JPS6237124A - Manufacture of linear coordination properties aromatic polyamide film - Google Patents

Abstract

PURPOSE:To obtain an aromatic polyamide film whose mechanical properties are favorable, by a method wherein a filmy dope is solidified after being changed from optically anisotropic to optically isotropic and a wet film containing water more than a specific quantity to a polymer by washing is dried after the same has bee oriented specific times longer in a uniaxial direction. CONSTITUTION:After a dope containing polyamide constituted of aromatic unit of linear coordination whose logarithmic viscosity etainh is more than 2.5 and at least a kind of a solvent selected out of sulfuric acid whose concentration is more than 98wt%, chlorosulfuric acid and fluorosulfuric acid and having optical anisotropy in the vicinity of a normal temperature has been made into a filmy state, the same is solidified by making the same change once to optical isotropy. After the solvent has been removed from a solidified film through washing with water, the same is oriented uniaxially in a wet state containing water. Water content of the film is more than 50wt.pt. to a 100wt.pt. polymer; as wet orientation brings out mechanical strength after dryness effectively, the film is oriented 1.05-2.5 times longer. The oriented film is dried to remove an adhering washing liquid.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing a linearly coordinated aromatic polyamide film, and more specifically, a method for forming an aromatic polyamide film from a solution, coagulating and washing it with water, and then wet-stretching it. The present invention relates to a manufacturing method for obtaining an aromatic polyamide film with improved mechanical properties.

(Prior art) So-called fully aromatic polyamides, in which aromatic compounds are directly connected through amide bonds, have excellent heat resistance and are therefore useful as molded products such as fibers and films. Fully aromatic polyamide in which amide groups are bonded coaxially or in parallel in the direction and the chain is connected linearly as a whole (hereinafter referred to as linear aromatic polyamide)
has particularly excellent crystallinity, high melting point, and high mechanical strength, and is a polymer material that has attracted particular attention in recent years.

In recent years, the performance requirements for films that require mechanical strength in the l-axis direction, such as base films for magnetic tapes, have become higher and higher. It is known that the mechanical strength is increased in one axis direction. For example, Tokuko Sho 59-145
No. 67 discloses a film obtained by extruding an aromatic polyamide solution having optical anisotropy through a slit.

However, this film has strong mechanical strength only in one axis direction, but extremely weak mechanical strength in the direction perpendicular to this direction.
It was easy to tear.

In general, aromatic polyamides have poor thermoplasticity, and linear coordination polyamides in particular tend to crystallize, and their glass transition temperature is unclear, making it almost impossible to further heat stretch the film after forming it. Furthermore, unlike polymers soluble in hydrazide and other organic solvents, linear aromatic polyamides cannot be stretched with the solvent remaining, and it is extremely difficult to improve the strength of the film by stretching. Even if hot stretching is possible, the film is highly oriented and highly crystallized, making it easy to form fibrils, and especially in the direction perpendicular to the stretching direction, even a small tearing force is applied to the film. It has the disadvantage of being stored away.

It is known that linearly coordinated aromatic polyamides have optical anisotropy in concentrated polymer solutions, that is, they take on a liquid crystal structure, and the polymers form a partially aligned domain structure and are dispersed. ing. Note that this optically anisotropic dope can be obtained, for example, by the method described in Japanese Patent Publication No. 50-8474.

If such an optically anisotropic dope is simply formed into a film, washed with water, and dried, it will be excessively oriented in the discharge direction, and as in the method described above (Japanese Patent Publication No. 59-14567), it will not be fibrillated even without hot stretching. Therefore, the direction perpendicular to the discharge direction becomes weak.

Therefore, a method of manufacturing a film that does not have the above-mentioned drawbacks was investigated. For example, Japanese Patent Publication No. 57-35088 discloses that a film with good isotropy can be obtained by simultaneously stretching an aromatic polyamide solution having optical anisotropy in a doped state in two axes using an inflation method. However, the film obtained by this method actually has the drawbacks of large unevenness and low mechanical strength. In addition, Japanese Patent Publication No. 57-17886 discloses that by heating an aromatic polyamide solution having optical anisotropy to a temperature at which the dope becomes optically isotropic immediately before solidifying it and then solidifying it, a transparent and mechanically It has been reported that a film with similar physical properties was obtained. Although this method is an excellent method based on a new concept, it lacks modern mechanical properties, and it is difficult to hot stretch the obtained film as in the conventional method.

(Problems to be Solved by the Invention) The object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to create a structure made of linearly coordinated wholly aromatic polyamide, which has sufficient mechanical strength in the width direction as well. The object of the present invention is to provide a method for industrially producing a film having high strength, high modulus, and high thermal dimensional stability in the longitudinal direction, which are unrealized by conventional films.

(Means for Solving the Problems) As the present inventors continued to study the stretching of the film obtained by the technique disclosed in Japanese Patent Publication No. 57-17886,
By wet-stretching a film that has been wet-formed under special conditions before its orientation and crystallization progress, and then drying it, it does not become fibrillated and does not tear in the direction of stretching or in the direction perpendicular to it. It was also discovered that a film with excellent mechanical properties in the stretching direction could be obtained, and the present invention was achieved.

That is, the present invention provides polyamides composed of linearly coordinating aromatic units having a logarithmic viscosity ηinh of 2.5 or more, and sulfuric acid, chlorosulfuric acid, and fluorosulfuric acid at a concentration of 98% by weight or more. In a method of manufacturing a film by wet-molding a dope containing at least one selected solvent and having optical anisotropy at least near room temperature, the film-like dope is subjected to optical anisotropy prior to solidification. After converting to optical isotropy, solidify,
Next, the wet film obtained by washing, which is substantially free of solvent and contains 50 parts by weight or more of water per 100 parts by weight of the polymer, is stretched in the axial direction by 1°05 to 2.5 times, This is a method for producing a linearly coordinated aromatic polyamide film, which is characterized by drying.

According to the present invention, as described above, excellent mechanical strength in the stretching direction is achieved by using a linearly coordinated aromatic polyamide having high mechanical strength and performing wet uniaxial stretching at a low magnification. It is possible to obtain a film that has the same properties as above, does not reduce its mechanical strength in the direction perpendicular to the stretching direction, and is difficult to tear in that direction.

The polymer used in the present invention is a polyamide consisting essentially of units selected from the group consisting of the following structural units.

-NHA r I NH-(1) -CO-A r 2- CO--(II)-NH-A
r 3-Co - (m) where A r 1
, A r 2 and Ar 3 are each linearly coordinating divalent aromatic nuclei, and (1) and (II) are substantially equimolar when present in the polymer. Linear coordination means that the bonds that grow the molecular chain are located coaxially or parallel to the aromatic nucleus in the opposite direction, as described above. Specific examples of the divalent aromatic nucleus include paraphenylene, 4,4'-biphenylene, 1,4-naphthylene, 1.
Examples include 5-naphthylene, 2,6-naphthylene, and 2°5-pyrylidine. They are substituted with one or more non-reactive groups such as halogen, lower alkyl, nitro, methoxy, and cyano groups and have double bond properties.

Specifically, as X, trans-CH=CH-2-N=
Examples include N-1-Hen-NH-. Arc, Ar2
(2) and Ar3 may both be two or more types, and may be the same or different.

The polymer used in the present invention can be produced from diamines, dicarboxylic acids, and aminocarboxylic acids corresponding to each unit by a method known so far. Specifically, there is a method in which a carboxylic acid group is first induced into an acid halide, an acid imidazolide, an ester, etc. and then reacted with an amino group, or a method in which an amino group is induced into an isocyanate group and then reacted with a carboxylic acid group. As for the polymerization method, so-called low-temperature solution polymerization method, interfacial polymerization method, melt polymerization method, solid phase polymerization method, etc. can be used.

Within the scope of achieving the object of the present invention, the linearly coordinating polyamide used in the present invention contains approximately 10 mol% or less of units other than the above, i.e., ortho or meta units other than linearly coordinating aromatic units. Bonding unit, aromatic nucleus in which phenyl nuclei are connected by an odd number of atoms such as diphenyl ether, aliphatic unit,
Alternatively, it may contain a bonding group other than amide, such as a urea bond or an imide bond.

The polymer used in the present invention may be a homopolymer or a copolymer, and in the case of a copolymer, it may be a regular copolymer or a random copolymer. Furthermore, in producing a film according to the method of the present invention, it is also permissible to use a mixture of two or more of the above-mentioned polymers.

If the degree of polymerization of the polymer used in the present invention is too low, it will not be possible to obtain a film with good mechanical properties, which is the objective of the present invention. ) is 2.5
In view of the above, a polymer having a degree of polymerization of 3.5 or more is preferably selected.

The solvent used to prepare the dope used for molding the polyamide film of the present invention is sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, or a mixture thereof at a concentration of 98% by weight or more. Sulfuric acid of 100% or more, ie, fuming sulfuric acid, trihalogenated acetic acid, etc., may be mixed and used within a range that does not impair the effects of the present invention.

The polymer concentration in the dope used in the present invention is at room temperature (
A concentration that exhibits optical anisotropy at a temperature of about 20 to 30° C. or higher is preferably used, specifically about 10% by weight or more, particularly about 12% by weight or more. At polymer concentrations below this, ie, polymer concentrations that do not exhibit optical anisotropy at ambient or higher temperatures, the molded polyamide film often does not have desirable mechanical properties. The upper limit of the polymer concentration of the dope is not particularly limited, but usually 25% by weight or less is preferably used.

The dope of the present invention may contain conventional additives, such as fillers, light removers, UV stabilizers, heat stabilizers, antioxidants, pigments, solubilizing agents, and the like.

When wet-forming a film by the method of the present invention, there is no need to use a special film-forming method. A method using a rotating drum in which all or most of the bone is immersed in a coagulation bath, a method in which a film is introduced from a die into a coagulation bath, a method in which a film is formed by flowing a dope stream from a goo simultaneously with a coagulation liquid, etc. be able to.

The dope used in the present invention is a solution or solid having optical anisotropy at least around room temperature.

Dopes that are solid at room temperature but turn into a solution with optical anisotropy when heated can also be used. If such an optically anisotropic dope is formed into a film and then solidified and formed into a film while maintaining its optical anisotropy, it will become an opaque film, but in the present invention, the optically anisotropic dope is formed into a film. A transparent film with excellent mechanical properties can be obtained by converting the film into a shape, first converting it to optical isotropy, and then solidifying it.

Whether the dope is optically anisotropic or optically isotropic can be determined by a known method, for example, the method described in Japanese Patent Publication No. 50-8474, but the critical point depends on the type of polymer,
Type of solvent, temperature, polymer concentration, degree of polymerization,
It depends on the content of non-solvent, etc., so by investigating these relationships in advance, you can create an optically anisotropic dope and change the conditions to an optically isotropic dope to change the optical anisotropic to optically isotropic dope. can be changed to

The method of converting optical anisotropy to optical isotropy is not particularly limited, but specifically, (1) the film-formed dope is made to absorb moisture prior to coagulation to lower the concentration of the solvent forming the dope. Alternatively, there are methods such as (2) heating, and further (3) using moisture absorption and heating simultaneously or sequentially. To make the dope absorb moisture, the absolute humidity is 1 g (water)/k
This can be achieved by passing through an atmosphere with a relative humidity of 99% or less and a relative humidity of 99% or less.

If the absolute humidity is less than 1 g (water)/kg (dry air), it is not practical because the rate of moisture absorption is slow, and especially when converting an optically anisotropic dope to an optically isotropic dope only by moisture absorption near room temperature, 3 g ( Water)/kg (dry air) or more is preferable,
More preferably, it is 10 g (water)/kg (dry air) or more, particularly preferably 20 g (water)/kg (dry air) or more. Furthermore, the idea of actively applying humidification to a normal humid atmosphere shortens the time until optical isotropy is achieved, and when heating is also used, the heating temperature can be lowered, and the transparency of the film can be further improved. This is a desirable embodiment in terms of improvements that can be made. If the relative humidity exceeds 99%, water condenses on the dope at low temperatures, resulting in partial coagulation and loss of flatness, which is not preferable. In addition, in the heating method, for example, when sulfuric acid is used as a solvent, the temperature at which optical anisotropy substantially disappears and the dope converts to optical anisotropy depends on the polymer concentration, polymerization degree of the polymer, sulfuric acid concentration,
Although it depends on the thickness of the dope, it is usually preferable to set the temperature to about 45° C. or higher. It is generally desirable that the upper limit of the conversion temperature is not too high when considering the decomposability of the polymer, and it is desirable that the upper limit of the conversion temperature be selected so that the temperature of the film-like dope does not exceed 200°C.

In the present invention, the coagulating liquid of the dope converted to optical isotropy is, for example, dilute sulfuric acid containing about 70% by weight or less of water, about 20% by weight or less of water,
Caustic soda aqueous solution and aqueous ammonia, not more than % by weight;
Up to about 50% by weight aqueous sodium chloride and calcium chloride solutions can be used. There are no particular restrictions on the temperature of the coagulation bath, but it is usually between 0°C and 8°C.
It is carried out in the range of 0°C.

In the present invention, after the solvent is removed by washing with water, the coagulated film is uniaxially stretched (so-called wet stretching) in a swollen state substantially free of solvent and containing water, before drying. . By washing the material prior to stretching and stretching it in a water-swollen state, it is possible to stretch at high stretching ratios, which was previously difficult to do with fibers or films made from linearly coordinated polyamide liquid crystal dope. Become.

Since the coagulated film contains acid as it is, in order to produce a film whose mechanical properties are less likely to deteriorate due to heating, it is desirable to wash and remove the acid content as much as possible. Specifically, the removal of this acid content is approximately 5000
It is preferable to reduce the amount to less than ppm, preferably less than 500 ppm.

Water is usually used as the cleaning liquid for the above-mentioned cleaning, but if necessary, warm water may be used, or washing may be performed with water after neutralization with an alkaline aqueous solution. Moreover, the cleaning method may be to run the film in a cleaning liquid or to spray the cleaning liquid. In addition, cleaning is divided into two or more stages,
Washing may be performed in the first stage under the above-mentioned conditions, and further washing may be performed after stretching. The moisture content of the coagulated and washed film generally depends on the polymer concentration in the dope and the temperature of the coagulation bath.
The amount is 50 parts by weight or more based on 100 parts by weight of the polymer. 5
If it does not reach 0 parts by weight, it is not possible to increase the stretching ratio, and even if the stretching ratio is increased, considerable degree of orientation and crystallization will occur, and the dried film will be fibrillated and in the stretching direction. This is not desirable because it forces you to avoid it in the right angle direction. The upper limit of the water content is not particularly limited, and - there may be water attached to the film surface other than swelling.

The stretching ratio in the wet stretching of the present invention is preferably 1.05 times or more, more preferably 1.2 times or more, in order to effectively bring out the mechanical strength after drying. In addition, if the maximum stretching ratio is 2.5 times or more, it will often break, and a high stretching ratio will increase the mechanical strength in the direction of stretching, but the mechanical strength in the direction perpendicular to the stretching direction will be weak.
A ratio of 2.5 times or less is preferably used because it not only becomes easy to tear but also causes fibrillation. The temperature during stretching may be any temperature as long as it can retain moisture (and may be in the air, in a water bath, or in a hot water bath).

Further, there is no need to use a special method for stretching, and for example, the stretching can be carried out by using a difference in the circumferential speed of rolls or by using a tenter.

The stretched film as described above is then dried.

Drying here refers to the operation of removing cleaning liquid etc. adhering to the film, and any method can be used as long as the cleaning liquid etc. can be removed (air drying at room temperature, heated inert gas, such as air, nitrogen, argon, etc.). Methods include drying in an atmosphere such as , drying in a heated roll, or drying in a heated atmosphere in a tenter.Also, when drying, it is usually done in order not to lose the stretching effect or to dry the film. In order to prevent wrinkles and loss of flatness, it is preferable to dry the film under tension or at a constant length to limit shrinkage.The drying temperature is not particularly limited, but is at room temperature or higher. , In order to effectively improve mechanical strength, high temperature is preferable, preferably 100°C or higher,
More preferably, the temperature is 200°C or higher. The maximum temperature for drying is not particularly limited, but is 500° C. or lower, taking into account drying energy and decomposability of the polymer.

In producing the film by the method of the present invention, all of the above steps may be carried out batchwise or continuously, and it is also preferable to produce the film while running it continuously throughout the entire process. This is one of the embodiments. Further, an oil agent, an identification dye, etc. may be applied to the film in any step.

Reference examples (polymer production examples) and examples are shown below, but these reference examples and examples are for explaining the present invention, and are not intended to limit the present invention. In the examples, parts by weight or weight % are shown unless otherwise specified.

In the examples, the logarithmic viscosity ηinh is 98% sulfuric acid 100 m
It was determined by dissolving 0.2 g of polymer in 1 liter of water and measuring it at 30° C. using a conventional method. The viscosity of the dope is determined by lrp using a B type viscosity needle.
It was measured at a rotational speed of m. The thickness of the film was measured using a dial gauge with a measuring surface of 2 mm in diameter. The strength and elongation and Young's modulus were determined by cutting the film sample into a rectangle of l Q Qmm - Calculated from an elongation curve drawn. Density measurements were performed using a density gradient tube method using carbon tetrachloride-toluene.

Next, the number of voids in the film was counted as follows.

That is, a film piece of an appropriate size is observed in at least five different fields of view at a magnification ranging from 100x to 400x using a normal optical microscope using transmitted light, and voids with a major axis of 30 μ or more are detected. Count the number and convert it per 1rrzd of film surface. 5 pieces/m cd
A film having a void number below has excellent transparency and mechanical properties, but if the void number exceeds this value, the mechanical properties deteriorate, and if the void number is extremely large, the film appears cloudy and the transparency is reduced. Films made from ordinary optically isotropic dopes usually contain 501 [1/mry? The number of voids above is observed.

The light transmittance was measured as follows. ordinary photoelectric photometer,
Alternatively, attach a film to the location where the liquid cell of the spectrophotometer is set, select visible light with a wavelength of 600 nm, and measure its transmittance.

One important feature of the film produced by the method of the present invention is its transparency. - Normally, the light transmittance is 10% or less (however, this does not apply to particularly thin films).

Although this light transmittance naturally decreases as the thickness of the film increases, the film produced by the method of the present invention has a transparency of well over 55% up to a thickness of about 200 μm, which is commonly used.

A known method can be used to measure the crystal orientation angle.
It was done as follows. A diffraction intensity curve is obtained by placing a counter at a predetermined angle of 20 degrees and rotating the film 180 inches.For TVs, the maximum intensity is at the center, and the diffraction intensity curve is
It should be rotated between 0°. The value of the arc length in degrees in the diffraction photograph corresponding to the point indicating half the intensity with respect to the baseline drawn between the highest and lowest intensity points of this curve, that is, with respect to the 50% point with respect to the baseline with the highest intensity. Measure the angle and use it as the crystal orientation angle of the sample. If necessary, the diffraction intensity may be measured by stacking several films.

The incidence of X-rays can be divided into two cases: a case where the X-rays are incident on the film surface at right angles (hereinafter referred to as the TV direction) and a case where the X-rays are incident on the film surface in parallel (hereinafter referred to as the SV direction).

The crystal structure of PPTA has been widely discussed, for example Takayanagi et al. (J, Appl, Polym.

Sci., Vol. 23, p. 915 (1979)]. The film produced by the method of the present invention has a large diffraction peak at 2θ#23°, which is the reflection of the (200) plane by X-rays from the TV direction, but the crystal in the direction in which the large diffraction intensity at 2θ#23° is maximum The orientation angle is 30° or more and less than 70". Furthermore, a large diffraction peak at 2θ #18°, which is a reflection of the (010) plane due to incidence from the Sv direction, appears on the equator line;゛Crystal orientation angle is 60' or less. Only when both of these crystal orientation angles are satisfied, the film produced by the method of the present invention has a planar orientation structure, and also has excellent mechanical properties in the uniaxial direction. Films with crystal orientation angles outside this range tend to avoid or become fibrillated in the uniaxial direction, or have low mechanical properties in the uniaxial direction, making it impossible to obtain a film with the desired high mechanical properties.

Furthermore, when the film obtained by the method of the present invention is observed under a polarizing microscope, no dense striped pattern is observed.

This striped pattern is considered to be related to the pleated sheet-like aggregate structure. Although the striped pattern can be seen using a normal optical microscope, when it is observed using a polarizing microscope in a state of crossed Nicols or close to crossed Nicols, it is more clearly observed as stripes with various colors. A normal magnification of 100 to 1000 times is sufficient for a polarizing microscope.

Note that normal measures such as using an immersion liquid such as olive oil or methylene iodide may be used during observation.

It is difficult to quantify the distance between stripes using polarized light microscopy alone. Therefore, "dense striped pattern" means that the spacing is large enough to be confirmed with the magnification used in a normal polarizing microscope. As mentioned above, a film obtained by simply extruding an optically anisotropic dope through a slit and solidifying it immediately has a striped pattern with an interval of 0.1 to 0.4 μm or less. It split in the direction perpendicular to the striped pattern and easily fibrillated.

Although the film produced by the method of the present invention is highly oriented in the l-axis direction, it does not have the striped pattern seen in the above-mentioned highly oriented PPTA film, so it has high strength and high modulus, and has high strength and high modulus in one direction. It has the excellent feature of not easily forming into fibrils.

Reference Example (Manufacture of polyparaphenylene terephthalamide) Polyparaphenylene terephthalamide (hereinafter referred to as PPTA) was obtained by a low temperature solution polymerization method as follows. Special Public Service 1977
70 parts of anhydrous calcium chloride was dissolved in 1000 parts of N-methylpyrrolidone in the polymerization apparatus shown in Japanese Patent No. 43986, and then 48.6 parts of paraphenylenediamine was dissolved therein. After cooling to 8°C, terephthalic acid dichloride 9
1.4 parts were added in powder form at once. After a few minutes, the polymerization reaction product solidified into a cheese-like shape, so the polymerization reaction product was discharged from the polymerization apparatus according to the method described in Japanese Patent Publication No. 53-43986, and immediately transferred to a twin-screw closed kneader. The polymerization reaction product was pulverized. Next, the finely ground product was transferred to a Henschel mixer, an approximately equal amount of water was added, and the mixture was further ground, filtered, washed several times in hot water, and dried in hot air at 110°C. 95 parts of pale yellow PPTA polymer with ηinh of 6.5 was obtained. Note that polymers with different ηinh can be easily obtained by changing the ratio of N-methylpyrrolidone and monomers (para-phenylenediamine and terephthalic acid dichloride), and/or the pressure between the monomers.

Example 1, Comparative Example 1 A PPTA polymer having ηinh of 5.5 was dissolved in 99.7% sulfuric acid at a polymer concentration of 13.0% to obtain a dope with optical anisotropy at 60°C. The viscosity of this dope was measured at room temperature and was found to be 14,500 voids. To facilitate film formation, this dope was placed in a tank and maintained at about 70°C. In this case as well, the dope had optical anisotropy as described above, and the viscosity was 4200 voids. A 1.5m curved pipe from the tank to the die via the gear pump was kept at about 70℃, and from the die with 0.2mm x 3QQ11 slits, it was cast onto a mirror-polished belt kept at 110℃, and at 20℃. After being kept in an atmosphere with a relative humidity of 68% for 40 seconds, it solidified and was continuously formed into a film. When the dope was sampled from the belt just before solidification during film formation, it was found to have a fairly high viscosity and optical isotropy.

Take out the coagulated film and wash it with room temperature water overnight.
When the moisture content was measured, it was found that for 100 parts by weight of the polymer,
It contained 350 parts by weight of water.

The film still containing water was placed in the chuck of a constant speed extension type strength and elongation measuring machine with a width of 100 mm, and from the length of 100 mm,
The film was stretched 1.5 times and dried by blowing hot air at 200°C. The obtained film (Example 1) and a film dried to a fixed length with hot air at the same temperature without stretching (Comparative Example 1) were transparent. The physical properties of these films and their mechanical properties in two directions were measured and were as shown in Table 1. As is clear from the table, the wet-stretched product (Example 1) has excellent mechanical properties in the stretching (longitudinal) direction;
Further, the physical properties in the transverse direction were not significantly deteriorated, and there were no cases where only the stretching direction was avoided.

Comparative Example 2 The dope prepared in Example 1 was placed in a box under a nitrogen atmosphere with a dew point of -40°C, and was kept at 110°C at 20°C.
A film was formed on a 0 mm square glass plate using an applicator with a step of 1 mm. After 40 seconds, the glass plate and the dope on the large plate were taken out from the drying box together with the glass plate while maintaining its optical anisotropy, and immediately placed in water at 20°C to solidify. The produced film was opaque and was washed and stretched in the same manner as in Example 1, but most of the films were cut and 1
．． Some were stretched twice as much, but when they were dried, they broke.

Example 2, Comparative Example 3 The dope prepared in the example process was prepared in the same manner as in Comparative Example 2.
A film was formed on a glass plate kept at 0°C.

After 30 seconds, the dope on the glass plate showed optical isotropy, so it was removed from the drying box and solidified in water. The resulting film was transparent.

Take out the coagulated film and wash it with room temperature water overnight.
When the moisture content was measured, it was found that for 100 parts by weight of the polymer,
It contained 320 parts by weight of water.

The film still containing water was prepared in the same manner as in Example 1.
．． It was stretched 4 times and dried at a constant length of 250°C. The obtained film (Example 2) and the film dried at a fixed length at the same temperature without stretching (Comparative Example 3) were transparent, and their physical properties and mechanical properties in each of the two directions were as shown in Table 1. The wet-stretched material has excellent physical properties in the stretching direction.
There was no avoidance in just one direction.

Comparative Example 4 The film produced in Example 1 after solidification was immediately taken out, and the sulfuric acid bone was titrated with 1/10N-NaOH''?: 40%.While this sulfuric acid remained, Example 1 It was stretched using the same method as above, but it was only stretched 1.1 times.1
．． The 1-fold stretched film was fixed, washed with water overnight, and then dried at 200° C. to obtain a transparent film.

The mechanical properties are shown in Table 1, and no improvement in physical properties was observed.

Example 3, Comparative Example 5 A PPTA polymer with ηinh of 4.6 was dissolved in a solvent consisting of 80% 99.3% sulfuric acid and 20% chlorosulfuric acid at a polymer concentration of 15%, and the optical anisotropy was determined at 70°C. Got dope. This dope was continuously formed into a film using the apparatus and conditions described in Example 1. When the water content of the washed film was measured, it contained 420 parts by weight of water per 100 parts by weight of the polymer.

The film still containing water was treated with the method described in Example 1.
It was stretched by 6 times and dried with hot air at 300°C for a fixed length. The obtained film (Example 3) and the film dried at a fixed length at the same temperature without stretching (Example 5) were transparent, and their physical properties and mechanical properties in each of the two directions were as shown in Table 1. The wet-stretched film had considerably high mechanical properties in the stretching direction, and did not tear in one direction.

Example 4 y+1nh5. The PPTA polymer of Q was dissolved in 99.6% sulfuric acid at 60°C with a polymer concentration of 11.0%.
An optically anisotropic dope was obtained at °C. The viscosity of this dope is 6
It was 6300 poise at 0°C. Add this dope to room temperature 3
A film was formed on a glass plate at 0° C. using an applicator with a step of 0.05 mm. At that time, the temperature was 30° C. and the relative humidity was 83%, and when the glass plate was left in that atmosphere for 120 seconds, the dope on the glass plate changed from optically anisotropic to optically isotropic. Immediately after that, it was placed in water to solidify.

The coagulated film was taken out, washed with water at room temperature overnight, and the water content was measured. It was found that 3 parts by weight of the polymer
It contained 80 parts by weight of water. The film containing water was stretched 1.4 times by the method of Example 1, and then stretched to 250
Dry with hot air at ℃. The obtained film was transparent, and its physical properties and mechanical properties in two directions were as shown in Table 1, with no deviation in one direction.

Below is a margin Example 5 99.
Dissolved in 7% sulfuric acid at a polymer concentration of 12.0% and heated at 60°C.
A dope with optical anisotropy was obtained. When the viscosity of this dope was measured at room temperature, it was found to be 16.3 QO voids. In order to facilitate film formation, this dope was degassed under vacuum while being maintained at about 80°C. This case also had the same optical anisotropy as above, and the viscosity was 6400 poise. From the tank, through the filter, through the gear pump, to the die 1
, a 5 m long curved pipe was maintained at approximately 75°C, and casted from a gou with a 0.21@X300 fin slit onto a mirror-polished Hastelloy belt (moving at 2 m/min), the relative temperature was approximately 90%. Blow air at about 85°C to make the cast dope optically isotropic (retention time for about 12 seconds), and then with the belt,
It was introduced into a 10% by weight aqueous sulfuric acid solution at a temperature of 0.degree. C. for coagulation. The coagulated film was then peeled off from the belt and washed by running it in warm water at about 30°C. The washed film was placed in a tenter dryer and dried at a fixed length first with hot air at 150°C and then with hot air at 220°C (Film A).

On the other hand, the washed film (containing about 320% moisture) was stretched about 1.5 times in the width direction at room temperature using a tenter, and then dried in the same manner as film A. The resulting film was called film B. do.

Further, the washed film was stretched approximately 1.6 times in the longitudinal direction at room temperature, and then dried in the same manner as Film A. The resulting film was designated as Film C.

The properties of these films are shown in Table 2. Note that Film A is a comparative example, and Films B and C are Examples of the present invention.

The following margin Example 6 77inh is 99% of 5.7dl/g PPTA polymer
．． Dissolved in 3% sulfuric acid at a polymer concentration of 12.3%,
A dope with optical anisotropy at ℃ was obtained. This dope is about 8
It was degassed under vacuum while being kept at 0°C.

This case also had optical anisotropy and a viscosity of 5800 poise. The 1.5 m long curved pipe from the tank, through the filter, to the gear pump, to the guide is maintained at approximately 75°C, and the temperature is 0.2 m.
Cast the dope from a uX300 Tsuru slit onto a mirror-polished tantalum belt (distance between the bottom end of the gou and the belt surface is approximately 1 cm), blow hot and humid air, and cast the dope onto an optical device. Both belts were introduced into water at 10° C. to solidify. The temperature of the air used to make the dope optically isotropic was 70° C. and a relative humidity of 98%, and the time the cast dope was exposed to this air was 4 seconds.

The coagulated film is then peeled off from the belt and heated to approximately 30°C.
of warm water, a 3% aqueous solution of caustic soda at room temperature, and water at room temperature in this order. The washed film (containing about 300% water) is stretched about 1.5 times in the longitudinal direction at room temperature, then placed in a tenter dryer, and stretched at a fixed length first with hot air at 150°C and then at 220°C. Dry with hot air.

The properties of the obtained film are shown in Table 3.

Margin below (Effects of the Invention) According to the present invention, as shown in the examples, an aromatic polyamide film is produced which has good mechanical properties expressed by high strength and high Young's modulus, which are not found in commercially available films. In particular, the mechanical properties in the stretching direction can be dramatically improved while maintaining the mechanical properties in the direction perpendicular to the stretching direction. In addition, the film obtained by the method of the present invention not only has outstanding mechanical properties such as tensile strength and tensile modulus, but also has a very dense structure, making it useful as a filtration membrane, packaging material, etc. Furthermore, it has excellent chemical resistance and is completely stable against other chemicals except for strong acids such as sulfuric acid. In addition, the film of the present invention can be used in fields where pressure resistance is required, and because it has particularly excellent electrical properties, it can be used in electrical insulating materials and wire coating materials that require heat resistance, oil resistance, and electrical properties, especially in fields where high mechanical strength is required. Therefore, it is effectively used in insulating materials for electrical equipment that rotates at high speed, magnetic tape, etc.

Claims (4)

[Claims] (1) A polyamide composed of linearly coordinated aromatic units having a logarithmic viscosity ηinh of 2.5 or more, and a polyamide selected from the group consisting of sulfuric acid, chlorosulfuric acid, and fluorosulfuric acid at a concentration of 98% by weight or more. In a method of manufacturing a film by wet-molding a dope containing at least one type of solvent and having optical anisotropy at least around room temperature,
Prior to coagulation, the film-like dope was converted from optically anisotropic to optically isotropic, and then coagulated and then washed to obtain a polymer containing substantially no solvent and water content of 100 parts by weight of the polymer. 1. A method for producing a linearly coordinating aromatic polyamide film, which comprises stretching a wet film containing 50 parts by weight or more in a uniaxial direction by 1.05 to 2.5 times, and then drying the film. (2) The method of converting a film-like dope from optical anisotropy to optical isotropy prior to solidification is based on an absolute humidity of 1 g (
(water)/kg (dry air) or more and in an atmosphere with a relative humidity of 99% or less, the dope is substantially converted into an optically isotropic dope by absorbing moisture. A method for producing a linearly coordinated aromatic polyamide film. (3) The method for converting the film-like dope from optical anisotropy to optical isotropy prior to solidification is characterized by heating the dope to a temperature at which it changes to optical isotropy. A method for producing a linearly coordinated aromatic polyamide film according to claim 1. (4) A method for converting a film-like dope from optically anisotropic to optically isotropic prior to coagulation is to convert the dope at an absolute humidity of 1 g (water)/kg (dry air) or more and a relative humidity of 99%. The invention is characterized in that the conversion is carried out by absorbing moisture to the extent that optical anisotropy is lost, or by heating to a temperature at which optical isotropy changes while absorbing moisture, in the following atmosphere: A method for producing a linearly coordinated aromatic polyamide film according to item 1.