Device and method for preparing aramid fiber precursor by dry-jet wet spinning

Abstract

The present invention provides a device for preparing aramid fiber precursor by dry-jet wet spinning, comprising a coagulation bath (1), a spinning assembly (3) and an air layer assembly (2). The air layer assembly (2) is arranged between the coagulation bath (1) and the spinning assembly (3), and comprises a cover (21), a bottom layer isolation sheet (22) arranged at the bottom of the cover (21), a pore plate (23) arranged at the top of the cover (21), an air guide pipe (24), an air component regulator (25) and an air flow baffle (26). The air component regulator (25) is connected to the air layer between the bottom layer isolation sheet (22) and the pore plate (23) through the air guide pipe (24). The air flow baffle (26) is arranged at the bottom of the pore plate (23) and has a gap between the bottom layer isolation sheet (22). The present invention also provides a method for preparing aramid fiber precursor. The present invention can promote the coagulation of spinning solution by using an air layer with a certain air flow, thereby solving the problem of doubling caused by incomplete solidification.

Description

Technical Field

[0001] The invention relates to the field of chemical synthetic fibers, in particular to the field of aramid fiber precursor production. Background Art

[0002] Para-aramid is a kind of aromatic polyamide fiber, and its full name is poly(p-phenylene terephthalamide) fiber, also known as aramid 1414. The main raw materials of para-aramid are terephthaloyl chloride and p-phenylenediamine. Para-aramid, carbon fiber and high-strength and high-modulus polyethylene are known as the world's three major high-performance fibers. It has excellent properties such as high strength and high modulus, high temperature resistance and flame retardancy. It also has the advantages of low relative density, fatigue resistance, shear resistance and good dimensional stability. It plays an irreplaceable and important role in personal protection, aerospace, electronic information and other fields. At present, low-temperature polycondensation and interfacial polymerization (only Teijin Co., Ltd. of Japan) are mainly used in industrial production. With the help of one or more of alkali metal or alkaline earth metal chlorides as cosolvents, two monomers are polymerized in a polar solvent to obtain PPTA polymer, which is then crushed, washed and dried to obtain PPTA powder, and then dissolved in a relatively high concentration of sulfuric acid to prepare a spinning solution with a certain concentration, and then wet spinning and dry-jet wet spinning processes are used to prepare para-aramid fiber.

[0003] The main difference between wet spinning and dry-jet wet spinning is whether the polymer solution passes through an air layer before entering the coagulation bath. The wet spinning spinneret is completely immersed in the coagulation bath when working, while the spinning solution in dry-jet wet spinning will first pass through a certain distance of air layer when it is ejected from the spinneret, and then enter the coagulation bath. It is the existence of the air layer that allows the spinning slurry to be initially solidified and stretched, and enter the coagulation bath at a higher speed for further stretching. However, since the solvent of the PPTA spinning slurry is sulfuric acid with a relatively high concentration, and the boiling point of sulfuric acid with a concentration of 98% and above is above 300 degrees Celsius, although the air layer can accelerate the solidification of the slurry, the PPTA-H2SO4 spinning slurry is still very easy to produce parallel threads when passing through the air layer. Therefore, the current technology mainly optimizes and improves this process based on the height of the air layer and the length of the coagulation bath.

[0004] The Chinese patent application with publication number CN110760941A proposed a spinning device for para-aramid dry-jet wet spinning, which controls the height of the coagulation bath to adjust the height of the air layer, and designs an overflow plate and a damping plate to achieve a stable flow of the coagulation bath for high-speed spinning. However, this technology still has the problem of the spinning slurry being doubly connected in the air layer.

[0005] In order to overcome the too fast coagulation flow rate caused by the coagulation forming device of dry jet-wet spinning, the Chinese patent application with publication number CN103498207A proposed using a U-shaped tubular coagulation forming device, and adjusting the relative movement speed of the coagulation bath and the fiber by controlling the height difference between the liquid inlet and the liquid outlet of the U-shaped coagulation tube. However, the specific height difference of the U-shaped pipe designed by this technology needs to be achieved by replacing the module, and continuous production adjustment cannot be achieved. Summary of the invention

[0006] The technical problem to be solved by the present invention is how to prevent the spinning slurry from being paralleled in the air layer.

[0007] The present invention solves the above-mentioned technical problems through the following technical means: a device for preparing aramid fiber precursor by dry-jet wet spinning, comprising a coagulation bath (1) and a spinning assembly (3), and also comprising an air layer assembly (2), wherein the air layer assembly (2) is arranged between the coagulation bath (1) and the spinning assembly (3), wherein the air layer assembly (2) comprises a cover (21), a bottom isolation sheet (22) arranged at the bottom of the cover (21), an air hole plate (23) arranged at the top of the cover (21), an air guide pipe (24), an air component regulator (25) and an air flow baffle (26), wherein the air component regulator (25) is connected to the air layer between the bottom isolation sheet (22) and the air hole plate (23) through the air guide pipe (24), and the air flow baffle (26) is arranged at the bottom of the air hole plate (23) and has a gap with the bottom isolation sheet (22).

[0008] As a further optimized technical solution, the cover shell (21) is a cylindrical metal cover, the bottom isolation sheet (22) is a metal sheet, and the periphery of the bottom isolation sheet (22) is welded to the cover shell (21).

[0009] As a further optimized technical solution, a first circular hole (222) is opened in the middle of the bottom isolation plate (22), a second circular hole (234) is opened in the middle of the pore plate (23), and the spinneret of the spinning assembly (3) is coaxial with the second circular hole (234) and the first circular hole (222) and has an aperture equal to or smaller than the aperture of the second circular hole (234) and the first circular hole (222).

[0010] As a further optimized technical solution, a passage through which air can flow is provided between the periphery of the air hole disk (23) and the inner wall of the housing (21), and air outlet holes are evenly distributed on the air hole disk (23).

[0011] As a further optimized technical solution, one end of an air guide tube (24) is fixed on the air hole disk (23), and the air guide tube (24) at this end is connected to the space between the air hole disk (23) and the bottom isolation plate (22), and the other end of the air guide tube (24) is connected to the air component regulator (25).

[0012] As a further optimized technical solution, the airflow baffle (26) is fixedly arranged at the bottom of the air hole disk (23), tilted from the periphery of the air hole disk (23) toward the inside, and is in the shape of an inverted truncated cone with openings at the upper and lower ends.

[0013] The present invention also provides a method for preparing aramid fiber precursor by using the device for preparing aramid fiber precursor by dry-jet wet spinning as described in any of the above schemes, wherein the filament bundle (5) flows out from the spinneret hole of the spinning assembly (3) to the air layer assembly (2), and the air flow velocity of the space layer between the air hole disk (23) and the bottom isolation sheet (22) is controlled by the air component regulator (25) to achieve micro-stretching of the fiber, and the gas flow velocity is 0.01-0.1m 3 / min.

[0014] As a further optimized technical solution, the air component regulator (25) continuously fills ammonia into the air layer, and the ammonia content is 0.03%-0.08%.

[0015] As a further optimized technical solution, the height of the air layer is 8-20 mm.

[0016] As a further optimized technical solution, the method specifically includes the following steps:

[0017] A 1300-1500 mesh, 5.0dL / g-6.5dL / g poly(p-phenylene terephthalamide) powder PPTA resin is dissolved in 99%-101% fuming sulfuric acid at a dissolution temperature of 8°C-85°C, and the mass fraction of the spinning solution is controlled to be 16%-18%. The solution is injected into a spinning machine, and after precise measurement, it reaches a spinning assembly (3) through a liquid infusion tube 4. Under the premise of applying a pressure of 0.1MPa-0.2MPa, the spinning solution flows out from the spinneret holes on the spinneret of the spinning assembly (3). After the spinning solution passes through a non-static air layer with a height of 8-20mm and an ammonia content of 0.03%-0.08%, it reaches a coagulation bath (1) with a temperature of 0-10 degrees Celsius for further solidification to form an initially stretched fiber.

[0018] The advantages of the present invention are:

[0019] 1. The present invention can promote the solidification of the spinning solution by using an air layer with a certain airflow, thereby solving the phenomenon of doubling caused by incomplete solidification;

[0020] 2. The present invention utilizes the same airflow direction as the spinning direction to promote the stretching of the spinning solution during the solidification process and further achieve the orderly arrangement of the PPTA molecular chains;

[0021] 3. The present invention can react with some sulfuric acid molecules in the spinning solution by mixing a trace amount of ammonia molecules in the air layer, consume some of the sulfuric acid molecules in the spinning solution, thereby further promoting the solidification of the original silk surface, reducing the occurrence of doubling, and achieving a higher yield spinning efficiency. The specific reaction equation is as follows:

[0022] 2NH+H SO=2(NH)SO; NH+H SO=NH HSO BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1 is a schematic diagram of an overall structure of a device for preparing aramid fiber precursor by dry-jet wet spinning in an embodiment of the present invention;

[0024] Figure 2 is a schematic structural diagram of an air layer assembly in an embodiment of the present invention;

[0025] Figure 3 Schematic diagram of the structure of an air layer assembly (with a filament bundle passing through) in an embodiment of the present invention;

[0026] Figure 4 is an electron microscope image of the fiber of Example 1;

[0027] Figure 5 This is the electron microscope image of the fiber of Comparative Example 1. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are 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.

[0029] See also Figure 1 As shown, this embodiment provides a device for preparing aramid fiber precursor by dry-jet wet spinning, comprising a coagulation bath 1, an air layer component 2 and a spinning component 3.

[0030] The coagulation bath 1 is located at the bottom layer and is a coagulation bath 1 of the prior art.

[0031] The air layer assembly 2 is located above the coagulation bath 1 and is a key component of the present invention, comprising a cover 21 , a bottom isolation sheet 22 , an air hole disk 23 , an air guide tube 24 , an air component regulator 25 and an air flow baffle 26 .

[0032] The cover 21 is open at both ends. Preferably, the cover 21 is a cylindrical metal cover. Considering the possible corrosion caused by the sulfuric acid environment, the material thereof can be acid-resistant metals such as 316L, 904L, and Hastelloy.

[0033] The bottom isolation sheet 22 is fixed to the lower opening of the cover shell 21, and the periphery of the bottom isolation sheet 22 is fixedly connected to the cover shell 21. Preferably, the bottom isolation sheet 22 is a metal sheet welded to the lower opening of the cover shell 21. A circular hole 222 of a certain size is opened in the middle of the bottom isolation sheet 22. The specific size of the circular hole 222 is determined by the size of the tow in the actual production of small and pilot tests, and generally has a diameter of about 2 cm to 15 cm.

[0034] The pore plate 23 is installed on the upper part of the housing 21, and there is a passage for air flow between the periphery of the pore plate 23 and the inner wall of the housing 21. The pore plate 23 is evenly distributed with air jet holes 232, and the aperture is generally 1-5 mm. A circular hole 234 is opened in the middle of the pore plate 23. The specific size of the circular hole 234 is determined by the size of the tow in the actual production of small-scale and pilot tests, and generally has a diameter of about 2 cm to 15 cm.

[0035] One end of an air guide tube 24 is fixed on the air hole disk 23 , and the air guide tube 24 at this end is connected to the space between the air hole disk 23 and the bottom isolation sheet 22 , and the other end of the air guide tube 24 is connected to the air component regulator 25 .

[0036] The air component regulator 25 is disposed outside the housing 21. As a specific solution, the air component regulator 25 is a gas flow pump.

[0037] The housing 21 is provided with a long strip groove in the height direction corresponding to the position of the air guide tube 24, and the air component regulator 25 can move up and down and be positioned at a position, thereby driving the air hole disk 23 to move up and down through the air guide tube 24, so that the height of the air hole disk 23 inside the housing 21 can be adjusted. The air component regulator 25 can move up and down and be positioned at a position using various existing positioning methods, such as the air component regulator 25 moving up and down on the track pre-set, each gear is positioned by a movable buckle structure, or a blocking mechanism is set beside the track where the air component regulator 25 moves up and down, when the air component regulator 25 moves to a predetermined height, the blocking mechanism extends to position the air component regulator 25, or the air component regulator 25 is fixed with a nut or a screw rod, and the air component regulator 25 is driven to move to a fixed position by the mutual movement of the nut and screw rod. In general, the way in which the air component regulator 25 moves up and down is not the focus of this application, and there are many existing technologies that can be used, which will not be repeated here.

[0038] The airflow baffle 26 is fixedly arranged at the bottom of the air hole plate 23 and is inclined from the periphery of the air hole plate 23 to the inside. There is a gap between the lower end of the airflow baffle 26 and the bottom isolation sheet 22. Preferably, the airflow baffle 26 is in the shape of an inverted truncated cone with upper and lower ends opened. The main function of the airflow baffle 26 is to achieve uniform and stable circulation of the airflow.

[0039] The spinning assembly 3 is located above the air layer assembly 2, and the spinning assembly 3 includes a spinneret with spinneret holes. The spinneret of the spinning assembly 3 is coaxial with the circular hole 234 and the circular hole 222, and the aperture is equal to or smaller than the aperture of the circular hole 234 and the circular hole 222. The spinning stock solution flows out from the spinneret holes of the spinning assembly 3, passes through the circular hole 234 and the circular hole 222 in sequence, and then enters the coagulation bath 1.

[0040] The working principle of the device for preparing aramid fiber precursor by dry-jet wet spinning is as follows:

[0041] By controlling the air component regulator 25, ammonia is filled into the space between the air hole disk 23 of the air layer component 2 and the bottom isolation sheet 22 through the air guide pipe 24. The space between the air hole disk 23 and the bottom isolation sheet 22 is called the air layer, so as to control the proportion of ammonia in the air layer. Because the air component regulator 25 continuously fills ammonia into the air layer, the air layer forms an air flow 201 from top to bottom. When a filament bundle 5 flows out from the spinneret hole of the spinning component 3, the air flow is in the same direction as the running direction of the filament bundle 5. The air flow 201 rises after passing through the bottom of the air flow baffle 26 and passes through The gap between the pore disk 23 and the cover shell 21 reaches the upper part of the pore disk 23, and then enters the air layer again through the air jet holes 232 evenly distributed on the pore disk 23, forming an air flow circulation loop. By controlling the speed of pumping ammonia gas by the air component regulator 25, the flow rate of the gas in the air layer is controlled to achieve micro-stretching of the fiber, which is beneficial to the running speed of the fiber. On the other hand, by adding a trace amount of ammonia gas, ammonia gas can react with sulfuric acid to promote the solidification of the filament stream, so as to achieve the preparation of aramid fiber at a higher line speed, thereby improving production capacity.

[0042] The following embodiments are processes for preparing aramid fiber precursor by dry-jet wet spinning using the above-mentioned device for preparing aramid fiber precursor by dry-jet wet spinning.

[0043] Embodiment 1:

[0044] The poly(p-phenylene terephthalamide) resin powder (1300 mesh, 5.0 dL / g) was dissolved in 99% fuming sulfuric acid (dissolving temperature was 83°C), and the mass fraction of the spinning solution was controlled to be 16%. The spinning solution was injected into the spinning machine, and after accurate measurement, it reached the spinning assembly 3 through the infusion tube 4. Under the premise of applying a pressure of 0.1 MPa, the spinning solution flowed out from the spinneret holes on the spinneret of the spinning assembly 3, and the spinning solution passed through a non-static air layer with a height of 10 mm and an ammonia content of 0.03% (gas flow rate 0.02 m / s). 3 / min), and then the fiber is further solidified in a coagulation bath 1 at a temperature of 0 degrees Celsius to form an initially drawn fiber. The spinning results show that there is no doubling of the initially drawn fiber bundles. The fiber electron microscope image of this embodiment is shown in FIG. Figure 4 shown.

[0045] Embodiment 2:

[0046] The poly(p-phenylene terephthalamide) resin powder (1400 mesh, 6.0 dL / g) was dissolved in 100% fuming sulfuric acid (dissolving temperature was 84°C), and the mass fraction of the spinning solution was controlled to be 17%. The spinning solution was injected into the spinning machine, and after accurate measurement, it reached the spinning assembly 3 through the infusion tube 4. Under the premise of applying a pressure of 0.15 MPa, the spinning solution flowed out from the spinneret holes on the spinneret of the spinning assembly 3, and the spinning solution passed through a non-static air layer with a height of 11 mm and an ammonia content of 0.05% (gas flow rate 0.04 m / s). 3 / min), and then it reaches the coagulation bath 1 at a temperature of 5 degrees Celsius for further solidification to form the initially drawn fiber. The spinning results show that there is no doubling in the initially drawn fiber bundle.

[0047] Embodiment 3:

[0048] The poly(p-phenylene terephthalamide) powder PPTA resin (1500 mesh, 6.5 dL / g) was dissolved in 101% fuming sulfuric acid (dissolving temperature was 85°C), and the mass fraction of the spinning solution was controlled to be 18%. The spinning solution was injected into the spinning machine, and after accurate measurement, it reached the spinning assembly 3 through the infusion tube 4. Under the premise of applying a pressure of 0.2 MPa, the spinning solution flowed out from the spinneret holes on the spinneret of the spinning assembly 3, and the spinning solution passed through a non-static air layer with a height of 12 mm and an ammonia content of 0.08% (gas flow rate 0.06 m / s). 3 / min), and then it reaches the coagulation bath 1 at a temperature of 10 degrees Celsius for further solidification to form the initially drawn fiber. The spinning results show that there is no doubling in the initially drawn fiber bundle.

[0049] Comparative Example 1:

[0050] The poly(p-phenylene terephthalamide) powder PPTA resin (150 mesh, 4.0 dL / g) was dissolved in 98% fuming sulfuric acid (dissolving temperature was 80°C), and the mass fraction of the spinning solution was controlled to be 15%. It was then injected into the spinning machine, and after precise measurement, it reached the spinning assembly 3 through the infusion tube 4. Under the premise of applying a pressure of 0.1 MPa, the spinning solution flowed out from the spinneret holes on the spinneret of the spinning assembly 3. After the spinning solution passed through a static air layer with a height of 8 mm and an ammonia content of 0% (i.e., there was no flowing air in the air layer), it reached the coagulation bath 1 at a temperature of 5 degrees Celsius for further solidification to form initially stretched fibers. The spinning results showed that the initially stretched filament bundle had a doubling situation. The fiber electron microscope image of this embodiment is shown in FIG. Figure 5 shown.

[0051] Comparative Example 2:

[0052] The poly(p-phenylene terephthalamide) powder PPTA resin (150 mesh, 4.0 dL / g) was dissolved in 98% fuming sulfuric acid (dissolving temperature was 80°C), and the mass fraction of the spinning solution was controlled to be 15%. The spinning solution was injected into the spinning machine, and after accurate measurement, it reached the spinning assembly 3 through the infusion tube 4. Under the premise of applying a pressure of 0.1 MPa, the spinning solution flowed out from the spinneret holes on the spinneret of the spinning assembly 3, and the spinning solution passed through a non-static air layer with a height of 8 mm and an ammonia content of 0% (gas flow rate 0.01 m / s). 3 / min), and then it reaches the coagulation bath 1 at a temperature of 5 degrees Celsius for further solidification to form the initially drawn fiber. The spinning results show that the doubling condition of the initially drawn fiber bundle is slightly improved.

[0053] Comparative Example 3:

[0054] The poly(p-phenylene terephthalamide) resin powder (1500 mesh, 6.5 dL / g) was dissolved in 104% fuming sulfuric acid (dissolving temperature was 90°C), and the mass fraction of the spinning solution was controlled to be 20%. The spinning solution was injected into the spinning machine, and after accurate measurement, it reached the spinning assembly 3 through the infusion tube 4. Under the premise of applying a pressure of 0.3 MPa, the spinning solution flowed out from the spinneret holes on the spinneret of the spinning assembly 3, and the spinning solution passed through a non-static air layer with a height of 20 mm and an ammonia content of 1% (gas flow rate 0.1 m / s). 3 / min), and then it reaches the coagulation bath 1 at a temperature of 15 degrees Celsius for further solidification to form the initially drawn fiber. The spinning results show that there is no doubling in the initially drawn filament bundle, but the performance of the fiber itself is reduced. This is because when the ammonia content is too high, the coagulation speed of the fiber will be faster, resulting in defects on the fiber surface.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for preparing aramid fiber precursor by dry-jet wet spinning, comprising a coagulation bath (1) and a spinning assembly (3), characterized in that: The invention also comprises an air layer component (2), wherein the air layer component (2) is arranged between the coagulation bath (1) and the spinning component (3), and the air layer component (2) comprises a cover (21), a bottom isolation sheet (22) arranged at the bottom of the cover (21), an air hole plate (23) arranged at the top of the cover (21), an air guide tube (24), an air component regulator (25) and an air flow baffle (26), wherein the air component regulator (25) is connected to the air layer between the bottom isolation sheet (22) and the air hole plate (23) through the air guide tube (24), and the air flow baffle (26) is arranged at the bottom of the air hole plate (23) and has a gap with the bottom isolation sheet (22). One end of an air guide tube (24) is fixed, and the air guide tube (24) at this end is connected to the space between the air hole disk (23) and the bottom isolation plate (22). The other end of the air guide tube (24) is connected to an air component regulator (25). The air flow velocity of the space layer between the air hole disk (23) and the bottom isolation plate (22) is controlled by the air component regulator (25). The air flow is in the same direction as the running direction of the filament bundle. The air component regulator (25) continuously fills ammonia into the air layer, and the ammonia content is 0.03%-0.08%. The air flow baffle (26) is fixedly arranged at the bottom of the air hole disk (23), and is inclined from the periphery of the air hole disk (23) to the inside, and is in the shape of an inverted truncated cone with openings at the upper and lower ends.

2. The device for preparing aramid fiber precursor by dry-jet wet spinning according to claim 1, characterized in that: The cover shell (21) is a cylindrical metal cover, the bottom isolation sheet (22) is a metal sheet, and the periphery of the bottom isolation sheet (22) is welded to the cover shell (21).

3. The device for preparing aramid fiber precursor by dry-jet wet spinning according to claim 1, characterized in that: A first circular hole (222) is formed in the middle of the bottom isolation plate (22), a second circular hole (234) is formed in the middle of the pore plate (23), and the spinneret of the spinning assembly (3) is coaxial with the second circular hole (234) and the first circular hole (222), and the aperture thereof is equal to or smaller than the apertures of the second circular hole (234) and the first circular hole (222).

4. The device for preparing aramid fiber precursor by dry-jet wet spinning as claimed in claim 3, characterized in that: A passage through which air can flow is provided between the periphery of the air hole disk (23) and the inner wall of the housing (21), and air outlet holes are evenly distributed on the air hole disk (23).

5. A method for preparing aramid fiber precursor by using the device for preparing aramid fiber precursor by dry-jet wet spinning according to any one of claims 1 to 4, characterized in that: The filament bundle (5) flows out from the spinneret hole of the spinning assembly (3) to the air layer assembly (2), and the air flow velocity of the space layer between the air hole disk (23) and the bottom isolation sheet (22) is controlled by the air component regulator (25) to achieve micro-stretching of the fiber, wherein the air flow velocity is 0.01-0.1 m 3 / min.

6. The method for preparing aramid fiber precursor by dry-jet wet spinning according to claim 5, characterized in that: The height of the air layer is 8-20 mm.

7. The method for preparing aramid fiber precursor by dry-jet wet spinning according to claim 5, characterized in that: The method specifically comprises the following steps: A 1300-1500 mesh, 5.0 dL / g-6.5 dL / g poly(p-phenylene terephthalamide) powder PPTA resin is dissolved in 99%-101% fuming sulfuric acid at a dissolution temperature of 83°C-85°C, and the mass fraction of the spinning solution is controlled to be 16%-18%. The solution is injected into a spinning machine and reaches a spinning assembly (3) through a liquid infusion tube (4) after precise measurement. Under the premise of applying a pressure of 0.1MPa-0.2MPa, the spinning solution flows out from the spinneret holes on the spinneret of the spinning assembly (3). After passing through a non-static air layer with a height of 8-20mm and an ammonia content of 0.03%-0.08%, the spinning solution reaches a coagulation bath (1) at a temperature of 0-10°C for further solidification to form an initially stretched fiber.

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