Multilayer structures, liquid paper containers and products

Abstract

To provide a multilayer structure that can maintain high water vapor barrier properties even when storing acidic beverages, etc., under high temperature and high humidity conditions, has high processing stability during film formation, and suppresses the occurrence of defects during recycling. [Solution] A multilayer structure comprising a paper layer (A), an inorganic vapor-deposited layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E), wherein the inorganic vapor-deposited layer (B), barrier resin layer (C), adhesive resin layer (D), and moisture-proof resin layer (E) are all directly laminated in this order, the average thickness of the inorganic vapor-deposited layer (B) is 5 nm to 200 nm, the barrier resin layer (C) mainly contains an ethylene-vinyl alcohol copolymer (c1) with an ethylene unit content of 20 mol% to 30 mol% and a degree of saponification of 90 mol% or more, the barrier resin layer (C) contains magnesium ions of 0.005 ppm to less than 10 ppm, the adhesive resin layer (D) mainly contains an adhesive resin (d), and the moisture-proof resin layer (E) mainly contains polyethylene (e).

Description

[Technical Field]

[0001] This invention relates to a multilayer structure, a liquid paper container, and a product. [Background technology]

[0002] Paper containers are widely used to hold beverages such as milk and juice, liquid foods such as soup, alcoholic beverages such as sake and shochu, and various other liquids besides food. For liquid paper containers, multilayer structures are widely used, consisting of a paper layer laminated with a resin layer, a vapor-deposited layer, or metal foil, from the viewpoint of barrier properties and heat sealability.

[0003] Patent Document 1 describes a paper container formed by a multilayer structure in which a synthetic resin layer or the like is laminated on one side of a base material mainly composed of a paper layer, and an intermediate layer, a barrier layer, and a sealant layer made of linear low-density polyethylene resin are laminated in that order on the other side of the base material. In the multilayer structure of Patent Document 1, a vapor-deposited film is used for the barrier layer, which is obtained by vapor-depositing an inorganic substance onto a polyethylene terephthalate resin film.

[0004] Packaging materials such as paper containers are desirable to be easily collected and reused (highly recyclable). However, in multilayer structures that have various resin layers in addition to the paper layer, if the resin layer is used for melt molding after the paper layer has been removed, defects may occur in the resulting recycled product (melt-molded product) due to differences in the melting temperature of the resins, cross-linking reactions of the resins, etc., resulting in a decrease in appearance and quality.

[0005] Patent Document 2 describes a multilayer structure having a paper layer, an inorganic vapor deposition layer, a barrier resin layer, an adhesive resin layer, and a moisture-proof resin layer, wherein the barrier resin layer contains an ethylene-vinyl alcohol copolymer as a main component. Specifically, an ethylene-vinyl alcohol-based polymer having an ethylene unit content of 27 to 44 mol% is used in the barrier resin layer of Patent Document 2. Further, Patent Document 2 states that from the viewpoint of suppressing the occurrence of defects during recycling, it is preferable that the barrier resin layer (C) contains at least one polyvalent metal ion selected from the group consisting of magnesium ions, calcium ions, and zinc ions in an amount of 10 ppm or more and 200 ppm or less.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0009] The purpose of the above is, [1] A multilayer structure comprising a paper layer (A), an inorganic vapor-deposited layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E), wherein the inorganic vapor-deposited layer (B), barrier resin layer (C), adhesive resin layer (D), and moisture-proof resin layer (E) are all directly laminated in this order, the average thickness of the inorganic vapor-deposited layer (B) is 5 nm to 200 nm, the barrier resin layer (C) mainly contains an ethylene-vinyl alcohol copolymer (c1) with an ethylene unit content of 20 mol% to 30 mol% and a degree of saponification of 90 mol% or more, the barrier resin layer (C) contains magnesium ions of 0.005 ppm to less than 10 ppm, the adhesive resin layer (D) mainly contains an adhesive resin (d), and the moisture-proof resin layer (E) mainly contains polyethylene (e); [2] A multilayer structure of [1] further comprising a thermoplastic resin layer (X) interposed between a paper layer (A) and the vapor-deposited laminate; [3] A multilayer structure of [1] or [2] having, in this order, a paper layer (A), an inorganic vapor deposition layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E); [4] A multilayer structure of any of [1] to [3], wherein the barrier resin layer (C) contains a polyolefin (c2) with a melt flow rate of 3 g / 10 min or more at 190°C and a 2.160 kg load as measured in accordance with JIS K7210 (2014), in an amount of 0.1 parts by mass to 20 parts by mass per 100 parts by mass of ethylene-vinyl alcohol copolymer (c1); [5] A multilayer structure of any of [1] to [4], wherein the laminate of a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E) is an unstretched or stretched co-extruded film, the average thickness of the co-extruded film is 8 μm or more and 120 μm or less, and an inorganic vapor-deposited layer (B) is provided on the barrier resin layer (C) side of the co-extruded film; [6] A multilayer structure of [5] wherein the average thickness of the barrier resin layer (C) is 0.2 μm or more and less than 30 μm, and the ratio of the average thickness of the barrier resin layer (C) to the average thickness of the co-extruded film is less than 25%; [7] A multilayer structure of [5] or [6] further comprising a moisture-proof resin layer (F) mainly composed of polyethylene (f); [8] A multilayer structure of [7] in which a moisture-proof resin layer (F) is directly laminated onto the co-extruded film; [9] A multilayer structure of any of [1] to [8] that does not have an adhesive layer made of a curing type adhesive;

[10] The basis weight of the paper layer (A) is 200 g / m² 2 More than 400g / m 2 A multilayer structure less than any of the [1] to [9];

[11] A multilayer structure of any of [1] to

[10] in which the total average thickness ratio of layers mainly composed of polyethylene resin in the parts other than the paper layer (A) is 0.75 or more;

[12] The water vapor transmission rate measured in accordance with JIS K7129-2 (infrared sensor method; 2019) under conditions of a temperature of 40°C, humidity of 90%RH on the water vapor supply side, and humidity of 0%RH on the carrier gas side was 2.0 g / (m³). 2 A multilayer structure of any of the [1] to

[11] types that is less than [day]; A liquid paper container having one of the multilayer structures described in

[13] [1] to

[12] ;

[14]

[13] A product in which a liquid with a pH of 2 to 6 is contained in a liquid paper container; This is achieved by providing [the necessary services / services]. [Effects of the Invention]

[0010] The present invention provides a multilayer structure that can maintain high water vapor barrier properties even when containing acidic beverages under high temperature and high humidity conditions, has high processing stability during film formation, and suppresses the occurrence of defects during recycling, as well as a liquid paper container and product using such a multilayer structure. [Modes for carrying out the invention]

[0011] <Multilayer structure> The multilayer structure of the present invention comprises a paper layer (A), an inorganic vapor-deposited layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E). The inorganic vapor-deposited layer (B), barrier resin layer (C), adhesive resin layer (D), and moisture-proof resin layer (E) are all directly laminated in this order, forming a vapor-deposited laminate. The average thickness of the inorganic vapor-deposited layer (B) is 5 nm to 200 nm. The barrier resin layer (C) mainly contains an ethylene-vinyl alcohol copolymer (c1) with an ethylene unit content of 20 mol% to 30 mol% and a degree of saponification of 90 mol% or more. The barrier resin layer (C) also contains magnesium ions at a concentration of 0.005 ppm to less than 10 ppm. The adhesive resin layer (D) mainly contains an adhesive resin (d), and the moisture-proof resin layer (E) mainly contains polyethylene (e). Hereinafter, the ethylene-vinyl alcohol copolymer will also be referred to as "EVOH".

[0012] The multilayer structure of the present invention can maintain high water vapor barrier properties even when containing acidic beverages and the like under high temperature and high humidity conditions, exhibits high processing stability during film formation, and suppresses the occurrence of defects during recycling. The reason for this is not entirely clear, but the following reasons are speculated. The multilayer structure has a structure in which an inorganic vapor-deposited layer (B) having a predetermined thickness range and a barrier resin layer (C) mainly composed of EVOH with an ethylene unit content of 20 mol% to 30 mol%, which has excellent barrier properties, are directly laminated, making it difficult for acidic components of acidic beverages and the like to permeate, thus maintaining high water vapor barrier properties even under high temperature and high humidity conditions. Furthermore, by keeping the magnesium ion content in the barrier resin layer (C) below 10 ppm, the viscosity stability of the resin composition for forming the barrier resin layer (C) is improved, and the occurrence of thickness unevenness during film formation can be reduced, resulting in high processing stability. Furthermore, the multilayer structure has a relatively thin average thickness for the inorganic vapor-deposited layer (B), and the barrier resin layer (C) and moisture-proof resin layer (E) are mainly composed of a predetermined resin, thereby suppressing the occurrence of defects during recycling.

[0013] In this specification, "main component" refers to the component that is present in the largest quantity by mass. The "average thickness" of each layer refers to the average value of the thickness measured at any five locations. "ppm" refers to the content by mass (mass ppm). "Polyethylene" refers to a homopolymer of ethylene, a copolymer of 80 mol% or more of ethylene and 20 mol% or less of α-olefin monomer, and a copolymer of 90 mol% or more of ethylene and less than 10 mol% of a non-olefin monomer whose functional groups do not contain atoms other than carbon, oxygen, and hydrogen atoms. "Acid-modified polyethylene" refers to a polymer obtained by modifying polyethylene with an acid. Acid-modified polyethylene may be a polymer in which at least one of an acidic group and an acid anhydride group is introduced to polyethylene. The term "polyethylene resin" refers to polyethylene and modified polyethylene (such as acid-modified polyethylene). Modified polyethylene refers to a polymer obtained by modifying polyethylene. In addition, the "surface" in the multilayer structure does not mean to distinguish between the front and back, but refers to the exposed surface. That is, there are two surfaces in the multilayer structure. Similarly, there are two outermost layers in the multilayer structure. In this specification, "A to B" means including A as the lower limit value and B as the lower limit value, that is, "A to B" means A or more and B or less.

[0014] Hereinafter, each layer, layer structure, etc. of the multilayer structure according to an embodiment of the present invention will be described in detail.

[0015] (Paper layer (A)) The paper layer (A) is usually the base layer in the multilayer structure of the present invention. As the paper layer (A), general paper mainly composed of plant-derived pulp can be used. In addition to pulp, the paper layer (A) may contain a sizing agent, a filler, a paper strength enhancer, a yield improver, a pH adjuster, a drainage improver, a water resistance agent, a softener, an antistatic agent, an antifoaming agent, a slime control agent, a dye, a pigment, etc.

[0016] Examples of the paper constituting the paper layer (A) include kraft paper, fine paper, medium paper, alkaline paper, cardboard, glassine paper, semi-glassine paper, parchment paper, etc. Kraft paper or cardboard is preferred, and cardboard is more preferred.

[0017] The basis weight (mass per unit area) of the paper layer (A) is not particularly limited, and for example, it can be 100 g / m 2 or more and 500 g / m 2 or less, but preferably 200 g / m 2 or more and 400 g / m 2 or less, more preferably 220 g / m 2 or more and 350 g / m 2 or less, and even more preferably 240 g / m 2 or more and 300 g / m 2A basis weight of less than the above lower limit is even more preferable. By having a basis weight of paper layer (A) equal to or greater than the above lower limit, the strength of the resulting paper container can be increased. Generally, the thicker the paper layer (A), the more moisture is absorbed into the paper layer (A) when left under high temperature and high humidity conditions, which can lead to deterioration of the inorganic vapor deposition layer (B). Therefore, in the case of a multilayer structure in which the basis weight of paper layer (A) is equal to or greater than the above lower limit, there is a great advantage in applying the present invention, which provides the effect of maintaining high water vapor barrier properties even when storing acidic beverages under high temperature and high humidity conditions. In other words, when the basis weight of paper layer (A) is equal to or greater than the above lower limit, it is possible to achieve both increased strength of the resulting paper container and the ability to maintain high water vapor barrier properties even when storing acidic beverages under high temperature and high humidity conditions. On the other hand, by having a basis weight of paper layer (A) less than the above upper limit, moldability can be improved.

[0018] For example, the density of the paper layer (A) is 0.5 g / cm³. 3 More than 1.5g / cm 3 The following is preferable: 0.7 g / cm³ 3 More than 1.3g / cm 3 The following are preferable.

[0019] The paper used in the paper layer (A) can be manufactured by known methods. Alternatively, commercially available paper can be used for the paper layer (A).

[0020] (vapor deposited laminate) The inorganic vapor-deposited layer (B), barrier resin layer (C), adhesive resin layer (D), and moisture-proof resin layer (E) of the multilayer structure of the present invention are all directly laminated in this order. The laminate of the inorganic vapor-deposited layer (B), barrier resin layer (C), adhesive resin layer (D), and moisture-proof resin layer (E) is called a vapor-deposited laminate. In other words, the multilayer structure has a paper layer (A) and a vapor-deposited laminate. Preferably, the vapor-deposited laminate is provided on the surface of the barrier resin layer (C) in a co-extruded film in which the barrier resin layer (C), adhesive resin layer (D), and moisture-proof resin layer (E) are laminated in this order, as will be described later. The vapor-deposited laminate may also be formed by laminating each layer by other methods.

[0021] (Inorganic vapor deposited layer (B)) The inorganic vapor-deposited layer (B) primarily serves to ensure barrier properties in the multilayer structure of the present invention.

[0022] The inorganic vapor-deposited layer (B) can be formed by depositing inorganic material. Typically, the inorganic vapor-deposited layer (B) is formed by depositing inorganic material onto the surface of the barrier resin layer (C). Examples of inorganic materials include metals (e.g., aluminum, copper, etc.), oxides (e.g., alumina, silica, etc.), nitrides (e.g., silicon nitride, etc.), nitride oxides (e.g., silicon oxynitride, etc.), and carbidine nitrides (e.g., silicon carbonitride, etc.).

[0023] As the inorganic vapor-deposited layer (B), a metal vapor-deposited layer or an inorganic oxide vapor-deposited layer is preferred. When light shielding and barrier properties after bending are important, a metal vapor-deposited layer is preferred as the inorganic vapor-deposited layer (B), a metal vapor-deposited layer mainly composed of aluminum is more preferred, and an aluminum vapor-deposited layer may also be used. On the other hand, when preventing discoloration during recycling is important, an inorganic oxide vapor-deposited layer is preferred as the inorganic vapor-deposited layer (B), and an inorganic oxide vapor-deposited layer mainly composed of alumina (aluminum oxide) or silica (silicon oxide) is more preferred. Thus, the inorganic vapor-deposited layer (B) is preferably a metal vapor-deposited layer mainly composed of aluminum or an inorganic oxide vapor-deposited layer mainly composed of alumina or silica.

[0024] Furthermore, in metal vapor deposition layers primarily composed of aluminum (inorganic vapor deposition layer (B)), irreversible oxidation occurs, and some aluminum oxide may be present. In metal vapor deposition layers primarily composed of aluminum (inorganic vapor deposition layer (B)), the molar ratio of oxygen atoms to aluminum atoms is (O mol / Al mol The value of ) is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.1 or less.

[0025] The lower limit of the average thickness of the inorganic vapor-deposited layer (B) is 5 nm, preferably 10 nm, more preferably 20 nm, and even more preferably 30 nm. A minimum average thickness of the inorganic vapor-deposited layer (B) above the above lower limit can further enhance barrier properties. The upper limit of the average thickness of the inorganic vapor-deposited layer (B) is 200 nm, preferably 150 nm, more preferably 120 nm, even more preferably 80 nm, and even more preferably 60 nm. A minimum average thickness of the inorganic vapor-deposited layer (B) above the above upper limit can suppress discoloration during recycling. Recycled products (molten products) with suppressed discoloration are preferable because they have a good appearance.

[0026] The inorganic vapor deposition layer (B) can be formed by known physical or chemical vapor deposition methods. Specifically, these include vacuum vapor deposition, sputtering, ion plating, ion beam mixing, plasma CVD, laser CVD, MO-CVD, and thermal CVD. Physical vapor deposition is preferred, and vacuum vapor deposition is more preferred.

[0027] Before performing vapor deposition, the surface of the layer to be deposited (for example, the barrier resin layer (C)) may be plasma-treated. Known methods can be used for plasma treatment, and atmospheric pressure plasma treatment is preferred. Examples of discharge gases in atmospheric pressure plasma treatment include nitrogen gas, helium, neon, argon, krypton, xenon, and radon. Among these, nitrogen, helium, and argon are preferred, and nitrogen is more preferred from the viewpoint of cost reduction.

[0028] The inorganic vapor-deposited layer (B) may consist of a single layer or multiple layers.

[0029] (Barrier resin layer (C)) The barrier resin layer (C) mainly contains EVOH(c1) with an ethylene unit content of 20 mol% to 30 mol% and a degree of saponification of 90 mol% or more. Because the multilayer structure of the present invention is equipped with such a barrier resin layer (C), it can suppress the occurrence of cracks in the inorganic vapor-deposited layer (B) due to the influence of the contents components, and thus can maintain high water vapor barrier properties even during long-term storage under high temperature and high humidity.

[0030] EVOH(c1) is a copolymer having ethylene units and vinyl alcohol units. EVOH(c1) is usually obtained by saponification of an ethylene-vinyl ester copolymer. EVOH(c1) may have residual vinyl ester units. The production and saponification of ethylene-vinyl ester copolymers can be carried out by known methods. Examples of vinyl esters include vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, vinyl versaticate, and other aliphatic carboxylic acid vinyl esters, with vinyl acetate being preferred.

[0031] The lower limit of the ethylene unit content of EVOH(c1) is 20 mol%, preferably 22 mol%, more preferably 24 mol%, and may also be 26 mol%. Having an ethylene unit content of EVOH(c1) above the above lower limit helps to suppress defects and discoloration during recycling. The upper limit of the ethylene unit content of EVOH(c1) is 30 mol%, more preferably 28 mol%, and may also be 26 mol%. Having an ethylene unit content of EVOH(c1) below the above upper limit suppresses crack formation in the inorganic vapor-deposited layer (B) due to the influence of the contents' components, and maintains high water vapor barrier properties even when storing acidic beverages under high temperature and high humidity conditions.

[0032] The lower limit of the degree of saponification of EVOH(c1) is 90 mol%, preferably 95 mol%, more preferably 99 mol%, and even more preferably 99.9 mol%. When the degree of saponification of EVOH(c1) is above the lower limit, the water vapor barrier properties tend to be higher. The upper limit of the degree of saponification of EVOH(c1) may be 100 mol%.

[0033] EVOH(c1) may have structural units other than ethylene units, vinyl alcohol units, and potentially residual vinyl ester units, to the extent that the objectives of the present invention are not hindered. In particular, by introducing a modified group containing a primary hydroxyl group having a specific structure, it may be possible to achieve a high level of both barrier properties and moldability of EVOH(c1). The content of other structural units is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably substantially absent. Monomers that give such other structural units include, for example, α-olefins such as propylene, n-butene, isobutylene, and 1-hexene; acrylic acid and its salts; unsaturated monomers having an acrylic acid ester group; methacrylic acid and its salts; unsaturated monomers having a methacrylic acid ester group; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salts, acrylamidepropyldimethylamine and its salts (e.g., quaternary salts); methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts (e.g., quaternary salts); methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl Examples include vinyl ethers such as ru 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; vinylidenes such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane, and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid, and their salts or esters; vinylsilane compounds such as vinyltrimethoxysilane; and isopropenyl acetate, 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyronyloxy-2-methylenepropane.

[0034] For EVOH(c1), the MFR (at 190°C, with a load of 2.160 kg) is preferably 0.5 g / 10 min to 12 g / 10 min, more preferably 0.8 g / 10 min to 8.0 g / 10 min, and even more preferably 1.2 g / 10 min to 6.0 g / 10 min.

[0035] EVOH(c1) may be used alone or in combination of two or more types.

[0036] EVOH(c1) may contain two or more types of EVOH with different ethylene unit content. The two types of EVOH with different ethylene unit content may be two types of EVOH with different melting points. For example, when the melting point is measured by DSC, the peak temperature corresponding to each EVOH may be confirmed. In the above-mentioned DSC measurement of the melting point, the temperature is raised from 30°C to 250°C at a rate of 10°C / min, cooled at 50°C / min, and the melting point is determined from the peak temperature measured by secondary heating.

[0037] Of the two types of EVOH(c1), the EVOH(c1-a) with a low ethylene unit content is preferably 20 mol% to 28 mol%, and more preferably 20 mol% to 26 mol%. Of the two types of EVOH(c1), the EVOH(c1-b) with a high ethylene unit content is preferably 22 mol% to 30 mol%, and more preferably 26 mol% to 30 mol%.

[0038] The difference in ethylene unit content between EVOH(c1-b) and EVOH(c1-a), that is, the value obtained by subtracting the ethylene unit content of EVOH(c1-a) from the ethylene unit content of EVOH(c1-b), is preferably 1 mol% or more and 10 mol% or less, more preferably 2 mol% or more and 8 mol% or less, and even more preferably 3 mol% or more and 6 mol% or less.

[0039] The mass ratio (c1-a / c1-b) of EVOH(c1-a) to EVOH(c1-b), that is, the mass ratio of the content of EVOH(c1-a) to the content of EVOH(c1-b), is preferably 50 / 50 or more and 95 / 5 or less, more preferably 60 / 40 or more and 90 / 10 or less, and more preferably 70 / 30 or more and 85 / 15 or less.

[0040] The lower limit of the EVOH(c1) content in the barrier resin layer (C) is preferably 70% by mass, more preferably 80% by mass, even more preferably 90% by mass, and may also be 95% by mass, 99% by mass, or 99.9% by mass, from the viewpoint of water vapor barrier properties, etc. The upper limit of the EVOH(c1) content in the barrier resin layer (C) may be 100% by mass, or may be 99.99% by mass, 99.9% by mass, or 99% by mass.

[0041] The barrier resin layer (C) contains magnesium ions. The lower limit of the magnesium ion content in the barrier resin layer (C) is 0.005 ppm. A magnesium ion content of the barrier resin layer (C) above this lower limit suppresses the occurrence of defects during recycling. The magnesium ion content in the barrier resin layer (C) is preferably 0.01 ppm or more, more preferably 0.05 ppm or more, and may be 0.1 ppm or more or 0.5 ppm or more. On the other hand, the magnesium ion content in the barrier resin layer (C) is less than 10 ppm. A magnesium ion content of less than 10 ppm in the barrier resin layer (C) reduces thickness unevenness during film formation, improves processing stability, and suppresses discoloration during recycling. The magnesium ion content in the barrier resin layer (C) is preferably 8 ppm or less, more preferably 6 ppm or less, and may be 4 ppm or less or 2 ppm or less.

[0042] The barrier resin layer (C) may contain magnesium ions as a polyvalent metal ion, as well as any calcium ions. The lower limit of the total content of magnesium and calcium ions in the barrier resin layer (C) is preferably 0.05 ppm, and may be 0.1 ppm or 0.5 ppm. By having the barrier resin layer (C) contain magnesium and calcium ions above the above lower limit, the occurrence of defects during recycling can be further suppressed. The total content of magnesium and calcium ions in the barrier resin layer (C) is preferably less than 10 ppm, more preferably 8 ppm or less, even more preferably 6 ppm or less, and may be 4 ppm or less or 2 ppm or less. When the total content of magnesium and calcium ions in the barrier resin layer (C) is less than 10 ppm, thickness unevenness during film formation can be further reduced, processing stability can be further improved, and discoloration during recycling can be suppressed.

[0043] The above-mentioned polyvalent metal ions (magnesium ions and any calcium ions) are preferably present in the barrier resin layer (C) as cations constituting the salt, and more preferably present in the barrier resin layer (C) as cations constituting the carboxylate salt. In salts such as carboxylate salts, the above-mentioned polyvalent metal ions and anions may be bonded or free.

[0044] The carboxylate salt containing the above-mentioned polyvalent metal ions is preferably a higher fatty acid salt. Specifically, it is preferably a salt of a carboxylic acid having 12 or more carbon atoms. When the above-mentioned polyvalent metal ions exist in the form of such a higher fatty acid salt, the occurrence of discoloration during recycling is further suppressed. Examples of carboxylic acids having 12 or more carbon atoms include lauric acid, lauric acid, tridecyl acid, myristic acid, pentadecyl acid, palmitic acid, heptadecyl acid, stearic acid, basic stearic acid, hydroxystearic acid, basic hydroxystearic acid, nonadecanoic acid, oleic acid, behenic acid, montanic acid, and linoleic acid. The number of carbon atoms in the above-mentioned carboxylic acid may be 12 to 30, 14 to 26, or 16 to 22. Thus, it is preferable that the barrier resin layer (C) contains magnesium ions as magnesium salts of higher fatty acids.

[0045] The above-mentioned polyvalent metal ions may be present in the barrier resin layer (C) as cations constituting fatty acid salts (acetates, propions, etc.) with 11 or fewer carbon atoms, or salts other than fatty acid salts (nitrates, sulfates, etc.). Some or all of the above-mentioned polyvalent metal ions may be present in a state coordinated to, for example, the hydroxyl group of EVOH(c1).

[0046] The barrier resin layer (C) may contain polyolefin (c2) having a melt flow rate (MFR) of 3 g / 10 min or more at 190°C and a 2.160 kg load, as measured in accordance with JIS K7210 (2014). If the barrier resin layer (C) further contains such polyolefin (c2), die build-up during film formation can be sufficiently suppressed, and processing stability can be further improved. The lower limit of the MFR (190°C, 2.160 kg load) of polyolefin (c2) is more preferably 10 g / 10 min, even more preferably 50 g / 10 min, even more preferably 100 g / 10 min, and may be 130 g / 10 min, 150 g / 10 min, 170 g / 10 min, or 180 g / 10 min. The upper limit of the MFR (190°C, 2.160 kg load) for polyolefin (c2) may be 1000 g / 10 min, or it may be 500 g / 10 min, 300 g / 10 min, 250 g / 10 min, or 220 g / 10 min.

[0047] The above MFR (Metal Flux Rate) is less accurate when it exceeds 1000 g / 10 min due to measurement limitations. Therefore, in this specification, when the MFR exceeds 1000 g / 10 min, the melt viscosity shall be defined by a different measurement method (BL-type viscometer). When the MFR of polyolefin (c2) exceeds 1000 g / 10 min, the melt viscosity of polyolefin (c2) measured at 140°C by a BL-type viscometer is preferably 300 to 10000 mPa·s, more preferably 1500 to 8000 mPa·s, and even more preferably 3000 to 6000 mPa·s.

[0048] Examples of polyolefins (c2) include polyethylene, polypropylene, poly(1-butene), poly(4-methyl-1-pentene), copolymers of polyolefins and maleic anhydride, ethylene-vinyl acetate copolymers (EVA) or their saponified products, ethylene-acrylic acid ester copolymers, or modified polyolefins obtained by graft-modifying these with unsaturated carboxylic acids or their derivatives. In particular, from the viewpoint of suppressing die buildup, it is preferable that the polyolefin be at least one selected from the group consisting of polyethylene, polypropylene, and EVA or their saponified products, more preferably at least one selected from the group consisting of polyethylene and EVA or their saponified products, even more preferably at least one selected from the group consisting of polyethylene and EVA saponified products, and from the viewpoint of recyclability, EVA saponified products are particularly preferred.

[0049] When the polyolefin (c2) is EVA or its saponified product, it is preferable that the ethylene unit content be 75 mol% or more and 98 mol% or less, from the viewpoint of suppressing die buildup. When the ethylene unit content is within the above range, the occurrence of die buildup during film formation tends to be further suppressed. The ethylene unit content of EVA or its saponified product is more preferably 85 mol% or more and 96 mol%, and even more preferably 90 mol% or more and 95 mol% or less. The ethylene unit content of EVA or its saponified product is 1 It can be determined by 1H-NMR measurement.

[0050] When the polyolefin (c2) is an EVA saponified product, from the viewpoint of suppressing die buildup, the degree of saponification is preferably 30 mol% or more, more preferably 50 mol% or more, even more preferably 70 mol% or more, and even more preferably 85 mol% or more. On the other hand, the above degree of saponification is preferably 99 mol% or less, and more preferably 96 mol% or less. The degree of saponification of the EVA saponified product is 1 It can be determined by 1H-NMR measurement.

[0051] The number-average molecular weight (hereinafter sometimes abbreviated as Mn) of polyolefin (c2) is preferably 3,000 to 25,000 from the viewpoint of suppressing die buildup. The Mn of polyolefin (c2) is more preferably 5,000 to 22,500, and even more preferably 10,000 to 20,000. The Mn of polyolefin (c2) is determined by GPC measurement.

[0052] When polyolefin (c2) is polyethylene, the MFR (Melting Fuel Rate) of polyolefin (c2) (190°C, 2.160 kg load) is preferably greater than 1000 g / 10 min. That is, when polyolefin (c2) is polyethylene, the melt viscosity of polyolefin (c2) measured at 140°C by a BL-type viscometer is preferably 300 to 10000 mPa·s, more preferably 1500 to 8000 mPa·s, and even more preferably 3000 to 6000 mPa·s. When polyolefin (c2) is EVA saponified, the lower limit of the MFR (Melting Fuel Rate) of polyolefin (c2) (190°C, 2.160 kg load) is preferably 10 g / 10 min, more preferably 50 g / 10 min, even more preferably 100 g / 10 min, even more preferably 130 g / 10 min, and may also be 150 g / 10 min or 170 g / 10 min. Furthermore, when the polyolefin (c2) is an EVA saponified product, the upper limit of the MFR (190°C, 2.160 kg load) of the polyolefin (c2) is preferably 500 g / 10 min, more preferably 400 g / 10 min, even more preferably 300 g / 10 min, and still more preferably 250 g / 10 min.

[0053] The lower limit of the polyolefin (c2) content per 100 parts by mass of EVOH (c1) in the barrier resin layer (C) is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, and still more preferably 1.0 part by mass. A polyolefin (c2) content above this lower limit enhances the effect of suppressing die buildup. The upper limit of the polyolefin (c2) content per 100 parts by mass of EVOH (c1) in the barrier resin layer (C) is preferably 20 parts by mass, more preferably 12 parts by mass, still more preferably 10 parts by mass, and still more preferably 5 parts by mass. A polyolefin (c2) content below this upper limit tends to result in better barrier properties.

[0054] The barrier resin layer (C) may contain optional components other than EVOH (c1), the above-mentioned polyvalent metal ions or salts containing the above-mentioned polyvalent metal ions, and polyolefin (c2), such as boron compounds, carboxylic acids, phosphorus compounds, metal ions other than the above-mentioned polyvalent metal ions, antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, heat stabilizers, and other resins other than EVOH (c1) and polyolefin (c2). The barrier resin layer (C) may contain two or more of these optional components.

[0055] Examples of boron compounds include boric acids such as orthoboric acid, metaboric acid, and tetraboric acid; boric acid esters such as triethyl borate and trimethyl borate; alkali metal salts or alkaline earth metal salts of the above boric acids, borates such as borax; and boron hydrides. The content of the boron compound in the barrier resin layer (C) is preferably 10 ppm to 1,000 ppm, and more preferably 50 ppm to 400 ppm. By setting the content of the boron compound within the above range, melt moldability, appearance, etc., are improved. The content of the boron compound is expressed in terms of elemental boron content.

[0056] Examples of carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, lactic acid, and their salts. Preferred carboxylic acids are those having four or fewer carbon atoms or saturated carboxylic acids, with acetic acid being more preferred. Furthermore, the carboxylic acids may also include carboxylic acid salts containing the polyvalent metal ions mentioned above.

[0057] Examples of phosphorus compounds include phosphates such as phosphoric acid and phosphorous acid. The phosphate may be in the form of monophosphate, dicphosphate, or tertiary phosphate. The cation species of the phosphate is not particularly limited, but alkali metal salts or alkaline earth metal salts are preferred, and among these, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, or dipotassium hydrogen phosphate are more preferred. The phosphorus compound content in the barrier resin layer (C) is preferably 1 ppm to 200 ppm, and more preferably 10 ppm to 100 ppm. By keeping the phosphorus compound content within the above range, thermal stability is improved and defects and discoloration during recycling are further suppressed. The phosphorus compound content is expressed in terms of phosphate root equivalent.

[0058] Examples of metal ions other than the polyvalent metal ions mentioned above include monovalent metal ions and other polyvalent metal ions, with monovalent metal ions being preferred. Among monovalent metal ions, alkali metal ions are preferred.

[0059] Examples of alkali metal ions include lithium ions, sodium ions, and potassium ions, with sodium ions or potassium ions being preferred from the viewpoint of industrial availability. Examples of alkali metal salts containing alkali metal ions include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, and metal complexes. Among these, aliphatic carboxylates or phosphates are preferred due to their availability, and specifically, sodium acetate, potassium acetate, sodium phosphate, or potassium phosphate are preferred. The alkali metal ion content in the barrier resin layer (C) is preferably 10 ppm to 1,000 ppm, and more preferably 100 ppm to 400 ppm. By keeping the alkali metal ion content within the above range, interlayer adhesion is improved, and discoloration during recycling is suppressed.

[0060] Examples of antioxidants include 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4'-thiobis(6-t-butylphenol), 2,2'-methylene-bis(4-methyl-6-t-butylphenol), and octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate.

[0061] Examples of UV absorbers include ethylene-2-cyano-3,3'-diphenyl acrylate, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, and 2-hydroxy-4-oxybenzophenone.

[0062] Examples of plasticizers include dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, and phosphate esters.

[0063] Examples of antistatic agents include pentaerythritol monostearate, sorbitan monopalmitate, sulfated polyolefins, polyethylene oxide, and polyethylene glycol (trade name: Carbowax).

[0064] Examples of lubricants include ethylenebisstearamide and butyl stearate.

[0065] Examples of colorants include carbon black, phthalocyanine, quinacridone, indoline, azo pigments, and red iron oxide.

[0066] Examples of fillers include glass fiber, wollastonite, calcium silicate, talc, and montmorillonite.

[0067] Examples of heat stabilizers include hindered phenol compounds and hindered amine compounds.

[0068] Other resins besides EVOH(c1) and polyolefin(c2) include, for example, polyamides and polyesters.

[0069] The barrier resin layer (C) may be an unstretched layer or a stretched layer. When the barrier resin layer (C) is a stretched layer, it can exhibit good water vapor barrier properties even when the barrier resin layer (C) is relatively thin.

[0070] The lower limit of the average thickness of the barrier resin layer (C) is preferably 0.2 μm, more preferably 0.3 μm, even more preferably 0.4 μm, and even more preferably 0.5 μm, 0.6 μm, 0.8 μm, or 1 μm, and may also be 2 μm. Having an average thickness of the barrier resin layer (C) above the above lower limit can further enhance barrier properties. The average thickness of the barrier resin layer (C) is preferably less than 30 μm, more preferably 20 μm or less, even more preferably 15 μm or less, and may also be 10 μm or less, 5 μm or less, 3 μm or less, or 2 μm or less. Having an average thickness of the barrier resin layer (C) below the above upper limit can suppress discoloration during recycling.

[0071] The barrier resin layer (C) may consist of a single layer or multiple layers.

[0072] (Adhesive resin layer (D)) The adhesive resin layer (D) mainly contains adhesive resin (d). The adhesive resin layer (D) adheres the barrier resin layer (C) and the moisture-proof resin layer (E).

[0073] The adhesive resin (d) is not particularly limited as long as it is an adhesive resin, and examples include acid-modified polyolefins (carboxylic acid-modified polyolefins, sulfonic acid-modified polyolefins, etc.) and epoxy-modified polyolefins. The adhesive resin (d) is preferably a thermoplastic resin. The adhesive resin (d) is preferably an acid-modified polyolefin (acid-modified polyethylene, acid-modified polypropylene, etc.), and more preferably acid-modified polyethylene. Furthermore, the adhesive resin (d) is also preferably a carboxylic acid-modified polyolefin, and more preferably carboxylic acid-modified polyethylene.

[0074] Carboxylic acid-modified polyolefins may be polyolefins having a carboxyl group or its anhydride group. Carboxylic acid-modified polyolefins (polyolefins having a carboxyl group or its anhydride group) can be obtained, for example, by chemically bonding an ethylenically unsaturated carboxylic acid or its anhydride to an unmodified polyolefin through an addition reaction, graft reaction, or the like.

[0075] Polyethylene is preferred as the unmodified polyolefin used in the production of carboxylic acid-modified polyolefins.

[0076] Examples of ethylenically unsaturated carboxylic acids and their anhydrides include monocarboxylic acids, monocarboxylic acid esters, dicarboxylic acids, dicarboxylic acid monoesters, dicarboxylic acid diesters, and dicarboxylic acid anhydrides. Specifically, examples include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, monomethyl maleic acid, monoethyl maleic acid, diethyl maleic acid, and monomethyl fumaric acid. Of these, dicarboxylic acid anhydrides such as maleic anhydride and itaconic anhydride are preferred, and maleic anhydride is more preferred. That is, the adhesive resin (d) is preferably a maleic anhydride-modified polyolefin, and more preferably a maleic anhydride-modified polyethylene.

[0077] Carboxylic acid-modified polyolefins are obtained by introducing an ethylenically unsaturated carboxylic acid or its anhydride into an unmodified polyolefin by an addition reaction or graft reaction in the presence of a solvent such as xylene and a catalyst such as a peroxide. The lower limit of the amount of carboxylic acid or its anhydride added or grafted (degree of modification) to the unmodified polyolefin is preferably 0.01% by mass, and more preferably 0.02% by mass, relative to the unmodified polyolefin. On the other hand, the upper limit of the above amount of addition or grafting (degree of modification) is preferably 15% by mass, and more preferably 10% by mass, relative to the unmodified polyolefin.

[0078] For acid-modified polyolefins such as carboxylic acid-modified polyolefins, the acid value is preferably 0.3 mg KOH / g or more and 5.0 mg KOH / g or less, and more preferably 1.0 mg KOH / g or more and 3.0 mg KOH / g or less.

[0079] The MFR (190°C, 2.160 kg load) of the adhesive resin (d) is preferably 0.5 g / 10 min to 12 g / 10 min, and more preferably 1.0 g / 10 min to 8.0 g / 10 min.

[0080] The adhesive resin (d) may be used alone or in combination of two or more types.

[0081] The content of the adhesive resin (d) in the adhesive resin layer (D) is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 97% by mass or more and 100% by mass or less. The adhesive resin layer (D) may also contain components other than the adhesive resin (d), such as antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, heat stabilizers, and other resins other than the adhesive resin (d).

[0082] The adhesive resin layer (D) may be an unstretched layer or a stretched layer.

[0083] The lower limit of the average thickness of the adhesive resin layer (D) is preferably 0.1 μm, more preferably 0.5 μm, even more preferably 1 μm, and may also be 2 μm. A minimum average thickness of the adhesive resin layer (D) above this lower limit ensures sufficient adhesion. The upper limit of the average thickness of the adhesive resin layer (D) is preferably 20 μm, more preferably 10 μm, even more preferably 5 μm, and may also be 3 μm or 2 μm. A minimum average thickness of the adhesive resin layer (D) above this upper limit helps to suppress defects and discoloration during recycling.

[0084] The adhesive resin layer (D) may consist of a single layer or multiple layers.

[0085] (Moisture-proof resin layer (E)) The moisture-proof resin layer (E) mainly contains polyethylene (e). Because the moisture-proof resin layer (E) mainly contains polyethylene (e), the multilayer structure of the present invention can exhibit sufficient moisture resistance. Furthermore, because the moisture-proof resin layer (E) mainly contains polyethylene (e), the multilayer structure of the present invention can form paper containers with sufficient strength, and can also suppress the occurrence of defects during recycling. The moisture-proof resin layer (E) may also be a heat-sealable layer for bonding moisture-proof resin layers (E) to each other, or to other layers by heat sealing. From the viewpoint of further increasing the strength of the resulting paper container, the moisture-proof resin layer (E) may be the outermost layer in the multilayer structure.

[0086] The type of polyethylene(e) is not particularly limited, and examples include high-density polyethylene, low-density polyethylene, and linear low-density polyethylene. Among these, linear low-density polyethylene, low-density polyethylene, or mixtures thereof are preferred. Linear low-density polyethylene is a resin obtained by polymerizing ethylene with an α-olefin having 3 or more carbon atoms. Examples of α-olefins having 3 or more carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and 4-methyl-1-pentene. Among these, linear low-density polyethylene is preferably obtained by polymerizing ethylene with an α-olefin having 6 or more carbon atoms, and more preferably obtained by polymerizing ethylene with an α-olefin having 8 or more carbon atoms. When the number of carbon atoms in the α-olefin copolymerized with ethylene is relatively large, various mechanical strengths such as puncture strength and tensile strength may be particularly improved. Furthermore, it is preferable to use a metallocene catalyst as the polymerization catalyst. Linear low-density polyethylene polymerized using a metallocene catalyst is produced by copolymerizing ethylene and α-olefin in the presence of a catalyst formed from a compound having at least one ligand with a cyclopentadienyl skeleton and a transition metal of Group 4 of the periodic table as the central metal atom (preferably a compound having zirconium as the central metal atom), an organoaluminum oxy compound, and various components added as needed. Linear low-density polyethylene polymerized using a metallocene catalyst has excellent melt-molding properties, and the resulting multilayer film has an excellent balance of heat resistance, flexibility, and mechanical strength. By using such polyethylene, the strength of the molded paper container can be further increased. One or more types of polyethylene(e) can be used.

[0087] For example, the upper limit of the density of polyethylene(e) is 0.96 g / cm³. 3 It can be made to be 0.940 g / cm³ 3 Preferably, 0.930 g / cm³ 3 This is more preferable. The lower limit of the density of polyethylene(e) is 0.880 g / cm³.3 Preferably, 0.890 g / cm³ 3 More preferably, 0.900 g / cm³ 3 Or 0.910 g / cm³ 3 This is also acceptable. By using polyethylene (e) with a relatively low density, the strength of the molded paper container can be increased.

[0088] For polyethylene(e), the MFR (at 190°C, with a load of 2.160 kg) is preferably 0.4 g / 10 min to 4.0 g / 10 min, and more preferably 0.8 g / 10 min to 2.0 g / 10 min.

[0089] The polyethylene(e) content in the moisture-proof resin layer (E) is preferably 80% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 97% to 100% by mass. The moisture-proof resin layer (E) may also contain components other than polyethylene(e), such as antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, heat stabilizers, and other resins other than polyethylene(e).

[0090] The moisture-proof resin layer (E) may be an unstretched layer or a stretched layer.

[0091] The lower limit of the average thickness of the moisture-proof resin layer (E) is preferably 1 μm, more preferably 5 μm, even more preferably 7 μm, even more preferably 10 μm, and may also be 15 μm. Having an average thickness of the moisture-proof resin layer (E) above the above lower limit allows for sufficient heat sealing, resulting in the formation of paper containers with higher strength. Furthermore, having an average thickness of the moisture-proof resin layer (E) above the above lower limit ensures sufficient moisture resistance. The upper limit of the average thickness of the moisture-proof resin layer (E) is preferably 200 μm, more preferably 100 μm, even more preferably 50 μm, and may also be 30 μm or 20 μm.

[0092] The moisture-proof resin layer (E) may consist of a single layer or multiple layers.

[0093] (Thermoplastic resin layer (X)) The multilayer structure of the present invention preferably further comprises a thermoplastic resin layer (X) interposed between the paper layer (A) and the vapor-deposited laminate (a laminate of an inorganic vapor-deposited layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E)). In other words, the multilayer structure of the present invention preferably has a layer configuration in which the paper layer (A) and the inorganic vapor-deposited layer (B) or the moisture-proof resin layer (E) are laminated via a thermoplastic resin layer (X). It may also be said that the paper layer (A) is laminated on one surface of the vapor-deposited laminate (a laminate of an inorganic vapor-deposited layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E)) via a thermoplastic resin layer (X). By having such a thermoplastic resin layer (X) in the multilayer structure, the adhesion between the paper layer (A) and the vapor-deposited laminate can be improved. Furthermore, because the paper layer (A) and the vapor-deposited laminate are bonded together by a thermoplastic resin layer (X), defects and discoloration during recycling can be further suppressed.

[0094] The thermoplastic resin layer (X) is mainly composed of a thermoplastic resin. The thermoplastic resin is not particularly limited and includes polyolefins, polystyrenes, polycarbonates, acrylic resins, and the adhesive resins mentioned above (such as acid-modified polyolefins). Among these, polyolefins or acid-modified polyolefins are preferred, polyolefins are more preferred, and polyethylene is even more preferred. By making the thermoplastic resin layer (X) mainly composed of such a thermoplastic resin, it is possible to suppress the occurrence of discoloration during recycling.

[0095] The thermoplastic resin content in the thermoplastic resin layer (X) is preferably 80% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 97% to 100% by mass. The thermoplastic resin layer (X) may also contain components other than the thermoplastic resin, such as antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, heat stabilizers, and other resins other than the thermoplastic resin.

[0096] The lower limit of the average thickness of the thermoplastic resin layer (X) is preferably 1 μm, more preferably 3 μm, even more preferably 5 μm, even more preferably 10 μm, and particularly preferably 15 μm. Having an average thickness of the thermoplastic resin layer (X) equal to or greater than the above lower limit improves the adhesion between the paper layer (A) and the vapor-deposited laminate. The upper limit of the average thickness of the thermoplastic resin layer (X) is preferably 100 μm, more preferably 50 μm, and may also be 30 μm.

[0097] The thermoplastic resin layer (X) is preferably an extruded resin layer. That is, the paper layer (A) and the vapor-deposited laminate are preferably laminated by sandwich lamination. The thermoplastic resin layer (X) may be an unstretched layer. The paper layer (A) and the vapor-deposited laminate may be laminated by other methods, such as dry lamination. In this case, the layer interposed between the paper layer (A) and the vapor-deposited laminate may be an adhesive layer other than the thermoplastic resin layer (X).

[0098] (Co-extruded film) In the multilayer structure of the present invention, the laminate of the barrier resin layer (C), adhesive resin layer (D), and moisture-proof resin layer (E) is preferably a co-extruded film. That is, the barrier resin layer (C), adhesive resin layer (D), and moisture-proof resin layer (E) are preferably formed by co-extrusion. This allows for a high level of balance between film properties such as barrier properties and flexibility, process passability, and economic efficiency. Furthermore, it is preferable that an inorganic vapor-deposited layer (B) is provided on the barrier resin layer (C) side of the co-extruded film. That is, in one preferred embodiment, the vapor-deposited laminate is one in which an inorganic vapor-deposited layer (B) is provided on the barrier resin layer (C) side of the co-extruded film. By using such a co-extruded film or vapor-deposited laminate, the productivity, barrier properties, etc., of the multilayer structure can be improved.

[0099] The lower limit of the average thickness of the co-extruded film described above is preferably 8 μm, more preferably 12 μm, and even more preferably 15 μm. An average thickness of the co-extruded film above this lower limit enhances barrier properties and the strength of the resulting paper container. The upper limit of the average thickness of the co-extruded film described above is preferably 120 μm, more preferably 80 μm, even more preferably 60 μm, and may also be 40 μm or 30 μm. An average thickness of the co-extruded film below this upper limit allows for the thinning of the multilayer structure. Note that the average thickness of the co-extruded film described above is equal to the sum of the average thicknesses of each layer of the co-extruded film.

[0100] From the viewpoint of barrier properties, recyclability, and economic efficiency, the average thickness of the barrier resin layer (C) in the co-extruded film is preferably 0.2 μm or more and less than 30 μm. It is also preferable that the ratio of the average thickness of the barrier resin layer (C) to the average thickness of the co-extruded film is less than 25%. More preferably, the ratio of the average thickness of the barrier resin layer (C) to the average thickness of the co-extruded film is less than 20%, and even more preferably less than 15%. The ratio of the average thickness of the barrier resin layer (C) to the average thickness of the co-extruded film may be, for example, 1% or more, 3% or more, 5% or more, or 7% or more.

[0101] The co-extruded film described above may be a substantially unstretched film, or a uniaxially or biaxially stretched film. When it is an unstretched film, the resulting paper container tends to have higher strength. When it is a stretched film, the barrier properties tend to be higher.

[0102] The above co-extruded film is preferably stretched by at least 3 times or more but less than 12 times in at least one axial direction, and more preferably stretched by at least 4 times or more but less than 10 times in at least one axial direction. Furthermore, the above co-extruded film is also preferably stretched by at least 3 times or more but less than 12 times in each of two axial directions, and more preferably stretched by at least 3.5 times or more but less than 10 times in each of two axial directions. By stretching the above co-extruded film at such magnifications, it is possible to further enhance the barrier properties of the multilayer structure.

[0103] (Moisture-proof resin layer (F)) The multilayer structure of the present invention preferably further comprises a moisture-proof resin layer (F) separate from the moisture-proof resin layer (E) described above. The moisture-proof resin layer (F) mainly comprises polyethylene (f). By further comprising such a moisture-proof resin layer (E) in the multilayer structure, moisture resistance, the strength of the resulting paper container, etc., can be further enhanced, and high water vapor barrier properties can be better maintained even when storing acidic beverages, etc., under high temperature and high humidity conditions. The moisture-proof resin layer (F) may also be a heat-sealable layer for bonding moisture-proof resin layers (F) to each other, or to the moisture-proof resin layer (F) to other layers by heat sealing. From the viewpoint of further enhancing the strength of the resulting paper container and better maintaining high water vapor barrier properties when storing acidic beverages, etc., under high temperature and high humidity conditions, the moisture-proof resin layer (F) may be the outermost layer in the multilayer structure. Furthermore, by making polyethylene (f) the main component of the moisture-proof resin layer (F), defects and discoloration during recycling are suppressed. In this specification, the moisture-proof resin layer provided on the side of the paper layer (A) opposite to the side where the inorganic vapor-deposited layer (B), etc., is provided (hereinafter also referred to as the "exposed surface side") shall be the moisture-proof resin layer (F). If there are multiple moisture-proof resin layers (F), a part of the moisture-proof resin layer (F) may be referred to as the moisture-proof resin layer (F'). Furthermore, any moisture-proof resin layer different from the moisture-proof resin layer (E) that constitutes the co-extruded film shall be the moisture-proof resin layer (F). On the other hand, if there are multiple moisture-proof resin layers that constitute the co-extruded film, all of these moisture-proof resin layers shall be the moisture-proof resin layer (E). If a multilayer structure does not have the co-extruded film and has multiple moisture-proof resin layers (except in the case of the moisture-proof resin layer on the exposed surface side of the paper layer (A)), all of these moisture-proof resin layers shall be the moisture-proof resin layer (E).

[0104] The types, physical properties, specific forms, and preferred forms of polyethylene(f) are the same as those of polyethylene(e) described above, except for MFR. For example, the density of polyethylene(f) is 0.880 g / cm³. 3 More than 0.940g / cm 3The following is preferable. Furthermore, polyethylene(f) is preferably linear low-density polyethylene, low-density polyethylene, or a mixture thereof. The MFR (190°C, 2.160 kg load) of polyethylene(f) is preferably 0.4 g / 10 min to 30.0 g / 10 min, more preferably 0.8 g / 10 min to 20.0 g / 10 min, and even more preferably 1.0 g / 10 min to 10.0 g / 10 min.

[0105] The polyethylene (f) content in the moisture-proof resin layer (F) is preferably 80% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 97% to 100% by mass. The moisture-proof resin layer (F) may also contain other components besides polyethylene (f), such as antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, heat stabilizers, and other resins other than polyethylene (f).

[0106] The moisture-proof resin layer (F) may be an unstretched layer or an stretched layer. In one embodiment, it is preferable that the moisture-proof resin layer (F) is an unstretched layer.

[0107] The lower limit of the average thickness of one layer of the moisture-proof resin layer (F) is preferably 1 μm, more preferably 5 μm, even more preferably 7 μm, even more preferably 10 μm, and may also be 15 μm, 20 μm, or 30 μm. Having an average thickness of the moisture-proof resin layer (F) above the above lower limit allows for sufficient heat sealing, resulting in the formation of a paper container with higher strength. Furthermore, having an average thickness of the moisture-proof resin layer (F) above the above lower limit ensures sufficient moisture resistance. The upper limit of the average thickness of one layer of the moisture-proof resin layer (F) is preferably 200 μm, more preferably 100 μm, even more preferably 50 μm, and may also be 40 μm, 30 μm, or 20 μm.

[0108] If there are multiple moisture-proof resin layers (F), the composition, thickness, etc. of the multiple moisture-proof resin layers (F) may be the same or different. Similarly, the composition, thickness, etc. of a moisture-proof resin layer (F') which is part of the multiple moisture-proof resin layers (F) and the other moisture-proof resin layers (F) may be the same or different.

[0109] In the multilayer structure of the present invention, the position of the moisture-proof resin layer (F) is not particularly limited. However, it is preferable that the moisture-proof resin layer (F) is directly laminated to the co-extruded film. In the case of such a multilayer structure, in addition to being able to further increase strength and the like, the occurrence of defects and discoloration during recycling tends to be further reduced due to the increased proportion of polyethylene-based resin used. In the multilayer structure of this embodiment, for example, the moisture-proof resin layer (F) can be laminated by directly melt-extruding polyethylene (f) onto the surface of the moisture-proof resin layer (E) of the co-extruded film.

[0110] In addition, the moisture-proof resin layer (F) may be laminated on the surface of the moisture-proof resin layer (E) of the co-extruded film via another layer (e.g., an adhesive resin layer, another adhesive layer, etc.). In such a multilayer structure, the moisture-proof resin layer (F) can be laminated by dry lamination, sandwich lamination, etc., of the co-extruded film and a single-layer film of the moisture-proof resin layer (F).

[0111] Furthermore, the moisture-proof resin layer (F) may be laminated directly or via another layer on the side of the paper layer (A) opposite to the inorganic vapor-deposited layer (B). In such a multilayer structure, the moisture-proof resin layer (F) can be laminated by melt extrusion of polyethylene (f) onto the surface of the paper layer (A), dry lamination of the paper layer (A) or the multilayer structure containing the paper layer (A) with a single-layer film of the moisture-proof resin layer (F), sandwich lamination, etc.

[0112] (Other layers) The multilayer structure of the present invention may have layers other than the paper layer (A), inorganic vapor deposition layer (B), barrier resin layer (C), adhesive resin layer (D), moisture-proof resin layer (E), moisture-proof resin layer (F), and thermoplastic resin layer (X) described above. Other layers that the multilayer structure of the present invention may have include other thermoplastic resin layers, adhesive layers, printing layers, etc. However, it is preferable that the multilayer structure does not have layers mainly composed of resin with a melting point of 200°C or higher and metal layers with an average thickness of 1 μm or higher. When the multilayer structure does not have layers mainly composed of resin with a melting point of 200°C or higher (for example, layers mainly composed of polyethylene terephthalate) and metal layers with an average thickness of 1 μm or higher (for example, metal foil layers with an average thickness of 1 μm or higher), defects are less likely to occur in recycled products during melt molding for recycling.

[0113] Furthermore, it is preferable that the multilayer structure of the present invention does not have an adhesive layer made of a curing type adhesive. By not having such an adhesive layer, drawbacks such as those during recycling are further suppressed.

[0114] (Layer composition, etc.) The multilayer structure of the present invention comprises a paper layer (A), an inorganic vapor-deposited layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E). Furthermore, the inorganic vapor-deposited layer (B), the barrier resin layer (C), the adhesive resin layer (D), and the moisture-proof resin layer (E) are all directly laminated in this order. Paper containers formed from this multilayer structure can maintain high gas barrier properties, especially when containing acidic beverages such as orange juice under high temperature and high humidity conditions, making them suitable for long-term storage of acidic beverages.

[0115] In the multilayer structure of the present invention, it is preferable to have a paper layer (A), an inorganic vapor-deposited layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E) in this order. In the case of a multilayer structure with such a layering order, the paper container is usually formed such that the paper layer (A) is on the outside and the moisture-proof resin layer (E) is on the inside (contents side), with the inorganic vapor-deposited layer (B) as the reference. In this case, the penetration of acidic components contained in the contents into the inorganic vapor-deposited layer (B) is particularly effectively blocked by the barrier resin layer (C) which has a predetermined EVOH (c1) as its main component. Therefore, a multilayer structure having a paper layer (A), an inorganic vapor-deposited layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E) in this order can maintain particularly high water vapor barrier properties even when storing acidic beverages, etc., under high temperature and high humidity conditions. In a multilayer structure having a paper layer (A), an inorganic vapor deposition layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E) in this order, other layers may exist between the paper layer (A) and the inorganic vapor deposition layer (B).

[0116] The multilayer structure of the present invention may have a paper layer (A), a moisture-proof resin layer (E), an adhesive resin layer (D), a barrier resin layer (C), and an inorganic vapor-deposited layer (B) in this order.

[0117] The paper layer (A) and the inorganic vapor-deposited layer (B) or moisture-proof resin layer (E) constituting the vapor-deposited laminate (a laminate of an inorganic vapor-deposited layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E)) may be directly laminated, but are usually laminated via other layers. Examples of layers interposed between the paper layer (A) and the vapor-deposited laminate include a thermoplastic resin layer (X) or other adhesive layers. Furthermore, the multilayer structure may further have a moisture-proof resin layer (F).

[0118] The multilayer structure of the present invention may have a paper layer (A) on one of its surfaces. That is, in the multilayer structure, one of the outermost layers may be a paper layer (A). In this case, when a paper container is formed from the multilayer structure, it is preferable that the surface with the exposed paper layer (A) becomes the outer surface. When the multilayer structure has a paper layer (A) on its surface, it becomes easier to detect the paper, specifically by measuring the infrared spectrum using, for example, total internal reflection. For this reason, the paper recycling rate can be increased in such a multilayer structure.

[0119] The multilayer structure of the present invention may also preferably have a moisture-proof resin layer (E) or a moisture-proof resin layer (F) on at least one surface. That is, in the multilayer structure, it is preferable that at least one of the outermost layers is a moisture-proof resin layer (E) or a moisture-proof resin layer (F). In one embodiment, when a paper container is formed from the multilayer structure, it is preferable that the surface on which the moisture-proof resin layer (E) or moisture-proof resin layer (F) is exposed becomes the inner surface. When the multilayer structure has a moisture-proof resin layer (E) or a moisture-proof resin layer (F) on its surface, these layers are bonded by heat sealing, and a paper container with higher strength can be formed. In another embodiment, when a paper container is formed from the multilayer structure, it is also preferable that the surface on which the moisture-proof resin layer (E) or moisture-proof resin layer (F) is exposed becomes the outer surface. In such a case, since the moisture absorption of the paper layer (A) when left under high temperature and high humidity is suppressed by the moisture-proof resin layer (E) or moisture-proof resin layer (F), a high water vapor barrier property can be maintained particularly well when storing acidic beverages, etc., under high temperature and high humidity. The multilayer structure may also preferably have a moisture-proof resin layer (E) or a moisture-proof resin layer (F) on both surfaces. That is, in the multilayer structure, it is preferable that the outermost layer on both the outer and inner surfaces when a paper container is formed is a moisture-proof resin layer (E) or a moisture-proof resin layer (F).

[0120] Furthermore, if the multilayer structure of the present invention has a moisture-proof resin layer (E) or a moisture-proof resin layer (F) on its surface, it becomes easier to detect polyethylene, specifically by measuring the infrared spectrum using, for example, total internal reflection. Therefore, the recycling rate of polyethylene can be increased in such a multilayer structure.

[0121] The multilayer structure of the present invention may have a paper layer (A) on one surface and a moisture-proof resin layer (E) or a moisture-proof resin layer (F) on the other surface. In such a case, when a paper container is formed from the multilayer structure, it is preferable that the surface with the paper layer (A) exposed becomes the outer surface, and the surface with the moisture-proof resin layer (E) or moisture-proof resin layer (F) exposed becomes the inner surface.

[0122] The following are examples of specific layer configurations for the multilayer structure of the present invention. However, the layer configuration of the multilayer structure is not limited to the following configurations. In the following examples of layer configurations, " / " indicates that the layers are directly laminated. Also, "Ad" indicates any adhesive layer. The adhesive layer represented by Ad may be a layer mainly composed of an adhesive resin (a layer made of the same material as the adhesive resin layer (D)). (1) A / X / B / C / D / E (2) A / Ad / B / C / D / E (3) A / X / B / C / D / E / F (4) A / X / B / C / D / E / Ad / F (5) F / A / X / B / C / D / E (6) F / A / Ad / B / C / D / E (7) F / A / X / B / C / D / E / F' (8) F / A / X / B / C / D / E / Ad / F' (9) F / Ad / A / X / B / C / D / E (10) F / Ad / A / Ad / B / C / D / E (11) F / Ad / A / X / B / C / D / E / F' (12) F / Ad / A / X / B / C / D / E / Ad / F' (13) A / X / E / D / C / B / F (14) A / X / E / D / C / B / Ad / F (15) A / Ad / E / D / C / B / F (16) A / Ad / E / D / C / B / Ad / F (17) F / A / X / E / D / C / B / F' (18) F / A / X / E / D / C / B / Ad / F' (19)F / Ad / A / X / E / D / C / B / F' (20)F / Ad / A / X / E / D / C / B / Ad / F' (21) F / A / Ad / E / D / C / B / F' (22) F / A / Ad / E / D / C / B / Ad / F' (23) F / Ad / A / Ad / E / D / C / B / F' (24) F / Ad / A / Ad / E / D / C / B / Ad / F'

[0123] The lower limit of the mass ratio of the paper layer (A) in the multilayer structure of the present invention may be, for example, 0.40 or 0.50 of the total mass ratio of the multilayer structure, but 0.60 is preferred, 0.70 is more preferred, and 0.75 is even more preferred. By having a mass ratio of paper layer (A) of 0.60 or higher than the above lower limit, the strength of the molded paper container can be increased. On the other hand, the upper limit of the mass ratio of paper layer (A) is 0.95, 0.90 is more preferred, and 0.86 is even more preferred. By having a mass ratio of paper layer (A) of 0.60 or higher than the above lower limit, the barrier properties and the strength of the molded paper container can be increased.

[0124] The lower limit of the total average thickness ratio of the polyethylene resin-based layer in the portion of the multilayer structure of the present invention other than the paper layer (A) is preferably 0.75, more preferably 0.80, even more preferably 0.85, and even more preferably 0.90. By increasing the total average thickness ratio of the polyethylene resin-based layer in the portion of the multilayer structure other than the paper layer (A), it is possible to further suppress the occurrence of discoloration during recycling. The upper limit of the total average thickness ratio of the polyethylene resin-based layer in the portion of the structure other than the paper layer (A) is preferably 0.995, more preferably 0.99, and may also be 0.98. Examples of layers mainly composed of polyethylene resin include a moisture-proof resin layer (E), a moisture-proof resin layer (F), an adhesive resin layer (D) when the adhesive resin (d) is, for example, acid-modified polyethylene, and a thermoplastic resin layer (X) when the main component is polyethylene resin (polyethylene or modified polyethylene).

[0125] The lower limit of the total average thickness ratio of the layers mainly composed of resin having ethylene units in the parts of the multilayer structure of the present invention other than the paper layer (A) is preferably 0.95, more preferably 0.98, and even more preferably 0.99. By increasing the total average thickness ratio of the layers mainly composed of resin having ethylene units in the parts other than the paper layer (A), compatibility during recycling is improved, and the occurrence of defects and discoloration can be further suppressed. The upper limit of the total average thickness ratio of the layers mainly composed of resin having ethylene units in the parts other than the paper layer (A) may be, for example, 0.9999. Examples of layers mainly composed of resin having ethylene units include the polyethylene resin layer mentioned above, as well as a barrier resin layer (C).

[0126] The lower limit of the total average thickness ratio of layers mainly composed of thermoplastic resin with a melting point of less than 200°C in the parts of the multilayer structure of the present invention other than the paper layer (A) is preferably 0.95, more preferably 0.98, and even more preferably 0.99. By increasing the total average thickness ratio of thermoplastic resin with a melting point of less than 200°C in the parts other than the paper layer (A), the melt moldability during recycling is improved, and the occurrence of defects and discoloration can be further suppressed. The upper limit of the total average thickness ratio of layers mainly composed of thermoplastic resin with a melting point of less than 200°C in the parts other than the paper layer (A) may be, for example, 0.9999.

[0127] The lower limit of the average thickness of the multilayer structure of the present invention (average thickness of the entire multilayer structure) is preferably 150 μm, more preferably 200 μm, even more preferably 250 μm, and even more preferably greater than 300 μm. Having an average thickness of the multilayer structure equal to or greater than the above lower limit can increase the strength of the molded paper container. On the other hand, the upper limit of the average thickness of the multilayer structure is preferably 1,000 μm, but may also be 700 μm or 500 μm. Having an average thickness of the multilayer structure equal to or less than the above upper limit can improve moldability.

[0128] In the multilayer structure of the present invention, the water vapor transmission rate measured in accordance with JIS K 7129-2 (infrared sensor method; 2019) under conditions of a temperature of 40°C, humidity of 90%RH on the water vapor supply side, and humidity of 0%RH on the carrier gas side is 2.0 g / (m³). 2 It is preferable that it be less than 1.0 g / (m²) 2 It is more preferable that it be less than 0.5 g / (m 2 It is even more preferable that it be less than 0.3 g / (m²) 2 It is particularly preferable that the water vapor permeation rate is less than the above upper limit. A water vapor permeation rate below the above upper limit makes it particularly suitable for use as a molding material for paper containers, etc. On the other hand, the lower limit of this oxygen permeation rate is 0.01 g / (m³). 2 It may also be 0.1g / (m 2 (day) is also acceptable.

[0129] The multilayer structure of the present invention can be crushed for reuse, separated into a paper layer (A) and a portion other than the paper layer (A), and the portion other than the paper layer (A) can be used as a melt molding material. By using the portion other than the paper layer (A) of the multilayer structure as a melt molding material, a melt-molded product (recycled product) with fewer defects can be obtained. The portion other than the paper layer (A) of the multilayer structure can be used in combination with other melt molding materials (other recycled resins, unused resins, etc.). The separated paper layer (A) can also be reused.

[0130] The method for manufacturing the multilayer structure of the present invention is not particularly limited. For example, (1) a co-extruded film of a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E) is produced by co-extrusion. (2) A vapor-deposited laminate is produced by providing an inorganic vapor-deposited layer (B) on the side of the co-extruded film facing the barrier resin layer (C). (3) A multilayer structure is obtained by laminating the paper layer (A), which is the paper layer, and the vapor-deposited laminate using known means such as sandwich lamination or dry lamination, such that the paper layer (A) and the inorganic vapor-deposited layer (B) or moisture-proof resin layer (E) face each other. If the multilayer structure of the present invention further comprises a moisture-proof resin layer (F), the moisture-proof resin layer (F) can be provided by known methods such as melt extrusion or dry lamination.

[0131] Alternatively, for example, a vapor-deposited laminate may be produced by first providing an inorganic vapor-deposited layer (B) on a single-layer film of the barrier resin layer (C), and then laminating an adhesive resin layer (D) and a moisture-proof resin layer (E). Or, a two-layer film of the inorganic vapor-deposited layer (B) and the barrier resin layer (C) may be bonded to a paper layer, and then laminating an adhesive resin layer (D) and a moisture-proof resin layer (E).

[0132] The multilayer structure of the present invention is suitably used as a molding material for paper containers. The use of the paper container is not particularly limited and may be a container for solids such as food, but it is preferably a container for liquids. The multilayer structure may also be used for purposes other than as a molding material for paper containers.

[0133] <Liquid paper containers> The liquid paper container of the present invention comprises the multilayer structure of the present invention. The liquid paper container may be a paper container formed by molding the multilayer structure. Because the paper container has excellent resistance to contents, it is possible to maintain high gas barrier properties even when storing acidic beverages such as orange juice under high temperature and high humidity conditions, making it suitable for long-term storage of acidic beverages. Furthermore, the multilayer structure used in the liquid paper container has high processing stability during film formation, and the occurrence of defects during recycling is suppressed. The liquid paper container is suitably used as a container for various liquids other than food, such as beverages such as milk and juice, liquid foods such as soup, alcoholic beverages such as sake and shochu, and in particular, it can be suitably used when storing liquids such as acidic beverages with a pH of 2 to 6 under high temperature and high humidity conditions for a long period of time.

[0134] The liquid paper container of the present invention is formed by folding the multilayer structure of the present invention into, for example, a box shape and bonding the overlapping portions by heat sealing or the like. In the liquid paper container, it is preferable that the paper layer (A) is located on the outer surface. In the liquid paper container, it is also preferable that the moisture-proof resin layer (E) or moisture-proof resin layer (F) is located on the outer surface. Furthermore, in the liquid paper container, it is also preferable that the moisture-proof resin layer (E) or moisture-proof resin layer (F) is located on the inner surface.

[0135] The shape of the liquid paper container of the present invention is not limited to a box shape, but may be other shapes (e.g., a bag shape). The liquid paper container may be bonded by a method other than heat sealing, and may have parts bonded by heat sealing and parts bonded by other methods. Furthermore, the liquid paper container may further have components other than the multilayer structure of the present invention.

[0136] <Product> The product of the present invention is a liquid paper container of the present invention containing an acidic liquid with a pH of 2 to 6. Examples of this acidic liquid include acidic beverages such as orange juice, apple juice, and sports drinks, alcoholic beverages such as wine and sake, and coffee. The pH of the acidic liquid may be 3 to 5. [Examples]

[0137] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0138] [Example 1] (1) Preparation of EVOH(c1)-containing resin composition for barrier resin layer (C) EVOH(c1-1) (ethylene unit content 27 mol%, degree of saponification 99.99 mol%, MFR (190℃, 2.160 kg load) 1.6 g / 10 min, contains sodium acetate 220 ppm in sodium ion equivalent, phosphate ions 30 ppm in phosphate root equivalent, boric acid 150 ppm in boron element equivalent, no polyvalent metal ions) 100 parts by mass and polyolefin(c2-1) (EVA saponified product (Tosoh Corporation "Mersen (trademark) H-6822X", ethylene unit content 94 mol%, degree of saponification 9 Two parts by mass of 2 mol% of a resin (MFR (190°C, 2.160 kg load) 190 g / 10 min, number average molecular weight (Mn) 16800) and magnesium stearate (Mg-St) were melt-kneaded to obtain resin composition pellets for the barrier resin layer (C) with a magnesium ion content of 1 ppm. The extruder used for melt-kneading was a twin-screw extruder with D (mm) = 25 and a fully meshed co-direction screw with L / D = 25. The resin temperature was set to 220°C.

[0139] (2) Preparation of the adhesive resin (d) containing resin composition for the adhesive resin layer (D) Admer® NF518, a maleic anhydride-modified polyethylene manufactured by Mitsui Chemicals, Inc. (MFR (190℃, 2.160kg load) 3.1g / 10min, density 0.91g / cm³) 3A solution with an acid value of 1.8 mg KOH / g was used as the adhesive resin (d-1). Pellets of this adhesive resin (d-1) were used as resin composition pellets for the adhesive resin layer (D).

[0140] (3) Preparation of polyethylene(e)-containing resin composition for moisture-proof resin layer (E) DOW's low-density polyethylene (LDPE) "INNATE (trademark) TF80" (MFR (190℃, 2.160kg load) 1.6g / 10min, density 0.926g / cm³) 3 The pellets of ) were made of polyethylene (e-1). These polyethylene (e-1) pellets were used as resin composition pellets for the moisture-proof resin layer (E).

[0141] (4) Preparation of co-extruded film Using the resin composition pellets described in (1) to (3) above, co-extruded films with a layer thickness and layer structure of C / D / E = 10 μm / 10 μm / 80 μm = EVOH10 / tie10 / PE80 were fabricated using a co-extrusion film manufacturing facility. These films were then stretched five times in the longitudinal direction to produce stretched co-extruded films with a layer thickness of 2 μm / 2 μm / 16 μm = EVOH2 / tie2 / PE16. "tie" represents the adhesive resin. The average thickness of the layers is also simply called the layer thickness. All extruders were single-screw extruders with D (mm) = 30, and full-flight screws with L / D = 28 and a compression ratio of 3.0 were used. A 350 mm wide feed block laminated T-die was used as the die. The temperature conditions at this time are shown below. Extrusion temperature of barrier resin layer (C): Feed unit / compression unit / metering unit / adapter = 175℃ / 220℃ / 220℃ / 220℃ Extrusion temperature of adhesive resin layer (D): Feed unit / Compression unit / Measuring unit / Adapter = 175℃ / 220℃ / 220℃ / 220℃ Extrusion temperature of moisture-proof resin layer (E): Feed unit / compression unit / metering unit / adapter = 175℃ / 220℃ / 220℃ / 220℃ Die temperature: 220℃ Cooling roll temperature: 80℃

[0142] (5) Fabrication of vapor-deposited laminates A 50 nm thick aluminum metal vapor-deposited layer (inorganic vapor-deposited layer (B)) was laminated onto the surface of the barrier resin layer (C) of the co-extruded film obtained in (4) above by a known vacuum deposition method, and a vapor-deposited laminate having a layer thickness and layer structure of B / C / D / E = 50 nm / 2 μm / 2 μm / 16 μm = Al (50 nm) / EVOH2 / tie2 / PE16 was fabricated.

[0143] (6) Fabrication of multilayer structures The paper layer (A) has a basis weight of 250 g / m². 2 White cardboard was prepared. In addition, as the resin for extrusion lamination (thermoplastic resin), linear low-density polyethylene (LLDPE) "LUMITAC(trademark) BL 600K" manufactured by Tosoh Corporation (MFR (190℃, 2.160kg load) 21g / 10min, density 0.898g / cm³) was used. 3 I prepared ). The above white cardboard is fed from the first paper feed section of the extrusion laminating equipment, and the vapor-deposited laminate obtained in (5) above is fed from the second paper feed section. Between them, the above linear low-density polyethylene is extruded at 300°C to laminate with a linear low-density polyethylene layer (thermoplastic resin layer (X)) having an average thickness of 20 μm, with A / X / B / C / D / E = 250 g / m 2 A multilayer structure was created with layer thicknesses and layer configurations of / 20μm / 50nm / 2μm / 2μm / 16μm = paper / PE20 / Al(50nm) / EVOH2 / tie2 / PE16. Furthermore, on the exposed surface of the paper layer (A) of the multilayer structure, a moisture-proof resin layer (F) of low-density polyethylene (LDPE) "INNATE(trademark) TF80" manufactured by DOW Corporation was applied (MFR (190℃, 2.160kg load) 1.6g / 10min, density 0.926g / cm³). 3 (f-1) is extruded at 300°C to laminate a low-density polyethylene layer with an average thickness of 15 μm, and on the exposed surface of the moisture-proof resin layer (E), DOW's low-density polyethylene (LDPE) "INNATE (trademark) TF80" (MFR (190°C, 2.160 kg load) 1.6 g / 10 min, density 0.926 g / cm³) is used as the moisture-proof resin layer (F'). 3 The multilayer structure of Example 1 was fabricated by extruding (f-1) at 300°C to laminate low-density polyethylene layers with an average thickness of 30 μm.

[0144] (7) Manufacturing of paper containers Two square-sized (150mm x 150mm) pieces of the multilayer structure obtained in (6) above were cut out, and the moisture-proof resin layer (F') sides were overlapped and the three sides were heat-sealed to produce a three-sided bag. Using the obtained three-sided bag, a container (15cm x 15cm) was formed at a sheet temperature of 180°C. 60g of pH 4.0 orange juice was filled into the obtained three-sided bag, and the opening was heat-sealed at 180°C to produce the paper container (product) of Example 1 with the contents filled.

[0145] Furthermore, the resins constituting the barrier resin layer (C), adhesive resin layer (D), moisture-proof resin layer (E), and thermoplastic resin layer (X) in the obtained multilayer structure all have a predetermined MFR at 190°C. Therefore, it is clear that the melting points of these resins are below 200°C. The same applies to the other examples described later.

[0146] (8) Evaluation of thickness variations in co-extruded films The co-extruded film obtained in (4) above was cut out, and the thickness of the center of the cut film in the TD direction (perpendicular to the take-up direction of the film during film formation; width direction) was measured 2m in the MD direction (take-up direction of the film during molding; length direction) using a continuous thickness gauge to evaluate the thickness unevenness. Points were taken at 25mm intervals, and the standard deviation (μm) was calculated to evaluate the thickness unevenness according to the following criteria. The results are shown in Table 2. A: 3.0μm or less B: More than 3.0μm and less than 5.0μm C: More than 5.0μm

[0147] (9) Measurement of water vapor transmission rate (WVTR) of multilayer structures For the multilayer structure obtained in (6) above, the water vapor transmission rate was measured with one side (the side closer to the paper layer (A)) as the water vapor supply side and the other as the carrier gas side. Specifically, using a water vapor transmission rate measuring device (MOCON PERMATRAN W3 / 33 manufactured by Modern Control Co., Ltd.), the water vapor transmission rate (unit: g / m³) was measured in accordance with JIS K7129-2 (infrared sensor method; 2019) under conditions of a temperature of 40°C, humidity of 90%RH on the water vapor supply side, and humidity of 0%RH on the carrier gas side. 2 The daytime temperature (·day) was measured and evaluated according to the following criteria. Nitrogen gas was used as the carrier gas. The results are shown in Table 2. Judgment criteria A: 0.3g / (m 2 Less than (day) B: 0.3g / (m 2 ·day) or more 0.5g / (m 2 Less than (day) C: 0.5g / (m 2 ·day) or more 1.0g / (m 2 Less than (day) D: 1.0g / (m 2 ·day) or more 2.0g / (m 2 Less than (day) E: 2.0g / (m 2 (day) or more

[0148] (10) Measurement of the water vapor transmission rate (WVTR after storage test) of the paper container containing the contents after the storage test. The paper containers obtained in (7) above were stored at 43°C and 78%RH for 90 days. After that, they were opened, the orange juice was removed, and the containers were washed with water. After drying overnight, the water vapor transmission rate was measured with one side (the side closer to the paper layer (A)) as the water vapor supply side and the other as the carrier gas side. Specifically, a water vapor transmission rate measuring device (MOCON PERMATRAN W3 / 33, manufactured by Modern Control Co., Ltd.) was used, and the water vapor transmission rate (unit: g / m³) was measured in accordance with JIS K7129-2 (infrared sensor method; 2019) under conditions of 40°C, 90%RH humidity on the water vapor supply side, and 0%RH humidity on the carrier gas side. 2The water vapor permeability rate (WVTR) of multilayer structures was measured and evaluated using the same criteria as described in "(9) Measurement of Water Vapor Permeability Rate (WVTR) of Multilayer Structures" above. Nitrogen gas was used as the carrier gas. The results are shown in Table 2.

[0149] (11) Evaluation of Dai Build Up The co-extruded film obtained in (4) above was prepared continuously for 6 hours, and the die build-up that occurred near the T-die lip on the layer (C) side was visually evaluated and assessed according to the following criteria. The results are shown in Table 2. A: No die buildup was observed across the entire width even after 6 hours of operation. B: A slight buildup of the die was observed after 6 hours of operation. C: Die buildup was observed 4 hours after operation, and an increase in die buildup was observed thereafter. D: Die buildup was observed 2 hours after operation, and an increase in die buildup was observed thereafter. E: Die buildup was observed 1 hour after operation, and an increase in die buildup was observed thereafter.

[0150] (12) Evaluation of the recyclability of parts other than the paper layer separated from the multilayer structure. The multilayer structure obtained in (6) above was crushed to a size of 4 mm square or less, and stirred in a 90°C sodium hydroxide aqueous solution (1 mol / L) for 30 minutes to remove the paper layer (A) from the multilayer structure. The portion consisting of the parts other than the paper layer (A) that were suspended in the aqueous solution was recovered, washed with room temperature water, and dried at 60°C for 24 hours. This recovered material was mixed with low-density polyethylene resin (LDPE) "Novatec (trademark) LD LJ400" manufactured by Nippon Polyethylene Co., Ltd. (MFR (190°C, 2.160 kg load) 1.5 g / 10 min, density 0.921 g / cm³). 3A single-layer film with a thickness of 50 μm was obtained by blending the two materials in a mass ratio (recovered material / low-density polyethylene resin) of 40 / 60 and performing single-layer film formation under the extrusion conditions shown below. As a control, a single-layer film with a thickness of 50 μm was similarly obtained using only the low-density polyethylene resin. The extruder was a single-screw extruder with D (mm) = 20, and a full-flight screw with L / D = 20 and a compression ratio of 3.5 was used. A 300 mm wide T-die was used as the die. The thickness of the single-layer film was adjusted by appropriately changing the screw rotation speed and the take-up roll speed. The temperature conditions at this time are shown below. Extrusion temperature: Feed unit / Compression unit / Measuring unit / Adapter = 175℃ / 220℃ / 220℃ / 220℃ Die temperature: 220℃ Cooling roll temperature: 80℃ The resulting single-layer films were visually evaluated for coloration and defects, and evaluated according to the following criteria. The results are shown in Table 2. Coloring judgment: Criteria A: Compared to the control, the degree of hue change was smaller. B: Mild discoloration was observed compared to the control. C: Moderate discoloration was observed compared to the control group. D: Significant discoloration was observed compared to the control group. E: Compared to the control group, significant discoloration was observed, along with uneven coloration. Criteria for determining defects: A: The amount of substance remained almost unchanged compared to the control group. B: Compared to the control, there was a slightly larger quantity of small particles. C: Compared to the control group, there was a greater quantity of small particles. D: Compared to the control group, there was a greater quantity of large objects. E: Compared to the control group, the amount of large particles was significantly higher.

[0151] [Example 2] Resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that the average thickness of the aluminum metal vapor-deposited layer was changed to 100 nm. Various measurements and evaluations were then performed. The results are shown in Table 2.

[0152] [Example 3] Resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that the aluminum metal vapor-deposited layer was replaced with an alumina (AlOx) vapor-deposited layer. Various measurements and evaluations were then performed. The results are shown in Table 2.

[0153] [Example 4] Resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that the aluminum metal vapor-deposited layer was replaced with a silica (SiOx) vapor-deposited layer. Various measurements and evaluations were then performed. The results are shown in Table 2.

[0154] [Examples 5-7] Except for changing the amount of magnesium stearate kneaded with EVOH(c1-1) and polyolefin(c2-1) in terms of magnesium (Mg) ions as shown in Table 1, resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0155] [Example 8] Resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that EVOH(c1-2) (ethylene unit content 24 mol%, degree of saponification 99.99 mol%, MFR (190℃, 2.160 kg load) 5.7 g / 10 min, containing 220 ppm sodium acetate in terms of sodium ions, 30 ppm phosphate ions in terms of phosphate roots, and no polyvalent metal ions) was used instead of EVOH(c1-1). Various measurements and evaluations were then performed. The results are shown in Table 2.

[0156] [Example 9] Except for changing the amount of polyolefin (c2-1) (PO(c2)) mixed with EVOH(c1-1) as shown in Table 1, resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0157] [Example 10] Instead of polyethylene (e-1), polyethylene (e-2) (linear low-density polyethylene (LLDPE) "LUMITAC™ BL 600K" manufactured by Tosoh Corporation) is used as the moisture-proof resin layer (E) (MFR (190℃, 2.160kg load) 21g / 10min, density 0.898g / cm³) 3 Resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that ) was used, and various measurements and evaluations were performed. The results are shown in Table 2.

[0158] [Example 11] Instead of polyethylene (f-1), polyethylene (f-2) (linear low-density polyethylene (LLDPE) "LUMITAC™ BL 600K" manufactured by Tosoh Corporation) is used as the moisture-proof resin layer (F) and moisture-proof resin layer (F'). 3 Resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that ) was used, and various measurements and evaluations were performed. The results are shown in Table 2.

[0159] [Example 12] Instead of polyethylene (e-1), polyethylene (e-3) is used as the moisture-proof resin layer (E) (high-density polyethylene (HDPE) "Novatec (trademark) HD ​​HY540" manufactured by Nippon Polyethylene Co., Ltd. (MFR (190℃, 2.160kg load) 1.0g / 10min, density 0.960g / cm³) 3 Resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that ) was used, and various measurements and evaluations were performed. The results are shown in Table 2.

[0160] [Example 13] Instead of polyethylene (f-1), polyethylene (f-3) is used as the moisture-proof resin layer (F) and moisture-proof resin layer (F') (Novatec® HD HY540, a high-density polyethylene (HDPE) manufactured by Nippon Polyethylene Co., Ltd. (MFR (190℃, 2.160kg load) 1.0g / 10min, density 0.960g / cm³) 3 Resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that ) was used, and various measurements and evaluations were performed. The results are shown in Table 2.

[0161] [Example 14] Except for not providing a moisture-proof resin layer (F) when fabricating the multilayer structure described in (6) above, resin composition pellets, co-extruded film, vapor-deposited laminate, multilayer structure, and paper container were fabricated in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0162] [Example 15] Except for not providing a moisture-proof resin layer (F') when fabricating the multilayer structure described in (6) above, resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were fabricated in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0163] [Example 16] Resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that a known dry lamination method was used to laminate the paper layer and the vapor-deposited laminate instead of extrusion lamination. Various measurements and evaluations were then performed. The results are shown in Table 2. A two-component reactive polyurethane adhesive was used as the adhesive for dry lamination, and it was used so that the average thickness after drying was 4 μm.

[0164] [Example 17] For the preparation of the co-extruded film, a co-extruded film with a layer thickness and layer structure of C / D / E = 32 μm / 32 μm / 576 μm = EVOH32 / tie32 / PE576 was prepared. This film was stretched four times in the longitudinal direction and then eight times in the shortening direction to produce a stretched co-extruded film of 1 μm / 1 μm / 18 μm = EVOH1 / tie1 / PE18, and this co-extruded film was used. Except for these points, resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0165] [Example 18] Paper layer (A) with a basis weight of 150 g / m² 2 Except for using white paper, resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0166] [Comparative Example 1] Resin composition pellets, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that a single-layer film of a moisture-proof resin layer (E) with an average thickness of 20 μm was used instead of the co-extruded film prepared in Example 1, and a vapor-deposited laminate was used in which an aluminum metal vapor-deposited layer was laminated on one side of the moisture-proof resin layer (E) using a known method, and an aluminum metal vapor-deposited layer was laminated on the corona-discharged surface. Various measurements and evaluations were then performed. The results are shown in Table 2.

[0167] [Comparative Example 2] Resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that EVOH(c1-3) (ethylene unit content 32 mol%, degree of saponification 99.99 mol%, MFR (190℃, 2.160 kg load) 5.7 g / 10 min, containing 220 ppm sodium acetate in terms of sodium ions, 30 ppm phosphate ions in terms of phosphate roots, and no polyvalent metal ions) was used instead of EVOH(c1-1). Various measurements and evaluations were then performed. The results are shown in Table 2.

[0168] [Comparative Example 3] Resin composition pellets, co-extruded films, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that an aluminum metal vapor deposition layer was not laminated. Various measurements and evaluations were then performed. The results are shown in Table 2.

[0169] [Comparative Example 4] Except for changing the amount of magnesium stearate kneaded with EVOH(c1-1) and polyolefin(c2-1) in terms of magnesium ions as shown in Table 1, resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0170] [Comparative Example 5] Except for changing the amount of magnesium stearate mixed with EVOH(c1-1) in terms of magnesium (Mg) ions as shown in Table 1, and not mixing polyolefin(c2-1) with EVOH(c1-1), resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0171] [Comparative Example 6] Instead of co-extruded film, Toray Industries, Inc.'s biaxially oriented polyethylene terephthalate film (PET) "LUMIRA® P60" (melting point 256℃, average thickness 12μm) was used, and the corona discharge treated surface of the PET was coated with Tosoh Corporation's linear low-density polyethylene (LLDPE) "LUMITAC® BL 600K" (MFR (190℃, 2.160kg load) 21g / 10min, density 0.898g / cm³). 3 Resin composition pellets, vapor-deposited laminates, multilayer structures, and paper containers were prepared in the same manner as in Example 1, except that a linear low-density polyethylene layer with an average thickness of 30 μm was laminated by extruding the material at 300°C. Various measurements and evaluations were then performed. The results are shown in Table 2.

[0172] [Reference example 1] In the preparation of the multilayer structure, resin composition pellets, co-extruded film, vapor-deposited laminate, multilayer structure, and container were prepared in the same manner as in Comparative Example 2, except that the paper layer (A) and the moisture-proof resin layer (F) covering the exposed surface of the paper layer (A) were not laminated. Various measurements and evaluations were then performed. Since the multilayer structure did not have a paper layer (A), a container was prepared using the same procedure as in the example, instead of the paper container. Furthermore, in the measurement of WVTR and WVTR after storage test, the thermoplastic resin layer (X) (PE20) side was used as the water vapor supply side, and the other side as the carrier gas side. The results are shown in Table 2.

[0173] [Reference example 2] In the preparation of the paper container, resin composition pellets, co-extruded film, vapor-deposited laminate, multilayer structure, and paper container were prepared in the same manner as in Comparative Example 2, except that tap water with a pH of 7.0 was used instead of orange juice. Various measurements and evaluations were then performed. The results are shown in Table 2.

[0174] [Reference example 3] Except for filling the container with tap water with a pH of 7.0 instead of orange juice, resin composition pellets, co-extruded films, vapor-deposited laminates, multilayer structures, and containers were prepared in the same manner as in Reference Example 1, and various measurements and evaluations were performed. The results are shown in Table 2.

[0175] Table 1 shows the type and basis weight of the paper layer (A) in each multilayer structure, the type and average thickness of the material constituting the inorganic vapor deposition layer (B), the type and ethylene (Et) unit content of the EVOH (c1) constituting the barrier resin layer (C), the magnesium (Mg) ion and polyolefin (PO) (c2) content, the type and density of the resin constituting the moisture-proof resin layer (E), and the type and density of the resin constituting the moisture-proof resin layer (F) and moisture-proof resin layer (F'). Table 2 shows the layer composition and average thickness of each layer in each multilayer structure, the stretching ratio of the co-extruded film (MD×TD), the paper layer ratio (mass ratio of the paper layer to the entire multilayer structure), and the PE ratio other than the paper layer (total average thickness ratio of layers mainly composed of polyethylene resin in the parts other than the paper layer), along with the evaluation results.

[0176] [Table 1]

[0177] [Table 2]

[0178] As shown in Table 2, the paper containers formed from each of the multilayer structures in Examples 1 to 18 received an A rating for thickness uniformity, an A rating for WVTR after storage testing, and a B or higher rating for defects in recyclability. Each of the multilayer structures in Examples 1 to 18 was able to maintain high water vapor barrier properties even when containing acidic beverages under high temperature and high humidity conditions, exhibited high processing stability during film formation, and suppressed the occurrence of defects during recycling.

[0179] Furthermore, while Comparative Example 2 received a WVTR evaluation of D after the storage test, Reference Example 1, which differed from Comparative Example 2 only in that it lacked a paper layer, received a WVTR evaluation of B after the storage test, and its water vapor barrier performance did not deteriorate significantly even when stored under high temperature and high humidity conditions with an acidic liquid. In addition, when stored under high temperature and high humidity conditions with a non-acidic liquid, as in Reference Examples 2 and 3, the WVTR evaluation after the storage test was A regardless of the presence or absence of a paper layer. Thus, the phenomenon of reduced water vapor barrier performance when stored under high temperature and high humidity conditions is a unique problem that occurs particularly when acidic liquids are stored in paper containers formed from a multilayer structure having a predetermined layer structure including a paper layer. Moreover, the containers of Reference Examples 1 and 3, which lacked a paper layer (A), were inferior in strength compared to the paper containers of the examples that had a paper layer (A).

Claims

1. It has a paper layer (A), an inorganic vapor deposition layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E), The inorganic vapor-deposited layer (B), barrier resin layer (C), adhesive resin layer (D), and moisture-proof resin layer (E) are all directly laminated in this order, forming a vapor-deposited laminate. The average thickness of the inorganic vapor-deposited layer (B) is between 5 nm and 200 nm. The barrier resin layer (C) mainly contains an ethylene-vinyl alcohol copolymer (c1) 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. The barrier resin layer (C) contains magnesium ions in an amount of 0.005 ppm or more and less than 10 ppm. The adhesive resin layer (D) contains adhesive resin (d) as its main component, A multilayer structure in which the moisture-proof resin layer (E) mainly contains polyethylene (e).

2. The multilayer structure according to claim 1, further comprising a thermoplastic resin layer (X) interposed between a paper layer (A) and the vapor-deposited laminate.

3. A multilayer structure according to claim 1 or 2, comprising a paper layer (A), an inorganic vapor deposition layer (B), a barrier resin layer (C), an adhesive resin layer (D), and a moisture-proof resin layer (E) in this order.

4. The multilayer structure according to claim 1 or 2, wherein the barrier resin layer (C) contains 0.1 parts by mass or more and 20 parts by mass or less of polyolefin (c2) having a melt flow rate of 3 g / 10 min or more at 190°C and a 2.160 kg load as measured in accordance with JIS K7210 (2014), per 100 parts by mass of ethylene-vinyl alcohol copolymer (c1).

5. The laminate of the barrier resin layer (C), adhesive resin layer (D), and moisture-proof resin layer (E) is an unstretched or stretched co-extruded film. The average thickness of the above co-extruded film is 8 μm or more and 120 μm or less. The multilayer structure according to claim 1 or 2, wherein an inorganic vapor deposition layer (B) is provided on the barrier resin layer (C) side of the co-extruded film.

6. The multilayer structure according to claim 5, wherein the average thickness of the barrier resin layer (C) is 0.2 μm or more and less than 30 μm, and the ratio of the average thickness of the barrier resin layer (C) to the average thickness of the co-extruded film is less than 25%.

7. The multilayer structure according to claim 5, further comprising a moisture-proof resin layer (F) mainly composed of polyethylene (f).

8. The multilayer structure according to claim 7, wherein a moisture-proof resin layer (F) is directly laminated onto the co-extruded film.

9. A multilayer structure according to claim 1 or 2, which does not have an adhesive layer made of a curing type adhesive.

10. The basis weight of the paper layer (A) is 200 g / m². ２ More than 400g / m ２ A multilayer structure according to claim 1 or 2, wherein the multilayer structure is less than [amount missing].

11. The multilayer structure according to claim 1 or 2, wherein the total average thickness ratio of the layers mainly composed of polyethylene resin in the portion other than the paper layer (A) is 0.75 or more.

12. The water vapor transmission rate measured in accordance with JIS K7129-2 (infrared sensor method; 2019) under conditions of a temperature of 40°C, humidity of 90% RH on the water vapor supply side, and humidity of 0% RH on the carrier gas side was 2.0 g / (m³). ２ A multilayer structure according to claim 1 or 2, wherein the number of days is less than 1 day.

13. A liquid paper container comprising the multilayer structure described in claim 1 or 2.

14. A product comprising a liquid paper container according to claim 13, in which a liquid with a pH of 2 or more and 6 or less is contained.

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