Multilayer structure

Abstract

The present invention relates to: a multilayer structure comprising a recycled resin layer (A) that contains a polyolefin-based resin (a) as a main component, and a barrier layer (B) that contains an ethylene-vinyl alcohol copolymer (b) as a main component, the recycled resin layer (A) having a thickness exceeding 200 μm; a multilayer blow-molded article comprising the multilayer structure; and a method for manufacturing the multilayer structure, the method comprising at least steps (1), (2) (the steps (1), (2) are as described in the description).

Description

multilayer structure

[0001] The present invention relates to a multilayer structure, a multilayer blow-molded article containing the multilayer structure, and a method for manufacturing the multilayer structure.

[0002] In recent years, driven by environmental and waste issues, there has been a growing global demand for so-called post-consumer recycling, which involves recovering and recycling products consumed in the market. For example, in the recycling of thermoplastic resins such as polyolefins, a common method involves cutting and / or crushing resin products or resin parts recovered from products consumed in the market, separating and / or washing them as necessary, then melting them using an extruder or the like to repelletize them as a recovered composition. Various molded articles are then manufactured using the recycled resin pellets obtained in this way. For example, Patent Document 1 discloses a multilayer structure having at least a recycled resin layer mainly composed of recycled resin, a layer mainly composed of polyolefin resin, and two or more barrier layers mainly composed of ethylene-vinyl alcohol copolymer resin, wherein the barrier layers are located on the outside and inside of the recycled resin layer, and the recycled resin layer further contains a compound having 30 or fewer carbon atoms and a lower SP value than the ethylene-vinyl alcohol copolymer resin.

[0003] Japanese Patent Publication No. 2021-28167

[0004] Unlike pre-consumer recycled resins, which are recycled trim and off-spec products generated during the manufacturing process before reaching consumers, post-consumer recycled resins, as mentioned above, are made from products that have already been distributed to the market. Therefore, they may contain a wide variety of components, such as printing inks, antiblocking (AB) agents, antioxidants, oils, lubricants, antistatic agents, nucleating agents, adhesives, pigments, light stabilizers, tackifiers, foaming agents, plasticizers, detergents, and fragrances. When resins containing such components are reused, there is a problem that odors and / or volatile organic compounds (VOCs) are more likely to be generated due to these components. For this reason, when using molded products made from post-consumer recycled resins, measures against odors and VOCs are even more necessary compared to pre-consumer recycled products. Furthermore, as the amount of recycled resin used in a molded product increases, the odor from the molded product tends to become stronger. Also, the amount of VOCs contained in recycled resin tends to increase as well. On the other hand, increasing the amount of recycled resin used in molded articles is desirable from the standpoint of contributing to environmental and waste management issues. Furthermore, increasing the amount of molded articles using recycled resin is also desirable from the standpoint of enabling applications that were previously difficult to use. For example, Patent Document 1 describes that if the thickness of the recycled resin layer containing recycled resin exceeds a certain thickness, the migration of the aforementioned undesirable components may increase. In other words, there was room for further consideration in adopting a recycled resin layer as a resin layer exceeding a certain thickness. Therefore, there is a need to study structures that can reduce the permeation of odors or VOCs even when the thickness of the recycled resin layer is relatively thick, and methods for manufacturing the same.

[0005] Therefore, the present invention aims to provide a novel multilayer structure that can suppress the permeation of odors originating from the recycled resin layer into the space on at least one side of the recycled resin layer, even when using a recycled resin layer mainly composed of polyolefin resin and having a specific thickness.

[0006] As a result of diligent research, the inventors have found that the above problems can be solved by creating a structure that satisfies specific requirements. That is, the present invention encompasses the following inventions: [1] A multilayer structure comprising: a recycled resin layer (A) mainly composed of a polyolefin resin (a); and a barrier layer (B) mainly composed of an ethylene-vinyl alcohol copolymer (b); wherein the thickness of the recycled resin layer (A) is greater than 200 μm. [2] The multilayer structure according to [1], wherein the recycled resin layer (A) is a post-consumer recycled product. [3] The multilayer structure according to [1] or [2], wherein the polyolefin resin (a) comprises at least one selected from the group consisting of polypropylene resin and polyethylene resin. [4] The multilayer structure according to any one of [1] to [3], wherein the recycled resin layer (A) comprises a hydrocarbon (X), and the hydrocarbon (X) is at least one selected from the group consisting of alicyclic hydrocarbons, derivatives of alicyclic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons. [5] A multilayer structure according to any one of [1] to [4], wherein the thickness of the recycled resin layer (A) is 250 to 10,000 μm. [6] A multilayer structure according to any one of [1] to [5], wherein the barrier layer (B) consists only of an ethylene-vinyl alcohol copolymer (b). [7] A multilayer structure according to any one of [1] to [6], comprising a barrier layer (B) and an adjacent adhesive layer (C). [8] A multilayer structure according to any one of [1] to [7], comprising a thermoplastic resin layer (D) at least one position between the recycled resin layer (A) and the barrier layer (B), and at the position of the barrier layer (B) opposite to the recycled resin layer (A). [9] A multilayer structure according to any one of [1] to [8], wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer (b) is 20 to 50 mol%.

[10] The multilayer structure according to any one of [1] to [9] above, wherein the thickness of the barrier layer (B) is 5 μm or more.

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

[10] , wherein the barrier layer (B) comprises two or more ethylene-vinyl alcohol copolymers (b) with different ethylene unit contents, and the difference (b2-b1) between the ethylene unit content of the ethylene-vinyl alcohol copolymer (b2) with the highest ethylene unit content and the ethylene unit content of the ethylene-vinyl alcohol copolymer (b1) with the lowest ethylene unit content is 4 mol% or more.

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

[11] , comprising only one barrier layer (B).

[13] A multilayer structure according to any one of [1] to

[12] , wherein the recycled resin layer (A) is a molded product by injection molding.

[14] A multilayer structure according to any one of [1] to

[13] , wherein the multilayer structure is a molded product by insert molding or TOM molding.

[15] A multilayer blow molded product comprising the multilayer structure according to any one of [1] to

[14] .

[16] A multilayer blow-molded article according to

[15] having a bottle shape.

[17] A method for producing a multilayer structure, comprising at least the following steps (1) and (2): (1) a step of injection molding a recycled resin composition containing a polyolefin resin (a) to obtain a recycled resin layer (A'); (2) a step of extrusion molding a resin composition mainly containing an ethylene-vinyl alcohol copolymer (b) to obtain a barrier layer (B);

[0007] According to the present invention, even when a recycled resin layer having a specific thickness and mainly composed of polyolefin resin is used, a novel multilayer structure can be provided that can suppress the permeation of odors originating from the recycled resin layer into the space on at least one side of the recycled resin layer.

[0008] The following description is based on examples of embodiments of the present invention (hereinafter also referred to as "one aspect of the present invention"). However, the embodiments shown below are illustrative examples for realizing the technical concept of the present invention, and the present invention is not limited to the following description. Embodiments in which any part of the description in this specification is arbitrarily selected or arbitrarily combined are also included in the present invention. In this specification, preferred forms of embodiments are shown, but combinations of two or more individual preferred forms are also preferred forms. Preferred provisions can be arbitrarily selected, and for example, a combination of preferred provisions can be said to be more preferred. In this specification, unless otherwise specified, the description of a numerical range as "XX to YY" means "XX or more and YY or less" (XX represents the lower limit and YY represents the upper limit). For example, when the numerical range is simply described as "10 to 90", it represents a range of 10 or more and 90 or less. In this specification, the lower and upper limits described in stages for numerical ranges (each characteristic value, each component content, each structural unit content, each manufacturing condition, and the values ​​calculated from them, each characteristic, and each condition, etc.) can be combined independently. For example, based on the description "preferably 10 to 90, more preferably 30 to 60" for the same item, it is possible to combine the "preferred lower limit (10)" and the "more preferred upper limit (60)" to arrive at "10 to 60". Regarding the numerical range, for example, based on the description "preferably 10 to 90, more preferably 30 to 60", it is possible to specify only the lower limit as "10 or more" or "30 or more" without specifically specifying the upper limit, and similarly, it is possible to specify only the upper limit as "90 or less" or "60 or less" without specifically specifying the lower limit. The same applies when the upper limit of the numerical range is "less than" and when the lower limit is "greater than". Similarly, for example, based on the descriptions "preferably 10 or more, more preferably 30 or more" and "preferably 90 or less, more preferably 60 or less" for the same item, it is possible to combine the "preferred lower limit (10)" and the "more preferred upper limit (60)" to arrive at "10 or more and 60 or less". Furthermore, as described above, the lower limit can be specified as "10 or more" or "30 or more," and similarly, the upper limit can be specified as "90 or less" or "60 or less."The same applies when the terms "greater than or equal to" and "less than or equal to" in the above explanation are replaced with "greater than" and "less than," respectively. That is, for example, based on the statement "preferably more than 10 and less than 90, more preferably 30 or more and 60 or less," the upper and lower limits can be combined to become "more than 10 and 60 or less" and "30 or more and less than 90."

[0009] In this specification, unless otherwise specified, the following terms have the meanings described below: “Main component” means the component that is present in the largest quantity by mass. “ppm” means the mass content (mass ppm). “Polyolefin resin” means polyolefin resin and modified polyolefin resin. Modified polyolefin resin means a polymer obtained by modifying polyolefin resin (acid-modified polyolefin resin, polyolefin resin ionomer, etc.). “Polyolefin resin” refers to a polymer having structural units derived from olefin monomers (excluding ethylene vinyl alcohol copolymers), such as polyethylene resin and polypropylene resin. “Acid-modified polyolefin resin” means a polymer obtained by modifying polyolefin resin with acid. Acid-modified polyolefin resin may be a polymer in which at least one of an acidic group and an acid anhydride group is introduced to the polyolefin resin. “Polyethylene resin” means polyethylene resin and modified polyethylene resin. Modified polyethylene resin means a polymer obtained by modifying polyethylene resin (acid-modified polyethylene resin, polyethylene resin ionomer, etc.). "Polyethylene resin" refers to a homopolymer of ethylene; a copolymer of ethylene and 80 mol% or more of ethylene and 20 mol% or less of α-olefin monomer in a total monomer amount of 100 mol%; and a copolymer obtained by copolymerizing 80 mol% or more of ethylene and 20 mol% or less of a non-olefin monomer whose functional groups do not contain atoms other than carbon, oxygen, and hydrogen atoms in a total monomer amount of 100 mol% (excluding ethylene vinyl alcohol copolymer). "Acid-modified polyethylene resin" refers to a polymer obtained by modifying polyethylene resin with acid. Acid-modified polyethylene resin may be a polymer in which at least one of an acidic group and an acid anhydride group is introduced to polyethylene resin. "Polypropylene resin" refers to polypropylene resin and modified polypropylene resin. Modified polypropylene resin refers to a polymer obtained by modifying polypropylene resin (acid-modified polypropylene resin, polypropylene resin ionomer, etc.)."Polypropylene resin" refers to a homopolymer of propylene; a copolymer of propylene and at least one selected from the group consisting of ethylene and α-olefin monomers having 4 or more carbon atoms (excluding the polyethylene resin mentioned above); and a copolymer of propylene and a non-olefin monomer whose functional groups do not contain atoms other than carbon atoms, oxygen atoms, and hydrogen atoms. "Acid-modified polypropylene resin" refers to a polymer obtained by modifying polypropylene resin with an acid. Acid-modified polypropylene resin may be a polymer in which at least one of an acidic group and an acid anhydride group is introduced to polypropylene.

[0010] In this specification, unless otherwise specified, the terms "oxygen gas barrier property," "hydrocarbon (X) barrier property," and "odor barrier property" refer to the properties of a multilayer structure that is one aspect of the present invention. These properties are specifically measured and evaluated by the methods described in the examples. In this specification, "oxygen gas barrier property" refers to the effect of suppressing the permeation of oxygen gas present in at least one space of the multilayer structure to the space opposite to the said space. In this specification, "hydrocarbon (X) barrier property" refers to the effect of suppressing the permeation of hydrocarbon (X) contained in the recycled resin layer (A) to at least one space of the recycled resin layer (A), or the permeation of hydrocarbon (X) present in at least one space of the recycled resin layer (A) to the space opposite to the said space. In this specification, "odor barrier property" refers to the effect of suppressing the permeation of odors originating from the recycled resin layer (A) to at least one space of the recycled resin layer (A).

[0011] [Multilayer Structure] A multilayer structure according to one aspect of the present invention (hereinafter also referred to as "the multilayer structure") comprises a recycled resin layer (A) (hereinafter also referred to as "layer (A)") mainly composed of a polyolefin resin (a); and a barrier layer (B) (hereinafter also referred to as "layer (B)") mainly composed of an ethylene-vinyl alcohol copolymer (b); wherein the thickness of the recycled resin layer (A) is greater than 200 μm. The multilayer structure, having the above aspect, can achieve the excellent effects of the present invention.

[0012] In one embodiment of the multilayer structure, it is preferable to include an adhesive layer (C) adjacent to the barrier layer (B) (hereinafter also referred to as "layer (C)"). The "adhesive layer (C) adjacent to the barrier layer (B)" means that layer (B) and layer (C) are laminated without any other layer in between. In one embodiment of the multilayer structure, the adhesive layer (C) may be adjacent to only one side of the barrier layer (B), or it may be adjacent to both sides of the barrier layer (B).

[0013] In one embodiment of the multilayer structure, it is preferable that the multilayer structure further includes a thermoplastic resin layer (D) (hereinafter also referred to as "layer (D)"), more preferably that the thermoplastic resin layer (D) is located at least one position between the recycled resin layer (A) and the barrier layer (B), and at least two positions on the barrier layer (B) opposite to the recycled resin layer (A), and even more preferably that the thermoplastic resin layer (D) is located at least two positions between the recycled resin layer (A) and the barrier layer (B), and at least two positions on the barrier layer (B) opposite to the recycled resin layer (A). In one embodiment of the multilayer structure, it is preferable that layers (C) and (D) are located between layers (A) and layer (B), more preferably that layers (C) and (D) are located at least two positions between layers (A) and layer (B), and at least two positions on the layer (B) opposite to layer (A). In the former case, it is even more preferable to laminate each layer in the order of layer (A) / layer (D) / layer (C) / layer (B), and in the latter case, it is even more preferable to laminate each layer in the order of layer (A) / layer (D) / layer (C) / layer (B) / layer (C) / layer (D). In this specification, in the examples of each layer configuration, " / " indicates that they are directly laminated. In this specification, "direct lamination" means that the layers to be laminated are laminated without any other layers in between. For example, the above "layer (A) / layer (D) / layer (C) / layer (B)" indicates that all the layers are directly laminated in this order, but in this case it means that the recycled resin layer (A), barrier layer (B), adhesive layer (C), and thermoplastic resin layer (D) are laminated in this order without any other layers in between layer (A) and layer (D), between layer (D) and layer (C), and between layer (C) and layer (B).

[0014] In one embodiment of the multilayer structure, layer (B) may be provided on both sides of layer (A), or only on one side of layer (A). In one embodiment of the multilayer structure, the multilayer structure may contain only one layer (B), or it may contain two or more layers (B). From the viewpoint of ease of manufacture, it is preferable that the multilayer structure contains only one layer (B). The layers, layer configurations, etc. of the multilayer structure according to one embodiment of the present invention will be described in detail below.

[0015] <Recycled resin layer (A)> The recycled resin layer (A) mainly contains polyolefin resin (a) and has a thickness (thickness per layer) of more than 200 μm. Here, as mentioned above, "main component" refers to the component that is present in the largest quantity by mass. In other words, the component that is present in the largest quantity by mass in layer (A) is polyolefin resin (a).

[0016] (Polyolefin resin (a)) Examples of the polyolefin resin (a) (hereinafter also referred to as "PO(a)") include polyethylene resin, polypropylene resin, poly-1-butene, and poly-4-methyl-1-pentene. The polyolefin resin (a) is preferably at least one selected from the group consisting of polyethylene resin and polypropylene resin, more preferably at least one selected from the group consisting of polyethylene resin and polypropylene resin, even more preferably polypropylene resin, and even more preferably polypropylene. The polyolefin resin (a) is preferably a post-consumer recycled resin. The polyolefin resin (a) may be used alone or in combination of two or more types.

[0017] [Polyethylene Resin] The type of polyethylene resin is not particularly limited, and examples include high-density polyethylene, low-density polyethylene, medium-density polyethylene, linear low-density polyethylene, etc. The linear low-density polyethylene is a resin obtained by polymerizing ethylene with an α-olefin having 3 or more carbon atoms. Examples of α-olefins having 3 or more carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, 4-methyl-hexene-1, 4,4-dimethylpentene-1, etc. The number of carbon atoms in the α-olefin having 3 or more carbon atoms may be, for example, 3 to 20, 3 to 14, or 3 to 10. One type of polyethylene resin may be used alone, or two or more types may be used in combination.

[0018] There are no particular restrictions on the polymerization catalyst used when polymerizing the polyethylene resin, and examples include catalysts such as Ziegler-Natta catalysts, Philips catalysts, metallocene catalysts, and post-metallocene catalysts.

[0019] The MFR (190°C, 2.16 kg load) of the polyethylene resin, measured in accordance with ISO 1133-1:2011, is not particularly limited, but is preferably 0.5 to 30 g / 10 min, more preferably 0.5 to 20 g / 10 min, and even more preferably 0.5 to 10 g / 10 min.

[0020] [Polypropylene Resin] The type of polypropylene resin is not particularly limited, and examples include polypropylene (propylene homopolymer), copolymers of propylene and at least one selected from the group consisting of ethylene and α-olefin monomers having 4 or more carbon atoms. Examples of the α-olefins having 4 or more carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, 4-methyl-hexene-1, 4,4-dimethylpentene-1, etc. The copolymer may be a random copolymer, a block copolymer, or a random block copolymer. The number of carbon atoms in the α-olefins having 4 or more carbon atoms may be, for example, 4 to 20, 4 to 14, or 4 to 10.

[0021] Specific examples of copolymers of propylene and at least one selected from the group consisting of ethylene and α-olefin monomers having 4 or more carbon atoms include propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-1-butene random copolymer, propylene-1-butene block copolymer, propylene-ethylene-1-butene random copolymer, propylene-ethylene-1-butene block copolymer, propylene-ethylene random block copolymer, and propylene-ethylene-1-butene random block copolymer. The polypropylene resin may be used alone or in combination of two or more types.

[0022] The content of structural units derived from propylene (hereinafter also referred to as "propylene units") in the polypropylene resin is not particularly limited, but for example, it is preferably 20 to 100 mol%, more preferably 20 to 100 mol%, even more preferably 40 to 100 mol%, even more preferably 50 to 100 mol%, even more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%, and even more preferably 80 to 100 mol%, out of 100 mol% of the total amount of structural units constituting the polypropylene resin. It may also be 85 to 100 mol%, 90 to 100 mol%, 95 to 100 mol%, 99 to 100 mol%, or 100 mol%.

[0023] The aforementioned polypropylene resin can be produced by known manufacturing methods. While there are no particular limitations on the polymerization catalyst that can be used when polymerizing the polypropylene resin, as long as the effects of the present invention are achieved, examples of such catalysts include Ziegler-Natta catalysts, Phillips catalysts, metallocene catalysts, and post-metallocene catalysts.

[0024] The MFR (at 230°C, 2.16 kg load) of the polypropylene resin, as measured in accordance with ISO 1133-1:2011, is preferably 0.5 to 30.0 g / 10 min, more preferably 1.0 to 25.0 g / 10 min, and even more preferably 3.0 to 20.0 g / 10 min.

[0025] The proportion of polyolefin resin (a) in the resin constituting layer (A) is preferably 35 to 100% by mass, more preferably 40 to 100% by mass, even more preferably 50 to 100% by mass, even more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass, out of 100% by mass of the total amount of resin constituting layer (A). It may also be 95 to 100% by mass, 99 to 100% by mass, 99.9 to 100% by mass, or 100% by mass.

[0026] In the polyolefin resin (a) constituting layer (A), the proportion of post-consumer recycled polyolefin resin is preferably 35 to 100% by mass, more preferably 40 to 100% by mass, even more preferably 50 to 100% by mass, even more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass, out of 100% by mass of the total amount of polyolefin resin (a) constituting layer (A). Alternatively, it may be 95 to 100% by mass, 99 to 100% by mass, 99.9 to 100% by mass, or 100% by mass.

[0027] From the viewpoint of making the effects of the present invention more pronounced, the content of polyolefin resin (a) in layer (A) is preferably 35% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, out of 100% by mass of the total amount of layer (A) (excluding the content of hydrocarbons (X) and heterocyclic compounds (Y)), and may also be 95% by mass or more, 99% by mass or more, or 99.9% by mass or more. Furthermore, the content of polyolefin resin (a) in layer (A) is 100% by mass or less, out of 100% by mass of the total amount of layer (A) (excluding the content of hydrocarbons (X) and heterocyclic compounds (Y)), and may also be 99.99% by mass or less. As described above, these lower and upper limits described in stages can be combined independently. For example, in one embodiment of the multilayer structure, the content of polyolefin resin (a) in layer (A) is preferably 35 to 100% by mass, more preferably 40 to 100% by mass, even more preferably 50 to 100% by mass, even more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass, out of 100% by mass of the total amount of layer (A) (excluding the content of hydrocarbons (X) and heterocyclic compounds (Y)). Alternatively, it may be 95 to 100% by mass, 99 to 100% by mass, 99.9 to 100% by mass, 70 to 99.99% by mass, 80 to 99.99% by mass, 90 to 99.99% by mass, 95 to 99.99% by mass, 99 to 99.99% by mass, or 99.9 to 99.99% by mass. In one embodiment of the multilayer structure, the content of polyolefin resin (a) in layer (A) may be 100% by mass of the total amount of layer (A) (excluding the content of hydrocarbons (X) and heterocyclic compounds (Y)). That is, the recycled resin layer (A) may consist of only at least one selected from the group consisting of polyolefin resin (a) and hydrocarbons (X) and heterocyclic compounds (Y). In layer (A), one type of polyolefin resin (a) may be used alone, or two or more types may be used in combination.If layer (A) contains two or more types of polyolefin resin (a), the content of the polyolefin resin (a) is the total content of the two or more types of polyolefin resin (a) contained therein.

[0028] (Hydrogen (X) and Heterocyclic Compound (Y)) From the viewpoint of making the effects of the present invention more pronounced, it is preferable that the layer (A) contains hydrocarbon (X), and that hydrocarbon (X) is at least one selected from the group consisting of alicyclic hydrocarbons, derivatives of alicyclic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons. In one embodiment of the present invention, the layer (A) may be a layer containing a heterocyclic compound (Y). It is preferable that the at least one selected from the group consisting of hydrocarbon (X) and heterocyclic compound (Y) is a component included because part or all of the polyolefin resin (a), which is the main component of the layer (A), is a recycled resin. It is even more preferable that the at least one selected from the group consisting of hydrocarbon (X) and heterocyclic compound (Y) is a component included because part or all of the polyolefin resin (a), which is the main component of the layer (A), is a polyolefin resin that has been collected from products that have been distributed to the market and processed for reuse, that is, because part or all of the polyolefin resin (a) is a post-consumer recycled resin. In one embodiment of the multilayer structure, it is more preferable that the recycled resin layer (A) is a post-consumer recycled product.

[0029] If part or all of the polyolefin resin (a) is a post-consumer recycled resin, it may contain components not found in polyolefin resins obtained by recovering trim or off-spec products generated during the manufacturing process or molding of polyolefin resins, such as pre-consumer recycled products. Post-consumer recycled resins obtained by recovering products that have been distributed in the market tend to contain, for example, volatile organic compounds (VOCs). VOCs can also be a cause of odors, etc.

[0030] Examples of the alicyclic hydrocarbons and derivatives of alicyclic hydrocarbons include alicyclic saturated hydrocarbons such as cyclohexane, cycloheptane, and cyclooctane, and their derivatives; and alicyclic unsaturated hydrocarbons such as cyclohexene, cycloheptene, cyclooctene, limonene, and α-pinene, and their derivatives. Examples of the aromatic hydrocarbons include benzene, toluene, xylene, ethylbenzene, trimethylbenzene, styrene, naphthalene, and phenol. Examples of the halogenated hydrocarbons include dichloromethane and chloroform.

[0031] There are no particular restrictions on the number of carbon atoms in hydrocarbon (X), but from the viewpoint of making the effects of the present invention more pronounced, it is preferable that it be 25 or less, more preferably 20 or less, and even more preferably 15 or less. Furthermore, it is preferable that the number of carbon atoms in hydrocarbon (X) is 5 or more. As described above, these lower and upper limits described in stages can be combined independently. For example, the number of carbon atoms in hydrocarbon (X) is preferably 5 to 25, more preferably 5 to 20, and even more preferably 5 to 15. Layer (A) may contain only one type of hydrocarbon (X), or it may contain two or more types.

[0032] Examples of heterocyclic compounds (Y) include piperidine derivatives, morpholine derivatives, and pyrrolidine derivatives, with piperidine derivatives being preferred. An example of the piperidine derivative is 2,2,6,6-tetramethylpiperidine-4-ol. Layer (A) may contain only one heterocyclic compound (Y), or it may contain two or more.

[0033] The hydrocarbon (X) barrier properties described above are evaluated as an effect that can suppress the permeation of at least xylene and toluene from the hydrocarbons (X) described above, and are preferably evaluated by the method described in the examples. This is because xylene and toluene are VOCs as described above, are highly volatile, and tend to cause harmful effects such as odor, so it is preferable to suppress the permeation of these hydrocarbons as much as possible. However, the layer (A) in the multilayer structure does not necessarily have to contain at least one hydrocarbon (X) selected from the group consisting of xylene and toluene. Those skilled in the art will understand that if it can be confirmed that odor permeation can be suppressed by the evaluation described in the examples below, and furthermore, if hydrocarbon (X) barrier properties are confirmed, the permeation of other hydrocarbons (X) that have similar molecular structures to xylene and toluene, as well as the aforementioned various hydrocarbons and heterocyclic compounds (Y) that can cause odor, can also be suppressed to a considerable extent. However, in one aspect of the present invention, from the viewpoint of making the effects of the present invention more pronounced, it is preferable that layer (A) contains at least a hydrocarbon (X), more preferably an aromatic hydrocarbon as the hydrocarbon (X), and even more preferably at least one selected from the group consisting of xylene and toluene. The at least one selected from the group consisting of hydrocarbons (X) and heterocyclic compounds (Y) may be a hydrocarbon or heterocyclic compound originating from a component other than the member constituting the multilayer structure. For example, in at least two spaces separated by the multilayer structure, the multilayer structure can be suitably used to suppress the permeation of at least one selected from the group consisting of hydrocarbons (X) and heterocyclic compounds (Y) present on one side of the space to the other side. Therefore, the at least one selected from the group consisting of hydrocarbons (X) and heterocyclic compounds (Y) present on the one side of the space does not have to originate from the recycled resin layer (A), but may be generated from, for example, another structure or its constituent members or materials present on the space side.

[0034] In one embodiment of the present invention, for example, if layer (A) contains at least one selected from the group consisting of hydrocarbons (X) and heterocyclic compounds (Y), the presence of hydrocarbons (X) or heterocyclic compounds (Y) can be confirmed, for example, by gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS), etc. Furthermore, the content of at least one selected from the group consisting of hydrocarbons (X) and heterocyclic compounds (Y) in layer (A) varies depending on the market-circulated product which is the raw material for the recycled resin, but for example, the concentration of at least one selected from the group consisting of hydrocarbons (X) and heterocyclic compounds (Y) detected when the recycled resin layer (A) is separated and measured by GC or GC-MS may be 10 ppm or more. Thus, the multilayer structure is also superior in that, when the recycled resin layer (A) is made of post-consumer recycled material, it can effectively suppress permeation even when the concentration of at least one selected from the group consisting of hydrocarbons (X) and heterocyclic compounds (Y) is relatively high compared to pre-consumer recycled material such as reground material that has not been used by consumers.

[0035] Layer (A) may, in addition to the polyolefin resin (a), contain other optional components other than at least one selected from the group consisting of hydrocarbons (X) and heterocyclic compounds (Y), such as antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, heat stabilizers, and resins other than the polyolefin resin (a), as long as the effects of the present invention are achieved. Layer (A) may contain only one of these optional other components, or it may contain two or more.

[0036] Examples of the resin other than the polyolefin resin (a) include, for example, polyolefin resins other than the polyolefin resin (a) contained as a main component in the layer (A) (for example, when the polyolefin resin (a) as the main component is a polypropylene resin, an acid-modified polypropylene resin contained as a component other than the main component, etc.); ethylene-vinyl alcohol copolymer; polyamide; polystyrene; polyvinyl chloride; acrylic resin; polyurethane; polycarbonate; thermoplastic resins such as polyvinyl acetate and the like. Specific examples of the antioxidant and the like are, for example, the same as those of the corresponding agents described later in the column of the barrier layer (B).

[0037] The content of the other component in the layer (A) is preferably 0 to 65% by mass, more preferably 0 to 60% by mass, still more preferably 0 to 50% by mass, even more preferably 0 to 30% by mass, even more preferably 0 to 20% by mass, even more preferably 0 to 10% by mass in 100% by mass of the total amount of the layer (A) (however, excluding the contents of the hydrocarbon (X) and the heterocyclic compound (Y)). Also, for example, it may be 0 to 5% by mass, 0 to 1% by mass, 0 to 0.1% by mass, 0.01 to 30% by mass, 0.01 to 20% by mass, 0.01 to 10% by mass, 0.01 to 5% by mass, 0.01 to 1% by mass, or 0.01 to 0.1% by mass.

[0038] In the layer (A), the total content of the polyolefin resin (a) and the other components contained as necessary does not include a combination exceeding 100% by mass in 100% by mass of the total amount of the layer (A) (however, excluding the contents of the hydrocarbon (X) and the heterocyclic compound (Y)). That is, in the layer (A), the total content of the polyolefin resin (a) and the other components contained as necessary is at most 100% by mass in 100% by mass of the total amount of the layer (A) (however, excluding the contents of the hydrocarbon (X) and the heterocyclic compound (Y)).

[0039] The thickness of layer (A) (thickness per layer) is preferably 250 μm or more, more preferably 350 μm or more, still more preferably 500 μm or more, even more preferably 700 μm or more, even more preferably 800 μm or more, and may be 1,000 μm or more, from the viewpoint of making the effects of the present invention more likely to be exhibited favorably. Also, the upper limit of the thickness of layer (A) (thickness per layer) can be appropriately set according to the use of the obtained multilayer structure and is not particularly limited. For example, it may be 10,000 μm. As described above, these stepwise-described lower limit values and upper limit values can be combined independently of each other. For example, as one aspect of the multilayer structure, the thickness of layer (A) (thickness per layer) is preferably more than 200 μm and 10,000 μm, more preferably 250 to 10,000 μm, still more preferably 350 to 10,000 μm, even more preferably 500 to 10,000 μm, even more preferably 700 to 10,000 μm, even more preferably 800 to 10,000 μm, and may be 1,000 to 10,000 μm.

[0040] In the multilayer structure which is one aspect of the present invention, layer (A) is preferably a molded article by injection molding.

[0041] <Barrier layer (B)> The barrier layer (B) contains an ethylene-vinyl alcohol copolymer (b) as a main component. Since the multilayer structure includes layer (B), it can exhibit high oxygen gas barrier property, hydrocarbon (X) barrier property, and odor barrier property. In the present specification, "ethylene-vinyl alcohol copolymer" is also abbreviated as "EVOH".

[0042] (Ethylene vinyl alcohol copolymer (b)) The ethylene-vinyl alcohol copolymer (b) (hereinafter also referred to as "EVOH(b)") preferably has an ethylene unit content of 20 to 50 mol%. From the viewpoint of further improving the oxygen gas barrier properties, the degree of saponification of EVOH(b) is preferably 90 to 100 mol%. The "ethylene unit content" in EVOH(b) refers to the content (mol%) of units derived from ethylene monomer in 100 mol% of the total amount of structural units constituting EVOH(b). The "degree of saponification" in EVOH(b) means the ratio (mol%) of vinyl alcohol units to the total number of vinyl alcohol units and vinyl ester units in EVOH(b). EVOH(b) is a copolymer having ethylene units and vinyl alcohol units. EVOH(b) is usually obtained by saponification of an ethylene-vinyl ester copolymer. EVOH(b) may have residual vinyl ester units.

[0043] Having an ethylene unit content of EVOH(b) of 20 mol% or more enhances thermal stability, among other things. From a similar viewpoint, the ethylene unit content is more preferably 22 mol% or more, even more preferably 24 mol% or more, even more preferably 25 mol% or more, and may be even more preferably 26 mol% or more, or 28 mol% or more. On the other hand, having an ethylene unit content of EVOH(b) of 50 mol% or less is preferable because it can further enhance oxygen gas barrier properties, hydrocarbon (X) barrier properties, and odor barrier properties. Furthermore, from the viewpoint of further enhancing oxygen gas barrier properties and hydrocarbon (X) barrier properties, the ethylene unit content is more preferably 47 mol% or less, even more preferably 45 mol% or less, even more preferably 40 mol% or less, may be even more preferably 35 mol% or less, or may be 30 mol% or less. As described above, these lower and upper limits described in stages can be combined independently. For example, in one embodiment of the multilayer structure, from the viewpoint of achieving a good balance of the aforementioned advantages, the ethylene unit content of EVOH(b) is more preferably 22 to 47 mol%, even more preferably 24 to 45 mol%, even more preferably 25 to 40 mol%, and even more preferably 26 to 35 mol%. The ethylene unit content of EVOH(b) may also be, for example, 28 to 35 mol%, or 24 to 30 mol%.

[0044] A degree of saponification of EVOH(b) of 90 mol% or more is preferable because it tends to further enhance oxygen gas barrier properties, hydrocarbon (X) barrier properties, and odor barrier properties. From the viewpoint of further improving oxygen gas barrier properties, hydrocarbon (X) barrier properties, and odor barrier properties, the degree of saponification is more preferably 95 mol% or more, even more preferably 99 mol% or more, and even more preferably 99.9 mol% or more. Also, the degree of saponification of EVOH(b) is 100 mol% or less. In other words, the degree of saponification of EVOH(b) is preferably 90 to 100 mol%, more preferably 95 to 100 mol%, even more preferably 99 to 100 mol%, and even more preferably 99.9 to 100 mol%. The ethylene unit content and degree of saponification of EVOH(b) are as follows: １This can be determined by 1H-NMR measurement. Specifically, it can be measured by the method described in the examples below.

[0045] The production and saponification of ethylene-vinyl ester copolymers can be carried out by known methods. Examples of vinyl esters include vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, vinyl versaticate, and other aliphatic carboxylic acid vinyl esters. Among these vinyl esters, vinyl acetate is preferred.

[0046] The total content of ethylene units, vinyl alcohol units, and vinyl ester units in EVOH(b) is preferably 90 to 100 mol%, more preferably 95 to 100 mol%, even more preferably 97 to 100 mol%, even more preferably 99 to 100 mol%, and may also be 100 mol%, out of 100 mol% of the total amount of structural units constituting EVOH(b). The content of ethylene units, vinyl alcohol units, and vinyl ester units in EVOH(b) is, respectively, １ This can be determined by 1H-NMR measurement. Specifically, it can be measured by the method described in the examples below.

[0047] EVOH(b) may have structural units other than ethylene units, vinyl alcohol units, and vinyl ester units, to the extent that the objectives of the present invention are not hindered. In particular, by introducing a modified group containing a primary hydroxyl group having a specific structure, it may be possible to achieve a high level of compatibility between the oxygen gas barrier properties, hydrocarbon (X) barrier properties, odor barrier properties, and moldability of EVOH(b). The content of other monomer units in 100 mol% of the total amount of structural units constituting EVOH(b) is preferably 0 to 10 mol%, more preferably 0 to 5 mol%, even more preferably 0 to 3 mol%, even more preferably 0 to 1 mol%, and even more preferably substantially absent. Specifically, "substantially absent" means that the content of the other structural units in 100 mol% of the total amount of structural units constituting EVOH(b) is 0 to 0.5 mol%, preferably 0 to 0.1 mol%, more preferably 0 to 0.05 mol%, and even more preferably 0 to 0.01 mol%.

[0048] Examples of the other structural units include units derived from monomers other than vinyl alcohol units, ethylene units, and vinyl ester units, and examples of the other monomers include alkenes such as propylene, butylene, pentene, and hexene; 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, 3,4-diasiloxy-1-butene, and 3-acyloxy-4-methyl-1- Butene, 4-acyloxy-1-butene, 3,4-diasiloxy-1-butene, 3-acyloxy-4-methyl-1-butene, 4-acyloxy-2-methyl-1-butene, 4-acyloxy-3-methyl-1-butene, 3,4-diasiloxy-2-methyl-1-butene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diasiloxy-1-pentene, 4-acyloxy-1-hexene, 5-acyl Examples include ester group-containing alkenes or saponifies thereof such as xy-1-hexene, 6-acyloxy-1-hexene, 5,6-diasiloxy-1-hexene, and 1,3-diacetoxy-2-methylenepropane; unsaturated acids or their anhydrides, salts, or mono- or dialkyl esters such as acrylic acid, methacrylic acid, crotonic acid, and itaconic acid; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids or their salts such as vinylsulfonic acid, allylsulfonic acid, and methallylsulfonic acid; vinylsilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, and γ-methacryloxypropylmethoxysilane; alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, and vinylidene chloride.

[0049] EVOH(b) may be modified as needed by urethaneization, acetalization, cyanoethylation, oxyalkyleneization, etc. Oxyalkyleneization can be carried out using epoxy compounds, for example, epoxyethane (ethylene oxide), epoxypropane, 1,2-epoxybutane, 2,3-epoxybutane, 3-methyl-1,2-epoxybutane, 1,2-epoxypentane, 3-methyl-1,2-epoxypentane, 1,2-epoxyhexane, 2,3-epoxyhexane, 3,4-epoxyhexane, 3-methyl-1,2-epoxyhexane, 3-methyl-1,2-epoxyheptane, 4-methyl-1,2-epoxyheptane, 1, Examples include 2-epoxyoctane, 2,3-epoxyoctane, 1,2-epoxynonane, 2,3-epoxynonane, 1,2-epoxydecane, 1,2-epoxydodecane, epoxyethylbenzene, 1-phenyl-1,2-propane, 3-phenyl-1,2-epoxypropane, various alkyl glycidyl ethers, various alkylene glycol monoglycidyl ethers, various alkenyl glycidyl ethers, various epoxy alkanols such as glycidol, various epoxycycloalkanes, and various epoxycycloalkenes. Among these, 1,2-epoxybutane, 2,3-epoxybutane, epoxypropane, epoxyethane, or glycidol are preferred, and epoxypropane or glycidol are more preferred.

[0050] The MFR (at 210°C and under a 2.16 kg load) of EVOH(b), measured in accordance with ISO 1133-1:2011, is preferably 1.0 g / 10 min or more, more preferably 1.5 g / 10 min or more, even more preferably 2.0 g / 10 min or more, and preferably 40 g / 10 min or less, more preferably 30 g / 10 min or less, and even more preferably 20 g / 10 min or less, from the viewpoint of improving the moldability of the barrier layer (B). As described above, these lower and upper limits described in stages can be combined independently. For example, in one embodiment of the structure, the MFR of EVOH(b) is preferably 1.0 to 40 g / 10 min, more preferably 1.5 to 30 g / 10 min, and even more preferably 2.0 to 20 g / 10 min.

[0051] The barrier layer (B) may contain two or more types of EVOH(b) with different ethylene unit contents. In such cases, for example, when molding using a film or sheet-like barrier layer (B) or a laminate containing the barrier layer (B) in a molding method such as vacuum forming or pressure forming, including insert molding and TOM molding (Three-dimensional Overlay Method) described later, the conformability of the barrier layer (B) or the laminate containing the barrier layer (B) to the mold is more easily improved, which is preferable from the viewpoint of increasing the freedom of moldability.

[0052] For example, if layer (B) contains two or more types of EVOH(b) with different ethylene unit content, from the viewpoint of improving the degree of freedom of moldability as described above, the difference (b2-b1) between the ethylene unit content of EVOH(b2) (hereinafter also referred to as "EVOH(b2)"), which has the highest ethylene unit content among the two or more types of EVOH(b), and the ethylene unit content of EVOH(b1) (hereinafter also referred to as "EVOH(b1)"), which has the lowest ethylene unit content among the two types of EVOH(b), is preferably 4 mol% or more, more preferably 8 mol% or more, even more preferably 12 mol% or more, even more preferably 15 mol% or more, and preferably 40 mol% or less, more preferably 30 mol% or less, even more preferably 25 mol% or less, and even more preferably 20 mol% or less. As described above, these progressively defined lower and upper limits can be combined independently. For example, in one embodiment of the multilayer structure, the difference in ethylene unit content (b2-b1) in layer (B) is preferably 4 to 40 mol%, more preferably 8 to 30 mol%, even more preferably 12 to 25 mol%, and even more preferably 15 to 20 mol%.

[0053] The mass ratio of EVOH(b1) to EVOH(b2) (b1 / b2), that is, the mass ratio of the content of EVOH(b1) to the content of EVOH(b2) in layer (B), is preferably 50 / 50 to 95 / 5, more preferably 60 / 40 to 90 / 10, and even more preferably 70 / 30 to 85 / 15.

[0054] From the viewpoint of making the effects of the present invention easier to achieve, the proportion of EVOH(b) in the resin constituting layer (B) is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass, out of 100% by mass of the total amount of resin constituting layer (B), and may also be 95 to 100% by mass, 99 to 100% by mass, 99.9 to 100% by mass, or 100% by mass.

[0055] From the viewpoint of making the effects of the present invention easier to achieve, the EVOH(b) content in layer (B) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, out of 100% by mass of the total amount of layer (B), and may also be 95% by mass or more, 99% by mass or more, or 99.9% by mass or more. Furthermore, the EVOH(b) content in layer (B) is 100% by mass or less, and may also be 99.99% by mass or less, out of 100% by mass of the total amount of layer (B). As described above, these lower and upper limits described in stages can be combined independently. For example, in one embodiment of the multilayer structure, the EVOH(b) content in layer (B) is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass, out of 100% by mass of the total amount of layer (B), and may also be 95 to 100% by mass, 99 to 100% by mass, 99.9 to 100% by mass, 70 to 99.99% by mass, 80 to 99.99% by mass, 90 to 99.99% by mass, 95 to 99.99% by mass, 99 to 99.99% by mass, or 99.9 to 99.99% by mass. In addition, in one embodiment of the multilayer structure, the EVOH(b) content in layer (B) may be 100% by mass out of 100% by mass of the total amount of layer (B). In other words, the barrier layer (B) may consist solely of an ethylene-vinyl alcohol copolymer (b). In layer (B), one type of EVOH(b) may be used alone, or two or more types may be used in combination. If two or more types of EVOH(b) are contained in the resin layer (B), the EVOH(b) content is the total content of the two or more types of EVOH(b) contained.

[0056] Layer (B) may contain other optional components besides EVOH(b), such as antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, heat stabilizers, and resins other than EVOH(b), as long as the effects of the present invention are achieved. Layer (B) may contain only one of these optional other components, or two or more.

[0057] Examples of the antioxidants include 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4'-thiobis(6-t-butylphenol), 2,2'-methylene-bis(4-methyl-6-t-butylphenol), octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate, and 4,4'-thiobis-(6-t-butylphenol). Examples of the ultraviolet absorbers include ethyl-2-cyano-3,3'-diphenyl acrylate, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, and 2-hydroxy-4-octoxybenzophenone. Examples of plasticizers include dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, and phosphate esters. Examples of antistatic agents include pentaerythritol monostearate, sorbitan monopalmitate, sulfated polyolefins, polyethylene oxide, and polyethylene glycol (trade name: Carbowax®, etc.). Examples of lubricants include ethylene bisstearamide and butyl stearate. Examples of colorants include carbon black, phthalocyanine, quinacridone, indoline, azo pigments, and red iron oxide. Examples of fillers include glass fiber, wollastonite, calcium silicate, talc, and montmorillonite. Examples of heat stabilizers include hindered phenol compounds and hindered amine compounds. Examples of resins other than EVOH(b) include thermoplastic resins such as polyolefin resins, polyamides, polystyrene, polyvinyl chloride, acrylic resins, polyurethanes, polycarbonates, and polyvinyl acetate.

[0058] The content of other optional components in layer (B) other than EVOH(b) is preferably 0 to 50% by mass, more preferably 0 to 30% by mass, even more preferably 0 to 20% by mass, and even more preferably 0 to 10% by mass, out of 100% by mass of the total amount of layer (B). Alternatively, it may be, for example, 0 to 5% by mass, 0 to 1% by mass, 0 to 0.1% by mass, 0 to 0.01% by mass, 0.01 to 20% by mass, 0.01 to 10% by mass, 0.01 to 5% by mass, 0.01 to 1% by mass, or 0.01 to 0.1% by mass.

[0059] In layer (B), the total content of EVOH(b) and other optional components, which may be included as needed, does not exceed 100% by mass of the total amount of layer (B). In other words, the total content of EVOH(b) and other optional components, which may be included as needed, in layer (B) is at most 100% by mass of the total amount of layer (B).

[0060] The thickness of layer (B) (thickness per layer) is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, even more preferably 20 μm or more, even more preferably 25 μm or more, even more preferably 50 μm or more, and may also be 70 μm or more, from the viewpoint of further enhancing oxygen gas barrier properties, hydrocarbon (X) barrier properties, and odor barrier properties. Furthermore, the thickness of layer (B) (thickness per layer) is preferably 2,000 μm or less, more preferably 1,000 μm or less, even more preferably 500 μm or less, even more preferably 300 μm or less, even more preferably 250 μm or less, and may also be 200 μm or less, from the viewpoint of further improving the degree of freedom of moldability as described above. As stated above, these lower and upper limits described in stages can be combined independently. For example, in one embodiment of the multilayer structure, from the viewpoint of further improving oxygen gas barrier properties, hydrocarbon (X) barrier properties and odor barrier properties, the thickness of layer (B) (thickness per layer) is preferably 5 to 2,000 μm, more preferably 10 to 1,000 μm, even more preferably 15 to 500 μm, even more preferably 20 to 300 μm, even more preferably 25 to 250 μm, even more preferably 50 to 200 μm, and may also be 70 to 200 μm. For example, in one embodiment of the multilayer structure, from the viewpoint of further improving the degree of freedom of moldability as described above, the thickness of layer (B) (thickness per layer) is preferably 5 to 200 μm, more preferably 5 to 100 μm, even more preferably 5 to 50 μm, even more preferably 10 to 50 μm, even more preferably 10 to 40 μm, even more preferably 15 to 40 μm, and may also be 15 to 30 μm.

[0061] The ratio of the total thickness of layer (B) (in μm) to the total thickness of layer (A) (in μm) [(total thickness of layer (B) (μm) / total thickness of layer (A) (μm)) × 100] (in %) is preferably 0.1% or more, more preferably 0.3% or more, from the viewpoint of easily improving recycling efficiency, oxygen gas barrier properties, hydrocarbon (X) barrier properties, and odor barrier properties. Furthermore, the ratio of the total thickness of layer (B) (in μm) to the total thickness of layer (A) (in μm) [(total thickness of layer (B) (μm) / total thickness of layer (A) (μm)) × 100] (in %) is preferably 15% or less, more preferably 10% or less, even more preferably 5.0% or less, even more preferably 2.5% or less, and even more preferably 1.5% or less, from the viewpoint of easily improving moldability. These lower and upper limits described in stages can be combined independently. For example, in one embodiment of the multilayer structure, from the viewpoint of easily achieving a good balance of recycling efficiency, oxygen gas barrier properties, hydrocarbon (X) barrier properties, odor barrier properties, and moldability, the ratio of the total thickness of layer (B) (unit: μm) to the total thickness of layer (A) (unit: μm) [(total thickness of layer (B) (μm) / total thickness of layer (A) (μm)) × 100] (unit: %) is, for example, preferably 0.1 to 15%, more preferably 0.1 to 10%, even more preferably 0.1 to 5.0%, even more preferably 0.1 to 2.5%, even more preferably 0.1 to 1.5%, even more preferably 0.3 to 1.5%, and even more preferably 0.3 to 1.5%. Alternatively, for example, it may be 0.3 to 15%, 0.3 to 10%, 0.3 to 5.0%, or 0.3 to 2.5%.

[0062] <Adhesive Layer (C)> The adhesive layer (C) is a layer adjacent to the barrier layer (B) and is used to bond the barrier layer (B) to other layers other than layer (B) via the adhesive layer (C). For example, the adhesive layer (C) may be a layer that bonds the recycled resin layer (A) to the barrier layer (B), or a layer that bonds the barrier layer (B) to the thermoplastic resin layer (D) described later. There are no particular restrictions on layer (C) as long as it is a layer that can bond layer (B) to other layers other than layer (B), but it is preferable that it is a layer that contains adhesive resin (c), and it is more preferable that it is a layer that contains adhesive resin (c) as its main component.

[0063] The adhesive resin (c) can be any resin that is adhesive to layer (B) and other layers other than layer (B) (for example, layer (A) or layer (D)), and an adhesive thermoplastic resin is preferred. Examples of the adhesive thermoplastic resin include acid-modified polyolefin resins (carboxylic acid-modified polyolefin resins, sulfonic acid-modified polyolefin resins, etc.) and epoxy-modified polyolefin resins. The adhesive resin (c) is preferably an acid-modified polyolefin resin (acid-modified polyethylene resin, acid-modified polypropylene resin, etc.), and more preferably at least one selected from acid-modified polyethylene resin and acid-modified polypropylene resin. Furthermore, for example, if layer (A) or layer (D), described later, is adjacent to the side of layer (C) opposite to layer (B), and layer (A) or layer (D), adjacent to layer (C), is a layer mainly composed of polypropylene resin, it is even more preferable that layer (C) mainly contains acid-modified polypropylene resin from the viewpoint of further improving the adhesion between layer (C) and the adjacent layer (A) or layer (D).

[0064] The adhesive resin (c) is preferably a carboxylic acid-modified polyolefin resin (for example, a polyolefin resin having a carboxyl group or an anhydride group thereof), and more preferably at least one selected from carboxylic acid-modified polyethylene resin and carboxylic acid-modified polypropylene resin.

[0065] The carboxylic acid-modified polyolefin resin may be a polyolefin resin having a carboxyl group or its anhydride group. The carboxylic acid-modified polyolefin resin can be obtained, for example, by chemically bonding an ethylenically unsaturated carboxylic acid or its anhydride to an unmodified polyolefin resin through an addition reaction, graft reaction, or the like. As the unmodified polyolefin resin used in the production of the carboxylic acid-modified polyolefin resin, at least one selected from polyethylene resin and polypropylene resin is preferred.

[0066] Examples of the ethylenically unsaturated carboxylic acids and their anhydrides include monocarboxylic acids, monocarboxylic acid esters, dicarboxylic acids, dicarboxylic acid monoesters, dicarboxylic acid diesters, and dicarboxylic acid anhydrides. Specifically, examples include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, monomethyl maleic acid, monoethyl maleic acid, diethyl maleic acid, and monomethyl fumaric acid. Among these, dicarboxylic acid anhydrides such as maleic anhydride and itaconic anhydride are preferred, and maleic anhydride is more preferred. That is, the adhesive resin (c) is preferably a maleic anhydride-modified polyolefin resin, and more preferably at least one selected from maleic anhydride-modified polyethylene resin and maleic anhydride-modified polypropylene resin. Therefore, in one embodiment of the adhesive resin (c), the acid-modified polyethylene resin is preferably a carboxylic acid-modified polyethylene resin, more preferably a maleic anhydride-modified polyethylene resin, and the acid-modified polypropylene resin is preferably a carboxylic acid-modified polypropylene resin, and more preferably a maleic anhydride-modified polypropylene resin.

[0067] Carboxylic acid-modified polyolefin resins are obtained, for example, by introducing an ethylenically unsaturated carboxylic acid or its anhydride into an unmodified polyolefin resin by an addition reaction or graft reaction in the presence of a solvent such as xylene and a catalyst such as a peroxide. The amount of carboxylic acid or its anhydride added or grafted (degree of modification) to the unmodified polyolefin resin is preferably 0.01 to 15% by mass, more preferably 0.02 to 10% by mass, based on 100% by mass of the unmodified polyolefin resin.

[0068] The MFR (at 190°C, 2.16 kg load) of the adhesive resin (c), measured in accordance with ISO 1133-1:2011, may be, for example, 0.5 to 15 g / 10 min, 1 to 20 g / 10 min, or 5 to 15 g / 10 min. When the adhesive resin (c) is an acid-modified polyethylene resin, the MFR (at 190°C, 2.16 kg load) of the acid-modified polyethylene resin is preferably 0.2 to 25 g / 10 min, more preferably 0.5 to 20 g / 10 min, and even more preferably 1.0 to 15 g / 10 min. When the adhesive resin (c) is an acid-modified polypropylene resin, the MFR (at 230°C, 2.16 kg load) of the acid-modified polypropylene resin is preferably 0.2 to 25 g / 10 min, more preferably 0.5 to 20 g / 10 min, and even more preferably 1.0 to 15 g / 10 min.

[0069] The content of adhesive resin (c) in layer (C) is preferably 60 to 100% by mass, more preferably 80 to 100% by mass, even more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, and even more preferably 97 to 100% by mass, out of 100% by mass of the total amount of resin in layer (C), and may also be 99 to 100% by mass, or even 100% by mass. In layer (C), the content of adhesive resin (c) is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, even more preferably 90 to 100% by mass, and even more preferably 95 to 100% by mass, out of 100% by mass of the total amount of layer (C), and may also be, for example, 50 to 99.99% by mass, 70 to 99.9% by mass, 90 to 99.8% by mass, or 95 to 99.5% by mass. In layer (C), one type of adhesive resin (c) may be used alone, or two or more types may be used in combination. If two or more types of adhesive resin (c) are included in layer (C), the content of the adhesive resin (c) is the total content of the two or more types of adhesive resin (c) included.

[0070] Layer (C) may contain other components besides the adhesive resin (c), as long as the effects of the present invention are not hindered. Examples of such other components include resins other than the adhesive resin (c), antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, and heat stabilizers. Layer (C) may contain only one of these other components, or it may contain two or more.

[0071] Examples of resins other than the adhesive resin (c) include thermoplastic resins such as polyolefin resins, ethylene-vinyl alcohol copolymers, polyamides, polystyrene, polyvinyl chloride, acrylic resins, polyurethanes, polycarbonates, and polyvinyl acetate. Specific examples of the antioxidants include those similar to those described above in the section on barrier layer (B).

[0072] The content of components other than the adhesive resin (c) in layer (C) is preferably 0 to 50% by mass, more preferably 0 to 30% by mass, even more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, based on 100% by mass of the total amount of layer (C). Alternatively, it may be, for example, 0.01 to 50% by mass, 0.1 to 30% by mass, 0.2 to 10% by mass, or 0.5 to 5% by mass.

[0073] In layer (C), the total content of adhesive resin (c) and other components other than adhesive resin (c), as needed, does not exceed 100% by mass of the total amount of layer (C). In other words, the total content of adhesive resin (c) and other components, as needed, in layer (C) is at most 100% by mass of the total amount of layer (C).

[0074] The thickness of the layer (C) (thickness per layer) is not particularly limited as long as the effects of the present invention are achieved, and can be appropriately selected depending on the application of the multilayer structure. In one embodiment of the present invention, the thickness of the layer (C) is not particularly limited as long as the effects of the present invention are achieved, but for example, from the viewpoint of stable adhesion, it is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, and for example, from the viewpoint of the balance of the overall layer configuration, it is preferably 1,000 μm or less, more preferably 500 μm or less, and even more preferably 250 μm or less. As described above, these lower and upper limits described in stages can be combined independently. For example, in one embodiment of the multilayer structure, the thickness of the layer (C) (thickness per layer) is preferably 5 to 1,000 μm, more preferably 10 to 500 μm, and even more preferably 20 to 250 μm.

[0075] <Thermoplastic Resin Layer (D)> In one embodiment of the present invention, the multilayer structure preferably includes a thermoplastic resin layer (D). Layer (D) is a layer other than the recycled resin layer (A), the barrier layer (B), and the adhesive layer (C), and contains a thermoplastic resin (d), preferably with thermoplastic resin (d) as the main component. Examples of thermoplastic resin (d) contained in layer (D) include EVOH other than EVOH (b), polyolefin resins, various polyamides (nylon 6, nylon 6・6, nylon 6 / 66 copolymer, nylon 11, nylon 12, polymetaxylylene adipamide, etc.), various polyesters (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polyurethane, polycarbonate, polyacetal, polyacrylate, and modified polyvinyl alcohol resin. Among these, the thermoplastic resin (d) is preferably a polyolefin resin, more preferably at least one selected from the group consisting of polyethylene resins and polypropylene resins, even more preferably at least one selected from the group consisting of polyethylene resins and polypropylene resins, and even more preferably a polypropylene resin.

[0076] For example, when layer (D) is used between the recycled resin layer (A) and the barrier layer (B), using a polyolefin resin as the thermoplastic resin (d) is preferable from the viewpoints of improving the mechanical properties of the multilayer structure, adhesion to the recycled resin layer (A), and suppressing the permeation of alcohols, etc. Furthermore, when layer (D) is used as the surface layer of the multilayer structure, using a polyolefin resin as the thermoplastic resin (d) is preferable from the viewpoint of providing heat sealability in addition to the expected effects mentioned above.

[0077] The content of the thermoplastic resin (d) in layer (D) is preferably 60 to 100% by mass, more preferably 80 to 100% by mass, even more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, and even more preferably 97 to 100% by mass, out of 100% by mass of the total amount of resin in layer (D), and may also be 99 to 100% by mass, or even 100% by mass. In layer (D), the content of the thermoplastic resin (d) is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, even more preferably 90 to 100% by mass, and even more preferably 95 to 100% by mass, out of 100% by mass of the total amount of layer (D), and may also be, for example, 50 to 99.99% by mass, 70 to 99.9% by mass, 90 to 99.8% by mass, or 95 to 99.5% by mass. In layer (D), the thermoplastic resin (d) may be used alone or in combination of two or more types. If two or more types of thermoplastic resin (d) are included in layer (D), the content of the thermoplastic resin (d) is the total content of the two or more types of thermoplastic resin (d).

[0078] Layer (D) may contain other components besides the thermoplastic resin (d), as long as the effects of the present invention are not hindered. Examples of other components in layer (D) besides the thermoplastic resin (d) include resins other than the thermoplastic resin (d), antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, and heat stabilizers. Layer (D) may contain only one of these other components, or two or more. Specific examples of the antioxidants, etc., include, for example, those similar to the corresponding agents described above in the section on barrier layer (B).

[0079] The content of the other components in layer (D) is preferably 0 to 50% by mass, more preferably 0 to 30% by mass, even more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, based on 100% by mass of the total amount of layer (D). Alternatively, it may be, for example, 0.01 to 50% by mass, 0.1 to 30% by mass, 0.2 to 10% by mass, or 0.5 to 5% by mass.

[0080] In layer (D), the total content of thermoplastic resin (d) and other components other than the thermoplastic resin (d), if included as needed, does not exceed 100% by mass of the total amount of layer (D). In other words, the total content of thermoplastic resin (d) and other components other than the thermoplastic resin (d), if included as needed, in the resin layer (D) is at most 100% by mass of the total amount of layer (D).

[0081] The thickness of the layer (D) (thickness per layer) is not particularly limited as long as the effects of the present invention are achieved, and can be appropriately selected depending on the application of the multilayer structure. In one embodiment of the present invention, the thickness of the layer (D) is not particularly limited as long as the effects of the present invention are achieved, but for example, from the viewpoint of adhesion to the recycled resin layer (A), it is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, and for example, from the viewpoint of balance of the layer configuration, it is preferably 1,000 μm or less, more preferably 500 μm or less, and even more preferably 250 μm or less. As described above, these lower and upper limits described in stages can be combined independently. For example, in one embodiment of the multilayer structure, the thickness of the layer (D) (thickness per layer) is preferably 5 to 1,000 μm, more preferably 10 to 500 μm, and even more preferably 20 to 250 μm.

[0082] <Other Layers> The multilayer structure may have layers other than the recycled resin layer (A), barrier layer (B), adhesive layer (C), and thermoplastic resin layer (D) described above (hereinafter also referred to as "other layers"). Examples of other layers that the multilayer structure may have include other thermoplastic resin layers (layers in which the main component thermoplastic resin is different from the main component thermoplastic resin in layers (A), (B), and (C)), printing layers, metal layers (such as metal vapor deposition layers), paper, and the like.

[0083] The thickness of the multilayer structure (the sum of the thicknesses of each layer) is not particularly limited as long as the effects of the present invention are achieved, and can be appropriately selected depending on the application of the multilayer structure. In one embodiment of the present invention, the thickness of the multilayer structure is not particularly limited as long as the effects of the present invention are achieved, but is preferably greater than 205 μm, more preferably 260 μm or more, even more preferably 365 μm or more, even more preferably 520 μm or more, even more preferably 725 μm or more, even more preferably 850 μm or more, even more preferably 1,000 μm or more, and preferably 20,000 μm or less, more preferably 15,000 μm or less, even more preferably 10,000 μm or less, even more preferably 8,000 μm or less, even more preferably 5,000 μm or less, even more preferably 4,000 μm or less, and even more preferably 3,000 μm or less. As described above, these stepwise lower and upper limits can be combined independently. For example, in one embodiment of the multilayer structure, the thickness of the multilayer structure is preferably more than 205 μm and 20,000 μm or less, more preferably 260 to 15,000 μm, even more preferably 365 to 10,000 μm, even more preferably 520 to 8,000 μm, even more preferably 725 to 8,000 μm, even more preferably 850 to 4,000 μm, and even more preferably 1,000 to 3,000 μm.

[0084] <Layer Structure, etc.> The multilayer structure has at least layer (A) and layer (B), and preferably further includes at least one layer selected from layer (C) and layer (D) as described above, and may include the other layers as needed. A specific layer structure of the multilayer structure is illustrated below. However, the layer structure of the multilayer structure is not limited to the following configuration. Also, as described above, as one embodiment of the multilayer structure, from the viewpoint of ease of molding, it is preferable that the multilayer structure includes only one layer (B), so a layer structure including only one layer (B) is illustrated. In the following examples of layer structures, only the layer symbols are indicated (e.g., layer (A) is simply written as (A)), and for example, the notation "(A) / (B)" indicates that layer (A) and layer (B) are directly laminated. Also, (X) represents a layer other than layer (C). In one embodiment of the present invention, the multilayer structure may further include, in the following layer configuration, at least one additional layer selected from the group consisting of layer (A), layer (B), layer (C), layer (D), and other layers, between each layer or on the surface of the multilayer structure. However, as described above, layer (C) is adjacent to layer (B) and located between layer (B) and the other layers.・(A) / (B) ・(A) / (C) / (B) ・(A) / (B) / (D) ・(A) / (C) / (B) / (D) ・(A) / (C) / (B) / (C) / (X) ・(A) / (C) / (B) / (C) / (D) ・(A) / (D) / (C) / (B)・(A) / (D) / (C) / (B) / (D) ・(A) / (D) / (C) / (B) / (C) / (X) ・(A) / (D) / (C) / (B) / (C) / (D) ・(D) / (A) / (B) ・(D) / (A) / (C) / (B) ・(D) / (A) / (B) / (D)・(D) / (A) / (C) / (B) / (C) / (X) ・(D) / (A) / (C) / (B) / (D) ・(D) / (A) / (C) / (B) / (C) / (D) ・(D) / (A) / (D) / (C) / (B) ・(D) / (A) / (D) / (C) / (B) / (C) / (X) ・(D) / (A) / (D) / (C) / (B) / (D) ・(D) / (A) / (D) / (C) / (B) / (C) / (D) Examples of manufacturing methods for the multilayer structure include lamination methods such as dry lamination; co-injection molding; co-extrusion molding, etc., but are not particularly limited.Furthermore, a method for manufacturing a multilayer structure, which is one aspect of the present invention described below, is also illustrated. In addition, each of the aforementioned layers may be stretched in a uniaxial or biaxial direction.

[0085] [Manufacturing method for multilayer structures]

[0086] One embodiment of the present invention provides a method for manufacturing a multilayer structure, comprising at least the following steps (1) and (2): (1) injection molding of a recycled resin composition containing a polyolefin resin (a) to obtain a recycled resin layer (A'); and (2) extrusion molding of a resin composition mainly containing an ethylene-vinyl alcohol copolymer (b) to obtain a barrier layer (B). The multilayer structure obtained by this method is preferably the multilayer structure described above in the section on multilayer structures, which is one embodiment of the present invention. Details of this preferred multilayer structure are as described above in the section on multilayer structures, and the preferred embodiment is the same.

[0087] <Step (1)> Step (1) is a step of injection molding a recycled resin composition containing a polyolefin resin (a) to obtain a recycled resin layer (A'). Details of the polyolefin resin (a) used in step (1) are as described above in the section on multilayer structures, and the preferred embodiments are the same. Furthermore, the recycled resin layer (A') obtained in step (1) is preferably the recycled resin layer (A), and details thereof are as described above in the section on multilayer structures, and the preferred embodiments are the same. In the multilayer structure which is one embodiment of the present invention, the layer (A') is preferably a molded product obtained by injection molding.

[0088] There are no particular restrictions on the conditions for injection molding layer (A'), and known conditions used for injection molding of polyolefin resins can be adopted.

[0089] <Step (2)> Step (2) is a step of obtaining a barrier layer (B) by extruding a resin composition mainly composed of an ethylene-vinyl alcohol copolymer (b). Details of the ethylene-vinyl alcohol copolymer (b) used in step (2) and the barrier layer (B) obtained in step (2) are as described above in the section on multilayer structures, and the preferred embodiments are also as described above.

[0090] There are no particular restrictions on the conditions for extruding the barrier layer (B), and known conditions used for extruding ethylene-vinyl alcohol copolymers can be adopted.

[0091] In one embodiment of the present invention, if the resulting multilayer structure includes at least one layer selected from an adhesive layer (C) and a thermoplastic resin layer (D), it is preferable in step (2) to co-extrude at least one layer selected from layers (C) and (D) with a barrier layer (B) to form a co-extruded film including layer (B) and at least one layer selected from layers (C) and (D); more preferably to co-extrude layers (C) and (D) with a barrier layer (B) to form a multilayer film including layers (B), (C), and (D); even more preferably to form a co-extruded film including layers (B), (C), and (D) in this order; and even more preferably to form a co-extruded film including a layer configuration in which layers (B), (C), and (D) are directly laminated in this order. There are no particular restrictions on the co-extrusion molding method when forming the co-extruded film, and the film can be formed by known methods, and either an annular die or a T-die can be used as the die. The molding temperature during melt molding can be appropriately adjusted based on the melting point and melt viscosity of the resin used, for example, it may be selected from a range of 150 to 300°C. Furthermore, when using the T-die method (casting method), the molding temperature during cooling with cooling rolls, etc., can also be appropriately adjusted based on the melting point and melt viscosity of the resin used, for example, it may be selected from a range of 20 to 100°C.

[0092] The above steps (1) and (2) may be performed in any order. That is, step (1) may be performed first, followed by step (2), or step (2) may be performed first, followed by step (1). Furthermore, there may be at least one additional step selected from the group consisting of before step (1), after step (2), and between steps (1) and (2). One embodiment of the method for manufacturing the multilayer structure is, for example, insert molding or TOM molding (TOM: Three-dimensional Overlay Molding). In the multilayer structure according to one embodiment of the present invention, the multilayer structure is preferably a molded product produced by insert molding or TOM molding.

[0093] When using the insert molding process, for example, step (2) is performed first to form a single-layer film of the barrier layer (B), or a multilayer film including at least one layer selected from layers (C) and (D), and layer (B). Then, the multilayer structure can be obtained by laminating the recycled resin layer (A) to at least one surface of the single-layer film of the barrier layer (B) or the multilayer film including the barrier layer (B) using step (1). Furthermore, the process may include trimming steps that are normally performed in insert molding. When using the multilayer film in the insert molding process, it is preferable to use the co-extruded film.

[0094] When using the TOM molding process, regardless of the order of steps (1) and (2), a single-layer film of the recycled resin layer (A') obtained in step (1) and the barrier layer (B) obtained in step (2), or a multilayer film including at least one layer selected from layers (C) and (D) and layer (B), is prepared through each respective step. Subsequently, the multilayer structure can be obtained by performing TOM molding using the recycled resin layer (A') as the substrate and the single-layer film or the multilayer film as the film to be pressed onto the substrate. Furthermore, the process may include trimming steps that are normally performed in TOM molding. When using the multilayer film in the TOM molding process, it is preferable to use the co-extruded film.

[0095] [Multilayer Blow Molded Article] A multilayer blow molded article according to one aspect of the present invention may include the multilayer structure and may be a multilayer blow molded article made of the multilayer structure. The shape of the multilayer blow molded article is not particularly limited, but for example, a multilayer blow molded article having a bottle shape can be mentioned. When the multilayer blow molded article is made of the multilayer structure, blow molding can be mentioned as one aspect of the method for manufacturing the multilayer structure.

[0096] [Applications of Multilayer Structures] There are no particular limitations on the applications of the multilayer structure according to one aspect of the present invention and the multilayer structure obtained by the method for manufacturing the multilayer structure according to one aspect of the present invention, but examples include packaging materials, automobile parts, electronic equipment parts, and building materials. Among these, from the viewpoint of achieving the effects of the present invention even in applications where the recycled resin layer is thicker, it can be more preferably used in automobile parts and electronic equipment parts. That is, one aspect of the present invention is an automobile part having the above structure. The same applies to the applications of the structure obtained by the method for manufacturing the above structure according to one aspect of the present invention.

[0097] [Method of using the barrier layer (B)] As a method of using the barrier layer (B) according to one aspect of the present invention, the barrier layer (B) or a laminate containing the barrier layer (B) is laminated on at least one surface side of a polyolefin resin layer mainly composed of a polyolefin resin (a), and a method is given in which odors originating from the polyolefin resin layer or at least one selected from the group consisting of hydrocarbons (X) and heterocyclic compounds (Y), or odors or at least one selected from the group consisting of hydrocarbons (X) and heterocyclic compounds (Y) present in the space on at least one surface side of the polyolefin resin layer, are prevented from permeating through the barrier layer (B) located on the opposite side of the space in the polyolefin resin layer and from permeating through the barrier layer (B) to the space on the opposite side of the space. The polyolefin resin (a) contained in the polyolefin resin layer used in the above method is the same as the polyolefin resin (a) described above in the section on multilayer structures, and the preferred embodiment is also the same. Furthermore, the preferred content of the polyolefin resin (a) in the polyolefin resin layer is the same as the preferred content of the polyolefin resin (a) in the recycled resin layer (A) described above in the section on multilayer structures. The polyolefin resin layer may also contain any other components that the recycled resin layer (A) described above in the section on multilayer structures may contain. The polyolefin resin layer used in the above method is preferably the recycled resin layer (A) described above in the section on multilayer structures or the recycled resin layer (A') described above in the section on the method for manufacturing the multilayer structure, and independently, the preferred embodiments of each are the same as those described above. The details of the barrier layer (B) used in the above method are the same as the barrier layer (B) described above in the section on multilayer structures, and the preferred embodiments are also the same. The details of the laminate including the barrier layer (B) used in the above method are preferably the laminate portion of the multilayer structure described above in the section on multilayer structures, excluding the recycled resin (A), and the preferred embodiments are also the same.

[0098] The embodiments of this model will be described in more detail below with reference to examples, but the embodiments are not limited to these examples.

[0099] The physical properties of the components used in the examples and comparative examples were measured or evaluated by the following methods.

[0100] [Ethylene unit content and degree of saponification of ethylene-vinyl alcohol copolymer (b)] Dry pellets of EVOH (b) were dissolved in deuterated dimethyl sulfoxide (DMSO-d6) containing tetramethylsilane (TMS) as an internal standard and trifluoroacetic acid (TFA) as an additive, and heated at 500 MHz. １ Measurements were taken at 80°C using 1H-NMR (JEOL Ltd.: "GX-500"), and the ethylene unit content and degree of saponification were determined from the peak intensity ratios of ethylene units, vinyl alcohol units, and vinyl ester units in the obtained NMR spectrum.

[0101] [MFR of each polymer] In accordance with ISO 1133-1:2011, the MFR of each polymer was measured at the measurement temperature and measurement load described in the description below.

[0102] The components used in the examples and comparative examples are shown below.

[0103] [Polyolefin resins (a) used in the recycled resin layer (A)] ・Recycled polypropylene: "CEV 802" manufactured by Ceville Materials ・Recycled high-density polyethylene: "CEV 701" manufactured by Ceville Materials

[0104] [Ethylene-vinyl alcohol copolymer (b)] ・EVOH (b-1): Ethylene-vinyl alcohol copolymer, "EVAL® F171" manufactured by Kuraray Co., Ltd., ethylene unit content 32 mol%, degree of saponification 99.9 mol%, MFR (210℃, 2.16 kg load) 3.8 g / 10 min ・EVOH (b-2): Ethylene-vinyl alcohol copolymer, "EVAL® L171B" manufactured by Kuraray Co., Ltd., ethylene unit content 27 mol%, degree of saponification 99.9 mol%, MFR (210℃, 2.16 kg load) 4.0 g / 10 min ・EVOH (b-3): Ethylene-vinyl alcohol copolymer, "EVAL® E105B" manufactured by Kuraray Co., Ltd., ethylene unit content 44 mol%, degree of saponification 99.9 mol%, MFR (210℃, 2.16 kg load) 11.2 g / 10 min EVOH(b-4): Ethylene-vinyl alcohol copolymer, manufactured by Kuraray Co., Ltd. as "EVAL® G156B", ethylene unit content 48 mol%, degree of saponification 99.9 mol%, MFR (210℃, 2.16 kg load) 13.2 g / 10 min

[0105] [Adhesive resin (c)] - Maleic anhydride-modified polypropylene: DuPont "BYNEL® 50E806", MFR (190°C, 2.16 kg load) 25 g / 10 min - Maleic anhydride-modified high-density polyethylene resin: Mitsui Chemicals "ADMER® GT6", MFR (190°C, 2.16 kg load) 1.1 g / 10 min

[0106] [Other resins] ・Polypropylene copolymer: Braskem's "TI6500WV", MFR (230℃, 2.16 kg load) 50 g / 10 min ・High-density polyethylene resin: Nippon Polyethylene Co., Ltd.'s "Novatec® HB111R", MFR (190℃, 21.6 kg load) 6 g / 10 min ・Polyamide: BASF's "Ultramid® C40LN", MFR (230℃, 2.16 kg load) 4 g / 10 min

[0107] [Example 1] A multilayer film was prepared using a co-extrusion multilayer casting apparatus, consisting of a thermoplastic resin layer (D) made of polypropylene copolymer (PP; Braskem's "TI6500WV"), an adhesive layer (C) made of maleic anhydride-modified polypropylene resin (DuPont's "BYNEL® 50E806"), and a barrier layer (B) made of EVOH (b-1) (Kuraray Co., Ltd.'s "EVAL® F171", with an ethylene unit content of 32 mol%). The layer structure of the multilayer film and the thickness of each layer were prepared in the following order from the outer layer: layer (D) / layer (C) / layer (B) / layer (C) / layer (D) = 100 μm / 50 μm / 100 μm / 50 μm / 100 μm. The obtained multilayer film was set in an injection molding die, and an insert molding was performed in which a recycled resin layer (A) made of polyolefin resin (a) (recycled polypropylene "CEV 802" manufactured by Ceville Materials) was injected onto the surface of one layer (D) of the multilayer film. The multilayer structure of Example 1 was produced by the insert molding. The layer configuration and the thickness of each layer of the multilayer structure of Example 1 were manufactured in the following order from the layer (A) side: layer (A) / layer (D) / layer (C) / layer (B) / layer (C) / layer (D) = 2,000 μm / 100 μm / 50 μm / 100 μm / 50 μm / 100 μm.

[0108] [Example 2] A multilayer structure of Example 2 was prepared in the same manner as in Example 1, except that EVOH(b-2) ("EVAL® L171B" manufactured by Kuraray Co., Ltd., ethylene unit content 27 mol%) was used instead of EVOH(b-1) used in the barrier layer (B).

[0109] [Example 3] A multilayer structure of Example 3 was prepared in the same manner as in Example 1, except that a mixture of EVOH(b-2) ("EVAL® L171B" manufactured by Kuraray Co., Ltd., ethylene unit content 27 mol%) and EVOH(b-3) ("EVAL® E105B" manufactured by Kuraray Co., Ltd., ethylene unit content 44 mol%) (EVOH(b-2) / EVOH(b-3) = 80 / 20 (mass ratio)) was used instead of EVOH(b-1) used in the barrier layer (B).

[0110] [Example 4] A multilayer structure of Example 4 was prepared in the same manner as in Example 1, except that EVOH(b-4) ("EVAL® G156B" manufactured by Kuraray Co., Ltd., ethylene unit content 48 mol%) was used instead of EVOH(b-1) used in the barrier layer (B).

[0111] [Example 5] A multilayer structure of Example 5 was fabricated in the same manner as in Example 1, except that the thickness of the barrier layer (B) was changed from 100 μm to 20 μm. The layer configuration and the thickness of each layer of the multilayer structure according to Example 5 were fabricated in the following order from the layer (A) side: layer (A) / layer (D) / layer (C) / layer (B) / layer (C) / layer (D) = 2,000 μm / 100 μm / 50 μm / 20 μm / 50 μm / 100 μm.

[0112] [Example 6] A multilayer structure of Example 6 was fabricated in the same manner as in Example 5, except that the thickness of the recycled resin layer (A) was changed from 2,000 μm to 3,000 μm. The layer configuration and the thickness of each layer of the multilayer structure according to Example 6 were fabricated in the following order from the layer (A) side: layer (A) / layer (D) / layer (C) / layer (B) / layer (C) / layer (D) = 3,000 μm / 100 μm / 50 μm / 20 μm / 50 μm / 100 μm.

[0113] [Example 7] A multilayer structure of Example 7 was fabricated in the same manner as in Example 1, except that the thickness of the barrier layer (B) was changed from 100 μm to 200 μm. The layer configuration and the thickness of each layer of the multilayer structure according to Example 7 were fabricated in the following order from the layer (A) side: layer (A) / layer (D) / layer (C) / layer (B) / layer (C) / layer (D) = 2,000 μm / 100 μm / 50 μm / 200 μm / 50 μm / 100 μm.

[0114] [Example 8] A multilayer structure of Example 8 was prepared in the same manner as in Example 1, except that recycled high-density polyethylene (CEV 701 from Ceville Materials) was used instead of the polyolefin resin (a) "CEV 802" used in the recycled resin layer (A), maleic anhydride-modified high-density polyethylene resin (ADMER GT6 from Mitsui Chemicals) was used instead of "BYNEL 50E806" as the adhesive resin (c), and Novatec HB111R from Nippon Polyethylene Co., Ltd. was used instead of Braskem's "TI6500WV" as the thermoplastic resin layer (D).

[0115] [Example 9] A multilayer structure was manufactured in the same manner as in Example 8, except that the manufacturing method was changed to multilayer blow molding. A blow-molded container having a three-layer structure of three types, consisting of (inner) recycled resin layer (A) / adhesive layer (C) / barrier layer (B) (outer), was manufactured at 210°C using a blow molding machine "TB-ST-6P" manufactured by Suzuki Iron Works Co., Ltd. The mold was cooled at 15°C for 20 seconds to form a bottle container with an average thickness of 2150 μm across all layers ((inner) recycled resin layer (A) / adhesive layer (C) / barrier layer (B) (outer) = (inner) 2000 / 50 / 100 μm (outer)).

[0116] [Comparative Example 1] A multilayer structure of Comparative Example 1 was prepared in the same manner as in Example 1, except that a polypropylene copolymer ("TI6500WV" manufactured by Braskem) was used instead of EVOH (b-1) used in the barrier layer (B).

[0117] [Comparative Example 2] A multilayer structure of Comparative Example 2 was fabricated in the same manner as in Example 1, except that polyamide (BASF's "Ultramid® C40LN") was used instead of EVOH (b-1) in the barrier layer (B).

[0118] The multilayer structures obtained in each example and comparative example were measured or evaluated by the following methods. The results are shown in Table 1 below.

[0119] [Thickness] A thin section of the multilayer structure was cut out using a microtome, and the thickness of each layer was measured by observing the cross-section with an optical microscope (Nikon Corporation's "ECLIPSE (registered trademark) Ci-E").

[0120] [Oxygen Transmission Rate (OTR)] For the multilayer structures obtained in each of the examples and comparative examples, after conditioning at 20°C and 65% RH for 1 month, with the recycled resin layer (A) side as the oxygen supply side and the barrier layer (B) side as the carrier gas side, the oxygen transmission rate was measured in accordance with the method described in JIS K 7126-2 (isobaric method: 2006). Specifically, an oxygen transmission rate measuring device (MOCON's "MOCON (registered trademark) OX-TRAN (registered trademark) 2 / 21") was used, and the oxygen transmission rate (unit: cc / (m ２ ·day·atm)) was measured under the conditions of a temperature of 20°C, a humidity of 65% RH on the oxygen supply side, a humidity of 65% RH on the carrier gas side, an oxygen pressure of 1 atm, and a carrier gas pressure of 1 atm.

[0121] [Xylene Permeability and Toluene Permeability] For the multilayer structures obtained in each of the examples and comparative examples, after conditioning at 20°C and 65% RH for 1 month, the xylene permeability and toluene permeability were measured using a flow-type gas / vapor permeability measuring device "GTR-30XFK-E" manufactured by GTR Tech Co., Ltd. The measurement was carried out at 60°C. Liquid xylene or toluene was poured into the device, and the recycled resin layer (A) side was made the supply side of the xylene vapor or toluene vapor to be measured, and the respective determinations were made according to the following criteria. [Criteria for Xylene Permeability Determination] A: Less than 0.02 g / (m ２ ·day·atm). B: 0.02 g / (m ２ ·day·atm) or more and less than 0.1 g / (m ２ ·day·atm). C: 0.1 g / (m ２ ·day·atm) or more. [Criteria for Toluene Permeability Determination] A: Less than 0.01 g / (m ２ ·day·atm). B: 0.01 g / (m ２ ·day·atm) or more and less than 0.1 g / (m ２ ·day·atm). C: 0.1 g / (m ２・day・atm) or more.

[0122] [Evaluation of moldability] The multilayer films used in each example and comparative example (multilayer films before molding the recycled resin layer (A)) were subjected to a thermoforming machine (Asano Research Institute Co., Ltd.: vacuum pressure deep drawing molding machine "FX-0431-3") with a sheet temperature of 160°C and compressed air (atm pressure of 5 kgf / cm²). ２ A thermoformed container was obtained by thermoforming it into a round cup shape (mold shape: upper part 75 mmφ, lower part 60 mmφ, depth 75 mm, drawing ratio S = 1.0) using the following method. The molding conditions and judgment criteria are shown below. [Molding conditions] Heater temperature: 400℃ Plug: 45φ × 65 mm Plug temperature: 150℃ Mold temperature: 70℃ [Judgment of moldability: criteria] A: No abnormalities B: There were areas with thinness

[0123] [Odor Evaluation] Two 10 cm square pieces were cut from the multilayer structures obtained in each example and comparative example, and the recycled resin layer (A) was placed on the inside. The four sides were heat-sealed at 150°C to create packaging material. The packaging material was placed in an aluminum bag and stored at 40°C for 10 days. After opening the aluminum bag, the odor was sensory evaluated according to the following criteria. The following judgments were made by five people, and the result with the highest number of votes was adopted. In the case of multiple results with the highest number of votes, the worst result was adopted. However, in the evaluation of each example and comparative example, all evaluation results were unanimous. [Odor Judgment: Criteria] A: No odor. B: Faint odor. C: Clearly odor.

[0124]

[0125] In Table 1, the following abbreviations refer to the following resins, respectively. • "PO(a)": Polyolefin resin (a) • "EVOH(b)": Ethylene-vinyl alcohol copolymer (b) • "RPP": Recycled polypropylene (CEV 802 manufactured by Ceville Materials) • "RHDPE": Recycled high-density polyethylene (CEV 701 manufactured by Ceville Materials) • "PP": Polypropylene copolymer (TI6500WV manufactured by Braskem) • "m-PP": Maleic anhydride modified polypropylene resin (BYNEL® 50E806 manufactured by DuPont) • "PA": Polyamide (Ultramid® C40LN manufactured by BASF) • "RHDPE": Recycled high-density polyethylene (Ceville・"CEV 701" manufactured by Materials Inc. ・"HDPE": High-density polyethylene resin ("Novatec® HB111R" manufactured by Nippon Polyethylene Co., Ltd.) ・"m-HDPE": Maleic anhydride modified high-density polyethylene resin ("ADMER® GT6" manufactured by Mitsui Chemicals Inc.) In Table 1, the notation "27 / 44" for the ethylene unit content [mol%] in Example 3 represents the ethylene unit content of EVOH(b-2) and the ethylene unit content of EVOH(b-3) of 44 mol% in the mixture including the barrier layer (B) (EVOH(b-2) / EVOH(b-3) = 80 / 20 (mass ratio)). In Table 1, the notation "Layer (B) thickness / Layer (A) thickness [%]" represents the ratio of the total thickness of layer (B) (in μm) to the total thickness of recycled resin layer (A) (in μm) [(Total thickness of layer (B) (μm) / Total thickness of layer (A) (μm)) × 100] (in %).

[0126] The multilayer structures of Examples 1-5 and 7-9 mainly consist of polyolefin resin (a) and use a thick recycled resin layer with a thickness of 2,000 μm. The multilayer structure of Example 6 uses an even thicker recycled resin layer with a thickness of 3,000 μm. However, from the results in Table 1, it was confirmed that the multilayer structures of Examples 1-7 were able to suppress the permeation of odors originating from the recycled resin layer into the space on at least one side of the recycled resin layer, and that the permeation of aromatic hydrocarbons such as xylene and toluene was also reduced. Furthermore, it was confirmed that the multilayer structures of Examples 1-3 and 5-9 had lower toluene permeation values ​​and were more effective in suppressing toluene permeation. Moreover, it was confirmed that the multilayer structures of Examples 1, 2, 5, and 7 had lower values ​​for both xylene and toluene permeation, and were more effective in suppressing the permeation of xylene and toluene. This further suppression of toluene and xylene permeation is thought to be due to the lower ethylene unit content of EVOH(b). The multilayer structure of Example 6 exhibited lower xylene permeability than Example 5, which is thought to be due to the use of a thicker recycled resin layer, 3,000 μm thick. However, even in this case, it was confirmed that xylene permeability could be suppressed to the same extent as in Examples 3 and 4. Furthermore, the multilayer structures of Examples 1 to 9 were confirmed to have low oxygen permeability values ​​and good oxygen gas barrier properties. In addition, Examples 3, 5, and 6 were confirmed to have better moldability for the multilayer film containing the barrier layer (B) (the multilayer film before molding the recycled resin layer (A)). This improved moldability is thought to be due to the use of two types of EVOH(b) with an ethylene unit content difference of 4 mol% or more in Example 3. On the other hand, in Examples 5 and 6, this is thought to be due to the thinner thickness of the barrier layer (B) compared to the multilayer structure of Example 1.

[0127] In the multilayer structures of Comparative Examples 1 and 2, a different resin layer from the barrier layer, mainly composed of EVOH(b), was used for the layer corresponding to the barrier layer (B). As a result, it was confirmed that the odor originating from the recycled resin layer, as well as xylene and toluene, could not be sufficiently suppressed from permeating into the space on at least one side of the recycled resin layer.

Claims

1. A multilayer structure comprising: a recycled resin layer (A) mainly composed of a polyolefin resin (a); and a barrier layer (B) mainly composed of an ethylene-vinyl alcohol copolymer (b); wherein the thickness of the recycled resin layer (A) exceeds 200 μm.

2. The multilayer structure according to claim 1, wherein the recycled resin layer (A) is a post-consumer recycled product.

3. The multilayer structure according to claim 1 or 2, wherein the polyolefin resin (a) comprises at least one selected from the group consisting of polypropylene resin and polyethylene resin.

4. The multilayer structure according to claim 1 or 2, wherein the recycled resin layer (A) contains a hydrocarbon (X), and the hydrocarbon (X) is at least one selected from the group consisting of alicyclic hydrocarbons, derivatives of alicyclic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons.

5. The multilayer structure according to claim 1 or 2, wherein the thickness of the recycled resin layer (A) is 250 to 10,000 μm.

6. The multilayer structure according to claim 1 or 2, wherein the barrier layer (B) consists solely of an ethylene-vinyl alcohol copolymer (b).

7. A multilayer structure according to claim 1 or 2, comprising a barrier layer (B) and an adjacent adhesive layer (C).

8. The multilayer structure according to claim 1 or 2, wherein a thermoplastic resin layer (D) is included at least one position between the recycled resin layer (A) and the barrier layer (B), and at a position on the opposite side of the barrier layer (B) from the recycled resin layer (A).

9. The multilayer structure according to claim 1 or 2, wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer (b) is 20 to 50 mol%.

10. The multilayer structure according to claim 1 or 2, wherein the thickness of the barrier layer (B) is 5 μm or more.

11. The multilayer structure according to claim 1 or 2, wherein the barrier layer (B) comprises two or more ethylene-vinyl alcohol copolymers (b) with different ethylene unit contents, and the difference (b2-b1) between the ethylene unit content of the ethylene-vinyl alcohol copolymer (b2) with the highest ethylene unit content and the ethylene unit content of the ethylene-vinyl alcohol copolymer (b1) with the lowest ethylene unit content is 4 mol% or more.

12. The multilayer structure according to claim 1 or 2, comprising only one barrier layer (B).

13. The multilayer structure according to claim 1 or 2, wherein the recycled resin layer (A) is a molded product produced by injection molding.

14. The multilayer structure according to claim 1 or 2, wherein the multilayer structure is a molded product produced by insert molding or TOM molding.

15. A multilayer blow-molded article comprising the multilayer structure described in claim 1 or 2.

16. A multilayer blow-molded article according to claim 15, having a bottle shape.

17. A method for producing a multilayer structure, comprising at least the following steps (1) and (2): (1) injection molding of a recycled resin composition containing a polyolefin resin (a) to obtain a recycled resin layer (A'); (2) extrusion molding of a resin composition mainly containing an ethylene-vinyl alcohol copolymer (b) to obtain a barrier layer (B);

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