate thereof, applying the mixed solution onto the vapor deposition layer by a method such as gravure coating, roll coating, or bar coating, and drying.

[0089] When the water-soluble polymer is polyvinyl alcohol, the content of polyvinyl alcohol in the mixed solution may be 20% by mass or more or 25% by mass or more based on the total solid content of the mixed solution from the viewpoint of facilitating the formation of a gas barrier coating layer, or 50% by mass or less or 40% by mass or less from the viewpoint of excellent gas barrier properties. The content of polyvinyl alcohol in the mixed solution may be 20 to 50% by mass or 25 to 40% by mass based on the total solid content of the mixed solution.

[0090] Although the gas barrier film according to one embodiment has been described above, the gas barrier film of the present disclosure is not limited to the above embodiment. The polypropylene film used as the base layer 21 does not necessarily have to include the second skin layer 10c.

[0091] The gas barrier film of the present disclosure may not have an anchor coat layer, may not have a gas barrier coating layer, or may not have both an anchor coat layer and a gas barrier coating layer. The gas barrier film of the present disclosure may also have a gas barrier coating layer between the polypropylene film and the vapor deposition layer.

[0092] [Laminate] A laminate according to an embodiment of the present disclosure will be described below. FIG. 4 is a schematic cross-sectional view showing a laminate according to an embodiment of the present disclosure. As shown in FIG. 4, a laminate 30 according to an embodiment has a laminate structure including, in this order, a sealant layer 31, a first adhesive layer 32a, a gas barrier film 20, a second adhesive layer 32b, and a second base layer 33. The base layer 21 serves as the first base layer. The laminate 30 can be suitably used as a packaging material. The laminate 30 is a gas barrier laminate having gas barrier properties. The sealant layer 31, the first and second adhesive layers 32, and the second base layer 33 will be described below.

[0093] [Sealant layer] The sealant layer includes a polypropylene film. The polypropylene film includes a polypropylene resin. The polypropylene film may be, for example, a film obtained by forming the polypropylene resin into a sheet and then stretching it to be uniaxially or biaxially oriented.

[0094] The content of the polypropylene resin may be 90% by mass or more, 95% by mass or more, or 99% by mass or more based on the total mass of the sealant layer, or may be substantially 100% by mass (an embodiment in which the sealant layer is made of polypropylene resin) based on the total mass of the sealant layer.

[0095] The thickness of the sealant layer may be 10 μm or more, or 20 μm or more, and may be 200 μm or less, or 100 μm or less. The thickness of the sealant layer may be 10 to 200 μm, or 20 to 100 μm.

[0096] [Adhesive layer] The adhesive layer may be formed of a polyurethane resin obtained by reacting a bifunctional or higher functional isocyanate compound with, for example, polyester polyol, polyether polyol, acrylic polyol, carbonate polyol, or the like.

[0097] In order to improve adhesiveness, the adhesive layer may contain, in addition to the polyurethane resin, a carbodiimide compound, an oxazoline compound, an epoxy compound, a phosphorus compound, a silane coupling agent, and the like.

[0098] The thickness of the adhesive layer is not particularly limited and may be, for example, 0.1 μm or more. By making the thickness of the adhesive layer 1 μm or more, sufficient adhesive strength can be obtained. The thickness of the adhesive layer may be 2 μm or more. The thickness of the adhesive layer may be 50 μm or less, 5 μm or less, or 3 μm or less.

[0099] [Second base layer] The second base layer includes a polypropylene film. The polypropylene film includes a polypropylene resin. The polypropylene film may be, for example, a film obtained by forming the polypropylene resin into a sheet and then stretching it to be uniaxially or biaxially oriented.

[0100] The polypropylene resin may be a crystalline polypropylene resin. From the viewpoint of improving heat resistance, the polypropylene resin may be a homopolypropylene resin, which is a homopolymer of propylene. The polypropylene resin may contain, for example, a random copolymer of propylene and an α-olefin.

[0101] The content of the polypropylene resin may be 90% by mass or more, 95% by mass or more, or 99% by mass or more, based on the total mass of the second base layer. The content of the polypropylene resin may be substantially 100% by mass, based on the total mass of the second base layer (an embodiment in which the base layer is made of polypropylene resin).

[0102] The second substrate layer may contain organic additives such as antiblocking agents (AB agents), antioxidants, stabilizers, lubricants, and antistatic agents, or may contain inorganic additives such as silica, zeolite, hydrotalcite, silicon particles, and siloid.

[0103] The anti-blocking agent may be either organic or inorganic particles. Examples of organic particles include polymethyl methacrylate particles, polystyrene particles, and polyamide particles. Examples of inorganic particles include silica particles, zeolite, talc, kaolinite, and feldspar. These anti-blocking agents may be used alone or in combination of two or more.

[0104] In consideration of anti-blocking performance, it is preferable to use an AB agent with an average particle size of 0.1 to 5 μm, where the average particle size is the weight average diameter measured by the coal tar method.

[0105] The thickness (total thickness) of the second base layer is not particularly limited, and may be, for example, 3 μm or more and 200 μm or less, 6 μm or more and 50 μm or less, or 10 μm or more and 30 μm or less.

[0106] The polypropylene used in the second base layer may be a resin polymerized from fossil fuel, a recycled resin, or a resin obtained by polymerizing raw materials derived from biomass such as plants. When using these resins, they may be used alone, or a mixture of a resin polymerized from fossil fuel and a recycled resin or a resin obtained by polymerizing raw materials derived from biomass such as plants may be used.

[0107] The laminate 30 makes it possible to produce a packaging material that has a sufficiently low oxygen permeability and excellent laminate strength even after heat sterilization. Therefore, packaging materials produced from the laminate 30 can contain foods, medicines, etc. The packaging material may be a packaging bag produced by making the laminate 30 into a bag. The packaging bag may be, for example, a bag-shaped packaging material obtained by folding one laminate 30 in half so that the sealant layers face each other and then heat-sealing the three sides other than the folded part, or a bag-shaped packaging material obtained by stacking two laminates 30 together so that the sealant layers face each other and then heat-sealing the four sides.

[0108] The packaging material may be equipped with a spout. In packaging material equipped with a spout, the spout may be sandwiched and fixed between two gas barrier films forming a packaging bag, or a hole may be drilled on one side of the packaging material and the spout may be glued to fix the spout. The spout may be provided on the top surface of the packaging material, or on the side, bottom, or diagonally upward of the packaging material. When the contents are liquid or gel-like, a straw that reaches the bottom of the packaging material may be provided in addition to the spout plug (so-called spout) so that the contents can be directly poured into the mouth and sucked out.

[0109] Another form of packaging material with a spout is a bag-in-box in which a bag (inner bag) containing a liquid such as a soft drink or alcoholic drink is placed in a carton (outer box). That is, the laminate 30 can be used for a bag-in-box bag, particularly a bag equipped with a spout (tube) for pouring.

[0110] When the laminate 30 is used as a packaging material with a spout, the spout portion and the entire spout of the cap may be formed from the same resin as the base layer of the gas barrier film, in order to improve recyclability.

[0111] Although the laminate according to one embodiment has been described above, the laminate according to the present disclosure is not limited to the above embodiment. For example, the laminate according to the present disclosure may not include a first adhesive layer, may not include a second adhesive layer, or may not include both a first adhesive layer and a second adhesive layer. Furthermore, the laminate according to the present disclosure may not include a second base layer. Furthermore, a gas barrier film according to another embodiment of the present disclosure may be used instead of the gas barrier film 20. [Example]

[0112] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0113] [Gas barrier film] <Examples 1 and 8> The first and second skin layers were made of ethylene-1-butene-propylene random copolymer resin (ethylene content: 2.5 mol%, 1-butene content: 3.5 mol%), and the core layer was made of homopolypropylene resin. These resins were co-extruded and then biaxially stretched to produce a polypropylene film (substrate layer) with a total thickness of 20 μm. The first and second skin layers were each 0.8 μm thick, and the core layer was 18.4 μm thick.

[0114] Subsequently, an acrylic primer solution was applied onto the second skin layer of the base layer by gravure coating and dried to form an anchor coat layer having a thickness of 0.1 μm.

[0115] Next, silicon oxide was deposited on the anchor coat layer by reactive deposition using radio frequency excited ion plating in an oxygen atmosphere under reduced pressure to form a deposition layer with a thickness of 30 nm.

[0116] A magnetron plasma processing apparatus with an AC power supply as shown in Figure 2 was prepared. Argon (Ar) gas was introduced into the apparatus at a flow rate of 200 sccm, and oxygen (O2) was introduced at a flow rate of 800 sccm (a total of 1000 sccm introduced), while the pressure was reduced to the specified level. The frequency of the high-frequency power from the AC power supply was set to 40 kHz, and plasma for plasma processing was generated. Next, the polypropylene film on which the above-mentioned vapor deposition layer was formed was inserted and transported into the magnetron plasma processing apparatus in which plasma was generated, with the first skin layer surface facing the discharge electrode unit, and plasma processing was performed on that surface. At this time, the EPD was 282 W·s / m 2 In this way, a first gas barrier film was produced.

[0117] Next, a solution made by mixing the following liquids A, B, and C in a mixing ratio (mass ratio) of 70 / 20 / 10 was applied onto the vapor deposition layer of the first gas barrier film by gravure coating, and dried at 80°C for 20 seconds to form a gas barrier coating layer 0.3 μm thick, thereby producing a second gas barrier film.

[0118] Liquid A: A hydrolysis solution (solid content 5% by mass (SiO2 equivalent)) in which 72.1 g of hydrochloric acid (0.1 N) was added to a mixed solution of 17.9 g of tetraethoxysilane and 10 g of methanol, and the mixture was stirred for 30 minutes to hydrolyze the solution. Liquid B: a water / methanol solution containing 5% by mass of polyvinyl alcohol (water / methanol weight ratio = 95 / 5). Solution C: Hydrochloric acid (1N) was gradually added to a mixed solution of β-(3,4-epoxycyclohexyl)trimethoxysilane and isopropyl alcohol (IPA solution), and the mixture was stirred for 30 minutes. The resulting hydrolyzed solution was then hydrolyzed with a water / IPA solution (water / IPA weight ratio = 1 / 1). The resulting hydrolyzed solution (solid content 5% by mass (R 2 Si(OH)3 equivalent)).

[0119] <Examples 2 and 3> First and second gas barrier films were produced in the same manner as in Example 1, except that the conditions were adjusted so that the Epd during the plasma treatment would be the values ​​shown in Table 1.

[0120] Example 4 The first and second gas barrier films were produced in the same manner as in Example 1, except that only Ar gas was used as the treatment gas, the flow rate was 1000 ppm, and the Epd during plasma treatment was adjusted as shown in Table 1.

[0121] <Example 5> The first and second gas barrier films were prepared in the same manner as in Example 1, except that an ethylene-1-butene-propylene random copolymer resin (ethylene content: 5 mol%, 1-butene content: 6 mol%) was used as the first skin layer.

[0122] Example 6 First and second gas barrier films were produced in the same manner as in Example 1, except that the thickness of the first skin layer was 0.4 μm and the thickness of the core layer was 18.8 μm.

[0123] Example 7 First and second gas barrier films were produced in the same manner as in Example 1, except that an ethylene-propylene random copolymer resin (ethylene content: 1.5 mol %) was used for the first skin layer.

[0124] <Comparative Example 1> First and second gas barrier films were produced in the same manner as in Example 1, except that the polypropylene film on which the vapor-deposited layer was formed was not subjected to plasma treatment.

[0125] <Comparative Examples 2 to 6> First and second gas barrier films were produced in the same manner as in Example 1, except that the Epd value and gas species during the plasma treatment were adjusted as shown in Table 1.

[0126] <Comparative Example 7> First and second gas barrier films were produced in the same manner as in Example 1, except that the first skin layer of the polypropylene film was made of the same homopolypropylene as the core layer.

[0127] [Laminate fabrication] <Examples 1 to 7, Comparative Examples 1 to 7> For the second gas barrier film prepared in each example, a biaxially oriented polypropylene film (thickness 20 μm) was attached to the gas barrier coating layer side, and an unoriented polypropylene film (thickness 60 μm) was attached to the opposite side by dry lamination using a solvent-based two-component curing urethane adhesive. The adhesive layer thickness was 2.5 μm. This produced a three-layer laminate.

[0128] Example 8 A laminate was produced in the same manner as in Example 1, except that a solvent-free two-component curing urethane adhesive was used as the adhesive for lamination. The thickness of the adhesive layer was 2 μm.

[0129] [evaluation] <First skin layer surface analysis method> The average value and standard deviation of the ratio of the number of oxygen atoms to the number of carbon atoms (O / C) were measured for the first skin layer surface of each laminate of each Example and Comparative Example. Specifically, narrow spectrum analysis of the first skin layer surface was performed using the following measuring equipment under the following measurement conditions to obtain narrow spectra of the O1s and C1s orbitals of the first skin layer surface. For each element, the relative sensitivity coefficients of 2.28 eV for O1s and 1.00 eV for C1s were used to determine the elemental quantitative value (atomic %) from each peak area, and the O / C ratio was calculated using the obtained elemental quantitative value. Measurements were performed at five randomly selected locations. The average value and standard deviation of the ratio of the number of oxygen atoms to the number of carbon atoms (O / C) were calculated from the measurement results of the five locations. The results are shown in Table 1.

[0130] (Measuring equipment) JEOL Ltd., JPS-9030 photoelectron spectrometer (Measurement conditions: Spectral collection conditions) Incident X-ray: MgKα (hν=1253.6eV) X-ray output: 100W (10kV 10mA) Measurement area: 6mm diameter circular area Photoelectron capture angle: 15° Dwell Time: 100ms Measurement step: 0.2 eV Pass energy: 10 eV Accumulation count: 5 times

[0131] <Method of processing the cross section of the sample for measuring the softening temperature> The laminates produced in the examples and comparative examples were used as measurement samples, and corona treatment was performed on both the front and back surfaces of the samples at 0.20 kW using a corona treatment machine (product name: CT-0212) manufactured by Kasuga Electric Co., Ltd.

[0132] After corona treatment of the front and back surfaces of the sample, the sample was cut into strips measuring 1.0 mm in base and 5.0 mm in height with a razor. The cut sample was embedded in a photocurable resin and cured under a halogen lamp (Kenko Tokina, product name: KTX-100R). The photocurable resin was a D-800 (product name) from Toa Gosei Co., Ltd. The photocured sample and embedding resin were fixed in an AFM sample holder insert. The sample was then cross-sectioned with a glass knife at room temperature (25°C). Finally, a final cross-section was performed at low temperature (-40°C) with a diamond knife at a cutting speed of 1.0 mm / s and a cutting film thickness of 100 nm. The cutting was completed when a mirror surface was obtained. An ultramicrotome (Leica, product name: EM UC7) and a cryosystem (Leica, product name: EM FC7) were used for cross-section cutting. The cutting direction of the knife was parallel to the layer interface and perpendicular to the long sides of the strip-shaped sample.

[0133] <Softening temperature measurement> The softening temperature of the first skin layer of the laminates produced in each example and comparative example was measured. The atomic force microscope (AFM) was an Oxford Instruments MFP-3D-SA (trade name), with a local thermal analysis option available as a Ztherm system (trade name), and the cantilever was an Anasys Instruments AN2-200 (trade name) with a spring constant of 0.5 to 3.5 N / m. Softening temperature measurements were performed at the center of the thickness direction of the first skin layer of the substrate layer.

[0134] When the sample surface was heated after detrend correction with a cantilever contact pressure (change in cantilever deflection) of 0.2 V, a voltage application rate (heating rate) of 0.5 V / s, and a maximum applied voltage of 5.5 V, the sample surface expanded and the cantilever position rose. Further heating of the sample surface softened it, and the measurement was terminated when the cantilever position dropped 10 nm. If the Z-displacement did not drop 10 nm from the change point and reached the maximum applied voltage, the maximum applied voltage during detrend correction and measurement was increased by 0.5 V and the measurement was repeated.

[0135] The voltage applied at the point where the vertical height (Z displacement) of the cantilever was maximum was taken as the voltage applied at the softening point, and the voltage value was read.

[0136] To calculate the softening temperature of the sample, a calibration curve was created to match the measurement conditions. The calibration samples were the following four polymer materials whose melting points (melting peak temperatures) had been measured in advance using a differential scanning calorimeter (DSC), and cross-sectional samples were prepared in an environment below their glass transition temperatures. Polycaprolactone pellets (melting point: 60°C) Low-density polyethylene pellets (melting point: 112°C) Polypropylene pellets (melting point: 166°C) Biaxially stretched polyethylene terephthalate film (melting point: 255°C)

[0137] Cross-sectional samples were prepared using an ultramicrotome and cryosystem at -80°C for polycaprolactone, -140°C for low-density polyethylene, -40°C for polypropylene, and room temperature (25°C) for polyethylene terephthalate. Measurement conditions were a voltage application rate (heating rate) of 0.5 V / s, with a maximum applied voltage of 3.5 V for polycaprolactone, 5 V for low-density polyethylene, 6 V for polypropylene, and 7.8 V for polyethylene terephthalate. The cantilever contact pressure (change in cantilever deflection) was set to 0.2 V for the calibration curve of the skin layer of the substrate. After detrend correction, the sample surface was heated and the applied voltage at the softening point was measured. The applied voltage at the softening point was measured 10 times at different measurement positions on the calibration sample. A calibration curve was created by approximating the average applied voltage at the softening point and the melting point (peak melting temperature) measured by DSC measurement with a cubic function using the least-squares method.

[0138] Using a calibration curve of applied voltage and temperature, the temperatures corresponding to the applied voltage at which the first skin layer of the base material layer softened were determined, and these temperatures were taken as the softening temperatures. The results are shown in Table 1.

[0139] <Wettability> Two A4-sized sheets were cut out from the first gas barrier film prepared in each Example and Comparative Example. The two sheets were stacked so that the vapor-deposited layer side of one sheet faced the substrate layer side of the other sheet, yielding a structure. This structure was stored for 8 hours while being pressed using a press (KVHC-II, manufactured by Kitagawa Seiki Co., Ltd.) under conditions of 4 MPa, 25°C, and 65% RH. The two sheets were then separated, and the wet surface tension of the vapor-deposited layer was measured according to the method of JIS K6738. This measurement value was used as an index of wettability. The wettability of the vapor-deposited layer surface was evaluated based on the following criteria. The results are shown in Table 1. High wettability indicates that the components of the first skin layer are inhibited from migrating to the vapor-deposited layer. The wet surface tension of the first skin layer surface was also measured in the same manner as for the vapor-deposited layer surface. The results are shown in Table 1.

[0140] (standard) A: Wetting surface tension 35mN / m or more B: Wetting surface tension less than 35mN / m

[0141] <Retort processing> The laminates prepared in the Examples and Comparative Examples were cut out and heat-sealed on three sides to produce pouches with openings. Water was poured into the pouches, and the openings were heat-sealed to obtain sealed pouches. The resulting sealed pouches were subjected to retort treatment at 130°C for 60 minutes using a hot water storage retort oven.

[0142] <Lamination strength> After retorting, the water was removed from the sealed pouch, and the laminate was dried. To evaluate the adhesion between the polypropylene film and the sealant layer of the laminate, the laminate strength between the first skin layer and the sealant layer was measured. Measurements were performed in accordance with JIS K6854, with a test width of 15 mm, a peel speed of 300 mm / min, and a peel angle of 180°. Measurements were performed at five randomly selected locations on the laminate. The minimum and maximum values ​​of the five measurements are shown in Table 1. Measurements were expressed in units of [N / 15 mm]. A minimum laminate strength measurement of 2.0 N / 15 mm or greater was considered to indicate excellent adhesion between the polypropylene film and the sealant layer in the laminate, as well as excellent adhesion stability.

[0143] [Table 1] [Explanation of symbols]

[0144] 10...polypropylene film, 10a...first skin layer, 10b...core layer, 10c...second skin layer, 20...gas barrier film, 22...anchor coat layer, 23...vapor deposition layer, 24...gas barrier coating layer, 30...laminate, 31...sealant layer.

Claims

1. A core layer; A first skin layer; a laminated structure comprising: A polypropylene film that is heat sterilized, the first skin layer is one outermost layer of the polypropylene film, the first skin layer comprises a copolymer of propylene and another monomer; A polypropylene film, wherein, when the surface of the first skin layer is subjected to elemental quantitative analysis by X-ray photoelectron spectroscopy, the average ratio of the number of oxygen atoms to the number of carbon atoms (O / C) is 0.010 to 0.050 and the standard deviation of the ratio (O / C) is 0.0010 to 0.0050.

2. The polypropylene film according to claim 1, wherein the other monomer comprises an α-olefin.

3. The polypropylene film according to claim 1, wherein the softening temperature of the first skin layer measured by local thermal analysis is 120°C or higher.

4. The polypropylene film according to any one of claims 1 to 3, a vapor-deposited layer containing an inorganic oxide located on the surface of the polypropylene film opposite to the first skin layer; A gas barrier film comprising:

5. The gas barrier film according to claim 4 , wherein the polypropylene film has a laminated structure further comprising a second skin layer as an outermost layer on the side opposite to the first skin layer.

6. The gas barrier film according to claim 4 , wherein the inorganic oxide comprises at least one selected from aluminum oxide and silicon oxide.

7. The gas barrier film according to claim 4 , further comprising a gas barrier coating layer between the polypropylene film and the vapor deposition layer or on the surface of the vapor deposition layer opposite to the polypropylene film.

8. The gas barrier film according to claim 4 , further comprising an anchor coat layer located between the polypropylene film and the vapor deposition layer.

9. The gas barrier film according to claim 4; a sealant layer comprising polypropylene; A laminate comprising:

10. The laminate according to claim 9 , further comprising a polypropylene film on the surface of the gas barrier film opposite to the sealant layer.

11. A packaging bag produced by producing the laminate according to claim 9.

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