JPH0376809B2 - - Google Patents

Description

[Detailed description of the invention]

"Field of Industrial Application" The present invention relates to an improved polyparaphenylene terephthalamide (hereinafter abbreviated as PPTA) film, and more specifically, it is transparent and exhibits excellent mechanical properties, particularly in the uniaxial direction. The present invention relates to a PPTA-based film that has excellent mechanical properties, and has sufficient mechanical properties for practical use even in a direction perpendicular to said direction. ``Prior art'' Linearly coordinated aromatic polyamides, such as PPTA, have attracted attention in recent years because of their excellent crystallinity, high melting point, and rigid molecular structure, resulting in heat resistance and high mechanical strength. It is a polymer material that has been However, a disadvantage of PPTA is that useful high molecular weight polymers are poorly soluble in organic solvents, and strong inorganic acids such as concentrated sulfuric acid must be used as the solvent. Publication No. 56-45421 discloses that by copolymerizing a unit in which a halogen group is introduced into the aromatic nucleus of a linearly coordinating aromatic polyamide and an aromatic polyamide other than PPTA that does not have a substituent in the aromatic nucleus, it can be used in organic solvents. There is also a proposal to make it soluble and make a film from it. However, this method has the disadvantage that the monomer is expensive, which increases the cost, and it also impairs the heat resistance and crystallinity of the linearly coordinated aromatic polyamide.
On the other hand, it has long been known both theoretically and experimentally that when a rigid polymer is dissolved in a solvent, it forms crystals at a certain degree of polymerization, at a certain concentration, and at a certain temperature. P. J. Flory:
Proc.Roy.Soc., A234, 73, (1956)]. In recent years, the performance requirements for films that require uniaxial mechanical properties, such as base films for magnetic tapes, have become higher and higher. If a film can be obtained by extruding the molecular solution through a slit without disturbing the crystal orientation, it is easily expected that the film will have high strength and high modulus. In fact, Special Publication No. 59-14567,
A method of extruding an aromatic polyamide solution having optical anisotropy from a slit through a short air layer into a coagulation bath has been disclosed, and high physical properties have been obtained. The mechanical strength is strong only in the film width direction (hereinafter abbreviated as TD direction), but the mechanical strength in the film width direction (hereinafter abbreviated as TD direction), which is perpendicular to this direction, is extremely weak, and not only can the film be easily torn and also easily fibrillated, but , because the polymer has a domain structure assembled as a liquid crystal,
The assembled domain structure remains and the resulting film is generally opaque. Therefore, various methods of producing films that do not have the above-mentioned drawbacks have been investigated. For example, special public service in 1977-
Publication No. 35088 discloses that a linearly coordinated aromatic polyamide solution having optical anisotropy is extruded from a ring die, simultaneously cast in a doped state in two axes using an inflation method, and then wet-cast. It is said that by solidifying it, a film with good isotropy can be obtained. However, the resulting film had the drawback of poor mechanical properties. Furthermore, Japanese Patent Publication No. 57-17886 discloses that a linearly coordinated aromatic polyamide solution having optical anisotropy is heated to a temperature at which the dope becomes optically isotropic immediately before solidification, and then solidified. As a result, a film is obtained that is transparent and has isotropic mechanical properties. Although this method is an excellent method based on a new concept, it still lacks mechanical properties, especially the modulus required for base films for magnetic tapes. In order to obtain mechanical properties in a uniaxial direction, hot stretching in that direction is usually carried out, but in general, linearly coordinated aromatic polyamides have poor thermoplasticity, and especially linearly coordinated polyamides. It is easy to crystallize, the glass transition temperature is unclear, and it is almost impossible to further heat stretch the film after forming it, and it is extremely difficult to improve the physical properties of the film by hot stretching. It is also difficult to hot stretch the film obtained by the method described above (method disclosed in Japanese Patent Publication No. 57-17886). ``Problem to be solved'' As described above, when a film is formed from linearly coordinated aromatic polyamide by optically anisotropic doping, the mechanical strength is strong only in the MD direction, and the mechanical strength in the TD direction is The only result is an extremely weak and easily torn film, or an opaque film in which a domain structure of liquid crystals remains. If an attempt is made to use an optically isotropic dope to avoid this, useful high molecular weight PPTA polymers have extremely high viscosity, and film formation becomes impossible unless the polymer concentration is approximately 5% by weight or less. Films made from isotropic dopes tend to produce voids during solidification, and their mechanical properties are also completely inadequate. PPTA or fibers already produced industrially
A film with excellent transparency and mechanical properties in the uniaxial direction, particularly high modulus, has not been realized using a PPTA-based polymer. An object of the present invention is to provide a PPTA film having such favorable characteristics. "Means for Solving the Problems" While continuing to study how to increase the modulus of a film obtained using the technique disclosed in Japanese Patent Publication No. 57-17886, the inventors of the present invention discovered that a wet-formed film was
A special step in the manufacturing process allows for more stretching than expected, and by drying it after stretching, it does not fibrillate, is resistant to tearing even in the direction perpendicular to the stretching direction, and has mechanical properties in the stretching direction. discovered that it was possible to obtain a film with particularly high modulus, and by this method it was possible to achieve a high degree of crystal orientation, and also to create a structure in which the dense stripes that are characteristic of conventional liquid crystal doping were not observed when observed with a polarizing microscope. It has the unexpected fact that it has high strength and high modulus in one direction, but also has sufficient practical physical properties in the direction perpendicular to it, and does not fibrillate or tear in one direction. Heading The present invention has been arrived at. That is, the present invention provides a film substantially made of PPTA with a logarithmic viscosity ηinh of 3.5 or more, a void count of 5 voids/mm ² or less, a light transmittance of 55% or more, and a film that is perpendicular to the film surface. The crystal orientation angle in the direction in which the diffraction intensity of the (200) plane due to incident X-rays is maximum is 30° or more and less than 70°, and the crystal orientation angle of the (010) plane due to incident X-rays parallel to the film surface is 30° or more and less than 70°. The present invention relates to a PPTA film characterized in that the angle is 60° or less, the elongation at break is 9% or more, and no dense striped pattern is observed when observed under a polarizing microscope. The film of the present invention comprises substantially It consists of the PPTA system represented by . here,
"Substantially" means that polymers other than PPTA [e.g., poly-(m-phenylene terephthalamide), poly-(p-phenylene terephthalamide)], isophthalamide), poly-(m-phenylene isophthalamide), poly-(methylene terephthalamide),
Aliphatic polyamide, aliphatic polyamide, polyester, polyimide, polyurethane, polyurea, etc.]
may be blended or blended with PPTA with other repeating units (e.g., nuclear substituted p-phenylene units, nuclear substituted or unsubstituted biphenylene units, o
-phenylene unit, m-phenylene unit, (poly)
This means that methylene units, pyridylene units, bonding units such as esters, urethanes, ureas, ethers, thioethers, etc.) may be copolymerized. 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, which is the objective of the present invention.
(The value measured at 30°C by dissolving 0.2 g of polymer in 100 ml of sulfuric acid) is selected. The film of the present invention can achieve its purpose only if it satisfies the following six requirements. First of all, the number of voids described below is 5/mm ²
Must be below. The number of voids is counted as follows. A piece of film of an appropriate size is magnified from 100x using an ordinary optical microscope using transmitted light.
Observe at least 5 different fields of view at a magnification of 400x, count the number of voids with a major axis of 30 μ or more, and calculate the number of voids per 1 mm ² of the film surface. Film with a number of voids of 5/mm2 or ^more ,)
Mechanical properties are poor, and in severe cases, the film appears cloudy and transparency is reduced. In films made from ordinary optically isotropic dopes, voids of 50/mm ² or more are usually observed. Second, the light transmittance must be 55% or more. Light transmittance is measured as follows. A film is pasted on the liquid cell of an ordinary photoelectric photometer or spectrophotometer, a visible light beam with a wavelength of 600 nm is selected, and its transmittance is measured. One important feature of the film according to the present invention is its transparency, and as mentioned above, the film obtained by extruding an optically anisotropic dope directly into a coagulation bath through a slight air gap is devitrified. ,
Normally, the light transmittance is 10% or less. (However, this does not apply to particularly thin films.) Of course, this light transmittance decreases as the thickness of the film increases, but the film according to the present invention has a sufficient transmittance of 55% up to a thickness of about 200μ, which is commonly used. It has superior transparency. Thirdly, it must have plane orientation defined by the crystal orientation angle determined by X-ray diffraction, which will be described below. In other words, the crystal orientation angle in the direction in which the diffraction intensity of the (200) plane is maximized by X-rays incident at right angles to the film surface is 30° or more and less than 70°, and the (010) direction is caused by X-rays incident parallel to the film surface. The crystal orientation angle of the plane must be 60° or less. As shown in Figure 2, the X-rays are incident at right angles to the film surface (hereinafter referred to as the TV direction).
and when the beam is incident parallel to the surface (hereinafter referred to as the SV direction). The crystal structure of PPTA has been widely discussed, for example, by Takayanagi et al. [J, Appl. Polym. Scl., No. 23]
Volume, 915 pages (1979)]. The film 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. must be greater than or equal to 30° 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, but the crystal orientation angle at 2θ≈18° needs to be 60° or less. Only when both of these crystal orientation angles are satisfied, the film of the present invention has a planar orientation structure and also has excellent mechanical properties in the uniaxial direction.On the other hand, a film with a crystal orientation angle outside of this range has A film that is fibrillated torn in the uniaxial direction or has low mechanical properties in the uniaxial direction cannot be obtained, and thus a film having the desired high mechanical properties cannot be obtained. A known method can be used to measure the crystal orientation angle, for example, as follows. A diffraction intensity curve is obtained by placing the counter at a predetermined 2θ angle and rotating the film 180°. For TVs, rotation should be made between 90 degrees forward and backward, centered on the highest intensity. 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, 50 degrees with respect to the highest intensity baseline.
Measure the angle with respect to the % point and use it as the crystal orientation angle of the sample. If necessary, the diffraction intensity can be measured by stacking several films. Fourthly, it is important that dense striped patterns are not observed when observed with a polarizing microscope. At this point, I should mention the structure of PPTA film. When the optically anisotropic dope described above is simply extruded through a slit and formed into a film, when the film is observed under a polarizing microscope under crossed Nicols (approximately 100 to 1000 times), a dense striped pattern as shown in Figure 1 is observed. Can be seen. This striped pattern is PPTA
fibers, using known methods (for example, Japanese Patent Publication No. 55-14170)
This can also be seen when observing Kepler, which is already on the market and produced using the method described in the publication, using the same polarizing microscope. This is based on Dobb et al. [J.Polym.Sci.Polym.Phys.,
It is presumed that this is related to the so-called pleated sheet structure proposed by Vol. 15, p. 2201 (1977). This striped pattern is considered to be related to the pleated sheet-like aggregate structure, as described above. Striped patterns can also be seen with a normal optical microscope, but when observed under a polarizing microscope at crossed Nicols or close to crossed Nicols, they become more clearly visible as stripes with various colors. It is observed as shown in Figure 1. The magnification in a polarized light microscope is
100 to 1000 times is sufficient. 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 film thickness of 0.1 as shown in Figure 1.
It had a striped pattern with an interval of ~0.4 um or less, was torn in a direction perpendicular to the striped pattern, and was easily fibrillated. Although the film of the present invention is highly uniaxially oriented, it does not have the striped pattern seen in the highly oriented PPTA film described above, so it has high strength and modulus, and does not tear in one direction. It has the excellent property of not being easily fibrillated. This is further guaranteed by the fifth requirement of the film of the present invention, which is that it has a breaking elongation of 9% or more and a strength of 51 kg/mm ² or more in one direction. be done. Also, as the sixth requirement, the density of the film of the present invention is 1.383
g/ ^cm3 . Next, a method for obtaining such a PPTA film will be described. A suitable solvent for preparing the dope used for molding the PPTA film of the present invention is 98% by weight.
sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, or a mixture thereof at a concentration above. 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. In addition, the polymer concentration in the dope is preferably a concentration that exhibits optical anisotropy at room temperature (approximately 20°C to 30°C) or higher.
Specifically, it is used in an amount of about 10% by weight or more, preferably about 12% by weight or more. Although the upper limit of the polymer concentration of the dope is not particularly limited, it is usually 25% by weight or less, and preferably 20% by weight or less for PPTA with particularly high ηinh. The dope may also contain conventional additives, such as fillers, deglossing agents, UV stabilizers, heat stabilizers, antioxidants, pigments, solubilizing agents, and the like. Whether the dope is optically anisotropic or optically isotropic is
This can be investigated using 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 investigating in advance, an optically anisotropic dope is created, and by changing the conditions for an optically isotropic dope, it is possible to change from optically anisotropic to optically isotropic. The method of obtaining a transparent film with excellent mechanical properties according to the present invention is characterized by forming a dope into a film on a support surface and then changing the dope from optically anisotropic to optically isotropic prior to solidification. However, the method of converting optical anisotropy to optical isotropy is, specifically, by forming an optically anisotropic dope in the form of a film on a support surface,
Prior to coagulation, the concentration of the solvent that forms the dope by absorbing moisture is lowered, and the dope is transformed into an optically isotropic region by changing the dissolving ability of the solvent and the polymer concentration, or the dope is transformed into an optically anisotropic region by absorbing moisture. This can be achieved by simultaneously or sequentially increasing the temperature of the dope by heating in addition to the change in temperature, and transforming the phase of the dope into optical isotropy. Absolute humidity 1 is the method for making dope absorb moisture.
g (water)/Kg (dry air) or more, preferably 3 g
(water)/Kg (dry air) or more, more preferably
This can be achieved by passing through an atmosphere of 10 g (water)/Kg (dry air) or more, particularly preferably 20 g (water)/Kg (dry air) or more, and a relative humidity of 99% or less. In addition, in a method that uses heating simultaneously with moisture absorption or after moisture absorption, for example, when sulfuric acid is used as a solvent, optical anisotropy substantially disappears,
The temperature at which the dope becomes optically isotropic varies depending on the polymer concentration, polymerization degree of the polymer, sulfuric acid concentration, dope thickness, and degree of moisture absorption, but is usually about
A temperature of 45°C or higher is preferably used. In this way, the optically anisotropic dope of the PPTA system is converted to optically isotropic, especially by using a combination of moisture absorption and heating.
The method of converting to optical isotropy is preferably used because the resulting film has better transparency, and is a means for easily obtaining the PPTA film of the present invention. For example, water, approx.
Examples include dilute sulfuric acid of 7.0% by weight or less, caustic soda aqueous solution and aqueous ammonia of about 20% by weight or less, sodium chloride aqueous solution and calcium chloride aqueous solution of about 50% by weight or less. The temperature of the coagulation bath is not particularly limited and is usually in the range of about 0°C to 80°C. Since the coagulated film as it is contains acid, it is necessary to wash and remove the acid as much as possible in order to produce a film with less deterioration of mechanical properties due to heating. Preferably it should be done to 500 ppm or less. Water is usually used as the cleaning liquid, but if necessary, hot water may be used, or washing may be carried out after neutralization with an alkaline aqueous solution, followed by washing with water or the like. Also,
The cleaning method may be to run the film in a cleaning liquid or to spray the cleaning liquid. In order to obtain a film with excellent mechanical properties according to the present invention, in addition to the above-described film forming method, it can be achieved by the following stretching process. That is, this is a so-called wet stretching method in which the coagulated film is uniaxially stretched in a swollen state substantially free of solvent and containing moisture after the solvent is removed by washing with water and before drying. 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, but in order to effectively carry out the present invention, the moisture content of the film should be 50 parts by weight or more per 100 parts by weight of the polymer. is preferably used, and stretching is carried out in the above-mentioned water-containing state by 1.05 times or more by a commonly used method, for example, by a roll peripheral speed difference or by using a tenter. The maximum stretching ratio here is approximately 2.5 times,
If it is stretched further than this, the crystal orientation angle in the direction of cutting or stretching becomes too small, the mechanical strength in the direction perpendicular to the direction of stretching is weak, and it not only becomes easy to tear, but also fibrillation occurs. 2.5 times or less is preferably used. Furthermore, if the stretching ratio is 1.05 times or less, the crystal orientation angle deviates from the crystal orientation angle of the present invention, and therefore the high strength and high modulus characteristic of the PPTA film of the present invention cannot be achieved. The stretched film is dried by any method, such as air drying at room temperature, drying in a heated inert gas atmosphere such as air, nitrogen, argon, etc., drying on a heated roll, or drying in a tenter. Any method such as drying under a heated atmosphere may be used. In addition, during drying, the film is usually shrunk under tension or under a certain length in order to maintain the stretching effect, to prevent the film from wrinkling, and to maintain the film's flatness. It is done in a limited manner.
The drying temperature is preferably room temperature or higher, and in order to effectively improve mechanical strength, a high temperature is preferred, and 100°C or higher, more preferably 200°C or higher.
The maximum temperature for drying is not particularly limited, but a temperature of 500° C. or lower is used in consideration of drying energy and decomposability of the polymer. In producing the film of the present invention, all of the above steps may be carried out batchwise or continuously, and it is also a preferred embodiment to produce the film while running it continuously throughout the entire process. It is one of the. Further, an oil agent, an identification dye, or the like may be applied to the film at an arbitrary step. Examples are shown below, but these examples are intended to illustrate the present invention and are not intended to limit the invention. In the examples, parts by weight or weight % are shown unless otherwise specified. Logarithmic viscosity ηinh is
0.2 g of polymer was dissolved in 100 ml of 98% sulfuric acid and measured at 30°C in a conventional manner. The viscosity of the dope was measured using a B-type viscometer 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. To measure the strength and elongation, cut the film sample into a rectangle of 100 mm x 10 mm using a constant speed extension type strength and elongation measuring machine, and draw a load-extension curve for 5 sheets at an initial grip length of 30 mm and a tensile speed of 30 mm/min. , calculated from this.
Density measurements were performed using a density gradient tube method using carbon tetrachloride-toluene. Reference Example Polyparaphenylene terephthalamide (hereinafter referred to as PPTA) was obtained by a low temperature solution polymerization method as follows. In the polymerization apparatus shown in Japanese Patent Publication No. 53-43986, N
- 70 parts of anhydrous lithium chloride in 1000 parts of methylpyrrolidone
Dissolve 48.6 parts of paraphenylenediamine and then dissolve 48.6 parts of paraphenylenediamine
part was dissolved. After cooling to 8° C., 91.4 parts of terephthalic acid dichloride was added all at once in powder form. After several 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 finely pulverized in the reactor. Next, the finely pulverized product was transferred to a Henschel mixer, and approximately the same amount of water was added thereto for further pulverization, followed by filtration, washing in hot water several times, and drying in hot air at 110°C. 95 parts of pale yellow PPTA polymer with ηinh6.5 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 A PPTA polymer having an ηinh of 5.5 was dissolved in 99.7% sulfuric acid at a polymer concentration of 13.0% to obtain an optically anisotropic dope at 60°C. When the viscosity of this dope was measured at room temperature, it was 14,500 poise. To make it easier to form a film, put this dope in a tank and heat it for about 70 minutes.
It was kept at ℃. At that time, it had the same optical anisotropy as above and a viscosity of 4200 poise. A 1.5m curved pipe from the tank to the die via the gear pump is maintained at approximately 70℃, and cast from the die with a 0.2mm x 300mm slit to a mirror-polished Hastelloy belt maintained at 110℃. After being kept in an atmosphere of 68% relative humidity at ℃ for 40 seconds, it solidified and was continuously formed into a film. When the dope was sampled from the belt immediately before solidification during film formation, it was found to have a fairly high viscosity and optical isotropy. The coagulated film was taken out and washed with water at room temperature overnight, and the moisture content was measured. It was found that it contained 350 parts by weight of water per 100 parts by weight of the polymer. The film, which still contains water, is placed in the 100 mm wide chuck of a constant speed stretching type strength and elongation measuring machine, stretched 1.5 times in the MD direction from a length of 100 mm, and then exposed to hot air at 200°C for constant length drying. Summer. The properties of this film are shown in Table 1. Comparative Example 1 In Example 1, the washed film containing water was not stretched, but was dried for a fixed length in a hot air dryer set at 200°C in the same manner as in Example 1. The properties of this film are shown in Table 1. Comparative Example 2 In Example 1, a coagulation bath filled with 25°C water was placed 5 cm below the die, and the dope was extruded from the die, passed through an air layer, and introduced into the coagulation bath. It was wound continuously at 3x. The coagulated film was taken out and washed with water at room temperature overnight, and the water content was measured, and it was found that it contained 280 parts by weight of water per 100 parts by weight of the polymer. The film still containing water was prepared in the same manner as in Example 1.
I tried to stretch it in the MD direction, but it was not possible because it easily tore in the TD direction. Therefore, the water-washed film was not stretched, but was dried in a fixed length with hot air at 100°C. Even so, it tore in the TD direction, but for some reason I was able to obtain one film, and the properties of this film are shown in Table 1. Comparative Example 3 The dope prepared in Example 1 was applied to a 200 mm square glass plate kept at 110° C. in a box under a nitrogen atmosphere with a -40° C. dew point, using an applicator with a 0.1 mm step. Then, a film was formed. After 40 seconds, the dope on the glass plate still maintained its optical anisotropy, but the dope was taken out of the drying box together with the glass plate and immediately placed in water at 20°C to solidify. The resulting film was opaque and was washed in the same manner as in Example 1 and stretched in the MD direction, but most of the films were broken, and some were stretched by about 1.2 times, but they were torn when they were dried. . Therefore, without stretching the film after washing with water,
Dry for a fixed length with hot air at ℃. The properties of this film are shown in Table 1. Example 2 PPTA having an ηinh of 6.2 was dissolved in 99.6% sulfuric acid at 60°C so that the polymer concentration was 14.0%. This dope exhibits optical anisotropy at 80℃ and has a viscosity of 3300
It was poise. This dope was applied onto a glass plate at 25° C. using an applicator with a step of 0.1 mm. After that, absolute humidity 7.5g (water)/Kg
When the dope was left for one minute in dry air at 18°C and analyzed, it was found that the dope had absorbed moisture to the extent that the sulfuric acid concentration had dropped to 94.4%. However, the dope was still opaque at this point, and when it was then heated to 120° C. for 90 seconds in a dry nitrogen oven, it became optically isotropic and became transparent. After coagulating this with 15°C water, it was neutralized with a 5% caustic soda aqueous solution, and then further washed with water to bring the acid concentration to 400 ppm. When the water content of this washed film was measured, it contained 330 parts by weight of water per 100 parts by weight of the polymer. The film still containing water was stretched 1.4 times in the MD direction in the same manner as in Example 1, and was then exposed to hot air at 250°C for fixed length drying. The properties of this film are shown in Table 1. Comparative Example 4 In Example 2, the washed water-containing film was not stretched, but was exposed to hot air at 250° C. and dried at a fixed length in the same manner as in Example 2. The first characteristic of this film is
Shown in the table.

【table】

[Table] Example 3 A PPTA polymer having an ηinh of 6.5 dl/g was dissolved in 99.7% sulfuric acid at a polymer concentration of 12.0% to obtain a dope with optical anisotropy at 60°C. When the viscosity of this dope was measured at room temperature, it was 16,300 poise. To facilitate film formation, this dope was degassed under vacuum while being maintained at approximately 80°C. This case also had optical anisotropy as above, and the viscosity was 6400 poise. The 1.5m curved pipe from the tank through the filter to the gear pump to the die is maintained at approximately 75℃.
The cast dope is cast from a die with a 0.2 mm x 300 mm slit onto a mirror-polished Hastelloy belt (moving at 2 m/min) and blown with air at about 85°C and a relative humidity of about 90%. Optically isotropic (approximately
12 seconds residence), 10% by weight at 0°C with belt
It was introduced into an aqueous sulfuric acid solution and solidified. 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% water) was moved in the width direction at room temperature using a tenter.
A film obtained by stretching 1.5 times and drying in the same manner as film A is designated as film B. 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 obtained film was designated as Film C. The properties of these films are shown in Table 2. Note that Film A is a comparative example outside the invention, and Films B and C are Examples of the invention.

【table】

[Table] Example 4 A PPTA polymer having an ηinh of 5.7 dl/g was dissolved in 99.3% sulfuric acid at a polymer concentration of 12.3% to obtain a dope with optical anisotropy at 60°C. This dope at about 80℃
It was degassed under vacuum while maintaining the temperature. This case also had optical anisotropy and a viscosity of 5800 poise. The 1.5m curved pipe from the tank through the filter to the gear pump to the die is maintained at approximately 75℃ and is 0.2mm×
The dope is cast from a die with a 300 mm slit onto a mirror-polished tantalum belt (distance between the bottom edge of the die and the belt surface is about 1 cm), and high temperature and high humidity air is blown to cast the dope onto an optical device. The material was solidified and introduced together with the belt into water at 10°C to solidify. The temperature of the air used for optical isotropy of the dope was 70° C. and 98% relative humidity, and the time the cast dope was exposed to this air was 4 seconds. The coagulated film is then peeled off from the belt,
Warm water at about 30℃, 3% caustic soda aqueous solution at room temperature,
Washed sequentially with room temperature water. The washed film (containing about 300% water) is stretched about 1.5 times in the longitudinal direction at room temperature, and then placed in a tenter dryer, where it is first stretched with hot air at 150℃ and then with hot air at 220℃ at a fixed length. Dry. The properties of the obtained film are shown in Table 3.

[Table] "Effects of the Invention" As shown in the examples, the film of the present invention has good mechanical properties as expressed by high strength and high Young's modulus, which are not found in commercially available films, especially in the stretching direction. The mechanical properties in the stretching direction, especially the modulus, were significantly better while maintaining the mechanical properties in the direction perpendicular to the drawing direction. Furthermore, the film of the present invention not only has outstanding mechanical properties such as tensile strength and tensile modulus, but also has a very dense structure, so it is useful as a filtration membrane, packaging material, etc. It has excellent chemical properties 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 as an insulating film for capacitors, and as an electrical insulation material and wire coating material that requires heat resistance, oil resistance, and electrical properties. In addition, in terms of particularly high mechanical strength, the above-mentioned good properties are fully exhibited when used as a magnetic tape by utilizing an insulating material for electrical equipment that rotates at high speed and a particularly high modulus.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the striped pattern observed when a highly oriented PPTA film produced using conventional technology is observed with a polarizing microscope. Figure 2 is a diagram of the incident X-ray pattern when determining the crystal orientation angle of the PPTA film. Show direction.

Claims (1)

[Claims] 1 A film consisting essentially of a polyparaphenylene terephthalamide-based polymer having a logarithmic viscosity ηinh of 3.5 or more, the number of voids as detailed in the specification is 5/mm ² or less, and as detailed in the specification The light transmittance is 55% or more, and the crystal orientation angle in the direction where the diffraction intensity of the (200) plane by X-rays incident at right angles to the film surface is maximum is 30° or more and less than 70°,
(010) due to X-rays incident parallel to the film surface
The crystal orientation angle of the plane is 60° or less, and the elongation at break is 9.
% or more, and has an intensity of 51 Kg/mm ² or more in one direction, a density of 1.383 g/cm ³ , and no dense striped pattern is observed when observed with a polarized light microscope. A new polyparaphenylene terephthalamide film.