Thermoplastic resin molded products and packaging materials

Abstract

To provide a thermoplastic resin molded body that has oxygen barrier properties required for packaging materials and can maintain delamination strength between a barrier layer and a heat seal layer that does not inhibit heat sealing properties in a packaging material configuration with a multilayer structure.SOLUTION: A thermoplastic molded body 1 of the present invention has an oxygen barrier layer 7 which contains a resin (A) having a water vapor barrier property and a resin (B) having an oxygen barrier property, in which the resin (B) exists as an island in the resin (A) to form a dispersed phase. The existence state of the aspect ratio in the dispersed phase is defined as the area average aspect (Aav=Sa / Ss) derived from the sum of the aspect ratios Sa, where Si is the area of each aspect ratio Ai of the dispersed layer in any thickness cross section in the molding direction and width direction, and Ss, the area of the total dispersed layer in the observation range, and the area average aspect ratio of the oxygen barrier layer 7 is 1 or more and 10 or less in the surface area, and is 5 or more and 40 or less in the central area, and the thickness of the oxygen barrier layer 7 is 20 μm or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a thermoplastic resin molded body and a packaging material having barrier properties.

Background Art

[0002] For packaging materials (packaging films, packages, containers), various resin films and resin molded bodies with excellent gas barrier properties are used from the perspective of protecting the contents. Materials commonly used for packaging materials mainly consist of materials based on olefin resins such as polyethylene (hereinafter referred to as "PE") and polypropylene (hereinafter referred to as "PP"). These olefin resins have excellent barrier properties against water vapor but are inferior in barrier properties against oxygen. On the other hand, hydrophilic resins such as ethylene-vinyl alcohol copolymer (hereinafter referred to as "EVOH") have excellent barrier properties against oxygen but are inferior in barrier properties against water vapor.

[0003] Among the characteristics required for packaging materials, there is heat sealability. In general, in order to obtain heat sealability, the resin on the surface layer needs to be a resin that does not inhibit heat sealability and a layer structure is required.

[0004] Among the barrier properties required for packaging materials, the compatibility of oxygen barrier properties and water vapor barrier properties is mentioned. Conventionally, in order to achieve compatibility of oxygen and water vapor, multiple resins having oxygen barrier properties and resins having water vapor barrier properties are laminated. Also, by arranging a layer specialized for heat sealability on the surface, the characteristics required for the packaging material have been obtained. In Patent Documents 1, 2, and 3, techniques for obtaining barrier properties by forming a sea-island structure of a barrier dispersant are disclosed. Also, in Patent Document 4, a technique for achieving both barrier properties and heat sealability by lamination is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, when barrier dispersions are structured in a sea-island configuration, it is necessary to select an appropriate shape to obtain both barrier properties and adhesion (peel strength) between heat-seal layers. When achieving barrier properties through lamination, there are issues with adhesion between each laminated film and the complexity of the manufacturing process. Furthermore, when a composite material is composed of polyolefin resins such as PE or PP for the surface layer and compatibilizers such as acid modifiers for EVOH or MXD nylon for the intermediate layer, there are problems with the adhesion between each layer of the laminated film and the complexity of the manufacturing process. Furthermore, when mixing materials with oxygen barrier properties and materials with water vapor barrier properties to obtain oxygen barrier properties, simply mixing them in a molten blend does not provide sufficient oxygen barrier properties, and the oxygen barrier material can hinder heat sealing. In addition, when a multilayer structure is formed by laminating an oxygen barrier layer and a heat-sealable layer using a mixture of oxygen barrier and water vapor barrier materials, insufficient peel strength at the layer interface can hinder heat sealing.

[0007] The present invention has been made in view of the above problems, and aims to provide a thermoplastic resin molded article and a packaging material using the same, characterized by improving the peel strength of the oxygen barrier layer / heat seal layer interface in order to obtain excellent oxygen barrier properties and the heat seal properties required for packaging, even when a multilayer structure of two or more layers is formed with a heat seal layer / oxygen barrier layer, by dispersing a material with excellent oxygen barrier properties in a material with excellent water vapor barrier properties and controlling the state of existence of the dispersed phase in the depth direction within the oxygen barrier layer. [Means for solving the problem]

[0008] To solve the above problems, a thermoplastic resin molded article according to one aspect of this disclosure has a multilayer structure including at least an oxygen barrier layer having oxygen barrier properties, The oxygen barrier layer comprises a resin (A) having water vapor barrier properties and a resin (B) having oxygen barrier properties. The oxygen barrier resin exists as islands within the water vapor barrier resin, forming a dispersed phase. The dispersed phase has different aspects (long axis length / short axis length) distributions depending on the depth in the thickness direction of the oxygen barrier layer. The state of existence of the aforementioned dispersed phase aspect ratio is such that the area of ​​each aspect ratio Ai of the dispersed layer in an arbitrary thickness cross-section in the molding direction and width direction is Si. The sum of aspect ratios Sa, weighted by the area of ​​each of the n (n = number of dispersed phases within the observed range) dispersed phases, is defined by the following equation (1): The total area Ss of the dispersion layers within the observation range is defined by the following equation (2): The area-average aspect ratio Aav, defined as Aav = Sa / Ss, In the surface region of the oxygen barrier layer, the value is between 1 and 10, and in the central region, it is between 5 and 40. The main point is that the thickness of the oxygen barrier layer is 20 μm or more.

[0009]

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[0010]

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[0011] To solve the above problems, the gist of the packaging material according to one aspect of this disclosure is that the thermoplastic resin molded body is made using a thermoplastic resin molded body. [Effects of the Invention]

[0012] Regarding a thermoplastic resin molded body and a packaging material using the same according to one aspect of the present disclosure, when a multilayer structure having a functional sharing with a heat seal layer / oxygen barrier layer is arranged, by controlling the dispersed existence state in the thickness direction of an ethylene-vinyl alcohol copolymer having oxygen barrier properties, it is possible to provide a thermoplastic resin molded body and a packaging material using the same that have the oxygen barrier properties required for the packaging material and can improve the peel strength between an oxygen barrier layer and a layer having a grounding interface necessary for expressing the heat seal properties required for the packaging material.

Brief Description of the Drawings

[0013] [Figure 1] It is a schematic diagram schematically showing a configuration example of a thermoplastic resin molded body according to this embodiment. [Figure 2] It is a cross-sectional view schematically showing a configuration example of a thermoplastic resin molded body according to this embodiment.

Modes for Carrying Out the Invention

[0014] An embodiment of the present disclosure will be described while referring to the drawings. Hereinafter, the present invention will be described in detail. The configurations shown in the drawings are schematic, and the sizes, shapes, etc. of each part are exaggerated as appropriate for easy understanding. Also, the embodiments shown below are examples of configurations for embodying the technical idea of the present invention, and the technical idea of the present invention is not limited to the following in terms of the material, shape, structure, etc. of the components. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

[0015] The basic configuration of the thermoplastic resin molded body according to this embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic diagram for explaining a configuration example of a thermoplastic resin molded body 1 according to this embodiment. The thermoplastic resin molded body 1 is composed of a heat-sealable resin layer (heat-seal layer 6) made of a polyolefin-based thermoplastic resin (A), a water vapor barrier resin, a functional group resin, and an oxygen barrier resin layer 3. In particular, the oxygen barrier layer 7 in the thermoplastic resin molded body 1 in this embodiment comprises a water vapor barrier polyolefin-based thermoplastic resin (A), a copolymer (C) of an olefin and a functional group-containing monomer, and an ethylene-vinyl alcohol copolymer (B) having oxygen barrier properties. As shown in Figure 1, the oxygen barrier layer 7 has a core-shell structure in which the copolymer (C) 4 of an olefin and a functional group-containing monomer encases the ethylene-vinyl alcohol copolymer (B) 5, which exists as an island in the continuous phase 3 containing the polyolefin-based thermoplastic resin (A).

[0016] In addition to polyolefin-based thermoplastic resins (A), copolymers of olefins and functional group-containing monomers (C), and ethylene-vinyl alcohol copolymers (B), the thermoplastic resin molded body 1 may also contain additives such as nucleating agents and reinforcing fillers. Examples of nucleating agents and reinforcing fillers include metals such as talc, silica, clay, montmorillonite, calcium carbonate, lithium alumina carbonate, titanium dioxide, aluminum, iron, silver, and copper; hydroxides such as aluminum hydroxide and magnesium hydroxide; celluloses such as cellulose microfibrils and cellulose acetate; fibrous fillers such as glass fibers, polyethylene terephthalate fibers, nylon fibers, polyethylene naphthalate fibers, aramid fibers, vinylon fibers, and polyacrylate fibers; and carbons such as carbon nanotubes. These may be used individually or in combination of two or more.

[0017] Furthermore, the thermoplastic resin molded body 1 may contain additives such as antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, flame retardants, and flame retardant aids. Examples of antioxidants include phenolic compounds, organic phosphite compounds, and thioether compounds. Examples of heat stabilizers include hindered amine compounds. Examples of ultraviolet absorbers include benzophenone compounds, benzotriazole compounds, and benzoate compounds. Examples of antistatic agents include nonionic compounds, cationic compounds, and anionic compounds. Examples of flame retardants include halogen compounds, phosphorus compounds, nitrogen compounds, inorganic compounds, boron compounds, silicone compounds, sulfur compounds, and red phosphorus compounds. Examples of flame retardant aids include antimony compounds, zinc compounds, bismuth compounds, magnesium hydroxide, and clayey silicates. These may be used individually or in combination of two or more.

[0018] In addition, the thermoplastic resin molded body 1 may contain additives such as weathering agents, light stabilizers, plasticizers, slip agents, antiblocking agents, antifogging agents, lubricants, pigments, dyes, dispersants, copper damage inhibitors, neutralizing agents, anti-bubble agents, weld strength improvers, natural oils, synthetic oils, and waxes. These may be used individually or in combination of two or more.

[0019] The thermoplastic resin molded body 1 may be used not only in a two-layer structure, but also as a laminate with other types of resin molded bodies.

[0020] (Continuous phase) The continuous phase 3 is composed of a resin having water vapor barrier properties. As the main material of the continuous phase 3, since the thermoplastic resin molded body 1 is formed by an extrusion molding machine capable of heating up to 340°C, any general thermoplastic resin can be used. However, in order to be suitable for use as a packaging material, it needs to have appropriate flexibility and good processability. In this embodiment, the continuous phase 3 is mainly composed of a polyolefin-based thermoplastic resin (A) with excellent water vapor barrier properties.

[0021] <Polyolefin-based thermoplastic resin> The polyolefin-based thermoplastic resin (A) can be any polymer having constituent units derived from olefins, and can be selected and used as appropriate from among olefin-based polypropylenes such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) obtained by copolymerizing α-olefin and ethylene, medium-density polyethylene (MDPE), high-density polyethylene (HDPE), homopolymers, random copolymers, block copolymers, etc., cycloolefin polymers, cycloolefin copolymers obtained by copolymerizing cycloolefins and olefins, and ethylene-vinyl acetate copolymers obtained by copolymerizing the above olefins with vinyl acetate, or ethylene-methyl acrylate copolymers (EMA), ethylene-ethyl acrylate copolymers (EEA), ethylene-butyl acrylate copolymers (EBA), ethylene-methacrylic acid copolymers (EMAA), etc., obtained by modifying the side chains of olefins, either individually or in combination.

[0022] (Heat seal layer) The heat seal layer 6 can be made by selecting and using, as appropriate, a single or multiple polyolefin-based thermoplastic resins (A) from the above-mentioned polyolefin-based thermoplastic resins (A).

[0023] (Oxygen barrier layer) The blending ratio of the polyolefin-based thermoplastic resin (A) is preferably 40% to 85% by mass relative to the total mass of the thermoplastic resin molded body 1, and it is even more preferable that the total of the polyolefin-based thermoplastic resin (A) and the copolymer (C) of olefin and functional group-containing monomer is 50% by mass or more. When the blending ratio of the polyolefin-based thermoplastic resin (A) is 85% by mass or less, a sufficient amount of ethylene-vinyl alcohol copolymer (B) can be ensured, improving the barrier properties. When the proportion of ethylene-vinyl alcohol copolymer (B) is 50% by mass or more, the so-called sea-island structure reverses. That is, EVOH becomes a continuous phase and easily absorbs water vapor, and since EVOH that has absorbed water vapor generally has reduced oxygen barrier properties, it is necessary to avoid this sea-island reversal phenomenon.

[0024] (Oxygen barrier layer - dispersed phase) As shown in Figure 1, the dispersed phase 2 exists dispersed within the continuous phase 3. The islands of the dispersed phase are dispersed in the surface region with an area-average aspect ratio of 1 to 10, and in the central region with an aspect ratio of 5 to 25. Furthermore, the thickness of the surface region is 5% to 25% of the total oxygen barrier layer thickness, while the thickness of the central region is 75% to 95% of the total oxygen barrier layer thickness. Furthermore, the dispersed phase 2 comprises a resin having oxygen barrier properties and a resin having functional groups. In this embodiment, the dispersed phase 2 may take the form of a core-shell structure comprising an ethylene-vinyl alcohol copolymer (B) with excellent oxygen barrier properties and a copolymer (C) of an olefin and a functional group-containing monomer. As shown in Figure 1, the dispersed phase 2 may be a core-shell structure in which the copolymer (B) of an olefin and a functional group-containing monomer encases the ethylene-vinyl alcohol copolymer (C), or a core-only structure.

[0025] <Copolymer of olefin and functional group-containing monomer> The copolymer (C) of olefin and functional group-containing monomer is a material that is incompatible with the polyolefin-based thermoplastic resin (A) and the ethylene-vinyl alcohol copolymer (B) described later. Therefore, when mixed, it reduces the interfacial tension between the two polymers and stabilizes the phase separation structure. The copolymer (C) of olefin and functional group-containing monomer is a different resin from the polyolefin-based thermoplastic resin (A) that constitutes continuous phase 3. It is a copolymer thermoplastic resin with a molecular structure that has been given reactive groups that can bond with the ethylene-vinyl alcohol copolymer (B), and functions as a compatibilizer that improves the affinity between the olefin-based resin and the ethylene-vinyl alcohol copolymer, which have poor chemical compatibility. Examples of thermoplastic resins that function as compatibilizers include ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-vinyl alcohol copolymer (EVOH), ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl methacrylate copolymer (EMMA), and maleic acid-modified polyolefin (hereinafter referred to as "PO-g-MAH"). In this embodiment, a copolymer (C) of an olefin and a functional group-containing monomer is used as the resin having a functional group, but it is not limited to this. For example, resins having hydroxyl groups, carbonyl groups, etc., can be used as the resin having a functional group.

[0026] The blending ratio of the copolymer (C) of olefin and functional group-containing monomer in the oxygen barrier layer 7, that is, the content of the copolymer (C) of olefin and functional group-containing monomer, is preferably 0.5% by mass or more and 15% by mass or less relative to the total mass of the thermoplastic resin molded body 1. When the blending ratio of the copolymer (C) of olefin and functional group-containing monomer is 0.5% by mass or more, it is present between the polyolefin-based thermoplastic resin (A) and the ethylene-vinyl alcohol copolymer (B), reducing the interfacial tension with the polyolefin-based thermoplastic resin (A), suppressing the occurrence of delamination between the polyolefin-based thermoplastic resin (A) and the ethylene-vinyl alcohol copolymer (B), and improving barrier properties. When the blending ratio of the copolymer (C) of olefin and functional group-containing monomer is 15% by mass or less, it prevents the dispersion size of (B) from becoming small, and in particular, improves oxygen barrier properties by obtaining barrier properties due to the labyrinth effect in the central region of the oxygen barrier layer 7.

[0027] <Ethylene-vinyl alcohol copolymer> Ethylene-vinyl alcohol copolymer (EVOH)(B) can be produced by saponifying ethylene-vinyl acetate copolymer (EVA), which is obtained by radical polymerization of ethylene and vinyl acetate. The oxygen barrier properties of ethylene-vinyl alcohol copolymer (EVOH) are improved by a lower ethylene content, a higher degree of hydrolysis or saponification, or high crystallinity. It is preferable to use an ethylene-vinyl alcohol copolymer having an ethylene component ratio of 20-50 mol% and a degree of hydrolysis of 90% or more.

[0028] The blending ratio of ethylene-vinyl alcohol copolymer (B) is preferably in the range of 15% to 50% by mass relative to the total mass of the thermoplastic resin molded body. If the blending ratio of ethylene-vinyl alcohol copolymer (B) is 50% by mass or less, the dispersed phase can form as islands in the continuous phase. If it is less than 15% by mass, the overlap of the dispersed phase tends to be insufficient, and as a result, the barrier properties due to the labyrinth effect may also be insufficient. Furthermore, the mass percentage of the oxygen barrier resin (B) is more preferably in the range of 15% by mass or more and 40% by mass or less, relative to the total mass of the thermoplastic resin molded body.

[0029] In the core-shell structure of dispersed phase 2, the ethylene-vinyl alcohol copolymer (B) exhibits an area-average aspect ratio of 1 to 10 in the surface or front-back layer region, which is between 5% and 25% of the total thickness of the oxygen barrier layer, in the cross-section of the thickness portion in the molding direction Dm and molding width direction Dw of the oxygen barrier layer 7 as shown in Figure 2. In the central region, which is between 75% and 95% of the total thickness of the oxygen barrier layer, the area-average aspect ratio is between 5 and 40.

[0030]

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[0031] Specifically, when the area of ​​each aspect ratio Ai of the dispersed layer in an arbitrary thickness cross-section in the molding direction Dm and width direction Dw is Si, The sum of aspect ratios Sa, weighted by the area of ​​each of the n (n = number of dispersed phases within the observed range) dispersed phases, is defined by the following equation (1): The total area Ss of the dispersion layers within the observation range is defined by the following equation (2): The area-average aspect ratio Aav, defined as Aav = Sa / Ss, In the surface region of the oxygen barrier layer 7, the value is between 1 and 10, and in the central region, it is between 5 and 40.

[0032]

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[0033]

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[0034] In the surface region, the ethylene-vinyl alcohol copolymer (B) provides a low barrier effect when the area-average aspect ratio Aav is 1 or greater, and maintains the peel strength at the interface with the heat seal layer 6 to the strength required for heat sealing when the area-average aspect ratio Aav is 10 or less.

[0035] In the central region, when the area-average aspect ratio is 5 or higher, high barrier properties can be achieved through the labyrinth effect. When the area-average aspect ratio exceeds 40, the dispersion is insufficient, and the number of dispersed phases decreases, resulting in very large distances between dispersed phases, making it difficult to form an effective labyrinth structure. A stable labyrinth structure can be formed when the area-average aspect ratio is between 5 and 25.

[0036] If the thickness of the surface region is less than 5% of the total thickness of the oxygen barrier layer, it reduces the peel strength at the heat seal layer interface and impairs heat sealing performance. If it exceeds 25%, it impairs oxygen barrier performance. If the thickness of the central region is less than 75%, it cannot provide sufficient oxygen barrier performance.

[0037] The overall thickness of the oxygen barrier layer 7 must exceed 20 μm; if it is less than 20 μm, the water vapor barrier properties will be insufficient.

[0038] Furthermore, the content of resin (A) having water vapor barrier properties in the surface region and the intermediate region may be 75% by mass or more, and the content of resin (C) having functional groups may be 10% by mass or less. By adopting such a composition ratio, the water vapor barrier properties can be improved.

[0039] (Method for manufacturing thermoplastic resin molded products) The method for producing the thermoplastic resin molded article of this embodiment is not particularly limited, and known methods can be used.

[0040] As for the method of producing the molded body, it is possible to use an injection molding machine, an extrusion molding machine, a method of forming a film with a T-die via a feed block or multi-manifold, or a film formation method using the inflation method. In this embodiment, a method of forming a film using an extrusion molding machine will be described.

[0041] In this embodiment, the thermoplastic resin molded body 1 described above is formed by co-extrusion molding. The thermoplastic resin molded body 1 is produced by mixing the above-mentioned thermoplastic resin and extruding the oxygen barrier layer 7 and heat seal layer 3, and then bonding them using a feed block method. The extrusion molding machine has a compression mechanism such as a breaker plate that promotes pressure increase to load the resin after the resin has passed through the screw.

[0042] Regarding the method of cooling the film, it is possible to use methods similar to those used in the molding machine described above. For example, in the T-die method, there are no particular restrictions on the cooling method, such as air cooling methods using an air chamber, vacuum chamber, or air knife, or water cooling methods such as dipping a cooling roll into a chilled water pan. However, when imparting surface irregularities through shaping, a method is particularly preferred in which molten resin is introduced into a contact area between a nip roll made of silicone rubber, NBR rubber, or fluororesin and a cooling roll made of machined metal, under a pressure of 0.1 MPa or higher, and then cooled.

[0043] The thermoplastic resin molded product obtained by this embodiment can be used as a single film or laminated with other substrates to form a packaging material. When used as a single film or laminate, it can be used for standing pouches, as well as three-sided pouches, gusseted pouches, spout pouches, beak pouches, etc. Furthermore, there are no particular restrictions on the manufacturing method of the packaging bag.

[0044] As described above, in both cases of single-film use and lamination with other substrates, surface modification treatments can be appropriately performed to improve suitability for post-processing. For example, surface modification treatments can be performed on the surface that comes into contact with other substrates to improve printability when using a single film, or to improve lamination suitability when using a laminate. Suitable surface modification treatments include methods that oxidize the film surface to express functional groups, such as corona discharge treatment, plasma treatment, and flame treatment, as well as wet processes such as coating with an easily adhesive layer.

[0045] (packaging material) One embodiment of the present invention is a packaging material formed using the thermoplastic resin molded body 1 described above. This configuration provides the necessary oxygen barrier properties for a packaging material, and allows for the effective use of a thermoplastic resin molded body in the form of a packaging material, while maintaining close contact between the barrier layer and the heat seal layer without hindering heat sealing. [Examples]

[0046] The following describes in detail some embodiments of the present invention, but the present invention is not limited to these embodiments.

[0047] (Example 1) For both the heat seal layer and the oxygen barrier layer, Prime Polymer Co., Ltd.'s homopolypropylene resin F-300SP was used as the polyolefin-based thermoplastic resin (A). Furthermore, for both the surface and central regions of the oxygen barrier layer in contact with the heat seal surface, Mitsubishi Chemical Corporation's EVOH resin Soanol D2908 (ethylene ratio 29 mol%) was used as the ethylene-vinyl alcohol copolymer (B). For the surface layer, Mitsui Chemicals, Inc.'s maleic anhydride-modified polypropylene Admer QE060 was used as the copolymer (B) of olefin and functional group-containing monomer. For the intermediate layer, Mitsui Dow Polychemical Co., Ltd.'s EVA resin Evaflex EV450 was used as the copolymer (B) of olefin and functional group-containing monomer.

[0048] The materials for the surface and central regions were a polyolefin-based thermoplastic resin (A), a copolymer of olefin and functional group-containing monomer (C), and an ethylene-vinyl alcohol copolymer (B). The mixing ratio (mass%) of each was adjusted to (A):(B):(C) = 49.5:50:0.5, dry-blended, and fed into two single-screw extruders. For the heat-seal layer, the polyolefin-based thermoplastic resin (A) alone was fed into a different single-screw extruder. The flow path was set to pass through a compression section with a compression ratio of 65% after the screw section. The layers were multilayered using a feed-block method to create a heat-seal layer / surface region / central region structure with thicknesses of 10 μm / 1 μm / 19 μm for each layer. The film was then manufactured by the T-die-casting method at a molding temperature of 250°C.

[0049] (Example 2) The film of Example 2 was formed in the same manner as in Example 1, except that the thickness of the surface region of the oxygen barrier layer was 5 μm and the thickness of the central region was 15 μm.

[0050] (Example 3) The film of Example 3 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=40:50:10.

[0051] (Example 4) The film of Example 4 was formed in the same manner as in Example 3, except that the thickness of the surface region of the oxygen barrier layer was 5 μm and the thickness of the central region was 15 μm.

[0052] (Example 5) The film of Example 5 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C) = 84.5:15:0.5.

[0053] (Example 6) The film of Example 6 was formed in the same manner as in Example 5, except that the thickness of the surface region of the oxygen barrier layer was 5 μm and the thickness of the central region was 15 μm.

[0054] (Example 7) The film of Example 6 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=75:15:10.

[0055] (Example 8) The film of Example 8 was formed in the same manner as in Example 7, except that the thickness of the surface region of the oxygen barrier layer was 5 μm and the thickness of the central region was 15 μm.

[0056] (Example 9) The film of Example 9 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C) = 84.5:15:0.5 for the surface region and (A):(B):(C) = 75:15:10 for the central region.

[0057] (Example 10) The film of Example 10 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to surface region (A):(B):(C) = 75:15:10 and central region (A):(B):(C) = 84.5:15:0.5.

[0058] (Example 11) The film of Example 11 was formed in the same manner as in Example 1, except that the surface region / central region was set to 3 μm / 27 μm.

[0059] (Example 12) The film of Example 12 was formed in the same manner as in Example 1, except that the surface region / central region was set to 1 μm / 29 μm.

[0060] (Example 13) The film of Example 13 was formed in the same manner as in Example 1, except that the surface region / central region was set to 8 μm / 27 μm.

[0061] (Example 14) The film of Example 14 was formed in the same manner as in Example 1, except that the surface region / central region was 1 μm / 29 μm, and the mixing ratio was adjusted to surface region (A):(B):(C) = 80:10:10 and central region (A):(B):(C) = 80:10:0.5.

[0062] (Example 15) The film of Example 15 was formed in the same manner as in Example 1, except that the surface region / central region was 8 μm / 27 μm, and the mixing ratio was adjusted to surface region (A):(B):(C) = 80:10:10 and central region (A):(B):(C) = 80:10:0.5.

[0063] (Comparative Example 1) A film of Comparative Example 1 was formed in the same manner as in Example 1, except that EVA resin Evaflex EV450 manufactured by Mitsui Dow Polychemical Co., Ltd. was used as the copolymer (B) of olefin and functional group-containing monomer for the surface layer.

[0064] (Comparative Example 2) The film of Comparative Example 2 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=45:55:0.

[0065] (Comparative Example 3) The film of Comparative Example 3 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=90:10:0.

[0066] (Comparative Example 4) The film of Comparative Example 4 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=100:0:0.

[0067] (Comparative Example 5) The film of Comparative Example 5 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=0:100:0.

[0068] (Comparative Example 6) The film of Comparative Example 6 was formed in the same manner as in Example 1, except that the thickness of the surface region was adjusted to 0 μm and the thickness of the central region to 20 μm.

[0069] (Comparative Example 7) A film of Comparative Example 7 was formed in the same manner as in Example 1, except that the surface region was composed solely of a polyolefin-based thermoplastic resin (A).

[0070] (Comparative Example 8) A film of Comparative Example 8 was formed in the same manner as in Example 1, except that the surface region consisted solely of EVOH resin Soanol D2908 (ethylene ratio 29 mol%) manufactured by Mitsubishi Chemical Corporation as the ethylene-vinyl alcohol copolymer (B).

[0071] (Comparative Example 9) In the central region, Admer QE060, a maleic anhydride-modified polypropylene manufactured by Mitsui Chemicals, Inc., was used as the copolymer (B) of the olefin and the functional group-containing monomer, and the mixing ratio was adjusted to (A):(B):(C) = 45:50:5. The film of Comparative Example 9 was formed in the same manner as in Example 1.

[0072] (Comparative Example 10) Comparative Example 10 was formed in the same manner as in Example 1, except that the total thickness of the barrier layer was adjusted to 19 μm, the thickness of the surface region to 1 μm, and the thickness of the central region to 18 μm.

[0073] <evaluation> The films obtained in Examples 1-15 and Comparative Examples 1-10 described above were evaluated as follows.

[0074] [Cross-sectional measurement of ethylene-vinyl alcohol copolymer (B)] Next, the cross-sectional area of ​​the ethylene-vinyl alcohol copolymer (C) was measured. Cross-sectional observation of the ethylene-vinyl alcohol copolymer (C) in the molding direction and molding width direction was performed by cutting out films of the examples and comparative examples to 2 mm × 5 mm (2 mm observation area), embedding them in JEOL Ltd.'s visible light curable embedding resin D-800, and then cross-sectioning with a glass knife and diamond knife using a Leica Microsystems ultramicrotome EM UC7i. Ten locations were randomly selected for cutting the observation test specimens in both the molding direction and molding width direction of each film. A Hitachi High-Technologies scanning electron microscope (SEM) S-4800 was used for observation, and after obtaining 3000x and 100,000x observation images, the cross-sectional area of ​​20 randomly selected dispersed phases in the images was measured. The aspect ratio was measured for the long axis length, short axis length, and aspect ratio of the cross-section of 20 similarly randomly selected dispersed phases.

[0075] [Oxygen barrier performance evaluation] The films obtained in the examples and comparative examples were cut to A4 size, and the oxygen permeability (cc / m³) was measured as a comparison with polypropylene alone using the GTR-3000 high-sensitivity water vapor permeability measuring device manufactured by GTR Tech Co., Ltd. at 30°C in a dry environment. 2 The oxygen permeability (day·atm) was measured. The measured oxygen permeability (measurement sample / polypropylene alone) was evaluated on a four-point scale: ◎, ○, △, and ×. An evaluation of ◎, ○, or △ according to the evaluation criteria below is considered to have achieved the objective of the present invention.

[0076] <Evaluation Criteria> ◎: When the oxygen permeability is 0.02 (1 / 50) or less compared to polypropylene alone. ○: When the oxygen permeability is 0.05 (1 / 20) or less compared to polypropylene alone. △: When the oxygen permeability is 0.1 (1 / 10) or less compared to polypropylene alone. ×: When the oxygen permeability is greater than 0.05 compared to polypropylene alone.

[0077] [Water vapor barrier properties] The films obtained in the examples and comparative examples were cut to A4 size, and the water vapor transmission rate (g / m³) was measured using the GTR-3000 high-sensitivity water vapor transmission rate measuring device manufactured by GTR Tech Co., Ltd. at 40°C and 90% RH compared to polypropylene alone. 2 The water vapor permeability ( / day) was measured. The measured water vapor permeability was evaluated on a four-point scale (◎, ○, △, ×) for (polypropylene alone / measured sample).

[0078] <Evaluation Criteria> ◎: When the water vapor transmission rate is 0.7 or higher. ○: When the water vapor transmission rate is 0.5 or higher. △: When the water vapor transmission rate is 0.3 or higher. ×: When the water vapor transmission rate is less than 0.5.

[0079] [Peel strength between heat seal layer and oxygen barrier layer - evaluation criteria] A heat seal test was conducted, and in n=5 tests, samples that did not experience delamination at the heat seal layer / oxygen barrier layer interface in all 5 tests were marked with ○, samples that did not experience delamination in 2 or more tests were marked with △, and all others were marked with ×.

[0080] (Heat seal test conditions) Following the method described in JIS Z0238, two sample films were prepared, with the heat-sealed surfaces facing each other. The two samples were then sandwiched between 12 μm PET sheets, and the upper seal bar was heated to 180°C. After heat sealing for 1 second, the samples were measured.

[0081] (Evaluation results) Tables 1-4 show the evaluation results for oxygen barrier properties, water vapor barrier properties, and peel strength between the heat seal layer and the oxygen barrier layer for each example and comparative example.

[0082] [Table 1]

[0083] [Table 2]

[0084] [Table 3]

[0085] [Table 4]

[0086] Examples 1 to 15 demonstrated oxygen barrier properties, water vapor barrier properties, and good peel strength between the heat seal layer and the oxygen barrier layer.

[0087] In Comparative Example 1, the dispersed phase in the surface region became coarser, reducing the peel strength between the heat seal layers, thus inhibiting the heat sealability.

[0088] In Comparative Example 2, homopropylene resin was dispersed in both the surface and central regions, resulting in a failure to obtain a water vapor barrier and a decrease in peel strength between heat seal layers, thus hindering heat sealability.

[0089] In Comparative Example 3, the dispersed phase in the surface region became coarser, which reduced the peel strength of the heat seal correlation and inhibited the heat sealability.

[0090] In Comparative Examples 4 and 5, a single resin phase was formed, and oxygen barrier or water vapor barrier properties were not obtained. In particular, when only an EVOH layer was formed, the peel strength between the heat seal layers was reduced, and the heat sealability was impaired.

[0091] In Comparative Example 6, the heat seal layer interface became the central layer, and since the central layer requires oxygen barrier properties, the dispersed phase became coarser. This coarsening of the dispersed phase reduced the peel strength between the heat seal layers, hindering the heat sealability.

[0092] In Comparative Example 7, since the surface region consisted solely of polypropylene, the peel strength between the surface region and the central region decreased, thus hindering the heat sealability.

[0093] In Comparative Example 8, the surface region was composed of EVOH, which reduced the peel strength between heat seal layers and impaired heat sealability. Furthermore, the reduced polypropylene content resulted in decreased water vapor barrier properties.

[0094] In Comparative Example 9, sufficient oxygen barrier properties were not obtained because the area-average aspect ratio of the dispersed phase in the central region was low.

[0095] In Comparative Example 10, the overall thickness of the oxygen barrier layer was reduced, resulting in a decrease in water vapor barrier properties due to the reduction in the amount of polypropylene.

[0096] Furthermore, the thermoplastic resin molded articles and packaging materials using the thermoplastic resin molded articles described herein are not limited to the embodiments and examples described above, and various modifications are possible as long as they do not impair the features of the invention. [Explanation of Symbols]

[0097] 1... Thermoplastic resin molded body 2. Dispersed phase (Copolymer of olefin and functional group-containing monomer (C) and ethylene-vinyl alcohol copolymer (B)) 3. Continuous phase (polyolefin-based thermoplastic resin (A)) 4. Copolymer of olefin and functional group-containing monomer (C) 5. Ethylene-vinyl alcohol copolymer (B) 6. Heat seal layer 7. Oxygen barrier layer

Claims

1. It has a multilayer structure including at least an oxygen barrier layer having oxygen barrier properties, The oxygen barrier layer comprises a resin (A) having water vapor barrier properties and a resin (B) having oxygen barrier properties. The oxygen barrier resin exists as islands within the water vapor barrier resin, forming a dispersed phase. The dispersed phase has different aspects (long axis length / short axis length) distributions depending on the depth in the thickness direction of the oxygen barrier layer. The state of existence of the aforementioned dispersed phase aspect ratio is such that the area of ​​each aspect ratio Ai of the dispersed layer in an arbitrary thickness cross-section in the molding direction and width direction is Si. The sum of aspect ratios Sa, weighted by the area of ​​each of the n (n = number of dispersed phases within the observed range) dispersed phases, is defined by the following equation (1): The total area Ss of the dispersed layers within the observation range is defined by the following equation (2): The area-average aspect ratio Aav, defined as Aav = Sa / Ss, In the surface region of the oxygen barrier layer, the value is 1 to 10, and in the central region, it is 5 to 40. A thermoplastic resin molded article characterized in that the thickness of the oxygen barrier layer is 20 μm or more. [Math 1] [Math 2]

2. The thermoplastic resin molded article according to claim 1, characterized in that the oxygen barrier resin (B) forming the dispersed phase is divided into at least two regions: the surface region and the central region of the oxygen barrier layer.

3. The thermoplastic resin molded article according to claim 1 or 2, characterized in that the thickness of the surface region is 5% or more and 25% or less of the total oxygen barrier layer.

4. The thermoplastic resin molded article according to any one of claims 1 to 3, characterized in that the thickness of the central region is 75% or more and 95% or less of the total oxygen barrier layer.

5. The thermoplastic resin molded article according to any one of claims 1 to 4, characterized in that the content of the oxygen barrier resin (B) in the surface region and the central region is 15% by mass or more and 50% by mass or less.

6. The oxygen barrier layer further comprises a resin (C) having a functional group, which includes a copolymer of an olefin and a functional group-containing monomer. The resin (C) having the functional group is a different resin from the resin (A) having water vapor barrier properties. The functional group has a reactive group that can bond with the oxygen barrier resin (B), A thermoplastic resin molded article according to any one of claims 1 to 5, characterized in that the resin (C) having the functional group forms a core-shell structure in which the resin (B) having oxygen barrier properties is encased.

7. The thermoplastic resin molded article according to claim 6, characterized in that the content of the water vapor barrier resin (A) in each of the surface region and the central region is 75% by mass or more, and the content of the functional group resin (C) is 10% by mass or less.

8. A packaging material characterized by being made using a thermoplastic resin molded body according to any one of claims 1 to 7.

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