JP7559705B2 - Barrier laminate - Google Patents

Description

The present invention relates to a barrier laminate that uses a paper substrate as a support.

Packaging materials that have been given gas barrier properties, such as water vapor barrier properties and oxygen barrier properties, based on a paper base have traditionally been used to prevent deterioration of the contents in packaging for foods, medical products, electronic components, etc.

A common method for imparting water vapor barrier properties or gas barrier properties to a paper base material is to laminate a synthetic resin film or metal foil with excellent gas barrier properties onto the paper base material. However, materials in which a synthetic resin film or the like is laminated onto a paper base material have environmental issues, as it is difficult to recycle the paper or synthetic resin after use.

Therefore, efforts are underway to develop barrier materials that do not require lamination of synthetic resin films, etc. For example, Patent Document 1 discloses a paper barrier packaging material in which a water vapor barrier layer and a gas barrier layer are provided on a paper base material. The water vapor barrier layer contains 50 to 100% by weight of kaolin with an average particle size of 5 μm or more and an aspect ratio of 10 or more relative to the total pigment, and the binder resin of the gas barrier layer is a polyvinyl alcohol resin.

Patent No. 5331265

In the case of a paper barrier packaging material such as that described in Patent Document 1, when producing a barrier laminate having a water vapor barrier layer and a gas barrier layer on a paper base material, the water vapor barrier layer is coated and dried on the paper base material, and then the oxygen barrier layer is coated and dried.
However, the above-mentioned manufacturing methods have problems such as a decrease in gas barrier properties and a poor appearance.

The present invention has been made in consideration of the above-mentioned circumstances. That is, the object of the present invention is to provide a barrier laminate that has excellent gas barrier properties and an improved appearance.

The inventors have discovered that in a barrier laminate having a first gas barrier layer, a second gas barrier layer, and a heat seal layer in this order on at least one surface of a paper substrate, by using a layered inorganic compound with an aspect ratio of 150 or more in the second gas barrier layer, and an inorganic compound whose aspect ratio and average particle size are equal to or less than a specific value, a barrier laminate with excellent gas barrier properties and improved appearance can be provided.

The present invention has been completed based on these findings. That is, the present invention has the following configuration.
[1] A barrier laminate having a first gas barrier layer, a second gas barrier layer and a heat seal layer, in this order, on at least one surface of a paper base material, wherein the second gas barrier layer contains a binder resin, a layered inorganic compound A having an aspect ratio of 150 or more, and an inorganic compound B having an aspect ratio of 50 or less and an average particle size of 1 μm or less, and the heat seal layer contains a water-dispersible resin.
[2] The barrier laminate according to [1], wherein the first gas barrier layer is a water vapor barrier layer and the second gas barrier layer is an oxygen barrier layer.
[3] The barrier laminate according to [1] or [2], wherein the binder resin contained in the second gas barrier layer is at least one selected from the group consisting of polyvinyl alcohol and modified products thereof, and polyurethane resins.
[4] The barrier laminate according to any one of [1] to [3], wherein the binder resin contained in the second gas barrier layer contains at least one selected from the group consisting of polyvinyl alcohol and modified products thereof, and the mass ratio (A/B) of the layered inorganic compound A to the inorganic compound B is 2/98 or more and 60/40 or less.
[5] The barrier laminate according to any one of [1] to [3], wherein the binder resin contained in the second gas barrier layer contains a polyurethane resin, and the mass ratio (A/B) of the layered inorganic compound A to the inorganic compound B is 10/90 or more and 80/20 or less.
[6] The barrier laminate according to any one of [1] to [5], wherein the first gas barrier layer contains a water-dispersible polymer, a layered inorganic compound, and a cationic resin.
[7] The barrier laminate according to [6], wherein the water-dispersible polymer contains at least one of an ethylene-acrylic copolymer, a styrene-butadiene copolymer, a styrene-acrylic copolymer, and a biodegradable resin.
[8] The barrier laminate according to [6] or [7], wherein the layered inorganic compound contained in the first gas barrier layer has an aspect ratio of 80 or more and a thickness of 120 nm or less.
[9] The barrier laminate according to any one of [6] to [8], wherein the cationic resin contained in the first gas barrier layer is at least one selected from the group consisting of polyamines, modified polyamides, modified polyamidoamines, polyamide epichlorohydrin, and polyethyleneimines.
[10] The barrier laminate according to any one of [1] to [9], wherein the heat seal layer contains at least one resin selected from the group consisting of ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid copolymers, and styrene-butadiene copolymers.
[11] The barrier laminate according to any one of [1] to [10], wherein the paper base material has a basis weight of 20 g/m2 or ^more and 500 g/ ^m2 or less, a density of 0.5 g/cm3 or ^more and 1.2 g/cm3 ^or less, and an Oken smoothness of 5 seconds or more.
[12] The barrier laminate according to any one of [1] to [11], which has an oxygen permeability of 10 mL/( ^m2 ·day·atm) or less at 23° C. and 50% RH.
[13] The barrier laminate according to any one of [1] to [12], which has a water vapor transmission rate of 10 g/( ^m2 ·day) or less at 40° C. and 90% RH.

The present invention provides a barrier laminate that suppresses the occurrence of blisters, has excellent water vapor barrier properties and oxygen barrier properties, and has an improved appearance.

1 is a schematic cross-sectional view showing a layer structure of a barrier laminate of the present invention.

The following is a detailed description of an embodiment of the present invention. The following description of the constituent elements may be based on a representative embodiment or specific example, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "~" means a range that includes the numerical values before and after "~" as the lower and upper limits. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined in any way. In this specification, "gas barrier" means at least one of an oxygen barrier and a water vapor barrier.

[Barrier laminate]
The barrier laminate of this embodiment is a barrier laminate having a first gas barrier layer, a second gas barrier layer and a heat seal layer, in this order, on at least one surface of a paper base material, wherein the second gas barrier layer contains a binder resin, a layered inorganic compound A having an aspect ratio of 150 or more, and an inorganic compound B having an aspect ratio of 50 or less and an average particle size of 1 μm or less, and the heat seal layer contains a water-dispersible resin.
According to the present embodiment, a barrier laminate having excellent gas barrier properties and improved appearance is provided. Furthermore, the present invention has an additional effect of excellent adhesion to the heat seal layer and excellent heat sealability. The mechanism by which this effect is achieved is unclear, but is presumed to be as follows.
When the second gas barrier layer is dried, the first gas barrier layer has already been formed, so that it is difficult for the solvent component of the coating liquid for the second gas barrier layer to escape to the paper substrate side. Therefore, the solvent component of the coating liquid for the second gas barrier layer needs to escape as a gas from the surface on which the heat seal layer is provided (hereinafter also referred to as the surface). Here, if the surface of the second gas barrier layer is easily dried and the film is formed quickly, it is considered that the solvent component is difficult to escape from the surface of the second gas barrier layer, and blisters are generated. In addition, if blisters are generated, not only the appearance is deteriorated, but also the performance of the second gas barrier layer (for example, oxygen barrier property when the second gas barrier layer is an oxygen barrier layer) is impaired, and the gas barrier property (oxygen barrier property) is also deteriorated.
In this embodiment, although the detailed reason is unclear, it is believed that the second gas barrier layer contains, in addition to layered inorganic compound A having an aspect ratio of 150 or more, inorganic compound B having an aspect ratio of 50 or less and an average particle size of 1 μm or less, thereby inhibiting rapid film formation on the surface of the second gas barrier layer, and the addition of inorganic compound B promotes the escape of the solvent component in a gaseous state, suppressing the occurrence of blisters, thereby improving the appearance. Furthermore, since inorganic compound B has an aspect ratio of 50 or less and an average particle size of 1 μm, it is believed that although it inhibits film formability during drying, it does not adversely affect the gas barrier properties after drying, and a barrier laminate with excellent gas barrier properties can be obtained.
Furthermore, in this embodiment, since the second gas barrier layer contains inorganic compound B, the adhesion to the heat seal layer formed on the second gas barrier layer is improved due to the anchor effect, and a barrier laminate with excellent heat sealability can be obtained.
The effects of the present invention are not limited to the above mechanism.
Each layer constituting the barrier laminate of this embodiment will be described below.

[Paper base material]
The paper base material used in the present embodiment is not particularly limited as long as it is a commonly used paper containing plant-derived wood pulp as the main component. Specific examples include bleached or unbleached kraft paper, fine paper, paperboard, liner paper, coated paper, one-sided gloss paper, glassine paper, graphene paper, etc. The paper base material is preferably a paper containing pulp as the main component, which is easily dispersible in water by mechanical disintegration.

From the viewpoint of improving the barrier properties, the disintegrated freeness (freeness) of the paper base material measured in accordance with JIS P 8121:2012 is preferably 800 mL or less, more preferably 550 mL or less. Here, disintegrated freeness refers to the Canadian standard freeness measured in accordance with JIS P 8121:2012 for the pulp obtained by disintegrating paper after papermaking in accordance with JIS P 8220-1:2012. A known method can be used to beat the pulp to prepare the disintegrated freeness.

The sizing degree of the paper base material is not particularly limited, but from the viewpoint of improving the barrier properties, the Stockigt sizing degree according to JIS P 8122:2004 is preferably 1 second or more, more preferably 5 seconds or more. The upper limit of the Stockigt sizing degree is not particularly limited, but is, for example, 180 seconds or less. The sizing degree of the paper base material can be controlled by the type and content of the internal sizing agent such as rosin-based, alkyl ketene dimer-based, alkenyl succinic anhydride-based, styrene-acrylic, higher fatty acid-based, petroleum resin-based, etc., the type of pulp, smoothing treatment, etc. The content of the internal sizing agent is not particularly limited, but is preferably in the range of about 0 to 3 parts by mass per 100 parts by mass of the pulp of the paper base material.

The paper base material can be appropriately supplemented with known internal additives. Examples of internal additives include fillers such as titanium dioxide, kaolin, talc, and calcium carbonate, paper strength enhancers, retention improvers, pH adjusters, drainage improvers, water resistance agents, softeners, antistatic agents, defoamers, slime control agents, dyes and pigments, etc.

In making paper substrates, a known wet papermaking machine (e.g., a Fourdrinier papermaking machine, a gap former type papermaking machine, a cylinder papermaking machine, a short wire papermaking machine, etc.) is appropriately selected and used. The paper layer formed by the papermaking machine is transported on a felt and dried in a dryer. A multi-stage cylinder dryer may be used as a pre-dryer before drying in the dryer.

The paper substrate obtained as described above may be surface-treated with a calendar to make the thickness and profile uniform. A known calendaring machine can be appropriately selected and used for the calendaring.

The basis weight of the paper substrate is not particularly limited, but is preferably 20 to 500 g/m ² , and more preferably 30 to 400 g/m ^2. The basis weight of the paper substrate is measured in accordance with JIS P 8124:2011.
From the viewpoint of gas barrier properties, the density of the paper substrate is preferably 0.5 to 1.2 g/cm ³ , and more preferably 0.6 to 1.0 g/cm ³ . The density of the paper substrate is calculated from the thickness of the paper substrate measured in accordance with JIS P 8118:2014 and the above-mentioned basis weight.
From the viewpoint of film-forming properties of the coating layer, the Oken smoothness of the paper substrate is preferably 5 seconds or more, more preferably 10 to 1000 seconds. The Oken smoothness is measured in accordance with JIS P 8155:2010.
From the viewpoint of printability, the paper base preferably has a 75° gloss of 5% or more, more preferably 5 to 70%. Furthermore, in a form in which a gas barrier layer and a heat seal layer are provided on only one side of the paper base, when printing is performed on the other side of the paper base (the side on which the paper base is exposed), from the viewpoint of printability (appearance of the print), the 75° gloss of that side is preferably 15% or more, more preferably 25% or more. The gloss is measured in accordance with JIS P 8142:2005.

In one embodiment of the present invention, the barrier laminate preferably comprises a water vapor barrier layer and an oxygen barrier layer as gas barrier layers, and it is preferable that the first gas barrier layer is a water vapor barrier layer and the second gas barrier layer is an oxygen barrier layer.
When the paper substrate, water vapor barrier layer, oxygen barrier layer and heat seal layer are laminated in this order, the water vapor barrier layer has already been formed when the oxygen barrier layer is dried, which inhibits the escape of the solvent (preferably water (water vapor)) of the coating liquid for the oxygen barrier layer from the paper substrate side, making blisters more likely to occur. Therefore, by configuring the oxygen barrier layer in this embodiment, the effects of the present invention are remarkable.
Hereinafter, an example will be described in which the first gas barrier layer is a water vapor barrier layer and the second gas barrier layer is an oxygen barrier layer.

[First Gas Barrier Layer]
The first gas barrier layer is preferably a water vapor barrier layer having a function of preventing the permeation of water vapor, and preferably contains a water-suspendable polymer, a layered inorganic compound, and a cationic resin.

(Layered inorganic compounds)
The layered inorganic compound has a flat shape. When a mixed solution of the layered inorganic compound, a water-suspendable polymer, and a cationic resin is prepared and applied onto a paper substrate, a water vapor barrier layer is formed. In the water vapor barrier layer, the flat layered inorganic compound is arranged in a state of being stacked almost parallel to the plane (surface) of the paper substrate. In this way, the area of the region where the layered inorganic compound is not present in the plane direction of the paper substrate is reduced, so that the permeation of water vapor is suppressed. In addition, in the thickness direction of the paper substrate, the flat layered inorganic compound is present in a state of being arranged parallel to the plane of the paper substrate, so that the water vapor in the water vapor barrier layer permeates while bypassing the layered inorganic compound, and the permeation of water vapor is suppressed by the maze effect. As a result, the water vapor barrier layer can exhibit excellent water vapor barrier properties.

The thickness of the layered inorganic compound is preferably 120 nm or less. The thickness of the layered inorganic compound is more preferably 100 nm or less, even more preferably 50 nm or less, and even more preferably 20 nm or less. The smaller the average thickness of the layered inorganic compound, the greater the number of layers of the layered inorganic compound in the water vapor barrier layer, and the higher the water vapor barrier property can be exhibited. Here, the thickness of the layered inorganic compound contained in the water vapor barrier layer is determined as follows. First, a magnified photograph is taken of the cross section of the water vapor barrier layer using an electron microscope. At this time, the magnification is set so that about 20 to 30 layered inorganic compounds are contained in the screen. Next, the thickness of each layered inorganic compound in the screen is measured. Then, the average value of the obtained thicknesses is calculated to be the thickness of the layered inorganic compound.

The length of the layered inorganic compound is preferably 1 μm to 100 μm. If the length is 1 μm or more, the layered inorganic compound is likely to be arranged parallel to the paper substrate. If the length is 100 μm or less, there is little concern that a part of the layered inorganic compound will protrude from the water vapor barrier layer. The length of the layered inorganic compound is more preferably 2 to 60 μm, and even more preferably 3 to 30 μm. Here, the length of the layered inorganic compound in the state in which it is contained in the water vapor barrier layer is obtained as follows. First, a magnified photograph is taken of the cross section of the water vapor barrier layer using an electron microscope. At this time, the magnification is set so that about 20 to 30 layered inorganic compounds are contained in the screen. Next, the length of each layered inorganic compound in the screen is measured. Then, the average value of the obtained lengths is calculated to be the length of the layered inorganic compound. The length of the layered inorganic compound may also be expressed as a particle size or an average particle size.

The aspect ratio of the layered inorganic compound is preferably 80 or more. When the aspect ratio is 80 or more, it is possible to achieve a predetermined water vapor barrier property. The aspect ratio of the layered inorganic compound is more preferably 100 or more, even more preferably 200 or more, even more preferably 300 or more, and particularly preferably 500 or more. The larger the aspect ratio, the more the water vapor transmission is suppressed and the water vapor barrier property is improved. In addition, the larger the aspect ratio, the less the amount of the layered inorganic compound added can be. There is no particular upper limit to the aspect ratio, and from the viewpoint of the viscosity of the coating liquid, it is preferably about 10,000 or less. Here, the aspect ratio is the value obtained by taking an enlarged photograph of the cross section of the water vapor barrier layer using an electron microscope, and dividing the average length of the layered inorganic compound obtained by the above-mentioned method by its average thickness.

Specific examples of layered inorganic compounds include micas such as those of the mica and brittle mica groups, synthetic micas (e.g., swelling mica and non-swelling mica), bentonite, kaolinite (kaolin mineral), pyrophyllite, talc, smectite, vermiculite, chlorite, septe chlorite, serpentine, stilpnomelane, and montmorillonite.

Among the layered inorganic compounds, at least one selected from mica, bentonite, kaolin, and talc is particularly preferred from the viewpoint of improving the barrier properties. Examples of mica include synthetic mica, white mica (muscovite), sericite, phlocopite, black mica (biotite), fluorine phlogopite (artificial mica), red mica, soda mica, vanadium mica, illite, chin mica, paragonite, and brittle mica. Examples of bentonite include montmorillonite. Kaolin is a clay formed by the weathering of rocks containing feldspar, and is mainly composed of kaolinite. Talc is a mineral composed of magnesium hydroxide and silicate, and is also called talc.

The content of the layered inorganic compound is preferably 80% by mass or less, more preferably 60% by mass or less, even more preferably 40% by mass or less, and even more preferably 20% by mass or less, based on the total solid content of the water vapor barrier layer. On the other hand, the content of the layered inorganic compound is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 5% by mass or more. By increasing the aspect ratio of the layered inorganic compound and reducing the thickness, the content of the layered inorganic compound can be reduced, and the falling off of the layered inorganic compound from the water vapor barrier layer can be suppressed.

The content of the layered inorganic compound is preferably 0.1 to 800 parts by mass relative to 100 parts by mass of the water-suspendable polymer (binder) of the water vapor barrier layer. The content of the layered inorganic compound is more preferably 0.3 to 400 parts by mass, even more preferably 1 to 200 parts by mass, even more preferably 3 to 100 parts by mass, particularly preferably 5 to 50 parts by mass, and most preferably 7 to 20 parts by mass relative to 100 parts by mass of the water-suspendable polymer (binder) of the water vapor barrier layer. When the content of the layered inorganic compound is 0.1 parts by mass or more relative to 100 parts by mass of the water-suspendable polymer (binder) of the water vapor barrier layer, the water vapor barrier property is easily exhibited. Also, when the content of the layered inorganic compound is 800 parts by mass or less relative to 100 parts by mass of the water-suspendable polymer (binder) of the water vapor barrier layer, a part of the layered inorganic compound is unlikely to be exposed from the layer surface, so that the water vapor barrier property is unlikely to decrease. Furthermore, if the content of the layered inorganic compound is 800 parts by mass or less per 100 parts by mass of the water-suspendable polymer of the water vapor barrier layer, when the first gas barrier layer is a water vapor barrier layer, the coatability of the gas barrier layer is improved and a uniform gas barrier layer is formed, resulting in good gas barrier properties.

(Cationic Resin)
By adding a cationic resin to the water vapor barrier layer containing a layered inorganic compound, the water vapor barrier property is significantly improved.
The reason why the water vapor barrier property is significantly improved by adding a cationic resin is not clear, but it is thought as follows. It is known that layered inorganic compounds have a so-called house-of-cards structure in which the planar parts of the flat plate form are easily charged with anionic charge and the edge parts are easily charged with cationic charge, so that the layered inorganic compounds are three-dimensionally aggregated with each other. Due to this house-of-cards structure, the viscosity of the aqueous dispersion of the layered inorganic compound becomes very high. On the other hand, since the house-of-cards structure is destroyed by the application of force such as by stirring, the aqueous dispersion of the layered inorganic compound exhibits thixotropy. Furthermore, when the house-of-cards structure is destroyed, the layered inorganic compounds undergo three-dimensional aggregation.

When an appropriate cationic resin is added to an aqueous dispersion of a layered inorganic compound, the cationic resin is adsorbed onto the anionic planar portions of the layered inorganic compound, destroying the house-of-cards structure. As a result, it is believed that the layered inorganic compound is prevented from aggregating three-dimensionally, making it easier for the flat-plate-like layered inorganic compound to be layered parallel to the plane of the paper substrate, leading to improved water vapor barrier properties.

Specific examples of cationic resins include polyamines, modified polyamides, modified polyamidoamines, polyamidoepichlorohydrin, polyethyleneimine, polyalkylenepolyamines, polyamide compounds, polyamidoamine-epihalohydrin or formaldehyde condensation reaction products, polyamine-epihalohydrin or formaldehyde condensation reaction products, polyamidepolyurea-epihalohydrin or formaldehyde condensation reaction products, polyaminepolyurea-epihalohydrin or formaldehyde condensation reaction products, polyamidoaminepolyurea-epihalohydrin or formaldehyde condensation reaction products, polyamidepolyurea compounds, polyaminepolyurea compounds, polyamidoaminepolyurea compounds and polyamidoamine compounds, polyvinylpyridine, amino-modified acrylamide compounds, polyvinylamine, polydiallyldimethylammonium chloride, etc. Of these, it is preferable to use at least one selected from polyamine, modified polyamide, modified polyamidoamine, polyamide epichlorohydrin, and polyethyleneimine.

The cationic resin preferably has a surface charge of 0.1 to 10 meq/g, more preferably 0.1 to 5.0 meq/g. If the surface charge of the cationic resin is within the above range, it is possible to destroy the house-of-cards structure, and it can coexist appropriately with the anionic binder described below.

The surface charge of the cationic resin is measured by the method described below. First, the sample polymer is dissolved in water to obtain a solution with a polymer concentration of 1 ppm. 0.001N sodium polyethylene sulfonate is dropped into the solution using a charge analyzer Mutek PCD-04 (manufactured by BTG) to measure the amount of charge.

The content of the cationic resin in the water vapor barrier layer may be appropriately determined depending on the type of layered inorganic compound and water-suspendable polymer used in the water vapor barrier layer, but from the viewpoint of improving the barrier properties, the content is preferably 1 to 300 parts by mass, more preferably 1 to 250 parts by mass, even more preferably 10 to 150 parts by mass, particularly preferably 15 to 100 parts by mass, and most preferably 20 to 50 parts by mass, per 100 parts by mass of the layered inorganic compound.

The content of the cationic resin is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, and even more preferably 1 to 10 parts by mass, per 100 parts by mass of the water-suspendable polymer (binder) of the water vapor barrier layer.

(Water-suspendable polymer)
A water-suspendable polymer is a polymer that can be suspended in water, and when forming a coating film, it is easy to prepare a coating liquid using water or an aqueous medium as a solvent. Therefore, it is preferable to form a water vapor barrier layer by applying and drying an aqueous coating liquid. In this specification, "aqueous" means that water is contained in an amount of 50 mass% or more, preferably 80 mass% or more (upper limit 100 mass%).
The water-dispersible polymer functions as a binder in the formation of a coating film, and therefore a coating film containing a layered inorganic compound, etc. can be formed on a paper substrate. The polymer that serves as the backbone of the water-dispersible polymer preferably contains at least one of an ethylene-acrylic copolymer, a styrene-butadiene copolymer, a styrene-acrylic copolymer, and a biodegradable resin, and more preferably is an ethylene-acrylic copolymer.

An ethylene-acrylic copolymer, which is a typical water-dispersible polymer, will be described below as an example. Examples of the acrylic monomer constituting the ethylene-acrylic copolymer include (meth)acrylic acid and its alkyl esters.
The number of carbon atoms in the alkyl group of the ester moiety of the (meth)acrylic acid alkyl ester is preferably 1 or more and 8 or less, more preferably 1 or more and 6 or less, and even more preferably 1 or more and 4 or less.
Here, (meth)acrylic acid means methacrylic acid and acrylic acid.
The acrylic monomer constituting the ethylene-acrylic copolymer may be one type, or two or more types may be used in combination.

The ethylene-acrylic copolymer is a copolymer obtained by emulsion polymerization of ethylene and the above-mentioned acrylic monomer. As the acrylic monomer, acrylic acid, methacrylic acid, etc. are suitable. As the ethylene-acrylic copolymer, one or more of ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-butyl acrylate copolymer, and ethylene-butyl methacrylate copolymer are preferred, and ethylene-acrylic acid copolymer and ethylene-methacrylic acid copolymer are more preferred. The copolymer may contain a small amount of monomers consisting of other compounds copolymerizable with ethylene and the acrylic monomer.

As a specific example of the ethylene-acrylic copolymer, for example, an aqueous dispersion of an ethylene-acrylic acid copolymer ammonium salt is commercially available as ZAIXXEN (registered trademark) AC or the like (manufactured by Sumitomo Seika Chemicals Co., Ltd., copolymerization ratio of acrylic acid: 20 mol%), and can be easily obtained and used.
Other examples of the ethylene-acrylic copolymer include MP4983R, MP4990R, and MICHEM FLEX HS1279.S manufactured by Michaelman Japan LLC, ZAIKXEN (registered trademark) A manufactured by Sumitomo Seika Chemicals Co., Ltd., and CHEMIPEARL S series manufactured by Mitsui Chemicals, Inc.

The ethylene-acrylic copolymer preferably has an acrylic monomer unit content of 1 to 50 mol%, more preferably 10 to 30 mol%. When the acrylic monomer unit content is within this range, the copolymer has excellent dispersibility.

The weight average molecular weight of the ethylene-acrylic copolymer is preferably 10,000 to 10 million, more preferably 50,000 to 5 million, from the viewpoint of the viscosity of the coating liquid and the strength of the coating film.

The content of the ethylene-acrylic copolymer is not particularly limited, but is preferably 20% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, particularly preferably 70% by mass or more, and most preferably 80% by mass or more of the total solid content of the water vapor barrier layer.

(styrene-butadiene copolymer)
Styrene-butadiene copolymers are copolymers obtained by emulsion polymerization of monomers consisting of styrene compounds such as styrene, α-methylstyrene, vinyltoluene, p-t-butylstyrene, and chlorostyrene, butadiene compounds such as 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene, and other compounds copolymerizable with these. Styrene is preferred as the styrene compound, and 1,3-butadiene is preferred as the butadiene compound.

(styrene-acrylic copolymer)
A styrene-acrylic copolymer is a copolymer obtained by emulsion polymerization of monomers consisting of a styrene compound such as styrene, α-methylstyrene, vinyltoluene, p-t-butylstyrene, chlorostyrene, etc., an acrylic compound such as acrylic acid, methacrylic acid, (meth)acrylic acid esters, (meth)acrylamidopropanesulfonic acid, (meth)acrylic acid sulfoalkyl sodium salts (the number of carbon atoms in the alkyl group is 2 to 3), etc., and other compounds copolymerizable therewith. Styrene is preferred as the styrene compound, and acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters are preferred as the acrylic compound.

(Biodegradable resin)
Specific examples of biodegradable resins are not particularly limited, and include, for example, polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), 3-hydroxybutanoic acid/3-hydroxyhexanoic acid copolymer (PHBH), etc. Among these, PBS and PLA are preferred, and PLA is more preferred. Packaging materials using a paper base material have the advantage of reducing the environmental load compared to packaging materials using a thermoplastic resin, but the environmental load can be further reduced by using a biodegradable resin as the water-suspendable polymer of the water vapor barrier layer.

The water-suspendable polymer (binder) in the water vapor barrier layer is preferably anionic. By using an anionic binder, the water vapor barrier property is further improved. As described above, the planar portion of the layered inorganic compound is anionic, but when a cationic resin is adsorbed, the surface becomes cationic. Therefore, the affinity with the anionic binder is increased.
When the skeleton of the water-dispersible polymer does not have an anionic group, it is preferable to introduce an acid group by copolymerizing with a monomer having an acid group such as a carboxy group.

The weight average molecular weight of the water-dispersible polymer is preferably from 10,000 to 10,000,000, and more preferably from 100,000 to 5,000,000, from the viewpoints of the viscosity of the coating liquid and the strength of the coating film.
[0043] The content ratio of the water-suspendable polymer in the water vapor barrier layer is not particularly limited, but is preferably 20 mass% or more, more preferably 50 mass% or more, even more preferably 60 mass% or more, still more preferably 70 mass% or more, and particularly preferably 80 mass% or more, of the total solid content of the water vapor barrier layer.

In addition to the water-suspendable polymer, layered inorganic compound, and cationic resin, dispersants, surfactants, defoamers, wetting agents, dyes, color adjusters, thickeners, etc. can be added to the water vapor barrier layer as needed.

The thickness of the water vapor barrier layer is preferably 1 to 30 μm, more preferably 3 to 20 μm, from the viewpoint of water vapor barrier properties and reducing the overall film thickness. From the same viewpoint, the coating amount of the water vapor barrier layer is preferably 1 to 30 g/m ² , more preferably 3 to 20 g/m ² in terms of solid content.

[Second Gas Barrier Layer]
The second gas barrier layer is preferably an oxygen barrier layer having a function mainly of preventing the permeation of oxygen gas.
The second gas barrier layer contains a binder resin, a layered inorganic compound A having an aspect ratio of 150 or more, and an inorganic compound B having an aspect ratio of 50 or less and an average particle size of 1 μm or less.

(Binder resin)
Examples of the binder resin contained in the oxygen barrier layer include polyvinyl alcohol, modified polyvinyl alcohol, starch and its derivatives, cellulose derivatives, polyvinylpyrrolidone, polyurethane resins, polyacrylic acid and its salts, casein, and polyethyleneimine.
Among these, the binder resin contained in the oxygen barrier layer is preferably at least one selected from the group consisting of polyvinyl alcohol and modified products thereof, and polyurethane resins.

<Polyvinyl alcohol or its modified product (modified polyvinyl alcohol)>
Polyvinyl alcohol or its modified product (modified polyvinyl alcohol) is preferred because it has better gas barrier properties. Examples of polyvinyl alcohol include fully saponified or partially saponified polyvinyl alcohol. Examples of modified polyvinyl alcohol include ethylene-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, etc. As the modified polyvinyl alcohol, ethylene-modified polyvinyl alcohol is preferred from the viewpoint of oxygen barrier properties.
The saponification degree of polyvinyl alcohol and its modified product is preferably high from the viewpoint of increasing the coating strength and decreasing the hygroscopicity, and specifically, the saponification degree is preferably 90% or more, more preferably 93% or more, even more preferably 95% or more, and even more preferably 97% or more (upper limit 100%). In this specification, the saponification degree is the value measured according to JIS K 6726:1994.
The polyvinyl alcohol and its modified products may be either synthetic products or commercially available products, such as EXCEVAL AQ-4104, RS-2117, and HR-3010 manufactured by Kuraray Co., Ltd.

<Polyurethane Resin>
The polyurethane-based resin contained in the oxygen barrier layer is not particularly limited, and is preferably one that can be prepared into one or more selected from the group consisting of polyurethane-based resin dispersions and emulsions, more preferably one that can be prepared into a polyurethane-based resin dispersion or emulsion, and particularly preferably one that can be prepared into a polyurethane-based resin dispersion.

The polyurethane resin contained in the oxygen barrier layer preferably contains at least one selected from the group consisting of a structural unit derived from meta-xylylene diisocyanate and a structural unit derived from hydrogenated meta-xylylene diisocyanate. When the polyurethane resin contains at least one of a structural unit derived from meta-xylylene diisocyanate and a structural unit derived from hydrogenated meta-xylylene diisocyanate, the total content of the structural units derived from meta-xylylene diisocyanate and the structural units derived from hydrogenated meta-xylylene diisocyanate relative to the total amount of the structural units derived from polyisocyanate is preferably 50 mol% or more. Such a polyurethane resin has excellent gas barrier properties because it exhibits high cohesive strength due to hydrogen bonds and, in the case of having a structural unit derived from meta-xylylene diisocyanate, the stacking effect between xylylene groups. The above content can be identified using a known analytical method such as ¹ H-NMR.

-Oxygen permeability-
The polyurethane resin contained in the oxygen barrier layer has an oxygen permeability at 23° C. and 50% RH when converted into a 25 μm thick sheet of preferably 100 mL/( ^m2 ·day·atm) or less, more preferably 50 mL/( ^m2 ·day·atm) or less, even more preferably 25 mL/( ^m2 ·day·atm) or less, and even more preferably 10 mL/( ^m2 ·day·atm) or less. In this specification, the oxygen permeability is measured using an oxygen permeability measuring device (OX-TRAN2/22, manufactured by MOCON) under conditions of 23° C. and 50% RH.

- Glass transition temperature -
From the viewpoint of improving the strength of the oxygen barrier layer and preventing blocking, the glass transition temperature of the polyurethane resin contained in the oxygen barrier layer is preferably 150° C. or less, more preferably 140° C. or less, and particularly preferably 135° C. or less. The lower limit of the glass transition temperature of the polyurethane resin is not particularly limited, but is preferably 50° C. or more. The glass transition temperature is measured in accordance with JIS K 7122:2012.

As the polyurethane-based resin, a synthetic product may be used, and examples thereof include the polyurethane-based resins described in WO 2015/016069.
As the polyurethane resin, commercially available products may be used, for example, "Takelac W series (product name)", "Takelac WPB series (product name)", "Takelac WS series (product name)" manufactured by Mitsui Chemicals, Inc., and the like, specifically, Takelac WPB-341 is exemplified. Other commercially available products include "HPU W-003" (hydroxyl value 235 mgKOH/g) manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.

The content of the binder resin is preferably 10 to 95% by mass, more preferably 20 to 90% by mass, and even more preferably 30 to 85% by mass, of the total solid content of the gas barrier layer.

(Layered inorganic compound A)
The oxygen barrier layer contains a layered inorganic compound A having an aspect ratio of 150 or more.
It is preferable that the oxygen barrier layer contains the layered inorganic compound A, since the gas barrier property, in particular the oxygen barrier property, is improved.
The aspect ratio of the layered inorganic compound A is 150 or more, preferably 200 or more, more preferably 300 or more, and even more preferably 500 or more. The larger the aspect ratio, the more oxygen permeation is suppressed and the oxygen barrier property is improved. In addition, the larger the aspect ratio, the less the amount of the layered inorganic compound added can be. The upper limit of the aspect ratio is not particularly limited, and is preferably about 10,000 or less from the viewpoint of the viscosity of the coating liquid. Here, the aspect ratio is a value obtained by dividing the average length of the layered inorganic compound A obtained by the above-mentioned method in the first gas barrier layer by its average thickness when an enlarged photograph of the cross section of the second gas barrier layer is taken using an electron microscope.

The thickness of the layered inorganic compound A is preferably 120 nm or less. The thickness of the layered inorganic compound is more preferably 100 nm or less, even more preferably 50 nm or less, and particularly preferably 20 nm or less. The thickness of the layered inorganic compound A is measured in the same manner as the thickness of the layered compound in the first barrier layer.

The length of the layered inorganic compound A is preferably 1 μm to 100 μm. If the length is 1 μm or more, the layered inorganic compound A is likely to be arranged parallel to the paper substrate. If the length is 100 μm or less, there is little concern that a part of the layered inorganic compound A will protrude from the oxygen barrier layer. The length of the layered inorganic compound A is more preferably 2 to 60 μm, and even more preferably 3 to 30 μm. Here, the length of the layered inorganic compound A in the state in which it is contained in the oxygen barrier layer is measured in the same manner as the length of the layered compound in the first barrier layer. The length of the layered inorganic compound A may also be expressed as a particle size or an average particle size.

Specific examples of layered inorganic compound A include micas such as mica and brittle mica, synthetic mica (e.g., swelling mica and non-swelling mica), bentonite, kaolinite (kaolin mineral), pyrophyllite, talc, smectite, vermiculite, chlorite, septe chlorite, serpentine, stilpnomelane, and montmorillonite.

Among the layered inorganic compounds A, at least one selected from mica, bentonite, kaolin, and talc is particularly preferred from the viewpoint of improving the barrier properties. Examples of mica include synthetic mica, white mica (muscovite), sericite, phlocopite, black mica (biotite), fluorine phlogopite (artificial mica), red mica, soda mica, vanadium mica, illite, chin mica, paragonite, and brittle mica. Examples of bentonite include montmorillonite. Kaolin is a clay formed by the weathering of rocks containing feldspar, and is mainly composed of kaolinite. Talc is a mineral composed of magnesium hydroxide and silicate, and is also called talc.

The content of the layered inorganic compound A is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 30% by mass or less, even more preferably 20% by mass or less, and particularly preferably 18% by mass or less, based on the total solid content of the oxygen barrier layer. On the other hand, the content of the layered inorganic compound is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. By increasing the aspect ratio of the layered inorganic compound A and reducing the thickness, the content of the layered inorganic compound can be reduced, and the falling off of the layered inorganic compound A from the oxygen barrier layer can be suppressed.

The content of the layered inorganic compound A is preferably 0.1 to 800 parts by mass relative to 100 parts by mass of the binder resin of the oxygen barrier layer. The content of the layered inorganic compound A is more preferably 0.3 to 400 parts by mass, even more preferably 1 to 200 parts by mass, even more preferably 3 to 100 parts by mass, particularly preferably 5 to 50 parts by mass, and most preferably 7 to 25 parts by mass relative to 100 parts by mass of the binder resin of the oxygen barrier layer. When the content of the layered inorganic compound A is 0.1 parts by mass or more relative to 100 parts by mass of the binder resin of the oxygen barrier layer, the oxygen barrier property is easily expressed. Also, when the content of the layered inorganic compound A is 800 parts by mass or less relative to 100 parts by mass of the binder resin of the oxygen barrier layer, a part of the layered inorganic compound A is unlikely to be exposed from the layer surface, so that the oxygen barrier property is unlikely to decrease. In addition, if the content of layered inorganic compound A is 800 parts by mass or less per 100 parts by mass of the binder resin of the oxygen barrier layer, when the second gas barrier layer is an oxygen barrier layer, the coatability of the heat seal layer is improved and a uniform heat seal layer is formed, resulting in good gas barrier properties.

(Inorganic Compound B)
The second gas barrier layer contains inorganic compound B having an aspect ratio of 50 or less and an average particle size of 1 μm or less, from the viewpoint of suppressing the occurrence of blisters and obtaining a barrier laminate having excellent gas barrier properties (for example, oxygen barrier properties when the second gas barrier layer is an oxygen barrier layer). As described above, the inclusion of inorganic compound B inhibits rapid film formation of the second gas barrier layer, suppressing the occurrence of blisters. Furthermore, the inclusion of inorganic compound B in the second gas barrier layer improves the adhesion between the second gas barrier layer and the heat seal layer.

The aspect ratio of inorganic compound B is 50 or less, preferably 45 or less, more preferably 40 or less, and even more preferably 35 or less, from the viewpoint of suppressing the occurrence of blisters and improving adhesion with the heat seal layer. There is no particular lower limit and it is sufficient if it is 1 or more, but from the viewpoint of gas barrier properties, it is preferably 3 or more, more preferably 10 or more, and even more preferably 20 or more.

The average particle size of the inorganic compound B is, from the viewpoint of suppressing the occurrence of blisters and improving adhesion to the heat seal layer, 1 μm or less, preferably 0.8 μm or less, more preferably 0.6 μm or less, even more preferably 0.4 μm or less, and still more preferably 0.3 μm or less, and from the same viewpoint, is preferably 0.05 μm or more, more preferably 0.10 μm or more, even more preferably 0.15 μm or more, and still more preferably 0.20 μm or more.
The average particle size of the inorganic compound B is measured in the same manner as the length of the layered compound in the first gas barrier layer.

The inorganic compound B is not particularly limited as long as it has the above-mentioned aspect ratio and average particle size, and various inorganic compounds used in conventional coating layers are exemplified.Specific examples include various kaolins such as kaolin, calcined kaolin, structured kaolin, and delaminated kaolin, talc, heavy calcium carbonate (ground calcium carbonate), light calcium carbonate (synthetic calcium carbonate), composite synthetic pigments of calcium carbonate and other hydrophilic organic compounds, satin white, lithopone, titanium dioxide, silica, barium sulfate, calcium sulfate, alumina, aluminum hydroxide, zinc oxide, magnesium carbonate, silicate, and colloidal silica.
Among these, kaolin is preferred from the viewpoint of suppressing the generation of blisters and improving adhesion to the heat seal layer. The inorganic compound B may be used alone or in combination of two or more kinds.

The content of inorganic compound B in the second gas barrier layer is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, even more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of suppressing blisters and improving adhesion with the heat seal layer, and is preferably 90% by mass or less, more preferably 70% by mass or less, even more preferably 65% by mass or less, and even more preferably 60% by mass or less, from the viewpoint of gas barrier properties (e.g., oxygen barrier properties).

The content of inorganic compound B in the second gas barrier layer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, and particularly preferably 20 parts by mass or more, per 100 parts by mass of binder resin, from the viewpoint of suppressing blisters and improving adhesion with the heat seal layer, and from the viewpoint of gas barrier properties (e.g., oxygen barrier properties), it is preferably 500 parts by mass or less, more preferably 300 parts by mass or less, even more preferably 250 parts by mass or less, even more preferably 200 parts by mass or less, and particularly preferably 150 parts by mass or less.

The mass ratio (A/B) of layered inorganic compound A to inorganic compound B in the second gas barrier layer is preferably 2/98 or more, more preferably 4/96 or more, even more preferably 6/94 or more, and even more preferably 7/93 or more, and is preferably 80/20 or less, more preferably 75/25 or less, and even more preferably 70/30 or less. When the above ratio is small, the occurrence of blisters tends to be suppressed, and when the above ratio is large, the gas barrier property (e.g., oxygen barrier property) tends to be excellent.
The preferred range of the mass ratio (A/B) of the layered inorganic compound A to the inorganic compound varies depending on the type of binder resin. Although the reason is unclear, it is believed that in the case of a binder resin that rapidly forms a film on the surface, it is preferable to increase the blending amount of the inorganic compound B.

When the binder resin contained in the second gas barrier layer contains at least one selected from the group consisting of polyvinyl alcohol and modified products thereof, the mass ratio (A/B) of layered inorganic compound A to inorganic compound B is, from the viewpoint of suppressing the occurrence of blisters and from the viewpoint of oxygen barrier property, preferably 2/98 or more, more preferably 4/96 or more, even more preferably 6/94 or more, still more preferably 7/93 or more, and is preferably 60/40 or less, more preferably 45/55 or less, even more preferably 30/70 or less, and still more preferably 15/85 or less.
In addition, since polyvinyl alcohol and its modified products have a faster film formation speed than the polyurethane-based resin described below, it is preferable to increase the amount of inorganic compound B compared to when a polyurethane-based resin is used as the binder resin.

When the binder resin contained in the second gas barrier layer contains a polyurethane resin, the mass ratio (A/B) of layered inorganic compound A to inorganic compound B is preferably 10/90 or more, more preferably 12/88 or more, even more preferably 15/85 or more, even more preferably 30/70 or more, from the viewpoint of suppressing the occurrence of blisters and from the viewpoint of oxygen barrier properties, and is preferably 80/20 or less, more preferably 70/30 or less, even more preferably 60/40 or less, even more preferably 50/50 or less.

In addition to the binder resin, layered inorganic compound A, and inorganic compound B, the oxygen barrier layer may contain appropriate additives such as pigments, dispersants, surfactants, defoamers, wetting agents, dyes, color adjusters, and thickeners, as necessary.

The thickness of the oxygen barrier layer is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.
The coating amount of the oxygen barrier layer is preferably 0.1 to 10 g/ ^m2 , and more preferably 0.5 to 5 g/ ^m2, in terms of solid content.

[Heat seal layer]
In the present invention, the barrier laminate has a heat seal layer on the second gas barrier layer, and the heat seal layer contains a water-dispersible resin.
(Water-dispersible resin)
The water-dispersible resin is not particularly limited as long as it is a water-dispersible resin and can impart heat sealability. The water-dispersible resin may be a dispersion-type water-dispersible resin or an emulsion-type water-dispersible resin. The water-dispersible resin may be used alone or in combination of two or more kinds.
In the barrier laminate of the present invention, since the heat seal layer contains a water-dispersible resin binder, the heat seal layer can be coated using an aqueous coating liquid, which is preferable because it suppresses problems with VOCs (volatile organic compounds).
Furthermore, since the second gas barrier layer contains the inorganic compound B, the adhesion between the second gas barrier layer and the heat seal layer is excellent.

The polymer that serves as the skeleton of the water-dispersible resin is not particularly limited, and examples thereof include polyolefin resins (polyethylene, polypropylene, etc.), ethylene-vinyl acetate copolymers, vinyl chloride resins, styrene resins, styrene-butadiene copolymers, styrene-unsaturated carboxylic acid copolymers (for example, styrene-(meth)acrylic acid copolymers), styrene-acrylic copolymers (for example, styrene-(meth)acrylic acid ester copolymers), acrylic resins obtained from at least one monomer selected from the group consisting of (meth)acrylic acid and (meth)acrylic acid esters, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers, ABS resins, AAS resins, AES resins, vinylidene chloride resins, polyurethane resins, poly-4-methylpentene-1 Resins, polybutene-1 resins, vinylidene fluoride resins, vinyl fluoride resins, fluorine resins, polycarbonate resins, polyamide resins, acetal resins, polyphenylene oxide resins, polyester resins (polyethylene terephthalate, polybutylene terephthalate, etc.), polyphenylene sulfide resins, polyimide resins, polysulfone resins, polyethersulfone resins, polyarylate resins, olefin-unsaturated carboxylic acid copolymers (ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers), biodegradable resins (polylactic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, 3-hydroxybutanoic acid-3-hydroxyhexanoic acid copolymers), and modified products thereof. These may be used alone or in combination of two or more.
Among these, the water-dispersible resin is preferably a polyolefin resin, an ethylene copolymer, or a styrene-butadiene copolymer from the viewpoint of heat sealability and adhesion.
As the polyolefin resin, polyethylene and polypropylene are preferred.
Examples of the ethylene copolymer include ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, and ethylene-aliphatic unsaturated carboxylic acid ester copolymer, and among these, ethylene-vinyl acetate copolymer and ethylene-aliphatic unsaturated carboxylic acid ester copolymer are preferred.
The water-dispersible resin is more preferably an ethylene copolymer or a styrene-butadiene copolymer, even more preferably an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, or a styrene-butadiene copolymer, still more preferably an ethylene-vinyl acetate copolymer, or an ethylene-aliphatic unsaturated carboxylic acid copolymer, and particularly preferably an ethylene-aliphatic unsaturated carboxylic acid copolymer.

<Styrene-butadiene copolymer>
Styrene-butadiene copolymers are copolymers obtained by emulsion polymerization of monomers consisting of styrene compounds such as styrene, α-methylstyrene, vinyltoluene, p-t-butylstyrene, and chlorostyrene, butadiene compounds such as 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene, and other compounds copolymerizable with these. Styrene is preferred as the styrene compound, and 1,3-butadiene is preferred as the butadiene compound.

<Ethylene-vinyl acetate copolymer>
The ethylene-vinyl acetate copolymer is a copolymer in which at least ethylene and vinyl acetate are copolymerized, and may further contain other monomers as the case may be. The content of the structural units derived from other monomers is preferably 30% by mass or less, more preferably 10% by mass or less, even more preferably 3% by mass or less, and even more preferably 1% by mass or less of the entire copolymer.
From the viewpoint of heat seal strength, the ethylene-vinyl acetate copolymer has a proportion of ethylene in all monomers constituting the copolymer of preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less.
The glass transition temperature of the ethylene-vinyl acetate copolymer is preferably 30° C. or lower, more preferably 20° C. or lower, even more preferably 10° C. or lower, and is preferably −30° C. or higher, more preferably −20° C. or higher, even more preferably −10° C. or higher.

As the ethylene-vinyl acetate copolymer, either a synthetic product or a commercially available product may be used. Commercially available products include Sumikaflex S-201HQ, S-305, S-305HQ, S-400HQ, S-401HQ, S-408HQE, S-450HQ, S-455HQ, S-456HQ, S-460HQ, S-467HQ, S-470HQ, and S-48HQ manufactured by Sumika Chemtex Corporation. 0HQ, S-510HQ, S-520HQ, S-752, S-755, Polysol AD-2, AD-5, AD-6, AD-10, AD-11, AD-14, AD-56, AD-70, AD-92 manufactured by Showa Denko K.K., and Aquatex EC1200, EC1400, EC1700, EC1800, MC3800 manufactured by Japan Coating Resins Co., Ltd., etc.

<Ethylene/Aliphatic Unsaturated Carboxylic Acid Copolymer>
Examples of the ethylene/aliphatic unsaturated carboxylic acid copolymer include ethylene/acrylic acid copolymer and ethylene/methacrylic acid copolymer.
The ethylene-acrylic acid copolymer and the ethylene-methacrylic acid copolymer may be blended in the heat seal layer as an ionomer. That is, it is preferable to use an ionomer as a raw material at least when producing the heat seal layer, and the heat seal layer after production does not need to contain the ethylene-acrylic acid copolymer and the ethylene-methacrylic acid copolymer in the form of an ionomer.
Here, ionomer is a general term for synthetic resins in which polymers are aggregated by utilizing the cohesive force of cations, and synthetic resins in which ethylene-methacrylic acid copolymers and ethylene-acrylic acid copolymers are aggregated with cations all fall under the category of ionomers.
Examples of the cation include metal ions, as well as ammonium ions (NH ₄ ⁺ ) and organic ammonium ions.
Examples of metal ions include alkali metal ions such as lithium ion (Li ⁺ ), sodium ion (Na ⁺ ), and potassium ion (K ⁺ ), alkaline earth metal ions such as magnesium ion (Mg ²⁺ ) and calcium ion (Ca ²⁺ ), and transition metal ions such as zinc ion (Zn ²⁺ ) and copper ion (Cu ²⁺ ). Among these, sodium ions are preferred as the metal ion from the viewpoint of availability and the like.
The ethylene-aliphatic unsaturated carboxylic acid copolymer is preferably an ethylene-(meth)acrylic acid copolymer ionomer, more preferably a metal salt of an ethylene-methacrylic acid copolymer, a metal salt of an ethylene-acrylic acid copolymer, or an ammonium salt of an ethylene-acrylic acid copolymer, still more preferably a metal salt of an ethylene-acrylic acid copolymer, or an ammonium salt of an ethylene-acrylic acid copolymer, and still more preferably an ammonium salt of an ethylene-acrylic acid copolymer.

From the viewpoint of heat sealability, the copolymerization ratio of (meth)acrylic acid in the ethylene-(meth)acrylic acid copolymer is preferably 1 mol% or more, more preferably 10 mol% or more, and is preferably 50 mol% or less, more preferably 30 mol% or less.

As the ethylene-(meth)acrylic acid copolymer, either a synthetic product or a commercially available product may be used. Commercially available products include MP4983R, MP4990R, and MICHEM FLEX HS1279.S manufactured by Michaelman Japan LLC, ZAIKXEN (registered trademark) A and ZAIKXEN (registered trademark) AC manufactured by Sumitomo Seika Chemicals Co., Ltd., and the Chemipearl S series manufactured by Mitsui Chemicals, Inc.

<Ethylene/Aliphatic Unsaturated Carboxylic Acid Ester Copolymer>
Examples of the ethylene-aliphatic unsaturated carboxylic acid ester copolymer include ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid ester copolymer, etc. As the acrylic acid ester and the methacrylic acid ester, esters with an aliphatic alcohol having 1 to 8 carbon atoms such as methanol and ethanol are preferably used. Among the ethylene-aliphatic unsaturated carboxylic acid ester copolymers, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, or ethylene-methyl methacrylate copolymer are preferred from the viewpoint of versatility.

The ethylene copolymer may be a multicomponent copolymer obtained by copolymerizing three or more monomer components. Examples of the multicomponent copolymer include copolymers obtained by copolymerizing at least three types of monomers selected from ethylene, an aliphatic unsaturated carboxylic acid ester, and an acid anhydride.

Among these, the ethylene copolymer is preferably an ethylene/aliphatic unsaturated carboxylic acid copolymer, since the ethylene/unsaturated carboxylic acid copolymer has excellent heat sealability.
The content of the water-dispersible resin binder in the solid content of the heat seal layer is preferably 50% by mass or more, more preferably 55% by mass or more, and preferably 100% by mass or less.

In addition to the above-mentioned water-dispersible resin, the heat seal layer may contain pigments, silane coupling agents, lubricants, dispersants, surfactants, defoamers, dyes, color adjusters, thickeners, etc., as necessary.

The thickness of the heat seal layer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm. The coating amount of the heat seal layer is preferably 0.1 to 10 g/ ^m2 , more preferably 0.5 to 5 g/ ^m2 , in terms of solid content.

As described above, it is preferable that the first gas barrier layer is a water vapor barrier layer and the second gas barrier layer is an oxygen barrier layer. However, it is also possible, for example, that the first gas barrier layer is an oxygen barrier layer and the second gas barrier layer is a water vapor barrier layer.
In this case, for example, the first gas barrier layer is configured to contain a binder resin and layered inorganic compound A, and the second gas barrier layer is configured to contain a layered inorganic compound, a cationic resin, a water-suspendable polymer, and inorganic compound B, and the layered inorganic compound contained in the water vapor barrier layer, which is the second gas barrier layer, is layered inorganic compound A having an aspect ratio of 150 or more.

[Barrier laminate]
1 is a schematic cross-sectional view showing the layer structure of a barrier laminate 10 of the present invention. A first gas barrier layer 2, a second gas barrier layer 3 and a heat seal layer 4 are present in this order on one surface of a paper substrate 1. It is preferable that the first gas barrier layer 2 is a water vapor barrier layer and the second gas barrier layer is an oxygen barrier layer.

The barrier laminate of this embodiment has excellent water vapor barrier properties and oxygen barrier properties.
Specifically, the water vapor barrier property is such that the water vapor permeability at 40°C and 90% RH is preferably 20 g/( ^m2 ·day) or less, more preferably 10 g/( ^m2 ·day) or less, even more preferably 5 g/( ^m2 ·day) or less, and still more preferably 4 g/( ^m2 ·day) or less.

Specifically, the oxygen barrier property is such that the oxygen permeability at 23°C and 50% RH is preferably 10 mL/( ^m2 ·day·atm) or less, more preferably 6 mL/( ^m2 ·day·atm) or less, and even more preferably 3 mL/( ^m2 ·day·atm) or less.

[Method of manufacturing the barrier laminate]
The barrier laminate of this embodiment has a first gas barrier layer, a second gas barrier layer, and a heat seal layer in this order on a paper substrate.
It is preferable to coat a first gas barrier layer coating liquid on a paper substrate, dry the coating liquid, coat a second gas barrier layer coating liquid and dry it, and then coat a heat seal layer coating liquid and dry it.
As described above, the present invention is not limited to the method of successively forming coating layers, and the film may be produced by a simultaneous multi-layer coating method, which is a method in which a plurality of types of coating liquids are ejected from separate slit-shaped nozzles to form a liquid laminate, which is then coated onto a paper substrate to simultaneously form multiple coating films. For example, see JP-T-2004-527669 and JP-T-2012-505321.

The solvent for the coating liquid is not particularly limited, and water or an organic solvent such as ethanol, isopropyl alcohol, methyl ethyl ketone, or toluene can be used, but an aqueous medium is preferable, and it is more preferable that the main component is water, and a water-miscible organic solvent is used in combination as necessary, and it is even more preferable that the solvent for the coating liquid is water.

The solids concentration of the coating liquid is not particularly limited and may be appropriately selected depending on the viscosity at which the coating can be performed, but from the viewpoint of facilitating drying, it is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and preferably 90% by mass or less, more preferably 70% by mass or less, even more preferably 50% by mass or less, and even more preferably 45% by mass or less.

Examples of methods for applying the coating liquid include bar coating, blade coating, squeeze coating, air knife coating, roll coating, gravure coating, and transfer coating, and a coating machine such as a fountain coater or a slit die coater may be used.
As a coating device for applying a coating liquid to a paper substrate by the simultaneous multi-layer coating method, a simultaneous multi-layer slide curtain type or simultaneous multi-layer slide bead type coating device capable of performing the simultaneous multi-layer coating method is used.

There are no particular limitations on the drying equipment used to dry the coating layer, and any known equipment can be used. Examples of drying equipment include hot air dryers, infrared dryers, gas burners, and hot plates.

The barrier laminate of this embodiment can be suitably used as a packaging material for food, medical products, electronic components, etc., taking advantage of the excellent water vapor barrier properties, gas barrier properties, and heat sealability described above.

The barrier laminate of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. In the examples and comparative examples, "parts" and "%" refer to "parts by mass" and "% by mass", respectively, unless otherwise specified.

The raw materials used in the examples and comparative examples are as follows.
(1) Paper base material Single-sided gloss paper: manufactured by Oji F-Tex, hardwood pulp content: 100% by mass, basis weight: 50 g/ ^m2 , thickness: 60 μm, density: 0.83 g/ ^cm3 , sizing degree: 9 seconds, Oken smoothness of one side: 499 seconds, Oken smoothness of the other side: 15 seconds, 75° gloss of coated side: 7%, 75° gloss of uncoated side: 29%
(2) Layered inorganic compound, layered inorganic compound A
Synthetic mica: Swellable mica, particle size 6.3 μm, aspect ratio about 1000, thickness about 5 nm, product name: NTO-05, manufactured by Topy Industries, Ltd., aqueous dispersion with a solid content of 6% (3) Inorganic compound B
Kaolin: Engineered kaolin, average particle size 0.26 μm, aspect ratio approximately 33, product name: Contour Xtreme, manufactured by Imerys Co., Ltd. (4) Inorganic compound B′ (comparative inorganic compound)
Kaolin: engineered kaolin, average particle size 10 μm, aspect ratio about 100, thickness about 100 nm, product name: Varisurf HX, manufactured by Imerys Co., Ltd. (4) Cationic resin Modified polyamide resin: solid content 53%, product name: SPI203(50)H, manufactured by Taoka Chemical Co., Ltd., surface charge 0.4 meq/g
(5) Water-suspendable polymer Ethylene-acrylic copolymer: Self-emulsifying ethylene-acrylic acid copolymer emulsion, solid content 29.2%, copolymerization ratio of acrylic acid 20 mol%, product name: ZAIKXEN AC, manufactured by Sumitomo Seika Chemicals Co., Ltd. (6) Binder resin Modified polyvinyl alcohol: Ethylene-modified polyvinyl alcohol, fully saponified type (saponification degree 98.5%), product name: EXCEVAL AQ-4104, manufactured by Kuraray Co., Ltd. Polyurethane emulsion: Polyurethane resin, product name: TAKELAC WPB-341, manufactured by Mitsui Chemicals, Inc., solid content concentration 30 mass%
(7) Water-dispersible resin for heat seal layer: Water dispersion of ethylene/acrylic acid copolymer (manufactured by Michaelman Co., Ltd., product name: MICHEM FLEX HS1279.S, solid content: 42.0%)

Example 1
To 30 parts of an aqueous dispersion of a layered inorganic compound (swellable mica, particle size 6.3 μm, aspect ratio approximately 1000, thickness approximately 5 nm, solid content 6%, product name: NTO-05, manufactured by Topy Industries, Ltd.), 34.3 parts of a self-emulsifying ethylene-acrylic acid copolymer emulsion (solid content 29.2%, product name: ZAIKXEN AC, manufactured by Sumitomo Seika Chemicals Co., Ltd.) was added with stirring, and the mixture was stirred. To this, 0.9 parts of a modified polyamide resin (solid content 53%, product name: SPI203(50)H, surface charge 0.4 meq/g, manufactured by Taoka Chemical Co., Ltd.) was added and stirred. Furthermore, 0.2 parts of a 25% aqueous ammonia solution was added and stirred. Furthermore, dilution water was added to adjust the solid content concentration to 18%, and a coating liquid for the water vapor barrier layer, which is the first gas barrier layer, was prepared.
To 100 parts of an aqueous solution of 15% solids concentration of ethylene-modified polyvinyl alcohol (fully saponified type, product name: EXCEVAL AQ-4104, manufactured by Kuraray Co., Ltd.), 25 parts of an aqueous dispersion of layered inorganic compound A (swellable mica, particle size 6.3 μm, aspect ratio approximately 1000, thickness approximately 5 nm, solids content 6%, product name: NTO-05, manufactured by Topy Industries, Ltd.) was added, and 2.7 parts of an aqueous dispersion of inorganic compound B (engineered kaolin, average particle size 0.26 μm, aspect ratio approximately 33, product name: Contour Xtreme, manufactured by Imerys) with a solids content of 55% was added, and dilution water was further added to prepare a coating fluid (solids concentration 10%) for the oxygen barrier layer, which is the second gas barrier layer.
The above water vapor barrier layer coating liquid was applied to the low smooth surface of one-sided glazed paper (Oji F-Tex, hardwood pulp content: 100% by mass, basis weight: 50 g/ ^m2 , thickness: 60 μm, density: 0.83 g/ ^cm3 , sizing degree: 9 seconds, Oken smoothness on one side: 499 seconds, Oken smoothness on the other side: 15 seconds) using a Mayer bar and dried at 120°C for 1 minute to form a water vapor barrier layer (first gas barrier layer, coating amount: 5 g/ ^m2 , thickness: 4 μm). Furthermore, the oxygen barrier layer coating liquid was applied to the water vapor barrier layer using a Mayer bar and dried at 120°C for 1 minute to form an oxygen barrier layer (second gas barrier layer, coating amount: 2 g/ ^m2 , thickness: 1 μm). Furthermore, on the oxygen barrier layer, an aqueous dispersion of ethylene-acrylic acid copolymer (MICHEM FLEX HS1279.S (product name) manufactured by Michelman, solid content: 42.0%) was applied as a heat seal layer coating material using a Mayer bar so that the coating amount of the heat seal layer after drying would be 3 g/ ^m2 (thickness: 3 μm), and then dried at 120°C for 1 minute to form a heat seal layer and obtain a barrier laminate.

Example 2
A barrier laminate was obtained in the same manner as in Example 1, except that the amount of the aqueous dispersion of engineered kaolin added to the oxygen barrier layer coating liquid was changed to 32.4 parts.

Example 3
A barrier laminate was obtained in the same manner as in Example 1, except that the amount of the aqueous dispersion of engineered kaolin added to the oxygen barrier layer coating liquid was changed to 54 parts.

Example 4
To 100 parts of a polyurethane emulsion (solid content concentration 30% by mass, product name: Takelac WPB-341, manufactured by Mitsui Chemicals, Inc.), 5.5 parts of an aqueous dispersion of 55% solid content obtained by dispersing inorganic compound B (engineered kaolin, average particle size 0.26 μm, aspect ratio about 33, product name: Contour Xtreme, manufactured by Imerys) in water was added and stirred. To this, 100 parts of an aqueous dispersion of layered inorganic compound A (swellable mica, particle size 6.3 μm, aspect ratio about 1000, thickness about 5 nm, solid content 6%, product name: NTO-05, manufactured by Topy Industries, Ltd.) was added and stirred. Further, dilution water was added so that the solid content concentration became 10% by mass, and a coating liquid for an oxygen barrier layer, which is a second gas barrier layer, was prepared. The polyurethane resin of the polyurethane emulsion had a solubility in water at 25° C. of 10 g/L or less. In addition, when the polyurethane emulsion A was subjected to ^1H -NMR measurement, it was found that the constituent units derived from metaxylylene diisocyanate accounted for 50 mol% or more of the constituent units derived from polyisocyanate. In addition, the oxygen transmission rate at 23°C and 50% RH when converted into a 25 μm thick sheet was 2.0 mL/( ^m2 ·day·atm).
A barrier laminate was obtained in the same manner as in Example 1, except that this coating liquid was used as the coating liquid for the oxygen barrier layer.

Example 5
A barrier laminate was obtained in the same manner as in Example 4, except that the amount of the aqueous dispersion of engineered kaolin added to the oxygen barrier layer coating liquid was changed to 16.4 parts.

Example 6
A barrier laminate was obtained in the same manner as in Example 4, except that the amount of the aqueous dispersion of engineered kaolin added to the oxygen barrier layer coating liquid was changed to 54.5 parts.

<Comparative Example 1>
A barrier laminate was obtained in the same manner as in Example 1, except that the aqueous dispersion of engineered kaolin, which was inorganic compound B, was not added to the coating liquid for the oxygen barrier layer.

<Comparative Example 2>
A barrier laminate was obtained in the same manner as in Example 4, except that the aqueous dispersion of engineered kaolin, which was inorganic compound B blended in the coating liquid for the oxygen barrier layer, was not blended.

<Comparative Example 3>
A barrier laminate was obtained in the same manner as in Example 2, except that the inorganic compound B incorporated in the oxygen barrier layer was changed from Contour Xtreme to a comparative inorganic compound B', Barisurf HX (engineered kaolin, average particle size 10 μm, aspect ratio approximately 100, manufactured by Imerys).

<Comparative Example 4>
A barrier laminate was obtained in the same manner as in Example 5, except that the inorganic compound B incorporated in the oxygen barrier layer was changed from Contour Xtreme to a comparative inorganic compound B', Barisurf HX (engineered kaolin, average particle size 10 μm, aspect ratio approximately 100, manufactured by Imerys).

(Evaluation Method)
(1) Water vapor permeability The water vapor permeability of the barrier laminate was measured in accordance with JIS Z 0208:1976 (cup method) B method (temperature 40±0.5°C, relative humidity 90±2%) with the paper substrate of the barrier laminate facing inward. Note that, as a standard for water vapor permeability, a water vapor barrier layer having a practical value of 10 g/( ^m2 ·day) or less is deemed to be practical.

(2) Oxygen permeability: Using an oxygen permeability measuring device (OX-TRAN2/22, manufactured by MOCON), measurements were taken under conditions of 23° C.-50% RH and 23° C.-85% RH. As a standard for oxygen permeability, if the oxygen permeability is 10 mL/( ^m2 ·day·atm) or less under conditions of 23° C.-50% RH, the film is practically usable as a gas barrier layer.

(3) Appearance Evaluation The barrier laminate was cut into an A4 size piece, and the surface of the coating layer was visually observed to check for the presence of blisters.
A: No blisters B: 1-2 blisters C: 3 or more blisters

(4) Cellopic: Cellophane tape was applied thoroughly to the surface of the coating layer of a barrier laminate, and the peeling behavior was examined when the tape was forcefully peeled off. In barrier laminates in which the adhesion of the coating layers (the first gas barrier layer, the second gas barrier layer, and the heat seal layer) was excellent, as well as the adhesion between the paper substrate and the coating layer, no peeling from the coating surface was observed, and the paper substrate was torn.
A: The paper substrate was torn and peeled off over the entire surface of the cellophane tape. B: The paper substrate was torn and peeled off over a portion of the cellophane tape. C: The paper substrate was not torn and peeled off from the coating layer.

(5) Heat sealability The barrier laminates of each example were stacked so that the heat seal layers were in contact with each other. A laminate was produced by heat sealing at 160°C, 2.0 kgf/ ^cm2 , and 1 second using a heat press tester. The laminate was cut into a rectangular measurement sample having a width of 15 mm.
The obtained sample was pulled by hand and peeled off to check how it broke.
A: The paper base material was torn and peeled off. C: The paper base material was not torn and peeled off from the coating layer.

As is clear from Table 1, all of the barrier laminates of Examples 1 to 6 had excellent water vapor barrier properties and oxygen barrier properties. In addition, no appearance defects due to the occurrence of blisters occurred, and a good appearance was obtained. Furthermore, the heat sealability was excellent, and the adhesion of the heat seal layer was high, and peeling of the coating layer was not confirmed in the cellopic test. On the other hand, the barrier laminates of Comparative Examples 1 and 2, which did not use inorganic compound B, had poor appearance due to the occurrence of blisters, and also had poor oxygen barrier properties, and further peeling of the coating layer was confirmed in the cellopic test. In the barrier laminates of Comparative Examples 3 and 4, which used an inorganic compound with an aspect ratio of more than 50 and an average particle size of more than 1 μm as inorganic compound B', the occurrence of blisters and peeling of the coating layer in the cellopic test were suppressed to some extent, but an increase in oxygen permeability (deterioration of oxygen barrier properties) was observed compared to the Examples.

1 Paper substrate 2 First gas barrier layer (e.g., water vapor barrier layer)
3. Second gas barrier layer (e.g., oxygen barrier layer)
4 Heat seal layer 10 Barrier laminate

Claims (13)

A barrier laminate having a first gas barrier layer, a second gas barrier layer and a heat seal layer in this order on at least one surface of a paper substrate,
the second gas barrier layer contains a binder resin, a layered inorganic compound A having an aspect ratio of 150 or more, and an inorganic compound B having an aspect ratio of 50 or less and an average particle size of 1 μm or less,
The heat seal layer contains a water-dispersible resin.
Barrier laminate. The barrier laminate according to claim 1, wherein the first gas barrier layer is a water vapor barrier layer and the second gas barrier layer is an oxygen barrier layer. The barrier laminate according to claim 1 or 2, wherein the binder resin contained in the second gas barrier layer is at least one selected from the group consisting of polyvinyl alcohol and its modified products, and polyurethane resins. The barrier laminate according to any one of claims 1 to 3, wherein the binder resin contained in the second gas barrier layer contains at least one selected from the group consisting of polyvinyl alcohol and modified products thereof, and the mass ratio (A/B) of layered inorganic compound A to inorganic compound B is 2/98 or more and 60/40 or less. The barrier laminate according to any one of claims 1 to 3, wherein the binder resin contained in the second gas barrier layer contains a polyurethane resin, and the mass ratio (A/B) of layered inorganic compound A to inorganic compound B is 10/90 or more and 80/20 or less. The barrier laminate according to any one of claims 1 to 5, wherein the first gas barrier layer contains a water-suspendable polymer, a layered inorganic compound, and a cationic resin. The barrier laminate according to claim 6, wherein the water-dispersible polymer contains at least one of an ethylene-acrylic copolymer, a styrene-butadiene copolymer, a styrene-acrylic copolymer, and a biodegradable resin. The barrier laminate according to claim 6 or 7, wherein the layered inorganic compound contained in the first gas barrier layer has an aspect ratio of 80 or more and a thickness of 120 nm or less. The barrier laminate according to any one of claims 6 to 8, wherein the cationic resin contained in the first gas barrier layer is at least one selected from polyamine, modified polyamide, modified polyamidoamine, polyamide epichlorohydrin, and polyethyleneimine. The barrier laminate according to any one of claims 1 to 9, wherein the heat seal layer contains at least one resin selected from the group consisting of ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid copolymers, and styrene-butadiene copolymers. The barrier laminate according to any one of claims 1 to 10, wherein the paper base material has a basis weight of 20 g/m2 or ^more and 500 g/ ^{m2 or less} , a density of 0.5 g/cm3 or ^more and 1.2 g/cm3 or less, and an Oken smoothness of 5 seconds or more. 12. The barrier laminate according to claim 1, which has an oxygen permeability of 10 mL/( ^m2 ·day·atm) or less at 23° C. and 50% RH. 13. The barrier laminate according to any one of claims 1 to 12, which has a water vapor permeability of 10 g/( ^m2 ·day) or less at 40°C and 90% RH.