Flame-retardant composite fiber fabric and preparation method thereof

Abstract

The invention discloses a flame-retardant composite fiber fabric and a preparation method thereof, and relates to the technical field of flame-retardant composite fiber fabrics, the flame-retardant composite fiber fabric comprises the following layered structures: a surface flame-retardant protective layer: aramid 1414 fibers and phosphorus copolymerized flame-retardant polyester fibers in a mass ratio of 4: 1 are prepared into double-strand blended yarns through a vortex spinning technology, the density of the double-strand blended yarn is 18-22 tex, the double-strand blended yarn is subjected to plain weaving to form base cloth, the surface of the base cloth is coated with a microcapsule coating containing a nitrogen-phosphorus graphene composite flame retardant, the thickness of the microcapsule coating is 50-80 microns, and the particle size distribution of microcapsules is 2-8 microns. According to the invention, the outer layer microcapsule is broken when encountering fire to release a gaseous flame retardant to inhibit combustion chain reaction, the middle layer silicate colloid is carbonized at high temperature to form a heat insulation barrier, the graphene is combined to enhance the heat conduction dispersibility, the inner layer aluminum hydroxide particles are heated to decompose and absorb heat and release water vapor, and the combustion temperature is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of flame-retardant composite fiber fabrics, and specifically to a flame-retardant composite fiber fabric and a preparation method thereof. Background Art

[0002] Although natural fibers such as cotton and linen are comfortable, their limiting oxygen index (LOI) is usually lower than 21, making them extremely flammable and burning quickly, unable to meet the safety protection requirements. Synthetic fibers such as polyester and nylon are prone to melting and dripping at high temperatures, which may cause secondary injuries. Flame-retardant composite fiber fabrics have been widely used in fields such as protective clothing, interior decoration of transportation vehicles, and public place decoration. However, existing flame-retardant composite fiber fabrics cannot reduce the combustion temperature.

[0003] The defects of existing flame-retardant composite fiber fabrics are as follows: 1. Patent document CN109338538A discloses a composite flame-retardant fabric fiber, "which is woven by blending a first flame-retardant fabric fiber and a second flame-retardant fabric fiber. The first flame-retardant fabric fiber is blended from poly(p-phenylene terephthaloyl oxalate) bis(imidazolium) metal chelate fiber, polyamide fiber, and calcium alginate fiber. The second flame-retardant fabric fiber is blended from phenolic fiber, polyester fiber, and poly(m-phenylene isophthalamide) fiber. The present invention improves the flame-retardant performance of the fabric and also improves the durability of the flame-retardant performance", but existing flame-retardant composite fiber fabrics cannot reduce the combustion temperature; 2. Patent document CN105274687A discloses a composite flame-retardant fabric fiber, "which is woven by blending a first flame-retardant fabric fiber and a second flame-retardant fabric fiber. The first flame-retardant fabric fiber is woven by blending poly(p-phenylene terephthaloyl oxalate) bis(imidazolium) metal chelate fiber, kapok fiber, and polyamide fiber. The second flame-retardant fabric fiber is woven by blending phenolic fiber, polyacrylonitrile fiber, and polyester fiber. The present invention is woven by blending multiple fibers and has the characteristics of good flame-retardant effect, high strength, suitability for wearing, and good safety", but the flame retardant of existing flame-retardant composite fiber fabrics is prone to falling off; 3. Patent document CN103122517A discloses a flame-retardant antibacterial composite fiber fabric. "The composite fiber is made by blending polyacrylonitrile carbon fiber, cotton fiber, corn fiber, aloe fiber, and hydroxyapatite. The weight percentages of each raw material are 20 - 30% for polyacrylonitrile carbon fiber, 10 - 40% for cotton fiber, 20 - 50% for corn fiber, 5 - 15% for aloe fiber, and 1 - 5% for hydroxyapatite. The present invention uses polyacrylonitrile carbon fiber added with hydroxyapatite, green and environmentally friendly cotton fiber, corn fiber, and a small amount of aloe fiber as raw materials to prepare the composite fiber fabric. Hydroxyapatite contains phosphorus atoms and has a certain flame-retardant ability. The fiber fabric made not only has the ability to adsorb heavy metals but also increases the flame-retardant performance of the fabric. The fabric of the present invention combines the advantages of each fiber, is soft and comfortable, has good air permeability, high strength, good elasticity, and no irritation to the skin", but the existing flame-retardant composite fiber fabric process has poor wash resistance and a stiff hand feeling; 4. Patent document CN109130359A discloses a novel flame-retardant composite fiber fabric. "It includes: a fabric base material layer (1), the fabric base material layer (1) is made by blending modified aramid fiber and polylactic acid fiber. A flame-retardant fiber fabric layer (2) is provided on the upper surface of the area base material layer (1), and a fireproof layer (3) is provided on the upper surface of the flame-retardant fiber fabric layer (2). The fabric base material layer (1), the flame-retardant fiber fabric layer (2), and the fireproof layer (3) are all compounded together through an adhesive. A protective layer (4) is provided on the lower surface of the fabric base material layer (1), and a heat-insulating layer is provided on the lower surface of the protective layer (4). By the above method, the present invention adopts an optimized structural design. The surface layer is a flame-retardant fiber fabric with a long-lasting flame-retardant effect, and the inner layer is a fireproof layer with good high-temperature resistance, which can greatly improve the long-term flame-retardant performance of the fiber fabric", but the existing flame-retardant composite fiber fabric structure is not dense and the production efficiency is low. Summary of the Invention

[0004] The purpose of the present invention is to provide a flame-retardant composite fiber fabric and its preparation method to solve the technical problem that the existing flame-retardant composite fiber fabric cannot reduce the combustion temperature as mentioned in the above background technology.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A flame-retardant composite fiber fabric, including the following layered structure: Surface flame-retardant protective layer: Made by vortex spinning technology from aramid 1414 fiber and phosphorus-based copolymer flame-retardant polyester fiber with a mass ratio of 4:1 into a double-strand blended yarn. The density of the double-strand blended yarn is 18 - 22 tex. The double-strand blended yarn is woven into a base fabric by plain weaving. A microcapsule coating containing a nitrogen-phosphorus graphene composite flame retardant is coated on the surface of the base fabric. The thickness of the microcapsule coating is 50 - 80 μm, and the particle size distribution of the microcapsules is 2 - 8 μm; Intermediate gradient barrier layer: It is formed by interweaving basalt fibers and polyimide fibers through a three-dimensional warp knitting process to form a hexagonal honeycomb grid structure. The grid aperture of the hexagonal honeycomb grid structure is 0.5 - 1.2 mm, and the pores of the grid are filled with a silicate zinc borate composite flame retardant colloid. The solid content of the silicate zinc borate composite flame retardant colloid is ≥ 85%. In the silicate zinc borate composite flame retardant colloid, graphene oxide nanosheets with a mass ratio of 0.8% - 1.5% and silicon carbide whiskers with a mass ratio of 2% - 3% are dispersed; Inner functional composite layer: It is formed by a circular knitting process of modified nitrile chloroprene fibers and viscose-based chitin fibers with a mass ratio of 3:2 to form a double-sided mesh structure. The fiber surface is grafted with nano-scale aluminum hydroxide and silica composite flame retardant particles through low-temperature plasma treatment, and the grafting density is 1200 - 1500 particles / μm², and the particle size is 50 - 150 nm; The surface flame retardant protection layer, the intermediate gradient barrier layer, and the inner functional composite layer form an integrated material through a gradient hot pressing composite process. The hot pressing parameters are a temperature of 185 - 195 °C, a pressure of 8 - 12 MPa, and a pressure holding time of 30 - 45 s.

[0006] Preferably, the nitrogen-phosphorus graphene composite flame retardant in the microcapsule coating is a composite of melamine polyphosphate and aluminum hypophosphite, with a mass ratio of 7:3, and the graphene doping amount is 1.2% - 1.8% of the total mass of the flame retardant. The microcapsule wall material adopts a three-layer coating structure of polyurethane - polyurea - chitosan, and the wall thickness is 0.5 - 1.2 μm.

[0007] Preferably, the single filament diameter of the basalt fibers in the intermediate gradient barrier layer is 9 - 12 μm, the polyimide fibers adopt a core-shell structure, the cortex is a brominated epoxy resin modified layer, and the core layer is a polyimide matrix material. The fiber breaking strength is ≥ 4.5 cN / dtex.

[0008] Preferably, the modification method of the modified nitrile chloroprene fibers includes: impregnating the nitrile chloroprene raw filaments in an ethanol solution containing 2% - 3% vinyltriethoxysilane for 30 - 45 minutes, pre-drying at 80 °C, and then performing heat treatment and curing at 160 - 180 °C under nitrogen protection. The limiting oxygen index LOI of the fibers is ≥ 32%.

[0009] Preferably, the low-temperature plasma treatment parameters are: power 400 - 600 W, treatment time 3 - 5 minutes, the working gas is a mixed gas of argon and oxygen, and the volume ratio of the mixed gas is 8:2, and the vacuum degree is maintained at 50 - 80 Pa.

[0010] Preferably, it includes the following preparation steps: Step 1, preparation of the surface flame retardant protection layer; The aramid 1414 fibers and phosphorus-based copolymer flame-retardant polyester fibers are made into 18.5 tex double-twist yarns through the processes of bale opening, carding, drawing, and vortex spinning, and are treated by a padding and spraying composite process: Padding with a nitrogen-phosphorus flame retardant containing 15%, the nitrogen-phosphorus flame retardant is an emulsion of melamine polyphosphate and aluminum hypophosphite with a ratio of 7:3, and the pick-up rate is 75%-80%; After padding and pre-drying at 80 °C, a microcapsule coating is loaded by electrostatic spraying technology, the spraying voltage is 45-50 kV, and the coating weight gain rate is 8%-10%; After spraying, it is cured by hot air at 120-130 °C for 10-15 minutes to form a surface flame-retardant protective layer; Step Two, forming the intermediate gradient barrier layer; 3D warp knitting is carried out on basalt fibers and polyimide fibers according to a warp density of 58 roots / cm and a weft density of 42 roots / cm; The solid content of the silicate zinc borate composite colloid is 85%, the silicate zinc borate composite colloid is highly dispersed and mixed with graphene oxide and silicon carbide whiskers, and a vacuum injection equipment is used to fill the grid pores, and the injection pressure is 0.3-0.5 MPa; It is cured in stages at 135-145 °C: the first stage is 40 °C / 20 min, the second stage is 80 °C / 30 min, and the third stage is 120 °C / 45 min to form the intermediate gradient barrier layer; Step Three: Treating the inner functional composite layer; The modified nitrile chloroprene fibers and viscose-based chitin fibers are knitted by a 24-needle circular knitting machine to form a double-sided mesh fabric with a surface density of 180-220 g / m²; Using a low-temperature plasma treatment system, an aluminum hydroxide and silicon dioxide suspension is introduced into the grafting cavity, the concentration of the aluminum hydroxide and silicon dioxide suspension is 8%-12%, and the particle deposition rate during the treatment process is controlled at 2-3 μm / min.

[0011] Preferably, the pH value of the nitrogen-phosphorus flame retardant emulsion in the first step is adjusted to 4.8-5.2 by citric acid, and the emulsion viscosity is controlled at 120-150 mPa·s.

[0012] Preferably, the vacuum degree of the vacuum injection equipment in the second step is maintained at -0.08~-0.1 MPa, and the colloid fluidity index is: the measured value by a rotational viscometer at 25 °C ≤ 5000 cP.

[0013] Preferably, in the water-cooling shaping process of the fourth step, a gradient cooling mode is adopted: the first stage is cooled to 80 °C within 5 s, the second stage is cooled to 40 °C within 10 s, and the third stage is naturally cooled to room temperature.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. In the present invention, the outer layer of microcapsules is installed to release gaseous flame retardants upon encountering fire, inhibiting the combustion chain reaction. The middle layer of silicate colloid forms a heat insulation barrier through high-temperature carbonization, combined with graphene to enhance thermal conductivity and dispersion. The inner layer of aluminum hydroxide particles decomposes upon heating, absorbing heat and releasing water vapor, reducing the combustion temperature.

[0015] 2. In the present invention, a fast response mechanism that triggers upon contact with a fire source is achieved through the installation of surface microcapsules, releasing flame retardant gases within the initial 3 seconds. A graphene-enhanced ceramization barrier is formed in the middle layer, with a thermal conductivity ≤ 0.15 W / m·K at 800 °C. The inner layer nanoparticle grafting technology enables a flame retardant shedding rate of < 3% / 50 washes.

[0016] 3. In the present invention, the installation of a three-dimensional grid middle layer enhances the tear resistance strength, the inner layer of chitin fibers imparts antibacterial properties, and the modified nitrile chloroprene provides a soft and skin-friendly touch.

[0017] 4. In the present invention, the chemical bonding of the flame retardant to the fiber is achieved through the installation of plasma grafting technology, avoiding the problem of shedding. The hot pressing composite process synchronously completes interlayer bonding and structural densification, with a 30% increase in production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a front view structural schematic diagram of the present invention; Figure 2 is a cross-sectional structural schematic diagram of the present invention.

[0019] In the figure: 1, surface flame retardant protection layer; 2, middle gradient barrier layer; 3, inner layer functional composite layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "front end", "rear end", "both ends", "one end", "the other end", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0022] In the description of the present invention, it should be noted that, unless otherwise clearly specified and defined, the terms "installed", "equipped with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components. For those of ordinary skill in the art, it can be understood according to specific circumstances.

[0023] Example 1: An example of the flame-retardant composite fiber fabric provided by the present invention includes the following layered structure. Surface flame-retardant protection layer: A double-stranded blended yarn is prepared from aramid 1414 fiber and phosphorus-based copolymer flame-retardant polyester fiber with a mass ratio of 4:1 through vortex spinning technology. The density of the double-stranded blended yarn is 18 - 22 tex. The double-stranded blended yarn is woven into a base fabric by plain weaving. A microcapsule coating containing a nitrogen-phosphorus graphene composite flame retardant is coated on the surface of the base fabric. The thickness of the microcapsule coating is 50 μm, and the particle size distribution of the microcapsules is 2 μm. Intermediate gradient barrier layer: A hexagonal honeycomb grid structure is formed by interweaving basalt fiber and polyimide fiber through three-dimensional warp knitting technology. The grid aperture of the hexagonal honeycomb grid structure is 0.5 - 1.2 mm, and the pores of the grid are filled with a silicate zinc borate composite flame retardant colloid. The solid content of the silicate zinc borate composite flame retardant colloid is ≥85%. Graphene oxide nanosheets with a mass ratio of 0.8% - 1.5% and silicon carbide whiskers with a mass ratio of 2% - 3% are dispersed in the silicate zinc borate composite flame retardant colloid. Inner layer functional composite layer: A double-sided mesh structure is formed by circular knitting of modified nitrile chloroprene fiber and viscose-based chitin fiber with a mass ratio of 3:2. Nano-scale aluminum hydroxide and silica composite flame retardant particles are grafted on the fiber surface through low-temperature plasma treatment. The grafting density is 1200 - 1500 particles / μm², and the particle size is 50 - 150 nm. The surface flame-retardant protection layer, intermediate gradient barrier layer, and inner layer functional composite layer are formed into an integrated material through gradient hot pressing composite technology. The hot pressing parameters are temperature 185 - 195 °C, pressure 8 - 12 MPa, and holding pressure time 30 - 45 s. The nitrogen-phosphorus graphene composite flame retardant in the microcapsule coating is a composite of melamine polyphosphate and aluminum hypophosphite, with a mass ratio of 7:3. The doping amount of graphene is 1.2% - 1.8% of the total mass of the flame retardant. The microcapsule wall material adopts a three-layer coating structure of polyurethane-polyurea-chitosan, with a wall thickness of 0.5 - 1.2 μm. The single filament diameter of the basalt fiber in the intermediate gradient barrier layer is 9 - 12 μm. The polyimide fiber has a skin-core structure. The skin layer is a brominated epoxy resin modified layer, and the core layer is a polyimide matrix material. The fiber breaking strength is ≥4.5 cN / dtex. The modification method of the modified nitrile chloroprene fiber includes: impregnating the nitrile chloroprene raw yarn in an ethanol solution containing 2% - 3% vinyltriethoxysilane for 30 - 45 minutes, pre-drying at 80 °C, and then performing heat treatment curing at 160 - 180 °C under nitrogen protection. The limiting oxygen index LOI of the fiber is ≥32. The low-temperature plasma treatment parameters are: power 400 - 600 W, treatment time 3 - 5 minutes, the working gas is a mixed gas of argon and oxygen, and the volume ratio of the mixed gas is 8:2. The vacuum degree is maintained at 50 - 80 Pa; It includes the following preparation steps: Step 1, preparation of the surface flame-retardant protection layer; The aramid 1414 fiber and the phosphorus-based copolymer flame-retardant polyester fiber are made into 18.5 tex double-strand yarn through the processes of bale opening, carding, drawing, and vortex spinning, and are treated by a padding and spraying composite process: Padding with a nitrogen-phosphorus flame retardant containing 15%, the nitrogen-phosphorus flame retardant is an emulsion with the ratio of melamine polyphosphate and aluminum hypophosphite being 7:3, and the padding pick-up rate is 75%-80%; After padding and pre-drying at 80 °C, a microcapsule coating is loaded by an electrostatic spraying technique, the spraying voltage is 45-50 kV, and the coating weight gain rate is 8%-10%; After spraying, it is cured by hot air at 120-130 °C for 10-15 minutes to form a surface flame-retardant protective layer; Step two, forming an intermediate gradient barrier layer; The basalt fiber and the polyimide fiber are three-dimensionally warp-knitted according to the warp density of 58 roots / cm and the weft density of 42 roots / cm; The solid content of the silicate zinc borate composite colloid is 85%, the silicate zinc borate composite colloid is highly dispersed and mixed with graphene oxide and silicon carbide whiskers, and a vacuum injection equipment is used to fill the grid pores, and the injection pressure is 0.3-0.5 MPa; It is cured in stages at 135-145 °C: the first stage is 40 °C / 20 min, the second stage is 80 °C / 30 min, and the third stage is 120 °C / 45 min to form an intermediate gradient barrier layer; Step three: treating the inner functional composite layer; The modified nitrile chloroprene fiber and the viscose-based chitin fiber are knitted by a 24-needle circular knitting machine to form a double-sided mesh fabric with a surface density of 180-220 g / m²; Using a low-temperature plasma treatment system, an aluminum hydroxide and silicon dioxide suspension is introduced into the grafting cavity, the concentration of the aluminum hydroxide and silicon dioxide suspension is 8%-12%, and the particle deposition rate during the treatment is controlled at 2-3 μm / min; The pH value of the nitrogen-phosphorus flame retardant emulsion described in step one is adjusted to 4.8-5.2 by citric acid, and the emulsion viscosity is controlled at 120-150 mPa·s; The vacuum degree of the vacuum injection equipment described in step two is maintained at -0.08~-0.1 MPa, and the colloid fluidity index is: the measured value by a rotary viscometer at 25 °C ≤ 5000 cP; In the water-cooling shaping process described in step four, a gradient cooling mode is adopted: the first stage is cooled to 80 °C within 5 s, the second stage is cooled to 40 °C within 10 s, and the third stage is naturally cooled to room temperature.

[0024] Example 2: An example provided by the present invention: A flame-retardant composite fiber fabric includes the following layered structure. Surface flame-retardant protective layer: A double-stranded blended yarn is prepared from aramid 1414 fiber and phosphorus-based copolymer flame-retardant polyester fiber with a mass ratio of 4:1 through vortex spinning technology. The density of the double-stranded blended yarn is 18 - 22 tex. The double-stranded blended yarn is woven into a base fabric by plain weaving. A microcapsule coating containing a nitrogen-phosphorus graphene composite flame retardant is coated on the surface of the base fabric. The thickness of the microcapsule coating is 60 μm, and the particle size distribution of the microcapsules is 4 μm. Intermediate gradient barrier layer: A hexagonal honeycomb grid structure is formed by interweaving basalt fiber and polyimide fiber through three-dimensional warp knitting technology. The grid aperture of the hexagonal honeycomb grid structure is 0.5 - 1.2 mm, and the pores of the grid are filled with a silicate zinc borate composite flame retardant colloid. The solid content of the silicate zinc borate composite flame retardant colloid is ≥85%. Graphene oxide nanosheets with a mass ratio of 0.8% - 1.5% and silicon carbide whiskers with a mass ratio of 2% - 3% are dispersed in the silicate zinc borate composite flame retardant colloid. Inner layer functional composite layer: A double-sided mesh structure is formed by circular knitting of modified nitrile chloroprene fiber and viscose-based chitin fiber with a mass ratio of 3:2. Nano-scale aluminum hydroxide and silica composite flame retardant particles are grafted on the fiber surface through low-temperature plasma treatment. The grafting density is 1200 - 1500 particles / μm², and the particle size is 50 - 150 nm. The surface flame-retardant protective layer, intermediate gradient barrier layer, and inner layer functional composite layer are formed into an integrated material through gradient hot pressing composite technology. The hot pressing parameters are temperature 185 - 195 °C, pressure 8 - 12 MPa, and holding time 30 - 45 s. The nitrogen-phosphorus graphene composite flame retardant in the microcapsule coating is a composite of melamine polyphosphate and aluminum hypophosphite, with a mass ratio of 7:3. The doping amount of graphene is 1.2% - 1.8% of the total mass of the flame retardant. The microcapsule wall material adopts a three-layer coating structure of polyurethane-polyurea-chitosan, with a wall thickness of 0.5 - 1.2 μm. The single filament diameter of the basalt fiber in the intermediate gradient barrier layer is 9 - 12 μm. The polyimide fiber has a skin-core structure. The skin layer is a brominated epoxy resin modified layer, and the core layer is a polyimide matrix material. The fiber breaking strength is ≥4.5 cN / dtex. The modification method of the modified nitrile chloroprene fiber includes: Immersing the nitrile chloroprene raw yarn in an ethanol solution containing 2% - 3% vinyltriethoxysilane for 30 - 45 minutes, pre-baking at 80 °C, and then performing heat treatment curing at 160 - 180 °C under nitrogen protection. The limiting oxygen index LOI of the fiber is ≥32. The low-temperature plasma treatment parameters are: power 400 - 600 W, treatment time 3 - 5 minutes, the working gas is a mixed gas of argon and oxygen, and the volume ratio of the mixed gas is 8:2. The vacuum degree is maintained at 50 - 80 Pa; The preparation includes the following steps: Step 1, preparation of the surface flame-retardant protective layer; Aramid 1414 fibers and phosphorus-based copolymer flame-retardant polyester fibers are made into 18.5 tex double-strand yarns through the processes of bale opening, carding, drawing, and vortex spinning, and are treated by a padding and spraying composite process: Padding with a nitrogen-phosphorus flame retardant containing 15%, the nitrogen-phosphorus flame retardant is an emulsion with a ratio of melamine polyphosphate to aluminum hypophosphite of 7:3, and the liquor pickup is 75%-80%; After padding and pre-drying at 80 °C, a microcapsule coating is loaded by electrostatic spraying technology, the spraying voltage is 45-50 kV, and the coating weight gain rate is 8%-10%; After spraying, it is cured by hot air at 120-130 °C for 10-15 minutes to form a surface flame-retardant protective layer; Step two, forming the intermediate gradient barrier layer; Basalt fibers and polyimide fibers are three-dimensionally warp-knitted according to a warp density of 58 per cm and a weft density of 42 per cm; The solid content of the silicate zinc borate composite colloid is 85%, the silicate zinc borate composite colloid is highly dispersed and mixed with graphene oxide and silicon carbide whiskers, and a vacuum injection equipment is used to fill the grid pores, and the injection pressure is 0.3-0.5 MPa; It is cured in stages at 135-145 °C: the first stage is 40 °C / 20 min, the second stage is 80 °C / 30 min, and the third stage is 120 °C / 45 min to form the intermediate gradient barrier layer; Step three: treating the inner functional composite layer; Modified nitrile chloroprene fibers and viscose-based chitin fibers are knitted by a 24-needle circular knitting machine to form a double-sided mesh fabric with a surface density of 180-220 g / m²; Using a low-temperature plasma treatment system, an aluminum hydroxide and silicon dioxide suspension is introduced into the grafting cavity, the concentration of the aluminum hydroxide and silicon dioxide suspension is 8%-12%, and the particle deposition rate during the treatment is controlled at 2-3 μm / min; The pH value of the nitrogen-phosphorus flame retardant emulsion described in step one is adjusted to 4.8-5.2 by citric acid, and the emulsion viscosity is controlled at 120-150 mPa·s; The vacuum degree of the vacuum injection equipment described in step two is maintained at -0.08~-0.1 MPa, and the colloid fluidity index is: the measured value by a rotary viscometer at 25 °C ≤ 5000 cP; In the water-cooling shaping process described in step four, a gradient cooling mode is adopted: the first stage is cooled to 80 °C within 5 s, the second stage is cooled to 40 °C within 10 s, and the third stage is naturally cooled to room temperature.

[0025] Example 3: An example provided by the present invention: A flame-retardant composite fiber fabric includes the following layered structure. Surface flame-retardant protection layer: A double-stranded blended yarn is prepared from aramid 1414 fiber and phosphorus-based copolymer flame-retardant polyester fiber with a mass ratio of 4:1 through vortex spinning technology. The density of the double-stranded blended yarn is 18 - 22 tex. The double-stranded blended yarn is woven into a base fabric by plain weaving. A microcapsule coating containing a nitrogen-phosphorus graphene composite flame retardant is coated on the surface of the base fabric. The thickness of the microcapsule coating is 70 μm, and the particle size distribution of the microcapsules is 6 μm. Intermediate gradient barrier layer: A hexagonal honeycomb grid structure is formed by interweaving basalt fiber and polyimide fiber through three-dimensional warp knitting technology. The grid aperture of the hexagonal honeycomb grid structure is 0.5 - 1.2 mm, and the pores of the grid are filled with a silicate zinc borate composite flame retardant colloid. The solid content of the silicate zinc borate composite flame retardant colloid is ≥85%. Graphene oxide nanosheets with a mass ratio of 0.8% - 1.5% and silicon carbide whiskers with a mass ratio of 2% - 3% are dispersed in the silicate zinc borate composite flame retardant colloid. Inner layer functional composite layer: A double-sided mesh structure is formed by circular knitting of modified nitrile chloroprene fiber and viscose-based chitin fiber with a mass ratio of 3:2. Nano-scale aluminum hydroxide and silica composite flame retardant particles are grafted on the fiber surface through low-temperature plasma treatment. The grafting density is 1200 - 1500 particles / μm², and the particle size is 50 - 150 nm. The surface flame-retardant protection layer, intermediate gradient barrier layer, and inner layer functional composite layer are formed into an integrated material through gradient hot pressing composite technology. The hot pressing parameters are temperature 185 - 195°C, pressure 8 - 12 MPa, and holding pressure time 30 - 45 s. The nitrogen-phosphorus graphene composite flame retardant in the microcapsule coating is a composite of melamine polyphosphate and aluminum hypophosphite, with a mass ratio of 7:3. The doping amount of graphene is 1.2% - 1.8% of the total mass of the flame retardant. The microcapsule wall material adopts a three-layer coating structure of polyurethane-polyurea-chitosan, with a wall thickness of 0.5 - 1.2 μm. The single filament diameter of the basalt fiber in the intermediate gradient barrier layer is 9 - 12 μm. The polyimide fiber has a skin-core structure. The skin layer is a brominated epoxy resin modified layer, and the core layer is a polyimide matrix material. The fiber breaking strength is ≥4.5 cN / dtex. The modification method of the modified nitrile chloroprene fiber includes: impregnating the nitrile chloroprene raw filament in an ethanol solution containing 2% - 3% vinyltriethoxysilane for 30 - 45 minutes, pre-drying at 80°C, and then performing heat treatment curing at 160 - 180°C under nitrogen protection. The limiting oxygen index LOI of the fiber is ≥32. The low-temperature plasma treatment parameters are: power 400 - 600 W, treatment time 3 - 5 minutes, the working gas is a mixed gas of argon and oxygen, and the volume ratio of the mixed gas is 8:2. The vacuum degree is maintained at 50 - 80 Pa; It includes the following preparation steps: Step 1, preparation of the surface flame-retardant protection layer; The aramid 1414 fiber and the phosphorus-based copolymer flame-retardant polyester fiber are made into 18.5 tex double-strand yarn through processes of bale opening, carding, drawing, and vortex spinning, and are treated by a padding and spraying composite process: Padding with a nitrogen-phosphorus flame retardant containing 15%, the nitrogen-phosphorus flame retardant is an emulsion with a ratio of melamine polyphosphate to aluminum hypophosphite of 7:3, and the padding pick-up rate is 75%-80%; After padding and pre-drying at 80 °C, a microcapsule coating is loaded by electrostatic spraying technology, the spraying voltage is 45-50 kV, and the coating weight gain rate is 8%-10%; After spraying, it is cured by hot air at 120-130 °C for 10-15 minutes to form a surface flame-retardant protective layer; Step two, forming an intermediate gradient barrier layer; The basalt fiber and the polyimide fiber are three-dimensionally warp-knitted according to a warp density of 58 roots / cm and a weft density of 42 roots / cm; The solid content of the silicate zinc borate composite colloid is 85%, the silicate zinc borate composite colloid is highly dispersed and mixed with graphene oxide and silicon carbide whiskers, and a vacuum injection equipment is used to fill the grid pores, and the injection pressure is 0.3-0.5 MPa; It is cured in stages at 135-145 °C: the first stage is 40 °C / 20 min, the second stage is 80 °C / 30 min, and the third stage is 120 °C / 45 min to form an intermediate gradient barrier layer; Step three: treating the inner functional composite layer; The modified nitrile chloroprene fiber and the viscose-based chitin fiber are knitted by a 24-needle circular knitting machine to form a double-sided mesh fabric with a surface density of 180-220 g / m²; Using a low-temperature plasma treatment system, an aluminum hydroxide and silicon dioxide suspension is introduced into the grafting cavity, the concentration of the aluminum hydroxide and silicon dioxide suspension is 8%-12%, and the particle deposition rate during the treatment is controlled at 2-3 μm / min; The pH value of the nitrogen-phosphorus flame retardant emulsion described in step one is adjusted to 4.8-5.2 by citric acid, and the emulsion viscosity is controlled at 120-150 mPa·s; The vacuum degree of the vacuum injection equipment described in step two is maintained at -0.08~-0.1 MPa, and the colloid fluidity index is: the measured value by a rotational viscometer at 25 °C ≤ 5000 cP; In the water-cooling shaping process described in step four, a gradient cooling mode is adopted: the first stage is cooled to 80 °C within 5 s, the second stage is cooled to 40 °C within 10 s, and the third stage is naturally cooled to room temperature.

[0026] Example 4: An example provided by the present invention: A flame-retardant composite fiber fabric includes the following layered structure. Surface flame-retardant protection layer: A double-stranded blended yarn is prepared from aramid 1414 fiber and phosphorus-based copolymer flame-retardant polyester fiber with a mass ratio of 4:1 through vortex spinning technology. The density of the double-stranded blended yarn is 18 - 22 tex. The double-stranded blended yarn is woven into a base fabric by plain weaving. A microcapsule coating containing a nitrogen-phosphorus graphene composite flame retardant is coated on the surface of the base fabric. The thickness of the microcapsule coating is 80 μm, and the particle size distribution of the microcapsules is 8 μm. Intermediate gradient barrier layer: A hexagonal honeycomb grid structure is formed by interweaving basalt fiber and polyimide fiber through three-dimensional warp knitting technology. The grid aperture of the hexagonal honeycomb grid structure is 0.5 - 1.2 mm, and the pores of the grid are filled with a silicate zinc borate composite flame retardant colloid. The solid content of the silicate zinc borate composite flame retardant colloid is ≥85%. Graphene oxide nanosheets with a mass ratio of 0.8% - 1.5% and silicon carbide whiskers with a mass ratio of 2% - 3% are dispersed in the silicate zinc borate composite flame retardant colloid. Inner layer functional composite layer: A double-sided mesh structure is formed by circular knitting of modified nitrile chloroprene fiber and viscose-based chitin fiber with a mass ratio of 3:2. Nano-scale aluminum hydroxide and silica composite flame retardant particles are grafted on the fiber surface through low-temperature plasma treatment. The grafting density is 1200 - 1500 particles / μm², and the particle size is 50 - 150 nm. The surface flame-retardant protection layer, intermediate gradient barrier layer, and inner layer functional composite layer are formed into an integrated material through gradient hot pressing composite technology. The hot pressing parameters are temperature 185 - 195 °C, pressure 8 - 12 MPa, and holding pressure time 30 - 45 s. The nitrogen-phosphorus graphene composite flame retardant in the microcapsule coating is a composite of melamine polyphosphate and aluminum hypophosphite, with a mass ratio of 7:3. The doping amount of graphene is 1.2% - 1.8% of the total mass of the flame retardant. The microcapsule wall material adopts a three-layer coating structure of polyurethane-polyurea-chitosan, with a wall thickness of 0.5 - 1.2 μm. The single filament diameter of the basalt fiber in the intermediate gradient barrier layer is 9 - 12 μm. The polyimide fiber has a skin-core structure. The skin layer is a brominated epoxy resin modified layer, and the core layer is a polyimide matrix material. The fiber breaking strength is ≥4.5 cN / dtex. The modification method of the modified nitrile chloroprene fiber includes: Immersing the nitrile chloroprene raw filament in an ethanol solution containing 2% - 3% vinyltriethoxysilane for 30 - 45 minutes, pre-drying at 80 °C, and then performing heat treatment curing at 160 - 180 °C under nitrogen protection. The limiting oxygen index LOI of the fiber is ≥32. The low-temperature plasma treatment parameters are: power 400 - 600 W, treatment time 3 - 5 minutes, the working gas is a mixed gas of argon and oxygen, and the volume ratio of the mixed gas is 8:2. The vacuum degree is maintained at 50 - 80 Pa; It includes the following preparation steps: Step 1, preparation of the surface flame-retardant protection layer; The aramid 1414 fiber and the phosphorus-based copolymer flame-retardant polyester fiber are made into 18.5 tex double-twist yarns through the processes of bale opening, carding, drawing, and vortex spinning, and are treated by a padding and spraying composite process: Padding with a nitrogen-phosphorus flame retardant containing 15%, the nitrogen-phosphorus flame retardant is an emulsion with a ratio of melamine polyphosphate to aluminum hypophosphite of 7:3, and the liquor pickup is 75%-80%; After padding and pre-drying at 80 °C, a microcapsule coating is loaded by electrostatic spraying technology, the spraying voltage is 45-50 kV, and the coating weight gain rate is 8%-10%; After spraying, it is hot air cured at 120-130 °C for 10-15 minutes to form a surface flame-retardant protective layer; Step two, forming an intermediate gradient barrier layer; The basalt fiber and the polyimide fiber are three-dimensionally warp knitted according to a warp density of 58 per cm and a weft density of 42 per cm; The solid content of the silicate zinc borate composite colloid is 85%, the silicate zinc borate composite colloid is highly dispersed and mixed with graphene oxide and silicon carbide whiskers, and a vacuum injection equipment is used to fill the grid pores, and the injection pressure is 0.3-0.5 MPa; It is cured in stages at 135-145 °C: the first stage is 40 °C / 20 min, the second stage is 80 °C / 30 min, and the third stage is 120 °C / 45 min to form an intermediate gradient barrier layer; Step three: treating the inner functional composite layer; The modified nitrile chloroprene fiber and the viscose-based chitin fiber are knitted by a 24-needle circular knitting machine to form a double-sided mesh fabric with a surface density of 180-220 g / m²; Using a low-temperature plasma treatment system, an aluminum hydroxide and silicon dioxide suspension is introduced into the grafting cavity, the concentration of the aluminum hydroxide and silicon dioxide suspension is 8%-12%, and the particle deposition rate during the treatment is controlled at 2-3 μm / min; The pH value of the nitrogen-phosphorus flame retardant emulsion described in step one is adjusted to 4.8-5.2 by citric acid, and the emulsion viscosity is controlled at 120-150 mPa·s; The vacuum degree of the vacuum injection equipment described in step two is maintained at -0.08~-0.1 MPa, and the colloid fluidity index is: the measured value by a rotational viscometer at 25 °C ≤ 5000 cP; In the water cooling and shaping process described in step four, a gradient cooling mode is adopted: the first stage is cooled to 80 °C within 5 s, the second stage is cooled to 40 °C within 10 s, and the third stage is naturally cooled to room temperature.

[0027] Comparative experiment: The difference between Comparative Example 1 and Example 1 is that; Surface flame-retardant protective layer: Twisted double-strand blended yarns are prepared from aramid 1414 fibers and phosphorus-based copolymer flame-retardant polyester fibers with a mass ratio of 4:1 through vortex spinning technology. The density of the double-strand blended yarns is 18 - 22 tex. The double-strand blended yarns are woven into a base fabric by plain weaving. A microcapsule coating containing a nitrogen-phosphorus graphene composite flame retardant is coated on the surface of the base fabric. The thickness of the microcapsule coating is 50 μm, and the particle size distribution of the microcapsules is 2 μm.

[0028] The difference between Comparative Example 1 and Example 2 lies in; Surface flame-retardant protective layer: Twisted double-strand blended yarns are prepared from aramid 1414 fibers and phosphorus-based copolymer flame-retardant polyester fibers with a mass ratio of 4:1 through vortex spinning technology. The density of the double-strand blended yarns is 18 - 22 tex. The double-strand blended yarns are woven into a base fabric by plain weaving. A microcapsule coating containing a nitrogen-phosphorus graphene composite flame retardant is coated on the surface of the base fabric. The thickness of the microcapsule coating is 60 μm, and the particle size distribution of the microcapsules is 4 μm.

[0029] The difference between Comparative Example 1 and Example 3 lies in; Surface flame-retardant protective layer: Twisted double-strand blended yarns are prepared from aramid 1414 fibers and phosphorus-based copolymer flame-retardant polyester fibers with a mass ratio of 4:1 through vortex spinning technology. The density of the double-strand blended yarns is 18 - 22 tex. The double-strand blended yarns are woven into a base fabric by plain weaving. A microcapsule coating containing a nitrogen-phosphorus graphene composite flame retardant is coated on the surface of the base fabric. The thickness of the microcapsule coating is 70 μm, and the particle size distribution of the microcapsules is 6 μm.

[0030] The difference between Comparative Example 1 and Example 4 lies in; Surface flame-retardant protective layer: Twisted double-strand blended yarns are prepared from aramid 1414 fibers and phosphorus-based copolymer flame-retardant polyester fibers with a mass ratio of 4:1 through vortex spinning technology. The density of the double-strand blended yarns is 18 - 22 tex. The double-strand blended yarns are woven into a base fabric by plain weaving. A microcapsule coating containing a nitrogen-phosphorus graphene composite flame retardant is coated on the surface of the base fabric. The thickness of the microcapsule coating is 80 μm, and the particle size distribution of the microcapsules is 8 μm.

[0031] The flame-retardant composite fiber fabrics of Example 1, Example 2, Example 3, and Example 4 of the present invention and the traditional flame-retardant composite fiber fabric (Comparative Example 1) are tested according to the GB / T 5455-2014 standard using a vertical burning test chamber, and the afterflame time and smoldering time are recorded respectively. According to the GB / T 3923.1-2013 standard, an electronic universal material testing machine is used to stretch the specimens at a speed of (500 ± 10) mm / min, and the breaking strength is recorded respectively. Their protection values are calculated and statistically analyzed. The results are shown in Table 1;

[0032] As can be seen from the data in Table 1, the breaking strength coefficients of the flame-retardant composite fiber fabrics in Examples 1, 2, 3, and 4 of the present invention are 850 N / 5 cm, 980 N / 5 cm, 1020 N / 5 cm, 1060 N / 5 cm, and 1080 N / 5 cm respectively, which are significantly higher than those of the flame-retardant composite fiber fabric in Comparative Example 1. Therefore, it shows that the toughness of the flame-retardant composite fiber fabric of the present invention is significantly improved.

[0033] As can be seen from the data in Table 1, the afterflame times of the flame-retardant composite fiber fabrics in Examples 1, 2, 3, and 4 of the present invention are 10 s, 6 s, 4 s, 3 s, and 2 s respectively, which are significantly lower than those of the flame-retardant composite fiber fabric in Comparative Example 1. Therefore, it shows that the afterflame time of the flame-retardant composite fiber fabric of the present invention is significantly reduced.

[0034] As can be seen from the data in Table 1, the smoldering times of the flame-retardant composite fiber fabrics in Examples 1, 2, 3, and 4 of the present invention are 12 s, 10 s, 9 s, 7 s, and 5 s respectively, which are significantly lower than those of the flame-retardant composite fiber fabric in Comparative Example 1. Therefore, it shows that the smoldering time of the flame-retardant composite fiber fabric of the present invention is significantly reduced.

[0035] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claimed rights.

Claims

1. A flame-retardant composite fiber fabric, characterized in that: It includes the following layered structures: Surface flame-retardant protective layer (1): A double-strand blended yarn is prepared from aramid 1414 fibers and phosphorus-based copolymer flame-retardant polyester fibers with a mass ratio of 4:1 through vortex spinning technology. The density of the double-strand blended yarn is 18 - 22 tex. The double-strand blended yarn is woven into a base fabric by plain weaving. A microcapsule coating containing a nitrogen-phosphorus graphene composite flame retardant is coated on the surface of the base fabric. The thickness of the microcapsule coating is 50 - 80 μm, and the particle size distribution of the microcapsules is 2 - 8 μm; Intermediate gradient barrier layer (2): It is formed by interweaving basalt fibers and polyimide fibers through a three-dimensional warp knitting process to form a hexagonal honeycomb grid structure. The grid aperture of the hexagonal honeycomb grid structure is 0.5 - 1.2 mm, and the pores of the grid are filled with a silicate zinc borate composite flame retardant colloid. The solid content of the silicate zinc borate composite flame retardant colloid is ≥85%. Graphene oxide nanosheets with a mass ratio of 0.8% - 1.5% and silicon carbide whiskers with a mass ratio of 2% - 3% are dispersed in the silicate zinc borate composite flame retardant colloid; Inner functional composite layer (3): It is formed by a double-sided mesh structure through a circular knitting process from modified nitrile chloroprene fibers and viscose-based chitin fibers with a mass ratio of 3:

2. Nano-scale aluminum hydroxide and silica composite flame retardant particles are grafted on the fiber surface through low-temperature plasma treatment. The grafting density is 1200 - 1500 particles / μm², and the particle size is 50 - 150 nm; The surface flame-retardant protective layer (1), the intermediate gradient barrier layer (2), and the inner functional composite layer (3) form an integrated material through a gradient hot pressing composite process. The hot pressing parameters are a temperature of 185 - 195 °C, a pressure of 8 - 12 MPa, and a holding pressure time of 30 - 45 s.

2. The flame-retardant composite fiber fabric according to claim 1, wherein: The nitrogen-phosphorus graphene composite flame retardant in the microcapsule coating is a composite of melamine polyphosphate and aluminum hypophosphite, with a mass ratio of 7:

3. The doping amount of graphene is 1.2% - 1.8% of the total mass of the flame retardant. The microcapsule wall material adopts a three-layer coating structure of polyurethane - polyurea - chitosan, and the wall thickness is 0.5 - 1.2 μm.

3. A flame-retardant composite fiber fabric according to claim 1, characterized in that: The single-filament diameter of the basalt fibers in the intermediate gradient barrier layer (2) is 9 - 12 μm. The polyimide fiber has a core-shell structure. The cortex is a brominated epoxy resin modified layer, and the core layer is a polyimide matrix material. The fiber breaking strength is ≥4.5 cN / dtex.

4. A flame-retardant composite fiber fabric according to claim 1, characterized in that: The modification method of the modified nitrile chloroprene fibers includes: impregnating the nitrile chloroprene raw filaments in an ethanol solution containing 2% - 3% vinyltriethoxysilane for 30 - 45 minutes, pre-baking at 80 °C, and then performing heat treatment and curing at 160 - 180 °C under nitrogen protection. The limiting oxygen index LOI of the fiber is ≥32%.

5. A flame-retardant composite fiber fabric according to claim 1, characterized in that: The low-temperature plasma treatment parameters are: a power of 400 - 600 W, a treatment time of 3 - 5 minutes, the working gas is a mixed gas of argon and oxygen, the volume ratio of the mixed gas is 8:2, and the vacuum degree is maintained at 50 - 80 Pa.

6. A method for preparing a flame-retardant composite fiber fabric, applicable to a flame-retardant composite fiber fabric according to any one of claims 1-5, characterized in that, The following preparation steps are included: Step 1, preparation of the surface flame-retardant protective layer (1); The aramid 1414 fibers and the phosphorus-based copolymer flame-retardant polyester fibers are made into 18.5 tex double-strand yarns through the processes of blowing-carding, drawing, and vortex spinning, and are treated by a padding and spraying composite process: Pad with a nitrogen-phosphorus flame retardant containing 15%, the nitrogen-phosphorus flame retardant is an emulsion of melamine polyphosphate and aluminum hypophosphite with a ratio of 7:3, and the pick-up rate is 75%-80%; After padding and pre-drying at 80°C, load the microcapsule coating by electrostatic spraying technology, the spraying voltage is 45-50 kV, and the coating weight gain rate is 8%-10%; After spraying, cure in hot air at 120-130°C for 10-15 minutes to form a surface flame retardant protective layer (1); Step two, form the intermediate gradient barrier layer (2); Perform three-dimensional warp knitting on basalt fiber and polyimide fiber according to the warp density of 58 roots / cm and the weft density of 42 roots / cm; The solid content of the zinc borosilicate composite colloid is 85%. The zinc borosilicate composite colloid is highly dispersed and mixed with graphene oxide and silicon carbide whiskers, and a vacuum injection equipment is used to fill the grid pores, and the injection pressure is 0.3-0.5 MPa; Cure in stages at 135-145°C: the first stage is 40°C / 20 min, the second stage is 80°C / 30 min, and the third stage is 120°C / 45 min to form the intermediate gradient barrier layer (2); Step three: Treat the inner functional composite layer (3); The modified nitrile chloroprene fiber and the viscose-based chitin fiber are knitted by a 24-needle circular knitting machine to form a double-sided mesh fabric with a surface density of 180-220 g / m²; Adopt a low-temperature plasma treatment system, and introduce an aluminum hydroxide and silicon dioxide suspension into the grafting cavity. The concentration of the aluminum hydroxide and silicon dioxide suspension is 8%-12%, and the particle deposition rate during the treatment process is controlled at 2-3 μm / min.

7. A flame-retardant composite fiber fabric according to claim 6, characterized in that: The pH value of the nitrogen-phosphorus flame retardant emulsion in step one is adjusted to 4.8-5.2 by citric acid, and the emulsion viscosity is controlled at 120-150 mPa·s.

8. A flame-retardant composite fiber fabric according to claim 6, characterized in that: The vacuum degree of the vacuum injection equipment in step two is maintained at -0.08~-0.1 MPa, and the colloid fluidity index is: the measured value of the rotational viscometer at 25°C ≤ 5000 cP.

9. A flame-retardant composite fiber fabric according to claim 6, characterized in that: In the water-cooling shaping process in step four, adopt a gradient cooling mode: the first stage drops to 80°C within 5 s, the second stage drops to 40°C within 10 s, and the third stage cools naturally to room temperature.

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