JP2024002482A - Gas barrier laminate, packaging bag, and packaged product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas barrier laminate that retains sufficient gas barrier properties even after bent, and also provide a packaging bag and a packaged product.

SOLUTION: A gas barrier laminate includes a paper substrate, a barrier layer, and an overcoat layer in this order. The overcoat layer includes a resin including a crosslinked polyolefin where a polyolefin with a carboxy group is crosslinked with a crosslinker including a plurality of reactive groups reactable with carboxy groups in one molecule.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present disclosure relates to gas barrier laminates, packaging bags, and packaging products.

BACKGROUND ART In many fields such as foods, beverages, pharmaceuticals, and chemicals, packaging materials are used depending on the contents. Packaging materials are required to have gas barrier properties that prevent the permeation of oxygen, water vapor, and the like, which cause deterioration of the contents.

In recent years, as environmental awareness has increased due to issues such as the problem of marine plastic waste, there has been a growing momentum to move away from plastics. From the viewpoint of reducing the amount of plastic materials used, the use of paper instead of plastic materials is being considered in various fields. Furthermore, paper has a crease retention property (also referred to as deadhold property), so it is easy to process. Therefore, gas barrier laminates using paper are also being considered in the field of packaging materials. For example, Patent Document 1 below discloses a gas barrier laminate in which an anchor coat layer, a barrier layer, and an overcoat layer are laminated in this order on paper. Specifically, in Patent Document 1 listed below, the anchor coat layer and the overcoat layer are each made of a polyolefin having a polar group, including a carboxyl group, a salt of a carboxy group, a carboxylic acid anhydride group, and a carboxylic acid ester. A gas barrier laminate has been proposed that contains sufficient gas barrier properties even after being bent and contributes to reducing the amount of plastic material used.

International Publication No. 2022/009609

However, the gas barrier laminate described in Patent Document 1 still has room for improvement in terms of gas barrier properties after being bent.

The present disclosure has been made in view of the above circumstances, and aims to provide a gas barrier laminate, a packaging bag, and a packaging product that have sufficient gas barrier properties even after being folded.

In order to solve the above problems, a first aspect of the present disclosure includes a paper base material, a barrier layer, and an overcoat layer in this order, and the overcoat layer contains a polyolefin having a carboxyl group. Provided is a gas barrier laminate containing a resin containing a crosslinked polyolefin crosslinked with a crosslinking agent having a plurality of reactive groups in one molecule.

The gas barrier laminate has sufficient gas barrier properties even after being bent.
The reason why the above effect is obtained is presumed as follows.
That is, the crosslinked polyolefin contained in the resin included in the overcoat layer has, in addition to the polyolefin site, a bonding site obtained by the reaction and bonding between the carboxy group of the polyolefin and the reactive group of the crosslinking agent. , elasticity is imparted to the overcoat layer. For this reason, even if excessive bending stress is likely to be applied to the barrier layer when the gas barrier laminate is bent to form a bent part in the gas barrier laminate, the excessive bending stress will be applied to the barrier layer, which will cause elasticity to be imparted. Mitigated by an overcoat layer. That is, when the barrier layer is bent, a force is exerted by the overcoat layer imparted with elasticity to return the barrier layer to its original shape. Therefore, generation of cracks in the barrier layer is suppressed. As a result, the gas barrier laminate can have sufficient gas barrier properties even after being bent.

A second aspect of the present disclosure provides a gas barrier laminate according to the first aspect, further comprising an anchor coat layer between the paper base material and the barrier layer.

A third aspect of the present disclosure is that in the gas barrier laminate according to the second aspect, the anchor coat layer binds the polyolefin having a carboxy group by a crosslinking agent having a plurality of reactive groups in one molecule that reacts with the carboxy group. A gas barrier laminate containing a resin containing a crosslinked polyolefin is provided.

A fourth aspect of the present disclosure provides the gas barrier laminate of the first aspect, wherein the barrier layer is a vapor deposited layer.

In a fifth aspect of the present disclosure, the gas barrier laminate on any one of the second to fourth aspects includes a heat seal layer, and the barrier layer is disposed between the heat seal layer and the anchor coat layer. A gas barrier laminate is provided.

A sixth aspect of the present disclosure provides a gas barrier laminate in which the overcoat layer also serves as the heat seal layer in the gas barrier laminate of the fifth aspect.

A seventh aspect of the present disclosure is a gas barrier laminate according to any one of the first to sixth aspects, wherein the overcoat layer is formed by coating an overcoat layer forming composition on the barrier layer. The obtained gas barrier laminate is provided.

An eighth aspect of the present disclosure provides a gas barrier laminate according to any one of the first to seventh aspects, wherein the overcoat layer has a thickness of 3 μm or less.

A ninth aspect of the present disclosure is that in the gas barrier laminate according to any one of the first to eighth aspects, the crosslinking agent is at least one selected from the group consisting of a carbodiimide compound, an oxazoline compound, and an epoxy compound. A gas barrier laminate is provided.

A tenth aspect of the present disclosure is a gas barrier laminate according to any one of the first to ninth aspects, wherein the weight ratio of plastic is 50% by mass or less based on the entire gas barrier laminate. Provide your body.

An eleventh aspect of the present disclosure provides a packaging bag including the gas barrier laminate of any one of the first to ninth aspects.

A twelfth aspect of the present disclosure also provides a packaging bag having a folded portion in the packaging bag of the eleventh aspect.

A thirteenth aspect of the present disclosure is a packaged product comprising a sealed bag and contents stored in the sealed bag, wherein the sealed bag is obtained using the packaging bag of the eleventh aspect or the twelfth aspect. I will provide a.

According to the present disclosure, a gas barrier laminate, a packaging bag, and a packaging product that have sufficient gas barrier properties even after being folded are provided.

FIG. 1 is a schematic cross-sectional view showing a gas barrier laminate according to an embodiment of the present disclosure. FIG. 1 is a perspective view showing a packaging bag according to an embodiment of the present disclosure.

Embodiments of the present disclosure will be described in detail below with reference to the drawings. However, the present disclosure is not limited to the following embodiments.

<Gas barrier laminate>
FIG. 1 is a schematic cross-sectional view showing a gas barrier laminate according to an embodiment of the present disclosure. As shown in FIG. 1, the gas barrier laminate 10 includes a paper base material 1, an anchor coat layer 2, a barrier layer 3, and an overcoat layer 4 in this order. The overcoat layer 4 contains a resin containing a crosslinked polyolefin obtained by crosslinking a polyolefin having a carboxyl group with a crosslinking agent having a plurality of reactive groups in one molecule that react with the carboxyl group.
The gas barrier laminate 10 has sufficient gas barrier properties even after being bent.

Hereinafter, the paper base material 1, anchor coat layer 2, barrier layer 3, and overcoat layer 4 will be explained in more detail.

[Paper base material]
The paper base material 1 is not particularly limited as long as it is a base material having paper. Here, paper refers to a material containing plant-derived pulp as a main component, and the main component refers to a component containing 50% by mass or more of plant-derived pulp in the material. By providing the gas barrier laminate 10 with the paper base material 1, it becomes possible to contribute to reducing the amount of plastic material used.
Specific examples of the paper base material 1 include wood-free paper, special wood-free paper, coated paper, art paper, cast-coated paper, imitation paper and kraft paper, and glassine paper. The thickness of the paper base material 1 may be, for example, 20 to 500 g/m ² or 30 to 100 g/m ² .

The paper base material 1 may further include a coat layer at least on the anchor coat layer 2 side of the paper. By having the paper base material 1 further include a coat layer, it is possible to prevent the anchor coat layer 2 from seeping into the paper, and it can also serve as a filler to fill in the unevenness of the paper, thereby preventing the anchor coat layer 2 from becoming defective. It is possible to form a film uniformly without any problems. The coat layer may further contain a binder resin and, if necessary, a filler. Examples of the binder resin include various copolymers such as styrene-butadiene copolymer, styrene-acrylic copolymer, ethylene-vinyl acetate copolymer, polyvinyl alcohol resin, cellulose resin, and the like. Examples of fillers include kaolin, calcium carbonate, talc, mica, and the like.

The thickness of the coating layer is not particularly limited, and may be, for example, 1 to 10 μm or 3 to 8 μm.

The weight ratio of plastic is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on the entire gas barrier laminate. When the weight ratio of plastic is 50% by mass or less based on the entire gas barrier laminate, the amount of plastic material used can be more sufficiently reduced, and the gas barrier laminate 10 has excellent recyclability.
Note that "plastic" refers to resin components other than inorganic compounds used in pulp and fillers made from plant fibers such as wood.
The weight ratio of the plastic may be 10% by mass or more, and may be 5% by mass or more based on the entire gas barrier laminate.

[Anchor coat layer]
The anchor coat layer 2 is provided to improve the adhesion between the paper base material 1 and the barrier layer 3. The material constituting the anchor coat layer 2 is not particularly limited, but may contain a resin containing a polyolefin having a carboxyl group, and one molecule of the polyolefin having a carboxyl group has a reactive group that reacts with the carboxyl group. It may contain a resin containing a crosslinked polyolefin crosslinked with a plurality of crosslinking agents, or may contain a resin other than the above polyolefin and the above crosslinked polyolefin.

In particular, the anchor coat layer 2 preferably contains a resin containing crosslinked polyolefin. A crosslinked polyolefin has a polyolefin site and a bonding site obtained by reacting and bonding a carboxy group and a reactive group. Since such an anchor coat layer 2 has excellent elasticity, it is possible to further suppress the occurrence of cracks in the barrier layer 3 after bending (after bending). Moreover, since the anchor coat layer 2 contains the polyolefin portion, a dense film can be formed due to the crystallinity of the polyolefin portion, and water vapor barrier properties are exhibited. Furthermore, in the anchor coat layer 2, the bonding portion has a polar group (for example, a carbonyl group) derived from a carboxyl group, so that adhesiveness between the anchor coat layer 2 and the barrier layer 3 is developed.

As the polyolefin having a carboxyl group, a copolymer of an olefin such as ethylene or propylene and an unsaturated carboxylic acid (an unsaturated compound having a carboxyl group such as acrylic acid, methacrylic acid, or maleic anhydride) is used.

Examples of polyolefins having a carboxyl group include copolymers of ethylene and acrylic acid, copolymers of ethylene and methacrylic acid, copolymers of propylene and acrylic acid, and copolymers of propylene and methacrylic acid. Examples include copolymers, copolymers of ethylene and maleic anhydride, and the like.

The crosslinking agent is not particularly limited as long as it is made of a material having a plurality of reactive groups in one molecule that react with carboxy groups.

The reactive group is not limited as long as it is a group that reacts with a carboxy group, and examples of such reactive groups include a carbodiimide group, an oxazoline group, an epoxy group, an amino group, and a hydroxyl group. The crosslinking agent may have one or more of these reactive groups. In other words, examples of the crosslinking agent include carbodiimide compounds, oxazoline compounds, epoxy compounds, amino compounds, and hydroxyl group-containing compounds. These compounds can be used alone or in combination of two or more.

The crosslinking agent can crosslink polyolefin by having two or more reactive groups in one molecule. The number of reactive groups is not particularly limited as long as it is 2 or more in one molecule, but if the number of reactive groups is large, the crosslinking rate will be high and elasticity will be easily imparted, whereas the number of reactive groups will be small. This makes it difficult for the viscosity of the coating liquid to increase and makes it easier to process, so an appropriate number of reactive groups may be selected depending on the required elasticity and ease of processing. Crosslinking agents include low molecular type, polymer type, water-soluble type, emulsion type, etc., and the crosslinking agent may be appropriately selected from these.

When the anchor coat layer 2 contains the polyolefin or the crosslinked polyolefin, the content of the polyolefin or the crosslinked polyolefin in the anchor coat layer 2 may be, for example, 50% by mass or more, and 70% by mass or more. It may be 90% by mass or more, and may be 100% by mass.

When the anchor coat layer 2 contains a resin other than the polyolefin and the crosslinked polyolefin, examples of such resin include polyacrylic, polyester, polyurethane, polycarbonate, polyurea, polyamide, polyimide, polyvinyl alcohol resin, etc. It will be done.

Anchor coat layer 2 may contain other components in addition to the above resin. Examples of other components include silane coupling agents, adhesion agents such as organometallic compounds, various antipackaging agents, and leveling agents.

The thickness of the anchor coat layer 2 may be, for example, 0.5 μm or more, 1 μm or more, or 2 μm or more. If the thickness of the anchor coat layer 2 is 0.5 μm or more, the unevenness of the paper base material 1 described above can be efficiently filled and the barrier layer 3 can be stacked uniformly, so that the thickness of the gas barrier laminate 10 is Gas barrier properties can be improved. The thickness of the anchor coat layer 2 may be 20 μm or less, 10 μm or less, or 5 μm or less. If the thickness of the anchor coat layer 2 is 20 μm or less, the barrier layer 3 can be uniformly laminated while keeping costs down.

As a method for forming the anchor coat layer 2, a method of obtaining the anchor coat layer 2 by applying a coating liquid (overcoat layer forming composition) containing the resin contained in the anchor coat layer 2 onto the paper base material 1. can be mentioned. In this way, when forming the anchor coat layer 2 by coating the overcoat layer forming composition on the barrier layer 3, the thickness of the anchor coat layer 2 can be reduced, so that Plastic ratio can be lowered.
When the anchor coat layer 2 contains a resin containing a crosslinked polyolefin, the polyolefin and the crosslinking agent may react after coating the composition for forming an overcoat layer containing a polyolefin having a carboxy group and a crosslinking agent. It is necessary to heat at a temperature.

Here, the polyolefin having a carboxyl group is a copolymer (first copolymer) of an olefin and an unsaturated carboxylic acid (an unsaturated compound having a carboxyl group such as acrylic acid, methacrylic acid, maleic anhydride), A copolymer (second copolymer) of an olefin and a salt obtained by neutralizing an unsaturated carboxylic acid (an unsaturated compound having a carboxy group such as acrylic acid, methacrylic acid, or maleic anhydride) with a basic compound, an olefin and an unsaturated carboxylic anhydride (maleic anhydride, etc.) (third copolymer) is dissolved in a solvent containing water to form a salt neutralized with a basic compound. It can be obtained by solubilization. This is because the first copolymer, the second copolymer, and the third copolymer each produce a polyolefin having a carboxy group through an equilibrium reaction in a water-containing solvent.

From the viewpoint of smoothing the surface of the anchor coat layer 2 and making it easier to form the barrier layer 3, when the polyolefin is included in the aqueous coating liquid, it is preferable that the particle size is small. Although the particle size is not particularly limited, it is preferably 1 μm or less, more preferably 0.7 μm or less, particularly preferably 0.5 μm or less.

Examples of the solvent contained in the coating liquid for anchor coat layer 2 include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, and dimethylacetamide. , toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination of two or more. Among these, from the viewpoint of properties, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred. Also, from the environmental point of view, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred.

[Barrier layer]
Barrier layer 3 is usually composed of a vapor deposited layer. The vapor deposition layer may be a layer obtained by vapor depositing a metal such as aluminum, or may be a layer containing an inorganic oxide such as aluminum oxide (AlO _x ) or silicon oxide (SiO _x ).

When the barrier layer 3 is a vapor deposited layer, the thickness of the barrier layer 3 may be appropriately set depending on the intended use, but is preferably 10 to 300 nm, more preferably 30 to 100 nm. By setting the thickness of the barrier layer 3 to 10 nm or more, it is easy to ensure sufficient continuity of the barrier layer 3, and by setting the thickness to 300 nm or less, the occurrence of curls and cracks in the barrier layer 3 can be sufficiently suppressed, and sufficient gas barrier performance can be achieved. and flexibility is easy to achieve.

When the barrier layer 3 is a vapor deposited layer, it is preferable to form the barrier layer 3 by vacuum film forming means from the viewpoint of oxygen gas barrier performance and film uniformity. Vacuum film forming means include known methods such as vacuum evaporation, sputtering, and chemical vapor deposition (CVD), but vacuum evaporation is preferred because of its fast film formation rate and high productivity. Among vacuum evaporation methods, electron beam heating is particularly effective because the deposition rate can be easily controlled by controlling the irradiation area, electron beam current, etc., and the temperature of the evaporation material can be raised and lowered in a short time. be.

Note that the barrier layer 3 may be made of metal foil. Examples of the metal foil include aluminum foil.

[Overcoat layer]
Overcoat layer 4 protects barrier layer 3 by sandwiching barrier layer 3 together with anchor coat layer 2 .

The overcoat layer 4 contains a resin containing a crosslinked polyolefin obtained by crosslinking a polyolefin having a carboxyl group with a crosslinking agent having a plurality of reactive groups in one molecule that react with the carboxyl group. A crosslinked polyolefin has a polyolefin site and a bonding site obtained by reacting and bonding a carboxy group and a reactive group. Such an overcoat layer 4 has excellent elasticity and can suppress the occurrence of cracks in the barrier layer 3 after being bent (bent). Moreover, since the overcoat layer 4 contains the polyolefin portion, a dense film can be formed due to the crystallinity of the polyolefin portion, and water vapor barrier properties are exhibited. Furthermore, in the overcoat layer 4, water vapor barrier properties are expressed due to the crystallinity of the polyolefin portion, and the bonding portion has a polar group (for example, a carbonyl group) derived from a carboxyl group, so that the overcoat layer 4 and the barrier layer 3 are bonded together. Adhesion is developed.

As the polyolefin having a carboxyl group, a copolymer of an olefin such as ethylene or propylene and an unsaturated carboxylic acid (an unsaturated compound having a carboxyl group such as acrylic acid, methacrylic acid, or maleic anhydride) is used. Examples of polyolefins having a carboxyl group include copolymers of ethylene and acrylic acid, copolymers of ethylene and methacrylic acid, copolymers of propylene and acrylic acid, and copolymers of propylene and methacrylic acid. Examples include copolymers, copolymers of ethylene and maleic anhydride, and the like.

The crosslinking agent is not particularly limited as long as it is made of a material having a plurality of reactive groups in one molecule that react with carboxy groups.

The reactive group is not limited as long as it is a group that reacts with a carboxy group, and examples of such reactive groups include a carbodiimide group, an oxazoline group, an epoxy group, an amino group, and a hydroxyl group. The crosslinking agent may have one or more of these reactive groups.

The crosslinking agent can crosslink polyolefin by having two or more reactive groups in one molecule. The number of reactive groups is not particularly limited as long as it is 2 or more in one molecule, but if the number of reactive groups is large, the crosslinking rate will be high and elasticity will be easily imparted, whereas the number of reactive groups will be small. This makes it difficult for the viscosity of the coating liquid to increase and makes it easier to process, so an appropriate number of reactive groups may be selected depending on the required elasticity and ease of processing. Crosslinking agents include low molecular type, polymer type, water-soluble type, emulsion type, etc., and the crosslinking agent may be appropriately selected from these.

The content of crosslinked polyolefin in the overcoat layer 4 may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass.

Overcoat layer 4 may contain other components in addition to the above resin. Examples of other components include silane coupling agents, adhesion agents such as organometallic compounds, various antipackaging agents, and leveling agents. Moreover, the overcoat layer 4 may contain additives such as wax in order to impart slipperiness and anti-blocking properties.

The thickness of the overcoat layer 4 may be, for example, 0.05 μm or more, 0.5 μm or more, or 1 μm or more. If the thickness of the overcoat layer 4 is 0.05 μm or more, when the overcoat layer 4 also serves as a heat seal layer, it can fully perform the role as the heat seal layer described above.
The thickness of the overcoat layer 4 may be 20 μm or less, 10 μm or less, 5 μm or less, or 3 μm or less. When the thickness of the overcoat layer 4 is 20 μm or less, it is possible to sufficiently exhibit adhesiveness and barrier properties with the barrier layer 3 while suppressing costs. In particular, when the thickness of the overcoat layer 4 is 3 μm or less, the proportion of plastic in the gas barrier laminate can be lowered, and more excellent flexibility can be imparted to the overcoat layer 4.

As a method for forming the overcoat layer 4, a coating liquid (composition for forming an overcoat layer) containing a polyolefin having a carboxyl group and a crosslinking agent is applied and heated at a temperature at which the polyolefin and the crosslinking agent can react. An example of this method is to obtain it by In this way, when forming the overcoat layer 4 by coating the overcoat layer forming composition on the barrier layer 3, the thickness of the overcoat layer 4 can be reduced, so that Plastic ratio can be lowered.

Here, the polyolefin having a carboxyl group is a copolymer (first copolymer) of an olefin and an unsaturated carboxylic acid (an unsaturated compound having a carboxyl group such as acrylic acid, methacrylic acid, maleic anhydride), A copolymer (second copolymer) of an olefin and a salt obtained by neutralizing an unsaturated carboxylic acid (an unsaturated compound having a carboxy group such as acrylic acid, methacrylic acid, or maleic anhydride) with a basic compound, an olefin and an unsaturated carboxylic anhydride (such as maleic anhydride) (third copolymer) is dissolved in a water-containing solvent to form a salt neutralized with a basic compound. It can be obtained by solubilization. This is because each of the first copolymer, second copolymer, and third copolymer produces a polyolefin having a carboxy group through an equilibrium reaction in a water-containing solvent.

When a polyolefin is included in an aqueous coating liquid, from the viewpoint of preventing blocking, it is preferable that the polyolefin has a large particle size so that the contact area is small. Although the particle size is not particularly limited, specifically, it may be 1 nm or more, 0.1 μm or more, and 1 μm or less, 0.7 μm or less, or 0.5 μm or less.

Examples of the solvent contained in the coating liquid for overcoat layer 4 include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, and dimethylacetamide. , toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination of two or more. Among these, from the viewpoint of properties, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred. Also, from the environmental point of view, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred.

When the anchor coat layer 2 contains a crosslinked polyolefin, this crosslinked polyolefin and the crosslinked polyolefin contained in the overcoat layer 4 may be of the same type or different types.

<Packaging bag>
Next, an embodiment of the packaging bag of the present disclosure will be described with reference to FIG. 2. FIG. 2 is a perspective view showing a packaging bag according to an embodiment of the present disclosure.
The packaging bag 20 shown in FIG. 2 is a gusset bag and is made of a gas barrier laminate 10. The packaging bag 20 has a portion (folded portion) B where the gas barrier laminate 10 is bent. The folded portion B is a portion where the gas barrier laminate 10 is mountain-folded when viewed from the innermost layer side.

The packaging bag 20 is formed into a bag shape by, for example, folding one gas barrier laminate in half so that the overcoat layer 4 faces, and then appropriately bending it into a desired shape and heat-sealing it. Alternatively, a plurality of gas barrier laminates 10 may be appropriately bent with the overcoat layer 4 facing inward and heat-sealed to each other to form a bag shape.

In the packaging bag 20, the heat sealing strength may be 2N or more, and may be 4N or more. Note that the upper limit of the heat seal strength is not particularly limited, but may be, for example, 10 N or less.

Note that in this embodiment, a gusset bag is cited as an example of the packaging bag 20, but the packaging bag of the present disclosure may be, for example, a pillow bag, a three-sided seal bag, or a standing pouch.

<Packaged products>
Next, the packaged product of the present disclosure will be described.
The packaged product of the present disclosure includes a sealed bag and contents contained within the sealed bag. A sealed bag is obtained using the packaging bag 20. Specifically, the sealed bag is obtained by sealing the upper opening of the packaging bag 20.
Examples of the contents include foods, medicines, and the like. The packaged product according to this embodiment has sufficient gas barrier properties even when the airtight bag has a folded portion.

Note that the present disclosure is not limited to the above embodiments. For example, although the gas barrier laminate 10 of the above embodiment does not include a heat seal layer, it may further include a heat seal layer on the overcoat layer 4.

Further, in the present embodiment, the gas barrier laminate 10 has the anchor coat layer 2, but the gas barrier laminate of the present disclosure does not necessarily need to have the anchor coat layer 2.

EXAMPLES Hereinafter, the present disclosure will be explained in more detail with reference to examples, but the present disclosure is not limited to these examples.

(Example 1)
<Preparation of composition for forming overcoat layer>
In a solution containing a polyolefin having an ammonium salt of a carboxy group (trade name "Zaixen AC", manufactured by Sumitomo Seika Co., Ltd., olefin-unsaturated carboxylic acid copolymer, particle size: <0.2 μm, solvent: water), An aqueous solution containing a carbodiimide compound as a crosslinking agent (trade name "Carbodilite V-02", manufactured by Nisshinbo Chemical Co., Ltd., polycarbodiimide resin, reactive group: carbodiimide group) was added to prepare an overcoat layer forming composition. . At this time, the overcoat layer was prepared so that the content of the crosslinking agent in the solid content was 3% by mass.

<Production of gas barrier laminate>
First, as a composition for forming an anchor coat layer, a solution of a polyolefin containing an ammonium salt of a carboxy group (trade name "Zaikusen AC", manufactured by Sumitomo Seika Co., Ltd., olefin-unsaturated carboxylic acid copolymer, particle size: < 0.2 μm, solvent: water) was prepared.
Next, this composition for forming an anchor coat layer was applied to clay coated paper (60 g/m ² , thickness of clay coat layer: 6 μm) as a paper base material formed by laminating a clay coat layer on one side of the paper. It was applied onto the surface of the coating layer using a bar coater and dried at 120°C for 1 minute. In this way, an anchor coat layer with a thickness of 3 μm was formed on the paper base material.
Next, aluminum was deposited on the anchor coat layer by vacuum deposition to form an AL deposited layer with a thickness of 50 nm.
Next, the composition for forming an overcoat layer is applied onto the AL vapor-deposited layer using a bar coater, and heated in an oven at 120° C. for 1 minute to react the polyolefin with the carbodiimide compound. A crosslinked polyolefin was obtained by crosslinking. In this way, an overcoat layer was formed on the barrier layer. At this time, the overcoat layer was formed so that the weight after drying was 3 g/m ² . The overcoat layer contains a crosslinked polyolefin obtained by crosslinking an olefin-unsaturated carboxylic acid copolymer with a crosslinking agent, and also serves as a heat seal layer. In this way, a gas barrier laminate was obtained. The weight ratio of plastic in the gas barrier laminate was 28% by mass.

(Example 2)
A gas barrier laminate was obtained in the same manner as in Example 1, except that the composition for forming an overcoat layer was prepared so that the content of the crosslinking agent in the solid content was 6% by mass. The weight ratio of plastic in the gas barrier laminate was 28% by mass.

(Example 3)
A gas barrier laminate was obtained in the same manner as in Example 1, except that the composition for forming an overcoat layer was prepared so that the content of the crosslinking agent in the solid content was 9% by mass. The weight ratio of plastic in the gas barrier laminate was 28% by mass.

(Example 4)
When preparing the composition for forming an overcoat layer, the crosslinking agent is changed from an aqueous solution containing a carbodiimide compound to a solution containing an oxazoline compound (trade name "Epocross WS-700", manufactured by Nippon Shokubai Co., Ltd., acrylic resin, reactive group). : Oxazoline group, solvent: water) A gas barrier laminate was obtained in the same manner as in Example 3, except that the solvent was changed to: oxazoline group, solvent: water). The weight ratio of plastic in the gas barrier laminate was 28% by mass.

(Example 5)
When preparing the composition for forming an overcoat layer, the crosslinking agent is changed from an aqueous solution containing a carbodiimide compound to a solution containing polyethylene glycol diglycidyl ether as an epoxy compound (trade name "Denacol EX-861", Nagase ChemteX Co., Ltd.). A gas barrier laminate was obtained in the same manner as in Example 1, except for changing to a reactive group (manufactured by the company) (reactive group: epoxy group). The weight ratio of plastic in the gas barrier laminate was 28% by mass.

(Comparative example 1)
A gas barrier laminate was prepared in the same manner as in Example 1, except that when preparing the composition for forming an overcoat layer, no crosslinking agent was added and the content of the crosslinking agent in the solid content was 0% by mass. Obtained. The weight ratio of plastic in the gas barrier laminate was 28% by mass.

<Measurement of water vapor permeability>
The water vapor permeability of the gas barrier laminates according to Examples and Comparative Examples was measured by the MOCON method. The measurement conditions were a temperature of 40° C. and a relative humidity of 90%. While rolling a roller weighing 2 kg once at a speed of 300 mm/min, creases were created in the gas barrier laminate, and the water vapor permeability of the gas barrier laminate after being opened was also measured in the same manner. The results are shown in Table 1. In Table 1, the unit of water vapor permeability is "g/m ² ·day".

From the results shown in Table 1, it was found that the gas barrier laminates of Examples 1 to 5 had sufficient gas barrier properties compared to the gas barrier laminate of Comparative Example 1 even after bending.
Therefore, it was confirmed that the gas barrier laminate of the present disclosure has sufficient gas barrier properties even after bending.

DESCRIPTION OF SYMBOLS 1...Paper base material, 2...Anchor coat layer, 3...Barrier layer, 4...Overcoat layer, 10...Gas barrier laminate, 20...Gusset bag (packaging bag), B...Bending portion.

Claims (13)

paper base material,
a barrier layer;
and an overcoat layer in this order,
A gas barrier laminate, wherein the overcoat layer contains a resin containing a crosslinked polyolefin obtained by crosslinking a polyolefin having a carboxyl group with a crosslinking agent having a plurality of reactive groups in one molecule that react with the carboxyl group. The gas barrier laminate according to claim 1, further comprising an anchor coat layer between the paper base material and the barrier layer. 3. The anchor coat layer contains a resin containing a crosslinked polyolefin obtained by crosslinking a polyolefin having a carboxyl group with a crosslinking agent having a plurality of reactive groups in one molecule that react with the carboxyl group. gas barrier laminate. The gas barrier laminate according to claim 1, wherein the barrier layer is a vapor deposited layer. Equipped with a heat seal layer,
The gas barrier laminate according to claim 2, wherein the barrier layer is disposed between the heat seal layer and the anchor coat layer. The gas barrier laminate according to claim 5, wherein the overcoat layer also serves as the heat seal layer. The gas barrier laminate according to claim 1, wherein the overcoat layer is obtained by applying a composition for forming an overcoat layer onto the barrier layer. The gas barrier laminate according to claim 1, wherein the overcoat layer has a thickness of 3 μm or less. The gas barrier laminate according to claim 1, wherein the crosslinking agent is at least one selected from the group consisting of carbodiimide compounds, oxazoline compounds, and epoxy compounds. The gas barrier laminate according to any one of claims 1 to 9, wherein the weight ratio of the plastic is 50% by mass or less based on the entire gas barrier laminate. A packaging bag comprising the gas barrier laminate according to any one of claims 1 to 9. The packaging bag according to claim 11, having a folded portion. sealed bag and
and contents contained in the sealed bag,
A packaged product, wherein the sealed bag is obtained using the packaging bag according to claim 11.

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