Laminate, packaging material, packaging bag, and package

Abstract

Provided is a laminate including: a base layer; a first solventless adhesive layer; an intermediate layer; a second solventless adhesive layer; and a sealant layer in this order. The intermediate layer includes a layer composed of a polyamide-based polymer film. The layer composed of the polyamide-based polymer film and the second solventless adhesive layer are in direct contact with each other, or the intermediate layer further includes an easily adhesive coat layer forming the surface of the intermediate layer on the second solventless adhesive layer side, and the thickness of the second solventless adhesive layer is 1.6-3.0 μm.

Description

Laminate, packaging material, packaging bag and packaging body

[0001] The present disclosure relates to a laminate, a packaging material, a packaging bag, and a packaging body.

[0002] Conventionally, laminates in which films having various functions are laminated have been used as packaging materials used for packaging foods, medicines, etc. For example, Patent Document 1 discloses a laminate film in which a laminated stretched polyamide film having an easy-adhesion layer laminated thereon and a linear low-density polyethylene film are laminated by a dry lamination method.

[0003] In recent years, from the viewpoint of reducing the environmental impact, the use of solvent-free adhesives as adhesives for forming the laminate has been considered. Solvent-free adhesives are characterized by the fact that they contain substantially no solvent, so that the environmental impact of the manufacturing process is low, and that they can be applied more thinly than solvent-based adhesives.

[0004] Japanese Patent Application Laid-Open No. 2022-161902

[0005] As in Patent Document 1, polyamide polymer films such as nylon films are sometimes used for the purpose of improving tensile strength, flexural strength, oil resistance, etc. However, packaging materials that use a solventless adhesive for laminating polyamide polymer films tend to cause foaming at the sealed portion during heat sealing the longer the storage period of the packaging material, which can cause poor appearance of the packaging bag.

[0006] Some aspects of the present disclosure aim to provide a packaging material that includes a polyamide-based polymer film laminated using a solvent-free adhesive, and that has improved storage stability and is less likely to cause poor appearance due to foaming at the sealed portion during heat sealing, as well as a laminate for use in the packaging material. Other aspects of the present disclosure aim to provide a packaging bag made from the packaging material, and a package using the packaging bag.

[0007] As a result of intensive research into the above-mentioned problem, the inventors have found that the above-mentioned poor appearance occurs significantly when an easy-adhesion coating layer is formed on the surface of a polyamide-based polymer film by an easy-adhesion treatment, and have also found that by bringing the polyamide-based polymer film and the adhesive layer into direct contact with each other, it is possible to suppress the above-mentioned poor appearance due to foaming, and to enable the packaging material to be stored stably for a longer period of time.

[0008] The present inventors have also found that even when an easy-adhesion coating layer is formed on the surface of a polyamide-based polymer film by an easy-adhesion treatment, by making the solvent-free adhesive layer (adhesive layer formed from a solvent-free adhesive) between the polyamide-based polymer film and the sealant layer thicker than usual, it is possible to suppress the above-mentioned poor appearance due to foaming, and the packaging material can be stored stably for a longer period of time.

[0009] Some aspects of the present disclosure provide the following [1] to

[16] .

[0010] [1] A laminate comprising a substrate layer, a first solvent-free adhesive layer, an intermediate layer, a second solvent-free adhesive layer, and a sealant layer in this order, wherein the intermediate layer comprises a layer made of a polyamide-based polymer film, and the layer made of the polyamide-based polymer film and the second solvent-free adhesive layer are in direct contact with each other, or the intermediate layer further comprises an easy-adhesion coating layer that forms a surface of the intermediate layer facing the second solvent-free adhesive layer, and the thickness of the second solvent-free adhesive layer is 1.6 to 3.0 μm.

[0011] [2] The laminate according to [1], wherein the layer made of the polyamide-based polymer film and the second solventless adhesive layer are in direct contact with each other.

[0012] [3] The laminate according to [2], wherein the thickness of the first solventless adhesive layer is 0.8 to 4.0 μm.

[0013] [4] The laminate according to [2] or [3], wherein the thickness of the second solventless adhesive layer is 0.8 to 4.0 μm.

[0014] [5] The laminate according to [1], wherein the intermediate layer includes the easy-adhesion coating layer, and the thickness of the second solventless adhesive layer is 1.6 to 3.0 μm.

[0015] [6] The laminate according to [5], wherein the thickness of the layer made of the polyamide-based polymer film is 10 to 35 μm.

[0016] [7] The laminate according to [5] or [6], wherein the thickness of the easy-adhesion coating layer is 0.01 to 3.0 μm.

[0017] [8] The laminate according to any one of [5] to [7], wherein the thickness of the first solventless adhesive layer is 1.6 to 3.0 μm.

[0018] [9] The laminate according to any one of [1] to [8], wherein the base layer has gas barrier properties.

[0019]

[10] The laminate according to any one of [1] to [9], wherein the thickness of the second solventless adhesive layer is greater than the thickness of the first solventless adhesive layer.

[0020]

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

[10] , further comprising a printed layer on a surface of the substrate layer facing the first solventless adhesive layer.

[0021]

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

[11] , wherein the sealant layer is made of an unstretched polypropylene film.

[0022]

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

[12] .

[0023]

[14] A packaging bag made from the packaging material according to

[13] .

[0024]

[15] The packaging bag according to

[14] , which is for boiling or retorting.

[0025]

[16] A package comprising the packaging bag according to

[14] and contents contained in the packaging bag.

[0026] According to the present disclosure, it is possible to provide a packaging material that includes a polyamide-based polymer film laminated using a solvent-free adhesive, and that has improved storage stability and is less likely to cause poor appearance due to foaming at the sealed portion during heat sealing, as well as a laminate for use in the packaging material. Furthermore, according to other aspects of the present disclosure, it is possible to provide a packaging bag made from the packaging material, and a package using the packaging bag.

[0027] Fig. 1 is a schematic cross-sectional view showing an example of a first embodiment of a laminate of the present disclosure. Fig. 2 is a schematic cross-sectional view showing another example of the first embodiment of a laminate of the present disclosure. Fig. 3 is a schematic cross-sectional view showing an example of a second embodiment of a laminate of the present disclosure. Fig. 4 is a schematic cross-sectional view showing another example of the second embodiment of a laminate of the present disclosure. Fig. 5 is a view showing an example of a sealed body showing each evaluation result of foamability.

[0028] Hereinafter, embodiments of the present disclosure will be described in detail, with reference to the drawings as needed. However, the present disclosure is not limited to the following embodiments.

[0029] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the units of the numerical values ​​before and after "to" are the same. In the numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range in a certain stage may be replaced with the upper limit or lower limit of a numerical range in another stage. Furthermore, in the numerical ranges described in this specification, the upper limit or lower limit of the numerical range may be replaced with a value shown in the examples. Furthermore, the upper limit and lower limit values ​​described individually can be combined in any combination.

[0030] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and duplicate explanations will be omitted. The dimensional ratios of the drawings are not limited to those shown in the drawings.

[0031] <Laminate> (First embodiment) Fig. 1 is a schematic cross-sectional view showing an example of a first embodiment of a laminate of the present disclosure. The laminate 10 of Fig. 1 includes, in this order, a substrate layer 11, a first solventless adhesive layer 12, an intermediate layer 15, a second solventless adhesive layer 16, and a sealant layer 17. The intermediate layer 15 includes a layer 13 made of a polyamide-based polymer film, and the layer 13 made of the polyamide-based polymer film and the second solventless adhesive layer 16 are in direct contact with each other. In the present disclosure, an adhesive layer formed from a solventless adhesive is referred to as a solventless adhesive layer.

[0032] The laminate 10 is suitable for use as a packaging material. The laminate 10 has improved storage stability, and provides a packaging material that is less likely to suffer from poor appearance due to foaming at the sealed portion during heat sealing.

[0033] The reason for the above-mentioned effect is unclear, but is presumed to be as follows. First, because polyamide-based polymer films are highly hygroscopic, packaging materials containing this material gradually begin to absorb moisture after production, resulting in moisture buildup. It is presumed that when this moisture evaporates due to the heat generated during heat sealing and reaches and diffuses into the sealant layer (sealed portion), bubbles are formed, resulting in the above-mentioned poor appearance. In particular, since the easy-adhesion coating layer formed on the surface of the polyamide-based polymer film has a property of being easily compatible with adhesives, when an easy-adhesion coating layer is formed on the polyamide-based polymer film, the interface between the easy-adhesion coating layer and the adhesive layer disappears, making the above-mentioned evaporated moisture more likely to diffuse to the sealant layer, thereby making the above-mentioned poor appearance more likely to occur. In contrast, in the laminate 10 of the above-mentioned embodiment, the layer 13 made of polyamide-based polymer film and the second solventless adhesive layer 16 are in direct contact with each other, so the interface disappears due to the easy-adhesion coating layer, and moisture diffusion to the sealant layer 17 is suppressed. For these reasons, it is presumed that a packaging material that is less likely to cause poor appearance due to foaming can be obtained by using the laminate 10. However, the reason why the above effect is obtained is not limited to the reason presumed above.

[0034] The thickness of the laminate 10 may be, for example, 35 to 275 μm, or 70 to 250 μm.

[0035] Each layer constituting the laminate 10 will now be described.

[0036] [Substrate Layer] The substrate layer 11 is a layer containing a substrate film. The substrate film may be a known resin film used for packaging bags. The substrate film is, for example, a stretched film such as a biaxially stretched resin film. Examples of resins constituting the resin film include polyesters such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, polyamides such as nylon, polypropylene, polystyrene, polyimide, polyvinyl alcohol, polyvinyl chloride, and ethylene-vinyl alcohol copolymers. As the resin film, a composite film in which two or more types of films are laminated can be used.

[0037] The thickness of the substrate film is, for example, 9 to 20 μm.

[0038] The base layer 11 preferably has gas barrier properties against gases such as oxygen and water vapor in order to prevent oxidation, corrosion, and spoilage of the contents. In order to impart gas barrier properties to the base layer 11, the base layer 11 may include a gas barrier layer on a base film.

[0039] The gas barrier layer is a layer that has barrier properties against at least one type of gas, such as oxygen gas or water vapor. The gas barrier layer may be a layer that has oxygen barrier properties, or may be a layer that has water vapor barrier properties. Here, the term "a layer has oxygen barrier properties" means that the layer has an oxygen transmission rate (OTR, unit: cc / m) measured under conditions of 25°C and 80% relative humidity using an oxygen transmission rate measuring device (OX-TRAN2 / 21 model manufactured by MOCON Corporation) in accordance with JIS K7126-2 (2006). ２ / day / atm) is 2cc / m ２The layer having water vapor barrier properties means that the water vapor transmission rate (WVTR, unit: g / m) is measured at 40°C and 90% relative humidity using a water vapor transmission rate measuring device (DELTAPERM manufactured by Technolox) in accordance with JIS K7129-5 (2016). ２ / day) is 1.0 g / m ２ The gas barrier layer may have not only gas barrier properties against oxygen gas and water vapor but also aroma retention properties for the contents.

[0040] The gas barrier layer may be composed of, for example, one or more layers selected from the group consisting of a metal foil layer, an inorganic vapor deposition layer, and a resin coating layer made of a barrier resin. In order to ensure visibility of the contents, to obtain transparency for back-printing a printed layer, or to enable compatibility with microwave ovens, the gas barrier layer is preferably an inorganic vapor deposition layer or a resin coating layer. A specific example of a substrate layer containing an inorganic vapor deposition layer is GL Film (manufactured by TOPPAN Corporation).

[0041] The metal foil layer is a layer formed by laminating foils made of various metals such as aluminum, stainless steel, and copper.

[0042] The inorganic vapor deposition layer is a layer formed by vapor deposition of an inorganic material such as a metal or metal oxide. Examples of metals include aluminum, stainless steel, and copper. Examples of metal oxides include silicon oxide and aluminum oxide. The metal oxide is preferably aluminum oxide. Examples of methods for forming the inorganic vapor deposition layer include physical vapor deposition methods (PVD methods) such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition methods (CVD methods) such as plasma-enhanced chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition.

[0043] The thickness of the inorganic vapor-deposited layer is preferably 1 to 200 nm. When the inorganic vapor-deposited layer is a vapor-deposited layer of silicon oxide or aluminum oxide (alumina), the thickness of the inorganic vapor-deposited layer is preferably 1 to 100 nm, more preferably 10 to 50 nm, and even more preferably 20 to 30 nm.

[0044] The resin coating layer is, for example, a dried coating film of a water-soluble polymer having a hydroxyl group. Examples of water-soluble polymers having a hydroxyl group include polyvinyl alcohol and polyvinyl acetal. Commercially available water-soluble polymers may be used. Examples of commercially available products include the Kuraray Poval, Elvanol, and Exeval series manufactured by Kuraray Co., Ltd., and the Gohsenol and Soarnol series manufactured by Mitsubishi Chemical Corporation.

[0045] The thickness (total thickness) of the gas barrier layer is, for example, 0.01 to 3.0 μm.

[0046] The thickness of the substrate layer 11 is, for example, 9 to 23 μm.

[0047] [First Solvent-Free Adhesive Layer] The first solvent-free adhesive layer 12 is a layer formed from a solvent-free adhesive (first solvent-free adhesive). Here, the solvent-free adhesive refers to an adhesive that does not substantially contain solvents (organic solvents and water) (the solvent content is 0.5 mass% or less). Whether the adhesive layer is formed from a solvent-free adhesive and not a solvent-based adhesive can be confirmed, for example, by analysis using Fourier transform infrared spectroscopy.

[0048] Examples of solvent-free adhesives include polyurethane adhesives. The polyurethane adhesive may be a one-component curing type or a two-component curing type, but is preferably a two-component curing type. From the viewpoint of excellent appearance, the solvent-free adhesive is preferably a two-component curing polyurethane adhesive.

[0049] The two-component curing polyurethane adhesive contains a base agent and a curing agent. Examples of base agents include polyester polyols, polyether polyols, acrylic polyols, polyether ester polyols, and polyurethane polyols. Of these, polyester polyols are preferably used. Examples of curing agents include polyisocyanate compounds having two or more functionalities. The polyisocyanate compound may be an aliphatic polyisocyanate, an aromatic polyisocyanate, or a mixture thereof. When the laminate of the present disclosure is used in a package containing food, from the viewpoint of food hygiene, the polyisocyanate compound is preferably an aliphatic polyisocyanate.

[0050] The polyester polyol is, for example, an ester reaction product of a polycarboxylic acid, a dialkyl ester of a polycarboxylic acid, or a mixture thereof with a glycol-based compound. Examples of polycarboxylic acids include succinic acid, glutaric acid, isophthalic acid, terephthalic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, and dimer acid. Examples of glycol-based solvents include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butylene glycol, neopentyl glycol, and 1,6-hexanediol.

[0051] Examples of the aliphatic polyisocyanate include tetramethylene diisocyanate, isopropylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, and derivatives thereof (such as isocyanurates).

[0052] The aromatic polyisocyanate may be, for example, tolylene diisocyanate, phenylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, or a derivative thereof (such as an isocyanurate).

[0053] The solvent-free adhesive is cured, for example, by reaction with heating or the like (for example, reaction between hydroxyl groups of the base agent and isocyanate groups of the curing agent) to form the first solvent-free adhesive layer 12. The first solvent-free adhesive layer 12 formed in this manner contains a cured product of the solvent-free adhesive.

[0054] From the viewpoint of obtaining sufficient adhesion, the thickness of the first solvent-free adhesive layer 12 is preferably 0.8 μm or more, more preferably 1.2 μm or more, and even more preferably 1.6 μm or more. From the viewpoint of suppressing slippage and peeling during processing or handling, the thickness of the first solvent-free adhesive layer 12 is preferably 4.0 μm or less, more preferably 3.5 μm or less, and even more preferably 3.0 μm or less. From the above viewpoints, the thickness of the first solvent-free adhesive layer 12 is preferably 0.8 to 4.0 μm, more preferably 1.2 to 3.5 μm, and even more preferably 1.2 to 3.0 μm. The thickness of the first solvent-free adhesive layer 12 can be adjusted by adjusting the coating amount of the solvent-free adhesive. Note that, considering productivity and from the viewpoint of reducing indirect work and time required for changing conditions, the thickness of the first solvent-free adhesive layer 12 may be approximately the same as the thickness of the second solvent-free adhesive layer 16 described below. On the other hand, when taking into consideration the cost associated with the packaging and minimizing the amount of adhesive used, the thickness of the first solvent-free adhesive layer 12 may be thinner than the thickness of the second solvent-free adhesive layer 16.

[0055] [Intermediate Layer] The intermediate layer 15 includes a layer 13 made of a polyamide polymer film. The intermediate layer 15 is provided to impart to the laminate the properties required for a packaging bag, such as drop resistance, pressure resistance, impact resistance, puncture resistance, and retort resistance.

[0056] The thickness of the intermediate layer 15 is, for example, 10 to 35 μm.

[0057] [Layer made of polyamide-based polymer film] A polyamide-based polymer film is a film made from a polyamide-based polymer as a raw material and contains at least a polyamide-based polymer. In the present disclosure, the term "polyamide-based polymer film" refers to a polyamide-based polymer film that has not been subjected to an easy-adhesion treatment, and is distinguished from a film that has been subjected to an easy-adhesion treatment. Hereinafter, for convenience, a polyamide-based polymer film that has been subjected to an easy-adhesion treatment (a laminate of a polyamide-based polymer film and an easy-adhesion coating layer) will be referred to as an easy-adhesion-treated polyamide-based polymer film. The same applies to nylon films, etc.

[0058] Examples of polyamide-based polymers include aliphatic polyamides such as 6-nylon and 6,6-nylon, and aromatic polyamides such as polymetaxylylene adipamide. The polyamide-based polymer is preferably an aliphatic polyamide from the viewpoints of appearance such as transparency, and imparting durability during handling of the package such as pinhole resistance (e.g., puncture strength) and bag drop resistance. The shape of the aliphatic polyamide may be linear or branched, but linear is preferred from the viewpoint of imparting durability during handling of the package such as pinhole resistance (e.g., puncture strength) and bag drop resistance.

[0059] The polyamide-based polymer film may consist solely of a polyamide-based polymer, or may contain known additives used in the production of polyamide-based polymer films. The polyamide-based polymer film may contain a polymer other than a polyamide-based polymer, but the content of the polyamide-based polymer is preferably 60 mass% or more based on the total mass of the film.

[0060] The polyamide-based polymer film may be a stretched film or a non-stretched film, but is preferably a stretched film from the viewpoint of durability. Furthermore, the polyamide-based polymer film may be a uniaxially stretched film or a biaxially stretched film.

[0061] The thickness of the polyamide-based polymer film (i.e., the thickness of the layer 13 made of a polyamide-based polymer film) may be 10 μm or more or 12 μm or more from the viewpoint of mechanical strength, and may be 35 μm or less, 28 μm or less, or 20 μm or less from the viewpoint of further suppressing foaming during heat sealing. From the above viewpoints, the thickness of the layer 13 made of a polyamide-based polymer film is preferably 10 to 35 μm, more preferably 12 to 28 μm, and even more preferably 12 to 20 μm.

[0062] The polyamide polymer film may be a commercially available nylon film, such as "EMBLEM ONBC" (manufactured by Unitika Ltd.), "HADEN N1202" (manufactured by Toyobo Co., Ltd.), or "UNILON G-101" (manufactured by Idemitsu Unitech Co., Ltd.).

[0063] In order to improve adhesion with adjacent layers and enhance the durability required of packaging bags, the surface of the intermediate layer 15 may be subjected to various pretreatments such as corona treatment, plasma treatment, ozone treatment, flame treatment, electron beam irradiation treatment, etc. When the surface of the intermediate layer 15 is subjected to such pretreatments, adhesion with adjacent layers can be improved while suppressing moisture diffusion without eliminating the interfaces between the intermediate layer 15 and adjacent layers (i.e., the first solvent-free adhesive layer 12 and the second solvent-free adhesive layer 16).

[0064] [Second Solvent-Free Adhesive Layer] The second solvent-free adhesive layer 16 is a layer formed from a solvent-free adhesive (second solvent-free adhesive), and is in direct contact with the layer 13 made of a polyamide-based polymer film. The second solvent-free adhesive layer 16 is formed by curing a solvent-free adhesive, similar to the first solvent-free adhesive layer 12 described above. The first solvent-free adhesive forming the first solvent-free adhesive layer 12 and the second solvent-free adhesive forming the second solvent-free adhesive layer 16 may be the same type or different types.

[0065] From the viewpoint of obtaining good adhesion and further suppressing foaming in the sealant layer during heat sealing, the thickness of the second solvent-free adhesive layer 16 is preferably 0.8 μm or more, more preferably 1.2 μm or more, even more preferably 1.6 μm or more, and particularly preferably greater than 1.8 μm. From the viewpoint of suppressing slippage and peeling during processing or handling, the thickness of the second solvent-free adhesive layer 16 is preferably 4.0 μm or less, more preferably 3.5 μm or less, and even more preferably 3.0 μm or less. From the above viewpoints, the thickness of the second solvent-free adhesive layer 16 is preferably 0.8 to 4.0 μm, more preferably 1.2 to 3.5 μm, even more preferably 1.2 to 3.0 μm, even more preferably 1.6 to 3.0 μm, and particularly preferably greater than 1.8 μm and 3.0 μm or less. The thickness of the second solvent-free adhesive layer 16 can be adjusted by adjusting the coating amount of the solvent-free adhesive.

[0066] From the viewpoint of reducing the amount of adhesive used to reduce production costs while enhancing the foaming suppression effect, the thickness of the second solvent-free adhesive layer 16 is preferably thicker than the thickness of the first solvent-free adhesive layer 12. In other words, the ratio of the thickness of the second solvent-free adhesive layer 16 to the thickness of the first solvent-free adhesive layer 12 (thickness of the second solvent-free adhesive layer 16 / thickness of the first solvent-free adhesive layer 12) preferably exceeds 1.

[0067] The ratio of the thickness of the second solvent-free adhesive layer 16 to the thickness of the first solvent-free adhesive layer 12 (thickness of the second solvent-free adhesive layer 16 / thickness of the first solvent-free adhesive layer 12) is preferably 0.2 to 5.0, more preferably 0.34 to 2.92, even more preferably 0.53 to 2.5, and particularly preferably 0.60 to 1.88, from the viewpoint of reducing production costs while maintaining basic performance as an adhesive layer, such as adhesion. From the viewpoint of further suppressing foaming in the sealant layer during heat sealing, the lower limit of these ranges may be 1 or more, or may even exceed 1. By reducing the thickness of the first solvent-free adhesive layer 12 and increasing the thickness of the second solvent-free adhesive layer 16 as much as possible, the foaming suppression effect can be maximized within the constraints of production costs.

[0068] [Sealant Layer] The sealant layer 17 is a layer for heat sealing when the laminate 10 is formed into a packaging bag, etc., and is formed of a material having thermal adhesive properties. The material, layer structure, and thickness of the sealant layer 17 can be appropriately selected depending on the application, shape, physical properties, etc. of the packaging bag.

[0069] Examples of materials for the sealant layer 17 include ethylene-based resins, polypropylene-based resins, propylene-based resins, ethylene-propylene copolymers, ethylene-α,β-unsaturated carboxylic acid copolymers, esters of ethylene-α,β-unsaturated carboxylic acid copolymers, acid anhydride-modified polyolefins, polyvinyl chloride-based resins, and blends of two or more of these.

[0070] Examples of ethylene-based resins include low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (L-LDPE), ethylene-vinyl acetate copolymer (EVA), and ethylene-α-olefin copolymer.

[0071] The polypropylene resin is, for example, homopolypropylene, block polypropylene, or random polypropylene.

[0072] The propylene-based resin is, for example, a propylene-α-olefin copolymer.

[0073] The ethylene-α,β-unsaturated carboxylic acid copolymer is, for example, an ethylene-acrylic acid copolymer or an ethylene-methacrylic acid copolymer.

[0074] The acid anhydride-modified polyolefin is, for example, an ethylene-maleic anhydride graft copolymer, or a terpolymer such as ethylene-ethyl acrylate-maleic anhydride.

[0075] Among the above-mentioned materials, polypropylene-based resin has excellent thermal adhesiveness, heat resistance, and oil resistance, and therefore, a laminate containing a polypropylene-based resin in the sealant layer 17 is suitable for use as a packaging material for producing packaging bags for boiling or retorting.

[0076] To impart sealing properties, heat resistance, and other functionalities, the sealant layer 17 may contain, for example, additives such as antioxidants, slip agents, flame retardants, antiblocking agents, light stabilizers, dehydrating agents, tackifiers, crystal nucleating agents, plasticizers, etc. The content of these additives is preferably 5 parts by mass or less, with the total mass of the sealant layer being 100 parts by mass.

[0077] The sealant layer 17 may have a single layer structure or a multi-layer structure. When the sealant layer 7 has a multi-layer structure, the materials of the layers may be the same or different.

[0078] The thickness of the sealant layer 17 is not particularly limited, and may be 15 to 200 μm, 30 to 200 μm, or 50 to 200 μm.

[0079] The sealant layer 17 may be made of a sealant film containing the above-mentioned material. A known sealant film made of the above-mentioned material can be used as the sealant film. Specific examples include sealant films whose main component is an olefin resin, such as a polyethylene resin or a polypropylene resin. The sealant film may be a stretched film or a non-stretched film, but a non-stretched film is preferred from the viewpoint of thermal adhesiveness. A preferred example of the non-stretched film is a non-stretched polypropylene (CPP) film.

[0080] The surface of the sealant layer 17 facing the second solventless adhesive layer 16 may be subjected to various pretreatments such as corona treatment, plasma treatment, ozone treatment, and flame treatment in order to enhance adhesion to the adhesive layer.

[0081] The laminate 10 can be manufactured, for example, by the following method. First, a substrate film constituting the substrate layer 11 and a polyamide-based polymer film constituting the intermediate layer 15 are laminated via a first solventless adhesive. Next, a sealant film constituting the sealant layer 17 is laminated onto the polyamide-based polymer film via a second solventless adhesive. Next, an aging treatment is performed to harden the first solventless adhesive and the second solventless adhesive. This allows the laminate 10 to be obtained. However, the manufacturing method of the laminate 10 is not limited to the above method. For example, the polyamide-based polymer film and the sealant film may be laminated before the polyamide-based polymer film and the substrate film are laminated. Alternatively, either the first solventless adhesive layer 12 or the second solventless adhesive layer 16 may be cured first. Alternatively, for example, a pre-laminated laminate (a laminate of a substrate film and a polyamide-based polymer film, or a laminate of a polyamide-based polymer film and a sealant film) may be used. The lamination conditions and the conditions for curing the solvent-free adhesive are not particularly limited, and may follow the conditions for using known solvent-free adhesives.

[0082] In the laminate 10, the second solventless adhesive layer 16 and the sealant layer 17 may or may not be adjacent to each other.

[0083] An example of the first embodiment of the laminate of the present disclosure has been described above, but the first embodiment of the laminate of the present disclosure is not limited to the above example.

[0084] For example, in the first embodiment of the laminate of the present disclosure, the intermediate layer may include an easy-adhesion coating layer formed on the surface of the layer made of polyamide-based polymer film facing the first solventless adhesive layer by an easy-adhesion treatment on the polyamide-based polymer film.

[0085] Furthermore, for example, the first embodiment of the laminate of the present disclosure may further include one or more other layers (e.g., films) to impart functions such as mechanical strength required of a packaging bag. The location of the other layer is not particularly limited. For example, the other layer may be provided between the substrate layer 11 and the first solventless adhesive layer 12, or between the second solventless adhesive layer 16 and the sealant layer 17. However, it is preferable that the intermediate layer 15, the second solventless adhesive layer 16, and the sealant layer 17 are adjacent to each other, as in the laminate 10 of FIG. 1. Examples of other layers include a printed layer. The printed layer is usually provided on at least one surface of the substrate layer, but from the viewpoint of protecting the printed layer, it is preferably provided between the substrate layer and the first adhesive layer.

[0086] Fig. 2 is a schematic cross-sectional view showing another example of the first embodiment of the laminate of the present disclosure. The laminate 20 of Fig. 2 further includes a printed layer 18 on the surface of the substrate layer 11 facing the first solvent-free adhesive layer 12, in addition to the substrate layer 11, the first solvent-free adhesive layer 12, the intermediate layer 15, the second solvent-free adhesive layer 16, and the sealant layer 17. The details of each layer other than the printed layer 18 are the same as those of the layers in the laminate 10, and therefore will not be described again.

[0087] Like laminate 10, laminate 20 has layer 13 made of a polyamide-based polymer film and second solventless adhesive layer 16 in direct contact with each other, thereby improving storage stability and providing a packaging material that is less likely to cause poor appearance due to foaming in the sealed area during heat sealing.

[0088] The thickness of the laminate 20 may be, for example, 35 to 275 μm, or 70 to 250 μm.

[0089] The laminate 20 can be produced in the same manner as the laminate 10, except that, for example, a printed layer 18 is formed on a substrate film constituting the substrate layer 11, a printed substrate film consisting of the substrate layer 11 and the printed layer 18 is obtained, and then the printed substrate film is used in place of the substrate film.

[0090] In the laminate 20, the base material layer 11 may be transparent so as to be able to display a pattern formed by the printing layer 18. Here, the base material layer 11 being transparent means that the total light transmittance of the film measured in accordance with JIS K7361-1:1997 using a color and turbidity simultaneous measuring device ("COH400" manufactured by Nippon Denshoku Industries Co., Ltd.) is 85% or more.

[0091] [Printed Layer] The printed layer is a layer formed by printing ink, and specifically, is formed from at least one type of ink, including a colored ink. The colored ink contains a pigment and a binder resin. Therefore, the printed layer contains at least a pigment and a binder resin. Note that the ink used as a printing material and the ink contained in the printed layer may have different compositions due to the influence of layer formation processes such as drying and curing, but in the present disclosure, for convenience, these are collectively referred to as ink.

[0092] As the color ink, known color inks (for example, white ink, red ink, yellow ink, indigo ink, black ink) can be used. The type of pigment contained in the color ink may be appropriately determined depending on the color to be expressed. For example, inorganic pigments or organic pigments may be used as the pigment. Examples of inorganic pigments include titanium oxide and carbon black (ink pigment). Examples of organic pigments include azo pigments, phthalocyanine pigments, dioxazine pigments, quinacridone pigments, isoindolinone pigments, and dye lake pigments. A combination of multiple types of pigments may be used as the pigment.

[0093] Examples of binder resins contained in color inks include alkyd resins, phenolic resins, maleic acid resins, natural resins, hydrocarbon resins, polyvinyl chloride resins, polyacetic acid resins, polystyrene resins, polyvinyl butyral resins, acrylic or methacrylic resins, polyamide resins, polyester resins, polyurethane resins, epoxy resins, urea resins, melamine resins, nitrocellulose, ethyl cellulose, etc. These may be used alone or in combination of two or more.

[0094] The ink used to form the printed layer may be either an aqueous ink or an oil-based ink, but from the viewpoint of environmental protection, an aqueous ink is preferred, and from the viewpoint of improving productivity and further suppressing poor appearance, an oil-based ink is preferred. When a material containing a water-based solvent, such as an aqueous ink, is used to form the printed layer, moisture may remain in the printed layer and diffuse into the intermediate layer and the sealant layer. However, this moisture diffusion can be suppressed by controlling the thickness of the first solvent-free adhesive layer (for example, by setting the thickness of the first solvent-free adhesive layer 12 within the above-mentioned range and setting the ratio of the thickness of the second solvent-free adhesive layer 16 to the thickness of the first solvent-free adhesive layer 12 within the above-mentioned range).

[0095] A solvent may be used when preparing the ink. That is, the ink may contain a solvent. As the solvent, a known solvent used in printing inks can be used.

[0096] The ink may contain, as necessary, one or more additives such as plasticizers, stabilizers, antioxidants, light stabilizers, ultraviolet absorbers, curing agents, crosslinking agents, lubricants, antistatic agents, and fillers.

[0097] The printing layer may be a layer that displays a pattern such as letters, figures, symbols, or designs. There are no particular limitations on the type of pattern that can be displayed by the printing layer, and the type of ink used may be determined appropriately depending on the type of pattern that can be displayed by the printing layer. The printing layer may be formed over the entire surface, or may be formed partially depending on the design.

[0098] The thickness of the printing layer is preferably 0.1 μm or more from the viewpoint of obtaining reproducibility of the image, and is preferably 4 μm or less from the viewpoint of reducing the step between the part where the printing layer is not formed and the part where the printing layer is formed. By reducing the step, for example, when forming a first solvent-free adhesive layer on the intermediate layer side and then laminating, the conformability of the solvent-free adhesive can be easily obtained, and more uniform adhesion can be achieved. Furthermore, when forming a first solvent-free adhesive layer on the substrate layer side including the printing layer and then laminating, the thickness variation of the first solvent-free adhesive layer is reduced.

[0099] The printed layer can be formed by a printing method such as gravure printing, letterpress printing, screen printing, transfer printing, offset printing, flexographic printing, inkjet printing, etc. The printed layer can also be formed by an electrophotographic method such as a laser printer.

[0100] Second Embodiment Figure 3 is a schematic cross-sectional view showing an example of a second embodiment of the laminate of the present disclosure. The laminate 30 of Figure 3 includes, in this order, a substrate layer 21, a first solventless adhesive layer 22, an intermediate layer 25, a second solventless adhesive layer 26, and a sealant layer 27. The intermediate layer 25 includes a layer 23 made of a polyamide-based polymer film and an easy-adhesion coating layer 24 formed by an easy-adhesion treatment on the polyamide-based polymer film, and the second solventless adhesive layer 26 has a thickness of 1.6 to 3.0 µm. The details of the substrate layer, sealant layer, and layer made of a polyamide-based polymer film in the second embodiment are the same as those of the first embodiment, and therefore will not be described again.

[0101] The laminate 30 is suitable for use as a packaging material. The laminate 30 has improved storage stability, and provides a packaging material that is less likely to suffer from poor appearance due to foaming at the sealed portion during heat sealing.

[0102] The reason for the above-mentioned effect is unclear, but is presumed to be as follows. First, because polyamide-based polymer films are highly hygroscopic, packaging materials containing this material gradually begin to absorb moisture after production, resulting in moisture buildup. It is presumed that when this moisture evaporates due to the heat generated during heat sealing and reaches and diffuses into the sealant layer (sealed portion), bubbles form, resulting in the above-mentioned poor appearance. In contrast, in the laminate 30 of the above-mentioned embodiment, the second solventless adhesive layer 26 between the intermediate layer 25 and the sealant layer 27 is formed thicker than conventional solventless adhesive layers (i.e., 1.6 μm or thicker). Therefore, it is presumed that the second solventless adhesive layer 26 suppresses moisture diffusion into the sealant layer 27. For these reasons, it is presumed that the laminate 30 provides a packaging material that is less likely to cause the above-mentioned foaming-related poor appearance. The reason for the above-mentioned effect is not limited to the reason presumed above.

[0103] The thickness of the laminate 30 may be, for example, 35 to 275 μm, or 70 to 250 μm.

[0104] [First Solvent-Free Adhesive Layer] The first solvent-free adhesive layer 22 is a layer formed from a solvent-free adhesive (first solvent-free adhesive). Examples of the solvent-free adhesive that forms the first solvent-free adhesive layer 22 include the same solvent-free adhesives as those that form the above-mentioned first solvent-free adhesive layer 12. Preferred examples of the solvent-free adhesive are also the same as those in the first embodiment.

[0105] From the viewpoint of obtaining sufficient adhesion, the thickness of the first solvent-free adhesive layer 22 is preferably 1.6 μm or more, more preferably 1.65 μm or more, and even more preferably 1.7 μm or more. From the viewpoint of suppressing winding slippage and peeling during handling, the thickness of the first solvent-free adhesive layer 22 is preferably 3.0 μm or less, more preferably 2.8 μm or less, and even more preferably 2.6 μm or less. From the above viewpoints, the thickness of the first solvent-free adhesive layer 22 is preferably 1.6 to 3.0 μm, more preferably 1.65 to 2.8 μm, and even more preferably 1.7 to 2.6 μm. The thickness of the first solvent-free adhesive layer 22 can be adjusted by adjusting the coating amount of the solvent-free adhesive. Note that, considering productivity and the ability to reduce indirect work and time required for changing conditions, the thickness of the first solvent-free adhesive layer 22 may be approximately the same as the thickness of the second solvent-free adhesive layer 26 described below. On the other hand, when taking into consideration the cost associated with the packaging and minimizing the amount of adhesive used, the thickness of the first solvent-free adhesive layer 22 may be thinner than the thickness of the second solvent-free adhesive layer 26.

[0106] [Intermediate Layer] The intermediate layer 25 includes a layer 23 made of a polyamide polymer film and an easy-adhesion coating layer 24 formed by subjecting the polyamide polymer film to an easy-adhesion treatment. In other words, the intermediate layer 25 includes a layer made of a polyamide polymer film that has been subjected to an easy-adhesion treatment. The intermediate layer 25 is provided to impart to the laminate the properties required for packaging bags, such as drop resistance, pressure resistance, impact resistance, puncture resistance, and retort resistance.

[0107] The thickness of the intermediate layer 25 is, for example, 10 to 38 μm or 12 to 38 μm.

[0108] The adhesive coating layer 24 is a layer formed by an adhesive treatment on the polyamide-based polymer film and forms the surface of the intermediate layer 25 on the side of the second solventless adhesive layer 26. The adhesive coating layer 24 functions to improve the adhesion of the polyamide-based polymer film layer 23 to an adjacent layer (i.e., the second solventless adhesive layer 26). The provision of the adhesive coating layer 24 enhances the adhesion between the intermediate layer 5 and the second solventless adhesive layer 26, thereby improving the durability of the packaging bag. For example, by providing the adhesive coating layer 24 on the intermediate layer 25, high adhesion can be maintained even after retort treatment, and the laminate strength between the adhesive coating layer 24 and the sealant layer 27 can be 10 N / 15 mm or more even after retort treatment. The adhesive coating layer 24 can also impart water resistance and oil resistance to the film surface. Therefore, particularly when the packaging bag contains contents containing liquids such as water or oil, the penetration of the liquid into the laminated interface of the packaging material can reduce adhesion and cause problems such as delamination, so providing the easy-adhesion coating layer 24 can prevent such problems from occurring. Note that the problem of reduced adhesion due to the liquid is particularly likely to occur when using a film with high liquid affinity, such as a polyamide-based polymer film. For this reason, it is common to provide an easy-adhesion coating layer on the surface of the polyamide-based polymer film.

[0109] The easy-adhesion coating layer 24 may be a layer formed, for example, by applying a known coating agent used in easy-adhesion treatment to the film constituting the intermediate layer and then performing a process such as drying as necessary. That is, the easy-adhesion coating layer 24 may be a coating layer formed from a known coating agent used in easy-adhesion treatment. Therefore, the easy-adhesion coating layer 24 contains components such as resin contained in the coating agent. As the coating agent, for example, a resin composition containing a urethane-based resin, an acrylic-based resin, a silicone-based resin, or a mixture of two or more of these can be used.

[0110] When the film constituting the intermediate layer is a stretched film, the coating agent forming the easy-adhesion coating layer 24 may be applied before or after the film is stretched.

[0111] The easy-adhesion coating layer 24 may be formed on at least a part of the surface of the layer 23 made of polyamide polymer film, but it is preferably formed on the entire surface.

[0112] From the viewpoint of improving adhesion between layers, the thickness of the easy-adhesion coating layer 24 is preferably 0.01 μm or more, more preferably 0.03 μm or more, and even more preferably 0.05 μm or more. Because the effect of improving adhesion saturates when the thickness of the easy-adhesion coating layer 24 exceeds a certain thickness, the thickness of the easy-adhesion coating layer 24 may be, for example, 3.0 μm or less, 2.0 μm or less, or 1.0 μm or less. From these viewpoints, the thickness of the easy-adhesion coating layer 24 may be 0.01 to 3.0 μm, 0.03 to 2.0 μm, or 0.05 to 1.0 μm.

[0113] The surface of the easy-adhesion coating layer 24 facing the second solventless adhesive layer 26 may be subjected to various pretreatments such as corona treatment, plasma treatment, ozone treatment, and flame treatment in order to enhance adhesion to the adhesive layer.

[0114] A commercially available nylon film that has been treated to make it easy to adhere may be used as the polyamide polymer film that has been treated to make it easy to adhere, which is used to form the intermediate layer 25. Examples of commercially available products include "EMBLEM ONMB" (manufactured by Unitika Ltd.) and "HADEN NAP22" (manufactured by Toyobo Co., Ltd.).

[0115] From the viewpoint of maintaining high adhesion after retort treatment, it is preferable that the intermediate layer 25 includes a layer made of nylon film that has been subjected to an easy-adhesion treatment (i.e., includes a layer made of nylon film and an easy-adhesion coating layer formed by easy-adhesion treatment on the nylon film).

[0116] [Second Solvent-Free Adhesive Layer] The second solvent-free adhesive layer 26 is a layer formed from a solvent-free adhesive (second solvent-free adhesive). The second solvent-free adhesive layer 26 is formed by curing a solvent-free adhesive, similar to the first solvent-free adhesive layer 22 described above. The first solvent-free adhesive forming the first solvent-free adhesive layer 22 and the second solvent-free adhesive forming the second solvent-free adhesive layer 26 may be the same type or different types.

[0117] The thickness of the second solvent-free adhesive layer 26 is 1.6 to 3.0 μm. From the viewpoint of further suppressing foaming in the sealant layer during heat sealing, the thickness of the second solvent-free adhesive layer 26 is preferably 1.65 μm or more, more preferably 1.7 μm or more, and even more preferably greater than 1.8 μm. From the viewpoint of suppressing winding slippage and peeling during handling, the thickness of the second solvent-free adhesive layer 26 is preferably 2.9 μm or less, more preferably 2.8 μm or less, and even more preferably 2.6 μm or less. From the above viewpoints, the thickness of the second solvent-free adhesive layer 26 is preferably 1.6 to 2.9 μm, more preferably 1.65 to 2.8 μm, even more preferably 1.7 to 2.6 μm, and particularly preferably greater than 1.8 μm and 2.6 μm or less. The thickness of the second solvent-free adhesive layer 26 can be adjusted by adjusting the coating amount of the solvent-free adhesive.

[0118] From the viewpoint of reducing the amount of adhesive used to reduce production costs while enhancing the foaming suppression effect, the thickness of the second solvent-free adhesive layer 26 is preferably thicker than the thickness of the first solvent-free adhesive layer 22. In other words, the ratio of the thickness of the second solvent-free adhesive layer 26 to the thickness of the first solvent-free adhesive layer 22 (thickness of the second solvent-free adhesive layer 26 / thickness of the first solvent-free adhesive layer 22) preferably exceeds 1.

[0119] The ratio of the thickness of the second solvent-free adhesive layer 26 to the thickness of the first solvent-free adhesive layer 22 (thickness of the second solvent-free adhesive layer 26 / thickness of the first solvent-free adhesive layer 22) is preferably 0.53 to 2.73, more preferably 0.53 to 1.88, even more preferably 0.57 to 1.76, even more preferably 0.63 to 1.65, and particularly preferably 0.69 to 1.53, from the viewpoint of reducing production costs while maintaining basic performance as an adhesive layer, such as adhesion. From the viewpoint of further suppressing foaming in the sealant layer during heat sealing, the lower limit of these ranges may be 1 or more, or may even exceed 1. By reducing the thickness of the first solvent-free adhesive layer 22 and making the thickness of the second solvent-free adhesive layer 26 as thick as possible, the foaming suppression effect can be maximized within the constraints of production costs.

[0120] The laminate 30 can be manufactured, for example, by the following method. First, the substrate film constituting the substrate layer 21 and the adhesion-treated polyamide-based polymer film constituting the intermediate layer 25 are laminated via a first solventless adhesive so that the adhesion-treated polyamide-based polymer film's adhesion-treated coating layer 24 faces away from the substrate film. Next, a sealant film constituting the sealant layer 27 is laminated onto the adhesion-treated polyamide-based polymer film's adhesion-treated coating layer 24 via a second solventless adhesive. Next, an aging treatment is performed to harden the first solventless adhesive and the second solventless adhesive. This allows the laminate 30 to be obtained. However, the manufacturing method of the laminate 30 is not limited to the above method. For example, the adhesion-treated polyamide-based polymer film and the sealant film may be laminated before the adhesion-treated polyamide-based polymer film and the substrate film are laminated. Alternatively, either the first solventless adhesive layer 22 or the second solventless adhesive layer 26 may be cured first. Alternatively, for example, a pre-laminated laminate (a laminate of a substrate film and a polyamide polymer film that has been treated for easy adhesion, or a laminate of a polyamide polymer film that has been treated for easy adhesion and a sealant film) may be used. The lamination conditions and the conditions for curing the solvent-free adhesive are not particularly limited, and may follow the conditions for using known solvent-free adhesives.

[0121] In the laminate 30, the intermediate layer 25 and the second solventless adhesive layer 26 may or may not be adjacent to each other. Also, in the laminate 30, the second solventless adhesive layer 26 and the sealant layer 27 may or may not be adjacent to each other.

[0122] An example of the second embodiment of the laminate of the present disclosure has been described above, but the laminate of the present disclosure is not limited to the above example.

[0123] For example, the second embodiment of the laminate of the present disclosure may further include one or more other layers (e.g., films) to impart functions such as mechanical strength required of a packaging bag. The location of the other layer is not particularly limited. For example, the other layer may be provided between the substrate layer 21 and the first solventless adhesive layer 22, between the intermediate layer 25 and the second solventless adhesive layer 26, or between the second solventless adhesive layer 26 and the sealant layer 27. However, it is preferable that the intermediate layer 25, the second solventless adhesive layer 26, and the sealant layer 27 are adjacent to each other, as in the laminate 30 of FIG. 3. Examples of other layers include a printed layer.

[0124] Fig. 4 is a schematic cross-sectional view showing another example of a laminate according to the second embodiment of the present disclosure. The laminate 40 in Fig. 4 further includes a printed layer 28 on the surface of the substrate layer 21 facing the first solvent-free adhesive layer 22, in addition to a substrate layer 21, a first solvent-free adhesive layer 22, an intermediate layer 25, a second solvent-free adhesive layer 26, and a sealant layer 27. Details of the printed layer in the second embodiment are the same as those of the printed layer in the first embodiment, and therefore will not be described further.

[0125] Like the laminate 30, the laminate 40 has a second solventless adhesive layer 26 having a thickness of 1.6 to 3.0 μm, and therefore has improved storage stability, and a packaging material is obtained that is less likely to cause poor appearance due to foaming in the sealed area during heat sealing.

[0126] The thickness of the laminate 40 may be, for example, 35 to 275 μm, or 70 to 250 μm.

[0127] The laminate 40 can be produced in the same manner as the laminate 40, except that, for example, a printed layer 28 is formed on a substrate film constituting the substrate layer 21, a printed substrate film consisting of the substrate layer 21 and the printed layer 28 is obtained, and then the printed substrate film is used in place of the substrate film.

[0128] In the laminate 40, the base material layer 21 may be transparent so as to be able to display a pattern formed by the printing layer 28. Here, the base material layer 21 being transparent means that the total light transmittance of the film measured in accordance with JIS K7361-1:1997 using a color and turbidity simultaneous measuring device ("COH400" manufactured by Nippon Denshoku Industries Co., Ltd.) is 85% or more.

[0129] <Packaging Material> Another embodiment of the present disclosure is a packaging material (e.g., packaging film) including the laminate of the present disclosure described above. The packaging material includes, for example, a sealant layer as the outermost layer. The packaging material may consist solely of the laminate of the present disclosure described above (e.g., laminate 10, 20, 30, or 40), or may be a processed version of the laminate.

[0130] The packaging material of this embodiment is suitable for use in forming a packaging bag (e.g., a flexible bag) for packaging contents. Specifically, for example, a packaging bag can be manufactured by bonding the sealant layers of a pair of packaging materials together and forming a bag. Alternatively, for example, a packaging bag can be manufactured by folding one piece of packaging material so that the sealant layer faces each other and then forming a bag.

[0131] The packaging material of this embodiment includes the laminate of the present disclosure, and therefore has improved storage stability compared to conventional packaging materials. That is, the packaging material of this embodiment is less likely to suffer from poor appearance due to foaming at the sealed portion during heat sealing, and can be stored for a longer period of time without the poor appearance caused by foaming. The period during which the packaging material can be stored stably (the period during which the packaging material can be stored without the poor appearance caused by foaming) varies depending on storage conditions, etc., but tends to be longer when the packaging material is stored in a moisture-proof environment.

[0132] <Packaging Bag> Another embodiment of the present disclosure is a packaging bag produced by manufacturing the packaging material of the above embodiment. The packaging bag of this embodiment may be for boiling or retorting. Examples of the packaging bag include a flat pouch-shaped packaging bag and a self-standing packaging bag (standing pouch).

[0133] The flat pouch-shaped packaging bag may be, for example, a bag-shaped bag made by folding one sheet of packaging material (packaging material including a sealant layer) in half so that the sealant layers face each other, and then heat-sealing three sides, or may be a bag-shaped bag made by stacking two sheets of packaging material (packaging material including a sealant layer) on top of each other so that the sealant layers face each other, and then heat-sealing four sides.

[0134] The self-standing packaging bag may be, for example, a bag-shaped bag made by stacking three sheets of packaging material (packaging material including a sealant layer) with the sealant layers of the two sheets facing each other, and then inserting one sheet of packaging material (packaging material including a sealant layer) between the two sheets, folded in half with the sealant layer facing outward, and then heat-sealing the four sides.

[0135] <Package> Another embodiment of the present disclosure includes the packaging bag of the above embodiment and a content accommodated in the packaging bag. The content may be a liquid such as a liquid seasoning, toiletry products, soup, or liquid detergent, a solid such as a simmered dish, or a solid-liquid mixture of a liquid and a solid such as curry.

[0136] Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples, but the present disclosure is not limited to these examples.

[0137] [Examples of First Embodiment] Example 1 (Preparation of Materials) The following materials were prepared.

[0138] [Printed substrate film] A polyethylene terephthalate film (manufactured by TOPPAN Corporation, product name "GL-ARH", thickness: 12 μm) having a gas barrier layer (aluminum oxide vapor-deposited layer) on one main surface was prepared as the substrate film, and a printed layer (thickness: maximum 3 μm) made of colored ink was formed by gravure printing on the gas barrier layer side of the substrate film. "Riogran" manufactured by Toyo Ink Co., Ltd. was used as the colored ink, and printing was carried out so as to form a test pattern including an area without a printed layer for evaluating the foaming property of the sealed area. A printed substrate film was obtained by the above operations.

[0139] [Polyamide-based polymer film] A biaxially stretched nylon film (manufactured by Unitika Ltd., trade name "Emblem ONBC", thickness: 15 μm, corona treated on both sides) having no adhesive coating layer was prepared as a polyamide-based polymer film.

[0140] [Solvent-free adhesive] A two-component curing urethane-based solvent-free adhesive was prepared containing the following polyol component and the following polyisocyanate component in an equivalent ratio of 1:1: Polyol component: "TSN-4864A" manufactured by Toyo-Morton Co., Ltd. Polyisocyanate component: "TSN-4864B-3" manufactured by Toyo-Morton Co., Ltd.

[0141] [Sealant Film] An unstretched polypropylene film (CPP film, manufactured by Toray Industries, Inc., trade name "Torayfan ZK-207", thickness: 60 μm, one side corona treated) was prepared as a sealant film.

[0142] (Production of Laminate) A solventless adhesive was applied to one main surface of a polyamide polymer film, and the polyamide polymer film and the printed substrate film were laminated (lamination temperature 50°C) so that the coated surface faced the printed layer of the printed substrate film, to obtain a laminate film A. Next, a solventless adhesive was applied to the corona-treated surface of the sealant film, and the sealant film and the laminate film A were laminated (lamination temperature 50°C) so that the coated surface faced the easy-adhesion coating layer of the laminate film A, to obtain a laminate film B. Thereafter, the laminate film B was aged (temperature: 40°C, period: 3 days) to cure the solventless adhesive, and a laminate (layer structure: substrate layer / printed layer / first solventless adhesive layer / intermediate layer / second solventless adhesive layer / sealant layer) was obtained in the form of a roll with a width of 800 mm and a length of 200 m. The thickness of each of the solvent-free adhesive layers (first solvent-free adhesive layer and second solvent-free adhesive layer) of the resulting laminate was 1.1 μm.

[0143] The thickness of the adhesive layer was determined by cutting the laminate parallel to the lamination direction using a microtome, observing the cross section using an electron microscope at a magnification of 10,000 times, and calculating the average thickness of three arbitrary points in the area of ​​the laminate where there was no printed layer (plain area).

[0144] Examples 2 to 8 Laminates were obtained in the same manner as in Example 1, except that the coating amount of the solventless adhesive was adjusted. The thicknesses of the solventless adhesive layers (first solventless adhesive layer and second solventless adhesive layer) of the laminates of Examples 2 to 8 were as shown in Table 1.

[0145] Example 9 A laminate was obtained in the same manner as in Example 1, except that a biaxially oriented nylon film without an easy-adhesion coating layer (manufactured by Toyobo Co., Ltd., product name "Harden N1202", thickness: 15 μm, corona-treated on both sides) was used as the polyamide-based polymer film, and the coating amount of the solvent-free adhesive was adjusted. The thicknesses of the solvent-free adhesive layers (first solvent-free adhesive layer and second solvent-free adhesive layer) of the laminate of Example 9 were both 1.6 μm.

[0146] Example 10 A laminate was obtained in the same manner as in Example 1, except that a biaxially oriented nylon film without an easy-adhesion coating layer (manufactured by Idemitsu Unitec Co., Ltd., product name "UNILON G-101", thickness: 15 μm, corona-treated on both sides) was used as the polyamide-based polymer film, and the coating amount of the solvent-free adhesive was adjusted. The thicknesses of the solvent-free adhesive layers (first solvent-free adhesive layer and second solvent-free adhesive layer) of the laminate of Example 10 were both 1.7 μm.

[0147] Example 11 A laminate was obtained in the same manner as in Example 1, except that a biaxially oriented nylon film without an easy-adhesion coating layer (manufactured by Mitsubishi Chemical Corporation, trade name "Santonil SNR", thickness: 15 μm, corona-treated on both sides) was used as the polyamide-based polymer film, and the coating amount of the solvent-free adhesive was adjusted. The thicknesses of the solvent-free adhesive layers (first solvent-free adhesive layer and second solvent-free adhesive layer) of the laminate of Example 11 were both 1.8 μm.

[0148] Comparative Example 1: Instead of the biaxially oriented nylon film without an easy-adhesion coating layer, an easy-adhesion-treated biaxially oriented nylon film (manufactured by Unitika Co., Ltd., trade name "ONMB", thickness: 15 μm, double-sided corona-treated) having an easy-adhesion coating layer (thickness: 0.1 to 0.2 μm) on one main surface was used, the easy-adhesion-treated biaxially oriented nylon film was laminated so that the easy-adhesion coating layer and the sealant layer faced each other, and the coating amount of the solventless adhesive was adjusted. A laminate (layer structure: substrate layer / printed layer / first solventless adhesive layer / layer consisting of polyamide-based polymer film / easy-adhesion coating layer / second solventless adhesive layer / sealant layer) was obtained in the same manner as in Example 1. The thicknesses of the solventless adhesive layers (first solventless adhesive layer and second solventless adhesive layer) of the laminate of Comparative Example 1 were both 1.1 μm.

[0149] <Evaluation Test> The following evaluation tests were carried out on each of the obtained laminates.

[0150] [Foamability] For the laminates of each Example and Comparative Example, immediately after aging and after storage at room temperature and humidity for 14 days, one laminate (15 cm in the machine direction, 6 cm in the width direction) was folded in the machine direction to face the sealant layers, and heat-sealed under the following heat-sealing conditions to obtain a sealed product. Heat-sealing conditions: Using a heat seal tester (manufactured by Tester Sangyo Co., Ltd., model number: TP-701-B), the sealant layers (6 cm in the width direction) located in the areas of the laminate where there was no printed layer (plain areas) were heat-sealed together under conditions of an upper temperature of 190°C, a lower temperature of 120°C, a pressure of 0.3 MPa, and a heating time of 0.3 seconds. Immediately after heat-sealing, a metal plate was pressed against the sealed areas to cool them.

[0151] Next, the appearance of the sealed portion of the obtained sealed body was visually observed, and foaming was evaluated according to the following evaluation criteria. The results are shown in Table 1. If the evaluation is A or B, foaming is sufficiently suppressed. Evaluation criteria: A: No foaming. B: Not noticeable on the outside, but small bubbles have occurred locally. C: Bubbles are visible and scattered. D: Bubbles are generated in a dense pattern, and there is a change in appearance such as whitening.

[0152] FIG. 5 shows examples of sealing bodies that were evaluated as A to D in the foaming property evaluation test.

[0153] [Retort Resistance] (Preparation of Packaging Bags) The retort resistance of the laminates of each Example, Comparative Example, and Reference Example after storage was evaluated using the following method. To evaluate retort resistance, first, one laminate (40 cm in the machine direction) was folded in half in the machine direction so that the sealant layers faced each other, and both sides were heat-sealed. Next, 200 mL of water was filled as the contents through the opening, and the opening was heat-sealed to produce a packaging bag measuring 20 cm wide x 17 cm long. Heat sealing was performed using a heat seal tester (manufactured by Tester Sangyo Co., Ltd., model number: TP-701-B) with a 10 mm wide seal bar under the following conditions: upper temperature 190°C, lower temperature 120°C, pressure 0.3 MPa, and heating time 0.3 seconds. Storage method: The entire surface of each laminate was covered with an aluminum-deposited PET film (thickness: 12 μm), and biaxially oriented polypropylene tape (OPP tape, manufactured by Nitto Denko CS Systems Corporation, product name "Damplon Tape") was attached to the seams to seal the laminate, and the laminate was stored at room temperature and normal humidity for 20 days.

[0154] The resulting packaging bag was retorted at 130°C for 35 minutes, and then a test piece 15 mm wide x 100 mm long was cut out from a portion of the packaging bag without a printed layer, and the laminate strength was measured by the following procedure.

[0155] (Measurement of Laminate Strength) The test specimen was longitudinally peeled approximately 20 mm between the base layer and intermediate layer, and between the intermediate layer and sealant layer. The peeled sections were attached to the grip of a tensile tester (autograph, manufactured by Shimadzu Corporation, model AGS-X), and a T-peel test was performed at a peel rate of 300 mm / min to measure the laminate strength between the base layer and intermediate layer, and between the intermediate layer and sealant layer. If significant fracture, such as tearing of the base layer, intermediate layer, or sealant layer, occurred shortly after the start of peeling, resulting in a maximum value in the tensile strength profile, this maximum value was recorded as the laminate strength. If uniform peeling occurred without fracture, the average value of the stable portion of the tensile strength profile, excluding the initial rise in tensile strength immediately after the start of peeling, was recorded as the laminate strength. The measured laminate strength was used to evaluate retort resistance according to the following criteria. The results are shown in Table 1. Evaluation criteria: A: The laminate strength after retort treatment between the base layer and intermediate layer is 1 N / 15 mm or more, and the laminate strength after retort treatment between the intermediate layer and sealant layer is 5 N / 15 mm or more. B: The laminate strength after retort treatment between the base layer and intermediate layer is less than 1 N / 15 mm, or the laminate strength after retort treatment between the intermediate layer and sealant layer is less than 5 N / 15 mm.

[0156]

[0157] [Example of Second Embodiment] <Preparation of Materials> The following materials were prepared.

[0158] [Printed Base Film] A printed base film identical to the printed base film in the example of the first embodiment described above was prepared.

[0159] [Polyamide-based polymer film with easy adhesion treatment] As the easy-adhesion-treated polyamide-based polymer film, an easy-adhesion-treated biaxially oriented nylon film (manufactured by Unitika Ltd., trade name "ONMB-RT", thickness: 15 μm) having an easy-adhesion coating layer (thickness: 0.1 to 0.2 μm) on one main surface was prepared. This easy-adhesion-treated biaxially oriented nylon film had been subjected to corona treatment on both main surfaces (the main surface of the nylon film and the main surface of the easy-adhesion coating layer).

[0160] [Solvent-free adhesive] The same solvent-free adhesive as the solvent-free adhesive in the example of the first embodiment described above was prepared.

[0161] [Sealant Film] A sealant film identical to the sealant film of the example of the first embodiment described above was prepared.

[0162] <Production of Laminate> (Example 12) A solventless adhesive was applied to the main surface of the easy-adhesion-treated polyamide polymer film opposite the surface on which the easy-adhesion coating layer was formed, and the easy-adhesion-treated polyamide polymer film and the printed base film were laminated (lamination temperature 50°C) so that this surface faced the printed layer of the printed base film, to obtain a laminate film C. Next, a solventless adhesive was applied to the corona-treated surface of the sealant film, and the sealant film and the laminate film C were laminated (lamination temperature 50°C) so that this surface faced the easy-adhesion coating layer of the laminate film C, to obtain a laminate film D. The laminate film D was then aged (temperature: 40°C, period: 4 days) to cure the solventless adhesive, and a laminate (layer structure: substrate layer / printed layer / first solventless adhesive layer / layer made of polyamide-based polymer film / easy-adhesion coating layer / second solventless adhesive layer / sealant layer) was obtained in the form of a roll with a width of 800 mm and a length of 200 m. The thicknesses of the solventless adhesive layers (first solventless adhesive layer and second solventless adhesive layer) of the obtained laminate were both 1.6 µm.

[0163] The thickness of the adhesive layer was determined in the same manner as in the example of the first embodiment described above.

[0164] (Examples 13 to 17 and Comparative Examples 2 and 3) Except for adjusting the coating amount of the solventless adhesive, laminates were obtained in the same manner as in Example 12. The thicknesses of the solventless adhesive layers (first solventless adhesive layer and second solventless adhesive layer) of the laminates of Examples 13 to 17 and Comparative Examples 2 and 3 were as shown in Table 2.

[0165] (Reference Example 1) A laminate was obtained in the same manner as in Example 12, except that a biaxially oriented nylon film without an easy-adhesion coating layer (manufactured by Unitika Ltd., product name "ONBC", thickness: 15 μm, corona-treated on both sides) was used instead of the easy-adhesion-treated biaxially oriented nylon film having an easy-adhesion coating layer on one main surface, and the coating amount of the solventless adhesive was adjusted. The thicknesses of the solventless adhesive layers (first solventless adhesive layer and second solventless adhesive layer) in Reference Example 1 were both 1.1 μm.

[0166] <Evaluation Test> The following evaluation tests were carried out on each of the obtained laminates.

[0167] [Foamability] For the laminates of each Example, Comparative Example, and Reference Example, immediately after aging and after storage by the following method, one laminate (15 cm in the machine direction, 6 cm in the width direction) was folded in the machine direction so that the sealant layers faced each other, and heat-sealed under the following heat-sealing conditions to obtain a sealed product. Storage method: The entire surface of each laminate was covered with an aluminum-deposited PET film (thickness: 12 μm), and biaxially oriented polypropylene tape (OPP tape, manufactured by Nitto Denko CS Systems Corporation, product name "Damplon Tape") was applied to the seams to seal the laminate, and the laminate was stored at room temperature and normal humidity for 20 days. Heat sealing conditions: Using a heat seal tester (manufactured by Tester Sangyo Co., Ltd., model number: TP-701-B), a 10 mm wide seal bar was used to heat seal the sealant layers (6 cm in the width direction) located in areas of the laminate where there was no printed layer (plain areas) under conditions of an upper temperature of 210°C, a lower temperature of 120°C, a pressure of 0.3 MPa, and a heating time of 0.3 seconds, and immediately after heat sealing, a metal plate was pressed against the sealed areas to cool them.

[0168] Next, the appearance of the sealed portion of the obtained sealed body was visually observed, and the foaming property was evaluated using the same evaluation criteria as in the example of the first embodiment described above. The results are shown in Table 2.

[0169] [Retort resistance] (Production of packaging bags) The retort resistance of the laminates of each of the Examples, Comparative Examples, and Reference Examples after 20 days of storage in the foamability evaluation test was evaluated. Specifically, first, packaging bags measuring 20 cm wide x 17 cm long and filled with 200 mL of water were produced in the same manner as in the example of the first embodiment described above, except that the heat-sealing conditions were changed to an upper temperature of 210°C, a lower temperature of 120°C, a pressure of 0.3 MPa, and a heating time of 0.3 seconds.

[0170] Next, the resulting packaging bag was retorted at 130°C for 35 minutes, and then a test piece 15 mm wide x 100 mm long was cut out from the portion of the packaging bag without a printed layer, and the laminate strength was measured using the same procedure as in the example of the first embodiment described above. Using the measured laminate strength, the retort resistance was evaluated using the same evaluation criteria as in the example of the first embodiment described above. The results are shown in Table 2.

[0171]

[0172] 10, 20, 30, 40...Laminate, 11, 21...Base material layer, 12, 22...First solventless adhesive layer, 13, 23...Layer made of polyamide-based polymer film, 24...Easy-adhesion coating layer, 15, 25...Intermediate layer, 16, 26...Second solventless adhesive layer, 17, 27...Sealant layer, 18, 28...Printed layer.

Claims

1. A laminate comprising a substrate layer, a first solvent-free adhesive layer, an intermediate layer, a second solvent-free adhesive layer, and a sealant layer in this order, wherein the intermediate layer comprises a layer made of a polyamide-based polymer film, and the layer made of the polyamide-based polymer film and the second solvent-free adhesive layer are in direct contact with each other, or the intermediate layer further comprises an easy-adhesion coating layer that forms the surface of the intermediate layer facing the second solvent-free adhesive layer, and the second solvent-free adhesive layer has a thickness of 1.6 to 3.0 μm.

2. The laminate according to claim 1, wherein the layer made of the polyamide polymer film and the second solventless adhesive layer are in direct contact with each other.

3. The laminate according to claim 2, wherein the thickness of the first solventless adhesive layer is 0.8 to 4.0 μm.

4. The laminate according to claim 2 or 3, wherein the second solventless adhesive layer has a thickness of 0.8 to 4.0 μm.

5. The laminate according to claim 1, wherein the intermediate layer includes the easy-adhesion coating layer, and the thickness of the second solventless adhesive layer is 1.6 to 3.0 μm.

6. The laminate according to claim 5, wherein the thickness of the layer made of the polyamide polymer film is 10 to 35 μm.

7. The laminate according to claim 5 or 6, wherein the thickness of the easy-adhesion coating layer is 0.01 to 3.0 μm.

8. The laminate according to any one of claims 5 to 7, wherein the first solventless adhesive layer has a thickness of 1.6 to 3.0 µm.

9. The laminate according to any one of claims 1 to 8, wherein the substrate layer has gas barrier properties.

10. The laminate according to any one of claims 1 to 9, wherein the thickness of the second solventless adhesive layer is greater than the thickness of the first solventless adhesive layer.

11. The laminate according to any one of claims 1 to 10, further comprising a printed layer on the surface of the substrate layer facing the first solventless adhesive layer.

12. The laminate according to any one of claims 1 to 11, wherein the sealant layer is made of a non-oriented polypropylene film.

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

14. A packaging bag made from the packaging material according to claim 13.

15. The packaging bag according to claim 14, which is for boiling or retorting.

16. A package comprising the packaging bag according to claim 14 and contents contained in the packaging bag.

Images