Anti-aging para-aramid fiber and preparation method thereof

Abstract

The invention relates to the technical field of aramid fiber materials, in particular to an anti-aging para-aramid fiber and a preparation method thereof.The preparation method comprises the steps that S1, UV-234 and concentrated sulfuric acid react to obtain a first reactant; s2, the first reactant and the second reactant PPTA are subjected to a blending reaction, and a spinning solution is obtained; and S3, carrying out a dry-jet wet spinning process on the spinning solution to obtain the anti-aging para-aramid fiber. In the step S1, the concentration of the concentrated sulfuric acid is 99.8-101% according to the content of SO3; the dosage of the UV-234 is 0.25%-2.5% of the mass of the concentrated sulfuric acid; in the step S2, the mass ratio of the first reactant to the second reactant PPTA is (4-4.13): 1. According to the anti-aging para-aramid fiber prepared by the preparation method, the anti-aging performance of the fiber is remarkably improved while relatively high strength is maintained, and the preparation method is simple and suitable for industrial application.

Description

Technical Field

[0001] The invention relates to an aging-resistant para-aramid fiber and a preparation method thereof, belonging to the technical field of aramid fiber materials. Background Art

[0002] Para-aramid is a high-performance synthetic fiber with the chemical name poly(p-phenylene terephthalamide) (PPTA). It is composed of highly oriented rigid linear polymer chains. Its molecular structure gives it ultra-high strength, high modulus, high temperature resistance, corrosion resistance and other properties. It is one of the important strategic materials and is widely used in aerospace, safety protection, industrial materials, building reinforcement, and rubber. However, the amide bond (-CO-NH-) in its molecular chain is easily broken under ultraviolet (UV) radiation, resulting in poor light aging resistance. It is prone to discoloration after exposure to light and has high requirements for storage conditions. This limits the long-term application of aramid in outdoor protective equipment, optical cable reinforcement materials, aerospace composite materials and other fields. Therefore, there is an urgent need to develop more efficient anti-aging technologies that do not affect the intrinsic properties of the fiber.

[0003] At present, there are several methods to improve the aging resistance of para-aramid fiber: 1. Surface coating / impregnation modification: The main method is to coat the fiber surface with an anti-UV agent (such as nano-TiO2, ZnO) or a hydrolysis-resistant coating (such as silicone, fluoride). The method disclosed in the patent application with publication number CN112048905A is to coat the fiber surface with an anti-UV agent. However, the problems with this method are: (1) the anti-UV agent has poor adhesion to the fiber: the aramid surface is smooth and inert, the coating easily falls off, and the protective effect decreases after long-term use; (2) it affects air permeability: thick coatings may reduce the flexibility and air permeability of the fiber, making it unsuitable for high dynamic load scenarios (such as protective clothing).

[0004] 2. Copolymerization modification: The main method is to introduce a third monomer (such as a compound containing an electron-withdrawing group) during the polymerization stage to reduce the reactivity of the amide bond. The method disclosed in patent application publication number CN118600743A is to embed the chromophoric monomer into the polymer chain segment of aromatic polyamide through copolymerization. However, the problems with this method are: (1) loss of fiber strength: the introduction of non-rigid chain segments may reduce the crystallinity and tensile strength of the fiber; (2) complex process: precise control of polymerization conditions is required, and solvent recovery is difficult (such as the NMP / lithium chloride system).

[0005] 3. Nanocomposite reinforcement The main method is to disperse nanomaterials (graphene, carbon nanotubes) into a spinning solution and prepare composite fibers through co-spinning. The method disclosed in the patent application with publication number CN120425479A is to mix poly(m-phenylene isophthalamide) copolymer, composite nano suspension and 4,4'-diaminodiphenylmethane in N-methylpyrrolidone, degas and prepare a modified polymer spinning solution, and then obtain coagulated fibers through dry-jet-wet spinning. However, the problems with this method are: (1) uneven dispersion: nanoparticles easily agglomerate, resulting in internal defects in the fiber; (2) high cost: high-quality nanomaterials (such as functionalized graphene) are expensive and difficult to industrialize.

[0006] From this, it can be seen that the various aramid fiber modification methods currently used in the industry are difficult to simultaneously meet the requirements of high strength, high weather resistance and low cost. At the same time, the stability during long-term use is insufficient, and the aging resistance of existing coatings or composite materials gradually decays with use time. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the present invention provides an aging-resistant para-aramid fiber and a preparation method thereof. The aging-resistant para-aramid fiber prepared by the preparation method significantly improves the aging resistance of the fiber while maintaining high strength. Moreover, the preparation method is simple and suitable for industrial application.

[0008] The technical solution of the present invention to solve the above technical problems is as follows: a method for preparing aging-resistant para-aramid fiber, the preparation method comprising: S1, UV-234 (2-[2'-hydroxy-3',5'-bis(α,α-dimethylbenzyl)phenyl]benzotriazole) and concentrated sulfuric acid react to obtain a first reactant; S2, the first reactant and the second reactant PPTA are blended to obtain a spinning solution; S3. The spinning solution is subjected to a dry-jet wet spinning process to obtain aging-resistant para-aramid fiber.

[0009] Furthermore, in step S1, the concentration of the concentrated sulfuric acid is 99.8-101% based on the SO3 content; The dosage of UV-234 is 0.25%-2.5% of the mass of concentrated sulfuric acid; In step S2, the mass ratio of the first reactant to the second reactant PPTA is (4-4.13):1.

[0010] Furthermore, in step S1, the reaction temperature is 20-60° C., and the reaction time is 2-6 h.

[0011] Furthermore, in step S2, the first reactant and the second reactant PPTA are blended and reacted in the cavity of a twin-screw reactor at a screw speed of 20-50 rpm.

[0012] Furthermore, in step S2, the blending reaction temperature is 80-90°C.

[0013] Furthermore, the spinning solution is in a liquid crystal state; and the solid content of the spinning solution is 19.5%-20.0% in terms of mass concentration.

[0014] Furthermore, in step S3, the dry-jet wet spinning process includes: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot drawn, oiled and wound to obtain the aging-resistant para-aramid fiber.

[0015] Furthermore, the draft ratio during the stretching process of the dry-jet wet spinning process is 6-12; and the temperature condition of the hot stretching is 150-200°C.

[0016] Furthermore, the coagulation bath is a sulfuric acid aqueous solution, the mass concentration of persulfate in the coagulation bath is 2%-8%, and the temperature of the coagulation bath is 5-35°C.

[0017] The invention also discloses an aging-resistant para-aramid fiber. The aging-resistant para-aramid fiber is prepared according to the preparation method of the invention.

[0018] The beneficial effects of the present invention are: The present invention successfully produces aging-resistant fibers by adding UV-234 to sulfuric acid, fully dissolving the UV-234 in the sulfuric acid, and preparing a UV-234 / sulfuric acid solution (the first reactant). The solution is then thoroughly mixed with PPTA through a twin-screw extruder. The aging-resistant fibers produced using the method of the present invention maintain their strength despite the addition of UV-234, retaining the high strength and high modulus characteristics of para-aramid fibers. Furthermore, the aramid fibers exhibit improved aging resistance, and the low UV-234 addition ratio results in low production costs.

[0019] In addition, in the preparation method of the present invention, UV-234 is first fully mixed with sulfuric acid and then mixed with PPTA. The additive UV-234 has good bonding performance with aramid fiber, so that the finally obtained aging-resistant para-aramid fiber has better long-term stability.

[0020] UV-234 reacts with sulfuric acid to produce sulfonation, generating sulfonic acid groups (-SO3H). The strong polarity of the sulfonic acid groups will competitively bind to the amide bonds on the PPTA chains, weakening the original intermolecular hydrogen bonds. In addition, the sulfonic acid groups are large in size, which can expand the distance between molecular chains, reduce the interchain packing density, and promote the dissolution of PPTA, which is conducive to the preparation of more uniform spinning solution, improve production and processing efficiency, and obtain high-quality target products. Moreover, the entire preparation method is simple to operate and suitable for industrial application. DETAILED DESCRIPTION

[0021] The present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific embodiments and are not intended to limit the present invention.

[0023] A method for preparing aging-resistant para-aramid fiber, the preparation method comprising: S1, UV-234 and concentrated sulfuric acid react to obtain a first reactant; S2, the first reactant and the second reactant PPTA are blended to obtain a spinning solution; S3. The spinning solution is subjected to a dry-jet wet spinning process to obtain aging-resistant para-aramid fiber.

[0024] Specifically, in step S1, the concentration of the concentrated sulfuric acid is 99.8-101% based on the SO3 content; The dosage of UV-234 is 0.25%-2.5% of the mass of concentrated sulfuric acid; In step S2, the mass ratio of the first reactant to the second reactant PPTA is (4-4.13):1.

[0025] Specifically, in step S1, the reaction temperature is 20-60° C., and the reaction time is 2-6 h.

[0026] Specifically, in step S2, the first reactant and the second reactant PPTA are blended and reacted in the cavity of a twin-screw reactor at a screw speed of 20-50 rpm.

[0027] More specifically, in step S2, the measured polymer (PPTA) is delivered to the reaction chamber of the twin-screw reactor through a feed screw; the prepared spinning solution is directly transported to the dry-jet wet spinning process production line through a pipeline.

[0028] More specifically, the PPTA used in the embodiments of the present invention is prepared by a low-temperature polycondensation reaction using terephthaloyl chloride and p-phenylenediamine as the polymerization monomers, N-methylpyrrolidone (NMP) as the solvent, and calcium chloride (CaCl2) as the cosolvent.

[0029] More specifically, when preparing PPTA, the molar ratio of terephthaloyl chloride to p-phenylenediamine is 1:1, the mass fraction of calcium chloride in the NMP / calcium chloride solution is 8-9%, the moisture content is controlled below 500 ppm, the amount of p-phenylenediamine added is 5-6% of the mass of the NMP / calcium chloride solution, the polycondensation reaction temperature is 0-10°C, the reaction time is 30-60 minutes, and the solid content in the system after the reaction is completed is 10-12%. PPTA is then obtained through solid-liquid separation, water washing, and drying. However, this does not constitute a limitation to the technology of the present invention. As long as conventional PPTA that can be used for spinning p-aramid fibers is used, the technical solution of the present invention can be used to obtain aging-resistant p-aramid fibers.

[0030] Specifically, in step S2, the blending reaction temperature is 80-90°C.

[0031] Specifically, the spinning solution is in a liquid crystal state; and the solid content of the spinning solution is 19.5%-20.0% in terms of mass concentration.

[0032] Specifically, in step S3, the dry-jet wet spinning process includes: after the spinning solution is sprayed, it is subjected to a coagulation bath, stretched, washed, dried, hot drawn, oiled and rolled to obtain the aging-resistant para-aramid fiber.

[0033] Specifically, the draft ratio during the stretching process of the dry-jet wet spinning process is 6-12; and the temperature condition of the hot stretching is 150-200°C.

[0034] Specifically, the coagulation bath is a sulfuric acid aqueous solution, the mass concentration of persulfate in the coagulation bath is 2%-8%, and the temperature of the coagulation bath is 5-35°C.

[0035] More specifically, the water washing process adopts a multi-pass water washing operation.

[0036] The invention also discloses an aging-resistant para-aramid fiber. The aging-resistant para-aramid fiber is prepared according to the preparation method of the invention.

[0037] Example 1 A method for preparing aging-resistant para-aramid fiber is as follows: S1. Add UV-234 to the measured concentrated sulfuric acid and dissolve it. After the UV-234 is dissolved, transfer it to an emulsification tank for reaction, control the reaction temperature and reaction time, and obtain the first reactant; The concentration of concentrated sulfuric acid is 99.9%, the mass of UV-234 added is 0.25% of the mass of concentrated sulfuric acid, the temperature of the dissolution process is controlled at 20°C; the reaction temperature in the emulsification tank is 20°C, and the reaction time is 3 hours.

[0038] S2, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of the first reactant to the second reactant PPTA is 4.1:1; The reaction temperature in the twin-screw reactor was 80° C., the screw speed was 20 rpm, and the solid content of the prepared spinning solution was 19.6% (mass content).

[0039] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the hot stretching is 150°C.

[0040] Example 2 A method for preparing aging-resistant para-aramid fiber is as follows: S1. Add UV-234 to the measured concentrated sulfuric acid and dissolve it. After the UV-234 is dissolved, transfer it to an emulsification tank for reaction, control the reaction temperature and reaction time, and obtain the first reactant; The concentration of concentrated sulfuric acid is 99.9%, the mass of UV-234 added is 1% of the mass of concentrated sulfuric acid, the temperature of the dissolution process is controlled at 20°C; the reaction temperature in the emulsification tank is 20°C, and the reaction time is 3 hours.

[0041] S2, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of the first reactant to the second reactant PPTA is 4.1:1; The reaction temperature in the twin-screw reactor was 80° C., the screw speed was 20 rpm, and the solid content of the prepared spinning solution was 19.6% (mass content).

[0042] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the hot stretching is 150°C.

[0043] Example 3 A method for preparing aging-resistant para-aramid fiber is as follows: S1. Add UV-234 to the measured concentrated sulfuric acid and dissolve it. After the UV-234 is dissolved, transfer it to an emulsification tank for reaction, control the reaction temperature and reaction time, and obtain the first reactant; The concentration of concentrated sulfuric acid is 99.9%, the mass of UV-234 added is 2.5% of the mass of concentrated sulfuric acid, the temperature of the dissolution process is controlled at 20°C; the reaction temperature in the emulsification tank is 20°C, and the reaction time is 3 hours.

[0044] S2, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of the first reactant to the second reactant PPTA is 4.1:1; The reaction temperature in the twin-screw reactor was 80° C., the screw speed was 20 rpm, and the solid content of the prepared spinning solution was 19.6% (mass content).

[0045] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the hot stretching is 150°C.

[0046] Example 4 A method for preparing aging-resistant para-aramid fiber is as follows: S1. Add UV-234 to the measured concentrated sulfuric acid and dissolve it. After the UV-234 is dissolved, transfer it to an emulsification tank for reaction, control the reaction temperature and reaction time, and obtain the first reactant; The concentration of concentrated sulfuric acid is 99.8%, the mass of UV-234 added is 1.5% of the mass of concentrated sulfuric acid, the temperature of the dissolution process is controlled at 40°C; the reaction temperature in the emulsification tank is 40°C, and the reaction time is 6 hours.

[0047] S2, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of the first reactant to the second reactant PPTA is 4.13:1; The reaction temperature in the twin-screw reactor was 90° C., the screw speed was 30 rpm, and the solid content of the prepared spinning solution was 19.5% (mass content).

[0048] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 12; the coagulation bath temperature is 25°C, and the coagulation bath is an aqueous sulfuric acid solution with a mass concentration of 8%; and the heating temperature of the hot stretching is 200°C.

[0049] Example 5 A method for preparing aging-resistant para-aramid fiber is as follows: S1. Add UV-234 to the measured concentrated sulfuric acid and dissolve it. After the UV-234 is dissolved, transfer it to an emulsification tank for reaction, control the reaction temperature and reaction time, and obtain the first reactant; The concentration of concentrated sulfuric acid was 101%, the mass of UV-234 added was 2.0% of the mass of concentrated sulfuric acid, the temperature of the dissolution process was controlled at 60°C; the reaction temperature in the emulsification tank was 60°C, and the reaction time was 2h.

[0050] S2, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of the first reactant to the second reactant PPTA is 4:1; The reaction temperature in the twin-screw reactor was 90° C., the screw speed was 50 rpm, and the solid content of the prepared spinning solution was 20.0% (mass content).

[0051] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 10; the coagulation bath temperature is 35°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 5%; and the heating temperature of the hot stretching is 180°C.

[0052] Example 6 A method for preparing aging-resistant para-aramid fiber is as follows: S1. Add UV-234 to the measured concentrated sulfuric acid and dissolve it. After the UV-234 is dissolved, transfer it to an emulsification tank for reaction, control the reaction temperature and reaction time, and obtain the first reactant; The concentration of concentrated sulfuric acid is 99.9%, the mass of UV-234 added is 1.5% of the mass of concentrated sulfuric acid, the temperature of the dissolution process is controlled at 30°C; the reaction temperature in the emulsification tank is 30°C, and the reaction time is 4 hours.

[0053] S2, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of the first reactant to the second reactant PPTA is 4.13:1; The reaction temperature in the twin-screw reactor was 85° C., the screw speed was 40 rpm, and the solid content of the prepared spinning solution was 19.5% (mass content).

[0054] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 6; the coagulation bath temperature is 5°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 5%; and the heating temperature of the hot stretching is 160°C.

[0055] Comparative Example 1 Para-aramid fiber was prepared by the same method as in Example 2, except that no ultraviolet absorber UV-234 was added in this comparative example 1. The specific preparation process is as follows: S1, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and performing a blending reaction with concentrated sulfuric acid (with a concentration of 99.9%) and the second reactant PPTA in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of concentrated sulfuric acid to the second reactant PPTA is 4.1:1; The reaction temperature in the twin-screw reactor was 80° C., the screw speed was 20 rpm, and the solid content of the prepared spinning solution was 19.6% (mass content).

[0056] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the hot stretching is 150°C.

[0057] Comparative Example 2 The para-aramid fiber was prepared by the same method as in Example 2, except that the amount of ultraviolet absorber UV-234 added was increased in this comparative example 2. The specific preparation process is as follows: S1. Add UV-234 to the measured concentrated sulfuric acid and dissolve it. After the UV-234 is dissolved, transfer it to an emulsification tank for reaction, control the reaction temperature and reaction time, and obtain the first reactant; The concentration of concentrated sulfuric acid is 99.9%, the mass of UV-234 added is 5% of the mass of concentrated sulfuric acid, the temperature of the dissolution process is controlled at 20°C; the reaction temperature in the emulsification tank is 20°C, and the reaction time is 3 hours.

[0058] S2, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of the first reactant to the second reactant PPTA is 4.1:1; The reaction temperature in the twin-screw reactor was 80° C., the screw speed was 20 rpm, and the solid content of the prepared spinning solution was 19.6% (mass content).

[0059] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the hot stretching is 150°C.

[0060] Comparative Example 3 The para-aramid fiber was prepared by the same method as in Example 2, except that the amount of the first reactant was increased in this comparative example 3. The specific preparation process is as follows: S1. Add UV-234 to the measured concentrated sulfuric acid and dissolve it. After the UV-234 is dissolved, transfer it to an emulsification tank for reaction, control the reaction temperature and reaction time, and obtain the first reactant; The concentration of concentrated sulfuric acid is 99.9%, the mass of UV-234 added is 1% of the mass of concentrated sulfuric acid, the temperature of the dissolution process is controlled at 20°C; the reaction temperature in the emulsification tank is 20°C, and the reaction time is 3 hours.

[0061] S2, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of the first reactant to the second reactant PPTA is 4.5:1; The reaction temperature in the twin-screw reactor was 80° C., the screw speed was 20 rpm, and the solid content of the prepared spinning solution was 18.2% (mass content).

[0062] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the hot stretching is 150°C.

[0063] Comparative Example 4 The para-aramid fiber was prepared by the same method as in Example 2, except that the amount of the first reactant was reduced in this comparative example 4. The specific preparation process is as follows: S1. Add UV-234 to the measured concentrated sulfuric acid and dissolve it. After the UV-234 is dissolved, transfer it to an emulsification tank for reaction, control the reaction temperature and reaction time, and obtain the first reactant; The concentration of concentrated sulfuric acid is 99.9%, the mass of UV-234 added is 1% of the mass of concentrated sulfuric acid, the temperature of the dissolution process is controlled at 20°C; the reaction temperature in the emulsification tank is 20°C, and the reaction time is 3 hours.

[0064] S2, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of the first reactant to the second reactant PPTA is 3.5:1; The reaction temperature in the twin-screw reactor was 80° C., the screw speed was 20 rpm, and the solid content of the prepared spinning solution was 22.2% (mass content).

[0065] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the hot stretching is 150°C.

[0066] Comparative Example 5 Para-aramid fiber was prepared by the same method as in Example 2, except that the reaction temperature in step S2 of this comparative example 5 was 95° C. (higher than the temperature conditions specified in the present invention). The specific preparation process was as follows: S1. Add UV-234 to the measured concentrated sulfuric acid and dissolve it. After the UV-234 is dissolved, transfer it to an emulsification tank for reaction, control the reaction temperature and reaction time, and obtain the first reactant; The concentration of concentrated sulfuric acid is 99.9%, the mass of UV-234 added is 1% of the mass of concentrated sulfuric acid, the temperature of the dissolution process is controlled at 20°C; the reaction temperature in the emulsification tank is 20°C, and the reaction time is 3 hours.

[0067] S2, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of the first reactant to the second reactant PPTA is 4.1:1; The reaction temperature in the twin-screw reactor was 95° C., the screw speed was 20 rpm, and the solid content of the prepared spinning solution was 19.6% (mass content).

[0068] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the hot stretching is 150°C.

[0069] Comparative Example 6 Para-aramid fiber was prepared by the same method as in Example 2, except that the reaction temperature in step S2 of this comparative example 6 was 75° C. (lower than the temperature condition specified in the present invention). The specific preparation process was as follows: S1. Add UV-234 to the measured concentrated sulfuric acid and dissolve it. After the UV-234 is dissolved, transfer it to an emulsification tank for reaction, control the reaction temperature and reaction time, and obtain the first reactant; The concentration of concentrated sulfuric acid is 99.9%, the mass of UV-234 added is 1% of the mass of concentrated sulfuric acid, the temperature of the dissolution process is controlled at 20°C; the reaction temperature in the emulsification tank is 20°C, and the reaction time is 3 hours.

[0070] S2, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of the first reactant to the second reactant PPTA is 4.1:1; The reaction temperature in the twin-screw reactor was 75° C., the screw speed was 20 rpm, and the solid content of the prepared spinning solution was 19.6% (mass content).

[0071] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the hot stretching is 150°C.

[0072] Comparative Example 7 Para-aramid fiber was prepared by the same method as in Example 2, except that the heating temperature for hot drawing in step S3 of this comparative example 7 was 220° C. (higher than the temperature condition specified in the present invention). The specific preparation process was as follows: S1. Add UV-234 to the measured concentrated sulfuric acid and dissolve it. After the UV-234 is dissolved, transfer it to an emulsification tank for reaction, control the reaction temperature and reaction time, and obtain the first reactant; The concentration of concentrated sulfuric acid is 99.9%, the mass of UV-234 added is 1% of the mass of concentrated sulfuric acid, the temperature of the dissolution process is controlled at 20°C; the reaction temperature in the emulsification tank is 20°C, and the reaction time is 3 hours.

[0073] S2, delivering the measured second reactant PPTA to the reaction chamber of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the chamber of the twin-screw reactor to obtain a spinning solution; The mass ratio of the first reactant to the second reactant PPTA is 4.1:1; The reaction temperature in the twin-screw reactor was 80° C., the screw speed was 20 rpm, and the solid content of the prepared spinning solution was 19.6% (mass content).

[0074] S3, obtaining aging-resistant para-aramid fiber through dry-jet wet spinning of the spinning solution, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the hot stretching is 220°C.

[0075] Comparative Example 8 Para-aramid fiber was prepared by the same method as in Example 2, except that UV-234 was directly added to the sulfuric acid solution of PPTA in this comparative example 8. The specific preparation process is as follows: S1. The measured second reactant PPTA is delivered to the reaction chamber of the twin-screw reactor via a feed screw. Concentrated sulfuric acid (99.9%) and the second reactant PPTA are blended and reacted in the twin-screw reactor chamber to obtain a spinning solution. The reaction temperature in the twin-screw reactor is 80°C, and the screw speed is 20 rpm.

[0076] Add UV-234 to the spinning solution and mix well. The added mass of UV-234 is 1% of the mass of concentrated sulfuric acid. The mass ratio of the first reactant to the second reactant PPTA is 4.1:1. The solid content of the prepared spinning solution is 19.6% (mass content).

[0077] S2. The spinning solution is subjected to a dry-jet wet spinning process to obtain an aging-resistant para-aramid fiber, wherein the dry-jet wet spinning process comprises: after the spinning solution is spun, the spinning solution is subjected to a coagulation bath, stretched, washed, dried, hot-drawn, oiled, and rolled to obtain the aging-resistant para-aramid fiber; The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6°C, and the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the hot stretching is 150°C.

[0078] The para-aramid fibers prepared in the above examples and comparative examples were subjected to performance tests. The specific test results are shown in Table 1 below. The test methods involved are as follows: Strength performance: High-strength wire fully automatic strength and elongation tester EMATER 680; Modulus: High-strength yarn fully automatic strength and elongation tester EMATER 680; Elongation at break: High-strength wire fully automatic strength and elongation tester EMATER 680; Aging resistance: Xenon lamp weathering test chamber 1.1kW, 39°C, 45% humidity, test time is 96h, and then calculate the percentage of fiber strength performance loss before and after aging resistance test.

[0079] Table 1 Performance test results

[0080] Note: The fiber fineness of the fibers prepared in the examples of the present invention and the comparison is between 1077-1144 dtex.

[0081] It can be seen from the data in the above table that the aging-resistant para-aramid fibers prepared by the preparation method of the present invention in Examples 1 to 6 have excellent strength and modulus properties while having better aging resistance and stability. The preparation method of the present invention adds UV-234 to sulfuric acid instead of adding UV-234 to a PPTA / sulfuric acid stock solution. In the preparation method of the present invention, UV-234 is fully dissolved in sulfuric acid to prepare a UV-234 / sulfuric acid solution, which is then fully mixed with PPTA through a twin-screw extruder. The UV-234 additive has a stronger binding force with the fiber and is more evenly dispersed. The prepared fiber has improved aging resistance while maintaining strength. In addition, UV-234 reacts with sulfuric acid to generate sulfonation. After the sulfonic acid group (-SO3H) is introduced, the strong polarity of the sulfonic acid group will competitively bind with the amide bond on the PPTA chain, weakening the original intermolecular hydrogen bond. In addition, the sulfonic acid group has a large volume, which can expand the distance between molecular chains, reduce the interchain packing density, promote the dissolution of PPTA, and prepare a more uniform spinning stock solution, thereby obtaining an excellent and stable aging-resistant para-aramid fiber.

[0082] From the comparison of the experimental results of Comparative Example 1 and Example 2, it can be seen that the aging-resistant para-aramid fiber prepared by the preparation method of the present invention in Example 2 has good aging resistance while maintaining good strength and modulus properties compared with the conventional para-aramid fiber in Comparative Example 1.

[0083] From the comparison of the experimental results of Comparative Example 2 and Example 2, it can be seen that if the addition amount of ultraviolet absorber UV-234 is increased, although the aging resistance of the fiber can be improved to a certain extent, the content is too high, which destroys the fiber structure and reduces the fiber strength. Therefore, the addition amount of UV-234 specified in the present invention is more conducive to obtaining aging-resistant para-aramid fiber with excellent comprehensive performance.

[0084] From the comparison of the experimental results of Comparative Example 3 and Example 2, it can be seen that if the dosage ratio of the first reactant is increased, the stock solution concentration is lower. When the stock solution concentration is 18%, the stock solution viscosity decreases, the spinnability deteriorates, and the fiber performance decreases.

[0085] From the comparison of the experimental results of Comparative Example 4 and Example 2, it can be seen that if the dosage ratio of the first reactant is reduced, the stock solution concentration is higher. When the stock solution concentration is 22.2%, the stock solution viscosity increases, the spinnability deteriorates, and the fiber performance decreases.

[0086] It can be seen from Comparative Examples 3 and 4 that the ratio of the first reactant to the second reactant needs to be controlled within an appropriate range. Therefore, the present invention is used to limit the ratio of the first reactant to the second reactant, thereby improving the aging resistance of the para-aramid fiber while ensuring the fiber strength.

[0087] From the comparison of the experimental results of Comparative Example 5 and Example 2, it can be seen that if the reaction temperature of the first reactant and the second reactant in step S2 is increased, when the reaction temperature exceeds 90°C, the degree of degradation of the stock solution in the dissolver is greater, resulting in a decrease in the strength performance of the fiber.

[0088] From the comparison of the experimental results of Comparative Example 6 and Example 2, it can be seen that if the reaction temperature of the first reactant and the second reactant in step S2 is lowered, when the reaction temperature is lower than 80°C, the fluidity of the stock solution degraded in the dissolver is poor, the viscosity is too high, the spinnability deteriorates, and the strength performance of the fiber is reduced.

[0089] It can be seen from Comparative Examples 5 and 6 that the reaction temperature of the first reactant and the second reactant in S2 needs to be controlled within an appropriate range. The temperature will affect the degree of fiber degradation. Too large or too small a degree of fiber degradation will lead to changes in fiber viscosity and poor spinnability. Therefore, the present invention is used to limit the reaction temperature of the first reactant and the second reactant in S2, thereby improving the aging resistance of para-aramid fiber while ensuring fiber strength.

[0090] From the comparison of the experimental results of Comparative Example 7 and Example 2, it can be seen that if the heating temperature of the hot stretching in step S3 is increased, the fiber will change color during the heating process, and UV-234 will undergo oxidative discoloration at high temperatures, affecting the fiber appearance and aging resistance of the fiber.

[0091] From the comparison of the experimental results of Comparative Example 8 and Example 2, it can be seen that if UV-234 is directly added to the PPTA / sulfuric acid stock solution during the preparation of aging-resistant para-aramid fibers, the UV-234 will not be mixed evenly in the fibers, resulting in poor uniformity of the stock solution, which not only affects the strength performance of the fibers, but also has limited improvement on the aging resistance of the fibers.

[0092] The technical features of the above-described embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] For those skilled in the art, several variations and improvements may be made without departing from the scope of the present invention, which all fall within the scope of protection of the present invention. The scope of protection of the present invention shall be based on the appended claims.

Claims

1. A method for preparing aging-resistant para-aramid fiber, characterized in that: The preparation method is: S1, UV-234 and concentrated sulfuric acid react to obtain a first reactant; S2, the first reactant and the second reactant PPTA are blended to obtain a spinning solution; S3. The spinning solution is subjected to a dry-jet wet spinning process to obtain aging-resistant para-aramid fiber.

2. The method for preparing an aging-resistant para-aramid fiber according to claim 1, characterized in that: In step S1, the concentration of the concentrated sulfuric acid is 99.8-101% based on the SO3 content; The dosage of UV-234 is 0.25%-2.5% of the mass of concentrated sulfuric acid; In step S2, the mass ratio of the first reactant to the second reactant PPTA is (4-4.13):

1.

3. The method for preparing aging-resistant para-aramid fiber according to claim 1, characterized in that: In step S1, the reaction temperature is 20-60° C., and the reaction time is 2-6 h.

4. The method for preparing aging-resistant para-aramid fiber according to claim 1, characterized in that: In step S2, the first reactant and the second reactant PPTA are blended and reacted in the cavity of a twin-screw reactor at a screw speed of 20-50 rpm.

5. The method for preparing aging-resistant para-aramid fiber according to claim 1, characterized in that: In step S2, the blending reaction temperature is 80-90°C.

6. The method for preparing aging-resistant para-aramid fiber according to claim 1, characterized in that: The spinning solution is in a liquid crystal state; and the solid content of the spinning solution is 19.5%-20.0% in terms of mass concentration.

7. The method for preparing aging-resistant para-aramid fiber according to claim 1, characterized in that: In step S3, the dry-jet wet spinning process includes: after the spinning solution is spun, it is subjected to a coagulation bath, stretched, washed, dried, hot drawn, oiled and rolled to obtain the aging-resistant para-aramid fiber.

8. The method for preparing aging-resistant para-aramid fiber according to claim 7, characterized in that: The draft ratio during the stretching process of the dry-jet wet spinning process is 6-12; the temperature condition of the hot stretching is 150-200°C.

9. The method for preparing aging-resistant para-aramid fiber according to claim 7, characterized in that: The coagulation bath is a sulfuric acid aqueous solution, the mass concentration of persulfuric acid in the coagulation bath is 2%-8%, and the temperature of the coagulation bath is 5-35°C.

10. An aging-resistant para-aramid fiber, characterized in that: The aging-resistant para-aramid fiber is prepared according to the preparation method according to any one of claims 1 to 9.

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