Preparation method of ultraviolet-resistant meta-aramid fiber

Abstract

The invention discloses a preparation method of ultraviolet-resistant meta-position aramid fiber, which comprises the following steps: uniformly dispersing a benzotriazole ultraviolet absorbent in a solvent, adding a light stabilizer and an antioxidant, uniformly stirring to obtain an anti-ultraviolet modifier solution, dissolving m-phenylenediamine, adding m-phthaloyl dichloride and the anti-ultraviolet modifier solution, uniformly stirring to obtain the anti-ultraviolet meta-position aramid fiber. The preparation method comprises the following steps: carrying out condensation polymerization at a low temperature to obtain a meta-aramid resin spinning solution containing anti-ultraviolet factors, finally treating the spinning solution, spraying the resin from a nozzle through dry-wet spinning, enabling the resin to enter a coagulating bath from an air layer to form nascent fibers, and finally treating to obtain the anti-ultraviolet meta-aramid fibers. The anti-ultraviolet modified solution is added by adopting an in-situ polymerization method, and a dry-wet spinning technology is combined, so that the ultraviolet resistance of the aramid fiber is effectively improved, and other properties are not influenced.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a preparation method of ultraviolet-resistant meta-aramid fiber. Background Art

[0002] In order to improve the ultraviolet resistance of meta-aramid fiber, there are various preparation strategies in the prior art. Chinese Patent Application Document CN114753154A discloses an anti-ultraviolet para-aramid fiber, its preparation method and an ultraviolet-resistant fabric, which is to coat an ultraviolet-resistant coating on the fiber surface, and the surface layer of the aramid fiber is coated with polyacrylonitrile. However, there is a separation interface between the coating layer (acrylic fiber) and the inner core layer (aramid fiber) in this method, and there are problems such as easy shedding and affecting the original performance of the fiber during later use. Chinese Patent Document CN109652977A discloses a method for preparing a flame-retardant ultraviolet-resistant aramid fiber, which is to soak the aramid fiber in a solution to achieve the purpose of physically or chemically adsorbing ultraviolet-resistant reagents on the fiber surface. This method has the problems that the combination between the fiber surface and the chemical reagent is not strong enough, it is easy to fall off, and the fiber is prone to discoloration after long-term exposure to the sun; since there is no ultraviolet-resistant reagent in the fiber core, once there is a notch or breakage on the fiber surface, the ultraviolet resistance of the fiber will be greatly reduced, and the impact will be inevitable. Chinese Patent Document CN109486185A discloses an aramid fiber-reinforced cyanate ester composite material, which immerses aramid cloth in a nano-particle modified solution and then prepares a flame-retardant ultraviolet-resistant aramid cloth by hot pressing. The hot pressing process will damage the combination between the nano-particles and the aramid cloth, resulting in the ultraviolet resistance effect not meeting the expectation. Summary of the Invention

[0003] In order to overcome the problems in the prior art, the present invention provides a preparation method of ultraviolet-resistant meta-aramid fiber, which adopts an in-situ polymerization method to add an anti-ultraviolet modified solution, effectively improving the ultraviolet resistance of the aramid fiber without affecting its original performance.

[0004] In order to solve the above technical problems, the technical solution proposed by the present invention is as follows: The present invention provides a preparation method of ultraviolet-resistant meta-aramid fiber, comprising the following steps: S1. Uniformly disperse a benzotriazole ultraviolet absorber in a solvent, then add a light stabilizer and an antioxidant, and stir evenly to obtain an anti-ultraviolet modifier solution.

[0005] S2. After dissolving m-phenylenediamine, add isophthaloyl chloride and the anti-ultraviolet modifier solution in step S1, and carry out a polycondensation reaction at low temperature to obtain a meta-aramid resin spinning solution containing ultraviolet-resistant factors.

[0006] S3. After treating the spinning solution in step S2, spray the resin from the nozzle through dry-wet spinning, enter a coagulation bath through an air layer to form a nascent fiber, and then obtain the ultraviolet-resistant meta-aramid fiber after treatment.

[0007] During the in-situ polymerization process of the present invention, the hydroxyl or amino group of the benzotriazole ultraviolet absorber reacts with the amide group to form an ester group and an amide bond, making the ultraviolet reagent a side group or block of the polymer chain. The benzotriazole ultraviolet absorber absorbs ultraviolet light through the resonance effect, converts the light energy into heat energy and releases it, thereby reducing the damage of ultraviolet rays to the aramid molecular chain; the antioxidant can combine with the peroxide by providing hydrogen atoms to be converted into alcohols or esters, protecting the amide bond and benzene ring of the aramid; when ultraviolet rays initiate a chain reaction, the stabilizer can quickly react with free radicals, interrupt the oxidation chain reaction in the middle section, and inhibit the molecular chain breakage and yellowing. The benzotriazole ultraviolet absorber, light stabilizer and antioxidant act synergistically, and by using the in-situ polymerization method, the ultraviolet resistance of aramid fibers is effectively improved.

[0008] As an alternative embodiment, in the preparation method provided by the present invention, in step S1, the mass ratio of the benzotriazole ultraviolet absorber, light stabilizer and antioxidant in the ultraviolet-resistant modifier is 2:1:1 to 10:1:1.

[0009] As an alternative embodiment, in the preparation method provided by the present invention, in step S1, the preparation temperature of the benzotriazole ultraviolet absorber solution is 40-80°C, and the stirring time is 2-10 h.

[0010] Furthermore, the preferred preparation temperature is 50-60°C, and the preferred stirring time is 2-5 h.

[0011] As an alternative embodiment, in the preparation method provided by the present invention, in step S2, the solid content of the ultraviolet-resistant modifier solution is 0.5-10% of the solid content of the aramid resin.

[0012] Furthermore, it is preferably 0.2-5%.

[0013] As an alternative embodiment, in the preparation method provided by the present invention, the benzotriazole ultraviolet absorber is 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol.

[0014] As an alternative embodiment, in the preparation method provided by the present invention, the light stabilizer is selected from one or more of salicylate esters, benzophenones, triazines, oxamides, and hindered amines. Benzophenones or hindered amines are preferred.

[0015] As an alternative embodiment, in the preparation method provided by the present invention, the antioxidant is selected from one or more of amines, hindered phenols, phosphite esters, thioesters, and organic metal salts. Amines and phenols are preferred.

[0016] As an alternative embodiment, in the preparation method provided by the present invention, in step S3, the process of treating the spinning solution is continuously passing through neutralization, defoaming and filtration. The defoaming temperature of the solution after neutralization is 40-70°C, and the apparent viscosity is 1-50 w centipoise.

[0017] Furthermore, the defoaming temperature is preferably 40-60°C, and the apparent viscosity is preferably 5-40 w centipoise.

[0018] As an alternative embodiment, in the preparation method provided by the present invention, in step S3, the coagulation bath is two-stage. The concentration of the first coagulation bath is 10-50%, and the temperature is 15-75°C; the concentration of the second coagulation bath is 20-70%, and the temperature is 15-85°C, and the plasticizing draw ratio is 1.1-3.

[0019] Furthermore, the concentration of the first coagulation bath is preferably 30-50%, the temperature is preferably 20-50°C, the concentration of the second coagulation bath is preferably 30-60%, the temperature is preferably 30-70°C, and the plasticizing draw ratio is preferably 1.2-2.0.

[0020] As an alternative embodiment, in the preparation method provided by the present invention, in step S3, the nascent fibers are washed with water, dried, heat-drawn and heat-set to obtain ultraviolet-resistant meta-aramid fibers.

[0021] As an alternative embodiment, in the preparation method provided by the present invention, in step S2, the temperature for carrying out the polycondensation reaction at low temperature is controlled at -20°C to 20°C, preferably -15 to 0°C, and the reaction time is 2-30 h, preferably 2-15 h.

[0022] Furthermore, the temperature is preferably -15 to 0°C, and the reaction time is preferably 2-15 h.

[0023] As an alternative embodiment, in the preparation method provided by the present invention, in step S2, the temperature for carrying out the polycondensation reaction at low temperature is controlled at -20°C to 20°C, preferably -15 to 0°C, and the reaction time is 2-30 h, preferably 2-15 h.

[0024] Furthermore, the temperature is preferably -15 to 0°C, and the reaction time is preferably 2-15 h.

[0025] As an alternative embodiment, in the preparation method provided by the present invention, the neutralizing agent used in the neutralization process is one or more of hydroxides, carbonates, alcohols, and organic amines in alkali metals.

[0026] Furthermore, it is preferably a hydroxide or a carbonate.

[0027] As an alternative embodiment, in the preparation method provided by the present invention, the shape of the spinneret is one of circular, square, U-shaped, annular, and fan-shaped, and a circular spinneret is preferably used. The number of holes ranges from 10 to 100,000, and preferably ranges from 100 to 10,000 holes.

[0028] As an alternative embodiment, in the preparation method provided by the present invention, during the dry-wet spinning process, the height range of the air layer is 0.1 to 50 cm.

[0029] Further, it is preferably 0.5 to 5 cm.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a preparation method for ultraviolet-resistant meta-aramid fibers. The anti-ultraviolet modifier solution (KL-01) is introduced into the meta-aramid resin by an in-situ polymerization method, which not only slows down the problem of yellowing and embrittlement of the resin under light, but also does not affect the performance of the resin. It effectively improves the barrier of aramid fiber products to ultraviolet light and maintains the stability of product performance. Moreover, the addition of KL-01 can improve the color and transparency of the resin, so that the prepared aramid fibers can maintain a bright color under light.

[0031] (2) The anti-ultraviolet modifier solution in the present invention provides a relatively stable ultraviolet-resistant environment for aramid fibers. The light stabilizer effectively shields the radiation energy of ultraviolet rays on the material, and the antioxidant can inhibit the oxidative degradation of the fiber. The three act synergistically, and the prepared anti-ultraviolet modifier solution effectively improves the ultraviolet resistance of the fiber.

[0032] (3) In the present invention, the meta-aramid resin spinning solution containing anti-ultraviolet factors is spun by dry-wet spinning, which is beneficial to further maintaining the stability of the resin product performance.

[0033] (4) The present invention modifies the meta-aramid fibers with an anti-ultraviolet modifier solution to endow them with excellent ultraviolet resistance. Such fibers have a broader application prospect in the fields of aerospace, military protection, electronics and electrical appliances, etc. Especially when used in outdoor environments, their service life can be significantly extended. Description of the Drawings

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0035] Figure 1The fiber appearance diagram of the meta-aramid fiber prepared in Example 1 after ten days of light exposure; Figure 2 The fiber appearance diagram of the meta-aramid fiber prepared in Comparative Example 2 after ten days of light exposure. Detailed implementation manners

[0036] For the convenience of understanding the present invention, the following will describe the present invention more comprehensively and meticulously in conjunction with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0037] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0038] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0039] Example 1 A preparation method of ultraviolet-resistant meta-aramid fiber, comprising the following steps: (1) Using DMAc as a solvent, slowly adding an ultraviolet absorber: 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol at 50 °C, and stirring well for 2 h to uniformly disperse 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol in the solvent to form a semi-transparent solution. Under light-shielded conditions, the light stabilizer added is a hindered amine light stabilizer: Tinuvin 770, and the antioxidant is a hindered phenol antioxidant: Irganox 1010. Stir well for 5 h to prepare an anti-ultraviolet additive (KL-01) with a molar mass ratio of ultraviolet absorber: light stabilizer: antioxidant = 2:1:1.

[0040] (2) Add m-phenylenediamine, isophthaloyl chloride, and KL-01 solution into DMAc solvent, and carry out in-situ polymerization and polycondensation reactions at -10°C for 12 h. The solid content of KL-01 is 0.5% of the solid content of the resin. After the resin is neutralized with calcium hydroxide, it is transferred to a storage tank and kept at 50°C. The resin is directly transported from the storage tank to a defoaming kettle for continuous defoaming, filtered through a filter, and the apparent viscosity of the resin is 23.3 w centipoise. It is extruded directly from a 100-hole nozzle through a metering pump, passes through a 2-cm air layer, and enters a primary coagulation bath (40%) and a secondary coagulation bath (50%) to obtain nascent fibers, which are plastically stretched by 1.5 times. The fibers enter a pure water pool (70°C) and a pure water shower area (80°C) for cleaning, and then are dried to remove water in a hot roll area (100°C - 150°C - 200°C), and then undergo a 1.5-fold hot stretching (330°C) and heat setting (300°C) to obtain ultraviolet-resistant fibers.

[0041] Example 2 A method for preparing ultraviolet-resistant meta-aramid fibers, comprising the following steps: (1) Use DMAc as a solvent, and slowly add an ultraviolet absorber: 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol at 60°C, and stir well for 2 h to uniformly disperse 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol in the solvent to form a semi-transparent solution. Under light-shielded conditions, the light stabilizer added is a hindered amine light stabilizer: Tinuvin 770, and the antioxidant is a hindered phenol antioxidant: Irganox 1010. Stir well for 5 h to prepare an anti-ultraviolet additive (KL-01) with a molar mass ratio of ultraviolet absorber: light stabilizer: antioxidant = 5:1:1.

[0042] (2) Add m-phenylenediamine, isophthaloyl chloride, and KL-01 solution into DMAc solvent, and carry out in-situ polymerization and polycondensation reactions at -10°C for 12 h. The solid content of KL-01 is 1.2% of the solid content of the resin. After the resin is neutralized with calcium hydroxide, it is transferred to a storage tank and kept at 50°C. The resin is directly transported from the storage tank to a defoaming kettle for continuous defoaming, filtered through a filter, and the apparent viscosity of the resin is 22.6 w centipoise. It is extruded directly from a 100-hole nozzle through a metering pump, passes through a 2-cm air layer, and enters a primary coagulation bath (37%) and a secondary coagulation bath (49%) to obtain nascent fibers, which are plastically stretched by 1.5 times. The fibers enter a pure water pool (70°C) and a pure water shower area (80°C) for cleaning, and then are dried to remove water in a hot roll area (105°C - 155°C - 205°C), and then undergo a 1.5-fold hot stretching (330°C) and heat setting (300°C) to obtain ultraviolet-resistant fibers.

[0043] Example 3 A method for preparing ultraviolet-resistant meta-aramid fiber, comprising the following steps: (1) Using DMAc as a solvent, slowly add an ultraviolet absorber: 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol at 50 °C, and stir well for 2 h to uniformly disperse 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol in the solvent to form a semi-transparent solution. Under light-shielded conditions, the light stabilizer added is a hindered amine light stabilizer: Tinuvin 770, and the antioxidant is a hindered phenol antioxidant: Irganox 1010. Stir well for 5 h to prepare an anti-ultraviolet additive (KL-01) with a molar mass ratio of ultraviolet absorber: light stabilizer: antioxidant = 10:1:1.

[0044] (2) Add m-phenylenediamine, m-phthaloyl chloride, and KL-01 solution to the DMAc solvent, and carry out in-situ polymerization and polycondensation reactions at -10 °C for 12 h. The solid content of KL-01 is 2.1% of the resin solid content. After the resin is neutralized with calcium hydroxide, it is transferred to a storage tank and kept at 50 °C. The apparent viscosity of the resin is 22.3 w centipoise. The resin is directly transported from the storage tank to a defoaming kettle for continuous defoaming, filtered through a filter, and directly extruded from a 100-hole nozzle through a metering pump, and enters a primary coagulation bath (35%) and a secondary coagulation bath (50%) through a 2-cm air layer to obtain nascent fibers. The plasticization and stretching are 1.4 times. The fibers enter a pure water pool (70 °C) and a pure water shower area (85 °C) for cleaning, and then are dried and dewatered in a hot roll area (110 °C - 150 °C - 210 °C), and then subjected to a 1.6-fold hot stretching (330 °C) and heat setting (300 °C) to obtain ultraviolet-resistant fibers.

[0045] Example 4 A method for preparing ultraviolet-resistant meta-aramid fiber, comprising the following steps: (1) Using DMAc as a solvent, slowly add an ultraviolet absorber: 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol at 50 °C, and stir well for 2 h to uniformly disperse 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol in the solvent to form a semi-transparent solution. Under light-shielded conditions, the light stabilizer added is a hindered amine light stabilizer: Tinuvin 770, and the antioxidant is a hindered phenol antioxidant: Irganox 1010. Stir well for 5 h to prepare an anti-ultraviolet additive (KL-01) with a molar mass ratio of ultraviolet absorber: light stabilizer: antioxidant = 2:1:1.

[0046] (2) Add m-phenylenediamine, isophthaloyl chloride, and KL-01 solution to DMAc solvent, and carry out in-situ polymerization and polycondensation reactions at -10°C for 12 h. The solid content of KL-01 is 5.6% of the resin solid content. After neutralizing the resin with calcium hydroxide, transfer it to a storage tank and keep it at 50°C. The apparent viscosity of the resin is 19.5 w centipoise. Transport the resin directly from the storage tank to a defoaming kettle for continuous defoaming, filter it through a filter, extrude it directly from a 100-hole nozzle through a metering pump, pass through a 2-cm air layer, and enter the primary coagulation bath (42%) and secondary coagulation bath (55%) to obtain nascent fibers. The plasticization draw ratio is 1.6 times. The fibers enter a pure water pool (80°C) and a pure water shower area (90°C) for cleaning, and then are dried to remove water in a hot roll area (100°C - 150°C - 200°C), and then undergo a 1.6-fold hot draw (330°C) and heat setting (300°C) to obtain ultraviolet-resistant fibers.

[0047] Comparative Example 1 (1) Use pure water as a solvent, and slowly add an ultraviolet absorber: 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol at 50°C, and stir well for 2 h to uniformly disperse 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol in the solvent to form a semi-transparent solution. The light stabilizer added under light-shielded conditions is a hindered amine light stabilizer: Tinuvin 770, and the antioxidant is a hindered phenol antioxidant: Irganox 1010. Stir well for 5 h to prepare an anti-ultraviolet additive (KL-01) with a molar mass ratio of ultraviolet absorber: light stabilizer: antioxidant = 2:1:1. Pour the prepared 20% KL-01 aqueous solution into an oiling bath.

[0048] (2) Add m-phenylenediamine and isophthaloyl chloride to DMAc solvent, and carry out a polycondensation reaction at -10°C for 12 h. After neutralizing with calcium hydroxide, transfer it to a storage tank and keep it at 50°C. The apparent viscosity of the resin is 27.7 w centipoise. Transport the resin directly from the storage tank to a defoaming kettle for continuous defoaming, filter it through a filter, extrude it directly from a 100-hole nozzle through a metering pump, pass through a 2-cm air layer, and enter the primary (40%) and secondary coagulation baths (50%) to obtain nascent fibers. The plasticization draw ratio is 1.5 times. The fibers enter a pure water pool (70°C) and a pure water shower area (80°C) for cleaning, and then are dried to remove water in a hot roll area (100 - 150 - 200°C). After undergoing a 1.5-fold hot draw (330°C) and heat setting (300°C), the fibers pass through an oiling bath of 20% KL-01 aqueous solution, and finally the filaments are wound up.

[0049] Comparative Example 2 m-Phenylenediamine and isophthaloyl chloride were added to DMAc solvent, and a polycondensation reaction occurred at -10°C for 12 hours. After the resin was neutralized with calcium hydroxide, it was transferred to a storage tank and kept at 50°C. The apparent viscosity of the resin was 28.2 w centipoise. The resin was directly transported from the storage tank to a defoaming kettle for continuous defoaming, filtered through a filter, and extruded directly from a 100-hole nozzle by a metering pump. After passing through a 2-cm air layer, it entered the first-stage (40%) and second-stage coagulation baths (50%) to obtain nascent fibers. The plasticizing draw ratio was 1.5 times. The fibers entered a pure water tank (70°C) and a pure water shower area (80°C) for cleaning, and then were dried to remove water in a hot roll area (100 - 150 - 200°C), followed by a 1.5-fold hot draw (330°C) and heat setting (300°C) to obtain fibers.

[0050] Comparative Example 3 (1) Using DMAc as a solvent, an ultraviolet absorber: 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol was slowly added at 50°C, and stirred thoroughly for 2 hours to uniformly disperse 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol in the solvent to form a translucent solution. The light stabilizer added under light-shielded conditions was a hindered amine light stabilizer: Tinuvin 770, and the antioxidant was a hindered phenol antioxidant: Irganox 1010. Stirred thoroughly for 5 hours to prepare an anti-ultraviolet additive (KL-01) with a molar mass ratio of ultraviolet absorber: light stabilizer: antioxidant = 2:1:1.

[0051] (2) m-Phenylenediamine and isophthaloyl chloride were added to DMAc solvent, and a polycondensation reaction occurred at -10°C for 12 hours. After the reaction ended, the KL-01 solution was added to the aramid resin solution for blending for 10 hours. The solid content of KL-01 was 1 of the resin solid content. After the reaction ended, it was neutralized with calcium hydroxide, transferred to a storage tank and kept at 50°C. The resin was directly transported from the storage tank to a defoaming kettle for continuous defoaming, filtered through a filter, and the apparent viscosity of the resin was 25.4 w centipoise. It was extruded directly from a 100-hole nozzle by a metering pump. After passing through a 2-cm air layer, it entered the first-stage (40%) and second-stage coagulation baths (50%) to obtain nascent fibers. The plasticizing draw ratio was 1.5 times. The fibers entered a pure water tank (70°C) and a pure water shower area (80°C) for cleaning, and then were dried to remove water in a hot roll area (100 - 150 - 200°C), followed by a 1.5-fold hot draw (330°C) and heat setting (300°C) to obtain ultraviolet-resistant fibers.

[0052] Comparative Example 4 (1) Using DMAc as the solvent, slowly add the ultraviolet absorber: 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol at 50 °C, and stir well for 2 h to uniformly disperse 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol in the solvent to form a translucent solution, which is stored in the dark.

[0053] (2) Add the m-phenylenediamine, isophthaloyl chloride ultraviolet absorber solution to the DMAc solvent, and carry out in-situ polymerization and polycondensation reactions at -10 °C for 12 h. The solid content of the ultraviolet absorber is 0.5% of the resin solid content. After the resin is neutralized with calcium hydroxide, it is transferred to a storage tank and kept at 50 °C. The resin is directly transported from the storage tank to a defoaming kettle for continuous defoaming, filtered through a filter, and the apparent viscosity of the resin is 23.3 w centipoise. It is directly extruded from a 100-hole nozzle by a metering pump, passes through a 2-cm air layer and enters the primary coagulation bath (40%) and the secondary coagulation bath (50%) to obtain the nascent fiber, which is plastically stretched 1.5 times. The fiber enters a pure water pool (70 °C) and a pure water shower area (80 °C) for cleaning, and then is dried to remove water in a hot roller area (100 °C - 150 °C - 200 °C), and then undergoes a 1.5-fold hot stretching (330 °C) and heat setting (300 °C) to obtain the ultraviolet-resistant fiber.

[0054] Comparative Example 5 (1) Using DMAc as the solvent, slowly add the ultraviolet absorber: 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol at 50 °C, and stir well for 2 h to uniformly disperse 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol in the solvent to form a translucent solution. The light stabilizer added under dark conditions is the hindered amine light stabilizer: Tinuvin 770, and the antioxidant is the hindered phenol antioxidant: Irganox 1010. Stir well for 5 h to prepare an anti-ultraviolet additive (KL-01) with a molar mass ratio of ultraviolet absorber: light stabilizer: antioxidant = 2:1:1.

[0055] (2) m-Phenylenediamine, isophthaloyl chloride, and KL-01 solution were added to DMAc solvent, and an in-situ polymerization and polycondensation reaction occurred at -10°C for 12 h. The solid content of KL-01 was 0.5% of the resin solid content. After the resin was neutralized with calcium hydroxide, it was transferred to a storage tank and kept at 50°C. The resin was directly transported from the storage tank to a defoaming kettle for continuous defoaming, filtered through a filter, and the apparent viscosity of the resin was 23.3 w centipoise. It was directly extruded from a 100-hole nozzle through a metering pump into a primary coagulation bath (40%) and a secondary coagulation bath (50%) to obtain nascent fibers, which were plastically stretched 1.5 times. The fibers entered a pure water pool (70°C) and a pure water shower area (80°C) for cleaning, and then were dried to remove water in a hot roll area (100°C - 150°C - 200°C), and then underwent a 1.5-fold hot stretch (330°C) and heat setting (300°C) to obtain ultraviolet-resistant fibers.

[0056] Comparative Example 6 m-Phenylenediamine and isophthaloyl chloride were added to DMAc solvent, and a polycondensation reaction occurred at -10°C for 12 h. After the resin was neutralized with calcium hydroxide, it was transferred to a storage tank and kept at 50°C. The apparent viscosity of the resin was 28.2 w centipoise. The resin was directly transported from the storage tank to a defoaming kettle for continuous defoaming, filtered through a filter, and the apparent viscosity of the resin was 23.3 w centipoise. It was directly extruded from a 100-hole nozzle through a metering pump into a primary coagulation bath (40%) and a secondary coagulation bath (50%) to obtain nascent fibers, which were plastically stretched 1.5 times. The fibers entered a pure water pool (70°C) and a pure water shower area (80°C) for cleaning, and then were dried to remove water in a hot roll area (100°C - 150°C - 200°C), and then underwent a 1.5-fold hot stretch (330°C) and heat setting (300°C) to obtain ultraviolet-resistant fibers.

[0057] The appearance of the meta-aramid fibers prepared in Example 1 and the meta-aramid fibers prepared in Comparative Example 2 after being irradiated with light for ten days was compared. The results are as Figure 1 and Figure 2 shown. After irradiation, the color and transparency of the aramid resin fibers obtained by in-situ polymerization with an anti-ultraviolet modifier solution in Example 1 remained unchanged.

[0058] The aramid fibers prepared in the examples and comparative examples were subjected to a 220 h UV radiation test. The results are shown in Table 1.

[0059] Table 1: Loss results of aramid fibers prepared in examples and comparative examples

[0060] As can be seen from Table 1, in the examples, in-situ polymerization was adopted to introduce the anti-ultraviolet modifier solution into the fiber resin. As the amount of the anti-ultraviolet reagent increased, the retention rates of the breaking strength and modulus of the fibers after irradiation increased. In Comparative Example 1, after the fiber was formed, the anti-ultraviolet modifier solution was surface-coated through an oiling bath, which belonged to post-treatment processing and physical coating. Compared with the in-situ polymerization method in Example 1, the retention rates of the breaking strength and modulus of the fibers after irradiation decreased. In Comparative Example 2, no anti-ultraviolet modifier solution was used, and the retention rates of the breaking strength and modulus of the fibers after irradiation decreased significantly. In Comparative Example 3, the anti-ultraviolet modifier solution and the aramid resin solution were co-mixed. Compared with the in-situ polymerization method in Example 1, the retention rates of the breaking strength and modulus of the fibers after irradiation decreased. Compared with Example 1 in which a benzotriazole-based ultraviolet absorber, a light stabilizer, and an antioxidant were used synergistically, in Comparative Example 4, no antioxidant and light stabilizer were added, and the retention rates of the breaking strength and modulus of the fibers after irradiation decreased. In Comparative Example 5, wet spinning was adopted. Compared with Example 1, although the retention rate of the breaking strength of the fibers did not decrease after light irradiation, the retention rate of the modulus decreased slightly. In Comparative Example 6, neither an anti-ultraviolet agent nor wet or dry spinning was used, and the retention rates of the breaking strength and modulus of the fibers after irradiation decreased significantly.

[0061] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A preparation method of ultraviolet-resistant meta-aramid fiber, characterized in that, It includes the following steps: S1. Uniformly disperse benzotriazole ultraviolet absorbers in a solvent, then add a light stabilizer and an antioxidant, and stir evenly to obtain an anti-ultraviolet modified agent solution; S2. After dissolving m-phenylenediamine, add isophthaloyl chloride and the anti-ultraviolet modified agent solution in step S1, and carry out a polycondensation reaction at a low temperature to obtain a meta-aramid resin spinning solution containing anti-ultraviolet factors; S3. After treating the spinning solution in step S2, spray the resin from a nozzle through dry-wet spinning, enter a coagulation bath through an air layer to form a nascent fiber, and then obtain ultraviolet-resistant meta-aramid fibers after treatment.

2. The preparation method of the ultraviolet-resistant meta-aramid fiber according to claim 1, characterized in that, In step S1, the mass ratio of the benzotriazole ultraviolet absorber, light stabilizer and antioxidant in the anti-ultraviolet modified agent is 2:1:1 to 10:1:

1.

3. The preparation method of the ultraviolet-resistant meta-aramid fiber according to claim 1, wherein, In step S1, the preparation temperature of the benzotriazole ultraviolet absorber solution is 40 - 80 °C, and the stirring time is 2 - 10 h.

4. The preparation method of the ultraviolet-resistant meta-aramid fiber according to claim 1, characterized in that, In step S2, the solid content of the anti-ultraviolet modified agent solution is 0.5 - 10% of the solid content of the aramid resin.

5. The preparation method of the ultraviolet-resistant meta-aramid fiber according to claim 1, characterized in that, The benzotriazole ultraviolet absorber is 2-(2H)-benzotriazol-2-yl-6-dodecyl-4-methylphenol; the light stabilizer is selected from one or more of salicylate esters, benzophenones, triazines, oxamides, and hindered amines; the antioxidant is selected from one or more of amines, hindered phenols, phosphite esters, thioesters, and organic metal salts.

6. The preparation method of the ultraviolet-resistant meta-aramid fiber according to claim 1, characterized in that, In step S3, the process of treating the spinning solution is to continuously pass through neutralization, degassing and filtration. The degassing temperature of the solution after neutralization is 40 - 70 °C, and the apparent viscosity is 1 - 50 w centipoise.

7. The preparation method of the ultraviolet-resistant meta-aramid fiber according to claim 1, characterized in that, In step S3, the coagulation bath is in two stages. The concentration of the first coagulation bath is 10 - 50%, and the temperature is 15 - 75 °C; the concentration of the second coagulation bath is 20 - 70%, and the temperature is 15 - 85 °C, and the plasticizing and stretching multiple is 1.1 - 3.

8. The preparation method of the ultraviolet-resistant meta-aramid fiber according to claim 1, characterized in that, In step S3, the nascent fibers are washed, dried, heat-stretched and heat-set to obtain ultraviolet-resistant meta-aramid fibers.

9. The preparation method of the ultraviolet-resistant meta-aramid fiber according to claim 8, characterized in that, The washing temperature is 20 - 90 °C, the drying temperature is 100 - 300 °C, the heat-stretching temperature is 200 - 350 °C, the heat-stretching multiple is 1.05 - 3, the heat-setting temperature is 240 - 360 °C, preferably 280 - 330 °C.

10. The preparation method of the ultraviolet-resistant meta-aramid fiber according to claim 1, wherein During the dry-wet spinning process, the height range of the air layer is 0.1 - 50 cm.

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