Multilayer structure, multilayer container, composite container, and recycling method thereof

Abstract

To provide a multilayer structure and a multilayer container excellent in heat resistance, moisture proofness and separability after use, and a recycling method thereof.SOLUTION: A multilayer structure has a substrate layer (A) containing polyester (a) as a main component on one surface, and a moisture-proof layer (B) containing polyethylene (b) as a main component on another surface. The multilayer structure has a total thickness of 200 μm or more, a ratio of thickness of the substrate layer (A) to the total thickness of the multilayer structure is 0.50 or more, and an interlaminar adhesive strength between the substrate layer (A) and a layer adjacent to the substrate layer (A) is less than 200 gf / 15 mm.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a multilayer structure, a multilayer container, and a composite container which are excellent in heat resistance and moisture resistance and in separation between specific layers, and a method for recycling the same. [Background technology]

[0002] Plastic packaging materials, including food packaging, are made by laminating a variety of materials with various functions such as mechanical properties, heat resistance, gas barrier properties, moisture resistance, and heat fusion properties. For example, polyamides are widely used to improve mechanical properties, polyesters to improve heat resistance, ethylene-vinyl alcohol copolymers and polyvinylidene chloride to improve gas barrier properties, and various polyolefins such as polyethylene and polypropylene to improve moisture resistance and heat fusion properties.

[0003] In recent years, environmental and waste problems have led to a growing global demand for post-consumer recycling (hereinafter sometimes simply referred to as recycling), which involves collecting and recycling packaging materials consumed in the market. In recycling, the collected packaging materials are generally crushed and cut, and after separation, classification and cleaning as necessary, they are melt-molded using an extruder and re-pelletized as recycled resin. The pellets thus obtained are used to manufacture various molded products. In this regard, packaging materials are required to be composed of a single material as much as possible (mono-materialization), which allows for the production of high-purity, high-quality recycled resin.

[0004] However, in order to maintain the necessary functions as a packaging material, it may be difficult to make it into a monomaterial. For example, polyester is widely used as a packaging container because it has excellent heat resistance and transparency and is easy to mold, but it is sometimes laminated with polyolefins such as polyethylene because it is poor in moisture resistance and heat fusion. However, since polyester and polyolefin have significantly different properties as resins, it is difficult to mix them as they are and melt mold them, and the quality of the recycled resin obtained is not satisfactory. On the other hand, recycling technologies for polyester and polyolefin are being established, and it is expected that high-quality recycled resins can be obtained if they can be separated and recovered. However, since polyester is colorless and transparent, which is directly linked to its market value, it is generally required to have a higher purity than polyolefins, which have a wide tolerance for appearance quality such as hue.

[0005] Patent Document 1 discloses that in a laminated sheet made of multiple material layers, the material layers are bonded together via an adhesive layer that bonds the layers together with a peelable adhesive strength. According to this, it is described that after use of a packaging bag made of the laminated sheet, the multiple material layers can be peeled and separated from each other, and can be separated and recycled. Patent Document 2 discloses a packaging material in which a base layer and a sealant layer made up of multiple layers are bonded via an adhesive layer, and a resin layer adjacent to the adhesive layer of the sealant layer contains a cyclic olefin resin. According to this, it is described that the interlayer adhesive strength is reduced by immersing the packaging material in salad oil under specific conditions, so that the base layer and the sealant layer can be peeled and separated from each other, making it easy to separate and recycle. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2022-20182 A [Patent Document 2] Patent Publication No. 2020-121455 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, even if a combination of materials is difficult to recycle as it is, a technology has been proposed to improve recyclability by separating the materials by peeling and separating them from each other. However, the above conventional technology requires special adhesives or layer structures to achieve peeling and separation, or a specific peeling and separation process using a solvent, so there are problems in economically applying it to various packaging materials. In addition, since part or all of the adhesive layer remains even after peeling, the purity of the recovered material decreases, and there is a concern that the adhesive layer may hinder recyclability.

[0008] The present invention is intended to solve the above problems, and has an object to provide a multilayer structure, a multilayer container, and a composite container which are excellent in heat resistance and moisture resistance and also in separability between specific layers, as well as a method for recycling the same. [Means for solving the problem]

[0009] The above issues are: [1] A multilayer structure having, on one surface thereof, a base layer (A) containing polyester (a) as a main component, and at least a moisture-proof layer (B) containing polyethylene (b) as a main component, on the other surface thereof, wherein the multilayer structure has a total thickness of 200 μm or more, the thickness ratio of the base layer (A) to the total thickness of the multilayer structure is 0.50 or more, and the interlayer adhesive strength between the base layer (A) and a layer adjacent to the base layer (A) is less than 200 gf / 15 mm; [2] The multilayer structure of [1], further comprising a barrier layer (C) containing, as a main component, an ethylene-vinyl alcohol copolymer (c) (hereinafter sometimes abbreviated as "EVOH (c)") having an ethylene unit content of 20 to 50 mol% and a degree of saponification of 90 mol% or more, and an adhesive layer (D) containing, as a main component, an adhesive resin (d); [3] The multilayer structure of [2], in which the base layer (A), the barrier layer (C), the adhesive layer (D) and the moisture-proof layer (B) are adjacent to one another in this order, the interlayer adhesive strength between the base layer (A) and the barrier layer (C) is less than 200 gf / 15 mm, and all interlayer adhesive strengths other than between the base layer (A) and the barrier layer (C) are 200 gf / 15 mm or more; [4] The multilayer structure of [2], in which a base layer (A), a moisture barrier layer (B), an adhesive layer (D), a barrier layer (C), an adhesive layer (D) and a moisture barrier layer (B) are adjacent to each other in this order, the interlayer adhesive strength between the base layer (A) and the moisture barrier layer (B) is less than 200 gf / 15 mm, and all interlayer adhesive strengths other than between the base layer (A) and the moisture barrier layer (B) are 200 gf / 15 mm or more; [5] The polyethylene (b) is a linear low-density polyethylene, a low-density polyethylene or a mixture thereof, and has a density of 0.880 to 0.940 g / cm 3 A multilayer structure according to any one of [1] to [4], [6] The multilayer structure of any one of [1] to [5], wherein at least the moisture-proof layer (B) located on the surface contains 100 to 7000 ppm of a higher fatty acid amide compound (x) having a melting point of 60 to 120°C; [7] The multilayer structure of any of [1] to [6], wherein the moisture proof layer (B) located at least on the surface contains 500 to 5,000 ppm of inorganic oxide particles (y) having an average particle diameter of 1 to 30 μm, and the inorganic oxide particles (y) are at least one type selected from the group consisting of silicon oxide particles and metal oxide particles; [8] The multilayer structure of any of [2] to [7], wherein the barrier layer (C) contains 10 to 200 ppm of at least one polyvalent metal ion (z) selected from the group consisting of magnesium ions, calcium ions, and zinc ions; [9] The oxygen transmission rate measured according to the method described in JIS K 7126-2:2006 under conditions of 20°C and 65% RH is 2.0 cc / (m 2 A multilayer structure of any one of [1] to [8], in which the thermal conductivity is less than 100% (day·atm);

[10] The multilayer structure of any one of [1] to [9], wherein the base layer (A) has a light transmittance of 70% or more at a wavelength of 600 nm;

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

[10] , which does not have a high-melting point resin layer containing, as a main component, a resin having a melting point of 200°C or higher, except for the base layer (A);

[12] A multilayer structure of any one of [1] to

[11] , which is a coextruded multilayer structure;

[13] A multilayer container obtained by secondary processing of the multilayer structure of any one of [1] to

[12] ;

[14] A composite container comprising a lid material having a heat-sealing layer containing polyethylene as a main component and the multilayer container of

[13] , wherein the lid material is heat-sealed to the multilayer container;

[15] A recycling method comprising a step of separating the multilayer container according to

[13] or the composite container according to

[14] into a portion consisting of the base material layer (A) and a portion consisting of other than the base material layer (A);

[16] The recycling method according to

[15] , comprising a step of melt-molding a portion consisting of the base material layer (A) and a portion consisting of other than the base material layer (A) independently; This is solved by providing Effect of the Invention

[0010] According to the present invention, it is possible to provide a multilayer structure, a multilayer container, and a composite container which are excellent in heat resistance and moisture resistance and also in separability between specific layers, and a method for recycling the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described. In the following description, specific materials (compounds, etc.) that exhibit a specific function may be exemplified, but the present invention is not limited to the embodiment using such materials. In addition, the exemplified materials may be used alone or in combination unless otherwise specified. In this specification, "contains as a main component" means more than 50 mass%. In addition, in this specification, "adjacent" means directly laminated. In addition, in this specification, "interlayer adhesive strength other than the base layer (A) and the layer adjacent to the base layer (A)" means, for example, the adhesive strength between the moisture-proof layer (B) and the adhesive layer (D) and the adhesive strength between the adhesive layer (D) and the barrier layer (C) in the case of a multilayer structure consisting of a layer structure of base layer (A) / moisture-proof layer (B) / adhesive layer (D) / barrier layer (C) / adhesive layer (D) / moisture-proof layer (B). In this specification, "defect" means gels, fish eyes, etc. that are observed during film formation.

[0012] The multilayer structure of the present invention has a substrate layer (A) on one surface and a moisture-proof layer (B) on at least the other surface, the multilayer structure has a total thickness of 200 μm or more, the ratio of the thickness of the substrate layer (A) to the total thickness of the multilayer structure is 0.50 or more, and the interlayer adhesive strength between the substrate layer (A) and a layer adjacent to the substrate layer (A) is less than 200 gf / 15 mm. Here, "having a substrate layer (A) on one surface and at least a moisture-proof layer (B) on the other surface" means that the outermost layer on one side of the multilayer structure is the substrate layer (A) and the outermost layer on the other side is the moisture-proof layer (B). The multilayer structure of the present invention has both the heat resistance of polyester and the moisture resistance of polyethylene, and exhibits good separability that allows the base material layer (A) containing polyester (a) as a main component, which has low recyclability with other materials, to be easily separated from other materials, and each separated material (a portion consisting of the base material layer (A) and a portion consisting of other than the base material layer (A)) can be recycled (melted and kneaded) independently to obtain a high-quality recycled resin. In one aspect of the present invention, the use of a special adhesive or a peeling process is not required, and recycling can be achieved simply and economically. In addition, since the multilayer container in one aspect of the present invention also has heat fusion properties, a sealable composite container can be provided by heat fusion of a lid material. This makes it possible to improve the recyclability of the packaging material without deteriorating its function or quality as a packaging material, and contribute to the realization of a recycling-oriented society.

[0013] [Base layer (A) and polyester (a)] The multilayer structure of the present invention has a base layer (A) containing polyester (a) as a main component on one surface. By having the base layer (A) on one surface, the heat resistance and transparency derived from the polyester can be improved. The base layer (A) may be a single layer or a multilayer. In addition, since polyester resins are widely used in packaging materials such as bottles and trays, recycling infrastructures for them are widely established in various countries. However, it is difficult to mix polyester resins with other resins and recycle them. From this perspective, the present invention, which improves the separability of the base layer (A), is of great technical significance.

[0014] The polyester (a) is a polyester resin composed of a dicarboxylic acid unit mainly composed of a terephthalic acid unit and a diol unit mainly composed of an ethylene glycol unit. As the polyester (a), a polyester composed only of a terephthalic acid unit and an ethylene glycol unit, and a polyester in which at least a part of the terephthalic acid unit is replaced with another dicarboxylic acid unit or a part of the ethylene glycol unit is replaced with another diol unit can be used. When the polyester (a) has other structural units (other dicarboxylic acid units and / or other diol units) other than the terephthalic acid unit and the ethylene glycol unit, the ratio of the other structural units is preferably 30 mol% or less of the total structural units constituting the polyester (a), more preferably 20 mol% or less, even more preferably 10 mol% or less, even more preferably 5 mol% or less, and particularly preferably 3 mol% or less. When the other structural units are more than 30 mol%, the obtained polyester becomes amorphous, and the heat resistance and mechanical strength may be insufficient, or when solid-phase polymerization is performed to reduce the oligomer contained in the resin, the resin is softened and sticks easily, making production difficult. The intrinsic viscosity of the polyester (a) is preferably 0.6 to 1.0 dl / g.

[0015] Examples of other dicarboxylic acid units that the polyester (a) may have include dicarboxylic acid units derived from aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, and sodium sulfoisophthalate; alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; aliphatic dicarboxylic acids such as malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, sebacic acid, and suberic acid; and ester-forming derivatives thereof. The polyester (a) may have only one type of the other dicarboxylic acid units described above, or may have two or more types.

[0016] Examples of other diol units that the polyester (a) may have include diol units derived from aliphatic diols such as tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentyl glycol, diethylene glycol, propylene glycol, neopentyl glycol, 2-methylpropanediol, 1,5-pentanediol, 1,1-cyclohexanedimethylol, 1,4-cyclohexanedimethylol, and cyclohexanediol; aromatic diols such as 2,2-bis(4-β-hydroxyethoxyphenyl)propane and bis(4-β-hydroxyethoxyphenyl)sulfone; and low molecular weight polyalkylene glycols such as diethylene glycol, polyethylene glycol, poly-1,3-propylene glycol, and polytetramethylene glycol. The polyester (a) may have only one type of the other diol units described above, or two or more types.

[0017] The polyester (a) may have one or more structural units derived from a trifunctional or higher monomer such as glycerin, trimethylolpropane, pentaerythritol, trimellitic acid, pyromellitic acid, etc., so long as the structural units account for 1 mol % or less of the total structural units. The polyester (a) may be used alone or in combination of two or more.

[0018] The base layer (A) may contain additives other than the polyester (a) as long as the effects of the present invention are not impaired. Examples of such additives include heat stabilizers, antioxidants, UV absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, stabilizers, surfactants, drying agents, crosslinking agents, and fiber reinforcement agents. The content of the additives in the polyester (a) is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less.

[0019] The content of the polyester (a) in the base layer (A) is more than 50% by mass, preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. When the content of the polyester (a) in the base layer (A) is more than 50% by mass, the heat resistance and transparency are improved, and the mechanical strength is also excellent.

[0020] The substrate layer (A) preferably does not contain any dye or pigment and is colorless and transparent. The light transmittance of the substrate layer (A) at a wavelength of 600 nm is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, and particularly preferably 85% or more.

[0021] [Moisture-proof layer (B) and polyethylene (b)] The multilayer structure of the present invention has at least a moisture-proof layer (B) containing polyethylene (b) as a main component on the other surface. By having the moisture-proof layer (B) on the surface of the multilayer structure of the present invention, the moisture-proof property derived from polyethylene can be improved and the heat-sealing property is also good. The moisture-proof layer (B) may be a single layer or a multilayer, and the multilayer structure of the present invention may have a plurality of moisture-proof layers (B). When the multilayer structure of the present invention has a plurality of moisture-proof layers (B), each moisture-proof layer (B) may be the same or different, but it is preferable that they are the same. Since polyethylene resin is widely used in packaging materials as a moisture-proof layer or a heat-sealing layer, the recycling infrastructure for it is widely developed in various countries, but it is difficult to mix polyester resin and polyethylene resin and recycle them, and from that point of view, the present invention, which improves the separability of the base layer (A), is of great technical significance.

[0022] Examples of the polyethylene (b) include various polyethylene resins such as linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene. Among them, the polyethylene (b) is preferably linear low-density polyethylene, low-density polyethylene, or a mixture thereof, and more preferably linear low-density polyethylene. When the polyethylene (b) is linear low-density polyethylene, it is preferably linear low-density polyethylene obtained by polymerizing ethylene with an α-olefin having 3 or more carbon atoms. Examples of the α-olefin 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. The polyethylene (b) is preferably linear low-density polyethylene obtained by polymerizing ethylene with an α-olefin having 6 or more carbon atoms, and more preferably linear low-density polyethylene obtained by polymerizing ethylene with an α-olefin having 8 or more carbon atoms. When the α-olefin copolymerized with ethylene has a relatively large number of carbon atoms, various mechanical strengths such as puncture strength and tensile strength and elongation may be particularly improved.

[0023] In addition, it is preferable to use a metallocene catalyst as a polymerization catalyst for polymerizing polyethylene (b). The linear low-density polyethylene polymerized using a metallocene catalyst is produced by copolymerizing ethylene and an α-olefin in the presence of a catalyst formed from a compound of a transition metal of Group 4 of the periodic table, preferably zirconium, having at least one ligand having a cyclopentadienyl skeleton, an organoaluminum oxy compound, and various components added as necessary. The linear low-density polyethylene polymerized using a metallocene catalyst has excellent melt moldability, and the multilayer structure obtained has an excellent balance of heat resistance, flexibility, and mechanical strength.

[0024] Linear low-density polyethylene obtained by polymerizing ethylene and an α-olefin having 6 or more carbon atoms using a metallocene catalyst is commercially available as industrially produced polyethylene, such as "Evolue (trademark)" (Prime Polymer Co., Ltd.), "Sumikasen (trademark)" (Sumitomo Chemical Co., Ltd.), "Yumerit (trademark)" (Ube Maruzen Polyethylene Co., Ltd.), and "Elite (trademark)" (Dow Chemical Co., Ltd.).

[0025] The density of polyethylene (b) is 0.880 to 0.940 g / cm 3 When the density is within the above range, the multilayer structure obtained has excellent moisture resistance, flexibility, and excellent handling properties. In addition, various mechanical strengths such as puncture strength and elongation and tensile strength and elongation and heat fusion properties are improved, so that the reliability of content retention when made into a multilayer container and the separability after use are excellent. The lower limit of the density is 0.885 g / cm 3 is preferred, and 0.890 g / cm 3 More preferably, 0.895 g / cm 3 The upper limit of the density is 0.925 g / cm 3 is preferred, and 0.915 g / cm 3 More preferably, 0.910 g / cm 3 is more preferred.

[0026] The MFR (190°C, under a load of 2.16 kg) of the polyethylene (b) is preferably 0.5 to 5.0 g / 10 min. When the MFR is in the above range, the polyethylene (b) has excellent melt processability, and the obtained multilayer structure has improved mechanical strengths such as puncture strength and tensile strength. The lower limit of the MFR is preferably 0.7 g / 10 min. The upper limit of the MFR is preferably 3.0 g / 10 min, more preferably 2.0 g / 10 min, further preferably 1.5 g / 10 min, and particularly preferably 1.0 g / 10 min. The MFR is measured at 190°C and under a load of 2.16 kg in accordance with JIS K 7210 (2014).

[0027] Polyethylene (b) may contain other monomer units other than ethylene and α-olefins, so long as the effects of the present invention are not impaired. Examples of such other monomers include vinyl acetate, acrylic acid and its salts or esters, methacrylic acid and its salts or esters, acrylonitrile, methacrylonitrile, vinyl chloride, vinyl fluoride, vinylidene chloride, vinylidene fluoride, unsaturated dicarboxylic acids and their salts or esters, such as maleic acid, itaconic acid, and fumaric acid, vinyltrimethoxysilane, and vinyltriethoxysilane. When polyethylene (b) has other monomer units, the ratio of the other monomer units is preferably 20 mol% or less, more preferably 10 mol% or less, even more preferably 5 mol% or less, and particularly preferably 3 mol% or less of the total monomer units constituting polyethylene (b). Polyethylene (b) may be used alone or in combination of two or more types.

[0028] <Higher fatty acid amide compound (x)> At least the moisture proof layer (B) located on the surface preferably contains 100 to 7000 ppm of a higher fatty acid amide compound (x) having a melting point of 60 to 120° C. When the moisture proof layer (B) contains the higher fatty acid amide compound (x) in the above range, the surface smoothness of the obtained multilayer structure and multilayer container is improved, and the handleability is excellent. When the moisture proof layer (B) is provided on a layer other than the surface, the moisture proof layer (B) may or may not contain the higher fatty acid amide compound (x).

[0029] The lower limit of the content of the higher fatty acid amide compound (x) in the moisture-proof layer (B) is preferably 300 ppm, more preferably 500 ppm, and even more preferably 700 ppm. The upper limit of the content of the higher fatty acid amide compound (x) is preferably 5000 ppm, more preferably 3000 ppm, even more preferably 2000 ppm, particularly preferably 1500 ppm, and may be 1000 ppm. When the content of the higher fatty acid amide compound (x) is within the above range, the surface smoothness can be effectively improved without impairing the transparency and uniformity of the appearance of the multilayer structure.

[0030] The higher fatty acid amide compound (x) is not particularly limited as long as it has a melting point of 60 to 120°C. The lower limit of the melting point of the higher fatty acid amide compound (x) is preferably 70°C. The upper limit of the melting point of the higher fatty acid amide compound (x) is preferably 110°C. The melting point can be controlled by the length of the carbon chain, the degree of unsaturation (the number of double bonds in the carbon chain), the number of amide groups, the presence or absence of other substituents, etc. Examples of the higher fatty acid amide compound (x) include saturated higher fatty acid bisamides, unsaturated higher fatty acid bisamides, saturated higher fatty acid monoamides, unsaturated higher fatty acid monoamides, and derivatives thereof, and it is preferable that the higher fatty acid amide compound (x) is at least one selected from the group consisting of saturated higher fatty acid monoamides and unsaturated higher fatty acid monoamides having 10 to 25 carbon atoms. Preferred examples of the saturated higher fatty acid monoamides having 10 to 25 carbon atoms include capric acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, arachidic acid amide, and behenic acid amide. Among these, from the viewpoints of economy and availability, lauric acid amide, stearic acid amide, and behenic acid amide are preferred, and stearic acid amide is more preferred. As the unsaturated higher fatty acid monoamide having 10 to 25 carbon atoms, from the viewpoint of suppressing coloration, monoene higher fatty acid monoamide having an unsaturation degree of 1 is preferred, and preferred examples include oleic acid amide, elaidic acid amide, vaccenic acid amide, gadoleic acid amide, eicosenoic acid amide, and erucic acid amide. Among these, from the viewpoints of economy and availability, oleic acid amide and erucic acid amide are preferred. From the viewpoint of the thermal stability of the higher fatty acid amide compound (x), saturated higher fatty acid monoamides are preferred, and from the viewpoint of exerting the effect in a wider range of processing conditions, unsaturated higher fatty acid monoamides are preferred. In addition, from the viewpoint of handleability in the process of manufacturing and processing the multilayer structure, the carbon number of the higher fatty acid amide compound (x) may be preferably 12 to 22. In addition, the higher fatty acid amide compound (x) may have a substituent such as a hydroxyl group.

[0031] In one aspect of the present invention, it is preferred that the higher fatty acid amide compound (x) contains two or more kinds of higher fatty acid amide compounds having different melting points. In particular, it is preferred that the higher fatty acid amide compound (x) contains an unsaturated higher fatty acid amide compound having a melting point of 60°C or more and less than 90°C and a saturated higher fatty acid amide compound having a melting point of 90°C or more and less than 120°C, since the surface activity of the multilayer structure and multilayer container obtained can be efficiently improved without being affected by environmental factors such as temperature and humidity.

[0032] <Inorganic oxide particles (y)> At least the moisture-proof layer (B) located on the surface preferably contains 500 to 5000 ppm of inorganic oxide particles (y) having an average particle size of 1 to 30 μm. By having the inorganic oxide particles (y) in the moisture-proof layer (B) in the above range, the surface smoothness of the obtained multilayer structure and multilayer container is improved, and the handleability is excellent. When the moisture-proof layer (B) is present in a portion other than the surface, the moisture-proof layer (B) may or may not contain inorganic oxide particles (y).

[0033] The lower limit of the content of the inorganic oxide particles (y) is preferably 750 ppm, more preferably 1000 ppm. The upper limit of the content of the inorganic oxide particles (y) is preferably 4500 ppm, more preferably 4000 ppm. The lower limit of the average particle size of the inorganic oxide particles (y) is preferably 2 μm, more preferably 3 μm. The upper limit of the average particle size of the inorganic oxide particles (y) is preferably 15 μm, more preferably 10 μm. The average particle size is a median size measured by a light scattering method while circulating the dispersion obtained after dispersing the inorganic oxide particles (y) in water or an organic solvent and thoroughly stirring it. The shape of the inorganic oxide particles (y) is preferably small in aspect ratio and close to a perfect sphere. In this way, the surface activity of the resulting multilayer structure and multilayer container may be efficiently improved without impairing the appearance characteristics such as transparency.

[0034] The inorganic oxide particles (y) are preferably at least one selected from the group consisting of silicon oxide particles and metal oxide particles. The metal constituting the metal oxide particles is preferably at least one selected from the group consisting of aluminum, magnesium, zirconium, cerium, tungsten, molybdenum, titanium and zinc. Specific examples of the inorganic oxide constituting the inorganic oxide particles (y) include silicon oxide, aluminum oxide, zirconium oxide, magnesium oxide, cerium oxide, tungsten oxide, molybdenum oxide, titanium oxide, zinc oxide and complexes thereof (e.g. complexes of silicon oxide and aluminum oxide), with silicon oxide being preferred.

[0035] The moisture-proof layer (B) may contain other components other than the polyethylene (b), the higher fatty acid amide compound (x) and the inorganic oxide particles (y) as long as the effects of the present invention are not impaired. Examples of other components include alkali metal ions, polyvalent metal ions, carboxylic acids, phosphoric acid compounds, boron compounds, oxidation promoters, antioxidants, plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorants, UV absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, bulking agents, pigments, dyes, processing aids, flame retardants, and antifogging agents. The content of other components in the moisture-proof layer (B) is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less. It is preferable that the moisture-proof layer (B) does not contain dyes or pigments and is colorless.

[0036] The moisture-proof layer (B) may further contain a thermoplastic resin other than the polyethylene (b). Examples of the thermoplastic resin other than the polyethylene (b) include various polyolefins (polypropylene, poly1-butene, poly4-methyl-1-pentene, ethylene-propylene copolymers, copolymers of ethylene and α-olefins having 4 or more carbon atoms, copolymers of polyolefins and maleic anhydride, ethylene-vinyl ester copolymers, ethylene-acrylic acid ester copolymers, and modified polyolefins obtained by graft-modifying these with unsaturated carboxylic acids or their derivatives, etc.), various polyamides (nylon 6, nylon 6·6, nylon 6 / 66 copolymers, nylon 11, nylon 12, polymetaxylylene adipamide, etc.), various polyesters (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polyurethane, polycarbonate, polyacetal, polyacrylate, and modified polyvinyl alcohol resins, etc. The content of the thermoplastic resin in the moisture proof layer (B) is less than 50% by mass, preferably less than 30% by mass, more preferably less than 10% by mass, even more preferably 5% by mass or less, and may be 1% by mass or less. In particular, when the moisture proof layer (B) further contains a thermoplastic resin other than the polyethylene (b), the contained thermoplastic resin is preferably a thermoplastic resin consisting of only carbon atoms, hydrogen atoms, and oxygen atoms, more preferably a thermoplastic resin consisting of only carbon atoms and hydrogen atoms, and even more preferably a thermoplastic resin consisting of only carbon atoms and hydrogen atoms and having a melting point of 150° C. or less.

[0037] The proportion of polyethylene (b) in the resin constituting the moisture-proof layer (B) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, or 99% by mass or more, or the resin constituting the moisture-proof layer (B) may be composed only of polyethylene (b). The proportion of polyethylene (b) in the moisture-proof layer (B) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, or 99% by mass or more, or the moisture-proof layer (B) may be composed substantially only of polyethylene (b).

[0038] The method for producing the resin composition constituting the moisture-proof layer (B) is not particularly limited, but it can be produced by melt-kneading polyethylene (b) and, if necessary, other additives such as higher fatty acid amide compound (x) and inorganic oxide particles (y). The higher fatty acid amide compound (x) may be blended in a solid state such as powder or as a melt, or may be blended as a solute contained in a solution or a dispersoid contained in a dispersion. As the solution and dispersion, an aqueous solution and an aqueous dispersion are preferable, respectively. For the melt-kneading, a known mixing or kneading device such as a kneader-ruder, an extruder, a mixing roll, or a Banbury mixer can be used. The temperature range during melt-kneading can be appropriately adjusted depending on the melting point of the polyethylene (b) used, and is usually 150 to 300°C.

[0039] In another embodiment, a master batch containing other additives such as higher fatty acid amide compound (x) and inorganic oxide particles (y) at a high concentration is produced by melt kneading with polyethylene (b) as necessary, and the master batch is dry-blended with polyethylene (b) that does not substantially contain other additives such as higher fatty acid amide compound (x) and inorganic oxide particles (y) to be used for producing a multilayer structure. In yet another embodiment, polyethylene (b) and other additives such as higher fatty acid amide compound (x) and inorganic oxide particles (y) as necessary can be dry-blended to be used for producing a multilayer structure. Dry blending refers to mechanical mixing in the form of powder or pellets. Mixing may be performed using a mixing device such as a tumbler, ribbon mixer, or Henschel mixer, or may be performed by manually stirring, shaking, or the like in a sealed container. The mixing temperature may be from room temperature to less than the melting point of polyethylene (b), and mixing can be performed under an air atmosphere or a nitrogen atmosphere.

[0040] [EVOH (c) and barrier layer (C)] The multilayer structure of the present invention preferably has a barrier layer (C) containing EVOH (c) as a main component. The barrier layer (C) may be a single layer or a multilayer. Since EVOH (c) has excellent gas barrier properties, a multilayer structure having a barrier layer (C) containing EVOH (c) as a main component is preferably used as a packaging material with excellent content preservation properties. In addition, since EVOH (c) can be easily melt-mixed with polyethylene resin, a packaging material with excellent recyclability with polyethylene resin can be provided. When the multilayer structure of the present invention has a plurality of barrier layers (C), the respective barrier layers (C) may be the same or different, but are preferably the same.

[0041] EVOH (c) is usually obtained by saponifying an ethylene-vinyl ester copolymer obtained by polymerizing ethylene and a vinyl ester. The ethylene unit content of EVOH (c) is 20 to 50 mol%. When the ethylene unit content is 20 mol% or more, the melt moldability of EVOH (c) and a resin composition containing EVOH (c) is improved. The ethylene unit content is preferably 23 mol% or more, more preferably 26 mol% or more, and may be 29 mol% or more. On the other hand, when the ethylene unit content is 50 mol% or less, the gas barrier property of the multilayer structure of the present invention is improved. The ethylene unit content is preferably 46 mol% or less, more preferably 42 mol% or less, and may be 38 mol% or less. The saponification degree of EVOH (c) is 90 mol% or more. The saponification degree means the ratio of the number of vinyl alcohol units to the total number of vinyl alcohol units and vinyl ester units in EVOH (c). When the saponification degree is 90 mol% or more, the gas barrier property of the multilayer structure of the present invention is improved. The saponification degree is preferably 95 mol% or more, more preferably 99 mol% or more, and even more preferably 99.9 mol% or more. The ethylene unit content and saponification degree of EVOH (c) are as follows: 1 It can be determined by H-NMR measurement.

[0042] EVOH (c) may be a mixture of two or more kinds of EVOH having different ethylene unit contents. In this case, the difference in ethylene unit contents between EVOH having the most different ethylene unit contents is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, and may be 3 mol% or more. Similarly, EVOH (c) may be a mixture of two or more kinds of EVOH having different saponification degrees. In this case, the difference in saponification degrees between EVOH having the most different ethylene unit contents is preferably 7% or less, more preferably 5% or less, and may be 0.5 mol% or more. When it is desired to achieve both thermoformability and gas barrier properties at a higher level, it is preferable to mix EVOH (c1) having an ethylene unit content of 24 mol% or more and less than 34 mol% and a saponification degree of 99 mol% or more with EVOH (c2) having an ethylene unit content of 34 mol% or more and less than 50 mol% and a saponification degree of 99 mol% or more at a blending mass ratio (c1 / c2) of 60 / 40 to 90 / 10 and use the mixture as EVOH (c).

[0043] EVOH (c) may contain other monomer units than ethylene, vinyl ester, and vinyl alcohol, so long as the effects of the present invention are not impaired. 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 the gas barrier property and the moldability of EVOH (c). The content of other monomer 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 none.Examples of such other monomers include 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, diacetone acrylamide, acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts (e.g., quaternary salts); and methacrylamide. , N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propanesulfonic acid and its salts, methacrylamide propyl dimethylamine and its salts (e.g., quaternary salts); vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, and 2,3-diacetoxy-1-vinyloxypropane; acrylonitrile, methacrylamide, methacrylamidopropanesulfonic acid and its salts, and methacrylamide propyl dimethylamine and its salts (e.g., quaternary salts); vinyl cyanides such as methyl methacrylate and ethyl methacrylate; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane and allyl chloride; unsaturated dicarboxylic acids and their salts or esters such as maleic acid, itaconic acid and fumaric acid; vinyl silane compounds such as vinyltrimethoxysilane; isopropenyl acetate, 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, 3,4-diacyloxy-1-butene , 3-acyloxy-4-methyl-1-butene, 4-acyloxy-2-methyl-1-butene, 4-acyloxy-3-methyl-1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diacyloxy-1-pentene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy-1-hexene, 5,6-diacyloxy-1-hexene, 1,3-diacetoxy-2-methylenepropane, and other alkenes having an ester group or saponification products thereof.

[0044] The MFR (190°C, under a load of 2.16 kg) of EVOH (c) measured in accordance with JIS K7210 (2014) is preferably 0.2 to 20 g / 10 min. The MFR of EVOH (c) is more preferably 0.5 g / 10 min or more, and even more preferably 0.8 g / 10 min or more. On the other hand, the MFR of EVOH (c) is more preferably 15 g / 10 min or less, even more preferably 10 g / 10 min or less, even more preferably 5 g / 10 min or less, and particularly preferably 3 g / 10 min or less. When the MFR of EVOH (c) is in the above range, the melt moldability of EVOH (c) and a resin composition containing EVOH (c) is improved.

[0045] The EVOH (c) may be used alone or in combination of two or more kinds.

[0046] <Polyvalent metal ions (z)> The barrier layer (C) preferably contains 10 to 200 ppm of at least one polyvalent metal ion (z) selected from the group consisting of magnesium ion, calcium ion, and zinc ion. By containing a certain amount of polyvalent metal ion (z), thickening, gelation, and resin adhesion to the screw during melt molding of EVOH (c) and a resin composition containing EVOH (c) are suppressed. The polyvalent metal ion (z) is preferably a magnesium ion or a calcium ion, and more preferably a magnesium ion. In addition, it is preferable to contain the polyvalent metal ion (z) as a carboxylate. The carboxylic acid in this case may be either an aliphatic carboxylic acid or an aromatic carboxylic acid, but an aliphatic carboxylic acid is preferable. Examples of the aliphatic carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, myristic acid, behenic acid, and montanic acid, and higher fatty acids having 10 to 25 carbon atoms are more preferable. In addition, from the viewpoint of suppressing coloring during melt molding, it is also preferable to contain the polyvalent metal ion (z) as a salt of a polyvalent carboxylic acid described later.

[0047] The content of the polyvalent metal ion (z) in the barrier layer (C) is preferably 10 to 200 ppm. When the content is 10 ppm or more, the viscosity stability is improved during recycling (melt-kneading) of the portion other than the base layer (A) (the portion containing EVOH (c) and polyethylene (b)) after the base layer (A) is separated in the multilayer structure of the present invention, and gelation of the resin and adhesion of the resin to the extruder screw are suppressed. The lower limit of the content of the polyvalent metal ion (z) is more preferably 20 ppm. On the other hand, when the content of the polyvalent metal ion (z) is 200 ppm or less, excessive decomposition is suppressed during recycling (melt-kneading) of the portion other than the base layer (A) (the portion containing EVOH (c) and polyethylene (b)) after the base layer (A) is separated in the multilayer structure of the present invention, and the color of the recycled resin is improved. The upper limit of the content of the polyvalent metal ion (z) is more preferably 160 ppm, and even more preferably 120 ppm.

[0048] The barrier layer (C) may contain other components other than EVOH (c) and polyvalent metal ions (z) as long as the effects of the present invention are not impaired. Examples of other components include alkali metal ions, polyvalent metal ions other than polyvalent metal ions (z), carboxylic acids, phosphoric acid compounds, boron compounds, oxidation promoters, antioxidants, plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorants, UV absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, bulking agents, pigments, dyes, processing aids, flame retardants, and antifogging agents. In particular, from the viewpoint of improving the interlayer adhesion and melt moldability of the laminate containing EVOH (c), it is preferable to contain alkali metal ions. In addition, from the viewpoint of suppressing coloring during melt molding of EVOH (c) and a resin composition containing EVOH (c), it is preferable to contain a carboxylic acid or phosphoric acid compound. Furthermore, by containing a boron compound, it is possible to control the melt viscosity of EVOH (c) and a resin composition containing EVOH (c), and it may be possible to improve the mechanical strength of the multilayer structure and multilayer container of the present invention. The content of other components in the barrier layer (C) is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less.

[0049] <Alkali metal ions> The barrier layer (C) preferably contains an alkali metal ion. The lower limit of the content of the alkali metal ion is preferably 100 ppm, more preferably 150 ppm. On the other hand, the upper limit of the content of the alkali metal ion is preferably 400 ppm, more preferably 350 ppm. When the content of the alkali metal ion is 100 ppm or more, the interlayer adhesion between the barrier layer (C) and the adhesive layer (D) described later is good. On the other hand, when the content of the alkali metal ion is 400 ppm or less, coloration tends to be suppressed. In addition, by controlling the content ratio of the alkali metal ion and the carboxylic acid described later, the melt moldability and coloration resistance can be further improved.

[0050] Examples of alkali metal ions include lithium, sodium, potassium, rubidium, and cesium ions, but sodium or potassium ions are preferred from the viewpoint of industrial availability. In particular, by using potassium ions alone or in combination with sodium ions and potassium ions, it may be possible to achieve high levels of both hue and interlayer adhesion with the adhesive layer (D). These may be used alone or in combination of two or more.

[0051] Examples of alkali metal salts that provide alkali metal ions include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, and metal complexes of alkali metals such as sodium and potassium. Specifically, sodium acetate, potassium acetate, sodium phosphate, and potassium phosphate are more preferred in terms of their easy availability.

[0052] <Carboxylic acid> The barrier layer (C) preferably contains a carboxylic acid. The lower limit of the content of the carboxylic acid is preferably 50 ppm, more preferably 100 ppm. On the other hand, the upper limit of the content of the carboxylic acid is preferably 400 ppm, more preferably 350 ppm. When the content of the carboxylic acid is 50 ppm or more, coloring tends to be suppressed. On the other hand, when the content of the carboxylic acid is 400 ppm or less, the decrease in interlayer adhesion with the adhesive layer (D) tends to be suppressed, and odor tends to be suppressed. The content of the carboxylic acid is determined by extracting 10 g of the resin composition constituting the barrier layer (C) with 50 ml of pure water at 95 ° C for 8 hours, and then titrating the resulting extract. Note that the content of the carboxylic acid in the resin composition does not take into account the carboxylic acid present as a salt in the extract. In addition, when the resin composition contains acidic compounds other than the carboxylic acid, the content of the carboxylic acid in the resin composition can be determined by subtracting the contribution of these acidic compounds from the measured value by titration.

[0053] The pKa of the carboxylic acid is preferably 3.5 to 5.5. When the pKa of the carboxylic acid is within the above range, the pH buffering ability in the weak acid range is increased, the melt moldability is further improved, and the coloring effect due to acidic or basic substances can be further reduced.

[0054] The carboxylic acid may be a monobasic carboxylic acid. These may be used alone or in combination of two or more. The monobasic carboxylic acid is a compound having one carboxyl group in the molecule. Examples of monobasic carboxylic acids having a pKa in the range of 3.5 to 5.5 include, but are not limited to, formic acid (pKa=3.77), acetic acid (pKa=4.76), propionic acid (pKa=4.85), and acrylic acid (pKa=4.25). These carboxylic acids may further have a substituent such as a hydroxyl group, an amino group, or a halogen atom. Among these, acetic acid is preferred because of its high safety and ease of availability and handling.

[0055] The carboxylic acid may be a polycarboxylic acid. When the carboxylic acid is a polycarboxylic acid, the coloring resistance of the EVOH (c) at high temperatures and the coloring resistance of the resin composition containing the EVOH (c) may be further improved. The polycarboxylic acid compound preferably has three or more carboxyl groups. In this case, the coloring resistance may be more effectively improved. The polycarboxylic acid is a compound having two or more carboxyl groups in the molecule. In this case, it is preferable that the pKa of at least one carboxyl group is in the range of 3.5 to 5.5, and examples of the polycarboxylic acid include oxalic acid (pKa2=4.27), succinic acid (pKa1=4.20), fumaric acid (pKa2=4.44), malic acid (pKa2=5.13), glutaric acid (pKa1=4.30, pKa2=5.40), adipic acid (pKa1=4.43, pKa 2=5.41), pimelic acid (pKa1=4.71), phthalic acid (pKa2=5.41), isophthalic acid (pKa2=4.46), terephthalic acid (pKa1=3.51, pKa2=4.82), citric acid (pKa2=4.75), tartaric acid (pKa2=4.40), glutamic acid (pKa2=4.07), aspartic acid (pKa=3.90), etc.

[0056] <Phosphate compounds> The barrier layer (C) may further contain a phosphate compound. The lower limit of the content of the phosphate compound is preferably 5 ppm in terms of phosphate radicals. On the other hand, the upper limit of the content of the phosphate compound is preferably 100 ppm in terms of phosphate radicals. By containing the phosphate compound in this range, coloration of the EVOH (c) and the resin composition containing EVOH (c) after melt molding may be suppressed, and thermal stability may be improved.

[0057] As the phosphoric acid compound, various acids such as phosphoric acid and phosphorous acid and their salts can be used. The phosphate may be any of primary phosphate, secondary phosphate, and tertiary phosphate. The cationic species of the phosphate is not particularly limited, but the cationic species is preferably an alkali metal or an alkaline earth metal. Among them, the phosphoric acid compound is preferably sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate.

[0058] <Boron compounds> The barrier layer (C) may further contain a boron compound. The lower limit of the content of the boron compound is preferably 50 ppm, more preferably 100 ppm, in terms of boron element. On the other hand, the upper limit of the content of the boron compound is preferably 400 ppm, more preferably 200 ppm, in terms of boron element. By containing the boron compound in this range, the thermal stability of the EVOH (c) and the resin composition containing the EVOH (c) during melt molding may be improved, and the occurrence of gels and bumps may be suppressed. In addition, the drawdown resistance and neck-in resistance during film formation may be improved, and the mechanical properties of the resulting multilayer structure or multilayer container may be improved. It is presumed that these effects are due to the occurrence of a chelating interaction between the EVOH (c) and the boron compound.

[0059] Examples of boron compounds include boric acid, boric acid esters, borate salts, and boron hydrides.Specific examples include boric acids such as orthoboric acid (H3BO3), metaboric acid, and tetraboric acid; boric acid esters such as trimethyl borate and triethyl borate; alkali metal salts or alkaline earth metal salts of the boric acid, and borate salts such as borax.Of these, orthoboric acid is preferred.

[0060] <Hindered phenol compounds> The barrier layer (C) may further contain, as an antioxidant, for example, a hindered phenol-based compound having an ester bond or an amide bond. The content of the hindered phenol-based compound is preferably 1000 to 10000 ppm. When the content is 1000 ppm or more, coloring, thickening, and gelation of the resin can be suppressed when EVOH (c) and a resin composition containing EVOH (c) are melt-molded. The content of the hindered phenol-based compound is more preferably 2000 ppm or more. On the other hand, when the content of the hindered phenol-based compound is 10000 ppm or less, coloring and bleeding out derived from the hindered phenol-based compound can be suppressed. The content of the hindered phenol-based compound is more preferably 8000 ppm or less.

[0061] The hindered phenol compound has at least one hindered phenol group. The hindered phenol group refers to a bulky substituent bonded to at least one carbon atom adjacent to the carbon atom bonded to the hydroxyl group of phenol. The bulky substituent is preferably an alkyl group having 1 to 10 carbon atoms, more preferably a t-butyl group.

[0062] The hindered phenol compound is preferably in a solid state at about room temperature. From the viewpoint of suppressing bleeding out of the compound, the melting point or softening temperature of the hindered phenol compound is preferably 50° C. or higher, more preferably 60° C. or higher, and even more preferably 70° C. or higher. From the same viewpoint, the molecular weight of the hindered phenol compound is preferably 200 or higher, more preferably 400 or higher, and even more preferably 600 or higher. Meanwhile, the molecular weight is usually 2000 or lower. In addition, from the viewpoint of facilitating mixing with EVOH (c), the melting point or softening temperature of the hindered phenol compound is preferably 200° C. or lower, more preferably 190° C. or lower, and even more preferably 180° C. or lower.

[0063] The hindered phenol compound has an ester bond or an amide bond. Examples of the hindered phenol compound having an ester bond include esters of aliphatic carboxylic acids having a hindered phenol group and aliphatic alcohols, and examples of the hindered phenol compound having an amide bond include amides of aliphatic carboxylic acids having a hindered phenol group and aliphatic amines. Among these, it is preferable that the hindered phenol compound has an amide bond from the viewpoint of facilitating mixing with EVOH (c).

[0064] Specific structures of the hindered phenol compounds include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] commercially available from BASF as Irganox 1010, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)stearylpropionate commercially available as Irganox 1076, 2,2'-thiodiethylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] commercially available as Irganox 1035, and 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate commercially available as Irganox 1135. octadecyl-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate, ethylene bis(oxyethylene) bis(3-tert-butyl-4-hydroxy-5-methylbenzenepropanoate) available commercially as Irganox 245, 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] available commercially as Irganox 259, and N,N'-hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide] available commercially as Irganox 1098. Among these, N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], commercially available as Irganox 1098, and pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], commercially available as Irganox 1010, are preferred, with the former being more preferred.

[0065] The barrier layer (C) may further contain a thermoplastic resin other than EVOH (c). As the thermoplastic resin, in addition to polyethylene (b), each of the resins exemplified as the thermoplastic resin that may be contained in the moisture-proof layer (B) may be used. The content of the thermoplastic resin other than EVOH (c) in the barrier layer (C) is less than 50% by mass, preferably less than 30% by mass, more preferably less than 10% by mass, further preferably 5% by mass or less, and may be 1% by mass or less.

[0066] The proportion of EVOH (c) in the resin constituting the barrier layer (C) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, or 99% by mass or more, or the resin constituting the barrier layer (C) may be composed only of EVOH (c). The proportion of EVOH (c) in the barrier layer (C) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, or 99% by mass or more, or the barrier layer (C) may be composed substantially only of EVOH (c).

[0067] When the barrier layer (C) contains a component other than EVOH (c), the method for producing the resin composition constituting the barrier layer (C) is not particularly limited, but the barrier layer (C) can be produced by melt-kneading EVOH (c) and other additives (polyvalent metal ions (z) and the like) as necessary. The other additives may be blended in a solid state such as powder or as a melt, or may be blended as a solute contained in a solution or a dispersoid contained in a dispersion. As the solution and dispersion, an aqueous solution and an aqueous dispersion are preferable. For the melt-kneading, a known mixing or kneading device such as a kneader-ruder, an extruder, a mixing roll, or a Banbury mixer can be used. The temperature range during melt-kneading can be appropriately adjusted depending on the melting point of the EVOH (c) used, and is usually 150 to 300°C. Alternatively, the barrier layer (C) may be produced by adding some components to the EVOH (c) in advance and then melt-kneading other components required as described above. An example of a method for adding some components to EVOH (c) in advance is a method in which EVOH (c) is immersed in the form of pellets or powder in a solution in which the added components are dissolved. As the solution, an aqueous solution is preferable.

[0068] In another embodiment, a master batch containing other additives at a high concentration relative to EVOH (c) is produced by melt kneading, and the master batch is dry-blended with EVOH (c) that does not substantially contain other additives, and can be used to produce a multilayer structure. In yet another embodiment, EVOH (c) and other additives can be dry-blended to produce a multilayer structure. Dry blending refers to mechanical mixing in the form of powder or pellets. Mixing may be performed using a mixing device such as a tumbler, ribbon mixer, or Henschel mixer, or may be performed by manually stirring or shaking in a closed container. The mixing temperature may be from room temperature to below the melting point of EVOH (c), and mixing can be performed under an air atmosphere or a nitrogen atmosphere.

[0069] [Adhesive resin (d) and adhesive layer (D)] The multilayer structure of the present invention preferably has an adhesive layer (D) containing an adhesive resin (d) as a main component. The adhesive layer (D) has a function of bonding the barrier layer (C) to the moisture proof layer (B) or a thermoplastic resin layer described below. Therefore, the adhesive layer (D) is preferably provided between the barrier layer (C) and the moisture proof layer (B) or the thermoplastic resin layer, and is preferably directly laminated to the barrier layer (C) and the moisture proof layer (B) or the thermoplastic resin layer.

[0070] The adhesive resin (d) may be, for example, a modified olefin polymer containing a carboxyl group obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to an olefin polymer by addition reaction or graft reaction. Examples of the unsaturated carboxylic acid or its anhydride include maleic acid, maleic anhydride, fumaric acid, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, citraconic acid, and hexahydrophthalic anhydride, among which maleic anhydride is preferably used. Specifically, one or a mixture of two or more selected from maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-propylene copolymer, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, and maleic anhydride graft-modified ethylene-vinyl acetate copolymer are preferably used, among which maleic anhydride graft-modified polyethylene is most preferable. The acid value of such adhesive resin (d) is usually 0.5 to 5 mgKOH / g, and preferably 1 to 4 mgKOH / g.

[0071] The adhesive resin (d) of the present invention may be a mixture of an unmodified resin (dx) and an acid-modified resin (dy). In this case, from the viewpoint of further increasing the mechanical strength, the unmodified resin (dx) preferably contains polyethylene (b), more preferably polyethylene (b). Here, when the unmodified resin (dx) contains polyethylene (b), the polyethylene (b) contained in the adhesive layer (D) and the polyethylene (b) contained in the moisture-proof layer (B) may be the same or different, but are preferably the same. In addition, the ratio (dx / dy) of the unmodified resin (dx) and the acid-modified resin (dy) in the adhesive resin (d) is preferably 55 / 45 to 95 / 5, more preferably 65 / 35 to 90 / 10. In this case, a resin having a relatively high degree of acid modification can be preferably used as the acid-modified resin (dy), and its acid value is preferably 5 to 30 mgKOH / g, more preferably 8 to 20 mgKOH / g. In this way, the mechanical strength of the resulting multilayer structure may be further improved while maintaining the necessary interlayer adhesive strength. When the adhesive resin (d) of the present invention is a mixture of an unmodified resin (dx) and an acid-modified resin (dy), the unmodified resin (dx) and the acid-modified resin (dy) may be melt-kneaded in advance, or the unmodified resin (dx) and the acid-modified resin (dy) may be dry-blended. For melt-kneading, known mixing or kneading devices such as a kneader-ruder, an extruder, a mixing roll, or a Banbury mixer may be used. The temperature range during melt-kneading can be appropriately adjusted depending on the melting points of the unmodified resin (dx) and the acid-modified resin (dy) used, and is usually 150 to 300°C. Dry blending refers to mechanical mixing in the form of powder or pellets. Mixing may be performed using a mixing device such as a tumbler, a ribbon mixer, or a Henschel mixer, or may be performed by manually stirring, shaking, or the like in a closed container. The mixing temperature may be from room temperature to below the melting points of the unmodified resin (dx) and the acid-modified resin (dy), and mixing can be carried out in an air atmosphere or a nitrogen atmosphere.

[0072] The adhesive layer (D) may contain other components other than the adhesive resin (d) as long as the effect of the present invention is not impaired. Examples of other components include alkali metal ions, polyvalent metal ions, carboxylic acids, phosphoric acid compounds, boron compounds, oxidation promoters, antioxidants, plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorants, UV absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, bulking agents, pigments, dyes, processing aids, flame retardants, and antifogging agents. The content of other components in the adhesive layer (D) is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less. The adhesive layer (D) may further contain a thermoplastic resin other than the adhesive resin (d). As the thermoplastic resin, in addition to polyethylene (b), the above-mentioned resins exemplified as the thermoplastic resin that may be contained in the moisture-proof layer (B) can be used. The content of the thermoplastic resin in the adhesive layer (D) is less than 50% by mass, preferably less than 30% by mass, more preferably less than 10% by mass, further preferably 5% by mass or less, and may be 1% by mass or less.

[0073] The proportion of the adhesive resin (d) in the resin constituting the adhesive layer (D) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, or 99% by mass or more, and the resin constituting the adhesive layer (D) may be composed only of the adhesive resin (d). The proportion of the adhesive resin (d) in the adhesive layer (D) is more than 50% by mass, preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, or 99% by mass or more, and the adhesive layer (D) may be substantially composed only of the adhesive resin (d).

[0074] [Multilayer structure] The multilayer structure of the present invention has a base layer (A) containing polyester (a) as a main component on one surface and a moisture-proof layer (B) containing polyethylene (b) as a main component on the other surface, the multilayer structure has a total thickness of 200 μm or more, the thickness ratio of the base layer (A) to the total thickness of the multilayer structure is 0.50 or more, and the interlayer adhesive strength between the base layer (A) and the layer adjacent to the base layer (A) is less than 200 gf / 15 mm. By having the above-mentioned configuration, the multilayer structure of the present invention can be easily separated from the base layer (A) and the portion other than the base layer (A) after use as a packaging material, for example. Therefore, the multilayer structure of the present invention is not only excellent in heat resistance and moisture resistance, but also excellent in recyclability, and a recycled resin with excellent quality can be obtained.

[0075] The multilayer structure of the present invention may further have a thermoplastic resin layer (R) containing, as a main component, a thermoplastic resin (r) which is a resin different from the polyester (a), the polyethylene (b), the EVOH (c) and the adhesive resin (d). The thermoplastic resin (r) is not particularly limited, and examples thereof include vinyl ester resin, polypropylene, propylene-α-olefin copolymer (α-olefin having 4 to 20 carbon atoms), polybutene, polypentene, and other olefins alone or copolymers thereof, polyamides such as nylon 6 and nylon 6,6, polystyrene, polyvinyl chloride, polyvinylidene chloride, acrylic resin, polycarbonate, chlorinated polyethylene, and chlorinated polypropylene. In particular, when the multilayer structure of the present invention further contains a thermoplastic resin layer (R), the thermoplastic resin (r) is preferably a thermoplastic resin consisting of only carbon atoms, hydrogen atoms and oxygen atoms, more preferably a thermoplastic resin consisting of only carbon atoms and hydrogen atoms, and even more preferably a thermoplastic resin consisting of only carbon atoms and hydrogen atoms and having a melting point of 150°C or less. As the thermoplastic resin having a melting point of 150° C. or less, a propylene-α-olefin copolymer (α-olefin having 4 to 20 carbon atoms) is preferable.

[0076] The proportion of the thermoplastic resin (r) in the resin constituting the thermoplastic resin layer (R) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, or 99% by mass or more, and the resin constituting the thermoplastic resin layer (R) may be composed only of the thermoplastic resin (r). The proportion of the thermoplastic resin (r) in the thermoplastic resin layer (R) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 95% by mass or more, 97% by mass or more, or 99% by mass or more, and the thermoplastic resin layer (R) may be substantially composed only of the thermoplastic resin (r).

[0077] On the other hand, the multilayer structure of the present invention preferably does not have a high melting point resin layer containing a resin having a melting point of 200°C or more as a main component, except for the base layer (A). In addition, the multilayer structure of the present invention preferably does not have a metal layer having a thickness of 1 μm or more. Furthermore, the multilayer structure of the present invention preferably does not have a curing type adhesive layer. By not having these layers, the recyclability of the multilayer structure can be further improved. Here, the metal layer refers to a layer having continuous and discontinuous surfaces made of metal, such as aluminum foil. In addition, the curing type adhesive layer refers to an adhesive layer that does not have plasticity after curing, such as a two-liquid reactive polyurethane adhesive layer in which a polyol component and a polyisocyanate component are mixed and reacted.

[0078] The multilayer structure of the present invention has a total thickness of 200 μm or more, preferably 300 μm or more, and may be 400 μm or more or 500 μm or more. If the multilayer structure of the present invention has a total thickness of less than 200 μm, the separation between the base layer (A) and other parts becomes insufficient. The multilayer structure of the present invention has a total thickness of usually 1000 μm or less, and may be 900 μm or less or 800 μm or less. With a total thickness in the above range, the multilayer structure of the present invention has sufficient mechanical strength while being lightweight, and is therefore preferably used for various packaging applications such as trays and cups.

[0079] The thickness ratio of the base layer (A) to the total thickness of the multilayer structure of the present invention is 0.50 or more, preferably 0.60 or more, preferably 0.70 or more, and may be 0.80 or more, or may be 0.95 or less. If the thickness ratio of the base layer (A) to the total thickness of the multilayer structure is less than 0.50, the separation between the base layer (A) and other parts becomes insufficient, and the recycled resin of the base layer (A) becomes a low-quality polyester resin. In addition, if the thickness ratio of the base layer (A) to the total thickness of the multilayer structure is within the above range, the multilayer structure of the present invention has excellent heat resistance and transparency.

[0080] In the multilayer structure of the present invention, the ratio of the total thickness of the layers containing polyethylene resin as a main component to the total thickness of the parts other than the base layer (A) is preferably 0.50 or more, more preferably 0.60 or more, even more preferably 0.70 or more, and may be 0.80 or more. When the requirement for gas barrier property is low and emphasis is placed on recyclability, the ratio is preferably 0.90 or more, more preferably 0.95 or more, and may be 0.97 or more. Here, "a layer containing polyethylene resin as a main component" mainly means the moisture-proof layer (B), and when the adhesive resin (d) is modified polyethylene, the adhesive layer (D) is also included as a layer containing polyethylene resin as a main component. When this ratio is within the above range, the multilayer structure of the present invention has excellent moisture resistance, and for example, after use as a packaging material, when the parts other than the base layer (A) are separated, recovered, and reused, a high-quality polyethylene recycled resin can be efficiently produced.

[0081] In the multilayer structure of the present invention, the ratio of the total thickness of the barrier layer (C) to the total thickness of the portion other than the base layer (A) is preferably 0.30 or less, more preferably 0.20 or less. When the requirement for gas barrier property is low and emphasis is placed on recyclability, the ratio is preferably 0.10 or less, more preferably 0.05 or less, and may be 0.03 or less. In the multilayer structure of the present invention, the ratio of the total thickness of the barrier layer (C) to the total thickness of the portion other than the base layer (A) is preferably 0.01 or more, more preferably 0.02 or more. When this ratio is within the above range, the multilayer structure of the present invention has excellent gas barrier property, while, for example, after use as a packaging material, when the portion other than the base layer (A) is separated, recovered, and reused, a high-quality polyethylene recycled resin can be efficiently produced.

[0082] The layer configuration of the multilayer structure of the present invention is as follows: the base layer (A) is indicated as "(A)", the moisture-proof layer (B) as "(B)", the barrier layer (C) as "(C)", the adhesive layer (D) as "(D)", and when direct lamination is indicated with " / ", for example, (A) / (B), (A) / (C) / (D) / (B), (A) / (B) / (D) / (C) / (D) / (B), (A) / ( From the viewpoint of achieving both productivity and gas barrier properties, the layer structure of (A) / (C) / (D) / (B) or (A) / (B) / (D) / (C) / (D) / (B) / (D) / (C) / (D) / (B) is preferred. The (A) / (C) / (D) / (B) structure has the advantage that the interlayer adhesive strength with the base layer (A) can be easily controlled by appropriately adjusting the composition of the barrier layer (C), and that the structure has excellent transparency. In addition, the (A) / (B) / (D) / (C) / (D) / (B) structure has adhesive layers (D) on both sides of the barrier layer (C), so that the adhesive resin (d) can easily function as a compatibilizer for the polyethylene (b) and EVOH (c), and has the advantage that high-quality recycled polyethylene resin can be produced more efficiently when the parts other than the base layer (A) are separated, recovered, and reused. When multiple moisture barrier layers (B), barrier layers (C), and adhesive layers (D) are used, different types of resins can be used for each.

[0083] The interlayer adhesive strength between the base layer (A) and the layer adjacent to the base layer (A) is less than 200 gf / 15 mm. If the interlayer adhesive strength is 200 gf / 15 mm or more, the separation between the base layer (A) and other parts becomes insufficient, making it difficult to properly recycle. The interlayer adhesive strength may be less than 150 gf / 15 mm or less than 100 gf / 15 mm. The interlayer adhesive strength is usually 10 gf / 15 mm or more. The interlayer adhesive strength can be adjusted by the composition of the adjacent layers, the molding temperature during lamination, etc. From the viewpoint of improving the recyclability of the base layer (A), it is preferable that the layer adjacent to the base layer (A) is not an adhesive or adhesive resin (adhesive layer (D)), and is preferably a moisture-proof layer (B) or a barrier layer (C).

[0084] On the other hand, the interlayer adhesive strength between the base material layer (A) and layers other than the layer adjacent to the base material layer (A) is preferably 200 gf / 15 mm or more, more preferably 300 gf / 15 mm or more, even more preferably 400 gf / 15 mm or more, and may be 500 gf / 15 mm or more. When the interlayer adhesive strength is within these ranges, the multilayer structure of the present invention is excellent in productivity and handling as a packaging material, while the base material layer (A) and the portion other than the base material layer (A) can be easily separated after use. The interlayer adhesive strength between the layers other than the base material layer (A) and the layer adjacent to the base material layer (A) can be adjusted by the type of adhesive layer (D) or by providing an adhesive layer (D) between each layer.

[0085] The oxygen transmission rate (OTR) of the multilayer structure of the present invention under conditions of 20° C. and 65% RH is not particularly limited and may be adjusted depending on the application. 2 ·day·atm) or less is preferable. OTR is 2.0cc / (m 2 The multi-layer structure has an OTR of 1.5cc / (m2) or less, and is suitable for use as a packaging material with excellent gas barrier properties and excellent preservation properties for the contents. 2 ·day·atm) or less is more preferable, and 1.0cc / (m 2 ·day·atm) or less is more preferable, and 0.5cc / (m 2The OTR is measured in accordance with JIS K 7126-2:2006, and specifically, the method described in the Examples is used.

[0086] As a method for producing the multilayer structure of the present invention, a conventional coextrusion method in which each resin is extruded from a separate die or a common die and laminated can be preferably used. That is, the multilayer structure of the present invention is preferably a coextrusion molded product, in other words, a coextrusion multilayer structure. As the die, either a circular die or a T-die can be used. The molding temperature during melt molding may be appropriately adjusted based on the melting point and melt viscosity of the resin used, and is often selected from the range of 150 to 300°C. The multilayer structure of the present invention may be unstretched, or may be uniaxially or biaxially stretched or rolled, but generally, an unstretched one is used, and when secondary processing such as thermoforming is performed in a subsequent process, an unstretched one is preferable. In another embodiment, the multilayer structure of the present invention can be produced by using an extrusion lamination method, a thermal lamination method, a dry lamination method, or the like, or by using a combination of a plurality of them. The multilayer structure can also be produced by a coinjection method.

[0087] The multilayer structure of the present invention may have layers other than those described above, provided that the effects of the present invention are not impaired. Examples of the other layers include a recovered layer. In particular, it is preferable to reuse a recovered composition containing a recycled resin (a-containing resin or b-containing resin) obtained after separating the base layer (A) of the multilayer structure of the present invention as a part or the whole of the recovered layer. Another example of the other layer is a printed layer. When the multilayer structure of the present invention is separated into the base layer (A) and the portion other than the base layer (A), the printed layer is preferably laminated at a position included in the portion other than the base layer (A). Examples of the printed layer include a film obtained by applying a solution containing a pigment or dye and, if necessary, a binder resin, and drying the applied solution. Examples of the coating method of the printed layer include gravure printing, as well as various coating methods using a wire bar, a spin coater, a die coater, and the like. The thickness of the printed layer is not particularly limited, but is preferably 0.5 to 10 μm, more preferably 1 to 4 μm.

[0088] The multilayer structure of the present invention can be reheated and then subjected to secondary forming by a known method such as deep drawing, blow molding, or press molding to produce the multilayer container of the present invention. The deep drawing may be vacuum deep drawing, compressed air deep drawing, or vacuum compressed air deep drawing. In this case, it is preferable to mold the base layer (A) so that it is on the outside of the multilayer container. In this way, the multilayer container has a transparent and glossy excellent appearance and excellent heat resistance. Furthermore, when producing a composite container to be described later, the moisture-proof layer (B) located on the inside of the container can exhibit excellent thermal fusion with the lid material, and after use, the parts other than the base layer (A) can be separated from the lid material as a whole, so that the container has excellent separability. The shape of the multilayer container of the present invention can be selected from any shape such as a tray or a cup.

[0089] A composite container obtained by heat-sealing a lid material having a heat-sealing layer containing polyethylene as a main component to the multilayer container of the present invention is also an embodiment of the present invention. The lid material preferably has gas barrier properties. The total thickness of the lid material is preferably 30 to 300 μm, more preferably 40 to 200 μm, and even more preferably 50 to 150 μm. The ratio of the total thickness of the layers containing polyethylene resin as a main component to the total thickness of the lid material is preferably 0.50 or more, preferably 0.60 or more, preferably 0.70 or more, and may be 0.80 or more. When the requirement for gas barrier properties is low and emphasis is placed on recyclability, the ratio is preferably 0.90 or more, more preferably 0.95 or more, and may be 0.97 or more. When the lid material satisfies such requirements, the composite container of the present invention has excellent storage properties for the contents, and after use, the lid material can be separated from the parts of the multilayer container other than the base layer (A) as a whole, so that high-quality recycled polyethylene resin can be efficiently produced.

[0090] After use as a container, the multilayer container or composite container of the present invention can be separated and recovered into a portion consisting of the base layer (A) and a portion consisting of other than the base layer (A), and each portion can be melt-molded independently to produce a high-quality recycled resin. The portion consisting of other than the base layer (A) can also be separated and recovered together with the lid material. In one aspect of the present invention, the separation work of the multilayer container or composite container can be performed manually without using tools, etc., but compared to conventional techniques, since no special adhesives or the like are used, it is easy to suppress the mixing of other components into the separated base layer (A), and since no special operation such as immersion in a solvent is required, it is possible to easily separate and obtain a high-quality recovered resin. Such separation and recovery operations are usually performed by the end consumer at the site where the packaging material is finally consumed, such as an ordinary home or a store. The portion consisting of the base layer (A) has an extremely high polyester ratio, so that a polyester recycled resin can be produced, and the portion consisting of other than the base layer (A) has a high polyethylene ratio, so that a polyethylene recycled resin can be produced. In addition, even if there are residues of the contents such as food in the container, the residues do not come into contact with or are mixed into the portion consisting of the base layer (A), so that recycled polyester resins of higher quality can be efficiently produced. The produced recycled resins can be used to produce various molded products by known molding methods such as extrusion molding, inflation extrusion, blow molding, melt spinning, and injection molding. The molding temperature during melt molding may be appropriately adjusted based on the melting point and melt viscosity of the resin used. When producing molded products using recycled resins, unused resins of the same type may be contained, and in this case, the content of recycled resin is preferably 10% by mass or more, more preferably 20% by mass or more, and may be 30% by mass or more.

[0091] The multilayer structure, multilayer container, or composite container of the present invention has excellent heat resistance and moisture resistance, and therefore can be suitably used as a material for various packaging such as food packaging, pharmaceutical packaging, industrial chemical packaging, and agricultural chemical packaging, but can also be used in a wider range of applications, and is not limited to these applications. In addition, the multilayer structure, multilayer container, or composite container of the present invention also has excellent separability after use, and therefore can greatly improve recyclability, thereby contributing to solving environmental and waste problems.

[0092] A preferred embodiment of the present invention is a package obtained by filling the multilayer container or composite container with a content. Contents that can be filled include, but are not limited to, beverages such as wine and fruit juice, foods such as fruits, nuts, vegetables, meat products, baby foods, coffee, jams, mayonnaise, ketchup, edible oils, dressings, sauces, foods boiled in soy sauce, dairy products, and other foods such as medicines and cosmetics. EXAMPLES

[0093] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples in any way.

[0094] Example 1 (1) Polyester (a)-containing resin composition for substrate layer (A) Polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") consisting of 50 mol% terephthalic acid units, 49 mol% ethylene glycol units, and 1 mol% diethylene glycol units and having an intrinsic viscosity of 0.75 dl / g was used as polyester (a-1) as resin composition pellets for the base layer (A).

[0095] (2) Preparation of polyethylene (b)-containing resin composition for moisture-proof layer (B) Dow Chemical's polyethylene (b-1) "Elite (trademark) AT6101" (linear low-density polyethylene polymerized with ethylene and 1-octene using a metallocene catalyst, MFR (190°C, 2.16 kg load) 0.8 g / 10 min, density 0.905 g / cm 3) and stearic acid amide (higher fatty acid amide compound (x-1)) (melting point 101°C) were melt-kneaded so that the content of stearic acid amide in the resulting resin composition was 4 mass%, to produce master batch pellets containing stearic acid amide. The melt-kneading was carried out using a twin-screw extruder (D (mm) = 25, L / D = 25, screws: same direction fully intermeshing type) manufactured by Toyo Seiki Seisakusho, Ltd., so that the resin temperature was 220°C. Next, polyethylene (b-1) pellets and the resulting master batch pellets were dry blended in a mass ratio of 98 / 2 to obtain a resin composition mixed pellet for the moisture-proof layer (B).

[0096] (3) Preparation of EVOH (c)-containing resin composition for barrier layer (C) EVOH (c-1) (ethylene unit content 32 mol%, saponification degree 99.99, MFR (190°C, 2.16 kg load) 1.6 g / 10 min, sodium acetate 220 ppm in terms of sodium ion, phosphate ion 30 ppm in terms of phosphate radical, boric acid 150 ppm in terms of boron element, no polyvalent metal ions) and magnesium stearate (Mg-St) were melt-kneaded so that the magnesium ion content in the resulting resin composition was 50 ppm, to obtain resin composition pellets for the barrier layer (C). The melt-kneading was performed using a twin-screw extruder (D (mm) = 25, L / D = 25, screws: same direction fully intermeshing type) manufactured by Toyo Seiki Seisakusho Co., Ltd., so that the resin temperature was 220°C.

[0097] (4) Resin composition containing adhesive resin (d) for adhesive layer (D) Maleic anhydride modified polyethylene "Admer (trademark) NF518" manufactured by Mitsui Chemicals (MFR (190°C, 2.16 kg load) 3.1 g / 10 min, density 0.91 g / cm 3 The resin composition pellets were used as they were as adhesive resin (d-1) for the adhesive layer (D).

[0098] (5) Fabrication of multilayer structures Using each of the resin composition pellets (1) to (4) above, a multilayer structure having a layer thickness and layer structure of (A) / (B) / (D) / (C) / (D) / (B)=500μm / 40μm / 6μm / 8μm / 6μm / 40μm=PET500 / PE40 / tie6 / EVOH8 / tie6 / PE40 was produced using a co-extrusion film-forming equipment. All extruders were single-screw extruders with D(mm)=30, and full-flight screws with L / D=28 and compression ratio of 3.0 were used. For layers with large thickness, such as the base layer (A), multiple extruders were used. In addition, a 350mm wide T-die with a feed block lamination method was used as the die. The temperature conditions at this time are shown below. Extrusion temperature of base layer (A): feeding section / compression section / metering section / adapter = 270 / 270 / 270 / 275°C Extrusion temperature of moisture-proof layer (B): Feeding section / compression section / metering section / adapter = 175 / 220 / 220 / 275℃ Extrusion temperature of barrier layer (C): feeding section / compression section / metering section / adapter = 175 / 220 / 220 / 275℃ Extrusion temperature of adhesive layer (D): feeding section / compression section / metering section / adapter = 175 / 220 / 220 / 275°C Die temperature: 275℃ Cooling roll temperature: 80℃

[0099] (6) Interlayer adhesive strength between layers of a multi-layer structure After conditioning the multilayer structure obtained in (5) above at 23°C and 50% RH, a sample with a length of 150 mm and a width of 15 mm was cut along the extrusion direction, and the peel strength was measured when peeled in a T-type peel mode at a tensile speed of 250 mm / min under an atmosphere of 23°C and 50% RH using an autograph "DCS-50M tensile tester" manufactured by Shimadzu Corporation. The measurement was performed on the peeled surface between each layer. The interlayer adhesive strength between the base layer (A) and the layer adjacent to the base layer (A) (moisture-proof layer (B)) was judged according to three criteria: less than 100 gf / 15 mm, 100 gf / 15 mm or more but less than 200 gf / 15 mm, and 200 gf / 15 mm or more. The results are shown in Table 3. In addition, the interlayer adhesion strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (the interlayer adhesion strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more.

[0100] (7) Evaluation of appearance characteristics of multi-layered structures (transparency evaluation) The multilayer structure obtained in (5) above was visually evaluated and judged according to the following criteria. The results are shown in Table 3. Judgment criteria A: High transparency and uniform appearance B: Slightly less transparent, but has a uniform appearance C: Slightly low transparency, slight unevenness, or slight defects D: Very low transparency, moderate unevenness, or moderate defects E: Low transparency, severe unevenness, or severe defects

[0101] (8) Measurement of oxygen transmission rate of multi-layer structure The multilayer structure obtained in (5) above was used to measure the oxygen transmission rate, with one side being the oxygen supply side and the other being the carrier gas side. Specifically, an oxygen transmission rate (unit: cc / (m)) was measured using an oxygen transmission amount measuring device ("MOCON OX-TRAN2 / 21" manufactured by Modern Controls) in accordance with JIS K 7126-2 (isobaric method; 2006) under the conditions of a temperature of 20°C, a humidity of 65% RH on the oxygen supply side, a humidity of 65% RH on the carrier gas side, an oxygen pressure of 1 atm, and a carrier gas pressure of 1 atm.2 The solubility in water of 1000 ml was measured and rated according to the following criteria. Nitrogen gas containing 2% by volume of hydrogen gas was used as the carrier gas. The results are shown in Table 3. Judgment criteria A: 0.5cc / (m 2 ·day·atm) B: 0.5cc / (m 2 ·day · atm) or more, 1.0cc / (m 2 ·day·atm) C: 1.0cc / (m 2 ·day · atm) or more, 1.5cc / (m 2 ·day·atm) D: 1.5cc / (m 2 ·day · atm) or more, 2.0cc / (m 2 ·day·atm) E: 2.0cc / (m 2 ·day · atm) or more

[0102] (9) Fabrication of multi-layer containers The multilayer structure obtained in (5) above was used in a thermoforming machine (Asanose Seisakusho: vacuum and compressed air deep drawing machine "FX-0431-3 type"), where the sheet temperature was set to 130°C and compressed air (pressure 5 kgf / cm) was used to form the multilayer structure. 2 ) into a round cup shape (mold shape: upper part 75 mmφ, lower part 60 mmφ, depth 37 mm, drawing ratio S = 0.5) to produce a multilayer container. The multilayer structure was thermoformed so that the base layer (A) side was on the outside of the container. The molding conditions are shown below. Heater temperature: 600℃ Plug: 45φ×65mm Mold temperature: 40℃

[0103] (10) Heat resistance evaluation of multi-layer containers The multilayer container obtained in (9) above was placed upside down on a horizontal table (with the bottom surface facing up and the opening facing down) and a 1 kg load was placed on top of it (above the bottom surface). It was left in this state at 90°C, and the state of the container and the load after 5 hours was observed and judged according to the following criteria. The results are shown in Table 3. Note that ratings D and E are unacceptable standards. Judgment criteria A: Almost no deformation is observed B: Slight deformation is observed (drop in the lowest part of the load is less than 1 cm) C: Slight deformation is observed (drop in the bottom of the load is 1 cm or more, but less than 1.5 cm) D: Moderate deformation is observed (drop in the bottom of the load is 1.5 cm or more, but less than 2 cm) E: Severe deformation is observed (drop of the bottom of the load is 2cm or more)

[0104] (11) Moisture resistance evaluation of multi-layer containers 20 g of powdered milk was placed into the opening of the multi-layer container obtained in (9) above, and a lid film having a structure of aluminum foil / polyethylene = 15 μm / 50 μm was heat-sealed (heat-sealed between the polyethylene lid and the moisture-proof layer (B) of the multi-layer container) to seal the opening of the multi-layer container, thereby producing a composite container containing powdered milk as the content. This container was left to stand at a temperature of 40°C and a humidity of 90%, and the state of the powdered milk after 5 days was observed and judged according to the following criteria. The results are shown in Table 3. Note that judgment E is an unacceptable criterion. Judgment criteria A: Almost no change was observed. B: A small amount of clumping is observed. C: Slight clumping or slight discoloration is observed. D: Moderate clumping or moderate discoloration E: Severe clumping or severe discoloration is observed.

[0105] (12) Evaluation of adhesion resistance of multi-layer containers Four of the multi-layer containers obtained in (9) above were stacked on a horizontal table with the openings at the bottom, and a 500 g load was placed on the upper bottom surface and left to stand at room temperature. After one hour, the stacked containers were separated by hand. The ease of separation was used as an index of adhesion resistance and was evaluated according to the following criteria. The results are shown in Table 3. Judgment criteria A: It can be disassembled smoothly. B: It takes some force to separate it. C: It is difficult to disassemble without applying a great deal of force, or slight adhesion marks or scratches remain on the container after disassembly. D: Difficult to disassemble, or container has moderate to severe adhesion marks or scratches after disassembly

[0106] (13) Evaluation of separation properties of multi-layer containers A composite container was produced by heat-sealing (heat-sealing between the polyethylene of the lid material and the moisture-proof layer (B) of the multilayer container) a lid material film having a polyethylene / adhesive resin / EVOH / adhesive resin / polyethylene=30μm / 4μm / 6μm / 4μm / 30μm structure to the multilayer container obtained in (9) above. At this time, a tab portion that can be held with fingers was molded in the lid material film. Next, the tab portion of the lid material film was held with fingers, and separated into a portion consisting of the base material layer (A) and a portion consisting of other than the base material layer (A) (including the lid material film), and the ease of separation was judged according to the following criteria. When separating, the lid material film and the portion consisting of other than the base material layer (A) of the multilayer container were not peeled off, and only the base material layer (A) of the multilayer container portion was peeled off and separated. The results are shown in Table 3. In addition, judgments D and E are unacceptable criteria. In addition, the separated portion consisting of other than the base material layer (A) has a high ratio of resin containing polyethylene as the main component, and is suitable for producing polyethylene-based recycled resin. Judgment criteria A: It can be separated smoothly. B: Cannot be separated without some force C: Separation is not possible without considerable force, the container is deformed during separation, making workability somewhat poor, or cracks occur in the part consisting of the base layer (A) or in the part consisting of a layer other than the base layer (A) during separation. D: Separation is not possible without applying a very strong force, the container is significantly deformed during separation, making the workability poor, or the part made of the base layer (A) or the part made of other than the base layer (A) is broken during separation. E: Cannot be separated at all

[0107] (10) Light transmittance of substrate layer (A) The multilayer container obtained in (9) above was separated into a portion consisting of the base layer (A) and a portion consisting of other than the base layer (A). The light transmittance of the separated portion consisting of the base layer (A) at a wavelength of 600 nm was measured using a Shimadzu Corporation ultraviolet-visible spectrophotometer "UV-2450" and was found to be 85% or more.

[0108] (14) Evaluation of recyclability of the part consisting of the base layer (A) separated from the multi-layer container The multilayer container obtained in (9) above was separated into a portion consisting of the base layer (A) and a portion consisting of other than the base layer (A), and the portion consisting of the base layer (A) was collected and crushed into pieces of 4 mm square or less. The crushed pieces were sandwiched between Teflon (registered trademark) sheets of 1 mm thickness and heat-pressed at 280°C to obtain a monolayer film of about 200 μm thickness. The obtained monolayer film was uniform, highly transparent, and had a good appearance.

[0109] (15) Recyclability evaluation of the parts other than the base layer (A) separated from the multi-layer container The multilayer container obtained in (9) above was separated into a portion consisting of the base layer (A) and a portion consisting of other than the base layer (A), and the portion consisting of other than the base layer (A) was collected and crushed into pieces of 4 mm square or less. The crushed pieces were mixed with a low-density polyethylene resin "Novatec LD LJ400" (MFR (190°C, 2.16 kg load) 1.5 g / 10 min, density 0.921 g / cm) manufactured by Japan Polyethylene Corporation. 3 ) was blended in a mass ratio (ground material / polyethylene resin) of 40 / 60, and a monolayer film with a thickness of 50 μm was obtained by performing monolayer film formation under the extrusion conditions shown below. The thickness of the monolayer film was adjusted by appropriately changing the screw rotation speed and the take-up roll speed. As a control, a monolayer film with a thickness of 50 μm was similarly obtained using only polyethylene resin. Extruder: Toyo Seiki Co., Ltd. single screw extruder Screw diameter: 20mmφ (L / D=20, compression ratio=3.5, full flight type) Extrusion temperature: feeding section / compression section / metering section / die = 230 / 230 / 230 / 230℃ Take-up roll temperature: 80℃ The state of lumps and coloring of the obtained monolayer film was evaluated on the following 5-level scale of A to E. The results are shown in Table 3. Judging the product: Criteria A: The amount of pimples was almost the same as the control. B: The amount of small particles was slightly more than in the control. C: Compared to the control, there were more small particles. D: Compared to the control, there was a greater amount of large bumps. E: The amount of large particles was significantly greater than in the control group. Judging color: Criteria A: The degree of color change was small compared to the control. B: Slight discoloration was observed compared to the control. C: Moderate coloring was observed compared to the control. D: Significant discoloration was observed compared to the control. E: Compared to the target, significant coloring and unevenness were observed. In addition, 60 g of this pulverized material was kneaded in a Labo Plastomill (biaxial counter-rotating) under nitrogen atmosphere at 230°C and 100 rpm, and the torque change was measured. The torque values ​​(TI) 10 minutes after the start of kneading and the torque values ​​(TF) 90 minutes after the start of kneading were calculated, and the viscosity stability was evaluated on a four-level scale (A to E) based on the ratio of these values ​​(TF / TI). The results are shown in Table 3. Judgment criteria A: 80 / 100 or more and less than 120 / 100 B: 70 / 100 or more but less than 80 / 100, or 120 / 100 or more but less than 130 / 100 C: 60 / 100 or more but less than 70 / 100, or 130 / 100 or more but less than 140 / 100 D: 50 / 100 or more but less than 60 / 100, or 140 / 100 or more but less than 150 / 100 E: Less than 50 / 100 or more than 150 / 100

[0110] Example 2 Instead of polyethylene (b-1), polyethylene (b-2) "Evolue (trademark) SP0510" manufactured by Prime Polymer Co., Ltd. (linear low-density polyethylene polymerized with ethylene and 1-octene using a metallocene catalyst, MFR (190°C, 2.16 kg load) 1.2 g / 10 min, density 0.903 g / cm 3 ), resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. The light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the crushed product was uniform, highly transparent, and had a good appearance. The multilayer structures obtained in Example 1 and Example 2 were conditioned for 24 hours under conditions of 23° C. and 50% RH, and then the puncture strength was measured when a needle with a tip diameter of 1 mm was pierced at a speed of 50 mm / min under the same conditions. The multilayer structure obtained in Example 2 had a slightly inferior puncture strength compared to the multilayer structure obtained in Example 1.

[0111] Example 3 Instead of polyethylene (b-1), polyethylene (b-3) "Evolue (trademark) SP0540" manufactured by Prime Polymer Co., Ltd. (linear low-density polyethylene polymerized with ethylene and 1-octene using a metallocene catalyst, MFR (190°C, 2.16 kg load) 3.8 g / 10 min, density 0.903 g / cm 3), resin composition pellets, a multilayer structure, a multilayer container, and a composite container were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. The light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and a single-layer film having a thickness of about 200 μm obtained by hot pressing the pulverized product was uniform, highly transparent, and had a good appearance. In addition, the multilayer structures obtained in Examples 2 and 3 were conditioned for 24 hours under conditions of 23°C and 50% RH, and then a 500 g weight was dropped from a height of 50 cm under the same conditions to check for the presence or absence of breakage. As a result, the rate and extent of breakage of the multilayer structure of Example 3 was slightly higher than that of the multilayer structure of Example 2.

[0112] Example 4 Instead of polyethylene (b-1), polyethylene (b-4) "Evolue (trademark) SP1510" manufactured by Prime Polymer Co., Ltd. (linear low-density polyethylene polymerized with ethylene and 1-octene using a metallocene catalyst, MFR (190°C, 2.16 kg load) 1.0 g / 10 min, density 0.915 g / cm 3), resin composition pellets, multilayer structures, multilayer containers, and composite containers were prepared in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (interlayer adhesive strengths of the base layer (B) and the adhesive layer (D), and the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. The light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the crushed product was uniform, highly transparent, and had a good appearance. Compared to Example 2, the moisture resistance was excellent, but the composite container obtained in Example 2 and the composite container obtained in Example 4 were filled with water as the content and dropped from a height of 1 m, and the number of times until the water of the content leaked out was evaluated. As a result, the composite container of Example 4 took slightly fewer times until the water of the content leaked out than the composite container of Example 2.

[0113] Example 5 Instead of polyethylene (b-1), polyethylene (b-5) "Evolue (trademark) SP1540" manufactured by Prime Polymer Co., Ltd. (linear low-density polyethylene polymerized with ethylene and 1-octene using a metallocene catalyst, MFR (190 °C, 2.16 kg load) 3.8 g / 10 min, density 0.913 g / cm 3), resin composition pellets, a multilayer structure, a multilayer container, and a composite container were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. The light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and a single-layer film having a thickness of about 200 μm obtained by hot pressing the pulverized product was uniform, highly transparent, and had a good appearance. In addition, the multilayer structures obtained in Examples 4 and 5 were conditioned for 24 hours under conditions of 23°C and 50% RH, and then a 500 g weight was dropped from a height of 50 cm under the same conditions to check for the presence or absence of breakage. As a result, the rate and extent of breakage of the multilayer structure of Example 5 was slightly higher than that of the multilayer structure of Example 4.

[0114] Example 6 Instead of polyethylene (b-1), polyethylene (b-6) "Novatec LD LJ400" manufactured by Japan Polyethylene Co., Ltd. (low density polyethylene, MFR (190°C, 2.16 kg load) 1.5 g / 10 min, density 0.921 g / cm 3), resin composition pellets, a multilayer structure, a multilayer container, and a composite container were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (the interlayer adhesive strengths of the base layer (B) and the adhesive layer (D), and the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. The light transmittance at a wavelength of 600 nm of the part consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the crushed product was uniform, highly transparent, and had a good appearance. Compared to Example 1, the moisture resistance was excellent, but the separation property of the composite container was poor. In addition, the composite containers obtained in Example 1 and Example 6 were filled with water and dropped from a height of 1 m to evaluate the number of times it took for the water to leak out.The composite container of Example 6 required fewer drops before the water leaked out compared to the composite container of Example 1.

[0115] Example 7 Instead of polyethylene (b-1), polyethylene (b-7) "Novatec LL UF943" (linear low-density polyethylene, MFR (190°C, 2.16 kg load) 2.1 g / 10 min, density 0.938 g / cm) manufactured by Japan Polyethylene Co., Ltd. was used. 3), resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (the interlayer adhesive strengths of the base layer (B) and the adhesive layer (D), and the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the part consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the crushed product was uniform, highly transparent, and had a good appearance. Compared to Example 6, the moisture resistance was superior. In addition, the evaluation of the separability of Examples 6 and 7 was both rated C, but the separability of the composite container of Example 7 was slightly inferior to that of Example 6. Furthermore, the composite containers obtained in Examples 6 and 7 were filled with water and dropped from a height of 1 m to evaluate the number of times it took for the water to leak out. The composite container of Example 7 took slightly fewer drops before the water leaked out than the composite container of Example 6.

[0116] Example 8 Instead of polyethylene (b-1), polyethylene (b-8) "Novatec HD HY540" manufactured by Japan Polyethylene Co., Ltd. (high density polyethylene, MFR (190°C, 2.16 kg load) 1.0 g / 10 min, density 0.960 g / cm 3), resin composition pellets, multilayer structures, multilayer containers, and composite containers were prepared in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the crushed product was uniform, highly transparent, and had a good appearance. The evaluations of moisture resistance and transparency of Examples 7 and 8 were both rated A, but the moisture resistance of Example 8 was superior to that of Example 7, while the transparency of Example 8 was inferior to that of Example 7. In addition, the separation properties of both Examples 7 and 8 were rated C, but the composite container of Example 8 was slightly inferior in separation properties to the composite container of Example 7. Furthermore, the composite containers obtained in Examples 7 and 8 were filled with water as the contents and dropped from a height of 1 m to evaluate the number of times until the water in the contents leaked out. As a result, the composite container of Example 8 required slightly fewer drops before the water in the contents leaked out compared to the composite container of Example 7.

[0117] Example 9 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that stearic acid amide (higher fatty acid amide compound (x-1)) was not used, and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the part consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the pulverized product was uniform, highly transparent, and had a good appearance. Compared to Example 1, the results showed that the anti-sticking properties were significantly inferior.

[0118] Examples 10 to 12 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that the dry blend ratio of polyethylene (b-1) pellets and stearic acid amide master batch pellets was changed so that the content of stearic acid amide (higher fatty acid amide compound (x-1)) in the moisture-proof layer (B) was as shown in Table 1, and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the part consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the pulverized product was uniform, highly transparent, and had a good appearance. As the content of stearic acid amide increased, the sticking resistance was improved, but when the content was too high, the appearance characteristics were deteriorated.

[0119] Example 13 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that oleic acid amide (higher fatty acid amide compound (x-2)) (melting point 72°C) was used instead of stearic acid amide (higher fatty acid amide compound (x-1)), and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200gf / 15mm or more. In addition, the light transmittance at a wavelength of 600nm of the part consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200μm obtained by hot pressing the pulverized product was uniform, highly transparent, and had a good appearance. The multi-layer container obtained in Example 1 and the multi-layer container obtained in Example 13 were evaluated in an environment of 0°C as described in (12) Evaluation of anti-sticking properties of multi-layer containers in Example 1. The multi-layer container obtained in Example 13 had slightly better anti-sticking properties in a low temperature environment than the multi-layer container obtained in Example 1.

[0120] Example 14 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that stearic acid amide (higher fatty acid amide compound (x-1)) and oleic acid amide (higher fatty acid amide compound (x-2)) were used in a mass ratio of 1 / 1 instead of stearic acid amide (higher fatty acid amide compound (x-1)), and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the pulverized product was uniform, highly transparent, and had a good appearance. The multi-layer containers obtained in Examples 1, 13, and 14 were subjected to the evaluation described in (12) Evaluation of anti-sticking properties of multi-layer containers in Example 1 after leaving them at 0°C for 1 hour, then at 40°C for 1 hour, and then at 80°C for 1 hour. Example 14, which used two or more higher fatty acid amide compounds with different melting points, showed superior anti-sticking properties compared to Examples 1 and 13, which used higher fatty acid amide compounds alone, and exhibited excellent anti-sticking properties over a wider temperature range, from low temperature to high temperature.

[0121] Example 15 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that 10% by mass of spherical silica particles having an average particle size of 3.9 μm were further added and melt-kneaded when preparing master batch pellets containing stearic acid amide, and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the part consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the pulverized product was uniform, highly transparent, and had a good appearance. Compared to Example 1, excellent sticking resistance was observed.

[0122] Example 16 Except for using EVOH (c-2) (ethylene unit content 27 mol%, saponification degree 99.99, MFR (190°C, 2.16 kg load) 1.5 g / 10 min, sodium acetate 220 ppm in terms of sodium ion, phosphate ion 30 ppm in terms of phosphate radical, boric acid 120 ppm in terms of boron element, no polyvalent metal ion) instead of EVOH (c-1), resin composition pellets, multilayer structure, multilayer container and composite container were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. The light transmittance of the portion consisting of the base layer (A) at a wavelength of 600 nm was 85% or more, and the crushed material was hot-pressed to obtain a single-layer film having a thickness of about 200 μm, which was uniform, highly transparent, and had a good appearance. Compared to Example 1, the recyclability was slightly decreased, but excellent gas barrier properties were observed.

[0123] Example 17 Except for using EVOH (c-3) (ethylene unit content 44 mol%, saponification degree 99.99, MFR (190°C, 2.16 kg load) 5.7 g / 10 min, sodium acetate 220 ppm in terms of sodium ion, phosphate ion 30 ppm in terms of phosphate radical, boric acid 100 ppm in terms of boron element, no polyvalent metal ion) instead of EVOH (c-1), resin composition pellets, multilayer structure, multilayer container and composite container were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. The light transmittance of the portion consisting of the base layer (A) at a wavelength of 600 nm was 85% or more, and the crushed material was hot-pressed to obtain a single-layer film having a thickness of about 200 μm, which was uniform, highly transparent, and had a good appearance. Compared to Example 1, the gas barrier property was slightly decreased, but excellent recyclability was observed.

[0124] Example 18 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that pellets obtained by dry blending EVOH (c-2) and EVOH (c-3) in a mass ratio of 80 / 20 were used instead of EVOH (c-1), and various measurements and evaluations were performed. The results are shown in Table 3. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the crushed product was uniform, highly transparent, and had a good appearance. Compared to Examples 16 and 17 in which EVOH was used alone, the balance of gas barrier properties, thermoformability, and recyclability was excellent. The thermoformability was evaluated by evaluating the unevenness in thickness of the side wall of the multi-layer container.

[0125] Example 19 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that EVOH (c-1) was used as EVOH-containing resin composition pellets without being kneaded with magnesium stearate, and EVOH (c-1) was used as it is as EVOH-containing resin composition pellets, and various measurements and evaluations were performed. The results are shown in Table 1. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. The light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the pulverized product was uniform, highly transparent, and had a good appearance.

[0126] Examples 20 to 22 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that the amount of magnesium stearate kneaded with EVOH (c-1) was changed as shown in Table 1, and various measurements and evaluations were performed. The results are shown in Tables 3 and 4. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. The light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the pulverized product was uniform, highly transparent, and had a good appearance.

[0127] Examples 23 to 25 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that the magnesium stearate kneaded with EVOH (c-1) was changed to calcium stearate (Ca-St) (Example 23), zinc stearate (Zn-St) (Example 24), and magnesium acetate (MgOAc) (Example 25), and various measurements and evaluations were performed. The results are shown in Table 4. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the pulverized product was uniform, highly transparent, and had a good appearance.

[0128] Examples 26 to 30 Except for changing the layer structure of the multilayer structure and the thickness of each layer as shown in Table 4 (the numerical values ​​described for the layer structure in Table 4 mean the thickness (μm) of each layer), resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 4. In Examples 26 to 29, the interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the crushed product was uniform, highly transparent, and had a good appearance.

[0129] Example 31 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that instead of polyester (a-1), a colored polyester (a-2) obtained by adding a white pigment to polyester (a-1) and melt-kneading the polyester was used, and various measurements and evaluations were performed. The results are shown in Table 4. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was less than 70%, and a single-layer film with a thickness of about 200 μm obtained by hot pressing the pulverized product was colored white, and the quality and economic value as a polyester-based recycled resin were reduced.

[0130] Examples 32 to 33 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that the thickness of each layer of the multilayer structure was changed as shown in Table 4, and various measurements and evaluations were performed. The results are shown in Table 4. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the pulverized product was uniform, highly transparent, and had a good appearance.

[0131] Example 34 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that polyethylene (b-1) was used as is as the resin composition for the moisture-proof layer (B) adjacent to the base layer (A), and various measurements and evaluations were performed. The results are shown in Table 4. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, and the single-layer film having a thickness of about 200 μm obtained by hot pressing the pulverized product was uniform, highly transparent, and had a good appearance.

[0132] Comparative Example 1 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that the thickness of each layer of the multilayer structure was changed as shown in Table 4, and various measurements and evaluations were performed. The results are shown in Table 4. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In addition, the light transmittance at a wavelength of 600 nm of the part consisting of the base layer (A) was 85% or more, but the monolayer film with a thickness of about 200 μm obtained by hot pressing the crushed product had slight defects.

[0133] Comparative Example 2 When producing a multilayer structure using a co-extrusion film production facility, the maleic anhydride modified polyolefin "Admer (trademark) SF741" (MFR (190 °C, 2.16 kg load) 6.0 g / 10 min, density 0.90 g / cm) manufactured by Mitsui Chemicals was used. 3 A 10 μm thick adhesive resin layer made of adhesive resin (d-2) was provided between the base material layer (A) and the moisture-proof layer (B), and the thickness of the PE adjacent to the PET500 was changed to 30 μm, resulting in a PET500 / tie * 10 / PE30 / tie6 / EVOH8 / tie6 / PE40(tie *means adhesive resin (d-2), and tie means adhesive resin (d-1). Except for producing a multilayer structure having a layer configuration of (a) and (b), resin composition pellets, a multilayer structure, a multilayer container, and a composite container were produced in the same manner as in Example 1, and various measurements and evaluations were carried out. The results are shown in Table 4. The interlayer adhesion strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesion strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In this comparative example, since the polyester and the adhesive resin have high interlayer adhesion, the base layer (A) could not be separated.

[0134] Comparative Example 3 The multilayer structure produced in Example 1 was separated into a portion consisting of the base layer (A) and a portion other than the base layer (A). Next, the portion consisting of the base layer (A) and the portion other than the base layer (A) were laminated via a 4 μm-thick two-liquid reactive polyurethane adhesive layer to form a multilayer structure of PET500 / Ad4 / PE40 / tie6 / EVOH8 / tie6 / PE40 (Ad is a polyurethane adhesive layer). Except for this, a multilayer container and a composite container were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 4. The interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In this comparative example, the polyester and the polyurethane adhesive layer have high interlayer adhesiveness, so the base layer (A) could not be separated.

[0135] Comparative Examples 4 to 6 Resin composition pellets, multilayer structures, multilayer containers, and composite containers were produced in the same manner as in Example 1, except that the layer structure of the multilayer structure and the thickness of each layer were changed as shown in Table 4, and various measurements and evaluations were performed. The results are shown in Table 4. In Comparative Examples 4 and 5, the interlayer adhesive strengths other than between the base layer (A) and the layer adjacent to the base layer (A) (interlayer adhesive strengths between the base layer (B) and the adhesive layer (D), and between the adhesive layer (D) and the barrier layer (C)) were all 200 gf / 15 mm or more. In Comparative Example 4, the light transmittance at a wavelength of 600 nm of the portion consisting of the base layer (A) was 85% or more, but the monolayer film with a thickness of about 200 μm obtained by hot pressing the crushed product had slight defects.

[0136] [Table 1]

[0137] [Table 2]

[0138] [Table 3]

[0139] [Table 4]

Claims

1. A multilayer structure having a base material layer (A) containing a polyester (a) as a main component on one surface and at least a moisture-proof layer (B) containing a polyethylene (b) as a main component on the other surface, wherein the total thickness of the multilayer structure is 200 μm or more, the thickness ratio of the base material layer (A) to the total thickness of the multilayer structure is 0.50 or more, and the interlayer adhesion strength between the base material layer (A) and the layer adjacent to the base material layer (A) is less than 200 gf / 15 mm.

2. The multilayer structure according to claim 1, further comprising a barrier layer (C) containing an ethylene-vinyl alcohol copolymer (c) having an ethylene unit content of 20 to 50 mol% and a saponification degree of 90 mol% or more as a main component and an adhesive layer (D) containing an adhesive resin (d) as a main component.

3. The multilayer structure according to claim 2, wherein the base material layer (A), the barrier layer (C), the adhesive layer (D), and the moisture-proof layer (B) are formed in a layer configuration adjacent to each other in this order, the interlayer adhesion strength between the base material layer (A) and the barrier layer (C) is less than 200 gf / 15 mm, and the interlayer adhesion strength of layers other than the interlayer between the base material layer (A) and the barrier layer (C) is 200 gf / 15 mm or more.

4. The multilayer structure according to claim 2, wherein the base material layer (A), the moisture-proof layer (B), the adhesive layer (D), the barrier layer (C), the adhesive layer (D), and the moisture-proof layer (B) are formed in a layer configuration adjacent to each other in this order, the interlayer adhesion strength between the base material layer (A) and the moisture-proof layer (B) is less than 200 gf / 15 mm, and the interlayer adhesion strength of layers other than the interlayer between the base material layer (A) and the moisture-proof layer (B) is 200 gf / 15 mm or more.

5. The polyethylene (b) is linear low density polyethylene, low density polyethylene or a mixture thereof, and has a density of 0.880 to 0.940 g / cm ３ The multilayer structure according to any one of claims 1 to 4, which is as described above.

6. The multilayer structure according to any one of claims 1 to 4, wherein the moisture-proof layer (B) located at least on the surface contains 100 to 7000 ppm of a higher fatty acid amide compound (x) having a melting point of 60 to 120°C.

7. The multilayer structure according to any one of claims 1 to 4, wherein the moisture-proof layer (B) located at least on the surface contains 500 to 5000 ppm of inorganic oxide particles (y) having an average particle diameter of 1 to 30 μm, and the inorganic oxide particles (y) are at least one selected from the group consisting of silicon oxide particles and metal oxide particles.

8. The multilayer structure according to any one of claims 2 to 4, wherein the barrier layer (C) contains 10 to 200 ppm of at least one polyvalent metal ion (z) selected from the group consisting of magnesium ions, calcium ions, and zinc ions.

9. The oxygen transmission rate under the conditions of 20 °C and 65% RH measured by the method described in JIS K 7126-2:2006 is less than 2.0 cc / (m ２ ·day·atm), and the multilayer structure according to any one of claims 1 to 4.

10. The multilayer structure according to any one of claims 1 to 4, wherein the light transmittance of the base material layer (A) at a wavelength of 600 nm is 70% or more.

11. The multilayer structure according to any one of claims 1 to 4, which does not have a high melting point resin layer containing a resin having a melting point of 200°C or higher as a main component, except for the base material layer (A).

12. The multilayer structure according to any one of claims 1 to 4, which is a coextruded multilayer structure.

13. A multilayer container obtained by secondary processing and molding the multilayer structure according to any one of claims 1 to 4.

14. A composite container having a lid material having a heat-sealing layer containing polyethylene as a main component and the multilayer container according to claim 13, wherein the lid material is heat-sealed to the multilayer container.

15. A recycling method including a step of separating the multilayer container according to claim 13 into a portion made of the base material layer (A) and a portion made of other than the base material layer (A).

16. The recycling method according to claim 15, including a step of independently melt-molding the portion made of the base material layer (A) and the portion made of other than the base material layer (A).