Multilayer structure, packaging material using the same, recovered composition, and method for producing recovered composition

Abstract

A multilayer structure having a polyolefin layer (A), an adhesive resin layer (B), and a resin composition layer (C), wherein: the polyolefin layer (A) is layered on at least one surface of the resin composition layer (C) with the adhesive resin layer (B) interposed therebetween, the polyolefin layer (A) not including a layer in which the main component is a resin having a melting point of 210°C or higher or a metal layer having a thickness of 1 μm or greater, and the main-component resin that constitutes the polyolefin layer (A) having a density of 0.850 g / cm3 to 0.940 g / cm3 (inclusive); and the resin composition layer (C) includes an ethylene-vinyl alcohol copolymer (c1) and polyvalent metal ions (c2), the ethylene unit content of the ethylene-vinyl alcohol copolymer (c1) being 20 to 50 mol% (inclusive), the degree of saponification being 90 mol% or higher, and the polyvalent metal ion (c2) content of the resin composition layer (C) being 10 to 400 ppm (inclusive).

Description

[Technical Field]

[0001] The present invention relates to a multilayer structure that is excellent in mechanical strength and recyclability and has an excellent appearance when formed into a film, a packaging material using the same, a recovered composition, and a method for producing the recovered composition. [Background technology]

[0002] Gas barrier resin films made of ethylene-vinyl alcohol copolymer (hereinafter sometimes referred to as EVOH) have been used as transparent packaging materials with high oxygen barrier properties. EVOH is also used for applications such as laminated packaging materials, taking advantage of its thermoformability in addition to its high gas barrier properties. Known examples of laminated packaging materials include laminated films in which polyamide resins (nylon) are co-extruded on both sides of EVOH to improve the strength of the laminated film (Patent Document 1).

[0003] Patent Document 2 describes a multilayer structure comprising a hard layer having a puncture strength of 40 N / mm or more and 150 N / mm or less and a resin composition layer containing EVOH having a melting point of 170° C. or more and modified EVOH having a melting point of less than 170° C. Patent Document 2 also describes that this multilayer structure is excellent in mechanical strength and thermoformability, and also that when the recovered material is melt-molded, the generation of lumps due to resin deterioration (gelation) is suppressed, resulting in excellent recyclability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-79996 [Patent Document 2] International Publication No. 2020 / 071513 Summary of the Invention [Problem to be solved by the invention]

[0005] The laminated film described in Patent Document 1 has low recyclability because, when it is collected and reused, the polyamide resin and EVOH undergo a chemical reaction, causing crosslinking and the generation of lumps. Furthermore, when the multilayer structure described in Patent Document 2 is formed, strong shear stress is applied between the adhesive resin layer and the EVOH layer, causing uneven thickness in the EVOH layer and disrupting the layer interface, resulting in poor film appearance.

[0006] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a multilayer structure that is excellent in mechanical strength, recyclability, appearance, and formability, as well as a packaging material that uses the multilayer structure, a recovered composition, and a method for producing the recovered composition. [Means for solving the problem]

[0007] The above issues are: (1) A multilayer structure having a polyolefin layer (A), an adhesive resin layer (B), and a resin composition layer (C), a polyolefin layer (A) is laminated on at least one surface of the resin composition layer (C) via an adhesive resin layer (B); It does not have a layer whose main component is a resin with a melting point of 210°C or higher, or a metal layer with a thickness of 1 μm or more, The resin constituting the polyolefin layer (A) has a density of 0.850 g / cm 3 More than 0.940g / cm 3 The following olefin-based polymer: the resin composition layer (C) contains an ethylene-vinyl alcohol copolymer (c1) and a polyvalent metal ion (c2); the ethylene-vinyl alcohol copolymer (c1) has an ethylene unit content of 20 mol% or more and 50 mol% or less and a saponification degree of 90 mol% or more; the content of the polyvalent metal ion (c2) in the resin composition layer (C) is 10 ppm or more and 400 ppm or less; a multilayer structure in which the polyvalent metal ion (c2) is at least one selected from the group consisting of magnesium ions, calcium ions, zinc ions, cobalt ions, and manganese ions; (2) The multilayer structure according to (1), in which the polyvalent metal ion (c2) is contained as a cation of a metal salt of a higher fatty acid; (3) The multilayer structure according to (1) or (2), which has a film shape having a longitudinal direction and a width direction, and in which, when the position of one end in the width direction of a cross section is taken as 0% and the position of the other end in the width direction is taken as 100%, the ratio (Cmin / Cmax) of the minimum thickness Cmin to the maximum thickness Cmax of the resin composition layer (C) observed within a range of 45% to 55% of the cross section is 0.70 or more; (4) At least a portion of the ethylene-vinyl alcohol copolymer (c1) has at least one of a carboxylic acid unit (I) and a lactone ring unit (II) located at a polymer terminal, the total content (i+ii) of the carboxylic acid unit (I) and the lactone ring unit (II) per 1 g of the ethylene-vinyl alcohol copolymer (c1) is 14 μmol / g or more and 78 μmol / g or less; The multilayer structure according to any one of (1) to (3), wherein the ratio (ii / (i+ii)) of the content (ii) of the lactone ring unit (II) to the total content (i+ii) of the carboxylic acid unit (I) and the lactone ring unit (II) is 40 mol% or more; (5) the resin composition layer (C) further contains aluminum ions (c3), The multilayer structure according to any one of (1) to (4), wherein the content of aluminum ions (c3) in the resin composition layer (C) is 5 ppb or more and 500 ppb or less; (6) The resin composition layer (C) further contains phosphate ions (c4) and alkali metal ions (c5), the content of phosphate ions (c4) in the resin composition layer (C) is 5 ppm or more and 200 ppm or less, and the content of alkali metal ions (c5) is 10 ppm or more and 400 ppm or less, The multilayer structure according to any one of (1) to (5), wherein the content ratio (c4 / c5) of the phosphate ions (c4) to the alkali metal ions (c5) is 0.01 or more and 2 or less, and the content ratio (c2 / c5) of the polyvalent metal ions (c2) to the alkali metal ions (c5) is 0.1 or more and 5 or less; (7) The multilayer structure according to (6), wherein the content ratio of the polyvalent metal ions (c2) to the phosphate ions (C4) is 1 or more and 15 or less; (8) The multilayer structure according to any one of (1) to (7), wherein the thickness of a region at the interface between the adhesive resin layer (B) and the resin composition layer (C) where the modulus of elasticity is 0.4 GPa or more and 0.8 GPa or less as measured and analyzed by an atomic force microscope is 50 nm or less; (9) The multilayer structure according to any one of (1) to (8), wherein the olefin polymer constituting the polyolefin layer (A) is a linear low-density polyethylene; (10) The multilayer structure according to (9), wherein the linear low-density polyethylene is polyethylene polymerized using a metallocene catalyst; (11) The multilayer structure according to any one of (1) to (10), wherein the ratio of the thickness of the polyolefin layer (A) to the total thickness of all layers is 0.75 or more; (12) A packaging material comprising the multilayer structure according to any one of (1) to (11); (13) A recovered composition containing a recovered multilayer structure according to any one of (1) to (11); (14) A method for producing a recycled composition, comprising a step of melt-kneading the recycled multilayer structure material according to any one of (1) to (11); This is solved by providing [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a multilayer structure that is excellent in mechanical strength, recyclability, appearance, and stable moldability, as well as a packaging material that uses the multilayer structure, a recovered composition, and a method for producing the recovered composition. DETAILED DESCRIPTION OF THE INVENTION

[0009] The multilayer structure of the present invention is a multilayer structure having a polyolefin layer (A), an adhesive resin layer (B), and a resin composition layer (C), a polyolefin layer (A) is laminated on at least one surface of the resin composition layer (C) via an adhesive resin layer (B); It does not have a layer whose main component is a resin with a melting point of 210°C or higher, or a metal layer with a thickness of 1 μm or more, The resin constituting the polyolefin layer (A) has a density of 0.850 g / cm 3 More than 0.940g / cm 3 The following olefin-based polymer: the resin composition layer (C) contains an ethylene-vinyl alcohol copolymer (c1) and a polyvalent metal ion (c2); the ethylene-vinyl alcohol copolymer (c1) has an ethylene unit content of 20 mol% or more and 50 mol% or less and a saponification degree of 90 mol% or more; the content of the polyvalent metal ion (c2) in the resin composition layer (C) is 10 ppm or more and 400 ppm or less; The multilayer structure is one in which the polyvalent metal ion (c2) is at least one selected from the group consisting of magnesium ions, calcium ions, zinc ions, cobalt ions, and manganese ions.

[0010] In this specification, the content of each component expressed in ppm or ppb is the content based on mass. The content ratio of each component is also the content ratio based on the content based on mass. Furthermore, the thickness of each layer (excluding the maximum thickness Cmax and minimum thickness Cmin) is the average value of values ​​measured at any five locations.

[0011] (Polyolefin layer (A)) The resin that constitutes the polyolefin layer (A) has a density of 0.850 g / cm 3 More than 0.940g / cm 3 When the density is within the above range, the resulting multilayer structure has sufficient stretchability and excellent puncture strength. The upper limit of this density is 0.930 g / cm. 3 is preferred, and 0.920 g / cm 3 More preferably, 0.910 g / cm 3 The lower limit of this density is 0.870 g / cm 3 is preferred, and 0.880 g / cm 3 is more preferred.

[0012] In this specification, the term "main component" refers to the component that is contained in the greatest amount by mass.

[0013] Examples of resins (polyolefin resins) used as the main component of the polyolefin layer (A) include linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), very low-density polyethylene (VLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), ethylene-vinyl acetate copolymer (EVA), olefin-unsaturated carboxylic acid copolymer ionomers, ethylene-propylene copolymers, ethylene-acrylate copolymers, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymers, polybutene, polypentene, and other olefin homo- or copolymers, graft-modified versions of these olefin homo- or copolymers with unsaturated carboxylic acids or their esters, and blends thereof. Among these, linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE) are preferred because they can increase the puncture strength of the polyolefin layer (A), and linear low-density polyethylene (LLDPE) is particularly preferred.

[0014] The linear low-density polyethylene is particularly preferably polyethylene (ethylene polymer or copolymer) polymerized using a metallocene catalyst. The polyethylene (ethylene polymer or copolymer) polymerized using a metallocene catalyst is preferably an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, produced by polymerizing ethylene or copolymerizing ethylene and the α-olefin in the presence of a catalyst formed from a compound of a transition metal of Group 4 of the periodic table, preferably zirconium, having at least one ligand having a cyclopentadienyl skeleton, an organoaluminum oxy compound, and various other components added as needed.

[0015] Examples of the α-olefin having 3 or more carbon atoms in the ethylene copolymer include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, etc. As the ethylene copolymer, a copolymer of an α-olefin having 3 to 12 carbon atoms is particularly preferred.

[0016] Industrially produced polyethylene (ethylene polymer or copolymer) polymerized using a metallocene catalyst is commercially available, and examples include "Kernel" (manufactured by Japan Polychem Corporation), "Evolue" (manufactured by Prime Polymer Corporation), "Exact" (manufactured by Exxon Chemical Company), "Affinity" and "Engage" (manufactured by The Dow Chemical Company).

[0017] The content of the resin as the main component in the polyolefin layer (A) is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The content of the resin as the main component in the polyolefin layer (A) may be 100% by mass or less. The polyolefin layer (A) may contain other optional components such as resins other than polyolefin resins, heat stabilizers, UV absorbers, antioxidants, colorants, and fillers.

[0018] The thickness of one polyolefin layer (A) is preferably from 10 μm to 1 mm, more preferably from 30 μm to 500 μm, and even more preferably from 50 μm to 200 μm.

[0019] (Resin composition layer (C)) The resin composition layer (C) is usually a layer containing EVOH (c1) as a main component. The ethylene unit content of the EVOH (c1) contained in the resin composition layer (C) is 20 mol% or more and 50 mol% or less. If the ethylene unit content is less than 20 mol%, the thermal stability during melt molding may decrease, and recyclability may deteriorate. The ethylene unit content is more preferably 22 mol% or more, and even more preferably 25 mol% or more. If the ethylene unit content exceeds 50 mol%, the gas barrier property may become insufficient. The ethylene unit content is more preferably 45 mol% or less, and even more preferably 40 mol% or less. The ethylene unit content of EVOH (c1) can be determined by the method described in the Examples.

[0020] The saponification degree of EVOH (c1) is 90 mol% or more. If the saponification degree is less than 90 mol%, the crystallinity of EVOH will be low, resulting in a decrease in gas barrier properties and a significant decrease in thermal stability during melt molding. The saponification degree is preferably 95 mol% or more, more preferably 98 mol% or more, and even more preferably 99 mol% or more. The upper limit of the saponification degree may be 100 mol%. The saponification degree of EVOH (c1) can be determined by the method described in the Examples.

[0021] At least a part of the EVOH (c1) preferably has at least one of a carboxylic acid unit (I) and a lactone ring unit (II) located at the polymer terminal (main chain terminal). The carboxylic acid unit (I) is a structural unit located at the polymer terminal and has a carboxy group. The carboxylic acid unit (I) is also called a terminal carboxylic acid unit. Some or all of the carboxy groups of the carboxylic acid unit (I) may be converted into a salt or an anion (-COO -The lactone ring unit (II) is a structural unit located at the terminal of the polymer and has a lactone ring. The lactone ring unit (II) is also called a terminal lactone ring unit. The number of ring members in the lactone ring is not particularly limited, and may be, for example, a 4- to 6-membered ring, with a 5-membered ring being preferred. The carboxylic acid unit (I) may be, for example, a structural unit represented by the following formula (1). The lactone ring unit (II) may be, for example, a structural unit represented by the following formula (2).

[0022] [ka]

[0023] In formula (1), X is a hydrogen atom, a hydroxy group, or an esterified hydroxy group, and Y is a hydrogen atom or a metal atom.

[0024] The esterified hydroxy group represented by X above includes acyloxy groups such as -OCO-CH3 and -OCO-C2H5.

[0025] Examples of the metal atom represented by Y include alkali metals such as sodium, alkaline earth metals such as magnesium and calcium, metals that are typical elements such as aluminum, and transition metals. Among these, typical elements are preferred, and alkali metals, alkaline earth metals, and aluminum are more preferred. When Y is aluminum, the aluminum is included in the aluminum ion (c3), and when Y is an alkali metal, the alkali metal is included in the alkali metal ion (c5). When Y is a divalent or higher metal atom, two or more carboxylate anions (-COO - ) may be bonded or coordinated.

[0026] The lower limit of the total content (i+ii) of carboxylic acid units (I) and lactone ring units (II) per gram of EVOH (c1), i.e., the total amount (amount of substance: number of moles) of carboxylic acid units (I) and lactone ring units (II) present in 1 gram of EVOH (A), is preferably 14 μmol / g, more preferably 18 μmol / g, and even more preferably 22 μmol / g. The lower limit of the total content of carboxylic acid units (I) and lactone ring units (II) relative to the total content of ethylene units, vinyl alcohol units, and vinyl ester units in EVOH (A) is preferably 0.10 mol%, more preferably 0.12 mol%, and even more preferably 0.14 mol%. When the total content of carboxylic acid units (I) and lactone ring units (II) is equal to or greater than the above lower limit, the appearance of the multilayer structure is improved.

[0027] On the other hand, the upper limit of the total content (i+ii) of the carboxylic acid units (I) and lactone ring units (II) per gram of EVOH (c1) is preferably 78 μmol / g, more preferably 70 μmol / g, even more preferably 60 μmol / g, even more preferably 50 μmol / g, and particularly preferably 40 μmol / g. Furthermore, the upper limit of the total content of the carboxylic acid units (I) and lactone ring units (II) relative to the total content of the ethylene units, vinyl alcohol units, and vinyl ester units in EVOH (A) is preferably 0.4 mol%, more preferably 0.3 mol%, even more preferably 0.25 mol%, and particularly preferably 0.21 mol% or less. If the amount of the carboxylic acid units (I) and lactone ring units (II) is too large, thermal stability is reduced. Specifically, the carboxylic acid units (I) and lactone ring units (II) can react with the hydroxy groups of EVOH (c1) at high temperatures to form a branched, highly polymerized polymer. Therefore, if the content of the carboxylic acid unit (I) and the lactone ring unit (II) is high, the melt-processability of the EVOH (c1) tends to decrease. Therefore, if the total content of the carboxylic acid unit (I) and the lactone ring unit (II) is not more than the above upper limit, the generation of lumps during melt-processing can be suppressed, and the appearance of the obtained multilayer structure can be improved.

[0028] The lower limit of the ratio (ii) of the lactone ring unit (II) content to the total content (i+ii) of the carboxylic acid units (I) and lactone ring units (II) in EVOH (c1) (ii / (i+ii):lactone ring unit ratio) is preferably 40 mol%, more preferably 50 mol%. By setting the lactone ring unit ratio (ii / (i+ii)) to the above lower limit or higher, the shear stress between the adhesive resin layer (B) and the resin composition layer (C) during melt molding is weakened, improving the appearance of the multilayer structure. On the other hand, the upper limit of this lactone ring unit ratio (ii / (i+ii)) may be, for example, 90 mol%, 80 mol%, or 70 mol%.

[0029] The total content (i+ii) of carboxylic acid units (I) and lactone ring units (II) per gram of EVOH (c1) is adjusted by, for example, polymerization conditions such as the type of polymerization initiator and drying conditions such as a dry atmosphere. In unbranched EVOH (c1), the total content (i+ii) of carboxylic acid units (I) and lactone ring units (II) tends to be relatively small as the degree of polymerization increases, but this tendency is not always observed. For example, as described in WO 2004 / 092234, the total content (i+ii) of carboxylic acid units (I) and lactone ring units (II) can be reduced by contacting an ethylene-vinyl ester copolymer or EVOH with a reducing agent. Conversely, the total content (i+ii) of carboxylic acid units (I) and lactone ring units (II) can be increased by contacting an ethylene-vinyl ester copolymer or EVOH with an oxidizing agent or drying in an oxidizing atmosphere. The ratio of the content (ii) of the lactone ring unit (II) to the total content (i+ii) of the carboxylic acid unit (I) and the lactone ring unit (II) (ii / (i+ii): lactone ring unit ratio) can be adjusted by adjusting the saponification conditions, etc. For example, when saponification is performed under conditions that accelerate saponification, the lactone ring unit ratio (ii / (i+ii)) tends to increase.

[0030] The total content (i+ii) of the carboxylic acid units (I) and the lactone ring units (II) located at the polymer terminals of the EVOH (c1) and the lactone ring unit ratio (ii / (i+ii)) are 1 The content of the carboxylic acid unit (I) and the lactone ring unit (II) (i+ii) is determined by H-NMR measurement. The inventors have found that the measurement results vary depending on the type of solvent used during the measurement. Therefore, the measurement is carried out using a mixed solvent of water and methanol (4 / 6 by mass, although the mass ratio is changed appropriately if the sample does not dissolve). Specifically, the total content (i+ii) of the carboxylic acid unit (I) and the lactone ring unit (II) and the lactone ring unit ratio (ii / (i+ii)) are values ​​measured by the method described in the Examples below.

[0031] EVOH (c1) may contain structural units derived from other monomers other than ethylene, vinyl esters, and saponified products thereof, provided that the effects of the present invention are not impaired. When EVOH (c1) contains units derived from other monomers, the content thereof is preferably 10 mol% or less, more preferably 5 mol% or less, and even more preferably 3 mol% or less, based on the total structural units in EVOH (c1). The content of structural units derived from other monomers may be 0.05 mol% or more. Examples of other monomers include vinylsilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, and γ-methacryloxypropylmethoxysilane.

[0032] EVOH (c1) may have at least one of a structural unit (I) represented by the following formula (I), a structural unit (II) represented by the following formula (II), and a structural unit (III) represented by the following general formula (III) within the scope of the present invention. When EVOH (c1) has such a structural unit, the thermoformability of the resulting multilayer structure can be improved.

[0033] [ka]

[0034] In formula (I), R 1 , R 2 and R 3 each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a hydroxyl group. 1 , R 2 and R 3 One pair of these may be bonded to one another. In addition, some or all of the hydrogen atoms in the aliphatic hydrocarbon group having 1 to 10 carbon atoms, the alicyclic hydrocarbon group having 3 to 10 carbon atoms, and the aromatic hydrocarbon group having 6 to 10 carbon atoms may be substituted with hydroxyl groups, carboxyl groups, or halogen atoms.

[0035] In formula (II), R 4 , R 5 , R 6 and R 7 each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a hydroxyl group. 4 and R 5 What is R? 6 and R 7 In addition, some or all of the hydrogen atoms in the aliphatic hydrocarbon group having 1 to 10 carbon atoms, the alicyclic hydrocarbon group having 3 to 10 carbon atoms, and the aromatic hydrocarbon group having 6 to 10 carbon atoms may be substituted with a hydroxyl group, an alkoxy group, a carboxyl group, or a halogen atom.

[0036] In formula (III), R 8 , R 9 , R 10 and R 11 R each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a hydroxyl group. Some or all of the hydrogen atoms in the aliphatic hydrocarbon group having 1 to 10 carbon atoms, the alicyclic hydrocarbon group having 3 to 10 carbon atoms, and the aromatic hydrocarbon group having 6 to 10 carbon atoms may be substituted with a hydroxyl group, an alkoxy group, a carboxyl group, or a halogen atom. 12 and R 13each independently represents a hydrogen atom, a formyl group, or an alkanoyl group having 2 to 10 carbon atoms.

[0037] When EVOH (c1) contains the structural units represented by the above formulae (I) to (III), the lower limit of the content is preferably 0.1 mol%, more preferably 0.5 mol%, and even more preferably 1 mol%. The upper limit of the content is preferably 30 mol%, more preferably 15 mol%, and even more preferably 10 mol%. When the content of the structural units represented by the above formulae is within the above range, the flexibility and processability of the resin composition are improved, and the thermoformability of the resulting multilayer structure is improved.

[0038] In the structural unit shown in the above formula, examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms include an alkyl group and an alkenyl group, examples of the alicyclic hydrocarbon group having 3 to 10 carbon atoms include a cycloalkyl group and a cycloalkenyl group, and examples of the aromatic hydrocarbon group having 6 to 10 carbon atoms include a phenyl group.

[0039] In the structural unit (I), R 1 , R 2 and R 3 are preferably each independently a hydrogen atom, a methyl group, an ethyl group, a hydroxyl group, a hydroxymethyl group, or a hydroxyethyl group, and among these, are preferably each independently a hydrogen atom, a methyl group, a hydroxyl group, or a hydroxymethyl group, from the viewpoint of further improving the thermoformability of the resulting multilayer structure.

[0040] In the structural unit (II), R 4 and R 5 Preferably, both R are hydrogen atoms. 4 and R 5 are both hydrogen atoms, and the R 6 and R 7 It is more preferable that one of R is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, and the other is a hydrogen atom. The aliphatic hydrocarbon group is preferably an alkyl group or an alkenyl group. From the viewpoint of placing particular importance on the gas barrier properties of the resulting multilayer structure, R 6 and R 7It is particularly preferred that one of the R 6 and R 7 One of them is (CH2) h It is particularly preferred that the other of the substituents represented by OH (wherein h is an integer of 1 to 8) is a hydrogen atom. h In the substituent represented by OH, h is preferably an integer of 1 to 4, more preferably 1 or 2, and particularly preferably 1.

[0041] In the structural unit (III), R 8 , R 9 , R 10 and R 11 is preferably a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms, and the aliphatic hydrocarbon group is preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, or an n-pentyl group.

[0042] The EVOH (c1) may be used alone or in combination of two or more kinds.

[0043] The content of EVOH (c1) in the resin composition layer (C) is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more. The content of EVOH (c1) in the resin composition layer (C) may be 100% by mass or less.

[0044] The content of polyvalent metal ions (c2) contained in the resin composition layer (C) is 10 ppm or more and 400 ppm or less. If the content of polyvalent metal ions (c2) is less than 10 ppm, the stress acting between the adhesive resin layer (B) and the resin composition layer (C) increases during molding of the multilayer structure, resulting in a deterioration in the appearance of the multilayer structure. The content of polyvalent metal ions (c2) is more preferably 20 ppm or more, even more preferably 50 ppm or more, and particularly preferably 80 ppm or more. On the other hand, if the content of polyvalent metal ions (c2) exceeds 400 ppm, the viscosity may decrease significantly during long-term melt-kneading, resulting in deterioration in stable moldability. The content of polyvalent metal ions (c2) is more preferably 300 ppm or less, even more preferably 250 ppm or less.

[0045] The polyvalent metal ion (c2) is at least one selected from the group consisting of magnesium ions, calcium ions, zinc ions, cobalt ions, and manganese ions. By incorporating at least one selected from this group into EVOH (c1), viscosity stability during melt molding is excellent. Magnesium ions, calcium ions, and zinc ions are more preferred as the polyvalent metal ion (c2) in terms of reducing discoloration of the resulting multilayer structure, and calcium ions and zinc ions are more preferred in terms of productivity, stable moldability, and the appearance of the resulting multilayer structure.

[0046] The polyvalent metal ions (c2) contained in the resin composition layer (C) may exist in a state dissociated from anions, in a state of a salt bonded to anions, or in a state of being coordinated with groups (e.g., carboxyl groups, hydroxyl groups, etc.) contained in the EVOH (c1) or other optional components.

[0047] The polyvalent metal ion (c2) is usually derived from a salt, but is preferably derived from a metal salt of a higher fatty acid having 12 or more carbon atoms because of its excellent effects on appearance and the like. In other words, the polyvalent metal ion (c2) is preferably contained as a cation of a metal salt of a higher fatty acid. That is, when it is contained in EVOH (c1), it is preferable that a metal salt of a higher fatty acid having 12 or more carbon atoms is added or contained as a component constituting the polyvalent metal ion (c2). The added metal salt of a higher fatty acid having 12 or more carbon atoms may be present in the resin composition in the form of a salt in which the polyvalent metal ion (c2) and the fatty acid anion remain bonded, or may be present in the resin composition in the form in which the polyvalent metal ion (c2) and the fatty acid anion are dissociated.

[0048] Examples of metal salts of higher fatty acids having 12 or more carbon atoms include metal salts of fatty acids such as lauric acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, basic stearic acid, hydroxystearic acid, basic hydroxystearic acid, nonadecanoic acid, oleic acid, behenic acid, montanic acid, and linoleic acid. From the viewpoint of dispersibility in EVOH (c1), one or more of these may be used as appropriate.

[0049] In addition, metal salts of fatty acids having 11 or less carbon atoms (acetates, propionates, etc.), metal salts other than fatty acid metal salts (nitrates, sulfates, etc.), etc. can also be used.

[0050] The resin composition layer (C) preferably further contains aluminum ions (c3) in an amount of 5 ppb to 500 ppb. The inclusion of aluminum ions (c3) improves thermal stability during melt molding and improves recyclability. The content of aluminum ions (c3) is more preferably 10 ppb to 250 ppb.

[0051] The aluminum ions (c3) contained in the resin composition layer (C) may exist in a state dissociated from an anion, in a state of a salt bonded to an anion, or in a state of being coordinated with groups (e.g., carboxyl groups, hydroxyl groups, etc.) contained in the EVOH (c1) or other optional components.

[0052] The aluminum ion (c3) is usually derived from a salt, but is preferably derived from a metal salt of a higher fatty acid having 12 or more carbon atoms because of its excellent action and effect. In other words, the aluminum ion (c3) is preferably contained as a cation of the metal salt of a higher fatty acid. That is, when the aluminum ion (c3) is contained in the EVOH (c1), it is preferable that an aluminum salt of a higher fatty acid having 12 or more carbon atoms is added or contained as a component constituting the aluminum ion (c3). The added aluminum salt of a higher fatty acid having 12 or more carbon atoms may be present in the resin composition in the form of a salt in which the aluminum ion (c3) and the fatty acid anion remain bonded, or may be present in the resin composition in the form in which the aluminum ion (c3) and the fatty acid anion are dissociated.

[0053] Examples of aluminum salts of fatty acids having 12 or less carbon atoms include aluminum salts of fatty acids such as aluminum laurate, aluminum laurate, aluminum tridecylate, aluminum myristate, aluminum pentadecylate, aluminum palmitate, aluminum heptadecylate, aluminum stearate, basic aluminum stearate, aluminum hydroxystearate, basic aluminum hydroxystearate, aluminum nonadecanoate, aluminum oleate, aluminum behenate, aluminum montanate, and aluminum linoleate. From the viewpoint of dispersibility in EVOH (c1), etc., any one or more of these may be used as appropriate.

[0054] In addition, aluminum salts of fatty acids having 11 or less carbon atoms (aluminum acetate, aluminum propionate, etc.), aluminum salts other than aluminum fatty acids (aluminum nitrate, aluminum sulfate, etc.), etc. can also be used.

[0055] The resin composition layer (C) further contains phosphate ions (c4), and the content of phosphate ions (c4) in the resin composition layer (C) is preferably 5 ppm or more and 200 ppm or less. This improves discoloration resistance during melt molding. When the content of phosphate ions (c4) is 5 ppm or more, discoloration resistance during melt molding is improved. On the other hand, when the content of phosphate ions (c4) is 200 ppm or less, viscosity stability is improved, and the appearance of the resulting multilayer structure is improved. The content of phosphate ions (c4) is more preferably 10 ppm or more and 100 ppm or less.

[0056] Examples of components constituting the phosphate ion (c4) include various acids such as phosphoric acid and phosphorous acid, and salts thereof. The phosphate may be contained in the form of any of primary phosphate, secondary phosphate, and tertiary phosphate, and the cationic species is not particularly limited.

[0057] The resin composition layer (C) further contains alkali metal ions (c5), and the content of alkali metal ions (c5) in the resin composition layer (C) is preferably 10 ppm or more and 400 ppm or less. This can suppress crosslinking of the resin, resulting in a multilayer structure with excellent recyclability. The content of alkali metal ions (c5) is more preferably 20 ppm or more and 200 ppm or less. Examples of the alkali metal ions (c5) include sodium ions and potassium ions, with sodium ions being preferred. The alkali metal ions (c5) may be contained as metal salts. Examples of alkali metal salts include metal salts of organic acids such as acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, oleic acid, and behenic acid, and inorganic acids such as sulfuric acid, sulfurous acid, carbonic acid, boric acid, and phosphoric acid.

[0058] The content ratio (c4 / c5) of the phosphate ions (c4) to the alkali metal ions (c5) contained in the resin composition layer (C) is preferably 0.01 or more and 2 or less. When the content ratio (c4 / c5) is within the above range, the presence of a predetermined ratio of alkali metal ions (c5) to phosphate ions (c4) effectively suppresses the generation of insoluble salts that are finer than conventionally known particles, i.e., compounds formed by the reaction of polyvalent metal ions (c2) with phosphate ions (c4). As a result, when the multilayer structure of the present invention is recovered and reused, the resulting recovered composition can ensure high transparency. When the content ratio (c4 / c5) is 0.01 or more, discoloration resistance during melt molding is improved. The lower limit of the content ratio (c4 / c5) is more preferably 0.05, and even more preferably 0.1. Furthermore, when the content ratio (c4 / c5) is 2 or less, fine insoluble salts derived from compounds formed by the reaction of polyvalent metal ions (c2) and phosphate ions (c4) during melt molding are less likely to be produced, improving the puncture strength, appearance, stable moldability, etc. of the multilayer structure. The upper limit of the content ratio (c4 / c5) is more preferably 1.2, and even more preferably 1.0.

[0059] The content ratio (c2 / c5) of the polyvalent metal ions (c2) to the alkali metal ions (c5) contained in the resin composition layer (C) is preferably 0.1 or more and 5 or less. When the content ratio (c2 / c5) is within the above range, a predetermined amount of alkali metal ions (c5) is present relative to the polyvalent metal ions (c2), thereby efficiently suppressing the generation of insoluble salts that are even finer than conventionally known particles, i.e., compounds formed by the reaction of polyvalent metal ions (c2) with phosphate ions (c4). As a result, when the multilayer structure of the present invention is recovered and reused, the resulting recovered composition can ensure high transparency. When the content ratio (c2 / c5) is 0.1 or more, discoloration resistance during melt molding is improved. The lower limit of the content ratio (c2 / c5) is more preferably 0.2, and even more preferably 0.5. Furthermore, when the content ratio (c2 / c5) is 5 or less, fine insoluble salts derived from compounds formed by the reaction of polyvalent metal ions (c2) and phosphate ions (c4) during melt molding are less likely to be produced, thereby improving the puncture strength of the multilayer structure. The upper limit of the content ratio (c2 / c5) is more preferably 3, and even more preferably 1.

[0060] The content ratio (c2 / c4) of the polyvalent metal ions (c2) to the phosphate ions (c4) contained in the resin composition layer (C) is preferably 1 or more and 15 or less. When the content ratio (c2 / c4) is 1 or more, the viscosity stability and the appearance of the multilayer structure are improved. The lower limit of the content ratio (c2 / c4) is preferably 2. When the content ratio (c2 / c4) is 15 or less, the discoloration resistance during melt molding is improved.

[0061] In the resin composition layer (C), it is preferable that the content ratios (c4 / c5), (c2 / c5), and (c2 / c4) all satisfy the above-mentioned suitable ranges. In such a case, the multilayer structure of the present invention has particularly excellent appearance, mechanical strength, etc.

[0062] As a method for incorporating the phosphate ions (c4) and the alkali metal ions (c5) into the resin composition layer (C), for example, a method in which they are incorporated into the EVOH (c1) in advance can be mentioned.

[0063] Examples of methods for incorporating phosphate ions (c4) and alkali metal ions (c5) into EVOH (c1) include: (1) contacting a porous precipitate of EVOH having a water content of 20 to 80% by mass with an aqueous solution of a phosphate compound to incorporate the alkali metal compound into the EVOH, followed by drying; (2) incorporating the phosphate compound and the alkali metal compound into a homogeneous solution of EVOH (e.g., a water / alcohol solution), extruding the solution into a coagulation liquid in the form of strands, cutting the resulting strands into pellets, and further drying; (3) mixing EVOH, the phosphate compound, and the alkali metal compound together and then melt-kneading them in an extruder or the like; and (4) neutralizing the alkali (e.g., sodium hydroxide, potassium hydroxide) used in the saponification step during the production of EVOH with acetic acid, and adjusting the amount of by-products such as sodium acetate and potassium acetate by washing with water. To achieve the effects of the present invention more significantly, methods (1), (2), and (4), which provide excellent dispersibility of phosphate ions and alkali metal ions, are preferred.

[0064] The thickness of one resin composition layer (C) is preferably from 0.1 μm to 100 μm, more preferably from 1 μm to 50 μm, and even more preferably from 3 μm to 25 μm.

[0065] (Adhesive resin layer (B)) The multilayer structure of the present invention further comprises an adhesive resin layer (B) between the polyolefin layer (A) and the resin composition layer (C). The adhesive resin layer (B) is typically a layer primarily composed of an adhesive resin. Examples of adhesive resins used in the adhesive resin layer (B) include modified olefin polymers containing carboxyl groups, which are obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to an olefin polymer by addition reaction, graft reaction, or the like. Examples of unsaturated carboxylic acids or their anhydrides include maleic acid, maleic anhydride, fumaric acid, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, citraconic acid, and hexahydrophthalic anhydride. Of these, maleic anhydride is preferred. Specifically, preferred examples include one or a mixture of two or more selected from maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-propylene copolymer, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer, and the like.

[0066] Adhesion can sometimes be improved by mixing adhesive resins with rubber or elastomer components such as polyisobutylene or ethylene-propylene rubber, or with polyolefin resins different from the base polyolefin resin of the adhesive resin.

[0067] The adhesive resin content in the adhesive resin layer (B) is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The adhesive resin content in the adhesive resin layer (B) may be 100% by mass or less.

[0068] The thickness of one adhesive resin layer (B) is preferably from 0.1 μm to 100 μm, more preferably from 1 μm to 50 μm, and even more preferably from 3 μm to 25 μm.

[0069] (Multilayer structure) The multilayer structure of the present invention has a polyolefin layer (A) laminated on at least one surface of a resin composition layer (C) via an adhesive resin layer (B). In this case, any other layer may be provided between the polyolefin layer (A) and the adhesive resin layer (B). The multilayer structure of the present invention does not have a layer whose main component is a resin having a melting point of 210°C or higher and a metal layer whose thickness is 1 μm or more. If the multilayer structure has a layer whose main component is a resin having a melting point of 210°C or higher and a metal layer whose thickness is 1 μm or more, the recyclability of the resulting multilayer structure when it is crushed and reused is reduced. The metal layer refers to a layer whose main component is metal. It is also preferable that the multilayer structure of the present invention does not have a layer whose main component is polyamide.

[0070] The melting points of the polyolefin resin contained in the polyolefin layer (A), the adhesive resin contained in the adhesive resin layer (B), and the EVOH (c1) contained in the resin composition layer (C) are preferably 150°C or higher and 205°C or lower, more preferably 155°C or higher and 200°C or lower.

[0071] When producing the multilayer structure, it is sufficient to obtain a multilayer structure having a layer structure of (A) / (B) / (C). A multilayer structure having a layer structure of (A) / (B) / (C) / (B) / (A) is particularly preferred. Examples of lamination methods include co-extrusion of the resins, melt-extrusion of a single-layer film to be used as the resin composition layer (C) or a multilayer [(B) / (C) / (B)] film to be used as the resin composition layer (C) and the adhesive resin layer (B), and dry-laminating a single-layer film or multilayer film made of another resin onto the single-layer or multilayer film using a known adhesive, and the like. Furthermore, when co-extrusion is performed by an inflation method, a multilayer film having a layer structure of [outside] (A) / (B) / (C) / (B) [inside] can be produced by first forming a multilayer film having a layer structure of [outside] (A) / (B) / (C) / (B) and then fusing the inner sides of the tubular film together using heat or the like and winding it up. The molding temperature during melt molding is often selected from the range of 150 to 300°C. It is also preferable to use the resin composition layer (C) as an intermediate layer, and provide adhesive resin layers (B) on both sides of the intermediate layer so as to be in direct contact with the intermediate layer, thereby forming an adhesive resin layer (B) / (C) / (B) layer structure. In this case, no other resin layer is included between the adhesive resin layer (B) and the resin composition layer (C).

[0072] In the multilayer structure of the present invention, the ratio of the thickness of the polyolefin layer (A) to the total thickness of all layers is preferably 0.75 or more. When this ratio is within the above range, the mechanical strength and appearance are excellent. This ratio is more preferably 0.80 or more. The upper limit of this ratio may be, for example, 0.95 or even 0.90. The total thickness of all layers in the multilayer structure of the present invention is, for example, preferably 50 μm or more and 3 mm or less, more preferably 100 μm or more and 1 mm or less.

[0073] The multilayer structure of the present invention is not limited to the above-described (A) / (B) / (C) / (B) / (A) layer structure. It may also have seven or more layers, such as (A) / (X) / (B) / (C) / (B) / (X) / (A), (X) / (A) / (B) / (C) / (B) / (A) / (X), or (X) / (A) / (X) / (B) / (C) / (B) / (X) / (A) / (X), in which an additional layer (X) is provided on the outer or inner side of the polyolefin layer (A). The resins and compositions used in layers with the same symbol in the layer structure may be the same or different. When a plurality of polyolefin layers (A) and adhesive resin layers (B) are used in the multilayer structure of the present invention, different types of resins may be used for each.

[0074] In the multilayer structure of the present invention, a layer-like region having an elastic modulus (Young's modulus) of 0.4 GPa or more and 0.8 GPa or less is preferably present at the interface between the adhesive resin layer (B) and the resin composition layer (C). This region having an elastic modulus of 0.4 GPa or more and 0.8 GPa or less is considered to be a region formed by reaction between the adhesive resin layer (B) and the resin composition layer (C). The upper limit of the thickness of this region is preferably 50 nm, more preferably 30 nm, and even more preferably 20 nm. By keeping the thickness of this interface region below the above upper limit, the appearance of the multilayer structure is improved. On the other hand, the lower limit of the thickness of this region is preferably, for example, 3 nm, more preferably 5 nm.

[0075] The modulus of elasticity at the interface between the adhesive resin layer (B) and the resin composition layer (C) can be determined by measuring and analyzing with an atomic force microscope (hereinafter sometimes simply referred to as "AFM"). The cross section of the multilayer structure is measured with an AFM, and the modulus of elasticity can be calculated at each measurement point (256 x 256 = 65,536 pixels) within a measurement range of 3 μm x 3 μm. In other words, this modulus of elasticity refers to the modulus of elasticity at each of multiple measurement points at the interface, and does not mean the average value in the interface region. Specifically, this modulus of elasticity can be determined using the apparatus and method described in the Examples.

[0076] The shape of the multilayer structure of the present invention is not particularly limited, but is preferably a film shape, more preferably a rectangular or strip-like film shape having a longitudinal direction and a width direction perpendicular to the longitudinal direction.

[0077] When the multilayer structure of the present invention has a film shape having a longitudinal direction and a width direction, the ratio (Cmin / Cmax) of the minimum thickness Cmin to the maximum thickness Cmax of the resin composition layer (C), as observed in a 45% to 55% range of the width cross section, where the position of one end in the width direction is 0% and the position of the other end is 100%, is preferably 0.70 or more. When this ratio is equal to or greater than the above-mentioned lower limit, light scattering occurring at the interface between the adhesive resin layer (B) and the resin composition layer (C) is suppressed, thereby preventing poor appearance of the multilayer structure. Furthermore, when this ratio is equal to or greater than the above-mentioned lower limit, recyclability is improved. The ratio is more preferably 0.80 or more, and even more preferably 0.85 or more. Furthermore, the ratio may be 1.0 or less, or may be 0.99 or less.

[0078] The puncture strength of the multilayer structure of the present invention is not particularly limited and may be adjusted depending on the application, but is preferably 4 to 40 N. Multilayer structures having a puncture strength within this range are suitable for use as packaging materials, etc. The puncture strength is more preferably 5 N or more, even more preferably 6 N or more, and particularly preferably 7.5 N or more. The puncture strength of the multilayer structure herein is measured in accordance with JIS Z 1707, and specifically, the method described in the examples is employed.

[0079] The puncture strength per unit thickness of the multilayer structure of the present invention is not particularly limited and can be adjusted depending on the application, but is preferably 30 to 200 N / mm. A multilayer structure with a puncture strength per unit thickness of less than 30 N / mm is not preferred because it requires a large thickness for use as a packaging material, etc., which increases production costs. The lower limit of the puncture strength is more preferably 40 N / mm or more, and even more preferably 50 N / mm or more.

[0080] The oxygen transmission rate (OTR) of the multilayer structure of the present invention may be adjusted depending on the application, but is not particularly limited. 2 The OTR is preferably 4 cc / m or less. A multilayer structure having an OTR in this range is suitable for use as a packaging material, etc. 2 .day.atm or less is preferable, and OTR is 3cc / m 2 .day.atm or less is more preferable, and OTR is 2cc / m 2 The pressure is particularly preferably 0.05 atm or less per day. The pressure is measured in accordance with JIS K 7126-2 (isobaric method; 2006), and specifically, the method described in the examples is employed.

[0081] Furthermore, in order to improve moldability and various physical properties, various additives, modifiers, fillers, other resins, etc. may be added to each layer of the multilayer structure of the present invention, within a range that does not impair the effects of the present invention.

[0082] It is preferable to reuse recovered materials (scrap) obtained by recovering end portions or defective products generated during the production of the multilayer structure of the present invention. That is, a recovered composition containing the multilayer structure of the present invention is also one aspect of the present invention. The recovered composition may be obtained by recovering the multilayer structure of the present invention. As described above, with regard to the recovery of multilayer structures, off-specification products generated during production may be recovered, but a preferred embodiment is to recover multilayer structures distributed on the market. The recovered composition containing recovered materials from the multilayer structure of the present invention is suitably used as a raw material for multilayer structures, etc.

[0083] The multilayer structure of the present invention can be crushed and remolded for reuse. Furthermore, the multilayer structure of the present invention has excellent mechanical strength and thermoformability. On the other hand, if the multilayer structure does not contain a polyamide-based resin layer, the occurrence of lumps, which is thought to be caused by crosslinking due to a chemical reaction between the polyamide-based resin and EVOH during melt molding, is reduced, and the recycled composition obtained by reuse has a better appearance. From the viewpoint of further reducing the occurrence of such lumps, it is preferable that all layers constituting the multilayer structure do not contain polyamide resin. The melting point of the polyamide resin is typically 210°C or higher. The recycled composition containing the recycled multilayer structure of the present invention is preferably produced by melt-kneading the recycled multilayer structure. That is, a method for producing a recycled composition including a step of melt-kneading the recycled multilayer structure of the present invention also constitutes one aspect of the present invention. The recycled material can be melt-molded by extrusion molding, inflation extrusion, blow molding, melt spinning, injection molding, etc. The melting temperature varies depending on the melting point of the copolymer, but is preferably about 150 to 270°C. The recovered composition may contain unused resin, but the content of recovered material in the recovered composition is preferably 10% by mass or more.

[0084] A preferred embodiment of the present invention is a packaging material made of the multilayer structure of the present invention. The packaging material is processed into a tube, bag, or other shape and is useful as a packaging material for various items such as food, beverages, pharmaceuticals, cosmetics, industrial chemicals, pesticides, and detergents, but it can be used for a wide range of purposes and is not limited to these.

[0085] A package obtained by filling the above-mentioned packaging material with contents is a preferred embodiment of the packaging material. The package of the present invention is useful because it can prevent deterioration of the flavor of the contents due to oxygen. Contents that can be filled include, but are not limited to, beverages such as wine and fruit juice; foods such as fruits, nuts, vegetables, meat products, baby foods, coffee, jam, mayonnaise, ketchup, edible oils, dressings, sauces, foods boiled in soy sauce, and dairy products; and other contents that are prone to deterioration in the presence of oxygen, such as pharmaceuticals, cosmetics, and gasoline. [Example]

[0086] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples at all.

[0087] <Quantitative measurement conditions of the primary structure of EVOH (NMR method)> Apparatus name: Superconducting nuclear magnetic resonance apparatus ECZ-600 manufactured by JEOL Observation frequency: 600 MHz ( 1 H) (1) Solvent: Heavy dimethyl sulfoxide (DMSO-d6) Polymer concentration: 5 mass% Measurement temperature: 25 °C, 80 °C Flip angle: 30° Number of integrations: 256 s Internal standard substance: Tetramethylsilane (TMS) (2) Solvent: Heavy water (D2O) + heavy methanol (MeOD) (mass ratio 4 / 6) Polymer concentration: 5 mass% Measurement temperature: 80 °C Flip angle: 30° Number of integrations: 1024 s Internal standard substance: Tetramethylsilane (TMS)

[0088] <Q <Quantification of ethylene unit content, saponification degree, terminal carboxylic acid unit content and terminal lactone ring unit content> The ethylene unit content (Et Cont.), saponification degree (SP), terminal carboxylic acid unit content (α) and terminal lactone ring unit content (β) of EVOH are 1 Calculated by the following formula using 1H-NMR measurement (measurement results at 25 °C and 80 °C in DMSO-d6 solvent, measurement results in D2O + MeOD solvent). The chemical shift value was based on the peak of TMS at 0 ppm. In the formula, VAc, VAl and Et represent vinyl acetate unit, vinyl alcohol unit and ethylene unit, respectively. I1, I3: Integration value of methylene hydrogen at 0.4 to 2.35 ppm (I1: Measurement value at 25 °C in DMSO-d6, I3: Measurement value at 80 °C in DMSO-d6) I9: Integrated value of methylene hydrogen from 0.4 to 2.8 ppm (measured in DO+MeOD solvent) I2: The integral value of methine hydrogens of vinyl alcohol units (methine hydrogens of vinyl alcohol on both sides of the same unit) from 3.4 to 4.0 ppm (measured in DMSO at 625°C) I4: The integral value of methine hydrogens of vinyl alcohol units (methine hydrogens of vinyl alcohol on both sides of the same unit) from 3.15 to 3.45 ppm (measured in DMSO at 680°C) I5: Integral value derived from hydrogen of the terminal methyl group in the vinyl acetate unit (measured at 680°C in DMSO) I6: Integrated value around 1.8 to 1.85 (measured value at DMSO-d680℃) I7: Integral value derived from hydrogen of methyl group in -CH(OH)CH3 group present at the polymer terminal of EVOH (measured in DMSO at 680°C) I8: Integral value derived from hydrogen of methyl group in -CH2CH3 group present at the polymer end of EVOH (measured in DMSO at 680°C) I10: Integrated value around 0.8 to 0.95 (measured in DO + MeOD solvent) I11: Integral value derived from hydrogen of CH2 unit adjacent to carbonyl group of terminal lactone ring unit (measured in DO+MeOD solvent) I12: Integral value derived from the linear COOH group of the terminal carboxylic acid unit (measured in DO + MeOD solvent) I13, I14: Integral values ​​derived from the carboxylate salt of the terminal carboxylic acid unit (measured in DO + MeOD solvent) The determined ethylene unit content (Et Cont.), terminal carboxylic acid unit content (α), and terminal lactone ring unit content (β) are all percentages (mol%) of the amount (mol) of each unit relative to the total amount (mol) of ethylene units, vinyl ester units, and vinyl alcohol units. However, the contents of units other than ethylene units, vinyl ester units, and vinyl alcohol units are extremely small compared to these units. Therefore, the determined ethylene unit content (Et Cont.), terminal carboxylic acid unit content (α), and terminal lactone ring unit content (β) are all substantially equal to the percentages (mol%) of the amount (mol) of each unit relative to the total amount (mol) of all structural units.

[0089]

number

[0090] [Example 1] (1) Preparation of EVOH resin composition pellets EVOH resin (MFR (190°C, 2.16 kg load) 1.67 g / 10 min, oxygen permeability (20°C, 65% RH) 0.29 cc·20 μm / (m 2 EVOH resin composition pellets were obtained by melt-kneading EVOH resin composition pellets at a resin temperature of 220°C using a 25 mm extruder (D (mm) = 25, L / D = 25, compression ratio = 2.0, screws: unidirectional fully intermeshing type) manufactured by Toyo Seiki Seisaku-sho, Ltd. (containing 160 ppm of sodium acetate in terms of sodium ions, 30 ppm of phosphate ions, and no polyvalent metal ions) and calcium stearate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) so that the content of polyvalent metal ions (c2) in the resulting resin composition was 140 ppm. The EVOH used had an ethylene unit content of 32 mol%, a degree of saponification of 99.9 mol%, a terminal lactone ring unit content of 0.11 mol%, a terminal carboxylic acid unit content of 0.08 mol%, a total content of terminal carboxylic acid units and terminal lactone ring units of 0.19 mol% (34.6 μmol / g), and a lactone ring unit ratio of 58 mol%.

[0091] (2) Fabrication of multilayer structure A multilayer structure (hereinafter also referred to as a "film") containing resin composition (C) was produced using the EVOH resin composition pellets obtained in (1). Using a coextrusion multilayer cast film-forming apparatus, a multilayer structure was obtained in which the polyolefin layer (A) consisted of linear low-density polyethylene (mLLDPE-1; Prime Polymer's "Evolue SP0510") polymerized using a metallocene catalyst, the adhesive resin layer (B) consisted of maleic anhydride-modified polyethylene (Mitsui Chemicals' "Admer NF518"), and the resin composition layer (C) consisted of the EVOH resin composition (a five-layer coextrusion multilayer cast film having a layer thickness and layer structure of (A) / (B) / (C) / (B) / (A) = 85 μm / 10 μm / 10 μm / 10 μm / 85 μm). The film-forming conditions were as follows: Co-extrusion conditions Extrusion temperature of polyolefin layer (A): feeding section / compression section / metering section / die = 170 / 220 / 220 / 220°C Extrusion temperature of adhesive resin layer (B): feeding section / compression section / metering section / die = 170 / 220 / 220 / 220°C Extrusion temperature of resin composition layer (C): feeding section / compression section / metering section / die=170 / 220 / 220 / 220°C Extruder: Polyolefin layer (A): 32φ extruder GT-32-A (manufactured by Plastics Technology Research Institute Co., Ltd.) Adhesive resin layer (B): 25φ extruder P25-18-AC type (Osaka Seiki Kogyo Co., Ltd.) Resin composition layer (C): 20φ extruder, laboratory machine ME type CO-EXT (manufactured by Toyo Seiki Seisakusho Co., Ltd.) T-die: 300mm wide, 3 types, 5 layers (manufactured by Plastics Technology Research Institute Co., Ltd.) Cooling roll temperature: 80℃ Take-up speed: 1.5m / min

[0092] (3) Film pretreatment The multilayer structure (film) prepared in (2) was embedded in an epoxy resin and cut with an ultramicrotome to obtain a smooth film cross section.

[0093] (4) Atomic force microscope (AFM) measurements The film pretreated in (3) above was set on the measurement stage so that the cross section was the measurement surface, and the film cross section was measured using the following equipment and measurement conditions. Measurements were performed in Peak Force QNM mode set on the following equipment, and analysis was performed based on DMT contact theory to determine the elastic modulus. From the obtained measurement results, the thickness of the region at the interface between the adhesive resin layer (B) and the resin composition layer (C) where the elastic modulus was 0.4 GPa or more and 0.8 GPa or less was determined. The results are shown in Table 1.

[0094] Measurement device: DimensionIcon (manufactured by Burker Corporation) Cantilever: OMCL-AC200TS (Olympus) (nominal spring constant 9N / m) Ramp rate: 0.5Hz Peak Force Frequency: 1kHz Maximum pressing force: 15nN Measurement range: 3 x 3 μm Number of measurement pixels: 256 x 256 pixels = 65,536 points

[0095] (5) Ratio of the minimum thickness Cmin of the resin composition layer (C) to the maximum thickness Cmax (Cmin / Cmax) Five rectangular samples were taken from the multilayer structure prepared in (2) so that one side of the cross section in the width direction spanned 45% to 55% of the width, where the position of one end in the width direction was 0% and the position of the other end was 100%. The width direction surfaces of the obtained samples were cut with a microtome, and the cut surfaces were observed under an optical microscope. Within the above range, the maximum and minimum thicknesses of the resin composition layer (C) on the cut surface of the multilayer structure were extracted and the thickness was measured. The maximum and minimum values ​​were determined for each of the five samples, and the average of the maximum thicknesses was defined as the maximum thickness (Cmax) of the resin composition layer (C), and the average of the minimum thicknesses was defined as the minimum thickness (Cmin) of the resin composition layer (C), and the ratio (Cmin / Cmax) was calculated. The results are shown in Table 1.

[0096] (6) Film appearance evaluation The multilayer structure obtained in (2) was cut into a 10 cm square, and its appearance was visually observed. The evaluation criteria were as follows. The results are shown in Table 1. A: No streaks or unevenness were observed. B: Streaks and unevenness were observed in some areas. C: Streaks and unevenness were observed throughout the film.

[0097] (7) Puncture strength of multilayer structure The multilayer structure obtained in (2) was conditioned at 23°C and 50% RH in accordance with JIS Z 1707, and then cut into a 10 cm diameter circle to obtain a test specimen. The test specimen was fixed using a jig, and a needle with a diameter of 1.0 mm and a semicircular tip with a radius of 0.5 mm was pierced into the test specimen at a rate of 50 mm / min using an AUTOGRAPH (Shimadzu Corporation, "AGS-H") to measure the maximum stress (N) until the needle penetrated, which was defined as the piercing strength of the multilayer structure. The results are shown in Table 1.

[0098] (8) Viscosity change during kneading of EVOH resin composition The EVOH resin composition obtained in (1) was kneaded under the following conditions using a roller mixer R60 manufactured by Toyo Seiki Seisakusho Co., Ltd., and the ratio of the torque value after 60 minutes to the torque value after 10 minutes from the kneading was defined as T 60 / T 10 The viscosity change during kneading was evaluated as follows: The better the evaluation, the higher the stability during melt molding and the smaller the stress applied to the interface with the adhesive layer. The results are shown in Table 1. <Mixer conditions> Screw rotation speed: 100 rpm Temperature setting: 230℃ Duration: 60 minutes Atmosphere: Nitrogen A: 0.2 <T 60 / T 10 ≦0.9 B: 0.1≦T 60 / T 10 ≦0.2, 0.9 <T 60 / T10 ≦1.5 C:T 60 / T 10 <0.1, 1.5 <T 60 / T 10

[0099] (9) Recyclability evaluation The multilayer structure obtained in (2) was pulverized, and the resulting material was extruded into a film with a thickness of 20 μm using a 20 mmφ extruder. The number of particles found per unit area of ​​the obtained film (number / m 2 The fewer the number of particles, the better the recyclability was evaluated. The results are shown in Table 1. A:500 pieces / m 2 less than B:500 pieces / m 2 More than 750 pieces / m 2 less than C:750 pieces / m 2 More than 1000 pieces / m 2 less than D:1000 pieces / m 2 End

[0100] [Examples 2 to 11, 16, and 17, and Comparative Examples 1 to 5] EVOH resin composition pellets and multilayer structures were prepared and evaluated in the same manner as in Example 1, except that the polyolefin layer (A), the type (physical properties) of EVOH (c1), the type and content of polyvalent metal ions (c2), and the contents of phosphate ions (c4) and alkali metal ions (c5) were changed as shown in Tables 1 to 4. In Comparative Example 5, 2800 ppm of stearic acid was added instead of the polyvalent metal ions (c2). The results are shown in Tables 1 to 4.

[0101] [Example 12] A multilayer structure was produced in the same manner as in Example 1, except that the thickness of the polyolefin layer (A) in the above multilayer structure was changed to 42 μm, and various evaluations were carried out. The results are shown in Table 2.

[0102] [Examples 13 and 14] The same EVOH resin as in Example 1, calcium stearate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and aluminum stearate ("Alste #50" manufactured by Kawamura Chemical Industries, Ltd.) were melt-kneaded so that the contents of polyvalent metal ions (c2) and aluminum ions (c3) in the resulting resin composition would be as shown in Table 3. The melt-kneading was carried out using a 25 mm extruder (D (mm) = 25, L / D = 25, compression ratio = 2.0, screws: unidirectional fully intermeshing type) manufactured by Toyo Seiki Seisaku-sho, Ltd., so that the resin temperature reached 220°C, and EVOH resin composition pellets were obtained. Using the obtained EVOH resin composition pellets, a multilayer structure was produced and various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 3.

[0103] [Example 15] A multilayer structure was produced in the same manner as in Example 1, except that the terminal lactone ring unit content and the terminal carboxylic acid unit content were changed, and various evaluations were performed. The EVOH resin was produced by the method described in WO2019 / 131844. The results are shown in Table 3.

[0104] Comparative Example 6 A layer made of polyamide (UBE Nylon SF1018A (melting point 221°C) manufactured by Ube Industries, Ltd.) was further included as another resin layer (D), and the layer thickness and layer configuration of the multilayer structure were changed to (A) / (B) / (D) / (C) / (D) / (B) / (A) = 75 μm / 10 μm / 10 μm / 10 μm / 10 μm / 10 μm / 75 μm, and a multilayer structure was produced. A four-type, seven-layer co-extruder was used to produce the multilayer structure. The film production conditions at this time are shown below. Co-extrusion conditions Extrusion temperature of polyolefin layer (A): feeding section / compression section / metering section / die = 170 / 230 / 230 / 235°C Extrusion temperature of adhesive resin layer (B): feeding section / compression section / metering section / die = 170 / 230 / 230 / 235°C Extrusion temperature of resin composition layer (C): feeding section / compression section / metering section / die=170 / 230 / 230 / 235°C Extrusion temperature of other resin layer (D): feeding section / compression section / metering section / die = 235 / 240 / 240 / 235°C Extruder: Polyolefin layer (A): 32φ extruder GT-32-A (manufactured by Plastics Technology Research Institute Co., Ltd.) Adhesive resin layer (B): 25φ extruder P25-18-AC type (Osaka Seiki Kogyo Co., Ltd.) Resin composition layer (C) and other resin layer (D) 20φ extruder, laboratory machine ME type CO-EXT (manufactured by Toyo Seiki Seisakusho Co., Ltd.) T-die: 300mm wide, 4 types, 7 layers (manufactured by Plastics Technology Research Institute Co., Ltd.) Cooling roll temperature: 80℃ Take-up speed: 1.5m / min The obtained multilayer structure was subjected to various evaluations, and the results are shown in Table 4.

[0105] In all Examples and Comparative Examples, the polyolefin resin contained in the polyolefin layer (A), the adhesive resin contained in the adhesive resin layer (B), and the EVOH contained in the resin composition layer (C) had melting points in the range of 155° C. or higher and 200° C. or lower. AFM measurements were performed only in some Examples and Comparative Examples.

[0106] The components in Tables 1 to 4 are as follows: mLLDPE-1: Prime Polymer "Evolue SP0510" mLLDPE-2: Prime Polymer "Evolue SP1510" mLLDPE-3: Prime Polymer "Evolue SP4510" HDPE: "Novatec HB332E" manufactured by Japan Polyethylene Corporation St-Ca: Calcium stearate St-Mg: Magnesium stearate St-Zn: Zinc stearate St-Co: Cobalt stearate St-OH: stearic acid

[0107] [Table 1]

[0108] [Table 2]

[0109] [Table 3]

[0110] [Table 4]

[0111] The results in Tables 1 to 4 show that the multilayer structures of each Example were excellent in film appearance, mechanical strength, viscosity change during kneading (stable moldability), and recyclability. On the other hand, the multilayer structures of Comparative Examples 1, 4, and 5, in which a resin composition layer containing no or only trace amounts of polyvalent metal ions (c2) was formed instead of the resin composition layer (C), exhibited poor film appearance. The multilayer structure of Comparative Example 2, in which a layer consisting solely of high-density polyethylene "Novatec HB332E" manufactured by Japan Polyethylene Corporation was formed instead of the polyolefin layer (A), exhibited poor puncture strength. The multilayer structure of Comparative Example 3, in which a resin composition layer containing an excess amount of polyvalent metal ions (c2) was formed instead of the resin composition layer (C), exhibited a large change in viscosity when the resin composition was melt-kneaded, resulting in poor stability during molding. The multilayer structure of Comparative Example 6, in which a polyamide layer was formed as the other resin layer (D), exhibited poor recyclability due to the generation of numerous particles when the recovered multilayer structure was melt-kneaded and reused.

Claims

1. A multilayer structure having a polyolefin layer (A), an adhesive resin layer (B), and a resin composition layer (C), a polyolefin layer (A) is laminated on at least one surface of the resin composition layer (C) via an adhesive resin layer (B); It does not have a layer whose main component is a resin having a melting point of 210°C or higher and a metal layer whose thickness is 1 μm or more, The resin as the main component constituting the polyolefin layer (A) has a density of 0.850 g / cm ３ 0.940g / cm or more ３ The following polyolefin resins: the resin composition layer (C) contains an ethylene-vinyl alcohol copolymer (c1) and a polyvalent metal ion (c2); the ethylene-vinyl alcohol copolymer (c1) has an ethylene unit content of 20 mol% or more and 50 mol% or less and a saponification degree of 90 mol% or more; the content of the polyvalent metal ion (c2) in the resin composition layer (C) is 10 ppm or more and 400 ppm or less; the polyvalent metal ion (c2) is at least one selected from the group consisting of magnesium ions, calcium ions, zinc ions, cobalt ions, and manganese ions; The polyvalent metal ion (c2) is contained as a cation of a higher fatty acid metal salt, the resin composition layer (C) further contains phosphate ions (c4) and alkali metal ions (c5); the content of phosphate ions (c4) in the resin composition layer (C) is 5 ppm or more and 200 ppm or less, and the content of alkali metal ions (c5) in the resin composition layer (C) is 10 ppm or more and 400 ppm or less; A multilayer structure, wherein the content ratio (c4 / c5) of phosphate ions (c4) to alkali metal ions (c5) is 0.01 or more and 2 or less, and the content ratio (c2 / c5) of polyvalent metal ions (c2) to alkali metal ions (c5) is 0.1 or more and 5 or less.

2. 2. The multilayer structure according to claim 1, wherein the multilayer structure has a film shape having a longitudinal direction and a width direction, and the ratio (Cmin / Cmax) of the minimum thickness Cmin of the resin composition layer (C) to the maximum thickness Cmax observed in a range of 45% to 55% of a cross section in the width direction, where the position of one end in the width direction is 0% and the position of the other end is 100%, is 0.70 or more.

3. At least a portion of the ethylene-vinyl alcohol copolymer (c1) has at least one of a carboxylic acid unit (I) and a lactone ring unit (II) located at a polymer terminal, the total content (i+ii) of the carboxylic acid unit (I) and the lactone ring unit (II) per gram of the ethylene-vinyl alcohol copolymer (c1) is 14 μmol / g or more and 78 μmol / g or less; 3. The multilayer structure according to claim 1, wherein the ratio (ii / (i+ii)) of the content (ii) of the lactone ring unit (II) to the total content (i+ii) of the carboxylic acid unit (I) and the lactone ring unit (II) is 40 mol% or more.

4. the resin composition layer (C) further contains aluminum ions (c3), 4. The multilayer structure according to claim 1, wherein the content of aluminum ions (c3) in the resin composition layer (C) is 5 ppb or more and 500 ppb or less.

5. 5. The multilayer structure according to claim 1, wherein the content ratio of the polyvalent metal ions (c2) to the phosphate ions (c4) is 1 or more and 15 or less.

6. 6. The multilayer structure according to claim 1, wherein the thickness of a region at the interface between the adhesive resin layer (B) and the resin composition layer (C) where the modulus of elasticity is 0.4 GPa or more and 0.8 GPa or less as measured and analyzed with an atomic force microscope is 50 nm or less.

7. 7. The multilayer structure according to claim 1, wherein the polyolefin resin constituting the polyolefin layer (A) is a linear low-density polyethylene.

8. 8. The multilayer structure of claim 7, wherein the linear low density polyethylene is a metallocene-catalyzed polyethylene.

9. 9. The multilayer structure according to claim 1, wherein the ratio of the thickness of the polyolefin layer (A) to the total thickness of all layers is 0.75 or more.

10. A packaging material comprising the multilayer structure according to any one of claims 1 to 9.

11. A recycled composition comprising the recycled multilayer structure according to any one of claims 1 to 9.

12. A method for producing a recycled composition, comprising the step of melt-kneading the recycled multilayer structure according to any one of claims 1 to 9.

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