Multilayer film, packaging material and reaction device

Abstract

Provided are: a multilayer film having excellent gas barrier properties and bending resistance and moderate flexibility; and a packaging material and a reaction device obtained using the multilayer film. The present invention is characterized by being provided with at least one layer (A) mainly composed of EVOH and at least one layer (B) mainly composed of a thermoplastic resin other than the EVOH, the ratio of the total thickness of the at least one layer (A) and the at least one layer (B) to the total thickness of all layers being 90% or more, and satisfying formula (1) and the like. In formula (1), LA is the total thickness of the at least one layer (A). LB is the total thickness of the at least one layer (B). And Et is the ethylene unit content (mol%) in the EVOH. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a multilayer film, a packaging material, and a reaction device. Background Art

[0002] Ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as "EVOH") is a polymer material having excellent gas barrier properties against oxygen, oil resistance, non-charging property, mechanical strength, melt moldability, and the like. Therefore, EVOH is widely used as a molding material for films, containers, tubes, and the like.

[0003] EVOH originally has low bend resistance. Therefore, in flexible containers and the like, a multilayer film in which a layer of EVOH is laminated with a layer of a thermoplastic resin having high bend resistance is sometimes used (see Patent Document 1). In addition, as one of the containers requiring gas barrier properties, a container of a bioreactor is known. For example, if oxygen is mixed into the system from outside during the cultivation in the bioreactor, it may sometimes affect the cultivation. Therefore, EVOH is sometimes used as a material for the container of the bioreactor (see Patent Document 2).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-272569

[0007] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2018-161145 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] Generally, in a reaction device such as a bioreactor, stirring blades are provided in the container in order to improve the uniformity of the reaction and the like. However, in the case of a reaction device having stirring blades provided in a flexible container, the container deforms with stirring, and as a result, pinholes sometimes occur on the inner surface of the container, which affects the gas barrier property. Therefore, for the container of the reaction device, in addition to desiring gas barrier properties, it is also desired to have high bend resistance and moderate flexibility. If the flexibility is too high, deformation easily occurs, and therefore, even if the bend resistance is high, pinholes sometimes occur. On the other hand, when the flexibility is too low (i.e., too hard), the handleability tends to decrease. In addition, in applications other than the container of the reaction device, it is also desired to develop a multilayer film having both gas barrier properties, bend resistance, and moderate flexibility.

[0010] The present invention has been made based on such circumstances, and an object thereof is to provide a multilayer film having good gas barrier properties and bend resistance and having moderate flexibility, and a packaging material and a reaction device obtained using such a multilayer film.

[0011] Means for solving the problem

[0012] The above object is achieved by providing the following technical solutions.

[0013] [1] A multilayer film, which comprises: at least one layer (A) having an ethylene-vinyl alcohol copolymer as a main component, and at least one layer (B) having a thermoplastic resin other than the above ethylene-vinyl alcohol copolymer as a main component, the ratio of the total thickness of the at least one layer (A) and the at least one layer (B) to the total thickness of all layers being 90% or more, and the multilayer film satisfies the following formulas (1) to (3);

[0014] [Mathematical formula 1]

[0015]

[0016] EA≥6.0…(2)

[0017]

[0018] In the above formulas (1) to (3), LA is the total thickness of the at least one layer (A). LB is the total thickness of the at least one layer (B). Et is the ethylene unit content (mol%) in the ethylene-vinyl alcohol copolymer. EA is the average composite elastic modulus (GPa) of the at least one layer (A). EB is the average composite elastic modulus (GPa) of the at least one layer (B).

[0019] [2] The multilayer film according to [1], wherein the at least one layer (B) includes a layer (B1) disposed as one surface layer and a layer (B2) disposed as the other surface layer;

[0020] [3] The multilayer film according to [2], wherein the melting point of the thermoplastic resin as the main component of the layer (B1) is lower than the melting point of the thermoplastic resin as the main component of the layer (B2), and the layer (B1) is thicker than the layer (B2);

[0021] [4] The multilayer film according to any one of [1] to [3], wherein the thermoplastic resin is a polyolefin resin;

[0022] [5] The multilayer film according to any one of [1] to [3], wherein the thermoplastic resin is a polyethylene resin;

[0023] [6] The multilayer film according to any one of [1] to [5], wherein the total thickness of the at least one layer (A) is 5 μm or more and less than 50 μm, and the ratio of the total thickness of the at least one layer (A) to the total thickness of all layers is less than 10%;

[0024] [7] The multilayer film according to any one of [1] to [6], wherein the oxygen transmission rate (under the conditions of 20 °C and 65% RH) measured according to the method described in JIS K 7126-2 (isobaric method; 2006) is 1.5 cc / (m 2 ·day·atm) or less;

[0025] [8] The multilayer film according to any one of [1] to [7], wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer is 18 mol% or more and less than 25 mol%, and the saponification degree is 90 mol% or more;

[0026] [9] The multilayer film according to any one of [1] to [7], wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer is 18 mol% or more and 32 mol% or less, and at least one layer (A) is stretched at least along a uniaxial direction;

[0027]

[10] The multilayer film according to [1] to [9], which comprises at least one layer (A) and at least one layer (B);

[0028]

[11] A packaging material comprising the multilayer film according to any one of [1] to

[10] ;

[0029]

[12] A reaction device comprising: a container formed of the multilayer film according to any one of [1] to

[10] , and stirring blades disposed inside the container.

[0030] Advantages of the Invention

[0031] According to the present invention, there can be provided a multilayer film having good gas barrier properties and flex resistance and having appropriate flexibility, and a packaging material and a reaction device obtained by using such a multilayer film. Detailed Description of the Invention

[0032] <Multilayer Film>

[0033] The multilayer film of the present invention comprises at least one layer (A) mainly composed of an ethylene-vinyl alcohol copolymer (EVOH) and at least one layer (B) mainly composed of a thermoplastic resin other than the above EVOH, and the ratio of the total thickness of the at least one layer (A) and the at least one layer (B) to the total thickness of all layers is 90% or more, and the multilayer film satisfies the following formulas (1) to (3).

[0034] [Mathematical Formula 2]

[0035]

[0036] EA≥6.0…(2)

[0037]

[0038] In the above formulas (1) to (3), LA is the total thickness of the at least one layer (A). LB is the total thickness of the at least one layer (B). Et is the ethylene unit content (mol%) in the above EVOH. EA is the average composite elastic modulus (GPa) of the at least one layer (A). EB is the average composite elastic modulus (GPa) of the at least one layer (B).

[0039] The gas barrier property and bending resistance of the multilayer film of the present invention are good, and it has appropriate flexibility. The reason is not yet determined, but it can be speculated as the following reasons. Regarding formula (1), if the total thickness (LA) of layer (A) is relatively large, the gas barrier property is improved. On the other hand, the bending resistance and flexibility are reduced. Conversely, if the total thickness (LB) of layer (B) is relatively large, the bending resistance and flexibility are improved. On the other hand, the gas barrier property is reduced. In addition, if EVOH with a low ethylene content (Et) is used, the gas barrier property is improved. On the other hand, the bending resistance and flexibility are reduced. Therefore, when the product of LA / LB and 1 / Et (LA / LB·1 / Et) is within a specified range, the gas barrier property, bending resistance, and flexibility are optimized in a good balance. In addition, regarding formula (2), by making the average composite elastic modulus (EA) of layer (A) high, the multilayer film has good gas barrier property. The reason is that EVOH with a low ethylene content (Et) or EVOH with a high draw ratio has a high composite elastic modulus (EA), and this EVOH has a high gas barrier property. In addition, by making the average composite elastic modulus (EA) of layer (A) high, the multilayer film also has sufficient hardness (the flexibility is not too low). And regarding formula (3), by making the ratio of the average composite elastic modulus (EA) of layer (A) to the average composite elastic modulus (EB) of layer (B) within a specified range, it becomes a range where layer (B) has appropriate elasticity. Therefore, the multilayer film has good bending resistance and appropriate flexibility. From this, it can be speculated that the multilayer film has good gas barrier property and bending resistance and has appropriate flexibility.

[0040] Regarding the above formula (1), as the lower limit of LA / LB·1 / Et, it is preferably 0.0008, more preferably 0.0011, and further preferably 0.0015. By making LA / LB·1 / Et above the above lower limit, the gas barrier property of the multilayer film of the present invention can be further improved, and the flexibility can be made more appropriate. On the other hand, as the upper limit of LA / LB·1 / Et, it is preferably 0.0028, more preferably 0.0024, and further preferably 0.0020. By making LA / LB·1 / Et below the above upper limit, the bending resistance of the multilayer film can be improved, and the flexibility can be made more appropriate.

[0041] Regarding the above formula (2), as the lower limit of EA, it is preferably 6.2, more preferably 6.4, and further preferably 6.5. By making EA above the above lower limit, the gas barrier property of the multilayer film of the present invention can be further improved, and more sufficient hardness can also be achieved. On the other hand, as the upper limit of EA, it is preferably 10.0, more preferably 9.0, still more preferably 8.0, and still more preferably 7.0. By making EA below the above upper limit, the bending resistance of the multilayer film can be further improved, and the flexibility can be made more appropriate. EA, that is, the average composite elastic modulus of at least one layer (A) reaches a high value by, for example, using EVOH with a low ethylene unit content and stretching layer (A).

[0042] Regarding the above formula (3), as the lower limit of EA / EB, it is preferably 8, more preferably 15, and further preferably 20. As the upper limit of EA / EB, it is preferably 36, more preferably 31, and further preferably 28. By making EA / EB within the above range, the flexibility of the multilayer film of the present invention becomes more appropriate, and the bending resistance is also further improved. In addition, as the lower limit of EB, it is preferably 0.10, more preferably 0.20. As the upper limit of EB, it is preferably 2.0, more preferably 1.0, and further preferably 0.4. By making EB within the above range, the flexibility of the multilayer film becomes more appropriate. EB, that is, the average composite elastic modulus of at least one layer (B) can be adjusted by the type of thermoplastic resin forming layer (B).

[0043] It should be noted that in this specification, the "main component" refers to the component with the highest content based on mass.

[0044] In addition, the "thickness" of a layer or the like refers to the average value (average thickness) of the measured values at any five positions.

[0045] In addition, the average composite elastic modulus refers to the thickness-based average value (weighted average value) of the composite elastic modulus measured for each layer. The composite elastic modulus of each layer is set to the value measured according to the following steps.

[0046] The sample (the multilayer film to be measured) is dried at a temperature of 90°C for 1 hour, and then vacuum dried at a temperature of 50°C for 60 hours using a vacuum dryer. Thereafter, it is placed in a dryer adjusted to a temperature of 23°C and a humidity of 40% RH for 1 week for humidity adjustment, cut into a size of 2 mm × 2 mm, and the sample thus obtained is subjected to measurement. Prepare multiple cut samples. In addition, expose the cross-section of each layer to be measured, change the position, and perform multiple measurements on the central part of the cross-section of each layer. The complex elastic modulus is measured by nanoindentation. Regarding the measurement conditions, it is carried out in an environment of a temperature of 23°C and a humidity of 40% RH. A Berkovich type indenter is used. The set load is set to a value within the range of 50 - 300 μN, and according to the setting of indenting for 3 seconds and pulling out for 3 seconds, a load-displacement curve is obtained. It should be noted that regarding the set load, in order to make the penetration depth reach about 200 nm, it is set within the range of 50 - 300 μN for the layer to be measured. The complex elastic modulus E (GPa) is calculated based on the reduction rate S (N) (dP / dh: P is the load, h is the displacement) of the load with respect to the displacement when reaching the maximum load and unloading in the load-displacement curve and the contact projected area A (mm 2 ), and is calculated using the following formula (4).

[0047] E = S√π / 2√A…(4)

[0048] For one cut sample, measurements are performed at 5 - 10 locations, and its average value is calculated. Further, the same measurements are performed on two or more and four or less samples, and the average value is taken as the complex elastic modulus of the layer. In nanoindentation measurement, layers with a thickness of each layer exceeding 1% of the total thickness of all layers are measured.

[0049] Hereinafter, each layer of the multilayer film according to an embodiment of the present invention will be described in detail.

[0050] (Layer (A))

[0051] Layer (A) is a layer mainly composed of EVOH. EVOH is a copolymer having ethylene units and vinyl alcohol units. EVOH is usually obtained by saponification of an ethylene-vinyl ester copolymer. EVOH may have residual vinyl ester units. The production and saponification of the ethylene-vinyl ester copolymer can be carried out by known methods. Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, vinyl versatate, and other aliphatic carboxylic acid vinyl esters, and preferably vinyl acetate.

[0052] As the ethylene unit content (Et) of EVOH, for example, it can be set to 15 mol% or more and 35 mol% or less, preferably 18 mol% or more and 32 mol% or less, more preferably 18 mol% or more and less than 25 mol%, further preferably 20 mol% or more and less than 25 mol%, and particularly preferably 22 mol% or more and less than 25 mol%. By making the ethylene content (Et) of EVOH below the above upper limit, the gas barrier property of the multilayer film of the present invention can be improved, and in addition, more appropriate flexibility (sufficient hardness) can be achieved. On the other hand, by making the ethylene unit content (Et) of EVOH above the above lower limit, the bending resistance and flexibility of the multilayer film can be improved. The ethylene unit content of EVOH refers to the content of ethylene units constituting EVOH relative to all structural units. In the case of using multiple EVOHs, the ethylene unit content (Et) is set as the average value based on mass.

[0053] The saponification degree of EVOH is preferably 90 mol% or more, more preferably 95 mol% or more, and further preferably 99 mol% or more. By making the saponification degree of EVOH above the above lower limit, there is a tendency for the gas barrier property etc. of the multilayer film of the present invention to be better. The saponification degree of EVOH can be 100 mol% or less, can be 99.97 mol% or less, and can be 99.94 mol% or less.

[0054] EVOH may have other structural units in addition to ethylene units, vinyl alcohol units, and vinyl ester units within the scope that does not impair the object of the present invention. In the case where EVOH has the above other structural units, the content of the above other structural units relative to all structural units of EVOH is sometimes preferably 30 mol% or less, more preferably 20 mol% or less, further preferably 10 mol% or less, still further preferably 5 mol% or less, and particularly preferably 1 mol% or less. In addition, in the case where EVOH has the above other structural units, its content can be 0.05 mol% or more and can be 0.10 mol% or more. Examples of the above other structural units include those derived from unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, or their anhydrides, salts, or esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as vinylsulfonic acid, allylsulfonic acid, and methallylsulfonic acid or their salts; vinylsilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxy-ethoxy)silane, and γ-methacryloxypropylmethoxysilane; and structural units of alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, and vinylidene chloride.

[0055] EVOH may be used alone or in combination of two or more kinds. For example, two or more kinds of EVOH may be contained in layer (A) of one layer. In addition, when there are two or more layers of layer (A), different EVOH may be used for each layer (A). From the viewpoints of gas barrier properties and the like, the content of EVOH in layer (A) is preferably 70% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, may be 95% by mass or more, may be 99% by mass or more, may be 99.9% by mass or more. The resin constituting layer (A) may consist essentially of only EVOH. On the other hand, the content of EVOH in layer (A) may be, for example, 99.9% by mass or less, may be 99% by mass or less.

[0056] In layer (A), as optional components other than EVOH, boron compounds, carboxylic acids, phosphorus compounds, metal ions, antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, heat stabilizers, other resins other than EVOH, metal salts of higher aliphatic carboxylic acids, etc. may be included. Layer (A) may contain two or more of these optional components.

[0057] Examples of the boron compound include boric acids such as orthoboric acid, metaboric acid, and tetraboric acid; borate esters such as triethyl borate and trimethyl borate; borates such as alkali metal salts or alkaline earth metal salts of the above boric acids, borax; and boron hydrides. As the lower limit of the content of the boron compound in layer (A), 100 ppm is preferable, and 500 ppm is more preferable. In addition, as the upper limit of the content of the boron compound in layer (A), 5,000 ppm is preferable, 3,000 ppm is more preferable, and 1,000 ppm is further preferable. By setting the content of the boron compound to be not less than the above lower limit, the torque fluctuation of an extrusion molding machine or the like can be sufficiently suppressed. On the other hand, by setting the content of the boron compound to be not more than the above upper limit, gelation is less likely to occur during melt molding, and the appearance of the multilayer film of the present invention is improved. It should be noted that the content of the boron compound is the content in terms of orthoboric acid of the boron compound.

[0058] Examples of the carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, lactic acid, and their salts. As the carboxylic acids, carboxylic acids having 4 or less carbon atoms or saturated carboxylic acids are preferred, and acetic acid-based compounds are more preferred. The acetic acid-based compounds include acetic acid and acetate salts. The lower limit of the content of the carboxylic acids in layer (A) is preferably 50 ppm, more preferably 100 ppm, and still more preferably 150 ppm. In addition, the upper limit of the content of the carboxylic acids in layer (A) is preferably 1,000 ppm, more preferably 500 ppm, and still more preferably 400 ppm. By setting the content of the carboxylic acids to be not less than the above lower limit, a sufficient effect of suppressing coloring can be obtained, and the occurrence of yellowing can be sufficiently suppressed. On the other hand, by setting the content of the carboxylic acids to be not more than the above upper limit, gelation is less likely to occur during melt molding, particularly during long-term melt molding, and the appearance of the multilayer film of the present invention becomes good.

[0059] Examples of the phosphorus compounds include phosphates such as phosphoric acid and phosphorous acid. The above-mentioned phosphates can be any form of dihydrogen phosphate, hydrogen phosphate, and phosphate. In addition, the cation species of the phosphate is not particularly limited, and alkali metal salts or alkaline earth metal salts are preferred. Among these, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, or dipotassium hydrogen phosphate is more preferred. The lower limit of the content of the phosphorus compounds in layer (A) is preferably 1 ppm, more preferably 10 ppm, still more preferably 20 ppm, and particularly preferably 30 ppm. The upper limit of the content of the phosphorus compounds in layer (A) is preferably 200 ppm, more preferably 150 ppm, and still more preferably 100 ppm. By setting the content of the phosphorus compounds to be not less than the above lower limit or not more than the above upper limit, the thermal stability is improved, and gel-like particulate matter is less likely to be generated and coloring is less likely to occur during long-term melt molding.

[0060] As the metal ion, monovalent metal ions, divalent metal ions, and other transition metal ions can be mentioned, and one or more of them may be included. Among them, monovalent metal ions or divalent metal ions are preferred. As the monovalent metal ion, an alkali metal ion is preferred, and examples thereof include ions of lithium, sodium, potassium, rubidium, and cesium. From the viewpoint of ease of industrial acquisition, sodium or potassium ions are preferred. In addition, as the alkali metal salt that provides the alkali metal ion, examples thereof include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, and metal complexes. Among them, from the viewpoint of ease of acquisition, aliphatic carboxylates or phosphates are preferred, and specifically, sodium acetate, potassium acetate, sodium phosphate, or potassium phosphate is preferred. Sometimes, divalent metal ions are also preferably included as the metal ion. When the metal ion includes divalent metal ions, for example, the thermal deterioration of EVOH during the recovery and reuse of scraps is sometimes suppressed, and the generation of gels and particulate matter in the obtained multilayer film is suppressed. As the divalent metal ion, examples thereof include ions of beryllium, magnesium, calcium, strontium, barium, and zinc. From the viewpoint of ease of industrial acquisition, magnesium, calcium, or zinc ions are preferred. In addition, as the divalent metal salt that provides the divalent metal ion, examples thereof include carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, and metal complexes, and carboxylates are preferred. As the carboxylic acid constituting the carboxylate, a carboxylic acid having 1 to 30 carbon atoms is preferred, and specifically, acetic acid, propionic acid, butyric acid, stearic acid, lauric acid, montanic acid, behenic acid, octanoic acid, sebacic acid, ricinoleic acid, myristic acid, palmitic acid, etc. can be mentioned. Among them, acetic acid or stearic acid is preferred. The lower limit of the content of the metal ion in layer (A) is preferably 1 ppm, more preferably 100 ppm, and further preferably 150 ppm. On the other hand, the upper limit of the content of the metal ion is preferably 1,000 ppm, more preferably 400 ppm, and further preferably 350 ppm. When the content of the metal ion in layer (A) is 1 ppm or more, the interlayer adhesiveness of the multilayer film of the present invention tends to be improved. On the other hand, when the content of the metal ion is 1,000 ppm or less, the coloring resistance tends to be improved.

[0061] Examples of the antioxidant include 2,5-di-tert-butylhydroquinone, 2,6-di-tert-butyl-p-cresol, 4,4'-thiobis(6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), octadecyl 3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, etc.

[0062] Examples of the ultraviolet absorber include, for example, ethylene-2-cyano-3,3'-diphenyl acrylate, 2-(2'-hydroxy-5'-methylphenyl) benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chloro benzotriazole, 2-hydroxy-4-methoxy benzophenone, 2,2'-dihydroxy-4-methoxy benzophenone, 2-hydroxy-4-octyloxy benzophenone, and the like.

[0063] Examples of the plasticizer include, for example, dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, phosphate ester, and the like.

[0064] Examples of the antistatic agent include, for example, pentaerythritol monostearate, sorbitan monopalmitate, sulfated polyolefins, polyethylene oxide, polyethylene glycol (trade name: CARBOWAX), and the like.

[0065] Examples of the lubricant include, for example, ethylene bisstearamide, butyl stearate, and the like.

[0066] Examples of the colorant include, for example, carbon black, phthalocyanine, quinacridone, indoline, azo pigments, Indian red, and the like.

[0067] Examples of the filler include, for example, glass fiber, wollastonite, calcium silicate, talc, montmorillonite, and the like.

[0068] Examples of the heat stabilizer include, for example, hindered phenol compounds, hindered amine compounds, and the like.

[0069] Examples of the resin other than EVOH include, for example, polyamide, polyolefin, and the like.

[0070] Examples of the metal salt of the higher aliphatic carboxylic acid include, for example, sodium stearate, potassium stearate, calcium stearate, magnesium stearate, and the like.

[0071] As the total thickness (LA) of all the layers (A) included in the multilayer film of the present invention, it is preferably 5 μm or more and less than 50 μm, more preferably 10 μm or more and 45 μm or less, and still more preferably 12 μm or more and 35 μm or less. The total thickness (LA) of the layer (A) can be 25 μm or less, and can be 15 μm or less. In addition, as the thickness of one layer of the layer (A), it is preferably 5 μm or more and less than 50 μm, more preferably 8 μm or more and 40 μm or less, and still more preferably 10 μm or more and 28 μm or less. The thickness of one layer of the layer (A) can be 20 μm or less, and can be 15 μm or less. By making the total thickness (LA) of the layer (A) or the thickness of one layer of the layer (A) be above the above lower limit, the gas barrier property of the multilayer film can be further improved, and in addition, more appropriate flexibility (sufficient hardness) can be achieved. On the other hand, by making the total thickness (LA) of the layer (A) or the thickness of one layer of the layer (A) less than the above upper limit, the bending resistance and flexibility of the multilayer film can be further improved.

[0072] As the ratio of the total thickness of all the layers (A) included in the multilayer film to the total thickness of all the layers of the multilayer film of the present invention, it is preferably less than 10%, more preferably less than 8%, and still more preferably less than 6%. By making the ratio of the total thickness of all the layers (A) included in the multilayer film to the total thickness of all the layers of the multilayer film less than the above upper limit, the bending resistance of the multilayer film becomes better and the flexibility also becomes more appropriate due to an increase in the ratio of the total thickness of the layer (B) or the like. In addition, in the multilayer film, by using EVOH or the like with a low ethylene unit content in the layer (A), good gas barrier property and appropriate flexibility (sufficient hardness) can be exhibited even when the ratio of the total thickness of the layer (A) is made low in this way. On the other hand, as the ratio of the total thickness of all the layers (A) included in the multilayer film to the total thickness of all the layers of the multilayer film, it is preferably 1% or more, more preferably 2% or more, and still more preferably 3% or more. By making the ratio of the total thickness of all the layers (A) included in the multilayer film to the total thickness of all the layers of the multilayer film be above the above lower limit, the gas barrier property of the multilayer film can be improved and the flexibility can be made more appropriate.

[0073] The number of layers of the layer (A) in the multilayer film of the present invention is not particularly limited, and can be 1 layer, or can be 2 layers or more. The upper limit of the number of layers of the layer (A) in the multilayer film can be, for example, 10 layers, 5 layers, 3 layers, 2 layers, or 1 layer.

[0074] Layer (A) can be an unstretched layer or a stretched layer. When it is a stretched layer, it can be stretched along a uniaxial direction or a biaxial direction. In the case where layer (A) is stretched, other layers such as layer (B) can be stretched or unstretched. Layer (A) is preferably a layer stretched at least along a uniaxial direction, more preferably stretched at least 2 times or more along a uniaxial direction, further preferably stretched at least 2 times or more and less than 12 times along a uniaxial direction, and even more preferably stretched along a biaxial direction, particularly preferably stretched 3 times or more and less than 12 times along each biaxial direction. When layer (A) is a layer stretched in this way, the gas barrier property can be further improved. For example, when layer (A) is stretched at least along a uniaxial direction (more preferably when layer (A) is stretched along a biaxial direction), if the ethylene unit content of EVOH contained in layer (A) is 18 mol% or more and 32 mol% or less, a particularly high gas barrier property can be exhibited.

[0075] (Layer (B))

[0076] Layer (B) is a layer mainly composed of a thermoplastic resin other than EVOH. It should be noted that hereinafter, "thermoplastic resin" refers to a thermoplastic resin other than EVOH. Examples of the thermoplastic resin include polyolefin resins such as linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, polybutene, and polyisopentene; polyesters such as polyethylene terephthalate; polyester elastomers; polyamides such as nylon-6 and nylon-66; polystyrene; polyvinyl chloride, polyvinylidene chloride, acrylic resins, vinyl ester resins, polyurethane elastomers, polycarbonate, chlorinated polyethylene, and chlorinated polypropylene.

[0077] As the thermoplastic resin, a polyolefin resin is preferred, and a polyethylene resin is more preferred. The polyolefin resin refers to a resin in which the structural unit contains a structural unit derived from an olefin (olefin unit). The polyethylene resin refers to a resin in which the structural unit contains a structural unit derived from ethylene (ethylene unit). As the lower limit of the content of the olefin unit in the polyolefin resin relative to all the structural units, for example, it is preferably 50 mol%, more preferably 70 mol%, and can be 90 mol%, 95 mol%, 98 mol% or 99 mol%. The upper limit of the content of the olefin unit in the polyolefin resin relative to all the structural units can be 100 mol%. As the lower limit of the content of the ethylene unit in the polyethylene resin relative to all the structural units, for example, it is preferably 50 mol%, more preferably 70 mol%, and can be 90 mol%, 95 mol%, 98 mol% or 99 mol%. The upper limit of the content of the ethylene unit in the polyethylene resin relative to all the structural units can be 100 mol%. As the thermoplastic resin, by using a polyolefin resin, particularly a polyethylene resin, the bending resistance of the multilayer film of the present invention can be further improved, and the flexibility can be made more appropriate, etc.

[0078] The thermoplastic resin can be an adhesive resin (a thermoplastic resin having adhesiveness). It should be noted that in layer (B), a layer containing an adhesive resin as the thermoplastic resin is sometimes referred to as an adhesive resin layer, and sometimes also referred to as layer (B AD ). Examples of the thermoplastic resin having adhesiveness include acid-modified polyolefins, epoxy-modified polyolefins, etc., preferably acid-modified polyolefins, more preferably carboxylic acid-modified polyolefins, and further preferably carboxylic acid-modified polyethylene. The carboxylic acid-modified polyolefin is a form of the polyolefin resin. In addition, the carboxylic acid-modified polyethylene is a form of the polyethylene resin. The carboxylic acid-modified polyolefin can be a polyolefin resin having a carboxyl group or its anhydride group. The polyolefin resin having a carboxyl group or its anhydride group can be obtained, for example, by chemically bonding an ethylenically unsaturated carboxylic acid or its anhydride to an unmodified polyolefin resin by an addition reaction, a graft reaction, etc.

[0079] Examples of the unmodified polyolefin resin used for manufacturing the carboxylic acid-modified polyolefin include the above various polyolefin resins, preferably polyethylene, ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer.

[0080] Examples of the ethylenically unsaturated carboxylic acid and its anhydride include, for example, monocarboxylic acid, monocarboxylic acid ester, dicarboxylic acid, dicarboxylic acid monoester, dicarboxylic acid diester, dicarboxylic acid anhydride, etc. Specifically, maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, monomethyl maleate, monoethyl maleate, diethyl maleate, monomethyl fumarate, etc. can be cited. Among these, dicarboxylic acid anhydrides such as maleic anhydride and itaconic anhydride are preferred, and maleic anhydride is more preferred.

[0081] The carboxylic acid-modified polyolefin is obtained by introducing an ethylenically unsaturated carboxylic acid or its anhydride into an unmodified polyolefin resin by an addition reaction or a graft reaction in the presence of a solvent such as xylene and a catalyst such as a peroxide. As the lower limit of the addition amount or graft amount (modification degree) of the carboxylic acid or its anhydride with respect to the unmodified polyolefin resin at this time, it is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, relative to the unmodified polyolefin resin. On the other hand, as the upper limit of the addition amount or graft amount (modification degree), it is preferably 15% by mass or less, more preferably 10% by mass or less, relative to the unmodified polyolefin resin.

[0082] The thermoplastic resin can be used alone or in combination of two or more. For example, two or more thermoplastic resins may be contained in one layer of layer (B). In addition, when there are two or more layers of layer (B), different thermoplastic resins may be used for each layer (B). The content of the thermoplastic resin in layer (B) is preferably 70% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 95% by mass or more, may be 99% by mass or more, may be 99.9% by mass or more. The resin constituting layer (B) may consist essentially of only a thermoplastic resin. On the other hand, the content of the thermoplastic resin in layer (B) may be, for example, 99.9% by mass or less, may be 99% by mass or less.

[0083] In layer (B), as optional components other than the thermoplastic resin, an antioxidant, an ultraviolet absorber, a plasticizer, an antistatic agent, a lubricant, a colorant, a filler, a heat stabilizer, other resins other than the thermoplastic resin, etc. may be included. Layer (B) may contain two or more of these optional components.

[0084] As the total thickness (LB) of all layers (B) provided in the multilayer film of the present invention, it is preferably 100 μm or more and less than 500 μm, more preferably 200 μm or more and 400 μm or less, further preferably 250 μm or more and 350 μm or less. By making the total thickness (LB) of layer (B) be above the above lower limit, the bending resistance of the multilayer film can be further improved, and the flexibility can be made more appropriate. On the other hand, by making the total thickness (LB) of layer (B) less than the above upper limit, thinning of the multilayer film can be achieved, etc.

[0085] The thickness of one layer of layer (B) is not particularly limited. For example, when layer (B) is an adhesive resin layer (layer (B ADIn the case of (( )), the average thickness of one layer of this layer is preferably 1 μm or more and 30 μm or less, more preferably 3 μm or more and 20 μm or less, and still more preferably 5 μm or more and 15 μm or less. When layer (B) is a layer other than the adhesive resin layer, the average thickness of one layer of this layer is preferably 30 μm or more and 300 μm or less, more preferably 50 μm or more and 250 μm or less. In addition, as described later, a more appropriate thickness corresponding to the arrangement position of layer (B) or the like can also be set.

[0086] As the ratio of the total thickness of all layers (B) included in this multilayer film to the total thickness of all layers of the multilayer film of the present invention, it is preferably more than 90% and 99% or less, more preferably more than 92% and 99% or less, and still more preferably more than 94% and 98% or less. By making the ratio of the total thickness of all layers (B) included in this multilayer film to the total thickness of all layers of this multilayer film exceed the above lower limit, the bending resistance of this multilayer film becomes better, and the flexibility also becomes more appropriate. In addition, in this multilayer film, by using EVOH or the like with a low ethylene unit content in layer (A), even if the ratio of the total thickness of layer (B) is made relatively high in this way, good gas barrier properties and appropriate flexibility (sufficient hardness) can be exhibited. In addition, by making the ratio of the total thickness of all layers (B) included in this multilayer film to the total thickness of all layers of this multilayer film be below the above upper limit, a sufficiently thick layer (A) can be provided, the gas barrier properties of this multilayer film can be improved, and the flexibility can be made more appropriate.

[0087] The number of layers of layer (B) in the multilayer film of the present invention is not particularly limited, and may be 1 layer or 2 or more layers. The lower limit of the number of layers of layer (B) in this multilayer film is preferably 2 layers, more preferably 4 layers. The upper limit of the number of layers of layer (B) in this multilayer film can be, for example, 20 layers, 10 layers, 8 layers, 6 layers, or 4 layers.

[0088] (Other layers)

[0089] The multilayer film of the present invention may have other layers in addition to layer (A) and layer (B). Examples of other layers include a metal layer, a paper layer, an inorganic vapor deposition layer, a layer mainly composed of a resin other than a thermoplastic resin, and the like. Among them, the ratio of the total thickness of all layer (A) and layer (B) provided in the multilayer film to the total thickness of all layers of the multilayer film is 90% or more, preferably 95% or more, more preferably 98% or more, and still more preferably 99% or more. By making the ratio of the total thickness of all layer (A) and layer (B) provided in the multilayer film to the total thickness of all layers of the multilayer film be above the above lower limit, the effects of good gas barrier properties, good flex resistance, and moderate flexibility are fully exhibited according to the above formulas (1) to (3). For this reason, the multilayer film preferably consists only of at least one layer (A) and at least one layer (B). In other words, the ratio of the total thickness of all layer (A) and layer (B) provided in the multilayer film to the total thickness of all layers of the multilayer film is preferably 100%.

[0090] (Layer structure, etc.)

[0091] In the layer structure of the multilayer film of the present invention, there is no particular limitation as long as there is at least one layer (A) and at least one layer (B). In this multilayer film, at least one layer (B) preferably includes layer (B1) disposed as one surface layer and layer (B2) disposed as the other surface layer. In this way, by disposing layer (B) on both surface layers, the thin and rigid layer (A) is protected or supported, the flex resistance is improved, and the generation of, for example, pinholes associated with bending is also suppressed. Further, layer (B1) is not an adhesive resin layer, and layer (B1) is preferably laminated on layer (A) via layer (B AD ). Similarly, layer (B2) is not an adhesive resin layer, and layer (B2) is preferably laminated on layer (A) via layer (B AD ). Examples of the multilayer film of this form include multilayer films having the layer structures (1) to (4) exemplified below. Among these, the multilayer film having the layer structure (1) below is preferred. Layer (B1) and layer (B2) may be adhesive resin layers. It should be noted that in the following examples of each layer structure, " / " indicates direct lamination. In addition, the layer abbreviated as "B" represents layer (B) that is not an adhesive resin layer.

[0092] (1) B1 / B AD / A / B AD / B2

[0093] (2) B1 / B AD / A / B AD / B / B AD / A / B AD / B2

[0094] (3) B1 / B AD / B / B AD / B / B AD / A / B AD / B2

[0095] (4) B1 / B AD / B / B AD / A / B AD / A / B AD / B2

[0096] In addition, as layer configurations including layer (B1) and layer (B2) in the multilayer film, the following (5) to (7) etc. can also be cited.

[0097] (5) B1 / A / B2

[0098] (6) B1 / B AD / A / B2

[0099] (7) B1 / B AD / B / B AD / A / B AD / B2

[0100] In the multilayer film of the present invention including layer (B1) and layer (B2), it is preferable that: the melting point of the thermoplastic resin as the main component of layer (B1) is lower than the melting point of the thermoplastic resin as the main component of layer (B2), and layer (B1) is thicker than layer (B2). This multilayer film is sometimes formed into a bag shape or the like by heat sealing and used as a container. In this case, layer (B1) obtained using a thermoplastic resin with a low melting point is heat-sealed in such a way as to become the innermost layer to be thermally welded. On the other hand, in order to prevent melting easily during heat sealing, layer (B2) as the outermost layer is preferably made of a thermoplastic resin with a high melting point. In such a container, by thickening layer (B1) as the innermost layer, the layer (A) with lower moisture resistance can be arranged at a position far from the inner surface of the container. Such a container can be particularly suitably used as a container for storing water-containing contents. In particular, when EVOH with a low ethylene unit content is used in layer (A), the moisture resistance decreases, so the effect of improving the moisture resistance brought about by thickening layer (B1) is significantly produced.

[0101] The difference between the melting point of the thermoplastic resin that is the main component of layer (B1) and the melting point of the thermoplastic resin that is the main component of layer (B2) is preferably 3°C or more and 30°C or less, more preferably 6°C or more and 20°C or less. Further, the melting point of the thermoplastic resin that is the main component of layer (B1) is preferably 90°C or more and 110°C or less, more preferably 95°C or more and 105°C or less. The melting point of the thermoplastic resin that is the main component of layer (B2) is preferably 100°C or more and 120°C or less, more preferably 105°C or more and 115°C or less. The melting point of the thermoplastic resin can be set as the melting peak temperature based on differential scanning calorimetry analysis.

[0102] As the main component of layer (B1), a polyethylene-based resin is preferred, more preferably polyethylene (linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, etc.), and further preferably linear low-density polyethylene or low-density polyethylene. As the main component of layer (B2), a polyethylene-based resin is preferred, more preferably polyethylene (linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, etc.), and further preferably low-density polyethylene, medium-density polyethylene, or high-density polyethylene.

[0103] As the thickness of layer (B1), it is preferably 100 μm or more and 300 μm or less, more preferably 150 μm or more and 280 μm or less, and further preferably 200 μm or more and 260 μm or less. As the thickness of layer (B2), it is preferably 10 μm or more and 200 μm or less, more preferably 20 μm or more and 100 μm or less, and further preferably 40 μm or more and 80 μm or less.

[0104] In the case where layer (A) is a single layer, also from the viewpoint of moisture resistance, the thickness ratio (I / O) of the total thickness I of all the layers including layer (B1) laminated on one side of layer (A) to the total thickness O of all the layers including layer (B2) laminated on the other side of layer (A) is preferably 60 / 40 or more and 90 / 10 or less, more preferably 70 / 30 or more and 85 / 15 or less.

[0105] In the multilayer film, it is also preferred that layer (B) exists on both sides of layer (A). The layer configurations (1) to (7) exemplified above are included within this form. In addition, for example, layer configurations such as (8) to (11) etc. where layer (A) is arranged as at least one surface layer are also one form of the multilayer film of the present invention.

[0106] (8) A / B

[0107] (9) A / B AD / B

[0108] (10) A / BAD / B / B AD / A

[0109] (11)A / B AD / B / B AD / A / B AD / B

[0110] There is no particular limitation on the total thickness (i.e., the overall thickness) of all the layers of the multilayer film of the present invention. That is, the multilayer film is not limited to a film having a thickness below a specified value. As the total thickness of all the layers of the multilayer film, it is preferably 100 μm or more and 600 μm or less, more preferably 200 μm or more and 500 μm or less, still more preferably 250 μm or more and 400 μm or less, and particularly preferably 300 μm or more and 350 μm or less. By making the total thickness of all the layers be above the above lower limit, gas barrier properties, flex resistance, etc. can be improved, and the flexibility can be made more appropriate. On the other hand, by making the total thickness of all the layers be below the above upper limit, flexibility, etc. can be improved.

[0111] In the multilayer film of the present invention, the oxygen transmission rate (under the conditions of 20 °C and 65% RH) measured according to the method described in JIS K7126-2 (isobaric method; 2006) is preferably 10 cc / (m 2 ·day·atm) or less, more preferably 5.0 cc / (m 2 ·day·atm) or less, still more preferably 1.0 cc / (m 2 ·day·atm) or less, even more preferably 0.5 cc / (m 2 ·day·atm) or less, and particularly preferably 0.2 cc / (m 2 ·day·atm) or less. By making the oxygen transmission rate be below the above upper limit, it can be particularly suitably used as various packaging materials, etc. On the other hand, the lower limit of the oxygen transmission rate can be 0.001 cc / (m 2 ·day·atm), and can be 0.01 cc / (m 2 ·day·atm).

[0112] The method for manufacturing the multilayer film of the present invention is not particularly limited, and examples thereof include a method of melt-extruding a thermoplastic resin constituting layer (B) onto a single-layer film containing layer (A); a method of co-extruding the resins constituting each layer; a method of laminating films corresponding to each layer using an adhesive, etc. The co-extrusion method is not particularly limited, and examples thereof include: a multi-manifold merging type T-die method, a feed block merging type T-die method, a blown film method, etc.

[0113] The multilayer film of the present invention can be a stretched film or an unstretched film (non-stretched film).

[0114] The multilayer film of the present invention can be suitably used as a material for various packages such as food packages, pharmaceutical packages, industrial pharmaceutical packages, pesticide packages, and various liquid preparation packages, that is, a packaging material. The multilayer film can be used for purposes other than packaging materials.

[0115] <Packaging material>

[0116] The packaging material of the present invention contains the multilayer film of the present invention. The packaging material may be formed only of the multilayer film of the present invention, or may contain the multilayer film of the present invention and other components. For example, a packaging material formed by laminating the multilayer film of the present invention on other components (substrates, etc.) is also one mode of the packaging material of the present invention. The packaging material can be used as it is in the form of a film, or can be used in a state formed into a container shape (such as a flexible pouch shape, a box shape, etc.). The container provided in the reaction device described later and other containers are also one mode of the packaging material. When the multilayer film having the layer (B1) and the layer (B2) is formed into a container shape, it is preferably formed in such a manner that the layer (B1) becomes the innermost layer and the layer (B2) becomes the outermost layer. In addition, the forming method when forming into a container shape is not particularly limited, and various known forming methods can be adopted in addition to the above heat sealing.

[0117] <Reaction device>

[0118] The reaction device of the present invention includes a container formed of the multilayer film of the present invention and a stirring blade disposed inside the container. The reaction device of the present invention may include a container formed of the packaging material of the present invention and a stirring blade disposed inside the container.

[0119] The container provided in the reaction device of the present invention can use the multilayer film of the present invention or the packaging material of the present invention, and is formed by, for example, heat sealing or various other forming methods. When using the above multilayer film having the layer (B1) and the layer (B2), it is preferable to form the container in such a manner that the layer (B1) becomes the innermost layer and the layer (B2) becomes the outermost layer. The container provided in this reaction device can also be referred to as a reaction tank. The stirring blade provided in this reaction device can use an existing well-known stirring blade.

[0120] The container provided in the reaction device of the present invention has good gas barrier properties and bending resistance, and has moderate flexibility. The flexibility of the container is moderate (in other words, it has moderate hardness). Therefore, when the stirring blade is operating, the container is not easily deformed. Moreover, the container has good bending resistance. Therefore, even when the container is deformed, it is not likely to generate pinholes or the like. It should be noted that if pinholes or the like are generated, the gas barrier properties and the like of this part may be reduced. Therefore, in this reaction device, even when the stirring blade continuously operates, it is possible to suppress, for example, the infiltration of oxygen from the outside into the container, and it is possible to continuously maintain a specified reaction environment. Furthermore, the container has moderate flexibility and is not too hard, so the processability is also excellent. This reaction device having such advantages can be suitably used as a bioreactor. A bioreactor is a device that uses a biocatalyst to carry out a biochemical reaction. This reaction device can be used as a reaction device other than a bioreactor.

[0121] Examples

[0122] Hereinafter, examples are given to explain the present invention in detail, but the present invention is not limited to these examples.

[0123] [Measurement of Melt Flow Rate (MFR)]

[0124] The MFR of the dried resin composition pellets obtained in each synthesis example was measured by the following method. The dried resin composition pellets were filled into a barrel with an inner diameter of 9.55 mm and a length of 162 mm of a melt flow index tester L 244 (manufactured by Toyo Seiki Seisaku-sho, Ltd.). After melting at 210°C, for the molten EVOH, a load of 2,160 g and a diameter of 9.48 mm was evenly applied using a plunger. The amount of the resin composition extruded per unit time from a small hole with a diameter of 2.1 mm provided in the center of the barrel (g / 10 minutes) was measured and taken as the MFR.

[0125] <Synthesis Example 1> Synthesis of EVOH-1

[0126] Into a 100 L pressurized reaction vessel equipped with a jacket, a stirrer, a nitrogen inlet, an ethylene inlet, and an initiator addition port, 40.0 kg of vinyl acetate (hereinafter sometimes referred to as VAc) and 9.8 kg of methanol (hereinafter sometimes referred to as MeOH) were charged, and nitrogen bubbling was carried out for 30 minutes to displace the nitrogen in the reaction vessel. Then, after adjusting the temperature inside the reaction vessel to 60 °C, ethylene was introduced so that the reaction vessel pressure (ethylene pressure) became 2.80 MPa, and 8.8 g of 2,2’-azobis(2,4-dimethylvaleronitrile) (“V-65” manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as an initiator to start the polymerization. During the polymerization, the ethylene pressure was maintained at 2.80 MPa, and the polymerization temperature was maintained at 60 °C. After 4 hours, when the conversion rate of VAc (polymerization rate based on VAc) reached 49.8%, cooling was carried out, and at the same time, a substance obtained by dissolving 0.2 g of copper acetate in 20 kg of methanol was added to the container to stop the polymerization. After opening the reaction vessel and removing ethylene, nitrogen was bubbled to completely remove ethylene. Then, the polymerization solution was taken out from the container and diluted with 20 L of MeOH. This liquid was fed into the top of a tower-shaped container, and MeOH vapor was fed into the bottom of the tower to remove the unreacted monomers remaining in the polymerization solution together with the MeOH vapor, and a MeOH solution of ethylene-vinyl acetate copolymer (hereinafter sometimes referred to as EVAc) was obtained. Next, 100 kg of a 20 mass% MeOH solution of EVAc was charged into a 300 L reaction vessel equipped with a jacket, a stirrer, a nitrogen inlet, a reflux condenser, and a solution addition port. While blowing nitrogen into this solution, the temperature was raised to 60 °C, and a MeOH solution with a sodium hydroxide concentration of 2 equivalents was added at a rate of 300 mL / min for 2 hours. After the addition of the sodium hydroxide MeOH solution was completed, the temperature inside the system was maintained at 60 °C, and while allowing MeOH and methyl acetate generated in the saponification reaction to flow out of the reaction vessel, stirring was carried out for 2 hours to carry out the saponification reaction. Thereafter, 8.7 kg of acetic acid was added to stop the saponification reaction. Thereafter, while heating and stirring at 80 °C, 120 L of ion-exchanged water was added to allow MeOH to flow out of the reaction vessel and precipitate EVOH. The EVOH precipitated by decantation was collected and pulverized using a pulverizer. The obtained EVOH powder was put into an acetic acid aqueous solution of 1 g / L (bath ratio: 20, that is, for 1 kg of powder, the aqueous solution is 20 L), and stirred and washed for 2 hours. After draining, it was further put into an acetic acid aqueous solution of 1 g / L (bath ratio: 20) and stirred and washed for 2 hours. The substance obtained by draining it was put into ion-exchanged water (bath ratio: 20), stirred and washed for 2 hours and drained, and the above operations were repeated 3 times for purification. The conductivity of the washing solution was 3 μS / cm (measured using “CM-30ET” manufactured by Toa Denpa Kogyo Co., Ltd.).Next, 250 L of an aqueous solution containing 0.5 g / L of acetic acid and 0.1 g / L of sodium acetate was stirred and impregnated for 4 hours, then drained, and dried at 60 °C for 16 hours, thereby obtaining 16.1 kg of a crude dried product of EVOH. The above operation was carried out again to obtain 15.9 kg of a crude dried product of EVOH, and thus a total of 32.0 kg of a crude dried product of EVOH (EVOH-1) was obtained.

[0127] 10.5 kg of the above-obtained crude dried product of EVOH (EVOH-1) was added to 94.5 L of an aqueous solution obtained by dissolving various components in water such that acetic acid was 0.364 g / L and sodium acetate was 0.455 g / L, and the mixture was impregnated for 6 hours with stirring at 25 °C. After the impregnated water-containing EVOH pellets were dehydrated by centrifugal drainage, they were dried in a hot air dryer at 80 °C for 3 hours, and then dried at 120 °C for 24 hours. Thus, a mixture of EVOH and a metal salt, that is, pellets of a dried EVOH resin composition (EVOH-1) were obtained. It should be noted that for EVOH-1, when the vinyl alcohol unit content, ethylene unit content, and saponification degree were analyzed by nuclear magnetic resonance (NMR) method, the vinyl alcohol unit content was 76 mol%, the ethylene unit content (Et) was 24 mol%, and the saponification degree was 99.98 mol% or more. In addition, the MFR of EVOH-1 was 2.2 g / 10 min.

[0128] <Synthesis Example 2> Synthesis of EVOH-2

[0129] The raw material addition amount used in the polymerization of EVOH, the polymerization conditions, the feeding amount in the saponification treatment, and the addition rate of a 2-equivalent sodium hydroxide MeOH solution were changed. Except for this, the same operation as in Synthesis Example 1 was carried out to obtain pellets of a dried EVOH resin composition containing EVOH (EVOH-2). For EVOH-2, when the vinyl alcohol unit content, ethylene unit content, and saponification degree were analyzed by nuclear magnetic resonance (NMR) method, the vinyl alcohol unit content was 68 mol%, the ethylene unit content (Et) was 32 mol%, and the saponification degree was 99.98 mol% or more. In addition, the MFR of EVOH-2 was 2.9 g / 10 min.

[0130] <Synthesis Example 3> Synthesis of EVOH-3

[0131] The amounts of raw materials used in the polymerization of EVOH, the polymerization conditions, the amounts of feedstock in the saponification treatment, and the addition rate of the 2-equivalent sodium hydroxide MeOH solution were changed. Otherwise, the same operations as in Synthesis Example 1 were carried out to obtain pellets of a dried EVOH resin composition containing EVOH (EVOH-3). When analyzing the vinyl alcohol unit content, ethylene unit content, and degree of saponification of EVOH-3 by nuclear magnetic resonance (NMR) method, the vinyl alcohol unit content was 62 mol%, the ethylene unit content (Et) was 38 mol%, and the degree of saponification was 99.98 mol% or more. In addition, the MFR of EVOH-3 was 3.8 g / 10 min.

[0132] [Example 1]

[0133] (Manufacture of unstretched multilayer film)

[0134] Pellets of the dried EVOH resin composition (EVOH-1) obtained in Synthesis Example 1, polyethylene resin-1 (“NOVATEC (trademark) LD LC600A” manufactured by Nippon Polyethylene Co., Ltd.; low-density polyethylene, melting point 107 °C), polyethylene resin-2 (“EVOLUE (trademark) SP0510” manufactured by Prime Polymer Co., Ltd.; linear low-density polyethylene, melting point 96 °C), and polyethylene adhesive resin (“ADMER (trademark) NF518” manufactured by Mitsui Chemicals, Inc.; linear low-density polyethylene adhesive resin graft-modified with maleic anhydride, melting point 120 °C) were used to form an unstretched multilayer film with an asymmetric structure of 3 layers and 5 layers (polyethylene resin-1 / polyethylene adhesive resin / EVOH-1 / polyethylene adhesive resin / polyethylene resin-2 = 60 μm / 8 μm / 12 μm / 8 μm / 240 μm). It should be noted that the ratio of the thickness of layer (A) (EVOH-1) (12 μm) to the total thickness of all layers (328 μm) was approximately 3.7%. The thickness of the multilayer film (coextruded film) was adjusted by appropriately changing the screw rotation speed and the take-up roll speed. In addition, the thickness of each layer was measured by the method described below.

[0135] The extruder and extrusion conditions, and the die used are as follows.

[0136] EVOH-1

[0137] Extruder: Single-screw extruder (Toyo Seiki Co., Ltd. test machine ME type CO-EXT)

[0138] Screw: Caliber L / D20, full-thread screw

[0139] Extrusion temperature: Feeding section / Compression section / Metering section / Die = 175 / 210 / 220 / 220 °C

[0140] Polyethylene adhesive resin

[0141] Extruder: Single-screw extruder (TECHNOVEL Corporation, SZW20GT - 20MG - STD)

[0142] Screw: Diameter L / D 20, full-thread screw

[0143] Extrusion temperature: Feeding section / Compression section / Metering section / Die = 175 / 200 / 220 / 220 °C

[0144] Polyethylene resins - 1, 2

[0145] Extruder: Single-screw extruder (Plastic Engineering Research Institute Co., Ltd., GT - 32 - A)

[0146] Screw: Diameter L / D 28, full-thread screw

[0147] Extrusion temperature: Feeding section / Compression section / Metering section / Die = 175 / 200 / 220 / 220 °C

[0148] Die: 3-layer hanger die for 3 types with a width of 300 mm (manufactured by Plastic Engineering Research Institute Co., Ltd.)

[0149] Die temperature: 220 °C

[0150] [Example 2]

[0151] In the manufacturing steps of Example 1, a thermoplastic elastomer resin ("Pebax 5533" manufactured by Arkema; melting point 159 °C) was used to replace polyethylene resins - 1, 2. Except for this, a multilayer film was obtained according to the same steps as in Example 1.

[0152] [Example 3]

[0153] In the manufacturing steps of Example 1, a polypropylene resin ("NOVATEC (trademark) PP EA7AD" manufactured by Japan Polypropylene Corporation; polypropylene, melting point 164 °C) was used to replace polyethylene resins - 1, 2, and an adhesive polypropylene resin ("ADMER (trademark) QF500" manufactured by Mitsui Chemicals, Inc.) was used to replace the polyethylene adhesive resin. Except for this, an unstretched multilayer film with an asymmetric structure of 3 types and 5 layers (polypropylene resin / adhesive polypropylene resin / EVOH - 1 / adhesive polypropylene resin / polypropylene resin = 60 μm / 8 μm / 12 μm / 8 μm / 240 μm) was obtained according to the same steps as in Example 1.

[0154] [Example 4]

[0155] (Manufacture of biaxially stretched film)

[0156] A single-layer film was produced from the pellets of the dried EVOH resin composition (EVOH-2) obtained in Synthesis Example 2. The single-layer film was brought into contact with warm water at 80°C for 10 seconds, and using a tenter-type simultaneous biaxial stretching machine, it was stretched 3.0 times longitudinally and 3.0 times transversely in an atmosphere at 90°C.

[0157] Furthermore, heat treatment was carried out for 5 seconds in a tenter set at 170°C, and the film ends were cut off, thereby obtaining a biaxially stretched film (thickness 12 μm, width 50 cm).

[0158] (Manufacture of Multilayer Film by Lamination)

[0159] A polyethylene adhesive resin layer (ADMER (trademark) NF518 manufactured by Mitsui Chemicals, Inc.) was provided on one surface of a single-layer film of polyethylene resin-1 (NOVATEC (trademark) LD LC600A manufactured by Nippon Polyethylene Co., Ltd.) to obtain a two-layer film A. Additionally, a polyethylene adhesive resin layer (ADMER (trademark) NF518 manufactured by Mitsui Chemicals, Inc.) was provided on one surface of a single-layer film of polyethylene resin-2 (EVOLUE (trademark) SP0510 manufactured by Prime Polymer Co., Ltd.) to obtain a two-layer film B. A two-component adhesive (TAKELAC (trademark) A-520 and TAKENATE (trademark) A-50 manufactured by Mitsui Chemicals, Inc.) was coated on the surfaces of the adhesive resin layers of the two-layer film A and the two-layer film B, respectively, so that the dry thickness became 2 μm and dried, and then laminated on both surfaces of the above-obtained biaxially stretched EVOH-2 film to obtain a multilayer film (polyethylene resin-1 / polyethylene adhesive resin / adhesive / EVOH-2 / adhesive / polyethylene adhesive resin / polyethylene resin-2 = 60 μm / 8 μm / 2 μm / 12 μm / 2 μm / 8 μm / 240 μm).

[0160] [Example 5]

[0161] (Manufacture of Uniaxially Stretched Film)

[0162] A single-layer film was produced from the pellets of the dried EVOH resin composition (EVOH-2) obtained in Synthesis Example 2. The single-layer film was brought into contact with warm water at 80°C for 10 seconds, and using a tenter-type uniaxial stretching machine, it was stretched 6.0 times longitudinally in an atmosphere at 90°C. Furthermore, heat treatment was carried out for 5 seconds in a tenter set at 170°C, and the film ends were cut off, thereby obtaining a uniaxially stretched film (thickness 12 μm, width 50 cm).

[0163] (Manufacture of Multilayer Film by Lamination)

[0164] In the manufacturing step of Example 4, the uniaxially stretched film obtained above was used instead of the biaxially stretched film, and the same operations as in Example 4 were carried out to obtain a multilayer film (polyethylene resin-1 / polyethylene adhesive resin / adhesive / EVOH-2 / adhesive / polyethylene adhesive resin / polyethylene resin-2 = 60 μm / 8 μm / 2 μm / 12 μm / 2 μm / 8 μm / 240 μm).

[0165] [Example 6]

[0166] (Manufacture of EVOH-4)

[0167] Using a twin-screw extruder (L / D = 30, screw diameter ), at a barrel temperature of 230 °C and a screw rotation speed of 100 rpm, 62.5 parts by mass of EVOH-1 and 37.5 parts by mass of EVOH-2 were melt-kneaded. The strands coming out of the die were cooled with a water bath and cut into pellet form using a strand cutter to manufacture EVOH-4. The ethylene unit content (Et) of EVOH-4 was 27 mol%, and the saponification degree was 99.98 mol% or more. In addition, the MFR of EVOH-4 was 2.5 g / 10 minutes.

[0168] (Manufacture of unstretched multilayer film)

[0169] In the manufacturing step of Example 1, EVOH-4 was used instead of EVOH-1, and the same steps as in Example 1 were followed to manufacture a multilayer film, obtaining an unstretched multilayer film (polyethylene resin-1 / polyethylene adhesive resin / EVOH-4 / polyethylene adhesive resin / polyethylene resin-2 = 60 μm / 8 μm / 12 μm / 8 μm / 240 μm).

[0170] [Comparative Example 1]

[0171] In the manufacturing step of Example 1, EVOH-3 was used instead of EVOH-1, and the same steps as in Example 1 were followed to manufacture a multilayer film.

[0172] [Comparative Example 2]

[0173] In the manufacturing step of Example 1, EVOH-3 was used instead of EVOH-1, and the thickness of each layer was set to polyethylene resin-1 / polyethylene adhesive resin layer / EVOH-3 / polyethylene adhesive resin layer / polyethylene resin-2 = 60 μm / 8 μm / 64 μm / 8 μm / 240 μm. Otherwise, the same steps as in Example 1 were followed to obtain a multilayer film.

[0174] [Comparative Example 3]

[0175] In the manufacturing step of Example 1, the thickness of each layer was set as polyethylene resin-1 / polyethylene adhesive resin layer / EVOH-1 / polyethylene adhesive resin layer / polyethylene resin-2 = 60 μm / 8 μm / 4 μm / 8 μm / 240 μm. Except for this, a multilayer film was obtained according to the same steps as in Example 1.

[0176] [Comparative Example 4]

[0177] In the manufacturing step of Example 1, EVAL (trademark) “E171B” (manufactured by Kuraray Co., Ltd.) with an ethylene unit content (Et) of 44 mol% was used to replace EVOH-1, and the thickness of each layer was set as polyethylene resin-1 / polyethylene adhesive resin layer / EVOH-1 / polyethylene adhesive resin layer / polyethylene resin-2 = 60 μm / 8 μm / 120 μm / 8 μm / 240 μm. Except for this, a multilayer film was obtained according to the same steps as in Example 1.

[0178] [Comparative Example 5]

[0179] (Manufacture of EVOH-5 containing filler)

[0180] Using a twin-screw extruder (L / D = 30, screw diameter ), at a barrel temperature of 230 °C and a screw rotation speed of 100 rpm, 10 parts by mass of magnesium hydroxide (Kisuma (trademark) 5A) and 90 parts by mass of EVOH-3 were melt-kneaded. The strands coming out of the die head were cooled with a water bath and cut into pellet form using a strand cutter to manufacture EVOH-5. The ethylene unit content (Et) of EVOH-5 was 38 mol%, and the saponification degree was 99.98 mol% or more. In addition, the MFR of EVOH-5 was 3.5 g / 10 minutes.

[0181] (Manufacture of polypropylene resin PP-1 containing filler)

[0182] Using a twin-screw extruder (L / D = 30, screw diameter ), at a barrel temperature of 230 °C and a screw rotation speed of 100 rpm, 20 parts by mass of magnesium hydroxide (Kisuma (trademark) 5A) and 80 parts by mass of polypropylene resin (“NOVATEC (trademark) PP EA7AD” manufactured by Japan Polypropylene Corporation; polypropylene, melting point 164 °C) were melt-kneaded. The strands coming out of the die head were cooled with a water bath and cut into pellet form using a strand cutter to manufacture polypropylene resin PP-1 containing filler.

[0183] (Manufacture of unstretched multilayer film)

[0184] In the manufacturing steps of Example 3, EVOH-5 was used to replace EVOH-1, and polypropylene resin containing a filler, PP-1, was used to replace the polypropylene resin. The thickness of each layer was set to PP-1 / polypropylene adhesive resin / EVOH-5 / polypropylene adhesive resin / PP-1 = 60 μm / 8 μm / 40 μm / 8 μm / 240 μm. Except for this, a multilayer film was obtained according to the same steps as in Example 3.

[0185] (Measurement of the thickness of each layer)

[0186] After cutting the multilayer films obtained in the examples and comparative examples with a microtome to expose the cross-section, using the backscattered electron detector of a scanning electron microscope ("ZEISS ULTRA55" manufactured by SII NanoTechnology Inc.), for each layer, five locations were changed to measure the cross-section, and thus the thickness (average thickness) of each layer was obtained.

[0187] (Measurement of the composite elastic modulus based on nanoindentation method)

[0188] For the multilayer films obtained in the examples and comparative examples, using the above method, the composite elastic modulus of each layer was measured by the nanoindentation method.

[0189] Based on the thickness and composite elastic modulus of each layer obtained, the total thickness LA of layer (A), the total thickness LB of layer (B), the average composite elastic modulus EA of layer (A), and the average composite elastic modulus EB of layer (B) were obtained. It should be noted that in any example and comparative example, layer (A) was 1 layer. And, based on these values and the ethylene content (Et) of the EVOH used in each layer (A), LA / LB·1 / Et and EA / EB were obtained. The values of LA / LB·1 / Et, EA, EB, EA / EB, and the ratio of the total thickness of layer (A) and layer (B) to the total thickness of all layers ((LA + LB) / L ALL ) are shown in Table 1.

[0190] (Evaluation of gas barrier property: Measurement of oxygen transmission rate (OTR))

[0191] The multilayer films obtained in the examples and comparative examples were installed in an oxygen transmission rate measuring device, and the oxygen transmission rate was measured by the isobaric method in accordance with JIS K7126-2:2006. The measurement conditions are as follows.

[0192] Device: MOCON OX-TRAN2 / 21 manufactured by MOCON Inc., Temperature: 20 °C

[0193] Humidity on the oxygen supply side: 65% RH

[0194] Humidity on the carrier gas side: 0% RH

[0195] Carrier gas flow rate: 10 mL / min

[0196] Oxygen pressure: 1.0 atm

[0197] Based on the oxygen permeability, the gas barrier property is evaluated according to the following criteria. In the case of A to B, it is judged that the gas barrier property is good. The results are shown in Table 1.

[0198] (Criteria)

[0199] A: Less than 0.2 cc / (m 2 ·day·atm)

[0200] B: 0.2 cc / (m 2 ·day·atm) or more and less than 0.5 cc / (m 2 ·day·atm)

[0201] C: 0.5 cc / (m 2 ·day·atm) or more and less than 1.0 cc / (m 2 ·day·atm)

[0202] D: 1.0 cc / (m 2 ·day·atm) or more and less than 5.0 cc / (m 2 ·day·atm)

[0203] E: 5.0 cc / (m 2 ·day·atm) or more

[0204] (Flex resistance evaluation)

[0205] For the multilayer films obtained in the examples and comparative examples, after conditioning in an atmosphere of 23°C and 50% RH, bending treatment was carried out using a Gelbo Flex Tester (manufactured by Rigaku Corporation). Specifically, first, the multilayer film was formed into a cylindrical shape with a diameter of 3.5 inches, and holding both ends thereof, a reciprocating motion composed of the following operations was performed 500 to 5000 times at a speed of 43 times / minute: the initial holding interval was 7 inches, the holding interval at maximum bending was 1 inch, a twist of 440 degrees was applied in the first 3.5 inches of the stroke, and the subsequent 2.5 inches was a linear forward horizontal movement. For the bent multilayer film, according to the number of times until one or more pinholes appeared, the flex resistance was evaluated according to the following criteria. In the case of A to C, it was judged that the flex resistance was good. The results are shown in Table 1.

[0206] (Criteria)

[0207] A: Even after 5000 times, no pinhole appeared

[0208] B: More than 4,500 times and less than 5,000 times

[0209] B - : More than 4,000 times and less than 4,500 times

[0210] C: More than 3,000 times and less than 4,000 times

[0211] D: More than 2,000 times and less than 3,000 times

[0212] E: Less than 2,000 times

[0213] (Flexibility evaluation)

[0214] For the multilayer film, after conditioning in an atmosphere of 23°C and 50% RH, the puncture strength is measured according to ISO1184 using AUTOGRAPH AGS-H (manufactured by Shimadzu Corporation). Based on the puncture strength when the puncture needle advances 1.5 mm from contacting the multilayer film, the flexibility is evaluated according to the following criteria. In the cases of A - D, it is judged to have appropriate flexibility. That is, in the case of E1 (less than 0.2 N) or E2 (10.0 N or more), it is judged that the flexibility is inappropriate. The results are shown in Table 1.

[0215] (Criteria)

[0216] A: 1.3 N or more and less than 1.6 N

[0217] B1: 1.0 N or more and less than 1.3 N

[0218] B2: 1.6 N or more and less than 2.5 N

[0219] C1: 0.5 N or more and less than 1.0 N

[0220] C2: 2.5 N or more and less than 4.0 N

[0221] D1: 0.2 N or more and less than 0.5 N

[0222] D2: 4.0 N or more and less than 10.0 N

[0223] E1: Less than 0.2 N

[0224] E2: 10.0 N or more

[0225] [Table 1]

[0226]

[0227] As shown in Table 1, the gas barrier properties and bending resistance of each of the multilayer films of Examples 1 to 6, where LA / LB·1 / Et is 0.0006 or more and 0.003 or less, EA is 6.0 or more, and EA / EB is 2 or more and 40 or less, are good, and they have appropriate flexibility.

[0228] Industrial applicability

[0229] The multilayer film of the present invention has good gas barrier properties and bending resistance and has appropriate flexibility. Therefore, it is also useful as a packaging material and can be used as a packaging material for reaction devices and the like.

Claims

1. A multilayer film, comprising: at least one layer (A) having an ethylene-vinyl alcohol copolymer as a main component; and at least one layer (B) having a thermoplastic resin other than the ethylene-vinyl alcohol copolymer as a main component, wherein the ratio of the total thickness of the at least one layer (A) and the at least one layer (B) to the total thickness of all layers is 90% or more, and the multilayer film satisfies the following formulas (1) to (3), [Mathematical formula 1] EA≥6.0…(2) In the above formulas (1) to (3), LA is the total thickness of the at least one layer (A); LB is the total thickness of the at least one layer (B); Et is the ethylene unit content (mol%) in the ethylene-vinyl alcohol copolymer; EA is the average composite elastic modulus (GPa) of the at least one layer (A); EB is the average composite elastic modulus (GPa) of the at least one layer (B).

2. The multilayer film according to claim 1, wherein the at least one layer (B) includes a layer (B1) disposed as one surface layer and a layer (B2) disposed as the other surface layer.

3. The multilayer film according to claim 2, wherein the melting point of the thermoplastic resin as the main component of the layer (B1) is lower than the melting point of the thermoplastic resin as the main component of the layer (B2), and the layer (B1) is thicker than the layer (B2).

4. The multilayer film according to any one of claims 1 to 3, wherein the thermoplastic resin is a polyolefin resin.

5. The multilayer film according to any one of claims 1 to 3, wherein the thermoplastic resin is a polyethylene resin.

6. The multilayer film according to any one of claims 1 to 5, wherein the total thickness of the at least one layer (A) is 5 μm or more and less than 50 μm, and the ratio of the total thickness of the at least one layer (A) to the total thickness of all layers is less than 10%.

7. The multilayer film according to any one of claims 1 to 6, wherein The oxygen permeation rate (under the conditions of 20 °C and 65% RH) measured by the method described in JIS K7126-2 (isobaric method; 2006) is 1.5 cc / (m 2 ·day·atm) or less.

8. The multilayer film according to any one of claims 1 to 7, wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer is 18 mol% or more and less than 25 mol%, and the saponification degree is 90 mol% or more.

9. The multilayer film according to any one of claims 1 to 7, wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer is 18 mol% or more and 32 mol% or less, and the at least one layer (A) is stretched at least uniaxially.

10. The multilayer film according to any one of claims 1 to 9, comprising the at least one layer of layer (A) and the at least one layer of layer (B).

11. A packaging material comprising the multilayer film according to any one of claims 1 to 10.

12. A reaction device, comprising: a container formed of the multilayer film according to any one of claims 1 to 10; and a stirring blade disposed inside the container.

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