Multilayer film, vapor-deposited multilayer film, multilayer structure and packaging material

Abstract

A multilayer film with a configuration in which a skin layer (A), a core layer (C), an adhesive layer (D), and a barrier layer (E) are arranged on top of each other at least in this order, wherein the skin layer (A) is arranged as one outermost layer of the multilayer film, the barrier layer (E) is arranged as the other outermost layer of the multilayer film, the core layer (C) is the thickest layer in the multilayer film, the skin layer (A) contains a polyethylene resin (a) as its main component, the core layer (C) contains a polyethylene resin (c) as its main component, the density (dA) of the skin layer (A) is greater than the density (dC) of the core layer (C), and the adhesive layer (D) contains an adhesive resin (d) with a melting point of less than 150 °C as its main component.the barrier layer (E) contains an ethylene-vinyl alcohol copolymer (e) with an ethylene unit content of 20 mol% or more and 30 mol% or less and a degree of saponification of 90 mol% or more as its main component, the multilayer film does not include a layer containing a resin with a melting point of 220 °C or more as its main component, and the multilayer film is stretched at least monoaxially by a factor of 3 or more.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a multilayer film, a vapor-deposited multilayer film or a multilayer structure and a packaging material. STATE OF THE ART

[0002] Ethylene-vinyl alcohol copolymers (hereinafter also abbreviated as "EVOH(s)") are characterized by transparency, gas barrier properties, fragrance retention properties, solvent resistance, oil resistance and the like, and are used for a wide variety of applications, for example for a variety of packaging such as food packaging, medical packaging, industrial chemical packaging and agrochemical packaging, industrial films, agricultural films, underfloor heating pipes, fuel tanks, etc.

[0003] In recent years, environmental and waste problems have triggered a growing global demand for so-called post-consumer recycling (hereafter sometimes simply referred to as "recycling"), in which packaging materials that have been used in the market are collected and reused. Therefore, packaging materials with excellent recyclability are desired. For example, attempts have been made to produce a packaging film based solely on polyethylene or polypropylene, these materials having low gas barrier properties, or a gas barrier packaging film with excellent recyclability in which a gas barrier material or the like, which can be mixed with polyethylene or polypropylene, is only minimally incorporated, or such a packaging film is coated with this gas barrier material.

[0004] Patent document 1 discloses that providing an EVOH layer of a specific thickness on the outermost layer of a layered arrangement enables an increase in heat-sealing speed when used as a packaging film, without impairing recyclability. When this layered arrangement is monoaxially stretched, a multilayer film can be obtained that is characterized by transparency and gas barrier properties.

[0005] According to patent document 2, if at least two types of EVOHs, which differ from each other in their content of ethylene units, are mixed and used as EVOH in a multilayer film comprising an EVOH layer as the outermost layer, a multilayer film can be obtained in which blocking between EVOH layers is prevented even when stretched after blow molding. DOCUMENTS STATE OF THE TECHNOLOGY Patent documents Patent document 1: International PCT application with publication number 2019 / 243456 Patent document 2: International PCT application with publication number 2021 / 210606 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] However, the multilayer films disclosed in patent documents 1 and 2, each comprising an EVOH layer as the outermost layer and stretched at least monoaxially, curl considerably, and therefore process problems such as wrinkling, curvature, or adhesive delamination can occur during forming processes like printing or lamination. It should be noted that if such a multilayer film has a symmetrical layer configuration, with polyolefin layers as both outermost layers and an EVOH layer as an intermediate layer, such process problems can be reduced to some extent.However, in this case, the adhesive strength with respect to an adhesive or printer ink may decrease, or the barrier properties may deteriorate if a vapor-deposited multilayer film is formed that includes a vapor-deposited inorganic layer on a polyolefin layer; therefore, a layer configuration is necessary that includes an EVOH layer at least as an outermost layer.

[0007] The present disclosure was made to solve the aforementioned problems, and its objective is to provide a multilayer film comprising an EVOH layer as an outermost layer, being at least monoaxially stretched, and exhibiting both gas barrier properties and low curling characteristics. A further objective is to provide a vapor-deposited multilayer film in which the multilayer film is used, a multilayer structure in which the multilayer film or the vapor-deposited multilayer film is used, and a packaging material comprising the multilayer structure. It should be noted that in this description, a condition in which the degree of curl of a film is reduced can be expressed as "low curling characteristics," and properties that allow for the film to be formed, such as...Pressure or lamination, process problems such as wrinkles, curvature or adhesive detachment, can be prevented and expressed as "formability". MEANS TO SOLVENT THE PROBLEMS

[0008] According to the present disclosure, the foregoing object can be achieved by providing one of the following configurations: (1) a multilayer film with a configuration in which a skin layer (A), a core layer (C), an adhesive layer (D) and a barrier layer (E) are arranged on top of each other in at least this order, where the skin layer (A) is arranged as one outermost layer of the multilayer film, and the barrier layer (E) is arranged as the other outermost layer of the multilayer film, the core layer (C) is the thickest layer in the multilayer film, the skin layer (A) contains a polyethylene resin (a) as its main component, the core layer (C) contains a polyethylene resin (c) as its main component, a density (dA) of the skin layer (A) is greater than a density (dC) of the core layer (C), the adhesive layer (D) contains an adhesive resin (d) with a melting point of less than 150 °C as its main component, the barrier layer (E) contains as its main component an ethylene-vinyl alcohol copolymer (e) with an ethylene unit content of 20 mol% or more and 30 mol% or less and a saponification level of 90 mol% or more, the multilayer film does not include a layer containing a resin with a melting point of 220 °C or higher as its main component, and the multilayer film is stretched at least monoaxially by a factor of 3 or more; (2) the multilayer film according to (1), further comprising: a subcutaneous layer (B) arranged between the skin layer (A) and the core layer (C) and containing a polyethylene resin (b) as its main component, wherein the density (dB) of the subcutaneous layer (B) is less than the density (dA) of the skin layer (A) and greater than the density (dC) of the core layer (C); (3) the multilayer film according to (1) or (2) wherein a density (dD) of the adhesive layer (D) is less than the density (dC) of the core layer (C); (4) the multilayer film according to one of (1) to (3), wherein the density (dA) of the skin layer (A) is 0.940 g / cm² 3 or more; (5) the multilayer film according to one of (1) to (4) wherein the density (dC) of the core layer (C) is 0.910 g / cm³ 3 or more and less than 0.940 g / cm² 3 amounts; (6) the multilayer film according to one of (1) to (5), wherein the ratio of the thickness of the core layer (C) to the total thickness of the multilayer film is 0.3 to 0.8; (7) the multilayer film according to one of (1) to (6), wherein the ratio of the thickness of the skin layer (A) to the total thickness of the multilayer film is 0.05 to 0.2; (8) the multilayer film according to one of (1) to (7), wherein the ratio of the thickness of the barrier layer (E) to the total thickness of the multilayer film is 0.05 to 0.2; (9) the multilayer film according to one of (1) to (8) wherein the adhesive resin (d) is an acid-modified polyethylene resin; (10) the multilayer film according to one of (1) to (9), wherein the barrier layer (E) contains 10 to 300 ppm of at least one polyvalent metal ion (f) selected from the group consisting of a magnesium ion, a calcium ion and a zinc ion; (11) the multilayer film according to one of (1) to (10), wherein the barrier layer (E) contains 100 to 4000 ppm of a higher aliphatic carboxylic acid (g) with 8 to 30 carbon atoms; (12) the multilayer film according to one of (1) to (11) which is stretched by a factor of 3 or more in the longitudinal direction and is substantially not stretched in the transverse direction; (13) the multilayer film according to one of (1) to (12) which is an inflated molded part; (14) a vapor-deposited multilayer film comprising: the multilayer film according to one of (1) to (13); and a vapor-deposited inorganic layer (I) on an exposed side of the barrier layer (E); (15) the vapor-deposited multilayer film according to (14), wherein the vapor-deposited inorganic layer (I) is a vapor-deposited metal layer containing aluminium as the main component or a vapor-deposited inorganic oxide layer containing aluminium oxide or silicon oxide as the main component; (16) a multi-layered structure comprising: the multilayer film according to one of (1) to (13) or the vapor-deposited multilayer film according to (14) or (15); and a resin layer (R) containing a thermoplastic resin (r) as its main component; (17) the multilayer structure according to (16), wherein the thermoplastic resin (r) contains a polyethylene resin as the main component; and (18) a packaging material comprising: the multilayer structure according to (16) or (17). EFFECTS OF INVENTION

[0009] According to the present disclosure, a multilayer film can be provided which comprises an EVOH layer as an outermost layer, is at least monoaxially stretched, and exhibits both gas barrier properties and low curling characteristics. Furthermore, a vapor-deposited multilayer film in which the multilayer film is used, a multilayer structure in which the multilayer film or the vapor-deposited multilayer film is used, and a packaging material comprising the multilayer structure can be provided. MODES FOR EXECUTING THE INVENTION

[0010] A multilayer film of the present disclosure has a configuration in which a skin layer (A), a core layer (C), an adhesive layer (D), and a barrier layer (E) are arranged one above the other at least in this order, wherein the skin layer (A) is arranged as one outermost layer of the multilayer film, the barrier layer (E) is arranged as the other outermost layer of the multilayer film, the skin layer (A) and the core layer (C) each contain a polyethylene resin as a major component, a density (dA) of the skin layer (A) is greater than a density (dC) of the core layer (C), the adhesive layer (D) contains an adhesive resin (d) with a melting point of less than 150 °C as a major component, and the barrier layer (E) contains an ethylene-vinyl alcohol copolymer (e) with an ethylene content of 20 mol% or more and 30 mol% or less and a degree of saponification of 90 mol% or more as a major component.the multilayer film does not include a layer containing a resin with a melting point of 220 °C or more as its main component, and the multilayer film is stretched at least monoaxially by a factor of 3 or more.

[0011] The statement that "the skin layer (A), the core layer (C), the adhesive layer (D), and the barrier layer (E) are arranged in at least this order" does not constitute a particular restriction, provided the multilayer film has a layer configuration in which the skin layer (A), the core layer (C), the adhesive layer (D), and the barrier layer (E) are arranged in this order; for example, it does not preclude the presence of another layer between these layers. In the context of the multilayer film or multilayer structure, the term "outermost layer" or "outermost surface" does not imply that the front and back sides are distinct, but rather refers to an exposed surface. This means that the multilayer film or multilayer structure will each have two outermost layers or two outermost surfaces.

[0012] A "main component" refers to a component with a content of more than 50% by mass.

[0013] "ppm" refers to a mass-based concentration (mass ppm).

[0014] A “polyethylene resin” refers to an ethylene homopolymer or a copolymer of 80 mol% or more ethylene and less than 20 mol% of a non-ethylene monomer. Typical and non-limiting examples of the non-ethylene monomer include α-olefins such as propylene, n-butene, isobutylene, 1-hexene, and 1-octene.

[0015] A range of values ​​with "to" means that values ​​before and after "to" are included as a lower and upper limit, respectively. That is, "α to β" means "α or more and β or less." An upper and a lower limit of a range of values ​​(of a content, physical properties, etc.) can be appropriately combined. Skin layer (A)

[0016] The multilayer film of the present disclosure comprises, on an outermost surface, a skin layer (A) containing a polyethylene resin (a) as its main component. Polyethylene resins, regardless of whether they possess gas barrier properties, are widely used for packaging materials, and their recycling infrastructure is therefore well-developed in every country. Thus, the presence of the skin layer (A) containing the polyethylene resin (a) as its main component improves the recyclability of the multilayer film of the present disclosure.

[0017] Examples of the polyethylene resin (a) include ethylene homopolymers and copolymers of 80 mol% or more ethylene and less than 20 mol% of a non-ethylene monomer, in particular high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, an ethylene-vinyl acetate copolymer (EVA), an ethylene-acrylic acid copolymer (EAA), an ethylene-methyl acrylate copolymer (EMA), an ethylene-ethyl acrylate copolymer (EEA), an ethylene-butyl acrylate copolymer (EBA), an ethylene-methacrylic acid copolymer (EMAA), an ethylene-methyl methacrylate copolymer (EMMA), an ethylene-ethyl methacrylate copolymer (EEMA), an ethylene-butyl methacrylate copolymer (EBMA) and the like.The polyethylene resin (a) is preferably at least one selected from high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene, or a mixture thereof, and more preferably substantially high-density polyethylene or a mixture of at least one selected from low-density polyethylene and linear low-density polyethylene, and high-density polyethylene. The polyethylene resin (a) preferably contains 60 wt% or more high-density polyethylene, more preferably 70 wt% or more high-density polyethylene, more preferably 80 wt% or more high-density polyethylene, and particularly preferably 90 wt% or more high-density polyethylene, and can consist substantially only of high-density polyethylene.If the polyethylene resin (a) contains a relatively high content of high-density polyethylene in this way, the low roll-in properties, heat resistance, moisture resistance and mechanical properties of the multilayer film of the present disclosure can be further improved.

[0018] The polyethylene resin (a) can be suitably selected as having a monopeaked or multipeaked molecular weight distribution; if a polyethylene resin with a multipeaked molecular weight distribution is used, the melt formability and mechanical properties can be exhibited at a high level with good balance. In a case where the polyethylene resin (a) contains an ethylene-α-olefin copolymer such as linear low-density polyethylene, the α-olefin copolymerized with ethylene is preferably an α-olefin with 4 or more carbon atoms, more preferably an α-olefin with 6 or more carbon atoms, and may be an α-olefin with 8 or more carbon atoms. In a case where the number of carbon atoms of the α-olefin copolymerized with ethylene is relatively large, various mechanical strengths, such as puncture resistance, tensile strength, and elongation, can be improved.The upper limit of the number of carbon atoms in the α-olefin is not particularly restricted and is generally 12 or less.

[0019] A metallocene catalyst is also suitable for use as a polymerization catalyst for the polyethylene resin (a). The polyethylene resin (a) polymerized using a metallocene catalyst is characterized by melt formability, and the resulting multilayer film exhibits an excellent balance between flexibility and mechanical strength.

[0020] The density (dA) of the skin layer (A) must be greater than the density (dC) of the core layer, for example 0.920 g / cm³ 3 or more, 0.930 g / cm² 3 or more or 0.935 g / cm² 3 or more, is preferably 0.940 g / cm² in view of the fact that the effects of the present disclosure are more significant. 3 or more, preferably 0.945 g / cm² 3or more, preferably 0.950 g / cm² 3 or more, especially preferably 0.955 g / cm² 3 or more, preferably 0.960 g / cm² 3 or more and can be 0.965 g / cm² 3 or more. If the density (dA) of the skin layer (A) is within the aforementioned range, the low curling properties can be improved. In particular, even if the barrier layer (E), which is located as one outermost layer of the multilayer film, is made of a material with curling properties, low curling properties can be achieved thanks to the skin layer (A), which is arranged as the other outermost layer of the multilayer film.

[0021] The melting point of the polyethylene resin (a) is preferably 120 °C or more, more preferably 123 °C or more, more preferably 125 °C or more, particularly preferably 130 °C or more, and may preferably be 133 °C or more or 135 °C or more. With a view to improving the melt formability and the mechanical properties of the multilayer film, the melt flow rate (hereinafter also referred to as MFR) (at 190 °C and a load of 2160 g) of the polyethylene resin (a), measured according to the method disclosed in JIS K 7210 (2014), is preferably 0.1 to 10 g / 10 min, more preferably 0.3 to 5.0 g / 10 min, and more preferably 0.5 to 2.0 g / 10 min.

[0022] The skin layer (A) may contain a component other than the polyethylene resin (a) in an area where the effects of the present disclosure are not prevented. Examples of the other component include an alkali metal ion, a polyvalent metal ion, a carboxylic acid, a phosphate compound, a boron compound, a pro-oxidant, an antioxidant, a plasticizer, a heat stabilizer (melt stabilizer), a photoinitiator, a deodorant, an ultraviolet absorber, an antistatic agent, a lubricant, a colorant, a filler, a drying agent, a filler material, a pigment, a dye, a processing aid, a flame retardant, an anti-fogging agent, and the like. The content of the other component in the skin layer (A) is generally 5 wt% or less, preferably 3 wt% or less, and more preferably 1 wt% or less.The skin layer (A) may further contain a resin other than the polyethylene resin (a). Examples of the resin other than the polyethylene resin (a) include thermoplastic resins such as polyolefins other than the polyethylene resin (a), polyamides, polyesters, polyvinyl chlorides, polyvinylidene chlorides, polystyrene, polyacrylonitrile, polyurethanes, polycarbonates, polyacetals, polyacrylates, and polyvinyl alcohol resins. The content of the resin other than the polyethylene resin (a) in the skin layer (A) is less than 50 wt%, preferably less than 30 wt%, more preferably less than 20 wt%, and even more preferably less than 10 wt%, and may be 5 wt% or less, 3 wt% or less, 1 wt% or less, 0.5 wt% or less, or 0.1 wt% or less.

[0023] The proportion of polyethylene resin (a) in resins forming the skin layer (A) is preferably 60 wt% or more, more preferably 80 wt% or more, even more preferably 90 wt% or more, and can be 95 wt% or more, 97 wt% or more, or 99 wt% or more, or the resins forming the skin layer (A) can consist solely of the polyethylene resin (a). The content of the polyethylene resin (a) in the skin layer (A) is more than 50 wt%, preferably 60 wt% or more, more preferably 80 wt% or more, even more preferably 90 wt% or more, and can be 95 wt% or more, 97 wt% or more, or 99 wt% or more, or the skin layer (A) can consist essentially solely of the polyethylene resin (a).

[0024] A method for producing a resin composition forming the skin layer (A) is not particularly limited and can be produced by hot kneading the polyethylene resin (a) and optionally another additive or additives. The hot kneading can be carried out, for example, using a known mixing or kneading device, such as a kneader rudder, an extruder, a mixing roller, or a Banbury mixer. The temperature range for the hot kneading can be appropriately adjusted according to the melting point of the polyethylene resin (a) to be used or the like, and a temperature range of 150 to 300 °C is generally employed.

[0025] In a further embodiment, a masterbatch, optionally containing a high concentration of the other additive(s) with respect to the polyethylene resin (a), can be produced by hot kneading. This masterbatch can be dry-mixed with the polyethylene resin (a), which contains essentially no other additive, and the resulting mixture can be used to produce the skin layer (A). In a still further embodiment, the polyethylene resin (a) and the other additive(s) can be dry-mixed and then used to produce the skin layer (A). Dry mixing means that materials in powder, granular, or pellet form are mechanically mixed. The mixing can be carried out using a mixing device, such as a mixer.Mixing can be carried out using a gyratory mixer, a belt mixer, or a Henschel mixer, or it can be carried out manually by stirring, shaking, or the like in an airtight container. Mixing can be performed at a mixing temperature from room temperature to lower than the melting point of the polyethylene resin (a) in an air atmosphere or a nitrogen atmosphere. Core layer (C)

[0026] The multilayer film of the present disclosure comprises the core layer (C), which contains a polyethylene resin (c) as its main component, the core layer (C) being the thickest layer in the multilayer film. Polyethylene resins, regardless of whether they possess gas barrier properties, are widely used for packaging materials, and their recycling infrastructure is therefore well developed in every country. Thus, the presence of the core layer (C), which contains the polyethylene resin (c) as its main component, improves the recyclability of the multilayer film of the present disclosure.Examples of the polyethylene resin (c) include ethylene homopolymers and copolymers of 80 mol% or more ethylene and less than 20 mol% of a non-ethylene monomer, in particular high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, an ethylene-vinyl acetate copolymer (EVA), an ethylene-acrylic acid copolymer (EAA), an ethylene-methyl acrylate copolymer (EMA), an ethylene-ethyl acrylate copolymer (EEA), an ethylene-butyl acrylate copolymer (EBA), an ethylene-methacrylic acid copolymer (EMAA), an ethylene-methyl methacrylate copolymer (EMMA), an ethylene-ethyl methacrylate copolymer (EEMA), an ethylene-butyl methacrylate copolymer (EBMA) and the like.The polyethylene resin (c) is preferably at least one selected from high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene, or a mixture thereof; more preferably at least one selected from low-density polyethylene and linear low-density polyethylene, or a mixture thereof; and more preferably essentially linear low-density polyethylene. The polyethylene resin (c) preferably contains 60 wt% or more of linear low-density polyethylene, more preferably 70 wt% or more of linear low-density polyethylene, more preferably 80 wt% or more of linear low-density polyethylene, and particularly preferably 90 wt% or more of linear low-density polyethylene, and can consist essentially of only linear low-density polyethylene.If the polyethylene resin (c) contains a relatively high content of linear low-density polyethylene in this way, the low curling properties and the mechanical strength of the multilayer film of the present disclosure can be further improved.

[0027] The polyethylene resin (c) can be suitably selected as having a monopeaked or multipeaked molecular weight distribution; if a polyethylene resin with a multipeaked molecular weight distribution is used, the melt formability and mechanical properties can be exhibited at a high level with good balance. In a case where the polyethylene resin (c) contains an ethylene-α-olefin copolymer such as linear low-density polyethylene, the α-olefin copolymerized with ethylene is preferably an α-olefin with 4 or more carbon atoms, more preferably an α-olefin with 6 or more carbon atoms, and may be an α-olefin with 8 or more carbon atoms. In a case where the number of carbon atoms of the α-olefin copolymerized with ethylene is relatively large, various mechanical strengths, such as puncture resistance, tensile strength, and elongation, can be improved.The upper limit of the number of carbon atoms in the α-olefin is not particularly restricted and is generally 12 or less.

[0028] A metallocene catalyst can also be used as a polymerization catalyst for the polyethylene resin (c). The polyethylene resin (c) polymerized using a metallocene catalyst is characterized by melt formability, and the resulting multilayer film exhibits an excellent balance between flexibility and mechanical strength.

[0029] The density (dC) of the core layer (C) can be, for example, 0.90 g / cm³ 3 or more and less than 0.94 g / cm² 3 or 0.905 g / cm³ 3 or more and less than 0.940 g / cm² 3 In view of the fact that the effects of the present disclosure are more significant, the amount is preferably 0.910 g / cm². 3 or more and less than 0.940 g / cm² 3 , preferred 0.915 g / cm³3 or more and less than 0.935 g / cm² 3 and preferably 0.916 g / cm² 3 or more and less than 0.930 g / cm² 3 To improve the low rolling resistance, the density (dA) of the skin layer (A) must be greater than the density (dC) of the core layer (C). The difference between the density (dA) of the skin layer (A) and the density (dC) of the core layer (C) is preferably 0.005 g / cm³. 3 or more, preferred 0.01 g / cm³ 3 or more, preferably 0.02 g / cm² 3 or more, even preferably 0.03 g / cm² 3 or more, especially preferably 0.04 g / cm² 3 or more and can be 0.045 g / cm² 3 or more or 0.05 g / cm² 3 or more. The upper limit of the difference between the density (dA) of the skin layer (A) and the density (dC) of the core layer (C) is not particularly limited and can, for example, be 0.5 g / cm³. 3or less, 0.3 g / cm³ 3 or less or 0.1 g / cm³ 3 or less.

[0030] The melting point of the polyethylene resin (c) is preferably 100 to 130 °C, more preferably 110 to 127 °C, and may preferably be 115 to 125 °C. With a view to improving the melt formability and the mechanical properties of the multilayer film, the melt flow rate (MFR) (at 190 °C and a load of 2160 g) of the polyethylene resin (c), measured according to the method disclosed in JIS K 7210 (2014), is preferably 0.1 to 10 g / 10 min, more preferably 0.3 to 5.0 g / 10 min, and even more preferably 0.5 to 2.0 g / 10 min.

[0031] The core layer (C) may contain a component other than the polyethylene resin (c) in an area where the effects of the present disclosure are not prevented. Examples of the other component include an alkali metal ion, a polyvalent metal ion, a carboxylic acid, a phosphate compound, a boron compound, a pro-oxidant, an antioxidant, a plasticizer, a heat stabilizer (melt stabilizer), a photoinitiator, a deodorant, an ultraviolet absorber, an antistatic agent, a lubricant, a colorant, a filler, a drying agent, a filler material, a pigment, a dye, a processing aid, a flame retardant, an anti-fogging agent, and the like. The content of the other component in the core layer (C) is generally 5 wt% or less, preferably 3 wt% or less, and more preferably 1 wt% or less.The core layer (C) may further contain a resin other than the polyethylene resin (c). Examples of the resin other than the polyethylene resin (c) include thermoplastic resins such as polyolefins other than the polyethylene resin (c), polyamides, polyesters, polyvinyl chlorides, polyvinylidene chlorides, polystyrene, polyacrylonitrile, polyurethanes, polycarbonates, polyacetals, polyacrylates, and polyvinyl alcohol resins. The content of the resin other than the polyethylene resin (c) in the core layer (C) is less than 50 wt%, preferably less than 30 wt%, more preferably less than 20 wt%, even more preferably less than 10 wt%, particularly preferably 5 wt% or less, and may be 3 wt% or less, 1 wt% or less, 0.5 wt% or less, or 0.1 wt% or less.

[0032] The proportion of polyethylene resin (c) in resins forming the core layer (C) is preferably 60 wt% or more, more preferably 80 wt% or more, more preferably 90 wt% or more, and can be 95 wt% or more, 97 wt% or more, or 99 wt% or more, or the resins forming the core layer (C) can consist solely of the polyethylene resin (c). The content of the polyethylene resin (c) in the core layer (C) is more than 50 wt%, preferably 60 wt% or more, more preferably 80 wt% or more, more preferably 90 wt% or more, and can be 95 wt% or more, 97 wt% or more, or 99 wt% or more, or the core layer (C) can consist essentially solely of the polyethylene resin (c).

[0033] A method for producing a resin composition forming the core layer (C) is not particularly limited and can be produced by hot kneading the polyethylene resin (c) and optionally another additive or additives. The hot kneading can be carried out, for example, using a known mixing or kneading device, such as a kneader rudder, an extruder, a mixing roller, or a Banbury mixer. The temperature range for the hot kneading can be appropriately adjusted according to the melting point of the polyethylene resin (c) to be used or the like, and generally a temperature range of 150 to 300 °C is employed.

[0034] In a further embodiment, a masterbatch, optionally containing a high concentration of the other additive(s) with respect to the polyethylene resin (c), can be produced by hot kneading. This masterbatch can be dry-mixed with the polyethylene resin (c), which contains essentially no other additive, and the resulting mixture can be used to produce the core layer (C). In a still further embodiment, the polyethylene resin (c) and the other additive(s) can be dry-mixed and then used to produce the core layer (C). Dry mixing means that materials in powder, granular, or pellet form are mechanically mixed. The mixing can be carried out using a mixing device, such as a mixer.Mixing can be carried out using a gyratory mixer, a belt mixer, or a Henschel mixer, or it can be done manually by stirring, shaking, or the like in an airtight container. Mixing can be performed at a mixing temperature from room temperature to below the melting point of the polyethylene resin (c) in an air or nitrogen atmosphere. Subcutaneous layer (B)

[0035] The multilayer film of the present disclosure preferably further comprises a sublayer (B) arranged between the skin layer (A) and the core layer (C), the sublayer containing a polyethylene resin (b) as its main component. Polyethylene resins, regardless of whether they possess gas barrier properties, are widely used for packaging materials, and their recycling infrastructure is therefore well-developed in every country. Thus, the presence of the sublayer (B), which contains the polyethylene resin (b) as its main component, improves the recyclability of the multilayer film of the present disclosure.Examples of the polyethylene resin (b) include ethylene homopolymers and copolymers of 80 mol% or more ethylene and less than 20 mol% of a non-ethylene monomer, in particular high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, an ethylene-vinyl acetate copolymer (EVA), an ethylene-acrylic acid copolymer (EAA), an ethylene-methyl acrylate copolymer (EMA), an ethylene-ethyl acrylate copolymer (EEA), an ethylene-butyl acrylate copolymer (EBA), an ethylene-methacrylic acid copolymer (EMAA), an ethylene-methyl methacrylate copolymer (EMMA), an ethylene-ethyl methacrylate copolymer (EEMA), an ethylene-butyl methacrylate copolymer (EBMA) and the like.The polyethylene resin (b) is preferably at least one selected from high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene, or a mixture thereof, and more preferably substantially high-density polyethylene or medium-density polyethylene, or a mixture of at least one selected from low-density polyethylene and linear low-density polyethylene, and at least one selected from high-density polyethylene and medium-density polyethylene. The polyethylene resin (b) preferably contains 30 wt% or more of high-density polyethylene or medium-density polyethylene, more preferably 40 wt% or more of high-density polyethylene or medium-density polyethylene, more preferably 50 wt% or more of high-density polyethylene or medium-density polyethylene, and may contain 60 wt% or more of high-density polyethylene or medium-density polyethylene.If the polyethylene resin (b) in this way contains a relatively high content of high-density polyethylene or medium-density polyethylene, the low curling properties, heat resistance, moisture resistance and mechanical properties of the multilayer film of the present disclosure can be further improved.

[0036] The polyethylene resin (b) can be suitably selected as having a monopeaked or multipeaked molecular weight distribution; if a polyethylene resin with a multipeaked molecular weight distribution is used, the melt formability and mechanical properties can be exhibited at a high level with good balance. In a case where the polyethylene resin (b) contains an ethylene-α-olefin copolymer such as linear low-density polyethylene, the α-olefin copolymerized with ethylene is preferably an α-olefin with 4 or more carbon atoms, more preferably an α-olefin with 6 or more carbon atoms, and may be an α-olefin with 8 or more carbon atoms. In a case where the number of carbon atoms of the α-olefin copolymerized with ethylene is relatively large, various mechanical strengths, such as puncture resistance, tensile strength, and elongation, can be improved.The upper limit of the number of carbon atoms in the α-olefin is not particularly restricted and is generally 12 or less.

[0037] A metallocene catalyst can also be used as a polymerization catalyst for the polyethylene resin (b). The polyethylene resin (b) polymerized using a metallocene catalyst is characterized by melt formability, and the resulting multilayer film exhibits an excellent balance between flexibility and mechanical strength.

[0038] In view of the fact that the effects of the present disclosure are more significant, the density (dB) of the subcutaneous layer (B) is preferably smaller than the density (dA) of the skin layer (A) and larger than the density (dC) of the core layer (C), for example being 0.91 to 0.96 g / cm³. 3 , preferably 0.915 to 0.955 g / cm³ 3 , preferably 0.920 to 0.950 g / cm³ 3and can range from 0.925 to 0.945 g / cm³ 3 be.

[0039] The melting point of the polyethylene resin (b) can be, for example, 115 to 135 °C or 118 to 130 °C. With a view to improving the melt formability and mechanical properties of the multilayer film, the MFR (at 190 °C and a load of 2160 g) of the polyethylene resin (b), measured according to the method disclosed in JIS K 7210 (2014), is preferably 0.1 to 10 g / 10 min, more preferably 0.3 to 5.0 g / 10 min, and even more preferably 0.5 to 2.0 g / 10 min.

[0040] The subcutaneous layer (B) may contain a component other than the polyethylene resin (b) in an area where the effects of the present disclosure are not prevented. Examples of the other component include an alkali metal ion, a polyvalent metal ion, a carboxylic acid, a phosphate compound, a boron compound, a pro-oxidant, an antioxidant, a plasticizer, a heat stabilizer (melt stabilizer), a photoinitiator, a deodorant, an ultraviolet absorber, an antistatic agent, a lubricant, a colorant, a filler, a drying agent, a filler material, a pigment, a dye, a processing aid, a flame retardant, an anti-fogging agent, and the like. The content of the other component in the subcutaneous layer (B) is generally 5 wt% or less, preferably 3 wt% or less, and more preferably 1 wt% or less.The subcutaneous layer (B) may further contain a resin other than the polyethylene resin (b). Examples of the resin other than the polyethylene resin (b) include thermoplastic resins, such as polyolefins other than the polyethylene resin (b), polyamides, polyesters, polyvinyl chlorides, polyvinylidene chlorides, polystyrene, polyacrylonitrile, polyurethanes, polycarbonates, polyacetals, polyacrylates, and polyvinyl alcohol resins. The content of the resin other than the polyethylene resin (b) in the subcutaneous layer (B) is less than 50 wt%, preferably less than 30 wt%, more preferably less than 20 wt%, even more preferably less than 10 wt%, and particularly preferably 5 wt% or less, and may be 3 wt% or less, 1 wt% or less, 0.5 wt% or less, or 0.1 wt% or less.

[0041] The proportion of polyethylene resin (b) in resins forming the subcutaneous layer (B) is preferably 60 wt% or more, more preferably 80 wt% or more, even more preferably 90 wt% or more, and can be 95 wt% or more, 97 wt% or more, or 99 wt% or more, or the resins forming the subcutaneous layer (B) can consist solely of the polyethylene resin (b). The content of the polyethylene resin (b) in the subcutaneous layer (B) is more than 50 wt%, preferably 60 wt% or more, more preferably 80 wt% or more, even more preferably 90 wt% or more, and can be 95 wt% or more, 97 wt% or more, or 99 wt% or more, or the subcutaneous layer (B) can consist essentially solely of the polyethylene resin (b).

[0042] A method for producing a resin composition forming the subcutaneous layer (B) is not particularly restricted and can be produced by hot kneading the polyethylene resin (b) and optionally another additive or additives. The hot kneading can be carried out, for example, using a known mixing or kneading device, such as a kneader rudder, an extruder, a mixing roller, or a Banbury mixer. The temperature range for the hot kneading can be appropriately adjusted according to the melting point of the polyethylene resin (b) to be used or the like, and generally a temperature range of 150 to 300 °C is employed.

[0043] In a further embodiment, a masterbatch, optionally containing a high concentration of the other additive(s) with respect to the polyethylene resin (b), can be produced by hot kneading. This masterbatch can be dry-mixed with the polyethylene resin (b), which contains essentially no other additive, and the resulting mixture can be used to produce the subcutaneous layer (B). In a still further embodiment, the polyethylene resin (b) and the other additive(s) can be dry-mixed and then used to produce the subcutaneous layer (B). Dry mixing means that materials in powder, granular, or pellet form are mechanically mixed. The mixing can be carried out using a mixing device, such as a mixer.Mixing can be carried out using a gyratory mixer, a belt mixer, or a Henschel mixer, or it can be done manually by stirring, shaking, or the like in an airtight container. Mixing can be carried out at a mixing temperature from room temperature to below the melting point of the polyethylene resin (b) in an air or nitrogen atmosphere. Adhesive layer (D)

[0044] The multilayer film of the present disclosure comprises the adhesive layer (D), which contains an adhesive resin (d) having a melting point of less than 150 °C as its main component. When the multilayer film of the present disclosure includes the adhesive layer (D), there is a tendency to obtain a multilayer film with good appearance and excellent interlayer adhesion. Examples of the adhesive resin (d) include acid-modified polyolefin resins, and among these, an acid-modified polyethylene resin is preferred. The acid-modified polyolefin resin is preferably a carboxylic acid-modified polyolefin resin, more preferably a polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof, and even more preferably a carboxylic acid-modified polyolefin resin obtained by graft polymerization of a polyolefin resin with an unsaturated carboxylic acid, such as...maleic anhydride, or a derivative thereof, and preferably a carboxylic acid-modified polyethylene resin obtained by graft polymerization of a polyethylene resin with an unsaturated carboxylic acid, such as maleic anhydride, or a derivative thereof. In this case, one of the polyethylene resins cited as examples of polyethylene resin (a), polyethylene resin (b), or polyethylene resin (c) may advantageously be used as the polyethylene resin.

[0045] The content of the acid-modified polyolefin resin in the adhesive resin (d) is preferably 70 wt% or more, more preferably 80 wt% or more, and even more preferably 95 wt% or more, or the adhesive resin (d) can consist essentially only of the modified polyolefin resin. The proportion of the adhesive resin (d) in the adhesive layer (D) is preferably 70 wt% or more, more preferably 80 wt% or more, even more preferably 95 wt% or more, and can be 97 wt% or more, 98 wt% or more, or 99 wt% or more, or the adhesive layer (D) can consist essentially only of the adhesive resin (d).

[0046] In view of the fact that the effects of the present disclosure are more significant, the density (dD) of the adhesive layer (D) is preferably smaller than the density (dC) of the core layer (C) and is, for example, less than 0.945 g / cm³. 3 , preferably 0.850 g / cm² 3 or more and less than 0.935 g / cm² 3 and preferred 0.880 g / cm²3 or more and less than 0.925 g / cm² 3 The melting point of the adhesive resin (d) is less than 150 °C and preferably 100 to 130 °C. To improve the melt formability and mechanical properties of the multilayer film, the melt flow rate (MFR) (at 190 °C and a load of 2160 g) of the adhesive resin (d), measured according to the method disclosed in JIS K 7210 (2014), is preferably 0.1 to 10 g / 10 min, more preferably 0.3 to 5.0 g / 10 min, and even more preferably 0.5 to 3.0 g / 10 min. The density, melting point, and MFR of the adhesive resin (d) depend mainly on the density, melting point, and MFR of the polyolefin resin prior to carboxylic acid modification. Barrier layer (E)

[0047] The multilayer film of the present disclosure comprises, as an outermost layer, the barrier layer (E), which contains an EVOH (e) as its main component. With this configuration, the multilayer film of the present disclosure exhibits advantageous gas barrier properties. The barrier layer (E) has an advantageous affinity with a vapor-deposited inorganic layer (I), which is described below, and therefore a vapor-deposited multilayer film in which the vapor-deposited inorganic layer (I) is adjacent to an exposed side of the barrier layer (E) exhibits more advantageous barrier properties and tends to maintain gas barrier properties, particularly under physical stress such as bending. In view of the production of such a vapor-deposited multilayer film, the multilayer film of the present disclosure must include the barrier layer (E) as its outermost layer.Multiple barrier layers (E) can be provided, in which case at least one barrier layer (E) can be provided as the outermost layer.

[0048] The EVOH(e) is generally obtained by saponification of an ethylene-vinyl ester copolymer obtained by polymerization of ethylene and vinyl ester. The ethylene unit content of the EVOH(e) is 20 mol% or more and 30 mol% or less. When the ethylene unit content is 20 mol% or more, the melt formability of the EVOH(e) and the recyclability of the multilayer film of this disclosure are improved. The ethylene unit content is preferably 21 mol% or more, more preferably 22 mol% or more, and may preferably be 23 mol% or more. Conversely, when the ethylene unit content is 30 mol% or less, even when the thickness of the barrier layer (E) is relatively small, the gas barrier properties of the multilayer film of this disclosure are improved, as are the low roll-in properties; therefore, the formability tends to become advantageous.The ethylene unit content is preferably 28 mol% or less, more preferably 27 mol% or less, and can be 26 mol% or less.

[0049] The degree of saponification of the EVOH(e) is 90 mol% or more. The degree of saponification refers to the proportion of vinyl alcohol units relative to the total number of vinyl alcohol and vinyl ester units in the EVOH(e). When the degree of saponification is 90 mol% or more, the gas barrier properties of the multilayer film of this disclosure are improved. The degree of saponification is preferably 95 mol% or more, more preferably 99 mol% or more, and even more preferably 99.9 mol% or more. The degree of saponification of the EVOH(e) is generally 100 mol% or less. The ethylene unit content and the degree of saponification of the EVOH(e) are determined by 1 Determined by H-NMR measurement.

[0050] The EVOH (e) can be a mixture of two or more types of EVOHs that differ in their content of ethylene units, or a mixture of two or more types of EVOHs that differ in their degree of saponification.

[0051] The EVOH(e) may contain a monomeric unit other than ethylene, vinyl esters, and vinyl alcohols, provided that the effects of the present disclosure are not prevented. In particular, if a modified group containing a primary hydroxyl group with a specific structure is introduced, the EVOH(e) may exhibit both gas barrier properties and high formability. The content of the other monomeric unit is preferably 5 wt% or less, more preferably 3 wt% or less, more preferably 1 wt% or less, and even more preferably 0.1 wt% or less, and it is particularly preferable that essentially no other monomeric unit is present. Examples of such another monomer include α-olefins, such as...Propylene, n-butene, isobutylene, and 1-hexene; acrylic acids and salts thereof; unsaturated monomers with an acrylic ester group; methacrylic acids and salts thereof; unsaturated monomers with a methacrylic ester group; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamide propanesulfonic acid and salts thereof, acrylamide propyldimethylamine and salts thereof (e.g., quaternary salts); methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamide propanesulfonic acid and salts thereof, methacrylamide propyldimethylamine and salts thereof (e.g., quaternary salts); vinyl ethers, such as... B. Methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether and 2,3-diacetoxy-1-vinyloxypropane; vinyl cyanides, such as acrylonitrile and methacrylonitrile; vinyl halides, such as vinyl chloride and vinyl fluoride; vinylidene halides, such asVinylidene chloride and vinylidene fluoride; allyl compounds, such as allyl acetates, 2,3-diacetoxy-1-allyloxypropane and allyl chloride; unsaturated dicarboxylic acids, such as maleic acid, itaconic acid and fumaric acid, and salts or esters thereof; vinylsilane compounds, such as vinyltrimethoxysilane; isopropenyl acetate; 1,3-diacetoxy-2-methylenepropane; 1,3-dipropionyloxy-2-methylenepropane; 1,3-dibutyronyloxy-2-methylenepropane; and the like.

[0052] The melt flow rate (MFR) (at 210 °C and a load of 2.16 kg) of EVOH(e), measured according to JIS K 7210 (2014), is preferably 0.2 to 10 g / 10 min. The MFR of EVOH(e) is more preferably 0.4 g / 10 min or more, and more preferably 0.6 g / 10 min or more. Alternatively, the MFR of EVOH(e) is more preferably 8 g / 10 min or less, more preferably 6 g / 10 min or less, even more preferably 5 g / 10 min or less, and may preferably be 4 g / 10 min or less, 3 g / 10 min or less, or 2.5 g / 10 min or less. If the MFR of the EVOH (e) is within the above range, the melt formability of the EVOH (e) and of a powdered product of the multilayer film containing the EVOH (e) is improved. multi-valent metal ion (f)

[0053] The barrier layer (E) preferably contains at least one polyvalent metal ion (f) selected from the group consisting of a magnesium ion, a calcium ion, and a zinc ion, and its content is preferably 10 to 300 ppm. If the content of the polyvalent metal ion (f) is 10 ppm or more, there is a tendency to prevent visual defects such as thickening and the formation of gel or bubbles during melt forming. Conversely, if the content of the polyvalent metal ion (f) is 300 ppm or less, there is a tendency to prevent excessive degradation and discoloration during melt forming.When the multilayer film of the present disclosure is recycled, a crosslinking reaction of the resins can proceed during the melt forming of a powdered product of the multilayer film, which can cause thickening or gelation; if a certain amount of the multivalent metal ion (f) is present, thickening, gelation, and adhesion of the resins to a screw can be prevented. In view of this fact, the content of the multivalent metal ion (f) is preferably 15 to 240 ppm, more preferably 20 to 200 ppm, more preferably 30 to 150 ppm, and can preferably be 30 to 100 ppm. In particular, the barrier layer (E) preferably contains a magnesium ion or a calcium ion, and more preferably a magnesium ion, as the multivalent metal ion (f).By controlling the ratio of the multivalent metal ion (f) to a carboxylic acid as described below, melt formability and discoloration resistance can be further improved.

[0054] Examples of a multivalent metal compound that imparts the multivalent metal ion (f) include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, hydroxides, and metal complexes of magnesium, calcium, and zinc. Among these, aliphatic carboxylates and hydroxides are preferred due to their availability and ease of handling. Acetates, caprylates, and stearates are preferred as aliphatic carboxylates. Higher aliphatic carboxylic acid (g)

[0055] The barrier layer (E) preferably contains a higher aliphatic carboxylic acid (g) with 8 to 30 carbon atoms, and its content is preferably 100 to 6000 ppm. The higher aliphatic carboxylic acid (g) may be present wholly or partially in the form of a salt or may be present as a salt of the polyvalent metal ion (f) or an alkali metal ion, as described below. The higher aliphatic carboxylic acid (g) is preferably a higher aliphatic carboxylic acid with 8 to 20 carbon atoms and preferably capric acid or stearic acid.The multilayer film of the present disclosure comprises the barrier layer (E) as an outermost layer. It is assumed that the higher aliphatic carboxylic acid (g) in a nozzle acts as a lubricant for a metal surface of the nozzle and can thus prevent an appearance defect resulting from an unevenness in the thickness of the multilayer film and the formation of gel or bubbles due to stagnant resin. The barrier layer (E) therefore preferably contains 100 ppm or more of the higher aliphatic carboxylic acid (g). Conversely, if the content of the higher aliphatic carboxylic acid (g) is 6000 ppm or less, there is a tendency to prevent thickening during melt forming of the barrier layer (E) and to maintain the interlayer adhesion with respect to the adhesive layer (D).In view of these facts, the content of the higher aliphatic carboxylic acid (g) is preferably 200 to 4000 ppm, more preferably 300 to 3000 ppm and may preferably be 400 to 2500 ppm, 500 to 2200 ppm, 600 to 2000 ppm or 700 to 1500 ppm.

[0056] The barrier layer (E) may, in an area where the effects of the present disclosure are not prevented, contain a component other than the EVOH (e), the polyvalent metal ion (f), and the higher aliphatic carboxylic acid (g). Examples of the other component include an alkali metal ion, an alkaline earth metal ion different from the polyvalent metal ion (f), a transition metal ion, a carboxylic acid different from the higher aliphatic carboxylic acid (g) (a monocarboxylic acid or a polyvalent carboxylic acid), a thermoplastic resin different from the EVOH (e), a phosphate compound, a boron compound, a pro-oxidant, an antioxidant (a hindered phenol compound, etc.).), a plasticizer, a heat stabilizer (melt stabilizer), a photoinitiator, a deodorizing agent, an ultraviolet absorber, an antistatic agent, a lubricant, a colorant, a filler, a drying agent, a filler material, a pigment, a dye, a processing aid, a flame retardant, an anti-fogging agent, and the like. To prevent bubble formation and discoloration during the melt forming of a powdered product of the multilayer film comprising the barrier layer (E), an alkali metal ion, a carboxylic acid, and / or a phosphate compound are preferably included. If a boron compound is included, the melt viscosity of the barrier layer (E) and of a powdered product of the multilayer film comprising the barrier layer (E) can be controlled. Alkali metal ion

[0057] The barrier layer (E) can contain 40 to 500 ppm of an alkali metal ion. If the barrier layer (E) contains the alkali metal ion within the aforementioned range, the interlayer adhesion with respect to the adhesive layer (D) tends to be significantly improved. Given this, the lower limit of the alkali metal ion content is preferably 80 ppm and more preferably 120 ppm. The upper limit of the alkali metal ion content is preferably 450 ppm and more preferably 400 ppm. If the alkali metal ion content is at or above the lower limit, thickening during melt forming or the formation of visual defects, such as gel or bubbles, is less likely, and the interlayer adhesion with respect to the adhesive layer (D) is further improved.Conversely, if the alkali metal ion content is at or below the upper limit, excessive degradation during melt forming can be easily prevented, and discoloration problems are less likely to occur. Controlling the ratio of the alkali metal ion to a carboxylic acid, as described below, can further improve melt formability and discoloration resistance.

[0058] Examples of alkali metal ions include lithium, sodium, potassium, rubidium, and cesium. For industrial reasons, a sodium or potassium ion is preferred, with sodium being more desirable. Using a potassium ion allows for high levels of both the color phase of the barrier layer (E) and the interlayer adhesion to the adhesive layer (D). One of these ions can be used alone, or two or more can be used in combination.

[0059] Examples of alkali metal compounds that impart the alkali metal ion include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, hydroxides, and metal complexes of alkali metals, such as lithium, sodium, and potassium. Among these, an aliphatic carboxylate and a phosphate are preferred for their availability and ease of handling. The aliphatic carboxylate is preferably an acetate, a caprylate, or a stearate. Carboxylic acid

[0060] The barrier layer (E) preferably contains a carboxylic acid that differs from the higher aliphatic carboxylic acid (g). The lower limit of the carboxylic acid content is preferably 50 ppm and more preferably 100 ppm. Conversely, the upper limit of the carboxylic acid content is preferably 400 ppm and more preferably 350 ppm. In the case where the carboxylic acid content is 50 ppm or more, discoloration resistance tends to be advantageous. In the case where, on the other hand, the carboxylic acid content is 400 ppm or less, there is a tendency to maintain the interlayer adhesion and prevent odor formation.

[0061] The pKa value of the carboxylic acid is preferably 3.5 to 5.5. If the pKa value of the carboxylic acid is in the aforementioned range, the pH buffering capacity of the barrier layer (E) to be obtained increases, the melt formability can thus be further improved, and at the same time discoloration due to an acidic or a basic substance can be further eliminated.

[0062] The carboxylic acid can be a monovalent carboxylic acid. One type can be used alone, or two or more types can be used in combination. A monovalent carboxylic acid is a compound whose molecule contains a carboxyl group. Monovalent carboxylic acids with a pKa value of 3.5 to 5.5 are not particularly limited, and examples include formic acid (pKa = 3.77), acetic acid (pKa = 4.76), propionic acid (pKa = 4.85), acrylic acid (pKa = 4.25), and the like. These carboxylic acids can each further contain a substituent, such as a hydroxyl group, an amino group, or a halogen atom. Acetic acid is particularly preferred because it is very safe, readily available, and easy to handle.

[0063] The carboxylic acid can also be a polyhydric acid. If the carboxylic acid is polyhydric, the discoloration resistance at high temperatures and the discoloration resistance of a melt-molded part of a powdered product of the multilayer film to be obtained can be further improved. The polyhydric carboxylic acid compound preferably has three or more carboxyl groups. In this case, the discoloration resistance can be improved more effectively. A polyhydric carboxylic acid is defined as a compound whose molecule has two or more carboxyl groups.In this case, the pKa value of at least one carboxyl group is preferably in the range of 3.5 to 5.5, and examples include oxalic acid (pKa2 = 4.27), succinic acid (pKa1 = 4.20), fumaric acid (pKa2 = 4.44), malic acid (pKa2 = 5.13), glutaric acid (pKa1 = 4.30, pKa2 = 5.40), adipic acid (pKa1 = 4.43, pKa2 = 5.41), pimelic acid (pKa1 = 4.71), phthalic acid (pKa2 = 5.41), isophthalic acid (pKa2 = 4.46), terephthalic acid (pKa1 = 3.51, pKa2 = 4.82), citric acid (pKa2 = 4.75), tartaric acid (pKa2 = 4.40), and glutamic acid (pKa2 = 4.07). Aspartic acid (pKa = 3.90) and the like. Phosphate compound

[0064] The barrier layer (E) may further contain a phosphate compound. The lower limit of the phosphate compound content is preferably 5 ppm with respect to a phosphate radical. Conversely, the upper limit of the phosphate compound content is preferably 100 ppm with respect to a phosphate radical. If the phosphate compound is contained within this range, discoloration of the barrier layer (E) to be obtained and of a melt-molded part of a powdered product of the multilayer film to be obtained can be prevented, and the heat stability can be improved. The term "with respect to a phosphate radical" refers to a value obtained by converting the content of a phosphorus element (P) to the content of a phosphate ion (PO4). 3- ) is converted.

[0065] Various acids, such as phosphoric acid and phosphonic acid, their salts, and the like, are used as phosphate compounds. The phosphate can be any primary, secondary, or tertiary phosphate. The cationic species of phosphate is not particularly restricted and is preferably an alkali metal or an alkaline earth metal. Sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate are particularly preferred as phosphate compounds. Boron compound

[0066] The barrier layer (E) may further contain a boron compound. In the case where the boron compound is present, the lower limit of the content in the barrier layer (E) is preferably 50 ppm and more preferably 100 ppm with respect to a boron element. On the other hand, the upper limit of the content of the boron compound in the barrier layer (E) is preferably 400 ppm, more preferably 300 ppm, and even more preferably 200 ppm with respect to a boron element. If the boron compound is present in this range, the heat stability of the barrier layer (E) and of a powdered product of the multilayer film to be obtained can be increased during melt forming, and the formation of gel or bubbles can be prevented. The sag resistance and neck-in resistance during film formation can be improved, or the mechanical properties of a molded part to be obtained can be enhanced.It is assumed that these effects are due to the occurrence of a chelate interaction between the EVOH (e) and the boron compound.

[0067] Examples of boron compounds include boric acids, boric esters, boric salts, and borohydrides. Specific examples include boric acids such as orthoboric acid (H3BO3), metaboric acid, and tetraboric acid; boric esters such as trimethyl borate and triethyl borate; boric salts such as alkali metal salts and alkaline earth metal salts of the aforementioned boric acids and borax; and the like. Among these, orthoboric acid is preferred.

[0068] The barrier layer (E) may further contain a thermoplastic resin different from the EVOH (e). Examples of thermoplastic resins different from the EVOH (e) include various polyolefins (e.g., polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, an ethylene-propylene copolymer, a copolymer of ethylene and an α-olefin with 4 or more carbon atoms, a copolymer of a polyolefin and maleic anhydride, an ethylene-vinyl ester copolymer, an ethylene-acrylic ester copolymer, and modified polyolefins grafted with an unsaturated carboxylic acid or a derivative thereof), various polyamides (e.g., nylon 6, nylon 6·6, a nylon 6 / 66 copolymer, nylon 11, nylon 12, and polymetaxylylene adipamide), various polyesters (e.g.,Polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate), polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polyurethane, polycarbonate, polyacetal, polyacrylate, a modified polyvinyl alcohol resin and the like. The thermoplastic resin content in the barrier layer (E) is generally less than 40 wt%, preferably less than 30 wt%, more preferably less than 20 wt%, even more preferably less than 10 wt% and may be less than 5 wt% or less than 1 wt%, and it is particularly preferable that essentially no thermoplastic resin is present.

[0069] The proportion of EVOH (e) in resins forming the barrier layer (E) is, in order to preserve the effects of the present disclosure more significantly, preferably 60 wt% or more, more preferably 70 wt% or more, more preferably 80 wt%, even more preferably 90 wt% or more, particularly preferably 95 wt% or more and may be 98 wt% or more or 99 wt% or more, or the resins forming the barrier layer (E) may consist essentially only of EVOH (e). The proportion of EVOH (e) in the barrier layer (E) is, in order to preserve the effects of the present disclosure more significantly, preferably 60 wt% or more, more preferably 70 wt% or more, more preferably 80 wt%, even more preferably 90 wt% or more, particularly preferably 95 wt% or more and may preferably be 98 wt% or more or 99 wt% or more, or the barrier layer (E) may consist essentially only of the EVOH (e).

[0070] A method for producing the barrier layer (E) is not particularly restricted, and it can be prepared by melt kneading the EVOH (e) and optionally the multivalent metal ion (f), the higher aliphatic carboxylic acid (g), and / or the other component. Each component can be added in a solid state, such as a powder, or as a molten material, or as a solute contained in a solution, or as a dispersoid contained in a dispersion. Suitable solutions and dispersions are aqueous solutions and aqueous dispersions, respectively. The melt kneading can be carried out, for example, using a known mixing or kneading device, such as a kneader paddle, an extruder, a mixing roller, or a Banbury mixer.The temperature range for melt kneading can be appropriately adjusted according to the melting points of the EVOH(e) to be used and each component, and generally a range of 150 to 250 °C is employed. The barrier layer (E) can also be produced by pre-adding some components to the EVOH(e) and then subjecting other necessary components to melt kneading in the manner described above. An example of the process in which some components are pre-added to the EVOH(e) is a process in which the EVOH(e) is immersed in a solution containing the added components as pellets or powder. Multilayer film

[0071] The multilayer film of the present disclosure has a layer configuration in which the skin layer (A), the core layer (C), the adhesive layer (D), and the barrier layer (E) are arranged one on top of the other at least in this order, wherein the skin layer (A) is arranged as one outermost layer of the multilayer film and the barrier layer (E) is arranged as the other outermost layer of the multilayer film. Preferably, the subcutaneous layer (B) is further provided between the skin layer (A) and the core layer (C). The following are examples of the configuration of the multilayer film. It should be noted that the skin layer (A) is referred to as "layer (A)," the subcutaneous layer (B) as "layer (B)," the core layer (C) as "layer (C)," the adhesive layer (D) as "layer (D)," and the barrier layer (E) as "layer (E)." " / " indicates that layers before and after this symbol are arranged directly on top of each other.Examples of the layer configuration of the multilayer film of the present disclosure include layer (A) / layer (C) / layer (D) / layer (E), layer (A) / layer (B) / layer (C) / layer (D) / layer (E), layer (A) / layer (C) / layer (D) / layer (E) / layer (D) / layer (E), layer (A) / layer (B) / layer (C) / layer (D) / layer (E) / layer (D) / layer (E) and the like; among these, layer (A) / layer (C) / layer (D) / layer (E) or layer (A) / layer (B) / layer (C) / layer (D) / layer (E) is preferred in view of industrial productivity, and in view of the fact that industrial productivity and the effects of the present disclosure are more significant, layer (A) / layer (B) / layer (C) / layer (D) / layer (E) is more preferred.In the layer configuration, preferably at least layer (C) and layer (D) are arranged in direct contact with each other, and furthermore preferably at least layer (D) and layer (E) are arranged in direct contact with each other. More preferably, at least layer (C), layer (D), and layer (E) are arranged in this order in direct contact with each other.

[0072] The overall thickness of the multilayer film of this disclosure can be adjusted appropriately according to the application. The overall thickness is preferably 10 µm or more and more preferably 12 µm or more. When the overall thickness is 10 µm or more, industrial productivity and mechanical properties tend to improve. The overall thickness is preferably 100 µm or less, more preferably 50 µm or less, and even more preferably 30 µm or less, and may preferably be 25 µm or less, 20 µm or less, or 15 µm or less. When the overall thickness is 100 µm or less, industrial productivity and economic efficiency tend to improve. It should be noted that the above suitable overall thickness of the multilayer film refers to the thickness after stretching.

[0073] The core layer (C) is the thickest layer in the multilayer film of the present disclosure, and the ratio of the thickness of the core layer (C) to the total thickness of the multilayer film of the present disclosure is preferably 0.3 to 0.8 in view of industrial productivity, low curling properties and mechanical properties. This ratio is preferably 0.35 to 0.80, more preferably 0.40 to 0.75 and may preferably be 0.45 to 0.73 or 0.50 to 0.70.

[0074] In view of industrial productivity, heat resistance, moisture resistance, low curling properties and mechanical properties, the ratio of the thickness of the skin layer (A) to the total thickness of the multilayer film of the present disclosure is preferably 0.05 to 0.2. This ratio is more preferably 0.05 to 0.20 and even more preferably 0.05 to 0.15.

[0075] In view of industrial productivity, heat resistance, gas barrier properties, low curling properties and mechanical properties, the ratio of the thickness of the barrier layer (E) to the total thickness of the multilayer film of the present disclosure is preferably 0.05 to 0.2. This ratio is more preferably 0.05 to 0.20, more preferably 0.05 to 0.18 and particularly preferably 0.05 to 0.15.

[0076] The multilayer film of the present disclosure is stretched at least monoaxially by a factor of 3 or more. If the multilayer film of the present disclosure is stretched by less than a factor of 3, there is a tendency for the thickness to become uneven due to the stretching or for the gas barrier properties to deteriorate. On the other hand, the upper limit of the stretch ratio of the multilayer film of the present disclosure is generally 12 times. The multilayer film of the present disclosure is preferably stretched at least monoaxially by a factor of 4 or more and more preferably by a factor of 5 or more. The multilayer film of the present disclosure is preferably stretched at least monoaxially by a factor of 10 or less and more preferably by a factor of 8 or less.The multilayer film of the present disclosure can be monoaxially or biaxially stretched and, with a view to high economic efficiency and easy tearability (when used as packaging material, the packaging material is easy to open), is preferably monoaxially stretched, more preferably monoaxially stretched in the longitudinal direction (flow direction, machine direction), and even more preferably by a factor of 3 (preferably by a factor of 3 or more and 12 or less, more preferably by a factor of 4 or more and 10 or less, and even more preferably by a factor of 5 or more and 8 or less) in the longitudinal direction. In this case, the multilayer film is preferably not substantially stretched in the lateral direction (transverse direction).

[0077] The multilayer film of the present disclosure is preferably an inflated molded part. In the case where the multilayer film of the present disclosure is an inflated molded part, the effects of the present disclosure are more effectively achieved.

[0078] A method for producing the multilayer film of the present disclosure preferably comprises, for example, a step (I) for producing an unstretched multilayer film in which the skin layer (A), the core layer (C), the adhesive layer (D), and the barrier layer (E) are arranged at least in this order, and a step (II) for stretching the resulting unstretched multilayer film at least monoaxially to produce the multilayer film of the present disclosure. A suitable manufacturing method of the present disclosure is described in detail below; however, the present disclosure is not limited to this embodiment.

[0079] In step (I), the unstretched multilayer film, in which the skin layer (A), core layer (C), adhesive layer (D), and barrier layer (E) are arranged on top of each other in at least this order, is formed. A method for producing the unstretched multilayer film is not particularly restricted, and in general, a conventional co-extrusion process, in which resins are extruded through separate dies or a common die and arranged on top of each other, can be used. Either an annular die or a T-die can be used as the die; for example, blow molds, casting molds, or the like can be employed, and blow molds are preferred with regard to productivity.

[0080] In step (II), the unstretched multilayer film obtained in step (I) is stretched at least monoaxially. A stretching method is not particularly restricted, and examples include a frame stretching method, a tube stretching method, a roller stretching method, and the like. With regard to productivity, the unstretched multilayer film is preferably stretched monoaxially by a roller stretching method. In the case where the unstretched multilayer film of the present disclosure is an inflated molded part, a roller stretching method is also preferred, considering that the unstretched multilayer film, which is folded cylindrically after inflating, can be easily stretched monoaxially. The temperature used for stretching is generally in a range of 50 °C to 140 °C, preferably in a range of 100 °C to 130 °C.

[0081] The multilayer film of the present disclosure does not include a layer containing a resin with a melting point of 220 °C or higher as its main component. If no layer containing a resin with a melting point of 220 °C or higher as its main component is provided, it is easily possible to prevent uneven mixing of recovered material with other components during the melt forming of a multilayer film, a vapor-deposited multilayer film, or a multilayer structure of the present disclosure described below. The multilayer film of the present disclosure preferably does not include a layer containing a resin with a melting point of 210 °C or higher as its main component, and preferably does not include a layer containing a resin with a melting point of 200 °C or higher as its main component.For the same reason, preferably no metal layer with a thickness of 1 µm or more is provided. Evaporated inorganic layer (I)

[0082] A vapor-deposited multilayer film comprising the multilayer film of the present disclosure and a vapor-deposited inorganic layer (I) on an exposed side of the barrier layer (E) is also an embodiment of the present disclosure. The vapor-deposited inorganic layer (I) is preferably arranged directly on the exposed side of the barrier layer (E) of the multilayer film or over a further layer, such as an anchor coating layer, and more preferably directly on the exposed side of the barrier layer (E). The vapor-deposited inorganic layer (I) can be formed by vapor deposition of an inorganic substance, such as a metal or an inorganic oxide, and is generally a layer that exhibits barrier properties against oxygen and water vapor.The barrier layer (E) exhibits a high affinity for metals and inorganic oxides compared to general thermoplastic resins. Therefore, when the evaporated inorganic layer (I) is placed directly onto the exposed side of the barrier layer (E), a dense and defect-free evaporated inorganic layer (I) can be formed. Furthermore, the interlayer adhesion between the barrier layer (E) and the evaporated inorganic layer (I) of the resulting evaporated multilayer film can be particularly advantageous. Since the barrier layer (E) has high gas barrier properties, a deterioration of the gas barrier properties can be prevented even if a defect occurs in the evaporated inorganic layer (I) due to bending or the like. The average thickness of the evaporated inorganic layer (I) is preferably less than 500 nm.If the average thickness is less than 500 nm, the viscosity during melt forming of a powdered product of the multilayer structure comprising the vapor-deposited inorganic layer (I) can be excellently stable, and the formation of gel or bubbles can be prevented.

[0083] The vapor-deposited inorganic layer (I) is preferably either a vapor-deposited metal layer containing aluminum as the main component or a vapor-deposited inorganic oxide layer containing an inorganic oxide as the main component. In cases where opacity is required, a vapor-deposited metal layer is preferred; however, given the visibility of the contents of a packaging material, its suitability for microwave use, and the prevention of gel or bubble formation during the melt forming of a powdered product, a vapor-deposited inorganic oxide layer is preferred. Furthermore, a vapor-deposited inorganic oxide layer is preferred to prevent discoloration during the recycling of the vapor-deposited multilayer film.

[0084] The vapor-deposited metal layer is a layer containing aluminum as its main component. The aluminum content in the vapor-deposited metal layer is preferably more than 50 mol%, more preferably 60 mol% or more, even more preferably 70 mol% or more, and most preferably 90 mol% or more, particularly preferably 95 mol% or more, and can preferably be 98 mol% or more, 99 mol% or more, or 99.9 mol% or more. The average thickness of the vapor-deposited metal layer is preferably 120 nm or less, more preferably 100 nm or less, and more preferably 90 nm or less. The average thickness of the vapor-deposited metal layer is preferably 25 nm or more, more preferably 35 nm or more, and more preferably 45 nm or more.The “average thickness of the vapor-deposited metal layer” refers to the average thickness at ten arbitrary points in a cross-section of the vapor-deposited metal layer, measured using an electron microscope. In the case where the multilayer film of the present disclosure comprises the vapor-deposited metal layer, the light transmittance at a wavelength of 600 nm can be reduced to 10% or less, thus achieving excellent opacity.

[0085] The vapor-deposited metal layer, which contains aluminum as its main component, may contain some aluminum oxide due to unavoidable oxidation. In the vapor-deposited metal layer, which contains aluminum as its main component, the molar ratio (0mol / almol) of oxygen atoms to aluminum atoms is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.1 or less.

[0086] The vapor-deposited inorganic oxide layer is a layer containing an inorganic oxide as its main component. The inorganic oxide content in the vapor-deposited metal layer is preferably more than 50 mol%, more preferably 60 mol% or more, even more preferably 70 mol% or more, and still more preferably 90 mol% or more, particularly preferably 95 mol% or more, and can preferably be 98 mol% or more, 99 mol% or more, or 99.9 mol% or more. Examples of the inorganic oxide include oxides of silicon, aluminum, magnesium, calcium, potassium, tin, sodium, boron, titanium, lead, zirconium, yttrium, and the like, with aluminum oxide or silicon oxide being preferred. The average thickness of the vapor-deposited inorganic oxide layer is preferably 60 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less.The average thickness of the deposited inorganic oxide layer is preferably 8 nm or more, more preferably 12 nm or more, and even more preferably 16 nm or more. The "average thickness of the deposited inorganic oxide layer" refers to the average thickness measured at ten arbitrary points in a cross-section of the deposited inorganic oxide layer using an electron microscope. In the case where the multilayer film of the present disclosure includes the deposited inorganic oxide layer, the light transmittance at a wavelength of 600 nm can be increased to 80% or more, thus providing excellent visibility of the contents in the case of a packaging material. With a view to further improving visibility, the light transmittance at a wavelength of 600 nm is preferably 90% or more.

[0087] The deposited inorganic layer (I) can be formed by a known physical or chemical vapor deposition process. Specific examples include a vacuum deposition process, a sputtering process, an ion plating process, an ion beam mixing process, a plasma CVD process, a laser CVD process, an MO CVD process, a thermal CVD process, and the like. A physical vapor deposition process is preferably used, and a vacuum deposition process is particularly preferred. The upper limit of the surface temperature of the barrier layer (E) during the formation of the deposited inorganic layer (I) is preferably 60 °C, more preferably 55 °C, and even more preferably 50 °C.The lower limit of the surface temperature of the barrier layer (E) during the formation of the deposited inorganic layer (I) is not particularly restricted and is preferably 0 °C, more preferably 10 °C, and even more preferably 20 °C. Before film formation, the exposed side of the barrier layer (E) can be subjected to plasma treatment. A known method can be used for the plasma treatment, and atmospheric pressure plasma treatment is preferred. Nitrogen, helium, neon, argon, krypton, xenon, radon, or the like is used as the discharge gas in atmospheric pressure plasma treatment. Of these, nitrogen, helium, or argon are preferably used, and nitrogen is particularly preferred because it reduces costs. Multi-layer structure

[0088] A multilayer structure comprising the multilayer film or the vapor-deposited multilayer film of the present disclosure and further a resin layer (R) containing a thermoplastic resin (r) as its main component is also an embodiment of the present disclosure. The content of the thermoplastic resin (r) in the resin layer (R) is more than 50 mol%, preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may preferably be 98 mol% or more, 99 mol% or more, or 99.9 mol% or more.Although the multilayer film or vapor-deposited multilayer film of the present disclosure can itself be used as a packaging material with gas barrier properties, the multilayer structure, in which at least one resin layer (R) containing the thermoplastic resin (r) as the main component is provided, can impart various functions to a packaging material, such as design and heat-sealability. The thermoplastic resin (r) is not particularly limited, and examples include homopolymers of olefins or copolymers thereof, such as linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, a vinyl ester resin, an ethylene-propylene copolymer, polypropylene, a propylene α-olefin copolymer (α-olefin with 4 to 20 carbon atoms), polybutene and polypentene, polyamides, such as nylon 6 and nylon 6,6, polyesters, such as...Polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polystyrene, polyvinyl chloride, polyvinylidene chloride, an acrylic resin, polycarbonate, chlorinated polyethylene, chlorinated polypropylene, and the like. Of these, a polyolefin is preferred with regard to obtaining excellent moisture resistance, mechanical properties, economic efficiency, heat-sealability, and the like, and a polyamide or a polyester is preferred with regard to obtaining excellent mechanical properties, heat resistance, and the like. In order to obtain, in particular, a multilayer structure with excellent recyclability, it is further preferable that the thermoplastic resin (r) be of the same type of polyethylene resin as above. The resin layer (R) may be unstretched, monoaxially or biaxially stretched, or rolled.With regard to improving mechanical strength, a biaxially stretched layer is preferred, and with regard to improving heat sealing capability, an unstretched layer is preferred.

[0089] In a case where the multilayer structure of the present disclosure comprises several resin layers (R), these may be identical or different from one another and are generally different. Furthermore, the resin layer (R) may be thicker or thinner than the core layer (C).

[0090] A film formation process for the resin layer (R) is not particularly restricted, and it is generally formed by melt extrusion using an extruder. Either an annular or a T-shaped die can be used. A method for monoaxial or biaxial stretching is also not particularly restricted, and the production can be carried out by stretching a film in the flow direction and / or width direction using a conventionally known stretching method, such as monoaxial roller-type stretching, simultaneous biaxial tube-type stretching, sequential biaxial stretching of a frame type, or simultaneous biaxial stretching of a frame type. Regarding the stretch ratio in the case of a monoaxially stretched layer, the area increase, considering the thickness uniformity and mechanical strength of the layer to be obtained, is preferably 3 to 10 times.The area increase is preferably fourfold or more. The area increase is preferably ninefold or less, and even more preferably eightfold or less. If the area increase is threefold or more, stretch marks are less likely to remain; if the area increase is tenfold or less, cracking of the layer during stretching is less likely. Regarding the stretch ratio in the case of a biaxially stretched layer, the area increase is preferably tenfold to sixtyfold, considering the thickness uniformity and mechanical strength of the layer to be obtained. The area increase is preferably twentyfold or more, even more preferably thirtyfold or more, and can be fortyfold or more. The area increase is preferably fifty-fivefold or less, and even more preferably fiftyfold or less.If the area increase is 10 times or more, stretch marks are less likely to remain; if the area increase is 60 times or less, a break in the layer is less likely to occur during stretching.

[0091] In view of industrial productivity, the thickness of the resin layer (R) is preferably 10 to 200 µm. In particular, in the case of an unstretched layer, the thickness is preferably 10 to 150 µm, and in the case of a monoaxially stretched layer or a biaxially stretched layer, the thickness is preferably 10 to 50 µm.

[0092] The total thickness of the multilayer structure of the present disclosure is preferably 300 µm or less, preferably 200 µm or less, and may preferably be 150 µm or less, 130 µm or less, 100 µm or less, or 80 µm or less. When the total thickness is within the aforementioned range, the multilayer structure of the present disclosure is lightweight and flexible and can therefore be advantageously used for flexible packaging. Since the amount of resin used in the multilayer structure is small, the environmental impact can be reduced.

[0093] The thickness of each layer in the multilayer structure of the present disclosure can be appropriately adjusted according to the application. With a view to preventing discoloration during the melt forming of a powdered product, increasing heat stability during melt forming, and preventing the formation of bubbles, the ratio of the total thickness of a layer containing a polyethylene resin as the main component to the total thickness of the multilayer structure is preferably 0.75 or more, more preferably 0.80 or more, more preferably 0.85 or more, and particularly preferably 0.90 or more, and may be 0.95 or more. With a view to improving the gas barrier properties, the aforementioned ratio is preferably 0.99 or less.

[0094] A method for arranging the resin layer (R) on the multilayer film of the present disclosure is not particularly limited, and examples include extrusion lamination, coextrusion lamination, dry lamination, and the like. When arranging the resin layer (R) on the multilayer film, an adhesive layer can be provided between the layers. The adhesive layer can be formed by applying and drying a known adhesive. The aforementioned adhesive is preferably a two-component polyurethane adhesive in which a polyisocyanate component and a polyol component are mixed and reacted together. The thickness of the adhesive layer is not particularly limited and is preferably 1 to 5 µm and more preferably 2 to 4 µm.

[0095] The layer configuration of the multilayer structure of the present disclosure is not particularly restricted, and the following are examples of the multilayer structure configuration. It should be noted that below, the multilayer film of the present disclosure is represented as "Film (AE)" and the resin layer (R) as "Layer (R)". The " / / " indicates that layers before and after this symbol are arranged directly on top of each other or via an adhesive layer. Examples of the layer configuration of the multilayer structure of the present disclosure include Layer (R) / / Film (AE), Film (AE) / / Layer (R), Layer (R) / / Film (AE) / / Layer (R), and the like.

[0096] The multilayer structure of the present disclosure may, in an area where the effects of the present disclosure are not prevented, comprise a layer other than those described above. An example of the other layer is a recovery layer. In particular, a recovered composition, as described below, which contains recovered material from the multilayer structure of the present disclosure, is preferably reused in whole or in part as a recovery layer. Another example of the other layer is a printed layer. The printed layer may be located at any position within the multilayer structure of the present disclosure. Examples of the printed layer include a film obtained by applying and drying a solution containing a pigment or dye and optionally a binder resin.Examples of methods for applying the printed layer include gravure printing and various coating processes using a wire doctor blade, centrifugal coater, nozzle coater, and the like. The thickness of an ink layer is not particularly limited and is preferably 0.5 to 10 µm and more preferably 1 to 4 µm.

[0097] The oxygen transmission rate (OTR) of the multilayer structure of the present disclosure under conditions of 20 °C and 65% RH can be adjusted according to the application and is not particularly limited. The multilayer structure of the present disclosure can be advantageously used for applications requiring high barrier properties when no evaporated inorganic layer (I) is provided, and for applications requiring even higher barrier properties when the evaporated inorganic layer (I) is provided. In the first case, the OTR is preferably 1 cc / (m²). 2 ·day·atm) or less, preferably 0.4 cc / (m³) 2 ·day·atm) or less and preferably 0.1 cc / (m 2 ·day·atm) or less. In the latter case, the OTR is preferably 0.1 cc / (m³). 2 ·day·atm) or less, preferably 0.05 cc / (m³) 2·day·atm) or less and preferably 0.03 cc / (m 2 ·day·atm) or less. If the OTR is kept low, especially after physical damage such as bending or stretching, its suitability as a packaging material can be further increased. The OTR is measured according to JIS K 7126-2 (Equal Pressure Method; 2006), and in particular, a method described in EXAMPLES is used.

[0098] The water vapor transmission rate (WVTR) of the multilayer structure of the present disclosure under conditions of 40 °C and 90% RH can be adjusted according to the application and is not particularly limited. The multilayer structure of the present disclosure can be advantageously used for applications requiring high barrier properties when no evaporated inorganic layer (I) is provided, and for applications requiring even higher barrier properties when the evaporated inorganic layer (I) is provided. In the first case, the WVTR is preferably 5 g / (m²). 2 (day) or less, preferably 4 g / (m²) 2 (day) or less and preferably 3 g / (m²) 2 ·day) or less. In the latter case, the WVTR is preferably 1 g / (m²). 2 (day) or less, preferably 0.5 g / (m²) 2 (day) or less and preferably 0.3 g / (m²) 2·day) or less. If the WVTR is kept low, especially after physical damage such as bending or stretching, its suitability as packaging material can be further increased. The WVTR is measured according to JIS K 7129-2 (Infrared Detection Sensor Method; 2019).

[0099] Preferably, recovered material from the multilayer film, vapor-deposited multilayer film, or multilayer structure of the present disclosure is reused. Examples of recovered material include recovered materials (scrap) obtained by collecting offcuts and defective products generated during the manufacture of the multilayer film, vapor-deposited multilayer film, or multilayer structure of the present disclosure. A method for recovering the multilayer film, vapor-deposited multilayer film, or multilayer structure, comprising a melt forming step after pulverizing the recovered material, and a recovered composition containing the recovered material are also suitable embodiments of the present disclosure.Furthermore, a method for producing a film using the recovered composition as a starting material is also a suitable embodiment of the present disclosure.

[0100] In the process for producing the recovered composition, the recovered material is first pulverized. The pulverized recovered material can be directly melt-molded to obtain the recovered composition, or it can optionally be melt-molded with another component to obtain the recovered composition. A preferred component added to the recovered material is preferably a polyolefin resin and more preferably one of the polyethylene resins described above. The pulverized recovered material can be used directly for the production of a molded part, such as a multilayer structure, or the pulverized recovered material can be melt-molded to obtain pellets of the recovered composition, and these pellets can then be used for the production of a molded part.

[0101] The mass ratio [EVOH(e) / polyolefin resin] of the EVOH(e) to the polyolefin resin in the recovered composition is preferably 0.01 / 99.99 to 20 / 80. If the above mass ratio is less than 0.01 / 99.99, the proportion of recovered material to be used may be reduced. Conversely, if the above mass ratio is greater than 20 / 80, the melt formability and mechanical properties of the recovered composition may be impaired. In order to improve the melt formability and mechanical properties of the recovered composition to be obtained, the above mass ratio is preferably 15 / 85 or less, more preferably 10 / 90 or less, and may be 5 / 95 or less.

[0102] Since the multilayer structure of the present disclosure exhibits high barrier properties and excellent formability, it can be suitable as a material for various packagings, such as food packaging, medical packaging, industrial chemical packaging and agrochemical packaging, and in particular, a packaging material comprising the multilayer structure of the present disclosure can be suitable as a packaging material with excellent recyclability. EXAMPLES

[0103] The present invention will now be described in more detail using examples. However, the present invention is not limited to these examples. Materials used - Polyethylene resin (a) a-1: High-density polyethylene, manufactured by Dow Chemical Company, “ELITE (trademark) AT6900” (Copolymer of ethylene and 1-octene; density: 0.969 g / cm³) 3; Melting point: 134 °C; MFR (190 °C, load of 2.16 kg): 1.2 g / 10 min) a-2: High-density polyethylene, manufactured by Dow Chemical Company, “ELITE (trademark) 5538G” (Copolymer of ethylene and 1-octene; density: 0.941 g / cm³) 3 ; Melting point: 129 °C; MFR (190 °C, load of 2.16 kg): 1.3 g / 10 min) a-3: Medium-density polyethylene, manufactured by Dow Chemical Company, “ELITE (trademark) 5110G” (Copolymer of ethylene and 1-octene; density: 0.926 g / cm³) 3 ; Melting point: 123 °C; MFR (190 °C, load of 2.16 kg): 0.85 g / 10 min) ac-1: linear low-density polyethylene, manufactured by Dow Chemical Company, “ELITE (trademark) 5400G” (copolymer of ethylene and 1-octene; density: 0.916 g / cm³) 3 ; Melting point: 123 °C; MFR (190 °C, load of 2.16 kg): 1.0 g / 10 min) - Polyethylene resin (b) b-1: High-density polyethylene, manufactured by Dow Chemical Company, “ELITE (trademark) 5538G” (copolymer of ethylene and 1-octene; density: 0.941 g / cm³) 3 ; Melting point: 129 °C; MFR (190 °C, load of 2.16 kg): 1.3 g / 10 min) b-2: Medium-density polyethylene, manufactured by Dow Chemical Company, “ELITE (trademark) 5110G” (Copolymer of ethylene and 1-octene; density: 0.926 g / cm³ 3 ; Melting point: 123 °C; MFR (190 °C, load of 2.16 kg): 0.85 g / 10 min) - Polyethylene resin (c) c-1: linear low-density polyethylene, manufactured by Dow Chemical Company, “ELITE (trademark) 5400G” (copolymer of ethylene and 1-octene; density: 0.916 g / cm³) 3 ; Melting point: 123 °C; MFR (190 °C, load of 2.16 kg): 1.0 g / 10 min) cc-1: High-density polyethylene, manufactured by Dow Chemical Company, “ELITE (trademark) AT6900” (Copolymer of ethylene and 1-octene; density: 0.969 g / cm³) 3; Melting point: 134 °C; MFR (190 °C, load of 2.16 kg): 1.2 g / 10 min) - Adhesive resin (d) d-1: Maleic anhydride-modified polyethylene, manufactured by Mitsui Chemicals, Inc., “ADMER (trademark) AT1955E” (density 0.89 g / cm³) 3 ; Melting point: 111 °C; MFR (190 °C, load of 2.16 kg): 2.6 g / 10 min) - EVOH (e), polyvalent metal ion (f) and higher aliphatic carboxylic acid (g) e-1: EVOH; ethylene unit content: 24 mol%; saponification level: 99.9 mol%; containing 250 ppm sodium acetate with respect to one sodium ion, 20 ppm phosphate ions with respect to one phosphate radical, and 50 ppm magnesium stearate with respect to one magnesium ion; MFR (210 °C, load of 2.16 kg): 2.2 g / 10 min e-2: EVOH; ethylene unit content: 27 mol%; saponification level: 99.9 mol%; Containing 250 ppm sodium acetate as a function of one sodium ion, 20 ppm phosphate ions as a function of one phosphate radical, 150 ppm boric acid as a function of one boron element, and 50 ppm magnesium stearate as a function of one magnesium ion; MFR (210 °C, load of 2.16 kg) 4.0 g / 10 min e-3: EVOH; Ethylene unit content: 24 mol%; Saponification level: 99.9 mol%; Containing 250 ppm sodium acetate with respect to one sodium ion and 20 ppm phosphate ions with respect to one phosphate radical; MFR (210 °C, load of 2.16 kg): 2.2 g / 10 mine-4: EVOH; Ethylene unit content: 24 mol%; Saponification level: 99.9 mol%; containing 250 ppm sodium acetate as a function of a sodium ion, 20 ppm phosphate ions as a function of a phosphate radical, and 25 ppm magnesium stearate as a function of a magnesium ion; MFR (210 °C, load of 2.16 kg): 2.2 g / 10 min e-5: EVOH; Ethylene unit content: 24 mol%; Saponification level: 99.9 mol%; containing 250 ppm sodium acetate as a function of a sodium ion, 20 ppm phosphate ions as a function of a phosphate radical, and 250 ppm magnesium stearate as a function of a magnesium ion; MFR (210 °C, load of 2.16 kg): 2.2 g / 10 min e-6: EVOH; Ethylene unit content: 24 mol%; Saponification level: 99.9 mol%; Containing 250 ppm sodium acetate with respect to one sodium ion, 20 ppm phosphate ions with respect to one phosphate radical, and 50 ppm calcium stearate with respect to one calcium ion; MFR (210 °C, load of 2.16 kg): 2.2 g / 10 min e-7: EVOH; Ethylene unit content: 24 mol%; Saponification level: 99.9 mol%; Containing 250 ppm sodium acetate with respect to one sodium ion, 20 ppm phosphate ions with respect to one phosphate radical, and 50 ppm zinc stearate with respect to one zinc ion; MFR (210 °C, load of 2.16 kg): 2.2 g / 10 min ec-1: EVOH; Ethylene unit content: 32 mol%; Saponification level: 99.9 mol%; Containing 300 ppm sodium acetate (referred to as one sodium ion), 30 ppm phosphate ions (referred to as one phosphate radical), 200 ppm boric acid (referred to as one boron element), and 50 ppm magnesium stearate (referred to as one magnesium ion); MFR (210 °C, load of 2.16 kg): 3.7 g / 10 min ec-2: EVOH; Ethylene unit content: 48 mol%; Saponification level: 99.9 mol%, containing 150 ppm sodium acetate relative to one sodium ion, 30 ppm phosphate ions relative to one phosphate radical, 250 ppm boric acid relative to one boron element, and 50 ppm magnesium stearate relative to one magnesium ion; MFR (210 °C, load of 2.16 kg): 6.5 g / 10 min Evaluation method(1) Measurement of the oxygen transmission rate of a multilayer film or a vapor-deposited multilayer film

[0104] Using multilayer films or vapor-deposited multilayer films obtained in examples and comparative examples, the oxygen transmission rate was measured, with one side of the skin layer (A) on the oxygen supply side and the other side on the carrier gas side. Specifically, the oxygen transmission rate (unit: cc / (m³)) was determined. 2The oxygen permeability (e.g., per day, atm) was measured using an oxygen permeation meter (“MOCON OX-TRAN2 / 21”, manufactured by Modern Control Co., Ltd.) according to JIS K 7126-2 (Equal Pressure Method; 2006) under conditions where the temperature was 20 °C, the humidity on the oxygen supply side was 65% RH, the humidity on the carrier gas side was 65% RH, the oxygen pressure was 1 atm, and the carrier gas pressure was 1 atm. A nitrogen gas containing 2 vol% hydrogen gas was used as the carrier gas. Based on the obtained oxygen transmission rate, the evaluation was performed according to the following criteria. It should be noted that in cases where the rating was “D” or “E”, the gas barrier properties were deemed insufficient. The results are shown in Table 1.

[0105] Evaluation criteria A: less than 0.1 cc / (m³) 2 (Day·atm) B: 0.1 cc / (m³) 2·day·atm) or more and less than 0.4 cc / (m³) 2 (Day·atm) C: 0.4 cc / (m³) 2 ·day·atm) or more and less than 1.0 cc / (m³) 2 (Day·atm) D: 1.0 cc / (m³) 2 ·day·atm) or more and less than 10 cc / (m³) 2 (Day·atm) E: 10 cc / (m 2 ·day·atm) or more (2) Evaluation of the low curling properties of the multilayer film or the vapor-deposited multilayer film

[0106] A 10 cm × 10 cm square film was cut from each of the multilayer films and vapor-deposited multilayer films obtained in the examples and comparison examples and left to stand still for 10 minutes in an atmosphere of 20 °C and 65% RH. The curling behavior was then observed and evaluated according to the following criteria. It should be noted that in one case where the rating was "D" or "E", the low curling properties were judged to be insufficient. The results are shown in Table 1.

[0107] Evaluation criteria A: very slight curling B: slight rolling C: medium roll-up D: strong curling E: very strong curling (3) Evaluation of the heat resistance of a multilayer structure

[0108] From each of the multilayer structures obtained in the examples and comparison examples, two A4-sized pieces were cut out and overlapped so that the resin layers (R) faced each other, one side was heat-sealed using a heat sealer at 120 °C for 2 seconds, and the sealed section was then visually observed and evaluated according to the following criteria.

[0109] Evaluation criteria A: good looks B: slight whitening C: slight whitening or small pores D: difficult whitening or difficult pores or deformation E: very difficult whitening or very difficult pores or deformation (4) Evaluation of the recyclability of the multilayer structure

[0110] Powdered products obtained by pulverizing multilayer structures, as found in the examples and comparative examples, to a size of 4 mm × 4 mm or less, and low-density polyethylene (LDPE) manufactured by Japan Polyethylene Corporation, “NOVATEC (trademark) LD LJ400” (density 0.921 g / cm³) 3Melting point: 111 °C; MFR (190 °C, load of 2.16 kg): 1.5 g / 10 min) were dry-mixed in a mass ratio (recovered material / low-density polyethylene) of 50 / 50, and a single-layer film was formed under the following extrusion conditions, yielding a single-layer film with an average thickness of 50 µm. For reference, a single-layer film with an average thickness of 50 µm was obtained using only the above low-density polyethylene in the same manner (hereinafter sometimes referred to simply as the "reference"). The extruder was a single-screw extruder with a diameter (D) of 20 mm, using a full-thread screw with an L / D ratio of 20 and a compaction ratio of 3.5. A 300 mm wide T-die was used.The average thickness of the single-layer film was controlled by appropriately varying the screw rotation speed and the winding speed. The following are the temperature conditions in this case. Extrusion temperature: Feed zone / Compression zone / Metering zone / Adapter = 175 / 230 / 230 / 230 °C Nozzle temperature: 220 °C Cooling roller temperature: 80 °C

[0111] The resulting single-layer film was visually compared to the reference with regard to discoloration and defects and evaluated according to the following criteria. The results are shown in Table 2.

[0112] Assessment of discoloration: Criteria A: small change in color phase compared to the reference B: slight discoloration compared to the reference C: Medium discoloration compared to the reference D: distinct discoloration compared to the reference E: significant discoloration and also unevenness compared to the reference.

[0113] Error assessment: Criteria A: almost the same number of bubbles as in the reference. B: a somewhat large number of small bubbles compared to the reference C: large number of small bubbles compared to the reference D: large number of large bubbles compared to the reference E: very large number of large bubbles compared to the reference Example 1

[0114] Polyethylene resin (a-1) was used as the starting material for the skin layer (A), polyethylene resin (b-1) was used as the starting material for the subcutaneous layer (B), polyethylene resin (c-1) was used as the starting material for the core layer (C), adhesive resin (d-1) was used as the starting material for the adhesive layer (D), resin composition (e-1) was used as the starting material for the barrier layer (E), and an unstretched multilayer film with layer thicknesses and a layer configuration of (A) / (B) / (C) / (D) / (E) = 12 µm / 12 µm / 72 µm / 12 µm / 12 µm was produced by means of a blowing extruder. The following are film formation conditions in this case.

[0115] Device: 5-layer inflation extruder of 5 types, manufactured by Dr. Collin; Nozzle temperature: 210 °C; Inflation ratio: 2.7; Drawing speed: 4 m / min; Film fold diameter: 25 cm Extruder conditions for the skin layer (A) Extruder: 30 φ single screw extruder (manufactured by Dr. Collin), extrusion temperature: feed zone / compression zone / metering zone = 170 °C / 190 °C / 210 °C.

[0116] Extruder conditions for the subcutaneous layer (B) Extruder: 20 φ single screw extruder (manufactured by Dr. Collin), extrusion temperature: feed zone / compression zone / metering zone = 170 °C / 190 °C / 210 °C.

[0117] Extruder conditions for the core layer (C) Extruder: 20 φ single screw extruder (manufactured by Dr. Collin), extrusion temperature: feed zone / compression zone / metering zone = 170 °C / 190 °C / 210 °C.

[0118] Extruder conditions for the adhesive layer (D) Extruder: 20 φ single-screw extruder (manufactured by Dr. Collin), extrusion temperature: feed zone / compression zone / metering zone = 170 °C / 190 °C / 210 °C.

[0119] Extruder conditions for the barrier layer (E) Extruder: 30 φ single screw extruder (manufactured by Dr. Collin), extrusion temperature: feed zone / compression zone / metering zone = 190 °C / 210 °C / 210 °C.

[0120] From the obtained cylindrical unstretched multilayer film, an unstretched multilayer film measuring 4 cm in the flow direction (machine direction) × 10 cm in the width direction (transverse direction) was cut and monoaxially stretched 5 times in the flow direction (machine direction) using a stretching device (SDR-506WK) manufactured by ETO Co., Ltd. at 125 °C to produce a multilayer film with layer thicknesses and a layer configuration of (A) / (B) / (C) / (D) / (E) = 2 µm / 2 µm / 12 µm / 2 µm / 2 µm.

[0121] A two-component polyurethane adhesive (24 parts by mass of "TAKELAC (trademark) A-520" and 4 parts by mass of "TAKENATE (trademark) A-50", both manufactured by Mitsui Chemicals, Inc.) was mixed with 37 parts by mass of ethyl acetate to create an adhesive solution. Next, one side of a polyethylene film (an unstretched polyethylene film "TUX (trademark) FCD" made of linear low-density polyethylene, manufactured by Mitsui Chemicals Tohcello, Inc.) was coated.) (of the resin layer (R)) with an average thickness of 40 µm was subjected to corona treatment by a known method, the adhesive solution was applied to the side subjected to corona treatment by means of a wire squeegee such that the resulting layer had an average thickness of 3 µm after drying, and the resulting layer was dried at 100 °C for 5 minutes and laminated with the exposed side of the barrier layer (E) of the multilayer film to produce a multilayer structure with layer thicknesses and a layer configuration of (A) / (B) / (C) / (D) / (E) / adhesive layer / (R) = 2 µm / 2 µm / 12 µm / 2 µm / 2 µm / 3 µm / 40 µm. During lamination, the adhesion temperature (temperature of the heating roller) was set to 80 °C, and then aging was carried out at 40 °C for 3 days. Examples 2 to 12 and comparative examples 1 to 10

[0122] Multilayer films and multilayer structures were produced and evaluated using the same procedure as in Example 1, except that the types of resin starting materials used to produce the multilayer film, the layer configuration, and the thickness were changed as shown in Tables 1 and 2. The results are shown in Tables 1 and 2. Example 13

[0123] A vapor-deposited multilayer film and a multilayer structure were fabricated and evaluated in the same manner as in Example 3, except that a vapor-deposited aluminum oxide (AlOx) layer (vapor-deposited inorganic layer (I)) with an average thickness of 30 nm was deposited by a known vacuum deposition technique on the exposed side of the barrier layer (E) of the stretched multilayer film obtained in Example 3. The results are shown in Tables 1 and 2. Example 14

[0124] A vapor-deposited multilayer film and a multilayer structure were fabricated and evaluated in the same manner as in Example 13, except that the vapor-deposited aluminum oxide layer was changed to a vapor-deposited silicon oxide (SiOx) layer. The results are shown in Tables 1 and 2. Example 15

[0125] A vapor-deposited multilayer film and a multilayer structure were fabricated and evaluated in the same manner as in Example 13, except that the vapor-deposited aluminum oxide layer was changed to a vapor-deposited aluminum metal (Al) layer and the thickness of the vapor-deposited inorganic layer (I) was set to 50 nm. The results are shown in Tables 1 and 2. Example 16

[0126] A vapor-deposited multilayer film and a multilayer structure were fabricated and evaluated in the same manner as in Example 1, except that a vapor-deposited silicon dioxide (SiOx) layer (vapor-deposited inorganic layer (I)) with an average thickness of 30 nm was deposited by a known vacuum deposition technique on the exposed side of the barrier layer (E) of the stretched multilayer film obtained in Example 1. The results are shown in Tables 1 and 2. Example 17

[0127] A vapor-deposited multilayer film and a multilayer structure were fabricated and evaluated in the same manner as in Example 16, except that the average layer thickness (R) was changed to 80 µm. The results are shown in Tables 1 and 2. Table 2 Table 2 Multi-layer structure Layer configuration / thickness Percentage of PE resin layer (thickness) Heat resistance Recyclability discoloration Mistake µm - - - - Example 1 A2 / B2 / Cl2 / D2 / E2 / Adhesive layer3 / R40 0,92 A B B Example 2 A2 / B2 / Cl2 / D2 / E2 / Adhesive layer3 / R40 0,92 B B B Example 3 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 B B B Example 4 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 C B B Example 5 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 D B B Example 6 A2 / C12 / D2 / E4 / Adhesive layer3 / R40 0,89 B B C Example 7 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 B B B Example 8 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 B B E Example 9 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 B B D Example 10 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 B D D Example 11 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 B B C Example 12 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 B B D Example 13 A2 / C14 / D2 / E2 / 10.03 / Adhesive layer3 / R40 0,92 B B B Example 14 A2 / C14 / D2 / E2 / 10.03 / Adhesive layer3 / R40 0,92 B B B Example 15 A2 / C14 / D2 / E2 / 10.05 / Adhesive Layer3 / R40 0,92 B E C Example 16 A2 / B2 / C12 / D2 / E2 / 10.03 / Adhesive Layer3 / R40 0,92 A B B Example 17 A2 / B2 / C12 / D2 / E2 / 10.03 / Adhesive Layer3 / R80 0,95 A A A Comparative example 1 A2 / C18 / Adhesive layer 3 / R40 0,95 B A A Comparative example 2 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 B B A Comparative example 3 A2 / C10 / D2 / E6 / Adhesive layer3 / R40 0,86 B B C Comparative example 4 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 B A A Comparative example 5 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 E B B Comparative example 6 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 A B B Comparative example 7 A2 / C14 / D2 / E2 / Adhesive layer3 / R40 0,92 D B B Comparative example 8 A11 / C5 / D2 / E2 / Adhesive layer 3 / R40 0,92 A B B Comparative example 9 A5 / B5 / C5 / D2 / E2 / Adhesive layer3 / R40 0,92 A B B Comparative example 10 A2 / B12 / C2 / D2 / E2 / Adhesive layer3 / R40 0,92 A B B

[0128] The multilayer films and the vapor-deposited multilayer films of Examples 1 to 17 exhibit both gas barrier properties and low curling properties. Conversely, the multilayer film of Comparative Example 1, which does not include a barrier layer (E), exhibits low gas barrier properties. The multilayer films of Comparative Examples 2 to 4, in which the ethylene EVOH content in the barrier layer (E) exceeds 30 mol%, do not exhibit both gas barrier properties and low curling properties. The multilayer films of Comparative Examples 5 to 7, 9, and 10, in which the density (dA) of the skin layer (A) is equal to the density (dC) of the core layer (C), do not exhibit low curling properties. The multilayer film of Comparative Example 8, in which the thickness of the skin layer (A) is greater than the thickness of the core layer (C), does not exhibit low curling properties. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2019 / 243456

[0005] WO 2021 / 210606

[0005] Cited non-patent literature

[0000] JIS K 7210

[0046] JIS K 7129-2

[0098]

Claims

[1] Multilayer film with a configuration in which a skin layer (A), a core layer (C), an adhesive layer (D) and a barrier layer (E) are arranged on top of each other in at least this order, where the skin layer (A) is arranged as one outermost layer of the multilayer film, and the barrier layer (E) is arranged as the other outermost layer of the multilayer film, the core layer (C) is the thickest layer in the multilayer film, the skin layer (A) contains a polyethylene resin (a) as its main component, the core layer (C) contains a polyethylene resin (c) as its main component, the density (dA) of the skin layer (A) is greater than the density (dC) of the core layer (C), the adhesive layer (D) contains an adhesive resin (d) with a melting point of less than 150 °C as its main component, the barrier layer (E) contains as its main component an ethylene-vinyl alcohol copolymer (e) with an ethylene unit content of 20 mol% or more and 30 mol% or less and a saponification level of 90 mol% or more, the multilayer film does not include a layer containing a resin with a melting point of 220 °C or higher as its main component, and The multilayer film is stretched at least monoaxially by a factor of 3 or more. [2] Multilayer film according to claim 1, further comprising: a subcutaneous layer (B) arranged between the skin layer (A) and the core layer (C) and containing a polyethylene resin (b) as its main component, wherein the density (dB) of the subcutaneous layer (B) is less than the density (dA) of the skin layer (A) and greater than the density (dC) of the core layer (C). [3] Multilayer film according to claim 1, wherein the density (dD) of the adhesive layer (D) is smaller than the density (dC) of the core layer (C). [4] Multilayer film according to claim 1, wherein the density (dA) of the skin layer (A) is 0.940 g / cm³ 3 or more. [5] Multilayer film according to claim 1, wherein the density (dC) of the core layer (C) is 0.910 g / cm³ 3 or more and less than 0.940 g / cm² 3 amounts. [6] Multilayer film according to claim 1, wherein the ratio of the thickness of the core layer (C) to the total thickness of the multilayer film is 0.3 to 0.

8. [7] Multilayer film according to claim 1, wherein the ratio of the thickness of the skin layer (A) to the total thickness of the multilayer film is 0.05 to 0.

2. [8] Multilayer film according to claim 1, wherein the ratio of the thickness of the barrier layer (E) to the total thickness of the multilayer film is 0.05 to 0.

2. [9] Multilayer film according to claim 1, wherein the adhesive resin (d) is an acid-modified polyethylene resin. [10] Multilayer film according to claim 1, wherein the barrier layer (E) contains 10 to 300 ppm of at least one polyvalent metal ion (f) selected from the group consisting of a magnesium ion, a calcium ion and a zinc ion. [11] Multilayer film according to claim 1, wherein the barrier layer (E) contains 100 to 4000 ppm of a higher aliphatic carboxylic acid (g) having 8 to 30 carbon atoms. [12] Multilayer film according to claim 1, which is stretched by a factor of 3 or more in the longitudinal direction and is substantially not stretched in the lateral direction. [13] Multilayer film according to claim 1, which is an inflated molded part. [14] Evaporated multilayer film comprising: the multilayer film according to any one of claims 1 to 13; and a vapor-deposited inorganic layer (I) on an exposed side of the barrier layer (E). [15] Evaporated multilayer film according to claim 14, wherein the evaporated inorganic layer (I) is an evaporated metal layer containing aluminium as the main component or an evaporated inorganic oxide layer containing aluminium oxide or silicon oxide as the main component. [16] Multilayer structure, comprising: the multilayer film according to any one of claims 1 to 13; and a resin layer (R) containing a thermoplastic resin (r) as its main component. [17] Multilayer structure, comprising: the vapor-deposited multilayer film according to claim 14; and a resin layer (R) containing a thermoplastic resin (r) as its main component. [18] Multilayer structure according to claim 16, wherein the thermoplastic resin (r) contains a polyethylene resin as the main component. [19] Multilayer structure according to claim 17, wherein the thermoplastic resin (r) contains a polyethylene resin as the main component. [20] Packaging material comprising: the multilayer structure according to claim 16. [21] Packaging material comprising: the multilayer structure according to claim 17.