JP2022107930A - Gas barrier films, laminates, and packaging materials - Google Patents

Abstract

To provide a laminate that has sufficient impact resistance when applied to a package, a standing pouch or the like, and can be easily recycled.SOLUTION: There is provided a gas barrier film 1 that comprises: a base material 10; an underlying layer 20 or an inorganic oxide layer 30 formed on a first surface 10a of the base material; and an oxygen barrier film 40 formed on the underlying layer or on the inorganic oxide layer. In the gas barrier film 1, a sum of the difference between maximum and minimum values of thermal strain in a MD direction when a thermal history of 20 to 120°C temperature rise and 120 to 20°C temperature drop is given and the difference between maximum and minimum values of the thermal strain in a TD direction is 0.03 or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to gas barrier films. Laminates and packaging materials using this gas barrier film are also referred to.

Packaging materials used for packaging food, pharmaceuticals, etc. are designed to prevent the ingress of gases (water vapor, oxygen, etc.) that denature the contents in order to prevent deterioration and putrefaction of the contents and maintain their functions and quality. It is required to have the property of preventing Therefore, film materials having gas barrier properties (gas barrier films) are used for these packaging materials.

As a gas barrier film, a film in which a gas barrier layer made of a material having gas barrier properties is provided on the surface of a resin substrate is known. As the gas barrier layer, a metal foil, a metal deposition film, and a film formed by a wet coating method are known. As a film, a resin film formed from a coating agent containing a resin such as a water-soluble polymer or polyvinylidene chloride, or a coating agent containing a water-soluble polymer and an inorganic layered mineral, which exhibits oxygen barrier properties. is known (Patent Document 1). Furthermore, as a gas barrier layer, a vapor deposition thin film layer made of an inorganic oxide and a gas barrier composite coating containing an aqueous polymer, an inorganic layered compound, and a metal alkoxide are successively laminated (Patent Document 2), and a polycarboxylic acid-based polymer is used. A gas barrier layer containing a polyvalent metal salt of a carboxylic acid that is a reaction product of a combined carboxyl group and a polyvalent metal compound has been proposed (Patent Document 3).

In order to improve the gas barrier properties, for example, Patent Document 4 discloses a gas barrier film in which a coating is formed on at least one surface of a substrate, and the surface roughness parameter Rt/Ra of the surface of the coating is 20 or less. is proposed. Here, Rt is the distance between the maximum peak and the deepest valley of the surface roughness curve. Ra is the center line average roughness. According to the gas barrier film of Patent Document 4, an improvement in gas barrier properties is achieved.

Japanese Patent No. 6191221 JP-A-2000-254994 Japanese Patent No. 4373797 JP-A-9-150484

A gas barrier film having a film formed on the surface of a base material by a wet coating method, a vapor deposition method, or a sputtering method may cause cracks due to dimensional change or stress, resulting in deterioration of the barrier property. When the base material is a polyolefin-based material such as OPP (biaxially oriented polypropylene) or PE (polyethylene), the Young's modulus is low and the dimensional change due to heating is large, which tends to cause such problems. In particular, when a gas barrier film is used as a packaging material for retort pouches, the gas barrier properties are likely to be deteriorated because the treatment is performed at a high temperature.

In view of the above circumstances, an object of the present invention is to provide a gas barrier film whose barrier properties are less likely to deteriorate even when subjected to high temperature treatment.

A first aspect of the present invention comprises a substrate, an underlayer or an inorganic oxide layer formed on the first surface of the substrate, and an oxygen barrier coating formed on the underlayer or the inorganic oxide layer. and a gas barrier film.
The difference between the maximum and minimum values of thermal strain in the MD direction and the maximum The sum of the difference between the value and the minimum value is 0.03 or less.

A second aspect of the present invention is a laminate comprising the gas barrier film according to the first aspect and a heat-sealable layer formed on the oxygen barrier film.
A third aspect of the present invention is a packaging material formed using the laminate according to the second aspect.

ADVANTAGE OF THE INVENTION According to this invention, the gas-barrier film which is hard to deteriorate even if it receives the process at a high temperature can be provided.

1 is a schematic cross-sectional view of a laminate according to one embodiment of the present invention; FIG. It is an enlarged photograph after retort processing of the packaging material concerning a comparative example.

An embodiment of the present invention will be described below with reference to FIG.
FIG. 1 is a schematic cross-sectional view of a gas barrier film 1 according to this embodiment. The gas barrier film 1 has a resin-containing substrate 10 , a base layer 20 , an inorganic oxide layer 30 , and an oxygen barrier coating 40 .

The underlying layer 20 is formed on the base material 10 . The inorganic oxide layer 30 is formed on the underlying layer 20 . The oxygen barrier coating 40 is formed on the inorganic oxide layer 30 .
In the gas barrier film according to this embodiment, one of the underlying layer 20 and the inorganic oxide layer 30 may be omitted. In this case, the inorganic oxide layer 30 may be formed on the base material 10 or the oxygen barrier coating 40 may be formed on the underlying layer 20 .

Examples of the resin constituting the base material 10 include olefin resins such as polyethylene, polypropylene, olefin polymers having 2 to 10 carbon atoms, and propylene-ethylene copolymer; polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and the like. polyester resins; aliphatic polyamides such as nylon 6 and nylon 66; polyamide resins such as aromatic polyamides such as polymetaxylylene adipamide; polystyrene, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol , vinyl resins such as ethylene-vinyl alcohol copolymers; acrylic resins such as homo- or copolymers of (meth)acrylic monomers such as polymethyl methacrylate and polyacrylonitrile; cellophane; engineering of polycarbonates, polyimides, etc. A plastic etc. are mentioned. These resins may be used individually by 1 type, and may use 2 or more types together.

The base material 10 may be either a single-layer film made of a single resin, or a single-layer or laminated film using a plurality of resins. Moreover, the various resins described above may be laminated on other base materials (metal, wood, paper, ceramics, etc.). The substrate 10 may be a single layer or two or more layers.
Among them, polyolefin resin films (especially polypropylene films), polyester resin films (especially polyethylene terephthalate resin films), polyamide resin films (especially nylon films), and the like are preferable as the substrate 10 .

The substrate 10 may be an unstretched film, or may be a stretched film such as a uniaxially stretched or biaxially stretched film. An OPP film is particularly preferable as the substrate 10 from the viewpoint of excellent water vapor barrier properties. The OPP film may be a film made of at least one polymer selected from homopolymers, random copolymers and block copolymers. A homopolymer is a polypropylene consisting of propylene alone. Random copolymers are polypropylenes in which the main monomer, propylene, and a small amount of comonomers different from propylene are randomly copolymerized to form a homogenous phase. A block copolymer is a polypropylene that forms a heterogeneous phase by block copolymerization or rubber-like polymerization of propylene, which is the main monomer, and the above comonomer. When the substrate 10 contains OPP, the OPP may be one layer or two or more layers.

In the substrate 10, the first surface 10a on which the base layer 20 or the inorganic oxide layer 30 is formed may be subjected to surface treatment such as chemical treatment, solvent treatment, corona treatment, low-temperature plasma treatment, ozone treatment, etc. good. Adhesion with the base layer and the inorganic oxide layer formed by this can be improved.

The substrate 10 may contain additives such as fillers, antiblocking agents (hereinafter sometimes referred to as "AB agents"), antistatic agents, plasticizers, lubricants, antioxidants, and the like. Any one of these additives may be used alone, or two or more thereof may be used in combination.

The AB agent is solid particles such as organic particles and inorganic particles. Examples of organic particles include polymethyl methacrylate particles, polystyrene particles, and polyamide particles. These organic particles are obtained by, for example, emulsion polymerization or suspension polymerization. Examples of inorganic particles include silica particles, zeolite, talc, kaolinite, and feldspar. Any one of these AB agents may be used alone, or two or more thereof may be used in combination.

When the base material 10 contains the AB agent, unevenness derived from the AB agent is generated on the first surface 10a. That is, a part of the AB agent particles protrudes from the first surface 10a, thereby reducing the contact area when the substrate is wound into a roll. As a result, the occurrence of blocking is suppressed, and the blocking resistance of the substrate 10 can be improved.

From the above point of view, the base material 10 preferably contains an AB agent. On the other hand, when a large convex portion is formed on the first surface 10a of the substrate 10, the base layer 20, the inorganic oxide layer 30, the oxygen barrier coating 40, etc. formed thereon become a path for gas permeation. Defects are likely to occur, and the oxygen barrier properties of the gas barrier film 1 may be lowered.
Considering this point and the appearance, transparency, possibility of dropping of the AB agent, and anti-blocking performance of the gas barrier film 1, the average particle size of the AB agent is preferably, for example, 0.1 to 5 μm. The average particle size of the AB agent is the weight average particle size measured by the Coulter method.

When the base material 10 contains the AB agent, the AB agent may be dispersed in the resin material before curing. The AB agent particles located near the surface of the substrate 10 may be covered with resin or may be exposed.
The content of the AB agent can be 0.05 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the resin forming the base material 10 . When the content of the AB agent is 0.05 parts by mass or more, it is easy to improve the processability of the film that is the raw material of the substrate 10 . When the content of the AB agent is 0.5 parts by mass or less, deterioration of the oxygen barrier properties of the gas barrier film 1 can be easily suppressed.

The thickness of the base material 10 is not particularly limited, and can be appropriately determined depending on the price and application while considering the suitability as a packaging material and the lamination suitability of other films. Practically, the thickness of the substrate 10 is preferably 3 μm to 200 μm, more preferably 5 μm to 120 μm, even more preferably 6 μm to 100 μm, and particularly preferably 10 μm to 30 μm.

The underlayer 20 contains an organic polymer. The organic polymer content in the underlying layer 20 may be, for example, 70% by mass or more, or may be 80% by mass or more. Examples of organic polymers include polyacrylic resins, polyester resins, polycarbonate resins, polyurethane resins, polyamide resins, polyolefin resins, polyimide resins, melamine resins, and phenol resins. Considering the hot water resistance of the adhesion strength between the base material 10 and the inorganic oxide layer 30 or the oxygen barrier film 40, among the above, polyacrylic resin, polyol resin, polyurethane resin, polyamide resin, or these organic Underlayer 20 preferably includes at least one polymeric reaction product.
The underlayer 20 may contain a silane coupling agent, an organic titanate, a modified silicone oil, or the like.

As the organic polymer used for the base layer 20, an organic polymer having a urethane bond generated by a reaction between a polyol having two or more hydroxyl groups at the polymer end and an isocyanate compound, or an organic polymer having two or more hydroxyl groups at the polymer end. and organic silane compounds such as silane coupling agents or hydrolysates thereof. One of these may be used, or both may be used.

Examples of the polyols include at least one selected from acrylic polyols, polyvinyl acetals, polystyrene polyols, polyurethane polyols, and the like. The acrylic polyol may be obtained by polymerizing an acrylic acid derivative monomer, or may be obtained by copolymerizing an acrylic acid derivative monomer and another monomer. Acrylic acid derivative monomers include ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. Examples of monomers to be copolymerized with acrylic acid derivative monomers include styrene.
The isocyanate compound has the effect of increasing the adhesion between the base material 10 and the inorganic oxide layer 30 or the oxygen barrier film 40 due to the urethane bond formed by reacting with the polyol. That is, the isocyanate compound functions as a cross-linking 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 isocyanate compounds described above may be used singly or in combination of two or more.
Examples of silane coupling agents include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ- methacryloxypropylmethyldimethoxysilane and the like. The organosilane compound may be a hydrolyzate of these silane coupling agents. The organic silane compound may contain one of the above-mentioned silane coupling agents and hydrolysates thereof alone or in combination of two or more thereof.

The underlayer 20 can be formed using a mixed solution in which the above components are blended in an organic solvent at an arbitrary ratio. The mixture includes, for example, tertiary amines, imidazole derivatives, carboxylic acid metal salt compounds, quaternary ammonium salts, quaternary phosphonium salts and other curing accelerators; phenolic, sulfur, and phosphite antioxidants; A leveling agent; a flow control agent; a catalyst; a cross-linking reaction accelerator;
The mixture is applied to the substrate 10 using a known printing method such as offset printing, gravure printing, or silk screen printing, or a known coating method such as roll coating, knife edge coating, or gravure coating. Can be arranged in layers. After placement, the underlying layer 20 can be formed by heating to, for example, 50 to 200.degree.

The thickness of the underlying layer 20 is not particularly limited, and can be, for example, 0.005 to 5 μm. The thickness can be appropriately determined depending on the application or required properties. The thickness of the underlying layer 20 is preferably 0.01 to 1 μm, more preferably 0.01 to 0.5 μm. If the thickness of the underlayer 20 is 0.01 μm or more, sufficient adhesion strength between the base material 10 and the inorganic oxide layer 30 or the oxygen barrier coating 40 can be obtained, and oxygen barrier properties are also improved. If the thickness of the base layer 20 is 1 μm or less, it is easy to form a uniform coated surface, and the drying load and manufacturing cost can be suppressed.

Examples of inorganic oxides forming the inorganic oxide layer 30 include aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, tin oxide, zinc oxide, and indium oxide. In particular, aluminum oxide or silicon oxide is preferable because it is excellent in productivity and has excellent oxygen barrier properties and water vapor barrier properties in heat resistance and moist heat resistance. The inorganic oxide layer 30 may be formed of one type of inorganic oxide, or may be formed of two or more appropriately selected inorganic oxides.

The thickness of the inorganic oxide layer 30 can be 1 nm or more and 200 nm or less. If the thickness is 1 nm or more, excellent oxygen barrier properties and water vapor barrier properties can be obtained. If the thickness is 200 nm or less, the manufacturing cost can be kept low, cracks due to external forces such as bending and pulling are less likely to occur, and deterioration of barrier properties can be suppressed.
The inorganic oxide layer 30 can be formed by a known film formation method such as vacuum deposition, sputtering, ion plating, or plasma chemical vapor deposition (CVD).

The oxygen barrier coating 40 may be a known oxygen barrier coating formed by a wet coating method. The oxygen barrier film 40 is obtained by forming a coating film made of a coating agent on the underlying layer 20 or the inorganic oxide layer 30 by a wet coating method, and drying the coating film. In this specification, the term "coating film" means a wet film, and the term "coating" means a dry film.

As the oxygen barrier coating 40, a coating containing at least one of metal alkoxide, its hydrolyzate, or its reaction product, and a water-soluble polymer (sometimes referred to as an "organic-inorganic composite coating") is used. may contain. Furthermore, it is preferable to further contain at least one of a silane coupling agent and a hydrolyzate thereof.

Metal alkoxides and hydrolysates thereof contained in the organic-inorganic composite film include, for example, tetraethoxysilane [Si _{( OC2H5} ) ₄ ] and triisopropoxyaluminum [A _{(OC3H7)3 ] .} Included are those represented by the formula M(OR) _n , as well as hydrolysates thereof. One of these may be contained alone or in combination of two or more.

The total content of at least one of the metal alkoxide and its hydrolyzate or its reaction product in the organic-inorganic composite film is, for example, 40 to 70% by mass. From the viewpoint of further reducing the oxygen permeability, the lower limit of the total content of at least one of the metal alkoxide and its hydrolyzate or its reaction product in the organic-inorganic composite membrane may be 50% by mass. From the same point of view, the upper limit of the total content of at least one of the metal alkoxide and its hydrolyzate or its reaction product in the organic-inorganic composite film may be 65% by mass.

The water-soluble polymer contained in the organic-inorganic composite film is not particularly limited, and examples thereof include polyvinyl alcohol-based polymers, acrylic polyol-based polymers, and polysaccharides such as starch, methylcellulose, and carboxymethylcellulose. From the viewpoint of further improving the oxygen gas barrier property, it is preferable to contain a polyvinyl alcohol-based polymer. The water-soluble polymer has a number average molecular weight of, for example, 40,000 to 180,000.

A polyvinyl alcohol-based water-soluble polymer can be obtained, for example, by saponifying polyvinyl acetate (including partial saponification). This water-soluble polymer may have several tens of percent of acetic acid groups remaining, or may have only several percent of acetic acid groups remaining.

The content of the water-soluble polymer in the organic-inorganic composite membrane is, for example, 15 to 50% by mass. When the content of the water-soluble polymer is 20 to 45% by mass, the oxygen permeability of the organic-inorganic composite membrane can be further reduced, which is preferable.

Examples of the silane coupling agent and its hydrolyzate contained in the organic-inorganic composite film include silane coupling agents having organic functional groups. Examples of such silane coupling agents and their hydrolysates include ethyltrimethoxysilane, vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ -methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and hydrolysates thereof. One of these may be contained alone or in combination of two or more.

At least one of the silane coupling agent and its hydrolyzate preferably has an epoxy group as an organic functional group. Silane coupling agents having an epoxy group include, for example, γ-glycidoxypropyltrimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. A silane coupling agent having an epoxy group and a hydrolyzate thereof may have an organic functional group different from the epoxy group, such as a vinyl group, an amino group, a methacryl group or a ureyl group.

The silane coupling agent having an organic functional group and its hydrolyzate improve the oxygen barrier properties of the oxygen barrier film 40 and the underlying layer 20 or inorganic oxidation by interaction between the organic functional group and the hydroxyl group of the water-soluble polymer. Adhesiveness to the material layer 30 can be further improved. In particular, the epoxy group of the silane coupling agent and its hydrolyzate and the hydroxyl group of polyvinyl alcohol can improve the adhesiveness of the oxygen barrier film 40 to the base layer 20 and the inorganic oxide layer 30 by interaction. can.

The total content of at least one of the silane coupling agent and its hydrolyzate or its reaction product in the organic-inorganic composite film is, for example, 1 to 15% by mass. When the total content of at least one of the silane coupling agent and its hydrolyzate or its reaction product is 2 to 12% by mass, the oxygen permeability of the organic-inorganic composite membrane can be further reduced, which is preferable.

The organic-inorganic composite film may contain a crystalline inorganic layered compound having a layered structure. Examples of inorganic layered compounds include clay minerals represented by kaolinite group, smectite group, mica group and the like. You may use these 1 type individually or in combination of 2 or more types. The particle size of the inorganic layered compound is, for example, 0.1 to 10 μm. The asbestos ratio of the inorganic layered compound is, for example, 50-5000.

As the inorganic layered compound, a smectite group clay mineral is preferable because a film having excellent oxygen barrier properties and adhesion strength can be formed by intercalation of the water-soluble polymer between the layers of the layered structure. Specific examples of smectite clay minerals include montmorillonite, hectorite, saponite, and water-swellable synthetic mica.

Another preferred example of the oxygen barrier film 40 includes a polyvalent metal salt of carboxylic acid, which is a reaction product between the carboxy group of the polycarboxylic acid polymer (A) and the polyvalent metal compound (B). Films (polyvalent metal salt films of polycarboxylic acids) can be mentioned. The polyvalent metal salt film of polycarboxylic acid may be formed by applying a coating agent obtained by mixing the polycarboxylic acid-based polymer (A) and the polyvalent metal compound (B), followed by heating and drying. A coating agent containing the acid-based polymer (A) as the main component is applied and dried to form the A film, and then a coating agent containing the polyvalent metal compound (B) as the main component is applied and dried to form the B film. and cross-linking between the A/B layers.

[Polycarboxylic acid polymer (A)]
A polycarboxylic acid polymer is a polymer having two or more carboxy groups in its molecule. Examples of polycarboxylic acid-based polymers include (co)polymers of ethylenically unsaturated carboxylic acids; copolymers of ethylenically unsaturated carboxylic acids and other ethylenically unsaturated monomers; alginic acid, carboxymethyl cellulose and acidic polysaccharides having a carboxyl group in the molecule such as pectin. Examples of ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and the like. Ethylenically unsaturated monomers copolymerizable with ethylenically unsaturated carboxylic acids include, for example, ethylene, propylene, saturated carboxylic acid vinyl esters such as vinyl acetate, alkyl acrylates, alkyl methacrylates, and alkyl itaconates. , vinyl chloride, vinylidene chloride, styrene, acrylamide, acrylonitrile and the like. These polycarboxylic acid-based polymers may be used singly or in combination of two or more.

Among the above, at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, itaconic acid, fumaric acid and crotonic acid from the viewpoint of the gas barrier properties of the resulting gas barrier film 1 Polymers containing derived structural units 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. preferable. In the 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, It is more preferably 90 mol % or more (provided that the total of all structural units constituting the polymer is 100 mol %). The polymer may be a homopolymer or a copolymer. When the polymer is a copolymer containing structural units other than the above structural units, the other structural units include, for example, ethylenically unsaturated monomers copolymerizable with the aforementioned ethylenically unsaturated carboxylic acids. Structural units derived from mers and the like are included.

The number average molecular weight of the polycarboxylic acid polymer is preferably in the range of 2,000 to 10,000,000, more preferably 5,000 to 1,000,000. If the number average molecular weight is less than 2,000, the resulting gas barrier film cannot achieve sufficient water resistance, and the gas barrier properties and transparency may deteriorate or whitening may occur due to moisture. On the other hand, if the number-average molecular weight exceeds 10,000,000, the viscosity of the coating agent used to form the oxygen barrier film 40 increases, which may impair the coatability. In addition, the said number average molecular weight is the number average molecular weight of polystyrene conversion calculated|required by the gel permeation chromatography (GPC).

When a coating agent containing a polycarboxylic acid-based polymer as a main component is applied and dried to form the A-film, and then the B-film is formed, the polycarboxylic acid-based polymer has a part of the carboxyl group preliminarily converted to a base. may be neutralized with a chemical compound. By partially neutralizing the carboxy groups of the polycarboxylic acid polymer in advance, the water resistance and heat resistance of the A film can be further improved. The basic compound is preferably at least one basic compound selected from the group consisting of polyvalent metal compounds, monovalent metal compounds and ammonia. As the polyvalent metal compound, compounds exemplified in the description of the polyvalent metal compound to be described later can be used. Examples of monovalent metal compounds include sodium hydroxide and potassium hydroxide.

Various additives can be added to the coating agent mainly composed of polycarboxylic acid polymer. Inhibitors, dispersants, surfactants, softeners, stabilizers, film-forming agents, thickeners and the like.

An aqueous medium is preferable as the solvent used for the coating agent containing a polycarboxylic acid-based polymer as a main component. Aqueous media include water, water-soluble or hydrophilic organic solvents, or mixtures thereof. The aqueous medium usually contains water or water as a main component. The content of water in the aqueous medium is preferably 70% by mass or more, 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 acetonitriles. mentioned.

[Polyvalent metal compound (B)]
The polyvalent metal compound is not particularly limited as long as it is a compound that reacts with the carboxyl groups of the polycarboxylic acid-based polymer to form a polyvalent metal salt of polycarboxylic acid, such as zinc oxide particles, magnesium oxide particles, magnesium methoxide. , copper oxide, calcium carbonate, and the like. These may be used singly or in combination. From the viewpoint of the oxygen barrier properties of the oxygen barrier coating, zinc oxide is preferred.

Zinc oxide is an inorganic material that has the ability to absorb ultraviolet light. Although the average particle size of the zinc oxide particles is not particularly limited, the average particle size is preferably 5 μm or less, more preferably 1 μm or less, and 0.1 μm or less from the viewpoint of gas barrier properties, transparency, and coatability. is particularly preferred.

When a coating agent containing a polyvalent metal compound as a main component is applied and dried to form a film, various additives may be added in addition to the zinc oxide particles, if necessary, as long as the effects of the present invention are not impaired. may contain. Examples of the additive include a resin soluble or dispersible in the solvent used for the coating agent, a dispersant soluble or dispersible in the solvent, a surfactant, a softening agent, a stabilizer, a film-forming agent, a thickener, and the like. can be exemplified.
Among the above, it is preferable to contain a resin that is soluble or dispersible in a solvent. This improves the coatability and film formability of the coating agent. Examples of such resins include alkyd resins, melamine resins, acrylic resins, urethane resins, polyester resins, phenol resins, amino resins, fluorine resins, epoxy resins, and isocyanate resins.

It is also preferable to contain a dispersant that is soluble or dispersible in the solvent. This improves the dispersibility of the polyvalent metal compound. As the dispersant, an anionic surfactant or a nonionic surfactant can be used. The surfactants include (poly)carboxylates, alkyl sulfates, alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkylsulfosuccinates, alkyldiphenyletherdisulfonates, alkylphosphates, aromatic Phosphate ester, polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, alkylallyl sulfate, polyoxyethylene alkyl phosphate, sorbitan alkyl ester, glycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid Various surfactants such as 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 can be mentioned. be done. These surfactants may be used alone or in combination of two or more.

When the additive is contained in the coating agent containing the polyvalent metal compound as the main component, the mass ratio of the polyvalent metal compound and the additive (polyvalent metal compound: additive) is 30:70 to 99. :1, preferably 50:50 to 98:2.

Examples of solvents for coating agents include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethylsulfoxide, dimethylformamide, dimethylacetamide, toluene, and hexane. , heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, butyl acetate. Moreover, these solvents may be used individually by 1 type, or may be used in mixture of 2 or more types. Among these, from the viewpoint of coatability, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred. Moreover, from the viewpoint of manufacturability, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferable.

In the case of applying and drying a coating agent obtained by mixing the polycarboxylic acid polymer (A) and the polyvalent metal compound (B) to form a polyvalent metal salt film of polycarboxylic acid, the polycarboxylic acid polymer (A), a polyvalent metal compound (B), water or alcohols as a solvent, a resin or dispersant that can be dissolved or dispersed in the solvent, and, if necessary, additives are mixed into a coating agent. can be done. By applying and drying this coating agent by a known coating method, a polyvalent metal salt film of polycarboxylic acid can be formed.
Coating methods include 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, A curtain coating method or the like can be exemplified.

The oxygen barrier film 40 may contain a polyurethane resin from the viewpoint of flexibility and gas barrier properties. That is, the oxygen barrier film 40 may be a cured product (polyurethane resin film) of an oxygen barrier film-forming raw material containing a polyvinyl alcohol-based resin, a polyurethane resin, and a silane compound. Polyurethane resins include water-based polyurethane resins.
Aqueous polyurethane resins include acid group-containing polyurethane resins and polyamine compounds. By using an aqueous polyurethane resin, flexibility and gas barrier properties, especially oxygen barrier properties can be easily imparted to the oxygen barrier film. In the water-based polyurethane resin, the acid group of the acid group-containing polyurethane resin is combined with a polyamine compound as a cross-linking agent to exhibit gas barrier properties. The bond between the acid group of the acid group-containing polyurethane resin and the polyamine compound may be an ionic bond (e.g., an ionic bond between a carboxyl group and a tertiary amino group) or a covalent bond (e.g., an amide bond). may be

Since the acid-group-containing polyurethane resin that constitutes the aqueous polyurethane resin has acid groups, it has anionicity and self-emulsifying properties, and is also called an anionic self-emulsifying polyurethane resin. The acid group of the acid group-containing polyurethane resin can bond with the amino group (primary amino group, secondary amino group, tertiary amino group, etc.) of the polyamine compound constituting the aqueous polyurethane resin. A carboxyl group, a sulfonic acid group, etc. are mentioned as an acid group. An acid group can usually be neutralized with a neutralizing agent (base), and may form a salt with a base. The acid group may be located at the end of the acid group-containing polyurethane resin or may be located in a side chain, but is preferably located at least in the side chain.

The acid value of the acid-group-containing polyurethane resin can be selected within a range in which the acid-group-containing polyurethane resin is water-dispersible. , 15 to 60 mg KOH/g. If the acid value of the acid-group-containing polyurethane resin is less than the lower limit of the above range, the water-dispersibility of the acid-group-containing polyurethane resin becomes insufficient, resulting in poor uniform dispersibility between the water-based polyurethane resin and other materials and dispersion of the coating agent. It may lead to a decrease in stability. If the acid value of the acid group-containing polyurethane resin exceeds the upper limit of the above range, the water resistance and gas barrier properties of the oxygen barrier film may be deteriorated. When the acid value of the acid group-containing polyurethane resin is within the above range, it becomes easier to avoid deterioration of dispersion stability, water resistance, and gas barrier properties. The acid value of the acid group-containing polyurethane resin can be measured by a method according to JIS K 0070.

The number average molecular weight of the acid group-containing polyurethane resin can be selected as appropriate, but is preferably 800 to 1,000,000, more preferably 800 to 200,000, and 800 to 100,000. is more preferred. If the number average molecular weight of the acid group-containing polyurethane resin exceeds the upper limit of the above range, the viscosity of the coating agent increases, which is undesirable. If the number average molecular weight of the acid-group-containing polyurethane resin is less than the lower limit of the above range, the gas barrier properties of the oxygen barrier film may be insufficient. The number average molecular weight of the acid group-containing polyurethane resin is a value converted to standard polystyrene measured by gel permeation chromatography (GPC).

The acid group-containing polyurethane resin may be crystalline in order to improve gas barrier properties. The glass transition temperature of the acid group-containing polyurethane resin is preferably 100° C. or higher, more preferably 110° C. or higher, and even more preferably 120° C. or higher. If the glass transition temperature of the acid group-containing polyurethane resin is less than 100°C, the gas barrier properties of the oxygen barrier film may be insufficient. The glass transition temperature of the acid group-containing polyurethane resin is typically about 200° C. or lower, further 180° C. or lower, further 150° C. or lower. It is substantially less likely that the glass transition temperature of the acid group-containing polyurethane resin that satisfies the preferred ranges of the above items will be higher than the above upper limits. Therefore, the glass transition temperature of the acid group-containing polyurethane resin is preferably 100 to 200°C, more preferably 110 to 180°C, even more preferably 120 to 150°C. The glass transition temperature of the acid group-containing polyurethane resin is measured by differential scanning calorimetry (DSC).

A polyamine compound that constitutes an aqueous polyurethane resin is a compound having two or more basic nitrogen atoms. The basic nitrogen atom is a nitrogen atom that can bond with the acid group of the acid group-containing polyurethane resin. mentioned. The polyamine compound is not particularly limited as long as it can bond with the acid group of the acid group-containing polyurethane resin and improve the gas barrier property, and various compounds having two or more basic nitrogen atoms can be used. can. As the polyamine compound, a polyamine compound having two or more amino groups of at least one kind selected from the group consisting of primary amino groups, secondary amino groups and tertiary amino groups is preferred.

Specific examples of polyamine compounds include alkylenediamines, polyalkylenepolyamines, and silicon compounds having a plurality of basic nitrogen atoms. Examples of alkylenediamines include alkylenediamines having 2 to 10 carbon atoms such as ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,4-butanediamine and 1,6-hexamethylenediamine. be done. Polyalkylenepolyamines include, for example, tetraalkylenepolyamine. Silicon compounds having a plurality of basic nitrogen atoms (including nitrogen atoms such as amino groups) include, for example, 2-[N-(2-aminoethyl)amino]ethyltrimethoxysilane, 3-[N-(2- Examples thereof include silane coupling agents having a plurality of basic nitrogen atoms, such as aminoethyl)amino]propyltriethoxysilane.

In the water-based polyurethane resin, the content of the polyamine compound is such that the molar ratio (acid group/basic nitrogen atom) of the acid group of the acid group-containing polyurethane resin and the basic nitrogen atom of the polyamine compound is 10/1 to 0.1. /1 is preferable, and the amount of 5/1 to 0.2/1 is more preferable. When the acid group/basic nitrogen atom content is within the above range, the crosslinking reaction between the acid group of the acid group-containing polyurethane and the polyamine compound occurs appropriately, and the oxygen barrier film exhibits excellent oxygen barrier properties.

The aqueous polyurethane resin is usually used in the form of a dispersion in an aqueous medium (aqueous dispersion). Aqueous media include water, water-soluble or hydrophilic organic solvents, or mixtures thereof. 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; is mentioned. As the aqueous medium, water or a medium containing water as a main component is preferable. The content of water in the aqueous medium is preferably 70% by mass or more, more preferably 80% by mass or more. The aqueous medium may or may not contain a neutralizing agent (base) that neutralizes the acid groups of the acid group-containing polyurethane resin. Neutralizing agents are usually included.

In the aqueous dispersion of the aqueous polyurethane resin, the average particle size of the dispersed particles (polyurethane resin particles) is not particularly limited, preferably 20 nm to 500 nm, more preferably 25 nm to 300 nm, still more preferably 30 nm to 200 nm. is. If the average particle size of the dispersed particles exceeds the upper limit of the above range, the uniform dispersibility of the dispersed particles and other materials and the dispersion stability of the coating agent will decrease, and the gas barrier of the oxygen barrier film formed from the coating agent will deteriorate. may become inadequate. If the average particle size of the dispersed particles is less than the lower limit of the above range, the effect of further improving the dispersion stability of the coating agent and the gas barrier properties of the oxygen barrier film formed from the coating agent cannot be expected. Also, obtaining such dispersions is substantially difficult. The average particle size of the dispersed particles can be measured with a concentrated particle size analyzer (FPAR-10, manufactured by Otsuka Electronics Co., Ltd.) using a dispersion having a solid concentration of 0.03 to 0.3% by mass.

As the water-based polyurethane resin, a commercially available one may be used, or one produced by a known production method may be used. Examples of commercially available products include Takelac WPB-341 manufactured by Mitsui Chemicals, Inc., and Hydran HW350 manufactured by DIC Corporation. The method for producing the water-based polyurethane resin is not particularly limited, and conventional techniques for making water-based polyurethane resins, such as the acetone method and prepolymer method, are used. In the urethanization reaction, urethanization catalysts such as amine-based catalysts, tin-based catalysts and lead-based catalysts may be used as necessary. For example, in an inert organic solvent such as ketones such as acetone, ethers such as tetrahydrofuran, and nitriles such as acetonitrile, a polyisocyanate compound, a polyhydroxy acid, and, if necessary, a polyol component and a chain extender component An acid group-containing polyurethane resin can be prepared by reacting with at least one of More specifically, in an inert organic solvent (especially a hydrophilic or water-soluble organic solvent), a polyisocyanate compound, a polyhydroxy acid, and a polyol component are reacted to obtain an isocyanate group at the end. After producing a prepolymer, neutralizing it with a neutralizing agent and dissolving or dispersing it in an aqueous medium, a chain extender component is added and reacted, and the organic solvent is removed to obtain an aqueous solution of an acid group-containing polyurethane resin. Dispersions can be prepared. An aqueous polyurethane resin in the form of an aqueous dispersion can be prepared by adding a polyamine compound to the aqueous dispersion of an acid group-containing polyurethane resin thus obtained and heating if necessary. When heating, the heating temperature is preferably 30 to 60°C.

When forming a polyurethane resin film, the amount of the polyurethane resin in the raw material for forming the polyurethane resin film is 0.9 to 4.0 parts by mass with respect to 1 part by mass of the polyvinyl alcohol-based resin, from the viewpoint of bending resistance and gas barrier properties. can. The amount of polyurethane resin is preferably 1.1 to 3.0 parts by mass, more preferably 1.2 to 2.5 parts by mass.

The thickness of the oxygen barrier coating 40 is set according to the required oxygen barrier properties, and can be, for example, 0.05 to 5 μm. The thickness of the oxygen barrier coating 40 is preferably 0.05-1 μm, more preferably 0.1-0.5 μm. If the thickness of the oxygen barrier coating 40 is 0.05 μm or more, sufficient oxygen barrier properties are likely to be obtained. If the thickness of the oxygen barrier film 40 is 1 μm or less, it is easy to form a uniform coating surface, and the drying load and manufacturing cost can be suppressed.

As the oxygen barrier film 40, a gas barrier film having the above-mentioned organic-inorganic composite film, polyvalent metal salt film of polycarboxylic acid, polyurethane resin film, or the like, exhibits excellent oxygen barrier properties even after boiling treatment or retort sterilization treatment. indicates

The above is the basic configuration of the gas barrier film 1 . When the gas barrier film 1 is provided with a heat seal layer, it becomes a laminate applicable to packaging materials. A packaging material using the gas barrier film 1 can be formed by preparing one or more sheets of this laminate, placing the heat-seal layers facing each other, and heat-sealing the peripheral edges. When this packaging material is applied to a packaging material for retort food, the gas barrier film is exposed to high temperatures associated with retort processing.
The inventors conducted various studies on the deterioration of barrier properties after high-temperature treatment, and found that there is a large difference between the degree of dimensional change of the heat seal layer due to high-temperature treatment and the degree of dimensional change of the base material 10 due to high-temperature treatment. It was found that cracks tend to occur in the oxygen barrier film 40 and the barrier properties tend to deteriorate.

The inventors produced gas barrier films using various base materials and examined them. It was found that it is possible to easily identify a configuration in which the
Specifically, in the completed gas barrier film, the difference between the maximum value and the minimum value of thermal strain in a certain direction when a thermal history of temperature rise and temperature drop is given in a certain temperature range, and When the sum of the difference between the maximum value and the minimum value of thermal strain in the direction orthogonal to the one direction is 0.03 or less, the barrier properties are less likely to deteriorate even in high-temperature treatment.

The temperature range of the thermal history can be determined based on the details of the high temperature treatment actually applied. If the high temperature treatment is retort treatment or boiling treatment, the temperature range can be 20°C to 120°C. The temperature increase rate and temperature decrease rate can be set to 10° C./min, for example.

When a stretched resin film is used as the substrate 10, the above "sum" can be calculated in the following procedure using thermomechanical analysis (TMA).
A 4 mm x 25 mm gas barrier film sample was prepared, and a TMA tension was applied with a profile of temperature rise from 20 to 120 ° C. and temperature drop from 120 to 20 ° C. at a heating rate and cooling rate of 10 ° C./min and a tension of 30 mN. Measure at velocity.
Difference between maximum value (thermal expansion) and minimum value (thermal contraction) of thermal strain in MD (machine direction) and TD (direction perpendicular to MD) in the sample ε Maximum value of thermal strain in _MD and TD directions and the difference ε _TD between the minimum values, the sum ε _MD +ε _TD is calculated. The maximum value ε _max of thermal strain in each direction appears when the temperature rises from 20 to 120°C, and the minimum value ε _min of thermal strain appears between the temperature at which the maximum value of thermal expansion is reached and the temperature falling to 20°C. , the difference ε _max −ε _min is ε _MD and ε _TD .

An example of the manufacturing procedure of the gas barrier film 1 will be described.
First, a substrate 10 is selected. The sum ε _{MD +ε TD of the gas barrier film 1 is greatly influenced by the sum ε MD + ε TD} of the substrate itself. Therefore, the above measurements are performed on the substrate to be used and the sum ε _MD +ε _TD is calculated.
The sum ε _MD +ε _TD of the base material alone is most preferably 0.03 or _{less .} , slightly lower than the sum ε _MD +ε _TD of the substrate alone. Therefore, depending on the structure of other layers, for example, if the sum ε _MD +ε _TD of the base material alone is 0.04 or less, a gas barrier film with a sum ε _MD +ε _TD of 0.03 or less should be produced. is possible.
The base material 10 may be a commercially available product or may be manufactured by a known method.

Next, a layer selected from the underlying layer 20 and the inorganic oxide layer 30 is formed on the base material 10 .
When forming the base layer 20, for example, a coating agent is applied to the first surface 10a of the base material 10 by a wet coating method to form a coating film, and the coating film is dried (solvent is removed).
As a method for applying the coating agent, a known wet coating method can be used. Wet coating methods include roll coating, gravure coating, reverse coating, die coating, screen printing, and spray coating.
As a method for drying a coating film made of a coating agent, a known drying method such as hot air drying, hot roll drying, infrared irradiation, or the like can be used. The drying temperature of the coating film can be, for example, 50 to 200°C. The drying time varies depending on the thickness of the coating film, the drying temperature, etc., but can be, for example, 1 second to 5 minutes.
The inorganic oxide layer 30 can be formed by the above-described vacuum deposition method, sputtering method, ion plating method, plasma vapor deposition method (CVD), or the like.

Subsequently, an oxygen barrier film 40 is formed on the underlying layer 20 or the inorganic oxide layer 30 .
The oxygen barrier film 40 can be formed, for example, by applying a coating agent by a wet coating method to form a coating film, and drying the coating film (removing the solvent).
As the coating method and drying method of the coating agent, the same methods as those mentioned in the description of the formation process of the underlayer 20 can be used.
The oxygen barrier film 40 may be formed by applying and drying once, or may be formed by repeating applying and drying multiple times with the same or different coating agents.

Through the above processes, the gas barrier film 1 is completed. In the gas barrier film 1, the difference between the maximum value and the minimum value of thermal strain in one predetermined direction when a thermal history of temperature rise and temperature drop in a certain temperature range is given, and the one direction on the surface of the base material The sum of the difference between the maximum value and the minimum value of thermal strain in the direction orthogonal to is suppressed to 0.03 or less.

If necessary, the gas barrier film 1 may further have a printed layer, a protective layer, a light shielding layer, an adhesive layer, a heat-sealable heat-sealable layer, other functional layers, and the like.
By providing the gas barrier film 1 with a heat-sealable layer, a laminate suitable for manufacturing various packaging materials such as packaging bags and pouches can be formed. Since the above sum of the gas barrier film 1 is 0.03 or less, the packaging material formed of the gas barrier film 1 can maintain suitable barrier properties even when subjected to high-temperature treatments such as boiling and retorting, and the adhesion of each layer can be maintained. The strength and seal strength are also good. Furthermore, it has a transparency that metal foils and vapor-deposited metal films do not have, so that the contents can be seen, and it has excellent resistance to bending and stretching, and there is no risk of generating harmful substances such as dioxins.

A CPP (unstretched polypropylene film) can be exemplified as the heat-sealable layer. The heat-sealable layer can be laminated by a known dry lamination method, extrusion lamination method, or the like using a known adhesive such as a polyurethane-based, polyester-based, or polyether-based adhesive.
By making both the base material 10 and the heat-sealable layer made of polypropylene, the content of polypropylene in the laminate and the packaging material can be 90% by mass or more. As a result, the laminate and the packaging material become a so-called monomaterial material, improving recyclability.

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 contents of Examples and Comparative Examples.

(Example)
As a base material, a 20 μm-thick biaxially oriented polypropylene film (VPH2011 manufactured by AJ Plast) was prepared, the first surface of which was subjected to corona treatment.
Mixed solution A prepared by the following procedure was applied to the first surface using a gravure printing machine to form a coating film, which was dried by passing through an oven at 80 ° C. for 10 seconds to a thickness of 0.1 μm. A stratum was formed.
(Adjustment procedure for mixed solution A)
Acrydic CL-1000 (manufactured by DIC Corporation) was used as the acrylic polyol, and TDI type curing agent Coronate 2030 (manufactured by Tosoh Corporation) was used as the isocyanate compound. The acrylic polyol and the isocyanate compound were blended so that the solid content weight ratio was 6:4, and a diluent solvent (ethyl acetate) was used to adjust the solid content to 2% by mass.

Next, a mixed material containing two or more of metallic silicon, silicon monoxide, and silicon dioxide is evaporated using a vacuum vapor deposition apparatus using an electron beam heating method, and a silicon oxide layer having a thickness of 30 nm is deposited on the underlying layer. An inorganic oxide layer was formed.

Next, on the inorganic oxide layer, a mixed solution B prepared by the following procedure is applied using a gravure printer to form a coating film, which is dried by passing through an oven at 80 ° C. for 10 seconds. An oxygen barrier film having a thickness of 0.3 μm was formed.
(Adjustment procedure of mixed solution B)
A polyurethane resin (Takelac WPB-341, manufactured by Mitsui Chemicals, Inc.), a 5% PVA aqueous solution (PVA124, manufactured by Kuraray Co., Ltd.), and a silane coupling agent (3-glycidoxypropyltriethoxysilane) were added to the solid content. After mixing at a ratio of 50:45:5, it was diluted with water and isopropanol to a solids content of 5% by weight. At this time, isopropanol was 10% by mass of the whole.
As described above, a gas barrier film according to an example was obtained.

(Comparative example)
In the same procedure as in Example 1, except that a 20 μm-thick biaxially oriented polypropylene film (ME-1 manufactured by Mitsui Chemicals Tohcello, Inc.) with a corona treatment applied to the first surface was used as the base material. A gas barrier film according to a comparative example was obtained.

The following items were evaluated using the gas barrier films of Examples and Comparative Examples.
(Thermal strain measurement)
A sample of 4 mm×25 mm was prepared by cutting the gas barrier film of each example.
A profile with a temperature increase of 20° C. to 120° C. and a temperature decrease of 120° C. to 20° C., with a temperature increase rate of 10° C./min;
Under the condition of a tension of 30 mN, the above-described ε _max and ε _min were measured in the tension mode of TMA, and the sum ε _MD +ε _TD was calculated.

(Oxygen barrier property before and after retort treatment)
On the oxygen barrier film of the gas barrier film of each example, a 60 μm thick CPP film (Torayfan ZK93KM manufactured by Toray Advanced Film Co., Ltd.) was adhered with an adhesive to form a heat-sealable layer.
As the adhesive, a two-component curing adhesive Takelac A620 (main agent)/Takenate A65 (curing agent) made by Mitsui Chemicals Polyurethane was used, and dry lamination was performed with a multi-coater TM-MC made by HIRANO TECSEED, at 40°C for 3 days. nurtured.
As described above, a laminate according to each example was obtained.

A plurality of four-sided seal pouches (packaging materials) of A5 size were prepared by sealing the periphery of the laminate of each example with the heat-sealable layers facing each other. Each pouch was filled with 200 ml of tap water, sealed, and subjected to heat sterilization (retort treatment) in hot water at 120° C. for 30 minutes.
A sample was cut out from each pouch before and after the retort treatment, and an oxygen permeability measurement device (trade name: OXTRAN-2/20, manufactured by MOCON) was used to measure the oxygen permeability in an atmosphere of 30 ° C. and 70% RH (relative humidity). The permeability (cm ³ /(m ² ·day · atm)) was measured.
Table 1 shows the results. Each value for thermal strain is rounded to four decimal places.

Both Examples and Comparative Examples use a biaxially oriented polypropylene film as the base material, and have almost the same layer structure. Furthermore, the oxygen permeability before retort treatment was the same between the example and the comparative example.
Nevertheless, the packaging materials according to the examples with ε _MD +ε _TD of 0.03 or less retain good oxygen barrier properties after retort processing, while the comparative examples with ε _MD +ε _TD greater than 0.03 The oxygen barrier properties of such packaging materials were significantly reduced after retorting.

FIG. 2 shows an enlarged photograph of the surface of the gas barrier film in Comparative Example after retort treatment. In the oxygen barrier coating 40, cracks were observed at the locations indicated by the arrows, and this was considered to be one of the causes of the deterioration of the oxygen barrier properties.

An embodiment and an example of the present invention have been described above, but the specific configuration is not limited to this embodiment, and modifications and combinations of configurations without departing from the gist of the present invention are also included. .

1 Gas barrier film 10 Base material 10a First surface 20 Base layer 30 Inorganic oxide layer 40 Oxygen barrier film

Claims (15)

a substrate;
a base layer or an inorganic oxide layer formed on the first surface of the substrate;
an oxygen barrier coating formed on the underlayer or on the inorganic oxide layer;
with
The difference between the maximum and minimum values of thermal strain in the MD direction and the difference between the maximum and minimum values of thermal strain in the TD direction when a thermal history of 20 to 120 ° C temperature rise and 120 to 20 ° C temperature drop is given. is 0.03 or less,
Gas barrier film. The base material is made of one resin selected from polypropylene, polyethylene terephthalate, and nylon.
The gas barrier film according to claim 1. the underlying layer is formed on the first surface;
The underlayer has a thickness of 0.01 to 1 μm,
The gas barrier film according to claim 1 or 2. the underlying layer is formed on the first surface;
The underlayer contains an organic polymer as a main component,
The organic polymer includes at least one of a polyacrylic resin, a polyol resin, a polyurethane resin, a polyamide resin, and a reaction product of these resins.
The gas barrier film according to any one of claims 1 to 3. The inorganic oxide layer is formed on the first surface directly or with the underlayer interposed therebetween,
The inorganic oxide layer has a thickness of 1 to 200 nm,
The gas barrier film according to claim 1. The inorganic oxide layer is formed on the first surface directly or with the underlayer interposed therebetween,
The inorganic oxide layer is aluminum oxide or silicon oxide,
The gas barrier film according to claim 1 or 5. The oxygen barrier coating has a thickness of 0.05 to 1 μm,
The gas barrier film according to any one of claims 1 to 6. The oxygen barrier film is
at least one of a metal alkoxide, a hydrolyzate of a metal alkoxide, and a reaction product of a metal alkoxide or a hydrolyzate of a metal alkoxide;
a water-soluble polymer,
The gas barrier film according to any one of claims 1 to 7. The oxygen barrier film contains at least one of a silane coupling agent, a hydrolyzate of the silane coupling agent, and a reaction product of the silane coupling agent or the hydrolyzate of the silane coupling agent,
The gas barrier film according to any one of claims 1 to 8. The oxygen barrier film contains a polyvalent metal salt of a carboxylic acid that is a reaction product between a carboxy group of a polycarboxylic acid-based polymer and a polyvalent metal compound,
The gas barrier film according to any one of claims 1 to 9. The oxygen-barrier film is a cured product of an oxygen-barrier film-forming raw material containing a polyvinyl alcohol-based resin, a polyurethane resin, and a silane compound.
The gas barrier film according to any one of claims 1 to 9. The gas barrier film according to any one of claims 1 to 11;
a thermal adhesive layer formed on the oxygen barrier coating;
comprising
laminate. The base material and the heat-sealable layer are mainly composed of polypropylene,
The laminate according to claim 12. Containing 90% by mass or more of the polypropylene,
The laminate according to claim 13. A packaging material formed from the laminate according to any one of claims 12 to 14.

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