KR100188467B1 - Biaxially stretching polyamide film - Google Patents

Abstract

In the present invention, the polyamide resin composition is 90mmφ in diameter, is heated and melted in two extruders having a temperature of 200 to 300 ° C, and is extruded through a circular die having a diameter of 400mmφ and a temperature of 200 to 270 ° C, but has an air pressure therein. Unstretched fabric was produced by expanding while feeding air of ˜10 mmH ₂ 0, and transferred to the stretching tower and introduced into the film between the upper nip roll at 10 to 60 m / min and the lower nip roll at 20 to 180 m / min. Stretched by a fluid pressure of 50 to 300 mmH ₂ 0 and simultaneously stretched in the longitudinal and width directions to prepare a stretched bubble film, and then folded and folded, the stretched film is opened with an air pressure of ₂₀ to 40 mmH ₂ 0 in a heat setting tower. While expanding and maintaining the tubular phase, heat-setting is primarily carried out using hot air and far-infrared rays at the film surface temperature of the following formula (I), and then separated into two pieces using a trimming device, and the separated film is subjected to secondary heat treatment. By passing through the secondary heat treatment at a temperature of the formula (II) and then winding each, it provides a method for producing a triaxial tubular biaxially stretched polyamide-based film, characterized in that produced by the present invention The biaxially stretched polyamide-based film has a small difference in thermal shrinkage and shrinkage in the film width direction, and also has excellent film flatness, and thus can be used for food packaging and industrial product packaging.

Description

Biaxially oriented polyamide based film, its manufacturing method and manufacturing apparatus

1 is a schematic configuration diagram of a biaxially stretched polyamide film production apparatus of the present invention.

* Explanation of symbols for main parts of the drawings

1,1 ': Hopper 55,55': Extruder

66: gear pump 77: accumulator

3: gas injection part 4: cooling water tank

5: air blowing part 6: sizing

7: guide plate 8: nip roll

9-15: guide roll 16, 24: nip roll

17: auxiliary hot air unit 18, 19: hot air heating unit

20: far infrared heating portion 21: air injection pipe

22: camera 23: guide roll

25 to 32: guide roll 33, 35: nip roll

34: air injector 36: hot air heating unit

37: far infrared heating unit 38: guide roll

39: trimming device 42: secondary heat setting roll

41: mill roll B1: extruded bubble film

B2: stretched tube B3: heat setting film

The present invention relates to a method for producing a biaxially stretched polyamide-based film, and more particularly, the shrinkage difference between the heat shrinkage rate and the film width direction is small, which is drawn and heat-set into the tubular phase by the triple bubble tubular method. The present invention also relates to a method for producing a biaxially stretched polyamide-based film which can be used without deformation in film post-processing (printing, laminating) and sterilization packaging process due to its excellent planarity.

Biaxially stretched polyamide-based films have excellent gas barrier properties, pinhole resistance, cold resistance, and heat resistance, compared to other materials, and are widely used for packaging materials for food packaging materials such as processed foods and retort foods and various industrial products.

Biaxially oriented polyamide-based films are often made of bags and used as food packaging materials, which often cause torsion during post-processing or hot water treatment, which can damage their appearance. The cause of the deformation is because the difference in the shrinkage in the width direction of the middle portion and the sock end portion of the film is large, it is known that the shrinkage difference for each part of the film is largely related to the film manufacturing process. That is, when extending | stretching by a tubular rather than a tenter system, the width direction shrinkage difference of a film becomes small. In addition, when the heat setting is performed by the tenter method, the shrinkage difference is larger than that by the tubular method, and even if the film is stretched by the tubular method, the heat shrinkage is also increased by the tenter method.

As an alternative for overcoming the problems of the tenter type heat setting method, Korean Patent Publication No. 92-2364 is applied by heating the film in close contact with the surface of a heating object such as a heat roller or a heat belt while holding the film in a flat shape. A method of cooling to the next low temperature is proposed.

However, this method also has a limitation in improving the shrinkage difference in the film width direction by holding and fixing the film in a flat shape as in the conventional flat heat setting method, there is a problem that is difficult to use other than the center portion, heating Since it adheres directly to the surface of the object has the disadvantage that the surface activity of the film is easily lost and whitening.

Therefore, in order to reduce the shrinkage difference in the film width direction, it is preferable to heat-set the tubular shape rather than the flat shape. By the way, when the heat setting in the tubular shape in this way, the shrinkage difference in the width direction is significantly reduced, but there is a problem that the uniformity and planarity of the thickness distribution of the film is lowered.

Accordingly, an object of the present invention is to overcome the problems of the prior art as described above, while having a small difference in thermal contraction rate and shrinkage rate in the film width direction, and at the same time excellent in planarity of the film, which can be used without deformation in post-processing and hot-water treatment processes. It is to provide a method for producing a axially stretched polyamide film.

That is, according to the present invention, the polyamide resin composition is injected into two extruders having a diameter of 90 mmφ and a temperature of 200-300 ° C., followed by heating and melting. The polyamide resin composition is extruded through a circular die having a diameter of 400 mm φ and a temperature of 200 to 270 ° C. to provide air pressure therein. Inflate this 1-10 mmH ₂ 0 air while inflating it to produce an unstretched fabric, and transfer it to the stretching tower, and then inside the film between the upper nip roll at 10 to 60 m / min and the lower film at 20 to 180 m / min. Expanded by a fluid pressure of 50 to 300 mmH ₂ 0 introduced to simultaneously stretch in the longitudinal and width directions to prepare a stretched bubble film, and then folded and folded, the stretched film is opened in a 20-40 mmH ₂ 0 After expanding by air pressure and maintaining it in tubular shape, it is first heat-set to the film surface temperature of the following formula (I) using hot air and far-infrared rays, and then separated into two pieces using a trimming device, and the separated film is subjected to secondary heat treatment. It is to provide a method for producing a biaxially stretched polyamide-based film of a triple bubble tubular system characterized by passing through a roll and performing secondary heat treatment at a temperature of the following formula (II).

According to another aspect, the present invention provides a hopper for supplying a polyamide resin composition, two extruders having a diameter of 90 mmφ for heating and melting a polyamide chip, a gear pump, a circular die for extruding a resin having a diameter of 400 mmφ, a gas. It is composed of injection part, sizing to maintain outer diameter of fabric, blower for cooling and solidifying circular resin from circular die, and cooling device, guide roll, and nip roll, and the shape of upper part of stretching tubular is The first bubble part designed to be 30 ° to 80 ° with respect to the vertical direction, and a pair of nip rolls, preheating part, far infrared heating part, hot air heating part, air injection pipe and guide roll coated with heat resistant fabric A second drawing bubble portion and a pair of nip rolls each having a far infrared ray heating portion and a hot air heating portion configured to rotate 360 ° at a rotational speed of 2π / 10min-2π / 30min. Is a trimming device for trimming using an elastic device, using a heat-setting tower, a guide roll coated with a heat-resistant fabric, an R-shaped blade having an angle of 20 to 30 ° between the direction of the heat-fixing film and the end of the blade. Biaxial stretching, comprising: a third row fixed bubble section consisting of a primary heat treatment roll and a winding device, and an accumulator capable of storing the stretched film between the second stretchable bubble section and the third row fixed bubble section An apparatus for producing a polyamide film is provided.

According to another aspect of the present invention, the heat shrinkage rate at 100 ° C. in all the planar directions is 4% or less with respect to the total width of the film produced by the method according to another aspect, and the heat shrinkage difference in the circumferential direction at the end of the film is 1.0 It provides a biaxially stretched polyamide based film that is within%.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In the case of producing a biaxially stretched polyamide-based film by the method of the present invention, the polyamide resin composition was quantitatively passed through two hoppers 1,1 'to two extruders 55 and 55' having a diameter of 90 mmφ. It is heated and melted, and the melt is recombined using the gear pump 66, and it is extruded into a circular die having a diameter of 400 mmφ and a temperature of 200 to 270 ° C. A band heater capable of controlling the temperature is mounted on the inside and the outside of the extruder and the extrusion die, and continuously monitors the temperature so that the extrusion pressure and the extrusion temperature can be adjusted according to the characteristics of the resin. At this time, it is preferable to adjust the temperature of an extrusion die to the range of 200-300 degreeC according to the kind of polyamide resin. If the melt viscosity of the polyamide resin is high, the extrusion temperature is increased. If the melt viscosity is low, the extrusion temperature is generally lowered. If the polyamide resin is a copolymer, it depends on its molecular weight, but it is generally higher than that of the nylon 6 homopolymer. Since it has a relatively high melt viscosity, it is advantageous to process at a higher extrusion temperature.

As the polyamide resin of the present invention, polyamide having an amide bond in the molecular chain can be used. Examples are epsilon -caprolactam, 6-aminohexane, 7-aminohaptanic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid. Polymerization products of aminocarboxylic acids such as p-aminocyclonuxylcarboxylic acid and the like, pentamethyldiamine, nuxamethyldiamine, methaxylenediamine, palacxylenediamine, 2,2,4 / 2,4,4-trimethylhexamethylenediamine And diamines such as 1,3-bisaminomethylcyclohemic acid, bis-p-aminocyclohexylmethane, adipic acid, sebacic acid, subberic acid, pimelic acid, isofbalic acid, 2,6-naphthalenedicarboxylic acid, and the like. Polycondensation products of the same dicarboxylic acid, copolymers prepared from polymerization of mixtures of the various types of monomers described above.

In a general tubular method, one extruder is used. In this case, the melt zone of the extruder is designed to be long in order to continuously melt-extrude a large amount of polyamide. However, as the melting zone becomes longer, carbides of polyamide resins or additives are generated inside the extruder, so that the pressure inside the extruder increases, foreign matter gets stuck in the extrusion die, and lines on the film surface have a fatal effect on the appearance of the film. The problem arises in that the process has to be temporarily stopped to clean the extruder. In order to solve this problem, in the present invention, since two extruders having excellent kneading effect and a short melting zone are used, the production cycle can be extended by reducing the occurrence of polyamide resin or addition system deterioration.

When the polyamide resin composition is formed into a film by the method of the present invention, the tubular extruded resin discharged by injecting air through the gas injection unit 3 inside the extrusion die is extruded into the tubular phase B1. . The pressure of the air inside the extrusion die is adjusted in the range of _{1 to} 10 mmH ₂ 0. The die lip of the annular dice is adjusted by the adjusting bolt, and by adjusting the bolt, the thickness of the extrusion tube B1 can be adjusted.

The extruded tubular resin is cooled to the outside by cold air and cooling water of the cooling water tank 4, and is produced as a tubular raw film having a constant outer diameter and thickness. An annular die from which the extruded melt emerges and the cooling water tank 4 are positioned at regular intervals, and an air blower 5 capable of primarily cooling the extruded tubular resin is provided therebetween. The temperature of the air blower (5) and the cooling water tank (4) can be controlled through a cooling device, the temperature of the air and the cooling water tank is adjusted to a range of 10 ~ 30 ℃. At this time, if the cooling temperature is less than 10 ℃ the cooling effect is saturated and there is no big difference, on the contrary, if the cooling temperature exceeds 30 ℃, the cooling effect does not appear, there is a problem that the transparency is impaired. The amount of cooling water in the cooling bath is closely related to the processing stability and the appearance, transparency, glossiness, and tensile properties of the final film, which are also related to the properties of the polyamide resin. If the glass transition temperature of the polyamide resin is low and the solidification does not occur easily, the film may be deformed or wrinkled on the surface of the film during the subsequent processing, that is, the drawing and heat treatment. It is time to solidify.

The size ring (6) attached to the inside of the cooling water tank in the apparatus of the present invention to uniformly hold the outer diameter of the original film, the brake action to prevent the cooling degree of the original fabric decreases as the speed of the nip roll to take the original fabric increases It is designed to show sufficient cooling effect. Such sizing 6 can be installed in one or two stages depending on the degree of cooling of the polyamide.

After passing through the cooling device, the raw film is transferred to the nip roll 8 by the guide plate 7 without deformation of the film, presses the nip roll to prevent air from entering, and folds the original film into two sheets, and then overlaps the stacked films. It passes to the nip roll 16 of the upper part of an extension tower through the dog guide rolls 9-15.

At the top of the stretching tower, an auxiliary hot air blower 17 capable of applying heated air to the outside of the film is mounted so that the original film is preheated to a low temperature before stretching. The hot air heaters 18 and 19 and the far-infrared heating unit 20 are positioned at regular intervals in the stretching tower, respectively, whereby the original film passing through the nip roll 16 on the upper portion of the stretching tower is heated. Through the air injection pipe 21 installed at the lower end of the stretching tower, a certain amount of air is injected into the overlapped fabric film to make the stretching bubble (B2). At this time, the air pressure is slightly different depending on the thickness and properties of the polyamide film, the range is 50 ~ 300mmH ₂ 0. The draw ratio in the width direction can be determined by the ratio of the length of the original film in the initial width direction and the length in the width direction to expand by injection of air.

When stretching, the temperature of the far-infrared heating unit 20 is maintained at 180 to 300 ° C., and the temperature of the hot air heating units 18 and 19 is maintained at 140 to 270 ° C., so that the film surface temperature is the glass transition temperature of the polyamide resin ( it is necessary to ensure that 10~50 ℃ a temperature above the T _g). At this time, when the film surface temperature is lower than the lower limit, the molecular orientation oriented by stretching is not fixed and becomes unstable. When the temperature exceeds the upper limit, the film may be softened.

It is important for the stretched bubble film B2 expanded by air injection to maintain a predetermined shape to prevent breakage or rupture occurring in the stretching process. Is designed to maintain 30 to 80 ° with respect to the vertical direction of the stretching tower system. At this time, it is important to secure the processing stability by maintaining the correct angle by installing the camera 22 in the first stretched portion to continuously record.

The leading end of the secondary bubble-shaped stretched film passes through the guide roll 23 in a multi-stage so that there is no problem when the folded film is folded in two pieces on the lower nip roll 24. At this time, it is possible to adjust the stretching ratio in the longitudinal direction through the speed ratio of the nip rolls of the upper and lower portions of the stretching tower.

After the stretching is completed, the two overlapped stretched films passing through the lower end of the stretching tower are transferred to the heat setting tower through the guide rolls 25-32. In the present invention, the heat setting tower used in the first heat setting step is a circulating type whose lower end is rotatable 360 ° and operated within a range of a rotational speed of 2π / 10 minutes to 2π / 30 minutes, and the far infrared heating unit 36 and The hot air heating unit 37 is configured to cross. The inside of each heating part is divided into several sections of several stages, and since the hot air of a constant pressure is applied evenly to the circumferential direction, the film excellent in planarity can be obtained. In addition, since the diameter and height of the heat-setting tower are predetermined in relation to the film specification, the film heat treatment time and temperature become variables, and can be determined by laboratory methods and calculations according to the final physical properties of the film.

In the first heat setting, open the overlapped stretched film at the bottom of the heat setting tower, and inject air at a pressure of 20-40 mmH ₂ 0 using an air injector 34 to make a third bubble-shaped heat setting film (B3), and the bottom of the heat setting The nip roll 35 is pressed to prevent the outflow of air. Like the elongation tower at the top of the heat-setting tower, a hot air heating unit is used to preheat the surface of the film, and the hot air heating unit 36 and the far-infrared heating unit 37 inside the heat-setting tower are installed to heat the bubble-shaped heat-setting film. do.

Next, the heat-treated heat-setting film is guided to the guide roll 38, and folded into two pieces with a nip roll 35 located at the bottom of the heat-setting tower, and then separated into two sheets with a trimming device 39, respectively.

Each of the two separated films is passed through a secondary heat treatment roll 40 to be secondly heat treated, and each is wound up using a mill roll 41 to prepare a final polyamide film.

Since the stretched stretched film is continuously transported during heat setting while transferring the stretched film to the third heat-fixed bubble part to form the third bubble, an apparatus for storing the stretched film is required. In the present invention, the second stretched bubble part and the third heat-fixed bubble are required. An accumulator 77 was installed between the sections to ensure the continuity of the polyamide film. The accumulator 77 keeps the stretched stretched film stacked without changing the dimensions of the film as the rolls move up and down alternately.

The guide roll at the top of the heat-setting tower exquisitely wraps the guide roll with a heat-resistant fabric to maintain the stability of the bubble by maximizing contact with the heat-setting film.

The initial heat treatment temperature of the heat setting tower is carefully determined in order to prevent the film from being deformed due to the sudden change in the thermal history of the film, and the temperature is performed at a temperature lower than the crystallization temperature T _c above T _g .

The middle and end heat treatment temperatures are mainly determined by the melting temperature (T _m ) and T _c of the polyamide resin composition, and the calculation formula relating to the heat treatment temperature (T _t ) on the film surface is as follows (I).

When the first heat setting is performed at a temperature exceeding the upper limit, the film surface is softened and the film is easily broken due to the tension of the film, and fusion occurs between the films, which makes it difficult to separate the sheet into two pieces after treatment. If it is carried out at, the heat setting effect is insufficient, and the torsion may occur due to residual shrinkage stress in the post-processing process. Therefore, in the present invention, it is essential that the primary heat setting temperature is within the above range.

The heat treatment time during the first heat setting may be slightly different depending on the type of polyamide resin, the thickness of the film, and the like, but is preferably heat treated for 6 seconds to 10 seconds.

Trimming device 39 for cutting the heat-fixed film into two sheets after the lower nip roll of the heat-setting tower is an elastic device (spring) in order to minimize the loss part in consideration of the heat shrinkage and bubble shaking of the film generated in the heat-setting tower. Trimming is used to use the R-shaped blade having an angle of 20 to 30 ° between the advancing direction of the film and the end of the blade.

The secondary heat treatment by the secondary heat treatment roll 41 after trimming is to stabilize the molecular arrangement of polyamide which is not stabilized while passing through the heat setting tower and cooling through the cooling wind and the guide roll. (T _t2 ) is T _cc +5 (° C.) T _t2 (° C.) T _g +50 (° C.), which is higher than T _{cc in} relation to the low temperature crystallization temperature (T _cc ) [T _cc ; Low temperature crystallization temperature, T _g ; Glass transition temperature].

In the present invention, if the second heat setting temperature is less than T _cc +5 (° C.), the heat setting effect is not exhibited. If the temperature exceeds T _g +50 (° C.), the film may expand again, resulting in flatness. Done.

The polyamide film produced by the triple bubble method of the present invention has excellent physical properties in which the thermal shrinkage at 100 ° C. is 4% or less in all planar directions of the film, and the thermal shrinkage difference in the circumferential direction of the film tip is 1.0% or less. . Therefore, there is no deformation during the post-processing treatment or the sterilization treatment by hot water when the packaging material of food and various industrial products has the advantage that the full width of the film can be utilized. In addition, the flatness of the film is not comparable to the existing tenter type heat setting method, so defects can be minimized even in post-processing processes such as printing and laminating.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are only intended to describe specific embodiments of the present invention, and the present invention is not limited to the following Examples. The physical property evaluation method of the film used in the present Example is as follows.

[Assessment Methods]

1. Heat transition temperature; Melting temperature, crystallization temperature, low temperature crystallization temperature, and glass transition temperature were measured using a thermal analyzer (Perkin-Elmer's DSC-7) at a temperature rise and fall rate of 20 ° C / min. As for glass transition temperature, 1/2 position of heat capacity was made into the value.

2. hot water extract; The polyamide resin was measured by weight loss after extraction with hot water at 100 ° C. for 12 hours using an extractor (Soxhlet).

3. relative viscosity; The polyamide resin was dissolved in concentrated sulfuric acid (98%) at a concentration of 0.25 g / di, and then measured using a Cannon-Fenske viscometer in a 25 ° C thermostat.

Relative viscosity = solution of falling water (aec) / pure sulfuric acid of falling sulfuric acid (sec)

4. molecular weight distribution; Obtained by GPC analysis using a 150-CALC model of Water (Water), the solvent and the fluid phase using a metacresol, the measurement temperature was carried out at 100 ℃.

Molecular weight distribution = weight average molecular weight / number average molecular weight

5. transparency; According to ASTM D-1003, haze was measured using the haze meter of the Japan Electric Company.

6. Surface glossiness; According to ASTM D-2457, the surface glossiness was measured at an incident angle of 20 °.

7. coefficient of friction; In accordance with ASTM D-1894, the static friction coefficient was measured under a friction coefficient meter at 20 ° C. and 65% relative humidity.

8. gel water; A film of 20 cm x 20 cm was accurately observed with the naked eye to count the gel number of 100 µm or more.

9. tensile strength; According to ASTM D-882, it was measured using a universal tensile tester in an atmosphere of 20 mu and relative humidity of 65%.

10. heat shrinkage; After dipping a film of 20 cm x 20 cm in hot water at 100 ° C. for 30 minutes, the length change rate in the longitudinal direction and the width direction was measured.

11. hygroscopic resistance; Tensile strength after immersing a 1 cm x 15 cm film in water at 25 ° C. for 24 hours was measured and expressed as a decrease rate before and after treatment.

12. Surface insulation resistance; Surface insulation resistance was measured using Takedai Co., Ltd. high resistance insulation tester at 23 ° C. and 50% relative humidity.

Example 1

Silica (Fuji Silysia Co., Ltd., average particle diameter: 1.4 μm, surface area: 300 m ² / g) was added to an aqueous solution of ε-caprolactam 50% by weight, and stirred using a homomixer for at least 2 hours to achieve a uniform dispersion state. A nylon 6 resin having a content of 0.08 wt% was polymerized to prepare a chip. Polyoxyethylene (20) sorbitan monostearate (20% by weight) of ethylene oxide added to sorbitan fatty acid ester in the following formulas (III) and (IV) based on 100 wt% of the nylon 6 resin prepared And 0.06% by weight of a nonionic ester-based surfactant in which glycerin monostearate (manufactured by Nippon Oil Industries, Inc.) of the following formula (V) was mixed in a ratio of 40/40/20 and 0.05% by weight of a dilauryl phosphate potassium salt as an antistatic agent. The mixture was evenly mixed in a dry mixer to prepare a polyamide resin composition for film production.

Subsequently, through two extruders, the die was extruded downward at 250 ° C. using an annular die having a diameter of 400 mm, and quenched with water at 15 ° C. to obtain an unstretched film fabric. This unstretched film fabric is fed bi-axially by feeding pressurized gas into the tubular between two sets of nip rollers of different speeds, and simultaneously biaxially stretching with MD / TD = 3 / 3.2 times, which has a film diameter of 700 mmφ and a thickness of 15 μm at a film surface temperature of 80 ° C. A axial stretched film was prepared. Then, the stretched film is transferred to the heat-setting tower through the guide roller, and then the low-pressure gas is fed into the film while passing the heat-setting tower at a speed of 60 m / min continuously in the tubular state with the previous stretching process. After primary heat setting and folding for 8 seconds so that the surface temperature is 180 ° C, the film is separated into two sheets. Each film is brought into contact with the secondary heat treatment roller, and secondary heat setting is performed at 90 ° C for 3 seconds, and then wound on a mill roll. Polyamide film was prepared. The physical properties of the obtained polyamide film was evaluated and the results are shown in Table 3 below.

EXAMPLES 2-8

Except for changing the composition and process conditions of the polyamide resin in Example 1 as shown in Table 1 and Table 2 to prepare a polyamide film by the same conditions and methods as in Example 1, and evaluated the physical properties It is shown together in Table 3.

[Comparative Examples 1-10]

Except for changing the composition and process conditions of the polyamide resin in Example 1 as shown in Table 1 and Table 2 to prepare a polyamide film by the same conditions and methods as in Example 1, and evaluated the physical properties It is shown together in Table 3.

Claims (4)

The polyamide resin composition was introduced into two extruders, each having a diameter of 90 mmφ and a temperature of 200 to 300 ° C., followed by heating and melting. The polyamide resin composition was extruded through a circular die having a diameter of 400 mm φ and a temperature of 200 to 270 ° C. to give an air pressure of 1-10 mmH _2. 50-300 mmH introduced into the film between the upper nip roll at 10-60 m / min speed and the lower nip roll at 20-180 m / min speed after inflating zero air to expand and produce unstretched fabric. Expanded by a fluid pressure of ₂ 0 pressure to simultaneously stretch in the longitudinal and width directions to prepare a stretched bubble film, and then folded and folded, the stretched film is opened in a fixed tower to expand to an air pressure of 20-40mmH ₂ 0 While maintaining a bladder, heat-setting is primarily carried out by using hot air and far infrared rays at the film surface temperature of the following formula (I), and then separated into two pieces using a trimming device, and the separated film is passed through a second heat treatment roll. Formula (Ⅱ) temperature in the second method of producing a biaxially stretched polyamide-based film, characterized in that each take volumes after primary heat treatment. The method for manufacturing a biaxially stretched polyamide film according to claim 1, wherein the stretching is performed at a temperature of the far-infrared heating portion of the stretching tower at 180 to 300 ° C and at a temperature of hot air heating at 140 to 270 ° C. 2. The biaxially stretched polyamide based film of claim 1, wherein the heat setting of the far-infrared heating portion of the heat setting tower is performed at 200 to 300 DEG C and the temperature of the hot air heating portion is set to 150 to 270 DEG C. Manufacturing method. Hopper for supplying polyamide resin composition, two extruders of the same specification having 90mmφ diameter for heating and melting polyamide chips, gear pump, circular die for extruding resin having a diameter of 400mmφ, gas injection portion, and maintaining outer diameter of fabric It consists of a sizing, a blower for cooling and solidifying the outside of the circular resin from the circular die, and a cooling device, a guide roll, and a nip roll, and the shape of the upper portion of the stretching tubular is 30 ° to 80 ° relative to the vertical direction of the stretching tower device. A first bubble portion designed to be °; A second drawing bubble portion consisting of a pair of nip rolls, a preheating portion, a far infrared ray heating portion, a hot air heating portion, an air injection pipe, and a guide roll coated with a heat resistant fabric which are operated at different speeds; A pair of nip rolls, a heat-setting tower consisting of a far-infrared heating unit and a hot air heating unit configured to rotate 360 ° at a rotational speed of 2π110min to 2π / 30min, a guide roll coated with a heat-resistant fabric, and a traveling direction and blade of the heat-setting film A third row fixed bubble part comprising a trimming device using a R-shaped blade having an angle of 20 to 30 ° and trimming using an elastic device, a secondary heat treatment, and a winding device; And an accumulator capable of storing the stretched film between the second stretched bubble portion and the third row fixed bubble portion.