A polyacrylonitrile fiber and a method for producing the same
By optimizing the drawing process and equipment wrap angle of polyacrylonitrile fibers, the problems of fiber structure damage and large equipment footprint were solved, enabling the production of polyacrylonitrile fibers with high density and high orientation, and reducing production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANXI GANGKE CARBON MATERIAL CO LTD
- Filing Date
- 2023-08-25
- Publication Date
- 2026-06-19
AI Technical Summary
Existing polyacrylonitrile fiber drawing processes are prone to fiber structure damage and fuzz formation, and the equipment layout requires a large area and is difficult to operate, affecting fiber density and orientation.
By optimizing the wrap angle and equipment layout of each step, and coordinating the design of the drawing process and equipment, we ensure that the wrap angle of the nascent fiber varies within a specific range during the washing, hot water drawing, drying and densification, and steam drawing processes. This avoids problems such as excessive or insufficient fiber tension. We also employ alternating multi-roller arrangements and reasonable temperature control.
It improves the density and orientation of polyacrylonitrile fibers, reduces production costs, ensures that the fiber surface is free of fuzz, and is easy to operate.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of fiber technology, specifically relating to a polyacrylonitrile fiber and its preparation method. Background Technology
[0002] Carbon fiber materials combine high performance and low density, making them a typical dual-use material and a leading example of the materials revolution. Carbon fibers can be classified according to their raw materials, such as polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, and viscose-based carbon fiber. Among these, polyacrylonitrile-based carbon fiber has the best overall performance and the widest application. Polyacrylonitrile fiber is the precursor for producing polyacrylonitrile-based carbon fiber, and its quality directly affects the overall performance of the polyacrylonitrile-based carbon fiber. Polyacrylonitrile fiber spinning methods include wet spinning, dry spinning, dry-jet wet spinning, gel spinning, and melt spinning. Dry-jet wet spinning and wet spinning are the mainstream preparation methods for polyacrylonitrile fiber production.
[0003] The preparation process of polyacrylonitrile (PA) fibers mainly includes coagulation bath, water washing, hot water drawing, oiling, drying and densification, and steam drawing. Among these, drawing is integral to the entire process and is the driving force for structural transformation. During drawing, the macromolecular chain segments or aggregated structural units of the PA fibers stretch and align along the fiber axis. Excessive drawing can easily damage the fiber structure and produce fuzz, while insufficient drawing can easily cause disorientation, resulting in low-strength fibers. Therefore, excellent drawing processes and drawing environments are prerequisites for producing high-quality PA fibers and are crucial to the performance of PA fibers and PA carbon fibers. Summary of the Invention
[0004] Therefore, the present invention provides a polyacrylonitrile fiber and a method for preparing the same, the main purpose of which is to combine the drawing process and equipment to obtain polyacrylonitrile fibers with good density, high orientation, and bright, filament-free appearance.
[0005] To achieve the above objectives, the present invention provides a method for preparing polyacrylonitrile fibers, comprising the following steps:
[0006] Solidification and forming step: The spun yarn is solidified and formed to obtain nascent fibers;
[0007] Washing and hot water stretching steps: The nascent fibers are subjected to washing and hot water stretching treatments;
[0008] Post-treatment: The fibers after hot water stretching are post-treated to obtain polyacrylonitrile fibers;
[0009] Before the washing step, the nascent fibers enter the washing tank under the traction of the first drive roller, and the wrap angle between the nascent fibers and the first drive roller is greater than 20° and less than 150°; during the washing and hot water stretching steps, the nascent fibers undergo washing and hot water stretching under the traction of the second drive roller, and the wrap angle between the nascent fibers and the second drive roller is greater than 25° and less than 100°.
[0010] Preferably, the first drive roller is at least three rollers, the wrap angle between the nascent fiber and the first roller is greater than 25° and less than 45°, the wrap angle between the nascent fiber and the second roller is greater than 90°, and the wrap angle between the nascent fiber and the third roller is less than 45°, and the nascent fiber enters the washing tank for washing under the traction of the third roller.
[0011] Preferably, the second drive roller is at least three rollers, the wrap angle between the nascent fiber and the first roller is less than 35°, the wrap angle between the nascent fiber and the second roller is greater than 60° and less than 85°, and the wrap angle between the nascent fiber and the third roller is less than 35°.
[0012] Preferably, the temperature of the water washing treatment is 40-70℃, the temperature of the hot water stretching treatment is 60-90℃, and the residual sulfoxide content of the fiber after the hot water stretching treatment is ≤0.03%.
[0013] Preferably, the post-processing step includes: sequentially applying oil, drying and densifying, and steam stretching to the fibers after hot water stretching treatment to obtain polyacrylonitrile fibers.
[0014] Preferably, the oiled fibers are dried and densified under the traction of the third drive roller, and the wrap angle between the oiled fibers and the third drive roller is greater than 40° and less than 100°.
[0015] Preferably, the third drive roller is at least five rollers, which are arranged alternately up and down. The wrap angle between the oiled fiber and the first roller is greater than 45° and less than 90°, the wrap angle between the fiber and the second, third and fourth rollers is greater than 80°, and the wrap angle between the fiber and the fifth roller is greater than 45° and less than 90°.
[0016] Preferably, the drying and densification process includes 5-15 stages, and the temperature of the drying and densification process is 90-200℃.
[0017] Preferably, the moisture content of the dried and densified fiber is ≤0.5%, and the fiber bundle tension after drying and densification is 3000-6000 cN.
[0018] Preferably, before the steam drawing process, the dried and densified fiber is subjected to steam drawing under the traction of the feed rollers, wherein the feed rollers are at least five rollers, and the wrap angle between the dried and densified fiber and the first and fifth rollers is greater than 15° and less than or equal to 45°, and the wrap angle between the fiber and the second, third and fourth rollers is greater than 60° and less than or equal to 120°.
[0019] The fiber exit direction of the steam-drawing treatment is tangent to the surface of the fifth roller.
[0020] Preferably, the steam-drawn fiber is fed to the take-up winding forming via a drawing roller, and the drawing roller has at least five rollers. The wrap angle between the steam-drawn fiber and the first and fifth rollers is greater than 15° and less than or equal to 45°, and the wrap angle between the fiber and the second, third and fourth rollers is greater than 60° and less than or equal to 120°.
[0021] The direction of fiber insertion after steam drawing is tangent to the surface of the first roller.
[0022] Preferably, the pressure of the steam drawing treatment is 0.2-0.6 MPa, the draw ratio of the steam drawing treatment is 2-4 times, and the fiber bundle tension before the steam drawing treatment is 3000-6000 cN.
[0023] Preferably, the fiber bundle tension during the steam drawing process is 5000-8000 cN, and the fiber bundle tension before take-up after the drawing roller is 500-1200 cN.
[0024] A polyacrylonitrile fiber, wherein the polyacrylonitrile is produced by the above-described method for preparing polyacrylonitrile fibers.
[0025] Preferably, the polyacrylonitrile fiber has an orientation degree of 85-95% and a bulk density of 1.17-1.19 g / cm³. 3 .
[0026] Preferably, the polyacrylonitrile fiber has an orientation degree of 88-93% and a bulk density of 1.18-1.19 g / cm³. 3 Preferably, the polyacrylonitrile fiber has an orientation degree of 90.5-92.5%.
[0027] The present invention provides a polyacrylonitrile fiber and its preparation method, which have the following beneficial effects:
[0028] This invention provides a polyacrylonitrile fiber and its preparation method. The nascent fiber enters a washing tank under the traction of a first drive roller. The wrap angle between the nascent fiber and the first drive roller is greater than 20° and less than 150°. The nascent fiber undergoes washing and hot water stretching treatment under the traction of a second drive roller. The wrap angle between the nascent fiber and the second drive roller is greater than 25° and less than 100°. To address the varying degrees of wrap angle required at different stages, this invention synergizes the drafting process with the equipment. Excessive wrap angle leads to excessive fiber tension, which can cause the fiber bundle to fray, become tangled in the rollers, and result in poor fiber appearance and excessive fuzz. Conversely, insufficient wrap angle results in loose fibers with poor bundle cohesion, making them prone to dispersion, sticking to the rollers, and tangling in the rollers, leading to unstable production. Furthermore, a small wrap angle results in a large spacing between the drive rollers, increasing the footprint, operational difficulty, and manufacturing costs. This invention proposes a method that, through the synergistic effect of wrap angles and process conditions at each stage, improves drafting efficiency, reduces manufacturing costs, and facilitates operation, producing polyacrylonitrile fibers with good density, high orientation, and a fuzz-free fiber surface. Detailed Implementation
[0029] To further illustrate the technical means and effects adopted by the present invention to achieve the intended inventive purpose, the following detailed description, in conjunction with preferred embodiments, provides a detailed explanation of the specific implementation methods, structures, features, and effects according to the present invention. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form. It should be noted that the terminology used herein is for describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form as well. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0030] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.
[0031] This invention provides a polyacrylonitrile fiber and a method for preparing the same, comprising the following steps:
[0032] 1) Solidification and forming step: The spun yarn undergoes solidification and forming treatment to obtain nascent fibers;
[0033] 2) Washing and hot water stretching steps: The nascent fibers are subjected to washing and hot water stretching treatments;
[0034] Before the washing step, the nascent fibers enter the washing tank under the traction of the first drive roller. The wrap angle between the nascent fibers and the first drive roller is greater than 20° and less than 150°. Preferably, the first drive roller has at least three rollers. The wrap angle between the nascent fibers and the first roller is greater than 25° and less than 45°, the wrap angle with the second roller is greater than 90°, and the wrap angle with the third roller is less than 45°. The nascent fibers enter the washing tank under the traction of the third roller for washing.
[0035] The nascent fibers undergo washing and hot water stretching under the traction of the second drive roller. The wrap angle between the nascent fibers and the second drive roller is greater than 25° and less than 100°. Preferably, the second drive roller has at least three rollers. The wrap angle between the nascent fibers and the first roller is less than 35°, the wrap angle with the second roller is greater than 60° and less than 85°, and the wrap angle with the third roller is less than 35°. Preferably, the washing temperature is 40-70°C, the hot water stretching temperature is 60-90°C, and the sulfoxide residue in the fibers after hot water stretching is ≤0.03%. Excessive sulfoxide residue in the fibers can lead to thermal melting during high-temperature calcination in the carbon fiber manufacturing process. Lower sulfoxide residue is better, but low sulfoxide residue requires extensive water washing, which increases costs. A reasonable setting of the sulfoxide residue can balance cost and fiber performance.
[0036] Here, the washing process mainly removes the solvent from the fibers. An excessively large or small wrap angle between the fibers and the first and second drive rollers is detrimental to washing. If the wrap angle is too small, the fiber bundle slips; if the wrap angle is too large, the fiber bundle is pulled too tightly, affecting the washing effect. This embodiment considers the impact of the wrap angle on the drafting process, coordinating the drafting process with the equipment to avoid excessive wrap angle, which leads to excessive fiber tension, easily causing the fiber bundle to fray and become entangled on the rollers; and insufficient wrap angle, resulting in loose fibers, poor bundle cohesion, and easy fiber dispersion and sticking to the rollers, causing roller entanglement and easy detachment, leading to production instability. Furthermore, a small wrap angle results in a large spacing between drive rollers, a large footprint, increased operational difficulty, and higher manufacturing costs. This embodiment proposes that, through the synergistic effect of the wrap angles and process conditions in each section of the equipment, the drafting effect can be improved, manufacturing costs reduced, and operation made more convenient. The resulting polyacrylonitrile fibers have good density, high orientation, and no fuzz on the fiber surface.
[0037] 3) The fibers after hot water stretching are sequentially subjected to oiling, drying and densification, and steam stretching to obtain polyacrylonitrile fibers. Among these,
[0038] 31) Drying and densification process:
[0039] The oiled fibers are dried and densified under the traction of the third drive roller. The wrap angle between the oiled fibers and the third drive roller is greater than 40° and less than 100°. Preferably, the third drive roller has at least five rollers, which are arranged alternately one above the other. The wrap angle between the oiled fibers and the first roller is greater than 45° and less than 90°, the wrap angle with the second, third, and fourth rollers is greater than 80°, and the wrap angle with the fifth roller is greater than 45° and less than 90°.
[0040] The drying and densification process includes 5-15 stages, and the temperature of the drying and densification process is 90-200℃. It is worth noting that the number of stages of the drying and densification process is consistent with the number of rollers in the third drive roller. Each roller of the third drive roller has a certain temperature to perform the drying and densification process on the oiled fibers. The temperature of the drying and densification process is also the temperature value of each roller. The moisture content of the fibers subjected to the drying and densification process is ≤0.5%, and the fiber bundle tension is 3000-6000 cN.
[0041] 32) Steam drawing process:
[0042] Before steam drawing, the dried and densified fibers are steam drawn under the traction of feed rollers, which are at least five rollers. The wrap angle between the dried and densified fibers and the first and fifth rollers is greater than 15° and less than or equal to 45°, and the wrap angle between the dried and densified fibers and the second, third, and fourth rollers is greater than 60° and less than or equal to 120°. The fiber exit direction of the steam-drawn fibers is tangent to the roller surface of the fifth roller.
[0043] The steam-drawn fibers are fed to the take-up winding forming via drawing rollers. There are at least five drawing rollers. The wrap angle between the steam-drawn fibers and the first and fifth rollers is greater than 15° and less than or equal to 45°, and the wrap angle between the steam-drawn fibers and the second, third, and fourth rollers is greater than 60° and less than or equal to 120°. The fiber entry direction after steam drawing is tangent to the roller surface of the first roller.
[0044] The steam drawing pressure is 0.2-0.6 MPa, the steam drawing ratio is 2-4 times, and the fiber bundle tension before steam drawing is 3000-6000 cN. The fiber bundle tension after steam drawing is 5000-8000 cN, and the fiber bundle tension after take-up at the drawing roller is 500-1200 cN.
[0045] Here, during the drying and densification process, the size of the wrap angle affects the duration of fiber drying and densification, thus directly affecting the drying and densification effect; fibers before and after steam drafting are prone to slipping off the rollers, and the size of the wrap angle also affects the steam drafting process. The above problems can be avoided by reasonably setting the size of the wrap angle.
[0046] Preferably, the fibers after the drying and densification treatment, before steam stretching, and after steam stretching are subjected to static electricity removal treatment. The static electricity removal treatment can be carried out by binding carbon fiber static brushes and installing static electricity devices.
[0047] In another aspect, embodiments of the present invention provide a polyacrylonitrile fiber, wherein the polyacrylonitrile fiber is prepared by the above-described method for preparing polyacrylonitrile fiber. The polyacrylonitrile fiber has an orientation degree of 85-95% and a bulk density of 1.17-1.19 g / cm³. 3 Preferably, the polyacrylonitrile fiber has an orientation degree of 88-93%, more preferably 90.5-92.5%, and a bulk density of 1.18-1.19 g / cm³. 3 .
[0048] The present invention will be further illustrated below with specific embodiments:
[0049] Example 1
[0050] This embodiment prepares a T800-12K polyacrylonitrile fiber, and the specific steps are as follows:
[0051] 1) After the spinning solution is solidified in the coagulation bath, nascent fibers are obtained.
[0052] 2) The nascent fibers enter the washing tank under the traction of the first drive roller. The first drive roller is a three-roller. The wrap angle between the nascent fibers and the first roller is 35°, the wrap angle with the second roller is 100°, and the wrap angle with the third roller is 35°. The nascent fibers enter the washing tank under the traction of the third roller for washing treatment.
[0053] 3) The nascent fibers undergo washing and hot water stretching under the traction of the second drive roller. The second drive roller is a three-roller system. The wrap angle between the nascent fibers and the first roller is 30°, the wrap angle with the second roller is 75°, and the wrap angle with the third roller is 30°. After the nascent fibers undergo three-stage washing treatment (the washing temperatures are 65°C, 68°C, and 70°C respectively), the residual solvent content of the fibers is 0.005%.
[0054] 4) After washing, the fibers undergo hot water stretching treatment (the hot water stretching temperatures are 85℃ and 90℃ respectively, and the stretching ratio is 1.8 times), two-stage oiling treatment (oiling temperature 20℃, concentration 1.5%), and eight-stage drying and densification treatment (the eight-stage drying and densification temperatures are 100℃, 105℃, 112℃, 115℃, 117℃, 120℃, 125℃, and 130℃ respectively).
[0055] 5) The oiled fibers are then dried and densified under the traction of the third drive roller, which is an eight-roller system. The wrap angle between the oiled fibers and the first roller is 60°, the wrap angle with the second to seventh rollers is 85°, and the wrap angle with the eighth roller is 60°. The moisture content of the dried and densified fibers is 0.1%. The fiber bundle tension after drying and densification is 4000 cN.
[0056] 6) After drying, the fibers are subjected to steam drawing treatment after static elimination. The dried and densified fibers are then subjected to steam drawing treatment under the traction of the feed rollers. There are five feed rollers. The wrap angle between the dried and densified fibers and the first and fifth rollers is 30°, and the wrap angle with the second, third and fourth rollers is 85°. The fiber exit direction of the steam drawing treatment is tangent to the roller surface of the fifth roller. The steam drawing pressure is 0.2MPa, the drawing ratio is 2.5 times, and the fiber bundle tension before steam drawing treatment is 5000cN.
[0057] 7) The steam-drawn fibers are fed to the take-up winding forming through the drawing rollers. There are five drawing rollers. The wrap angle between the steam-drawn fibers and the first and fifth rollers is 30°, and the wrap angle between the steam-drawn fibers and the second, third and fourth rollers is 80°. The steam-drawn fibers are tangent to the roller surface of the first roller. The tension of the fiber bundle after steam drawing is 6000cN, and the tension of the fiber bundle before take-up after the drawing rollers is 1000cN.
[0058] 8) T800-12k polyacrylonitrile fiber was obtained, with an orientation degree of 90.5% and a bulk density of 1.18 g / cm³. 3 .
[0059] Example 2
[0060] 1) After the spinning solution is solidified in the coagulation bath, nascent fibers are obtained.
[0061] 2) The nascent fibers enter the washing tank under the traction of the first drive roller. The first drive roller consists of three rollers. The wrap angle between the nascent fibers and the first roller is 30°, the wrap angle with the second roller is 120°, and the wrap angle with the third roller is 30°. Under the traction of the third roller, the fibers enter the washing tank for washing.
[0062] 3) The nascent fibers undergo washing and hot water stretching under the traction of the second drive roller. The second drive roller is a three-roller system. The wrap angle between the nascent fibers and the first roller is 30°, the wrap angle with the second roller is 75°, and the wrap angle with the third roller is 30°. After the nascent fibers undergo four stages of washing (the washing temperatures are 40°C, 50°C, 60°C, and 70°C respectively), the residual solvent content of the fibers is 0.03%.
[0063] 4) After washing, the fibers are subjected to hot water stretching treatment (temperatures of 75℃ and 85℃, with a stretch ratio of 2.2 times), one oiling (oiling temperature of 20℃, concentration of 2.0%), and ten-stage drying and densification treatment (ten-stage drying and densification temperatures of 120℃, 120℃, 130℃, 130℃, 140℃, 140℃, 150℃, 150℃, 160℃, 160℃).
[0064] 5) The oiled fibers are dried and densified under the traction of the third drive roller. The third drive roller is a ten-roller. The wrap angle between the oiled fiber and the first roller is 60°, the wrap angle between the oiled fiber and the second to ninth rollers is 85°, and the wrap angle between the oiled fiber and the tenth roller is 60°. The moisture content of the dried and densified fiber is 0.1%, and the fiber bundle tension is 4500cN.
[0065] 6) After drying, the fibers are destaticated and then steam-drawn. The dried and densified fibers are steam-drawn under the traction of the feed rollers. There are five feed rollers. The wrap angle between the dried and densified fibers and the first and fifth rollers is 30°, and the wrap angle between the dried and densified fibers and the second, third and fourth rollers is 85°. The fibers are tangent to the surface of the fifth roller during steam drawing. The steam drawing pressure is 0.6 MPa, the drawing ratio is 3.5 times, and the fiber bundle tension before steam drawing is 5500 cN.
[0066] 7) The steam-drawn fibers are fed to the take-up winding forming through the drawing rollers. There are five drawing rollers. The wrap angle between the steam-drawn fibers and the first and fifth rollers is 30°, and the wrap angle between the steam-drawn fibers and the second, third and fourth rollers is 80°. The fiber entry direction after steam drawing is tangent to the roller surface of the first roller. The fiber bundle tension after steam drawing is 6500cN, and the fiber bundle tension before take-up after drawing is 900cN.
[0067] 8) T800S-12k polyacrylonitrile fiber was obtained, with an orientation degree of 92.5% and a bulk density of 1.18 g / cm³. 3 .
[0068] Example 3
[0069] This embodiment prepares a T700S-12K polyacrylonitrile fiber, and the specific steps are as follows:
[0070] 1) After the spinning solution is solidified in the coagulation bath, nascent fibers are obtained.
[0071] 2) The nascent fibers enter the washing tank under the traction of the first drive roller. The first drive roller is a three-roller. The wrap angle between the nascent fibers and the first roller is 30°, the wrap angle with the second roller is 120°, and the wrap angle with the third roller is 30°. The nascent fibers enter the washing tank under the traction of the third roller for washing treatment.
[0072] 3) The nascent fibers undergo washing and hot water stretching under the traction of the second drive roller. The second drive roller is a three-roller system. The wrap angle between the nascent fibers and the first roller is 30°, the wrap angle with the second roller is 75°, and the wrap angle with the third roller is 30°. After the nascent fibers undergo four stages of washing (the washing temperatures are 40°C, 50°C, 60°C, and 70°C respectively), the residual solvent content of the fibers is 0.03%.
[0073] 4) After washing, the fibers are subjected to hot water stretching treatment (temperatures of 75℃ and 85℃, with a stretching ratio of 2.2 times), one oiling (oiling temperature of 20℃, concentration of 2.0%), and eight-stage drying and densification treatment (eight-stage drying and densification temperatures of 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, and 180℃).
[0074] 5) The oiled fibers are dried and densified under the traction of the third drive roller. The third roller is an eight-roller. The wrap angle between the oiled fiber and the first roller is 60°, the wrap angle between the oiled fiber and the second to seventh rollers is 85°, and the wrap angle between the oiled fiber and the eighth roller is 60°. The moisture content of the dried and densified fiber is 0.2%, and the fiber bundle tension is 4500cN.
[0075] 6) After drying, the fibers are destaticated and then steam-drawn. The dried and densified fibers are steam-drawn under the traction of the feed rollers. There are five feed rollers. The wrap angle between the dried and densified fibers and the first and fifth rollers is 30°, and the wrap angle between the dried and densified fibers and the second, third and fourth rollers is 85°. The fiber exit direction of the steam-drawn fibers is tangent to the roller surface of the fifth roller. The steam drawing pressure is 0.6 MPa, the drawing ratio is 3.3 times, and the fiber bundle tension before steam drawing is 5300 cN.
[0076] 7) The steam-drawn fibers are fed to the take-up winding forming through the drawing rollers. There are five drawing rollers. The wrap angle between the steam-drawn fibers and the first and fifth rollers is 30°, and the wrap angle between the second, third and fourth rollers is 80°. The steam-drawn fibers are tangent to the roller surface of the first roller. The tension of the fiber bundle after steam drawing is 6300cN, and the tension of the fiber bundle before take-up after drawing is 800cN.
[0077] 8) T700S-12k polyacrylonitrile fiber was obtained. The orientation degree of T700S-12k polyacrylonitrile fiber was 91.8%, and the bulk density was 1.18 g / cm³. 3 .
[0078] Example 4
[0079] This embodiment prepares a T700-12K polyacrylonitrile fiber, and the specific steps are as follows:
[0080] 1) After the spinning solution is solidified in the coagulation bath, nascent fibers are obtained.
[0081] 2) The nascent fibers enter the washing tank under the traction of the first drive roller. The first drive roller is a three-roller. The wrap angle between the nascent fibers and the first roller is 35°, the wrap angle with the second roller is 100°, and the wrap angle with the third roller is 35°. Under the traction of the third roller, the fibers enter the washing tank for washing.
[0082] 3) The nascent fibers undergo washing and hot water stretching under the traction of the second drive roller. The second drive roller is a three-roller system. The wrap angle between the nascent fibers and the first roller is 30°, the wrap angle with the second roller is 75°, and the wrap angle with the third roller is 30°. After the nascent fibers undergo three-stage washing treatment (the washing temperatures are 65°C, 68°C, and 70°C respectively), the residual solvent content of the fibers is 0.003%.
[0083] 4) After washing, the fibers undergo hot water stretching treatment (the hot water stretching temperatures are 85℃ and 90℃ respectively, and the stretching ratio is 1.8 times), two-stage oiling (oiling temperature 20℃, concentration 1.2%), and seven-stage drying and densification treatment (the seven-stage drying and densification temperatures are 100℃, 105℃, 112℃, 115℃, 117℃, 120℃, and 125℃ respectively).
[0084] 5) The oiled fibers are then dried and densified under the traction of the third drive roller (a seven-roller system). The wrap angle between the oiled fibers and the first roller is 60°, the wrap angle with the second to sixth rollers is 85°, and the wrap angle with the seventh roller is 60°. The moisture content of the dried and densified fibers is 0.1%. The fiber bundle tension after drying and densification is 3900 cN.
[0085] 6) After drying, the fibers are destaticated and then steam drawn. Before steam drawing, the fibers after drying and densification are steam drawn under the traction of the feed rollers. There are five feed rollers. The wrap angle between the dried and densified fibers and the first and fifth rollers is 30°, and the wrap angle between the fibers and the second, third and fourth rollers is 85°. The fibers for steam drawing are tangent to the roller surface of the fifth roller. The steam drawing pressure is 0.2 MPa, the drawing ratio is 2.5 times, and the fiber bundle tension before steam drawing is 5000 cN.
[0086] 7) The steam-drawn fibers are fed to the take-up winding forming through the drawing rollers. There are five drawing rollers. The wrap angle between the steam-drawn fibers and the first and fifth rollers is 30°, and the wrap angle between the steam-drawn fibers and the second, third and fourth rollers is 80°. The fiber entry direction after steam drawing is tangent to the roller surface of the first roller. The fiber bundle tension after steam drawing is 6000cN, and the fiber bundle tension before take-up after drawing is 1000cN.
[0087] 8) T700-12k polyacrylonitrile fiber was obtained, with an orientation degree of 91.0% and a bulk density of 1.18 g / cm³. 3 .
[0088] Comparative Example 1
[0089] The specific steps for preparing T700S-12K polyacrylonitrile fiber in this embodiment are as follows:
[0090] After the spinning solution is solidified in the coagulation bath, nascent fibers are obtained. The nascent fibers enter the washing tank under the traction of the first drive roller. The first drive roller is a three-roller. The wrap angle between the nascent fibers and the first roller is 60°, the wrap angle with the second roller is 60°, and the wrap angle with the third roller is 60°. Under the traction of the third roller, the fibers enter the washing tank for washing treatment.
[0091] Other processes are the same as in Example 3.
[0092] The fiber exhibited excessive fuzz during processing, resulting in a poor appearance for the obtained T700S-12k polyacrylonitrile fiber. The T700S-12k polyacrylonitrile fiber had an orientation degree of 90% and a bulk density of 1.180 g / cm³. 3 .
[0093] Comparative Example 2
[0094] The specific steps for preparing T700S-12K polyacrylonitrile fiber in this embodiment are as follows:
[0095] The nascent fibers undergo washing and hot water stretching under the traction of the second drive roller. The second drive roller is a three-roller system. The wrap angle between the nascent fibers and the first roller is 60°, the wrap angle with the second roller is 90°, and the wrap angle with the third roller is 60°. After the nascent fibers undergo three-stage washing treatment (the washing temperatures are 65°C, 68°C, and 70°C respectively), the fiber solvent residue is 0.1%.
[0096] Other processes are the same as in Example 3.
[0097] During fiber processing, the fiber bundle is kept taut, resulting in a high sulfoxide residue in the obtained T700S-12k polyacrylonitrile fiber. The orientation degree of the T700S-12k polyacrylonitrile fiber is 88%, and the bulk density is 1.178 g / cm³. 3.
[0098] Comparative Example 3
[0099] The specific steps for preparing T700S-12K polyacrylonitrile fiber in this embodiment are as follows:
[0100] After oiling, the fibers are dried and densified under the traction of the third drive roller. The wrap angle between the oiled fibers and the first roller is 60°, the wrap angle with the second roller is 45°, and the wrap angle with the third roller is 60°. The moisture content of the dried and densified fibers is 2.0%, and the fiber bundle tension is 4500cN.
[0101] Other processes are the same as in Example 3.
[0102] The fibers were not completely dried after the drying and densification treatment, resulting in poor density. The orientation degree of the obtained T700S-12k polyacrylonitrile fiber was 82%, and the bulk density was 1.17 g / cm³. 3 .
[0103] Comparative Example 4
[0104] This embodiment prepares a T700S-12K polyacrylonitrile fiber, and the specific steps are as follows:
[0105] After steam drawing, the fibers are fed to the take-up winding forming through the drawing rollers. There are five drawing rollers. The wrap angle between the steam-drawn fiber and the fifth roller is 10°, and the wrap angle between the fiber and the second, third and fourth rollers is 80°. The fiber exit direction after steam drawing is tangent to the roller surface of the fifth roller. The fiber bundle tension after steam drawing is 6000cN, and the fiber bundle tension before take-up after drawing is 400cN.
[0106] Other processes are the same as in Example 3.
[0107] After passing through the drafting rollers, the fibers diverged, resulting in severe fiber adhesion to the roller surface and a tendency for fibers to entangle and break. The resulting T700S-12k polyacrylonitrile fiber had an orientation degree of 91% and a bulk density of 1.18 g / cm³. 3 .
[0108] It will be readily understood by those skilled in the art that the aforementioned advantageous methods can be freely combined and superimposed without conflict.
[0109] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above are merely preferred embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.
Claims
1. A process for the production of polyacrylonitrile fibers, characterized in that, Includes the following steps: Solidification and forming step: The spun yarn is solidified and formed to obtain nascent fibers; Washing and hot water stretching steps: The nascent fibers are subjected to washing and hot water stretching treatments; Post-treatment: The fibers after hot water stretching are post-treated to obtain polyacrylonitrile fibers; Before the washing step, the nascent fibers enter the washing tank under the traction of the first drive roller, and the wrap angle between the nascent fibers and the first drive roller is greater than 20° and less than 150°; during the washing and hot water stretching steps, the nascent fibers undergo washing and hot water stretching under the traction of the second drive roller, and the wrap angle between the nascent fibers and the second drive roller is greater than 25° and less than 100°. The post-processing steps include: sequentially applying oil, drying and densifying, and steam drawing to the fibers after hot water stretching treatment to obtain polyacrylonitrile fibers; Before steam drawing, the dried and densified fibers are steam drawn under the traction of feed rollers, which are at least five rollers. The wrap angle between the dried and densified fibers and the first and fifth rollers is greater than 15° and less than or equal to 45°, and the wrap angle between the dried and densified fibers and the second, third, and fourth rollers is greater than 60° and less than or equal to 120°. The fiber exit direction of the steam-drawn fibers is tangent to the roller surface of the fifth roller. The fiber bundle tension of the steam-drawn fibers is 5000-8000 cN, and the fiber bundle tension after the drawing rollers and before take-up is 500-1200 cN.
2. The method for preparing polyacrylonitrile fibers according to claim 1, characterized in that, The first drive roller has at least three rollers. The wrap angle between the nascent fiber and the first roller is greater than 25° and less than 45°, the wrap angle between the nascent fiber and the second roller is greater than 90°, and the wrap angle between the nascent fiber and the third roller is less than 45°. The nascent fiber enters the washing tank for washing under the traction of the third roller.
3. The method for preparing polyacrylonitrile fibers according to claim 1, characterized in that, The second drive roller has at least three rollers, the wrap angle between the nascent fiber and the first roller is less than 35°, the wrap angle between the nascent fiber and the second roller is greater than 60° and less than 85°, and the wrap angle between the nascent fiber and the third roller is less than 35°.
4. The method of producing polyacrylonitrile fibers according to claim 1, characterized by, The washing temperature is 40-70℃, the hot water stretching temperature is 60-90℃, and the residual sulfoxide content of the fiber after the hot water stretching treatment is ≤0.03%.
5. The method for preparing polyacrylonitrile fibers according to claim 1, characterized in that, The oiled fibers are dried and densified under the traction of the third drive roller. The wrap angle between the oiled fibers and the third drive roller is greater than 40° and less than 100°.
6. The process for the preparation of polyacrylonitrile fibers according to claim 5, characterized in that, The third drive roller consists of at least five rollers arranged alternately up and down. The wrap angle between the oiled fiber and the first roller is greater than 45° and less than 90°, the wrap angle between the fiber and the second, third, and fourth rollers is greater than 80°, and the wrap angle between the fiber and the fifth roller is greater than 45° and less than 90°.
7. The method for preparing polyacrylonitrile fibers according to claim 1, characterized in that, The drying and densification process includes 5-15 stages, and the temperature of the drying and densification process is 90-200℃.
8. The process for the preparation of polyacrylonitrile fibers according to claim 7, characterized in that, The moisture content of the dried and densified fiber is ≤0.5%, and the fiber bundle tension after drying and densification is 3000-6000 cN.
9. The process for the production of polyacrylonitrile fibers according to any one of claims 1 to 8, characterized in that, The steam-drawn fibers are fed to the take-up winding forming via drawing rollers. There are at least five drawing rollers. The wrap angle between the steam-drawn fibers and the first and fifth rollers is greater than 15° and less than or equal to 45°, and the wrap angle between the steam-drawn fibers and the second, third, and fourth rollers is greater than 60° and less than or equal to 120°. The direction of fiber insertion after steam drawing is tangent to the surface of the first roller.
10. The method of producing polyacrylonitrile fibers according to claim 1, characterized by, The steam drawing treatment pressure is 0.2-0.6 MPa, the steam drawing ratio is 2-4 times, and the fiber bundle tension before steam drawing treatment is 3000-6000 cN.
11. A polyacrylonitrile fiber, characterized by, The polyacrylonitrile is produced by the method for preparing polyacrylonitrile fibers according to any one of claims 1 to 10.
12. The polyacrylonitrile fiber according to claim 11, characterized in that, The polyacrylonitrile fibers have an orientation degree of 88-93% and a bulk density of 1.18-1.19 g / cm³. 3 .