Flame-retardant shielding military tent fabric prepared by recycling waste aramid fabric

Abstract

The invention relates to the field of aramid fabric recycling and reusing, in particular to a method for preparing flame-retardant shielding military tent fabric by recycling waste aramid fabric, which comprises the following steps: step 1, treating the waste aramid fabric with ionic liquid; 2, opening the aramid fabric and recycling aramid fibers; step 3, preparing regenerated flame-retardant prefabricated filaments; step 4, preparing tent base cloth; and step 5, preparing the heat-insulating shielding military tent fabric. Starting from multiple dimensions of aramid fiber recycling and reusing, micro-nano flame-retardant fiber preparation, fabric structure design, functional finishing and the like, more than 98% of flame-retardant viscose and aramid fiber in the aramid fiber blended fabric are recycled and utilized at high value, and the military tent fabric finally developed has the advantages that the flame-retardant viscose and the aramid fiber in the aramid fiber blended fabric are recycled and utilized at high value; the composite material integrates multiple functions of shielding and wave absorbing (the shielding rate is 72dB, the reflectivity is 34.32 dB, and the effective bandwidth is 13.8 GHz), flame retardance, heat insulation, water resistance, oil repellency, air permeability, moisture permeability, weather resistance, softness, durability and the like, and can be used for developing military tents.

Description

Technical Field

[0001] The invention relates to the field of aramid fabric recycling and reuse, and in particular to a flame-retardant shielding military tent fabric prepared by recycling waste aramid fabric. Background Art

[0002] With the rapid development of society and the significant improvement of people's living standards, people's demand for fashionable clothing has led to more frequent replacement of textiles and shorter life cycles of new textiles, which has generated a large number of waste textiles. At the same time, due to technical and economic bottlenecks, the industrial chain of my country's waste textile recycling industry needs to be improved urgently. A large number of waste textiles cannot be recycled, which has brought great pressure to the environment and great risks to human health.

[0003] As an important strategic raw material for national defense and military industry, aramid fiber has remarkable properties such as flame retardancy, high temperature resistance, light weight, high modulus and high strength, which makes it widely used in aerospace, automobile, protective products, sporting goods and other fields. Due to the high temperature resistance and flame retardancy of aramid fiber and its stable chemical properties, the traditional incineration and landfill methods cannot be used to treat waste aramid fabrics. With the annual growth of my country's aramid fiber production capacity, the recycling of waste aramid fiber products is also a huge challenge that people have to face. How to deeply realize the recycling of aramid fiber in a greener and more environmentally friendly way has received more and more attention.

[0004] In the information warfare era, many military equipment will generate electromagnetic waves, and a large number of electromagnetic waves will interfere with communication equipment and precision electronic instruments. Military tents with shielding functions can suppress electromagnetic leakage emissions from electronic equipment, have strong resistance to electromagnetic interference and electromagnetic weapon attacks, and can protect information security in field conditions. They are usually used for electromagnetic information protection in confidential places such as conference rooms, combat command rooms, important communication hubs, and confidential rooms of important command organizations. They can also provide protection for combatants and weapons and equipment to avoid being attacked by electromagnetic weapons in order to maintain life and war power.

[0005] The military undertakes the duties of field training, disaster relief, emergency response, military exercises, etc. Military tents can provide fast and convenient shelter. In summer, due to long-term exposure to the sun, the surface temperature of the tent is as high as 50°C, and the air temperature inside the tent will be as high as 40°C even if the door is open. The convection heat of the high-temperature air and the radiant heat of the high-temperature tent surface make the thermal environment in the tent extremely uncomfortable in summer. In order to enhance the thermal insulation performance of the tent cloth and create a comfortable working environment for soldiers, it is very necessary to develop lightweight thermal insulation and warmth-keeping military tent fabrics.

[0006] In terms of the recycling of waste aramid fabrics, no corresponding technical solutions have been retrieved. At present, the main method is to recycle and reuse waste aramid composite materials, and there are two main technical paths. The first is to use physical methods to sort them and then use chemical methods to prepare new fiber materials or aramid pulp. For example, CN 108219190B involves a method for preparing aramid pulp using scrapped bulletproof helmets, in which the dismantled and crushed helmets are soaked in solvents, centrifuged to remove resin, and finally the aramid fibers are subjected to decomposition and grinding to obtain aramid pulp; the second method is to recover aramid fibers from aramid fiber composite materials with the help of chemical solvents or physical methods, and finally prepare aramid nanofiber insulation paper. For example, CN 109836610 B places an aramid fiber / phenolic resin composite material in a mixed recovery solution of phosphoric acid and glacial acetic acid, washes the product after the reaction, and obtains recycled aramid fibers.

[0007] In terms of the preparation of military tent fabrics, the current technical approaches for the development of military tents are mainly:

[0008] One is to obtain a multi-layer composite shielding fabric by hot-pressing multiple fabrics. For example, CN203175149U discloses a functional composite tent cloth for shielding electromagnetic radiation. The outer layer is a flame-retardant vinyl camouflage water-repellent coating fabric, and the reverse side is an adhesive layer, which is hot-pressed and composited with a membrane layer PTFE film. The membrane layer PTFE film is then coated with a silicone adhesive as an adhesive layer B, which is laminated and composited with an inner layer of nickel-copper checkered conductive cloth.

[0009] The second is to prepare electromagnetic shielding materials by coating. For example, CN106012568B discloses a tent cloth with anti-ultraviolet function, which is composed of warp knitted cloth and anti-ultraviolet coating. The prepared tent cloth has good light corrosion resistance, can reflect a large amount of visible light, and can also shield ultraviolet rays. The use of hollow microsphere zinc oxide can play a certain role in heat insulation, but the coating is easy to fall off and does not have flame retardant function.

[0010] The third is to use stainless steel fiber, silver-plated filaments, etc. as shielding raw materials to construct a double-layer fabric structure to obtain shielding fabric. For example, CN116804298A discloses a high-performance electromagnetic shielding fabric and its manufacturing method and application. The designed fabric structure is double-layer, the outer layer is aramid / stainless steel blended yarn, and the inner layer is mainly silver-plated filament fabric. The fabric has a shielding efficiency of ≥50dB in the electromagnetic wave frequency range of 300MHz to 20GHz, and does not have the functions of wave absorption and heat insulation.

[0011] It can be seen that the main technical defects of aramid fabric recycling and reuse technology and flame retardant shielding tent fabric preparation are:

[0012] First, current recycling and reuse technologies are mainly targeted at aramid composite materials, and there is almost no research on the recycling and reuse of aramid fibers in waste aramid fabrics. In addition, when recycling and reusing aramid-based composite materials, physical and chemical recycling methods are mainly used, and the products formed by recycling are mainly activated carbon fabrics and composite materials. In addition, the existing physical recycling method has strong mechanical force, large fiber damage, and will cause fiber breakage. After opening, the fiber length is mostly below 20mm, making it difficult to achieve the recycling and reuse of longer aramid fibers, which limits the further application of recycled aramid fibers, and cannot be developed and prepared for high-end textiles, and high-value reuse has not been achieved.

[0013] Second, in order to improve the flame retardancy, heat insulation and thermal insulation properties of military tents, the existing technology adopts the technical measure of adding a layer of needle felt in the middle of the tent cloth to achieve thermal insulation, but this significantly increases the weight of the tent, making it inconvenient to carry and use, and difficult to adapt to the fast and flexible combat needs in modern warfare; or aerogel nanomaterials are attached to the tent fabric with the help of coating technology. This technical measure can easily cause the aerogel material structure to rupture and lose its thermal insulation properties during coating, and the aerogel is prone to "powdering", and the aerogel sealing technology is insufficient.

[0014] Third, the fiber raw materials used in military tent fabrics are all ordinary natural or chemical fibers, mainly cotton fiber, viscose fiber, nylon fiber, polyester and polyvinyl alcohol fiber. Cotton fiber and viscose tent fabrics have poor strength, heat resistance and fatigue resistance, are not flame retardant, and can no longer meet the demand; the mechanical properties of nylon, polyester and polyvinyl alcohol fiber tent fabrics have been improved, but they do not have flame retardant properties. High-performance, intrinsically flame-retardant fibers such as aramid fibers are rarely used, and the flame retardant, strength, wear resistance, and weather resistance of military tent fabrics are insufficient. Therefore, it is urgent to introduce high-performance, intrinsically flame-retardant fibers such as aramid fibers to realize the development of lightweight, flame-retardant, weather-resistant and mildew-proof, high-strength and wear-resistant military tent fabrics.

[0015] Fourth, the electromagnetic shielding, waterproof and oil repellent, breathable and moisture permeable, soft and durable properties of military tent fabrics circulating in the market have not been effectively taken into account, making it difficult to meet the needs of military protection. Existing shielding materials are mainly based on traditional metal bases, which have high density and poor corrosion resistance. At the same time, when realizing key functions such as electromagnetic shielding, waterproof and oil repellent, most of the existing technologies are to directly attach functional materials to the base fabric by physical means of coating or filling, which weakens the air permeability and softness of the fabric. Functional materials that are coated or filled are often prone to agglomeration, and it is difficult to achieve a high content and uniform dispersion state, which affects the protective performance of the fabric. In addition, the combination between functional materials and fabrics relies on physical bonding, and its bonding strength is relatively weak. Once part of the functional materials fall off, it will directly weaken the overall protective effectiveness of the tent and affect the use effect and cycle.

[0016] It can be seen that the existing technology is mainly aimed at the recycling and reuse of waste aramid composite materials, and there is a technical gap in the recycling and reuse of waste aramid fabrics. At the same time, the existing shielding tent fabrics are mostly made of ordinary fibers, and the mechanical properties of the fabrics need to be improved. Flame-retardant tents are mostly obtained by finishing with flame-retardant coatings, which are not wear-resistant and have poor thermal insulation effects. In addition, the existing shielding tents have a single function and can only reflect and shield electromagnetic waves, but do not have the function of absorbing waves, which can easily cause secondary pollution of electromagnetic waves. Summary of the invention

[0017] In view of the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a method for recycling waste aramid fabric to prepare flame-retardant shielding military tent fabric. The steps include:

[0018] Step 1, treating waste aramid fabric with ionic liquid: first, sterilize and cut the waste aramid fabric, place it in a solution containing ionic liquid and stir to dissolve it, take out the undissolved aramid fabric, wash it, dehydrate it and dry it, and filter the ionic liquid solution containing flame retardant viscose for later use;

[0019] Step 2, flexible opening of aramid fabric and recovery of aramid fiber: spraying the undissolved loose aramid fabric with oil agent for pretreatment, and then opening it with an opening machine to obtain loose aramid fiber of a certain length, that is, recovering the aramid fiber;

[0020] Step 3, preparation of regenerated flame-retardant prefabricated filaments: adding a heat-expandable microsphere foaming agent to the ionic liquid solution dissolved with the flame-retardant viscose obtained in step 1, stirring to obtain a spinning solution, filtering and degassing the spinning solution in turn, and placing it in a wet spinning device, squeezing the spinning solution from a spinneret, and obtaining flame-retardant prefabricated filaments through processes such as coagulation, hot drawing, oiling, and packaging;

[0021] Step 4, preparation of tent base fabric: the recycled aramid fiber obtained in step 2 is sequentially subjected to oiling and moistening, premixing, carding and combing, drawing and roving processes to form aramid fiber roving; then the flame-retardant prefabricated filament obtained in step 3 is used as the core layer, and the outer layer is coated with the recycled aramid fiber spinning yarn, and the coaxial yarn is sequentially subjected to warping, sizing, reeding, weaving, and cloth repairing to obtain the tent base fabric;

[0022] Step 5, preparation of heat-insulating and shielding military tent fabric: the surface layer of the tent base fabric obtained in step 4 is treated with anti-ultraviolet additives and waterproof and oil-repellent additives in turn, and the inner layer of the base fabric is treated with a shielding and absorbing finishing agent. Finally, it is subjected to high-temperature treatment so that the heat-expandable microsphere foaming agent evenly distributed in the flame-retardant prefabricated filament matrix is ​​expanded by heat to finally prepare a multi-dimensional three-dimensional lightweight heat-insulating and shielding military tent fabric.

[0023] Furthermore, the content of flame retardant viscose in the waste aramid fabric described in step 1 is 20 to 70 parts, the content of meta-aramid is 30 to 80 parts, the content of para-aramid is 5 to 20 parts, and the total mass of the fibers is 100 parts.

[0024] Furthermore, the dissolving temperature in step 1 is 140° C. to 160° C., the stirring speed is 120 rpm to 160 rpm, and the dissolving time is 12 min to 15 min.

[0025] Furthermore, the washing time in step 1 is 10 min to 15 min, the dehydration time is 5 min to 8 min, and the drying temperature is 180° C. to 200° C.

[0026] Furthermore, in step 2, the mass ratio of the oil agent to the undissolved loosely structured aramid fabric is (2-5):100, and the pretreatment time is 18h-22h.

[0027] Furthermore, the oil agent in step 2 comprises a mixture of equal masses of hexadecyltrimethylammonium chloride, polyquaternium-7 and polyquaternium-10.

[0028] Furthermore, in the opening process described in step 2, the licker-in speed is 600 r / min to 800 r / min, the cylinder speed is 360 r / min to 420 r / min, the cover speed is 30 mm / min to 50 mm / min, and the doffer speed is 20 r / min to 60 r / min.

[0029] Furthermore, the main body length of the recycled aramid fiber described in step 2 is 30 mm to 36 mm.

[0030] Furthermore, in the spinning solution described in step 3, the heat-expandable microsphere foaming agent accounts for 25 to 40 parts, and the rest is the flame-retardant viscose ionic liquid solution.

[0031] Furthermore, the average particle size of the heat-expandable microsphere foaming agent described in step 3 is 300nm to 400nm.

[0032] Furthermore, in the hot stretching process described in step 3, the hot stretching temperature is 100° C. to 120° C., and the stretching ratio is 1.5 to 3.0 times.

[0033] Furthermore, the linear density of the flame retardant prefabricated filament described in step 3 is 4.44tex to 11.11tex.

[0034] Furthermore, in the yarn described in step 4, the content of flame-retardant prefabricated filaments is 30 parts to 50 parts, and the content of recycled aramid fibers is 50 parts to 70 parts.

[0035] Furthermore, the military tent base fabric structure described in step 4 is formed by interweaving and connecting two types of warp and weft yarns, the outer layer and the inner layer, through the surface weft and the inner warp.

[0036] Furthermore, the outer fabric structure in step 4 is plain weave or twill weave, and the inner fabric structure is plain weave or twill weave.

[0037] Furthermore, the linear density of the yarn in step 4 is 11.81 tex×2 to 18.45 tex×2.

[0038] Furthermore, the tent base fabric described in step 4 has a warp density of 565 to 605 strands / 10 cm, and a weft density of 465 to 535 strands / 10 cm.

[0039] Furthermore, the mass per unit area of ​​the tent base fabric in step 4 is 320 g / m 2 ~380g / m 2 .

[0040] Furthermore, during the surface coating finishing described in step 5, the thickness of the anti-ultraviolet coating is 0.10 mm to 0.30 mm, the thickness of the waterproof and oil-repellent coating is 0.20 mm to 0.50 mm, the coating speed is 8 m / min to 12 m / min, and the baking temperature is 100° C. to 120° C.

[0041] Furthermore, in the shielding and absorbing finishing agent described in step 5, the nano shielding and absorbing powder accounts for 30 to 60 parts, the adhesive accounts for 5 to 10 parts, the dispersant accounts for 5 to 10 parts, and the rest is water, and the total mass of the above various components is 100 parts.

[0042] Furthermore, in the nano-shielding absorbing powder described in step 5, silver accounts for 35 to 45 parts, copper accounts for 25 to 35 parts, nickel accounts for 1.5 to 5 parts, MXene accounts for 4 to 10 parts, graphene accounts for 6 to 10 parts, barium ferrite accounts for 10 to 15 parts, carbon nanotubes account for 0.5 to 2 parts, and carbonyl iron accounts for 0.5 to 3 parts, and the total mass of the above components is 100 parts.

[0043] Furthermore, when the inner shielding and absorbing coating described in step 5 is finished, the thickness of the coating is 0.20 mm to 0.50 mm, and the baking temperature is 100° C. to 120° C.

[0044] Furthermore, the high temperature treatment temperature in step 5 is 160°C to 180°C.

[0045] The beneficial effects of the present invention are:

[0046] First, the present invention creatively realizes the recycling and reuse of aramid fabrics, filling the technical gap of the existing recycling and reuse of aramid fabrics. The present invention first uses ionic liquid to fully dissolve the flame retardant viscose in aramid blended fabrics, and while realizing the recycling of flame retardant viscose, forms a fluffy aramid fabric, which significantly reduces the difficulty of opening aramid fabrics. The ionic liquid solution plays the dual role of "recycling agent" and "treatment agent"; and through oil pretreatment, opening equipment transformation and process optimization, it breaks through the technical barriers of existing waste recycling and opening technology with a fiber length of less than 30mm, and innovatively realizes the recycling of waste aramid fibers with a maximum fiber length of 36mm, reducing the difficulty of spinning and weaving the fibers again, and improving the recycling value of aramid blended fabrics.

[0047] Secondly, the present invention creatively reuses the ionic liquid solution obtained by recycling flame-retardant viscose, by adding heat-expandable microsphere foaming agent to the flame-retardant viscose ionic liquid solution, and under the action of cross-linking agent, causing it to undergo chemical cross-linking reaction with the flame-retardant viscose fiber matrix, so that the self-made flame-retardant prefabricated fiber is almost the same as the commonly used textile fiber in performance when not subjected to heat expansion treatment. The flame-retardant prefabricated fiber has good spinnability when blended with other fibers, and theoretically there is no upper limit to the amount of addition, which can maximize its function and performance.

[0048] Third, the flame-retardant and heat-insulating military tent fabric described in the present invention creatively performs high-temperature heating treatment on the final flame-retardant and heat-insulating military tent base fabric to obtain a micro-nano porous heat-insulating structure, which reduces the processing difficulty caused by poor mechanical properties of microstructure or aerogel fibers, and at the same time, avoids the damage to the fiber structure caused by the long process of directly using microstructure or aerogel fibers from spinning to weaving, ensuring thermal protection performance. In addition, it also solves a series of technical problems such as aerogel collapse and "powder loss" that exist when aerogel is attached to tent fabrics using coating finishing.

[0049] Fourth, the flame-retardant and heat-insulating military tent fabric described in the present invention creatively performs high-temperature heating treatment on the final military tent base fabric, so that the thermal expansion material in the formed flame-retardant prefabricated filament expands. In microscopic morphology, the flame-retardant and heat-insulating military tent fabric is evenly distributed with various micro-nano-sized closed independent (closed-cell) and mutually interpenetrating (open-cell) mixed hole structures. The air and the bubble wall in the mixed hole structure form a unique gas chamber. The unique properties of the air give the fabric low density and low thermal conductivity, which improves the thermal insulation performance of the fabric; in macroscopic morphology, the special double-layer composite structure fabric of the present invention can further improve the thermal insulation performance of the military tent fabric by means of the energy dissipation of multiple reflections of sunlight between the double-layer fabrics when exposed to sunlight. At the same time, the micro-nano porous structure constructed is creatively effectively combined with the macroscopic fabric double-layer structure, and the thermal insulation performance of the military tent fabric is significantly improved through the "micro-meso-macro" cross-size synergistic effect, creating a comfortable environment for soldiers that is warm in winter and cool in summer.

[0050] Fifth, the present invention innovatively combines shielding materials with different shielding and absorbing mechanisms into multiple components, and then constructs multi-layer electromagnetic shielding, waterproof and oil-repellent, and UV-proof nano-functional membrane structures on the inner and outer surfaces of military tent fabrics through alternating composite finishing. With the help of fiber surface molecular engineering technology, the interfacial bonding force between shielding and absorbing materials and fiber substrates is improved, and the functional materials are firmly loaded on military tent fabrics, improving the durability of shielding and absorbing materials; and through molecular structure design, a topological system catalytic network is formed on the fiber surface to alleviate the agglomeration of shielding and absorbing nano-powders, achieve uniform high-content loading, realize the linkage and functional integration of the reflection and loss mechanisms of composite shielding materials, and significantly improve the shielding effectiveness and functional stability of military tent fabrics.

[0051] It can be seen that the present invention has implemented technical breakthroughs in multiple dimensions such as recycling and reuse of fiber raw materials, preparation of functional regenerated fibers, yarn fabric structure design, and functional finishing, achieving the recovery and high-value utilization of more than 98% of flame-retardant viscose and aramid fibers in aramid blended fabrics. The developed multifunctional composite military tent fabric integrates electromagnetic shielding, flame retardancy, thermal insulation, waterproof and oil repellent, breathable and moisture permeable, weather-resistant and high-strength, soft and durable, etc., which fully meets the quality requirements of military shielding tents. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0053] Figure 1 This is the SEM image of the flame retardant prefabricated filament in Example 1.

[0054] Figure 2 This is a SEM image of the micro-nano flame-retardant filaments formed by high temperature treatment in Example 1. DETAILED DESCRIPTION

[0055] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] Example 1

[0057] This embodiment provides a method for recycling waste aramid fabric to prepare flame-retardant shielding military tent fabric, the steps comprising:

[0058] Step 1: Treatment of waste aramid fabric with ionic liquid: First, the waste aramid fabric is sterilized and cut, and then placed in a container containing ionic liquid and stirred to dissolve at 160°C, the stirring speed is 160 rpm, and the dissolution time is 15 minutes. The undissolved aramid fabric is taken out and washed with water for 10 minutes, dehydrated for 5 minutes, and dried at a temperature of 200°C. The ionic liquid solution containing the flame-retardant viscose is filtered for later use;

[0059] The ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate, purchased from Zhengzhou Huiju Chemical Co., Ltd.

[0060] The content of flame retardant viscose in the waste aramid fabric is 20 parts, the content of meta-aramid is 70 parts, the content of para-aramid is 10 parts, and the total mass of the fibers is 100 parts.

[0061] Step 2: Flexible opening of aramid fabric and recovery of aramid fiber: After pre-treatment by spraying oil on the undissolved loose aramid fabric, an opening machine is used for opening, with the licker-in speed of 600r / min, the cylinder speed of 360r / min, the cover speed of 30mm / min, and the doffer speed of 20r / min; a certain length of bulk aramid fiber is obtained, i.e., the recovered aramid fiber; the main length of the recovered aramid fiber is 36mm;

[0062] The mass ratio of the oil agent to the undissolved loosely structured aramid fabric is 4:100, and the pretreatment time is 20 hours; the oil agent includes a mixture of equal masses of hexadecyltrimethylammonium chloride, polyquaternium-7 and polyquaternium-10.

[0063] Step 3: Preparation of regenerated flame-retardant prefabricated filaments: Add a heat-expandable microsphere foaming agent to the ionic liquid solution dissolved with flame-retardant viscose obtained in step 1, stir and obtain a spinning solution, the weight ratio of the heat-expandable microsphere foaming agent to the spinning solution is 40 parts, and the average particle size of the heat-expandable microsphere foaming agent is 300nm; the spinning solution is filtered and degassed in turn and placed in a wet spinning device, the spinning solution is extruded from the spinneret, solidified and formed, and hot-stretched at a temperature of 100°C, with a stretching multiple of 1.5 times, followed by oiling, packaging and other processes to obtain flame-retardant prefabricated filaments; the linear density of the surface flame-retardant prefabricated filaments is 11.11tex, and the linear density of the inner layer flame-retardant prefabricated filaments is 8.88tex;

[0064] The thermal expansion microsphere foaming agent model is 186DU20, purchased from Polychem in the United States.

[0065] Step 4: Preparation of tent base fabric: The recycled aramid fiber obtained in step 2 is sequentially subjected to the processes of oiling and moistening, premixing, carding, drawing and roving to form aramid fiber roving; then the flame-retardant prefabricated filament obtained in step 3 is used as the core layer, and the outer layer is coated with the recycled aramid fiber to spin the yarn, wherein the content of the flame-retardant prefabricated filament in the yarn is 50 parts, and the content of the recycled aramid fiber is 50 parts; the coaxial yarn is sequentially warped, sizing, reeding, weaving, and cloth repairing to obtain the tent base fabric; the warp density of the tent base fabric is 605 strands / 10cm, and the weft density is 520 strands / 10cm; the unit area mass of the tent base fabric is 380g / m 2 The tent base fabric structure is made of two types of warp and weft yarns, the outer layer and the inner layer, interwoven and connected by the outer weft and the inner warp; the outer layer fabric structure is plain weave, and the inner layer fabric structure is twill weave;

[0066] Among them, the linear density of the surface yarn in step 4 is 16.87tex×2, and the linear density of the inner yarn is 14.06tex×2.

[0067] Step 5: Preparation of heat-insulating and shielding military tent fabric: The surface layer of the tent base fabric obtained in step 4 is treated with an anti-ultraviolet agent and a waterproof and oil-repellent agent in turn, and the inner layer of the base fabric is treated with a shielding and absorbing finishing agent, and finally subjected to a high-temperature treatment at a temperature of 180°C to finally prepare a multi-dimensional, three-dimensional, lightweight, heat-insulating and shielding military tent fabric; when the surface coating is treated, the thickness of the anti-ultraviolet coating is 0.30mm, the thickness of the waterproof and oil-repellent coating is 0.50mm, the coating speed is 8 meters / minute, and the baking temperature is 120°C; when the inner shielding and absorbing coating is treated, the thickness of the coating is 0.50mm, and the baking temperature is 120°C; the high-temperature treatment temperature is 180°C.

[0068] Among them, the anti-UV additive was purchased from Shandong Jinyufeng New Materials Co., Ltd., and the waterproof and oil-repellent additive was purchased from Changzhou Youfang New Materials Technology Co., Ltd.

[0069] Among them, in the shielding and absorbing finishing agent, the nano shielding and absorbing powder accounts for 60 parts, the adhesive accounts for 10 parts, the dispersant accounts for 10 parts, and the rest is water, and the total mass of the above various components is 100 parts;

[0070] The adhesive is a high temperature resistant water-based polyurethane purchased from Guangzhou Ruilin New Materials Co., Ltd., and the dispersant is a water-based dispersant SYZ-8412 purchased from Dongguan Siyezi Plastic Co., Ltd.;

[0071] Among them, the nano-shielding absorbing powder contains 35 parts of silver, 25 parts of copper, 5 parts of nickel, 10 parts of MXene, 10 parts of graphene, 10 parts of barium ferrite, 2 parts of carbon nanotubes, and 3 parts of carbonyl iron. The total mass of the above components is 100 parts.

[0072] Figure 1 is a SEM image of the flame retardant prefabricated filament in Example 1; Figure 2 is a SEM image of the micro-nano flame-retardant filament formed by high temperature treatment in Example 1;

[0073] Depend on Figure 1 It is known that the flame-retardant prefabricated filaments before high-temperature treatment have uniform texture, high molecular orientation, and excellent mechanical properties, which are not much different from conventional textile fibers;

[0074] Depend on Figure 2 It is known that after high-temperature treatment, the flame-retardant prefabricated filaments will have a micro-nano porous structure in the cross section, which is beneficial to the improvement of the thermal insulation performance of military shielding tent fabrics.

[0075] Example 2

[0076] This embodiment provides a method for recycling waste aramid fabric to prepare flame-retardant shielding military tent fabric, the steps comprising:

[0077] Step 1: Treatment of waste aramid fabric with ionic liquid: First, the waste aramid fabric is sterilized and cut, and then placed in a container containing ionic liquid and stirred to dissolve at 140°C, with a stirring speed of 120 rpm and a dissolution time of 12 min. The undissolved aramid fabric is taken out and washed with water for 15 min, dehydrated for 8 min, and dried at 180°C. The ionic liquid solution containing the flame-retardant viscose is filtered for later use.

[0078] The ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate, purchased from Zhengzhou Huiju Chemical Co., Ltd.

[0079] The content of flame retardant viscose in the waste aramid fabric is 70 parts, and the content of meta-aramid is 30 parts.

[0080] Step 2: Flexible opening of aramid fabric and recovery of aramid fiber: After pre-treatment by spraying oil on the undissolved loose aramid fabric, an opening machine is used for opening, with the licker-in speed of 800r / min, the cylinder speed of 420r / min, the cover speed of 50mm / min, and the doffer speed of 60r / min; a certain length of bulk aramid fiber is obtained, i.e., the recovered aramid fiber; the main length of the recovered aramid fiber is 35mm;

[0081] The mass ratio of the oil agent to the undissolved loosely structured aramid fabric is 2:100, and the pretreatment time is 18 hours; the oil agent includes a mixture of equal masses of hexadecyltrimethylammonium chloride, polyquaternium salt-7 and polyquaternium salt-10.

[0082] Step 3: Preparation of regenerated flame-retardant prefabricated filaments: Add a heat-expandable microsphere foaming agent to the ionic liquid solution dissolved with flame-retardant viscose obtained in step 1, stir and obtain a spinning solution, the weight ratio of the heat-expandable microsphere foaming agent to the spinning solution is 25 parts, and the average particle size of the heat-expandable microsphere foaming agent is 400nm; the spinning solution is filtered and degassed in turn and placed in a wet spinning device, the spinning solution is extruded from the spinneret, solidified and formed, and hot-stretched at a temperature of 120°C, with a stretching multiple of 3.0 times, followed by oiling, packaging and other processes to obtain flame-retardant prefabricated filaments; the linear density of the surface flame-retardant prefabricated filaments is 8.88tex, and the linear density of the inner layer flame-retardant prefabricated filaments is 4.44tex;

[0083] The thermal expansion microsphere foaming agent model is 186DU20, purchased from Polychem in the United States.

[0084] Step 4: Preparation of tent base fabric: The recycled aramid fiber obtained in step 2 is sequentially subjected to the processes of oiling and moistening, premixing, carding, drawing and roving to form aramid fiber roving; then the flame-retardant prefabricated filament obtained in step 3 is used as the core layer, and the outer layer is coated with the recycled aramid fiber to spin the yarn, wherein the content of the flame-retardant prefabricated filament in the yarn is 40 parts, and the content of the recycled aramid fiber is 60 parts; the coaxial yarn is sequentially subjected to warping, sizing, reeding, weaving, and cloth repairing to obtain the tent base fabric; the warp density of the tent base fabric is 602 yarns / 10cm, and the weft density is 535 yarns / 10cm; the unit area mass of the tent base fabric is 320g / m 2 The tent base fabric structure is made of two types of warp and weft yarns, the outer layer and the inner layer, interwoven and connected by the outer weft and the inner warp; the outer layer fabric structure is plain weave, and the inner layer fabric structure is plain weave;

[0085] Among them, the linear density of the surface yarn in step 4 is 14.06tex×2, and the linear density of the inner yarn is 11.81tex×2.

[0086] Step 5: Preparation of heat-insulating and shielding military tent fabric: The surface layer of the tent base fabric obtained in step 4 is finished with an anti-ultraviolet agent and a waterproof and oil-repellent agent in turn, and the inner layer of the base fabric is finished with a shielding and absorbing finishing agent, and finally subjected to a high-temperature treatment at a temperature of 160°C to finally prepare a multi-dimensional, three-dimensional, lightweight, heat-insulating and shielding military tent fabric; when the surface coating is finished, the thickness of the anti-ultraviolet coating is 0.10mm, the thickness of the waterproof and oil-repellent coating is 0.20mm, the coating speed is 12 meters / minute, and the baking temperature is 100°C; when the inner shielding and absorbing coating is finished, the thickness of the coating is 0.20mm, and the baking temperature is 100°C; the high-temperature treatment temperature is 160°C.

[0087] Among them, the anti-UV additive was purchased from Shandong Jinyufeng New Materials Co., Ltd., and the waterproof and oil-repellent additive was purchased from Changzhou Youfang New Materials Technology Co., Ltd.

[0088] Among them, in the shielding and absorbing finishing agent, the nano shielding and absorbing powder accounts for 30 parts, the adhesive accounts for 5 parts, the dispersant accounts for 5 parts, and the rest is water, and the total mass of the above various components is 100 parts;

[0089] The adhesive is a high temperature resistant water-based polyurethane purchased from Guangzhou Ruilin New Materials Co., Ltd., and the dispersant is a water-based dispersant SYZ-8412 purchased from Dongguan Siyezi Plastic Co., Ltd.;

[0090] Among them, the nano-shielding absorbing powder contains 45 parts of silver, 30 parts of copper, 1.5 parts of nickel, 3.5 parts of MXene, 6 parts of graphene, 10 parts of barium ferrite, 1 part of carbon nanotubes, and 3 parts of carbonyl iron. The total mass of the above components is 100 parts.

[0091] Example 3

[0092] This embodiment provides a method for recycling waste aramid fabric to prepare flame-retardant shielding military tent fabric, the steps comprising:

[0093] Step 1: Treatment of waste aramid fabric with ionic liquid: First, the waste aramid fabric is sterilized and cut, and then placed in a container containing ionic liquid and stirred to dissolve at 160°C, the stirring speed is 160 rpm, and the dissolution time is 15 minutes. The undissolved aramid fabric is taken out and washed with water for 15 minutes, dehydrated for 8 minutes, and dried at a temperature of 200°C. The ionic liquid solution containing the flame-retardant viscose is filtered for later use;

[0094] The ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate, purchased from Zhengzhou Huiju Chemical Co., Ltd.

[0095] The content of flame retardant viscose in the waste aramid fabric is 50 parts, the content of meta-aramid is 30 parts, the content of para-aramid is 20 parts, and the total mass of the fibers is 100 parts.

[0096] Step 2: Flexible opening of aramid fabric and recovery of aramid fiber: After pre-treatment by spraying oil on the undissolved loose aramid fabric, an opener is used for opening, with the licker-in speed of 700r / min, the cylinder speed of 400r / min, the cover speed of 40mm / min, and the doffer speed of 40r / min; a certain length of loose aramid fiber is obtained, i.e., the recovered aramid fiber; the main length of the recovered aramid fiber is 32mm;

[0097] The mass ratio of the oil agent to the undissolved loosely structured aramid fabric is 4:100, and the pretreatment time is 20 hours; the oil agent includes a mixture of equal masses of hexadecyltrimethylammonium chloride, polyquaternium-7 and polyquaternium-10.

[0098] Step 3: Preparation of regenerated flame-retardant prefabricated filaments: Add a heat-expandable microsphere foaming agent to the ionic liquid solution dissolved with flame-retardant viscose obtained in step 1, stir and obtain a spinning solution, the weight ratio of the heat-expandable microsphere foaming agent to the spinning solution is 30 parts, and the average particle size of the heat-expandable microsphere foaming agent is 300nm; the spinning solution is filtered and degassed in turn and placed in a wet spinning device, the spinning solution is extruded from the spinneret, solidified and formed, and hot-stretched at a temperature of 100°C, with a stretching multiple of 2.0 times, followed by oiling, packaging and other processes to obtain flame-retardant prefabricated filaments; the linear density of the surface flame-retardant prefabricated filaments is 10.00tex, and the linear density of the inner layer flame-retardant prefabricated filaments is 7.77tex;

[0099] The thermal expansion microsphere foaming agent model is 186DU20, purchased from Polychem in the United States.

[0100] Step 4: Preparation of tent base fabric: The recycled aramid fiber obtained in step 2 is sequentially subjected to the processes of oiling and moistening, premixing, carding, drawing and roving to form aramid fiber roving; then the flame-retardant prefabricated filament obtained in step 3 is used as the core layer, and the outer layer is coated with the recycled aramid fiber to spin the yarn, wherein the content of the flame-retardant prefabricated filament in the yarn is 45 parts, and the content of the recycled aramid fiber is 55 parts; the coaxial yarn is sequentially subjected to warping, sizing, reeding, weaving, and cloth repairing to obtain the tent base fabric; the warp density of the tent base fabric is 585 yarns / 10cm, and the weft density is 465 yarns / 10cm; the unit area mass of the tent base fabric is 340g / m 2 The tent base fabric structure is made of two types of warp and weft yarns, the outer layer and the inner layer, interwoven and connected by the outer weft and the inner warp; the outer layer fabric structure is twill weave, and the inner layer fabric structure is plain weave;

[0101] Among them, the linear density of the surface yarn in step 4 is 16.87tex×2, and the linear density of the inner yarn is 13.12tex×2.

[0102] Step 5: Preparation of heat-insulating and shielding military tent fabric: The surface layer of the tent base fabric obtained in step 4 is treated with an anti-ultraviolet agent and a waterproof and oil-repellent agent in turn, and the inner layer of the base fabric is treated with a shielding and absorbing finishing agent, and finally subjected to a high-temperature treatment at a temperature of 170°C to finally prepare a multi-dimensional, three-dimensional, lightweight, heat-insulating and shielding military tent fabric; when the surface coating is treated, the thickness of the anti-ultraviolet coating is 0.30mm, the thickness of the waterproof and oil-repellent coating is 0.40mm, the coating speed is 10 meters / minute, and the baking temperature is 110°C; when the inner shielding and absorbing coating is treated, the thickness of the coating is 0.40mm, and the baking temperature is 110°C; the high-temperature treatment temperature is 170°C.

[0103] Among them, the anti-UV additive was purchased from Shandong Jinyufeng New Materials Co., Ltd., and the waterproof and oil-repellent additive was purchased from Changzhou Youfang New Materials Technology Co., Ltd.

[0104] Among them, in the shielding and absorbing finishing agent, the nano shielding and absorbing powder accounts for 50 parts, the adhesive accounts for 8 parts, the dispersant accounts for 6 parts, and the rest is water, and the total mass of the above various components is 100 parts;

[0105] The adhesive is a high temperature resistant water-based polyurethane purchased from Guangzhou Ruilin New Materials Co., Ltd., and the dispersant is a water-based dispersant SYZ-8412 purchased from Dongguan Siyezi Plastic Co., Ltd.;

[0106] Among them, the nano-shielding absorbing powder contains 35 parts of silver, 25 parts of copper, 3 parts of nickel, 7 parts of MXene, 10 parts of graphene, 15 parts of barium ferrite, 2 parts of carbon nanotubes, and 3 parts of carbonyl iron. The total mass of the above components is 100 parts.

[0107] Example 4

[0108] This embodiment provides a method for recycling waste aramid fabric to prepare flame-retardant shielding military tent fabric, the steps comprising:

[0109] Step 1: Treatment of waste aramid fabric with ionic liquid: First, the waste aramid fabric is sterilized and cut, and then placed in a container containing ionic liquid and stirred to dissolve at 150°C, with a stirring speed of 140 rpm and a dissolution time of 13 min. The undissolved aramid fabric is taken out and washed with water for 12 min, dehydrated for 6 min, and dried at 190°C. The ionic liquid solution containing the flame-retardant viscose is filtered for later use.

[0110] The ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate, purchased from Zhengzhou Huiju Chemical Co., Ltd.

[0111] The content of flame retardant viscose in the waste aramid fabric is 40 parts, the content of meta-aramid is 40 parts, the content of para-aramid is 20 parts, and the total mass of the fibers is 100 parts.

[0112] Step 2: Flexible opening of aramid fabric and recovery of aramid fiber: After pre-treatment by spraying oil on the undissolved loose aramid fabric, an opener is used for opening, with the licker-in speed of 650r / min, the cylinder speed of 380r / min, the cover speed of 40mm / min, and the doffer speed of 50r / min; a certain length of loose aramid fiber is obtained, i.e., the recovered aramid fiber; the main length of the recovered aramid fiber is 30mm;

[0113] The mass ratio of the oil agent to the undissolved loosely structured aramid fabric is 4:100, and the pretreatment time is 20 hours; the oil agent includes a mixture of equal masses of hexadecyltrimethylammonium chloride, polyquaternium-7 and polyquaternium-10.

[0114] Step 3: Preparation of regenerated flame-retardant prefabricated filaments: Add a heat-expandable microsphere foaming agent to the ionic liquid solution dissolved with flame-retardant viscose obtained in step 1, stir and obtain a spinning solution, wherein the weight ratio of the heat-expandable microsphere foaming agent to the spinning solution is 30 parts, and the average particle size of the heat-expandable microsphere foaming agent is 350nm; the spinning solution is filtered and degassed in turn and placed in a wet spinning device, the spinning solution is extruded from the spinneret, solidified and formed, and hot-stretched at a temperature of 110°C, with a stretching multiple of 1.5 times, followed by oiling, packaging and other processes to obtain flame-retardant prefabricated filaments; the linear density of the surface flame-retardant prefabricated filaments is 11.11tex, and the linear density of the inner layer flame-retardant prefabricated filaments is 8.88tex;

[0115] The thermal expansion microsphere foaming agent model is 186DU20, purchased from Polychem in the United States.

[0116] Step 4: Preparation of tent base fabric: The recycled aramid fiber obtained in step 2 is sequentially subjected to the processes of oiling and moistening, premixing, carding and combing, drawing and roving to form aramid fiber roving; then the flame-retardant prefabricated filament obtained in step 3 is used as the core layer, and the outer layer is coated with the recycled aramid fiber to spin the yarn, wherein the content of the flame-retardant prefabricated filament in the yarn is 50 parts, and the content of the recycled aramid fiber is 50 parts; the coaxial yarn is sequentially subjected to warping, sizing, reeding, weaving, and cloth repairing to obtain the tent base fabric; the warp density of the tent base fabric is 565 yarns / 10cm, and the weft density is 480 yarns / 10cm; the unit area mass of the tent base fabric is 380g / m 2 The tent base fabric structure is made of two types of warp and weft yarns, the outer layer and the inner layer, interwoven and connected by the surface weft and the inner warp; the outer layer fabric structure is twill weave, and the inner layer fabric structure is twill weave;

[0117] Wherein, the linear density of the surface yarn in step 4 is 16.45tex×2, and the linear density of the inner yarn is 14.76tex×2.

[0118] Step 5: Preparation of heat-insulating and shielding military tent fabric: The surface layer of the tent base fabric obtained in step 4 is treated with an anti-ultraviolet agent and a waterproof and oil-repellent agent in turn, and the inner layer of the base fabric is treated with a shielding and absorbing finishing agent, and finally subjected to a high-temperature treatment at a temperature of 170°C to finally prepare a multi-dimensional, three-dimensional, lightweight, heat-insulating and shielding military tent fabric; when the surface coating is treated, the thickness of the anti-ultraviolet coating is 0.20mm, the thickness of the waterproof and oil-repellent coating is 0.40mm, the coating speed is 10 meters / minute, and the baking temperature is 110°C; when the inner shielding and absorbing coating is treated, the thickness of the coating is 0.40mm, and the baking temperature is 110°C; the high-temperature treatment temperature is 170°C.

[0119] Among them, the anti-UV additive was purchased from Shandong Jinyufeng New Materials Co., Ltd., and the waterproof and oil-repellent additive was purchased from Changzhou Youfang New Materials Technology Co., Ltd.

[0120] Among them, in the shielding and absorbing finishing agent, the nano shielding and absorbing powder accounts for 40 parts, the adhesive accounts for 8 parts, the dispersant accounts for 6 parts, and the rest is water, and the total mass of the above various components is 100 parts;

[0121] The adhesive is a high temperature resistant water-based polyurethane purchased from Guangzhou Ruilin New Materials Co., Ltd.; the dispersant is a water-based dispersant SYZ-8412 purchased from Dongguan Siyezi Plastic Co., Ltd.;

[0122] Among them, the nano-shielding absorbing powder contains 40 parts of silver, 30 parts of copper, 2 parts of nickel, 5 parts of MXene, 8 parts of graphene, 12 parts of barium ferrite, 1 part of carbon nanotubes, and 2 parts of carbonyl iron. The total mass of the above components is 100 parts.

[0123] Comparative Example 1

[0124] A flame-retardant shielding military tent fabric is prepared by recycling waste aramid fabric. In step 2, the undissolved loose aramid fabric is not treated in any way. The length of the recycled aramid fiber obtained after opening is 20 mm, which is difficult to spin normally and cannot be reused through the spinning and weaving processing flow.

[0125] Comparative Example 2

[0126] A flame-retardant shielding military tent fabric is prepared by recycling waste aramid fabric. No high-temperature treatment is performed in step 5, and the rest is the same as in Example 1.

[0127] The length of the recycled aramid fibers obtained in Examples 1-4 and Comparative Examples 1-2 was tested according to the standard GB / T 16257-2008 "Single Fiber Measurement Method for Determination of Short Fiber Length and Length Distribution of Textile Fibers"; the flame retardant and shielding military tent fabric prepared by recycling aramid fabric was washed 100 times in an A2 automatic washing machine with a neutral detergent according to the 4N method in GB / T 8629-2017, and then the shielding performance was tested in the band of 4GHz to 14GHz according to GJB 6190-2008 "Test Method for Shielding Effectiveness of Electromagnetic Shielding Materials", and the absorbing performance (emissivity) was characterized according to GJB 2038A-2011 "Test Method for Reflectivity of Radar Absorbing Materials"; the flame retardant and thermal insulation performance tests were carried out according to the standards GB 8965.1-2020 "Protective Clothing Flame Retardant Clothing" and GB 38453-2019 "Protective Clothing Thermal Insulation Clothing"; the flame retardant and thermal insulation performance tests were carried out according to GB / Z 27735-2022 "Camping Tents" evaluates the water seepage and weather resistance of tent fabrics. The test data is as follows:

[0128] Table 1 Performance index test results

[0129]

[0130] By comparing and analyzing the lengths of the aramid fibers recovered in Example 1 and Comparative Example 1, it can be seen that after treatment with the reagent, the main length of the recovered aramid fibers can be increased from 20 mm (Comparative Example 1) to 36 mm (Example 1), thus realizing the recycling and reprocessing of waste aramid fabrics.

[0131] By comparing and analyzing the test data of the flame-retardant shielding military tent fabrics prepared in Example 1 and Comparative Example 2, it can be seen that when the final tent fabric is not subjected to high-temperature treatment, the heat-expandable material evenly distributed in the tent fabric does not expand, resulting in a sharp decrease in the thermal protection coefficient of the tent fabric. The thermal protection coefficient of the protective material (Example 1) after thermal expansion is 2095kW·s / m 2 , the thermal protection coefficient of the unexpanded protective material (Comparative Example 2) is 1302kW·s / m 2, it can be seen that after the fabric is subjected to high temperature treatment, the thermal protection coefficient of the protective material after expansion can be increased by 60.9%. At the same time, by comparing and analyzing the thermal insulation performance, it is found that when the flame-retardant shielding military tent fabric is not subjected to high temperature treatment (Comparative Example 2), its convective heat conduction level is B2, the radiation heat conduction level is C2, and the contact heat conduction level is F1. After high temperature treatment and expansion, the convective heat conduction level of the fabric (Example 1) is B3, the radiation heat conduction level is C4, and the contact heat conduction level is F3, and its technical advantages are obvious. In addition, by comparing and analyzing the thermal protection and thermal insulation performance of Examples 1-5, its technical index values ​​are positively correlated with the content of the flame-retardant prefabricated filaments. It can be seen that the flame-retardant prefabricated filaments prepared by the present invention significantly improve the comprehensive performance of the fabric without increasing the technical difficulty.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for recycling waste aramid fabric to prepare flame-retardant shielding military tent fabric, characterized in that the steps include: Step 1, treating waste aramid fabric with ionic liquid: first, sterilize and cut the waste aramid fabric, place it in a solution containing ionic liquid and stir to dissolve it, take out the undissolved aramid fabric, wash it, dehydrate it and dry it, and filter the ionic liquid solution containing flame retardant viscose for later use; Step 2, flexible opening of aramid fabric and recovery of aramid fiber: spraying the undissolved loose aramid fabric in step 1 with an oil agent for pretreatment, and then opening it with an opening machine to obtain loose aramid fibers of a certain length, thereby obtaining recovered aramid fibers; Step 3, preparation of regenerated flame-retardant prefabricated filaments: adding a heat-expandable microsphere foaming agent to the ionic liquid solution dissolved with the flame-retardant viscose obtained in step 1, stirring to obtain a spinning solution, filtering and degassing the spinning solution in turn, and placing it in a wet spinning device, squeezing the spinning solution from a spinneret, and obtaining flame-retardant prefabricated filaments through processes such as coagulation, hot drawing, oiling, and packaging; Step 4, preparation of tent base fabric: the recycled aramid fiber obtained in step 2 is sequentially subjected to oiling and moistening, premixing, carding, drawing and roving processes to form aramid fiber roving; then the flame-retardant prefabricated filament obtained in step 3 is used as the core layer, and the outer layer is coated with the recycled aramid fiber to spin coaxial yarn, and the coaxial yarn is sequentially subjected to warping, sizing, reeding, weaving, and cloth repairing to obtain the tent base fabric; Step 5, preparation of heat-insulating and shielding military tent fabric: the surface layer of the tent base fabric obtained in step 4 is treated with anti-ultraviolet additives and waterproof and oil-repellent additives in turn, and then the inner layer of the base fabric is treated with a shielding and absorbing finishing agent, and finally subjected to high-temperature treatment to finally prepare a multi-dimensional three-dimensional lightweight heat-insulating and shielding military tent fabric.

2. The flame retardant and shielding military tent fabric prepared by recycling waste aramid fabric according to claim 1, characterized in that: The content of flame retardant viscose in the waste aramid fabric described in step 1 is 20 to 70 parts, the content of meta-aramid is 30 to 80 parts, the content of para-aramid is 5 to 20 parts, and the total mass of fiber is 100 parts; the dissolution temperature described in step 1 is 140° C. to 160° C., the stirring speed is 120 to 160 rpm, and the dissolution time is 12 min to 15 min; the washing time described in step 1 is 10 min to 15 min, the dehydration time is 58 min to 8 min, and the drying temperature is 180° C. to 200° C.

3. The flame retardant and shielding military tent fabric prepared by recycling waste aramid fabric according to claim 1, characterized in that: In the step 2, the mass ratio of the oil agent to the undissolved loosely structured aramid fabric is (2-5):100, and the pretreatment time is 18h-22h.

4. The method of recycling waste aramid fabric to prepare flame-retardant shielding military tent fabric according to claim 1, characterized in that: The oil agent in step 2 comprises a mixture of equal masses of hexadecyltrimethylammonium chloride, polyquaternium-7 and polyquaternium-10.

5. The method of recycling waste aramid fabric to prepare flame-retardant shielding military tent fabric according to claim 1, characterized in that: In the opening process described in step 2, the licker-in speed is 600-800 r / min, the cylinder speed is 360-420 r / min, the cover speed is 30-50 mm / min, and the doffer speed is 20-60 r / min. The main body length of the recycled aramid fiber described in step 2 is 30-36 mm.

6. The flame retardant and shielding military tent fabric prepared by recycling waste aramid fabric according to claim 1, characterized in that: In the step 3, the thermally expandable microsphere foaming agent accounts for 25 to 40 parts of the spinning solution, and the average particle size of the thermally expandable microsphere foaming agent is 300 nm to 400 nm.

7. The flame retardant and shielding military tent fabric prepared by recycling waste aramid fabric according to claim 1, characterized in that: In the hot stretching process described in step 3, the hot stretching temperature is 100° C. to 120° C., and the stretching ratio is 1.5 to 3.0 times; the linear density of the flame-retardant prefabricated filament described in step 3 is 4.44 tex to 11.11 tex.

8. The flame retardant and shielding military tent fabric prepared by recycling waste aramid fabric according to claim 1, characterized in that: In the yarn in step 4, the content of flame-retardant prefabricated filaments is 30 parts to 50 parts, and the content of recycled aramid fibers is 50 parts to 70 parts.

9. The flame retardant and shielding military tent fabric prepared by recycling waste aramid fabric according to claim 1, characterized in that: In the shielding and absorbing finishing agent described in step 5, nano-shielding and absorbing powder accounts for 30 to 60 parts, adhesive accounts for 5 to 10 parts, dispersant accounts for 5 to 10 parts, and the rest is water, and the total mass of the above components is 100 parts; in the nano-shielding and absorbing powder, silver accounts for 35 to 45 parts, copper accounts for 25 to 35 parts, nickel accounts for 1.5 to 5 parts, MXene accounts for 4 to 10 parts, graphene accounts for 6 to 10 parts, barium ferrite accounts for 10 to 15 parts, carbon nanotubes account for 0.5 to 2 parts, and carbonyl iron accounts for 0.5 to 3 parts, and the total mass of the above components is 100 parts.

10. The flame retardant and shielding military tent fabric prepared by recycling waste aramid fabric according to claim 1, characterized in that: When the surface coating described in step 5 is finished, the thickness of the anti-ultraviolet coating is 0.10mm~0.30mm, the thickness of the waterproof and oil-repellent coating is 0.20mm~0.50mm, the coating speed is 8m / min~12m / min, and the baking temperature is 100℃~120℃; when the inner shielding and absorbing coating described in step 5 is finished, the thickness of the coating is 0.20mm~0.50mm, and the baking temperature is 100℃~120℃; the high temperature treatment temperature is 160℃~180℃.

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