Antistatic flame-retardant fiber and preparation method thereof

Abstract

The invention discloses an antistatic flame-retardant fiber and a preparation method thereof, and relates to the technical field of functional textile materials. When the antistatic flame-retardant fiber is prepared, the multi-walled carbon nanotube is carboxylated to prepare the modified multi-walled carbon nanotube; carrying out surface free radical polymerization on the modified multi-walled carbon nanotubes and caprolactam to obtain modified polyamide 6 slices; the modified polyamide 6 is sliced and spun, and modified polyamide 6 fibers are prepared; the preparation method comprises the following steps: respectively reacting phytic acid and 2, 3-epoxypropyl trimethyl ammonium chloride with chitosan to prepare a polyanion / cation modified chitosan solution; the modified polyamide 6 fiber is alternately soaked in two modified chitosan solutions, and is treated by cocamidopropyl betaine to prepare the antistatic flame-retardant fiber. The antistatic flame-retardant fiber prepared by the invention has excellent antistatic property, flame retardance and mechanical strength.

Description

Technical Field

[0001] This invention relates to the field of functional textile materials technology, specifically to an antistatic and flame-retardant fiber and its preparation method. Background Technology

[0002] Polyamide fiber is one of the earliest synthetic fibers to be industrially produced. Due to its excellent mechanical properties, abrasion resistance, and acid and alkali resistance, it is widely used in the textile industry. Polycaprolactam fiber is the main type of polyamide fiber, but its inherent flammability and tendency to accumulate static electricity severely limit its application in safety-sensitive environments. Its flammability causes it to rapidly spread molten droplets upon contact with fire, threatening the lives of users; static electricity accumulation can easily lead to the breakdown of electronic components and discharge in explosive environments, posing significant risks in medical, military, and other applications.

[0003] In recent years, with the rapid growth in demand for new energy, semiconductors, and high-level protective equipment, the application of polyamide 6 fabrics in flammable, explosive, and dry environments has surged. While traditional flame retardants (such as halogenated compounds) and antistatic coatings can improve performance in the short term, they suffer from problems such as toxic pollution, easy shedding of functional components, and loss of mechanical strength, making it difficult to meet the dual requirements of long-term safety protection and green manufacturing. Therefore, it is necessary to simultaneously improve the inherent flame retardancy and permanent antistatic capabilities of polyamide 6 fibers through bulk modification technology. Summary of the Invention

[0004] The purpose of this invention is to provide an antistatic and flame-retardant fiber and its preparation method to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: An antistatic and flame-retardant fiber, wherein the antistatic and flame-retardant fiber is prepared by layer-by-layer self-assembly of modified polyamide 6 fiber with polycationically modified chitosan and polyanionically modified chitosan.

[0006] As an optimization, the polyanionic modified chitosan is prepared by reacting chitosan with phytic acid.

[0007] As an optimization, the polycationically modified chitosan is prepared by reacting chitosan with 2,3-epoxypropyltrimethylammonium chloride.

[0008] As an optimization, the modified polyamide 6 fiber is obtained by spinning after reacting caprolactam and modified multi-walled carbon nanotubes.

[0009] As an optimization, the modified multi-walled carbon nanotubes are prepared by treating multi-walled carbon nanotubes with potassium sulfate and sodium hydroxide.

[0010] A method for preparing antistatic and flame-retardant fibers includes the following preparation steps: (1) Multi-walled carbon nanotubes and deionized water were mixed evenly at a mass ratio of 1:300~500, and then ultrasonicated for 20~40 min at a power of 200~400W to prepare a multi-walled carbon nanotube dispersion; in a nitrogen atmosphere, the multi-walled carbon nanotube dispersion, potassium persulfate, and sodium hydroxide were mixed evenly at a mass ratio of 1:(0.01~0.03):(0.02~0.06), and then stirred at 60~100℃ and 200~400r / min for 1~5 h. After cooling, a 38% hydrochloric acid solution was used to prepare the p Adjust the pH to 2-4, vacuum filter, and dry to obtain modified carbon nanotubes; mix caprolactam, modified carbon nanotubes, and deionized water at a mass ratio of 1:(0.06-0.1):(0.1-0.5) and add to a high-pressure reactor, react at 200-250℃ and 0.3-0.7MPa for 1-3 hours, release the pressure to atmospheric pressure, continue the reaction under nitrogen protection for 3-7 hours, vacuum, and discharge; obtain modified polyamide 6 chips by casting and pelletizing; dry the modified polyamide 6 chips and spin them to obtain modified polyamide 6 fibers; (2) Mix chitosan powder with 1% acetic acid at a mass ratio of 1:90~110 until the chitosan powder is completely dissolved. Add phytic acid at a mass ratio of 2~4 times that of the chitosan powder. Stir at 50~70℃ and 200~400r / min for 1~3h. Wash with deionized water by centrifugation 3~5 times and dry to obtain modified chitosan. Mix modified chitosan with deionized water at a mass ratio of 1:90~100 to obtain polyanionic modified chitosan solution. Mix chitosan powder with deionized water at a mass ratio of 1:90~100. Add 2,3-epoxypropyltrimethylammonium chloride at a mass ratio of 2~4 times that of the chitosan. Stir at 65~85℃ and 200~400r / min for 12~18h. After cooling, adjust the pH to 2.5~3.5 with 10% hydrochloric acid solution to obtain polycationic modified chitosan solution. (3) The modified polyamide 6 fiber was immersed in a polycationically modified chitosan solution for 5-10 min, washed with distilled water 2-3 times, and dried at 40-60℃ for 0.5-1 h; then immersed in a polyanionic modified chitosan solution for 5-10 min, washed with distilled water 2-3 times, and dried at 40-60℃ for 0.5-1 h; this process was repeated for 8-12 cycles; then immersed in cocamidopropyl betaine, stirred at 30-50℃ and 50-150 r / min for 10-30 min, centrifuged to dehydrate, and dried at 40-60℃ for 0.5-1 h to obtain antistatic flame-retardant fiber.

[0011] As an optimization, the multi-walled carbon nanotubes in step (1) are industrial grade and manufactured by Nanjing Xianfeng Nanomaterials Technology Co., Ltd.

[0012] As an optimization, the modified polyamide 6 fiber spinning method in step (1) is as follows: the modified polyamide 6 chips are placed in a vacuum drying oven at 90~110℃ and dried for 24~36h, placed in the feeding cylinder of a high-shear screw spinning device, heated to 270~290℃, and melt-spun using a spinneret with an aperture of 0.35~0.45mm. The nascent fiber is subjected to 3.0~4.5 times hot stretching through a hot plate at 90~110℃ and a hot plate at 180~200℃, and the fiber is wound with an electric winding machine at a speed of 300~500rpm to obtain modified polyamide 6 fiber.

[0013] As an optimization, the degree of deacetylation of the chitosan in step (2) is ≥95%, and the manufacturer is Shanghai McLean Biochemical Technology Co., Ltd.

[0014] As an optimization, the cocamidopropyl betaine in step (3) has a purity of 35% and is manufactured by Sinopharm Chemical Reagent Co., Ltd.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are: In preparing antistatic and flame-retardant fibers, this invention involves carboxylating multi-walled carbon nanotubes to obtain modified multi-walled carbon nanotubes; then, by surface free radical polymerization of the modified multi-walled carbon nanotubes and caprolactam, modified polyamide 6 chips are obtained; the modified polyamide 6 chips are spun to obtain modified polyamide 6 fibers; phytic acid and 2,3-epoxypropyltrimethylammonium chloride are reacted with chitosan to obtain polyanionic / cationic modified chitosan solutions; the modified polyamide 6 fibers are alternately impregnated with the two modified chitosan solutions for 10 cycles, and then treated with cocamidopropyl betaine to obtain antistatic and flame-retardant fibers.

[0016] First, carboxylated multi-walled carbon nanotubes were chemically bonded to caprolactam via surface free radical polymerization to obtain modified polyamide 6 chips, which were then spun into fibers. The in-situ polymerization process firmly anchored the carbon nanotubes to the polyamide 6 molecular chains through chemical bonds, achieving uniform and stable dispersion within the matrix. This effectively avoided the nanotube agglomeration problem common in physical blending methods, ensuring the formation of a continuous and efficient conductive network between the carbon nanotubes. This conductive network rapidly dissipates static charge accumulated on the fiber surface, significantly reducing the fiber's surface resistivity and endowing it with excellent intrinsic antistatic properties. The chemical bonding achieves uniform dispersion and strong interfacial bonding of carbon nanotubes in the polyamide matrix, significantly improving the fiber's tensile strength, modulus, and impact resistance. Furthermore, the excellent thermal conductivity of carbon nanotubes accelerates heat diffusion within the fiber during combustion, reducing localized heat accumulation and thus synergistically enhancing flame retardant properties.

[0017] Secondly, chitosan was modified with phytic acid and 2,3-epoxypropyltrimethylammonium chloride, respectively, to prepare negatively charged polyanionic modified chitosan and positively charged polycationic modified chitosan. Modified polyamide 6 fibers were alternately impregnated in two solutions with opposite charges for 10 cycles. Based on the principle of electrostatic layer-by-layer self-assembly, a dense and uniform multilayer nanocomposite coating was precisely constructed on the fiber surface. Phytic acid in the coating is a highly efficient bio-based phosphorus flame retardant that can catalyze dehydration into char during combustion. Quaternary ammonium salt groups also have a certain flame retardant effect and can produce a phosphorus-nitrogen synergistic flame retardant effect with phytic acid. When exposed to fire, this alternating layered structure can rapidly expand to form a dense and continuous char foam layer. This char layer has excellent heat insulation, oxygen barrier, and smoke suppression functions, effectively blocking the transmission of the three elements of combustion and greatly improving the flame retardant performance of the fiber. The layered structure formed by alternating deposition has excellent stability and bonding force with the fiber matrix. Subsequent treatment with cocamidopropyl betaine solution, with its amphiphilic structure, can further improve the hydrophilicity, antistatic durability, and skin affinity of the fiber surface. Furthermore, the ionic groups rich in the multilayer structure provide an efficient charge conduction path, significantly reducing the surface resistivity of the fiber and endowing it with durable and efficient antistatic ability. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] To more clearly illustrate the method provided by the present invention, the following embodiments will be described in detail. Example 1:

[0020] A method for preparing antistatic and flame-retardant fibers mainly includes the following preparation steps: (1) Multi-walled carbon nanotubes and deionized water were mixed evenly at a mass ratio of 1:300 and then sonicated for 20 min under an ultrasonic power of 200 W to prepare a multi-walled carbon nanotube dispersion. In a nitrogen atmosphere, the multi-walled carbon nanotube dispersion, potassium persulfate, and sodium hydroxide were mixed evenly at a mass ratio of 1:0.01:0.02 and stirred at 60℃ and 200 r / min for 1 h. After cooling, the pH was adjusted to 2 with a 38% hydrochloric acid solution, vacuum filtered, and dried to obtain modified carbon nanotubes. Caprolactam, modified carbon nanotubes, and deionized water were mixed evenly at a mass ratio of 1:0.08:0.1. The mixture was then added to a high-pressure reactor and reacted at 230℃ and 0.3MPa for 1 hour. The pressure was then released to atmospheric pressure, and the reaction continued for 5 hours under nitrogen protection. The mixture was then evacuated and discharged. Modified polyamide 6 chips were obtained by casting and pelletizing. The modified polyamide 6 chips were then dried in a vacuum drying oven at 90℃ for 24 hours. They were then placed in the feeding cylinder of a high-shear screw spinning device and heated to 270℃. Melt spinning was performed using a spinneret with a 0.35mm orifice. The nascent fibers were subjected to 3.0 times hot stretching via a 90℃ hot plate and a 180℃ hot plate. The fibers were then wound using an electric winding machine at a speed of 300rpm to obtain modified polyamide 6 fibers. (2) Chitosan powder and 1% acetic acid are mixed evenly at a mass ratio of 1:90 until the chitosan powder is completely dissolved. Phytic acid with a mass ratio of 3 times that of chitosan powder is added. The mixture is stirred at 60℃ and 200r / min for 2h. The mixture is washed three times by centrifugation with deionized water and dried to obtain modified chitosan. Modified chitosan is mixed and dissolved with deionized water at a mass ratio of 1:90 to obtain polyanionic modified chitosan solution. Chitosan powder and deionized water are mixed and dissolved at a mass ratio of 1:90. 2,3-epoxypropyltrimethylammonium chloride with a mass ratio of 3 times that of chitosan is added. The mixture is stirred at 75℃ and 200r / min for 15h. After cooling, the pH is adjusted to 2.5 with a mass fraction of 10% hydrochloric acid solution to obtain polycationic modified chitosan solution. (3) The modified polyamide 6 fiber was immersed in a polycationically modified chitosan solution for 5 min, washed twice with distilled water, and dried at 40℃ for 0.5 h; then immersed in a polyanionic modified chitosan solution for 5 min, washed twice with distilled water, and dried at 40℃ for 0.5 h; this process was repeated for 10 cycles; then the fiber was immersed in cocamidopropyl betaine, stirred at 30℃ and 50 r / min for 10 min, centrifuged to dehydrate, and dried at 40℃ for 0.5 h to obtain antistatic flame-retardant fiber. Example 2:

[0021] A method for preparing antistatic and flame-retardant fibers mainly includes the following preparation steps: (1) Multi-walled carbon nanotubes and deionized water were mixed evenly at a mass ratio of 1:400 and then sonicated for 30 min at a power of 300 W to prepare a multi-walled carbon nanotube dispersion. In a nitrogen atmosphere, the multi-walled carbon nanotube dispersion, potassium persulfate, and sodium hydroxide were mixed evenly at a mass ratio of 1:0.02:0.04 and stirred at 300 r / min for 3 h at 80 °C. After cooling, the pH was adjusted to 3 with a 38% hydrochloric acid solution, vacuum filtered, and dried to obtain modified carbon nanotubes. Caprolactam, modified carbon nanotubes, and deionized water were mixed evenly at a mass ratio of 1:0.08:0.3. The mixture was then added to a high-pressure reactor and reacted at 230℃ and 0.5MPa for 2 hours. The pressure was then released to atmospheric pressure, and the reaction continued for 5 hours under nitrogen protection. The mixture was then evacuated and discharged. Modified polyamide 6 chips were obtained by casting and pelletizing. The modified polyamide 6 chips were then dried in a vacuum drying oven at 100℃ for 30 hours. They were then placed in the feeding cylinder of a high-shear screw spinning device and heated to 280℃. Melt spinning was performed using a spinneret with a 0.4mm orifice. The nascent fibers were subjected to a 4-fold hot stretching between a 100℃ hot plate and a 190℃ hot plate. The fibers were then wound using an electric winding machine at a speed of 400rpm to obtain modified polyamide 6 fibers. (2) Chitosan powder and 1% acetic acid are mixed evenly at a mass ratio of 1:100 until the chitosan powder is completely dissolved. Phytic acid with a mass ratio of 3 times that of chitosan powder is added. The mixture is stirred at 60℃ and 300r / min for 2h. The mixture is washed 4 times by centrifugation with deionized water and dried to obtain modified chitosan. Modified chitosan is mixed and dissolved with deionized water at a mass ratio of 1:95 to obtain polyanionic modified chitosan solution. Chitosan powder and deionized water are mixed and dissolved at a mass ratio of 1:95. 2,3-epoxypropyltrimethylammonium chloride with a mass ratio of 3 times that of chitosan is added. The mixture is stirred at 75℃ and 300r / min for 15h. After cooling, the pH is adjusted to 3 with a mass fraction of 10% hydrochloric acid solution to obtain polycationic modified chitosan solution. (3) The modified polyamide 6 fiber was immersed in a polycationically modified chitosan solution for 7 min, washed with distilled water 3 times, and dried at 50℃ for 0.75 h; then immersed in a polyanionic modified chitosan solution for 7 min, washed with distilled water 3 times, and dried at 50℃ for 0.75 h; this process was repeated 10 times; then the fiber was immersed in cocamidopropyl betaine, stirred at 40℃ and 100 r / min for 20 min, centrifuged to dehydrate, and dried at 50℃ for 0.75 h to obtain antistatic flame-retardant fiber. Example 3:

[0022] A method for preparing antistatic and flame-retardant fibers mainly includes the following preparation steps: (1) Multi-walled carbon nanotubes and deionized water were mixed evenly at a mass ratio of 1:500 and then sonicated at 400W for 40 min to obtain a multi-walled carbon nanotube dispersion. In a nitrogen atmosphere, the multi-walled carbon nanotube dispersion, potassium persulfate, and sodium hydroxide were mixed evenly at a mass ratio of 1:0.03:0.06 and stirred at 100℃ and 400r / min for 5 h. After cooling, the pH was adjusted to 4 with a 38% hydrochloric acid solution, vacuum filtered, and dried to obtain modified carbon nanotubes. Caprolactam, modified carbon nanotubes, and deionized water were mixed evenly at a mass ratio of 1:0.08:0.5. The mixture was added to a high-pressure reactor and reacted at 230℃ and 0.7MPa for 3 hours. The pressure was then released to atmospheric pressure, and the reaction continued for 5 hours under nitrogen protection. The mixture was then evacuated and discharged. Modified polyamide 6 chips were obtained by casting and pelletizing. The modified polyamide 6 chips were placed in a vacuum drying oven and dried at 110℃ for 36 hours. They were then placed in the feeding cylinder of a high-shear screw spinning device and heated to 290℃. Melt spinning was performed using a spinneret with a 0.45mm orifice. The nascent fibers were subjected to 4.5 times hot stretching through a 110℃ hot plate and a 200℃ hot plate. The fibers were then wound using an electric winding machine at a speed of 500rpm to obtain modified polyamide 6 fibers. (2) Chitosan powder and 1% acetic acid are mixed evenly at a mass ratio of 1:110 until the chitosan powder is completely dissolved. Phytic acid with a mass ratio of 3 times that of chitosan powder is added. The mixture is stirred at 60℃ and 400r / min for 2h. The mixture is washed 5 times by centrifugation with deionized water and dried to obtain modified chitosan. Modified chitosan is mixed and dissolved with deionized water at a mass ratio of 1:100 to obtain polyanionic modified chitosan solution. Chitosan powder and deionized water are mixed and dissolved at a mass ratio of 1:100. 2,3-epoxypropyltrimethylammonium chloride with a mass ratio of 3 times that of chitosan is added. The mixture is stirred at 75℃ and 400r / min for 15h. After cooling, the pH is adjusted to 3.5 with a mass fraction of 10% hydrochloric acid solution to obtain polycationic modified chitosan solution. (3) The modified polyamide 6 fiber was immersed in a polycationically modified chitosan solution for 10 min, washed with distilled water 3 times, and dried at 60℃ for 1 h; then immersed in a polyanionic modified chitosan solution for 10 min, washed with distilled water 3 times, and dried at 60℃ for 1 h; this process was repeated 10 times; then it was immersed in cocamidopropyl betaine, stirred at 50℃ and 150 r / min for 30 min, centrifuged to dehydrate, and dried at 60℃ for 1 h to obtain antistatic flame-retardant fiber.

[0023] Comparative Example 1: The only difference from Example 2 is the difference in step (1). In step (1), "mix caprolactam, modified carbon nanotubes and deionized water in a mass ratio of 1:0.08:0.5 and add them to a high-pressure reactor. React at 230°C and 0.7MPa for 3 hours, release the pressure to atmospheric pressure, continue the reaction under nitrogen protection for 5 hours, evacuate the vacuum, and discharge the material". The phrase "mix in a mass ratio of 1:0.08:0.5" is changed to "mix in a mass ratio of 1:0.06:0.5".

[0024] Comparative Example 2: The only difference from Example 2 is the step (1), where “mix evenly at a mass ratio of 1:0.08:0.5” is changed to “mix evenly at a mass ratio of 1:0.07:0.5”.

[0025] Comparative Example 3: The only difference from Example 2 is the step (1), where “mix evenly at a mass ratio of 1:0.08:0.5” is changed to “mix evenly at a mass ratio of 1:0.09:0.5”.

[0026] Comparative Example 4: The only difference from Example 2 is the step (1), where “mix evenly at a mass ratio of 1:0.08:0.5” is changed to “mix evenly at a mass ratio of 1:0.1:0.5”.

[0027] Comparative Example 5: The only difference from Example 2 is the difference in step (1). In step (1), "mix caprolactam, modified carbon nanotubes and deionized water in a mass ratio of 1:0.08:0.5 and add them to a high-pressure reactor. React at 230°C and 0.7MPa for 3 hours, release the pressure to atmospheric pressure, continue the reaction under nitrogen protection for 5 hours, evacuate the vacuum, and discharge the material". The "at 230°C" in step (1) is changed to "at 200°C".

[0028] Comparative Example 6: The only difference from Example 2 is step (1), where “at 230°C” is changed to “at 210°C”.

[0029] Comparative Example 7: The only difference from Example 2 is step (1), where “at 230°C” is changed to “at 220°C”.

[0030] Comparative Example 8: The only difference from Example 2 is step (1), where “at 230°C” is changed to “at 240°C”.

[0031] Comparative Example 9: The only difference from Example 2 is step (1), where “at 230°C” is changed to “at 250°C”.

[0032] Comparative Example 10: The only difference from Example 2 is the difference in step (1). In step (1), "mix caprolactam, modified carbon nanotubes and deionized water in a mass ratio of 1:0.08:0.5 and add them to a high-pressure reactor. React at 230°C and 0.7MPa for 3 hours, release the pressure to atmospheric pressure, continue the reaction under nitrogen protection for 5 hours, evacuate the vacuum, and discharge the material". The phrase "continue the reaction under nitrogen protection for 5 hours" is changed to "continue the reaction under nitrogen protection for 3 hours".

[0033] Comparative Example 11: The only difference from Example 2 is the step (1), which changes "continue reaction under nitrogen protection for 5 hours" to "continue reaction under nitrogen protection for 4 hours".

[0034] Comparative Example 12: The only difference from Example 2 is the step (1), which changes "continue reaction under nitrogen protection for 5 hours" to "continue reaction under nitrogen protection for 6 hours".

[0035] Comparative Example 13: The only difference from Example 2 is the step (1), which changes "continue reaction under nitrogen protection for 5 hours" to "continue reaction under nitrogen protection for 7 hours".

[0036] Comparative Example 14: The only difference from Example 2 is the step (2), which is to add "phytic acid with a mass of 3 times that of chitosan powder" or "phytic acid with a mass of 2 times that of chitosan powder".

[0037] Comparative Example 15: The only difference from Example 2 is the step (2), which involves adding "phytic acid with a mass of 3 times that of chitosan powder" or "phytic acid with a mass of 4 times that of chitosan powder".

[0038] Comparative Example 16: The only difference from Example 2 is the difference in step (2). In step (2), "mix chitosan powder and 1% acetic acid at a mass ratio of 1:100 until the chitosan powder is completely dissolved, add phytic acid with a mass of 3 times that of chitosan powder, stir at 60°C and 300r / min for 2h, wash with deionized water 4 times by centrifugation, dry, and obtain modified chitosan", the "at 60°C" is changed to "at 50°C".

[0039] Comparative Example 17: The only difference from Example 2 is step (2), where “at 60°C” is changed to “at 70°C”.

[0040] Comparative Example 18: The only difference from Example 2 is the difference in step (2). In step (2), "mix chitosan powder and 1% acetic acid at a mass ratio of 1:100 until the chitosan powder is completely dissolved, add phytic acid with a mass of 3 times that of chitosan powder, stir at 300 r / min for 2 h at 60 °C, wash 4 times with deionized water by centrifugation, dry, and obtain modified chitosan" is changed from "stir at 300 r / min for 2 h".

[0041] Comparative Example 19: The only difference from Example 2 is step (2), where “stirring at 300 r / min for 2 hours” is changed to “stirring at 300 r / min for 3 hours”.

[0042] Comparative Example 20: The only difference from Example 2 is the difference in step (3). In step (3), "immerse the modified polyamide 6 fiber in the polycation-modified chitosan solution for 7 min, wash it with distilled water 3 times, and dry it at 50°C for 0.75 h; then immerse it in the polyanion-modified chitosan solution for 7 min, wash it with distilled water 3 times, and dry it at 50°C for 0.75 h; repeat 10 cycles", the "repeat 10 cycles" is changed to "repeat 8 cycles".

[0043] Comparative Example 21: The only difference from Example 2 is step (3), where “repeating 10 cycles” is changed to “repeating 9 cycles”.

[0044] Comparative Example 22: The only difference from Example 2 is step (3), which changes "repeated 10 times" to "repeated 11 times".

[0045] Comparative Example 23: The only difference from Example 2 is step (3), where “repeating 10 cycles” is changed to “repeating 12 cycles”.

[0046] Comparative Example 24: A method for preparing antistatic and flame-retardant fibers mainly includes the following preparation steps: (1) After uniformly mixing caprolactam and deionized water at a mass ratio of 1:0.3, add them to a high-pressure reactor and react at 230℃ and 0.5MPa for 2h. Then, release the pressure to 0MPa, continue the reaction under nitrogen protection for 5h, evacuate the vacuum, and discharge the material. Polyamide 6 chips are obtained by casting and pelletizing. The polyamide 6 chips are placed in a vacuum drying oven and dried at 100℃ for 30h. They are then placed in the feeding cylinder of a high-shear screw spinning equipment and heated to 280℃. Melt spinning is performed using a spinneret with a 0.4mm aperture. The nascent fibers are subjected to 4 times hot stretching through a 100℃ hot plate and a 190℃ hot plate. The fibers are then wound by an electric winding machine at a speed of 400rpm to obtain polyamide 6 fibers. (2) Chitosan powder and 1% acetic acid are mixed evenly at a mass ratio of 1:100 until the chitosan powder is completely dissolved. Phytic acid with a mass ratio of 3 times that of chitosan powder is added. The mixture is stirred at 60℃ and 300r / min for 2h. The mixture is washed 4 times by centrifugation with deionized water and dried to obtain modified chitosan. Modified chitosan is mixed and dissolved with deionized water at a mass ratio of 1:95 to obtain polyanionic modified chitosan solution. Chitosan powder and deionized water are mixed and dissolved at a mass ratio of 1:95. 2,3-epoxypropyltrimethylammonium chloride with a mass ratio of 3 times that of chitosan is added. The mixture is stirred at 75℃ and 300r / min for 15h. After cooling, the pH is adjusted to 3 with a mass fraction of 10% hydrochloric acid solution to obtain polycationic modified chitosan solution. (3) The polyamide 6 fiber was immersed in the polycationically modified chitosan solution for 7 min, washed with distilled water 3 times, and dried at 50℃ for 0.75 h; then immersed in the polyanionic modified chitosan solution for 7 min, washed with distilled water 3 times, and dried at 50℃ for 0.75 h; this process was repeated 10 times; then the fiber was immersed in cocamidopropyl betaine, stirred at 40℃ and 100 r / min for 20 min, centrifuged to dehydrate, and dried at 50℃ for 0.75 h to obtain the antistatic flame-retardant fiber.

[0047] Comparative Example 25: A method for preparing antistatic and flame-retardant fibers mainly includes the following preparation steps: (1) Caprolactam, multi-walled carbon nanotubes and deionized water were mixed uniformly in a mass ratio of 1:0.08:0.3 and added to a high-pressure reactor. The mixture was reacted at 230℃ and 0.5MPa for 2 hours. The pressure was released to 0MPa and the reaction was continued for 5 hours under nitrogen protection. The mixture was then evacuated and discharged. Composite polyamide 6 chips were obtained by casting and pelletizing. The composite polyamide 6 chips were dried in a vacuum drying oven at 100℃ for 30 hours. They were then placed in the feeding cylinder of a high-shear screw spinning equipment and heated to 280℃. Melt spinning was performed using a spinneret with a 0.4mm aperture. The nascent fibers were stretched 4 times by a 100℃ hot plate and a 190℃ hot plate. The fibers were then wound by an electric winding machine at a speed of 400rpm to obtain modified polyamide 6 fibers. (2) Chitosan powder and 1% acetic acid are mixed evenly at a mass ratio of 1:100 until the chitosan powder is completely dissolved. Phytic acid with a mass ratio of 3 times that of chitosan powder is added. The mixture is stirred at 60℃ and 300r / min for 2h. The mixture is washed 4 times by centrifugation with deionized water and dried to obtain modified chitosan. Modified chitosan is mixed and dissolved with deionized water at a mass ratio of 1:95 to obtain polyanionic modified chitosan solution. Chitosan powder and deionized water are mixed and dissolved at a mass ratio of 1:95. 2,3-epoxypropyltrimethylammonium chloride with a mass ratio of 3 times that of chitosan is added. The mixture is stirred at 75℃ and 300r / min for 15h. After cooling, the pH is adjusted to 3 with a mass fraction of 10% hydrochloric acid solution to obtain polycationic modified chitosan solution. (3) The modified polyamide 6 fiber was immersed in a polycationically modified chitosan solution for 7 min, washed with distilled water 3 times, and dried at 50℃ for 0.75 h; then immersed in a polyanionic modified chitosan solution for 7 min, washed with distilled water 3 times, and dried at 50℃ for 0.75 h; this process was repeated 10 times; then the fiber was immersed in cocamidopropyl betaine, stirred at 40℃ and 100 r / min for 20 min, centrifuged to dehydrate, and dried at 50℃ for 0.75 h to obtain antistatic flame-retardant fiber.

[0048] Comparative Example 26: A method for preparing antistatic and flame-retardant fibers mainly includes the following preparation steps: (1) Multi-walled carbon nanotubes and deionized water were mixed evenly at a mass ratio of 1:400 and then sonicated for 30 min at a power of 300 W to prepare a multi-walled carbon nanotube dispersion. In a nitrogen atmosphere, the multi-walled carbon nanotube dispersion, potassium persulfate, and sodium hydroxide were mixed evenly at a mass ratio of 1:0.02:0.04 and stirred at 300 r / min for 3 h at 80 °C. After cooling, the pH was adjusted to 3 with a 38% hydrochloric acid solution, vacuum filtered, and dried to obtain modified carbon nanotubes. Caprolactam, modified carbon nanotubes, and deionized water were mixed evenly at a mass ratio of 1:0.08:0.3. The mixture was then added to a high-pressure reactor and reacted at 230℃ and 0.5MPa for 2 hours. The pressure was then released to atmospheric pressure, and the reaction continued for 5 hours under nitrogen protection. The mixture was then evacuated and discharged. Modified polyamide 6 chips were obtained by casting and pelletizing. The modified polyamide 6 chips were then dried in a vacuum drying oven at 100℃ for 30 hours. They were then placed in the feeding cylinder of a high-shear screw spinning device and heated to 280℃. Melt spinning was performed using a spinneret with a 0.4mm orifice. The nascent fibers were subjected to a 4-fold hot stretching between a 100℃ hot plate and a 190℃ hot plate. The fibers were then wound using an electric winding machine at a speed of 400rpm to obtain modified polyamide 6 fibers. (2) Chitosan powder and deionized water were mixed and dissolved at a mass ratio of 1:95. 2,3-epoxypropyltrimethylammonium chloride with a mass of 3 times that of chitosan was added. The mixture was stirred at 75°C and 300 r / min for 15 h. After cooling, the pH was adjusted to 3 with a 10% hydrochloric acid solution to obtain a polycation-modified chitosan solution. (3) The modified polyamide 6 fiber was immersed in the polycation-modified chitosan solution for 7 min, washed with distilled water 3 times, and dried at 50℃ for 0.75 h; then it was immersed in cocamidopropyl betaine, stirred at 40℃ and 100 r / min for 20 min, centrifuged to dehydrate, and dried at 50℃ for 0.75 h to obtain antistatic flame-retardant fiber.

[0049] Comparative Example 27: A method for preparing antistatic and flame-retardant fibers mainly includes the following preparation steps: (1) Multi-walled carbon nanotubes and deionized water were mixed evenly at a mass ratio of 1:400 and then sonicated for 30 min at a power of 300 W to prepare a multi-walled carbon nanotube dispersion. In a nitrogen atmosphere, the multi-walled carbon nanotube dispersion, potassium persulfate, and sodium hydroxide were mixed evenly at a mass ratio of 1:0.02:0.04 and stirred at 300 r / min for 3 h at 80 °C. After cooling, the pH was adjusted to 3 with a 38% hydrochloric acid solution, vacuum filtered, and dried to obtain modified carbon nanotubes. Caprolactam, modified carbon nanotubes, and deionized water were mixed evenly at a mass ratio of 1:0.08:0.3. The mixture was then added to a high-pressure reactor and reacted at 230℃ and 0.5MPa for 2 hours. The pressure was then released to atmospheric pressure, and the reaction continued for 5 hours under nitrogen protection. The mixture was then evacuated and discharged. Modified polyamide 6 chips were obtained by casting and pelletizing. The modified polyamide 6 chips were then dried in a vacuum drying oven at 100℃ for 30 hours. They were then placed in the feeding cylinder of a high-shear screw spinning device and heated to 280℃. Melt spinning was performed using a spinneret with a 0.4mm orifice. The nascent fibers were subjected to a 4-fold hot stretching between a 100℃ hot plate and a 190℃ hot plate. The fibers were then wound using an electric winding machine at a speed of 400rpm to obtain modified polyamide 6 fibers. (2) Chitosan powder and 1% acetic acid are mixed evenly at a mass ratio of 1:100 until the chitosan powder is completely dissolved. Phytic acid with a mass ratio of 3 times that of chitosan powder is added. The mixture is stirred at 60℃ and 300r / min for 2h. The mixture is washed 4 times by centrifugation with deionized water and dried to obtain modified chitosan. Modified chitosan is mixed and dissolved with deionized water at a mass ratio of 1:95 to obtain polyanionic modified chitosan solution. Chitosan powder is mixed and dissolved with deionized water at a mass ratio of 1:95. Then, the pH is adjusted to 3 with a mass fraction of 10% hydrochloric acid solution to obtain polycationic chitosan solution. (3) The modified polyamide 6 fiber was immersed in a polycationic modified chitosan solution for 7 min, washed with distilled water 3 times, and dried at 50℃ for 0.75 h; then immersed in a polyanionic chitosan solution for 7 min, washed with distilled water 3 times, and dried at 50℃ for 0.75 h; this process was repeated 10 times; then the fiber was immersed in cocamidopropyl betaine, stirred at 40℃ and 100 r / min for 20 min, centrifuged to dehydrate, and dried at 50℃ for 0.75 h to obtain antistatic flame-retardant fiber.

[0050] Experimental Example 1: Determination of optimal conditions for modified polyamide 6 chips (reaction temperature, amount of modified carbon nanotubes added, reaction time) Test method: Grafting rate was analyzed using Soxhlet extraction. The dried modified polyamide 6 slices were accurately weighed and wrapped in filter paper or an ashless filter cartridge. The wrapped sample was placed in the sleeve of the extractor. Formic acid extraction was performed for 48 hours.

[0051] Grafting rate:

[0052] Wherein, W1 is the dry weight of modified polyamide 6, and W0 is the dry weight of the original modified carbon nanotubes.

[0053] The results are shown in Table 1.

[0054] Table 1

[0055] Comparing Examples 2 and 1-4, it was found that the grafting rate increased with increasing modified carbon nanotube content. The highest grafting rate (77.5%) was achieved when the mass ratio of modified carbon nanotubes to caprolactam was 0.08. Further increasing the modified carbon nanotube content decreased the grafting rate. This is because excessively high content reduces the amount of caprolactam allocated to each unit mass of carbon nanotubes, leading to a lower proportion of active sites and reduced grafting efficiency. Furthermore, high content makes carbon nanotubes more prone to aggregation, and the modified carbon nanotubes within the aggregates cannot fully contact the caprolactam, resulting in a reduced effective reaction area and limited grafting. Therefore, the optimal modified carbon nanotube content was determined to be 0.08 times the mass of caprolactam.

[0056] A comparison of Examples 2 and Comparative Examples 5-9 reveals that the grafting rate is highest at a reaction temperature of 230℃. Below 230℃, the caprolactam ring-opening polymerization rate is slow, limiting the grafting reaction kinetics and resulting in a lower grafting rate. At excessively high temperatures, the polyamide 6 chain undergoes chain scission and amide bond hydrolysis, leading to a decrease in molecular weight and easy detachment of the grafted chains. Simultaneously, the functional groups on the modified carbon nanotube surface may decarboxylate and lose their grafting sites. Therefore, the optimal reaction temperature is controlled at 230℃.

[0057] A comparison of Example 2 and Comparative Examples 10-13 reveals that the grafting rate initially increases rapidly with increasing reaction time, then levels off. When the reaction time is less than 5 hours, the ring-opening polymerization is incomplete, the grafting reaction is insufficient, and the grafting rate is low. At a reaction time of 5 hours, the grafting rate is at its maximum; further extending the reaction time leads to equilibrium, and the grafting rate remains essentially unchanged. Therefore, a reaction time of 5 hours is recommended.

[0058] Experimental Example 2: Determination of optimal conditions for modified chitosan (reaction temperature, phytic acid addition, reaction time) Test method: The flame retardant performance was tested according to GB / T5454-1997 "Test for Burning Performance of Textiles - Oxygen Index Method", using a limiting oxygen index tester to measure the limiting oxygen index. The results are shown in Table 2.

[0059] Table 2

[0060] A comparison of Example 2 and Comparative Examples 14-15 reveals that the effect of phytic acid addition on the limiting oxygen index follows a non-linear pattern of "first increasing and then decreasing." When the phytic acid addition is less than three times the mass of chitosan, the amount of flame-retardant phosphorus bound is low, resulting in limited improvement in the limiting oxygen index. When the phytic acid addition is too high, unreacted phytic acid is physically adsorbed on the chitosan surface and easily washed away, reducing the effective phosphorus content. Therefore, the optimal phytic acid addition is three times the mass of chitosan.

[0061] A comparison of Example 2 and Comparative Examples 16-17 reveals that the limiting oxygen index is highest at a reaction temperature of 60°C. Insufficient temperature results in a slow esterification reaction rate and incomplete formation of the flame-retardant structure; excessively high temperature leads to partial thermal degradation of the chitosan molecular chains, disrupting the char-forming framework structure. Therefore, the optimal reaction temperature is controlled at 60°C.

[0062] A comparison of Example 2 and Comparative Examples 18-19 reveals that the limiting oxygen index initially increases and then stabilizes with increasing reaction time. The optimal reaction time was determined experimentally to be 2 hours.

[0063] Experimental Example 3: Determining the optimal repetition cycle for layer-by-layer self-assembly Test method: The surface resistance of the antistatic flame-retardant fiber was tested using a four-probe resistance tester (ST2258C, Suzhou Jingge Instrument Co., Ltd.) based on the conductivity properties.

[0064] Flame retardancy performance was tested using a limiting oxygen index (LOI) tester, referring to GB / T5454-1997 "Test for Burning Performance of Textiles - Oxygen Index Method". The ignition time of the fiber sample was recorded, and the LIO index of the fiber sample was calculated.

[0065] The results are shown in Table 3.

[0066] Table 3

[0067] A comparison of Example 2 and Comparative Examples 20-23 reveals that an excessive number of layer-by-layer self-assembly cycles of modified polyamide 6 fibers in polyanionic and cationic solutions significantly impacts the fiber itself and its properties. With too many cycles, an excessively thick insulating chitosan layer hinders electron transport, leading to a decrease in conductivity. Simultaneously, an excessively thick coating causes cracking and peeling, reducing fiber flexibility. The limiting oxygen index increases with the number of cycles, but the increase is minimal after 10 cycles. Therefore, the optimal number of repeated layer-by-layer self-assembly cycles is 10.

[0068] Experimental Example 4: Testing of antistatic properties, flame retardant properties, and tensile strength.

[0069] Antistatic performance test method: The test was conducted in accordance with GB / T12703.1—2008 "Evaluation of Electrostatic Properties of Textiles". A YG(L)342D electrostatic tester was used to measure the electrostatic voltage of fibers from each example and comparative examples 24~27. The discharge voltage during the test was set to 10kV, the instrument rotation speed was 1400r / min, and the duration of a single test was 35s. Flame retardant performance test method: Referring to GB / T5454-1997 "Test for Burning Performance of Textiles - Oxygen Index Method", the limiting oxygen index of fibers in each example and comparative examples 24-27 was tested using a limiting oxygen index tester. The ignition time of the fiber samples was recorded, and the limiting oxygen index of the fiber samples was calculated.

[0070] Breaking strength test: The breaking strength of fibers of each embodiment and comparative examples 24-27 was tested using a fully automatic single yarn tensile tester and an evenness tester.

[0071] The results are shown in Table 4.

[0072] Table 4

[0073] A comparison of the experimental data from Examples 1-3 and Comparative Examples 24-27 in Table 4 reveals that the antistatic and flame-retardant materials prepared by this invention possess excellent antistatic properties, flame-retardant properties, and tensile strength.

[0074] By comparing Examples 1-3 and Comparative Example 24, it can be found that adding multi-walled carbon nanotubes during the preparation of polyamide 6 fibers can effectively improve the antistatic properties and tensile strength of the fibers.

[0075] A comparison of Examples 1-3 and Comparative Example 25 reveals that surface free radical polymerization of modified multi-walled carbon nanotubes with caprolactam via chemical bonding allows the carbon nanotubes to be firmly anchored to the polyamide 6 molecular chain through chemical bonds. This enables uniform and stable dispersion within the matrix, effectively avoiding the nanotube agglomeration problem common in physical blending methods. It ensures the formation of a continuous and efficient conductive network between the carbon nanotubes, which rapidly dissipates static charge accumulated on the fiber surface, improving the fiber's surface conductivity and endowing it with excellent antistatic properties. Simultaneously, the uniform dispersion and strong interfacial bonding of carbon nanotubes in the polyamide matrix through chemical bonding significantly enhances the fiber's tensile strength.

[0076] A comparison of Examples 1-3 and Comparative Example 26 reveals that the introduction of phytic acid into the coating significantly improves the flame retardant properties of the fiber. Phytic acid is a highly efficient bio-based phosphorus flame retardant that can catalyze dehydration into char during combustion. Furthermore, the abundant ionic groups in the multilayer structure provide an efficient charge conduction pathway, significantly reducing the surface resistivity of the fiber and endowing it with antistatic properties.

[0077] A comparison of Examples 1-3 and Comparative Example 27 reveals that the introduction of quaternary ammonium salt groups in the coating synergistically enhances the flame-retardant properties of the fiber. The coating itself also possesses a certain flame-retardant effect and can produce a phosphorus-nitrogen synergistic flame-retardant effect with phytic acid. This alternating layered structure exhibits excellent heat insulation, oxygen barrier, and smoke suppression functions when exposed to fire, effectively blocking the transmission of the three elements of combustion and improving the flame-retardant properties of the fiber.

Claims

1. An antistatic and flame-retardant fiber, characterized in that, The antistatic and flame-retardant fiber is prepared by the self-assembly of modified polyamide 6 fiber through layers of polycationically modified chitosan and polyanionically modified chitosan.

2. The antistatic and flame-retardant fiber according to claim 1, characterized in that, The polyanionic modified chitosan is prepared by reacting chitosan with phytic acid.

3. The antistatic and flame-retardant fiber according to claim 1, characterized in that, The polycationically modified chitosan is prepared by reacting chitosan with 2,3-epoxypropyltrimethylammonium chloride.

4. The antistatic and flame-retardant fiber according to claim 1, characterized in that, The modified polyamide 6 fiber is spun from a polymer obtained by polymerization reaction of caprolactam and modified multi-walled carbon nanotubes.

5. The antistatic flame-retardant fiber according to claim 4, characterized in that, The modified multi-walled carbon nanotubes are prepared by treating multi-walled carbon nanotubes with potassium sulfate and sodium hydroxide.

6. A method for preparing antistatic and flame-retardant fibers, characterized in that, The preparation steps include the following: (1) Multi-walled carbon nanotubes and deionized water were mixed evenly at a mass ratio of 1:300~500, and then ultrasonicated for 20~40 min at a power of 200~400W to prepare a multi-walled carbon nanotube dispersion; in a nitrogen atmosphere, the multi-walled carbon nanotube dispersion, potassium persulfate, and sodium hydroxide were mixed evenly at a mass ratio of 1:(0.01~0.03):(0.02~0.06), and then stirred at 60~100℃ and 200~400r / min for 1~5 h. After cooling, a 38% hydrochloric acid solution was used to prepare the p Adjust the pH to 2-4, vacuum filter, and dry to obtain modified carbon nanotubes; mix caprolactam, modified carbon nanotubes, and deionized water at a mass ratio of 1:(0.06-0.1):(0.1-0.5) and add to a high-pressure reactor, react at 200-250℃ and 0.3-0.7MPa for 1-3 hours, release the pressure to atmospheric pressure, continue the reaction under nitrogen protection for 3-7 hours, vacuum, and discharge; obtain modified polyamide 6 chips by casting and pelletizing; dry the modified polyamide 6 chips and spin them to obtain modified polyamide 6 fibers; (2) Mix chitosan powder with 1% acetic acid at a mass ratio of 1:90~110 until the chitosan powder is completely dissolved. Add phytic acid at a mass ratio of 2~4 times that of the chitosan powder. Stir at 50~70℃ and 200~400r / min for 1~3h. Wash with deionized water by centrifugation 3~5 times and dry to obtain modified chitosan. Mix modified chitosan with deionized water at a mass ratio of 1:90~100 to obtain polyanionic modified chitosan solution. Mix chitosan powder with deionized water at a mass ratio of 1:90~100. Add 2,3-epoxypropyltrimethylammonium chloride at a mass ratio of 2~4 times that of the chitosan. Stir at 65~85℃ and 200~400r / min for 12~18h. After cooling, adjust the pH to 2.5~3.5 with 10% hydrochloric acid solution to obtain polycationic modified chitosan solution. (3) The modified polyamide 6 fiber was immersed in the polycation-modified chitosan solution for 5-10 min, washed with distilled water 2-3 times, and dried at 40-60℃ for 0.5-1 h; then immersed in the polycation-modified chitosan solution for 5-10 min, washed with distilled water 2-3 times, and dried at 40-60℃ for 0.5-1 h; this process was repeated for 8-12 cycles; then immersed in cocamidopropyl betaine, stirred at 30-50℃ and 50-150 r / min for 10-30 min, centrifuged to dehydrate, and dried at 40-60℃ for 0.5-1 h to obtain antistatic flame-retardant fiber.

7. The method for preparing an antistatic flame-retardant fiber according to claim 6, characterized in that, The multi-walled carbon nanotubes mentioned in step (1) are industrial grade.

8. The method for preparing an antistatic flame-retardant fiber according to claim 6, characterized in that, The modified polyamide 6 fiber spinning method in step (1) is as follows: the modified polyamide 6 chips are placed in a vacuum drying oven at 90~110℃ and dried for 24~36h. They are then placed in the feeding cylinder of a high-shear screw spinning device and heated to 270~290℃. Melt spinning is performed using a spinneret with an aperture of 0.35~0.45mm. The nascent fibers are subjected to 3.0~4.5 times hot stretching through a hot plate at 90~110℃ and a hot plate at 180~200℃. The fibers are then wound around an electric winding machine at a speed of 300~500rpm to obtain modified polyamide 6 fibers.

9. The method for preparing an antistatic flame-retardant fiber according to claim 6, characterized in that, The degree of deacetylation of the chitosan in step (2) is ≥95%.

10. The method for preparing an antistatic flame-retardant fiber according to claim 6, characterized in that, The cocamidopropyl betaine in step (3) has a purity of 35%.

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