Multilayer film, multilayer structure, packaging material, recovery composition, and method for recovering a multilayer film or multilayer structure

Abstract

To provide a multilayer film which is excellent in appearance characteristics, gas barrier properties, mechanical properties and recyclability, and a packaging material using the multilayer film.SOLUTION: A multilayer film has a barrier layer (A) containing EVOH (a) having an ethylene unit content of 20-50 mol% and a saponification degree of 90 mol% or more as a main component, an adhesive layer (B) containing an adhesive resin (b) as a main component, and a heat fusion layer (C) containing an ethylene-α-olefin copolymer resin (c) having density of 0.880-0.920 g / cm3 as a main component, does not have a layer containing a resin having a melting point of 200°C or higher as a main component and a metal layer having thickness of 1 μm or more, and when a temperature is raised from -50°C to 220°C at 10°C / min by DSC (first temperature rising), and the temperature is lowered to -50°C at 10°C / min and is further raised to 220°C at 10°C / min (second temperature rising), a ratio of total melting heat (H1) at 0-150°C in the first temperature rising to total melting heat (H2) at 0-150°C in the second temperature rising is 0.90 to 1.07.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a multilayer film, a multilayer structure excellent in appearance characteristics, gas barrier properties, mechanical properties, and recyclability, a packaging material using the same, a recovered composition, and a recovery method.

Background Art

[0002] Packaging materials for long-term preservation of foods often require gas barrier properties including oxygen barrier properties. By using a packaging material with high gas barrier properties, oxidative deterioration of foods due to oxygen ingress and propagation of microorganisms can be suppressed. As a layer for improving gas barrier properties, metal foils such as aluminum and inorganic vapor deposition layers such as silicon oxide and aluminum oxide are widely used. On the other hand, resin layers having gas barrier properties such as vinyl alcohol-based polymers and polyvinylidene chloride are also widely used. Vinyl alcohol-based polymers have a characteristic of exhibiting gas barrier properties by crystallization and densification due to hydrogen bonding between hydroxyl groups in the molecule. Among them, ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as "EVOH") is suitable for melt molding because of its excellent thermal stability. With the development of coextrusion technology, multilayer films having an EVOH layer in the intermediate layer are widely used as gas barrier packaging materials.

[0003] In recent years, triggered by environmental problems and waste problems, the demand for so-called post-consumer recycling (hereinafter sometimes simply abbreviated as recycling), which recovers and reuses packaging materials consumed in the market, has been increasing worldwide. In recycling, a process of cutting the recovered packaging material, sorting and washing it as necessary, and then melt-mixing it using an extruder is generally adopted. In this regard, it is required that the packaging material be composed of a single material as much as possible (monomaterialization), whereby a high-purity and high-quality recycled raw material can be obtained.

[0004] Patent Document 1 describes a multilayer film having a hard layer with a piercing strength of 40 N / mm or more and 150 N / mm or less and (1) a resin composition layer having EVOH with a melting point of 170°C or more and EVOH with a melting point of less than 170°C, or (2) a resin composition layer having modified EVOH containing a modified group having a specific primary hydroxyl group. Despite not having a polyamide layer, the multilayer film is excellent in mechanical strength and thermoformability. When melt-molding the recovered material, the occurrence of lumps due to resin deterioration (gelation) is suppressed, and it is also excellent in recyclability.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when used as a packaging material with a large weight of the contents, higher mechanical strength is tend to be required, and the multilayer film described in Patent Document 1 may have insufficient mechanical strength. Also, although the mechanical strength can be improved by increasing the thickness of the multilayer film, since the amount of resin used for the packaging material increases, it is required to efficiently improve the mechanical strength while suppressing the thickness as much as possible.

[0007] The present invention has been made to solve the above problems, and an object thereof is to provide a multilayer film, a multilayer structure, and a packaging material using the same, which are excellent in appearance characteristics, gas barrier properties, mechanical properties, and recyclability.

Means for Solving the Problems

[0008] According to the present invention, the above object is [1] A barrier layer (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 (hereinafter may be abbreviated as "EVOH(a)"), an adhesive layer (B) containing as a main component an adhesive resin (b), and a heat-sealing layer (C) containing as a main component an ethylene-α-olefin copolymer resin (c) having a density of 0.880 to 0.920 g / cm 3 and having no layer containing as a main component a resin having a melting point of 200°C or higher and no metal layer with a thickness of 1 μm or more. When the temperature is raised from -50°C to 220°C at a rate of 10°C / min (first temperature rise) using a differential scanning calorimeter (DSC), then the temperature is lowered to -50°C at a rate of 10°C / min, and then the temperature is raised to 220°C at a rate of 10°C / min (second temperature rise), the ratio (H1 / H2) of the total heat of fusion (H1) at 0 to 150°C during the first temperature rise to the total heat of fusion (H2) at 0 to 150°C during the second temperature rise is 0.90 to 1.07, a multilayer film; [2] The multilayer film according to [1], wherein the MFR (at 190°C, under a load of 2.16 kg) of the ethylene-α-olefin copolymer resin (c) measured in accordance with JIS K7210 (2014) is 0.5 to 2.0 g / 10 min; [3] The multilayer film according to [1] or [2], wherein the ethylene-α-olefin copolymer resin (c) is a linear low-density polyethylene obtained by copolymerizing ethylene and an α-olefin having 6 or more carbon atoms; [4] The multilayer film according to any one of [1] to [3], wherein the heat-sealing layer (C) contains 100 to 7000 ppm of a higher fatty acid amide compound (d) having a melting point of 60 to 120°C; [5] The multilayer film according to any one of [1] to [4], wherein the heat-sealing layer (C) contains 500 to 5000 ppm of inorganic oxide particles (e) having an average particle diameter of 1 to 30 μm, and the inorganic oxide particles (e) are at least one selected from the group consisting of silicon oxide particles and metal oxide particles; [6] The multilayer film according to any one of [1] to [5], wherein the barrier layer (A) contains 10 to 200 ppm of at least one polyvalent metal ion (f) selected from the group consisting of magnesium ions, calcium ions, and zinc ions; [7] A multilayer film according to any one of [1] to [6], wherein the total thickness of the entire layer is 200 μm or less, and the ratio of the thickness of the barrier layer (A) to the total thickness of the entire layer is 0.10 or less; [8] A multilayer film according to any one of [1] to [7], wherein the oxygen transmission rate under the conditions of 20 °C and 65% RH is 5 cc / (m 2 ·day·atm) or less; [9] A multilayer film according to any one of [1] to [8], wherein after conditioning at 23 °C and 50% RH for 24 hours, the elongation at break when a needle with a tip diameter of 1 mm is pierced at a speed of 50 mm / min under the same conditions is 13.0 mm or more;

[10] A multilayer film according to any one of [1] to [9], wherein after conditioning at 23 °C and 50% RH for 24 hours, the breaking strength when a needle with a tip diameter of 1 mm is pierced at a speed of 50 mm / min under the same conditions is 11.0 N or more;

[11] A multilayer structure obtained by laminating a multilayer film according to any one of [1] to

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

[12] A multilayer structure according to

[11] , wherein the thermoplastic resin (g) contains a polyethylene resin as a main component;

[13] A packaging material containing a multilayer film or a multilayer structure according to any one of [1] to

[12] ;

[14] A recovered composition containing a recovered product of a multilayer film or a multilayer structure according to any one of [1] to

[12] ;

[15] A method for recovering a multilayer film or a multilayer structure, which comprises melt-molding after pulverizing a multilayer film or a multilayer structure according to any one of [1] to

[12] ; It is achieved by providing the above.

Advantages of the Invention

[0009] The multilayer film, multilayer structure, and packaging material using the same of the present invention are excellent in appearance characteristics, gas barrier properties, mechanical properties, and recyclability.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described. In the following description, specific materials (such as compounds) may be exemplified as those that exhibit specific functions, but the present invention is not limited to embodiments using such materials. Also, the exemplified materials may be used alone or in combination, unless otherwise specified.

[0011] The multilayer film of the present invention includes a barrier layer (A) mainly containing EVOH (a) with an ethylene unit content of 20 to 50 mol% and a saponification degree of 90 mol% or more, an adhesive layer (B) mainly containing an adhesive resin (b), and a heat-sealing layer (C) mainly containing an ethylene-α-olefin copolymer resin (c) with a density of 0.880 to 0.920 g / cm 3 It has no layer mainly containing a resin with a melting point of 200°C or higher and no metal layer with a thickness of 1 μm or more. When the temperature is raised from -50°C to 220°C at a rate of 10°C / min (first temperature rise) using a differential scanning calorimeter (DSC), then cooled to -50°C at a rate of 10°C / min, and further raised to 220°C at a rate of 10°C / min (second temperature rise), the ratio (H1 / H2) of the total heat of fusion (H1) at 0 to 150°C during the first temperature rise to the total heat of fusion (H2) at 0 to 150°C during the second temperature rise is 0.90 to 1.07. Here, "mainly containing" means containing more than 50% by mass, preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, or 99% by mass or more. The multilayer film of the present invention tends to enhance gas barrier properties while maintaining recyclability by providing the barrier layer (A). Also, by providing the adhesive layer (B), the mechanical strength and recyclability tend to be enhanced. Further, the main component of the heat-sealing layer (C) is 0.880 to 0.920 g / cm 3By being the ethylene-α-olefin copolymer resin (c), it tends to be able to achieve excellent mechanical strength. Further, since the multilayer film of the present invention does not have a layer containing a resin having a melting point of 200°C or higher as a main component and a metal layer having a thickness of 1 μm or more, it can exhibit good recyclability. Furthermore, by setting the ratio (H1 / H2) of the heat of fusion of the multilayer film of the present invention to 0.90 to 1.07, even if the thickness of the multilayer film is thin (for example, 200 μm or less), the mechanical strength can be efficiently improved. The recyclability in this specification can be evaluated by the evaluation of lumps and coloring in the melt-molded product of the crushed material of the multilayer film and the melt viscosity stability of the crushed material of the multilayer film, and specifically, it can be evaluated by the method described in the examples. The mechanical strength in this specification can be evaluated by the puncture breaking strength and elongation, impact strength, and drop bag breakage resistance evaluation, and specifically, it can be evaluated by the method described in the examples.

[0012] <EVOH (a) and barrier layer (A)> The multilayer film of the present invention has a barrier layer (A) containing EVOH (a) as a main component. Since EVOH (a) has excellent gas barrier properties, a multilayer film having a layer containing EVOH (a) as a main component is preferably used as a packaging material with high content preservation properties. Further, since EVOH (a) can be easily melt-mixed with a polyethylene resin, a packaging material excellent in recyclability can be provided. Further, the content of EVOH (a) in the barrier layer (A) needs to be more than 50% by mass, preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0013] 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 the crushed material of EVOH (a) and the multilayer film 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. Further, 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 the saponification degree of EVOH (a) are 1 determined by 1H-NMR measurement.

[0014] EVOH (a) may be a mixture of two or more types of EVOH having different ethylene unit contents. In this case, the difference in the ethylene unit contents between the EVOHs with the most different ethylene unit contents is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, and may be 3 mol% or more. Similarly, EVOH (a) may be a mixture of two or more types of EVOH having different saponification degrees. In this case, the difference in the saponification degrees between the EVOHs with the most different saponification degrees 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 high thermoformability and gas barrier property at a higher level, EVOH (a-1) having an ethylene unit content of 24 mol% or more and less than 34 mol% and a saponification degree of 99 mol% or more, and EVOH (a-2) having an ethylene unit content of 34 mol% or more and less than 50 mol% and a saponification degree of 99 mol% or more are mixed so that the blending mass ratio (a-1 / a-2) is 60 / 40 to 90 / 10, and it is preferably used as EVOH (a).

[0015] EVOH(a) may contain other monomer units other than ethylene, vinyl ester and vinyl alcohol as long as the effects of the present invention are not inhibited. In particular, by introducing a modified group containing a primary hydroxyl group having a specific structure, it may be possible to achieve both high gas barrier properties and moldability of EVOH(a) at a high level. The content of other monomer units is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less, and particularly preferably substantially not contained. Examples of such other monomers include α-olefins such as propylene, n-butene, isobutylene, 1-hexene; acrylic acid and its salts; unsaturated monomers having an acrylate group; methacrylic acid and its salts; unsaturated monomers having a methacrylate group; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salts, acrylamidepropyldimethylamine and its salts (e.g., quaternary salts); methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts (e.g., quaternary salts); vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, 2,3-diacetoxy-1-vinyloxypropane; vinyl cyanides such as acrylonitrile, methacrylonitrile; vinyl halides such as vinyl chloride, vinyl fluoride; vinylidene halides such as vinylidene chloride, vinylidene fluoride; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane, allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid and their salts or esters; vinyl silane compounds such as vinyltrimethoxysilane; isopropenyl acetate, 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, 1,3-dibutyryloxy-2-methylenepropane, etc.

[0016] The MFR (at 190 °C and under a load of 2.16 kg) measured in accordance with JIS K7210 (2014) of EVOH(a) 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, still more preferably 5 g / 10 min or less, and particularly preferably 3 g / 10 min or less. When the MFR of EVOH(a) is within the above range, the melt moldability of the pulverized product of EVOH(a) and the multilayer film (the multilayer film of the present invention) containing EVOH(a) is improved.

[0017] <Polyvalent metal ion (f)> The barrier layer (A) preferably contains at least one polyvalent metal ion (f) selected from the group consisting of magnesium ions, calcium ions, and zinc ions in an amount of 10 to 200 ppm. By containing a certain amount of the polyvalent metal ion (f), thickening, gelation, and resin adhesion to the screw during melt molding of the pulverized product of EVOH(a) and the multilayer film containing EVOH(a) are suppressed. Among them, the barrier layer (A) preferably contains magnesium ions or calcium ions as the polyvalent metal ion (f), and more preferably contains magnesium ions. Further, it is preferable to contain the polyvalent metal ion (f) as a carboxylate. The carboxylic acid at this time may be either an aliphatic carboxylic acid or an aromatic carboxylic acid, but an aliphatic carboxylic acid is preferred. Examples of the aliphatic carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, myristic acid, behenic acid, montanic acid, etc., and higher fatty acids having 10 to 25 carbon atoms are more preferred. Also, from the viewpoint of suppressing coloring during melt molding, it is also preferable to contain the polyvalent metal ion (f) as a salt of a polycarboxylic acid described later.

[0018] The content of the polyvalent metal ions (f) in the barrier layer (A) is preferably 10 to 200 ppm in terms of metal atoms. When the content is 10 ppm or more, the viscosity stability of the pulverized product of EVOH (a) and the multilayer film containing EVOH (a) becomes good, and the gelation of the resin and the adhesion of the resin to the extruder screw are suppressed. The lower limit of the content of the polyvalent metal ions (f) is more preferably 20 ppm. On the other hand, when the content of the polyvalent metal ions (f) is 200 ppm or less, excessive decomposition of the pulverized product of the multilayer film containing EVOH (a) is suppressed, and the hue of the recovered composition becomes good. The upper limit of the content of the polyvalent metal ions (f) is more preferably 160 ppm, and even more preferably 120 ppm.

[0019] The barrier layer (A) may contain other components other than EVOH (a) and the polyvalent metal ions (f) as long as the effects of the present invention are not inhibited. Examples of other components include alkali metal ions, polyvalent metal ions other than the polyvalent metal ions (f), carboxylic acids, phosphate compounds, boron compounds, oxidation accelerators, antioxidants, plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorants, ultraviolet absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, fillers, pigments, dyes, processing aids, flame retardants, and antifogging agents. In particular, from the viewpoint of improving the interlayer adhesiveness and melt moldability of the laminate containing EVOH (a), it is preferable to contain alkali metal ions. Also, from the viewpoint of suppressing coloring when melt-molding the recycled resin containing EVOH (a) and EVOH (a), it is preferable to contain a carboxylic acid or a phosphate compound. Furthermore, by containing a boron compound, the melt viscosity of the recycled resin containing EVOH (a) and EVOH (a) can be controlled, and the mechanical strength of the multilayer film of the present invention may be improved. The content of other components in the barrier layer (A) is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less.

[0020] <Alkali metal ions> The barrier layer (A) preferably contains alkali metal ions. The lower limit of the content of alkali metal ions is preferably 100 ppm, more preferably 150 ppm. On the other hand, the upper limit of the content of alkali metal ions is preferably 400 ppm, more preferably 350 ppm. When the content of alkali metal ions is less than 100 ppm, the interlayer adhesiveness of the multilayer molded body including the layer obtained by molding EVOH (a) may be insufficient. On the other hand, when the content of alkali metal ions exceeds 400 ppm, coloring due to thermal degradation may become a problem. Further, by controlling the content ratio of alkali metal ions and carboxylic acid described later, melt moldability and coloring resistance can be further improved.

[0021] Examples of the alkali metal ions include ions of lithium, sodium, potassium, rubidium, and cesium. From the viewpoint of industrial availability, sodium or potassium ions are preferred. In particular, by using potassium ions, it may be possible to achieve both high levels of hue and interlayer adhesiveness with the adhesive layer (B). These may be used alone or in combination of two or more.

[0022] Examples of the alkali metal salt that provides alkali metal ions include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, and metal complexes of alkali metals such as sodium and potassium. Among them, sodium acetate, potassium acetate, sodium phosphate, and potassium phosphate are more preferred from the viewpoint of easy availability.

[0023] <Carboxylic acid> The barrier layer (A) preferably contains a carboxylic acid. 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 less than 50 ppm, the coloring resistance may be insufficient. On the other hand, when the carboxylic acid content exceeds 400 ppm, the interlayer adhesiveness with the adhesive layer (B) may be insufficient or odor may become a problem. The carboxylic acid content is determined by titrating the extract obtained after extracting 10 g of the resin composition constituting the barrier layer (A) with 50 ml of pure water at 95 °C for 8 hours. Note that, as the carboxylic acid content in the resin composition, the carboxylic acid present as a salt in the extract is not considered. Further, when the resin composition contains acidic compounds other than carboxylic acids, the carboxylic acid content in the resin composition can be determined by subtracting the contribution of these acidic compounds from the measured value by titration.

[0024] 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 in the weak acid range is enhanced, the melt moldability is further improved, and the coloring effect caused by acidic substances and basic substances can be further reduced.

[0025] The carboxylic acid may be a monovalent carboxylic acid. These may be used alone or in combination of two or more. A monovalent carboxylic acid is a compound having one carboxyl group in the molecule. The monovalent carboxylic acid having a pKa in the range of 3.5 to 5.5 is not particularly limited, and examples thereof include formic acid (pKa = 3.77), acetic acid (pKa = 4.76), propionic acid (pKa = 4.85), acrylic acid (pKa = 4.25), and the like. These carboxylic acids may further have substituents such as a hydroxyl group, an amino group, and a halogen atom. Among them, acetic acid is preferred because of its high safety and easy availability and handling.

[0026] The carboxylic acid may be a polyvalent carboxylic acid. When the carboxylic acid is a polyvalent carboxylic acid, the coloring resistance of EVOH(a) at high temperatures and the coloring resistance of the melt-molded product of the crushed multilayer film containing EVOH(a) may be further improved. Further, the polyvalent carboxylic acid compound preferably has three or more carboxyl groups. In this case, the coloring resistance may be more effectively improved. A polyvalent carboxylic 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. For example, oxalic acid (pKa2 = 4.27), succinic acid (pKa1 = 4.20), fumaric acid (pKa2 = 4.44), malic acid (pKa2 = 5.13), glutaric acid (pKa1 = 4.30, pKa2 = 5.40), adipic acid (pKa1 = 4.43, pKa2 = 5.41), 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. may be mentioned.

[0027] <Phosphate compound> The barrier layer (A) may further contain a phosphate compound. The lower limit of the content of the phosphate compound is preferably 5 ppm in terms of phosphate radical. On the other hand, the upper limit of the content of the phosphate compound is preferably 100 ppm in terms of phosphate radical. By containing the phosphate compound within this range, the coloring of the melt-molded product of the crushed EVOH(a) and the multilayer film may be suppressed, and the thermal stability may be improved.

[0028] As the phosphate compound, for example, various acids such as phosphoric acid and phosphorous acid and their salts are used. The phosphate may be any of primary phosphate, secondary phosphate, and tertiary phosphate. The cation species of the phosphate is not particularly limited, but the cation species is preferably an alkali metal or an alkaline earth metal. Among them, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate are preferable as the phosphate compound.

[0029] <Boron compound> The barrier layer (A) may further contain a boron compound. The lower limit of the content of the boron compound is preferably 50 ppm, more preferably 100 ppm in terms of boron element. On the other hand, the upper limit of the content of the boron compound is preferably 400 ppm, more preferably 200 ppm in terms of boron element. By containing the boron compound within this range, the thermal stability during the melt molding of the pulverized product of EVOH (a) and the multilayer film can be improved, and the generation of gels and lumps may be suppressed. In addition, the draw-down resistance and the neck-in resistance during film formation may be improved, or the mechanical properties of the multilayer film may be improved. These effects are presumably due to the occurrence of chelate interaction between EVOH (a) and the boron compound.

[0030] Examples of the boron compound include boric acid, borate esters, borates, and boron hydrides. Specifically, boric acids such as orthoboric acid (H3BO3), metaboric acid, and tetraboric acid; borate esters such as trimethyl borate and triethyl borate; alkali metal salts or alkaline earth metal salts of the above boric acids, borates such as borax, etc. are mentioned. Among them, orthoboric acid is preferred.

[0031] <Hindered phenol compound> The barrier layer (A) may further contain a hindered phenol compound having an ester bond or an amide bond. The content of the hindered phenol compound 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 film is melt-molded. The content of the hindered phenol compound is more preferably 2000 ppm or more. On the other hand, when the content of the hindered phenol compound is 10000 ppm or less, coloring and bleed-out derived from the hindered phenol compound can be suppressed. The content of the hindered phenol compound is more preferably 8000 ppm or less.

[0032] The hindered phenol-based compound has at least one hindered phenol group. The hindered phenol group refers to a group in which a bulky substituent is bonded to at least one of the carbons adjacent to the carbon to which the hydroxyl group of phenol is bonded. As the bulky substituent, an alkyl group having 1 to 10 carbon atoms is preferable, and a t-butyl group is more preferable.

[0033] The hindered phenol-based compound is preferably in a solid state near room temperature. From the viewpoint of suppressing the bleed-out of the compound, the melting point or softening temperature of the hindered phenol-based 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-based compound is preferably 200 or higher, more preferably 400 or higher, and even more preferably 600 or higher. On the other hand, the molecular weight is usually 2000 or less. Also, from the viewpoint of facilitating the mixing with EVOH(a), the melting point or softening temperature of the hindered phenol-based compound is preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower.

[0034] The hindered phenol-based compound has an ester bond or an amide bond. Examples of the hindered phenol-based 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-based compound having an amide bond include amides of aliphatic carboxylic acids having a hindered phenol group and aliphatic amines. Among them, from the viewpoint of facilitating the mixing with EVOH(a), it is preferable that the hindered phenol-based compound has an amide bond.

[0035] Specific structures of the hindered phenol compounds include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], which is commercially available from BASF as Irganox 1010; stearyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, which is commercially available as Irganox 1076; 2,2'-thiodiethyl bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], which is commercially available as Irganox 1035; octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, which is commercially available as Irganox 1135; 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'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], which is commercially available as Irganox 1098. Among them, N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], which is commercially available as Irganox 1098, and pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], which is commercially available as Irganox 1010, are preferred, and the former is more preferred.

[0036] The barrier layer (A) may further contain a thermoplastic resin other than EVOH (a). Examples of the thermoplastic resin other than EVOH (a) include various polyolefins (such as polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, copolymer of ethylene and α-olefin having 4 or more carbon atoms, copolymer of polyolefin and maleic anhydride, ethylene-vinyl ester copolymer, ethylene-acrylic ester copolymer, or modified polyolefin obtained by graft-modifying these with an unsaturated carboxylic acid or its derivative, etc.), various polyamides (such as nylon 6, nylon 6·6, nylon 6 / 66 copolymer, nylon 11, nylon 12, polymetaxylylene adipamide, etc.), various polyesters (such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polyurethane, polycarbonate, polyacetal, polyacrylate, and modified polyvinyl alcohol resin, etc. The content of the thermoplastic resin in the barrier layer (A) is less than 50% by mass, preferably less than 30% by mass, more preferably less than 10% by mass, still more preferably 5% by mass or less, and may even be 1% by mass or less.

[0037] The proportion of EVOH (a) as the resin constituting the barrier layer (A) is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may even be 95% by mass or more, 97% by mass or more, 99% by mass or more, and the resin constituting the barrier layer (A) may consist only of EVOH (a). Also, the proportion of EVOH (a) occupying the barrier layer (A) is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may even be 95% by mass or more, 97% by mass or more, 99% by mass or more, and the barrier layer (A) may be substantially composed only of EVOH (a).

[0038] When the barrier layer (A) contains components other than EVOH (a), the method for producing the resin composition constituting the barrier layer (A) is not particularly limited, but it can be produced by melt-kneading EVOH (a) and, if necessary, other additives (such as polyvalent metal ions (f)). The other additives 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 dispersed substance contained in a dispersion. As the solution and the dispersion, an aqueous solution and an aqueous dispersion are preferably used, respectively. For melt-kneading, known mixing devices or kneading devices such as a kneader extruder, an extruder, a mixing roll, and a Banbury mixer can be used. The temperature range during melt-kneading can be appropriately adjusted according to the melting point of the EVOH (a) used, etc., and usually, 150 to 300 °C is adopted.

[0039] In another aspect, a masterbatch containing other additives in a high concentration with respect to EVOH (a) is produced by melt-kneading, and the masterbatch can be dry-blended with EVOH (a) substantially free of other additives and used for the production of a multilayer film. In yet another aspect, EVOH (a) and other additives can be used for the production of a multilayer film by dry-blending. Dry-blending means mechanically mixing in a granular or pelletized form. The mixing may be carried out using a mixing device such as a tumbler, a ribbon mixer, or a Henschel mixer, or may be carried out by manually stirring, shaking, etc. inside a sealed container. The mixing temperature may be from room temperature to less than the melting point of EVOH (a), and the mixing can be carried out in an air atmosphere or a nitrogen atmosphere.

[0040] <Adhesive resin (b) and adhesive layer (B)> The multilayer film of the present invention has an adhesive layer (B) mainly composed of an adhesive resin (b). The adhesive layer (B) has a function of adhering the barrier layer (A) to the heat-sealing layer (C) or the thermoplastic resin layer described later. Therefore, the adhesive layer (B) is preferably provided between the barrier layer (A) and the heat-sealing layer (C) or the thermoplastic resin layer, and is preferably directly laminated with the barrier layer (A) and the heat-sealing layer (C) or the thermoplastic resin layer. The content of the adhesive resin (b) in the adhesive layer (B) needs to be more than 50% by mass, preferably 70% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more.

[0041] Examples of the adhesive resin (b) include modified olefin-based polymers containing carboxyl groups obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to an olefin-based polymer by an addition reaction, a graft reaction, or the like. Examples of the unsaturated carboxylic acid or its anhydride include maleic acid, maleic anhydride, fumaric acid, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, citraconic acid, hexahydrophthalic anhydride, etc. Among them, maleic anhydride is preferably used. Specifically, one or more mixtures selected from maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-propylene copolymer, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer, etc. are preferably used, and among these, maleic anhydride graft-modified polyethylene is the most preferred. The acid value of such an adhesive resin (b) is usually 0.5 to 5 mgKOH / g, and preferably 1 to 4 mgKOH / g.

[0042] The adhesive resin (b) of the present invention may be a mixture of an unmodified resin (bx) and an acid-modified resin (by). In this case, from the viewpoint of further enhancing the mechanical strength, it is preferable that the unmodified resin (bx) contains an ethylene-α-olefin copolymer resin (c) described later, and it is more preferable that it is an ethylene-α-olefin copolymer resin (c). Here, when the unmodified resin (bx) contains the ethylene-α-olefin copolymer resin (c), the ethylene-α-olefin copolymer resin (c) contained in the adhesive layer (B) and the ethylene-α-olefin copolymer resin (c) contained in the heat-fusion layer (C) may be the same or different, but it is preferable that they are the same. Further, the ratio (bx / by) of the unmodified resin (bx) to the acid-modified resin (by) in the adhesive resin (b) is preferably 55 / 45 to 95 / 5, and more preferably 65 / 35 to 90 / 10. In this case, as the acid-modified resin (by), a resin having a relatively high degree of acid modification can be preferably used, and its acid value is preferably 5 to 30 mgKOH / g, and more preferably 8 to 20 mgKOH / g. By doing so, the mechanical strength of the obtained multilayer film may be further improved while maintaining the required interlayer adhesion strength. When the adhesive resin (b) of the present invention is a mixture of an unmodified resin (bx) and an acid-modified resin (by), a melt-kneaded product of the unmodified resin (bx) and the acid-modified resin (by) in advance may be used, or a dry blend of the unmodified resin (bx) and the acid-modified resin (by) may be used. For melt-kneading, known mixing devices or kneading devices such as a kneader extruder, an extruder, a mixing roll, and a Banbury mixer can be used. The temperature range during melt-kneading can be appropriately adjusted according to the melting points of the unmodified resin (bx) and the acid-modified resin (by) used, and usually, 150 to 300 °C is adopted. Dry blending means mechanically mixing in a powdery or pelletized form. The mixing may be carried out using a mixing device such as a tumbler, a ribbon mixer, or a Henschel mixer, or may be mixed by manually stirring, shaking, etc. in a sealed container. The mixing temperature may be from room temperature to less than the melting points of the unmodified resin (bx) and the acid-modified resin (by), and the mixing can be carried out in an air atmosphere or a nitrogen atmosphere.

[0043] The subsequent layer (B) may contain other components other than the adhesive resin (b) as long as the effects of the present invention are not inhibited. Examples of the other components include alkali metal ions, polyvalent metal ions, carboxylic acids, phosphate compounds, boron compounds, oxidation accelerators, antioxidants, plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorants, ultraviolet absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, fillers, pigments, dyes, processing aids, flame retardants, and antifogging agents. The content of the other components in the adhesive layer (B) is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less. Further, the adhesive layer (B) may further contain a thermoplastic resin other than the adhesive resin (b). As the thermoplastic resin, the above resins exemplified as the thermoplastic resins that may be contained in the barrier layer (A) can be used. The content of the thermoplastic resin in the adhesive layer (B) is less than 50% by mass, preferably less than 30% by mass, more preferably less than 10% by mass, further preferably 5% by mass or less, and may be 1% by mass or less.

[0044] The proportion of the adhesive resin (b) as the resin constituting the adhesive layer (B) is preferably 60% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, 99% by mass or more, and the resin constituting the adhesive layer (B) may consist only of the adhesive resin (b). Further, the proportion of the adhesive resin (b) in the adhesive layer (B) is preferably 60% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, 99% by mass or more, and the adhesive layer (B) may be substantially composed only of the adhesive resin (b).

[0045] <Ethylene-α-olefin copolymer resin (c) and heat-sealing layer (C)> The multilayer film of the present invention has a density of 0.880 to 0.920 g / cm 3It has a heat-sealing layer (C) mainly composed of an ethylene-α-olefin copolymer resin (c). In addition to the function as a sealing layer when forming a packaging material, the heat-sealing layer (C) has a function of enhancing various mechanical strengths such as puncture strength and tensile strength. The content of the ethylene-α-olefin copolymer resin (c) in the heat-sealing layer (C) needs to be more than 50% by mass, preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0046] The density of the ethylene-α-olefin copolymer resin (c) is 0.880 to 0.920 g / cm 3 When the density is within the above range, the resulting multilayer film is flexible and has excellent handleability, and various mechanical strengths such as puncture strength and tensile strength are improved. The lower limit of the density is preferably 0.885 g / cm 3 more preferably 0.890 g / cm 3 even more preferably 0.895 g / cm 3 The upper limit of the density is preferably 0.915 g / cm 3 more preferably 0.910 g / cm 3 even more preferably 0.905 g / cm 3

[0047] The MFR (at 190 °C under a load of 2.16 kg) of the ethylene-α-olefin copolymer resin (c) is preferably 0.5 to 2.0 g / 10 min. When the MFR is within the above range, the ethylene-α-olefin copolymer resin (c) has excellent melt processability, and various mechanical strengths such as puncture strength and tensile strength of the resulting multilayer film are improved. The lower limit of the MFR is preferably 0.7 g / 10 min. The upper limit of the MFR is preferably 1.5 g / 10 min, more preferably 1.0 g / 10 min. The MFR is measured at 190 °C under a load of 2.16 kg in accordance with JIS K 7210 (2014).

[0048] ​When the ethylene-α-olefin copolymer resin (c) is heated at a rate of 10°C / min with a differential scanning calorimeter (DSC), the total heat of fusion in the melting curve is preferably 150 J / g or less. When the total heat of fusion is within the above range, the ethylene-α-olefin copolymer resin (c) has excellent melt processability, and the resulting multilayer film is flexible, and various mechanical strengths such as puncture strength and tensile strength are improved. The total heat of fusion is more preferably 125 J / g or less, further preferably 100 J / g or less, and particularly preferably 90 J / g or less. The lower limit of the total heat of fusion is not particularly limited, but from the viewpoints of the handleability and heat resistance of the resulting multilayer film, 70 J / g or more is preferable, and 80 J / g or more is more preferable. The total heat of fusion can be adjusted by the type of α-olefin, the ratio of ethylene to α-olefin, the distribution in the polymer chain, the degree of polymerization, etc.

[0049] In the melting curve when the ethylene-α-olefin copolymer resin (c) is heated at a rate of 10°C / min with a differential scanning calorimeter (DSC), when the melting peak is divided with 100°C as the boundary, the heat of fusion at 100°C or higher is preferably 60 J / g or less. When the heat of fusion at 100°C or higher is within the above range, the ethylene-α-olefin copolymer resin (c) has both flexibility and toughness, and various mechanical strengths such as puncture strength and tensile strength may be improved. The heat of fusion at 100°C or higher is more preferably 50 J / g or less, further preferably 40 J / g or less, particularly preferably 30 J / g or less, and may even be 20 J / g or less. The lower limit of the heat of fusion at 100°C or higher is not particularly limited, but from the viewpoints of the handleability and heat resistance of the resulting multilayer film, 5 J / g or more is preferable, and 10 J / g or more is more preferable. The heat of fusion at 100°C or higher can be adjusted by the type of α-olefin, the ratio of ethylene to α-olefin, the distribution in the polymer chain, the degree of polymerization, etc.

[0050] When the melting curve of the ethylene-α-olefin copolymer resin (c) is heated at a rate of 10 °C / min using a differential scanning calorimeter (DSC), when the melting peak is divided with 100 °C as the boundary, the ratio (percentage) of the heat of fusion below 100 °C to the total heat of fusion is preferably 45% or more. When the ratio of the heat of fusion below 100 °C is within the above range, the resulting multilayer film is flexible and various mechanical strengths such as puncture strength at break and tensile strength at break are improved. The ratio of the heat of fusion below 100 °C is more preferably 60% or more, and even more preferably 75% or more. The upper limit of the ratio of the heat of fusion below 100 °C is not particularly limited, but from the viewpoints of the handleability and heat resistance of the resulting multilayer film, it is preferably 90% or less, and more preferably 85% or less. The above ratio can be adjusted by the type of α-olefin, the ratio of ethylene to α-olefin, the distribution in the polymer chain, the degree of polymerization, etc.

[0051] The ethylene-α-olefin copolymer resin (c) is a resin obtained by polymerizing ethylene and an α-olefin having 3 or more carbon atoms. Examples of the α-olefin having 3 or more carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, etc. Among these, the ethylene-α-olefin copolymer resin (c) is preferably a linear low-density polyethylene obtained by polymerizing ethylene and an α-olefin having 6 or more carbon atoms, and more preferably a linear low-density polyethylene obtained by polymerizing ethylene and an α-olefin having 8 or more carbon atoms. When the carbon number of the α-olefin copolymerized with ethylene is relatively large, various mechanical strengths such as puncture strength at break and tensile strength at break may be particularly improved.

[0052] In addition, as the polymerization catalyst, it is preferable to use a metallocene catalyst. The linear low-density polyethylene polymerized using a metallocene catalyst is a compound of a Group 4 transition metal of the periodic table, preferably zirconium, having at least one ligand having a cyclopentadienyl skeleton, an organoaluminum oxy compound, and various components added as necessary. It is produced by copolymerizing ethylene and an α-olefin in the presence of a catalyst formed from these. The linear low-density polyethylene polymerized using a metallocene catalyst has excellent melt moldability, and the resulting multilayer film has an excellent balance of heat resistance, flexibility, and mechanical strength.

[0053] Commercially available linear low-density polyethylene obtained by polymerizing ethylene and an α-olefin having 6 or more carbon atoms using a metallocene catalyst includes "Evolue (trademark)" (manufactured by Prime Polymer Co., Ltd.), "Sumikasen (trademark)" (manufactured by Sumitomo Chemical Co., Ltd.), "Yumelite (trademark)" (manufactured by Ube Maruzen Polyethylene Co., Ltd.), "Elite (trademark)" (manufactured by Dow Chemical Co., Ltd.), and the like.

[0054] <Higher fatty acid amide compound (d)> The heat-sealing layer (C) preferably contains 100 to 7000 ppm of a higher fatty acid amide compound (d) having a melting point of 60 to 120°C. By having the higher fatty acid amide compound (d) in the above range in the heat-sealing layer (C), the variation in the mechanical strength measurement value can be made small regardless of the storage environment and measurement position, and the stability of the mechanical strength can be improved. In particular, even when the multilayer film is stored at a high temperature for a long time, the variation in mechanical strength can be suppressed, so the reliability as a packaging material can be improved.

[0055] The lower limit of the content of the higher fatty acid amide compound (d) in the heat-sealing layer (C) is preferably 100 ppm, more preferably 300 ppm, still more preferably 500 ppm, and particularly preferably 700 ppm. The upper limit of the content of the higher fatty acid amide compound (d) is preferably 7000 ppm, more preferably 5000 ppm, still more preferably 3000 ppm, particularly preferably 1500 ppm, and may be 1000 ppm. When the content of the higher fatty acid amide compound (d) is within the above range, the transparency and the appearance uniformity of the multilayer film are excellent, the variation in mechanical strength can be effectively suppressed, and thus the reliability as a packaging material can be improved.

[0056] The higher fatty acid amide compound (d) is not particularly limited as long as its melting point is 60 to 120°C. The lower limit of the melting point of the higher fatty acid amide compound (d) is preferably 70°C. The upper limit of the melting point of the higher fatty acid amide compound (d) is preferably 110°C. The melting point can be controlled by the length of the carbon chain, the degree of unsaturation (the number of double bonds in the carbon chain), the number of amide groups, and the presence or absence of other substituents. Examples of the higher fatty acid amide compound (d) include saturated higher fatty acid bisamides, unsaturated higher fatty acid bisamides, saturated higher fatty acid monoamides, unsaturated higher fatty acid monoamides, and their derivatives. However, it is preferably at least one selected from the group consisting of saturated higher fatty acid monoamides and unsaturated higher fatty acid monoamides having 10 to 25 carbon atoms. Preferred examples of the saturated higher fatty acid monoamides having 10 to 25 carbon atoms include capric acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, arachidic acid amide, behenic acid amide, etc. Among these, from the viewpoints of economy and availability, lauric acid amide, stearic acid amide, and behenic acid amide are preferred, and stearic acid amide is more preferred. Preferred examples of the unsaturated higher fatty acid monoamides having 10 to 25 carbon atoms include monoene higher fatty acid monoamides having an unsaturation degree of 1 from the viewpoint of suppressing coloring, such as oleic acid amide, elaidic acid amide, vaccenic acid amide, gadoleic acid amide, eicosenoic acid amide, erucic acid amide, etc. Among these, from the viewpoints of economy and availability, oleic acid amide and erucic acid amide are preferred. From the viewpoint of the thermal stability of the higher fatty acid amide compound (d), saturated higher fatty acid monoamides are preferred, and from the viewpoint of exhibiting effects in a wider range of processing conditions, unsaturated higher fatty acid monoamides are preferred. Also, from the viewpoint of handleability in the process of manufacturing and processing a multilayer film, the carbon number of the higher fatty acid amide compound (d) may preferably be 12 to 22. Further, the higher fatty acid amide compound (d) may have substituents such as a hydroxyl group.

[0057] In one aspect of the present invention, the higher fatty acid amide compound (d) preferably contains two or more higher fatty acid amide compounds having different melting points. In particular, it preferably contains an unsaturated higher fatty acid amide compound (d1) having a melting point of 60°C or higher and less than 90°C and a saturated higher fatty acid amide compound (d2) having a melting point of 90°C or higher and less than 120°C. By doing so, even in a more diverse storage environment with large fluctuations in temperature and humidity, the fluctuations in the measured mechanical strength values can be reduced, and the stability of the mechanical strength may be further improved more efficiently.

[0058] <Inorganic oxide particles (e)> The heat-sealing layer (C) preferably contains 500 to 5000 ppm of inorganic oxide particles (e) having an average particle diameter of 1 to 30 μm. By doing so, the handleability in the process of manufacturing and processing the multilayer film can be improved, and the stability of the mechanical strength of the multilayer film may be further improved. The average particle diameter of the inorganic oxide particles (e) is preferably 2 to 15 μm or more, and more preferably 3 to 10 μm or more. The average particle diameter is the median diameter measured by the light scattering method while circulating the dispersion obtained after dispersing the inorganic oxide particles (e) in water or an organic solvent and sufficiently stirring. The content of the inorganic oxide particles (e) is preferably 750 to 4500 ppm, and more preferably 1000 to 4000 ppm. Further, the shape of the inorganic oxide particles (e) preferably has a small aspect ratio and is close to a true spherical shape.

[0059] The inorganic oxide particles (e) are preferably at least one selected from the group consisting of silicon oxide particles and metal oxide particles. The metal constituting the metal oxide particles is preferably at least one selected from the group consisting of aluminum, magnesium, zirconium, cerium, tungsten, molybdenum, titanium, and zinc. Specific examples of the inorganic oxide constituting the inorganic oxide particles (e) include silicon oxide, aluminum oxide, zirconium oxide, magnesium oxide, cerium oxide, tungsten oxide, molybdenum oxide, titanium oxide, zinc oxide, and composites thereof (such as composites of silicon oxide and aluminum oxide), etc., and silicon oxide is preferred.

[0060] The heat-sealing layer (C) may contain components other than the ethylene-α-olefin copolymer resin (c), the higher fatty acid amide compound (d), and the inorganic oxide particles (e) as long as the effects of the present invention are not inhibited. Examples of other components include alkali metal ions, polyvalent metal ions, carboxylic acids, phosphate compounds, boron compounds, oxidation accelerators, antioxidants, plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorants, ultraviolet absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, fillers, pigments, dyes, processing aids, flame retardants, and antifogging agents. The content of other components in the heat-sealing layer (C) is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less. Further, the heat-sealing layer (C) may further contain a thermoplastic resin other than the ethylene-α-olefin copolymer resin (c). As the thermoplastic resin, the above-mentioned resins exemplified as the thermoplastic resins that may be contained in the barrier layer (A) can be used. The content of the thermoplastic resin in the heat-sealing layer (C) is less than 50% by mass, preferably less than 30% by mass, more preferably less than 10% by mass, still more preferably 5% by mass or less, and may be 1% by mass or less.

[0061] The proportion of the ethylene-α-olefin copolymer resin (c) as the resin constituting the heat-sealing layer (C) is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, 99% by mass or more, and the resin constituting the heat-sealing layer (C) may consist only of the ethylene-α-olefin copolymer resin (c). Further, the proportion of the ethylene-α-olefin copolymer resin (c) in the heat-sealing layer (C) is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, 99% by mass or more, and the heat-sealing layer (C) may be substantially composed only of the ethylene-α-olefin copolymer resin (c).

[0062] The manufacturing method of the resin composition constituting the heat-sealing layer (C) is not particularly limited, but it can be manufactured by melt-kneading an ethylene-α-olefin copolymer resin (c) and, if necessary, other additives such as a higher fatty acid amide compound (d) and inorganic oxide particles (e). The higher fatty acid amide compound (d) 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 the dispersion, an aqueous solution and an aqueous dispersion are respectively preferable. For melt-kneading, known mixing devices or kneading devices such as a kneader extruder, an extruder, a mixing roll, and a Banbury mixer can be used. The temperature range during melt-kneading can be appropriately adjusted according to the melting point etc. of the ethylene-α-olefin copolymer resin (c) used, and usually, 150 to 300 °C is adopted.

[0063] In another aspect, a masterbatch containing, if necessary, other additives such as a higher fatty acid amide compound (d) and inorganic oxide particles (e) in a high concentration with respect to the ethylene-α-olefin copolymer resin (c) is manufactured by melt-kneading, and the masterbatch is dry-blended with an ethylene-α-olefin copolymer resin (c) substantially free of other additives such as a higher fatty acid amide compound (d) and inorganic oxide particles (e) and can be used for the production of a multilayer film. Further, in yet another aspect, the ethylene-α-olefin copolymer resin (c) and, if necessary, other additives such as a higher fatty acid amide compound (d) and inorganic oxide particles (e) can be used for the production of a multilayer film by dry-blending. Dry-blending means mechanically mixing in a powdery, granular or pelletized form. The mixing may be carried out using a mixing device such as a tumbler, a ribbon mixer, a Henschel mixer, etc., or may be mixed by manually stirring, shaking, etc. inside a sealed container. The mixing temperature may be carried out at room temperature to less than the melting point of the ethylene-α-olefin copolymer resin (c), and mixing can be carried out in an air atmosphere or a nitrogen atmosphere.

[0064] <Multilayer film> The multilayer film of the present invention has at least a barrier layer (A), an adhesive layer (B), and a heat-sealing layer (C), and does not have a layer containing a resin having a melting point of 200 °C or higher as a main component and a metal layer having a thickness of 1 μm or more. By not having a layer containing a resin having a melting point of 200 °C or higher as a main component and a metal layer having a thickness of 1 μm or more, it is possible to suppress uneven mixing with other components when melt-molding the pulverized product of the multilayer film. Here, the metal layer is a layer having continuous and discontinuous surfaces made of metal, such as an aluminum foil. Further, it is preferable that at least one set of the barrier layer (A) and the adhesive layer (B) are laminated adjacent to each other. By doing so, a multilayer film having high gas barrier properties and recyclability and excellent mechanical strength and its stability can be obtained.

[0065] When the multilayer film of the present invention is heated from -50 °C to 220 °C at a rate of 10 °C / min (first heating) with a differential scanning calorimeter (DSC), then cooled to -50 °C at a rate of 10 °C / min, and further heated to 220 °C at a rate of 10 °C / min (second heating), the ratio (H1 / H2) of the total heat of fusion (H1) at 0 to 150 °C during the first heating and the total heat of fusion (H2) at 0 to 150 °C during the second heating is 0.90 to 1.10. By setting the ratio of the heat of fusion (H1 / H2) to 0.90 to 1.07, the mechanical strength can be efficiently improved while suppressing the total thickness. From the viewpoint of further improving the mechanical strength, the upper limit of the ratio of the heat of fusion (H1 / H2) is preferably 1.05, more preferably 1.03, and even more preferably 1.01. On the other hand, from the viewpoint of improving the heat resistance and handleability of the multilayer film, the lower limit of the ratio of the heat of fusion (H1 / H2) may be preferably 0.95. The ratio of the heat of fusion (H1 / H2) can be controlled by the set temperature of the extruder and die when manufacturing the multilayer film and the cooling rate after being discharged from the die. The cooling rate after being discharged from the die can be controlled by the distance (air gap) or time from being discharged from the die until contacting the first cooling roll, or the temperature of the cooling roll, etc., when using a T-die. When using an annular die, it can be controlled by the conditions of air cooling and water cooling after being discharged from the die. Further, when heat treatment is performed again after once cooling, it can also be controlled by the temperature and time, etc.

[0066] As a lamination method for manufacturing the above multilayer film, 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 an annular die or a T-die can be used. The molding temperature during melt molding may be appropriately adjusted based on the melting point and melt viscosity of the resin to be used, and is often selected from the range of 150 to 300°C.

[0067] The total thickness of the multilayer film of the present invention is preferably 15 to 300 μm, more preferably 25 to 250 μm, still more preferably 35 to 200 μm, and particularly preferably 45 to 150 μm. Since the multilayer film of the present invention is lightweight and flexible when the total thickness is within the above range, it is preferably used for soft packaging applications. In addition, the amount of resin used in the multilayer film is small, and the environmental load is suppressed.

[0068] In the multilayer film of the present invention, the ratio of the thickness of the barrier layer (A) to the total thickness of all layers is preferably 0.10 or less. When this ratio is within the above range, the recyclability and mechanical strength are improved. The lower limit of the ratio of the thickness of the barrier layer (A) to the total thickness of all layers is not particularly limited, but is generally 0.005 or more in order to exhibit sufficient gas barrier properties. On the other hand, in the multilayer film of the present invention, the ratio of the thickness of the heat-sealing layer (C) to the total thickness of all layers is preferably 0.60 or more, more preferably 0.70 or more, and still more preferably 0.80 or more. When this ratio is within the above range, the recyclability and mechanical strength are improved.

[0069] As the layer structure of the multilayer film of the present invention, for example, layer structures such as (A) / (B) / (C) and (C) / (B) / (A) / (B) / (C) are typical, but it may further have other layers. In addition, when a plurality of any of the barrier layer (A), the adhesive layer (B), and the heat-sealing layer (C) are used, different types of resins can also be used.

[0070] The oxygen transmission rate (OTR) of the multilayer film of the present invention under the conditions of 20°C and 65% RH may be adjusted according to the application and is not particularly limited, but is 5 cc / (m2 .day.atm) or less is preferable. A multilayer film with an OTR within this range has excellent gas barrier properties and is suitably used as a packaging material. The OTR is 4 cc / (m 2 .day.atm) or less is more preferable, and 3 cc / (m 2 .day.atm) or less is even more preferable, and 2 cc / (m 2 .day.atm) or less is particularly preferable. The OTR is measured in accordance with JIS K 7126-2 (isobaric method; 2006), and specifically, the method described in the examples is adopted.

[0071] The multilayer film of the present invention preferably has an elongation at break (penetration break elongation) of 13.0 mm or more when a needle with a tip diameter of 1 mm is pierced at a speed of 50 mm / min under the conditions of 23°C and 50% RH after conditioning for 24 hours under the same conditions. A multilayer film with an elongation at break within this range has excellent mechanical strength and is less likely to break due to external impacts or the like, and thus is suitably used as a packaging material. The penetration elongation is more preferably 14.0 mm or more, even more preferably 15.0 mm or more, and particularly preferably 16.0 mm or more. The penetration elongation may be 20.0 mm or less.

[0072] The multilayer film of the present invention preferably has a breaking strength (penetration breaking strength) of 11.0 N or more when a needle with a tip diameter of 1 mm is pierced at a speed of 50 mm / min under the conditions of 23°C and 50% RH after conditioning for 24 hours under the same conditions. A multilayer film with a penetration strength within this range has excellent mechanical strength and is less likely to break due to external impacts or the like, and thus is suitably used as a packaging material. The penetration elongation is more preferably 11.5 N or more, even more preferably 12.0 N or more, and particularly preferably 12.5 N or more. The penetration strength may be 20.0 N or less.

[0073] The coefficient of variation (the value obtained by dividing the standard deviation by the average value) of the puncture breaking strength of the multilayer film of the present invention is preferably 0.05 or less. A multilayer film with a coefficient of variation within this range is excellent in the stability of mechanical strength and is less likely to break due to external impacts or the like, so it is preferably used as a packaging material. The coefficient of variation is more preferably 0.03 or less, even more preferably 0.015 or less, and particularly preferably 0.010 or less.

[0074] <Multilayer structure> The multilayer film of the present invention itself can be used as a packaging material having gas barrier properties, but by forming a multilayer structure in which at least one resin layer (R) containing a thermoplastic resin (g) as a main component is further laminated, various functions as a packaging material such as heat resistance and designability can be imparted. The thermoplastic resin (g) is not particularly limited, and examples 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, chlorinated polypropylene, and the like. Among them, polyolefins are preferred from the viewpoints of excellent moisture resistance, mechanical properties, heat sealability, and economy, and polyamides and polyesters are preferred from the viewpoints of excellent mechanical properties and heat resistance. In particular, in order to obtain a multilayer structure with excellent recyclability, it is more preferable that the thermoplastic resin (g) contains a polyethylene resin as a main component, and it is even more preferable that it is a polyethylene resin. Such a resin layer (R) may be a single layer or a multilayer composed of a plurality of layers. Further, such a resin layer (R) may be unstretched, or may be stretched or rolled in a uniaxial direction or a biaxial direction. From the viewpoint of improving mechanical strength, a biaxially stretched layer is preferable, and from the viewpoint of improving heat sealability, an unstretched layer is preferable.

[0075] 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 an annular die or a T-die can be used. The method of stretching in the uniaxial direction or the biaxial direction is also not particularly limited, and it can be manufactured by a conventionally known stretching method such as roll-type uniaxial stretching, tubular simultaneous biaxial stretching, tenter-type sequential biaxial stretching, tenter-type simultaneous biaxial stretching, etc., by stretching in the flow direction of the film and / or in the direction perpendicular to the flow direction, that is, the width direction. From the viewpoint of the thickness uniformity and mechanical strength of the resulting layer, the area magnification is preferably 8 to 60 times. The area magnification is more preferably 55 times or less, and even more preferably 50 times or less. Also, the area magnification is more preferably 9 times or more. If the area magnification is less than 8 times, stretching marks may remain, and if it exceeds 60 times, the layer is likely to break during stretching.

[0076] From the viewpoint of industrial productivity, the thickness of the resin layer (R) is preferably 10 to 200 μm. Specifically, the thickness in the case of the non-stretched layer is more preferably 10 to 150 μm, and the thickness in the case of the biaxially stretched layer is more preferably 10 to 50 μm.

[0077] Also, the total thickness of the multilayer structure of the present invention is preferably 300 μm or less. Since the multilayer structure of the present invention is lightweight and flexible within the above range, it is preferably used for soft packaging applications. Also, the amount of resin used in the multilayer structure is small, and the environmental load is suppressed.

[0078] The thickness of each layer in the multilayer structure of the present invention may be appropriately adjusted according to the application, but from the viewpoint of suppressing coloring when the pulverized material is melt-molded, improving the thermal stability during melt-molding, and suppressing the generation of defects, the ratio of the total thickness of the layer mainly containing the polyethylene resin (resin layer (R), adhesive layer (B), and heat-sealing layer (C)) to the total thickness of the multilayer structure is preferably 0.80 or more, more preferably 0.85 or more, even more preferably 0.90 or more, and particularly preferably 0.95 or more.

[0079] The multilayer structure of the present invention preferably does not have a layer containing a resin having a melting point of 200°C or higher as a main component and a metal layer having a thickness of 1 μm or more. By not having a layer containing a resin having a melting point of 200°C or higher as a main component and a metal layer having a thickness of 1 μm or more, it is possible to suppress non-uniform mixing with other components when melt-molding the pulverized product of the multilayer structure. Here, the metal layer is a layer having continuous and discontinuous surfaces made of a metal such as aluminum foil.

[0080] The method of laminating the resin layer (R) on the multilayer film of the present invention is not particularly limited, and examples include extrusion lamination, co-extrusion lamination, dry lamination, and the like. When laminating the resin layer (R) on the multilayer film, an adhesive layer may be provided. As the adhesive layer, the adhesive layer (B) may be used, or it can be formed by applying a known adhesive and drying it. The adhesive is preferably a two-component reaction type polyurethane-based adhesive obtained by mixing and reacting a polyisocyanate component and a polyol component. The thickness of the adhesive layer is not particularly limited, but is preferably 1 to 5 μm, and more preferably 2 to 4 μm.

[0081] The multilayer structure of the present invention may have other layers other than those described above as long as the effects of the present invention are not inhibited. Examples of other layers include a recovery layer. In particular, it is preferable to reuse a recovery composition containing the recovered product of the multilayer film or multilayer structure of the present invention described later as part or all of the recovery layer. Another example of other layers includes, for example, a printing layer. The printing layer may be included at any position of the multilayer structure of the present invention. Examples of the printing layer include a film obtained by applying and drying a solution containing, for example, a pigment or a dye and, if necessary, a binder resin. Examples of the coating method of the printing layer include various coating methods using a gravure printing method, a wire bar, a spin coater, a die coater, etc., in addition to the gravure printing method. The thickness of the printing layer is not particularly limited, but is preferably 0.5 to 10 μm, and more preferably 1 to 4 μm.

[0082] When manufacturing the multilayer film or multilayer structure of the present invention, it is preferable to collect and reuse the ends and defective products generated. Further, it is also a preferred embodiment to collect and reuse the multilayer film and multilayer structure that have been circulated in the market. A method for recovering a multilayer film and a multilayer structure that are melt-molded after pulverizing the multilayer film and multilayer structure of the present invention, and a recovered composition containing the recovered product of the multilayer film and multilayer structure of the present invention are also preferred embodiments of the present invention. Here, the recovered product of the multilayer film and multilayer structure of the present invention also includes the recovered product of the packaging material containing the multilayer film or multilayer structure of the present invention.

[0083] When recovering the multilayer film and multilayer structure of the present invention, first, the recovered product of the multilayer film and multilayer structure of the present invention is pulverized. The pulverized recovered product may be directly melt-molded to obtain a recovered composition, or may be melt-molded together with other components as necessary to obtain a recovered composition. As a preferable component to be added to the recovered product, a polyolefin resin is preferable, and a polyethylene resin is more preferable. The pulverized recovered product may be directly used for manufacturing molded products such as multilayer structures, or the pulverized recovered product may be melt-pelletized to obtain pellets composed of a recovered composition, and then the pellets may be used for manufacturing molded products. As the melt-molding method of the recovered composition, extrusion molding, inflation extrusion, blow molding, melt spinning, injection molding, etc. are possible. The molding temperature during melt molding may be appropriately adjusted based on the melting point and melt viscosity of the resin used, and is often selected from the range of 150 to 300°C. The recovered composition may contain an unused resin, but the content of the recovered product in the recovered composition is preferably 10% by mass or more, more preferably 20% by mass or more, and may be 30% by mass or more. Further, the content of EVOH(a) in the recovered composition is preferably 20% by mass or less, more preferably 10% by mass or less, and may be 5% by mass or less.

[0084] Since the multilayer structure of the present invention is excellent in appearance characteristics, gas barrier properties, mechanical properties, and recyclability, it can be suitably used as a material for various packaging such as food packaging, pharmaceutical packaging, industrial chemical packaging, and agricultural chemical packaging, but can be used for a wider range of applications and is not limited to these applications.

[0085] A package obtained by filling the packaging material with contents is a preferred embodiment of the packaging material. Examples of the contents that can be filled include, in the case of beverages, wine, fruit juice, etc.; in the case of foods, fruits, nuts, vegetables, meat products, baby foods, coffee, jam, mayonnaise, ketchup, edible oil, dressing, sauces, simmered foods, dairy products, etc.; and in other cases, pharmaceuticals, cosmetics, gasoline, etc., and contents that are likely to deteriorate in the presence of oxygen, but are not limited thereto.

Example

[0086] Hereinafter, the present invention will be described more specifically using examples, but the present invention is not limited by these examples at all.

[0087] Example 1 (1) Preparation of an EVOH (a)-containing resin composition for the barrier layer (A) EVOH (a-1) (ethylene unit content: 32 mol%, saponification degree: 99.99, MFR (190 ° C, 2.16 kg load): 1.6 g / 10 min, containing 220 ppm of sodium acetate in terms of sodium ions, 30 ppm of phosphate ions in terms of phosphate radicals, 150 ppm of boric acid in terms of boron element, and no polyvalent metal ions) and magnesium stearate were melt-kneaded so that the content of magnesium ions in the resulting resin composition was 50 ppm to obtain resin composition pellets for the barrier layer (A). The melt-kneading was carried out using a twin-screw extruder (D (mm) = 25, L / D = 25, screw: co-rotating fully intermeshing type) manufactured by Toyo Seiki Seisakusho Co., Ltd., and the resin temperature was set to 220 ° C.

[0088] (2) Preparation of an adhesive resin (b)-containing resin composition for the adhesive layer (B) Maleic anhydride-modified polyethylene "Admer (trademark) NF518" (MFR (190 ° C, 2.16 kg load): 3.1 g / 10 min, density: 0.91 g / cm 3 , acid value: 1.8 mgKOH / g) manufactured by Mitsui Chemicals, Inc. was used as the adhesive resin (b-1) and used as it was as resin composition pellets for the adhesive layer (B).

[0089] (3) Preparation of a resin composition containing an ethylene-α-olefin copolymer resin (c) for the heat-sealing layer (C) Linear low-density polyethylene (c-1) "Elite (trademark) AT6101" manufactured by The Dow Chemical Company (polymerized ethylene and 1-octene with a metallocene catalyst, MFR (190 °C, 2.16 kg load) 0.8 g / 10 min, density 0.905 g / cm 3 ) and stearic acid amide (S1A) (melting point 101 °C) were melt-kneaded so that the content of stearic acid amide in the resulting resin composition was 4% by mass to produce stearic acid amide masterbatch pellets. The melt-kneading was carried out using a twin-screw extruder (D (mm) = 25, L / D = 25, screw: co-rotating fully intermeshing type) manufactured by Toyo Seiki Seisakusho Co., Ltd., and the resin temperature was set to 220 °C. Next, the linear low-density polyethylene (c-1) pellets and the obtained stearic acid amide masterbatch pellets were dry-blended at a mass ratio of 98 / 2 to obtain resin composition mixed pellets for the heat-sealing layer (C). Here, for the linear low-density polyethylene (c-1), when the temperature was raised from 20 °C to 250 °C at a rate of 10 °C / min using a differential scanning calorimeter DSC ("Q2000" manufactured by TA Instrument), the total heat of fusion in the melting curve was 86.8 J / g, and the ratio (percentage) of the heat of fusion below 100 °C to the total heat of fusion was 79.7%.

[0090] (4) Preparation of a multilayer film Using the respective resin composition pellets obtained in the above (1) to (3), a multilayer film having a layer thickness and layer structure of (C) / (B) / (A) / (B) / (C) = 51 μm / 6 μm / 6 μm / 6 μm / 51 μm was produced using a 3-kind 5-layer co-extrusion film-forming equipment. The film-forming conditions at this time are shown below. Barrier layer (A): 20φ single-screw extruder, Labo machine ME type CO-EXT (manufactured by Toyo Seiki Seisakusho Co., Ltd.) Adhesive layer (B): 25φ single-screw extruder, P25-18-AC type (manufactured by Osaka Seiki Kogyosha Co., Ltd.) Heat-sealing layer (C): 32φ single-screw extruder, GT-32-A type (manufactured by Plastic Engineering Laboratory Co., Ltd.) T-Die: For 3 types of 5 layers with a width of 300 mm (manufactured by Plastic Engineering Research Institute Co., Ltd.) Extrusion temperature of the barrier layer (A): Feeding section / Compression section / Metering section / Die = 170 / 220 / 220 / 220 °C Extrusion temperature of the adhesive layer (B): Feeding section / Compression section / Metering section / Die = 170 / 220 / 220 / 220 °C Extrusion temperature of the heat-sealing layer (C): Feeding section / Compression section / Metering section / Die = 170 / 220 / 220 / 220 °C Distance from the die to the cooling roll (air gap): 7 cm Temperature of the cooling roll: 40 °C Take-up speed: 1.5 m / min

[0091] (5) Melting heat quantity analysis of the multilayer film Regarding the multilayer film obtained in (4) above, using a differential scanning calorimeter DSC (TA Instrument's "Q2000"), the temperature was raised from -50 °C to 220 °C at a rate of 10 °C / min (first heating), then cooled to -50 °C at a rate of 10 °C / min, and further heated to 220 °C at a rate of 10 °C / min (second heating). The ratio (H1 / H2) of the total melting heat (H1) at 0 - 150 °C during the first heating and the total melting heat (H2) at 0 - 150 °C during the second heating was calculated. The results are shown in Table 2.

[0092] (6) Evaluation of the appearance characteristics of the multilayer film The multilayer film obtained in (4) above was visually evaluated and judged according to the following criteria. The results are shown in Table 2. Note that D1 - D3 are unacceptable criteria. Judgment: Criteria A: The appearance is uniform, without coloring, and is good B1: Slight defects such as bumps can be seen B2: Slight coloring (yellowing) can be seen B3: Slight unevenness (thickness, bleed-out) can be seen C1: Medium-level defects such as bumps can be seen C2: Medium-level coloring (yellowing) can be seen C3: Medium-level unevenness (thickness, bleed-out) can be seen D1: Severe defects such as bumps can be seen D2: Severe coloring (yellowing) is observed. D3: Severe unevenness (thickness, bleed-out) is observed.

[0093] (7) Measurement of oxygen transmission rate of multilayer film Using the multilayer film obtained in (4) above, the oxygen transmission rate was measured with one side as the oxygen supply side and the other side as the carrier gas side. Specifically, an oxygen transmission rate measuring device ("MOCON OX-TRAN2 / 21" manufactured by Modern Controls) was used, and in accordance with JIS K 7126-2 (isobaric method; 2006), at a temperature of 20 °C, a humidity of 65% RH on the oxygen supply side, a humidity of 65% RH on the carrier gas side, an oxygen pressure of 1 atm, and a carrier gas pressure of 1 atm, the oxygen transmission rate (unit: cc / (m 2 ·day·atm)) was measured. Nitrogen gas containing 2% by volume of hydrogen gas was used as the carrier gas. The results are shown in Table 2.

[0094] (8) Measurement of puncture breaking elongation and strength of multilayer film After conditioning the multilayer film obtained in (4) above at 23 °C and 50% RH for 24 hours, the breaking elongation and breaking strength when a needle with a tip diameter of 1 mm was pierced at a speed of 50 mm / min under the same conditions were measured. The measurement was performed 10 times while changing the location, and the average value was adopted as the measurement result. The results are shown in Table 2. When the puncture breaking elongation was less than 13.0 mm, it was judged that the mechanical properties were insufficient. Also, when the puncture breaking strength was less than 11.0 N, it was judged that the mechanical properties were insufficient.

[0095] (9) Evaluation of drop bag resistance of multilayer film Two pieces of the multilayer film obtained in (4) above were cut out to A4 size, overlapped, and heat-sealed on three sides with a width of 5 mm. Then, 1 L of water was filled from the opening, and the remaining side was heat-sealed to create a water-filled bag. This water-filled bag was freely dropped from a height of 1 m in the upright direction under the conditions of 20 °C and 70% RH. It was dropped 20 times, and those without water leakage were judged as qualified, and those with water leakage were judged as unqualified. The results are shown in Table 2.

[0096] (10) Bumps and coloring of the melt-molded product of the pulverized multi-layer film The multi-layer film obtained in (4) above was pulverized into a size of 4 mm square or less. This pulverized material and the low-density polyethylene resin "Novatec LD LJ400" manufactured by Nippon Polyethylene Co., Ltd. (MFR (190 ° C, 2.16 kg load) 1.5 g / 10 min, density 0.921 g / cm 3 ) were blended at a mass ratio (pulverized material / polyethylene resin) of 40 / 60, and a single-layer film with a thickness of 50 μm was obtained by performing single-layer film formation under the extrusion conditions shown below. The thickness of the single-layer film was adjusted by appropriately changing the screw rotation speed and the take-up roll speed. Also, as a control, a single-layer film with a thickness of 50 μm was obtained using only the polyethylene resin in the same manner. Extruder: Single-screw extruder manufactured by Toyo Seiki Seisakusho Screw diameter: 20 mm φ (L / D = 20, compression ratio = 3.5, full flight type) Extrusion temperature: Feeding section / Compression section / Measuring section / Die = 230 / 230 / 230 / 230 °C Take-up roll temperature: 80 °C The bumps and coloring status of the obtained single-layer film were evaluated in 5 grades from A to E below. The results are shown in Table 2. Note that E is the unacceptable standard. Criteria for judging bumps A: Compared with the control, the amount of bumps hardly changed B: Compared with the control, the amount of small bumps was slightly more C: Compared with the control, the amount of small bumps was more D: Compared with the control, the amount of large bumps was more E: Compared with the control, the amount of large bumps was very much more Criteria for judging coloring A: Compared with the control, the degree of hue change was small B: Compared with the control, slight coloring was observed C: Compared with the control, medium coloring was observed D: Compared with the control, significant coloring was observed E: Compared with the control, significant coloring was observed and unevenness was also observed

[0097] (11) Melting Viscosity Stability of Ground Product of Multilayer Film The multilayer film obtained in (4) above was ground into a size of 4 mm square or less. The torque change was measured when 60 g of this ground product was kneaded using a lab plastomill (biaxial anisotropy) under a nitrogen atmosphere at 230 °C and 100 rpm. The torque values (TI and TF respectively) 10 minutes and 90 minutes after the start of kneading were calculated, and the ratio (TF / TI) of these values was used to evaluate in the following four grades A to E. The results are shown in Table 2. Note that E is an unacceptable criterion. Judgment Criteria A: 80 / 100 or more and less than 120 / 100 B: 70 / 100 or more and less than 80 / 100, or 120 / 100 or more and less than 130 / 100 C: 60 / 100 or more and less than 70 / 100, or 130 / 100 or more and less than 140 / 100 D: 50 / 100 or more and less than 60 / 100, or 140 / 100 or more and less than 150 / 100 E: Less than 50 / 100, or 150 / 100 or more

[0098] (12) Production of Multilayer Structure A two-component reactive polyurethane-based adhesive (24 parts by mass of "Takelac A-520" and 4 parts by mass of "Takenate A-50" manufactured by Mitsui Chemicals, Inc.) was mixed with 37 parts by mass of ethyl acetate to prepare an adhesive solution. Next, the adhesive solution was applied onto a uniaxially stretched polyethylene film (resin layer (R)) with a thickness of 25 μm using a bar coater so that the thickness after drying would be 2 μm, dried at 100 °C for 5 minutes, and laminated with the multilayer film obtained in (4) above to produce a multilayer structure having a layer thickness and layer configuration of (R) / adhesive / (C) / (B) / (A) / (B) / (C) = 25 μm / 2 μm / 51 μm / 6 μm / 6 μm / 6 μm / 51 μm. The obtained multilayer structure is flexible while having firmness, and is excellent in any of appearance characteristics, gas barrier properties, and mechanical properties, so it can be preferably used as a packaging material. In addition, since the ratio of the polyethylene-based material exceeds 0.9, it can also be preferably used for recycling as a so-called single-material packaging material.

[0099] Examples 2 to 5, Comparative Examples 1 to 2 A multilayer film was produced in the same manner as in Example 1 except that the die temperature, the distance from the die to the cooling roll (air gap), and the cooling roll temperature were as shown in Table 1. Various measurements and evaluations were performed. However, for Examples 4 and 5, a cooling treatment was performed in which cold air at 10 °C was blown in the air gap. The results are shown in Table 2.

[0100] Example 6 A multilayer film was produced in the same manner as in Example 1 except that EVOH(a-2) (ethylene unit content 32 mol%, saponification degree 99.99, MFR (190 °C, 2.16 kg load) 4.4 g / 10 min, containing 220 ppm of sodium acetate in terms of sodium ions, 30 ppm of phosphate ions in terms of phosphate radicals, and no boron compound and polyvalent metal ions) was used instead of EVOH(a-1). Various measurements and evaluations were performed. The results are shown in Table 2.

[0101] Example 7 A multilayer film was produced in the same manner as in Example 1 except that EVOH(a-3) (ethylene unit content 27 mol%, saponification degree 99.99, MFR (190 °C, 2.16 kg load) 1.5 g / 10 min, containing 220 ppm of sodium acetate in terms of sodium ions, 30 ppm of phosphate ions in terms of phosphate radicals, 120 ppm of boric acid in terms of boron element, and no polyvalent metal ions) was used instead of EVOH(a-1). Various measurements and evaluations were performed. The results are shown in Table 2.

[0102] Example 8 A multilayer film was produced in the same manner as in Example 1 except that EVOH(a-4) (ethylene unit content 44 mol%, saponification degree 99.99, MFR (190 °C, 2.16 kg load) 1.7 g / 10 min, containing 220 ppm of sodium acetate in terms of sodium ions, 30 ppm of phosphate ions in terms of phosphate radicals, 100 ppm of boric acid in terms of boron element, and no polyvalent metal ions) was used instead of EVOH(a-1). Various measurements and evaluations were performed. The results are shown in Table 2.

[0103] Example 9 A multilayer film was produced in the same manner as in Example 1, except that magnesium stearate was not kneaded with EVOH(a-1), and various measurements and evaluations were performed. The results are shown in Table 2.

[0104] Examples 10 to 11 A multilayer film was produced in the same manner as in Example 1, except that the amount of magnesium stearate kneaded with EVOH(a-1) was changed as shown in Table 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0105] Examples 12 to 14 A multilayer film was produced in the same manner as in Example 1, except that the magnesium stearate kneaded with EVOH(a-1) was changed to calcium stearate, zinc stearate, and magnesium acetate, respectively, and various measurements and evaluations were performed. The results are shown in Table 2.

[0106] Example 15 A multilayer film was produced in the same manner as in Example 1, except that the following adhesive resin (b-2) was used instead of the adhesive resin (b-1), and various measurements and evaluations were performed. The results are shown in Table 2. Adhesive resin (b-2): Linear low-density polyethylene (c-1) and maleic anhydride-modified polyethylene "Bynel CXA417E10" manufactured by Dow Chemical Company (MFR (190 °C, 2.16 kg load) 2.7 g / 10 min, density 0.91 g / cm 3 , acid value 10.7 mgKOH / g) were dry-blended at a mass ratio of 85 / 15

[0107] Example 16 A multilayer film was produced in the same manner as in Example 1, except that the stearic acid amide masterbatch pellet was not used, and various measurements and evaluations were performed. The results are shown in Table 2. The multilayer film of this example tended to have a larger variation in mechanical properties after storage under high-temperature and high-humidity conditions such as 40 °C and 90% RH compared to the multilayer film of Example 1.

[0108] Example 17 A multilayer film was produced in the same manner as in Example 1, except that stearic acid amide and oleic acid amide were used in a mass ratio of 1 / 1 instead of stearic acid amide, and various measurements and evaluations were performed. The results are shown in Table 2. The multilayer film of this Example, which used two or more higher fatty acid amide compounds with different melting points, had less variation in puncture breaking strength even when stored long-term under harsher conditions such as 60 °C, 90% RH or 85 °C, 85% RH, compared to the multilayer film of Example 1 which used a higher fatty acid amide compound alone, and was excellent in the stability of mechanical properties.

[0109] Example 18 A multilayer film was produced in the same manner as in Example 1, except that 10% by mass of spherical silica particles with an average particle diameter of 3.9 μm were added to the stearic acid amide masterbatch pellets, and various measurements and evaluations were performed. The results are shown in Table 2. The multilayer film of this Example was excellent in the slipperiness of the film surface and had good handleability compared to the multilayer film of Example 1.

[0110] Example 19 A multilayer film was produced in the same manner as in Example 1, except that "Evolue (trademark) SP0510" (a linear low density polyethylene (c-2) manufactured by Prime Polymer Co., Ltd., polymerized ethylene and 1-octene using a metallocene catalyst, MFR (190 °C, 2.16 kg load) 1.2 g / 10 min, density 0.903 g / cm 3 , DSC measurement results are as described in Table 1) was used instead of linear low density polyethylene (c-1), and various measurements and evaluations were performed. The results are shown in Table 2.

[0111] Comparative Example 3 A multilayer film was produced in the same manner as in Example 19, except that the die temperature, the distance from the die to the cooling roll (air gap), and the cooling roll temperature during the production of the multilayer film were as shown in Table 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0112] Comparative Example 4 Instead of the linear low-density polyethylene (c-1), a low-density polyethylene (c-3) "Novatech LD LJ400" manufactured by Nippon Polyethylene Co., Ltd. (MFR (190 °C, 2.16 kg load) 1.5 g / 10 min, density 0.921 g / cm 3 , except for using the DSC measurement results shown in Table 1), a multilayer film was produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0113] Comparative Example 5 A multilayer film was produced in the same manner as in Comparative Example 4, except that the die temperature, the distance from the die to the cooling roll (air gap), and the cooling roll temperature during the production of the multilayer film were as shown in Table 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0114] Comparative Example 6 Instead of the linear low-density polyethylene (c-1), a high-density polyethylene (c-4) "Novatech HD HY540" manufactured by Nippon Polyethylene Co., Ltd. (MFR (190 °C, 2.16 kg load) 1.0 g / 10 min, density 0.960 g / cm 3 , except for using the DSC measurement results shown in Table 1), a multilayer film was produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0115] Comparative Example 7 A multilayer film was produced in the same manner as in Comparative Example 6, except that the die temperature, the distance from the die to the cooling roll (air gap), and the cooling roll temperature during the production of the multilayer film were as shown in Table 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0116] Comparative Example 8 In Example 1, when extruding the resin using a three-layer five-layer coextrusion film production facility, the resin was extruded onto an aluminum foil with a thickness of 9 μm, thereby producing a multilayer film having a layer thickness and layer structure of aluminum foil / (C) / (B) / (A) / (B) / (C)=9 μm / 51 μm / 6 μm / 6 μm / 6 μm / 51 μm. This multilayer film had excellent gas barrier properties, but there were a very large number of large bumps and significant coloring in the melt-molded product of the pulverized multilayer film, and it was not at a practical level.

[0117] [Table 1]

[0118] [Table 2]

Claims

1. A barrier layer (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, an adhesive layer (B) containing, as a main component, an adhesive resin (b), and a heat-sealing layer (C) containing, as a main component, an ethylene-α-olefin copolymer resin (c) having a density of 0.880 to 0.920 g / cm ３ is provided with a heat-sealing layer (C) containing, as a main component, an ethylene-α-olefin copolymer resin (c) having a density of 0.880 to 0.920 g / cm It does not have a layer containing a resin with a melting point of 200°C or higher as a main component and a metal layer with a thickness of 1 μm or more. When the temperature is raised from -50°C to 220°C at a rate of 10°C / min using a differential scanning calorimeter (DSC) (first temperature rise), then the temperature is lowered to -50°C at a rate of 10°C / min, and then the temperature is raised to 220°C at a rate of 10°C / min (second temperature rise), the ratio (H1 / H2) of the total heat of fusion (H1) at 0 to 150°C during the first temperature rise and the total heat of fusion (H2) at 0 to 150°C during the second temperature rise is 0.90 to 1.

07. The adhesive layer (B) is a layer located between the barrier layer (A) and the heat-sealing layer (C), and the heat-sealing layer (C) is a layer that functions as a seal layer. A multilayer film.

2. The multilayer film according to claim 1, wherein the MFR (at 190°C, under a load of 2.16 kg) of the ethylene-α-olefin copolymer resin (c) measured in accordance with JIS K7210 (2014) is 0.5 to 2.0 g / 10 min.

3. The multilayer film according to claim 1 or 2, wherein the ethylene-α-olefin copolymer resin (c) is a linear low-density polyethylene obtained by copolymerizing ethylene and an α-olefin having 6 or more carbon atoms.

4. The multilayer film according to any one of claims 1 to 3, wherein the heat-sealing layer (C) contains 100 to 7000 ppm of a higher fatty acid amide compound (d) having a melting point of 60 to 120°C.

5. The multilayer film according to any one of claims 1 to 4, wherein the heat-sealing layer (C) contains 500 to 5000 ppm of inorganic oxide particles (e) having an average particle diameter of 1 to 30 μm, and the inorganic oxide particles (e) are at least one selected from the group consisting of silicon oxide particles and metal oxide particles.

6. The multilayer film according to any one of claims 1 to 5, wherein the barrier layer (A) contains 10 to 200 ppm of at least one polyvalent metal ion (f) selected from the group consisting of magnesium ions, calcium ions, and zinc ions.

7. The multilayer film according to any one of claims 1 to 6, wherein the total thickness of all layers is 200 μm or less, and the ratio of the thickness of the barrier layer (A) to the total thickness of all layers is 0.10 or less.

8. The multilayer film according to any one of claims 1 to 7, having an oxygen transmission rate of 5 cc / (m ２ ·day·atm) or less under the conditions of 20°C and 65% RH.

9. The multilayer film according to any one of claims 1 to 8, wherein the elongation at break is 13.0 mm or more when a needle with a tip diameter of 1 mm is pierced at a speed of 50 mm / min under the conditions of 23°C and 50% RH after conditioning for 24 hours under the same conditions.

10. The multilayer film according to any one of claims 1 to 9, wherein after conditioning at 23°C and 50% RH for 24 hours, the breaking strength when a needle with a tip diameter of 1 mm is pierced at a speed of 50 mm / min under the same conditions is 11.0 N or more.

11. A multilayer structure in which a multilayer film according to any one of claims 1 to 10 and at least one resin layer (R) containing a thermoplastic resin (g) as a main component are laminated.

12. The multilayer structure according to claim 11, wherein the thermoplastic resin (g) contains a polyethylene resin as a main component.

13. A packaging material comprising the multilayer film or multilayer structure according to any one of claims 1 to 12.

14. A recovered composition comprising a recovered material of the multilayer film or multilayer structure according to any one of claims 1 to 12.

15. A method for recovering a multilayer film or multilayer structure, which comprises melt-molding after pulverizing the multilayer film or multilayer structure according to any one of claims 1 to 12.

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