JP2023028513A - Gas barrier layer-forming composition, gas barrier film, laminate and wrapper - Google Patents

Abstract

To provide a gas barrier layer-forming composition capable of forming a gas barrier layer less prone to deterioration of gas barrier properties after heating.SOLUTION: A gas barrier layer-forming composition contains an aqueous polyurethane resin (A) containing an acid group-containing polyurethane resin, and a water-soluble polymer (B). The aqueous polyurethane resin (A) is free of polyurethane resin particles with a circle equivalent diameter exceeding 20 μm. A mass ratio between the aqueous polyurethane resin (A) and the water-soluble polymer (B) in a solid content (aqueous polyurethane resin (A)/water-soluble polymer (B)) is 85/15-10/90.SELECTED DRAWING: None

Description

The present disclosure relates to a composition for forming a gas barrier layer, a gas barrier film, a laminate, and a packaging bag.

In packaging bags used for packaging food, pharmaceuticals, etc., the intrusion of water vapor, oxygen, and other gases that alter the quality of the contents is suppressed in order to prevent deterioration and putrefaction of the contents and maintain their functions and properties. gas barrier properties are required. Therefore, conventionally, gas barrier films are used in these packaging bags.

A gas barrier film generally has a gas barrier layer on one side of a resin substrate, and the gas barrier layer is formed by coating and curing a composition for forming a gas barrier layer capable of imparting a gas barrier function to one side of the resin substrate. formed by

Various films have been developed as such gas barrier films.

For example, Patent Document 1 below describes gas barrier properties in which a gas barrier layer is formed using a composition containing a solid content consisting of a polyurethane resin, a water-soluble polymer, an inorganic layered mineral, and a silane coupling agent as a composition for forming a gas barrier layer. A film is disclosed.

JP 2017-222151 A

However, the gas barrier film described in Patent Literature 1 has a problem that the gas barrier property may deteriorate after heat treatment.

The present disclosure has been made in view of the above problems of the prior art, and includes a composition for forming a gas barrier layer capable of forming a gas barrier layer capable of suppressing deterioration of gas barrier properties after heat treatment, and a composition using the same. An object of the present invention is to provide a gas barrier film, a laminate, and a packaging bag.

As a result of repeated research to solve the above problems, the inventors of the present invention have found that gas barrier films provided with a gas barrier layer using a polyurethane resin may have different performance depending on the polyurethane resin used. In particular, it was confirmed that when heat sterilization such as retort treatment is performed, the deterioration of the gas barrier properties due to the heat treatment may increase. The present inventors have made intensive studies to find a method for forming a gas barrier layer that exhibits stable gas barrier properties even after heat treatment.

That is, the present disclosure provides a composition for forming a gas barrier layer containing an aqueous polyurethane resin (A) containing an acid group-containing polyurethane resin and a water-soluble polymer (B), wherein the aqueous polyurethane resin (A) However, it does not contain polyurethane resin particles with an equivalent circle diameter exceeding 20 μm, and the mass ratio of solids between the aqueous polyurethane resin (A) and the water-soluble polymer (B) (aqueous polyurethane resin (A)/highly water-soluble Provided is a composition for forming a gas barrier layer, wherein the molecule (B)) is 80/20 to 65/35.

When a gas barrier layer is formed using a composition for forming a gas barrier layer containing coarse particles of a polyurethane resin, voids and cracks are likely to occur around the coarse particles, and these become more pronounced after heat treatment. The inventors have found. In addition, when the gas barrier layer is formed on a resin base material made of a polyolefin film, the heat shrinkage of the polyolefin film is greater than that of the polyester film commonly used in the past. Voids and cracks are more likely to occur around coarse particles inside. When these voids, cracks, and the like are generated in the gas barrier layer, the gas barrier properties are degraded. The present inventors removed coarse particles from the water-based polyurethane resin (A) using filters of various sizes and studied the effect on the gas barrier properties. Therefore, it was found that even when a polyolefin film is used as a resin base material, a gas barrier layer capable of suppressing deterioration of gas barrier properties after heat treatment can be formed. That is, according to the composition for forming a gas barrier layer of the present disclosure having the above configuration, it is possible to form a gas barrier layer capable of suppressing deterioration of gas barrier properties after heat treatment.

The composition for forming a gas barrier layer may further contain a silane coupling agent (C). By containing the silane coupling agent (C) in the composition for forming a gas barrier layer, the resulting gas barrier layer can further suppress the deterioration of the gas barrier properties after heat treatment, and increase the laminate strength to the resin substrate. can be improved.

The present disclosure also provides a gas barrier film comprising a resin substrate and a gas barrier layer formed on one side of the resin substrate using the composition for forming a gas barrier layer of the present disclosure. According to the gas barrier film, it is possible to suppress deterioration of the gas barrier properties after heat treatment.

In the gas barrier film, the gas barrier layer may have a thickness of 0.1 to 10 μm at locations where polyurethane resin particles having an equivalent circle diameter of more than 10 μm are not present.

The gas barrier film may further include an inorganic oxide layer containing an inorganic oxide between the resin substrate and the gas barrier layer. By providing the inorganic oxide layer, the gas barrier property of the gas barrier film can be further improved.

In the gas barrier film, the resin substrate may be a polyolefin film. The polyolefin film may be a polyethylene film.

The present disclosure also provides a laminate (which retains high gas barrier properties even after heat treatment) comprising the gas barrier film of the present disclosure and a sealant layer laminated on the gas barrier film.

In the laminate, both the resin base material and the sealant layer in the gas barrier film may be polyethylene films, or both may be polypropylene films. By using the same material for the resin base material and the sealant layer, it is possible to further improve the recyclability of the laminate and the packaging bag using the same.

The present disclosure also provides a packaging bag (which retains high gas barrier properties even after heat treatment) formed by bonding the sealant layers to each other using the laminate of the present disclosure.

According to the present disclosure, a gas barrier layer-forming composition capable of forming a gas barrier layer capable of suppressing deterioration of gas barrier properties after heat treatment, a gas barrier film, a laminate, and a packaging bag using the same are provided. can be done.

1 is a schematic cross-sectional view showing one embodiment of a gas barrier film of the present disclosure; FIG. 1 is a schematic cross-sectional view showing an embodiment of a laminate of the present disclosure; FIG.

Hereinafter, embodiments of the present disclosure will be described in detail.

<Composition for forming gas barrier layer>
The composition for forming a gas barrier layer contains an aqueous polyurethane resin (A) containing an acid group-containing polyurethane resin and a water-soluble polymer (B). Here, the water-based polyurethane resin (A) does not contain polyurethane resin particles having an equivalent circle diameter exceeding 20 μm. Further, the mass ratio of the solid content of the aqueous polyurethane resin (A) and the water-soluble polymer (B) (aqueous polyurethane resin (A)/water-soluble polymer (B)) is 85/15 to 10/90. is. The gas barrier layer-forming composition may further contain a silane coupling agent (C). Each component constituting the composition for forming a gas barrier layer will be described in detail below.

(Aqueous polyurethane resin (A))
The aqueous polyurethane resin (A) includes an acid group-containing polyurethane resin containing acid groups. The water-based polyurethane resin (A) is used to impart flexibility and gas barrier properties, particularly oxygen barrier properties, to the gas barrier layer.

The acid-group-containing polyurethane resin constituting the water-based polyurethane resin (A) has an acid group and thus has anionic and self-emulsifying properties, and is also called an anionic self-emulsifying polyurethane resin. A carboxyl group, a sulfonic acid group, etc. are mentioned as an acid group. An acid group can usually be neutralized with a neutralizing agent (base), and may form a salt with a base. The acid group may be located at the end of the acid group-containing polyurethane resin or may be located in a side chain, but is preferably located at least in the side chain.

The water-based polyurethane resin (A) may further contain a polyamine compound. A polyamine compound functions as a cross-linking agent. In the water-based polyurethane resin (A), the gas barrier properties can be improved by bonding the acid groups of the acid group-containing polyurethane resin to a polyamine compound as a cross-linking agent. In this case, the acid group of the acid group-containing polyurethane resin is capable of bonding with the amino group (primary amino group, secondary amino group, tertiary amino group, etc.) of the polyamine compound. The bond between the acid group of the acid group-containing polyurethane resin and the polyamine compound may be an ionic bond (e.g., an ionic bond between a carboxyl group and a tertiary amino group) or a covalent bond (e.g., an amide bond). may be

The acid value of the acid-group-containing polyurethane resin can be selected within a range in which the acid-group-containing polyurethane resin is water-dispersible. , 15 to 60 mg KOH/g. When the acid value of the acid group-containing polyurethane resin is at least the lower limit of the above range, the water dispersibility of the acid group-containing polyurethane resin is improved, and the uniform dispersibility of the aqueous polyurethane resin and other materials and the composition for forming a gas barrier layer are improved. It can improve the dispersion stability of the product. When the acid value of the acid group-containing polyurethane resin is equal to or less than the upper limit of the above range, the water resistance and gas barrier properties of the gas barrier layer can be improved. The acid value of the acid group-containing polyurethane resin is measured by a method according to JIS K0070.

The total of the urethane group concentration and the urea group (urea group) concentration of the acid group-containing polyurethane resin is preferably 15% by mass or more, more preferably 20 to 60% by mass, from the viewpoint of gas barrier properties. When the sum of the urethane group concentration and the urea group concentration is equal to or higher than the above lower limit, the gas barrier properties of the gas barrier layer are likely to be improved. When the sum of the urethane group concentration and the urea group concentration is equal to or less than the upper limit of the above range, the flexibility of the gas barrier layer is likely to be improved.

The urethane group concentration means the ratio of the molecular weight of the urethane group (59 g/equivalent) to the molecular weight of the repeating structural unit of the polyurethane resin. The urea group concentration means the ratio of the molecular weight of the urea group (primary amino group (amino group): 58 g/equivalent, secondary amino group (imino group): 57 g/equivalent) to the molecular weight of the repeating structural unit of the polyurethane resin. do. When a mixture of two or more types of acid group-containing polyurethane resin is used, the urethane group concentration and the urea group concentration can be calculated based on the amount of reaction components charged, that is, the proportion of each component used.

The acid-group-containing polyurethane resin may usually have at least rigid units (units composed of hydrocarbon rings) and short-chain units (eg, units composed of hydrocarbon chains). That is, the constituent units of the acid group-containing polyurethane resin are usually derived from a polyisocyanate component, a polyhydroxy acid component, a polyol component, or a chain extender component (particularly, at least the polyisocyanate component), and have hydrocarbon rings (aromatic and at least one non-aromatic hydrocarbon ring).

The proportion of units composed of hydrocarbon rings in the constituent units of the acid group-containing polyurethane resin is usually 10 to 70% by mass, preferably 15 to 65% by mass, and more It is preferably 20 to 60% by mass. When the ratio of the unit composed of a hydrocarbon ring is at least the lower limit of the above range, the gas barrier properties of the gas barrier layer are likely to be improved. When the ratio of the units composed of hydrocarbon rings is equal to or less than the upper limit of the above range, the flexibility of the gas barrier layer is likely to be improved.

The number average molecular weight of the acid group-containing polyurethane resin can be selected as appropriate, but is preferably 800 to 1,000,000, more preferably 800 to 200,000, and 800 to 100,000. is more preferred. When the number average molecular weight of the acid group-containing polyurethane resin is equal to or less than the upper limit of the above range, it is easy to suppress an increase in the viscosity of the composition for forming a gas barrier layer. When the number average molecular weight of the acid group-containing polyurethane resin is at least the lower limit of the above range, the gas barrier properties of the gas barrier layer are likely to be improved. The number average molecular weight of the acid group-containing polyurethane resin is a value converted to standard polystyrene measured by gel permeation chromatography (GPC).

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

The polyamine compound constituting the aqueous polyurethane resin (A) is a compound having two or more basic nitrogen atoms. The basic nitrogen atom is a nitrogen atom that can bond with the acid group of the acid group-containing polyurethane resin. mentioned.

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

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

When the aqueous polyurethane resin (A) contains a polyamine compound, the content of the polyamine compound is the molar ratio of the acid groups of the acid group-containing polyurethane resin to the basic nitrogen atoms of the polyamine compound (acid group/basic nitrogen atom). is preferably 10/1 to 0.1/1, more preferably 5/1 to 0.2/1. If the acid group/basic nitrogen atom content is within the above range, the cross-linking reaction between the acid group of the acid group-containing polyurethane and the polyamine compound occurs appropriately, and the oxygen barrier properties of the gas barrier layer can be further improved.

The aqueous polyurethane resin (A) is usually used in the form of a dispersion in an aqueous medium (aqueous dispersion). Aqueous media include water, water-soluble or hydrophilic organic solvents, or mixtures thereof. Examples of water-soluble or hydrophilic organic solvents include alcohols such as methanol, ethanol and isopropanol; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran; cellosolves; is mentioned.

As the aqueous medium, water or a medium containing water as a main component is preferable. The content of water in the aqueous medium is preferably 70% by mass or more, more preferably 80% by mass or more. The aqueous medium may or may not contain a neutralizing agent (base) that neutralizes the acid groups of the acid group-containing polyurethane resin. Neutralizing agents are usually included.

The water-based polyurethane resin (A) does not contain polyurethane resin particles having an equivalent circle diameter exceeding 20 µm. The absence of polyurethane resin particles having an equivalent circle diameter exceeding 20 μm can be confirmed by the following method. That is, the particle size distribution of the equivalent circle diameter of the water-based polyurethane resin (A) is measured using the following measuring equipment and conditions. From the result of measuring 300 particles, the maximum equivalent circle diameter of the polyurethane resin particles contained in the water-based polyurethane resin (A) is obtained. does not contain polyurethane resin particles exceeding 20 μm. Therefore, the fact that the water-based polyurethane resin (A) does not contain polyurethane resin particles having an equivalent circle diameter of more than 20 μm means that the maximum equivalent circle diameter of the polyurethane resin particles in the water-based polyurethane resin (A) measured by the above method is 20 μm or less. It is synonymous with something. From the particle size distribution when 300 particles are measured by this measurement method, the average equivalent circle diameter of the polyurethane resin particles and the number of polyurethane resin particles having an equivalent circle diameter equal to or larger than a predetermined value can be obtained.

(Measuring equipment and conditions)
Equipment used: Particle shape image analyzer (manufactured by Seishin Enterprise Co., Ltd., trade name: PITA-04)
Analysis principle: dynamic image analysis method Particle size measurement range: 1 to 1000 μm
Particle size distribution: volume/area equivalent particle size distribution

The water-based polyurethane resin (A), which does not contain polyurethane resin particles with an equivalent circle diameter exceeding 20 μm, can be obtained, for example, by passing the water-based polyurethane resin (A) through a filter of a predetermined size (opening) to remove coarse particles. Obtainable.

The maximum equivalent circle diameter of the polyurethane resin particles in the water-based polyurethane resin (A) measured by the above method is 20 µm or less. It may be less than or equal to 10 μm or less.

The average equivalent circle diameter of the polyurethane resin particles in the aqueous polyurethane resin (A) measured by the above method may be 15 μm or less from the viewpoint of further suppressing the deterioration of the gas barrier properties of the gas barrier layer after heat treatment. , 10 μm or less.

The number (percentage) of polyurethane resin particles having an equivalent circle diameter of 10 μm or more in the water-based polyurethane resin (A) measured by the above method is determined from the viewpoint of further suppressing deterioration of the gas barrier properties of the gas barrier layer after heat treatment. , 9/300 (3%) or less, 5/300 (1.7%) or less, or 0/300 (0%).

(Water-soluble polymer (B))
A water-soluble polymer refers to a polymer that can be dissolved in water. The term "dissolution" as used herein refers to a state in which the solute polymer is dispersed in the solvent water at the molecular chain level to form a homogeneous system. More specifically, it refers to a state in which the intermolecular force with water molecules is stronger than the intermolecular force between the polymer chains, the entanglement of the polymer chains is broken, and the particles are evenly dispersed in water. The water-soluble polymer (B) is used particularly to improve the flexibility of the gas barrier layer and to suppress deterioration of the gas barrier properties due to post-processing.

Specific examples of the water-soluble polymer (B) include, for example, polyvinyl alcohol resins such as polyvinyl alcohol polymers and derivatives thereof; polyvinylpyrrolidone, polyacrylic acid, polymethacrylic acid or esters, salts thereof, and copolymers thereof; , vinyl polymers such as polyhydroxyethyl methacrylate and copolymers thereof; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; starches such as oxidized starch, etherified starch and dextrin; containing polar groups such as sulfoisophthalic acid Copolyester having an acid component; water-soluble urethane polymer; and functional group-modified polymers obtained by modifying the functional groups (carboxyl group, etc.) of these various polymers. Derivatives of polyvinyl alcohol polymers include, for example, graft polymers obtained by graft polymerization of monomers to the side chains of polyvinyl alcohol.

The water-soluble polymer (B) preferably has a degree of polymerization of 200 or more in consideration of film cohesive strength. The water-soluble polymer (B) contained in the composition for forming a gas barrier layer may be one kind or two or more kinds.

The water-soluble polymer (B) contains at least one polyvinyl alcohol resin selected from the group consisting of polyvinyl alcohol-based polymers and derivatives thereof, from the viewpoint of achieving both gas barrier properties and flexibility of the gas barrier layer. is preferred, and it is particularly preferred to contain a polyvinyl alcohol resin having a degree of saponification of 95% or more and a degree of polymerization of 300 or more. The polymerization degree of the polyvinyl alcohol resin is preferably 300-2400, particularly preferably 450-2000.

The higher the degree of saponification and polymerization, the lower the hygroscopic swelling property of the polyvinyl alcohol resin and the higher the gas barrier property. When the degree of saponification of the polyvinyl alcohol resin is 95% or more, it is easy to obtain sufficient gas barrier properties. When the degree of polymerization of the polyvinyl alcohol resin is 300 or more, it is easy to suppress deterioration of gas barrier properties and film cohesive strength. When the degree of polymerization of the polyvinyl alcohol resin is 2000 or less, it is easy to suppress the increase in viscosity of the composition for forming a gas barrier layer, it is easy to uniformly mix with other components, and it is easy to suppress deterioration in gas barrier properties and adhesion strength.

(Silane coupling agent (C))
As the silane coupling agent (C), one commonly used can be used, and examples thereof include compounds having an alkoxy group bonded to a silicon atom and an organic reactive group.

Examples of the silane coupling agent (C) include compounds represented by RSiX ₃ (wherein R is an organic reactive group and X is an alkoxy group). Examples of the organic reactive group include those having an amino group, (meth)acryl group, epoxy group, vinyl group, mercapto group, isocyanate group, isocyanurate group and the like. (Meth)acrylic groups refer to both acrylic and methacrylic groups. Examples of alkoxy groups include methoxy groups and ethoxy groups.

Examples of the silane coupling agent (C) include silane coupling agents having a vinyl group, such as vinyltrimethoxysilane and vinyltriethoxysilane. Silane coupling agents having an epoxy group include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxy propylmethyldimethoxysilane, 3-glycidoxypropylethyldiethoxysilane, and the like. Silane coupling agents having an amino group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane and the like. Silane coupling agents having a mercapto group include 3-mercaptopropyltrimethoxysilane and 3-mercaptopropylmethyldimethoxysilane. Silane coupling agents having (meth)acryl groups include 3-acryloxypropyltrimethoxysilane. Examples of silane coupling agents having an isocyanate group include 3-isocyanatopropyltriethoxysilane. Examples of silane coupling agents having an isocyanurate group include tris-(trimethoxysilylpropyl)isocyanurate. Any one of these silane coupling agents may be used alone, or two or more thereof may be used in combination.

As the silane coupling agent (C), an organic reactive group having reactivity with components in the gas barrier layer-forming composition is preferably used. As the silane coupling agent (C), one having an epoxy group is preferred. Since the epoxy group has good reactivity with the hydroxyl group of the water-based polyurethane resin (A) or the water-soluble polymer (B), the gas barrier properties of the gas barrier layer can be further improved.

(other ingredients)
The composition for forming a gas barrier layer may contain components other than those described above within a range that does not impair the gas barrier properties of the gas barrier layer. Examples of other components include additives such as antioxidants, weathering agents, heat stabilizers, lubricants, crystal nucleating agents, UV absorbers, plasticizers, antistatic agents, coloring agents, fillers, and surfactants. be done.

The composition for forming a gas barrier layer preferably does not contain an inorganic layered mineral from the viewpoint of further suppressing deterioration of gas barrier properties after heat treatment. Even when the composition for forming a gas barrier layer contains an inorganic layered mineral, the content thereof is preferably less than 2% by mass based on the total solid content of the composition for forming a gas barrier layer.

Examples of inorganic layered minerals include hydrous silicates such as phyllosilicate minerals. Specific examples of hydrous silicates include: kaolinite group clay minerals such as halloysite, kaolinite and endellite; antigorite group clay minerals such as antigorite and chrysotile; smectite group clay minerals such as montmorillonite and beidellite. vermiculite group clay minerals such as vermiculite; mica such as synthetic mica, muscovite, and phlogopite;

(Content of each component)
In the composition for forming a gas barrier layer, the solid mass ratio of the water-based polyurethane resin (A) and the water-soluble polymer (B) (water-based polyurethane resin (A)/water-soluble polymer (B)) was 85/ 15 to 10/90, preferably 75/25 to 20/80, particularly preferably 70/30 to 25/75.

When the solid content mass ratio of the water-based polyurethane resin (A)/water-soluble polymer (B) is within the above range, the composition for forming a gas barrier layer can be applied evenly, and gas barrier properties and flexibility can be improved. It is possible to form a gas barrier layer which is excellent and which can suppress deterioration of gas barrier properties after heat treatment. If the content of the aqueous polyurethane resin (A) is greater than the solid content mass ratio of the aqueous polyurethane resin (A)/water-soluble polymer (B) of 85/15, unevenness may occur during coating. . Unevenness during coating leads to deterioration of appearance and deterioration of gas barrier properties. If the content of the water-based polyurethane resin (A) is less than the water-based polyurethane resin (A)/water-soluble polymer (B) ratio of 10/90, the oxygen barrier properties may be insufficient.

The content (solid content) of the silane coupling agent (C) in the gas barrier layer-forming composition is 0.5% by mass or more and 30% by mass or less based on the total solid content in the gas barrier layer-forming composition. It is preferably 1% by mass or more and 25% by mass or less, and particularly preferably 3% by mass or more and 20% by mass or less. When the content of the silane coupling agent (C) is within the above range, the cohesive force and gas barrier properties of the gas barrier layer are sufficiently enhanced while maintaining the flexibility of the gas barrier layer formed from the composition for forming a gas barrier layer. be able to.

The total content (solid content) of the water-based polyurethane resin (A), the water-soluble polymer (B), and the silane coupling agent (C) in the gas barrier layer-forming composition is It is preferably 85% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on the total solid content. The upper limit of the total content is not particularly limited, and may be 100% by mass.

<Gas barrier film>
FIG. 1 is a schematic cross-sectional view showing one embodiment of the gas barrier film of the present disclosure. In FIG. 1, the gas barrier film 10 includes a resin substrate 1 and a gas barrier layer 4 provided on one side of the resin substrate 1. Between the resin substrate 1 and the gas barrier layer 4, a resin substrate The base layer 2 and the inorganic oxide layer 3 are provided in order from the material 1 side. The gas barrier layer 4 is formed using the gas barrier layer-forming composition described above.

The resin substrate 1, the underlayer 2, the inorganic oxide layer 3, and the gas barrier layer 4 are described in detail below.

(Resin base material)
The resin base material 1 is a base material that serves as a support for the gas barrier layer 4 and contains a resin. Examples of resins include polyolefin resins, polyester resins, polyamide resins, polyether resins, acrylic resins, polyimide resins, epoxy resins, and natural polymer compounds (cellulose acetate, etc.). These may be composed alone or as a mixture of two or more.

Among them, polyolefin resin is preferably used from the viewpoint of recycling. Examples of polyolefin resins include polyethylene and polypropylene, and polypropylene is preferable from the viewpoint of resistance to retort treatment. Here, the polypropylene may be a homopolypropylene or a propylene copolymer, but from the viewpoint of oxygen barrier properties, the polypropylene constituting at least the surface layer of the resin base material 1 on the side of the gas barrier layer 4 is more preferably a polypropylene copolymer. preferable.

The resin substrate 1 may be a stretched film or an unstretched film, but from the viewpoint of oxygen barrier properties, it is preferably a stretched film. Here, the stretched film includes a uniaxially stretched film and a biaxially stretched film, but the biaxially stretched film is preferable because it improves heat resistance.

The thickness of the resin base material 1 is not particularly limited, and may be, for example, 10 μm or more and 0.1 mm or less.

The resin base material 1 may contain additives such as an antistatic agent, an ultraviolet absorber, a plasticizer, and a lubricant, if necessary.

(Underlayer)
The underlayer 2 is a layer for improving the adhesion between the resin substrate 1 and the inorganic oxide layer 3 , and is sandwiched between the resin substrate 1 and the inorganic oxide layer 3 .

The material constituting the underlayer 2 is not particularly limited as long as it can improve the adhesion between the resin substrate 1 and the inorganic oxide layer 3. Such materials include: It includes reactants of an organosilane or organometallic compound, a polyol compound, and an isocyanate compound. That is, it can also be said that the base layer 2 is a urethane-based adhesive layer. Organosilanes are, for example, trifunctional organosilanes or hydrolysates of trifunctional organosilanes. Organometallic compounds are, for example, metal alkoxides or hydrolysates of metal alkoxides. Metal elements contained in the organometallic compounds are, for example, Al, Ti, Zr, and the like. Each of the organosilane hydrolyzate and the metal alkoxide hydrolyzate should have at least one hydroxyl group. From the viewpoint of transparency, the polyol compound is preferably acrylic polyol. The isocyanate compound functions mainly as a cross-linking agent or curing agent. Polyol compounds and isocyanate compounds may be monomers or polymers.

The thickness of the underlayer 2 is not particularly limited as long as it can improve the adhesion between the resin substrate 1 and the inorganic oxide layer 3, but is preferably 30 nm or more. In this case, good adhesion between the resin base material 1 and the inorganic oxide layer 3 is more likely to be obtained than when the thickness of the underlayer 2 is less than 30 nm. Moreover, the durability of the underlying layer 2 is further improved. The thickness of the underlying layer 2 is preferably 30 nm or more, more preferably 35 nm or more, and even more preferably 40 nm or more. By increasing the thickness of the underlayer 2, it is possible to further suppress the deterioration of the water vapor barrier properties when an external force such as stretching is applied. The thickness of the underlayer 2 is preferably less than 200 nm. In this case, compared with the case where the thickness of the underlayer 2 is 200 nm or more, the underlayer 2 tends to be less prone to cracking.

(Inorganic oxide layer)
The inorganic oxide layer 3 is a layer containing an inorganic oxide. By having the inorganic oxide layer 3, the gas barrier film 10 can have more excellent water vapor barrier properties.

Inorganic oxides include oxides of Si (SiOx) and metal oxides. At least one kind of atom selected from the group consisting of Al, Mg, Sn, Ti, and In can be mentioned as the metal constituting the metal oxide. As the inorganic oxide, SiO _x or AlO _x is preferable from the viewpoint of water vapor barrier properties. Among them, SiO _x is preferable as the inorganic oxide. In this case, the gas barrier film 10 can have more excellent water vapor barrier properties.

The inorganic oxide layer 3 may consist of a single layer, or may consist of multiple layers.

Although the thickness of the inorganic oxide layer 3 is not particularly limited, it is preferably 10 nm or more and 100 nm or less. In this case, the water vapor barrier properties of the gas barrier film 10 are more likely to be improved than when the thickness of the inorganic oxide layer 3 is less than 10 nm. In addition, compared with the case where the thickness of the inorganic oxide layer 3 exceeds 100 nm, cracks due to an increase in internal stress are less likely to occur, and deterioration of the water vapor barrier properties can be further suppressed.

More preferably, the thickness of the inorganic oxide layer 3 is 10 nm or more and 100 nm or less.

(Gas barrier layer)
The gas barrier layer 4 is a layer formed using the composition for forming a gas barrier layer described above. The gas barrier layer 4 may be composed of a cured product of a composition for forming a gas barrier layer.

The thickness of the gas barrier layer 4 is not particularly limited. .1 to 1 μm, more preferably 0.1 to 0.5 μm.

When the thickness of the gas barrier layer 4 is 0.1 μm or more, the gas barrier properties of the gas barrier layer 4 can be further improved compared to when the thickness is less than 0.1 μm. On the other hand, when the thickness of the gas barrier layer 4 is 10 μm or less, the flexibility of the gas barrier layer 4 can be further improved compared to when the thickness exceeds 10 μm.

<Method for producing gas barrier film>
Next, a method for producing the gas barrier film 10 will be described.

First, the resin base material 1 is prepared.

Next, the base layer 2 is formed on one surface of the resin base material 1 .

Specifically, a composition containing, for example, an organosilane or an organometallic compound, a polyol compound, and an isocyanate compound is applied to one surface of the resin substrate 1, and heated and dried to form the underlayer 2. be able to. At this time, the heating temperature is, for example, 50 to 200° C., and the drying time is, for example, about 10 seconds to 10 minutes.

Next, an inorganic oxide layer 3 is formed on the underlying layer 2 .

The inorganic oxide layer 3 can be formed, for example, by a vacuum deposition method. Vacuum deposition methods include physical vapor deposition and chemical vapor deposition. Examples of the physical vapor deposition method include a vacuum deposition method, a sputter deposition method, an ion plating method, and the like. A vacuum vapor deposition method is particularly preferably used as the physical vapor deposition method. The vacuum deposition method includes a resistance heating vacuum deposition method, an EB (Electron Beam) heating vacuum deposition method, and an induction heating vacuum deposition method. Examples of chemical vapor deposition methods include thermal CVD, plasma CVD, and optical CVD.

Next, the gas barrier layer 4 is formed on the inorganic oxide layer 3 (gas barrier layer forming step).

The gas barrier layer 4 can be formed, for example, by applying a composition for forming a gas barrier layer onto the surface of the inorganic oxide layer 3 opposite to the underlying layer 2 and drying the composition.

As a method for applying the composition for forming a gas barrier layer, a known method can be employed. Specific examples of coating methods include wet film formation methods such as roll coating, gravure coating, dip coating, reverse coating, wire bar coating, die coating, screen printing, and spray coating. .

As a method for drying the coating film composed of the gas barrier layer-forming composition, 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 production of the gas barrier film 10 is completed as described above.

<Laminate>
Next, one embodiment of the laminate of the present disclosure will be described with reference to FIG. In addition, in FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and redundant explanations are omitted.

FIG. 2 is a schematic cross-sectional view showing one embodiment of the laminate of the present disclosure. As shown in FIG. 2 , the laminate 20 includes a gas barrier film 10 and a sealant layer 21 laminated on the gas barrier film 10 . placed on one side. In FIG. 2 , the gas barrier layer 4 and the sealant layer 21 of the gas barrier film 10 are adhered by the adhesive layer 22 .

As a material for the adhesive layer 22, for example, polyester-isocyanate resin, urethane resin, polyether resin, or the like can be used. In order to use the laminate 20 for retort applications, a two-liquid curable urethane-based adhesive that is resistant to retort treatment can be preferably used.

(sealant layer)
Examples of the material for the sealant layer 21 include thermoplastic resins such as polyolefin resins and polyester resins, and polyolefin resins are generally used. Specifically, polyolefin resins include low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), linear low-density polyethylene resin (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-α Olefin copolymers, ethylene-based resins such as ethylene-(meth)acrylic acid copolymers, homopolypropylene resins (PP), propylene-ethylene random copolymers, propylene-ethylene block copolymers, propylene-α olefin copolymers Polypropylene-based resins such as coalesced, or mixtures thereof and the like can be used. The material of the sealant layer 21 can be appropriately selected from among the thermoplastic resins described above depending on the intended use and temperature conditions such as boiling treatment and retort treatment.

The thickness of the sealant layer 21 is appropriately determined according to the mass of the contents, the shape of the packaging bag, etc., but from the viewpoint of the flexibility and adhesiveness of the laminate 20, it is preferably 30 to 150 μm.

From the viewpoint of obtaining a (mono-material) laminate made of a single material with excellent recyclability, in the laminate 20, the resin base material 1 and the sealant layer 21 are preferably made of the same material, and both are polyolefin films. More preferably, both are polyethylene films, or both are more preferably polypropylene films.

<Method for manufacturing laminate>
Next, a method for manufacturing the laminate 20 will be described.

First, the gas barrier film 10 is manufactured by the method for manufacturing a gas barrier film described above (gas barrier film manufacturing process).

Next, the sealant layer 21 is adhered with the adhesive layer 22 so as to be arranged on one side of the resin substrate 1 of the gas barrier film 10, and laminated to obtain the laminate 20 (sealant layer lamination step).

Since the laminate 20 to be manufactured has the sealant layer 21, it is possible to easily manufacture a packaging bag that can ensure sealing by bonding the sealant layers 21 to each other.

Although the laminate 20 has an adhesive layer 22, when the sealant layer 21 is made of the above-described thermoplastic resin and can be adhered to the gas barrier layer 4 of the gas barrier film 10 by thermal fusion, Adhesive layer 22 may be omitted. In this case, the sealant layer 21 can be bonded to the resin substrate 1 by an extrusion lamination method or the like in which the gas barrier film 10 is heated and melted, extruded in a curtain shape, and bonded.

<Packaging bag>
Next, embodiments of the packaging bag of the present disclosure will be described. The packaging bag is a packaging bag formed by using the laminate 20 and bonding the sealant layers 21 to each other. Since the packaging bag is formed using the laminate 20 having the sealant layer 21, sufficient sealing performance can be ensured.

<Method for manufacturing packaging bag>
Next, a method for manufacturing the packaging bag will be described.

First, the laminated body 20 is manufactured by the manufacturing method of the laminated body 20 mentioned above (laminated body manufacturing process).

Next, using the laminate 20, the sealant layers 21 are bonded to each other so as to form openings to obtain a bonded body. After the contents such as foodstuffs and medicines are accommodated through the opening of the joined body, the opening of the joined body is sealed to manufacture a packaging bag (laminated body joining step).

In the laminate bonding step, the bonded body is formed by bending one laminate 20 so that the sealant layers 21 face each other, and then heat-sealing the peripheral edges of the facing sealant layers 21, or 2 After stacking the laminate 20 so that the sealant layers 21 face each other, the peripheral edge portions of the facing sealant layers 21 are heat-sealed to each other.

In addition, in the laminate bonding step, the content does not necessarily have to be accommodated in the bonded body. In this case, the assembly having the opening becomes the packaging bag.

The present disclosure is not limited to the above embodiments. For example, in the above embodiment, the gas barrier film 10 includes the underlayer 2 and the inorganic oxide layer 3, but at least one of the underlayer 2 and the inorganic oxide layer 3 can be omitted.

Further, in the above-described embodiment, in the laminate 20, the sealant layer 21 is arranged on one surface side (gas barrier layer 4 side) of the resin substrate 1 of the gas barrier film 10, but the sealant layer 21 is disposed on the resin substrate. 1 (the side opposite to the gas barrier layer 4).

EXAMPLES The present disclosure will be specifically described below with reference to Examples, but the present disclosure is not limited to these Examples.

<Preparation of aqueous dispersion of aqueous polyurethane resin>
(Aqueous dispersion of aqueous polyurethane resin (A0))
An aqueous dispersion (A0) of an aqueous polyurethane resin was prepared by dispersing an acid group-containing polyurethane resin satisfying the following conditions in water.
Acid group-containing polyurethane resin (polyurethane resin having structural units derived from polyisocyanate component, polyhydroxy acid component, polyol component and chain extender component, total urethane group concentration and urea group concentration: 40% by mass, total amount of structural units Proportion of units composed of hydrocarbon rings based on: 50% by mass, acid value: 40 mgKOH / g, number average molecular weight: 900)

(Aqueous dispersion of aqueous polyurethane resin (A1))
A polyamine compound (dimethylethanolamine, isophorodiamine) is added to the aqueous polyurethane resin aqueous dispersion (A0) so that the molar ratio (acid group/basic nitrogen atom) to the aqueous polyurethane resin is 0.1/1. After that, it was passed through a filter with an opening of 5 μm. The solid content concentration of the dispersion that passed through the filter was adjusted to 30% by mass to obtain an aqueous dispersion (A1) of an aqueous polyurethane resin.

(Aqueous Dispersion of Aqueous Polyurethane Resin (A2) to (A5))
Aqueous dispersion of aqueous polyurethane resin (A2)- (A5) was obtained.

<Particle size distribution measurement>
Regarding the aqueous dispersions (A1) to (A5) of the aqueous polyurethane resin, the particle size distribution of the equivalent circle diameter of the polyurethane resin particles contained in the dispersions was measured using the following measurement equipment and conditions. From the results of measuring 300 particles, the average equivalent circle diameter and maximum equivalent circle diameter of the polyurethane resin particles contained in the dispersion, and the number of polyurethane resin particles having an equivalent circle diameter of 10 μm or more in 300 particles were determined. Table 1 shows the results. When the maximum equivalent circle diameter is 20 μm or less, it can be determined that the aqueous dispersion of the aqueous polyurethane resin does not contain polyurethane resin particles with an equivalent circle diameter exceeding 20 μm.

(Measuring equipment and conditions)
Equipment used: Particle shape image analyzer (manufactured by Seishin Enterprise Co., Ltd., trade name: PITA-04)
Analysis principle: dynamic image analysis method Particle size measurement range: 1 to 1000 μm
Particle size distribution: volume/area equivalent particle size distribution

Materials used in Examples and Comparative Examples are shown below.
(water-soluble polymer)
Polyvinyl alcohol with a degree of saponification of 98.5% and a degree of polymerization of 500 (trade name: Poval PVA-105, manufactured by Kuraray Co., Ltd.).
(Silane coupling agent)
3-glycidoxypropyltriethoxysilane (trade name: KBE-403, manufactured by Shin-Etsu Silicone Co., Ltd.).

(Resin base material)
Biaxially oriented polypropylene film (manufactured by Mitsui Chemicals Tohcello, Inc., trade name: U-1, thickness 20 μm, hereinafter referred to as “OPP”).
Biaxially stretched polyethylene terephthalate film (hereinafter referred to as "PET").
High density polyethylene film (hereinafter referred to as "HDPE").

(Composition for forming base 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. β-(3,4 Epoxycyclohexyl)trimethoxysilane was further added to the mixed solution after dilution so as to be 5 parts by mass with respect to the total amount of 100 parts by mass of acrylic polyol and tolylene diisocyanate, and these were mixed. By doing so, an underlayer-forming composition (anchor coating agent) was prepared.

(sealant layer)
Unstretched polypropylene film (hereinafter referred to as "CPP").
Linear low-density polyethylene resin film (hereinafter referred to as "LLDPE").

[Example 1]
(Preparation of composition for forming gas barrier layer)
55 parts by mass (solid content) of the aqueous dispersion (A1) of the aqueous polyurethane resin, 35 parts by mass of the water-soluble polymer, and 10 parts by mass of the silane coupling agent were blended to obtain a composition for forming a gas barrier layer. rice field.

(Preparation of laminate)
A coating film was formed by applying the underlayer-forming composition onto OPP as a resin base material by a gravure coating method. The obtained coating film was heated at 120° C. for 10 seconds and dried to form a 100 nm-thick base layer. Next, silicon oxide was evaporated using a vacuum deposition apparatus using an electron beam heating method to form an inorganic oxide layer having a thickness of 40 nm on the underlying layer. Next, the composition for forming a gas barrier layer was applied onto the inorganic oxide layer using a bar coater. The obtained coating film was dried in an oven at 60° C. for 1 minute to form a gas barrier layer having a thickness of 500 nm, thereby obtaining a gas barrier film having a laminated structure of resin substrate/underlying layer/inorganic oxide layer/gas barrier layer. Obtained.

CPP as a sealant layer was dry-laminated on the gas barrier layer of the gas barrier film using an adhesive to obtain a laminate. As the adhesive, a urethane-based two-liquid type adhesive (manufactured by Mitsui Chemicals, Inc., trade names: Takelac A525, Takenate A52) was used.

A sample with a size of 148 mm × 210 mm was cut out from the obtained laminate, and the two cut samples were stacked so that the sealant layers faced each other, and heat-sealed on three sides in the form of a pouch to obtain a packaging bag. .

[Examples 2 to 4 and Comparative Example 1]
A composition for forming a gas barrier layer and a gas barrier were prepared in the same manner as in Example 1, except that the aqueous polyurethane resin dispersions (A2) to (A5) were used instead of the aqueous polyurethane resin dispersion (A1). A flexible film, a laminate and a packaging bag were produced.

[Examples 5 to 8 and Comparative Example 2]
A composition for forming a gas barrier layer, a gas barrier film, a laminate, and a packaging bag were produced in the same manner as in Examples 1 to 4 and Comparative Example 1, except that HDPE was used as the resin base material and LLDPE was used as the sealant layer. bottom.

[Comparative Example 3]
A composition for forming a gas barrier layer, a gas barrier film, a laminate, and a packaging bag were produced in the same manner as in Comparative Example 2, except that PET was used instead of HDPE as the resin base material.

[Examples 9 to 12 and Comparative Example 4]
Except that in the preparation of the gas barrier layer-forming composition, 59 parts by mass (solid content) of the aqueous dispersion of the aqueous polyurethane resin, 31 parts by mass of the water-soluble polymer, and 10 parts by mass of the silane coupling agent were blended. A composition for forming a gas barrier layer, a gas barrier film, a laminate and a packaging bag were produced in the same manner as in Examples 1 to 4 and Comparative Example 1.

[Examples 13-14 and Comparative Example 5]
Except that in the preparation of the gas barrier layer-forming composition, 72 parts by mass (solid content) of the aqueous dispersion of the aqueous polyurethane resin, 18 parts by mass of the water-soluble polymer, and 10 parts by mass of the silane coupling agent were blended. A composition for forming a gas barrier layer, a gas barrier film, a laminate and a packaging bag were produced in the same manner as in Examples 1 to 4 and Comparative Example 1.

[Comparative Example 6]
A composition for forming a gas barrier layer, a gas barrier film, a laminate, and a packaging bag were produced in the same manner as in Comparative Example 5, except that PET was used instead of OPP as the resin base material.

<Evaluation of gas barrier properties>
(Preparation of test sample)
The laminate obtained in each example was used as a test sample before retort treatment. On the other hand, test samples after retort treatment were prepared as follows. The packaging bag obtained in each example was filled with 250 ml of distilled water, and a sealant layer was heat-sealed to prepare a sealed pouch. The obtained pouch was subjected to heat treatment (retort treatment) at 121° C. for 30 minutes. The laminate after this retort treatment was used as a test sample after retort treatment.

(Measurement of oxygen transmission rate (OTR))
Using an oxygen permeability measuring device (product name "OX-TRAN2/20", manufactured by MOCON), the oxygen permeability (unit: cc/m ² · day·atm) was measured. At this time, the measurement was performed according to JIS K-7126-2. Table 2 shows the results.

(Measurement of water vapor transmission rate (WTR))
Using a water vapor transmission rate measuring device (product name "PERMATRAN 3/31", manufactured by MOCON), the water vapor transmission rate (unit: g / m ² · day) of the above test sample under the conditions of a temperature of 40 ° C. and a relative humidity of 90% was measured. At this time, the measurement was performed according to JIS K-7129. Table 2 shows the results.

DESCRIPTION OF SYMBOLS 1... Resin base material, 2... Base layer, 3... Inorganic oxide layer, 4... Gas barrier layer, 10... Gas barrier film, 20... Laminate, 21... Sealant layer, 22... Adhesive layer.

Claims (9)

A composition for forming a gas barrier layer containing an aqueous polyurethane resin (A) containing an acid group-containing polyurethane resin and a water-soluble polymer (B),
The water-based polyurethane resin (A) does not contain polyurethane resin particles having an equivalent circle diameter exceeding 20 μm,
The mass ratio of solids between the aqueous polyurethane resin (A) and the water-soluble polymer (B) (aqueous polyurethane resin (A)/water-soluble polymer (B)) is 85/15 to 10/90. A composition for forming a gas barrier layer. The composition for forming a gas barrier layer according to claim 1, further comprising a silane coupling agent (C). A gas barrier film comprising a resin substrate and a gas barrier layer formed on one side of the resin substrate using the composition for forming a gas barrier layer according to claim 1 or 2. 4. The gas barrier film according to claim 3, wherein the gas barrier layer has a thickness of 0.1 to 10 .mu.m at locations where polyurethane resin particles having an equivalent circle diameter of more than 10 .mu.m are not present. The gas barrier film according to claim 3 or 4, further comprising an inorganic oxide layer containing an inorganic oxide between the resin substrate and the gas barrier layer. The gas barrier film according to any one of claims 3 to 5, wherein the resin substrate is a polyolefin film. A laminate comprising the gas barrier film according to any one of claims 3 to 6 and a sealant layer laminated on the gas barrier film. The laminate according to claim 7, wherein both the resin base material and the sealant layer in the gas barrier film are polyethylene films, or both are polypropylene films. A packaging bag formed by using the laminate according to claim 7 or 8 and bonding the sealant layers to each other.

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