Laminated film, laminate, and package

Abstract

[Problem] There are evaporation films having various heat shrinkage properties depending on the base film. In the case where a laminate is produced using an evaporation film having a high heat shrinkage rate in the length direction, and subjected to retort processing, the barrier property is sometimes deteriorated. In the improvement of the base film, there is a difficulty that a dedicated product must be set up because of a large amount of production at one time.[Solution] A laminate is provided, whereby the water vapor permeability after retort processing can be suppressed to 2.5 g / m 2 · 1.2% or less in the MD direction before and after retort processing in the width direction, and the difference Δ between the maximum MD shrinkage rate and the minimum MD shrinkage rate in the width direction is 0.4% or less.

Description

Technical Field

[0001] This invention relates to laminated films used in the packaging of food, pharmaceuticals, industrial products, etc. More specifically, it relates to laminated films that exhibit good gas barrier properties and sealing properties by controlling the physical properties of the films when forming gas barrier laminated films having inorganic film layers. Background Technology

[0002] Packaging materials used in food and pharmaceuticals are required to possess the property of blocking gases such as oxygen and water vapor; that is, gas barrier properties are needed to maintain the oxidation inhibition of proteins and fats, preserve flavor and freshness, and maintain the efficacy of pharmaceuticals. Furthermore, gas barrier materials used in electronic devices and components such as solar cells and organic EL devices require gas barrier properties that are even higher than those used in food packaging materials.

[0003] For food applications requiring the blocking of various gases such as water vapor and oxygen, gas-barrier laminated films are commonly used. These films typically consist of a metal film (such as aluminum) or an inorganic film (such as silicon dioxide or aluminum oxide) formed on the surface of a plastic substrate film. Films made of inorganic oxides such as silicon dioxide, aluminum oxide, or mixtures thereof are transparent and allow for visualization of the contents, thus they are widely used.

[0004] However, inorganic films lack flexibility. Therefore, when the film is subjected to bending, impact, or high-temperature treatment such as boiling, problems such as pinholes, defects, and reduced gas barrier properties may easily occur.

[0005] To address the aforementioned issues, an attempt was made to further incorporate a protective layer onto the inorganic thin film. For example, it is known that a laminated thin film containing a resin formed from a water-soluble polymer or a solvent-soluble resin on the inorganic thin film can improve the stability of gas barrier properties.

[0006] However, these laminated films exhibit varying rates of thermal shrinkage depending on the location of the substrate film and the winding conditions during the lamination of inorganic films. When using laminated films with high thermal shrinkage rates to bond sealant layers to produce laminates, and then subjecting them to a cooking process, the laminates elongate and shrink during the high-humidity heat treatment. This causes tensile and compressive stresses to be applied to the gas barrier layer, resulting in cracks and reduced barrier properties.

[0007] Against this backdrop, methods are known to maintain gas barrier properties and airtightness by applying an online coating layer or anchoring coating layer to a substrate film and then performing a damp heat treatment. Methods are also known to improve the flexibility of the substrate by using a substrate film containing a polyester resin with butylene terephthalate units as the main constituent unit, thus maintaining good gas barrier properties even after damp heat treatment. Furthermore, methods are known to maintain good gas barrier properties even after hot water treatment by using a laminated film of shrink film and polyamide film and adjusting the shrinkage rate. (Patent Document 5)

[0008] However, any of the above methods requires changing the raw materials of the substrate film itself, and must have a dedicated batch, which may lead to problems such as being unable to handle multiple varieties and small batches.

[0009] Furthermore, it is known that controlling the thermal shrinkage rate through the drying process of the substrate can improve the interlayer bonding strength (Patent Document 6). However, no mention is made of damp heat treatment.

[0010] In addition, when forming a wide-width laminated film, high-temperature treatments such as boiling are performed based on the difference in thermal shrinkage rate in the width direction of the substrate film, which can cause pinholes and defects in the inorganic film, resulting in reduced gas barrier properties.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent No. 6631098

[0014] Patent Document 2: Japanese Patent No. 6507847

[0015] Patent Document 3: Japanese Patent Application Publication No. 2019-014043

[0016] Patent Document 4: Japanese Patent No. 6879292

[0017] Patent Document 5: Japanese Patent Application Publication No. 2018-089800

[0018] Patent Document 6: Japanese Patent Application Publication No. 2017-144593 Summary of the Invention

[0019] The problem the invention aims to solve

[0020] The purpose of this invention is to provide a laminated film with good gas barrier properties in a wide-width laminated film, and with minimal fluctuations in gas barrier properties in the width direction after cooking treatment.

[0021] Solution for solving the problem

[0022] The inventors have discovered that by controlling the tension in the coating process of the protective layer, the surface temperature of the film is made above the cooking temperature, thereby producing a laminated film with a desired thermal shrinkage rate at the end of the coating process, and thus maintaining gas barrier properties during the cooking process.

[0023] That is, the present invention comprises the following components.

[0024] (1) A laminated film with gas barrier properties, characterized in that it comprises: a resin substrate, an inorganic film layer laminated on at least one side of the resin substrate, and a protective layer laminated on the inorganic film layer, and satisfies the following conditions (I) to (III).

[0025] (I) No layer is provided between the resin substrate and the inorganic film layer.

[0026] (II) The thermal shrinkage rate in the MD direction before and after the 130℃ 30-minute cooking treatment is less than 1.2%.

[0027] (III) A polyurethane-based two-component curable adhesive is applied to the protective layer surface of the aforementioned laminated film to a thickness of 4 μm after drying. A 15 μm biaxially stretched nylon film and a 70 μm unstretched polypropylene film are then laminated onto the protective layer surface of the aforementioned laminated film using a dry lamination method. After curing at 40°C for 4 days, and then undergoing a 30-minute damp heat treatment at 130°C, the water vapor transmission rate is 2.5 g / m². 2 Within the heavens.

[0028] (2) The laminated film according to (1), wherein the width of the laminated film is 1000 mm or more, and the difference between the maximum MD shrinkage rate and the minimum MD shrinkage rate in the width direction during the cooking treatment at 130°C for 30 minutes is within 0.4%.

[0029] (3) The laminated film according to (1) or (2), wherein the aforementioned inorganic film layer contains at least one inorganic oxide comprising silicon oxide and / or aluminum oxide.

[0030] (4) The laminated film according to any one of (1) to (3), wherein the aforementioned protective layer contains at least one of polyurethane resin or ester resin.

[0031] (5) The laminated film according to any one of (1) to (4) contains a silane coupling agent in the aforementioned protective layer.

[0032] (6) A laminate having a heat-sealing layer laminated on the surface of the protective layer of the laminated film described in any one of (1) to (5) above.

[0033] (7) A packaging bag, characterized in that at least a portion of it uses the laminate described in (6) above.

[0034] The effects of the invention

[0035] According to the present invention, a laminated film with good gas barrier properties and a desired thermal shrinkage rate at the end of coating can be obtained in a wide laminated film. Even if the gas barrier properties fluctuate in the width direction during the cooking process, good gas barrier properties can be maintained. Detailed Implementation

[0036] The laminated film of the present invention is a gas-barrier laminated film comprising: a resin substrate, an inorganic film layer laminated on at least one side of the resin substrate, and a protective layer laminated on the inorganic film layer. The difference between the maximum and minimum MD shrinkage rates (Δ) in the width direction of the film during a 30-minute cooking treatment at 130°C is within 0.4%. A polyurethane-based two-component curable adhesive is coated on the surface of the protective layer of the laminated film to a thickness of 4 μm after drying. A 15 μm biaxially stretched nylon film and a 70 μm unstretched polypropylene film are bonded to the surface of the protective layer of the laminated film and laminated to form a laminate. After curing at 40°C for 4 days, the maximum water vapor transmission rate in the width direction after a 30-minute wet heat treatment at 130°C is 2.5 g / m². 2 Within a day. First, the plastic substrate film will be described, followed by the inorganic film layer and protective layer laminated thereon, and then the other layers.

[0037] [Substrate Film]

[0038] As the substrate film used in this invention (hereinafter sometimes referred to as "substrate film"), for example, a stretched film can be used, which is formed by melting and extruding plastic and stretching, cooling, and heat-setting it as needed along the length direction (MD direction) and / or the width direction (TD direction). In terms of obtaining mechanical strength, a biaxially stretched film stretched along both the length and width directions is preferred. As plastics, in addition to polyamides represented by nylon 4.6, nylon 6, nylon 6.6, nylon 12, etc.; polyesters represented by polyethylene terephthalate, polybutylene terephthalate, polyethylene 2,6-naphthalenedicarboxylate, etc.; and polyolefins represented by polyethylene, polypropylene, polybutene, etc., examples include polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, fully aromatic polyamides, polyamide-imide, polyimide, polyether-imide, polysulfone, polystyrene, polylactic acid, etc. Among these, polyester is preferred in terms of heat resistance, dimensional stability and transparency, and copolymers of polyethylene terephthalate and polyethylene terephthalate with other components are particularly preferred.

[0039] As a substrate film, any film thickness can be used depending on the desired purpose and application, such as mechanical strength and transparency. There is no particular limitation on the film thickness, but 5 to 250 μm is generally recommended. When used as packaging material, 10 to 60 μm is desirable. From the viewpoint of processing operations, subsequent processes, and machinery costs, the width of the substrate film is preferably 1000 mm or more and 5000 mm or less, more preferably 3000 mm or less, and more preferably 2000 mm or less. The transparency of the substrate film is not particularly limited, but when used as a packaging material requiring transparency, a light transmittance of 50% or more is desirable.

[0040] The substrate film can be a single-layer film formed from only one type of plastic, or a laminated film consisting of two or more types of plastic films. There are no particular limitations on the type of laminated films, the number of layers, or the lamination method used when forming the laminated film; any known method can be selected depending on the purpose. Furthermore, as long as it does not impair the purpose of this invention, surface treatments such as corona discharge, glow discharge, flame treatment, and surface roughening treatment can be applied to the substrate film. Additionally, known anchoring coating, printing, and decoration treatments can also be performed.

[0041] MD shrinkage rate refers to Machine Direction, i.e., longitudinal shrinkage rate, while TD shrinkage rate refers to Transverse Direction, i.e., lateral shrinkage rate.

[0042] The MD heat shrinkage rate of the substrate film before and after the initial 130°C 30-minute cooking treatment must be less than 1.6%, typically preferably less than 1.5%, and more preferably less than 1.4%. The difference in MD heat shrinkage rate Δ in the width direction is preferably less than 0.6%, more preferably less than 0.5%, and more preferably less than 0.4%. In addition, the TD heat shrinkage rate is preferably more than -0.6%, more preferably more than -0.5%, and more preferably more than -0.4%.

[0043] [Inorganic Thin Film Layer]

[0044] The laminated film of the present invention has an inorganic film layer on the aforementioned substrate film. The inorganic film layer is directly laminated on the resin substrate, and no layer is disposed between the two layers.

[0045] The inorganic thin film layer is a thin film formed from metals or inorganic oxides. There are no particular restrictions on the materials used to form the inorganic thin film layer, as long as they can be made into a thin film. From the viewpoint of gas barrier properties, inorganic oxides such as alumina, silicon dioxide, and mixtures of silicon dioxide and alumina are preferred. From a productivity viewpoint, alumina is particularly preferred. Furthermore, the laminated film composed of the protective layer specified in this application (described later) and the inorganic thin film layer formed from alumina has a significant improvement effect, particularly in oxygen permeability after acid treatment and lamination strength with water, and is therefore preferred. It should be noted that, here, silicon dioxide refers to various silicon oxides such as SiO and SiO2, or mixtures thereof, and alumina refers to various aluminum oxides such as AlO and Al2O3, or mixtures thereof.

[0046] The thickness of the inorganic thin film layer is typically 1–100 nm, preferably 3–50 nm, and more preferably 5–20 nm. If the thickness of the inorganic thin film layer is less than 1 nm, it can sometimes be difficult to obtain satisfactory gas barrier properties. On the other hand, even if it is too thick, exceeding 100 nm, it does not achieve the same improvement in gas barrier properties and becomes disadvantageous in terms of bending resistance and manufacturing cost.

[0047] There are no particular limitations on the method for forming inorganic thin film layers. For example, physical vapor deposition (PVD) methods such as vacuum evaporation, sputtering, and ion plating, or known vapor deposition methods such as chemical vapor deposition (CVD) can be used. Hereinafter, a typical method for forming inorganic thin film layers will be described using alumina thin film as an example. For example, in the case of vacuum evaporation, Al₂O₃ or Al is preferably used as the deposition material. These deposition materials are usually granular, but in this case, it is desirable that the size of each particle is such that the pressure during evaporation does not change; the preferred particle size is 1 mm to 5 mm. Heating can be performed using resistance heating, high-frequency induction heating, electron beam heating, laser heating, etc. In addition, oxygen, nitrogen, hydrogen, argon, carbon dioxide, water vapor, etc., can be introduced as reactant gases, or reactive vapor deposition using ozone addition, ion assistance, etc., can also be used. Furthermore, the film formation conditions can be arbitrarily changed, such as applying a bias voltage to the deposited object (the laminated thin film to be deposited), or heating or cooling the deposited object. The vapor deposition materials, reaction gases, bias voltage of the vapor-deposited body, heating and cooling can all be changed in the same way as in sputtering and CVD methods.

[0048] [Protective Layer]

[0049] In this invention, a protective layer is provided on the aforementioned inorganic thin film layer. The inorganic thin film layer laminated on the plastic film is not a completely dense film, and small defects are dispersed within it. By coating the inorganic thin film layer with a specific protective layer resin composition (described later) to form a protective layer, the resin in the protective layer resin composition penetrates into the defects of the inorganic thin film layer, resulting in effects such as stable gas barrier properties. Furthermore, the protective layer itself uses a gas barrier material, thereby significantly improving the gas barrier properties of the laminated film.

[0050] In this invention, the coating amount of the protective layer is preferably set to 0.05–0.60 g / m². 2 Therefore, uniformity can reduce coating unevenness and defects, and the anchoring effect can improve adhesion. Furthermore, the improved cohesion of the protective layer itself strengthens the bond between the inorganic film layer and the protective layer, also improving water resistance. The preferred coating amount for the protective layer is 0.08 g / m². 2 Above, more preferably 0.10 g / m 2 The above, further optimized, is 0.15g / m 2 The preferred value is 0.50 g / m³. 2 Below, more preferably 0.45g / m 2 The following is a further preferred option: 0.40 g / m 2 The following applies: If the coating amount of the protective layer exceeds 0.60 g / m². 2 While this improves gas barrier properties, it also weakens the cohesive force within the protective layer, raising concerns about reduced adhesion. Furthermore, it can sometimes result in uneven coating appearance, defects, or an inability to fully demonstrate the gas barrier and adhesion properties achieved after hydrothermal treatment. On the other hand, if the protective layer thickness is less than 0.10 g / m²... 2 There are concerns that insufficient air barrier properties, interlayer adhesion, and ink penetration may not be achieved.

[0051] As a component of the protective layer, any of solvent-dispersible resins or water-dispersible resins can be used. Solvent-dispersible resins are particularly preferred to improve adhesion to the inorganic film layer. Furthermore, to obtain high gas barrier properties, a resin comprising a polyester polyol component obtained by reacting a dicarboxylic acid with a polyol, and a polyisocyanate component, is preferred.

[0052] (A) Polyester composition

[0053] Polyester components are obtained by reacting polycarboxylic acids and polyols.

[0054] As polycarboxylic acids, they include aromatic polycarboxylic acids, alicyclic polycarboxylic acids, and aliphatic polycarboxylic acids. From the viewpoint of gas barrier properties, aromatic polycarboxylic acids are preferred. Examples include phthalic acid, isophthalic acid, terephthalic acid, 1,2-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, anthracene-1,2-dicarboxylic acid, and anthraquinone-2,3-dicarboxylic acid.

[0055] As polyols, a range of diols from low to high molecular weight can be used, but from the viewpoint of gas barrier properties and flexibility based on the amorphous portion, low molecular weight diols such as alkylene glycols (e.g., straight-chain or branched C2-10 alkylene glycols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, neopentanediol, heptanediol, octanediol, etc.) and (poly)oxy C2-4 alkylene glycols (diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, etc.) are used. Preferred diol components are C2-8 polyol components [e.g., C2-6 alkylene glycols (especially ethylene glycol, 1,2- or 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, etc.)], di- or tri-oxo C2-3 alkylene glycols (diethylene glycol, triethylene glycol, dipropylene glycol, etc.), with particularly preferred diol components being C2-8 alkylene glycols (especially C2-6 alkylene glycols).

[0056] These diol components can be used alone or in combination of two or more. Further, as needed, low molecular weight diol components such as aromatic diols (e.g., bisphenol A, dihydroxyethyl terephthalate, catechol, resorcinol, hydroquinone, 1,3- or 1,4-benzenedimethanol or mixtures thereof), and alicyclic diols (e.g., hydrogenated bisphenol A, benzenediethanol, cyclohexanediol, cyclohexanediol, etc.) can also be used in combination. Furthermore, as needed, polyol components with three or more functionalities, such as glycerol, trimethylolethane, trimethylolpropane, polyester polyols, polycarbonate polyols, and polyether polyols, can also be used in combination. The polyol components preferably contain at least C2-8 polyol components (especially C2-6 alkylene diols).

[0057] (B) Polyisocyanate components

[0058] As polyisocyanate components, they include aromatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates. Diisocyanate compounds are commonly used as polyisocyanate compounds.

[0059] Examples of aromatic diisocyanates include toluene diisocyanate (2,4- or 2,6-toluene diisocyanate or mixtures thereof) (TDI), phenyl diisocyanate (m- or p-phenyl diisocyanate or mixtures thereof), 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), diphenylmethane diisocyanate (4,4'-, 2,4'-, or 2,2'-diphenylmethane diisocyanate or mixtures thereof) (MDI), 4,4'-toluidine diisocyanate (TODI), and 4,4'-diphenyl ether diisocyanate. Examples of aromatic aliphatic diisocyanates include xylene diisocyanate (1,3- or 1,4-xylene diisocyanate or mixtures thereof) (XDI), tetramethylxylene diisocyanate (1,3- or 1,4-tetramethylxylene diisocyanate or mixtures thereof) (TMXDI), and ω,ω'-diisocyanate-1,4-diethylbenzene.

[0060] Examples of alicyclic diisocyanates include 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate), 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), methylene bis(cyclohexyl isocyanate) (4,4'-, 2,4'- or 2,2'-methylene bis(cyclohexyl isocyanate) (hydrogenated MDI), methylcyclohexane diisocyanate (methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate), bis(isocyanate methyl)cyclohexane (1,3- or 1,4-bis(isocyanate methyl)cyclohexane or mixtures thereof) (hydrogenated XDI), etc.

[0061] Examples of aliphatic diisocyanates include trimethylene diisocyanate, 1,2-propylidene diisocyanate, butylidene diisocyanate (tetramethylene diisocyanate, 1,2-butylidene diisocyanate, 2,3-butylidene diisocyanate, 1,3-butylidene diisocyanate), hexamethylene diisocyanate, pentamethylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, and methyl caffeate 2,6-diisocyanate.

[0062] Polyurethane resin is obtained by reacting polyester component (A) and polyisocyanate component (B). The weight ratio of polyester component to polyisocyanate component, based on solid components, is 9:1 to 1:9. Preferably, it is 8:2 to 2:8, and more preferably, it is 6:4 to 4:6.

[0063] The protective layer resin composition of the present invention preferably contains a silane coupling agent, as described below; however, various additives may be incorporated as needed, without compromising gas barrier properties. Examples of additives include layered inorganic compounds, stabilizers (antioxidants, heat stabilizers, ultraviolet absorbers, etc.), plasticizers, antistatic agents, lubricants, anti-blocking agents, colorants, fillers, and nucleating agents.

[0064] Silane coupling agents are effective in improving the adhesion of protective layers to inorganic thin film layers. Examples of silane coupling agents include hydrolyzable alkoxysilane compounds, such as halogenated alkoxysilanes (e.g., 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, etc., chloroC2-4 alkyltriC1-4 alkoxysilanes), and epoxy-containing alkoxysilanes [2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, 3-glycidoxyethyltriethoxysilane, etc.]. Glycidoxy-C2-4 alkyltriC1-4 alkoxysilanes such as 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-(3,4-epoxycyclohexyl)ethyltriethoxysilane, etc.4-Epoxycyclohexyl)propyltrimethoxysilane, etc. (epoxycycloalkyl)C2-4 alkyltriC1-4 alkoxysilanes, etc., alkoxysilanes containing amino groups [2-aminoethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc., aminoC2-4 alkyltriC1-4 alkoxysilanes, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, etc., aminodiC2-4 alkyldiC1-4 alkoxysilanes, 2-[N-(2-aminoethyl)amino]ethyl Trimethoxysilane, 3-[N-(2-aminoethyl)amino]propyltrimethoxysilane, 3-[N-(2-aminoethyl)amino]propyltriethoxysilane, etc. (2-aminoC2-4 alkyl)aminoC2-4 alkyltriC1-4 alkoxysilane, 3-[N-(2-aminoethyl)amino]propylmethyldimethoxysilane, 3-[N-(2-aminoethyl)amino]propylmethyldiethoxysilane, etc. (aminoC2-4 alkyl)aminodiC2-4 alkyldiC1-4 alkoxysilane, etc., alkanes with mercapto groups alkyl silanes (such as 2-mercaptoethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, etc., thiol-C2-4 alkyltriC1-4 alkoxysilanes, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, etc., thiol-diC2-4 alkyldiC1-4 alkoxysilanes, etc.), vinyl alkoxysilanes (such as vinyltrimethoxysilane, vinyltriethoxysilane, etc., vinyltriC1-4 alkoxysilanes, etc.), and alkoxysilanes with olefinic unsaturated bonding groups. [2-(meth)acryloyloxyethyltrimethoxysilane, 2-(meth)acryloyloxyethyltriethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, etc. (meth)acryloyloxyC2-4alkyltriC1-4alkoxysilanes, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, etc. (meth)acryloyloxydiC2-4alkyldiC1-4alkoxysilanes, etc.] etc. Among the aforementioned silane coupling agents, alkoxysilane compounds having an amino group are preferred, and aminopropyltrimethoxysilane is particularly preferred. These silane coupling agents can be used alone or in combination of two or more.

[0065] The content of the silane coupling agent relative to the protective layer is less than 5.0% by weight, preferably 2.0 to 4.5% by weight, and more preferably about 3.0 to 4.0% by weight.

[0066] When the protective layer is formed by the protective layer resin composition, a coating liquid (coating solution) containing the aforementioned composition and an organic solvent is prepared, coated onto the substrate film, and dried. As the organic solvent, individual or mixed solvents selected from alcohols such as methanol, ethanol, and isopropanol (IPA), 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. From the viewpoint of coating processing and odor control, methyl ethyl ketone and ethyl acetate are preferred.

[0067] The coating method for the protective layer resin composition is not particularly limited as long as it is a method for forming a layer on the film surface. For example, common coating methods such as gravure coating, reverse roller coating, wire rod coating, and die coating can be used. From the viewpoint of productivity and coating stability, wire rod coating and gravure coating are suitable.

[0068] It should be noted that, in this invention, specific process conditions are used when coating and drying the protective layer, as follows, so that while obtaining the specified thermal shrinkage rate in the laminated film, the fluctuation of the thermal shrinkage rate in the width direction can be reduced.

[0069] When forming the protective layer, it is preferable to coat the protective layer resin composition and then heat-dry it. The drying temperature is preferably 110–210°C, more preferably 115–205°C, and even more preferably 120–200°C. If the drying temperature is below 110°C, insufficient drying or insufficient aggregation due to heat may occur in the protective layer, raising concerns that the surface hardness may fall outside the specified range. As a result, there are concerns that the adhesion and water resistance of the protective layer may decrease after boiling or boiling treatments. On the other hand, if the drying temperature exceeds 210°C, excessive aggregation of the protective layer may occur, the film may harden, the barrier layer may be damaged, and there are concerns that the barrier performance may decrease. In addition, there are concerns that excessive heat may be applied to the film itself, which serves as the substrate, causing the film to become brittle or shrink and resulting in poor processability. It should be noted that, unlike drying, applying additional heat treatment (e.g., 150–190°C) is also effective in promoting the drying of the protective layer.

[0070] The drying time of the protective layer is preferably within 30 seconds. If the drying time exceeds 30 seconds, it will not only cause the protective layer to dry but also cause the substrate film to shrink, resulting in cracks in the gas barrier layer and a decrease in gas barrier performance. On the other hand, if the drying time is less than 5 seconds, the protective layer will not cure, resulting in a decrease in adhesion and barrier properties. From a productivity point of view, 5 to 25 seconds is further preferred, and 10 to 20 seconds is more preferred. If the film is heated rapidly, the film will shrink significantly, generating compressive stress in the gas barrier layer and reducing barrier performance. It is preferable to gradually increase the temperature at a rate of 50°C / second or less. It is further preferred to increase the temperature at 30°C / second or less, and more preferably at 20°C / second or less.

[0071] The surface temperature during heating in the process of forming the protective layer is preferably 100-150°C, more preferably 105-145°C, and even more preferably 110-140°C.

[0072] The film tension during heating in the process of forming the protective layer is preferably 30 to 90 N / m. More preferably, it is 40 to 80 N / m, and even more preferably, it is 50 to 70 N / m. If it is below 20 N / m, poor winding will occur, and if it exceeds 100 N / m, tensile stress will be generated in the gas barrier layer, and the barrier performance will be reduced.

[0073] The MD heat shrinkage rate before and after the lamination film undergoes a 30-minute cooking treatment at 130°C must be 0.0% or more and 1.2% or less, preferably 0.1% or more and 1.1% or less, more preferably 0.2% or more and 1.0% or less, and even more preferably 0.3% or more and 0.9% or less. The difference in MD heat shrinkage rate Δ in the width direction is preferably 0.3% or less, even more preferably 0.2% or less, and even more preferably 0.1% or less. In addition, the TD heat shrinkage rate is preferably -0.5% or more and 0.4% or less, even more preferably -0.4% or more and 0.3% or less, and even more preferably -0.3% or more and 0.2% or less.

[0074] Even if the thermal shrinkage rate of the substrate film with the inorganic thin film layer fluctuates in the MD and TD directions, a thermal shrinkage rate without fluctuation in the width direction can be obtained by drying at a specified temperature and under a specified tension within a fluctuation of Δ3℃ in the width direction during the process of forming the protective layer.

[0075] [Heat-sealing layer]

[0076] When using a gas-barrier laminated film with an inorganic thin film layer as a packaging material, a heat-sealing layer, known as a sealant, is preferably formed. The heat-sealing layer is typically placed on the inorganic film layer, but sometimes it is placed on the outside of the substrate film (the side opposite to the protective layer forming surface). The heat-sealing resin is usually formed by extrusion lamination or dry lamination. As the thermoplastic polymer forming the heat-sealing resin layer, any resin that sufficiently exhibits the adhesive properties of the sealant can be used, such as polyethylene resins like HDPE, LDPE, and LLDPE, polypropylene resins, ethylene-vinyl acetate copolymers, ethylene-α-olefin random copolymers, and ionomer resins. When performing a wet heat treatment such as a retorting process, polypropylene resin is preferably used and formed by dry lamination. A heat-sealing layer thickness of 20–250 μm is generally recommended, but when used as a packaging material, a thickness of 40–100 μm is desirable.

[0077] In bonding the protective layer to the heat-sealing layer, polyurethane resin, polyisocyanate resin, polyester resin, ether resin, etc., are used. When performing a hydrothermal treatment such as boiling, it is preferable to use the reactant of polyurethane resin and polyisocyanate resin as the adhesive. The coating amount varies depending on the material of the film to be bonded, but is preferably 1–20 g / m². 2 Further optimization of 2-10 g / m 2 More preferably 3-6 g / m 2 The bonding temperature is set according to the thickness of the heat-sealing layer and the thickness of the adhesive, preferably 50-120°C, more preferably 55-100°C, and even more preferably 60-80°C.

[0078] Based on the above, the laminated film of the present invention has excellent water vapor barrier properties and appearance after normal and cooking treatments, and also has good adhesion when processed by printing, lamination and other processes. Moreover, it is easy to manufacture and becomes an economical gas barrier laminated film (laminated film).

[0079] [Other layers]

[0080] In the gas barrier laminated film having an inorganic film layer formed using the laminated film of the present invention, in addition to the aforementioned substrate film, inorganic film layer, and protective layer, various layers known to be present in gas barrier laminated films can be provided as needed. For example, providing a polyamide resin as an interlayer between the gas barrier laminated film and the heat-sealing layer can improve the adhesion and flexibility of the laminate. Furthermore, a cover layer may be provided to improve adhesion by reacting with oxygen-deficient portions and metal hydroxides of the inorganic oxides generated during the formation of the inorganic film layer.

[0081] Furthermore, in the gas barrier laminated film having an inorganic thin film layer, at least one or more printed layers, other plastic substrates and / or paper substrates may be laminated between or on the outside of the inorganic thin film layer or the substrate film and the heat-sealing resin layer.

[0082] As the printing ink for forming the printing layer, water-based and solvent-based resins are preferred. Examples of resins used in this printing ink include acrylic resins, polyurethane resins, polyester resins, vinyl chloride resins, vinyl acetate copolymer resins, and mixtures thereof. The printing ink may also contain known additives such as antistatic agents, light-blocking agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, defoamers, crosslinking agents, anti-blocking agents, and antioxidants. The printing method for setting the printing layer is not particularly limited, and known printing methods such as offset printing, gravure printing, and screen printing can be used. Known drying methods such as hot air drying, hot roller drying, and infrared drying can be used for drying the solvent after printing.

[0083] On the other hand, from the viewpoint of obtaining sufficient stiffness and strength of the laminated film, paper, polyester resin, polyamide resin, and biodegradable resin are preferred as other plastic or paper substrates. Furthermore, for forming films with excellent mechanical strength, biaxially stretched polyester films, biaxially stretched nylon films, and other stretched films are preferred.

[0084] In particular, when using a gas-barrier laminated film with an inorganic film layer as a packaging material, it is preferable to laminate a nylon film between the inorganic film layer and the heat-sealing resin layer to improve mechanical properties such as pinhole resistance and puncture strength. Common types of nylon used here include nylon 6, nylon 66, and adipamide. The thickness of the nylon film is typically 10–30 μm, preferably 15–25 μm. If the nylon film is thinner than 10 μm, there is a concern that it will become insufficiently strong; on the other hand, if it exceeds 30 μm, it will be too stiff and sometimes unsuitable for processing. As for the nylon film, a biaxially stretched film with a stretch ratio in both longitudinal and transverse directions of typically 2 times or more, preferably around 2.5 to 4 times, is preferred.

[0085] The laminated film of the present invention further includes a configuration having layers other than the substrate layer, the inorganic film layer, and the protective layer.

[0086] The water vapor transmission rate of the laminated film of the present invention is preferably 2.5 g / m. 2 Less than 1 day, preferably 2.0 g / m 2 · Less than 1 day, further optimized to 1.5g / m 2 • Less than 1 day. Additionally, the water vapor transmission rate during the cooking process is preferably 2.5 g / m³. 2 Less than 1 day, preferably 2.0 g / m 2 · Less than 1 day, further optimized to 1.5g / m 2 Below the heavens.

[0087] Example

[0088] The following examples illustrate the present invention in more detail, but the present invention is not limited to the following examples. Appropriate modifications can be made within the scope of the preceding and following descriptions, and these modifications are all included within the technical scope of the present invention. It should be noted that, unless otherwise specified, "%" refers to "mass %".

[0089] The processing methods and evaluation / property measurement methods used in each embodiment and comparative example are described below.

[0090] (1) Methods for measuring the surface temperature of thin films

[0091] The surface temperature of the thin film is measured using a thermocouple (AEROPAK sheathed thermocouple manufactured by Okazaki Manufacturing Co., Ltd.).

[0092] (2) Evaluation of the fabrication of laminated films

[0093] Using a dry lamination method, a 15 μm thick biaxially stretched nylon film (Harden film N1102, manufactured by Toyobo Co., Ltd.) and a 70 μm thick unstretched polypropylene film (P1146, manufactured by Toyobo Co., Ltd.) serving as a heat-sealing resin layer were sequentially laminated onto each other using a polyurethane-based two-component curable adhesive (mixed with Mitsui Chemicals Co., Ltd.'s "TAKELAC (registered trademark)" A525S and "TAKENATE (registered trademark)" A50, manufactured by Toyobo Co., Ltd.). The films were then cured at 40°C for 4 days to obtain the gas barrier laminated film for evaluation. It should be noted that the adhesive layer formed by the urethane-based two-component curable adhesive had a dry thickness of approximately 4 μm. Samples were cut at 500 mm intervals in the width direction, and water vapor transmission rate was measured.

[0094] (3) Steaming / cooking treatment method

[0095] The laminated film or the laminate obtained in (2) above was subjected to a hot water spray sterilization apparatus (RCS-60SPXTG manufactured by Nissaka Manufacturing Co., Ltd.) at 130°C for 30 minutes. Afterwards, it was dried in a room at 40°C for 1 day to obtain the laminate.

[0096] (4) Evaluation method of thermal shrinkage rate before and after cooking treatment

[0097] A film measuring 210 mm × 297 mm in the TD direction was cut from the end face of the self-rolled film, extending 50 mm into the inner side. Furthermore, a film measuring 210 mm × 297 mm in the TD direction was also cut from the center of the film in the TD direction, creating a test piece. Marking lines of 15 mm in the MD direction and 10 mm in the TD direction were made at the center of the resulting film. The spacing of the marking lines on the test piece before the cooking treatment was measured with an accuracy of 0.1 mm. The test piece was placed in a hot water spray sterilization apparatus (RCS-60SPXTG, manufactured by Nissaka Manufacturing Co., Ltd.) and treated under humid heat conditions at 130°C for 30 minutes. After removing the test piece from the apparatus and cooling it to room temperature, the length and width were measured for the same portion as the initial measurement. The dimensional change rate of each test piece was calculated as a percentage of the initial dimensional change in both the MD and TD directions. The dimensional change rate in each direction was recorded as the average of the measured values ​​in that direction.

[0098] (5) Evaluation method of water vapor transmission rate

[0099] For the laminated films obtained in (2) and (3) above, the water vapor transmission rate was measured using a water vapor transmission rate measuring device (MOCON "PERMATRAN-3 / 33MW") at a temperature of 40°C and a relative humidity of 90%, according to JIS-K7129. It should be noted that the water vapor transmission rate was measured in the direction from the substrate film side of the unlaminated protective layer to the protective layer side.

[0100] (6) Evaluation methods for appearance

[0101] Visually confirm the appearance of the rolled-up roll after the coating liquid has been applied using the roller method.

[0102] The materials used to form the protective layer in each embodiment and comparative example are prepared as follows.

[0103] <Preparation of materials for the formation of protective layer A (coating solution a)>

[0104] 30% of a polyester resin (a polyester mainly composed of a polycarboxylic acid component containing at least one ortho-oriented aromatic dicarboxylic acid or its anhydride and a polyol component) with a number average molecular weight of 450-3000 was dissolved in 70% methyl ethyl ketone (polyester solution). A solution of silane coupling agent (Shin-Etsu Chemical Co., Ltd. "KBM-603") dissolved in acetone and a trimethylolpropane adduct of m-xylene diisocyanate (Mitsui Chemicals Co., Ltd. "TAKENATE D-110N": solids concentration 75%) were mixed and stirred with a magnetic stirrer for 10 minutes. The resulting mixture was diluted with methyl ethyl ketone, and the polyester solution was further added to obtain a polyester urethane coating solution a with a solids concentration of 5%.

[0105] <Preparation of materials for the formation of protective layer B (coating solution b)>

[0106] A polyester resin with a weight average molecular weight of 35,000 (a polyester mainly composed of terephthalic acid, isophthalic acid, ethylene glycol, and propylene glycol) was dissolved at 25% in a solution of 35% propyl acetate and 40% ethyl acetate (polyester solution). This solution was then mixed with 14.00% ethyl acetate, 41.40% propyl acetate, 43.10% polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) containing isocyanate groups, and 0.2% silane coupling agent ("KBM-903", manufactured by Shin-Etsu Chemical Co., Ltd.) to obtain a polyester urethane coating solution b with a solid content concentration of 5%.

[0107] <Preparation of materials for the formation of protective layer C (coating solution c)>

[0108] Polymethacrylic acid with a weight average molecular weight of 30,000 was diluted with a mixed solvent of ethyl acetate / isopropanol (ethyl acetate / isopropanol = 1:1 (mass ratio)) to obtain a polymethacrylic acid coating solution c with a solid component concentration of 5%.

[0109] (Example 1)

[0110] The coating solutions a to c obtained were applied using a roller coating method onto a biaxially stretched polyester film layer with a thickness of 12 μm and a width of 1000 mm, containing an inorganic film layer of alumina and with a pre-determined thermal shrinkage rates in the MD and TD directions. The film was heated and cooled at a rate below 20°C / second, with an oven residence time of 10 seconds, and dried to the surface temperature as described in Table 1 to obtain a protective layer. The coating weight after drying was 0.3 g / m². 2 The tension after passing through the dryer was set to 50 N / m by adjusting the rotational speed ratio of the rollers before and after the oven. As described above, a laminated film comprising a resin substrate / inorganic film layer / protective layer was fabricated. For the obtained laminated film, the thermal shrinkage rates in the MD and TD directions were measured, and a laminated laminate was fabricated as described above. Furthermore, a cooking treatment at 130°C for 30 minutes was performed, and the change in water vapor transmission rate was evaluated. The results are shown in Table 1.

[0111] (Examples 2-4)

[0112] The surface temperature of the protective layer and film and the tension after passing through the furnace were varied as shown in Table 1. Otherwise, the laminate was made in the same manner as in Example 1, and the water vapor transmission rate was evaluated.

[0113] (Example 5)

[0114] Biaxially stretched polyester films with inorganic vapor-deposited layers of varying blank widths were used, and laminates were fabricated in the same manner as in Example 1 to evaluate water vapor permeability.

[0115] (Comparative Examples 1-2)

[0116] The film surface temperature and the tension after passing through the furnace were changed in the manner shown in Table 1. Otherwise, the laminate was made in the same manner as in Example 1, and the water vapor transmission rate was evaluated. The result was that the value after the cooking treatment was reduced.

[0117] (Comparative Example 3)

[0118] When the film surface temperature is as shown in Table 1, the coated film has strong wrinkles. The laminate was made in the same manner as in Example 1, and the water vapor transmission rate was evaluated. The result showed that the value was also reduced before the cooking treatment.

[0119] (Comparative Example 4)

[0120] When the film surface temperature is as shown in Table 1, the processed film surface is sticky and cannot be evaluated.

[0121] (Comparative Example 5)

[0122] When the tension after passing through the dryer is as shown in Table 1, the tension value is too weak to roll the film into a roll.

[0123] (Comparative Example 6)

[0124] As shown in Table 1, the protective layer was changed. Otherwise, the laminate was made in the same manner as in Example 1, and the water vapor transmission rate was evaluated. The result showed that the value decreased after the cooking treatment.

[0125] (Comparative Example 7)

[0126] No coating liquid was applied to the biaxially stretched polyester film with an inorganic thin film layer of alumina, and only a drying process was performed. Otherwise, the laminate was made in the same manner as in Example 1, and the water vapor transmission rate was evaluated. The result showed that the value was also reduced before the cooking treatment.

[0127] [Table 1A]

[0128]

[0129] [Table 1B]

[0130]

[0131] Industrial availability

[0132] According to the present invention, a laminated film with excellent gas barrier properties under normal conditions and also with excellent gas barrier properties after undergoing a cooking process can be provided. The gas barrier laminated film of the present invention has the advantages of being easy to manufacture, economical, having excellent production stability, and being easy to obtain homogeneous properties. Furthermore, due to process improvements, it is also easy to handle multiple varieties and small batches. Therefore, the gas barrier laminated film is not limited to food packaging for cooking processes; in addition to packaging applications for various foods, pharmaceuticals, and industrial products, it can also be widely used in industrial applications such as solar cells, electronic paper, organic EL components, and semiconductor components.

Claims

1. A laminated thin film with gas barrier properties, characterized in that, It comprises: 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. The resin substrate is a polyester film. The inorganic thin film layer is a thin film formed of metal or inorganic oxide. The protective layer comprises polyester urethane resin. The laminated film satisfies the following conditions (1) to (3), (1) The inorganic thin film layer is directly laminated onto the resin substrate, without a layer between the two layers. (2) The thermal shrinkage rate in the MD direction before and after steaming at 130℃ for 30 minutes is less than 1.2%. (3) A polyurethane-based two-component curable adhesive is applied to the protective layer surface of the laminated film to achieve a thickness of 4 μm after drying. A 15 μm biaxially stretched nylon film and a 70 μm unstretched polypropylene film are then laminated onto the protective layer surface of the laminated film using a dry lamination method. After curing at 40°C for 4 days, and then undergoing a 30-minute wet heat treatment at 130°C, the water vapor transmission rate is 2.5 g / m². 2 •Below the heavens.

2. The laminated film according to claim 1, wherein, The laminated film has a width of 1000 mm or more, and the difference between the maximum MD shrinkage rate and the minimum MD shrinkage rate in the width direction during the cooking treatment at 130°C for 30 minutes is within 0.4%.

3. The laminated film according to claim 1, wherein, The inorganic thin film layer contains at least one inorganic oxide comprising silicon oxide and / or aluminum oxide.

4. The laminated film according to any one of claims 1 to 3, wherein the protective layer contains a silane coupling agent.

5. A laminate having a heat-sealing layer laminated on the surface of the protective layer of the laminated film according to any one of claims 1 to 4.

6. A packaging bag, characterized in that, At least a portion of it uses the laminate as described in claim 5.

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