JP2001150609A - Multilayered structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered structure excellent in barrier properties, hydrothermal resistance and straight cutting properties. SOLUTION: A multilayered structure is constituted of a layer comprising an ethylene/vinyl alcohol copolymer resin composition (A) consisting of 70-95 parts by weight of an ethylene/vinyl alcohol copolymer (a1) and 5-30 parts by weight of polyamide (a2) and a layer comprising a polyamide resin composition (B) consisting of 60-95 parts by weight of aliphatic polyamide (b1) and 5-40 parts by weight of semi-aromatic polyamide (b2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer structure excellent in barrier properties, hot water resistance, and straight cutting properties.

[0002]

2. Description of the Related Art Ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH) is a resin having excellent barrier properties against oxygen, odor, flavor and the like, and is used as a packaging material for foods and the like. It is preferably used.
Such packaging materials are often subjected to heat treatment with hot water or steam after filling the contents such as food, but EVOH is treated with hot water or steam for a long time,
There is a risk that problems such as whitening may occur, and the ability to maintain the shape may be insufficient. In addition, such packaging materials are often filled with a liquid material, and from the viewpoint of preventing the contents from spilling,
The packaging material has been required to have excellent straight-line cutting properties.

In order to impart hot water resistance to EVOH,
(1) A resin composition composed of EVOH and polyamide and a multilayer structure obtained by laminating the resin composition and polyamide are disclosed (JP-A-1-253442). However, in the examples of the prior art, nylon-6 is used as the polyamide to be laminated with the resin composition, and there is no description about using a mixture of an aliphatic polyamide and a semi-aromatic polyamide in a specific ratio. There is no mention of straight cutability.

Japanese Patent Application Laid-Open No. 1-154,752 discloses (2) a polyamide composition comprising 30 to 90% by weight of an aliphatic polyamide and a partially aromatic polyamide, and a vinyl alcohol content of 40 to 85% by mole. And a composite film formed by co-extrusion with EVOH. However, there is no description in this publication about laminating a resin composition comprising EVOH and polyamide with a polyamide composition, and no mention is made of straight cutability.

[0005] JP-A-5-77352 discloses (3)
A heat-shrinkable multilayer film having an EVOH composition layer comprising an ethylene content of 20 to 60 mol%, 10 to 95% by weight of EVOH having a saponification degree of 90% or more, and 5 to 90% by weight of an aromatic polyamide resin and a polyamide layer is provided. It has been disclosed. However, the publication does not disclose using a polyamide resin composition in which an aliphatic polyamide and a semi-aromatic polyamide are blended at a specific ratio, and does not mention linear cutability.

[0006] JP-A-8-216221 discloses that
(4) Ethylene content 20 to 60 mol%, saponification degree 90
% Or more of the EVOH (A) layer and the crystalline polyamide 65-3
There is disclosed a multilayer body obtained by co-extrusion coating a substrate with a molten multilayer body comprising at least two layers of a polyamide composition layer (B) comprising 5% by weight and 35 to 65% by weight of an amorphous polyamide. The publication states that a polyamide may be blended with the EVOH to be used, but the blending ratio is not described at all. Further, as Comparative Example 1 which does not exert the effect of the invention, it is described that a polyamide composition layer (B) composed of polyamide-6 (50% by weight) and polymethaxylylene adipamide (50% by weight) is used. There is no description about blending a polyamide with EVOH used in Comparative Example 1. No mention is made of straight-line cutability.

As described above, many techniques have been disclosed for a multilayer structure composed of an EVOH layer and a polyamide layer. However, a multilayer structure that simultaneously satisfies excellent barrier properties, hot water resistance, and straight cut properties has not been developed. Had not been developed.

[0008]

Therefore, the barrier property,
A multilayer structure excellent in hot water resistance and straight cut property is desired.

[0009]

The above object is achieved by the present invention. That is, the present invention relates to an ethylene-vinyl alcohol copolymer (a1) having 70 to 95% by weight and a polyamide (a2) having 5 to 30% by weight.
A vinyl alcohol copolymer resin composition (A) layer and a polyamide resin composition (B) layer composed of 5 to 40% by weight of an aliphatic polyamide (b1) and 60 to 95% by weight of a semi-aromatic polyamide (b2) The present invention relates to a multilayer structure formed by laminating.

In a preferred embodiment, the polyamide (a) used in the EVOH resin composition (A) layer is nylon-6.
It is.

In a preferred embodiment, the aliphatic polyamide (b1) in the polyamide resin composition (B) layer is nylon-6.
And the semi-aromatic polyamide (b2) is polymethaxylylene adipamide.

In a preferred embodiment, the multilayer structure of the present invention is formed by laminating a polyolefin (C) layer.

Further, in a preferred embodiment, the multilayer structure of the present invention has a total thickness of 50 to 300 μm and an ethylene-vinyl alcohol copolymer resin composition (A) having a thickness of 3 to 50 μm. is there.

In a preferred embodiment, the multilayer structure of the present invention is a multilayer structure for boil sterilization or retort sterilization.

[0015] In a preferred embodiment, the multilayer structure of the present invention is used as a multilayer film or a multilayer container. More preferably, the multilayer container has the polyamide resin composition (B) layer as an outer layer, the ethylene-vinyl alcohol copolymer resin composition (A) layer as an intermediate layer, and the polyolefin (C) layer as an inner layer.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The EVOH (a1) used in the EVOH resin composition (A) layer of the present invention is ethylene-
The one obtained by saponifying a vinyl ester copolymer is preferable, and among them, the ethylene content is preferably 15 to 70 mol%, more preferably 20 to 65 mol%, and most preferably 25 to 60 mol%. % Is preferable,
Further, the degree of saponification of the vinyl ester component is 85% or more,
More preferably, 90% or more can be used. If the ethylene content is less than 15 mol%, melt moldability is poor, and water resistance and hot water resistance may be reduced. On the other hand, if it exceeds 70 mol%, the barrier properties may be insufficient. If the saponification degree is less than 85%, the barrier properties and thermal stability may be deteriorated. Further, when the ethylene content exceeds 70 mol% or the saponification degree is less than 85%, the barrier properties may be reduced.

A typical example of the vinyl ester used in the production of EVOH is vinyl acetate.
Other fatty acid vinyl esters (vinyl propionate,
Vinyl pivalate) can also be used. Also, EVOH
Is a vinyl silane compound as a copolymer component 0.0002 to
0.2 mol% can be contained. Here, as the vinylsilane-based compound, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (β
-Methoxy-ethoxy) silane and γ-methacryloxypropylmethoxysilane. Among them, vinyltrimethoxysilane and vinyltriethoxysilane are preferably used. Further, other comonomer such as propylene, butylene, or unsaturated monomer such as (meth) acrylic acid, methyl (meth) acrylate or ethyl (meth) acrylate, as long as the object of the present invention is not hindered. A carboxylic acid or an ester thereof and vinylpyrrolidone such as N-vinylpyrrolidone can also be copolymerized.

Further, a boron compound may be blended with EVOH (a1) within a range not to impair the object of the present invention. Here, examples of the boron compound include boric acids, borate esters, borates, borohydrides, and the like. Specifically, examples of boric acids include orthoboric acid, metaboric acid, tetraboric acid, and the like.Examples of borate esters include triethyl borate, trimethyl borate, and the like. Examples include alkali metal salts, alkaline earth metal salts of acids, borax, and the like. Of these compounds, orthoboric acid (hereinafter sometimes simply referred to as boric acid) is preferred.

When a boron compound is blended, the content of the boron compound is preferably 20 to 2 in terms of boron element.
000 ppm, more preferably 50 to 1000 ppm. By being in this range, it is possible to obtain EVOH in which torque fluctuation during heating and melting is suppressed. If it is less than 20 ppm, such an effect is small, and if it exceeds 2,000 ppm, gelation is likely to occur, resulting in poor moldability.

The EVOH (a) used in the present invention
Contrary to 1), it is also preferable to include an alkali metal salt in an amount of 5 to 5000 ppm in terms of an alkali metal element, since this is effective for improving interlayer adhesion and compatibility. The more preferable content of the alkali metal salt is 20 to 1000 ppm, more preferably 30 to 500 ppm in terms of the alkali metal element.
It is. Here, examples of the alkali metal include lithium, sodium, and potassium, and examples of the alkali metal salt include a monovalent metal aliphatic carboxylate, an aromatic carboxylate, a phosphate, and a metal complex. Examples include sodium acetate, potassium acetate, sodium phosphate, lithium phosphate, sodium stearate, potassium stearate, and sodium salt of ethylenediaminetetraacetic acid. Among them, sodium acetate, potassium acetate and sodium phosphate are preferred.

The EVOH (a) used in the present invention
In contrast to 1), a phosphorus compound is converted to 2-200 p in terms of phosphorus element.
pm, more preferably 3 to 150 ppm, most preferably 5 to 1 ppm
It is also preferable to make it contain 00 ppm. If the phosphorus concentration in the EVOH is less than 2 ppm or more than 200 ppm, problems may occur in melt moldability and thermal stability. In particular, problems such as the occurrence of gel-like bumps and coloring during long-time melt molding are likely to occur.

The type of the phosphorus compound to be incorporated into the EVOH (a1) is not particularly limited. Various acids such as phosphoric acid and phosphorous acid and salts thereof can be used. The phosphate may be contained in any form of a first phosphate, a second phosphate, and a third phosphate, and the cationic species thereof is not particularly limited. And alkaline earth metal salts. Among them, it is preferable to add a phosphorus compound in the form of sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate.

Suitable melt flow rate (MFR) of EVOH (a1) used in the present invention (190 ° C., 2160 g
(Under load) is 0.1 to 50 g / 10 min, more preferably 0.3 to 40 g / 10 min, and even more preferably 0.5 to 30 g / 10 min.
g / 10 minutes. However, those having a melting point of around 190 ° C. or exceeding 190 ° C. are measured under a load of 2160 g at a plurality of temperatures equal to or higher than the melting point. Expressed as a value extrapolated to 190 ° C. These EVOH resins can be used alone or in combination of two or more.

The polyamide (a2) used in the EVOH resin composition (A) layer of the present invention is a polymer having an amide bond. Specifically, any of the diamine component and the dicarboxylic acid component contains an aliphatic or alicyclic component as a main component, and any of an aliphatic polyamide, a diamine component or a dicarboxylic component that does not contain an aromatic group in a substantial amount. The semi-aromatic polyamide in which only the aromatic component is the main component and the other component is mainly the aliphatic or alicyclic component, and the aromatic polyamide in which both the diamine component and the dicarboxylic acid component are mainly the aromatic component And the like.

As the aliphatic polyamide, for example, polycaproamide (nylon-6), polyundecaneamide (nylon-11), polylauryl lactam (nylon-12), polyhexamethylene adipamide (nylon-6
6,6), polyhexamethylene sebacamide (nylon-
6,12), caprolactam / lauryl lactam copolymer (nylon-6 / 12), caprolactam / aminoundecanoic acid polymer (nylon-6 / 1)
1), a caprolactam / ω-aminononanoic acid polymer (nylon-6, 9), a caprolactam / hexamethylenediammonium adipate copolymer (nylon-6 / 6,
6), caprolactam / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6 / 6, 6/6, 12).

Examples of the semi-aromatic polyamide include polymers of aromatic diamines such as meta-xylylenediamine and para-xylylenediamine and aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and terephthalic acid and isophthalic acid. Such an aromatic dicarboxylic acid and hexamethylenediamine, 2,2,4 and / or 2,4,4-trimethylhexamethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, bis-
Examples thereof include polymers with aliphatic or alicyclic diamines such as (4-aminocyclohexyl) methane.

Examples of the aromatic polyamide include a polymer of an aromatic diamine such as meta-xylylenediamine and para-xylylenediamine and an aromatic dicarboxylic acid such as terephthalic acid and isophthalic acid.

As the polyamide (a2) used in the EVOH resin composition (A) layer, each of the above polyamides can be used alone, or two or more can be used in combination. Among the above polyamides, aliphatic polyamides are preferable, and polyamides containing a nylon-6 component (e.g., nylon-6, nylon-6,1) are preferable from the viewpoint of compatibility with EVOH, barrier properties, hot water resistance and the like.
2, nylon-6 / 12, nylon-6 / 6, 6) are preferred, and nylon-6 is most preferred.

A suitable melt flow rate (MFR) of the polyamide (a2) used in the present invention (230 ° C., 21
Under a load of 60 g; measured in accordance with the condition 14 of JIS K7210) is 1 to 100 g / 10 min. It is. The lower limit of the suitable MFR of the polyamide (at 230 ° C. under a load of 2160 g) is more preferably 10 g / 10 min. And more preferably 30 g / 10 min. And particularly preferably 60 g / 10 min. And optimally 70g / 10m
in. It is. In addition, suitable MFR (23
The upper limit of 0 ° C under a load of 2160 g) is more preferably 90 g.
/ 10 min. It is. In particular, the M of the polyamide (a2)
FR (230 ° C, under 2160g load) 60g / 10m
in. In the case of the above, the thermal stability and the hot water resistance of the EVOH (A) resin composition are remarkably improved, and the multilayer structure of the present invention has good straight cutting properties. From this viewpoint, the MFR of the polyamide (a2) (230 ° C., 2160
g load) is 60 to 100 g / 10 min. Is particularly preferable, and 70 to 90 g / 10 min. Is most preferred. However, those having a melting point of around 230 ° C. or exceeding 230 ° C. are measured under a load of 2160 g at a plurality of temperatures equal to or higher than the melting point. Expressed as a value extrapolated to 230 ° C.

The EVOH resin composition layer (A) used in the present invention comprises 70 to 95% by weight of EVOH (a1) and 5 to 30% by weight of polyamide (a2). EVOH
When the content of (a1) is less than 70% by weight or when the content of polyamide (a2) is more than 30% by weight, the film-forming property becomes poor. The EVOH (a1) content is 95%.
When the amount exceeds 5% by weight or when the amount of the polyamide (a2) is less than 5% by weight, the effects of improving hot water resistance and straight-line cut properties become insufficient. From the viewpoint of hot water resistance, EVO
The upper limit of the content of H (a1) is preferably 85% by weight or less. Similarly, from the viewpoint of hot water resistance, the lower limit of the content of the polyamide (a2) is preferably 15% by weight or more.

The EVOH resin composition (A) used in the present invention contains EVOH (a1) and polyamide (a
In addition to 2), suitable additives (e.g., heat stabilizers, plasticizers, antioxidants, ultraviolet absorbers, coloring agents, fillers) may be included, and these additives are used in the present invention. Used within a range that does not inhibit the effect.

As the aliphatic polyamide (b1) and the semi-aromatic polyamide (b2) used in the polyamide resin composition (B) layer, those exemplified above can be used. Among these, from the viewpoint of barrier properties, hot water resistance, etc., as the aliphatic polyamide (b1), a polyamide containing a nylon-6 component (for example, nylon-6, nylon-6,
12, nylon-6 / 12, nylon-6 / 6,6 etc.)
Is preferable, and nylon-6 is most preferable.

As the semi-aromatic polyamide (b2), metaxylylene adipamide (hereinafter sometimes abbreviated as MXD-6), which is a polymer of metaxylylenediamine and adipic acid, may be used. preferable. In particular, when a polyamide containing a nylon-6 component is used as the aliphatic polyamide (b1), the semi-aromatic polyamide (b2)
It is preferable to use MXD-6 from the viewpoint of compatibility and the like, and it is possible to impart particularly excellent barrier properties, hot water resistance and linear cut properties to the multilayer structure of the present invention.

The polyamide resin composition (B) layer used in the present invention comprises 60 to 95% by weight of an aliphatic polyamide (b1) and 5 to 40% by weight of a semi-aromatic polyamide (b2). When the content of (b1) and (b2) is in such a range, an excellent straight-cutting effect can be obtained when laminated with the EVOH resin composition (A) layer. From the viewpoint of linear cut property, the polyamide resin composition (B) layer is
Preferably, the aliphatic polyamide (b1) comprises 70 to 90% by weight and the semi-aromatic polyamide (b2) 10 to 30% by weight, and more preferably, the aliphatic polyamide (b1).
75-85% by weight and semi-aromatic polyamide (b2) 1
5 to 25% by weight.

The polyamide resin composition (B) layer is preferably stretched at least uniaxially, particularly preferably biaxially, from the viewpoint of mechanical strength, hot water resistance and the like.

The method for producing the above-mentioned EVOH resin composition (A) and polyamide resin composition (B) is not particularly limited. For example, the desired components can be easily obtained by melt-kneading the components using a conventional melt-kneading apparatus. A resin composition can be obtained. The method of blending each component is not particularly limited, and examples thereof include a method of melt-kneading with a single-screw or twin-screw extruder or the like, and pelletizing and drying. In the melt compounding operation, there is a possibility that the blend becomes non-uniform, and gels and lumps are generated and mixed.Therefore, in the case of blend pelletization, use an extruder with a high degree of kneading as much as possible, and use a nitrogen gas It is desirable to extrude at a low temperature.

The multilayer structure of the present invention is preferably laminated with a polyolefin (C) layer from the viewpoint of imparting heat sealability. As the polyolefin (C) used in the present invention, homopolymers of α-olefins such as high-density or low-density polyethylene, polypropylene and polybutene-1, ethylene, propylene and butene-
1, a copolymer of α-olefins selected from hexene-1 and the like. Further, those obtained by copolymerizing the following components with an α-olefin: diolefin, vinyl compounds such as vinyl chloride and vinyl acetate, and unsaturated carboxylic esters such as acrylic acid esters and methacrylic acid esters are also included. Among them, it is preferable to use polypropylene from the viewpoint of the mechanical strength of the multilayer structure, and particularly to use a non-stretched polypropylene film from the viewpoint of hot water resistance and heat sealing property.

The layer structure of the multilayer structure of the present invention is not particularly limited. When the EVOH resin composition (A) layer is A, the polyamide resin composition (B) layer is (C), the polyolefin (C) layer is C, and the adhesive resin layer is Ad, B / A / Ad /
Typical examples include C, A / B / Ad / C, C / Ad / A / B / Ad / C, and B / A / Ad / C.
It is particularly preferable to have the structure of C from the viewpoint of straight-line cutability and the like. When the multilayer structure of the present invention is used as a multilayer container, the outer layer side is (outside) and the inner layer side is (inside).
In this case, it is preferable to have a configuration of (outside) B / A / Ad / C (inside) from the viewpoints of hot water resistance and linear cutability. When a polyolefin (C) layer is provided on both outer layers, the resins may be the same or different. Also, within a range that does not impair the effects of the present invention,
It is optional to blend scrap such as trim generated at the time of molding with the polyolefin (C) layer, or to provide a separate recovery layer for reuse.

The thickness structure of the multilayer structure of the present invention is arbitrary, but the total thickness of the multilayer structure is preferably 50 to 300 μm. If the total thickness is less than 30 μm, the mechanical strength and the hot water resistance may be insufficient.
If it exceeds μm, there is a possibility that the straight-line cut property may be unsatisfactory. Further, the thickness of the EVOH resin composition (A) layer is preferably 3 to 50 μm. If the thickness of the EVOH resin composition (A) layer is less than 3 μm, the barrier properties may be unsatisfactory. When the total thickness of the multilayer structure is 300 μm or less and the EVOH resin composition (A) layer exceeds 50 μm, the linear cut property and the hot water resistance may be unsatisfactory. Further, the thickness of the polyamide resin composition (B) layer is preferably 15 to 50 μm. If the thickness of the polyamide resin composition (B) layer is less than 15 μm, the hot water resistance and mechanical strength may be unsatisfactory. When the total thickness of the multilayer structure is 300 μm or less and the thickness of the polyamide resin composition (B) layer exceeds 50 μm, the linear cut property may be unsatisfactory.

The method for obtaining the multilayer structure of the present invention is not particularly limited, and examples thereof include dry lamination, extrusion lamination, coextrusion lamination, coextrusion molding, coextrusion pipe molding, coinjection molding, and solution coating. Laminates are particularly preferred. The multilayer structure of the present invention includes a biaxially stretched polyamide resin composition (B) layer and a non-stretched E layer.
A multilayer structure obtained by laminating a VOH resin composition (A) and a non-stretched polyolefin (C) layer is preferable, and a multilayer structure obtained by laminating each layer by dry lamination is particularly preferable in the present invention. It is an embodiment. When forming a multilayer film by dry lamination, the flow direction (M
It is particularly preferable that D) is laminated in the same direction, from the viewpoint of linear cutability.

The linear cut property in the present invention means that, for example, one side of a rectangular multilayer film composed of the multilayer structure of the present invention is held in both hands and torn in a vertical direction from the side held by the hand to the opposite side. The linearity of the cutting line. In other words, being superior in straight line cutability means that when the cutting line is linear and tears in the vertical direction from the tear start position, a straight line drawn vertically on the opposite side from the tear end position and the tear start position This means that the deviation from the position in contact with the opposite side is small.

The linear cut property is particularly important when the multilayer structure of the present invention is used as a multilayer container filled with contents, particularly as a flexible pouch. If the straight-line cutability is insufficient, the contents are easily spilled when the multilayer container is torn open.

The multilayer structure of the present invention is extremely useful in that it has excellent barrier properties, hot water resistance and linear cut properties at the same time. The multilayer structure of the present invention is effective as a packaging film for food and the like, and especially as a flexible pouch, due to its excellent properties. Further, as is apparent from the examples, when the multilayer structure of the present invention is laminated with the same flow direction (MD direction) at the time of film forming of each resin film, a straight line cut when the resin film is torn in the MD direction. Not only is it excellent in cutting properties, but also excellent in straight-line cutability when it is torn in the TD direction (direction perpendicular to the MD direction). Specifically, in a flexible pouch or the like that has conventionally been torn only from a single direction, it can be torn from various directions. From such a viewpoint, the significance of the multilayer structure of the present invention is great.

[0044]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Table 1 shows a list of resins used in Examples and Comparative Examples.
Shown in

Example 1 75% by weight of EVOH (a-1) having an ethylene content of 27 mol%, a saponification degree of 99.7%, and a melt flow rate of 4 g / 10 min (210 ° C., 2160 g load) and a polyamide (melting point: 220 ° C.) , MFR 80 g / 10 min.
Under a load of 160 g)) (a-2) Using a single-screw extruder with kneading of 25% by weight of the compound, a resin temperature of 250 ° C.
To produce a 15 μm thick EVOH resin composition (A) single-layer cast film.

Next, a biaxially stretched film of a polyamide resin composition (B) comprising two components of nylon-6 and MXD-6 (b-1: Idemitsu Petrochemical TB-1000, 15 μm)
m), the EVOH resin composition (A) film, and a non-stretched polypropylene film as a polyolefin (C) layer (Tocelo Chemical Co., Tocello CP, RXC18, 60
μm) by dry lamination (B)
A multilayer film having a laminated structure of / (A) / (C) was prepared. In addition, when laminating | stacking each layer, it arrange | positioned so that the film flow direction (MD direction) of each layer might become parallel. The adhesive was laminated using Takeda Pharmaceutical Co., Ltd., Takelac, A385 / A50 to a coating amount of 4 g / m ² , a temperature of 70 ° C., and aging at 40 ° C. for 5 days.

The obtained multilayer film was evaluated according to the following method.

Measurement of barrier property (oxygen permeation amount) After the obtained multilayer film was conditioned for 3 weeks at 20 ° C. and 65% RH, a 2/20 type oxygen permeation measurement manufactured by Mocon Corporation (USA) was measured. Oxygen permeation amount (ml / m ²⁾ according to JIS K 7126 at 20 ° C. and 65% RH using a device
.Day.atm).

○ Straight cutting property The multilayer film obtained by the above method is 90 mm (MD)
× 90 mm (TD). A notch having a depth of 1 mm was provided at the center of one side of the multilayer film, the film was torn in a vertical direction toward the opposite side, and the amount of displacement (mm) of the tear termination position from the center of the opposite side was measured. Such tearing was performed in the MD direction and the TD direction of the multilayer film. Table 2 shows the results.

耐熱 Hot water resistance test The multilayer film obtained by the above method was
D) Two pieces cut to a size of 170 mm (TD), one of which has three unstretched polypropylene film layers as inner surfaces.
The bag was heat-sealed with a width of 0 mm to obtain a three-sided bag. A mixed solution of 180 g of water / 20 g of tempura oil was filled from the opening, and the opening was heat-sealed with a width of 10 mm. A multilayer bag filled with such contents is manufactured by Hisaka Seisakusho (RCS-40RTGN).
The heat treatment was performed using a heat sterilizer (model: retort apparatus). The treatment was carried out under two conditions: a hot water type of heating at 95 ° C. for 30 minutes and a steam type of heating at 120 ° C. for 30 minutes. The evaluation criteria for the hot water test are as follows. （(Good): The form is maintained, and no whitening is observed. Δ (possible): The form is maintained, but slightly whitened. X (bad): whitening is not maintained and the form is not maintained. Table 2 shows the evaluation results of the hot water resistance of the obtained structure films.

Examples 2 and 3 A laminate was prepared and evaluated in the same manner as in Example 1 except that the resin shown in Table 1 was used and the EVOH resin composition (A) shown in Table 2 was used as an intermediate layer. Was. Table 2 shows the evaluation results.

Comparative Examples 1 to 3 Biaxially stretched films made of nylon-6 were used as the intermediate layer, and the polyamide resin composition (B) was used as the intermediate layer, using the resins shown in Table 1 as the resins shown in Table 1. (B-2;
A laminate was prepared and evaluated in the same manner as in Example 1 except that Unitika ON-RT (15 μm) was used. Table 2 shows the evaluation results.

Comparative Examples 4 and 5 A laminate was prepared and evaluated in the same manner as in Example 1 except that the resin shown in Table 1 was used and the EVOH resin composition (A) shown in Table 2 was used as an intermediate layer. Was. Table 2 shows the evaluation results.

[0054]

[Table 1]

[0055]

[Table 2]

The multilayer films of Examples 1 to 3 having the constitution of the present invention and the flexible pouches made of the films were all excellent in barrier properties, hot water resistance and straight-cut properties. On the other hand, the multilayer films of Comparative Examples 1 to 3 having no configuration of the present invention and the flexible pouch made of the films were unsatisfactory in the linear cut property. Further, the composition of Comparative Example 4 in which the blending amount of the polyamide (a2) of the EVOH resin composition (A) was less than 5% by weight was insufficient in hot water resistance, and the EVOH resin composition (A)
In the case of Comparative Example 5 in which the amount of EVOH (a1) was less than 70% by weight, the effect of improving the barrier property and the linear cut property was insufficient.

[0057]

The multilayer structure of the present invention is excellent in barrier properties, hot water resistance and straight-cutting properties. From such useful properties, it is suitable to be used as a packaging container for foods and the like, particularly as a flexible pouch.

Claims (10)

[Claims] 1. 70 to 95% by weight of an ethylene-vinyl alcohol copolymer (a1) and a polyamide (a2) 5
An ethylene-vinyl alcohol copolymer resin composition (A) layer comprising from 30 to 30% by weight, and an aliphatic polyamide (b1).
60-95% by weight and semi-aromatic polyamide (b2) 5
A multilayer structure obtained by laminating a polyamide resin composition (B) layer of from 40 to 40% by weight. 2. The multilayer structure according to claim 1, wherein the polyamide (a2) is nylon-6. 3. The aliphatic polyamide (b1) is nylon-
The multilayer structure according to claim 1, wherein the number is 6. 4. The multilayer structure according to claim 1, wherein the semi-aromatic polyamide (b2) is polymethaxylylene adipamide. 5. The multilayer structure according to claim 1, wherein a polyolefin (C) layer is laminated. 6. The multilayer according to claim 1, wherein the total layer thickness is 50 to 300 μm, and the thickness of the ethylene-vinyl alcohol copolymer resin composition (A) layer is 3 to 50 μm. Structure. 7. The multilayer structure for sterilizing boil or retort according to any one of claims 1 to 6. 8. A multilayer film comprising the multilayer structure according to claim 1. 9. A multilayer container comprising the multilayer structure according to claim 1. 10. The multilayer according to claim 9, wherein the polyamide resin composition (B) layer is an outer layer, the ethylene-vinyl alcohol copolymer resin composition (A) layer is an intermediate layer, and the polyolefin (C) layer is an inner layer. container.