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

Abstract

The invention provides a multilayer container, a method for producing a regenerated polyamide resin, and a method for producing a multilayer container. A multilayer container having: a first multilayer body including a sealing layer containing an aromatic polyamide resin and a base material layer containing an aliphatic polyamide resin; and a second multilayer body including a sealant layer containing an aromatic polyamide resin and a base material layer containing an aliphatic polyamide resin, the sealing layer of the first multilayer body and the sealing layer of the second multilayer body face each other and are partially welded, and the thickness of the sealing layer of the first multilayer body and the thickness of the sealing layer of the second multilayer body are independently 4 m or more and are 40% or less of the total thickness of the first multilayer body or the second multilayer body. 95% by mass or more of the resin component contained in the multilayer container is a polyamide resin.

Description

Technical Field

[0001] This invention relates to multilayer containers, methods for manufacturing recycled polyamide resin, and methods for manufacturing multilayer containers. In particular, it relates to multilayer containers with polyamide resin as the main component. Background Technology

[0002] Packaging materials used for food and other products require multiple functions to protect the contents from various processes such as circulation and heat sterilization, including strength, pinhole resistance, heat resistance, and visibility of the contents. Furthermore, to maintain the quality of the contents, barrier properties are also required to prevent the permeation of oxygen and moisture. To meet these multiple requirements, multi-layered containers with layers of different properties are used (Patent Document 1, Patent Document 2, etc.).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2023-068909

[0006] Patent Document 2: Japanese Patent Application Publication No. 2011-057237 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, as described above, multilayer containers are difficult to separate the resins that make up the layers, making them unsuitable for regeneration. Therefore, it is ideal for multilayer containers to be formed from a single material or a similar composition.

[0009] On the other hand, films using polyamide resins exhibit excellent heat resistance, strength, and oxygen barrier properties. However, polyamide resins tend to lack heat-sealing properties. Furthermore, the sealing layer requires resins other than polyamide resins, making it difficult to achieve a single material solution. Consequently, when using aromatic polyamide resins, the film's impact resistance cannot be considered sufficient.

[0010] The purpose of this invention is to provide a multilayer container with excellent recyclability, excellent heat-sealing properties and excellent impact resistance, which aims to solve the above-mentioned problems, as well as a method for manufacturing recycled polyamide resin and a method for manufacturing multilayer containers.

[0011] Solution for solving the problem

[0012] Based on the above-mentioned issues, the inventors conducted research and found that by fusing a sealing layer containing aromatic polyamide resin with a substrate layer containing aliphatic polyamide resin to form a container shape, the thickness of the sealing layer is reduced, and the entire multi-layer container is composed of more than 95% polyamide resin, thereby solving the above-mentioned issues.

[0013] Specifically, the above-mentioned problems were solved through the following solution.

[0014] <1> A multi-layer container having:

[0015] The first multilayer comprises a sealing layer containing polyamide resin and a substrate layer containing aliphatic polyamide resin; and

[0016] The second multilayer comprises a sealing layer containing polyamide resin and a substrate layer containing aliphatic polyamide resin.

[0017] The sealing layer of the first multilayer body faces the sealing layer of the second multilayer body, and a portion of them are fused together.

[0018] The thickness of the sealing layer of the first multilayer body and the thickness of the sealing layer of the second multilayer body are each independently 4µm or more, and are less than 40% of the total thickness of the first or second multilayer body.

[0019] The polyamide resin contained in the sealing layer of the first multilayer and the polyamide resin contained in the sealing layer of the second multilayer are each independently a resin in which more than 30% by mass of all structural units, excluding terminal groups, are derived from aromatic monomers.

[0020] The aliphatic polyamide resin contained in the first multilayer and the aliphatic polyamide resin contained in the second multilayer are each independently resins in which more than 80% by mass of all structural units, excluding terminal groups, are derived from aliphatic monomers.

[0021] The resin component contained in the multilayer container is more than 95% by mass of polyamide resin.

[0022] <2> according to <1> The multilayer container wherein the moisture content of the first multilayer body and the second multilayer body is independently below 10,000 ppm by mass before sealing.

[0023] <3> according to <1> or <2> The multilayer container wherein the thickness of the sealing layer of the first multilayer body and the sealing layer of the second multilayer body are each independently greater than 6µm.

[0024] <4> according to <1> ~ <3> The multilayer container according to any one of the following, wherein the polyamide resin contained in the sealing layer of the first multilayer and the polyamide resin contained in the sealing layer of the second multilayer each independently comprises a phenylenediamine-based polyamide resin, the phenylenediamine-based polyamide resin comprising structural units derived from diamine and structural units derived from dicarboxylic acids, and more than 70 mol% of the structural units derived from diamine are derived from phenylenediamine.

[0025] <5> according to <4> In the multilayer container, more than 70 mol% of the dicarboxylic acid-derived structural units in the diphenyl dimethylamine polyamide resin are structural units derived from α,ω-linear aliphatic dicarboxylic acids with 4 to 20 carbon atoms.

[0026] <6> according to <1> ~ <5> The multilayer container according to any one of the following methods, wherein the moisture content of the first multilayer body and the second multilayer body is each independently below 10,000 ppm by mass just before sealing.

[0027] The thickness of the sealing layer of the first multilayer body and the sealing layer of the second multilayer body are each independently greater than 6µm.

[0028] The polyamide resin contained in the sealing layer of the first multilayer and the polyamide resin contained in the sealing layer of the second multilayer each independently comprises a phenylene dimethylamine-based polyamide resin, wherein the phenylene dimethylamine-based polyamide resin comprises structural units derived from diamine and structural units derived from dicarboxylic acids, and more than 70 mol% of the structural units derived from diamine are derived from phenylene dimethylamine.

[0029] Of the structural units derived from dicarboxylic acids, more than 70 mol% are structural units derived from α,ω-linear aliphatic dicarboxylic acids with 4 to 20 carbon atoms.

[0030] <7> according to <1> ~ <6> The multilayer container according to any one of the following, wherein the sealing layer of at least one of the first multilayer body and the second multilayer body is in direct contact with the substrate layer or in contact with the substrate layer through an adhesive layer, and the sealing layer is an unstretched film.

[0031] <8> A method for manufacturing recycled polyamide resin, comprising: <1> ~ <7> The multi-layered container mentioned in any one of the above statements is broken.

[0032] <9> A method for manufacturing a multilayer container includes: fusing a first multilayer body and a second multilayer body in such a way that the sealing layers of the first multilayer body and the sealing layers of the second multilayer body face each other, wherein the first multilayer body includes a sealing layer containing polyamide resin and a substrate layer containing aliphatic polyamide resin, and the second multilayer body includes a sealing layer containing polyamide resin and a substrate layer containing aliphatic polyamide resin.

[0033] The thickness of the sealing layer of the first multilayer body and the thickness of the sealing layer of the second multilayer body are each independently 4µm or more, and are less than 40% of the total thickness of the first or second multilayer body.

[0034] The polyamide resin contained in the sealing layer of the first multilayer and the polyamide resin contained in the sealing layer of the second multilayer are each independently a resin in which more than 30% by mass of all structural units, excluding terminal groups, are derived from aromatic monomers.

[0035] The aliphatic polyamide resin contained in the first multilayer and the aliphatic polyamide resin contained in the second multilayer are each independently resins in which more than 80% by mass of all structural units, excluding terminal groups, are derived from aliphatic monomers.

[0036] The resin component contained in the multilayer container is more than 95% by mass of polyamide resin.

[0037] The moisture content of the first and second multilayer bodies during welding is independently below 10,000 ppm by mass before sealing.

[0038] <10> according to <9> The method for manufacturing a multi-layer container, wherein the multi-layer container is... <1> ~ <7> The multi-layer container as described in any one of the above.

[0039] The effects of the invention

[0040] According to the present invention, a multilayer container with excellent recyclability, excellent heat-sealing properties and excellent impact resistance, a method for manufacturing recycled polyamide resin and a method for manufacturing multilayer containers can be provided. Attached Figure Description

[0041] Figure 1 This is a schematic cross-sectional view illustrating an example of the multi-layer container of the present invention. Detailed Implementation

[0042] Hereinafter, a method for implementing the present invention (hereinafter referred to as "this embodiment") will be described in detail. It should be noted that the following embodiment is an example for illustrating the present invention, and the present invention is not limited to this embodiment.

[0043] It should be noted that in this specification, "~" is used to encompass the values ​​listed before and after it as the lower and upper limits.

[0044] Unless otherwise specified, all physical property values ​​and characteristic values ​​in this manual are set at 23°C.

[0045] Unless otherwise specified, "ppm" in this manual is defined as "mass ppm".

[0046] Unless otherwise specified, the measurement methods described in the standards shown in this instruction manual may vary depending on the year, and are based on the standards as of January 1, 2023.

[0047] Figure 1 Sometimes the scale and other parameters do not match reality.

[0048] The multilayer container of this embodiment is characterized by having: a first multilayer body comprising a sealing layer containing polyamide resin and a substrate layer containing aliphatic polyamide resin; and a second multilayer body comprising a sealing layer containing polyamide resin and a substrate layer containing aliphatic polyamide resin; the sealing layers of the first multilayer body and the second multilayer body face each other and are partially fused together; the thickness of the sealing layer of the first multilayer body and the thickness of the sealing layer of the second multilayer body are each independently 4µm or more and are less than 40% of the total thickness of the first multilayer body or the second multilayer body; the polyamide resin contained in the sealing layer of the first multilayer body and the polyamide resin contained in the sealing layer of the second multilayer body are each independently a resin from which at least 30% by mass of all structural units except 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 from which at least 80% by mass of all structural units except terminal groups are derived from aliphatic monomers; and at least 95% by mass of the resin component contained in the multilayer container is polyamide resin.

[0049] By designing the structure in this way, multi-layer containers with excellent recyclability, heat sealability, and impact resistance can be provided.

[0050] That is, by using a polyamide resin (sometimes referred to as "aromatic polyamide resin" in this specification) containing structural units derived from aromatic monomers in the resin constituting the sealing layer, and setting its thickness to 4µm or more, the sealing layers can be fused together. Furthermore, by using an aliphatic polyamide resin in the resin constituting the substrate layer, a resin with a near-single-material composition consisting only of polyamide resin and excellent recyclability can be obtained. Furthermore, in this embodiment, by making the thickness of the sealing layer containing aromatic polyamide resin relatively thin, a multilayer with excellent impact resistance can be obtained.

[0051] <Layer structure of multi-layer containers>

[0052] The multi-layer container of this embodiment is, for example, as shown in the example below. Figure 1 As shown in (a), the multilayer body 1 has a first multilayer body 1 and a second multilayer body 2. The first multilayer body 1 has a sealing layer 12 containing an aromatic polyamide resin and a substrate layer 13 containing an aliphatic polyamide resin. The second multilayer body 2 has a sealing layer 22 containing an aromatic polyamide resin and a substrate layer 23 containing an aliphatic polyamide resin. Furthermore, in the multilayer body 10 of this embodiment, the sealing layers of the first multilayer body and the sealing layers of the second multilayer body face each other and a portion thereof is fused together. Figure 1 (b)). By performing welding in this way, it can be used as a packaging container.

[0053] exist Figure 1In the multilayer container shown, the sealing layer is in direct contact with the substrate layer, but the sealing layer and the substrate layer can also be in contact through an adhesive layer.

[0054] In this embodiment, it is preferable that there is no adhesive layer, and the sealing layer is in direct contact with the substrate layer. In this embodiment, it can be manufactured in the form of a co-extruded product formed by co-extruding the sealing layer and the substrate layer, thus enabling the sealing layer and the substrate layer to be bonded without an adhesive.

[0055] Furthermore, the multilayer in this embodiment can be manufactured using known methods such as co-extrusion, various lamination methods, and various coating methods, depending on the properties of various materials, processing purposes, and processing steps. The manufacturing method is not particularly limited. The manufacturing of the multilayer can be done using common methods for laminated packaging materials, such as wet lamination, dry lamination, solvent-free dry lamination, extrusion lamination, T-die co-extrusion molding, co-extrusion lamination, and blow molding.

[0056] When manufacturing the above-mentioned multilayer bodies, pretreatments such as corona treatment and ozone treatment can be performed on the thin film as needed.

[0057] On the other hand, when the sealing layer and the substrate layer are in contact through an adhesive layer, the adhesive layer is preferably a dry lamination adhesive with adhesive properties. Examples of dry lamination adhesives include, for example, a one-component type using only a urethane adhesive having isocyanate groups, and a two-component type using a mixture of a hydroxyl-based main agent and an isocyanate-based curing agent; two-component urethane adhesives are particularly preferred.

[0058] When manufacturing a co-extruded multilayer, the adhesive layer preferably comprises a thermoplastic resin with adhesive properties. Examples of such 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 thermoplastic elastomers with polyester block copolymers as the main component; acid-modified polyolefin resins are preferred. More specifically, when using a polypropylene polymer as the polyolefin resin, the adhesive layer may contain an acid-modified polypropylene polymer. The adhesive layer may also be a terpolymer that does not contain olefin-(meth)acrylate-unsaturated carboxylic acid.

[0059] When manufacturing multilayer bodies using extrusion lamination, the adhesive layer can use known anchoring coatings and adhesives such as isocyanate-based (urethane-based), polyethyleneimine-based, polybutadiene-based, organotitanium-based, polyurethane-based, polyacrylic acid-based, polyester-based, epoxy-based, polyvinyl acetate-based, and cellulose-based laminating adhesives.

[0060] The adhesive layer may contain only one type of adhesive thermoplastic resin, or it may contain two or more types. Furthermore, the total amount of adhesive thermoplastic resin in the adhesive layer is preferably 80% or more by mass, more preferably 90% or more by mass. Examples of components other than the adhesive thermoplastic resin in the adhesive layer include additives such as antioxidants, matting agents, weather stabilizers, UV absorbers, nucleating agents, plasticizers, flame retardants, and antistatic agents.

[0061] From the viewpoint of ensuring both practical adhesive strength and processability, the lower limit of the adhesive layer thickness is preferably 2µm or more, more preferably 3µm or more. The upper limit of the thickness is preferably 100µm or less, more preferably 90µm or less, even more preferably 50µm or less, even more preferably 30µm or less, even more preferably 10µm or less, and may also be 5µm or less.

[0062] In addition, the substrate layer can be a stretched film or an unstretched film. When the substrate layer is a stretched film, the sealing layer and the substrate layer are preferably bonded together using an adhesive.

[0063] Furthermore, the multilayer container of this embodiment may have other layers without departing from the spirit of the 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 of polyamide resin.

[0064] The thickness of the sealing layer of the first multilayer and the thickness of the sealing layer of the second multilayer are each independently 4µm or more, preferably 5µm or more, more preferably 6µm or more, further preferably 7µm or more, even more preferably 8µm or more, and preferably 30µm or less, more preferably 25µm or less, even more preferably 23µm or less, even more preferably 20µm or less, even more preferably 19µm or less, and even more preferably 10µm or less. By setting the thickness to the lower limit or above, there is a tendency to further improve the heat sealing strength. Furthermore, by setting the thickness to the upper limit or below, there is a tendency to further improve the impact resistance and pinhole resistance.

[0065] The ratio of the thickness of the first sealing layer to the total thickness of the first multilayer body and the ratio of the thickness of the second sealing layer to the total thickness of the second multilayer body are each independently 40% or less. With such a configuration, the brittleness derived from the aromatic polyamide resin can be compensated by the flexibility of the aliphatic polyamide of the substrate, and there is a tendency to improve the flexibility and impact resistance of the multilayer container.

[0066] The ratio of the thickness of the first sealing layer to the total thickness of the first multilayer body, and the ratio of the thickness of the second sealing layer to the total thickness of the second multilayer body, are each preferably 35% or less, more preferably 32% or less, further preferably 30% or less, even more preferably 28% or less, and even more preferably 27% or less. Setting these values ​​below the upper limit tends to result in excellent flexibility and impact resistance as a container. Furthermore, the lower limit values ​​for the ratio of the thickness of the first sealing layer to the total thickness of the first multilayer body, and the ratio of the thickness of the second sealing layer to the total thickness of the second multilayer body, are preferably 1% or more, more preferably 2% or more, further preferably 3% or more, even more preferably 6% or more, even more preferably 7% or more, even more preferably 9% or more, and may also be 10% by mass or more. Setting these values ​​above the lower limit tends to result in increased heat-sealing strength.

[0067] The thickness of the substrate layer of the first multilayer and the thickness of the substrate layer of the second multilayer are each independently 30µm or more, more preferably 35µm or more, further preferably 40µm or more, even more preferably 45µm or more, and preferably 180µm or less, more preferably 140µm or less, even more preferably 100µm or less, even more preferably 80µm or less, even more preferably 75µm or less, and even more preferably 70µm or less. By setting these values ​​above the lower limit, there is a tendency for improved strength and excellent protection of the contents as a multilayer container. Furthermore, by setting these values ​​below the upper limit, there is a tendency for further improved flexibility and impact resistance.

[0068] The thickness of the main body of the multilayer container in this embodiment (the thickness of each of the first multilayer and the second multilayer) is preferably 20µm or more, more preferably 30µm or more, even more preferably 40µm or more, even more preferably 45µm or more, even more preferably 50µm or more, even more preferably 55µm or more, particularly more preferably 60µm or more, and even more particularly preferably 65µm or more. Furthermore, the thickness of the main body of the multilayer container in this embodiment (the thickness of each of the first multilayer and the second multilayer) is preferably 200µm or less, more preferably 150µm or less, even more preferably 100µm or less, even more preferably 90µm or less, even more preferably 85µm or less, even more preferably 82µm or less, and even more preferably 81µm or less.

[0069] In this embodiment, the first and second multilayer bodies typically have one sealing layer and one substrate layer, but they can also be sealing layers and substrate layers of two or more multilayer bodies. When the sealing layer and / or substrate layer are formed of two or more layers, their total thickness is assumed to satisfy the aforementioned desired composition.

[0070] The shape of the multi-layer container is not particularly limited. For example, it can be a shaped container such as a bottle, cup, tube, tray, or tuberware. Alternatively, it can be a pouch, self-supporting bag, or zippered storage bag. In this embodiment, a pouch is preferred.

[0071] From the perspective of preserving the contents, the capacity of the multi-layer container in this embodiment is preferably 0.01~2.0L, more preferably 0.02~1.0L, and even more preferably 0.03~0.5L.

[0072] For details regarding the multi-layered container, please refer to paragraphs 0104 to 0133 of International Publication No. 2017 / 141969 without departing from the spirit of the invention, the contents of which are incorporated herein by reference.

[0073] There are no particular limitations on the objects that can be stored in the multi-layered container of this embodiment. Examples include food, cosmetics, pharmaceuticals, toiletries, mechanical / electrical / electronic components, oils, resins, etc. In particular, it is suitable as a container for storing food.

[0074] Examples include processed aquatic products, processed livestock products, rice dishes, and liquid foods. It is particularly suitable for the preservation of foods that are easily affected by oxygen. For details, please refer to paragraphs 0032 to 0035 of Japanese Patent Application Publication No. 2011-37199, and this information is incorporated into this specification.

[0075] There are no particular restrictions on the food fillings. Specific examples include, for instance, vegetable juice, fruit juice, tea, coffee / coffee beverages, milk / dairy beverages, mineral water, electrolyte drinks, alcoholic beverages, lactic acid bacteria drinks, soy milk, etc.; tofu, egg tofu, jelly, pudding, yogurt, mousse, yogurt, almond tofu, and other gel-like foods; sauces, soy sauce, ketchup, noodle soup, etc. Seasonings such as base, dipping sauces, vinegar, mirin, sauces, jams, mayonnaise, miso, pickling seasonings, and ground spices; processed meat products such as salami, ham, sausages, chicken skewers, meatballs, hamburger patties, char siu, and beef jerky; processed seafood products such as pomfret, boiled clams, boiled fish, and chikuwa; processed rice products such as porridge, rice, gome-me-onnaise, and red bean rice; sauces such as meat sauce, mapo sauce, pasta sauce, curry, stew, and sambal sauce; processed dairy products such as cheese, butter, cream, and condensed milk; processed egg products such as boiled eggs and onsen eggs; boiled vegetables / beans; cooked foods such as fried foods, steamed foods, stir-fried foods, boiled foods, and baked foods; pickled vegetables; noodles such as udon noodles, soba noodles, and pasta; and pickled fruits.

[0076] Depending on the object being stored, ultraviolet light, electron beams, gamma rays, X-rays, etc., can also be used to sterilize or disinfect multi-layer containers.

[0077] <Composition of the first and second multilayer bodies>

[0078] Next, the composition of the first multilayer body and the second multilayer body of this embodiment will be described.

[0079] In this embodiment, the first and second multilayer bodies each independently comprise a sealing layer containing an aromatic polyamide resin and a substrate layer containing an aliphatic polyamide resin. By welding (sealing) the sealing layer portions of the multilayer bodies containing such sealing layers towards each other, a multilayer container is obtained.

[0080] The first and second multilayer bodies can be the same or different.

[0081] The sealing layers contained in the first and second multilayers each independently contain polyamide resin.

[0082] The polyamide resin contained in the sealing layer of the first and second multilayer bodies is a resin in which 30% or more of the structural units other than the terminal groups are derived from aromatic monomers, preferably a resin in which 40% or more of the structural units other than the terminal groups are derived from aromatic monomers, and preferably a resin in which 70% or less of the structural units other than the terminal groups are derived from aromatic monomers, more preferably a resin in which 60% or less of the structural units other than the terminal groups are derived from aromatic monomers.

[0083] Such polyamide resins can consist solely of aromatic polyamide resins, or they can be blends of aromatic and aliphatic polyamide resins. At least 30% by mass of all structural units (excluding terminal groups) of the polyamide resin contained in the sealing layer must be structural units derived from aromatic monomers.

[0084] Examples of aromatic polyamide resins include poly(hexamethylene terephthalamide) (polyamide 6T), poly(hexamethylene isophthalamide) (polyamide 6I), polyamide 66 / 6T, polyamide 9T, polyamide 9MT, polyamide 10T, polyamide 6I / 6T, and diphenylamine-based polyamide resins described later, with diphenylamine-based polyamide resins being preferred.

[0085] In this embodiment, the phenylenediamine-based polyamide resin refers to a polyamide resin containing structural units derived from diamine and structural units derived from dicarboxylic acid, wherein more than 70 mol% of the structural units derived from diamine are derived from phenylenediamine.

[0086] The dicarboxylic acid-derived structural units of the phenylenediamine-based polyamide resin preferably comprise 50 mol% or more, more preferably 70 mol% or more, derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms. The multilayer container of this embodiment can utilize the inherent strength and chemical resistance of the phenylenediamine-based polyamide resin.

[0087] In diamine-derived structural units of phenylenediamine-based polyamide resins, 75 mol% or more, more preferably 80 mol% or more, further preferably 85 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and particularly more preferably 99 mol% or more are derived from phenylenediamine (preferably p-phenylenediamine and / or m-phenylenediamine, more preferably m-phenylenediamine). Furthermore, in dicarboxylic acid-derived structural units of phenylenediamine-based polyamide resins, 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and particularly more preferably 99 mol% or more are derived from α,ω-linear aliphatic dicarboxylic acids (preferably adipic acid) having 4 to 20 carbon atoms.

[0088] In this embodiment, when the total amount of m-phenylenediamine and p-phenylenediamine in diphenylenediamine is set to 100 moles, the molar ratio of m-phenylenediamine to p-phenylenediamine is preferably 00~100 / 100~0, preferably 10~100 / 90~0, more preferably 40~100 / 60~0, further preferably 60~100 / 40~0, even more preferably 80~100 / 20~0, and even more preferably 90~100 / 10~0.

[0089] Besides m-phenylenediamine and p-phenylenediamine, other diamines that can be used as raw material components in phenylenediamine-based polyamide resins include tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2,2,4-trimethyl-hexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine, etc. (aliphatic diamines); 1,3-bis( Alicyclic diamines such as aminomethylcyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, bis(4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminomethyl)decahydronaphthalene, and bis(aminomethyl)tricyclodecane, as well as diamines with aromatic rings such as bis(4-aminophenyl)ether, p-phenylenediamine, and bis(aminomethyl)naphthalene, may be used, either one or a mixture of two or more.

[0090] As described above, the phenylene dimethylamine-based polyamide resin preferably has 50 mol% or more of its structural units derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms. The α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms preferably has 6 or more carbon atoms, and more preferably 18 or less, more preferably 16 or less, even more preferably 14 or less, even more preferably 13 or less, even more preferably 12 or less, even more preferably 10 or less, and particularly preferably 8 or less.

[0091] The preferred dicarboxylic acid component used as a raw material for phenylenediamine-based polyamide resins is an α,ω-linear aliphatic dicarboxylic acid with 4 to 20 carbon atoms. Examples of such dicarboxylic acids include succinic acid, glutaric acid, pimelic acid, octanoic acid, azelaic acid, adipic acid, sebacic acid, undecanoic acid, and dodecanoic acid. One type or two or more types can be used. Among these, one or more types of adipic acid, sebacic acid, and dodecanoic acid are more preferred, and one or more types of adipic acid and sebacic acid are even more preferred. Adipic acid is even more preferred.

[0092] As a preferred embodiment of the phenylenediamine-based polyamide resin in this embodiment, a polyamide resin derived from dicarboxylic acid structural units with 50 mol% or more (preferably 70 mol% or more, more preferably 90 mol% or more) of dicarboxylic acid structural units can be exemplified.

[0093] As dicarboxylic acid components other than the aforementioned α,ω-linear aliphatic dicarboxylic acids with 4 to 20 carbon atoms, examples include phthalic acid compounds such as isophthalic acid, terephthalic acid, and phthalic acid; 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, etc., one type or two or more types can be used.

[0094] It should be noted that the phenylene dimethylamine-based polyamide resin contains structural units derived from diamine and structural units derived from dicarboxylic acids as main components, but does not completely exclude structural units other than these. It may also 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 phenylene dimethylamine-based polyamide resin in which the total number of structural units derived from diamine and dicarboxylic acids is the largest among all structural units. In this embodiment, the total number of structural units derived from diamine and dicarboxylic acids in the phenylene dimethylamine-based polyamide resin preferably accounts for 90% or more by mass, more preferably 95% or more by mass, further preferably 97% or more by mass, and even more preferably 99% or more by mass.

[0095] The proportion of aromatic polyamide resin (preferably phenylene dimethylamine-based polyamide resin) in the sealing layer of both the first and second multilayer bodies is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more in 100% by mass of the sealing layer. By setting this lower limit or above, there is a tendency to further improve the heat-sealing strength. In addition, in this embodiment, the proportion of aromatic polyamide resin in the sealing layer of both the first and second multilayer bodies is 100% by mass or less in 100% by mass of the sealing layer.

[0096] The sealing layer of this embodiment may contain only one type of aromatic polyamide resin, or it may contain two or more types. When it contains two or more types, the total amount is preferably within the range described above.

[0097] On the other hand, examples of aliphatic polyamide resins that can be included in the sealing 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. By including an aliphatic polyamide resin in the sealing layer, there is a tendency to further improve pinhole resistance.

[0098] The sealing layer in this embodiment may not contain aliphatic polyamide resin, may contain only one type, or may contain two or more types.

[0099] Aromatic polyamide resins and aliphatic polyamide resins are also preferred, especially aromatic polyamide resins (biomass thermoplastic resins) manufactured using recycled resins and biomass raw materials. By using biomass thermoplastic resins, environmental impact can be reduced.

[0100] For example, in phenylenediamine-based polyamide resins, bio-based adipic acid can be used as a biomass feedstock. Alternatively, adipic acid with ISCC Plus certification can also be used. ISCC Plus certification refers to the quantitative determination of the extent to which renewable raw materials and bio-based feedstocks are used, the extent to which products are produced, and the shipment of products in a factory or production facility, ensuring quality along with the overall quality.

[0101] The glass transition temperature of the polyamide resin contained in the sealing layer is preferably 50°C or higher, more preferably 60°C or higher, and preferably 160°C or lower, more preferably 120°C or lower. In this embodiment, when the sealing layer contains two or more aromatic polyamide resins, the glass transition temperature of the aromatic polyamide resin is set to the glass transition temperature of the resin with the highest content.

[0102] The melting point of the polyamide resin contained in the sealing layer is preferably 150°C or higher, more preferably 180°C or higher, even more preferably 200°C or higher, and still more preferably 205°C or higher. Furthermore, the melting point of the polyamide resin contained in the sealing 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 still more preferably 250°C or lower. In this embodiment, when the sealing layer contains two or more aromatic polyamide resins, the melting point of the aromatic polyamide resin is set to the melting point of the resin with the highest content.

[0103] In this specification, the glass transition temperature (Tg) and melting point (Tm) are set as values ​​determined by differential scanning calorimetry (DSC) according to ISO 11357. Using a differential scanning calorimeter, the resin is placed in the measuring pan of the DSC and heated to a temperature exceeding the melting point at a rate of 10°C / min under a nitrogen atmosphere. After a rapid cooling pretreatment, the temperature is measured. The measurement conditions are as follows: a heating rate of 10°C / min is applied, and the temperature is held at 280°C for 5 minutes, followed by a cooling rate of -5°C / min until the temperature reaches 100°C. The glass transition temperature (Tg) and melting point (Tm) are then determined.

[0104] As a differential scanning calorimeter, the "DSC-60" manufactured by Shimadzu Corporation was used.

[0105] The lower limit of the number average molecular weight (Mn) of the polyamide resin contained in the sealing layer is preferably 6,000 or more, more preferably 8,000 or more, even more preferably 10,000 or more, and preferably 100,000 or less, more preferably 50,000 or less. In this embodiment, when the sealing layer contains two or more polyamide resins, the number average molecular weight is set to that of the mixture.

[0106] The number-average molecular weight (Mn) of the aromatic polyamide resin was determined by conversion based on standard polymethyl methacrylate (PMMA) values ​​measured by gel permeation chromatography (GPC). Two columns were used, packed with styrene-based polymers as the packing material. The solvent used was hexafluoroisopropanol (HFIP) at a concentration of 2 mmol / L sodium trifluoroacetate. The resin concentration was 0.02% by mass, the column temperature was 40 °C, the flow rate was 0.3 mL / min, and measurements were taken using a refractive index detector (RI). Furthermore, the calibration curve was determined by dissolving six levels of PMMA in HFIP.

[0107] The sealing layer used in this embodiment may contain thermoplastic resins other than polyamide resins, or it may not contain any, without compromising the purpose or effect of the present invention.

[0108] In this embodiment, the total mass percentage of the sealing layer of polyamide resin (aromatic polyamide resin and aliphatic polyamide resin) is preferably 90% or more, more preferably 95% or more, even more preferably 97% or more, even more preferably 98% or more, and may also be 99% or more. In addition, it is preferably 100% or less.

[0109] The sealing layer used in this embodiment preferably does not contain thermoplastic resins other than polyamide resins. Specifically, the content of thermoplastic resins other than polyamide resins in the sealing layer of this embodiment is preferably less than 1% by mass, more preferably less than 0.1% by mass, in 100% by mass of the sealing layer.

[0110] The sealing layer used in this embodiment may contain resin additives such as antioxidants, heat stabilizers, hydrolysis resistance modifiers, weathering stabilizers, matting agents, ultraviolet absorbers, nucleating agents, plasticizers, dispersants, flame retardants, antistatic agents, anti-coloring agents, anti-gelling agents, colorants, and release agents. For details, please refer to paragraphs 0130-0155 of Japanese Patent No. 4894982 and paragraphs 0047-0103 of International Publication No. 2021 / 241471, and these contents are incorporated herein by reference.

[0111] In this embodiment, the total content of resin additives in the sealing layer is preferably 0 to 5% by mass of the sealing layer, more preferably 0 to 3% by mass.

[0112] In the multilayer container of this embodiment, the total amount of polyamide resin containing aromatic polyamide resin and aliphatic polyamide resin is preferably 95% by mass or more, more preferably 97% by mass or more, and may also be 99% by mass or more. Furthermore, it is preferably set to 100% by mass or less. By setting it to the lower limit or above, the recyclability of the multilayer container can be further improved.

[0113] The resin composition here refers to polyamide resin, other thermoplastic resins, and resin additives, typically all components contained in multilayer containers except for filler materials and solvents.

[0114] In addition, the total amount of components other than polyamide resin contained in the resin composition is preferably 0 to 3% by mass, more preferably 0 to 1% by mass.

[0115] In this embodiment, the sealing layers in the multi-layer container can be the same or different.

[0116] The sealing layers included in the first multilayer and the sealing layers included in the second multilayer preferably have at least 80% by mass identical composition, more preferably at least 90% by mass identical composition, and even more preferably at least 95% by mass identical composition. This configuration improves the weld strength between the multilayers.

[0117] The substrate layers contained in the first and second multilayers each independently contain aliphatic polyamide resin.

[0118] The aliphatic polyamide resin is a resin in which at least 80% by mass of all structural units, excluding terminal groups, are derived from aliphatic monomers; more preferably, it is a resin in which at least 85% by mass of all structural units, excluding terminal groups, are derived from aliphatic monomers; more preferably, it is a resin in which at least 90% by mass of all structural units, excluding terminal groups, are derived from aliphatic monomers; even more preferably, it is a resin in which at least 95% by mass of all structural units, excluding terminal groups, are derived from aliphatic monomers; and even more preferably, it is a resin in which at least 97% by mass 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.

[0119] 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, with polyamide 6, polyamide 66, and polyamide 666 being more preferred, and polyamide 6 being even more preferred.

[0120] Aliphatic polyamide resins are preferably made from recycled resins or biomass raw materials (biomass thermoplastic resins). Using biomass thermoplastic resins can reduce environmental impact.

[0121] The proportion of aliphatic polyamide resin in the substrate layer of both the first and second multilayer bodies is independently 93% by mass or more, more preferably 95% by mass or more, further 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, out of 100% by mass of the substrate layer. By setting this lower limit or above, there is a tendency to further improve flexibility and impact resistance. Furthermore, in this embodiment, the proportion of aliphatic polyamide resin in the substrate layer of both the first and second multilayer bodies is 100% by mass or less out of 100% by mass of the substrate layer.

[0122] The substrate layer of this embodiment may contain only one type of aliphatic polyamide resin, or it may contain two or more types. When it contains two or more types, the total amount is preferably within the range described above.

[0123] Without impairing the purpose or effect of the present invention, the substrate layer used in this embodiment may contain polyamide resin other than aliphatic polyamide resin, thermoplastic resin other than polyamide resin, or may not contain any.

[0124] The substrate layer used in this embodiment preferably does not contain thermoplastic resins other than polyamide resins. Specifically, the content of thermoplastic resins other than polyamide resins in the substrate layer of this embodiment is preferably less than 1% by mass, and more preferably less than 0.1% by mass, out of 100% by mass of the substrate layer.

[0125] Furthermore, the substrate layer used in this embodiment preferably does not contain polyamide resin other than aliphatic polyamide resin. Specifically, the content of polyamide resin other than aliphatic polyamide resin in the substrate layer of this embodiment is preferably less than 10% by mass, more preferably less than 5% by mass, further preferably less than 3% by mass, even more preferably less than 1% by mass, and even more preferably less than 0.1% by mass in 100% by mass of the substrate layer.

[0126] The substrate layer used in this embodiment may contain resin additives such as antioxidants, heat stabilizers, hydrolysis resistance modifiers, weathering stabilizers, matting agents, ultraviolet absorbers, nucleating agents, plasticizers, dispersants, flame retardants, antistatic agents, anti-coloring agents, anti-gelling agents, colorants, and release agents. For details, please refer to paragraphs 0130-0155 of Japanese Patent No. 4894982 and paragraphs 0047-0103 of International Publication No. 2021 / 241471, and these contents are incorporated herein by reference.

[0127] In this embodiment, the total content of resin additives in the substrate layer is preferably 0 to 5% by mass of the substrate layer, and more preferably 0 to 3% by mass.

[0128] In this embodiment, the substrate layers in the multilayer container can be the same or different.

[0129] The substrate layer contained in the first multilayer and the substrate layer contained in the second multilayer preferably have at least 80% by mass the same composition, more preferably at least 90% by mass, and even more preferably at least 95% by mass.

[0130] <Manufacturing Method of Multi-Layer Containers>

[0131] The manufacturing method of the multilayer container in this embodiment is not particularly limited, and it can be manufactured using known methods. Generally, it is preferable to weld a portion of the first multilayer body and the second multilayer body together with the sealing layers of the first multilayer body and the second multilayer body facing each other. The meanings of the first multilayer body and the second multilayer body are the same as those described in the section on multilayer containers above, and the preferred ranges are also the same. In addition, in the multilayer container of this embodiment, the moisture content of the first multilayer body and the second multilayer body at the time of welding is preferably 10,000 ppm by mass or less before sealing (welding). By setting this moisture content, welding at low temperature is possible. Furthermore, when the polyamide resin is a crystalline resin, there is a tendency for the crystallization rate to slow down, allowing for slow welding and further improving the sealing strength, which is therefore preferable.

[0132] The moisture content is more preferably 9000 ppm by mass or less, more preferably 7000 ppm by mass or less, even more preferably 5000 ppm by mass or less, and even more preferably 4500 ppm by mass or less. Depending on the application, it may also be 3500 ppm by mass or less, 3000 ppm by mass or less, or 2500 ppm by mass or less. In addition, the lower limit of the moisture content is 0 ppm by mass or more.

[0133] In this embodiment, in order to maintain the aforementioned moisture content, the manufactured first and second multilayer bodies are preferably stored under conditions that do not easily absorb moisture until just before sealing.

[0134] Based on the glass transition temperature (Tg) of the polyamide resin, the welding temperature is preferably above Tg, more preferably above Tg+20°C, even more preferably above Tg+30°C, even more preferably above Tg+35°C, and even more preferably above Tg+45°C. Setting the temperature above or above these lower limits tends to improve the heat-sealing strength. Furthermore, based on the glass transition temperature (Tg) of the polyamide resin, the welding temperature is preferably below Tg+140°C, more preferably below Tg+130°C, even more preferably below Tg+120°C, even more preferably below Tg+110°C, and even more preferably below Tg+100°C. Setting the temperature below these upper limits tends to result in a better appearance of the heat-sealed portion.

[0135] In addition, the temperature during heat fusion is preferably below 200°C, more preferably below 180°C, even more preferably below 160°C, and even more preferably below 140°C depending on the application, etc. In addition, it is preferably above 80°C, more preferably above 100°C, even more preferably above 110°C, and even more preferably above 130°C depending on the application, etc.

[0136] Furthermore, the temperature during heat fusion can be constant, or it can be gradually increased and / or decreased. In this case, the temperature within the range mentioned above is preferred when the heat fusion temperature is at its highest.

[0137] There is no particular limitation on the welding time; for example, it can be more than 1 second and less than 1 minute. There is no particular limitation on the welding pressure; for example, it can be more than 0.2 MPa and less than 0.5 MPa.

[0138] <Manufacturing Method of Recycled Polyamide Resin>

[0139] This embodiment discloses a method for manufacturing recycled polyamide resin, which includes crushing the aforementioned multilayer container. That is, the multilayer container of this embodiment is mostly composed of polyamide resin, thus approximating a single material, and can be crushed to produce recycled polyamide resin.

[0140] Furthermore, it is preferable to use the recycled polyamide resin obtained by the manufacturing method of the recycled polyamide resin of this embodiment to form the substrate layer of the multilayer container of this embodiment.

[0141] Example

[0142] The following examples illustrate the present invention in more detail. The materials, amounts, proportions, processing contents, and processing steps shown in the following examples can be appropriately modified without departing from the spirit of the invention. Therefore, the scope of protection of the present invention is not limited to the specific examples shown below.

[0143] If the measuring instruments used in the embodiments are difficult to obtain due to production stoppages or other reasons, other instruments with equivalent performance can be used for measurement.

[0144] 1. Raw materials

[0145] PA-1: A polyamide resin (MXD6) synthesized from m-phenylenediamine and adipic acid, manufactured by Mitsubishi Gas Chemical Co., Ltd., S6007, melting point 237°C, glass transition temperature 85°C.

[0146] PA-2: A polyamide resin (MXD6) synthesized from isophthalic acid, adipic acid, and isophthalic acid; manufactured by Mitsubishi Gas Chemical Co., Ltd.; S7007; melting point 229°C; glass transition temperature 92°C.

[0147] PA6: Polyamide 6, manufactured by UBE, product number 1022B

[0148] PA666: Polyamide 666, manufactured by UBE, product number 5023B

[0149] PA6I / 6T: Polyamide 6I / 6T, manufactured by Emmans Corporation, G21.

[0150] 2. Examples 1-19, Comparative Examples 1-5

[0151] <Manufacturing of Multilayers>

[0152] Using a multilayer sheet manufacturing apparatus equipped with two extruders, a feed head, a T-die, a cooling roller, a winding machine, etc., PA6 is extruded from the first extruder at 240°C and the sealing layer resin described in the example is extruded from the second extruder at 260°C, respectively, and two types of two-layer structures of PA6 / sealing layer are manufactured by means of the feed head.

[0153] The obtained multilayer bodies were stored in a sealed container within a moisture-proof film until all tests were conducted.

[0154] <Method for determining the moisture content of multilayer materials>

[0155] Moisture content was determined using a Karl Fischer moisture meter according to ISO 15512. Units are expressed in ppm.

[0156] The Karl Fischer moisture meter uses the CA-200 model, a trace moisture determination device manufactured by Nitto Seiko Analytech (formerly Mitsubishi Chemical Analysis Technology Co., Ltd.), which is based on an electrostatic titration method.

[0157] <Heat seal strength>

[0158] For the two multilayer bodies obtained above, the sealing layer is placed in opposite directions. The bonding strength when fused at sealing temperatures of 120°C and 150°C is evaluated as follows.

[0159] The heat-sealed film was conditioned for one week at 23°C and 50%RH. The sealed portion was cut into 15mm wide pieces, and a T-peel test was performed using a Strograph manufactured by Toyo Seiki Co., Ltd. at a speed of 300mm / min. The maximum point load during peeling was measured and taken as the T-peel load to evaluate the seal strength. It should be noted that five measurements were taken for each test, and the average value was recorded. The unit is expressed in N / 15mm.

[0160] Impact resistance

[0161] For the multilayer obtained above, a thin film impact test is performed as follows.

[0162] The obtained stretched film was cut into 10cm squares, and the impact value was determined using a film impact testing machine according to ASTM D3420. In this embodiment, an ORIENTEC FT-60 film impact testing machine was used. The unit is expressed in kgfcm.

[0163] <Pinhole Resistance>

[0164] Pinhole resistance was determined using the Gelbo Flex test as follows.

[0165] The obtained stretched film was cut into 25cm squares and mounted on a pinhole resistance testing machine. A continuous 440° torsional motion and 65mm linear motion were applied to the film at a speed of 40 times / minute, causing the film to bend 1000 times. The number of pinholes in the bent film was measured using a pinhole inspection machine, and the number of pinholes per 100cm was calculated. 2 The number of pinholes in the film. Here, the number is calculated per 100 cm of film. 2 The number of pinholes is calculated as follows.

[0166] Number of pinholes (per 100cm) 2 = Total number of pinholes (holes) / Effective test area (cm²) 2 In this embodiment, the Gelbo Flex Tester manufactured by Rigaku Corporation is used as the pinhole resistance testing machine, and the POROSCOPE DC manufactured by Fischer Corporation is used as the pinhole inspection machine.

[0167] The number of pinholes formed during 20, 50, 200, and 400 Gelbo Flex tests was determined.

[0168] [Table 1]

[0169]

[0170] [Table 2]

[0171]

[0172] [Table 3]

[0173]

[0174] [Table 4]

[0175]

[0176] [Table 5]

[0177]

[0178] The results above demonstrate that the multilayer container of this embodiment exhibits high impact resistance and strong sealing strength. Furthermore, it also demonstrates excellent resistance to pinholes. In addition, since it can be constructed solely from polyamide resin, its recyclability is improved.

[0179] Explanation of reference numerals in the attached figures

[0180] 1. First multilayer body

[0181] 12 Sealing layer contained in the first multilayer body

[0182] 13. Substrate layer contained in the first multilayer body

[0183] 2. Second multilayer body

[0184] 22 Sealing layer contained in the second multilayer body

[0185] 23. Substrate layer contained in the second multilayer body

[0186] 10+ layer containers

Claims

1. A multilayer container, comprising: a first multilayer body including a seal layer containing a polyamide resin and a base material layer containing an aliphatic polyamide resin; and a second multilayer body including a seal layer containing a polyamide resin and a base material layer containing an aliphatic polyamide resin; the seal layer of the first multilayer body and the seal layer of the second multilayer body are opposed to each other and a part of them is fusion-bonded, the thickness of the seal layer of the first multilayer body and the thickness of the seal 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 seal layer of the first multilayer body and the polyamide resin contained in the seal 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 an aromatic monomer, 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 an aliphatic monomer, 95% by mass or more of the resin components contained in the multilayer container are polyamide resins.

2. The multilayer container of claim 1, wherein, the moisture content of the first multilayer body and the second multilayer body immediately before sealing is each independently 10,000 mass ppm or less.

3. The multilayer container of claim 1 or 2, wherein, the thickness of the seal layer of the first multilayer body and the thickness of the seal layer of the second multilayer body are each independently 6 μm or more.

4. The multilayer container according to any one of claims 1 to 3, wherein, the polyamide resin contained in the seal layer of the first multilayer body and the polyamide resin contained in the seal layer of the second multilayer body each independently include a xylylenediamine-based polyamide resin containing a structural unit derived from a diamine and a structural unit derived from a dicarboxylic acid, and 70% by mole or more of the structural unit derived from the diamine is derived from a xylylenediamine.

5. The multilayer container of claim 4, wherein, 70% by mole or more of the structural unit derived from the dicarboxylic acid in the xylylenediamine-based polyamide resin is a structural unit derived from an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 4 to 20.

6. The multilayer container of any of claims 1-5, wherein, the moisture content of the first multilayer body and the second multilayer body immediately before sealing is each independently 10,000 mass ppm or less, the thickness of the seal layer of the first multilayer body and the thickness of the seal layer of the second multilayer body are each independently 6 μm or more, the polyamide resin contained in the seal layer of the first multilayer body and the polyamide resin contained in the seal layer of the second multilayer body each independently include a xylylenediamine-based polyamide resin containing a structural unit derived from a diamine and a structural unit derived from a dicarboxylic acid, and 70% by mole or more of the structural unit derived from the diamine is derived from a xylylenediamine, 70% by mole or more of the structural unit derived from the dicarboxylic acid is a structural unit derived from an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 4 to 20.

7. The multilayer container of any of claims 1 to 6, wherein, the seal layer of at least one of the first multilayer body and the second multilayer body is in direct contact with the base material layer or in contact with the base material layer via an adhesive layer, and the seal layer is an unstretched film.

8. A method for producing a recycled polyamide resin, comprising crushing the multilayer container according to any one of claims 1 to 7.

9. A method of making a multilayer container comprising: a first multilayer body and a second multilayer body are partially fused with the sealing layer of the first multilayer body and the sealing layer of the second multilayer body facing each other, the first multilayer body comprising a sealing layer containing a polyamide resin and a substrate layer containing an aliphatic polyamide resin, the second multilayer body comprising a sealing layer containing a polyamide resin and a substrate layer containing an aliphatic polyamide resin; the thickness of the sealing layer of the first multilayer body and the thickness of the sealing 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 sealing layer of the first multilayer body and the polyamide resin contained in the sealing 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 an aromatic monomer, 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 an aliphatic monomer, 95% by mass or more of the resin components contained in the multilayer container are polyamide resins, the moisture content of the first multilayer body and the second multilayer body immediately before sealing at the time of fusion is each independently 10,000 ppm by mass or less.

10. The method of manufacturing a multilayer container according to claim 9, wherein, the multilayer container is the multilayer container according to any one of claims 1 to 7. the multilayer container is the multilayer container according to any one of claims 1 to 7.

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