gas barrier film

Abstract

To provide a gas barrier film having high resistance to a hot-water treatment and suppressed in the environmental load.SOLUTION: A gas barrier film 1 comprises a base material 10 made of polypropylene as a main component, a gas barrier layer 20 formed on a first surface 10a of the substrate, and a coating layer 30 formed on the gas barrier layer. In an infrared spectroscopy measurement of a first side, a ratio of a peak intensity I1 present at 1360 to 1390 cm-1 and a peak intensity I2 present at 1440-1480 cm-1 satisfies equation I1 / I2≤1.65.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a gas barrier film and a method for manufacturing a gas barrier film. The gas barrier film of this invention is suitable for packaging food, pharmaceuticals, precision electronic components, and the like. [Background technology]

[0002] In packaging materials used for food, non-food items, pharmaceuticals, etc., gas barrier properties are sometimes required to block oxygen, water vapor, and other gases that alter the contents from permeating the packaging material, in order to suppress deterioration of the contents and maintain their functions and properties. As a packaging material with gas barrier properties, gas barrier films are known that use metal foil such as aluminum as a gas barrier layer, which is less affected by temperature, humidity, and other factors.

[0003] Other gas barrier films are known in which an inorganic oxide film, such as silicon oxide or aluminum oxide, is deposited on a base film made of polymer material by vacuum deposition or sputtering (see, for example, Patent Document 1). These gas barrier films are transparent and have gas barrier properties against oxygen, water vapor, and other gases. Polyethylene terephthalate (PET) is commonly used as the base film. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 60-49934 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In recent years, there has been a growing demand for gas barrier films using polypropylene (PP) or polyethylene (PE) base films from the perspective of reducing environmental impact. Patent Document 1 also describes the use of PP base films. However, the inventor's research revealed that a gas barrier film simply formed by creating a barrier layer on a PP base film does not actually have sufficient resistance to hot water treatments such as boiling or retorting.

[0006] Based on the above circumstances, the present invention aims to provide a gas barrier film that has high resistance to hot water treatment and also reduces environmental impact, as well as a method for manufacturing the same. [Means for solving the problem]

[0007] The present invention relates to a gas barrier film comprising a base material mainly composed of polypropylene, a gas barrier layer formed on the first surface of the base material, and a coating layer formed on the gas barrier layer. The first surface contains a copolymer of propylene and ethylene. In infrared spectroscopy measurements of the first surface of this gas barrier film, the reading was 1360–1390 cm⁻¹. -1 The peak intensity I1 present is at 1440-1480 cm. -1 The ratio of the peak intensity I2 present in the region satisfies the following equation (1). I1 / I2 ≤ 1.60 …(1) [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a gas barrier film that has high resistance to hot water treatment and also reduces environmental impact. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view of a gas barrier film according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] One embodiment of the present invention will be described below with reference to Figure 1. Figure 1 is a schematic cross-sectional view of the gas barrier film 1 according to this embodiment. The gas barrier film 1 comprises a substrate 10, a gas barrier layer 20, a coating layer 30, an adhesive layer 40, and a sealant layer 50.

[0011] The base material 10 has two or more resin layers, with polypropylene as the main component. The base material of this embodiment has two resin layers: a base layer 11 and a surface layer 12 laminated on the base layer 11. A substrate 10 having two or more resin layers can be formed, for example, by co-extrusion. The total thickness of the substrate 10, which is the sum of the base layer 11 and the surface layer 12, can be, for example, 3 to 200 μm, and is preferably 15 to 60 μm.

[0012] Polypropylene is used as the main component resin for each layer of the base material 10, from the viewpoint of ease of availability, water vapor barrier properties, and minimizing environmental impact. The polypropylene may be a homopolymer, random copolymer, block copolymer, or terpolymer. Homopolymer is polypropylene consisting only of propylene. Random copolymer is polypropylene in which propylene, the main monomer, and a different type of comonomer are randomly copolymerized to form a homogeneous phase. Block copolymer is polypropylene in which propylene, the main monomer, and the above comonomers copolymerize in a block-like manner or polymerize into a rubbery state to form a heterogeneous phase. Terpolymer is polypropylene in which propylene, the main monomer, and two different types of comonomers are copolymerized. Any one of these polyolefin resins may be used alone, or two or more may be used in a blend. The raw material for the base layer 11 is preferably a homopolymer, random copolymer, or block copolymer. The raw material for the surface layer 12 is preferably a random copolymer, block copolymer, or terpolymer.

[0013] The gas barrier layer 20 is formed on the first surface 10a of the base material 10 composed of the surface layer 12. The gas barrier layer 20 is a layer mainly composed of any one of metallic aluminum, aluminum oxide, and silicon oxide, and exhibits barrier properties against predetermined gases such as oxygen and water vapor. The gas barrier layer 20 can be configured to be either transparent or opaque depending on the material selected.

[0014] The thickness of the gas barrier layer 20 can be appropriately determined based on the performance required for the gas barrier layer while considering the type, composition, formation method, etc. of the inorganic compound used, but it can generally be in the range of 3 to 300 nm. If the film thickness is less than 3 nm, a uniform film may not be obtained or the film thickness may not be sufficient, making it difficult to ensure the function as a gas barrier material. When the film thickness exceeds 300 nm, the flexibility of the film decreases, and cracks are likely to occur in the thin film due to external factors such as bending and stretching after film formation. Therefore, it is more preferable that the thickness of the gas barrier layer 20 is within the range of 6 to 150 nm.

[0015] There is no particular limitation on the formation method of the gas barrier layer 20, and examples include vacuum evaporation, sputtering, ion plating, ion beam, plasma chemical vapor deposition (CVD), etc. The gas barrier layer may be formed densely by combining the above-described methods with a plasma assist method or an ion beam assist method to improve the barrier properties and adhesion.

[0016] The coating layer 30 mainly has gas barrier properties against oxygen. The coating layer 30 is formed using a coating agent mainly composed of an aqueous solution or a water / alcohol mixed solution containing a water-soluble polymer and one or more metal alkoxides or their hydrolyzates. For example, a coating agent is prepared by mixing a water-soluble polymer dissolved in an aqueous (water or water / alcohol mixed) solvent with a metal alkoxide that has been directly treated or previously hydrolyzed. After applying this coating agent onto the gas barrier layer 20 and drying it, the coating layer 30 can be formed.

[0017] The components contained in the coating agent for forming the coating layer 30 will be described in detail. Examples of the water-soluble polymer used in the coating agent include polyvinyl alcohol (PVA), polyvinyl pyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, and the like. In particular, the use of PVA is preferable because excellent gas barrier properties can be obtained. PVA is generally obtained by saponifying polyvinyl acetate. As PVA, either so-called partially saponified PVA in which several tens of % of acetic acid groups remain, or completely saponified PVA in which only several % of acetic acid groups remain can be used. PVA in the middle of both may also be used.

[0018] The metal alkoxide used in the coating agent is a compound represented by the general formula M(OR)n (M: metal such as Si, Al; R: alkyl group such as CH 3、 C2H5). Specific examples include tetraethoxysilane [Si(OC2H5)4], triisopropoxyaluminum Al[OCH(CH3)2]3, and the like. Examples of the silane coupling agent include those having an epoxy group such as 3-glycidoxypropyltrimethoxysilane, those having an amino group such as 3-aminopropyltrimethoxysilane, those having a mercapto group such as 3-mercaptopropyltrimethoxysilane, those having an isocyanate group such as 3-isocyanatopropyltriethoxysilane, and tris-(3-trimethoxysilylpropyl)isocyanurate. There is no limitation on the coating method of the coating agent, and conventionally known methods such as the dipping method, roll coating method, screen printing method, spraying method, and gravure printing method that are usually used can be appropriately selected.

[0019] The thickness of the coating layer 30 can be appropriately determined based on the composition of the coating agent and coating conditions, and there are no particular restrictions. However, if the film thickness of the coating layer 30 after drying is 0.01 μm or less, a uniform coating film may not be formed, and sufficient gas barrier properties may not be obtained. If the film thickness after drying exceeds 50 μm, cracks are more likely to occur in the coating layer 30. Therefore, a suitable thickness for the coating layer 30 is, for example, in the range of 0.01 to 50 μm. The optimal thickness for the coating layer 30 is, for example, in the range of 0.1 to 10 μm.

[0020] The sealant layer 50 is a layer that is joined by heat fusion when forming a bag-shaped packaging body or the like using the gas barrier film 1. Examples of materials for the sealant layer 60 include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, and metal crosslinked products thereof. The thickness of the sealant layer 60 is determined according to the purpose, but can be in the range of 15 to 200 μm, for example.

[0021] The adhesive layer 40 bonds the sealant layer 50 and the coating layer 30. By using the adhesive layer 40, the resin film that will become the sealant layer 50 and the substrate 10 on which the gas barrier layer 20 and the coating layer 30 are formed can be bonded together by dry lamination. An example of the material for the adhesive layer 40 is a two-component curing polyurethane adhesive. A packaging material can be created by laminating a printed layer, an intervening film, a sealant layer, etc., on the coating layer 30. When laminating, an extrusion lamination method may be used to directly form the sealant layer on the coating layer 30 without using an adhesive.

[0022] The first surface 10a of the substrate 10 measured 1370-1380 cm⁻¹ in infrared spectroscopy. -1 The peak intensity (I1) present at 1450-1460 cm -1The intensity ratio with respect to the peak intensity (I2) present is within the range of equation (1). That is, I1 is 1.65 times or less of I2. In this embodiment, this intensity ratio is brought about by the material properties of the surface layer 12 constituting the first surface 10a. I1 / I2 ≤ 1.65 …(1)

[0023] The value in equation (1) above indicates the proportion of polypropylene in the resin components at the measurement site. I1 represents the amount of polypropylene, and I2 represents the sum of polyethylene and polypropylene. Therefore, homopolymers have a larger value in equation (1) compared to copolymers and terpolymers, while in copolymers and terpolymers, the value in equation (1) decreases as the amount of components other than polypropylene increases. The inventors conducted various studies when constructing a gas barrier film using a substrate mainly composed of polypropylene. As a result, they found that on the first surface 10a where the gas barrier layer 20 is formed, if the value of formula (1) on the first surface 10a is 1.65 or less within the range where polypropylene is the main component, the gas barrier layer is formed in a good condition without defects, and the cohesive force is excellent, improving the adhesion strength of the gas barrier layer. The value of formula (1) on the first surface 10a is preferably between 1.30 and 1.60, and more preferably between 1.30 and 1.55. If it is 1.30 or less, the heat resistance is poor, resulting in poor gas barrier properties. Also, if it is 1.60 or more, the cohesive force is poor, and the adhesion strength tends to decrease. As described above, the gas barrier film 1 of this embodiment maintains a monomaterial structure mainly composed of polypropylene, thereby suppressing environmental impact, while the gas barrier layer exhibiting suitable gas barrier properties is well bonded to the substrate and configured to be resistant to peeling.

[0024] As a result of further investigation by the inventors, they found that the overall properties of the substrate 10 are further improved by adding a base layer 11 with a larger value in formula (1) to the surface layer 12 including the first surface having the above-mentioned properties. By laminating a layer with a larger value in formula (1), that is, a layer with a higher proportion of polypropylene than the layer including the first surface, the heat resistance of the substrate 10 as a whole is improved. As a result, sufficient heat can be applied to the substrate 10 when forming the coating layer 30, and the barrier performance of the coating layer 30 can be improved. Furthermore, when the gas barrier film after manufacturing undergoes hot water treatment such as retort treatment or boiling treatment, the base layer 11 suppresses the shrinkage of the surface layer 12, thereby suitably suppressing cracks in the gas barrier layer 20 due to shrinkage, which would reduce the gas barrier function, and preventing the gas barrier layer 20 from easily peeling off from the substrate 10. The surface layer 12 of the base material 10 is a resin copolymerized with polyethylene such as HDPE (high-density polyethylene), LDPE (low-density polyethylene), or LLDPE (linear low-density polyethylene) with a melting point 0.1 to several tens of percent lower than propylene homopolymer, or with α-olefin resins such as 1-butene, or rubber components such as elastomers, or a mixture of polyethylene resin and polypropylene resin in a predetermined ratio. The base layer 11 uses a propylene homopolymer resin, and the mixture is kneaded with multiple screws and extruded to form a film. Generally, polypropylene films have lower heat resistance than PET films, but by manufacturing as described above, a base material 10 with excellent heat resistance can be realized by having a highly heat-resistant propylene homopolymer in the base layer 11 while controlling the surface layer 12 that constitutes the surface to satisfy formula (1). From this perspective, the value of formula (1) on the second surface 10b of the base layer 11 is preferably greater than the value on the first surface, and more preferably 1.65 or greater.

[0025] In the substrate 10, a smooth surface on the first surface 10a is preferable, as it further reduces the likelihood of defects in the formed gas barrier layer 20. Average surface roughness Sa can be used as an indicator of smoothness, and its value is preferably 10 nm or less. The average surface roughness Sa is measured in an area where no fine particles are present, as described later.

[0026] The base material 10 may contain additives other than resin components. These additives can be appropriately selected from a variety of known additives. Examples of additives include antiblocking agents (AB agents), heat stabilizers, weather stabilizers, UV absorbers, lubricants, slip agents, nucleating agents, antistatic agents, antifogging agents, pigments, and dyes. The AB agents may be organic or inorganic. These additives may be used individually or in combination of two or more. Of these, lubricants and slip agents are preferred from the viewpoint of processability. The content of additives in the base material 10 can be appropriately adjusted within a range that does not hinder the effects of the present invention. If these additives maintain a granular state within the substrate 10, excessive protrusion onto the first surface 10a can cause minute defects in the gas barrier layer 20 and the coating layer 30. The inventors' studies have shown that by keeping the number of fine particles made of materials other than polypropylene protruding onto the first surface, and their protrusion height, below predetermined values, minute defects are less likely to occur. An example of these predetermined values ​​is 100 particles or less per square area with sides of 250 μm, and an average protrusion length of 5 μm or less. However, the specific content of the indicator is not limited as long as it has substantially the same meaning. When the number of particles exceeds 100 and the average protrusion height exceeds 5 μm, the barrier properties decrease. Therefore, it is best to have 100 or fewer particles and an average protrusion height of 5 μm or less.

[0027] A method for manufacturing the gas barrier film 1 of this embodiment having the above configuration will be described. First, a gas barrier layer 20 is formed on the first surface 10a of the substrate 10 by an appropriate method (first step). In the first step, before forming the gas barrier layer, a coating layer such as a thermoplastic resin, thermosetting resin, or ultraviolet curing resin may be formed on the first surface 10a to improve barrier properties and adhesion, or a pretreatment such as corona treatment, plasma treatment, ozone treatment, or flame treatment may be performed on the first surface 10a to provide a pretreatment layer between the first surface 10a and the gas barrier layer 20. By providing a pretreatment layer, the adhesion between the substrate 10 and the gas barrier layer 20 can be further improved. Among the pretreatment methods described above, plasma treatment, which can be performed in-line, is preferred from a productivity standpoint. The plasma treatment is not particularly limited and can include glow discharge, ion beam, etc., and magnets may be used to increase the plasma density. The gas used during plasma treatment can be selected from oxygen, nitrogen, argon, or one or more of these.

[0028] Next, the coating agent described above is applied to the gas barrier layer 20 and dried to form a coating layer 30 on the gas barrier layer (second step). Furthermore, an adhesive that will become the adhesive layer 40 is applied to the coating layer 30, and a resin film that will become the sealant layer 50 is bonded to it (third step), completing the gas barrier film 1.

[0029] The gas barrier film of this embodiment will be further described using examples and comparative examples. The present invention is not limited in any way by the specific details of the examples and comparative examples.

[0030] (Example 1) A biaxially oriented polypropylene film A with a thickness of 20 μm was used as the base material 10. Polypropylene film A is a co-extruded film having two layers: a base layer 11 and a surface layer 12. The first surface of polypropylene film A, consisting of a surface layer 12, was subjected to corona treatment. In a vacuum chamber, a mixture of silicon and silicon oxide was sublimated, and a gas barrier layer 20 (30 nm thick) made of silicon oxide was formed by electron beam deposition.

[0031] A coating agent, prepared by mixing liquids (1) and (2) below in a mass ratio of 6:4, was applied to the gas barrier layer 20 by gravure coating and dried to form a coating layer 30 with a thickness of 0.4 μm. (1) Solution: Add 89.6g of hydrochloric acid (0.1N) to 10.4g of tetraethoxysilane, stir for 30 minutes to hydrolyze, and obtain a hydrolyzed solution with a solid content of 3 wt% (in terms of SiO2). (2) Solution: 3 wt% water / isopropyl alcohol solution of polyvinyl alcohol (water:isopropyl alcohol weight ratio 90:10)

[0032] Finally, an unstretched polypropylene film (70 μm thick) was laminated onto the coating layer 30 by dry lamination using a two-component curing polyurethane adhesive to obtain the gas barrier film of Example 1.

[0033] (Example 2) A gas barrier film of Example 2 was fabricated in the same manner as in Example 1, except that aluminum was used as the deposition material and a 10 nm thick gas barrier layer 20 made of metallic aluminum was formed by electron beam deposition.

[0034] (Example 3) A gas barrier film of Example 3 was fabricated in the same manner as in Example 1, except that aluminum was used as the deposition material and a 10 nm thick gas barrier layer 20 made of aluminum oxide was formed by electron beam deposition under oxygen introduction.

[0035] (Example 4) A biaxially oriented polypropylene film B with a thickness of 20 μm was used as the base material 10. Polypropylene film B is a co-extruded film having two layers, a base layer 11 and a surface layer 12, but it is a different film from polypropylene film B. Except as described above, the gas barrier film of Example 4 was prepared in the same manner as in Example 1.

[0036] (Example 5) The gas barrier film of Example 5 was prepared in the same manner as in Example 2, except that polypropylene film B was used as the base material 10.

[0037] (Example 6) A gas barrier film of Example 6 was prepared in the same manner as in Example 3, except that polypropylene film B was used as the base material 10.

[0038] (Example 7) A biaxially oriented polypropylene film C with a thickness of 20 μm was used as the base material 10. Polypropylene film C is a co-extruded film having two layers, a base layer 11 and a surface layer 12, but it is a different film from both polypropylene films A and B. Except as described above, the gas barrier film of Example 7 was prepared in the same manner as in Example 1.

[0039] (Example 8) The gas barrier film of Example 8 was prepared in the same manner as in Example 2, except that polypropylene film C was used as the base material 10.

[0040] (Example 9) The gas barrier film of Example 9 was prepared in the same manner as in Example 3, except that polypropylene film C was used as the base material 10.

[0041] (Example 10) A biaxially oriented polypropylene film D with a thickness of 20 μm was used as the base material 10. Polypropylene film D is a co-extruded film having two layers, a base layer 11 and a surface layer 12, but it is a different film from any of polypropylene films A to C. Except as described above, the gas barrier film of Example 10 was prepared in the same manner as in Example 1.

[0042] (Example 11) The gas barrier film of Example 11 was prepared in the same manner as in Example 2, except that polypropylene film D was used as the base material 10.

[0043] (Example 12) A gas barrier film of Example 12 was prepared in the same manner as in Example 3, except that polypropylene film D was used as the base material 10.

[0044] (Example 13) A biaxially oriented polypropylene film E with a thickness of 20 μm was used as the base material 10. Polypropylene film E is a co-extruded film having two layers, a base layer 11 and a surface layer 12, but it is a different film from any of the polypropylene films A through D. Except as described above, the gas barrier film of Example 13 was prepared in the same manner as in Example 1.

[0045] (Example 14) A gas barrier film of Example 14 was prepared in the same manner as in Example 2, except that polypropylene film E was used as the base material 10.

[0046] (Example 15) A gas barrier film of Example 15 was prepared in the same manner as in Example 3, except that polypropylene film E was used as the base material 10.

[0047] (Example 16) A gas barrier film of Example 16 was prepared in the same manner as in Example 1, except that a polypropylene film A with a thickness of 15 μm was used as the base material 10.

[0048] (Example 17) The gas barrier film of Example 17 was prepared in the same manner as in Example 2, except that the substrate was the same as in Example 16.

[0049] (Example 18) The gas barrier film of Example 18 was prepared in the same manner as in Example 3, except that the substrate was the same as in Example 16.

[0050] (Example 19) A gas barrier film of Example 19 was prepared in the same manner as in Example 1, except that a polypropylene film A with a thickness of 40 μm was used as the base material 10.

[0051] (Example 20) The gas barrier film of Example 20 was prepared in the same manner as in Example 2, except that the substrate was the same as in Example 19.

[0052] (Example 21) The gas barrier film of Example 21 was prepared in the same manner as in Example 3, except that the substrate was the same as in Example 19.

[0053] (Example 22) A biaxially oriented polypropylene film F with a thickness of 20 μm was used as the base material 10. Polypropylene film F is a co-extruded film having two layers, a base layer 11 and a surface layer 12, but it is a different film from any of the polypropylene films A through E. Except as described above, the gas barrier film of Example 22 was prepared in the same manner as in Example 1.

[0054] (Example 23) A biaxially oriented polypropylene film G with a thickness of 20 μm was used as the base material 10. Polypropylene film G is a co-extruded film having two layers, a base layer 11 and a surface layer 12, but it is a different film from any of the polypropylene films A through F. Except as described above, the gas barrier film of Example 23 was prepared in the same manner as in Example 1.

[0055] (Example 24) A biaxially oriented polypropylene film H with a thickness of 20 μm was used as the base material 10. Polypropylene film H is a co-extruded film having two layers, a base layer 11 and a surface layer 12, but it is a different film from any of the polypropylene films A through G. Except as described above, the gas barrier film of Example 24 was prepared in the same manner as in Example 1.

[0056] (Example 25) A biaxially oriented polypropylene film I with a thickness of 20 μm was used as the base material 10. Polypropylene film I is a co-extruded film having two layers, a base layer 11 and a surface layer 12, but it is a different film from any of the polypropylene films A through H. Except as described above, the gas barrier film of Example 25 was prepared in the same manner as in Example 1.

[0057] (Example 26) The gas barrier film of Example 26 was prepared in the same manner as in Example 1, except that the substrate was subjected to plasma treatment with Ar gas as a pretreatment to continuously form silicon oxide.

[0058] (Example 27) A gas barrier film of Example 27 was prepared in the same manner as in Example 1, except that a 50 nm thick acrylic urethane resin layer was applied to the substrate surface as a pretreatment, in which the NCO / OH ratio of the acrylic resin containing hydroxyl groups and the isocyanate curing agent was adjusted to 1.0.

[0059] (Example 28) A biaxially oriented polypropylene film J with a thickness of 20 μm was used as the base material 10. Polypropylene film J is a co-extruded film having two layers, a base layer 11 and a surface layer 12, but it is a different film from any of the polypropylene films A through I. Except as described above, the gas barrier film of Example 28 was prepared in the same manner as in Example 1.

[0060] (Example 29) A biaxially oriented polypropylene film K with a thickness of 20 μm was used as the base material 10. Polypropylene film K is a co-extruded film having two layers, a base layer 11 and a surface layer 12, but it is a different film from any of the polypropylene films A through J. Except as described above, the gas barrier film of Example 29 was prepared in the same manner as in Example 1.

[0061] (Example 30) A biaxially oriented polypropylene film L with a thickness of 20 μm was used as the base material 10. Polypropylene film L is a co-extruded film having two layers, a base layer 11 and a surface layer 12, but it is a different film from any of the polypropylene films A through K. Except as described above, the gas barrier film of Example 30 was prepared in the same manner as in Example 1.

[0062] (Comparative Example 1) A biaxially oriented polypropylene film M with a thickness of 20 μm was used as the base material 10. The polypropylene film M is a co-extruded film having at least two layers, a base layer 11 and a surface layer 12, but is different from any of the polypropylene films A to L. A gas barrier film for Comparative Example 1 was prepared in the same manner as in Example 1, except as described above.

[0063] (Comparative Example 2) A gas barrier film of Comparative Example 2 was prepared in the same manner as in Example 3, except that polypropylene film M was used as the base material 10.

[0064] (Comparative Example 3) A biaxially oriented polypropylene film N with a thickness of 20 μm was used as the base material 10. Polypropylene film N is a co-extruded film having at least two layers, a base layer 11 and a surface layer 12, but is different from any of the polypropylene films A to M. A gas barrier film for Comparative Example 3 was prepared in the same manner as in Example 1, except for the points mentioned above.

[0065] (Comparative Example 4) A gas barrier film of Comparative Example 4 was prepared in the same manner as in Example 3, except that polypropylene film N was used as the base material 10.

[0066] (Comparative Example 5) A biaxially oriented polypropylene film O with a thickness of 20 μm was used as the base material 10. The polypropylene film O is a co-extruded film having at least two layers, a base layer 11 and a surface layer 12, but is different from any of the polypropylene films A through N. A gas barrier film for Comparative Example 5 was prepared in the same manner as in Example 1, except for the points mentioned above.

[0067] (Comparative Example 6) A gas barrier film of Comparative Example 6 was prepared in the same manner as in Example 3, except that a polypropylene film O was used as the base material 10.

[0068] (Comparative Example 7) A biaxially oriented polypropylene film P with a thickness of 20 μm was used as the base material 10. The polypropylene film P is a co-extruded film having at least two layers, a base layer 11 and a surface layer 12, but is different from any of the polypropylene films A through O. A gas barrier film for Comparative Example 7 was prepared in the same manner as in Example 1, except for the points mentioned above.

[0069] (Comparative Example 8) A gas barrier film of Comparative Example 8 was prepared in the same manner as in Example 3, except that a polypropylene film P was used as the base material 10.

[0070] (Comparative Example 9) A biaxially oriented polypropylene film Q with a thickness of 20 μm was used as the base material 10. Polypropylene film Q is a co-extruded film having at least two layers, a base layer 11 and a surface layer 12, but is different from any of the polypropylene films A through P. A gas barrier film for Comparative Example 9 was prepared in the same manner as in Example 1, except as described above.

[0071] (Comparative Example 10) A gas barrier film of Comparative Example 10 was prepared in the same manner as in Example 3, except that polypropylene film Q was used as the base material 10.

[0072] (Comparative Example 11) A biaxially oriented polypropylene film R with a thickness of 20 μm was used as the base material 10. The polypropylene film R is a co-extruded film having at least two layers, a base layer 11 and a surface layer 12, but is different from any of the polypropylene films A through Q. A gas barrier film for Comparative Example 11 was prepared in the same manner as in Example 1, except as described above.

[0073] (Comparative Example 12) A gas barrier film of Comparative Example 12 was prepared in the same manner as in Example 3, except that polypropylene film R was used as the base material 10.

[0074] (Comparative Example 13) A biaxially oriented polypropylene film S with a thickness of 20 μm was used as the base material 10. The polypropylene film S is a co-extruded film having at least two layers, a base layer 11 and a surface layer 12, but is different from any of the polypropylene films A to R. A gas barrier film for Comparative Example 13 was prepared in the same manner as in Example 1, except as described above.

[0075] (Comparative Example 14) A gas barrier film of Comparative Example 14 was prepared in the same manner as in Example 3, except that polypropylene film S was used as the base material 10.

[0076] (Comparative Example 15) A biaxially oriented polypropylene film T with a thickness of 20 μm was used as the base material 10. The polypropylene film T is a co-extruded film having at least two layers, a base layer 11 and a surface layer 12, but is different from any of the polypropylene films A to S. A gas barrier film for Comparative Example 15 was prepared in the same manner as in Example 1, except for the points mentioned above.

[0077] (Comparative Example 16) A gas barrier film of Comparative Example 16 was prepared in the same manner as in Example 3, except that a polypropylene film T was used as the base material 10.

[0078] (Comparative Example 17) A biaxially oriented polypropylene film U with a thickness of 20 μm was used as the base material 10. Polypropylene film U is a co-extruded film having at least two layers, a base layer 11 and a surface layer 12, but is different from any of the polypropylene films A to T. A gas barrier film for Comparative Example 17 was prepared in the same manner as in Example 1, except for the points mentioned above.

[0079] (Comparative Example 18) A gas barrier film of Comparative Example 18 was prepared in the same manner as in Example 3, except that polypropylene film U was used as the base material 10.

[0080] (Comparative Example 19) A gas barrier film of Comparative Example 19 was prepared in the same manner as in Example 2, except that polypropylene film U was used as the base material 10.

[0081] The evaluation items and measurement methods for each example and comparative example are shown below. (Infrared spectroscopy measurements of the first and second surfaces) The measurements were performed on both sides in the thickness direction of each substrate before the gas barrier film was fabricated, using a Fourier transform infrared spectrophotometer FT / IR-4000 (manufactured by JASCO Corporation). The measurement conditions were as follows. Measurement conditions: ATR method Prism: Ge Resolution: 4cm -1 Total number of times: 64 Furthermore, when performing the above measurements using the fabricated gas barrier film, a cross-section of the gas barrier film can be formed by cutting, and measurements of the base layer and surface layer can be performed using this cross-section.

[0082] (Surface measurement of the first surface) The following procedure was performed using each substrate before manufacturing. • Average surface roughness Sa Using a scanning probe microscope, the average surface roughness Sa was calculated by measuring a randomly selected 1 μm × 1 μm area from the first surface 10a. Measurements were performed in areas free of fine particles. • Number of particles and protrusion height The surface of the first surface 10a was observed using a laser microscope, and the number of microparticles per unit area and their protrusion height were measured. The observation magnification was 50x. The number of microparticles per unit area was measured in a randomly selected area of ​​257 μm × 259 μm (0.067 mm). 2 Measurements were taken in the first area, and two adjacent areas of the same size to its right, and the arithmetic mean of the three areas was used. The protrusion height was the arithmetic mean of all particles counted in the three areas.

[0083] (Evaluation of gas barrier layer adhesion immediately after fabrication) Test pieces were cut out from the gas barrier films of each example in accordance with JIS K 6854-2 and JIS K 6854-3, and the peel strength of the gas barrier layer 20 measured using the Orientec tensilon universal testing machine RTC-1250 was measured as an index of adhesion. The measurement was carried out for two types, T-peel and 180° peel, respectively, under normal conditions (Dry) and at the measurement site when wet (Wet).

[0084] (Evaluation of the adhesion of the gas barrier layer after heat treatment) Two gas barrier films of each example were overlapped with the sealant layer 50 facing each other, and three sides were joined by heat fusion to produce a pouch (packaging container) of each example. After filling each pouch with water as the content, the open side was sealed by heat fusion. Thereafter, as a heat treatment, retort sterilization treatment (121 °C for 30 minutes) was carried out. After the heat treatment, test pieces were cut out from the parts of each pouch in contact with the content in accordance with JIS K 6854-2 and JIS K 6854-3, and the peel strength of the gas barrier layer 20 measured using RTC-1250 was measured as an index of adhesion. The measurement was carried out for two types, T-peel and 180° peel, respectively, under normal conditions (Dry) and at the measurement site when wet (Wet).

[0085] (Evaluation of the gas barrier performance immediately after production and after heat treatment) For each pouch produced by the above procedure, immediately after production and after heat treatment, the pouch was opened and the oxygen transmission rate (OTR) (unit: cc / m 2 ·day·atm, measurement conditions: 30 °C - 70% RH), and the water vapor transmission rate (WVTR) (unit: g / m 2 ·day, measurement conditions: 40 °C - 90% RH) were evaluated.

[0086] The configurations of the examples and comparative examples are shown in Tables 1 and 2 respectively, and the evaluation results of the examples and comparative examples are shown in Tables 3 to 5 respectively.

[0087]

Table 1

[0088] [Table 2]

[0089] [Table 3]

[0090] [Table 4]

[0091] [Table 5]

[0092] In all of the gas barrier films in the examples, high adhesion between the substrate 10 and the gas barrier layer 20 was maintained even after hot water treatment. Furthermore, the oxygen permeability remained at 5.0 cc / m² even after hot water treatment. 2 • Less than 2 days, and with a water vapor transmission rate of 2.0 g / m². 2 It demonstrated good gas barrier performance for 2 days.

[0093] On the other hand, the gas barrier films of Comparative Examples 9 to 19, in which the value of equation (1) on the first surface exceeded 1.65, showed poor adhesion between the gas barrier layer 20 and the substrate after hot water treatment. In Comparative Examples 1 to 8, where the values ​​of equation (1) for both the first and second surfaces were less than 1.65, both OTR and WVTR decreased after hot water treatment. This was thought to be due to the substrate shrinking due to the hot water treatment, which damaged the gas barrier layer 20 and the coating layer 30.

[0094] Although one embodiment of the present invention and its examples have been described above, the specific configuration is not limited to this embodiment, and modifications and combinations of the configuration that do not depart from the spirit of the present invention are also included.

[0095] Furthermore, in the gas barrier film of the present invention, a printed layer may be provided at an appropriate position. In addition, an intervening film may be attached on the coating layer to impart desired physical properties to the gas barrier film, such as pinhole resistance, cold resistance, heat resistance, bag drop resistance, and tear resistance.

[0096] Furthermore, adhesive layers and sealant layers are not essential in the gas barrier film of the present invention. In other words, adhesive layers and sealant layers may be provided as needed, taking into consideration the specific application of the gas barrier film. [Explanation of symbols]

[0097] 1. Gas barrier film 10 Base material 10a Front page 10b Second side 11 Base layer 12 Surface layer 20 Gas barrier layer 30 Covering layer 40 Adhesive layer 50 sealant layer

Claims

1. A base material mainly composed of polypropylene, A gas barrier layer formed on the first surface of the substrate, A coating layer formed on the gas barrier layer, Equipped with, The first surface comprises a copolymer of propylene and ethylene, In the infrared spectroscopic measurement of the first surface, 1360–1390 cm⁻¹ －１ The peak intensity I1 present is at 1440-1480 cm. －１ A gas barrier film whose ratio to the peak intensity I2 present satisfies the following equation (1). I1 / I2≦1.60…(1)

2. The aforementioned substrate is The surface layer constituting the first surface, It has a base layer that constitutes a second surface opposite to the first surface, The value of equation (1) in the infrared spectroscopic measurement of the second surface is greater than the value of equation (1) in the first surface. The gas barrier film according to claim 1.

3. On the aforementioned first surface, fine particles made of a material other than polypropylene protrude, The number of the aforementioned fine particles is 100 or less per area with sides of 250 μm. The average protrusion height of the fine particles is 5 μm or less. The gas barrier film according to claim 1.

4. The average surface roughness Sa of the first surface is 10 nm or less. The gas barrier film according to claim 1.

5. The aforementioned gas barrier layer is mainly composed of aluminum, aluminum oxide, silicon oxide, or silicon oxide containing carbon. The gas barrier film according to claim 1.

6. The coating layer contains one or more alkoxides or their hydrolysates and a water-soluble polymer. The gas barrier film according to claim 1.

7. The material further comprises a heat-sealable sealant layer, wherein the sealant layer is bonded to the coating layer by an adhesive layer. The gas barrier film according to claim 1.

8. Oxygen permeability is 3.0 cc / m³ ２ - Less than 1 day and with a water vapor transmission rate of 1.5 g / m ２ - less than or equal to day, The peel strength between the substrate and the gas barrier layer is 1.0 N / 15 mm or more, in accordance with JIS K 6854-2 and JIS K 6854-3. The gas barrier film according to claim 1.

9. After hot water treatment at 121°C for 30 minutes, Oxygen permeability is 5.0 cc / m³ ２ - Less than 2 days and with a water vapor transmission rate of 2.0 g / m³ ２ - less than or equal to day, The peel strength between the substrate and the gas barrier layer is 1.0 N / 15 mm or more, in accordance with JIS K 6854-2 and JIS K 6854-3. The gas barrier film according to claim 1.

10. Between the first surface and the gas barrier layer, there is a pre-treatment layer made of a thermoplastic resin, a thermosetting resin, an ultraviolet curing resin, and a plasma treatment. The gas barrier film according to claim 1.

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