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] This disclosure relates to laminated films and packaging films comprising the same. [Background technology]

[0002] Conventionally, gas barrier films are known in which a laminated film with gas barrier properties is formed on a base film to suppress the permeation of oxygen, water vapor, etc. For example, laminated films are known in which an inorganic oxide vapor-deposited film is provided on a base film, or laminated films in which a barrier resin is laminated on a base film.

[0003] To obtain high gas barrier properties, it is preferable to have a structure that includes a vapor-deposited film. However, when the substrate layer is an olefin-based resin film such as OPP, it is difficult to obtain sufficient gas barrier properties by forming a vapor-deposited film alone. Therefore, an anchor coat layer is also provided between the substrate layer and the vapor-deposited film.

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

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-024136 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Patent Document 1 describes examples 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 reduced gas barrier properties after retort processing, and the adhesion between the sealant layer and the vapor-deposited film also tends to decrease.

[0007] This disclosure aims to provide a laminated film that can obtain a packaging film that maintains high gas barrier properties and adhesion to a sealant layer even after retort processing, and a packaging film equipped with the same. [Means for solving the problem]

[0008] As a result of diligent study, the inventors of the present invention have found that the above problem can be solved if the laminated film comprises 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 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. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a laminated film that can obtain a packaging film that maintains high gas barrier properties and adhesion to a sealant layer even after retort processing, and a packaging film equipped therewith. [Modes for carrying out the invention]

[0010] Hereinafter, an embodiment of the present disclosure will be described in detail. However, the scope of the present disclosure is not limited to the embodiment described here, 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 features disclosed in this specification. Also, when multiple upper and lower limit values are described for a specific parameter, any upper limit value and lower limit value can be combined to form a suitable numerical range. Further, the lower limit value and / or upper limit value of the numerical range described in the present disclosure can be replaced with a numerical value within that numerical range and shown in the examples. The expression "X~Y" indicating a numerical range means "X or more and Y or less". Also, unless otherwise noted, all test temperatures are room temperature (20°C ± 5°C). When the specific description given for one embodiment also applies to other embodiments, the description may be omitted in other embodiments.

[0011] Each configuration and their combinations, etc. in each embodiment are examples, and within the scope not departing from the gist of the present disclosure, additions, omissions, substitutions, and other changes to the configuration can be made as appropriate. The present disclosure is not limited by the embodiments and is limited only by the claims. Each aspect disclosed in this specification can be combined with any other features disclosed in this specification.

[0012] [Laminated Film] The first embodiment of the present disclosure relates to a laminated film. The laminated film according to the first embodiment includes 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. The base material 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 a metal and an inorganic oxide as a main component. According to the laminated film according to the first embodiment, a packaging film that can maintain high gas barrier properties and adhesion to a sealant layer even after retort treatment can be provided. In the present disclosure, "retort treatment" refers to treating a packaging film under conditions of 121°C or higher.

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

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

[0015] Examples of the polyethylene resin 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, ethylene-(meth)acrylic acid copolymer resin, and the like.

[0016] Examples of polypropylene resins include homopolypropylene resins, block polypropylene resins, random polypropylene resins, and copolymer resins of propylene and other monomers. Examples of other monomers include α-olefins such as ethylene, 1-butene, 1-hexene, 1-octene, 3-methylpentene, and 4-methylpentene. The polypropylene resin may also be a copolymer resin obtained by combining two or more other monomers with propylene. When the substrate layer contains the copolymer resin, it is preferable that the monomer component contains 80% by mass or more of propylene, more preferably 90% by mass or 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 embodiments in which only homopolypropylene resin is included as the polyolefin resin, the effects of the present disclosure are more likely to be obtained. In one embodiment, the base layer is preferably a polypropylene resin film (particularly a homopolypropylene film). This film may be a uniaxially oriented film, a biaxially oriented film, or an unoriented film. The base layer may also consist of a single film or a laminate of two or more films. When the base 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] Furthermore, the polyolefin resin contained in the base layer may be a polyolefin resin derived from biomass, or a polyolefin resin that has been mechanically or chemically recycled.

[0020] (Other thermoplastic resins) The base layer may contain thermoplastic resins other than polyolefin resins (other thermoplastic resins). Examples of other thermoplastic resins include polyester resins (polyethylene naphthalate, polyethylene terephthalate, etc.), polyamide 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 resins (triacetylcellulose, diacetylcellulose, etc.). These thermoplastic resins may be used individually or in combination of two or more. Since an olefin-based resin film (preferably a polypropylene film) is often used as the sealant layer described later, it is preferable that the base layer contains only polyolefin 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, nucleating agents, ultraviolet absorbers, colorants, and antiblocking agents, to the extent that the effects described herein are not hindered. For example, at least one resin selected from petroleum resins and terpene resins may be added to improve the water vapor barrier properties of the base layer. If the base layer contains these resins, their total content may be 1% by mass or more, 2% by mass or more, 15% by mass or less, or 10% by mass or less, based on the total mass of the resin composition for the base layer.

[0022] Furthermore, to improve the adhesion between the substrate layer and the first layer, corona discharge treatment, plasma treatment, etc., may be performed on the surface of the substrate layer. If necessary, corona discharge treatment or plasma treatment may also be performed on the surface where the first layer is not laminated (the uncoated side).

[0023] The thickness of the base layer is not particularly limited and can be set appropriately depending on the application of the packaging film. In one embodiment, the thickness of the base layer may be 5 μm or more, 10 μm or more, or 15 μm or more. The upper limit of the thickness of the base layer may be 100 μm or less, 90 μm or less, or 80 μm or less. That is, the thickness of the base 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 food packaging, the base layer is particularly preferably an OPP film with a thickness of 5 to 80 μm.

[0024] <First layer> The laminated film according to the first embodiment comprises 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 the substrate layer. Alternatively, the first layer may be laminated on a surface of the substrate layer that has been treated with corona discharge or plasma. 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 polyurethane resin (A) and a crosslinking agent (B), and a layered inorganic compound (D). By having such a first layer, a packaging film can be obtained that maintains high gas barrier properties and adhesion to the sealant layer even after retort processing.

[0025] (Polyurethane resin (A)) The first layer comprises 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 according to JIS K 7126-2 (hereinafter sometimes referred to as "oxygen permeability (a1)") of 100 cc / m². 2 Preferably less than / day·μm, 80cc / m 2 It is more preferable that the concentration is less than or equal to / day·μm, and 50cc / m2 It is even more preferable that the value be less than or equal to / day·μm. 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 maintains high gas barrier properties even after retort processing.

[0027] From the viewpoint of easily achieving the high gas barrier properties mentioned 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 the reaction of 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 by a chain extender.

[0029] • Polyisocyanate components The polyisocyanate component is not particularly limited and includes aliphatic polyisocyanates, aromatic polyisocyanates, aromatic aliphatic 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, and 4,4'-diphenyl ether diisocyanate. These may be used individually 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), and ω,ω'-diisocyanate-1,4-diethylbenzene. These may be used individually 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 include MDI, 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, methyl-2,6-cyclohexane diisocyanate, etc. These may be used individually 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, and 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate.

[0034] Furthermore, the polyisocyanate component may include polymers of the above-mentioned polyisocyanate (e.g., dimers, trimers, pentamers, heptamers, etc.), biuret-modified products produced by the reaction of the above-mentioned polyisocyanate with water, allophanate-modified products produced by the reaction of the above-mentioned polyisocyanate with a monool or polyhydric alcohol (described later), oxadiazinetrione-modified products produced by the reaction of the above-mentioned polyisocyanate with carbon dioxide, and the like.

[0035] Of 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; and IPDI, H 12 It is preferable to use alicyclic polyisocyanates such as MDI, H6XDI, and NBDI; or aliphatic polyisocyanates such as HDI. Furthermore, two or more of these may be used in combination.

[0036] • Polyol components As the polyol component, a relatively low molecular weight polyol is preferred. Examples of relatively low molecular weight polyols include polyols with a mass-average molecular weight (Mw) (or molar mass) of 400 or less. Preferred such polyols include the low molecular weight polyols shown below; polyether polyols obtained by adding an alkylene oxide to the low molecular weight polyol as an initiator; and polycarbonate polyols obtained by reacting the low molecular weight polyol with phosgene, dialkyl carbonate, diallyl carbonate, alkylene carbonate, etc., 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, and hexaoxypropylene glycol. Of 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 the inclusion of ethylene glycol and diethylene glycol is 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, and oxetane compounds. 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 isocyanate components and one or more polyol components such 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% by mass or 3 to 15% by mass, based on 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 5000 or 500 to 3000.

[0040] The polyurethane resin (A) may include polyurethane resins other than gas barrier polyurethane prepolymers (other polyurethane resins). Other urethane resins include, for example, 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 a molar mass of more than 400 (Mw); polyester polyols obtained by adding an alkylene oxide to the polyol; and polycarbonate polyols obtained from the polyol. Two or more of these isocyanate and polyol components can be used in combination.

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

[0042] The polyurethane resin (A) preferably contains a gas barrier urethane prepolymer as its main component. That is, the proportion of the gas barrier urethane prepolymer to the total mass of the polyurethane resin (A) is preferably more than 50% by mass. This proportion can be adjusted to any proportion within the range of more than 50% by mass and 100% by mass or less. 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] A commercially available polyurethane resin (A) may be used. Examples of commercially available products include "Takelac® WPB-341M" manufactured by Mitsui Chemicals, Inc.

[0044] <Crosslinking agent (B)> The crosslinking agent (B) is a compound having a crosslinkable functional group that reacts with the polyurethane resin (A) to form a reactant (C) with excellent gas barrier properties and 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 agent (B) may be used alone or in combination of two or more types. In a preferred embodiment, from the viewpoint of easily obtaining a packaging film that maintains high gas barrier properties even after retort processing, the crosslinking agent (B) includes a carbodiimide compound.

[0045] Carbodiimide compounds are compounds having one or more carbodiimide groups (-N=C=N-) in their molecules. Examples of carbodiimide compounds include aliphatic carbodiimide compounds with an aliphatic main chain, alicyclic carbodiimide compounds with an alicyclic main chain, aromatic carbodiimide compounds with an aromatic main chain, and carbodiimide resins. One or more selected from these can be used.

[0046] Examples of aliphatic carbodiimide compounds include diisopropylcarbodiimide and dioctyldecylcarbodiimide. Examples of alicyclic carbodiimide compounds include dicyclohexylcarbodiimide. These can be used individually or in combination of two or more.

[0047] 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 include mono- or 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 can be used individually or in combination of two or more.

[0048] Examples of carbodiimide resins include hydrophilic group-containing carbodiimide resins. The carbodiimide equivalent (amount of chemical formula per mole of carbodiimide groups) in the carbodiimide resin may be 300 to 500, or 350 to 450. Commercially available carbodiimide resins may be used; for example, the Carbodilite® series manufactured by Nisshinbo Chemical Co., Ltd. can be used.

[0049] In one embodiment, the ratio of crosslinking agent (B) to 100 parts by mass of polyurethane resin (A) is preferably 10 to 30 parts by mass. That is, the reactant (C) is preferably a reactant of a resin composition containing 10 to 30 parts by mass of crosslinking agent (B) per 100 parts by mass of polyurethane resin (A). The ratio of the crosslinking agent (B) is more preferably greater than 10 parts by mass and 30 parts by mass or less, and even more preferably 18 to 27 parts by mass. According to the inventors' studies, it has been found that by including a reactant (C) obtained by reacting 10 to 30 parts by mass of crosslinking agent (B) (preferably a carbodiimide compound) per 100 parts by mass of polyurethane resin (A) in the first layer, adhesion to the second layer is further improved, and gas barrier properties are also more easily improved. By including such a first layer, it becomes easier to obtain a packaging film that can maintain high gas barrier properties and adhesion to the protective layer even after retort processing.

[0050] <Reactant (C)> The reactant (C) is a resin component obtained by the reaction of the aforementioned polyurethane resin (A) and crosslinking agent (B). In one embodiment, the first layer preferably contains reactant (C) as the main component. The proportion of reactant (C) in the first layer is preferably more than 50% by mass and 90% by mass or less, more preferably 60-92% by mass, and even more preferably 70-92% by mass.

[0051] <Layered inorganic compound (D)> The first layer further contains a layered inorganic compound (D). By providing the 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, resulting in a packaging film in which gas barrier properties and adhesion to the sealant layer do not deteriorate easily even after retort processing. In this disclosure, "layered inorganic compound" means an inorganic compound in which unit crystal layers are stacked to form a layered structure.

[0052] The layered inorganic compound (D) preferably contains a swollen layered inorganic compound (D1). Swellable layered inorganic compounds (D1) refer to inorganic compounds that have a structure in which unit crystal layers are stacked and exhibit the property of swelling or cleavage by coordinating or absorbing a solvent (especially water) between the layers. Examples of such inorganic compounds include swelling hydrated silicates, such as smectite group clay minerals (montmorillonite, beidelite, nontronite, saponite, hectorite, souconite, stevensite, etc.), vermiculite group clay minerals (vermiculite, etc.), kaolin-type minerals (haloysite, kaolinite, endelite, dickite, etc.), phyllosilicates (talc, pyrophyllite, mica, margalite, muscovite, phlogopite, tetrasilicic mica, teniolite, etc.), jamonite group minerals (antigorite, etc.), and chlorite group minerals (chlorite, cookite, nanthite, etc.). These swelling layered inorganic compounds (D1) may be natural products or synthetic products. The laminated film according to the first embodiment may contain one type of the aforementioned swelling layered inorganic compound (D1) alone or two or more types in the first layer. Of these swelling layered inorganic compounds (D1), it is preferable to include smectite group clay minerals, and it is particularly preferable to include montmorillonite.

[0053] The swellable layered inorganic compound (D1) is preferably subjected to micronization treatment from the viewpoint of adhesion between the substrate layer and the second layer, and gas barrier properties of the laminated film. The micronized swellable layered inorganic compound usually has a plate-like or flattened shape, but its planar shape is not particularly limited and may be amorphous or the like. The average particle size (average particle size in planar shape) of the micronized 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 laser diffraction / scattering. The average particle size refers to the median diameter (D50) of the volume-based average particle size measured by laser diffraction / scattering.

[0054] When using a swellable layered inorganic compound (D1) that has been micronized, it is preferable to perform the micronization treatment by dispersing the swellable layered inorganic compound (D1) under high pressure in a solution. Examples of solvents include water or water-soluble solvents (such as lower alcohols like methanol and ethanol, or acetone). Water is typically used. The processing pressure in high-pressure dispersion processing is, for example, 20 MPa (approximately 200 kgf / cm²). 2 The pressure is above (for example, 20 to 100 MPa), preferably around 20 to 80 MPa, and more preferably around 40 to 60 MPa. One possible processing method is to swell the swellable layered inorganic compound (D1) in a solvent and then disperse it under high pressure by stirring it with a high-pressure homogenizer at the aforementioned pressure. This 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 inventors of this application have found that by using a first layer containing a reactant (C) and a layered inorganic compound (D) as a coating layer between the substrate layer and the second layer, a packaging film obtained from a laminated film having the first layer can maintain high gas barrier properties and adhesion to the protective layer even after retort processing. It is expected that higher gas barrier properties will be exhibited as the amount of layered inorganic compound (D) added increases. On the other hand, the inventors' studies have shown that if the amount added is too high, the adhesion between the second layer and the first layer, and the adhesion (laminate strength) between the laminated film and the sealant layer tend to decrease, and consequently, the gas barrier properties may decrease (in particular, oxygen permeability may increase). 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 and 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 layered inorganic compound (D) in the first layer refers to the content of 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 inventors of the present invention have found that by combining the reactant (C) and the layered inorganic compound (D), good gas barrier properties can be easily 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 base layer and the first layer. The anchor coat layer can be formed by applying an anchor coat agent to the base layer. Conventional 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 crosslinking agent (B) described above, it has good adhesion to the base layer, and the first layer itself functions as an anchor coat layer between the base layer and the second layer. From the viewpoint of easily achieving the effects of this disclosure, it is preferable to have a configuration in which the first layer is directly laminated on the base layer.

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

[0059] The second layer comprises at least one selected from metals and inorganic oxides as its main component. In a preferred embodiment, the second layer is a vapor-deposited film comprising an inorganic oxide as its main component. Aluminum is preferred as the metal included in the second layer. Metal oxides are preferred as the inorganic oxides included in the second layer. Preferred examples include aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. Of these, the second layer is preferably a vapor-deposited film mainly composed of at least one selected from aluminum oxide and silicon oxide, and is particularly preferably a vapor-deposited film mainly composed of aluminum oxide. In this 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 perspective 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, carboxymethyl cellulose, etc., 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 perspective of easily improving the adhesion between the second layer and the protective layer, and also from the perspective 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 perspective of easily improving the gas barrier property, the protective layer is composed of a water-soluble polymer and the general formula: M(OR) nIt is preferable to include a metal alkoxide represented by and / or its hydrolysate, and more preferably to include a water-soluble polymer and a siloxane compound in which M in the above general formula is silicon. Furthermore, it is preferable that the water-soluble polymer includes a polyvinyl alcohol-based resin.

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

[0065] The oxygen permeability of the laminated film according to the first embodiment, measured at 20°C / 90%RH in accordance with JIS K7126-2, is 5 cc / m². 2 Preferably, the oxygen permeability is 4 cc / m³. In a more preferred embodiment, the oxygen permeability is 4 cc / m³. 2 Less than or equal to / day, more preferably 3cc / m³ 2 Less than or equal to / day, particularly preferably 2cc / m³ 2 The oxygen permeability is less than / day. 2 It may be less than / day.

[0066] Furthermore, the water vapor transmission rate of the laminated film according to the first embodiment, measured at 40°C / 90%RH in accordance with JIS K7129-2, was 5.0 g / m². 2 Preferably less than / day, and 4.0 g / m² 2 Less than / day is more preferable. The laminated film according to the first embodiment has superior gas barrier properties under high humidity conditions compared to, for example, the laminated film described in Patent Document 1.

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

[0068] <Method for manufacturing laminated film> The method for manufacturing the laminated film according to the first embodiment is not particularly limited, and can be manufactured by a method that includes laminating a first layer on the substrate layer (step (1)), and laminating a second layer mainly composed of an inorganic oxide on the first layer. The following describes an example of a manufacturing method including steps (1) and (2).

[0069] <Process (1): Lamination of 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 aforementioned resin composition for the first layer) by mixing a polyurethane resin (A), a crosslinking agent (B), and a layered inorganic compound (D), and then apply the coating agent to the substrate layer. In one embodiment, a step of preparing the 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 a 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 solid content concentration in the coating agent can be within any range, but in one embodiment it may be 5 to 20%.

[0071] The obtained coating agent is applied onto a substrate layer. It is preferable to use the aforementioned film as the substrate layer to which the coating agent is applied. In one preferred embodiment, the substrate layer is a polypropylene resin film, and an OPP film is particularly preferred.

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

[0073] The amount of coating agent applied (weight of the first layer after drying) can be appropriately selected according to the size of the substrate layer, the desired thickness of the first layer, etc. In one embodiment, 0.3 to 5.0 g / m² 2 It may also be 0.5~2.4g / m 2 It may also be 0.5~1.8g / m 2 That's fine.

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

[0075] By heat treatment after coating, the polyurethane resin (A) and the crosslinking agent (B) react to prepare a reactant (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 amount of coating and the temperature.

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

[0077] <Process (2): Lamination of the second layer> Step (2) involves laminating a second layer, mainly composed of an inorganic oxide, onto 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) includes forming a vapor-deposited film of an inorganic oxide on the first layer, preferably on the surface of the first layer. The inorganic oxides mentioned above can be used.

[0078] The deposition method is not particularly limited, and known methods and apparatus can be used. It may be physical vapor deposition (PVD) or chemical vapor deposition (CVD). Examples of physical vapor deposition methods include vacuum deposition, reactive 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 to obtain a second layer of the desired thickness.

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

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

[0081] <Sealant layer> Examples of sealant layers include the thermoplastic resins described in the above-mentioned base layer section. The sealant layer preferably contains a polyolefin resin, is preferably a film composed of the same polyolefin resin as the base layer, and is even more preferably a film composed of a polypropylene resin. This film may be uniaxially oriented, biaxially oriented, or unoriented. Furthermore, the sealant layer may consist of a single film or a laminate of two or more films. If the sealant layer is a laminate of two or more films, the type of thermoplastic resin (preferably polyolefin resin) contained in each layer may be the same or different.

[0082] The sealant layer may contain the additives described in the description of the substrate layer. The proportion of the additives may be 10% by mass or less of the total mass of the resin composition constituting the sealant layer (hereinafter sometimes referred to as "resin composition for sealant layer").

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

[0084] The thickness of the sealant layer is not particularly limited and can be set appropriately 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 food packaging, the sealant layer is particularly preferably a CPP film with a thickness of 5 to 80 μm.

[0085] The packaging film may have at least one laminated layer of a printed layer or other plastic substrate and / or paper substrate.

[0086] In one embodiment, the oxygen permeability of the packaging film after retort treatment, measured according to JIS K7126-2 at 20°C / 90%RH, was 6 cc / m². 2 Preferably, the oxygen permeability is 5 cc / m³ or less. In a more preferred embodiment, the oxygen permeability is 5 cc / m³. 2 Less than or equal to / day, more preferably 4cc / m³ 2 Less than or equal to / day, particularly preferably 3cc / m³ 2 It is less than or equal to / day.

[0087] <Manufacturing method for packaging film> The packaging film according to the second embodiment can be manufactured by a method that includes laminating a sealant layer on the second layer or protective layer of the laminated film according to the first embodiment. For laminating the sealant layer, extrusion lamination or dry lamination can be used.

[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 processing. For this reason, it can be suitably used for food packaging applications.

[0089] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of this disclosure is provided below. [1] Substrate layer and A first layer laminated on at least one surface of the substrate layer, It comprises a second layer stacked on the preceding layer, The base layer contains a polyolefin resin, The aforementioned layer comprises a reaction product (C) of a polyurethane resin (A) and a crosslinking agent (B), and a layered inorganic compound (D). A laminated film in which the second layer comprises, as a main component, at least one selected from metals and inorganic oxides. [2] The laminated film according to [1], wherein the reactant (C) is a reactant 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) comprises a carbodiimide compound. [4] A 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] A 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) at 20°C / 90%RH, as measured in accordance with JIS K 7126-2, is 50 cc / m³. 2 A laminated film according to any of [1] to [6], having a thickness of / day·μm or less. [8] The oxygen permeability of the laminated film at 20°C / 90%RH, as measured in accordance with JIS K7126-2, is 5 cc / m². 2 A laminated film according to any of [1] to [7], which is less than or equal to / day. [9] The laminated film according to any one of [1] to [8] further comprising a protective layer laminated on the second layer. A packaging film comprising a laminated film according to any one of [1] to [9] and a sealant layer.

[11] The packaging film according to

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

[12] The oxygen permeability of the packaging film after retort treatment, measured in accordance with JIS K7126-2 at 20°C / 90%RH, is 6 cc / m². 2 The packaging film described in

[10] or

[11] is less than or equal to / day.

[13] A packaging film for food packaging, as described in any of

[10] to

[12] . [Examples]

[0090] The effects of this disclosure will be demonstrated below by the examples provided, but this disclosure should not be interpreted restrictively 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): Manufactured by Mitsui Chemicals, Inc., product name "Takelac WPB-341M", oxygen permeability (a1): 45 cc / m 2 / day·μm. • Polyurethane resin (A2): Solvent-based polyurethane resin (a reaction product obtained by reacting Mitsui Chemicals, Inc.'s product name "Takelac® A310" and product name "Takenate A3" in a 10:1 ratio), oxygen permeability (a1): 100 cc / m 2 / day μm). <Crosslinking agent (B)> • Carbodiimide resin: Manufactured by Nisshinbo Chemical Co., Ltd., product name "Carbodilite SV-02" (carbodiimide equivalent: 430). <Layered inorganic compound (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 20g of (average pentamer) (manufactured by Colcoat Co., Ltd., product name "Ethyl Silicate 40"), 10g of IPA, 20g of 0.05% hydrochloric acid, and 50g of pure water, and then stirring at 50°C for 2 hours. An aqueous solution prepared by dissolving 8g of fully saponified polyvinyl alcohol resin (manufactured by Kuraray Co., Ltd., product name "Kuraray Poval® 28-98") in 92g of pure water was mixed with the siloxane compound solution to prepare a coating solution for forming a protective layer. <Other ingredients> • Cross-linked polyvinyl alcohol resin: A reaction product obtained by reacting carbonyl-modified polyvinyl alcohol resin (manufactured by Nippon Vipoval Co., Ltd., product name "DF-05") with adipic acid dihydrazide in a 100:5 (mass ratio).

[0092] [Manufacturing of laminated films] [Example 1] A polyurethane resin (A1) and a crosslinking agent (B) were added to an aqueous dispersion of a swellable layered inorganic compound (D1), and the mixture was stirred for 5 minutes to obtain a coating agent for the first layer resin composition having the composition shown in Table 1. Next, a biaxially oriented polypropylene film (20 μm thick) treated with corona discharge was prepared as a base layer. The coating agent was applied to the corona discharge treated surface of this base layer at a rate of 0.6 g / m² after drying. 2 The first layer was formed by applying the specified amount (the thickness of the first layer was 0.5 μm) and drying it at 100°C for 1 minute. Next, aluminum oxide (AlOx) was deposited onto the surface of the first layer by physical vapor deposition (PVD) to form the second layer (thickness 40 nm). After drying, 0.4 g / m² of protective coating agent was applied to the deposited layer. 2 The laminated film of Example 1 was obtained by applying the specified amount and drying it at 100°C for 1 minute.

[0093] [Examples 2-5] A laminated film was prepared 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 1-3] A laminated film was prepared in the same manner as in Example 1, except that a second layer and a protective layer were not provided on top of the first layer, and the composition of the coating agent was as shown in Table 1.

[0095] [Comparative Examples 4-5] A laminated film was prepared 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℃ / 90%RH)> In accordance with JIS K7126-2, the oxygen permeability was measured using an oxygen permeability measuring device (MOCON Corporation, product name "OX-TRA N2 / 20"), with the unit being cc / m³. 2 The energy ( / day) was measured. The measurement conditions were 20°C and 90% RH relative humidity. 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 transmission rate was measured using a water vapor transmission rate measuring device (manufactured by MOCON, product name "PERMATRAN"), with the unit being g / m³. 2 The energy ( / day) was measured. The measurement conditions were 40°C and 90% RH relative humidity. The results are shown in Tables 1 and 2.

[0099] [Manufacturing of packaging film] A packaging film was obtained by dry laminating an unoriented polypropylene film (manufactured by Futamura Chemical Co., Ltd., product name "FRTK-G", thickness 70 μm) as a sealant layer onto the second layer of the laminated film obtained in each example (on the first layer in Comparative Examples 1-4 and 6-7), and then aging it at 40°C for 3 days.

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

[0101] <Lamination Strength> The packaging film for each example was cut to a width of 15 mm, and the peel strength between the laminated film and the sealant layer (unoriented polypropylene film) was measured using a tensile testing machine (ORIENTEC, product name "RTC-1210") under conditions of 23°C and 50% RH relative humidity. 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] In Table 2, "unmeasurable" means that the oxygen permeability value was too high to be measured. As shown in Tables 1 and 2, the packaging film obtained from the laminated film according to the first embodiment maintained high barrier properties even after retort treatment. Furthermore, the decrease in laminate strength was minimal after retort treatment, and adhesion was maintained. On the other hand, the laminated films of Comparative Examples 1 to 3 had very low gas barrier properties, and therefore their gas barrier properties after retort treatment as packaging films were also very low. For the packaging film of Comparative Example 4, it was not possible to measure the gas barrier properties of both the laminated film and the packaging film. In addition, although the laminated film of Comparative Example 5 had high gas barrier properties, it was not possible to measure its gas barrier properties after retort treatment as a packaging film. Based on the above results, it was confirmed that the laminated film according to the first embodiment can provide a packaging film that maintains high gas barrier properties and adhesion to the sealant layer even after retort processing.

Claims

1. A base layer and A first layer laminated on at least one surface of the substrate layer, It comprises a second layer laminated on the preceding layer, The base layer contains a polyolefin resin, The aforementioned layer comprises a reaction product (C) of a polyurethane resin (A) containing an isocyanate group-terminated prepolymer and a crosslinking agent (B) containing a carbodiimide compound, and a layered inorganic compound (D). The second layer comprises, as a main component, at least one selected from metals and inorganic oxides. The reactant (C) is a reactant 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), A laminated film in which the proportion of the layered inorganic compound (D) in the single layer is 1% by mass or more and less than 10% by mass.

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

3. The laminated film according to claim 1 or 2, wherein the thickness of the first layer is 0.2 to 4.0 μm.

4. The oxygen permeability of the laminated film at 20°C / 90%RH, measured according to JIS K7126-2, was 5 cc / m³. ２ The laminated film according to claim 1 or 2, wherein the number of days is less than or equal to / day.

5. Furthermore, the laminated film according to claim 1 or 2 comprises a protective layer laminated on the second layer.

6. A method for manufacturing a laminated film according to claim 1 or 2, The manufacturing method includes laminating the first layer on the base layer, and laminating the second layer on the first layer. Laminating the aforementioned layer results in an oxygen permeability of 50 cc / m³ at 20°C / 90% RH, as measured according to JIS K 7126-2. ２ A method for manufacturing a laminated film, comprising: preparing a coating agent by mixing a polyurethane resin (A) having a diameter of / day·μm or less, a crosslinking agent (B), and a layered inorganic compound (D); and applying the coating agent to the substrate layer.

7. A packaging film comprising a laminated film according to claim 1 or 2 and a sealant layer.

8. The packaging film according to claim 7, wherein the sealant layer comprises a polyolefin resin.

9. The oxygen permeability of the aforementioned packaging film after retort processing, measured according to JIS K7126-2 at 20°C / 90% RH, was 6 cc / m³. ２ The packaging film according to claim 7, wherein the number of days is less than or equal to / day.

10. A packaging film according to claim 7, for use in food packaging.

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