JPH0379175B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a film made of poly(p-phenylene terephthalamide) (hereinafter referred to as PPTA) and a method for producing the same, and more specifically, the present invention relates to a film made of poly(p-phenylene terephthalamide) (hereinafter referred to as PPTA) and a method for producing the same. ) and the width direction (TD direction), as well as a PPTA film that has excellent surface properties and slipperiness, and a method for producing the same. (Prior art) PPTA has particularly excellent crystallinity and a high melting point, and due to its rigid molecular structure, it has heat resistance and high mechanical strength, and has been attracting particular attention in recent years as a polymer. It is the material. It has also been reported that fibers spun from concentrated solutions exhibiting optical anisotropy exhibit high strength and modulus, and have already been implemented industrially, but there are few proposals for application to films. There are still no known examples of practical use. The problem with PPTA is that its useful high molecular weight polymer is poorly soluble in organic solvents, and strong inorganic acids such as concentrated sulfuric acid must be used as a solvent. For example, in Japanese Patent Publication No. 56-45421, by copolymerizing a unit in which a halogen group is introduced into the aromatic nucleus of a linearly coordinated aromatic polyamide and an aromatic polyamide other than PPTA that does not have a substituent on the aromatic group, Attempts have been made to make it soluble in organic solvents and to obtain films from it. However, since the monomer is expensive, this increases the cost and has the drawback of impairing the heat resistance and crystallinity of the linearly coordinated aromatic polyamide. On the other hand, Japanese Patent Publication No. 59-14567 discloses a method of extruding an aromatic polyamide solution having optical anisotropy from a slit through a short air space into a coagulation bath. The mechanical strength was strong only in the TD direction, but the mechanical strength in the TD direction perpendicular to this was extremely weak and could only be easily torn. In this way, simply extruding an optically anisotropic dope of aromatic polyamide and solidifying it as is,
Because the film is excessively oriented in the discharge direction, it tends to become fibrillated and is weak in the TD direction. Various film manufacturing methods have been studied to improve this problem. For example, in Japanese Patent Publication No. 57-35088, an aromatic polyamide solution having optical anisotropy is extruded from a ring die, and after being simultaneously cast in a doped state in two axes using an inflation method, It is said that an isotropic film can be obtained by wet coagulation. However, this method has the disadvantage that it is difficult to obtain a transparent film with a uniform thickness, and its mechanical strength, especially its tear strength, is low. Also, Japanese Patent Publication No. 59-5407, Japanese Patent Publication No. 54-132674
In the publication, an optically anisotropic or optically isotropic dope of a linearly coordinated aromatic polyamide is mechanically applied with a shearing force in a direction perpendicular to the extrusion direction in a die, so that the dope is aligned with the extrusion direction during extrusion. Although it has been proposed that the die be oriented in two axes perpendicular to that direction, the structure of the die is complicated and there are difficulties in industrial implementation. Furthermore, J.Appl.Polym.Sci.vol.27, No.8, P.2965
~2935 (1982), it was proposed to obtain a biaxially oriented film by extruding an optically anisotropic dope of PPTA from a ring die onto an oil-coated conical mandrel. teeth,
Although the mechanical strength is isotropic, it is low, and when drafted, the mechanical strength is high in the MD direction, but
The disadvantage is that it is extremely low in the TD direction. Japanese Patent Publication No. 57-17836 discloses that an optically anisotropic dope of a linearly coordinated aromatic polyamide is coated immediately before solidification,
It is described that a transparent film having isotropic mechanical properties can be obtained by heating until it becomes optically isotropic and then solidifying it. This method is an original method that goes against the conventional concept of achieving high performance by utilizing optically anisotropic doping.
At the same time as relaxing the axial orientation, the liquid crystal domain structure of the optically anisotropic dope remained even after the dope was extruded, and succeeded in preventing it from solidifying into an opaque film. However, nothing is disclosed about a film that is easy to slip, which is necessary for improving the handling properties during production and use. (Problems to be Solved by the Invention) An object of the present invention is to provide a high-performance film that is easily slippery, and a method for producing the same, using PPTA, whose industrial production has already begun. It is something. (Means for Solving the Problems) The present inventors have made the following findings as a result of extensive research to obtain a PPTA film that meets the above objectives. That is, by the technique disclosed in Japanese Patent Publication No. 57-17886 (a method of first making an optically anisotropic dope of PPTA, making it optically isotropic and solidifying it,
To obtain a transparent PPTA film with excellent mechanical performance), it is easier to produce a film from the PPTA dope by adding inorganic fine particles that do not dissolve in the sulfuric acid dope and do not react with the sulfuric acid. Discovering that it can be made into a sex film,
After further research, the present invention was completed. That is, the first aspect of the present invention is a film made of poly(p-phenylene terephthalamide) having a logarithmic viscosity of 3.5 or more, and having a tensile elongation of 8 in all directions.
% or more, and contains inorganic particles of 2 μm or less that are poorly soluble in sulfuric acid and non-reactive with sulfuric acid. - phenylene terephthalamide), 95% by weight or more of sulfuric acid, and inorganic particles of 2 μm or less that are poorly soluble in sulfuric acid and non-reactive with sulfuric acid, while maintaining optical anisotropy. After casting the dope onto a supporting surface and converting the dope to optically isotropic by moisture absorption and/or heating,
This method of producing a polyamide film is characterized by coagulating it in an aqueous solution of 30% by weight or more of sulfuric acid maintained at 10°C or lower, then washing, and further drying while limiting shrinkage of the film. The PPTA used in the present invention is essentially It is a polymer represented by the formula, and is conveniently produced from conventionally known paraphenylene diamine and terephthaloyl chloride by a low-temperature solution polymerization method. If the degree of polymerization of the polymer of the present invention is too low, it will not be possible to obtain a film with good mechanical properties.
(value measured at 30°C by dissolving 0.5 g of polymer in 100 ml of sulfuric acid). The film of the present invention can achieve its purpose only if it satisfies the following two requirements. First of all, the film of the present invention must have a tensile elongation of 8% or more in all directions. This is because a film having an elongation smaller than 8% is easily torn and is not practical. The tensile elongation is preferably 10% or more. On the other hand, the PPTA film made by the method described in Japanese Patent Publication No. 55-14170 is
In addition to having high elongation in the MD direction of 4 to 6%, TD
The elongation in the direction is less than 1% and it is extremely easy to tear. The high elongation of the film of the present invention is related to the process of casting an optically anisotropic dope onto a supporting surface and then making it optically isotropic. Second, the film of the present invention contains inorganic particles with a size of 2 μm or less that are poorly soluble in sulfuric acid and non-reactive with sulfuric acid. Particle size is preferably 1μ
m or less, more preferably 0.5 μm or less. By containing inorganic particles, slipperiness can be imparted to the film, but the size of the particles
If it exceeds 2 μm, the smoothness will be impaired, making it unsuitable for use as a magnetic tape, for example. Specifically, the inorganic particles used in the present invention include:
Examples include, but are not limited to, calcium sulfate, magnesium sulfate, sodium sulfate, graphite, tantalum oxide, and silicon dioxide. The requirement to be non-reactive with sulfuric acid and poorly soluble in sulfuric acid is based solely on the fact that PPTA does not melt and can practically only be molded from sulfuric acid dope. Note that the term "slightly soluble" should be understood as a broad concept that also includes insolubility. The amount of inorganic particles contained in the film of the present invention is PPTA
It is preferably in the range of 0.01 to 5% by weight, more preferably in the range of 0.1 to 1% by weight. The content is determined by the performance of the film (slidability, mechanical performance, etc.)
It should be determined from both the film manufacturing operability (dope viscosity, ejectability, etc.). The film of the present invention preferably also has the following properties. For example, the film of the present invention has a Young's modulus in at least one direction of 1000 Kg/mm ² or more. This condition is closely related to the deformation resistance of the film. For example, in relation to jitter characteristics when used as a magnetic tape, the Young's modulus in at least one direction is preferably 1300 Kg/mm ² or more, and most preferably 1500 Kg/mm ² or more.
The film of the present invention has two types; one is a balanced type in which the vertical and horizontal Young's moduli are approximately equal to 1000 Kg/mm ² or more, and the other is a balanced type in which either the vertical or horizontal Young's modulus is approximately equal. Its Young's modulus is large 1000
It is a tensilized type with a weight of Kg/mm ² or more. The film of the present invention is preferably a thin film of about 12 μm or less. Particularly preferably, the thickness is 10 μm or less. For example, when used as a videotape, the bulkiness per length increases in proportion to the thickness, so it meets the needs of being small, lightweight, and long in recording time. The film of the present invention is also preferably substantially void-free. Furthermore, the film of the present invention usually has a density of
It is in the range of 1370-1420g/ ^cm3 . This density value was measured at 30°C by density gradient tube method using carbon tetrachloride-toluene. This density range is from 1.43 g/cm ³ to that of known PPTA fibers.
This value is considerably smaller than the range of 1.46 g/cm ³ . If the density is less than 1.370 g/cm ³ , the mechanical properties will deteriorate, and if it exceeds 1.420 g/cm ³ , the film will have poor planar orientation and therefore isotropy in mechanical properties. In any case, this low density results in a light and high-strength film. The film of the present invention preferably has a plane orientation defined by the crystal orientation angle determined by X-ray diffraction as described below. In other words, the crystal orientation angle with respect to the 2θ≒23° peak due to X-rays incident at right angles to the film surface is 30° or more, and the crystal orientation angle with respect to the 2θ≒18° peak due to X-rays incident parallel to the film surface is 30° or more. Preferably, the angle is 60° or less. The incidence of X-rays can be divided into two cases: one is incident perpendicularly to the film surface (hereinafter referred to as the TV direction) and the other is incident parallel to the surface (hereinafter referred to as the SV direction). The film of the present invention is exposed to X-rays from the TV direction.
It has a large diffraction peak at 2θ≒23°, but this 2θ≒
The crystal orientation angle at 23° is preferably 30° or more, and more preferably 50° or more. Further, when incident from the SV direction, a large diffraction peak of 2θ≈18° appears on the equator line, but it is preferable that the crystal orientation angle at 2θ≈1R is 60° or less.
When both of these crystal orientation angles are satisfied, it can be said that the film of the present invention has a so-called plane-oriented structure, and has high mechanical properties both in the direction in which the film is taken and in the direction perpendicular thereto. It is highly preferred because it has high tear strength. A known method can be used to measure the crystal orientation angle, and for example, the following method may be used. Place the counter at the specified 2θ angle and insert the film.
Obtain the diffraction intensity curve by rotating 130°.
In addition, for TVs, the rotation is performed between 90 degrees in front and back, centering on the highest intensity. The highest intensity of this curve,
Measure the arc length in degrees in the diffraction photograph corresponding to the point showing half the intensity with respect to the baseline drawn between the lowest intensity points (i.e., the angle with respect to the 50% point with respect to the highest intensity baseline). , which is taken as the crystal orientation angle of the sample. During measurement, the diffraction intensity can be measured by stacking several films if necessary. Next, a method for obtaining such a PPTA film will be explained. In the method of the present invention, it is first necessary to prepare an optically anisotropic dope of PPTA. A suitable solvent for preparing the dope used for forming the PPTA film of the present invention is sulfuric acid at a concentration of 95% by weight or more. If the sulfuric acid content is less than 95%, it will be difficult to dissolve the dope, and the dope will have an abnormally high viscosity after being dissolved. The dope of the present invention may contain a small amount of chlorosulfuric acid, fluorosulfuric acid, phosphorus pentoxide, trihalogenated acetic acid, and the like. Sulfuric acid can be used in a concentration of 100% by weight or more, but from the viewpoint of stability and solubility of the polymer, a concentration of 98 to 100% by weight is preferably used. The concentration of the polymer in the dope used in the present invention is preferably at least a concentration that exhibits optical anisotropy at room temperature (approximately 20°C to 30°C) or higher, and specifically, approximately 10% by weight. It is preferably used in an amount of about 12% by weight or more. At a polymer concentration below this range, that is, at a polymer concentration that does not exhibit optical anisotropy at room temperature or higher temperatures, the formed PPTA film often does not have desirable mechanical properties. The upper limit of the polymer concentration of the dope is not particularly limited, but is usually 20% by weight or less, particularly preferably 13% by weight or less for PPTA with a high ηinh, and more preferably 16% by weight or less. In the dope of the present invention, it is necessary to add inorganic particles of 2 μm or less that are poorly soluble in sulfuric acid and non-reactive with sulfuric acid. Inorganic particles can be added to sulfuric acid before adding PPTA, added at the same time as PPTA, added after forming an optically anisotropic dope, or added inorganic particles after some PPTA is added and dissolved. This can be carried out by any method such as adding the remaining PPTA. In order to prevent agglomeration of inorganic particles and improve dispersibility, it is also a preferred embodiment to use, for example, a homogenizer or static mixer. Also,
In the case of a method in which inorganic particles are added after making an optically anisotropic dope, it is necessary to remove as much insoluble dust, foreign matter, etc. as possible by sieving prior to addition, and to remove particles generated or rolled up during dissolution. It is preferable to remove gases such as air that may be present. Deaeration is
This can be carried out once the dope has been prepared, or it can be carried out under vacuum (reduced pressure) from the stage of charging the raw materials for preparation.
Preparation of the dope can be carried out continuously or batchwise. In the present invention, the amount of inorganic particles added to the dope is preferably about 0.001 to 3% by weight (based on the total amount of dope). Other conventional additives may be incorporated into the dope of the present invention, such as fillers, anti-glare agents, UV stabilizers, heat stabilizers, antioxidants, pigments, solubility aids, etc. Whether the dope is optically anisotropic or optically isotropic is
It can be investigated by known methods, such as the method described in Japanese Patent Publication No. 50-8474, but the critical point depends on the type of solvent, temperature, polymer concentration, degree of polymerization of the polymer, content of non-solvent, etc. By examining these relationships in advance, it is possible to change from optical anisotropy to optical isotropy by creating an optically anisotropic dope and changing the conditions to produce an optically isotropic dope. The dope prepared in this way can be transferred from a die, for example, a slit die, while maintaining its optical anisotropy.
Cast onto a supporting surface. In addition, in the laboratory, it can be cast onto a glass plate using a doctor knife. In the present invention, even if steps such as casting and subsequent conversion to optical isotropy, coagulation, washing, stretching, and drying are performed continuously, all or part of these steps may be performed intermittently.
In other words, you may go for the batch method. Preferably, the casting process is carried out continuously, and moreover, the moving speed of the support surface on which the dope is cast is at least twice the linear speed at which the dope is discharged from the die. The support surface used in the present invention is in the form of a belt or drum, or is used as a plate. The material is not particularly limited as long as it is acid resistant and has a surface finish. For example, glass, hastelloy, tantalum, gold, platinum, plated metal such as titanium nitride, etc. are preferably used, and particularly preferred. These materials have a so-called mirror finish. The method for obtaining the film of the present invention is to cast the dope onto a support surface and then convert the dope from optically anisotropic to optically isotropic prior to solidification. To change optical anisotropy to optical isotropy, specifically, before solidifying an optically anisotropic dope cast on a support surface, the concentration of the solvent forming the dope is lowered by absorbing moisture. Transform the dope into an optically isotropic region by changing the solubility and polymer concentration, or increase the temperature of the dope by heating to transform the dope phase to optically isotropic, or absorb moisture and heat simultaneously or sequentially. This can be achieved by using them together. In particular, methods that utilize moisture absorption, including methods that use heating in combination, are useful because optical anisotropy can be made optically isotropic efficiently and without causing decomposition of PPTA. To make the dope absorb moisture, air at normal temperature and humidity may be used, but humidified or heated and humidified air is preferably used. The humidified air may contain mist-like moisture exceeding the saturated vapor pressure, or may be so-called water vapor. However, supersaturated steam at a temperature of about 45° C. or lower is not preferable because it often contains large particles of condensed water. Moisture absorption is usually from room temperature to about 130
It is carried out using humidified air at a temperature of 50 to 150°C. In the case of a heating method, the heating means is not particularly limited, and examples include a method of applying humidified air to the casting dope as described above, a method of irradiating with an infrared lamp, and a method of dielectric heating. The optically isotropic cast dope on the support surface is then solidified. In the present invention, an aqueous sulfuric acid solution of 30% by weight or more can be used as the dope coagulation liquid. If the sulfuric acid aqueous solution is less than 30%, it becomes difficult to obtain a film with excellent surface precision, probably because the coagulation rate of the dope including water is too high.
The coagulation bath is preferably a 40-70% by weight aqueous sulfuric acid solution. In the present invention, the temperature of the coagulating liquid needs to be 10°C or less. This is because it has been found that the lower the temperature, the lower the solidification rate and the tendency for fewer voids to be included in the film, thus improving the surface precision of the film.
The coagulation bath temperature is preferably 5°C or lower, more preferably 0°C to 40°C. Since the solidified film as it is contains acid, it is necessary to wash and remove the acid content as much as possible in order to produce a film whose mechanical properties are less likely to deteriorate due to heating. Specifically, it is desirable to remove the acid content to about 500 ppm or less. Water is usually used as the cleaning liquid, but if necessary, warm water may be used, or washing may be performed after neutralization with an alkaline aqueous solution and then with water. Cleaning is performed, for example, by running the film in a cleaning liquid or by spraying the cleaning liquid. The washed film may then be stretched in the wet state if desired before being subjected to drying. Stretching is performed in one direction or two directions at a stretching ratio of 1.05 times or more. At this time, it is often seen that the moisture contained within the film comes out like sweat. In the case of stretching in one direction, it may be either in the MD direction or in a direction perpendicular to the MD direction, and the stretching is preferably performed by about 1.1 to 1.7 times. The stretching in two directions may be simultaneous biaxial stretching or sequential uniaxial stretching. In the case of bidirectional stretching, it is preferably carried out at a stretching ratio of about 1.07 to 1.5 times. Stretching allows the PPTA molecular chains to be oriented in the stretching direction, resulting in improved mechanical properties. Drying must be carried out under tension, at a constant length, or with slight stretching to limit shrinkage of the film.
If a film that tends to shrink with the removal of a cleaning solution (e.g., water) is dried without any restriction on shrinkage, micro-heterogeneity may occur due to structure formation (crystallization, etc.). The light transmittance of the resulting film will be reduced. Furthermore, the flatness of the film may be impaired or the film may curl. To dry while limiting shrinkage, for example, a tenter dryer or drying by sandwiching between metal frames can be used. Other conditions related to drying are not particularly limited, and may include methods using heated gas (air, nitrogen, argon, etc.) or room temperature gas, methods using radiant heat such as electric heaters or infrared lamps, dielectric heating methods, etc. It can be freely selected, and the drying temperature is not particularly limited as long as it is room temperature or higher. However, in order to increase the mechanical strength, a high temperature is preferable, and a temperature of 100°C or higher, more preferably 200°C or higher is used. The maximum temperature for drying is not particularly limited, but in consideration of drying energy and decomposability of the polymer, it is preferably 500° C. or lower. (Example) Below are examples and reference examples (manufacturing example of PPTA)
However, 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. Logarithmic viscosity ηinh is 98%
0.5 g of polymer was dissolved in 100 ml of sulfuric acid and measured at 30°C in a conventional manner. The viscosity of the dope is measured using a B-type viscometer.
Measurements were taken at a rotation speed of 1 rpm. 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 are determined by measuring the film sample using a constant speed extension type strength and elongation measuring machine.
A rectangle of 100 mm x 10 mm was cut out, and a load-extension curve was drawn five times at an initial grip length of 30 mm and a pulling speed of 30 mm/min, and the calculation was made from this. Reference Example (Production of PPTA) PPTA was obtained as follows by a low temperature solution polymerization method. In a polymerization apparatus shown in Japanese Patent Publication No. 53-43986, 70 parts of anhydrous lithium chloride was dissolved in 1000 parts of N-methylpyrrolidone, and then 48.6 parts of paraphenylenediamine were dissolved therein. After cooling to 8° C., 91.4 parts of terephthalic acid dichloride was added all at once in powder form. 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. 53-43936, and immediately transferred to a twin-screw closed kneader. The polymerization reaction product was finely pulverized. Next, the finely pulverized product was transferred to a Hexiel mixer, and approximately the same amount of water was added thereto for further pulverization, followed by washing in hot water several times and drying in hot air at 110°C. 95 parts of pale yellow PPTA polymer with ηinh of 5.8 was obtained. Note that polymers with different ηinh can be easily obtained by changing the ratio of N-methylpyrrolidone and monomers (paraphenylenediamine and terephthalic acid dichloride), and/or the ratio between monomers. Example 1 99.6% calcium sulfate with a particle size of approximately 0.5-1 μm
of sulfuric acid and stirred vigorously. At this time, the ratio of calcium sulfate to sulfuric acid was 0.5% by weight. Next, PPTA with ηinh = 5.8 was dissolved in this dispersion so that the polymer concentration was 12% by weight, and the mixture was heated at 60°C.
A dope with optical anisotropy was obtained. This dope was 9600 poise at approximately 30°C. this dope
Degassed under vacuum at 55-65°C for about 4 hours. This dope was cast onto a glass plate with a carefully finished surface while maintaining the temperature at approximately 65°C, and then cast into a film using a doctor knife. The cast optically anisotropic dope is heated together with the glass plate on a hot plate at 120°C, and heated at 32°C to 80°C.
% humidity air and converted into a dispersed optically isotropic dope of calcium sulfate. Next, the glass plate on which the dope was cast was heated to −15°C.
It was immersed in a 35% aqueous solution of sulfuric acid to solidify it. about 10
After immersion for several minutes, the formed film was taken out from the aqueous sulfuric acid solution, left standing in water at about 25° C. for 2 days and nights (however, the water was changed a total of 7 times), and washed. The obtained wet film was stretched 1.2 times in one direction as it was, then placed between stainless steel frames and dried at a fixed length. Drying was carried out by leaving it in the air at approximately 32°C for one day and night. After drying, the film has a thickness of 8.3 μm, a tensile strength in the stretching direction of 27 Kg/mm ² , a tensile elongation of 15%, and a Young's modulus of 1340.
Kg/ ^mm2 , tensile strength in the direction perpendicular to the stretching direction 16Kg/
^mm2 , tensile elongation 32%, Young's modulus 850Kg/ ^mm2 ,
When tensile tests were performed in directions 30°, 45°, and 60° from the drawing direction, the elongations were all between 20 and 30%. In addition, during film preparation, the center line average roughness (Ra) of the side that was not in contact with the glass plate was 0.07, and the Ra of the side that was in contact with the glass plate was 0.20, indicating that it was in contact with the glass plate. When I rubbed the surfaces together, they were extremely smooth. (Ra was measured according to JIS.) Also, the density of the film was 1404g/cm ³ , TV
The crystal orientation angle at 2θ≒23° with respect to the direction is 55°,
At 2θ≒18° in the SV direction, it was 36°. Furthermore, when the film was observed under a microscope, it was found that 1μ
Calcium sulfate of less than m was uniformly dispersed. Examples 2 to 5 A PPTA polymer having an ηinh of 5.5 was dissolved in 99.7% sulfuric acid at a polymer concentration of 11.5% to obtain a dope with optical anisotropy at 60°C. When the viscosity of this dope was measured at room temperature, it was 10,600 poise. This dope was heated to about 70° C., and about 0.1% by weight of silica gel finely ground to about 0.3 μm or less was added to the dope, and thoroughly kneaded with a kneader. This dope about 70
It was degassed under vacuum while being kept at ℃. This case also had optical anisotropy as above, and the viscosity was 4400 poise. A 1.5m curved pipe from the tank passes through a static mixer to a gear pump to the die, which is maintained at approximately 70℃, and cast from the die with a 0.15mm x 300mm slit onto a mirror-polished tantalum belt. The cast dope was made optically isotropic by blowing air at about 90°C with a relative humidity of about 85%, and then introduced together with the belt into a 30% by weight aqueous sulfuric acid solution at -20°C to solidify. The coagulated film was then peeled off from the belt and washed by running it in warm water at about 40°C.
The washed film was stretched in a tenter as it was or without drying, and then dried with hot air at 240° C. in a fixed length using another tenter. The results are shown in Table 1. Both films contain silica gel (SiO ₂ ) as fine particles of 0.3 μm or less.
It was contained in a dispersed form of 0.4 to 0.5% by weight. In addition, the mass count of the surface that was in contact with the belt is sometimes small,
It was slippery.

[Table] *The belt surface refers to the surface that was in contact with the tantalum belt, and the non-belt surface refers to the opposite surface.
(Effects of the Invention) As shown in the examples, the film of the present invention has good mechanical properties, such as high strength and high Young's modulus, which are not found in commercially available films, and also has good surface precision. It has both a very good surface and a slippery surface. In addition to these properties, it also has excellent electrical insulation, heat resistance, oil resistance, pressure resistance, resistance to chemicals other than strong acids, and precision in manufacturing. Therefore, the film of the present invention can be suitably used for insulating materials and magnetic tapes for electrical equipment that rotates at high speed, flexible printed wiring systems, thermal transfer printers, wire coating materials, membranes, etc. Due to its outstanding transparency,
It is also useful for packaging materials, plate-making materials, photographic films, etc. In particular, the film of the present invention has a high Young's modulus, strong tear resistance, high surface precision, and easy sliding properties, so it can be used in video tapes, computer tapes, etc.
It is useful as a magnetic tape for audio tapes, floppy disks, various cards (telephones, train tickets, commuter passes, etc.), and is especially useful as a high-quality video tape with excellent image clarity and stability.

Claims (1)

[Claims] 1. A film made of poly(p-phenylene terephthalamide) having a logarithmic viscosity of 3.5 or more,
A slippery polyamide film having a tensile elongation of 8% or more in all directions and containing inorganic particles of 2 μm or less that are poorly soluble in sulfuric acid and non-reactive with sulfuric acid. 2 Optically anisotropic dope consisting essentially of poly(p-phenylene terephthalamide) with a logarithmic viscosity of 3.5 or more, 95% by weight or more of sulfuric acid, and inorganic particles of 2 μm or less that are poorly soluble in sulfuric acid and non-reactive with sulfuric acid. The dope is cast onto a support surface while maintaining its optical anisotropy, and the dope is converted to optical isotropy by moisture absorption and/or heating. 1. A method for producing a polyamide film, which comprises coagulating the film, washing it, and drying it while limiting shrinkage of the film.