gas barrier film

Abstract

To provide a gas barrier film with excellent gas barrier performance as a packaging material. [Solution] The gas barrier film 1 comprises a base material 10 mainly composed of polyethylene and a gas barrier layer 30 laminated on a first surface 10a, which is one surface of the base material 10. The base material 10 has a first resin layer 11 constituting the first surface 10a, which mainly consists of one of low-density polyethylene, linear low-density polyethylene, or ultra-low-density polyethylene. The crystallinity of the base material 10 is less than 35%, calculated by measuring the diffraction angle in the range of 10° to 30° using a 2θ / θ scan measurement with a parallel beam method of X-ray diffraction, and by the ratio of the crystal peak areas of PE(110) and PE(200) to the total peak area.

Description

[Technical Field]

[0001] This invention relates to 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, pharmaceuticals, and other products, gas barrier properties are required to prevent deterioration of the contents and maintain their functions and properties. These properties include blocking oxygen, water vapor, and other gases that can alter the contents from permeating the packaging material. As a packaging material with gas barrier properties, gas barrier films are known that use metal foil such as aluminum, which is less affected by temperature and humidity, as the gas barrier layer.

[0003] Another type of gas barrier film is one in which an inorganic oxide film, such as silicon dioxide or aluminum oxide, is formed on a base layer film made of polymer material by vacuum deposition or sputtering. These gas barrier films are transparent and have gas-blocking properties against oxygen, water vapor, and other gases. Polyethylene terephthalate (PET) is commonly used as the base layer film.

[0004] Furthermore, in recent years, due to growing environmental awareness stemming from issues such as marine plastic waste, there has been a demand for even greater efficiency in the sorting, collection, and recycling of plastic waste. For this reason, there is a growing demand for gas barrier films using polypropylene (PP) or polyethylene (PE) base layer films.

[0005] Patent Document 1 below proposes a highly recyclable barrier film (laminated) using polyethylene. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-055157 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, gas barrier films such as those described in Patent Document 1, which simply have a vapor-deposited film formed as a barrier layer on a polyethylene base film, may not have sufficient gas barrier performance.

[0008] This invention has been made in view of the above-mentioned problems, and provides a gas barrier film having excellent gas barrier performance as a packaging material. [Means for solving the problem]

[0009] To achieve the above objective, the present invention employs the following means. In other words, the gas barrier film according to the present invention comprises a substrate mainly composed of polyethylene, A gas barrier film comprising a gas barrier layer laminated on a first surface, which is one surface of the substrate, wherein the substrate has a first resin layer constituting the first surface, mainly composed of low-density polyethylene, linear low-density polyethylene, and ultra-low-density polyethylene, and the degree of crystallinity of the substrate, calculated by the ratio of the crystal peak areas of PE(110) and PE(200) to the total peak area using a 2θ / θ scan measurement with a parallel beam method of X-ray diffraction in the range of diffraction angles from 10° to 30°, is less than 35%. [Effects of the Invention]

[0010] The present invention provides a gas barrier film having excellent gas barrier performance as a packaging material. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing a gas barrier film according to one embodiment of the present invention. [Figure 2]It is a cross-sectional view schematically showing a gas barrier film according to Modification 1 of the present invention. [Figure 3] It is a cross-sectional view schematically showing a gas barrier film according to Modification 2 of the present invention.

Mode for Carrying Out the Invention

[0012] A gas barrier film according to an embodiment of the present invention will be described. It is a cross-sectional view schematically showing a gas barrier film according to an embodiment of the present invention. As shown in FIG. 1, the gas barrier film 1 includes a base material 10 and a gas barrier layer 30.

[0013] The base material 10 is a film having a resin mainly composed of polyethylene. One surface of the base material 10 is defined as the first surface 10a, and the other surface of the base material 10 is defined as the second surface 10b. The gas barrier layer 30 is laminated on the first surface 10a of the base material 10.

[0014] The base material 10 has a first resin layer 11 and a second resin layer 12. The first resin layer 11 constitutes the first surface 10a. The second resin layer 12 is disposed closer to the second surface 10b side than the first resin layer 11. In the present embodiment, the second resin layer 12 is disposed adjacent to the first resin layer 11 and constitutes the second surface 10b.

[0015] The first resin layer 11 is a resin layer mainly composed of any one of low-density polyethylene, linear low-density polyethylene, and ultra-low-density polyethylene. For example, typically, the first resin layer 11 contains only any one of low-density polyethylene, linear low-density polyethylene, and ultra-low-density polyethylene as a resin component. The thickness of the first resin layer 11 is preferably in the range of 1 to 40 μm.

[0016] The second resin layer 12 is a resin layer mainly composed of polyethylene having a density of 0.930 g / cm 3 or more. For example, the second resin layer 12 has a density of 0.930 g / cm as a resin component 3A typical example is one containing only the polyethylene described above. The thickness of the second resin layer 12 is preferably in the range of 2 to 160 μm.

[0017] By configuring the base material 10 as described above, it is possible to obtain a film with sufficient tensile strength to withstand processing such as the formation of the gas barrier layer 30, and with a surface shape that is suitable for the formation of the gas barrier layer 30.

[0018] In addition, the base material 10 only needs to have at least one first resin layer 11 on the first surface 10a side, and the first resin layer 11 may be provided on both sides of the second resin layer 12. In that case, the polyethylene density may be different between one first resin layer 11 and the other first resin layer 11 with the second resin layer 12 in between. Furthermore, a different resin layer may be provided between the first resin layer 11 and the second resin layer 12. The first resin layer 11 and the second resin layer 12 are joined without the use of adhesive, and are joined by extrusion lamination using a fluid resin, or by an inflation method, etc.

[0019] There are no particular restrictions on the thickness of the base material 10. Considering the processability when forming the gas barrier layer 30 and the coating layer 60 described later, the thickness of the base material 10 is practically preferably in the range of 3 to 200 μm, and particularly preferably in the range of 6 to 90 μm. Furthermore, there are no particular restrictions on the thickness of each layer constituting the base material 10 or the ratio of the thicknesses of each layer, and they can be selected from any range.

[0020] 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, but it is preferable that they are not added to the first surface 10a of the base material 10, as they may adversely affect the formation of the gas barrier layer. 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 the additives in the base material 10 can be appropriately adjusted within a range that does not hinder the effects of this embodiment.

[0021] The base material 10 may be an unstretched film, or it may be a stretched film such as a uniaxially stretched or biaxially stretched film.

[0022] The substrate 10 is preferably measured on its first surface 10a using a 2θ / θ scan with the parallel beam method of X-ray diffraction (XRD) in the range of diffraction angles from 10° to 30°, and the degree of crystallinity calculated from the ratio of the crystal peak areas of polyethylene (110) and polyethylene (200) to the total peak area is less than 35%. By setting the degree of crystallinity of the substrate 10 to less than 35%, good adhesion can be obtained when multiple resin films are laminated.

[0023] An example of a method for measuring crystallinity is described below.

[0024] The degree of crystallinity of a resin film can be determined by performing an out-of-plane X-ray diffraction measurement using a 2θ / θ scan, which yields an X-ray diffraction pattern. When measuring resin films, it is preferable to use a method (parallel beam method) in which characteristic X-rays CuKα are used, the X-rays are parallelized using a multilayer mirror and incident on the resin film, and a scintillation detector with a flat plate collimator is used as the light receiving unit. While the focusing method is known as an X-ray diffraction method other than the parallel beam method, with the focusing method, when the sample has surface irregularities such as those of a resin film, the measurement results are easily affected by the positional displacement of the measurement surface, such as peak broadening. In contrast, with the parallel beam method, even when the sample has surface irregularities, the positional displacement of the measurement surface has little effect on the measurement results. When the resin film is a polyethylene film, it is preferable to perform scanning in the diffraction angle range of 10° to 30°. When scanning in this range, two sharp crystalline peaks and a broad amorphous peak (halo peak) corresponding to the PE(110) plane and PE(200) plane are observed. These three peaks are separated and analyzed, the areas of the crystalline and amorphous peaks are calculated, and the degree of crystallinity can be determined from equation (1). Crystallinity = Crystalline peak area / (Crystalline peak area + Amorphous peak area) ... (1) Since the surface of the resin film is not flat and there is a possibility of misalignment on the measurement surface, it is preferable to use the parallel beam method.

[0025] Crystallinity shows a certain correlation with the degree of orientation of the resin film, and tends to be lower in unstretched films, although the crystallinity of a very small number of stretched films may also fall within the above numerical range. In other words, crystallinity is a parameter independent of the general distinction between stretched and unstretched resin films.

[0026] The gas barrier layer 30 is laminated on the first surface 10a of the substrate 10. Note that, as long as the gas barrier layer 30 is laminated on the first surface 10a of the substrate 10, other layers may be interposed between the gas barrier layer 30 and the substrate 10.

[0027] The gas barrier layer 30 is an inorganic oxide layer. The gas barrier layer 30 is a layer containing one of the following: silicon oxide, silicon oxide containing carbon, silicon nitride, metallic aluminum, or aluminum oxide. The gas barrier layer 30 is a layer that exhibits barrier properties against a predetermined gas, such as oxygen or water vapor. The gas barrier layer 30 may be transparent or opaque.

[0028] The thickness of the gas barrier layer 30 varies depending on the type of components used, their composition, and the film deposition method, but it can generally be set appropriately within the range of 3 to 300 nm. If the thickness of the gas barrier layer 30 is less than 3 nm, a uniform film may not be obtained, or the film thickness may be insufficient, and the gas barrier layer may not fully perform its function. If the thickness of the gas barrier layer 30 exceeds 300 nm, cracks may form in the gas barrier layer 30 due to external factors such as bending and stretching after film deposition, potentially causing it to lose its barrier properties. A thickness of the gas barrier layer 30 is more preferably within the range of 6 to 150 nm.

[0029] There are no restrictions on the method of forming the gas barrier layer 30; for example, vacuum deposition, plasma-activated deposition, ion beam deposition, ion plating, sputtering, and plasma chemical vapor deposition (PECVD) can be used. By combining plasma-assisted methods or ion beam-assisted methods, the gas barrier layer 30 can be formed more densely, improving its barrier properties.

[0030] According to the gas barrier film 1 of this embodiment, the substrate 10 has a first surface 10a comprising a first resin layer 11 mainly composed of one of low-density polyethylene, linear low-density polyethylene, and ultra-low-density polyethylene, and a second surface 10b of the substrate 10 located on the side of the first resin layer 11 with a density of 0.930 g / cm³. 3 The substrate 10 has a second resin layer 12 mainly composed of polyethylene. The substrate 10 was measured using a 2θ / θ scan measurement with a parallel beam method of X-ray diffraction in the range of diffraction angles from 10° to 30°, and the degree of crystallinity calculated from the ratio of the crystal peak areas of PE(110) and PE(200) to the total peak area is less than 35%. Therefore, it has excellent gas barrier performance as a packaging material.

[0031] The configuration of the gas barrier film in this embodiment is not limited to the configuration described above.

[0032] (Variation 1) As shown in Figure 2, the modified gas barrier film 1A of the first example includes a pretreatment layer 20 provided between the substrate 10 and the gas barrier layer 30. The pretreatment layer 20 may be provided before forming the gas barrier layer 30 on the first surface 10a of the substrate 10. Providing the pretreatment layer 20 can improve the film-forming properties and adhesion strength of the gas barrier layer 30. There are no restrictions on the composition or formation method of the pretreatment layer 20, and it can be selected from thermoplastic resins, thermosetting resins, UV-curable resins, or plasma treatment, etc.

[0033] When a resin layer is used for the pretreatment layer 20, the content of the organic polymer in the pretreatment layer 20 may be, for example, 70% by mass or more, or 80% by mass or more. Examples of organic polymers include polyacrylic resin, polyester resin, polycarbonate resin, polyurethane resin, polyamide resin, polyolefin resin, polyimide resin, melamine resin, phenolic resin, etc. Considering the adhesion strength between the pretreatment layer 20 and the gas barrier layer 30, it is preferable that the organic polymer contains at least one of polyacrylic resin, polyol resin, polyurethane resin, polyamide resin, or reaction products of these organic polymers. The pretreatment layer 20 may also contain a silane coupling agent, organic titanate, or modified silicone oil.

[0034] More preferably, the organic polymer used in the pretreatment layer 20 is an organic polymer having a urethane bond produced by the reaction of polyols having two or more hydroxyl groups at the polymer ends with an isocyanate compound, and / or an organic polymer containing a reaction product of polyols having two or more hydroxyl groups at the polymer ends with an organic silane compound such as a silane coupling agent or its hydrolysate.

[0035] Examples of polyols include at least one selected from acrylic polyols, polyvinyl acetals, polysyl polyols, and polyurethane polyols. Acrylic polyols may be obtained by polymerizing acrylic acid derivative monomers, or by copolymerizing acrylic acid derivative monomers with other monomers. Examples of acrylic acid derivative monomers include ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. Examples of monomers copolymerized with acrylic acid derivative monomers include styrene.

[0036] The isocyanate compound enhances the adhesion between the pretreatment layer 20 and the gas barrier layer 30 through urethane bonding formed by reaction with the polyol. In other words, the isocyanate compound functions as a crosslinking agent or curing agent. Examples of isocyanate compounds include monomers such as aromatic tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), aliphatic xylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), and isophorone diisocyanate (IPDI), polymers thereof, and derivatives thereof. The above-mentioned isocyanate compounds may be used individually or in combination of two or more.

[0037] Examples of silane coupling agents include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidooxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane. The organosilane compound may be a hydrolysate of these silane coupling agents. The organosilane compound may contain one of the above-mentioned silane coupling agents and their hydrolysates alone, or in combination of two or more.

[0038] The resin layer to be provided as the pretreatment layer 20 can be formed on the first surface 10a of the substrate 10 using a mixture prepared by blending the above-mentioned components in an organic solvent in any proportion. The mixture may contain, for example, curing accelerators such as tertiary amines, imidazole derivatives, metal salt compounds of carboxylic acids, quaternary ammonium salts, and quaternary phosphonium salts; antioxidants such as phenolic, sulfuric, and phosphite-based agents; leveling agents; flow regulators; catalysts; crosslinking reaction accelerators; fillers, etc.

[0039] The mixture can be coated onto the first surface 10a of the substrate 10 using a well-known printing method such as offset printing, gravure printing, or screen printing, or a well-known coating method such as roll coating, knife edge coating, or gravure coating. After coating, the pre-treatment layer 20 can be formed by heating to, for example, 50-200°C and drying and / or curing.

[0040] The thickness of the resin layer formed as the pretreatment layer 20 may be adjusted according to the application or required properties, but is preferably 0.01 to 1 μm, and more preferably 0.01 to 0.5 μm. If the thickness of the pretreatment layer 20 is 0.01 μm or more, sufficient adhesion strength between the pretreatment layer 20 and the gas barrier layer 30 can be obtained, and the gas barrier properties will also be good. If the thickness of the pretreatment layer 20 is 1 μm or less, it is easy to form a uniform coated surface, and drying load and manufacturing costs can be suppressed.

[0041] When the pretreatment layer 20 is formed by plasma treatment, in-line plasma treatment is preferred from a productivity standpoint. The plasma treatment method is not particularly limited and can be glow discharge or other methods, 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.

[0042] (Modification 2) As shown in Figure 3, the modified gas barrier film 1B of the 2nd example includes a coating layer provided on the side of the gas barrier layer 30 facing away from the substrate 10. The coating layer 60 protects the gas barrier layer 30 and further enhances the barrier properties of the gas barrier film 1.

[0043] The coating layer 60 can be made from a thermoplastic resin, a thermosetting resin, an ultraviolet curing resin, a metal alkoxide, a water-soluble polymer, a polycarboxylic acid polymer, a polyvalent metal compound, or a polyvalent metal salt of a carboxylic acid which is a reaction product of a polycarboxylic acid polymer and a polyvalent metal compound. Metal alkoxides and water-soluble polymers, which have excellent oxygen barrier properties, are particularly preferred. This is formed using a coating agent whose main component is an aqueous solution or water / alcohol mixture containing a water-soluble polymer and one or more metal alkoxides or their hydrolysates. For example, a coating agent can be prepared by dissolving a water-soluble polymer in an aqueous solvent (water or a water / alcohol mixture) and mixing it with a metal alkoxide, either directly or after being treated by hydrolysis. After applying this coating agent onto the gas barrier layer 30, the coating layer 60 can be formed by drying.

[0044] The components of the coating agent used to form the coating layer 60 will be described in more detail. Examples of water-soluble polymers used in the coating agent include polyvinyl alcohol (PVA), polyvinylpyrrolidone, starch, methylcellulose, carboxymethylcellulose, and sodium alginate. In particular, PVA is preferred because it provides excellent gas barrier properties. PVA is generally obtained by saponifying polyvinyl acetate. As PVA, either so-called partially saponified PVA, in which several tens of percent of acetate groups remain, or fully saponified PVA, in which only a few percent of acetate groups remain, can be used. PVA intermediate between the two may also be used.

[0045] Metal alkoxides used as coating agents are compounds that can be represented by the general formula M(OR)n (M: metal such as Si or Al, R: alkyl group such as CH3 or C2H5). Specifically, examples include tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum Al[OCH(CH3)2]3. Examples of silane coupling agents include those having epoxy groups such as 3-glycidoxypropyltrimethoxysilane, those having amino groups such as 3-aminopropyltrimethoxysilane, those having mercapto groups such as 3-mercaptopropyltrimethoxysilane, those having isocyanate groups such as 3-isocyanatetopropyltriethoxysilane, and tris-(3-trimethoxysilylpropyl)isocyanurate.

[0046] Polycarboxylic acid polymers are polymers having two or more carboxyl groups in their molecules. Examples of polycarboxylic acid polymers include (co)polymers of ethylenically unsaturated carboxylic acids; copolymers of ethylenically unsaturated carboxylic acids with other ethylenically unsaturated monomers; and acidic polysaccharides having carboxyl groups in their molecules, such as alginic acid, carboxymethylcellulose, and pectin. Examples of ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of ethylenically unsaturated monomers copolymerizable with ethylenically unsaturated carboxylic acids include ethylene, propylene, vinyl acetate and other saturated vinyl carboxylic acid esters, alkyl acrylates, alkyl methacrylates, alkyl itaconates, vinyl chloride, vinylidene chloride, styrene, acrylamide, and acrylonitrile. These polycarboxylic acid polymers may be used individually or in combination of two or more types.

[0047] From the viewpoint of gas barrier properties, polymers containing structural units derived from at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, itaconic acid, fumaric acid, and crotonic acid are preferred, and polymers containing structural units derived from at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, and itaconic acid are particularly preferred. In the above polymer, the proportion of structural units derived from at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, and itaconic acid is preferably 80 mol% or more, and more preferably 90 mol% or more (provided that the total of all structural units constituting the polymer is 100 mol%). This polymer may be a homopolymer or a copolymer. If the polymer is a copolymer containing structural units other than the above structural units, examples of other structural units include structural units derived from ethylenically unsaturated monomers copolymerizable with the aforementioned ethylenically unsaturated carboxylic acids.

[0048] The number-average molecular weight of the polycarboxylic acid polymer is preferably in the range of 2,000 to 10,000,000, and more preferably in the range of 5,000 to 1,000,000. If the number-average molecular weight is less than 2,000, the water resistance of the gas barrier film may be insufficient depending on the application, and moisture may cause deterioration of gas barrier properties and transparency, or whitening may occur. On the other hand, if the number-average molecular weight exceeds 10,000,000, the viscosity of the coating agent may increase, impairing the coating properties. In this embodiment, the number-average molecular weight is the number-average molecular weight on a polystyrene basis, determined by gel permeation chromatography (GPC).

[0049] Various additives can be added to coating agents primarily composed of polycarboxylic acid polymers, including crosslinking agents, curing agents, leveling agents, defoaming agents, antiblocking agents, antistatic agents, dispersants, surfactants, softeners, stabilizers, film-forming agents, and thickeners, as long as they do not impair the barrier performance.

[0050] For coating agents mainly composed of polycarboxylic acid polymers, an aqueous medium is preferred as the solvent. Examples of aqueous mediums include water, water-soluble or hydrophilic organic solvents, or mixtures thereof. The aqueous medium is usually water or mainly composed of water. The water content in the aqueous medium is preferably 70% by mass or more, and more preferably 80% by mass or more. Examples of water-soluble or hydrophilic organic solvents include alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran; cellosolves; carbitols; and nitriles such as acetonitrile.

[0051] The polyvalent metal compound is not particularly limited as long as it is a compound that reacts with the carboxyl group of the polycarboxylic acid polymer to form a polyvalent metal salt of the polycarboxylic acid, and examples include zinc oxide particles, magnesium oxide particles, magnesium methoxide, copper oxide, and calcium carbonate. These may be used individually or in combination. From the viewpoint of the oxygen barrier properties of the oxygen barrier film, zinc oxide particles are preferred among the above. Zinc oxide is an inorganic material that has ultraviolet light absorption ability. The average particle size of zinc oxide particles is not particularly limited, but from the viewpoint of gas barrier properties, transparency, and coating suitability, the average particle size is preferably 5 μm or less, more preferably 1 μm or less, and particularly preferably 0.1 μm or less.

[0052] When applying and drying a coating agent mainly composed of polyvalent metal compounds to form a film, various additives may be included in addition to zinc oxide particles as needed, to the extent that they do not impair the effects of this embodiment. These additives may include resins soluble or dispersible in the solvent used in the coating agent, dispersants soluble or dispersible in the solvent, surfactants, softeners, stabilizers, film-forming agents, thickeners, etc. Among these, it is preferable to include a resin soluble or dispersible in the solvent used in the coating agent. This improves the coating properties and film-forming properties of the coating agent. Examples of such resins include alkyd resins, melamine resins, acrylic resins, urethane resins, polyester resins, phenolic resins, amino resins, fluororesins, epoxy resins, and isocyanate resins. It is also preferable to include a dispersant soluble or dispersible in the solvent used in the coating agent. This improves the dispersibility of the polyvalent metal compounds. Anionic surfactants or nonionic surfactants can be used as the dispersant. Examples of such surfactants include (poly)carboxylates, alkyl sulfates, alkylbenzene sulfons, alkylnaphthalene sulfons, alkyl sulfosuccinates, alkyl diphenyl ether disulfons, alkyl phosphates, aromatic phosphates, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, alkyl allyl sulfates, polyoxyethylene alkyl phosphates, sorbitan alkyl esters, glycerin fatty acid esters, sorbitan fatty acid esters, sucrose fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene sorbitan alkyl esters, polyoxyethylene alkyl allyl ethers, polyoxyethylene derivatives, polyoxyethylene sorbitol fatty acid esters, polyoxy fatty acid esters, and polyoxyethylene alkylamines. These surfactants may be used individually or in combination of two or more.When a coating agent mainly composed of a polyvalent metal compound contains additives, the mass ratio of the polyvalent metal compound to the additive (polyvalent metal compound:additive) is preferably in the range of 30:70 to 99:1, and preferably in the range of 50:50 to 98:2.

[0053] Examples of solvents used in coating agents mainly composed of polyvalent metal compounds include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used individually or in combination of two or more. Among these, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred from the viewpoint of coating properties. Furthermore, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred from the viewpoint of manufacturability.

[0054] When a coating agent mainly composed of a polycarboxylic acid polymer is applied and dried to form a film, and then a film of a polyvalent metal compound is formed, some of the carboxyl groups of the polycarboxylic acid polymer may be neutralized in advance with a basic compound. By neutralizing some of the carboxyl groups of the polycarboxylic acid polymer in advance, the water resistance and heat resistance of the film made of the polycarboxylic acid polymer can be further improved. As the basic compound, at least one basic compound selected from the group consisting of the above-mentioned polyvalent metal compounds, monovalent metal compounds, and ammonia is preferred. Examples of monovalent metal compounds include sodium hydroxide and potassium hydroxide.

[0055] When applying and drying a coating agent that is a mixture of a polycarboxylic acid polymer and a polyvalent metal compound to form a film, the coating agent is prepared by mixing the polycarboxylic acid polymer, the polyvalent metal compound, water or alcohols as a solvent, a resin or dispersant that can be dissolved or dispersed in the solvent, and additives as needed. The coating layer 60 can also be formed by applying and drying such a coating agent using a known coating method.

[0056] Examples of coating methods for the coating layer 60 include the casting method, dipping method, roll coating method, gravure coating method, screen printing method, reverse coating method, spray coating method, kit coating method, die coating method, metering bar coating method, chamber doctor combined coating method, and curtain coating method.

[0057] The thickness of the coating layer 60 varies depending on the composition of the coating agent used and the coating conditions, and there are no particular restrictions. However, if the drying thickness of the coating layer 60 is less than 0.01 μm, a uniform coating film may not be formed, and sufficient gas barrier properties may not be obtained. If the drying thickness exceeds 50 μm, cracks are more likely to occur in the coating layer 60. Therefore, a suitable thickness for the coating layer 60 is, for example, in the range of 0.01 to 50 μm, and the optimal thickness for the coating layer 60 is, for example, in the range of 0.1 to 10 μm.

[0058] The gas barrier film 1 of this embodiment, having the above configuration, exhibits high gas barrier properties, while its main resin component is polyethylene, and it is easy to make the ratio of the main resin component to the gas barrier film 1 90% by mass or more. In other words, the gas barrier film 1 can be constructed as a highly recyclable monomaterial.

[0059] When manufacturing packaging materials such as packaging bags using the gas barrier film 1, if a heat-sealable heat-seal layer 50 is further provided on the gas barrier layer 30, the packaging material can be easily manufactured by heat-sealing the heat-seal layers together. In this case as well, by using polyethylene as the main resin component of the heat-seal layer 50, the packaging material can be made from a single material. If a coating layer 60 is provided, the heat-seal layer 50 should be provided on the surface of the coating layer 60 that faces away from the base material 10. In addition, other layers may be provided between the heat-seal layer 50 and the gas barrier layer 30 or the coating layer 60 as appropriate.

[0060] The heat seal layer 50 is made of the same polyethylene as the base material 10, making it recyclable. For the polyethylene resin used in the heat seal layer 50, it is preferable to use low-density polyethylene or linear low-density polyethylene because it is easily heat-sealed. The thickness of the heat seal layer 50 can be determined according to the purpose, but can be, for example, about 50 to 200 μm. The heat seal layer 50 is laminated on the gas barrier layer 30 or coating layer 60 via an adhesive layer 40 made of adhesive.

[0061] A known dry laminating adhesive can be used for the adhesive layer 40. While not particularly limited, examples of dry laminating adhesives include two-component curing ester-based adhesives, ether-based adhesives, and urethane-based adhesives. The heat seal layer 50 may also be laminated by extrusion lamination using a fluid resin.

[0062] A gas barrier adhesive may be used for the adhesive layer 40. Applying a gas barrier adhesive to the adhesive layer 40 can further improve the gas barrier properties. The oxygen permeability of the gas barrier adhesive is 150 cc / m². 2 It is preferable that the pressure be less than or equal to 100cc / m³. 2 It is more preferable that it be less than or equal to 80cc / m². 2 It is even more preferable that it be less than or equal to 50cc / m². 2It is particularly preferable that the oxygen permeability is below day·atm. By having the oxygen permeability within the above range, the gas barrier properties of the gas barrier film can be sufficiently improved, and even if minor cracks occur in the gas barrier layer 30, the gas barrier adhesive can fill the gaps and compensate for them, thereby suppressing a decrease in gas barrier properties.

[0063] A gas barrier adhesive can be any adhesive that exhibits gas barrier properties after curing, such as epoxy adhesives or polyester / polyurethane adhesives. Specific examples include "Maxive" from Mitsubishi Gas Chemical Company and "Paslim" from DIC Corporation.

[0064] The thickness of the adhesive layer 40 is preferably 0.1 to 20 μm, more preferably 0.5 to 10 μm, and even more preferably 1 to 5 μm. When the thickness of the adhesive layer 40 is greater than or equal to the lower limit, cushioning properties that mitigate external impacts can be obtained, preventing the gas barrier layer 30 from cracking due to impact. On the other hand, when the thickness of the adhesive layer 40 is less than or equal to the upper limit, the flexibility of the gas barrier laminate tends to be sufficiently maintained.

[0065] In addition to the above conditions, it is particularly preferable that the thickness of the adhesive layer 40 be 50 times or more the thickness of the gas barrier layer 30. By satisfying the above conditions for the thickness of the adhesive layer 40, cracking of the gas barrier layer 30 can be more effectively suppressed, and if a gas barrier adhesive is used for the adhesive layer 40, the gas barrier properties of the gas barrier film 1 can be further improved. Furthermore, by satisfying the above conditions for the thickness of the adhesive layer 40, the cushioning properties that mitigate external impacts can be further enhanced, preventing the gas barrier layer 30 from cracking due to impact. On the other hand, from the viewpoint of maintaining the flexibility of the gas barrier film 1, processability, and cost, it is preferable that the thickness of the adhesive layer 40 be 300 times or less the thickness of the gas barrier layer 30.

[0066] The adhesive for forming the adhesive layer 40 can be applied by methods such as bar coating, dipping, roll coating, gravure coating, reverse coating, air knife coating, comma coating, die coating, screen printing, spray coating, and gravure offset. The temperature at which the coating film is dried can be, for example, 30 to 200°C, and preferably 50 to 180°C. The temperature at which the coating film is cured can be, for example, room temperature (27°C) to 70°C, and preferably 30 to 60°C. By keeping the drying and curing temperatures within the above ranges, the occurrence of cracks in the gas barrier layer 30 and the adhesive layer 40 can be further suppressed, and excellent gas barrier properties can be achieved.

[0067] From the viewpoint of preventing cracking of the gas barrier layer 30, it is more preferable that the adhesive layer 40 and the gas barrier layer 30 are in direct contact. Therefore, it is preferable to form the adhesive by applying it onto the gas barrier layer 30 and allowing it to dry and harden.

[0068] A printing layer can be provided on the base material 10 or the heat-seal layer 50. Generally, the printing layer is provided in a position visible from the outside of the gas barrier film for the purpose of displaying information about the contents, identifying the contents, or improving the design of the packaging bag. The printing method and printing ink are not particularly limited and are appropriately selected from known printing methods and printing inks, taking into consideration suitability for printing on the film, design such as color tone, adhesion, and safety as a food container. Examples of printing methods that can be used include gravure printing, offset printing, gravure offset printing, flexographic printing, and inkjet printing. Among these, gravure printing is preferred from the viewpoint of productivity and high resolution of the image. The printing layer may or may not be provided depending on the intended use.

[0069] To improve the adhesion of the printed layer, various pretreatments such as corona treatment, plasma treatment, and flame treatment, as well as coating layers such as easy-adhesion layers, may be applied to the surface of the layer forming the printed layer.

[0070] On the second surface 10b side, which is the side opposite to the first surface 10a of the base material 10, a printing base material may be bonded as the second base material 70. By using the same polyethylene as the base material 10 for the material of the second base material 70, recycling becomes possible. On the second surface 10b of the base material, various pre-treatments such as corona treatment, plasma treatment, frame treatment, etc., or a coating layer such as an easy-adhesion layer may be provided to enhance the adhesion to the second base material 70. Dry lamination or extrusion lamination using a known adhesive for dry lamination can be used. Specifically, the base material 10 and the second base material 70 can be adhered via the aforementioned adhesive layer 40.

[0071] The oxygen permeability of the gas barrier film 1 is 3.0 cc / (m 2 ·day·atm) or less, and the water vapor permeability is 3.0 g / (m 2 ·day) or less.

[0072] The gas barrier film of the present embodiment will be further described using examples and comparative examples. The present invention is not limited by the specific contents of the examples and comparative examples.

[0073] (Example 1) On both sides of a resin layer mainly composed of polyethylene with a density of 0.948 g / cm 3 a resin layer mainly composed of low-density polyethylene with a density of 0.926 g / cm 3 was laminated, and a film (thickness 30 μm) with a crystallinity of 13.5% was used as the base material 10. In a vacuum device, SiO was sublimated, and a gas barrier layer 30 (film thickness 30 nm) made of silicon oxide (SiOx) was formed on the first surface 10a of the base material 10 by electron beam evaporation.

[0074] Next, adhesive A, an epoxy adhesive, was prepared on the gas barrier layer 30 by mixing 23 parts by mass of a solvent (ethyl acetate and methanol in a 1:1 mass ratio) with 16 parts by mass of Maxive C93T manufactured by Mitsubishi Gas Chemical Co., Ltd. and 5 parts by mass of Maxive M-100 manufactured by Mitsubishi Gas Chemical Co., Ltd. to form an adhesive layer 40. A heat seal layer 50, LLDPE film MC-S (60 μm thick) from Tosello Co., Ltd., was laminated via adhesive A. Based on the above, the gas barrier film 1 of Example 1 was prepared.

[0075] (Example 2) The gas barrier film 2 of Example 2 was fabricated in the same manner as in Example 1, except that the thickness of the gas barrier layer 30 was set to 40 nm.

[0076] (Example 3) Density of base material 10: 0.946 g / cm³ 3 A film (40 μm thick) with a crystallinity of 23.0% was used, in which a resin layer mainly composed of linear low-density polyethylene was laminated on both sides of a resin layer mainly composed of polyethylene. A thermosetting resin layer was prepared as a pretreatment layer 20 on the first surface 10a of the substrate 10. The thermosetting resin layer was prepared by mixing an acrylic polyol and tolylene diisocyanate such that the number of NCO groups of tolylene diisocyanate was equal to the number of OH groups of the acrylic polyol, and then diluting it with ethyl acetate so that the total solids content (total amount of acrylic polyol and tolylene diisocyanate) was 5% by mass. To the diluted mixture, β-(3,4-epoxycyclohexyl)trimethoxysilane was added in an amount of 5 parts by mass per 100 parts by mass of the total amount of acrylic polyol and tolylene diisocyanate, and these were mixed to prepare the layer. The thermosetting resin was applied to the first surface 10a by gravure coating, dried, and cured to form a thermosetting resin layer. Furthermore, a gas barrier layer 30 (thickness: 10 nm) made of silicon dioxide (SiOx) was formed on the pretreatment layer 20. The gas barrier film 1 of Example 3 was fabricated in the same manner as in Example 1.

[0077] (Example 4) The density of base material 10 is 0.940 g / cm³. 3 A film (30 μm thick) was used in which a resin layer mainly composed of linear low-density polyethylene was laminated on the first surface 10a side of a resin layer mainly composed of polyethylene, and the degree of crystallinity was 33.2%. Plasma treatment with Ar gas at 100 W·sec / m² is performed on the first surface 10a of the substrate 10, which is laminated with a resin layer mainly composed of polyethylene, as a pretreatment layer 20. 2 The process was carried out at the specified treatment intensity. Furthermore, a gas barrier layer 30 (film thickness: 40 nm) made of silicon dioxide (SiOx) was formed on the pre-treatment layer 20. The gas barrier film 1 of Example 4 was fabricated in the same manner as in Example 3. The calculation of the plasma treatment intensity is as follows. Power density [W / m 2 ] = Input power [W] / Cathode area [m²] 2 ] Processing time [sec] = Electrode MD width [m] / Processing speed [m / sec] Processing power = Power density [W / m²] 2 Processing time [sec]

[0078] (Example 5) A coating agent, obtained by mixing liquids (1) and (2) below in a weight ratio of 6:4, was applied to the gas barrier layer 30 by gravure coating and dried to form a coating layer 60 with a thickness of 0.4 μm. A heat seal layer 50 was then bonded to the gas barrier layer 40 using a two-component curing polyurethane adhesive by dry lamination, and the thickness of the gas barrier layer 30, which is made of silicon dioxide (SiOx), was set to 25 nm. Except for these differences, the gas barrier film 1 of Example 5 was prepared in the same manner as in Example 1. (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)

[0079] (Example 6) The gas barrier film 1 of Example 6 was prepared in the same manner as in Example 1, except that a gas barrier layer (thickness 9 nm) made of aluminum oxide (AlOx) was formed as the gas barrier layer 30 by electron beam deposition.

[0080] (Example 7) The gas barrier film 1 of Example 7 was prepared in the same manner as in Example 3, except that a gas barrier layer (thickness 20 nm) made of aluminum oxide (AlOx) was formed as the gas barrier layer 30 by electron beam deposition.

[0081] (Example 8) The gas barrier film 1 of Example 8 was prepared in the same manner as in Example 5, except that a gas barrier layer (thickness 3 nm) made of aluminum oxide (AlOx) was formed as the gas barrier layer 30 by electron beam deposition.

[0082] (Example 9) The gas barrier film of Example 9 was prepared in the same manner as in Example 1, except that a gas barrier layer (thickness 10 nm) made of metallic aluminum (Al) was formed as the gas barrier layer 30 by electron beam deposition.

[0083] (Example 10) The gas barrier film of Example 10 was fabricated in the same manner as in Example 1, except that hexamethyldisiloxane (HMDSO) was introduced into a vacuum apparatus as the gas barrier layer 30, and a gas barrier layer (thickness 30 nm) made of silicon oxide containing carbon (SiOxCy) was formed by plasma CVD.

[0084] (Example 11) The gas barrier film of Example 11 was fabricated in the same manner as in Example 1, except that monosilane (SiH4), ammonia (NH3), and nitrogen (N2) were introduced into a vacuum apparatus as the gas barrier layer 30, and a gas barrier layer (thickness 30 nm) made of silicon nitride (SiNx) was formed by plasma CVD.

[0085] (Example 12) Plasma treatment with Ar gas is performed on the second surface 10b of the substrate 10 at 100 W·sec / m 2 After performing the treatment with the specified strength, a two-component curing polyurethane adhesive was used as the adhesive layer 40, and an HDPE film was laminated as the second substrate 70 by dry lamination. The gas barrier film 1 of Example 12 was prepared in the same manner as in Example 1 otherwise. (Comparative Example 1) Density of base material 10: 0.946 g / cm³ 3 A gas barrier film of Comparative Example 1 was prepared in the same manner as in Example 1, except that it consisted only of a polyethylene-based resin layer and used a film (32 μm thick) with a crystallinity of 14.9%.

[0086] (Comparative Example 2) Density of base material 10: 0.928 g / cm³ 3 A gas barrier film for Comparative Example 2 was prepared in the same manner as in Example 1, except that it consisted only of a polyethylene-based resin layer and used a film (30 μm thick) with a crystallinity of 79.2%.

[0087] The evaluation items and measurement methods for each example and comparative example are described below.

[0088] (Measuring the degree of crystallinity of PE films and laminates) The crystallinity of PE films and laminates was measured using a Rigaku ATX-G X-ray diffractometer, and X-ray diffraction patterns were obtained using the out-of-plane method. The obtained X-ray diffraction patterns were separated into three peaks: amorphous PE, PE(110), and PE(200). The area intensity of each peak was analyzed, and the aforementioned crystallinity was calculated.

[0089] (Evaluation of gas barrier properties of laminates) (Oxygen transmission rate: OTR) The oxygen permeability of the laminate was measured under conditions of 30°C and 70% RH (relative humidity) using the Mocon method. (Water vapor transmission rate: WVTR) The water vapor transmission rate of the laminate was measured under conditions of 40° and 90% RH using the Mocon method.

[0090] Table 1 shows the structure of the laminate and the evaluation results.

[0091] [Table 1]

[0092] In Examples 1 to 12, the substrate 10 had a density of 0.930 g / cm³. 3 A resin mainly composed of low-density polyethylene, linear low-density polyethylene, or ultra-low-density polyethylene was laminated on at least one side of the polyethylene-based resin layer described above, and since the degree of crystallinity was less than 35%, good gas barrier properties were confirmed.

[0093] In Comparative Example 1, the substrate 10 had a density of 0.930 g / cm³. 3 Because the polyethylene film consisted only of the resin layers described above, its gas barrier properties were inferior to those of Examples 1 to 12.

[0094] In Comparative Example 2, the substrate 10 had a density of 0.930 g / cm³. 3 The polyethylene film consisted only of a resin layer of less than 35%, and furthermore, its crystallinity was 35% or higher, resulting in inferior gas barrier properties compared to Examples 1 to 12.

[0095] 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 are also included without departing from the spirit of the present invention. [Industrial applicability]

[0096] The gas barrier film of the present invention is suitable for use mainly as a packaging material because it has high recyclability as a polyethylene material, exhibits excellent gas barrier properties, and has good tear resistance. [Explanation of symbols]

[0097] 1. Gas barrier film 10 Base material 10a Front page 10b Second side 11 First resin layer 12 Second resin layer 20 Pre-treatment layer 30 Gas barrier layer 40 Adhesive layer 50 Heat seal layers 60 Covering layer

Claims

1. A base material mainly composed of polyethylene, A gas barrier film comprising a gas barrier layer laminated on a first surface, which is one surface of the substrate, The aforementioned substrate is The first surface comprises a first resin layer mainly composed of one of low-density polyethylene, linear low-density polyethylene, and ultra-low-density polyethylene, The substrate is a gas barrier film in which the degree of crystallinity, calculated by measuring the diffraction angle in the range of 10° to 30° using a 2θ / θ scan measurement with a parallel beam method of X-ray diffraction, is less than 35% based on the ratio of the crystal peak areas of PE(110) and PE(200) to the total peak area.

2. The aforementioned substrate is The first resin layer has a second resin layer on the side opposite to the gas barrier layer, The second resin layer has a density of 0.930 g / cm³. ３ A gas barrier film according to claim 1, mainly comprising polyethylene as described above.

3. The aforementioned substrate is The first resin layer has a second resin layer on the side opposite to the gas barrier layer, The second resin layer has a density of 0.940 g / cm³. ３ A gas barrier film according to claim 1, mainly comprising polyethylene as described above.

4. The gas barrier film according to any one of claims 1 to 3, wherein no antiblocking agent is added to the first surface of the substrate.

5. The gas barrier film according to any one of claims 1 to 4, wherein the gas barrier layer is an inorganic oxide layer.

6. The gas barrier film according to claim 5, wherein the inorganic oxide layer contains any of silicon oxide, carbon-containing silicon oxide, silicon nitride, metallic aluminum, and aluminum oxide.

7. A gas barrier film according to any one of claims 1 to 6, comprising a pretreatment layer provided between the substrate and the gas barrier layer.

8. A gas barrier film according to any one of claims 1 to 7, comprising a coating layer provided on the surface of the gas barrier layer facing away from the substrate.

9. The gas barrier film according to claim 8, wherein the coating layer contains any of the following: a metal alkoxide, a hydrolysate of a metal alkoxide, a water-soluble polymer, a polycarboxylic acid polymer, a polyvalent metal compound, and a polyvalent metal salt of a carboxylic acid which is a reaction product of a polycarboxylic acid polymer and a polyvalent metal compound.

10. A gas barrier film according to any one of claims 1 to 7, wherein a heat seal layer is laminated via an adhesive on the surface of the gas barrier layer facing away from the substrate.

11. The gas barrier film according to claim 8 or 9, wherein a heat-seal layer is laminated via an adhesive on the surface of the coating layer facing away from the substrate.

12. The gas barrier film according to claim 10 or 11, wherein the adhesive is a gas barrier adhesive.

13. The gas barrier film according to any one of claims 10 to 12, wherein the heat seal layer is low-density polyethylene or linear low-density polyethylene.

14. The gas barrier film according to any one of claims 1 to 13, wherein the proportion of polyethylene in the gas barrier film is 90% by mass or more.

15. The oxygen permeability of the gas barrier film is 3.0 cc / (m²). ２ The humidity is less than or equal to (day / atm), and the water vapor transmission rate is 3.0 g / (m³). ２ A gas barrier film according to any one of claims 1 to 14, wherein the number of days is less than or equal to the number of days.

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