Laminate and packaging bag

Abstract

The present invention provides a laminate comprising: a resin base material; an inorganic thin film layer laminated on at least one surface side of the resin base material; a protective layer laminated on the inorganic thin film layer; a nylon film laminated by applying a two-part liquid curable adhesive to the surface of the protective layer and then bonding the nylon film therewith by dry lamination; and a cast polypropylene film laminated by applying a two-part liquid curable adhesive to the surface of the nylon film and then bonding the cast polypropylene film therewith by dry lamination, wherein the laminate has gas barrier properties satisfying the following requirements (1) to (3). (1) No layer is provided between the resin base material and the inorganic thin film layer. (2) The nylon film has a heat shrinkage between 2.0% and 6.0% inclusive in MD before and after retorting at 130°C for 30 minutes. (3) After subjecting the laminate to heat-moisture treatment at 130°C for 30 minutes, no delamination occurs and the water vapor permeability is not more than 2.5 g / m2·day.

Description

Laminate and packaging bag

[0001] The present invention relates to a laminate used in the field of packaging food, pharmaceuticals, industrial products, etc. More specifically, the present invention relates to a laminate that can exhibit good gas barrier properties and adhesion by controlling the physical properties of a gas barrier laminate film having an inorganic thin film layer and an adhesive film.

[0002] Packaging materials used for food, pharmaceuticals, etc. are required to have gas barrier properties, i.e., the ability to block gases such as oxygen and water vapor, in order to inhibit oxidation of proteins and fats and oils, preserve flavor and freshness, and maintain the efficacy of pharmaceuticals. Furthermore, gas barrier materials used in electronic devices and electronic components, such as solar cells and organic electroluminescence (EL), require even higher gas barrier properties than packaging materials for food, etc.

[0003] Conventionally, in food applications that require blocking various gases such as water vapor and oxygen, gas barrier laminate films have generally been used, in which a thin metal film made of aluminum or the like or a thin inorganic film made of an inorganic oxide such as silicon oxide or aluminum oxide is formed on the surface of a plastic substrate film. In particular, films formed with a thin film of an inorganic oxide such as silicon oxide, aluminum oxide, or a mixture thereof are widely used because they are transparent and allow the contents to be confirmed.

[0004] However, inorganic thin films have poor flexibility, and therefore pinholes and defects are likely to occur when the film is bent or subjected to impact, or when the film is subjected to high-temperature treatment such as retort treatment, resulting in problems such as a decrease in gas barrier properties.

[0005] To address the above-mentioned problems, attempts have been made to provide an additional protective layer on the inorganic thin film. For example, a laminated film in which a water-soluble polymer resin or a solvent-soluble resin is provided on an inorganic thin film is known, which can improve the stability of the gas barrier property.

[0006] However, these laminate films have various heat shrinkage rates depending on the position of the base film and the winding conditions during lamination of the inorganic thin film. When a laminate product is produced by laminating a sealant layer using a laminate film with a high heat shrinkage rate and then subjected to retort treatment, the laminate product elongates and shrinks during high-humidity heat treatment, causing tensile and compressive stresses in the gas barrier layer, resulting in cracks and a decrease in barrier performance.

[0007] Against this background, methods have been known in which a coating layer such as an inline coating layer or an anchor coating layer is applied to a substrate film, thereby maintaining gas barrier properties and adhesion even after wet heat treatment (Patent Documents 1 and 2). Another method has been known in which a substrate film containing a polyester resin whose main constituent unit is butylene terephthalate units is used to improve the flexibility of the substrate itself, thereby maintaining good gas barrier properties even after wet heat treatment (Patent Documents 3 and 4). Another method has been known in which a laminated film of a shrink film and a polyamide film is used to adjust the shrinkage rate, thereby maintaining good gas barrier properties even after hot water treatment (Patent Document 5).

[0008] However, in any of the above-mentioned methods, it is necessary to change the raw material of the base film itself, and a dedicated lot must be prepared, which poses the problem that it is not possible to handle a wide variety of products in small lots.

[0009] Furthermore, a method is also known in which the thermal shrinkage rate can be controlled by a drying process of the substrate, thereby improving the interlayer adhesion strength (Patent Document 6). However, there is no mention of moist heat treatment.

[0010] In addition, a method is known in which a laminated film having a desired heat shrinkage rate is produced during the coating process of the protective layer laminated on the resin substrate, and the gas barrier properties can be maintained when the film is subjected to retort treatment (Patent Document 7).

[0011] Japanese Patent No. 6631098 Japanese Patent No. 6507847 Japanese Patent Publication No. 2019-014043 Japanese Patent No. 6879292 Japanese Patent Publication No. 2018-089800 Japanese Patent Publication No. 2017-144593 Japanese Patent Publication No. 07279759

[0012] An object of the present invention is to provide a laminate that has good gas barrier properties, has little variation in gas barrier properties even after retort treatment, and is free from delamination.

[0013] The present inventors have carefully investigated the film-forming method and stretching ratio when forming a nylon film, and have produced a nylon film having a desired heat shrinkage rate. They have found that when the nylon film is laminated with a resin substrate and subjected to a retort treatment, the gas barrier properties are maintained and further, no delamination occurs.

[0014] That is, the present invention has the following configuration. 1. A laminate having gas barrier properties, comprising a resin substrate, an inorganic thin film layer laminated on at least one side of the resin substrate, a protective layer laminated on the inorganic thin film layer, a nylon film laminated by applying a two-component curing adhesive to the surface of the protective layer and laminating them together by dry lamination, and an unstretched polypropylene film laminated by applying a two-component curing adhesive to the surface of the nylon film and laminating them together by dry lamination, and characterized by satisfying the following requirements (1) to (3): (1) no layer is provided between the resin substrate and the inorganic thin film layer; (2) the heat shrinkage rate of the nylon film in the MD direction before and after retort treatment at 130°C for 30 minutes is 2.0% or more and 6.0% or less; and (3) after wet heat treatment of the laminate at 130°C for 30 minutes, no delamination occurs and the water vapor permeability is 2.5 g / m ２ - days or less. 2. The laminate according to 1., wherein the inorganic thin film layer contains at least one type of inorganic oxide including silicon oxide and / or aluminum oxide. 3. The laminate according to 1., wherein the protective layer contains at least one type of urethane resin or ester resin. 4. The laminate according to 1., wherein the protective layer contains a silane coupling agent. 5. A packaging bag, at least a part of which uses the laminate according to 4.

[0015] According to the present invention, it is possible to provide a laminate that has good gas barrier properties, has little variation in gas barrier properties even after retort treatment, and is free from delamination.

[0016] The present invention provides a gas-barrier laminate comprising a resin substrate, an inorganic thin film layer laminated on at least one side of the resin substrate, a protective layer laminated on the inorganic thin film layer, a nylon film laminated by applying a two-component curing adhesive to the surface of the protective layer and laminating them together by dry lamination, and an unstretched polypropylene film laminated by applying a two-component curing adhesive to the surface of the nylon film and laminating them together by dry lamination, the laminate satisfying the following requirements (1) to (3): (1) no layer is provided between the resin substrate and the inorganic thin film layer; (2) the heat shrinkage rate of the nylon film in the MD direction before and after retort treatment at 130°C for 30 minutes is 2.0% to 6.0%; and (3) after wet heat treatment of the laminate at 130°C for 30 minutes, no delamination occurs and the water vapor permeability is 2.5 g / m ２ ・It must be less than day.

[0017] [Substrate Film (Resin Substrate)] The substrate film (hereinafter sometimes referred to as "substrate film") used in the present invention may be, for example, a stretched film obtained by melt-extruding a plastic and, if necessary, stretching it in the longitudinal direction (MD direction) and / or the width direction (TD direction), cooling, and heat setting. Biaxially stretched films stretched in the longitudinal and width directions are preferred in terms of obtaining sufficient mechanical strength. Examples of plastics include polyamides such as nylon 4.6, nylon 6, nylon 6.6, and nylon 12; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate; polyolefins such as polyethylene, polypropylene, and polybutene; as well as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, wholly aromatic polyamide, polyamideimide, polyimide, polyetherimide, polysulfone, polystyrene, and polylactic acid. Among these, polyester is preferred in terms of heat resistance, dimensional stability and transparency, and polyethylene terephthalate and copolymers in which polyethylene terephthalate is copolymerized with other components are particularly preferred.

[0018] The substrate film can have any thickness depending on the desired purpose and application, such as mechanical strength and transparency. While the thickness is not particularly limited, a thickness of 5 to 250 μm is usually recommended, and when used as a packaging material, a thickness of 10 to 60 μm is desirable. From the viewpoints of handling during processing, post-processing, and machine costs, the width of the substrate film is preferably 1,000 mm or more and 5,000 mm or less, more preferably 3,000 mm or less, and even more preferably 2,000 mm or less. The transparency of the substrate film is not particularly limited, but when used as a packaging material requiring transparency, a substrate film with a light transmittance of 50% or more is desirable.

[0019] The substrate film may be a monolayer film made of one type of plastic, or a laminated film in which two or more types of plastic films are laminated. When a laminated film is used, the type of laminated film, the number of layers, the lamination method, etc. are not particularly limited, and can be arbitrarily selected from known methods depending on the purpose. Furthermore, the substrate film may be subjected to surface treatment such as corona discharge treatment, glow discharge, flame treatment, surface roughening treatment, etc., as long as it does not impair the purpose of the present invention, and may also be subjected to known anchor coating treatment, printing, decoration, etc.

[0020] The MD shrinkage rate is the shrinkage rate in the machine direction, i.e., the longitudinal direction, and the TD shrinkage rate is the shrinkage rate in the transverse direction, i.e., the horizontal direction.

[0021] The initial MD heat shrinkage value of the substrate film used before and after retort treatment at 130°C for 30 minutes is preferably 2.0% or less, more preferably 1.6% or less, even more preferably 1.5% or less, and even more preferably 1.4% or less. The widthwise MD heat shrinkage difference Δ is preferably 0.6% or less, more preferably 0.5% or less, and even more preferably 0.4% or less. The TD heat shrinkage is preferably -0.6% or more, more preferably -0.5% or more, and even more preferably -0.4% or more.

[0022] [Inorganic Thin Film Layer] The laminate film of the present invention has an inorganic thin film layer on the substrate film. The inorganic thin film layer is laminated directly on the resin substrate (substrate film), with no layer provided between the two layers.

[0023] The inorganic thin film layer is a thin film made of a metal or inorganic oxide. There are no particular limitations on the material forming the inorganic thin film layer as long as it can be formed into a thin film. However, from the viewpoint of gas barrier properties, inorganic oxides such as aluminum oxide (alumina), silicon oxide (silica), and a mixture of silicon oxide and aluminum oxide are preferred. Aluminum oxide is particularly preferred from the viewpoint of productivity. Furthermore, a laminate film having a configuration in which a predetermined protective layer described below is combined with an inorganic thin film layer made of aluminum oxide is preferred because it exhibits significant improvements in oxygen permeability and water-lamination strength, particularly after acid treatment. Here, silicon oxide refers to various silicon oxides such as SiO and SiO2 or a mixture thereof, and aluminum oxide refers to various aluminum oxides such as AlO and Al2O3 or a mixture thereof.

[0024] The thickness of the inorganic thin film layer is usually 1 to 100 nm, preferably 3 to 50 nm, and more preferably 5 to 20 nm. If the thickness of the inorganic thin film layer is less than 1 nm, it may be difficult to obtain satisfactory gas barrier properties. On the other hand, even if the thickness is excessively greater than 100 nm, the corresponding improvement in gas barrier properties cannot be obtained and is actually disadvantageous in terms of flex resistance and production costs.

[0025] The method for forming the inorganic thin film layer is not particularly limited, and any known vapor deposition method, such as physical vapor deposition (PVD) methods (e.g., vacuum deposition, sputtering, ion plating), or chemical vapor deposition (CVD), may be appropriately employed. A typical method for forming the inorganic thin film layer will be described below, using an aluminum oxide thin film as an example. For example, when using vacuum deposition, Al2O3 or Al is preferably used as the deposition source material. These deposition sources are typically particles, and the particle size is preferably large enough to prevent pressure changes during deposition, with a preferred particle diameter of 1 mm to 5 mm. Heating methods such as resistance heating, high-frequency induction heating, electron beam heating, and laser heating can be used. Reactive vapor deposition can also be employed, using reactive gases such as oxygen, nitrogen, hydrogen, argon, carbon dioxide, and water vapor, or by adding ozone or using ion-assisted deposition. Furthermore, film formation conditions can be freely modified, such as by applying a bias to the deposition target (the laminate film to be deposited) or by heating or cooling the deposition target. The deposition material, reactive gas, bias of the deposition target, heating / cooling, etc. can be changed in the same manner when sputtering or CVD is employed.

[0026] [Protective Layer] In the present invention, a protective layer is provided on the inorganic thin film layer. The inorganic thin film layer laminated on the plastic film is not a completely dense film, but has minute defects scattered therein. By forming a protective layer by coating the inorganic thin film layer with a specific resin composition for the protective layer described below, the resin in the resin composition for the protective layer penetrates into the defects in the inorganic thin film layer, resulting in stable gas barrier properties. In addition, by using a material with gas barrier properties for the protective layer itself, the gas barrier performance of the laminate film is also greatly improved.

[0027] In the present invention, the coating amount of the protective layer is 0.05 to 0.60 g / m 2This makes it possible to reduce coating unevenness and defects due to uniformity, while enhancing adhesion through the anchor effect. In addition, the cohesive force of the protective layer itself is improved, strengthening adhesion between the inorganic thin film layer and the protective layer, and improving water resistance. The coating amount of the protective layer is preferably 0.08 g / m 2 More preferably, 0.10 g / m 2 More preferably, 0.15 g / m 2 or more, and preferably 0.50 g / m 2 or less, more preferably 0.45 g / m 2 More preferably, 0.40 g / m or less 2 The coating amount of the protective layer is 0.60 g / m or less. 2 If the thickness of the protective layer exceeds 0.10 g / m, the gas barrier property is improved, but the cohesive force inside the protective layer may be insufficient, resulting in a risk of reduced adhesion. Furthermore, unevenness or defects may occur in the coating appearance, and the gas barrier property and adhesiveness may not be fully exhibited after moist heat treatment. On the other hand, if the thickness of the protective layer exceeds 0.10 g / m, 2 If the thickness is less than this, there is a risk that sufficient gas barrier properties, interlayer adhesion, and ink permeability may not be obtained.

[0028] The protective layer may be made of either a solvent-dispersed resin or a water-dispersed resin. Solvent-dispersed resins are particularly preferred for improving adhesion to the inorganic thin film layer. Furthermore, resins made of a polyester polyol component obtained by reacting a dicarboxylic acid with a polyhydric alcohol and a polyisocyanate component are preferred for achieving high gas barrier properties.

[0029] (A) Polyester Component The polyester component is obtained by reacting a polycarboxylic acid with a polyhydric alcohol.

[0030] The polycarboxylic acid includes aromatic polycarboxylic acids, alicyclic polycarboxylic acids, aliphatic polycarboxylic acids, etc. From the viewpoint of gas barrier properties, aromatic polycarboxylic acids are preferred. Examples include orthophthalic acid, isophthalic acid, terephthalic acid, 1,2-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, anthracene-1,2-dicarboxylic acid, and anthraquinone-2,3-dicarboxylic acid.

[0031] As the polyhydric alcohol, glycols ranging from low molecular weight to high molecular weight can be used. However, from the viewpoint of gas barrier properties and flexibility due to the amorphous portion, alkylene glycols (e.g., linear or branched C alkylene glycols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, neopentyl glycol, heptanediol, and octanediol) are preferred. 2-10 alkylene glycol), (poly)oxy C 2-4 Low molecular weight glycols such as alkylene glycols (diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, etc.) are used. 2-8 Polyol component [e.g., C 2-6 alkylene glycols (especially ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol), etc.], di- or tri-oxy C 2-3 Alkylene glycol (diethylene glycol, triethylene glycol, dipropylene glycol, etc.), and particularly preferred diol components are C 2-8 Alkylene glycol (especially C 2-6 alkylene glycol).

[0032] These diol components can be used alone or in combination of two or more. Furthermore, if necessary, low-molecular-weight diol components such as aromatic diols (e.g., bisphenol A, bishydroxyethyl terephthalate, catechol, resorcinol, hydroquinone, 1,3- or 1,4-xylylenediol or a mixture thereof), alicyclic diols (e.g., hydrogenated bisphenol A, xylylenediol, cyclohexanediol, cyclohexanedimethanol), etc. may be used in combination. Furthermore, if necessary, tri- or higher-functional polyol components, such as glycerin, trimethylolethane, trimethylolpropane, polyester polyol, polycarbonate polyol, and polyether polyol may also be used in combination. The polyol component should preferably contain at least C 2-8Polyol component (especially C 2-6 Preferably, the solvent contains an alkylene glycol.

[0033] (B) Polyisocyanate Component The polyisocyanate component includes aromatic polyisocyanates, alicyclic polyisocyanates, aliphatic polyisocyanates, etc. As the polyisocyanate compound, a diisocyanate compound is usually used.

[0034] Examples of aromatic diisocyanates include tolylene diisocyanate (2,4- or 2,6-tolylene diisocyanate or a mixture thereof) (TDI), phenylene diisocyanate (m-, p-phenylene diisocyanate or a mixture thereof), 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), diphenylmethane diisocyanate (4,4'-, 2,4'-, or 2,2'-diphenylmethane diisocyanate or a mixture thereof) (MDI), 4,4'-toluidine diisocyanate (TODI), and 4,4'-diphenyl ether diisocyanate. Examples of the araliphatic diisocyanate include xylylene diisocyanate (1,3- or 1,4-xylylene diisocyanate or a mixture thereof) (XDI), tetramethyl xylylene diisocyanate (1,3- or 1,4-tetramethyl xylylene diisocyanate or a mixture thereof) (TMXDI), ω,ω'-diisocyanato-1,4-diethylbenzene, and the like.

[0035] Examples of alicyclic diisocyanates include 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorodiisocyanate, IPDI), methylenebis(cyclohexyl isocyanate) (4,4'-, 2,4'-, or 2,2'-methylenebis(cyclohexyl isocyanate)) (hydrogenated MDI), methylcyclohexane diisocyanate (methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate), bis(isocyanatomethyl)cyclohexane (1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or a mixture thereof) (hydrogenated XDI), and the like.

[0036] Examples of aliphatic diisocyanates include trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate), hexamethylene diisocyanate, pendanthemylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, and 2,6-diisocyanate methyl caffeate.

[0037] A urethane resin is obtained by reacting a polyester component (A) with a polyisocyanate component (B). The weight ratio of the polyester component to the polyisocyanate component is 9:1 to 1:9 on a solids basis, preferably 8:2 to 2:8, and more preferably 6:4 to 4:6.

[0038] The resin composition for a protective layer of the present invention preferably contains a silane coupling agent as described below, but may also contain various additives as needed within a range that does not impair the gas barrier properties. Examples of additives include layered inorganic compounds, stabilizers (antioxidants, heat stabilizers, ultraviolet absorbers, etc.), plasticizers, antistatic agents, lubricants, antiblocking agents, colorants, fillers, and crystal nucleating agents.

[0039] Silane coupling agents are effective in improving the adhesion of a protective layer to an inorganic thin film layer. Examples of silane coupling agents include hydrolyzable alkoxysilane compounds, such as halogen-containing alkoxysilanes (chloro C2-4 alkyl tri C1-4 alkoxysilanes such as 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-chloropropyltrimethoxysilane, and 3-chloropropyltriethoxysilane), and alkoxysilanes having an epoxy group (2-glycidyloxyethyltrimethoxysilane, 2-glycidyloxyethyltriethoxysilane, 3-glycidyloxypropyltriethoxysilane, and the like). glycidyloxy C2-4 alkyltriC1-4 alkoxysilanes such as 3-glycidyloxypropyltriethoxysilane, glycidyloxydiC2-4 alkyldiC1-4 alkoxysilanes such as 3-glycidyloxypropylmethyldimethoxysilane and 3-glycidyloxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-(3,4-epoxycyclohexyl)propyl (epoxycycloalkyl)C2-4 alkyltriC1-4 alkoxysilanes such as 2-aminoethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc.], alkoxysilanes having an amino group [aminoC2-4 alkyltriC1-4 alkoxysilanes such as 2-aminoethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc., aminodiC2-4 alkyldiC1-4 alkoxysilanes such as 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, etc., 2-[N-(2-aminoethyl)amino] (2-aminoC alkyl)aminoC alkyltriC alkoxysilanes such as 3-[N-(2-aminoethyl)amino]ethyltrimethoxysilane, 3-[N-(2-aminoethyl)amino]propyltrimethoxysilane, and 3-[N-(2-aminoethyl)amino]propyltriethoxysilane; (aminoC alkyl)aminodiC alkyldiC alkoxysilanes such as 3-[N-(2-aminoethyl)amino]propylmethyldimethoxysilane and 3-[N-(2-aminoethyl)amino]propylmethyldiethoxysilane;Alkoxysilanes having a mercapto group (mercapto C2-4 alkyltri C1-4 alkoxysilanes such as 2-mercaptoethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, etc., mercaptodi C2-4 alkyldi C1-4 alkoxysilanes such as 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, etc.), alkoxysilanes having a vinyl group (vinyltri C1-4 alkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, etc.), ethylene Examples of suitable silane coupling agents include alkoxysilanes having a hydrophilic unsaturated bond group [(meth)acryloxyC2-4 alkyltriC1-4 alkoxysilanes such as 2-(meth)acryloxyethyltrimethoxysilane, 2-(meth)acryloxyethyltriethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, and 3-(meth)acryloxypropyltriethoxysilane, and (meth)acryloxydiC2-4 alkyldiC1-4 alkoxysilanes such as 3-(meth)acryloxypropylmethyldimethoxysilane and 3-(meth)acryloxypropylmethyldiethoxysilane, etc.]. Among the above-mentioned silane coupling agents, alkoxysilane compounds having an amino group are preferred, with aminopropyltrimethoxysilane being particularly preferred. These silane coupling agents can be used alone or in combination of two or more.

[0040] The content of the silane coupling agent is 5.0% by weight or less, preferably 2.0 to 4.5% by weight, and more preferably 3.0 to 4.0% by weight, based on the weight of the protective layer.

[0041] When forming a protective layer using a resin composition for a protective layer, a coating liquid (coating liquid) containing the composition and an organic solvent is prepared, and the coating liquid is applied to a substrate film and dried. As the organic solvent, a single or mixed solvent selected from alcohols such as methanol, ethanol, isopropyl alcohol (IPA), etc., ketones such as acetone and methyl ethyl ketone, ethers such as propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate, and esters such as ethyl acetate and propyl acetate can be used, and methyl ethyl ketone and ethyl acetate are preferred from the viewpoints of coating film processing and odor.

[0042] The coating method for the resin composition for the protective layer is not particularly limited as long as it is a method that coats the film surface to form a layer. For example, conventional coating methods such as gravure coating, reverse roll coating, wire bar coating, and die coating can be used. From the viewpoints of productivity and coating stability, wire bar coating and gravure coating are preferably used. In the present invention, by adopting specific process conditions when coating and drying the protective layer as described below, it is possible to obtain a predetermined heat shrinkage rate in the laminate film and reduce variation in the heat shrinkage rate in the width direction.

[0043] When forming a protective layer, it is preferable to apply a protective layer resin composition and then heat-dry it. The drying temperature is preferably 110 to 210°C, more preferably 115 to 205°C, and even more preferably 120 to 200°C. Drying temperatures below 110°C can result in insufficient drying or insufficient heat-induced cohesion of the protective layer, resulting in a surface hardness outside the specified range. This can result in reduced adhesion and water resistance of the protective layer when subjected to boiling or retort treatment. On the other hand, drying temperatures above 210°C can result in excessive cohesion of the protective layer, resulting in film hardness and destruction of the barrier layer, resulting in reduced barrier performance. Furthermore, excessive heat applied to the film substrate itself can cause the film to become brittle or shrink, resulting in poor processability. In addition to drying, additional heat treatment (e.g., 150 to 190°C) can also be effective in accelerating the drying of the protective layer.

[0044] The drying time for the protective layer is preferably 30 seconds or less. If the drying time exceeds 30 seconds, not only will the protective layer not dry, but the base film will shrink, causing cracks in the gas barrier layer and a decrease in gas barrier performance. On the other hand, if the drying time is shorter than 5 seconds, the protective layer will not harden, resulting in a decrease in adhesion and barrier properties. From the viewpoint of productivity, the drying time is more preferably 5 to 25 seconds, and more preferably 10 to 20 seconds. If the film is heated suddenly, the film will shrink significantly, causing compressive stress in the gas barrier layer and a decrease in barrier performance. It is preferable to increase the temperature at a rate of 50°C / second or less. More preferably, the drying time is 30°C / second or less, and more preferably, 20°C / second or less.

[0045] The surface temperature during heating in the step of forming the protective layer is preferably 100 to 150°C, more preferably 105 to 145°C, and even more preferably 110 to 140°C.

[0046] The film tension during heating in the step of forming the protective layer is preferably 30 to 90 N / m, more preferably 40 to 80 N / m, and even more preferably 50 to 70 N / m. If it is less than 20 N / m, poor winding occurs, and if it exceeds 100 N / m, tensile stress is generated in the gas barrier layer, reducing the barrier performance.

[0047] [Nylon Film] The biaxially stretched polyamide film (nylon film) of the present invention contains, as a polyamide resin, polyamide 6 as a main component. The polyamide resin may be made from a biomass-derived raw material or a recycled raw material.

[0048] The MD heat shrinkage of the nylon film before and after retort treatment at 130°C for 30 minutes must be 2.0% to 6.0%, preferably 2.2% to 5.5%, and more preferably 2.4% to 5.0%, and the TD heat shrinkage is preferably 2.0% to 10.0%, more preferably 2.5% to 9.0%, and more preferably 3.0% to 8.0%.

[0049] The nylon film is laminated by applying a two-component curing adhesive to the surface of the protective layer and laminating them by a dry lamination method. By using the two-component curing adhesive to attach the nylon film to the surface of the protective layer, the two-component curing adhesive can be cured and bonded in a short time.

[0050] [Heat Seal Layer (Unstretched Polypropylene Film)] When a gas barrier laminate film having an inorganic thin film layer is used as a packaging material, it is preferable to form a heat seal layer called a sealant. The heat seal layer is usually formed on the inorganic thin film layer, but it can also be formed on the outer side of the base film (the side opposite the protective layer). The heat seal layer is usually formed by extrusion lamination or dry lamination. The thermoplastic polymer forming the heat seal layer can be any polymer that can sufficiently exhibit sealant adhesion, and examples include polyethylene resins such as HDPE, LDPE, and LLDPE, polypropylene resin, ethylene-vinyl acetate copolymer, ethylene-α-olefin random copolymer, and ionomer resin. When performing moist heat treatment such as retort processing, it is preferable to form the heat seal layer using a polypropylene resin by the dry lamination method. In this embodiment, an unstretched polypropylene film composed of polypropylene resin is used as the heat seal layer. The heat seal layer is usually recommended to be 20 to 250 μm thick, and when used as a packaging material, it is desirable to have a thickness of 40 to 100 μm.

[0051] Polyurethane resin, polyisocyanate resin, polyester resin, ether resin, etc. are used to bond the protective layer to the nylon film layer, and to bond the nylon film layer to the heat seal layer. When performing a moist heat treatment such as retort treatment, it is preferable to use a reaction product of polyurethane resin and polyisocyanate resin as the adhesive. The amount of application varies depending on the material of the film to be laminated, but is generally 1 to 20 g / m. ２ is preferable, and more preferably 2 to 10 g / m ２ and more preferably 3 to 6 g / m ２The bonding temperature is set depending on the thickness of the heat seal layer and the thickness of the adhesive, but is preferably 50 to 120°C, more preferably 55 to 100°C, and even more preferably 60 to 80°C. In this embodiment, a two-component curing adhesive is used, among the adhesives using the above resins, to bond the protective layer to the nylon film layer and to bond the nylon film layer to the heat seal layer. As the two-component curing adhesive, a conventionally known two-component curing adhesive using the above resin can be used, for example, a polyurethane-based two-component curing adhesive (a blend of "Takelac (registered trademark) A525S" and "Takenate (registered trademark) A50" manufactured by Mitsui Chemicals, Inc., in a ratio of 13.5:1 (by mass)).

[0052] As described above, the laminate film of the present invention is a gas barrier laminate film (laminate film) that has excellent water vapor barrier properties and appearance both in the normal state and after retort treatment, and has good adhesion even when subjected to processing such as printing and lamination, and is easy to produce and has excellent economical efficiency.

[0053] [Other Layers] In addition to the above-mentioned base film, inorganic thin film layer, and protective layer, the gas barrier laminate film having an inorganic thin film layer formed using the laminate film of the present invention may have various layers, as necessary, that are provided in known gas barrier laminate films. For example, a polyamide resin may be provided as an intermediate layer between the gas barrier laminate film and the heat seal layer to improve the adhesion and flexibility of the laminate. In addition, a coating layer may be provided to react with oxygen-deficient portions of inorganic oxides or metal hydroxides generated during the formation of the inorganic thin film layer, thereby improving adhesion.

[0054] Furthermore, the gas barrier laminate film having an inorganic thin film layer may have at least one or more printed layers or other plastic substrates and / or paper substrates laminated between or on the outside of the inorganic thin film layer or the substrate film and the heat-sealable resin layer.

[0055] As the printing ink for forming the printing layer, aqueous and solvent-based resin-containing printing inks are preferably used. Examples of resins used in printing inks include acrylic resins, urethane resins, polyester resins, vinyl chloride resins, vinyl acetate copolymer resins, and mixtures thereof. The printing ink may contain known additives such as antistatic agents, light-blocking agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, defoamers, crosslinking agents, anti-blocking agents, and antioxidants. The printing method for forming the printing layer is not particularly limited, and known printing methods such as offset printing, gravure printing, and screen printing can be used. To dry the solvent after printing, known drying methods such as hot air drying, heat roll drying, and infrared drying can be used.

[0056] On the other hand, as other plastic substrates or paper substrates, from the viewpoint of obtaining sufficient rigidity and strength of the laminated film, paper, polyester resin, polyamide resin, biodegradable resin, etc. are preferably used. In addition, in order to obtain a film with excellent mechanical strength, stretched films such as biaxially stretched polyester film and biaxially stretched nylon film are preferred.

[0057] In particular, when a gas barrier laminate film having an inorganic thin film layer is used as a packaging material, it is preferable to laminate a nylon film between the inorganic thin film layer and the heat-sealable resin layer to improve mechanical properties such as pinhole resistance and puncture resistance. Typical types of nylon used here include nylon 6, nylon 66, and metaxylene adipamide. The nylon film typically has a thickness of 10 to 30 μm, preferably 15 to 25 μm. A nylon film thinner than 10 μm may lack strength, while a nylon film thicker than 30 μm may be too stiff and unsuitable for processing. A biaxially stretched nylon film with a stretch ratio of typically 2 times or more, preferably 2.5 to 4 times, in both the longitudinal and transverse directions is preferred.

[0058] The laminate film of the present invention also includes an embodiment having the above-mentioned layers other than the substrate layer, inorganic thin film layer, and protective layer.

[0059] The water vapor permeability of the laminated film of the present invention is 2.5 g / m２ ・day or less, more preferably 2.0 g / m ２ day or less, and more preferably 1.5 g / m ２ The water vapor permeability after retort treatment is 2.5 g / m ２ ・day or less, more preferably 2.0 g / m ２ day or less, and more preferably 1.5 g / m ２ ・day or less.

[0060] The smaller the difference in shrinkage rate in the MD direction between the laminate film and the nylon film before and after retort treatment, the less the laminate moves during retort treatment, and cracking of the inorganic thin film layer can be prevented. Cracking of the inorganic thin film layer is related to water vapor permeability, and preventing cracking can also prevent deterioration of water vapor permeability. The difference in shrinkage rate between the nylon film and the laminate film before and after retort treatment is preferably 0.0% or more and 4.5% or less, more preferably 0.5% or more and 4.0% or less, and even more preferably 1.0% or more and 3.5% or less.

[0061] Delamination refers to the formation of tunnel-shaped cavities of 1 mm or more due to peeling from the edge of the laminate toward the inside. Delamination occurs when the difference in shrinkage stress between the laminated film and the nylon film exceeds the adhesive strength. Shrinkage stress can be expressed as the shrinkage rate. The greater the difference in shrinkage rate before and after retort treatment, the more likely delamination is to occur.

[0062] 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 and can be practiced with appropriate modifications within the scope of the above and below-described aims, all of which are included in the technical scope of the present invention. Unless otherwise specified, "%" means "% by mass."

[0063] The processing methods and evaluation and property measurement methods used in each of the examples and comparative examples are as follows.

[0064] (1) Preparation of Laminated Films for Evaluation Various nylon films and a 70 μm thick unstretched polypropylene film (P1146 manufactured by Toyobo Co., Ltd.) serving as a heat-sealable resin layer were laminated in this order onto the protective layer of a laminate film comprising a resin substrate, an inorganic thin film layer laminated on at least one side of the resin substrate, and a protective layer laminated on the inorganic thin film layer using a polyurethane-based two-component curing adhesive (Mitsui Chemicals, Inc.'s "Takelac® A525S" and "Takenate® A50" blended in a ratio of 13.5:1 (mass ratio)). The laminated gas barrier laminates for evaluation were obtained by laminating the laminated films in this order using a dry lamination method, and aging at 40°C for 4 days. The thickness of the adhesive layer formed with the urethane-based two-component curing adhesive after drying was approximately 4 μm.

[0065] (2) Preparation of evaluation bags The film obtained in (1) above was cut to a size of 210 x 294 mm, folded in half to a size of 147 x 210 mm, and the heat-sealable resin surfaces were pressed together. After sealing three sides, 200 mL of water was inserted and the remaining side was sealed to obtain a bag. The heat sealer sealing conditions were an upper bar temperature of 200°C, a lower bar temperature of 100°C, a pressure of 0.2 MPa, and a time of 2 seconds.

[0066] (3) Retort Treatment Method The laminate obtained in (1) and the bag obtained in (2) were subjected to retort treatment at 130°C for 30 minutes using a hot water spray retort sterilizer ("RCS-60SPXTG" manufactured by Hisaka Works, Ltd.), followed by drying for 1 day in a 40°C room to obtain a sample.

[0067] (4) Evaluation Method for Thermal Shrinkage Before and After Retort Treatment A 15 mm mark was made in the center of each film and the laminate obtained in (1) and (3) above along the MD direction and a 10 mm mark was made in the TD direction. The spacing of the mark on the test specimen before retort treatment was measured to an accuracy of 0.1 mm. The test specimen was placed in a hot water spray retort sterilizer (Hisaka Works, Ltd., "RCS-60SPXTG") and treated under moist heat conditions at 130°C for 30 minutes. After removing the test specimen from the apparatus and cooling to room temperature, the length and width were measured at the same location as the initial measurement. The dimensional change of each test specimen was calculated as a percentage of the initial dimensional change in the MD and TD directions. The dimensional change in each direction was calculated as the average of the measurements in that direction.

[0068] (5) Evaluation Method of Water Vapor Permeability The water vapor permeability of the laminates obtained in (1) and (3) above was measured in accordance with JIS-K 7129 using a water vapor permeability measuring device ("PERMATRAN-3 / 33MW" manufactured by MOCON Co., Ltd.) under an atmosphere of a temperature of 40°C and a relative humidity of 90%. The water vapor permeability was measured in the direction in which water vapor permeated from the substrate film side on which no protective layer was laminated to the protective layer side.

[0069] (6) Evaluation Method for Delamination The bag products obtained in (1) to (3) above were evaluated for the presence or absence of delamination of 1 mm or more on the end surface of the bag product after retort treatment.

[0070] The materials used to form the protective layers in the examples and comparative examples were prepared as follows.

[0071] Example 1 Preparation of Materials Used to Form the Protective Layer of the Laminated Film A polyester polyol consisting of phthalic anhydride and ethylene glycol with a number average molecular weight of 900 was dissolved in methyl ethyl ketone to a concentration of 30% polyester polyol (polyester solution). A solution of 1.6 g of a silane coupling agent ("KBM-603" manufactured by Shin-Etsu Chemical Co., Ltd.) in 50 g of acetone was mixed with 26.7 g of a trimethylolpropane adduct of meta-xylylene diisocyanate ("Takenate D-110N" manufactured by Mitsui Chemicals, Inc.: solids concentration 75%) and stirred for 10 minutes using a magnetic stirrer. 78.3 g of the resulting mixture was diluted with 681.5 g of methyl ethyl ketone, and 100 g of the polyester solution was added to obtain a polyester urethane coating solution with a solids concentration of 5%.

[0072] <Preparation of Laminated Film> The obtained coating liquid was applied by a roll method onto the inorganic thin film layer of a 12 μm thick, 1,000 mm wide biaxially stretched polyester film on which a 10 nm inorganic thin film layer of aluminum oxide had been formed, and the thermal shrinkage in the MD and TD directions had been measured in advance. The temperature was then raised and lowered at a heating rate of 20° C. / sec or less so that the residence time in an oven was 10 seconds, thereby obtaining a protective layer. The coating amount after drying was 0.3 g / m ２ The tension after passing through the dryer was set to 50 N / m by adjusting the rotation speed ratio of the rolls before and after the oven. In this manner, a laminate film comprising a resin substrate, an inorganic thin film layer, and a protective layer was produced. The thermal shrinkage of the obtained laminate film in the MD and TD directions was measured.

[0073] <Preparation of Nylon Film> Using an apparatus consisting of an extruder and a 380 mm wide T-die, the following molten resin composition was extruded from the T-die into a film, which was then cast onto a cooling roll whose temperature was controlled to 20°C and electrostatically adhered to obtain an unstretched film having a thickness of 200 μm.

[0074] (Resin Composition) 92 parts by mass of polyamide 6 (a-1), 5 parts by mass of polyamide 6 (a-2), 3 parts by mass of polyamide 11 (manufactured by Arkema, relative viscosity 2.5, melting point 186°C), 0.45% by mass of porous silica fine particles (manufactured by Fuji Silysia Chemical Ltd., average particle size 2.0 μm, pore volume 1.6 ml / g), and 0.15% by mass of fatty acid bisamide (ethene bisstearic acid amide, manufactured by Kyoeisha Chemical Co., Ltd.) were mixed.

[0075] The resulting unstretched film was introduced into a roll-type stretching machine, and by utilizing the difference in peripheral speed of the rolls, it was stretched 1.73 times in the MD direction at 80° C., and then further stretched 1.85 times at 70° C. Subsequently, this uniaxially stretched film was continuously introduced into a tenter-type stretching machine, preheated at 110° C., and then stretched 1.2 times in the TD direction at 120° C., 1.7 times at 130° C., and 2.0 times at 160° C., heat-set at 218° C., and then subjected to a 7% relaxation treatment at 200° C. The surface to be dry-laminated with a linear low-density polyethylene film was then corona-discharge-treated to obtain a nylon film (biaxially stretched nylon film).

[0076] A polyurethane-based two-component curing adhesive (a mixture of Mitsui Chemicals' "Takelac (registered trademark) A525S" and "Takenate (registered trademark) A50" in a mass ratio of 13.5:1) was applied to the surface of the protective layer of the laminated film, and the nylon film was bonded to the adhesive by a dry lamination method.

[0077] A polyurethane-based two-component curing adhesive (a mixture of Mitsui Chemicals' "Takelac (registered trademark) A525S" and "Takenate (registered trademark) A50" in a mass ratio of 13.5:1) was applied to the surface of the nylon film, and a 70 μm-thick unstretched polypropylene film (Toyobo Co., Ltd.'s "P1146") was bonded to the nylon film by dry lamination.

[0078] In this way, a laminate according to Example 1 was obtained.

[0079] (Examples 2-3) In "<Preparation of nylon film>", laminates were prepared in the same manner as in Example 1, except that the stretching ratio was changed in both the MD and TD directions of the unstretched film, and the heat shrinkage rate of the nylon film was changed to obtain Examples 2-3, and evaluations of water vapor permeability and delamination were performed.

[0080] (Comparative Examples 1 and 2) Laminates were prepared in the same manner as in Example 1, except that the stretching ratio was changed and the heat shrinkage rate of the nylon film was changed to obtain Comparative Examples 1 and 2, and evaluations of water vapor permeability and delamination were performed.

[0081] Comparative Example 3 A laminate was produced in the same manner as in Example 1 except that no nylon film was used, and the water vapor permeability and delamination were evaluated.

[0082]

[0083] The present invention has made it possible to provide a laminate that exhibits excellent gas barrier properties and does not cause delamination, not only under normal conditions but also after retort treatment. The gas barrier laminate film of the present invention has the advantages of being easy to produce, being economical and stable in production, and easily achieving uniform properties. Therefore, the gas barrier laminate film can be widely used not only for food packaging for retort treatment, but also for packaging various foods, pharmaceuticals, industrial products, etc., as well as for industrial applications such as solar cells, electronic paper, organic EL elements, and semiconductor elements.

Claims

1. A laminate having gas barrier properties, comprising a resin substrate, an inorganic thin film layer laminated on at least one side of the resin substrate, a protective layer laminated on the inorganic thin film layer, a nylon film laminated by applying a two-component curable adhesive on the surface of the protective layer and laminating by a dry lamination method, and an unstretched polypropylene film laminated by applying a two-component curable adhesive on the surface of the nylon film and laminating by a dry lamination method, and satisfying the following requirements (1) to (3). (1) No layer is provided between the resin substrate and the inorganic thin film layer. (2) The heat shrinkage rate in the MD direction of the nylon film before and after retort treatment at 130°C for 30 minutes is 2.0% or more and 6.0% or less. (3) After the laminate is subjected to wet heat treatment at 130°C for 30 minutes, no delamination occurs and the water vapor transmission rate is 2.5 g / m ２ ·day or less.

2. The laminate according to claim 1, wherein the inorganic thin film layer contains at least one kind of inorganic oxide containing silicon oxide and / or aluminum oxide.

3. The laminate according to claim 1, wherein the protective layer contains at least one kind of urethane resin or ester resin.

4. The laminate according to claim 1, wherein a silane coupling agent is contained in the protective layer.

5. A packaging bag characterized by using at least a part of the laminate according to claim 4.

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