A polyacrylonitrile fiber and its preparation method

Abstract

This invention provides a polyacrylonitrile fiber and its preparation method. The preparation method includes the following steps: nascent fiber stage: the spinning fluid undergoes coagulation and forming treatment to obtain nascent fiber; washing and hot water drawing stage: the nascent fiber is sequentially subjected to washing and hot water drawing treatment; cooling and dehumidification stage: the fiber after hot water drawing treatment is first subjected to cooling and dehumidification treatment; oiling stage: the fiber after cooling and dehumidification treatment is oiled; post-treatment: the oiled fiber is post-treated to obtain polyacrylonitrile fiber. In the cooling and dehumidification stage, the cooling and dehumidification treatment is carried out in a chamber equipped with a drive roller for cooling the fiber. The fiber after hot water drawing treatment is cooled by the drive roller under its traction and then dehumidified in the chamber. This invention synergizes the drawing process and equipment, improving the drawing effect and producing polyacrylonitrile fiber with uniform oiling and stable fiber quality.

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] Polyacrylonitrile (PAC) fiber is a prerequisite for producing high-performance carbon fiber. In carbon fiber production, PAC fiber accounts for 50% of the total cost, and high production costs are a key factor restricting the development of domestically produced carbon fiber. The PAC fiber production process includes spinning, coagulation bath, washing, hot drawing, oiling, drying and densification, steam drawing, and winding. Among these, the oiling process is the most costly and crucial step in the precursor fiber production, affecting the final quality of the carbon fiber. Oiling the PAC fiber forms a film on its surface, preventing filament adhesion or tangling, reducing friction and wear between filament surfaces during pre-oxidation, and decreasing friction between the fiber bundle and the drive rollers. This reduces fuzz and surface defects introduced during pre-oxidation, thereby improving the performance of the carbon fiber.

[0003] When fibers are drawn through hot water into the oiling tank, a large amount of water is introduced, reducing the oil concentration. Oil needs to be added to balance the concentration, and the high fiber temperature leads to a high oil temperature in the oiling tank, accelerating its spoilage. The continuous water carried by the fibers and the metered replenishment of oil cause the oil level in the circulation tank to rise, eventually overflowing into the oiling pit. Alternatively, waste oil needs to be periodically extracted, and the oiling tank cleaned, resulting in oil waste and increased costs. This is especially true in the dry-jet wet-spinning process of polyacrylonitrile fiber production, where the amount of oil used is large, generating even more waste oil and higher costs. Current technology typically involves spraying cooling water onto the fibers after hot water drawing, followed by at least two pressure rollers to cool the fibers and remove excess moisture before they enter the oiling tank for oiling. While existing technologies can achieve the purpose of cooling, repeated pressing by rollers can easily cause fiber fuzzing and fiber breakage. At the same time, the pressing process can easily cause the material clumps brought in by the fibers to stick to the surface of the rollers, which can lead to fiber breakage and roller entanglement during long-term accumulation. In addition, because the fiber speed is relatively fast after hot water stretching, the spray cooling time is short, the cooling effect is generally poor, and the temperature difference between the fiber surface and core is large after spray cooling, which is not conducive to the uniformity of subsequent oiling and the final quality stability of the fiber.

[0004] In existing technologies, fibers are cooled by spraying with cooling water after being drawn in hot water, and then squeezed by at least two pressure rollers. Excessive squeezing can easily cause the fibers to become fuzzy, break, and become entangled in the rollers. Furthermore, the high temperature and water introduced during cooling can cause waste oil and oil agent to deteriorate during oiling, resulting in poor fiber quality stability and high production costs. Therefore, this invention studies and designs a polyacrylonitrile fiber and its preparation method. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects in the prior art where the fiber is sprayed with cooling water after being stretched in hot water and then squeezed to remove water by at least two pressure rollers, which leads to fiber fuzzing and waste oil generation during oiling. Thus, the present invention provides a polyacrylonitrile fiber and its preparation method.

[0006] To address the above problems, this invention provides a method for preparing polyacrylonitrile fibers, comprising the following steps:

[0007] Initial step: The spinning fluid undergoes a solidification and shaping process to obtain nascent fibers;

[0008] Washing and hot water stretching steps: The nascent fibers are sequentially subjected to washing and hot water stretching treatments;

[0009] Cooling and dehumidification steps: The fibers after hot water stretching are first subjected to cooling and dehumidification treatment;

[0010] Oiling step: Apply oil to the fibers after cooling and dehumidification treatment;

[0011] Post-treatment: The oiled fibers are post-treated to obtain polyacrylonitrile fibers;

[0012] In the cooling and dehumidification step, the cooling and dehumidification process is carried out in a box. The box is equipped with a transmission roller for cooling the fibers. The fibers after hot water stretching are cooled by the transmission roller under its traction and dehumidified in the box.

[0013] In some embodiments, the drive rollers are at least two rollers, arranged at intervals in the vertical direction. After hot water stretching treatment, the running direction of the fiber is tangent to the roller surface of the first roller. The wrap angle between the fiber and the second roller is greater than 90°. The fiber is oiled after passing through the second roller.

[0014] In some embodiments, during the cooling and dehumidification step, the temperature Q2 of the drive roller is 0-20°C, and the humidity inside the chamber is less than 60%.

[0015] The temperature Q1 inside the chamber is 10-30℃, and when the fibers after cooling and dehumidification are oiled, the wetting angle between the oil and the fibers is less than 40°; or, the temperature Q1 inside the chamber is 10-20℃, and when the fibers after cooling and dehumidification are oiled, the wetting angle between the oil and the fibers is 20-30°.

[0016] In some embodiments, during the oiling step, the oiling temperature is no higher than 30°C, the oil concentration is 2-5%, and the oil circulation rate is 6-10 m³ / h. 3 / h, the oiling time is 1-10s, and the draw ratio of the oiling roller is 0.95-1.05; or, in the oiling step, the oiling temperature is 15-25℃, the oil concentration is 2.5-3.5%, and the oil circulation rate is 7-8m. 3 / h, oiling time is 2-5s, and the draw ratio of the oiling roller is 0.98-1.00.

[0017] In some embodiments, during the cooling and dehumidification step, the time for the fibers after hot water stretching treatment to pass through the drive roller is 1-10 seconds, and the stretching ratio of the drive roller is 0.90-1.00.

[0018] In some embodiments, the housing has an exhaust vent, and the inner peripheral wall of the drive roller is provided with a cooling pipe arranged in a spiral shape. The cooling pipe is used to circulate coolant to cool the drive roller.

[0019] In some embodiments, before the cooling and dehumidification step, the fibers after hot water stretching treatment must meet the following requirements: fiber sulfoxide content not greater than 0.03%, fiber monofilament diameter 24-28μm, fiber swelling degree less than 50%, width 30-40mm, and number of spinnerets not greater than 30. In the cooling and dehumidification step, the diameter of the drive roller is 500-1000mm, and the length of the drive roller is not greater than 2000mm.

[0020] In some embodiments, the post-processing steps include: sequentially drying and densifying the hot water-stretched and oil-treated fibers, steam-stretching the fibers, and winding them to obtain polyacrylonitrile fibers.

[0021] In some embodiments, the fiber temperature Q3 after cooling and dehumidification treatment is ≤30°C, and the fiber moisture content is ≤20%.

[0022] The present invention also provides a polyacrylonitrile fiber, wherein the polyacrylonitrile is prepared by the above-described method for preparing polyacrylonitrile fiber.

[0023] In some embodiments, the polyacrylonitrile fibers obtained after post-treatment have a strength >600MPa, an oiling rate of 1.0-3.0%, a CV value ≤3%, and an ash content ≤0.25%.

[0024] The present invention provides a polyacrylonitrile fiber and its preparation method, which have the following beneficial effects:

[0025] In the cooling step, the fibers, after being drawn by hot water, are cooled by the drive rollers and dehumidified within the housing. This synergistic effect of the drawing process and cooling prevents waste oil generation and oil agent spoilage caused by high temperatures and water ingress, avoids fiber fuzzing, breakage, and roller entanglement due to excessive compression, and reduces surface and core differences in fibers. It also improves oiling uniformity and fiber quality stability, reduces production costs, and produces high-quality fibers. This invention proposes that by combining the cooling of the drive rollers, dehumidification of the housing, and the synergistic effect of process conditions, the oiling effect can be improved, manufacturing costs reduced, operation convenient, and the prepared polyacrylonitrile fibers exhibiting strong oiling uniformity and fiber quality stability, thus enabling the production of high-quality fibers. Attached Figure Description

[0026] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0027] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0028] Figure 1 This is a perspective view of the transmission roller in the method for preparing polyacrylonitrile fiber according to an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the decomposed oil agent in the preparation method of polyacrylonitrile fiber in Comparative Example 2 of the present invention. Detailed Implementation

[0030] 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, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. 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.

[0032] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0033] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0034] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0035] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0036] 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.

[0037] According to an embodiment of the present invention, a method for preparing polyacrylonitrile fibers is provided, comprising the following steps:

[0038] 1) Initial step: The spinning fluid undergoes a solidification and shaping process to obtain nascent fibers;

[0039] 2) Washing and Hot Water Drawing Steps: The nascent fibers are sequentially subjected to washing and hot water drawing treatments. Specifically, before the cooling step, the fibers after hot water drawing treatment must meet the following requirements: sulfoxide content not exceeding 0.03%, single filament diameter of 24-28 μm, fiber swelling degree less than 50%, width of 30-40 mm, and spinning number not exceeding 30. In the cooling and dehumidification step, the diameter of the drive roller is 500-1000 mm, and the roller length is not greater than 2000 mm.

[0040] The residual sulfoxide content should not exceed 0.03%. High sulfoxide content can cause fiber adhesion, affecting cooling and oiling effects, as well as fiber strength and appearance, failing to meet the performance indicators of the polyacrylonitrile fiber prepared by this invention. The fiber monofilament diameter is 24-28 μm and the width is 30-40 mm, corresponding to a drive roller length of less than 2000 mm. Because this cooling method uses a drive roller, the fibers must be laid flat on the roller surface to ensure cooling effectiveness. If the fibers are bundled, only the surface can be cooled, and the core fibers cannot be cooled, resulting in uneven cooling. For ease of operation, the spinning lines are all single-support rollers. Single-support rollers are prone to poor parallelism and large diameter jumps, which are not conducive to producing fibers with stable and uniform performance. Therefore, in this invention, the drive roller length must not exceed 2000 mm, which limits the number of fiber spins and the width of the filament bundle. The monofilament diameter corresponds to the width. Under the aforementioned limitations on monofilament diameter, width, and number of spins, each filament bundle is ensured to be laid flat on the roller surface to guarantee optimal cooling and oiling effects. Fiber swelling degree should be less than 50%. Fiber swelling degree reflects fiber porosity and corresponds to an oil-fiber wetting angle of less than 40°. High swelling degree indicates high fiber porosity, making the fiber easier to oil. Conversely, a small wetting angle allows oil to easily penetrate the fiber interior, resulting in high oiling rate and high ash content. Excessive ash content or oil penetration into the fiber's internal structure can lead to defects and low strength in the prepared carbon fibers. Fibers after hot water drawing treatment must meet the following requirements: sulfoxide content not exceeding 0.03%, single filament diameter of 24-28 μm, fiber swelling degree less than 50%, width of 30-40 mm, and spinning number not exceeding 30. This ensures good fiber specifications and effective cooling and oiling.

[0041] 3) Cooling and dehumidification step: The fibers after hot water stretching are first subjected to cooling and dehumidification treatment;

[0042] 31) In the cooling and dehumidification step, the cooling and dehumidification treatment is carried out in a chamber. The chamber is equipped with a transmission roller for cooling the fibers. The fibers, after hot water drawing, are cooled by the transmission roller and dehumidified within the chamber. After the hot water drawing treatment, cooling by the transmission roller, and dehumidification within the chamber, the fiber temperature Q3 ≤ 30℃, Q2 ≤ Q1 ≤ Q3, and the fiber moisture content ≤ 20%. This ensures that the fibers are evenly oiled and have a high oil film coverage during oiling, thereby reducing friction between the fiber bundle and the transmission roller, reducing fuzz, and minimizing surface defects introduced during pre-oxidation, thus improving the performance of the carbon fiber.

[0043] Specifically, there are at least two drive rollers, arranged at intervals in the vertical direction. After hot water stretching treatment, the fiber's running direction is tangent to the surface of the first roller. The wrap angle between the fiber and the second roller is greater than 90°. The fiber is oiled after passing through the second roller. The wrap angle greater than 90° ensures that the fiber is sufficiently cooled on the drive rollers, further guaranteeing the stretching effect of the drive rollers.

[0044] In some embodiments, during the cooling and dehumidification step, the temperature Q2 of the drive roller is 0-20°C, the temperature Q1 inside the housing is 10-30°C, and the humidity inside the housing is less than 60%. When the fibers after cooling and dehumidification are oiled, the wetting angle between the oil and the fiber is less than 40°. The cooling time, drive roller temperature, and draw ratio are coordinated to ensure that the fiber moisture content after cooling is ≤20% and the fiber temperature is ≤30°C. Preferably, the temperature Q2 of the drive roller is 10-20°C, the temperature Q1 inside the housing is 10-20°C, and the humidity inside the housing is <60%. When the fibers after cooling and dehumidification are oiled, the wetting angle between the oil and the fiber is 20-30°. In this invention, preferably, maintaining the same temperature between the drive roller and the housing further improves the cooling efficiency of the drive roller and avoids the temperature inside the housing affecting the temperature of the drive roller. Specifically, the surface of the drive roller is made of ceramic or chrome-plated material with a roughness ≤Ra0.1. Ensure the surface of the drive roller is smooth to prevent scratching the fibers during fiber drawing and improve fiber quality.

[0045] In the cooling and dehumidification step, the time for the fibers after hot water stretching treatment to pass through the drive rollers is 1-10 seconds, and the stretching ratio of the drive rollers is 0.90-1.00. Here, the time for the fibers after hot water stretching treatment to pass through the drive rollers is the total time for the fibers to pass through all rollers, and the stretching ratio is the stretching ratio of each drive roller.

[0046] In some embodiments, the housing has an exhaust vent, see reference [link to previous document]. Figure 1As shown, cooling pipes are provided on the inner circumferential wall of the transmission roller. These cooling pipes are arranged in a spiral shape and are used to circulate coolant, thus cooling the transmission roller. Alternatively, grooves can be provided circumferentially on the inner circumferential wall of the transmission roller, and these grooves are arranged in a spiral shape along the axial direction of the transmission roller. Cooling pipes are placed within these grooves and are used to circulate coolant, thus cooling the transmission roller. The enclosure is a closed space, and the enclosure uses air conditioning for temperature and humidity control. An exhaust vent is located above the cooling roller inside the enclosure, at a 45-60° angle to the left of the cooling roller. A line connects the exhaust vent to the center of the enclosure. Using the longitudinal section of the enclosure as the projection plane, the enclosure has a vertical centerline with an angle of 45-60° between the vertical centerline and this line. The chamber is used to control the cooling and humidity environment to avoid high ambient temperature or high humidity, excessive water on the roller surface, and high fiber moisture content, which would lead to excessive oil and water, making it difficult to control the oil concentration, causing oil film formation defects, and subsequently introducing surface defects during the pre-oxidation process. The chamber uses air conditioning to control temperature and humidity, ensuring that no cold air accumulates inside the chamber.

[0047] In the cooling and dehumidification step, the temperature Q2 of the transmission roller is 0-20℃, and the humidity inside the chamber is less than 60%; the temperature Q1 inside the chamber is 10-30℃. When the fibers after cooling and dehumidification are oiled, the wetting angle between the oil and the fibers is less than 40°. By maintaining the temperature Q2 of the transmission roller at 10-20℃, the humidity inside the chamber at less than 60%, and the temperature Q1 inside the chamber at 20-30℃, the moisture content and temperature of the fibers after cooling and dehumidification are significantly reduced. Therefore, when the fibers after cooling and dehumidification only need oiling, the wetting angle only needs to be less than 40°. This ensures uniform oiling and the integrity of the oil film, and also prevents the oil from entering the fiber interior. High oiling rate and high ash content, or excessive ash content or oil penetration into the fiber structure, can easily cause defects in the prepared carbon fibers.

[0048] Preferably, in the cooling and dehumidification step, the temperature Q2 of the drive roller is 10-20℃, and the humidity inside the chamber is less than 60%; the temperature Q1 inside the chamber is 10-20℃, and the wetting angle between the oil and the fiber is 20-30° when the fiber after cooling and dehumidification is oiled. This synergistic effect of the drawing process and cooling maintains the same temperature between the drive roller and the chamber, further improving the cooling efficiency of the drive roller and preventing the temperature inside the chamber from affecting the temperature of the drive roller. This ensures that the moisture content and temperature reduction efficiency of the fiber after cooling and dehumidification are guaranteed, resulting in a significant reduction in moisture content and temperature, ensuring uniform oiling, the integrity of the oil film, and preventing the oil from entering the fiber interior.

[0049] In the cooling and dehumidification step, the fiber being drawn by the drive roller is cooled by cooling the drive roller itself. This synergistic effect between the drafting process and cooling prevents waste oil generation and oil agent spoilage caused by high temperature and water introduction, avoids fiber fuzzing, breakage, and roller entanglement due to excessive compression, and improves fiber surface and core differences. It also enhances oiling uniformity and fiber quality stability, reduces production costs, and produces high-quality fibers. At least two rollers are used for cooling to ensure effectiveness. Simultaneously, the first roller acts as a guide and buffer for the nascent fibers being cooled, preventing them from directly passing through the drive roller at an angle greater than 90°, which could lead to fiber breakage. This invention proposes that, through the synergistic effect of drive roller cooling, equipment wrap angle, and process conditions, the drafting effect can be improved, manufacturing costs reduced, and operation made easier, resulting in polyacrylonitrile fibers with good density, high orientation, and a fuzz-free fiber surface. The wrap angle refers to the central angle subtended by the arc of contact between the fiber and the drive roller.

[0050] 4) Oiling step: Apply oil to the fibers after cooling and dehumidification treatment;

[0051] In the oiling step, the oiling temperature is no higher than 30℃, the oil concentration is 2-5%, and the oil circulation rate is 6-10m. 3 The oiling rate is 1-10 seconds per hour, and the draw ratio of the oiling roller is 0.95-1.05. Preferably, the oiling temperature is 15-25℃, the oil concentration is 2.5-3.5%, and the oil circulation rate is 7-8 m³ / h. 3 The oiling time is 2-5 seconds, and the draw ratio of the oiling roller is 0.98-1.00. This prevents the oil from entering the fiber interior during oiling, which could cause defects in the fiber's internal structure, reduce fiber strength, and increase ash content. It ensures that the oil completely covers the fiber surface during oiling, forming an oil film, reducing fuzz and improving the performance of the carbon fiber.

[0052] 5) Post-treatment: The oiled fibers are post-treated to obtain polyacrylonitrile fibers;

[0053] The further post-processing steps include: sequentially subjecting the fibers after hot water stretching treatment to drying and densification treatment, steam stretching treatment, and winding to obtain polyacrylonitrile fibers.

[0054] This invention also provides a polyacrylonitrile fiber, wherein the polyacrylonitrile is prepared by the above-described method for preparing polyacrylonitrile fibers. Preferably, the fiber temperature Q3 after cooling and dehumidification treatment is ≤30℃, and the fiber moisture content is ≤20%. Preferably, the polyacrylonitrile fiber obtained after post-treatment has a strength >600MPa, an oiling rate of 1.0-3.0%, a CV value (coefficient of variation of fiber oiling rate between different spinning positions over the same spinning length) ≤3%, and an ash content ≤0.25%.

[0055] The present invention will be further illustrated below with specific embodiments:

[0056] Example 1

[0057] The specific steps for preparing T800S-12K polyacrylonitrile fiber in this embodiment are as follows:

[0058] 1) The spinning fluid undergoes a solidification and shaping process to obtain nascent fibers;

[0059] 2) The nascent fibers are sequentially subjected to water washing and hot water stretching treatment;

[0060] After hot water stretching, the fiber sulfoxide retention is 0.01%, the fiber monofilament diameter is 25μm, the fiber swelling degree is 45%, the width is 38mm, and the number of spindles is 25.

[0061] 3) The fibers after hot water stretching are first subjected to cooling and dehumidification treatment;

[0062] Specifically, the cooling and dehumidification process is carried out in a chamber, which is equipped with a drive roller for cooling the fibers. The fibers, after hot water stretching treatment, are cooled by the drive roller and dehumidified within the chamber. The temperature Q1 inside the chamber is 25°C, the humidity is 55%, and the exhaust vent is located 50° above and to the left of the drive roller.

[0063] The drive rollers consist of 5 rollers. The fibers are cooled by passing through the 5 rollers in the housing. The drive rollers are arranged alternately at the top and bottom. The fiber running direction is tangent to the roller surface of the first roller and the wrap angle with the intermediate roller is 120°. The intermediate roller refers to the roller after the first roller. Preferably, the intermediate roller can be the roller between the first roller and the last roller. The last roller is the roller before the oiling step. The fiber running direction is tangent to the roller surface of the last roller. The temperature of all drive rollers is 15°C. The cooling time of the fibers through all drive rollers is 1.8s. The draw ratio of each drive roller is 0.99. The diameter of the drive roller is 600mm and the length is 1300mm. The surface is chrome-plated and the roughness Ra is 0.1.

[0064] After being cooled by the drive roller, the fiber temperature is 30℃ and the fiber moisture content is 14%.

[0065] 4) The fibers after cooling and dehumidification are then oiled. The oiling temperature is 28℃, the concentration is 3%, and the oil circulation rate is 7.5m³. 3 The oiling time is 1.77s, the wetting angle between the oil and the fiber is 25°, and the draw ratio of the oiling roller is 0.99.

[0066] 5) After the oiled fibers are dried and densified, steam-stretched, and then wound into shape, the resulting polyacrylonitrile fibers have a strength of 600 MPa, an oiling rate of 1.2%, a CV value of 2.8%, and an ash content of 0.10%.

[0067] No waste oil is generated during the production process, there is no oil agent spoilage, no accumulation of flocculent matter, and no need to stop the production line to clean the oil tank and change the oil.

[0068] Example 2

[0069] The specific steps for preparing T700S-12K polyacrylonitrile fiber in this embodiment are as follows:

[0070] 1) The spinning fluid undergoes a solidification and shaping process to obtain nascent fibers;

[0071] 2) The nascent fibers are sequentially subjected to water washing and hot water stretching treatment;

[0072] After hot water stretching treatment, the fiber sulfoxide retention was 0.03%, the fiber monofilament diameter was 27 μm, the fiber swelling degree was 40%, the width was 35 mm, and the number of spindles was 22.

[0073] 3) The fibers after hot water stretching are first subjected to cooling and dehumidification treatment;

[0074] Specifically, the cooling and dehumidification process is carried out in a chamber, which is equipped with a drive roller for cooling the fibers. The fibers, after hot water stretching treatment, are cooled by the drive roller and dehumidified within the chamber. The temperature Q1 inside the chamber is 20°C, the humidity is 55%, and the exhaust vent is located 45° above and to the left of the drive roller.

[0075] The drive rollers consist of two rollers. The fibers are cooled by passing through the two rollers in the housing. The drive rollers are arranged alternately on the top and bottom. The direction of fiber running is tangent to the roller surface of the first roller and the wrap angle with the second roller is 150°. The temperature of the drive rollers is 10℃. The cooling time of the fibers through the drive rollers is 1.7s. The draft ratio of each drive roller is 0.90. The diameter of the drive roller is 1000mm and the length is 1100mm. The surface is chrome-plated and the roughness is Ra0.1.

[0076] After the drive roller is cooled, the fiber temperature is 22℃ and the fiber moisture content is 16%.

[0077] 4) The fibers after cooling and dehumidification are then oiled. The oiling temperature is 28℃, the concentration is 3%, and the oil circulation rate is 7.5m³. 3 The oiling time is 1.77s, the wetting angle between the oil and the fiber is 25°, and the draw ratio of the oiling roller is 0.99.

[0078] 5) After the oiled fibers are dried and densified, steam-stretched, and then wound into shape, the resulting polyacrylonitrile fibers have a strength of 700 MPa, an oiling rate of 1.0%, a CV value of 2.5%, and an ash content of 0.08%.

[0079] No waste oil is generated during the production process, and there is no oil corrosion or accumulation of flocculent matter. There is no need to stop the production line to clean the oil tank and change the oil.

[0080] Example 3

[0081] The specific steps for preparing T700S-12K polyacrylonitrile fiber in this embodiment are as follows:

[0082] 1) The spinning fluid undergoes a solidification and shaping process to obtain nascent fibers;

[0083] 2) The nascent fibers are sequentially subjected to water washing and hot water stretching treatment;

[0084] After hot water stretching, the fiber sulfoxide retention is 0.03%, the fiber monofilament diameter is 28μm, the fiber swelling degree is 48%, the width is 40mm, and the number of spindles is 30.

[0085] 3) The fibers after hot water stretching are first subjected to cooling and dehumidification treatment;

[0086] Specifically, the cooling and dehumidification process is carried out in a chamber, which is equipped with a drive roller for cooling the fibers. The fibers, after hot water stretching treatment, are cooled by the drive roller and dehumidified within the chamber. The temperature Q1 inside the chamber is 30°C, the humidity is 59%, and the exhaust vent is located 60° above and to the left of the drive roller.

[0087] The drive rollers consist of 10 rollers. The fibers are cooled by the 10 rollers in the drive roller cooling and regulating box. The drive rollers are arranged at intervals, and the fiber running direction is tangent to the roller surfaces of the first and last rollers, with a wrap angle of 90° with the intermediate rollers. The intermediate rollers can be all rollers between the first and last rollers. The temperature of the drive rollers, Q2, is 20℃. The fiber is cooled by the drive rollers for 2 seconds. The elongation ratio of each drive roller is 1.00. The diameter of the drive roller is 500mm, the length of the roller is 1990mm, and the surface is made of ceramic-coated material with a roughness Ra of 0.08.

[0088] After being cooled by the drive roller, the fiber temperature is 28℃ and the fiber moisture content is 17%.

[0089] 4) Apply oil to the fibers after cooling and dehumidification. The oiling temperature is 30℃, the concentration is 5%, and the oil circulation rate is 10m³. 3 / h, oiling time is 1s, the wetting angle between oil and fiber is 39°, and the draft ratio of the drive roller is 1.00.

[0090] 5) After the oiled fibers are dried and densified, steam-stretched, and then wound into shape, the resulting polyacrylonitrile fibers have a strength of 750 MPa, an oiling rate of 2.0%, a CV value of 3%, and an ash content of 0.25%.

[0091] No waste oil is generated during the production process, and there is no oil corrosion or accumulation of flocculent matter. There is no need to stop the production line to clean the oil tank and change the oil.

[0092] Example 4

[0093] The specific steps for preparing T700S-12K polyacrylonitrile fiber in this embodiment are as follows:

[0094] 1) The spinning fluid undergoes a solidification and shaping process to obtain nascent fibers;

[0095] 2) The nascent fibers are sequentially subjected to water washing and hot water stretching treatment;

[0096] After hot water stretching treatment, the fiber sulfoxide retention is 0.03%, the fiber monofilament diameter is 27μm, the fiber swelling degree is 40%, the width is 35mm, and the number of spindles is 22.

[0097] 3) The fibers after hot water stretching are first subjected to cooling and dehumidification treatment;

[0098] Specifically, the cooling and dehumidification process is carried out in a chamber, which is equipped with a drive roller for cooling the fibers. The fibers, after hot water stretching treatment, are cooled by the drive roller and dehumidified within the chamber. The temperature Q1 inside the chamber is 25°C, the humidity is 59%, and the exhaust vent is located 60° above and to the left of the drive roller.

[0099] The drive rollers consist of 8 rollers. The fibers are cooled by passing through the 8 rollers in the housing. The drive rollers are arranged at intervals, and the fiber running direction is tangent to the roller surfaces of the first and last rollers. The wrap angle with the intermediate rollers is 150°. The intermediate rollers can be all rollers between the first and last rollers. The temperature of the drive rollers, Q2, is 18°C. The cooling time of the fibers through the drive rollers is 2.5s. The draft ratio of each drive roller is 1.00.

[0100] The drive roller has a diameter of 500mm, a length of 800mm, and a ceramic-coated surface with a roughness of Ra0.05.

[0101] After the drive roller is cooled, the fiber temperature is 24℃ and the fiber moisture content is 18%.

[0102] 4) The fibers after cooling and dehumidification are then oiled. The oiling temperature is 27℃, the concentration is 2%, and the oil circulation rate is 6m³. 3 / h, oiling time is 2s, the wetting angle between oil and fiber is 20°, and the draw ratio of the oiling roller is 1.00.

[0103] 5) After the oiled fibers are dried and densified, steam-stretched, and then wound into shape, the resulting polyacrylonitrile fibers have a strength of 710 MPa, an oiling rate of 1.3%, a CV value of 2.2%, and an ash content of 0.15%.

[0104] No waste oil is generated during the production process, and there is no oil corrosion or accumulation of flocculent matter. There is no need to stop the production line to clean the oil tank and change the oil.

[0105] Example 5

[0106] The specific steps for preparing T800S-12K polyacrylonitrile fiber in this embodiment are as follows:

[0107] 1) The spinning fluid undergoes a solidification and shaping process to obtain nascent fibers;

[0108] 2) The nascent fibers are sequentially subjected to water washing and hot water stretching treatment;

[0109] After hot water stretching, the fiber sulfoxide retention is 0.03%, the fiber monofilament diameter is 24μm, the fiber swelling degree is 49%, the width is 30mm, and the number of spindles is 25.

[0110] 3) The fibers after hot water stretching are first subjected to cooling and dehumidification treatment;

[0111] Specifically, the cooling and dehumidification process is carried out in a chamber, which is equipped with a drive roller for cooling the fibers. The fibers, after hot water stretching treatment, are cooled by the drive roller and dehumidified within the chamber. The temperature Q1 inside the chamber is 10℃, the humidity is 59%, and the exhaust vent is located 50° above and to the left of the drive roller.

[0112] The drive rollers consist of 12 rollers. The fibers are cooled by passing through these 12 rollers in the housing. The drive rollers are arranged alternately, with the fiber running direction tangent to the surface of the first roller and a wrap angle of 300° with the intermediate rollers. The intermediate rollers refer to the rollers after the first roller. Preferably, the intermediate rollers can be the rollers between the first and last rollers. The last roller is the roller before the oiling step. The fiber running direction is tangent to the surface of the last roller. The temperature of all drive rollers is 0°C. The cooling time of the fibers through all drive rollers is 10 seconds. The draw ratio of each drive roller is 0.99. The diameter of the drive roller is 1000 mm, the length of the roller is 1000 mm, and the surface is chrome-plated with a roughness Ra of 0.1.

[0113] After being cooled by the drive roller, the fiber temperature is 15℃ and the fiber moisture content is 20%.

[0114] 4) The fibers after cooling and dehumidification are then oiled. The oiling temperature is 15℃, the concentration is 5%, and the oil circulation rate is 7.5m³. 3 The oiling time is 1.77s, the wetting angle between the oil and the fiber is 25°, and the draw ratio of the oiling roller is 0.99.

[0115] 5) After the oiled fibers are dried and densified, steam-stretched, and then wound into shape, the resulting polyacrylonitrile fibers have a strength of 630 MPa, an oiling rate of 3.0%, a CV value of 3.0%, and an ash content of 0.25%.

[0116] No waste oil is generated during the production process, there is no oil agent spoilage, no accumulation of flocculent matter, and no need to stop the production line to clean the oil tank and change the oil.

[0117] Comparative Example 1

[0118] The specific steps for preparing T700S-12K polyacrylonitrile fiber in this embodiment are as follows:

[0119] After the fibers are stretched with hot water, they are sprayed and cooled, and then oiled. The remaining steps are the same as in Example 4.

[0120] The fiber moisture content is 50% after spraying and before oiling. New oil needs to be added daily to ensure the oil concentration. 200 kg of waste oil is generated daily.

[0121] Comparative Example 2

[0122] The specific steps for preparing T700S-12K polyacrylonitrile fiber in this embodiment are as follows:

[0123] After the fiber is cooled by the drive roller, it is oiled. The drive roller is not enclosed in the regulating box, and the ambient temperature and humidity of the drive roller cooling environment are not controlled. The remaining steps are the same as in Example 4.

[0124] After being cooled by the drive roller, the fiber temperature was 32°C, which was worse than the cooling effect in Example 4. The oil was prone to spoilage, and flocculent jelly-like substances were produced by the oil in the oil tank during operation. The oil application rate CV value of polyacrylonitrile fiber was 3.2%.

[0125] See also Figure 2 The image shows a view of the oil in the oil tank on the tank wall. The attached material shown in the image is the oil. According to the attached... Figure 2 It is known that after the oil decomposes, it will form clumps (jelly-like substances) and strips (flocculated substances). These substances make the oil unusable and can only be used for waste oil treatment.

[0126] In summary, the polyacrylonitrile fiber preparation method provided in this invention uses a transmission roller to cool the fiber, avoiding the generation of waste oil and oil agent spoilage caused by high temperature and water introduction, preventing fiber fuzzing, breakage, and roller entanglement caused by excessive compression, avoiding differences between the fiber surface and core, improving oiling uniformity and fiber quality stability, and reducing production costs. Through the synergy of the oiling equipment and process, high-quality fibers are produced.

[0127] It will be readily understood by those skilled in the art that the aforementioned advantageous methods can be freely combined and superimposed without conflict.

[0128] 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 method for preparing polyacrylonitrile fibers, characterized in that, Includes the following steps: Initial step: The spinning fluid undergoes a solidification and shaping process to obtain nascent fibers; Washing and hot water stretching steps: The nascent fibers are sequentially subjected to washing and hot water stretching treatments; Cooling and dehumidification steps: The fibers after hot water stretching are first subjected to cooling and dehumidification treatment; Oiling step: Apply oil to the fibers after cooling and dehumidification treatment; Post-treatment: The oiled fibers are post-treated to obtain polyacrylonitrile fibers; In the cooling and dehumidification step, the cooling and dehumidification process is carried out in a box, which is equipped with a transmission roller for cooling the fibers. The fibers after hot water stretching are cooled by the transmission roller under its traction and dehumidified in the box. The drive rollers are at least two rollers, and in the vertical direction, the drive rollers are arranged at intervals. After hot water stretching treatment, the running direction of the fiber is tangent to the roller surface of the first roller. The wrap angle between the fiber and the second roller is greater than 90°. The fiber is oiled after passing through the second roller. Before the cooling and dehumidification step, the fibers after hot water drawing treatment must meet the following requirements: fiber monofilament diameter of 24-28μm, width of 30-40mm, and number of spinnerets not exceeding 30. In the cooling and dehumidification step, the diameter of the drive roller is 500-1000mm, and the length of the drive roller is not greater than 2000mm.

2. The method for preparing polyacrylonitrile fibers according to claim 1, characterized in that, In the cooling and dehumidification step, the temperature Q2 of the transmission roller is 0-20℃, and the humidity inside the chamber is less than 60%. The temperature Q1 inside the chamber is 10-30℃, and when the fiber after cooling and dehumidification is oiled, the wetting angle between the oil and the fiber is less than 40°. Alternatively, the temperature Q1 inside the chamber is 10-20℃, and when the fibers after cooling and dehumidification are oiled, the wetting angle between the oil and the fibers is 20-30°.

3. The method for preparing polyacrylonitrile fibers according to claim 1, characterized in that, In the oiling step, the oiling temperature is no higher than 30℃, the oil concentration is 2-5%, and the oil circulation rate is 6-10m. 3 / h, oiling time is 1-10s, and the draw ratio of the oiling roller is 0.95-1.05; Alternatively, in the oiling step, the oiling temperature is 15-25℃, the oil concentration is 2.5-3.5%, and the oil circulation rate is 7-8m³. 3 / h, oiling time is 2-5s, and the draw ratio of the oiling roller is 0.98-1.

00.

4. The method for preparing polyacrylonitrile fibers according to claim 2, characterized in that, In the cooling and dehumidification step, the time for the fibers after hot water stretching treatment to pass through the drive roller is 1-10 seconds, and the stretching ratio of the drive roller is 0.90-1.

00.

5. The method for preparing polyacrylonitrile fibers according to claim 1, characterized in that, The housing has an exhaust vent, and the inner circumferential wall of the transmission roller is provided with a cooling pipe. The cooling pipe is arranged in a spiral shape and is used to circulate coolant to cool the transmission roller.

6. The method for preparing polyacrylonitrile fibers according to claim 1, characterized in that, Before the cooling and dehumidification step, the fibers after hot water stretching treatment must meet the following requirements: fiber sulfoxide retention of no more than 0.03% and fiber swelling degree of less than 50%.

7. The method for preparing polyacrylonitrile fibers according to claim 1, characterized in that, After cooling and dehumidification treatment, the fiber temperature Q3 ≤ 30℃ and the fiber moisture content ≤ 20%.

8. A polyacrylonitrile fiber, characterized in that, The polyacrylonitrile is produced by the method for preparing polyacrylonitrile fibers according to any one of claims 1 to 7.

9. The polyacrylonitrile fiber according to claim 8, characterized in that, The polyacrylonitrile fibers obtained after post-treatment have a strength >600MPa, an oiling rate of 1.0-3.0%, a CV value ≤3%, and an ash content ≤0.25%.

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