JP2014054797A - Biaxially oriented nylon film, laminate film, laminate packaging material, and production method of biaxially oriented nylon film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a biaxially oriented nylon film in which white unevenness is not distinguished after printing and laminating; a laminate film using the film; a laminate packaging material using the laminate film; and a production method of a biaxially oriented nylon film.SOLUTION: In a biaxially oriented nylon film made by drawing an original fabric film using a nylon resin as a raw material in a tube shape, the raw material includes at least 200 mass ppm and at most 1,500 mass ppm of a water repellency agent, only an external surface of a resin web in which the raw material is melted and extruded in a tube shape is cooled by water to form the original fabric film, and a surface of the biaxial oriented nylon film corresponding to the external surface is surface-treated.

Description

  The present invention relates to a biaxially stretched nylon film subjected to a surface treatment, a laminate film using the film, a laminate packaging material using the laminate film, and a method for producing a biaxially stretched nylon film.

Since biaxially stretched nylon films are excellent in strength and impact resistance, they are often used in fields with severe use conditions such as heavy weight packaging and water packaging. In recent years, it is also used for deep drawing as a battery case film. In particular, the biaxially stretched nylon film formed by the tubular method is superior in pinhole resistance and impact resistance than those formed by the tenter method, and the demand for deep drawing applications is increasing. (See Patent Documents 1 to 3).
Such a biaxially stretched nylon film is generally used by being subjected to various printings on the surface and laminated with another film.

JP 2008-0420209 A JP 2008-045015 A JP 2008-045016 A

  On the other hand, in a biaxially stretched nylon film obtained by a tubular system, so-called white unevenness may occur after printing and laminating. That is, when the picture printed on the back side through the film surface is viewed, white unevenness that impairs the beauty of the picture may be noticeable.

  The present invention relates to a biaxially stretched nylon film that has sufficient laminating strength after printing and laminating and has no noticeable white unevenness, a laminate film using the film, a laminate packaging material using the laminate film, and biaxially stretched nylon It aims at providing the manufacturing method of a film.

In order to solve the above problems, the present invention provides the following biaxially stretched nylon film, a laminate film using the film, a laminate packaging material using the laminate film, and a method for producing the biaxially stretched nylon film. To do.
(1) A biaxially stretched nylon film obtained by stretching a raw film made of a nylon resin into a tube shape, wherein the raw material contains a water repellent at 200 ppm by mass or more and 1500 ppm by mass or less, The raw film is formed by cooling only the outer surface of the resin web formed by extruding the raw material in a tube shape with water, and the surface corresponding to the outer surface of the biaxially stretched nylon film is surface-treated. A biaxially stretched nylon film characterized by
(2) The biaxially stretched nylon film as described in (1) above, wherein the surface treatment is a corona treatment.
(3) The biaxially stretched nylon film described in (1) or (2) above, wherein the nylon resin is nylon 6.
(4) The biaxially stretched nylon film according to any one of (1) to (3) above, wherein the surface-treated surface is a printed surface or an adhesive surface. Stretched nylon film.
(5) A laminate film obtained by laminating the biaxially stretched nylon film described in (4) above and another film, and the other film is laminated on the surface-treated surface. A laminate film characterized by that.
(6) A laminate packaging material using the laminate film described in (5) above.
(7) In the method for producing a biaxially stretched nylon film using a nylon resin as a raw material, the raw material contains a water repellent at 200 ppm by mass or more and 1500 ppm by mass or less, and an extrusion process in which the raw material is melt extruded into a tube shape And a raw film manufacturing process for obtaining a raw film by cooling only the outer surface of the resin web melt-extruded into a tube with water, a biaxial stretching process for stretching the raw film into a tube, A heat treatment step of performing a heat treatment on the film after the biaxial stretching step, and a surface treatment step of performing a surface treatment on a surface corresponding to the outer surface of the film after the heat treatment step. A method for producing an axially stretched nylon film.

  According to the present invention, it is possible to provide a biaxially stretched nylon film in which white unevenness is not noticeable after printing and laminating, and a method for producing the same. Furthermore, when the biaxially stretched nylon film of the present invention is used, the laminate strength can be sufficiently increased, and a laminate film having excellent drawability can be provided.

The schematic block diagram which shows an example of the apparatus which manufactures the biaxially stretched nylon film of this invention.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.
[Configuration of biaxially stretched nylon film]
The biaxially stretched nylon film (hereinafter also referred to as “ONy film”) according to this embodiment is formed by stretching a raw film made of a nylon resin as a raw material into a tube shape. Moreover, the said raw film is formed by cooling only the outer surface of a molten resin tube-shaped resin web with water, and the surface corresponding to the said outer surface of the said ONy film is surface-treated.
The surface treatment is not particularly limited as long as it improves the printability and adhesiveness of the ONy film, but corona treatment is preferable in that the surface energy can be effectively increased.

  Examples of the raw material nylon resin (polyamide resin) include nylon 6, nylon 66, nylon 9, nylon 10, nylon 11, nylon 12, nylon 46, nylon 610, nylon 611, and nylon 612. Nylon 6 is preferable from the viewpoints of physical properties, melting characteristics, and ease of handling.

Moreover, the above-described raw material contains a water repellent at 200 mass ppm or more and 1500 mass ppm or less, and preferably 300 mass ppm or more and 1200 mass ppm or less.
The raw film is manufactured (molded) by rapidly cooling the molten nylon resin, which is the raw material, with water, but when the water repellent is added to the raw material in an amount of 200 ppm by mass or more, the molten nylon resin comes into contact with the cooling water. When this occurs, the growth of spherulites is moderately hindered, the film surface becomes a moderately smooth surface, and the white unevenness of the original fabric itself can be suppressed.
However, if the addition amount of the water repellent exceeds 1500 ppm by mass, the molten nylon resin is cooled too slowly and spherulites are hardly generated in the surface layer of the original film, and the surface of the original film is also very There is a possibility that the film becomes smooth and the slipperiness of the film deteriorates even after biaxial stretching (the static / dynamic friction coefficient becomes too high). Moreover, the bubble at the time of biaxial stretching may become unstable.
Here, examples of the water repellent include ethylene bis stearamide (EBS).

Moreover, it is preferable to add 300 mass ppm or more and 2500 mass ppm or less of an antiblocking agent in a raw material, and it is more preferable to add 500 mass ppm or more and 2000 mass ppm or less. When the anti-blocking agent is less than 300 mass ppm, the inner surface of the tube constituting the raw film becomes too smooth, and when the film is wound after being stretched, and further when the stretched film is printed and laminated (during secondary processing) ) May deteriorate the slipperiness and cause wrinkles. On the other hand, if it exceeds 2500 mass ppm of the anti-blocking agent, the amount of generated scum increases when the raw material is melt-extruded, and the continuous productivity may be lowered because it is necessary to increase the frequency of cleaning the die of the extruder.
Examples of the anti-blocking agent include silica, talc, kaolin, diatomaceous earth, and the like.

[Composition of laminate film]
In the laminate film of this embodiment, printing is performed on the surface-treated surface of the above-described ONy film, and various films are further laminated as a laminate base material on this surface. Examples of the laminating method include dry lamination, extrusion lamination, and polysand lamination.
As a sealant film for dry laminating or polysand laminating, various polypropylene and polyethylene films are used. In addition, as a laminated base material, you may further laminate | stack the film containing not only the said sealant film but an aluminum layer and an aluminum layer.
According to the laminate film of this embodiment, the white unevenness of the ONy surface is not noticeable, so that the finish of the back printing is very beautiful. In addition, since the ONy surface is surface-treated, it has a sufficient laminate strength.

  The thickness of the ONy film used for the laminate film is preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 30 μm or less. Here, when the thickness of the ONy film is less than 5 μm, the impact resistance of the laminate film tends to be low. On the other hand, when the thickness of the ONy film exceeds 50 μm, it is difficult to obtain the effect of further improving the impact resistance of the laminate film, which is not preferable because the total thickness of the laminate film increases.

[Composition of laminate packaging material]
The laminate packaging material (various packaging bags etc.) of this embodiment is comprised from the above-mentioned laminate film. Therefore, it is possible to provide a laminate packaging material that is beautiful and has a back printing that is not noticeably white and has a sufficiently high laminate strength.

[ONy film manufacturing equipment]
Next, an apparatus for producing the ONy film of this embodiment will be described with an example.
As shown in FIG. 1, a film manufacturing apparatus 100 includes an original fabric manufacturing apparatus 90 for manufacturing an original fabric film 1, a biaxial stretching apparatus (tubular stretching apparatus) 10 for stretching the original fabric film 1, and stretching. A first heat treatment device 20 (preheating furnace) that preheats a base film 2 that is folded later (hereinafter also simply referred to as “film 2”), a separation device 30 that separates the preheated film 2 into two upper and lower sheets, A second heat treatment device 40 that heat-treats (heat-set) the separated film 2, a tension control device 50 that applies tension to the film 2 from the downstream side when the film 2 is heat-set, and the film 2 is heat-set. A biaxially stretched nylon film 3 (hereinafter also simply referred to as “film 3”) and a corona discharge device 70 are provided.

As shown in FIG. 1, the raw fabric manufacturing apparatus 90 includes an extruder 91, a circular die 92, a water cooling ring 93, a stabilizer plate 94, and a pinch roll 95.
The tubular stretching device 10 is a device for producing a film 2 by biaxially stretching (bubble stretching) a tubular raw film 1 with the pressure of internal air. As shown in FIG. 1, the tubular stretching device 10 includes a pinch roll 11, a heating unit 12, a guide plate 13, and a pinch roll 14.
The first heat treatment apparatus 20 is an apparatus for preliminarily heat-treating the flat film 2. As shown in FIG. 1, the first heat treatment apparatus 20 includes a tenter 21 and a heating furnace 22.
As shown in FIG. 1, the separating device 30 includes a guide roll 31, a trimming device 32, separating rolls 33A and 33B, and grooved rolls 34A to 34C. Further, the trimming device 32 has a blade 321.

The second heat treatment apparatus 40 includes a tenter 41 and a heating furnace 42 as shown in FIG.
As shown in FIG. 1, the tension controller 50 includes guide rolls 51 </ b> A and 51 </ b> B and a tension roll 52.
As shown in FIG. 1, the winding device 60 includes a guide roll 61 and a winding roll 62.
As shown in FIG. 1, the corona discharge device 70 is a device for applying a corona discharge treatment to the heat-fixed film 3 after passing through the guide roll 61 of the winding device 60.

[ONy film manufacturing method]
Next, each process which manufactures an ONy film using this film manufacturing apparatus 100 is demonstrated in detail.

(Raw film production process)
As shown in FIG. 1, the raw material nylon resin is melt-kneaded by an extruder 91 and extruded into a tube shape by a circular die 92. The tubular molten resin is cooled by a water cooling ring 93. The raw film 1 is formed by rapidly cooling a molten nylon resin as a raw material by a water cooling ring 93. The cooled original film 1 is folded by the stabilizer 94. The folded original fabric film 1 is sent to the next biaxial stretching process by a pinch roll 95 as a flat film.
When the tubular molten resin is rapidly cooled by the water cooling ring 93, the outer surface of the tubular molten resin is cooled by water, and the inner surface is cooled by air. Therefore, in the following films, a surface cooled by water is sometimes referred to as a water-cooled surface, and a surface cooled by air is sometimes referred to as an air-cooled surface.

(Biaxial stretching process)
As shown in FIG. 1, the original film 1 manufactured by the original film manufacturing process is introduced into the apparatus as a flat film by a pinch roll 11. The introduced raw film 1 is bubble-stretched by being heated with infrared rays at the heating unit 12. Thereafter, the film 2 after being bubble-stretched is folded by the guide plate 13. The folded film 2 is pinched by the pinch roll 14 and sent to the next first heat treatment step as a flat film 2.
At this time, the draw ratios in the MD direction and the TD direction are each preferably 2.8 times or more. If the draw ratio is less than 2.8 times, the impact strength may be reduced, causing a problem in practicality.

(First heat treatment process)
The film 2 sent from the biaxial stretching step is at or above the shrinkage start temperature of the film 2 and about 30 ° C. higher than the melting point of the film 2 while being gripped at both ends by clips (not shown) of the tenter 21. The film 2 is preheated at a low temperature or lower and sent to the next separation step.
The heat treatment temperature in the first heat treatment is preferably 120 ° C. or higher and 190 ° C. or lower, and the relaxation rate is preferably 15% or lower.
By this first heat treatment step, the crystallinity of the film 2 is increased, and the slipping property between the overlapping films is improved.

(Separation process)
As shown in FIG. 1, the flat film 2 sent through the guide roll 31 is cut into both ends by a blade 321 of a trimming device 32 and separated into two films 2A and 2B. And film 2A, 2B is isolate | separated, interposing air between film 2A, 2B by a pair of separation roll 33A, 33B located up and down apart. The incision of the flat film 2 may be performed so that a part of the ear is generated by positioning the blade 321 slightly inward from both ends, or by positioning the blade 321 in the fold portion of the film 2. , It may be performed so that the ear does not occur.
These films 2A and 2B are overlapped again by three grooved rolls 34A to 34C positioned in order in the film flow direction, and sent to the next second heat treatment step. In addition, these grooved rolls 34A to 34C are obtained by plating the surface after the grooved processing. A good contact state between the films 2A and 2B and the air can be obtained through the grooves.

(Second heat treatment process (heat setting process))
The overlapped films 2A and 2B are heat-treated at a temperature equal to or lower than the melting point of the resin constituting the film 2 and about 30 ° C. lower than the melting point while being gripped at both ends by clips (not shown) of the tenter 41. It is (heat-set) and becomes a biaxially stretched nylon film 3 (hereinafter also referred to as film 3) having stable physical properties, and is sent to the next winding step.
The heat treatment temperature in the second heat treatment (heat setting) is preferably 190 ° C. or higher and 215 ° C. or lower, and the relaxation rate is preferably 15% or lower. When the heat treatment temperature is less than the lower limit, the film shrinkage rate increases and the risk of delamination tends to increase. On the other hand, if the upper limit is exceeded, the bowing phenomenon at the time of heat setting increases, and the anisotropy of the film tends to increase, and the crystallinity increases and the density becomes too high, and the film is difficult to deform. Tend to be. Therefore, the heat treatment temperature is preferably in the above range.
Further, a strong tension is applied to the films 2A and 2B in the heating furnace 42 by the tension control device 50 located on the downstream side.

(Winding process)
The film 3 heat-set in the second heat treatment step is wound as films 3A and 3B on the two winding rolls 62 via the guide roll 61 via the tension control device 50.

(Corona treatment process)
Before and after the winding step, the corona discharge device 70 applies a corona treatment to the water-cooled surface (the surface corresponding to the outer surface of the tubular molten resin) of the film 3 heat-set in the second heat treatment step. The By such corona treatment, the surface energy can be made sufficiently high, and the ONy film of this embodiment can be obtained.

[Modification of Embodiment]
The aspect described above shows one aspect of the present invention, and the present invention is not limited to the above-described embodiment, and has the configuration of the present invention and can achieve the object and effect. It goes without saying that modifications and improvements within the scope are included in the content of the present invention. In addition, the specific structure and shape in carrying out the present invention may be used as other structures and shapes within the scope of achieving the object and effect of the present invention.
For example, in the present embodiment, means for performing corona discharge treatment on the heat-fixed film is adopted, but not limited thereto, other surface treatment means such as flame treatment (flame treatment) may be adopted.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples.

[Example 1]
An ONy film was produced in the following manner using a material obtained by adding 800 mass ppm of a water repellent (EBS) to nylon 6 resin. In addition, the ONy film was further subjected to solid printing and then dry lamination to obtain a laminate film having the ONy film as a front substrate.
(Raw film production process)
As shown in FIG. 1, after Ny6 pellets were melt-kneaded at 275 ° C. in an extruder 91, the melt was extruded as a tubular film from a circular die 92, and then rapidly cooled with water (20 ° C.). Film 1 was obtained.
What was used as Ny6 was Ube Industries, Ltd. nylon 6 [UBE nylon 1022FD (trade name), relative viscosity ηr = 3.5].

(Biaxial stretching process)
Next, as shown in FIG. 1, the raw film 1 is inserted between a pair of pinch rolls 11, and then heated by the heating unit 12 while a gas is being pressed into the film 1, and blown to the stretching start point to form bubbles. The biaxial stretching in the MD direction and the TD direction was performed by the tubular method by expanding and taking up with a pair of downstream pinch rolls 14. The magnification during this stretching was 3.0 times in the MD direction and 3.3 times in the TD direction.

(First heat treatment step and second heat treatment step)
Next, as shown in FIG. 1, the film 2 is subjected to heat treatment at a temperature of 170 ° C. by the first heat treatment apparatus 20, and then passed through the separation apparatus 30 and then heat treated at a temperature of 210 ° C. by the second heat treatment apparatus 40. And heat fixed.

(Winding process, corona treatment process)
Next, as shown in FIG. 1, the film 3 heat-set in the second heat treatment step is wound as two films 3 </ b> A and 3 </ b> B on two winding rolls 62 via a guide roll 61 via a tension control device 50. An ONy film was obtained. At that time, the corona treatment was performed on the water-cooled surface of the film 3 (corresponding to the water-cooled surface of the original film 1) by the corona discharge device 70. The thickness of the obtained ONy film was 15 μm.

(Printing on ONy film)
The ONy film obtained by the above-described manufacturing method was solid-printed with black ink on the corona-treated surface.

(Production of laminate film)
A laminate film was obtained by dry laminating an ONy film after printing as a front substrate film and a CPP film having a thickness of 60 μm as a sealant film. The laminated film after dry lamination was aged at 40 ° C. for 3 days.

[Examples 2 to 5]
An ONy film was obtained in the same manner as in Example 1 except that the amount of the water repellent (EBS) was changed as shown in Table 1. Printing and laminating were performed in the same manner as in Example 1.

[Comparative Example 1]
An ONy film was obtained in the same manner as in Example 1 except that the corona treatment on the film 3 was performed on the air-cooled surface (corresponding to the air-cooled surface of the original film 1). Printing and laminating were performed in the same manner as in Example 1.

[Comparative Example 2]
An ONy film was obtained in the same manner as in Example 1 except that the corona treatment was not performed on the film 3. Printing and laminating were performed in the same manner as in Example 1 on the water-cooled surface.

[Comparative Example 3]
An ONy film was obtained in the same manner as in Example 1 except that the corona treatment was not performed on the film 3. Printing and laminating were performed in the same manner as in Example 1 on the air-cooled surface.

[Comparative Examples 4 and 5]
An ONy film was obtained in the same manner as in Example 1 except that the amount of the water repellent (EBS) was changed as shown in Table 1. Printing and laminating were performed in the same manner as in Example 1.
[Comparative Example 6]
In the raw film production process of Example 1, an ONy film was obtained in the same manner as in Example 1 except that not only the outside of the tube-shaped molten resin but also the inside was cooled with 20 ° C. water. Printing and laminating were performed in the same manner as in Example 1 on the water-cooled surface (external).

〔Evaluation method〕
Various characteristics (white unevenness, laminate strength, drawability) were evaluated by the following methods for the ONy film and printing / laminate film obtained by the above method. The results are shown in Table 1.

(External appearance of ONy film: white unevenness)
The film surface (about 1 m ² ) was observed with a clean room light (Polarion Co., Ltd.) at an angle of 45 ° and visually observed for white unevenness, and evaluated according to the following criteria.
○: No white unevenness ×: White unevenness

(Appearance of laminate film: white unevenness)
A clean room light (manufactured by Polarion Co., Ltd.) was observed at an angle of 45 ° on the ONy film side of the laminate film (about 1 m ² ), and the presence or absence of white unevenness was visually observed and evaluated according to the following criteria.
○: No white unevenness ×: White unevenness

(Lamination strength)
A strip-shaped test piece having a width of 15 mm was cut out from the laminate film, and the interface was peeled by several cm from the end by hand to separate it into an ONy film and a sealant film. Thereafter, each film piece was set in a tensile tester (Instron universal tester 1123 type), and a peel test of the laminate portion was performed at a speed of 300 mm / min (90 ° peel). And it evaluated on the following references | standards.
○: 5 N / 15 mm or more Δ: 2 N / 15 mm or more and less than 5 N / 15 mm ×: less than 2 N / 15 mm

(Drawing formability)
The laminate film was cut to prepare a 120 × 80 mm strip piece as a sample. Using a 33 x 55 mm rectangular mold, press it with a surface pressure of 0.1 MPa, change the molding depth from 0.5 mm to 0.5 mm, and cold mold each 10 samples. (One-stage pull-in molding). The molding depth at which no pinhole was generated in any of the 10 samples in the aluminum foil was taken as the limit molding depth, and the molding depth was shown as an evaluation value. In addition, confirmation of the pinhole confirmed the transmitted light visually.
○: The limit molding depth is 7 mm or more.
Δ: The limit molding depth is 5 mm or more and less than 7 mm.
X: The limit molding depth is less than 5 mm, or delamination occurs.

(Comprehensive evaluation)
From each evaluation mentioned above, comprehensive evaluation was performed according to the following criteria.
◎: When all evaluations are 〇 〇: When there is even one evaluation △: When there is even one evaluation x

〔Evaluation results〕
As shown in Table 1, the ONy film according to the present example contains a predetermined amount of water repellent in the raw material, and the water-cooled surface is corona-treated, and is printed and laminated on the surface. The so-called white unevenness is hardly noticeable. Therefore, the printed surface viewed through the front substrate is beautiful. Furthermore, since the corona treatment is performed, the laminate strength is sufficient and the drawability is excellent. In particular, when the ONy films of Examples 1 to 3 in which the addition amount of the water repellent is limited to 300 to 1200 mass ppm, the laminate strength becomes very high and the practicality is excellent.
On the other hand, in the ONy film of Comparative Example 1, white unevenness is not noticeable with the ONy film alone, but the white unevenness becomes noticeable after printing and laminating because the corona treatment is performed on the air-cooled surface. Therefore, the beautiful effect by back printing could not be demonstrated. In Comparative Example 2, the corona treatment was not performed, and the water-cooled surface was printed and laminated. Even with the ONy film alone, white unevenness is not noticeable even after printing and laminating, but the laminating strength is low, so that the drawability is also inferior. In Comparative Example 3, the corona treatment was not performed, but printing / laminating was performed on the air-cooled surface. Although the white unevenness is not noticeable with the ONy film alone, the white unevenness becomes conspicuous after printing and laminating. Similar to Comparative Example 2, the laminate strength is low and the drawability is inferior. In Comparative Example 4, the amount of water repellent added was very small, but white unevenness was already observed with the ONy film alone, and white unevenness was further clearly observed after printing and laminating. Also, the laminate strength and drawability are inferior. In contrast, in Comparative Example 5, the amount of the water repellent was considerably increased, but the laminate strength was very low. In addition, delamination occurs during draw forming, and there is a problem in practicality. The comparative example 6 is a manufacturing process of the raw film 1, and both surfaces of the tube-shaped molten resin are cooled with water. As a result, white unevenness was already observed with the ONy film alone, and white unevenness was further clearly observed after printing and laminating.

  The biaxially stretched nylon film of the present invention is used in industrial fields (such as lithium battery packaging materials mounted on electric vehicles, tablet terminal devices, smartphones, etc.), pharmaceutical fields (such as PTP packaging materials), and daily necessities fields ( It can be suitably used as a packaging material in the field of food detergents (such as retort food packaging materials).

  3, 3A, 3B ... Biaxially stretched nylon film

Claims (7)

A biaxially stretched nylon film obtained by stretching a raw film made of nylon resin into a tube shape,
The raw material contains a water repellent at 200 mass ppm or more and 1500 mass ppm or less,
The raw film is formed by cooling with water only the outer surface of the resin web formed by melting and extruding the raw material in a tube shape,
The surface corresponding to the said outer surface of the said biaxially stretched nylon film is surface-treated. The biaxially stretched nylon film characterized by the above-mentioned. In the biaxially stretched nylon film according to claim 1,
The biaxially stretched nylon film, wherein the surface treatment is a corona treatment. In the biaxially stretched nylon film according to claim 1 or 2,
The biaxially stretched nylon film, wherein the nylon resin is nylon 6. In the biaxially stretched nylon film according to any one of claims 1 to 3,
The biaxially stretched nylon film, wherein the surface-treated surface is a printed surface or an adhesive surface. A laminated film obtained by laminating the biaxially stretched nylon film according to claim 4 and another film,
The laminate film, wherein the other film is laminated on the surface treated. A laminate packaging material comprising the laminate film according to claim 5. In the method for producing a biaxially stretched nylon film using a nylon resin as a raw material,
The raw material contains a water repellent at 200 mass ppm or more and 1500 mass ppm or less,
An extrusion step of melt-extruding the raw material in a tube shape;
An original film production process for obtaining an original film by cooling only the outer surface of the resin web melt-extruded into a tube with water,
A biaxial stretching step of stretching the raw film into a tube,
A heat treatment step of performing a heat treatment on the film after the biaxial stretching step;
A surface treatment step of performing a surface treatment on a surface corresponding to the outer surface of the film after the heat treatment step. A method for producing a biaxially stretched nylon film.

Images