Laminate, laminate film, and package

Abstract

To provide a laminate capable of detecting gas generated from a stored object.SOLUTION: A laminate includes a resin layer (I), a moisture absorption layer (II), a gas sensitive part (III), and a resin layer (IV), wherein the resin layer (I), the moisture absorption layer (II), and the resin layer (IV) are laminated in this order, the gas sensitive part (III) is arranged so as to come in contact with the moisture absorption layer (II), oxygen permeability measured according to JIS K 7126-2 (2006) of the resin layer (I) is 5 cc / m2 day / atm or less, and water vapor permeability measured according to JIS Z 0208 (1976) of the resin layer (IV) is 10 g / m2 day or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminate, a laminate film, and a package, and more particularly to a laminate, a laminate film, and a package that can detect gas. [Background technology]

[0002] BACKGROUND ART Laminates and films that prevent corrosion and decay of the contents and enable long-term storage are widely used as packaging materials for packaging foodstuffs, pharmaceuticals, medical products, industrial parts, and the like. Known examples of such laminates and laminate films include laminates and laminate films in which a layer (referred to as an "inorganic layer") primarily made of an inorganic material, such as an inorganic oxide vapor deposition layer, is formed on the surface of a substrate containing a thermoplastic resin.

[0003] Furthermore, when packaging is used, it is usually difficult to check the state of the contents, so methods for checking the state of the contents from the outside have been studied.

[0004] For example, Patent Document 1 discloses a detector having a sensing part made of a binder and a reactive dye that changes color upon reacting with ammonia, an odorous component produced as food decays.

[0005] Furthermore, Patent Document 2 discloses a detector in which an adhesive label having a functional part capable of detecting oxygen is attached to the outside of a package, and the detector passes through an air passage to detect the environment inside the package.

[0006] Furthermore, Patent Document 3 discloses a freshness label that includes a component that reacts with components generated by food spoilage along with a support, and the amount of reaction changes gradually depending on the degree of spoilage. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-278926 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-313934 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-184332 Summary of the Invention [Problem to be solved by the invention]

[0008] The techniques disclosed in Patent Documents 1 and 3 require a detector or a freshness label to be placed inside the package. The technique disclosed in Patent Document 2 requires a hole to be drilled in the package and a detector to be attached. Therefore, there is a demand for a method that allows the state of the contents to be checked more easily.

[0009] Therefore, an object of the present invention is to provide a laminate, a laminate film, and a package that can detect gas generated from a contained item. [Means for solving the problem]

[0010] In view of the above-mentioned circumstances, the inventors have conducted extensive research and have found that gas generated from the contents can be easily detected by arranging a gas sensing unit (III) in contact with the moisture absorbent layer (II) in a laminate in which a resin layer (I), a moisture absorbent layer (II), and a resin layer (IV) are laminated in this order, and by setting the oxygen permeability of the resin layer (I) and the water vapor permeability of the resin layer (IV) within specific ranges, thereby completing the present invention.

[0011] That is, the present invention has the following aspects. [1] A laminate comprising a resin layer (I), a moisture absorbing layer (II), a gas sensing part (III), and a resin layer (IV), the resin layer (I), the moisture absorption layer (II), and the resin layer (IV) are laminated in this order; the gas sensing part (III) is disposed in contact with the moisture absorbing layer (II), The resin layer (I) has an oxygen permeability of 5 cc / m as measured in accordance with JIS K7126-2 (2006). 2 -day / atm or less, The water vapor permeability of the resin layer (IV) measured in accordance with JIS Z0208 (1976) is 10 g / m 2 · Day or more, laminate. [2] The laminate according to [1], wherein the resin layer (IV) has a layer made of a composition containing polymethylpentene as a main component. [3] The laminate according to [1] or [2], wherein the moisture-absorbing layer (II) is made of a composition containing a polyvinyl alcohol-based resin as a main component. [4] The laminate according to [3], wherein the polyvinyl alcohol resin has an average degree of saponification of 86 to 100 mol %. [5] The laminate according to [3] or [4], wherein the polyvinyl alcohol resin has an average degree of polymerization of 200 to 3,000. [6] The laminate according to any one of [1] to [5], wherein the gas sensing part (III) contains a pH-discoloring dye. [7] The laminate according to any one of [1] to [6], wherein the gas sensing part (III) is formed on the moisture absorbing layer (II). [8] The laminate according to any one of [1] to [7], wherein the moisture absorbing layer (II) comprises the gas sensing part (II). [9] The laminate according to any one of [1] to [7], wherein the moisture absorbing layer (II) has a thickness of 1 to 60 μm.

[10] The laminate according to any one of [1] to [9], wherein the resin layer (I) contains at least one thermoplastic resin selected from the group consisting of polyamide-based resins, polyolefin-based resins, polyester-based resins, and polystyrene-based resins.

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

[10] , wherein the resin layer (I) is composed of at least two layers and has a barrier layer.

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

[11] , wherein the resin layer (I) is stretched in at least one direction.

[13] A laminate film comprising the laminate according to any one of [1] to

[12] .

[14] A package using the laminated film described in

[13] . [Effects of the Invention]

[0012] The laminate of the present invention can easily detect gases generated from contained items, and therefore the laminate of the present invention can be suitably used as a material for packaging. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described below based on examples of embodiments for carrying out the present invention, but the present invention is not limited to the embodiments described below.

[0014] In this specification, "X and / or Y (X and Y are any configurations)" means at least one of X and Y, and means three possibilities: X only, Y only, and X and Y. When expressed as "X to Y" (X and Y are any numbers), unless otherwise specified, it means "X or more and Y or less," as well as "preferably larger than X" or "preferably smaller than Y." When expressed as "X or more" (X is any number) or "Y or less" (Y is any number), it also means that "it is preferably greater than X" or "it is preferably less than Y." In the present specification, when numerical ranges are described in stages, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In addition, in the numerical ranges described in this specification, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the examples. In this specification, the term "main component" means a component that has a significant effect on the properties of the target object, and the content of the component is usually 50% by mass or more in the target object, preferably 55% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass. In this specification, the term "film" has a comprehensive meaning ranging from thick sheets to thin films.

[0015] <<Laminate>> A laminate according to one embodiment of the present invention (hereinafter referred to as "the laminate") is a laminate comprising a resin layer (I), a moisture absorbing layer (II), a gas sensing part (III), and a resin layer (IV), in which the resin layer (I), moisture absorbing layer (II), and resin layer (IV) are laminated in this order, the gas sensing part (III) is disposed in contact with the moisture absorbing layer (II), and the resin layer (I) has a specific oxygen permeability, and the resin layer (IV) has a specific water vapor permeability.

[0016] In this specification, "the gas sensing unit (III) is arranged in contact with the moisture absorption layer (II)" means that a part or all of the gas sensing unit (III) is arranged in direct contact with the moisture absorption layer (II), but also includes an arrangement in which the gas sensing unit (III) is in indirect contact with the moisture absorption layer (II) via another member or the like. More specifically, the gas sensing unit (III) is arranged so that the shortest distance from the moisture absorption layer (II) is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less. If the shortest distance between the gas sensing unit (III) and the moisture absorption layer (II) is within this range, an effect equivalent to that obtained when they are in contact with each other can be obtained.

[0017] In the present laminate, the resin layer (I) is an outer layer, and the resin layer (IV) is an inner layer. Here, the "outer layer" means the layer that comes into contact with the outside air when the laminate is made into a package, and the "inner layer" means the layer that is closest to the contents. Furthermore, "a layer in contact with the outside air" means that the layer is placed in direct contact with the outside air, but it may also be placed in indirect contact with the outside air via other members, etc. More specifically, the layer is preferably placed so that the shortest distance between the outside air and the "outer layer" is 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less. If the shortest distance between the outside air and the "outer layer" is within this range, an effect equivalent to that of contact can be obtained.

[0018] When this laminate is used as a package, it can detect gases generated from the contents contained therein, and the mechanism by which this occurs is presumed to be as follows. In this laminate, the resin layer (IV) has a relatively high water vapor permeability. Therefore, water vapor and the like inside the package permeate through the resin layer (IV), which is the inner layer, and is absorbed and retained by the moisture-absorbing layer (II). Furthermore, gas generated from the contents is also absorbed by the moisture-absorbing layer (II) and is retained in the moisture-absorbing layer (II). In addition, the resin layer (I), which is the outer layer of this laminate, has a low oxygen permeability, so the gas retained in the moisture-absorbing layer (II) can be kept in the moisture-absorbing layer (II). Therefore, this laminate can detect the generated gas by the gas-sensing unit (III) arranged in contact with the moisture-absorbing layer (II).

[0019] There are no particular limitations on the gases that can be detected by the present laminate, but it is preferable that they are volatile amines such as ammonia, monomethylamine, dimethylamine, and trimethylamine, which are generated when protein-rich foods such as meat and fish spoil.

[0020] The shape of the present laminate is not particularly limited, and may be a plate or film, but it is preferably a film, that is, the present laminate is preferably a laminate film. Each layer of the laminate will now be described.

[0021] <Resin layer (I)> The resin layer (I) has an oxygen permeability of 5 cc / m as measured in accordance with JIS K7126-2 (2006). 2 day / atm or less, preferably 4cc / m 2 ·day / atm or less, preferably 2cc / m 2 ·day / atm or less. By setting the oxygen permeability of the resin layer (I) within the above range, gas generated from the contents can be trapped in the moisture absorption layer (II), making it easier for the gas sensing part (III) to sense the gas. Also, by setting the oxygen permeability within the above range, it is possible to prevent the intrusion of oxygen and the like from the outside, thereby maintaining the freshness of the contents.

[0022] The resin layer (I) can be formed into a plate or film shape, and may be a single layer or multiple layers as long as it satisfies the above oxygen permeability. The resin layer (I) preferably has a substrate layer formed from a composition containing a thermoplastic resin, and the thermoplastic resin is more preferably the main component of the composition. When the resin layer (I) is multi-layered, substrate layers containing the same type of thermoplastic resin may be laminated, or substrate layers containing different types of thermoplastic resin may be laminated. When the resin layer (I) has multiple layers, the layers can be laminated together by a general molding method such as coextrusion or dry lamination.

[0023] [Thermoplastic resin] The thermoplastic resin preferably includes at least one thermoplastic resin selected from the group consisting of polyamide-based resins, polyolefin-based resins, polyester-based resins, and polystyrene-based resins, more preferably polyolefin-based resins, polyester-based resins, and polystyrene-based resins, and particularly preferably polyester-based resins.

[0024] [Polyamide resin] Examples of the polyamide resin include polyamide resins obtained by polycondensation of aliphatic, alicyclic, or aromatic diamines such as hexamethylenediamine, decamethylenediamine, dodecamethylenediamine, trimethylhexamethylenediamine, 1,3- or 1,4-bis(aminomethyl)cyclohexane, bis(p-aminocyclohexylmethane), or m- or p-xylylenediamine with aliphatic, alicyclic, or aromatic dicarboxylic acids such as adipic acid, suberic acid, sebacic acid, cyclohexanedicarboxylic acid, terephthalic acid, or isophthalic acid; polyamide resins obtained by condensation of aminocarboxylic acids such as ε-aminocaproic acid and 11-aminoundecanoic acid; polyamide resins obtained from lactams such as ε-caprolactam and ε-laurolactam; and copolymer polyamide resins thereof.

[0025] Specific examples of polyamide resins include polyamide-6, polyamide-6,6, polyamide-6,10, polyamide-9, polyamide-11, polyamide-12, polyamide-6 / 6,6, polyamide-6 / 6,10, and polyamide-6 / 11.

[0026] [Polyolefin resin] Examples of the polyolefin resin include homopolymers obtained by polymerizing α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene, and copolymers containing α-olefins as the main monomer component. Among these, polyethylene resins containing ethylene as the main monomer component and polypropylene resins containing propylene as the main monomer component are preferred from the standpoint of transparency, etc. Here, the main monomer component refers to a monomer component that accounts for 50 to 100% by mass of the resin.

[0027] The polyethylene resin is not particularly limited as long as it is a resin containing ethylene as the main monomer component, and examples thereof include low-density polyethylene, linear low-density polyethylene, linear very low-density polyethylene, medium-density polyethylene, and high-density polyethylene. The polyethylene resin may be an ethylene homopolymer, or a copolymer containing ethylene as a main monomer component and other copolymerizable monomer components.

[0028] Examples of the other copolymerizable monomer components (comonomers) include α-olefins having 3 to 10 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene, vinyl esters such as vinyl acetate and vinyl propionate, unsaturated carboxylic acid esters such as methyl (meth)acrylate and ethyl (meth)acrylate, and ionomers thereof, and unsaturated compounds such as conjugated dienes and non-conjugated dienes. These can be used alone or in combination of two or more.

[0029] Examples of the polypropylene resin include a homopolymer of propylene, and a random copolymer or block copolymer containing propylene as a main monomer and other copolymerizable monomers.

[0030] Examples of the other copolymerizable monomers include α-olefins having 2 to 20 carbon atoms, such as ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene, and dienes, such as divinylbenzene, 1,4-cyclohexadiene, dicyclopentadiene, cyclooctadiene, and ethylidene norbornene, etc. These can be used alone or in combination of two or more.

[0031] Specific examples of the polypropylene copolymer include propylene-ethylene copolymer, propylene-α-olefin copolymer, propylene-ethylene-butene-1 copolymer, propylene-ethylene-α-olefin copolymer, block polypropylene, random polypropylene, and homopropylene.

[0032] [Polyester resin] The polyester resin may be, for example, a resin obtained by copolymerizing a diol component and a dicarboxylic acid component.

[0033] Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, tetramethylcyclobutanediol, 2,2-bis(4-hydroxyethoxyphenyl)propane, 4,4'-thiodiphenol, bisphenol A, 4,4'-methylenediphenyl, 4,4'-hydroxybiphenol, and dihydroxybenzene. These diol components can be used alone or in combination of two or more.

[0034] Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, diphenylcarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfoisophthalic acid, and phthalic acid, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, eicosanoic acid, adipic acid, sebacic acid, dimer acid, dodecanedioic acid, maleic acid, and fumaric acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and polyfunctional acids such as trimellitic acid and pyromellitic acid. These dicarboxylic acid components can be used alone or in combination of two or more.

[0035] Specific examples of the polyester resin include polyethylene terephthalate, polyethylene naphthalate, and glycol-modified polyethylene terephthalate, with polyethylene terephthalate being preferred.

[0036] [Polystyrene resin] The polystyrene resin is a resin having a styrene structure as part or all of the repeating unit, and examples thereof include copolymers of styrene monomers such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, p-chlorostyrene, p-nitrostyrene, p-aminostyrene, p-carboxystyrene, and p-phenylstyrene with other monomers such as ethylene, propylene, butadiene, isoprene, acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, acrylic acid, methacrylic acid, maleic anhydride, and vinyl acetate. Other examples of polystyrene resins include polystyrene mixed with a small amount of butadiene rubber particles, known as high impact polystyrene (HIPS).

[0037] [Other resins] The composition may contain resins other than the thermoplastic resins described above, such as thermosetting resins such as epoxy resins, polyphenylene ether resins, polyimide resins, phenolic resins, and orthodivinylbenzene resins, silicone resins, and fluororesins, which may be used alone or in combination of two or more.

[0038] When the composition contains other resins, the content thereof is usually 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 1% by mass or less, relative to 100% by mass of the total of the components contained in the composition, from the viewpoint of mechanical properties and heat resistance.

[0039] Furthermore, the composition may contain, as necessary, conventionally known additives such as antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, ultraviolet absorbers, etc., to the extent that the effects of the present invention are not impaired. These may be used alone or in combination of two or more.

[0040] The substrate layer can be obtained by molding a composition containing the thermoplastic resin into a plate or film shape by melt extrusion or the like using a general molding method such as melt extrusion molding, hot pressing, etc. However, the method for manufacturing the substrate layer is not limited to this method.

[0041] The resin layer (I) is preferably made up of at least two layers and has a barrier layer, that is, the resin layer (I) has a barrier layer in addition to the substrate layer, in order to reduce oxygen permeability.

[0042] [Barrier layer] The barrier layer may be an inorganic layer or a barrier resin layer.

[0043] [Inorganic layer] The inorganic layer may be, for example, a layer containing an inorganic substance, particularly an inorganic oxide, an inorganic nitride, or an inorganic oxynitride, as a main component.

[0044] Examples of the inorganic substance include inorganic compounds such as silicon oxide, silicon nitride, silicon oxynitride, silicon oxide carbide, silicon oxide carbonitride, aluminum oxide, aluminum nitride, aluminum oxynitride, and aluminum oxide carbide. These may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of silicon oxide, silicon nitride, and aluminum oxide is preferred.

[0045] The inorganic layer may contain alkali metal ions or alkaline earth metal ions to reduce oxygen permeability.

[0046] The inorganic layer may contain an organic material in addition to the inorganic material. By mixing the inorganic and organic materials to form the inorganic layer, the inorganic layer can be made relatively flexible. Providing such a flexible layer can sometimes reduce the oxygen permeability. That is, if the inorganic layer does not contain an organic material and the substrate layer has coarse protrusions on its surface, these coarse protrusions can act as starting points to cause tiny defects called pinholes on the surface of the inorganic layer. Furthermore, if the substrate layer has coarse protrusions on its surface, the raw material may fly in clumps and adhere to the surface of the inorganic layer when the inorganic layer is formed by vapor deposition, causing tiny defects on the surface of the inorganic layer. Gas may pass through the voids created by these defects, increasing the oxygen permeability of the resin layer (I). In such cases, mixing an organic material to make the inorganic layer flexible can reduce the oxygen permeability of the resin layer (I).

[0047] Examples of the organic material include organic polymers such as polyester resins, acrylic resins, urethane resins, and polyvinyl alcohol resins, as well as organic fillers, etc. These can be used alone or in combination of two or more.

[0048] When the inorganic layer contains an organic substance, the mass ratio of the inorganic substance to the organic substance (inorganic substance / organic substance) is usually 1 / 99 to 99 / 1, preferably 10 / 90 to 80 / 20, and more preferably 20 / 80 to 60 / 40. When the ratio of the inorganic substance to the organic substance is within the above range, the inorganic layer tends to be a flexible layer.

[0049] Examples of the inorganic layer include a PVD inorganic layer formed by a physical vapor deposition (PVD) method, a plasma-assisted deposition inorganic layer formed by a plasma-assisted deposition method, a CVD inorganic layer formed by a chemical vapor deposition (CVD) method, and a coated inorganic layer formed by a method in which an inorganic substance is dispersed in an organic polymer and coated.

[0050] [Barrier resin layer] The barrier resin layer is formed from a composition containing a barrier resin as a main component. Examples of the barrier resin include polyamide resins and ethylene vinyl alcohol resins (EVOH).

[0051] (Polyamide resin) As the polyamide-based resin, the polyamide-based resins described above can be used.

[0052] (EVOH) The EVOH is a resin obtained by saponifying a copolymer of ethylene and vinyl acetate with an alkali catalyst or the like.

[0053] The content of ethylene structural units in the EVOH is not particularly limited, but from the viewpoint of film formation stability, it is usually 20 mol% or more, preferably 29 mol% or more, and more preferably 32 mol% or more, and from the viewpoint of gas barrier properties, it is usually 60 mol% or less, preferably 47 mol% or less, and more preferably 44 mol% or less. The saponification degree of EVOH is usually 90% or more, preferably 95% or more. By setting the content of ethylene structural units and the degree of saponification of EVOH within the above ranges, it tends to be possible to improve the gas barrier properties, mechanical strength, etc. These may be used alone or in combination of two or more.

[0054] It should be noted that the EVOH is not limited to those produced by saponification, as long as they have a similar chemical structure.

[0055] Furthermore, the composition for forming the barrier resin layer may contain, as necessary, conventionally known additives such as antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, ultraviolet absorbers, etc., to the extent that the effects of the present invention are not impaired. These may be used alone or in combination of two or more.

[0056] The barrier resin layer can be obtained by forming a composition containing the above-mentioned thermoplastic resin into a plate or film shape by melt extrusion or other common forming methods such as melt extrusion, hot pressing, etc. However, the method for producing the barrier resin layer is not limited to this method. The substrate layer and the barrier resin layer can be laminated together by a general molding method such as coextrusion or dry lamination.

[0057] [Other ingredients] The resin layer (I) may contain particles mainly for the purpose of roughening the surface of the resin layer (I) to impart slipperiness and preventing scratches during the manufacturing steps described below.

[0058] The particles are not particularly limited as long as they are particles that can impart lubricity, and examples thereof include inorganic particles such as silica calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, and organic particles such as acrylic resins, styrene resins, urea resins, phenolic resins, epoxy resins, and benzoguanamine resins. These particles can be used alone or in combination of two or more.

[0059] The shape of the particles is not particularly limited, and may be, for example, spherical, blocky, rod-like, flat, or the like. Furthermore, there are no particular limitations on the hardness, specific gravity, color, etc. of the particles as long as they do not affect the effects of the present invention.

[0060] The average particle size of the particles is usually 5 μm or less, preferably 0.01 to 3.0 μm, and more preferably 0.5 to 2.5 μm.

[0061] When the resin layer (I) contains particles, the content thereof is usually 5% by mass or less, preferably 0.0003 to 3% by mass, and more preferably 0.01 to 2% by mass, relative to 100% by mass of the total components contained in the resin layer (I). By setting the particle content within this range, it tends to be possible to achieve both smoothness and transparency of the resin layer (I).

[0062] When the resin layer (I) is in the form of a film, the resin layer (I) may be unstretched or stretched, but from the viewpoint of mechanical strength, it is preferable that it is stretched in at least one direction, and more preferably that it is biaxially stretched. The stretching may be uniaxial or biaxial according to a known method. When the resin layer (I) is a biaxially stretched film, the biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching.

[0063] The stretching ratio, in terms of area ratio, is usually 1.2 to 8, preferably 1.3 to 7, and more preferably 1.5 to 5. When the stretching ratio is within the above range, the film tends to be able to be stretched without breaking.

[0064] The thickness of the resin layer (I) is usually 1 to 100 μm, preferably 2 to 80 μm, and more preferably 5 to 30 μm. When the thickness of the resin layer (I) is within the above range, gas generated from the contents tends to be easily retained in the moisture absorbing layer (II) and the intrusion of oxygen and the like from the outside tends to be prevented.

[0065] <Moisture absorption layer (II)> In this laminate, water vapor and the like are absorbed by the moisture absorption layer (II), and gas generated from the contents is dissolved in this moisture absorption layer (II), so that the gas is retained in the moisture absorption layer (II), and gas can be detected by the gas sensing part (III) in contact with the moisture absorption layer (II).

[0066] The moisture-absorbing layer (II) is preferably formed from a composition containing, as a main component, a moisture-absorbing resin such as a polyvinyl alcohol resin or cellulose acetate. These moisture-absorbing resins can be used alone or in combination of two or more. Among them, polyvinyl alcohol resins are preferred in terms of moisture absorption. A polyvinyl alcohol (hereinafter referred to as "PVA")-based resin, which is a preferred hygroscopic resin, will be described below.

[0067] [PVA resin] The PVA resin generally excludes resins known as EVOH (ethylene content: 20 to 60 mol%).

[0068] The PVA resin is preferably an unmodified PVA resin, but a modified PVA resin may also be used.

[0069] The unmodified PVA resin can usually be produced by saponifying a polyvinyl ester resin obtained by polymerizing a vinyl ester monomer. The modified PVA resin can be produced by saponifying a polyvinyl ester resin, which is a polymer of a vinyl ester monomer and another unsaturated monomer, or by post-modifying an unmodified PVA resin.

[0070] Examples of the vinyl ester monomer include aliphatic vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versatate, and vinyl trifluoroacetate, and aromatic vinyl esters such as vinyl benzoate. Among these, aliphatic vinyl esters having 3 to 20 carbon atoms are preferred, more preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms, with vinyl acetate being particularly preferred. These monomers are usually used alone, but multiple types may be used simultaneously as necessary.

[0071] Examples of the other unsaturated monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid, or their salts or mono- or di-alkyl esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid, or their salts; alkyl vinyl ethers; N-acrylamidomethyltrimethylammonium chloride; allyl trimethylammonium chloride; dimethylallyl vinyl ketone; N-vinylpyrrolidone; vinyl chloride; vinylidene chloride; polyoxyethylene; Examples of suitable olefins include polyoxyalkylene (meth)allyl ethers such as polyethylene (meth)allyl ether and polyoxypropylene (meth)allyl ether, polyoxyalkylene (meth)acrylates such as polyoxyethylene (meth)acrylate and polyoxypropylene (meth)acrylate, polyoxyalkylene (meth)acrylamides such as polyoxyethylene (meth)acrylamide and polyoxypropylene (meth)acrylamide, polyoxyethylene (1-(meth)acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, and polyoxypropylene vinylamine. These may be used alone or in combination of two or more. The term "(meth)allyl" refers to allyl or methallyl, "(meth)acrylate" refers to acrylate or methacrylate, and "(meth)acrylic" refers to acrylic or methacrylic, respectively.

[0072] The PVA resin can be obtained by any known polymerization method, saponification method, or post-modification method.

[0073] The amount of the other unsaturated monomer introduced and the amount of modification by post-modification are appropriately set depending on the type of monomer, but are usually 15 mol% or less, preferably 10 mol%, and more preferably 5 mol% or less. If the amount of introduction and the amount of modification are within the above-mentioned ranges, the crystallinity of the PVA resin becomes appropriate, and the water resistance of the film tends to be improved.

[0074] The average saponification degree of the PVA resin is usually 70 to 100 mol%, preferably 80 to 100 mol%, particularly preferably 85 to 100 mol%, further preferably 86 to 100 mol%, and particularly preferably 90 to 99.99 mol%. When the average saponification degree of the PVA resin is within the above range, it tends to have excellent moisture absorption properties. The average saponification degree is measured in accordance with JIS K6726 (1994).

[0075] The average degree of polymerization of the PVA resin is usually 100 to 4000, preferably 200 to 3000, and particularly preferably 250 to 2500. When the average degree of polymerization is within the above range, the PVA resin tends to have excellent moisture absorption properties. The average degree of polymerization is measured in accordance with JIS K6726 (1994).

[0076] Furthermore, two or more types of PVA resins differing in the type of modification, the amount of modification, the average degree of saponification, the average degree of polymerization, etc. may be used in combination.

[0077] The PVA resin generally contains a carboxylate salt, which is a by-product of the saponification of a polyvinyl ester resin during the production of the PVA resin, due to a reaction between a carboxylic acid derived from a vinyl ester monomer and a saponification catalyst. In the moisture absorption layer (II), the content of carboxylate contained in the PVA resin tends to be relatively small, which makes it easier to sense gases.

[0078] Examples of the carboxylic acid in the carboxylate include formic acid, acetic acid, propionic acid, butyric acid, and valeric acid, and acetic acid is preferred.

[0079] Examples of the carboxylic acid salt include alkali metal salts, alkaline earth metal salts, and ammonium salts, with alkali metal salts being preferred. Examples of the alkali metal include lithium, sodium, and potassium, with sodium being preferred.

[0080] The content of the carboxylate in the moisture-absorbing layer (II) [a composition containing a moisture-absorbing resin as a main component] is usually 0.01 to 2 mass%, preferably 0.01 to 1 mass%, and more preferably 0.0.1 to 0.5 mass%. When the content of the carboxylate is within this range, gas detection tends to be easier. If the content of the carboxylate is too high, the buffering effect tends to make it difficult to change the pH, making gas detection difficult. If the content is too low, the PVA resin tends to be hydrolyzed, resulting in poor gas absorption. The content of the carboxylate salt is determined in accordance with the method for measuring the amount of sodium acetate specified in JIS K6726.

[0081] Examples of methods for adjusting the content of the carboxylate in the moisture-absorbing layer (II) to fall within the above range include i) adding the carboxylate to a composition containing a moisture-absorbing resin as a main component, and ii) adjusting the content of the carboxylate by washing the carboxylate produced as a by-product during the production of the PVA-based resin. Among these, method ii) is preferred.

[0082] Methanol is usually used as the washing solution in the method ii), and washing is carried out using methanol in a bath ratio of 2 to 20 times (preferably 5 to 12 times) the weight of the PVA-based resin to be washed. The washing temperature is 10 to 50°C (preferably 15 to 30°C), the washing time is 10 minutes to 5 hours (preferably 1 to 4 hours), and the number of washings is 0 to 3 times (preferably 0 or 1 time).

[0083] Furthermore, the composition containing the moisture-absorbing resin as a main component may also contain, as necessary, a thermoplastic resin other than the moisture-absorbing resin, or conventionally known additives such as antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, ultraviolet absorbers, etc., within the range that does not impair the effects of the present invention. These may be used alone or in combination of two or more.

[0084] The moisture-absorbing layer (II) can be obtained by coating a composition containing a moisture-absorbing resin as a main component in a liquid state, dissolved and dispersed in an appropriate solvent, preferably onto the resin layer (I) and / or the resin layer (IV), and then drying the layer.

[0085] The solvent is not particularly limited as long as it dissolves or disperses the hygroscopic resin, and examples thereof include water, alcohol, etc. Usually, a combination of water and alcohol is used. Examples of the alcohol include lower alcohols having 1 to 5 carbon atoms such as methanol, ethanol, propanol, n-butanol, isopropanol, etc., and ethanol is preferred.

[0086] When the solvent contains water and alcohol, the ratio of water present in the solvent (water / alcohol) is preferably 5 or more, more preferably 6 or more, even more preferably 7 or more, and particularly preferably 8 or more. The upper limit is usually 25, preferably 20. When the ratio of water present is within the above range, the storage stability of the liquid tends to be improved. The ratio of water present in the solvent is the value obtained by dividing the mass of water in the solvent by the mass of alcohol in the solvent.

[0087] As for the drying conditions, the drying temperature is usually 50 to 150° C., preferably 60 to 120° C., and particularly preferably 70 to 90° C. The drying time is usually 1 to 20 minutes, preferably 2 to 15 minutes, and particularly preferably 3 to 10 minutes.

[0088] The thickness of the moisture absorption layer (II) is preferably 1 to 60 μm, more preferably 2 to 40 μm, and particularly preferably 5 to 20 μm. When the thickness of the moisture absorption layer (II) is within the above range, it tends to be able to better retain gas generated from the contents.

[0089] <Gas sensing section (III)> This laminate can check the condition of the contents by detecting gases generated from the contents with the gas sensing part (III). In particular, when the contents are protein-rich foods such as meat or fish, they spoil and generate various volatile amines such as ammonia, monomethylamine, dimethylamine, and trimethylamine as gases. By detecting these volatile amine components, the condition of the contents can be checked without opening the package.

[0090] When the gas sensing unit (III) detects volatile amines, the gas sensing unit (III) is preferably formed from a composition containing a dye that changes color depending on pH (hereinafter also referred to as "pH-color-changing dye"). Furthermore, in consideration of the possibility that the pH-discoloring dye may come into contact with the contents, it is preferable that the pH-discoloring dye is derived from a natural product and has low toxicity.

[0091] Examples of the pH-discoloring pigments derived from natural products include anthocyanin pigments such as red cabbage pigment, purple sweet potato pigment, grape skin pigment, grape juice pigment, elderberry pigment, purple cornstarch pigment, perilla pigment, and hibiscus pigment. In addition to the above, other dyes that react with decaying components may be used, such as quinone dyes such as cochineal dye, lac dye, and madder dye, which develop a purple-red color in alkaline conditions, turmeric dyes that turn reddish-brown in alkaline conditions, carotenoid dyes, flavonoid dyes, and porphyrin dyes.

[0092] Furthermore, in this laminate, since the contents are not in direct contact with the gas sensing unit (III), a chemical generally used as a pH indicator may be used as the pH color-changing dye. Examples of the pH indicator include malachite green, thymol blue, methyl yellow, bromophenol blue, methyl orange, bromocresol green, methyl red, bromocresol purple, bromothymol blue, phenol red, naphtholphthalein, phenolphthalein, and thymolphthalein. These can be used alone or in combination of two or more. Among these, bromothymol blue is particularly preferred due to its high sensitivity.

[0093] The content of the pH-discoloring dye is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 1 part by mass, and particularly preferably 0.1 to 0.5 part by mass, relative to 100 parts by mass of the solid content of the composition containing the hygroscopic resin as a main component. When the content of the pH-discoloring dye is within the above range, the gas sensitivity tends to be excellent.

[0094] The composition containing the pH-discoloring dye may also contain a binder. Examples of the binder include rosin, ceramic, rosin-modified phenolic resin, ketone resin, butyral resin, styrene-maleic acid resin, acrylic resin, polyester resin, alkyd resin, polyamide resin, epoxy resin, polyurethane resin, vinyl acetate resin, PVA resin, sodium polyacrylate, polyvinylpyrrolidone, polyethylene glycol, cellulose esters, methylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, gelatin, agar, agarose, starch, sodium alginate, locust bean gum, carrageenan, etc. These may be used alone or in combination of two or more.

[0095] The composition containing the pH-discoloring dye is usually used in the form of a liquid dissolved or dispersed in a suitable solvent. The solvent is not particularly limited as long as it is a solvent that dissolves or disperses, and examples thereof include water, alcohol, etc., and a combination of water and alcohol is usually used. Examples of the alcohol include lower alcohols having 1 to 5 carbon atoms, such as methanol, ethanol, propanol, n-butanol, and isopropanol. These can be used alone or in combination of two or more. Among these, ethanol is preferred.

[0096] When the solvent contains water and alcohol, the ratio of water present in the solvent (water / alcohol) is preferably 5 or more, more preferably 6 or more, even more preferably 7 or more, and particularly preferably 8 or more. The upper limit is usually 25, preferably 20. When the ratio of water present is within the above range, the storage stability of the liquid tends to be improved. The ratio of water present in the solvent is the value obtained by dividing the mass of water in the solvent by the mass of alcohol in the solvent.

[0097] As described above, in this laminate, the gas sensing part (III) is disposed in contact with the moisture absorbing layer (II). The gas sensing part (III) may be disposed in contact with the moisture absorbing layer (II) by, for example, (1) A method in which a composition containing a pH-discoloring dye is blended with a composition for forming the moisture-absorbing layer (II), and then the blended composition is applied to form the moisture-absorbing layer (II) having the gas-sensing part (III); (2) A method in which a moisture-absorbing layer (II) is formed, and then a composition containing a pH-discoloring dye is dropped, coated, printed, or the like onto the moisture-absorbing layer (II) to form a gas-sensing part (III); (3) A method in which a gas sensing part (III) is formed on the resin layer (I) and / or the resin layer (IV) by dropping, coating, printing, or the like of a composition containing a pH-discoloring dye, and then the gas sensing part (III) is laminated with the moisture absorbing layer (II); etc.

[0098] The dropping, coating, and printing methods may be any known method, and may be appropriately selected depending on the liquid properties such as viscosity of the composition containing the pH-discoloring dye, the properties such as compatibility with the resin layer (I), the moisture-absorbing layer (II), and the resin layer (IV), the size, and the intended use.

[0099] Specific examples of the dropping method include an applicator or a dispenser, examples of the coating method include bar coating, spray coating, and brush coating, and examples of the printing method include letterpress printing, lithographic printing, gravure printing, flexographic printing, and screen printing.

[0100] In the present laminate, it is desirable that the gas sensing element (III) is solid. As a method for drying or solidifying the composition containing the pH-color-changing dye after dropping, coating, or printing, any known method may be used, and may be appropriately selected depending on the pH-color-changing dye and binder used, the application of the present laminate, and the like. Specific examples that can be used include external heat drying, electromagnetic wave heat drying, natural drying, external heat curing, ultraviolet curing, polymerization curing, cooling solidification, gelation, and sol-gel solidification.

[0101] <Resin layer (IV)> The resin layer (IV) has a water vapor permeability of 10 to 80 g / m as measured in accordance with JIS Z0208 (1976). 2 ·day, preferably 12 to 50 g / m 2 day, particularly preferably 15 to 40 g / m 2 ·day. By setting the water vapor transmission rate of the resin layer (IV) within the above range, water vapor, gases, etc. within the package can easily permeate the resin layer (IV) and be absorbed by the moisture absorbing layer (II).

[0102] The resin layer (IV) can be formed into a plate or film shape, and may be a single layer or a multilayer as long as it satisfies the water vapor permeability. However, it is preferable that the resin layer (IV) has heat sealability in terms of sealing properties when used as a package. Therefore, the resin layer (IV) preferably has a layer formed from a composition containing a polyolefin resin as a main component. When the resin layer (IV) is a multilayer, layers containing the same type of polyolefin resin may be laminated, or layers containing different types of polyolefin resin may be laminated. When the resin layer (IV) is multi-layered, the layers can be laminated together by a general molding method such as coextrusion or dry lamination.

[0103] [Polyolefin resin] Examples of the polyolefin resin include homopolymers obtained by polymerizing α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene, and copolymers containing α-olefins as the main monomer component. Among these, polyethylene resins containing ethylene as the main monomer component, polypropylene resins containing propylene as the main monomer component, and polymethylpentene resins containing 4-methyl-1-pentene as the main monomer component are preferred, and polymethylpentene resins are particularly preferred from the viewpoint of gas permeability.

[0104] Examples of the polymethylpentene resin include a homopolymer of 4-methyl-1-pentene, as well as a copolymer having 60 to 99 mol % of structural units derived from 4-methyl-1-pentene and 1 to 40 mol % of structural units derived from an α-olefin having 2 to 20 carbon atoms other than 4-methyl-1-pentene, in which the total of the structural units derived from 4-methyl-1-pentene and the structural units derived from an α-olefin having 2 to 20 carbon atoms other than 4-methyl-1-pentene is 100 mol %.

[0105] [Other resins] The composition forming the resin layer (IV) may contain thermoplastic resins other than the polyolefin resins described above, or other resins, such as thermosetting resins such as epoxy resins, polyphenylene ether resins, polyimide resins, phenolic resins, orthodivinylbenzene resins, silicone resins, fluororesins, etc. These may be used alone or in combination of two or more.

[0106] When the composition contains other resins, the content thereof is usually 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 1% by mass or less, relative to 100% by mass of the total of the components contained in the composition, from the viewpoint of mechanical properties and heat resistance.

[0107] Furthermore, the composition may contain, as necessary, conventionally known additives such as antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, ultraviolet absorbers, etc., to the extent that the effects of the present invention are not impaired. These may be used alone or in combination of two or more.

[0108] The resin layer (IV) can be obtained by melt-extrusion of a composition containing the polyolefin resin into a plate or film using a general molding method such as melt extrusion molding, hot pressing, etc. However, the method for producing the base layer is not limited to this method.

[0109] The resin layer (IV) preferably has a heat seal strength at a temperature of 140° C. in accordance with JIS Z1526 of 6 to 50 N / 15 mm, more preferably 8 to 40 N / 15 mm, and particularly preferably 10 to 30 N / 15 mm.

[0110] The thickness of the resin layer (IV) is usually 5 to 200 μm, and preferably 10 to 150 μm.

[0111] The present laminate can be obtained by preparing each layer and laminating them by a method such as dry lamination, wet lamination, sand lamination, or extrusion lamination.

[0112] [Physical properties of the present laminate] The present laminate can have the following physical properties.

[0113] [Oxygen barrier properties] This laminate has an oxygen transmission rate (OTR) of 5cc / m2 measured at 23°C and 80% relative humidity according to JIS K7126-2 (2006). 2·day·atm or less, preferably 3cc / m 2 ·day·atm or less, preferably 1cc / m 2 ·day·atm or less.

[0114] [Water vapor barrier properties] This laminate has a water vapor transmission rate (WVTR) of 10 g / m2 at 40°C and 90% relative humidity, measured in accordance with JIS Z0208 (1976). 2 ・day or more, preferably 20g / m 2 ·day, more preferably 30g / m 2 ·day.

[0115] The present laminate has an oxygen transmission rate (OTR) and a water vapor transmission rate (WVTR) that satisfy the above-mentioned ranges, but it is more preferable that both the oxygen transmission rate (OTR) and the water vapor transmission rate (WVTR) satisfy the above-mentioned ranges.

[0116] [Uses of the present laminate] The laminate can be used as it is to make a packaging film or a packaging material. Furthermore, the present laminate is suitable for packaging foods such as raw meat, prepared foods, processed meat products, and processed seafood products, but the objects to be packaged are not limited to these, and it can also be suitably used for packaging various industrial materials, precision parts, intermediate industrial products, miscellaneous goods, sanitary products, medical equipment, pharmaceuticals, and the like.

[0117] <<Packaging>> When the present laminate is used to make a package, the laminate is used as a lid material for a base material for placing contents, and the two are heat-sealed. Among these, the package is preferably a MAP package in which the air inside the package is replaced with a gas such as nitrogen, or a skin pack package in which the air inside the package is removed to create a vacuum. [Example]

[0118] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are by mass.

[0119] Prior to the examples, the following materials were prepared. [Resin layer (I)] BF: Transparent vapor-deposited barrier film (Mitsubishi Chemical Corporation's "Techbarrier VX", silica-deposited biaxially oriented PET film, oxygen permeability 0.5cc / m 2 ·day, thickness 12μm) PET: Biaxially stretched PET film (Futamura Chemical Co., Ltd., one side corona treated, oxygen permeability 31cc / m 2 ·day, thickness 38μm) [Moisture absorption layer (II)] PVA1: Unmodified PVA resin (manufactured by Mitsubishi Chemical Corporation, average polymerization degree 1100, average saponification degree 99 mol%, sodium acetate content 0.1%) PVA2: Unmodified PVA resin (manufactured by Mitsubishi Chemical Corporation, average polymerization degree 1100, average saponification degree 99 mol%, sodium acetate content 0.4%) PVA3: Unmodified PVA resin (manufactured by Mitsubishi Chemical Corporation, average polymerization degree 1700, average saponification degree 99 mol%, sodium acetate content 0.8%) PVA4: Unmodified PVA resin (manufactured by Mitsubishi Chemical Corporation, average degree of polymerization 500, average degree of saponification 88 mol%, sodium acetate content 1.0%) [Gas sensing section (III)] pH-changing dye: BTB solution (Hayashi Pure Chemical Industries, Ltd., Bromothymol Blue solution, concentration 0.04%) [Resin layer (IV)] TPX: Polymethylpentene resin (Mitsui Chemicals) melt-cast film (water vapor permeability 20g / m 2 ·day, thickness 50μm) CPP: Non-oriented polypropylene film (Futamura Chemical Co., Ltd., water vapor permeability 8g / m 2 ·day, thickness 40μm)

[0120] Example 1 20 g of a 9% aqueous solution of PVA1 and 14.85 g of the BTB solution were mixed so that the BTB solid concentration relative to PVA1 was 0.33%, and the mixture was stirred until homogenous. This solution was coated on the TPX resin layer (IV) and dried at 80°C for 5 minutes to prepare a moisture absorbing layer (II) having a 10 µm thick gas sensing element (III). Next, a solution of ethyl acetate containing a 30% concentration of laminating adhesive (manufactured by Toyo-Morton, AD-900 / CAT-RT85=10 / 1.5) was applied to the silica-deposited surface of BF, which constituted the resin layer (I), using a bar coater (#8), and dried at 80°C for 1 minute. Immediately after drying, this was laminated with the moisture-absorbing layer (II) equipped with the gas sensing element (III), and aged for 3 days in a thermostatic oven at 40°C to produce the laminate of Example 1 (TPX / BTB+PVA1 / adhesive / BF).

[0121] <Example 2> A laminate of Example 2 was produced in the same manner as in Example 1, except that the PVA resin of the moisture absorption layer (II) was changed to PVA2.

[0122] Example 3 A laminate of Example 3 was produced in the same manner as in Example 1, except that the PVA resin of the moisture absorption layer (II) was changed to PVA3.

[0123] Example 4 A laminate of Example 4 was produced in the same manner as in Example 1, except that the PVA resin of the moisture absorption layer (II) was changed to PVA4.

[0124] <Comparative Example 1> A laminate of Comparative Example 1 was produced in the same manner as in Example 1, except that the BF of the resin layer (I) was changed to PET.

[0125] <Comparative Example 2> A laminate of Comparative Example 2 was produced in the same manner as in Example 1, except that the TPX in the resin layer (IV) was changed to CPP.

[0126] [Gas sensing evaluation] The obtained laminates of Examples 1 to 4 and Comparative Examples 1 and 2 were each placed in a 10 cm×15 cm Tupperware container with the resin layer (IV) side facing up. Next, place a container containing 50 ml of purified water in the Tupperware, then cover the Tupperware to seal it, and leave it for one day. * The values ​​were measured by a transmission method using a spectrophotometer CM-3600 manufactured by Konica Minolta. After leaving it for one day, 5 ml of 0.025 mol / L ammonia water was added to purified water (ammonia concentration in the system: 20 ppm), and the Tupperware was sealed and left to stand for one day. * The values ​​were measured by a transmission method using a spectrophotometer CM-3600 manufactured by Konica Minolta. b after adding aqueous ammonia * From the value, b before adding ammonia water * The difference between the values ​​is Δb * The results are shown in Table 1 below. [Evaluation criteria] ◎:Δb * is less than or equal to -5 ○:Δb * is greater than -5 and less than or equal to 0 ×:Δb * is greater than 0

[0127] [Table 1]

[0128] From the results in Table 1, it was found that the laminates of Examples 1 to 4 reacted with ammonia, and a change in color was apparent from their appearance. On the other hand, no change in color was apparent from the appearance of the laminate of Comparative Example 1. This is presumably because the high oxygen permeability of the resin layer (I) allowed ammonia to permeate, preventing the ammonia from being retained in the moisture absorbing layer (II). Furthermore, no change in color was apparent from the appearance of the laminate of Comparative Example 2. This is presumably because the water vapor permeability of the resin layer (IV) was low, so that ammonia could not permeate the resin layer (IV) and was not retained in the moisture absorbing layer (II). [Industrial Applicability]

[0129] The laminate of the present invention can be used as a packaging film or a packaging body, and is particularly suitable for packaging foods such as raw meat, prepared foods, processed meat products, and processed seafood products.

Claims

1. A laminate comprising a resin layer (I), a moisture absorbing layer (II), a gas sensing part (III), and a resin layer (IV), the resin layer (I), the moisture absorption layer (II), and the resin layer (IV) are laminated in this order; the gas sensing part (III) is disposed in contact with the moisture absorbing layer (II), The oxygen permeability of the resin layer (I) measured in accordance with JIS K7126-2 (2006) is 5 cc / m 2 - day / atm or less, The water vapor permeability of the resin layer (IV) measured in accordance with JIS Z0208 (1976) is 10 g / m 2 - A laminate having a temperature of 100°C or more.

2. The laminate according to claim 1, wherein the resin layer (IV) comprises a layer made of a composition containing polymethylpentene as a main component.

3. 2. The laminate according to claim 1, wherein the moisture-absorbing layer (II) is made of a composition containing a polyvinyl alcohol-based resin as a main component.

4. 4. The laminate according to claim 3, wherein the polyvinyl alcohol resin has an average degree of saponification of 86 to 100 mol %.

5. 4. The laminate according to claim 3, wherein the polyvinyl alcohol resin has an average degree of polymerization of 200 to 3,000.

6. The laminate according to claim 1 , wherein the gas-sensing element (III) comprises a pH-changing dye.

7. 2. The laminate according to claim 1, wherein the gas sensing portion (III) is formed on the moisture absorbing layer (II).

8. The laminate according to claim 1 , wherein the moisture absorbing layer (II) comprises the gas sensing portion (II).

9. 2. The laminate according to claim 1, wherein the moisture-absorbing layer (II) has a thickness of 1 to 60 μm.

10. 2. The laminate according to claim 1, wherein the resin layer (I) contains at least one thermoplastic resin selected from the group consisting of polyamide-based resins, polyolefin-based resins, polyester-based resins, and polystyrene-based resins.

11. The laminate according to claim 1 , wherein the resin layer (I) comprises at least two layers and has a barrier layer.

12. The laminate according to claim 1, wherein the resin layer (I) is stretched in at least one direction.

13. A laminate film comprising the laminate according to any one of claims 1 to 12.

14. A package using the laminated film according to claim 13.

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