JPS62174129A - Poly-para-phenylene terephthalamide-based film - Google Patents

Abstract

PURPOSE:To improve the mechanical properties in the direction of orientation and resistance to chemicals and further enhance the characteristics of the field, in which pressure resistance is requested, especially electrical characteristic by poly-para- phenylene terephthalamide (PPTA), which has specified polymerization degree, number of voids, light transmittance, diffraction strength by X-rays and the like. CONSTITUTION:A film made substantially of poly-para-phenylen terephthalamide (PPTA), the inherent viscosity etainh of which is 2.5 or more, is used. First, the number of voids of said film must be 5 or less square millimeters. Secondly, its light transmittance must be 55% or more. The transparency of the film must fully exceed 55%, provided the film has the conventional thickness or about 200mu and less. Thirdly, the film must have the areal orienting property, which is defined by the crystal orientation angle by means of X-ray diffraction. Concretely, the crystal orientation angle to the direction to which the diffraction strength of a (200) surface by X-rays incident normal to the surface of the film becomes maximum, must be hot less than 30 deg. and less than 70 deg. and the crystal orientation angle of a (010) surface by X-rays incident parallel to the the surface of the film must be 60 deg. or less. Fourthly, in addition, it is indispensable that no dense fringe pattern is observed when the film is seen through a polarization microscope.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention relates to an improved polyparaphenylene terephthalamide (hereinafter abbreviated as PPTA) based film, and more specifically, it is transparent and has excellent mechanical properties. show,
In particular, P that has excellent mechanical properties in the axial direction and also has mechanical properties that are sufficient for practical use in the direction perpendicular to the axial direction.
This relates to PTA-based films.

``Conventional technology I Linearly coordinated aromatic polyamides, represented by PPTA, have particularly excellent crystallinity, a high melting point, and a rigid molecular structure, resulting in heat resistance and high mechanical strength. It is a polymer material that is attracting attention.

However, a disadvantage of PPTA is that polymers with useful molecular weights are poorly soluble in organic solvents, and strong inorganic acids such as concentrated sulfuric acid must be used as solvents.
To avoid this, for example,
: In Publication No. 2/, a hitting machine solvent is produced 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. There is also a proposal to make it soluble in water and make a film out of it. However, this method has the disadvantage that not only does it increase the cost because the hexamer is expensive, but it also impairs the heat resistance and crystallinity of the linearly coordinating aromatic polyamide. on the other hand,
When a rigid polymer is dissolved in a solvent, if the degree of polymerization exceeds a certain degree,
It has been known for a long time both theoretically and experimentally that CP forms a liquid crystal at a certain concentration and above a certain temperature condition.
, J. Flory --: Proc, Roy;
Soc, A 2 3 4 and 73.
(/93r Otsu)].

In recent years, the performance requirements for films that require mechanical properties in the axial direction, such as base films for magnetic tapes, have become increasingly demanding. If a film can be obtained by extruding a polymer solution through a slit without disturbing the arrangement of liquid crystals, it is easily expected that the film will have high strength and high modulus. In fact, Japanese Patent Publication No. Shoj9-/'13-Otsu No. 2 discloses a method of extruding an aromatic polyamide solution having optical anisotropy from a slit into a coagulation bath through a short air space, thereby obtaining high physical properties. However, with this, the mechanical strength is only strong in the longitudinal direction of the film (hereinafter abbreviated as MD direction), and the mechanical strength in the width direction of the film (hereinafter abbreviated as TD direction) perpendicular to this direction is extremely weak. Not only is it easy to tear and only a fibrillated film is obtained, but since the polymer has a domain structure in which the polymer is aggregated as a liquid crystal, the aggregated domain structure remains and the obtained film is generally opaque.

Therefore, various methods for producing films that do not have the above-mentioned drawbacks have been investigated. For example, Japanese Patent Publication No. 57-3-00 Za♂ discloses that a linearly coordinated aromatic polyamide solution with optical anisotropy is extruded from a ring die, and simultaneously in a doped state in the λ axis direction. After casting,
It is said that a film with good isotropy can be obtained by wet coagulation. However, the resulting film had the drawback of poor mechanical properties.

In addition, Japanese Patent Publication No. 37-/7 Zaza No. 6 discloses that immediately before solidification, a linearly coordinated aromatic polyamide solution having optical anisotropy is heated to a temperature at which the dope becomes optically isotropic, 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 with a new concept,
The mechanical properties, especially the modulus required for base films for magnetic tapes, etc., are insufficient.

- In order to obtain mechanical properties in the axial direction, hot stretching in that direction is usually carried out, but linearly coordinated aromatic polyamides generally have poor thermoplasticity, and especially linearly coordinated polyamides. It is easy to crystallize and the glass transition temperature is unclear, so 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 (method disclosed in Japanese Patent Publication No. 37-/7♂f6).

[Problems 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 Those that are extremely weak and tear easily, or those that are r-, can only yield 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 is impossible unless the polymer concentration is about J weight coefficient or less. Films made from isotropic dopes tend to generate voids during solidification, and their mechanical properties are also completely inadequate.

PPTA or PPT whose fibers are already produced industrially
A film with excellent transparency and mechanical properties in the uniaxial direction, particularly high modulus, has not been realized using a k-based polymer.

The object of the present invention is to produce PPT having such favorable properties.
Our goal is to provide A-type films.

"Means for Solving the Problems" While continuing to study how to increase the modulus of a film that can be obtained using the technique disclosed in Japanese Patent Publication No. 37-/7♂♂B, the present inventors discovered that a wet film A special step in the manufacturing process allows for more stretching than expected, and by drying it after stretching, it does not become fibrillated, is resistant to tearing even in the direction perpendicular to the stretching direction, and has mechanical properties in the stretching direction. discovered that a film with a particularly good modulus could be obtained, and by this method could achieve a high degree of crystal orientation, and also create a structure in which dense stripes, which are unique to conventional liquid crystal dopes, are not observed when observed with a polarized light microscope. has,
We discovered the unexpected fact that while it has high strength and high modulus in one direction, it also has sufficient practical physical properties in the direction perpendicular to it, does not form into fibrils, and does not tear in the / direction.We have arrived at the present invention. did.

That is, in the present invention, the logarithmic viscosity ηinh is 2. ．． A film consisting essentially of PPTA with a void count of 3- or more! /rtj or less, the light transmittance is above the SS coefficient, and the X-rays incident at right angles to the film surface (,
The crystal orientation angle in the direction in which the diffraction intensity of the 2θ0) plane is maximum is 30° or more and less than 70°, and the crystal orientation angle of the (0/θ) plane due to X-rays incident parallel to the film surface is less than θ0. This invention relates to a PPTA-based film characterized in that dense striped patterns are not observed when observed under a polarizing microscope.

The film of the present invention consists essentially of a system. Here, "substantially" means:
Polymers other than PPTAfi [e.g. poly-(m
-phenylene terephthalamide), poly-(p-phenylene isophthalamide), poly-(m-phenylene isophthalamide), poly-(methylene terephthalamide)
, aliphatic polyamide, aliphatic polyamide, polyester, polyimide, polyurethane, polyurea, etc.], or PPTA is blended with other repeating units (e.g., nuclear-substituted p-phenylene units, nuclear-substituted or unsubstituted p-phenylene units, etc.). This means that biphenylene units, o-phenylene units, m-phenylene units, (poly)methylene units, pyridylene units, bonding units such as esters, urethanes, ureas, ethers, thioethers, etc.) may be copolymerized. do.

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, so the logarithmic viscosity η1nh (sulfuric acid A polymer with a degree of polymerization that gives a value measured at 30°C by dissolving the polymer 0.2) in - is selected.

The film of the present invention can achieve its purpose only if it satisfies the following requirements.

First of all, the number of voids described below must be less than or equal to j voids/mm2. The number of voids is counted as follows. Suitably sized pieces of film were examined by conventional optical microscopy using transmitted light at magnifications ranging from 100x to yoox at least! Observe the field of view, count the number of voids whose major axis is 3θμ or more, and measure the film surface/
-Convert into a hit. A film having j/- or more voids has poor mechanical properties, and in severe cases, the film appears cloudy and its transparency is reduced. A film made from an ordinary optically unidirectional dope usually has jθ pieces/-
The number of voids above is observed.

Second, the light transmittance must be 33% or more.

Light transmittance is measured as follows. A film is attached to the place where the liquid barrel of an ordinary photoelectric photometer or spectrophotometer is set, visible light with a wavelength of 0 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 earlier, the film obtained by extruding optically anisotropic dope directly into a coagulation bath through a small air gap is devitrified. The light transmittance is usually less than /θ. (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 is sufficient up to a thickness of about θQμ, which is commonly used! It has a transparency of more than j%.

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 (,2θθ) plane is maximized by X-rays incident at right angles to the film surface is 30° or more and less than 70°, and the X-rays are incident parallel to the film surface. The crystal orientation angle of the (θ10) plane determined by X-rays must be less than or equal to θ0.

As shown in FIG. 2, the incidence of X-rays can be divided into two cases: a case where the X-ray is incident at right angles to the film surface (hereinafter referred to as the TV direction) and a case where the X-ray is incident parallel to the surface (hereinafter referred to as the 8V direction).

The crystal structure of P P i' A has been widely discussed, for example, by Takayanagi et al.
8ci, Volume 23, Page 9/j (/ri7wo)]. The film of the present invention has a large diffraction peak at 2Uζ23°, which is the (2θ0) reflection of X-rays from the TV direction, but the crystal orientation angle in the direction in which the large diffraction intensity at 20# and 23° is the maximum is 300 or more, 7
Must be less than 00. Furthermore, a large diffraction peak of 1θ: /fo, which is a reflection of the (010) plane due to incidence from the SV force direction, appears on the equator line, but this:l
The crystal orientation angle at ##/cf" needs to be less than O θ0. Only when both of these crystal orientation angles are satisfied, the film of the present invention has a planar orientation structure, and further /
Films with excellent mechanical properties in the axial direction, but with crystal orientation angles outside this range, may tear or fibrillate in the axial direction, or have poor mechanical properties in the axial direction, making it difficult to achieve the desired Films with high mechanical properties cannot be obtained.

A known method can be used to measure the crystal orientation angle.
For example, do the following: A diffraction intensity curve is obtained by placing a counter at a predetermined 20 angles and rotating the film by /♂θ0. In the case of a TV, it should be rotated between front and rear angles θ0 with the highest intensity as the center. Between the highest and lowest intensity points of this curve (the value expressed in degrees of the arc length in the diffraction photograph, which corresponds to the point showing half the intensity with respect to the baseline minus 1, that is, the point of the jθ coefficient with respect to the baseline with the highest intensity) Measure the angle with respect to the diffraction angle and use it as the crystal orientation angle of the sample.If necessary, remove several films and measure the diffraction intensity.

Thirdly, it is important that dense striped patterns are not observed when observed with a polarizing microscope.

At this point, the structure of the PPTA film should be mentioned. When the above-mentioned optically anisotropic dope is simply extruded through a slit and formed into a film, when this film is observed under a polarizing microscope under crossed Nicols (approximately 700~/θθθ times), a dense striped pattern as shown in Figure 7 is observed. can be seen. This striped pattern is made of P PTA fibers manufactured by a known method (for example, the method disclosed in Japanese Patent Publication No. 55-/G/7θ).
This can also be seen when observing the already commercially available Gubler [F] using the same polarizing microscope. This is the result of Dobb et al. [t+, Pol
ym.

Sci, Polym, Phys, Volume 1j, No.
2. ．． 20/Page (/977)], it is presumed that this is related to the so-called pleated sheet structure.

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 using a polarizing microscope in a state of crossed Nicols or near-crossed Nicols, they become more clearly visible as stripes with various colors. Observed as shown in the figure. The magnification in a polarized light microscope is
700 to 7000 times the normal amount is sufficient. Note that normal measures such as using a dipping 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, an optically anisotropic doped film simply extruded through a slit and immediately solidified usually has stripes with an interval of θ, /~0.4 tum or less, as shown in Figure 7. It had a pattern, tore in the direction perpendicular to the striped pattern, and easily fibrillated.

Although the film of the present invention is highly oriented in the axial 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.
It has the excellent characteristics of not tearing in any direction and being resistant to fibrillation.

Next, to obtain such a PPTA film -/4t
- Describe the method.

Suitable solvents for preparing the dope for forming the PPT A film of the present invention include sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, or mixtures thereof at a concentration of 9% by weight or higher. Sulfuric acid having a ratio of /θθ or higher, such as 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 concentration of the polymer in the dope is preferably at least a concentration that exhibits optical anisotropy at room temperature (approximately -θ°C to 30°C) or higher; specifically, approximately lθwt% or more. , preferably about /
, 2 weight Ll) or more. The upper limit of the polymer concentration of the dope is not particularly limited, but is usually 2.
It is preferably used in an amount of 5% by weight or less, particularly 20% by weight or less for PPTA of ηinh.

Dope also contains common additives, such as fillers, deglazing agents, UV stabilizers, heat stabilizers, antioxidants, pigments,
A solubilizing agent or the like may be mixed.

Whether the dope is optically anisotropic or optically isotropic can be determined by the method described in Japanese Patent Publication No. 7-7, but the critical point depends on the type of solvent, temperature, and polymer concentration. , depends on the degree of polymerization of the polymer, the content of non-solvent, etc., so by investigating these relationships in advance, an optically anisotropic dope can be created, and by changing the conditions to an optically isotropic dope, optically anisotropic It is possible to change from optical isotropy to optical isotropy.

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 supporting 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 involves, prior to coagulating, an optically anisotropic dope formed into a film on a support surface, using a solvent that absorbs moisture to form the dope. By lowering the concentration, the dope can be transferred to an optically isotropic region by changing the dissolving ability of the solvent and the polymer concentration, or by increasing the temperature of the dope by heating in addition to changing the optically isotropic region of the dope due to moisture absorption. This can be achieved by simultaneously or sequentially using the phase transition to optical isotropy.

Absolute temperature/f (water) is a method for making dope absorb moisture.
/Kg(dry air) or more, preferably 3v(water)/su(dry air) or more, more preferably /θ1(water)/su(dry air) or more, particularly preferably koθt(water)/Kl
This can be achieved by passing through an atmosphere with a relative humidity of more than (dry air) and less than a touch of relative humidity. 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, the temperature at which optical anisotropy substantially disappears and the dope converts to optical isotropy depends on the polymer concentration, degree of polymerization, sulfuric acid concentration, thickness of the dope, and moisture absorption. Although it varies depending on the degree of temperature change, a temperature of about 4tt°C or higher is usually preferably used.

In this way, the method of converting a PPTA-based optically anisotropic dope into optically isotropic, especially by using a combination of moisture absorption and heating, provides a much better transparency of the resulting film. This is a preferred means for easily obtaining the PPTA film of the present invention.

The coagulating liquid that can be used is, for example, water, dilute sulfuric acid of about 7.0% by weight or less, aqueous sodium chloride solution and aqueous ammonia of about 20% by weight or less, and aqueous sodium chloride solution and calcium chloride solution of about 50% by weight or less. etc. The temperature of the coagulation bath is not particularly limited, and is usually about θ℃~
It is carried out in a range of >0°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 make a film with less deterioration of mechanical properties due to heating. Preferably jθo
ppm or less.

Water is usually used as the cleaning liquid, but if necessary, it is also possible to use warm water, or to neutralize and clean with an alkaline aqueous solution and then wash with water. Further, as a cleaning method, the film may be run in a cleaning liquid, or the cleaning liquid may be sprayed.

In order to obtain the film with excellent mechanical properties of the present invention, in addition to the above-mentioned film forming method, it can be achieved by the following stretching method.

That is, the coagulated film is washed with water to -l ♂
- After removing the solvent and before drying, the film is stretched in a swollen state substantially free of solvent and containing moisture, which is a so-called wet stretching method.

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.
It is preferably used in an amount of at least 5 parts by weight based on the above-mentioned water content, and the stretching is carried out in a state containing the above water and at 5 times or more by a commonly used method, for example, by a roll circumferential speed difference or by using a tenter. The maximum stretching ratio here is approximately 2
．． If the film is stretched more than 5 times, it will not only be cut or the crystal orientation angle in the stretched direction will become too small, the mechanical strength in the direction perpendicular to the stretched direction will be weak, and it will not only tear easily but also cause fibrillation. Therefore, a value equal to or less than λ is preferably used.

Further, if the stretching ratio is less than 0, 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, but drying methods may be used, 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 with a tenter. Any method such as drying in a heated atmosphere may be used. In addition, during drying, the film is usually shrunk under tension or at a constant length in order to maintain its stretching effect, to prevent the film from wrinkling, and to make the film flat. It is done in a limited manner. The drying temperature should be at least room temperature.In addition, 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 less 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. There are seven of them. Further, an oil agent, an identification dye, etc. may be applied to the film in any step.

Examples are shown below, but these examples are intended to illustrate the present invention, and are not intended to limit the invention. In addition, unless otherwise specified in the examples, parts by weight or parts by weight are shown. The logarithmic viscosity ηinh was measured by a conventional method at 3θ°C by dissolving polymers θ and 2f in 11 sulfuric acid/θθ−. The viscosity of the dope was measured using a B-type viscometer at a rotation speed of /rpm. The thickness of the film is determined by the diameter, 2. Measurements were made using a dial gauge with a measuring surface on the pharynx. Strength and elongation and modulus are determined by cutting a film sample into a rectangle of 10 θ × / θ using a constant-speed extension type strength and elongation measuring machine, and applying a load of 5 sheets at an initial grip length of 3 θ and a tensile speed of 3 θ per minute. - Calculated from an elongation curve drawn. 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. 'Tokuko Showa 55
-47392? In the polymerization apparatus shown in Publication No. O, 2θ parts of anhydrous lithium chloride was dissolved in 77,000 parts of N-methylpyrrolide, and then phenylene diamine ♂ and Otsu parts were dissolved. After cooling to ♂°C, 9/1 part of terephthalic acid dichloride was added in powder form. After a few minutes, the polymerization reaction product solidified into a cheese-like shape, so the
The polymerization reaction product was discharged from the polymerization apparatus according to the method described in Publication No. ♂6, and immediately transferred to a closed type kneader with a λ axis, and the polymerization reaction product was pulverized in the same kneader. Next, the finely pulverized material was transferred to a Henschel mixer, an approximately equal amount of water was added thereto, further pulverized, filtered, washed several times in hot water, and heated to 770°C.
dried in hot air. ηinh, evening light yellow PPT
9j parts of A polymer were 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 ratio between monomers.

1 -- Example/ ηinh is 1, PPTA polymer is added to 99.7% sulfuric acid at polymer concentration/3. The dope was dissolved at θ°C, and an optically anisotropic dope was obtained at θ°C. When the viscosity of this dope was measured at room temperature, it was /gjθθpoise. In order to facilitate film formation, this dope was placed in a tank and maintained at about 7θ°C. At that time as well, it had optical anisotropy as described above, and the viscosity was 20θ voids. From the tank to the die via the gear pump/,jm curved pipe maintained at approximately 7θ℃, θ,,:2w
From a die with slits in the order of n x 3θθ, it was cast onto a mirror-polished Hastelloy belt maintained at 770°C, and the relative humidity was lowered to 20°C. ? After being kept in the same atmosphere for 90 seconds, it solidified and was continuously formed into a gA film. When the dope was sampled from the belt just before solidification during film formation,
It had a fairly high viscosity and was optically isotropic.

The coagulated film was taken out and washed with room temperature water for 7 nights.
When the moisture content was measured, it was found that for 700 parts by weight of the polymer,
It contained 350 parts by weight of water.

The water-containing film was placed between the /θOrtm width chucks of the constant-speed stretching type strength and elongation measuring machine, and stretched 5 times in the MD force direction from the length of the θθ duck and then exposed to hot air at 2θO℃. Fixed length drying was performed. The seventh property of this film is
Shown in the table.

Comparative Example/In Example/, the washed water-containing film was not stretched, but was dried at a fixed length in a hot air dryer set at θθ°C in the same manner as in Example/. The properties of this film are shown in Table 7.

Comparative Example λ In Example/, a coagulation bath containing water at 25°C was placed directly 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.

Take out the coagulated film and wash it with room temperature water/night.
When the moisture content was measured, it was found that for 700 parts by weight of the polymer,
It contained water of 2.1+″θ east volume.

The film still containing water was M
Stretching in the D force direction was attempted, but the film could not be stretched because it easily tore in the TD force direction. Therefore, the water-washed film was not stretched but was dried in a fixed length with hot air at 700°C. Still TD
Although the film tore in the force direction, for some reason 7 films were obtained, and the properties of this film are shown in Table 7.

Comparative Example 3 The doped sample prepared in Example 1 was kept at 770°C in a box under a dry nitrogen atmosphere.
A film was formed on a glass plate with an angle of θ0 rran using an applicator with steps of θ and /lea.

After θ seconds, the dope on the glass plate still maintained its optical anisotropy, but the dope was taken out from the drying box together with the glass plate and immediately put into water at 20° C. to solidify. The resulting film was opaque and was washed in the same manner as in Examples and stretched in the MD force direction, but most of the films were broken, and some were stretched about 7.2 times, but they were torn when dried. Oops. Therefore, the water-washed film was not stretched but was dried in a fixed length with hot air at 700°C. The properties of this film are shown in Table 7.

-2ter Example PPTA of 0.2 in.+7inh was dissolved in 99.6% sulfuric acid so that the polymer concentration became //θ at θ°C. This dope exhibited optical anisotropy at 20° C. and had a viscosity of 33θθ poise. This dope was applied onto a glass plate at 2J° C. using an applicator with steps of θ, /++ll11. After that, absolute humidity 7.3-9 (
When the dope was collected and analyzed after being left for 7 minutes in air at ie°C maintained in an atmosphere of water)/odor (dry air), it was found that the dope had absorbed moisture to the extent that the sulfuric acid concentration had decreased to 9 g, g%. I found out that there is. However, the dope is still opaque at this point, and after this it is heated to 720°C in a dry nitrogen oven.
When heated for 2θ seconds at ℃, the dope became optically isotropic and became transparent. After solidifying this with 75℃ water,
It was neutralized with an aqueous solution of caustic soda J-4, and then further washed with water to adjust the acid concentration to θθppm.

When the water content of this washed film was measured, it contained 33θ parts by weight of water based on 700 parts by weight of the polymer. The water-containing film was stretched in the same manner as in Example 1 in the MD force direction, and then dried at a fixed length by applying hot air at 2jθ°C.

The properties of this film are shown in Table 7.

Comparative Example In Example C, the washed water-containing film was not stretched, but was exposed to hot air at 2jθ°C and dried at a fixed length in the same manner as in Example C. The properties of this film are shown in Table 7.

7- Example 3 ηinh is 1. ,! dt/? A PPTA polymer was dissolved in 2 ml of sulfuric acid at a polymer concentration of 2.0 To to obtain a dope having optical anisotropy at θ°C. When the viscosity of this dope was measured at room temperature, it was found to be /63θθpoise. In order to facilitate film formation, this dope was heated to about 0°C.
It was degassed under vacuum while maintaining the temperature. This case also had optical anisotropy as described above, and the viscosity was θ θ θ poise. From the tank, pass through the filter, go through the gear pump, and reach the die. Keep the 5 m bent pipe at about 75°C, and set the temperature to θ1.2I.
A Hastelloy bell mounted on a mirror surface from a die with slits in the order of III++×3θθ (moves at 2 m/min)
The casting dope is made optically isotropic by blowing air at about ♂S℃ with a relative humidity of about 9θ, and the cast dope is made optically isotropic (retention time is about 72 seconds). It was placed in acid and coagulated. The coagulated film was then peeled off from the belt and washed by running it in warm water at about 3θ°C.

The washed film was placed in a tenter dryer and dried at a fixed length first with hot air at /jθ°C and then with hot air at 22θ°C. (Film A) On the other hand, the washed film (containing water of about 3:2θ ratio) was stretched about 7.5 times in the width direction at room temperature using a tenter, and then dried in the same way as Film A. The obtained film is referred to as film B.

Furthermore, the washed film is heated at room temperature in the longitudinal direction by approximately
A film obtained by tail stretching and drying in the same manner as film A is 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.

Below is a blank example. A PPTA polymer with a power of 3.7 di/f is dissolved in 99.3 sulfuric acid at a polymer concentration of 2.3%, and a dope with optical anisotropy is prepared at θ°C. I got it. The dope was degassed under vacuum while being maintained at approximately 0°C. This case also had optical anisotropy, and the viscosity was ♂θθpoise. From the tank, pass through the filter, go through the gear pump, and reach the die. Keep the curved pipe of f m at about 7j℃, θ,
,,! Cast from a die with slits in the order of mn x 3θθ onto a mirror-polished tantalum belt (distance between the bottom edge of the die and the belt direction is approx./cm), and blow hot and humid air to cast the material. The doped optically isotropic resin and belt were introduced into water at 70°C to solidify.

The temperature of the air used for the optical isodynamic ratio of the dope was 70
It had a relative humidity of 9 degrees Celsius and the time the cast dope was exposed to this air was long.

The coagulated film is then peeled off from the belt and heated to approximately 3θ℃.
The sample was washed with warm water, a 3-line caustic soda aqueous solution at room temperature, and water at room temperature in this order. The washed film (containing water at approximately 3θθ) is stretched approximately 7.5 times in the longitudinal direction at room temperature, then placed in a tenter dryer, and then mulched with hot air at θ°C at a fixed length. It was dried with hot air at u°C. The properties of the obtained film are shown in Table 3.

Above margin ``Effects of the Invention'' As shown in the examples, the film of the present invention has good mechanical properties expressed by high strength and high Young's modulus, which are not found in commercially available films, especially in the stretching direction. While maintaining the mechanical properties in the orthogonal direction, the mechanical properties in the stretching direction, particularly the modulus, were dramatically improved. In addition, 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 suitable for use as filtration membranes, packaging materials, etc., and is chemically resistant. 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.It can also be used as an electrical insulation material that requires heat resistance, oil resistance, and electrical properties, and as a heavy-ray coating. In terms of material and particularly strong mechanical strength, the above-mentioned good properties are fully exhibited when used as a magnetic tape by utilizing the insulating material of magnetic equipment that rotates at cylinder speed and especially the tuning modulus. .

Figure 7 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 showing the incident X-ray pattern when determining the crystal orientation angle of the PPTA film Show direction.

Claims (1)

[Scope of Claims] A film consisting essentially of a polyparaphenylene terephthalamide-based polymer having a logarithmic viscosity ηinh of 2.5 or more, the number of voids detailed in the specification being 5/mm^2
or less, the light transmittance detailed in the specification is 55% or more, and the X-rays incident at right angles to the film surface (2
00) The crystal orientation angle in the direction where the diffraction intensity of the plane is maximum is 3
0° or more and less than 70°, the crystal orientation angle of the (010) plane by X-rays incident parallel to the film surface is 60° or less, and no dense striped pattern is observed when observed with a polarizing microscope. A new polyparaphenylene terephthalamide film featuring: