JPH02277814A - Production of copolyimide fiber - Google Patents

Abstract

PURPOSE:To easily produce the subject fiber having excellent heat-resistance, high elastic modulus and strength and moderate elongation and useful for the use in an aerospace field, etc., by spinning a forming dope composed of a copolyamic acid having a specific structure using a specific spinning method. CONSTITUTION:The objective fiber can be produced by preparing a forming dope containing a copolyamic acid composed of a unit of formula I(R is H or 1-4C alkyl), a unit of formula II (X1 is 1-2C alkyl or alkoxy; n is 1-2) and a unit selected from formula III to formula V (X2 is O, SO2, etc.) at a ratio (m2/m3) of 95/5 to 80/20 wherein m2 and m3 are molar percentage of the unit of formula II in the total diamine component and that of the unit selected from formula III to formula V, respectively, extruding the forming dope into an inert atmosphere and introducing the extrudate into an aqueous coagulation bath. The above copolyamic acid is preferably produced by the solution polymerization of pyromellitic anhydride and/or its derivative, a benzene compound having alkyl or alkoxy substituent on the nucleus and a rigid diamine.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is directed to the production of copolyimide fibers that are useful in the fields of space and aviation, electronic materials, etc., and have excellent heat resistance and mechanical properties. It is about the method.

(Conventional technology) Conventionally, polyimide has excellent heat resistance, mechanical properties, electrical properties,
It is known to be useful as a raw material for weather-resistant layered fibers, films, and other molded products. For example, 4,4
A film having excellent heat resistance can be obtained from polyimide produced from '-diaminodiphenyl ether and pyromellitic dianhydride, and is widely used for electrical insulation purposes.

In addition, in the field of heat-resistant fibers and films, aramid-based 41M, synthetic paper, and polyimide-based films and films are used, but with the advancement of advanced materials for space and aviation applications, higher heat-resistant materials are being used. In recent years, there has been a demand for materials with mechanical properties such as high strength, high strength, and high modulus. Therefore, in order to improve the mechanical properties of polyimide, which has excellent heat resistance, the importance of rigid skeleton polyimide is being recognized.

By the way, as polyimide is often insoluble and infusible, the general manufacturing method for polyimide is to dry or wet mold a molding dope made of polyamic acid, which is its precursor, and to ring-close the polyamic acid during the molding process. A method of obtaining a polyimide molded body is adopted.

At this time, there are the following problems.

1. Poly-p-phenylene (or 4,4'-biphenylene) pyromellitimide, which forms a completely rigid skeleton, undergoes heat treatment because its crystallization rapidly regresses during the imidization process due to its rigidity. It has poor stretchability and, as a result, does not exhibit high mechanical properties.

Furthermore, due to the low mobility of molecular chains, internal stress increases during the imidization and accompanying crystallization process, resulting in cracks and cracks during film production.

2. Polyamic acid, which is a precursor of polyimide, generally has poor coagulation properties during wet molding, which is a factor that hinders the development of physical properties.

To give an example regarding 1, Fiber Science Society Journal Vol. 4ONα
12. As described in T-480 to T-487, poly-4,4'-biphenylenepyromellitimide has an initial elastic modulus of 1,000 y/da or more and a strength of 10
S? Fibers with a high modulus of elasticity and high strength, such as /de or more, are rejected.At the same time, it is widely known that only brittle films that cannot be used practically can be obtained from such polyimides.

In consideration of the above problems, various polyimides have been proposed that exhibit good mechanical properties by reducing crystallinity and improving moldability without extremely reducing the rigidity of molecular chains.

For example, JP-A-60-97834, JP-A-62-
No. 77921, Japanese Unexamined Patent Publication No. 62-117815, etc. disclose copolyimides in which a part of a heptamer having a bent chain is copolymerized with an acid component or a diamine component constituting the polyimide. Although molded bodies with high strength can certainly be obtained from these copolyimides, it is difficult to achieve a high modulus of elasticity due to the presence of bent chains. Further, all of the copolyimide precursors have poor coagulability.

Also, JP-A-61-188127, JP-A-627
According to Publication No. 9227 and the like, a copolypyromellitimide is disclosed in which two or more kinds of rigid diamines are used, and at least one of them is a nuclear chlorine-substituted rigid diamine.

These can achieve a higher modulus of elasticity than those described above. However, the nuclear chlorine-substituted rigid diamine, which is an essential component, has poor reactivity, and as a result, it is not possible to obtain a polyimide with a high degree of polymerization, leaving problems in fatigue resistance and the like.

In addition, the diamines are generally expensive, and it is difficult to provide inexpensive materials that are advantageous for industrial use.

Furthermore, the polyimide contains chlorine and poses a problem of environmental pollution during combustion and disposal. Note that these copolyimide precursors also have poor coagulability.

Incidentally, polyimide having a rigid skeleton is attracting attention from the viewpoint of low thermal expansion even in insulation coating applications in the semiconductor field, and various polyimides have been proposed.

For example, JP-A-62-253621 discloses a polyimide using a rigid diamine. However, according to the publication, as a more preferable embodiment, it is specified that 25 mol% or more of a 3,3',4,4'-biphenyltetracarboxylic acid derivative having a bent part in the acid component is used. Furthermore, there is no mention of mechanical properties or coagulation properties during wet molding. Further, JP-A-63-191830 also proposes a copolyimide consisting of 3,3'-dimethylbenzidine and a rigid diamine of p-phenylenediamine derivative, but the composition of the precursor of the copolyimide is as follows: It also has poor coagulability.

As mentioned above, it can be said that problem 2 has not been improved at all in all of the above polyimides. That is, a solution of polyamic acid, which is a precursor of the polyimide, does not exhibit good coagulation properties in an aqueous coagulation bath, which is the easiest to handle.

In order to improve problem 2, the following method has been proposed.

That is, according to JP-A No. 60-65112, a soluble polyimide whose main component is 3.3', 4.4'-biphenyltetracarboxylic acid (derivative) is used as the acid component, and molding made of the polyimide is performed. A method of coagulating a liquid solution is disclosed. Although this molding solution exhibits good coagulation properties, an alcoholic solution such as methanol is used as the coagulation bath, and it lacks ease of handling.

Furthermore, since the polyimide is mainly composed of the above-mentioned acid component, it also has the problem that a high modulus of elasticity cannot be achieved.

Further, according to Japanese Patent Application Laid-open No. 59-157319, a method has been proposed in which polyamic acid is partially imidized with acetic anhydride or the like to improve its coagulability.

This method is applicable to almost all polyamic acids, but since the molding solution becomes a multi-component system and imidization progresses over time, it is difficult to control and it is difficult to maintain a uniform molding solution. This includes the problem of not being able to provide the same information.

In view of this, the present inventors previously filed a patent application in
No. 63411 proposed a method of improving the coagulability of a molding solution by adding amines and/or metal salts of acids with a pKa of 4.3 or higher. Although this method can provide a stable solution that does not change over time,
After all, the molding solution is a multicomponent system.

As described above, it can be said that there is still no polyamic acid that can simultaneously solve the above two problems and provide a polyimide molded article with excellent mechanical properties through a simple process.

By the way, the present inventors previously filed Japanese Patent Application No. 63-87312.
In Japanese Patent Application No. 1987-87313, a method for producing a high elastic modulus fiber of homopolyimide consisting of a pyromellitic acid derivative) and a rigid diamine was disclosed. proposed a polymer. At this time, the diamine components include 3.3'-dimethylbenzidine, 3.3'-dimethoxybenzidine and 2.
, 2'-dimethylbenzidine was found to exhibit good coagulation properties in an aqueous coagulation bath. Moreover, the polyimide fiber obtained from the polyamic acid exhibits excellent mechanical properties. However, since the polyimide is a homopolymer, it is highly crystalline, and as a result, its elongation is somewhat insufficient, and it is easily broken, resulting in problems in handleability, etc.

(Object of the Invention) The object of the present invention is to solve the above-mentioned problems and provide a method for producing a copolyimide fiber having excellent heat resistance and mechanical properties, that is, high modulus of elasticity, high strength, and appropriate elongation. It's about doing.

(Structure of the Invention) In order to achieve the above object, the present inventors conducted intensive research on both the chemical structure of polyimide and the spinning conditions, and found that a copolyimide having a specific chemical structure, although a copolymer, is inferior to a homopolymer. Furthermore, surprisingly, the fiber exhibits good coagulation properties in wet molding using an aqueous coagulation bath, and has the above properties. In order to achieve this, it was found that it is essential to enhance the molecular orientation at the early stage of the molding process, and this led to the completion of the present invention.

Thus, according to the present invention, substantially the manure constituent unit (I)
When manufacturing polyimide fibers from a molding dope containing a copolyamic acid formed from ~<m> and satisfying the following formula A, the molding dope is once discharged into an inert atmosphere, A method for producing copolyimide fibers is provided, the method comprising introducing copolyimide fibers into a coagulation bath.

A: 95/5≧1112/+113
At least one type selected from ≧80/20.

The present invention will be explained in detail below.

In the copolyamic acid used in the present invention, the acid component is essentially pyromellitic anhydride and/or its derivative IA, and the diamine component is alkyl or alkoxy-substituted benzidine (hydrochloride > I [A and the following It is synthesized by ordinary solution polymerization from at least one rigid diamine (hydrochloride) selected from A. Here, "substantially" means that 95 mol% or more of the acid component of the copolyamic acid is ■△, meaning that 95 mol% or more of the diamine component is the above IIA or I[IA,
If other components are included outside the range, problems such as deterioration of the mechanical properties of the resulting copolyimide fibers occur, making it impossible to achieve the object of the present invention.

In order to achieve the purpose of the present invention, it is necessary to satisfy the above copolymer composition, but if DIA is used beyond the above range, the wet moldability 2 modulus of elasticity will decrease significantly, and When I[[A is used, the elongation decreases. Also,
Preferably, 12/13: 95/5 to 85/15, more preferably Ugly z/Ia: 95/5 to 90/1
When I[A and lI[A satisfy the range of 0, the mechanical properties of the resulting fiber will be more excellent.

Next, the following diamine component IIA is the most important in terms of coagulability in the present invention.

3.31-dimethylbenzidine, 3.3'-diethylbenzidine, 3.3', 5.5'-tetramethylbenzidine, 3.3'-dimethoxybenzidine, 2.2'
-Dimethylbenzidine Also, the following aromatic diamines may be used as the diamine component in combination with IIA.

4.4'-diaminodiphenyl ether, 3.4'-diaminodiphenyl ether, 4.4'-diaminodiphenylsulfone, 4,4'-diaminodiphenyl sulfide, 4.4'-diaminobenzophenone, 1.
4-bis(4-aminophenoxy)benzene, 4,4'
-bis(4-7minophenoxy)biphenyl and their hydrochlorides Note that other acid components and diamine components may be used without departing from the scope of the present invention.

Examples of acid components include the following:

[Aromatic diacid anhydride] 3.3', 4.4'-diphenyltetracarboxylic diacid anhydride, 2,3.3', 4'-diphenyltetracarboxylic diacid anhydride, 3.3' , 4.4'-diphenyloxytetracarboxylic dianhydride, 3.3'
, 4.4'benzophenonetetracarboxylic dianhydride,
3.3', 4.4'-diphenylsulfone tetracarboxylic acid diacid anhydride, 3.3', 4.4'-diphenylalkylenetetracarboxylic acid diacid anhydride, 1.
4-bis(3,4-dicarboxyphenoxy)benzenedic anhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzenedic anhydride, p-phenylene-bis-trimellitate dioic anhydride.

[Aromatic Tetracarboxylic W1 Derivative] Diester diacid chloride of tetracarboxylic acids, diester of tetracarboxylic acids, and salt of tetracarboxylic acids.

Further, examples of the diamine component include the following.

[Diamine] p-phenylenediamine, 2-methyl-p-phenylenediamine, 2-ethyl-〇-phenylenediamine, 2-
Methoxy-p-phenylenediamine, 2-ethoxy-p
-phenylenediamine, 2.5-dimethyl-p-phenylenediamine, 2.6-dimethyl-p-phenylenediamine, 2.6-dimethoxy-p-phenylenediamine, 2
, 3.5-trimethyl-p-phenylenediamine, 2,
3.5-trimethoxy-p-phenylenediamine, 2,
3,5.6-butramethyl-p-phenylenediamine,
2.3,5.6-tetramethoxy-p-phenylenediamine, 2.4-diaminotoluene, diaminobenzanilide, diaminodiphenylmethane, 2,2-bis(aminophenyl)propane, 1.4-bis(3-amino phenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 4,4'-bis(aminophenoxy)
Diphenyl ether, 4,4'-bis(aminophenoxy)diphenylsulfone, 2,2-bis((aminophenoxy)phenyl)propane, 2,2-bis((aminophenoxy)phenyl)hexafluoropropane, diaminonaphthalene, and these hydrochloride.

The copolyamic acid used in the present invention is the acid component IA described above.
, diamine components 11A and lI[A are obtained by solution polymerization in a solvent, and the solvent used at this time will be described below.

Any solvent may be used as long as it is non-reactive with the monomer used and dissolves the precursor at a high concentration, but the following solutions are preferably used for ease of handling.

[Solvent] N-methyl-2-pyrrolidone (NMP), N-ethyl-
2-pyrrolidone (NEP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (D
MAc), N,N-diethylacetamide (DEA
c) ,N,N-dimethylpropionamide (DMP
r ), N, N-dimethylbutyramide (NMBA)
, N, N-dimethylisobutyramide (NMrB), N
-Methylcaprolactam (NMC>, N,N-dimethylmethoxyacetamide, N-acetylpyrrolidine (N
A''Pr), N-acetylpiperidine, N-methylpiperidone-2 (NMPD), N,N'-dimethylethyleneurea, N,N'-dimethylpropyleneurea, N
, N, N', N'-tetramethylmalonamide, N
-Acetylpyrrolidone, N,N,N'N'-tetramethylurea (TMU), dimethyl sulfoxide (DMSO)
, hexamethylphosphoramide (HMPA).

etc.

Regarding the solution polymerization, the usual method used in the polymerization of polyamic acids is applied, but as shown in Example 1 below, 3,3'-dimethylbenzidine and 4,4'
- While maintaining the NMP solution containing diaminodiphenyl ether at -10°C, add pyromellitic anhydride to approximately the same amount as the above diamine and stir vigorously.The solution gradually increases in viscosity, and if stirring is continued, the viscosity increases. A solution was obtained, and its intrinsic viscosity was measured to be 5.3, confirming that a copolyamic acid with a high degree of polymerization was produced.

Measurement of intrinsic viscosity (η1nh) was carried out in NMP at 35°C and m degree 0.
．． 59/old using an Ostwald viscometer, 1/C[1n
'(t/lo)].

Further, when using diester diacid chloride of tetracarboxylic acids or hydrochloride of diamine, solution polymerization may be carried out in the same manner, but at that time, a dehydrochlorination agent such as a tertiary amine may be added.

The copolyamic acid thus obtained is then made into polyimide fibers by the following method.

[Preparation of molding dope] To prepare a molding dope, the polymer concentration is adjusted so that the copolyamic acid solution subjected to solution polymerization has a viscosity suitable for formation, and the solution may be used as a molding dope as it is, In addition, once the polymer is isolated by mixing with a non-solvent,
It can also be redissolved in a suitable solvent and used as a molding dope. Although either method can be employed in the present invention, the former method is industrially preferred. In addition, in the present invention, the molding dope can be used as it is because it exhibits excellent coagulation properties in an aqueous coagulation bath. 63-226344
The method of adding amines and/or metal salts of weak acids to the polyamic acid solution proposed in the above issue, or the method of adding a chemical cyclizing agent to the polyamic acid solution and partially imidizing the polyamic acid in the solution. There is no harm in arguing passionately about using it.

[iIM Manufacturing Method 1] In the present invention, as described above, high-quality fiber properties are finally obtained by increasing molecular orientation at the initial stage of molding. This can be achieved by first discharging the above-mentioned copolyamic acid forming dope into an inert atmosphere and then introducing it into an aqueous coagulation bath for wet forming. This makes it possible to increase the spinning draft, improve molecular orientation, and make the coagulation state of the fiber surface denser, thereby suppressing the generation of defects such as voids. The result is a high degree of tampering.

The inert atmosphere here refers to nitrogen and argon.

It refers to something that is substantially non-reactive with the dope, such as air, and air is preferably used for ease of use.

In normal wet spinning, contact with a coagulant occurs at the same time as discharge, making it difficult to obtain a large spinning draft, and because the solidified surface is stretched, vertical grooves are formed in the 11M direction. and the occurrence of voids. These not only make it difficult to sufficiently advance molecular orientation, but also create defects that are undesirable for improving mechanical properties, and further cause fibrillation. The present invention solves both problems at the same time.

The production method of the present invention can be applied to all polyimide fibers, but in order to obtain fibers with excellent mechanical properties, which is the object of the present invention, it is necessary to use the above-mentioned specific polyamic acid as a polyimide precursor. There is.

For example, when the yarn-making method of the present invention is applied to a precursor of pyromellitimide whose diamine component is a rigid diamine such as p-phenylenediamine or benzidine, the orientation and physical properties of the coagulated yarn are improved, but on the other hand, It becomes almost impossible to carry out such rapid hot drawing, and high mechanical properties cannot be expected, and only fragile yarns with low elongation can be obtained. Furthermore, since the precursor has poor coagulation properties, the coagulated threads are devitrified due to voids and the like.

The present invention aims to pursue the simplest process, and therefore uses an aqueous coagulation bath, which is superior to the method using an alcohol-based coagulation bath as disclosed in Japanese Patent Publication No. 57-37687. This is because there is nothing superior to water-based systems in terms of ease of handling. To explain the aqueous coagulation bath in more detail, it is preferably composed of water or water and a solvent constituting the precursor solution, and may contain an inorganic compound for the purpose of improving coagulation properties.

The coagulated yarn is then subjected to an appropriate process and then subjected to hot drawing and heat treatment, or a combination of both hot drawings to finally obtain fibers with excellent mechanical properties.

To give an example of the above process: (1) Hot stretching the coagulated thread.

(2) The coagulated thread is stretched in air or in an aqueous bath, and then hot stretched.

(3) After imidizing the solid yarn, hot stretching is carried out.

(4) The coagulated thread is stretched in air or in an aqueous bath, then imidized and hot stretched.

etc., and there is no problem in performing it in any way, but basically, performing hot drawing under as high a tension as possible leads to improvement in physical properties, so it is recommended to increase the fiber strength before hot drawing. In this sense, the above method (4) can be said to be preferable, but in order to increase the U & miscellaneous strength to some extent and pursue a simple process, method ('2I) can be used. Regarding imidization, there are two methods: thermal imidization by heating, and chemical imidization using a chemical cyclizing agent (described later). Either method may be used, but chemical imidization is preferable in terms of suppressing crystallization. In terms of process simplification, thermal imidization is suitable.

Next, the above chemical imidization method will be explained.

[Chemical imidization method 1] This refers to the process of ring-closing imidization of polyamic acid using a dehydrating agent such as anhydrous acid M.
) can also be used in combination with a tertiary amine such as pyridine to increase the imidization rate. In imidization of yarn,
Specifically, after coagulation, the thread is wound onto a bobbin and then the bobbin is immersed in the above chemical cyclizing agent, or the thread after coagulation is passed through a bath containing a chemical cyclizing agent. The yarn and the chemical cyclizing agent may be brought into contact with each other by a method such as the above, and the method is not particularly limited. The immersion time is from several seconds to 12 hours. In addition, at this time, the present inventors previously filed Japanese Patent Application No. 62-272342 and Japanese Patent Application No. 63-
If the yarn imidization method proposed in No. 226344 is used, imidization can proceed more efficiently.

The copolyimide mH of the present invention has improved hot stretchability compared to a homopolymer due to the substituent effect of the nuclear-substituted benzidine and the copolymerization effect, and can highly enhance molecular orientation. The drawn yarn is preferably subjected to high-temperature heat treatment in order to further improve physical properties by promoting crystallization, and is heated to 400 to 650°C under tension, preferably 400 to 650°C.
Process at 50-550°C.

Although the fibers obtained as described above are copolymers, they exhibit high elastic modulus and also have appropriate elongation.

(Operations and Effects of the Invention) The greatest feature of the copolyimide fiber obtained by the present invention is that it is formed from a highly polymerized polymer that is advantageous in various mechanical properties, and that it exhibits a high modulus of elasticity even though it is a copolymer. The point is that it has appropriate elongation. Part 1! Fibers exhibit excellent performance in the field of advanced composite materials (A, CM, etc.).

Furthermore, the production method of the present invention has specific excellent coagulation properties in an aqueous coagulation bath, which is the easiest to handle in a wet molding process, and there is no need to use various methods to improve coagulation properties. The process will be the simplest.

(Example) The present invention will be explained below with reference to Examples.

First, the preparation of the forming stock solution, the spinning method, and the heat treatment method used in the present invention will be explained.

[Preparation of molding stock solution] N-methylgorolidone (NMP) obtained by dehydrating at least one aromatic diamine component with molecular sieves.
After the amine solution was externally cooled to -10'C, pyromellitic anhydride (PMDA) was added in an amount equivalent to the diamine, and a polymerization reaction was carried out under high speed stirring. A portion of the obtained high viscosity copolyamic acid solution is taken out and diluted to a concentration of 0.5 (j/old) to measure ηinh.

[Dry-Wet Spinning (Spinning Method A) 1 The copolyamic acid solution obtained as described above was immediately mixed with a pore size of 0. IM, discharge speed 3 through a nozzle with 12 holes
171/LIlin into the air, and after passing through a 10-thick air layer, water/NMP (volume ratio 90/10)
After passing through the bath for about 3 m, it was stretched to about twice its original size in a stretching bath consisting of water/NMP (volume ratio 95/5), and then taken out into the air and adjusted at a winding speed. 20
Wind it up with R/win. (Hereinafter, this will be referred to as spinning method A.

) CFJ spinning (spinning method B)] The above copolyamic acid solution is carried out in the same manner as the spinning method except that the above copolyamic acid solution is not passed through an air layer. (below,
This is called the spinning method B.) [Chemical imidization-heat treatment (
Heat treatment method A)] The wound yarn was immediately immersed together with the bobbin in a separate bath of anhydrous vinegar If/pyridine (volume ratio 70/30) for 1 hour to advance imidization, and the yarn was After washing and drying, stepwise heating treatment is performed on a plate at 250° C. and 450 to 600° C. (the optimum value is selected depending on the copolyamic acid used) to obtain copolyimide m fibers. At this time, stretching is performed at a ratio that allows stable winding (hereinafter referred to as heat treatment method A) [thermal imidization (heat treatment method B)] In the above-mentioned spinning methods A and B, when winding the yarn The yarn is passed through a hot roller heated to about 100°C, and the dried yarn is subjected to stepwise heating heat treatment on a plate at 250°C and 450 to 600°C (the optimum value is selected depending on the copolyamic acid used). At this time, the copolyimide fiber is obtained by stretching at a ratio that allows stable winding. (Hereinafter, this will be referred to as heat treatment method B.) In the examples, intrinsic viscosity ri<ηinh
) is the value measured at 35° C. after diluting the precursor solution with a solvent so that the polymer concentration was 0.5 ff/dl. Further, the bow tension properties were measured on the yarn using Tensilon manufactured by Toyo ■ at a sample length of 100 mm and a tensile speed of 50 mm/min. It should be noted that there was a maximum difference of about 20% in tensile properties between single yarn and yarn.

The abbreviations in Examples are shown below.

PMOA: Pyromellitic diacid anhydride BPDA:
3,3',4,4'-biphenyltetracarboxylic acid anhydride 0-TOL: 3,3'-dimethylbenzidine 1-TOL: 2,2'-dimethylbenzidine D
SB: 3,3'-dimethoxybenzidine 4D
APE: 4,4'-diaminodiphenyl ether 3DAPE: 3,4'-diaminodiphenyl ether TPE-Q: 1.4-bis(aminophenoxy)benzene BAP8: 4.4'-bis(4-aminophenoxy)biphenyl 3CBZ: 3 ,3'-di')DAtbenzidi>
20BZ: 2,2'-dichlorobenzidine 2CP
:2-chloro-p-phenylenediamine 250BZ:
2.2',5.5'-tetrachlorobenzidine 3DAS = 3,3'-diaminosulfone 3BAS:
4.4'-bis(3-aminophenoxy)diphenylsulfone TPE-M: 1,3-bis(3-aminophenoxy)benzene 3DABA: 3,3'-diaminobenzanilide MPDA: +-phenylenediamine then copolyamic Acid solutions 1 to 12 were mixed into the above-mentioned spinning A.
Copolyimide fibers were obtained by dry-wet spinning using method A and method B. The physical properties of the obtained fibers are shown in Table 2.

(The heat treatment temperature was varied, and the one that showed the best physical properties was described. The same applies hereinafter.) All of the m fibers had a strength of 15
It exhibited excellent physical properties, with an initial elastic modulus of 1,200 g/de or higher, and a breaking elongation of 1.5% or higher. In addition, the coagulation property during spinning was also good, and the material was almost transparent.

Example 1 3.3'-dimethylbenzidine (o-Tol)4.
499.4,4'-diaminodiphenyl ether (4
DAPE) 0.22 g (molar ratio 95/5), PM
4.86 g of DA was polymerized by the above-mentioned molding stock solution preparation method to obtain a polyamic acid molding stock solution. ηinh of the solution
was 5.8, indicating that a polyamic acid with a high degree of polymerization was polymerized. Hereinafter, various copolyamic acids were polymerized with various diamine components. The results are shown in Table-1.

Comparative Example 1 A copolyamic acid was obtained according to the method described above using the diamine shown in Table 1, which used PMOA as the acid component and an aromatic diamine substituted with nuclear chlorine as the diamine component. The results are shown in Table 1, and the degree of polymerization was lower than in Example 1.

Copolyamic acid solutions 3 to 7 were wet-dry spun using the above-mentioned spinning method A, and heat-treated using method A and method B, respectively, to obtain 411 tl of copolyimide. The physical property values of the obtained fibers are also listed in Table 2. Compared to the copolyimide fiber of Example 1, the physical properties were clearly inferior. Furthermore, all of the spun threads had poor coagulation properties and were devitrified compared to those of Example 1.

Table *: The degree of polymerization hardly increased Comparative Example 2 For the copolyamic acid of Example 1, spinning method B and heat treatment method A were employed to obtain copolyimide fibers, and the results are shown in Tables 3 to 3. Compared to Example 1, the physical properties were significantly inferior.

Table-3 *: T/M/E: Breaking strength (9/d)/Initial modulus of elasticity (g
/d)/Elongation at break (%) Comparative Example 3 Various homopolyamic acids using the acid component and diamine component used in the present invention were obtained according to the above-mentioned method, and the corresponding polyimide was obtained by spinning method A and heat treatment A method. Obtained fiber. Table 4 shows the intrinsic viscosity and fiber properties of polyamic acid.
It was shown to. A polyamic acid having a high degree of polymerization and a high elastic modulus was obtained, but the elongation was insufficient compared to Example 1.

Comparative Example 4 Using PMDA as the acid component, a copolyamic acid solution with a diamine copolymerization ratio outside the range of the present invention was obtained, and spinning A
Copolyimide fibers were obtained by heat treatment method A, and their physical properties are listed in Table 5. It has become clear that the physical properties decrease as the copolymerization ratio deviates from the range of the present invention. In particular, as the ratio of copolymerized components increased, the coagulability deteriorated and the devitrification phenomenon of the spun yarn became more severe.

Table 5 Table 4 Comparative Example 5 A copolyamic acid solution was produced using a diamine other than those specified in the present invention and PMDA, and subjected to spinning method A and heat treatment A.
A copolyimide fiber was obtained by the method, and its physical properties are listed in Table 6. Compared to Example 1, physical property values with a balanced IflJ were shown.

Corresponding copolyimide fibers were obtained using Process A method. The physical property values are shown in Table-7. The coagulability was further improved, and the physical properties were improved compared to Example 1.

Table 6 Example 3 Pyridine was added to each copolyamic acid solution obtained in Example 1 in an amount of 0.3 units of amic acid, and the resulting solution was used as a molding dope to perform spinning Δ method and thermal patent. Applicant Teijin Ltd.

Claims (1)

[Claims] Substantially formed from the following structural units (I) to (III),
When producing polyimide fiber from a molding dope containing copolyamic acid that also satisfies the following formula A,
A method for producing copolyimide fibers, which comprises discharging the molding dope into an inert atmosphere and then introducing the molding dope into an aqueous coagulation bath. I: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, the bonds between adjacent -COOR and -CO- groups may be switched.) II: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ III: At least one type selected from ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼. However, R is hydrogen or an alkyl group of C_1 to_4, X_1
is C_1 to_2 alkyl group or alkoxy group X_2 is -O-, -SO_2-, -S-, or -CO-, n is 1
An integer between ~2. A: 95/5≧m_2/m_3≧80/20 (in the formula, m
_2 and m_3 are the mole percentages of II and III in the total diamine component constituting the copolyamic acid, respectively. )