Aging-resistant p-aramid fiber and preparation method thereof

Abstract

The present application relates to aramid fiber material technical field, specifically in kind, the present application relates to a kind of anti-aging p-aramid fiber and its preparation method, the preparation method is: S1, UV-234 and concentrated sulfuric acid are reacted to obtain first reactant;S2, first reactant and second reactant PPTA are blended to obtain spinning dope;S3, spinning dope is obtained by dry spraying wet spinning process to obtain anti-aging p-aramid fiber.Step S1, according to SO3 content, the concentration of the concentrated sulfuric acid is 99.8-101%;The amount of the UV-234 is 0.25%-2.5% of the mass of concentrated sulfuric acid;Step S2, the mass ratio of the first reactant and second reactant PPTA is (4-4.13):1.The anti-aging p-aramid fiber prepared by the preparation method keeps higher strength while the aging resistance of the fiber is significantly improved, and the preparation method is simple and suitable for industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of aging-resistant para-aramid fiber and its preparation method, belong to aramid fiber material technical field. BACKGROUND

[0002] Para-aramid is a kind of high-performance synthetic fiber, chemical name is poly-p-phenylene terephthalamide (PPTA), by rigid linear macromolecular chain highly oriented arrangement, its molecular structure gives it super high strength, high modulus, high temperature resistance, corrosion resistance and other characteristics, is one of important strategic materials, has a wide range of applications in aerospace, safety protection, industrial materials, building increases, rubber field, but the amide bond (-CO-NH-) in its molecular chain is easily broken under ultraviolet (UV) irradiation, resulting in its light aging resistance performance is poor, it is easy to discolor after light, the storage condition is higher, limit aramid in outdoor protective equipment, optical cable reinforcing material, aerospace composite material and other fields long-term application, therefore, it is urgent to develop more efficient, do not affect the intrinsic properties of the aging-resistant technology of fiber.

[0003] At present, the methods for improving the aging resistance of para-aramid fiber are as follows:

[0004] 1. Surface coating / immersion modification:

[0005] The main method is: coating anti-UV agent (such as nano-TiO2, ZnO) or hydrolysis-resistant coating (such as siloxane, fluoride) on the surface of the fiber. The method disclosed in the patent application with publication number CN112048905A is to coat anti-UV agent on the surface of the fiber. However, this method has the following problems: (1) poor adhesion of anti-UV agent on the fiber: the surface of aramid is smooth and inert, the coating is easy to fall off, and the protective effect decreases after long-term use; (2) affects the air permeability: thick coating may reduce the flexibility and air permeability of the fiber, which is not suitable for high dynamic load scenarios (such as protective clothing).

[0006] 2. Copolymerization modification:

[0007] The main method is: introducing a third monomer (such as a compound containing an electron-withdrawing group) during polymerization to reduce the reactivity of the amide bond. The method disclosed in the patent application with publication number CN118600743A is to embed the chromogenic monomer into the high molecular chain segment of the aromatic polyamide by copolymerization. However, this method has the following problems: (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: the polymerization conditions need to be accurately controlled, and the solvent recovery is difficult (such as NMP / lithium chloride system).

[0008] 3. Nano-composite reinforcement

[0009] The main method is: dispersing nanomaterials (graphene, carbon nanotubes) into the spinning solution, and preparing composite fibers by blending spinning. The method disclosed in the patent application with publication number CN120425479A is to mix poly-m-phenylene isophthalamide copolymer, composite nanosuspension and 4, 4'-diamino diphenyl methane in N-methyl pyrrolidone, deaerate to prepare a modified polymer spinning solution, and dry spray-wet spinning to obtain a coagulation fiber. However, the method has the following problems: (1) uneven dispersion: nanoparticles are prone to agglomeration, resulting in internal defects of the fiber; (2) high cost: high-quality nanomaterials (such as functionalized graphene) are expensive, and industrialization is difficult.

[0010] As can be seen, the current industry's common modification methods of various aramid fibers cannot simultaneously meet the requirements of high strength, high weather resistance and low cost, and the stability of the existing coating or composite material is insufficient during long-term use, and the aging resistance effect of the existing coating or composite material gradually decreases with the use time. SUMMARY

[0011] The present application provides a kind of aging-resistant p-aramid fiber and its preparation method, the aging-resistant p-aramid fiber prepared by the preparation method has significantly improved aging resistance while maintaining high strength, and the preparation method is simple and suitable for industrial application.

[0012] The technical scheme for solving the above technical problems is as follows: a preparation method of an aging-resistant p-aramid fiber, the preparation method is:

[0013] S1, UV-234 (2-[2'-hydroxy-3',5'-bis (α, α-dimethylbenzyl) phenyl] benzotriazole) and concentrated sulfuric acid are reacted to obtain a first reactant;

[0014] S2, the first reactant and the second reactant PPTA are blended and reacted to obtain a spinning dope;

[0015] S3, the spinning dope is obtained by dry jet wet spinning process to obtain an aging-resistant p-aramid fiber.

[0016] Further, in step S1, the concentration of the concentrated sulfuric acid is 99.8-101% by SO3 content;

[0017] The amount of UV-234 is 0.25%-2.5% of the mass of concentrated sulfuric acid;

[0018] In step S2, the mass ratio of the first reactant to the second reactant PPTA is (4-4.13):1.

[0019] Further, in step S1, the reaction temperature is 20-60℃, and the reaction time is 2-6h.

[0020] Further, in step S2, the first reactant and the second reactant PPTA are blended and reacted in the double screw reactor cavity, and the screw rotation speed is 20-50 rpm.

[0021] Further, in step S2, the blending and reaction temperature is 80-90 DEG C.

[0022] Further, the spinning dope is in a liquid crystal state, and the solid content of the spinning dope is 19.5%-20.0% by mass concentration.

[0023] Further, in step S3, the dry-jet wet spinning process comprises: after the spinning dope is jetted, the spinning dope is subjected to coagulation bath, drawing, washing, drying, heat drawing, oiling and winding to obtain the aging-resistant para-aramid fiber.

[0024] Further, the drawing ratio in the drawing process of the dry-jet wet spinning process is 6-12, and the temperature condition of the heat drawing is 150-200 DEG C.

[0025] Further, the coagulation bath is a sulfuric acid aqueous solution, the mass concentration of the persulfuric acid in the coagulation bath is 2%-8%, and the coagulation bath temperature is 5-35 DEG C.

[0026] The application further discloses an aging-resistant para-aramid fiber, which is prepared by the preparation method.

[0027] The application has the following beneficial effects:

[0028] The application adds UV-234 into sulfuric acid, the UV-234 is fully dissolved in the sulfuric acid to prepare a UV-234 / sulfuric acid solution (first reactant), and then the double screw extruder is used to fully mix the first reactant with PPTA to successfully prepare the aging-resistant fiber.

[0029] In addition, in the preparation method, the UV-234 is fully mixed with sulfuric acid first, and then mixed with PPTA, the additive UV-234 has good combination with the aramid fiber, so that the long-term stability of the aging-resistant para-aramid fiber prepared finally is good.

[0030] The UV-234 reacts with sulfuric acid to generate sulfonation, and a sulfonic group (-SO3H) is generated. The strong polarity of the sulfonic group competes with the amide bond on the PPTA chain to weaken the original intermolecular hydrogen bond. In addition, the sulfonic group has a large volume, which can expand the molecular chain spacing, reduce the chain stacking density, promote the dissolution of PPTA, facilitate the preparation of more uniform spinning solution, improve the production and processing efficiency, and obtain high-quality target products. Moreover, the whole preparation method is simple in operation and suitable for industrial application. DETAILED DESCRIPTION

[0031] The specific embodiments of the present application will be described in detail below. The present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application. Therefore, the present application is not limited by the specific embodiments disclosed.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terms used are only for describing specific embodiments and are not intended to limit the present application.

[0033] A preparation method of an anti-aging para-aramid fiber, the preparation method comprises the following steps:

[0034] S1, UV-234 and concentrated sulfuric acid are reacted to obtain a first reactant;

[0035] S2, the first reactant and the second reactant PPTA are blended and reacted to obtain a spinning solution;

[0036] S3, the spinning solution is obtained by a dry-jet wet spinning process to obtain an anti-aging para-aramid fiber.

[0037] Specifically, in step S1, the concentration of the concentrated sulfuric acid is 99.8-101% in terms of SO3 content;

[0038] The amount of the UV-234 is 0.25%-2.5% of the mass of the concentrated sulfuric acid;

[0039] In step S2, the mass ratio of the first reactant to the second reactant PPTA is (4-4.13):1.

[0040] Specifically, in step S1, the reaction temperature is 20-60℃, and the reaction time is 2-6h.

[0041] Specifically, in step S2, the first reactant and the second reactant PPTA are blended and reacted in the cavity of a double-screw reactor, and the screw rotation speed is 20-50rpm.

[0042] More specifically, in step S2, the metered polymer (PPTA) is transported into the reaction cavity of the twin-screw reactor by a feeding screw; and the prepared spinning dope is directly transported to the dry-jet wet spinning process production line through a pipeline.

[0043] More specifically, the PPTA used in the embodiment of the present application is prepared by low-temperature polycondensation reaction, wherein the polymerized monomers are terephthaloyl chloride and p-phenylenediamine, the solvent is N-methyl pyrrolidone (NMP), and the cosolvent is calcium chloride (CaCl2).

[0044] More specifically, in the preparation of 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 to be 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℃, the reaction time is 30-60 min, the solid content in the system after the reaction is 10-12%, and then PPTA is obtained through solid-liquid separation, water washing, and drying. However, this does not constitute a limitation on the present application, and as long as a conventional PPTA that can be used for spinning of para-aramid fibers is used, the present application can be used to obtain the anti-aging para-aramid fiber.

[0045] Specifically, in step S2, the blending reaction temperature is 80-90℃.

[0046] Specifically, the spinning dope is in a liquid crystal state, and the solid content of the spinning dope is 19.5%-20.0% by mass concentration.

[0047] Specifically, in step S3, the dry-jet wet spinning process includes: after the spinning dope is spun, the spinning dope is subjected to coagulation bath, stretching, water washing, drying, heat drawing, oiling, and winding to obtain the anti-aging para-aramid fiber.

[0048] Specifically, the drawing ratio in the stretching process of the dry-jet wet spinning process is 6-12, and the temperature condition for the heat drawing is 150-200℃.

[0049] Specifically, the coagulation bath is a sulfuric acid aqueous solution, the mass concentration of the persulfate in the coagulation bath is 2%-8%, and the temperature of the coagulation bath is 5-35℃.

[0050] More specifically, multiple water washing operations are adopted in the water washing process.

[0051] The present application also discloses an anti-aging para-aramid fiber, which is prepared by the preparation method of the present application.

[0052] Example 1

[0053] A preparation method of an anti-aging para-aramid fiber is as follows:

[0054] S1, adding UV-234 in the metered concentrated sulfuric acid for dissolution, after the UV-234 is dissolved, it is transferred to the emulsification tank for reaction, the reaction temperature and the reaction time are controlled, and the first reactant is obtained;

[0055] Among them, 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, and the temperature of the dissolution process is controlled at 20 DEG C; the reaction temperature in the emulsification tank is 20 DEG C, and the reaction time is 3h.

[0056] S2, the metered second reactant PPTA is conveyed to the reaction cavity of the double screw reactor through the feeding screw rod, and the first reactant and the second reactant PPTA are blended and reacted in the cavity of the double screw reactor to obtain a spinning dope;

[0057] Among them, the mass ratio of the first reactant and the second reactant PPTA is 4.1:1;

[0058] The reaction temperature in the double screw reactor is 80 DEG C, the screw rod rotation speed is 20 rpm, and the prepared spinning dope solid content is 19.6% (mass content).

[0059] S3, the spinning dope is obtained by a dry spraying wet spinning process to obtain the aging-resistant para-aramid fiber, the dry spraying wet spinning process comprises: after the spinning dope is jetted, it is subjected to coagulation bath, stretching, washing, drying, heat drawing, oiling and winding to obtain the aging-resistant para-aramid fiber;

[0060] Among them, the drawing ratio in the stretching process is 6; the coagulation bath temperature is 6 DEG C, and the coagulation bath is a 2% sulfuric acid aqueous solution; the heating temperature of the heat drawing is 150 DEG C.

[0061] Example 2

[0062] A preparation method of an aging-resistant para-aramid fiber is:

[0063] S1, adding UV-234 in the metered concentrated sulfuric acid for dissolution, after the UV-234 is dissolved, it is transferred to the emulsification tank for reaction, the reaction temperature and the reaction time are controlled, and the first reactant is obtained;

[0064] Among them, the concentration of concentrated sulfuric acid is 99.9%, the mass of UV-234 added is 1% of the mass of concentrated sulfuric acid, and the temperature of the dissolution process is controlled at 20 DEG C; the reaction temperature in the emulsification tank is 20 DEG C, and the reaction time is 3h.

[0065] S2, the metered second reactant PPTA is conveyed to the reaction cavity of the double screw reactor through the feeding screw rod, and the first reactant and the second reactant PPTA are blended and reacted in the cavity of the double screw reactor to obtain a spinning dope;

[0066] The mass ratio of the first reactant and the second reactant PPTA is 4.1:1.

[0067] The reaction temperature in the twin-screw reactor is 80 DEG C, the screw rotation speed is 20 rpm, and the prepared spinning dope solid content is 19.6% (mass content).

[0068] S3, the spinning dope is obtained by a dry-jet wet spinning process to obtain the aging-resistant para-aramid fiber, the dry-jet wet spinning process comprises: after the spinning dope is jetted, the aging-resistant para-aramid fiber is obtained through a coagulation bath, stretching, washing, drying, heat drawing, oiling and winding.

[0069] In the stretching process, the draw ratio is 6; the coagulation bath temperature is 6 DEG C, the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the heat drawing is 150 DEG C.

[0070] Example 3

[0071] A preparation method of an aging-resistant para-aramid fiber is as follows:

[0072] S1, UV-234 is added in the measured concentrated sulfuric acid for dissolution, after the UV-234 is dissolved, the solution is transferred to an emulsifying tank for reaction, the reaction temperature and reaction time are controlled, and a first reactant is obtained;

[0073] The concentration of the concentrated sulfuric acid is 99.9%, the added mass of the UV-234 is 2.5% of the mass of the concentrated sulfuric acid, and the temperature in the dissolution process is controlled at 20 DEG C; the reaction temperature in the emulsifying tank is 20 DEG C, and the reaction time is 3 h.

[0074] S2, the measured second reactant PPTA is conveyed to the reaction cavity of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the cavity of the twin-screw reactor to obtain a spinning dope;

[0075] The mass ratio of the first reactant and the second reactant PPTA is 4.1:1.

[0076] The reaction temperature in the twin-screw reactor is 80 DEG C, the screw rotation speed is 20 rpm, and the prepared spinning dope solid content is 19.6% (mass content).

[0077] S3, the spinning dope is obtained by a dry-jet wet spinning process to obtain the aging-resistant para-aramid fiber, the dry-jet wet spinning process comprises: after the spinning dope is jetted, the aging-resistant para-aramid fiber is obtained through a coagulation bath, stretching, washing, drying, heat drawing, oiling and winding.

[0078] In the stretching process, the draw ratio is 6; the coagulation bath temperature is 6 DEG C, the coagulation bath is a sulfuric acid aqueous solution with a mass concentration of 2%; and the heating temperature of the heat drawing is 150 DEG C.

[0079] Example 4

[0080] A preparation method of the aging-resistant para-aramid fiber is as follows:

[0081] S1, UV-234 is added to the measured concentrated sulfuric acid for dissolution, and after the UV-234 is dissolved, it is transferred to an emulsifying tank for reaction, the reaction temperature and reaction time are controlled, and a first reactant is obtained;

[0082] The concentration of the concentrated sulfuric acid is 99.8%, the mass of the added UV-234 is 1.5% of the mass of the concentrated sulfuric acid, and the temperature of the dissolution process is controlled at 40°C; the reaction temperature in the emulsifying tank is 40°C, and the reaction time is 6h.

[0083] S2, the measured second reactant PPTA is conveyed into the reaction cavity of the double-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the cavity of the double-screw reactor to obtain a spinning dope;

[0084] The mass ratio of the first reactant to the second reactant PPTA is 4.13:1.

[0085] The reaction temperature in the double-screw reactor is 90°C, the screw rotation speed is 30rpm, and the prepared spinning dope has a solid content of 19.5% (mass content).

[0086] S3, the spinning dope is obtained by a dry-jet wet spinning process to obtain the aging-resistant para-aramid fiber, the dry-jet wet spinning process comprising: after the spinning dope is jetted, it is subjected to a coagulation bath, stretching, washing, drying, heat drawing, oiling and winding to obtain the aging-resistant para-aramid fiber.

[0087] The draw ratio in the stretching process is 12; the coagulation bath temperature is 25°C, and the coagulation bath is an 8% mass concentration sulfuric acid aqueous solution; and the heating temperature of the heat drawing is 200°C.

[0088] Example 5

[0089] A preparation method of the aging-resistant para-aramid fiber is as follows:

[0090] S1, UV-234 is added to the measured concentrated sulfuric acid for dissolution, and after the UV-234 is dissolved, it is transferred to an emulsifying tank for reaction, the reaction temperature and reaction time are controlled, and a first reactant is obtained;

[0091] The concentration of the concentrated sulfuric acid is 101%, the mass of the added UV-234 is 2.0% of the mass of the concentrated sulfuric acid, and the temperature of the dissolution process is controlled at 60°C; the reaction temperature in the emulsifying tank is 60°C, and the reaction time is 2h.

[0092] S2, the metered second reactant PPTA is transported into the reaction cavity of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the twin-screw reactor cavity to obtain a spinning dope;

[0093] The mass ratio of the first reactant to the second reactant PPTA is 4:1.

[0094] The reaction temperature in the twin-screw reactor is 90℃, the screw rotation speed is 50rpm, and the prepared spinning dope has a solid content of 20.0% (mass content).

[0095] S3, the spinning dope is obtained by a dry-jet wet spinning process to obtain the aging-resistant para-aramid fiber, the dry-jet wet spinning process comprises: after the spinning dope is jetted, the aging-resistant para-aramid fiber is obtained through a coagulation bath, stretching, washing, drying, heat drawing and oiling and winding.

[0096] In the stretching process, the draw ratio is 10; the coagulation bath temperature is 35℃, the coagulation bath is a 5% sulfuric acid aqueous solution; the heating temperature of the heat drawing is 180℃.

[0097] Example 6

[0098] A method for preparing an aging-resistant para-aramid fiber comprises:

[0099] S1, adding UV-234 in the metered concentrated sulfuric acid for dissolution, after the UV-234 is dissolved, transferring to an emulsifying tank for reaction, controlling the reaction temperature and reaction time to obtain a first reactant;

[0100] The concentration of the concentrated sulfuric acid is 99.9%, the added mass of the UV-234 is 1.5% of the mass of the concentrated sulfuric acid, and the temperature of the dissolution process is controlled at 30℃; the reaction temperature in the emulsifying tank is 30℃, and the reaction time is 4h.

[0101] S2, the metered second reactant PPTA is transported into the reaction cavity of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA are blended and reacted in the twin-screw reactor cavity to obtain a spinning dope;

[0102] The mass ratio of the first reactant to the second reactant PPTA is 4:1.

[0103] The reaction temperature in the twin-screw reactor is 90℃, the screw rotation speed is 50rpm, and the prepared spinning dope has a solid content of 20.0% (mass content).

[0104] S3, the spinning dope is obtained by a dry-jet wet spinning process to obtain the aging-resistant para-aramid fiber, the dry-jet wet spinning process comprises: after the spinning dope is jetted, the aging-resistant para-aramid fiber is obtained through a coagulation bath, stretching, washing, drying, heat drawing, oiling and winding.

[0105] In the stretching process, the draw ratio is 6; the coagulation bath temperature is 5 DEG C, the coagulation bath is a 5% sulfuric acid aqueous solution; the heating temperature of the heat drawing is 160 DEG C.

[0106] Comparative Example 1

[0107] The para-aramid fiber is prepared by the same method as in Example 2, except that no UV-234 is added in Comparative Example 1, and the specific preparation process is as follows:

[0108] S1, the metered second reactant PPTA is transported into the reaction cavity of the double-screw reactor by a feeding screw, and the concentrated sulfuric acid (concentration of 99.9%) and the second reactant PPTA are blended and reacted in the double-screw reactor cavity to obtain a spinning dope;

[0109] In the stretching process, the draw ratio is 6; the coagulation bath temperature is 5 DEG C, the coagulation bath is a 5% sulfuric acid aqueous solution; the heating temperature of the heat drawing is 160 DEG C.

[0110] The reaction temperature in the double-screw reactor is 80 DEG C, the screw rotation speed is 20 rpm, and the prepared spinning dope has a solid content of 19.6% (mass content).

[0111] S3, the spinning dope is obtained by a dry-jet wet spinning process to obtain the aging-resistant para-aramid fiber, the dry-jet wet spinning process comprises: after the spinning dope is jetted, the aging-resistant para-aramid fiber is obtained through a coagulation bath, stretching, washing, drying, heat drawing, oiling and winding.

[0112] In the stretching process, the draw ratio is 6; the coagulation bath temperature is 5 DEG C, the coagulation bath is a 5% sulfuric acid aqueous solution; the heating temperature of the heat drawing is 160 DEG C.

[0113] Comparative Example 2

[0114] The para-aramid fiber is prepared by the same method as in Example 2, except that the amount of UV-234 added is increased in Comparative Example 2, and the specific preparation process is as follows:

[0115] S1, UV-234 is added to the metered concentrated sulfuric acid for dissolution, and after the UV-234 is dissolved, it is transferred to an emulsifying tank for reaction, and the reaction temperature and reaction time are controlled to obtain a first reactant;

[0116] The concentration of concentrated sulfuric acid is 99.9%, the added mass of UV-234 is 5% of the mass of concentrated sulfuric acid, and the temperature of the dissolution process is controlled at 20 DEG C; the reaction temperature in the emulsifying tank is 20 DEG C, and the reaction time is 3h.

[0117] S2, the metered second reactant PPTA is transported into the reaction cavity of the double-screw reactor through the feeding screw rod, and the first reactant and the second reactant PPTA are blended and reacted in the double-screw reactor cavity to obtain a spinning dope;

[0118] The mass ratio of the first reactant to the second reactant PPTA is 4.1:1.

[0119] The reaction temperature in the double-screw reactor is 80 DEG C, the screw rod rotation speed is 20 rpm, and the prepared spinning dope has a solid content of 19.6% (mass content).

[0120] S3, the spinning dope is obtained by a dry-jet wet spinning process to obtain the aging-resistant para-aramid fiber, the dry-jet wet spinning process comprises: after the spinning dope is jetted, it is subjected to coagulation bath, stretching, washing, drying, heat drawing, oiling and winding to obtain the aging-resistant para-aramid fiber.

[0121] The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6 DEG C, and the coagulation bath is a 2% sulfuric acid aqueous solution; the heating temperature of the heat drawing is 150 DEG C.

[0122] Comparative Example 3

[0123] The para-aramid fiber is prepared by the same method as in Example 2, except that the proportion of the first reactant is increased in Comparative Example 3, and the specific preparation process is as follows:

[0124] S1, UV-234 is added to the metered concentrated sulfuric acid for dissolution, and after the UV-234 is dissolved, it is transferred to an emulsifying tank for reaction, and the reaction temperature and reaction time are controlled to obtain a first reactant.

[0125] The concentration of concentrated sulfuric acid is 99.9%, the added mass of UV-234 is 5% of the mass of concentrated sulfuric acid, and the temperature of the dissolution process is controlled at 20 DEG C; the reaction temperature in the emulsifying tank is 20 DEG C, and the reaction time is 3h.

[0126] S2, the metered second reactant PPTA is transported into the reaction cavity of the double-screw reactor through the feeding screw rod, and the first reactant and the second reactant PPTA are blended and reacted in the double-screw reactor cavity to obtain a spinning dope;

[0127] The mass ratio of the first reactant to the second reactant PPTA is 4.1:1.

[0128] The reaction temperature in the twin-screw reactor was 80℃, the screw rotation speed was 20rpm, and the prepared spinning dope solid content was 18.2% (mass content).

[0129] S3, the spinning dope was used to prepare the aging-resistant para-aramid fiber through a dry-jet wet spinning process, which included: after the spinning dope was jetted, it was subjected to coagulation bath, drawing, washing, drying, heat drawing, oiling and winding to obtain the aging-resistant para-aramid fiber.

[0130] In the drawing process, the draw ratio was 6; the coagulation bath temperature was 6℃, the coagulation bath was a sulfuric acid aqueous solution with a mass concentration of 2%; the heating temperature of the heat drawing was 150℃.

[0131] Comparative Example 4

[0132] The para-aramid fiber was prepared by the same method as in Example 2, except that the proportion of the first reactant was reduced in Comparative Example 4, and the specific preparation process was as follows:

[0133] S1, UV-234 was added to the measured concentrated sulfuric acid for dissolution, and after the UV-234 was dissolved, it was transferred to an emulsifying tank for reaction, and the reaction temperature and reaction time were controlled to obtain the first reactant;

[0134] In the emulsifying tank, the reaction temperature was 20℃, and the reaction time was 3h.

[0135] S2, the measured second reactant PPTA was conveyed into the reaction cavity of the twin-screw reactor through a feeding screw, and the first reactant and the second reactant PPTA were subjected to blending reaction in the cavity of the twin-screw reactor to obtain the spinning dope;

[0136] The mass ratio of the first reactant to the second reactant PPTA was 3.5:1.

[0137] The reaction temperature in the twin-screw reactor was 80℃, the screw rotation speed was 20rpm, and the prepared spinning dope solid content was 22.2% (mass content).

[0138] S3, the spinning dope was used to prepare the aging-resistant para-aramid fiber through a dry-jet wet spinning process, which included: after the spinning dope was jetted, it was subjected to coagulation bath, drawing, washing, drying, heat drawing, oiling and winding to obtain the aging-resistant para-aramid fiber.

[0139] In the drawing process, the draw ratio was 6; the coagulation bath temperature was 6℃, the coagulation bath was a sulfuric acid aqueous solution with a mass concentration of 2%; the heating temperature of the heat drawing was 150℃.

[0140] Comparative Example 5

[0141] The para aramid fiber was prepared by the same method as example 2, except that the reaction temperature in step S2 of the present comparative example 5 was 95℃ (higher than the temperature condition defined in the present application), and the specific preparation process was as follows:

[0142] S1, UV-234 was added for dissolution in the measured concentrated sulfuric acid, and after the UV-234 was dissolved, it was transferred to the emulsification tank for reaction, and the reaction temperature and reaction time were controlled to obtain the first reactant;

[0143] Among them, the concentration of concentrated sulfuric acid is 99.9%, the mass of UV-234 added is 1% of the mass of concentrated sulfuric acid, and the temperature control during the dissolution process is 20℃; the reaction temperature in the emulsification tank is 20℃, and the reaction time is 3h.

[0144] S2, the metered second reactant PPTA was conveyed into the reaction cavity of the double screw reactor by the feeding screw, and the first reactant and the second reactant PPTA were blended and reacted in the cavity of the double screw reactor to obtain the spinning dope;

[0145] Among them, the mass ratio of the first reactant and the second reactant PPTA is 4.1:1;

[0146] The reaction temperature in the double screw reactor was 95℃, the screw rotation speed was 20rpm, and the prepared spinning dope had a solid content of 19.6% (mass content).

[0147] S3, the spinning dope was obtained by dry jet wet spinning process to obtain the aging-resistant para aramid fiber, which included: after the spinning dope was jetted, it was subjected to coagulation bath, stretching, washing, drying, heat drawing, oiling and winding to obtain the aging-resistant para aramid fiber;

[0148] Among them, the draw ratio in the stretching process was 6; the coagulation bath temperature was 6℃, and the coagulation bath was a 2% mass concentration sulfuric acid aqueous solution; the heating temperature of the heat drawing was 150℃.

[0149] Comparative example 6

[0150] The para aramid fiber was prepared by the same method as example 2, except that the reaction temperature in step S2 of the present comparative example 6 was 75℃ (lower than the temperature condition defined in the present application), and the specific preparation process was as follows:

[0151] S1, UV-234 was added for dissolution in the measured concentrated sulfuric acid, and after the UV-234 was dissolved, it was transferred to the emulsification tank for reaction, and the reaction temperature and reaction time were controlled to obtain the first reactant;

[0152] The concentration of concentrated sulfuric acid is 99.9%, the added mass of UV-234 is 1% of the mass of concentrated sulfuric acid, and the temperature of the dissolution process is controlled at 20°C; the reaction temperature in the emulsifying tank is 20°C, and the reaction time is 3h.

[0153] S2, the metered second reactant PPTA is transported into the reaction cavity of the double-screw reactor through the feeding screw rod, and the first reactant and the second reactant PPTA are blended and reacted in the double-screw reactor cavity to obtain a spinning dope;

[0154] The mass ratio of the first reactant to the second reactant PPTA is 4.1:1.

[0155] The reaction temperature in the double-screw reactor is 75°C, the screw rod rotation speed is 20rpm, and the prepared spinning dope has a solid content of 19.6% (mass content).

[0156] S3, the spinning dope is obtained by a dry-jet wet spinning process to obtain the aging-resistant para-aramid fiber, the dry-jet wet spinning process comprises: after the spinning dope is jetted, it is subjected to a coagulation bath, stretching, washing, drying, heat drawing, oiling and winding to obtain the aging-resistant para-aramid fiber.

[0157] The drawing ratio during the stretching process is 6; the coagulation bath temperature is 6°C, and the coagulation bath is a 2% sulfuric acid aqueous solution; and the heating temperature of the heat drawing is 150°C.

[0158] Comparative Example 7

[0159] The para-aramid fiber is prepared by the same method as in Example 2, except that the heating temperature of the heat drawing in step S3 of the comparative example 7 is 220°C (higher than the temperature condition defined in the application), and the specific preparation process is as follows:

[0160] S1, UV-234 is added to the metered concentrated sulfuric acid for dissolution, and after the UV-234 is dissolved, it is transferred to an emulsifying tank for reaction, and the reaction temperature and reaction time are controlled to obtain a first reactant;

[0161] The concentration of concentrated sulfuric acid is 99.9%, the added mass of UV-234 is 1% of the mass of concentrated sulfuric acid, and the temperature of the dissolution process is controlled at 20°C; the reaction temperature in the emulsifying tank is 20°C, and the reaction time is 3h.

[0162] S2, the metered second reactant PPTA is transported into the reaction cavity of the double-screw reactor through the feeding screw rod, and the first reactant and the second reactant PPTA are blended and reacted in the double-screw reactor cavity to obtain a spinning dope;

[0163] The mass ratio of the first reactant to the second reactant PPTA is 4.1:1.

[0164] The reaction temperature in the twin-screw reactor was 80°C, the screw rotation speed was 20 rpm, and the prepared spinning dope solid content was 19.6% (mass content).

[0165] S3, the spinning dope was used to prepare the aging-resistant para-aramid fiber through a dry-jet wet spinning process, which included: after the spinning dope was jetted, the aging-resistant para-aramid fiber was obtained through a coagulation bath, stretching, washing, drying, heat drawing, oiling and winding.

[0166] In the stretching process, the draw ratio was 6; the coagulation bath temperature was 6°C, the coagulation bath was a 2% sulfuric acid aqueous solution by mass concentration; and the heat drawing temperature was 220°C.

[0167] Comparative Example 8

[0168] The para-aramid fiber was prepared by the same method as in Example 2, except that in Comparative Example 8, UV-234 was directly added to the sulfuric acid solution of PPTA, and the specific preparation process was as follows:

[0169] S1, a metered second reactant PPTA was transported into the reaction cavity of the twin-screw reactor through a feeding screw, and the concentrated sulfuric acid (concentration of 99.9%) and the second reactant PPTA were blended and reacted in the twin-screw reactor cavity to obtain a spinning dope; the reaction temperature in the twin-screw reactor was 80°C, and the screw rotation speed was 20 rpm.

[0170] UV-234 was added to the spinning dope and mixed uniformly, wherein the mass of UV-234 was 1% of the mass of the concentrated sulfuric acid, and the mass ratio of the first reactant to the second reactant PPTA was 4.1:1;

[0171] The prepared spinning dope solid content was 19.6% (mass content).

[0172] S2, the spinning dope was used to prepare the aging-resistant para-aramid fiber through a dry-jet wet spinning process, which included: after the spinning dope was jetted, the aging-resistant para-aramid fiber was obtained through a coagulation bath, stretching, washing, drying, heat drawing, oiling and winding.

[0173] In the stretching process, the draw ratio was 6; the coagulation bath temperature was 6°C, the coagulation bath was a 2% sulfuric acid aqueous solution by mass concentration; and the heat drawing temperature was 150°C.

[0174] The para-aramid fibers prepared in the above examples and comparative examples were tested for performance, and the specific test results are shown in Table 1 below, wherein the test methods involved are as follows:

[0175] Strength performance: high-strength filament full-automatic strength tester EMATER 680;

[0176] Modulus: High strength filament full-automatic strength and elongation tester EMATER 680;

[0177] Elongation at break: High strength filament full-automatic strength and elongation tester EMATER 680;

[0178] Aging resistance: Xenon lamp weathering test box 1.1 kW, 39℃, 45% humidity, and the experimental time is 96h, and then the percentage of the loss of fiber strength performance before and after the aging resistance performance test is calculated.

[0179] Table 1 performance test results

[0180]

[0181] Note: The fineness of the fibers prepared by the inventive examples and the comparative examples is between 1077-1144dtex.

[0182] From the above table data, it can be seen that the aging-resistant para-aramid fibers prepared by the preparation method of the present application in examples 1-6 have good strength, modulus performance, and better aging resistance and stability. In the preparation method of the present application, UV-234 is added in sulfuric acid instead of adding UV-234 in PPTA / sulfuric acid stock solution. In the preparation method of the present application, UV-234 is fully dissolved in sulfuric acid to prepare UV-234 / sulfuric acid solution, and then fully mixed with PPTA through a double screw extruder. The combination of UV-234 additive and fiber is stronger, and the dispersion is more uniform. The prepared fiber improves the aging resistance of the fiber while maintaining the strength. In addition, UV-234 reacts with sulfuric acid to generate sulfonation, and after introducing sulfonic group (-SO3H), the strong polarity of sulfonic group will compete with the amide bond on PPTA chain, weaken the original intermolecular hydrogen bond, in addition, the large volume of sulfonic group can expand the molecular chain spacing, reduce the chain packing density, promote the dissolution of PPTA, and prepare more uniform spinning stock solution, so as to obtain aging-resistant para-aramid fiber with excellent performance and stability.

[0183] 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 application in example 2 has good aging resistance while maintaining good strength and modulus performance compared with the conventional para-aramid fiber of comparative example 1.

[0184] From the comparison of the experimental results of comparative example 2 and example 2, it can be seen that if the amount of ultraviolet absorber UV-234 is increased, the aging resistance of the fiber can be improved to a certain extent, but if the content is too high, the fiber structure will be damaged and the fiber strength performance will decrease, therefore, the limited amount of UV-234 in the present application is more conducive to obtaining aging-resistant para-aramid fiber with excellent comprehensive performance.

[0185] From the comparison of the experimental results of Comparative Example 3 and Example 2, it can be seen that if the proportion of the first reactant is increased, the concentration of the dope is lower, when the concentration of the dope is 18%, the viscosity of the dope decreases, the spinnability becomes poor, and the fiber performance decreases.

[0186] From the comparison of the experimental results of Comparative Example 4 and Example 2, it can be seen that if the proportion of the first reactant is reduced, the concentration of the dope is higher, when the concentration of the dope is 22.2%, the viscosity of the dope increases, the spinnability becomes poor, and the fiber performance decreases.

[0187] From Comparative Example 3 and Comparative Example 4, it can be seen that the ratio of the first reactant and the second reactant needs to be controlled within a suitable range, so the present application limits the ratio of the first reactant and the second reactant to improve the aging resistance of the para-aramid fiber while ensuring the strength of the fiber.

[0188] 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℃, the degree of degradation of the dope in the dissolving machine is greater, which can cause the fiber strength performance to decrease.

[0189] 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 reduced, when the reaction temperature is lower than 80℃, the flowability of the dope in the dissolving machine is poor, the viscosity is too high, the spinnability becomes poor, and the fiber strength performance decreases.

[0190] From Comparative Example 5 and Comparative Example 6, it can be seen that the reaction temperature of the first reactant and the second reactant in S2 needs to be controlled within a suitable range, and the temperature will affect the degree of degradation of the fiber, and too large or too small degree of degradation of the fiber will cause the viscosity of the fiber to change, and the spinnability becomes poor, so the present application limits the reaction temperature of the first reactant and the second reactant in S2 to improve the aging resistance of the para-aramid fiber while ensuring the strength of the fiber.

[0191] 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 heat drawing in step S3 is increased, the fiber will change color during the heating process, and UV-234 will oxidize and discolor at high temperature, affecting the appearance of the fiber and the aging resistance of the fiber.

[0192] 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 dope during the preparation of the aging-resistant para-aramid fiber, the mixing of UV-234 in the fiber is uneven, causing poor uniformity of the dope, which not only affects the fiber strength performance, but also has limited improvement in the aging resistance of the fiber.

[0193] The technical features of the above-described embodiments can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features in the above-described embodiments are listed, however, as long as the combinations of the technical features do not contradict each other, they should be considered to be within the scope of the present disclosure.

[0194] Those skilled in the art will appreciate that, without departing from the concept of the present disclosure, a number of variations and modifications can be made, and these should be considered to be within the scope of the present disclosure, which is defined by the appended claims.

Claims

1. A method for preparing aging-resistant para-aramid fibers, characterized in that, The preparation method is as follows: S1, UV-234, and concentrated sulfuric acid react to obtain the first reactant; the amount of UV-234 used is 0.25%-2.5% of the mass of concentrated sulfuric acid. S2, the first reactant, and the second reactant PPTA are blended together to obtain the spinning solution; The mass ratio of the first reactant to the second reactant PPTA is (4-4.13):1; the blending reaction temperature is 80-90℃. S3. The spinning solution is used to obtain aging-resistant para-aramid fibers through a dry-jet wet spinning process. In step S3, the dry-jet wet spinning process includes: after the spinning solution is spun, it undergoes coagulation bath, stretching, washing, drying, hot stretching, oiling and winding to obtain the aging-resistant para-aramid fiber. The temperature conditions for the thermal stretching are 150-200℃.

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.

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℃ and the reaction time is 2-6h.

4. The method for preparing an aging-resistant para-aramid fiber according to claim 1, characterized in that, In step S2, the first reactant and the second reactant PPTA undergo a blending reaction in the chamber of a twin-screw reactor, with the screw speed being 20-50 rpm.

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

6. The method for preparing an aging-resistant para-aramid fiber according to claim 1, characterized in that, The draw ratio during the stretching process of the dry-jet wet spinning process is 6-12.

7. The method for preparing an aging-resistant para-aramid fiber according to claim 1, characterized in that, The coagulation bath is an aqueous solution of sulfuric acid, the mass concentration of sulfuric acid in the coagulation bath is 2%-8%, and the temperature of the coagulation bath is 5-35℃.

8. An aging-resistant para-aramid fiber, characterized in that, The aging-resistant para-aramid fiber is prepared according to the preparation method described in any one of claims 1-7.

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