JP2014050995A - Polyamide based resin laminate film - Google Patents

Abstract

【Task】
Provided is a polyamide-based resin laminated film excellent in oxygen gas barrier property, transparency, bending pinhole property, and thermal stability.
[Solution]
It has a layer (A) composed of an aliphatic polyamide (a) as both outermost layers, and the polymetaxylylene adipamide (b) and the modified ethylene-acrylic ester copolymer (c) in a mass ratio of (b) / (C) A polyamide-based resin laminated film having a laminated structure of at least three layers, the layer (B) containing at a ratio of 97/3 to 85/15 mass% as an inner layer, wherein the modified ethylene -The polyamide-type resin laminated | multilayer film characterized by the mass ratio of the ethylene component of an acrylic ester copolymer (c) and an acrylic ester component being in the range of 90 / 10-70 / 30 mass%.
[Selection figure] None

Description

  The present invention relates to a polyamide-based resin laminated film that can be boiled or retortized and used for a food barrier packaging material with excellent gas barrier properties.

  Conventionally, polyamide-based resin films are used alone or as laminates with other films for various packaging materials. For example, in order to improve gas barrier properties, they are laminated with various gas barrier resins. Has been done. Particularly in food packaging applications, such polyamide-based resin laminated films are often used from the viewpoints of excellent oxygen gas barrier properties, bending pinhole properties, transparency, heat resistance, and the like.

  In such a polyamide-based resin laminated film, in order to improve the flex pinhole resistance of the polyamide resin, it is possible to add a flex pinhole improvement material such as a thermoplastic elastomer within a range that does not impair the oxygen gas barrier property. it can. In particular, an olefin-based elastomer is preferably used for reasons such as low cost and excellent flexibility.

  Patent Document 1 discloses a polyamide resin (X) 80 obtained from a diamine containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid containing 70 mol% or more of an α, ω-aliphatic dicarboxylic acid having 6 to 12 carbon atoms. -99% by mass and a mixed resin (Z) composed of 20 to 1% by mass of a resin obtained by graft-modifying ethylene-ethyl acrylate copolymer resin with maleic anhydride (Y) and melt-kneaded and extruded to form a film After that, a stretched polyamide film obtained by biaxial stretching is disclosed.

  Patent Document 2 discloses a polyamide resin obtained from a diamine component containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid component containing 70 mol% or more of an α, ω-aliphatic dicarboxylic acid having 6 to 12 carbon atoms. (X) A mixed resin (Z) comprising a mixture of 80 to 99% by mass and a resin obtained by graft copolymerization of polymethyl methacrylate with a mixture of ethylene-propylene rubber and isotactic-polypropylene (Y) 20 to 1% by mass It is disclosed a stretched polyamide film obtained by melt kneading and extruding to form a film and then biaxially stretching.

JP 2002-226612 A JP 2004-346103 A

  Patent Document 1 discloses a polyamide-based resin film having improved bending pinhole resistance by blending a predetermined amount of an ethylene-ethyl acrylate copolymer resin modified with maleic anhydride into polymetaxylylene adipamide, and at least the film Although the polyamide-based resin laminated film including one layer is disclosed, the ratio of the ethyl acrylate component contained in the bending-resistant pinhole improving material is as large as 50 to 95 mol%, and the thermal stability is poor. It can be a cause.

  In Patent Document 2, a predetermined amount of a resin obtained by graft copolymerization of polymethylmethacrylate with a mixture of ethylene-propylene rubber and isotactic-polypropylene with polymetaxylylene adipamide is improved in bending pinhole resistance. Although a polyamide-based resin film and a polyamide-based resin laminated film including at least one layer of the film are disclosed, since the bending-resistant pinhole improving material is not acid-modified, whether a sufficient modification effect can be obtained. The question remains about. In fact, the bending-resistant pinhole test using a gelboflex tester is performed under conditions of 500 times at 23 ° C., and how many tests are performed at 3000 ° C. at 23 ° C. and 500 times at 5 ° C. It is not disclosed whether or not bending pinhole resistance is manifested. Moreover, since the interfacial tension of the bending-resistant pinhole improving material is large, the dispersion diameter in polymetaxylylene adipamide is large, and the transparency may be impaired.

  An object of the present invention is to solve the above-mentioned problems of the prior art, that is, to provide a polyamide-based resin laminated film excellent in bending pinhole resistance and thermal stability while maintaining oxygen gas barrier properties and transparency. And

  This invention has the layer (A) which consists of aliphatic polyamide (a) as both outermost layers, and polymetaxylylene adipamide (b) and a modified ethylene-acrylic acid ester copolymer (c) by mass ratio. (B) / (c) = A polyamide-based resin laminated film having a layered structure consisting of at least three layers (B) having a layer (B) contained at a ratio of 97/3 to 85/15% by mass as an inner layer, The weight ratio of the ethylene component and the acrylate component of the modified ethylene-acrylate copolymer (c) is in the range of 90/10 to 70/30% by mass. Is.

  According to the present invention, it is possible to provide a polyamide-based resin laminated film excellent in bending pinhole resistance and thermal stability while maintaining oxygen gas barrier properties and transparency, and when used as a food packaging film. In addition, the entry of oxygen gas from the outside can be reduced and the food can be kept fresh.

The present invention is described in detail below.
The polyamide-based resin laminated film of the present invention has a layer (A) composed of an aliphatic polyamide (a) as an outermost layer, and comprises polymetaxylylene adipamide (b) and a modified ethylene-acrylate copolymer (c And a layered structure consisting of at least three layers including the layer (B) consisting of The aliphatic polyamide resin (a), polymetaxylylene adipamide (b), and modified ethylene-acrylic acid ester copolymer (c) will be described below.

[Aliphatic polyamide (a)]
Preferred examples of the aliphatic polyamide (a) used in the present invention include a ring-opening polymer of cyclic lactam, a polycondensate of aminocarboxylic acid, and a polycondensate of dicarboxylic acid and diamine. Specifically, a homopolymer of ε-caprolactam called nylon-6, polyhexamethylene adipamide called nylon-66, etc. can be obtained at low cost, and the stretching operation can be performed smoothly. It is preferable from the point of obtaining.

[Polymetaxylylene adipamide (b)]
The polymetaxylylene adipamide (b) used in the present invention mainly means a polyamide resin obtained by polymerizing metaxylylenediamine and adipic acid.

  The diamine component constituting the polymetaxylylene adipamide (b) is 70 mol% or more, preferably 80 mol% or more, and more preferably 90 mol% or more is metaxylylenediamine. It may contain less than 30 mol% of isomers such as orthoxylylenediamine and paraxylylenediamine, or aliphatic diamines having 6 to 12 carbon atoms, but these are included if possible from the viewpoint of gas barrier properties and heat resistance. It is better not to.

  The dicarboxylic acid component constituting the polymetaxylylene adipamide (b) is 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more is adipic acid. The gas barrier may contain an aliphatic dicarboxylic acid having 7 to 12 carbon atoms, an aromatic dicarboxylic acid such as terephthalic acid or isophthalic acid, or a cyclic aliphatic dicarboxylic acid such as 1,4-cyclohexanedicarboxylic acid. From the viewpoint of properties and stretchability, it is preferable that these are not included if possible.

[Modified ethylene-acrylic acid ester copolymer (c)]
The modified ethylene-acrylic acid ester copolymer (c) used in the present invention is a copolymer obtained by polymerizing ethylene, acrylic acid ester and carboxylic acid anhydride.

As the acrylate ester, it is preferable to use methyl acrylate, ethyl acrylate, or butyl acrylate. If the carbon chain of the alcohol-derived hydrocarbon group in the acrylate ester is longer than this, the thermal stability is deteriorated, causing foreign matters during molding, and the appearance of the film may be significantly deteriorated.
The modified ethylene-acrylic acid ester copolymer (c) includes other monomers, for example, vinyl acetate or a partially saponified product thereof, acrylic acid, methacrylic acid, acrylic acid esters, and partial metal neutralized products of methacrylic acid esters. (Ionomers), 1-alkenes such as butene, alkadienes, styrene and the like may be included, and a plurality of these structural units may be included. The modified ethylene-acrylic acid ester copolymer (c) may be used in combination of two or more different types.

The mass ratio of the ethylene component and the acrylate component contained in the modified ethylene-acrylic acid ester copolymer (c) is 90/10 to 70/30% by mass, preferably 85/15 to 75/25% by mass, More preferably, it is 85 / 15-80 / 20 mass%.
When the mass ratio of the ethylene component is larger than 90% by mass, the modified ethylene-acrylic acid ester copolymer (c) has a small polarity and is dispersed in the polymetaxylylene adipamide (b) having an amide bond having a large polarity. Sexuality gets worse. Due to poor dispersibility in polymetaxylylene adipamide (b), the total surface area of the interface between polymetaxylylene adipamide (b) and the modified ethylene-acrylate copolymer (c) is reduced. As a result, when the film is bent, the stress tends to concentrate on the interface, and a sufficient effect of improving the resistance to bending pinholes cannot be expected. Further, the dispersion diameter of the elastomer is increased and the haze is increased, so that transparency is impaired. Conversely, when the weight ratio of the acrylic acid ester component having a thermal stability smaller than 70% by mass is increased, the thermal stability of the resin itself is deteriorated. As a result, the modified ethylene-acrylic acid ester copolymer (c) is gelled at the time of forming the film, which may cause foreign matters such as fish eyes, and the appearance of the film may be remarkably deteriorated.

  Examples of the carboxylic acid anhydride contained in the modified ethylene-acrylic acid ester copolymer (c) include acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, and the like. Acid is preferred.

  The carboxylic acid anhydride contained in the modified ethylene-acrylic acid ester copolymer (c) is preferably 0.1 to 1% by mass. When it is less than 0.1% by mass, the interfacial tension of the bending-resistant pinhole property improving material in the polymetaxylylene adipamide (b) is not reduced, and a sufficient bending-resistant pinhole property improving effect cannot be obtained. On the other hand, if it is larger than 1% by mass, the carboxylic acid anhydride is liberated at the time of molding and use as a packaging material, which may cause changes in foreign matter and taste. By modifying within the above range, the resistance to bending pinholes can be improved without affecting the appearance of the product and the taste of food.

  In the present invention, the modified ethylene-acrylic acid ester copolymer (c) is added to the layer (B) in an amount of 3 to 15 masses from the viewpoints of improvement in bending pinhole resistance and improvement in transparency when formed into a film. % Content is preferable. If it is less than 3% by mass, sufficient bending-resistant pinhole property cannot be expected, and if it is more than 15% by mass, the gas barrier property is lowered. By containing in the above range, the bending-resistant pinhole property can be improved while maintaining the gas barrier property.

  Moreover, in this invention, it is preferable to provide an adhesive layer (C) layer from the point of interlayer adhesiveness between (A) layer and (B) layer. Although there is no restriction | limiting in particular as a component which comprises an adhesive layer, The mixture of aliphatic polyamide (a) and polymetaxylylene adipamide (b), polyolefin type, and polyester type adhesive resins etc. should be used suitably. I can do it.

  The mixture of the aliphatic polyamide (a) and the polymetaxylylene adipamide (b) is preferably a homogeneous mixture composition of the aliphatic polyamide (a) and the polymetaxylylene adipamide (b). This mixed composition may be a mixture of the raw material aliphatic polyamide (a) and the raw material polymetaxylylene adipamide (b), or it is out of specification when the polyamide-based laminated film of the present invention is produced. It may be prepared by adding a raw material to a raw material mixture generated as a film or a cut end material (ear trim) or a generated raw material mixture. The composition (mixing ratio) of the above mixture is selected from a range of 95/5 to 70/30 by mass ratio of aliphatic polyamide (a) and polymetaxylylene adipamide (b) from the viewpoint of interlayer adhesion. It is preferable.

  If the composition of the adhesive layer (C) made of a mixture of the aliphatic polyamide (a) and the polymetaxylylene adipamide (b) is clearly different from that of the aliphatic polyamide (a) (A) In the layer (B) composed of the polymetaxylylene adipamide (b) and the ethylene-acrylate copolymer (c), a polyamide other than the main component can be contained up to about 30% by weight. For example, a small amount of polymetaxylylene adipamide (b) is added to the (A) layer made of aliphatic polyamide (a), and polymetaxylylene adipamide (b) and an ethylene-acrylate copolymer (c) A small amount of the aliphatic polyamide (a) may be contained in the layer (B) comprising

In the present invention, the aliphatic polyamide (a), the polymetaxylylene adipamide (b), and the mixture of the aliphatic polyamide (a) and the polymetaxylylene adipamide (b) are often hygroscopic. Therefore, it is preferable that the water content is usually 0.1% by mass or less by drying in advance. Thereby, when a raw material is heat-melted and extruded, there is no generation of water vapor and oligomers, and film formation can be performed satisfactorily.
Various additives such as a lubricant, an antistatic agent, an antioxidant, an antiblocking agent, a stabilizer, a dye, a pigment, and inorganic fine particles can be added to these raw material polyamide and polyamide mixed composition.

  The polyamide-based resin laminated film of the present invention having the above-described structure has (A) layers made of aliphatic polyamide (a) in both outermost layers, and includes polymetaxylylene adipamide (b) and modified ethylene- It has at least three layers of laminate structure (B) layer made of acrylic ester copolymer (c) in the inner layer, and if necessary, aliphatic polyamide (a) and polymetaxylylene adipamide (b) Or a layer (C) made of a polyolefin-based or polyester-based adhesive resin.

As a layer structure of the polyamide-type resin laminated film of this invention, three-layer structure, such as (A) / (B) / (A), (A) / (C) / (B) / (C) / (A) The five-layer configuration such as the above is preferably exemplified, but is not limited to those exemplified. Further, an adhesive layer may be further provided between the above layers.
Moreover, as thickness of each layer, from the point of bending-resistant pinhole property, (A) layer is 5 to 70% of all layers, (B) layer is 8 to 40% of all layers, and (C) layer is all layers. It is desirable to set it as 3 to 40%.
The total thickness of the polyamide-based resin laminated film of the present invention is 10 to 40 μm in view of the balance between oxygen gas barrier properties and flex pinhole resistance, wear resistance, and suitable for flexible packaging applications. Is preferable in obtaining.

  When the polyamide-based resin laminated film of the present invention is used as a packaging bag, a gas barrier resin layer is further laminated on the surface of the polyamide-based resin laminated film from the viewpoint of maintaining the quality of the contents and preventing corruption. Gas barrier properties and moisture-proof properties can be imparted by vapor-depositing a metal oxide such as silicon dioxide or alumina, or applying a gas barrier coating agent.

[Film Production Method]
The polyamide-based resin laminated film according to the present invention can be produced by various methods, but for example, it is preferably produced by the following method. That is, using a polyamide-based resin as a raw material, a substantially amorphous and non-oriented film (hereinafter referred to as “unstretched film”) is usually produced by a coextrusion method. The unstretched film is produced, for example, by melting the above raw material with 1 to 5 extruders, extruding from a flat die or an annular die, and then rapidly cooling to obtain a flat or annular unstretched film. A coextrusion method can be employed.

Next, the above-mentioned unstretched film is usually 2.5 to at least in one direction from the viewpoint of stretching effect, film strength, etc. The film is stretched 5 times, preferably 2.6 to 3.5 times in the longitudinal and lateral biaxial directions.
As the biaxial stretching method, any conventionally known stretching method such as tenter-type sequential biaxial stretching, tenter-type simultaneous biaxial stretching, tubular simultaneous biaxial stretching, and the like can be adopted. For example, in the case of the tenter type sequential biaxial stretching method, the unstretched film is heated to a temperature range of 50 to 110 ° C., and stretched 2.6 to 3.5 times in the longitudinal direction by a roll type longitudinal stretching machine, Then, it can manufacture by extending | stretching 2.6 to 3.5 time in a horizontal direction within the temperature range of 60-140 degreeC with a tenter type horizontal extending | stretching machine. Moreover, in the case of the tenter type simultaneous biaxial stretching and the tubular type simultaneous biaxial stretching method, for example, in the temperature range of 60 to 130 ° C., it is manufactured by stretching 2.5 to 5 times in each axial direction simultaneously in the longitudinal and lateral directions. can do.

  The biaxially stretched film stretched by the above method is subsequently heat-set. Dimensional stability at room temperature can be imparted by heat setting. The treatment temperature in this case is preferably selected in the range of 210 ° C. to 225 ° C., more preferably 210 to 220 ° C. If the heat setting temperature is within the above range, the heat setting is sufficiently performed, the stress at the time of stretching is relaxed, and a sufficient lamination strength is maintained. Moreover, sufficient mechanical strength, impact resistance and pinhole resistance of the film can be obtained, and an excellent film free from troubles such as breakage and whitening of the film surface can be obtained.

  In the present invention, in order to relieve the stress of crystallization shrinkage due to heat fixation, relaxation is performed sufficiently in the range of 0 to 15%, preferably 3 to 10% in the width direction during heat fixation. Since the film is uniformly relaxed in the width direction of the film, the shrinkage rate in the width direction becomes uniform, and a film having excellent room temperature dimensional stability can be obtained. Further, since relaxation is performed following the shrinkage of the film, there is no fluttering in the film, no fluttering in the tenter, and no breakage of the film.

In the present invention, after the relaxation, the film is stretched again at a temperature of 140 ° C. to 200 ° C. in the range of 2 to 9%, preferably 3 to 7%, more preferably 4 to 7%.
If the re-lateral stretching temperature is within the above range, an appropriate stress at the time of stretching can be obtained, and uniform stretching can be performed, so that the lateral shrinkage in the width direction becomes uniform. In addition, heat setting is not applied after stretching, and the transverse shrinkage tends to be developed.
Further, if the re-lateral stretching ratio is within the above range, a sufficient transverse shrinkage rate to follow the solidification shrinkage of the sealant is obtained, the appearance of the seal part is good, and an appropriate shrinkage rate is obtained, Occurrence of problems such as wrinkles and misalignment can be prevented in printing and laminating processes.
The stretched film formed by the above method is cooled and wound by a conventional method.

  Moreover, the polyamide-based resin laminated film of the present invention can be subjected to further processing by laminating a sealant layer. By providing a coating layer of vinylidene chloride resin, polyvinyl alcohol resin, ethylene-vinyl acetate copolymer saponified resin, etc. on this film, the gas barrier property is further improved, and the film has excellent bending pinhole resistance Is obtained. Moreover, the laminated body obtained by laminating | stacking with a various single layer or laminated | multilayer film by the dry lamination method, the wet lamination method, the extrusion lamination method, etc. becomes the thing excellent in the bending pinhole property.

The number of pinholes generated after a bending test with a gelbo flex tester is 3000 times at 23 ° C. and 500 times at 5 ° C. at a relative humidity of 50% of the polyamide-based resin laminated film formed by the above method is 1 piece / 0. .05m ² or less is preferable. If the number of occurrences of pinholes is within such a range, holes will not be opened due to bending during food packaging or transportation.

The polyamide resin laminated film molded by the above method preferably has an oxygen permeability of 20 cc / m ² · day · atm or less at a thickness of 15 μm under conditions of 23 ° C. and 0% relative humidity. As long as the oxygen permeability is within such a range, the oxygen gas barrier property sufficient to keep the content food fresh as a food packaging film can be maintained.

  Moreover, it is preferable that the total haze of the polyamide-type resin laminated film shape | molded by the said method is 10% or less. If the total haze is within such a range, sufficient transparency as a food packaging film can be maintained.

  Furthermore, the puncture impact strength of the polyamide-based resin laminated film formed by the above method is preferably 15 kg · cm / sheet or more. If the puncture impact strength is within the range, sufficient strength as a food packaging film can be maintained.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the following examples, the obtained film was evaluated by the following method. Table 1 shows the layer structure and evaluation results of the film in each example.

(1) Bending-resistant pinhole property A film cut into a size of 20 cm x 27.5 cm was conditioned for 24 hours or longer under conditions of a temperature of 23 ° C and a relative humidity of 50%, and a gelbo flex tester (Science Using a No.901 type manufactured by Kogyo Co., Ltd. (compliant with the MIL-B-131C standard), the bending test was repeated as follows, and the number of pinholes per 0.05 m ² was measured.
The rectangular test film is formed into a cylindrical shape having a length of 20 cm, and one end of the wound cylindrical film is fixed to the outer periphery of the tester disk-shaped fixed head, and the other end is fixed to the outer periphery of the tester disk-shaped movable head. While the movable head is brought close to 8.8 cm along the axis of both heads facing in parallel to the fixed head (the fixed head and the movable head are opposed to each other with a distance of 17.5 cm), 440 °. A bending test is performed for 1 minute, in which the stroke until the movable head is returned to the initial position is 1 cycle. 17.5 cm excluding the fixed head of the tested film and the portion fixed to the outer periphery of the movable head after performing 3000 cycles continuously at a speed of 40 cycles per The pin number of holes generated in the portion of the 27.5cm, pinhole tester (Sanko Electronic Laboratory Ltd., TRD-type) by applying a voltage of 1kV was thus measured. A case where the number of bent pinholes generated per film of 0.05 m ² was 1 or less was evaluated as ◯, and a case where the number was more than 1 was evaluated as ×.

(2) Oxygen gas barrier properties
Oxygen permeability at 23 ° C. and 0% RH (cc / m ² · 24 h · atm) in accordance with JIS K-7126 B method using MOCON oxygen permeability measuring device OX-TRAN from Hitachi High-Technologies Corporation ) Was measured. Those gas permeability of not more than ^{20cc / m 2 · 24h · atm} ○, and as × larger than ^{20cc / m 2 · 24h · atm} .

(3) Total haze The total light transmittance (%) was measured based on JIS K-7105 using a Nippon Denshoku Industries Co., Ltd. haze meter NDH-5000. A sample having a total haze of 10% or less was evaluated as ◯, and a sample having a total haze greater than 10% as ×.

(4) Puncture impact test
Using a puncture type film impact tester manufactured by Toyo Seiki Seisakusho, puncture impact strength (kg · cm / sheet) was measured in accordance with JIS K-7221. A sample having a puncture impact strength of 15 kg · cm / sheet or more was rated as “◯”, and a sample having a puncture impact strength of less than 15 kg · cm / sheet was marked as “X”.

(5) Appearance When the film was visually observed, a transparent film having no streaks or irregularities was marked with “◯”, a film with some streaks or irregularities was marked with “Δ”, and a film with a lot of streaks or irregularities with a markedly bad appearance was marked with “X”.

[Aliphatic polyamide (a)]
(A) -1: Nylon 6 (Ube Industries, UBE nylon 1022FD37)

[Polymetaxylylene adipamide (b)]
(B) -1: Polymetaxylylene adipamide (Mitsubishi Gas Chemical Co., Ltd., MX nylon S6010)

[(C) Modified ethylene-acrylic acid ester copolymer (c)]
(C) -1: ethylene-methyl acrylate copolymer (manufactured by DuPont, DPA21E810, ethylene content: 80 mass%, maleic anhydride content: 0.1 mass%)
(C) -2: ethylene-butyl acrylate copolymer (manufactured by Arkema, Rotoryl 17BA04, ethylene content: 83% by mass, maleic anhydride content: 0.1% by mass)
(C) -3: Ethylene-ethyl acrylate copolymer (manufactured by Arkema, Bondine AX8390, ethylene content: 68% by mass, maleic anhydride content: 0.3% by mass)
(C) -4: ethylene-methyl acrylate copolymer (manufactured by Nippon Polyethylene, Lexpearl ET220X, ethylene content: 93% by mass, maleic anhydride content: 0.1% by mass)
(C) -5: ethylene-ethyl acrylate copolymer (manufactured by DuPont, Everflex EEA A703P, ethylene content 75% by mass, no maleic anhydride modification)

Example 1
(A) layer (a) -1 and (B) layer (b) -1 and (c) -1 mixed at a ratio (mass ratio) of 90:10 as layer (C) A mixture of (a) -1 and (b) -1 at a ratio (mass ratio) of 85:15 was melted separately using three 65 mmφ extruders. Next, the (A) layer and the (C) layer are divided almost in half by the distribution block, and in the coextrusion T die in the order of (A) / (C) / (B) / (C) / (A). And then extruded as a laminated film having a five-layer structure, and tightly cooled to a cast roll at 30 ° C., respectively, (A) layer is 35 μm, (C) layer is 20 μm, (B) layer is 40 μm, (C) layer is An unstretched laminated film having a thickness of 20 μm and a layer (A) of 35 μm was obtained.

The obtained unstretched laminated film was stretched three times in the machine direction by a roll-type stretcher under the condition of 60 ° C., and then the end of the longitudinally stretched film was held with a tenter clip, and was 100 ° C. in a tenter oven. The film was stretched 3.5 times in the transverse direction under the above conditions, heat-set at 220 ° C., subjected to 7% transverse relaxation, cooled to 180 ° C., and subjected to 5% re-lateral stretching.
The film after re-lateral stretching is cooled to room temperature, both end portions corresponding to the gripping portion of the clip are trimmed, and the product film portion after trimming is wound up in a roll shape, and the layer (A) is 3.5 μm. (A) / (C) / (B) / (C) / (A) having a total thickness of (A) / (C) / (B) / (C) / (A), wherein the (C) layer is 2.0 μm and the (B) layer is 4 μm. A laminated biaxially stretched film of 15 μm was obtained. The evaluation results of the film are shown in Table 1.

(Example 2)
A laminated biaxially stretched film was produced and evaluated in the same manner as in Example 1 except that (b) -2 was used as the bending-resistant pinhole property improving material. The results are shown in Table 1.

(Example 3)
A laminated biaxially stretched film was produced and evaluated in the same manner as in Example 2 except that the mass ratio of (b) -1 and (c) -1 in the (B) layer was 97/3. The results are shown in Table 1.

(Comparative Example 1)
A laminated biaxially stretched film was produced and evaluated in the same manner as in Example 1 except that the bending-resistant pinhole property improving material was not added to the layer (B). The results are shown in Table 1.

(Comparative Example 2)
A laminated biaxially stretched film was produced and evaluated in the same manner as in Example 1 except that (c) -3 was used as the bending-resistant pinhole improving material. The results are shown in Table 1.

(Comparative Example 3)
A laminated biaxially stretched film was produced and evaluated in the same manner as in Example 1 except that (c) -4 was used as the bending-resistant pinhole improving material. The results are shown in Table 1.

(Comparative Example 4)
A laminated biaxially stretched film was produced and evaluated in the same manner as in Example 1 except that (c) -5 was used as the bending-resistant pinhole improving material. The results are shown in Table 1.

(Comparative Example 5)
The bending-resistant pinhole improving material is an ethylene-butene 1 copolymer (manufactured by Mitsui Chemicals, Admer NF307: ethylene content 83 mass%, maleic anhydride content: 0.1 mass%, hereinafter abbreviated as (n) -1. A laminated biaxially stretched film was produced and evaluated in the same manner as in Example 1 except that it was sometimes. The results are shown in Table 1.

  The polyamide-based resin laminated film of the present invention is excellent in bending pinhole resistance and heat resistance, can be boiled and retorted, has excellent transparency and oxygen gas barrier properties, and is suitable for applications such as food packaging materials. Used for.

Claims (11)

  It has a layer (A) composed of an aliphatic polyamide (a) as both outermost layers, and the polymetaxylylene adipamide (b) and the modified ethylene-acrylic ester copolymer (c) in a mass ratio of (b) / (C) A polyamide-based resin laminated film having a laminated structure of at least three layers, the layer (B) containing at a ratio of 97/3 to 85/15 mass% as an inner layer, wherein the modified ethylene -The polyamide-type resin laminated | multilayer film characterized by the mass ratio of the ethylene component of an acrylic ester copolymer (c) and an acrylic ester component being in the range of 90 / 10-70 / 30 mass%.   2. The polyamide-based resin laminated film according to claim 1, wherein a ratio of the carboxylic acid anhydride in the modified ethylene-acrylic acid ester copolymer (c) is 0.1 to 1% by mass.   The polyamide-based resin laminated film according to claim 1 or 2, wherein the acrylic ester in the modified ethylene-acrylic ester copolymer (c) is any of methyl acrylate, ethyl acrylate, and butyl acrylate. ^{2. The} number of pinholes generated after performing a bending test with a gelboflex tester 3000 times at 23 ° C. and 500 times at 5 ° C. under a relative humidity of 50% is 1 / 0.05 m ² or less. The polyamide-type resin laminated film in any one of -3. The polyamide-based resin laminated film according to any one of claims 1 to 4, wherein an oxygen permeability at a thickness of 15 µm under conditions of 23 ° C and 0% relative humidity is 20 cc / m ² · day · atm or less.   The polyamide-based resin laminated film according to any one of claims 1 to 5, wherein the total haze is 10% or less.   The polyamide-based resin laminated film according to claim 1, which has a puncture impact strength of 15 kg · cm / sheet or more.   The polyamide-based resin laminated film according to any one of claims 1 to 7, wherein the aliphatic polyamide (a) is nylon 6 or nylon 66.   The polyamide-based resin laminated film was sequentially biaxially stretched at a draw ratio of MD / TD = 2.5 to 5.0 times / 2.6 to 3.5 times, and then heat-set at 210 ° C. to 225 ° C. The polyamide-type resin laminated film in any one of Claims 1-8 obtained by these.   The polyamide resin laminated film according to claim 1, which has a sealant layer on at least one surface of the polyamide resin laminated film.   A food packaging film using the polyamide-based resin laminated film according to any one of claims 1 to 10, and a food packaging body in which food is packaged with the film.