JPH0429771B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing aromatic heterocyclic polyimide fiber. Specifically, the present invention relates to a method for producing a novel aromatic heterocyclic polyimide fiber containing a benzobisazole skeleton in the main chain, which has a high modulus of elasticity and excellent heat resistance. (Prior Art) Aromatic heterocyclic polymers are expected to be materials with high strength, high elastic modulus, and high heat resistance, but polymers other than polyimide and polybenzimidazole are still at the research stage. Among them, poly-p-phenylenebenzobisthiazole (PBT), which is said to produce high modulus fibers, is produced by combining 2,5-diaminobenzene-1,4-dithiol dihydrochloride and terephthalic acid in polyphosphoric acid. It is a rigid linear polymer obtained by long-term reaction at high temperatures of 160 to 200°C, and has more than twice the strength of poly-p-phenylene terephthalamide (PPTA) (Kevlar), a type of wholly aromatic polyamide. Gives tensile modulus (310GPa). However, PBT is insoluble in solvents other than strong acids such as methanesulfonic acid and chlorosulfonic acid, and furthermore, such solvents are highly corrosive to equipment, which is also an obvious industrial disadvantage. (Problems to be Solved by the Present Invention) An object of the present invention is to produce fibers having a high elastic modulus and excellent heat resistance without using such highly corrosive solvents. (Means for Solving the Problems) That is, the present invention provides a method for producing polyimide fibers from an aromatic heterocyclic polyimide containing the following benzobisazole skeleton in the main chain. The gist of the present invention is a method for producing aromatic heterocyclic polyimide fibers, which is characterized by performing tension heat treatment at a final heat treatment temperature of 420 to 550°C while applying a tension of 1000 MPa. Aromatic heterocyclic polyimide containing a benzobisazole skeleton: The total amount of each of the structural units selected from Group A and Group O is substantially equivalent, and the structure () shown below in Group A is 30 to 100 moles. %, the structure () is 70 to 0 mol%, and the structure () is 70 to 100 mol% in the O group,
Structure () and/or () has a structure of 30 to 0 mol%. Group A: N-Ar ₁ -N () Otsu group: (In the formula, X represents S, O or NH, and Ar ¹
teeth

【formula】

【formula】

[Formula] or , and Ar ² is

[Formula], Y, Y ¹ , Y ² and Y ³ represent H, an alkyl group, an alkoxy group or a halogen atom, and Z, Z ¹ and Z ² are a single bond, -O-, -CH _2- , -S-,

[Formula] −SO ₂ −,

[Formula] or

Represents [formula]. ) Specific examples of monomers necessary for producing the polymer of the present invention include the following compounds. That is, as aromatic diamines, 2,6-(4,4'-diamino-diphenyl)benzo[1,2-d:4,5-d']bisthiazole, 2,6- (4,4'-diamino-diphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(4,4'-diamino-
diphenyl)benzo[1,2-d:4,5-d']
Bisimidazole, giving structure (), m- and p-phenylenediamine, 2,5-diaminotoluene, 4,4'- and 3,3'-diaminodiphenyl ether, 4,4'- and 3,3 '-Diaminodiphenylmethane, 4,4'- and 3,3'-thiodianiline, 4,4'- and 3,3'-diaminobiphenyl, 4,4'- and 3,3'-diaminodiphenyl sulfone , bis(4-aminophenyl)isopropane, bis-(4-aminophenyl)bis(trifluoromethyl)methane, 4,4'-diaminobenzophenone, 4,4'-methylenebis-(o
-chloroaniline), 4,4'-methylenebis-(3
-methylaniline), 4,4'-methylenebis-(2
-methoxyaniline), 4,4'-methylenebis-
(2-methylaniline), 4,4'-oxybis-
(2-methoxyaniline), 4,4'-oxybis-
(2-chloroaniline), 4,4'-thiobis-(2
-methylaniline), 4,4'-thiobis-(2-methoxyaniline), 4,4'-thiobis-(2-chloroaniline), 4,4'-sulfonylbis-(2-methylaniline), 4, 4′-sulfonylbis-(2-
ethoxyaniline), 4,4'-sulfonylbis-
(2-chloroaniline), 3,3-dimethyl-4,
4'-Diaminobenzophenone, 3,3'-dimethoxy-4,4'-diaminobenzophenone, 3,3'-
dichloro-4,4'-diaminobenzophenone,
3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 3,3'-dichlorobenzidine,
2,2'-bis[4-(4-aminophenoxy)phenyl]propane, bis[4-(4-aminophenoxy)phenyl]sulfone, 1,4bis(4-
aminophenoxy)benzene, 1,3-bis(4
-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, and the like. In addition, aromatic tetracarboxylic dianhydrides include pyromellitic anhydride, which gives structure (), and structure ().
3,4,3',4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenyltetracarboxylic dianhydride, 2,2',3,
3'-diphenyltetracarboxylic dianhydride, 2,
2'-bis(3,4-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)bis(trifluoromethyl)methane dianhydride, bis(3,4-dicarboxyphenyl) enyl) sulfone dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, etc.
In addition, trimellitic anhydride, trimellitic anhydride chloride and the like can be mentioned as those giving the structure (). Amide solvents used in polymerization include N-methyl-2-pyrrolidone (MMP), 1,3-dimethyl-2-imidazolinone (DMI), N,N'-dimethylformamide (DMF), N,N' Examples include -dimethylacetamide (DMAc), hexamethylphosphortriamide (HMPA), and mixed solvents thereof. A polyamic acid solution is obtained by reacting the aromatic diamine with the aromatic carboxylic acid derivative in the amide solvent described above. The present invention focuses on the fact that polyimide is produced using polyamic acid as its precursor. The polyimide acids used in the present invention are aromatic diamines, aromatic tetracarboxylic acid anhydrides and/or aromatic dicarboxylic acid anhydrides, and monocarboxylic acids having the structures shown in Group A and Group B above in amide solvents. However, since they all have more flexibility in the final polyimide structure, they have lower solubility in polar organic solvents such as amide solvents. Excellent,
A fibrous material can be spun very easily from such a solution. In the present invention, having such a specific structure,
Polyimide fibers with high elastic modulus and excellent heat resistance are produced by amidating polyamic acid spun fibers and subjecting them to specific treatments. That is, when subjecting the spun fibers to tension heating heat treatment, the final heat treatment temperature is set at 420 to 550°C while applying a tension of 10 to 1000 MPa, preferably 50 to 700 MPa.
Preferably, the temperature is maintained at 480 to 510°C. In the method of the present invention, such tension treatment and heat treatment are essential to each other, and if either one of them is not satisfied, the object of the present invention cannot be achieved. That is, it is essential for the tension to exceed 10 MPa and the heat treatment temperature to exceed 420°C to obtain a high modulus fiber. However, applying tension exceeding 1000MPa to fibers may cause yarn breakage during heat treatment, and
Heat treatment at temperatures exceeding 550°C causes significant thermal deterioration of the fibers. As a method for obtaining spun fibers, a known wet spinning method can be mentioned. Thereafter, imide ring closure is carried out, and the method may be to dry the fiber obtained by spinning it in a coagulation bath, remove the solvent, and combine it under the above treatment conditions, or to perform imide ring closure. - Spinning and imide ring-closing may be carried out simultaneously by coexisting an imide ring-closing reagent such as pyridine in the coagulation bath or coagulation bath. (Examples) The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples. Polymerization of polyamic acid was carried out at room temperature under a nitrogen stream. Further, the logarithmic viscosity ηinh of the polyamic acid was measured at 30°C after diluting with N-methyl-2-pyrrolidone so that the polymer concentration was 0.2 g/dl. In addition, 2,6-(4,4'-diamino-diphenyl)
benzo[1,2-d:4,5-d']bisthiazole with DAPBT, pyromellitic dianhydride with
PMDA, N-methyl-2-pyrrolidone, NMP,
1,3-dimethyl-2-imidazolidinone
Abbreviated as DMI. Reference Example 1 4.494 g (12 mmol) of DAPBT was slurried in 45 ml of NMP. To this slurry, 2.592 g (11.6 mmol) of PMDA powder was added together with 20 ml of NMP to initiate polymerization. The solution gradually became viscous and homogeneous. 7 hours after the start of polymerization,
A polyamic acid solution with ηinh of 3.2 dl/g was obtained. Examples 1 to 5 The polyamic acid solution obtained in Reference Example 1 was poured into acetic anhydride/pyridine=70/30 through a 0.5φ single-hole nozzle.
It was spun into a coagulation bath consisting of (volume ratio). Further, the fibers were immersed in a solution of the same composition for a day and night to chemically close the ring and obtain polyimide fibers. Next, this fiber was transferred to toluene and immersed for 3 hours, and then dried at room temperature while being stretched 1.5 times.
The fiber diameter at this point was 160μ. The fibers were subjected to the heat treatment shown below while applying a constant load. 100℃ for 10 seconds, 160℃ for 10 seconds, 200℃ for 10 seconds, 250
℃ for 10 seconds, 350℃ for 10 seconds, 400℃ for 10 seconds, 500℃
10 seconds. The dynamic elastic modulus of the polyimide fiber obtained in this way was measured using Viblon, manufactured by Toyo Baldwin Co., Ltd.
Measured with a DOV type device. The results obtained are shown in Table 1. Note that the tension in Table 1 was calculated from the load and the final fiber diameter.

[Table] Comparative Example 1 Polyimide fibers were obtained in the same manner as in Example 1 except that no tension was applied. The final fiber diameter of this fiber was 140μ. The dynamic elastic modulus was 60GPa. Comparative Example 2 During the heat treatment process in Examples 1 to 5,
Polyimide fibers were obtained in the same manner as in Examples 1 to 5, except that the maximum heat treatment temperature was kept at 400° C., and the heat treatment was performed while applying the same load. However, all of the obtained fibers were brittle, and it was not possible to measure their elastic modulus. (Effects of the Invention) According to the method of the present invention, an aromatic heterocyclic polyimide fiber having a high elastic modulus and excellent heat resistance can be obtained.

Claims (1)

[Claims] 1. When producing polyimide fiber from an aromatic heterocyclic polyimide containing the following benzobisazole skeleton in the main chain,
The final heat treatment temperature was adjusted while applying a tension of 1000MPa.
A method for producing aromatic heterocyclic polyimide fiber, characterized by subjecting it to tension heat treatment at 420 to 550°C. Aromatic heterocyclic polyimide containing a benzobisazole skeleton: The total amount of each of the structural units selected from Group A and Group O is substantially equivalent, and the structure () shown below in Group A is 30 to 100 moles. %, the structure () is 70 to 0 mol%, and the structure () is 70 to 100 mol% in the O group,
Structure () and/or () has a structure of 30 to 0 mol%. Group A: N-Ar ¹ -N () Otsu group: (In the formula, X represents S, O or NH, and Ar ¹
is [expression] [expression] [expression] or , Ar ² represents [Formula], Y, Y ¹ , Y ² and Y ³ represent H, an alkyl group, an alkoxy group or a halogen atom, and Z, Z ¹ and Z ² are single bonds, -O-, -CH ₂ -, -S-, [Formula] -SO ₂ -, [Formula] or [Formula]. )