JP2003103708A - Gas barrier multilayer structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas barrier multilayer structure having practically sufficiently high reliability while maintaining a high gas barrier property derived from a liquid crystal polymer and extremely low moisture absorption. SOLUTION: The gas barrier multilayer structure has a moisture permeability (measured at 40 ° C. and a relative humidity of 90%) of 40 g / g.
an outer layer (A) of a resin having a value of m ² / day or more, an intermediate layer (B) of a thermoplastic polymer capable of forming an optically anisotropic molten phase, and an outer layer of a thermoplastic resin (B). And a thermoplastic resin inner layer (C) having a moisture permeability lower than that of (A).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a multilayer structure having a high gas barrier property. INDUSTRIAL APPLICABILITY The multilayer structure of the present invention is useful as a packaging material having excellent preservability for foods and the like, and is also a material for a container for retort sterilization (hereinafter, this may be abbreviated as a retort), particularly a lid material for a retort. It is also useful as a material for forming a retort pouch and a cup-shaped or tray-shaped retort container.

[0002]

2. Description of the Related Art Conventionally, a thermoplastic polymer capable of forming an optically anisotropic molten phase (hereinafter sometimes referred to as "thermoplastic liquid crystal polymer") has a high gas barrier property and extremely low property. It is known that not only it has hygroscopicity, but also has properties such as heat resistance, high frequency characteristics, and chemical resistance that are higher than those of existing general-purpose resins.

In recent years, thermoplastic liquid crystal polymers having these excellent features have been attracting attention as useful materials in the fields of electric and electronic fields, and have been partially commercialized. Specific examples thereof include airtight sealing materials of various gases, electronic circuit board materials such as flexible printed wiring boards, and electric / electronic parts such as connectors and sockets. Among them, in electronic circuit board applications, it has a very low water absorption rate and excellent moisture absorption dimensional stability compared to other polymers, and particularly has excellent electric characteristics with a low dielectric constant and dielectric loss tangent at high frequencies. And that it can be thermally laminated with a metal such as copper foil without using an adhesive.

However, the thermoplastic liquid crystal polymer has not yet been put into practical use as a packaging material which makes use of the high gas barrier properties and extremely low hygroscopicity.

[0005]

The biggest reason why thermoplastic liquid crystal polymers have not been put into practical use as a packaging material, particularly as a film for retorts represented by pouches and lids, is the use of a thermoplastic liquid crystal polymer as a film. That is, the tear strength or edge tear strength is insufficient.
As a method of increasing these strengths to such an extent that they can be practically used, it has been proposed to blend a thermoplastic resin having a large tensile elongation such as polyamide or polyarylate, but it is superior to the thermoplastic liquid crystal polymer. The gas barrier property and the hygroscopic property are impaired. Moreover, since the thermoplastic liquid crystal polymer which is a heat resistant resin and the thermoplastic resin having a large tensile elongation are largely different in thermal characteristics, it is difficult to stably produce a homogeneous film.

The present invention aims to provide a novel material composed of a thermoplastic liquid crystal polymer, which can be used as a packaging material.

[0007]

Means for Solving the Problems As a result of earnest research on practical application of a thermoplastic liquid crystal polymer as a packaging material, the present inventors have laminated a film made of a thermoplastic liquid crystal polymer and a film made of a specific resin. The present invention has been completed by finding that the structure can solve the problems of tear strength or end tear strength while maintaining the high gas barrier properties and extremely low hygroscopicity of the thermoplastic liquid crystal polymer. Came to.

That is, in the present invention, the water vapor permeability (measured under the conditions of 40 ° C. and 90% relative humidity) is 40 g / m ² / day.
From the resin outer layer (A) having the above values, the intermediate layer (B) made of a thermoplastic polymer capable of forming an optically anisotropic molten phase, and the moisture permeability of the outer layer (A) made of a thermoplastic resin, A multilayer structure having an inner layer (C) having a low moisture permeability is provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The thermoplastic liquid crystal polymer constituting the intermediate layer (B) is not particularly limited, but specific examples thereof include known thermotropic liquid crystal polyesters derived from the compounds shown below and derivatives thereof. And thermotropic liquid crystal polyesteramides. However, it goes without saying that a suitable combination of repeating units is required in order to obtain a polymer capable of forming an optically anisotropic molten phase. Further, the thermoplastic liquid crystal polymer may be blended with an appropriate amount of additives such as a lubricant and an antioxidant.

(1) Aromatic or aliphatic dihydroxy compounds (see Table 1 for representative examples)

[0011]

[Table 1]

(2) Aromatic or aliphatic dicarboxylic acid (see Table 2 for representative examples)

[0013]

[Table 2]

(3) Aromatic hydroxycarboxylic acid (see Table 3 for representative examples)

[0015]

[Table 3]

(4) Aromatic diamine, aromatic hydroxyamine or aromatic aminocarboxylic acid (see Table 4 for representative examples)

[0017]

[Table 4]

As typical examples of thermoplastic liquid crystal polymers obtained from these raw material compounds, copolymers (a) to (e) having the structural units shown in Table 5 can be mentioned.

[0019]

[Table 5]

The thickness of the intermediate layer (B) is not particularly limited, but in the multilayer structure of the present invention, the intermediate layer (B) plays the role of a gas barrier material, and its thickness is particularly It directly affects the barrier performance. The thickness of the intermediate layer (B) is usually in the range of 5 to 250 μm, preferably 10 to 150.
It is in the range of μm. In the present invention, the intermediate layer (B) is preferably composed of a film made of a thermoplastic liquid crystal polymer. In that case, one thermoplastic liquid crystal polymer film may be used as the intermediate layer (B), or if desired, a plurality of thermoplastic liquid crystal polymer films may be laminated to form the intermediate layer (B). Further, the thermoplastic liquid crystal polymer film can be reshaped into a desired shape to form the intermediate layer (B). The thickness of the thermoplastic liquid crystal polymer film is not particularly limited, but is usually 5 to 100 μm, preferably 10 to 50 μm.

The thermoplastic liquid crystal polymer film is obtained by extruding a thermoplastic liquid crystal polymer. Although any extrusion molding method is used for this purpose, the well-known T-die method, inflation method and the like are industrially advantageous. In particular, in the inflation method, stress is applied not only in the MD direction of the film but also in the TD direction, so that a film having a well-balanced mechanical property and thermal property between the MD direction and the TD direction can be obtained. It can be used more preferably.

More specifically, since the thermoplastic liquid crystal polymer has a high orientation during melt extrusion, the anisotropy of the mechanical and thermal properties of the film produced from the thermoplastic liquid crystal polymer is likely to be high. Have a tendency. That is, when a thermoplastic liquid crystal polymer is melt-extruded from a T-die, shear stress or stress is applied only in the machine axis direction (hereinafter referred to as MD direction), so that a uniaxially oriented film is obtained. This uniaxially oriented film is M
Although the tensile modulus and mechanical strength in the D direction are high, the direction orthogonal to the MD direction (hereinafter referred to as the TD direction)
In addition to the drawbacks that these values are low and breaks easily occur in the MD direction, the film has a drawback that the film is warped because the dimensional change rate during heating differs between the MD direction and the TD direction. In order to improve this anisotropy of mechanical and thermal properties, the inflation method is applied to the melt extrusion of a thermoplastic liquid crystal polymer, whereby the film is stressed not only in the MD direction but also in the TD direction. Therefore, a biaxially oriented film in which breaks in the MD direction hardly occur can be obtained. Further, according to the inflation method, a film having a well-balanced mechanical property and thermal property between the MD direction and the TD direction can be obtained.

Among the thermoplastic liquid crystal polymer films, a film having a molecular orientation degree SOR of 1.3 or less is MD
It is more practical because it has a good balance of mechanical and thermal properties between the TD and TD directions. The thermoplastic liquid crystal polymer film used in the present invention is naturally different in the degree of molecular orientation SOR required depending on its application field. However, when SOR ≧ 1.5, the deviation of the orientation of the thermoplastic liquid crystal polymer molecules is remarkable, so that the film is a film. Becomes harder,
And it is easy to tear in the MD direction. In the case of application fields where morphological stability is required, such as no warping during heating, SOR ≤
It is desirable that 1.3 be satisfied, and especially when it is necessary to substantially eliminate warpage during heating, SOR ≦ 1.03 is desirable.

Here, the degree of molecular orientation SOR (Segment Orie
ntation Ratio) is an index that gives the degree of molecular orientation of a segment composed of molecules, and is a value that considers the thickness of an object, unlike general MOR (Molecular Orientation Ratio). This degree of molecular orientation S
The OR is calculated as follows.

First, in a well-known microwave molecular orientation degree measuring instrument, a thermoplastic liquid crystal polymer film is inserted into a microwave resonance waveguide so that the film surface is perpendicular to the traveling direction of microwaves, The electric field intensity of microwaves transmitted through the film (microwave transmission intensity) is measured. Then, based on this measured value, the m value (referred to as the refractive index) is calculated by the following equation. m = (Zo / Δz) × [1−νmax / νo] where Zo is the device constant, Δz is the average thickness of the object, and νmax
Is the frequency that gives the maximum microwave transmission intensity when the microwave frequency is changed, and νo is the frequency that gives the maximum microwave transmission intensity when the average thickness is zero (that is, when there is no object).

Next, when the rotation angle of the object with respect to the vibration direction of the microwave is 0 °, that is, the direction of vibration of the microwave and the direction in which the molecules of the object are best oriented, the minimum microwave transmission. The degree of molecular orientation SOR is calculated by m ₀ / m _90, where m ₀ is the m value when the direction in which the strength is given matches, and m ₉₀ is the m value when the rotation angle is 90 °.

The intralayer peel strength of the thermoplastic liquid crystal polymer film is preferably 0.5 kg / cm or more, and 1
More preferably, it is at least kg / cm. The intra-layer peel strength of a film obtained by extrusion-molding a thermoplastic liquid crystal polymer is generally less than 0.5 kg / cm, so containers using this as pouches, lids, trays, cups, etc. May be destroyed during retort treatment, boil sterilization, or during normal handling. In order to solve these problems, (1) a method of heat-treating the thermoplastic liquid crystal polymer film between pressure rolls, or (2) a method of heating the thermoplastic liquid crystal polymer film to melt the polymer, etc. Can be adopted. More specifically, in the case of the above (1), within a range from a temperature 80 ° C. lower than the melting point of the thermoplastic liquid crystal polymer to a temperature 5 ° C. lower than the melting point, the linear pressure of the pressure roll is 20 to 400.
It is effective to apply a pressure within the range of kg / cm. In the method (2), the thermoplastic liquid crystal polymer film is heated in a state where at least one surface of the thermoplastic liquid crystal polymer film is in contact with the support to melt the polymer, and then the polymer layer is cooled and solidified. Is effectively separated from the support.

By performing the above-mentioned treatments, the intralayer peel strength of the thermoplastic liquid crystal polymer film can be increased to the above-mentioned strength which can be preferably used in the present invention.

Next, the resin in the multilayer structure of the present invention,
The outer layer (A) will be described. The moisture permeability of the outer layer (A) is
Careful selection is required as it affects the multilayer structure of the present invention, especially the appearance and gas barrier properties after retort treatment. In this case, good results are obtained such that the higher the moisture permeability of the outer layer (A), the better the appearance and gas barrier properties after the retort treatment. When the multilayer structure of the present invention is subjected to so-called boil sterilization treatment at 100 ° C. or lower, a resin having low heat resistance can be used.
When the temperature is higher than 0 ° C, particularly when the retort treatment is performed at 105 ° C to 135 ° C, it is necessary to consider heat resistance. Further, strength as an external member of a product using the multilayer structure is also required.

Water vapor permeability of the outer layer (A) (unit: g / m ² · da)
y) is preferably selected so as to exhibit a value of 40 or more, in particular 100 or more, more preferably 200 or more. When the outer layer having a value lower than 40 is used, the gas barrier property after the retort treatment is recovered slowly. As a method for evaluating the moisture permeability, JIS Z 02
The method shown in 08, that is, the film was attached to a cup containing a hygroscopic agent, sealed, fixed, and then left in a thermo-hygrostat controlled at 40 ° C. and 90% relative humidity to measure the rate of weight increase. By doing so, the method of obtaining is simple.

In the present invention, the resin of the outer layer (A) preferably used is polyamide, polyester or polycarbonate, and the most preferably used resin is polyamide. Especially nylon-6, nylon-6
6, Nylon-6 / 6,6 and the like are preferable. The water vapor permeability per thickness of 10 μm of this resin is 900 to 11 for the unstretched product.
00g / m ² · day, about 39 for biaxially stretched products
It is 0 g / m ² · day. Therefore, the non-stretched nylon is used at 275 μm or less, particularly 110 μm or less, and more preferably 15 to 40 μm. If it is a biaxially stretched film, it is 97 μm or less, especially 39 μm or less,
More preferably, it can be used in a thickness of 10 to 20 μm.
As another resin, a polycarbonate resin (having a water vapor permeability of 10 μm and a moisture permeability of 120 to 150 g / m ² · day) can be exemplified, and it is preferably used in the range of 10 to 35 μm. Also, polyester resins can be adopted in the present invention. Especially for polyethylene terephthalate resin, the moisture permeability of the stretched film is 60 g per 10 μm thickness.
Since it is / m ² · day, it is used at 15 μm or less.

Also, polyvinyl chloride and polystyrene are
Since it has high moisture permeability, it can be used as a resin forming the outer layer (A). However, since polyvinyl chloride and polystyrene have low heat resistance, the resulting multilayer structure is not suitable for use at high temperatures, and is suitable for applications such as low temperature sterilization.

As the outer layer (A), a film made of the above resin is used alone or in a plurality of layers. When the outer layer (A) has a laminated structure of two or more layers, the moisture permeability as a whole may be within the above range. Moreover, you may form the outer layer (A) using the laminated body which consists of 2 or more types of these resins as needed. Furthermore, the resin forming the outer layer (A) may contain additives such as an antioxidant, a colorant, and a filler.

The moisture permeability of the resin used for the outer layer (A) may be measured in the case of a single layer film, while the moisture permeability of each film may be measured for those laminated by the dry lamination method. Good. Usually, the influence on the moisture permeability of the adhesive in the dry lamination is small, so that it is not necessary to consider it. For a multilayer structure (laminated product or coextruded product) that has already been laminated, the moisture permeability of a film obtained by forming the resin used for the outer layer (A) in a single layer is used as the outer layer (A) of the multilayer structure. ) Of water vapor permeability. When the outer layer (A) is composed of two or more layers, the moisture permeability of the multilayer outer layer (A) can be determined by a conventional method from the moisture permeability of the film formed of a single layer for each of the constituent resins. it can. This concept of moisture permeability can be applied to the inner layer (C) described below.

In the multilayer structure of the present invention, the inner layer (C)
Has a moisture permeability lower than that of the outer layer (A). The thermoplastic resin forming the inner layer (C) is not particularly limited, but it is preferable to select it in consideration of moisture permeability, heat resistance, heat sealability and the like.

More specifically, the lower the moisture permeability of the inner layer (C), the higher the gas barrier property of the obtained multilayer structure. The inner layer (C) is 40 ° C,
Water vapor transmission rate measured under conditions of 90% relative humidity is 20 g / m
² · day or less, more preferably 10 g / m ² · da
It is preferably y or less. A polypropylene resin is preferably used as the thermoplastic resin forming the inner layer (C). For example, a suitable result can be obtained by using a polypropylene film having a thickness of 50 μm (water vapor permeability 7 g / m ² · day) as the inner layer (C). This film is also satisfactory in terms of heat resistance and heat sealability.
Polypropylene is suitable as the resin constituting the inner layer (C) for many purposes, but other thermoplastic resins can also be used.

Examples of the thermoplastic resin constituting the inner layer (C) include, in addition to polypropylene described above, for example, polyolefin resin, polyamide resin, polyester resin different from thermoplastic liquid crystal polymer, polystyrene resin, polyvinyl chloride. System resin, acrylic resin, polyvinylidene chloride resin, polyacetal resin, polypropylene resin such as polycarbonate resin, etc.,
Films made of these thermoplastic resins can be used alone or in a laminated form. Moreover, you may form the inner layer (C) using the laminated body which consists of 2 or more types of these thermoplastic resins as needed. Further, the thermoplastic resin forming the inner layer (C) may contain additives such as an antioxidant, a colorant and a filler.

In order to make the moisture permeability of the inner layer (C) lower than that of the outer layer (A), the resin forming the inner layer (C) is appropriately selected, or the inner layer (C) and the outer layer (A) are It is advisable to adjust the thickness ratio.

In the multilayer structure of the present invention, the outer layer (A), the intermediate layer (B) and the inner layer (C) may be directly bonded, or the outer layer (A) and the intermediate layer (B) or the intermediate layer ( B) and the inner layer (C) may be joined via an adhesive layer (Ad). The adhesive layer (Ad) is, for example, urethane resin,
It is made of epoxy resin or the like. These resins may include polyamide, polyolefin and the like. The thickness of the adhesive layer is preferably in the range of 2 to 20 μm.

The multi-layer structure of the present invention can be produced by a known laminating method such as a dry laminating method, a coextrusion method, a sand laminating method, an extrusion laminating method and a coextrusion laminating method. The dry laminating method is generally a method of laminating three or more kinds of films of an outer layer (A), an intermediate layer (B) and an inner layer (C) with an appropriate adhesive. As the film used for the outer layer (A), a commercially available film can be applied, and a non-stretched nylon film (CN), a biaxially stretched nylon film (ON), a biaxially stretched polyethylene terephthalate film (PET), a polycarbonate film and the like are preferable. However, a biaxially stretched film, especially a biaxially stretched nylon film is the best. As the film used for the inner layer (C), in addition to nylon film (CN or ON), non-stretched polypropylene film (CPP), biaxially stretched polypropylene film (O
PP), polyethylene film, polyvinylidene chloride film and the like are preferable, but when retortability and heat sealability are important, it is desirable to use an unstretched polypropylene film as the innermost layer.

The multilayer structure of the present invention comprises a packaging film,
Especially, when it is used as a packaging material for a retort, its characteristics are most exerted. Examples of the packaging material for the retort include lid materials, pouches, and vacuum packaging. Further, the multilayer structure of the present invention can be used by molding it into a container such as a cup or a tray.

The retort treatment is carried out by filling the packaging material or container made of the multilayer structure of the present invention with food or the like and then degassing the inside by a known means, or by inert gas such as nitrogen or carbon dioxide. Replace the inside with gas,
It is carried out after sealing by means such as heat sealing.
The retort treatment can be carried out by a known method.

The multi-layer structure of the present invention can be used for food, medicine,
It can be used as a packaging material or container for agricultural chemicals, cosmetics, detergents, various industrial products, and the like. In addition, the multilayer structure of the present invention can also be used in applications such as gas storage containers and balloons for airships.

[0044]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Reference Example 1 Thermoplastic liquid crystal polymer having a film thickness of 50 μm by melt extrusion of a thermoplastic liquid crystal polymer having a melting point of 283 ° C., which is a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. The film was formed. Subsequently, the obtained film was fed between a pair of metal pressure rolls (surface temperature: 250 ° C.) under the conditions of a roll linear velocity of 1.0 m / min and a roll linear pressure of 280 kg / cm to obtain a molecular orientation degree. A film having an SOR of 1.02 and an intralayer peel strength of 1.2 kg / cm was obtained. This thermoplastic liquid crystal polymer film is referred to as film B1. In addition,
The intra-layer peel strength was determined by fixing the film B1 on a flat plate with a double-sided adhesive, and further sticking a copper foil serving as a handle on the film B1 with the double-sided adhesive,
It is the peel strength when the film is moved in the direction of 80 degrees at a speed of 50 mm / min and peeled so as to tear in the film.

Reference Example 2 A thermoplastic liquid crystal polymer having a melting point of 330 ° C., which is a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, is melt extruded, and a film having a thickness of 25 μm is formed by an inflation molding method. A plastic liquid crystal polymer film was formed. Subsequently, the obtained film was thermocompression-bonded together with a copper foil having a thickness of 18 μm at 290 ° C., and then left at 340 ° C. for 5 minutes. After cooling, the copper foil is removed by etching from the laminate to obtain a molecular orientation degree SOR of 1.01,
A film having an intralayer peel strength of 1.3 kg / cm was obtained. This liquid crystal polymer film is referred to as film B2.

Example 1 The film B1 obtained in Reference Example 1 was used as the intermediate layer (B) and the outer layer
Commercially available biaxially stretched nylon-6 film as (A) [Unitika Emblem ON (trade name), manufactured by Unitika Ltd.,
Thickness: 15 μm, water vapor permeability measured under the conditions of 40 ° C., 90% relative humidity: 260 g / m ² / day], and a commercially available unstretched polypropylene film [Tosoh Corporation, Tosero Co., Ltd.] as the inner layer (C). CP (trade name), thickness: 50 μm, moisture permeability: 7 g / m ² / day measured under conditions of 40 ° C. and relative humidity of 90% was used to obtain a laminated film by a dry lamination method. Takelac A-385 (trade name) as an adhesive for dry lamination
Takenate A with [Takeda Pharmaceutical Co., Ltd.] as the main ingredient
-50 (trade name) [manufactured by Takeda Pharmaceutical Co., Ltd.] was used as a curing agent, and the laminate was cured at 40 ° C. for 3 days.

This laminated film was thermocompression-bonded to a cup-shaped container made of polypropylene containing water with a non-stretched polypropylene layer as an inner surface by a heat sealer. Thus
The cup-shaped container was covered with the laminated film. Retort device (high-temperature high-pressure cooking sterilization tester) for the container after being covered [Hisaka Seisakusho Co., Ltd., RCS-40RTGN
(Trade name)] was used for retort treatment at 120 ° C. for 30 minutes.

After retort treatment and drying at 80 ° C. for 5 minutes, the lid made of the three-layer film had a good appearance with no wavy pattern. Also, immediately after drying, the outer layer (stretched nylon side) of the film used for the lid material is 65% R
H, inner layer (non-stretched polypropylene side) 100% RH,
The temperature was adjusted to 20 ° C. and the humidity was adjusted to control the oxygen transmission rate (hereinafter, this may be referred to as OTR) of OXTRAN.
It was measured using -10 / 50A (trade name) [manufactured by MOCON]. Table 6 shows the measurement results and the visual evaluation of the appearance. Here, the OTR immediately after drying is 0.
9cc / m ² · day · atm, but then OT
R decreased rapidly and after 12 hours 0.2 cc / m ² ·
day · atm is shown.

Example 2 A laminated film was prepared in the same manner as in Example 1 except that a thickened biaxially stretched nylon film (25 μm) was used as the outer layer (A). The cup-shaped container was covered with a lid and then subjected to retort treatment. Table 6 shows the results of OTR measurement and the evaluation of the appearance of the lid.

Example 3 Example 1 was repeated except that a biaxially stretched nylon film (37 μm) having a further increased thickness was used as the outer layer (A).
A laminated film was prepared in the same manner as in (1), and the cup-shaped container was covered with the film and then subjected to retort treatment. Table 6 shows the results of OTR measurement and the evaluation of the appearance of the lid.

Example 4 A laminated film was prepared in the same manner as in Example 1 except that a non-stretched nylon film was used as the outer layer (A) instead of the biaxially stretched nylon film. The cup-shaped container was covered with the film, and then retort-treated. Table 6 shows the results of OTR measurement and the evaluation of the appearance of the lid.

Example 5 A laminated film was prepared in the same manner as in Example 1 except that the film B2 obtained in Reference Example 2 was used as the intermediate layer (B) in place of the film B1. After making and covering the cup-shaped container with the film,
Retort processed. Table 6 shows the results of OTR measurement and the evaluation of the appearance of the lid.

Example 6 An example except that a biaxially oriented polyethylene terephthalate film [Lumirror (trade name) manufactured by Toray Industries, Inc.] was used as the outer layer (A) in place of the biaxially oriented nylon film in Example 5. The same operation as in 1 was carried out to prepare a laminated film, the cup-shaped container was covered with the film, and then the retort treatment was performed. Table 6 shows the results of OTR measurement and the evaluation of the appearance of the lid.

Comparative Example 1 In Example 1, instead of the film B1, the thickness was 25 μm.
m polyvinylidene chloride film [Asahi Kasei Kogyo Co., Ltd., SARAN-UB (trade name)] was used in the same manner as in Example 1 except that two layers were used as the intermediate layer (B). A laminated film was prepared, a cup-shaped container was covered with the film, and then a retort treatment was performed. Table 6 shows the results of OTR measurement and the evaluation of the appearance of the lid.

[0055]

[Table 6]

[0056]

According to the present invention, it is possible to obtain a multi-layer structure which is composed of a thermoplastic liquid crystal polymer and can be used as a packaging material.

Continued front page    F term (reference) 3E067 AA03 AA11 AB01 BA07A                       BA10A BA12A BB14A BB25A                       CA04 CA17 FA01 FB13 FC01                       GC02                 3E086 AA01 AB01 AC07 AD01 BA04                       BA15 BB01 BB02 BB85 CA03                       DA08                 4F100 AK01B AK01C AK07C AK41A                       AK45A AK46A AK48 BA03                       BA07 BA10A BA10C EH23                       EH232 GB16 GB23 JA20B                       JB16B JB16C JC00 JD04A                       JK06B JN10B JN30B YY00A                       YY00B

Claims (8)

[Claims] 1. A resin outer layer (A) having a water vapor permeability (measured under conditions of 40 ° C. and 90% relative humidity) of 40 g / m ² / day or more and an optically anisotropic molten phase. A multilayer structure comprising an intermediate layer (B) made of a thermoplastic polymer that can be formed and an inner layer (C) made of a thermoplastic resin and having a moisture permeability lower than that of the outer layer (A). 2. An outer layer (A), an intermediate layer (B), an inner layer (C)
The multi-layer structure according to claim 1, wherein each of the two is bonded via an adhesive layer. 3. The intermediate layer (B) has a molecular orientation degree (SOR).
The multi-layer structure according to claim 1 or 2, which comprises a film having a ratio of 1.3 or less. 4. The intermediate layer (B) has an intralayer peel strength of 1 kg.
The multilayer structure according to any one of claims 1 to 3, which is formed of a film having a thickness of at least 1 / cm. 5. The multilayer structure according to claim 1, wherein the resin used in the outer layer (A) is at least one resin selected from polyamide, polyester and polycarbonate. 6. The multilayer structure according to claim 1, wherein the thermoplastic resin used for the inner layer (C) is a polypropylene resin. 7. A packaging material comprising the multilayer structure according to any one of claims 1 to 6. 8. A container for a retort, at least a part of which is composed of the multilayer structure according to any one of claims 1 to 6.