JP2025009949A - Laminate and packaging container - Google Patents

Abstract

To provide a laminate which enables manufacture of a packaging container that easily reduces a used amount of a resin in a barrier layer, is excellent in gas barrier property, improves working suitability, and is excellent in content resistance, and a packaging container using the same.SOLUTION: A laminate 10 includes at least a first layer 11 and a barrier layer 12, wherein the barrier layer 12 is two layers of co-extrusion layers of a gas barrier resin layer 14 and an adhesive resin layer 15, the gas barrier resin layer 14 is positioned between the first layer 11 and the adhesive resin layer 15, the gas barrier resin layer 14 contains an ethylene-vinyl alcohol copolymer, the adhesive resin layer 15 is composed of a resin composition containing unmodified polyolefin and maleic anhydride modified polyolefin, a content of the unmodified polyolefin in the adhesive resin layer 15 is 10 mass% or more and 40 mass% or less, and thickness of the adhesive resin layer 15 is 3 μm or more and 20 μm or less.SELECTED DRAWING: Figure 1

Description

This disclosure relates to a laminate and a packaging container.

Conventionally, resin films made of resin materials have been used as a constituent material of packaging materials, and packaging material laminates made of multiple resin films are widely used. Packaging materials are required to have various functions depending on the contents to be filled. For example, gas barrier properties such as oxygen barrier properties and water vapor barrier properties are required to prevent deterioration of the contents over time.

2. Description of the Related Art Laminates for packaging materials having improved gas barrier properties using ethylene-vinyl alcohol copolymer (EVOH), a gas barrier resin, have been proposed so far.
For example, Patent Document 1 describes a barrier packaging material in which a base film, a barrier film, and a sealant film are laminated in this order, and the barrier film is a co-extruded film having a structure of an ethylene-vinyl alcohol copolymer layer/an adhesive resin layer/a polyolefin layer. This barrier packaging material has appropriate gas barrier properties and aroma retention properties.
Patent Document 2 describes a laminate including a substrate and a barrier layer, the barrier layer being formed by co-extrusion of three types of five layers: polyolefin resin/adhesive resin/ethylene-vinyl alcohol copolymer/adhesive resin/polyolefin resin. This laminate can be widely used for packaging materials that require barrier properties or packaging materials that have quality requirements for high resistance.
Furthermore, Patent Document 3 describes a paper container for liquids that is composed of a laminate using a nylon film or an EVOH film as a barrier layer. This paper container for liquids can prevent a decrease in the adhesive strength of the adhesive layer used to bond the barrier layer and the sealant layer.

Japanese Patent Application Publication No. 7-304139 JP 2012-76305 A JP 2013-144556 A

In recent years, in order to reduce the environmental burden, such as by reducing carbon dioxide emissions, there has been a strong demand for a reduction in the amount of plastic used, even in laminates that make up packaging materials. Furthermore, there is also the advantage that a reduction in the amount of plastic used also leads to cost reduction. Therefore, instead of the three-kind, three-layer coextrusion described in Patent Document 1 or the three-kind, five-layer coextrusion described in Patent Document 2, there is a demand to produce a film by two-kind, two-layer coextrusion to reduce the number of layers and the amount of resin.

The coextrusion layers described in Patent Documents 1 and 2 are formed by coextrusion of three types of resin: an ethylene-vinyl alcohol copolymer, an adhesive resin, and a polyolefin resin. If polyolefin is excluded from these three types of resin and a two-layer film is formed by coextrusion using only an ethylene-vinyl alcohol copolymer and an adhesive resin, the following problems arise.

Maleic anhydride-modified polyolefin has been used as an adhesive resin. Maleic anhydride-modified polyolefin is a resin in which maleic anhydride, an adhesive component, is graft-polymerized onto a polyolefin to enhance adhesion to an ethylene-vinyl alcohol copolymer layer compared to unmodified polyolefin. Since maleic anhydride-modified polyolefin contains an excess of maleic anhydride, an adhesive component, it is easy to adhere to a metal chill roll or a rubber nip roll used in the process of producing a laminate.
When a film is produced by co-extrusion of two layers of an ethylene-vinyl alcohol copolymer and a maleic anhydride-modified polyolefin, the layer of maleic anhydride-modified polyolefin constituting one side of the produced film adheres to a metal chill roll or a rubber nip roll, making it difficult to remove the film from the metal chill roll or the rubber nip roll, and thus a problem has arisen in that it is difficult to process the film into a laminate.

Ethylene-vinyl alcohol copolymers and adhesive resins may change color or emit odors or foreign matter due to decomposition at high temperatures, but unmodified polyolefins are less likely to suffer from such phenomena. For this reason, unmodified polyolefins can be said to be resins with relatively excellent heat resistance. In the co-extrusion of three resins described in Patent Documents 1 and 2, unmodified polyolefins with excellent heat resistance are extruded at high temperatures, and the entire co-extruded layer is heated to a high temperature, so that the layers melt together and the adhesive strength between the layers is increased.
When unmodified polyolefin is excluded from the three resins used for coextrusion and a two-layer film is produced by coextrusion of an ethylene-vinyl alcohol copolymer and an adhesive resin, the absence of unmodified polyolefin with excellent heat resistance in the coextruded layer makes it difficult to maintain the entire coextruded layer at a high temperature, and the coextruded layers are less likely to fuse together, which leads to a decrease in adhesive strength. As a result, there are problems such as delamination occurring easily and a decrease in gas barrier properties.

Also, instead of using an ethylene-vinyl alcohol copolymer, a gas barrier layer such as a silica-deposited polyethylene terephthalate film, an alumina-deposited polyethylene terephthalate film, or an aluminum foil is laminated to improve the gas barrier properties of the laminate. However, in packaging containers made from laminates having such a gas barrier layer, delamination may occur in the laminate depending on the contents filled therein.
For example, when a silica-deposited polyethylene terephthalate film or an alumina-deposited polyethylene terephthalate film is used for a packaging container filled with an alkaline content, the polyethylene terephthalate is hydrolyzed by the alkali, and delamination may occur in the laminate. Also, when an aluminum foil is used for a packaging container filled with an acidic content, the aluminum foil is corroded by the acid, and delamination may occur in the laminate. Furthermore, when a solvent is filled as the content in a packaging container, the adhesive used in the laminate is dissolved by the solvent, and delamination may occur in the laminate.
Therefore, there has been a demand for a packaging container having excellent content resistance suitable for use with a variety of contents, and a laminate from which such a packaging container can be produced.

Therefore, an object of the present disclosure is to provide a laminate that can be used to produce a packaging container that can easily reduce the amount of resin used in the barrier layer, has excellent gas barrier properties, improved processability, and excellent content resistance. Another object of the present disclosure is to provide a packaging container that uses the laminate.

The present inventors have discovered that the above problems can be solved by forming a single layer from a resin composition in which an adhesive resin and an unmodified polyolefin are mixed, instead of forming a layer of an adhesive resin and a layer of an unmodified polyolefin as separate layers.
In a resin composition obtained by mixing an adhesive resin with an unmodified polyolefin, the adhesiveness is appropriately reduced compared to the adhesive resin before being mixed with the unmodified polyolefin, and adhesion to a metal chill roll or a rubber nip roll is suppressed, thereby improving processability.
Furthermore, by co-extruding the resin composition with an ethylene-vinyl alcohol copolymer at a certain thickness or more, a certain amount of heat or more is stored in the resin composition, making it easier to maintain the entire co-extruded layer at a high temperature, and the layers are sufficiently fused together. Even if the adhesiveness of the resin composition is reduced, the interlayer adhesive strength of the laminate is less likely to decrease, and as a result, the gas barrier property is less likely to decrease.
Furthermore, by using an ethylene-vinyl alcohol copolymer in the laminate instead of a gas barrier layer such as a silica-deposited polyethylene terephthalate film, an alumina-deposited polyethylene terephthalate film, or an aluminum foil, a packaging container produced using the laminate has excellent resistance to contents.
The present disclosure has been completed based on these findings and through further investigation.

The present disclosure is solved by the following embodiments.
＜1＞
A laminate comprising at least a first layer and a barrier layer,
the barrier layer is a co-extruded layer of two layers, a gas barrier resin layer and an adhesive resin layer,
the gas barrier resin layer is located between the first layer and the adhesive resin layer,
the gas barrier resin layer contains an ethylene-vinyl alcohol copolymer,
the adhesive resin layer is made of a resin composition containing an unmodified polyolefin and a maleic anhydride-modified polyolefin,
The content of the unmodified polyolefin in the adhesive resin layer is 10% by mass or more and 80% by mass or less,
The thickness of the adhesive resin layer is 3 μm or more and 20 μm or less.
＜2＞
The laminate according to <1>, wherein the content of groups derived from maleic anhydride in the adhesive resin layer is 0.18% by mass or more and 0.25% by mass or less.
＜3＞
The laminate according to <1> or <2>, wherein the melt flow rate of the resin composition is 2 g/10 min or more and 13 g/10 min or less.
＜4＞
The laminate according to any one of <1> to <3>, wherein the gas barrier resin layer has a thickness of 3 μm to 20 μm.
＜5＞
The laminate according to any one of <1> to <4>, wherein the ethylene-vinyl alcohol copolymer has a content of structural units derived from ethylene of 20 mol % or more and 60 mol % or less.
＜6＞
The laminate according to any one of <1> to <5>, wherein the ethylene-vinyl alcohol copolymer has a melt flow rate of 0.1 g/10 min or more and 15 g/10 min or less.
＜７＞
The laminate according to any one of <1> to <6>, wherein the barrier layer has a thickness of 10 μm or more and 30 μm or less.
＜8＞
The laminate according to any one of <1> to <7>, further comprising a second layer on the adhesive resin layer.
＜9＞
The laminate according to <8>, wherein the second layer is a sealant film.
＜10＞
The laminate according to any one of <1> to <9>, wherein the first layer comprises paper.
<11>
The oxygen permeability measured in accordance with JIS K 7126-2:2006 under an environment of a temperature of 23° C. and a relative humidity of 60% RH is 10 cc/m ² ·day ·atm or less.
<10> The laminate according to any one of <10>.
＜12＞
A packaging container comprising the laminate according to any one of <1> to <11>.
＜13＞
The packaging container according to <12>, which is a liquid paper container.

The present disclosure can provide a laminate that can easily reduce the amount of resin used in the barrier layer, has excellent gas barrier properties, and can be used to produce a packaging container that has improved processability and excellent content resistance.
The present disclosure also provides a packaging container using the laminate.

1 is a schematic cross-sectional view showing one embodiment of a laminate according to the present disclosure. 1 is a schematic cross-sectional view showing one embodiment of a laminate according to the present disclosure. FIG. 1 is a perspective view showing a standing pouch which is one embodiment of a packaging container according to the present disclosure. FIG. 1 is a front view showing a pillow bag, which is one embodiment of a packaging container according to the present disclosure. 1 is a front view showing a three-sided sealed bag, which is one embodiment of a packaging container according to the present disclosure. 1 is a front view showing a four-sided sealed bag, which is one embodiment of a packaging container according to the present disclosure. 1 is a perspective view showing a Gabel-top type liquid paper container which is one embodiment of a packaging container according to the present disclosure. FIG. FIG. 1 is a perspective view showing a flat-top type liquid paper container which is one embodiment of a packaging container according to the present disclosure. FIG. 1 is a perspective view showing a brick-shaped liquid paper container, which is one embodiment of a packaging container according to the present disclosure. 1 is a perspective view of a paper cup, which is one embodiment of a packaging container according to the present disclosure, with a portion cut away. 1 is a partially cutaway front view of a paper cup, which is one embodiment of a packaging container according to the present disclosure.

Below, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the following embodiments. Furthermore, the components in the following embodiments include those that a person skilled in the art would easily imagine and those that are substantially the same. Furthermore, the components disclosed in the following embodiments can be combined as appropriate.

As shown in FIG. 1, the laminate 10 of the present disclosure includes at least a first layer 11 and a barrier layer 12. The barrier layer 12 is a coextrusion layer of a gas barrier resin layer 14 and an adhesive resin layer 15. The gas barrier resin layer 14 is located between the first layer 11 and the adhesive resin layer 15.

In one embodiment of the present disclosure, the laminate 10 includes a first layer 11, a barrier layer 12, and a second layer 13, as shown in FIG. 2. The barrier layer 12 is a coextrusion layer of a gas barrier resin layer 14 and an adhesive resin layer 15. The gas barrier resin layer 14 is located between the first layer 11 and the adhesive resin layer 15. The adhesive resin layer 15 is located between the gas barrier resin layer 14 and the second layer 13. The laminate 10 shown in FIG. 2 further includes a second layer 13 on the adhesive resin layer 15 of the laminate 10 shown in FIG. 1.

In the laminate of the present disclosure, the oxygen transmission rate measured in accordance with JIS K 7126-2:2006 under an environment of a temperature of 23° C. and a relative humidity of 60% RH is preferably 10 cc/ ^m2 ·atm·day or less, more preferably 5 cc/ ^m2 ·atm·day or less, even more preferably 2 cc/ ^m2 ·atm·day or less, and particularly preferably 1 cc/ ^m2 ·atm·day or less. If the oxygen transmission rate of the laminate satisfies the above numerical range, the laminate has suitable oxygen barrier properties, and therefore, when used in a packaging container, adverse effects on the contents of the packaging container can be suppressed.
The laminate of the present disclosure is preferably impermeable to oxygen. Therefore, the oxygen permeability of the laminate of the present disclosure is most preferably 0 cc/ ^m2 ·atm·day, but is practically 0.01 cc/ ^m2 ·atm·day or more, more practically 0.05 cc/ ^m2 ·atm·day or more, and even more practically 0.1 cc/ ^m2 ·atm·day or more.
The oxygen permeability of the laminate is measured using an oxygen permeability measuring device, specifically, by the method described in the Examples below.

The layers that make up the laminate of this disclosure are described below.

[First layer]
As the first layer, any resin film or sheet can be used depending on the application of the laminate. For example, when the laminate is applied to a refill pouch for sealing and packaging refillable shampoo or rinse, the first layer is preferably excellent in mechanical strength such as tensile strength, flexural strength, and impact strength, as well as printability. For example, as the first layer, a nylon film, a polyester film such as a polyethylene terephthalate film or a polybutylene terephthalate film, or a polyolefin film such as a polypropylene film or a polyethylene film can be suitably used. These films may be unstretched films, uniaxially stretched films, or biaxially stretched films. They may also be vapor-deposited films in which a metal such as aluminum or an inorganic oxide such as aluminum oxide or silicon oxide is vapor-deposited on these films.
Alternatively, any paper can be used as the first layer. For example, known papers such as fine paper, imitation paper, art paper, coated paper, pure white roll paper, kraft paper, label paper with improved water resistance, cup base paper, card paper, ivory paper, paperboard such as manila cardboard, milk carton base paper, cup base paper, synthetic paper, clay-coated paper, etc. can be used. When the first layer is paper, the packaging container using the laminate of the present disclosure, coupled with the fact that the amount of resin used in the barrier layer can be easily reduced, makes it easier to obtain a paper mark for paper container packaging based on the Resource Effective Utilization Promotion Act (Act on Promotion of Effective Utilization of Resources).
Alternatively, a metal foil obtained by rolling a metal can also be used as the first layer. As the metal foil, a conventionally known metal foil can be used. From the viewpoints of gas barrier properties that prevent the transmission of oxygen gas, water vapor, etc., and light blocking properties that prevent the transmission of visible light, ultraviolet light, etc., aluminum foil is preferred.
These films, sheets, papers, or metal foils may be used alone or in combination. For example, a laminated paper may be used in which an anchor coat layer described below is formed on one side of a paper and a resin is extruded onto the anchor coat layer to form a laminate.
In order to improve the ease of opening, the first layer may be subjected to SC processing, laser processing, sewing machine processing or slit processing.

[Printed layer]
The laminate of the present disclosure may include a printed layer. The printed layer is a layer on which any desired printed pattern such as letters, numbers, pictures, figures, symbols, designs, etc. is formed for decoration, indication of contents, indication of expiration date, indication of manufacturer, indication of seller, imparting aesthetic feeling, etc.
When the laminate of the present disclosure includes a printed layer, the printed layer is preferably formed on either one surface of the first layer.

[Anchor coat layer]
In one embodiment, the laminate of the present disclosure may further include an anchor coat layer on the first layer or on the surface of the first layer on which the printed layer is formed. This can improve the interlayer adhesion between the first layer and the gas barrier resin layer. The anchor coat layer is formed from an anchor coating agent.

Examples of anchor coating agents include polyurethane-based, polyolefin-based, or epoxy resin-based anchor coating agents. In one embodiment, the anchor coating agent is a two-component curing resin, and is composed of, for example, a polyol base and a polyisocyanate curing agent.

Examples of the polyol include polyether polyol, polyester polyol, and (meth)acrylic polyol. Examples of the polyisocyanate include aromatic polyisocyanates such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenylene polyisocyanate, and aliphatic polyisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate.

In one embodiment, the anchor coat layer is made of polyurethane obtained by reacting a polyol with a polyisocyanate. Specific examples of polyurethane include polyether polyurethane, polyester polyurethane, and poly(meth)acrylic polyurethane.

The anchor coat layer can be formed, for example, by applying an anchor coat agent onto the first layer or onto the surface of the first layer on which the printed layer is formed. The anchor coat agent can be applied, for example, by a coating method such as roll coating, gravure roll coating, or kiss coating, or by a printing method.

The dry coating amount of the anchor coating agent is, for example, from 0.01 g/ ^m2 to 1 g/ ^m2 , preferably from 0.03 g/ ^m2 to 0.5 g/ ^m2 , and more preferably from 0.05 g/ ^m2 to 0.4 g/ ^m2 .

The thickness of the anchor coat layer is, for example, 0.05 μm or more and 3.0 μm or less, preferably 0.1 μm or more and 2.0 μm or less, and more preferably 0.2 μm or more and 1.0 μm or less.

[Gas barrier resin layer]
The gas barrier resin layer contains an ethylene-vinyl alcohol copolymer as a gas barrier resin, which can improve the gas barrier properties of the laminate and can provide a laminate body from which a packaging container having excellent resistance to contents can be produced.

In the ethylene-vinyl alcohol copolymer, the content of structural units derived from ethylene (hereinafter referred to as "ethylene content") is preferably 20 mol % or more, more preferably 25 mol % or more, and even more preferably 32 mol % or more. This can improve the processability of the laminate.
The ethylene content of the ethylene-vinyl alcohol copolymer is preferably 60 mol % or less, more preferably 48 mol % or less, and even more preferably 44 mol % or less, thereby improving the gas barrier properties of the laminate.
The ethylene content of the ethylene-vinyl alcohol copolymer is a value measured by the NMR method.

The melting point (Tm) of the ethylene-vinyl alcohol copolymer is preferably 130°C or higher and 200°C or lower, more preferably 140°C or higher and 195°C or lower, and even more preferably 150°C or higher and 190°C or lower.

From the viewpoint of processability, the melt flow rate (MFR) of the ethylene-vinyl alcohol copolymer is preferably 0.1 g/10 min or more, more preferably 0.3 g/10 min or more, even more preferably 0.5 g/10 min or more, and particularly preferably 1 g/10 min or more.
Moreover, from the viewpoint of facilitating the production of a laminate having a good appearance, the melt flow rate of the ethylene-vinyl alcohol copolymer is preferably 15 g/10 min or less, more preferably 10 g/10 min or less, even more preferably 5 g/10 min or less, and particularly preferably 4 g/10 min or less.
The melt flow rate of the ethylene-vinyl alcohol copolymer is a value measured in accordance with JIS K7210-1:2014 under conditions of a temperature of 190°C and a load of 2.16 kg. However, when the melting point of the ethylene-vinyl alcohol copolymer exceeds 190°C, the value is measured at a temperature of 210°C.

The content of the ethylene-vinyl alcohol copolymer in the gas barrier resin layer is, for example, 50% by mass or more, preferably 75% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, and particularly preferably 90% by mass or more. This improves the gas barrier properties of the laminate.

The gas barrier resin layer may further contain a gas barrier resin other than the ethylene-vinyl alcohol copolymer. For example, it may contain at least one selected from polyamide, polyvinyl alcohol, polyacrylonitrile, polyester, polyurethane, and (meth)acrylic resin.

The gas barrier resin layer may contain various additives to the extent that the properties are not impaired. Examples of additives include antioxidants, slip agents, plasticizers, UV stabilizers, color inhibitors, matting agents, deodorants, flame retardants, weather resistance agents, antistatic agents, thread friction reducers, release agents, ion exchange agents, antiblocking agents, and color pigments.

The thickness of the gas barrier resin layer is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 8 μm or more. This can improve the gas barrier properties of the laminate. The thickness of the gas barrier resin layer is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. This can reduce the amount of resin used in the barrier layer.
It has been conventional to improve the gas barrier properties of a laminate by laminating an ethylene-vinyl alcohol copolymer film. However, compared with the thickness of a gas barrier resin layer that can be formed by extrusion of an ethylene-vinyl alcohol copolymer, the thickness of a conventional ethylene-vinyl alcohol copolymer film is large, and there has been a problem that it is difficult to process into a packaging container such as a liquid paper container. In the present disclosure, the gas barrier resin layer is a certain thickness or less, so that the suitability for processing into a packaging container is excellent.

[Adhesive resin layer]
The adhesive resin layer is composed of a resin composition containing an unmodified polyolefin and a maleic anhydride modified polyolefin.
The unmodified polyolefin refers to a polyolefin that has not been modified, and examples of the unmodified polyolefin include high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and polypropylene (PP).
Maleic anhydride modified polyolefin is a resin in which maleic anhydride is graft-polymerized onto the main chain of a polyolefin. Examples of polyolefins that can be modified with maleic anhydride include high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and polypropylene (PP).

The resin composition may contain two or more kinds of unmodified polyolefins. For example, the resin composition may contain an unmodified low-density polyethylene and an unmodified linear low-density polyethylene.
The resin composition may contain two or more kinds of maleic anhydride-modified polyolefins. For example, the resin composition may contain a low-density polyethylene modified with maleic anhydride and a linear low-density polyethylene modified with maleic anhydride.

The content of unmodified polyolefin in the adhesive resin layer (total content when the resin composition constituting the adhesive resin layer contains two or more kinds of unmodified polyolefin) is 10% by mass or more, preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. Also, the content of unmodified polyolefin in the adhesive resin layer (total content when the resin composition constituting the adhesive resin layer contains two or more kinds of unmodified polyolefin) is 80% by mass or less, preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less.
The content of maleic anhydride-modified polyolefin in the adhesive resin layer (total content when the resin composition constituting the adhesive resin layer contains two or more types of maleic anhydride-modified polyolefin) is preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more. The content of maleic anhydride-modified polyolefin in the adhesive resin layer (total content when the resin composition constituting the adhesive resin layer contains two or more types of maleic anhydride-modified polyolefin) is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less.

In the conventional technology, maleic anhydride-modified polyolefins have been used alone in the adhesive resin layer. However, commercially available maleic anhydride-modified polyolefins have an excessive amount of maleic anhydride, which is an adhesive component, grafted onto the polyolefin, and therefore tend to adhere to a metal chill roll or a rubber nip roll used in the process of producing a laminate.
On the other hand, when an unmodified polyolefin is used alone instead of a maleic anhydride-modified polyolefin, the adhesive component maleic anhydride is not present in the unmodified polyolefin, so that the adhesive strength between the adhesive resin layer and the second layer or the adhesive strength between the adhesive resin layer and the gas barrier resin layer decreases, making the laminate more susceptible to interlayer delamination and reducing the gas barrier properties.
In the present disclosure, the resin composition constituting the adhesive resin layer contains a certain proportion of unmodified polyolefin that does not contain an adhesive component, in addition to maleic anhydride modified polyolefin that contains an adhesive component, so that the adhesive resin layer exhibits appropriate adhesion such that it is difficult to adhere to a metal chill roll or a rubber nip roll, but is easy to adhere to the second layer and the gas barrier resin layer, thereby achieving both excellent gas barrier properties and improved processability.

The content of unmodified polyolefin and the content of maleic anhydride modified polyolefin in the adhesive resin layer can be analyzed from peaks detected by, for example, differential scanning calorimetry (DSC), infrared spectroscopy (IR), and nuclear magnetic resonance (NMR).

Since the resin composition constituting the adhesive resin layer contains unmodified polyolefin in addition to maleic anhydride-modified polyolefin, the content of groups derived from maleic anhydride in the adhesive resin layer is smaller than that of an adhesive resin layer formed from a commercially available maleic anhydride-modified polyolefin. In the present disclosure, the content of groups derived from maleic anhydride in the adhesive resin layer is preferably 0.29% by mass or less, more preferably 0.25% by mass or less, and even more preferably 0.23% by mass or less. This makes it difficult for the adhesive resin layer to adhere to a metal chill roll or a rubber nip roll during the process of producing the laminate. In addition, the content of groups derived from maleic anhydride in the adhesive resin layer is preferably 0.1% by mass or more, more preferably 0.15% by mass or more, and even more preferably 0.2% by mass or more. This makes it easier for the adhesive resin layer to adhere to the second layer and the gas barrier resin layer, and prevents delamination of the laminate.
The content of the group derived from maleic anhydride in the adhesive resin layer is the ratio of the mass of the group derived from maleic _anhydride ( _{--C.sub.4H.sub.3O.sub.3 )} to the mass of all the components constituting the adhesive resin layer.
The content of the group derived from maleic anhydride in the adhesive resin layer is measured by infrared absorption spectroscopy, specifically, by the method described in the Examples below.

From the viewpoint of processability, the melt flow rate of the resin composition is preferably 2 g/10 min or more, more preferably 5 g/10 min or more, and even more preferably 6 g/10 min or more.
From the viewpoint of facilitating the production of a laminate having a good appearance, the melt flow rate of the resin composition is preferably 13 g/10 min or less, more preferably 10 g/10 min or less, and even more preferably 7 g/10 min or less.
The melt flow rate of the resin composition is a value measured in accordance with JIS K7210-1:2014 under conditions of a temperature of 190°C and a load of 2.16 kg.

The resin composition may further contain other resins in addition to the unmodified polyolefin and the maleic anhydride-modified polyolefin. For example, the resin composition may contain at least one resin selected from polyolefins modified with substances other than maleic anhydride (e.g., maleic acid, fumaric acid, esters, or metal salts), vinyl resins, polyethers, polyesters, polyamides, polyurethanes, silicone resins, epoxy resins, and phenolic resins.

The resin composition may contain various additives to the extent that the properties are not impaired. Examples of additives include antioxidants, slip agents, plasticizers, UV stabilizers, color inhibitors, matting agents, deodorants, flame retardants, weather resistance agents, antistatic agents, thread friction reducers, release agents, ion exchange agents, antiblocking agents, and color pigments.

The thickness of the adhesive resin layer is 3 μm or more, preferably 6 μm or more, and more preferably 9 μm or more. This makes it easier to heat the entire co-extrusion layer to a high temperature when extruding the resin composition in the process of producing the laminate. As a result, the layers are sufficiently fused together, and the adhesive strength between the layers of the produced laminate can be maintained. In addition, the thickness of the adhesive resin layer is 20 μm or less, preferably 15 μm or less, and more preferably 10 μm or less. This makes it possible to reduce the amount of resin used in the barrier layer.

[Barrier layer]
The barrier layer is a coextrusion layer of two layers, a gas barrier resin layer and an adhesive resin layer. The coextrusion layer is a layer formed by a coextrusion method.
Unlike the dry lamination method in which simple single films are bonded together, the film formation by the co-extrusion method is carried out by extruding multiple molten resins through multiple thin slit-like gaps. Therefore, the interface between layers formed by the co-extrusion method shows a very unique structure. This structure is significantly different from the interlayer structure caused by entanglement interactions such as self-adhesion in the dry lamination method. Specifically, the interface between layers formed by the co-extrusion method forms an interlocking structure in which the crystals of each resin penetrate each other, and has a very complex structure.

The barrier layer can be formed, for example, by co-extruding the resin constituting the gas barrier resin layer and the resin composition constituting the adhesive resin layer. More specifically, it can be produced by simultaneously extruding two layers, an ethylene-vinyl alcohol copolymer and an adhesive resin, onto the first layer using a co-extrusion molding device. This results in a laminate in which the barrier layer, which is a two-layer co-extrusion of a gas barrier resin layer and an adhesive resin layer, and the first layer are laminated together. Note that the barrier layer produced by the co-extrusion method is an unstretched layer.

From the viewpoint of obtaining a laminate having excellent gas barrier properties, the thickness of the barrier layer is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 16 μm or more. Furthermore, from the viewpoint of reducing the amount of resin used in the barrier layer, the thickness of the barrier layer is preferably 30 μm or less, more preferably 24 μm or less, and even more preferably 20 μm or less.

[Second layer]
As the second layer, the same film, sheet or paper as the first layer can be used.
The second layer is preferably a film having excellent heat sealability, i.e., a sealant film, which can be melted by heating or the like to perform heat sealing in which the second layers are fused together, and a packaging container can be easily produced from the laminate.
Specific examples of heat seals include bar seals, rotary roll seals, belt seals, impulse seals, high frequency seals, and ultrasonic seals.

The second layer and the barrier layer can be bonded to each other by extrusion lamination (so-called sandwich lamination) via an adhesive layer. In this case, the adhesive layer can be made of a polyolefin-based heat-adhesive resin (e.g., LDPE), as well as a simple substance such as an ethylene-methacrylic acid copolymer, an ethylene-acrylic acid copolymer, or an ionomer, or a resin obtained by blending these with an adhesion improver such as a hard resin.
Alternatively, a gas barrier resin layer and an adhesive resin layer may be co-extruded onto the first layer, and the first layer and the second layer may be laminated via the gas barrier resin layer and the adhesive resin layer, and bonded together by a co-extrusion method, which makes it possible to omit a dry laminate layer or an adhesive layer between the adhesive resin layer and the second layer, and thus reduces the amount of resin used.

The laminate according to the present disclosure may have an intermediate layer between the second layer and the barrier layer. Examples of the intermediate layer include a light-shielding layer and a strength-improving layer.

The second layer and the intermediate layer, and the intermediate layer and the barrier layer can be laminated by extrusion lamination, coextrusion, etc., in the same manner as the bonding between the second layer and the barrier layer described above.

The layers constituting the first layer may be bonded together by dry lamination, or may be laminated by extrusion lamination, co-extrusion, or the like as described above.

In either case, the adhesive strength between layers can be increased by applying an anchor coating agent to the laminated surfaces beforehand or by pre-treating them with a corona treatment or other method.

[Packaging container]
The laminate of the present disclosure can be suitably used for packaging containers. Examples of packaging containers include packaging bags, lids, laminate tubes, liquid containers, paper cups, various label materials, etc. Examples of packaging bags include packaging bags of various shapes such as standing pouch type, side seal type, two-sided seal type, three-sided seal type, four-sided seal type, envelope seal type, joint seal type (pillow seal type), pleated seal type, flat bottom seal type, square bottom seal type, and gusset type.
The thickness of the laminate can be appropriately determined depending on the application. For example, by reducing the thickness of the laminate, the stiffness of the laminate itself can be reduced, and the suitability for packaging machines such as bag making machines and filling machines can be improved. The thickness of the laminate is, for example, 30 μm or more and 300 μm or less, preferably 35 μm or more and 180 μm or less.

[Standing pouch]
The application of the laminate of the present disclosure to a standing pouch will be described.
Fig. 3 is a diagram showing a simplified example of the configuration of a standing pouch. As shown in Fig. 3, the standing pouch 30 is composed of two side sheets 31 and one bottom sheet 32. In the standing pouch 30, the side sheet 31 and the bottom sheet 32 are composed of different members. The standing pouch 30 is a packaging bag formed by using a sealant film as the second layer of the laminate of the present disclosure constituting the side sheet 31, and making the sealant film into the innermost layer. In the present disclosure, the side sheet 31 and the bottom sheet 32 of the standing pouch 30 are composed of different members, but this is not limited thereto, and the side sheet 31 and the bottom sheet 32 may be composed of the same member.
In addition, in the standing pouch 30, the side sheet 31 is formed using the laminate of the present disclosure, but the standing pouch of the present disclosure is not limited to this, and the bottom sheet 32 may be formed using the laminate of the present disclosure, or both the side sheet 31 and the bottom sheet 32 may be formed using the laminate of the present disclosure.

The standing pouch 30 can be suitably used as a packaging container for filling liquids, for packaging chemical products, medicines, quasi-drugs, cosmetics, food, etc., for example, as an outer bag for patches, or as a standing pouch used for refill contents such as liquid detergent, liquid fabric softener, liquid soap, etc.

[Pillow bags, three-side sealed bags and four-side sealed bags]
Depending on the form of heat sealing of the laminate, various packaging bags can be made in addition to the standing pouch. Fig. 4 is a diagram showing an example of a pillow bag, Fig. 5 is a diagram showing an example of a three-sided sealed bag, and Fig. 6 is a diagram showing an example of a four-sided sealed bag. In Figs. 4 to 6, the heat-sealed parts are indicated by hatching. The pillow bag 41 shown in Fig. 6 is obtained by using a sealant film as the second layer of the laminate, making a bag so that the sealant film is the innermost layer, and heat-sealing and bonding two opposing sides of the laminate. The three-sided sealed bag 42 shown in Fig. 7 is obtained by using a sealant film as the second layer of the laminate, making a bag so that the sealant film is the innermost layer, and heat-sealing and bonding three sides of the laminate. The four-sided sealed bag 43 shown in Fig. 8 is obtained by using a sealant film as the second layer of the laminate, making a bag so that the sealant film is the innermost layer, and heat-sealing and bonding four sides of the laminate.

[Liquid carton]
Next, a case where a liquid-storing paper container is formed using the laminate of the present disclosure will be described.
Fig. 7 is a perspective view showing an example of a liquid-storing paper container 60. As shown in Fig. 7, the liquid-storing paper container 60 has a rectangular tubular body 61 including a side surface, a rectangular plate-shaped bottom 62, and an upper portion 63.
The upper portion 63 has a pair of opposing inclined plates 63a and a pair of folded portions 64 that are located between the inclined plates 63a and are folded between the inclined plates 63a. A margin 65 is provided at the upper end of each of the pair of inclined plates 63a, and the pair of inclined plates 63a are bonded to each other by the margin 65 provided at the upper end of each of the pair of inclined plates 63a. A spout may be attached to one of the pair of inclined plates 63a, and the spout may be sealed with a cap.

The liquid paper container 60 employs paper or laminated paper as the first layer of the laminate of the present disclosure, and can be manufactured using the laminate by a conventionally known method. For example, the laminate can be made into a box to manufacture liquid paper containers 60 of various shapes, such as a Gabeltop type with a gable roof-like upper part, a flat top type with a flat upper part and a spout plug, and a brick type with a flat upper part and a straw hole, etc.
An example of a Gabeltop type liquid paper container is a liquid paper container 60 having a gable roof-shaped upper portion 63 as shown in FIG.
An example of a flat-top type liquid-containing paper container is a liquid-containing paper container 60 having a flat top 63 and a spout plug 66 as shown in FIG.
An example of a brick-type liquid paper container is a liquid paper container 60 having a flat top 63 and a straw hole 67, as shown in FIG.

The liquid paper container 60 can be used as a packaging paper container for all types of liquids, including alcoholic beverages such as sake, shochu, and wine, dairy drinks such as milk, soft drinks such as orange juice and tea, and chemical products such as car wax, shampoo, and detergent.

[Paper cups]
Next, a paper cup formed using the laminate of the present disclosure will be described.
Fig. 10 is a perspective view of a paper cup with a part cut away. As shown in Fig. 10, the paper cup 70 has a cylindrical body 72 with a flange 71 at the top and a diameter gradually increasing toward the opening, and a bottom 73 provided at the lower end (one end) of the body 72. The body 72 has a flange 71 with its upper end rounded outward. After the contents are placed in the paper cup 70, the paper cup 70 may be sealed by attaching a lid (not shown) along the flange 71 of the body 72. It is preferable that the lid has gas barrier properties.
The paper cup 70 can be manufactured by a conventionally known method by employing paper or laminated paper as the first layer of the laminate of the present disclosure and using the laminate for the body 72. However, the paper cup of the present disclosure is not limited to this, and the bottom 73 may be formed using the laminate of the present disclosure, or both the body 72 and the bottom 73 may be formed using the laminate of the present disclosure.

The paper cup 70 may also have an exterior body 74 on the outer periphery of the body 72, as shown in FIG. 11. The exterior body 74 may be, for example, paper. The body 72 is formed with a protrusion 75. The protrusion 75 is formed to provide an air gap 76 between the body 72 and the exterior body 74. One or more protrusions 75 are provided in the horizontal direction, and for example, two protrusions can be provided as shown in FIG. 11.

The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to the following examples.

The various raw materials used in the laminates of the following Examples 1 to 19 and Comparative Examples 1 to 6 are as follows.
Gas barrier resin A
Ethylene-vinyl alcohol copolymer, product name: F171B, manufactured by Kuraray Co., Ltd., ethylene content: 32 mol%, melt flow rate: 1.7 g/10 min (the melt flow rate is a value measured in accordance with JIS K7210-1:2014 under conditions of a temperature of 190°C and a load of 2.16 kg)
Gas barrier resin B
Ethylene-vinyl alcohol copolymer, product name: F104B, manufactured by Kuraray Co., Ltd., ethylene content: 32 mol%, melt flow rate: 4.4 g/10 min (melt flow rate is a value measured in accordance with JIS K7210-1:2014 under conditions of a temperature of 190°C and a load of 2.16 kg)
Gas barrier resin C
Ethylene-vinyl alcohol copolymer, product name: E173B, manufactured by Kuraray Co., Ltd., ethylene content: 44 mol%, melt flow rate: 2.5 g/10 min (melt flow rate is a value measured in accordance with JIS K7210-1:2014 under conditions of a temperature of 190°C and a load of 2.16 kg)
Gas barrier resin D
Ethylene-vinyl alcohol copolymer, product name: DC3212B, manufactured by Mitsubishi Chemical Corporation, ethylene content: 32 mol%, melt flow rate: 12 g/10 min (the melt flow rate is a value measured in accordance with JIS K7210-1:2014 under conditions of a temperature of 210°C and a load of 2.16 kg)
Adhesive resin A
A resin composition obtained by mixing 60% by mass of linear low-density polyethylene modified with maleic anhydride (product name: NE827, manufactured by Mitsui Chemicals, Inc.; melt flow rate measured in accordance with JIS K7210-1:2014 at a temperature of 190°C and a load of 2.16 kg: 5.6 g/10 min) and 40% by mass of unmodified low-density polyethylene (product name: CE4009, manufactured by Sumitomo Chemical Co., Ltd.; melt flow rate measured in accordance with JIS K7210-1:2014 at a temperature of 190°C and a load of 2.16 kg: 7.0 g/10 min). Melt flow rate of adhesive resin A: 6.2 g/10 min (melt flow rate measured in accordance with JIS K7210-1:2014 at a temperature of 190°C and a load of 2.16 kg)
Adhesive resin B
A resin composition obtained by mixing 20% by mass of low-density polyethylene modified with maleic anhydride (product name: 40E710, manufactured by Dow Chemical Japan Co., Ltd., melt flow rate measured in accordance with JIS K7210-1:2014 at a temperature of 190 ° C. and a load of 2.16 kg: 2.5 g / 10 min) and 80% by mass of unmodified low-density polyethylene (product name: CE4009, manufactured by Sumitomo Chemical Co., Ltd., melt flow rate measured in accordance with JIS K7210-1:2014 at a temperature of 190 ° C. and a load of 2.16 kg: 7.0 g / 10 min). Melt flow rate of adhesive resin B: 6.1 g / 10 min (melt flow rate is a value measured in accordance with JIS K7210-1:2014 at a temperature of 190 ° C. and a load of 2.16 kg)
Adhesive resin C
A resin composition obtained by mixing 75% by mass of maleic anhydride-modified polypropylene (product name: QE840, manufactured by Mitsui Chemicals, Inc.; melt flow rate measured in accordance with JIS K7210-1:2014 at a temperature of 190°C and a load of 2.16 kg: 8 g/10 min) and 25% by mass of unmodified polypropylene (product name: F329RA, manufactured by Prime Polymer Co., Ltd.; melt flow rate measured in accordance with JIS K7210-1:2014 at a temperature of 190°C and a load of 2.16 kg: 27 g/10 min). Melt flow rate of adhesive resin C: 12.8 g/10 min (melt flow rate measured in accordance with JIS K7210-1:2014 at a temperature of 190°C and a load of 2.16 kg)
Adhesive resin D
Linear low-density polyethylene modified with maleic anhydride (product name: NE827, manufactured by Mitsui Chemicals, Inc., melt flow rate measured in accordance with JIS K7210-1:2014 at a temperature of 190°C and a load of 2.16 kg: 5.6 g/10 min)
Adhesive resin E
Ethylene-methacrylic acid copolymer (product name: N1108C, manufactured by Dow Mitsui Polychemicals Co., Ltd., melt flow rate measured in accordance with JIS K7210-1:2014 at a temperature of 190°C and a load of 2.16 kg: 10 g/10 min)
・Low density polyethylene A
Product name: CE4009, manufactured by Sumitomo Chemical Co., Ltd., Melt flow rate measured in accordance with JIS K7210-1:2014 at a temperature of 190°C and a load of 2.16 kg: 7.0 g/10 min. Low density polyethylene B
Product name: Novatec LD LC520, manufactured by Japan Polyethylene Co., Ltd., Melt flow rate measured in accordance with JIS K7210-1:2014 at a temperature of 190°C and a load of 2.16 kg: 3.6 g/10 min

[Example 1]
A urethane-based anchor coating agent was applied to one side of the first layer of biaxially oriented polyethylene terephthalate film (product name: E5100, manufactured by Toyobo Co., Ltd., thickness: 25 μm) in a dry coating amount of 0.4 g/m ² to form an anchor coat layer. On the anchor coat layer, gas barrier resin A and adhesive resin A were co-extruded using a co-extruder, while the second layer of polyethylene film (product name: LL-XMTN, manufactured by Futamura Chemical Co., Ltd., thickness: 20 μm) was laminated via gas barrier resin A and adhesive resin A. At that time, the thickness of the gas barrier resin layer made of gas barrier resin A was set to 10 μm, and the thickness of the adhesive resin layer made of adhesive resin A was set to 10 μm.
In this manner, a laminate of Example 1 was obtained in which the first layer, the anchor coat layer, the gas barrier resin layer, the adhesive resin layer, and the second layer were laminated in this order.

[Example 2]
A laminate of Example 2 was obtained in the same manner as in Example 1, except that the thickness of the gas barrier resin layer was adjusted to 5 μm.

[Example 3]
A laminate of Example 3 was obtained in the same manner as in Example 1, except that the thickness of the gas barrier resin layer was 8 μm and the thickness of the adhesive resin layer was 8 μm.

[Example 4]
A laminate of Example 4 was obtained in the same manner as in Example 1, except that the thickness of the gas barrier resin layer was adjusted to 15 μm and the thickness of the adhesive resin layer was adjusted to 15 μm.

[Example 5]
A laminate of Example 5 was obtained in the same manner as in Example 2, except that an unstretched polypropylene film (product name: FCMN, manufactured by Futamura Chemical Co., Ltd., thickness: 20 μm) was used as the second layer instead of the polyethylene film.

[Example 6]
A laminate of Example 6 was obtained in the same manner as in Example 1, except that an unstretched polypropylene film (product name: FCMN, manufactured by Futamura Chemical Co., Ltd., thickness: 20 μm) was used instead of the polyethylene film as the second layer.

[Example 7]
The laminate of Example 7 was obtained in the same manner as in Example 1, except that a biaxially oriented polyethylene terephthalate film having a thickness of 12 μm (product name: E5100, manufactured by Toyobo Co., Ltd.) was used as the first layer instead of a biaxially oriented polyethylene terephthalate film having a thickness of 25 μm (product name: E5100, manufactured by Toyobo Co., Ltd.), and a polyethylene terephthalate film having a vapor-deposited film made of aluminum (product name: 1012, manufactured by Toray Film Processing Co., Ltd., thickness: 12 μm) was used as the second layer instead of the polyethylene film.

[Example 8]
A laminate of Example 8 was obtained in the same manner as in Example 1, except that gas barrier resin B was used instead of gas barrier resin A as the gas barrier resin.

[Example 9]
A laminate of Example 9 was obtained in the same manner as in Example 1, except that gas barrier resin C was used instead of gas barrier resin A as the gas barrier resin.

[Example 10]
A laminate of Example 10 was obtained in the same manner as in Example 1, except that adhesive resin B was used instead of adhesive resin A as the adhesive resin.

[Example 11]
A laminate of Example 11 was obtained in the same manner as in Example 6, except that adhesive resin C was used instead of adhesive resin A as the adhesive resin.

[Example 12]
A laminate of Example 12 was obtained in which the first layer, anchor coat layer, gas barrier resin layer, and adhesive resin layer were laminated in that order in the same manner as in Example 1, except that the second layer was not laminated and the gas barrier resin A and adhesive resin A were simply co-extruded onto the anchor coat layer.

[Example 13]
A laminate of Example 13 was obtained in the same manner as in Example 1, except that gas barrier resin D was used instead of gas barrier resin A as the gas barrier resin.

[Example 14]
A urethane-based anchor coating agent was applied to one side of a milk carton base paper having a basis weight of 382 g/ ^m2 in a dry coating amount of 0.4 g/ ^m2 to form an anchor coating layer. Low-density polyethylene A was extruded onto the anchor coating layer with an extruder to a thickness of 25 μm. In this way, a first layer consisting of the milk carton base paper, the anchor coating layer, and the low-density polyethylene layer was produced.
A urethane-based anchor coating agent was applied to the surface of the milk carton base paper in the first layer in a dry coating amount of 0.4 g/ ^m2 to form an anchor coat layer. Gas barrier resin A and adhesive resin A were co-extruded onto the anchor coat layer using a co-extruder, while the second layer, a polyethylene film (product name: LL-XMTN, manufactured by Futamura Chemical Co., Ltd., thickness: 40 μm), was laminated via the gas barrier resin A and adhesive resin A. At that time, the thickness of the gas barrier resin layer made of the gas barrier resin A was set to 10 μm, and the thickness of the adhesive resin layer made of the adhesive resin A was set to 10 μm.
In this manner, a laminate of Example 14 was obtained in which the first layer, anchor coat layer, gas barrier resin layer, adhesive resin layer, and second layer were laminated in this order.

[Example 15]
A laminate of Example 15 was obtained in the same manner as in Example 14, except that gas barrier resin B was used instead of gas barrier resin A as the gas barrier resin.

[Example 16]
A laminate of Example 16 was obtained in the same manner as in Example 14, except that gas barrier resin C was used instead of gas barrier resin A as the gas barrier resin.

[Example 17]
A laminate of Example 17 was obtained in the same manner as in Example 14, except that gas barrier resin D was used instead of gas barrier resin A as the gas barrier resin.

[Example 18]
A laminate of Example 18 was obtained in the same manner as in Example 17, except that a milk carton base paper having a basis weight of 320 g/ ^m2 was used instead of the milk carton base paper having a basis weight of 382 g/ ^m2 .

[Example 19]
A laminate of Example 19 was obtained in the same manner as in Example 17, except that a milk carton base paper having a basis weight of 400 g/ ^m2 was used instead of the milk carton base paper having a basis weight of 382 g/ ^m2 .

[Example 20]
A urethane-based anchor coating agent was applied to the surface of a polyethylene terephthalate film (product name: IB-PET, manufactured by Dai Nippon Printing Co., Ltd., thickness: 12 μm) on which a vapor deposition film made of silicon oxide was formed, in a dry coating amount of 0.4 g/m ² to form an anchor coat layer. On the anchor coat layer, gas barrier resin A and adhesive resin A were co-extruded using a co-extruder, while a second layer of polyethylene film (product name: M2005, manufactured by Aicello Co., Ltd., thickness: 40 μm) was laminated through the gas barrier resin A and adhesive resin A to produce a laminate. At that time, the thickness of the gas barrier resin layer made of gas barrier resin A was set to 10 μm, and the thickness of the adhesive resin layer made of adhesive resin A was set to 10 μm. Hereinafter, this laminate will be referred to as laminate A.
Next, a polyethyleneimine-based anchor coating agent was applied to one side of a milk carton base paper (manufactured by Clearwater Paper Corporation, basis weight: 382 g/ ^m2 ) in a dry coating amount of 0.1 g/ ^m2 , and low-density polyethylene A was extruded onto the anchor coating layer using an extruder to a thickness of 25 μm to produce a laminate. Hereinafter, this laminate will be referred to as Laminate B.
A polyethyleneimine-based anchor coating agent was applied to the milk carton base paper surface of laminate B at a dry coating amount of 0.1 g/ ^m2 , and adhesive resin C was extruded onto the anchor coating layer using an extruder to a thickness of 20 μm, and the layer was bonded to the vapor-deposited film surface of laminate A via adhesive resin C.
In this way, a laminate of Example 20 was obtained in which the first layer, anchor coat layer, gas barrier resin layer, adhesive resin layer, and second layer were laminated in this order. The first layer in Example 20 was a laminate of a low-density polyethylene layer, anchor coat layer, milk carton base paper, anchor coat layer, adhesive layer, and vapor-deposited film laminated in this order.

[Example 21]
A dry lamination adhesive was applied to one side of a biaxially oriented polyethylene terephthalate film (product name: E5100, manufactured by Toyobo Co., Ltd., thickness: 12 μm) in a dry coating amount of 3.0 g/m ² , and then laminated to an aluminum foil (product name: 1N30, manufactured by Toyo Aluminum Co., Ltd., thickness: 7 μm). A urethane-based anchor coating agent was applied to the other side of the biaxially oriented polyethylene terephthalate film in a dry coating amount of 0.4 g/m ² to form an anchor coat layer. A laminate was produced by laminating a second layer of a polyethylene film (product name: M2005, manufactured by Aicello Co., Ltd., thickness: 40 μm) to the anchor coat layer through the gas barrier resin A and the adhesive resin A while co-extruding the gas barrier resin A and the adhesive resin A using a co-extruder. At that time, the thickness of the gas barrier resin layer made of the gas barrier resin A was set to 10 μm, and the thickness of the adhesive resin layer made of the adhesive resin A was set to 10 μm. Hereinafter, this laminate is referred to as laminate C.
Laminate B was prepared in the same manner as in Example 20. A polyethyleneimine-based anchor coating agent was applied to the milk carton base paper surface of laminate B in a dry coating amount of 0.1 g/ ^m2. Adhesive resin C was extruded onto the anchor coating layer using an extruder to a thickness of 20 μm, and the laminate was bonded to the vapor-deposited film surface of laminate C via adhesive resin C.
In this way, a laminate of Example 21 was obtained in which the first layer, anchor coat layer, gas barrier resin layer, adhesive resin layer, and second layer were laminated in this order. The first layer in Example 21 was a laminate of a low-density polyethylene layer, anchor coat layer, milk carton base paper, anchor coat layer, adhesive layer, metal foil, dry laminate layer, and polyethylene terephthalate film laminated in this order.

[Example 22]
A laminate of Example 22 was obtained in the same manner as in Example 20, except that the thickness of the gas barrier resin layer was changed to 5 μm.

[Example 23]
A laminate of Example 23 was obtained in the same manner as in Example 20, except that the thickness of the gas barrier resin layer was changed to 15 μm.

[Example 24]
A laminate of Example 24 was obtained in the same manner as in Example 20, except that gas barrier resin B was used instead of gas barrier resin A as the gas barrier resin.

[Example 25]
A laminate of Example 25 was obtained in the same manner as in Example 20, except that gas barrier resin C was used instead of gas barrier resin A as the gas barrier resin.

[Example 26]
A laminate of Example 26 was obtained in the same manner as in Example 20, except that gas barrier resin D was used instead of gas barrier resin A as the gas barrier resin.

[Example 27]
A laminate of Example 27 was obtained in the same manner as in Example 20, except that adhesive resin B was used instead of adhesive resin A as the adhesive resin.

[Comparative Example 1]
A polyurethane-based anchor coating agent was applied to one side of the first layer of biaxially oriented polyethylene terephthalate film (trade name: E5100, manufactured by Toyobo Co., Ltd., thickness: 25 μm) in a dry coating amount of 0.4 g/m ² to form an anchor coat layer. On the anchor coat layer, gas barrier resin A, adhesive resin D, and low density polyethylene A were co-extruded using a co-extruder, while the second layer of polyethylene film (trade name: LL-XMTN, manufactured by Futamura Chemical Co., Ltd., thickness: 20 μm) was laminated via the gas barrier resin A, adhesive resin D, and low density polyethylene A. At that time, the thickness of the gas barrier resin layer made of the gas barrier resin A was 10 μm, the thickness of the adhesive resin layer made of the adhesive resin D was 5 μm, and the thickness of the low density polyethylene layer made of the low density polyethylene A was 10 μm.
In this manner, a laminate of Comparative Example 1 was obtained in which the first layer, anchor coat layer, gas barrier resin layer, adhesive resin layer, low density polyethylene layer, and second layer were laminated in this order.

[Comparative Example 2]
A urethane-based anchor coating agent was applied to one side of the first layer of biaxially oriented polyethylene terephthalate film (trade name: E5100, manufactured by Toyobo Co., Ltd., thickness: 25 μm) in a dry coating amount of 0.4 g/m ² to form an anchor coat layer. On the anchor coat layer, low-density polyethylene A, adhesive resin D, gas barrier resin A, adhesive resin D, and low-density polyethylene A were co-extruded using a co-extruder, and the second layer of polyethylene film (trade name: LL-XMTN, manufactured by Futamura Chemical Co., Ltd., thickness: 20 μm) was laminated via low-density polyethylene A, adhesive resin D, gas barrier resin A, adhesive resin D, and low-density polyethylene A. At that time, the thickness of the gas barrier resin layer made of gas barrier resin A was 10 μm, the thickness of each of the adhesive resin layers made of adhesive resin D was 5 μm, and the thickness of each of the low-density polyethylene layers made of low-density polyethylene A was 10 μm.
In this way, a laminate of Comparative Example 2 was obtained, in which a first layer, an anchor coat layer, a low-density polyethylene layer, an adhesive resin layer, a gas barrier resin layer, an adhesive resin layer, a low-density polyethylene layer, and a second layer were laminated in that order.

[Comparative Example 3]
A laminate of Comparative Example 3 was obtained in the same manner as in Example 12, except that adhesive resin D was used instead of adhesive resin A as the adhesive resin.

[Comparative Example 4]
A first layer similar to that of Example 14 was prepared, and a urethane-based anchor coating agent was applied to the milk carton base paper surface of the first layer in a dry coating amount of 0.4 g/m ² to form an anchor coating layer. An ethylene-vinyl alcohol copolymer film (product name: ZEX101, manufactured by Tamapoly Co., Ltd., thickness: 50 μm) was laminated on the anchor coating layer while extruding adhesive resin E to a thickness of 20 μm using an extruder. A urethane-based anchor coating agent was applied to the ethylene-vinyl alcohol copolymer film in a dry coating amount of 0.4 g/m ² to form an anchor coating layer. A low-density polyethylene A was extruded to a thickness of 40 μm using an extruder on the anchor coating layer to form a second layer.
In this manner, a laminate of Comparative Example 4 was obtained in which the first layer, anchor coat layer, adhesive resin layer, ethylene-vinyl alcohol copolymer film, anchor coat layer, and second layer were laminated in this order.

[Comparative Example 5]
A first layer similar to that of Example 14 was prepared, and a urethane-based anchor coating agent was applied to the milk carton base paper surface of the first layer in a dry coating amount of 0.4 g/m ² to form an anchor coating layer. An adhesive resin E was extruded onto the anchor coating layer in a thickness of 20 μm using an extruder, and the adhesive resin E was laminated to the deposition surface of a polyethylene terephthalate film (product name: 1012, manufactured by Toray Film Processing Co., Ltd., thickness: 12 μm) on which an aluminum deposition film was formed. A urethane-based anchor coating agent was applied onto the polyethylene terephthalate film in a dry coating amount of 0.4 g/m ² to form an anchor coating layer. An extruder was used to extrude low-density polyethylene A in a thickness of 20 μm onto the anchor coating layer, and the low-density polyethylene A was laminated to the second layer, a polyethylene film (product name: LL-XMTN, manufactured by Futamura Chemical Co., Ltd., thickness: 40 μm), via the low-density polyethylene A.
In this way, a laminate of Comparative Example 5 was obtained, in which a first layer, an anchor coat layer, an adhesive resin layer, a polyethylene terephthalate film having an aluminum vapor deposition film formed thereon, an anchor coat layer, a low-density polyethylene layer, and a second layer were laminated in that order.

[Comparative Example 6]
A urethane-based anchor coating agent was applied to one side of a milk carton base paper having a basis weight of 383 g/ ^m2 in a dry coating amount of 0.4 g/ ^m2 to form an anchor coating layer. Low-density polyethylene A was extruded onto the anchor coating layer with an extruder to a thickness of 25 μm. In this way, a first layer consisting of the milk carton base paper, the anchor coating layer, and the low-density polyethylene layer was produced.
A urethane-based anchor coating agent was applied to the surface of the milk carton base paper in the first layer with a dry coating amount of 0.4 g/ ^m2 to form an anchor coating layer. An adhesive resin E was extruded onto the anchor coating layer with a thickness of 20 μm using an extruder, and an aluminum foil (product name: 1N30, manufactured by Toyo Aluminum Co., Ltd., thickness: 7 μm) was laminated via the adhesive resin E. A urethane-based anchor coating agent was applied to the aluminum foil with a dry coating amount of 0.4 g/ ^m2 to form an anchor coating layer. A low-density polyethylene A was extruded onto the anchor coating layer with a thickness of 20 μm using an extruder, and a polyethylene film (product name: LL-XMTN, manufactured by Futamura Chemical Co., Ltd., thickness: 40 μm) was laminated as the second layer with the low-density polyethylene A interposed therebetween.
In this way, a laminate of Comparative Example 6 was obtained in which the first layer, anchor coat layer, adhesive resin layer, aluminum foil, anchor coat layer, low-density polyethylene layer, and second layer were laminated in this order.

[Comparative Example 7]
A laminate of Comparative Example 7 was obtained in the same manner as in Example 20, except that, instead of co-extruding the gas barrier resin A and the adhesive resin A, the low-density polyethylene B was extruded to a thickness of 20 μm.

[Comparative Example 8]
A laminate of Comparative Example 8 was obtained in the same manner as in Example 21, except that, instead of co-extruding the gas barrier resin A and the adhesive resin A, the low-density polyethylene B was extruded to a thickness of 20 μm.

[Comparative Example 9]
A laminate of Comparative Example 9 was obtained in the same manner as in Comparative Example 7, except that a three-layer film (product name: DIAMIRON (registered trademark), manufactured by Mitsubishi Chemical Corporation, thickness: 120 μm) in which a layer made of polyethylene, a layer made of ethylene-vinyl alcohol copolymer, and a layer made of polyethylene were laminated in that order was used instead of a polyethylene film (product name: M2005, manufactured by Aicello Co., Ltd., thickness: 40 μm) as the second layer.

The layer structures of the laminates of Examples 1 to 27 and Comparative Examples 1 to 9 are shown in Tables 1 and 2. Note that in Tables 1 and 2, the layers between the first layer and the barrier layer are omitted.

[Measurement of the content of groups derived from maleic anhydride in the adhesive resin layer]
A Ge prism was pressed against adhesive resins A to E, and infrared absorption spectra were measured under the following measurement conditions using a Fourier transform infrared spectrometer (product name: Nicolet 6700, manufactured by Thermo Scientific). For adhesive resins A to D, it was confirmed that a peak of a group derived from maleic anhydride appeared at a wave number of about 1700 cm ^-1 , and the content of the group derived from maleic anhydride was calculated from the peak absorption intensity. The measurement results are shown in Table 2.
For adhesive resin E, since no peak of groups derived from maleic anhydride appeared at a wave number of about 1700 cm ⁻¹ , the content of groups derived from maleic anhydride was determined to be 0.00% by mass.
(Measurement conditions)
Incident angle: 45 degrees Resolution: 4cm ^-1
Measurement wave number range: 700 to 4000 cm ^-1
Number of times: 64

[Evaluation of processability of laminate]
In the process of producing the laminates of Examples 1 to 27 and Comparative Examples 1 to 9, the state of adhesion between the extruded adhesive resin and the metal chill roll or rubber nip roll was visually confirmed. The evaluation criteria were as follows. The results are shown in Table 3.
(Evaluation Criteria)
A: The adhesive resin did not adhere to either the metal chill roll or the rubber nip roll.
B: The adhesive resin adhered to the metal chill roll or rubber nip roll.

[Evaluation of suitability for processing into liquid paper containers]
Blank sheets were prepared by forming lines on the laminates of Examples 14 to 27 and Comparative Examples 4 to 9 and punching them with a punching machine. The blank sheets were then side-sealed with a frame sealing machine to prepare sleeves, and liquid paper containers with a capacity of 500 mL and a height of 135 mm and a side length of 70 mm were prepared with a hot air type filling and molding machine.
In the process of producing the liquid-holding paper containers, the suitability for processing into liquid-holding paper containers was evaluated according to the following evaluation criteria. The results are shown in Table 3.
(Evaluation Criteria)
A: The laminate was folded at the punched-out portion, and the top portion was able to remain closed after the liquid paper container was produced, and the liquid paper container could be produced as desired.
B: The laminate was bent in areas other than the punched areas, or the top of the liquid paper container opened on its own after production, and it was not possible to process it into the desired liquid paper container.

[Appearance evaluation]
The appearance of the laminates of Examples 1 to 13 and Comparative Examples 1 to 3 was visually confirmed. The evaluation criteria were as follows. The results are shown in Table 3.
(Evaluation Criteria)
A: No spots were observed on the laminate.
B: Spots were observed on the laminate.

[Oxygen permeability measurement]
For the laminates of Examples 1 to 27 and Comparative Examples 1 to 9, the oxygen transmission rate (unit: cc/m2·atm·day) was measured in accordance with JIS K 7126-2:2006 using an oxygen transmission rate measuring device (model name: ^OX -TRAN 2/21, manufactured by Modern Control (MOCON)) under an environment of a temperature of 23°C and a relative humidity of 60% RH, with the laminates set so that the oxygen supply side was the first layer of the laminate. The smaller the oxygen transmission rate, the more excellent the gas barrier property of the laminate. The measurement results are shown in Table 3.

[Comprehensive evaluation of the amount of resin used in the barrier layer and gas barrier properties]
The thickness and oxygen permeability of the barrier layer in the laminate of Comparative Example 1 were used as the standards, and the amount of resin used in the barrier layer and the gas barrier properties were comprehensively evaluated for the laminates of Examples 1 to 27 and Comparative Examples 2 to 9. The evaluation criteria were as follows. The results are shown in Table 3.
A: The thickness of the barrier layer is 25 μm or less, and the amount of resin used in the barrier layer is small.
B: Although the thickness of the barrier layer exceeds 25 μm, the oxygen permeability is smaller than that of the laminate of Comparative Example 1, and the large amount of resin used in the barrier layer contributes to the improvement of the gas barrier properties.
C: The thickness of the barrier layer exceeds 25 μm, and the oxygen permeability is equal to or higher than that of the laminate of Comparative Example 1. The large amount of resin used in the barrier layer does not contribute to improving the gas barrier properties.

[Evaluation of suitability for contents resistance]
Using the laminates of Examples 1 to 6, 8 to 11, and 13 and Comparative Examples 1 and 2 as the wall and bottom films, standing pouches with outer dimensions of 170 mm height x 130 mm width, 40 mm height of the bottom fold-in part, and 5 mm seal width as shown in Fig. 3 were produced. The bottom was heat sealed with a boat-bottom seal pattern.
The standing pouch was filled with 200 cc of an acidic solution (product name: Good Sense, manufactured by C.B.S. Co., Ltd., deodorant containing organic acid, pH: 3.5) as the content, and heat-sealed to seal. The filled standing pouch was stored for 6 weeks in an environment of a temperature of 40° C. and a relative humidity of 90% RH. The state of the laminate after storage was visually confirmed, and the suitability for resistance to the content was evaluated according to the following evaluation criteria.
The storage test was also carried out in the same manner when the contents were replaced with an alkaline solution (product name: Laundrysh Pro, manufactured by C.B.S. Co., Ltd., laundry detergent containing 2-aminoethanol, pH: 10.4), PGMEA (propylene glycol monomethyl ether acetate), cyclohexane, ethyl acetate, and 99.5% ethanol, and the suitability for resistance to the contents was evaluated.
For the laminates of Examples 14 to 27 and Comparative Examples 4 to 9, the suitability for resistance to contents was evaluated in the same manner as for the laminates of Examples 1 to 6, 8 to 11, and 13, and Comparative Examples 1 and 2, except that after evaluating the suitability for processing into liquid paper containers, each liquid paper container was filled with each content and a storage test was conducted.
The results are shown in Table 3.
(Evaluation Criteria)
A: No delamination occurred in the laminate.
B: Interlayer peeling occurred in the laminate.

As is clear from Tables 1 to 3 above, the laminates of Examples 1 to 3 and 5 to 13 each had a barrier layer consisting of two layers, and thus the thickness of the barrier layer could be made smaller than that of the laminates of Comparative Examples 1 and 2, each consisting of three or five layers, allowing the amount of resin used to be reduced and allowing excellent gas barrier properties to be exhibited. Moreover, the laminate of Example 4, although consisting of only two layers of the barrier layer, was able to exhibit even better gas barrier properties by deliberately increasing the thickness of the barrier layer.
On the other hand, the laminate of Comparative Example 3 had a two-layer barrier layer, but the adhesive resin layer adhered to the metal chill roll or rubber nip roll during the production of the laminate, making it difficult to process.

As is clear from Table 3 above, the laminates of Examples 1 to 6, 8 to 11, and 13 to 27 did not experience delamination even when various contents were stored, and had excellent suitability for content resistance. In addition, the laminates of Examples 14 to 27 could be processed into the desired paper containers for liquids, and had excellent suitability for processing into paper containers for liquids.

Reference Signs List 10 Laminate 11 First layer 12 Barrier layer 13 Second layer 14 Gas barrier resin layer 15 Adhesive resin layer 30 Standing pouch 31 Side sheet 32 Bottom sheet 41 Pillow bag 42 Three-sided sealed bag 43 Four-sided sealed bag 60 Liquid paper container 61 Body 62 Bottom 63 Upper part 63a Inclined plate 64 Folded part 65 Glue margin 66 Spout plug 67 Straw hole 70 Paper cup 71 Flange 72 Body 73 Bottom 74 Exterior body 75 Convex part 76 Gap

Claims (13)

A laminate comprising at least a first layer and a barrier layer,
the barrier layer is a co-extruded layer of two layers, a gas barrier resin layer and an adhesive resin layer,
the gas barrier resin layer is located between the first layer and the adhesive resin layer,
the gas barrier resin layer contains an ethylene-vinyl alcohol copolymer,
the adhesive resin layer is made of a resin composition containing an unmodified polyolefin and a maleic anhydride-modified polyolefin,
The content of the unmodified polyolefin in the adhesive resin layer is 10% by mass or more and 80% by mass or less,
The thickness of the adhesive resin layer is 3 μm or more and 20 μm or less. The laminate according to claim 1, wherein the content of groups derived from maleic anhydride in the adhesive resin layer is 0.18% by mass or more and 0.25% by mass or less. The laminate according to claim 1 or 2, wherein the melt flow rate of the resin composition is 2 g/10 min or more and 13 g/10 min or less. The laminate according to claim 1 or 2, wherein the thickness of the gas barrier resin layer is 3 μm or more and 20 μm or less. The laminate according to claim 1 or 2, wherein the content of structural units derived from ethylene in the ethylene-vinyl alcohol copolymer is 20 mol% or more and 60 mol% or less. The laminate according to claim 1 or 2, wherein the melt flow rate of the ethylene-vinyl alcohol copolymer is 0.1 g/10 min or more and 15 g/10 min or less. The laminate according to claim 1 or 2, wherein the thickness of the barrier layer is 10 μm or more and 30 μm or less. The laminate according to claim 1 or 2, further comprising a second layer on the adhesive resin layer. The laminate according to claim 8, wherein the second layer is a sealant film. The laminate of claim 1 or 2, wherein the first layer comprises paper. 3. The laminate according to claim 1 or 2, having an oxygen permeability of 10 cc/ ^m2 ·day·atm or less, measured in accordance with JIS K 7126-2:2006 under an environment of a temperature of 23° C. and a relative humidity of 60% RH. A packaging container comprising the laminate according to claim 1 or 2. The packaging container according to claim 12, which is a liquid paper container.