Laminate, paper processed article, and method for producing laminate

Abstract

This laminate includes a thermoplastic resin layer, a paper substrate, a gas barrier resin layer, an adhesive protective layer, and a sealant layer provided in this order. The laminate has an oxygen permeability of 10.0 mL / m2･day･atm or less at 23°C and 85% RH.

Description

Laminate, paper processed product, and method for manufacturing laminate

[0001] The present disclosure relates to a laminate, a paper product, and a method for manufacturing a laminate.

[0002] BACKGROUND ART Packaging materials in which barrier properties such as gas barrier properties (oxygen barrier properties) and water vapor barrier properties are imparted to a paper base material are widely used in packaging for foods, medical products, electronic components, and the like, in order to prevent deterioration of the quality of the contents.

[0003] A common method for imparting barrier properties to a paper substrate is to laminate a barrier layer onto the paper substrate. For example, Patent Document 1 (JP 2021-138434 A) describes a packaging paper having a paper substrate, a gas barrier layer containing polyhydroxyurethane, and a heat seal layer.

[0004] The packaging paper described in Patent Document 1 has a single gas barrier layer, which allows for a reduction in the amount of plastic material used. However, this is not sufficient from the perspective of achieving a higher level of gas barrier property. Furthermore, depending on the conditions for forming the heat seal layer, the adhesive strength between the gas barrier layer and the heat seal layer may be reduced.

[0005] An object of the present disclosure is to provide a laminate having high gas barrier properties and excellent interlayer adhesion.

[0006] The inventors of the present disclosure have found that the above-mentioned problems can be solved by providing an adhesive protective layer between a gas barrier resin layer and a sealant layer.

[0007] [1] A film comprising a thermoplastic resin layer, a paper substrate, a gas barrier resin layer, an adhesive protective layer, and a sealant layer in this order, and having an oxygen permeability of 10.0 mL / m at 23°C and 85% RH. ２ [2] The adhesive protective layer has a basis weight of 0.1 g / m or less. ２[3] The laminate according to [1], wherein the adhesive protective layer comprises one or more resins (preferably polyalkyleneimine) selected from the group consisting of vinyl alcohol polymers, polyalkyleneimines, polyurethane resins, styrene-acrylic copolymers, olefin-unsaturated carboxylic acid copolymers, and acrylic resins. [4] The laminate according to any one of [1] to [3], wherein the adhesive protective layer comprises polyethyleneimine. [5] The laminate according to any one of [1] to [4], wherein the gas barrier resin layer comprises one or more gas barrier resins (preferably one or more resins selected from the group consisting of polyurethane resins, vinyl alcohol polymers, and polyvinylidene chloride, preferably polyurethane resins) selected from the group consisting of polyurethane resins, vinyl alcohol polymers, and polyvinylidene chloride. [6] The laminate according to any one of [1] to [5], wherein the gas barrier resin layer comprises a gas barrier resin, a swellable layered silicate, and a cationic resin (in this case, the gas barrier resin preferably comprises one or more selected from the group consisting of a polyurethane resin and a vinyl alcohol-based polymer, more preferably comprises a polyurethane resin, and even more preferably comprises a hydroxy polyurethane). [7] The laminate according to [6], wherein the gas barrier resin layer further comprises a film-forming aid, and the film-forming aid comprises one or more selected from the group consisting of a water-soluble polymer other than the gas barrier resin and a water-dispersible polymer other than the gas barrier resin. [8] The laminate according to [7], wherein the content of the film-forming aid in the gas barrier resin layer is 2.0 to 50.0 mass%. [9] The laminate according to [7] or [8], wherein the ratio of the mass of the gas barrier resin to the mass of the film-forming aid in the gas barrier resin layer (mass of the gas barrier resin:mass of the film-forming aid) is 50:50 to 95:5.

[10] The laminate according to any one of [7] to [9], wherein the water-soluble polymer comprises at least one selected from the group consisting of a vinyl alcohol polymer and a polyalkyleneimine, and the water-dispersible polymer comprises an olefin-unsaturated carboxylic acid copolymer.

[11] The laminate according to any one of [7] to

[10] , wherein the film-forming aid comprises the water-soluble polymer and the water-dispersible polymer, and the combination of the water-soluble polymer and the water-dispersible polymer is the combination (A) or (B) below: (A) Water-soluble polymer: polyvinyl alcohol, water-dispersible polymer: ethylene-acrylic acid copolymer (B) Water-soluble polymer: polyvinyl alcohol and polyethyleneimine, water-dispersible polymer: ethylene-acrylic acid copolymer

[12] The laminate according to any one of [1] to

[11] , wherein the gas barrier resin layer contains 30.0 to 80.0 mass% of a gas barrier resin (preferably a polyurethane resin).

[13] The laminate according to any one of [1] to

[12] , wherein an undercoat layer is provided between the paper substrate and the gas barrier resin layer, and the undercoat layer contains an inorganic pigment and a binder.

[14] The laminate according to

[13] , wherein the inorganic pigment comprises one or more selected from the group consisting of kaolin, talc, and mica (preferably kaolin), and the binder comprises one or more selected from the group consisting of styrene-(meth)acrylic copolymer, ethylene-(meth)acrylic acid copolymer, and polylactic acid (preferably styrene-(meth)acrylic copolymer).

[15] A processed paper product (for example, a liquid paper container) having the laminate according to any of [1] to

[14] .

[16] A method for producing the laminate according to any of [1] to

[14] , comprising: a coating step of forming the gas barrier resin layer and the adhesive protective layer in this order on one side of the paper base material by coating; an extrusion lamination step of forming the sealant layer on the adhesive protective layer by extrusion lamination; and a thermoplastic resin layer formation step of forming the thermoplastic resin layer on the other side of the paper base material.

[0008] FIG. 2 is a schematic diagram illustrating an example of a laminate according to the present embodiment.

[0009] In the present disclosure, the expressions "X or more and Y or less" and "X to Y" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. When the lower limit and upper limit of a numerical range are stated separately, the numerical range can be a combination of any lower limit and any upper limit. Furthermore, in the present disclosure, the expression "X such as X1, X2, and X3" means that X1, X2, and X3 are given as examples of X, and does not mean that X is limited to X1, X2, and X3.

[0010] In the present disclosure, a description such as "one or more selected from the group consisting of X, Y, and Z" means any of X, Y, Z, a combination of X and Y, a combination of X and Z, a combination of Y and Z, or a combination of X, Y, and Z. In the present disclosure, "(meth)acrylic" is a general term for acrylic and methacrylic.

[0011] <1. Laminate> The laminate according to the first embodiment of the present disclosure includes a thermoplastic resin layer, a paper substrate, a gas barrier resin layer, an adhesive protective layer, and a sealant layer, in this order. The oxygen permeability of the laminate according to this embodiment at 23°C and 85% RH is 10.0 mL / m ２ ・day・atm or less.

[0012] According to this embodiment, it is possible to provide a laminate having high gas barrier properties (particularly gas barrier properties under high humidity) and excellent interlayer adhesion. The laminate according to this embodiment has excellent interlayer adhesion, which has the advantage that the layers constituting the laminate, particularly the sealant layer, are less likely to peel or float from the laminate. The laminate according to this embodiment has excellent gas barrier properties, particularly under high humidity, and is therefore suitable for use as a processed paper product exposed to a high humidity environment, for example, as a liquid paper container. In this disclosure, "gas barrier properties" means "oxygen barrier properties" unless otherwise specified. Furthermore, when simply referring to "barrier properties," it means both "gas barrier properties" and "water vapor barrier properties."

[0013] One embodiment of the laminate according to the present invention is shown in Figure 1. In Figure 1, the laminate 10 comprises, in this order, a thermoplastic resin layer 1, a paper substrate 3, a gas barrier resin layer 5, an adhesive protective layer 7, and a sealant layer 9. The laminate 10 may also comprise other layers (not shown), as described below, between either or both of the thermoplastic resin layer 1 and the paper substrate 3 and the paper substrate 3 and the gas barrier resin layer 5. It is preferable that each layer in the laminate has a different composition from the adjacent layers, and it is particularly preferable that the gas barrier resin layer and the adhesive protective layer adjacent thereto have different compositions.

[0014] <1-1. Thermoplastic Resin Layer> The thermoplastic resin layer is a layer that becomes the outer surface (printing surface) of a paper product (e.g., a liquid paper container) when the paper product is formed, and the thermoplastic resin layer and the sealant layer are heat-sealed when the paper product is formed. The thermoplastic resin layer is a layer whose main component is a thermoplastic resin and may contain components other than the thermoplastic resin. In the present disclosure, the term "main component" means that the content in the thermoplastic resin is 50 to 100% by mass, preferably 80 to 100% by mass, and more preferably 90 to 100% by mass.

[0015] The thermoplastic resin used in the thermoplastic resin layer is not particularly limited as long as it is heat-sealable with the sealant layer, but it is preferable that the thermoplastic resin itself has heat-sealability.

[0016] Specific examples of thermoplastic resins include polyolefin resins such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), ethylene-propylene copolymer, ethylene-butene copolymer, propylene-butene copolymer, propylene homopolymer, propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-ethylene-butene copolymer, ethylene-vinyl acetate copolymer, and polymethylpentene; and olefin-unsaturated copolymers such as ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl methacrylate copolymer. Examples of suitable thermoplastic resins include carboxylic acid copolymers, polyester resins such as cyclohexanedimethanol-modified polyethylene terephthalate copolymer, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyester copolymers; polystyrene; polyvinyl chloride; acrylonitrile-butadiene-styrene (ABS) resin; acrylic resins; modified polyphenylene ether (PPE); polyamide resins; biodegradable resins such as polylactic acid (PLA), polyhydroxybutyric acid (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-butylene terephthalate) (PBAT), polycaprolactone (PCL), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH); and the like. Thermoplastic resins may be used singly or in any combination and ratio of two or more.

[0017] The method for forming the thermoplastic resin layer is not particularly limited, and may be lamination or coating using a coating liquid containing a thermoplastic resin.

[0018] When the thermoplastic resin layer is formed by lamination, the resin used for the thermoplastic resin layer preferably contains at least one selected from the group consisting of polyethylene and biodegradable resins, more preferably at least one selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and biodegradable resins, even more preferably at least one selected from the group consisting of low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), and even more preferably low-density polyethylene (LDPE). Because polyethylene is low cost and has appropriate flexibility, it is preferable to use a polyethylene layer as the thermoplastic resin layer when the laminate is used as a liquid paper container material.

[0019] When the thermoplastic resin layer is formed by coating, the resin used for the thermoplastic resin layer is preferably an acrylic resin, which has the advantage that physical properties such as heat sealability, printability, and film-forming property can be easily controlled.

[0020] The acrylic resin may be either a commercially available product or a synthetic product. Examples of commercially available acrylic resins include Brightone FC-640V (manufactured by Sakata Inx Corporation), JONCRYL PDX7326 (manufactured by BASF Japan Ltd.), JONCRYL JDX-6500 (manufactured by BASF Japan Ltd.), SEIKOAT RE-2016 (manufactured by Seiko PMC Corporation), and SEIKOAT RE-2194 (manufactured by Seiko PMC Corporation).

[0021] The thermoplastic resin layer may have a single layer structure or a multilayer structure, and each layer may contain a single resin or a mixed resin in which two or more resins are mixed in any combination and in any ratio.

[0022] (Basis Weight of Thermoplastic Resin Layer) The basis weight (mass per unit area) of the thermoplastic resin layer is not particularly limited, but is preferably 1 to 50 g / m ２ , more preferably 2 to 30 g / m ２The thickness of the thermoplastic resin layer is not particularly limited, but is preferably 5 to 100 μm, more preferably 10 to 50 μm, from the viewpoint of moldability.

[0023] (Thickness of Thermoplastic Resin Layer) The thickness of the thermoplastic resin layer is not particularly limited, but is preferably 1 to 50 μm, more preferably 5 to 40 μm, and even more preferably 10 to 30 μm.

[0024] <1-2. Paper Base> The paper base is not particularly limited, and any commonly used paper can be used. Examples of the paper include paper whose main component is plant-derived pulp, and paper whose main component is wood pulp is preferred. Examples of wood pulp include hardwood pulp and softwood pulp. The paper base may also include non-wood pulp such as cotton pulp, hemp pulp, kenaf pulp, and bamboo pulp; and fiber materials other than pulp, such as synthetic fibers (e.g., rayon fibers and nylon fibers), as long as the effects of the present disclosure are not impaired.

[0025] Specific paper substrates include bleached kraft paper, unbleached kraft paper, fine paper, paperboard, liner paper, coated paper, one-side gloss bleached kraft paper, glassine paper, graphene paper, etc. Among these, the paper substrate is preferably bleached kraft paper, unbleached kraft paper, fine paper, or one-side gloss bleached kraft paper, more preferably bleached kraft paper or one-side gloss bleached kraft paper, and even more preferably one-side gloss bleached kraft paper.

[0026] The paper substrate may contain additives as long as they do not impair the effects of the present disclosure. Examples of additives include pH adjusters (e.g., sodium bicarbonate and sodium hydroxide), dry strength agents (e.g., polyacrylamide and starch), wet strength agents (e.g., polyamide polyamine epichlorohydrin resin, melamine-formaldehyde resin, and urea-formaldehyde resin), internal sizing agents (e.g., rosin-based and alkyl ketene dimers), drainage retention aids, antifoaming agents, fillers (e.g., calcium carbonate and talc), and dyes. These additives may be used alone, or two or more may be used in any combination and in any ratio. The content of the additives is not particularly limited and may be within a commonly used range.

[0027] (Basis Weight) The basis weight of the paper substrate is not particularly limited, but is preferably 20 to 600 g / m ２ When the laminate is used for a packaging bag, the basis weight of the paper substrate is preferably 20 to 150 g / m ２ , more preferably 30 to 100 g / m ２ , more preferably 40 to 70 g / m ２ When the laminate is used for containers such as liquid paper containers, paper containers, and paper cups, the basis weight of the paper substrate is preferably 150 to 600 g / m ２ , more preferably 200 to 400 g / m ２ The basis weight of the paper substrate is measured in accordance with JIS P 8124:2011 (Paper and paperboard -- Determination of basis weight; revised March 22, 2011).

[0028] (Paper Thickness) The thickness of the paper substrate is not particularly limited, but is usually 20 to 1,000 μm. When the laminate is used for a packaging bag, the thickness of the paper substrate is preferably 20 to 250 μm, more preferably 25 to 170 μm, and even more preferably 30 to 100 μm. When the laminate is used for a container such as a paper container for liquids, a paper container, or a paper cup, the thickness of the paper substrate is preferably 150 to 1,000 μm, more preferably 200 to 650 μm. The thickness of the paper substrate is measured in accordance with JIS P 8118:2014 (Paper and paperboard - Test methods for thickness, density, and specific volume; revised November 20, 2014).

[0029] (Mass ratio of paper substrate) The mass ratio of the paper substrate is a value obtained by calculating the percentage as follows, based on the total mass of the laminate: (Mass ratio of paper substrate) = (Mass of paper substrate) / (Mass of laminate) x 100 The mass ratio of the paper substrate is preferably 75 to 99%, more preferably 80 to 95%. When the mass ratio of the paper substrate is equal to or greater than the above lower limit, a laminate with a high biomass ratio and a low environmental impact can be provided.

[0030] (Method for manufacturing paper base material) A method for manufacturing a paper base material includes a method of making a paper stock containing pulp. The paper stock may further contain additives. Examples of additives include the additives described above.

[0031] The stock can be prepared by adding additives to a pulp slurry. The pulp slurry can be obtained by beating pulp in the presence of water. The method and apparatus for beating the pulp are not particularly limited, and any method and apparatus, such as a known method and apparatus or a method and apparatus equivalent thereto, can be used. The pulp content in the stock is not particularly limited, and may be within a normal range (e.g., 60% by mass or more and less than 100% by mass).

[0032] Papermaking from the stock can be carried out by a conventional method. For example, the stock is cast onto a wire or the like, dewatered to obtain a wet paper, and multiple wet papers are stacked as necessary, and this single-layer or multi-layer wet paper is pressed and dried. In this case, if multiple wet papers are not stacked, a single-layer paper is obtained, and if multiple wet papers are stacked, a multi-layer paper is obtained. When multiple wet papers are stacked, an adhesive may be applied to the surface of the wet paper (the surface on which other wet papers are stacked).

[0033] <1-3. Gas Barrier Resin Layer> The gas barrier resin layer is a layer containing a barrier resin having gas barrier properties. The barrier resin layer may have a single-layer structure or a multi-layer structure, but from the viewpoint of production costs, a single-layer structure is preferable. Furthermore, each layer may be a layer containing a single resin as the resin, or a layer containing a mixed resin in which two or more resins are mixed in any combination and in any ratio.

[0034] The barrier resin layer preferably contains a swellable layered silicate and a cationic resin in addition to the gas barrier resin, and from the viewpoint of improving film formability, preferably further contains a film-forming aid. The film-forming aid contains one or more selected from the group consisting of water-soluble polymers other than the gas barrier resin (hereinafter sometimes simply referred to as "water-soluble polymers") and water-suspendable polymers other than the gas barrier resin (hereinafter sometimes simply referred to as "water-suspendable polymers").

[0035] (Gas barrier resin) The gas barrier resin is not particularly limited as long as it is a resin having gas barrier properties, and any gas barrier resin can be used. In the present disclosure, the term "resin having gas barrier properties" refers to a resin having an oxygen permeability of 5 mL / m when a resin film having a thickness of 20 μm is formed at 23° C. and 50% RH. ２ The resin film may be formed by extrusion molding or by coating a resin on a release paper and then peeling off only the resin film, and the method may be appropriately selected depending on the type of resin.

[0036] The gas barrier resin layer preferably contains one or more gas barrier resins selected from the group consisting of polyurethane resins, vinyl alcohol polymers, and polyvinylidene chloride. Of these, the gas barrier resin layer more preferably contains one or more gas barrier resins selected from the group consisting of polyurethane resins and vinyl alcohol polymers, in terms of low environmental impact. Furthermore, the gas barrier resin is preferably a vinyl alcohol polymer, in terms of exhibiting high film-forming properties without the use of a film-forming aid, as described below. Note that, from the viewpoint of gas barrier properties (particularly gas barrier properties under high humidity), the gas barrier resin layer preferably contains a polyurethane resin. The preferred content of polyurethane resin in the gas barrier resin layer is as described below.

[0037] The polyurethane resin is not particularly limited as long as it is a polymer having a urethane bond, and any known polyurethane resin can be used.

[0038] From the viewpoint of achieving both higher gas barrier properties and water vapor barrier properties, the polyurethane resin preferably contains at least one selected from the group consisting of polyurethanes having structural units derived from meta-xylylene diisocyanate and hydroxy polyurethanes, and more preferably contains hydroxy polyurethanes. Polyurethane resins are generally obtained by the reaction of polyisocyanate with polyols having two or more hydroxy groups, and "polyurethanes having structural units derived from meta-xylylene diisocyanate" refers to polyurethane resins obtained by the above reaction using meta-xylylene diisocyanate in part or in whole as the polyisocyanate. Furthermore, "hydroxy polyurethane" refers to polyurethane resins having hydroxy groups.

[0039] The hydroxyl value of the hydroxy polyurethane is preferably 100 to 500 mgKOH / g, more preferably 150 to 400 mgKOH / g, and even more preferably 200 to 350 mgKOH / g. When the hydroxyl value of the hydroxy polyurethane is within the above range, the cohesive strength of the hydroxy polyurethane is increased, and the hydroxy polyurethane is more likely to exhibit high gas barrier property and water vapor barrier property.

[0040] The hydroxy polyurethane may have an acid group. The acid value of the hydroxy polyurethane is preferably 5 to 100 mgKOH / g, more preferably 10 to 70 mgKOH / g, and even more preferably 15 to 60 mgKOH / g.

[0041] The acid value and hydroxyl value of the hydroxy polyurethane are measured by titration in accordance with JIS K 1557-1:2007 (Plastics - Test methods for polyurethane raw polyols - Part 1: Determination of hydroxyl value; established on February 20, 2007).

[0042] When the polyurethane resin contains meta-xylylene diisocyanate-derived structural units, the content of meta-xylylene diisocyanate-derived structural units relative to the total amount of polyisocyanate-derived structural units is preferably 50 mol % or more. Such polyurethane resins exhibit high cohesive strength due to hydrogen bonding and the stacking effect between xylylene groups, and are therefore thought to have better gas barrier properties and water vapor barrier properties.

[0043] The content of metaxylylene diisocyanate-derived structural units is: １ Identified by H-NMR.

[0044] The glass transition temperature of the polyurethane resin is preferably 50 to 200°C, more preferably 65 to 200°C, and may be 90 to 200°C or 110 to 200°C.

[0045] The glass transition temperature of the polyurethane resin is measured in accordance with JIS K 7121 (Method for measuring glass transition temperature of plastics; revised on July 20, 2012).

[0046] As the hydroxy polyurethane, commercially available products can be used. Examples of commercially available hydroxy polyurethanes include HPU W-001, HPU W-003, and HPU-W013A (all manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.). Examples of polyurethanes having structural units derived from metaxylylene diisocyanate include Takelac WPB-341(30) (manufactured by Mitsui Chemicals, Inc.).

[0047] Examples of vinyl alcohol polymers include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Generally, saponified products of polyvinyl acetate and ethylene-vinyl acetate copolymers can be used as polyvinyl alcohol and ethylene-vinyl alcohol copolymers, respectively. The saponification degree of the saponified product is preferably 80.0 to 100.0 mol%, more preferably 85.0 to 99.8 mol%, even more preferably 90.0 to 99.8 mol%, still more preferably 96.0 to 99.8 mol%, even more preferably 98.0 to 99.8 mol%, and particularly preferably 98.5 to 99.5 mol%.

[0048] Commercially available vinyl alcohol polymers can be used. Examples of commercially available polyvinyl alcohol products include the POVAL series and EXCEVAL series (all manufactured by Kuraray Co., Ltd.), the Gohsenol series, and the Nichigo G Polymer series (all manufactured by Mitsubishi Chemical Corporation).

[0049] Commercially available polyvinylidene chloride products can be used, including the Diofan series (manufactured by Solvay Specialty Polymers Japan Co., Ltd.).

[0050] The content of the gas barrier resin (preferably one or more selected from the group consisting of polyurethane resins, vinyl alcohol-based polymers, and polyvinylidene chloride, more preferably one or more selected from the group consisting of polyurethane resins and vinyl alcohol-based polymers, and even more preferably polyurethane resin) in the gas barrier resin layer is preferably 20.0 to 100.0 mass%, more preferably 25.0 to 90.0 mass%, even more preferably 30.0 to 80.0 mass%, still more preferably 40.0 to 75.0 mass%, and particularly preferably 50.0 to 70.0 mass%. Having the gas barrier resin content within the above range makes it easier to further enhance the barrier properties of the laminate. Furthermore, having the gas barrier resin content within the above range increases the strength of the gas barrier resin layer and can further improve interlayer adhesion.

[0051] (Swellable layered silicate) From the viewpoint of further improving the gas barrier property and water vapor barrier property, the gas barrier resin layer preferably contains a swellable layered silicate in addition to the gas barrier resin, and more preferably contains a swellable layered silicate and a cationic resin.

[0052] "Swellable layered silicate" is a layered inorganic compound that swells in water and whose layers are easily cleaved by shear to a thickness on the order of nanometers. By combining a gas barrier resin with a swellable layered silicate, the swellable layered silicate is dispersed in the gas barrier resin, which inherently has gas barrier properties, and the gas barrier properties and water vapor barrier properties can be improved due to the labyrinth effect.

[0053] The swellable layered silicate is preferably in the form of a plate. By incorporating a plate-like swellable layered silicate into the gas barrier resin layer, the plate-like swellable layered silicate is easily laminated substantially parallel to the plane (surface) of the paper substrate. This reduces the area where the swellable layered silicate is not present in the plane direction, making it easier to suppress water vapor permeation. Furthermore, in the thickness direction, the plate-like swellable layered silicate is arranged parallel to the plane of the paper substrate, and water vapor and oxygen in the gas barrier resin layer permeate while bypassing the swellable layered silicate, resulting in a maze effect that suppresses water vapor permeation. As a result, the gas barrier property and water vapor barrier property of the gas barrier resin layer can be further improved.

[0054] The average thickness of the swellable layered silicate is not particularly limited, but is preferably 2 to 200 nm, more preferably 2 to 120 nm, even more preferably 3 to 50 nm, still more preferably 4 to 25 nm, and particularly preferably 5 to 10 nm. By setting the average thickness of the swellable layered silicate to the above upper limit or less, the number of layers of the swellable layered silicate in the gas barrier resin layer increases, and high water vapor barrier properties can be exhibited.

[0055] The average thickness of the swellable layered silicate, when the swellable layered silicate is contained in the gas barrier resin layer, can be determined as follows. First, a magnified photograph of the cross section of the gas barrier resin layer is taken using an electron microscope. The photograph is taken at a magnification such that approximately 20 to 30 pieces of swellable layered silicate are included within the image. Next, the thickness of each piece of swellable layered silicate within the image is measured. The average value of the obtained thicknesses is then calculated to be the average thickness of the swellable layered silicate.

[0056] The average length of the swellable layered silicate is not particularly limited, but is preferably 1 to 100 μm, more preferably 2 to 50 μm, even more preferably 3 to 30 μm, and even more preferably 5 to 15 μm. By setting the average length of the swellable layered silicate to be equal to or greater than the above-mentioned lower limit, the swellable layered silicate is more likely to be aligned parallel to the paper substrate. Furthermore, by setting the average length of the swellable layered silicate to be equal to or less than the above-mentioned upper limit, it is less likely that part of the swellable layered silicate will protrude from the gas barrier resin layer.

[0057] The average length of the swellable layered silicate, when the swellable layered silicate is contained in the gas barrier resin layer, can be determined as follows. First, a magnified photograph is taken of the cross section of the gas barrier resin layer using an electron microscope. The photograph is taken at a magnification such that approximately 20 to 30 swellable layered silicates are included within the image. Next, the length (major axis) of each swellable layered silicate within the image is measured. The average of the lengths obtained is then calculated to be the average length of the swellable layered silicate. The length of the swellable layered silicate is sometimes expressed as particle diameter.

[0058] The aspect ratio of the swellable layered silicate is not particularly limited, but is preferably 50 to 10,000, more preferably 80 to 5,000, even more preferably 300 to 2,000, and even more preferably 500 to 1,500. By ensuring that the aspect ratio of the swellable layered silicate is at least the above lower limit, the water vapor barrier property of the laminate is likely to be improved, and even if the amount of swellable layered silicate added is reduced, the effect of improving the water vapor barrier property can be fully exerted.

[0059] In the present disclosure, the aspect ratio is the average length of the swellable layered silicate divided by its average thickness.

[0060] Specific examples of swellable layered silicates include micas such as mica group mica and brittle mica group mica; bentonite; kaolinite (kaolin mineral); pyrophyllite; talc; smectites such as sodium smectite, sodium hectorite, and lithium taeniolite; vermiculite; chlorites such as chlorite and septe chlorite; serpentine; stilpnomelane; and montmorillonites such as sodium montmorillonite.

[0061] Among these, from the viewpoint of improving the gas barrier property and water vapor barrier property, the swellable layered silicate preferably contains one or more selected from the group consisting of mica and bentonite, more preferably contains mica or bentonite, and even more preferably contains mica.

[0062] More specifically, preferred examples of mica include swellable mica, white mica (muscovite), sericite (sericite), phloxopite, biotite (biotite), sodium tetrasilicic mica, fluorine phlogopite (artificial mica), red mica, soda mica, vanadium mica, illite, zinc mica, paragonite, and brittle mica. The swellable layered silicates may be used alone or in any combination and in any ratio of two or more.

[0063] Commercially available mica can be used, such as NTO-05 (manufactured by Topy Industries) and Somasif ME300B-4T (manufactured by Katakura Co-op Agri Co., Ltd.).

[0064] When the gas barrier resin layer contains a swellable layered silicate, the content of the swellable layered silicate in the gas barrier resin layer is preferably 5.0 to 30.0 mass%, more preferably 10.0 to 25.0 mass%, and even more preferably 13.0 to 20.0 mass%. By setting the content of the swellable layered silicate within the above range, the gas barrier property and water vapor barrier property of the laminate can be further improved.

[0065]

[0044] (Cationic Resin) From the viewpoint of improving the water vapor barrier property, the gas barrier resin layer preferably contains a cationic resin in addition to the gas barrier resin, and more preferably contains a swellable layered silicate and a cationic resin. By using a gas barrier resin, a swellable layered silicate, and a cationic resin in combination, the gas barrier property and the water vapor barrier property, in particular the water vapor barrier property, can be greatly improved.

[0066] The swellable layered silicate particle surface is easily charged anionic and the particle end faces are easily charged cationic, so the surface and end faces attract each other and form a house-of-cards aggregation structure. However, the cationic resin can block the anionic groups on the particle surface of the swellable layered silicate with cations, thereby destroying the house-of-cards aggregation structure. Therefore, when the swellable layered silicate and the cationic resin coexist, the steric aggregation of the swellable layered silicate is suppressed, and the swellable layered silicate can be aligned parallel to the plane of the paper substrate, thereby fully demonstrating the maze effect. As a result, the laminate can be endowed with very high gas barrier properties and water vapor barrier properties.

[0067] Specific examples of the cationic resin include polyamide compounds, modified polyamide compounds, polyamine compounds, modified polyamine 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, and polydiallyldimethylammonium chloride. Among these, the cationic resin is preferably a modified polyamide compound, and more preferably a modified polyamide resin.

[0068] The modified polyamide resin may be a commercially available product, such as SPI203(50)H (manufactured by Taoka Chemical Co., Ltd.).

[0069]

[0083] When the gas barrier resin layer contains a cationic resin, the content of the cationic resin in the gas barrier resin layer is preferably 1.0 to 20.0% by mass, more preferably 1.5 to 10.0% by mass, even more preferably 2.0 to 8.0% by mass, still more preferably 2.5 to 5.0% by mass, even more preferably 3.0 to 5.0% by mass, and particularly preferably 3.5 to 5.0% by mass, from the viewpoint of improving barrier properties (particularly water vapor barrier properties) and / or heat sealability.

[0070] The surface charge of the cationic resin is not particularly limited, but is preferably 0.1 to 10.0 meq / g, more preferably 0.1 to 5.0 meq / g, even more preferably 0.2 to 4.0 meq / g, even more preferably 0.2 to 2.0 meq / g, and particularly preferably 0.3 to 1.0 meq / g. By setting the surface charge of the cationic resin at or above the lower limit, the effect of adding the cationic resin can be more fully achieved. By setting the surface charge of the cationic resin at or below the upper limit, the effect of the cationic resin can be more fully exerted while suppressing aggregation of the swellable layered silicate.

[0071] The surface charge of a cationic resin is measured by the following method. First, a sample cationic resin is dissolved in water to prepare a solution with a cationic resin concentration of 1 ppm. Next, using a charge analyzer Mutek PCD-04 (manufactured by BTG), 0.001N sodium polyethylene sulfonate is dropped into this solution and the amount of charge is measured.

[0072]

[0043] (Film-forming aid) The film-forming aid preferably contains one or more selected from the group consisting of water-soluble polymers other than the gas barrier resin and water-dispersible polymers other than the gas barrier resin. By using the film-forming aid in addition to the gas barrier resin, the film-forming properties of the gas barrier resin layer are improved, and as a result, the gas barrier properties of the laminate can be further improved.

[0073]

[0003] Studies by the inventors of the present disclosure have revealed that although the three components of a gas barrier resin, a swellable layered silicate, and a cationic resin are good in terms of gas barrier property and water vapor barrier property, depending on the type of gas barrier resin, they are insufficient in terms of film-formability of the gas barrier resin layer. This problem is particularly pronounced when a polyurethane resin (particularly, a hydroxy polyurethane) is used as the gas barrier resin. Therefore, the inventors of the present disclosure have discovered that the film-formability of the gas barrier resin layer is improved by using a water-suspendable polymer other than the gas barrier resin or a water-soluble polymer other than the gas barrier resin in addition to the three components of a gas barrier resin (particularly, a polyurethane resin, specifically, a hydroxy polyurethane), a swellable layered silicate, and a cationic resin, and as a result, the gas barrier property and water vapor barrier property are improved.

[0074] When forming a gas barrier resin layer by aqueous coating, a water-soluble polymer is more effective at improving film-forming properties than a water-suspendable polymer. Furthermore, from the viewpoint of improving the water resistance of the gas barrier resin layer and further improving the water vapor barrier properties, it is preferable to use a water-suspendable polymer in addition to a water-soluble polymer. That is, the gas barrier resin layer preferably contains a water-suspendable polymer and a water-soluble polymer. In this case, the water-suspendable polymer preferably contains an olefin-unsaturated carboxylic acid copolymer, and more preferably contains an ethylene-(meth)acrylic acid copolymer. Furthermore, the water-soluble polymer preferably contains at least one selected from the group consisting of a vinyl alcohol-based polymer and a polyalkyleneimine, more preferably contains a vinyl alcohol-based polymer, and even more preferably contains polyvinyl alcohol.

[0075] When the gas barrier resin layer contains a swellable layered silicate, a cationic resin, and a film-forming aid in addition to a gas barrier resin, the ratio of the mass of the gas barrier resin to the mass of the film-forming aid (mass of gas barrier resin:mass of film-forming aid) is not particularly limited, but from the viewpoint of achieving both gas barrier properties and film-formability, it is preferably 50:50 to 95:5, more preferably 55:45 to 90:10, even more preferably 60:40 to 85:15, and even more preferably 65:35 to 85:15. In addition, the ratio of the mass of the gas barrier resin to the mass of the film-forming aid is, in other words, the ratio of the mass of the gas barrier resin to the total mass of water-soluble polymers other than the gas barrier resin and water-suspendable polymers other than the gas barrier resin (mass of gas barrier resin:total mass of water-soluble polymers other than the gas barrier resin and water-suspendable polymers other than the gas barrier resin).

[0076]

[0063] When the gas barrier resin layer contains a film-forming aid, the content of the film-forming aid in the gas barrier resin layer is not particularly limited, but from the viewpoint of achieving both gas barrier properties and film-formability, it is preferably 1.0 to 50.0 mass%, more preferably 2.0 to 50.0 mass%, even more preferably 5.0 to 40.0 mass%, still more preferably 10.0 to 30.0 mass%, and particularly preferably 10.0 to 20.0 mass%.

[0077]

[0062] When the gas barrier resin layer contains a water-soluble polymer other than the gas barrier resin, the content of the water-soluble polymer other than the gas barrier resin in the gas barrier resin layer is, from the viewpoint of achieving both gas barrier properties and film-formability, preferably 1.0 to 20.0 mass%, more preferably 2.0 to 15.0 mass%, even more preferably 2.0 to 10.0 mass%, even more preferably 3.0 to 7.0 mass%, and particularly preferably 3.5 to 5.0 mass%.

[0078]

[0047] When the gas barrier resin layer contains a water-suspendable polymer other than the gas barrier resin, the content of the water-suspendable polymer other than the gas barrier resin in the gas barrier resin layer is preferably 1.0 to 40.0 mass%, more preferably 5.0 to 30.0 mass%, even more preferably 8.0 to 20.0 mass%, and still more preferably 10.0 to 15.0 mass%, from the viewpoint of achieving both gas barrier properties and film-formability.

[0079]

[0044] When the gas barrier resin layer contains a water-soluble polymer other than the gas barrier resin and a water-suspendable polymer other than the gas barrier resin, the mass ratio of the content of the water-soluble polymer to the content of the water-suspendable polymer (mass of water-soluble polymer: mass of water-suspendable polymer) is preferably 2:1 to 1:20, more preferably 3:2 to 1:10, even more preferably 4:3 to 1:5, still more preferably 5:4 to 1:4, and particularly preferably 1:2 to 1:4.

[0080] (Water-soluble polymer) The water-soluble polymer other than the gas barrier resin preferably contains at least one selected from the group consisting of a vinyl alcohol polymer and a polyalkyleneimine. When the gas barrier resin layer contains a polyalkyleneimine, the adhesion to the adhesive protective layer can be improved. The water-soluble polymer may be used alone or in any combination and ratio of two or more.

[0081] As the vinyl alcohol polymer, the same vinyl alcohol polymer as explained as the gas barrier resin may be used.

[0082] When a vinyl alcohol polymer is used as the water-soluble polymer, the degree of saponification thereof is, from the viewpoint of adhesiveness and compatibility with other resin components, specifically, preferably 80.0 to 99.0 mol%, more preferably 85.0 to 98.0 mol%, even more preferably 90.0 to 99.6 mol%, still more preferably 91.0 to 99.5 mol%, still more preferably 91.5 to 98.0 mol%, and particularly preferably 92.0 to 95.0 mol%.

[0083] Commercially available vinyl alcohol polymers can be used. Examples of commercially available polyvinyl alcohol products include the POVAL series and EXCEVAL series (all manufactured by Kuraray Co., Ltd.), the Gohsenol series, and the Nichigo G Polymer series (all manufactured by Mitsubishi Chemical Corporation).

[0084] As described above, the vinyl alcohol-based polymer is a resin having gas barrier properties and can also function as a gas barrier resin. Therefore, in the present embodiment, for example, when the gas barrier resin layer does not contain any gas barrier resin other than the vinyl alcohol-based polymer, the vinyl alcohol-based polymer in the gas barrier resin is treated as a gas barrier resin, not as a film-forming aid.

[0085] From the viewpoint of improving adhesion to the adhesive protective layer, the polyalkyleneimine is preferably a polyalkyleneimine having an alkylene group with 1 to 5 carbon atoms, and is preferably polyethyleneimine. The polyethyleneimine may be a linear polyethyleneimine or a branched polyethyleneimine.

[0086] The number average molecular weight of the polyalkyleneimine is not particularly limited, but is preferably 300 to 1,000,000, more preferably 1,000 to 100,000, even more preferably 10,000 to 100,000, still more preferably 30,000 to 100,000, and particularly preferably 50,000 to 100,000. The number average molecular weight is a value calculated by a viscosity method.

[0087] Commercially available polyalkyleneimines can be used, including the Epomin series (manufactured by Nippon Shokubai Co., Ltd.).

[0088] (Water-Suspendable Polymer) The water-suspendable polymer other than the gas barrier resin preferably contains at least one selected from the group consisting of an olefin-unsaturated carboxylic acid copolymer such as an ethylene-(meth)acrylic acid copolymer; a rubber-based resin such as a styrene-butadiene-based copolymer; an acrylic resin such as a styrene-acrylic copolymer; a polyolefin resin such as an ethylene-vinyl acetate copolymer; a polyester resin; and a urethane resin, and more preferably contains an olefin-unsaturated carboxylic acid copolymer. The water-suspendable polymer may be used alone or in any combination and ratio of two or more.

[0089] The olefin-unsaturated carboxylic acid copolymer is a copolymer or a salt thereof obtained by polymerizing an olefin, an unsaturated carboxylic acid and / or an unsaturated carboxylic acid ester, and, if necessary, other polymerizable compounds, although the method for producing the olefin-unsaturated carboxylic acid copolymer is not limited thereto.

[0090] The olefin is preferably an α-olefin such as ethylene or propylene, and more preferably ethylene. Examples of the unsaturated carboxylic acid include (meth)acrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butene tricarboxylic acid. One or more selected from the group consisting of (meth)acrylic acid, itaconic acid, and fumaric acid are preferred, and (meth)acrylic acid is more preferred. Examples of the unsaturated carboxylic acid ester include alkyl esters of unsaturated polycarboxylic acids having one or more carboxy groups, such as itaconic acid monoethyl ester, fumaric acid monobutyl ester, and maleic acid monobutyl ester. Examples of the salt include ammonium salts and alkali metal salts, and preferably ammonium salts.

[0091] The olefin-unsaturated carboxylic acid copolymer is preferably an ethylene-(meth)acrylic acid copolymer or a salt thereof, more preferably an ethylene-acrylic acid copolymer or a salt thereof.

[0092] The olefin-unsaturated carboxylic acid copolymer may be a commercially available product, such as ZAIKXEN AC (manufactured by Sumitomo Seika Chemicals Co., Ltd., an aqueous dispersion of ethylene-acrylic acid copolymer ammonium salt (acrylic acid copolymerization ratio 20%)).

[0093] The film-forming aid preferably contains both a water-soluble polymer and a water-suspendable polymer. When the film-forming aid contains a water-soluble polymer and a water-suspendable polymer, from the viewpoint of improving film-forming properties, gas barrier properties, and water vapor barrier properties, the combination of the water-soluble polymer and the water-suspendable polymer is preferably a combination in which the water-soluble polymer contains at least one selected from the group consisting of a vinyl alcohol polymer and a polyalkyleneimine, and the water-suspendable polymer contains an olefin-unsaturated carboxylic acid copolymer. More specifically, the combination of the water-soluble polymer and the water-suspendable polymer is preferably the combination (A) or (B) below. In the combination (A) or (B) below, another water-suspendable polymer and / or a water-soluble polymer may be further used in combination. For example, in the combination (A) or (B), it is also preferable that the water-soluble polymer further contains polyethyleneimine. (A) Water-soluble polymer: polyvinyl alcohol, water-suspendable polymer: ethylene-acrylic acid copolymer (B) Water-soluble polymer: polyvinyl alcohol and polyethyleneimine, water-suspendable polymer: ethylene-acrylic acid copolymer

[0094] (Other Components) The gas barrier resin layer may contain other additives as needed, as long as the effects of the present disclosure are not impaired. Examples of other additives include non-swelling layered silicates, dispersants, surfactants, antifoaming agents, wetting agents, dyes, color adjusters, and thickeners. Among these, the gas barrier resin layer preferably contains a non-swelling layered silicate, as this can improve the adhesion between the gas barrier resin layer and the adhesive protective layer. Examples of non-swelling layered silicates include kaolin, smectite, and sepiolite. When the gas barrier resin layer contains a non-swelling layered silicate, the content of the non-swelling layered silicate in the gas barrier resin layer is preferably 5 to 40% by mass, more preferably 10 to 35% by mass, and even more preferably 20 to 30% by mass.

[0095] Furthermore, the gas barrier resin layer may contain other resins in addition to the gas barrier resin, as long as the effects of the present disclosure are not impaired. Examples of other resins include, but are not limited to, vinyl chloride resins, acrylonitrile-butadiene copolymers, ABS resins, AAS resins, AES resins, vinylidene fluoride resins, vinyl fluoride resins, fluororesins, polycarbonate resins, acetal resins, polyphenylene oxide resins, polyester resins (e.g., polyethylene terephthalate and polybutylene terephthalate), polyphenylene sulfide resins, polyimide resins, polysulfone resins, polyethersulfone resins, aromatic polyester resins, polyarylate resins, polysaccharide resins (e.g., starch and starch derivatives), naturally occurring thermosetting resins (e.g., natural rubber and shellac), and modified versions thereof. The other resins may be used alone, or two or more may be used in any combination and in any ratio.

[0096] (Basis Weight of Gas Barrier Resin Layer) The basis weight (mass per unit area) of the gas barrier resin layer is not particularly limited, but is preferably 1 to 15 g / m ２ , more preferably 2 to 10 g / m ２ , more preferably 2 to 8 g / m ２ , and even more preferably 2 to 6 g / m ２ By setting the basis weight of the gas barrier resin layer to the above lower limit or more, the gas barrier properties of the laminate can be improved. On the other hand, by setting the basis weight of the gas barrier resin layer to the above upper limit or less, the redisintegration properties can be improved.

[0097] (Method for forming gas barrier resin layer) The method for forming the gas barrier resin layer is not particularly limited, but a preferred example is a coating method in which a coating liquid in which a gas barrier resin and, if necessary, an additive are dispersed in a solvent is applied to a paper substrate (or to an undercoat layer, if the laminate has an undercoat layer described below) and then dried.

[0098] The solvent for the coating liquid is not particularly limited, and examples thereof include water; and organic solvents such as ethanol, isopropyl alcohol, methyl ethyl ketone, and toluene. Among these, from the viewpoint of avoiding the problems of volatile organic solvents, an aqueous medium is preferred as the solvent for the coating liquid, and water is more preferred. In the present disclosure, "aqueous medium" means a medium containing 50% by mass or more of water.

[0099] <1-4. Adhesive Protective Layer> The adhesive protective layer is a layer disposed between the gas barrier resin layer and the sealant layer, and preferably has one surface in contact with the gas barrier resin layer and the other surface in contact with the sealant layer. The adhesive protective layer ensures adhesion between the gas barrier resin layer and the sealant layer, contributing to improving the gas barrier properties of the laminate. Furthermore, as described below, the adhesive protective layer can suppress deterioration and interlayer delamination of the gas barrier resin layer even when the sealant layer is formed by extrusion lamination.

[0100] The adhesive protective layer preferably contains a heat-resistant adhesive resin. Such adhesive resins preferably contain one or more selected from the group consisting of vinyl alcohol polymers, polyalkyleneimines, polyurethane resins, styrene-acrylic copolymers, olefin-unsaturated carboxylic acid copolymers, and acrylic resins, more preferably polyalkyleneimines, and even more preferably polyethyleneimines. The adhesive resins may be used alone or in any combination and ratio of two or more.

[0101] Examples of vinyl alcohol polymers include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Generally, saponified products of polyvinyl acetate and ethylene-vinyl acetate copolymers can be used as polyvinyl alcohol and ethylene-vinyl alcohol copolymers, respectively. The degree of saponification of the saponified product is preferably 80.0 to 100.0 mol%, more preferably 85.0 to 99.5 mol%, even more preferably 90.0 to 99.0 mol%, and even more preferably 90.0 to 95.0 mol%.

[0102] Commercially available vinyl alcohol polymers can be used. Examples of commercially available polyvinyl alcohol products include the EXCEVAL series (manufactured by Kuraray Co., Ltd.).

[0103] From the viewpoint of improving adhesion to the gas barrier resin layer, the polyalkyleneimine is preferably a polyalkyleneimine having an alkylene group with 1 to 5 carbon atoms, and is preferably polyethyleneimine. The polyethyleneimine may be a linear polyethyleneimine or a branched polyethyleneimine.

[0104] The number average molecular weight of the polyalkyleneimine is not particularly limited, but is preferably 300 to 1,000,000, more preferably 1,000 to 100,000, even more preferably 10,000 to 100,000, still more preferably 30,000 to 100,000, and particularly preferably 50,000 to 100,000. The number average molecular weight is a value calculated by a viscosity method.

[0105] Commercially available polyalkyleneimines can be used, including the Epomin series (manufactured by Nippon Shokubai Co., Ltd.).

[0106] Polyalkyleneimine exhibits high adhesiveness. Therefore, not only when polyalkyleneimine is used alone as an adhesive resin, but also when it is used in a blend with other adhesive resins, it is possible to further improve the adhesiveness between the gas barrier resin layer and the sealant layer. When polyalkyleneimine is blended with other adhesive resins, the other adhesive resins preferably contain one or more selected from the group consisting of vinyl alcohol polymers, styrene-acrylic copolymers, olefin-unsaturated carboxylic acid copolymers, and acrylic resins, and more preferably contain a vinyl alcohol polymer. Furthermore, when the polyalkyleneimine is used in combination with another adhesive resin, the ratio of the mass of the other resin to the mass of the polyalkyleneimine (mass of the other resin:polyalkyleneimine) is preferably 100:3 to 100:300, more preferably 100:5 to 100:250, even more preferably 100:10 to 100:200, still more preferably 100:20 to 100:150, and particularly preferably 100:30 to 100:120.

[0107] The polyurethane resin is not particularly limited as long as it is a polymer having a urethane bond, and any known polyurethane resin can be used.

[0108] Commercially available polyurethane resins can be used, such as the Takelac series (manufactured by Mitsui Chemicals, Inc.), NeoRez R-600 (manufactured by Kusumoto Chemicals Co., Ltd.), and Pascol WCT-304 (manufactured by Meisei Chemical Industry Co., Ltd.).

[0109] Styrene-acrylic copolymers are copolymers obtained by polymerizing a styrene compound, an acrylic compound, and, if necessary, other polymerizable compounds. Examples of styrene compounds include styrene, α-methylstyrene, vinyltoluene, p-tert-butylstyrene, and chlorostyrene, with styrene being preferred. Examples of acrylic compounds include (net)acrylic acid, (meth)acrylic acid esters, (meth)acrylamidopropanesulfonic acid, and (meth)acrylic acid sulfoalkyl sodium salts (the alkyl group has 2 to 3 carbon atoms). One or more compounds selected from the group consisting of (meth)acrylic acid and (meth)acrylic acid esters are preferred, with acrylic acid esters being more preferred. Examples of (meth)acrylic acid esters include alkyl esters of acrylic acid, with alkyl esters of acrylic acid having 1 to 6 carbon atoms being more preferred.

[0110] Commercially available styrene-acrylic copolymers can be used, including JONCRYL HSL-9012 (a styrene-acrylic copolymer manufactured by BASF) and ACRONAL S728 (a styrene-acrylic ester copolymer manufactured by BASF).

[0111] The olefin-unsaturated carboxylic acid copolymer is a copolymer or a salt thereof obtained by polymerizing an olefin, an unsaturated carboxylic acid and / or an unsaturated carboxylic acid ester, and, if necessary, other polymerizable compounds, although the method for producing the olefin-unsaturated carboxylic acid copolymer is not limited thereto.

[0112] The olefin is preferably an α-olefin such as ethylene or propylene, with ethylene being more preferred. The unsaturated carboxylic acid is preferably (meth)acrylic acid, with acrylic acid being more preferred. The unsaturated carboxylic acid ester includes alkyl esters of unsaturated polycarboxylic acids having one or more carboxy groups, such as itaconic acid monoethyl ester, fumaric acid monobutyl ester, and maleic acid monobutyl ester. The salt includes ammonium salts and alkali metal salts, with ammonium salts being preferred.

[0113] The olefin-unsaturated carboxylic acid copolymer is preferably an ethylene-(meth)acrylic acid copolymer or a salt thereof, more preferably an ethylene-acrylic acid copolymer or a salt thereof.

[0114] The olefin-unsaturated carboxylic acid copolymer may be a commercially available product, such as ZAIKXEN AC (manufactured by Sumitomo Seika Chemicals Co., Ltd., an aqueous dispersion of ethylene-acrylic acid copolymer ammonium salt (acrylic acid copolymerization ratio 20%)).

[0115] The acrylic resin is a polymer of one or more acrylic monomers selected from the group consisting of acrylic acid and acrylic acid esters, or a salt thereof, and is a polymer other than the above-mentioned "styrene-acrylic copolymer."

[0116] The acrylic resin may be either a commercially available product or a synthetic product. Examples of commercially available acrylic resins include Brightone FC-640V (manufactured by Sakata Inx Corporation), JONCRYL PDX7326 (manufactured by BASF Japan Ltd.), JONCRYL JDX-6500 (manufactured by BASF Japan Ltd.), SEIKOAT RE-2016 (manufactured by Seiko PMC Corporation), and SEIKOAT RE-2194 (manufactured by Seiko PMC Corporation).

[0117] The adhesive protective layer may contain other additives as needed, as long as they do not impair the effects of the present disclosure. Examples of other additives include dispersants, surfactants, antifoaming agents, wetting agents, dyes, color adjusters, and thickeners.

[0118] The adhesive protective layer may have a single-layer structure or a multi-layer structure, but from the viewpoint of production costs, a single-layer structure is preferable. Furthermore, each layer may be a layer containing a single resin, or a layer containing a mixed resin in which two or more resins are mixed in any combination and in any ratio.

[0119] (Basis Weight of Adhesive Protective Layer) The basis weight (mass per unit area) of the adhesive protective layer is not particularly limited, but is preferably 0.1 g / m ２or more, more preferably 0.2 to 7 g / m ２ , more preferably 0.3 to 5 g / m ２ , and even more preferably 0.5 to 4 g / m ２ , particularly preferably 0.6 to 3 g / m ２ , most preferably 0.7 to 2 g / m ２ By setting the basis weight of the adhesive protective layer to the above lower limit or more, it is possible to more effectively prevent deterioration of the gas barrier resin layer due to heat generated when the sealant layer is extrusion laminated. Furthermore, by setting the basis weight of the adhesive protective layer to the above upper limit or less, it is possible to ensure sufficient adhesion between the gas barrier resin layer and the sealant layer.

[0120] (Thickness of Adhesive Protective Layer) The thickness of the adhesive protective layer is not particularly limited, but from the same viewpoint as the basis weight of the adhesive protective layer, it is preferably 0.1 μm or more, more preferably 0.2 to 7 μm, even more preferably 0.3 to 5 μm, still more preferably 0.5 to 4 μm, particularly preferably 0.6 to 3 μm, and most preferably 0.7 to 2 μm.

[0121] (Method of Forming Adhesive Protective Layer) The method of forming the adhesive protective layer is not particularly limited, and may be lamination or coating using a coating liquid containing the above-mentioned resin, but coating is preferred.

[0122] The solvent for the coating liquid is not particularly limited, and examples thereof include water; and organic solvents such as ethanol, isopropyl alcohol, methyl ethyl ketone, and toluene. Among these, from the viewpoint of not causing problems associated with volatile organic solvents, aqueous media are preferred, and water is more preferred, as the solvent for the coating liquid.

[0123] <1-5. Sealant layer> The sealant layer is a layer that becomes the inner surface (liquid-contacting surface) of a paper product (e.g., a liquid paper container) when the paper product is formed, and the thermoplastic resin layer and the sealant layer are heat-sealed when the paper product is formed. The sealant layer is a layer that melts and adheres by heating treatment, ultrasonic treatment, etc. The sealant layer is a layer whose main component is a heat-sealable resin, and may contain components other than the heat-sealable resin (e.g., wax, pigment, etc.).

[0124] The method for forming the sealant layer is not particularly limited, and may be lamination or coating using a coating liquid in which a heat-sealable resin is dissolved or dispersed in a solvent.

[0125] When the sealant layer is formed by lamination, an adhesive layer may be formed on one side of the heat-sealable resin film, and the adhesive layer and the gas-barrier resin layer may be bonded together by dry lamination to form the sealant layer, or the sealant layer may be formed by applying a heat-sealable resin to an adhesive protective layer by extrusion lamination without using an adhesive. In the case of dry lamination, aging may be performed.

[0126] Among lamination methods, extrusion lamination has the advantages of low production costs, high production speed, and the absence of solvents, which can suppress odors in the finished product. On the other hand, forming a sealant layer by extrusion lamination has the disadvantage that the heat generated during extrusion lamination can cause the gas barrier resin layer to deteriorate, reducing the gas barrier properties of the laminate, or the adhesive strength between the gas barrier resin layer and the sealant layer to decrease, causing delamination. However, in this embodiment, the adhesive protective layer protects the gas barrier resin layer from the heat generated during extrusion lamination and can suppress deterioration of the gas barrier resin layer, thereby enabling a laminate with excellent gas barrier properties to be obtained, even when the sealant layer is formed by extrusion lamination. Furthermore, the adhesive protective layer functions as an adhesive, which can compensate for the decrease in adhesion between the gas barrier resin layer and the sealant layer due to the heat generated during extrusion lamination, thereby suppressing delamination of the sealant layer.

[0127] The heat-sealable resin is not particularly limited, but is preferably at least one selected from the group consisting of polyethylene, polyester resin, and biodegradable resin, more preferably at least one selected from the group consisting of low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), and even more preferably low-density polyethylene (LDPE). The low-density polyethylene (LDPE) may be plant-derived biomass low-density polyethylene (biomass LDPE).

[0128] The heat-sealable resin film may be a vapor-deposited film. That is, the laminate of this embodiment may further have a vapor-deposited layer. Examples of the vapor-deposited layer include a vapor-deposited layer of a metal such as aluminum, and a vapor-deposited layer of an inorganic oxide such as silica or alumina. The vapor-deposited layer can be formed by any method such as a vacuum deposition method or a sputtering method. However, it is preferable that the laminate of this embodiment does not have a metal layer or an inorganic oxide layer.

[0129] The adhesive used in the adhesive layer is not particularly limited, and any adhesive that can be used for lamination can be used. Commercially available adhesives may be used. Examples of commercially available adhesives include DIC Dry LX-500 / K W-75 (manufactured by DIC Corporation; urethane adhesive), PASLIM VM001 / 108CP (manufactured by DIC Corporation; gas barrier urethane adhesive), and MAXIVE M-100 (manufactured by Mitsubishi Gas Chemical Company, Inc.; gas barrier epoxy adhesive).

[0130] When the sealant layer is formed by lamination, the thickness of the sealant layer is not particularly limited, but is preferably 10 to 75 μm, more preferably 15 to 50 μm. By making the thickness of the sealant layer equal to or greater than the above-mentioned lower limit, the heat sealability can be improved. Furthermore, by making the thickness of the sealant layer equal to or less than the above-mentioned upper limit, the environmental impact can be reduced.

[0131] When the sealant layer is formed by lamination, the basis weight (mass per unit area) of the sealant layer is not particularly limited, but is preferably 10 to 75 g / m ２ , more preferably 15 to 50 g / m ２ By making the thickness of the sealant layer equal to or greater than the lower limit, the heat sealability can be improved, while by making the thickness of the sealant layer equal to or less than the upper limit, the environmental impact can be reduced.

[0132] When the sealant layer is formed by coating, a coating liquid in which a heat-sealable resin is dissolved or dispersed in a solvent is used. The coating liquid is preferably a liquid in which a water-dispersible resin is dispersed in a solvent. Here, "water-based" means that the liquid contains 50% by mass or more of water. That is, the sealant layer preferably contains a water-dispersible resin.

[0133] Examples of water-dispersible resins include those mentioned as water-suspendable polymers other than gas barrier resins. Preferred examples include polyolefin resins such as ethylene-vinyl acetate copolymers; acrylic resins such as styrene-acrylic copolymers; olefin-unsaturated carboxylic acid copolymers such as ethylene-(meth)acrylic acid copolymers; polyester resins; rubber-based resins such as styrene-butadiene copolymers, urethane resins; and polyamide resins. Among these, the water-suspendable polymer preferably contains an acrylic resin, and more preferably contains an aqueous acrylic resin such as a styrene-acrylic copolymer. The advantages of acrylic resins are as described above. As the acrylic resin, either commercially available or synthetic products may be used. Examples of commercially available products include those exemplified in <1-1. Thermoplastic Resin Layer>. The water-suspendable polymer may be used alone, or two or more types may be used in any combination and in any ratio.

[0134] When the sealant layer is formed by coating, the sealant layer may contain additives such as an antiblocking agent, an oil resistance improver, and a pigment. Examples of the antiblocking agent or oil resistance improver include paraffin wax, carnauba wax, and polyolefin wax. Examples of the pigment include silica and kaolin.

[0135] The solvent for the coating liquid is not particularly limited, and examples thereof include water; and organic solvents such as ethanol, isopropyl alcohol, methyl ethyl ketone, and toluene. Among these, from the viewpoint of not causing problems associated with volatile organic solvents, aqueous media are preferred, and water is more preferred, as the solvent for the coating liquid.

[0136] When the sealant layer is formed by coating, the coating amount (in terms of solid content) is not particularly limited, but is preferably 1 to 20 g / m ２ , more preferably 2 to 15 g / m ２ By setting the coating weight to the above lower limit or more, the heat sealability can be improved, and by setting the coating weight to the above upper limit or less, the redisintegration property can be improved.

[0137] <1-6. Undercoat layer> The laminate according to this embodiment preferably has an undercoat layer (hereinafter also referred to as a "clay coat layer") between the paper substrate and the gas barrier resin layer. This allows the paper substrate to be sealed and smoothed, thereby improving the gas barrier properties of the laminate.

[0138] The undercoat layer preferably contains an inorganic pigment and a binder, and more preferably is composed mainly of an inorganic pigment and a binder. The phrase "the undercoat layer is composed mainly of an inorganic pigment and a binder" means that the total content of the inorganic pigment and the binder in the undercoat layer is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, even more preferably 70 to 100% by mass, still more preferably 80 to 100% by mass, particularly preferably 90 to 100% by mass, and most preferably 95 to 100% by mass.

[0139] The undercoat layer is preferably formed by coating, in which an aqueous coating liquid is applied to the paper substrate and then dried. Forming the undercoat layer in this manner results in a undercoat layer with a high filling effect on the paper substrate. Furthermore, forming the undercoat layer in this manner allows the components of the undercoat layer to be redispersed in water when the laminate is redisintegrated, allowing for a high recovery rate of pulp, thereby improving the recyclability of the laminate.

[0140] In summary, the undercoat layer preferably contains an inorganic pigment and a binder, and is preferably formed by applying a coating liquid in which the inorganic pigment and the binder are dispersed in an aqueous medium, and then drying the coating liquid.

[0141] The inorganic pigment is not particularly limited, but examples thereof include clays such as kaolin, talc, and mica; and metal oxides. Among these, the inorganic pigment preferably contains clay, and more preferably contains kaolin. The inorganic pigment may be used alone, or two or more types may be used in any combination and in any ratio.

[0142] The aspect ratio of the inorganic pigment is preferably 1 to 10,000, more preferably 10 to 10,000, even more preferably 20 to 50, and even more preferably 30 to 40. By setting the aspect ratio of the inorganic pigment to the above upper limit or less, particularly 50 or less or 40 or less, it becomes possible to finely disperse the inorganic pigment in the undercoat layer, and the disintegration property of the paper base material during recycling can be improved.

[0143] The average particle size of the inorganic pigment is preferably 0.05 to 5 μm, more preferably 0.10 to 3 μm, and even more preferably 0.10 to 1 μm. By setting the average particle size of the inorganic pigment to the above upper limit or less, it becomes possible to finely disperse the inorganic pigment in the undercoat layer and improve the disintegration properties of the paper substrate during recycling. The term "average particle size" refers to the median diameter (d50) measured by laser diffraction / scattering particle size distribution measurement.

[0144] The content of the inorganic pigment in the undercoat layer is preferably 50 to 98% by mass, more preferably 60 to 95% by mass, even more preferably 65 to 90% by mass, and even more preferably 65 to 95% by mass. By setting the content of the inorganic pigment at or above the lower limit, the recyclability of the laminate can be improved. Furthermore, by setting the content of the inorganic pigment at or below the upper limit, the adhesion between the paper substrate and the undercoat layer can be increased, and the gas barrier properties can be further improved.

[0145] The binder is not particularly limited, but a water-dispersible polymer is preferred. From the viewpoint of recyclability, the glass transition temperature of the water-dispersible polymer is preferably −5 to 20° C., more preferably −5 to 10° C. The glass transition temperature of the water-dispersible polymer is measured in accordance with JIS K 7121 (Method for measuring the glass transition temperature of plastics; revised July 20, 2012).

[0146] The water-dispersible polymer is not particularly limited, but examples thereof include styrene-butadiene resins, (meth)acrylic (co)polymers, styrene-(meth)acrylic copolymers, olefin-unsaturated carboxylic acid copolymers such as ethylene-(meth)acrylic acid copolymers, and polylactic acid. Among these, the binder preferably contains one or more selected from the group consisting of styrene-butadiene resins, styrene-(meth)acrylic copolymers, olefin-unsaturated carboxylic acid copolymers, and polylactic acid, more preferably contains one or more selected from the group consisting of styrene-(meth)acrylic copolymers, ethylene-(meth)acrylic acid copolymers, and polylactic acid, and even more preferably contains a styrene-(meth)acrylic copolymer.

[0147] The (meth)acrylic (co)polymer is a (co)polymer of one or more monomers selected from (meth)acrylic acid and (meth)acrylic acid esters. The (meth)acrylic acid ester is not particularly limited, but is preferably an alkyl ester of (meth)acrylic acid having 1 to 12 carbon atoms. The styrene-(meth)acrylic copolymer is a copolymer of styrene and at least one monomer selected from (meth)acrylic acid and (meth)acrylic acid esters.

[0148] The binder content in the undercoat layer is preferably 2 to 50% by mass, more preferably 5 to 50% by mass, even more preferably 10 to 40% by mass, and even more preferably 15 to 40% by mass. By setting the inorganic pigment content at or above the lower limit, adhesion between the paper substrate and the undercoat layer can be increased, and gas barrier properties can be further improved. Furthermore, by setting the binder content at or below the upper limit, the recyclability of the laminate can be improved.

[0149] The undercoat layer may further contain optional components in addition to the inorganic pigment and binder, such as a dispersant, a surfactant, an antioxidant, an antistatic agent, a dye, a plasticizer, a lubricant, and a release agent.

[0150] The basis weight (mass per unit area) of the undercoat layer is preferably 3 to 30 g / m ２ , more preferably 5 to 20 g / m ２By setting the basis weight of the undercoat layer to the above lower limit or more, the sealing effect of the paper substrate can be improved. Furthermore, by setting the basis weight of the undercoat layer to the above upper limit or less, the recyclability of the laminate can be improved.

[0151] The method for forming the undercoat layer is not particularly limited, but a method of applying a dispersion containing an inorganic pigment and a binder to a paper substrate and drying it is preferred. The dispersion containing an inorganic pigment and a binder is preferably one that uses an aqueous medium such as an aqueous dispersion as a solvent.

[0152] <1-7. Optional Layer> The laminate according to this embodiment may include an optional layer other than the layers described above. However, the optional layer is a layer disposed at a position other than between the gas barrier resin layer and the adhesive protective layer, and between the adhesive protective layer and the sealant layer. Examples of the optional layer include an adhesive layer (adhesive resin layer), an inorganic substance layer, a printed layer, and a light-shielding layer. When even higher gas barrier properties are required of the laminate, the laminate preferably includes an inorganic substance layer. The material constituting the optional layer may be appropriately selected from any material, such as known materials or materials equivalent thereto. For example, examples of the inorganic substance layer include a vapor-deposited layer of a metal such as aluminum, and a vapor-deposited layer of an inorganic oxide such as silica or alumina. The vapor-deposited layer can be formed by any method, such as a vacuum deposition method or a sputtering method. However, it is preferable that the laminate according to this embodiment does not include an inorganic substance layer.

[0153] <1-8. Barrier properties of laminate> The oxygen permeability of the laminate according to this embodiment at 23°C and 85% RH is usually 10.0 mL / m ２ day atm or less, preferably 6.0 mL / m ２ ·day·atm or less, more preferably 4.0 mL / m ２ day atm or less, more preferably 3.0 mL / m ２ day atm or less, and even more preferably 2.0 mL / m ２ day atm or less, more preferably 1.5 mL / m ２ The oxygen permeability of the laminate according to this embodiment at 23°C and 85% RH is usually 0.0 mL / m ２ ・day・atm or more.

[0154] An oxygen transmission rate at 23° C. and 85% RH within the above range indicates that the film exhibits sufficient gas barrier properties even in a high humidity environment.

[0155] The oxygen permeability of the laminate according to this embodiment at 23°C and 50% RH is preferably 5.0 mL / m ２ ·day·atm or less, more preferably 3.0 mL / m ２ day atm or less, more preferably 2.0 mL / m ２ day atm or less, and even more preferably 1.5 mL / m ２ day atm or less, more preferably 1.0 mL / m ２ day atm or less, particularly preferably 0.5 mL / m ２ The oxygen permeability of the laminate according to this embodiment at 23°C and 50% RH is usually 0.0 mL / m ２ ・day・atm or more.

[0156] The oxygen permeability of the laminate at 23°C and 85% RH or 50% RH is measured in accordance with JIS K 7126-2:2006 (Plastics - Films and sheets - Gas permeability test method - Part 1: differential pressure method; established on August 20, 2006).

[0157] The water vapor permeability of the laminate according to this embodiment at 40°C and 90% RH is preferably 25 g / m ２ day or less, more preferably 20 g / m ２ day or less, more preferably 15 g / m ２ day or less, even more preferably 10 g / m ２ The water vapor permeability of the laminate according to this embodiment at 40°C and 90% RH is usually 0 g / m ２ ・day or more.

[0158] A water vapor transmission rate at 40° C. and 90% RH within the above range indicates very high water vapor barrier properties.

[0159] The water vapor permeability of the laminate at 40°C and 90% RH is measured in accordance with JIS Z 0208:1976 (Test method for moisture permeability of moisture-proof packaging materials (cup method), Method B (40±0.5°C, 90±2% RH); revised March 1, 1976).

[0160] The oxygen permeability and water vapor permeability of the laminate can be controlled, for example, by selecting the thickness of the gas barrier resin layer or the components contained in the gas barrier resin layer.

[0161] <2. Manufacturing Method of Laminate> The manufacturing method of the laminate according to this embodiment is not particularly limited, and any lamination method may be used to laminate the thermoplastic resin layer, paper base material, gas barrier resin layer, adhesive protective layer, and sealant layer in this order.

[0162] A suitable method for producing the laminate according to this embodiment includes a coating step of forming a gas barrier resin layer and an adhesive protective layer in this order on one side of a paper substrate by coating, an extrusion lamination step of forming a sealant layer on the adhesive protective layer by extrusion lamination, and a thermoplastic resin layer formation step of forming a thermoplastic resin layer on the other side of the paper substrate.

[0163] The coating in the coating step is as explained in <1-3. Gas barrier resin layer> and <1-4. Adhesive protective layer>. That is, the coating step is a step in which a coating liquid containing the constituent materials of the gas barrier resin layer is applied to a paper substrate (or to the undercoat layer if the laminate has an undercoat layer) and dried to form a gas barrier resin layer, and a coating liquid containing the constituent materials of the adhesive protective layer is applied to the gas barrier resin layer and dried to form an adhesive protective layer.

[0164] The device used to apply the coating liquid is not particularly limited and can be appropriately selected from any coating device, such as an air knife coater, blade coater, gravure coater, rod blade coater, roll coater, reverse roll coater, Mayer bar coater, curtain coater, die slot coater, champlex coater, metering blade type size press coater, short dwell coater, spray coater, gate roll coater, and lip coater.

[0165] The coating liquid may be dried using any drying device such as an oven. The drying conditions are not particularly limited as long as they are capable of removing the solvent from the coating liquid, but preferred examples include heating conditions of 50 to 200°C for 30 seconds to 30 minutes. The coating liquid may be dried under reduced pressure, but is preferably dried under normal pressure to prevent voids from forming in the layer.

[0166] As the extrusion lamination in the extrusion lamination step, known extrusion lamination methods or methods equivalent thereto can be used. The extrusion temperature in extrusion lamination is not particularly limited and can be appropriately selected depending on the type of resin used in the sealant layer. For example, when forming a sealant layer made of LLDPE, the extrusion temperature is preferably 150 to 350°C. If the extrusion temperature is too high, deterioration of the gas barrier resin layer may progress, so the extrusion temperature is preferably below the above upper limit.

[0167] The thermoplastic resin layer may be formed by lamination or coating in the thermoplastic resin layer forming step, as described in <1-1. Thermoplastic resin layer>. When the thermoplastic resin layer is formed by lamination, the lamination method can be an extrusion lamination method. When the thermoplastic resin layer is formed by coating, the same method as the coating method can be used.

[0168] <3. Paper Products> The laminate according to this embodiment has excellent gas barrier properties (particularly gas barrier properties under high humidity conditions), and therefore can be suitably used as a paper product. Preferred examples of paper products include liquid paper containers, paper containers, and paper cups, as well as packaging materials, with liquid paper containers being particularly suitable. Due to its high gas barrier properties under high humidity conditions, the laminate according to this embodiment is suitable as a packaging material for products exposed to high humidity conditions, such as food, cosmetics, daily necessities, medical products, and electronic components, as well as contents that have a fragrance or odor.

[0169] The liquid-storing paper container can be manufactured by molding the laminate of this embodiment by a known method. The shape of the liquid-storing paper container is not particularly limited, and may be, for example, a roof type (gable top type), a rectangular parallelepiped type (flat top type, brick type, straight type, etc.), a triangular pyramid type, a slant top type, a regular tetrahedron type, a cup type, a tray type, etc. Furthermore, the liquid-storing paper container may be equipped with a straw insertion hole, a spout, a lid material, etc., as long as the gas barrier properties are not impaired.

[0170] The liquid to be contained in the liquid paper container is not particularly limited and may be either food or non-food. More specifically, examples of liquids to be contained in the liquid paper container include alcoholic beverages such as sake, shochu, and wine; dairy beverages such as milk; beverages such as juice, coffee, tea, and black tea; foods such as instant foods, microwaveable foods, beverages (e.g., yogurt, jelly, and pudding), and prepared dishes; pharmaceuticals; and chemical products such as car wax, shampoo, conditioner, detergent, bath additives, hair dye, and toothpaste.

[0171] The present disclosure will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present disclosure. Therefore, the scope of the present disclosure should not be interpreted as being limited by the specific examples shown below.

[0172] Unless otherwise specified, the following operations were carried out at 25°C and a relative humidity of 50% RH. In the examples and comparative examples, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0173] Example 1 A coating liquid for forming a clay coating layer was prepared by mixing 70 parts by mass (solid content) of kaolin (Contour Xtreme, manufactured by Imerys, aspect ratio 33, average particle size d50: 0.26 μm) and 30 parts by mass (solid content) of a styrene-acrylic copolymer (ACRONAL S504, manufactured by BASF, glass transition temperature 5° C.).

[0174] Ethylene-modified polyvinyl alcohol (product name: EXCEVAL RS-1717, saponification degree 92.0 to 94.0 mol%, manufactured by Kuraray Co., Ltd.) was dissolved in water to a solids concentration of 10% by mass to obtain 100 parts by mass (solids content), to which 100 parts by mass (solids content) of polyethyleneimine (Epomin P-1000, number average molecular weight: approximately 70,000, manufactured by Nippon Shokubai) was added and stirred, and dilution water was added to make the solids concentration 8.0% by mass, thereby preparing a coating liquid for forming an adhesive protective layer.

[0175] 20.0 parts by mass (solids content) of an aqueous dispersion of swellable layered silicate (swellable mica, average length 6.3 μm, aspect ratio 1260, average thickness approximately 5 nm, solids concentration 6 mass%, product name: NTS-10NC, manufactured by Topy Industries, Ltd.) was mixed with 15.0 parts by mass (solids content) of a self-emulsifying emulsion of ethylene-acrylic acid copolymer (solids concentration 29.2 mass%, product name: ZAIKXEN AC, manufactured by Sumitomo Seika Chemicals Co., Ltd.) while stirring, and further mixed with 80.0 parts by mass (solids content) of a self-emulsifying aqueous emulsion of hydroxy polyurethane (solids concentration 30 mass%, product name: HPU-W013A, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., hydroxyl value 235 mg KOH / g, acid value 30 mg KOH / g, glass transition temperature 70° C.). To the resulting mixture, 6.0 parts by mass (solids content) of a modified polyamide resin (surface charge 0.4 meq / g, solids concentration 53% by mass, product name: SPI203(50)H, manufactured by Taoka Chemical Co., Ltd.) was added, followed by 5.0 parts by mass (solids content) of an aqueous solution prepared by dissolving ethylene-modified polyvinyl alcohol (product name: EXCEVAL RS-1717, saponification degree 92.0 to 94.0 mol%, manufactured by Kuraray Co., Ltd.) in water to a solids concentration of 10% by mass. 0.50 parts by mass of a 25% by mass aqueous ammonia solution was added to the resulting mixture, and then dilution water was added to adjust the solids concentration to 13% by mass, thereby preparing a coating solution for forming a gas barrier resin layer.

[0176] Basis weight 330g / m ２ A coating solution for forming a clay coating layer was applied to the back side (non-printing side) of a 450 μm thick paper substrate (OK Pienas, manufactured by Oji Materia Co., Ltd.) in a coating amount (solid content equivalent) of 6 g / m ２ The clay coating layer was formed by applying the coating so that the clay layer was coated with the coating solution in the following manner and drying it at 120°C for 60 seconds.

[0177] A coating solution for forming a gas barrier resin layer was applied onto the clay coating layer in an amount (solid content equivalent) of 2 g / m ２ The mixture was dried at 120° C. for 60 seconds to form a gas barrier resin layer.

[0178] The coating liquid for forming the adhesive protective layer was applied to the gas barrier resin layer of the paper substrate in an amount (solid content equivalent) of 1.0 g / m ２The adhesive protective layer was formed by coating the adhesive layer so that the adhesive protective layer was coated on the substrate in the following manner and then drying the coated adhesive layer at 120°C for 60 seconds.

[0179] A laminate having a gas barrier resin layer and a protective layer on one side of a paper substrate in that order was laminated on both sides of which polyethylene resin (Novatec LD LC522, manufactured by Japan Polyethylene Co., Ltd.) was melted at a temperature of 330°C to a thickness of 30 μm per side (basis weight: approximately 27 g / m ２ ) to form a thermoplastic resin layer and a sealant layer (LDPE layer), thereby obtaining a laminate.

[0180] Example 2 A laminate was obtained in the same manner as in Example 1, except that in preparing the coating liquid for forming the adhesive protective layer, the amount of polyethyleneimine (Epomin P-1000, manufactured by Nippon Shokubai) used was 5.0 parts by mass (solid content).

[0181] Example 3 A laminate was obtained in the same manner as in Example 1, except that an aqueous solution prepared by dissolving ethylene-modified polyvinyl alcohol (product name: EXCEVAL RS-1717, manufactured by Kuraray Co., Ltd.) alone in water to a solid content concentration of 10% by mass was used as the coating liquid for forming the adhesive protective layer.

[0182] Example 4 A laminate was obtained in the same manner as in Example 1, except that an aqueous solution in which polyethyleneimine (Epomin P-1000, manufactured by Nippon Shokubai) was dissolved alone in water to a solid content concentration of 10 mass % was used as the coating liquid for forming the adhesive protective layer.

[0183] Example 5 The coating amount (solid content equivalent) of the coating liquid for forming the adhesive protective layer was 0.3 g / m ２ A laminate was obtained in the same manner as in Example 1 except that:

[0184] Example 6 The coating amount (solid content equivalent) of the coating liquid for forming the adhesive protective layer was 4.0 g / m ２ A laminate was obtained in the same manner as in Example 1 except for the above.

[0185] Example 7 A laminate was obtained in the same manner as in Example 1, except that a polyurethane dispersion (solid content concentration 30% by mass, product name: Takelac WPB-341 (30), manufactured by Mitsui Chemicals, Inc.) was used alone as the coating liquid for forming the adhesive protective layer.

[0186] Example 8 A laminate was obtained in the same manner as in Example 1, except that a coating liquid for forming an adhesive protective layer was prepared by mixing 100 parts by mass (solid content) of an aqueous acrylic dispersion (styrene-acrylic acid ester copolymer, solid content concentration 50% by mass, product name: ACRONAL S728, manufactured by BASF Corporation) and 50 parts by mass (solid content) of polyethyleneimine (Epomin P-1000, manufactured by Nippon Shokubai).

[0187] Example 9 A laminate was obtained in the same manner as in Example 1, except that a coating liquid for forming an adhesive protective layer was prepared by mixing 100 parts by mass (solid content) of an aqueous acrylic dispersion (ethylene-acrylic acid copolymer, solid content concentration 29.2% by mass, product name: ZAIKUSEN AC, manufactured by Sumitomo Seika Chemicals) and 50 parts by mass (solid content) of polyethyleneimine (EPOMIN P-1000, manufactured by Nippon Shokubai).

[0188] Example 10 A laminate was obtained in the same manner as in Example 1, except that a coating liquid for forming an adhesive protective layer was prepared by mixing 100 parts by mass (solid content) of an aqueous acrylic dispersion (acrylic acid ester copolymer, solid content concentration 27.8% by mass, product name: Hi-Loss X PE-2273, manufactured by Seiko PMC Corporation) and 30 parts by mass (solid content) of polyethyleneimine (Epomin P-1000, manufactured by Nippon Shokubai).

[0189] Example 11 A laminate having a layer structure of paper substrate / gas barrier resin layer / adhesive protective layer was prepared in the same manner as in Example 1, and then a linear low-density polyethylene resin (Yumerit 015AN, manufactured by Ube Maruzen Polyethylene Co., Ltd.) was melted at a temperature of 300°C to a thickness of 30 μm (basis weight: approximately 27 g / m ２ A sealant layer (LLDPE layer) was formed by extrusion lamination. A polyethylene resin (Novatec LD LC522, manufactured by Japan Polyethylene Co., Ltd.) was melted on the paper substrate at a melting temperature of 330°C to a thickness of 30 μm (basis weight: approximately 27 g / m). ２ ) to form a thermoplastic resin layer (LDPE layer), thereby obtaining a laminate.

[0190] Example 12 A laminate was obtained in the same manner as in Example 1, except that a biomass LDPE resin (plant-derived polyethylene SBC818, manufactured by Toyota Tsusho Corporation) was used for the thermoplastic resin layer and the sealant layer.

[0191] Example 13 A laminate was obtained in the same manner as in Example 1, except that 1 part by mass (solid content) of polyethyleneimine (Epomin P-1000, number average molecular weight: approximately 70,000, manufactured by Nippon Shokubai Co., Ltd.) was further mixed in the coating liquid for forming the gas barrier resin layer.

[0192] Example 14 A laminate was obtained in the same manner as in Example 1, except that 50 parts by mass (solid content) of kaolin (Contour Xtreme, manufactured by Imerys, aspect ratio 33, average particle size d50: 0.26 μm) was further mixed in the coating liquid for forming the gas barrier resin layer.

[0193] Example 15: No clay coating layer was provided on the paper substrate, and the coating amount (solid content equivalent) was 4.0 g / m ２ A laminate was obtained in the same manner as in Example 1, except that the gas barrier resin layer was formed directly on the paper substrate.

[0194] Example 16 A laminate was obtained in the same manner as in Example 1, except that 80.0 parts by mass (solids content) of a self-emulsifying aqueous emulsion of hydroxy polyurethane (solids content concentration 30% by mass, product name: HPU-W013A, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) in the coating liquid for forming the gas barrier resin layer was changed to 80.0 parts by mass (solids content) of a polyurethane dispersion having meta-xylylene diisocyanate-derived structural units (solids content concentration 30% by mass, product name: Takelac WPB-341(30), manufactured by Mitsui Chemicals, Inc.). When 1H-NMR measurement was performed on the polyurethane resin, the content of meta-xylylene diisocyanate-derived structural units relative to the total amount of polyisocyanate-derived structural units was 50 mol% or more. The glass transition temperature of the polyurethane resin was 130°C.

[0195] Example 17 A coating liquid for forming a gas barrier resin layer was prepared by adding 100 parts by mass (solid content) of an aqueous solution prepared by dissolving 6.0 parts by mass (solid content) of a modified polyamide resin (surface charge 0.4 meq / g, solid content 53% by mass, product name: SPI203(50)H, product of Taoka Chemical Co., Ltd.) and ethylene-modified polyvinyl alcohol (product name: EXCEVAL HR-3010, saponification degree 99.0 to 99.4 mol%, product of Kuraray Co., Ltd.) in water to a solid content of 10% by mass to 20.0 parts by mass (solid content) of an aqueous dispersion of swellable layered silicate (swellable mica, major axis (average length) 6.3 μm, aspect ratio 1260, average thickness approximately 5 nm, solid content 6% by mass, product name: NTS-10NC, product of Topy Industries), and adding dilution water to adjust the solid content to 8% by mass.

[0196] The coating solution for forming the gas barrier resin layer was applied to the clay coating layer of the paper substrate in an amount (solid content equivalent) of 4 g / m ２ and dried at 120°C for 60 seconds to form a gas barrier resin layer.

[0197] Example 18 A laminate was obtained in the same manner as in Example 17, except that 50 parts by mass (solid content) of kaolin (Contour Xtreme, manufactured by Imerys, aspect ratio 33, average particle size d50: 0.26 μm) was further mixed in the coating liquid for forming the gas barrier resin layer.

[0198] Example 19 A coating solution for forming a gas barrier resin layer containing polyvinylidene chloride (Diofan B204, manufactured by Solvay Specialty Polymers Japan K.K.) was applied to a substrate in a coating amount (solid content equivalent) of 4 g / m ２ A laminate was obtained in the same manner as in Example 1, except that the gas barrier resin layer was formed by coating the clay layer with the mixture in a manner such that the composition satisfies the following formula (1) and drying at 120°C for 60 seconds.

[0199] Comparative Example 1 A laminate was obtained in the same manner as in Example 1, except that the coating liquid for forming the adhesive protective layer was not applied onto the gas barrier resin layer.

[0200] Comparative Example 2 The coating liquid for forming an adhesive protective layer was applied to the gas barrier resin layer of the paper substrate in a coating amount (solid content equivalent) of 0.06 g / m ２ A laminate was obtained in the same manner as in Example 1, except that the coating was performed so that the thickness of the coated layer was 1 / 4 of the total thickness of the coated layer.

[0201] Comparative Example 3 A laminate was obtained in the same manner as in Example 1, except that the modified polyamide resin (surface charge 0.4 meq / g, solid content concentration 53 mass%, product name: SPI203(50)H, manufactured by Taoka Chemical Co., Ltd.) was not mixed in the coating liquid for forming the gas barrier resin layer.

[0202] <Evaluation Method> [Oxygen Permeability] Using an oxygen permeability measuring device (OX-TRAN2 / 22 manufactured by MOCON Corporation), the oxygen permeability of the laminate was measured under conditions of 23°C and 50% RH, or 23°C and 85% RH. Specifically, the oxygen permeability of the laminates obtained in the examples and comparative examples was measured under conditions of 23°C and 50% RH, or 23°C and 85% RH in accordance with JIS K 7126-2:2006 (Plastics - Films and sheets - Gas permeability test methods - Part 1: Differential pressure method; established on August 20, 2006). The results are shown in Tables 1 and 2. The lower the oxygen permeability value, the better the gas barrier property.

[0203] [Water vapor permeability] The water vapor permeability of the laminate was measured with the sealant layer facing inward under conditions of 40°C and 90% RH in accordance with JIS Z 0208:1976 (Test method for moisture permeability of moisture-proof packaging materials (cup method), Method B (40±0.5°C, 90±2% RH); revised on March 1, 1976). The results are shown in Tables 1 and 2.

[0204] [Lamination Adhesion] After extrusion lamination, a thin cross-shaped cut was made with a cutter in the sealant layer, and the laminated portion was thinly peeled off starting from the cut. The behavior when peeled off was visually observed and evaluated according to the following criteria. If the paper substrate is destroyed, it is judged to be good because the adhesion of each layer is high. The results are shown in Tables 1 and 2. (Evaluation Criteria) S: The paper substrate is destroyed, and no lifting of the laminate at the edges is observed. A: The paper substrate is destroyed, and lifting of the laminate at the edges is observed in some places. B: The paper substrate is destroyed, but lifting of the laminate at the edges is observed overall. C: The paper substrate is not destroyed. (A rating of B or higher is considered to be a pass)

[0205]

[0206]

[0207] 10 Laminate 1 Thermoplastic resin layer 3 Paper substrate 5 Gas barrier resin layer 7 Adhesive protective layer 9 Sealant layer

Claims

1. It comprises a thermoplastic resin layer, a paper substrate, a gas barrier resin layer, an adhesive protective layer, and a sealant layer in this order, and the oxygen permeability at 23°C and 85% RH is 10.0 mL / m ２ ·day·atm or less, a laminate.

2. The basis weight of the adhesive protective layer is 0.1 g / m ２ or more, and the laminate according to claim 1.

3. The laminate according to claim 1 or 2, wherein the adhesive protective layer contains at least one selected from the group consisting of a vinyl alcohol polymer, a polyalkyleneimine, a polyurethane resin, a styrene-acrylic copolymer, an olefin-unsaturated carboxylic acid copolymer, and an acrylic resin.

4. The laminate according to any one of claims 1 to 3, wherein the adhesive protective layer contains polyethyleneimine.

5. The laminate according to any one of claims 1 to 4, wherein the gas barrier resin layer contains at least one gas barrier resin selected from the group consisting of a polyurethane resin, a vinyl alcohol polymer, and polyvinylidene chloride.

6. The laminate according to any one of claims 1 to 5, wherein the gas barrier resin layer contains a gas barrier resin, a swellable layered silicate, and a cationic resin.

7. The laminate according to claim 6, wherein the gas barrier resin layer further contains a film-forming aid, and the film-forming aid contains at least one selected from the group consisting of a water-soluble polymer other than the gas barrier resin and a water-suspensible polymer other than the gas barrier resin.

8. The laminate according to claim 7, wherein the content of the film-forming aid in the gas barrier resin layer is 2.0 to 50.0% by mass.

9. The laminate according to claim 7 or 8, wherein the ratio of the mass of the gas barrier resin to the mass of the film-forming aid (mass of the gas barrier resin: mass of the film-forming aid) in the gas barrier resin layer is 50:50 to 95:

5.

10. The laminate according to any one of claims 7 to 9, wherein the water-soluble polymer contains at least one selected from the group consisting of a vinyl alcohol polymer and a polyalkyleneimine, and the water-suspensible polymer contains an olefin-unsaturated carboxylic acid copolymer.

11. The laminate according to any one of claims 7 to 10, wherein the film-forming aid contains the water-soluble polymer and the water-suspensible polymer, and the combination of the water-soluble polymer and the water-suspensible polymer is the combination of the following (A) or (B). (A) Water-soluble polymer: polyvinyl alcohol, water-suspensible polymer: ethylene-acrylic acid copolymer (B) Water-soluble polymer: polyvinyl alcohol and polyethyleneimine, water-suspensible polymer: ethylene-acrylic acid copolymer 12. The laminate according to any one of claims 1 to 11, wherein the gas barrier resin layer contains 30.0 to 80.0% by mass of a gas barrier resin.

13. The laminate according to any one of claims 1 to 12, having an undercoat layer between the paper base material and the gas barrier resin layer, the undercoat layer containing an inorganic pigment and a binder.

14. The laminate according to claim 13, wherein the inorganic pigment contains one or more selected from the group consisting of kaolin, talc, and mica, and the binder contains one or more selected from the group consisting of styrene-(meth)acrylic copolymers, ethylene-(meth)acrylic acid copolymers, and polylactic acid.

15. A paper processed product having the laminate according to any one of claims 1 to 14.

16. A method for manufacturing a laminate according to any one of claims 1 to 14, the method comprising: a coating step of forming the gas barrier resin layer and the adhesive protective layer in this order by coating on one surface of the paper base material; an extrusion lamination step of forming the sealant layer by extrusion lamination on the adhesive protective layer; and a thermoplastic resin layer forming step of forming the thermoplastic resin layer on the other surface of the paper base material.

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