Multilayer film, packaging material, and reaction apparatus

Abstract

Provided are: a multilayer film having good gas-barrier properties and flex resistance and having appropriate flexibility; a packaging material using such a multilayer film; and a reaction apparatus. The present invention comprises at least one layer (A) that contains EVOH as the main component and at least one layer (B) that contains a thermoplastic resin other than the EVOH as the main component. The percentage of the total thickness of the at least one layer (A) and the at least one layer (B) with respect to the total thickness of all of the layers is 90% or more, and satisfies 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). Et is the ethylene unit content (mol%) in the EVOH.

Description

Multilayer films, packaging materials and reaction equipment

[0001] The present invention relates to multilayer films, packaging materials and reactors.

[0002] Ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as "EVOH") is a polymer material that has excellent gas barrier properties such as oxygen barrier properties, oil resistance, anti-static properties, mechanical strength, melt moldability, etc. For this reason, EVOH is widely used as a molding material for films, containers, pipes, etc.

[0003] EVOH inherently has low flex resistance. Therefore, in flexible containers and the like, a multilayer film in which an EVOH layer and a thermoplastic resin layer with high flex resistance are laminated is sometimes used (see Patent Document 1). Bioreactor containers are known as one type of container that requires gas barrier properties. For example, if oxygen is introduced from outside the system during culture in a bioreactor, the culture may be affected. For this reason, EVOH is sometimes used as a material for bioreactor containers (see Patent Document 2).

[0004] JP 2006-272569 A JP 2018-161145 A

[0005] Typically, reactors such as bioreactors are equipped with stirring blades in their vessels to improve the uniformity of the reaction. However, in the case of reactors equipped with stirring blades in flexible vessels, the vessels may deform due to stirring, resulting in pinholes on the inner surface of the vessel, which may affect the gas barrier properties. Therefore, reactor vessels are desired to have not only gas barrier properties but also high flex resistance and moderate flexibility. If the flexibility is too high, deformation is likely to occur, and pinholes may occur even if the flex resistance is high. On the other hand, if the flexibility is too low (i.e., if the film is too hard), handling tends to be impaired. Furthermore, the development of multilayer films that combine gas barrier properties, flex resistance, and moderate flexibility is expected for applications other than reactor vessels.

[0006] The present invention has been made based on the above circumstances, and an object of the present invention is to provide a multilayer film that has good gas barrier properties and bending resistance and has appropriate flexibility, as well as a packaging material and a reaction device that use such a multilayer film.

[0007] The above object is to provide a multilayer film comprising: [1] at least one layer (A) containing an ethylene-vinyl alcohol copolymer as a main component; and at least one layer (B) containing 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 film satisfies the following formulas (1) to (3): 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 complex modulus (GPa) of the at least one layer (A). EB is the average complex modulus (GPa) of the at least one layer (B). [2] The multilayer film of [1], wherein the at least one layer (B) comprises a layer (B1) disposed as one surface layer and a layer (B2) disposed as the other surface layer; [3] The multilayer film of [2], wherein the melting point of the thermoplastic resin that is the main component of the layer (B1) is lower than the melting point of the thermoplastic resin that is the main component of the layer (B2), and the layer (B1) is thicker than the layer (B2); [4] The multilayer film of any of [1] to [3], wherein the thermoplastic resin is a polyolefin-based resin; [5] The multilayer film of any of [1] to [3], wherein the thermoplastic resin is a polyethylene-based resin; [6] The multilayer film of any 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%; [7] The multilayer film of any of [1] to [5], wherein the at least one layer (A) has a thickness of 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%; The oxygen transmission rate (under conditions of 20°C and 65% RH) measured in accordance with the method described in JP 7126-2 (isobaric method; 2006) is 1.5 cc / (m ２[8] the multilayer film of any of [1] to [7], wherein the ethylene-vinyl alcohol copolymer has an ethylene unit content of 18 mol% or more and less than 25 mol%, and a degree of saponification of 90 mol% or more; [9] the multilayer film of any of [1] to [7], wherein the ethylene-vinyl alcohol copolymer has an ethylene unit content of 18 mol% or more and less than 32 mol%, and wherein the at least one layer (A) is stretched at least in one direction;

[10] the multilayer film of [1] to [9], which consists of the at least one layer (A) and the at least one layer (B);

[11] a packaging material comprising the multilayer film of any of [1] to

[10] ;

[12] a reaction device comprising a container formed from the multilayer film of any of [1] to

[10] , and a stirring blade disposed inside the container.

[0008] According to the present invention, it is possible to provide a multilayer film that has good gas barrier properties and flex resistance and has appropriate flexibility, as well as a packaging material and a reaction device that use such a multilayer film.

[0009] <Multilayer Film> The multilayer film of the present invention comprises at least one layer (A) containing an ethylene-vinyl alcohol copolymer (EVOH) as a main component and at least one layer (B) containing a thermoplastic resin other than the EVOH 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): 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 EVOH. EA is the average composite modulus (GPa) of the at least one layer (A). EB is the average composite modulus (GPa) of the at least one layer (B).

[0010] The multilayer film of the present invention has good gas barrier properties and flex resistance, and moderate flexibility. Although the reason for this is unclear, the following reasons are presumed. Regarding formula (1), when the total thickness (LA) of layer (A) is relatively large, the gas barrier properties are enhanced while the flex resistance and flexibility are reduced. Conversely, when the total thickness (LB) of layer (B) is relatively large, the flex resistance and flexibility are enhanced while the gas barrier properties are reduced. Furthermore, when an EVOH with a low ethylene content (Et) is used, the gas barrier properties are enhanced while the flex resistance and flexibility are reduced. Therefore, when the product of LA / LB and 1 / Et (LA / LB·1 / Et) is within a predetermined range, the gas barrier properties, flex resistance, and flexibility are optimized in a balanced manner. Regarding formula (2), the high average composite modulus (EA) of layer (A) results in the multilayer film having good gas barrier properties. The reason for this is that EVOH with a low ethylene content (Et) or a high elongation ratio has a high composite modulus (EA), and such EVOH has high gas barrier properties. Furthermore, because the average composite modulus (EA) of Layer (A) is high, the multilayer film also has sufficient hardness (flexibility is not too low). Regarding Formula (3), the ratio of the average composite modulus (EA) of Layer (A) to the average composite modulus (EB) of Layer (B) is within a predetermined range, so that Layer (B) has a suitable elasticity, and the multilayer film has good flex resistance and suitable flexibility. For these reasons, it is presumed that the multilayer film has good gas barrier properties and flex resistance, and suitable flexibility.

[0011] With respect to the above formula (1), the lower limit of LA / LB·1 / Et is preferably 0.0008, more preferably 0.0011, and even more preferably 0.0015. When LA / LB·1 / Et is equal to or greater than the above lower limit, the gas barrier properties of the multilayer film of the present invention can be further improved and the flexibility can be made more appropriate. On the other hand, the upper limit of LA / LB·1 / Et is preferably 0.0028, more preferably 0.0024, and even more preferably 0.0020. When LA / LB·1 / Et is equal to or less than the above upper limit, the bending resistance of the multilayer film can be improved and the flexibility can be made more appropriate.

[0012] With respect to the above formula (2), the lower limit of EA is preferably 6.2, more preferably 6.4, and even more preferably 6.5. When EA is equal to or greater than the above lower limit, the gas barrier properties of the multilayer film of the present invention can be further improved and the film can have a more sufficient hardness. On the other hand, the upper limit of EA is preferably 10.0, more preferably 9.0, even more preferably 8.0, and even more preferably 7.0. When EA is equal to or less than the above upper limit, the multilayer film can have a higher bending resistance and more appropriate flexibility. The EA, i.e., the average composite modulus of at least one layer (A), can be increased by, for example, using EVOH with a low ethylene unit content, stretching the layer (A), etc.

[0013] With respect to the above formula (3), the lower limit of EA / EB is preferably 8, more preferably 15, and even more preferably 20. The upper limit of EA / EB is preferably 36, more preferably 31, and even more preferably 28. When EA / EB is in the above range, the flexibility of the multilayer film of the present invention becomes more appropriate and the flex resistance is further improved. Furthermore, the lower limit of EB is preferably 0.10, and more preferably 0.20. The upper limit of EB is preferably 2.0, more preferably 1.0, and even more preferably 0.4. When EB is in the above range, the flexibility of the multilayer film becomes more appropriate. EB, i.e., the average composite modulus of at least one layer (B), can be adjusted by, for example, the type of thermoplastic resin forming layer (B).

[0014] In this specification, the term "main component" refers to the component that is contained in the greatest amount by mass.

[0015] The "thickness" of a layer or the like refers to the average value (average thickness) of measurements taken at any five points.

[0016] The average composite modulus refers to the thickness-based average value (weighted average value) of the composite modulus measured for each layer. The composite modulus of each layer is measured using the following procedure. The sample (the multilayer film to be measured) is dried at 90°C for 1 hour, and then vacuum-dried in a vacuum dryer at 50°C for 60 hours. The sample is then left for 1 week in a desiccator conditioned at 23°C and 40% RH to condition the humidity, and cut into 2 mm x 2 mm samples are used for measurement. Multiple cut samples are prepared. The cross section of each layer to be measured is exposed, and the central portion of the cross section of each layer is measured multiple times at different locations. The composite modulus is measured using a nanoindentation method. The measurement is performed in an environment with a temperature of 23°C and a humidity of 40% RH. A Berkovich-type indenter is used. A load is set within the range of 50 to 300 μN, and a load-displacement curve is obtained by pressing for 3 seconds and withdrawing for 3 seconds. The load is set to the layer to be measured within the range of 50 to 300 μN so that the insertion depth is approximately 200 nm. The composite elastic modulus E (GPa) is calculated by multiplying the ratio S (N) of the load reduction rate to the displacement when the maximum load is reached and the load is released on the load-displacement curve (dP / dh: P is the load, h is the displacement) and the contact projection area A (mm ２ ) and is calculated by the following formula (4): E = S√π / 2√A (4) Measurements are made at 5 to 10 points on one cut sample, and the average value is calculated. Similar measurements are made on two to four samples, and the average value is used as the composite elastic modulus of that layer. Nanoindentation measurements are made on layers where the thickness of each layer exceeds 1% of the total thickness of all layers.

[0017] Each layer of the multilayer film according to one embodiment of the present invention will be described in detail below.

[0018] (Layer (A)) Layer (A) is a layer containing EVOH as a main component. 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 contain residual vinyl ester units. The production and saponification of the ethylene-vinyl ester copolymer can be carried out by known methods. Examples of vinyl esters 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, with vinyl acetate being preferred.

[0019] The ethylene unit content (Et) of EVOH can be, for example, 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%, even more preferably 20 mol% or more and less than 25 mol%, and particularly preferably 22 mol% or more and less than 25 mol%. When the ethylene content (Et) of EVOH is equal to or less than the above upper limit, the gas barrier properties of the multilayer film of the present invention can be improved and the multilayer film can have more appropriate flexibility (sufficient hardness). On the other hand, when the ethylene unit content (Et) of EVOH is equal to or more than 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 relative to all structural units constituting EVOH. When multiple types of EVOH are used, the ethylene unit content (Et) is an average value based on mass.

[0020] The saponification degree of EVOH is preferably 90 mol% or more, more preferably 95 mol% or more, and even more preferably 99 mol% or more. When the saponification degree of EVOH is equal to or higher than the above lower limit, the gas barrier properties of the multilayer film of the present invention tend to be better. The saponification degree of EVOH may be 100 mol% or less, 99.97 mol% or less, or 99.94 mol% or less.

[0021] EVOH may contain structural units other than ethylene units, vinyl alcohol units, and vinyl ester units, provided that the object of the present invention is not impaired. When EVOH contains such structural units, the content of such structural units relative to the total structural units of EVOH is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, even more preferably 5 mol% or less, and sometimes particularly preferably 1 mol% or less. When EVOH contains such structural units, the content may be 0.05 mol% or more, or 0.10 mol% or more. Examples of the other structural units include structural units derived from unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, etc., or anhydrides, salts, or esters thereof; nitriles such as acrylonitrile, methacrylonitrile, etc.; amides such as acrylamide, methacrylamide, etc.; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, methallylsulfonic acid, etc., or salts thereof; vinyl silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, γ-methacryloxypropylmethoxysilane, etc.; alkyl vinyl ethers, vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, etc.

[0022] One type of EVOH may be used alone, or two or more types may be used in combination. For example, two or more types of EVOH may be contained in one layer (A). When two or more layers (A) are present, different EVOH may be used in each layer (A). From the viewpoint of gas barrier properties, etc., 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, and may be 95% by mass or more, 99% by mass or more, or 99.9% by mass or more. The resin constituting layer (A) may be substantially composed of EVOH alone. On the other hand, the content of EVOH in layer (A) may be, for example, 99.9% by mass or less, or may be 99% by mass or less.

[0023] The layer (A) may contain, 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, resins other than EVOH, metal salts of higher aliphatic carboxylic acids, etc. The layer (A) may contain two or more of these optional components.

[0024] Examples of boron compounds include boric acids such as orthoboric acid, metaboric acid, and tetraboric acid; boric acid esters such as triethyl borate and trimethyl borate; alkali metal or alkaline earth metal salts of the above boric acids, borax, and other boric acid salts; and boron hydrides. The lower limit of the content of the boron compound in Layer (A) is preferably 100 ppm, more preferably 500 ppm. The upper limit of the content of the boron compound in Layer (A) is preferably 5,000 ppm, more preferably 3,000 ppm, and even more preferably 1,000 ppm. By controlling the content of the boron compound to be equal to or greater than the lower limit, torque fluctuations in an extruder or the like can be sufficiently suppressed. On the other hand, by controlling the content of the boron compound to be equal to or less than the upper limit, gelation is less likely to occur during melt molding, improving the appearance of the multilayer film of the present invention. The content of the boron compound is the content of the boron compound converted into orthoboric acid.

[0025] Examples of carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, lactic acid, and salts thereof. As the carboxylic acids, carboxylic acids having 4 or less carbon atoms or saturated carboxylic acids are preferred, and acetic acids are more preferred. The acetic acids include acetic acid and acetate salts. The lower limit of the carboxylic acid content in Layer (A) is preferably 50 ppm, more preferably 100 ppm, and even more preferably 150 ppm. The upper limit of the carboxylic acid content in Layer (A) is preferably 1,000 ppm, more preferably 500 ppm, and even more preferably 400 ppm. By setting the carboxylic acid content at or above the lower limit, a sufficient coloration suppression effect can be obtained, and the occurrence of yellowing can be sufficiently suppressed. On the other hand, by setting the carboxylic acid content at or below the 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 is improved.

[0026] Examples of phosphorus compounds include phosphates such as phosphoric acid and phosphorous acid. The phosphate may be in the form of a primary phosphate, a secondary phosphate, or a tertiary phosphate. The cation species of the phosphate is not particularly limited, but alkali metal salts or alkaline earth metal salts are preferred, and 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 compound in layer (A) is preferably 1 ppm, more preferably 10 ppm, even more preferably 20 ppm, and particularly preferably 30 ppm. The upper limit of the content of the phosphorus compound in layer (A) is preferably 200 ppm, more preferably 150 ppm, and even more preferably 100 ppm. By setting the content of the phosphorus compound to be equal to or greater than the above lower limit or equal to or less than the above upper limit, thermal stability is improved, and the generation of gel-like particles, coloration, etc. during long-term melt molding is less likely to occur.

[0027] Examples of metal ions include monovalent metal ions, divalent metal ions, and other transition metal ions, and these may be used alone or in combination. Among these, monovalent metal ions or divalent metal ions are preferred. As monovalent metal ions, alkali metal ions are preferred, such as lithium, sodium, potassium, rubidium, and cesium ions. From the viewpoint of industrial availability, sodium or potassium ions are preferred. Furthermore, examples of alkali metal salts that provide alkali metal ions include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, and metal complexes. Among these, aliphatic carboxylates or phosphates are preferred from the viewpoint of availability, and specifically, sodium acetate, potassium acetate, sodium phosphate, or potassium phosphate is preferred. It may also be preferable to include a divalent metal ion as the metal ion. When the metal ion includes a divalent metal ion, for example, thermal degradation of EVOH when trim is recovered and reused may be suppressed, and the occurrence of gels and lumps in the resulting multilayer film may be suppressed. Examples of divalent metal ions include beryllium, magnesium, calcium, strontium, barium, and zinc ions, with magnesium, calcium, or zinc ions being preferred from the viewpoint of industrial availability. Divalent metal salts that provide divalent metal ions include, for example, carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, and metal complexes, with carboxylates being preferred. The carboxylic acid constituting the carboxylate is preferably a carboxylic acid having 1 to 30 carbon atoms, specifically, acetic acid, propionic acid, butyric acid, stearic acid, lauric acid, montanic acid, behenic acid, octylic acid, sebacic acid, ricinoleic acid, myristic acid, palmitic acid, etc., with acetic acid or stearic acid being preferred. The lower limit of the metal ion content in layer (A) is preferably 1 ppm, more preferably 100 ppm, and even more preferably 150 ppm. The upper limit of the metal ion content is preferably 1,000 ppm, more preferably 400 ppm, and even more preferably 350 ppm. When the content of metal ions in layer (A) is 1 ppm or more, the interlayer adhesion of the multilayer film of the present invention tends to be good.On the other hand, if the content of metal ions is 1,000 ppm or less, the coloring resistance tends to be good.

[0028] Examples of antioxidants include 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4'-thiobis(6-t-butylphenol), 2,2'-methylene-bis(4-methyl-6-t-butylphenol), and octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate.

[0029] 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, and 2-hydroxy-4-oxybenzophenone.

[0030] Examples of the plasticizer include dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, and phosphate esters.

[0031] Examples of antistatic agents include pentaerythritol monostearate, sorbitan monopalmitate, sulfated polyolefins, polyethylene oxide, and polyethylene glycol (trade name: Carbowax).

[0032] Examples of the lubricant include ethylene bisstearamide and butyl stearate.

[0033] Examples of colorants include carbon black, phthalocyanine, quinacridone, indoline, azo pigments, and red iron oxide.

[0034] Examples of fillers include glass fiber, wollastonite, calcium silicate, talc, and montmorillonite.

[0035] Examples of the heat stabilizer include hindered phenol compounds and hindered amine compounds.

[0036] Examples of resins other than EVOH include polyamides and polyolefins.

[0037] Examples of metal salts of higher aliphatic carboxylic acids include sodium stearate, potassium stearate, calcium stearate, and magnesium stearate.

[0038] The total thickness (LA) of all layers (A) included in the multilayer film of the present invention is preferably 5 μm or more and less than 50 μm, more preferably 10 μm or more and 45 μm or less, and even more preferably 12 μm or more and 35 μm or less. The total thickness (LA) of the layers (A) may be 25 μm or less, or may be 15 μm or less. The thickness of a single layer (A) is preferably 5 μm or more and less than 50 μm, more preferably 8 μm or more and 40 μm or less, and even more preferably 10 μm or more and 28 μm or less. The thickness of a single layer (A) may be 20 μm or less, or may be 15 μm or less. When the total thickness (LA) of the layers (A) or the thickness of a single layer (A) is equal to or greater than the above lower limit, the gas barrier properties of the multilayer film can be further improved and more appropriate flexibility (sufficient hardness) can be achieved. On the other hand, when the total thickness (LA) of the layers (A) or the thickness of one layer (A) is less than the above upper limit, the bending resistance and flexibility of the multilayer film can be further improved.

[0039] The ratio of the total thickness of all layers (A) in the multilayer film of the present invention to the total thickness of all layers is preferably less than 10%, more preferably less than 8%, and even more preferably less than 6%. By setting the ratio of the total thickness of all layers (A) in the multilayer film to the total thickness of all layers of the multilayer film to be less than the above-mentioned upper limit, the ratio of the total thickness of layer (B) is increased, thereby improving the bending resistance of the multilayer film and making its flexibility more appropriate. Furthermore, by using EVOH with a low ethylene unit content in layer (A), the multilayer film can exhibit good gas barrier properties and appropriate flexibility (sufficient hardness) even when the ratio of the total thickness of layer (A) is relatively low. Meanwhile, the ratio of the total thickness of all layers (A) in the multilayer film to the total thickness of all layers of the multilayer film is preferably 1% or more, more preferably 2% or more, and even more preferably 3% or more. When the ratio of the total thickness of all layers (A) in the multilayer film to the total thickness of all layers in the multilayer film is at least the above lower limit, the gas barrier properties of the multilayer film can be improved and the flexibility can be made more appropriate.

[0040] The number of layers (A) in the multilayer film of the present invention is not particularly limited and may be 1, 2 or more layers. The upper limit of the number of layers (A) in the multilayer film may be, for example, 10 layers, 5 layers, 3 layers, 2 layers, or 1 layer.

[0041] The layer (A) may be either an unstretched layer or a stretched layer. When the layer (A) is stretched, it may be uniaxially stretched or biaxially stretched. When the layer (A) is stretched, the other layers, such as the layer (B), may be stretched or not. The layer (A) is preferably a layer stretched at least uniaxially, more preferably at least 2 times uniaxially stretched, even more preferably at least 2 times but less than 12 times uniaxially stretched, even more preferably biaxially stretched, and particularly preferably at least 3 times but less than 12 times in each of the two directions. When the layer (A) is stretched in this manner, the gas barrier property can be further improved. For example, when the layer (A) is stretched at least uniaxially (more preferably when the layer (A) is biaxially stretched), particularly high gas barrier property can be exhibited when the ethylene unit content of the EVOH contained in the layer (A) is 18 mol% or more and 32 mol% or less.

[0042] (Layer (B)) Layer (B) is a layer containing a thermoplastic resin other than EVOH as a main component. Hereinafter, "thermoplastic resin" refers to a thermoplastic resin other than EVOH. Examples of thermoplastic resins 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 polypentene; 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.

[0043] As the thermoplastic resin, a polyolefin-based resin is preferred, and a polyethylene-based resin is more preferred. A polyolefin-based resin refers to a resin containing a structural unit derived from an olefin (olefin unit) in its structural unit. A polyethylene-based resin refers to a resin containing a structural unit derived from ethylene (ethylene unit) in its structural unit. The lower limit of the content of olefin units relative to all structural units in a polyolefin-based resin is, for example, preferably 50 mol%, more preferably 70 mol%, and may be 90 mol%, 95 mol%, 98 mol%, or 99 mol%. The upper limit of the content of olefin units relative to all structural units in a polyolefin-based resin may be 100 mol%. The lower limit of the content of ethylene units relative to all structural units in a polyethylene-based resin is, for example, preferably 50 mol%, more preferably 70 mol%, and may be 90 mol%, 95 mol%, 98 mol%, or 99 mol%. The upper limit of the content of ethylene units relative to all structural units in a polyethylene-based resin may be 100 mol%. By using a polyolefin resin, particularly a polyethylene resin, as the thermoplastic resin, it is possible to further increase the bending resistance of the multilayer film of the present invention and to make the flexibility more appropriate.

[0044] The thermoplastic resin may be an adhesive resin (a thermoplastic resin having adhesive properties). In addition, a layer of the layer (B) containing an adhesive resin as a thermoplastic resin is sometimes referred to as an adhesive resin layer, and is also referred to as the layer (B ＡＤ). Examples of thermoplastic resins having adhesive properties include acid-modified polyolefins and epoxy-modified polyolefins, with acid-modified polyolefins being preferred, carboxylic acid-modified polyolefins being more preferred, and carboxylic acid-modified polyethylene being even more preferred. Carboxylic acid-modified polyolefins are a type of polyolefin-based resin. Carboxylic acid-modified polyethylene is a type of polyethylene-based resin. Carboxylic acid-modified polyolefins may be polyolefin-based resins having a carboxy group or an anhydride group thereof. Polyolefin-based resins having a carboxy group or an anhydride group thereof can be obtained, for example, by chemically bonding an ethylenically unsaturated carboxylic acid or an anhydride thereof to an unmodified polyolefin-based resin by addition reaction, graft reaction, or the like.

[0045] Examples of unmodified polyolefin resins used in the production of carboxylic acid-modified polyolefins include the various polyolefin resins mentioned above, with polyethylene, ethylene-vinyl acetate copolymer, and ethylene-ethyl acrylate copolymer being preferred.

[0046] Examples of ethylenically unsaturated carboxylic acids and anhydrides thereof include monocarboxylic acids, monocarboxylic acid esters, dicarboxylic acids, dicarboxylic acid monoesters, dicarboxylic acid diesters, dicarboxylic acid anhydrides, etc. Specific examples include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, etc. Among these, dicarboxylic acid anhydrides such as maleic anhydride and itaconic anhydride are preferred, and maleic anhydride is more preferred.

[0047] Carboxylic acid-modified polyolefins can be obtained by introducing an ethylenically unsaturated carboxylic acid or its anhydride into an unmodified polyolefin resin by addition reaction or graft reaction in the presence of a solvent such as xylene and a catalyst such as peroxide. The lower limit of the amount of carboxylic acid or its anhydride added to or grafted onto the unmodified polyolefin resin (modification degree) is preferably 0.01% by mass, more preferably 0.02% by mass, based on the unmodified polyolefin resin. On the other hand, the upper limit of the amount of addition or grafting (modification degree) is preferably 15% by mass, more preferably 10% by mass, based on the unmodified polyolefin resin.

[0048] The thermoplastic resin may be used alone or in combination of two or more. For example, two or more types of thermoplastic resins may be contained in one layer (B). Furthermore, when two or more layers (B) are present, different thermoplastic resins may be used in 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, 99% by mass or more, or 99.9% by mass or more. The resin constituting layer (B) may be substantially composed 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, or may be 99% by mass or less.

[0049] The layer (B) may contain, 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, a resin other than the thermoplastic resin, etc. The layer (B) may contain two or more of these optional components.

[0050] The total thickness (LB) of all layers (B) included in the multilayer film of the present invention is preferably 100 μm or more and less than 500 μm, more preferably 200 μm or more and 400 μm or less, and even more preferably 250 μm or more and 350 μm or less. When the total thickness (LB) of layers (B) is equal to or greater than the above lower limit, the multilayer film can have higher bending resistance and more appropriate flexibility. On the other hand, when the total thickness (LB) of layers (B) is less than the above upper limit, the multilayer film can be made thinner.

[0051] The thickness of one layer of the layer (B) is not particularly limited. For example, when the layer (B) is an adhesive resin layer (layer (B ＡＤ )), the average thickness of one layer of this layer is, for example, preferably 1 μm or more and 30 μm or less, more preferably 3 μm or more and 20 μm or less, and even more preferably 5 μm or more and 15 μm or less. When layer (B) is a layer other than an 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. Furthermore, as will be described later, a more appropriate thickness can be set depending on the location of arrangement of layer (B), etc.

[0052] The ratio of the total thickness of all layers (B) in the multilayer film of the present invention to the total thickness of all layers is preferably more than 90% but not more than 99%, more preferably more than 92% but not more than 99%, and even more preferably more than 94% but not more than 98%. By setting the ratio of the total thickness of all layers (B) in the multilayer film to the total thickness of all layers of the multilayer film above the above-mentioned lower limit, the multilayer film has better bending resistance and more moderate flexibility. Furthermore, by using EVOH with a low ethylene unit content in layer (A), the multilayer film can exhibit good gas barrier properties and moderate flexibility (sufficient hardness) even when the ratio of the total thickness of layer (B) is relatively high. Furthermore, by setting the ratio of the total thickness of all layers (B) in the multilayer film to the total thickness of all layers of the multilayer film below the above-mentioned upper limit, layer (A) of sufficient thickness can be provided, thereby improving the gas barrier properties of the multilayer film and making the flexibility more moderate.

[0053] The number of layers (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 (B) in the multilayer film is preferably 2 layers, more preferably 4 layers. The upper limit of the number of layers (B) in the multilayer film may be, for example, 20 layers, 10 layers, 8 layers, 6 layers, or 4 layers.

[0054] (Other Layers) The multilayer film of the present invention may include layers other than layer (A) and layer (B). Examples of such layers include metal layers, paper layers, inorganic vapor-deposited layers, and layers primarily composed of resins other than thermoplastic resins. The ratio of the total thickness of all layers (A) and (B) contained 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 even more preferably 99% or more. When the ratio of the total thickness of all layers (A) and (B) contained in the multilayer film to the total thickness of all layers of the multilayer film is equal to or greater than the lower limit, the effects of good gas barrier properties and flex resistance and moderate flexibility based on the above formulas (1) to (3) are fully achieved. For these reasons, the multilayer film preferably consists of at least one layer (A) and at least one layer (B). In other words, the ratio of the total thickness of all layers (A) and (B) in the multilayer film to the total thickness of all layers in the multilayer film is preferably 100%.

[0055] (Layer Structure, etc.) The layer structure of the multilayer film of the present invention is not particularly limited as long as it contains at least one layer (A) and at least one layer (B). In the multilayer film, it is preferable that 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. By disposing the layer (B) on both surface layers in this way, the relatively thin and rigid layer (A) is protected or supported, the bending resistance is improved, and the occurrence of pinholes due to bending, for example, is suppressed. Furthermore, the layer (B1) does not correspond to an adhesive resin layer, and the layer (B1) is an adhesive resin layer relative to the layer (A). ＡＤSimilarly, it is preferable that the layer (B2) does not correspond to an adhesive resin layer, and the layer (B2) is laminated with the layer (A) through the layer (B ＡＤ ) is preferably laminated via a layer (B1 / B2). Examples of such a multilayer film include multilayer films having the layer structures (1) to (4) shown below. Among these, a multilayer film having the layer structure (1) below is preferred. Layer (B1) and layer (B2) may be adhesive resin layers. In the examples of each layer structure below, " / " indicates that they are directly laminated. Furthermore, a layer simply marked "B" indicates a layer (B) that does not fall under the category of an adhesive resin layer. (1) B1 / B ＡＤ / A / B ＡＤ / B2 (2)B1 / B ＡＤ / A / B ＡＤ / B / B ＡＤ / A / B ＡＤ / B2 (3)B1 / B ＡＤ / B / B ＡＤ / B / B ＡＤ / A / B ＡＤ / B2 (4)B1 / B ＡＤ / B / B ＡＤ / A / B ＡＤ / A / B ＡＤ / B2

[0056] Other examples of the layer structure of the multilayer film containing the layer (B1) and the layer (B2) include the following (5) to (7): (5) B1 / A / B2 (6) B1 / B ＡＤ / A / B2 (7) B1 / B ＡＤ / B / B ＡＤ / A / B ＡＤ / B2

[0057] In the multilayer film of the present invention containing layer (B1) and layer (B2), it is preferable that the melting point of the thermoplastic resin that is the main component of layer (B1) is lower than the melting point of the thermoplastic resin that is the main component of layer (B2), and layer (B1) is thicker than layer (B2). The multilayer film may be formed into a bag or the like by heat sealing and used as a container. In this case, layer (B1), which uses a thermoplastic resin with a low melting point, is heat-sealed so as to become the innermost layer to be heat-sealed. On the other hand, a thermoplastic resin with a high melting point is preferably used for layer (B2), which is the outermost layer, so that melting during heat sealing is less likely to occur. In such a container, by thickening layer (B1), the innermost layer, layer (A), which has relatively low moisture resistance, can be positioned away from the inner surface of the container. Such a container is particularly suitable for use as a container for storing contents containing water. In particular, when EVOH having a low ethylene unit content is used in the layer (A), moisture resistance decreases, and therefore the effect of improving moisture resistance by increasing the thickness of the layer (B1) is remarkable.

[0058] 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. 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 the melting peak temperature determined by differential scanning calorimetry.

[0059] The main component of layer (B1) is preferably a polyethylene resin, more preferably polyethylene (linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, etc.), and even more preferably linear low-density polyethylene or low-density polyethylene. The main component of layer (B2) is preferably a polyethylene resin, more preferably polyethylene (linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, etc.), and even more preferably low-density polyethylene, medium-density polyethylene, or high-density polyethylene.

[0060] The thickness of layer (B1) is preferably from 100 μm to 300 μm, more preferably from 150 μm to 280 μm, and even more preferably from 200 μm to 260 μm. The thickness of layer (B2) is preferably from 10 μm to 200 μm, more preferably from 20 μm to 100 μm, and even more preferably from 40 μm to 80 μm.

[0061] Similarly, when the layer (A) is a single layer, from the viewpoint of moisture resistance, the thickness ratio (I / O) of the total thickness I of all layers including the layer (B1) laminated on one surface of the layer (A) to the total thickness O of all layers including the layer (B2) laminated on the other surface of the layer (A) is preferably 60 / 40 or more and 90 / 10 or less, and more preferably 70 / 30 or more and 85 / 15 or less.

[0062] In the multilayer film, it is also preferable that layer (B) is present on both sides of layer (A). The layer structures (1) to (7) exemplified above are included in this embodiment. In addition, layer structures in which layer (A) is disposed as at least one surface layer, such as the following examples (8) to (11), are also embodiments of the multilayer film of the present invention. (8) A / B (9) A / B ＡＤ / B (10) A / B ＡＤ / B / B ＡＤ / A (11) A / B ＡＤ / B / B ＡＤ / A / B ＡＤ / B

[0063] The total thickness of all layers of the multilayer film of the present invention (i.e., the overall thickness) is not particularly limited. That is, the multilayer film is not limited to a predetermined thickness or less. The total thickness of all layers of the multilayer film is preferably 100 μm or more and 600 μm or less, more preferably 200 μm or more and 500 μm or less, even more preferably 250 μm or more and 400 μm or less, and particularly preferably 300 μm or more and 350 μm or less. When the total thickness of all layers is equal to or greater than the above lower limit, the gas barrier property and flex resistance can be improved, and flexibility can be made more appropriate. On the other hand, when the total thickness of all layers is equal to or less than the above upper limit, flexibility can be improved.

[0064] In the multilayer film of the present invention, the oxygen transmission rate (under conditions of 20°C and 65% RH) measured in accordance with the method described in JIS K 7126-2 (isobaric method; 2006) is 10 cc / (m ２ ·day·atm) or less, and ２ ·day·atm) or less, and 1.0 cc / (m ２ ·day·atm) or less, and more preferably 0.5 cc / (m ２ ·day·atm) or less, and more preferably 0.2 cc / (m ２ It is particularly preferable that the oxygen transmission rate is equal to or less than the above upper limit, so that the material can be particularly suitably used as various packaging materials. On the other hand, the lower limit of the oxygen transmission rate is 0.001 cc / (m ２ ·day·atm), and 0.01 cc / (m ２ ・day・atm).

[0065] The method for producing 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 monolayer film consisting of layer (A), a method of co-extruding 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 converging T-die method, a feed block converging T-die method, and an inflation method.

[0066] The multilayer film of the present invention may be a stretched film or a non-stretched film.

[0067] The multilayer film of the present invention is suitably used as a material for various types of packaging, i.e., as a packaging material, such as food packaging, pharmaceutical packaging, industrial chemical packaging, agricultural chemical packaging, and various liquid packaging. The multilayer film may also be used for purposes other than packaging.

[0068] <Packaging Material> The packaging material of the present invention includes the multilayer film of the present invention. The packaging material may consist solely of the multilayer film of the present invention, or may consist of the multilayer film of the present invention and another component. For example, a packaging material formed by laminating the multilayer film of the present invention on another component (such as a substrate) is also an embodiment of the packaging material of the present invention. The packaging material may be used as is in the form of a film, or may be used after being formed into a container (e.g., a pouch, a box, etc.). Containers provided in the reaction apparatus described below and other containers are also embodiments of the packaging material. When the multilayer film having the above-described layer (B1) and layer (B2) is formed into a container, it is preferable that layer (B1) be formed as the innermost layer and layer (B2) be formed as the outermost layer. Furthermore, the forming method for forming into a container is not particularly limited, and various known forming methods can be used in addition to the above-described heat sealing.

[0069] <Reaction Apparatus> The reaction apparatus of the present invention comprises a container formed from the multilayer film of the present invention and an agitating blade disposed inside the container. The reaction apparatus of the present invention may comprise a container formed from the packaging material of the present invention and an agitating blade disposed inside the container.

[0070] The container provided in the reaction apparatus of the present invention can be formed using the multilayer film of the present invention or the packaging material of the present invention by, for example, heat sealing or other various forming methods. When using a multilayer film having the above-mentioned layer (B1) and layer (B2), it is preferable that the container is formed so that layer (B1) is the innermost layer and layer (B2) is the outermost layer. The container provided in the reaction apparatus may also be called a reaction tank. Conventionally known stirring blades can be used for the reaction apparatus.

[0071] The container provided in the reaction apparatus of the present invention has good gas barrier properties and bending resistance, and has moderate flexibility. Because the container has moderate flexibility (in other words, because it has moderate hardness), the container is less likely to deform even when the stirring blade is operated. Furthermore, because the container has good bending resistance, even if the container is deformed, pinholes and the like are less likely to occur. If pinholes and the like occur, the gas barrier properties of that area may be reduced. Therefore, in this reaction apparatus, even if the stirring blade is continuously operated, for example, oxygen penetration from the outside into the container is suppressed, and a predetermined reaction environment can be maintained. Furthermore, because the container has moderate flexibility and is not too hard, it is also easy to handle. This reaction apparatus, which has these advantages, can be suitably used as a bioreactor. A bioreactor is a device that performs biochemical reactions using a biocatalyst. This reaction apparatus may also be used as a reaction apparatus other than a bioreactor.

[0072] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0073] [Melt Flow Rate (MFR) Measurement] 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 cylinder of a Melt Indexer L 244 (manufactured by Takara Kogyo Co., Ltd.) with an inner diameter of 9.55 mm and a length of 162 mm, and melted at 210°C. A load of 2,160 g and a plunger with a diameter of 9.48 mm was uniformly applied to the molten EVOH. The amount of resin composition extruded per unit time (g / 10 min) through an orifice with a diameter of 2.1 mm provided in the center of the cylinder was measured, and this was taken as the MFR.

[0074] Synthesis Example 1 Synthesis of EVOH-1 A 100 L pressurized reactor equipped with a jacket, a stirrer, a nitrogen inlet, an ethylene inlet, and an initiator addition port was charged with 40.0 kg of vinyl acetate (hereinafter sometimes referred to as VAc) and 9.8 kg of methanol (hereinafter sometimes referred to as MeOH), and the atmosphere inside the reactor was replaced with nitrogen by bubbling with nitrogen for 30 minutes. Next, the temperature inside the reactor was adjusted to 60°C, and ethylene was introduced so that the reactor pressure (ethylene pressure) was 2.80 MPa. 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 initiate 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 VAc conversion (polymerization rate based on VAc) reached 49.8%, the system was cooled, and 0.2 g of copper acetate dissolved in 20 kg of methanol was added to the vessel to terminate the polymerization. The reaction vessel was opened to remove ethylene, and nitrogen gas was bubbled through to completely remove ethylene. The polymerization solution was then withdrawn from the vessel and diluted with 20 L of MeOH. This solution was fed into a column-type vessel from the top, and MeOH vapor was fed from the bottom to remove any unreacted monomer remaining in the polymerization solution together with the MeOH vapor, yielding a MeOH solution of ethylene-vinyl acetate copolymer (hereinafter sometimes referred to as EVAc). Next, 100 kg of a 20% by 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. The solution was heated to 60°C while nitrogen gas was blown into it, and a 2N MeOH solution containing sodium hydroxide 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 in the system was maintained at 60°C, and the saponification reaction was allowed to proceed with stirring for 2 hours while draining MeOH and methyl acetate produced by the saponification reaction out of the reaction vessel. 8.7 kg of acetic acid was then added to terminate the saponification reaction. Subsequently, 120 L of ion-exchanged water was added while heating and stirring at 80°C, and MeOH was drained out of the reaction vessel, precipitating EVOH. The precipitated EVOH was collected by decantation and pulverized in a mill. The resulting EVOH powder was introduced into a 1 g / L aqueous acetic acid solution (bath ratio 20: 20 L of aqueous solution per 1 kg of powder) and washed with stirring for 2 hours.The resulting product was dewatered and then poured into a 1 g / L aqueous acetic acid solution (bath ratio: 20) and washed with stirring for 2 hours. The dewatered product was then poured into ion-exchanged water (bath ratio: 20), washed with stirring for 2 hours, and then drained. This procedure was repeated three times for purification. The electrical conductivity of the washing solution was 3 μS / cm (measured using a CM-30ET from Toa Denpa Kogyo Co., Ltd.). The product was then immersed in 250 L of an aqueous solution containing 0.5 g / L acetic acid and 0.1 g / L sodium acetate with stirring for 4 hours, then drained. This product was then dried at 60°C for 16 hours to obtain 16.1 kg of crude dried EVOH. The above procedure was repeated to obtain 15.9 kg of crude dried EVOH, yielding a total of 32.0 kg of crude dried EVOH (EVOH-1).

[0075] 10.5 kg of the crude dried EVOH (EVOH-1) obtained above was added to 94.5 L of an aqueous solution prepared by dissolving acetic acid and sodium acetate in water to a concentration of 0.364 g / L and 0.455 g / L, respectively, and immersed at 25°C for 6 hours with occasional stirring. The immersed hydrous EVOH pellets were dehydrated by centrifugal dewatering and then dried in a hot air dryer at 80°C for 3 hours and then at 120°C for 24 hours. This resulted in pellets of a dried EVOH resin composition (EVOH-1), which was a mixture of EVOH and a metal salt. The vinyl alcohol unit content, ethylene unit content, and degree of saponification of EVOH-1 were analyzed by nuclear magnetic resonance (NMR) spectroscopy. The vinyl alcohol unit content, ethylene unit content, and degree of saponification were found to be 76 mol%, 24 mol%, and greater than 99.98 mol%, respectively. The MFR of EVOH-1 was 2.2 g / 10 min.

[0076] Synthesis Example 2: Synthesis of EVOH-2 Dry EVOH resin composition pellets containing EVOH (EVOH-2) were obtained in the same manner as in Synthesis Example 1, except that the amounts of raw materials used in the EVOH polymerization, the polymerization conditions, the amounts charged in the saponification treatment, and the rate of addition of 2N sodium hydroxide MeOH solution were changed. When the vinyl alcohol unit content, ethylene unit content, and degree of saponification of EVOH-2 were analyzed by nuclear magnetic resonance (NMR), the vinyl alcohol unit content was 68 mol%, the ethylene unit content (Et) was 32 mol%, and the degree of saponification was 99.98 mol% or more. The MFR of EVOH-2 was 2.9 g / 10 min.

[0077] Synthesis Example 3: Synthesis of EVOH-3 Dry EVOH resin composition pellets containing EVOH (EVOH-3) were obtained in the same manner as in Synthesis Example 1, except that the amounts of raw materials used in the EVOH polymerization, the polymerization conditions, the amounts charged in the saponification treatment, and the rate of addition of 2N sodium hydroxide MeOH solution were changed. When the vinyl alcohol unit content, ethylene unit content, and degree of saponification of EVOH-3 were analyzed by nuclear magnetic resonance (NMR), 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. The MFR of EVOH-3 was 3.8 g / 10 min.

[0078] Example 1 Production of Unstretched Multilayer Film Using pellets of the dried EVOH resin composition obtained in Synthesis Example 1 (EVOH-1), polyethylene resin-1 (Novatec™ LD LC600A manufactured by Japan Polyethylene Co., Ltd.; low-density polyethylene, melting point 107°C), polyethylene resin-2 (Evolue™ SP0510 manufactured by Prime Polymer Co., Ltd.; linear low-density polyethylene, melting point 96°C), and polyethylene adhesive resin (Admer™ NF518 manufactured by Mitsui Chemicals, Inc.; maleic anhydride-grafted linear low-density polyethylene adhesive resin, melting point 120°C), an asymmetric three-kind, five-layer unstretched multilayer film (polyethylene resin-1 / polyethylene adhesive resin / EVOH-1 / polyethylene adhesive resin / polyethylene resin-2 = 60 μm / 8 μm / 12 μm / 8 μm / 240 μm) was produced. 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 (co-extruded film) was adjusted by appropriately changing the screw rotation speed and the take-up roll speed. The thickness of each layer was measured by the method described below. The extruder, extrusion conditions, and die used were as follows. EVOH-1 Extruder: Single-screw extruder (Toyo Seiki Co., Ltd., Lab Machine ME Type CO-EXT) Screw: Diameter 20 mm φ, L / D 20, full-flight screw Extrusion temperature: Feeding section / compression section / metering section / die = 175 / 210 / 220 / 220°C Polyethylene adhesive resin Extruder: Single-screw extruder (Technovel Co., Ltd., SZW20GT-20MG-STD) Screw: Diameter 20 mm φ, L / D 20, full-flight screw Extrusion temperature: Feeding section / compression section / metering section / die = 175 / 200 / 220 / 220°C Polyethylene resin-1, 2 Extruder: Single-screw extruder (Plastics Technology Research Institute Co., Ltd., GT-32-A) Screw: Diameter 32 mm φ, L / D 28, full-flight screw Extrusion temperature: feeding section / compression section / metering section / die = 175 / 200 / 220 / 220°C Die: 300mm wide, 3-type, 3-layer coat hanger die (manufactured by Plastics Technology Research Institute Co., Ltd.) Die temperature: 220°C

[0079] [Example 2] A multilayer film was obtained in the same manner as in Example 1, except that a thermoplastic elastomer resin ("Pebax 5533" manufactured by Arkema Inc.; melting point: 159°C) was used instead of polyethylene resins-1 and -2.

[0080] [Example 3] In the production procedure of Example 1, a polypropylene resin ("Novatec (trademark) PP EA7AD" manufactured by Japan Polypropylene Corporation; polypropylene, melting point 164 ° C.) was used instead of polyethylene resin-1 and 2, and a polypropylene adhesive resin (manufactured by Mitsui Chemicals, Inc.) "Admer (trademark) QF500" was used instead of polyethylene adhesive resin. Except for this, a three-kind, five-layer unstretched multilayer film (polypropylene resin / polypropylene adhesive resin / EVOH-1 / polypropylene adhesive resin / polypropylene resin = 60 μm / 8 μm / 12 μm / 8 μm / 240 μm) having an asymmetrical structure was obtained in the same manner as in Example 1.

[0081] [Example 4] (Production of Biaxially Stretched Film) A monolayer film was produced from the pellets (EVOH-2) of the dried EVOH resin composition obtained in Synthesis Example 2. This monolayer film was brought into contact with 80°C hot water for 10 seconds, and stretched to 3.0 times in the longitudinal direction and 3.0 times in the transverse direction in a 90°C atmosphere using a tenter-type simultaneous biaxial stretching machine, and further heat-treated for 5 seconds in the tenter set at 170°C, and the film edges were cut to obtain a biaxially stretched film (thickness 12 µm, width 50 cm).

[0082] (Production of multilayer films by lamination) A layer of polyethylene adhesive resin ("Admer (trademark) NF518" manufactured by Mitsui Chemicals, Inc.) was provided on one side of a monolayer film of polyethylene resin-1 ("Novatec (trademark) LD LC600A" manufactured by Japan Polyethylene Corporation) to obtain a two-layer film A. Also, a layer of polyethylene adhesive resin ("Admer (trademark) NF518" manufactured by Mitsui Chemicals, Inc.) was provided on one side of a monolayer film of polyethylene resin-2 ("Evolue (trademark) SP0510" manufactured by Prime Polymer Co., Ltd.) to obtain a two-layer film B. The adhesive resin layer side of each of the two-layer films A and B was Each of the two-component adhesives ("Takelac (trademark) A-520" and "Takenate (trademark) A-50" manufactured by Mitsui Chemicals, Inc.) was applied to a dry thickness of 2 μm, dried, and laminated to both sides of the biaxially stretched EVOH-2 film obtained above 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).

[0083] [Example 5] (Production of uniaxially stretched film) A monolayer film was produced from the pellets (EVOH-2) of the dried EVOH resin composition obtained in Synthesis Example 2. This monolayer film was brought into contact with 80°C hot water for 10 seconds, stretched 6.0 times in the machine direction in a 90°C atmosphere using a tenter-type coaxial stretching machine, and further heat-treated for 5 seconds in the tenter set at 170°C, and the film edges were cut to obtain a uniaxially stretched film (thickness 12 μm, width 50 cm).

[0084] (Production of multilayer film by lamination) 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) was obtained in the same manner as in Example 4, except that the uniaxially stretched film obtained above was used instead of the biaxially stretched film in the production procedure of Example 4.

[0085] Example 6 (Production of EVOH-4) Using a twin-screw extruder (L / D=30, screw diameter φ25 mm), 62.5 parts by mass of EVOH-1 and 37.5 parts by mass of EVOH-2 were melt-kneaded at a cylinder temperature of 230°C and a screw rotation speed of 100 rpm, and the strand emerging from the die was cooled in a water bath and cut into pellets with a strand cutter to produce EVOH-4. The ethylene unit content (Et) of EVOH-4 was 27 mol%, and the degree of saponification was 99.98 mol% or more. The MFR of EVOH-4 was 2.5 g / 10 min.

[0086] (Production of Unstretched Multilayer Film) A multilayer film was produced in the same manner as in Example 1, except that EVOH-4 was used instead of EVOH-1 in the production procedure of Example 1, to obtain 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).

[0087] Comparative Example 1 A multilayer film was produced in the same manner as in Example 1, except that EVOH-3 was used instead of EVOH-1.

[0088] Comparative Example 2 A multilayer film was obtained in the same manner as in Example 1, except that in the production procedure of Example 1, EVOH-3 was used instead of EVOH-1, and the thicknesses of the layers were 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.

[0089] Comparative Example 3 A multilayer film was obtained in the same manner as in Example 1, except that the thicknesses of the layers in the production procedure of Example 1 were 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.

[0090] Comparative Example 4 A multilayer film was obtained in the same manner as in Example 1, except that in the production procedure of Example 1, EVAL (trademark) "E171B" (manufactured by Kuraray Co., Ltd.), an EVOH having an ethylene unit content (Et) of 44 mol%, was used instead of EVOH-1, and the thicknesses of the individual layers were 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.

[0091] Comparative Example 5 (Production of Filler-Containing EVOH-5) Using a twin-screw extruder (L / D=30, screw diameter φ25 mm), 10 parts by mass of magnesium hydroxide (Kisuma™ 5A) and 90 parts by mass of EVOH-3 were melt-kneaded at a cylinder temperature of 230°C and a screw rotation speed of 100 rpm, and the strand emerging from the die was cooled in a water bath and cut into pellets with a strand cutter to produce EVOH-5. The ethylene unit content (Et) of EVOH-5 was 38 mol%, and the degree of saponification was 99.98 mol% or more. The MFR of EVOH-5 was 3.5 g / 10 min.

[0092] (Production of filler-containing polypropylene resin PP-1) Using a twin-screw extruder (L / D = 30, screw diameter φ25 mm), 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 at a cylinder temperature of 230°C and a screw rotation speed of 100 rpm, and the strand emerging from the die was cooled in a water bath and cut into pellets with a strand cutter to produce filler-containing polypropylene resin PP-1.

[0093] (Production of Unstretched Multilayer Film) A multilayer film was obtained in the same manner as in Example 3, except that in the production procedure of Example 3, EVOH-5 was used instead of EVOH-1, filler-containing polypropylene resin PP-1 was used instead of the polypropylene resin, and the thicknesses of the individual layers were PP-1 / polypropylene adhesive resin / EVOH-5 / polypropylene adhesive resin / PP-1=60 μm / 8 μm / 40 μm / 8 μm / 240 μm.

[0094] (Measurement of thickness of each layer) The multilayer films obtained in the examples and comparative examples were cut with a microtome to expose the cross section, and then the cross section was measured at five different points for each layer using a backscattered electron detector of a scanning electron microscope ("ZEISS ULTRA55" manufactured by SII Nanotechnology Inc.) to determine the thickness (average thickness) of each layer.

[0095] (Measurement of Composite Elastic Modulus by Nanoindentation Method) For the multilayer films obtained in the Examples and Comparative Examples, the composite elastic modulus of each layer was measured by the nanoindentation method as described above.

[0096] From the thickness and composite modulus of each layer thus determined, the total thickness LA of layer (A), the total thickness LB of layer (B), the average composite modulus EA of layer (A), and the average composite modulus EB of layer (B) were determined. Note that in all Examples and Comparative Examples, there was one layer (A). From these values ​​and the ethylene content (Et) of the EVOH used in each layer (A), LA / LB·1 / Et and EA / EB were determined. 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.

[0097] (Gas barrier property evaluation: measurement of oxygen transmission rate (OTR)) The multilayer films obtained in the examples and comparative examples were attached to 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 were as follows. Device: MOCON OX-TRAN2 / 21 manufactured by MOCON Corporation Temperature: 20°C Humidity on oxygen supply side: 65% RH Humidity on carrier gas side: 0% RH Carrier gas flow rate: 10 mL / min Oxygen pressure: 1.0 atm Based on the oxygen transmission rate, the gas barrier property was evaluated according to the following criteria. In the cases of A to B, the gas barrier property was judged to be good. The results are shown in Table 1. (Criteria) A: 0.2 cc / (m ２ · day · atm) or less B: 0.2 cc / (m ２ ・day・atm) or more 0.5cc / (m ２ ・day・atm) C: 0.5cc / (m２ ・day・atm) or more 1.0cc / (m ２ · day · atm) or less D: 1.0 cc / (m ２ ・day・atm) or more 5.0cc / (m ２ ・day・atm) less than E: 5.0cc / (m ２ ・day・atm) or more

[0098] (Evaluation of Flexibility) The multilayer films obtained in the Examples and Comparative Examples were conditioned in an atmosphere of 23°C and 50% RH, and then subjected to a bending treatment using a Gelbo Flex Tester (manufactured by Rigaku Kogyo Co., Ltd.). Specifically, the multilayer film was first formed into a cylindrical shape with a diameter of 3.5 inches. Both ends of the film were gripped, and the initial gripping distance was 7 inches, the gripping distance at maximum bending was 1 inch. A 440° twist was applied in the first 3.5 inches of the stroke, followed by a straight horizontal motion for the next 2.5 inches. This reciprocating motion was repeated 500 to 5,000 times at a speed of 43 times / minute. The bending resistance of the multilayer film after bending was evaluated based on the number of times it took for one or more pinholes to appear, according to the following criteria. Cases A to C were judged to have good bending resistance. The results are shown in Table 1. (Criteria) A: No pinholes were observed even after 5,000 times. B: 4,500 times or more but less than 5,000 times. － C: 4,000 times or more but less than 4,500 times D: 3,000 times or more but less than 4,000 times D: 2,000 times or more but less than 3,000 times E: Less than 2,000 times

[0099] (Flexibility Evaluation) After conditioning the humidity of the multilayer film in an atmosphere of 23°C and 50% RH, puncture strength was measured in accordance with ISO 1184 using an AUTOGRAPH AGS-H (manufactured by Shimadzu Corporation). Flexibility was evaluated according to the following criteria based on the puncture strength measured when the puncture needle advanced 1.5 mm from contact with the multilayer film. Grades A to D were judged to have adequate flexibility. That is, grades E1 (less than 0.2 N) and E2 (10.0 N or more) were judged to have inadequate flexibility. The results are shown in Table 1. (Criteria) A: 1.3N or more and less than 1.6N B1: 1.0N or more and less than 1.3N B2: 1.6N or more and less than 2.5N C1: 0.5N or more and less than 1.0N C2: 2.5N or more and less than 4.0N D1: 0.2N or more and less than 0.5N D2: 4.0N or more and less than 10.0N E1: Less than 0.2N E2: 10.0N or more

[0100]

[0101] As shown in Table 1, each of the multilayer films of Examples 1 to 6, in which LA / LB·1 / Et was 0.0006 or more and 0.003 or less, EA was 6.0 or more, and EA / EB was 2 or more and 40 or less, had good gas barrier properties and flex resistance, and had appropriate flexibility.

[0102] The multilayer film of the present invention has good gas barrier properties and bending resistance, and has appropriate flexibility, and is therefore useful as a packaging material, and can be used as a packaging material for a reaction apparatus, etc.

Claims

1. At least one layer (A) mainly composed of an ethylene-vinyl alcohol copolymer, and At least one layer (B) mainly composed of a thermoplastic resin other than the above ethylene-vinyl alcohol copolymer are provided, 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, A multilayer film satisfying the following formulas (1) to (3). 【Number 1】 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 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 melting point of the thermoplastic resin that is the main component of the layer (B1) is lower than the melting point of the thermoplastic resin that is the main component of the layer (B2), and the layer (B1) is thicker than the layer (B2). The multilayer film according to claim 2.

4. The multilayer film according to claim 1, wherein the thermoplastic resin is a polyolefin-based resin.

5. The multilayer film according to claim 1, wherein the thermoplastic resin is a polyethylene-based resin.

6. 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%. The multilayer film according to claim 1.

7. Measured in accordance with the method described in JIS K 7126-2 (isobaric method; 2006), the oxygen transmission rate (under the conditions of 20 °C and 65% RH) is 1.5 cc / (m ２ ·day·atm) or less, the multilayer film according to claim 1.

8. 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. The multilayer film according to claim 1.

9. 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 in at least one axial direction. The multilayer film according to claim 1.

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

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

12. A container formed from the multilayer film according to any one of claims 1 to 10, and a stirring blade disposed inside the container A reactor comprising the same.

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