JP7707569B2 - Thermoplastic resin moldings and packaging materials - Google Patents

Description

The present invention relates to a thermoplastic resin molded body and a packaging material.

From the perspective of protecting the contents, various resin films and resin moldings with excellent gas barrier properties are used in packaging materials (packaging films, packages, containers). Materials commonly used in packaging materials are mainly composed of olefin resins such as polyethylene (hereinafter "PE") and polypropylene (hereinafter "PP"), and these olefin resins have excellent barrier properties against water vapor but poor barrier properties against oxygen. On the other hand, hydrophilic resins such as ethylene-vinyl alcohol copolymer (hereinafter "EVOH") have excellent barrier properties against oxygen but poor barrier properties against water vapor.

The barrier properties required for packaging materials include both oxygen barrier properties and water vapor barrier properties, but traditionally, barrier properties that combine oxygen and water vapor have been achieved by laminating multiple resins with oxygen barrier properties and water vapor barrier properties. In Patent Document 1, both barrier properties are achieved by laminating, but there are problems with adhesion between each layer of laminated film and the complexity of the manufacturing process.

In Patent Document 2, the surface layer is made of a polyolefin resin such as PE or PP, the middle layer is made of EVOH, and the MXD nylon is composited with a compatibilizer such as an acid modification, resulting in a laminate, which, like Patent Document 1, has problems with adhesion and a complicated manufacturing process.

Japanese Patent Application Publication No. 10-080984 JP 2008-150539 A

When mixing a material with oxygen barrier properties and a material with water vapor barrier properties, which is a method of achieving both oxygen and water vapor barrier properties, there is a problem in that sufficient oxygen barrier properties cannot be obtained by simply melt blending the materials together.

The present invention aims to provide a thermoplastic resin molded body and a packaging material using the same, which can optimize the maze effect, which is effective in providing an oxygen barrier, by dispersing a material with excellent oxygen barrier properties in a material with excellent water vapor barrier properties and controlling the shape of the oxygen barrier resin, which is the dispersed phase.

In order to solve the above problems, a thermoplastic resin molded body according to one embodiment of the present disclosure and a packaging material using the same contain a resin having water vapor barrier properties, a resin having functional groups, and a resin having oxygen barrier properties, the resin having the functional groups is a resin different from the resin having water vapor barrier properties, the functional groups have reactive groups capable of bonding with the resin having oxygen barrier properties, and the core-shell structure in which the resin having functional groups encapsulates the resin having oxygen barrier properties forms a dispersed phase that exists as islands in the resin having water vapor barrier properties.

The thermoplastic resin molded body according to one embodiment of the present disclosure and the packaging material using the same can provide a thermoplastic resin molded body and a packaging material using the same that have the oxygen barrier properties required for packaging materials, as well as the impact resistance and heat seal performance required for packaging materials, by controlling the dispersion shape of the ethylene-vinyl alcohol copolymer that has oxygen barrier properties.

FIG. 1 is a schematic diagram showing a configuration example of a thermoplastic resin molded body according to an embodiment of the present invention. FIG. 1 is a cross-sectional view illustrating a schematic configuration example of a thermoplastic resin molded body according to an embodiment of the present invention.

An embodiment of the present disclosure will be described with reference to the drawings.
The present invention will be described in detail below. Note that the configurations shown in the drawings are schematic, and the size and shape of each part are appropriately exaggerated to facilitate understanding. Furthermore, 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 materials, shapes, structures, etc. of the components described below. The technical idea of the present invention can be modified in various ways within the technical scope defined by the claims.

(Configuration of thermoplastic resin molded body)
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 one configuration example of a thermoplastic resin molded body 1 according to this embodiment.
The thermoplastic resin molded body 1 contains a resin having water vapor barrier properties, a resin having functional groups, and a resin having oxygen barrier properties. In particular, the thermoplastic resin molded body 1 in this embodiment includes a polyolefin-based thermoplastic resin (A) having water vapor barrier properties, a copolymer (B) of an olefin and a functional group-containing monomer, and an ethylene-vinyl alcohol copolymer (C) having oxygen barrier properties. As shown in FIG. 1, the thermoplastic resin molded body 1 includes 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), forming a dispersed phase 2 that exists as islands in a continuous phase 3 containing the polyolefin-based thermoplastic resin (A).

Figure 2 is a cross-sectional view for explaining one configuration example of the thermoplastic resin molded body 1 according to this embodiment. In the thermoplastic resin molded body 1 of this embodiment, as shown in Figure 2, in both the cross section of the thickness part in the molding direction Dm and the cross section of the thickness part in the molding width direction Dw, a copolymer (B) of an olefin and a functional group-containing monomer containing an ethylene-vinyl alcohol copolymer (C) is dispersed inside the polyolefin-based thermoplastic resin (A) that serves as the base phase.

In addition to the polyolefin thermoplastic resin (A), the copolymer of an olefin and a functional group-containing monomer (B), and the ethylene-vinyl alcohol copolymer (C), additives such as a nucleating agent and a reinforcing filler may be used in the thermoplastic resin molded body 1. Examples of the nucleating agent and the reinforcing filler include talc, silica, clay, montmorillonite, calcium carbonate, lithium alumina carbonate, titanium oxide, metals such as 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 alone or in combination of two or more.

Additives such as antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, flame retardants, and flame retardant assistants may be blended into the thermoplastic resin molded body 1. 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 assistants include antimony compounds, zinc compounds, bismuth compounds, magnesium hydroxide, and clay silicates. These may be used alone or in combination of two or more.

Additives such as weathering agents, light stabilizers, plasticizers, slip agents, antiblocking agents, antifogging agents, lubricants, pigments, dyes, dispersants, copper damage inhibitors, neutralizing agents, bubble inhibitors, weld strength improvers, natural oils, synthetic oils, and waxes may also be used in the thermoplastic resin molded body 1. These may be used alone or in combination of two or more.

The thermoplastic resin molded body 1 of the present invention may be used not only as a single layer, but also as a laminate with other types of resin molded bodies.

(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, any general thermoplastic resin can be used since the thermoplastic resin molded body 1 is formed into a film by an extrusion molding machine capable of heating up to 340°C, but in order to be suitably used as a packaging material, it is necessary that the resin has a suitable flexibility and good processability. In this embodiment, the continuous phase 3 is mainly made of a polyolefin-based thermoplastic resin (A) having excellent water vapor barrier properties.

<Polyolefin-based thermoplastic resin>
The polyolefin-based thermoplastic resin (A) may be any polymer having a structural unit derived from an olefin, and may be appropriately selected from among olefin-based low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) obtained by copolymerizing α-olefin and ethylene, medium-density polyethylene (MDPE), high-density polyethylene (HDPE), polypropylene having a homopolymer, random copolymer, block copolymer, or the like, cycloolefin polymer, cycloolefin copolymer obtained by copolymerizing cycloolefin and olefin, and ethylene-vinyl acetate copolymer obtained by copolymerizing the above-mentioned olefin and vinyl acetate, and ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-methacrylic acid copolymer (EMAA), and the like obtained by modifying the side chain of olefin, and may be used alone or in combination as appropriate.

The blending ratio of polyolefin-based thermoplastic resin (A) is preferably 40% by mass or more and 79.5% by mass or less with respect to the total mass of the thermoplastic resin molded body 1. When the blending ratio of polyolefin-based thermoplastic resin (A) is 40% by mass or more, by suppressing an increase in the blending amount of ethylene-vinyl alcohol copolymer (C), it is possible to prevent a decrease in heat sealability, ensure high flexibility, and improve impact resistance. Also, when the blending ratio of polyolefin-based thermoplastic resin (A) is 79.5% by mass or less, it is possible to ensure a sufficient blending amount of ethylene-vinyl alcohol copolymer (C) and improve barrier properties.

(dispersed phase)
As shown in Fig. 1, the dispersed phase 2 is present so as to be dispersed in the continuous phase 3. The dispersed phase 2 includes a resin having oxygen barrier properties and a resin having a functional group. In this embodiment, the dispersed phase 2 is configured to include an ethylene-vinyl alcohol copolymer (C) having excellent oxygen barrier properties, and a copolymer (B) of an olefin and a functional group-containing monomer. As shown in Fig. 1, the dispersed phase 2 has 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).

<Copolymer of Olefin and Functional Group-Containing Monomer>
The copolymer (B) of an olefin and a functional group-containing monomer reduces the interfacial tension between the two polymers during mixing, and stabilizes the phase separation structure, since the polyolefin thermoplastic resin (A) and the ethylene-vinyl alcohol copolymer (C) described later are incompatible materials. The copolymer (B) of an olefin and a functional group-containing monomer is a resin different from the polyolefin thermoplastic resin (A) constituting the continuous phase 3, and is a copolymer thermoplastic resin having a molecular structure to which a reactive group capable of bonding with the ethylene-vinyl alcohol copolymer (C) is added, and functions as a compatibilizer that plays a role in improving the affinity between the olefin resin and the ethylene-vinyl alcohol copolymer, which are chemically incompatible. Examples of the thermoplastic resin that functions as a compatibilizer include 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), maleic acid modified polyolefin (hereinafter "PO-g-MAH"), etc. In this embodiment, the copolymer (B) of an olefin and a functional group-containing monomer is used as the resin having a functional group, but is not limited thereto. For example, a resin having a hydroxyl group, a carbonyl group, or the like can be used as the resin having a functional group.

The total blending ratio of the polyolefin thermoplastic resin (A) and the copolymer (B) of an olefin and a functional group-containing monomer is preferably 50% by mass or more and 80% by mass or less with respect to the total mass of the thermoplastic resin molded body 1. When the total blending ratio of the polyolefin thermoplastic resin (A) and the copolymer (B) of an olefin and a functional group-containing monomer is 50% by mass or more, by suppressing an increase in the blending ratio of the ethylene-vinyl alcohol copolymer (C), it is possible to prevent a decrease in heat sealability, ensure high flexibility, and improve impact resistance. In addition, when the total blending ratio of the polyolefin thermoplastic resin (A) and the copolymer (B) of an olefin and a functional group-containing monomer is 80% by mass or less, it is possible to ensure a sufficient amount of the ethylene-vinyl alcohol copolymer (C) and improve barrier properties.

In addition, the blending ratio of the copolymer (B) of olefin and functional group-containing monomer in the thermoplastic resin molded body 1, i.e., the content of the copolymer (B) of olefin and functional group-containing monomer, is preferably 0.5% by mass or more and 10% by mass or less with respect to the total mass of the thermoplastic resin molded body 1. When the blending ratio of the copolymer (B) of olefin and functional group-containing monomer is 0.5% by mass or more, it is possible to prevent the interface energy between the polyolefin thermoplastic resin (A) and the ethylene-vinyl alcohol copolymer (C) from decreasing, and also to suppress the occurrence of delamination between the polyolefin thermoplastic resin (A) and the ethylene-vinyl alcohol copolymer (C), thereby improving the barrier property. When the blending ratio of the copolymer (B) of olefin and functional group-containing monomer is 10% by mass or less, it is possible to prevent the dispersion size of (C) from becoming small, and to obtain barrier property due to the maze effect, thereby improving the oxygen barrier property.

<Ethylene-vinyl alcohol copolymer>
The ethylene-vinyl alcohol copolymer (EVOH) (C) can be produced by saponifying an ethylene-vinyl acetate copolymer (EVA) obtained by radical polymerization of ethylene and vinyl acetate, etc. The oxygen barrier property of the ethylene-vinyl alcohol copolymer (EVOH) is improved by a lower ethylene content, a high degree of hydrolysis or saponification, and high crystallinity, and it is preferable to use an ethylene-vinyl alcohol copolymer having an ethylene component ratio of 20 to 50 mol % and a degree of hydrolysis of 90% or more.

The blending ratio of the ethylene-vinyl alcohol copolymer (C) is preferably in the range of 20% by mass or more and 50% by mass or less with respect to the total mass of the thermoplastic resin molded body. If the blending ratio of the ethylene-vinyl alcohol copolymer (C) is 50% by mass or less, a dispersed phase can be formed as islands in the continuous phase. In addition, by making the mass ratio smaller than that of the polyolefin-based thermoplastic resin (A) which is the main phase, the inversion of the sea and islands can be prevented, and impact resistance can be ensured without impairing the flexibility as a packaging material. Furthermore, if the blending ratio of the ethylene-vinyl alcohol copolymer (C) is 50% by mass or less, an increase in the proportion of the ethylene-vinyl alcohol copolymer appearing on the packaging material surface can be prevented, and high heat sealability can be ensured when used as a packaging film material. If the blending ratio of the ethylene-vinyl alcohol copolymer (C) is 20% by mass or more, a decrease in the presence ratio of the ethylene-vinyl alcohol copolymer (C) can be prevented, thereby improving the barrier property obtained by the maze effect.

The ethylene-vinyl alcohol copolymer (C) in the core-shell structure of the dispersed phase 2 has a cross-sectional area of 4 μm ² or more and 400 μm ² or less in a cross section of the thickness portion in the molding direction Dm of the thermoplastic resin molded body 1 as shown in FIG. 2. Similarly, the ethylene-vinyl alcohol copolymer (C) has a cross-sectional area of 4 μm ² or more and 400 μm ² or less in a cross section of the thickness portion in the molding width direction Dw of the thermoplastic resin molded body 1. When the cross-sectional area of the ethylene-vinyl alcohol copolymer (C) is 4 μm ² or more, high barrier properties can be obtained due to the labyrinth effect. When the cross-sectional area of the ethylene-vinyl alcohol copolymer (C) is 400 μm ² or less, impact resistance can be ensured without impairing flexibility as a packaging material.

As shown in FIG. 1, when the long axis length of the ethylene-vinyl alcohol copolymer (C) is d1 and the short axis length is d2, the aspect ratio in the molding direction Dm of the ethylene-vinyl alcohol copolymer (C), i.e., the ratio of the long axis length d1 to the short axis length d2 of the ethylene-vinyl alcohol copolymer (C), is within the range of 15 to 100, and the aspect ratio in the molding width direction Dw is within the range of 15 to 100. If the aspect ratio of the ethylene-vinyl alcohol copolymer (C) in the molding direction Dm and in the molding width direction Dw is within the range of 15 to 100, it is advantageous for the formation of a labyrinth structure and the barrier properties are improved.

(Method for producing thermoplastic resin molded body)
The method for producing the thermoplastic resin molded body of this embodiment is not particularly limited, and any known method can be used.

Methods for producing molded bodies include injection molding machines, extrusion molding machines, and film-forming methods using a T-die via a feed block or multi-manifold, as well as film-forming methods using the inflation method. In this embodiment, a film-like molding method using an extrusion molding machine will be described.

In this embodiment, the thermoplastic resin of the present invention is mixed and extruded in an extrusion molding machine to produce the thermoplastic resin molded body 1 of the present invention. The extrusion molding machine has a compression mechanism such as a breaker plate that applies a load to the resin and promotes pressure increase after the resin passes through the screw.

The film can be cooled in a manner similar to that of the molding machine described above. For example, in the T-die method, there are no particular limitations on the air-cooling method, such as an air chamber, vacuum chamber, or air knife, or the water-cooling method, such as dipping a cooling roll in a cold water pan. However, when imparting a surface irregularity by shaping, it is particularly preferable to apply a pressure of 0.1 MPa or more between a nip roll made of silicone rubber, NBR rubber, or fluororesin, and a cooling roll made of machined metal, and then flow molten resin into the contact area to cool it.

The film form of the thermoplastic resin molded product obtained by the present invention can be used as a packaging material either alone or by laminating it with another substrate. When used as a single film or a laminate, it can be used for three-sided bags, palm-shaped bags, gusseted bags, pouches with spouts, pouches with beaks, etc. in addition to standing pouches. There are no particular limitations on the manufacturing style of the packaging bag.

As mentioned above, in both cases of a standalone film and a film laminated with another substrate, it is possible to carry out a surface modification treatment to improve suitability for subsequent processes as appropriate. For example, it is possible to carry out a surface modification treatment on the surface that comes into contact with another substrate to improve printability when using a standalone film, and lamination suitability when using a laminate. For the surface modification treatment, methods that develop functional groups by oxidizing the film surface, such as corona discharge treatment, plasma treatment, and frame treatment, and modification by a wet process, such as coating an easy-adhesion layer, can be suitably used.

(packaging material)
The packaging material according to one embodiment of the present invention is formed using the above-described thermoplastic resin molded body 1. By configuring in this manner, the thermoplastic resin molded body has the oxygen barrier property required for a packaging material, and also has high impact resistance and heat sealability, and can be effectively used in the form of a packaging material.

<Effects of this embodiment>
The above-described thermoplastic resin molded body 1 has the following effects.
(1) The thermoplastic resin molded body 1 of the present disclosure contains a resin (A) having water vapor barrier properties, a resin (B) having functional groups, and a resin (C) having oxygen barrier properties.
This allows the thermoplastic resin molded body 1 to have both water vapor barrier properties and oxygen barrier properties.

(2) The resin (B) having a functional group of the present disclosure is a resin different from the resin (A) having water vapor barrier properties, and the functional group has a reactive group that can bond with the resin (C) having oxygen barrier properties.
This reduces the interfacial tension between the resin (A) having water vapor barrier properties and the resin (C) having oxygen barrier properties in the thermoplastic resin molded body 1, thereby stabilizing the phase separation structure.

(3) In the thermoplastic resin molded body 1 of the present disclosure, a core-shell structure in which a resin (B) having functional groups encapsulates a resin (C) having oxygen barrier properties forms a dispersed phase that exists as islands in a resin (A) having water vapor barrier properties.
This allows the thermoplastic resin molded body 1 to optimize the labyrinth effect, which is effective as an oxygen barrier.

The following describes in detail the examples of the present invention, but the present invention is not limited to the following examples.

Example 1
As the resin used for the polyolefin thermoplastic resin (A), homopolypropylene resin F-300SP manufactured by Prime Polymer Co., Ltd. was used. In addition, as the copolymer (B) of an olefin and a functional group-containing monomer, Admer QE060, a maleic anhydride-modified polypropylene manufactured by Mitsui Chemicals, Inc., was used. And as the ethylene-vinyl alcohol copolymer (C), EVOH resin Soarnol D2908 (ethylene ratio 29 mol%) manufactured by Mitsubishi Chemical Co., Ltd. was used. The mixing ratios (mass%) of the polyolefin thermoplastic resin (A), the copolymer (B) of an olefin and a functional group-containing monomer, and the ethylene-vinyl alcohol copolymer (C) were adjusted to (A):(B):(C) = 49.5:0.5:50, dry blended, and fed into a single-screw extruder. A flow path was set so that the screw section passed through a compression section with a compression ratio of 65%, and a film having a thickness of 100 μm was formed by a T-die casting method at a molding temperature of 250 ° C.
In this manner, the film of Example 1 was formed.

Example 2
A film of Example 2 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=40:10:50.

Example 3
A 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)=79.5:0.5:20.

Example 4
A film of Example 4 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=70:10:20.

Example 5
A 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)=45:5:50.

Example 6
A 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)=75:5:20.

(Example 7)
A film of Example 7 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=62:20:18.

(Example 8)
A film of Example 8 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=60:20:20.

(Example 9)
A 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)=72:10:18.

(Example 10)
A film of Example 10 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=49.7:0.3:50.

Example 11
A film of Example 11 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=79.7:0.3:20.

Example 12
A film of Example 12 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=39:11:50.

Example 13
A film of Example 13 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=69:11:20.

(Example 14)
A film of Example 14 was formed in the same manner as in Example 1, except that the mixing ratio was adjusted to (A):(B):(C)=84.5:0.5:15.

(Comparative Example 1)
A film of Comparative Example 1 was formed in the same manner as in Example 1, except that the copolymer (B) of an olefin and a functional group-containing monomer was not used and the mixing ratio was adjusted to (A):(C) = 50:50.

(Comparative Example 2)
A film of Comparative Example 2 was formed in the same manner as in Example 1, except that the copolymer (B) of an olefin and a functional group-containing monomer was not used and the mixing ratio was adjusted to (A):(C) = 80:20.

(Comparative Example 3)
A 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)=44.5:0.5:55.

(Comparative Example 4)
A film of Comparative Example 4 was formed in the same manner as in Example 1, except that the copolymer of olefin and functional group-containing monomer (B) and the ethylene-vinyl alcohol copolymer (C) were not used, and only the polyolefin-based thermoplastic resin (A) was used.

<Evaluation>
The films obtained in the above-mentioned Examples 1 to 14 and Comparative Examples 1 to 4 were subjected to the following evaluations.

[Measurement of Dispersion Profile of Mass Proportion of Ethylene-Vinyl Alcohol Copolymer (C)]
The long axis length, short axis length and aspect ratio of the ethylene-vinyl alcohol copolymer (C) were measured. The shape of the dispersed phase was observed using a scanning electron microscope (SEM) S-4800 manufactured by Hitachi High-Technologies Corporation, and an image was obtained at a magnification of 1000 times. The average long axis dispersion diameter (long axis length) and short axis dispersion diameter (short axis length) of each of 20 dispersed phases randomly selected in the image were calculated. The ratio of the measured long axis length to the short axis length (long axis length/short axis length) was taken as the aspect ratio.

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 the films of the examples and comparative examples to 2 mm x 5 mm (2 mm observation area), embedding them in visible light curable embedding resin D-800 manufactured by JEOL Ltd., and cutting out the cross-section with a glass knife and a diamond knife using an ultramicrotome EM UC7i manufactured by Leica Microsystems. The observation specimens were cut out at 10 randomly selected locations in both the film molding direction and molding width direction. For the observation, a scanning electron microscope (SEM) S-4800 manufactured by Hitachi High-Technologies was used to obtain 3,000x and 100,000x observation images, and then the cross-sectional areas of 20 randomly selected dispersed phases in the images were measured.

[Oxygen Barrier Property Evaluation]
The films obtained in the examples and comparative examples were cut to A4 size, and the oxygen permeability (cc/ ^m2 /day/atm) was measured in a dry environment at 30°C relative to polypropylene alone using a highly sensitive water vapor permeability measuring device GTR-3000 manufactured by GTR Tech Co., Ltd. The measured oxygen permeability was evaluated using the following three levels: ◎, ◯, and △.
<Evaluation criteria>
⊚: Oxygen permeability is 0.02 (1/50) or less.
◯: Oxygen permeability is 0.05 (1/20) or less.
Δ: Oxygen permeability is in the range of 0.1 or more and less than 0.6.

[Impact resistance performance evaluation]
In the impact resistance evaluation, a drop bag evaluation was carried out. The details of the drop bag evaluation are explained below.
A 12 μm thick PET (PTMB-12 manufactured by Unitika Co., Ltd.), a 15 μm thick ONy (ON#15 manufactured by Unitika Co., Ltd.), and the film obtained in the examples and comparative examples were laminated and dry laminated to prepare a three-layered sample. The sample was laminated using an adhesive (A626/A-50 manufactured by Mitsui Chemicals, Inc., main agent or curing agent) to prepare a sample. This sample was cut to prepare two samples with outer dimensions of 130×200 mm and inner dimensions of 90×160 mm. Two samples were stacked, and one side of the longitudinal end and two sides of both lateral ends were heat sealed over a width of 5 mm with a heat sealer under conditions of 200° C., 0.15 MPa, and 1 second to prepare a pouch with one side of the longitudinal end open. Next, 150 ml of water at 5° C. was filled as the contents from the opening of the pouch. Thereafter, the opening was heat sealed over a width of 5 mm using a heat sealer under conditions of 200° C., 0.15 MPa, and 1 second to hermetically seal the pouch.

The sealed pouch was put into a high-temperature, high-pressure cooking sterilizer, and then subjected to high-temperature steam retort treatment. The pouch after the retort treatment was stored in a refrigerator. The pouch was then taken out of the refrigerator and dropped horizontally from a height of 150 cm. The number of drops was 30, and the number of pouches dropped horizontally was 20. After the 30 horizontal drops, each of the 20 pouches was visually checked for breakage. The drop strength was evaluated in the following three stages: ◎, ○, and ×.
<Evaluation criteria>
◎: Non-broken pouch rate (proportion of unbroken pouches) is 70% or more of the total. ○: Non-broken pouch rate is 60% or more and less than 70% of the total. ×: Non-broken pouch rate is less than 60% of the total.

[Evaluation of heat sealability]
The heat sealability was evaluated by overlapping the front or back surfaces of the films obtained in the Examples and Comparative Examples with each other and sealing them with a heat sealer (model number TP-701-B) manufactured by Tester Sangyo under a sealing pressure of 0.2 MPa, a sealing time of 1 second, a sealing width of 10 mm, and a sealing temperature of 180° C. The sealed films were cut into pieces of 15 mm width x 100 mm, and the seal strength was measured when peeled at 180° T-shape using a tensile tester (model number AGS-500NX) manufactured by Shimadzu Corporation with a chuck distance of 50 mm and a pulling speed of 300 mm/min. The measured seal strength was evaluated on the following three levels: ◯, △, and ×.
<Evaluation criteria>
◯: When the seal strength is 10.0 N or more △: When the seal strength is 9.0 N or more ×: When the seal strength is less than 9.0 N, it is marked as ×.

(Evaluation Results)
The film configurations of the examples and comparative examples are shown in Table 1. The oxygen barrier properties, impact resistance, and heat sealability of the examples and comparative examples are shown in Table 2.

As shown in Tables 1 and 2, the evaluation results of Examples 1 to 14 and Comparative Examples 1 and 2 show that when the copolymer (B) of an olefin and a functional group-containing monomer is included as in Examples 1 to 14, the oxygen barrier properties are higher than when the copolymer (B) of an olefin and a functional group-containing monomer is not included as in Comparative Examples 1 and 2, because the copolymer (B) of an olefin and a functional group-containing monomer plays a role in compatibilizing the parent phase and the dispersed phase.

In addition, the evaluation results of Examples 1 to 14 and Comparative Example 3 showed that when the polyolefin thermoplastic resin (A) exists as a continuous phase and the ethylene-vinyl alcohol copolymer (C) exists as a dispersed phase, as in Examples 1 to 14, the impact resistance and heat sealability were higher than when the polyolefin thermoplastic resin (A) changed to a continuous phase and the ethylene-vinyl alcohol copolymer (C) changed to a dispersed phase, as in Comparative Example 3.

In addition, the evaluation results for Examples 1 to 14 and Comparative Example 4 showed that when ethylene-vinyl alcohol copolymer (C) was included as in Examples 1 to 14, the oxygen barrier properties were higher than when ethylene-vinyl alcohol copolymer (C) was not included as in Comparative Examples 1 and 2.

In addition, from the evaluation results of Examples 1 to 9, 12 to 14 and Examples 10 and 11, it was found that when the copolymer (B) of an olefin and a functional group-containing monomer is contained at 0.5 mass% or more as in Examples 1 to 9, 12 to 14, the occurrence of delamination is prevented and impact resistance is high compared to when the copolymer (B) of an olefin and a functional group-containing monomer is not contained at 0.5 mass% or more as in Examples 10 and 11.

In addition, from the evaluation results of Examples 1 to 11, 14 and Examples 12 and 13, it was found that when the copolymer (B) of an olefin and a functional group-containing monomer is contained at 10% by mass or less as in Examples 1 to 11, 14, the aspect ratio of the dispersed phase does not become too small by preventing fine dispersion of the dispersed phase, and high oxygen barrier properties are provided, compared to when the copolymer (B) of an olefin and a functional group-containing monomer is not contained at 10% by mass or more as in Examples 12 and 13.

The thermoplastic resin molded body and packaging material using the thermoplastic resin molded body disclosed herein are not limited to the above-mentioned embodiments and examples, and various modifications are possible within the scope that does not impair the characteristics of the invention.

1: Thermoplastic resin molded body 2: Dispersed phase (copolymer (B) of olefin and functional group-containing monomer and ethylene-vinyl alcohol copolymer (C))
3: Continuous phase (polyolefin-based thermoplastic resin (A))
4: Copolymer of olefin and functional group-containing monomer (B)
5: Ethylene-vinyl alcohol copolymer (C)

Claims (7)

The resin includes a resin having water vapor barrier properties, a resin having functional groups, and a resin having oxygen barrier properties,
the resin having a functional group is a resin different from the resin having water vapor barrier property, and the functional group has a reactive group capable of bonding with the resin having oxygen barrier property,
the core-shell structure in which the resin having the functional group envelops the resin having oxygen barrier property forms a dispersed phase that exists as islands in the resin having water vapor barrier property,
The resin having water vapor barrier properties includes a polyolefin-based thermoplastic resin,
the resin having oxygen barrier properties contains an ethylene-vinyl alcohol copolymer,
The resin having a functional group includes a copolymer of an olefin and a functional group-containing monomer,
The functional group-containing monomer has a hydroxyl group or a carbonyl group as the functional group,
The resin having oxygen barrier properties in the core-shell structure has an average cross-sectional area per core-shell structure in each of the molding direction and the molding width direction of 4 ^μm2 or more and 400 ^μm2 or less, an aspect ratio in the molding direction of 15 or more and 100 or less, and an aspect ratio in the molding width direction of 15 or more and 100 or less, to form a thermoplastic resin molded product. The resin includes a resin having water vapor barrier properties, a resin having functional groups, and a resin having oxygen barrier properties,
the resin having a functional group is a resin different from the resin having water vapor barrier property, and the functional group has a reactive group capable of bonding with the resin having oxygen barrier property,
the core-shell structure in which the resin having the functional group envelops the resin having oxygen barrier property forms a dispersed phase that exists as islands in the resin having water vapor barrier property,
The resin having water vapor barrier properties includes a polyolefin-based thermoplastic resin,
the resin having oxygen barrier properties contains an ethylene-vinyl alcohol copolymer,
the resin having a functional group is an ethylene-methyl acrylate copolymer, an ethylene-ethyl acrylate copolymer, an ethylene-butyl acrylate copolymer, an ethylene-vinyl alcohol copolymer, an ethylene-methacrylic acid copolymer, an ethylene-methyl methacrylate copolymer, or a maleic acid-modified polyolefin;
The resin having oxygen barrier properties in the core-shell structure has an average cross-sectional area per core-shell structure in each of the molding direction and the molding width direction of 4 ^μm2 or more and 400 ^μm2 or less, an aspect ratio in the molding direction of 15 or more and 100 or less, and an aspect ratio in the molding width direction of 15 or more and 100 or less, to form a thermoplastic resin molded product. The resin includes a resin having water vapor barrier properties, a resin having functional groups, and a resin having oxygen barrier properties,
the resin having a functional group is a resin different from the resin having water vapor barrier property, and the functional group has a reactive group capable of bonding with the resin having oxygen barrier property,
the core-shell structure in which the resin having the functional group envelops the resin having oxygen barrier property forms a dispersed phase that exists as islands in the resin having water vapor barrier property,
The resin having water vapor barrier properties includes a polyolefin-based thermoplastic resin,
the resin having oxygen barrier properties contains an ethylene-vinyl alcohol copolymer,
the resin having a functional group is maleic anhydride-modified polypropylene ,
The resin having oxygen barrier properties in the core-shell structure has an average cross-sectional area per core-shell structure in each of the molding direction and the molding width direction of 4 ^μm2 or more and 400 ^μm2 or less, an aspect ratio in the molding direction of 15 or more and 100 or less, and an aspect ratio in the molding width direction of 15 or more and 100 or less, to form a thermoplastic resin molded product. The resin having oxygen barrier properties in the core-shell structure is such that the average cross-sectional area of the resin having oxygen barrier properties per core-shell structure calculated for 20 randomly selected core-shell structures observed within a cross-sectional observation region of 2 mm x 2 mm in each of the molding direction and molding width direction is 4 μm ² 400 μm or more ² 4. The thermoplastic resin molded body according to claim 1, wherein the thermoplastic resin molded body is within the following range: The thermoplastic resin molded body according to any one of claims 1 to 4, characterized in that the mass ratio of the resin having oxygen barrier properties is within the range of 20 mass% to 50 mass% relative to the mass of the entire thermoplastic resin molded body. the blending ratio of the resin having water vapor barrier properties is 40% by mass or more and 79.5% by mass or less with respect to the total mass of the thermoplastic resin molded body,
The blending ratio of the resin having a functional group is 0.5% by mass or more and 10% by mass or less with respect to the total mass of the thermoplastic resin molded body,
6. The thermoplastic resin molded body according to claim 1, wherein a total blending ratio of the resin having water vapor barrier properties and the resin having a functional group is 50 mass% or more and 80 mass% or less with respect to a total mass of the thermoplastic resin molded body. A packaging material characterized by using a thermoplastic resin molded body according to any one of claims 1 to 6.