JPH02277815A - 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 as an advanced composite material by spinning 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 units of formula I and formula II (R and R' are H or 1-4C alkyl) derived from an aromatic carboxylic acid component and units of formula III and formula IV or V(X1 and X3 are 1-2C alkyl or alkoxy; X2 is H or X1; n is 0-4) derived from an aromatic diamine component and simultaneously satisfying the relationships m1/m2=100/0 to 75/25, m3/m4=100/0 to 70/30 and m2+m4=5 to 30 wherein m1 and m2 are molar percentages of the unit I and unit II in the total constituent units derived from the acid component and m3 and m4 are molar percentages of the unit of formula III and formula IV or V in the total constituent units derived from the diamine component, extruding the dope in an inert atmosphere and introducing the extrudate into an aqueous coagulation bath.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to a novel copolyimide Il fiber obtained from Il111 with excellent heat resistance and mechanical properties, which is useful in the space/aerospace field or the electronic material field. The present invention relates to a manufacturing method.

(Conventional technology) Conventionally, polyimide has excellent heat resistance, mechanical properties, electrical properties,
It is known to be useful as a raw material for materials such as miscellaneous materials, films, and other molded products with excellent weather resistance. 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 fibers, synthetic papers, polyimide films, etc. are used, but with the advancement of advanced materials for space and aircraft applications, they are becoming more heat resistant and more durable. In recent years, materials with mechanical properties such as strength and high modulus have been required.

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, since polyimide is often insoluble and infusible, the general method for manufacturing polyimide is to dry or wet mold a molding dope made of polyamic acid, which is its precursor, and to add polyamic acid during the molding process. A method of ring-closing and 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, rapidly crystallizes during the imidization process due to its rigidity. It has poor stretchability and, as a result, does not exhibit high mechanical properties.

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

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

To give an example regarding 1, the Journal of the Fiber Science Society vol. 1.4ONα
12. As described in T-480-T-487, poly-4,4'-biphenylenepyromellitimide has an initial elastic modulus of 1,000 g/de or more and a strength of 10
! ? It is widely known that fibers with high elastic modulus and high strength such as /de or more cannot be obtained, and at the same time, 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, JP-A-62-117815, etc. disclose copolyimides in which a monomer having a bent chain is partially 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 the precursors of the copolyimide have poor coagulability.

Also, JP-A-61-188127, JP-A-62-
According to Publication No. 79227 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-containing 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, which poses the problem of environmental pollution during combustion and disposal. In addition,
Precursors of these copolyimides 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. but,
According to this publication, as a more preferable embodiment, it is specified that 25 mol% or more of 3,3',4,4'-biphenyltetracarboxylic acid (derivative) having a bent part is used in the acid component, and this composition is suitable for wet processing. It has poor moldability (no mention is made of coagulation during wet molding),
There is also no mention of mechanical properties. Also,
3,3′ −
A copolyimide consisting of a rigid diamine of dimethylbenzidine and a p-phenylenediamine derivative has been proposed, but the composition of the precursor of this copolyimide still has poor coagulability.

As mentioned above, it can be said that all the polyimides mentioned above have not improved the problem 2 at all, that is, they do not exhibit good coagulation properties in an aqueous coagulation bath, which is the easiest to handle.

By the way, in order to improve problem 2, the following method has been proposed.

That is, according to JP-A No. 60-65112, a soluble polyimide containing 3.3', 4,4'-biphenyltetracarboxylic acid (derivative) as the main component is used as the acid component.
A method of coagulating a molding solution comprising the polyimide 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. 6344, amines and/or p were added to the molding solution.
We proposed a method of improving the coagulability of the solution by adding a metal salt of an acid with a Ka of 4.3 or higher. Although this method can provide a stable solution that does not change over time, the molding solution is still a multicomponent system.

As described above, it can be said that there is still no known method for producing polyimide m-fibers that simultaneously solve the above two problems and have excellent mechanical properties.

By the way, the present inventors previously filed Japanese Patent Application No. 63-87312.
In this issue, we proposed a method for producing high-modulus homopolyimide fibers consisting of a polymeric acid derivative) and a rigid diamine. At this time, it was found that polyamic acids using 3,3'-dimethylbenzidine and 3,3'-dimethoxybenzidine as diamine components exhibit good coagulation properties in an aqueous coagulation bath.

In addition, polyimide mlt obtained from the polyamic acid
shows excellent mechanical properties. However, since the polyimide is a homopolymer, it is highly crystalline, and as a result, its elongation is somewhat lacking, and it easily breaks, leaving problems in handling.
It was something.

(Object of the Invention) The object of the present invention is to solve the above-mentioned problems and to produce a copolyimide fiber having excellent heat resistance and mechanical properties, that is, a high modulus of elasticity, a strength of 1:1, and an appropriate elongation. The purpose is to provide a method.

(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 copolyamic acid having a specific chemical structure is a homopolymer even though it is a copolymer. It is possible to obtain polyimide fibers with an equally high modulus of elasticity and moderate elongation.
More surprisingly, it has been found that the copolyamic acid exhibits good coagulation properties in wet molding using an aqueous coagulation bath, and furthermore, in order to obtain fibers with the above properties, it is necessary to The present invention was completed based on the realization that it is essential to improve the orientation.

Thus, according to the present invention, the structural units derived from the aromatic carboxylic acid component are substantially composed of the following (1) and II, and the structural units derived from the aromatic diamine component are substantially the following (6).
and IV, in which 1. The molar percentage of II is significant ml rA2, and the molar percentage of III and IV in the total structural units derived from the diamine component is significant ff13
, 1l14, when manufacturing a polyimide fiber by spinning a molding dope mainly formed from a copolyamic acid that simultaneously satisfies the following formulas <A) to (C), the dope was once discharged into an inert atmosphere. A method for producing copolyimide fibers is provided, which comprises introducing the copolyimide fibers into an aqueous coagulation bath.

At least one selected from:

(A) IL/mz: 100/
O~75/25(B) m3/mA
: 100/0~70/30(C) l
1lz + 1m4: 5-30 Below, the present invention will be explained in detail.

The copolyamic acid used in the present invention essentially contains pyromellitic anhydride (and/or its derivatives>(IA) and 3.3',4.4'-diphenyltetracarboxylic diacid anhydride as acid components). (and/or derivatives thereof)
(IIA>, as the diamine component, the following II[A,
It is synthesized by normal solution polymerization from a rigid diamine (hydrochloride) selected from IVA. Here, "substantially" means that 95 mol% or more of the acid component of the copolyamic acid is the above IA or mA, and 95 mol% or more of the diamine component is the above I[A or rVA. However, if other constituents are included outside of this range, problems such as deterioration of the mechanical properties of the resulting copolyimide may occur, making it impossible to achieve the purpose of the present invention. .

In order to achieve the object of the present invention, it is necessary to further satisfy the above-mentioned copolymer composition.
If A or IV A is used, the elastic modulus decreases, and below the above range, I[A or IV A is used, the elongation decreases. Preferably IJ/12:10
G/0~80/2011a/+14:
100/0~80/20112+14:
When the range of 5 to 20 is satisfied and the mechanical properties of the fibers obtained are more excellent.

In the present invention, in order to provide a polyamic acid with good wet moldability, it is important to use, for example, the following benzidine derivatives as the diamine component mA.

3.3'-Dimethylbenzidine, 3.3'-diethylbenzidine, 3.3',5.5'-tetramethylbenzidine, 3,3'-dimethoxybenzidine.

In addition, diamine component VA used as a copolymerization component
The following can be mentioned:

[p-phenylenediamine derivative] p-phenylenediamine, 2-methyl-〇-phenylenediamine, 2-ethyl-p-phenylenediamine, 2-
Metho-1-cyp-phenylenediamine, 2-ethoxy-p-phenylenediamine, 2,5-dimethyl-p-
phenylenediamine, 2,6-dimethyl-p-phenylenediamine, 2,6-simethoxy〇-phenylenediamine, 2,3,5. -trimethyl-〇-furynylenediamine, 2,3.5-trimethoxy-p-phenylenediamine, 2,3,5.6-tetramethyl-p-phenylenediamine, 2,3゜5.6-tetramethoxy-p -phenylenediamines and their hydrochlorides.

[Diaminobenzanilide derivatives 4.4'-Diaminobenzanilide and their hydrochlorides.

Note that other acid components or diamine components may be used without departing from the scope of the present invention.

Examples of acid components include the following:

[Aromatic diacid anhydride 1 3.3',4.4'-diphenyltetracarboxylic diacid anhydride, 3.3',4.4'-diphenyloxytetracarboxylic diacid anhydride, 3.3 ' , 4.4'
-benzophenonetetracarboxylic diacid anhydride, 3.
3'4.4'-Diphenylsulfonetetracarboxylic acid dianhydride, 3;3',4.4'-diphenylalkylenetetracarboxylic acid dianhydride, 1,4-bis(
3,4-dicarboxyphenoxy)benzenedic acid anhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzenedic acid anhydride, p-phenylene-bis-trimellitate diacid anhydride.

[Tetracarvone II! 2 Derivatives] Diester diacid chlorides of tetracarboxylic acids, diesters of tetracarboxylic acids, and salts of tetracarboxylic acids.

Further, examples of the diamine component include the following.

metaphenylenediamine, 2,4-diaminotoluene,
Diaminodiphenyl ether, diaminobenzophenone, diaminodiphenylsulfone, diaminodiphenyl sulfide, simiamiminodiphenylmethane, 3,3'
-diaminobenzanilide, 2.2-bis(aminophenyl)propane, 1.4bis(aminophenoxy)benzene, 1.3-bis(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 their hydrochlorides.

The copolyamic acid used in the present invention is the acid component IA described above.
, I[A and the diamine component I[[A, IVA 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 (DEAc)
), N,N-dimethylpropionamide (DMPr
), N, N-dimethylbutyramide (NMBA), N,
N-dimethylisobutyramide (NMIB), N-methylcaprolactam (NMC), N,N-dimethylmethoxyacetamide, N-acetylpyrrolidine (NAPr)
, N-acetylpiperidine, N-methylpiperidone-2
(NMPD), N,N'-dimethylethyleneurea,
N,N'-dimethylpropyleneurea, N,N,N'
, N'-tetramethylmalonamide, N-acetylpyrrolidone, N,N,N'N'-tetramethylurea (TM
U), dimethyl sulfoxide (DMSO), hexamethylphosphoramide (1-IMPA).

etc.

Regarding solution polymerization, the usual method used for polymerization of polyamic acid is applied, but as shown in Example 1 below, an NMP solution in which 3,31-dimethylbenzidine and p-phelenediamine were dissolved was used. While maintaining the temperature at -10°C, pyromellitic anhydride was added in an amount approximately equivalent to the above diamine and stirred vigorously, the solution gradually increased in viscosity, and when stirring was continued, a highly viscous solution was obtained, and the intrinsic viscosity was measured. The value was 5.5, confirming that a copolyamic acid with a high degree of polymerization was produced. Intrinsic viscosity (η1n
h) was measured using an Ostwald viscometer at 35°C and 11 degrees in NMP at 0.5 g/d1.
] Calculated using.

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 1152 hydrogen chloride agent such as a tertiary amine may be added.

Next, a method for producing copolyimide fibers with high strength, high elastic modulus, and high elongation using the thus obtained copolyamic acid will be described in detail.

[Preparation of a molding dope] To prepare a molding dope, the polymer concentration of a copolyamic acid solution subjected to solution polymerization is adjusted to a viscosity suitable for molding, 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, since the molding solution made of the copolyamic acid of the present invention exhibits excellent coagulation properties in an aqueous coagulation bath, it can be used as a molding dope as is. previously proposed in Japanese Patent Application No. 63-226344 of adding amines and/or metal salts of weak acids to a polyamic acid solution, or adding a chemical cyclizing agent to a polyamic acid solution to reduce the amount of polyamic acid in the solution. Of course, a method of partially imidizing may also be used.

[$a miscellaneous manufacturing method] As described above, the feature of the manufacturing method of the present invention is that the molecular orientation is enhanced in the initial process of molding, and a high degree of IIi miscellaneous property is finally obtained. This is 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. By doing this, it becomes possible to increase the spinning draft and improve the molecular orientation.
The solidified state of the m-fiber surface becomes denser, and the generation of defects such as voids is suppressed.

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 direction of the fibers. 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.

Although the production method of the present invention can be applied to all polyimide fibers, in particular, 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 a need.

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, Subsequent hot stretching becomes almost impossible, high mechanical properties cannot be expected, and only a fragile yarn 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. Moreover, in polyimide into which bent chains have been introduced, the latent performance itself is deteriorated to begin with, and the effects of the present invention cannot be fully exhibited.

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 molding dope, 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 coagulated thread, it is hot stretched.

(4) The coagulated thread is stretched in air or in an aqueous bath to make it invasive and then hot-stretched.

etc., and there is no problem in implementing it in any way. Basically, performing hot drawing under as high a tension as possible leads to improved physical properties, so it is important to increase the fiber strength before hot drawing, and in this sense, method (4) above is preferable. However, in order to increase the fiber strength to some extent before hot drawing and to pursue a simple process, method (2) 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] This refers to the process of ring-closing imidization of polyamic acid using a dehydrating agent such as acetic anhydride. At this time, a tertiary amine such as pyridine is used as a catalyst to increase the imidization rate. You can also do it. In the imidization of yarn, specifically, after coagulation, the yarn is wound onto a bobbin and then the whole bobbin is immersed in the chemical cyclizing agent mentioned above, or the yarn after coagulation is soaked in the chemical cyclizing agent. By methods such as passing through a bath with
The method is not particularly limited as long as the yarn and the chemical cyclizing agent are brought into contact with each other. The immersion time is from several seconds to 12 hours. In addition, at this time, the present inventors had previously filed Japanese Patent Application No. 62-272342 and Japanese Patent Application No. 63-2.
If the method for promoting imidization of yarn proposed in No. 26344 is used, imidization can be more efficiently progressed.

The copolyimide used in the present invention has improved hot stretchability compared to homopolymers due to the substituent effect of benzidine substituted with alkyl and/or alkoxy nuclei 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 the treatment is carried out under tension at 450 to 650°C, preferably 475 to 600°C.

The IIN obtained as described above exhibits a high elastic modulus even though it is a copolymer, and furthermore has an appropriate elongation.

(Operations and Effects of the Invention) The characteristics of the copolyamic acid used in the present invention are that it achieves a high degree of polymerization that is advantageous in various mechanical properties, and although it is a copolymer, it exhibits a high modulus of elasticity and has an appropriate elongation. It is possible to obtain a copolyimide valt with

Further, by applying the 1II production method of the present invention to the above-mentioned copolyamic acid, it becomes possible to obtain a fiber having excellent mechanical properties, that is, a high modulus of elasticity and yet a suitable elongation.

The polyimide fiber thus obtained is an advanced composite material <A
, C, M, ), etc.

Furthermore, the copolyamic acid used in 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 resulting process will be the simplest one.

(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 1 At least one diamine component is dissolved in 150 d of N-methylpyrrolidone (NMP) dehydrated with molecular sieves in a stream of dry nitrogen, and after externally cooling this amine solution to -10°C, Mellitic acid anhydride (PMOA) or PMDA and 3.3', 4.4' diphenyltetracarboxylic anhydride (DPDA) are added in approximately equivalent amounts of diamine, and a polymerization reaction is carried out under high speed stirring. A portion of the obtained high viscosity copolyamic acid solution was taken out and 0.5 g/l of
Dilute to 1li and measure ηinh.

[Dry-wet spinning (spinning method A)] The copolyamic acid solution obtained as described above was immediately discharged into the air at a discharge rate of 37 FL/min through a nozzle with a hole diameter of 0.35 HR and a number of holes of 12. ! I
After passing through the air layer of M, water/NMP (volume ratio 90
After passing about 3 m through the bath, it was stretched to about twice its size in a stretching bath consisting of water/NMP (volume ratio 95/5), and then taken out into the air and rolled. Wind up at a winding speed of 20m/1n. (Hereinafter, this will be referred to as spinning A.
It's called law. ) [Wet spinning (spinning method B)] All steps are performed in the same manner as in the spinning method A, except that the above copolyamic acid solution is not passed through an air layer. (Hereinafter, this will be referred to as the spinning method B.) [Chemical imidization-heat treatment (heat treatment method A)] The wound yarn is immediately treated with a bobbin of acetic anhydride/pyridine (volume ratio 70/30). After being immersed in a bath for 1 hour to advance imidization, the yarn was washed with water and dried, and then subjected to stepwise heating heat treatment on a plate at 250°C and 450 to 600°C (the optimum value was selected depending on the copolyamic acid used). to obtain copolyimide fibers. On this occasion,
Stretching is performed at a magnification that allows stable winding. (Hereinafter, this will be referred to as heat treatment method A.) [Thermal imidization (heat treatment method B)] In the above-mentioned spinning method A or B, when winding the yarn, it is passed through a hot roller heated to about 100 ° C. 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, stretching is performed at a magnification that allows stable winding to obtain a copolyimide fiber miscellaneous. Hereinafter, this will be referred to as heat treatment method B. ) The tensile properties were measured using Tensilon manufactured by Toyo ■, using a test rod of 100 #III + tensile speed of 50 m/
Measurements were made on yarn at ff1in. There was a maximum difference of about 20% in tensile properties between single yarn and yarn.

Further, the abbreviations of compounds in Examples are as follows.

PMDA: Pyromellitic diacid anhydride DPDA:
From 3,3',4,4'-diphenyltetracarboxylic acid A: 3,3',4,4'-benzophenonetetracarboxylic acid diacid anhydride o-TOL: 3,3'-dimethylbenzidine D
SB: 3.3'-dimethoxybenzidine PP
DA: p-phenylenediamine DMPPDA: 2,5-dimethyl-p-phenylenediamine 4DABA: 4,4'-diaminobenzamide 3
0BZ: 3.3'-dichlorobenzidine 20BZ
: 2.2'-dichlorobenzidine 2CP :2
-Chlor-p-phenylenediamine 250BZ:
2,2',5,5'-tetrachlorobenzidine 3DABA: 3,3'-diaminobenzamide 8
APP: 2,2-bis((4-aminophenoxy)phenyl)propane MPDA: ra-phenylenediamine Example 1 o-TOL 3.97 g, PPDA O, 51 g,
(mole ratio 95/5), 5.10 g of PMDA was polymerized by the above-mentioned method for preparing a molding stock solution to obtain a polyamic acid molding stock solution. The ηinh of the solution was 5.5, and a polyamic acid with a high degree of polymerization was polymerized. Hereinafter, various copolyamic acids were polymerized by changing the acid component and diamine component. The results are shown in Table-1.

Next, this copolyamic acid solution was wet-dry spun using the above-mentioned spinning method A, and heat-treated using methods A and B to obtain copolyimide fibers.

The physical property values of the obtained fibers are shown in Table 2 (the heat treatment temperature was variously changed, and the one that showed the best physical properties was described. The same applies hereinafter). Each fiber has a strength of 15! J/de or more, initial elastic modulus 1200g/de or more, breaking elongation 1.5
% or more, showing excellent physical property values. In addition, the coagulation property during spinning was also good, and the coagulation $l11t was almost transparent.

Wet-dry spinning was performed using Method A, and heat treatment was performed using Method A and Method B to obtain copolyimide I fibers.

The physical property values of the obtained m miscellaneous materials 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.

Comparative Example 1 Various nuclear chlorine-substituted aromatic diamines and PPDA were used as the diamine component, and PMDA was used as the acid component.

A copolyamic acid was polymerized using DPDA according to the method described above. The results are also listed in Table 1, and the degree of polymerization was much lower than in Example 1.

These copolyamic acid solutions 3 to 5 were added to the above-mentioned spinning coating Table-2.
/d)/Elongation at break (%) **: Coagulation is poor and welding between single yarns occurs during chemical imidization, making hot stretching impossible.

Comparative Example 2 For the copolyamic acid of Example 1, spinning method B and heat treatment method A were adopted to create a copolyimide! Obtain IN and show the results in Table-3
It was shown to. Compared to Example 1, the physical properties were significantly inferior.

Table 3 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 corresponding polyimide fibers were obtained by spinning method A and heat treatment method A. Table 4 shows the intrinsic viscosity and lI impurity properties of polyamic acid. A polyamic acid with a high degree of polymerization is obtained,
Although a fiber having a high elastic modulus was obtained, the elongation was insufficient compared to Example 1.

Table 4 Comparative Example 4 A copolyamic acid solution was obtained in which the copolymerization ratio of the acid component and the diamine component was outside the range of the present invention, and copolyimide fibers were obtained by spinning method A and heat treatment method A, and the physical properties are shown. -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.

Comparative Example 5 A copolyamic acid solution was produced using an acid component or a diamine component other than those specified in the present invention, and a copolyamic acid solution was prepared using 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 were unbalanced.

Example 2 Pyridine was added to each of the copolyamic acid solutions obtained in Example 1 at 0.3 parts per amic acid unit, and the resulting solution was used as a molding dope to perform spinning method A and heat treatment method A. Corresponding copolyimide fibers were obtained. 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-7

Claims (1)

[Scope of Claims] A copolyamic acid in which the structural units derived from the aromatic carboxylic acid component consist of the following I and II, and the structural units derived from the aromatic diamine component consist of the following III and IV. The mole percentages of I and II in the total structural units derived from the acid component, m_1 and m_2, respectively, and the molar percentages of III and IV, respectively, in the total structural units derived from the diamine component, m_3 and m_4, are as follows. When producing polyimide fibers by spinning a forming dope mainly formed from a copolyamic acid that satisfies formulas (A) to (C) at the same time, the dope is once discharged into an inert atmosphere, and then an aqueous coagulation bath is applied. 1. A method for producing copolyimide fibers, which comprises introducing copolyimide fibers into a copolyimide fiber. I: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, the bonds between adjacent -COOR and -CO- groups may be reversed.) II:▲There are mathematical formulas, chemical formulas, tables, etc.▼ ( However, the bonds between the adjacent -COOR' and -CO- groups may be reversed.) III: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ IV:▲There are mathematical formulas, chemical formulas, tables, etc.▼ At least one type selected from ▲mathematical formulas, chemical formulas, tables, etc.▼. [In the formula, R and R' are each hydrogen or an alkyl group having 1 to 4 carbon atoms, X_1 and X_3 are an alkyl group or an alkoxy group having 1 to 2 carbon atoms, X_2 is hydrogen or X_1, and n is 0 to
Indicates an integer of 4. ] (A) m_1/m_2: 100/0 to 75/25 (B)
m_3/m_4: 100/0 to 70/30 (C) m_2
+m_4:5~30