Multilayer film, vapor deposition multilayer film, multilayer structure body, packaging material, recovery composition, and recovery method of multilayer structure body

Abstract

To provide a multilayer film excellent in appearance characteristics, gas barrier characteristics, and recyclability.SOLUTION: A multilayer film has a layer (X) for an outermost layer, and a configuration laminated with the layer (X), a layer (Y), and a layer (Z) in this order. The multilayer film has no layer including a resin having a melting point of 200°C or higher as a main constituent, and no metal layer having an average thickness of 1 μm or more, where the layer (X) is a layer composed of a resin composition (A) including EVOH (a) as a main constituent, the layer (Y) includes an adhesive resin (B) having a melting point of lower than 170°C as a main constituent, the layer (Z) includes a polyolefin resin (C) having a melting point of lower than 170°C as a main constituent, and the resin composition (A) includes 40-500 ppm of an alkali metal ion (b), and exerts a specific weight phenomenon behavior in thermogravimetric measurement (TG).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a multilayer film, a vapor-deposited multilayer film, and a multilayer structure that are excellent in appearance characteristics, gas barrier properties, and recyclability, as well as a packaging material, a recovered composition, and a recovery method each using the same. [Background technology]

[0002] Packaging materials for long-term food storage are often required to have gas barrier properties, including oxygen barrier properties. By using packaging materials with high gas barrier properties, it is possible to suppress oxidative deterioration of foods caused by oxygen intrusion and the proliferation of microorganisms. Metal foils such as aluminum and metal deposition layers, and inorganic oxide deposition layers such as silicon oxide and aluminum oxide are widely used as layers that improve gas barrier properties. On the other hand, resin layers having gas barrier properties such as vinyl alcohol polymers and polyvinylidene chloride are also widely used. Vinyl alcohol polymers have the characteristic that they crystallize and become highly densified by hydrogen bonding between hydroxyl groups in the molecules, thereby exhibiting gas barrier properties. Among them, ethylene-vinyl alcohol copolymers (hereinafter sometimes abbreviated as "EVOH") are suitable for melt molding due to their excellent thermal stability, and with the development of coextrusion technology, multilayer films having an EVOH layer as an intermediate layer are widely used as gas barrier packaging materials (Patent Document 1).

[0003] In recent years, environmental and waste problems have led to a worldwide demand for so-called post-consumer recycling (hereinafter sometimes abbreviated as recycling), which involves recovering and recycling packaging materials consumed in the market. In recycling, a process is generally adopted in which the recovered packaging materials are cut, separated and washed as necessary, and then melt-mixed using an extruder. Various molded products are manufactured using the pellets thus obtained. In this regard, it is required that the packaging material be composed of a single material as much as possible (mono-materialization), which allows for the production of high-purity, high-quality recycled resin. For this purpose, there is an increasing demand for barrier films made mainly of polyolefins, which are widely used as packaging materials. For this purpose, in order to achieve extremely high gas barrier properties, a vapor-deposited multilayer film has also been proposed in which an inorganic vapor-deposited layer is laminated on the surface of the EVOH layer of a polyolefin-based multilayer film, the outermost layer of which is an EVOH layer (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2020 / 071513 issue [Patent Document 2] WO2021 / 261560 issue Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a polyolefin-based multilayer film in which an EVOH layer is the outermost layer is produced by melt molding, the EVOH, which has a high metal affinity, tends to remain inside the die, causing viscosity changes and degradation, and the EVOH also tends to expand in volume at the die exit, causing contact with the die exit, which leads to problems such as poor appearance of the resulting multilayer film. Furthermore, when an inorganic vapor deposition layer is laminated on the surface of the EVOH layer of such a multilayer film, the gas barrier properties may be insufficient.

[0006] In view of the above circumstances, a first object of the present invention is to provide a multilayer film excellent in appearance characteristics, gas barrier properties and recyclability. A second object of the present invention is to provide, by using the multilayer film, a vapor-deposited multilayer film excellent in appearance, gas barrier properties and recyclability, a multilayer structure, a packaging material containing the multilayer structure, a recovered composition containing a recovered product of the multilayer structure, and a recovery method thereof. [Means for solving the problem]

[0007] According to the present invention, the above object is to [1] A multilayer film having a structure in which a layer (X) is an outermost layer, and a layer (X), a layer (Y), and a layer (Z) are laminated adjacent to each other in this order, wherein the layer (X) is a layer made of a resin composition (A) containing, as a main component, an ethylene-vinyl alcohol copolymer (a) having an ethylene unit content of 20 to 50 mol% and a degree of saponification of 90 mol% or more, the layer (Y) contains, as a main component, an adhesive resin (B) having a melting point of less than 170°C, and the layer (Z) contains, as a main component, a polyolefin resin (C) having a melting point of less than 170°C, the resin composition (A) contains 40 to 500 ppm of an alkali metal ion (b), and the film satisfies the following condition 1, and does not have a layer containing, as a main component, a resin having a melting point of 200°C or more and a metal layer having an average thickness of 1 μm or more. (Condition 1) In thermogravimetry (TG), the weight loss W1 when held at 200°C for 30 minutes in a nitrogen atmosphere is 0.01 to 0.3%, the weight loss W2 when held at 280°C for 30 minutes in a nitrogen atmosphere is 0.5 to 9.0%, and the ratio W2 / W1 is 6 to 700; [2] The multilayer film of [1], wherein the adhesive resin (B) is an acid-modified polyethylene or an acid-modified polypropylene; [3] The multilayer film of [1] or [2], wherein the polyolefin resin (C) is polyethylene or polypropylene; [4] The multilayer film of any of [1] to [3], wherein the resin composition (A) contains 10 ppm or more and 300 ppm or less of at least one polyvalent metal ion (c) selected from the group consisting of magnesium ions, calcium ions, and zinc ions; [5] The multilayer film of any of [1] to [4], wherein the resin composition (A) contains 100 to 4,000 ppm of a higher aliphatic carboxylic acid (d) having 8 to 30 carbon atoms; [6] The multilayer film of any of [1] to [5], 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 total average thickness of all layers of the multilayer film is less than 25%; [7] The multilayer film according to any one of [1] to [6], wherein the multilayer film is not stretched; [8] The multilayer film of any one of [1] to [6], wherein the multilayer film is stretched uniaxially by 3 times or more and less than 12 times; [9] The multilayer film of any one of [1] to [6], wherein the multilayer film is stretched in each of two axial directions by a factor of 3 or more and less than 12.

[10] The multilayer film of any one of [1] to [9], in which the total average thickness ratio of layers mainly composed of a polyethylene resin or a polypropylene resin is 0.75 or more;

[11] A vapor-deposited multilayer film comprising an inorganic layer (I) on the exposed surface side of the layer (X) in the multilayer film according to any one of [1] to

[10] ;

[12] The vapor-deposited multilayer film of

[11] , wherein the inorganic layer (I) is a vapor-deposited metal layer mainly composed of aluminum or a vapor-deposited inorganic oxide layer mainly composed of alumina or silica;

[13] The oxygen transmission rate measured according to the method described in JIS K 7126-2:2006 under conditions of 20°C and 65% RH is 60cc / (m 2 any one of the multilayer films or vapor-deposited multilayer films of [1] to

[12] , wherein the thermal expansion coefficient is less than 1.0·day·atm;

[14] A multilayer structure comprising a multilayer film or a vapor-deposited multilayer film according to any one of [1] to

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

[15] The multilayer structure of

[14] , wherein the thermoplastic resin (D) is polyethylene or polypropylene;

[16]

[14] or

[15] a packaging material having a multilayer structure;

[17] A recovered composition comprising a recovered multilayer structure of

[14] or

[15] ;

[18] A method for recovering a multilayer structure comprising crushing the multilayer structure according to

[14] or

[15] and then melt-molding the same;

[19] A method for producing a multilayer film according to any one of [1] to

[10] , comprising the step of melt-molding a resin composition (A) that satisfies the following condition 1 to form a layer (X): (Condition 1) In thermogravimetry (TG), the weight loss W1 when held at 200°C for 30 minutes in a nitrogen atmosphere is 0.01 to 0.3%, the weight loss W2 when held at 280°C for 30 minutes in a nitrogen atmosphere is 0.5 to 9.0%, and the ratio W2 / W1 is 6 to 700; This is solved by providing Effect of the Invention

[0008] According to the present invention, a multilayer film having excellent appearance characteristics, gas barrier properties, and recyclability can be provided. In addition, by using the multilayer film, a vapor-deposited multilayer film having excellent appearance, gas barrier properties, and recyclability, and a multilayer structure and a packaging material using the same can be provided. In addition, since the multilayer structure has good recyclability, a recovered composition containing the recovered multilayer structure and a recovery method thereof can be provided. Here, in the present specification, "recyclability" means that when the recovered multilayer structure or packaging material of the present invention is melt-kneaded to produce a recovered composition, gelation of the resin is suppressed, and a recovered composition having excellent appearance can be efficiently produced, and can be evaluated by a defect evaluation in the recyclability evaluation described in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment 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 the embodiment using such materials. Furthermore, the exemplified materials may be used alone or in combination, unless otherwise specified.

[0010] The multilayer film of the present invention has a structure in which a layer (X) is an outermost layer, and a layer (X), a layer (Y), and a layer (Z) are laminated adjacent to each other in this order, the layer (X) being a layer made of a resin composition (A) containing, as a main component, an ethylene-vinyl alcohol copolymer (a) (hereinafter sometimes referred to as "EVOH (a)") having an ethylene unit content of 20 to 50 mol% and a degree of saponification of 90 mol% or more, the layer (Y) containing, as a main component, an adhesive resin (B) having a melting point of less than 170°C, the layer (Z) containing, as a main component, a polyolefin resin (C) having a melting point of less than 170°C, the resin composition (A) containing 40 to 500 ppm of an alkali metal ion (b), and satisfying the following condition 1, and not containing a layer containing, as a main component, a resin having a melting point of 200°C or more and a metal layer having an average thickness of 1 μm or more. (Condition 1) In thermogravimetry (TG), the weight loss W1 when held at 200°C for 30 minutes in a nitrogen atmosphere is 0.01 to 0.3%, and the weight loss W2 when held at 280°C for 30 minutes in a nitrogen atmosphere is 0.5 to 9.0%, and the ratio W2 / W1 is 6 to 700.

[0011] EVOH (a) has excellent gas barrier properties, and the multilayer film of the present invention having layer (X) as the outermost layer can achieve high gas barrier properties. In addition, the resin composition (A) containing EVOH (a) as the main component shows a specific range of weight loss at 200°C and 280°C under a nitrogen atmosphere. These weight losses reflect the low molecular weight components contained in the resin composition (A) and the decomposition characteristics of EVOH (a) due to heat, and by using the resin composition (A) that satisfies these requirements, a multilayer film with excellent appearance properties can be obtained over a long period of time. Furthermore, since both the layer (Y) and the layer (Z) contain a resin having a melting point of less than 170°C as the main component, and the polyolefin resin (C) contained in the layer (Z) and EVOH (a) can be easily melt-mixed, the multilayer film of the present invention having a structure in which the layer (X), layer (Y), and layer (Z) are laminated adjacent to each other in this order is easy to recycle. In this case, the resin composition (A) contains 40 to 500 ppm of alkali metal ions (b) to exhibit even better recyclability.

[0012] In this specification, "layer (X), layer (Y), and layer (Z) are stacked adjacent to each other in this order" means that adjacent layers are directly stacked, and specifically means that layer (X), layer (Y), and layer (Z) are stacked in this order, layer (X) and layer (Y) are directly stacked, and layer (Y) and layer (Z) are directly stacked. "Major component" means a component that is contained in an amount of more than 50% by mass. The "average thickness" of each layer, etc., refers to the average value of thicknesses measured at any five points, unless otherwise specified. "ppm" means the content by mass (ppm by mass). "Polyethylene" means 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 non-olefin monomers whose functional groups contain atoms other than carbon, oxygen, and hydrogen atoms. "Polypropylene" refers to homopolymers of propylene, copolymers of 80 mol % or more propylene and 20 mol % or less α-olefin monomers, and copolymers 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. The term "acid-modified polyethylene" refers to a polymer obtained by modifying polyethylene with an acid. The acid-modified polyethylene may be a polymer in which at least one of an acid group and an acid anhydride group is introduced into polyethylene. The term "acid-modified polypropylene" refers to a polymer obtained by modifying polypropylene with an acid. The acid-modified polypropylene may be a polymer in which at least one of an acidic group and an acid anhydride group is introduced into polypropylene. "Polyethylene resin" refers to polyethylene and modified polyethylene (acid-modified polyethylene, etc.). Modified polyethylene refers to a polymer obtained by modifying polyethylene. "Polypropylene-based resin" refers to polypropylene and modified polypropylene (acid-modified polypropylene, etc.). Modified polypropylene refers to a polymer obtained by modifying polypropylene. In addition, the term "surface (or surface layer)" in a multilayer film or a multilayer structure does not mean to distinguish between the front and back, but refers to the exposed surface. In other words, a multilayer film or a multilayer structure has two surfaces. Similarly, a multilayer film or a multilayer structure has two outermost layers. In this specification, "consists essentially of" means that optional components may be contained within a range that does not affect the effects of the present invention, and "consists only of" means that optional components other than impurities that are inevitably contained are excluded.

[0013] <Resin composition (A) and layer (X)> The multilayer film constituting the multilayer film of the present invention has, as its outermost layer, a layer (X) 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 and containing 40 to 500 ppm of alkali metal ions (b), and satisfying the following condition 1: (Condition 1) In thermogravimetry (TG), the weight loss W1 when held at 200°C for 30 minutes in a nitrogen atmosphere is 0.01 to 0.3%, and the weight loss W2 when held at 280°C for 30 minutes in a nitrogen atmosphere is 0.5 to 9.0%, and the ratio W2 / W1 is 6 to 700.

[0014] <EVOH(a)> EVOH(a) is usually 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%. When the ethylene unit content is 20 mol% or more, the melt moldability of EVOH(a) and the pulverized product of a multilayer film or multilayer structure containing EVOH(a) is improved. 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, when the ethylene unit content is 50 mol% or less, the gas barrier property of the multilayer film of the present invention is improved. 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 means 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 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. The ethylene unit content and saponification degree of EVOH (a) are as follows: 1 It can be determined by H-NMR measurement.

[0015] EVOH (a) may be a mixture of two or more EVOHs 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 EVOHs having different saponification degrees. In this case, the difference in saponification degree between the EVOHs having the most different ethylene unit contents is preferably 7% or less, more preferably 5% 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 preferable to mix 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 with 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 and use the mixture as EVOH (a).

[0016] EVOH (a) may be EVOH (a') having a melting point of less than 150°C. When the melting point of EVOH (a') is less than 150°C, the appearance and interlayer adhesion of a multilayer film having a layer (X) mainly composed of EVOH (a') as the outermost layer may be improved. The reason for this is that the melting point of EVOH (a') is less than 150°C, which improves the fluidity of the polymer chain, and therefore stress can be effectively relieved even at a relatively low temperature during secondary processing such as melt molding and stretching, and the adhesive reaction activity with adjacent layers can be maintained. From the viewpoint of making the effects of the present invention more prominent, the melting point of EVOH (a') is preferably less than 140°C, more preferably less than 130°C, and may be less than 125°C or less than 120°C. On the other hand, from the viewpoint of processability during secondary processing such as melt molding and stretching, and from the viewpoint of heat resistance as a packaging material, the melting point of EVOH (a') is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher. The melting point of EVOH (a') can be controlled by one or a combination of the following methods, and in the present invention, the following method (3) can be preferably used. (1) Changing the ethylene unit content (increasing the ethylene unit content decreases the melting point) (2) Change the degree of saponification (lowering the degree of saponification lowers the melting point) (3) Introducing a modifying group containing a primary hydroxyl group (introducing a modifying group containing a primary hydroxyl group lowers the melting point.

[0017] The primary hydroxyl group-containing modifying group used in (3) is preferably a primary hydroxyl group-containing modifying 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 to be introduced, but when 1 mol % of the primary hydroxyl group-containing modifying group represented by the following general formula (I) is introduced, the melting point generally decreases by about 6 to 9°C. When the melting point is controlled by this method, the melting point can be reduced while relatively maintaining the gas barrier property and thermal stability, and the decrease in interlayer adhesion with the layer (Y) and inorganic layer (I) described later is also suppressed, so that a multilayer film with particularly excellent quality and performance can be provided. The reason for this is considered to be that the melting point can be reduced while maintaining the amount of hydroxyl groups, and that the primary hydroxyl group has high adhesive reaction activity with the layer (Y) and inorganic layer (I) described later. The content of the modifying group containing a primary hydroxyl group in EVOH (a') may be appropriately adjusted in consideration of the balance between the melting point and various physical properties, but a content of 2 mol% or more and less than 20 mol% often leads to 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. [ka] [wherein X is a hydrogen atom, a methyl group or R 2 R represents a group represented by -OH. 1 ,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.

[0018] 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. 1 is 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.

[0019] EVOH (a) may contain other monomer units other than ethylene units, vinyl ester units, vinyl alcohol units, and the modifying group containing the primary hydroxyl group, as long as the effects of the present disclosure are not impaired. The content of other monomer 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 such other monomers include α-olefins such as propylene, n-butene, isobutylene, and 1-hexene; acrylic acid and its salts; unsaturated monomers having an acrylic acid ester group; methacrylic acid and its salts; unsaturated monomers having a methacrylic acid 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 ethers such as acrylonitrile, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, 2,3-diacetoxy-1-vinyloxypropane, and the like; vinyl cyanides such as acrylonitrile, methacrylonitrile, and the like; vinyl halides such as vinyl chloride, vinyl fluoride, and the like; vinylidene halides such as vinylidene chloride, vinylidene fluoride, and the like; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane, and allyl chloride, and the like; unsaturated dicarboxylic acids and salts or esters thereof such as maleic acid, itaconic acid, and fumaric acid, and the like; vinyl silane compounds such as vinyltrimethoxysilane, and the like; isopropenyl acetate, 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyronyloxy-2-methylenepropane, and the like.

[0020] 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, even more preferably 5 g / 10 min or less, and particularly preferably 3 g / 10 min or less. When the MFR of EVOH(a) is in the above range, the melt moldability of EVOH(a) and the pulverized product of the multilayer film and multilayer structure containing EVOH(a) is improved.

[0021] <Alkali metal ion (b)> The resin composition (A) contains 40 to 500 ppm of alkali metal ion (b). When the resin composition (A) contains the alkali metal ion (b) in the above range, the interlayer adhesion with the layer (Y) described later tends to be significantly improved. If the alkali metal ion (b) is less than 40 ppm, the resin composition (A) is likely to thicken during melt molding, causing appearance defects such as gels and bumps, and the interlayer adhesion with the layer (Y) described later may decrease. On the other hand, if the alkali metal ion (b) is more than 500 ppm, the resin composition (A) may decompose excessively during melt molding, or coloring may become a problem. In addition, in the multilayer structure of the present invention, if the content of the alkali metal ion (b) is less than 40 ppm, gelation of the resin cannot be suppressed when melt-kneading the recovered multilayer structure or packaging material to produce a recovered composition, and recyclability is deteriorated. On the other hand, if the content of the alkali metal ion (b) exceeds 500 ppm, when the recovered multilayer structure or packaging material is melt-kneaded to produce a recovered composition, an excessive decomposition reaction occurs in the resin, and recyclability is deteriorated. From this viewpoint, the lower limit of the content of the alkali metal ion (b) is preferably 80 ppm, more preferably 120 ppm. The upper limit of the content of the alkali metal ion (b) is preferably 400 ppm, more preferably 300 ppm. In addition, by controlling the content ratio of the alkali metal ion (b) to the carboxylic acid described later, the melt moldability and coloring resistance of the obtained resin composition (A) can be further improved.

[0022] 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, by using potassium ions, the hue of the resin composition (A) and the interlayer adhesion with the layer (Y) described below can be simultaneously achieved at a high level, and recyclability also tends to be improved. These may be used alone or in combination of two or more.

[0023] Examples of the alkali metal compound that gives 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 they are easily available and easy to handle. As the aliphatic carboxylates, acetates, caprylates, and stearates are preferred.

[0024] <Polyvalent metal ions (c)> The resin composition (A) preferably contains at least one polyvalent metal ion (c) selected from the group consisting of magnesium ions, calcium ions, and zinc ions in an amount of 10 ppm or more and 300 ppm or less. When the polyvalent metal ion (c) is contained in an amount of 10 ppm or more, the resin composition (A) tends to be able to suppress appearance defects such as thickening and the generation of gels or bumps during melt molding. On the other hand, when the content of the polyvalent metal ion (c) is 300 ppm or less, the resin composition (A) tends to be able to suppress excessive decomposition and coloration during melt molding. In addition, in the multilayer structure of the present invention, the crosslinking reaction of the resin may progress during recycling, causing thickening and gelation, but when the multilayer structure of the present invention 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 the polyvalent metal ion (c) is 300 ppm or less, the resin composition tends to suppress the occurrence of defects during recycling while suppressing the deterioration of the hue during recycling. From this viewpoint, the content of the polyvalent metal ion (c) is preferably 20 ppm or more and 200 ppm or less, more preferably 30 ppm or more and 150 ppm or less. The resin composition (A) preferably contains magnesium ions or calcium ions as the polyvalent metal ions (c), more preferably magnesium ions. In addition, by controlling the content ratio of the polyvalent metal ions (c) and the carboxylic acid described later, the melt moldability and coloring resistance of the obtained resin composition (A) can be further improved.

[0025] 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 they are easily available and easy to handle. As aliphatic carboxylates, acetates, caprylates, and stearates are preferred.

[0026] <Higher aliphatic carboxylic acids (d)> The resin composition (A) preferably contains 100 to 4000 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 may be contained 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 of the present invention has a layer (X) made of the resin composition (A) as the outermost layer, and it is considered that the higher aliphatic carboxylic acid (d) acts as a lubricant with the die metal surface in the die, thereby suppressing the occurrence of poor appearance due to uneven thickness of the multilayer film and gels and bumps 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, the resin composition (A) tends to be prevented from thickening during melt molding, and to maintain interlayer adhesion with the layer (Y) described below. From these viewpoints, the content of the higher aliphatic carboxylic acid (d) is more preferably from 200 to 3000 ppm, and further preferably from 300 to 2500 ppm.

[0027] The resin composition (A) may contain other components other than 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, polyvalent carboxylic acids) other than higher aliphatic carboxylic acids (d), thermoplastic resins other than EVOH (a), phosphoric acid compounds, boron compounds, oxidation promoters, antioxidants (hindered phenol compounds, etc.), plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorants, ultraviolet absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, bulking agents, pigments, dyes, processing aids, flame retardants, antifogging agents, etc. From the viewpoint of suppressing coloring when melt-molding the pulverized product of the 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, the melt viscosity of the pulverized product of the resin composition (A) and the multilayer structure containing the resin composition (A) can be controlled.

[0028] <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 good. 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.

[0029] The pKa of the carboxylic acid is preferably 3.5 to 5.5. When the pKa of the carboxylic acid is within the above range, the pH buffering ability of the resulting resin composition (A) is increased, and the melt moldability is further improved, and coloring due to acidic or basic substances can be further improved.

[0030] The carboxylic acid may be a monovalent carboxylic acid. These may be used alone or in combination of two or more. The monovalent carboxylic acid is a compound having one carboxyl group in the molecule. Examples of monovalent carboxylic acids having a pKa in the range of 3.5 to 5.5 include, but are not limited to, 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 them, acetic acid is preferred because of its high safety and ease of availability and handling.

[0031] The carboxylic acid may be a polycarboxylic acid. When the carboxylic acid is a polycarboxylic acid, the coloring resistance of the resin composition (A) at high temperatures and the coloring resistance of the melt-molded product of the crushed product of the multilayer structure obtained may be further improved. The polycarboxylic acid compound preferably has three or more carboxyl groups. In this case, the coloring resistance may be more effectively improved. The polycarboxylic acid is a compound having two or more carboxyl groups in the molecule. In this case, it is preferable that the pKa of at least one carboxyl group is in the range of 3.5 to 5.5, and examples of the polycarboxylic acid 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, pKa 2=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.

[0032] <Phosphate compounds> The resin composition (A) may further contain a phosphoric acid compound. The lower limit of the content of the phosphoric acid compound is preferably 5 ppm in terms of phosphoric acid radicals. On the other hand, the upper limit of the content of the phosphoric acid compound is preferably 100 ppm in terms of phosphoric acid radicals. By containing the phosphoric acid compound in this range, coloration of the resulting resin composition (A) and the melt-molded product of the pulverized product of the resulting multilayer structure may be suppressed, and thermal stability may be improved.

[0033] As the phosphoric acid 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 cationic species of the phosphate is not particularly limited, but the cationic species is preferably an alkali metal or an alkaline earth metal. Among them, as the phosphoric acid compound, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate are preferred.

[0034] <Boron compounds> The resin composition (A) may further contain a boron compound. When the resin composition (A) contains a boron compound, the lower limit of the content in the resin composition (A) is preferably 50 ppm, more preferably 100 ppm, calculated as boron element. 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, calculated as boron element. By containing the boron compound in this range, the thermal stability of the resin composition (A) and the pulverized product of the resulting multilayer structure during melt molding may be improved, and the occurrence of gels and bumps 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 molded product may be improved. It is presumed that these effects are due to the occurrence of a chelate interaction between the EVOH (a) and the boron compound.

[0035] Examples of boron compounds include boric acid, boric acid esters, borate salts, and boron hydrides.Specific examples include boric acids such as orthoboric acid (H3BO3), metaboric acid, and tetraboric acid; boric acid esters such as trimethyl borate and triethyl borate; alkali metal salts or alkaline earth metal salts of the boric acid, and borate salts such as borax.Of these, orthoboric acid is preferred.

[0036] <Hindered phenol compounds> The resin composition (A) may further contain a hindered phenol-based compound as an antioxidant. When the resin composition (A) contains a hindered phenol-based compound, the content of the hindered phenol-based compound in the resin composition (A) is preferably 1000 to 10000 ppm. When the content is 1000 ppm or more, coloring, thickening, and gelation of the resin can be suppressed when the pulverized product of the multilayer structure is melt-molded. The content of the hindered phenol-based compound is more preferably 2000 ppm or more. On the other hand, when the content of the hindered phenol-based compound is 10000 ppm or less, coloring and bleeding out derived from the hindered phenol-based compound can be suppressed. The content of the hindered phenol-based compound is more preferably 8000 ppm or less.

[0037] The hindered phenol compound has at least one hindered phenol group. The hindered phenol group refers to a bulky substituent bonded to at least one carbon atom adjacent to the carbon atom bonded to the hydroxyl group of phenol. The bulky substituent is preferably an alkyl group having 1 to 10 carbon atoms, more preferably a t-butyl group.

[0038] The hindered phenol compound is preferably in a solid state around room temperature. From the viewpoint of suppressing bleeding 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. In addition, 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.

[0039] 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.

[0040] Specific examples of the structure of the hindered phenol compound 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)stearylpropionate 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 include octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate, which is commercially available; ethylene bis(oxyethylene) bis(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'-hexamethylene bis[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.

[0041] The resin composition (A) may further contain a thermoplastic resin other than EVOH (a). Examples of the thermoplastic resin other than EVOH (a) include various polyolefins (polyethylene, polypropylene, poly1-butene, poly4-methyl-1-pentene, ethylene-propylene copolymers, copolymers of ethylene and α-olefins having 4 or more carbon atoms, copolymers of polyolefins and maleic anhydride, ethylene-vinyl ester copolymers, ethylene-acrylic acid ester copolymers, or modified polyolefins obtained by graft-modifying these with unsaturated carboxylic acids or their derivatives, etc.), various polyamides (nylon 6, nylon 6·6, nylon 6 / 66 copolymers, 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, etc. The content of the thermoplastic resin in the resin composition (A) is usually less than 40 mass%, preferably less than 30 mass%, more preferably less than 20 mass%, even more preferably less than 10 mass%, may be less than 5 mass% or even less than 1 mass%, and it is particularly preferable that it is substantially absent.

[0042] The proportion of EVOH (a) in the resin constituting the 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, and particularly preferably 95% by mass or more, from the viewpoint of more prominently exhibiting the effects of the present invention, the resin constituting the resin composition (A) may be substantially only EVOH (a), or the resin constituting the resin composition (A) may be only EVOH (a). The proportion of EVOH (a) in the resin composition (A) is more than 50% by mass, and from the viewpoint of more prominently exhibiting the effects of the present invention, it 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, or it may be 98% by mass or more, or 99% by mass or more, and the resin composition (A) may be substantially only EVOH (a) and alkali metal ions (b).

[0043] The resin composition (A) must satisfy the following condition 1 in thermogravimetry (TG), and the layer (X) is preferably a layer formed by melt molding the resin composition (A) that satisfies the following condition 1. (Condition 1) In thermogravimetry (TG), the weight loss W1 when held at 200°C for 30 minutes in a nitrogen atmosphere is 0.01 to 0.3%, and the weight loss W2 when held at 280°C for 30 minutes in a nitrogen atmosphere is 0.5 to 9.0%, and the ratio W2 / W1 is 6 to 700.

[0044] The weight losses W1 and W2 reflect the decomposition characteristics of the EVOH (a) due to low molecular weight components contained in the resin composition (A) and heat, and since the layer (X) is made of the resin composition (A) that satisfies the condition 1, a multilayer film having excellent appearance characteristics can be stably produced over a long period of time. From the viewpoint of stable production of a multilayer film having better appearance characteristics, the weight loss W1 when held at 200°C for 30 minutes in a nitrogen atmosphere is preferably 0.02 to 0.15, more preferably 0.03 to 0.10, and even more preferably 0.04 to 0.08. From the viewpoint of stable production of a multilayer film having better appearance characteristics, the weight loss W2 when held at 280°C for 30 minutes in a nitrogen atmosphere is preferably 1.0 to 7.0, more preferably 1.5 to 6.0, and even more preferably 2.0 to 5.0. Furthermore, the ratio W2 / W1 is preferably 10 to 350, more preferably 15 to 200, and even more preferably 25 to 125. W1, W2 and the ratio W2 / W1 can be controlled by the ethylene unit content and degree of saponification of EVOH (a), the types and contents of alkali metal ions (b), polyvalent metal ions (c), higher aliphatic carboxylic acids (d) and other components contained in resin composition (A), and the production conditions (particularly thermal history such as temperature and time) when producing resin composition (A).

[0045] The method for producing the resin composition (A) is not particularly limited, but it can be produced by melt-kneading EVOH (a) and alkali metal ions (b), and other components such as polyvalent metal ions (c) and higher aliphatic carboxylic acids (d) as necessary. Each component may be blended in a solid state such as powder, or as a melt, or may be blended as a solute contained in a solution or a dispersoid contained in a dispersion. As the solution and dispersion, an aqueous solution and an aqueous dispersion are preferable, respectively. For melt-kneading, a known mixing or kneading device such as a kneader-ruder, an extruder, a mixing roll, or a Banbury mixer can be used. The temperature range during melt-kneading can be appropriately adjusted depending on the melting points of the EVOH (a) and each component used, and is usually 150 to 250°C. In addition, the resin composition (A) may be produced by adding some components to EVOH (a) in advance and then melt-kneading other components required as described above. An example of a method for adding some components to EVOH (a) in advance is a method in which EVOH (a) is immersed as pellets or powder in a solution in which the added components are dissolved. The solution is preferably an aqueous solution.

[0046] <Adhesive resin (B) and layer (Y)> The multilayer film of the present invention has a layer (Y) containing an adhesive resin (B) having a melting point of less than 170°C as a main component. By including the layer (Y) in the multilayer film of the present invention, a multilayer film having excellent appearance and interlayer adhesion tends to be obtained. In addition, by including the layer (Y), the compatibility between the layer (X) and the layer (Z) is improved during recycling, so that the recyclability tends to be improved. Examples of the adhesive resin (B) include acid-modified polyolefins obtained by using an acid to obtain a polyolefin, and more specifically, carboxylic acid-modified polyolefin resins obtained by graft-polymerizing an unsaturated carboxylic acid such as maleic anhydride or a derivative thereof to a polyolefin resin. The melting point of the adhesive resin (B) mainly depends on the polyolefin resin before the carboxylic acid modification. The contents described for the polyolefin resin (C) described later can be applied as they are to the polyolefin resin, but the adhesive resin (B) is preferably an acid-modified polyethylene or an acid-modified polypropylene.

[0047] The proportion of the acid-modified polyolefin resin 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 may be substantially composed of the acid-modified polyolefin resin alone, or may be composed of the acid-modified polyolefin resin alone. The proportion of the adhesive resin (B) in the layer (Y) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 95% by mass or more, and may be substantially composed of the adhesive resin (B) alone, or may be composed of the adhesive resin (B) alone.

[0048] <Polyolefin resin (C) and layer (Z)> The multilayer film of the present invention has a layer (Z) containing a polyolefin resin (C) having a melting point of less than 170°C as a main component. The polyolefin resin (C) is not particularly limited as long as it is a polyolefin having a melting point of less than 170°C, 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 such as homopolypropylene, random polypropylene, and block polypropylene; vinyl ester resins; ethylene-propylene copolymers; propylene-α-olefin copolymers (α-olefins having 4 to 20 carbon atoms); olefins such as polybutene and polypentene, or copolymers thereof; and chlorinated polyethylene. From the viewpoint of improving the recyclability of the multilayer structure containing the polyolefin resin (C), the polyolefin resin (C) preferably contains a polyethylene-based resin or a polypropylene-based resin as a main component, more preferably polyethylene or polypropylene, and even more preferably polyethylene. Since polyethylene-based resins and polypropylene-based resins are widely used in packaging materials regardless of whether they have gas barrier properties or not, recycling infrastructures for them have been widely established in various countries. When the polyolefin resin (C) contains polyethylene as a main component, the polyethylene is preferably at least one selected from linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene, and more preferably at least one selected from linear low-density polyethylene and low-density polyethylene, or a mixture of at least one selected from linear low-density polyethylene and low-density polyethylene and high-density polyethylene.

[0049] From the viewpoint of making the effects of the present invention more remarkable, the melting point of the polyolefin resin (C) is preferably less than 160 ° C, more preferably less than 150 ° C, and may be less than 140 ° C or less than 130 ° 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 resin (C) is preferably 80 ° C or more, more preferably 90 ° C or more. In addition, from the viewpoint of improving melt moldability, the melt flow rate (MFR) (190 ° C, under a load of 2160 g) of the polyolefin resin (C) measured in accordance with the method described in JIS K7210 (2014) is preferably 0.1 to 30 g / 10 min, more preferably 0.3 to 25 g / 10 min, and even more preferably 0.5 to 20 g / 10 min.

[0050] When the polyolefin resin (C) contains a polyethylene resin or a polypropylene resin as a main component, the content of the polyethylene resin or the polypropylene resin in the polyolefin resin (C) is more preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 95% by mass or more, and the polyolefin resin (C) may be substantially composed of only a polyethylene resin or a polypropylene resin, or the polyolefin resin (C) may be substantially composed of only a polyethylene resin or a polypropylene resin. The proportion of the polyolefin resin (C) in the layer (Z) 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 layer (Z) may be substantially composed of only a polyolefin resin (C), or the layer (Z) may be substantially composed of only a polyolefin resin (C).

[0051] The layers (Y) and (Z) contain adhesive resin (B) and polyolefin resin (C) as main components, respectively, but these layers may contain other components such as antioxidants, plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorants, 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, 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% by mass, less than 3% by mass, or less than 1% by mass, relative to each layer.

[0052] <Multilayer film> The multilayer film constituting the multilayer film of the present invention has a layer (X) as the outermost layer, and has a structure in which at least layer (X), layer (Y), and layer (Z) are laminated adjacent to each other in this order. The multilayer film may have a plurality of layers each of layer (X), layer (Y), and layer (Z). Examples of the layer structure of the multilayer film of the present invention include X / Y / Z, X / Y / Z / Y / X, X / Y / Z / Y / X / Y / Z / Y / X / Y / Z / Y / X, etc., where layer (X) is represented by X, layer (Y) is represented by Y, and layer (Z) is represented by Z, and " / " indicates that they are directly laminated.

[0053] From the viewpoints of gas barrier properties, recyclability, and economic efficiency, the average thickness of the layer (X) 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 layer (X) to the total average thickness of the multilayer film is less than 25%. The average thickness of the layer (X) 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 layer (X) to the total average thickness of the multilayer film is more preferably less than 20%, and even more preferably less than 15%. The ratio of the average thickness of the layer (X) to the total average thickness of the multilayer film may be 1% or more.

[0054] From the viewpoints of interlayer adhesion, recyclability, and economic efficiency, the average thickness of the layer (Y) 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 layer (Y) to the total average thickness of the multilayer film is less than 25%. The average thickness of the layer (Y) 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 layer (Y) to the total average thickness of the multilayer film is more preferably less than 20%, and even more preferably less than 15%. The ratio of the average thickness of the layer (Y) to the total average thickness of the multilayer film may be 1% or more.

[0055] From the viewpoint of recyclability, the average thickness of the layer (Z) 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 layer (Z) to the total average thickness of the multilayer film is more than 55%. The average thickness of the layer (Z) is more preferably 5 μm or more, more preferably 10 μm or more, and may be 20 μm or more. The average thickness of the layer (Z) is more preferably 100 μm or less, and may be 50 μm or less. The ratio of the average thickness of the layer (Z) to the total average thickness of the multilayer film is more preferably more than 60%, and more preferably more than 70%. The ratio of the average thickness of the layer (Z) to the total average thickness of the multilayer film may be 98% or less. 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 described later, the average thickness of the stretched multilayer film is preferably 10 μm or more and less than 50 μm, and more preferably 10 μm or more and less than 40 μm.

[0056] The multilayer film may be a non-stretched multilayer film, or may be a stretched multilayer film stretched uniaxially or biaxially (at least uniaxially). The non-stretched multilayer film means a multilayer film that is not stretched, but some orientation during film formation (for example, orientation as if stretched 1.01 times) is considered to be unstretched. In addition, a uniaxially stretched multilayer film that is stretched only in a uniaxial direction is considered to be uniaxially stretched, ignoring some orientation in the other axial direction during film formation (for example, orientation as if stretched 1.01 times). In the case of a non-stretched multilayer film, it has excellent impact resistance and can be suitably used as a heat-sealed film. On the other hand, by stretching in a uniaxial or biaxial direction, the mechanical properties and gas barrier properties of the resulting multilayer film can be improved. From the viewpoint of economy and ease of tearing the multilayer film (ease of opening the packaging material when used as a packaging material), the multilayer film is preferably a uniaxially stretched multilayer film, and from the viewpoint 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 viewpoint of uniformity of thickness and mechanical strength of the obtained multilayer film, it is preferable that the multilayer film is stretched at least 3 times and less than 12 times in one axial direction. In the case of a uniaxially stretched multilayer film, it is preferably stretched 3 times or more and less than 12 times in one axial direction, and more preferably stretched 4 times or more and less than 10 times. In addition, in the case of a uniaxially stretched multilayer film, the stretching axis is preferably the flow direction (MD direction) or a direction perpendicular to the flow direction, that is, the width direction (TD direction), and more preferably the flow direction (MD direction). In the case of a biaxially stretched multilayer film, it is preferably stretched 3 times or more and less than 12 times in each of the two axial directions, and more preferably stretched 4 times or more and less than 10 times.

[0057] The method for producing the multilayer film is not particularly limited, but generally, a conventional coextrusion method in which each resin is extruded from a separate die or a common die and laminated can be used. As the die, either a circular die or a T-die can be used. The method for stretching in the uniaxial or biaxial direction is also not particularly limited, and the film can be produced by stretching in the flow direction and / or the direction perpendicular to the flow direction, i.e., the width direction, by a conventionally known stretching method such as roll-type uniaxial stretching, tubular-type simultaneous biaxial stretching, tenter-type sequential biaxial stretching, and tenter-type simultaneous biaxial stretching. Among them, the effect of the present invention is particularly remarkable in the case of a multilayer film produced by tenter-type sequential biaxial stretching. From the viewpoint of processability, the temperature during stretching is usually 40 to 170°C, and more preferably 50 to 160°C. If necessary, it is preferable to perform a so-called heat setting operation by heating at a temperature equal to or higher than the glass transition point and lower than the melting point after the stretching process to increase the crystallinity and fix the orientation of the molecular chains.

[0058] The method for producing the multilayer film of the present invention preferably includes a step of melt-molding a resin composition (A) that satisfies the following condition 1 to form a layer (X). The resin temperature during melt-molding of the resin composition (A) is preferably controlled in a temperature range 10 to 50° C. higher than the melting point of EVOH (a). (Condition 1) In thermogravimetry (TG), the weight loss W1 when held at 200°C for 30 minutes in a nitrogen atmosphere is 0.01 to 0.3%, and the weight loss W2 when held at 280°C for 30 minutes in a nitrogen atmosphere is 0.5 to 9.0%, and the ratio W2 / W1 is 6 to 700. By including the above steps, the appearance of the obtained multilayer film tends to be good.

[0059] In the production method having a step of melt-molding a resin composition (A) satisfying the condition 1 to form a layer (X), it is preferable that the resin composition (A) satisfying the condition 1 is a resin composition (A) pellet obtained by melt-kneading EVOH (a) and an alkali metal ion (b), and, if necessary, other components such as a polyvalent metal ion (c) and a higher aliphatic carboxylic acid (d).

[0060] <Inorganic layer (I)> The multilayer film of the present invention may be a vapor-deposited multilayer film having an inorganic layer (I) on the surface side of the layer (X) of the multilayer film. The inorganic layer (I) is preferably laminated directly or via another layer such as an adhesive layer on the surface side of the layer (X) of the multilayer film, and is preferably laminated directly on the surface side of the layer (X). The inorganic layer (I) means a layer made of an inorganic material such as a metal or an inorganic oxide and having gas barrier properties against oxygen and water vapor. The layer (X) has a higher affinity with metals and inorganic oxides than ordinary thermoplastic resins, and can form a dense inorganic layer (I) without defects, and the interlayer adhesion between the layer (X) and the inorganic layer (I) in the obtained multilayer film is good. In addition, since the layer (X) has gas barrier properties, even when defects occur in the inorganic layer (I) due to bending or the like, the 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 is stable 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.

[0061] The inorganic layer (I) is preferably an inorganic vapor deposition layer, and is preferably either a metal vapor deposition layer containing aluminum as a main component or an inorganic oxide vapor deposition layer containing alumina or silica as a main component. A metal vapor deposition layer is preferable when light-shielding properties are to be imparted, but an inorganic oxide vapor deposition layer is preferable from the viewpoints of visibility of the contents as a packaging material, suitability for use in a microwave oven, and suppression of the generation of gels and lumps when pulverized materials are melt-molded. In addition, an inorganic oxide vapor deposition layer is preferable from the viewpoint of suppressing coloration during recycling of the multilayer structure of the present invention.

[0062] The metal deposition layer is a layer containing aluminum as a main component. The content of aluminum atoms in the metal 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 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 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 deposition layer is the average thickness at any 10 points on the cross section of the metal deposition layer measured by an electron microscope. When the multilayer film of the present invention has a metal deposition layer, the light transmittance at a wavelength of 600 nm can be 10% or less, and the light shielding property is excellent.

[0063] In the metal deposition layer mainly composed of aluminum, oxidation inevitably occurs, and aluminum oxide may be contained in some parts. In the metal deposition layer mainly composed of aluminum (inorganic deposition layer (B)), 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.

[0064] The inorganic oxide deposition layer may be a deposition film of an inorganic oxide, such as an oxide of silicon, aluminum, magnesium, calcium, potassium, tin, sodium, boron, titanium, lead, zirconium, or yttrium, preferably alumina or silica. The average thickness of the inorganic oxide deposition 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 deposition 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 deposition layer is the average value of the thicknesses at any 10 points on the cross section of the inorganic oxide deposition layer measured by an electron microscope. When the multilayer film of the present invention has an inorganic oxide deposition layer, the light transmittance at a wavelength of 600 nm can be 80% or more, and the visibility of the contents when used as a packaging material is excellent. From the viewpoint of further improving the 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 the unevenness in the thickness of the multilayer film used in the production of the multilayer film. An example of a method for further suppressing unevenness in the thickness of the multilayer film is stretching the film in at least one axial direction. The multilayer film preferably has a light transmittance of 80% or more at a wavelength of 600 nm, and more preferably has a light transmittance of 90% or more.

[0065] The inorganic layer (I) can be formed by a known physical vapor deposition method or chemical vapor deposition method. Specifically, examples of the method include vacuum vapor deposition, sputtering, ion plating, ion beam mixing, plasma CVD, laser CVD, MO-CVD, and thermal CVD. It is preferable to use a physical vapor deposition method, and particularly preferable to use a vacuum vapor deposition method. The upper limit of the surface temperature of the layer (X) 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 layer (X) 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. Before the film formation, the exposed surface of the layer (X) may be plasma-treated. The plasma treatment can be performed by a known method, and atmospheric pressure plasma treatment is preferable. In the atmospheric pressure plasma treatment, nitrogen, helium, neon, argon, krypton, xenon, radon, etc. are used as a discharge gas. Among these, nitrogen, helium and argon are preferably used, and nitrogen is particularly preferred because it can reduce costs.

[0066] <Protective layer (P)> The vapor-deposited multilayer film of the present invention may have a protective layer (P) on the exposed surface side of the inorganic layer (I) of the vapor-deposited multilayer film. The protective layer (P) is preferably laminated directly on the inorganic layer (I). That is, the layer structure is preferably such that the layer (X), the inorganic layer (I) and the protective layer (P) are laminated directly in this order. The protective layer (P) has the effect of improving the stability of the gas barrier property of the multilayer structure by suppressing the deterioration of the barrier property in a converting process such as printing or lamination. The protective layer (P) itself does not need to have gas barrier property, but it is preferable that it has gas barrier property.

[0067] The protective layer (P) may be made of a composition containing at least one metal compound selected from the group consisting of metal alkoxides, hydrolysates of metal alkoxides, and hydrolysis condensates of metal alkoxides, and a water-soluble resin. The metal alkoxide is a compound represented by the general formula: 3 n M(OR 4 ) m(In the formula, M is a metal atom, R 3 , R 4 is an organic group having 1 to 8 carbon atoms, n is 0 or more, m is an integer of 1 or more, and n+m represents the atomic valence of M), and at least one of these metal alkoxides, partial hydrolysates of metal alkoxides, or hydrolyzed condensates of metal alkoxides can be used. 3 n M(OR 4 ) m In the formula, the metal atom represented by M may be silicon, zirconium, titanium, aluminum, etc., and is preferably silicon. These alkoxides may be used alone or in the form of a mixture of two or more different metal atoms in the same solution.

[0068] organic group R 3 Specific examples of the organic group R include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, n-hexyl, and n-octyl. 4 Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a sec-butyl group, etc. These alkyl groups may be the same or different in the same molecule.

[0069] Among alkoxides, alkoxysilanes in which M is silicon (Si) are preferred, and the alkoxysilanes are represented by Si(ORa)4, where Ra is a lower alkyl group, such as a methyl group, an ethyl group, an n-propyl group, or an n-butyl group. Specific examples of alkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. In addition, alkylalkoxysilanes Rb m Si(ORc) 4-mcan be used (m is an integer of 1, 2, or 3). Methyl groups, ethyl groups, and the like are used as Rb and Rc, and specific examples of alkylalkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, and dimethyldiethoxysilane. These alkoxysilanes and alkylalkoxysilanes can be used alone or in combination of two or more. Furthermore, condensation polymers of alkoxysilanes can also be used, and specific examples include polytetramethoxysilane, polytetraethoxysilane, and the like.

[0070] Two or more of these alkoxides may be mixed and used. In particular, by using an alkoxysilane and a zirconium alkoxide in a mixture, the toughness, heat resistance, etc. of the resulting protective layer (P) may be improved. In the present invention, a silane coupling agent may be used in combination with the above alkoxide. As the silane coupling agent, a known organoalkoxysilane containing an organic reactive group may be used. In particular, an organoalkoxysilane having an epoxy group or an amino group is suitable. Examples of such silane coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-aminopropyltrimethoxysilane, and γ-aminopropyltriethoxysilane. Two or more of these silane coupling agents may be mixed and used. The amount of such silane coupling agent used is within the range of 0.1 to 20 parts by weight based on 100 parts by weight of the above alkoxysilane.

[0071] Examples of the water-soluble resin include resins having hydroxyl groups such as polyvinyl alcohol and poly(2-hydroxyethyl methacrylate), resins having carboxyl groups such as polyacrylic acid and carboxymethyl cellulose, resins having amino groups such as polyallylamine and polyethyleneimine, resins having amide groups such as polyacrylamide, poly N,N-dimethylacrylamide and poly N-isopropylacrylamide, resins having sulfonic acid groups such as polystyrene sulfonic acid and polyvinyl sulfonic acid, resins having polyether groups such as polyethylene oxide and polyethylene glycol, and polyvinylpyrrolidone, polyoxazoline, etc. Among the water-soluble resins mentioned above, polymers having hydrogen bond groups are preferred, water-soluble resins having hydroxyl groups, polyamides, polyethers, polyvinylpyrrolidone, polyoxazoline, etc. are more preferred, water-soluble resins having hydroxyl groups are even more preferred, and polyvinyl alcohol is particularly preferred. The polyvinyl alcohol may be one or more compounds selected from the group consisting of copolymers containing vinyl alcohol units such as ethylene-vinyl alcohol copolymers. These may be used alone or in combination of two or more.

[0072] The polyvinyl alcohol may be a homopolymer of vinyl alcohol or a copolymer containing other monomer units. The saponification degree is preferably closer to 100% from the viewpoint of gas barrier properties, but is usually 90% or more, preferably 95% or more. The number average polymerization degree is usually 50 or more and 5000 or less.

[0073] In the composition of the protective layer (P), the ratio of at least one metal compound selected from the group consisting of metal alkoxides, hydrolysates of metal alkoxides, and hydrolyzed condensates of metal alkoxides to the water-soluble resin is preferably 55 / 45 to 95 / 5, more preferably 65 / 35 to 90 / 10, and even more preferably 75 / 25 to 85 / 15. When a resin composition of a hydrolyzed condensate of a metal alkoxide and a water-soluble resin is used as the protective layer (P), it is particularly preferable that the resin composition contains a hydrolyzed condensate of a silane alkoxide and polyvinyl alcohol.

[0074] When the protective layer (P) is a layer made of the above-mentioned resin composition, the proportion of the total mass of the metal compound and the water-soluble resin in the protective layer (P) is preferably 80 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and particularly preferably 99 mass% or more, and the protective layer (P) may essentially consist of only the metal compound and the water-soluble resin.

[0075] In the present invention, the protective layer (P) made of the above composition is specifically laminated, for example, as follows. First, a coating liquid is prepared by mixing a metal alkoxide, a water-soluble resin, a sol-gel catalyst, an acid, water, an organic solvent, etc. Here, hydrolysis and polycondensation reactions of the metal alkoxide gradually proceed in the above coating liquid. Next, the above coating liquid can be applied and dried by a conventional method on the exposed surface side of the inorganic layer (I) to laminate it.

[0076] The protective layer (P) may be made of a composition containing a polyurethane resin as a main component. The protective layer (P) containing a polyurethane resin as a main component tends to have a small adverse effect on recyclability and to produce a high-quality recovered resin. The urethane resin is preferable because the polar group of the urethane bond interacts with the inorganic layer (I) and has flexibility due to the presence of amorphous parts, so that damage to the inorganic layer (I) can be suppressed even when dimensional changes or bending loads are applied. The acid value of the urethane resin is preferably within the range of 10 to 60 mgKOH / g. More preferably, it is within the range of 15 to 55 mgKOH / g, and further preferably, it is within the range of 20 to 50 mgKOH / g. When the acid value of the urethane resin is within the above range, the liquid stability is improved when it is made into an aqueous dispersion, and the protective layer (P) can be uniformly laminated on the inorganic layer (I), so that the appearance is good. In addition, the glass transition temperature (Tg) of the urethane resin is preferably 80°C or higher, and more preferably 90°C or higher. By setting the Tg at 80° C. or higher, the deterioration of the gas barrier properties of the multilayer film during the converting process can be efficiently suppressed.

[0077] From the viewpoint of improving gas barrier properties, it is more preferable to use a urethane resin containing an aromatic or araliphatic diisocyanate component as a main component. Here, the "component" in relation to the urethane resin means the structural unit (structural component) that constitutes the urethane resin. Among them, it is particularly preferable to include a urethane resin containing a metaxylylene diisocyanate component. By using the above resin, the cohesive force of the urethane bond can be further increased due to the stacking effect between aromatic rings, resulting in good gas barrier properties.

[0078] In the present invention, the ratio of aromatic or araliphatic diisocyanate in the urethane resin is preferably in the range of 50 mol% or more (50 to 100 mol%) in 100 mol% of the polyisocyanate component. The total amount of aromatic or araliphatic diisocyanate is preferably 60 to 100 mol%, more preferably 70 to 100 mol%, and even more preferably 80 to 100 mol%. As such a resin, the "Takelac (registered trademark) WPB" series commercially available from Mitsui Chemicals, Inc. can be suitably used. When the total amount of aromatic or araliphatic diisocyanate is 50 mol% or more, the protective layer (P) itself tends to exhibit good gas barrier properties.

[0079] From the viewpoint of improving the affinity with the inorganic layer (I), the urethane resin preferably has a carboxylic acid group (carboxyl group). In order to introduce a carboxylic acid (salt) group into the urethane resin, for example, a polyol compound having a carboxylic acid group, such as dimethylolpropionic acid or dimethylolbutanoic acid, may be introduced as a copolymerization component as a polyol component. In addition, after synthesizing the urethane resin containing a carboxylic acid group, the urethane resin in a water dispersion can be obtained by neutralizing it with a salt forming agent. Specific examples of the salt forming agent include ammonia, trialkylamines such as trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, and tri-n-butylamine, N-alkylmorpholines such as N-methylmorpholine and N-ethylmorpholine, and N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These may be used alone or in combination of two or more.

[0080] In the present invention, the protective layer (P) made of the above composition can be laminated on the exposed surface of the inorganic layer (I) by applying and drying a coating liquid which is an aqueous solution or dispersion of a urethane resin by a conventional method.

[0081] The protective layer (P) of the present invention may contain a crosslinking agent, another polymer, a tackifier, inorganic particles, a pigment, a dye, etc., in order to further improve the performance depending on the purpose.

[0082] As the crosslinking agent, a crosslinking agent having self-crosslinking properties, a compound having a plurality of reactive functional groups in the molecule, a metal having a polyvalent coordination site, etc. can be used.Specific examples include oxazoline group-containing compounds, isocyanate group-containing compounds, epoxy group-containing compounds, carbodiimide group-containing compounds, melamine compounds, urea compounds, zirconium salt compounds, silane coupling agents, etc., and a plurality of them may be mixed and used as necessary.Among them, from the viewpoint of ease of handling, oxazoline group-containing compounds, isocyanate group-containing compounds, and epoxy group-containing compounds are preferred.

[0083] The oxazoline group-containing compound is not particularly limited as long as it has at least two or more oxazoline groups in the molecule. For example, compounds having oxazoline groups such as 2,2'-bis(2-oxazoline), 2,2'-ethylene-bis(4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis(2-oxazoline), and bis(2-oxazolinylcyclohexane)sulfide, and oxazoline group-containing polymers can be mentioned. One or more of these can be used. Among these, oxazoline group-containing polymers are preferred because of their ease of handling.

[0084] The oxazoline group-containing polymer can be obtained by polymerizing an addition-polymerizable oxazoline such as 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, or 2-isopropenyl-2-oxazoline. The oxazoline group-containing polymer may be copolymerized with other monomers as necessary. The polymerization method of the oxazoline group-containing polymer is not particularly limited, and any known polymerization method can be used.

[0085] Commercially available oxazoline group-containing polymers include the Epocross series manufactured by Nippon Shokubai Co., Ltd., such as the water-soluble types "WS-500" and "WS-700" and the emulsion types "K-1010E", "K-1020E", "K-1030E", "K-2010E", "K-2020E", and "K-2030E".

[0086] The isocyanate group-containing compound is not particularly limited as long as it has at least two or more isocyanate groups in the molecule. For example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane 2,4'- or 4,4'-diisocyanate, polymethylene polyphenyl diisocyanate, tolidine diisocyanate, 1,4-diisocyanatobutane, hexamethylene diisocyanate, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3- or 1,4-diisocyanatocyclohexane, 1- ... Examples of the isocyanate compounds include polyfunctional isocyanate compounds such as isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane, 4,4'-diisocyanatodicyclohexylmethane, hexahydrotoluene 2,4- or 2,6-diisocyanate, perhydro-2,4'- or 4,4'-diphenylmethane diisocyanate, naphthalene 1,5-diisocyanate, xylylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and tetramethylxylylene diisocyanate, or modified products thereof. Here, the modified product is obtained by modifying a diisocyanate of a polyfunctional isocyanate compound by a known method, and examples thereof include polyfunctional isocyanate compounds having an allophanate group, a biuret group, a carbodiimide group, a uretonimine group, a uretdione group, an isocyanurate group, and an adduct type polyfunctional isocyanate compound modified with a polyfunctional alcohol such as trimethylolpropane. The isocyanate group-containing compound may contain monoisocyanate in an amount of 20% by mass or less. In addition, one or more of these can be used.

[0087] The isocyanate group-containing compound can usually be obtained by reacting a polyfunctional isocyanate compound with a mono- or poly-hydric nonionic polyalkylene ether alcohol. Examples of commercially available aqueous polyfunctional isocyanate compounds include Bayhydur 3100, Bayhydur VPLS2150 / 1, SBU Isocyanate L801, Desmodur N3400, Desmodur VPLS2102, Desmodur VPLS2025 / 1, SBU Isocyanate 0772, and Desmodur DN, all manufactured by Sumitomo Bayer Urethane Co., Ltd.; Takenate WD720, Takenate WD725, and Takenate WD730, all manufactured by Takeda Pharmaceutical Co., Ltd.; Duranate WB40-100, Duranate WB40-80D, and Duranate WX-1741, all manufactured by Asahi Kasei Corporation; and Basonat HW-100 and Basonat LR-9056, all manufactured by BASF.

[0088] The epoxy group-containing compound is not particularly limited as long as it has at least two or more epoxy groups in the molecule. For example, glycidyl ether type such as bisphenol A diglycidyl ether, bisphenol A β-dimethylglycidyl ether, bisphenol F diglycidyl ether, tetrahydroxyphenylmethane tetraglycidyl ether, resorcinol diglycidyl ether, brominated bisphenol A diglycidyl ether, chlorinated bisphenol A diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, diglycidyl ether of bisphenol A alkylene oxide adduct, novolac glycidyl ether, polyalkylene glycol diglycidyl ether, glycerin triglycidyl ether, pentaerythritol diglycidyl ether, and epoxy urethane resin; glycidyl ether ester type such as p-oxybenzoic acid glycidyl ether ester; phthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, Examples of the epoxy resin include glycidyl esters such as diglycidyl hexahydrophthalate, diglycidyl acrylic acid, and diglycidyl dimer acid; glycidyl amines such as glycidyl aniline, tetraglycidyl diaminodiphenylmethane, triglycidyl isocyanurate, and triglycidyl aminophenol; linear aliphatic epoxy resins such as epoxidized polybutadiene and epoxidized soybean oil; and alicyclic epoxy resins such as 3,4-epoxy-6 methylcyclohexylmethyl-3,4-epoxy-6 methylcyclohexane carboxylate, 3,4-epoxycyclohexylmethyl (3,4-epoxycyclohexane) carboxylate, bis(3,4-epoxy-6 methylcyclohexylmethyl) adipate, vinylcyclohexene diepoxide, dicyclopentadiene oxide, bis(2,3-epoxycyclopentyl) ether, and limonene dioxide. One or more of these may be used.

[0089] Examples of commercially available epoxy group-containing compounds that are suitable for the present invention include the Denacol series (EX-313, EM-150, EM-101, etc.) manufactured by Nagase ChemteX Corporation and the Adeka Resin series (EM-0517, EM-0526, EM-11-50B, EM-051R) manufactured by ADEKA Corporation.

[0090] The melamine compound is not particularly limited as long as it has a melamine skeleton in the molecule. For example, an alkylolated melamine derivative, a compound obtained by reacting an alkylolated melamine derivative with an alcohol to partially or completely etherify it, and a mixture thereof can be used. As the alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol, etc. are preferably used. In addition, the melamine compound may be either a monomer or a polymer of dimer or more, or a mixture thereof may be used.

[0091] Commercially available melamine compounds include, for example, Cymel 323, Cymel 325, Cymel 327, Cymel 328, and Cymel 370 manufactured by Nippon Cytec Industries Co., Ltd.

[0092] The carbodiimide group-containing compound is not particularly limited as long as it has at least two or more carbodiimide groups in the molecule. For example, compounds having a carbodiimide group such as p-phenylene-bis(2,6-xylylcarbodiimide), tetramethylene-bis(t-butylcarbodiimide), cyclohexane-1,4-bis(methylene-t-butylcarbodiimide), and polycarbodiimide, which is a polymer having a carbodiimide group, can be mentioned. One or more of these can be used. Among these, polycarbodiimide is preferable because of its ease of handling. Examples of commercially available polycarbodiimide products include the Carbodilite series manufactured by Nisshinbo Corporation. Specific examples of products include water-soluble types "SV-02", "V-02", "V-02-L2", and "V-04", emulsion types "E-01" and "E-02", organic solution types "V-01", "V-03", "V-07", and "V-09", and solvent-free type "V-05".

[0093] The content of the crosslinking agent is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, and even more preferably 0.5 to 10 parts by mass, relative to 100 parts by mass of the polyurethane resin, from the viewpoint of improving the heat resistance or water resistance of the coating film. When the content of the crosslinking agent is 0.01 part by mass or more, the coating film performance of the protective layer (P) is improved, and when it is 80 parts by mass or less, the coating stability of the protective layer (P) may be improved. From the viewpoint of the recyclability of the multilayer structure of the present invention, it may be preferable that the protective layer (P) does not contain a crosslinking agent.

[0094] Other polymers and tackifiers are not particularly limited. For example, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester-maleic anhydride copolymer, styrene-maleic acid resin, styrene-butadiene resin, butadiene resin, acrylonitrile-butadiene resin, poly(meth)acrylonitrile resin, (meth)acrylamide resin, chlorinated polyethylene resin, chlorinated polypropylene resin, polyester resin, modified nylon resin, tackifier resin such as rosin, phenol resin, silicone resin, epoxy resin, etc. may be mentioned, and a plurality of them may be mixed and used as necessary. Note that these polymers may be used in the solid form, but from the viewpoint of maintaining stability in the coating liquid, it is preferable to use those processed into an aqueous dispersion.

[0095] 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, from the viewpoint of stability in the coating liquid. A mixture of multiple inorganic particles may 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.

[0096] Examples of pigments and dyes include titanium oxide, zinc oxide, carbon black, etc. Any of disperse dyes, acid dyes, cationic dyes, reactive dyes, etc. can be used. The protective layer (P) of the present invention can further contain various chemicals such as leveling agents, defoamers, anti-popping agents, pigment dispersants, ultraviolet absorbers, thickeners, weather resistance agents, and flame retardants, if necessary.

[0097] When the protective layer (P) contains a urethane resin, the proportion of the urethane resin in the protective layer (P) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more, and the protective layer (P) may be substantially composed of only the urethane resin. When the protective layer (P) contains a urethane resin and a crosslinking agent, the proportion of the total mass of the urethane resin and the crosslinking agent in the protective layer (P) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more, and the protective layer (P) may be substantially composed of only the urethane resin and the crosslinking agent.

[0098] From the viewpoints of gas barrier properties, recyclability, and economic efficiency, when the vapor-deposited multilayer film has a protective layer (P), the average thickness of the protective layer (P) 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 further preferably 0.6 μm or more and less than 1.5 μm.

[0099] The lower limit of the total average thickness ratio of the layers mainly composed of a polyethylene resin or a polypropylene resin in the 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 total average thickness ratio of the layers mainly composed of a polyethylene resin or a polypropylene resin in the multilayer film, the recyclability can be improved. The upper limit of the total average thickness ratio of the layers mainly composed of a polyethylene resin or a polypropylene resin in the multilayer film is preferably 0.995, more preferably 0.99, and may be 0.98. Examples of the layer mainly composed of a polyethylene resin or a polypropylene resin include a layer (Y) when the adhesive resin (B) is, for example, an acid-modified polyethylene or an acid-modified polypropylene, and a layer (Z) when the polyolefin resin (C) is polyethylene or polypropylene. It is preferable that the adhesive resin (B) and the polyolefin resin (C) are the same type of resin. For example, when the adhesive resin (B) is an acid-modified polyethylene, it is preferable that the polyolefin resin (C) is polyethylene, and when the adhesive resin (B) is an acid-modified polypropylene, it is preferable that the polyolefin resin (C) is polypropylene.

[0100] The multilayer film of the present invention does not have a layer containing a resin having a melting point of 200° C. or more as a main component, and a metal layer having an average thickness of 1 μm or more. In other words, the layers (X), (Y) and (Z) do not contain a resin having a melting point of 200° C. or more as a main component. By not having a layer containing a resin having a melting point of 200° C. or more as a main component and a metal layer having an average thickness of 1 μm or more, it is possible to prevent the pulverized product of the multilayer film from being mixed with other components in a non-uniform manner when the product is melt-molded. Here, the metal layer refers to a layer having continuous and discontinuous surfaces made of metal, such as aluminum foil.

[0101] The multilayer film or vapor-deposited multilayer film of the present invention has an oxygen transmission rate (under conditions of 20°C and 65% RH) of 60 cc / (m2) measured in accordance with the method described in JIS K 7126-2 (isobaric method; 2006). 2 ·day·atm), and preferably less than 10cc / (m 2·day·atm), and more preferably less than 3cc / (m 2 ·day·atm), and more preferably less than 0.5cc / (m 2 A multilayer film having an oxygen transmission rate in the above range has excellent gas barrier properties.

[0102] <Multilayer structure> The multilayer film or vapor-deposited 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 (D) 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 (D) is not particularly limited, 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), polybutene, polypentene, and other olefins alone or 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 them, polyolefin is preferred from the viewpoint of excellent moisture resistance, mechanical properties, economical efficiency, heat sealability, etc., and polyamide and polyester are preferred from the viewpoint of excellent mechanical properties, heat resistance, etc. In order to obtain a multilayer structure with particularly excellent recyclability, the thermoplastic resin (D) is preferably the same as the above-mentioned polyolefin resin (C). For example, when the polyolefin resin (C) is polyethylene, it is preferably polyethylene, and when the polyolefin resin (C) is polypropylene, it is preferably polypropylene. In addition, the thermoplastic resin (D) is preferably a polyolefin resin having a melting point of less than 170 ° C., more preferably contains a polyethylene-based resin or a polypropylene-based resin as a main component, further preferably polyethylene or polypropylene, and particularly preferably polyethylene. Therefore, in order to obtain a multilayer structure with excellent recyclability, the polyolefin resin (C) and the thermoplastic resin (D) are preferably contained as a polyethylene-based resin or a polypropylene-based resin as a main component, more preferably polyethylene or polypropylene, and further preferably polyethylene.The resin layer (R) may be unstretched, or may be uniaxially or biaxially stretched or rolled. From the viewpoint of improving mechanical strength, it is preferably a biaxially stretched layer, and from the viewpoint of improving heat sealability, it is preferably a unstretched layer.

[0103] The method for forming the resin layer (R) is not particularly limited, but it is generally formed by melt extrusion using an extruder. As the die, either a circular die or a T-die can be used. The method for stretching in the uniaxial or biaxial direction is also not particularly limited, and the film can be produced by stretching in the flow direction of the film and / or the direction perpendicular to the flow direction, i.e., in the width direction, by a conventionally known stretching method such as roll-type uniaxial stretching, tubular-type simultaneous biaxial stretching, tenter-type sequential biaxial stretching, and tenter-type simultaneous biaxial stretching. The stretching ratio is preferably 8 to 60 times in area from the viewpoint of the uniformity of the thickness of the obtained layer and mechanical strength. The area ratio is more preferably 55 times or less, and even more preferably 50 times or less. 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 easily break during stretching.

[0104] 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 a non-oriented layer, and more preferably 10 to 50 μm in the case of a biaxially oriented layer.

[0105] The average thickness of the multilayer structure of the present invention is preferably 300 μm or less. With the average thickness in the above range, the multilayer structure of the present invention is lightweight and flexible, and is therefore preferably used for soft packaging. In addition, the amount of resin used in the multilayer structure is small, and the environmental load is suppressed.

[0106] 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 coloration during melt molding of the pulverized material, improving thermal stability during melt molding, and suppressing the generation of bumps, at least one of the layer (Z) and the resin layer (R) contains a polyethylene resin or a polypropylene resin as a main component, and the ratio of the total average thickness of the layers containing a polyethylene resin or a polypropylene 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, more preferably 0.995, and may be 0.993.

[0107] The method of laminating the resin layer (R) on the multilayer film of the present invention is not particularly limited, and examples thereof include extrusion lamination, coextrusion lamination, dry lamination, etc. When laminating the resin layer (R) on the multilayer film, an adhesive layer may be provided. In addition, each layer constituting the multilayer structure of the present invention may be laminated via an adhesive layer as necessary. However, there is no adhesive layer between the layer (X) and the layer (Y) of the multilayer film and between the layer (Y) and the layer (Z). The adhesive layer can be formed by applying a known adhesive and drying it. The adhesive is preferably a two-liquid 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.

[0108] The multilayer structure of the present invention is not particularly limited, and from the viewpoint of obtaining a multilayer structure excellent in recyclability, for example, the following layer structure is preferable. In the following layer structure, layer (X) is expressed as X, layer (Y) as Y, layer (Z) as Z, inorganic layer (I) as I, and layer (R) as R, and " / " means that they are directly laminated, and " / / " means that they are laminated via an adhesive layer or directly laminated, but it is a preferred embodiment that they are laminated via an adhesive layer. (1) Z / Y / X / I / / R (2) R / Z / Y / X / I / R In the above layer structure, the layer (X), the layer (Y) and the layer (Z) are preferably stretched at least uniaxially, and more preferably biaxially. The layer (Z) and the layer (R) are preferably polyethylene-based resin or polypropylene-based resin, and the layer (Y) is preferably maleic anhydride-modified polyethylene-based resin or maleic anhydride-modified polypropylene-based resin. In addition, when recycling the packaging material of the present invention, it is preferable that both outermost layers of the multilayer structure of the present invention have a layer containing a polyethylene-based resin or a polypropylene-based resin as a main component so that the pulverized product obtained by pulverizing the packaging material can be recovered as a polyethylene-based resin or a polypropylene-based resin. That is, when the resin layer (R) is arranged on both outermost layers, the resin layer (R) is preferably a layer containing a polyethylene-based resin or a polypropylene-based resin as a main component, and when the layer (Z) and the resin layer (R) are arranged on both outermost layers, the layer (Z) and the resin layer (R) are preferably a layer containing a polyethylene-based resin or a polypropylene-based resin as a main component. It is preferable that one of the outermost layers is a non-stretched layer, and in some cases it is preferable that the other is a layer that is stretched at least in one direction, from the viewpoint of obtaining a multilayer structure that has both heat sealability and mechanical properties.

[0109] The multilayer structure of the present invention may have layers other than those described above, as long as the effects of the present invention are not impaired. Examples of the other layers include a recovery layer. In particular, it is preferable to reuse a recovery composition containing the recovered material of the multilayer structure of the present invention described below as a part or all of the recovery layer. Another example of the other layer is, for example, a printed layer. The printed layer may be included at 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, if necessary, a binder resin, and drying it. Examples of the coating method of the printed layer include gravure printing and various coating methods using a wire bar, a spin coater, a die coater, etc. The average thickness of the ink layer is not particularly limited, but is preferably 0.5 to 10 μm, more preferably 1 to 4 μm.

[0110] It is preferable to reuse scraps (ends or defective products) that are recovered during the production of the multilayer structure of the present invention. A method for recovering the multilayer structure of the present invention by crushing the multilayer structure of the present invention and then melt-molding it, and a recovered composition containing the recovered multilayer structure of the present invention are also preferred embodiments of the present invention.

[0111] When recovering the multilayer structure of the present invention, the recovered multilayer structure of the present invention is first pulverized. The pulverized recovered material may be melt-molded as it is to obtain a recovered composition, or may be melt-molded together with other components as necessary to obtain a recovered composition. A preferred component to be added to the recovered material is a polyolefin resin, and a polyethylene-based resin or a polypropylene-based resin is more preferred. As the polyolefin resin, the same type of polyolefin resin (C) as described above for use in the multilayer film of the present invention is used. The pulverized recovered material may be directly used to produce a molded product such as a multilayer structure, or the pulverized recovered material may be melt-molded to obtain pellets of the recovered composition, and the pellets may then be used to produce a molded product.

[0112] In the recovered composition, the mass ratio of the resin composition (A) to the polyolefin resin [resin composition (A) / polyolefin resin] is preferably 0.01 / 99.99 to 20 / 80. If the mass ratio is less than 0.01 / 99.99, the usage ratio of the recovered material may decrease. On the other hand, if the mass ratio exceeds 20 / 80, the melt moldability and mechanical properties of the recovered composition may decrease. From the viewpoint of improving the melt moldability and mechanical properties of the obtained recovered composition, the mass ratio is more preferably 15 / 85 or less, further preferably 10 / 90 or less, and may be 5 / 95 or less.

[0113] The multilayer structure of the present invention has excellent appearance, gas barrier properties, and recyclability, and can therefore be suitably used as a material for various types of packaging, such as food packaging, pharmaceutical packaging, industrial chemical packaging, agricultural chemical packaging, and vacuum insulation boards. In particular, a packaging material comprising the multilayer structure of the present invention can be suitably used as a packaging material with excellent recyclability. EXAMPLES

[0114] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples in any way.

[0115] Example 1 (1) Preparation of EVOH (a)-containing resin composition (A) for layer (X) EVOH (a-1) (ethylene unit content 32 mol%, saponification degree 99.99 mol%, MFR (190 ° C, 2.16 kg load) 1.6 g / 10 min, melting point 183 ° C, volatile content 0.8%, sodium acetate 180 ppm in terms of sodium ion, phosphate ion 30 ppm in terms of phosphate radical, boric acid 150 ppm in terms of boron element, polyvalent metal ion not included) and magnesium stearate were melt-kneaded so that the content of magnesium ions in the resulting resin composition was 50 ppm, and resin composition (A) pellets for layer (X) were obtained. The extruder used for melt-kneading was a twin-screw extruder with D (mm) = 25, and a co-directional fully intermeshing screw with L / D = 30 was used. A mixing zone consisting of a feed type kneading disc, a neutral type kneading disc, and a return type kneading disc was placed in the middle of the screw, and a vacuum vent was placed downstream of the zone. The resin temperature was set to 240°C. (2) Thermogravimetry (TG) of Resin Composition (A) Pellets Using the obtained resin composition (A) pellets, thermogravimetry (TG) was carried out under the conditions of 1) holding at 200° C. for 30 minutes in a nitrogen atmosphere, and 2) holding at 280° C. for 30 minutes in a nitrogen atmosphere. The results are shown in Table 1.

[0116] (3) Resin composition containing adhesive resin (B) for layer (Y) Maleic anhydride modified polyethylene "ADMER (trademark) NF518" manufactured by Mitsui Chemicals Inc. (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) was used as it was as the adhesive resin (B) and as the resin composition pellets for layer (Y).

[0117] (4) Polyolefin resin (C)-containing resin composition for layer (Z) DOW's low-density polyethylene "INNATE (trademark) TF80" (MFR (190°C, 2.16 kg load) 1.6 g / 10 min, melting point 124°C, density 0.926 g / cm 3 ) was used as it was as the polyolefin resin (C) and as the resin composition pellets for layer (Z).

[0118] (5) Preparation of multilayer film Using each of the resin composition pellets obtained in (1), (3) and (4) above, a multilayer film having an average thickness and layer structure of (X) / (Y) / (Z)=4μm / 4μm / 32μm=EVOH4 / Tie4 / PE32 was produced using a co-extrusion film-forming facility. All extruders were single-screw extruders with D(mm)=30, and full-flight screws with L / D=28 and compression ratio of 3.0 were used. As the die, a 350mm wide feed block lamination type T die was used. The temperature conditions at this time are shown below. Extrusion temperature of resin composition (A): feeding section / compression section / metering section / adapter=175 / 220 / 220 / 220°C Extrusion temperature of adhesive resin (B)-containing resin composition: feeding section / compression section / metering section / adapter=175 / 220 / 220 / 220° C. Extrusion temperature of the resin composition containing polyolefin resin (C): feeding section / compression section / metering section / adapter=175 / 220 / 220 / 220°C Die temperature: 220℃ Cooling roll temperature: 80℃

[0119] (6) Appearance evaluation of multilayer films The above-mentioned (5) multilayer film was continuously produced for 6 hours, and the appearance of the multilayer film was visually evaluated 1 hour and 6 hours after the start, and judged according to the following criteria. When the evaluation was E, the appearance characteristics were judged to be poor. The results are shown in Table 1. Judgment criteria A: No changes in appearance were observed 1 hour and 6 hours after starting. B: A slight increase in defects, streaks, or both was observed 6 hours after the start of treatment compared to 1 hour after the start of treatment. C: A slight increase in defects, streaks, or both was observed 6 hours after the start of treatment compared to 1 hour after the start of treatment. D: A moderate increase in defects, streaks, or both was observed 6 hours after the start of treatment compared to 1 hour after the start of treatment. E: Compared to 1 hour after the start, 6 hours later, there was a significant increase in defects, streaks, or both.

[0120] (7) Oxygen permeability of multilayer film For the multilayer film obtained in (5) above, the oxygen transmission rate was measured in accordance with the method described in JIS K 7126-2 (isobaric method; 2006) with layer (Z) as the oxygen supply side. 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 temperature 20°C, humidity 65% ​​RH on the oxygen supply side, humidity 65% ​​RH on the carrier gas side, oxygen pressure 1 atm, and carrier gas pressure 1 atm. 2 The gas barrier properties were evaluated according to the following criteria. Nitrogen gas containing 2% by volume of hydrogen gas was used as the carrier gas. If the evaluation was E, it was determined that the gas barrier properties were poor. The results are shown in Table 1. Judgment criteria A: 1cc / (m 2 ·day·atm) B: 1cc / (m 2 ·day · atm) or more, 3cc / (m 2 ·day·atm) C: 3cc / (m 2 ·day · atm) or more, 10cc / (m 2 ·day·atm) D: 10cc / (m 2 ·day · atm) or more, 60cc / (m 2 ·day·atm) E: 60cc / (m 2 ·day · atm) or more

[0121] (8) Fabrication of multilayer structures A two-liquid reactive polyurethane adhesive (24 parts by mass of "Takelac (trademark) A-520" and 4 parts by mass of "Takenate (trademark) A-50" manufactured by Mitsui Chemicals, Inc.) was mixed with 37 parts by mass of ethyl acetate to prepare an adhesive solution. Next, one side of a polyethylene film (resin layer (R)) having an average thickness of 50 μm was corona-treated by a known method, and the adhesive solution was applied to the corona-treated surface with a wire bar so that the average thickness after drying was 2 μm, and then dried at 100 ° C. for 5 minutes and laminated with the multilayer film obtained in (5) above to produce a multilayer structure having an average thickness and layer structure of (R) / adhesive / (X) / (Y) / (Z) = 50 μm / 2 μm / 4 μm / 4 μm / 32 μm. The adhesion temperature (heat roll temperature) during lamination was 80 ° C., and then aging was performed at 40 ° C. for 3 days.

[0122] (9) Evaluation of coloring and recyclability of multi-layer structures The multilayer structure obtained in (8) above was crushed to a size of 4 mm square or less, and the crushed product was mixed with low-density polyethylene (LDPE) "Novatec (trademark) LD LJ400" (MFR (190°C, 2.16 kg load) 1.5 g / 10 min, melting point 111°C, density 0.921 g / cm) manufactured by Japan Polyethylene Co., Ltd. 3 ) was dry-blended in a mass ratio (recycled material / low-density polyethylene) of 50 / 50, and a monolayer film was formed under the extrusion conditions shown below to obtain a monolayer film (recycled material) with an average thickness of 100 μm. As a control, a monolayer film with an average thickness of 100 μm was obtained similarly using only the low-density polyethylene (hereinafter, sometimes simply referred to as "control"). The extruder was a single-screw extruder with D (mm) = 20, and a full-flight screw with L / D = 20 and a compression ratio of 3.5 was used. A T-die with a width of 300 mm was used as the die. The average thickness of the monolayer film was adjusted by appropriately changing the screw rotation speed and the take-up roll speed. The temperature conditions at this time are shown below. Extrusion temperature: feeding section / compression section / metering section / adapter = 175 / 230 / 230 / 230℃ Die temperature: 220℃ Cooling roll temperature: 80℃ The coloration and defects of the obtained monolayer film (recycled material) were visually compared with the control and judged according to the following criteria. When the defect rating was E, it was judged that the recyclability was insufficient. The results are shown in Table 1. Judging color: Criteria A: The degree of color change was small compared to the control. B: Slight discoloration was observed compared to the control. C: Moderate coloration was observed compared to the control. D: Significant color change was observed compared to the control. E: Compared to the control, significant coloring and unevenness were observed. Determination of defects (recyclability): Criteria A: The amount of pimples was almost the same as the control. B: The amount of small particles was slightly more than in the control. C: Compared to the control, there were more small particles. D: Compared to the control, there was a greater amount of large bumps. E: The amount of large particles was significantly greater than in the control group.

[0123] Example 2 In producing the resin composition (A), except that an open vent was used instead of a vacuum vent, a resin composition pellet, a multilayer film and a multilayer structure were produced in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0124] Example 3 Except for not using a vacuum vent when preparing the resin composition (A), resin composition pellets, a multilayer film and a multilayer structure were prepared in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0125] Example 4 Instead of EVOH (a-1), EVOH (a-1A) was used, which is equivalent to EVOH (a-1) except that the sodium acetate content was 100 ppm calculated as sodium ion, and melt-kneaded without adding magnesium stearate. Resin composition pellets, a multilayer film, and a multilayer structure were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 1.

[0126] Example 5 Resin composition pellets, multilayer films and multilayer structures were produced in the same manner as in Example 1, except that EVOH (a-1B), which is equivalent to EVOH (a-1) except that the sodium acetate content was 150 ppm calculated as sodium ions, was used instead of EVOH (a-1), and the amount of magnesium stearate to be kneaded was changed as shown in Table 1. The results are shown in Table 1.

[0127] Example 6 Resin composition pellets, multilayer films and multilayer structures were produced in the same manner as in Example 1, except that EVOH (a-1C), which is equivalent to EVOH (a-1) except that the sodium acetate content was 250 ppm calculated as sodium ions, was used instead of EVOH (a-1), and the amount of magnesium stearate to be kneaded was changed as shown in Table 1. Various measurements and evaluations were performed. The results are shown in Table 1.

[0128] Example 7 Resin composition pellets, multilayer films and multilayer structures were produced and various measurements and evaluations were carried out in the same manner as in Example 6, except that the amount of magnesium stearate to be kneaded was changed as shown in Table 1. The results are shown in Table 1.

[0129] Example 8 Resin composition pellets, multilayer films and multilayer structures were produced in the same manner as in Example 1, except that EVOH (a-1D), which is equivalent to EVOH (a-1) except that the sodium acetate content was 350 ppm calculated as sodium ions, was used instead of EVOH (a-1), and the amount of magnesium stearate to be kneaded was changed as shown in Table 1. The results are shown in Table 1.

[0130] Example 9 Resin composition pellets, multilayer films and multilayer structures were produced in the same manner as in Example 1, except that EVOH (a-2) (ethylene unit content 27 mol%, saponification degree 99.99 mol%, MFR (210°C, 2.16 kg load) 4.0 g / 10 min, melting point 191°C, volatile content 0.8%, sodium acetate 180 ppm in terms of sodium ions, phosphate ions 30 ppm in terms of phosphate radicals, boric acid 150 ppm in terms of boron element, no polyvalent metal ions) was used instead of EVOH (a-1), and various measurements and evaluations were performed. The results are shown in Table 1.

[0131] Example 10 Resin composition pellets, multilayer films and multilayer structures were produced in the same manner as in Example 1, except that EVOH (a-3) (ethylene unit content 44 mol%, saponification degree 99.99 mol%, MFR (190°C, 2.16 kg load) 5.7 g / 10 min, melting point 165°C, volatile content 0.8%, sodium acetate 180 ppm in terms of sodium ions, phosphate ions 30 ppm in terms of phosphate radicals, no polyvalent metal ions) was used instead of EVOH (a-1), and various measurements and evaluations were performed. The results are shown in Table 1.

[0132] Example 11 Resin composition pellets, a multilayer film and a multilayer structure were produced in the same manner as in Example 1, except that EVOH (a-2) and EVOH (a-3) were mixed (dry blended) in a weight ratio of 75 / 25 instead of EVOH (a-1), and various measurements and evaluations were carried out. The results are shown in Table 1.

[0133] Example 12 Resin composition pellets, multilayer films and multilayer structures were produced in the same manner as in Example 1, except that EVOH (a-1E), which is equivalent to EVOH (a-1) except that it contains potassium acetate instead of sodium acetate, was used instead of EVOH (a-1). Various measurements and evaluations were performed. The results are shown in Table 1.

[0134] Examples 13-14 Except for changing the magnesium stearate kneaded with EVOH (a-1) to calcium stearate (Example 13) or zinc stearate (Example 14), resin composition pellets, multilayer films, and multilayer structures were produced in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0135] Example 15 A resin composition pellet, a multilayer film, and a multilayer structure were prepared in the same manner as in Example 1, except that an alumina deposition layer AlOx (inorganic layer (I)) having an average thickness of 30 nm was laminated on the surface of layer (X) of the multilayer film obtained in (5) above by a known vacuum deposition method, and various measurements and evaluations were performed. The results are shown in Table 1.

[0136] Example 16 Except for changing the alumina deposition layer to a silica (SiOx) deposition layer, resin composition pellets, a multilayer film, and a multilayer structure were produced in the same manner as in Example 15, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0137] Example 17 Except for changing the alumina deposition layer to an aluminum metal (Al) deposition layer, resin composition pellets, a multilayer film, and a multilayer structure were produced in the same manner as in Example 15, and various measurements and evaluations were carried out. The results are shown in Table 1.

[0138] Example 18 Resin composition pellets, multilayer films and multilayer structures were produced and various measurements and evaluations were carried out in the same manner as in Example 1, except that the average thickness of each layer of the multilayer film was changed as shown in Table 1. The results are shown in Table 1.

[0139] Example 19 Using each of the resin composition pellets obtained in (1), (3) and (4) above, a co-extruded film having an average thickness and layer structure of (X) / (Y) / (Z)=20μm / 20μm / 160μm=EVOH20 / Tie20 / PE160 was produced, and stretched 5 times in the longitudinal direction to produce a multilayer film having an average thickness and layer structure of 4μm / 4μm / 32μm=EVOH4 / Tie4 / PE32 instead of the multilayer film of Example 1. Except for this, resin composition pellets, multilayer films and multilayer structures were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 1.

[0140] Example 20 Resin composition (A) pellets were prepared in the same manner as in Example 1, except that EVOH (a-4) (ethylene unit content 44 mol%, saponification degree 99.99 mol%, epoxypropane modification degree 4.6 mol%, MFR (190°C, 2.16 kg load) 5.6 g / 10 min, volatile content 0.8%, melting point 122°C, sodium acetate 220 ppm in terms of sodium ion, phosphate ion 30 ppm in terms of phosphate radical, boric acid 150 ppm in terms of boron element, and zinc acetate 30 ppm in terms of zinc ion) was used instead of EVOH (a-1). Using the obtained resin composition (A) pellets and the resin composition pellets obtained in the above (3) and (4), (X) / (Y) / (Z)=128 μm / 128 μm / 1024 μm= A coextruded film having an average thickness and layer structure of EVOH128 / Tie128 / PE1024 was produced, and stretched 4 times in the longitudinal direction and then 8 times in the transverse direction to produce a multilayer film having an average thickness and layer structure of 4 μm / 4 μm / 32 μm = EVOH4 / Tie4 / PE32. Except for using this instead of the multilayer film of Example 1, resin composition pellets, multilayer film and multilayer structure were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 1.

[0141] Example 21 As the adhesive resin (B), a maleic anhydride modified polypropylene "Admer (trademark) QF551" manufactured by Mitsui Chemicals Inc. (MFR (230°C, 2.16 kg load) 5.7 g / 10 min, melting point 144°C, density 0.89 g / cm 3 ) was used as polyolefin resin (C), and polypropylene "Novatec (trademark) PP EA7AD" (MFR (230°C, 2.16 kg load) 1.4 g / 10 min, melting point 161°C, density 0.90 g / cm 3 ) was used as the resin layer (R) and a polypropylene film having an average thickness of 50 μm was used as the resin layer (R), and in the same manner as in Example 1, a resin composition pellet, a multilayer film and a multilayer structure were produced and various measurements and evaluations were carried out. The results are shown in Table 1.

[0142] Comparative Example 1 In producing the resin composition (A), a resin composition pellet, a multilayer film and a multilayer structure were produced in the same manner as in Example 1, except that a vacuum vent was not used and the resin temperature was set to 200° C., and various measurements and evaluations were carried out. The results are shown in Table 1.

[0143] Comparative Example 2 Instead of EVOH (a-1), EVOH (a-1F), which is equivalent to EVOH (a-1) except that it does not contain sodium acetate, was used, and melt-kneading was performed without adding magnesium stearate. In the same manner as in Example 1, resin composition pellets, a multilayer film, and a multilayer structure were produced, and various measurements and evaluations were performed. The results are shown in Table 1.

[0144] Comparative Example 3 Resin composition pellets, multilayer films and multilayer structures were produced in the same manner as in Example 1, except that EVOH (a-1G), which is equivalent to EVOH (a-1) except that the sodium acetate content was 450 ppm calculated as sodium ions, was used instead of EVOH (a-1), and the amount of magnesium stearate to be kneaded was changed as shown in Table 1. Various measurements and evaluations were performed. The results are shown in Table 1.

[0145] Comparative Example 4 Resin composition pellets, multilayer films and multilayer structures were produced in the same manner as in Example 1, except that EVOH (a-1H), which is equivalent to EVOH (a-1) except that the sodium acetate content was 550 ppm calculated as sodium ions, was used instead of EVOH (a-1), and the amount of magnesium stearate to be kneaded was changed as shown in Table 1. The results are shown in Table 1.

[0146] Comparative Example 5 A multilayer film and a multilayer structure were produced in the same manner as in Example 1, except that a layer (Z) having an average thickness of 40 μm was used instead of the multilayer film, and various measurements and evaluations were performed. The layer (Z) having an average thickness of 40 μm was produced by extruding only the polyolefin resin (C)-containing resin composition without simultaneously extruding the resin composition (A) and the adhesive resin (B) when producing the multilayer film in Example 1, and adjusting the average thickness. The results are shown in Table 1.

[0147] [Table 1]

Claims

1. The laminate has a layer (X) as an outermost layer, and has a configuration in which the layer (X), the layer (Y), and the layer (Z) are laminated adjacent to each other in this order, the layer (X) is a layer made of a resin composition (A) containing, as a main component, 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 layer (Y) contains, as a main component, an adhesive resin (B) having a melting point of less than 170°C; the layer (Z) contains, as a main component, a polyolefin resin (C) having a melting point of less than 170°C; The resin composition (A) contains 40 to 500 ppm of alkali metal ions (b) and satisfies the following condition 1: A multilayer film that does not have a layer containing, as a main component, a resin having a melting point of 200°C or higher and a metal layer having an average thickness of 1 μm or more. (Condition 1) In thermogravimetry (TG), the weight loss W1 when held at 200°C for 30 minutes in a nitrogen atmosphere is 0.01 to 0.3%, the weight loss W2 when held at 280°C for 30 minutes in a nitrogen atmosphere is 0.5 to 9.0%, and the ratio W2 / W1 is 6 to 700.

2. The multilayer film according to claim 1, wherein the adhesive resin (B) is an acid-modified polyethylene or an acid-modified polypropylene.

3. 2. The multilayer film according to claim 1, wherein the polyolefin resin (C) is polyethylene or polypropylene.

4. 2. The multilayer film according to claim 1, wherein the resin composition (A) contains 10 ppm or more and 300 ppm or less of at least one polyvalent metal ion (c) selected from the group consisting of magnesium ions, calcium ions, and zinc ions.

5. 2. The multilayer film according to claim 1, wherein the resin composition (A) contains 100 to 4000 ppm of a higher aliphatic carboxylic acid (d) having 8 to 30 carbon atoms.

6. 2. The multilayer film according to claim 1, 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 total average thickness of all layers of the multilayer film is less than 25%.

7. The multilayer film of claim 1 , wherein the multilayer film is unoriented.

8. The multilayer film according to claim 1 , wherein the multilayer film is stretched uniaxially by a factor of 3 or more but less than 12.

9. The multilayer film according to claim 1 , wherein the multilayer film is biaxially stretched by a factor of 3 or more but less than 12.

10. 2. The multilayer film according to claim 1, wherein the total average thickness ratio of the layers containing the polyethylene resin or polypropylene resin as the main component is 0.75 or more.

11. A vapor-deposited multilayer film comprising an inorganic layer (I) on the exposed surface side of the layer (X) in the multilayer film according to claim 1.

12. 12. The vapor-deposited multilayer film according to claim 11, 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.

13. The oxygen transmission rate measured by the method described in JIS K 7126-2:2006 under conditions of 20°C and 65% RH is 60 cc / (m ２ The multilayer film or vapor-deposited multilayer film according to any one of claims 1 to 12, wherein the viscosity is less than 1 / 2 day atm.

14. A multilayer structure comprising the multilayer film or vapor-deposited multilayer film according to any one of claims 1 to 12 laminated with at least one resin layer (R) containing a thermoplastic resin (D) as a main component.

15. 15. The multilayer structure according to claim 14, wherein the thermoplastic resin (D) is polyethylene or polypropylene.

16. A packaging material comprising the multilayer structure of claim 14.

17. A reclaimed composition comprising the reclaimed multilayer structure of claim 14.

18. A method for recovering a multilayer structure, comprising crushing the multilayer structure according to claim 14 and then melt-molding the crushed multilayer structure.

19. A method for producing the multilayer film according to any one of claims 1 to 10, comprising the step of melt-molding a resin composition (A) that satisfies the following condition 1 to form a layer (X): (Condition 1) In thermogravimetry (TG), the weight loss W1 when held at 200°C for 30 minutes in a nitrogen atmosphere is 0.01 to 0.3%, the weight loss W2 when held at 280°C for 30 minutes in a nitrogen atmosphere is 0.5 to 9.0%, and the ratio W2 / W1 is 6 to 700.