Multilayer container, method for producing recycled polyamide resin, and method for producing multilayer container

Abstract

Provided are a multilayer container, a method for producing a recycled polyamide resin, and a method for producing a multilayer container. The multilayer container comprises: a sealant layer containing an aromatic polyamide resin; a first multilayer body including a substrate layer containing an aliphatic polyamide resin; a sealant layer containing an aromatic polyamide resin; and a second multilayer body including a substrate layer containing an aliphatic polyamide resin, wherein a sealant layer of the first multilayer body and a sealant layer of the second multilayer body face each other and are partially fused together, and the thickness of the sealant layer of the first multilayer body and the thickness of the sealant layer of the second multilayer body are each independently 4 μm or more, and 40% or less of the total thickness of the first multilayer body or the second multilayer body, and 95 mass% or more of a resin component included in the multilayer container is a polyamide resin.

Description

Multilayer container, method for producing recycled polyamide resin, and method for producing multilayer container

[0001] The present invention relates to a multilayer container, a method for producing a recycled polyamide resin, and a method for producing a multilayer container, and more particularly to a multilayer container containing a polyamide resin as a main component.

[0002] Packaging materials used for packaging foods and the like are required to have a wide range of functions, such as strength, pinhole resistance, heat resistance, and visibility of the contents, in order to protect the contents from various processes such as distribution and heat sterilization. Furthermore, barrier properties are also required to prevent the permeation of oxygen and moisture in order to maintain the quality of the contents. To satisfy these various requirements, multilayer containers in which layers with different properties are stacked are used (see, for example, Patent Documents 1 and 2).

[0003] JP 2023-068909 A JP 2011-057237 A

[0004] However, such multilayer containers are difficult to separate the resins that make up each layer, making them unsuitable for recycling. Therefore, it would be ideal if multilayer containers could be formed from a single material or a composition close to that. On the other hand, films using polyamide resins have excellent heat resistance, strength, and oxygen gas barrier properties, but polyamide resins tend to have poor heat-sealing properties. Furthermore, since a resin other than polyamide resin is required for the sealant layer, it has been difficult to create a single-material container. Furthermore, when aromatic polyamide resins are used, the impact resistance of the film is insufficient. The present invention aims to solve these problems by providing a multilayer container that is excellent in recyclability, heat-sealing properties, and impact resistance, as well as a method for producing a recycled polyamide resin and a method for producing a multilayer container.

[0005] In light of the above-mentioned problems, the present inventors have conducted research and found that the above-mentioned problems can be solved by forming a container by fusing a sealant layer containing an aromatic polyamide resin and a substrate layer containing an aliphatic polyamide resin, and further reducing the thickness of the sealant layer so that 95% by mass or more of the entire multilayer container is polyamide resin. Specifically, the above-mentioned problems have been solved by the following means. <1> A multilayer container having: a first multilayer body including a sealant layer containing a polyamide resin and a substrate layer containing an aliphatic polyamide resin; and a second multilayer body including a sealant layer containing a polyamide resin and a substrate layer containing an aliphatic polyamide resin, wherein the sealant layer of the first multilayer body and the sealant layer of the second multilayer body face each other and are partially fused together; the thickness of the sealant layer of the first multilayer body and the thickness of the sealant layer of the second multilayer body are each independently 4 μm or more and 40% or less of the total thickness of the first multilayer body or the second multilayer body; the polyamide resin contained in the sealant layer of the first multilayer body and the polyamide resin contained in the sealant layer of the second multilayer body are each independently resins in which 30% by mass or more of all structural units excluding terminal groups are derived from aromatic monomers; the aliphatic polyamide resin contained in the first multilayer body and the aliphatic polyamide resin contained in the second multilayer body are each independently resins in which 80% by mass or more of all structural units excluding terminal groups are derived from aliphatic monomers; A multilayer container, wherein 95% by mass or more of the resin components contained in the multilayer container are polyamide resins.<2> The multilayer container according to <1>, wherein the first multilayer body and the second multilayer body each independently have a moisture content of 10,000 ppm by mass or less immediately before sealing.<3> The multilayer container according to <1> or <2>, wherein the sealant layer of the first multilayer body and the sealant layer of the second multilayer body each independently have a thickness of 6 μm or more.<4> The multilayer container according to any one of <1> to <3>, wherein the polyamide resin contained in the sealant layer of the first multilayer body and the polyamide resin contained in the sealant layer of the second multilayer body each independently contain diamine-derived structural units and dicarboxylic acid-derived structural units, and wherein 70 mol% or more of the diamine-derived structural units comprise a xylylenediamine-based polyamide resin derived from xylylenediamine.<5> The multilayer container according to <4>, wherein 70 mol % or more of the dicarboxylic acid-derived structural units in the xylylenediamine-based polyamide resin are structural units derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms. <6> The multilayer container according to any one of <1> to <5>, wherein the first multilayer body and the second multilayer body each independently have a moisture content of 10,000 mass ppm or less immediately before sealing, the sealant layer of the first multilayer body and the sealant layer of the second multilayer body each independently have a thickness of 6 μm or more, the polyamide resin contained in the sealant layer of the first multilayer body and the polyamide resin contained in the sealant layer of the second multilayer body each independently contain diamine-derived structural units and dicarboxylic acid-derived structural units, and the polyamide resin comprises a xylylenediamine-based polyamide resin derived from xylylenediamine, and 70 mol % or more of the dicarboxylic acid-derived structural units are structural units derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms. <7> The multilayer container according to any one of <1> to <6>, wherein in at least one of the first multilayer body and the second multilayer body, the sealant layer and the base layer are in contact with each other directly or via an adhesive layer, and the sealant layer is an unstretched film. <8> A method for producing a recycled polyamide resin, comprising crushing the multilayer container according to any one of <1> to <7>.<9> A method for producing a multilayer container, comprising: fusing a first multilayer body including a sealant layer containing a polyamide resin and a substrate layer containing an aliphatic polyamide resin; and a second multilayer body including a sealant layer containing a polyamide resin and a substrate layer containing an aliphatic polyamide resin, so that the sealant layer of the first multilayer body and the sealant layer of the second multilayer body face each other; wherein the thickness of the sealant layer of the first multilayer body and the thickness of the sealant layer of the second multilayer body are each independently 4 μm or more and 40% or less of the total thickness of the first multilayer body or the second multilayer body; the polyamide resin contained in the sealant layer of the first multilayer body and the polyamide resin contained in the sealant layer of the second multilayer body are each independently resins in which 30% or more by mass of all structural units excluding terminal groups are derived from aromatic monomers; and the aliphatic polyamide resin contained in the first multilayer body and the aliphatic polyamide resin contained in the second multilayer body are each independently resins in which 80% or more by mass of all structural units excluding terminal groups are derived from aliphatic monomers. The method for producing a multilayer container according to <9>, wherein 95% by mass or more of the resin components contained in the multilayer container is a polyamide resin, and the first multilayer body and the second multilayer body at the time of the fusion bonding each independently have a moisture content of 10,000 ppm by mass or less immediately before sealing. <10> The method for producing a multilayer container according to <9>, wherein the multilayer container is the multilayer container according to any one of <1> to <7>.

[0006] According to the present invention, it is possible to provide a multilayer container having excellent recyclability, excellent heat sealing properties, and excellent impact resistance, a method for producing a recycled polyamide resin, and a method for producing a multilayer container.

[0007] 1 is a cross-sectional schematic view showing an example of a multilayer container of the present invention.

[0008] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the following present embodiment is an example for explaining the present invention, and the present invention is not limited to this embodiment. Note that in this specification, the term "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits. In this specification, various physical property values ​​and characteristic values ​​are at 23°C unless otherwise specified. In this specification, "ppm" means "mass ppm" unless otherwise specified. If the measurement method, etc. described in the standards shown in this specification varies depending on the fiscal year, it will be based on the standard as of January 1, 2023, unless otherwise specified. In Figure 1, the scale may not be consistent with reality.

[0009] The multilayer container of this embodiment is a multilayer container having a first multilayer body including a sealant layer containing a polyamide resin and a substrate layer containing an aliphatic polyamide resin, and a second multilayer body including a sealant layer containing a polyamide resin and a substrate layer containing an aliphatic polyamide resin, wherein the sealant layer of the first multilayer body and the sealant layer of the second multilayer body face each other and are partially fused together, and the thickness of the sealant layer of the first multilayer body and the thickness of the sealant layer of the second multilayer body are each independently 4 μm or more and account for 40% or more of the total thickness of the first multilayer body or the second multilayer body. The polyamide resin contained in the sealant layer of the first multilayer body and the polyamide resin contained in the sealant layer of the second multilayer body are each independently a resin in which 30% by mass or more of all structural units excluding terminal groups are derived from aromatic monomers, the aliphatic polyamide resin contained in the first multilayer body and the aliphatic polyamide resin contained in the second multilayer body are each independently a resin in which 80% by mass or more of all structural units excluding terminal groups are derived from aliphatic monomers, and 95% by mass or more of the resin components contained in the multilayer container are polyamide resins. By adopting such a configuration, it is possible to provide a multilayer container that has excellent recyclability, excellent heat-sealing properties, and excellent impact resistance.

[0010] That is, by using a polyamide resin containing structural units derived from aromatic monomers (sometimes referred to as "aromatic polyamide resin" in this specification) as the resin constituting the sealant layer and setting the thickness to 4 μm or more, the sealant layers could be fused together. Furthermore, by using an aliphatic polyamide resin as the resin constituting the base layer, a structure close to a single material consisting of only polyamide resin could be achieved, resulting in a product with excellent recyclability. Furthermore, in this embodiment, by making the thickness of the sealant layer containing aromatic polyamide resin relatively thin, a multilayer body with excellent impact resistance was obtained.

[0011] <Layer structure of multilayer container> As shown in Figure 1(a), the multilayer container of this embodiment has a first multilayer body 1 and a second multilayer body 2. The first multilayer body 1 has a sealant layer 12 containing an aromatic polyamide resin and a substrate layer 13 containing an aliphatic polyamide resin. The second multilayer body 2 has a sealant layer 22 containing an aromatic polyamide resin and a substrate layer 23 containing an aliphatic polyamide resin. In the multilayer body 10 of this embodiment, the sealant layer of the first multilayer body and the sealant layer of the second multilayer body face each other and are partially fused together (Figure 1(b)). This fusion allows the container to be used as a packaging container.

[0012] In the multilayer container shown in FIG. 1 , the sealant layer and the substrate layer are in direct contact with each other; however, they may be in contact with each other via an adhesive layer. In this embodiment, it is preferable that the sealant layer and the substrate layer are in direct contact with each other without an adhesive layer. In this embodiment, the sealant layer and the substrate layer can be produced as a coextruded body by coextrusion, allowing the sealant layer and the substrate layer to be bonded without an adhesive. Furthermore, the multilayer body in this embodiment can be produced using known methods such as coextrusion, various lamination methods, and various coating methods depending on the properties, processing purpose, processing steps, etc. of the various materials, and the production method is not particularly limited. The multilayer body can be produced by methods for laminating conventional packaging materials, such as wet lamination, dry lamination, solventless dry lamination, extrusion lamination, T-die coextrusion molding, coextrusion lamination, inflation, etc. When producing the above multilayer body, pretreatments such as corona treatment and ozone treatment can be applied to the film, etc., as needed.

[0013] On the other hand, when the sealant layer and the substrate layer are in contact with each other via an adhesive layer, the adhesive layer is preferably a dry lamination adhesive. Examples of dry lamination adhesives include one-component adhesives using a urethane adhesive having an isocyanate group alone, and two-component adhesives using a two-component mixture of a base agent having a hydroxyl group and a curing agent having an isocyanate group. Two-component adhesives are particularly preferred. When producing a multilayer body by co-extrusion, the adhesive layer preferably contains an adhesive thermoplastic resin. Examples of adhesive thermoplastic resins include acid-modified polyolefin resins obtained by modifying polyolefin resins such as polyethylene or polypropylene with acids such as unsaturated carboxylic acids (acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, etc.), and polyester-based thermoplastic elastomers whose main component is a polyester-based block copolymer. Acid-modified polyolefin resins are preferred. More specifically, when a polypropylene-based polymer is used as the polyolefin resin, the resin contained in the adhesive layer may be an acid-modified polypropylene-based polymer. The adhesive layer may also be an embodiment that does not contain a ternary copolymer of alkene-(meth)acrylic acid ester-unsaturated carboxylic acid. When a multilayer body is produced by extrusion lamination, the adhesive layer may contain known anchor coating agents, adhesives, etc., such as isocyanate-based (urethane-based), polyethyleneimine-based, polybutadiene-based, and organotitanium-based anchor coating agents, or laminating adhesives such as polyurethane-based, polyacrylic-based, polyester-based, epoxy-based, polyvinyl acetate-based, and cellulose-based. The adhesive layer may contain only one adhesive thermoplastic resin, or two or more adhesive thermoplastic resins. Furthermore, the total amount of adhesive thermoplastic resins in the adhesive layer preferably accounts for 80% by mass or more of the total, and more preferably 90% by mass or more. Examples of components other than the adhesive thermoplastic resin contained in the adhesive layer include additives such as antioxidants, matting agents, weather stabilizers, UV absorbers, crystallization nucleating agents, plasticizers, flame retardants, and antistatic agents.From the viewpoint of ensuring moldability while exhibiting practical adhesive strength, the thickness of the adhesive layer has a lower limit of preferably 2 μm or more, more preferably 3 μm or more. The upper limit of the thickness is preferably 100 μm or less, more preferably 90 μm or less, even more preferably 50 μm or less, still more preferably 30 μm or less, and even more preferably 10 μm or less, and may be 5 μm or less.

[0014] The substrate layer may be a stretched film or an unstretched film. When the substrate layer is a stretched film, it is preferable that the sealant layer and the substrate layer are bonded together using an adhesive. The multilayer container of this embodiment may also have other layers within the scope of the present invention. For example, a design layer may be provided on the surface of the substrate layer. In this case, it is preferable that the design layer is also formed from a polyamide resin.

[0015] The thickness of the sealant layer of the first multilayer body and the thickness of the sealant layer of the second multilayer body are each independently 4 μm or more, preferably 5 μm or more, more preferably 6 μm or more, even more preferably 7 μm or more, and even more preferably 8 μm or more, and are preferably 30 μm or less, more preferably 25 μm or less, even more preferably 23 μm or less, even more preferably 20 μm or less, even more preferably 19 μm or less, and even more preferably 10 μm or less. By making the thickness equal to or greater than the lower limit, the heat seal strength tends to be further improved. On the other hand, by making the thickness equal to or less than the upper limit, the impact resistance and pinhole resistance tend to be further improved.

[0016] The thickness ratio of the first sealant layer to the total thickness of the first multilayer body and the thickness ratio of the second sealant layer to the total thickness of the second multilayer body are each independently 40% or less. This configuration allows the flexibility of the aliphatic polyamide base material to compensate for the brittleness inherent in the aromatic polyamide resin, tending to improve the flexibility and impact resistance of the multilayer container. The thickness ratio of the first sealant layer to the total thickness of the first multilayer body and the thickness ratio of the second sealant layer to the total thickness of the second multilayer body are each independently preferably 35% or less, more preferably 32% or less, even more preferably 30% or less, even more preferably 28% or less, and even more preferably 27% or less. By keeping them below the upper limit, the flexibility and impact resistance of the container tend to be excellent. The lower limit values ​​of the thickness ratio of the first sealant layer to the total thickness of the first multilayer body and the thickness ratio of the second sealant layer to the total thickness of the second multilayer body are each preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, still more preferably 6% or more, even more preferably 7% or more, still more preferably 9% or more, and may be 10% by mass or more. By making the ratios equal to or greater than the lower limit values, the heat seal strength tends to be improved.

[0017] The thickness of the base layer of the first multilayer body and the thickness of the base layer of the second multilayer body are each independently 30 μm or more, more preferably 35 μm or more, even more preferably 40 μm or more, and even more preferably 45 μm or more, and are preferably 180 μm or less, more preferably 140 μm or less, even more preferably 100 μm or less, even more preferably 80 μm or less, even more preferably 75 μm or less, and even more preferably 70 μm or less. By setting the thickness at or above the lower limit, the strength of the multilayer container is improved and the content protection tends to be excellent. Furthermore, by setting the thickness at or below the upper limit, flexibility and impact resistance tend to be further improved.

[0018] In the multilayer container of this embodiment, the thickness of the body (the thickness of each of the first multilayer body and the second multilayer body) is preferably 20 μm or more, more preferably 30 μm or more, even more preferably 40 μm or more, even more preferably 45 μm or more, still more preferably 50 μm or more, even more preferably 55 μm or more, particularly more preferably 60 μm or more, and most particularly more preferably 65 μm or more. Furthermore, in the multilayer container of this embodiment, the thickness of the body (the thickness of each of the first multilayer body and the second multilayer body) is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, even more preferably 90 μm or less, even more preferably 85 μm or less, even more preferably 82 μm or less, and even more preferably 81 μm or less.

[0019] The first multilayer body and the second multilayer body in the multilayer body of this embodiment usually have one sealant layer and one substrate layer, but may have two or more sealant layers and two or more substrate layers. When the sealant layer and / or the substrate layer are two or more layers, the total of the layers satisfies the above-mentioned thickness and desired composition.

[0020] The shape of the multilayer container is not particularly limited, and may be, for example, a molded container such as a bottle, cup, tube, tray, or Tupperware, or a bag-like container such as a pouch, a standing pouch, or a zippered storage bag. In this embodiment, a pouch is preferred.

[0021] The capacity of the multilayer container of this embodiment is preferably 0.01 to 2.0 L, more preferably 0.02 to 1.0 L, and even more preferably 0.03 to 0.5 L, in view of the preservation of the contents.

[0022] For details of the multilayer container, reference can be made to paragraphs 0104 to 0133 of International Publication No. 2017 / 141969 within the scope of the present invention, the contents of which are incorporated herein by reference.

[0023] The objects to be stored in the multilayer container of this embodiment are not particularly limited, and examples thereof include food, cosmetics, pharmaceuticals, toiletries, mechanical, electrical, and electronic parts, oils, and resins, but the container is particularly suitable for use as a container for storing food. Examples include processed seafood products, processed livestock products, rice, and liquid foods. The container is particularly suitable for storing foods that are susceptible to oxygen. For details, please refer to paragraphs 0032 to 0035 of JP 2011-37199 A, the contents of which are incorporated herein by reference. The food to be filled is not particularly limited, but specific examples include beverages such as vegetable juice, fruit juice, tea, coffee and coffee drinks, milk and dairy drinks, mineral water, ionic drinks, alcoholic beverages, lactic acid bacteria drinks, and soy milk; gel foods such as tofu, egg tofu, jellies, puddings, mizu yokan, mousse, yogurt, and almond tofu; condiments such as sauce, soy sauce, ketchup, noodle soup, sauce, vinegar, mirin, dressing, jam, mayonnaise, miso, pickle base, and grated spices; salami, ham, sausage, yakitori, Examples of suitable containers include processed meat products such as meatballs, hamburgers, roast pork, and beef jerky; processed seafood products such as kamaboko, boiled shellfish, boiled fish, and chikuwa; processed rice products such as rice porridge, cooked rice, mixed rice, and red rice; sauces such as meat sauce, mapo sauce, pasta sauce, curry, stew, and hayashi sauce; processed dairy products such as cheese, butter, cream, and condensed milk; processed egg products such as boiled eggs and soft-boiled eggs; boiled vegetables and boiled beans; prepared dishes such as fried, steamed, stir-fried, simmered, and grilled foods; pickles; noodles and pasta such as udon, soba, and spaghetti; and fruits preserved in syrup. Depending on the item to be preserved, the multilayer container may be sterilized or disinfected using ultraviolet light, electron beams, gamma rays, X-rays, or the like.

[0024] <Composition of the First Multilayer Body and the Second Multilayer Body> Next, the compositions of the first multilayer body and the second multilayer body of this embodiment will be described. The first multilayer body and the second multilayer body of this embodiment each independently include a sealant layer containing an aromatic polyamide resin and a substrate layer containing an aliphatic polyamide resin. Multilayer bodies containing such sealant layers are fused (sealed) together with the sealant layer portions facing each other to obtain a multilayer container. The first multilayer body and the second multilayer body may be the same or different.

[0025] The sealant layers contained in the first multilayer body and the second multilayer body each independently contain a polyamide resin. The polyamide resin contained in the sealant layers contained in the first multilayer body and the second multilayer body is preferably a resin in which 30% by mass or more of all structural units excluding terminal groups are derived from aromatic monomers, and 40% by mass or more of all structural units excluding terminal groups are derived from aromatic monomers. It is also preferable that 70% by mass or less of all structural units excluding terminal groups are derived from aromatic monomers, and more preferably 60% by mass or less of all structural units excluding terminal groups are derived from aromatic monomers. Such a polyamide resin may consist solely of an aromatic polyamide resin, or may be a blend of an aromatic polyamide resin and an aliphatic polyamide resin. It is sufficient that 30% by mass or more of all structural units excluding terminal groups in the polyamide resin contained in the sealant layer are derived from aromatic monomers.

[0026] Examples of aromatic polyamide resins include polyhexamethylene terephthalamide (polyamide 6T), polyhexamethylene isophthalamide (polyamide 6I), polyamide 66 / 6T, polyamide 9T, polyamide 9MT, polyamide 10T, polyamide 6I / 6T, and xylylenediamine-based polyamide resins described below, with xylylenediamine-based polyamide resins being preferred.

[0027] The xylylenediamine-based polyamide resin in this embodiment is a polyamide resin containing diamine-derived structural units and dicarboxylic acid-derived structural units, with 70 mol% or more of the diamine-derived structural units being derived from xylylenediamine. Preferably, the xylylenediamine-based polyamide resin has, for example, 50 mol% or more, and preferably 70 mol% or more of the dicarboxylic acid-derived structural units derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms. The multilayer container of this embodiment can exhibit the strength and chemical resistance inherent to the xylylenediamine-based polyamide resin.

[0028] The xylylenediamine-based polyamide resin preferably contains at least 75 mol%, more preferably at least 80 mol%, even more preferably at least 85 mol%, even more preferably at least 90 mol%, still more preferably at least 95 mol%, and particularly preferably at least 99 mol% of diamine-derived structural units derived from xylylenediamine (preferably paraxylylenediamine and / or metaxylylenediamine, more preferably metaxylylenediamine). The xylylenediamine-based polyamide resin contains at least 60 mol%, even more preferably at least 70 mol%, even more preferably at least 80 mol%, even more preferably at least 90 mol%, still more preferably at least 95 mol%, and particularly preferably at least 99 mol% of dicarboxylic acid-derived structural units derived from a C4-C20 α,ω-linear aliphatic dicarboxylic acid (preferably adipic acid).

[0029] In the present embodiment, the molar ratio of meta-xylylenediamine to para-xylylenediamine in the xylylenediamine, when the total of meta-xylylenediamine and para-xylylenediamine is 100 moles, is preferably meta-xylylenediamine / para-xylylenediamine is 00 to 100 / 100 to 0, preferably 10 to 100 / 90 to 0, more preferably 40 to 100 / 60 to 0, even more preferably 60 to 100 / 40 to 0, still more preferably 80 to 100 / 20 to 0, and even more preferably 90 to 100 / 10 to 0.

[0030] Diamines other than metaxylylenediamine and paraxylylenediamine that can be used as raw diamine components for xylylenediamine-based polyamide resins include aliphatic diamines such as tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2,2,4-trimethyl-hexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine; 1,3-bis( Examples of the diamine include alicyclic diamines such as bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, bis(4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminomethyl)decalin, and bis(aminomethyl)tricyclodecane; and diamines having an aromatic ring such as bis(4-aminophenyl)ether, paraphenylenediamine, and bis(aminomethyl)naphthalene, and these can be used alone or in combination of two or more.

[0031] As described above, the xylylenediamine-based polyamide resin preferably has 50 mol % or more of the dicarboxylic acid-derived structural units derived from an α,ω-straight-chain aliphatic dicarboxylic acid having 4 to 20 carbon atoms. The number of carbon atoms in the α,ω-straight-chain aliphatic dicarboxylic acid having 4 to 20 carbon atoms is preferably 6 or more, and is preferably 18 or less, more preferably 16 or less, even more preferably 14 or less, still more preferably 13 or less, even more preferably 12 or less, still more preferably 10 or less, and particularly preferably 8 or less. Examples of α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms suitable for use as the raw dicarboxylic acid component of xylylenediamine-based polyamide resins include succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, adipic acid, sebacic acid, undecanedioic acid, and dodecanedioic acid. These can be used alone or in combination of two or more. Among these, one or more of adipic acid, sebacic acid, and dodecanedioic acid are more preferred, one or more of adipic acid and sebacic acid are even more preferred, and adipic acid is even more preferred. A preferred embodiment of the xylylenediamine-based polyamide resin in this embodiment is one in which 50 mol % or more (preferably 70 mol % or more, more preferably 90 mol % or more) of the dicarboxylic acid-derived structural units are derived from adipic acid.

[0032] Examples of dicarboxylic acid components other than the above-mentioned α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms include phthalic acid compounds such as isophthalic acid, terephthalic acid, and orthophthalic acid, and isomers of naphthalenedicarboxylic acid such as 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid, and these can be used alone or in combination of two or more.

[0033] Although the xylylenediamine-based polyamide resin contains diamine-derived structural units and dicarboxylic acid-derived structural units as its main components, it does not completely exclude other structural units, and may, of course, contain structural units derived from lactams such as ε-caprolactam and laurolactam, and aliphatic aminocarboxylic acids such as aminocaproic acid and aminoundecanoic acid. Here, "main component" refers to the structural units constituting the xylylenediamine-based polyamide resin in which the total number of diamine-derived structural units and dicarboxylic acid-derived structural units is the largest among all structural units. In this embodiment, the total of the diamine-derived structural units and dicarboxylic acid-derived structural units in the xylylenediamine-based polyamide resin preferably accounts for 90% by mass or more of all structural units, more preferably 95% by mass or more, even more preferably 97% by mass or more, and even more preferably 99% by mass or more.

[0034] The content of the aromatic polyamide resin (preferably a xylylenediamine-based polyamide resin) in the sealant layers contained in the first multilayer body and the second multilayer body is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on 100% by mass of the sealant layer. By adjusting the content to be equal to or greater than the above lower limit, the heat seal strength tends to be further improved. Furthermore, the content of the aromatic polyamide resin in the sealant layers contained in the first multilayer body and the second multilayer body of this embodiment is 100% by mass or less, based on 100% by mass of the sealant layer. The sealant layer of this embodiment may contain only one type of aromatic polyamide resin, or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0035] On the other hand, examples of aliphatic polyamide resins that can be contained in the sealant layer include polyamide 4, polyamide 46, polyamide 410, polyamide 6, polyamide 66, polyamide 666, polyamide 610, polyamide 11, polyamide 116, polyamide 12, and polyamide 612, with polyamide 6, polyamide 66, and polyamide 666 being more preferred, and polyamide 6 being even more preferred. When the sealant layer contains an aliphatic polyamide resin, pinhole resistance tends to be further improved. The sealant layer of this embodiment may contain no aliphatic polyamide resin, or may contain only one type, or may contain two or more types.

[0036] For aromatic polyamide resins and aliphatic polyamide resins, it is also preferable to use aromatic polyamide resins (biomass thermoplastic resins) produced using recycled resins or biomass raw materials. Using biomass thermoplastic resins can reduce environmental impact. For example, in xylylenediamine-based polyamide resins, bioadipic acid can be used as the biomass raw material. Mass balance certified (ISCC PLUS) adipic acid can also be used. Mass balance certification means that the amount of renewable or bio-based raw materials used at each factory or production facility and the amount of products produced or shipped are quantified and guaranteed along with their quality.

[0037] The glass transition temperature of the polyamide resin contained in the sealant layer is preferably 50° C. or higher, more preferably 60° C. or higher, and is preferably 160° C. or lower, more preferably 120° C. or lower. When the sealant layer in this embodiment contains two or more aromatic polyamide resins, the glass transition temperature of the aromatic polyamide resin is the glass transition temperature of the resin with the largest content.

[0038] The melting point of the polyamide resin contained in the sealant layer is preferably 150° C. or higher, more preferably 180° C. or higher, even more preferably 200° C. or higher, and even more preferably 205° C. or higher. The melting point of the polyamide resin contained in the sealant layer is preferably 350° C. or lower, more preferably 330° C. or lower, even more preferably 300° C. or lower, even more preferably 280° C. or lower, even more preferably 260° C. or lower, and even more preferably 250° C. or lower. When the sealant layer in this embodiment contains two or more aromatic polyamide resins, the melting point of the aromatic polyamide resin is the melting point of the resin with the largest content.

[0039] In this specification, the glass transition temperature (Tg) and melting point (Tm) are values ​​measured by differential scanning calorimetry (DSC) in accordance with ISO 11357. Using a differential scanning calorimeter, the resin is placed in the measurement pan of the differential scanning calorimeter, heated to a temperature above the melting point at a heating rate of 10 ° C. / min under a nitrogen atmosphere, and then rapidly cooled before measurement. The measurement conditions are a heating rate of 10 ° C. / min, held at 280 ° C. for 5 minutes, and then cooled to 100 ° C. at a cooling rate of -5 ° C. / min to determine the glass transition temperature (Tg) and melting point (Tm). As the differential scanning calorimeter, a "DSC-60" manufactured by Shimadzu Corporation is used.

[0040] The lower limit of the number average molecular weight (Mn) of the polyamide resin contained in the sealant layer is preferably 6,000 or more, more preferably 8,000 or more, and even more preferably 10,000 or more, and is preferably 100,000 or less, more preferably 50,000 or less. When the sealant layer used in this embodiment contains two or more types of polyamide resins, the number average molecular weight is the number average molecular weight of the mixture.

[0041] The number average molecular weight (Mn) of the aromatic polyamide resin is measured by gel permeation chromatography (GPC) using a standard polymethyl methacrylate (PMMA) equivalent value. Two columns packed with a styrene polymer are used as the packing material, and hexafluoroisopropanol (HFIP) with a sodium trifluoroacetate concentration of 2 mmol / L is used as the solvent. The resin concentration is 0.02 mass%, the column temperature is 40 ° C, the flow rate is 0.3 mL / min, and the measurement is performed using a refractive index detector (RI). In addition, the calibration curve is measured by dissolving six levels of PMMA in HFIP.

[0042] The sealant layer used in this embodiment may or may not contain a thermoplastic resin other than polyamide resin, as long as the object and effect of the present invention are not impaired.

[0043] In the sealant layer used in this embodiment, the polyamide resins (aromatic polyamide resin and aliphatic polyamide resin) in total preferably account for 90% by mass or more of the sealant layer, more preferably 95% by mass or more, even more preferably 97% by mass or more, still more preferably 98% by mass or more, or may account for 99% by mass or more, and preferably 100% by mass or less.

[0044] The sealant layer used in this embodiment preferably does not substantially contain any thermoplastic resin other than polyamide resin. Specifically, the content of thermoplastic resin other than polyamide resin contained in the sealant layer in this embodiment is preferably less than 1% by mass, and more preferably less than 0.1% by mass, based on 100% by mass of the sealant layer.

[0045] The sealant layer used in this embodiment may contain resin additives such as antioxidants, stabilizers such as heat stabilizers, hydrolysis resistance improvers, weathering stabilizers, matting agents, UV absorbers, nucleating agents, plasticizers, dispersants, flame retardants, antistatic agents, coloring inhibitors, antigelling agents, colorants, and release agents. For details, see paragraphs 0130 to 0155 of Japanese Patent No. 4,894,982 and paragraphs 0047 to 0103 of International Publication No. 2021 / 241471, the contents of which are incorporated herein by reference. The total content of the resin additives in the sealant layer used in this embodiment is preferably 0 to 5% by mass of the sealant layer, and more preferably 0 to 3% by mass.

[0046] In the multilayer container of this embodiment, the total amount of polyamide resins, including aromatic polyamide resins and aliphatic polyamide resins, is preferably 95% by mass or more, more preferably 97% by mass or more, and may be 99% by mass or more, and preferably 100% by mass or less, of the resin components contained in the multilayer container. By making the amount equal to or greater than the lower limit, the recyclability of the multilayer container can be further improved. Here, "resin components" refers to polyamide resins, other thermoplastic resins, and resin additives, and typically refers to all components contained in the multilayer container other than fillers and solvents. Furthermore, the total amount of components other than polyamide resin contained in the resin components is preferably 0 to 3% by mass, more preferably 0 to 1% by mass.

[0047] In the multilayer container of this embodiment, the sealant layers may be the same or different. The sealant layer contained in the first multilayer body and the sealant layer contained in the second multilayer body preferably have at least 80% by weight of their composition in common, more preferably at least 90% by weight, and even more preferably at least 95% by weight. This configuration can increase the fusion strength between the multilayer bodies.

[0048] The base layers included in the first multilayer body and the second multilayer body each independently contain an aliphatic polyamide resin. The aliphatic polyamide resin is preferably a resin in which 80% by mass or more of all structural units excluding terminal groups are derived from aliphatic monomers, and 85% by mass or more of all structural units excluding terminal groups are derived from aliphatic monomers. More preferably, 90% by mass or more of all structural units excluding terminal groups are derived from aliphatic monomers. Even more preferably, 95% by mass or more of all structural units excluding terminal groups are derived from aliphatic monomers. Even more preferably, 97% by mass or more of all structural units excluding terminal groups are derived from aliphatic monomers. The upper limit of the proportion of structural units derived from aliphatic monomers in the aliphatic polyamide resin is 100% by mass of all structural units excluding terminal groups.

[0049] Examples of aliphatic polyamide resins include polyamide 4, polyamide 46, polyamide 410, polyamide 6, polyamide 66, polyamide 666, polyamide 610, polyamide 11, polyamide 116, polyamide 12, and polyamide 612, of which polyamide 6, polyamide 66, and polyamide 666 are more preferred, and polyamide 6 is even more preferred.

[0050] It is also preferable to use an aliphatic polyamide resin produced using recycled resin or biomass raw material (biomass thermoplastic resin) as the aliphatic polyamide resin. By using a biomass thermoplastic resin, it is possible to reduce the environmental load.

[0051] The content of the aliphatic polyamide resin in the base layer contained in the first multilayer body and the second multilayer body is preferably 93% by mass or more, more preferably 95% by mass or more, even more preferably 96% by mass or more, even more preferably 97% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more, based on 100% by mass of the base layer. By setting the content at or above the lower limit, flexibility and impact resistance tend to be further improved. Furthermore, the content of the aliphatic polyamide resin in the base layer contained in the first multilayer body and the second multilayer body of this embodiment is 100% by mass or less, based on 100% by mass of the base layer. The base layer of this embodiment may contain only one type of aliphatic polyamide resin, or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0052] The substrate layer used in this embodiment may or may not contain a polyamide resin other than an aliphatic polyamide resin or a thermoplastic resin other than a polyamide resin, as long as the objectives and effects of the present invention are not impaired. Preferably, the substrate layer used in this embodiment is substantially free of thermoplastic resins other than polyamide resins. Specifically, the content of thermoplastic resins other than polyamide resins contained in the substrate layer in this embodiment is preferably less than 1% by mass, more preferably less than 0.1% by mass, based on 100% by mass of the substrate layer. Furthermore, it is preferable that the substrate layer used in this embodiment is substantially free of polyamide resins other than aliphatic polyamide resins. Specifically, the content of polyamide resins other than aliphatic polyamide resins contained in the substrate layer in this embodiment is preferably less than 10% by mass, more preferably less than 5% by mass, even more preferably less than 3% by mass, even more preferably less than 1% by mass, and even more preferably less than 0.1% by mass, based on 100% by mass of the substrate layer.

[0053] The substrate layer used in this embodiment may contain resin additives such as antioxidants, stabilizers such as heat stabilizers, hydrolysis resistance improvers, weathering stabilizers, matting agents, UV absorbers, nucleating agents, plasticizers, dispersants, flame retardants, antistatic agents, coloring inhibitors, antigelling agents, colorants, and release agents. For details, see paragraphs 0130 to 0155 of Japanese Patent No. 4,894,982 and paragraphs 0047 to 0103 of International Publication No. 2021 / 241471, the contents of which are incorporated herein by reference. The total content of the resin additives in the substrate layer used in this embodiment is preferably 0 to 5% by mass of the substrate layer, and more preferably 0 to 3% by mass.

[0054] In the multilayer container of this embodiment, the base layers may be the same or different. The base layer contained in the first multilayer body and the base layer contained in the second multilayer body preferably have 80% by mass or more of their composition in common, more preferably 90% by mass or more of their composition in common, and even more preferably 95% by mass or more of their composition in common.

[0055] <Method for Manufacturing Multilayer Container> The method for manufacturing the multilayer container of this embodiment is not particularly limited, and the container can be manufactured by a known method. Typically, the first multilayer body and the second multilayer body are preferably manufactured by partially fusing them together so that the sealant layer of the first multilayer body faces the sealant layer of the second multilayer body. The first multilayer body and the second multilayer body have the same meanings as those described in the multilayer container section above, and the preferred ranges are also the same. Furthermore, in the multilayer container of this embodiment, it is preferable that the moisture content of each of the first multilayer body and the second multilayer body, independently, immediately before sealing (fusion) is 10,000 mass ppm or less. This moisture content enables fusion at low temperatures. Furthermore, when the polyamide resin is a crystalline resin, the crystallization rate is slowed, allowing for slow fusion, and seal strength tends to be further improved, which is preferable.

[0056] The moisture content is more preferably 9000 ppm by mass or less, even more preferably 7000 ppm by mass or less, even more preferably 5000 ppm by mass or less, and still more preferably 4500 ppm by mass or less, and may be 3500 ppm by mass or less, 3000 ppm by mass or less, or 2500 ppm by mass or less depending on the application, etc. The lower limit of the moisture content is 0 ppm by mass or more.

[0057] In this embodiment, in order to maintain the moisture content, the first and second multilayer bodies produced are preferably stored under conditions that make them less likely to absorb moisture until immediately before sealing.

[0058] The temperature during the fusion bonding is preferably equal to or higher than the glass transition temperature (Tg) of the polyamide resin, more preferably Tg + 20°C or higher, even more preferably Tg + 30°C or higher, even more preferably Tg + 35°C or higher, and even more preferably Tg + 45°C or higher. By setting the temperature at or above the lower limit, the heat seal strength tends to be improved. Furthermore, the upper limit of the temperature during the fusion bonding is preferably equal to or lower than Tg + 140°C, more preferably equal to or lower than Tg + 130°C, even more preferably equal to or lower than Tg + 120°C, even more preferably equal to or lower than Tg + 110°C, and even more preferably equal to or lower than Tg + 100°C. By setting the temperature at or below the upper limit, the appearance of the heat-sealed portion tends to be more excellent.

[0059] The temperature during heat fusion is preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 160°C or lower. Depending on the application, it is even more preferably 140°C or lower, and is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher. Depending on the application, it is even more preferably 130°C or higher. The temperature during heat fusion may be constant, or may be gradually increased and / or decreased. In this case, it is preferable that the highest heat fusion temperature falls within the above range. The fusion time is not particularly specified, but is, for example, 1 second or longer and 1 minute or shorter. The pressure during fusion is not particularly specified, but is, for example, 0.2 MPa or higher and 0.5 MPa or lower.

[0060] <Method for producing recycled polyamide resin> This embodiment discloses a method for producing recycled polyamide resin, which includes crushing the multilayer container. That is, since the multilayer container of this embodiment is mostly composed of polyamide resin, it is close to a single material and can be crushed to produce recycled polyamide resin. Furthermore, it is also preferable to form the base layer of the multilayer container of this embodiment using the recycled polyamide resin obtained by the method for producing recycled polyamide resin of this embodiment.

[0061] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or the like, measurements can be made using other instruments with equivalent performance.

[0062] 1. Raw Materials PA-1: Polyamide resin (MXD6) synthesized from metaxylylenediamine and adipic acid, manufactured by Mitsubishi Gas Chemical Company, Inc., S6007, melting point: 237°C, glass transition temperature: 85°C PA-2: Polyamide resin (MXD6) synthesized from metaxylylenediamine, adipic acid, and isophthalic acid, manufactured by Mitsubishi Gas Chemical Company, Inc., S7007, melting point: 229°C, glass transition temperature: 92°C

[0063] PA6: Polyamide 6, manufactured by UBE, product number 1022B, PA666: Polyamide 666, manufactured by UBE, product number 5023B PA6I / 6T: Polyamide 6I / 6T, manufactured by EMS Co., Ltd., G21,

[0064] 2. Examples 1 to 19 and Comparative Examples 1 to 5 <Production of Multilayer Body> Using a multilayer sheet production apparatus equipped with two extruders, a feed block, a T-die, a cooling roll, a winder, etc., PA6 was extruded from the first extruder at 240°C, and the sealant layer resin described in the Examples was extruded from the second extruder at 260°C, and a multilayer body having a two-layer structure of PA6 / sealant layer was produced via the feed block. The obtained multilayer body was stored sealed in a moisture-proof film until each test was performed.

[0065] <Method for measuring moisture content of multilayer body> The moisture content was measured using a Karl Fischer moisture meter in accordance with ISO 15512. The unit is ppm. The Karl Fischer moisture meter used was a coulometric titration trace moisture analyzer CA-200 manufactured by Nitto Seiko Analytech (formerly Mitsubishi Chemical Analytech).

[0066] <Heat Seal Strength> Two sheets of the multilayer body obtained above were placed with the sealant layers facing each other and fused at sealing temperatures of 120°C and 150°C. The adhesive strength was evaluated as follows. The heat-sealed film was conditioned for one week in an environment of 23°C and 50% RH. A 15 mm wide piece of the sealed portion was cut out and subjected to a T-peel test at a speed of 300 mm / min using a Strograph manufactured by Toyo Seiki Seisaku-sho. The maximum point load during peeling was measured, and this was taken as the T-peel load to evaluate the seal strength. Five measurements were taken for each piece, and the average value was calculated. The unit was N / 15 mm.

[0067] <Impact Resistance> A film impact test was carried out on the multilayer body obtained above as follows. The obtained stretched film was cut into a 10 cm square, and the film impact value was measured using a film impact tester in accordance with ASTM D3420. In this example, an FT-60 film impact tester manufactured by Orientec Co., Ltd. was used. The unit of impact resistance was kgfcm.

[0068] <Pinhole Resistance> The pinhole resistance was measured by the Gelboflex test as follows. The obtained stretched film was cut into a 25 cm square and attached to a pinhole resistance tester. The film was subjected to a 440° twisting motion and a 65 mm linear motion continuously at a speed of 40 times / min, and the film was bent 1000 times. The number of pinholes in the film after bending was measured using a pinhole tester. 2 The number of pinholes per 100 cm of film was calculated. 2 The number of pinholes per 100cm is calculated as follows: Number of pinholes (pcs / 100cm) 2 ) = total number of pinholes (pieces) / effective test area (cm 2 ) × 100 In this example, a Gelbo Flex Tester manufactured by Rigaku Corporation was used as the pinhole resistance tester, and a POROSCOPE DC manufactured by Fischer was used as the pinhole inspection machine. The Gelbo Flex test was performed 20 times, 50 times, 200 times, and 400 times, and the number of pinholes formed was measured.

[0069]

[0070]

[0071]

[0072]

[0073]

[0074] As is clear from the above results, the multilayer container of this embodiment had high impact resistance and strong sealant strength. Furthermore, it also had excellent pinhole resistance. Furthermore, because it was made only of polyamide resin, it was possible to improve recyclability.

[0075] REFERENCE SIGNS LIST 1 First multilayer body 12 Sealant layer contained in first multilayer body 13 Base layer contained in first multilayer body 2 Second multilayer body 22 Sealant layer contained in second multilayer body 23 Base layer contained in second multilayer body 10 Multilayer container

Claims

1. A first multilayer body comprising a sealant layer containing a polyamide resin and a substrate layer containing an aliphatic polyamide resin, A second multilayer body comprising a sealant layer containing a polyamide resin and a substrate layer containing an aliphatic polyamide resin. A multilayer container having, The first multilayer sealant layer and the second multilayer sealant layer are facing each other and are partially fused together. The thickness of the sealant layer of the first multilayer and the thickness of the sealant layer of the second multilayer are, independently, 4 μm or more, and 40% or less of the total thickness of the first or second multilayer. The polyamide resin contained in the sealant layer of the first multilayer and the polyamide resin contained in the sealant layer of the second multilayer are, independently, resins in which 30% or more of the total constituent units excluding the end groups are derived from aromatic monomers. The aliphatic polyamide resin contained in the first multilayer and the aliphatic polyamide resin contained in the second multilayer are, independently of each other, resins in which 80% or more by mass of all constituent units excluding terminal groups are derived from aliphatic monomers. 95% or more by mass of the resin component contained in the aforementioned multilayer container is polyamide resin. Multilayer container.

2. The multilayer container according to claim 1, wherein the first multilayer and the second multilayer each independently have a moisture content of 10,000 ppm by mass or less immediately before sealing.

3. The multilayer container according to claim 1, wherein the first multilayer sealant layer and the second multilayer sealant layer each independently have a thickness of 6 μm or more.

4. The multilayer container according to claim 1, wherein the polyamide resin contained in the sealant layer of the first multilayer and the polyamide resin contained in the sealant layer of the second multilayer independently contain diamine-derived structural units and dicarboxylic acid-derived structural units, and 70 mol% or more of the diamine-derived structural units contain a xylylenediamine-based polyamide resin derived from xylylenediamine.

5. The multilayer container according to claim 4, wherein 70 mol% or more of the dicarboxylic acid-derived structural units in the xylylenediamine-based polyamide resin are structural units derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms.

6. The first multilayer and the second multilayer each independently have a moisture content of 10,000 ppm by mass or less immediately before sealing. The first multilayer sealant layer and the second multilayer sealant layer each independently have a thickness of 6 μm or more. The polyamide resin contained in the sealant layer of the first multilayer and the polyamide resin contained in the sealant layer of the second multilayer each independently contain diamine-derived structural units and dicarboxylic acid-derived structural units, and 70 mol% or more of the diamine-derived structural units contain xylylenediamine-based polyamide resin derived from xylylenediamine. The multilayer container according to claim 1, wherein 70 mol% or more of the constituent units derived from the dicarboxylic acid are constituent units derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms.

7. The multilayer container according to claim 1 or 6, wherein at least one of the first multilayer and the second multilayer has a sealant layer and a substrate layer in contact directly or via an adhesive layer, and the sealant layer is an unstretched film.

8. A method for producing recycled polyamide resin, comprising crushing a multilayer container according to any one of claims 1 to 6.

9. A method for manufacturing a multilayer container, comprising fusing a portion of a first multilayer body comprising a sealant layer containing a polyamide resin and a base layer containing an aliphatic polyamide resin, and a second multilayer body comprising a sealant layer containing a polyamide resin and a base layer containing an aliphatic polyamide resin, such that the sealant layer of the first multilayer body and the sealant layer of the second multilayer body face each other. The thickness of the sealant layer of the first multilayer and the thickness of the sealant layer of the second multilayer are, independently, 4 μm or more, and 40% or less of the total thickness of the first or second multilayer. The polyamide resin contained in the sealant layer of the first multilayer and the polyamide resin contained in the sealant layer of the second multilayer are, independently of each other, resins in which 30% or more of the mass of all constituent units excluding end groups are derived from aromatic monomers. The aliphatic polyamide resin contained in the first multilayer and the aliphatic polyamide resin contained in the second multilayer are, independently of each other, resins in which 80% or more by mass of all constituent units excluding terminal groups are derived from aliphatic monomers. 95% or more by mass of the resin component contained in the aforementioned multilayer container is polyamide resin. A method for manufacturing a multilayer container, wherein the first multilayer and the second multilayer at the time of fusion each independently have a moisture content of 10,000 ppm by mass or less immediately before sealing.

10. The method for manufacturing a multilayer container according to claim 9, wherein the multilayer container is a multilayer container according to any one of claims 1 to 6.