Comfortable flame-retardant aramid fabric and preparation method thereof

Abstract

The invention relates to the field of flame-retardant textile fabrics, and provides a comfortable flame-retardant aramid fabric and a preparation method thereof. The composite filler with the average length of 3.0-8.0 mu m and the diameter of 0.4-1.0 mu m is prepared by adopting the design of multielement blended composite fibers of hydroxyapatite / magnesium hydroxide composite filler, meta-aramid polymer, para-aramid polymer, polybenzimidazole and the like through a hydro-thermal synthesis process of performing silanization surface activation and accurately controlling the molar ratio of calcium to phosphorus to be 1.60-1.67. The preparation method comprises the following steps: preparing the composite filler with the average length of 3.0-8.0 mu m and the diameter of 0.4-1.0 mu m; then industrial production processes such as graded shearing dispersion, continuous wet spinning, multi-stage stretching heat setting and after-finishing are performed, so that synergistic improvement of flame retardant performance and comfort performance is achieved, and the technical problems that a traditional aramid fiber fabric is poor in flame retardant effect, poor in comfort, unstable in processing performance and the like are solved; the fabric has wide application value in high-end application fields such as fire protection clothing, industrial protection textiles and military protection equipment.

Description

Technical Field

[0001] This invention relates to the field of coating materials, specifically to a comfortable flame-retardant aramid fabric and its preparation method. Background Technology

[0002] With the continuous improvement of modern industrial safety protection standards and the increasing complexity of special working environments, high-risk work fields such as fire rescue, petrochemicals, metallurgy, power, and military protection have placed more stringent performance requirements on personal protective equipment. In these application scenarios, protective clothing not only needs to possess excellent flame-retardant properties to resist the damage of high-temperature flames and heat radiation, but also needs to have good comfort performance to ensure the physiological health and work efficiency of workers during long-term wear. As the core material of high-performance protective textiles, the flame-retardant properties of aramid fiber are directly related to the safety protection level of protective clothing, while its comfort performance determines the breathability, softness, and wearing comfort of the protective clothing. This coordinated unity of flame retardancy and comfort performance can not only significantly improve the overall protective effect and user experience of protective equipment, but also effectively reduce worker fatigue and operational errors caused by poor protective clothing comfort, thereby promoting the improvement of safety levels and technological progress in the entire high-risk work industry. Therefore, developing aramid fabric technology with excellent flame-retardant and comfort performance has important practical significance and broad application prospects for meeting the urgent needs of the modern safety protection field.

[0003] Currently, aramid fabrics are widely used in the field of flame-retardant protective textiles, but there are still many technical bottlenecks and application limitations in the synergistic development of flame retardancy and comfort performance. Existing aramid fabrics generally face the contradiction of not being able to simultaneously achieve flame retardancy and comfort performance. The main reason is that traditional flame-retardant modification methods often improve the flame-retardant effect by increasing the amount of flame retardant added, but this method significantly reduces the flexibility and breathability of the fibers, while increasing the stiffness and heaviness of the fabric, seriously affecting wearing comfort. Furthermore, conventional single flame-retardant systems are prone to producing toxic gases or having low flame-retardant efficiency under high-temperature conditions, while simple physical blending modification methods suffer from uneven dispersion of flame retardants, poor interfacial bonding, and easy migration and precipitation, resulting in unstable flame-retardant performance and poor durability. At the same time, the microstructure design of existing aramid fabrics lacks targeted optimization, and the fiber surface lacks effective functional modification, making it difficult to effectively integrate comfort functions such as moisture permeability, breathability, antibacterial properties, and odor control while maintaining good flame retardant performance. For example, Chinese patent CN111549415B discloses a flame-retardant and antibacterial protective sock made of aramid fiber, but it suffers from insufficient flame retardancy and comfort. These technical bottlenecks severely restrict the further development and application of aramid fabrics in the field of high-end protective equipment, and breakthroughs are urgently needed through innovative material design concepts and manufacturing processes. Summary of the Invention

[0004] (1) Technical problem to be solved: The purpose of this invention is to provide a comfortable flame-retardant aramid fabric and its preparation method, so as to solve the problem that the flame-retardant and comfort performance of current aramid fabrics is insufficient.

[0005] (2) Technical solution: In order to achieve the above objectives, the present invention provides the following technical solution: a comfortable flame-retardant aramid fabric, wherein the fabric is made of flame-retardant aramid fibers containing hydroxyapatite / magnesium hydroxide composite filler by weaving, knitting or non-woven forming process.

[0006] The flame-retardant aramid fiber is prepared by uniformly dispersing hydroxyapatite / magnesium hydroxide composite filler in an aramid fiber matrix.

[0007] The flame-retardant aramid fiber is prepared from the following raw materials in parts by weight: 15.0-20.0 parts of hydroxyapatite / magnesium hydroxide composite filler, 72.0-78.0 parts of meta-aramid polymer, 12.0-18.0 parts of para-aramid polymer, 2.5-4.0 parts of polybenzimidazole, 3.0-5.0 parts of melamine polyphosphate, 2.0-3.0 parts of dispersant, 0.4-0.6 parts of coupling agent, 0.4-0.6 parts of antioxidant, 0.3-0.5 parts of antistatic agent, 0.3-0.6 parts of softener, 450.0-550.0 parts of N-methylpyrrolidone, and 15.0-18.0 parts of CaCl2 cosolvent.

[0008] The hydroxyapatite / magnesium hydroxide composite filler consists of magnesium hydroxide nanorods and hydroxyapatite particles loaded on the surface of the magnesium hydroxide nanorods.

[0009] Furthermore, the mass ratio of magnesium hydroxide to hydroxyapatite in the hydroxyapatite / magnesium hydroxide composite filler is 70:30~80:20.

[0010] Furthermore, the composite filler has an average length of 3.0~8.0μm and an average diameter of 0.4~1.0μm.

[0011] Furthermore, the dispersant is polyvinylpyrrolidone or polyethylene glycol monomethyl ether; the coupling agent is γ-aminopropyltriethoxysilane or silane coupling agent KH-792; and the antioxidant is antioxidant 1010 or butylated hydroxytoluene.

[0012] This invention utilizes a synergistic design of hydroxyapatite / magnesium hydroxide composite filler and a multi-component aramid polymer matrix, primarily to enhance the flame retardant and comfort properties of aramid fabrics. By constructing a unique composite structure with hydroxyapatite particles loaded on the surface of magnesium hydroxide nanorods, the synergistic flame retardant mechanism of the two inorganic flame-retardant materials is fully utilized. During thermal decomposition, magnesium hydroxide releases water of crystallization, creating a water vapor dilution effect, while hydroxyapatite provides char formation barrier for phosphorus-based flame retardants. The organic combination of these two materials achieves a dual flame-retardant protection effect of gas-phase dilution and condensed-phase barrier, significantly improving the overall flame-retardant efficiency. The optimized mass ratio of magnesium hydroxide to hydroxyapatite in the composite filler ensures maximum flame-retardant performance, while the nanorod morphology and suitable aspect ratio of the composite filler facilitate the formation of an effective flame-retardant network structure within the fiber matrix. In terms of polymer matrix design, the blending of meta-aramid and para-aramid polymers achieves a balanced optimization of flexibility and strength. The excellent thermal stability and flexibility of meta-aramid complement the high strength and modulus of para-aramid, providing a solid foundation for the fabric's mechanical properties. The introduction of polybenzimidazole further enhances the high-temperature resistance and flame retardant properties of the polymer matrix. Its unique molecular structure maintains stable chemical bonds under high-temperature conditions, effectively inhibiting the thermal degradation process of the polymer. The addition of melamine polyphosphate as an intumescent flame retardant, through its foaming and charring mechanism during combustion, forms a multi-layered flame retardant protection system with the composite filler, achieving more comprehensive and efficient flame retardant protection. The use of γ-aminopropyltriethoxysilane or silane coupling agent KH-792 significantly improves the interfacial compatibility between inorganic fillers and the organic matrix. Through chemical bonding, it enhances the interfacial bonding force, not only improving the mechanical properties of the composite material but also ensuring the stable dispersion and long-term retention of the flame retardant components in the fiber. The selection of polyvinylpyrrolidone or polyethylene glycol monomethyl ether dispersants ensures the uniform distribution of the composite filler during spinning, avoiding the adverse effects of agglomeration on fiber properties. The addition of antioxidant 1010 or butylated hydroxytoluene effectively prevents oxidative degradation of the polymer during high-temperature processing, maintaining the excellent properties of the fiber. The synergistic effect of antistatic agents and softeners not only improves the processing performance and hand feel of the fiber but also endows the fabric with good antistatic properties and wearing comfort. This results in a final product that maintains excellent flame retardant properties while possessing good comfort, achieving a synergistic optimization of safety protection and wearing experience.

[0013] Furthermore, the preparation method of the hydroxyapatite / magnesium hydroxide composite filler includes: a) using a continuous stirred reactor, 1.5-2.5 parts of γ-aminopropyltriethoxysilane are pre-hydrolyzed at pH 3.8-4.2 for 40-50 min, then dispersed with 100 parts of magnesium hydroxide nanorods and 220-280 parts of deionized water, and the pre-hydrolyzed γ-aminopropyltriethoxysilane is added. The reaction is carried out at 65-75°C for 2.5-3.5 h with a stirring rate of 250-350 rpm and a Reynolds number of Re=1500-2500 to complete the silanization activation. During the reaction, the pH is monitored in real time and automatically adjusted by an online pH monitor.

[0014] b) Strictly control the calcium-to-phosphorus molar ratio to 1.60–1.67. Use a twin-screw metering pump to precisely control the feed rate. Add 1.0–1.5 parts of polyvinylpyrrolidone dispersant to 20–22 parts of a 15–20 wt% calcium nitrate tetrahydrate aqueous solution and 8–12 wt% diammonium hydrogen phosphate aqueous solution, respectively, and disperse at high speed for 30–40 min. Then, simultaneously add the two solutions dropwise to the activated suspension at a dropping rate of 1.0–1.5 mL / min. During the dropping process, maintain a stirring rate of 400–500 rpm and simultaneously add ammonia water via an automatic liquid addition system to adjust the pH of the system to 9.8–10.2. React at 85±2°C for 2.0–2.5 h, then transfer to an industrial-grade stainless steel high-pressure reactor and hydrothermally heat at 110±5°C for 5–7 h. Filter using a plate and frame filter with a 0.3–0.4 μm pore size membrane and wash until the pH reaches 6.8–7.2. Dry in a fluidized bed dryer at 90±5°C for 8–12 h. The hydroxyapatite / magnesium hydroxide composite filler was obtained.

[0015] Further, the preparation method of the magnesium hydroxide nanorods includes the following steps: Using a continuous stirred tank reactor, 100 parts of magnesium chloride hexahydrate are dissolved in 450-550 parts of deionized water to prepare a solution; 2.0-3.0 parts of sodium citrate are added to form a complexing solution; 3.0-5.0 parts of sodium dodecyl sulfate are dissolved in an ethanol-water mixed solvent with a volume ratio of 1:2.5-1:4, consisting of 25-35 parts of anhydrous ethanol and 250-350 parts of deionized water, to form a micelle system; this system is then added to the complexing solution and stirred at a stirring rate of 200-300 rpm for 40-50 min; then the temperature is increased to 50±3°C at a heating rate of 2-5°C / min; and 65-75 parts of 20-25 wt% sodium hydroxide solution are added dropwise using a peristaltic pump at a dropping rate of 1.5-2.5 mL / min, maintaining the pH at 11.5±0.3. The reaction is carried out for 80-100 minutes. The reaction mixture was transferred to an industrial-grade high-pressure reactor using a program-controlled reactor and hydrothermally heated at 140-150°C for 7-10 hours. After being filtered and washed to pH 6.8-7.2 using a centrifuge and washing tower system, it was dried in an airflow dryer at 70-75°C for 6-10 hours to obtain the final product.

[0016] This invention employs a stepwise silanization activation and in-situ loading precipitation preparation design primarily to enhance the interfacial bonding performance and flame-retardant synergistic effect of hydroxyapatite / magnesium hydroxide composite fillers. Through a meticulously designed pre-preparation process for magnesium hydroxide nanorods, utilizing the complexation effect of sodium citrate and the micelle system formed by sodium dodecyl sulfate in an ethanol-water mixed solvent, the growth process of magnesium hydroxide crystals is effectively controlled, ensuring the regularity of the nanorod morphology and the controllability of its size, providing an ideal support basis for subsequent hydroxyapatite loading. Pre-hydrolysis treatment of γ-aminopropyltriethoxysilane under strictly controlled pH conditions allows for the complete hydrolysis of silane molecules to form active silanol groups. The subsequent silanization activation reaction on the surface of the magnesium hydroxide nanorods forms a uniform organosilane layer on the support surface through chemical bonding. This surface modification not only enhances the compatibility between magnesium hydroxide and the organic matrix but also provides favorable nucleation sites and a favorable chemical environment for the in-situ growth of hydroxyapatite. Strictly controlled calcium-to-phosphorus molar ratios and a simultaneous two-liquid addition process ensured the purity and stoichiometric accuracy of the hydroxyapatite crystal phase. Precise control via a twin-screw metering pump and pH adjustment by an automatic addition system enabled uniform precipitation and robust bonding of hydroxyapatite onto the activated magnesium hydroxide nanorods. The addition of polyvinylpyrrolidone dispersant during precipitation effectively prevented particle agglomeration, ensuring uniform dispersion and controllable particle size on the carrier surface. Hydrothermal treatment, utilizing a high-temperature, high-pressure environment, promoted the optimal growth of hydroxyapatite crystals and their tight bonding with the carrier, while also further enhancing the crystallinity and thermal stability of the composite filler. The coordinated use of continuous stirred reactors, industrial-grade stainless steel high-pressure reactors, plate and frame filters, and fluidized bed dryers throughout the preparation process not only ensured process stability and reproducibility but also enabled continuous and industrialized production. This meticulously designed composite filler preparation process enables hydroxyapatite and magnesium hydroxide to form a tight interfacial bond at the molecular level. The synergistic effect of the two flame-retardant components far exceeds the effect of using them alone. During combustion, they can simultaneously exert multiple flame-retardant mechanisms such as gas phase dilution, condensed phase char formation, and heat absorption, significantly improving the overall flame-retardant efficiency and thermal stability of the composite filler, and laying a solid material foundation for the preparation of high-performance flame-retardant aramid fabrics.

[0017] This invention also discloses a method for preparing a comfortable flame-retardant aramid fabric, comprising the following steps: S1. Continuous preparation of spinning solution: Using a multi-stage mixer system, meta-aramid polymer, para-aramid polymer, and polybenzimidazole are premixed in a premixer at 100-120°C for 45-60 min, and then added to a solvent system containing N-methylpyrrolidone and CaCl2 co-solvent. The solution is dissolved in a dissolving vessel at 110-130°C and a stirring rate of 150-250 rpm for 3-5 h until the polymer is completely dissolved. Dispersant, coupling agent, antioxidant, antistatic agent, and softener are added sequentially, and each component is dispersed in a disperser for 30-60 min. Then, using an industrial-grade high-shear disperser, hydroxyapatite / magnesium hydroxide composite filler and melamine polyphosphate are added in batches using a staged shearing method. After treatment by an industrial ultrasonic system for 30-60 min, the solution is deaerated by a continuous deaerator for 1-3 h and filtered through a precision filter to obtain a solid content of 18-22%. Spinning solution with a viscosity of 80~150 Pa·s and a weight percentage of wt%.

[0018] S2. Continuous fiber preparation: Using an industrial wet spinning production line, the spinning solution is extruded through an industrial spinneret with 200-800 holes and a pore size of 0.08-0.12 mm at a spinning speed of 80-200 m / min into a coagulation bath at a temperature of 20-30°C, composed of NMP and deionized water in a volume ratio of 35:65-45:55, and solidified for 15-45 s. After washing at 40-60°C for 10-25 min in a continuous washing device, industrial multi-stage stretching and continuous heat setting are performed to obtain modified aramid fibers with a linear density of 1.5-4.0 dtex and a breaking strength of 20-28 cN / dtex.

[0019] S3. Fabric weaving and forming: Modified aramid fibers are prepared into yarns with a linear density of 25~55 tex using industrial spinning equipment. During the spinning process, the draft ratio is controlled at 18~22 times and the twist coefficient is 380~420. Then, the yarns are woven into plain or twill fabrics with a warp density of 140~180 threads / 10cm and a weft density of 120~160 threads / 10cm using industrial looms, or knitted into knitted fabrics with a warp density of 160~200 stitches / 5cm and a weft density of 200~260 rows / 5cm using industrial knitting machines. After weaving, the yarns are continuously pre-shrinked and set at 150~170°C for 5~15 minutes using a tenter frame.

[0020] S4. Finishing process: The fabric is scouring, bleaching and softening in sequence to obtain a comfortable flame-retardant aramid fabric.

[0021] Furthermore, in step S1, the graded shearing method involves first adding 30% of the hydroxyapatite / magnesium hydroxide composite filler under low-speed shearing conditions, then adding the remaining 50% of the filler under medium-speed shearing conditions, and finally adding the remaining 20% ​​of the filler and melamine polyphosphate under high-speed shearing conditions to achieve uniform distribution of the filler. The low-speed shearing rate is 3000.0~5000.0 rpm, the medium-speed shearing rate is 6000.0~10000.0 rpm, and the high-speed shearing rate is 10000.0~15000.0 rpm.

[0022] Furthermore, the multi-stage stretching treatment in step S2 includes a first-stage stretching ratio of 1.5 to 3.0 times and a stretching temperature of 100.0 to 150.0°C, a second-stage stretching ratio of 2.0 to 4.0 times and a stretching temperature of 150.0 to 200.0°C, a third-stage stretching ratio of 1.2 to 2.5 times and a stretching temperature of 200.0 to 280.0°C, with the total stretching ratio controlled at 5.0 to 12.0 times, and a heat setting treatment temperature of 220 to 280°C and a treatment time of 1.0 to 10.0 min.

[0023] Furthermore, in step S4, the scouring process involves treatment in an alkaline scouring solution at 80.0~95.0°C and pH 9.0~11.0 for 30.0~60.0 min; the bleaching process involves treatment in a hydrogen peroxide bleaching solution at 60.0~80.0°C for 20.0~45.0 min; and the softening process involves treatment with an organosilicon softener at 40.0~60.0°C for 15.0~30.0 min. After each process, the fabric is thoroughly washed with deionized water and dried at 100.0~130.0°C for 10.0~20.0 min, ultimately yielding a comfortable flame-retardant aramid fabric with an areal density of 120.0~300.0 g / m², a limiting oxygen index ≥32.0%, a moisture absorption rate ≥8.0%, a moisture permeability ≥8000.0 g / m²·24h, and an antibacterial rate ≥95.0%.

[0024] This invention employs a multi-stage mixing and dispersion and continuous processing design primarily to enhance the overall performance and processing stability of flame-retardant aramid fabrics. A multi-stage mixer system enables high-temperature premixing of meta-aramid polymers, para-aramid polymers, and polybenzimidazole, promoting the entanglement and improved compatibility of different polymer chains. The synergistic effect of the N-methylpyrrolidone and CaCl2 co-solvent system improves polymer dissolution efficiency and enhances the rheological properties of the spinning solution. The CaCl2 co-solvent effectively reduces intermolecular forces and promotes polymer chain extension. The sequential dispersion of dispersants, coupling agents, antioxidants, antistatic agents, and softeners in each component disperser ensures uniform additive distribution. The graded shearing method of the industrial-grade high-shear disperser, through progressive shear strength and batch feeding strategies, achieves ideal dispersion of hydroxyapatite / magnesium hydroxide composite filler and melamine polyphosphate. An industrial ultrasonic system further eliminates micro-agglomeration. Industrialized wet spinning production lines achieve continuous and stable extrusion through precisely controlled industrial spinnerets and optimized coagulation bath composition. A coagulation bath with a specific volume ratio of NMP to deionized water provides an ideal environment for polymer phase separation and fiber structure formation. Multi-stage stretching treatment enhances the ordered orientation and crystallinity of fiber molecular chains through increasing stretch ratios and temperature gradients, while continuous heat setting stabilizes the fiber microstructure. Precise control of industrial spinning equipment and reasonable design of draft ratios and twist coefficients balance yarn strength and softness, while flexible selection of weaving and knitting processes meets diverse application requirements. The sequential finishing processes of scouring, bleaching, and softening significantly improve fabric comfort through the synergistic effects of impurity removal, improved appearance, and enhanced hand feel. Alkaline scouring solution removes residual substances, hydrogen peroxide bleach improves whiteness, and silicone softener imparts excellent softness, ultimately achieving synergistic optimization of flame retardant, comfort, and antibacterial properties.

[0025] (3) Beneficial technical effects: 1. Through the synergistic design of hydroxyapatite / magnesium hydroxide composite filler and multi-component aramid polymer matrix, this invention achieves simultaneous improvement in flame retardancy and comfort performance, solves the technical problems of poor flame retardancy and poor comfort of traditional aramid fabrics, and provides high-performance solutions for fire protection, industrial safety and other fields.

[0026] 2. This invention achieves molecular-level interfacial bonding between hydroxyapatite and magnesium hydroxide through stepwise silanization activation and in-situ loading precipitation processes, synergistically leveraging the dual flame-retardant mechanisms of gas-phase dilution and condensed-phase char formation, significantly improving the flame-retardant efficiency and thermal stability of the composite filler. Attached Figure Description

[0027] Figure 1 This is a morphology diagram of the magnesium hydroxide nanorods prepared in Example 1 of the present invention.

[0028] Figure 2XRD phase analysis of the magnesium hydroxide nanorods prepared in Example 1 of this invention.

[0029] Figure 3 This is a morphology diagram of the hydroxyapatite / magnesium hydroxide composite filler prepared in Example 1 of the present invention.

[0030] Figure 4 XRD phase analysis of the hydroxyapatite / magnesium hydroxide composite filler prepared in Example 1 of this invention.

[0031] Figure 5 This is a morphology diagram of the hydroxyapatite / magnesium hydroxide composite filler prepared in Comparative Example 2 of the present invention.

[0032] Figure 6 The images show the results of a vertical burning experiment on the comfortable flame-retardant aramid fabric prepared in Example 1 of this invention.

[0033] Figure 7 The image shows the results of vertical burning of the comfortable flame-retardant aramid fabric prepared in Comparative Example 15 of this invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0035] Example 1: A comfortable flame-retardant aramid fabric, wherein the fabric is made of flame-retardant aramid fibers containing hydroxyapatite / magnesium hydroxide composite filler through weaving, knitting or non-woven forming processes.

[0036] The flame-retardant aramid fiber of this embodiment is prepared by uniformly dispersing hydroxyapatite / magnesium hydroxide composite filler in an aramid fiber matrix.

[0037] The flame-retardant aramid fiber of this embodiment is prepared from the following raw materials in parts by weight: 17.5 parts of hydroxyapatite / magnesium hydroxide composite filler, 75.0 parts of meta-aramid polymer, 15.0 parts of para-aramid polymer, 3.2 parts of polybenzimidazole, 4.0 parts of melamine polyphosphate, 2.5 parts of dispersant, 0.5 parts of coupling agent, 0.5 parts of antioxidant, 0.4 parts of antistatic agent, 0.4 parts of softener, 500.0 parts of N-methylpyrrolidone, and 16.5 parts of CaCl2 cosolvent.

[0038] The hydroxyapatite / magnesium hydroxide composite filler in this embodiment consists of magnesium hydroxide nanorods and hydroxyapatite particles loaded on the surface of the magnesium hydroxide nanorods.

[0039] In this embodiment, the mass ratio of magnesium hydroxide to hydroxyapatite in the hydroxyapatite / magnesium hydroxide composite filler is 75:25.

[0040] In this embodiment, the composite filler has an average length of 5.5 μm and an average diameter of 0.7 μm.

[0041] Furthermore, the dispersant is polyvinylpyrrolidone; the coupling agent in this embodiment is γ-aminopropyltriethoxysilane; and the antioxidant in this embodiment is antioxidant 1010.

[0042] The preparation method of the hydroxyapatite / magnesium hydroxide composite filler in this embodiment includes: a) using a continuous stirred reactor, 2.0 parts of γ-aminopropyltriethoxysilane are pre-hydrolyzed at pH 4.0 for 45 min, then dispersed with 100 parts of magnesium hydroxide nanorods and 250 parts of deionized water, and the pre-hydrolyzed γ-aminopropyltriethoxysilane is added. The reaction is carried out at 70°C for 3.0 h with a stirring speed of 300 rpm and a Reynolds number of Re=2000 to complete the silanization activation. During the reaction, the pH is monitored in real time and automatically adjusted by an online pH monitor.

[0043] b) The calcium-to-phosphorus molar ratio was strictly controlled at 1.65. A twin-screw metering pump was used to precisely control the feed rate. 1.2 parts of polyvinylpyrrolidone dispersant were added to 21 parts of a 17.5 wt% calcium nitrate tetrahydrate aqueous solution and 10 wt% diammonium hydrogen phosphate aqueous solution, respectively, and dispersed at high speed for 35 min. The two solutions were then simultaneously added dropwise to the activated suspension at a dropping rate of 1.2 mL / min. During the dropping process, the stirring rate was maintained at 450 rpm, and ammonia water was added dropwise simultaneously through an automatic liquid addition system to adjust the pH of the system to 10.0. After reacting at 85°C for 2.2 h, the mixture was transferred to an industrial-grade stainless steel high-pressure reactor and hydrothermally heated at 110°C for 6 h. The mixture was then filtered and washed with a 0.35 μm pore size filter membrane using a plate and frame filter until the pH reached 7.0. Finally, it was dried in a fluidized bed dryer at 90°C for 10 h to obtain the hydroxyapatite / magnesium hydroxide composite packing.

[0044] The preparation method of magnesium hydroxide nanorods in this embodiment includes the following steps: A continuous stirred tank reactor is used. 100 parts of magnesium chloride hexahydrate are dissolved in 500 parts of deionized water to prepare a solution. 2.5 parts of sodium citrate are added to form a complex solution. 4.0 parts of sodium dodecyl sulfate are dissolved in a 1:3 volume ratio ethanol-water mixed solvent consisting of 30 parts of anhydrous ethanol and 300 parts of deionized water to form a micelle system. This system is then added to the complex solution and stirred at 250 rpm for 45 min. The temperature is then increased to 50°C at a rate of 3.5°C / min. 70 parts of 22.5 wt% sodium hydroxide solution are added dropwise at a rate of 2.0 mL / min using a peristaltic pump to maintain the pH at 11.5 for 90 min. The reaction mixture is then transferred to an industrial-grade high-pressure reactor using a programmable reactor and hydrothermally heated at 145°C for 8.5 h. After filtration and washing to pH 7.0 using a centrifuge and washing tower system, the mixture is dried in a 72°C airflow dryer for 8 h to obtain the final product.

[0045] This embodiment describes a method for preparing a comfortable flame-retardant aramid fabric, comprising the following steps: S1. Continuous preparation of spinning solution: Using a multi-stage mixer system, meta-aramid polymer, para-aramid polymer, and polybenzimidazole are premixed in a premixer at 110°C for 52 min, and then added to a solvent system containing N-methylpyrrolidone and CaCl2 co-solvent. The solution is dissolved in a dissolving vessel at 120°C and a stirring rate of 200 rpm for 4 h until the polymer is completely dissolved. Dispersant, coupling agent, antioxidant, antistatic agent, and softener are added sequentially, and each component is dispersed in a disperser for 45 min. Then, using an industrial-grade high-shear disperser, hydroxyapatite / magnesium hydroxide composite filler and melamine polyphosphate are added in batches using a graded shearing method. After being treated by an industrial ultrasonic system for 45 min, the solution is deaerated by a continuous deaerator for 2 h and filtered through a precision filter to obtain a spinning solution with a solid content of 20 wt% and a viscosity of 115 Pa·s.

[0046] S2. Continuous fiber preparation: Using an industrial wet spinning production line, the spinning solution is extruded through an industrial spinneret with 500 holes and a diameter of 0.10 mm at a spinning speed of 140 m / min into a coagulation bath at a temperature of 25°C, composed of NMP and deionized water in a volume ratio of 40:60, and solidified for 30 s. After washing at 50°C for 17 min in a continuous washing device, it undergoes industrial multi-stage stretching and continuous heat setting to obtain modified aramid fibers with a linear density of 2.7 dtex and a breaking strength of 24 cN / dtex.

[0047] S3. Fabric weaving and forming: Modified aramid fibers are prepared into yarn with a linear density of 40 tex using industrial spinning equipment. During the spinning process, the draft ratio is controlled at 20 times and the twist coefficient is 400. Then, the yarn is woven into a plain weave fabric with a warp density of 160 threads / 10cm and a weft density of 140 threads / 10cm using an industrial loom. After weaving, the fabric is continuously pre-shrinked and set at 160°C for 10 minutes using a tenter frame.

[0048] S4. Finishing process: The fabric is scouring, bleaching and softening in sequence to obtain a comfortable flame-retardant aramid fabric.

[0049] In step S1 of this embodiment, the graded shearing method involves first adding 30% of the hydroxyapatite / magnesium hydroxide composite filler under low-speed shearing conditions, then adding the remaining 50% of the filler under medium-speed shearing conditions, and finally adding the remaining 20% ​​of the filler and melamine polyphosphate under high-speed shearing conditions to achieve uniform distribution of the filler. The low-speed shearing rate is 4000.0 rpm, the medium-speed shearing rate is 8000.0 rpm, and the high-speed shearing rate is 12500.0 rpm.

[0050] In step S2 of this embodiment, the multi-stage stretching process includes a first-stage stretching ratio of 2.2 times and a stretching temperature of 125.0°C, a second-stage stretching ratio of 3.0 times and a stretching temperature of 175.0°C, a third-stage stretching ratio of 1.8 times and a stretching temperature of 240.0°C, with the total stretching ratio controlled at 8.5 times. The heat setting temperature is 250°C and the processing time is 5.5 minutes.

[0051] In step S4 of this embodiment, scouring is performed in an alkaline scouring solution at 87.5°C and pH 10.0 for 45.0 min; bleaching is performed in a hydrogen peroxide bleaching solution at 70.0°C for 32.5 min; and softening is performed using an organosilicon softener at 50.0°C for 22.5 min. After each process, the fabric is thoroughly washed with deionized water and dried at 115.0°C for 15.0 min, ultimately yielding a comfortable flame-retardant aramid fabric with an areal density of 210.0 g / m², a limiting oxygen index of 34.5%, a moisture absorption rate of 9.2%, a moisture permeability of 8850 g / m²·24h, and an antibacterial rate of 96.8%.

[0052] This embodiment employs moderate parameter configurations, exhibiting good process stability and operability. The composite filler addition amount is 17.5 parts, the mass ratio of magnesium hydroxide to hydroxyapatite is 75:25, and the composite filler size is moderate (length 5.5 μm, diameter 0.7 μm), achieving a good balance between flame retardant properties and processing performance. The preparation process parameters are relatively conservatively selected, such as a silanization reaction temperature of 70°C, a reaction time of 3.0 h, and hydrothermal treatment conditions of 110°C / 6 h, ensuring process reproducibility and stability. The spinning process uses a moderate spinning speed of 140 m / min and a moderate draw ratio of 8.5 times, ultimately obtaining a fabric with an areal density of 210 g / m², a limiting oxygen index of 34.5%, a moisture absorption rate of 9.2%, a moisture permeability of 8850 g / m²·24 h, and an antibacterial rate of 96.8%, demonstrating balanced performance across various indicators.

[0053] Example 2: A comfortable flame-retardant aramid fabric, wherein the fabric is made of flame-retardant aramid fibers containing hydroxyapatite / magnesium hydroxide composite filler through weaving, knitting or non-woven forming processes.

[0054] The flame-retardant aramid fiber of this embodiment is prepared by uniformly dispersing hydroxyapatite / magnesium hydroxide composite filler in an aramid fiber matrix.

[0055] The flame-retardant aramid fiber of this embodiment is prepared from the following raw materials in parts by weight: 20.0 parts of hydroxyapatite / magnesium hydroxide composite filler, 72.0 parts of meta-aramid polymer, 18.0 parts of para-aramid polymer, 4.0 parts of polybenzimidazole, 5.0 parts of melamine polyphosphate, 3.0 parts of dispersant, 0.6 parts of coupling agent, 0.6 parts of antioxidant, 0.5 parts of antistatic agent, 0.6 parts of softener, 550.0 parts of N-methylpyrrolidone, and 18.0 parts of CaCl2 cosolvent.

[0056] The hydroxyapatite / magnesium hydroxide composite filler in this embodiment consists of magnesium hydroxide nanorods and hydroxyapatite particles loaded on the surface of the magnesium hydroxide nanorods.

[0057] In this embodiment, the mass ratio of magnesium hydroxide to hydroxyapatite in the hydroxyapatite / magnesium hydroxide composite filler is 80:20.

[0058] In this embodiment, the composite filler has an average length of 8.0 μm and an average diameter of 1.0 μm.

[0059] Furthermore, the dispersant is polyethylene glycol monomethyl ether; the coupling agent in this embodiment is silane coupling agent KH-792; and the antioxidant in this embodiment is butylated hydroxytoluene.

[0060] The preparation method of the hydroxyapatite / magnesium hydroxide composite filler in this embodiment includes: a) using a continuous stirred reactor, 2.5 parts of γ-aminopropyltriethoxysilane are pre-hydrolyzed for 50 min under pH 4.2 conditions, then dispersed with 100 parts of magnesium hydroxide nanorods and 280 parts of deionized water, and the pre-hydrolyzed γ-aminopropyltriethoxysilane is added. The reaction is carried out at 75°C for 3.5 h under stirring speed of 350 rpm and Reynolds number Re=2500 to complete silanization activation. During the reaction, the pH is monitored in real time and automatically adjusted by an online pH monitor.

[0061] b) The calcium-to-phosphorus molar ratio was strictly controlled at 1.67. A twin-screw metering pump was used to precisely control the feed rate. 22 parts of a 20 wt% calcium nitrate tetrahydrate aqueous solution and 1.5 parts of polyvinylpyrrolidone dispersant were added to a 12 wt% diammonium hydrogen phosphate aqueous solution and dispersed at high speed for 40 min. The two solutions were then simultaneously added dropwise to the activated suspension at a dropping rate of 1.5 mL / min. During the dropping process, the stirring rate was maintained at 500 rpm, and ammonia water was added dropwise simultaneously through an automatic liquid addition system to adjust the pH of the system to 10.2. After reacting at 87°C for 2.5 h, the mixture was transferred to an industrial-grade stainless steel high-pressure reactor and hydrothermally heated at 115°C for 7 h. The mixture was then filtered and washed with a 0.4 μm pore size filter membrane using a plate and frame filter until the pH reached 7.2. Finally, it was dried in a fluidized bed dryer at 95°C for 12 h to obtain the hydroxyapatite / magnesium hydroxide composite packing.

[0062] The preparation method of magnesium hydroxide nanorods in this embodiment includes the following steps: A continuous stirred tank reactor is used. 100 parts of magnesium chloride hexahydrate are dissolved in 550 parts of deionized water to prepare a solution. 3.0 parts of sodium citrate are added to form a complex solution. 5.0 parts of sodium dodecyl sulfate are dissolved in a 1:4 volume ratio ethanol-water mixed solvent consisting of 35 parts anhydrous ethanol and 350 parts deionized water to form a micelle system. This system is then added to the complex solution and stirred at 300 rpm for 50 min. The temperature is then increased to 53°C at a rate of 5°C / min. 75 parts of 25wt% sodium hydroxide solution are added dropwise at a rate of 2.5 mL / min using a peristaltic pump to maintain the pH at 11.8 for 100 min. The reaction mixture is transferred to an industrial-grade high-pressure reactor using a programmable reactor and hydrothermally heated at 150°C for 10 h. After filtration and washing to pH 7.2 using a centrifuge and washing tower system, the mixture is dried in a 75°C airflow dryer for 10 h to obtain the final product.

[0063] This embodiment describes a method for preparing a comfortable flame-retardant aramid fabric, comprising the following steps: S1. Continuous preparation of spinning solution: Using a multi-stage mixer system, meta-aramid polymer, para-aramid polymer, and polybenzimidazole are premixed in a premixer at 120°C for 60 min, and then added to a solvent system containing N-methylpyrrolidone and CaCl2 co-solvent. The solution is dissolved in a dissolving vessel at 130°C and a stirring rate of 250 rpm for 5 h until the polymer is completely dissolved. Dispersant, coupling agent, antioxidant, antistatic agent, and softener are added sequentially, and each component is dispersed in a disperser for 60 min. Then, using an industrial-grade high-shear disperser, hydroxyapatite / magnesium hydroxide composite filler and melamine polyphosphate are added in batches using a graded shearing method. After being treated by an industrial ultrasonic system for 60 min, the solution is deaerated by a continuous deaerator for 3 h and filtered through a precision filter to obtain a spinning solution with a solid content of 22 wt% and a viscosity of 150 Pa·s.

[0064] S2. Continuous fiber preparation: Using an industrial wet spinning production line, the spinning solution is extruded through an industrial spinneret with 800 holes and a diameter of 0.12 mm at a spinning speed of 200 m / min into a coagulation bath at a temperature of 30°C, composed of NMP and deionized water in a volume ratio of 45:55, and solidified for 45 s. After washing at 60°C for 25 min in a continuous washing device, industrial multi-stage stretching and continuous heat setting are performed to obtain modified aramid fibers with a linear density of 4.0 dtex and a breaking strength of 28 cN / dtex.

[0065] S3. Fabric weaving and forming: Modified aramid fibers are prepared into yarn with a linear density of 55 tex using industrial spinning equipment. During the spinning process, the draft ratio is controlled at 22 times and the twist coefficient is 420. Then, an industrial knitting machine is used to knit the fabric into a knitted fabric with a warp density of 200 stitches / 5cm and a weft density of 260 rows / 5cm. After knitting, the fabric is continuously pre-shrinked and set at 170°C for 15 minutes using a tenter frame.

[0066] S4. Finishing process: The fabric is scouring, bleaching and softening in sequence to obtain a comfortable flame-retardant aramid fabric.

[0067] In step S1 of this embodiment, the graded shearing method involves first adding 30% of the hydroxyapatite / magnesium hydroxide composite filler under low-speed shearing conditions, then adding the remaining 50% of the filler under medium-speed shearing conditions, and finally adding the remaining 20% ​​of the filler and melamine polyphosphate under high-speed shearing conditions to achieve uniform distribution of the filler. The low-speed shearing rate is 5000.0 rpm, the medium-speed shearing rate is 10000.0 rpm, and the high-speed shearing rate is 15000.0 rpm.

[0068] In step S2 of this embodiment, the multi-stage stretching process includes a first-stage stretching ratio of 3.0 times and a stretching temperature of 150.0°C, a second-stage stretching ratio of 4.0 times and a stretching temperature of 200.0°C, a third-stage stretching ratio of 2.5 times and a stretching temperature of 280.0°C, with the total stretching ratio controlled at 12.0 times, and a heat setting temperature of 280°C and a processing time of 10.0 min.

[0069] In step S4 of this embodiment, scouring is performed in an alkaline scouring solution at 95.0°C and pH 11.0 for 60.0 min; bleaching is performed in a hydrogen peroxide bleaching solution at 80.0°C for 45.0 min; and softening is performed using an organosilicon softener at 60.0°C for 30.0 min. After each process, the fabric is thoroughly washed with deionized water and dried at 130.0°C for 20.0 min, ultimately yielding a comfortable flame-retardant aramid fabric with an areal density of 300.0 g / m², a limiting oxygen index of 37.8%, a moisture absorption rate of 6.7%, a moisture permeability of 6520 g / m²·24h, and an antibacterial rate of 98.5%.

[0070] This embodiment prioritizes high flame retardant performance, employing the highest composite filler addition amount of 20.0 parts and the highest magnesium hydroxide ratio (80:20), with the composite filler size reaching its maximum value (8.0 μm length, 1.0 μm diameter) to achieve optimal flame retardant effect. The preparation process parameters favor reinforcement treatment, with the silanization reaction using the highest temperature of 75°C and the longest duration of 3.5 h, and hydrothermal treatment conditions of 115°C / 7 h, ensuring sufficient reaction and crystallization of the composite filler. The spinning process uses the highest spinning speed of 200 m / min and the maximum stretch ratio of 12.0 times, with the most intensive finishing conditions, ultimately obtaining a heavy-duty flame-retardant fabric with an areal density of 300 g / m² and a limiting oxygen index of 37.8%. However, the moisture absorption rate is correspondingly reduced to 6.7%, and the moisture permeability is reduced to 6520 g / m²·24h, reflecting the trade-off between high flame retardant performance and comfort.

[0071] Example 3: A comfortable flame-retardant aramid fabric, wherein the fabric is made of flame-retardant aramid fibers containing hydroxyapatite / magnesium hydroxide composite filler through weaving, knitting or non-woven forming processes.

[0072] The flame-retardant aramid fiber of this embodiment is prepared by uniformly dispersing hydroxyapatite / magnesium hydroxide composite filler in an aramid fiber matrix.

[0073] The flame-retardant aramid fiber of this embodiment is prepared from the following raw materials in parts by weight: 15.0 parts of hydroxyapatite / magnesium hydroxide composite filler, 78.0 parts of meta-aramid polymer, 12.0 parts of para-aramid polymer, 2.5 parts of polybenzimidazole, 3.0 parts of melamine polyphosphate, 2.0 parts of dispersant, 0.4 parts of coupling agent, 0.4 parts of antioxidant, 0.3 parts of antistatic agent, 0.3 parts of softener, 450.0 parts of N-methylpyrrolidone, and 15.0 parts of CaCl2 cosolvent.

[0074] The hydroxyapatite / magnesium hydroxide composite filler in this embodiment consists of magnesium hydroxide nanorods and hydroxyapatite particles loaded on the surface of the magnesium hydroxide nanorods.

[0075] In this embodiment, the mass ratio of magnesium hydroxide to hydroxyapatite in the hydroxyapatite / magnesium hydroxide composite filler is 70:30.

[0076] In this embodiment, the composite filler has an average length of 3.0 μm and an average diameter of 0.4 μm.

[0077] Furthermore, the dispersant is polyvinylpyrrolidone; the coupling agent in this embodiment is γ-aminopropyltriethoxysilane; and the antioxidant in this embodiment is antioxidant 1010.

[0078] The preparation method of the hydroxyapatite / magnesium hydroxide composite filler in this embodiment includes: a) using a continuous stirred reactor, 1.5 parts of γ-aminopropyltriethoxysilane are pre-hydrolyzed at pH 3.8 for 40 min, then dispersed with 100 parts of magnesium hydroxide nanorods and 220 parts of deionized water, and the pre-hydrolyzed γ-aminopropyltriethoxysilane is added. The reaction is carried out at 65°C for 2.5 h at a stirring rate of 250 rpm and a Reynolds number of Re=1500 to complete the silanization activation. During the reaction, the pH is monitored in real time and automatically adjusted by an online pH monitor.

[0079] b) The calcium-to-phosphorus molar ratio was strictly controlled at 1.60. A twin-screw metering pump was used to precisely control the feed rate. 1.0 part of polyvinylpyrrolidone dispersant was added to 20 parts of a 15 wt% calcium nitrate tetrahydrate aqueous solution and 8 wt% diammonium hydrogen phosphate aqueous solution, and dispersed at high speed for 30 min. The two solutions were then simultaneously added dropwise to the activated suspension at a dropping rate of 1.0 mL / min. During the dropping process, the stirring speed was maintained at 400 rpm, and ammonia water was added dropwise simultaneously through an automatic liquid addition system to adjust the pH of the system to 9.8. After reacting at 83°C for 2.0 h, the mixture was transferred to an industrial-grade stainless steel high-pressure reactor and hydrothermally heated at 105°C for 5 h. The mixture was then filtered and washed with a 0.3 μm pore size filter membrane using a plate and frame filter until the pH reached 6.8. Finally, it was dried in a fluidized bed dryer at 85°C for 8 h to obtain the hydroxyapatite / magnesium hydroxide composite packing.

[0080] The preparation method of magnesium hydroxide nanorods in this embodiment includes the following steps: A continuous stirred tank reactor is used. 100 parts of magnesium chloride hexahydrate are dissolved in 450 parts of deionized water to prepare a solution. 2.0 parts of sodium citrate are added to form a complex solution. 3.0 parts of sodium dodecyl sulfate are dissolved in a 1:2.5 volume ratio ethanol-water mixed solvent consisting of 25 parts anhydrous ethanol and 250 parts deionized water to form a micelle system. This system is then added to the complex solution and stirred at 200 rpm for 40 min. The temperature is then increased to 47°C at a rate of 2°C / min. 65 parts of 20wt% sodium hydroxide solution are added dropwise at a rate of 1.5 mL / min using a peristaltic pump to maintain the pH at 11.2 for 80 min. The reaction mixture is transferred to an industrial-grade high-pressure reactor using a programmable reactor and hydrothermally heated at 140°C for 7 h. After filtration and washing to pH 6.8 using a centrifuge and washing tower system, the mixture is dried in a 70°C airflow dryer for 6 h to obtain the final product.

[0081] This embodiment describes a method for preparing a comfortable flame-retardant aramid fabric, comprising the following steps: S1. Continuous preparation of spinning solution: Using a multi-stage mixer system, meta-aramid polymer, para-aramid polymer, and polybenzimidazole are premixed in a premixer at 100°C for 45 min, and then added to a solvent system containing N-methylpyrrolidone and CaCl2 co-solvent. The solution is dissolved in a dissolving vessel at 110°C and a stirring rate of 150 rpm for 3 h until the polymer is completely dissolved. Dispersant, coupling agent, antioxidant, antistatic agent, and softener are added sequentially, and each component is dispersed in a disperser for 30 min. Then, using an industrial-grade high-shear disperser, hydroxyapatite / magnesium hydroxide composite filler and melamine polyphosphate are added in batches using a graded shearing method. After being treated by an industrial ultrasonic system for 30 min, the solution is degassed by a continuous deaerator for 1 h and filtered through a precision filter to obtain a spinning solution with a solid content of 18 wt% and a viscosity of 80 Pa·s.

[0082] S2. Continuous fiber preparation: Using an industrial wet spinning production line, the spinning solution is extruded through an industrial spinneret with 200 holes and a diameter of 0.08 mm at a spinning speed of 80 m / min into a coagulation bath at a temperature of 20°C, composed of NMP and deionized water in a volume ratio of 35:65, and solidified for 15 seconds. After washing at 40°C for 10 minutes in a continuous washing device, it undergoes industrial multi-stage stretching and continuous heat setting to obtain modified aramid fibers with a linear density of 1.5 dtex and a breaking strength of 20 cN / dtex.

[0083] S3. Fabric weaving and forming: Modified aramid fibers are prepared into yarn with a linear density of 25 tex using industrial spinning equipment. During the spinning process, the draft ratio is controlled at 18 times and the twist coefficient is 380. Then, the yarn is woven into a twill fabric with a warp density of 140 threads / 10cm and a weft density of 120 threads / 10cm using an industrial loom. After weaving, the fabric is continuously pre-shrinked and set at 150°C for 5 minutes using a tenter frame.

[0084] S4. Finishing process: The fabric is scouring, bleaching and softening in sequence to obtain a comfortable flame-retardant aramid fabric.

[0085] In step S1 of this embodiment, the graded shearing method involves first adding 30% of the hydroxyapatite / magnesium hydroxide composite filler under low-speed shearing conditions, then adding the remaining 50% of the filler under medium-speed shearing conditions, and finally adding the remaining 20% ​​of the filler and melamine polyphosphate under high-speed shearing conditions to achieve uniform distribution of the filler. The low-speed shearing rate is 3000.0 rpm, the medium-speed shearing rate is 6000.0 rpm, and the high-speed shearing rate is 10000.0 rpm.

[0086] In step S2 of this embodiment, the multi-stage stretching process includes a first-stage stretching ratio of 1.5 times and a stretching temperature of 100.0°C, a second-stage stretching ratio of 2.0 times and a stretching temperature of 150.0°C, a third-stage stretching ratio of 1.2 times and a stretching temperature of 200.0°C, with the total stretching ratio controlled at 5.0 times, and a heat setting temperature of 220°C and a processing time of 1.0 min.

[0087] In step S4 of this embodiment, scouring is performed in an alkaline scouring solution at 80.0°C and pH 9.0 for 30.0 min; bleaching is performed in a hydrogen peroxide bleaching solution at 60.0°C for 20.0 min; and softening is performed using an organosilicon softener at 40.0°C for 15.0 min. After each process, the fabric is thoroughly washed with deionized water and dried at 100.0°C for 10.0 min, ultimately yielding a comfortable flame-retardant aramid fabric with an areal density of 120.0 g / m², a limiting oxygen index of 32.3%, a moisture absorption rate of 11.6%, a moisture permeability of 9760 g / m²·24h, and an antibacterial rate of 95.2%.

[0088] This embodiment prioritizes lightweight design and optimized comfort, employing a minimum composite filler addition of 15.0 parts, a magnesium hydroxide to hydroxyapatite mass ratio of 70:30, and minimal composite filler size (3.0 μm length, 0.4 μm diameter). This maximizes comfort while ensuring basic flame retardant properties. The manufacturing process parameters are relatively mild: silanization reaction at 65°C for 2.5 h and hydrothermal treatment at 105°C for 5 h, minimizing the impact of process strength on fiber flexibility. The spinning process uses a minimum spinning speed of 80 m / min and a minimum stretch ratio of 5.0 times. The finishing process is also mild, ultimately yielding a lightweight and comfortable fabric with an areal density of 120 g / m², a moisture absorption rate of 11.6%, and a moisture permeability of 9760 g / m²·24 h. However, the limiting oxygen index is relatively low at 32.3%, highlighting its superior comfort performance.

[0089] Example 4: A comfortable flame-retardant aramid fabric, wherein the fabric is made of flame-retardant aramid fibers containing hydroxyapatite / magnesium hydroxide composite filler through weaving, knitting or non-woven forming processes.

[0090] The flame-retardant aramid fiber of this embodiment is prepared by uniformly dispersing hydroxyapatite / magnesium hydroxide composite filler in an aramid fiber matrix.

[0091] The flame-retardant aramid fiber of this embodiment is prepared from the following raw materials in parts by weight: 18.5 parts of hydroxyapatite / magnesium hydroxide composite filler, 74.5 parts of meta-aramid polymer, 16.5 parts of para-aramid polymer, 3.7 parts of polybenzimidazole, 4.5 parts of melamine polyphosphate, 2.7 parts of dispersant, 0.55 parts of coupling agent, 0.55 parts of antioxidant, 0.45 parts of antistatic agent, 0.5 parts of softener, 525.0 parts of N-methylpyrrolidone, and 17.2 parts of CaCl2 cosolvent.

[0092] The hydroxyapatite / magnesium hydroxide composite filler in this embodiment consists of magnesium hydroxide nanorods and hydroxyapatite particles loaded on the surface of the magnesium hydroxide nanorods.

[0093] In this embodiment, the mass ratio of magnesium hydroxide to hydroxyapatite in the hydroxyapatite / magnesium hydroxide composite filler is 77:23.

[0094] In this embodiment, the composite filler has an average length of 6.5 μm and an average diameter of 0.8 μm.

[0095] Furthermore, the dispersant is polyethylene glycol monomethyl ether; the coupling agent in this embodiment is silane coupling agent KH-792; and the antioxidant in this embodiment is butylated hydroxytoluene.

[0096] The preparation method of the hydroxyapatite / magnesium hydroxide composite filler in this embodiment includes: a) using a continuous stirred reactor, 2.2 parts of γ-aminopropyltriethoxysilane are pre-hydrolyzed at pH 4.1 for 47 min, then dispersed with 100 parts of magnesium hydroxide nanorods and 265 parts of deionized water, and the pre-hydrolyzed γ-aminopropyltriethoxysilane is added. The reaction is carried out at 72°C for 3.2 h with a stirring rate of 325 rpm and a Reynolds number of Re=2200 to complete the silanization activation. During the reaction, the pH is monitored in real time and automatically adjusted by an online pH monitor.

[0097] b) The calcium-to-phosphorus molar ratio was strictly controlled at 1.63. A twin-screw metering pump was used to precisely control the feed rate. 1.3 parts of polyvinylpyrrolidone dispersant were added to 21.5 parts of an aqueous solution of 18.5 wt% calcium nitrate tetrahydrate and 10.5 wt% diammonium hydrogen phosphate aqueous solution, respectively, and dispersed at high speed for 37 min. The two solutions were then simultaneously added dropwise to the activated suspension at a dropping rate of 1.3 mL / min. During the dropping process, the stirring rate was maintained at 475 rpm, and ammonia water was added dropwise simultaneously through an automatic liquid addition system to adjust the pH of the system to 10.1. After reacting at 86°C for 2.3 h, the mixture was transferred to an industrial-grade stainless steel high-pressure reactor and hydrothermally heated at 112°C for 6.5 h. The mixture was then filtered and washed with a 0.37 μm filter membrane using a plate and frame filter until the pH reached 7.1. Finally, it was dried in a fluidized bed dryer at 92°C for 11 h to obtain the hydroxyapatite / magnesium hydroxide composite packing.

[0098] The preparation method of magnesium hydroxide nanorods in this embodiment includes the following steps: A continuous stirred tank reactor is used. 100 parts of magnesium chloride hexahydrate are dissolved in 525 parts of deionized water to prepare a solution. 2.7 parts of sodium citrate are added to form a complex solution. 4.5 parts of sodium dodecyl sulfate are dissolved in a 1:3.7 volume ratio ethanol-water mixed solvent consisting of 32 parts of anhydrous ethanol and 325 parts of deionized water to form a micelle system. This system is then added to the complex solution and stirred at a stirring rate of 275 rpm for 47 min. The temperature is then increased to 52°C at a rate of 4.2°C / min. 72 parts of 23.5 wt% sodium hydroxide solution are added dropwise at a rate of 2.2 mL / min using a peristaltic pump to maintain the pH at 11.6 for 95 min. The reaction mixture is then transferred to an industrial-grade high-pressure reactor using a programmable reactor and hydrothermally heated at 147°C for 9.2 h. After filtration and washing to pH 7.1 using a centrifuge and washing tower system, the mixture is dried in a 73°C airflow dryer for 8.5 h to obtain the final product.

[0099] This embodiment describes a method for preparing a comfortable flame-retardant aramid fabric, comprising the following steps: S1. Continuous preparation of spinning solution: Using a multi-stage mixer system, meta-aramid polymer, para-aramid polymer, and polybenzimidazole are premixed in a premixer at 115°C for 55 min, and then added to a solvent system containing N-methylpyrrolidone and CaCl2 co-solvent. The solution is dissolved in a dissolving vessel at 125°C and a stirring rate of 225 rpm for 4.5 h until the polymer is completely dissolved. Dispersant, coupling agent, antioxidant, antistatic agent, and softener are added sequentially, and each component is dispersed in a disperser for 52 min. Then, using an industrial-grade high-shear disperser, hydroxyapatite / magnesium hydroxide composite filler and melamine polyphosphate are added in batches using a graded shearing method. After being treated by an industrial ultrasonic system for 52 min, the solution is deaerated in a continuous deaerator for 2.5 h and filtered through a precision filter to obtain a spinning solution with a solid content of 21 wt% and a viscosity of 132 Pa·s.

[0100] S2. Continuous fiber preparation: Using an industrial wet spinning production line, the spinning solution is extruded through an industrial spinneret with 650 holes and a diameter of 0.105 mm at a spinning speed of 170 m / min into a coagulation bath at a temperature of 27°C, composed of NMP and deionized water in a volume ratio of 42:58, and solidified for 37 s. After washing at 55°C for 22 min in a continuous washing device, industrial multi-stage stretching and continuous heat setting are performed to obtain modified aramid fibers with a linear density of 3.2 dtex and a breaking strength of 26 cN / dtex.

[0101] S3. Fabric weaving and forming: Modified aramid fibers are prepared into yarn with a linear density of 47 tex using industrial spinning equipment. During the spinning process, the draft ratio is controlled at 21 times and the twist coefficient is 410. Then, the yarn is woven into a plain weave fabric with a warp density of 170 threads / 10cm and a weft density of 150 threads / 10cm using an industrial loom. After weaving, the fabric is continuously pre-shrinked and set at 165°C for 12 minutes using a tenter frame.

[0102] S4. Finishing process: The fabric is scouring, bleaching and softening in sequence to obtain a comfortable flame-retardant aramid fabric.

[0103] In step S1 of this embodiment, the graded shearing method involves first adding 30% of the hydroxyapatite / magnesium hydroxide composite filler under low-speed shearing conditions, then adding the remaining 50% of the filler under medium-speed shearing conditions, and finally adding the remaining 20% ​​of the filler and melamine polyphosphate under high-speed shearing conditions to achieve uniform distribution of the filler. The low-speed shearing rate is 4500.0 rpm, the medium-speed shearing rate is 9000.0 rpm, and the high-speed shearing rate is 13500.0 rpm.

[0104] In step S2 of this embodiment, the multi-stage stretching process includes a first-stage stretching ratio of 2.7 times and a stretching temperature of 137.5°C, a second-stage stretching ratio of 3.5 times and a stretching temperature of 187.5°C, a third-stage stretching ratio of 2.1 times and a stretching temperature of 262.5°C, with the total stretching ratio controlled at 10.2 times. The heat setting temperature is 265°C and the processing time is 7.5 minutes.

[0105] In step S4 of this embodiment, scouring is performed in an alkaline scouring solution at 92.5°C and pH 10.5 for 52.5 minutes; bleaching is performed in a hydrogen peroxide bleach solution at 75.0°C for 37.5 minutes; and softening is performed using an organosilicon softener at 55.0°C for 27.5 minutes. After each process, the fabric is thoroughly washed with deionized water and dried at 122.5°C for 17.5 minutes. The final product is a comfortable flame-retardant aramid fabric with an areal density of 265.0 g / m², a limiting oxygen index of 36.1%, a moisture absorption rate of 8.4%, a moisture permeability of 7890 g / m²·24h, and an antibacterial rate of 97.3%.

[0106] This embodiment demonstrates the refined control of parameters and the optimization of performance balance. The composite filler addition amount is 18.5 parts, the mass ratio of magnesium hydroxide to hydroxyapatite is 77:23, and the composite filler size is 6.5μm×0.8μm. All parameters are at a medium-to-high level. The preparation process parameters were finely adjusted, such as the silanization reaction at 72°C / 3.2h and the hydrothermal treatment at 112°C / 6.5h, reflecting precise control of process conditions. The spinning process adopted a medium-to-high spinning speed of 170m / min and a draw ratio of 10.2 times. The selection of each process parameter reflects a comprehensive consideration of different performance indicators. Finally, a fabric with optimized comprehensive performance was obtained with an areal density of 265g / m², a limiting oxygen index of 36.1%, a moisture absorption rate of 8.4%, a moisture permeability of 7890g / m²·24h, and an antibacterial rate of 97.3%, achieving a good balance between flame retardancy and comfort.

[0107] Comparative Example 1: Basically the same as Example 1, except that the amount of hydroxyapatite / magnesium hydroxide composite filler is 10.0 parts, the amount of meta-aramid polymer is adjusted to 77.0 parts, and the amounts of other components remain unchanged.

[0108] Comparative Example 2: Basically the same as Example 1, except that the mass ratio of magnesium hydroxide to hydroxyapatite in the hydroxyapatite / magnesium hydroxide composite filler is 90:10. This mass ratio is achieved by adjusting the amount of calcium nitrate tetrahydrate aqueous solution in preparation step b) to 10.0 parts and correspondingly reducing the amount of diammonium hydrogen phosphate aqueous solution.

[0109] Comparative Example 3: It is basically the same as Example 1, except that the average length of the composite filler is 1.5 μm and the average diameter is 0.2 μm. This size specification is obtained by reducing the hydrothermal temperature to 120°C and shortening the hydrothermal time to 4 hours during the preparation of magnesium hydroxide nanorods.

[0110] Comparative Example 4: It is basically the same as Example 1, except that the dispersant used is polyvinyl alcohol, with an amount of 2.0 parts, instead of polyvinylpyrrolidone or polyethylene glycol monomethyl ether.

[0111] Comparative Example 5: Basically the same as Example 1, except that the coupling agent used is γ-methacryloxypropyltrimethoxysilane, with an amount of 0.4 parts, replacing γ-aminopropyltriethoxysilane or silane coupling agent KH-792.

[0112] Comparative Example 6: It is basically the same as Example 1, except that the silanization activation reaction temperature in step a) of the composite filler preparation is 45°C and the reaction time is 1.5 hours, while other preparation conditions remain unchanged.

[0113] Comparative Example 7: Basically the same as Example 1, except that the calcium-to-phosphorus molar ratio in step b) of the composite filler preparation is 1.45, which is achieved by reducing the amount of calcium nitrate tetrahydrate aqueous solution to 18.0 parts.

[0114] Comparative Example 8: Basically the same as Example 1, except that the pH value of the dropwise addition process in step b) of the composite filler preparation is controlled at 8.5, and this pH value is maintained by reducing the amount of ammonia added.

[0115] Comparative Example 9: Basically the same as Example 1, except that sodium citrate complexing agent was not added during the preparation of magnesium hydroxide nanorods, and magnesium chloride hexahydrate was directly dissolved in deionized water for subsequent reactions.

[0116] Comparative Example 10: Basically the same as Example 1, except that a pure water medium system was used in the preparation of magnesium hydroxide nanorods, without adding sodium dodecyl sulfate and ethanol, and only 300 parts of deionized water were used as the reaction medium.

[0117] Comparative Example 11: It is basically the same as Example 1, except that in the spinning solution preparation step S1, a single high-speed shearing method is used to add all the hydroxyapatite / magnesium hydroxide composite filler and melamine polyphosphate at a shear rate of 12000.0 rpm and disperse them for 60 minutes.

[0118] Comparative Example 12: Basically the same as Example 1, except that in fiber preparation step S2, the coagulation bath composition is pure deionized water, the temperature is 25°C, the coagulation time is 30 seconds, and a mixed coagulation bath of NMP and deionized water is not used.

[0119] Comparative Example 13: It is basically the same as Example 1, except that a two-stage stretching process is used in fiber preparation step S2. The first-stage stretching ratio is 3.0 times and the stretching temperature is 120.0°C. The second-stage stretching ratio is 3.0 times and the stretching temperature is 180.0°C. The total stretching ratio is 6.0 times.

[0120] Comparative Example 14: Basically the same as Example 1, except that in the finishing process step S4, the refining treatment is carried out in a neutral refining solution at a temperature of 65.0°C and a pH of 7.5 for 20.0 minutes, while other finishing conditions remain unchanged.

[0121] Comparative Example 15: Basically the same as Example 1, except that no hydroxyapatite / magnesium hydroxide composite filler was added, and the amounts of other components remained unchanged.

[0122] Characterization tests: The nano-hexagonal boron nitride prepared in Example 1 was observed using transmission electron microscopy in this invention, such as... Figure 1 As shown, the nano-hexagonal boron nitride exhibits a typical nanolayered structure. Raman spectroscopy was then used to analyze the composition of the prepared hexagonal boron nitride. Figure 2 A Raman absorption peak can be seen at 1367 cm⁻¹. -1 Location, typical of SP 2 Hybridized hexagonal boron nitride structure.

[0123] Then, urchin-shaped boron nitride was prepared by hexagonal boron nitride, and its morphology was observed by scanning electron microscopy. Figure 3 The urchin-shaped boron nitride is uniformly dispersed, with numerous wrinkled fringes on its surface. These wrinkled fringes provide more bonding sites for the boron nitride and polyurethane, increasing the contact area and facilitating bonding. Furthermore, the wrinkled fringes increase the surface area of ​​the urchin-shaped boron nitride, enhancing light scattering and producing a matte finish. Phase analysis of the urchin-shaped boron nitride was then performed using Fourier transform infrared spectroscopy (FTIR). Figure 4 The absorption peaks observed in the mid-FTIR can be seen as typical SP. 3 The hybrid cubic boron nitride phase proves that the urchin-like boron nitride phase is cubic boron nitride.

[0124] Performance Testing: Flame Retardant Performance Test Experiment: The test object is a finished comfort-type flame-retardant aramid fabric. The purpose of the test is to evaluate the flame-retardant characteristics and combustion behavior of the fabric. The test principle is based on the ease of ignition, combustion speed, and self-extinguishing performance of the material under specific combustion conditions. The experimental method adopts a vertical combustion test. A fabric sample with dimensions of 300mm × 75mm is vertically clamped in a combustion test chamber. A specified ignition source is used to ignite the sample at its lower end for 10 seconds, and then the sample is removed. The afterflame time, smoldering time, and burning length are recorded. The standard is based on GB / T 5455-2014. Key parameters include an ambient temperature of 20±2°C, a relative humidity of 65±5%, and a methane flame with a height of 38mm as the ignition source. Data processing evaluates the flame retardant rating by calculating the average values ​​of the afterflame time, smoldering time, and damage length.

[0125] Limiting Oxygen Index (LOI) Test Experiment: The test subject is a strip sample of a comfort-type flame-retardant aramid fabric. The purpose of the test is to determine the minimum oxygen concentration required for the material to sustain combustion in an oxygen-nitrogen mixed gas flow. The test principle is based on the changing combustion characteristics of the material under different oxygen concentrations. Experimental Method: A 150mm × 6.5mm strip sample is vertically clamped in a transparent combustion chamber. Oxygen-nitrogen mixed gases of different oxygen concentrations are introduced. The top of the sample is ignited with an igniter. The combustion behavior is observed, and the oxygen concentration is adjusted until the critical point is found. The standard is based on GB / T 5454-1997. Key parameters include a gas flow velocity of 40±10mm / s, a combustion chamber inner diameter of 75-100mm, and an ignition time not exceeding 30 seconds. Data Processing: The limiting oxygen index (LOI) value is determined using either the up-and-down method or calculation. Generally, flame-retardant materials require an LOI ≥ 26%.

[0126] Tensile strength test experiment: The test object is a rectangular specimen of a comfortable flame-retardant aramid fabric. The purpose of the test is to evaluate the mechanical strength and breaking performance of the fabric. The test principle is based on the stress-strain relationship of the material under uniaxial tensile load. Experimental method: The specimen with dimensions of 200mm × 50mm is clamped in the fixture of a universal testing machine with a distance of 100mm between the fixtures. It is stretched at a constant rate of 100mm / min until fracture, and the maximum tensile force and elongation at break are recorded. The standard is based on GB / T3923.1-2013. Key parameters include pretension of 2N, tensile speed of 100±10mm / min, standard ambient temperature of 20±2°C, and relative humidity of 65±4%. Data processing: The breaking strength, breaking power, and elongation at break are calculated and statistically analyzed.

[0127] Moisture permeability test experiment: The test object is a circular sample of comfortable flame-retardant aramid fabric. The purpose of the test is to evaluate the water vapor permeability of the fabric. The test principle is based on the diffusion mass transfer process of water molecules through the pores and interfibers of the fabric. The experimental method involves sealing a 70mm diameter fabric sample on a moisture permeability cup containing desiccant and placing it in a constant temperature and humidity chamber at 38±1°C and 90±2% relative humidity. The mass change of the moisture permeability cup is measured periodically. The standard is GB / T 12704.1-2009. Key parameters include test temperature 38±1°C, relative humidity 90±2%, weighing interval of 1 hour, and test cycle of 24 hours. Data processing calculates the moisture permeability and moisture permeability coefficient. The moisture permeability is expressed as g / (m²·24h).

[0128] Moisture Absorption Rate Test: The test subject was a square sample of a comfortable flame-retardant aramid fabric. The purpose of the test was to determine the equilibrium moisture absorption capacity of the fabric under standard atmospheric conditions. The test principle is based on the response of the fiber material to environmental humidity and the equilibrium of moisture adsorption. Experimental Method: The fabric sample was first dried to constant weight in an oven at 105±2°C, then transferred to a standard environment at 20±2°C and 65±2% relative humidity for 24 hours to equilibrate before weighing. The standard is GB / T 9995-1997. Key parameters include drying temperature 105±2°C, drying time to constant weight, conditioning temperature 20±2°C, conditioning humidity 65±2%, and equilibration time 24 hours. Data Processing: The moisture absorption rate was determined by calculating the mass difference before and after equilibration, expressed as a percentage.

[0129] Antistatic Performance Test: The test object is a finished comfort-type flame-retardant aramid fabric. The purpose of the test is to evaluate the antistatic performance and charge dissipation ability of the fabric. The test principle is based on the accumulation and dissipation of static charge on the material surface. The experimental method uses a triboelectric voltage test. A standard friction cloth is used to rub the fabric surface under a specified pressure. Then, a non-contact electrostatic voltmeter is used to measure the surface potential and record the half-life. The standard is GB / T 12703.4-2010. Key parameters include friction pressure 9N, friction speed 60 times / min, test ambient temperature 20±2°C, and relative humidity 30±3%. Data processing records the initial voltage, half-life, and final voltage to evaluate the antistatic level.

[0130] Antibacterial performance test: The test object was a circular sample of a comfortable flame-retardant aramid fabric. The purpose of the test was to evaluate the fabric's ability to inhibit and kill bacteria. The test principle is based on the mechanism of action of antibacterial agents on the bacterial cell wall and cell membrane. The experimental method used was the shaking method, in which the fabric sample was in contact with a standard bacterial solution for incubation. After a specified time, the change in the number of viable bacteria in the bacterial solution was measured. The standard was based on GB / T 20944.3-2008. Key parameters included the test strains being Staphylococcus aureus and Escherichia coli, contact time of 18±1 hours, incubation temperature of 37±1°C, and bacterial concentration of 1×10⁻⁶.5 CFU / mL. Data processing was used to calculate the antibacterial rate and antibacterial effect; an antibacterial rate ≥90% was considered effective antibacterial performance.

[0131] Abrasion Resistance Test: The test object was a square sample of a comfortable flame-retardant aramid fabric. The purpose of the test was to evaluate the abrasion resistance and service life of the fabric under repeated friction. The test principle is based on the fiber breakage, pilling, and mass loss characteristics of the fabric under cyclic friction loads. The test method used a Martindale abrasion tester. A circular sample with a diameter of 38 mm was rubbed against a standard felt in a planar circular motion under a specified pressure. The surface condition of the sample was checked after a certain number of friction cycles until a hole appeared or the specified number of cycles was reached. The standard was GB / T 21196.1-2007. Key parameters included friction pressure 12±0.2 kPa, friction trajectory diameter 60.5±0.5 mm, friction speed 47.5±2.5 cycles / min, standard ambient temperature 20±2°C, and relative humidity 65±4%. Data processing recorded the number of friction cycles at which the sample broke or the mass loss rate after the specified number of cycles. An abrasion resistance of ≥60,000 cycles indicates that the fabric has excellent abrasion resistance.

[0132] Tear Strength Test: The test object is a trapezoidal sample of a comfort-type flame-retardant aramid fabric. The purpose of the test is to evaluate the fabric's resistance to tear propagation and mechanical strength. The test principle is based on the tear propagation mechanism and energy consumption process of a pre-cut slit under tensile force. The experimental method uses the strip method. A 200mm × 25mm strip sample is pre-cut with a 20mm length in the middle. Then, the two sides of the slit are clamped on a tensile testing machine and stretched at a constant rate until the sample is completely torn. The maximum force value during the tearing process is recorded. The standard is GB / T 3917.1-2009. Key parameters include pre-cut slit length 20±0.5mm, clamp distance 75mm, tensile speed 100±10mm / min, pretension 2N, test ambient temperature 20±2°C, and relative humidity 65±4%. Data Processing: The warp and weft tear strengths are measured separately, and the average values ​​are calculated for evaluation. A warp and weft tear strength ≥50N indicates that the fabric has good tear resistance.

[0133] The performance of the fabrics from Examples 1-4 and Comparative Examples 1-15 is summarized in Table 1. The table shows that reducing the content of composite filler significantly weakens the flame-retardant effect, as the flame-retardant concentration is positively correlated with flame-retardant performance. Simultaneously, reducing filler content lowers material density but results in a relatively loose structure, improving moisture permeability but reducing antibacterial activity due to insufficient antibacterial components. An imbalance in the mass ratio of magnesium hydroxide to hydroxyapatite disrupts the synergistic effect of the two flame retardants. While an excessively high magnesium hydroxide ratio provides more flame-retardant groups, it increases material brittleness, affecting mechanical properties. Insufficiently small composite filler size reduces the aspect ratio and specific surface area, weakening flame-retardant efficiency. Furthermore, the interfacial bonding between small-sized fillers and the matrix is ​​not tight enough, easily leading to stress concentration and affecting tensile strength. Changes in the type of dispersant, such as using polyvinyl alcohol, can cause uneven filler dispersion due to poor compatibility with NMP solvent systems, leading to localized agglomeration and stress concentration, reducing mechanical properties and flame-retardant uniformity. Changing the type of coupling agent, such as replacing aminosilane with methacryloxysilane, can weaken the interfacial bonding strength between the filler and the matrix due to differences in functional group reactivity and bonding mechanisms, affecting load transfer efficiency and flame retardant synergy. Insufficient silanization reaction conditions, such as excessively low temperature or short reaction time, can lead to incomplete formation of the silane coupling layer, poor surface modification of the filler, and weakened interfacial bonding, directly affecting the overall performance of the composite material. A calcium-to-phosphorus molar ratio deviating from the stoichiometric ratio of hydroxyapatite can introduce crystal structure defects, reducing the thermal stability and structural integrity of the crystals, thus weakening its effect as a flame retardant. Improper pH control during preparation can affect the crystallization process of hydroxyapatite. When the pH is too low, incomplete crystallization results in small grains with more defects, affecting the thermal stability and flame retardant properties of the material. The lack of a complexing agent can lead to uneven distribution of metal ions, failure to control the morphology of magnesium hydroxide nanorods, a deterioration in the composite effect with hydroxyapatite, and a decline in the overall filler performance. The lack of surfactants and co-solvents can cause severe agglomeration of magnesium hydroxide particles, resulting in poor dispersion of the composite filler and uneven distribution within the matrix, negatively impacting various properties to varying degrees. Improper shearing methods during spinning, such as single high-speed shearing, can simultaneously lead to filler agglomeration and polymer chain breakage, resulting in an uneven fiber microstructure and a significant decrease in mechanical properties. Changes in the coagulation bath composition, such as using pure water, can cause excessively rapid phase separation, forming a loose, porous structure within the fiber. While density may increase, actual strength decreases. Simplification of the stretching process, such as reducing the number of stretching stages and the total stretch ratio, can lead to insufficient molecular chain orientation, decreased fiber crystallinity and mechanical properties, but a relatively smaller impact on flame retardant properties. Overly mild finishing conditions, such as neutral scouring, cannot adequately remove oils and impurities from the fiber surface, affecting the adsorption and penetration of functional finishing agents, leading to a significant decrease in antibacterial and other functional properties.The complete absence of flame-retardant fillers will cause the limiting oxygen index to drop to the level of the matrix material itself, and the flame-retardant properties will be basically lost. However, at the same time, the fiber's flexibility will reach its optimal state, and the comfort properties such as moisture permeability and moisture absorption will be excellent, which reflects the restrictive relationship between flame-retardant properties and comfort properties.

[0134] Table 1 summarizes the performance of the fabrics from Examples 1-4 and Comparative Examples 1-15:

[0135]

[0136] The comprehensive characterization analysis results strongly demonstrate the scientific nature and superiority of the technical solution of this invention. Figure 1 and Figure 2 The characterization results confirmed that Example 1 successfully prepared nanomaterials with regular rod-shaped morphology and pure phase magnesium hydroxide crystal structure. The XRD diffraction peaks were in complete agreement with the standard card, indicating that the preparation process using sodium citrate complexing agent and sodium dodecyl sulfate surfactant can effectively control the crystal growth and morphological evolution of magnesium hydroxide. Figure 3 and Figure 4 Further verification confirmed the successful loading of hydroxyapatite onto the surface of magnesium hydroxide nanorods to form a composite structure. SEM morphology images showed that hydroxyapatite particles were uniformly distributed on the surface of the magnesium hydroxide support. XRD phase analysis detected characteristic diffraction peaks of both magnesium hydroxide and hydroxyapatite without the formation of any impurity phases, demonstrating the successful preparation and good compatibility of the composite filler. Figure 5 The morphological analysis of Comparative Example 2 clearly shows that when the hydroxyapatite content is insufficient, the surface loading of the composite filler is significantly reduced, and the particle distribution is sparse and uneven, which is in stark contrast to Example 1. This explains the fundamental reason for the decline in its flame retardant performance from the perspective of microstructure. Figure 6 and Figure 7 The vertical combustion test results provide the most intuitive evidence for performance comparison. The fabric prepared in Example 1 only showed slight charring and maintained an intact fabric structure after the combustion test, while Comparative Example 15 showed severe combustion damage and large-area charring due to the lack of flame-retardant filler. The huge difference in combustion behavior between the two directly verifies the key role of hydroxyapatite / magnesium hydroxide composite filler in flame-retardant aramid fabric, and at the same time proves the correctness and practical value of the technical solution of the present invention in terms of material design, preparation process and performance optimization.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A comfortable flame-retardant aramid fabric, characterized in that, The fabric is made of flame-retardant aramid fibers containing hydroxyapatite / magnesium hydroxide composite filler through weaving, knitting, or non-woven forming processes. The flame-retardant aramid fibers are prepared by uniformly dispersing the hydroxyapatite / magnesium hydroxide composite filler in an aramid fiber matrix. The flame-retardant aramid fibers are prepared from the following raw materials in parts by weight: 15.0-20.0 parts hydroxyapatite / magnesium hydroxide composite filler, 72.0-78.0 parts meta-aramid polymer, 12.0-18.0 parts para-aramid polymer, and polystyrene. The composition includes 2.5-4.0 parts of imidazole, 3.0-5.0 parts of melamine polyphosphate, 2.0-3.0 parts of dispersant, 0.4-0.6 parts of coupling agent, 0.4-0.6 parts of antioxidant, 0.3-0.5 parts of antistatic agent, 0.3-0.6 parts of softener, 450.0-550.0 parts of N-methylpyrrolidone, and 15.0-18.0 parts of CaCl2 cosolvent; the hydroxyapatite / magnesium hydroxide composite filler is composed of magnesium hydroxide nanorods and hydroxyapatite particles loaded on the surface of magnesium hydroxide nanorods.

2. The comfortable flame-retardant aramid fabric as described in claim 1, characterized in that, The mass ratio of magnesium hydroxide to hydroxyapatite in the hydroxyapatite / magnesium hydroxide composite filler is 70:30~80:

20.

3. The comfortable flame-retardant aramid fabric as described in claim 1, characterized in that, The composite filler has an average length of 3.0~8.0μm and an average diameter of 0.4~1.0μm.

4. The comfortable flame-retardant aramid fabric as described in claim 1, characterized in that, The dispersant is polyvinylpyrrolidone or polyethylene glycol monomethyl ether; the coupling agent is γ-aminopropyltriethoxysilane or silane coupling agent KH-792; the antioxidant is antioxidant 1010 or butylated hydroxytoluene.

5. The comfortable flame-retardant aramid fabric as described in claim 1, characterized in that, The preparation method of the hydroxyapatite / magnesium hydroxide composite filler includes: a) using a continuous stirred reactor, pre-hydrolyzing 1.5-2.5 parts of γ-aminopropyltriethoxysilane at pH 3.8-4.2 for 40-50 min, then dispersing it with 100 parts of magnesium hydroxide nanorods and 220-280 parts of deionized water, and adding the pre-hydrolyzed γ-aminopropyltriethoxysilane. The reaction is carried out at 65-75°C for 2.5-3.5 h at a stirring speed of 250-350 rpm and a Reynolds number Re=1500-2500 to complete the silanization activation. The reaction is monitored and automatically adjusted in real time by an online pH monitor; b) strictly controlling the calcium-to-phosphorus molar ratio to 1.60-1.67, and using a twin-screw metering pump to precisely control the feed rate, mixing 20-22 parts of an aqueous solution of 15-20 wt% calcium nitrate tetrahydrate with 8-12... 1.0–1.5 parts of polyvinylpyrrolidone dispersant were added to a wt% diammonium hydrogen phosphate aqueous solution and dispersed at high speed for 30–40 min. The two solutions were then simultaneously added dropwise to the activated suspension at a dropping rate of 1.0–1.5 mL / min. During the dropwise addition, the stirring speed was maintained at 400–500 rpm, and ammonia water was added dropwise simultaneously through an automatic liquid addition system to adjust the pH of the system to 9.8–10.

2. The reaction was carried out at 85±2°C for 2.0–2.5 h, and then transferred to an industrial-grade stainless steel high-pressure reactor and hydrothermally heated at 110±5°C for 5–7 h. The mixture was then filtered and washed with a plate and frame filter using a 0.3–0.4 μm pore size membrane until the pH reached 6.8–7.2, and then dried in a fluidized bed dryer at 90±5°C for 8–12 h to obtain the hydroxyapatite / magnesium hydroxide composite packing.

6. The comfortable flame-retardant aramid fabric as described in claim 1, characterized in that, The preparation method of the magnesium hydroxide nanorods includes the following steps: Using a continuous stirred tank reactor, 100 parts of magnesium chloride hexahydrate are dissolved in 450-550 parts of deionized water to prepare a solution. 2.0-3.0 parts of sodium citrate are added to form a complexing solution. 3.0-5.0 parts of sodium dodecyl sulfate are dissolved in a 1:2.5-1:4 volume ratio ethanol-water mixed solvent (25-35 parts anhydrous ethanol and 250-350 parts deionized water) to form a micelle system. This system is then added to the complexing solution and stirred at 200-300 rpm for 40-50 min. The temperature is then increased to 50±3°C at a rate of 2-5°C / min. 65-75 parts of 20-25 wt% sodium hydroxide solution are added dropwise using a peristaltic pump at a dropping rate of 1.5-2.5 mL / min, maintaining the pH at 11.5±0.

3. The reaction proceeds for 80-100 minutes. The reaction mixture was transferred to an industrial-grade high-pressure reactor using a program-controlled reactor and hydrothermally heated at 140-150°C for 7-10 hours. After being filtered and washed to pH 6.8-7.2 using a centrifuge and washing tower system, it was dried in an airflow dryer at 70-75°C for 6-10 hours to obtain the final product.

7. A method for preparing a comfortable flame-retardant aramid fabric as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Continuous preparation of spinning solution: Using a multi-stage mixer system, meta-aramid polymer, para-aramid polymer and polybenzimidazole are premixed in a premixer at 100-120°C for 45-60 min, and then added to a solvent system containing N-methylpyrrolidone and CaCl2 co-solvent. The solution is dissolved in a dissolving vessel at 110-130°C and a stirring rate of 150-250 rpm for 3-5 h until the polymer is completely dissolved. Dispersant, coupling agent, antioxidant, antistatic agent and softener are added sequentially and dispersed one component at a time in a disperser for 30-60 min. Then, hydroxyapatite / magnesium hydroxide composite filler and melamine polyphosphate are added in batches using a graded shearing method in an industrial-grade high-shear disperser and treated by an industrial ultrasonic system for 30-60 min. After degassing in a continuous deaerator for 1-3 h, the solution is filtered through a precision filter to obtain a spinning solution with a solid content of 18-22 wt% and a viscosity of 80-150 Pa·s. S2. Continuous Fiber Preparation: Using an industrial wet spinning production line, the spinning solution is extruded through an industrial spinneret with 200-800 holes and a pore size of 0.08-0.12 mm at a spinning speed of 80-200 m / min into a coagulation bath at a temperature of 20-30°C, composed of NMP and deionized water in a volume ratio of 35:65-45:55, and solidified for 15-45 s. After washing at 40-60°C for 10-25 min in a continuous washing machine, industrial multi-stage stretching and continuous heat setting are performed to obtain modified aramid fibers with a linear density of 1.5-4.0 dtex and a breaking strength of 20-28 cN / dtex. S3. Fabric Weaving and Forming: The modified aramid fibers are prepared into fibers with a linear density of 25-55 cN / dtex using industrial spinning equipment. The tex yarn is spun with a draft ratio controlled at 18-22 times and a twist coefficient of 380-420. It is then woven into plain or twill fabric with a warp density of 140-180 threads / 10cm and a weft density of 120-160 threads / 10cm using an industrial loom, or knitted into a fabric with a warp density of 160-200 stitches / 5cm and a weft density of 200-260 rows / 5cm using an industrial knitting machine. After knitting, the fabric is continuously pre-shrinked and set at 150-170°C for 5-15 minutes using a tenter frame. S4. Finishing process: The fabric is scouring, bleaching and softening to obtain a comfortable flame-retardant aramid fabric.

8. The method for preparing a comfortable flame-retardant aramid fabric as described in claim 7, characterized in that, In step S1, the graded shearing method involves first adding 30% of the hydroxyapatite / magnesium hydroxide composite filler under low-speed shearing conditions, then adding the remaining 50% of the filler under medium-speed shearing conditions, and finally adding the remaining 20% ​​of the filler and melamine polyphosphate under high-speed shearing conditions to achieve uniform distribution of the filler. The low-speed shearing rate is 3000.0~5000.0 rpm, the medium-speed shearing rate is 6000.0~10000.0 rpm, and the high-speed shearing rate is 10000.0~15000.0 rpm.

9. The method for preparing a comfortable flame-retardant aramid fabric as described in claim 7, characterized in that, The multi-stage stretching process in step S2 includes a first-stage stretching ratio of 1.5 to 3.0 times and a stretching temperature of 100.0 to 150.0°C, a second-stage stretching ratio of 2.0 to 4.0 times and a stretching temperature of 150.0 to 200.0°C, a third-stage stretching ratio of 1.2 to 2.5 times and a stretching temperature of 200.0 to 280.0°C, with the total stretching ratio controlled at 5.0 to 12.0 times. The heat setting treatment temperature is 220 to 280°C and the treatment time is 1.0 to 10.0 min.

10. The method for preparing a comfortable flame-retardant aramid fabric as described in claim 7, characterized in that, In step S4, the scouring process involves treatment in an alkaline scouring solution at 80.0~95.0°C and pH 9.0~11.0 for 30.0~60.0 min; the bleaching process involves treatment in a hydrogen peroxide bleaching solution at 60.0~80.0°C for 20.0~45.0 min; and the softening process involves treatment with an organosilicon softener at 40.0~60.0°C for 15.0~30.0 min. After each process, the fabric is thoroughly washed with deionized water and dried at 100.0~130.0°C for 10.0~20.0 min, ultimately yielding a comfortable flame-retardant aramid fabric with an areal density of 120.0~300.0 g / m², a limiting oxygen index ≥32.0%, a moisture absorption rate ≥8.0%, a moisture permeability ≥8000.0 g / m²·24h, and an antibacterial rate ≥95.0%.

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