Multilayer film, vapor-deposited multilayer film, multilayer structure, packaging material, recovered composition, and recycling method

Abstract

To provide a multilayer film etc. that has both appearance properties and interlayer adhesiveness. [Solution] A co-extruded multilayer film having layer (X) as the outermost layer, and layer (X), layer (Y), and layer (Z) directly laminated in this order, wherein layer (X) contains, as a main component, an ethylene-vinyl alcohol copolymer having an ethylene unit content of 20 to 59 mol% and a saponification degree of 80 mol% or more; layer (Y) contains, as a main component, a saponified ethylene-vinyl ester copolymer having an ethylene unit content of 60 to 99 mol% and a saponification degree of 1 to 99 mol%; layer (Z) contains, as a main component, a thermoplastic resin (z); and the multilayer film has an average thickness of 300 μm or less, and the average thickness of layer (X) is 30 μm or less.

Description

[Technical Field]

[0001] The present invention relates to a multilayer film, a vapor-deposited multilayer film, a multilayer structure, a packaging material, a recovered composition, and a recycling method. [Background technology]

[0002] Packaging materials for long-term storage of foods and other foods often require gas barrier properties, including oxygen barrier properties. The use of packaging materials with high gas barrier properties can prevent oxidative deterioration of foods and other foods due to oxygen intrusion, as well as microbial growth. Metal foils and metal vapor-deposited layers, such as aluminum foils, and inorganic oxide vapor-deposited layers, such as silicon oxide and aluminum oxide, are widely used to improve gas barrier properties. Meanwhile, resin layers with gas barrier properties, such as vinyl alcohol polymers and polyvinylidene chloride, are also widely used. Vinyl alcohol polymers exhibit gas barrier properties through hydrogen bonding between hydroxyl groups in the molecules, resulting in crystallization and densification. Among these, ethylene-vinyl alcohol copolymers (hereinafter also referred to as "EVOH") are suitable for melt molding due to their excellent thermal stability. With the development of coextrusion technology, coextruded multilayer films with EVOH layers have become widely used as gas barrier packaging materials. Furthermore, it is widely known that the oxygen barrier and water vapor barrier can be improved by vapor-depositing aluminum on the EVOH surface of a multilayer film having EVOH as the outermost layer. For example, Patent Document 1 describes a vapor-deposited multilayer film in which aluminum is vapor-deposited on a co-extruded multilayer film in which an EVOH layer, an adhesive resin layer, and a polyolefin layer are laminated in this order. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 261560 Summary of the Invention [Problem to be solved by the invention]

[0004] In coextruded multilayer films having an EVOH layer on the surface, such as the coextruded multilayer film described in Patent Document 1, acid-modified polyolefins are widely used in the adhesive resin layer for adhering the EVOH layer. However, such conventional coextruded multilayer films may have problems such as poor appearance.

[0005] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a coextruded multilayer film having a layer containing EVOH as a main component, which multilayer film achieves both good appearance properties and interlayer adhesion, as well as a vapor-deposited multilayer film, a multilayer structure, a packaging material, a recovered composition, and a recycling method using such a multilayer film. [Means for solving the problem]

[0006] The above objectives are: [1] A co-extruded multilayer film having layer (X) as the outermost layer, in which layer (X), layer (Y) and layer (Z) are directly laminated in this order, wherein layer (X) contains, as a main component, an ethylene-vinyl alcohol copolymer (x) having an ethylene unit content of 20 to 59 mol% and a saponification degree of 80 mol% or more, layer (Y) contains, as a main component, a saponified ethylene-vinyl ester copolymer (y) having an ethylene unit content of 60 to 99 mol% and a saponification degree of 1 to 99 mol%, layer (Z) contains, as a main component, a thermoplastic resin (z), and has an average thickness of 300 μm or less, and layer (X) has an average thickness of 30 μm or less; [2] The multilayer film of [1], wherein the thermoplastic resin (z) is polyethylene or polypropylene; [3] The multilayer film of [1] or [2], wherein the thermoplastic resin (z) is polyethylene; [4] The multilayer film of any one of [1] to [3], wherein the average thickness of the layer (X) is 0.2 μm or more and less than 20 μm, and the ratio of the average thickness of the layer (X) to the average thickness of the multilayer film is less than 25%; [5] The multilayer film of any one of [1] to [4], wherein the average thickness of the layer (Y) is 0.2 μm or more and less than 20 μm, and the ratio of the average thickness of the layer (Y) to the average thickness of the multilayer film is less than 20%; [6] A multilayer film of any one of [1] to [5], which is an unstretched film; [7] A multilayer film according to any one of [1] to [5], which is a stretched film stretched at least uniaxially by 3 times or more but less than 12 times; [8] A vapor-deposited multilayer film comprising the multilayer film according to any one of [1] to [7] and an inorganic vapor-deposited layer (I) which is a metal vapor-deposited layer mainly composed of aluminum or an inorganic oxide vapor-deposited layer mainly composed of alumina or silica, laminated on the exposed surface of the layer (X); [9] A multilayer structure comprising the multilayer film of any one of [1] to [7] or the vapor-deposited multilayer film of [8], and at least one layer (R) containing a thermoplastic resin (r) as a main component, laminated on the multilayer film or the vapor-deposited multilayer film;

[10] The multilayer structure of [9], wherein the thermoplastic resin (r) is polyethylene or polypropylene;

[11] The multilayer structure of [9] or

[10] , wherein the content of polyethylene or polypropylene in the multilayer structure is 80% by mass or more;

[12] A packaging material having a multilayer film of any one of [1] to [7], a vapor-deposited multilayer film of [8], or a multilayer structure of any one of [9] to

[11] ;

[13] A recovered composition comprising a recovered multilayer film of any one of [1] to [7], a vapor-deposited multilayer film of [8], or a recovered multilayer structure of any one of [9] to

[11] ;

[14] A recycling method comprising a step of crushing the multilayer film of any one of [1] to [7], the vapor-deposited multilayer film of [8], or the multilayer structure of any one of [9] to

[11] to obtain crushed material, and a step of melt-molding a composition containing the crushed material; This is achieved by providing [Effects of the Invention]

[0007] The present invention provides a coextruded multilayer film having a layer containing EVOH as a primary component, which exhibits both excellent appearance properties and excellent interlayer adhesion, as well as a vapor-deposited multilayer film, a multilayer structure, a packaging material, a recovered composition, and a recycling method using such a multilayer film. Here, "appearance properties" refers to the appearance of the multilayer film, particularly the state of streaks in the multilayer film, which can be evaluated by observing the film with an image clarity measuring device, and can be evaluated specifically by the method described in the Examples. Furthermore, "interlayer adhesion" refers to the adhesion between the layer containing EVOH as a primary component in the multilayer film and the layer directly laminated thereto, and can be evaluated specifically by the method described in the Examples. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described. 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.

[0009] The "outermost layer" is not limited to the layer present on the front side, distinguishing between the front and back sides. In other words, the layer having the exposed surface is the outermost layer. "Main component" refers to a component that is contained in an amount of 50% by mass or more. A numerical range expressed as "A to B" means that A is included as the lower limit and B is included as the upper limit. In other words, "A to B" is equal to greater than or equal to A and less than or equal to B. Unless otherwise specified, the "average thickness" of each layer, etc. refers to the average value of thicknesses measured at any five points. "Polyethylene" means a homopolymer of ethylene, a copolymer of 80 mol% or more ethylene and 20 mol% or less α-olefin monomers, and a copolymer of 95 mol% or more ethylene and less than 5 mol% non-olefin monomers whose functional groups contain atoms other than carbon, oxygen, and hydrogen atoms. "Polypropylene" refers to a homopolymer of propylene, a copolymer of 80 mol% or more propylene and 20 mol% or less α-olefin monomers, and a copolymer of 95 mol% or more propylene and less than 5 mol% non-olefin monomers whose functional groups contain atoms other than carbon, oxygen, and hydrogen atoms. In this specification, when describing a layer structure, " / " indicates that the layers are directly laminated, and " / / " indicates that the layers are laminated directly or via an adhesive layer.

[0010] <Multilayer film> The multilayer film of the present invention is a co-extruded multilayer film having Layer (X) as the outermost layer, and Layer (X), Layer (Y), and Layer (Z) laminated directly in this order, wherein Layer (X) contains, as a main component, an ethylene-vinyl alcohol copolymer (x) (hereinafter also referred to as "EVOH (x)") having an ethylene unit content of 20 to 59 mol% and a saponification degree of 80 mol% or more; Layer (Y) contains, as a main component, a saponified ethylene-vinyl ester copolymer (y) (hereinafter also referred to as "copolymer (y)") having an ethylene unit content of 60 to 99 mol% and a saponification degree of 1 to 99 mol%; Layer (Z) contains, as a main component, a thermoplastic resin (z) and has an average thickness of 300 μm or less; and Layer (X) has an average thickness of 30 μm or less.

[0011] The multilayer film of the present invention is a coextruded multilayer film having a layer (X) containing EVOH (x) as a primary component, and exhibits both excellent appearance and interlayer adhesion. While the reason for this is unclear, the following is presumed. In conventional coextruded multilayer films in which an EVOH-based layer and an adhesive resin layer are directly laminated together and an acid-modified polyolefin is used as the adhesive resin, excessive chemical bonding between the EVOH and the acid-modified polyolefin (esterification reaction between the hydroxyl groups of the EVOH and the acidic groups of the acid-modified polyolefin) occurs during melt extrusion, leading to localized crosslinking at the interface and causing poor appearance. In contrast, the multilayer film of the present invention uses a copolymer (y) highly compatible with EVOH (x) as the resin that bonds the layer (X) containing EVOH (x) as a primary component. In this case, the EVOH (x) and copolymer (y) become miscible at the interface during melt extrusion, thereby bonding the layers together. As described above, in the multilayer film of the present invention, the layer (X) containing EVOH (x) as a main component and the layer (Y) laminated directly to this layer (X) are bonded together by utilizing the compatibility of the resins rather than by a chemical reaction, and therefore the appearance is good and the adhesion between the layers is also considered to be high.

[0012] Furthermore, the multilayer film of the present invention has excellent gas barrier properties because the layer (X) containing EVOH (x) as a main component has little local crosslinking, etc., and a highly homogeneous layer (X) is formed. Furthermore, a vapor-deposited multilayer film obtained by laminating an inorganic vapor-deposited layer (I) on the surface of such a layer (X) can also exhibit excellent gas barrier properties.

[0013] (layer(X)) The layer (X) is the outermost layer on at least one side of the multilayer film and contains, as a main component, EVOH(x) (ethylene-vinyl alcohol copolymer (x)) having an ethylene unit content of 20 to 59 mol% and a saponification degree of 80 mol% or more.

[0014] EVOH(x) is a copolymer obtained by saponifying an ethylene-vinyl ester copolymer obtained by polymerizing ethylene and a vinyl ester. Examples of the vinyl ester include vinyl acetate, vinyl propionate, and vinyl pivalate, with vinyl acetate being preferred.

[0015] The lower limit of the ethylene unit content of EVOH(x) is 20 mol%, preferably 24 mol%, and may be 30 mol%, 35 mol%, or 40 mol%. Having an ethylene unit content of EVOH(x) equal to or greater than the above lower limit can improve melt moldability, etc. On the other hand, the upper limit of the ethylene unit content of EVOH(x) is 59 mol%, preferably 55 mol%, more preferably 50 mol%, and even more preferably 45 mol%, and may be 40 mol%, 35 mol%, or 30 mol%. Having an ethylene unit content of EVOH(x) equal to or less than the above upper limit can improve gas barrier properties, etc. Furthermore, having an ethylene unit content of EVOH(x) equal to or less than the above upper limit can improve adhesion to the inorganic vapor deposition layer (I), which will be described later, etc. The ethylene unit content is the content (mol%) of ethylene units relative to all structural units constituting the polymer (EVOH(x), etc.).

[0016] The lower limit of the saponification degree of EVOH(x) is 80 mol%, preferably 85 mol%, more preferably 90 mol%, even more preferably 95 mol%, and even more preferably 97 mol%, 98 mol% or 99 mol%. The saponification degree of EVOH(x) or the like means the ratio of the number of vinyl alcohol units to the total number of vinyl alcohol units and vinyl ester units in EVOH(x) or the like. When the saponification degree of EVOH(x) is equal to or higher than the above lower limit, it is possible to further improve the gas barrier property, etc. The upper limit of the saponification degree of EVOH(x) may be 100 mol% or may be 99.9 mol%. The ethylene unit content and saponification degree of EVOH(x) or the like are 1 It can be determined by H-NMR measurement.

[0017] EVOH (x) may contain structural units other than ethylene units, vinyl alcohol units, and optionally remaining vinyl ester units, as long as the effects of the present invention are not impaired. Examples of monomers that provide these 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, and i-propyl vinyl ether. vinyl ethers such as acrylonitrile, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, and 2,3-diacetoxy-1-vinyloxypropane; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinyl 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.

[0018] The EVOH (x) may or may not be post-modified by a method such as urethanization, acetalization, cyanoethylation, or oxyalkylenation.

[0019] When EVOH(x) has other structural units, it is preferable that EVOH(x) has a structural unit represented by the following formula (I).

[0020] [ka]

[0021] In formula (I), X is a hydrogen atom, a methyl group, or R 2 R 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 hydroxy group, an alkoxy group, or a halogen atom.

[0022] X is preferably a hydrogen atom or R 2 is a group represented by —OH, and more preferably R 2 It is a group represented by -OH.

[0023] R 1 or R 2 The alkylene and alkyleneoxy groups used as R may contain hydroxy groups, alkoxy groups, or halogen atoms. 1 and R 2 is preferably an alkylene group or alkyleneoxy group having 1 to 5 carbon atoms, and more preferably an alkylene group or alkyleneoxy group having 1 to 3 carbon atoms.

[0024] Specific examples of the structural unit represented by formula (I) include structural units represented by the following formulas (II), (III) and (IV), and among these, the structural unit represented by formula (II) is preferred.

[0025] [ka]

[0026] In formula (II), R 3 and R 4are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and the alkyl group may contain a hydroxy group, an alkoxy group, or a halogen atom.

[0027] [ka]

[0028] In 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 hydroxy group, an alkoxy group, or a halogen atom.

[0029] [ka]

[0030] In formula (IV), R 7 and R 8 each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, or a hydroxy group. Some or all of the hydrogen atoms in the alkyl group and cycloalkyl group may be substituted with a hydroxy group, an alkoxy group, or a halogen atom.

[0031] R in formula (I) 1 is a single bond, and X is a hydroxymethyl group (R 3 , R 4 is preferably a hydrogen atom). Use of EVOH(x) having this structural unit tends to improve secondary processability such as stretchability and thermoformability without significantly deteriorating gas barrier properties. When EVOH(x) contains the above structural unit, the lower limit of its content is preferably 0.1 mol%, more preferably 0.4 mol%, and even more preferably 1.0 mol%. On the other hand, from the viewpoint of improving gas barrier properties, the upper limit of the content of the above structural unit is preferably 20 mol%, more preferably 10 mol%, even more preferably 8 mol%, and particularly preferably 5 mol%.

[0032] R in formula (I) 1 is a hydroxymethylene group, X is a hydrogen atom (R 5 , R 6 is also preferably a hydrogen atom). Use of EVOH(x) having this structural unit tends to improve secondary processability such as stretchability and thermoformability without significantly deteriorating gas barrier properties. When EVOH(x) contains the above structural unit, the lower limit of its content is preferably 0.1 mol%, more preferably 0.4 mol%, and even more preferably 1.0 mol%. On the other hand, the upper limit of the content of the above structural unit is preferably 20 mol%, more preferably 10 mol%, even more preferably 8 mol%, and particularly preferably 5 mol%, from the viewpoint of improving gas barrier properties.

[0033] R in formula (I) 1 It is also preferred that R is a methylmethyleneoxy group and X is a hydrogen atom. By using EVOH (x) having this structural unit, secondary processability such as stretchability and thermoformability tends to be improved without significantly deteriorating gas barrier properties. In addition, the methylmethyleneoxy group has an oxygen atom bonded to a carbon atom in the main chain. That is, in formula (IV), R 7 , R 8 Preferably, one of these structural units is a methyl group and the other is a hydrogen atom. When EVOH (x) contains the above structural unit, the lower limit of the content is preferably 0.1 mol%, more preferably 0.5 mol%, even more preferably 1.0 mol%, and particularly preferably 2.0 mol%. On the other hand, from the viewpoint of improving gas barrier properties, the upper limit of the content of the above structural unit is preferably 20 mol%, more preferably 15 mol%, and even more preferably 10 mol%.

[0034] The upper limit of the content of other structural units (structural units other than ethylene units, vinyl alcohol units, and optionally remaining vinyl ester units) relative to the total structural units of EVOH (x) is preferably 5 mol%, more preferably 3 mol%, and even more preferably 1 mol%. In other words, the lower limit of the total content of ethylene units, vinyl alcohol units, and optionally remaining vinyl ester units relative to the total structural units of EVOH is preferably 95 mol%, more preferably 97 mol%, and even more preferably 99 mol%. EVOH (x) may not have other structural units.

[0035] The lower limit of the MFR (190°C, 2.16 kg load) of EVOH(x) is preferably 0.5 g / 10 min, more preferably 1.0 g / 10 min, and even more preferably 1.5 g / 10 min. The upper limit of the MFR (190°C, 2.16 kg load) of EVOH(x) is preferably 10 g / 10 min, more preferably 5.0 g / 10 min, and even more preferably 3.0 g / 10 min. The lower limit of the MFR (210°C, 2.16 kg load) of EVOH(x) is preferably 1.0 g / 10 min, more preferably 2.0 g / 10 min, and even more preferably 3.0 g / 10 min. The upper limit of the MFR (210°C, 2.16 kg load) of EVOH(x) is preferably 20 g / 10 min, more preferably 10.0 g / 10 min, and even more preferably 5.0 g / 10 min. When the MFR of EVOH(x) is within the above range, it is possible to exhibit good melt moldability, etc. The MFR of EVOH(x) or the like is measured in accordance with JIS K7210-1 (2014).

[0036] The lower limit of the melting point of EVOH (x) is preferably 120° C., more preferably 130° C., even more preferably 140° C., even more preferably 150° C., and particularly preferably 160° C. The upper limit of the melting point of EVOH (x) is preferably 230° C., more preferably 220° C., even more preferably 210° C., and even more preferably 200° C. When the melting point of EVOH (x) is within the above range, good melt moldability can be exhibited.

[0037] EVOH(x) can be produced by a conventionally known method. As the EVOH(x), commercially available products may be used.

[0038] The lower limit of the content of EVOH (x) in layer (X) is preferably 70% by mass, more preferably 80% by mass, and even more preferably 90% by mass, and may be 95%, 99%, or 99.9% by mass. The upper limit of the content of EVOH (x) in layer (X) may be 100%, 99.99%, 99.9%, or 99% by mass.

[0039] The layer (X) may contain components other than EVOH (x). Examples of other components include boron compounds, carboxylic acids, phosphorus compounds, metal ions, resins other than EVOH (x), antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, and heat stabilizers. The layer (X) may contain two or more of these optional components.

[0040] The average thickness of layer (X) is 30 μm or less, preferably less than 20 μm. Having the average thickness of layer (X) equal to or less than the above upper limit allows for a thinner and lighter multilayer film, and improves recyclability, flexibility, etc. The upper limit of the average thickness of layer (X) is more preferably 10 μm, even more preferably 7 μm, and may be 5 μm, 4 μm, or 3 μm. On the other hand, the lower limit of the average thickness of layer (X) is preferably 0.2 μm, more preferably 0.5 μm, even more preferably 1 μm, and may be 1.5 μm or 2 μm. Having the average thickness of layer (X) equal to or greater than the above lower limit allows for improved gas barrier properties, etc. When layer (X) is composed of multiple layers, the average thickness of the layer (X) is the total average thickness of the multiple layers (X). In other words, when multiple layers (X) are present in the multilayer film, the "average thickness of layer (X)" is the sum of the average thicknesses of all layers (X) included in the multilayer film. For example, if a multilayer film includes two layers (X) each having an average thickness of 10 μm, the "average thickness of layer (X)" in this multilayer film is 20 μm. The same applies to the average thicknesses of the other layers.

[0041] The ratio of the average thickness of layer (X) to the average thickness of the multilayer film is preferably less than 25%. Having the average thickness ratio of layer (X) less than the above upper limit can improve recyclability, etc. The upper limit of the average thickness ratio is more preferably 20%, and even more preferably 15%. The lower limit of the average thickness ratio may be, for example, 1%, 3%, or 5%.

[0042] The layer (X) may consist of a single layer or multiple layers. In one embodiment, the layer (X) is preferably a single layer. When multiple layers made of materials of the same composition are directly laminated, they are considered to be one layer. The same applies to other layers.

[0043] (Layer(Y)) The layer (Y) is a layer disposed between the layer (X) and the layer (Z). The layer (Y) contains, as a main component, a copolymer (y) (saponified ethylene-vinyl ester copolymer (y)) having an ethylene unit content of 60 to 99 mol% and a saponification degree of 1 to 99 mol%.

[0044] Copolymer (y) is a copolymer obtained by partially saponifying an ethylene-vinyl ester copolymer obtained by polymerizing ethylene and a vinyl ester. Examples of vinyl esters include vinyl acetate, vinyl propionate, and vinyl pivalate, with vinyl acetate being preferred. Copolymer (y) in which the vinyl ester is vinyl acetate, i.e., a saponified ethylene-vinyl acetate copolymer, is also called "partially saponified EVA." Copolymer (y) is preferably partially saponified EVA.

[0045] The lower limit of the ethylene unit content of copolymer (y) is 60 mol%, preferably 70 mol%, more preferably 80 mol%, and even more preferably 85 mol%. When the ethylene unit content of copolymer (y) is equal to or greater than the above lower limit, it is possible to improve melt moldability and adhesion to layer (Z). When layer (Z) is mainly composed of polyolefin, especially polyethylene, when the ethylene unit content of copolymer (y) is equal to or greater than the above lower limit, adhesion to layer (Z) tends to be particularly improved. On the other hand, the upper limit of the ethylene unit content of copolymer (y) is 99 mol%, preferably 96 mol%, more preferably 93 mol%, and even more preferably 90 mol%. When the ethylene unit content of copolymer (y) is equal to or less than the above upper limit, it is possible to improve adhesion to layer (X).

[0046] The lower limit of the saponification degree of copolymer (y) is 1 mol%, preferably 5 mol%, more preferably 8 mol%, even more preferably 15 mol%, and even more preferably 20 mol%, 25 mol%, 30 mol%, or 35 mol%. The upper limit of the saponification degree of copolymer (y) is 99 mol%, preferably 98 mol%, more preferably 90 mol%, even more preferably 80 mol%, and even more preferably 70 mol%, 60 mol%, 50 mol%, or 40 mol%. When the saponification degree of copolymer (y) is within the above range, adhesion to layer (X) can be improved.

[0047] The lower limit of the content of vinyl ester units relative to all structural units of copolymer (y) is preferably 0.2 mol%, more preferably 0.5 mol%, even more preferably 1 mol%, and even more preferably 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, or 7 mol%. When the content of vinyl ester units relative to all structural units of copolymer (y) is equal to or greater than the above lower limit, adhesion to layer (X) can be further improved. The upper limit of the content of vinyl ester units relative to all structural units of copolymer (y) is preferably 20 mol%, more preferably 15 mol%, even more preferably 10 mol%, and even more preferably 8 mol%.

[0048] The lower limit of the content of vinyl alcohol units relative to all structural units of copolymer (y) is preferably 0.2 mol%, more preferably 0.5 mol%, even more preferably 1 mol%, and even more preferably 2 mol% or 3 mol%. When the content of vinyl alcohol units relative to all structural units of copolymer (y) is equal to or greater than the above lower limit, adhesion to layer (X) can be further improved. The upper limit of the content of vinyl alcohol units relative to all structural units of copolymer (y) is preferably 20 mol%, more preferably 15 mol%, even more preferably 10 mol%, and even more preferably 8 mol%, 6 mol%, or 5 mol%.

[0049] From the viewpoint of adhesion to the layer (X), the lower limit of the content of vinyl ester units and the lower limit of the content of vinyl alcohol units relative to all structural units of the copolymer (y) are both preferably 0.2 mol%, more preferably 0.5 mol%, and even more preferably 1 mol%, 2 mol%, or 3 mol%.

[0050] The copolymer (y) may contain structural units other than ethylene units, vinyl ester units, and vinyl alcohol units, as long as the effects of the present invention are not impaired. The monomers that provide the other structural units are the same as those exemplified as the monomers that provide the other structural units in EVOH (x).

[0051] The upper limit of the content of other structural units (structural units other than ethylene units, vinyl ester units, and vinyl alcohol units) relative to all structural units of copolymer (y) is preferably 5 mol%, more preferably 3 mol%, and even more preferably 1 mol%. In other words, the lower limit of the total content of ethylene units, vinyl ester units, and vinyl alcohol units relative to all structural units of copolymer (y) is preferably 95 mol%, more preferably 97 mol%, and even more preferably 99 mol%. In particular, from the viewpoint of suppressing deterioration of appearance due to excessive crosslinking reaction with EVOH (x), the upper limit of the content of structural units having an acidic group relative to all structural units of copolymer (y) is preferably 5 mol%, more preferably 3 mol%, more preferably 1 mol%, and even more preferably 0.5 mol%. Copolymer (y) may not have other structural units.

[0052] The lower limit of the MFR (190°C, 2.16 kg load) of copolymer (y) is preferably 0.5 g / 10 min, more preferably 1.0 g / 10 min, and even more preferably 2.0 g / 10 min. The upper limit of the MFR (190°C, 2.16 kg load) of partially saponified EVA is preferably 15 g / 10 min, more preferably 10 g / 10 min, and even more preferably 7.0 g / 10 min. When the MFR of copolymer (y) is within the above range, it is possible to exhibit good melt moldability, etc.

[0053] The lower limit of the melting point of copolymer (y) is preferably 50°C, more preferably 60°C, and even more preferably 70°C. The upper limit of the melting point of copolymer (y) is preferably 150°C, more preferably 120°C, even more preferably 100°C, even more preferably 90°C, and particularly preferably 80°C. When the melting point of copolymer (y) is within the above range, it is possible to improve adhesion to layer (X) and to exhibit good melt moldability. In particular, when the melting point of copolymer (y) is equal to or lower than the above upper limit, adhesion to layer (X) tends to be further improved.

[0054] The copolymer (y) can be produced by a conventionally known method, and commercially available copolymers may be used as the copolymer (y).

[0055] The lower limit of the content of copolymer (y) in layer (Y) is preferably 70% by mass, more preferably 80% by mass, and even more preferably 90% by mass, and may be 95%, 99%, or 99.9% by mass. The upper limit of the content of copolymer (y) in layer (Y) may be 100%, 99.99%, 99.9%, or 99% by mass.

[0056] The layer (Y) may contain components other than the copolymer (y). Examples of the other components include boron compounds, carboxylic acids, phosphorus compounds, metal ions, resins other than the copolymer (y), antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, and heat stabilizers. The layer (Y) may contain two or more of these optional components.

[0057] The average thickness of the layer (Y) is preferably less than 20 μm. When the average thickness of the layer (Y) is less than the above upper limit, the multilayer film can be made thinner and lighter, and recyclability can be improved. The upper limit of the average thickness of the layer (Y) is more preferably 10 μm, even more preferably 7 μm, and may be 5 μm, 4 μm, or 3 μm. On the other hand, the lower limit of the average thickness of the layer (Y) is preferably 0.2 μm, more preferably 0.5 μm, even more preferably 1 μm, and may be 1.5 μm or 2 μm. When the average thickness of the layer (Y) is equal to or greater than the above lower limit, interlayer adhesion can be improved. When the layer (Y) is composed of multiple layers, the average thickness of the layer (Y) is the total average thickness of the multiple layers (Y).

[0058] The ratio of the average thickness of layer (Y) to the average thickness of the multilayer film is preferably less than 25%. Having the average thickness ratio of layer (Y) less than the above upper limit can improve recyclability, etc. The upper limit of the average thickness ratio is more preferably 20%, and even more preferably 15%. The lower limit of the average thickness ratio may be, for example, 1%, 3%, or 5%.

[0059] The layer (Y) may consist of a single layer or multiple layers. In one embodiment, the layer (Y) is preferably a single layer.

[0060] (Layer(Z)) Layer (Z) is a layer laminated on the side of layer (Y) opposite to layer (X). Layer (Z) may be the outermost layer on the side opposite to layer (X) in the multilayer film. When layer (Z) is the outermost layer, layer (Z) may also function as a sealant layer (heat seal layer). Layer (Z) contains thermoplastic resin (z) as a main component.

[0061] Examples of the thermoplastic resin (z) include polyolefin, polyester (polyethylene terephthalate, etc.), polyamide (nylon-6, nylon-66, etc.), polystyrene, polyvinyl chloride, polyvinylidene chloride, acrylic resin, vinyl ester resin, polyurethane, and polycarbonate.

[0062] The thermoplastic resin (z) is preferably a polyolefin. Examples of polyolefins include polyethylene, polypropylene, polybutene, and polypentene. Polyethylene or polypropylene is preferred, and polyethylene is more preferred. Polyethylene and polypropylene are widely used in packaging materials, regardless of whether they have gas barrier properties or not, and therefore recycling infrastructure for them is widely established in various countries. Therefore, the use of these resins can improve recyclability. Furthermore, the use of these resins can allow the layer (Z) to function favorably as a sealant layer (heat seal layer).

[0063] Examples of polyethylene include high-density polyethylene, low-density polyethylene, very low-density polyethylene, linear low-density polyethylene, etc. The density of high-density polyethylene is, for example, 0.930 g / cm 3 More than 0.980g / cm 3 The density of low density polyethylene is, for example, 0.910 g / cm 3 More than 0.930g / cm 3 The density of ultra-low density polyethylene is, for example, 0.910 g / cm3 The density of linear low density polyethylene is, for example, 0.910 g / cm 3 More than 0.925g / cm 3 is less than.

[0064] Examples of polypropylene include homopolypropylene, random copolymer polypropylene (e.g., polypropylene randomly copolymerized with ethylene), block copolymer polypropylene (e.g., block copolymer polypropylene having an ethylene block and a propylene block), and terpolymer polypropylene (e.g., terpolymer polypropylene randomly copolymerized with ethylene and butene).

[0065] The lower limit of the MFR (190°C, 2.16 kg load) of the thermoplastic resin (z) is preferably 0.5 g / 10 min, more preferably 1.0 g / 10 min, and even more preferably 1.5 g / 10 min. The upper limit of the MFR (190°C, 2.16 kg load) of the thermoplastic resin (z) is preferably 15 g / 10 min, more preferably 10.0 g / 10 min, and even more preferably 7.0 g / 10 min. When the MFR of the thermoplastic resin (z) is within the above range, it is possible to exhibit good melt moldability, etc.

[0066] The lower limit of the melting point of the thermoplastic resin (z) is preferably 90°C, more preferably 100°C, and even more preferably 110°C. The upper limit of the melting point of the thermoplastic resin (z) is preferably 150°C, more preferably 140°C, and even more preferably 130°C. When the melting point of the thermoplastic resin (z) is in the above range, it is possible to exhibit good melt moldability and improve heat sealability. In particular, when the layer (Z) is located as the outermost layer and is composed of multiple layers, it is preferable that the melting point of the thermoplastic resin layer (z) that is the main component of the outermost layer of the multiple layers (Z) (the layer located farthest from the layer (Y)) is in the above range. In such a case, there is an advantage that the outermost layer of the layer (Z) can function suitably as a sealant layer.

[0067] The thermoplastic resin (z) can be produced by a conventionally known method, and commercially available products may also be used.

[0068] The lower limit of the content of thermoplastic resin (z) in layer (Z) is preferably 70% by mass, more preferably 80% by mass, and even more preferably 90% by mass, and may be 95%, 99%, or 99.9% by mass. The upper limit of the content of thermoplastic resin (z) in layer (Z) may be 100%, 99.99%, 99.9%, or 99% by mass.

[0069] The layer (Z) may contain components other than the thermoplastic resin (z). Examples of other components include antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, heat stabilizers, and resins other than the thermoplastic resin (z). The layer (Z) may contain two or more of these optional components.

[0070] The upper limit of the average thickness of layer (Z) is preferably 200 μm, more preferably 100 μm, even more preferably 50 μm, and even more preferably 30 μm. When the average thickness of layer (Z) is equal to or less than the above upper limit, it is possible to reduce the thickness of the multilayer film. The lower limit of the average thickness of layer (Z) is preferably 1 μm, more preferably 5 μm, even more preferably 10 μm, even more preferably 15 μm, and particularly preferably 20 μm. When the average thickness of layer (Z) is equal to or more than the above lower limit, it is possible to further improve melt moldability, barrier properties, etc. When layer (Z) is composed of multiple layers, the average thickness of layer (Z) is the total average thickness of the multiple layers (Z).

[0071] The lower limit of the ratio of the average thickness of layer (Z) to the average thickness of the multilayer film is preferably 50%, more preferably 60%, and even more preferably 70% or 80%. When the average thickness ratio of layer (Z) is equal to or greater than the above lower limit, recyclability can be improved. The upper limit of the average thickness ratio is preferably 95%, more preferably 90%.

[0072] The layer (Z) may consist of a single layer or multiple layers. In one embodiment, the layer (Z) is preferably a single layer.

[0073] Examples of the layer (Z) consisting of multiple layers include one having a layer mainly composed of polyamide and one having a layer mainly composed of polyolefin, one consisting of multiple layers mainly composed of polyolefin, etc. Examples of the layer (Z) consisting of multiple layers mainly composed of polyolefin include one consisting of multiple layers mainly composed of polyethylene where adjacent layers are made of different types of polyethylene, one consisting of multiple layers mainly composed of polypropylene where adjacent layers are made of different types of polypropylene, one having a layer mainly composed of polyethylene and a layer mainly composed of polypropylene, etc.

[0074] When layer (Z) is the outermost layer and is composed of multiple layers, it is preferable that the outermost layer (the layer farthest from layer (Y)) of the multiple layers (Z) is primarily composed of polyethylene or polypropylene. Furthermore, when layer (Z) is composed of multiple layers primarily composed of polyethylene, it is preferable that the polyethylene primarily composed of the outermost layer of the multiple layers (Z) has a lower melting point than the polyethylene primarily composed of the other layers. Similarly, when layer (Z) is composed of multiple layers primarily composed of polypropylene, it is preferable that the polypropylene primarily composed of the outermost layer of the multiple layers (Z) has a lower melting point than the polypropylene primarily composed of the other layers. Layer (Z) having such a layer structure has the advantage that the outermost layer of layer (Z) can function favorably as a sealant layer.

[0075] (Layer structure of multilayer film, etc.) The multilayer film of the present invention usually consists of only layer (X), layer (Y), and layer (Z). The multilayer film may further comprise layers other than layer (X), layer (Y), and layer (Z). When layer (X) is represented by X, layer (Y) is represented by Y, and layer (Z) is represented by Z, the layer structure of the multilayer film may be X / Y / Z, X / Y / Z / Y / X, etc., with X / Y / Z being preferred.

[0076] The upper limit of the average thickness of the multilayer film is 300 μm, preferably 200 μm, more preferably 100 μm, even more preferably 70 μm, and in some cases even more preferably 60 μm, 50 μm, or 40 μm. Having an average thickness of the multilayer film equal to or less than the above upper limit allows for thinner films and reduced costs. Furthermore, the multilayer film of the present invention and vapor-deposited multilayer films using this multilayer film can exhibit excellent barrier properties despite their thinness. The lower limit of the average thickness of the multilayer film is preferably 5 μm, more preferably 10 μm, even more preferably 15 μm, and in some cases even more preferably 20 μm or 25 μm. Having an average thickness of the multilayer film equal to or greater than the above lower limit allows for improved barrier properties.

[0077] The multilayer film of the present invention may be an unstretched film or a stretched film stretched at least uniaxially. An unstretched film means a film that has not been stretched, but a film that has undergone some orientation during film formation (for example, orientation as if stretched 1.01 times) is considered to be unstretched. An unstretched film has advantages such as excellent impact resistance and, for example, when layer (Z) is located as the outermost layer, layer (Z) functions particularly effectively as a sealant layer.

[0078] When the multilayer film of the present invention is a stretched film, it is preferably stretched at least uniaxially by 3 times or more but less than 12 times, and more preferably stretched at least uniaxially by 4 times or more but less than 8 times. When the multilayer film is a stretched film, it may be a uniaxially stretched film or a biaxially stretched film. A uniaxially stretched film stretched only in one direction is considered to be uniaxially stretched, ignoring any slight orientation in the other axial direction during film formation (for example, orientation as if stretched 1.01 times). When the multilayer film is a stretched film, it can further improve barrier properties, mechanical properties, etc.

[0079] The multilayer film of the present invention is a coextruded multilayer film. That is, the multilayer film is a film produced by a coextrusion method. By employing a coextrusion method, a multilayer film having excellent film properties such as barrier properties and flexibility can be produced with high productivity. Examples of coextrusion methods include coextrusion cast molding, coextrusion inflation molding, and coextrusion coating molding. The method of uniaxial or biaxial stretching is not particularly limited, and the film can be produced by stretching 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, tenter-type uniaxial stretching, tubular-type simultaneous biaxial stretching, tenter-type sequential biaxial stretching, or tenter-type simultaneous biaxial stretching. Furthermore, in the tenter-type sequential biaxial stretching, a tenter-type stretching may be used for both axes, or a combination of roll-type stretching and tenter-type stretching may be used. The temperature during stretching is typically 40 to 170°C, preferably 50 to 160°C, from the viewpoint of processability. 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.

[0080] <Vapor-deposited multilayer film> The vapor-deposited multilayer film of the present invention comprises the above-described multilayer film of the present invention and an inorganic vapor-deposited layer (I). The inorganic vapor-deposited layer (I) is a metal vapor-deposited layer containing aluminum as the main component or an inorganic oxide vapor-deposited layer containing alumina or silica as the main component, laminated on the exposed surface of layer (X) in the multilayer film. The vapor-deposited multilayer film uses a multilayer film that combines appearance properties and interlayer adhesion, and also has excellent gas barrier properties.

[0081] (Inorganic vapor deposited layer (I)) In this vapor-deposited multilayer film, the inorganic vapor-deposited layer (I) is usually laminated directly on the exposed surface of the layer (X). The inorganic vapor-deposited layer (I) is a layer with excellent barrier properties against oxygen, water vapor, and the like. Compared to ordinary thermoplastic resins, the layer (X) has a higher affinity with metals and inorganic oxides, making it possible to form a dense, defect-free inorganic vapor-deposited layer (I). The resulting vapor-deposited multilayer film has good interlayer adhesion between the layer (X) and the inorganic vapor-deposited layer (I). Furthermore, because the layer (X) and the like have barrier properties, even when defects occur in the inorganic vapor-deposited layer (I) due to bending or the like, a decrease in barrier properties can be suppressed.

[0082] The inorganic vapor-deposited layer (I) is 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, while an inorganic oxide vapor-deposited layer is preferred from the viewpoints of visibility of the contents as a packaging material, microwave suitability, and suppression of discoloration when the pulverized material is melt-molded.

[0083] The lower limit of the aluminum atom content in the metal vapor deposition layer is preferably 70 mass %, more preferably 90 mass %, and even more preferably 95 mass %, and the upper limit of the aluminum atom content in the metal vapor deposition layer may be 100 mass %.

[0084] In a metal vapor deposition layer containing aluminum as a main component, oxidation occurs irreversibly, and aluminum oxide may be partially contained. In a metal vapor deposition layer containing aluminum as a main component (inorganic vapor deposition layer (I)), the molar ratio of the oxygen atom content to the aluminum atom content (O mol / Al mol) is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.1 or less.

[0085] The lower limit of the alumina or silica content in the inorganic oxide vapor-deposited layer is preferably 70 mass%, more preferably 90 mass%, and even more preferably 95 mass%, and the upper limit of the alumina or silica content in the inorganic oxide vapor-deposited layer may be 100 mass%.

[0086] The upper limit of the average thickness of the inorganic vapor deposition layer (I) is preferably 200 nm, more preferably 120 nm, even more preferably 100 nm, even more preferably 80 nm, and particularly preferably 60 nm. By controlling the average thickness of the inorganic vapor deposition layer (I) to the above upper limit or less, productivity can be increased, and, particularly when the inorganic vapor deposition layer (I) is an inorganic oxide vapor deposition layer, visibility, light transmittance, and the like can be improved. The lower limit of the average thickness of the inorganic vapor deposition layer (I) is preferably 10 nm, more preferably 20 nm, even more preferably 30 nm, and even more preferably 40 nm. By controlling the average thickness of the inorganic vapor deposition layer (I) to the above lower limit or more, barrier properties can be further improved, and, particularly when the inorganic vapor deposition layer (I) is a metal vapor deposition layer, light blocking properties can be improved. When the inorganic vapor deposition layer (I) is composed of multiple layers, the average thickness of the inorganic vapor deposition layer (I) may be the total average thickness of the multiple inorganic vapor deposition layers (I) or the average thickness of a single inorganic vapor deposition layer (I).

[0087] The inorganic vapor deposition layer (I) may consist of a single layer or multiple layers. In one embodiment, the inorganic vapor deposition layer (I) is preferably a single layer.

[0088] The inorganic vapor deposition 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, with vacuum vapor deposition being particularly preferred. The upper limit of the surface temperature of layer (X) during the formation of inorganic vapor deposition layer (I) is preferably 60°C, more preferably 55°C, and even more preferably 50°C. The lower limit of the surface temperature of layer (X) during the formation of inorganic vapor deposition layer (I) is not particularly limited, but is preferably 0°C, more preferably 10°C, and even more preferably 20°C. The exposed surface of layer (X) may be plasma-treated before film formation. The plasma treatment can be performed by a known method, with atmospheric pressure plasma treatment being 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. A known protective layer or the like may be provided on the inorganic vapor deposition layer (I) to improve flex resistance.

[0089] (Layer structure of vapor-deposited multilayer film, etc.) The vapor-deposited multilayer film of the present invention may further include layers other than layer (X), layer (Y), layer (Z), and inorganic vapor-deposited layer (I). Examples of such layers include other resin layers. It may be preferable that the vapor-deposited multilayer film does not include any layers other than layer (X), layer (Y), layer (Z), and inorganic vapor-deposited layer (I). When layer (X) is represented by X, layer (Y) by Y, layer (Z) by Z, and inorganic vapor-deposited layer (I) by I, the layer structure of the vapor-deposited multilayer film may be I / X / Y / Z, I / X / Y / Z / Y / X / I, etc., with I / X / Y / Z being preferred.

[0090] The upper limit of the average thickness of the vapor-deposited multilayer film is preferably 300 μm, more preferably 200 μm, even more preferably 100 μm, and in some cases even more preferably 70 μm, 60 μm, 50 μm, or 40 μm. Having an average thickness of the vapor-deposited multilayer film equal to or less than the above upper limit allows for a thinner film. Furthermore, the vapor-deposited multilayer film of the present invention can exhibit excellent barrier properties despite being such a thin vapor-deposited multilayer film. The lower limit of the average thickness of the vapor-deposited multilayer film is preferably 5 μm, more preferably 10 μm, even more preferably 15 μm, and in some cases even more preferably 20 μm or 25 μm. Having an average thickness of the vapor-deposited multilayer film equal to or greater than the above lower limit allows for improved barrier properties.

[0091] <Multilayer structure> The multilayer structure of the present invention comprises the above-described multilayer film or vapor-deposited multilayer film of the present invention and a layer (R).

[0092] (Layer(R)) For example, the layer (R) may be laminated on the exposed surface of the layer (X) in the multilayer film, directly or through another layer, or on the exposed surface of the layer (Z) in the multilayer film, directly or through another layer. The layer (R) may be laminated on the exposed surface of the inorganic vapor deposition layer (I) in the vapor-deposited multilayer film, directly or through another layer, or on the exposed surface of the layer (Z) in the vapor-deposited multilayer film, directly or through another layer. The layer (R) can impart various functions such as design, durability (mechanical strength), and protection of the inorganic vapor deposition layer (I). In addition, the layer (R) may function as a sealant layer. The layer (R) may be the outermost layer in the multilayer structure.

[0093] The layer (R) contains a thermoplastic resin (r) as a main component. Specific examples of the thermoplastic resin (r) are the same as those of the thermoplastic resin (z) described above. The thermoplastic resin (r) is preferably a polyolefin, more preferably polyethylene or polypropylene. From the viewpoint of recyclability, the thermoplastic resin (r) is preferably the same type of resin as the thermoplastic resin (z). For example, when the thermoplastic resin (z) is polyethylene, the thermoplastic resin (r) is preferably also polyethylene. When the thermoplastic resin (z) is polypropylene, the thermoplastic resin (r) is preferably also polypropylene.

[0094] The lower limit of the content of thermoplastic resin (r) in layer (R) is preferably 70% by mass, more preferably 80% by mass, and even more preferably 90% by mass, and may be 95%, 99%, or 99.9% by mass. The upper limit of the content of thermoplastic resin (r) in layer (R) may be 100%, 99.99%, 99.9%, or 99% by mass. Layer (R) may contain one or more optional components similar to those exemplified for layer (Z).

[0095] The layer (R) may be unstretched or stretched. That is, for example, the layer (R) may be an unstretched film or a stretched film stretched at least uniaxially. From the viewpoint of improving mechanical strength, it is preferable that the layer (R) is stretched, but from the viewpoint of improving heat sealability, it is preferable that the layer (R) is not stretched. When the layer (R) is stretched, it is preferably stretched at least uniaxially by 2 times or more but less than 12 times. The layer (R) may be stretched only uniaxially or biaxially.

[0096] The lower limit of the average thickness of the layer (R) is preferably 5 μm, more preferably 10 μm, and even more preferably 20 μm. When the average thickness of the layer (R) is equal to or greater than the above lower limit, it is possible to increase the mechanical strength of the multilayer structure, etc. The upper limit of the average thickness of the layer (R) is preferably 200 μm, more preferably 100 μm, even more preferably 50 μm, and even more preferably 30 μm. When the average thickness of the layer (R) is equal to or less than the above upper limit, it is possible to reduce the thickness of the multilayer structure, etc. When the layer (R) is composed of multiple layers, the average thickness of the layer (R) may be the total average thickness of the multiple layers (R) or the average thickness of a single layer (R).

[0097] The layer (R) may consist of a single layer or multiple layers. In one embodiment, the layer (R) is preferably a single layer.

[0098] The method for laminating the layer (R) onto the multilayer film or vapor-deposited multilayer film is not particularly limited, and can be performed by known methods such as dry lamination and extrusion lamination. The adhesive used for dry lamination is preferably a two-component reactive polyurethane adhesive in which a polyisocyanate component and a polyol component are mixed and reacted. To further enhance the barrier properties of the multilayer structure, it is also preferable to use a barrier adhesive such as "PASLIM" manufactured by DIC Corporation. It is also preferable to coat the surface of the inorganic vapor-deposited layer (I) with a topcoat agent (e.g., "MFB1002" manufactured by Michelman or "Takelac™ WPB-341" manufactured by Mitsui Chemicals, Inc.), and then laminate the film serving as the layer (R).

[0099] An adhesive layer may be formed between the multilayer film or vapor-deposited multilayer film and layer (R). The average thickness of the adhesive layer is, for example, preferably 0.5 to 5 μm, more preferably 1 to 3 μm.

[0100] (Layer structure of multilayer structure, etc.) The multilayer structure of the present invention may further include other layers as long as the effects of the present invention are not impaired. Examples of such other layers include metal foil layers and other resin layers. However, it may be preferable that the multilayer structure of the present invention does not include any layers other than the layers constituting the multilayer film or vapor-deposited multilayer film, layer (R), and adhesive layer.

[0101] The layer structure of the multilayer structure of the present invention is as follows: when the layer (X) is represented by X, the layer (Y) is represented by Y, the layer (Z) is represented by Z, the inorganic vapor deposition layer (I) is represented by I, and the layer (R) is represented by R: R / / X / Y / Z, X / Y / Z / / R, R / / X / Y / Z / / R, R / / I / X / Y / Z, R / / I / X / Y / Z / / R, R / / X / Y / Z / Y / X / / R, Examples include R / / I / X / Y / Z / Y / X / I / / R.

[0102] The upper limit of the average thickness of the multilayer structure of the present invention is preferably 300 μm, more preferably 200 μm, and even more preferably 100 μm. When the average thickness is equal to or less than the above upper limit, the multilayer structure of the present invention is lightweight and flexible, and is therefore preferably used for flexible packaging. Furthermore, the amount of resin used in the multilayer structure is small, thereby reducing the environmental impact. The lower limit of the average thickness of the multilayer structure of the present invention is preferably 10 μm, and may be 20 μm, 30 μm, 40 μm, or 50 μm.

[0103] In the multilayer structure of the present invention, from the viewpoint of recyclability, it is preferable that the content (content ratio) of polyethylene or polypropylene is high. From this viewpoint, it is preferable that the main components of Layer (Z) and Layer (R) are all polyethylene or all polypropylene. For example, the ratio of the total average thickness of layers containing polyethylene as the main component to the average thickness of the multilayer structure is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, and even more preferably 85% or more. Furthermore, the ratio of the total average thickness of layers containing polypropylene as the main component to the average thickness of the multilayer structure is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, and even more preferably 85% or more. Similarly, from the viewpoint of recyclability, the content of polyethylene or polypropylene in the multilayer structure of the present invention is preferably 80% by mass or more, and more preferably 85% by mass or more.

[0104] In particular, in the multilayer structure of the present invention, both Layer (X) and Layer (Y) contain a polymer having an ethylene unit as a main component, and therefore, when both Layer (Z) and Layer (R) contain polyethylene as a main component, each resin layer of the multilayer structure contains a resin of high quality as a main component, which improves recyclability.

[0105] <Applications of multilayer films, vapor-deposited multilayer films, and multilayer structures> The multilayer film, vapor-deposited multilayer film, and multilayer structure of the present invention can be suitably used as a packaging material. The multilayer film, vapor-deposited multilayer film, and multilayer structure may also be used for applications other than packaging. Furthermore, the multilayer film, vapor-deposited multilayer film, and multilayer structure of the present invention have high gas barrier properties and can be highly recyclable, and therefore can 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 comprising the multilayer film, vapor-deposited multilayer film, and multilayer structure of the present invention can be suitably used as packaging materials with excellent recyclability.

[0106] In the multilayer film, vapor-deposited multilayer film, and multilayer structure of the present invention, the oxygen transmission rate measured in accordance with the method described in JIS K7126-2 (isobaric method; 2006), with the side of the multilayer film on which layer (Z) is provided as the oxygen supply side, under 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, using nitrogen gas containing 2% by volume of hydrogen gas as the carrier gas, is 0.5 cc / (m 2 ·day·atm), and preferably less than 0.1cc / (m 2 ·day·atm), and more preferably less than 0.05cc / (m 2 It is more preferable that the temperature is less than 100°C / day.

[0107] The multilayer film, vapor-deposited multilayer film, and multilayer structure of the present invention preferably do not have a layer containing, as a main component, a resin with a melting point of 200°C or higher, or a metal layer with an average thickness of 1 μm or higher. In other words, Layer (X), Layer (Y), Layer (Z), and Layer (R) preferably do not contain, as a main component, a resin with a melting point of 200°C or higher. By not having a layer containing, as a main component, a resin with a melting point of 200°C or higher, or a metal layer with an average thickness of 1 μm or higher, it is possible to prevent uneven mixing with other components when a pulverized product such as a 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.

[0108] <Packaging material> The packaging material of the present invention comprises the multilayer film, vapor-deposited multilayer film, or multilayer structure of the present invention. The packaging material may consist of the multilayer film, vapor-deposited multilayer film, or multilayer structure of the present invention. The packaging material is used for packaging purposes, and its shape is not limited. The packaging material may be in the form of a sheet, or may be formed into a predetermined shape such as a bag or a tube. From the viewpoint of heat sealability, etc., it is preferable that layer (Z) or layer (R) be located as the outermost layer, and it is more preferable that the unstretched layer (Z) or unstretched layer (R) be located as the outermost layer.

[0109] The packaging material of the present invention is used for packaging, for example, foods, beverages, pharmaceuticals, industrial chemicals, agricultural chemicals, medical equipment, machine parts, clothing, etc. In particular, the packaging material is preferably used in applications requiring barrier properties against water vapor and oxygen, applications in which the interior of the packaging material is replaced with various functional gases, etc.

[0110] <Recovered composition and recycling method> It is preferable to reuse scraps (recycled materials) obtained by recovering end portions or defective products generated during the production, etc., of the multilayer film, vapor-deposited multilayer film, or multilayer structure of the present invention. In other words, a recycled composition containing recycled materials of the multilayer film, vapor-deposited multilayer film, or multilayer structure of the present invention is also a preferred embodiment of the present invention.

[0111] The recycling method of the present invention also includes a step of crushing the multilayer film, vapor-deposited multilayer film, or multilayer structure of the present invention to obtain crushed material, and a step of melt-molding a composition containing the crushed material.

[0112] In the recycling method of the present invention, first, the recovered multilayer film, vapor-deposited multilayer film, or multilayer structure (recovered multilayer film, vapor-deposited multilayer film, or multilayer structure) is crushed. The crushed material obtained by crushing, to which other components are added as needed, is the recovered composition. The other components added to the crushed material are preferably polyolefins, more preferably polyethylene or polypropylene. The recovered composition may be in a crushed state or may be in a melted state.

[0113] The recovered composition (a composition containing the recovered multilayer film, vapor-deposited multilayer film, or crushed pieces of the multilayer structure) may be directly melt-molded and used to produce a molded article. Alternatively, the recovered composition (a composition containing the recovered multilayer film, vapor-deposited multilayer film, or crushed pieces of the multilayer structure) may be melt-molded to obtain pellets of the recovered composition, and the pellets may then be used to produce a molded article.

[0114] When the multilayer film, vapor-deposited multilayer film, or multilayer structure of the present invention has a high polyethylene or polypropylene content, the recovered composition is particularly useful as a recycled material. Similarly, when the multilayer film, vapor-deposited multilayer film, or multilayer structure of the present invention has a high polyethylene or polypropylene content, it can be efficiently recycled by the above-mentioned recycling method. [Example]

[0115] The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples in any way.

[0116] (Materials used) EVOH(x) for layer(X) x-1: EVOH (ethylene unit content 44 mol%, saponification degree 99 mol%, MFR (190°C, 2.16 kg load) 1.7 g / 10 min, melting point 165°C) x-2: EVOH (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)

[0117] Copolymer (y) for layer (Y) y-1: Partially saponified EVA "MERSEN (trademark) H3051R" manufactured by Tosoh Corporation (ethylene unit content 88.9 mol%, vinyl acetate unit content 7.1 mol%, vinyl alcohol unit content 4.0 mol%, saponification degree 36 mol%, MFR (190°C, 2.16 kg load) 5.5 g / 10 min, melting point 77°C) y-2: Partially saponified EVA "MERSEN (trademark) MX13" manufactured by Tosoh Corporation (ethylene unit content 92.6 mol%, vinyl acetate unit content 6.8 mol%, vinyl alcohol unit content 0.6 mol%, saponification degree 8.1 mol%, MFR (190°C, 2.16 kg load) 2.0 g / 10 min, melting point 98°C) y-3: Partially saponified EVA "MERSEN (trademark) H6051K" manufactured by Tosoh Corporation (ethylene unit content 88.8 mol%, vinyl acetate unit content 0.3 mol%, vinyl alcohol unit content 10.9 mol%, saponification degree 97.3 mol%, MFR (190°C, 2.16 kg load) 6.2 g / 10 min, melting point 110°C) y-4: Maleic anhydride-modified polyethylene "ADMER™ NF518" manufactured by Mitsui Chemicals, Inc. (MFR (190°C, 2.16 kg load) 3.1 g / 10 min, density 0.91 g / cm 3 ) y-5: Ethylene vinyl acetate copolymer "Evaflex™ EV270" manufactured by Mitsui Dow Polychemicals Co., Ltd. (ethylene unit content 88.9 mol%, vinyl acetate unit content 11.1 mol%, saponification degree 0 mol%, MFR (190°C, 2.16 kg load) 1.0 g / 10 min, density 0.95 g / cm 3 )

[0118] Thermoplastic resin (z) for layer (Z) z-1: Low-density polyethylene "INNATE (trademark) TF80" manufactured by DOW (MFR (190°C, 2.16 kg load) 1.6 g / 10 min, melting point 124°C, density 0.926 g / cm 3 )

[0119] Thermoplastic resin film for layer (R) R1: Uniaxially oriented polyethylene film "Hibron (trademark) P" (density 0.95 g / cm) manufactured by Tokyo Ink Co., Ltd. 3 , average thickness 25 μm)

[0120] [Examples 1 to 4, Comparative Examples 1 and 2] (1) Preparation of multilayer film The materials listed in Table 1 were used to form layers (X), (Y), and (Z). Multilayer films with an average thickness and layer structure of X / Y / Z = 3 μm / 3 μm / 24 μm were produced using a three-type, three-layer cast coextrusion film production system. All extruders were single-screw extruders with a D (mm) of 30 and a full-flight screw with an L / D of 28 and a compression ratio of 3.0. A 300 mm wide feedblock lamination T-die was used. The temperature conditions used are shown below. The average thickness of the multilayer film was 30 μm, and the average thickness ratio of the layer containing polyethylene as the primary component to the average thickness of the multilayer film was 80%. Extrusion temperature of layer (X): Feeding section / Compression section / Metering section / Adapter = 175 / 220 / 220 / 220℃ Extrusion temperature of layer (Y): feeding section / compression section / metering section / adapter = 120 / 220 / 220 / 220°C Extrusion temperature of layer (Z): Feeding section / Compression section / Metering section / Adapter = 175 / 220 / 220 / 220℃ Die temperature: 220℃

[0121] (2) Appearance evaluation of multilayer film (image clarity measurement) The image clarity of the multilayer film obtained in (1) above was measured at an optical comb width of 2.0 mm. Specifically, an image clarity measuring device ("IC-T" manufactured by Suga Test Instruments Co., Ltd.) was used to measure the center position in the width direction of the multilayer film, and the average value of three measurements was calculated. Based on this average value, the appearance was judged according to the following criteria. A rating of D was considered to be poor appearance. The results are shown in Table 1. Judgment criteria A: 80% or more B: 50% or more but less than 80% C: 20% or more but less than 50% D: Less than 20%

[0122] (3) Evaluation of interlayer adhesion of multilayer films The interlayer adhesion of the multilayer film obtained in (1) above was evaluated. Specifically, the procedure was as follows: Strip-shaped test specimens measuring 200 mm in the longitudinal direction (MD) and 15 mm in the transverse direction (TD) were cut out of the obtained test specimens. The edge of the interface between layer (X) and layer (Y) was peeled off from the obtained test specimens, and the T-peel strength (gf / 15 mm) between layers (X) and (Y) was measured using a Shimadzu Autograph AGS-H under conditions of a chuck spacing of 50 mm and a pulling speed of 250 mm / min. Measurements were performed on five test specimens (test specimens centered at 10%, 25%, 50%, 75%, and 90% positions in the width direction of the multilayer film, with one end position being 0% and the other end position being 100%), and the average value was calculated. Based on the average value, the interlayer adhesion was evaluated according to the following criteria. A rating of D was considered to indicate poor interlayer adhesion. The results are shown in Table 1. Judgment criteria A:300gf / 15mm or more B: 250gf / 15mm or more and less than 300gf / 15mm C: 200gf / 15mm or more and less than 250gf / 15mm D: Less than 200gf / 15mm

[0123] (4) Preparation of vapor-deposited multilayer film An aluminum vapor-deposited layer (inorganic vapor-deposited layer (I)) having an average thickness of 50 nm was laminated on the surface of layer (X) of the multilayer film obtained in (1) above by a known vacuum vapor deposition method to prepare a vapor-deposited multilayer film.

[0124] (5) Measurement of oxygen transmission rate (OTR) of vapor-deposited multilayer film The oxygen transmission rate of the vapor-deposited multilayer film obtained in (4) above was measured in accordance with the method described in JIS K7126-2 (isobaric method; 2006) using layer (Z) as the oxygen supply side. Specifically, the oxygen transmission rate (unit: cc / (m)) was measured using an oxygen transmission rate 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. 2The gas barrier properties were evaluated based on the following criteria. Nitrogen gas containing 2% by volume of hydrogen gas was used as the carrier gas. A rating of D was determined to indicate poor gas barrier properties. The results are shown in Table 1. Judgment criteria A: 0.2cc / (m 2 ·day·atm) B: 0.2cc / (m 2 ·day · atm) or more 0.5cc / (m 2 ·day·atm) C: 0.5cc / (m 2 ·day · atm) or more 1.0cc / (m 2 ·day·atm) D: 1.0cc / (m 2 ·day · atm) or more

[0125] [Table 1]

[0126] [Example 5] (6) Fabrication of multilayer structures 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 a uniaxially oriented polyethylene film (R1) using a wire bar so that the average thickness after drying would be 2 μm. The applied film was then dried at 100°C for 5 minutes and laminated to the exposed surface of the inorganic vapor deposition layer (I) of the vapor-deposited multilayer film obtained in Example 1 to obtain a multilayer structure. The obtained multilayer structure had a layer structure with an average thickness of R / adhesive layer / I / X / Y / Z = 25 μm / 2 μm / 50 nm / 3 μm / 3 μm / 24 μm. The average thickness of the entire multilayer structure was 57 μm, and the ratio of the total average thickness of the layers containing polyethylene as the main component to the average thickness of the multilayer structure was 86%. The polyethylene content in the multilayer structure was 85% by mass. The interlayer adhesion of the obtained multilayer structure was evaluated and the oxygen transmission rate (OTR) was measured according to the methods described in (3) and (5) above. The interlayer adhesion was rated as A, and the oxygen transmission rate (OTR) was rated as B.

[0127] As shown in Table 1, the multilayer films of Examples 1 to 4 were evaluated as good in both appearance and interlayer adhesion. Each of the vapor-deposited multilayer films of Examples 1 to 4 had high gas barrier properties. The multilayer structure of Example 5 also had high interlayer adhesion and gas barrier properties. Furthermore, each of the multilayer films, vapor-deposited multilayer films, and multilayer structures of the Examples had a high polyethylene content and were excellent in recyclability.

Claims

1. A co-extruded multilayer film having a layer (X) as an outermost layer, and a layer (X), a layer (Y), and a layer (Z) directly laminated in this order, the layer (X) contains, as a main component, an ethylene-vinyl alcohol copolymer (x) having an ethylene unit content of 20 to 59 mol% and a saponification degree of 80 mol% or more; the layer (Y) contains, as a main component, a saponified ethylene-vinyl ester copolymer (y) having an ethylene unit content of 60 to 99 mol% and a saponification degree of 1 to 99 mol%, The layer (Z) contains a thermoplastic resin (z) as a main component, The average thickness is 300 μm or less, A multilayer film in which the average thickness of the layer (X) is 30 μm or less.

2. 2. The multilayer film according to claim 1, wherein the thermoplastic resin (z) is polyethylene or polypropylene.

3. 3. The multilayer film of claim 2, wherein the thermoplastic resin (z) is polyethylene.

4. The average thickness of the layer (X) is 0.2 μm or more and less than 20 μm, 4. The multilayer film according to claim 1, wherein the ratio of the average thickness of layer (X) to the average thickness of the multilayer film is less than 25%.

5. The average thickness of the layer (Y) is 0.2 μm or more and less than 20 μm, 4. The multilayer film according to claim 1, wherein the ratio of the average thickness of layer (Y) to the average thickness of the multilayer film is less than 20%.

6. The multilayer film according to any one of claims 1 to 3, which is an unstretched film.

7. The multilayer film according to any one of claims 1 to 3, which is a stretched film stretched at least uniaxially by 3 times or more but less than 12 times.

8. The multilayer film of claim 1; an inorganic vapor-deposited layer (I) which is a metal vapor-deposited layer mainly composed of aluminum or an inorganic oxide vapor-deposited layer mainly composed of alumina or silica, laminated on the exposed surface of the layer (X); A vapor-deposited multilayer film comprising:

9. The multilayer film according to claim 1 or the vapor-deposited multilayer film according to claim 8; At least one layer (R) containing a thermoplastic resin (r) as a main component, laminated on the multilayer film or the vapor-deposited multilayer film; A multilayer structure comprising:

10. 10. The multilayer structure of claim 9, wherein the thermoplastic resin (r) is polyethylene or polypropylene.

11. 10. The multilayer structure according to claim 9, wherein the content of polyethylene or polypropylene in the multilayer structure is 80% by mass or more.

12. A packaging material comprising the multilayer film according to claim 1 or the vapor-deposited multilayer film according to claim 8.

13. A recycled composition comprising a recycled multilayer film of claim 1 or a recycled vapor-deposited multilayer film of claim 8.

14. A step of crushing the multilayer film according to claim 1 or the vapor-deposited multilayer film according to claim 8 to obtain crushed material; and a step of melt-molding a composition containing the crushed material A recycling method comprising:

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