Large tow carbon fiber precursor washing device and washing method

Abstract

The application discloses a kind of large tow carbon fiber precursor washing device and washing method, device includes multiple washing units, each washing unit includes washing tank, spraying unit, pump and drafting roller group, the drainage end of pump is connected with the spraying unit being arranged above washing tank by liquid discharge pipe, and the spraying pipe of spraying unit is arranged towards the fiber on drafting roller group;Method includes 1) device parameter adjustment;2) fiber washing, complete washing and enter next process.The scheme of the present application solves the uniformity of 24K or more large tow precursor washing and the high efficiency of washing, reduces the residue of solvent in nascent fiber.The large tow precursor obtained by the washing method of the present application has low solvent residue, and can achieve uniform solvent residue in each fiber of large tow precursor, and can ensure that the solvent residue uniformity of large tow precursor between different spinning positions on a production line in industrial production.

Description

Technical Field

[0001] This invention relates to the field of polyacrylonitrile fiber manufacturing technology, specifically to a washing device and method for large-tow carbon fiber precursors. Background Technology

[0002] Carbon fiber, hailed as the king of new materials, plays an increasingly important role in my country's industrial restructuring and the upgrading of traditional materials due to its superior performance. The surge in demand for large-tow carbon fiber has spurred continuous breakthroughs in its preparation and industrialization technologies. Compared to small-tow carbon fiber, the preparation technology for large-tow carbon fiber is more challenging across its various stages.

[0003] High-performance precursor fibers are a prerequisite for producing high-performance carbon fibers. Washing the carbon fiber precursor fibers is a crucial step in the production process. Regardless of the production method, any residual solvent in the precursor fibers will affect their quality and ultimately reduce the performance of the finished carbon fiber product. Therefore, precursor fiber manufacturers strive to develop effective washing methods to minimize solvent residue in the precursor fibers.

[0004] The washing process of raw yarn is a dual diffusion process involving solvent and water. Many factors influence this process. One aspect comes from the raw yarn itself, including the composition of the polymer, the molecular weight of the polymer, and the solid content of the spinning solution. Another aspect is the influence of the washing process parameters, including washing temperature and flow rate. Finally, the washing method and equipment also play a role.

[0005] There are many existing methods and equipment for washing carbon fiber precursors, including immersion, spraying, ultrasonic, and beating. The washing process is a double diffusion process, a solvent removal process, and also a fiber shrinkage process. Ultrasonic and beating methods can easily damage the fibers, causing fuzz and breakage in the precursor. Immersion or spraying methods have low washing efficiency and high water consumption.

[0006] Chinese invention patent CN 106319689 A discloses a carbon fiber precursor washing device and method. This invention discloses a carbon fiber precursor washing device in which multiple washing tanks are arranged from top to bottom. The carbon fiber precursor passes through guide rollers in each washing tank in an "S" shape, layer by layer. The difference in rotational speed of the multiple guide rollers pre-stretches the carbon fiber precursor during the washing process, squeezing out the solvent that has penetrated into the carbon fiber precursor, thus improving the washing effect. This type of washing device is suitable for washing small tows of precursor fibers, but it consumes a relatively large amount of water.

[0007] Chinese invention patent CN 107268215 A discloses a carbon fiber precursor washing device and method. The device consists of a washing machine guide roller assembly, a circulating water tank, a spray pump, spray nozzles, and a rinsing tank. After acid washing, the fiber bundle passes through the washing machine. Spray water is atomized from the spray nozzles to wash the fiber bundle. After washing, the fiber bundle enters the rinsing tank for rinsing, with the fiber bundle moving in the opposite direction to the flow of deionized water in the rinsing tank. This invention can reduce sodium ions in the fiber bundle and improve the quality of the carbon fiber precursor. However, this process structure of the washing device cannot fully utilize the washing water, consumes a lot of energy, and results in uneven washing of the precursor, making it unsuitable for washing large tows of precursor.

[0008] The application of low-cost, large-tow carbon fiber is key to the development of low-cost carbon fiber composite technology. Compared to small-tow carbon fiber, the biggest advantage of large-tow carbon fiber is that it can significantly increase the single-line production capacity of carbon fiber under the same production conditions, thereby achieving low-cost production. As the number of fibers in the tow increases, the difficulty of ensuring the uniformity of each fiber increases significantly compared to small-tow carbon fiber. Summary of the Invention

[0009] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a washing device and washing method for large tow carbon fiber precursors, which can solve the above-mentioned problems.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A washing device for large-tow carbon fiber precursor fibers includes multiple washing units. Each washing unit includes a washing tank, a spray unit, a pump, and a drawing roller assembly. The pump's inlet is connected to a drain outlet at the bottom of the washing tank via an inlet pipe, and the pump's outlet is connected to a spray unit located above the washing tank via a drain pipe, thereby circulating the washing liquid in the washing tank. The spray pipes of the spray unit are positioned towards the fibers on the drawing roller assembly, thereby spraying the fibers being conveyed on the drawing roller assembly with the washing liquid. The number of washing units, n, satisfies the formula: Solvent residue in the fiber = Solvent amount in the nascent fiber upon entering the washing tank × (1 - Average solvent removal rate of each washing tank). n <0.002%.

[0012] Preferably, each washing unit is equipped with a set of drawing rollers, each set of drawing rollers including an upper roller, a lower front roller and a lower rear roller. The upper roller is located above the inlet of the washing tank and near the front end of the lower front roller in the tank. The lower rear roller is located near the rear end of the washing tank. The angle α between the upper fiber surface A of the carbon fiber precursor conveyed by the lower rear roller of the previous washing unit and the upper roller of the next washing unit and the horizontal plane is 30°≤α≤60°. The angle γ ≥ α between the lower fiber surface B of the carbon fiber precursor conveyed by the upper roller and the lower front roller in the same washing unit and the horizontal plane is 100°.

[0013] Preferably, 40°≤α≤45°.

[0014] Preferably, each washing unit is equipped with an independent frequency conversion control for the stretching roller group to independently adjust the washing speed; the average solvent removal rate in each washing tank is 78% to 93%, preferably 85% to 88%.

[0015] Preferably, spray units are provided on both the fiber front side of the upper fiber surface A and the fiber back side of the lower fiber surface B; the spray center of the spray unit makes an angle β with both the upper fiber surface A and the lower fiber surface B, and the angle β is 30°≤β≤60°, preferably 40°≤β≤45°.

[0016] Preferably, multiple spray pipes are arranged side by side on the spray unit, and a nozzle is provided at the front end of each spray pipe. The spray direction of the nozzle can be controlled by adjusting the spray pipe.

[0017] Preferably, the number of spray pipes on each spray unit is twice the number of yarns spun.

[0018] Preferably, a spray port is provided, and a spray pipe is provided on each spray port.

[0019] Preferably, the spray angle of the nozzle is 90°, and the vertical distance from the sprayed water to the fiber is 100mm; the effective immersion length L of the fiber in the washing tank is 1.5m to 3.5m; the spray pipe is a corrosion-resistant, flexible, and shape-maintaining hose; the draw ratio in the washing tank is controlled to be 90% to 99% by setting the speed of the draw roller group. The effective immersion length L is preferably 2.0m ≤ L ≤ 2.5m; the draw ratio is preferably 95% to 96%.

[0020] The present invention also provides a method for preparing polyacrylonitrile-based large-tow carbon fiber precursor using the aforementioned water washing apparatus, the method comprising the following steps:

[0021] 1) Adjust the device parameters. According to the fiber washing requirements and the number of yarns spun, set the number of spray pipes, the tortuosity and the distance to the upper and lower fiber surfaces B of the spray unit. Set the speed of the drafting roller group to adjust the drafting rate in the washing tank. Match the corresponding fiber washing mode to adjust the solvent removal rate in the washing tank and supply pure hot water as the washing medium.

[0022] 2) Fiber feeding and washing: The fiber enters the drafting roller group of the first washing unit, is sprayed by the spraying unit and then enters the washing tank. It runs in sequence and comes out from the drafting roller of the last unit, completing the washing and entering the next process.

[0023] Preferably, hot pure water enters from the last washing unit and is pumped into the previous washing unit, proceeding sequentially in the opposite direction to the fiber; the average solvent removal rate in each washing tank is 78%–93%; the spray water pressure at the nozzles is 0.10–0.18 MPa, preferably 0.15 MPa.

[0024] Compared to existing technologies, the advantages of this invention are as follows: The solution of this invention solves the problems of uniformity and high efficiency in washing large-tow carbon fiber precursor fibers with a K content of 24K or higher, and reduces solvent residue in nascent fibers. The washing method of this invention uses a large-tow carbon fiber precursor washing device, resulting in large-tow precursor fibers with low solvent residue. Furthermore, it achieves uniform solvent residue in each fiber of the large-tow precursor fiber, ensuring uniform solvent residue across different spinning positions on a production line in industrial production. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a water washing device;

[0026] Figure 2 This is a schematic diagram of the spray unit.

[0027] The components are: 1. Fiber; 2. Drafting roller assembly; 3. Washing tank; 4. Pump; 5. Spraying unit; 21. Upper roller; 22. Lower front roller; 23. Lower rear roller; 51. Spray pipe; 52. Nozzle. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In the process of preparing carbon fiber tow precursors using polyacrylonitrile-based materials, the nascent fibers formed after extrusion of the obtained polyacrylonitrile solution need to be washed with water to remove the solvent from the nascent fibers. Therefore, see [link to relevant documentation]. Figure 1A washing device for large-tow carbon fiber precursor is provided. The washing device includes multiple washing units. Each washing unit includes a washing tank 3, a spray unit 5, a pump 4, and a drafting roller assembly 2. The water inlet of the pump 4 is connected to a drain outlet at the bottom of the washing tank 3 via an inlet pipe. The drain outlet of the pump 4 is connected to the spray unit 5 located above the washing tank 3 via a drain pipe, thereby circulating the washing liquid in the washing tank 3. The spray pipe 51 of the spray unit 5 is positioned towards the fiber 1 on the drafting roller assembly 2, thereby spraying the fiber conveyed on the drafting roller assembly 2 with the washing liquid. The number n of the washing units satisfies the formula: Solvent residue in the fiber = Solvent amount in the nascent fiber when entering the washing tank × (1 - Average solvent removal rate of each washing tank). n <0.002%.

[0030] In this system, the washing tanks in each washing unit do not have overflow plates; the washing water in the washing tanks 3 is entirely replaced by pump 4. Hot pure water, as the washing medium, enters from the last washing unit and is pumped into the previous washing unit by pump 4, proceeding sequentially in the opposite direction to fiber 1. The average solvent removal rate in each washing tank 3 is 78%–93%.

[0031] Each washing unit is equipped with a stretching roller group 2. Each stretching roller group 2 includes an upper roller 21, a lower front roller 22, and a lower rear roller 23. The upper roller 21 is located above the inlet of the washing tank 3, the lower front roller 22 is located in the washing tank 3 near the front end, and the lower rear roller 23 is located in the washing tank 3 near the rear end.

[0032] Furthermore, the angle α between the upper fiber surface A of the carbon fiber precursor conveying unit, where the lower rear roller 23 of the previous washing unit and the upper roller 21 of the next washing unit are located, and the horizontal plane is 30°≤α≤60°, preferably 40°≤α≤45°.

[0033] Furthermore, in the same washing unit, the angle γ between the lower fiber surface B of the carbon fiber precursor conveying the upper roller 21 and the lower front roller 22 and the horizontal plane is ≥ α.

[0034] Each washing unit is equipped with an independent frequency conversion control for the stretching roller group 2 to independently adjust the washing speed; the average solvent removal rate in each washing tank 3 is 78% to 93%, preferably 85% to 88%.

[0035] Furthermore, spray units 5 are provided on both the fiber front side of the upper fiber surface A and the fiber back side of the lower fiber surface B; the angle between the spray center of the spray unit 5 and the upper fiber surface A and the lower fiber surface B is β, and the angle β is 30°≤β≤60°, preferably 40°≤β≤45°.

[0036] The spray unit 5 comprises multiple spray pipes 51 arranged side-by-side, each spray pipe 51 having a nozzle 52 at its front end. The spray direction of the nozzle 52 is controlled by adjusting the spray pipes 51. The spray water pressure of the nozzle 52 is 0.10–0.18 MPa, preferably 0.15 MPa.

[0037] Furthermore, the number of spray pipes 51 on each spray unit 5 is twice the number of yarns spun. In one embodiment, each spray unit 5 has two spray pipes 51 and corresponding nozzles 52 at its spray port.

[0038] Furthermore, the spray angle of the nozzle 52 is 90°, and the vertical distance from the sprayed water to the fiber is 100mm; the effective immersion length L of the fiber 1 in the washing tank 3 is 1.5m to 3.5m, preferably 2.0m ≤ L ≤ 2.5m. The spray pipe is a corrosion-resistant, flexible, and shaped hose, i.e., made of corrosion-resistant material, not too soft and flexible, allowing control of the spray direction of the nozzles on the spray pipe. The draw ratio in the washing tank 3 is controlled to be 90% to 99% by setting the speed of the draw roller assembly.

[0039] A method for preparing polyacrylonitrile-based large-tow carbon fiber precursor using the above-mentioned water washing apparatus includes the following steps.

[0040] 1) Adjust the device parameters. According to the fiber washing requirements and the number of yarns spun, set the number of spray pipes 51 of the spray unit 5, the tortuous angle and the distance to the upper and lower fiber surfaces B. Set the speed of the drafting roller group 2 to adjust the drafting rate in the washing tank. Match the corresponding fiber washing mode to adjust the solvent removal rate in the washing tank and supply pure hot water as the washing medium.

[0041] 2) Fiber washing: The fiber enters the drafting roller group 2 of the first washing unit, is sprayed by the spraying unit 5 and then enters the washing tank 3. The process is repeated in sequence, and the fiber exits from the drafting roller of the last unit, completing the washing and entering the next process.

[0042] For verification and comparison, please refer to the different embodiments and comparative examples in the table below.

[0043] Different embodiments and comparative examples of table-water washing devices

[0044]

[0045]

[0046] Therefore, it is evident that even with an increase in the number of individual filament bundles, the residual solvent content in the fiber remains low, and uniform solvent residue rates are achieved among the fibers in each bundle, ensuring uniform solvent residue rates across all filament bundles on a single spinning line. Specifically, the large-bundle filament produced using this invention exhibits a solvent residue rate of <0.002%, a solvent residue rate CV <1% among different fibers within each bundle, and a solvent residue rate CV <2% between different spinning positions per bundle.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A washing device for large-tow carbon fiber precursor fibers, comprising multiple washing units, each washing unit comprising a washing tank (3), a spray unit (5), a pump (4), and a drawing roller assembly (2), wherein the inlet end of the pump (4) is connected to a drain outlet at the bottom of the washing tank (3) via an inlet pipe, and the drain end of the pump (4) is connected to a spray unit (5) located above the washing tank (3) via a drain pipe, thereby circulating the washing liquid in the washing tank (3); the spray pipe of the spray unit (5) (51) The fibers (1) are positioned toward the drawing roller assembly (2) so as to spray washing liquid onto the fibers being conveyed on the drawing roller assembly (2); each drawing roller assembly (2) includes an upper roller (21), a lower front roller (22) and a lower rear roller (23), the upper roller (21) being positioned above the inlet of the washing tank (3), the lower front roller (22) being positioned in the washing tank (3) near the front end, and the lower rear roller (23) being positioned in the washing tank (3) near the rear end; characterized in that, The number n of the water washing units satisfies the following formula: Solvent residue in fiber = Solvent amount in nascent fiber when entering water washing × (1 - average solvent removal rate of each washing tank) n < 0.002%; Furthermore, the angle α between the upper fiber surface A of the carbon fiber precursor conveying the lower rear roller (23) of the previous washing unit and the upper roller (21) of the next washing unit and the horizontal plane is 30°≤α≤60°. In the same washing unit, the angle γ between the lower fiber surface B of the carbon fiber precursor conveying the upper roller (21) and the lower front roller (22) and the horizontal plane is ≥ α. The spray unit (5) is located on the fiber front side of the upper fiber surface A and / or the fiber back side of the lower fiber surface B. The angle β between the spray center of the spray unit (5) and the corresponding fiber surface is 30°≤β≤60°.

2. The washing device for large-tow carbon fiber precursor fibers according to claim 1, characterized in that: Each washing unit is equipped with an independent frequency conversion control for the stretching roller group (2) to independently adjust the washing speed; the average solvent removal rate in each washing tank (3) is 78% to 93%.

3. The washing device for large-tow carbon fiber precursor fibers according to claim 1, characterized in that: Multiple spray pipes (51) are arranged side by side on the spray unit (5). Each spray pipe (51) has a nozzle (52) at its front end. The spray direction of the nozzle (52) can be controlled by adjusting the spray pipe (51).

4. The washing device for large-tow carbon fiber precursor fibers according to claim 3, characterized in that: The number of spray pipes (51) on each spray unit (5) is twice the number of yarns spun.

5. The washing device for large-tow carbon fiber precursor fibers according to claim 4, characterized in that: The spray pipe is a corrosion-resistant, flexible, and shape-adjustable hose.

6. The washing device for large-tow carbon fiber precursor fibers according to claim 3, characterized in that: The spray angle of the nozzle (52) is 90°, and the vertical distance from the sprayed water to the fiber is 100mm; the effective immersion length L of the fiber (1) in the washing tank (3) is 1.5m to 3.5m; the draw ratio in the washing tank (3) is controlled to be 90% to 99% by setting the speed of the draw roller group.

7. A method for preparing polyacrylonitrile-based large-tow carbon fiber precursor using the washing apparatus according to any one of claims 1-6, characterized in that, The method includes the following steps: 1) Adjust the device parameters. According to the fiber washing requirements and the number of yarns spun, set the number of spray pipes (51) of the spray unit (5), the tortuous angle and the distance to the upper and lower fiber surfaces B. Set the speed of the drafting roller group (2) to adjust the drafting rate in the washing tank. Match the corresponding fiber washing mode to adjust the solvent removal rate in the washing tank and supply pure hot water as the washing medium. 2) Fiber washing: The fiber enters the drawing roller group (2) of the first washing unit, is sprayed by the spray unit (5) and then enters the washing tank (3). The process is repeated in sequence, and the fiber exits from the drawing roller of the last unit, completing the washing and entering the next process.

8. The method according to claim 7, characterized in that: Hot pure water enters from the last washing unit and is pumped into the previous washing unit by pump (4), and so on, running in the opposite direction to the fiber (1); the average solvent removal rate in each washing tank (3) is 78% to 93%; the spray water pressure of the nozzle (52) is 0.10 to 0.18 MPa.

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