JP2002137288A - Manufacturing method for aromatic polyamide film, and aromatic polyamide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for an aromatic polyamide film which enables execution of orientation at a high rate of multiplication, shows high productivity and enables attainment of the film of a high grade. SOLUTION: A polymer sheet containing a solvent and an aromatic polyamide is heated to be oriented by using a noncontact type heating method. The noncontact type heating method includes at least either a method of bringing a heated fluid into contact with the sheet or a method of irradiating it with electromagnetic waves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aromatic polyamide film having high productivity and process stability and capable of obtaining a high-quality film.

[0002]

2. Description of the Related Art Conventionally, aromatic polyamide films have been widely used as industrial materials. In particular, due to advances in digital recording technology and the development of external memory in computers, the demand for thinner and higher-density recording of magnetic tapes has increased, and aromatics having excellent heat resistance, mechanical properties, and thermal stability have been developed. Polyamide films have been increasingly used as base films for magnetic tapes. For example, as one of high-performance magnetic materials in recent years, it has been rapidly expanded to digital data storage applications, and with the expansion of the use to these applications, higher productivity and higher mechanical properties have been demanded. .

As a means for achieving such high productivity and high mechanical properties, a method of stretching at a high magnification in a film production process can be considered.

Japanese Patent Application Laid-Open Nos. 52-56169, 53-42265, 53-42266 and 53-42267 disclose a method of stretching an aromatic polyamide film. Gazette, JP-A-53-4
No. 2268. Each of these discloses a method of stretching in a state containing an amide-based solvent.However, since stretching is performed at room temperature, there are problems such as a large stretching tension, a large load on an apparatus, and an insufficient stretching ratio. there were. Japanese Patent Application Laid-Open No. H11-48334 describes a method in which an aromatic polyamide film is stretched in a longitudinal direction in the air and in a liquid bath while containing a solvent. However, since the temperature at the time of stretching is low, the stretching ratio in the air is at most 1.6 times, and the productivity cannot be said to be high yet. Further, stretching in a liquid bath has problems such that the film becomes slippery due to the liquid and the stretchability becomes unstable.

On the other hand, the inventors of the present invention have found that the stretching ratio is greatly improved when the film is heated and stretched in a state containing a solvent. However, in this method, since the film is heated in a very unstable state including a solvent, the surface of the film is damaged due to thermal expansion or the like at the time of heating, and it is difficult to obtain a high-quality film. there were. Such scratches on the film surface have become a serious problem particularly in applications requiring a smooth surface such as a high-density magnetic recording medium.

[0006]

SUMMARY OF THE INVENTION In the production of an aromatic polyamide film using heat stretching, the present invention provides a heating method prior to stretching, thereby further improving the stretchability and preventing the film surface from being damaged. It is an object of the present invention to provide a method for producing an aromatic polyamide film capable of suppressing generation.

[0007]

This object is achieved by heating and stretching a polymer sheet containing a solvent and an aromatic polyamide using a non-contact method.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic polyamide used in the present invention has a repeating unit represented by the following formula (1) and / or formula (2). Equation (1):

[0009]

Embedded image Equation (2):

[0010]

Embedded image Here, as Ar ₁ , Ar ₂ and Ar ₃ , for example,

[0011]

Embedded image And X and Y are respectively -O- and-
_{CH 2 -, - CO -,} - CO 2 -, - S -, - SO 2 -,
—C (CH ₃ ) ₂ — and the like.

Further, part of the hydrogen atoms on these aromatic rings may be halogen groups such as fluorine, bromine and chlorine (particularly chlorine),
Those substituted with substituents such as nitro groups, alkyl groups (especially methyl groups) such as methyl, ethyl and propyl, and alkoxy groups such as methoxy, ethoxy and propoxy reduce the moisture absorption rate and cause the film to change due to humidity changes. It is preferable to reduce dimensional change. Further, hydrogen in the amide bond constituting the polymer may be substituted by another substituent. In the aromatic polyamide used in the present invention, the aromatic ring having para-orientation preferably accounts for 80% or more, more preferably 90% or more of the total aromatic ring. The term “para-orientation” as used herein refers to a state in which divalent bonds forming the main chain on the aromatic ring are coaxial or parallel to each other. If this para-orientation is less than 80%,
The rigidity and heat resistance of the film may be insufficient. Further, it is preferable that the aromatic polyamide contains the repeating unit represented by the formula (3) in an amount of 60 mol% or more, since the stretchability and the physical properties of the film are particularly excellent. Equation (3):

[0013]

Embedded image When the aromatic polyamide used in the present invention is obtained from an aromatic diacid chloride and an aromatic diamine, a solution in an aprotic organic polar solvent such as N-methyl-2-pyrrolidone, dimethylacetamide, or dimethylformamide is used. It can be synthesized by a polymerization method.

At this time, in order to suppress the formation of low molecular weight substances, it is necessary to avoid mixing of water and other substances that would hinder the reaction, and it is preferable to use efficient stirring means. Further, calcium chloride, magnesium chloride, lithium chloride, lithium bromide, lithium nitrate, or the like may be added as a dissolution aid.

When an aromatic diacid chloride and an aromatic diamine are used as monomers, hydrogen chloride is produced as a by-product. When neutralizing this, cations of Group I or Group II of the periodic table and hydroxides are used. It is preferable to use an inorganic neutralizing agent represented by a salt comprising an anion such as an ion or a carbonate ion, or an organic neutralizing agent such as ethylene oxide, propylene oxide, ammonia, triethylamine, triethanolamine, and diethanolamine. . Also, for the purpose of improving the humidity characteristics of the base film, benzoyl chloride, phthalic anhydride, acetic chloride, aniline, etc. are added to the system after polymerization,
The terminal functional groups of the polymer may be blocked.

In order to obtain the film of the present invention, a polymer
Has an intrinsic viscosity (measured at 30 ° C. as a 100 ml solution of 0.5 g of polymer in sulfuric acid) of 0.5 or more.

As a membrane-forming stock solution, the polymer solution after neutralization may be used as it is, or once the polymer is isolated,
Those re-dissolved in a solvent may be used. As the solvent,
Organic polar solvents such as N-methyl-2-pyrrolidone, dimethylacetamide, and dimethylformamide are most preferable because of easy handling, but strongly acidic solvents such as concentrated sulfuric acid, concentrated nitric acid, and polyphosphoric acid are also preferably used. The polymer concentration in the film forming solution is preferably in the range of 2 to 20% by weight.

The film-forming stock solution prepared as described above is formed into a film by a dry method, a dry-wet method, a wet method, or the like, but the dry-wet method is preferable because a high-quality film is obtained.

First, the dry-wet method will be described as an example.

The stock solution is extruded from a die onto a support such as a drum or an endless belt to form a thin film, and the solvent is scattered from the thin film to obtain a polymer sheet which can be peeled from the support. As used herein, the polymer sheet refers to a self-supporting film or sheet containing a solvent, a dissolution aid, and the like in addition to the polymer. The drying temperature at this time is 80 to 2 because the smoothness of the film surface is improved.
It is preferably in the range of 00 ° C.

The solvent content of the polymer sheet is from 30 to
Preferably it is in the range of 70% by weight. When the solvent content exceeds 70% by weight, the self-supporting property of the polymer sheet is insufficient, and the polymer sheet tends to stick to a nip roll, a heating roll, a stretching roll, and the like. From the viewpoint of more stable stretching, the solvent content of the polymer sheet is more preferably in the range of 35 to 70% by weight, and still more preferably in the range of 35 to 60% by weight. In addition, this solvent content means that the solvent and other solids are extracted from the polymer sheet with water at 30 ° C., the weight of the remaining polymer is obtained, and the weight of the polymer and the solid is subtracted from the weight of the polymer sheet. Means the value calculated.

With respect to the composition of the solvent contained in the polymer sheet, the organic polar solvent and / or the strongly acidic solvent is at least 10% by weight, preferably at least 20% by weight, more preferably at least 20% by weight, based on the total solvent. Is preferably 30% by weight or more because the film is hardly broken even when stretched at a high magnification. The solvent includes amines as the above-described neutralizing agent, water produced as a by-product of the neutralization reaction, and the like. These are poor solvents for the polymer. Plasticization is not sufficient, and the draw ratio tends to decrease. In addition, the composition of the solvent in the present invention refers to a value obtained by extracting the solvent from the polymer sheet with methanol and measuring this solution by gas chromatography.

The polymer sheet released from the support is then heated and then introduced into a stretching step.

As the heating method, a non-contact heating method,
That is, it is necessary to adopt a method in which a rigid body such as a heating body is not brought into direct contact with the polymer sheet. In a method in which a heating element is brought into direct contact with a polymer sheet, for example, a method in which a heated metal roll or a rubber roll is brought into contact with a polymer sheet, the surface of the polymer sheet is soft and is easily slipped on the roll due to thermal expansion. It becomes easy to stick. Therefore, in the present invention, for example, a method is used in which a fluid such as a liquid or a gas is brought into contact with the polymer sheet or an electromagnetic wave is applied to heat and stretch the polymer sheet. Examples of such a method include a method using a heated gas (hot air), a method of contacting with steam, a method of irradiating infrared rays using a radiation heater, a method of irradiating microwaves, and a method of performing induction heating. Can be used. Of course, each of the above-described methods may be used alone, or the polymer sheet may be efficiently heated by irradiating an electromagnetic wave such as an infrared ray while contacting the heated fluid.

Among the above, when using hot air, it is preferable to use a hot air generating nozzle to blow hot air onto the polymer sheet surface as shown in FIG. Here, it is preferable that the nozzle and the device (blower) that generates hot air are connected by a heat-insulated duct or the like. A nozzle has a structure in which an air supply port is provided at one end and air is ejected from a blowing slit provided on the outer surface of the other end, but an air balance adjustment plate, a rectifying plate, a damper, etc. Is preferred. The width of the nozzle needs to be at least equal to the width of the polymer sheet, but is preferably equal to or more than (the width of the polymer sheet + 20 cm) because the polymer sheet can be stably heated even at the end. The distance between the polymer sheet and the nozzle is preferably 5 cm or less, more preferably 3 cm or less, in order to minimize the time required for the polymer sheet to rise in temperature. However, since the polymer sheet vibrates (flutters) to some extent, it is preferable to separate the polymer sheet by 5 mm or more. If the polymer sheet is thin, the nozzle can be heated sufficiently if it is placed on one side. However, it is more preferable that the nozzles be placed on both sides to make the temperature of the front and back more constant and to suppress the flutter of the polymer sheet. Further, in order to reduce unevenness in physical properties in the width direction of the film, it is preferable to adjust the slit interval and the wind speed so that unevenness in hot air temperature and wind speed in the width direction of the nozzle is minimized. For this reason, the slit interval is preferably 1 cm or less, more preferably 5 mm or less, but is usually preferably 2 mm or more so that the air volume does not become too small. The higher the wind speed is, the smaller the unevenness in the width direction is. Therefore, it is preferable that the speed is 1.5 times or more of the conveying speed of the polymer sheet. However, the speed is preferably 50 m / s or less because the evaporation of the solvent increases.

When the radiation heat of infrared rays is used by using a radiation heater, it is preferable to use infrared rays having a wavelength close to the infrared absorption spectrum of the solvent and the aromatic polyamide because the temperature can be raised efficiently. Specifically, it is preferable to use a wavelength within the range of 5.5 to 8.5 μm, which is the main absorption band of the aromatic polyamide (N-methyl-
Absorption bands of aprotic organic polar solvents such as 2-pyrrolidone, dimethylacetamide, dimethylformamide and the like have almost the same wavelength). Also, as in the case of using hot air, the width of the heater is preferably equal to or greater than the width of the polymer sheet,
It is preferable to install on both the front and back sides because heating can be performed uniformly. However, an explosion-proof type is preferably used because the solvent may evaporate.

Among the above methods, a method using hot air is particularly preferable because of its good heat conduction efficiency and high safety.

When the temperature of the polymer sheet rises, the thermal behavior of the polymer sheet changes. Therefore, as shown in FIG. 1, the tension is reduced by a nip roll so that the tension is not transmitted to the support such as a belt. It is preferable to heat after cutting.

The non-contact heating method described above may be carried out separately from the stretching step described below, or may be carried out in the course of the stretching. Specifically, when the stretching step is performed using a stretching roll, for example, a film (polymer sheet) in a stretching section between the stretching rolls
It can be realized by applying the non-contact heating method described above to the above.

The temperature of the polymer sheet during stretching (after heating) is preferably in the range of 100 to 200 ° C.
When the temperature at the time of stretching is lower than 100 ° C., the polymer sheet is not sufficiently softened, and the film may be broken at a low magnification. When the temperature exceeds 200 ° C., the solvent evaporates. In some cases, film tearing may occur at low magnification. Since the stretching limit is further improved, the stretching temperature is more preferably in the range of 100 to 180 ° C, and even more preferably in the range of 120 to 180 ° C. Further, since film tearing is likely to occur starting from the end, it is particularly important to keep the temperature of the end within the above range. In addition, the temperature of the polymer sheet in the present invention refers to the average value of the center of the heated polymer sheet in the width direction measured on the front and back sides using a contact thermometer.

The stretching ratio at this time is preferably in the range of 1.5 to 5 times. If the ratio is less than 1.5 times, the productivity is low, and the Young's modulus of the film may not be sufficient. If the ratio exceeds 5 times, the molecular chains may be too oriented to be easily torn. The stretching ratio is more preferably in the range of 1.5 to 3 times, and even more preferably in the range of 1.5 to 2 times, because the film has a better balance between Young's modulus and elongation. As a stretching method, a method of stretching in the longitudinal direction (longitudinal direction) by using a stretching roll and changing the peripheral speed between the stretching rolls, a method of gripping with a chuck and stretching in the longitudinal or width direction or simultaneously in the longitudinal and width directions. Etc., but a method using a stretching roll is preferable because productivity is better.

Next, the polymer sheet that has been subjected to the above-mentioned stretching step is introduced into a wet process, and is subjected to desalting, solvent removal, and the like. If the heat treatment is performed as it is without passing through the wet process, the surface may be roughened or curl may occur.

The film having undergone the wet process is subjected to moisture drying and heat treatment. Furthermore, at the time of heat treatment, stretching in the longitudinal or width direction may be performed again. The heat treatment temperature is preferably in the range of 200 to 400C. When the heat treatment temperature is lower than 200 ° C., the Young's modulus of the film is reduced, and the film is easily broken when stretched.
Conversely, if the temperature exceeds 400 ° C., the crystallization of the film may proceed too much, resulting in a hard and brittle film. Since the physical properties of the film are better, the heat treatment temperature is 240 to 320.
More preferably, it is within the range of ° C. In the case of stretching, the area magnification (magnification obtained by multiplying all the stretching magnifications in the longitudinal and width directions) is preferably 8 times or less.
When it exceeds 8 times, the film tends to be too brittle even if the orientation is excessively advanced.

After stretching or heat treatment, it is effective to gradually cool the film, and it is effective to cool the film at a rate of 50 ° C./sec or less.

The dry method is a film forming method in which the wet process is omitted from the above-mentioned dry-wet method, and the other steps preferably satisfy the same requirements as the dry-wet method. However, it is preferable that inorganic salts and the like that cannot be removed in the drying step due to the absence of the wet step are previously removed from the stock solution for film formation.

Next, the wet method will be described.

The stock solution is extruded from a die onto a support such as a drum or an endless belt to form a thin film, and introduced into a coagulation bath to remove additives such as a solvent and a solubilizing agent. At this time,
In order to remove the solvent as gently as possible, it is preferable to use a mixed solvent of a good solvent such as a polymerization solvent and a poor solvent such as water for the coagulation bath. Also, calcium chloride as a poor solvent,
A bath prepared by adding an inorganic salt such as magnesium chloride, lithium chloride, lithium bromide or lithium nitrate may be used. The polymer sheet from which the solvent has been extracted is stripped from the support, stretched in the longitudinal direction or the width direction, and then formed into a film by the same method as the dry-wet method. The solvent content and stretching conditions of the polymer sheet at the time of peeling need only satisfy the same requirements as in the dry-wet method. Further, in the wet method, a poor solvent is also present as a solvent contained in the polymer sheet, but an organic polar solvent and / or a strongly acidic solvent which is a good solvent is contained in 10% of the total solvent.
It is more preferable that the content is not less than 20% by weight, more preferably not less than 20% by weight, and still more preferably not less than 30% by weight, because it is difficult to be broken even when stretched at a high magnification.

The film produced by the method of the present invention may be a laminated film. For example, in the case of two layers, the polymerized aromatic polyamide solution is bisected, and different particles are added to each, and then the layers are laminated. The same applies to the case of three or more layers. As a method of lamination, for example, lamination in a die, lamination in a composite pipe, a method of once forming one layer and then forming another layer thereon can be used.

Next, the physical properties of the aromatic polyamide film obtained by the production method of the present invention will be described.

According to the production method of the present invention, an aromatic polyamide film in which the number of flaws having a width of 1 μm or more and a length of 50 μm or more on at least one surface is 10 / cm ² or less is suitably obtained. 10 scratches / c above
If it exceeds m ² , when used as an optical film, optical isotropy is disturbed, and when it is used as a magnetic recording medium, dropout tends to occur. The scratch on the film surface in the present invention is obtained by observing the film surface with a differential interference microscope under magnification. The magnification can be appropriately selected depending on the size of the flaw, the density of existence, and the like.
It may be about 0 times.

The aromatic polyamide film obtained by the production method of the present invention can have a tensile Young's modulus of at least 9.8 GPa and an elongation of at least 5% in at least one direction. When the Young's modulus is less than 9.8 GPa,
In some cases, it is not possible to withstand high tension and fluctuations in tension during processing or winding when formed into a tape and used. Further, when the elongation is less than 5%, the film may be brittle and easily cut. The aromatic polyamide film of the present invention has a Young's modulus in at least one direction of 11.7 GP.
It is more preferably at least a, especially at least 12.7 GPa, because it is suitable for thinning the film. Further, the Young's modulus in all directions is more preferably 9.8 GPa or more. Further, it is more preferable that the aromatic polyamide film of the present invention has an elongation of 10% or more, particularly 20% or more, since it can have appropriate flexibility when processed into tape.

The aromatic polyamide film obtained by the production method of the present invention can have a moisture absorption of 5% or less, and if it is 3% or less, particularly 2% or less, it can suppress a dimensional change due to a humidity change. Is preferred.

The aromatic polyamide film obtained by the production method of the present invention can have a heat shrinkage of 0.5% or less at 200 ° C. for 10 minutes. It is more preferable because the dimensional change of the tape due to the change is small.

The aromatic polyamide film of the present invention is preferably used for various uses such as a flexible printed board, a capacitor, a printer ribbon, an acoustic diaphragm, and a base film of a solar cell. When used as a medium, the effect of the aromatic polyamide film of the present invention having both high Young's modulus and smoothness without scratches on the surface is sufficiently exhibited, and therefore it is particularly preferable.

[0045]

EXAMPLES The methods for measuring physical properties and the methods for evaluating effects in the examples were performed according to the following methods. (1) Solvent content in polymer sheet A sample of 10 cm on a side was cut out from the center in the width direction of the polymer sheet, and its weight was measured. Next, the polymer sheet was washed in a water bath at 30 ° C. to completely remove solids such as a solvent and a dissolution aid, and then dried in an oven at 300 ° C. to measure the weight of the final film (polymer). .
The weight of the solvent was determined by subtracting the weight of the polymer and the weight of the solid component such as the dissolution aid from the weight of the polymer sheet, and expressed as a weight fraction. (2) Temperature of polymer sheet The temperature of the polymer sheet after heating was measured using a contact type thermometer SK-2000MC manufactured by Sato Keiki Co., Ltd. The measurement location is the center of the stretching section in the longitudinal direction (in FIG. 1, the middle between the rolls 5 and 6 and the rolls 7 and 8), and the center in the width direction and a point 5 cm from one of the ends, respectively. Was measured and the average value was determined. (3) Stretching limit In FIG. 1 (FIG. 2), by changing the number of rotations between the rolls 5, 6 (13, 14) and the rolls 7, 8 (15, 16), the polymer sheet is stretched in the longitudinal direction. Stretched. Rolls 1 to 6 (9 to 14) rotate at substantially the same speed as the support. The number of rotations of the rolls 7, 8 (15, 16) was increased, and the magnification at which the film was cut was taken as the stretching limit. An average was obtained by performing the test three times. (4) Scratches on the film surface A total of three places, that is, a central part in the width direction and 5 cm from both ends, were sampled into a rectangle of 0.5 cm in the width direction × 5 cm in the length direction, and dust on the surface was sufficiently removed with compressed air or the like. Then, using a differential interference microscope HFX-II manufactured by Nikon Corporation, the surface not in contact with the belt was magnified by reflected light at a magnification of 340.
Observation was performed at × 2, and the average value was determined.

A line-like object having a width of 1 μm or more and a length of 50 μm or more was regarded as a scratch. Deposits can be distinguished by changing the direction of the shadow when the sample is rotated.

When it is difficult to observe the film surface, black magic may be applied to the back surface or aluminum may be evaporated on the observation surface.

Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to these.

Example 1 85 mol% of 2-chloroparaphenylenediamine and 15 mol% of 4,4'-diaminodiphenyl ether were dissolved in dehydrated N-methyl-2-pyrrolidone. To this, 2-chloroterephthalic acid chloride corresponding to 98.5 mol% was added, and after polymerization for 2 hours with stirring, neutralization was performed with lithium carbonate to obtain an aromatic polyamide solution having a polymer concentration of 11% by weight.

The aromatic polyamide solution was supplied to a 830 mm wide die with an extruder, and was cast on a stainless steel belt whose surface rotating at 7 m / min was mirror-finished.
The solvent was evaporated by heating with hot air at ℃ and peeled off. The solvent content of the peeled polymer sheet was 40.2% by weight.

The polymer sheet was heated by two hot-air nozzles 3 and 4 using the stretching apparatus shown in FIG. 1 and then stretched. The nozzle was adjusted to have a width of 90 cm, a slit interval of 3 mm, a hot air temperature of 150 ° C. from the slit, a temperature unevenness in the width direction of 10 ° C. or less, and a wind speed of 12 m / sec. The distance between the nozzle and the polymer sheet was 1.5 cm.

The rolls 5 and 6 were also heated to 150 ° C. to keep the polymer sheet warm.
Has a surface covered with silicone rubber, and the rest is a metal roll.

The temperature of the film during stretching was 102 ° C. at the center and 89 ° C. at the end.

When the stretching limit was measured, it was 1.9 times.

Further, separately in the longitudinal direction under the above conditions,
The polymer sheet stretched twice is passed through a water tank for 2 minutes to perform water extraction of the residual solvent and the inorganic salt generated by neutralization.
The film was stretched 2.0 times in the width direction and heat-treated in a tenter at 0 ° C to obtain a biaxially stretched aromatic polyamide film having a thickness of 4.4 µm.

There were no scratches on the film surface. Example 2 In Example 1, the temperature of hot air coming out of the slit was set to 180 ° C.
The temperature unevenness in the width direction was adjusted to 5 ° C. or less and the wind speed to 15 m / sec.
The temperature was 35 ° C., the end was 127 ° C., and the stretching limit was 2.2 times.

Further, a biaxially stretched film was formed in the same manner as in Example 1, but no damage was found on the film surface. Example 3 In Example 1, when the hot air temperature at the time of drying the solvent was set to 180 ° C., the solvent content of the peeled polymer sheet was 2
It was 7.6% by weight. Thereafter, when the film was stretched by heating in the same manner as in Example 1, the temperature of the film at the time of stretching was 1 center.
The temperature was 00 ° C. and the end was 83 ° C., and the stretching limit was 1.7 times.

Further, a biaxially stretched film was formed in the same manner as in Example 1, but no damage was found on the film surface. Example 4 Heat stretching was performed in the same manner as in Example 1 except that the polymer sheet peeled from the belt was once introduced into a water tank and the solvent was replaced with water.

The solvent content after introduction into the water tank was 45.1% by weight.
The temperature of the heated film was 98 ° C. at the center and 8 at the end.
At 5 ° C., the stretching limit was 1.6 times. Since the content of the organic polar solvent in the solvent was low, the stretching limit was lowered as compared with Example 1.

A polymer sheet stretched 1.4 times in the longitudinal direction under the above conditions was formed into a film in the same manner as in Example 1 to obtain an aromatic polyamide film having a thickness of 5.0 μm.

There were almost no scratches on the film surface. Comparative Example 1 A polymer sheet having a solvent content of 40.2% by weight was obtained in the same manner as in Example 1.

Next, the polymer sheet was heated by two silicon rolls 11 and 12 heated at 150 ° C. using the stretching apparatus shown in FIG.

When the temperature of the film after heating was measured, it was 143 ° C. at the center and 141 ° C. at the end. When the stretching limit was measured, it was 2.3 times.

Further, when a biaxially stretched film was formed in the same manner as in Example 1, there were many scratches on the film surface. Comparative Example 2 The same procedure as in Comparative Example 1 was carried out except that the polymer sheet peeled off from the belt was once introduced into a water tank, and the solvent was replaced with water.

The solvent content after introduction into the water tank was 45.1% by weight.
The temperature of the film after heating was 131 ° C. at the center and 125 ° C. at the end, and the stretching limit was 1.6 times.

A polymer sheet stretched 1.4 times in the longitudinal direction under the above conditions was formed into a film in the same manner as in Comparative Example 1 to obtain an aromatic polyamide film having a thickness of 5.0 μm.

There were many scratches on the film surface.

[0068]

[Table 1]

[0069]

According to the method for producing an aromatic polyamide film of the present invention, it is possible to obtain a high-quality film which can be stretched at a high magnification, has high productivity, and is hardly damaged on the film surface.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of an apparatus for explaining a heating step and an example in the present invention.

FIG. 2 is a schematic longitudinal sectional view of an apparatus for explaining a comparative example in the present invention.

[Description of Signs] 1: Nip roll (normal temperature) 2: Nip roll (normal temperature) 3: Hot air generation nozzle 4: Hot air generation nozzle 5: Heating roll (stretching roll) 6: Heating roll (stretching roll) 7: Cooling roll ( Stretching roll) 8: Cooling roll (stretching roll) 9: Nip roll (room temperature) 10: Nip roll (room temperature) 11: Heating roll 12: Heating roll 13: Heating roll (stretching roll) 14: Heating roll (stretching roll) 15: Cooling Roll (stretching roll) 16: Cooling roll (stretching roll)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F210 AA30 AG01 AK08 AR06 QA03 QD02 QD32 QD38 5D006 CB03 CB07

Claims (7)

[Claims] 1. A method for producing an aromatic polyamide film, in which a polymer sheet containing a solvent and an aromatic polyamide is heated and stretched using a non-contact heating method. 2. The method for producing an aromatic polyamide film according to claim 1, wherein the non-contact heating method includes at least one of a method of contacting a heated fluid and a method of irradiating an electromagnetic wave. 3. The method according to claim 2, wherein hot air is used as the fluid, or irradiation of electromagnetic waves is performed using a radiation heater.
3. The method for producing an aromatic polyamide film according to item 1. 4. The temperature of the polymer sheet is 100 to 200 ° C.
The method for producing an aromatic polyamide film according to any one of claims 1 to 3, wherein the film is stretched in the range of 5. The solvent content of the polymer sheet is 30 to 70.
The method for producing an aromatic polyamide film according to any one of claims 1 to 4, wherein the stretching is performed in a state of being within the range of weight%. 6. The stretching wherein the solvent contains an organic polar solvent and / or a strongly acidic solvent, and the content of the organic polar solvent and / or the strongly acidic solvent relative to the total solvent is 10% by weight or more. Item 6. The method for producing an aromatic polyamide film according to any one of Items 1 to 5. 7. An aromatic polyamide film obtained by the production method according to any one of claims 1 to 6,
1 μm width on at least one surface of the film
The number of scratches having a length of 50 m or more and a length of m or more is 10 /
cm ² or less aromatic polyamide film.