A method for recycling meta-aramid fiber waste

Abstract

The application provides a meta-aramid fiber waste silk recycling method, which comprises the following steps: dissolving meta-aramid fiber waste silk in a double solvent system composed of N,N-dimethylformamide and acetone, the ratio of the mass of meta-aramid fiber waste silk to the total volume of the double solvent system being (1-2) g:(8.3-33.3) mL, then adding lithium chloride until complete dissolution to obtain an electrospinning stock solution; electrospinning the electrospinning stock solution under the condition that the rotating speed is 50-150 rpm and the relative humidity is 40%-50% to obtain a spinning fiber; removing the excess double solvent system from the spinning fiber to obtain regenerated meta-aramid nanofiber with a wrinkle structure, a large number of interconnected pores exist in the interior, particulate pollutants (PMs) can be effectively intercepted, PMs can be removed from the pollution source, and the regenerated meta-aramid nanofiber can be applied in the field of high-temperature air filtration and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of meta-aramid fiber recycling, in particular to a meta-aramid fiber waste silk recycling method. BACKGROUND

[0002] Meta-aramid fiber generally has excellent mechanical properties and thermal stability, and its structural composite materials (such as honeycomb structure) can be used to replace metal materials for lightweight structure weight reduction field, so it is widely used in aerospace and military fields, and is a strategic key material that cannot be replaced.

[0003] With the continuous expansion of meta-aramid fiber production line scale and output, waste from waste fiber silk, stripped silk from waste optical cable and waste aramid rope, etc. cause waste of meta-aramid fiber. Because meta-aramid fiber is difficult to be degraded in the environment, the pollution problem caused by its waste has gradually emerged.

[0004] At present, there is no relevant report on recycling of waste meta-aramid fiber silk, stripped silk from waste optical cable and other waste materials. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a meta-aramid fiber waste silk recycling method, which has a three-dimensional net-like structure and a large number of interconnected pores inside, can effectively intercept particulate pollutants (PMs), remove PMs from the pollution source, and can be applied in the field of high-temperature air filtration.

[0006] The present application is realized by the following technical scheme:

[0007] A meta-aramid fiber waste silk recycling method, comprising the following steps:

[0008] S1, dissolve the meta-aramid fiber waste silk in a double solvent system composed of N,N-dimethylformamide and acetone, the ratio of the mass of meta-aramid fiber waste silk to the total volume of the double solvent system is (1-2) g:(8.3-33.3) mL, then add lithium chloride until completely dissolved, to obtain an electrospinning stock solution;

[0009] S2, electrospinning the electrospinning stock solution under the condition of a rotation speed of 50-150 rpm and a relative humidity of 40%-50%, to obtain a spinning fiber;

[0010] S3, remove the excess double solvent system from the spinning fiber, to obtain regenerated meta-aramid nanofiber with a wrinkle structure.

[0011] Preferably, in S1, the temperature of the double solvent system composed of N,N-dimethylformamide and acetone is 60-100℃.

[0012] Preferably, in S1, the mass ratio of meta-aramid fiber waste silk and lithium chloride is 5:2.

[0013] Preferably, in S1, the meta-aramid fiber waste silk and lithium chloride are stirred for 12-36h after being added.

[0014] Preferably, in S1, the volume ratio of N,N-dimethylformamide and acetone is (1-3):1.

[0015] Preferably, in S2, the positive voltage of electrospinning is 10-20kV, applied to the needle tip of the syringe, and the negative voltage is 10-20kV, applied to the collector.

[0016] Further, in S2, the collector is covered with an aluminum foil, and the distance between the needle tip of the syringe and the aluminum foil is 10-20cm.

[0017] Preferably, in S2, the flow rate of the electrospinning solution is 0.1-0.3mL / h.

[0018] Preferably, in S2, the temperature of electrospinning is 20-25℃, and the electrospinning is carried out at the temperature for 12-24h to obtain the spinning fiber.

[0019] Preferably, in S3, the spinning fiber is dried in a vacuum at 0.05-0.08MPa and at 60-100℃ for 12-24h to obtain the regenerated meta-aramid nanofiber with a wrinkle structure.

[0020] Compared with the prior art, the present application has the following beneficial technical effects:

[0021] The present application is a method for recycling meta-aramid fiber waste silk. In view of the stable structure and acid and alkali resistance of meta-aramid fiber waste, the meta-aramid fiber waste silk is dissolved in a DMF / acetone mixed solvent with the assistance of LiCl to form a spinning solution. Due to the difference in volatility of the DMF and acetone solvents, the solvent vapor condenses and adheres to the fiber surface due to rapid evaporation, causing the fiber to be in a thermodynamic unstable state, and thus phase separation occurs on the fiber surface, thereby preparing a regenerated meta-aramid nanofiber with a wrinkle structure on the surface. The present application solves the problems of waste and pollution of meta-aramid fiber waste, and also obtains a regenerated meta-aramid nanofiber membrane with a wrinkle structure. The membrane has a three-dimensional network structure and a large number of interconnected pores inside, can effectively intercept particulate pollutants (PMs), removes PMs from the source of pollution, and can be applied in the field of high-temperature air filtration, thus having good application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Scanning electron microscope image of the regenerated meta-aramid nanofiber obtained in Example 1 of the present application.

[0023] Figure 2 Scanning electron microscope image of regenerated meta-aramid nanofiber obtained from Example 2 of the present application.

[0024] Figure 3 Scanning electron microscope image of regenerated meta-aramid nanofiber obtained from Example 3 of the present application. DETAILED DESCRIPTION

[0025] The present application will be further described in conjunction with specific examples, which are intended to explain but not limit the present application.

[0026] The present application is a method for recycling meta-aramid fiber waste (waste refers to discarded filaments), the specific steps are as follows:

[0027] (1) Dissolve 1-2 g of meta-aramid fiber waste in 8.3-33.3 mL of N,N-dimethylformamide (DMF) / acetone double solvent system at 60-100°C, and add lithium chloride (LiCl), the mass ratio of meta-aramid fiber waste to LiCl is 5:2, stir for 12-36 h until all dissolved, wherein the volume ratio of DMF to acetone is (1-3):1, to prepare an electrospinning stock solution with a polymer mass percentage of 6-12%.

[0028] (2) Place the electrospinning stock solution in a 10 mL syringe, which is equipped with a steel needle with an inner diameter of 0.2-0.4 mm. Apply a positive voltage of 10-20 kV to the tip of the syringe, and apply a negative voltage of 10-20 kV to the collector.

[0029] The collector is covered with aluminum foil and placed 10-20 cm away from the needle tip. The collector rotates at a speed of 50-150 rpm, and the spinning solution flows at a rate of 0.1-0.3 mL / h. The temperature and relative humidity in the electrospinning device are maintained at 20-25°C and 40-50%, respectively. Continuous spinning is carried out for 12-24 h, and the regenerated meta-aramid nanofiber after spinning is denoted as r-ANF.

[0030] (3) Dry the r-ANF obtained by electrospinning in a vacuum oven at 60-100°C under a vacuum degree of 0.05-0.08 MPa for 12-24 h to remove excess solvent, and finally obtain r-ANF with a pleated structure.

[0031] Example 1:

[0032] The present application is a method for recycling meta-aramid fiber waste, the specific steps are as follows:

[0033] (1) 1 g of meta-aramid fiber waste silk was dissolved in 8.3 mL of N, N- dimethylformamide (DMF) / acetone double solvent system at 80°C, and lithium chloride (LiCl) was added, the mass ratio of meta-aramid fiber waste silk to LiCl was 5:2, and stirring was carried out for 24 h until complete dissolution, wherein the volume ratio of DMF to acetone was 2:1, and an electrospinning stock solution with a polymer mass percentage of 10% was prepared.

[0034] (2) The electrospinning stock solution was placed in a 10 mL syringe equipped with a steel needle with an inner diameter of 0.33 mm. A positive voltage of 15 kV was applied to the needle tip of the syringe, and a negative voltage of 10 kV was applied to the collector.

[0035] The collector was covered with aluminum foil and placed 15 cm away from the needle tip. The rotation speed of the collector was 100 rpm, and the flow rate of the spinning solution was 0.2 mL / h. The temperature and relative humidity in the electrospinning device were maintained at 25°C and 50%, respectively. Continuous spinning was carried out for 12 h, and the regenerated meta-aramid nanofiber after spinning was denoted as r-ANF-1.

[0036] (3) The r-ANF-1 obtained by electrospinning was placed in a 60°C vacuum oven at a vacuum degree of 0.06 MPa for 24 h to remove excess solvent, and finally the r-ANF-1 with a wrinkle structure was obtained.

[0037] Figure 1 The scanning electron microscope image of the regenerated meta-aramid nanofiber obtained in this example showed that the surface of r-ANF-1 produced a partial wrinkle structure, and the fiber surface was relatively rough.

[0038] Example 2:

[0039] The specific steps of the method for recycling meta-aramid fiber waste silk according to the present application are as follows:

[0040] (1) 2 g of meta-aramid fiber waste silk was dissolved in 25 mL of N, N- dimethylformamide (DMF) / acetone double solvent system at 60°C, and lithium chloride (LiCl) was added, the mass ratio of meta-aramid fiber waste silk to LiCl was 5:2, and stirring was carried out for 12 h until complete dissolution, wherein the volume ratio of DMF to acetone was 1:1, and an electrospinning stock solution with a polymer mass percentage of 8% was prepared.

[0041] (2) The electrospinning stock solution was placed in a 10 mL syringe equipped with a steel needle with an inner diameter of 0.2 mm. A positive voltage of 10 kV was applied to the needle tip of the syringe, and a negative voltage of 15 kV was applied to the collector.

[0042] The collector was covered with aluminum foil and placed 10 cm away from the needle tip. The collector rotated at 50 rpm, and the spinning solution flowed at a rate of 0.1 mL / h. The temperature and relative humidity in the electrospinning device were maintained at 22°C and 46%, respectively. Continuous spinning was performed for 18 h, and the regenerated meta-aramid nanofiber after spinning was denoted as r-ANF-2.

[0043] (3) The r-ANF-2 obtained by electrospinning was placed in a vacuum oven at 70°C under a vacuum degree of 0.05 MPa for 12 h to remove excess solvent, and finally r-ANF-2 with a wrinkle structure was obtained.

[0044] Figure 2 The scanning electron microscope image of the regenerated meta-aramid nanofiber obtained in this example is shown in the figure. As can be seen from the figure, a large number of wrinkle structures are generated on the surface of r-ANF-2, and the fiber surface is the roughest.

[0045] Example 3:

[0046] The specific steps of the method for recycling meta-aramid fiber waste silk according to the present application are as follows:

[0047] (1) 1.5 g of meta-aramid fiber waste silk was dissolved in a 12.5 mL N,N-dimethylformamide (DMF) / acetone double solvent system at 100°C, and lithium chloride (LiCl) was added. The mass ratio of meta-aramid fiber waste silk to LiCl was 5:2, and the solution was stirred for 36 h until all the meta-aramid fiber waste silk was dissolved. The volume ratio of DMF to acetone was 3:1, and an electrospinning stock solution with a polymer mass percentage of 12% was prepared.

[0048] (2) The electrospinning stock solution was placed in a 10 mL syringe equipped with a steel needle with an inner diameter of 0.4 mm. A positive voltage of 20 kV was applied to the needle tip of the syringe, and a negative voltage of 20 kV was applied to the collector.

[0049] The collector was covered with aluminum foil and placed 20 cm away from the needle tip. The collector rotated at 150 rpm, and the spinning solution flowed at a rate of 0.3 mL / h. The temperature and relative humidity in the electrospinning device were maintained at 20°C and 40%, respectively. Continuous spinning was performed for 24 h, and the regenerated meta-aramid nanofiber after spinning was denoted as r-ANF-3.

[0050] (3) The r-ANF-3 obtained by electrospinning was placed in a vacuum oven at 80°C under a vacuum degree of 0.08 MPa for 18 h to remove excess solvent, and finally r-ANF-3 with a wrinkle structure was obtained.

[0051] Figure 3 The scanning electron microscope image of the regenerated meta-aramid nanofiber obtained in this example is shown in the figure. As can be seen from the figure, the wrinkle structure on the surface of r-ANF-3 is less, and the fiber surface is smoother.

Claims

1. A method for recycling meta-aramid fiber waste, characterized by, The method comprises the following steps: S1, dissolving meta-aramid fiber waste in a 60-100℃ double solvent system composed of N,N-dimethylformamide and acetone, the ratio of the mass of meta-aramid fiber waste to the total volume of the double solvent system being (1-2) g:(8.3-33.3) mL, the volume ratio of N,N-dimethylformamide to acetone being (1-3):1, then adding lithium chloride until completely dissolved, the mass ratio of meta-aramid fiber waste to lithium chloride being 5:2, to obtain an electrospinning stock solution; S2, electrospinning the electrospinning stock solution under the conditions of a rotation speed of 50-150 rpm and a relative humidity of 40%-50%, the flow rate of the electrospinning stock solution being 0.1-0.3 mL / h, the positive voltage of electrospinning being 10-20 kV, applied to the needle tip of the syringe, the negative voltage being 10-20 kV, applied to the collector, the temperature of electrospinning being 20-25℃, and electrospinning for 12-24 h at the temperature to obtain a spinning fiber; S3, vacuum drying the spinning fiber at 60-100℃ under a pressure of 0.05-0.08 MPa for 12-24 h to obtain regenerated meta-aramid nanofiber with a pleated structure.

2. The meta-aramid fiber floc reclaiming method according to claim 1, characterized by, In S1, after adding lithium chloride, stirring is performed for 12-36 h to obtain the electrospinning stock solution.

3. The meta-aramid fiber floc reclaiming method according to claim 1, characterized by, In S2, the collector is covered with aluminum foil, and the distance between the needle tip of the syringe and the aluminum foil is 10-20 cm.

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