JPS6329008B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a novel aromatic polyimide fiber and a method for producing the same. [Prior art] Aromatic polyimide is a polymer compound consisting of repeating units derived from an aromatic diamine component and repeating units derived from an aromatic tetracarboxylic acid component equivalent to the repeating unit, and has a high heat resistance. Because of its excellent properties, it is already widely used in films, varnishes, etc. Attempts have also been made to make aromatic polyimide into fibers, and these methods can be roughly divided into the following two methods (1) and (2). (1) A method in which a polyamic acid solution is made by reacting a tetracarboxylic acid anhydride and a diamine, which is wet-spun into fibers, and then converted into polyimide fibers by heating. (2) A method of synthesizing solvent-soluble polyimide and wet spinning it to obtain polyimide fibers. Method (1) is disclosed in, for example, Japanese Patent Publication No. 42-2936 and Japanese Patent Publication No. 57-37687. However, this method requires careful control as water is generated when imidizing polyamic acid fibers, and the generation of water tends to create pores in the fibers, making it difficult to create high-strength fibers. Can not. Specifically, in the method disclosed in Japanese Patent Publication No. 42-2936, the strength of the obtained fibers is only 2.8 to 6.6 g/
d, and the initial elastic modulus is also small at 31 to 77 g/d. On the other hand, although the method disclosed in Japanese Patent Publication No. 57-37687 has been improved, the fiber strength is 10
In many cases, it was about g/d, which was still insufficient. On the other hand, method (2), for example,
Although it is disclosed in Publication No. 17133, the strength of the obtained fiber is only 1.27 to 2.65 g/d, and the initial elastic modulus is 32.
~70g/d, and satisfactory characteristics were not obtained in either case. In general, it is difficult to make fibers with sufficiently high strength and elastic modulus using soft molecules that are easily soluble in solvents, and rigid polymers are difficult to dissolve in solvents and are difficult to form into fibers. In addition, as a polyamide fiber with high strength and high elasticity, Kevlar (trade name) manufactured by DuPont
However, this fiber cannot exhibit sufficient properties in terms of moisture resistance and light resistance. [Object of the Invention] The first object of the present invention is to provide a polyimide fiber that has a high level of strength and elastic modulus that could not be achieved with conventional polyimide fibers, and also has excellent moisture resistance and light resistance. There is a particular thing. A second object of the present invention is to provide a method for producing polyimide fibers that can stably and reproducibly produce polyimide fibers endowed with such excellent properties. The first object of the present invention is to provide a polyimide fiber having repeating units derived from equimolar moles of an aromatic diamine component and an aromatic tetracarboxylic acid component, wherein the aromatic diamine component and the aromatic tetracarboxylic acid component The composition with the components is as follows: (i) The molar ratio (d/c) of the component d of the following formula (D) to the component c moles of the following formula (C), which is the aromatic tetracarboxylic acid component, is less than 1/4. The ratio (b/a) of component b mole of the following formula (B) to component a mole of the following formula (A) which is the aromatic diamine component.
is 1/9 to 1, or (ii) the ratio (b/a) of component b mole of formula (B) to component a mole of formula (A) is 0 to 3/7,
Consisting of an aromatic polyimide soluble in a phenolic solvent, the ratio (d/c) of d moles of the component of the formula (D) to c moles of the component of the formula (C) is 1/4 to 3/7. This is achieved using polyimide fibers characterized by: Formula (A): Formula (B): Formula (C): Formula (D): A second object of the present invention is to provide a polyimide fiber having repeating units derived from equimolar moles of an aromatic diamine component and an aromatic tetracarboxylic acid component, wherein the aromatic diamine component and the aromatic tetracarboxylic acid component The composition with the carboxylic acid component is as follows: (i) The ratio (d/c) of d moles of the component of the following formula (D) to c moles of the component of the following formula (C), which is the aromatic tetracarboxylic acid component, is 1/4. the ratio (b/a) of component b mole of the following formula (b) to component a mole of the following formula (A) which is the aromatic diamine component;
is 1/9 to 1, or (ii) the ratio (b/a) of component b mole of formula (B) to component a mole of formula (A) is 0 to 3/7,
The ratio (d/c) of d moles of the component of formula (D) to c moles of the component of formula (C) is 1/4 to 3/7, and the copolyimide has a logarithmic viscosity of 1.5 or more in a phenolic solvent. After dissolving this dope into the air through a nozzle and forming it into a filament, the filament is introduced into a coagulation bath that is compatible with the phenolic solvent and insoluble in polyimide. After coagulating the fibers, winding
This is achieved by a method for producing polyimide fibers, which is characterized in that after washing and drying, hot stretching is carried out at 250 to 420°C to double or more. Formula (A): Formula (B): Formula (C): Formula (D): [Embodiment] As described above, the polyimide fiber of the present invention has an aromatic composition in which paraphenylene diamine of the formula (B) is added to 3,4'-diaminodiphenyl ether of the formula (A) as necessary. group diamine component and 3 of the above formula (C),
A repeating unit derived from equimolar amounts of 3',4,4'-diphenyltetracarboxylic anhydride and an aromatic tetracarboxylic anhydride obtained by adding the pyromellitic anhydride of the formula (D) as necessary. It has
Equimolar conditions, that is, a+b=c+d, are necessary conditions for producing a high molecular weight polyimide. Among the blending ratios of the components (A) to (D), the most preferred blending ratios are in the following two cases (i) and (ii). (i) d/c is less than 1/4 and b/a is 1/9~
In case 1 (ii) b/a is 0 to 3/7 and d/c
is from 1/4 to 3/7, that is, the blending ratio of b/a and d/c, including the optimal ratios listed in (i) and (ii), defines the preferred range of molecular rigidity. It is. In other words, the (B) component and (D) component are rigid components,
Component (C) is a slightly soft component, and (A) is the softest component, but when attempting to synthesize polyimide consisting only of rigid components such as (B) and (D), it becomes a precipitation polycondensation system. It is not possible to obtain polyimide with high molecular weight. Furthermore, since the produced polymer does not dissolve in the phenolic solvent, it becomes difficult to perform spinning. However, although polyimides consisting only of soft components such as (A) and (C) are easily soluble in solvents and can be easily spun, the resulting fibers are soft, so it is difficult to add one or both of (B) and (D). Furthermore, it is preferable to select the ratios of b/a and d/c to define a suitable range of molecular rigidity. In this regard, it is believed that the reason why conventional polyimide fibers cannot achieve high strength and high elasticity is due to a lack of molecular rigidity. In the present invention, according to the blending ratios (i) to (iii) above, polyimide having an initial elastic modulus of 400 g/d or more and a tensile strength of 13 g/d or more after spinning using a phenolic solvent and heat treatment. It is possible to obtain polyimide fibers that have high levels of strength and elastic modulus in general, and have excellent heat resistance, acid resistance, moisture resistance, and light resistance. Here, the expression "excellent light resistance" means that it is superior to aromatic polyamide (trade name: Kevlar), which is currently the only commercially available high-strength, high-modulus fiber. The reason for the poor light resistance of polyamide fibers is thought to be that the N—H bonds in the amide bonds are easily broken by light, which becomes an initiation reaction and causes a photodegradation chain reaction. On the other hand, polyimide

[Formula] Since it consists of bonds and does not contain N--H bonds, it is considered to have high resistance to light. The copolyimide that is the raw material for the polyimide fiber of the present invention can be produced by polycondensing the aromatic diamine component and the aromatic tetracarboxylic acid component in a solvent. The method can be said to be the same as the method described in Japanese Patent Application No. 173394/1983. The polycondensation reaction can be carried out either continuously or batchwise. As the polycondensation reaction apparatus, various types such as a stirring tank type and a kneader mixer type can be used. The reaction must be carried out with air and moisture excluded. Furthermore, in order to discharge water produced in the condensation reaction out of the system, it is useful to flow a dry inert gas (for example, high-purity nitrogen gas) into the reaction system. When the solvent and raw materials are solid at room temperature, they can be supplied as solids to the reaction vessel and then gradually heated and melted to form a reaction liquid. Alternatively, a method may be used in which a solid solvent is heated and melted, and an aromatic diamine component and an aromatic tetracarboxylic acid component are added thereto and dissolved. Examples of solvents used in the above solution polycondensation reaction include p-chlorophenol, phenol, m
-cresol, p-cresol, 2,4-dichlorophenol or mixtures thereof. In addition, at this time, p
-Hydroxybenzoic acid can also be added.
The monomer concentration in the reaction solution is preferably in the range of 2 to 15% by weight. The reaction temperature varies depending on the boiling point of the solvent, but
Generally, a range of 160 to 210°C is suitable. The reaction time is preferably several hours to several hundred hours. The logarithmic viscosity (molecular weight) of the polymer (copolyimide) produced by the above polycondensation reaction increases with reaction time. In order to produce polyimide fibers with excellent physical properties, it is preferable that the polyimide material is a high molecular weight polymer. However, if the reaction time is too long in order to increase the molecular weight, a gel will form, which is not preferable. After the reaction is completed, the reaction solution is poured into a precipitation solvent such as methanol, ethanol, acetone, or a mixture thereof, and vigorously stirred to separate the polymer and the solvent. The polymer is filtered, washed and dried. In order to obtain polyimide fibers with high elasticity and high strength, which is the object of the present invention, the polyimide obtained as described above has a logarithmic viscosity (IV) of 1.5 dl/g.
It is necessary that it is above. Polymers with low IV tend to break during spinning and hot drawing operations;
Furthermore, the strength of the obtained fibers is also insufficient. Nao (IV)
is an abbreviation for intrinsic viscosity, but logarithmic viscosity is generally used as an approximate value of intrinsic viscosity. The conditions for measuring logarithmic viscosity in the present invention are as follows. Solvent: Concentrated sulfuric acid 99-100% Polymer concentration: 0.5 g/dl Measurement temperature: 30°C Logarithmic viscosity is calculated from the measured value using a Canon Fuenske viscometer using the following formula. IV=1/cln (t/to) where c: polymer concentration g/dl ln: natural logarithm t: flow time of sample solution to: flow time of solvent Next, the copolyimide powder produced as described above was A dope (spinning stock solution) is prepared by dissolving it in a solvent, but the polycondensation reaction solution can also be used as it is as a dope solution. The phenolic solvents used in the production of the dope solution include phenol, p-chlorophenol, m-cresol, and p-chlorophenol.
-cresols or mixtures thereof. The dope solution is prepared by dissolving the copolyimide at 50 to 120℃ using a stirring tank or kneader.
It is desirable to knead under reduced pressure while heating the mixture. Next, the dope liquid is discharged into the air from a nozzle using a known wet spinning device and formed into a filament shape. The filament, which has passed through the 0.5 cm to 5 cm air space, is introduced into a coagulation bath and wound into a winder as a fully coagulated fiber. As the coagulation bath, a solvent that is compatible with the phenolic solvent and insoluble in the copolyimide, such as methanol, ethanol, a mixture thereof, or a mixture of these alcohols and water, can be used. The temperature of the coagulation bath is not particularly limited. Due to vapor pressure, the temperature is often 60°C or lower. Generally, room temperature or lower is preferred.
There is no particular limitation on the length of the coagulation bath, but generally a coagulation bath length of several tens of centimeters to several meters is used.The spun and dried fibers are hot drawn using an electric furnace or a hot pin. This hot stretching operation can be performed using known techniques. The conditions for hot stretching are the temperature
It is desirable to conduct the stretching operation by heating at 250° C. to 420° C. for 15 seconds or less and at a stretching ratio of 2.0 times or more. The heat treatment temperature is particularly important for the polyimide fibers of the present invention, and it is desirable to perform the treatment at as high a temperature as possible. The fiber properties were measured using a monofilament tensile test in accordance with JIS-L1069. The tensile testing machine used was manufactured by Shinko Tsushin Kogyo, and the tensile speed was 10 mm/min. Next, the present invention will be explained in more detail with reference to Examples. Example 1 As an amine component constituting polyimide, 3,
4'-Diamine diphenyl ether (DADE) and p
- Consists of phenylene diamine (PPD) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) as the acid component, and the ratio of these components is DADE:PPD:BPDA=7: 3:10
A copolyimide was produced. 4-port 300 with stainless steel stirring bar, nitrogen gas inlet, nitrogen gas outlet, and sample inlet
BPDA7.3555g (0.025g in ml separable flask)
mol) and 174.2 g of phenol, and under a nitrogen stream,
The mixture was stirred for 30 minutes while being heated to 60°C in an oil bath.
Next, 3.5025g (0.0175mol) of DADE is added to this.
Add 0.8111g (0.0075mol) of PPD to this temperature 1.5
Stir for hours. Then, 8.625g of p-hydroxybenzoic acid (PHBA), a polymerization aid, was added to this reaction system.
(0.0625 mol) was added. Next, the temperature of the oil bath was raised to 175°C over about 1 hour to start the polyimidation reaction. As the bath temperature rose, the turbidity of the reaction solution disappeared and became a brown transparent liquid, and time passed. As time went on, it became viscous. Polymerization was carried out for 32 hours while stirring at a bath temperature of around 175°C. This polymerization solution was poured into methanol, pulverized with a mixer, and washed three times with a large excess of methanol. The polymer was taken out and dried at 100° C. under vacuum. Yellow powdery polymer yield
Obtained at 100%. This polymer was added to 100% H ₂ SO ₄ at a concentration of 0.5 g/dl.
using a Canon Fuenske viscometer.
When its logarithmic viscosity (IV value) was measured at 30℃
It was 2.81 dl/g. FIG. 1 shows the infrared absorption spectrum of this polymer measured by the film method. Table 1 shows the elemental analysis results of this polymer.

[Table] Table 2 also shows the thermobalance measurement results of this polymer. The temperature was measured in air at a heating rate of 5° C./min using a DuPont Model 951 thermobalance device.

[Table] Example 2 8 parts of polyimide powder produced in Example 1 and p-
92 parts of chlorphenol was placed in a separable flask equipped with a Teflon stirring blade, and stirred for 2 hours while heating to 90°C to prepare a uniform viscous solution. This solution was degassed under reduced pressure at 110° C. and 80 mmHg for 2 hours, and filtered under pressure using a filter made of a combination of a 100-mesh wire mesh and a stainless steel nonwoven fabric (20 μ absolute) to prepare a spinning stock solution (dope). This dope was placed in the nozzle holder of the wet spinning device shown in Figure 1, and extruded through a nozzle (hole diameter 0.15 mm, 1 hole) at a discharge temperature of 120°C and a nitrogen pressure of 3 kg/cm ² G.
After passing through an air layer of about 2 cm, it was passed through an ethanol coagulation bath (effective bath length 5 m) and wound up at a speed of 18.9 m/min. The speed of the dipping roller is 17.1m/
I set it to min. This fiber was soaked in methanol overnight as a bobbin, washed, and then air-dried. This undrawn yarn was hot-stretched using the hot-stretching apparatus shown in FIG. 2 to obtain high-strength, high-elasticity fibers as shown in Table 3. The stretching ratio was calculated using the following formula. (Stretching ratio) = (Fineness of undrawn yarn) / (Fineness of hot drawn yarn)

[Table] Example 3 Preparation of 3,4'-diaminodiphenyl ether (DADE), 3,3',4,4'-diphenyltetracarboxylic anhydride (BPDA), and pyromellitic dianhydride (PMDA) Copolyimide fibers with a ratio of 10:7:3 were produced. In the apparatus of Example 1, 5.1489 g (0.0175 mol) of BPDA, 1.6359 g (0.0075 mol) of PMDA, and 176.1 g of phenol were charged and stirred for 30 minutes while heating to 60° C. under a nitrogen atmosphere. Then in this solution
After adding 5.0061 g (0.0025 mol) of DADE and continuing stirring for 1.5 hours, 8.625 g (0.0625 mol) of PHBA, a polymerization aid, was added.
mol) and raise the oil bath temperature to 175℃.
In this reaction system, the liquid becomes viscous over time. The liquid was slightly cloudy. After heating and stirring for 30 hours, the reaction solution was poured into methanol in the same manner as in Example 1 and pulverized with a mixer to recover the polymer. Yield: 10.8g. Yield 99%. of this polymer
The IV value was 1.96 dl/g. Figure 3 shows the infrared absorption spectrum (obtained by the film method) of this polymer. In addition, the elemental analysis values of this polymer are shown in Table 4.

[Table] Table 5 shows the thermobalance measurement results of this polymer. The measuring device and conditions were the same as those shown in Example 1.

[Table] A spinning dope was prepared by heating, mixing, and dissolving 9 parts of this polyimide powder and 91 parts of p-chlorophenol. Wet spinning and hot stretching were carried out in the same manner as in Example 2, except that the discharge temperature was 110°C. The obtained fiber properties are shown in the table below.

[Table] Example 4 Using the apparatus described in Example 1, in the same manner.
The ratio of DADE to PPD to BPDA to PMDA is 8:2:
An 8:2 copolyimide was prepared.
BPDA5.8844g (0.020mol) and PNDA1.0906g
(0.005 mol) and phenol
DADE4.0048g (0.020mol) and PPD0.5407g
(0.005 mol) and further 6.900 g (0.05 mol) of PHBA.
mol) and polyimidation at a bath temperature of around 175°C.
A polymer with an I.V value of 2.02 dl/g was obtained. A spinning dope was prepared from 8 parts of this polyimide powder and 92 parts of p-chlorophenol. Discharge temperature
Spinning and hot stretching were carried out in the same manner as in Example 2, except that the temperature was 90° C. and the nitrogen pressure was 2.8 Kg/cm ² G. The obtained fiber properties are shown in the table below.

[Table] Example 5 Using the apparatus described in Example 1 and in a similar manner, copolyimides consisting of DADE, PPD, and BPDA were produced with varying ratios of DADE and PPD. Phenol is used as a polymerization solvent and PHBA is used as a polymerization aid.
was used. The amount added was twice the molar amount of the amine component. The results are summarized in the table below.

[Table] A dope for spinning was prepared from 8 parts of polyimide powder of 3,4'-DADE:PPD:BPDA=9:1:10 and 92 parts of p-chlorophenol. Spinning and hot stretching were carried out in the same manner as in Example 2, except that the discharge temperature was 90° C. and the nitrogen pressure was 2.2 Kg/cm ² G. The obtained fiber properties are shown below.
9. For the other three polyimides, spinning dopes were prepared using 8 parts of their powders and 92 parts of p-chlorophenol, and the dopes were spun and hot-stretched. however
3.4′-DADE:PPD:BPDA=8:2:10, the discharge temperature is 100℃, the nitrogen pressure is 2.8Kg/cm ² G, and 6:
In the case of 4:10, the spinning conditions were 90° C. and 3 Kg/cm ² G. In the case of 5:10, the spinning conditions were 90° C. and 2.8 Kg/cm ² G. The obtained fiber properties are shown in Tables 10 to 12.

【table】

【table】

【table】

[Table] Example 6 Using the apparatus described in Example 1, in the same manner.
Consisting of DADE, BPDA and PMDA, BPDA
A copolyimide with a PMDA ratio of 8:2 was prepared. Phenol was used as the polymerization solvent, and the monomer concentration charged was 5 wt%. In addition, p-
Using HBA, the amount added is based on the amine component.
It was 2.0 times the molar amount. Under these polymerization conditions, the bath temperature
The reaction was carried out at around 175°C for 43 hours to obtain a copolyimide with an IV value of 2.25 dl/g. A spinning dope was prepared from 8 parts of this polyimide powder and 92 parts of p-chlorophenol. Discharge temperature
Spinning and hot stretching were carried out in the same manner as in Example 2, except that the temperature was 100° C. and the nitrogen pressure was 2.4 Kg/cm ² G. The obtained fiber properties are shown in the table below.

[Table] Example 7 DADE, PPD and BPDA (DADE/PPD=7/3)
In producing the copolyimide consisting of the following, polymerization was carried out without adding p-HBA as a polymerization aid. For example, the polymerization apparatus, polymerization method, conditions, etc. were the same as those described in Example 1, except that phenol was used as the solvent and the concentration was 5 wt%. As a result, a copolyimide having a polymerization time of 62 hours and an IV value of 2.27 dl/g was obtained. Example 8 This example consists of DADE, PPD, and BPDA.
When producing a copolyimide with a charging ratio of DADE and PPD of 8:2, PCP is used as a polymerization solvent, and the resulting polymerization solution is directly poured into a large excess of methanol without any post-treatment. This is an example in which a copolyimide fiber was produced by spinning and then hot drawing. 5.8844 g of BPDA in the apparatus described in Example 1
(0.02 mol) and 126.5 g of PCP were added while heating at 75°C under a nitrogen stream, and after stirring for 30 minutes,
DADE3.2039g (0.016mol) and PPD0.4326g
(0.004 mol) and stirred for 1.5 hours, p-
5.52 g (0.04 mol) of HBA was added, and the bath temperature was raised to around 175° C. over 1 hour to initiate polymerization.
The monomer charge concentration was 7 wt%. After polymerization was carried out in this manner for 16 hours, the resulting brown and transparent polymerization liquid was filtered as it was, defoamed, and then packed into a spinning tube, and spun and hot-stretched in the same manner as in Example 2. The discharge temperature was 100°C and the nitrogen pressure was 3Kg/cm ² G. A portion of this polymerization solution was sampled and the copolyimide IV value obtained after treatment was measured.
It was 3.36 dl/g.

[Table] Comparative Example 1 Using the apparatus described in Example 1, a polyimide consisting of DADE and BPDA was produced in the same manner. Both monomer components were charged so that the monomer concentration was 6 wt% and polymerized in phenol in the presence of p-HBA for 69.5 hours to obtain a polyimide with an IV value of 2.64 dl/g. A spinning dope was prepared from 8 parts of this polyimide powder and 92 parts of p-chlorophenol. Discharge temperature
Spinning and hot stretching were carried out in the same manner as in Example 2, except that the temperature was 120° C. and the nitrogen pressure was 2.2 Kg/cm ² G. The obtained fiber properties are shown in the table below.

[Table] Comparative Example 2 Using the apparatus described in Example 1, in the same manner.
It consists of DADE, BPDA and PMDA, and BPDA and
A copolyimide with a PMDA ratio of 9:1 was prepared in phenol in the presence of p-HBA at a monomer concentration of 5 wt%, and a copolyimide with an IV value of 2.13 was obtained after polymerization for 69 hours. A spinning dope was prepared from 8 parts of this polyimide powder and 92 parts of p-chlorophenol. Discharge temperature 90
℃ and nitrogen pressure of 3.2 Kg/cm ² G, spinning and hot stretching were carried out in the same manner as in Example 2. The obtained fiber properties are shown in the table below.

[Table] Comparative Example 3 Using the apparatus described in Example 1, in the same manner.
Consisting of DADE, PPD and BPDA, DADE and PPD
A copolyimide with a ratio of 4:6 was prepared in the presence of p-HBA. The monomer concentration charged was 5 wt%. Polymerization progressed heterogeneously, with a polymerization time of 120 hours.
A copolyimide with an IV value of 2.26 dl/g was obtained. In order to make fibers from this polymer, an attempt was made to manufacture a dope by dissolving 8 parts of polymer and 92 parts of PCP using the method described in Example 2, but the polymer did not dissolve in PCP, resulting in a non-uniform dope, making it impossible to spin. It was hot. Comparative Example 4 Using the apparatus described in Example 1, in the same manner.
Consisting of DADE, BPDA and PMDA, BPDA
A copolyimide with a PMDA ratio of 6:4 was prepared by p
- Manufactured in the presence of HBA at a monomer concentration of 5wt%. The polymerization reaction proceeded heterogeneously, and the IV value of the obtained copolyimide was as small as 0.73 dl/g, making it impossible to spin. Example 9 The present invention shows that the polyimide fiber of the present invention has excellent light resistance. The polyimide fiber used in this example was a heat treated system having a composition of DADE-PPD-BPDA (7:3:10). For comparison, aromatic polyamide fiber Kevlar 49 was tested at the same time. The test equipment used was a Weather-O-Meter MHQ-1 model manufactured by Toyo Seiki Co., Ltd., which was partially modified to shorten the distance between the sample and the light source and increase the intensity of the light hitting the sample. It is something. That is, an aluminum cylinder (approximately 20 cm in diameter and 33 cm in height) was placed around the 6000 W xenon arc lamp at the center of the above apparatus, and 7 polyimide fibers with a length of approximately 15 cm and 7 polyamide fibers for comparison were placed on the inner wall of this cylinder. ~Ten
Samples were removed from each book at predetermined time intervals and a tensile test was performed on the single fibers. The surface temperature of the aluminum cylinder reached approximately 100°C. No water injection was performed on the sample. The deterioration of fibers is due in part to the action of light. The aromatic polyamide fibers used in the comparative tests were washed with methanol, water, and n-hexane before use. The test results are shown in Tables 17 and 18. From these tables, it can be seen that Kevlar 49's strength decreases to 5.2 g/d after 24 hours of irradiation, and the strength retention rate is only 20%, but the polyimide fiber of the present invention maintains its strength even after 24 hours.
It has a strength of 17.4 g/d and a strength retention rate of 84%. Furthermore, although the specification of Japanese Patent Application No. 173394 states that polyimide fibers using tolidine have better light resistance than Kevlar 49, the present invention provides that the polyimide fibers using tolidine are even more superior in light resistance than the polyimide fibers described in Japanese Patent Application No. 173394. Lightfastness has been improved.

【table】

[Table] Example 10 This example shows the results of a dry heat degradation experiment on fibers. 3,4'-DADE:PPD:BPDA=7:
A 3:10 hot drawn yarn was wound around a frame under constant tension (0.34 g/d) and placed in an oven at 300°C. After a predetermined period of time had elapsed, it was taken out of the oven, left to cool, and the strength and elongation was measured. For comparison, a similar experiment was conducted using commercially available poly-p-phenylene terephthalamide fiber (Kevlar 49, Du Pout). The results are shown in the table below.

[Table] Example 11 This example shows the results of a wet heat deterioration experiment on fibers. 3,4'-DADE:PPD:BPDA=7:
A 3:10 hot-drawn yarn was wound around a frame under constant tension (0.34 g/d), placed in an autoclave, and subjected to steam treatment at 200°C. After the specified time has passed,
It was taken out from the autoclave, left to cool and dry, and then its strength and elongation were measured. For comparison, Kevlar 49
A similar experiment was conducted for The results are shown in the table below.

[Table] Example 12 This example shows the results regarding the acid resistance of the fibers. 3,4'-DADE:PPD:BPDA=7:
A 3:10 hot drawn yarn was immersed in a 40% sulfuric acid aqueous solution and a 40% acetic acid aqueous solution and treated at 85° C. for a predetermined time. after that,
Water washing and methanol washing were repeated, and after drying, strength and elongation were measured. For comparison, a similar experiment was conducted using Kevlar 49. Table the results -21, -22
Shown below.

【table】

〔Effect of the invention〕

The polyimide fiber of the present invention has, compared to polyimide fiber manufactured from conventional polyimide dope,
It has significantly improved strength and elasticity, and also exhibits excellent light resistance. Furthermore, as demonstrated in the examples, it can also exhibit excellent properties in terms of chemical resistance (acid resistance), steam resistance, and heat resistance. Furthermore, polyimide fibers exhibiting such excellent properties can be produced stably and with good reproducibility, especially by the method for producing polyimide fibers of the present invention.

[Brief explanation of the drawing]

FIGS. 1 and 3 are diagrams showing infrared absorption spectrum curves of the polyamide according to the present invention produced in "Example". FIG. 2 is a schematic diagram showing an example of a spinning device used in the present invention. 1... Nitrogen cylinder, 2... Nitrogen intermediate distiller, 3...
Pressure gauge, 4... nozzle holder, 5... nozzle,
6... Coagulation bath, 7... Guide, 8... Dipping roller, 9... Winding bobbin, 10... Temperature controller.

Claims (1)

[Scope of Claims] 1. A polyimide fiber having repeating units derived from equimolar moles of an aromatic diamine component and an aromatic tetracarboxylic acid component, wherein the aromatic diamine component and the aromatic tetracarboxylic acid component are The composition is such that (i) the ratio (d/c) of d moles of the component of the following formula (D) to c moles of the component of the following formula (C), which is the aromatic tetracarboxylic acid component, is less than 1/4, Ratio (b/a) of component b mole of the following formula (b) to component a mole of the following formula (A) which is the aromatic diamine component
is 1/9 to 1, or (ii) the ratio (b/a) of component b mole of formula (B) to component a mole of formula (A) is 0 to 3/7,
Consisting of an aromatic polyimide soluble in a phenolic solvent, the ratio (d/c) of d moles of the component of the formula (D) to c moles of the component of the formula (C) is 1/4 to 3/7. A polyimide fiber characterized by Formula (A): Formula (B): Formula (C): Formula (D): 2 Initial elastic modulus 400g/d or more, tensile strength 13
The polyimide fiber according to claim 1, which has a polyimide fiber of at least g/d. 3. A polyimide fiber having repeating units derived from equimolar moles of an aromatic diamine component and an aromatic tetracarboxylic acid component, wherein the composition of the aromatic diamine component and aromatic tetracarboxylic acid component is (i) The ratio (d/c) of d moles of the component of the following formula (D) to c moles of the component of the following formula (C) which is the aromatic tetracarboxylic acid component is less than 1/4, and the aromatic diamine component is Ratio of component b mole of the following formula (b) to component a mole of the following formula (A) (b/a)
is 1/9 to 1, or (ii) the ratio (b/a) of component b mole of formula (B) to component a mole of formula (A) is 0 to 3/7,
The ratio (d/c) of d moles of the component of the formula (D) to c moles of the component of the formula (C) is 1/4 to 3/7, and the copolyimide has a logarithmic viscosity of 1.5 or more in a phenolic solvent. A dope solution is prepared by dissolving this dope solution into the air through a nozzle to form a filament, and then the filament is placed in a coagulation bath that is compatible with the phenolic solvent and insoluble in the copolyimide. After introducing and coagulating the fibers,
A method for producing polyimide fibers, which comprises winding, washing and drying the fibers, and then hot-stretching the fibers by twice or more at 250 to 420°C. Formula (A): Formula (B): Formula (C): Formula (D):