A preparation process for high-toughness flame-retardant yarn

Abstract

The present invention discloses a process for preparing high-toughness flame-retardant yarn, which belongs to the field of high-tech yarn technology. A process for preparing high-toughness flame-retardant yarn, wherein the flame-retardant components chitosan and DOPO are grafted onto polyester fibers through a grafting reaction, effectively improving their flame-retardant properties. Aramid fibers, cross-linking agents, toughening agents, fillers and antioxidants are further added to enhance the mechanical properties, toughness and oxidation resistance of the yarn. The specific process is: first, chitosan and DOPO are combined with polyester fibers through chemical grafting, and then auxiliary materials such as aramid fibers are added, and through appropriate heat treatment and cross-linking reactions, a composite yarn with excellent flame retardant, toughening and antioxidant properties is formed. The yarn not only has excellent flame retardant properties, but also has high antioxidant capacity and heat resistance while maintaining good mechanical properties. It is suitable for fields requiring high-performance flame retardant materials, especially in fire-resistant clothing, building materials and other industries, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of high-tech yarns, and more particularly to a process for preparing high-toughness flame-retardant yarns. Background Art

[0002] Yarn, as a fundamental material in the textile industry, has a wide range of applications. Early yarns were primarily made from natural fibers such as cotton, wool, and linen. These fibers possessed excellent moisture absorption, breathability, and comfort, but their strength, heat resistance, and flame retardancy were relatively poor, failing to meet the high-performance material requirements of modern industry. With the development of synthetic fiber technology, synthetic fibers such as polyester and nylon have gradually become the primary raw materials for yarn. These synthetic fibers possess excellent mechanical properties and durability, but their poor flame retardancy limits their application in high-temperature environments.

[0003] While some flame-retardant fibers are currently used in yarn materials, their flame retardancy is often unstable and can degrade over time due to environmental influences. Furthermore, some flame-retardant treatments often reduce the mechanical properties of the fibers, impacting their lifespan and safety. Therefore, developing a technology that can maintain the yarn's excellent mechanical properties while enhancing its flame retardancy has become an important area of ​​research in yarn materials.

[0004] Currently, the application of yarns is no longer limited to the traditional clothing and home textile industries. In specialized fields involving high temperatures and high fire hazards, such as aerospace, electricity, firefighting, and military equipment, the flame retardant and mechanical properties of yarns are even more stringent. To address the shortcomings of existing yarn materials, recent research has gradually combined chemical modification with composite materials technology. In the future, with the continuous improvement of environmental protection and safety standards, the research of yarn materials will develop in a more efficient and sustainable direction. Optimization of flame retardancy, mechanical properties, anti-aging properties, and other aspects will become a future focus, and the application of composite materials will also become more extensive. In addition, with the rise of smart textiles, the multifunctionalization of high-performance flame-retardant yarns (such as intelligent sensing and temperature control) will also become a research hotspot. Summary of the Invention

[0005] The object of the present invention is to provide a process for preparing high-toughness flame-retardant yarn, which has excellent mechanical properties, toughness and oxidation resistance.

[0006] (1) Preparation of epoxy-modified chitosan: deionized water solvent and chitosan were added to the reaction flask in sequence, ultrasonically dispersed, acetic acid was slowly added dropwise, ultrasonically dispersed, 1 mol / L sodium hydroxide was used to adjust the pH of the solution to 11-13, placed under nitrogen protection, 1,2-epoxychlorobutane was slowly added dropwise, reacted at 50-70 ° C for 4-6 h, cooled to room temperature, ethanol was added to precipitate the product, centrifuged, washed with deionized water and ethanol, and dried to obtain epoxy-modified chitosan;

[0007] (2) Preparation of carboxyl-epoxy modified chitosan: N,N-dimethylformamide solvent, deionized water solvent, epoxy modified chitosan, 5-chloroisophthalic acid, and activator N-hydroxypyrrolidone were added to the reaction bottle in sequence, ultrasonically dispersed, reacted, centrifuged, washed with ethanol and dried to obtain carboxyl-epoxy modified chitosan;

[0008] (3) Preparation of carboxyl-DOPO modified chitosan: N,N-dimethylformamide solvent, carboxyl-epoxy modified chitosan, DOPO, and catalyst triethylamine were added to the reaction flask in sequence, ultrasonically dispersed, reacted, centrifuged, washed with ethanol, and dried to obtain carboxyl-DOPO modified chitosan;

[0009] (4) Preparation of functionalized polyester: Carboxyl-DOPO modified chitosan, dimethyl terephthalate, polyethylene glycol-2000, and titanium isopropoxide catalyst were added to the reactor in sequence, mixed evenly, reacted, cooled naturally to room temperature, washed with N,N-dimethylformamide, and dried to obtain functionalized polyester;

[0010] (5) Preparation of high-toughness flame-retardant yarn: Functionalized polyester, aramid fiber, cross-linking agent melamine, toughening agent polyurethane elastomer, filler silica, and antioxidant tert-butylhydroquinone are dried at 100-120°C for 1-3 hours, mixed evenly, and sent into a spinning machine. The fiber is stretched at 260-280°C for 20-40 minutes using thermal spinning technology. The yarn is then set in a heat setting machine with the temperature controlled at 150-170°C for 1-3 minutes. The yarn is then quickly cooled at 20-40°C to obtain high-toughness flame-retardant yarn.

[0011] Preferably, in step (1), the formula ratio of deionized water solvent, chitosan, acetic acid, and 1,2-epoxychlorobutane is 180-220 mL:10 g:4-6 mL:2-4 mL.

[0012] Preferably, in step (2), the formula ratio of N,N-dimethylformamide solvent, deionized water solvent, epoxy-modified chitosan, 5-chloroisophthalic acid, and N-hydroxypyrrolidone is 180-220 mL: 20-40 mL: 10 g: 4-6 mL: 0.4-0.8 mL.

[0013] Preferably, the reaction conditions in step (2) are: pre-activation at room temperature for 20-40 minutes, and then reaction at 50-70°C for 6-8 hours.

[0014] Preferably, in step (3), the formula ratio of N,N-dimethylformamide solvent, carboxyl-epoxy modified chitosan, DOPO, and triethylamine is 180-220 mL:10 g:4-8 g:0.2-0.4 mL.

[0015] Preferably, the reaction conditions in step (3) are to react at 70-90° C. for 7-9 hours under nitrogen protection.

[0016] Preferably, in step (4), the formula ratio of carboxyl-DOPO modified chitosan, dimethyl terephthalate, polyethylene glycol-2000, and titanium isopropoxide is 6-10g:20-40g:100g:2-4g.

[0017] Preferably, the reaction conditions in step (4) are as follows: first placing the mixture in a vacuum state, then injecting nitrogen atmosphere, preheating at 140-160° C. and homogeneously mixing for 1-3 h, and then heating to 200-220° C. and reacting for 4-6 h.

[0018] Preferably, in step (5), the formula ratio of functionalized polyester, aramid fiber, melamine, polyurethane elastomer, silica, and tert-butylhydroquinone is 100g:20-30g:2-4g:8-12g:2-4g:2-4g.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] (1) In the present invention, in an alkaline environment, the hydroxyl groups on chitosan react with the chlorine atoms on 1,2-epoxychlorobutane to undergo nucleophilic substitution reaction to obtain epoxy-modified chitosan. The activator can activate the chlorine atoms on 5-chloroisophthalic acid, which then reacts with the amino groups on the epoxy-modified chitosan to obtain carboxyl-epoxy-modified chitosan. Under the action of the catalyst triethylamine, the P=O on DOPO reacts with the epoxy groups on the carboxyl-epoxy-modified chitosan to undergo a ring-opening reaction to obtain carboxyl-DOPO-modified chitosan. The chitosan is then used as a functionalized modified substance and copolymerized with methyl terephthalate and polyethylene glycol-2000 under the action of the catalyst titanium isopropoxide to obtain functionalized polyester, which greatly improves the dispersibility of the flame retardant in the polyester and makes it evenly dispersed.

[0021] (2) In the present invention, chitosan forms a pyrolysis layer at high temperature through its rich amino and hydroxyl groups. This layer can play a role of heat insulation and shielding, slowing down the spread of flames, and the decomposition products at high temperature can form a carbonized layer. This carbonized layer can effectively prevent the entry of oxygen, reduce the occurrence of oxidation reactions, and thus inhibit the spread of flames. In addition, chitosan interacts with the polyester matrix through its amino and hydroxyl groups, further enhancing the thermal stability of the fiber. DOPO, as a phosphorus-based flame retardant, can release phosphoric acid compounds at high temperatures. These phosphoric acid compounds form a flame-retardant protective film on the surface of the polyester material. The phosphates and acidic substances produced by the phosphorus-based flame retardant during the pyrolysis process can promote the formation of the carbonized layer, forming a physical barrier to prevent the spread of flames. At the same time, DOPO can also inhibit the generation of free radicals through chemical reactions, reducing the flammability of the polyester material during combustion.

[0022] (3) In the present invention, the molecular structure of chitosan has a strong hydrogen bonding force, which enables it to improve the overall structural stability of the fiber when combined with the polyester matrix. During high temperature or long-term use, chitosan enhances the toughness and tensile strength of the polyester fiber through physical interaction with the polyester molecules. DOPO is also a compound that can exist stably at high temperatures. After combining with polyester, DOPO can strengthen the overall structure of the polyester by forming a chemical bond of phosphate, so that it exhibits better tensile strength and thermal stability under high temperature and stress conditions. In addition, the addition of DOPO promotes the cross-linking degree of the polyester fiber, enhances the mechanical properties of the fiber, and improves its impact resistance and wear resistance.

[0023] (4) In the present invention, aramid fiber is added. This formula significantly improves the tensile strength, abrasion resistance, and impact resistance of the yarn while maintaining its flexibility. Aramid fiber has excellent mechanical properties, making the yarn more durable, stable, and less prone to breakage during use, thereby enhancing the overall toughness of the material.

[0024] (5) In the present invention, the addition of the crosslinking agent melamine improves the thermal stability of the yarn. Melamine has good high-temperature resistance and can effectively delay the thermal degradation of the material in a high-temperature environment, further improving the high-temperature resistance of the yarn and adapting it to more extreme working environments.

[0025] (6) In the present invention, the polyurethane elastomer, as a toughening agent, not only enhances the flexibility of the yarn but also has an anti-aging effect, effectively slowing down the aging process of the fiber during long-term use and extending its service life. In addition, the silica filler also enhances the wear resistance and oxidation resistance of the yarn, making the yarn more stable in harsh environments.

[0026] (7) In the present invention, tert-butylhydroquinone, as an antioxidant, plays an important role in preventing fiber oxidation degradation. It can effectively inhibit the oxidation reaction on the fiber surface, reduce the performance degradation caused by oxidation, and further improve the durability of the yarn, especially in long-term high temperature or humid environments. DETAILED DESCRIPTION

[0027] Example 1:

[0028] (1) Preparation of epoxy-modified chitosan: 180 mL of deionized water solvent and 10 g of chitosan were added to the reaction flask in sequence, and ultrasonically dispersed them uniformly. 4 mL of acetic acid was slowly added dropwise, and ultrasonically dispersed them uniformly. 1 mol / L sodium hydroxide was used to adjust the pH of the solution to 11. Under nitrogen protection, 2 mL of 1,2-epoxychlorobutane was slowly added dropwise. The reaction was carried out at 50 °C for 4 h, cooled to room temperature, and ethanol was added to precipitate the product. The product was centrifuged and washed with deionized water and ethanol, and dried to obtain epoxy-modified chitosan.

[0029] (2) Preparation of carboxyl-epoxy modified chitosan: 180 mL of N,N-dimethylformamide solvent, 20 mL of deionized water solvent, 10 g of epoxy modified chitosan, 4 mL of 5-chloroisophthalic acid, and 0.4 mL of activator N-hydroxypyrrolidone were added to the reaction bottle in sequence, and ultrasonically dispersed uniformly. The mixture was pre-activated at room temperature for 20 minutes, reacted at 50°C for 6 hours, centrifuged, washed with ethanol, and dried to obtain carboxyl-epoxy modified chitosan.

[0030] (3) Preparation of carboxyl-DOPO modified chitosan: 180 mL of N,N-dimethylformamide solvent, 10 g of carboxyl-epoxy modified chitosan, 4 g of DOPO, and 0.2 mL of catalyst triethylamine were added to the reaction flask in sequence, and ultrasonically dispersed uniformly. The mixture was placed under nitrogen protection and reacted at 70 °C for 7 h. The mixture was centrifuged, washed with ethanol, and dried to obtain carboxyl-DOPO modified chitosan.

[0031] (4) Preparation of functionalized polyester: 6 g of carboxyl-DOPO modified chitosan, 20 g of dimethyl terephthalate, 100 g of polyethylene glycol-2000, and 2 g of titanium isopropoxide catalyst were added to the reactor in sequence, mixed evenly, placed in a vacuum state and nitrogen atmosphere, preheated at 140 ° C and homogeneously mixed for 1 h, heated to 200 ° C and reacted for 4 h, cooled naturally to room temperature, washed with N, N-dimethylformamide and dried to obtain functionalized polyester;

[0032] (5) Preparation of high-toughness flame-retardant yarn: 100g of functionalized polyester, 20g of aramid fiber, 2g of cross-linking agent melamine, 8g of toughening agent polyurethane elastomer, 2g of filler silica, and 2g of antioxidant tert-butylhydroquinone were dried at 100℃ for 1h, mixed evenly and sent into a spinning machine. The fiber was stretched at 260℃ for 20 minutes using hot spinning technology, and then the yarn was set in a heat setting machine with the temperature controlled at 150℃ for 1 minute. It was quickly cooled at 20℃ to obtain high-toughness flame-retardant yarn.

[0033] Example 2:

[0034] (1) Preparation of epoxy-modified chitosan: 190 mL of deionized water solvent and 10 g of chitosan were added to the reaction flask in sequence, and ultrasonically dispersed them uniformly. 4.5 mL of acetic acid was slowly added dropwise, and ultrasonically dispersed them uniformly. 1 mol / L sodium hydroxide was used to adjust the pH of the solution to 11.5. Under nitrogen protection, 2.5 mL of 1,2-epoxychlorobutane was slowly added dropwise. The reaction was carried out at 55 °C for 4.5 h, cooled to room temperature, and ethanol was added to precipitate the product. The product was centrifuged and washed with deionized water and ethanol, and dried to obtain epoxy-modified chitosan.

[0035] (2) Preparation of carboxyl-epoxy modified chitosan: 190 mL N,N-dimethylformamide solvent, 25 mL deionized water solvent, 10 g epoxy modified chitosan, 4.5 mL 5-chloroisophthalic acid, and 0.5 mL activator N-hydroxypyrrolidone were added to the reaction bottle in sequence, ultrasonically dispersed evenly, pre-activated at room temperature for 25 minutes, reacted at 55 ° C for 6.5 hours, centrifuged, washed with ethanol and dried to obtain carboxyl-epoxy modified chitosan;

[0036] (3) Preparation of carboxyl-DOPO modified chitosan: 190 mL of N,N-dimethylformamide solvent, 10 g of carboxyl-epoxy modified chitosan, 5 g of DOPO, and 0.25 mL of catalyst triethylamine were added to the reaction flask in sequence, and ultrasonically dispersed uniformly. The mixture was placed under nitrogen protection and reacted at 75 °C for 7.5 h. The mixture was centrifuged, washed with ethanol, and dried to obtain carboxyl-DOPO modified chitosan.

[0037] (4) Preparation of functionalized polyester: 7 g of carboxyl-DOPO modified chitosan, 25 g of dimethyl terephthalate, 100 g of polyethylene glycol-2000, and 2.5 g of titanium isopropoxide catalyst were added to the reactor in sequence, mixed evenly, placed in a vacuum state and nitrogen atmosphere, preheated at 145 ° C and homogeneously mixed for 1.5 h, heated to 205 ° C and reacted for 4.5 h, cooled naturally to room temperature, washed with N, N-dimethylformamide and dried to obtain functionalized polyester;

[0038] (5) Preparation of high-toughness flame-retardant yarn: 100g functionalized polyester, 22.5g aramid fiber, 2.5g cross-linking agent melamine, 9g toughening agent polyurethane elastomer, 2.5g filler silica, and 2.5g antioxidant tert-butylhydroquinone were dried at 105°C for 1.5h, mixed evenly and sent into a spinning machine. The fiber was stretched at 265°C for 25 minutes using hot spinning technology, and then the yarn was set in a heat setting machine with the temperature controlled at 155°C for 1.5 minutes. It was then quickly cooled at 25°C to obtain high-toughness flame-retardant yarn.

[0039] Example 3:

[0040] (1) Preparation of epoxy-modified chitosan: 200 mL of deionized water solvent and 10 g of chitosan were added to the reaction flask in sequence, and ultrasonically dispersed them uniformly. 5 mL of acetic acid was slowly added dropwise, and ultrasonically dispersed them uniformly. 1 mol / L sodium hydroxide was used to adjust the pH of the solution to 12. Under nitrogen protection, 3 mL of 1,2-epoxychlorobutane was slowly added dropwise. The reaction was carried out at 60 ° C for 5 h, cooled to room temperature, and ethanol was added to precipitate the product. The product was centrifuged and washed with deionized water and ethanol and dried to obtain epoxy-modified chitosan.

[0041] (2) Preparation of carboxyl-epoxy modified chitosan: 200 mL of N,N-dimethylformamide solvent, 30 mL of deionized water solvent, 10 g of epoxy modified chitosan, 5 mL of 5-chloroisophthalic acid, and 0.6 mL of activator N-hydroxypyrrolidone were added to the reaction bottle in sequence, and ultrasonic dispersion was performed uniformly. The mixture was pre-activated at room temperature for 30 minutes, reacted at 60°C for 7 hours, centrifuged, washed with ethanol, and dried to obtain carboxyl-epoxy modified chitosan.

[0042] (3) Preparation of carboxyl-DOPO modified chitosan: 200 mL of N,N-dimethylformamide solvent, 10 g of carboxyl-epoxy modified chitosan, 6 g of DOPO, and 0.3 mL of catalyst triethylamine were added to the reaction flask in sequence, and ultrasonically dispersed uniformly. The mixture was placed under nitrogen protection and reacted at 80 °C for 8 h. The mixture was centrifuged, washed with ethanol, and dried to obtain carboxyl-DOPO modified chitosan.

[0043] (4) Preparation of functionalized polyester: 8 g of carboxyl-DOPO modified chitosan, 30 g of dimethyl terephthalate, 100 g of polyethylene glycol-2000, and 3 g of titanium isopropoxide catalyst were added to the reactor in sequence, mixed evenly, placed in a vacuum state and nitrogen atmosphere, preheated at 150 ° C and homogeneously mixed for 2 h, heated to 210 ° C and reacted for 5 h, cooled naturally to room temperature, washed with N, N-dimethylformamide and dried to obtain functionalized polyester;

[0044] (5) Preparation of high-toughness flame-retardant yarn: 100g functionalized polyester, 25g aramid fiber, 3g cross-linking agent melamine, 10g toughening agent polyurethane elastomer, 3g filler silica, and 3g antioxidant tert-butylhydroquinone were dried at 110°C for 2h, mixed evenly and sent into a spinning machine. The fiber was stretched at 270°C for 30 minutes using hot spinning technology, and then the yarn was set in a heat setting machine with the temperature controlled at 160°C for 2 minutes. It was then quickly cooled at 30°C to obtain high-toughness flame-retardant yarn.

[0045] Example 4:

[0046] (1) Preparation of epoxy-modified chitosan: 210 mL of deionized water solvent and 10 g of chitosan were added to the reaction flask in sequence, and ultrasonically dispersed them uniformly. 5.5 mL of acetic acid was slowly added dropwise, and ultrasonically dispersed them uniformly. 1 mol / L sodium hydroxide was used to adjust the pH of the solution to 12.5. Under nitrogen protection, 3.5 mL of 1,2-epoxychlorobutane was slowly added dropwise. The reaction was carried out at 65 ° C for 5.5 h, cooled to room temperature, and ethanol was added to precipitate the product. The product was centrifuged and washed with deionized water and ethanol and dried to obtain epoxy-modified chitosan.

[0047] (2) Preparation of carboxyl-epoxy modified chitosan: 210 mL N,N-dimethylformamide solvent, 35 mL deionized water solvent, 10 g epoxy modified chitosan, 5.5 mL 5-chloroisophthalic acid, and 0.7 mL activator N-hydroxypyrrolidone were added to the reaction bottle in sequence, and ultrasonic dispersion was performed uniformly. The mixture was pre-activated at room temperature for 35 minutes, reacted at 65 ° C for 7.5 hours, centrifuged, washed with ethanol and dried to obtain carboxyl-epoxy modified chitosan.

[0048] (3) Preparation of carboxyl-DOPO modified chitosan: 210 mL of N,N-dimethylformamide solvent, 10 g of carboxyl-epoxy modified chitosan, 7 g of DOPO, and 0.35 mL of catalyst triethylamine were added to the reaction flask in sequence, and ultrasonically dispersed uniformly. The mixture was placed under nitrogen protection and reacted at 85 °C for 8.5 h. The mixture was centrifuged, washed with ethanol, and dried to obtain carboxyl-DOPO modified chitosan.

[0049] (4) Preparation of functionalized polyester: 9 g of carboxyl-DOPO modified chitosan, 35 g of dimethyl terephthalate, 100 g of polyethylene glycol-2000, and 3.5 g of catalyst titanium isopropoxide were added to the reactor in sequence, mixed evenly, placed in a vacuum state and nitrogen atmosphere, preheated at 155 ° C and homogeneously mixed for 2.5 h, heated to 215 ° C and reacted for 5.5 h, cooled naturally to room temperature, washed with N, N-dimethylformamide and dried to obtain functionalized polyester;

[0050] (5) Preparation of high-toughness flame-retardant yarn: 100g functionalized polyester, 27.5g aramid fiber, 3.5g cross-linking agent melamine, 11g toughening agent polyurethane elastomer, 3.5g filler silica, and 3.5g antioxidant tert-butylhydroquinone were dried at 105°C for 2.5h, mixed evenly and sent into a spinning machine. The fiber was stretched at 275°C for 35 minutes using hot spinning technology, and then the yarn was set in a heat setting machine with the temperature controlled at 165°C for 2.5 minutes. It was then quickly cooled at 35°C to obtain high-toughness flame-retardant yarn.

[0051] Example 5:

[0052] (1) Preparation of epoxy-modified chitosan: 220 mL of deionized water solvent and 10 g of chitosan were added to the reaction flask in sequence, and ultrasonically dispersed them uniformly. 6 mL of acetic acid was slowly added dropwise, and ultrasonically dispersed them uniformly. 1 mol / L sodium hydroxide was used to adjust the pH of the solution to 13. Under nitrogen protection, 4 mL of 1,2-epoxychlorobutane was slowly added dropwise. The reaction was carried out at 70 °C for 6 h, cooled to room temperature, and ethanol was added to precipitate the product. The product was centrifuged and washed with deionized water and ethanol, and dried to obtain epoxy-modified chitosan.

[0053] (2) Preparation of carboxyl-epoxy modified chitosan: 220 mL of N,N-dimethylformamide solvent, 40 mL of deionized water solvent, 10 g of epoxy modified chitosan, 6 mL of 5-chloroisophthalic acid, and 0.8 mL of activator N-hydroxypyrrolidone were added to the reaction bottle in sequence, and ultrasonic dispersion was performed uniformly. The mixture was pre-activated at room temperature for 40 minutes, reacted at 70 °C for 8 hours, centrifuged, washed with ethanol, and dried to obtain carboxyl-epoxy modified chitosan.

[0054] (3) Preparation of carboxyl-DOPO modified chitosan: 220 mL of N,N-dimethylformamide solvent, 10 g of carboxyl-epoxy modified chitosan, 8 g of DOPO, and 0.4 mL of catalyst triethylamine were added to the reaction flask in sequence, and ultrasonically dispersed uniformly. The mixture was placed under nitrogen protection and reacted at 90 °C for 9 h. The mixture was centrifuged, washed with ethanol, and dried to obtain carboxyl-DOPO modified chitosan.

[0055] (4) Preparation of functionalized polyester: 10 g of carboxyl-DOPO modified chitosan, 40 g of dimethyl terephthalate, 100 g of polyethylene glycol-2000, and 4 g of titanium isopropoxide catalyst were added to the reactor in sequence, mixed evenly, placed in a vacuum state and nitrogen atmosphere, preheated at 160 ° C and homogeneously mixed for 3 h, heated to 220 ° C and reacted for 6 h, cooled naturally to room temperature, washed with N, N-dimethylformamide and dried to obtain functionalized polyester;

[0056] (5) Preparation of high-toughness flame-retardant yarn: 100g of functionalized polyester, 30g of aramid fiber, 4g of cross-linking agent melamine, 12g of toughening agent polyurethane elastomer, 4g of filler silica, and 4g of antioxidant tert-butylhydroquinone were dried at 120℃ for 3h, mixed evenly and sent into a spinning machine. The fiber was stretched at 280℃ for 40 minutes using hot spinning technology, and then the yarn was set in a heat setting machine with the temperature controlled at 170℃ for 3 minutes. It was quickly cooled at 40℃ to obtain high-toughness flame-retardant yarn.

[0057] Performance Testing

[0058] UL 94 vertical burning test

[0059] The polyester material of Examples 1-5 was formed into a 100 mm × 10 mm strip according to the UL 94 standard and subjected to the UL 94 vertical flame test using a Lab-Test Instruments UL-94 flame tester. The sample was suspended vertically in the flame tester, ensuring that the bottom of the sample was approximately 25 mm from the flame nozzle. The flame height was adjusted between 20 mm and 40 mm, ensuring that the flame was applied vertically to the bottom of the sample. Propane gas was ignited and the gas flow rate was adjusted to ensure a stable flame. The flame was applied to the bottom of the sample and maintained for 10 seconds. After the flame was removed, the sample was observed to see if it extinguished on its own, and the duration of the burning was recorded. If the burning was not extinguished, the sample was observed to see if any burning products dripped, and the amount of dripping was recorded. With reference to the national standard GB / T5455-2014, the test results are shown in the following table:

[0060] Example 1 Example 2 Example 3 Example 4 Example 5 Self-extinguishing time after flame is removed (s) 6 5 4 4 3 Continued burning time (s) 3 2 1 1 0 Is there any burning material dripping? no no no no no Rating V-0 V-0 V-0 V-0 V-0

[0061] Limiting oxygen index test

[0062] The polyester material in Examples 1-5 was formed into a 100 mm × 10 mm strip. The limiting oxygen index of the sample was tested using a LabTestInstruments LOI Tester. The sample was installed in the combustion chamber of the oxygen index tester, ensuring that the sample was fixed vertically and its bottom was a certain distance (usually 10 mm) from the flame source, with the sample surface facing upward. The oxygen and nitrogen mixture ratio was adjusted, starting with a low oxygen concentration (e.g., 21% oxygen, 79% nitrogen) and gradually increasing the oxygen concentration. The gas flow rate during the test was 200 L / h. The bottom of the sample was ignited using a designated ignition device, and stable flame combustion was maintained. The initial ignition time was typically 5 seconds. The reaction of the sample under the flame was observed. The oxygen concentration was repeatedly adjusted from low to high to find the minimum oxygen concentration that allowed for sustained combustion, which was the limiting oxygen index of the sample. Referring to the national standard GB / T2406-2009, the test results are shown in the following table:

[0063] Example 1 Example 2 Example 3 Example 4 Example 5 Limiting Oxygen Index (LOI) 28% 33% 36% 34% 31%

[0064] Tensile properties testing

[0065] The polyester material in Examples 1-5 was formed into a 250 mm × 20 mm strip. The tensile properties of the sample were tested using an Instron 5960 universal testing machine. The sample was mounted in the fixture of the universal testing machine, ensuring that both ends of the sample were perpendicular to the fixture and securely fixed. The tensile speed of the testing machine was set to 5 mm / min, typically 5 mm / min. The tensile strength and elongation at break of the sample were recorded, referring to the national standard GB / T 14344-2015. The test results are shown in the following table:

[0066] Example 1 Example 2 Example 3 Example 4 Example 5 Tensile strength (MPa) 225 237 245 239 231 Elongation at break (%) 17 20 21 19 16

[0067] Fracture toughness testing

[0068] The polyester material in Examples 1-5 was formed into a 250 mm × 20 mm strip. The fracture toughness of the sample was tested using an Instron 5960 universal testing machine. The sample was mounted in the fixture of the universal testing machine, ensuring that both ends of the sample were perpendicular to the fixture and securely fixed. The tensile speed of the testing machine was set to 5 mm / min. The maximum stress and maximum elongation of the material during the tensile process were recorded, and the fracture toughness (force × elongation) was calculated with reference to the national standard GB / T528-2009. The test results are shown in the following table:

[0069] Example 1 Example 2 Example 3 Example 4 Example 5 Fracture toughness (N·mm) 75 80 82 79 76

[0070] Tear strength test

[0071] The polyester material in Examples 1-5 was formed into a 50 mm × 50 mm disc. The tear strength of the sample was tested using an Instron 5567 tear tester. The sample was mounted in the fixture of the tear tester, ensuring that both ends of the sample were perpendicular to the fixture and securely fixed. The tear speed of the tester was set to 5 mm / min, typically 5 mm / min, and the tear force of the sample was recorded, referring to the national standard GB / T 1040.3-2006. The test results are shown in the following table:

[0072] Example 1 Example 2 Example 3 Example 4 Example 5 Tear strength (N) 36 40 43 41 37

[0073] Antioxidant testing

[0074] The polyester materials of Examples 1-5 were prepared into 10 g samples, and the oxidation resistance of the samples was tested using a Mettler Toledo OIT 2200 Oxidation Induction Time Tester. The samples were placed in the Oxidation Induction Time Tester, set to 200°C, and oxidized. The time when oxidation started was recorded, and the Oxidation Induction Time of the samples was determined. The test results were based on the national standard GB / T2951.40-2008. The following table shows the test results:

[0075] Example 1 Example 2 Example 3 Example 4 Example 5 Oxidation induction time (min) 48 54 57 55 52

Claims

1. A process for preparing high-toughness flame-retardant yarn, characterized in that: The steps include: (1) Preparation of epoxy-modified chitosan: deionized water solvent and chitosan were added to the reaction flask in sequence, ultrasonically dispersed, acetic acid was slowly added dropwise, ultrasonically dispersed, 1 mol / L sodium hydroxide was used to adjust the pH of the solution to 11-13, placed under nitrogen protection, 1,2-epoxychlorobutane was slowly added dropwise, reacted at 50-70 ° C for 4-6 h, cooled to room temperature, ethanol was added to precipitate the product, centrifuged, washed with deionized water and ethanol, and dried to obtain epoxy-modified chitosan; (2) Preparation of carboxyl-epoxy modified chitosan: N,N-dimethylformamide solvent, deionized water solvent, epoxy modified chitosan, 5-chloroisophthalic acid, and activator N-hydroxypyrrolidone were added to the reaction bottle in sequence, ultrasonically dispersed, reacted, centrifuged, washed with ethanol and dried to obtain carboxyl-epoxy modified chitosan; (3) Preparation of carboxyl-DOPO modified chitosan: N,N-dimethylformamide solvent, carboxyl-epoxy modified chitosan, DOPO, and catalyst triethylamine were added to the reaction flask in sequence, ultrasonically dispersed, reacted, centrifuged, washed with ethanol, and dried to obtain carboxyl-DOPO modified chitosan; (4) Preparation of functionalized polyester: Carboxyl-DOPO modified chitosan, dimethyl terephthalate, polyethylene glycol-2000, and titanium isopropoxide catalyst were added to the reactor in sequence, mixed evenly, reacted, cooled naturally to room temperature, washed with N,N-dimethylformamide, and dried to obtain functionalized polyester; (5) Preparation of high-toughness flame-retardant yarn: Functionalized polyester, aramid fiber, cross-linking agent melamine, toughening agent polyurethane elastomer, filler silica, and antioxidant tert-butylhydroquinone are dried at 100-120°C for 1-3 hours, mixed evenly, and sent into a spinning machine. The fiber is stretched at 260-280°C for 20-40 minutes using thermal spinning technology. The yarn is then set in a heat setting machine with the temperature controlled at 150-170°C for 1-3 minutes. The yarn is then quickly cooled at 20-40°C to obtain high-toughness flame-retardant yarn.

2. The process for preparing a high-toughness flame-retardant yarn according to claim 1, characterized in that: In the step (1), the formula ratio of deionized water solvent, chitosan, acetic acid, and 1,2-epoxychlorobutane is 180-220 mL:10 g:4-6 mL:2-4 mL.

3. The process for preparing a high-toughness flame-retardant yarn according to claim 1, characterized in that: In the step (2), the formula ratio of N,N-dimethylformamide solvent, deionized water solvent, epoxy-modified chitosan, 5-chloroisophthalic acid, and N-hydroxypyrrolidone is 180-220 mL: 20-40 mL: 10 g: 4-6 mL: 0.4-0.8 mL.

4. The process for preparing a high-toughness flame-retardant yarn according to claim 3, characterized in that: The reaction conditions in step (2) are: pre-activation at room temperature for 20-40 minutes, and then reaction at 50-70°C for 6-8 hours.

5. The process for preparing a high-toughness flame-retardant yarn according to claim 1, characterized in that: In step (3), the formula ratio of N,N-dimethylformamide solvent, carboxyl-epoxy modified chitosan, DOPO, and triethylamine is 180-220 mL:10 g:4-8 g:0.2-0.4 mL.

6. The process for preparing a high-toughness flame-retardant yarn according to claim 1, characterized in that: The reaction conditions in step (3) are to place the mixture under nitrogen protection at 70-90° C. for 7-9 hours.

7. The process for preparing high-toughness flame-retardant yarn according to claim 1, characterized in that: In the step (4), the formula ratio of carboxyl-DOPO modified chitosan, dimethyl terephthalate, polyethylene glycol-2000, and titanium isopropoxide is 6-10g:20-40g:100g:2-4g.

8. The process for preparing high-toughness flame-retardant yarn according to claim 1, characterized in that: The reaction conditions in step (4) are as follows: first placing the mixture in a vacuum state, then injecting nitrogen atmosphere, preheating at 140-160° C. and homogeneously mixing for 1-3 hours, and then heating to 200-220° C. and reacting for 4-6 hours.

9. The process for preparing high-toughness flame-retardant yarn according to claim 1, characterized in that: In step (5), the formula ratio of functionalized polyester, aramid fiber, melamine, polyurethane elastomer, silica, and tert-butylhydroquinone is 100g:20-30g:2-4g:8-12g:2-4g:2-4g.