JP5467296B2 - Polyamide-based laminated film with excellent water vapor and alcohol permeability - Google Patents

Description

The present invention relates to a polyamide-based laminated film obtained by laminating an ethylene-vinyl acetate copolymer resin on a polyamide film having high moisture permeability and alcohol permeability and excellent mechanical strength, which is used in food, pharmaceuticals, industrial material packaging fields, etc. It relates to the manufacturing method.

Biaxially stretched polyamide film has excellent properties such as toughness, pinhole resistance, heat resistance, etc., so it is mainly used for packaging films, especially food, pharmaceuticals and industrial materials packaging fields.
It is used as a base material for single-layer films or laminate films.

On the other hand, in desiccant packages and alcohol-based freshness-keeping packages, specific water vapor and gas permeability are required, but polyamide films generally have high moisture permeability and alcohol permeability. Are also used (see, for example, Patent Documents 1 and 2).
Patent Document 3 discloses a biaxially stretched polyamide film having excellent dimensional stability and high water vapor permeability. By selecting stretching and heat treatment conditions under specific conditions, a film having a high α-type crystallinity and a small crystal size can be obtained. Thereby, it is possible to improve the elongation at the time of moisture absorption from the conventional 3% to 0.7% while maintaining the conventional water vapor permeability.
Moreover, some examples are shown as a laminated film for the same use and a similar use. (
For example, Patent Documents 4 to 8) However, none of them defines a biaxially stretched nylon film, and is implemented by using a special resin or a porous film, drilling, partially laminating, etc. In addition, there are problems of quality instability and manufacturing cost due to an increase in the number of processes. In addition, because pattern laminate has high permeability of the alcohol content,
There is a possibility of delamination and there is a safety problem.
In Patent Document 9, the description of reducing the thickness of the biaxially stretched polyamide film is shown in the examples. However, not only by simply reducing the thickness, sufficient moisture permeability and alcohol permeability cannot be expressed.
It becomes difficult to obtain the seal strength required for the product.

JP 2003-21604 A JP 2002-204652 A JP-A-56-056827 JP-A-8-52844 Japanese Patent Laid-Open No. 10-120038 JP H11-965 JP 2000-318765 A JP 2005-231717 A JP 2007-236245 A

Although the biaxially stretched polyamide film has excellent mechanical properties, at present, sufficient moisture permeability and alcohol permeability are not obtained due to its molecular orientation and high crystallinity. In the above-mentioned Patent Document 1, a polyamide film is used as a film having high ethanol permeability used for the constituting sheet, but the ethanol permeability is 4 in the example using 12 μm.
50 cc / m ² · 24 hr (40 ° C., 50% RH) is insufficient as a single film.

In Patent Document 2, an appropriate moisture vapor permeability is required to maintain the freshness of loquat, and a polyamide film having good moisture permeability is used. However, depending on the application, a film with higher moisture permeability is required, but it is difficult to use a biaxially stretched polyamide film obtained by a conventional production method.
As a method of increasing the gas permeability of the film, there is a method of reducing the thickness of the film. However, when the thickness is reduced, the strength is lowered and the toughness that is characteristic of polyamide is impaired, so there is a practical limit.

On the other hand, it is conventionally known that the gas permeability of a crystalline polymer film, not limited to polyamide, depends on the crystallinity of the molecule. The lower the crystallinity, the better the permeability.
Although Patent Document 3 shows that the dimensions are further stabilized by controlling the crystal structure even at the same crystallinity, the water vapor permeability is not different from the prior art level and is not necessarily high in permeability.

Since the biaxially stretched polyamide film has a large internal strain such as shrinkage stress as it is, a film having a stabilized dimension can be obtained by usually promoting crystallization in the subsequent heat treatment step. However, the heat treatment of the stretched film not only lowers the gas permeability because it promotes crystallization, but also reduces the physical properties due to relaxation of molecular orientation. Therefore, it has been difficult for the conventional biaxially stretched polyamide film to achieve both strength and dimensional stability and gas permeability. Accordingly, the present invention is to provide a polyamide film having high moisture permeability and alcohol permeability in a film used in foods, pharmaceuticals, industrial material packaging fields, etc., and excellent in mechanical strength and dimensional stability.

That is, the gist of the present invention is as follows.
(1) The tensile strength is 1.8 × 10 ³ kgf / cm ² or more for both MD and TD, the water vapor transmission rate is 5000 g · μm / m ² · 24 hr (90% RH / 40 ° C.) or more, or the ethanol transmission rate is An ethylene-vinyl acetate copolymer resin is applied to a biaxially stretched polyamide film having a moisture permeability or alcohol permeability of 6000 g · μm / m ² · 24 hr (50% RH / 40 ° C.) or more and a thickness of 25 μm or less. A laminated polyamide film.
(2) The tensile strength is 1.8 × 10 ³ kgf / cm ² or more for both MD and TD, the water vapor transmission rate is 5000 g · μm / m ² · 24 hr (90% RH / 40 ° C.) or more, and the ethanol transmission rate is An ethylene-vinyl acetate copolymer resin is applied to a biaxially stretched polyamide film having a moisture permeability or alcohol permeability of 6000 g · μm / m ² · 24 hr (50% RH / 40 ° C.) or more and a thickness of 25 μm or less. A laminated polyamide film.
(3) A polyamide system obtained by laminating an ethylene-vinyl acetate copolymer resin on a biaxially stretched polyamide film according to claim 1 or 2, wherein the hot water shrinkage rate at 100 ° C. for 30 minutes is 5% or less for both MD and TD. Laminated film.
(4) A polyamide-based laminated film obtained by laminating an ethylene-vinyl acetate copolymer resin on a third biaxially stretched polyamide film having a thickness of 12 μm or less.
(5) A polyamide-based laminate obtained by laminating an ethylene-vinyl acetate copolymer resin on a biaxially stretched polyamide film according to claim 3, wherein the ethanol permeability is 500 g / m ² · 24 hr (50% RH / 40 ° C.) or more. the film.
(6) In a method of obtaining a film having excellent strength properties by stretching a polyamide resin obtained mainly by polymerizing ε-caprolactam, extruding from a die, and then stretching,
A polyamide for packaging excellent in moisture permeability and alcohol permeability, characterized in that the stretching ratio of MD and TD is 2 times or more, and the heat setting temperature after stretching is 180 ° C. or more and processed within 1.5 seconds. A method for producing a polyamide-based laminated film obtained by laminating an ethylene-vinyl acetate copolymer resin on a film.
(7) The method for producing a polyamide-based laminated film according to claim 5, wherein the ethylene-vinyl acetate copolymer resin has a vinyl acetate content of 15% or more and less than 23%.
(8) The method for producing a polyamide-based laminated film according to claim 5, wherein the ethylene-vinyl acetate copolymer resin has a thickness of 50 µm or less.
(9) The method for producing a polyamide-based laminated film according to claim 5, wherein the ethylene-vinyl acetate copolymer resin has a thickness of 50 µm or less and further laminated with a nonwoven fabric.
It is. The present invention will be described in detail below.

(Biaxially stretched polyamide film)
The biaxially stretched polyamide film of the present invention is obtained by biaxially stretching an unstretched raw film of a polyamide resin represented by nylon 6 obtained by polymerizing ε-caprolactam and heat-treating it under specific conditions. is there. Thus, by performing biaxial stretching and heat treatment, a polyamide film having excellent mechanical strength and stable dimensions can be obtained.

The polyamide film of the present invention has a tensile strength of 1.8 × 10 ³ kgf / cm ² or more for both MD and TD. If it is less than this, it is likely to cause pinholes and tears when used as a packaging material. Depending on the application, both moisture permeability and alcohol permeability are required. In this case the water vapor permeability ^{5000g · μm / m 2 · 24hr} (40 ℃) or higher, and ethanol transmittance ^{6000g · μm / m 2 · 24hr} (50% RH / 40 ℃) more preferably 8000g · μm / ^{m 2} -It is 24 hr (50% RH / 40 ° C) or more. Thereby, high moisture permeability and alcohol permeability can be exhibited while maintaining practical film strength properties. In addition, since this polyamide film does not have a sealing function, it is possible to obtain a structure that can actually be used as a polyamide-based laminated film by laminating a resin such as an ethylene-vinyl acetate copolymer resin.

In applications where either moisture permeability or alcohol permeability is required, the water vapor transmission rate is 5000.
^{g · μm / m 2 · 24hr} (40 ℃) or higher, or ethanol transmittance ^{6000g · μm / m 2 · 24hr} (50% RH / 40 ℃) more preferably ^{8000g · μm / m 2 · 24hr} (50% RH / 40 ° C) or higher. Accordingly, high moisture permeability or alcohol permeability can be exhibited while maintaining practical film strength properties.

The thickness of the polyamide film is 25 μm or less, preferably 15 μm or less, and more preferably 5 to 12 μm. If the thickness is less than 5 μm, the permeability is high, but the stiffness and physical properties are insufficient, and in some cases, it is not practical. On the other hand, if it is thicker than 25 μm, the permeability is lowered, which is not preferable. In particular, when the thickness is 12 μm or less, high permeability of ethanol permeability of 600 g / m ² · 24 hr (50% RH / 40 ° C.) or more is also possible.

The hot water shrinkage at 100 ° C. for 30 minutes is preferably 5% or less for both MD and TD, and more preferably 3% or less. When the hot water shrinkage is greater than 5%, curling and wrinkles due to moisture absorption become a problem, and lamination and printing become difficult.

(Production method of polyamide film)
The biaxially stretched polyamide film as described above is mainly obtained by polymerizing ε-caprolactam. After a polyamide resin is melt extruded from a die to obtain a raw film, it is stretched twice or more in each of MD and TD. After biaxial stretching, the heat treatment can be performed at a temperature of at least 180 ° C. and within 1.5 seconds.

The polyamide resin is mainly obtained by polymerizing ε-caprolactam. As the relative viscosity (η _rel ) of the polyamide resin, it was dissolved in 98% sulfuric acid at a concentration of 1% at 25 ° C. (JIS K- 6810) is suitable in the range of 2-5. If the relative viscosity is too high, extrusion molding becomes difficult. If the relative viscosity is too low, extrusion molding becomes difficult and not only the mechanical strength of the film decreases, but also the crystallinity increases, so the water vapor and ethanol permeability is low. It is not preferable.

Lubricants such as bisamide compounds may be added to the polyamide resin, and within the range not impairing the effects of the present invention, antioxidants, weather resistance improvers, mold release agents, antistatic agents, antiblocking agents,
You may mix | blend additives, such as dye and a pigment. In addition, the polyamide resin may be blended with inorganic fillers or other polymers for improving strength, elastomers for improving pinhole resistance, and other polymers for improving gas permeability. The blend may be blended within a range not impairing the effects of the present invention.

As the biaxial stretching method, for example, simultaneous biaxial stretching by the tubular method or tenter method or sequential biaxial stretching can be adopted, but it is desirable to perform by simultaneous biaxial stretching by the tubular method from the viewpoint of the longitudinal and lateral strength balance. .
The draw ratio is 2 times or more, preferably 2.7 to 5 times. If it is less than 2 times, even if good moisture permeability or alcohol permeability is obtained, sufficient strength, impact resistance, and pinhole resistance are lowered and lack practicality.

A polyamide film excellent in mechanical strength and dimensional stability with high moisture permeability and alcohol permeability according to the present invention can be obtained by subjecting the stretched film thus obtained to the heat treatment described below.

The heat treatment method is not particularly limited, such as a hot roll treatment in which a heated roll is brought into contact with the heated roll or a tenter heat treatment. However, since the film is gradually cooled unless special measures are taken after the film is heated, it is preferable to provide a cooling facility after the heat treatment under the condition of the heat treatment in a short time of the present invention. Although cooling is not particularly limited by water cooling, roll cooling, cold air, etc., a cooling roll treatment is most preferable as a method capable of rapid cooling without affecting the film characteristics.

The heat treatment temperature is 180 ° C. or higher and the melting point or lower. A heat treatment at less than 180 ° C. does not provide a sufficient heat treatment effect and lacks dimensional stability. The heat treatment time is within 1.5 seconds. Conventional heat treatment is usually performed for 5 to 20 seconds in order to obtain sufficient dimensional stability. The long heat treatment is sufficient for the relaxation time of the molecules, and although the dimensional stability is increased, the crystallinity is increased, and the gas permeability is accordingly decreased. However, according to the heat treatment conditions of the present invention, the gas permeability is dramatically improved in order to suppress the increase in crystallinity. Further, since the decrease in film strength due to heat treatment is kept to a minimum, a polyamide film having excellent strength and dimensional stability and good moisture permeability and alcohol permeability can be obtained.

Furthermore, by laminating an ethylene-vinyl acetate copolymer resin on this polyamide film, a highly practical structure having a sealing function can be obtained as a polyamide-based laminated film.
The characteristics of ethylene-vinyl acetate copolymer resin are vinyl acetate distribution, short chain branching, long chain branching,
Although it depends on the molecular weight and molecular weight distribution, moisture permeability and alcohol permeability vary greatly depending on the content of vinyl acetate to be copolymerized. This is attributed to a decrease in crystallinity due to the introduction of vinyl acetate. For this application, the vinyl acetate content is 15% or more, 23%
Less than is most preferred. If it is 15% or less, the moisture permeability and alcohol permeability are insufficient, and if it is 23% or more, the permeability is sufficient, but the film becomes sticky, and winding and filling packaging are actually difficult.

Regarding the ethylene-vinyl acetate copolymer resin used here, any resin having equivalent moisture permeability and alcohol permeability can be used without any problem. For example, ethylene-ethyl acrylate copolymer resin (EEA), ethylene-acrylic acid copolymer resin (EAA), ethylene-
A methyl acrylate copolymer resin (EMA), an ethylene-methyl methacrylate copolymer resin (EMMA), an ionomer, and the like are conceivable. However, ethylene-vinyl acetate copolymer resin is the most versatile and advantageous in terms of cost.
In addition, the present invention can add a new material without changing the gist thereof. Although this structure has sufficient practicality, for example, it is conceivable to add a non-woven fabric in order to add the waist and beauty of the film. Nonwoven fabrics are suitable for this application because they have high moisture permeability and alcohol permeability.

In addition, the actual package is generally printed with product names and precautions.
Biaxially stretched polyamide films are widely used as materials suitable for printing, and are also suitable in this respect. Moreover, in the structure using the previous nonwoven fabric, printing on a nonwoven fabric is also possible.
The thickness of the ethylene-vinyl acetate copolymer resin is 10 to 50 μm, preferably 20 to 40 μm.
m is preferred. When it is thin, the moisture permeability and alcohol permeability are sufficient, but it is difficult to obtain the sealing strength necessary for a package. If it is 50 μm or more, the permeability may be insufficient.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples unless it exceeds the gist.
The film was evaluated based on the following measurement method.
(Measuring method)
1. The average thickness was measured based on JIS standard Z1714.
2. The haze was measured based on JIS standard K7105.
3. Tensile strength Measured based on JIS standard Z1714.
4). Tensile elongation was measured based on JIS standard Z1714.
5. Hot water shrinkage MD and TD were each immersed in boiling hot water for 30 minutes, and the shrinkage when MD and TD before hot water immersion were 100% in length was determined.
6). Water vapor transmission rate and water vapor transmission rate Based on JIS standard Z0208, the water vapor transmission rate and the water vapor transmission rate were measured under the conditions of 90% relative humidity and 40 ° C.
7). Ethanol permeability and ethanol permeability Put absorbent cotton soaked with ethanol in a cup, cover the cup with a film, and reduce ethanol weight when left for 24 hours under conditions of 50% relative humidity and 40 ° C. The degree and ethanol permeability were measured.
8). Crystallinity parameter Polarization direction is perpendicular to the reflecting surface, and the film is set so that the polarization direction is parallel to the MD direction and TD direction, and the polarized ATR spectrum (Ge45 °) is made by JASCO Corporation FT-IR
Measured with a spectrometer. From the obtained spectrum was determined absorbance ratio of 1199cm ^-1 and 1172cm ^-1.

Example 1
A polyamide resin (1024FD31, manufactured by Ube Industries, Ltd.) having a relative viscosity ηrel = 3.8 obtained by polymerizing ε-caprolactam was melt-extruded from an annular die and solidified by cooling with water to form an original film having a tubular film thickness of 135 μm. Obtained. This original fabric was reheated and simultaneously biaxially stretched at 50 to 100 ° C. so that each of MD and TD was tripled by two sets of nip rolls having different peripheral speeds and compressed air in the tube. The film was then brought into contact with a metal roll heated to 175 ° C. for 0.3 seconds and immediately cooled to room temperature, further heated and cooled with a 200 ° C. metal roll, and further heated similarly with a 180 ° C. metal roll. It heat-processed by cooling and obtained the 15 micrometer biaxially stretched polyamide film.
The average thickness, haze, tensile strength, tensile elongation, water vapor permeability, ethanol permeability and crystallization parameters of the obtained film were measured and shown in Table 1.

(Example 2)
The thickness of the raw fabric was set to 108 μm, and the heat treatment conditions were brought into contact with a metal roll heated to 180 ° C. for 0.3 seconds, then immediately cooled to room temperature, further heated and cooled with a metal roll at 200 ° C., and further 19
A 12 μm biaxially stretched polyamide film was obtained as in Example 1 except that it was similarly heated and cooled with a metal roll at 0 ° C. The physical properties of the film were measured in the same manner as in Example 1.

(Example 3)
Heat treatment conditions were brought into contact with a metal roll heated to 175 ° C. for 0.3 seconds, then immediately cooled to room temperature, further heated and cooled similarly with a 190 ° C. metal roll, and further heated and cooled similarly with a 180 ° C. metal roll. Obtained a biaxially stretched polyamide film as in Example 2, and the physical properties of the film were measured in the same manner as in Example 1.

Example 4
The thickness of the raw fabric was set to 225 μm, and the heat treatment conditions were brought into contact with a metal roll heated to 181 ° C. for 0.5 seconds, then immediately cooled to room temperature, and further heated and cooled with a metal roll at 200 ° C.
A 25 μm biaxially stretched polyamide film was obtained as in Example 1 except that it was similarly heated and cooled with a metal roll at 0 ° C., and the physical properties of the film were measured in the same manner as in Example 1.

(Comparative Example 1)
Under the same conditions as in Example 1 except that the first heat treatment condition was 120 ° C. for 0.3 seconds, the second heat treatment was 120 ° C. for 0.3 seconds, and the third heat treatment was 120 ° C. for 0.3 seconds. A biaxially stretched polyamide film was obtained.

(Comparative Examples 2 and 3)
Unitika's Emblem ON 12 μm and 15 μm were measured for physical properties in the same manner as in Example 1.

(Comparative Example 4)
Up to the third heat treatment condition, the same treatment as in Example 3 was performed, and a heat treatment was further performed at 190 ° C. for 10 seconds using a tenter to obtain a biaxially stretched polyamide film.

(Comparative Example 5)
Up to the third heat treatment condition, the same treatment as in Example 3 was performed, and a heat treatment was further performed at 200 ° C. for 10 seconds using a tenter to obtain a biaxially stretched polyamide film.

(Comparative Example 6)
Up to the third heat treatment condition, the same treatment as in Example 3 was performed, and further a heat treatment was performed at 210 ° C. for 5 seconds using a tenter to obtain a biaxially stretched polyamide film.

(Comparative Example 7)
Up to the third heat treatment condition, the same procedure as in Example 3 was performed, and a heat treatment was further performed at 215 ° C. for 5 seconds using a tenter to obtain a biaxially stretched polyamide film.
The polyamide films of Examples 1 to 4 each have an MD and TD tensile strength of 1.8 kgf / cm @ 2.
More than it has good strength, water vapor transmission rate of ^{5000g · μm / m 2 · 24hr} (40 ℃) above or ethanol transmittance ^{6000g · μm / m 2 · 24hr} (50% RH / 40 ℃) And showed good permeability. Furthermore, the 12 μm and 15 μm polyamide films of Examples 1 to 3 were even better with ethanol permeability of 500 g / m ² · 24 hr (50% RH / 40 ° C.) or higher. In Examples 1, 2 and 4, the heat treatment temperature of 200 ° C. or higher was 100 ° C., and the hot water shrinkage rate for 30 minutes was 5% or less for MD and TD, respectively, which was excellent in dimensional stability.

On the other hand, in the heat treatment at 120 ° C. in which the heat treatment temperature of Comparative Example 1 was less than 180 ° C., not only the hot water shrinkage ratio was large and the dimensional stability was lacking, but also the water vapor permeability and ethanol permeability were lower than in the examples. In addition, the water vapor permeability and the ethanol permeability were low in the commercially available biaxially stretched polyamides of Comparative Examples 2 and 3.

In Comparative Examples 4 to 7, the heat treatment time of 180 or more was 5 seconds or more, and the film carried out under the conventionally known heat treatment conditions had low water vapor vapor permeability and ethanol permeability.
The degree of crystallization represented by the crystallization parameters in the tables of Examples and Comparative Examples is higher as the heat treatment temperature is higher and the heat treatment time is longer. In the comparative example, the permeability decreased as the crystallinity increased, but in the examples, the permeability increased.

(Example 5)
To the biaxially stretched polyamide film prepared in Example 2 above, ethylene-vinyl acetate copolymer resin (NUC-3461 manufactured by Dow Chemical Co., vinyl acetate [VA] content 19%) was added 3
A 0 μm extruded laminate was obtained. The ethanol permeability was 390 (g / m ² · 24 hr), and the laminate had sufficient permeability for this purpose.

(Example 6)
Ethylene-ethyl acrylate copolymer resin (Evaflex manufactured by Mitsui DuPont Polychemical Co., Ltd.) having the same ethanol permeability as the ethylene-vinyl acetate copolymer resin for the biaxially stretched polyamide film prepared in Example 2 above. EEA A702, ethyl acrylate [
EA] content 19%) was obtained by extrusion lamination of 30 μm. Ethanol permeability is 380 (
g / m ² · 24 hr) and the laminate had sufficient permeability for this purpose.

(Example 7)
For the biaxially stretched polyamide film prepared in Example 2 above, a non-woven fabric (Mitsui Chemicals, Inc.
Syntex PB-0220, 20 g / m ² ) is urethane-adhesive (DIC Corporation Dick Dry LX-703 / KR-90, aliphatic polyester), and is further laminated with ethylene-vinyl acetate copolymer resin (Dow). Chemical company NUC-3461, vinyl acetate [
VA] content 19%) was obtained by extrusion lamination of 30 μm. Ethanol permeability is 340 (
g / m ² · 24 hr) and sufficient permeability for this purpose. In all of Examples 5 to 7, sufficient laminate strength and seal strength were obtained, and there was no practical problem.

(Comparative Example 8)
3 ethylene-vinyl acetate copolymer resin (NUC-3461 manufactured by Dow Chemical Co., vinyl acetate (VA) content 19%) was added to the biaxially stretched polyamide film used in Comparative Example 2 above.
A 0 μm extruded laminate was obtained. The ethanol permeability was 180 (g / m ² · 24 hr), which was insufficient for this purpose.

(Comparative Example 9)
For the biaxially stretched polyamide film used in Comparative Example 2 above, an ethylene-vinyl acetate copolymer resin having a higher vinyl acetate content than Example 5 (Evaflex V431 manufactured by Mitsui DuPont Polychemical Co., Ltd., vinyl acetate [ VA] content 25%) was obtained by extrusion lamination of 30 μm. Although the ethanol permeability was sufficient, wrinkles were generated in the laminate due to the stickiness of the film, and winding was impossible.

(Comparative Examples 10 and 11)
An ethylene-vinyl acetate copolymer resin (NUC-3461 manufactured by Dow Chemical Co., vinyl acetate [VA] content 19%, 15%) was used for the biaxially stretched polyamide film used in Comparative Example 2 above.
A laminated body obtained by polysanding an LLDPE film (TUX-MCD (30 μm) manufactured by Tosero Co., Ltd.) was obtained through 40 μg / m ² · 24 hr. (Perforated by Tech Inter, 7% open area) was also carried out, but ethanol permeability did not reach a practical level.

(Comparative Example 12)
To the biaxially stretched polyamide film used in Comparative Example 2 above, ethylene-vinyl acetate copolymer resin (NUC-3461 manufactured by Dow Chemical Co., vinyl acetate [VA] content 19%) was added.
A 0 μm extruded laminate was obtained. Ethanol permeability was 210 (g / m ² · 24 hr), which was insufficient for this purpose.

According to the present invention, it is possible to obtain a polyamide film-based laminated film having high moisture permeability and alcohol permeability and excellent mechanical strength, and can be used in the fields of food, medicine, industrial material packaging, and the like.

Claims (3)

Tensile strength is 1.8 × 10 ³ kgf / cm ² or more for both MD and TD, ethanol permeability is 6000 g · μm / m ² · 24 hr (50% RH / 40 ° C.) or more , and ethanol permeability is 500 g / m. Polyamide-based laminated film obtained by laminating an ethylene-vinyl acetate copolymer resin on a biaxially stretched polyamide film having an alcohol permeability of ² · 24 hr (50% RH / 40 ° C.) or more and a thickness of 25 μm or less . 2. The polyamide-based laminated film according to claim 1, wherein the biaxially stretched polyamide film has a hot water shrinkage of 100% at 30 ° C. for 30 minutes for MD and TD of 5% or less. The polyamide-based laminated film according to claim 1 or 2, wherein the ethylene-vinyl acetate copolymer resin is laminated by 20 to 40 µm.