Composite multilayer film, multilayer structure, packaging material, and product

Abstract

Provided is a composite multilayer film that is based on polyolefin, that has an inorganic layer on an EVOH layer exposed surface side located on the outermost layer, and that can suppress a decrease in gas barrier properties even when being stored for a certain period or more in a state of having packaged therein a content including a specific amount of water and oil. This composite multilayer film has a barrier layer (A) on the outermost layer. In a multilayer film having a structure in which the barrier layer (A), an adhesive layer (B), and a core layer (C) are directly laminated in the stated order, a protective layer (P) and an inorganic layer (I) located adjacent to each other are provided on the exposed surface side of the barrier layer (A). The barrier layer (A) is formed of a resin composition (A') containing, as the main component, an EVOH (a) having an ethylene unit content of 20-50 mol% and a saponification degree of 90 mol% or more. The adhesive layer (B) contains an adhesive resin (b) as the main component. The core layer (C) contains a polyolefin (c) as the main component. The protective layer (P) contains a vinyl alcohol-based polymer.

Description

Composite multilayer films, multilayer structures, packaging materials and products

[0001] The present invention relates to a composite multilayer film, a multilayer structure containing the composite multilayer film, and packaging materials and products using the same.

[0002] Packaging materials for long-term food storage are often required to have gas barrier properties, including oxygen barrier properties. The use of packaging materials with high gas barrier properties can prevent oxidative deterioration of food caused by oxygen penetration and the growth of microorganisms. Metal foils such as aluminum foils, metal vapor deposition layers, and inorganic oxide vapor deposition layers such as silicon oxide and aluminum oxide are widely used as inorganic layers for improving gas barrier properties (Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 62-101428 International Publication No. 2021 / 261560

[0004] Meanwhile, in recent years, driven by environmental and waste issues, there has been a growing global demand for so-called post-consumer recycling (hereinafter sometimes simply referred to as "recycling"), which involves recovering and recycling packaging materials consumed in the market. Recycling typically involves cutting recovered packaging materials, separating and cleaning them as necessary, and then melt-mixing them using an extruder. In this regard, packaging materials are required to be composed of as few materials as possible (mono-materialization), which allows for the production of high-purity, high-quality recycled raw materials. In particular, aluminum foil and polyester film are known to hinder recyclability due to their poor compatibility and dispersibility with polyolefin-based resins, which are widely used as packaging materials. Therefore, multilayer structures containing inorganic vapor-deposited films with a polyolefin-based resin substrate are in demand, instead of multilayer structures containing inorganic vapor-deposited films with aluminum foil or polyester film substrates. For example, Patent Document 2 proposes a vapor-deposited multilayer film in which an inorganic vapor-deposited layer is laminated on the surface of the EVOH layer of a polyethylene-based multilayer film, the outermost layer of which is an EVOH layer, thereby achieving both gas barrier properties and recyclability.

[0005] However, when packaging materials using the above-mentioned conventional multilayer films, particularly vapor-deposited multilayer films in which an inorganic vapor-deposited layer is laminated on the surface side of the EVOH layer of a polyolefin-based multilayer film in which the EVOH layer is the outermost layer, are used to achieve mono-materialization, it has been found that when contents containing specific amounts of moisture and oil are stored in a packaged state for a certain period of time or longer, the gas barrier properties deteriorate.

[0006] In view of the above circumstances, an object of the present invention is to provide a composite multilayer film having an inorganic layer on the surface side of the EVOH layer of a polyolefin-based multilayer film in which the EVOH layer is the outermost layer, which composite multilayer film can suppress deterioration in gas barrier properties even when contents containing specific amounts of moisture and oil are stored for a certain period of time or longer in a packaged state, and a multilayer structure, packaging material, and product including the composite multilayer film.

[0007] The above-mentioned problems are solved by the following: [1] A composite multilayer film having a barrier layer (A) as an outermost layer, and having a configuration in which the barrier layer (A), adhesive layer (B) and core layer (C) are directly laminated in this order, and comprising a protective layer (P) and an inorganic layer (I) adjacent to each other on the exposed surface side of the barrier layer (A), wherein the barrier layer (A) is made of a resin composition (A') containing as a main component an ethylene-vinyl alcohol copolymer (a) (hereinafter may be referred to as "EVOH (a)") having an ethylene unit content of 20 to 50 mol% and a saponification degree of 90 mol% or more, the adhesive layer (B) contains as a main component an adhesive resin (b), the core layer (C) contains as a main component a polyolefin (c), and the protective layer (P) contains a vinyl alcohol-based polymer; [2] A composite multilayer film according to [1], having a configuration in which the inorganic layer (I), protective layer (P) and barrier layer (A) are laminated adjacently in this order; [3] The composite multilayer film of [1], which has a configuration in which a protective layer (P), an inorganic layer (I), and a barrier layer (A) are laminated adjacent to each other in this order; [4] The composite multilayer film of any of [1] to [3], in which the adhesive resin (b) is an acid-modified polyolefin; [5] The composite multilayer film of any of [1] to [4], in which the inorganic layer (I) is a metal vapor-deposited layer containing aluminum as a main component or an inorganic oxide vapor-deposited layer containing alumina or silica as a main component; [6] The composite multilayer film of any of [1] to [5], in which the vinyl alcohol-based polymer is a modified polyvinyl alcohol having a modifying group; [7] The composite multilayer film of [6], in which the vinyl alcohol-based polymer having a modifying group is an ethylene-modified polyvinyl alcohol having an ethylene unit content of 1 to 15 mol% and a saponification degree of 80 to 99.9 mol%; [8] The composite multilayer film of [6], in which the vinyl alcohol-based polymer having a modifying group has a modifying group containing a primary hydroxyl group represented by the following general formula (I): [wherein X is a hydrogen atom, a methyl group, or R ２ represents a group represented by —OH. １ and R ２ each independently represents a single bond, an alkylene group having 1 to 9 carbon atoms, or an alkyleneoxy group having 1 to 9 carbon atoms, and the alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom.] [9] R in the general formula (I) １

[10] A composite multilayer film according to [8], wherein R in the general formula (I) is a single bond and X is a hydroxymethyl group; １ is a hydroxymethylene group, and X is a hydrogen atom;

[11] A multilayer structure obtained by laminating the composite multilayer film of any of [1] to

[10] and at least one resin layer (R) containing a thermoplastic resin (r) as a main component;

[12] The multilayer structure of

[11] , wherein the thermoplastic resin (r) is a polyolefin;

[13] The multilayer structure of

[11] or

[12] , wherein the ratio of the total average thickness of the layers containing a polyolefin resin as a main component to the average thickness of the multilayer structure is 0.75 or more;

[14] The multilayer structure of any of

[11] to

[13] , which does not have a layer containing a resin containing as a main component a melting point of 200°C or more and a metal layer having an average thickness of 1 μm or more;

[15] A packaging material having the multilayer structure of any of

[11] to

[14] ;

[16] The problem is solved by providing a product having the packaging material of

[15] and a content, wherein the content contains 5% by mass or more of moisture and at least one selected from the group consisting of 1% by mass or more of lipid, 1% by mass or more of sodium chloride, and 0.5% by mass or more of acetic acid.

[0008] According to the present invention, there are provided a composite multilayer film having an inorganic layer on the EVOH layer surface side of a polyolefin multilayer film in which an EVOH layer is the outermost layer, the composite multilayer film being capable of suppressing a decrease in gas barrier property even when contents containing specific amounts of moisture or oil are stored in a packaged state for a certain period of time or longer, as well as a multilayer structure, packaging material, and product including the composite multilayer film. Note that "gas barrier property after storing contents containing specific amounts of moisture or oil in a packaged state for a certain period of time or longer" is sometimes referred to as "gas barrier property after storage test," and can be specifically evaluated by the method described in the Examples.

[0009] Hereinafter, embodiments of the present invention will be described. Note that in the following description, specific materials (compounds, etc.) that exhibit specific functions may be exemplified, but the present invention is not limited to embodiments using such materials. Furthermore, the exemplified materials may be used alone or in combination, unless otherwise specified.

[0010] <Composite Multilayer Film> The composite multilayer film of the present invention has a barrier layer (A) as the outermost layer, and is configured such that the barrier layer (A), adhesive layer (B), and core layer (C) are directly laminated in this order. The composite multilayer film is provided with a protective layer (P) and an inorganic layer (I) adjacent to each other on the exposed surface of the barrier layer (A), wherein the barrier layer (A) is made of a resin composition (A') containing, as a main component, EVOH (a) having an ethylene unit content of 20 to 50 mol% and a saponification degree of 90 mol% or more, the adhesive layer (B) contains, as a main component, an adhesive resin (b), the core layer (C) contains, as a main component, a polyolefin (c), and the protective layer (P) contains a vinyl alcohol-based polymer.

[0011] Because EVOH (a) has good affinity with the inorganic layer (I) and the protective layer (P), by providing the inorganic layer (I) and the protective layer (P) on the surface side of the barrier layer (A) of a multilayer film having the barrier layer (A) as the outermost layer, the composite multilayer film of the present invention can achieve high gas barrier properties. Furthermore, by having the inorganic layer (I) and the protective layer (P) adjacent to each other, deterioration of gas barrier properties after storage tests can be suppressed. Note that, although the reason is unclear, the structure required to achieve both mono-materialization and gas barrier properties (barrier layer (A) / adhesive layer (B) / core layer (C)) is susceptible to moisture and oil in the contents, and dimensional changes occur when stored in contact with moisture and oil, which is thought to cause cracks or the like in the inorganic layer (I) provided on the surface side of the barrier layer (A), resulting in a deterioration of gas barrier properties. Therefore, the problem of a decrease in gas barrier property after a storage test can be said to be a problem specific to a composite multilayer film having a barrier layer (A) as the outermost layer, and a configuration in which the barrier layer (A), an adhesive layer (B), and a core layer (C) are directly laminated in this order, and having an inorganic layer (I) on the exposed surface side of the barrier layer (A). The present invention solves this problem by providing a protective layer (P) and an inorganic layer (I) adjacent to each other on the exposed surface side of the barrier layer (A).

[0012] In this specification, the phrase "the barrier layer (A), the adhesive layer (B), and the core layer (C) are directly laminated in this order" means that adjacent layers are directly laminated. Specifically, it means that the barrier layer (A), the adhesive layer (B), and the core layer (C) are laminated in this order, the barrier layer (A) and the adhesive layer (B) are directly laminated, and the adhesive layer (B) and the core layer (C) are directly laminated. "Major component" refers to a component contained in an amount of more than 50% by mass. The "average thickness" of each layer other than the inorganic layer (I) refers to the average thickness measured at any five locations. "ppm" refers to the content by mass (ppm by mass). "Polyethylene" refers to a homopolymer of ethylene, a copolymer of 80 mol% or more ethylene and 20 mol% or less α-olefin monomer, and a copolymer of 90 mol% or more ethylene and less than 10 mol% of a non-olefin monomer whose functional group does not contain atoms other than carbon, oxygen, and hydrogen atoms. "Acid-modified polyethylene" refers to a polymer obtained by modifying polyethylene with an acid. Acid-modified polyethylene may be a polymer in which at least one of an acidic group and an acid anhydride group has been introduced into polyethylene. "Polyethylene-based resin" refers to polyethylene and modified polyethylene (such as acid-modified polyethylene). Modified polyethylene refers to a polymer obtained by modifying polyethylene. "Polypropylene" refers to a propylene homopolymer, a copolymer of 80 mol% or more propylene and 20 mol% or less α-olefin monomer, and a copolymer of 90 mol% or more propylene and less than 10 mol% non-olefin monomers whose functional groups contain atoms other than carbon, oxygen, and hydrogen atoms. "Acid-modified polypropylene" refers to a polymer obtained by modifying polypropylene with an acid. Acid-modified polypropylene may be a polymer in which at least one of an acidic group and an acid anhydride group has been introduced into polypropylene. "Polypropylene-based resin" refers to polypropylene and modified polypropylene (such as acid-modified polypropylene). Modified polypropylene refers to a polymer obtained by modifying polypropylene. "Polyolefin" refers to polyethylene, polypropylene, and other polyolefins."Acid-modified polyolefin" refers to a polymer obtained by modifying a polyolefin with an acid. Acid-modified polyolefins may be polymers in which at least one of an acidic group and an acid anhydride group has been introduced into a polyolefin. "Polyolefin-based resin" refers to polyolefins and modified polyolefins (such as acid-modified polyolefins). "Modified polyolefin" refers to a polymer obtained by modifying a polyolefin. "Consisting essentially of" allows for the inclusion of optional components to the extent that the effects of the present invention are not affected. In this specification, "consisting only of" means excluding optional components other than unavoidable impurities. Numerical ranges described using "to" include the numerical values ​​before and after "to" as the lower and upper limits. The upper and lower limits of numerical ranges (content, physical properties, etc.) can be combined as appropriate. Furthermore, the "surface (or surface layer)" of a composite multilayer film, multilayer structure, etc. does not refer to a front or back, but rather to the exposed surface. In other words, composite multilayer films, multilayer structures, etc. have two surfaces. Similarly, in a composite multilayer film, multilayer structure, etc., there are two outermost layers.

[0013] <Resin Composition (A') and Barrier Layer (A)> The multilayer film constituting the composite multilayer film of the present invention has, as its outermost layer, a barrier layer (A) made of a resin composition (A') containing, as a main component, an EVOH (a) having an ethylene unit content of 20 to 50 mol% and a saponification degree of 90 mol% or more. The resin composition (A') may contain alkali metal ions (b'); at least one polyvalent metal ion (c') selected from the group consisting of magnesium ions, calcium ions, and zinc ions; a higher aliphatic carboxylic acid (d') having 8 to 30 carbon atoms; and other components described below. These will be described in detail below.

[0014] <EVOH (a)> EVOH (a) is typically obtained by saponifying an ethylene-vinyl ester copolymer obtained by polymerizing ethylene and a vinyl ester. The ethylene unit content of EVOH (a) is 20 to 50 mol%. An ethylene unit content of 20 mol% or more improves the melt moldability of EVOH (a) and the pulverized composite multilayer film containing EVOH (a). The ethylene unit content is preferably 23 mol% or more, more preferably 26 mol% or more, and may be 29 mol% or more. On the other hand, an ethylene unit content of 50 mol% or less improves the gas barrier properties of the composite multilayer film of the present invention. The ethylene unit content is preferably 46 mol% or less, more preferably 42 mol% or less, and may be 38 mol% or less. The saponification degree of EVOH (a) is 90 mol% or more. The saponification degree refers to the ratio of the number of vinyl alcohol units to the total number of vinyl alcohol units and vinyl ester units in EVOH (a). When the saponification degree is 90 mol% or more, the gas barrier property of the composite multilayer film of the present invention is improved. The saponification degree is preferably 95 mol% or more, more preferably 99 mol% or more, and even more preferably 99.9 mol% or more, and may be 100 mol% or less. The ethylene unit content and saponification degree of EVOH (a) are as follows: １ It is determined by H-NMR measurement.

[0015] EVOH (a) may be a mixture of two or more types of EVOH having different ethylene unit contents. In this case, the difference in ethylene unit content between the EVOHs having the most different ethylene unit contents is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, and may be 3 mol% or more. Similarly, EVOH (a) may be a mixture of two or more types of EVOH having different degrees of saponification. In this case, the difference in saponification degree between the EVOHs having the most different ethylene unit contents is preferably 7 mol% or less, more preferably 5 mol% or less, and may be 0.5 mol% or more. When it is desired to achieve both thermoformability and gas barrier property at a higher level, it is preferred to use as EVOH (a) a mixture of EVOH (a-1) having an ethylene unit content of 24 mol% or more and less than 34 mol% and a degree of saponification of 99 mol% or more and EVOH (a-2) having an ethylene unit content of 34 mol% or more and less than 50 mol% and a degree of saponification of 99 mol% or more in a blending mass ratio (a-1 / a-2) of 60 / 40 to 90 / 10.

[0016] EVOH (a) may have a modifying group (unit containing a primary hydroxyl group) containing a primary hydroxyl group represented by the following general formula (I): The degree of melting point reduction per introduction rate of the modifying group varies depending on the structure of the primary hydroxyl group-containing modifying group introduced. However, the introduction of 1 mol % of the modifying group containing a primary hydroxyl group represented by the following general formula (I) generally reduces the melting point by approximately 6 to 9°C. Controlling the melting point in this manner can reduce the melting point while relatively maintaining gas barrier properties and thermal stability. Furthermore, deterioration in interlayer adhesion with the adhesive layer (B) and inorganic layer (I), described below, is also suppressed, resulting in a composite multilayer film with particularly excellent quality and performance. This reduction is thought to be due to the ability to reduce the melting point while maintaining the hydroxyl group content and the high adhesive reactivity of the primary hydroxyl group with the adhesive layer (B) and inorganic layer (I), described below. When EVOH (a) contains a modifying group containing a primary hydroxyl group, its content can be adjusted appropriately taking into consideration the balance between the melting point and various physical properties, but a content of 2 mol% or more and less than 20 mol% often results in a good balance of physical properties. The lower limit of the content of the modifying group containing a primary hydroxyl group in EVOH (a) is more preferably 4 mol%, and even more preferably 6 mol%. On the other hand, the upper limit of the content of the modifying group containing a primary hydroxyl group in EVOH (a) is more preferably 15 mol%, and even more preferably 10 mol%. The modifying group containing a primary hydroxyl group can be introduced by copolymerization or polymer reaction. The content of the modifying group containing a primary hydroxyl group (unit containing a primary hydroxyl group) means the content of the modifying group containing a primary hydroxyl group (unit containing a primary hydroxyl group) relative to all structural units constituting EVOH (a). [wherein X is a hydrogen atom, a methyl group, or R ２ represents a group represented by —OH. １ and R ２ each independently represents a single bond, an alkylene group having 1 to 9 carbon atoms, or an alkyleneoxy group having 1 to 9 carbon atoms, and the alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom.

[0017] In the general formula (I), X is preferably a hydrogen atom or R ２ R is a group represented by —OH, and more preferably a hydrogen atom. １is preferably a single bond, an alkylene group having 1 to 5 carbon atoms, or an alkyleneoxy group having 1 to 5 carbon atoms, and more preferably a methylmethyleneoxy group. X is a hydrogen atom, and R １ The unit in which is a methylmethyleneoxy group can be obtained, for example, by reacting EVOH with epoxypropane and then modifying it.

[0018] EVOH (a) may contain structural units other than ethylene units, vinyl ester units, vinyl alcohol units, and the modifying groups containing primary hydroxyl groups (units containing primary hydroxyl groups) as long as the effects of the present disclosure are not impaired. The content of such structural units relative to the total structural units is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably substantially none. Examples of monomers that provide other structural units include α-olefins such as propylene, n-butene, isobutylene, and 1-hexene; acrylic acid and its salts; unsaturated monomers having an acrylic ester group; methacrylic acid and its salts; unsaturated monomers having a methacrylic ester group; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts (e.g., quaternary salts); methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidopropanesulfonic acid and its salts, methacrylamidopropyldimethylamine and its salts (e.g., quaternary salts); methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane and allyl chloride; unsaturated dicarboxylic acids and salts or esters thereof such as maleic acid, itaconic acid and fumaric acid; vinylsilane compounds such as vinyltrimethoxysilane; isopropenyl acetate, 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane and 1,3-dibutyronyloxy-2-methylenepropane.

[0019] The MFR (190°C, under a load of 2.16 kg) of EVOH (a), measured in accordance with JIS K7210 (2014), is preferably 0.2 to 20 g / 10 min. The MFR of EVOH (a) is more preferably 0.5 g / 10 min or more, and even more preferably 0.8 g / 10 min or more. On the other hand, the MFR of EVOH (a) is more preferably 15 g / 10 min or less, even more preferably 10 g / 10 min or less, and may be 5 g / 10 min or less, or 3 g / 10 min or less. When the MFR of EVOH (a) is within the above range, the melt moldability of EVOH (a) and the pulverized product of a composite multilayer film containing EVOH (a) is improved.

[0020] <Alkali Metal Ion (b')> The resin composition (A') may contain 40 to 500 ppm of alkali metal ion (b'). When the resin composition (A') contains alkali metal ion (b') in the above range, the interlayer adhesion with the adhesive layer (B) described below tends to be improved. When the alkali metal ion (b') is 40 ppm or more, thickening of the resin composition (A') during melt molding can be suppressed, thereby suppressing appearance defects such as gels and bumps, and the interlayer adhesion with the adhesive layer (B) described below tends to be improved. On the other hand, when the alkali metal ion (b') is 500 ppm or less, excessive decomposition and coloration during melt molding of the resin composition (A') tend to be suppressed. Furthermore, in the composite multilayer film, multilayer structure, etc. of the present invention, when the alkali metal ion (b') content is 40 ppm or more, gelation of the resin can be suppressed when recycled materials such as multilayer structures and packaging materials are melt-kneaded to produce a recycled composition, thereby improving recyclability. On the other hand, when the content of alkali metal ions (b') is 500 ppm or less, excessive decomposition reaction of the resin can be suppressed when melt-kneading recovered materials such as multilayer structures and packaging materials to produce a recovered composition, thereby improving recyclability. From this viewpoint, the lower limit of the content of alkali metal ions (b') is preferably 80 ppm, more preferably 120 ppm. The upper limit of the content of alkali metal ions (b') is preferably 400 ppm, more preferably 300 ppm. Furthermore, by controlling the content ratio of alkali metal ions (b') to a carboxylic acid described below, the melt moldability and coloration resistance of the resulting resin composition (A') can be further improved.

[0021] Examples of the alkali metal ion (b') include lithium, sodium, potassium, rubidium, and cesium ions, but sodium or potassium ions are preferred from the viewpoint of industrial availability. In particular, the use of potassium ions may sometimes achieve high levels of both the hue of the resin composition (A') and the interlayer adhesion with the adhesive layer (B) described below. These may be used alone or in combination of two or more.

[0022] Examples of alkali metal compounds that provide the alkali metal ion (b') include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, hydroxides, and metal complexes of alkali metals such as lithium, sodium, and potassium. Among these, aliphatic carboxylates and phosphates are more preferred because of their ease of availability and handling. Preferred aliphatic carboxylates are acetates, caprylates, and stearates.

[0023] <Polyvalent Metal Ion (c')> The resin composition (A') may contain 10 to 300 ppm of at least one polyvalent metal ion (c') selected from the group consisting of magnesium ions, calcium ions, and zinc ions. When the resin composition (A') contains 10 ppm or more of the polyvalent metal ion (c'), poor appearance such as thickening and the generation of gels or lumps during melt molding of the resin composition (A') tends to be suppressed. On the other hand, when the content of the polyvalent metal ion (c') is 300 ppm or less, excessive decomposition and discoloration during melt molding of the resin composition (A') tends to be suppressed. Furthermore, in the composite multilayer film, multilayer structure, etc. of the present invention, crosslinking reaction of the resin may proceed during recycling, causing thickening and gelation. However, when the resin contains 10 ppm or more of the polyvalent metal ion (c'), thickening, gelation, and adhesion of the resin to the screw are suppressed. On the other hand, when the content of polyvalent metal ions (c') is 300 ppm or less, the occurrence of defects during recycling tends to be suppressed while deterioration of hue during recycling tends to be suppressed. From this viewpoint, the content of polyvalent metal ions (c') is preferably 20 to 200 ppm, more preferably 30 to 150 ppm. The resin composition (A') preferably contains magnesium ions or calcium ions as the polyvalent metal ions (c'), more preferably magnesium ions. Furthermore, by controlling the content ratio of the polyvalent metal ions (c') to the carboxylic acid described below, the melt moldability and coloration resistance of the resulting resin composition (A') can be further improved.

[0024] Examples of polyvalent metal compounds that provide the polyvalent metal ions (c') include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, hydroxides, and metal complexes of magnesium, calcium, and zinc. Among these, aliphatic carboxylates and hydroxides are more preferred because of their ease of availability and handling. Preferred aliphatic carboxylates are acetates, caprylates, and stearates.

[0025] <Higher Aliphatic Carboxylic Acid (d')> The resin composition (A') may contain 100 to 4,000 ppm of a higher aliphatic carboxylic acid (d') having 8 to 30 carbon atoms. The higher aliphatic carboxylic acid (d') may be contained in part or in whole in the form of a salt, or as a salt of an alkali metal ion (b') or a polyvalent metal ion (c'). The higher aliphatic carboxylic acid (d') is preferably caprylic acid or stearic acid. The multilayer film constituting the composite multilayer film of the present invention has a barrier layer (A) made of the resin composition (A') as the outermost layer. It is believed that the higher aliphatic carboxylic acid (d') acts as a lubricant for the die metal surface in the die, thereby suppressing poor appearance due to thickness unevenness of the multilayer film and the occurrence of gels and lumps due to retained resin. For this reason, the resin composition (A') preferably contains 100 ppm or more of the higher aliphatic carboxylic acid (d'). On the other hand, if the content of the higher aliphatic carboxylic acid (d') is 4000 ppm or less, thickening of the resin composition (A') during melt molding tends to be suppressed and interlayer adhesion with the adhesive layer (B) described below tends to be maintained. From these viewpoints, the content of the higher aliphatic carboxylic acid (d') is more preferably 200 to 3000 ppm, and even more preferably 300 to 2500 ppm.

[0026] The resin composition (A') may contain other components in addition to EVOH (a), alkali metal ions (b'), polyvalent metal ions (c'), and higher aliphatic carboxylic acids (d'), as long as the effects of the present invention are not impaired. Examples of other components include alkaline earth metal ions and transition metal ions other than polyvalent metal ions (c'), carboxylic acids (monocarboxylic acids, polycarboxylic acids) other than higher aliphatic carboxylic acids (d'), thermoplastic resins other than EVOH (a), phosphoric acid compounds, boron compounds, antioxidants, hindered phenol compounds, plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorizers, UV absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, bulking agents, pigments, dyes, processing aids, flame retardants, and antifogging agents. From the viewpoint of suppressing coloration during melt molding of the pulverized multilayer structure containing the resin composition (A'), it is preferable to contain a carboxylic acid and / or a phosphoric acid compound. Furthermore, by including a boron compound, it is possible to control the melt viscosity of the resin composition (A') and the pulverized product of a composite multilayer film, a multilayer structure, etc. containing the resin composition (A').

[0027] <Carboxylic Acid> The resin composition (A') preferably contains a carboxylic acid other than the higher aliphatic carboxylic acid (d'). The lower limit of the carboxylic acid content is preferably 50 ppm, more preferably 100 ppm. On the other hand, the upper limit of the carboxylic acid content is preferably 400 ppm, more preferably 350 ppm. When the carboxylic acid content is 50 ppm or more, the coloring resistance tends to be improved. On the other hand, when the carboxylic acid content is 400 ppm or less, the interlayer adhesion tends to be maintained and the generation of odor tends to be suppressed.

[0028] The pKa of the carboxylic acid is preferably 3.5 to 5.5. When the pKa of the carboxylic acid is within this range, the pH buffering ability of the resulting resin composition (A) is enhanced, further improving the melt moldability and further improving the coloration caused by acidic or basic substances.

[0029] The carboxylic acid may be a monocarboxylic acid. These may be used alone or in combination of two or more. A monocarboxylic acid is a compound having one carboxyl group in the molecule. Monocarboxylic acids having a pKa in the range of 3.5 to 5.5 are not particularly limited, and examples thereof include formic acid (pKa = 3.77), acetic acid (pKa = 4.76), propionic acid (pKa = 4.85), and acrylic acid (pKa = 4.25). These carboxylic acids may further have a substituent such as a hydroxyl group, an amino group, or a halogen atom. Among these, acetic acid is preferred because of its high safety and ease of availability and handling.

[0030] The carboxylic acid may be a polycarboxylic acid. When the carboxylic acid is a polycarboxylic acid, the discoloration resistance of the resin composition (A') at high temperatures and the discoloration resistance of the melt-molded product of the pulverized product of the resulting multilayer structure may be further improved. It is also preferable that the polycarboxylic acid compound has three or more carboxyl groups. In this case, discoloration resistance may be more effectively improved. A polycarboxylic acid is a compound having two or more carboxy groups in the molecule. In this case, it is preferable that the pKa of at least one carboxy group is in the range of 3.5 to 5.5, and examples thereof include oxalic acid (pKa2=4.27), succinic acid (pKa1=4.20), fumaric acid (pKa2=4.44), malic acid (pKa2=5.13), glutaric acid (pKa1=4.30, pKa2=5.40), adipic acid (pKa1=4.43, pKa2=5.50), and the like. = 5.41), pimelic acid (pKa1 = 4.71), phthalic acid (pKa2 = 5.41), isophthalic acid (pKa2 = 4.46), terephthalic acid (pKa1 = 3.51, pKa2 = 4.82), citric acid (pKa2 = 4.75), tartaric acid (pKa2 = 4.40), glutamic acid (pKa2 = 4.07), aspartic acid (pKa = 3.90), etc.

[0031] <Phosphate Compound> The resin composition (A') may further contain a phosphate compound. The lower limit of the content of the phosphate compound is preferably 5 ppm in terms of phosphate radicals. On the other hand, the upper limit of the content of the phosphate compound is preferably 100 ppm in terms of phosphate radicals. By containing the phosphate compound in this range, coloration of the resulting resin composition (A') and the resulting composite multilayer film, multilayer structure, or other melt-molded product of the pulverized material may be suppressed, and thermal stability may be improved.

[0032] As the phosphate compound, various acids such as phosphoric acid and phosphorous acid and their salts can be used. The phosphate may be any of primary phosphate, secondary phosphate, and tertiary phosphate. The cation species of the phosphate is not particularly limited, but the cation species is preferably an alkali metal or alkaline earth metal. Among them, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate are preferred as the phosphate compound.

[0033] <Boron Compound> The resin composition (A') may further contain a boron compound. When a boron compound is contained, the lower limit of the content in the resin composition (A') is preferably 50 ppm, more preferably 100 ppm, in terms of elemental boron. On the other hand, the upper limit of the content of the boron compound in the resin composition (A') is preferably 400 ppm, more preferably 200 ppm, in terms of elemental boron. By containing the boron compound within this range, the thermal stability of the resin composition (A') and the resulting composite multilayer film, multilayer structure, and other pulverized products during melt molding may be improved, and the occurrence of gels and lumps may be suppressed. In addition, the drawdown resistance and neck-in resistance during film formation may be improved, and the mechanical properties of the resulting composite multilayer film and other films may be improved. These effects are presumably due to the occurrence of a chelating interaction between the EVOH (a) and the boron compound.

[0034] Examples of boron compounds include boric acid, boric acid esters, borate salts, and boron hydrides. ３ BO ３boric acid such as tetraboric acid, metaboric acid, and the like; boric acid esters such as trimethyl borate and triethyl borate; alkali metal salts or alkaline earth metal salts of the above boric acid; and boric acid salts such as borax. Of these, orthoboric acid is preferred.

[0035] <Hindered Phenol Compound> The resin composition (A) may further contain a hindered phenol compound as an antioxidant. When a hindered phenol compound is contained, the content of the hindered phenol compound in the resin composition (A) is preferably 1,000 to 10,000 ppm. When the content is 1,000 ppm or more, coloration, thickening, and gelation of the resin can be suppressed when the pulverized material, such as a composite multilayer film or a multilayer structure, is melt-molded. The content of the hindered phenol compound is more preferably 2,000 ppm or more. On the other hand, when the content of the hindered phenol compound is 10,000 ppm or less, coloration and bleed-out resulting from the hindered phenol compound can be suppressed. The content of the hindered phenol compound is more preferably 8,000 ppm or less.

[0036] The hindered phenol compound has at least one hindered phenol group. A hindered phenol group is a group in which a bulky substituent is bonded to at least one carbon atom adjacent to the carbon atom to which a hydroxyl group of a phenol is bonded. The bulky substituent is preferably an alkyl group having 1 to 10 carbon atoms, and more preferably a t-butyl group.

[0037] The hindered phenol compound is preferably in a solid state at around room temperature. From the viewpoint of suppressing bleed-out of the compound, the melting point or softening temperature of the hindered phenol compound is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher. From the same viewpoint, the molecular weight of the hindered phenol compound is preferably 200 or higher, more preferably 400 or higher, and even more preferably 600 or higher. Meanwhile, the molecular weight is usually 2000 or lower. Furthermore, from the viewpoint of facilitating mixing with EVOH (a), the melting point or softening temperature of the hindered phenol compound is preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower.

[0038] The hindered phenol compound preferably has an ester bond or an amide bond. Examples of the hindered phenol compound having an ester bond include esters of aliphatic carboxylic acids having a hindered phenol group and aliphatic alcohols, and examples of the hindered phenol compound having an amide bond include amides of aliphatic carboxylic acids having a hindered phenol group and aliphatic amines. Among these, it is preferable that the hindered phenol compound has an amide bond.

[0039] Specific structures of hindered phenol compounds having an ester bond or an amide bond include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] commercially available from BASF as Irganox 1010, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)stearyl propionate commercially available from Irganox 1076, 2,2'-thiodiethylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] commercially available from Irganox 1035, and 2,2'-thiodiethylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] commercially available from Irganox 1135. Examples of such an acid include octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate, which is commercially available; ethylene bis(oxyethylene)(3-tert-butyl-4-hydroxy-5-methylbenzenepropanoate), which is commercially available as Irganox 245; 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], which is commercially available as Irganox 259; and N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], which is commercially available as Irganox 1098. Among these, N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide] commercially available as Irganox 1098 and pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] commercially available as Irganox 1010 are preferred, with the former being more preferred.

[0040] The resin composition (A') may further contain a thermoplastic resin other than the EVOH (a). Examples of the thermoplastic resin other than the EVOH (a) include various polyolefin resins (polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, copolymer of ethylene and an α-olefin having 4 or more carbon atoms, copolymer of polyolefin and maleic anhydride, ethylene-vinyl ester copolymer, ethylene-acrylic acid ester copolymer, and modified polyolefins obtained by graft-modifying these with unsaturated carboxylic acid or a derivative thereof), various polyamides (nylon 6, nylon 6.6, nylon 6 / 66 copolymer, nylon 11, nylon 12, polymetaxylylene adipamide, etc.), various polyesters (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polyurethane, polycarbonate, polyacetal, polyacrylate, and modified polyvinyl alcohol resins. The content of the thermoplastic resin in the resin composition (A') is typically less than 40% by mass, preferably less than 30% by mass, more preferably less than 20% by mass, even more preferably less than 10% by mass, and may be less than 5% by mass or even less than 1% by mass, and it is particularly preferred that it is substantially absent.

[0041] The proportion of EVOH (a) in the resin constituting resin composition (A') is, from the viewpoint of more significantly achieving the effects of the present invention, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may be 97% by mass or more or 99% by mass or more. The resin constituting resin composition (A') may be essentially EVOH (a) alone. Furthermore, from the viewpoint of more significantly achieving the effects of the present invention, the proportion of EVOH (a) in resin composition (A') is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may be 98% by mass or more or 99% by mass or more.

[0042] The method for producing the resin composition (A') is not particularly limited. It can be produced by melt-kneading other components, such as EVOH (a), alkali metal ions (b'), polyvalent metal ions (c'), and higher aliphatic carboxylic acids (d'), as needed. Each component may be blended as a solid, such as a powder, or as a melt. It may also be blended as a solute in a solution or a dispersoid in a dispersion. An aqueous solution and an aqueous dispersion are preferred as the solution and dispersion, respectively. For melt-kneading, known mixing or kneading devices, such as a kneader-ruder, extruder, mixing roll, or Banbury mixer, can be used. The temperature range during melt-kneading can be adjusted appropriately depending on the EVOH (a) used and the melting points of each component, and is typically 150 to 250°C. Alternatively, the resin composition (A') may be produced by adding some components to EVOH (a) in advance and then melt-kneading additional components as described above. An example of a method for adding some components to EVOH (a) in advance is to immerse EVOH (a) in the form of pellets or powder in a solution in which the added components are dissolved. The solution is preferably an aqueous solution.

[0043] <Adhesive Resin (b) and Adhesive Layer (B)> The composite multilayer film of the present invention has an adhesive layer (B) containing an adhesive resin (b) as a main component. The inclusion of the adhesive layer (B) in the composite multilayer film of the present invention tends to result in a composite multilayer film with excellent appearance and interlayer adhesion. Furthermore, the inclusion of the adhesive layer (B) improves the compatibility between the barrier layer (A) and the core layer (C) during recycling, thereby tending to improve recyclability. Preferred adhesive resins (b) include modified polyolefins, with acid-modified polyolefins being preferred. Examples of acid-modified polyolefins include acid-modified polyolefins obtained by graft polymerizing an unsaturated carboxylic acid, such as maleic anhydride, or a derivative thereof onto a polyolefin. The acid-modified polyolefin may be a carboxylic acid-modified polyolefin. Examples of acid-modified polyolefins include acid-modified polyethylene and acid-modified polypropylene. The melting point of the adhesive resin (b) is preferably less than 170°C. The melting point of the adhesive resin (b) primarily depends on the polyolefin before acid modification. The polyolefin (c) described below can be applied to this polyolefin.

[0044] The proportion of the acid-modified polyolefin in the adhesive resin (b) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 95% by mass or more, and the adhesive layer (B) may be composed essentially of the acid-modified polyolefin resin alone. The proportion of the adhesive resin (b) in the adhesive layer (B) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 95% by mass or more, and the adhesive layer (B) may be composed essentially of the adhesive resin (b) alone.

[0045] <Polyolefin (c) and Core Layer (C)> The composite multilayer film of the present invention has a core layer (C) containing polyolefin (c) as a primary component. The polyolefin (c) is not particularly limited as long as it is a polyolefin, and examples thereof include polyethylene-based resins such as linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene; polypropylene-based resins; vinyl ester resins; ethylene-propylene copolymers; propylene-α-olefin copolymers (α-olefins having 4 to 20 carbon atoms); and olefins such as polybutene and polypentene, or copolymers thereof. From the viewpoint of improving the recyclability of composite multilayer films and multilayer structures containing polyolefin (c), polyolefin (c) preferably contains polyethylene or polypropylene as a primary component, and more preferably polypropylene. Polypropylene is widely used in packaging materials, regardless of whether it has gas barrier properties or not, and recycling infrastructure for it is widely established in various countries. Polyolefin (c) may also be polyethylene.

[0046] From the viewpoint of making the effects of the present invention more pronounced, the melting point of the polyolefin (c) is preferably less than 170° C. On the other hand, from the viewpoint of processability during melt molding and secondary processing such as stretching, and from the viewpoint of heat resistance as a packaging material, the melting point of the polyolefin (c) is preferably 80° C. or higher, more preferably 90° C. or higher. Furthermore, from the viewpoint of improving melt moldability, the melt flow rate (MFR) (190° C., under a load of 2160 g) of the polyolefin (c) measured in accordance with the method described in JIS K7210 (2014) is preferably 0.1 to 50 g / 10 min.

[0047] The proportion of polyolefin (c) in the core layer (C) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 95% by mass or more, and the core layer (C) may be composed essentially of polyolefin (c) alone.

[0048] The adhesive layer (B) and the core layer (C) each contain an adhesive resin (b) and a polyolefin (c) as their main components, but these layers may also contain other components such as antioxidants, plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorizers, UV absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, bulking agents, pigments, dyes, processing aids, flame retardants, and antifogging agents, as long as the effects of the present invention are not impaired. However, the total amount of these components is less than 50% by mass of each layer, preferably less than 40% by mass, more preferably less than 30% by mass, even more preferably less than 20% by mass, and particularly preferably less than 10% by mass, and may be less than 5%, 3%, or 1% by mass.

[0049] <Multilayer film> The multilayer film constituting the composite multilayer film of the present invention has a barrier layer (A) as the outermost layer, and has a configuration in which at least the barrier layer (A), adhesive layer (B), and core layer (C) are directly laminated in this order. The multilayer film may have multiple barrier layers (A), adhesive layers (B), and core layers (C). Examples of the layer configuration of the multilayer film of the present invention include A / B / C, A / B / C / B / A, and A / B / C / B / A / B / C / B / A, where A represents the barrier layer (A), B represents the adhesive layer (B), and C represents the core layer (C), and " / " indicates that they are directly laminated.

[0050] From the viewpoints of gas barrier properties, recyclability, and economy, the average thickness of the barrier layer (A) in the multilayer film is preferably 0.2 μm or more and less than 20 μm. It is also preferable that the ratio of the average thickness of the barrier layer (A) to the average thickness of the multilayer film is less than 25%. The average thickness of the barrier layer (A) is more preferably 0.4 μm or more and less than 16 μm, and even more preferably 0.6 μm or more and less than 12 μm. The ratio of the average thickness of the barrier layer (A) to the average thickness of the multilayer film is more preferably less than 20%, and even more preferably less than 15%.

[0051] From the viewpoints of interlayer adhesion, recyclability, and economy, the average thickness of the adhesive layer (B) of the multilayer film is preferably 0.2 μm or more and less than 20 μm. It is also preferable that the ratio of the average thickness of the adhesive layer (B) to the average thickness of the multilayer film is less than 25%. The average thickness of the adhesive layer (B) is more preferably 0.4 μm or more and less than 16 μm, and even more preferably 0.6 μm or more and less than 12 μm. The ratio of the average thickness of the adhesive layer (B) to the average thickness of the multilayer film is more preferably less than 20%, and even more preferably less than 15%.

[0052] From the viewpoint of recyclability, the average thickness of the core layer (C) of the multilayer film is preferably 1 μm or more and less than 200 μm. It is also preferable that the ratio of the average thickness of the core layer (C) to the average thickness of the multilayer film is more than 55%. The average thickness of the core layer (C) is more preferably 5 μm or more, even more preferably 10 μm or more, and may be 20 μm or more. The average thickness of the core layer (C) is more preferably 100 μm or less, and may be 50 μm or less. The ratio of the average thickness of the core layer (C) to the average thickness of the multilayer film is more preferably more than 60%, even more preferably more than 70%. The average thickness of the multilayer film is usually 10 μm or more and less than 200 μm, and preferably 10 μm or more and less than 150 μm. In the case of a stretched multilayer film, which will be described later, the average thickness of the multilayer film is preferably 10 μm or more and less than 50 μm, and more preferably less than 40 μm.

[0053] The multilayer film may be an unstretched multilayer film, or may be a stretched multilayer film stretched uniaxially or biaxially (at least uniaxially). Unstretched multilayer films have excellent impact resistance and can be suitably used as heat-sealed films. On the other hand, stretching the multilayer film uniaxially or biaxially can improve the mechanical properties and gas barrier properties of the resulting multilayer film. From the viewpoints of economy and ease of tearing the multilayer film (making it easy to open packaging materials when used as packaging materials), the multilayer film is preferably a uniaxially stretched multilayer film. From the viewpoints of obtaining a film with little anisotropy in mechanical properties and a strong film, the multilayer film is preferably a biaxially stretched multilayer film. From the viewpoints of thickness uniformity and mechanical strength of the resulting multilayer film, it is preferably stretched at least 3 times but less than 12 times in the uniaxial direction. In the case of a uniaxially stretched multilayer film, it is preferably stretched uniaxially 3 times but less than 12 times, and more preferably stretched 4 times but less than 10 times. In the case of a biaxially stretched multilayer film, it is preferably stretched 3 times or more but less than 12 times in each of the two axial directions, and more preferably stretched 4 times or more but less than 10 times.

[0054] The method for producing the multilayer film is not particularly limited. Generally, conventional coextrusion methods can be used, in which the resins are extruded through separate dies or a common die and then laminated. Either a circular die or a T-die can be used. The method for uniaxial or biaxial stretching is also not particularly limited. The film can be produced by stretching the film in the machine direction and / or the direction perpendicular to the machine direction, i.e., the width direction, using a conventional stretching method such as roll-type uniaxial stretching, tubular-type simultaneous biaxial stretching, tenter-type sequential biaxial stretching, or tenter-type simultaneous biaxial stretching. From the viewpoint of processability, the temperature during stretching is typically 40 to 150°C, more preferably 50 to 140°C, and may be 60 to 130°C. The multilayer film constituting the composite multilayer film of the present invention has the advantage that problems such as poor appearance and reduced interlayer adhesion after stretching are unlikely to occur, even when the stretching temperature is relatively low, such as 120°C. If necessary, after the stretching treatment, it is preferable to carry out a so-called heat setting operation by heating at a temperature above the glass transition point and below the melting point to increase the crystallinity and fix the orientation of the molecular chains.

[0055] <Inorganic Layer (I)> The composite multilayer film of the present invention includes an inorganic layer (I) and a protective layer (P) on the exposed surface side of the barrier layer (A) of the multilayer film. The inorganic layer (I) is preferably laminated on the exposed surface side of the barrier layer (A) of the multilayer film directly, via the protective layer (P), or via another layer such as an adhesive layer. It is more preferable that the inorganic layer (I) is laminated on the exposed surface side of the barrier layer (A) directly or via the protective layer (P), and it is even more preferable that the inorganic layer (I) is laminated on the exposed surface side of the barrier layer (A). The inorganic layer (I) refers to a layer made of an inorganic substance such as a metal or an inorganic oxide, and has gas barrier properties against oxygen and water vapor. The barrier layer (A) has a higher affinity with metals and inorganic oxides than ordinary thermoplastic resin layers, allowing the formation of a dense, defect-free inorganic layer (I). The resulting composite multilayer film exhibits good interlayer adhesion between the barrier layer (A) and the inorganic layer (I). Furthermore, since the barrier layer (A) has gas barrier properties, even when defects occur in the inorganic layer (I) due to bending, etc., deterioration of the gas barrier properties can be suppressed. The average thickness of the inorganic layer (I) is generally less than 500 nm. When the average thickness is less than 500 nm, the viscosity stability is excellent when the pulverized product of the multilayer structure including the inorganic layer (I) is melt-molded, and the generation of gels and lumps can be suppressed.

[0056] The inorganic layer (I) is preferably an inorganic vapor-deposited layer, and is preferably either a metal vapor-deposited layer containing aluminum as a main component or an inorganic oxide vapor-deposited layer containing alumina or silica as a main component. A metal vapor-deposited layer is preferred when light-shielding properties are to be imparted, but an inorganic oxide vapor-deposited layer is preferred from the viewpoints of the visibility of the contents as a packaging material, microwave suitability, and the ability to suppress the generation of gels and lumps and coloring when melt-molding pulverized materials. Since a metal vapor-deposited layer is more susceptible to the effects of the contents, an inorganic oxide vapor-deposited layer containing alumina or silica as a main component is preferred from the viewpoint of further suppressing the deterioration of gas barrier properties after a storage test.

[0057] The metal vapor deposition layer is a layer containing aluminum as a main component. The aluminum atom content in the metal vapor deposition layer is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more. The average thickness of the metal vapor deposition layer is preferably 120 nm or less, more preferably 100 nm or less, and even more preferably 90 nm or less. The average thickness of the metal vapor deposition layer is preferably 25 nm or more, more preferably 35 nm or more, and even more preferably 45 nm or more. The average thickness of the metal vapor deposition layer is the average value of thicknesses at any 10 points on the cross section of the metal vapor deposition layer measured with an electron microscope. When the composite multilayer film of the present invention has a metal vapor deposition layer, the light transmittance at a wavelength of 600 nm can be 10% or less, and the film has excellent light-blocking properties.

[0058] In a metal vapor deposition layer containing aluminum as a main component, oxidation may occur irreversibly, and aluminum oxide may be partially contained. In the metal vapor deposition layer containing aluminum as a main component (inorganic layer (I)), the molar ratio of the content of oxygen atoms to the content of aluminum atoms (O mol / Al mol) is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.1 or less.

[0059] The average thickness of the inorganic oxide vapor-deposited layer is preferably 60 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less. The average thickness of the inorganic oxide vapor-deposited layer is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. The average thickness of the inorganic oxide vapor-deposited layer is the average value of thicknesses at any 10 points on a cross section of the inorganic oxide vapor-deposited layer measured using an electron microscope. When the composite multilayer film of the present invention has an inorganic oxide vapor-deposited layer, the light transmittance at a wavelength of 600 nm can be increased to 80% or more, thereby providing excellent visibility of the contents when used as a packaging material. From the viewpoint of further improving visibility, the light transmittance at a wavelength of 600 nm is more preferably 90% or more. The light transmittance can be increased, for example, by suppressing thickness unevenness of the multilayer film used in producing the composite multilayer film. A means for further suppressing thickness unevenness of the multilayer film includes, for example, stretching the multilayer film in at least one direction. The light transmittance of the multilayer film at a wavelength of 600 nm is preferably 80% or more, more preferably 90% or more.

[0060] The inorganic layer (I) can be formed by a known physical vapor deposition method or chemical vapor deposition method. Specific examples include vacuum deposition, sputtering, ion plating, ion beam mixing, plasma CVD, laser CVD, MO-CVD, and thermal CVD. Physical vapor deposition is preferred, and vacuum vapor deposition is particularly preferred. The upper limit of the surface temperature of the barrier layer (A) during the formation of the inorganic layer (I) is preferably 60°C, more preferably 55°C, and even more preferably 50°C. The lower limit of the surface temperature of the barrier layer (A) during the formation of the inorganic layer (I) is not particularly limited, but is preferably 0°C, more preferably 10°C, and even more preferably 20°C. Prior to the formation of the inorganic layer (I), the exposed surface of the barrier layer (A) may be plasma-treated. This plasma treatment can be performed by a known method, and atmospheric pressure plasma treatment is preferred. In atmospheric pressure plasma treatment, nitrogen, helium, neon, argon, krypton, xenon, radon, or the like is used as a discharge gas. Among these, nitrogen, helium and argon are preferably used, and nitrogen is particularly preferred because it can reduce costs.

[0061] <Protective Layer (P)> The composite multilayer film of the present invention includes a protective layer (P) and an inorganic layer (I) adjacent to each other on the exposed surface side of the barrier layer (A) of the multilayer film. The protective layer (P) is preferably laminated directly on the inorganic layer (I). For example, preferred layer configurations include a layer configuration in which the inorganic layer (I), the protective layer (P), and the barrier layer (A) are adjacent in this order, and a layer configuration in which the protective layer (P), the inorganic layer (I), and the barrier layer (A) are adjacent in this order. Among these, a layer configuration in which the protective layer (P), the inorganic layer (I), and the barrier layer (A) are directly laminated in this order is particularly preferred. The protective layer (P) can significantly suppress deterioration of gas barrier property after a storage test.

[0062] The protective layer (P) contains a vinyl alcohol-based polymer. Examples of vinyl alcohol-based polymers include polyvinyl alcohol and EVOH, with polyvinyl alcohol being preferred. The preferred embodiment of EVOH contained in the protective layer (P) is the same as that of EVOH (a). The saponification degree of the polyvinyl alcohol contained in the protective layer (P) is preferably 90 mol% or more, more preferably 95 mol% or more, and may be 100 mol% or less. From the viewpoint of gas barrier properties, the saponification degree of the polyvinyl alcohol is preferably closer to 100 mol%. The viscosity of the polyvinyl alcohol in a 4% aqueous solution at 20°C is preferably 1.0 mP·s or more and 70 mP·s or less, and in some cases, 1.0 mP·s or more and 40 mP·s or less. The polyvinyl alcohol is preferably a modified polyvinyl alcohol having a modifying group other than a vinyl alcohol unit and a vinyl ester unit. The modifying group may be a structural unit other than a vinyl alcohol unit and a vinyl ester unit. Among these, ethylene-modified polyvinyl alcohol or modified polyvinyl alcohol having a primary hydroxyl group is more preferable, and modified polyvinyl alcohol having a primary hydroxyl group is even more preferable. When the protective layer (P) contains modified polyvinyl alcohol, the deterioration of the gas barrier property after the storage test tends to be more significantly suppressed. The modifying group can be introduced by copolymerization or polymer reaction.

[0063] When the modifying group is ethylene, the ethylene-modified polyvinyl alcohol preferably has an ethylene unit content of 1 to 15 mol% and a saponification degree of 80 to 99.9 mol%. When the ethylene unit content is 15 mol% or less, when solution coating is selected to form the protective layer (P), the solubility in a solvent tends to be improved, and stable coating tends to be possible when forming the protective layer (P).

[0064] When the modifying group is a modifying group containing a primary hydroxyl group, it is preferably a modifying group containing a primary hydroxyl group (unit containing a primary hydroxyl group) represented by the following general formula (I). Use of a modified polyvinyl alcohol into which this modifying group has been introduced tends to more significantly suppress deterioration in gas barrier property after a storage test. The content of the modifying group containing a primary hydroxyl group (unit containing a primary hydroxyl group) represented by the following general formula (I) relative to all structural units constituting the modified polyvinyl alcohol is preferably 1 to 15 mol%, as this often results in a good balance of physical properties. The lower limit of the content of the modifying group containing a primary hydroxyl group (unit containing a primary hydroxyl group) is more preferably 2 mol%. On the other hand, the upper limit of the content of the modifying group containing a primary hydroxyl group (unit containing a primary hydroxyl group) is more preferably 10 mol%, even more preferably 8 mol%, and particularly preferably 6 mol%. [wherein X is a hydrogen atom, a methyl group, or R ２ represents a group represented by —OH. １ and R ２ each independently represents a single bond, an alkylene group having 1 to 9 carbon atoms, or an alkyleneoxy group having 1 to 9 carbon atoms, and the alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom.

[0065] In the general formula (I), X is preferably a hydrogen atom or R ２ It is a group represented by —OH. １ and R ２is preferably a single bond, an alkylene group having 1 to 5 carbon atoms, or an alkyleneoxy group having 1 to 5 carbon atoms, and more preferably a single bond, an alkylene group having 1 to 3 carbon atoms, or an alkyleneoxy group having 1 to 3 carbon atoms. However, the alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom.

[0066] Specific examples of the modifying group containing a primary hydroxyl group (unit containing a primary hydroxyl group) represented by general formula (I) include structural units represented by the following general formula (II).

[0067]

[0068] In the general formula (II), R ３ and R ４ each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and the alkyl group may contain a hydroxyl group, an alkoxy group, or a halogen atom. １ is a single bond, and X is a hydroxymethyl group (R ３ and R ４ is preferably a hydrogen atom). Polyvinyl alcohol having such a modifying group containing a primary hydroxyl group tends to be able to more significantly suppress the deterioration of gas barrier properties after a storage test.

[0069] Other specific examples of the modifying group containing a primary hydroxyl group (unit containing a primary hydroxyl group) represented by general formula (I) include structural units represented by the following general formula (III).

[0070]

[0071] In the general formula (III), R ５ has the same meaning as X in formula (I). ６ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and the alkyl group may contain a hydroxyl group, an alkoxy group, or a halogen atom. １ is a hydroxymethylene group, and X is a hydrogen atom (R ５ and R ６is preferably a hydrogen atom). A modified polyvinyl alcohol having such a modifying group containing a primary hydroxyl group tends to be able to more significantly suppress the deterioration of gas barrier properties after a storage test.

[0072] The vinyl alcohol polymer may contain structural units other than ethylene units, vinyl ester units, vinyl alcohol units, and the modifying groups containing primary hydroxyl groups (units containing primary hydroxyl groups), as long as the effects of the present disclosure are not impaired. The content of other structural units is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably substantially none. Examples of monomers that provide such other structural units include α-olefins such as propylene, n-butene, and isobutylene; (meth)acrylic acid and its salts; (meth)acrylic acid esters; (meth)acrylamide; (meth)acrylamide derivatives such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, diacetone(meth)acrylamide, (meth)acrylamidopropanesulfonic acid and its salts, (meth)acrylamidopropyldimethylamine and its salts or quaternary salts, and N-methylol(meth)acrylamide and its derivatives; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, and i-butyl vinyl ether. vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid, and salts or esters thereof; vinyl silyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; vinylformamide; vinylpyrrolidone; isopropenyl acetate, 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyronyloxy-2-methylenepropane.

[0073] The protective layer (P) of the present invention may contain a crosslinking agent, other polymers, an adhesion promoter, inorganic particles, pigments, dyes, waxes, etc. in order to further improve the performance depending on the purpose.

[0074] Examples of the wax include polyethylene wax, carnauba wax, soybean wax, paraffin wax, scale wax, slack wax, other vegetable waxes, or mixtures and combinations thereof. When the protective layer (P) contains the wax, the abrasion resistance may be improved.

[0075] The protective layer (P) preferably contains an adhesion promoter from the viewpoint of increasing the adhesive strength between the protective layer (P) and the inorganic layer (I) and further suppressing the deterioration of the gas barrier property after a storage test. Examples of the adhesion promoter include polyethyleneimine adhesion promoters, aliphatic polyurethane dispersions, hydrogenated hydrocarbon rosin or rosin ester dispersions, and amorphous acrylic polymer dispersions. When the protective layer (P) is located between the barrier layer (A) and the inorganic layer (I), the adhesion promoter tends to increase the adhesive strength between the barrier layer (A) and the inorganic layer (I). Examples of polyethyleneimine include Lupasol P, PEI Loxanol (registered trademark) MI6730, and Polymin P available from BASF, Epomin available from Nippon Shokubai, and Polymin P available from Nippon Soda Co. Examples of suitable adhesives include TITA Bond T100 available from Epson Corporation and D1 Dry AC-108 available from DIC Graphics. Examples of suitable polyurethanes include 86A available from 3M, SYNTEGRA available from Dow Chemical, Desmophen available from Bayer AG, and Loctite 3951 available from Loctite. When the protective layer (P) contains an adhesion promoter, the content thereof is preferably 0.1% by mass or more and 15% by mass or less. In order to enhance the effect of the adhesion promoter, it may be preferable to further contain formaldehyde or the like.

[0076] The protective layer (P) preferably contains a crosslinking agent that crosslinks the vinyl alcohol polymer. The presence of a crosslinking agent in the protective layer (P) tends to further suppress deterioration of gas barrier properties after a storage test. Examples of crosslinking agents include aldehydes, dialdehydes, organic salts, inorganic salts, and combinations thereof. Among these, formaldehyde-based crosslinking agents are preferred. Suitable examples include melamine formaldehyde, urea formaldehyde, glyoxal, glutaraldehyde, zirconium oxide, zinc oxide, and titanium lactate, with melamine formaldehyde or urea formaldehyde being more preferred. The vinyl alcohol polymer in the protective layer (P) is susceptible to moisture, such as humidity. However, crosslinking enhances moisture resistance, and tends to further suppress deterioration of gas barrier properties after a storage test. When the protective layer (P) contains a crosslinking agent, the content thereof is preferably 0.5% by mass or more and 10% by mass or less.

[0077] Crosslinkers include Cymel 385 resin manufactured by Allnex (Brussels, Belgium), and Aerotex 3030, Aerotex 3730, or Aerotex M3 manufactured by Emerald Performances Materials (Charlotte, North Carolina), Beetle PT312 resin available from BIP Company (Oldbury, UK), Cymel grade crosslinkers, and the like.

[0078] When the protective layer (P) contains a crosslinking agent, it may be preferable to contain a catalyst from the viewpoint of promoting crosslinking of the vinyl alcohol polymer. When the protective layer (P) contains a catalyst, the content thereof is preferably 0.01% by mass or more and 10% by mass or less. Examples of the catalyst include an organic acid catalyst, an inorganic acid catalyst, or a salt thereof. When an acid catalyst is used as the catalyst, the pH of the coating liquid for forming the protective layer (P) is preferably 2 to 7, and more preferably 2 to 6.

[0079] Examples of the catalyst include citric acid, hydrochloric acid, orthophosphoric acid, nitric acid, maleic acid, lactic acid, acetic acid, paratoluenesulfonic acid, and salts thereof. These may be used alone or in combination of two or more.

[0080] The protective layer (P) may also contain biocides, such as those commercially available under the trade name Proxel®, such as Proxel® GXL 5% available from Lonza Group (Basel, Switzerland).

[0081] The protective layer (P) may contain inorganic particles. Examples of inorganic particles include metal oxides such as magnesium oxide, zinc oxide, and tin oxide; inorganic particles such as calcium carbonate and silica; and layered inorganic compounds such as vermiculite, montmorillonite, hectorite, hydrotalcite, and synthetic mica. The average particle size of these inorganic particles is preferably 0.005 to 10 μm, and more preferably 0.005 to 5 μm. A mixture of multiple inorganic particles may also be used. Zinc oxide can be used for the purpose of blocking ultraviolet rays, and tin oxide can be used for the purpose of antistatic properties. From the perspective of recyclability, it may be preferable for the protective layer (P) to not contain inorganic particles.

[0082] The protective layer (P) may further contain at least one metal compound selected from the group consisting of metal alkoxides, hydrolysates of metal alkoxides, and hydrolysis condensates of metal alkoxides. The reaction of these metal compounds with the vinyl alcohol-based polymer tends to exhibit high gas barrier properties. On the other hand, from the viewpoints of recyclability, quality stability when used as a packaging material, and gas barrier properties after a storage test, it may be preferable that the protective layer (P) does not contain more than 10% by mass of these metal compounds. The content of the metal compound in the protective layer (P) is more preferably 5% by mass or less, even more preferably 1% by mass or less, and it is particularly preferable that the protective layer (P) does not contain the metal compound.

[0083] The protective layer (P) may contain a pigment or dye. Examples of pigments and dyes include titanium oxide, zinc oxide, and carbon black. Any of disperse dyes, acid dyes, cationic dyes, and reactive dyes can be used. The protective layer (P) may contain various chemicals such as a leveling agent, an antifoaming agent, an anti-foaming agent, a pigment dispersant, an ultraviolet absorber, a thickener, a weathering agent, and a flame retardant.

[0084] The content of the vinyl alcohol polymer in the protective layer (P) is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and may be 60% by mass or more, 65% by mass or more, or 70% by mass or more. The content of the vinyl alcohol polymer in the protective layer (P) is preferably 100% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less.

[0085] The means for laminating the protective layer (P) is not particularly limited. For example, the protective layer (P) can be laminated by applying a coating liquid, which is an aqueous solution or aqueous dispersion containing a vinyl alcohol polymer, to the exposed surface of the inorganic layer (I) or the exposed surface of the barrier layer (A) by a conventional method and drying the coating liquid.

[0086] From the viewpoints of gas barrier property, recyclability, and economy, the average thickness of the protective layer (P) of the composite multilayer film is preferably 0.05 μm or more and less than 10 μm, more preferably 0.2 μm or more and less than 4 μm, and even more preferably 0.6 μm or more and less than 3 μm.

[0087] The lower limit of the ratio of the total average thickness of the layers containing polyolefin resin as a main component to the average thickness of the composite multilayer film of the present invention is preferably 0.75, more preferably 0.80, even more preferably 0.85, and even more preferably 0.88. By increasing the ratio of the total average thickness of the layers containing polyolefin resin as a main component in the composite multilayer film, recyclability can be improved. The upper limit of the ratio of the total average thickness of the layers containing polyolefin resin as a main component in the composite multilayer film is preferably 0.995, more preferably 0.99, and may be 0.98. Examples of layers containing polyolefin resin as a main component include an adhesive layer (B) and a core layer (C) when the adhesive resin (b) is, for example, an acid-modified polyolefin.

[0088] The lower limit of the ratio of the total average thickness of layers containing a resin having ethylene units or propylene units as a main component to the average thickness of the composite multilayer film of the present invention is preferably 0.80, more preferably 0.85, and even more preferably 0.90. By increasing the ratio of the total average thickness of layers containing a resin having ethylene units or propylene units as a main component in the composite multilayer film, recyclability can be improved. The upper limit of the ratio of the total average thickness of layers containing a resin having ethylene units or propylene units as a main component in the composite multilayer film may be, for example, 0.9999. Examples of layers containing a resin having ethylene units or propylene units as a main component include the above-mentioned layers containing a polyolefin resin as a main component, as well as the barrier layer (A).

[0089] The composite multilayer film of the present invention preferably does not have a metal layer with an average thickness of 1 μm or more. By not having a metal layer with an average thickness of 1 μm or more, it is possible to prevent non-uniform mixing with other components when the pulverized composite multilayer film is melt-molded. Here, the metal layer refers to a layer having continuous and discontinuous surfaces made of metal, such as aluminum foil.

[0090] The composite multilayer film of the present invention has an oxygen transmission rate (under conditions of 20°C and 65% RH) of 0.5 cc / (m) as measured in accordance with the method described in JIS K 7126-2 (isobaric method; 2006). ２·day·atm), and ２ ·day·atm), and more preferably less than 0.1 cc / (m ２ A composite multilayer film having an oxygen transmission rate in the above range has excellent gas barrier properties.

[0091] <Multilayer Structure> The composite multilayer film of the present invention itself can be used as a packaging material having gas barrier properties, but by laminating at least one resin layer (R) containing a thermoplastic resin (r) as a main component to form a multilayer structure, various functions as a packaging material, such as designability and heat-sealability, can be imparted. The thermoplastic resin (r) is preferably one having a melting point of less than 200°C, and examples thereof include linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, vinyl ester resin, ethylene-propylene copolymer, polypropylene, propylene-α-olefin copolymer (α-olefin having 4 to 20 carbon atoms), olefin homopolymers such as polybutene and polypentene, copolymers thereof, polyamides such as nylon 6 and nylon 6,6, polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polystyrene, polyvinyl chloride, polyvinylidene chloride, acrylic resin, polycarbonate, chlorinated polyethylene, and chlorinated polypropylene. Among these, polyolefins are preferred from the viewpoints of excellent moisture resistance, mechanical properties, economy, heat sealability, etc., and polyamides and polyesters are preferred from the viewpoints of excellent mechanical properties, heat resistance, etc. In particular, to obtain a multilayer structure with excellent recyclability, the melting point is preferably less than 200°C, and it is more preferable that the thermoplastic resin (r) is the same type as the above-mentioned polyolefin (c). Therefore, to obtain a multilayer structure with excellent recyclability, it is preferable that both the polyolefin (c) and the thermoplastic resin (r) contain polyolefin as the main component, more preferably polyolefin, and particularly preferably polypropylene. It is also preferable that both the polyolefin (c) and the thermoplastic resin (r) are polyethylene. Such a resin layer (R) may be unstretched, or may be uniaxially or biaxially stretched or rolled. From the viewpoint of improving mechanical strength, a biaxially stretched layer is preferred, and from the viewpoint of improving heat sealability, a non-stretched layer is preferred.

[0092] The method for producing the resin layer (R) is not particularly limited, but it is generally produced by melt extrusion using an extruder. Either a circular die or a T-die can be used as the die. The method for uniaxial or biaxial stretching is also not particularly limited, and the film can be produced by stretching the film in the machine direction and / or the direction perpendicular to the machine direction, i.e., the width direction, using a conventionally known stretching method such as roll-type uniaxial stretching, tubular-type simultaneous biaxial stretching, tenter-type sequential biaxial stretching, or tenter-type simultaneous biaxial stretching. From the viewpoint of the thickness uniformity and mechanical strength of the resulting layer, the area ratio is preferably 8 to 60 times. The area ratio is more preferably 55 times or less, and even more preferably 50 times or less. Furthermore, the area ratio is more preferably 9 times or more. If the area ratio is less than 8 times, stretching unevenness may remain, and if it exceeds 60 times, the layer may be more likely to break during stretching.

[0093] The average thickness of the resin layer (R) is preferably 10 to 200 μm from the viewpoint of industrial productivity. Specifically, the average thickness is more preferably 10 to 150 μm in the case of an unstretched layer, and more preferably 10 to 50 μm in the case of a biaxially stretched layer.

[0094] The average thickness of the multilayer structure of the present invention is preferably 300 μm or less. With an average thickness in the above range, the multilayer structure of the present invention is lightweight and flexible, making it suitable for use in flexible packaging. Furthermore, the amount of resin used in the multilayer structure is small, thereby reducing the environmental impact.

[0095] The average thickness of each layer in the multilayer structure of the present invention may be adjusted appropriately depending on the application, but from the viewpoints of suppressing discoloration during melt molding of the pulverized material, improving thermal stability during melt molding, and suppressing the occurrence of lumps, the ratio of the total average thickness of the layers containing a polyolefin resin as a main component to the average thickness of the multilayer structure is preferably 0.80 or more, more preferably 0.85 or more. On the other hand, from the viewpoint of improving gas barrier properties, the ratio is preferably 0.997 or less, more preferably 0.995 or less, and may be 0.993 or less.

[0096] The method for laminating the resin layer (R) to the composite multilayer film of the present invention is not particularly limited, and examples include extrusion lamination, coextrusion lamination, dry lamination, etc. An adhesive layer may be provided when laminating the resin layer (R) to the composite multilayer film. Furthermore, each layer constituting the multilayer structure of the present invention may be laminated via an adhesive layer, if necessary. However, no adhesive layer is present between the barrier layer (A) and adhesive layer (B) of the multilayer film, and between the adhesive layer (B) and core layer (C). The adhesive layer can be formed, for example, by applying and drying a known adhesive. The adhesive is preferably a two-component reactive polyurethane adhesive in which a polyisocyanate component and a polyol component are mixed and reacted. The average thickness of the adhesive layer is not particularly limited, but is preferably 1 to 5 μm, more preferably 2 to 4 μm.

[0097] The multilayer structure of the present invention preferably has the following layer configuration, for example, from the viewpoint of obtaining a multilayer structure with stable gas barrier properties and excellent recyclability. In the following layer configurations, the barrier layer (A) is represented as A, the adhesive layer (B) as B, the core layer (C) as C, the protective layer (P) as P, the inorganic layer (I) as I, and the resin layer (R) as R, where " / " means that the layers are directly laminated, and " / / " means that the layers are laminated via an adhesive layer. (1) R / / P / I / A / B / C / / R (2) R / / I / P / A / B / C / / R (3) R / / P / I / A / B / C (4) R / / I / P / A / B / C In the above layer configurations, the barrier layer (A), adhesive layer (B), and core layer (C) are preferably stretched at least uniaxially, and more preferably biaxially. The core layer (C) and resin layer (R) are preferably made of a polyolefin resin.

[0098] The multilayer structure of the present invention may include layers other than those described above, provided that the effects of the present invention are not impaired. The other layers preferably do not include a layer containing a resin having a melting point of 200°C or higher as a main component, and preferably do not include a metal layer having an average thickness of 1 μm or more. An example of the other layer is a recovered layer made of a resin composition recovered through recycling. Another example of the other layer is a printed layer. The printed layer may be included in any position of the multilayer structure of the present invention. Examples of the printed layer include a film obtained by applying a solution containing a pigment or dye, and optionally a binder resin, and then drying the applied solution. Examples of coating methods for the printed layer include gravure printing and various coating methods using a wire bar, spin coater, die coater, etc. The average thickness of the printed layer is not particularly limited, but is preferably 0.5 to 10 μm, more preferably 1 to 4 μm.

[0099] The multilayer structure of the present invention has excellent appearance, gas barrier properties, recyclability, and content resistance, and can therefore be suitably used as a material for various types of packaging, such as food packaging, pharmaceutical packaging, industrial chemical packaging, and pesticide packaging. In particular, packaging materials having the multilayer structure of the present invention can be suitably used as packaging materials for foods that contain moisture or oil.

[0100] <Packaging Material> The packaging material of the present invention includes the multilayer structure. The packaging material preferably has a core layer (C) or a resin layer (R) of the multilayer structure on the inner side, and is obtained by welding these inner layers together. The packaging material is used for packaging purposes, and its shape is not limited. The packaging material may be in sheet form or may be formed into a predetermined shape such as a bag. The packaging material can be formed into various forms depending on the application, such as a vertical form-fill-seal bag, a pouch with a spout, a laminated tube container, or a container lid.

[0101] <Product> The product of the present invention comprises the packaging material of the present invention and a content. The content contains 5% by mass or more of moisture and at least one selected from the group consisting of 1% by mass or more of lipid, 1% by mass or more of sodium chloride, and 0.5% by mass or more of acetic acid. In the product of the present invention, even if the content is stored for a long period of time inside the packaging material, deterioration of gas barrier property can be suppressed. The moisture content of the content may be 5% by mass or more and 90% by mass or less. The content may also contain at least one of 1% by mass or more and 90% by mass or less of lipid, 1% by mass or more and 90% by mass or less of sodium chloride, and 0.5% by mass or more and 90% by mass or less of acetic acid. When the content contains moisture, the moisture content is preferably 7% by mass or more, more preferably 10% by mass or more, and may be 80% by mass or less. When the content contains 1% by mass or more of lipid, the lipid content may be 30% by mass or more, 50% by mass or more, or 85% by mass or less. Furthermore, when sodium chloride is contained in an amount of 1% by mass or more, the content of sodium chloride may be 1.5% by mass or more, or may be 50% by mass or less, 30% by mass or less, 10% by mass or less, or 5% by mass or less.

[0102] Examples of the contents include dairy products such as cheese, oils and fats such as butter and margarine, spices such as wasabi and mustard, and seasonings such as sauces, ketchup, mayonnaise, and dressings. These may be in liquid, paste, or solid form. Of these, mayonnaise, ketchup, dressing, and the like are preferred.

[0103] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples in any way.

[0104] [Materials Used] EVOH (a) EVOH1: EVOH pellets, ethylene unit content 48 mol%, saponification degree 99 mol%, MFR (190°C, 2.16 kg load) 6.4 g / 10 min, melting point 157°C, density 1.12 g / cm ３EVOH2: EVOH pellet, ethylene unit content 32 mol%, saponification degree 99 mol%, MFR (190°C, 2.16 kg load) 1.6 g / 10 min, melting point 183°C, density 1.19 g / cm ３ EVOH3: EVOH pellet, ethylene unit content 27 mol%, saponification degree 99 mol%, MFR (210°C, 2.16 kg load) 4.0 g / 10 min, melting point 190°C, density 1.21 g / cm ３ , sodium acetate 160 ppm in terms of sodium ions, and phosphate ions 10 ppm in terms of phosphate radicals. Adhesive resin (b) MAhPP1: "ADMER (trademark) QF500" (manufactured by Mitsui Chemicals, Inc., maleic anhydride-modified polypropylene, MFR (230°C, 2.16 kg load) 3.0 g / 10 min) MAhPE1: ADMER (trademark) NF518" (manufactured by Mitsui Chemicals, Inc., maleic anhydride-modified polyethylene, MFR (190°C, 2.16 kg load) 3.1 g / 10 min, melting point 121°C, density 0.91 g / cm ３ , acid value 1.8 mgKOH / g) Polyolefin (c) PP1: "Novatec (trademark) PP EA7AD" (Japan Polypropylene Corporation, polypropylene, MFR (230°C, 2.16 kg load) 1.4 g / 10 min, density 0.90 g / cm ３ PE1: "INNATE (trademark) TF80" (manufactured by DOW, linear low-density polyethylene, MFR (190 ° C, 2.16 kg load) 1.6 g / 10 min, melting point 124 ° C, density 0.926 g / cm ３ Vinyl alcohol polymers PVA-1: PVA, saponification degree 98.5 mol%, viscosity 27 mP·s (4%, 20°C) PVA-2: ethylene-modified PVA, ethylene unit content 3 mol%, saponification degree 99 mol%, viscosity 14 mP·s (4%, 20°C) PVA-3: 2-methylene 1,3-propanediol (MPDA)-modified PVA (in the above general formula (I), R １is a single bond, X is a hydroxymethyl group), modification level 3 mol%, viscosity 20 mP·s (4%, 20°C) (Method for synthesizing PVA-3) 640 parts by mass of vinyl acetate, 300 parts by mass of methanol, and 18 parts by mass of 2-methylene-1,3-diacetoxypropane as a comonomer were charged into a reactor equipped with a stirrer, a reflux condenser, an argon inlet, and an initiator addition port, and the system was purged with argon for 30 minutes while bubbling with argon. The reactor temperature was then increased, and when the internal temperature reached 60°C, 0.15 g of 2,2'-azobisisobutyronitrile was added to initiate polymerization. After 218 minutes of polymerization at 60°C, the polymerization was terminated by cooling. The conversion at the time of termination of polymerization was 40%. Subsequently, unreacted monomers were removed under reduced pressure while occasionally adding methanol, yielding a methanol solution of vinyl acetate-2-methylene-1,3-diacetoxypropane copolymer (concentration 33.5%). Next, 95.8 parts by mass of methanol was added to 149 parts by mass of this methanol solution, and 4.72 g of a sodium hydroxide methanol solution (concentration 13.3%) was further added, followed by saponification at 40°C. A gel formed approximately 7 minutes after the addition of the sodium hydroxide methanol solution. This gel was then pulverized in a grinder and allowed to stand at 40°C for a further 53 minutes to allow saponification to proceed, after which 200 parts by mass of methyl acetate was added to neutralize the remaining alkali. After confirming completion of neutralization using a phenolphthalein indicator, the mixture was filtered to obtain a white solid, to which 500 g of methanol was added and heated under reflux for 1 hour. The above washing procedure was repeated three times, and the white solid obtained by centrifugal dehydration was then dried in a vacuum dryer at 40°C for 24 hours to obtain MPDA-modified PVA (PVA-3). PVA-4: "Nichigo G Polymer (trademark) AZF8035Q" (manufactured by Mitsubishi Chemical Corporation, 1-butene-3,4-diol modified PVA (in the above general formula (I), R １is a hydroxymethylene group, X is a hydrogen atom), modification amount 3 mol%, saponification degree 99 mol%, viscosity 3.0 mP·s (4%, 20°C) Resin layer (R) BOPP: "Pylen (trademark) Film-OT P2161" (manufactured by Toyobo Co., Ltd., biaxially oriented polypropylene film, average thickness 20 μm) CPP: "RXC-22" (manufactured by Mitsui Chemicals Tocello Inc., unoriented polypropylene film, average thickness 50 μm) HDPE: high-density polyethylene film (reduced production product, sheet type) manufactured by Ube Film Co., Ltd., average thickness 20 μm LLDPE: "Unilux (trademark) LS-760C" (manufactured by Idemitsu Unitech Co., Ltd., linear low-density polyethylene, average thickness 50 μm)

[0105] [Evaluation Method] (1) Oxygen Transmission Rate (OTR) The oxygen transmission rate of the composite multilayer films and multilayer structures obtained in the Examples and Comparative Examples was measured in accordance with the method described in JIS K 7126-2 (isobaric method; 2006). Specifically, the oxygen transmission rate (unit: cc / (m)) was measured using an oxygen transmission amount measuring device ("MOCON OX-TRAN2 / 21" manufactured by Modern Control) under the conditions of a temperature of 20°C, a humidity of 65% RH on the oxygen supply side, a humidity of 65% RH on the carrier gas side, an oxygen pressure of 1 atmosphere, and a carrier gas pressure of 1 atmosphere. ２ The oxygen supplying side was measured. Nitrogen gas containing 2% by volume of hydrogen gas was used as the carrier gas. In the composite multilayer film, the core layer (C) was arranged to be the oxygen supplying side, and in the multilayer structure, the BOPP or HDPE side was arranged to be the oxygen supplying side.

[0106] (2) OTR after storage test The products obtained in the Examples and Comparative Examples were stored for 30 days under conditions of 34°C and 78% RH, and then opened, the mayonnaise inside was taken out, washed with water, and then the OTR was measured by the method described in the above evaluation method (1).

[0107] Example 1 Using EVOH1 as the material for the barrier layer (A), MAhPP1 as the material for the adhesive layer (B), and PP1 as the material for the core layer (C), a three-kind, three-layer multilayer film (barrier layer (A) / adhesive layer (B) / core layer (C) = average thickness of 50 μm / 50 μm / 500 μm) was produced using a co-extrusion film-producing device. The thickness of the multilayer film was adjusted by appropriately changing the screw rotation speed and take-up roll speed. The extruder, extrusion conditions, and die used were as follows: Barrier layer (A) Extruder: Single-screw extruder (Toyo Seiki Co., Ltd., Lab machine ME type CO-EXT) Screw: Diameter 20 mm φ, L / D 20, full-flight screw Extrusion temperature: Feeding section / compression section / metering section / die = 230 / 230 / 230 / 230°C Adhesive layer (B) Extruder: Single-screw extruder (Technovel Co., Ltd., SZW20GT-20MG-STD) Screw: Diameter 20 mm φ, L / D 20, full-flight screw Extrusion temperature: Feeding section / compression section / metering section / die = 150 / 200 / 220 / 230°C Core layer (C) Extruder: Single-screw extruder (Plastics Technology Research Institute Co., Ltd., GT-32-A) Screw: Diameter 32 mm φ, L / D 28, full-flight screw Extrusion temperature: feeding section / compression section / metering section / die = 170 / 220 / 230 / 230°C Die: 300mm wide, 3-type, 3-layer coat hanger die (manufactured by Plastics Engineering Research Institute) Die temperature: 230°C

[0108] The obtained multilayer film was stretched 5 times in the longitudinal direction and then 5 times in the transverse direction at 150°C using a tenter-type sequential biaxial stretching apparatus, to obtain a three-kind, three-layer biaxially oriented multilayer film (barrier layer (A) / adhesive layer (B) / core layer (C)=average thickness of 2 μm / 2 μm / 20 μm).

[0109] An alumina vapor-deposited layer AlOx (inorganic layer (I)) having an average thickness of 30 nm was laminated on the surface of the barrier layer (A) of the obtained biaxially stretched multilayer film by a known vacuum deposition method, thereby obtaining a biaxially stretched vapor-deposited multilayer film.

[0110] A coating solution for the protective layer (P) was prepared containing 87.6 parts by mass of deionized water, 8.60 parts by mass of PVA-1, 1.80 parts by mass of "Cymel (trademark) 385" (manufactured by Allnex, melamine-formaldehyde resin (crosslinking agent)), 0.95 parts by mass of "Loxanol (trademark) MI6730" (manufactured by BASF, polyethyleneimine (adhesion promoter)), 0.70 parts by mass of an aqueous orthophosphoric acid solution (85% by mass concentration) (catalyst), 0.19 parts by mass of an aqueous formaldehyde solution (37% by mass concentration) (crosslinking agent for polyethyleneimine), and 0.16 parts by mass of "Proxel GXL" (5% by mass concentration) (biocide). The resulting coating solution was applied to the alumina vapor-deposited AlOx layer surface of the biaxially stretched vapor-deposited multilayer film obtained above using a wire bar to an average dry thickness of 2 μm, and then dried at 100°C for 5 minutes to laminate a protective layer (P). In this manner, a composite multilayer film was produced having a layer structure of protective layer (P) / inorganic layer (I) / barrier layer (A) / adhesive layer (B) / core layer (C) = 2 μm / 30 nm / 2 μm / 2 μm / 20 μm and an average thickness. The OTR of the resulting composite multilayer film was measured according to the evaluation method described above. The results are shown in Table 1.

[0111] An adhesive solution was prepared by mixing 24 parts by mass of a two-component reactive polyurethane adhesive (24 parts by mass of "Takelac™ A-520" and 4 parts by mass of "Takenate™ A-50" manufactured by Mitsui Chemicals, Inc.) with 37 parts by mass of ethyl acetate. The adhesive solution was applied to the corona-treated surface of BOPP (resin layer (R-1)) using a wire bar so that the average thickness after drying would be 2 μm, and the applied film was dried at 100°C for 5 minutes and laminated to the exposed surface of the protective layer (P) of the composite multilayer film obtained above. Next, the adhesive solution was applied to the corona-treated surface of the CPP (resin layer (R-2)) using a wire bar so that the average thickness after drying would be 2 μm, and the applied solution was dried at 100°C for 5 minutes. This was then laminated to the exposed surface of the core layer (C) of the composite multilayer film after lamination with the BOPP to produce a multilayer structure having an average thickness and layer structure of resin layer (R-1) / adhesive layer / protective layer (P) / inorganic layer (I) / barrier layer (A) / adhesive layer (B) / core layer (C) / adhesive layer / resin layer (R-2) = 20 μm / 2 μm / 2 μm / 30 nm / 2 μm / 2 μm / 20 μm / 2 μm / 50 μm. The adhesion temperature (heating roll temperature) during lamination was 80°C, and after production of the multilayer structure, it was aged at 40°C for 3 days. The OTR of the resulting multilayer structure was measured according to the evaluation method described above. The results are shown in Table 1.

[0112] The resulting multilayer structure was cut into two pieces measuring A4 size (210 mm x 297 mm), and the CPP2 pieces were stacked together and heat-sealed along three sides to create a three-sided bag. The resulting three-sided bag was filled with 10 g of mayonnaise, and the opening was heat-sealed at 150°C to create a pouch (product) filled with the contents. The OTR of the resulting product after the storage test was measured according to the evaluation method described above. The results are shown in Table 1.

[0113] [Examples 2 to 7] Composite multilayer films, multilayer structures, and products were prepared and evaluated in the same manner as in Example 1, except that the average thickness of each layer, whether or not stretching was performed, the type of inorganic layer (I), the type of vinyl alcohol polymer used as the main component of the protective layer (P), and the lamination position of the protective layer (P) were changed as shown in Table 1. The results are shown in Table 1. In Example 6, the protective layer (P) was formed on the exposed side of the barrier layer (A) of the biaxially stretched multilayer film, and the inorganic layer (I) was formed on the protective layer (P).

[0114] [Example 8] Using EVOH2 as the material for the barrier layer (A), MAhPE1 as the material for the adhesive layer (B), and PE1 as the material for the core layer (C), a three-kind, three-layer multilayer film (barrier layer (A) / adhesive layer (B) / core layer (C) = average thickness of 20 μm / 20 μm / 200 μm) was produced using a co-extrusion film-forming device. The thickness of the multilayer film was adjusted by appropriately changing the screw rotation speed and take-up roll speed. The extruder, extrusion conditions, and die used were as follows. Barrier layer (A) Extruder: Single-screw extruder (Toyo Seiki Co., Ltd., Lab machine ME type CO-EXT) Screw: Diameter 20 mm φ, L / D 20, full-flight screw Extrusion temperature: Feeding section / compression section / metering section / die = 175 / 220 / 220 / 220°C Adhesive layer (B) Extruder: Single-screw extruder (Technovel Co., Ltd., SZW20GT-20MG-STD) Screw: Diameter 20 mm φ, L / D 20, full-flight screw Extrusion temperature: Feeding section / compression section / metering section / die = 175 / 220 / 220 / 220°C Core layer (C) Extruder: Single-screw extruder (Plastics Technology Research Institute Co., Ltd., GT-32-A) Screw: Diameter 32 mm φ, L / D 28, full-flight screw Extrusion temperature: feeding section / compression section / metering section / die = 175 / 220 / 230 / 220°C Die: 300mm wide, 3-type, 3-layer coat hanger die (manufactured by Plastics Engineering Research Institute) Die temperature: 220°C

[0115] The obtained multilayer film was stretched 5 times in the longitudinal direction at 120°C using a uniaxial stretching device to obtain a three-kind, three-layer uniaxially stretched multilayer film (barrier layer (A) / adhesive layer (B) / core layer (C)=average thickness of 4 μm / 4 μm / 40 μm).

[0116] An alumina vapor-deposited layer AlOx (inorganic layer (I)) having an average thickness of 30 nm was laminated on the surface of the barrier layer (A) of the obtained uniaxially stretched multilayer film by a known vacuum deposition method, thereby obtaining a uniaxially stretched vapor-deposited multilayer film.

[0117] The coating solution for the protective layer (P) prepared in Example 1 was applied to the surface of the alumina vapor-deposited layer AlOx (inorganic layer (I)) of the obtained multilayer film using a wire bar so that the average thickness after drying would be 2 μm, and the coating was dried at 100° C. for 5 minutes to laminate the protective layer (P). In this way, a composite multilayer film was prepared with average thicknesses of protective layer (P) / inorganic layer (I) / barrier layer (A) / adhesive layer (B) / core layer (C) = 2 μm / 30 nm / 4 μm / 4 μm / 40 μm. The OTR of the obtained composite multilayer film was measured according to the evaluation method described above. The results are shown in Table 1.

[0118] An adhesive solution was prepared by mixing 24 parts by mass of a two-component reactive polyurethane adhesive (24 parts by mass of "Takelac™ A-520" and 4 parts by mass of "Takenate™ A-50" manufactured by Mitsui Chemicals, Inc.) with 37 parts by mass of ethyl acetate. The adhesive solution was then applied to the corona-treated surface of HDPE (resin layer (R-1)) using a wire bar so that the average thickness after drying would be 2 μm, and the applied layer was dried at 100°C for 5 minutes, followed by lamination with the composite multilayer film obtained above. Next, the adhesive solution was applied with a wire bar to the corona-treated surface of a polyethylene film (resin layer (R-2)) with an average thickness of 50 μm so that the average thickness after drying would be 2 μm, and then dried at 100°C for 5 minutes. This was then laminated to the exposed surface of the core layer (C) of the composite multilayer film after lamination with HDPE to produce a multilayer structure having an average thickness and layer structure of resin layer (R-1) / adhesive layer / protective layer (P) / inorganic layer (I) / barrier layer (A) / adhesive layer (B) / core layer (C) / adhesive layer / resin layer (R-2) = 20 μm / 2 μm / 2 μm / 30 nm / 4 μm / 4 μm / 40 μm / 2 μm / 50 μm. The adhesion temperature (heating roll temperature) during lamination was 80°C, and after production of the multilayer structure, it was aged at 40°C for 3 days. The OTR of the resulting multilayer structure was measured according to the evaluation method described above. The results are shown in Table 1.

[0119] Except for using the obtained multilayer structure, products were produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0120] [Examples 9 to 15] Composite multilayer films, multilayer structures, and products were prepared and evaluated in the same manner as in Example 8, except that the average thickness of each layer, whether or not stretching was performed, the type of inorganic layer (I), the type of vinyl alcohol polymer used as the main component of the protective layer (P), and the lamination position of the protective layer (P) were changed as shown in Table 1. The results are shown in Table 1. In Example 13, the protective layer (P) was formed on the exposed surface of the barrier layer (A) of the uniaxially stretched multilayer film, and the inorganic layer (I) was formed on the protective layer (P).

[0121] [Comparative Example 1] A composite multilayer film, a multilayer structure, and a product were produced and evaluated in the same manner as in Example 1, except that the protective layer (P) was not formed and a biaxially stretched vapor-deposited multilayer film was used as the composite multilayer film. The results are shown in Table 1.

[0122] [Comparative Example 2] Resin composition pellets, a multilayer film, a composite multilayer film, a multilayer structure, and a packaging container were produced in the same manner as in Example 8, except that the protective layer (P) was not formed and a uniaxially stretched vapor-deposited multilayer film was used as the composite multilayer film, and various measurements and evaluations were performed.

[0123]

[0124] As shown in Table 1, the multilayer structures of Examples 1 to 15 were inhibited from decreasing in gas barrier property after the storage test, and the gas barrier property itself after the storage test was sufficiently excellent.

Claims

1. A composite multilayer film having a barrier layer (A) as the outermost layer, and a configuration in which the barrier layer (A), adhesive layer (B), and core layer (C) are directly laminated in this order, and having a protective layer (P) and an inorganic layer (I) adjacent to each other on the exposed surface of the barrier layer (A), wherein the barrier layer (A) is made of a resin composition (A') mainly composed of an ethylene-vinyl alcohol copolymer (a) having an ethylene unit content of 20 to 50 mol% and a saponification degree of 90 mol% or more, the adhesive layer (B) mainly contains an adhesive resin (b), the core layer (C) mainly contains a polyolefin (c), and the protective layer (P) contains a vinyl alcohol-based polymer.

2. The composite multilayer film according to claim 1, which has a structure in which the inorganic layer (I), the protective layer (P) and the barrier layer (A) are laminated adjacently in this order.

3. The composite multilayer film according to claim 1, which has a structure in which a protective layer (P), an inorganic layer (I) and a barrier layer (A) are laminated adjacently in this order.

4. The composite multilayer film according to any one of claims 1 to 3, wherein the adhesive resin (b) is an acid-modified polyolefin.

5. The composite multilayer film according to any one of claims 1 to 3, wherein the inorganic layer (I) is a vapor-deposited metal layer containing aluminum as a main component or a vapor-deposited inorganic oxide layer containing alumina or silica as a main component.

6. The composite multi-layer film according to any one of claims 1 to 3, wherein the vinyl alcohol polymer is a modified polyvinyl alcohol having a modifying group.

7. The composite multi-layer film according to claim 6, wherein the vinyl alcohol polymer having a modifying group is an ethylene-modified polyvinyl alcohol having an ethylene unit content of 1 to 15 mol% and a degree of saponification of 80 to 99.9 mol%.

8. The composite multi-layer film according to claim 6, wherein the vinyl alcohol polymer having a modifying group has a modifying group containing a primary hydroxyl group represented by the following general formula (I): [wherein X is a hydrogen atom, a methyl group, or R ２ represents a group represented by —OH. １ and R ２ each independently represents a single bond, an alkylene group having 1 to 9 carbon atoms, or an alkyleneoxy group having 1 to 9 carbon atoms, and the alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom.

9. R in the general formula (I) １ 9. The composite multilayer film of claim 8, wherein is a single bond and X is a hydroxymethyl group.

10. R in the general formula (I) １ 9. The composite multilayer film of claim 8, wherein is a hydroxymethylene group and X is a hydrogen atom.

11. A multilayer structure comprising the composite multilayer film according to any one of claims 1 to 3 laminated with at least one resin layer (R) containing a thermoplastic resin (r) as a main component.

12. The multilayer structure of claim 11, wherein the thermoplastic resin (r) is a polyolefin.

13. The multilayer structure according to claim 11, wherein the ratio of the total average thickness of the layers containing polyolefin resin as the main component to the average thickness of the multilayer structure is 0.75 or more.

14. The multilayer structure according to claim 11, which does not have any layer containing as its main component a resin having a melting point of 200° C. or higher and no metal layer having an average thickness of 1 μm or higher.

15. A packaging material comprising the multilayer structure of claim 11.

16. A product comprising the packaging material and contents according to claim 15, wherein the contents contain 5% by mass or more of moisture and at least one selected from the group consisting of 1% by mass or more of lipids, 1% by mass or more of sodium chloride, and 0.5% by mass or more of acetic acid.

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