A meta-aramid / mica composite fiber and its preparation method

Abstract

A meta-aramid / mica composite fiber and its preparation method of the present invention. First, mica powder and an aqueous solution of hydroxyethyl cellulose are ball-milled, then deionized water is added for secondary ball-milling. After washing the ball-milled product, it is dried and dispersed in deionized water to form a dispersion with a mass percentage of 0.05%-0.5%. After homogenization, it is centrifuged and washed; the obtained mica nanosheet / water dispersion is washed, then N-methylpyrrolidone is added to remove the excess deionized water. Under an anaerobic environment, CaCl2 is dissolved in the obtained nano-mica sheet / NMP dispersion, and the same molar amount of m-phenylenediamine and isophthaloyl chloride are added for in-situ polycondensation reaction at 0-5°C for 60-90 minutes to obtain a reaction solution; the reaction solution is defoamed under vacuum, then spun, solidified, washed, dried and wound up to obtain the meta-aramid / mica composite fiber, which greatly improves the mechanical properties, insulation properties and heat resistance of the meta-aramid fiber.

Description

Technical Field

[0001] The present invention relates to the field of modification of meta-aramid fibers, and specifically to a meta-aramid / mica composite fiber and a preparation method thereof. Background Art

[0002] Meta-aramid is the fastest-growing and high-value-added military and civilian dual-use special chemical fiber among organic high-temperature-resistant fibers in the world at present. It has excellent thermal stability, flame retardancy, electrical insulation and radiation resistance, and is an important basic material in the fields of aviation, aerospace, national defense, environmental protection, chemical industry and ocean development. At present, there have been significant developments in both the production scale and production technology of meta-aramid globally, and low cost, high performance and differentiation will become the main development directions in the future.

[0003] In recent years, the single fiber breaking strength index of meta-aramid has received increasing attention. Higher requirements for the single fiber breaking strength of meta-aramid have been put forward in both the flame retardant protection field and the high-temperature filtration field. However, the current breaking strength of meta-aramid is insufficient, thus unable to improve the durability and tear resistance of meta-aramid products, etc.

[0004] Meta-aramid, namely poly(m-phenylene isophthalamide), can be synthesized by low-temperature polycondensation of m-phenylenediamine and m-phthaloyl chloride in a dimethylacetamide (DMAc) / LiCl system, and is a regularly arranged zigzag macromolecule. At present, the breaking strength of meta-aramid fibers is mainly improved by improving the spinning process, but the improvement amplitude is limited, and the durability and tear resistance of meta-aramid products, etc. still cannot be improved. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a meta-aramid / mica composite fiber and a preparation method thereof, which greatly improve the mechanical properties, insulation properties and heat resistance of meta-aramid fibers without affecting their flexibility and processability.

[0006] The present invention is realized through the following technical solutions:

[0007] A preparation method of a meta-aramid / mica composite fiber includes the following steps:

[0008] S1, first perform primary ball milling on mica powder and an aqueous solution of hydroxyethyl cellulose, then add deionized water for secondary ball milling, wash the ball-milled product and dry it, then disperse it with deionized water into a dispersion with a mass percentage of 0.05%-0.5%, homogenize it under a pressure of 50-150 MPa, and finally perform centrifugal washing to obtain a mica nanosheet / water dispersion;

[0009] S2. Wash the mica nanosheet / water dispersion, then add N-methylpyrrolidone. After removing the excess deionized water, a nano mica sheet / NMP dispersion is obtained. Under an anaerobic environment, dissolve CaCl2 in the nano mica sheet / NMP dispersion, and then add the same molar amount of m-phenylenediamine and isophthaloyl chloride to carry out an in-situ polycondensation reaction at 0-5°C for 60-90 min. The ratio of m-phenylenediamine to the mica powder in S1 is 0.02 mol:(0.25-1) g to obtain a reaction solution.

[0010] S3. After vacuum defoaming the reaction solution, carry out melt spinning, coagulation, washing, drying and winding and coiling in sequence to obtain meta-aramid / mica composite fibers.

[0011] Preferably, the mass percentage of the hydroxyethyl cellulose aqueous solution in S1 is 1%-20%, and the ratio of the hydroxyethyl cellulose aqueous solution to the mica powder is (5-60) mL:(0.25-1) g.

[0012] Furthermore, the particle size of the mica powder in S1 is 10-50 μm, the ball-to-material ratio during the first ball milling is (50-150):1, and the first ball milling is carried out for 12-48 h.

[0013] The ratio of deionized water to the mica powder in the first ball milling during the secondary ball milling is (30-100) mL:(0.25-1) g, and the secondary ball milling is carried out for 3-6 h.

[0014] Preferably, the homogenization in S1 is carried out 40-100 times, and finally centrifuged at 5000-6000 rpm for 10-15 min to remove the supernatant to obtain a mica nanosheet / water dispersion.

[0015] Preferably, in S2, the mica nanosheet / water dispersion is centrifugally washed successively with deionized water, N,N-dimethylformamide, acetone, ethanol, isopropanol and N-methylpyrrolidone, and then N-methylpyrrolidone is added.

[0016] Furthermore, after adding N-methylpyrrolidone in S2, add a molecular sieve dried at 400-600°C and let it stand for 12-18 h to obtain a nano mica sheet / NMP dispersion.

[0017] Preferably, in S2, heat the nano mica sheet / NMP dispersion to 100-120°C under an anaerobic environment, add CaCl2 and stir for 30-60 min. The ratio of CaCl2 to the nano mica sheet / NMP dispersion is (5-10) g:100 mL, and then add m-phenylenediamine and isophthaloyl chloride.

[0018] Further, after cooling the nano-mica sheet / NMP dispersion solution dissolved with CaCl2 to 0-5°C in S2, m-phenylenediamine is first added and stirred at 300-500 rpm, and then isophthaloyl chloride is added at 1500-2000 rpm to carry out the in-situ polycondensation reaction.

[0019] Preferably, the coagulation in S3 is carried out successively in a primary coagulation bath at 75-85°C and a secondary coagulation bath at 85-90°C. Both the primary coagulation bath and the secondary coagulation bath are water and N-methylpyrrolidone. The mass ratio of water to N-methylpyrrolidone in the primary coagulation bath is 1:1, and the mass ratio of water to N-methylpyrrolidone in the secondary coagulation bath is 4:1.

[0020] A meta-aramid / mica composite fiber obtained by the preparation method of the meta-aramid / mica composite fiber described in any one of the above.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] In the preparation method of a meta-aramid / mica composite fiber of the present invention, first, during the ball milling process of mica powder with an aqueous solution of hydroxyethyl cellulose and deionized water, the mica powder is exfoliated, and then is micronized and homogenized by homogenization in deionized water to obtain a dispersion solution containing ultra-thin mica nanosheets. Then, after washing and adding the solvent NMP, m-phenylenediamine and isophthaloyl chloride are added to the nano-mica sheet / NMP dispersion solution for in-situ polymerization reaction. The ultra-thin mica nanosheets can be introduced into the meta-aramid fibers, and the mica sheets can induce the molecular chain orientation crystallization of poly(m-phenylene isophthalamide), thereby greatly improving the mechanical properties, insulation properties and heat resistance of the aramid fibers, and not affecting their flexibility and processability. Furthermore, it can solve the problems that the breaking strength of the current meta-aramid is insufficient and the durability and tear resistance of meta-aramid products cannot be improved, and has a wide application prospect. Description of the Drawings

[0023] Figure 1 It is a process flow chart of the preparation of the meta-aramid / mica composite fiber described in the present invention.

[0024] Figure 2 It is a mechanical property diagram of pure meta-aramid fiber and the meta-aramid / mica composite fiber obtained in Example 1 of the present invention.

[0025] Figure 3 It is an insulation property diagram of pure meta-aramid fiber.

[0026] Figure 4 It is an insulation property diagram of the meta-aramid / mica composite fiber obtained in Example 1 of the present invention.

[0027] Figure 5It is a graph showing the temperature resistance performance of pure meta-aramid fiber and the meta-aramid / mica composite fiber obtained in Example 1 of the present invention.

[0028] Figure 6 It is a physical picture of the meta-aramid / mica composite fiber obtained in Example 1 of the present invention. Detailed implementation manners

[0029] The following further elaborates on the present invention in detail with specific examples, which are explanations of the present invention rather than limitations.

[0030] A preparation method of a meta-aramid / mica composite fiber of the present invention is as Figure 1 shown, and the specific steps are as follows:

[0031] Step 1, preparation of nano mica flakes:

[0032] Add a certain mass of mica powder (particle size 10 - 50 μm, 0.25 - 1 g) into an aqueous solution of hydroxyethyl cellulose (HEC) (mass percentage 1 - 20%, 5 - 60 mL), and ball mill in a planetary ball mill for 12 - 48 h, where the ball-to-material ratio is (50 - 150):1. Then add a certain amount of deionized water (30 - 100 mL) for secondary ball milling (3 - 6 h). After ball milling, the obtained product is centrifugally washed with deionized water 3 - 5 times, the supernatant is removed, and the product I is obtained by drying.

[0033] Disperse product I with deionized water to a dispersion with a mass percentage of 0.05 - 0.5%, then homogenize with a high-pressure homogenizer at a pressure of 50 - 150 MPa for 40 - 100 times, and then centrifuge at 5000 - 6000 rpm for 10 - 15 min, and remove the supernatant to obtain a mica nanosheet / water dispersion.

[0034] Step 2, preparation of nano mica flake / N-methylpyrrolidone (NMP) dispersion:

[0035] Centrifugally wash the mica nanosheet / water dispersion with deionized water (that is, first centrifuge and pour out the supernatant, and then filter until there is no deionized water visually), and then successively centrifuge and wash with N,N-dimethylformamide (DMF), acetone, ethanol, isopropanol, and NMP 3 - 5 times. The specific centrifugal washing operation of each of these 5 reagents is the same as that of deionized water. Finally, add NMP for dispersion, add molecular sieves dried at 400 - 600 °C, and let stand for 12 - 18 h to remove the excess deionized water to obtain a nano mica flake / NMP dispersion.

[0036] Step 3, preparation of meta-aramid / nano mica flakes:

[0037] Add 100 mL of the nano-mica sheet / NMP dispersion into a flask under N₂ protection and heat it to 100 - 120 °C. Add 5 - 10 g of CaCl₂ and stir for 30 - 60 min until it is completely dissolved. Then, cool the system to 0 - 5 °C, add m-phenylenediamine, stir it at 300 - 500 rpm until it is dissolved, and then add isophthaloyl chloride under the condition of 1500 - 2000 rpm. Both m-phenylenediamine and isophthaloyl chloride are 0.02 mol. Conduct an in-situ polymerization reaction at 0 - 5 °C for 60 - 90 minutes. At this time, the Weissenberg effect will appear. After the reaction ends, a mixed solution with uniformly dispersed poly(m-phenylene isophthalamide) (PMIA) and nano-mica sheets is obtained.

[0038] Step 4, prepare meta-aramid / mica composite fibers by wet spinning:

[0039] The obtained mixed solution with uniformly dispersed PMIA and nano-mica sheets is defoamed under vacuum and then transported to a spinneret for spinning. After that, it is injected into a primary coagulation bath (with water and N-methylpyrrolidone each accounting for 50% by mass) at a bath temperature of 75 - 85 °C to obtain nascent fibers. Then, in a secondary coagulation bath (with water accounting for 80% by mass and N-methylpyrrolidone accounting for 20% by mass) at a bath temperature of 85 - 90 °C, after washing and drying, the original fibers are obtained. Finally, they are automatically wound and collected to obtain meta-aramid / mica composite fibers.

[0040] Example 1:

[0041] A preparation method of a meta-aramid / mica composite fiber according to the present invention comprises the following specific steps:

[0042] Step 1, preparation of nano-mica sheets:

[0043] Add 0.25 g of mica powder with a particle size of 10 μm into 5 mL of a 1% (by mass) hydroxyethyl cellulose (HEC) solution and ball-mill it in a planetary ball mill for 12 h with a ball-to-material ratio of 50:1. Then, add 30 mL of deionized water and ball-mill for 3 h. After the ball-milling ends, wash the obtained product 4 times by centrifugation with deionized water, remove the supernatant, and dry to obtain product I.

[0044] Disperse product I with deionized water to a dispersion with a mass percentage of 0.05%. Then, use a high-pressure homogenizer to homogenize it 40 times at a pressure of 50 MPa, centrifuge it at 5500 rpm for 12 min, and remove the supernatant to obtain a mica nano-sheet / water dispersion.

[0045] Step 2, preparation of nano-mica sheet / N-methylpyrrolidone (NMP) dispersion:

[0046] The mica nanosheets / water dispersion was centrifuged and washed with deionized water, and then centrifuged and washed 4 times successively with N,N-dimethylformamide (DMF), acetone, ethanol, isopropanol, and NMP. NMP was added, and molecular sieves dried at 400 °C were added, followed by standing for 15 h to obtain a nanoscale mica sheet / NMP dispersion.

[0047] Step 3, Preparation of meta-aramid / nano mica sheets:

[0048] 100 mL of the nanoscale mica sheet / NMP dispersion was added to a flask under N2 protection and heated to 100 °C. 5 g of CaCl2 was added and stirred for 30 min to completely dissolve it. Then, after cooling the system to 0 °C, 0.02 mol of m-phenylenediamine was added and stirred at 400 rpm to dissolve it. Subsequently, 0.02 mol of isophthaloyl chloride was added under the condition of 2000 rpm, and in-situ polymerization reaction was still carried out at 4 °C for 70 minutes. At this time, the Weissenberg effect would occur, and after the reaction ended, a mixed solution in which poly(m-phenylene isophthalamide) (PMIA) and nano mica sheets were uniformly dispersed was obtained.

[0049] Step 4, Preparation of meta-aramid / mica composite fibers by wet spinning:

[0050] The obtained mixed solution in which PMIA and nano mica sheets were uniformly dispersed was subjected to vacuum defoaming treatment and then transported to a spinneret, and injected into a primary coagulation bath (with water and N-methylpyrrolidone each accounting for 50% by mass) with a bath temperature of 80 °C to obtain nascent fibers. Then, in a secondary coagulation bath (with water accounting for 80% by mass and N-methylpyrrolidone accounting for 20% by mass) with a bath temperature of 88 °C, after washing and drying, precursor fibers were obtained. Finally, they were automatically wound and collected to obtain meta-aramid / mica composite fibers.

[0051] Example 2:

[0052] A method for preparing meta-aramid / mica composite fibers according to the present invention comprises the following specific steps:

[0053] Step 1, Preparation of nano mica sheets:

[0054] 1 g of mica powder with a particle size of 50 μm was added to 60 mL of a 20% (by mass) hydroxyethyl cellulose (HEC) solution and ball-milled in a planetary ball mill for 48 h with a ball-to-material ratio of 150:1. Then, 100 mL of deionized water was added and ball-milled for 6 h. After the ball milling was completed, the obtained product was centrifuged and washed 4 times with deionized water, the supernatant was removed, and the product I was obtained after drying.

[0055] Product I was dispersed in deionized water to a dispersion with a mass percentage of 0.5%, and then homogenized 100 times under a pressure of 150 MPa using a high-pressure homogenizer, centrifuged at 5500 rpm for 12 min, and the supernatant was removed to obtain a mica nanosheet / water dispersion.

[0056] Step 2, Preparation of nano-mica flakes / N-methylpyrrolidone (NMP) dispersion:

[0057] Centrifuge and wash the mica nano-flakes / water dispersion with deionized water, and then centrifuge and wash it successively with N,N-dimethylformamide (DMF), acetone, ethanol, isopropanol, and NMP four times. Add NMP, add molecular sieve dried at 600 °C, and let it stand for 15 h to obtain the nano-mica flakes / NMP dispersion.

[0058] Step 3, Preparation of meta-aramid / nano-mica flakes:

[0059] Add 100 mL of the nano-mica flakes / NMP dispersion to a flask under N2 protection and heat it to 120 °C. Add 10 g of CaCl2 and stir for 60 min until it is completely dissolved. Then, cool the system to 0 °C, add 0.02 mol of m-phenylenediamine, stir at 400 rpm until it is dissolved, and then add 0.02 mol of isophthaloyl chloride at 2000 rpm. Still carry out in-situ polymerization reaction at 2 °C for 90 minutes. At this time, the Weissenberg effect will appear. After the reaction is completed, a mixed solution in which poly(m-phenylene isophthalamide) (PMIA) and nano-mica flakes are uniformly dispersed is obtained.

[0060] Step 4, Preparation of meta-aramid / mica composite fiber by wet spinning:

[0061] The obtained mixed solution in which PMIA and nano-mica flakes are uniformly dispersed is subjected to vacuum defoaming treatment and then transported to a spinneret, and injected into a primary coagulation bath (water and N-methylpyrrolidone each account for 50% by mass) with a bath temperature of 80 °C to obtain nascent fibers. Then, in a secondary coagulation bath (water accounts for 80% by mass, N-methylpyrrolidone accounts for 20% by mass) with a bath temperature of 88 °C, after washing and drying, the original fibers are obtained. Finally, they are automatically wound and collected to obtain meta-aramid / mica composite fibers.

[0062] Example 3:

[0063] A method for preparing a meta-aramid / mica composite fiber according to the present invention specifically comprises the following steps:

[0064] Step 1, Preparation of nano-mica flakes:

[0065] Add 0.375 g of mica powder with a particle size of 25 μm to 30 mL of a 10% (by mass) hydroxyethyl cellulose (HEC) solution and ball mill it in a planetary ball mill for 30 h with a ball-to-material ratio of 100:1. Then add 65 mL of deionized water and ball mill it for 4.5 h. After the ball milling is completed, centrifuge and wash the obtained product with deionized water four times, remove the supernatant, and dry it to obtain product I.

[0066] The product I was dispersed in deionized water to form a dispersion with a mass percentage of 0.275%, and then homogenized 70 times at a pressure of 100 MPa using a high-pressure homogenizer, centrifuged at 5500 rpm for 12 min, and the supernatant was removed to obtain a mica nanosheet / water dispersion.

[0067] Step 2, Preparation of nano mica sheet / N-methylpyrrolidone (NMP) dispersion:

[0068] The mica nanosheet / water dispersion was centrifuged and washed with deionized water, and then successively centrifuged and washed 4 times with N,N-dimethylformamide (DMF), acetone, ethanol, isopropanol, and NMP. NMP was added, and molecular sieves dried at 500 °C were added, and the mixture was allowed to stand for 18 h to obtain a nano mica sheet / NMP dispersion.

[0069] Step 3, Preparation of meta-aramid / nano mica sheet:

[0070] 100 mL of the nano mica sheet / NMP dispersion was added to a flask under N2 protection and heated to 110 °C, and 7.5 g of CaCl2 was added and stirred for 45 min to completely dissolve it. Then, after the system was cooled to 0 °C, 0.02 mol of m-phenylenediamine was added and stirred at 400 rpm to dissolve it, and then 0.02 mol of isophthaloyl chloride was added under the condition of 2000 rpm, and the in-situ polymerization reaction was still carried out at 5 °C for 60 minutes. At this time, the Weissenberg effect would appear, and the reaction ended to obtain a mixed solution in which poly(m-phenylene isophthalamide) (PMIA) and nano mica sheets were uniformly dispersed.

[0071] Step 4, Preparation of meta-aramid / mica composite fiber by wet spinning:

[0072] The obtained mixed solution in which PMIA and nano mica sheets were uniformly dispersed was subjected to vacuum defoaming treatment and then transported to a spinneret plate and injected into a primary coagulation bath (with water and N-methylpyrrolidone each accounting for 50% by mass) at a bath temperature of 80 °C to obtain nascent fibers. Then, in a secondary coagulation bath (with water accounting for 80% by mass and N-methylpyrrolidone accounting for 20% by mass) at a bath temperature of 88 °C, they were washed and dried to obtain precursor fibers, and finally automatically wound and collected to obtain meta-aramid / mica composite fibers.

[0073] Figure 2It is the mechanical property diagram of pure meta-aramid fiber and meta-aramid / mica composite fiber. It can be seen that the mechanical strength of pure meta-aramid fiber (by replacing the dispersion liquid II in step 3 of Example 1 with N-methylpyrrolidone and then obtaining it according to the same steps) can reach 429 Mpa. The mechanical strength of meta-aramid fiber after mica doping can reach 717 MPa, and the mechanical strength of meta-aramid fiber after mica doping is enhanced by 67%. The elongation at break of pure meta-aramid fiber can reach 27%, and the elongation at break of meta-aramid fiber after mica doping can reach 30%, with the elongation at break increasing by 11%. Therefore, mica doping can improve the mechanical properties of meta-aramid fiber.

[0074] Figure 3 and Figure 4 They are the insulation property diagrams of each pure meta-aramid fiber and meta-aramid / mica composite fiber respectively, where the maximum probability value is taken by parallel testing 10 times. It can be seen from the figure that the electrical breakdown strength of pure meta-aramid fiber paper can reach 18.73 kV / mm, and the electrical breakdown strength of meta-aramid fiber after mica doping can reach 29.08 kV / mm. The electrical breakdown strength of meta-aramid fiber after mica doping is enhanced by 55.3%. Therefore, mica doping can improve the insulation properties of meta-aramid fiber.

[0075] Figure 5 It is the heat resistance property of pure meta-aramid fiber and meta-aramid / mica composite fiber. It can be seen that the highest decomposition temperature of pure meta-aramid fiber can reach 472 °C, and the remaining mass accounts for 48.0% of the initial mass. The highest decomposition temperature of meta-aramid fiber after mica doping can reach 504 °C, and the remaining mass accounts for 43.5% of the initial mass. Therefore, mica doping can improve the heat resistance property of meta-aramid fiber.

[0076] Figure 6 It is the physical diagram of the flexibility of meta-aramid / mica composite fiber. It can be seen that the fiber can still be folded and curled after adding mica, without affecting the processing performance of the fiber.

Claims

1. A preparation method of meta-aramid / mica composite fiber, characterized in that It includes the following steps: S1. First, conduct the first ball milling on mica powder and hydroxyethyl cellulose aqueous solution, then add deionized water for secondary ball milling. After washing and drying the ball milling product, disperse it with deionized water into a dispersion with a mass percentage of 0.05%-0.5%, homogenize it under a pressure of 50-150 MPa, and finally centrifuge and wash to obtain mica nanosheet / water dispersion; S2. Wash the mica nanosheet / water dispersion, then add N-methylpyrrolidone. After removing the excess deionized water, obtain mica nanosheet / NMP dispersion. Under an anaerobic environment, dissolve CaCl2 in the mica nanosheet / NMP dispersion, then add the same molar amount of m-phenylenediamine and isophthaloyl chloride and conduct an in-situ polycondensation reaction at 0-5°C for 60-90 min. The ratio of m-phenylenediamine to the mica powder in S1 is 0.02 mol:(0.25-1) g to obtain a reaction solution; S3. After vacuum defoaming the reaction solution, conduct spinning, coagulation, washing, drying and winding and coiling in sequence to obtain meta-aramid / mica composite fiber.

2. The preparation method of the meta-aramid / mica composite fiber according to claim 1, characterized in that, In S1, the mass percentage of the hydroxyethyl cellulose aqueous solution is 1%-20%, and the ratio of the hydroxyethyl cellulose aqueous solution to the mica powder is (5-60) mL:(0.25-1) g.

3. The preparation method of the meta-aramid / mica composite fiber according to claim 2, wherein, In S1, the particle size of the mica powder is 10-50 μm, the ball-to-material ratio during the first ball milling is (50-150):1, and the first ball milling is carried out for 12-48 h; In the secondary ball milling, the ratio of deionized water to the mica powder in the first ball milling is (30-100) mL:(0.25-1) g, and the secondary ball milling is carried out for 3-6 h.

4. The preparation method of the meta-aramid / mica composite fiber according to claim 1, characterized in that, In S1, the homogenization is carried out 40-100 times, and finally centrifuge at 5000-6000 rpm for 10-15 min to remove the supernatant to obtain mica nanosheet / water dispersion.

5. The preparation method of the meta-aramid / mica composite fiber according to claim 1, characterized in that, S2 centrifugally washes the mica nanosheet / water dispersion with deionized water, N,N-dimethylformamide, acetone, ethanol, isopropanol and N-methylpyrrolidone in sequence, and then adds N-methylpyrrolidone.

6. The preparation method of the meta-aramid / mica composite fiber according to claim 5, characterized in that, After adding N-methylpyrrolidone in S2, add a molecular sieve dried at 400-600°C and let it stand for 12-18 h to obtain mica nanosheet / NMP dispersion.

7. The preparation method of the meta-aramid / mica composite fiber according to claim 1, wherein In S2, heat the mica nanosheet / NMP dispersion to 100-120°C under an anaerobic environment, then add CaCl2 and stir for 30-60 min. The ratio of CaCl2 to the mica nanosheet / NMP dispersion is (5-10) g:100 mL, and then add m-phenylenediamine and isophthaloyl chloride.

8. The preparation method of the meta-aramid / mica composite fiber according to claim 7, characterized in that, After cooling the mica nanosheet / NMP dispersion dissolved with CaCl2 to 0-5°C in S2, first add m-phenylenediamine and stir at 300-500 rpm, and then add isophthaloyl chloride at 1500-2000 rpm to conduct the in-situ polycondensation reaction.

9. The preparation method of the meta-aramid / mica composite fiber according to claim 1, characterized in that, The coagulation described in S3 is carried out successively in a primary coagulation bath at 75 - 85 °C and a secondary coagulation bath at 85 - 90 °C. Both the primary coagulation bath and the secondary coagulation bath are water and N-methylpyrrolidone. The mass ratio of water to N-methylpyrrolidone in the primary coagulation bath is 1:1, and the mass ratio of water to N-methylpyrrolidone in the secondary coagulation bath is 4:

1.

10. A meta-aramid / mica composite fiber obtained by the method for preparing a meta-aramid / mica composite fiber according to any one of claims 1 - 9.

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