Method for recycling high-quality aramid fiber from waste aramid fabric

Abstract

The invention relates to the field of aramid fabric recovery, in particular to a method for recovering high-quality aramid fiber from waste aramid fabric, which comprises the following steps: step 1, pretreatment of waste aramid fabric; 2, preparing the fluffy waste aramid fiber fabric; and 3, flexibly opening the fluffy waste aramid fiber fabric and recycling the aramid fiber. Through oiling agent treatment, expansion and loosening, opening equipment transformation and process optimization, the technical blank of recycling the aramid fibers from the existing waste pure aramid fabric is filled up, the waste aramid fibers with the maximum fiber length of 38mm are innovatively recycled, a material source is provided for spinning, weaving and reprocessing of the recycled aramid fibers, and the method is suitable for industrial production. The recycling value of the waste aramid fiber fabric is remarkably improved, and the recycling method is short in technological process, environmentally friendly and easy to industrialize.

Description

Technical Field

[0001] The invention relates to the field of aramid fabric recycling, and in particular to a method for recycling high-quality aramid fibers from waste aramid fabrics. Background Art

[0002] Aramid fiber is a new type of high-performance synthetic fiber prepared by spinning aromatic polyamide resin. It has excellent properties such as ultra-high strength, high modulus, high temperature resistance, acid and alkali resistance, and long life cycle. It is an important strategic raw material for national defense and military industry. The flame-retardant and high-temperature resistant aramid fabric developed using aramid fiber (meta-aramid-aramid 1313 and para-aramid-aramid 1414) has no smoldering, small damage length, no molten droplets in case of fire, no toxic substances, high temperature resistance, washing resistance, and wear resistance. It has excellent protective performance and good wearing comfort and has been widely used in personal safety protective clothing in the fields of military police, fire fighting, petrochemical, metallurgy, electricity, welding, etc.

[0003] According to the weight and aramid content of protective clothing in the market, the aramid content of a single set of clothing is expected to be between 0.5kg and 2.0kg. According to the number of people in various industries shown by the National Bureau of Statistics and the Global Network, based on the standard of 40% equipment ratio and an average annual quantity of 3 sets, the content of aramid fiber in flame-retardant fabrics in 2023 is estimated to be 14,000 tons. Considering the continued promotion and implementation of regulations / standards, the annual demand growth rate of aramid flame-retardant fabrics is expected to be 15%, and the content of aramid fiber in aramid textiles will reach 19,000 tons by 2025. At 200,000 yuan per ton of aramid fiber, the annual market value of aramid fabrics is as high as 3.8 billion yuan.

[0004] Due to the excellent flame retardancy and stable chemical properties of aramid fiber, it cannot be treated by incineration or landfilling, which is used in the treatment of ordinary waste textiles. Therefore, how to deeply realize the recycling of aramid fiber in a greener and more environmentally friendly way has received more and more attention. At the same time, since the price of aramid fiber is 6 to 10 times that of ordinary fiber, if the high-value recycling of aramid waste textiles can be achieved, it will also generate 6 to 10 times the economic benefits, and at the same time will further improve the resource utilization efficiency of the textile industry, promote the construction of ecological civilization, and improve my country's waste textile recycling system.

[0005] At present, there are two main technical approaches for recycling and reusing aramid fabrics. 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 relates to a method for preparing aramid pulp using scrapped bulletproof helmets, which belongs to the field of polymer material technology. First, the helmet is dismantled, cut and crushed into strips, then soaked in solvent and stripped off the resin attached to the fiber surface with a ball mill, and then the resin is removed by centrifugal separation, and finally the aramid fiber is subjected to decompression and grinding to obtain aramid pulp.

[0006] 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 provides a method for recovering aramid fibers from aramid fiber / phenolic resin composite waste, specifically placing the aramid fiber / phenolic resin composite material in a mixed recovery solution of phosphoric acid and glacial acetic acid, and placing it in a sealed reactor; reacting for 6 to 12 hours in an environment with a temperature of 150 to 200°C and a gas phase partial pressure of 2 to 4 MPa; washing the reaction product to obtain the recovered aramid fiber. This invention avoids the significant decline in various properties of aramid fibers under other recovery solvents and recovery conditions by improving the degradation ability of the mixed recovery solvent on phenolic resin. The strength retention rate is as high as 86.3%, and the length of the recovered aramid fiber is unclear.

[0007] In summary, the current recycling targets are mainly aramid composite materials, which are mainly prepared by physical and chemical recycling methods, such as fiber and aramid paper. At the same time, the process is long, the energy consumption is high, and the recycled fiber is short. The products formed by reprocessing are mainly activated carbon fabrics and composite materials. In addition, the oil agent for producing recycled fibers from waste textiles is limited to ordinary textiles such as pure cotton, and there are no corresponding products for the oil agent used for recycling waste aramid fabrics. It can be seen that the recycling of aramid fibers in waste aramid fabrics is blank. Summary of the invention

[0008] In view of the above-mentioned deficiencies of the prior art, the object of the present invention is to provide a method for recycling high-quality aramid fibers from waste aramid fabrics. The steps include:

[0009] Step 1: Pretreatment of waste aramid fabrics: First, disinfect and cut the waste aramid fabrics, spray them with aramid composite oil and let them stand to reduce the friction between the fibers of the aramid fabrics.

[0010] Step 2: Preparation of fluffy waste aramid fabric: After the waste aramid fabric treated with the aramid composite oil agent in step 1 is impregnated with a fluffy treatment agent, it is passed through a rolling mill and an oven in sequence, using a "one rolling and one baking" method to allow the fluffy treatment agent distributed in the fiber gaps to fully expand to obtain a loosely structured, fluffy waste aramid fabric.

[0011] Step 3: Flexible opening of fluffy waste aramid fabric and recovery of aramid fiber: The loose and fluffy aramid fabric is opened by an opening machine to obtain bulk aramid fiber, which is then washed and dried to obtain recycled aramid fiber.

[0012] Furthermore, the waste aramid fabric described in step 1 has a content of 40 to 95 parts of intermediate aramid, a content of 5 to 60 parts of para-aramid, and a total mass of aramid fibers of 100 parts, and is a pure aramid fabric.

[0013] Furthermore, the aramid composite oil agent in step 1 is an emulsion formed by stirring cetyltrimethylammonium chloride, polyquaternium-7, polyquaternium-10, graphene and Marktain 963.

[0014] Furthermore, in the aramid composite oil agent in step 1, the content of hexadecyltrimethylammonium chloride is 0.5 to 1.0 parts, the content of polyquaternium-7 is 0.3 to 0.7 parts, the content of polyquaternium-10 is 0.5 to 0.8 parts, the content of graphene is 0.4 to 0.7 parts, the content of Marktain 963 is 0.7 to 1.3 parts, and the rest is water.

[0015] Furthermore, in step 1, the mass ratio of the oil agent to the loosely structured fluffy aramid fabric is (2-5):100, and the pretreatment time is 18h-22h.

[0016] Furthermore, the wall material of the expanded microcapsules in step 2 is one of thermoplastic elastomer styrene divinyl benzene (SBC), thermoplastic polyurethane (TPU) and thermoplastic vulcanized rubber (TPV), and the core material is a mixture of equal mass of petroleum ether, propane, ethyl acetate and ethylene dichloride; the core material is a mixture of equal mass of petroleum ether, propane, ethyl acetate and ethylene dichloride.

[0017] Furthermore, in step 2, the fluffy treatment agent is an aqueous solution of expanded microcapsules, the content of the expanded microcapsules is 8 parts to 15 parts, and the rest is water.

[0018] Furthermore, in step 2, the baking temperature is 130° C. to 170° C., and the output speed of the waste aramid fabric is 5 m / min to 8 m / min.

[0019] Furthermore, the multi-tooth composite cylinder card clothing described in step 3 has a needle tooth tip thickness of 0.03 mm to 0.06 mm, a needle tooth depth of 0.32 mm to 0.37 mm, and a needle tooth working angle of 40° to 50°;

[0020] Furthermore, the multi-tooth composite doffer card clothing described in step 3 has a needle tooth depth of 2.4 mm to 2.8 mm and a needle tooth working angle of 30° to 40°.

[0021] Furthermore, in the opening process described in step 3, 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 50 r / min.

[0022] Furthermore, the washing temperature in step 3 is 85° C. to 95° C., the washing time is 3 min to 5 min, the drying temperature is 110° C. to 140° C., and the main body length of the recycled aramid fiber is 32 mm to 38 mm.

[0023] The beneficial effects of the present invention are:

[0024] In view of the characteristics of aramid fibers that are different from conventional fibers such as polyester and cotton, such as high rigidity, not easy to curl, easy to generate static electricity and small breaking elongation, the present invention mixes emulsifiers, surfactants and antistatic agents in a certain proportion to prepare an aramid composite oil agent, which significantly reduces the friction between aramid fibers, solves the technical problem of electrostatic adsorption and entanglement of aramid fibers, and fills the technical gap in oil agents for treating waste aramid fabrics.

[0025] When treating waste pure aramid fabric, the present invention first uses a fluffing treatment agent composed of an expanded microcapsule solution to impregnate the densely structured aramid fabric, so that the gaps between the fibers and yarns of the aramid fabric are filled with the expanded microcapsule solution, and innovatively bakes the expanded microcapsules to expand, and the expanded volume is 30 times the original volume. The elastic force (internal stress) generated can cause the densely arranged fibers and yarns to shift, and finally promotes the dense waste aramid fabric to form a loose structure, which is beneficial to the loosening of the pure waste aramid fabric.

[0026] It can be seen that the present invention fills the technical gap of recycling high-quality aramid fibers from existing waste aramid fabrics through oil treatment, expansion and loosening, and process optimization, and innovatively realizes the recycling of waste aramid fibers with a maximum fiber length of 38 mm, reduces the difficulty of spinning and weaving the fibers again, and improves the recycling value of aramid blended fabrics, so that the recycled aramid fibers can be recycled and used in textile and clothing products, thereby realizing the recycling of aramid fabrics; at the same time, the present technical scheme realizes the direct recycling of aramid fibers, with a short recycling process and no need to dissolve the fibers again through chemical reagents, which effectively saves energy consumption while improving the value of resource recycling and helps achieve the "dual carbon" goals. DETAILED DESCRIPTION

[0027] 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.

[0028] Step 1: Pretreatment of waste aramid fabrics: First, disinfect and cut the waste aramid fabrics, spray them with aramid composite oil and let them stand to reduce the friction between the fibers of the aramid fabrics.

[0029] Furthermore, the waste aramid fabric described in step 1 has a content of 40 to 95 parts of intermediate aramid, a content of 5 to 60 parts of para-aramid, and a total mass of aramid fibers of 100 parts, and is a pure aramid fabric.

[0030] Furthermore, the aramid composite oil agent in step 1 is an emulsion formed by stirring cetyltrimethylammonium chloride, polyquaternium-7, polyquaternium-10, graphene and Marktain 963.

[0031] Furthermore, in the aramid composite oil agent in step 1, the content of hexadecyltrimethylammonium chloride is 0.5 to 1.0 parts, the content of polyquaternium-7 is 0.3 to 0.7 parts, the content of polyquaternium-10 is 0.5 to 0.8 parts, the content of graphene is 0.4 to 0.7 parts, the content of Marktain 963 is 0.7 to 1.3 parts, and the rest is water.

[0032] Furthermore, in step 1, the mass ratio of the oil agent to the loosely structured fluffy aramid fabric is (2-5):100, and the pretreatment time is 18h-22h.

[0033] In this step, an aramid fiber is prepared by mixing an emulsifier (hexadecyltrimethylammonium chloride), a surfactant (polyquaternium-7 and polyquaternium-10) and an antistatic agent (graphene and Marktain 963) in a certain proportion, targeting the characteristics of the aramid fiber that are different from conventional fibers such as polyester and cotton, such as high rigidity, difficulty in curling, easy generation of static electricity and low elongation at break. The friction between the aramid fibers is significantly reduced, the technical problem of electrostatic adsorption and entanglement of the aramid fibers is solved, and the technical gap in the oil agent for treating waste aramid fabrics is filled.

[0034] Step 2: Preparation of fluffy waste aramid fabric: After the waste aramid fabric treated with the aramid composite oil agent in step 1 is impregnated with a fluffy treatment agent, it is passed through a rolling mill and an oven in sequence, using a "one rolling and one baking" method to allow the fluffy treatment agent distributed in the fiber gaps to fully expand to obtain a loosely structured, fluffy waste aramid fabric.

[0035] Furthermore, the wall material of the expanded microcapsules in step 2 is one of thermoplastic elastomer styrene divinyl benzene (SBC), thermoplastic polyurethane (TPU) and thermoplastic vulcanizate (TPV), and the core material is a mixture of petroleum ether, propane, ethyl acetate and ethylene dichloride of equal mass.

[0036] Furthermore, in step 2, the fluffy treatment agent is an aqueous solution of expanded microcapsules, the content of the expanded microcapsules is 8 parts to 15 parts, and the rest is water.

[0037] Furthermore, in step 2, the baking temperature is 130° C. to 170° C., and the output speed of the waste aramid fabric is 5 m / min to 8 m / min.

[0038] In this step, when treating waste pure aramid fabric, the fluffy treatment agent composed of expanded microcapsule solution is first used to impregnate the dense pure aramid fabric, and the fluffy treatment agent (expanded microcapsule solution) is filled in the gaps between the fibers and yarns of the aramid fabric. The core material of the expanded microcapsule (a mixture of petroleum ether, propane, ethyl acetate and dichloroethane of equal mass) is heated to cause the wall material (polyurethane elastomer) to expand, and its expanded volume is 30 times the original volume. The elastic force (internal stress) generated can cause the densely arranged fibers and yarns to move, and finally cause the dense waste aramid fabric to form a loose structure, which is beneficial to the loosening of the pure waste aramid fabric.

[0039] Step 3: Flexible opening of fluffy waste aramid fabric and recovery of aramid fiber: The loose and fluffy aramid fabric is opened by an opening machine to obtain bulk aramid fiber, which is then washed and dried to obtain recycled aramid fiber.

[0040] Furthermore, the multi-tooth composite cylinder card clothing described in step 3 has a needle tooth tip thickness of 0.03 mm to 0.06 mm, a needle tooth depth of 0.32 mm to 0.37 mm, and a needle tooth working angle of 40° to 50°;

[0041] Furthermore, the multi-tooth composite doffer card clothing described in step 3 has a needle tooth depth of 2.4 mm to 2.8 mm and a needle tooth working angle of 30° to 40°.

[0042] Furthermore, in the opening process described in step 3, 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 50 r / min.

[0043] Furthermore, the washing temperature in step 3 is 85° C. to 95° C., the washing time is 3 min to 5 min, the drying temperature is 110° C. to 140° C., and the main body length of the recycled aramid fiber is 32 mm to 38 mm.

[0044] This step uses a double-cylinder opening machine equipped with a multi-tooth composite cylinder needle cloth. By optimizing the opening process parameters, it breaks through the technical barrier of existing waste recycling opening technology with a fiber length of less than 30 mm, and innovatively realizes the recycling of waste aramid fibers with a maximum fiber length of 38 mm, reducing the difficulty of spinning and weaving the fibers again and improving the recycling value of aramid blended fabrics.

[0045] The present application is described in detail below in conjunction with the examples, but the present application is not limited to these examples. In the present invention, the antistatic agent Marktain 963 was purchased from Shanghai Jingdong Chemical Raw Materials Co., Ltd., the thermoplastic elastomer styrene divinylbenzene (SBC) was purchased from Shandong Gaotai Chemical Technology Co., Ltd., the thermoplastic polyurethane (TPU) was purchased from Lubrizol Specialty Chemicals (Shanghai) Co., Ltd., the thermoplastic vulcanized rubber (TPV) was purchased from Celanese Corporation of the United States, and petroleum ether, propane, ethyl acetate and ethylene dichloride were purchased from Tianjin Damao Chemical Reagent Factory.

[0046] Example 1

[0047] This embodiment provides a method for recycling high-quality aramid fibers from waste aramid fabrics, the steps comprising:

[0048] Step 1: Pretreatment of waste aramid fabrics: First, disinfect and cut the waste aramid fabrics, spray them with aramid composite oil and let them stand to reduce the friction between the fibers of the aramid fabrics.

[0049] Step 2: Preparation of fluffy waste aramid fabric: After the waste aramid fabric treated with the aramid composite oil agent in step 1 is impregnated with a fluffy treatment agent, it is passed through a rolling mill and an oven in sequence, using a "one rolling and one baking" method to allow the fluffy treatment agent distributed in the fiber gaps to fully expand to obtain a loosely structured, fluffy waste aramid fabric.

[0050] Step 3: Flexible opening of fluffy waste aramid fabric and recovery of aramid fiber: The loose and fluffy aramid fabric is opened by an opening machine equipped with a multi-tooth composite needle cloth and a double-cylinder structure to obtain bulk aramid fiber, which is then washed and dried to obtain recycled aramid fiber.

[0051] The content of the intermediate aramid in the waste aramid fabric in step 1 is 95 parts, the content of the para-aramid is 5 parts, and the total mass of the fiber is 100 parts; the aramid composite oil in the above step 1 is composed of hexadecyltrimethylammonium chloride, polyquaternium-7, polyquaternium-10, graphene and Marktain 963 stirred to form an emulsion; in step 1, the content of hexadecyltrimethylammonium chloride in the aramid composite oil agent is 0.5 parts, the content of polyquaternium salt-7 is 0.7 parts, the content of polyquaternium salt-10 is 0.8 parts, the content of graphene is 0.7 parts, the content of Marktain963 is 0.7 parts, and the rest is water; in step 1, the mass ratio of the oil agent to the loosely structured fluffy aramid fabric is 5:100, and the pretreatment time is 22h; the wall material of the microcapsule is thermoplastic polyurethane (TPU), and the core material is a mixture of petroleum ether, propane, ethyl acetate and ethylene dichloride of equal mass; in step 2, the fluffy treatment agent is an aqueous solution of expanded microcapsules, the content of expanded microcapsules is 15 parts, and the rest is water; The baking temperature in step 2 is 150°C, and the output speed of the waste aramid fabric is 8 m / min; the multi-tooth composite cylinder card clothing in step 3 has a needle tooth tip thickness of 0.03 mm, a needle tooth depth of 0.32 mm, and a needle tooth working angle of 40°; the multi-tooth composite doffer card clothing in step 3 has a needle tooth depth of 2.4 mm and a needle tooth working angle of 30°; the opening process in step 3 has a licker-in speed of 600 r / min, a cylinder speed of 360 r / min, a cover speed of 30 mm / min, and a doffer speed of 20 r / min; the washing temperature in step 3 is 95°C, the washing time is 3 min, the drying temperature is 110°C, and the main body length of the recovered aramid fiber is 38.0 mm.

[0052] Example 2

[0053] This embodiment provides a method for recycling high-quality aramid fibers from waste aramid fabrics, the steps comprising:

[0054] Step 1: Pretreatment of waste aramid fabrics: First, disinfect and cut the waste aramid fabrics, spray them with aramid composite oil and let them stand to reduce the friction between the fibers of the aramid fabrics.

[0055] Step 2: Preparation of fluffy waste aramid fabric: After the waste aramid fabric treated with the aramid composite oil agent in step 1 is impregnated with a fluffy treatment agent, it is passed through a rolling mill and an oven in sequence, using a "one rolling and one baking" method to allow the fluffy treatment agent distributed in the fiber gaps to fully expand to obtain a loosely structured, fluffy waste aramid fabric.

[0056] Step 3: Flexible opening of fluffy waste aramid fabric and recovery of aramid fiber: The loose and fluffy aramid fabric is opened by an opening machine equipped with a multi-tooth composite needle clothing and a double-cylinder structure to obtain bulk aramid fiber, i.e., to recover aramid fiber.

[0057] The waste aramid fabric in step 1 has an intermediate aramid content of 50 parts, a para-aramid content of 50 parts, and a total fiber mass of 100 parts; the aramid composite oil in step 1 is composed of hexadecyltrimethylammonium chloride, polyquaternium-7, polyquaternium-10, graphene and Marktain 963 stirred to form an emulsion; in step 1, the content of hexadecyltrimethylammonium chloride in the aramid composite oil agent is 1.0 part, the content of polyquaternium salt-7 is 0.3 part, the content of polyquaternium salt-10 is 0.5 part, the content of graphene is 0.4 part, the content of Marktain963 is 1.3 parts, and the rest is water; in step 1, the mass ratio of the oil agent to the loosely structured fluffy aramid fabric is 2:100, and the pretreatment time is 18h; the wall material of the microcapsule is styrene divinylbenzene (SBC), and the core material is a mixture of petroleum ether, propane, ethyl acetate and dichloroethane of equal mass; in step 2, the fluffy treatment agent is an aqueous solution of expanded microcapsules, the content of expanded microcapsules is 8 parts, and the rest is water; step The baking temperature in step 2 is 170°C, and the output speed of the waste aramid fabric is 5 m / min; the multi-tooth composite cylinder card clothing in step 3 has a needle tooth tip thickness of 0.06 mm, a needle tooth depth of 0.35 mm, and a needle tooth working angle of 45°; the multi-tooth composite doffer card clothing in step 3 has a needle tooth depth of 2.5 mm and a needle tooth working angle of 35°; in the opening process in step 3, the licker-in speed is 800 r / min, the cylinder speed is 360 r / min, the cover speed is 50 mm / min, and the doffer speed is 50 r / min; in step 3, the washing temperature is 85°C, the washing time is 5 min, the drying temperature is 140°C, and the main body length of the recovered aramid fiber is 32.0 mm.

[0058] Example 3

[0059] This embodiment provides a method for recycling high-quality aramid fibers from waste aramid fabrics, the steps comprising:

[0060] Step 1: Pretreatment of waste aramid fabrics: First, disinfect and cut the waste aramid fabrics, spray them with aramid composite oil and let them stand to reduce the friction between the fibers of the aramid fabrics.

[0061] Step 2: Preparation of fluffy waste aramid fabric: After the waste aramid fabric treated with the aramid composite oil agent in step 1 is impregnated with a fluffy treatment agent, it is passed through a rolling mill and an oven in sequence, using a "one rolling and one baking" method to allow the fluffy treatment agent distributed in the fiber gaps to fully expand to obtain a loosely structured, fluffy waste aramid fabric.

[0062] Step 3: Flexible opening of fluffy waste aramid fabric and recovery of aramid fiber: The loose and fluffy aramid fabric is opened by an opening machine equipped with a multi-tooth composite needle clothing and a double-cylinder structure to obtain bulk aramid fiber, i.e., to recover aramid fiber.

[0063] The waste aramid fabric in step 1 has an intermediate aramid content of 80 parts, a para-aramid content of 20 parts, and a total fiber mass of 100 parts; the aramid composite oil in step 1 is composed of hexadecyltrimethylammonium chloride, polyquaternium-7, polyquaternium-10, graphene and Marktain 963 stirred to form an emulsion; in the aramid composite oil in step 1, the content of hexadecyltrimethylammonium chloride is 0.8 parts, the content of polyquaternium salt-7 is 0.5 parts, the content of polyquaternium salt-10 is 0.6 parts, the content of graphene is 0.5 parts, the content of Marktain963 is 1.0 parts, and the rest is water; in step 1, the mass ratio of the oil to the loosely structured fluffy aramid fabric is 3:100, and the pretreatment time is 20h; the wall material of the microcapsule is thermoplastic vulcanized rubber (TPV), and the core material is a mixture of petroleum ether, propane, ethyl acetate and ethylene dichloride of equal mass; in step 2, the fluffy treatment agent is an aqueous solution of expanded microcapsules, the content of expanded microcapsules is 10 parts, and the rest is water; The baking temperature in step 2 is 140°C, and the output speed of the waste aramid fabric is 7 m / min; the multi-tooth composite cylinder card clothing in step 3 has a needle tooth tip thickness of 0.05 mm, a needle tooth depth of 0.34 mm, and a needle tooth working angle of 43°; the multi-tooth composite doffer card clothing in step 3 has a needle tooth depth of 2.4 mm and a needle tooth working angle of 30°; in the opening process in step 3, the licker-in speed is 720 r / min, the cylinder speed is 400 r / min, the cover speed is 40 mm / min, and the doffer speed is 40 r / min; in step 3, the washing temperature is 90°C, the washing time is 4 min, the drying temperature is 120°C, and the main body length of the recovered aramid fiber is 36.4 mm.

[0064] Example 4

[0065] This embodiment provides a method for recycling high-quality aramid fibers from waste aramid fabrics, the steps comprising:

[0066] Step 1: Pretreatment of waste aramid fabrics: First, disinfect and cut the waste aramid fabrics, spray them with aramid composite oil and let them stand to reduce the friction between the fibers of the aramid fabrics.

[0067] Step 2: Preparation of fluffy waste aramid fabric: After the waste aramid fabric treated with the aramid composite oil agent in step 1 is impregnated with a fluffy treatment agent, it is passed through a rolling mill and an oven in sequence, using a "one rolling and one baking" method to allow the fluffy treatment agent distributed in the fiber gaps to fully expand to obtain a loosely structured, fluffy waste aramid fabric.

[0068] Step 3: Flexible opening of fluffy waste aramid fabric and recovery of aramid fiber: The loose and fluffy aramid fabric is opened by an opening machine equipped with a multi-tooth composite needle clothing and a double-cylinder structure to obtain bulk aramid fiber, i.e., to recover aramid fiber.

[0069] The waste aramid fabric in step 1 has an intermediate aramid content of 40 parts, an intermediate aramid content of 60 parts, and a total fiber mass of 100 parts; the aramid composite oil in step 1 is an emulsion formed by stirring hexadecyltrimethylammonium chloride (emulsifier), polyquaternium-7, polyquaternium-10, graphene, and Marktain 963; the aramid composite oil in step 1 has an intermediate aramid content of 40 parts, an intermediate aramid content of 60 parts, and a total fiber mass of 100 parts; the aramid composite oil in step 1 has an intermediate aramid content of 0.6 parts, a para-aramid content of 0.5 parts, a para-aramid content of 0.8 parts, a graphene content of 0.6 parts, and a Marktain The content of 963 is 1.2 parts, and the rest is water; in step 1, the mass ratio of the oil agent to the loosely structured fluffy aramid fabric is 4:100, and the pretreatment time is 20 hours; the wall material of the microcapsule is thermoplastic polyurethane (TPU), and the core material is a mixture of petroleum ether, propane, ethyl acetate and dichloroethane of equal mass; in step 2, the fluffy treatment agent is an aqueous solution of expanded microcapsules, the content of expanded microcapsules is 12 parts, and the rest is water; in step 2, the baking temperature is 130°C, and the output speed of the waste aramid fabric is 6 meters / minute; in step 3, the multi-tooth composite cylinder needle clothing, the needle teeth The tip thickness is 0.04mm, the needle tooth depth is 0.35mm, and the needle tooth working angle is 40°; the multi-tooth composite doffer needle clothing in step 3 has a needle tooth depth of 2.6mm and a needle tooth working angle of 40°; in the opening process in step 3, the licker-in speed is 680r / min, the cylinder speed is 360r / min, the cover speed is 35mm / min, and the doffer speed is 24r / min; in step 3, the washing temperature is 95°C, the washing time is 4min, the drying temperature is 130°C, and the main body length of the recovered aramid fiber is 34.5mm.

[0070] Comparative Example 1

[0071] A method for recovering aramid fibers from waste aramid fabrics, wherein in step 1, no aramid composite oil agent is sprayed on the waste aramid fabrics, and the rest is the same as in embodiment 1.

[0072] Comparative Example 2

[0073] A method for recycling aramid fibers from waste aramid fabrics, according to the process conditions of Example 1 in the specification of invention patent CN 113802375 B, 70 parts of light white oil W2-40, 25 parts of polyoxyethylene (9) laurate and 5 parts of stearic acid are taken, mixed, and stirred at a speed of 900 rpm for 35 minutes. The prepared oil replaces the aramid composite oil in Example 1 of the present invention, and the rest is the same as Example 1.

[0074] Comparative Example 3

[0075] A method for recovering aramid fibers from waste aramid fabrics, wherein the content of expanded microcapsules in step 2 is 0 parts, and the rest is the same as in embodiment 1.

[0076] The aramid fibers recovered in Examples 1-4 and Comparative Examples 1-3 were tested for their fiber lengths according to standard GB / T 16257-2008 “Determination of length and length distribution of textile staple fibers - Single fiber measurement method”, and the breaking strength of the original aramid fibers and the recycled aramid fibers was tested according to standard GB / T 14337-2022 “Test method for tensile properties of chemical staple fibers”, and their strength damage rates were calculated. The measured data are shown in Table 1.

[0077] Table 1 Recycled aramid fiber test data

[0078] project Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Body length (mm) 38.0 32.0 36.4 34.5 17.2 19.4 23.5 Breaking strength loss rate (%) 2.3 3.8 2.6 3.2 9.4 8.6 7.7

[0079] By comparing and analyzing the lengths of the aramid fibers recovered in Example 1 and Comparative Example 1, it can be seen that when the waste aramid fabric is not sprayed with the aramid composite oil agent, the main body length of the recovered aramid fiber tested is 17.2 mm, and the breaking strength loss rate is 9.4%. It can be seen that after spraying the aramid composite oil agent, the friction between the fibers is reduced to a certain extent, and the main body length of the recovered aramid fiber can be increased from 17.2 mm (Comparative Example 1) to 38 mm (Example 1), and the breaking strength loss rate is reduced from 9.4% to 2.3%, thereby achieving high-quality recovery of aramid fibers from waste aramid fabrics.

[0080] By comparing and analyzing the lengths of the aramid fibers recovered in Example 1 and Comparative Example 2, it can be seen that when the oil prepared by the prior art is sprayed on the waste aramid fabric, the main body length of the recovered aramid fiber tested is 19.4 mm, and the breaking strength loss rate is 8.6%. It can be seen that due to the large difference in performance between aramid fiber and ordinary fiber, the oil prepared by the prior art is not suitable for the recovery of aramid fibers of waste aramid fabrics. When the aramid composite oil unique to the aramid fiber of the present invention is sprayed, it is more conducive to the improvement of the friction and electrostatic effect between the aramid fibers, and the main body length of the recovered aramid fiber can be increased from 19.4 mm (Comparative Example 2) to 38 mm (Example 1), and the breaking strength loss rate is reduced from 8.6% to 2.3%, thereby achieving high-quality recovery of aramid fibers of waste aramid fabrics.

[0081] By comparing and analyzing the lengths of the aramid fibers recovered in Example 1 and Comparative Example 3, it can be seen that when the waste aramid fabric is not impregnated with the bulking agent (expanded microcapsule solution), the main body length of the recovered aramid fiber tested is 23.5 mm, and the breaking strength loss rate is 7.7%. It can be seen that when the waste aramid fabric is not impregnated with the bulking agent (expanded microcapsule solution), the structure of the waste aramid fabric is dense, and the subsequent opening treatment is likely to cause the fiber to break, resulting in a significant decrease in fiber length; after the bulking agent (expanded microcapsule solution) is sprayed and impregnated, the effect of the expanded microcapsules can be used to form a fluffy, loosely structured waste aramid fabric, which is beneficial to fiber opening and reduces the degree of fiber damage. The main body length of the recovered aramid fiber can be increased from 23.5 mm (Comparative Example 2) to 38 mm (Example 1), and the breaking strength loss rate is reduced from 7.7% to 2.3%, thereby achieving high-quality recovery of aramid fibers from waste aramid fabrics.

[0082] 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 recovering high-quality aramid fibers from waste aramid fabrics, characterized in that the steps include: Step 1, pretreatment of waste aramid fabric: first, the waste aramid fabric is disinfected and cut, and then sprayed with aramid composite oil for pretreatment; Step 2, preparation of fluffy waste aramid fabric: the waste aramid fabric treated with the aramid composite oil agent in step 1 is impregnated with a fluffy treatment agent, and then passed through a padder and a baking device in sequence to obtain a fluffy waste aramid fabric; Step 3, flexible opening of fluffy waste aramid fabric and recovery of aramid fiber: loose and fluffy waste aramid fabric is opened to obtain bulk aramid fiber, and then the recycled aramid fiber is obtained after washing and drying.

2. The method for recovering high-quality aramid fibers from waste aramid fabrics according to claim 1, characterized in that: The waste aramid fabric described in step 1 has a content of 40 to 95 parts of intermediate aramid, a content of 5 to 60 parts of para-aramid, and a total mass of aramid fibers of 100 parts, and is a pure aramid fabric.

3. The method for recovering high-quality aramid fibers from waste aramid fabrics according to claim 1, characterized in that: In the step 1, the aramid composite oil agent is an emulsion formed by stirring cetyltrimethylammonium chloride, polyquaternium-7, polyquaternium-10, graphene and Marktain 963.

4. The method for recovering high-quality aramid fibers from waste aramid fabrics according to claim 3, characterized in that: The composite oil agent contains 0.5 to 1.0 parts of hexadecyltrimethylammonium chloride, 0.3 to 0.7 parts of polyquaternium-7, 0.5 to 0.8 parts of polyquaternium-10, 0.4 to 0.7 parts of graphene, 0.7 to 1.3 parts of Marktain963, and the rest is water.

5. The method for recovering high-quality aramid fibers from waste aramid fabrics according to claim 1, characterized in that: In the step 1, the mass ratio of the aramid composite oil agent to the aramid fabric is (2-5):100, and the pretreatment time is 18h-22h.

6. The method for recovering high-quality aramid fibers from waste aramid fabrics according to claim 1, characterized in that: The fluffy treatment agent in step 2 is an expanded microcapsule solution, the expanded microcapsule content is 8 to 15 parts, and the rest is water; the wall material of the expanded microcapsule in step 2 is one of thermoplastic elastomer styrene divinyl benzene, thermoplastic polyurethane and thermoplastic vulcanized rubber, and the core material is a mixture of petroleum ether, propane, ethyl acetate and ethylene dichloride of equal mass.

7. The method for recovering high-quality aramid fibers from waste aramid fabrics according to claim 1, characterized in that: In the step 2, the baking temperature is 130° C. to 170° C., and the output speed of the waste aramid fabric is 5 m / min to 8 m / min.

8. The method for recovering high-quality aramid fibers from waste aramid fabrics according to claim 1, characterized in that: The cylinder card clothing described in step 3 has a needle tooth tip thickness of 0.03mm-0.06mm, a needle tooth depth of 0.32mm-0.37mm, and a needle tooth working angle of 40°-50°; the doffer card clothing in step 3 has a needle tooth depth of 2.4mm-2.8mm, and a needle tooth working angle of 30°-40°.

9. The method for recovering high-quality aramid fibers from waste aramid fabrics according to claim 1, characterized in that: In the opening process described in step 3, the licker-in speed is 600r / min-800r / min, the cylinder speed is 360r / min-420r / min, the cover speed is 30mm / min-50mm / min, and the doffer speed is 20r / min-50r / min.

10. The method for recovering high-quality aramid fibers from waste aramid fabrics according to claim 1, characterized in that: The washing temperature in step 3 is 85° C. to 95° C., the washing time is 3 min to 5 min, the drying temperature is 110° C. to 140° C., and the main body length of the recovered aramid fiber is 32 mm to 38 mm.