Laminated film and packaging film comprising the same

Abstract

To provide a laminated film that enables obtaining a packaging film which retains high gas barrier properties and adhesion to a sealant layer even after retort processing, and a packaging film comprising the laminated film.SOLUTION: A laminated film comprises a base material layer, a first layer laminated on at least one surface of the base material layer, and a second layer laminated on the first layer, wherein the base material layer contains a polyolefin-based resin, the first layer contains a reaction product (C) of a polyurethane resin (A) and a crosslinking agent (B), and a layered inorganic compound (D), and the second layer contains, as a main component, at least one selected from metals and inorganic oxides.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a laminated film and a packaging film including the same. [Background technology]

[0002] Conventionally, gas barrier films have been known in which a laminated film having gas barrier properties is formed on a film serving as a base layer to suppress the permeation of oxygen, water vapor, etc. For example, a laminated film in which an inorganic oxide vapor deposition film is provided on a film serving as a base layer, or a laminated film in which a barrier resin is laminated on a film serving as a base layer, etc. are known.

[0003] To obtain high gas barrier properties, it is preferable to have a configuration including a vapor-deposited film, but when the base layer is an olefin-based resin film such as OPP, it is difficult to obtain sufficient gas barrier properties by simply forming a vapor-deposited film. For this reason, an anchor coat layer is sometimes provided between the base layer and the vapor-deposited film.

[0004] For example, Patent Document 1 proposes that a multilayer substrate layer is formed by providing a resin material having a polar group as a coating layer on a stretched polypropylene resin layer, thereby improving the adhesion between the vapor-deposited film and the multilayer substrate layer and improving the gas barrier properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-024136 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 describes an example in which polyvinyl alcohol (PVA) or ethylene vinyl alcohol copolymer (EVOH) is used as the coating layer. However, packaging films obtained by providing a sealant layer on a laminated film having such an anchor coating layer tend to have poor gas barrier properties after retort treatment, and the adhesion between the sealant layer and the vapor-deposited film also tends to be poor.

[0007] An object of the present disclosure is to provide a laminated film that can provide a packaging film that can maintain high gas barrier properties and adhesion to a sealant layer even after retort treatment, and a packaging film that includes the laminated film. [Means for solving the problem]

[0008] As a result of extensive research, the inventors of the present application have found that the above-mentioned problems can be solved by a laminate film comprising a base layer, a first layer laminated on at least one surface of the base layer, and a second layer laminated on the first layer, wherein the base layer contains a polyolefin-based resin, the first layer contains a reaction product (C) of a polyurethane resin (A) and a crosslinking agent (B), and a layered inorganic compound (D), and the second layer contains, as a main component, at least one selected from a metal and an inorganic oxide. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a laminate film that can provide a packaging film that can maintain high gas barrier properties and adhesion to a sealant layer even after retort treatment, and a packaging film including the laminate film. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present disclosure will be described in detail below. However, the scope of the present disclosure is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the present disclosure. Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Furthermore, when multiple upper and lower limit values ​​are described for a particular parameter, any of these upper and lower limit values ​​can be combined to form a suitable numerical range. Furthermore, the lower and / or upper limit values ​​of a numerical range described in this disclosure are numerical values ​​within that numerical range and may be replaced with numerical values ​​shown in the examples. The expression "X to Y" indicating a numerical range means "X or more and Y or less." Furthermore, unless otherwise noted, all test temperatures were room temperature (20°C ± 5°C). When a particular description given for one embodiment is applicable to other embodiments, that description may be omitted in the other embodiments.

[0011] The configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible as appropriate within the scope of the present disclosure. The present disclosure is not limited by the embodiments, but is limited only by the claims. Each feature disclosed herein may be combined with any other feature disclosed herein.

[0012] [Laminated film] A first embodiment of the present disclosure relates to a laminated film. The laminated film according to the first embodiment comprises a substrate layer, a first layer laminated on at least one surface of the substrate layer, and a second layer laminated on the first layer, wherein the substrate layer contains a polyolefin resin, the first layer contains a reaction product (C) of a polyurethane resin (A) and a crosslinking agent (B) and a layered inorganic compound (D), and the second layer contains at least one selected from metals and inorganic oxides as a main component. The laminated film according to the first embodiment can provide a packaging film that maintains high gas barrier properties and adhesion to a sealant layer even after retort treatment. In this disclosure, "retort treatment" refers to treating a packaging film at 121°C or higher.

[0013] <Base material layer> The substrate layer contains a polyolefin-based resin. That is, the substrate layer is composed of a resin composition containing a polyolefin-based resin (hereinafter, also referred to as a "substrate layer resin composition"). In a preferred embodiment, the substrate layer is a film composed of a resin composition containing a polyolefin-based resin.

[0014] (Polyolefin resin) Examples of polyolefin resins include polyethylene resins and polypropylene resins.

[0015] Examples of polyethylene resins include low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), linear low-density polyethylene resin (LLDPE), ethylene-vinyl acetate copolymer (EVA) resin, ethylene-α-olefin copolymer resin, and ethylene-(meth)acrylic acid copolymer resin.

[0016] The polypropylene-based resin may be, for example, a homopolypropylene resin, a block polypropylene resin, a random polypropylene resin, or a copolymer resin of propylene and another monomer. Examples of the other monomer include α-olefins such as ethylene, 1-butene, 1-hexene, 1-octene, 3-methylpentene, and 4-methylpentene. The polypropylene-based resin may also be a copolymer resin obtained by combining propylene with two or more other monomers. When the base layer contains the copolymer resin, it preferably contains 80% by mass or more of propylene as a monomer component, more preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 98% by mass or more.

[0017] Furthermore, the polypropylene resin may have an atactic structure, an isotactic structure, a syndiotactic structure, or a metallocene structure.

[0018] In an embodiment containing only a homopolypropylene resin as the polyolefin resin, the effects of the present disclosure are more likely to be achieved. In one embodiment, the substrate layer is preferably a polypropylene resin film (particularly a homopolypropylene film). This film may be a uniaxially stretched film, a biaxially stretched film, or an unstretched film. The substrate layer may be composed of a single-layer film or a laminate of two or more films. When the substrate layer is a laminate of two or more films, the types of polyolefin resins contained in each layer may be the same or different.

[0019] The polyolefin resin contained in the substrate layer may be a biomass-derived polyolefin resin or a mechanically recycled or chemically recycled polyolefin resin.

[0020] (Other thermoplastic resins) The substrate layer may contain a thermoplastic resin other than a polyolefin-based resin (another thermoplastic resin). Examples of other thermoplastic resins include polyester-based resins (polyethylene naphthalate, polyethylene terephthalate, etc.), polyamide-based resins (nylon-6, nylon-66, etc.), polystyrene resins, ethylene-vinyl alcohol copolymer resins, polyvinyl chloride resins, polyimide resins, polyvinyl alcohol resins, polycarbonate resins, polyethersulfone resins, acrylic resins, and cellulose-based resins (triacetyl cellulose, diacetyl cellulose, etc.). These thermoplastic resins may be used alone or in combination of two or more. Note that, since an olefin-based resin film (preferably a polypropylene film) is often used as the sealant layer described below, it is preferable that the substrate layer contain only a polyolefin-based resin as the thermoplastic resin from the viewpoint of improving recyclability by using the same material (monomaterial) as the sealant layer.

[0021] (additives) The resin composition for the base layer may contain known additives such as antioxidants, weather stabilizers, heat stabilizers, lubricants, crystal nucleating agents, UV absorbers, colorants, and antiblocking agents, as long as the effects of the present disclosure are not impaired. For example, at least one resin selected from petroleum resins and terpene resins may be blended in to improve the water vapor barrier properties of the base layer. When the base layer contains these resins, the total content thereof may be 1% by mass or more, 2% by mass or more, 15% by mass or less, or 10% by mass or less, relative to the total mass of the resin composition for the base layer.

[0022] Furthermore, for the purpose of improving the adhesion between the substrate layer and the first layer, the surface of the substrate layer may be subjected to corona discharge treatment, plasma treatment, etc. If necessary, the surface on which the first layer is not laminated (the uncoated surface) may be subjected to corona discharge treatment or plasma treatment.

[0023] The thickness of the substrate layer is not particularly limited and can be appropriately set depending on the application of the packaging film. In one embodiment, the thickness of the substrate layer may be 5 μm or more, 10 μm or more, or 15 μm or more. The upper limit of the thickness of the substrate layer may be 100 μm or less, 90 μm or less, or 80 μm or less. That is, the thickness of the substrate layer may be 5 to 100 μm, 10 to 90 μm, or 15 to 80 μm. When the laminated film is used as a packaging film for packaging food, it is particularly preferable that the substrate layer is an OPP film having a thickness of 5 to 80 μm.

[0024] <First layer> The laminate film according to the first embodiment includes a first layer containing a reaction product (C) of a polyurethane resin (A) and a crosslinking agent (B), and a layered inorganic compound (D). The first layer is laminated on at least one surface of a substrate layer. The first layer may also be laminated on a corona discharge-treated or plasma-treated surface of the substrate layer. The first layer is composed of a resin composition (hereinafter sometimes referred to as the "first layer resin composition") containing a reaction product (C) of a polyurethane resin (A) and a crosslinking agent (B) and a layered inorganic compound (D). By providing such a first layer, it is possible to obtain a packaging film that can maintain high gas barrier properties and adhesion to the sealant layer even after retort treatment.

[0025] (Polyurethane resin (A)) The first layer contains a reaction product (C) of a polyurethane resin (A) and a crosslinking agent (B). The polyurethane resin (A) constituting the reaction product (C) is preferably a polyurethane resin with high gas barrier properties.

[0026] In one embodiment, the polyurethane resin (A) has an oxygen permeability at 20°C / 90% RH measured in accordance with JIS K 7126-2 (hereinafter, also referred to as "oxygen permeability (a1)") of 100 cc / m 2 / day·μm or less is preferable, and 80cc / m 2 / day·μm or less is more preferable, and 50cc / m2 It is more preferable that the average particle diameter is 1 / day·μm or less. By including a reaction product (C) obtained by reacting a polyurethane resin (A) having such oxygen permeability with a crosslinking agent (B), it becomes easier to obtain a packaging film that can maintain high gas barrier properties even after retort treatment.

[0027] From the viewpoint of easily achieving the high gas barrier properties described above, it is preferable that the polyurethane resin (A) contains a gas barrier urethane prepolymer.

[0028] (gas barrier urethane prepolymer) Examples of gas-barrier urethane prepolymers include isocyanate-terminated prepolymers obtained by reacting a polyisocyanate component with a relatively low molecular weight polyol component (or diamine component). The average molecular weight of the isocyanate-terminated prepolymer may be adjusted with a chain extender.

[0029] Polyisocyanate component The polyisocyanate component is not particularly limited, and examples thereof include aliphatic polyisocyanates, aromatic polyisocyanates, araliphatic polyisocyanates, and alicyclic polyisocyanates.

[0030] Examples of aromatic polyisocyanates include 4,4'-, 2,4'-, or 2,2'-diphenylmethane diisocyanate or a mixture thereof (MDI), 2,4- or 2,6-tolylene diisocyanate or a mixture thereof (TDI), 4,4'-toluidine diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), m- or p-phenylene diisocyanate or a mixture thereof, 4,4'-diphenyl diisocyanate, 4,4'-diphenyl ether diisocyanate, etc. These may be used alone or in combination of two or more.

[0031] Examples of aromatic aliphatic polyisocyanates include 1,3- or 1,4-xylylene diisocyanate or a mixture thereof (XDI), 1,3- or 1,4-tetramethylxylylene diisocyanate or a mixture thereof (TMXDI), ω,ω'-diisocyanato-1,4-diethylbenzene, etc. These may be used alone or in combination of two or more.

[0032] Examples of alicyclic polyisocyanates include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), 4,4'-, 2,4'-, or 2,2'-dicyclohexylmethane diisocyanate, or mixtures thereof (H 12 Examples of suitable isocyanates include 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or a mixture thereof (hydrogenated xylylene diisocyanate, H6XDI), bis(isocyanatomethyl)norbornane (NBDI), 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, and methyl-2,6-cyclohexane diisocyanate. These may be used alone or in combination of two or more.

[0033] Examples of aliphatic polyisocyanates include hexamethylene diisocyanate (HDI), trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, 1,2-, 2,3- or 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, and the like.

[0034] The polyisocyanate component may also include a polymer (e.g., dimer, trimer, pentamer, heptamer, etc.) of the above polyisocyanate, a biuret-modified product produced by the reaction of the above polyisocyanate with water, an allophanate-modified product produced by the reaction of the above polyisocyanate with a monool or a polyhydric alcohol (described later), an oxadiazinetrione-modified product produced by the reaction of the above polyisocyanate with carbon dioxide, and the like.

[0035] Among these, from the viewpoint of gas barrier properties, aromatic polyisocyanates such as MDI, TDI, TODI, and NDI; aromatic aliphatic polyisocyanates such as XDI and TMXDI; IPDI, H 12 It is preferable to use alicyclic polyisocyanates such as MDI, H6XDI, NBDI, etc., or aliphatic polyisocyanates such as HDI, etc. Two or more of these may be used in combination.

[0036] Polyol component The polyol component is preferably a polyol having a relatively low molecular weight. Examples of relatively low molecular weight polyols include polyols having a mass average molecular weight (Mw) (or molar mass) of 400 or less. Preferred examples of such polyols include the low molecular weight polyols shown below; polyether polyols obtained by adding alkylene oxide to the low molecular weight polyols as an initiator; and polycarbonate polyols obtained by reacting phosgene, dialkyl carbonate, diallyl carbonate, alkylene carbonate, or the like with the low molecular weight polyols as an initiator.

[0037] Examples of low molecular weight polyols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, diethylene glycol, trioxyethylene glycol, tetraoxyethylene glycol, pentaoxyethylene glycol, hexaoxyethylene glycol, dipropylene glycol, trioxypropylene glycol, tetraoxypropylene glycol, pentaoxypropylene glycol, hexaoxypropylene glycol, etc. Among these, ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexanediol, diethylene glycol, trioxyethylene glycol, dipropylene glycol, and trioxypropylene glycol are preferred, and ethylene glycol and diethylene glycol are more preferred.

[0038] Examples of alkylene oxides include alkylene oxides having 2 to 5 carbon atoms such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, 3-methyltetrahydrofuran, oxetane compounds, etc. Of these, ethylene oxide and propylene oxide are preferred.

[0039] The gas-barrier urethane prepolymer is preferably a polymer obtained by reacting one or more of the above-mentioned isocyanate components with one or more of the above-mentioned polyol components so that the equivalent ratio of hydroxyl groups to isocyanate groups (OH / NCO) is greater than 1. In one embodiment, the isocyanate group content in the gas-barrier urethane prepolymer may be 2 to 20 mass % or 3 to 15 mass % relative to the total mass of the urethane prepolymer. In one embodiment, the number average molecular weight (Mn) of the gas barrier urethane prepolymer may be 400 to 5,000, or 500 to 3,000.

[0040] The polyurethane resin (A) may contain urethane resins other than the gas-barrier urethane prepolymer (other urethane resins). Other examples of urethane resins include urethane prepolymers obtained by reacting the aforementioned isocyanate component with a relatively high molecular weight polyol component. Examples of relatively high molecular weight polyol components include polyols with an Mw or molar mass of more than 400; polyterpolyols obtained by adding alkylene oxides to such polyols; and polycarbonate polyols obtained from such polyols. Two or more of these isocyanate components and polyol components can be used in combination.

[0041] In one embodiment, the acid value of the polyurethane resin (A), measured in accordance with JIS K0070 (1992), may be 5 to 50 mgKOH / g, 5 to 40 mgKOH / g, or 10 to 30 mgKOH / g.

[0042] The polyurethane resin (A) preferably contains a gas-barrier urethane prepolymer as a main component. That is, the proportion of the gas-barrier urethane prepolymer relative to the total mass of the polyurethane resin (A) is preferably greater than 50% by mass. This proportion can be adjusted to any value within the range of greater than 50% by mass and not greater than 100% by mass. For example, the proportion of the gas-barrier urethane prepolymer in the polyurethane resin (A) may be adjusted so that the oxygen permeability (a1) of the polyurethane resin (A) falls within the aforementioned preferred range.

[0043] The polyurethane resin (A) may be a commercially available product, such as "Takelac (registered trademark) WPB-341M" manufactured by Mitsui Chemicals, Inc.

[0044] <Crosslinking agent (B)> The crosslinking agent (B) is a compound having a crosslinkable functional group and capable of reacting with the polyurethane resin (A) to form a reaction product (C) that has high gas barrier properties and excellent adhesion to the second layer. Examples of such crosslinking agents (B) include oxazoline compounds, melamine compounds, epoxy compounds, carbodiimide compounds, isocyanate compounds, and silane coupling compounds. The crosslinking agents (B) may be used alone or in combination of two or more. In a preferred embodiment, from the viewpoint of easily obtaining a packaging film that can maintain high gas barrier properties even after retort treatment, the crosslinking agent (B) contains a carbodiimide compound.

[0045] The carbodiimide compound is a compound having one or more carbodiimide groups (-N=C=N-) in the molecule. Examples of the carbodiimide compound include aliphatic carbodiimide compounds having an aliphatic main chain, alicyclic carbodiimide compounds having an alicyclic main chain, aromatic carbodiimide compounds having an aromatic main chain, and carbodiimide resins, and one or more selected from these can be used.

[0046] Examples of the aliphatic carbodiimide compound include diisopropylcarbodiimide, dioctyldecylcarbodiimide, etc. Examples of the alicyclic carbodiimide compound include dicyclohexylcarbodiimide, etc. These may be used alone or in combination of two or more.

[0047] Examples of aromatic carbodiimide compounds include diphenylcarbodiimide, di-2,6-dimethylphenylcarbodiimide, N-triyl-N'-phenylcarbodiimide, di-p-nitrophenylcarbodiimide, di-p-aminophenylcarbodiimide, di-p-hydroxyphenylcarbodiimide, di-p-chlorophenylcarbodiimide, di-p-methoxyphenylcarbodiimide, di-3,4-dichlorophenylcarbodiimide, di-2,5-dichlorophenylcarbodiimide, di-o-chlorophenylcarbodiimide, p-phenylene-bis-di-o-triylcarbodiimide, p-phenylene-bis-dicyclohexylcarbodiimide, p-phenylene-bis-di-p-chlorophenylcarbodiimide, ethylene- Examples of suitable carbodiimide compounds include mono- and dicarbodiimide compounds such as bis-diphenylcarbodiimide; and polycarbodiimide compounds such as poly(4,4'-diphenylmethanecarbodiimide), poly(3,5'-dimethyl-4,4'-biphenylmethanecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(3,5'-dimethyl-4,4'-diphenylmethanecarbodiimide), poly(naphthylenecarbodiimide), poly(1,3-diisopropylphenylenecarbodiimide), poly(1-methyl-3,5-diisopropylphenylenecarbodiimide), poly(1,3,5-triethylphenylenecarbodiimide), and poly(triisopropylphenylenecarbodiimide). These compounds may be used alone or in combination of two or more.

[0048] The carbodiimide resin may be, for example, a hydrophilic group-containing carbodiimide resin. The carbodiimide equivalent (chemical formula weight per mole of carbodiimide group) in the carbodiimide resin may be 300 to 500, or 350 to 450. As the carbodiimide resin, a commercially available product may be used, for example, the Carbodilite (registered trademark) series manufactured by Nisshinbo Chemical Inc.

[0049] In one embodiment, the ratio of the crosslinking agent (B) to 100 parts by mass of the polyurethane resin (A) is preferably 10 to 30 parts by mass. That is, the reaction product (C) is preferably a resin composition containing 10 to 30 parts by mass of the crosslinking agent (B) to 100 parts by mass of the polyurethane resin (A). The ratio of the crosslinking agent (B) is more preferably more than 10 parts by mass and not more than 30 parts by mass, and even more preferably 18 to 27 parts by mass. According to the inventors' investigations, it has been found that when the first layer contains a reaction product (C) obtained by reacting 10 to 30 parts by mass of the crosslinking agent (B) (preferably a carbodiimide compound) with 100 parts by mass of the polyurethane resin (A), adhesion to the second layer is further improved, and gas barrier properties are also likely to be improved. The inclusion of such a first layer makes it easier to obtain a packaging film that maintains high gas barrier properties and adhesion to the protective layer even after retort treatment.

[0050] <Reactant (C)> The reactant (C) is a resin component obtained by reacting the polyurethane resin (A) with the crosslinking agent (B). In one embodiment, the first layer preferably contains the reactant (C) as a main component. The proportion of the reactant (C) in the first layer is preferably more than 50% by mass and not more than 90% by mass, more preferably 60 to 92% by mass, and even more preferably 70 to 92% by mass.

[0051] <Layered inorganic compounds (D)> The first layer further contains a layered inorganic compound (D). By providing a first layer, which is a combination of the reactant (C) and the layered inorganic compound (D), as an anchor coat layer between the substrate layer and the second layer, the adhesion between the substrate layer and the second layer is improved, and a packaging film is obtained in which the gas barrier properties and adhesion to the sealant layer are not easily reduced even after retort treatment. In the present disclosure, the term "layered inorganic compound" refers to an inorganic compound in which unit crystal layers are stacked to form a layered structure.

[0052] The layered inorganic compound (D) preferably contains a swellable layered inorganic compound (D1). The swellable layered inorganic compound (D1) refers to an inorganic compound having a structure in which unit crystal layers are stacked and exhibiting the property of swelling or cleavage by coordinating or absorbing a solvent (especially water) between the layers. Examples of such inorganic compounds include swellable hydrous silicates, such as smectite group clay minerals (montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, stevensite, etc.), vermiculite group clay minerals (vermiculite, etc.), kaolin-type minerals (halloysite, kaolinite, endelite, dickite, etc.), phyllosilicates (talc, pyrophyllite, mica, margarite, muscovite, phlogopite, tetrasilicic mica, taeniolite, etc.), jamonite group minerals (antigorite, etc.), and chlorite group minerals (chlorite, cookite, nanite, etc.). These swellable layered inorganic compounds (D1) may be natural or synthetic. The laminated film according to the first embodiment may contain one or more of the swellable layered inorganic compounds (D1) in the first layer. Among these swellable layered inorganic compounds (D1), it is preferable to contain a smectite clay mineral, and it is particularly preferable to contain montmorillonite.

[0053] The swellable layered inorganic compound (D1) is preferably subjected to microparticulation treatment from the viewpoints of adhesion between the base layer and the second layer and the gas barrier properties of the laminated film. The microparticulated swellable layered inorganic compound usually has a plate-like or flat shape, but its planar shape is not particularly limited and may be amorphous, etc. The average particle size (average particle size of planar shape) of the microparticulated swellable layered inorganic compound (D1) is preferably 0.01 to 5 μm, more preferably 0.05 to 3 μm, and even more preferably 0.1 to 1 μm. The average particle size of the swellable layered inorganic compound (D1) can be measured by a laser diffraction / scattering method. The average particle size refers to the median diameter (D50) of the volume-based average particle size measured by the laser diffraction / scattering method.

[0054] When a swellable layered inorganic compound (D1) that has been subjected to a microparticulation treatment is used, the microparticulation treatment is preferably a high-pressure dispersion treatment of the swellable layered inorganic compound (D1) in a solution. Examples of the solvent include water or water-soluble solvents (lower alcohols such as methanol and ethanol, acetone, etc.), and usually water is used. The processing pressure in the high-pressure dispersion treatment is, for example, 20 MPa (approximately 200 kgf / cm 2 ) or more (for example, 20 to 100 MPa), preferably about 20 to 80 MPa, and more preferably about 40 to 60 MPa. As a treatment method, for example, a method of high-pressure dispersion by swelling the swellable layered inorganic compound (D1) in a solvent and then stirring it at the above-mentioned pressure with a high-pressure homogenizer can be mentioned. Such high-pressure dispersion treatment is carried out multiple times (for example, 2 to 10 times), preferably 2 to 7 times, and more preferably 2 to 5 times.

[0055] The present inventors have found that by using a first layer containing a reactant (C) and a layered inorganic compound (D) as a coating layer between a substrate layer and a second layer, a packaging film obtained from a laminate film including the first layer can maintain high gas barrier properties and adhesion to a protective layer even after retort treatment. It is expected that the greater the amount of layered inorganic compound (D) added, the higher the gas barrier properties will be. However, the present inventors have found that if the amount added is too high, the adhesion between the second layer and the first layer and the adhesion between the laminate film and the sealant layer (lamination strength) tend to decrease, and this can lead to a decrease in gas barrier properties (particularly, an increase in oxygen permeability). Therefore, from the viewpoint of achieving both adhesion and gas barrier properties, the proportion of layered inorganic compound (D) contained in the first layer is preferably 1% by mass or more but less than 10% by mass, more preferably 1 to 8% by mass, even more preferably 1 to 6% by mass, and particularly preferably 1 to 5% by mass. The proportion of the layered inorganic compound (D) in the first layer refers to the content of the layered inorganic compound (D) relative to the total mass of the resin composition for the first layer.

[0056] In one embodiment, the thickness of the first layer is preferably 0.2 to 4.0 μm. The present inventors have found that by combining the reactant (C) and the layered inorganic compound (D), good gas barrier properties are likely to be obtained even when the thickness of the first layer is reduced. In one embodiment, the thickness of the first layer may be 0.2 to 2.0 μm, 0.4 to 2.0 μm, or 0.4 to 1.5 μm.

[0057] In one embodiment, an anchor coat layer may be formed between the substrate layer and the first layer. The anchor coat layer can be formed by applying an anchor coat agent to the substrate layer. Conventionally known anchor coat agents can be used as the anchor coat agent, and anchor coat agents for food packaging films are particularly preferred. Since the first layer contains the reaction product (C) of the polyurethane resin (A) and the crosslinking agent (B) described above, it has good adhesion to the substrate layer, and the first layer itself functions as an anchor coat layer between the substrate layer and the second layer. From the perspective of easily achieving the effects of the present disclosure, it is preferable to have the first layer laminated directly on the substrate layer.

[0058] <Second layer> The second layer is formed by laminating it on the first layer, and if necessary, other layers may be further laminated on the second layer.

[0059] The second layer contains, as a main component, at least one selected from a metal and an inorganic oxide. In a preferred embodiment, the second layer is a vapor-deposited film containing, as a main component, an inorganic oxide. The metal contained in the second layer is preferably aluminum. The inorganic oxide contained in the second layer is preferably a metal oxide. Preferred examples include aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. Of these, the second layer is preferably a vapor-deposited film containing at least one selected from aluminum oxide and silicon oxide as a main component, and is particularly preferably a vapor-deposited film containing aluminum oxide as a main component. In the present disclosure, aluminum oxide is AlO xIt may be (0 < x ≤ 1.5), and the silicon oxide is SiO x It may be (0 < x ≤ 2.0). Within a range where the effects of the present disclosure are not inhibited, the second layer may contain other elements other than aluminum oxide and silicon oxide.

[0060] From the viewpoint of the gas barrier property of the laminated film and the adhesion to the sealant layer, the thickness of the second layer is preferably 3 nm or more, more preferably 10 nm or more, and even more preferably 30 nm or more. Also, the upper limit is preferably 300 nm or less, and more preferably 100 nm or less. When the second layer is a vapor deposition film, the thickness of the second layer can be adjusted according to the vapor deposition conditions described later.

[0061] <Protective layer> The laminated film according to the first embodiment may further include a protective layer. The protective layer is a layer laminated on the second layer. By providing the protective layer, the gas barrier property of the laminated film is more likely to be further improved. The protective layer can include, for example, water-soluble polymers such as polyvinyl alcohol-based resins, polysaccharides such as starch, methyl cellulose, and carboxymethyl cellulose, and hydroxyl group-containing polymer acrylic resins; polyurethane-based resins; polyester-based resins; acrylic resins; titanium-based resins; isocyanate-based resins; imine-based resins; polybutadiene-based resins, etc. These may be used alone or in combination of two or more. Also, these resins and a curing agent may be used in combination.

[0062] In one embodiment, from the viewpoint of easily improving the adhesion between the second layer and the protective layer, and also from the viewpoint of easily improving the adhesion between the sealant layer and the second layer, the protective layer preferably contains a polyurethane-based resin. As the polyurethane-based resin, the same resin as the aforementioned polyurethane resin (A) may be used, or a different polyurethane resin may be used.

[0063] In one embodiment, from the viewpoint of easily improving the gas barrier property, the protective layer includes a water-soluble polymer and a general formula: M(OR) nand / or a hydrolyzate thereof, and more preferably a water-soluble polymer and a siloxane-based compound in which M in the above general formula contains silicon. The water-soluble polymer preferably contains a polyvinyl alcohol-based resin.

[0064] The thickness of the protective layer is not particularly limited as long as the effects of the present disclosure are achieved, but it can be, for example, 0.1 to 1.0 μm.

[0065] The oxygen permeability of the laminated film according to the first embodiment at 20°C / 90%RH measured in accordance with JIS K7126-2 is 5 cc / m 2 In a more preferred embodiment, the oxygen permeability is 4 cc / m 2 / day or less, more preferably 3cc / m 2 / day or less, particularly preferably 2cc / m 2 / day or less. The oxygen permeability is 1 cc / m 2 It can be less than / day.

[0066] The water vapor permeability of the laminated film according to the first embodiment at 40°C / 90%RH measured in accordance with JIS K7129-2 is 5.0 g / m 2 / day or less is preferable, and 4.0 g / m 2 / day or less is more preferable. The laminate film according to the first embodiment is superior in gas barrier properties under high humidity conditions compared to the laminate film described in Patent Document 1, for example.

[0067] [Application] As described above, the laminate film according to the first embodiment has excellent gas barrier properties, particularly gas barrier properties under high humidity conditions. Furthermore, the adhesion between the base layer and the second layer is also good. Such a laminate film can be suitably used, for example, as a packaging film for food packaging. It is preferably used for food packaging applications that require retort processing or the like. The laminated film according to the first embodiment also has high water resistance, and therefore the content of volatile components such as water can be reduced, which allows for stable deposition processing with less outgassing during deposition processing.

[0068] <Laminated film manufacturing method> The method for producing the laminated film according to the first embodiment is not particularly limited, and the film can be produced, for example, by a production method including laminating a first layer on the substrate layer (step (1)), and laminating a second layer containing an inorganic oxide as a main component on the first layer. An example of the production method including steps (1) and (2) will be described below.

[0069] <Step (1): Laminating the first layer> Step (1) is a step of laminating a first layer on a substrate layer. Specifically, it is preferable to prepare a coating agent (a coating agent containing the resin composition for the first layer described above) by mixing a polyurethane resin (A), a crosslinking agent (B), and a layered inorganic compound (D), and apply the coating agent to the substrate layer. In one embodiment, a step of preparing a coating agent (step (1')) may be included before step (1).

[0070] (Step (1'): Preparation of coating agent) The coating agent can be prepared, for example, by adding predetermined amounts of polyurethane resin (A) and crosslinking agent (B) to a dispersion containing the layered inorganic compound (D) and mixing them. The polyurethane resin (A) and / or crosslinking agent (B) may also be added to the layered inorganic compound (D) as a dispersion in a medium. The dispersion medium for the layered inorganic compound (D) and polyurethane resin (A) (or crosslinking agent (B)) preferably contains water. The solids concentration in the coating agent can be set within any range, but in one embodiment, it may be 5 to 20%.

[0071] The obtained coating agent is applied onto a substrate layer. As the substrate layer to which the coating agent is applied, it is preferable to use the above-mentioned film. In a preferred embodiment, the substrate layer is a polypropylene-based resin film, and an OPP film is particularly preferred.

[0072] In a preferred embodiment, step (1) includes directly applying the coating agent onto a substrate layer. Because reactant (C) has excellent adhesion to the substrate layer, the first layer can be laminated directly onto the substrate layer.

[0073] The amount of coating agent applied (weight of the first layer after drying) can be appropriately selected depending on the size of the substrate layer, the desired thickness of the first layer, etc. In one embodiment, it is 0.3 to 5.0 g / m 2 and may be 0.5 to 2.4 g / m 2 and may be 0.5 to 1.8 g / m 2 may be.

[0074] The coating method is not particularly limited, and known methods and devices such as gravure coating, reverse coating, doctor coating, bar coating, and dip coating can be used.

[0075] By heat treating after coating, the polyurethane resin (A) and the crosslinking agent (B) react to prepare a reaction product (C). The heat treatment temperature may be, for example, 80°C or higher, 90°C or higher, or 100°C or higher. The upper limit may be 140°C or lower, or 120°C or lower. The heat treatment time can be appropriately changed depending on the coating amount and temperature.

[0076] In one embodiment, an aging treatment may be further performed after the heat treatment. The temperature of the aging treatment may be 40° C. or higher, or 50° C. or higher, and the upper limit may be 60° C. or lower. The time for the aging treatment may be, for example, one day or longer.

[0077] <Step (2): Laminating the second layer> Step (2) involves laminating a second layer containing an inorganic oxide as a main component on the first layer obtained in step (1). From the viewpoint of easily obtaining a laminated film with excellent gas barrier properties, the second layer is preferably a vapor-deposited film. In this case, step (2) involves forming a vapor-deposited film of an inorganic oxide on the first layer, preferably on the surface of the first layer. As the inorganic oxide, those described above can be used.

[0078] The deposition method is not particularly limited, and known methods and devices can be used, and may be physical vapor deposition (PVD) or chemical vapor deposition (CVD). Examples of physical vapor deposition methods include vacuum deposition, reactive vapor deposition, sputtering, reactive sputtering, ion plating, and reactive ion plating. Examples of chemical vapor deposition methods include plasma CVD and laser CVD. The deposition conditions may be appropriately selected so as to obtain a second layer of a desired thickness.

[0079] <Step (3): Laminating the protective layer> The manufacturing method according to this embodiment may further include laminating a protective layer on the second layer (step (3)). The protective layer may be formed by applying a coating agent containing a protective layer resin composition containing the above-mentioned resin, or a protective layer resin composition containing a water-soluble polymer and a metal alkoxide and / or its hydrolysate, onto the second layer. The coating agent may contain a solvent or a dispersion medium. The same coating method as exemplified in step (1) can be used.

[0080] [Packaging film] A second embodiment of the present disclosure relates to a packaging film including the laminate film according to the first embodiment and a sealant layer. The sealant layer is provided on the second layer or the protective layer of the laminate film. The packaging film according to the second embodiment can maintain high gas barrier properties and adhesion between the laminate film and the sealant layer even after retort treatment.

[0081] <Sealant layer> Examples of the sealant layer include the thermoplastic resins described above for the base layer. Among these, the sealant layer preferably contains a polyolefin-based resin, and is preferably a film made of the same polyolefin-based resin as the base layer, and more preferably a film made of a polypropylene-based resin. This film may be a uniaxially stretched film, a biaxially stretched film, or an unstretched film. Furthermore, the sealant layer may be made of a single-layer film, or may be a laminate of two or more films. When the sealant layer is a laminate of two or more films, the types of thermoplastic resins (preferably polyolefin-based resins) contained in each layer may be the same or different.

[0082] The sealant layer may contain the additives described above for the base layer, and the proportion of the additives may be 10% by mass or less relative to the total mass of the resin composition constituting the sealant layer (hereinafter, also referred to as the "sealant layer resin composition").

[0083] Furthermore, in order to improve the adhesion between the sealant layer and the second layer or the protective layer, the surface of the sealant layer that comes into contact with the second layer or the protective layer may be subjected to corona discharge treatment, plasma treatment, or the like.

[0084] The thickness of the sealant layer is not particularly limited and can be appropriately set depending on the application of the packaging film. In one embodiment, the thickness of the sealant layer may be 5 to 100 μm, 10 to 90 μm, or 15 to 80 μm. When the packaging film is for packaging food, the sealant layer is particularly preferably a CPP film having a thickness of 5 to 80 μm.

[0085] The packaging film may be laminated with at least one printed layer, other plastic substrate and / or paper substrate.

[0086] In one embodiment, the packaging film has an oxygen permeability of 6 cc / m at 20°C / 90% RH measured according to JIS K7126-2 after retort treatment. 2 In a more preferred embodiment, the oxygen permeability is 5 cc / m 2 / day or less, more preferably 4cc / m 2 / day or less, particularly preferably 3cc / m 2 / day or less.

[0087] <Packaging film manufacturing method> The packaging film according to the second embodiment can be produced by a method comprising laminating a sealant layer onto the second layer or protective layer of the laminate film according to the first embodiment. The sealant layer can be laminated by extrusion lamination or dry lamination.

[0088] <Application> The packaging film according to the third embodiment includes the laminated film according to the first embodiment, and therefore can maintain high gas barrier properties and adhesion to the sealant layer even after retort treatment, making it suitable for use in food packaging.

[0089] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure are set forth below. [1] A substrate layer; a first layer laminated on at least one surface of the base material layer; a second layer laminated on the first layer, the substrate layer contains a polyolefin-based resin, the first layer contains a reaction product (C) of a polyurethane resin (A) and a crosslinking agent (B), and a layered inorganic compound (D), A laminated film, wherein the second layer contains, as a main component, at least one selected from a metal and an inorganic oxide. [2] The laminated film according to [1], wherein the reaction product (C) is a reaction product of a resin composition containing 10 to 30 parts by mass of the crosslinking agent (B) per 100 parts by mass of the polyurethane resin (A). [3] The laminated film according to [1] or [2], wherein the crosslinking agent (B) contains a carbodiimide compound. [4] The laminated film according to any one of [1] to [3], wherein the layered inorganic compound (D) contains montmorillonite. [5] The laminated film according to any one of [1] to [4], wherein the proportion of the layered inorganic compound (D) in the first layer is 1% by mass or more and less than 10% by mass. [6] The laminated film according to any one of [1] to [5], wherein the thickness of the first layer is 0.2 to 4.0 μm. [7] The oxygen permeability of the polyurethane resin (A) measured in accordance with JIS K 7126-2 at 20°C / 90%RH is 50 cc / m 2 The laminated film according to any one of [1] to [6], wherein the thickness is 1 / day·μm or less. [8] The oxygen permeability of the laminated film measured in accordance with JIS K7126-2 at 20°C / 90%RH is 5 cc / m 2 / day or less. [9] The laminated film according to any one of [1] to [8], further comprising a protective layer laminated on the second layer.

[10] A packaging film comprising the laminate film according to any one of [1] to [9] and a sealant layer.

[11] The packaging film according to

[10] , wherein the sealant layer contains a polyolefin resin.

[12] The oxygen permeability of the packaging film after retort treatment, measured according to JIS K7126-2 at 20°C / 90%RH, is 6 cc / m 2 / day or less.

[13] The packaging film according to any one of

[10] to

[12] , which is for food packaging. [Example]

[0090] The effects of the present disclosure will be clarified below by examples, but the present disclosure should not be interpreted as being limited based on the description of these examples.

[0091] The following raw materials were used in the examples and comparative examples. <Polyurethane resin (A)> Polyurethane resin (A1): Mitsui Chemicals, Inc., product name "Takelac WPB-341M", oxygen permeability (a1): 45cc / m 2 / day·μm. Polyurethane resin (A2): Solvent-based polyurethane resin (manufactured by Mitsui Chemicals, Inc., product name "Takelac (registered trademark) A310" and product name "Takenate A3" reacted in a 10:1 ratio), oxygen permeability (a1): 100 cc / m 2 / day μm). <Crosslinking agent (B)> Carbodiimide resin: Manufactured by Nisshinbo Chemical Inc., product name "Carbodilite SV-02" (carbodiimide equivalent: 430). <Layered inorganic compounds (D)> Swellable layered inorganic compound (D1): Montmorillonite (manufactured by Kunimine Industries Co., Ltd., product name "Kunipia-G"). Average particle size: 0.17 μm. <Coating agent for protective layer> Si5O4(OEt) 12 A siloxane compound solution was prepared by mixing 20 g of ethyl silicate 40 (average pentamer) (manufactured by Colcoat Co., Ltd.), 10 g of IPA, 20 g of 0.05% hydrochloric acid, and 50 g of pure water, followed by stirring at 50° C. for 2 hours. The siloxane compound solution was mixed with an aqueous solution prepared by dissolving 8 g of fully saponified polyvinyl alcohol resin (manufactured by Kuraray Co., Ltd., product name Kuraray Poval (registered trademark) 28-98) in 92 g of pure water to prepare a coating liquid for forming a protective layer. <Other ingredients> Cross-linked polyvinyl alcohol resin: A reaction product of carbonyl-modified polyvinyl alcohol resin (manufactured by Nippon Vinegar Vipbal Co., Ltd., product name "DF-05") and adipic acid dihydrazide in a 100:5 (mass ratio).

[0092] [Laminated film manufacturing] [Example 1] To the aqueous dispersion of the swellable layered inorganic compound (D1), the polyurethane resin (A1) and the crosslinking agent (B) were added and stirred for 5 minutes to obtain a coating agent of the resin composition for the first layer having the composition shown in Table 1. Next, a corona-discharge-treated biaxially oriented polypropylene film (thickness: 20 μm) was prepared as the substrate layer. The coating agent was applied to the corona-discharge-treated surface of this substrate layer at a concentration of 0.6 g / m after drying. 2 The coating material for the protective layer was applied in an amount of 0.4 g / m2 after drying at 100°C for 1 minute to form a first layer. Next, aluminum oxide (AlOx) was deposited on the surface of the first layer by physical vapor deposition (PVD) to form a second layer (thickness: 40 nm). After drying, the coating material for the protective layer was applied to the deposited layer at a concentration of 0.4 g / m2. 2 The coating was dried at 100° C. for 1 minute to obtain a laminated film of Example 1.

[0093] [Examples 2 to 5] A laminated film was produced in the same manner as in Example 1, except that the composition and thickness of the first layer were as shown in Table 1.

[0094] [Comparative Examples 1 to 3] A laminated film was prepared in the same manner as in Example 1, except that the second layer and the protective layer were not provided on the first layer and the composition of the coating agent was as shown in Table 1.

[0095] [Comparative Examples 4 to 5] A laminated film was produced in the same manner as in Example 1, except that the composition and thickness of the first layer were as shown in Table 1.

[0096] The gas barrier properties (oxygen permeability and water vapor permeability) of the laminated films obtained in each example were evaluated as follows.

[0097] <Gas barrier properties (oxygen permeability: 20°C / 90%RH)> In accordance with JIS K7126-2, oxygen permeability (unit: cc / m) was measured using an oxygen permeability measuring device (MOCON, product name "OX-TRA N2 / 20"). 2 / day) was measured. The measurement conditions were 20°C and a relative humidity of 90% RH. The results are shown in Tables 1 and 2.

[0098] <Gas barrier properties (water vapor permeability)> In accordance with JIS K7129-2, the water vapor permeability (unit: g / m) was measured using a water vapor permeability measuring device (manufactured by MOCON, product name "PERMATRAN"). 2 / day) was measured. The measurement conditions were 40°C and a relative humidity of 90% RH. The results are shown in Tables 1 and 2.

[0099] [Packaging film manufacturing] A non-oriented polypropylene film (manufactured by Futamura Chemical Co., Ltd., product name "FRTK-G", thickness 70 μm) was dry laminated as a sealant layer on the second layer of the laminated film obtained in each example (on the first layer in Comparative Examples 1 to 4 and 6 to 7), and the film was aged at 40°C for 3 days to obtain a packaging film.

[0100] The lamination strength of each packaging film was measured under the following conditions. Then, each packaging film was retorted at 121°C for 30 minutes. The gas barrier properties (oxygen permeability and water vapor permeability) of the packaging film after retort treatment were measured under the same conditions as above.

[0101] <Lamination strength> The packaging film of each example was cut into a 15 mm width, and the peel strength between the laminated film and the sealant layer (unstretched polypropylene film) was measured using a tensile tester (manufactured by ORIENTEC, product name "RTC-1210") under conditions of a temperature of 23°C and a relative humidity of 50%RH. The measurement was performed using the T-peel method. The results are shown in Tables 1 and 2.

[0102] [Table 1]

[0103] [Table 2]

[0104] "Not measurable" in Table 2 means that the oxygen permeability value was so high that it could not be measured. As shown in Tables 1 and 2, the packaging films obtained from the laminate film according to the first embodiment were able to maintain high barrier properties even after retort treatment. Furthermore, there was little decrease in laminate strength even after retort treatment, and adhesion was maintained. On the other hand, the laminate films of Comparative Examples 1 to 3 had very low gas barrier properties, and therefore the gas barrier properties after retort treatment as a packaging film were also very low. For the packaging film of Comparative Example 4, the gas barrier properties of the laminate film and packaging film could not be measured. Furthermore, for the laminate film of Comparative Example 5, although the gas barrier properties of the laminate film were high, the gas barrier properties after retort treatment as a packaging film could not be measured. From the above results, it was confirmed that the laminated film according to the first embodiment can provide a packaging film that can maintain high gas barrier properties and adhesion to the sealant layer even after retort treatment.

Claims

1. a substrate layer; a first layer laminated on at least one surface of the base material layer; a second layer laminated on the first layer, the substrate layer contains a polyolefin-based resin, the first layer contains a reaction product (C) of a polyurethane resin (A) and a crosslinking agent (B), and a layered inorganic compound (D), A laminated film, wherein the second layer contains, as a main component, at least one selected from a metal and an inorganic oxide.

2. The laminate film according to claim 1, wherein the reaction product (C) is a reaction product of a resin composition containing 10 to 30 parts by mass of the crosslinking agent (B) relative to 100 parts by mass of the polyurethane resin (A).

3. The laminated film according to claim 1 or 2, wherein the crosslinking agent (B) comprises a carbodiimide compound.

4. The laminated film according to claim 1 or 2, wherein the layered inorganic compound (D) comprises montmorillonite.

5. 3. The laminate film according to claim 1, wherein the proportion of the layered inorganic compound (D) in the first layer is 1% by mass or more and less than 10% by mass.

6. 3. The laminated film according to claim 1, wherein the thickness of the first layer is 0.2 to 4.0 μm.

7. The polyurethane resin (A) has an oxygen permeability of 50 cc / m at 20°C / 90% RH as measured in accordance with JIS K 7126-2. ２ The laminated film according to claim 1 or 2, wherein the thickness is 1 / day·μm or less.

8. The oxygen permeability of the laminated film measured in accordance with JIS K7126-2 at 20°C / 90% RH is 5 cc / m ２ The laminated film according to claim 1 or 2, wherein the average particle size is 1 / day or less.

9. The laminated film according to claim 1 or 2, further comprising a protective layer laminated on the second layer.

10. A packaging film comprising the laminate film according to claim 1 or 2 and a sealant layer.

11. The packaging film according to claim 10 , wherein the sealant layer comprises a polyolefin resin.

12. The oxygen permeability of the packaging film after retort treatment at 20°C / 90%RH measured in accordance with JIS K7126-2 is 6 cc / m ２ The packaging film according to claim 10, wherein the film thickness is 1 / day or less.

13. The packaging film according to claim 10, which is for packaging food.

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