JP7613007B2 - Gas Barrier Film - Google Patents

Description

The present invention relates to a gas barrier film.

Packaging materials used for packaging food, medicines, etc. are required to have the property of preventing the intrusion of gases (water vapor, oxygen, etc.) that denature the contents, in order to prevent deterioration or spoilage of the contents and to maintain their functionality and quality. In other words, they are required to have gas barrier properties. For this reason, film materials with gas barrier properties (gas barrier films) are used for these packaging materials.

A known gas barrier film is one in which a gas barrier layer made of a material having gas barrier properties is provided on the surface of a resin substrate. Known gas barrier layers include metal foils, metal deposition films, and films formed by wet coating. As the above-mentioned films, resin films formed from coating agents containing water-soluble polymers and resins such as polyvinylidene chloride, and inorganic layered mineral composite resin films formed from coating agents containing water-soluble polymers and inorganic layered minerals are known to exhibit oxygen barrier properties (see, for example, Patent Document 1).

Furthermore, as the gas barrier layer, there have been proposed a vapor-deposited thin film layer made of an inorganic oxide (see, for example, Patent Document 2), a gas barrier layer in which a gas barrier composite coating containing an aqueous polymer, an inorganic layered compound, and a metal alkoxide is laminated in sequence (see, for example, Patent Document 3), and a gas barrier layer containing a polyvalent metal salt of a carboxylic acid, which is a reaction product between a carboxy group of a polycarboxylic acid polymer and a polyvalent metal compound (see, for example, Patent Document 4).

These gas barrier films are transparent and have oxygen blocking properties. The base film that is often used is made of polyethylene terephthalate (PET).

Patent No. 6176239 Japanese Patent Application Laid-Open No. 60-49934 JP 2000-254994 A Patent No. 4373797

However, gas barrier films in which a coating is formed on the surface of a resin substrate by a wet coating method, a vapor deposition method, or a sputtering method sometimes have unstable oxygen barrier properties depending on the production lot. Specifically, the oxygen barrier properties of the gas barrier film are sometimes inferior to the inherent oxygen barrier properties, that is, the oxygen barrier properties expected from the material constituting the coating and the thickness of the coating. In particular, such problems tend to occur more easily when the coating is thin.

In recent years, there has been an increasing demand for gas barrier films that use base films made of polypropylene (PP) or polyethylene (PE) in order to reduce the burden on the environment. However, the inventors' research has revealed that gas barrier films that simply have a barrier layer formed on a PP base film do not actually have sufficient resistance to hot water treatments such as boiling and retorting.

In light of the above circumstances, the present invention aims to provide a gas barrier film that can fully exhibit its inherent oxygen barrier properties even when the thickness of the film used to impart oxygen barrier properties is thin, has high resistance to hot water treatment, and has a reduced environmental impact.

The present invention provides a gas barrier film comprising a substrate containing polypropylene as a main component and an oxygen barrier coating on a first surface of the substrate, and when, in infrared spectroscopy measurement of the first surface, the ratio of a peak intensity I1 present at 1,360 to 1,390 cm ^-1 to a peak intensity I2 present at 1,440 to 1,480 cm ^-1 satisfies the following formula (1), the gas barrier film has sufficient hot water resistance with an adhesion strength of 1.0 N/15 mm or more after hot water treatment, and also has a reduced environmental impact.
I1/I2≦1.65…(1)

In addition, if the number of microparticles added to prevent blocking of the resin substrate is 100 or less per area of 250 μm on a side, and the average protrusion height is 2.5 μm or less, defects in the oxygen barrier film that act as paths for gas permeation are minimized, and a gas barrier film with high oxygen barrier properties can be provided.

The present invention is based on the above findings and has the following aspects.
[1] A base material mainly composed of polypropylene;
The substrate has an oxygen barrier coating on a first surface side thereof,
a base layer, or both a base layer and an inorganic oxide layer, between the resin substrate and the oxygen barrier coating;
In infrared spectroscopy of the first surface, a ratio of a peak intensity I1 present in the range of 1360 to 1390 cm ⁻¹ to a peak intensity I2 present in the range of 1440 to 1480 cm ⁻¹ satisfies the following formula (1):
I1/I2≦1.65…(1)
the first surface has protruding particles formed of a material other than polypropylene;
The number of the microparticles is 100 or less per region of 250 μm on a side,
A gas barrier film, wherein the fine particles have an average protrusion height of 2.5 μm or less.
[2] The substrate has two or more resin layers including a base layer and a surface layer constituting the first surface,
The value of the formula (1) in infrared spectroscopy of the resin layer on the second surface opposite to the first surface is
The gas barrier film according to [1], wherein the value of formula (1) is greater than that of the first surface.
[3] The gas barrier film according to [1] or [2], wherein the thickness of the undercoat layer is 0.01 to 1 μm.
[4] The underlayer contains an organic polymer as a main component,
The gas barrier film according to any one of [1] to [3], wherein the organic polymer comprises at least one of a polyacrylic resin, a polyol resin, a polyurethane resin, a polyamide resin, or a reaction product of these organic polymers.
[5] The gas barrier film according to any one of [1] to [4], wherein the inorganic oxide layer has a thickness of 1 to 200 nm.
[6] The gas barrier film according to any one of [1] to [5], wherein the inorganic oxide layer is aluminum oxide or silicon oxide.
[7] The gas barrier film according to any one of [1] to [6], wherein the oxygen barrier coating has a thickness of 0.05 to 1 μm.
[8] The gas barrier film according to any one of [1] to [7], wherein the oxygen barrier coating is a coating containing at least one of a metal alkoxide, a hydrolysate thereof, or a reaction product thereof, and a water-soluble polymer.
[9] The gas barrier film according to [8], wherein the oxygen barrier coating further contains at least one of a silane coupling agent, a hydrolyzate thereof, and a reaction product thereof.
[10] The gas barrier film according to any one of [1] to [7], wherein the oxygen barrier coating contains a polyvalent metal salt of a carboxylic acid which is a reaction product between a carboxy group of the polycarboxylic acid polymer (A) and a polyvalent metal compound (B).
[11] The gas barrier film according to any one of [1] to [10], wherein the substrate further comprises a heat-sealable sealant layer, and the sealant layer is bonded to the oxygen barrier coating by an adhesive layer.
[12] After hot water treatment at 120 ° C. for 30 minutes,
The oxygen permeability is 5.0 cc/ ^m2 ·day or less,
The gas barrier film according to any one of [1] to [11], wherein a peel strength between the substrate and the sealant layer is 1.0 N/15 mm or more.

The present invention provides a gas barrier film that is highly resistant to hot water treatment and has a reduced environmental impact. Furthermore, even if the thickness of the film for imparting oxygen barrier properties is thin, the inherent oxygen barrier properties can be fully expressed, resulting in excellent oxygen barrier properties.

1 is a schematic cross-sectional view of a gas barrier film according to an embodiment of the present invention.

The gas barrier film of the present invention will be described with reference to an embodiment.

Figure 1 is a schematic cross-sectional view of a gas barrier film 100 according to an embodiment of the present invention. The dimensional ratios in Figure 1 are different from the actual ones for the sake of convenience.

The gas barrier film 100 has a resin substrate 10, an underlayer 13, an inorganic oxide layer 14, and an oxygen barrier coating 15. The inorganic oxide layer 14 is not essential.

The substrate 10 has two or more resin layers and includes at least a surface layer 11 and a base layer 12, and the surface layer 11 has fine particles 16.

The undercoat layer 13 is located in contact with the first surface 10a of the resin substrate 10, and the inorganic oxide layer 14 or the oxygen barrier film 15 is located in contact with the opposite surface.

The gas barrier film 100 has a sealant layer 18, which is in contact with the adhesive layer 17, and the adhesive layer 17 is in contact with the oxygen barrier coating 15.

The substrate 10 has two or more resin layers whose main component is polypropylene. The substrate of this embodiment has two resin layers: a base layer 12 and a surface layer 11 laminated on the base layer 12.

The substrate 10 having two or more resin layers can be formed, for example, by co-extrusion. The total thickness of the substrate 10, which is the sum of the film thicknesses of the base layer 12 and the surface layer 11, can be, for example, 3 to 200 μm, and is preferably 15 to 60 μm.

The resin used as the raw material for each layer of the substrate 10 is mainly polypropylene, from the viewpoints of ease of acquisition, water vapor barrier properties, and suppression of environmental impact. The polypropylene may be any of homopolymer, random copolymer, block copolymer, and terpolymer. The homopolymer is polypropylene consisting of only propylene alone. The random copolymer is polypropylene in which the main monomer propylene and a type of comonomer different from propylene are randomly copolymerized to form a homogeneous phase. The block copolymer is polypropylene in which the main monomer propylene and the above-mentioned comonomer are copolymerized in blocks or polymerized in a rubber-like form to form a heterogeneous phase. The terpolymer is polypropylene in which the main monomer propylene and two types of comonomers different from propylene are copolymerized. These polyolefin resins may be used alone or in a blend of two or more types. The raw material for the base layer 12 is preferably any of homopolymer, random copolymer, and block copolymer. The raw material for the surface layer 11 is preferably a random copolymer, a block copolymer, or a terpolymer.

The base layer 12 may contain additives. The additives can be appropriately selected from various known additives. Examples of additives include antiblocking agents (AB agents), heat stabilizers, weather stabilizers, UV absorbers, lubricants, slipping agents, nucleating agents, antistatic agents, antifogging agents, pigments, and dyes. Any one of these additives may be used alone, or two or more may be used in combination. Of the above, lubricants and slipping agents are preferred from the viewpoint of processing suitability. The content of the additives in the base layer 12 can be appropriately adjusted within a range that does not impede the effects of the present invention. The base layer 12 typically does not contain an AB agent.

The base layer 12 may have a single-layer structure or a multi-layer structure. The thickness of the base layer 12 may be, for example, 3 to 200 μm, or 6 to 30 μm.

The raw material for the surface layer 11 is preferably a random copolymer, a block copolymer, or a terpolymer.

The surface layer 11 contains fine particles, typically AB agents. If the number of fine particles is 100 or less per area of 250 μm on a side, and the average protrusion height is 5 μm or less, the occurrence of defects that serve as paths for gas permeation can be suppressed when forming the oxygen barrier coating 15, and excellent oxygen barrier properties are achieved.

The surface layer 11 may contain additives other than the AB agent. The additives may be appropriately selected from various known additives. Examples of additives include heat stabilizers, weather stabilizers, UV absorbers, lubricants, slipping agents, nucleating agents, antistatic agents, antifogging agents, pigments, and dyes. Any one of these additives may be used alone, or two or more may be used in combination. Of the above, lubricants and slipping agents are preferred from the viewpoint of processing suitability. The content of the additives in the surface layer 11 may be appropriately adjusted within a range that does not interfere with the effects of the present invention.

The thickness of the surface layer 11 may be, for example, 0.1 to 10 μm, or even 0.5 to 5.0 μm.

The fine particles 16 are typically AB agents, and are solid particles, and examples of the fine particles include organic particles and inorganic particles. Examples of the organic particles include polymethyl methacrylate particles, polystyrene particles, polyamide particles, and the like. These organic particles are obtained, for example, by emulsion polymerization or suspension polymerization. Examples of the inorganic particles include silica particles, zeolite, talc, kaolinite, feldspar, and the like. These AB agents may be used alone or in combination of two or more. As the fine particles 16, polymethyl methacrylate particles are preferred for the organic system, and silica particles are preferred for the inorganic system.

The average particle size of the microparticles 16 is preferably 0.1 μm or more and 5 μm or less, taking into consideration the appearance of the first surface 10a, the transparency of the substrate 10, the possibility of the microparticles 16 falling off, and the anti-blocking performance.

The amount of the fine particles 16 added to the surface layer 11 is, for example, 0.1 to 0.4 mass % with respect to the total mass of the surface layer 11. The amount of the fine particles 16 added to the surface layer 11 is specifically calculated by the following formula.
Amount of fine particles added [mass %]={(i)/100}×{(ii)/100}×100
In the formula, (i) represents the concentration (mass%) of fine particles in masterbatch resin chips obtained by adding fine particles to a resin, stirring the mixture, feeding the mixture into an extruder and kneading the mixture, and melt-extruding the mixture into pellets;
(ii) indicates the concentration (mass %) of masterbatch resin chips containing fine particles relative to the total mass of resin pellets constituting the surface layer 11 when the masterbatch resin chips containing fine particles are blended with a resin not containing fine particles.

The microparticles 16 may be included on the second surface 10b of the substrate 10, and are preferably included in consideration of anti-blocking performance.

The resin substrate 10 is preferably a coextruded film in which each layer, including the surface layer 11 and the base layer 12, is laminated by coextrusion. The resin substrate 10 may be a stretched film or an unstretched film.

The resin substrate 10 preferably has a biaxially oriented polypropylene film. Since biaxially oriented polypropylene film has particularly excellent water vapor barrier performance, the gas barrier film 100 has excellent water vapor barrier properties by having a biaxially oriented polypropylene film. The biaxially oriented polypropylene film may be at least one of homopolymers, random copolymers, block copolymers, etc., processed into a film shape. The biaxially oriented polypropylene film is preferably a coextruded film.

The thickness of the resin substrate 10 can be adjusted according to the application, the desired characteristics, etc., and is not particularly limited, but may be, for example, 3 to 200 μm, or even 6 to 30 μm. The thickness of the resin substrate 10 is the thickness of the portion where there are no protrusions resulting from the microparticles 16.

The surfaces of the resin substrate 10 (first surface 10a, second surface 10b) may be subjected to at least one treatment selected from the group consisting of chemical treatment, solvent treatment, corona treatment, plasma treatment, and ozone treatment.

(Base layer)
The underlayer 13 is provided between the resin substrate 10 and the inorganic oxide layer 14 or the oxygen barrier film 15 .

The underlayer 13 is a layer containing an organic polymer as a main component, and is sometimes called a primer layer. By providing the underlayer 13, it is possible to improve the film-forming properties and adhesion strength of the inorganic oxide layer 14 or the oxygen barrier film 15.

The content of the organic polymer in the undercoat layer 13 may be, for example, 70% by mass or more, or 80% by mass or more. Examples of the organic polymer include polyacrylic resin, polyester resin, polycarbonate resin, polyurethane resin, polyamide resin, polyolefin resin, polyimide resin, melamine resin, and phenolic resin. Considering the hot water resistance of the adhesive strength between the resin substrate 10 and the inorganic oxide layer 14 or the oxygen barrier film 15, it is preferable that the undercoat layer 13 contains at least one of polyacrylic resin, polyol resin, polyurethane resin, polyamide resin, or reaction products of these organic polymers. The undercoat layer 13 may also contain a silane coupling agent, an organic titanate, or a modified silicone oil.

More preferably, the organic polymer is an organic polymer having a urethane bond formed by the reaction of a polyol having two or more hydroxyl groups at the polymer end with an isocyanate compound, and/or an organic polymer containing a reaction product of a polyol having two or more hydroxyl groups at the polymer end with an organic silane compound such as a silane coupling agent or a hydrolyzate thereof.

The polyols include, for example, at least one selected from acrylic polyol, polyvinyl acetal, polystyrene polyol, polyurethane polyol, 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 with another monomer. Examples of the acrylic acid derivative monomer include ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. Examples of the monomer to be copolymerized with the acrylic acid derivative monomer include styrene, and the like.

The isocyanate compound has the effect of increasing the adhesion between the resin substrate 10 and the inorganic oxide layer 14 or the oxygen barrier film 15 by forming a urethane bond by reacting with the polyol. That is, the isocyanate compound functions as a crosslinking agent or a curing agent. Examples of the isocyanate compound include aromatic tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), aliphatic xylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), and isophorone diisocyanate (IPDI) monomers, polymers thereof, and derivatives thereof. The above-mentioned isocyanate compounds may be used alone or in combination of two or more.

Examples of silane coupling agents include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane. The organic silane 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 their hydrolyzates alone, or two or more of them in combination.

The undercoat layer 13 can be formed by preparing a mixed solution by mixing the above-mentioned components in an organic solvent in any ratio, and using the mixed solution prepared on the first surface 10a of the resin substrate 10. The mixed solution may contain, for example, a curing accelerator such as a tertiary amine, an imidazole derivative, a metal salt compound of a carboxylic acid, a quaternary ammonium salt, or a quaternary phosphonium salt; an antioxidant such as a phenol-based, sulfur-based, or phosphite-based antioxidant; a leveling agent; a flow control agent; a catalyst; a crosslinking reaction accelerator; a filler, etc.

The mixed liquid can be coated onto the resin substrate 10 using a known printing method such as offset printing, gravure printing, or silk screen printing, or a known application method such as roll coating, knife edge coating, or gravure coating. After coating, the mixture can be heated to, for example, 50 to 200°C and dried and/or cured to form the undercoat layer 13.

The thickness of the undercoat layer 13 is not particularly limited and may be, for example, 0.005 to 5 μm. The thickness may be adjusted according to the application or the desired characteristics. The thickness of the undercoat layer 13 is preferably 0.01 to 1 μm, and more preferably 0.01 to 0.5 μm. If the thickness of the undercoat layer 13 is 0.01 μm or more, sufficient adhesion strength is obtained between the resin substrate 10 and the inorganic oxide layer 14 or the oxygen barrier film 15, and the oxygen barrier properties are also good. If the thickness of the undercoat layer 27 is 1 μm or less, it is easy to form a uniform coating surface, and the drying load and manufacturing costs can be suppressed.

(Inorganic oxide layer)
Examples of materials for the inorganic oxide layer 14 include aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, tin oxide, zinc oxide, and indium oxide. In particular, aluminum oxide or silicon oxide is preferred because it has excellent productivity and excellent oxygen barrier properties and water vapor barrier properties in heat resistance and wet heat resistance. The inorganic oxide layer 14 may contain one of these materials alone or two or more of them in combination. The thickness of the inorganic oxide layer 14 is preferably 1 to 200 nm. If the thickness is 1 nm or more, excellent oxygen barrier properties and water vapor barrier properties are obtained, and 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 unlikely to occur, and deterioration of the barrier properties can be suppressed. The inorganic oxide layer 14 can be formed by a known film formation method such as a vacuum deposition method, a sputtering method, an ion plating method, or a plasma vapor phase deposition method (CVD).

(Oxygen barrier film)
The oxygen barrier film 15 may be a known oxygen barrier film formed by a wet coating method. The oxygen barrier film 15 is obtained by forming a coating film made of a coating agent on the underlayer 13 or the inorganic oxide layer 14 by a wet coating method, and drying the coating film. The coating film is a wet film, and the film is a dry film.

As the oxygen barrier film 15, a film (organic-inorganic composite film) containing at least one of a metal alkoxide and its hydrolysate or its reaction product, and a water-soluble polymer is preferable. Furthermore, a film further containing at least one of a silane coupling agent and its hydrolysate is preferable.

Examples of metal alkoxides and hydrolysates thereof contained in the organic-inorganic composite film include those represented by the general formula M(OR) _n , such as _{tetraethoxysilane} [Si( _OC2H5 ) ₄ ] and _{triisopropoxyaluminum} [Al( _OC3H7 ) ₃ ], and their hydrolysates. One of these may be contained alone, or two or more may be contained in combination.

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

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

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

The content of the water-soluble polymer in the organic-inorganic composite film is, for example, 15 to 50 mass%. The lower limit of the content of the water-soluble polymer in the organic-inorganic composite film may be 20 mass% from the viewpoint of further reducing oxygen permeability. The upper limit of the content of the water-soluble polymer in the organic-inorganic composite film may be 45 mass% from the viewpoint of further reducing oxygen permeability.

The silane coupling agent and its hydrolysate contained in the organic-inorganic composite film include silane coupling agents having an organic functional group. Such silane coupling agents and their hydrolysates include ethyltrimethoxysilane, vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and their hydrolysates. One of these may be contained alone, or two or more may be contained in combination.

At least one of the silane coupling agent and its hydrolysate preferably has an epoxy group as an organic functional group. Examples of silane coupling agents having an epoxy group include γ-glycidoxypropyltrimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. Silane coupling agents having an epoxy group and their hydrolysates may have an organic functional group other than the epoxy group, such as a vinyl group, an amino group, a methacryl group, or a ureyl group.

A silane coupling agent having an organic functional group and its hydrolysate can further improve the oxygen barrier properties of the oxygen barrier film 15 and the adhesion to the underlayer 13 or inorganic oxide layer 14 by interaction between the organic functional group and the hydroxyl group of the water-soluble polymer. In particular, the epoxy groups of the silane coupling agent and its hydrolysate and the hydroxyl groups of polyvinyl alcohol can form an oxygen barrier film 15 that is particularly excellent in oxygen barrier properties and adhesion to the underlayer 13 or inorganic oxide layer 14 by interaction.

The total content of the silane coupling agent and at least one of its hydrolysates or reaction products in the organic-inorganic composite film is, for example, 1 to 15 mass%. From the viewpoint of further reducing oxygen permeability, the lower limit of the total content of the silane coupling agent and at least one of its hydrolysates or reaction products in the organic-inorganic composite film may be 2 mass%. From the same viewpoint, the upper limit of the total content of the silane coupling agent and at least one of its hydrolysates or reaction products in the organic-inorganic composite film may be 12 mass%.

The organic-inorganic composite film may contain a crystalline inorganic layered compound having a layered structure. Examples of the inorganic layered compound include clay minerals such as kaolinite, smectite, and mica. These may be used alone or in combination of two or more. The particle size of the inorganic layered compound is, for example, 0.1 to 10 μm. The aspect ratio of the inorganic layered compound is, for example, 50 to 5000.

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

Another preferred example of the oxygen barrier film 15 is a film containing 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) (polycarboxylic acid polyvalent metal salt film). In this case, the polycarboxylic acid polyvalent metal salt film may be formed by applying a coating agent in which the polycarboxylic acid polymer (A) and the polyvalent metal compound (B) are mixed and then drying by heating. Alternatively, the polycarboxylic acid polyvalent metal salt film may be formed by applying a coating agent mainly composed of the polycarboxylic acid polymer (A) and drying to form the A film, applying a coating agent mainly composed of the polyvalent metal compound (B) and drying to form the B film, and then crosslinking the A/B layers to form the polycarboxylic acid polyvalent metal salt film.

[Polycarboxylic acid polymer (A)]
A polycarboxylic acid polymer is a polymer having two or more carboxyl groups in a molecule. Examples of polycarboxylic acid polymers include (co)polymers of ethylenically unsaturated carboxylic acids; copolymers of ethylenically unsaturated carboxylic acids and other ethylenically unsaturated monomers; and acidic polysaccharides having a carboxyl group in a molecule, such as alginic acid, carboxymethylcellulose, and pectin. Examples of the 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 the ethylenically unsaturated carboxylic acids include saturated carboxylic acid vinyl esters such as ethylene, propylene, and vinyl acetate, alkyl acrylates, alkyl methacrylates, alkyl itaconates, vinyl chloride, vinylidene chloride, styrene, acrylamide, and acrylonitrile. These polycarboxylic acid polymers may be used alone or in combination of two or more.

Of the above, from the viewpoint of the gas barrier properties of the resulting gas barrier film, preferred components are 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, and particularly preferred are 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.

In the polymer, the proportion of the 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 (where 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, examples of the other structural units include structural units derived from ethylenically unsaturated monomers copolymerizable with the above-mentioned ethylenically unsaturated carboxylic acid.

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 5,000 to 1,000,000. If the number average molecular weight is less than 2,000, the resulting gas barrier film will not achieve sufficient water resistance, and moisture may cause the gas barrier properties and transparency to deteriorate, or whitening may occur. On the other hand, if the number average molecular weight exceeds 10,000,000, the viscosity of the coating agent when forming the oxygen barrier film 15 may increase, and the coatability may be impaired. The number average molecular weight is the number average molecular weight calculated in terms of polystyrene, as determined by gel permeation chromatography (GPC).

When a coating agent mainly composed of a polycarboxylic acid polymer (A) is applied and dried to form an A film, and then the B film is formed, the polycarboxylic acid polymer may have a part of its carboxyl groups neutralized in advance with a basic compound. By neutralizing a part of the carboxyl groups of the polycarboxylic acid polymer in advance, the water resistance and heat resistance of the A film can be further improved. As the basic compound, at least one basic compound selected from the group consisting of polyvalent metal compounds, monovalent metal compounds, and ammonia is preferable. As the polyvalent metal compound, the compounds exemplified in the description of the polyvalent metal compound (B) described later can be used. As the monovalent metal compound, for example, sodium hydroxide, potassium hydroxide, etc. can be mentioned.

Various additives can be added to coating agents whose main component is polycarboxylic acid polymer (A), including crosslinking agents, curing agents, leveling agents, defoamers, antiblocking agents, antistatic agents, dispersants, surfactants, softeners, stabilizers, film-forming agents, thickeners, etc., within the limits that do not impair the barrier performance.

The solvent used in the coating agent containing polycarboxylic acid polymer (A) as the main component is preferably an aqueous medium. Examples of the aqueous medium include water, water-soluble or hydrophilic organic solvents, or mixtures thereof. The aqueous medium usually contains water or water as the 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 the water-soluble or hydrophilic organic solvent 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.

[Polyvalent metal compound (B)]
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 polycarboxylic acid, and examples thereof include zinc oxide particles, magnesium oxide particles, magnesium methoxide, copper oxide, calcium carbonate, etc. These may be used alone or in combination. Zinc oxide is preferred from the viewpoint of the oxygen barrier properties of the oxygen barrier coating.

Zinc oxide is an inorganic material that has ultraviolet absorbing properties. The average particle size of the zinc oxide particles is not particularly limited, but from the viewpoints 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.

When a coating agent mainly composed of a polyvalent metal compound (B) is applied and dried to form a B film, various additives may be contained in addition to zinc oxide particles as necessary within a range that does not impair the effects of the present invention. The additives may include a resin that is soluble or dispersible in the solvent used in the coating agent, a dispersant that is soluble or dispersible in the solvent, a surfactant, a softener, a stabilizer, a film-forming agent, a thickener, etc.

Among the above, it is preferable to contain a resin that is soluble or dispersible in the solvent used in the coating agent. This improves the coatability 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 that the coating agent contains a dispersant that is soluble or dispersible in the solvent used in the coating agent. This improves the dispersibility of the polyvalent metal compound. Anionic surfactants and nonionic surfactants can be used as the dispersant. Examples of the surfactant include (poly)carboxylates, alkyl sulfates, alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl sulfosuccinates, alkyldiphenyl ether disulfonates, 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 alone or in combination of two or more.

When an additive is contained in a coating agent mainly composed of a polyvalent metal compound (B), the mass ratio of the polyvalent metal compound to the additive (polyvalent metal compound:additive) is preferably within the range of 30:70 to 99:1, and more preferably within the range of 50:50 to 98:2.

Examples of solvents used in coating agents containing polyvalent metal compound (B) as a main component 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 alone or in combination of two or more. Among these, from the viewpoint of coatability, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred. From the viewpoint of manufacturability, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred.

When a coating agent containing a mixture of a polycarboxylic acid polymer (A) and a polyvalent metal compound (B) is applied and dried to form a polycarboxylic acid polyvalent metal salt film, the polycarboxylic acid polyvalent metal salt film can be formed by mixing the polycarboxylic acid polymer (A) and the polyvalent metal compound (B) with a solvent of water or alcohol, a resin or dispersant that can be dissolved or dispersed in the solvent, and additives as necessary, and applying and drying the mixture as a coating agent by a known coating method. Examples of coating methods include casting, dipping, roll coating, gravure coating, screen printing, reverse coating, spray coating, kit coating, die coating, metaling bar coating, chamber doctor combined coating, curtain coating, etc.

The thickness of the oxygen barrier film 15 is set according to the required oxygen barrier properties, and may be, for example, 0.05 to 5 μm. The thickness of the oxygen barrier film 15 is preferably 0.05 to 1 μm, and more preferably 0.1 to 0.5 μm. If the thickness of the oxygen barrier film 15 is 0.05 μm or more, sufficient oxygen barrier properties are easily obtained. If the thickness of the oxygen barrier film 15 is 1 μm or less, the presence or absence of protrusions derived from the AB agent on the first surface 10a has a large effect on the oxygen barrier properties, and the usefulness of the present invention is high. In addition, if the thickness of the oxygen barrier film 15 is 1 μm or less, it is easy to form a uniform coating surface, and drying load and manufacturing costs can be suppressed.

Gas barrier films having the above-mentioned organic-inorganic composite film or the above-mentioned polyvalent metal salt film of polycarboxylic acid as a gas barrier film exhibit excellent oxygen barrier properties even when subjected to boiling or retort sterilization, and when laminated with a sealant film, have sufficient adhesion strength and sealing strength as packaging materials for boiling or retort treatment.Furthermore, they have advantages such as transparency not found in metal foils or metal vapor deposition films, excellent bending resistance and stretching resistance, and no risk of generating harmful substances such as dioxins.

The sealant layer 18 is a layer that is bonded by heat fusion when the gas barrier film 100 is used to form a bag-shaped package or the like. Examples of materials for the sealant layer 18 include resin materials such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, and metal cross-linked products thereof. The thickness of the sealant layer 60 is determined according to the purpose, but can be in the range of 15 to 200 μm, for example.

The adhesive layer 17 bonds the sealant layer 18 and the oxygen barrier film 15. By using the adhesive layer 17, the resin film that becomes the sealant layer 18 and the substrate 10 on which the oxygen barrier film 15 is formed can be bonded together by dry lamination. An example of the material for the adhesive layer 17 is a two-component curing polyurethane adhesive.

A printed layer, an intervening film, a sealant layer, etc. can be laminated on the oxygen barrier film 15 to form a packaging material. When laminating, an extrusion lamination method can be used in which a sealant is formed directly on the coating layer 30 without an adhesive.

In infrared spectroscopy, the first surface 10a of the substrate 10 has an intensity ratio between a peak intensity (I1) at 1370 to 1380 cm ^-1 and a peak intensity (I2) at 1450 to 1460 cm ^-1 that is within the range of formula (1). That is, I1 is 1.65 times or less than I2. In this embodiment, this intensity ratio is brought about by the material properties of the surface layer 11 that constitutes the first surface 10a.
I1/I2≦1.65…(1)

The value of the above formula (1) indicates the proportion of polypropylene in the resin components at the measurement point. I1 indicates the amount of polypropylene, and I2 indicates the sum of polyethylene and polypropylene. Therefore, the value of formula (1) is larger for homopolymers than for copolymers and terpolymers, and in copolymers and terpolymers, the value of formula (1) decreases as the amount of components other than polypropylene increases.

The inventors conducted various studies when constructing a gas barrier film using a base material mainly composed of polypropylene. As a result, they found that in the first surface 10a on which the oxygen barrier coating 15 is formed, the adhesion strength of the gas barrier layer is improved when the proportion of polypropylene is low within the range of the main component. The value of formula (1) in the first surface 10a is preferably 1.55 or less, and more preferably 1.50 or less.

The gas barrier film 100 of this embodiment is constructed so that the gas barrier layer exhibits suitable gas barrier properties and is well bonded to the substrate and does not peel off easily, while maintaining a mono-material structure with polypropylene as the main component and reducing the environmental impact.

As a result of further investigation, the inventors found that the overall properties of the substrate 10 are further improved by adding a base layer 12 having a larger value of formula (1) to the surface layer 11 including the first surface having the above characteristics. By laminating a layer having a larger value of formula (1), i.e., a layer having a higher proportion of polypropylene than the layer including the first surface, the heat resistance of the substrate 10 as a whole is improved. As a result, sufficient heat can be applied to the substrate 10 when forming the oxygen barrier coating 15, and the barrier performance of the oxygen barrier coating 15 can be improved. Furthermore, when the manufactured gas barrier film is subjected to a hot water treatment such as a retort treatment or a boiling treatment, the base layer 12 suppresses the shrinkage of the surface layer 11, and preferably suppresses the occurrence of cracks or the like in the oxygen barrier coating 15 due to shrinkage, thereby reducing the gas barrier function, and the oxygen barrier coating 15 becoming easily peeled off from the substrate 10.

From this perspective, the value of the above formula (1) on the second surface 10b that constitutes the base layer 12 is preferably greater than the value on the first surface 10a, and is more preferably 1.65 or greater.

(Method for producing gas barrier film)
The gas barrier film 100 can be produced by forming an underlayer 13, or both the underlayer 13 and the inorganic oxide layer 14, on the first surface 10a of the resin substrate 10, and then forming an oxygen barrier coating 15 on the underlayer 13 or the inorganic oxide layer 14.

The resin substrate 10 may be a commercially available product or may be manufactured by a known method.

As described above, the undercoat layer 13 is obtained by forming a coating film made of a coating agent on the first surface 10a of the resin substrate 10 by a wet coating method, and then drying this coating film. As the wet coating method, known wet coating methods such as roll coating, gravure coating, reverse coating, die coating, screen printing, and spray coating can be used. As a method for drying the coating film made of the coating agent, known drying methods such as hot air drying, hot roll drying, and infrared irradiation can be used. Drying conditions include, for example, 90°C for 10 seconds.

The inorganic oxide layer 14 is obtained by forming a film on the underlayer 13 by the above-mentioned vacuum deposition method, sputtering method, ion plating method, plasma chemical vapor deposition (CVD) method, or the like.

The oxygen barrier film 15 is obtained by forming a coating film made of the above-mentioned coating agent on the underlayer 13 or the inorganic oxide layer 14 by a wet coating method, and drying the coating. As the wet coating method, known wet coating methods such as roll coating, gravure coating, reverse coating, die coating, screen printing, and spray coating can be used. As a method for drying the coating film made of the coating agent, known drying methods such as hot air drying, hot roll drying, and infrared irradiation can be used. As a drying condition, for example, a condition of 90°C for 10 seconds can be mentioned. The oxygen barrier film 15 may be formed by a single coating and drying, or may be formed by repeated coating and drying multiple times using the same or different coating agents.

(Action and Effect)
The gas barrier film 100 described above includes a resin substrate 10 having at least a surface layer 11 and a base layer 12, and a base layer 13, or a base layer 13 and an inorganic oxide layer 14, on a first surface 10a of the resin substrate 10, and further includes an oxygen barrier coating 15. The number of fine particles 16 contained in the surface layer 11 is 100 or less per region of 250 μm on a side, and the average protruding height of the fine particles 16 is 2.5 μm or less, so that the inherent oxygen barrier properties can be fully exhibited and the gas barrier film 100 has excellent oxygen barrier properties. In addition, since the thickness of the oxygen barrier coating 15 can be reduced, the gas barrier film 100 can be provided at low cost.

The reason why the oxygen barrier film 15 can fully exhibit its inherent oxygen barrier properties even when it is thin is thought to be as follows.

Generally, resin substrates contain fine particles 16 of AB agent to prevent blocking, and protrusions caused by the AB agent are present on both sides (first and second sides) of the resin substrate. When a coating agent is applied to this resin substrate by wet coating, particularly when the amount of application is small, a coating film is not formed locally at the positions of the protrusions, resulting in defects. These defects become paths for gas permeation, and oxygen barrier properties are not fully expressed.

Although the present invention has been described above by showing embodiments, the present invention is not limited to the above embodiments. Each configuration and their combinations in the above embodiments are merely examples, and additions, omissions, substitutions, and other modifications of configurations are possible without departing from the spirit of the present invention.

The gas barrier film may further have a printing layer, an anchor coat layer, an overcoat layer, a light-shielding layer, an oxygen absorbing layer, an adhesive layer, a heat-sealable heat-fusible layer, and other functional layers, as necessary.

When the gas barrier film has a heat-sealable sealant layer 18, this sealant layer 18 is disposed on at least one outermost surface of the gas barrier film. By having the gas barrier film have the sealant layer 18, the gas barrier film becomes sealable by heat sealing. The sealant layer 18 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.

The present invention will be described in more detail below with reference to examples and comparative examples, although the present invention is not limited to the following examples.

[Materials used]
<Resin substrate>
α1: Biaxially oriented polypropylene film (product name: M-1, thickness 20 μm, one side corona treated, manufactured by Mitsui Chemicals Tocello Co., Ltd.).
α2: Biaxially oriented polypropylene film (product name: ME-1, thickness 20 μm, one side corona treated, manufactured by Mitsui Chemicals Tohcello Co., Ltd.).
α3: Biaxially oriented polypropylene film (product name: P2111, thickness 20 μm, one side corona treated, manufactured by Toyobo Co., Ltd.).
α4: Biaxially oriented polypropylene film (product name: P2102, thickness 20 μm, one side corona treated, manufactured by Toyobo Co., Ltd.).
α5: Biaxially oriented polypropylene film (product name: VPH2011, thickness 20 μm, one side corona treated, average particle size of AB agent on the corona treated side 2 μm, manufactured by A.J. Plast).
α6: Biaxially oriented polypropylene film (product name: PB210J, thickness 20 μm, one side corona treated, manufactured by Futamura Chemical Co., Ltd.).
α7: Biaxially oriented polypropylene film (product name: U-1, thickness 20 μm, one side corona treated, manufactured by Mitsui Chemicals Tocello Co., Ltd.).
α8: Biaxially oriented polypropylene film (product name: P2171, thickness 20 μm, one side corona treated, manufactured by Toyobo Co., Ltd.).
α9: Biaxially oriented polypropylene film (product name: P2161, thickness 20 μm, one side corona treated, manufactured by Toyobo Co., Ltd.).
α10: Biaxially oriented polypropylene film (product name: VPH2011, thickness 20 μm, one side corona treated, average particle size of AB agent on the corona treated side 4 μm, manufactured by A.J. Plast).

<Production Example 1>
Using ACRYDIC CL-1000 (DIC Corporation) as the acrylic polyol and TDI type curing agent CORONATE 2030 (Tosoh Corporation) as the isocyanate compound, the acrylic polyol and the isocyanate compound were mixed in a solids weight ratio of 6:4, and a dilution solvent (ethyl acetate) was used to prepare a mixed liquid (solids content: 2 mass%) for forming an undercoat layer.

<Production Example 2>
An aqueous solution of polyvinyl alcohol resin (PVA, product name: Poval PVA-105, manufactured by Kuraray Co., Ltd., polyvinyl alcohol with a saponification degree of 98-99% and a polymerization degree of 500) dissolved therein, and an aqueous solution of tetraethoxysilane (TEOS) and γ-glycidoxypropyltrimethoxysilane (GPTMS, product name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) each hydrolyzed with 0.02 mol/L hydrochloric acid were prepared, and the aqueous solutions were blended so that the weight ratio of PVA:TEOS:GPTMS before hydrolysis was 40:50:10. Further, a diluting solvent was added so that the solvent components of the blended aqueous solution had a mass ratio of water:isopropyl alcohol of 90:10, to prepare a coating agent (5% by mass) for forming an organic-inorganic composite film.

[Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4]
The mixed solution for forming the undercoat layer prepared in Production Example 1 was applied to the corona-treated surface of the resin substrate described in Table 1 using a gravure printer to form a coating film, and the coating film was passed through an oven at 100° C. for 10 seconds to dry, thereby forming a 0.1 μm-thick undercoat layer. Next, a vacuum deposition device using an electron beam heating system was used to evaporate a mixed material containing two or more of metallic silicon, silicon monoxide, and silicon dioxide, thereby forming an inorganic oxide layer made of silicon oxide having a thickness of 30 nm on the undercoat layer. Next, the coating agent for forming the organic-inorganic composite coating prepared in Production Example 2 was applied to the inorganic oxide layer formed using a gravure printer to form a coating film, and the coating film was passed through an oven at 100° C. for 10 seconds to dry, thereby forming an oxygen barrier coating made of an organic-inorganic composite coating having a thickness of 0.3 μm, thereby obtaining the gas barrier films of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4.

The evaluation items and measurement methods in each of the examples and comparative examples are shown below.
<Infrared spectroscopic measurement of the first and second surfaces>
Using a Fourier transform infrared spectrophotometer FT/IR-4000 (manufactured by JASCO Corporation), measurements were performed on both sides in the thickness direction of each substrate before the gas barrier film was produced. The measurement conditions were as follows.
Measurement conditions: ATR method Prism: Ge
Resolution: 4 ^cm
Accumulation count: 64

<Number of particles and average protruding height>
The surface of the first surface 10a was observed using a laser microscope LEXT OLS-4000 (manufactured by Olympus Corporation), and the number of fine particles per unit area and the protruding height were measured. The observation magnification was 50 times. The number per unit area was measured in a randomly selected area of 257 μm × 259 μm (area 0.067 mm ² ) and two areas of the same size adjacent to the right of the area, and the arithmetic average value of the three areas was used. The protruding height was used as the arithmetic average value of all fine particles counted in the three areas.

<Oxygen barrier properties after hot water treatment>
The gas barrier film of each example was laminated with CPP (polypropylene film) using an adhesive to produce a gas barrier laminate film for retort processing having a gas barrier film/adhesive/CPP configuration. The adhesive used was a two-liquid curing adhesive made by Mitsui Chemicals Polyurethane, Takelac (registered trademark) A620 (base material)/Takenate (registered trademark) A65 (curing agent), and the CPP was a polypropylene film made by Toray Film Processing, Torayfan ZK93KM (60 μm). The films were dry laminated using a multi-coater TM-MC made by HIRANO TECSEED and aged at 40° C. for 3 days. The oxygen barrier coating of the gas barrier film was placed on the adhesive side.

The resulting gas barrier laminate film was used to create an A5-sized, four-sided sealed pouch, which was filled with 150 ml of tap water and then sterilized by heating (retort processing) in hot water at 120°C for 30 minutes.

The gas barrier laminate film after the hot water treatment was measured for oxygen permeability (cm ^{3 /} (m 2 ·day·atm)) under an atmosphere of 30° C. and 70% RH using an oxygen permeability measuring device (product name: OXTRAN- ² /20, manufactured by MOCON Corporation).

<Adhesion strength after hot water treatment>
Immediately after production of the pouches of each example prepared by the above procedure and after hot water treatment, test pieces were cut out from the part of each pouch that had been in contact with the contents in accordance with JIS Z1707, and the peel strength of the gas barrier layer 20 was measured as an index of adhesion using an Orientec Co., Ltd. Tensilon universal testing machine RTC-1250. Measurements were performed in two types, T-type peel and 180° peel, both in normal state (dry) and with the measurement part wet (wet).

The measurement results for Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4 are shown in Table 1.

From the results shown in Table 1, the gas barrier films of Examples 1-1 to 1-6 had a value of formula (1) of 1.65 or less on the first surface, and all of them maintained high adhesion between the substrate 10 and the sealant layer 18 after hot water treatment. In addition, even after hot water treatment, the oxygen transmission rate was 5.0 cc/ ^m2 ·day·atm or less, showing good gas barrier performance.

On the other hand, the gas barrier films of Comparative Examples 1-1 to 1-3 had a value of formula (1) of the first surface of more than 1.65, and had poor adhesion after hot water treatment. The gas barrier film of Comparative Example 1-4 had an average protrusion height of the fine particles 16 of more than 2.5 μm and an oxygen permeability of more than 5.0 cc/ ^m2 day atm after hot water treatment, and did not achieve good gas barrier performance.

<Production Example 3>
20 parts by mass of an aqueous solution of polyacrylic acid having a number average molecular weight of 200,000 (Toagosei Aron A-10H, solid content concentration 25% by mass) was diluted with 58.9 parts by mass of distilled water. Then, 0.44 parts by mass of aminopropyltrimethoxysilane (APTMS, manufactured by Aldrich) was added and stirred to obtain a uniform solution, thereby preparing a coating agent mainly composed of a polycarboxylic acid polymer.

<Production Example 4>
A coating agent containing a polyvalent metal compound as a main component was prepared by mixing 100 parts by mass of an aqueous dispersion of zinc oxide particles (ZE143 manufactured by Sumitomo Osaka Cement) and 2 parts by mass of a hardener Liofol HAERTER UR 5889-21 (manufactured by Henkel).

[Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-4]
On the corona-treated surface of the resin substrate described in Table 2, the mixed solution for forming the undercoat layer prepared in Production Example 1 was applied using a gravure printer to form a coating film, and the coating film was passed through an oven at 100 ° C. for 10 seconds to dry, thereby forming a 0.1 μm thick undercoat layer. Next, the coating agent mainly composed of the polycarboxylic acid polymer prepared in Production Example 3 was applied to form a coating film, and the coating film was passed through an oven at 100 ° C. for 10 seconds to dry, thereby forming a 0.2 μm thick polycarboxylic acid polymer film. Further, the coating agent mainly composed of the polyvalent metal compound prepared in Production Example 4 was applied using a gravure printer on the polycarboxylic acid polymer film to form a coating film, and the coating film was passed through an oven at 100 ° C. for 10 seconds to dry, thereby forming a 0.2 μm thick polyvalent metal compound film, thereby forming an oxygen barrier film consisting of a polyvalent metal salt film of polycarboxylic acid, and the gas barrier films of Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-4 were obtained.

[Examples 2-7 to 2-10 and Comparative Examples 2-5 to 2-6]
The mixed solution for forming the undercoat layer prepared in Production Example 1 was applied to the corona-treated surface of the resin substrate shown in Table 2 using a gravure printing machine to form a coating film, and the coating film was passed through an oven at 100° C. for 10 seconds to dry, thereby forming an undercoat layer having a thickness of 0.1 μm. Next, a vacuum deposition apparatus using an electron beam heating system was used to evaporate a mixed material containing two or more of silicon metal, silicon monoxide, and silicon dioxide, thereby forming an inorganic oxide layer made of silicon oxide having a thickness of 30 nm on the undercoat layer. Next, on the inorganic oxide layer thus formed, a coating agent mainly composed of the polycarboxylic acid polymer prepared in Production Example 3 was applied using a gravure printing machine to form a coating film, and the coating was passed through an oven at 100°C for 10 seconds to dry, thereby forming a polycarboxylic acid polymer film having a thickness of 0.2 μm. Further, on the polycarboxylic acid polymer film, a coating agent mainly composed of the polyvalent metal compound prepared in Production Example 4 was applied using a gravure printing machine to form a coating film, and the coating was passed through an oven at 100°C for 10 seconds to dry, thereby forming a polyvalent metal compound film having a thickness of 0.2 μm. Thus, an oxygen barrier film consisting of a polyvalent metal salt film of polycarboxylic acid was formed, and the gas barrier films of Examples 2-7 to 2-10 and Comparative Examples 2-5 to 2-6 were obtained.

[Examples 2-11 to 2-14 and Comparative Examples 2-7 to 2-8]
The mixed solution for forming the undercoat layer prepared in Production Example 1 was applied to the corona-treated surface of the resin substrate shown in Table 2 using a gravure printer to form a coating film, which was then passed through an oven at 100° C. for 10 seconds to dry, forming an undercoat layer with a thickness of 0.1 μm. Next, metallic aluminum was evaporated using a vacuum deposition apparatus using an electron beam heating system, and oxygen gas was introduced therein to form an inorganic oxide layer made of aluminum oxide with a thickness of 20 nm on the undercoat layer. Next, on the inorganic oxide layer thus formed, a coating agent mainly composed of the polycarboxylic acid polymer prepared in Production Example 3 was applied using a gravure printing machine to form a coating film, and the coating was passed through a 100°C oven for 10 seconds to dry, thereby forming a polycarboxylic acid polymer film having a thickness of 0.2 μm. Further, on the polycarboxylic acid polymer film, a coating agent mainly composed of the polyvalent metal compound prepared in Production Example 4 was applied using a gravure printing machine to form a coating film, and the coating was passed through a 100°C oven for 10 seconds to dry, thereby forming a polyvalent metal compound film having a thickness of 0.2 μm. Thus, an oxygen barrier film consisting of a polyvalent metal salt film of polycarboxylic acid was formed, and the gas barrier films of Examples 2-11 to 2-14 and Comparative Examples 2-7 to 2-8 were obtained.

From the results shown in Table 2, the gas barrier films of Examples 2-1 to 2-14 had a value of formula (1) of 1.65 or less on the first surface, and all of them maintained high adhesion between the substrate 10 and the sealant layer 18 after hot water treatment. In addition, even after hot water treatment, the oxygen transmission rate was 5.0 cc/ ^m2 ·day·atm or less, showing good gas barrier performance.

On the other hand, in the gas barrier films of Comparative Examples 2-1 to 2-3 and 2-5 to 2-8, the value of formula (1) on the first surface was greater than 1.65, and the adhesion after hot water treatment was poor. In the gas barrier film of Comparative Example 2-4, the average protrusion height of the fine particles 16 was greater than 2.5 μm, and the oxygen permeability after hot water treatment exceeded 5.0 cc/ ^m2 day atm, and good gas barrier performance was not obtained.

The above describes one embodiment of the present invention and examples, but the specific configuration is not limited to this embodiment, and includes configuration changes and combinations that do not deviate from the gist of the present invention.

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

Furthermore, in the gas barrier film of the present invention, an adhesive layer or a sealant layer is not essential. In other words, an adhesive layer or a sealant layer may be provided as necessary, taking into consideration the specific use of the gas barrier film, etc.

The gas barrier film of the present invention exhibits excellent adhesion strength and gas barrier properties even after hot water treatment. In addition, the quality can be stabilized even if the oxygen barrier coating is made thin, making it possible to reduce raw material costs.

The gas barrier film of the present invention can be suitably used, for example, as a packaging material, and can also be suitably used as a packaging material for boiling and retort treatments. By using the gas barrier film of the present invention as a packaging material, the quality retention of the contents can be improved.

The gas barrier film of the present invention can be used for purposes other than packaging materials. Examples of uses other than packaging materials include films for electronic devices, films for solar cells, various functional films for fuel cells, substrate films, etc.

Reference Signs List 100 Gas barrier film 10 Resin substrate 11 Resin substrate Surface layer 12 Resin substrate Base layer 13 Undercoat layer 14 Inorganic oxide layer 15 Oxygen barrier film 16 Fine particles 17 Adhesive layer 18 Sealant layer

Claims (12)

A base material mainly composed of polypropylene;
The substrate has an oxygen barrier coating (excluding those containing an inorganic layered compound) on a first surface side thereof,
a base layer, or both a base layer and an inorganic oxide layer, between the substrate and the oxygen barrier coating;
In infrared spectroscopy of the first surface, a ratio of a peak intensity I1 present at 1360 to 1390 cm ⁻¹ to a peak intensity I2 present at 1440 to 1480 cm ⁻¹ satisfies the following formula (1):
I1/I2≦1.65…(1)
the first surface has protruding particles formed of a material other than polypropylene;
The number of the microparticles is 78 or less per 257 μm×259 μm region (area 0.067 mm ² );
A gas barrier film, wherein the fine particles have an average protrusion height of 1.2 μm or less. the substrate has two or more resin layers including a base layer and a surface layer constituting the first surface,
The I1/I2 value in infrared spectroscopy of the resin layer on the second surface opposite to the first surface is
The gas barrier film according to claim 1 , wherein the I1/I2 value is greater than the I1/I2 value on the first surface. The gas barrier film according to claim 1 or 2, wherein the thickness of the undercoat layer is 0.01 to 1 μm. The underlayer contains an organic polymer as a main component,
The gas barrier film according to any one of claims 1 to 3, wherein the organic polymer comprises at least one of a polyacrylic resin, a polyol resin, a polyurethane resin, a polyamide resin, or a reaction product of these organic polymers. the underlayer and the inorganic oxide layer are provided between the substrate and the oxygen barrier coating,
The gas barrier film according to any one of claims 1 to 4, wherein the inorganic oxide layer has a thickness of 1 to 200 nm. the underlayer and the inorganic oxide layer are provided between the substrate and the oxygen barrier coating,
The gas barrier film according to any one of claims 1 to 5, wherein the inorganic oxide layer is aluminum oxide or silicon oxide. The gas barrier film according to any one of claims 1 to 6, wherein 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 7, wherein the oxygen barrier coating is a coating containing at least one of a metal alkoxide and its hydrolysate or its reaction product, and a water-soluble polymer. The gas barrier film according to claim 8, wherein the oxygen barrier coating further contains at least one of a silane coupling agent, a hydrolyzate thereof, or a reaction product thereof. The gas barrier film according to any one of claims 1 to 7, wherein the oxygen barrier coating contains a polyvalent metal salt of a carboxylic acid which is a reaction product between a carboxy group of a polycarboxylic acid polymer (A) and a polyvalent metal compound (B). The gas barrier film according to any one of claims 1 to 10, wherein the substrate further comprises a heat-sealable sealant layer, and the sealant layer is bonded to the oxygen barrier coating by an adhesive layer. After hot water treatment at 120°C for 30 minutes,
The oxygen permeability is 5.0 cc/ ^m2 ·day or less,
The gas barrier film according to claim 11, wherein the peel strength between the substrate and the sealant layer is 1.0 N/15 mm or more.