Multilayer film with excellent recyclability

Abstract

A multilayer film which comprises a layer of a resin composition (A) that contains an ethylene-vinyl alcohol copolymer (a1) having an ethylene unit content of from 20% by mole to 60% by mole and an ethylene-vinyl alcohol copolymer (a2) having a higher ethylene unit content than the ethylene-vinyl alcohol copolymer (a1), and a layer of a thermoplastic resin (B), with the layer of the resin composition (A) being arranged as the outermost layer. This multilayer film is stretched from 3 to 12 times at least in a uniaxial direction. Consequently, the present invention provides: a multilayer film which is provided with a layer containing EVOH as the outermost layer and maintains good gas barrier properties, while being suppressed in blocking of the layer containing EVOH even during the stretching after inflation molding; a method for producing this multilayer film; a vapor deposition multilayer film which uses this multilayer film; a multilayer structure which uses this multilayer film or this vapor deposition multilayer film; and a packaging material which is provided with this multilayer structure.

Description

Technical Field

[0001] The present invention relates to a multilayer film having a resin composition layer containing an ethylene-vinyl alcohol copolymer on the outermost layer, which is stretched in at least one axial direction, a method for producing the same, a vapor-deposited multilayer film using the multilayer film, a multilayer structure using the multilayer film or the vapor-deposited multilayer film, and a packaging material including the multilayer structure.

Background Art

[0002] Ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as "EVOH") is excellent in transparency, gas barrier property, fragrance retention property, solvent resistance, oil resistance, etc. Taking advantage of such properties, it is used in various packaging such as food packaging, pharmaceutical packaging, industrial chemical packaging, and agricultural chemical packaging, as well as a wide range of applications such as industrial films, agricultural films, floor heating pipes, and fuel containers.

[0003] In recent years, due to 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 globally, and packaging materials with excellent recyclability are desired. For example, attempts have been made to manufacture a film for a gas barrier packaging material with excellent recyclability by low-mixing or laminating a packaging film based only on polyethylene or polypropylene with low gas barrier properties, or a gas barrier material that allows mixing with polyethylene or polypropylene.

[0004] Patent Document 1 describes that by providing an EVOH layer with a specific thickness on the outermost layer of a laminate, the heat seal speed when used as a packaging film can be increased without impairing recyclability. Further, it is described that by stretching these laminates in one axial direction, they will be excellent in transparency and gas barrier properties.

Prior Art Documents

Patent Documents

[0005] Patent Document 1 WO2019 / 243456 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] When producing a laminate having an EVOH layer on the outermost layer described in Patent Document 1 by inflation molding, a cylindrical laminate having an EVOH layer on the outermost layer on the inner surface side is molded, and the inner surfaces (EVOH layers) are in contact with each other. It may be stretched in a folded state. However, in this case, since the EVOH layers located on the outermost layer on the inner surface side are overlapped and stretched, there is a problem that the EVOH layers are blocked (stuck). When producing the laminate described in Patent Document 1 by inflation molding, when the EVOH layer is used as the outermost layer on the outer surface side, EVOH easily adheres to the outer surface of the discharge port (die lip) of the molten resin. Therefore, the generation of die eye (deposits on the outer surface of the die lip. Examples of the components of the deposits include low molecular weight components such as polymerization catalyst residues, low molecular weight polymers, thermally decomposed deteriorated resin components, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, and stabilizers that may be present in the resin composition) tends to be significant. In addition, since the inner flow path in the die until discharge becomes longer than the innermost layer on the inner side, the heating and melting time becomes longer, and the EVOH is likely to undergo thermal degradation. Therefore, when producing a laminate having an EVOH layer on the outermost layer by inflation molding, it is preferable to make the EVOH layer the outermost layer on the inner surface side.

[0007] The present invention has been made to solve the above problems, and its object is to maintain good gas barrier properties in a multilayer film having a layer containing EVOH on the outermost layer, and also to prevent blocking between the layers containing EVOH even during stretching after inflation molding. Provided are a multilayer film, a method for manufacturing the same, a vapor-deposited multilayer film using the multilayer film, a multilayer structure using the multilayer film or the vapor-deposited multilayer film, and a packaging material including the multilayer structure. MEANS FOR SOLVING THE PROBLEMS

[0008] According to the present invention, the above object is achieved by [1] A resin composition (A) layer (hereinafter may be abbreviated as "resin composition (A) layer") containing an ethylene-vinyl alcohol copolymer (a1) having an ethylene unit content of 20 mol% or more and 60 mol% or less (hereinafter may be abbreviated as "EVOH (a1)") and an ethylene-vinyl alcohol copolymer (a2) having a higher ethylene unit content than EVOH (a1) (hereinafter may be abbreviated as "EVOH (a2)"), and a thermoplastic resin (B) layer, The resin composition (A) layer is provided on the outermost layer, A multilayer film stretched at least in one axial direction by 3 times or more and 12 times or less. [2] The multilayer film of [1], further having an adhesive resin (C) layer; [3] The multilayer film of [2], in which the thermoplastic resin (B) layer is laminated on the resin composition (A) layer via the adhesive resin (C) layer; [4] The multilayer film according to any one of [1] to [3], wherein the multilayer film is an inflation molded body; [5] The multilayer film according to [1] to [4], wherein the mass ratio [a1 / a2] of the content of EVOH (a1) to the content of EVOH (a2) in the resin composition (A) layer is 2 / 98 or more and 98 / 2 or less; [6] The multilayer film according to [1] to [5], wherein the ethylene unit content difference (a2 - a1) between EVOH (a2) and EVOH (a1) in the resin composition (A) layer is 3 mol% or more. [7] The multilayer film according to [1] to [6], wherein the ethylene unit content of EVOH (a1) is less than 40 mol% and the ethylene unit content of EVOH (a2) is 40 mol% or more; [8] The multilayer film according to [1] to [7], wherein the melt flow rate of at least one of EVOH (a1) and EVOH (a2) at 210°C and a load of 2160 g measured according to JIS K 7210:2014 is 5 to 30 g / 10 min; [9] The multilayer film of [1] to [8], wherein the thickness of the resin composition (A) layer is 0.5 to 20 μm, and the ratio of the thickness of the resin composition (A) layer to the total thickness of all layers of the multilayer film is 30% or less;

[10] The multilayer film of [1] to [9], wherein the thermoplastic resin (B) layer contains a polyethylene resin as a main component;

[11] A vapor deposition multilayer film in which an inorganic vapor deposition (D) layer (hereinafter sometimes referred to as the "inorganic vapor deposition (D) layer") is adjacent to the surface side of the resin composition (A) layer of the multilayer film of [1] to

[10] ;

[12] A multilayer structure further comprising a thermoplastic resin (E) layer on the vapor deposition multilayer film of

[11] .;

[13] A multilayer structure further comprising a thermoplastic resin (E) layer on the multilayer film of [1] to

[10] ;

[14] The multilayer structure of

[12] or

[13] , wherein both the thermoplastic resin (B) layer and the thermoplastic resin (E) layer contain a polyethylene resin as a main component;

[15] A packaging material comprising the multilayer structure of

[12] to

[14] ;

[16] A method for producing the multilayer film of [1] to

[10] , which includes a step (I) of forming a cylindrical multilayer film having the resin composition (A) layer and the thermoplastic resin (B) layer by inflation molding, wherein the outermost layer on the inner surface side is the resin composition (A) layer, a step (II) of folding and stretching the cylindrical multilayer film so that the inner surfaces are in contact with each other, and a step (III) of cutting at least a part of the stretched cylindrical multilayer film to obtain a planar multilayer film; which is achieved by providing the above.

Advantages of the Invention

[0009] According to the present invention, there can be provided a multilayer film having an EVOH layer on the outermost layer, which maintains good gas barrier properties and suppresses blocking between layers containing EVOH even during stretching after inflation molding, a method for producing the same, a vapor-deposited multilayer film using the multilayer film, a multilayer structure using the multilayer film or the vapor-deposited multilayer film, and a packaging material including the multilayer structure. In this specification, the performance of "suppressing blocking between layers containing EVOH even during stretching after inflation molding" may be simply expressed as "blocking resistance".

Embodiments for Carrying Out the Invention

[0010] The multilayer film of the present invention has a resin composition (A) layer containing EVOH (a1) and EVOH (a2) and a thermoplastic resin (B) layer, and has the resin composition (A) layer on the outermost layer, and is stretched at least in one axial direction by 3 times or more and 12 times or less.

[0011] <Resin Composition (A Layer)> By providing the resin composition (A) layer on the outermost layer, the multilayer film of the present invention tends to have good blocking resistance while maintaining gas barrier properties. Further, since the resin composition (A) layer has good affinity with the inorganic vapor-deposited (D) layer described later, a vapor-deposited multilayer film in which the inorganic vapor-deposited (D) layer is adjacent to the surface of the resin composition (A) layer exhibits good gas barrier properties, and in particular, the gas barrier properties tend to be maintained even when subjected to physical stress such as bending. From the viewpoint of manufacturing such a vapor-deposited multilayer film, it is also preferable to provide the resin composition (A) layer on the outermost layer. The resin composition (A) layer contains EVOH (a1) and EVOH (a2), so that the multilayer film of the present invention tends to have excellent blocking resistance. Note that a plurality of resin composition (A) layers may be provided, and in the case of providing a plurality of resin composition (A) layers, "providing the resin composition (A) layer on the outermost layer" means that at least one resin composition (A) layer is provided on the outermost layer.

[0012] EVOH (a1) and EVOH (a2) can usually be obtained by saponifying an ethylene-vinyl ester copolymer. The production and saponification of the ethylene-vinyl ester copolymer can be carried out by known methods. As the vinyl ester, vinyl acetate is typical, but other fatty acid vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl caprinate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versatate may also be used.

[0013] The ethylene unit content of EVOH (a1) is 20 mol% or more, preferably 22 mol% or more, more preferably 25 mol% or more, and even more preferably 28 mol% or more. Also, the ethylene unit content of EVOH (a1) is 60 mol% or less, preferably less than 40 mol%, more preferably 37 mol% or less, even more preferably 34 mol% or less, and may be 32 mol% or less. When the ethylene unit content of EVOH (a1) is 20 mol% or more, the melt moldability and gas barrier properties under high humidity tend to be good. When the ethylene unit content is 60 mol% or less, the gas barrier properties tend to be good. The ethylene unit content of EVOH can be determined by nuclear magnetic resonance (NMR) method.

[0014] The ethylene unit content of EVOH (a2) is not particularly limited as long as it is more than that of EVOH (a1). For example, it may be 20 mol% or more and 60 mol% or less. The ethylene unit content of EVOH (a2) is preferably 40 mol% or more, more preferably 42 mol% or more. Also, the ethylene unit content of EVOH (a2) is preferably 55 mol% or less, more preferably 50 mol% or less. When the ethylene unit content of EVOH (a2) is 20 mol% or more, the melt moldability tends to be good. When it is 60 mol% or less, the gas barrier properties tend to be good.

[0015] If the ethylene unit content of EVOH(a2) is higher than that of EVOH(a1), the difference is not particularly limited. However, from the perspective of enhancing blocking resistance while maintaining gas barrier properties, the difference in ethylene unit content (a2 - a1) between EVOH(a2) and EVOH(a1) is preferably 3 mol% or more, more preferably 6 mol% or more, and even more preferably 8 mol% or more. The difference in ethylene unit content (a2 - a1) may be 30 mol% or less, or may be 20 mol% or less.

[0016] It is preferable that the ethylene unit content of EVOH(a1) in the resin composition (A) layer is less than 40 mol% and the ethylene unit content of EVOH(a2) is 40 mol% or more, from the viewpoint of achieving a good balance between the gas barrier properties of the multilayer film of the present invention and the appearance characteristics after stretching (suppression of film surface roughness). More preferably, the ethylene unit content of EVOH(a1) is less than 37 mol% and the ethylene unit content of EVOH(a2) is 42 mol% or more.

[0017] The saponification degree of the vinyl ester units of EVOH(a1) and EVOH(a2) is preferably 90 mol% or more, more preferably 98 mol% or more, even more preferably 99 mol% or more, and may be 100 mol%. The saponification degree of EVOH can be determined by nuclear magnetic resonance (NMR) method.

[0018] EVOH (a1) and EVOH (a2) may have units derived from monomers other than ethylene, vinyl esters, and their saponified products, as long as the object of the present invention is not inhibited. When EVOH (a1) and EVOH (a2) have the above-mentioned other monomer units, the content of each of the above-mentioned other monomer units with respect to all the structural units of each of EVOH (a1) and EVOH (a2) is preferably 30 mol% or less, more preferably 20 mol% or less, still more preferably 10 mol% or less, and particularly preferably 5 mol% or less. Further, when EVOH (a1) and EVOH (a2) have units derived from the above-mentioned other monomers, the lower limit may be 0.05 mol% or 0.10 mol%. Examples of the above-mentioned other monomers include alkenes such as propylene, butylene, pentene, and hexene; alkenes having an ester group such as 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-methyl-1-butene, 4-acyloxy-2-methyl-1-butene, 4-acyloxy-3-methyl-1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diacyloxy-1-pentene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy-1-hexene, 5,6-diacyloxy-1-hexene, 1,3-diacetoxy-2-methylenepropane, or their saponified products; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, and itaconic acid, or their anhydrides, salts, or mono- or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, or their salts; vinyl silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxy-ethoxy)silane, and γ-methacryloxypropylmethoxysilane; alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, etc.

[0019] EVOH(a1) and EVOH(a2) may be post-modified by methods such as urethanization, acetalization, cyanoethylation, oxyalkylation, etc.

[0020] The melt flow rate (MFR) of EVOH(a1) at 210°C and a load of 2160 g measured according to JIS K 7210:2014 is preferably 1.0 g / 10 min or more, more preferably 3.0 g / 10 min or more, and even more preferably 6.0 g / 10 min or more. When the MFR of EVOH(a1) is at or above the above lower limit, the fluidity of the resin during inflation molding is improved, and adhesion to the die lip holes can be suppressed. Also, the MFR of EVOH(a1) may be 30.0 g / 10 min or less, or may be 20.0 g / 10 min or less.

[0021] The melt flow rate (MFR) of EVOH(a2) at 210°C and a load of 2160 g measured according to JIS K 7210:2014 is preferably 3.0 g / 10 min or more, more preferably 5.0 g / 10 min or more, even more preferably 7.0 g / 10 min or more, and particularly preferably 10.0 g / 10 min or more. When the MFR of EVOH(a2) is at or above the above lower limit, the fluidity of the resin during inflation molding is improved, and adhesion to the die lip holes can be suppressed. Also, the MFR of EVOH(a2) may be 30.0 g / 10 min or less, or may be 20.0 g / 10 min or less.

[0022] From the viewpoint of suppressing adhesion to the die lip holes during inflation molding, the MFR of at least one of EVOH(a1) and EVOH(a2) contained in the resin composition (A) layer at 210°C and a load of 2160 g measured according to JIS K 7210:2014 is preferably 5 to 30 g / 10 min, and more preferably 7 to 25 g / 10 min. Also, from the viewpoint of further suppressing adhesion to the die lip holes, it is preferable that the MFR of both EVOH(a1) and (a2) contained in the resin composition (A) layer at 210°C and a load of 2160 g measured according to JIS K 7210:2014 is 5 to 30 g / 10 min, and more preferably 7 to 25 g / 10 min.

[0023] In the resin composition (A) layer, the mass ratio [a1 / a2] of EVOH (a1) to EVOH (a2) is preferably 2 / 98 or more, more preferably 40 / 60 or more, still more preferably 57 / 43 or more, even more preferably 70 / 30 or more, and particularly preferably 75 / 25 or more. When the mass ratio [a1 / a2] is 2 / 98 or more, the blocking resistance tends to be good. Also, the mass ratio [a1 / a2] is preferably 98 / 2 or less, more preferably 96 / 4 or less, and still more preferably 92 / 8 or less. When the mass ratio [a1 / a2] is 98 / 2 or less, the blocking resistance tends to be good.

[0024] EVOH (a1) and EVOH (a2) may be used alone or in combination of two or more. Further, the resin composition (A) layer may further contain another EVOH having a different ethylene unit content from EVOH (a1) and EVOH (a2).

[0025] The resin composition (A) layer may contain other components such as, for example, an antiblocking agent, a processing aid, a resin other than EVOH (a1) and EVOH (a2), a carboxylic acid compound, a phosphoric acid compound, a boron compound, a metal salt, a stabilizer, an antioxidant, an ultraviolet absorber, a plasticizer, an antistatic agent, a lubricant, a colorant, a filler, a surfactant, a desiccant, a crosslinking agent, and a reinforcing agent such as various fibers, as long as the effects of the present invention are not inhibited.

[0026] Examples of the antiblocking agent include inorganic oxides, inorganic nitrides, and inorganic oxynitrides selected from silicon, aluminum, magnesium, zirconium, cerium, tungsten, molybdenum, etc. Among them, silicon oxide is desirable because of its easy availability. When the resin composition (A) layer contains an antiblocking agent, the blocking resistance tends to be further enhanced.

[0027] Examples of the processing aid include fluorine-based processing aids such as Kynar (trademark) manufactured by Arkema and Dynamar (trademark) manufactured by 3M. When the resin composition (A) layer contains a processing aid, it tends to be more effective in preventing adhesion to the die lip.

[0028] Examples of resins other than EVOH(a1) and EVOH(a2) include polyolefin, polyamide, polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, epoxy resin, acrylic resin, urethane resin, polyester resin, etc. These resins may be acid-modified resins.

[0029] When the resin composition (A) layer contains a carboxylic acid compound, it tends to be less likely to be colored during melt molding. The carboxylic acid may be a monocarboxylic acid or a polycarboxylic acid, or a combination thereof. Further, the carboxylic acid may be an ion, and such a carboxylic acid ion may form a salt with a metal ion.

[0030] When the resin composition (A) layer contains a phosphoric acid compound, it tends to be less likely to be colored during melt molding. The phosphoric acid compound is not particularly limited, and various acids such as phosphoric acid and phosphorous acid and their salts can be used. The phosphate may be contained in any form of primary phosphate, secondary phosphate, or tertiary phosphate, but primary phosphate is preferred. The cation species thereof is also not particularly limited, but an alkali metal salt is preferred. Among these, sodium dihydrogen phosphate and potassium dihydrogen phosphate are preferred. When the resin composition (A) layer contains a phosphoric acid compound, the content of the phosphoric acid compound is preferably 5 to 200 ppm in terms of phosphate radical. When the content of the phosphoric acid compound is 5 ppm or more, the color resistance during melt molding tends to be good. On the other hand, when the content of the phosphoric acid compound is 200 ppm or less, the melt moldability tends to be good, and more preferably 160 ppm or less.

[0031] When the resin composition (A) layer contains a boron compound, torque fluctuations during heat melting tend to be suppressed. The boron compound is not particularly limited, and examples include boric acids, borate esters, borates, boron hydrides, etc. Specifically, examples of boric acids include orthoboric acid, metaboric acid, tetraboric acid, etc.; examples of borate esters include triethyl borate, trimethyl borate, etc.; examples of borates include alkali metal salts, alkaline earth metal salts, borax, etc. of the various boric acids described above. Among these compounds, orthoboric acid (hereinafter may be simply referred to as boric acid) is preferred. When the resin composition (A) layer contains a boron compound, the content of the boron compound is preferably 20 to 2000 ppm in terms of boron element. When the content of the boron compound is 20 ppm or more, torque fluctuations during heat melting tend to be suppressed, and more preferably it is 50 ppm or more. On the other hand, when the content of the boron compound is 2000 ppm or less, the moldability tends to be good, and more preferably it is 1000 ppm or less.

[0032] When the resin composition (A) layer contains an alkali metal salt, in the multilayer film of the present invention, the interlayer adhesiveness between the resin composition (A) layer and other resin layers (for example, the thermoplastic resin (B) layer or the adhesive resin (C) layer) tends to be good. The cation species of the alkali metal salt is not particularly limited, but sodium salts or potassium salts are preferred. The anion species of the alkali metal salt is also not particularly limited. It can be added as carboxylates, carbonates, bicarbonates, phosphates, hydrogen phosphates, hydrochlorides, nitrates, sulfates, borates, hydroxides, etc. When the resin composition (A) layer contains an alkali metal salt, the content of the alkali metal salt is preferably 10 to 500 ppm in terms of metal element. The content of the alkali metal salt is more preferably 50 ppm or more. On the other hand, when the content of the alkali metal salt is 500 ppm or less, the melt stability tends to be good, and more preferably it is 300 ppm or less.

[0033] When the resin composition (A) layer contains an alkaline earth metal salt, deterioration of the resin and generation of deteriorated products such as gels during repeated melt molding tend to be suppressed. The cation species of the alkaline earth metal salt is not particularly limited, but magnesium salts or calcium salts are preferred. The anion species of the alkaline earth metal salt is also not particularly limited. It can be added as carboxylate salts, carbonate salts, bicarbonate salts, phosphate salts, hydrogen phosphate salts, hydrochloride salts, nitrate salts, sulfate salts, borate salts, hydroxides, etc.

[0034] Examples of stabilizers for improving melt stability and the like include hydrotalcite compounds, hindered phenol-based heat stabilizers, hindered amine-based heat stabilizers, metal salts of higher aliphatic carboxylic acids (for example, calcium stearate, magnesium stearate, etc.). When the resin composition (A) layer contains a stabilizer, the content is preferably 0.001 to 1% by mass.

[0035] Examples of antioxidants include 2,5-di-t-butyl-hydroquinone, 2,6-di-t-butyl-p-cresol, 4,4'-thiobis-(6-t-butylphenol), 2,2'-methylene-bis-(4-methyl-6-t-butylphenol), octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate, 4,4'-thiobis-(6-t-butylphenol), etc.

[0036] Examples of ultraviolet absorbers include ethylene-2-cyano-3',3'-diphenylacrylate, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)5-chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, etc.

[0037] Examples of plasticizers include dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, phosphate esters, etc.

[0038] Examples of the antistatic agent include pentaerythritol monostearate, sorbitan monopalmitate, sulfated polyolefins, polyethylene oxide, carbowax, and the like.

[0039] Examples of the lubricant include ethylene bisstearamide, butyl stearate, and the like.

[0040] Examples of the colorant include carbon black, phthalocyanine, quinacridone, indoline, azo pigments, red iron oxide, and the like.

[0041] Examples of the filler include glass fiber, asbestos, ballast stone, calcium silicate, and the like.

[0042] As for the ratio of EVOH (a1) and EVOH (a2) as the resin constituting the resin composition (A) layer, 80% by mass or more is preferable, 90% by mass or more is more preferable, 95% by mass or more is further preferable, and 98% by mass or more is particularly preferable. The resin constituting the resin composition (A) layer may be substantially composed of only EVOH (a1) and EVOH (a2), or may be composed of only EVOH (a1) and EVOH (a2). Also, as for the ratio of EVOH (a1) and EVOH (a2) in the resin composition (A) layer, 80% by mass or more is preferable, 90% by mass or more is more preferable, 95% by mass or more is further preferable, and 98% by mass or more is particularly preferable. The resin composition (A) layer may be substantially composed of only EVOH (a1) and EVOH (a2), or may be composed of only EVOH (a1) and EVOH (a2).

[0043] The thickness of the resin composition (A) layer is preferably 0.5 μm or more, more preferably 0.8 μm or more, and may be 1 μm or more. When the thickness of the resin composition (A) layer is 0.5 μm or more, the gas barrier property tends to be improved. Also, the thickness of the resin composition (A) layer is preferably 20 μm or less, more preferably 10 μm or less, and may be 5 μm or less. When the thickness of the resin composition (A) layer is 20 μm or less, the appearance characteristics (film surface) after stretching tend to be good. Note that the suitable thickness of the resin composition (A) layer means the thickness after stretching.

[0044] From the viewpoints of industrial productivity and mechanical properties, the ratio of the thickness of the resin composition (A) layer to the total thickness of all layers of the multilayer film of the present invention is preferably 30% or less, more preferably 20% or less, and may be 10% or less, or even 5% or less. From the viewpoint of further enhancing the gas barrier property, the multilayer film of the present invention may have an EVOH layer different from the resin composition (A) layer, and the number of such layers is not particularly limited.

[0045] <Thermoplastic resin (B) layer> The multilayer film of the present invention contains a thermoplastic resin (B) layer, thereby enhancing the mechanical strength and the barrier property against water vapor of the multilayer film of the present invention. Further, by forming a film in multiple layers with the resin composition (A) layer, the film thickness of the resin composition (A) layer tends to be reduced, and as a result, the recycling of the multilayer structure of the present invention described later tends to be facilitated. In addition, characteristics such as heat sealability and mechanical strength can be imparted according to the type of the thermoplastic resin constituting the thermoplastic resin (B) layer. Examples of the thermoplastic resin used for the thermoplastic resin (B) layer include polyethylene such as linear low density polyethylene, low density polyethylene, ultra low density polyethylene, medium density polyethylene, and high density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-propylene (block or random) copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylate copolymer, polypropylene, propylene-α-olefin copolymer, polybutene, polypentene, and other olefin homopolymers or copolymers, or those obtained by graft-modifying these with unsaturated carboxylic acids or their esters, etc. polyolefins; polyesters; polyamides (including copolymer polyamides); polyvinyl chloride; polyvinylidene chloride; acrylic resins; polystyrene; polyvinyl esters; polyester elastomers; polyurethane elastomers; chlorinated polystyrene; chlorinated polypropylene; aromatic polyketones or aliphatic polyketones, and polyalcohols obtained by reducing these; polyacetals; polycarbonates, and the like. Among them, polyolefins are preferable from the viewpoint of excellent heat sealability and mechanical properties. On the other hand, from the viewpoint of improving the recyclability of the multilayer structure including the multilayer film of the present invention, the thermoplastic resin (B) layer preferably contains polyethylene as a main component. Here, the "main component" means a component having a proportion of more than 50% by mass in the thermoplastic resin (B) layer. The proportion of polyethylene in the thermoplastic resin (B) layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably the thermoplastic resin (B) layer is composed only of polyethylene. Since polyethylene is widely used as a packaging material regardless of the presence or absence of gas barrier properties, its recycling infrastructure has been widely established in each country.Furthermore, it is preferable to use polyethylene because it can be formed at a lower temperature compared to polypropylene, can be heat-sealed at a lower temperature, and has excellent strength. When the thermoplastic resin (B) layer contains polyethylene as a main component, the polyethylene is preferably at least one selected from linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene, more preferably at least one selected from linear low-density polyethylene and low-density polyethylene, or a mixture of at least one selected from linear low-density polyethylene and low-density polyethylene and high-density polyethylene.

[0046] In the thermoplastic resin (B) layer, the proportion of the thermoplastic resin is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, particularly preferably 98% by mass or more. The thermoplastic resin (B) layer may be substantially composed of only the thermoplastic resin or may be composed of only the thermoplastic resin.

[0047] The melt flow rate (MFR) of the thermoplastic resin constituting the thermoplastic resin (B) layer measured according to JIS K 7210:2014 at 190°C and a load of 2160 g is preferably 0.10 to 10.0 g / 10 min, more preferably 0.30 to 5.0 g / 10 min. When the MFR of the thermoplastic resin constituting the thermoplastic resin (B) layer is within the above range, the molding stability during inflation molding tends to be good.

[0048] From the viewpoints of industrial productivity and mechanical properties, the thickness of the thermoplastic resin (B) layer is preferably 7 to 100 μm, more preferably 10 to 50 μm. Note that the preferred thickness of the thermoplastic resin (B) layer means the thickness after stretching. When the thermoplastic resin (B) layer has a plurality of layers, the total thickness is preferably within the above range.

[0049] In the multilayer film of the present invention, the thermoplastic resin (B) layer may be provided as one layer or multiple layers. When multiple thermoplastic resin (B) layers are provided, if the thermoplastic resin (B) layers made of the same material are continuously laminated, they are regarded as one layer. For example, for a multilayer film of thermoplastic resin (B) layer / thermoplastic resin (B) layer / thermoplastic resin (B) layer / adhesive resin (C) layer / resin composition (A) layer, when all the materials of the thermoplastic resin (B) layers are the same, the above multilayer film is regarded as a multilayer film of thermoplastic resin (B) layer / adhesive resin (C) layer / resin composition (A) layer, and the thickness of each layer of the thermoplastic resin (B) layer is the sum of the thicknesses of the three layers. On the other hand, if the materials of the thermoplastic resin (B) layers are different in the above example, they shall be considered as independent layers. In addition, the " / " used in the above configuration example of the multilayer film means that the layers on both sides are directly laminated.

[0050] <Adhesive resin (C) layer> From the viewpoint of making the appearance characteristics (film surface) of the stretched multilayer film of the present invention good and maintaining quality stability, it is preferable that the multilayer film of the present invention has an adhesive resin (C) layer, and it is more preferable that the resin composition (A) layer and the thermoplastic resin (B) layer are laminated via the adhesive resin (C) layer. In addition, when recycling the multilayer structure of the present invention described later, the presence of the adhesive resin (C) layer can enhance the compatibility between the resin composition (A) layer and the thermoplastic resin (B) layer, and the recyclability tends to be improved. Therefore, from this viewpoint, it is also preferable to have an adhesive resin (C) layer. As the adhesive resin constituting the adhesive resin (C) layer, it is preferable to use a polyolefin having a carboxy group, a carboxylic anhydride group or an epoxy group, and it is more preferable to use a polyolefin having a carboxylic anhydride group. Such an adhesive resin is also excellent in adhesiveness to the resin composition (A) layer or the thermoplastic resin (B) layer.

[0051] Examples of the polyolefin containing a carboxy group include polyolefins copolymerized with acrylic acid or methacrylic acid. At this time, all or part of the carboxyl groups contained in the polyolefin may be present in the form of metal salts as represented by ionomers. Examples of the polyolefin having a carboxylic anhydride group include polyolefins graft-modified with maleic anhydride or itaconic acid. Examples of the polyolefin having an epoxy group include polyolefins copolymerized with glycidyl methacrylate. Among them, polyolefins having a carboxylic anhydride group such as maleic anhydride are preferably used, and polyethylene having a carboxylic anhydride group is particularly preferably used.

[0052] The melt flow rate (MFR) of the adhesive resin constituting the adhesive resin (C) measured according to JIS K 7210:2014 at 190 ° C and a load of 2160 g is preferably 0.1 to 20.0 g / 10 min, more preferably 1.0 to 10.0 g / 10 min. When the MFR of the thermoplastic resin (C) is within the above range, the film-forming stability tends to be good during inflation molding.

[0053] The thickness of the adhesive resin (C) layer is preferably 0.5 to 20 μm, more preferably 1 to 10 μm, from the viewpoints of industrial productivity and quality stability. The preferred thickness of the adhesive resin (C) layer means the thickness after stretching. When the multilayer film of the present invention has a plurality of resin composition (A) layers and thermoplastic resin (B) layers, or when it includes an EVOH layer different from the resin composition (A) layer, the adhesive resin (C) layer may be provided between each layer, and the number of adhesive resin (C) layers in the multilayer film of the present invention is not particularly limited.

[0054] <Multilayer film> The layer structure of the multilayer film of the present invention is not particularly limited as long as it has a resin composition (A) layer on the outermost layer and a thermoplastic resin (B) layer. For example, the following multilayer film structures are exemplified. Hereinafter, the resin composition (A) layer is denoted as "layer (A)", the thermoplastic resin (B) layer is denoted as "layer (B)", and the adhesive resin (C) layer is denoted as "layer (C)". In the following examples, the adhesive resin (C) layer may not be provided, but it is preferable to have the adhesive resin (C) layer from the viewpoints of quality stability and recyclability. Also, " / " means that the layers on both sides are directly laminated. Examples of the layer structure of the multilayer film of the present invention include, for example, layer (B) / layer (C) / layer (A), layer (B) / layer (C) / layer (A) / layer (C) / layer (A), layer (A) / layer (C) / layer (B) / layer (C) / layer (A), layer (B) / layer (C) / layer (A) / layer (C) / layer (B) / layer (C) / layer (A), etc. Among them, layer (B) / layer (C) / layer (A) is preferable from the viewpoint of industrial productivity.

[0055] The total thickness of the multilayer film of the present invention can be appropriately set according to the application. The total thickness is preferably 10 μm or more, more preferably 15 μm or more. When the total thickness is 10 μm or more, the industrial productivity and mechanical properties tend to improve. Also, the total thickness is preferably 100 μm or less, more preferably 50 μm or less. When the total thickness is 100 μm or less, the industrial productivity and economy tend to improve. Note that the preferred total thickness of the multilayer film means the thickness after stretching.

[0056] The method for manufacturing the multilayer film of the present invention is not particularly limited. Generally, a conventional coextrusion method in which each resin is extruded from a separate die or a common die and laminated can be used. As the die, either an annular die or a T-die can be used. Examples include cast molding, inflation molding, etc. Considering the effect of the present invention of suppressing the blocking between the resin composition (A) layers when stretching is performed with the resin composition (A) layers in contact with each other, it is preferable to manufacture by inflation molding using an annular die. Also, inflation molding is preferable in terms of cost. That is, the multilayer film of the present invention is preferably an inflation molded body. Here, in the present specification, the inflation molded body means a molded product obtained through inflation molding. For example, a packaging container obtained after film formation by inflation molding and then through secondary processing (such as press molding, etc.) also corresponds to the inflation molded body. In addition, as long as the stretching is performed in a mode where the resin composition (A) layers are in contact with each other, since the anti-blocking effect of the present invention can be sufficiently obtained, the manufacturing method of the present invention preferably includes a step of performing stretching with the resin composition (A) layers in contact with each other, such as stacking the multilayer film obtained by cast molding so that the resin composition (A) layers are in contact with each other and then performing stretching.

[0057] When using inflation molding in manufacturing the multilayer film of the present invention, known means can be used as the inflation molding method.

[0058] The multilayer film of the present invention is stretched at least 3 times and at most 12 times in at least one axial direction. If the stretching of the multilayer film of the present invention is less than 3 times, thickness unevenness due to stretching tends to occur, and the gas barrier property tends to decrease. On the other hand, if the stretching of the multilayer film of the present invention exceeds 12 times, the film surface after stretching tends to deteriorate. The multilayer film of the present invention is preferably stretched at least 4 times in at least one axial direction, and more preferably stretched 5 times or more. Further, the multilayer film of the present invention is preferably stretched at most 10 times in at least one axial direction, and more preferably stretched 8 times or less. The multilayer film of the present invention may be stretched uniaxially or biaxially. However, from the viewpoints of economy and ease of tearing the multilayer film (easy to open the packaging material when used as a packaging material), uniaxial stretching is preferred, and uniaxial stretching in the longitudinal direction (MD direction) is particularly preferred. In this case, it is preferably not substantially stretched in the width direction (TD direction). Further, even when the multilayer film of the present invention is biaxially stretched, it is preferably mainly stretched in the longitudinal direction (MD direction), and the ratio (MD / TD) of the stretching ratio in the longitudinal direction (MD direction) to the stretching ratio in the width direction (TD direction) is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more. Also, the ratio of the stretching ratios (MD / TD) may be 12 or less. When the stretching is less than 3 times, even if the resin composition (A) layers are stretched in contact with each other, blocking hardly occurs, so the merit of applying the present invention becomes small.

[0059] The stretching method of the multilayer film of the present invention is not particularly limited, and examples thereof include a tenter stretching method, a tubular stretching method, a roll stretching method, and the like. From the viewpoint of manufacturing cost, uniaxial stretching by a roll stretching method is preferred. Further, when the multilayer film of the present invention is an inflation molded body, the roll stretching method is also preferred from the viewpoint of being able to easily stretch the folded cylindrical multilayer film in the uniaxial direction after inflation molding.

[0060] The manufacturing method of the multilayer film of the present invention includes, for example, by inflation molding, a step (I) of molding a cylindrical multilayer film having the resin composition (A) layer and the thermoplastic resin (B) layer, with the outermost layer on the inner surface side being the resin composition (A) layer, a step (II) of folding and stretching the cylindrical multilayer film so that the inner surfaces are in contact with each other, and a step (III) of cutting at least a part of the stretched cylindrical multilayer film to obtain a planar multilayer film. Hereinafter, the preferred manufacturing method of the present invention will be described in detail, but the aspects of the present invention are not limited thereto.

[0061] In step (I), a resin composition containing EVOH (a1) and EVOH (a2) and a thermoplastic resin are melt-extruded from an annular die to form a cylindrical multilayer film. When forming a cylindrical film, it is preferable to make the resin composition (A) layer the outermost layer on the inner surface side from the viewpoint of suppressing the thermal deterioration of EVOH and the adhesion of eye mucus to the die lip. When the resin composition (A) layer is the outermost layer on the outer surface side, although the problem of blocking in the stretching step described later is eliminated, there is concern about the thermal deterioration of EVOH due to the extension of the melting time based on the extension of the flow path. Also, as described later, in inflation molding, gas is supplied to the inner space of the cylindrical multilayer film to expand the multilayer film, so EVOH easily adheres to the die lip, and for example, compared with the case where the resin composition (A) layer is the outermost layer on the inner surface side, the adhesion of eye mucus tends to increase.

[0062] In the melt-extruded cylindrical multilayer film, gas is supplied to the inner space and expanded to a predetermined size by the internal pressure. The expanded cylindrical multilayer film is folded by a pair of nip rolls so that the inner surfaces are in contact with each other and wound up by a roll. At this time, conditions such as the blow-up ratio indicating the degree of expansion and the take-up speed when winding up by the roll are not particularly limited, and known conditions can be appropriately selected.

[0063] In step (II), the multilayer film folded in step (I) is stretched in at least one axial direction.

[0064] When stretching in one axis, roll stretching is preferably used. Generally, a temperature range of 50°C to 130°C is adopted as the temperature during stretching.

[0065] In biaxial stretching, the tenter stretching method is preferably used. In the case of simultaneous biaxial stretching, when the temperature is in the range of 70°C to 100°C, a biaxially stretched film with fewer stretching marks can be obtained. In sequential biaxial stretching, when stretching in the longitudinal direction of the roll, a temperature range of 70°C to 100°C is adopted, and when stretching in the width direction of the roll, a temperature range of 80°C to 120°C is adopted, whereby a biaxially stretched film with fewer stretching marks can be obtained.

[0066] In step (III), at least a part of the stretched cylindrical multilayer film obtained in step (II) is cut to obtain a planar multilayer film. The multilayer film of the present invention obtained through step (III) tends to be such that, for example, in the case of a vapor deposition multilayer film described later or when manufacturing a multilayer structure, another layer (inorganic vapor deposition (D) layer or thermoplastic resin (E) layer) can be easily laminated on the outermost resin composition (A) layer.

[0067] A vapor deposition multilayer film in which an inorganic vapor deposition (D) layer is adjacent to the surface side of the resin composition (A) layer of the multilayer film of the present invention is a preferred embodiment of the multilayer film. Here, being adjacent means being in direct contact. Since the resin composition (A) layer has good affinity with the inorganic vapor deposition (D) layer, the vapor deposition multilayer film of the present invention has high gas barrier properties and tends to maintain good gas barrier properties even when subjected to physical stresses such as bending.

[0068] <Inorganic vapor deposition (D) layer> The inorganic vapor deposition (D) layer is usually a layer having barrier properties against oxygen and water vapor. Therefore, the vapor deposition multilayer film of the present invention tends to have good gas barrier properties by including the inorganic vapor deposition (D) layer. The inorganic vapor deposition (D) layer can be formed by vapor depositing an inorganic substance. Examples of the inorganic substance include metals (e.g., aluminum), metal oxides (e.g., silicon oxide, aluminum oxide), metal nitrides (e.g., silicon nitride), metal oxynitrides (e.g., silicon oxynitride), or metal carbonitrides (e.g., silicon carbonitride), etc. Among them, an inorganic vapor deposition (D) layer formed of aluminum, aluminum oxide, silicon oxide, magnesium oxide, or silicon nitride is preferable from the viewpoint of industrial productivity, and an inorganic vapor deposition (D) layer formed of aluminum is more preferable. Note that even if it is a metal vapor deposition layer of aluminum, irreversible oxidation may occur and a part of aluminum oxide may be included. When a part of aluminum oxide is included in the metal vapor deposition layer, the ratio of the amount of substance of oxygen atoms (O mol ) to the amount of substance of aluminum atoms (Al mol ) constituting the metal vapor deposition layer (O mol / Al mol ) is preferably 0.5 or less, more preferably 0.3 or less, still more preferably 0.1 or less, and particularly preferably 0.05 or less.

[0069] The method for forming the inorganic vapor deposition (D) layer is not particularly limited, and includes physical vapor deposition methods such as vacuum vapor deposition methods (e.g., resistance heating vapor deposition, electron beam vapor deposition, molecular beam epitaxy method, etc.), sputtering methods, and ion plating methods; chemical vapor deposition methods such as thermal chemical vapor deposition methods (e.g., catalytic chemical vapor deposition method), photo chemical vapor deposition method, plasma chemical vapor deposition methods (e.g., capacitively coupled plasma, inductively coupled plasma, surface wave plasma, electron cyclotron resonance, dual magnetron, atomic layer deposition method, etc.), and metal organic chemical vapor deposition methods.

[0070] The inorganic vapor deposition (D) layer is provided adjacent to the surface side of the resin composition (A) layer of the multilayer film of the present invention. By providing the inorganic vapor deposition (D) layer in the resin composition (A) layer, the gas barrier property tends to be good even after being subjected to physical stresses such as gas barrier property and bending. The average thickness of the inorganic vapor deposition (D) layer is preferably 150 nm or less, more preferably 120 nm or less, and even more preferably 100 nm or less. Further, the average thickness of the inorganic vapor deposition (D) layer is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. Note that the average thickness of the inorganic vapor deposition (D) layer is the average value of the thicknesses at any 10 points of the cross-section of the inorganic vapor deposition (D) layer measured by an electron microscope. From the viewpoint of reducing the coloring of the recovered composition of the multilayer structure, when the multilayer structure has a plurality of inorganic vapor deposition (D) layers, the total thickness of the inorganic vapor deposition (D) layers is preferably 1 μm or less.

[0071] The layer structure of the vapor deposition multilayer film of the present invention is not particularly limited as long as the inorganic vapor deposition (D) layer is adjacent to the surface side of the resin composition (A) layer of the multilayer film of the present invention. For example, layer (B) / layer (C) / layer (A) / layer (D), layer (B) / layer (C) / layer (A) / layer (C) / layer (A) / layer (D), layer (A) / layer (C) / layer (B) / layer (C) / layer (A) / layer (D), layer (B) / layer (C) / layer (A) / layer (C) / layer (B) / layer (C) / layer (A) / layer (D), etc. can be mentioned. Among them, from the viewpoint of industrial productivity, layer (B) / layer (C) / layer (A) / layer (D) is preferable.

[0072] <Thermoplastic resin (E) layer> The multilayer film and vapor-deposited multilayer film of the present invention may further be a multilayer structure including a thermoplastic resin (E) layer. When the multilayer structure of the present invention has a thermoplastic resin (E) layer, the film thickness ratio of the resin composition (A) layer in the multilayer structure of the present invention tends to be reduced, and as a result, the recycling of the multilayer structure of the present invention described below tends to be facilitated. Further, characteristics such as heat sealability and mechanical strength can be imparted according to the type of the thermoplastic resin constituting the thermoplastic resin (E) layer. When obtaining the multilayer structure of the present invention by laminating a thermoplastic resin (E) layer on the vapor-deposited multilayer film of the present invention, it is preferable to provide the thermoplastic resin (E) layer on the surface side of the inorganic vapor deposition (D) layer of the vapor-deposited multilayer film, and it is more preferable that an adhesive layer is provided between the inorganic vapor deposition (D) layer and the thermoplastic resin (E) layer. Examples of the thermoplastic resin used for the thermoplastic resin (E) layer include polyethylene such as linear low-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, medium-density polyethylene, and high-density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-propylene (block or random) copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylate copolymer, polypropylene, propylene-α-olefin copolymer, polybutene, polypentene, and other olefin homopolymers or copolymers, or those graft-modified with an unsaturated carboxylic acid or its ester; polyester; polyamide (including copolymer polyamide); polyvinyl chloride; polyvinylidene chloride; acrylic resin; polystyrene; polyvinyl ester; polyester elastomer; polyurethane elastomer; chlorinated polystyrene; chlorinated polypropylene; aromatic polyketone or aliphatic polyketone, and polyalcohol obtained by reducing these; polyacetal; polycarbonate, and the like. Among them, polyolefin is preferable from the viewpoint of excellent heat sealability. On the other hand, from the viewpoint of improving the recyclability of the multilayer structure of the present invention, the thermoplastic resin (E) layer preferably contains polyethylene as a main component, and more preferably is composed only of polyethylene. Since polyethylene is widely used as a packaging material regardless of the presence or absence of gas barrier properties, its recycling infrastructure has been widely established in each country.Furthermore, it is preferable to use polyethylene because it can be formed at a lower temperature compared to polypropylene, can be heat-sealed at a lower temperature, and has excellent strength. When the thermoplastic resin (E) layer contains polyethylene as a main component, the polyethylene is preferably at least one selected from linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene, more preferably at least one selected from linear low-density polyethylene and low-density polyethylene, or a mixture of at least one selected from linear low-density polyethylene and low-density polyethylene and high-density polyethylene.

[0073] Examples of the configuration of the multilayer structure of the present invention include layer (E) / / layer (B) / layer (C) / layer (A), layer (E) / / layer (B) / layer (C) / layer (A) / / layer (E), layer (B) / layer (C) / layer (A) / / layer (E), layer (E) / / layer (B) / layer (C) / layer (A) / layer (D), layer (E) / / layer (B) / layer (C) / layer (A) / layer (D) / / layer (E), layer (B) / layer (C) / layer (A) / layer (D) / / layer (E), etc. Among them, from the viewpoints of particularly excellent gas barrier properties and providing a layer for printing or a heat-sealing layer in the multilayer structure, layer (E) / / layer (B) / layer (C) / layer (A) / layer (D) / / layer (E) or layer (B) / layer (C) / layer (A) / layer (D) / / layer (E) is preferable. Note that " / / " used in the above configuration examples means that they are laminated via an adhesive layer.

[0074] As a manufacturing method for obtaining a multilayer structure by laminating a thermoplastic resin (E) layer on the multilayer film or vapor-deposited multilayer film of the present invention, various known manufacturing methods can be adopted, such as a dry lamination method, a sand lamination method, an extrusion lamination method, a coextrusion lamination method, a solution coating method, etc. When laminating the thermoplastic resin (E) layer, an adhesive layer may be provided between the multilayer film or vapor-deposited multilayer film of the present invention and the thermoplastic resin (E) layer. As such an adhesive layer, for example, a known adhesive for lamination such as a two-component reaction type polyurethane-based adhesive obtained by mixing and reacting a polyisocyanate component and a polyol component is preferably used.

[0075] The multilayer film, vapor-deposited multilayer film, and multilayer structure of the present invention may be provided with a vapor-deposited layer separately from the inorganic vapor-deposited (D) layer. Such a vapor-deposited layer may be provided, for example, by using a thermoplastic resin (B) layer or a thermoplastic resin (E) layer as a base material. That is, a vapor-deposited layer may be provided on the thermoplastic resin (B) layer or on the thermoplastic resin (E) layer. As components constituting such a vapor-deposited layer, known components used as a vapor-deposited layer can be appropriately used.

[0076] The multilayer structure of the present invention preferably has excellent recyclability. In recent years, due to environmental and waste problems, the demand for so-called post-consumer recycling (hereinafter sometimes simply abbreviated as recycling), which involves collecting and recycling packaging materials consumed in the market, has been increasing globally. In recycling, a process is generally adopted in which the collected packaging materials are cut, sorted and washed as necessary, and then melt-mixed using an extruder. Polyester films, polyamide films, etc. are difficult to be uniformly mixed with other components in the melt-mixing process when recycled, which has become an obstacle to recycling. Therefore, from the viewpoint of enhancing recyclability, it is preferable that the thermoplastic resin (B) layer and / or the thermoplastic resin (E) layer do not contain polyester and polyamide. The multilayer film, vapor-deposited multilayer film and multilayer structure of the present invention are preferably based on polyolefins such as polyethylene and polypropylene (the main component of the multilayer structure is polyolefin), and particularly preferably based on polyethylene from the viewpoint that recycling infrastructure has been widely established in each country. Generally, EVOH has a melting temperature close to that of polyolefins and excellent recyclability, but in order not to affect the mechanical properties of the composition after recycling, the proportion of EVOH in the multilayer structure of the present invention is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. On the other hand, from the viewpoint of enhancing recyclability, the proportion of polyolefin in the multilayer structure of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. In particular, the proportion of polyethylene in the multilayer structure of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0077] The multilayer film, vapor-deposited multilayer film and multilayer structure of the present invention can be suitably used as materials for various types of packaging such as food packaging, pharmaceutical packaging, industrial chemical packaging, and agricultural chemical packaging. In particular, the packaging material provided with the multilayer structure of the present invention can be suitably used as a packaging material with excellent recyclability.

Examples

[0078] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0079] <Materials Used in Examples and Comparative Examples> ·EVOH a-1: EVOH with an ethylene unit content of 32 mol%, saponification degree of 99.9 mol% or more, MFR (at 210 °C, under a load of 2160 g), 4.0 g / 10 min a-2: EVOH with an ethylene unit content of 27 mol%, saponification degree of 99.9 mol% or more, MFR (at 210 °C, under a load of 2160 g), 4.0 g / 10 min a-3: EVOH with an ethylene unit content of 44 mol%, saponification degree of 99.9 mol% or more, MFR (at 210 °C, under a load of 2160 g), 12.0 g / 10 min a-4: EVOH with an ethylene unit content of 48 mol%, saponification degree of 99.9 mol% or more, MFR (at 210 °C, under a load of 2160 g), 15.0 g / 10 min a-5: EVOH with an ethylene unit content of 32 mol%, saponification degree of 99.9 mol% or more, MFR (at 210 °C, under a load of 2160 g), 9.0 g / 10 min a-6: EVOH with an ethylene unit content of 35 mol%, saponification degree of 99.9 mol% or more, MFR (at 210 °C, under a load of 2160 g), 19.0 g / 10 min a-7: EVOH with an ethylene unit content of 44 mol%, saponification degree of 99.9 mol% or more, MFR (at 210 °C, under a load of 2160 g), 4.0 g / 10 min · Thermoplastic resin used in the thermoplastic resin (B) layer B-1: "Lumicene (trademark) Supertough 40ST05" (polyethylene, manufactured by Total, MFR (at 190 °C, under a load of 2160 g), 0.50 g / 10 min) · Adhesive resin used in the adhesive resin (C) layer C-1: "Admer (trademark) NF528" (a polyethylene-based adhesive resin, manufactured by Mitsui Chemicals, Inc., MFR (at 190 °C, under a load of 2160 g), 2.5 g / 10 min) · Film used as the thermoplastic resin (E) layer E-1: Uniaxially stretched PE film, thickness 30 μm E-2: "UNIX (trademark) LS-760C" (manufactured by Idemitsu Unitech Co., Ltd., LLDPE film, thickness 50 μm)

[0080] [Evaluation method] (1) Blocking evaluation after stretching Using the stretched multilayer films obtained from the examples and comparative examples, the presence or absence of blocking was visually confirmed and evaluated in three grades of A, B, and C as follows. Judgment: Criteria A: No blocking was confirmed. B: Local blocking was confirmed. C: Blocking was confirmed over a wide range.

[0081] (2) Die lip adhesion (fish eyes) evaluation After continuously film-forming for 1 hour under the conditions for producing the inflation films of the examples and comparative examples, the operation was stopped, and the fish eyes adhering to the surface of the die lip at the discharge port of the resin composition (A) were visually confirmed and evaluated in three grades of A, B, and C as follows. Judgment: Criteria A: No fish eyes were confirmed. B: A small amount of fish eyes were confirmed. C: A large amount of fish eyes were confirmed.

[0082] (3) Film surface evaluation after stretching The appearance of the stretched multilayer films of the examples and comparative examples was visually confirmed and evaluated in three grades of A, B, and C as follows. Judgment: Criteria A: No appearance abnormality was confirmed. B: Local stretching unevenness was confirmed. C: Stretching unevenness was confirmed over a wide range.

[0083] (4) OTR (Oxygen Transmission Rate) before and after vapor deposition (4-1) OTR (Oxygen Transmission Rate) before vapor deposition Using the drawn multi-layer films obtained in the examples and comparative examples, the oxygen transmission rate was measured with the resin composition (A) layer on the oxygen supply side and the thermoplastic resin (B) layer on the carrier gas side. Specifically, using an oxygen permeation measuring device ("MOCON OX-TRAN2 / 21" manufactured by Modern Controls), the oxygen transmission rate (unit: cc / (m 2 ·day·atm)) was measured under the conditions of a temperature of 20°C, a humidity of 65% RH on the oxygen supply side, a humidity of 65% RH on the carrier gas side, an oxygen pressure of 1 atm, and a carrier gas pressure of 1 atm. Nitrogen gas containing 2% by volume of hydrogen gas was used as the carrier gas. The results were evaluated in two levels, A and B, as follows. Judgment Criteria A: 0.5 cc / (m 2 ·day·atm) or more and less than 2 cc / (m 2 ·day·atm) B: 2 cc / (m 2 ·day·atm) or more (4-2) OTR (Oxygen Transmission Rate) after vapor deposition Using the vapor-deposited multi-layer films obtained in the examples and comparative examples, the oxygen transmission rate was measured with the inorganic vapor-deposited (D) layer on the oxygen supply side and the thermoplastic resin (B) layer on the carrier gas side. Specifically, using an oxygen permeation measuring device ("MOCON OX-TRAN2 / 21" manufactured by Modern Controls), the oxygen transmission rate (unit: cc / (m 2 ·day·atm)) was measured under the conditions of a temperature of 20°C, a humidity of 65% RH on the oxygen supply side, a humidity of 65% RH on the carrier gas side, an oxygen pressure of 1 atm, and a carrier gas pressure of 1 atm. Nitrogen gas containing 2% by volume of hydrogen gas was used as the carrier gas. The results were evaluated in three levels, A to C, as follows. Judgment Criteria A: Less than 0.1 cc / (m 2 ·day·atm) B: 0.1 cc / (m 2 ·day·atm) or more and less than 0.5 cc / (m 2 ·day·atm) C: 0.5 cc / (m 2 ·day·atm) or more and less than 2 cc / (m 2 ·day·atm)

[0084] [Example 1] 97 parts by mass of EVOH (a-1) having an ethylene content of 32 mol%, a saponification degree of 99.9 mol%, and an MFR (210°C, 2.16 kg load) of 4.0 g / 10 min and 3 parts by mass of EVOH (a-3) having an ethylene content of 44 mol%, a saponification degree of 99.9 mol%, and an MFR (210°C, 2.16 kg load) of 12.0 g / 10 min were kneaded under the following conditions using a twin-screw extruder "TEX30α" manufactured by The Japan Steel Works, Ltd. to obtain a resin composition. <Extruder conditions> Equipment: 30mmφ twin screw extruder L / D:45.5 Screw: Same direction full intermeshing type Extrusion temperature: 220℃ Rotational speed: 200 rpm Discharge amount: 20kg / hr

[0085] Using the obtained resin composition, a cylindrical multilayer film was produced under the following conditions using an inflation extrusion molding machine. During the production of the multilayer film, die lip adhesion evaluation was performed according to the method described in the above evaluation method (2). The results are shown in Table 1. The thermoplastic resin (B) layer was laminated in three layers with a thickness of 30 μm, and as a result, one thermoplastic resin (B) layer with a thickness of 90 μm was considered as one layer. <Multilayer film manufacturing conditions> Layer structure of multilayer film: [Outer surface side] Thermoplastic resin (B) layer / Adhesive resin (C) layer / Resin composition (A) layer [Inner surface side] = 90 μm / 20 μm / 20 μm (total thickness 130 μm) Thermoplastic resin (B) layer: B-1 (polyethylene resin, Lumicene (trademark) Supertough 40ST05) Adhesive resin (C) layer: C-1 (polyethylene adhesive resin, Admer (trademark) NF528) Resin composition (A) layer: the resin composition obtained above Equipment: 5-type, 5-layer inflation extrusion molding machine (Dr Collin) Die temperature: 210℃. Blow-up ratio: 2.7. Take-off speed: 4m / min. Film folding width: 25cm <Conditions of extruder 1 for thermoplastic resin (B) layer> Extruder: 30φ single-screw extruder (manufactured by Dr Collin). Rotation speed: 60 rpm. Extrusion temperature: feeding section / compression section / measurement section = 170°C / 190°C / 210°C. <Conditions of the extruder for the thermoplastic resin (B) layer 2> Extruder: 20φ single-screw extruder (manufactured by Dr Collin). Rotation speed: 70 rpm. Extrusion temperature: feeding section / compression section / measurement section = 170°C / 190°C / 210°C. <Conditions of the extruder for the thermoplastic resin (B) layer 3> Extruder: 20φ single-screw extruder (manufactured by Dr Collin). Rotation speed: 70 rpm. Extrusion temperature: feeding section / compression section / measurement section = 170°C / 190°C / 210°C. <Conditions of the extruder for the adhesive resin (C) layer> Extruder: 20φ single-screw extruder (manufactured by Dr Collin). Rotation speed: 70 rpm. Extrusion temperature: feeding section / compression section / measurement section = 170°C / 190°C / 210°C <Conditions of the extruder for the resin composition (A) layer> Extruder: 30φ single-screw extruder (manufactured by Dr Collin). Rotation speed: 24 rpm. Extrusion temperature: feeding section / compression section / measurement section = 190°C / 210°C / 210°C

[0086] The obtained cylindrical multilayer film was folded so that the resin composition (A) layers overlapped, and using the stretching device (SDR-506WK) of Eto Co., Ltd., it was uniaxially stretched 6 times in the longitudinal direction (MD direction) at 120°C, and a multilayer film after stretching (thermoplastic resin (B) layer / adhesive resin (C) layer / resin composition (A) layer = 15 μm / 3.3 μm / 3.3 μm) was obtained. Regarding the obtained multilayer film after stretching, the blocking evaluation and film surface evaluation after stretching were carried out according to the methods described in the above evaluation methods (1) and (3). The results are shown in Table 1.

[0087] Both ends of the obtained stretched multilayer film were cut to produce a planar multilayer film. For the obtained planar multilayer film, the oxygen transmission rate before vapor deposition was measured by the method described in the above evaluation method (4). The results are shown in Table 1. Using the obtained planar multilayer film and "EWA-105" manufactured by Nippon Vacuum Technology Co., Ltd., aluminum was vacuum-deposited on the resin composition (A) layer side to a thickness of 40 nm to produce a vapor-deposited multilayer film. For the obtained vapor-deposited multilayer film, the oxygen permeability was measured by the method described in the above evaluation method (4). The results are shown in Table 1.

[0088] <Fabrication of Multilayer Structure> Two types of multilayer structures with the following layer configurations were fabricated using the obtained stretched multilayer films before and after vapor deposition, and the 30-μm uniaxially stretched PE film (E-1) and 50-μm LLDPE film (E-2) as the thermoplastic resin (E) layer. One layer configuration is a multilayer structure composed of a thermoplastic resin (B) layer / an adhesive resin (C) layer / a resin composition (A) layer / an LLDPE film, and the other layer configuration is a multilayer structure composed of a uniaxially stretched PE film / a thermoplastic resin (B) layer / an adhesive resin (C) layer / a resin composition (A) layer / an inorganic vapor deposition (D) layer / an LLDPE film. When laminating the uniaxially stretched PE film and the LLDPE film to the multilayer film and the vapor-deposited multilayer film, a two-component urethane-based adhesive ("Takelac A-520" and "Takonate A-50" manufactured by Mitsui Chemicals, Inc.) was applied to a dry thickness of 2 μm and laminated by the dry lamination method.

[0089] [Examples 2 to 15, Comparative Examples 1 to 2] As shown in Table 1, except for changing the types and ratios (a1 / a2) of EVOH (a1) and EVOH (a2), multilayer films, vapor-deposited multilayer films, and multilayer structures were fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0090]

Table 1

[0091] From Comparative Examples 1 and 2 and Example 1, it can be seen that the antiblocking property is improved by having two types of EVOH (A) with different ethylene unit contents. From the comparison of Examples 1 to 6 and 10, it can be read that when the ratio (a1 / a2) of EVOH (A) is less than 97 / 3, the results of the antiblocking property, the stability of the film surface after stretching, and the die lip adhesion evaluation are further improved, and when it exceeds 50 / 50, it can be read that the gas barrier property is further improved. From Examples 7 and 9, it can be seen that when the ethylene unit content of the ethylene-vinyl alcohol copolymer (a1) is less than 40 mol% and the ethylene unit content of the ethylene-vinyl alcohol copolymer (a2) is 40 mol% or more, the film surface after stretching tends to be good while maintaining the oxygen barrier property of the multilayer film. From Examples 9, 10, and 13, it can be seen that when the melt flow rate of at least one of the ethylene-vinyl alcohol copolymers is 5 to 30 g / 10 min, the die lip adhesion tends to decrease. From Examples 10, 11, and 15, it can be seen that when the ethylene unit content of the ethylene-vinyl alcohol copolymer (a1) is more than 27 mol% and less than 35 mol%, the stability of the film surface after stretching tends to be good while maintaining the oxygen barrier property of the multilayer film, and the oxygen barrier after aluminum vapor deposition also tends to be excellent.

[0092] To confirm the recyclability, each of the multilayer structures obtained in Example 1 was crushed into a size of 4 mm square or less, and a single-layer film with a thickness of 20 μm was obtained by performing single-layer film formation under the extrusion conditions shown below. No bumps or streaks were confirmed on the obtained single-layer films. <Extrusion Conditions> 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: C1 / C2 / C3 / D = 190 / 230 / 230 / 230 °C Take-up roll temperature: 80 °C

Claims

1. A resin composition (A) layer containing an ethylene-vinyl alcohol copolymer (a1) having an ethylene unit content of 20 mol% or more and 60 mol% or less, and an ethylene-vinyl alcohol copolymer (a2) having a higher ethylene unit content than the ethylene-vinyl alcohol copolymer (a1), a thermoplastic resin (B) layer, and an adhesive resin (C) layer, The resin composition (A) layer is provided on the outermost surface, The resin composition (A) layer of a multilayer film formed by inflation molding with the resin composition (A) layer on the innermost surface side and stretched at least 3 times and 12 times or less in at least one axial direction, and an inorganic vapor deposition (D) layer having an average thickness of 10 nm or more and 150 nm or less is in direct contact with the surface of the resin composition (A) layer, and the layer structure is layer (B) / layer (C) / layer (A) / layer (D), layer (B) / layer (C) / layer (A) / layer (C) / layer (A) / layer (D), layer (A) / layer (C) / layer (B) / layer (C) / layer (A) / layer (D) or layer (B) / layer (C) / layer (A) / layer (C) / layer (B) / layer (C) / layer (A) / layer (D), a vapor deposition multilayer film.

2. The vapor deposition multilayer film according to Claim 1, wherein the mass ratio [a1 / a2] of the content of the ethylene-vinyl alcohol copolymer (a1) and the content of the ethylene-vinyl alcohol copolymer (a2) in the resin composition (A) layer is 2 / 98 or more and 98 / 2 or less.

3. The vapor deposition multilayer film according to Claim 1 or 2, wherein the ethylene unit content difference (a2 - a1) between the ethylene-vinyl alcohol copolymer (a2) and the ethylene-vinyl alcohol copolymer (a1) in the resin composition (A) layer is 3 mol% or more.

4. The vapor deposition multilayer film according to any one of Claims 1 to 3, wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer (a1) is less than 40 mol%, and the ethylene unit content of the ethylene-vinyl alcohol copolymer (a2) is 40 mol% or more.

5. The vapor deposition multilayer film according to any one of claims 1 to 4, wherein at least one of the ethylene-vinyl alcohol copolymer (a1) and the ethylene-vinyl alcohol copolymer (a2) has a melt flow rate at 210 °C and a load of 2160 g measured according to JIS K 7210:2014 of 5 g / 10 min or more and 30 g / 10 min or less.

6. The vapor deposition multilayer film according to any one of claims 1 to 5, wherein the thickness of the resin composition (A) layer is 0.5 μm or more and 20 μm or less, and the ratio of the thickness of the resin composition (A) layer to the total thickness of all layers of the multilayer film is 30% or less.

7. The vapor deposition multilayer film according to any one of claims 1 to 6, wherein the thermoplastic resin (B) layer is mainly composed of a polyethylene resin.

8. A multilayer structure further comprising a thermoplastic resin (E) layer on the vapor deposition multilayer film according to any one of claims 1 to 7.

9. The multilayer structure according to claim 8, wherein both the thermoplastic resin (B) layer and the thermoplastic resin (E) layer are mainly composed of a polyethylene resin.

10. A packaging material comprising the multilayer structure according to claim 8 or 9.

11. A method for manufacturing the vapor deposition multilayer film according to any one of claims 1 to 7, comprising: Step (I) of forming a cylindrical multilayer film having the resin composition (A) layer and the thermoplastic resin (B) layer by inflation molding, wherein the outermost layer on the inner surface side is the resin composition (A) layer; Step (II) of folding and stretching the cylindrical multilayer film so that the inner surfaces are in contact with each other; Step (III) of cutting at least a part of the stretched cylindrical multilayer film to obtain a planar multilayer film; and A manufacturing method including a step of forming an inorganic vapor deposition (D) layer by vapor-depositing an inorganic substance on the surface of the resin composition (A) layer of the planar multilayer film.

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