A method for producing short fibers from carbon fiber scraps

Abstract

The present invention provides a method for producing short fibers, comprising the following steps: conveying scraps from the production of pitch-based carbon fiber filaments and felts; cutting the scraps; secondary cutting; sorting by category; classified storage; automatic packaging; and dust disposal. Advantageously, the present invention achieves the recycling and utilization of waste generated during the production of pitch-based carbon fiber filaments and felts, thereby saving costs and increasing production efficiency. The recycled short fibers are used to prepare negative electrode materials, which, after being assembled into batteries, undergo electrical performance testing, demonstrating superior electrical performance compared to similar products.

Description

Technical Field

[0001] The present invention relates to the field of recycling scraps generated in the production process of asphalt-based carbon fiber yarns and felts, and in particular to a method for producing short fibers from asphalt-based carbon fiber yarn scraps. Background Art

[0002] In the fiber and textile industry, after mechanical or manual cutting according to product size, a large amount of scraps of different sizes are usually left over. Since the size of the remaining scraps does not meet the requirements of product manufacturing and becomes industrial waste, it is difficult to handle. Therefore, how to recycle these scraps has become a research trend in current technology. Pitch-based carbon fiber refers to a type of carbon fiber prepared by polymerization, spinning, infusibility, and carbonization using asphalt and other materials rich in polycyclic aromatic hydrocarbons as raw materials. High-performance asphalt-based carbon fiber has the advantages of high modulus, high heat transfer, high electrical conductivity and low thermal expansion coefficient, and can be used in high-tech fields such as aerospace and nuclear energy. Therefore, the recycling of asphalt-based carbon fiber has become a research focus of current technology.

[0003] Chinese patent application CN111809276A discloses a method for recycling and reusing planar fiber scraps. This method involves cutting the planar recycled material into small strips and sheets, then dispersing or breaking up the fibers. This method achieves fiber recovery from the scraps. The recovered short fibers are used to make needle-punched or non-needled fiber mats, with performance similar to that of new fiber products. However, the fiber size requirements for the recycled material used in the fiber mats are not very high, and the fiber size after cutting fluctuates significantly.

[0004] Chinese patent application CN106987926A discloses a method for preparing pitch-based carbon fibers, which is specifically implemented by the following steps: heating the pitch to 473-600K under an inert atmosphere; then applying a pressure of 0.1-0.65 MPa to spin hollow fibers, collecting the prepared fibers with a collection device, and adjusting process parameters to prepare a series of fibers; the series of fibers are sequentially cured, carbonized, and graphitized to produce a series of carbon fibers with excellent graphite structural characteristics. However, the preparation method of the above carbon fibers is complex and costly. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention provides a method for producing asphalt-based short fibers. The method cuts the scraps generated during the production of asphalt-based carbon fibers twice, and the obtained ultra-short materials of different sizes are classified and used to prepare negative electrode materials with better performance than similar products. The method realizes the recycling of waste materials, saves costs, and has high production efficiency.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] This application provides a method for producing short fibers, the specific steps of which are as follows:

[0008] (1) The scraps are cut into short fibers;

[0009] (2) further cutting the short fiber filaments in step (1) to obtain ultra-short fiber filaments;

[0010] (3) classifying, storing and packaging the ultrashort fibers obtained in step (2);

[0011] (4) The ultra-short material dust generated in step (2) and step (3) is collected, filtered and discharged through a purification system.

[0012] The length of the scrap in step (1) is 0.1 to 10 m, and the length of the short fiber is 0.1 to 3 mm;

[0013] The length of the ultra-short fiber filaments in step (2) is 0.1 to 100 μm.

[0014] Furthermore, the short fibers are asphalt-based short fibers.

[0015] Furthermore, the cutting rate in step (1) is 4 to 6 m / min, and the negative pressure is set to -0.5 to -0.05 MPa.

[0016] Furthermore, the length of the ultrashort fiber filaments in step (2) is 5 to 90 μm.

[0017] Furthermore, the length of the ultrashort fiber filaments in step (2) is 20 to 60 μm.

[0018] Furthermore, the cutting temperature in step (2) is set to 10-30° C., and the cutting rate is 1.5-2.5 m / min.

[0019] Furthermore, the classified storage in step (3) is vertical storage of multiple layers of materials with different mesh lengths.

[0020] Furthermore, the different mesh sizes are set as follows: first layer: 450-550 mesh, second layer: 750-850 mesh, third layer: 1050-1150 mesh, fourth layer: 1450-1550 mesh, fifth layer: 1950-2050 mesh.

[0021] Furthermore, the purification system in step (4) includes a dust collector, a centrifugal fan and a chimney.

[0022] Furthermore, the internal process of the dust collector is bag filtration, and the mesh number of the filter bag is set to 2400-2600 mesh.

[0023] Furthermore, the purification steps of the purification system are as follows: the centrifugal fan generates negative pressure to absorb the ultra-short material dust into the dust collector for filtration, and the filtered dust can be directly discharged to the outside, with a filtration efficiency between 95% and 98%.

[0024] Furthermore, the ultrashort fibers obtained by the method are used in the preparation of negative electrode materials.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention cuts the scraps generated during the production of asphalt-based carbon fibers twice, classifies the resulting ultra-short materials of different sizes, and uses them to prepare negative electrode materials. After assembling them into batteries, the electrical performance is tested, and the electrical performance is superior to that of similar products.

[0027] (2) The present invention realizes the recycling and utilization of asphalt-based short fiber waste, saves costs, has high production efficiency, and can be produced on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Create a process flow chart for staple fibers;

[0029] The markings in the figure are: 1- conveyor belt, 2- short fiber machine, 3- micro powder machine, 4- dust collector, 5- swing screen, 6- centrifugal fan, 7- chimney. DETAILED DESCRIPTION

[0030] It is worth noting that the raw materials used in the present invention are all common commercially available products, and their sources are not specifically limited.

[0031] Asphalt-based carbon fiber (Manufacturer: Henan Yongshun Da Trading Co., Ltd., Product No.: LQJ-0329).

[0032] Example 1

[0033] The steps for making short fibers from scraps are as follows:

[0034] (1) The scraps with a length of about 10 m were cut into short fiber filaments of about 2 mm using a short fiber machine. The cutting speed was set to 5 m / min and the negative pressure was set to -0.2 MPa.

[0035] (2) The short fiber filaments in step (1) are further cut by a micronizer to obtain ultra-short fiber filaments of about 45 μm, wherein the cutting rate is set to 2 m / min and the cutting temperature is set to 25° C.;

[0036] (3) The ultra-short material obtained in step (2) is sorted and collected through a swing screen, and then automatically packaged by a packaging machine, wherein the mesh size of each layer of the swing screen is set to: first layer: 500 mesh, second layer: 800 mesh, third layer: 1100 mesh, fourth layer: 1500 mesh, and fifth layer: 2000 mesh;

[0037] (4) The ultra-short material dust generated in step (2) and step (3) is sucked into a dust collector by a centrifuge, and discharged after being filtered through a bag, wherein the mesh number of the filter bag is set to 2500 mesh.

[0038] The specific steps for preparing lithium-ion batteries are as follows:

[0039] (1) Preparation of negative electrode materials:

[0040] The ultrashort fiber filaments obtained in step (2) of preparing short fibers from scraps of Example 1 were mixed with carbon black and a binder in a mass ratio of 7.5:2.5:1, and the mixture was ground evenly to obtain an electrode material. The electrode material was coated on a copper film with a doctor blade, and then vacuum dried to obtain a negative electrode material.

[0041] (2) Assembling the battery:

[0042] The negative electrode material prepared in the above steps is assembled with an electrolyte and a lithium positive electrode into a lithium ion battery;

[0043] (3) Performance testing:

[0044] The lithium-ion battery obtained in the above steps was cycled at a current density of 0.1 A / g to test the battery performance. The cycle performance of the battery is shown in Table 1. After 5 cycles, the discharge capacity was 391.2 mAh / g, and after 15 cycles, the discharge capacity was 375.2 mAh / g.

[0045] Example 2

[0046] The steps for making short fibers from scraps are as follows:

[0047] The cutting rate in step (1) was set to 6 m / min and the negative pressure was set to -0.1 MPa; the cutting rate in step (2) was set to 1.5 m / min and the cutting temperature was set to 15°C. The remaining steps were the same as in Example 1.

[0048] The specific steps for preparing lithium-ion batteries are as follows:

[0049] (1) Preparation of negative electrode materials:

[0050] The ultrashort fiber filaments obtained in step (2) of preparing short fibers from scraps of Example 2 were mixed with carbon black and a binder in a mass ratio of 7.5:2.0:1, and ground evenly to obtain an electrode material. The electrode material was coated on a copper film with a doctor blade, and then vacuum dried to obtain a negative electrode material;

[0051] (2) Assembling the battery:

[0052] The negative electrode material prepared in the above steps is assembled with an electrolyte and a lithium positive electrode into a lithium ion battery;

[0053] (3) Performance testing:

[0054] The lithium-ion battery obtained in the above steps was cycled at a current density of 0.1 A / g to test the battery performance. The cycle performance of the battery is shown in Table 1. After 5 cycles, the discharge capacity was 387.6 mAh / g, and after 15 cycles, the discharge capacity was 370.2 mAh / g.

[0055] Example 3

[0056] The steps for making short fibers from scraps are as follows:

[0057] The cutting rate in step (1) of making short fibers from scraps was set to 7 m / min and the negative pressure was set to -0.6 MPa; the cutting rate in step (2) was set to 1 m / min and the cutting temperature was set to 35°C. The remaining steps were the same as in Example 1.

[0058] (1) Preparation of negative electrode materials:

[0059] The ultrashort fiber filaments obtained in step (2) of preparing short fibers from scraps of Example 3 were mixed with carbon black and a binder in a mass ratio of 7.5:2.5:1, and ground evenly to obtain an electrode material. The electrode material was coated on a copper film with a doctor blade, and then vacuum dried to obtain a negative electrode material;

[0060] (2) Assembling the battery:

[0061] The negative electrode material prepared in the above steps is assembled with an electrolyte and a lithium positive electrode into a lithium ion battery;

[0062] (3) Performance testing:

[0063] The lithium-ion battery obtained in the above steps was cycled at a current density of 0.1 A / g to test the battery performance. The cycle performance of the battery is shown in Table 1. After 5 cycles, the discharge capacity was 369.2 mAh / g, and after 15 cycles, the discharge capacity was 353.2 mAh / g.

[0064] Comparative Example 1

[0065] In the step of preparing the lithium-ion battery in Example 1, the ultra-short fiber filaments were replaced with ordinary commercially available asphalt-based carbon fiber materials, and the remaining steps were the same as in Example 1. The resulting battery was cycled at a current density of 0.1 A / g to test the battery performance. The cycle performance of the battery is shown in Table 1. After 5 cycles, the discharge specific capacity was 371.2 mAh / g, and after 15 cycles, the discharge specific capacity was 355.2 mAh / g.

[0066] Table 1 Battery performance test results of products

[0067]

[0068]

[0069] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. An application of ultrashort fiber in preparing negative electrode materials, characterized in that: The method for producing the ultra-short fiber comprises the following steps: (1) The scraps are cut into short fiber yarns by a short fiber machine; (2) The short fiber filaments in step (1) are further cut by a micronizer to obtain ultra-short fiber filaments; (3) Classifying, storing and packaging the ultrashort fibers obtained in step (2); (4) collecting, filtering and discharging the ultra-short material dust generated in step (2) and step (3) through a purification system; The length of the scrap in step (1) is 0.1-10m, and the length of the short fiber is 0.1-3mm; The length of the ultrashort fiber in step (2) is 0.1-100 μm; The cutting speed in step (1) is 4-6 m / min, and the negative pressure is set to -0.5~-0.05 MPa; The cutting temperature in step (2) is set to 10-30°C and the cutting rate is 1.5-2.5 m / min; The scraps are scraps generated during the production process of asphalt-based carbon fibers.

2. The use according to claim 1, characterized in that: The length of the ultrashort fiber filaments in step (2) is 5-90 μm.

3. The use according to claim 2, characterized in that: The length of the ultrashort fiber filaments in step (2) is 20-60 μm.

4. The use according to claim 1, characterized in that: The classification and storage described in step (3) is vertical storage of multiple layers of materials with different mesh lengths.

5. The use according to claim 4, characterized in that: The different mesh sizes are set as follows: first layer: 450-550 mesh, second layer: 750-850 mesh, third layer: 1050-1150 mesh, fourth layer: 1450-1550 mesh, and fifth layer: 1950-2050 mesh.

6. The use according to claim 1, characterized in that: The purification system in step (4) includes a dust collector, a centrifugal fan and a chimney.

7. The use according to claim 6, characterized in that: The internal process of the dust collector is bag filtration, and the mesh number of the filter bag is set to 2400-2600 mesh.

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