JPH1199594A - Multilayer structure for thermoforming and thermoformed container prepared by molding it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a multilayer structure for thermoforming excellent in gas barrier properties, thermoforming properties, dynamical characteristics, and appearance and a thermoformed container. SOLUTION: A resin composition layer which consists of 60-99 wt.% of an ethylene-vinyl alcohol copolymer (EVOH) of 20-60 mol.% ethylene content and of at least 90% degree of saponification and 40-1 wt.% of an ethylene-(meth) acrylic acid copolymer of 1-30 wt.% (meth)acrylic acid content and in which ethylene-(meth)acrylic acid copolymer particles are dispersed in an ethylene-vinyl alcohol matrix and a layer of polystyrene are belongings. It is preferable that the EVOH comprises a mixture of at least two kinds of EVOHs having different ethylene contents and each resin component in the resin composition has a specified dispersion form.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoforming multilayer structure excellent in gas barrier properties, thermoformability, mechanical properties, appearance and the like, and a thermoformed container obtained by thermoforming the same.

[0002]

2. Description of the Related Art Ethylene-vinyl alcohol copolymer (EVOH) is suitably used as a material for packaging contents, such as foods and pharmaceuticals, for which quality is important. There are various forms of packaging containers using such EVOH, and among them, containers obtained by thermoforming a multilayer body having an EVOH layer are widely used.

[0003] In particular, in the field of food packaging, cups and trays that can be eaten and consumed as they are, without having to transfer the contents to another container after purchasing the product at a store, are actively used. . Specifically, a container for packaging jelly, pudding, yogurt, juice, and the like can be given as a typical example. Also, containers such as miso cups that can be used as storage containers without transferring the contents to other containers are used.

[0004] Generally, thermoformed containers are used as these packaging materials. Thermoformed containers require form stability and oxygen barrier properties to maintain the quality of the contents.
Representative examples of resins used from the viewpoint of shape maintenance include:
A homopolymer of polypropylene (hereinafter sometimes abbreviated as "homopolypropylene") having an excellent balance between its rigidity and impact resistance is exemplified. In order to prevent the contents from being oxidized and deteriorated, it is common to use EVOH having excellent oxygen barrier properties as a barrier layer.

[0005] However, when the homopolypropylene is used as the inner and outer layers and the EVOH layer is used as the intermediate layer, the transparency is insufficient, the contents inside are difficult to see, and the impact resistance of the homopolypropylene layer and the EVOH layer is insufficient. The impact resistance of the whole container is insufficient. Furthermore, cracks and wavy patterns may occur on the side surfaces of the container due to insufficient thermoformability of EVOH, and a thermoformed container having excellent appearance may not be obtained. Various proposals have been made such as a method of adding nylon to EVOH (US Pat. No. 4,079,850) to improve the thermoformability and impact resistance, but the thermoformability is not sufficient.
There is a problem in that the gas barrier property is reduced, there is a problem in thermal stability at the time of film formation, or there is a problem in that the transparency is lowered depending on the type and dispersion state of the resin, and thus the method has not been sufficiently improved.

In recent years, as a container for pudding or jelly, a container made of a polystyrene base material having excellent shape retention even when relatively thin and having good gloss has been used. In such a case, for example, when the content is fruit jelly, etc.,
Since a barrier property is required to prevent the taste of the fruit from being impaired, a thermoformed container formed of a laminate of polystyrene and EVOH is also used. However, polystyrene also has a lower temperature suitable for thermoforming as compared with homopolypropylene, so that the thermoformability of the barrier layer, EVOH, is further deteriorated, resulting in cracks and wavy patterns.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermoforming multilayer structure excellent in gas barrier properties, thermoformability, mechanical properties, appearance, and the like, and thermoforming obtained by thermoforming the same. It is to provide a container.

[0008]

The object of the present invention is to provide an ethylene copolymer having an ethylene content of 20 to 60 mol% and a saponification degree of 90% or more.
An ethylene- (meth) acrylic acid copolymer having 60 to 99% by weight of a vinyl alcohol copolymer and 40 to 1% by weight of an ethylene- (meth) acrylic acid copolymer having a (meth) acrylic acid content of 1 to 30% by weight; This is achieved by providing a multilayer structure for thermoforming having a resin composition layer in which ethylene- (meth) acrylic acid copolymer particles are dispersed, and a layer made of polystyrene.

In particular, the EVOH comprises a mixture of two types of EVOH (a) and (b) having different ethylene contents, wherein (a) has an ethylene content of 20 to 45 mol%, (b)
Has an ethylene content of 45 to 65 mol%, the difference between the ethylene contents of (a) and (b) is 8 mol% or more, and the blending weight ratio {(a) / (b)} is 2/1 to 50 / 1 is preferably achieved by providing a thermoformed multilayer structure.

[0010] Further, ethylene- (meth) acrylic acid copolymer particles dispersed in a matrix of EVOH are dispersed in a columnar shape elongated in a uniaxial direction parallel to the surface of the multilayer structure, Also suitable is a thermoforming multilayer structure having an average particle cross-sectional diameter of 0.2 to 1.3 μm when cut along a plane perpendicular to the uniaxial direction.

The object of the present invention is also attained by providing a thermoformed container obtained by thermoforming the above-mentioned multilayer structure. In particular, the total thickness of the thickest portion of the container is set to T μm. Tμ is the total thickness of the thin part
m, when the drawing ratio of the container is S, the following formulas (1) to
This is suitably achieved by providing a thermoformed container that satisfies (3). S ≦ T / t ≦ 20S (1) 300 <T ≦ 3000 (2) t ≧ 100 (3) However, the draw ratio S of the container is a value represented by the following equation (4). S = (depth of the container) / (diameter of the circle having the largest diameter inscribed in the opening of the container) (4)

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The EVOH of the present invention is obtained by saponifying a copolymer comprising ethylene and vinyl ester using an alkali catalyst or the like. As a vinyl ester, vinyl acetate is mentioned as a typical example, but other fatty acid vinyl esters (vinyl propionate, vinyl pivalate, etc.) can also be used.

In the present invention, the ethylene content of EVOH is 20 to 60 mol%, preferably 25 to 50 mol%.
More preferably, it is 25 to 45 mol%. Here, E
When the VOH is composed of a blend of two or more EVOHs having different ethylene contents, the average value calculated from the blending weight ratio is defined as the ethylene content. Ethylene content is 20 mol%
If it is less than 3, the gas barrier property under high humidity is reduced, and the melt moldability is also deteriorated. If it exceeds 60 mol%, sufficient gas barrier properties cannot be obtained.

The degree of saponification of the vinyl ester component of the EVOH of the present invention is 90% or more, preferably 95% or more, more preferably 98% or more. Here, EV
When OH is composed of a mixture of two or more types of EVOH having different degrees of saponification, the average value calculated from the blending weight ratio is defined as the degree of saponification. If the saponification degree is less than 90 mol%, not only does the gas barrier property at high humidity decrease, but also the thermal stability of EVOH deteriorates, and gels are likely to be generated in molded products.

Further, a small amount of another monomer can be copolymerized with the EVOH as long as the object of the present invention is not impaired. Examples of monomers that can be copolymerized include α-olefins such as propylene, butene, isobutene, 4-methylpentene-1, hexene, and octene; and unsaturated carboxylic acids such as itaconic acid, methacrylic acid, acrylic acid, and maleic anhydride. Examples thereof include acids, salts thereof, partial or complete esters thereof, nitriles thereof, amides thereof, anhydrides thereof, vinylsilane compounds such as vinyltrimethoxysilane, unsaturated sulfonic acids, salts thereof, alkylthiols, and vinylpyrrolidone.

In particular, when EVOH contains 0.0002 to 0.2 mol% of a vinylsilane compound as a copolymerization component, the consistency of the melt viscosity with the base resin at the time of coextrusion is improved, and a homogeneous copolymer is obtained. Not only is it possible to produce an extruded multilayer film, but also the dispersibility when EVOHs are used in a blend is improved, and this is also effective in improving moldability and the like. Here, as the vinylsilane-based compound, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (β-methoxy-ethoxy) silane,
γ-methacryloxypropylmethoxysilane and the like. Among them, vinyltrimethoxysilane and vinyltriethoxysilane are preferably used.

The phosphorus compound concentration in the EVOH of the present invention is:
1 to 200 ppm, preferably 2 to 1 ppm in terms of phosphorus element weight
It is preferably from 50 ppm, most preferably from 5 to 100 ppm, from the viewpoint of film forming properties and thermal stability.

Further, the addition of 10 to 500 ppm of alkali metal ions such as sodium ion, potassium ion and lithium ion to EVOH in terms of metal weight enhances the effect of the present invention and improves the interlayer adhesion and compatibility. It is effective for Examples of the alkali metal compound include an aliphatic carboxylate, an aromatic carboxylate, a phosphate, and a metal complex of a monovalent metal. Specific examples thereof include sodium acetate, potassium acetate, sodium phosphate, and phosphoric acid. Lithium, sodium stearate, potassium stearate, sodium ethylenediaminetetraacetate and the like are preferred, and preferred are sodium acetate, potassium acetate and sodium phosphate.

The preferred melt flow rate (MFR) of the EVOH used in the present invention (value measured at 210 ° C. under a load of 2160 g) is preferably 0.1 to 50 g / 10.
Min, optimally between 0.5 and 20 g / 10 min. Here, when the EVOH is composed of a blend of two or more types of EVOH having different melt flow rates, the average value calculated from the blending weight ratio is defined as the melt flow rate.

The EVOH used in the present invention includes two or more EVOHs having different ethylene contents and / or degrees of saponification.
It is preferable to use a blend of OH. In particular, EV
OH is two types of EVOH (a) having different ethylene contents
And (b), wherein the ethylene content of (a) is 20 to 45 mol% and the ethylene content of (b) is 45 to 6 mol%.
5 mol%, the difference between the ethylene contents of (a) and (b) is 8 mol% or more, and the blending weight ratio ((a) / (b))
Is preferably from 2/1 to 50/1 for achieving both good gas barrier properties and thermoformability.

At this time, the ethylene content of the EVOH (a) is preferably 20 to 45 mol%. More preferably, it is 25 to 42 mol%, and still more preferably 30 to 40 mol%.
Mol%. If the ethylene content of the EVOH (a) is less than 20 mol%, the thermoformability deteriorates, and if it exceeds 45 mol%, the gas barrier properties decrease.

The ethylene content of the EVOH (b) is preferably 45 to 65 mol%. More preferably, it is 47 to 62 mol%, and still more preferably 50 to 60 mol%. When the ethylene content of the EVOH (b) is in such a range, the thermoformability is sufficiently improved.

Further, the difference between the ethylene contents of the EVOHs (a) and (b) is preferably at least 8 mol%. It is more preferably at least 12 mol%, even more preferably at least 15 mol%.
Mol% or more. If the difference in the ethylene content of EVOH (a) is less than 8 mol%, the effect of improving thermoformability is small.

It is preferable that the compounding weight ratio {(a) / (b)} of the EVOHs (a) and (b) is 2/1 to 50/1. More preferably, it is 3/1 to 40/1, and still more preferably, it is 4/1 to 30/1. If the compounding weight ratio is less than 2/1, the gas barrier properties decrease, and if it exceeds 50/1, the effect of improving thermoformability is small.

The ethylene- (meth) acrylic acid copolymer used in the present invention refers to a polymer obtained by copolymerizing acrylic acid or methacrylic acid with ethylene as a main component. In the present invention, it does not include a so-called ionomer in which the carboxyl group in the copolymer exists in the form of a salt of a metal such as sodium or zinc. It is not clear why the object of the present invention is not achieved when such an ionomer is used, but it is as shown in Comparative Examples described later.

The (meth) acrylic acid content in the ethylene- (meth) acrylic acid copolymer is from 1 to 30% by weight,
Preferably 2 to 25% by weight, more preferably 3 to 20% by weight
It is. If the (meth) acrylic acid content is less than 1% by weight, the dispersion of the resin particles becomes poor, and the thermoformability deteriorates. If it exceeds 30% by weight, the thermal stability becomes poor.

The ethylene- (meth) used in the present invention
Suitable melt flow rate of acrylic acid copolymer (MF
R) (value measured at 210 ° C. under a load of 2160 g)
Preferably from 0.1 to 80 g / 10 min, optimally from 0.5 to 5
0 g / 10 minutes. In the present invention, the ethylene- (meth) acrylic acid copolymer may be used by blending two or more ethylene- (meth) acrylic acid copolymers having different (meth) acrylic acid contents and / or different MFRs. it can.

The content of EVOH in the resin composition of the present invention is 60 to 99% by weight, preferably 70 to 97% by weight, more preferably 80 to 95% by weight. The content of the ethylene- (meth) acrylic acid copolymer is 1 to 40.
%, Preferably 3 to 30% by weight, more preferably 5 to 20% by weight. When the blending ratio of the ethylene- (meth) acrylic acid copolymer is less than 1% by weight, excellent thermoformability cannot be obtained, and the intersection of the side and bottom portions of the thermoformed container and the corner portion of the thermoformed container cannot be obtained. The wall thickness becomes too thin, and the impact resistance of the molded product decreases. Also, ethylene-
When the blending ratio of the (meth) acrylic acid copolymer is more than 40% by weight, the gas barrier properties are remarkably reduced, and the obtained thermoforming container has a large molding shrinkage, which is not suitable for practical use.

The resin composition of the present invention is one in which ethylene- (meth) acrylic acid copolymer particles are dispersed in a matrix of EVOH. By having such a dispersion form, good gas barrier properties, thermoformability, and mechanical properties can be maintained. When EVOH is dispersed in the matrix of the ethylene- (meth) acrylic acid copolymer or when both resins are connected continuously, the gas barrier property is remarkably reduced.

The melt flow rate (MF) of the EVOH and ethylene- (meth) acrylic acid copolymer used in the present invention
R) (value measured at 210 ° C. under a load of 2160 g) The ratio of EVOH MFR (A) to ethylene- (meth)
MFR (B) ratio (A) / (B) of acrylic acid copolymer
Is preferably 0.1 to 5.0, more preferably 0.15 to 3.0, and most preferably 0.2 to 2.0. By combining resins having MFR ratios in such a range, the resin can be well dispersed and the object of the present invention can be achieved.

The resin composition of the present invention contains a hydrotalcite-based compound, a hindered phenol-based, a hindered amine-based heat stabilizer, a higher aliphatic acid, in order to enhance the effects of the present invention and to improve the melt stability and the like. It is preferable to add one or more metal salts of carboxylic acids (for example, calcium stearate, magnesium stearate, etc.) to the resin composition in an amount of 0.01 to 1% by weight.

Various additives can be added to the resin composition of the present invention, if necessary. Examples of such additives include antioxidants, plasticizers, heat stabilizers, ultraviolet absorbers, antistatic agents, lubricants, colorants, fillers, or other high molecular compounds, and Blends can be blended as long as the effects of the present invention are not impaired. Specific examples of the additives include the following.

Antioxidants: 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4'-thiobis- (6-t-butylphenol), 2,2 '-Methylene-bis- (4-methyl-6-
t-butylphenol), octadecyl-3- (3 ′,
5'-di-t-butyl-4'-hydroxyphenyl) propionate, 4,4'-thiobis- (6-t-butylphenol) and the like.

UV absorber: ethylene-2-cyano-
3,3′-diphenyl acrylate, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole,
2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5 '-Methylphenyl) 5-
Chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone and the like.

Plasticizer: dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, phosphate ester and the like. Antistatic agents: pentaerythritol monostearate, sorbitan monopalmitate, sulfated polyolefins,
Polyethylene oxide, carbowax, etc. Lubricants: ethylene bis stearamide, butyl stearate and the like. Colorants: carbon black, phthalocyanine, quinacridone, indoline, azo pigments, red iron, etc. Filler: glass fiber, asbestos, ballastonite, calcium silicate, etc.

Many other high molecular compounds can be blended to such an extent that the effects of the present invention are not impaired.

In the resin composition of the present invention, it is preferable that ethylene- (meth) acrylic acid copolymer particles having an average particle diameter of 0.3 to 1.5 μm are dispersed in a matrix of EVOH. More preferably, it is 0.3 to 1.0 μm. By having such a dispersion form, good gas barrier properties, thermoformability, mechanical properties, and transparency can be obtained. When the average particle size is larger than 1.5 μm, uneven dispersion in the composition is apt to occur, which causes a problem at the time of thermoforming and tends to lower the gas barrier property. When the average particle size is 0.3 μm or less, the effect of containing the dispersed particles is not utilized in the thermoformability of the composition, and it is difficult to obtain good thermoformability.

Such a dispersion form is mainly observed in the form of pellets as raw materials such as films or sheets. Observation can be performed by scanning electron microscope observation of the fracture surface, transmission electron microscope observation of the thin section, or the like. The outline of the photograph obtained by observation with an electron microscope or the like was specified by image processing, and the particle diameter of each particle was determined from the average of the major axis and the minor axis of the identified particle. The simple average of the particle diameters of the particles thus obtained was defined as the dispersed particle diameter. At this time, in order to eliminate the difference in particle diameter depending on the observation direction, an average value of particles obtained by observation from three directions perpendicular to each other was adopted.

In order to obtain such a dispersed form, the kneading operation in the present invention is important. As a kneader for obtaining a composition having a high degree of dispersion, a continuous kneader such as a continuous intensive mixer or a kneading type twin screw extruder (in the same direction or a different direction) is most suitable. And a batch-type kneader such as an intensive mixer or a pressure kneader. As another continuous kneading device, a device using a rotating disk having a grinding mechanism such as a stone mill, for example, a KCK manufactured by KCK Co., Ltd.
A CK kneading extruder can also be used. Among those usually used as a kneader, a single-screw extruder provided with a kneading section (Dalmage, CTM, etc.) or a simple kneader such as a Brabender mixer can be mentioned.

Among them, the most preferred one for the purpose of the present invention is a continuous intensive mixer. Commercially available models include FCM manufactured by Farrel, CIM manufactured by Japan Steel Works, Ltd., KCM, LCM, ACM manufactured by Kobe Steel Works, Ltd., and the like. In practice, it is preferable to employ a device that has a single screw extruder below these kneaders and that simultaneously performs kneading and extrusion pelletization. Also, a twin-screw kneading extruder having a kneading disk or a kneading rotor, for example, TEX manufactured by Japan Steel Works, ZSK manufactured by Werner & Pfleiderer, TEM manufactured by Toshiba Machine Co., Ltd., PCM manufactured by Ikekai Iron Works Co., Ltd. Are also used for the purpose of kneading in the present invention.

In using these continuous kneaders, the shapes of the rotor and the disk play an important role. In particular, the gap (chip clearance) between the mixing chamber and the rotor chip or the disk chip is important. If the gap is too narrow or too wide, the composition having good dispersibility of the present invention cannot be obtained. 1-5mm as chip clearance
Is optimal.

In order to obtain a composition having good dispersibility according to the present invention, the specific energy of the kneader is 0.1 k.
Wh / kg or more, desirably 0.2 to 0.8 kWh / k
It has been found that kneading with g is best. The specific energy is the energy used for kneading (power consumption; k
W) is obtained by dividing kneading processing amount per hour (kg), and the unit is kWh / kg. It is necessary to knead the mixture at a specific energy higher than the value used in ordinary kneading in order to obtain the composition of the present invention, and in order to make the specific energy 0.1 kWh / kg or more, simply use a kneading machine. It is not sufficient to simply increase the number of revolutions, and it is preferable to cool the kneaded composition by a jacket or the like to lower the temperature and increase the viscosity. If the composition is kneaded with a reduced viscosity, it is difficult to obtain the composition of the present invention. Therefore, it is effective that the kneading temperature is in the range of the melting point of EVOH to the melting point + 40 ° C. at the temperature of the discharged resin at the outlet of the kneading section.

The rotation speed of the rotor of the kneader is 100
~ 1200 rpm, preferably 150 ~ 1000 rpm
m, more preferably in the range of 200 to 800 rpm. The inner diameter (D) of the kneader chamber is 30 mm or more, preferably 50 to 400 mm. The ratio L / D with respect to the chamber length (L) of the kneader is 4
~ 30 is preferred. In addition, one kneading machine may be used,
Two or more can be used in combination.

The longer the kneading time, the better the result.
-600 seconds, preferably 15-200 seconds, optimally 15-150 seconds.

The resin composition obtained as described above is
It is useful as a multilayer structure for thermoforming. The term “thermoforming” as used in the present invention means that a film or a sheet is heated and softened and then formed into a mold. As a forming method, a method of forming into a mold shape using a vacuum or a pressurized air and further using a plug as necessary (straight method, drape method, air slip method, snapback method, plug assist method, etc.) or press forming is used. And the like. Various molding conditions such as the molding temperature, the degree of vacuum, the pressure of the compressed air or the molding speed are appropriately set depending on the shape of the plug, the shape of the mold, the properties of the raw material film or sheet, and the like.

The molding temperature is not particularly limited.
It is sufficient that the temperature is sufficient to soften the resin for molding, but the suitable temperature range varies depending on the raw material film or sheet. For example, when thermoforming a film, the film is not heated to a temperature high enough to cause melting of the film due to heating or to transfer irregularities on the metal surface of the heater plate to the film, but to a temperature low enough for insufficient shaping. Preferably, the film temperature is 50 to 120 ° C, preferably 60 to 110 ° C, more preferably 70 to 100 ° C. On the other hand, when thermoforming a sheet having a thickness greater than that of a film, molding may be possible even at a higher temperature than in the case of a film, and molding is performed in a temperature range of 130 to 180 ° C.

The thermoformed container of the present invention is a three-dimensionally thermoformed container in which a concave portion is formed in the plane of a film or sheet. The shape of the concave portion is determined according to the shape of the contents. In particular, as the depth of the concave portion becomes deeper and the shape of the concave portion becomes less smooth, unevenness in thickness tends to occur in a normal EVOH laminate, and corner portions and the like are formed. Since the thickness becomes extremely thin, the improvement effect of the present invention is large. When the thermoformed container is formed by forming a film, the drawing ratio (S)
Is preferably 0.2 or more, more preferably 0.3 or more, and even more preferably 0.4 or more, the effect of the present invention is more effectively exhibited. When the thermoformed container is formed by forming a sheet thicker than a film, the drawing ratio (S) is preferably 0.3 or more, more preferably 0.5 or more, and still more preferably 0 or more. .8 or more, the effect of the present invention is more effectively exhibited.

Here, the aperture ratio (S) is defined by the following equation (4).
Means the value indicated by S = (depth of the container) / (diameter of the circle having the largest diameter inscribed in the opening of the container) (4) That is, the drawing ratio (S) means the value of the depth of the deepest portion of the container, This is obtained by dividing by the diameter of the largest inscribed circle in contact with the shape of the concave portion (opening) formed in the plane of the sheet. For example, when the shape of the concave portion is a circle, its diameter is obtained, when the shape is an ellipse, its short diameter is obtained, and when it is rectangular, the length of its short side is the diameter of the inscribed maximum circle.

The multilayer structure of the present invention includes the above-mentioned resin composition layer and a layer made of polystyrene. As such polystyrene, not only a homopolymer of styrene, but also one obtained by copolymerizing a small amount of a monomer component other than styrene, or one obtained by blending a small amount of a resin obtained by polymerizing a monomer other than styrene. Well, the styrene component is 80
It suffices if it is at least% by weight. Therefore, the polystyrene of the present invention includes so-called HIPS (high impact polystyrene) containing a small amount of a rubber component.

Since such polystyrene has high rigidity, it is thin and can maintain its shape. Further, since it has excellent gloss, it is possible to obtain a molded article having an excellent appearance regardless of whether it is transparent or opaque. Furthermore, a homopolymer of styrene is excellent in transparency, and a container using the same is excellent in visibility of contents.

The melt flow rate of polystyrene is not particularly limited, but is preferably 0.01 to 20 g / 10 min, more preferably 0.1 to 1 in consideration of moldability and the like.
0 g / 10 minutes. Further, different kinds of polystyrene may be used in combination.

Here, the layer composed of polystyrene is not limited to polystyrene alone, and may be a layer composed of a composition containing polystyrene as a main component. For example, EVOH,
A recovery composition (regrind) layer containing an ethylene- (meth) acrylic acid copolymer, an adhesive resin and the like can also be used.

The dispersion state of each resin in the resin composition layer of the multilayer structure for thermoforming is such that ethylene- (meth) acrylic acid copolymer particles dispersed in the EVOH matrix are parallel to the surface of the multilayer structure. It is preferable that the particles are dispersed in a columnar shape elongated in a uniaxial direction. Where 1
The axial direction is the direction of extrusion of the multilayer structure. At this time, the average diameter of the particle cross section when cut along a plane perpendicular to the uniaxial direction is preferably 0.2 to 1.3 μm,
More preferably, it is 0.3 to 1.0 μm. When the average diameter of the particle cross section is larger than 1.3 μm, uneven dispersion in the composition is apt to occur, which causes a problem during thermoforming and lowers the gas barrier property. When the average diameter of the particle cross section is less than 0.2 μm, the effect of containing the dispersed particles is not utilized in the thermoformability of the composition, and good thermoformability cannot be obtained.

The following procedure is shown as a method for measuring the average diameter of the particle cross section in the present invention. First, a fracture surface of a sample on a surface perpendicular to the extrusion direction of the multilayer structure is photographed by a scanning electron microscope, a transmission electron microscope, or the like. Subsequently, the contours of the photographs obtained by these electron microscope observations and the like are specified by image processing, the average value of the major axis and the minor axis of the contours of the identified particles is defined as the diameter of the particles, and the obtained particles are obtained. The simple average value of the diameter was determined as the average diameter of the particle cross section.

The layer structure of the multilayer structure for thermoforming of the present invention is as follows.
It is not particularly limited except that it has the above-mentioned resin composition layer and a layer made of polystyrene, but a configuration having a layer made of polystyrene via an adhesive resin layer on the inner and outer layers of the resin composition layer is particularly preferable. As This is because by covering both sides of the resin composition layer with polystyrene, it is possible to prevent a decrease in gas barrier properties due to moisture absorption of the resin composition layer, and it is possible to secure good adhesiveness between the two layers with the adhesive resin layer.

The resin used in the adhesive resin layer is not particularly limited, but may be a polyurethane-based or polyester-based one-pack or two-pack curable adhesive, an unsaturated carboxylic acid or an anhydride thereof (anhydrous). Those obtained by copolymerizing or graft-modifying maleic acid, etc.) to an olefin polymer or copolymer (carboxylic acid-modified polyolefin resin)
Is preferably used. By providing such an adhesive resin layer, a thermoformed container having excellent interlayer adhesion can be obtained.

Among these, it is more preferable that the adhesive resin is a carboxylic acid-modified polyolefin resin from the viewpoint of adhesion to the resin composition layer containing EVOH or copolymerized polypropylene, or compatibility at the time of scrap recovery. . Examples of such a carboxylic acid-modified polyethylene resin include polyethylene ｛low-density polyethylene (LD
PE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE), polypropylene, copolymerized polypropylene, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylate (methyl ester or ethyl) Ester) copolymers modified with carboxylic acid.

Specific examples of the constitution of the multilayer structure for thermoforming of the present invention are represented by EVOH (EVOH composition), PS (polystyrene), AD (adhesive), and REG (recovery layer). EVOH / AD / PS, PS / AD
/ EVOH / AD / REG, PS / AD / EVOH / A
D / REG / PS and the like are shown as preferred. However, the layer configuration of the multilayer structure for thermoforming of the present invention is not limited to the above-mentioned layer configuration example. Other resin layers such as polypropylene, polyethylene, polyamide or polyester may be added to each of the above configuration examples.

The method for obtaining the multilayer structure for thermoforming of the present invention is not particularly limited, but the molding methods used in the field of general polyolefins, such as T-die molding, inflation molding, Extrusion molding,
Dry lamination molding or the like can be employed, and co-extrusion molding is particularly preferred.

The molding temperature at the time of thermoforming the obtained multilayer structure is not particularly limited as long as the resin is softened enough to be molded. The temperature range is different. For example, when thermoforming a sheet, the sheet is not heated to a temperature high enough to cause melting of the sheet due to heating or to transfer irregularities on the metal surface of the heater plate to the film, but to a low temperature such that shaping is not sufficient. It is preferable that the sheet temperature is not 1
30-180 ° C, preferably 135-160 ° C, more preferably 135-155 ° C.

When homopolypropylene and EVOH are laminated, the melting temperature of homopolypropylene is high, so that the sheet temperature during molding can be increased.
As a result, EVOH also has sufficient thermoformability to increase flexibility at high temperatures, but when polystyrene and EVOH are laminated, the softening point of polystyrene is low.
It is necessary to mold at relatively low sheet temperatures.
In this case, EVOH cannot provide sufficient flexibility and cannot obtain excellent thermoformability as a multilayer sheet.
The present invention achieves excellent thermoformability even when laminated with polystyrene by using a specific composition containing EVOH as a main component instead of EVOH.

The preferred shape of the molding container for thermoforming a multilayer structure having a layer made of polystyrene as described above, particularly a sheet-like multilayer structure, is as follows.
That is, the total layer thickness in the thickest part (the same part as the thickness of the multilayer structure before molding) of the obtained thermoformed container is represented by T
μm, the total layer thickness at the thinnest part is tμm,
It is preferable that the following expression is satisfied using the above-described container squeezing ratio S. S ≦ T / t ≦ 20S (1) 300 <T ≦ 3000 (2) t ≧ 100 (3) Here, the expressions (1), (2) and (3) are more preferably 1.5S ≦ T / t ≦ 15S (1 ′) 500 ≦ T ≦ 2000 (2 ′) t ≧ 200 (3 ′), more preferably 2S ≦ T / t ≦ 10S (1 ″) 800 ≦ T ≦ 1500 (2 ″) t ≧ 300 (3 ″).

When the value of T / t is less than S, the container is shaped so as to be easily thermoformed so that the constitution of the present invention is not required, and the value of T / t is larger as the value exceeds 20S. Occasionally, the thickness of the container is so large that the container does not have a preferable shape. If the total layer thickness (T) at the thickest part exceeds 3000 μm, the weight of the container becomes unnecessarily large, which is not only unfavorable in terms of cost but also makes molding difficult. If the total layer thickness (T) at the thickest portion is less than 300 μm, the thickness of the molded container becomes too thin, resulting in insufficient rigidity.
In the thinnest part, the total layer thickness (t) is 10
The case where the thickness is less than 0 μm is not preferable for the same reason.

Various thermoformed containers formed from the above-mentioned sheets are used for various applications. Among them, the superiority of using the resin composition of the present invention, which is excellent in gas barrier properties, is exerted greatly when used as various packaging containers. It is particularly suitable as a packaging container for foods, pharmaceuticals, agricultural chemicals and the like, whose quality is likely to deteriorate due to the presence of oxygen, such as pudding, jelly and miso cups.

[0065]

The present invention will be further described with reference to the following examples.
The multilayer structure for thermoforming and the thermoforming container obtained in the examples were evaluated according to the following methods.

The average diameter of the cross section of the dispersed particles in the multilayer structure for thermoforming The cross section of the sample perpendicular to the extrusion direction of the multilayer structure was observed with a scanning electron microscope, and the magnification was 3000 to 20000.
Photographs were taken twice. When observing the dispersed particles, if it is difficult to observe due to the type of the compounded resin, if necessary, smooth the fracture surface of the pellet with a microtome, or dissolve the dispersed particles with xylene etc. Or the method of observing was adopted. The outline of the dispersed particle cross section in the obtained photograph is specified using an image measurement tool system ASPECT manufactured by KY Electronics Co., Ltd., and the average value of the major axis and the minor axis of the identified particle is defined as the particle diameter, The average value of the diameter values of the obtained particles was determined as the average diameter of the particle cross section. The number of dispersed particles to be measured was 30 or more.

Oxygen Permeation A part of the multilayered structure for thermoforming was cut off at 20 ° C.-85%
After adjusting the humidity to RH, the oxygen permeation amount of the multilayer structure was measured with a barrier measuring device (OX-TRAN-10 / 50A, manufactured by Modern Control). The oxygen permeation amount referred to here is the oxygen permeation amount (unit: ml) measured in the multilayer structure
/ M ² · day · atm) to the gas barrier resin layer 20
Value converted to the amount of oxygen permeated per μm (ml · 20 μm
/ M ² · day · atm). The oxygen permeation amounts of the inner and outer layers and the adhesive resin layer were far larger than those of the gas barrier resin layer, and were therefore ignored and calculated.

-External view of thermoformed container Cup (vertical: 1) formed at a sheet heating temperature of 150 ° C.
(Formed with a rectangular parallelepiped mold having a width of 30 mm, a width of 110 mm and a depth of 50 mm) was visually observed, and the shaping properties, the occurrence of cracks and the occurrence of corrugations were evaluated. The evaluation criteria of the shaping property here are visually determined whether or not the corners (intersecting lines between the side surfaces and the bottom surface) are formed accurately,
All evaluation samples were classified into four grades (good: A>B>C> D: bad). The state of occurrence of cracks is visually determined by the state of occurrence of a crack (crack) having a length of about 2 mm in the vicinity of the bottom of the side surface. B>C> D: bad). The appearance of the wavy pattern is determined by visually checking the wavy appearance unevenness mainly occurring on the side surface of the cup, and all the evaluation samples are evaluated in four stages (good: A>B>) according to the visibility.
C> D: bad). The thickness of the thinnest part is
It was determined by measuring the thinnest part near the intersection of the bottom and the side of the molded product.

Drop Test 200 cc of water was poured into the formed cup, and the same cup was turned down and heated and welded. The container was dropped on concrete, and the height at which the container was broken (water inside the container leaked) was determined. The breaking height was determined as a 50% breaking height by using the test method of n = 30 and the calculation method shown in the JIS test method (“8. Calculation” of K7211).

EXAMPLE 1 Sodium acetate was converted to 65 pp in terms of sodium element by weight.
m, EVOH containing a phosphorus compound in the form of a phosphate in an amount of 100 ppm by weight per phosphorus atom, ethylene content 32 mol%, degree of saponification 99.6%, MFR = 3.1 g / 10 min (210 ° C., 2160 g load )｝ 90% by weight and ethylene-methacrylic acid copolymer (hereinafter abbreviated as EMAA)
｛Content of methacrylic acid (MAA): 9% by weight, DuPont Mitsui Chemical “Nucrel 0903HC”, MFR =
5.7g / 10min (210 ° C, 2160g load)｝ 10
% By dry blending, and then a 30 mmφ twin screw extruder having a kneading disk (TEK manufactured by Nippon Steel Works, Ltd.).
X30: L / D = 30), the cylinder temperature was 190 ° C. in the lower part of the feed, and 210 ° C. in the vicinity of the kneading part and the nozzle.
, The rotor speed of the extruder is 610 rpm,
The mixture was melted and kneaded at a motor rotation speed of the feeder of 250 rpm to form pellets. The extrusion rate at this time is 20 kg per hour, and the resin pressure inside the cylinder is 20 kg / cm.
^{Was 2} . The specific energy at this time is 0.6 kWh /
kg.

The obtained pellets were used as a resin composition layer, and high impact polystyrene (HIPS) “Idemitsu Styrol ET61” manufactured by Idemitsu Petrochemical, MFR = 3 g / 10 M
FRn (2160 g load)} inner and outer layers, partially saponified ethylene-vinyl acetate copolymer {Mersen M-
5430 ", MFR = 6 g / 10 MFRn (210 ° C.,
2160 g load)｝ is the adhesive (AD) layer,
5 layers in 3 types (HIPS / A) with co-extruder equipped with T-type die
D / resin composition layer / AD / HIPS = 400μ / 50μ
/ 100μ / 50μ / 400μ) and the total thickness is 1000
A μm thermoforming sheet was obtained. The cross-sectional diameter of the dispersed particles in the composition layer of the obtained sheet, the haze value of the sheet, and the oxygen permeability of the sheet were measured.

The sheet thus obtained was thermoformed into a cup shape (mold shape 70φ × 70 mm, drawing ratio S = 1.0) by changing the sheet temperature using a thermoforming machine (manufactured by Asano Seisakusho). 5 kg / cm ² , plug: 45φ × 65 mm,
(Syntax foam, plug temperature: 150 ° C., mold temperature: 70 ° C.). The appearance of the molded cup was visually evaluated. The thickness of the thinnest part was determined by measuring the thinnest part near the intersection of the bottom and the side of the molded product. Further, water was put into the obtained container, and then subjected to a drop test. The evaluation results of these thermoforming sheets and thermoforming containers are summarized in Tables 1 and 2.

Comparative Example 1 A sample was prepared and tested in the same manner as in Example 1, except that the same EVOH resin as used in Example 1 was used alone instead of the resin composition layer. I did it. The obtained resin composition pellets, film for thermoforming,
The evaluation results of the thermoformed container are summarized in Tables 1 and 2.

Examples 2 and 3, Comparative Example 2 The same EVOH and EMA as used in Example 1
A, using a mixing ratio of 95% by weight of EVOH, EMAA
5% by weight (Example 2), 80% by weight of EVOH, EMAA
20% by weight (Example 3), 50% by weight of EVOH, EMA
Example 1 except that A was changed to 50% by weight (Comparative Example 2).
In the same manner, a sample was prepared and tested. The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 2.

Examples 4 and 5 EVOH used in Example 1 was obtained by mixing EVOH having different ethylene contents with ethylene content of 27 mol% and saponification degree of 9
9.6%, MFR = 3.9 g / 10 min (210 ° C., 21
60 g load) (Example 4), {ethylene content 44 mol%, saponification degree 99.7%, MFR = 3.5 g / 10 min (210 ° C., 2160 g load)} (Example 5) A sample was prepared and tested in the same manner as in Example 1. The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 2.

Examples 6 to 9 Samples were prepared and tested in the same manner as in Example 1 except that 90% by weight of EVOH used in Example 1 was replaced with two types of EVOH mixed at the following ratios. I did it. The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 2. Example 6; ethylene content 32 mol%, degree of saponification 99.6%, MFR
= 3.1g / 10min (210 ° C, 2160g load) E
VOH 85 parts by weight Ethylene content 51 mol%, degree of saponification 96%, MFR = 1
5.1g / 10min (210 ° C, 2160g load) EV
OH 5 parts by weight Example 7 Ethylene content 38 mol%, saponification degree 99.7%, MFR
= 3.8g / 10min (210 ° C, 2160g load) E
VOH 85 parts by weight Ethylene content 51 mol%, degree of saponification 96%, MFR = 1
5.1g / 10min (210 ° C, 2160g load) EV
OH 5 parts by weight Example 8 Ethylene content 38 mol%, saponification degree 99.7%, MFR
= 3.8g / 10min (210 ° C, 2160g load) E
VOH 85 parts by weight Ethylene content 44 mol%, saponification degree 99.7%, MFR
= 3.5g / 10min (210 ° C, 2160g load) E
VOH 5 parts by weight Example 9; ethylene content 32 mol%, degree of saponification 99.6%, MFR
= 3.1g / 10min (210 ° C, 2160g load) E
VOH 50 parts by weight Ethylene content 51 mol%, degree of saponification 96%, MFR = 1
5.1g / 10min (210 ° C, 2160g load) EV
40 parts by weight of OH

Examples 10 to 12, Comparative Examples 3 to 7 EMAA used in Example 1 Methacrylic acid content: 9% by weight, Mitsui Dupont Chemical "Nucrel 09"
03HC, MFR = 5.7 g / 10 min (210 ° C., 21
A sample was prepared and tested in the same manner as in Example 1 except that the following resin was used instead of (｝ 60 g load)｝. The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 3. Example 10: EMAA @ methacrylic acid content: 4% by weight, DuPont Mitsui Chemical "Nucrel AN4214"
C ", MFR = 12.2 g / 10 min (210 ° C., 216
Example 11; EMAA {methacrylic acid content: 12% by weight; DuPont Mitsui Chemical "Nucrel 1207C";
MFR = 13.4 g / 10 min (210 ° C., 2160 g load)} Example 12: Ethylene-acrylic acid copolymer (hereinafter EA)
A) ｛Acrylic acid (AA) content: 9.0% by weight, Dow Chemical “Primacol 1430, MFR =
8.7 g / 10 min (210 ° C., 2160 g load) Comparative Example 3 Ethylene-methyl methacrylate copolymer 共 Methyl methacrylic acid (MMA) content: 18% by weight, Sumitomo Chemical “Aclift WH303, MFR = 12.
1 g / 10 min (210 ° C., 2160 g load) Comparative Example 4: Maleic anhydride-modified polyethylene {MFR =
3.6 g / 10 min (210 ° C., 2160 g load), “Admer NF500” manufactured by Mitsui Petrochemical Co., Ltd. Comparative Example 5: Ionomer {Mitsui DuPont Chemical “Himilan 1652, MFR = 7.6 g / 10 min (210
Comparative Example 6; LDPE "Milason B32 manufactured by Mitsui Petrochemical Co., Ltd.)
4. MFR = 3.4 g / 10 min (210 ° C., 2160 g
Load)｝ Comparative Example 7; Nylon ｛Nylon 6 (PA-6) ｛MFR
= 7.2 g / 10 min (230 ° C, 2160 g load), “UBE nylon 1022B” manufactured by Ube Industries, Ltd.

Examples 13 to 16 Samples were prepared and tested in the same manner as in Example 1 except that the following EVOH and ethylene- (meth) acrylic acid copolymer were used in combination. At this time, by changing the MFR of the EVOH and the ethylene- (meth) acrylic acid copolymer used, the ratio MFR (A) / MFR
(B) was adjusted. The evaluation results of the obtained resin composition pellets, thermoforming film and thermoforming container are shown in Tables 1 and 3.
Are shown together. Example 13 EVOH @ ethylene content 32 mol%, saponification degree 99.6
%, MFR = 1.2 g / 10 min (210 ° C., 2160 g
Load)｝, EMAA ｛Methacrylic acid content: 9% by weight,
Mitsui Dupont Chemical "Nucrel NC0908H
G ", MFR = 15.3 g / 10 min (210 ° C., 216
Example 14 EVOH ethylene content 32 mol%, saponification degree 99.6
%, MFR = 33.0 g / 10 min (210 ° C., 2160
g load), EMAA, methacrylic acid content: 9% by weight, Mitsui Dupont Chemical "Nucrel 0903HC,
MFR = 5.7 g / 10 min (210 ° C., 2160 g load) Example 15 EVOH ethylene content 32 mol%, saponification degree 99.6
%, MFR = 1.2 g / 10 min (210 ° C., 2160 g
Load) 荷重, EAA ｛Acrylic acid content: 9% by weight, Dow Chemical “Primacol 3440”, MFR = 18.0
g / 10 min (210 ° C., 2160 g load) Example 16 EVOH ethylene content 32 mol%, saponification degree 99.6
%, MFR = 33.0 g / 10 min (210 ° C., 2160
g load)｝, EAA ｛Acrylic acid content: 9% by weight, Dow Chemical “Primacol 1420”, MFR = 5.6
g / 10 minutes (210 ° C, 2160g load)｝

Example 17 In Example 1, the melt kneading of EVOH and EMAA was carried out for 2 minutes.
Instead of using a screw extruder, using a single screw extruder (GT-40-A made by Placo, L / D = 26, using a full flight type screw), the cylinder temperature is 190 ° C. at the lower part of the feed, near the kneading part and the nozzle. Is set to 210 ° C., the number of revolutions of the rotor of the extruder is 1500 rpm, and the mixture is melt-kneaded to form pellets. At this time, the extrusion rate is 20 kg per hour, and the resin pressure inside the cylinder is 8 kg / c.
m ² , the specific energy at this time is 0.1 KWh / Kg
A sample was prepared and tested in the same manner as in Example 1 except that The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 3.

Example 18 A sample was prepared and tested in the same manner as in Example 17 except that the screw was changed from a full-flight type screw to a screw having a kneading portion at the tip. At this time, the resin pressure inside the cylinder is 10kg
/ Cm ² , and the specific energy at this time is 0.15 KWh.
/ Kg. The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 3.

Example 19, Comparative Example 8 A sample was prepared in the same manner as in Example 1 except that the high impact polystyrene (HIPS) of the inner and outer layers used in Example 1 was changed to the following resin or resin composition. The test was performed. The evaluation results of the obtained sheet and thermoformed container are summarized in Tables 4 and 5. Example 19: Styrene homopolymer (PS) “Idemitsu Styrol HH30E manufactured by Idemitsu Petrochemical, MFR = 4 g /
10 minutes (200 ° C., 2160 g load) Comparative Example 8: Homopolypropylene “J103” made by Grand Polymer, MFR = 3.0 g / 10 minutes (230 ° C.,
2160g load), Vicat softening point 155 ℃

Example 20, Comparative Example 9 A sample was prepared in the same manner as in Example 6 except that the high impact polystyrene (HIPS) of the inner and outer layers used in Example 6 was changed to the following resin or resin composition. The test was performed. The evaluation results of the obtained sheet and thermoformed container are summarized in Tables 4 and 5. Example 20; Homopolymer of styrene (PS) “Idemitsu Styrol HH30E manufactured by Idemitsu Petrochemical, MFR = 4 g /
10 minutes (200 ° C., 2160 g load) Comparative Example 9: Homopolypropylene “J103” made by Grand Polymer, MFR = 3.0 g / 10 minutes (230 ° C.,
2160g load), Vicat softening point 155 ℃

Comparative Examples 10 and 11 Samples were prepared and tested in the same manner as in Comparative Example 1 except that the high impact polystyrene (HIPS) of the inner and outer layers used in Comparative Example 1 was changed to the following resin or resin composition. I did it. The evaluation results of the obtained sheet and thermoformed container are summarized in Tables 4 and 5. Comparative Example 10: Styrene homopolymer (PS) “Idemitsu Styrol HH30E manufactured by Idemitsu Petrochemical, MFR = 4 g /
10 minutes (200 ° C., 2160 g load) Comparative Example 11: Homopolypropylene “J103” made by Grand Polymer, MFR = 3.0 g / 10 minutes (230 ° C.,
2160g load), Vicat softening point 155 ℃

Example 21 The procedure of Example 1 was repeated except that the thermoformed sheet obtained in Example 1 was pulverized and remelted into pellets, and the recovered composition was used in place of the outer layer of high impact polystyrene (HIPS). And (HIPS / AD / resin composition / AD
/ Recovery composition = 400μ / 50μ / 100μ / 50μ /
A sheet having a structure of 400 μ) was prepared, and a thermoformed container was prepared in the same manner as in Example 1 so that the collected material layer was on the outside. The evaluation results of the obtained sheet and thermoformed container are summarized in Tables 4 and 5.

[0085]

[Table 1]

[0086]

[Table 2]

[0087]

[Table 3]

[0088]

[Table 4]

[0089]

[Table 5]

[0090]

The multilayer structure for thermoforming of the present invention can provide a thermoformed container having good thermoformability, excellent gas barrier properties, and excellent mechanical properties. Such thermoformed containers are:
Since it has good appearance, excellent mechanical performance and excellent gas barrier properties, it has excellent performance as various packaging containers.

Claims (5)

[Claims] 1. An ethylene-vinyl alcohol copolymer 6 having an ethylene content of 20 to 60 mol% and a saponification degree of 90% or more.
0-99% by weight and (meth) acrylic acid content 1-30
40% by weight of ethylene- (meth) acrylic acid copolymer
Multilayer structure for thermoforming comprising 1% by weight, a resin composition layer in which ethylene- (meth) acrylic acid copolymer particles are dispersed in a matrix of an ethylene-vinyl alcohol copolymer, and a layer made of polystyrene body. 2. An ethylene-vinyl alcohol copolymer comprising a mixture of two kinds of ethylene-vinyl alcohol copolymers (a) and (b) having different ethylene contents, wherein the ethylene content of (a) is 20 to 45. Mol%, (b)
Has an ethylene content of 45 to 65 mol%, the difference between the ethylene contents of (a) and (b) is 8 mol% or more, and the blending weight ratio {(a) / (b)} is 2/1 to 50 The multi-layer structure for thermoforming according to claim 1, wherein the ratio is / 1. 3. A columnar shape in which ethylene- (meth) acrylic acid copolymer particles dispersed in an ethylene-vinyl alcohol copolymer matrix are stretched in a uniaxial direction parallel to the surface of the multilayer structure. 3. The multilayer structure for thermoforming according to claim 1, wherein the particles have an average diameter of 0.2 to 1.3 μm when cut along a plane perpendicular to the uniaxial direction. 4. 4. A thermoformed container obtained by thermoforming the multilayer structure according to claim 1. 5. The following formula (1), where T μm is the total layer thickness at the thickest portion of the container, t μm is the total layer thickness at the thinnest portion, and S is the drawing ratio of the container.
The thermoformed container according to claim 4, which satisfies (3) to (3). S ≦ T / t ≦ 20S (1) 300 <T ≦ 3000 (2) t ≧ 100 (3) However, the draw ratio S of the container is a value represented by the following equation (4). S = (depth of the container) / (diameter of the circle having the largest diameter inscribed in the opening of the container) (4)