JP2023001746A - Gas barrier film, laminate, and packaging material - Google Patents

Abstract

To provide a gas barrier film that can form a laminate including a substrate and a heat seal layer in a sufficiently bonded state and is easy to recycle.SOLUTION: A gas barrier film 10 comprises a substrate 11 having polyethylene as a main resin component, and an inorganic oxide layer 13 formed on a first surface 11a side of the substrate. A crystallinity on the first surface 11a side of the substrate 11 is 35% or less. A proportion of the polyethylene in the entire gas barrier film is 90 mass% or more.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, there is known one in which a gas barrier layer made of a material having gas barrier properties is provided on the surface of a resin substrate. 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 recent years, due to the growing environmental awareness stemming from the problem of marine plastic litter and the like, there is a growing demand for more efficient separate collection and recycling of plastic materials. Laminates for packaging, which have achieved high performance by combining various different types of materials, are no exception, and there is a growing demand for monomaterials.

In order to realize a mono-material in the laminate, it is necessary to use the same resin material for the films constituting each layer. For example, polyethylene, which is a type of polyolefin, is widely used as a packaging material, and therefore, it is expected that a laminate using polyethylene will be made into a monomaterial.

In order to realize monomaterialization, for example, Patent Document 4 proposes a laminate using a polyethylene film having a vapor deposition layer on at least one surface of a base material and a heat seal layer. From the standpoint of suitability for bags, oriented polyethylene is disclosed as the base material.

Japanese Patent No. 6191221 JP-A-2000-254994 Japanese Patent No. 4373797 JP 2020-055157 A

The present inventors have found that when the laminate described in Patent Document 4 is applied to a packaging bag, standing pouch, etc., the adhesion between the stretched polyethylene base material constituting the laminate and the linear low-density polyethylene that is the heat seal layer It has been found that the properties may not be sufficient depending on the contents to be packaged. Insufficient adhesion may result in delamination of the laminate or tearing of the packaging material.
The inventors have solved this problem while maintaining a monomaterialized configuration.

In view of the above circumstances, an object of the present invention is to provide a gas barrier film in which a base material and a heat seal layer are sufficiently adhered to form a laminate that is easy to recycle.

A first aspect of the present invention is a gas barrier film comprising a substrate containing polyethylene as a main resin component and an inorganic oxide layer formed on the first surface side of the substrate.
This gas barrier film has a crystallinity of 35% or less on the first surface side of the substrate.
The proportion of polyethylene in the entire gas barrier film is 90% by mass or more.

A second aspect of the present invention is the gas barrier film according to the first aspect, and a heat seal layer containing polyethylene as a main resin component and bonded to the gas barrier film such that an inorganic oxide layer is sandwiched between the base material and the gas barrier film. and a laminate.
The proportion of polyethylene in the entire laminate is 90% by mass or more.
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 base material and a heat-sealing layer contact|adhere sufficiently, and the gas barrier film which can comprise the laminated body which is easy to recycle can be provided.

1 is a schematic cross-sectional view of a laminate according to one embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of a laminate according to an example; FIG.

An embodiment of the present invention will be described below with reference to FIG.
FIG. 1 is a schematic cross-sectional view of a laminate 1 according to this embodiment. A laminate 1 includes a gas barrier film 10 and a heat seal layer 30 . The gas barrier film 10 of this embodiment is one aspect of the gas barrier film according to the present invention.
The gas barrier film 10 and the heat seal layer 30 are bonded by the adhesive layer 20 .
The proportion of polyethylene in the laminate 1 is 90% by mass or more. Thereby, the laminate 1 is configured as a highly recyclable monomaterial.

The gas barrier film 10 includes a sheet-like substrate 11, and an undercoat layer 12, an inorganic oxide layer 13, and an overcoat layer 14 which are sequentially formed on the first surface 11a of the substrate 11. As shown in FIG.
The proportion of polyethylene in the gas barrier film 10 is 90% by mass or more. Thereby, the gas barrier film 10 is configured as a highly recyclable monomaterial.
Each configuration of the gas barrier film 10 will be described below.

The base material 11 contains polyethylene (PE). The base material 11 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.). That is, the substrate 11 may be a single layer or two or more layers.

The substrate 11 may be an unstretched film, or may be a uniaxially stretched or biaxially stretched film.
The density of PE contained in the base material 11 is preferably 0.935 or more, more preferably 0.940 or more. When the density of PE is within the above range, it is easy to prevent the substrate 11 from being stretched and wrinkled during rolling, and it is easy to prevent the inorganic oxide layer 13 from being cracked.
PE may be at least one polymer selected from homopolymers, random copolymers and block copolymers. A homopolymer is a polyethylene consisting of only polyethylene. Random copolymers are polyethylenes in which ethylene, the main monomer, and a small amount of comonomers different from ethylene (such as α-olefins) are randomly copolymerized to form a homogeneous phase. A block copolymer is a polyethylene that forms a heterogeneous phase by blockwise copolymerization or rubber-like polymerization of ethylene, which is the main monomer, and the comonomer (eg, α-olefin).

The substrate 11 may have a multi-layer construction comprising multiple layers (films) each containing PE with different densities. The base material 11 is desirably multi-layered as appropriate in consideration of processability, rigidity, stiffness, heat resistance, powder falling off during transportation, etc. of the film constituting each layer. The film constituting the substrate 11 can be produced by appropriately selecting and using high-density polyolefin, medium-density polyolefin, low-density polyolefin, or the like. Also in this case, the density of the base material 11 as a whole is preferably 0.935 or more.
Each layer of the base material 11 may contain a slip agent, an antistatic agent, and the like, and the content or content thereof may be different for each layer. Substrate 11 comprising multiple layers can be produced by extrusion coating, co-extrusion coating, sheet molding, co-extrusion blow molding, and the like.
The first surface 11a of the base material 11 is subjected to surface treatment such as chemical treatment, solvent treatment, corona treatment, low-temperature plasma treatment, ozone treatment, etc., in order to improve adhesion with the undercoat layer 12 and the inorganic oxide layer 13. may be applied. Furthermore, the second surface 11b on the opposite side of the first surface 11a may also be subjected to a similar surface treatment for the purpose of bonding to the printing base material.

The substrate 11 may contain additives such as fillers, antiblocking agents, antistatic agents, plasticizers, lubricants, and antioxidants. Any one of these additives may be used alone, or two or more thereof may be used in combination.

The thickness of the base material 11 is not particularly limited, and can be appropriately determined depending on the price and application while considering suitability as a packaging material and lamination suitability with other films. Practically, the thickness of the substrate 11 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 40 μm.

(Undercoat layer 12)
The undercoat layer 12 is a layer containing an organic polymer as a main component, and is sometimes called a primer layer. By providing the undercoat layer, the film formability and adhesion strength of the inorganic oxide layer 13 can be improved.
The content of the organic polymer in the undercoat layer 12 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 substrate 11 and the inorganic oxide layer 13, among the above, polyacrylic resins, polyol resins, polyurethane resins, polyamide resins, or reaction products of these organic polymers Preferably, the undercoat layer 12 includes at least one.
The undercoat layer 12 may contain a silane coupling agent, an organic titanate, a modified silicone oil, or the like.

As the organic polymer used for the undercoat layer 12, 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 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, hydroxybutyl methacrylate, and the like. 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 11 and the inorganic oxide layer 13 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 be one of the above-mentioned silane coupling agents and hydrolysates thereof, or may contain two or more of them in combination.

The undercoat layer 12 can be formed using a mixture of the above components 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 onto the substrate 11 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 undercoat layer 12 can be formed by heating to, for example, 50 to 200.degree.

The thickness of the undercoat layer 12 is not particularly limited, and can be, for example, 0.005 to 5 μm. The thickness can be appropriately determined depending on the application and required properties. The thickness of the undercoat layer 12 is preferably 0.01 to 1 μm, more preferably 0.01 to 0.5 μm. If the thickness of the undercoat layer 12 is 0.01 μm or more, sufficient adhesion strength between the base material 11 and the inorganic oxide layer 13 can be obtained, and the oxygen barrier property is also improved. When the thickness of the undercoat layer 12 is 1 μm or less, it is easy to form a uniform coated surface, and the drying load and manufacturing cost can be suppressed.

(Inorganic oxide layer 13)
Examples of inorganic oxides forming the inorganic oxide layer 13 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 13 may be formed of one type of inorganic oxide, or may be formed of two or more types of appropriately selected inorganic oxides.

The thickness of the inorganic oxide layer 13 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 13 can be formed by a known film forming method such as vacuum deposition, sputtering, ion plating, or plasma chemical vapor deposition (CVD).

(Overcoat layer 14)
A known oxygen barrier film formed by a wet coating method can be used as the overcoat layer 14 . The overcoat layer is optional and may not be provided.
The overcoat layer 14 is formed by forming a coating film made of a coating agent on any one of the substrate 11, the undercoat layer 12, and the inorganic oxide layer 13 by a wet coating method, and drying the coating film. obtained by In this specification, the term "coating film" means a wet film, and the term "coating" means a dry film.

The overcoat layer 14 includes a film containing at least one of a metal alkoxide, a hydrolyzate thereof, or a reaction product thereof, and a water-soluble polymer (hereinafter sometimes referred to as an "organic-inorganic composite film"). It's okay. 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 coating include, for example, tetraethoxysilane [Si(OC ₂ H ₅ ) ₄ ] and triisopropoxyaluminum [Al(OC ₃ H ₇ ) ₃ ]. Included are those of the formula M(OR) _n , as well as hydrolysates thereof. Only one of these may be contained, or two or more may be contained in an appropriate combination.

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

The water-soluble polymer contained in the organic-inorganic composite film is not particularly limited, and examples thereof include various polymers such as polyvinyl alcohol, polysaccharides such as starch, methylcellulose, and carboxymethylcellulose, and acrylic polyol. 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 coating is, for example, 15-50% 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. Only one of these may be contained, or two or more may be contained in an appropriate combination.

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 overcoat layer 14 and the undercoat layer 12 or inorganic oxidation by interaction between the organic functional group and the hydroxyl group of the water-soluble polymer. Adhesiveness to the material layer 13 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 form an overcoat layer 14 that is particularly excellent in oxygen barrier properties and adhesion through interaction.

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 coating can be further reduced, which is preferable.

The organic-inorganic composite coating 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. These can be used alone or in suitable combination of two or more. 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.

The thickness of the overcoat layer 14 is set according to the required oxygen barrier property, and can be, for example, 0.05 to 5 μm, preferably 0.05 to 1 μm, more preferably 0.1 to 0.5 μm. If the thickness of the overcoat layer 14 is 0.05 μm or more, it is easy to obtain sufficient oxygen barrier properties. If the thickness of the overcoat layer 14 is 1 μm or less, it is easy to form a uniform coated surface, and the drying load and manufacturing cost can be suppressed.

The overcoat layer 14 made of an organic-inorganic composite film exhibits excellent oxygen barrier properties even after boiling treatment or retort sterilization treatment. The laminate 1 in which the sealant film is bonded to the gas barrier film 10 has sufficient adhesion strength and sealing strength as a packaging material for boiling and retort processing, and furthermore, it has transparency and bending resistance that are not found in metal foils and metal deposition films. It has both flexibility and stretch resistance. Furthermore, there is an advantage that there is no risk of generation of harmful substances such as dioxin.

(Adhesion layer 20)
A known dry lamination adhesive can be used as the adhesive layer 20 . Any adhesive for dry lamination can be used without any particular limitation, and specific examples thereof include two-liquid curing type ester-based adhesives, ether-based adhesives, and urethane-based adhesives.

A gas-barrier adhesive that exhibits gas-barrier properties after curing can also be used for the adhesive layer 20 . By using the gas barrier adhesive, the gas barrier properties of the laminate 1 can be improved. The oxygen permeability of the gas barrier adhesive is preferably 150 cc/m ² ·day·atm or less, more preferably 100 cc/m ² ·day·atm or less, and 80 cc/m ² ·day·atm or less. is more preferably 50 cc/m ² ·day·atm or less. When the oxygen permeability is within the above range, the gas barrier properties of the laminate 1 can be sufficiently improved, and even if minor cracks or the like occur in the inorganic oxide layer 13 or the overcoat layer 14, However, it is possible to suppress the deterioration of the gas barrier property by entering the gas barrier adhesive into the gap.
Gas barrier adhesives include epoxy-based adhesives, polyester/polyurethane-based adhesives, and the like. Specific examples of the gas barrier adhesive include "Maxieve" manufactured by Mitsubishi Gas Chemical Company, Ltd., and "Paslim" manufactured by DIC Corporation.

When the adhesive layer 20 is made of a gas barrier adhesive, its thickness is preferably 50 times or more the thickness of the inorganic oxide layer 13 . When the thickness is within the above range, cracking of the inorganic oxide layer 13 can be more sufficiently suppressed, and the gas barrier properties of the laminate 1 can be further improved. Furthermore, the adhesive layer 20 can be provided with a cushioning property to absorb external impact, and the inorganic oxide layer 13 can be prevented from cracking due to the impact. The thickness is preferably 300 times or less the thickness of the inorganic oxide layer 13 from the standpoints of maintaining the flexibility of the laminate 1, processability, and cost.
Expressing such a thickness numerically, it is, for example, 0.1 to 20 μm, preferably 0.5 to 10 μm, more preferably 1 to 5 μm.

The adhesive that forms the adhesive layer 20 is, for example, a bar coating method, a dipping method, a roll coating method, a gravure coating method, a reverse coating method, an air knife coating method, a comma coating method, a die coating method, a screen printing method, a spray coating method, It can be applied by a gravure offset method or the like. The temperature for drying the coating film of the adhesive can be, for example, 30 to 200.degree. C., preferably 50 to 180.degree. The temperature for curing the coating film can be, for example, room temperature to 70°C, preferably 30 to 60°C. By setting the drying and curing temperatures within the above range, cracks in the inorganic oxide layer 13 and the adhesive layer 20 can be further suppressed, and excellent gas barrier properties can be exhibited.

From the viewpoint of preventing cracking of the inorganic oxide layer 13, it is preferable that the adhesive layer 20 and the inorganic oxide layer 13 are in direct contact. There may be.

(Heat seal layer 30)
The heat seal layer 30 is a layer containing polyolefin, and functions as a sealant when manufacturing a packaging bag or the like using the laminate 1 . A polyolefin film can be used as the heat seal layer 30 . By using a polyethylene film as the heat seal layer 30, the laminate 1 can be made into a monomaterial.

Polyolefin resins used for the heat seal layer 30 include low density polyethylene resin (LDPE), medium density polyethylene resin (MDPE), linear low density polyethylene resin (LLDPE), ethylene-vinyl acetate copolymer (EVA), Ethylene-based resins such as ethylene-α-olefin copolymers and ethylene-(meth)acrylic acid copolymers, blended resins of polyethylene and polybutene, homopolypropylene resins (PP), propylene-ethylene random copolymers, propylene- Polypropylene-based resins such as ethylene block copolymers and propylene-α-olefin copolymers can be used. These thermoplastic resins can be appropriately selected depending on the application and temperature conditions such as boiling treatment.

Various additives such as flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, and tackifiers may be added to the heat seal layer 30 .
The thickness of the heat seal layer 30 can be appropriately set in consideration of the shape of the packaging bag to be manufactured, the mass of the content to be accommodated, and the like, and can be, for example, 30 to 150 μm.

When manufacturing a laminate 1 having an adhesive layer 20 and a heat seal layer 30 using a polyolefin film, a dry lamination method of laminating with an adhesive such as a one-component curing type or two-component curing type urethane adhesive, Any non-solvent dry lamination method, in which a non-solvent adhesive is used for bonding, can be applied.
As another method, the heat seal layer 30 can be formed by an extrusion lamination method or the like in which a thermoplastic resin is heated and melted, extruded in a curtain shape, and laminated. In this case, the adhesive layer 20 may be omitted.

The above is the basic configuration of the laminate 1 . In the laminate 1, the inorganic oxide layer 13 is located between the substrate 11 and the heat seal layer.
The gas barrier film 10 can be used alone for various packaging materials that require gas barrier properties. By heat-sealing the peripheral edges, various packaging materials such as packaging bags and standing pouches using the laminate 1 can be formed.

The inventors have investigated various cases in which the adhesion between the polyethylene substrate and the heat seal layer is insufficient, and found that the adhesion varies depending on the degree of crystallinity of the substrate. Specifically, it was found that when the degree of crystallinity of the base material is 35% or less, the substrate adheres well to the heat seal layer. Based on this finding, the crystallinity of the substrate 11 of the present embodiment is set to 35% or less.

The crystallinity of the resin film can be measured by X-ray diffraction (XRD). An X-ray diffraction pattern is obtained by performing a 2θ/θ scan in out-of-plane measurement of the X-ray diffraction method. When the resin film is a polyethylene film, scanning is preferably performed within a diffraction angle range of 10° to 30°. When scanning in this range, two sharp crystalline peaks corresponding to the PE (110) plane and the PE (200) plane and a broad amorphous peak (halo peak) are observed. By separating and analyzing these three peaks and calculating the areas of the crystalline peak and the amorphous peak, the degree of crystallinity can be obtained from the formula (1).
Crystallinity = crystalline peak area/(crystalline peak area + amorphous peak area) (1)
It is preferable to use the parallel beam method because the surface of the resin film is not flat and there is a possibility that the measurement surface may be deviated.

According to the inventors' study, it was found that the adhesion strength between the base material 11 provided with the inorganic oxide layer 13 and the heat seal layer 30 can be sufficiently ensured when the degree of crystallinity is 35% or less.
In the present specification, "sufficient adhesion strength" means that the laminate strength between the base material 11 and the heat seal layer 30 measured according to JIS K6854 is 2N or more. As will be described later using examples, in the laminate 1 according to the present embodiment, the adhesion strength between the base material 11 and the heat seal layer 30 is sufficiently ensured.

The degree of crystallinity shows a certain correlation with the degree of orientation of the resin film, and the value tends to be small in the unstretched film. There is That is, the degree of crystallinity is a parameter that is independent of the general distinction between stretched and unstretched resin films. is.

An example of manufacturing procedures for the gas barrier film 10 and the laminate 1 will be described.
First, a substrate 11 having a degree of crystallinity of 35% or less is selected. The base material 11 may be a commercially available product or may be manufactured by a known method.
The substrate 11 may be a laminate of a plurality of resin films. In this case, if the degree of crystallinity of all of the plurality of resin films is 35% or less, the interlayer bonding strength of the substrate can be kept high, which is preferable.

Next, an undercoat layer 12 (if necessary) and an inorganic oxide layer 13 are formed on the substrate 11 .
When forming the undercoat layer 12, for example, a mixed solution for forming the undercoat layer 12 is applied to the first surface 11a to form a coating film, and the coating film is dried (solvent is removed). .
As a method for applying the mixed liquid, 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 the coating film composed of the mixed solution, 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 13 can be formed by the above-described vacuum deposition method, sputtering method, ion plating method, plasma vapor deposition method (CVD), or the like.

An overcoat layer 14 is formed on the inorganic oxide layer 13 as necessary.
The overcoat layer 14 can be formed, for example, by applying a mixed liquid for forming the overcoat layer 14 to form a coating film, and drying the coating film.
As the coating method and the drying method of the mixed liquid, the same methods as those mentioned in the description of the formation process of the undercoat layer 12 can be used.
The overcoat layer 14 may be formed by coating and drying once, or may be formed by repeating coating and drying multiple times with the same or different mixed liquids.

The laminated body 1 may be further provided with a printing layer, a protective layer, a light shielding layer, other functional layers, and the like, if necessary.
The printed layer can be provided at a position visible from the outside in the state of the laminate or packaging material for the purpose of displaying information about the contents, identifying the contents, or improving the design of the packaging bag. The printing method and printing ink are not particularly limited, and can be appropriately selected from known printing methods and printing inks in consideration of printability on film, design properties such as color tone, adhesion, safety as a food container, and the like. .
Examples of printing methods include gravure printing, offset printing, gravure offset printing, flexographic printing, and inkjet printing. Among them, the gravure printing method is preferable from the viewpoint of productivity and high definition of the pattern. In order to increase the adhesion of the printed layer, the surface of the layer forming the printed layer may be subjected to various pretreatments such as corona treatment, plasma treatment, and flame treatment, or may be provided with a coating layer such as an easy-adhesion layer. .
The printed layer can be provided between the inorganic oxide layer and the adhesive layer, between the overcoat layer and the adhesive layer, or the like. Furthermore, as will be described later, when the substrate has a multi-layer structure, it can also be provided within the substrate.

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.

Resin films used in Examples and Comparative Examples are shown below.
α1: unstretched polyethylene film (thickness 32 μm, density 0.950 g/cm ³ , single-sided corona treatment)
α2: unstretched polyethylene film (thickness 25 μm, density 0.952 g/cm ³ , single-sided corona treatment)
α3: Uniaxially stretched polyethylene film (thickness: 25 μm, density: 0.950 g/cm ³ , corona treatment on one side)
α4: Biaxially oriented polyethylene film (thickness 25 μm, density 0.950 g/cm ³ , single-sided corona treatment)
α5: unstretched polyethylene film (thickness 35 μm, density 0.926 g/cm ³ , single-sided corona treatment)
α6: Uniaxially stretched polyethylene film (thickness: 25 μm, density: 0.957 g/cm ³ , corona treatment on one side)

(Preparation of mixed solution for undercoat layer)
Acrylic polyol and tolylene diisocyanate are mixed so that the number of NCO groups of tolylene diisocyanate is equal to the number of OH groups of acrylic polyol, and the total solid content (total amount of acrylic polyol and tolylene diisocyanate ) was diluted with ethyl acetate to 5% by mass. Further, β-(3,4-epoxycyclohexyl)trimethoxysilane was added to 5 parts by mass with respect to 100 parts by mass of the total amount of the acrylic polyol and tolylene diisocyanate and mixed.
As described above, a liquid mixture for an undercoat layer was obtained.

(Preparation of mixture for overcoat layer)
Liquid A, liquid B and liquid C shown below were mixed in a mass ratio of 70/20/10, respectively, to obtain a mixed liquid for an overcoat layer.
A solution: _Solid content ₅ % by mass ₍ SiO ₂ conversion) hydrolysis solution B solution: 5% by mass water / methanol solution of polyvinyl alcohol (mass ratio of water: methanol is 95: 5)
Solution C: 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate was diluted with a mixture of water/isopropyl alcohol (mass ratio of water:isopropyl alcohol is 1:1) to a solid content of 5% by mass. hydrolysis solution

Two types of adhesives used for the adhesive layer are shown below.
(urethane adhesive)
An adhesive (gas barrier adhesive) obtained by mixing 100 parts by mass of Takelac A525 manufactured by Mitsui Chemicals, 11 parts by mass of Takenate A52 manufactured by Mitsui Chemicals, and 84 parts by mass of ethyl acetate.
Adhesion obtained by mixing 23 parts by mass of a solvent obtained by mixing ethyl acetate and methanol at a mass ratio of 1:1, 16 parts by mass of Maxieve C93T manufactured by Mitsubishi Gas Chemical Co., Ltd., and 5 parts by mass of Maxibe M-100 manufactured by Mitsubishi Gas Chemical Co., Ltd. agent

(Example 1)
A resin film α1 was used as a base material. The undercoat layer mixture was applied to the corona-treated surface (first surface) of the base material by gravure coating, dried and cured to form an undercoat layer with a coating amount of 0.1 g/m ² .
Next, on the undercoat layer, a transparent inorganic oxide layer (silica deposition film) made of silicon oxide and having a thickness of 30 nm was formed using a vacuum deposition apparatus employing an electron beam heating system. The O/Si ratio of the inorganic oxide layer was set to 1.8.
Furthermore, on the inorganic oxide layer, the mixture for overcoat layer was applied by gravure coating, dried and cured to form an overcoat layer having a thickness of 0.3 μm.
As described above, a gas barrier film according to Example 1 was obtained.
On the overcoat layer of the gas barrier film according to Example 1, the urethane-based adhesive was applied by gravure coating and dried to form an adhesive layer having a thickness of 3 μm. A 60 μm-thick unstretched LLDPE film (trade name: TUX-MCS, manufactured by Mitsui Chemicals Tocello Co., Ltd.) was laminated as a heat seal layer to this adhesive layer by dry lamination. After that, aging was performed at 40° C. for 4 days. Thus, a laminate according to Example 1 was obtained.

(Example 2)
A gas barrier film and a laminate according to Example 2 were obtained in the same manner as in Example 1, except that the resin film α2 was used as the base material.
(Example 3)
A gas barrier film according to Example 3 was obtained in the same manner as in Example 1, except that no overcoat layer was provided.
On the inorganic oxide layer of the gas barrier film according to Example 3, the gas barrier adhesive was applied by gravure coating and dried to form an adhesive layer having a thickness of 3 μm. A 60 μm-thick unstretched LLDPE film (trade name: TUX-MCS, manufactured by Mitsui Chemicals Tocello Co., Ltd.) was laminated as a heat seal layer to this adhesive layer by dry lamination. After that, aging was performed at 40° C. for 4 days. Thus, a laminate according to Example 3 was obtained.
(Example 4)
A gas barrier film and a laminate according to Example 4 were obtained in the same manner as in Example 3, except that the resin film α2 was used as the base material.

(Example 5)
A pattern was printed on one surface of the resin film α1 by gravure printing to provide a printed layer. The above urethane-based adhesive is applied onto the printed layer, and the substrate of the gas barrier film according to Example 1 is adhered to the surface (second surface) on which the inorganic oxide layer is not provided by dry lamination. A gas barrier film according to Example 5 was produced. Similarly, the printed resin film α1 was attached to the laminate according to Example 1, and a laminate according to Example 5 was produced.
FIG. 2 shows the layer structure of the laminate according to Example 5. As shown in FIG. The base material of the laminate 1A shown in FIG. 2 is configured by bonding the first polyethylene film 111 having the printed layer 115 to the second surface 11b of the base material 11 with the adhesive layer 120 . That is, the base material according to Example 5 has a structure in which two polyethylene layers are joined by an adhesive layer.

(Example 6)
A gas barrier film and laminate according to Example 6 were obtained in the same manner as in Example 5, except that the gas barrier film and laminate according to Example 3 were used.

(Example 7)
A gas barrier film and a laminate according to Example 7 were obtained in the same manner as in Example 3, except that the resin film α5 was used as the base material and no undercoat layer was provided.

(Example 8)
A gas barrier film and laminate according to Example 8 were obtained in the same procedure as in Example 5, except that the gas barrier film and laminate according to Example 7 were used.

(Comparative example 1)
A gas barrier film and a laminate according to Comparative Example 1 were obtained in the same manner as in Example 1, except that the resin film α3 was used as the base material.

(Comparative example 2)
A gas barrier film and a laminate according to Comparative Example 2 were obtained in the same manner as in Example 3, except that the resin film α3 was used as the base material.

(Comparative Example 3)
A gas barrier film and a laminate according to Comparative Example 3 were obtained in the same manner as in Example 3, except that the resin film α4 was used as the base material.

(Comparative Example 4)
A gas barrier film and a laminate according to Comparative Example 4 were obtained in the same manner as in Example 7, except that the resin film α6 was used as the base material.

The following items were evaluated using the gas barrier films and laminates of Examples and Comparative Examples.
(Measurement of crystallinity of substrate)
Before producing the gas barrier film, the crystallinity of the substrate was measured under the following conditions.
The X-ray diffraction pattern of the base material was obtained by out-of-plane measurement using a wide-angle X-ray diffractometer manufactured by Rigaku Corporation. obtained by scanning. A characteristic X-ray CuKα was used as the X-ray, which was collimated by a multi-layer film mirror and incident thereon, and a scintillation detector equipped with a flat plate collimator was used as the light-receiving unit.
From the obtained X-ray diffraction pattern, the areas of crystalline peaks and amorphous peaks were determined, and the ratio of the crystalline peak area to the total peak area was calculated as the degree of crystallinity.
When the substrate had multiple layers, the crystallinity of the layer constituting the first surface was measured.

(recyclability)
Based on the following formula (1), the ratio (wt%) of polyethylene in the laminate of each example was calculated.
(mass of resin films α1 to α4 used + mass of heat seal layer)/mass of entire laminate x 100 (1)
Evaluation was made into the following two grades.
○ (good): the proportion of polyethylene in the laminate is 90 wt% or more × (bad): the proportion of polyethylene in the laminate is less than 90 wt%

(Laminate strength between base material and heat seal layer)
According to JIS Z1707, a 15 mm width strip-shaped test piece was cut out from the laminate of each example, and the lamination strength between the substrate and the heat seal layer was measured using a Tensilon universal tester RTC-1250 by Orientec Co., Ltd. The following two conditions were used.
T-type peeling Normal state (DryT)
T-type peel Measurement site wetness (WetT)

(Oxygen permeability: OTR)
The laminate of each example was measured under conditions of 30° and 70% RH (relative humidity) by the Mocon method.
(Water vapor permeability: WVTR)
The laminate of each example was measured under conditions of 40° and 90% RH by the Mocon method.
Table 1 shows the results.

All of the examples had good recyclability and sufficient adhesion strength between the substrate and the heat seal layer. All the examples exhibited good gas barrier properties, but Examples 3, 4, and 6, in which a gas barrier adhesive was used for the adhesive layer, were particularly excellent in gas barrier properties.
On the other hand, although each comparative example had good recyclability, the adhesion strength between the base material and the heat seal layer was not sufficient, and there was concern that delamination or bag breakage might occur depending on the application. .

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, 1A laminate 10 gas barrier film 11, 11A substrate 11a first surface 12 undercoat layer 13 inorganic oxide layer 14 overcoat layer 20 adhesive layer 30 heat seal layer

A first aspect of the present invention is a gas barrier film comprising a substrate containing polyethylene as a main resin component and an inorganic oxide layer formed on the first surface side of the substrate.
This gas barrier film has a crystallinity of 35% or less on the first surface side of the substrate.
The proportion of polyethylene in the entire gas barrier film is 90% by mass or more.
This gas barrier film does not have an oxygen barrier coating containing water-swellable mica.

A first aspect of the present invention is a gas barrier film comprising a substrate containing only polyethylene as a resin component, and an inorganic oxide layer formed on the first surface side of the substrate.
This gas barrier film has a crystallinity of 35% or less on the first surface side of the substrate.
The proportion of polyethylene in the entire gas barrier film is 90% by mass or more.
This gas barrier film does not have an oxygen barrier coating containing water-swellable mica.

A second aspect of the present invention is a gas barrier film according to the first aspect, and a heat seal that contains only polyethylene as a resin component and is bonded to the gas barrier film so as to sandwich an inorganic oxide layer and a substrate. A laminate comprising a layer.
The proportion of polyethylene in the entire laminate is 90% by mass or more.
A third aspect of the present invention is a packaging material formed using the laminate according to the second aspect.

Claims (8)

a base material containing polyethylene as a main resin component;
an inorganic oxide layer formed on the first surface side of the substrate;
with
The crystallinity of the first surface side of the substrate is 35% or less,
The ratio of the polyethylene to the whole is 90% by mass or more,
gas barrier film. Further comprising an undercoat layer provided between the base material and the inorganic oxide layer,
The gas barrier film according to claim 1. The base material has a plurality of layers containing the polyethylene as a main resin component,
The gas barrier film according to claim 1 or 2. a gas barrier film according to any one of claims 1 to 3;
a heat seal layer having polyethylene as a main resin component and bonded to the gas barrier film so as to sandwich the inorganic oxide layer and the base material;
with
The ratio of the polyethylene to the whole is 90% by mass or more,
laminate. wherein the gas barrier film and the heat seal layer are bonded by an adhesive layer;
The laminate according to claim 4. The adhesive layer is made of a gas barrier adhesive,
The laminate according to claim 5. Further comprising an overcoat layer provided between the inorganic oxide layer and the heat seal layer,
The layered product according to any one of claims 4 to 6. A packaging material formed using the laminate according to any one of claims 4 to 7.

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