High-flame-retardant pre-oxidized fiber cloth material and preparation method thereof

Abstract

The invention relates to a high-flame-retardant pre-oxidized fiber cloth material and a preparation method thereof. The material is a woven reinforced fabric with a multi-layer twill structure, and is composed of at least two pre-oxidized fiber split film flat silk woven layers and a thermal bonding reinforced layer. The pre-oxidized fiber split film flat filament has specific thickness and width, adopts a twill interweaving structure, and has high strength and excellent thermal stability; the thermal bonding enhancement layer is a phosphorus-containing silicon hybrid coating formed through thermal treatment, the particle size is smaller than 500 nm, and interlayer efficient bonding and heat-resistant and flame-retardant performance are ensured. The preparation method comprises the steps of acrylonitrile copolymerization, wet spinning, high-temperature pre-oxidation and hot drawing, flat filament twill weaving, water bath wetting treatment and heat setting, and finally, the heat bonding enhancement layer is constructed by dipping a phosphorus-silicon-containing hybrid precursor and carrying out heat curing. According to the preparation method, the structural stability, the interlayer bonding strength and the flame retardant property of the fabric are comprehensively improved through pre-oxidized fiber film splitting, hybrid coating bonding and process parameter coordinated regulation and control, and the preparation method is suitable for the fields of high-temperature protection, fire resistance, flame retardance and the like.

Description

Technical Field

[0001] This invention relates to the technical field of flame-retardant fabrics, and in particular to a highly flame-retardant pre-oxidized filament fabric material and its preparation method. Background Technology

[0002] Pre-oxidized fiber is a high-performance intermediate fiber made primarily from polyacrylonitrile through continuous high-temperature stabilization treatment in air. It possesses excellent thermal stability, oxidative inertness, and intrinsic flame retardancy. Due to its resistance to melting and dripping at high temperatures, low pyrolysis rate, and high carbonization residue, it is widely used in heat protection materials such as flame-retardant fabrics, thermal insulation blankets, and protective clothing.

[0003] Existing pre-oxidized filament fabrics still have significant shortcomings in terms of performance consistency, interlayer bonding strength, and manufacturing process stability. Firstly, regarding yarn structure, the diameter and twist of traditional pre-oxidized filament fibers are difficult to control precisely, leading to problems such as fraying, looseness, and misalignment during weaving. This results in poor fabric surface smoothness and insufficient structural density, ultimately affecting the mechanical properties and dimensional stability of the final fabric. Secondly, existing multilayer fabrics often lack effective interlayer bonding mechanisms, relying heavily on physical pressing or inefficient resin coating. This makes them prone to interlayer slippage under heat or external force, and the bonding strength is insufficient to meet the demands of harsh application environments.

[0004] Furthermore, although existing research has attempted to improve the thermal flame retardancy of fabrics by introducing organophosphorus or organosilicon flame-retardant coatings onto the fabric surface, poor adhesion or incomplete curing often leads to uneven coating distribution and brittle structure, affecting not only the fabric's flexibility but also its breathability and comfort. In industrial applications, existing technologies struggle to achieve an effective balance among the comprehensive requirements of good flame retardancy, flexibility, heat-sealing ability, and breathability.

[0005] In summary, there is an urgent need to develop a high-performance pre-oxidized filament fabric material that is structurally stable, highly flame-retardant, has strong interlayer bonding, and is also breathable, along with a set of efficient and controllable preparation methods, in order to solve the technical bottlenecks of existing pre-oxidized filament fabric materials in terms of monofilament thermal stability, fabric structure density, interlayer bonding efficiency, and overall heat sealing performance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a high flame-retardant pre-oxidized filament fabric material and its preparation method.

[0007] A high flame-retardant pre-oxidized filament fabric material is a multi-layered twill woven reinforcing fabric, consisting of at least two layers of pre-oxidized split-film flat filament weave and one thermally bonded reinforcing layer, wherein: The thickness of the pre-oxidized fibrous membrane flat filament is 20–40 μm, and the width is 0.15–0.25 mm; The pre-oxidized filament layer adopts a twill interwoven structure, with a base fabric weight of 450-520 g / m² and a warp and weft density of 55-65 threads / cm; The thermally bonded reinforcing layer is disposed between two pre-oxidized filament layers and is composed of a hydrophobic phosphorus-silicon hybrid coating formed by heat treatment. The coating has a particle size of less than 500 nm and a thermal curing temperature of 160–180 °C.

[0008] Preferably, the pre-oxidized fibrous film flat yarn is made from polyacrylonitrile fiber by continuous constant temperature pre-oxidation treatment at 230-280°C in air atmosphere for 8-12 hours, and its carbon content is not less than 60%.

[0009] Preferably, the polyacrylonitrile fiber raw material is obtained by copolymerizing acrylonitrile and methacrylamide monomers, with the mass fraction of methacrylamide being 1-5%. The copolymer is synthesized by solution polymerization and then concentrated and dried to serve as a precursor polymer for wet spinning.

[0010] Preferably, the polyacrylonitrile fiber raw material is further mixed with polytetrafluoroethylene micro powder with a particle size of 0.1 to 1 μm in a mass ratio of 1:5.5 to 19 with the polyacrylonitrile raw material. The raw material is dispersed by high-speed shearing and then wet-spun to obtain the precursor fiber.

[0011] Preferably, the precursor fiber is subjected to hot stretching treatment at a temperature of 160-200°C, with a stretching ratio of 2.0-3.5 times and a treatment time of 3-6 minutes.

[0012] Preferably, the thermally bonded reinforcing layer is obtained by dissolving a mixed precursor of aluminum phosphate, ethyltriethoxysilane and aminopropyltriethoxysilane in a mass ratio of 1:(0.5-1.5):(0.5-1.5) in ethanol and applying it to the surface of the intermediate layer by impregnation.

[0013] Preferably, the mixed precursor also contains 0.5-2% triethylamine by mass, and is heat-cured at 170-180°C after application, with a heat treatment time of 2-4 minutes.

[0014] A method for preparing a highly flame-retardant pre-oxidized filament fabric includes the following steps: S1: Acrylonitrile and methacrylamide are copolymerized in a mass fraction ratio, and a polymer solution is synthesized by solution polymerization. The polymer solution is then washed with water and dried to obtain a precursor polymer for spinning. S2: The precursor polymer is mixed with polytetrafluoroethylene micro powder with a particle size of 0.1-1 μm in a certain proportion, dispersed by high-speed shearing, and then wet-spun to obtain the precursor fiber; S3: The filament obtained from spinning is continuously pre-oxidized at a constant temperature of 230-280°C in air for 8-12 hours, and then subjected to hot stretching treatment at 160-200°C for 3-6 minutes with a stretching ratio of 2.0-3.5 times. The interval between the pre-oxidation temperature and the hot stretching temperature shall not exceed 50°C. S4: The heat-treated pre-oxidized slit flat yarn is woven into two layers of fabric using a twill weave method. Before weaving, the flat yarn is moistened in a water bath at 75-85℃ for 10-20 minutes. After weaving, it is heat-set at 110-130℃ for 20-30 minutes. S5: Dissolve aluminum phosphate, ethyltriethoxysilane and aminopropyltriethoxysilane in an ethanol aqueous solution in proportion, add 0.5-2% triethylamine, apply it between two pre-oxidized filament layers by impregnation, and heat cure at 170-180℃ for 32-34 minutes.

[0015] Preferably, after the S2 wet spinning step, the raw yarn is surface-dried by hot air at 40-60°C without being wound, and is directly fed into the pre-oxidation section. The conveying time between the spinning outlet and the pre-oxidation inlet is controlled to be 2-3 minutes.

[0016] Preferably, the twill weave adopts a three-up-two-down or three-down-two-up weave structure, and a gap of 0.1 to 0.3 mm is left between the upper and lower layers of fabric after the weave is completed.

[0017] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following aspects: 1. The use of pre-oxidized flat yarn with a split film is limited to its thickness and width range. Combined with continuous constant temperature pre-oxidation and hot stretching treatment, the monofilament itself has excellent thermal stability and flame retardancy, thereby enhancing the fabric's smoothness, structural density and yarn synergistic load-bearing capacity.

[0018] 2. A phosphorus-silicon hybrid coating precursor system was incorporated into the thermally bonded reinforcement layer, with specific precursor ratios and thermosetting parameters determined. Triethylamine was added as a catalyst to promote coating densification and hybridization, resulting in a stable and continuous thermally bonded coating. This coating not only provides flame-retardant reinforcement but, more importantly, achieves efficient and uniform bonding between the upper and lower layers, solving the problems of easy interlayer slippage and insufficient adhesion in existing multi-layer fabric structures.

[0019] 3. By specifically setting key steps such as water bath wetting treatment, heat setting, fabric gap and coating heat curing, the overall fabric maintains structural stability while possessing good air permeability and heat sealing performance. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the embodiments.

[0021] Example 1: This example provides a method for preparing a high flame-retardant pre-oxidized filament fabric. The material is a multi-layer twill woven reinforcing fabric, comprising two layers of pre-oxidized split-film flat yarns and a thermally bonded reinforcing layer. The specific process is as follows: S1: Precursor polymer synthesis: In a reactor, acrylonitrile and methacrylamide were added, and N,N-dimethylformamide was added as a solvent. After heating to 55°C, nitrogen gas was purged for 30 minutes. Then, azobisisobutyronitrile (AIBN) was added as an initiator, and the reaction was continued at 55°C for 6 hours.

[0022] After the reaction was completed, the reaction solution was slowly poured into anhydrous ethanol to precipitate the polymer. The polymer was then filtered and dried under vacuum at 50°C for 12 hours to obtain a precursor polymer powder for wet spinning.

[0023] Components used and their mass ratios: Acrylonitrile: 95 wt% Methacrylamide: 5 wt% N,N-Dimethylformamide: 180% of the total monomer mass; AIBN: 0.5% of the total mass of monomers.

[0024] S2: Wet spinning and air intervention treatment: The dried precursor polymer is mixed with polytetrafluoroethylene micro powder (particle size 0.5μm), deionized water is added, and the mixture is stirred at 8000rpm for 30 minutes in a high-speed shear disperser to form a uniform slurry.

[0025] The slurry was used for wet spinning with a spinneret orifice diameter of 0.12 mm. A water / ethanol (volume ratio 7:3) coagulation bath was used with a temperature of 5°C and a draw ratio of 2.5 times to obtain the precursor fiber.

[0026] The obtained raw yarn is dried with hot air at 40℃ for 3 minutes, and then directly enters the pre-oxidation section without being wound. The conveying time from the spinning outlet to the pre-oxidation inlet is controlled to be 2.5 minutes.

[0027] Components used and their mass ratios: Precursor polymer: 85 wt% Polytetrafluoroethylene micro powder: 15wt% Deionized water: 1:1 mass ratio with solids; The coagulation bath composition is: water / ethanol = 7:3 (volume ratio).

[0028] S3: Pre-oxidation and hot drawing treatment: The air-dried raw yarn is continuously pre-oxidized for 10 hours in an air atmosphere at a constant temperature of 230°C. The conveying rate and furnace temperature uniformity are controlled to ensure uniform carbonization.

[0029] Immediately afterwards, a hot stretching treatment was performed at 180℃ with a stretch ratio of 3.0 times and a stretching time of 4 minutes to ensure that the fiber maintained its integrity and had a certain degree of orientation. The temperature difference between pre-oxidation and hot stretching was controlled within 50℃.

[0030] Key parameters: Pre-oxidation temperature: 230℃; Pre-oxidation time: 10 hours; Hot drawing temperature: 180℃; Stretch ratio: 3.0 times; Stretch time: 4 minutes; Conveying interval: 2.5 minutes; S4: Preparation and weaving of pre-oxidized fiber split-film flat yarn: The heat-treated pre-oxidized fiber is split-film treated to obtain a split-film flat yarn with a thickness of 30μm and a width of 0.20mm.

[0031] The flat yarn is immersed in an 80℃ water bath for 15 minutes to moisten it. After being taken out and naturally cooled, it is immediately put into the weaving process. A three-up, two-down twill weave is used, and the weft and warp densities are both controlled at 60 threads / cm to weave a two-layer fabric.

[0032] After the fabric is woven, it is placed in a heat setting machine and heat-set at 120°C for 25 minutes. After setting, a 0.2mm gap is naturally formed between the fabric layers.

[0033] Key parameters: Dimensions of the split-film flat filament: 30μm (thickness) × 0.20mm (width); Water bath wetting treatment: 80℃×15min; Weave structure: 3-up, 2-down twill; Weft density: 60 warp threads / cm; Heat setting: 120℃ × 25 min; Interlayer gap: 0.2mm; S5: Application and curing of the thermal bonding reinforcement layer: Aluminum phosphate, ethyltriethoxysilane and aminopropyltriethoxysilane are mixed in a mass ratio of 1:1:1, and then a water / ethanol (volume ratio 7:3) solution is added and ultrasonically dispersed for 10 minutes. Triethylamine is added as a catalyst to form a coating liquid.

[0034] Turn the fabric over and apply the coating liquid to the area between the two layers of fabric using the immersion method, controlling the immersion thickness and coating uniformity.

[0035] The coated fabric is then placed in a heat curing device and heat-treated at 175°C for 33 minutes to form a hydrophobic phosphorus-silicon hybrid coating.

[0036] Components used and their mass ratios: Aluminum phosphate: 1 part; Ethyltriethoxysilane: 1 part; aminopropyltriethoxysilane: 1 part; Triethylamine: 1.5 wt% of total mass; Water / ethanol (volume ratio 7:3): 10 times the total amount of precursor; Heat treatment conditions: Thermosetting temperature: 175℃; Time: 33 minutes.

[0037] Example 2: This example provides a method for preparing a high flame retardant pre-oxidized filament fabric. Compared with Example 1, the main difference is the adjustment of the composition ratio and weaving density of the pre-oxidized filaments.

[0038] S1: Precursor polymer synthesis: In a reactor, acrylonitrile and methacrylamide were added, and N,N-dimethylformamide was added as a solvent. After heating to 55°C, nitrogen gas was purged for 30 minutes. Then, azobisisobutyronitrile (AIBN) was added as an initiator, and the reaction was continued at 55°C for 6 hours.

[0039] After the reaction was completed, the reaction solution was slowly poured into anhydrous ethanol to precipitate the polymer. The polymer was then filtered and dried under vacuum at 50°C for 12 hours to obtain a precursor polymer powder for wet spinning.

[0040] Components used and their mass ratios: Acrylonitrile: 97wt% Methacrylamide: 3 wt% N,N-Dimethylformamide: 180% of the total monomer mass; AIBN: 0.5% of the total mass of monomers.

[0041] S2: Wet spinning and air intervention treatment: The dried precursor polymer is mixed with polytetrafluoroethylene micro powder (particle size 0.5μm), deionized water is added, and the mixture is stirred at 8000rpm for 30 minutes in a high-speed shear disperser to form a uniform slurry.

[0042] The slurry is used for wet spinning, with a spinneret orifice diameter of 0.12 mm. The coagulation bath is water / ethanol (volume ratio 7:3), the temperature is set at 5℃, and the draw ratio is 2.8. The precursor yarn is air-dried with hot air at 50℃ for 3 minutes, and without winding, it directly enters the pre-oxidation section, with the conveying time controlled within 2 minutes.

[0043] Components used and their mass ratios: Precursor polymer: 90 wt% Polytetrafluoroethylene micro powder: 10wt% Deionized water: 1:1 mass ratio with solids; The coagulation bath composition is: water / ethanol = 7:3 (volume ratio).

[0044] S3: Pre-oxidation and hot drawing treatment: The air-dried raw yarn is pre-oxidized in air at 240℃ for 9 hours, followed by hot drawing at 190℃ with a draw ratio of 2.5 times and a drawing time of 5 minutes. The temperature difference between the pre-oxidation and drawing sections shall not exceed 60℃.

[0045] Key parameters: Pre-oxidation temperature: 240℃; Pre-oxidation time: 9 hours; Hot drawing temperature: 190℃; Stretch ratio: 2.5 times; Stretch time: 5 minutes; Delivery interval: 2 minutes.

[0046] S4: Preparation and Weaving of Pre-oxidized Split-Film Flat Yarns: The heat-treated pre-oxidized split-film was processed to obtain flat yarns with a thickness of 25 μm and a width of 0.18 mm. The flat yarns were then immersed in an 80℃ water bath for 20 minutes, followed by a three-down, two-up twill weave with a warp density of 58 weft threads / cm, forming two layers of fabric. Heat setting was performed at 115℃ for 30 minutes, naturally forming a 0.15 mm gap between the fabric layers.

[0047] Key parameters: Dimensions of the split-film flat filament: 25μm × 0.18mm; Water bath wetting treatment: 80℃×20min; Weave structure: 3-down, 2-up twill; Weft density: 58 warp threads / cm; Heat setting: 115℃ × 30 min; Interlayer gap: 0.15mm.

[0048] S5: Application and curing of the heat-bonded reinforcing layer: Mix aluminum phosphate, ethyltriethoxysilane and aminopropyltriethoxysilane in a 1:1:1 mass ratio, add water / ethanol (volume ratio 7:3) and ultrasonically disperse for 10 minutes, then add triethylamine to form a coating solution. Apply the coating solution between two layers of fabric using the impregnation method and heat-cur at 170°C for 34 minutes.

[0049] Components used and their mass ratios: Aluminum phosphate: 1 part; Ethyltriethoxysilane: 1 part; aminopropyltriethoxysilane: 1 part; Triethylamine: 1 wt% of total mass; Water / ethanol (volume ratio 7:3): 10 times the total amount of precursor; Heat treatment conditions: Thermosetting temperature: 170℃; Time: 34 minutes.

[0050] Example 3: This example provides a method for preparing a high flame-retardant pre-oxidized filament fabric material, including the following steps: S1: Precursor polymer synthesis: Acrylonitrile and methacrylamide were added to a reaction vessel at a set mass ratio, and N,N-dimethylformamide was added as a solvent. After nitrogen protection at 55°C for 30 minutes, azobisisobutyronitrile (AIBN) was added as an initiator, and the reaction was maintained at a constant temperature with stirring for 6 hours. After the reaction was completed, the reaction solution was poured into anhydrous ethanol to precipitate the polymer, which was then filtered and dried to obtain a precursor polymer powder for wet spinning.

[0051] Components used and their mass ratios: Acrylonitrile: 99wt% Methacrylamide: 1 wt% N,N-Dimethylformamide: 180% of the total monomer mass; AIBN: 0.5% of the total mass of monomers.

[0052] S2: Wet spinning and air intervention treatment: The dried precursor polymer and polytetrafluoroethylene micropowder (0.5 μm particle size) were mixed at a mass ratio of 95:5, deionized water was added, and the mixture was stirred at 8000 rpm for 30 minutes using a high-speed shear disperser to form a slurry. The slurry was used for wet spinning with a spinneret orifice diameter of 0.12 mm, a coagulation bath of water / ethanol (volume ratio 7:3), a temperature of 6 °C, and a draw ratio of 2.2. The resulting precursor fiber was air-dried with hot air at 45 °C for 3 minutes and transported to the pre-oxidation stage within 2.5 minutes.

[0053] Components used and their mass ratios: Precursor polymer: 95wt% Polytetrafluoroethylene micro powder: 5wt% Deionized water: 1:1 mass ratio with solids; Coagulation bath: water / ethanol = 7:3 (volume ratio).

[0054] S3: Pre-oxidation and hot stretching treatment: The raw yarn is continuously pre-oxidized in air at 230℃ for 12 hours, and then hot-stretched at 190℃ with a stretch ratio of 3.5 times and a stretching time of 3 minutes. The temperature interval between pre-oxidation and stretching is controlled within 60℃.

[0055] Key parameters: Pre-oxidation temperature: 230℃; Pre-oxidation time: 12 hours; Hot drawing temperature: 190℃; Strength ratio: 3.5 times; Stretch time: 3 minutes; Delivery interval: 2.5 minutes.

[0056] S4: Preparation and Weaving of Pre-oxidized Split-Film Flat Yarn: The heat-treated pre-oxidized yarn was split-filmed to obtain split-film flat yarns with a thickness of 35μm and a width of 0.22mm. After wetting the flat yarns in an 80℃ water bath for 15 minutes, they were woven using a 3-up-2-down twill weave, with the weft density controlled at 62 warp threads / cm, forming two layers of fabric. The fabric was heat-set at 130℃ for 20 minutes, resulting in a 0.3mm gap between the layers.

[0057] Key parameters: Crack size: 35μm × 0.22mm; Water bath wetting treatment: 80℃×15min; Weave structure: 3-up, 2-down twill; Weft density: 62 warp threads / cm; Heat setting: 130℃ × 20 min; Interlayer gap: 0.3mm.

[0058] S5: Application and curing of the thermal bonding reinforcement layer: Aluminum phosphate, ethyltriethoxysilane, and aminopropyltriethoxysilane are mixed in a 1:1:1 mass ratio. After adding 10 times the mass of a water / ethanol solution (volume ratio 7:3), the mixture is ultrasonically dispersed for 10 minutes. Triethylamine (2wt%) is then added to form a coating solution. The coating is applied between two fabric layers using an impregnation method and thermally cured at 175°C for 32 minutes.

[0059] Components used and their mass ratios: Aluminum phosphate: 1 part; Ethyltriethoxysilane: 1 part; aminopropyltriethoxysilane: 1 part; Triethylamine: 2 wt% of total mass; Water / ethanol (volume ratio 7:3) solution: 10 times the total mass of the precursor.

[0060] Heat treatment conditions: Thermosetting temperature: 175℃; Time: 32 minutes.

[0061] Example 4: This example provides a method for preparing a high flame-retardant pre-oxidized filament fabric material, including the following steps: S1: Precursor polymer synthesis: Acrylonitrile and methacrylamide were added to a reaction vessel at a set mass ratio, and N,N-dimethylformamide was added as a solvent. After nitrogen protection at 55°C for 30 minutes, azobisisobutyronitrile (AIBN) was added as an initiator, and the reaction was maintained at a constant temperature with stirring for 6 hours. After the reaction was completed, the reaction solution was poured into anhydrous ethanol to precipitate the polymer, which was then filtered and dried to obtain a precursor polymer powder for wet spinning.

[0062] Components used and their mass ratios: Acrylonitrile: 99wt% Methacrylamide: 1 wt% N,N-Dimethylformamide: 180% of the total monomer mass; AIBN: 0.5% of the total mass of monomers.

[0063] S2: Wet spinning and air intervention treatment: The dried precursor polymer and polytetrafluoroethylene micropowder (0.5 μm particle size) were mixed at a mass ratio of 95:5, deionized water was added, and the mixture was stirred at 8000 rpm for 30 minutes using a high-speed shear disperser to form a slurry. The slurry was used for wet spinning with a spinneret orifice diameter of 0.12 mm, a coagulation bath of water / ethanol (volume ratio 7:3), a temperature of 6 °C, and a draw ratio of 2.2. The resulting precursor fiber was air-dried with hot air at 45 °C for 3 minutes and transported to the pre-oxidation stage within 2.5 minutes.

[0064] Components used and their mass ratios: Precursor polymer: 95 wt% Polytetrafluoroethylene micro powder: 5wt% Deionized water: 1:1 mass ratio with solids; Coagulation bath: water / ethanol = 7:3 (volume ratio).

[0065] S3: Pre-oxidation and hot stretching treatment: The raw yarn is continuously pre-oxidized in air at 230℃ for 12 hours, and then hot-stretched at 180℃ with a stretch ratio of 3.5 times and a stretching time of 3 minutes. The temperature interval between pre-oxidation and stretching is controlled within 60℃.

[0066] Key parameters: Pre-oxidation temperature: 230℃; Pre-oxidation time: 12 hours; Hot drawing temperature: 180℃; Strength ratio: 3.5 times; Stretch time: 3 minutes; Delivery interval: 2.5 minutes.

[0067] S4: Preparation and Weaving of Pre-oxidized Split-Film Flat Yarn: The heat-treated pre-oxidized yarn was split-filmed to obtain split-film flat yarns with a thickness of 35μm and a width of 0.22mm. After wetting the flat yarns in an 80℃ water bath for 15 minutes, they were woven using a 3-up-2-down twill weave, with the weft density controlled at 62 warp threads / cm, forming two layers of fabric. The fabric was heat-set at 130℃ for 20 minutes, resulting in a 0.3mm gap between the layers.

[0068] Key parameters: Crack size: 35μm × 0.22mm; Water bath wetting treatment: 80℃×15min; Weave structure: 3-up, 2-down twill; Weft density: 62 warp threads / cm; Heat setting: 130℃ × 20 min; Interlayer gap: 0.3mm.

[0069] S5: Application and curing of the thermal bonding reinforcement layer: Aluminum phosphate, ethyltriethoxysilane, and aminopropyltriethoxysilane are mixed in a 1:1:1 mass ratio. After adding 10 times the mass of a water / ethanol solution (volume ratio 7:3), the mixture is ultrasonically dispersed for 10 minutes. Triethylamine (2wt%) is then added to form a coating solution. The coating is applied between two fabric layers using an impregnation method and thermally cured at 175°C for 32 minutes.

[0070] Components used and their mass ratios: Aluminum phosphate: 1 part; Ethyltriethoxysilane: 1 part; aminopropyltriethoxysilane: 1 part; Triethylamine: 2 wt% of total mass; Water / ethanol (volume ratio 7:3) solution: 10 times the total mass of the precursor.

[0071] Heat treatment conditions: Thermosetting temperature: 175℃; Time: 32 minutes.

[0072] Example 5: This example provides a method for preparing a high flame-retardant pre-oxidized filament fabric material, including the following steps: S1: Precursor polymer synthesis: Acrylonitrile and methacrylamide were added to a reaction vessel at a set mass ratio, and N,N-dimethylformamide was added as a solvent. After nitrogen protection at 55°C for 30 minutes, azobisisobutyronitrile (AIBN) was added as an initiator, and the reaction was maintained at a constant temperature with stirring for 6 hours. After the reaction was completed, the reaction solution was poured into anhydrous ethanol to precipitate the polymer, which was then filtered and dried to obtain a precursor polymer powder for wet spinning.

[0073] Components used and their mass ratios: Acrylonitrile: 96 wt% Methacrylamide: 4 wt% N,N-Dimethylformamide: 180%; AIBN: 0.5%.

[0074] S2: Wet spinning and air intervention treatment: The dried precursor polymer was mixed with polytetrafluoroethylene micropowder (0.5 μm particle size) at a mass ratio of 88:12 and stirred at 8000 rpm for 30 minutes in a high-speed shear disperser to form a slurry. The slurry was used for wet spinning with a spinneret orifice diameter of 0.12 mm, a coagulation bath of water / ethanol (volume ratio 7:3), a temperature of 4°C, and a draw ratio of 2.0. The precursor fiber was air-dried with hot air at 40°C for 3 minutes, without winding, and the conveying time was controlled at 2.8 minutes.

[0075] Components used and their mass ratios: Precursor polymer: 88wt% Polytetrafluoroethylene micro powder: 12wt% Deionized water: 1:1 mass ratio with solids; Coagulation bath: water / ethanol = 7:3.

[0076] S3: Pre-oxidation and hot stretching treatment: The air-dried raw yarn is continuously pre-oxidized for 8 hours in an air atmosphere at 240℃, and then hot-stretched at 200℃ with a stretch ratio of 2.0 times and a stretching time of 6 minutes. The temperature difference between pre-oxidation and stretching does not exceed 70℃.

[0077] Key parameters: Pre-oxidation temperature: 240℃; Pre-oxidation time: 8 hours; Hot drawing temperature: 200℃; Stretch ratio: 2.0 times; Stretch time: 6 minutes; Delivery interval: 2.8 minutes.

[0078] S4: Preparation and Weaving of Pre-oxidized Split-Film Flat Yarn: The heat-treated pre-oxidized yarn was split-filmed to obtain split-film flat yarns with a thickness of 40μm and a width of 0.25mm. The flat yarns were wetted in an 80℃ water bath for 20 minutes and woven using a 3-up-2-down twill weave, with the weft density controlled at 55 warp threads / cm, forming two layers of fabric. The fabric was heat-set at 110℃ for 30 minutes, forming a 0.25mm gap between the fabric layers.

[0079] Key parameters: Crack size: 40μm × 0.25mm; Water bath wetting treatment: 80℃×20min; Weave structure: 3-up, 2-down twill; Weft density: 55 warp threads / cm; Heat setting: 110℃ × 30 min; Interlayer gap: 0.25mm.

[0080] S5: Application and curing of the thermally bonded reinforcing layer: Aluminum phosphate, ethyltriethoxysilane, and aminopropyltriethoxysilane are mixed in a 1:1:1 mass ratio. After ultrasonic dispersion for 10 minutes in a 10-fold volume ratio of water / ethanol (7:3), triethylamine (0.5 wt%) is added to form a coating solution. The coating is applied to the area between the two fabric layers using an impregnation method and thermally cured at 160°C for 34 minutes.

[0081] Components used and their mass ratios: Aluminum phosphate: 1 part; Ethyltriethoxysilane: 1 part; aminopropyltriethoxysilane: 1 part; Triethylamine: 0.5 wt% of total mass; Water / ethanol (volume ratio 7:3) solution: 10 times the total mass of the precursor.

[0082] Heat treatment conditions: Thermosetting temperature: 160℃; Time: 34 minutes.

[0083] Comparative Example 1: This comparative example discloses a method for preparing a pre-oxidized filament fabric material, including the following steps: S1: Synthesis of precursor polymer: Acrylonitrile and methacrylamide were added to a reactor at a mass ratio of 95:5, followed by the addition of N,N-dimethylformamide. The mixture was ventilated at 55°C under nitrogen protection for 30 minutes, then AIBN was added, and the reaction was stirred for 6 hours. After the reaction was complete, the polymer was precipitated with ethanol, filtered, and dried to obtain the precursor powder.

[0084] Components used and their mass ratios: Acrylonitrile: 95 wt% Methacrylamide: 5 wt% N,N-Dimethylformamide: 180%; AIBN: 0.5%.

[0085] S2: Wet spinning and air intervention treatment: The precursor polymer and PTFE micro powder (particle size 0.5μm) were mixed at a mass ratio of 85:15, and an equal mass of deionized water was added. The mixture was sheared and dispersed at 8000 rpm for 30 minutes. The spinneret diameter for wet spinning was 0.12 mm, the coagulation bath temperature was 5℃, and the draw ratio was 2.5. Air drying conditions: 40℃ × 3 minutes, and the transfer to the pre-oxidation section was controlled within 2.5 minutes.

[0086] Components used and their mass ratios: Precursor polymer: 85 wt% Polytetrafluoroethylene micro powder: 15wt% Deionized water: 1:1; Coagulation bath: water / ethanol = 7:3.

[0087] S3: Pre-oxidation and hot stretching treatment: continuous pre-oxidation in air atmosphere at 230℃ for 10 hours, followed by hot stretching treatment at 180℃ with a stretch ratio of 3.0 times for 4 minutes.

[0088] Key parameters: Pre-oxidation temperature: 230℃; Pre-oxidation time: 10 hours; Hot drawing temperature: 180℃; Stretch ratio: 3.0 times; Stretch time: 4 minutes.

[0089] S4: Preparation and weaving of pre-oxidized filament split film flat yarn: After heat treatment, the flat yarn is split film with a thickness of 30μm and a width of 0.20mm. It is then wetted in a water bath for 15 minutes and adopts a three-up, two-down twill structure with a weft density of 60 warp threads / cm.

[0090] The heat setting process was omitted in this comparative example.

[0091] Key parameters: Crack size: 30μm × 0.20mm; Water bath wetting treatment: 80℃×15min; Weft density: 60 warp threads / cm; Heat setting: Not performed; Interlayer gaps: not fixed, easily deformed.

[0092] S5: Application and curing of the thermal bonding reinforcement layer: The same coating liquid formulation and application method as in Example 1 are used.

[0093] Comparative Example 2: This comparative example discloses a method for preparing a pre-oxidized filament fabric material, including the following steps: S1–S4: Same as Example 1: The steps of precursor polymer preparation, wet spinning, heat treatment, and film splitting weaving in this comparative example are completely consistent with those in Example 1.

[0094] S5: Application and curing of the heat-bonded reinforcing layer: Mix aluminum phosphate, ethyltriethoxysilane and aminopropyltriethoxysilane in a mass ratio of 1:1:1, add 10 times the mass of ethanol and ultrasonically disperse for 10 minutes, without adding triethylamine, to form a coating liquid, apply it by impregnation, heat curing temperature 175℃, time 33 minutes.

[0095] Comparative Example 3: This comparative example discloses a method for preparing a pre-oxidized filament fabric material, including the following steps: S1: Synthesis of precursor polymer: Acrylonitrile and methacrylamide were added to a reactor at a mass ratio of 95:5, N,N-dimethylformamide was added, nitrogen gas was introduced, and AIBN was added. After the reaction was initiated for 6 hours, the precipitate was dried to obtain polymer powder.

[0096] Components used and their mass ratios: Acrylonitrile: 95 wt% Methacrylamide: 5 wt% DMF: 180%; AIBN: 0.5%.

[0097] S2: Wet spinning and air intervention treatment: Using only the above-mentioned precursor polymer, without adding polytetrafluoroethylene micro powder, it is directly dissolved in deionized water for dispersion and pulping, sheared for 30 minutes, with a spinneret diameter of 0.12 mm, a coagulation bath temperature of 5°C, and a draw ratio of 2.5. Air-dry at 40°C for 3 minutes, with a conveying time of 2.5 minutes.

[0098] Components used and their mass ratios: Precursor polymer: 100wt% PTFE micro powder: Not added; Water: 1:1; Coagulation bath: water / ethanol = 7:3.

[0099] S3–S5: The process parameters are the same as in Example 1.

[0100] Performance testing: 1. Thermogravimetric analysis: Method: Thermogravimetric analysis (TGA).

[0101] Procedure: Take a sample of about 10 mg and place it in a TGA device. Heat it to 800 °C in air (20 °C / min). Record the residual mass percentage at each temperature point of 300 °C, 400 °C, 500 °C, 600 °C, and 700 °C.

[0102] Calculation: Thermal weight loss rate = (initial mass – mass at specified temperature) / initial mass × 100%.

[0103] Standard: Refer to GB / T24508-2009 "General Rules for Thermogravimetric Analysis".

[0104] 2. Limiting Oxygen Index (LOI) Test: Method: Oxygen index method.

[0105] Procedure: According to GB / T5454, the sample is cut into strips of 100mm×10mm, clamped, and the oxygen concentration is tested in the LOI instrument.

[0106] Requirement: The higher the LOI value, the better the flame retardancy of the material.

[0107] Standard: Refer to GB / T2406.2-2009 "Oxygen Index Method for Burning Performance of Plastics".

[0108] 3. Interlayer peel strength test: Method: Tensile peel test using a peel tester.

[0109] Procedure: Cut a 50mm×200mm sample, insert a stretching sheet between the two fabric layers, set the peeling rate to 50mm / min, and record the maximum peeling force.

[0110] Unit: N / 5cm.

[0111] Standard: Refer to FZ / T01085-2009 "Test Method for Adhesive Strength of Textiles".

[0112] 4. Water vapor transmission index (WVPI): Method: Moisture-permeable cup method.

[0113] Method: Moisture permeable cup method (GB / T12704.2-2009).

[0114] Conditions: 38℃, 90%RH, test for 24 hours.

[0115] step: (1) Original sample: The sample was cut immediately after the fabric was woven in S4 without heat setting and coating treatment; (2) Processed sample: refers to the final fabric of the embodiment or comparative example after being processed through the entire process of S4-S5; (3) The WVTR (g·m) of the two types of samples was measured respectively. -2 24h -1 Two parallel samples were taken from each category, and the average value was calculated. (4) Moisture permeability retention index WVPI = (WVTR_treated sample / WVTR_original sample) × 100%.

[0116] The test results are shown in Table 1 below.

[0117] Table 1:

[0118] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A high flame-retardant pre-oxidized filament fabric material, characterized in that, The material is a multi-layered twill woven reinforcing fabric, consisting of at least two layers of pre-oxidized split-film flat yarns and one thermally bonded reinforcing layer, wherein: The thickness of the pre-oxidized fibrous membrane flat filament is 20–40 μm, and the width is 0.15–0.25 mm; The pre-oxidized filament layer adopts a twill interwoven structure, with a base fabric weight of 450-520 g / m² and a warp and weft density of 55-65 threads / cm; The thermally bonded reinforcing layer is disposed between two pre-oxidized filament layers and is composed of a hydrophobic phosphorus-silicon hybrid coating formed by heat treatment. The coating has a particle size of less than 500 nm and a thermal curing temperature of 160–180 °C.

2. The high flame-retardant pre-oxidized filament fabric material according to claim 1, characterized in that, The pre-oxidized fibrous film flat yarn is made from polyacrylonitrile fiber by continuous constant temperature pre-oxidation treatment at 230-280°C in air atmosphere for 8-12 hours, and its carbon content is not less than 60%.

3. The high flame-retardant pre-oxidized filament fabric material according to claim 2, characterized in that, The polyacrylonitrile fiber raw material is obtained by copolymerizing acrylonitrile and methacrylamide monomers, with a mass fraction of methacrylamide of 1-5%. The copolymer is synthesized by solution polymerization and then concentrated and dried to serve as a precursor polymer for wet spinning.

4. The high flame-retardant pre-oxidized filament fabric material according to claim 3, characterized in that, The polyacrylonitrile fiber raw material also contains polytetrafluoroethylene micro powder with a particle size of 0.1 to 1 μm, which is mixed in a mass ratio of 1:5.5 to 19 with the polyacrylonitrile raw material. The raw material is dispersed by high-speed shearing and then wet-spun to obtain the precursor fiber.

5. The high flame-retardant pre-oxidized filament fabric material according to claim 4, characterized in that, The precursor fiber is subjected to hot stretching treatment at a temperature of 160-200℃, with a stretch ratio of 2.0-3.5 times and a treatment time of 3-6 minutes.

6. The high flame-retardant pre-oxidized filament fabric material according to claim 1, characterized in that, The thermally bonded reinforcing layer is obtained by dissolving a mixed precursor of aluminum phosphate, ethyltriethoxysilane and aminopropyltriethoxysilane in a mass ratio of 1:(0.5-1.5):(0.5-1.5) in ethanol and applying it to the surface of the intermediate layer by impregnation.

7. The high flame-retardant pre-oxidized filament fabric material according to claim 6, characterized in that, The mixed precursor also contains 0.5-2% triethylamine by mass, and is heat-cured at 170-180°C after application, with a heat treatment time of 32-34 minutes.

8. A method for preparing a high flame-retardant pre-oxidized filament fabric according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Acrylonitrile and methacrylamide are copolymerized in a mass fraction ratio, and a polymer solution is synthesized by solution polymerization. The polymer solution is then washed with water and dried to obtain a precursor polymer for spinning. S2: The precursor polymer is mixed with polytetrafluoroethylene micro powder with a particle size of 0.1-1 μm in a certain proportion, dispersed by high-speed shearing, and then wet-spun to obtain the precursor fiber; S3: The filament obtained from spinning is continuously pre-oxidized at a constant temperature of 230-280°C in air for 8-12 hours, and then subjected to hot stretching treatment at 160-200°C for 3-6 minutes with a stretching ratio of 2.0-3.5 times. The interval between the pre-oxidation temperature and the hot stretching temperature shall not exceed 50°C. S4: The heat-treated pre-oxidized slit flat yarn is woven into two layers of fabric using a twill weave method. Before weaving, the flat yarn is moistened in a water bath at 75-85℃ for 10-20 minutes. After weaving, it is heat-set at 110-130℃ for 20-30 minutes. S5: Dissolve aluminum phosphate, ethyltriethoxysilane and aminopropyltriethoxysilane in an ethanol aqueous solution in proportion, add 0.5-2% triethylamine, apply it between two pre-oxidized filament layers by impregnation, and heat cure at 170-180℃ for 32-34 minutes.

9. The method for preparing a high flame-retardant pre-oxidized filament fabric according to claim 8, characterized in that, After the S2 wet spinning step, the raw yarn is surface-dried by hot air at 40-60°C without being wound, and is directly fed into the pre-oxidation section. The conveying time between the spinning outlet and the pre-oxidation inlet is controlled at 2-3 minutes.

10. The method for preparing a high flame-retardant pre-oxidized filament fabric according to claim 8, characterized in that, The twill weave adopts a three-up-two-down or three-down-two-up weave structure, and a gap of 0.1 to 0.3 mm is left between the upper and lower layers of fabric after the weave is completed.

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