Hot water drawing device and method for use in the production of dry-jet wet-spun polyacrylonitrile filaments

Abstract

This invention relates to a hot water drawing device and method for preparing dry-jet wet-spun polyacrylonitrile precursor fibers. The hot water drawing device includes a tank, a feed roller, and a first drawing roller. The tank is used to hold a bath solution. The tank has a first end and a second end arranged opposite to each other. The feed roller is located at the first end of the tank; the fiber bundle enters the tank through the feed roller. The first drawing roller is located at the second end of the tank; the fiber bundle exits the tank through the first drawing roller; the lower edge of the feed roller is immersed in the bath solution within the tank; the lower edge of the first drawing roller is positioned above the surface of the bath solution within the tank. This invention primarily addresses the technical problem in the existing hot water drawing process for preparing dry-jet wet-spun polyacrylonitrile precursor fibers: "A large amount of hot water is carried outside the bath on the fiber exit side, resulting in large fluctuations in the bath solution surface, causing an uneven drawing medium environment for the fiber bundle, and easily leading to fuzzy fibers wrapping around the roller."

Description

Technical Field

[0001] This invention relates to the field of polyacrylonitrile-based carbon fiber technology, and in particular to a hot water drawing device and method for preparing dry-jet wet-spinning polyacrylonitrile precursor fibers. Background Technology

[0002] Polyacrylonitrile-based carbon fiber possesses advantages such as high specific strength, high specific modulus, low density, and resistance to chemical corrosion, making it widely used in aerospace, wind turbine blades, and building reinforcement. Polyacrylonitrile precursor (also known as polyacrylonitrile-based carbon fiber precursor, or simply PAN precursor) is the precursor to polyacrylonitrile-based carbon fiber. During the pre-oxidation process, PAN precursor gradually evolves into a heat-resistant oxygen-containing structure, and after carbonization, carbon fibers with a carbon content of over 90% are obtained.

[0003] The mainstream production processes for polyacrylonitrile (PA) precursor fibers are divided into wet spinning and dry-jet wet spinning. Compared with the traditional wet spinning process, the biggest advantage of the dry-jet wet spinning process is that it can achieve a high take-up speed (300-500 m / min), which can greatly improve production efficiency and reduce production costs. Regardless of the process used, the production process of PA precursor fibers mainly includes steps such as solution filtration, metering, coagulation, washing, hot water drawing, oiling, drying and densification, steam drawing, and winding. Among these, the drawing process is the key process for achieving fine denier and high strength of the precursor fibers.

[0004] Hot water is a crucial medium in the hot water drawing process of polyacrylonitrile precursor fiber preparation. In traditional wet spinning processes, the hot water drawing bath is heated by heating coils at the bottom of the bath, thus controlling the temperature of the drawing medium to achieve high fiber drawing ratios. After the hot-drawn fiber bundle leaves the hot water drawing bath, pressure rollers are typically used to remove excess water. The drive rollers controlling the fiber bundle drawing ratio at the hot drawing inlet and outlet are on the same horizontal plane (see related technologies such as patents CN105624809B, CN105624812B, CN106637512A, and CN114381816A).

[0005] In the industrial production of carbon fiber precursor, dry-jet wet spinning is commonly used to produce high-performance carbon fibers. The inventors of this invention have discovered that existing hot water drafting devices and processes in dry-jet wet spinning suffer from at least the following problems:

[0006] (1) Due to the high speed of the yarn bundle in the dry-jet wet spinning process (3-4 times that of the wet spinning process) and the large number of yarn bundle stations, the force of the yarn bundle on the hot water drawing bath is more obvious, and the disturbance of the liquid surface of the hot drawing bath is large on the yarn exit side. When using traditional hot water drawing devices and methods, a large amount of hot water will be carried out of the bath on the yarn exit side, and the liquid surface of the hot drawing bath is prone to large fluctuations, making the yarn bundle drawing medium environment uneven, which leads to problems such as frequent roller wrapping. At the same time, a large amount of water stains are spilled near the outlet of the hot drawing bath, affecting personnel operation.

[0007] (2) After the filament bundle leaves the hot water drawing bath, it enters the oiling process. The water content and temperature of the filament bundle directly affect the oil concentration and temperature stability in the oiling process. Therefore, pressure rollers are usually used to squeeze out excess water from the hot drawn filament bundle. However, when the pressure rollers are lowered to squeeze the filament bundle, the torque of the corresponding drawing roller motor increases, which may cause the motor to stop due to overcurrent. Summary of the Invention

[0008] In view of this, the present invention provides a hot water drawing device and method for the preparation of dry-jet wet-spinning polyacrylonitrile precursor, the main purpose of which is to solve the technical problem that existing hot water drawing devices in the dry-jet wet-spinning process of polyacrylonitrile precursor production have the following problems: "a large amount of hot water is carried out of the bath on the yarn exit side, the bath liquid level fluctuates greatly, resulting in an uneven yarn drawing medium environment and easy fuzz entanglement on the rollers".

[0009] To achieve the above objectives, the present invention mainly provides the following technical solutions:

[0010] On one hand, embodiments of the present invention provide a hot water drawing device for use in the preparation of dry-jet wet-spun polyacrylonitrile precursor, wherein the hot water drawing device comprises:

[0011] A tank for holding bath liquid; wherein the tank has a first end and a second end disposed opposite to each other;

[0012] A fiber feeding roller is located at the first end of the trough; wherein the fiber bundle enters the trough through the fiber feeding roller.

[0013] A first drafting roller is located at the second end of the groove; wherein the fiber bundle leaves the groove after passing through the first drafting roller.

[0014] The lower edge of the feed roller is immersed in the bath liquid in the tank; the lower edge of the first drawing roller is located above the surface of the bath liquid in the tank.

[0015] Preferably, the hot water stretching device further includes:

[0016] The fiber bundle entering the tank first passes through the guide roller and then through the first drawing roller; wherein, the lower edge of the guide roller is immersed in the bath liquid in the tank. Preferably, the guide roller is a fixed roller; wherein, the diameter of the guide roller is 35-45mm and the surface roughness is ≤Ra0.8μm.

[0017] Preferably, the distance from the lower edge of the guide roller to the surface of the bath liquid is D1; ​​the distance from the lower edge of the feed roller to the surface of the bath liquid is D2; wherein the ratio of D1 to D2 is 0.3-1.0.

[0018] Preferably, the distance D2 from the lower edge of the feed roller to the surface of the bath liquid is 25-35 mm;

[0019] Preferably, the lifting angle α of the fiber bundle between the guide roller and the first drawing roller along the wire feeding direction; wherein, α is 6-11°.

[0020] Preferably, the horizontal distance D3 between the center of the feed roller and the center of the first drafting roller along the wire feeding direction is 3800-4200mm.

[0021] Preferably, the horizontal distance D4 between the center of the feed roller and the center of the guide roller along the wire feeding direction is 3000-3400mm.

[0022] Preferably, the bottom of the tank includes a first bottom and a second bottom; wherein the first bottom includes a portion of the bottom located on and near the yarn inlet side, and the second bottom includes a portion of the bottom located on the yarn outlet side; wherein, along the yarn feeding direction, the first bottom forms a downward-extending slope, preferably, the angle of the slope is 2-5°; the second bottom is parallel to the surface of the bath liquid; preferably, the first bottom and the second bottom are connected.

[0023] Preferably, the hot water stretching device further includes:

[0024] The first water supply pipeline passes through the preheater and connects to the tank body; wherein the connection point between the first water supply pipeline and the tank body is located on the bottom of the tank body at the wire outlet side.

[0025] Preferably, the hot water stretching device further includes:

[0026] The second water supply pipeline passes through the cooler and is connected to a spraying device; wherein the spraying device is used to spray water onto the fiber bundle after it has passed through the first drafting roller.

[0027] Preferably, the hot water stretching device further includes:

[0028] A pressure roller is used to compress the fiber bundles after water spraying treatment; wherein the pressure roller is made of rubber material with a Shore hardness of 60-70 and a compression deformation of 20-30%.

[0029] Preferably, the hot water drawing device includes a drawing roller group; wherein the drawing roller group includes a first drawing roller, a second drawing roller, a third drawing roller, a fourth drawing roller, and a fifth drawing roller; wherein the fiber bundle passing through the first drawing roller passes sequentially through the second drawing roller, the third drawing roller, the fourth drawing roller, and the fifth drawing roller; wherein the spraying device is located above the third drawing roller; and the pressure roller is located above the fourth drawing roller.

[0030] On the other hand, embodiments of the present invention provide a hot water drawing method for preparing dry-jet wet-spun polyacrylonitrile precursor, wherein the fiber bundle is hot-drawn using the hot water drawing device described in any of the above-mentioned embodiments for preparing dry-jet wet-spun polyacrylonitrile precursor; preferably, the hot water drawing temperature is 65-85°C, and the drawing ratio is 2.0-3.0; preferably, the spraying device is used to spray cooling water at a temperature of 14-18°C onto the fiber bundle to reduce the temperature of the fiber bundle to a set temperature. Preferably, the pressure of the pressure roller is set to 2-5 bar.

[0031] In another aspect, embodiments of the present invention provide a method for preparing dry-jet wet-spun polyacrylonitrile precursor fibers, which includes the following steps:

[0032] 1) The spinning solution is spun and solidified to obtain nascent fibers;

[0033] 2) The nascent fibers are subjected to water washing, hot water drawing, oiling, drying and densification, steam drawing and winding treatment to obtain polyacrylonitrile precursor fibers;

[0034] Among them, the hot water drawing device used in the preparation of dry-jet wet-spinning polyacrylonitrile precursor is used for hot water drawing treatment according to any one of the above-mentioned methods.

[0035] Preferably, the temperature for hot water stretching is 65-85℃, and the stretching ratio is 2.0-3.0;

[0036] Preferably, when performing hot water stretching treatment, the spraying device is used to spray cooling water at a temperature of 14-18°C onto the fiber bundle;

[0037] Preferably, when performing hot water stretching treatment, the pressure of the pressure roller is set to 2-5 bar;

[0038] Preferably, the polyacrylonitrile precursor fiber has a fineness of 0.7-1.2 dtex, a tensile strength ≥630 MPa, and a tensile modulus ≥14 GPa.

[0039] Compared with the prior art, the hot water drawing device and method of the present invention for the preparation of dry-jet wet-spun polyacrylonitrile precursor fibers have at least the following beneficial effects:

[0040] On one hand, embodiments of the present invention provide a hot water drawing device for use in the preparation of dry-jet wet-spinning polyacrylonitrile precursor fibers. By immersing the lower edge of the feed roller into the bath liquid in the tank and positioning the lower edge of the first drawing roller above the surface of the bath liquid in the tank (i.e., the outlet drawing roller is higher than the inlet feed roller), this arrangement ensures that most of the hot water carried on the fiber bundle at the fiber exit side is filtered into the bath liquid. This solves the problem in the prior art where "a large amount of hot water is carried out of the bath liquid at the fiber exit side, causing large fluctuations in the bath liquid surface, resulting in an uneven fiber bundle drawing medium environment and easy fuzz entanglement on the roller."

[0041] Furthermore, this embodiment of the invention provides a hot water drawing device for preparing dry-jet wet-spinning polyacrylonitrile precursor fibers, which further includes: a guide roller, wherein the fiber bundle entering the tank first passes through the guide roller and then through the first drawing roller; wherein the lower edge of the guide roller is immersed in the bath liquid in the tank. The lifting angle α of the fiber bundle between the guide roller and the first drawing roller along the fiber feeding direction; wherein α is 6-11°; here, setting the guide roller can ensure the residence time of the fiber bundle in the hot water drawing process, so that the nascent fibers after washing are uniformly drawn and the macromolecular chains are oriented in the hot water, laying the foundation for the preparation of high-performance carbon fiber precursor fibers; by adjusting the height of the guide roller from the liquid surface, the fiber feeding angle between the guide roller and the first drawing roller (exit drawing roller) is realized, the fiber bundle tension is reasonably controlled, and the phenomenon of the drawing roller wrapping is eliminated. Furthermore, the guide roller is a fixed roller with a diameter of 25-35mm and a surface roughness of ≤Ra0.8μm, which can prevent fuzz from forming on the surface of the guide roller and improve the quality of carbon fiber precursor products.

[0042] Furthermore, this embodiment of the invention provides a hot water drawing device for use in the preparation of dry-jet wet-spinning polyacrylonitrile precursor fibers. The first bottom of the tank (the portion of the bottom located near the fiber inlet side) is configured as a downward-sloping section extending along the fiber feeding direction, and the second bottom (the portion of the bottom located on the fiber outlet side) is configured parallel to the bath liquid surface (horizontal). Since the flow direction of the hot water in the tank is opposite to the direction of fiber bundle movement, this configuration allows the added deionized water to maintain a low flow rate after entering the tank, reducing the flow rate of the bath liquid at the outlet side of the hot water drawing bath. This reduces the fluctuation of the bath liquid surface during production, helps maintain a stable bath liquid surface, and ensures the uniformity of the temperature field within the hot water drawing device, thereby further reducing the occurrence of fuzzy fibers and fiber breakage.

[0043] Furthermore, this embodiment of the invention provides a hot water drawing device for use in the preparation of dry-jet wet-spinning polyacrylonitrile precursor fibers. The device uses a preheater to preheat the deionized water added to the tank, reducing the load on the heating device in the tank and thus reducing the temperature fluctuation in the hot water drawing tank, further promoting a reduction in the frequency of fuzzy fibers and fiber breakage.

[0044] Furthermore, this embodiment of the invention provides a hot water drafting device for use in the preparation of dry-jet wet-spinning polyacrylonitrile precursor. By reasonably matching the pressure roller parameters and spray temperature, the pressure roller is made to be in an elastic extrusion state, thereby achieving effective control of the torque of the drafting roller motor. This enables the preparation of high-performance polyacrylonitrile carbon fiber precursor and promotes the improvement of production efficiency.

[0045] On the other hand, embodiments of the present invention provide a hot water drawing method for preparing dry-jet wet-spinning polyacrylonitrile precursor. Since the hot water drawing device described in any of the above claims is used for hot water drawing treatment, it has the beneficial effects described in any of the above claims, which will not be elaborated here.

[0046] On another front, embodiments of the present invention provide a method for preparing polyacrylonitrile precursor fibers, comprising the following steps: spinning and coagulating a spinning solution to obtain nascent fibers; washing, hot water drawing, oiling, drying and densifying, steam drawing, and winding the nascent fibers to obtain polyacrylonitrile precursor fibers; wherein the hot water drawing process is performed using a hot water drawing device described above for preparing dry-jet wet-spinning polyacrylonitrile precursor fibers. Since the hot water drawing process in preparing polyacrylonitrile precursor fibers uses a hot water drawing device described above for preparing dry-jet wet-spinning polyacrylonitrile precursor fibers, this method can produce high-performance polyacrylonitrile carbon fiber precursor fibers and improves production efficiency.

[0047] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0048] Figure 1 This is a front view of a hot water stretching device provided in an embodiment of the present invention;

[0049] Figure 2 This is a front view of a prior art hot water stretching device;

[0050] Figure 3 This is a graph showing the trend of motor torque change of the stretching roller before and after the pressure roller is lowered when performing hot water stretching processing using the hot water stretching device provided in the embodiments of the present invention. Detailed Implementation

[0051] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. 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 can be combined in any suitable form.

[0052] Based on the technical problems mentioned in the background section, this invention provides a hot water drafting device and method for preparing polyacrylonitrile precursor yarn in dry-jet wet spinning. Its main objective is to solve the technical problems existing in current hot water drafting devices during dry-jet wet spinning precursor yarn production, such as "large fluctuations in the bath liquid level, resulting in uneven temperature field and easy filament entanglement on the rollers." Furthermore, a further objective is to indirectly control the temperature of the pressure roller by controlling the temperature of the yarn bundle at the hot drafting exit, and by coordinating the pressure roller parameters, to solve the technical problem of high torque on the motor corresponding to the pressure roller during hot water drafting in dry-jet wet spinning, which easily causes overcurrent faults in the motor's frequency converter.

[0053] The technical solution of the present invention will be described below through specific embodiments:

[0054] Example 1

[0055] This embodiment provides a hot water drawing device for use in the preparation of dry-jet wet-spun polyacrylonitrile precursor fibers, such as... Figure 1 As shown, the hot water drawing device of this embodiment includes: a tank 1, a feeding roller 2, and a first drawing roller 4 (i.e., an outlet drawing roller). The tank 1 is used to hold bath liquid; the tank 1 has a first end and a second end arranged opposite to each other. The feeding roller 2 is located at the first end of the tank 1; the fiber bundle enters the tank 1 through the feeding roller 2. The first drawing roller 4 is located at the second end of the tank 1; the fiber bundle exits the tank 1 through the first drawing roller 4. The lower edge of the feeding roller 2 is immersed in the bath liquid in the tank 1. The lower edge of the first drawing roller 4 is positioned above the surface of the bath liquid in the tank 1 (i.e., the first drawing roller 4 is directly above the surface of the bath liquid at the second end of the tank; when the fiber bundle passes through the first drawing roller 4, some of the hot water carried on the fiber bundle can fall into the tank 1).

[0056] This embodiment provides a hot water drawing device for the preparation of dry-jet wet-spun polyacrylonitrile precursor fibers. Through the above-mentioned configuration, it can avoid the phenomenon in the prior art where "when the fiber bundle leaves the tank of the hot water drawing device, due to the interaction force between the fiber bundle and the bath liquid, a large amount of hot water is carried out of the tank, resulting in large fluctuations in the liquid level." Here, when the fiber bundle passes through the first drawing roller, the hot water in the fiber bundle can be filtered out, thereby ensuring the uniformity of the environment inside the hot water drawing tank, greatly reducing the occurrence of fuzzy and broken fibers, and preventing the fiber bundle from carrying too much water into the subsequent oiling process, which would affect the stability of the oil concentration.

[0057] Example 2

[0058] Preferably, this embodiment provides a hot water drawing device for use in the preparation of dry-jet wet-spun polyacrylonitrile precursor fibers, such as... Figure 1 As shown, compared with the above embodiments, this embodiment further includes the following settings:

[0059] The hot water drawing device in this embodiment also includes a guide roller 3, which serves to guide the fibers. The fiber bundles entering the tank 1 first pass through the guide roller 3 and then through the first drawing roller 4. The lower edge of the guide roller 3 is immersed in the bath liquid in the tank 1.

[0060] Preferably, the distance from the lower edge of the guide roller 3 to the surface of the bath liquid is D1; ​​the distance from the lower edge of the feed roller 2 to the surface of the bath liquid is D2; wherein the ratio of D1 to D2 is 0.3-1.0. This arrangement allows for the regulation of the yarn tension, enabling adjustable and controllable yarn lifting angle and preventing roller entanglement.

[0061] Preferably, the distance D2 from the lower edge of the feed roller 2 to the surface of the bath liquid is 25-35 mm. This setting effectively avoids the impact of bath liquid disturbance on the fiber bundle, reducing the occurrence of fuzzing and breakage during hot water drawing.

[0062] Preferably, the lifting angle α of the fiber bundle between the guide roller 3 and the first drafting roller 4 along the yarn feeding direction is 6-11°. Here, the yarn feeding angle of the fiber bundle between the guide roller and the first drafting roller 4 (exit drafting roller) can be flexibly adjusted, the yarn bundle tension can be reasonably controlled, and the occurrence of the drafting roller wrapping phenomenon can be eliminated.

[0063] Preferably, the horizontal distance D3 between the center of the feed roller and the center of the first drawing roller along the yarn feeding direction is 3800-4200 mm. Preferably, the horizontal distance D4 between the center of the feed roller and the center of the guide roller along the yarn feeding direction is 3000-3400 mm. This arrangement ensures the dwell time during the hot water drawing process of the fiber bundle, allowing the macromolecular chains in the nascent fibers after washing to align in an orientational manner, improving the fiber orientation degree, and laying the foundation for the preparation of high-performance carbon fiber precursor.

[0064] Preferably, the guide roller is a fixed roller with a diameter of 25-35mm and a surface roughness of ≤Ra0.8μm, which can prevent fuzz from forming on the surface of the guide roller and improve the quality of carbon fiber precursor products.

[0065] In this embodiment, the guide roller is designed to ensure the dwell time of the fiber bundle during the hot water drawing process, allowing the nascent fibers to be uniformly drawn and oriented in the hot water after washing, laying the foundation for the preparation of high-performance carbon fiber precursor. By adjusting the height of the guide roller from the liquid surface, the fiber bundle feed angle between the guide roller and the first drawing roller (exit drawing roller) is adjusted, the fiber bundle tension is reasonably controlled, and the phenomenon of the drawing roller getting tangled is eliminated.

[0066] Example 3

[0067] Preferably, this embodiment provides a hot water drawing device for use in the preparation of dry-jet wet-spun polyacrylonitrile precursor fibers, such as... Figure 1 As shown, compared with the above embodiments, this embodiment further includes the following settings:

[0068] The bottom of the tank 1 in this embodiment includes a first bottom 11 and a second bottom 12; wherein, the first bottom 11 includes a portion of the bottom located on and near the yarn inlet side of the tank 1, and the second bottom 12 includes a portion of the bottom located on the yarn outlet side of the tank 1; wherein, along the yarn feeding direction, the first bottom 11 forms a downwardly extending slope, preferably, the angle of the slope is 2-5°; the second bottom 12 is parallel to the surface of the bath liquid; preferably, the first bottom 11 and the second bottom 12 are connected.

[0069] Here, the flow direction of the hot water in the tank 1 of the hot water stretching device is opposite to the running direction of the fiber bundle. Through this arrangement, the added deionized water can maintain a low flow rate after entering the tank, which helps to keep the liquid level in the tank stable.

[0070] Example 4

[0071] Preferably, this embodiment provides a hot water drawing device for use in the preparation of dry-jet wet-spun polyacrylonitrile precursor fibers, such as... Figure 1 As shown, compared with the above embodiments, this embodiment further includes the following settings:

[0072] The hot water drawing device in this embodiment also includes a first water supply pipe for replenishing the bath liquid in the tank with deionized water; wherein, the first water supply pipe passes through the preheater 7 and is connected to the tank 1; wherein, the connection between the first water supply pipe and the tank 1 is located at the bottom of the tank 1 on the wire exit side (i.e., the first water supply pipe is connected to the second bottom of the tank).

[0073] Here, the preheater 7 can preheat the replenished deionized water, reducing the load on the heating device in the tank 1, reducing the temperature fluctuation in the tank 1, and promoting a reduction in the frequency of fuzzing and filament breakage.

[0074] Example 5

[0075] Preferably, this embodiment provides a hot water drawing device for use in the preparation of dry-jet wet-spun polyacrylonitrile precursor fibers, such as... Figure 1 As shown, compared with the above embodiments, this embodiment further includes the following settings:

[0076] On one hand, the hot water drawing device in this embodiment also includes a second water supply pipeline; here, the second water supply pipeline passes through the cooler 8 and is connected to the spraying device 6; wherein, the spraying device 6 is used to spray water onto the fiber bundle after passing through the first drawing roller 4 to cool the fiber bundle and reduce its temperature to a set temperature. Here, after being cooled, the deionized water can reduce the temperature of the hot water drawn fiber bundle at the exit, preventing the local oil solution temperature from becoming too high when the fiber bundle enters the subsequent oiling process, thus avoiding the occurrence of oil spoilage.

[0077] On the other hand, the hot water drawing device in this embodiment also includes a pressure roller 5, which is used to compress the fiber bundles after water spraying. The pressure roller helps prevent the fiber bundles from carrying excessive moisture into the subsequent oiling process. The pressure roller 5 is made of rubber with a Shore hardness of 60-70 and a compression set of 20-30%. The preferred material and hardness of the pressure roller are to prevent excessive motor torque from causing overcurrent and shutdown.

[0078] The following explanation is required regarding the solution in this embodiment:

[0079] The moisture content and temperature of the fiber bundles after hot water drawing treatment affect the oiling process. High moisture content in the fiber bundles affects the concentration of the oiling agent; conversely, high fiber bundle temperature affects the oiling agent's temperature, making it more prone to spoilage. Furthermore, while high pressure from the pressure rollers can reduce the moisture content of the fiber bundles, it can also easily lead to high motor torque in the drawing rollers. Conversely, excessively low fiber bundle temperature results in high pressure roller stiffness, which in turn also increases the motor torque in the drawing rollers.

[0080] Here, because the high temperature of the fiber bundle after hot water drawing will affect the stability of the oil in the subsequent oiling process, this embodiment uses a spraying device to cool the fiber bundle down to the set temperature (controlling a suitable spraying temperature). By selecting a pressure roller of appropriate material and coordinating the pressure of the pressure roller, the pressure roller is in an elastic extrusion state, which effectively controls the torque of the drawing roller motor without affecting the stability of the oil. This allows for the preparation of high-performance polyacrylonitrile precursor fibers, promoting the improvement of production efficiency.

[0081] Here, when using the hot water stretching device provided in this embodiment for hot water stretching processing, the trend of the motor torque change of the stretching roller before and after the pressure roller is lowered is shown in [reference needed]. Figure 3 As shown, from Figure 3 It can be seen that the motor torque does not change much before and after the pressure roller is lowered.

[0082] Additionally, the hot water drawing device includes a drawing roller assembly; wherein the drawing roller assembly includes a first drawing roller 4, a second drawing roller, a third drawing roller, a fourth drawing roller, and a fifth drawing roller; wherein the fiber bundle passing through the first drawing roller passes sequentially through the second drawing roller, the third drawing roller, the fourth drawing roller, and the fifth drawing roller; wherein the spraying device is located above the third drawing roller; and the pressure roller 5 is located above the fourth drawing roller.

[0083] In addition, regarding the above embodiment, a water receiving trough is provided below the second to fifth drafting rollers.

[0084] Example 6

[0085] On the other hand, this embodiment provides a hot water drawing method for use in the preparation of dry-jet wet-spun polyacrylonitrile precursor fibers, such as... Figure 1 As shown, compared with the above embodiments, this embodiment further includes the following settings:

[0086] The hot water drawing device described in any of the above embodiments for preparing dry-jet wet-spinning polyacrylonitrile precursor fibers is used to perform hot water drawing treatment on the fiber bundle. The temperature of the hot water drawing treatment is 65-85℃, and the draw ratio is 2.0-3.0. The spraying device is used to spray cooling water at a temperature of 14-18℃ onto the fiber bundle. The pressure of the pressure roller is set to 2-5 bar.

[0087] The hot water drafting method provided in this embodiment for the preparation of dry-jet wet-spinning polyacrylonitrile precursor yarn, by employing the apparatus described in any of the above embodiments for hot water drafting and simultaneously setting the corresponding hot water drafting temperature, drafting ratio, spray temperature, and pressure roller pressure, can solve the technical problems of large fluctuations in the bath liquid level, uneven temperature field, and easy filament entanglement on the rollers that exist in existing hot water drafting devices during dry-jet wet-spinning precursor yarn production. Furthermore, by controlling the temperature of the yarn bundle at the hot drafting exit to indirectly control the pressure roller temperature and matching the pressure roller material and pressure settings, while ensuring the stability of the oiling agent in the subsequent oiling process, it also solves the technical problem of high torque of the motor corresponding to the pressure roller during hot water drafting of dry-jet wet-spinning, which easily causes overcurrent failure of the motor frequency converter.

[0088] Example 7

[0089] Furthermore, this embodiment provides a method for preparing dry-jet wet-spun polyacrylonitrile precursor fibers, which includes the following steps:

[0090] 1) The spinning solution is spun and solidified to obtain nascent fibers;

[0091] 2) The nascent fibers are subjected to water washing, hot water drawing, oiling, drying and densification, steam drawing and winding treatment to obtain polyacrylonitrile precursor fibers;

[0092] The hot water drawing device described in any of the above embodiments for preparing dry-jet wet-spinning polyacrylonitrile precursor fibers is used for hot water drawing treatment; wherein the hot water drawing temperature is 65-85℃ and the drawing ratio is 2.0-3.0; preferably, during the hot water drawing treatment, the spraying device is used to spray cooling water at a temperature of 14-18℃ onto the fiber bundle; preferably, during the hot water drawing treatment, the pressure of the pressure roller is set to 2-5 bar.

[0093] In this embodiment, the polyacrylonitrile precursor fiber has a fineness of 0.7-1.2 dtex, a tensile strength ≥630 MPa, and a tensile modulus ≥14 GPa.

[0094] The hot water drawing device provided by the above technical solution is used to prepare polyacrylonitrile precursor fibers for use in the field of polyacrylonitrile carbon fibers. The following detailed description, through preferred experimental examples and comparative examples, further illustrates the process:

[0095] Experimental Example 1

[0096] This embodiment provides a method for preparing polyacrylonitrile precursor fibers, the main steps of which are as follows:

[0097] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 12 m / min.

[0098] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The coagulation bath temperature is 6℃, the coagulation bath concentration is 35%, and the draw ratio is 2.67.

[0099] (3) Washing: The nascent fibers enter the washing process at a rate of 32 m / min, the washing temperature is 50-55℃, and the residence time is 75 s.

[0100] (4) Hot water stretching:

[0101] See the structure of the hot water stretching device. Figure 1 As shown, the first bottom 11 of the tank 1 is a downward-sloping section with an angle of 3° along the yarn feeding direction; the second bottom 12 is parallel to the surface of the hot water drawing bath. The horizontal distance between the center points of the feed roller 2 and the guide roller 3 along the yarn feeding direction is 3200mm, and the horizontal distance between the center points of the feed roller 2 and the first drawing roller 4 along the yarn feeding direction is 4000mm. The distance from the lower edge of the feed roller 2 to the surface of the bath is 30mm, and the ratio of the distance from the lower edge of the guide roller 3 to the surface of the bath to the distance from the lower edge of the feed roller 2 to the surface of the bath is 1.0. Specifically, the distance from the lower edge of the guide roller 3 to the surface of the bath is 30mm. The lower edge of the first drawing roller 4 is 125.5mm higher than the surface of the bath in the tank, and the lifting angle of the fiber bundle between the guide roller 3 and the first drawing roller 4 along the yarn feeding direction is 11°. Among them, the guide roller 3 is a fixed roller; the diameter of the guide roller 3 is 35mm and the surface roughness is ≤Ra0.8μm.

[0102] After washing, the fibers enter the hot water drawing device's tank 1 for hot water drawing. The first water supply line, after passing through preheater 7, maintains the temperature of the deionized water at 70℃, while the hot water drawing temperature is 75℃, with a drawing ratio of 2.5. The fiber bundle's running speed at the outlet side of tank 1 is 80 m / min, and the liquid level at the outlet side of tank 1 remains stable, with no overflow caused by the fibers. The motor torque of each drawing roller is 16-19%.

[0103] After being cooled by cooler 8, the second water supply pipeline contains deionized water at a temperature of 15℃ and a flow rate of 0.5m³ / h. 3 / h, by spraying the fiber bundle with the spray device 6. To further prevent the fiber bundle from carrying too much moisture into the subsequent oiling process, a pressure roller 5 is placed above the fourth drafting roller. The pressure roller 5 is made of rubber with a Shore hardness of 60-70 and a compression deformation of 20-30%, and the pressure of the pressure roller 5 is 4 bar. After the pressure roller 5 is placed, the motor torque of the fourth drafting roller increases by 28-31%. During operation, there are few fuzzy fibers on the drafting roller, and no roller entanglement occurs.

[0104] (5) Oiling and Drying Densification: After hot water stretching, the fibers are oiled once and then dried and densified. The concentration of the oiling agent is 3%, and the drying and densification temperature is 130-170℃. During the oiling process, the oiling agent does not deteriorate significantly, the oiling agent is replaced every 30 days, and the liquid level in the oiling agent tank is stable.

[0105] (6) Steam drawing and yarn taking: The dried and densified fibers are steam drawn at a pressure of 0.6 MPa and a drawing ratio of 3.5. Polyacrylonitrile precursor fibers are taken at a speed of 280 m / min.

[0106] The polyacrylonitrile precursor fiber prepared in this embodiment has a fineness of 1.1 dtex, a tensile strength of 645 MPa, and a tensile modulus of 14.7 GPa.

[0107] The polyacrylonitrile precursor fiber prepared in this embodiment is then subjected to processes such as pre-oxidation, carbonization, surface treatment, and sizing to obtain polyacrylonitrile-based carbon fiber. The polyacrylonitrile-based carbon fiber has a tensile strength of 5.03 GPa and a tensile modulus of 250 ± 10 GPa.

[0108] Experimental Example 2

[0109] This embodiment provides a method for preparing polyacrylonitrile precursor fibers, the main steps of which are as follows:

[0110] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 12 m / min.

[0111] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The temperature of the coagulation bath is 6℃, the concentration of the coagulation bath is 35%, and the draw ratio is 2.67.

[0112] (3) Washing: The nascent fibers enter the washing process at a rate of 32 m / min, with the water flow direction opposite to the fiber's spinning direction. The washing temperature is 50-55℃, and the residence time is 75 s.

[0113] (4) Hot water stretching:

[0114] See hot water stretching device Figure 1 As shown, the first bottom 11 of the trough 1 is a downward-sloping section with an angle of 3° along the yarn feeding direction; the second bottom 12 is parallel to the surface of the hot water drawing bath. The horizontal distance between the center points of the feed roller 2 and the guide roller 3 along the yarn feeding direction is 3200mm, and the horizontal distance between the center points of the feed roller 2 and the first drawing roller 4 along the yarn feeding direction is 4000mm. The distance from the lower edge of the feed roller 2 to the surface of the bath is 30mm, and the ratio of the distance from the lower edge of the guide roller 3 to the surface of the bath to the distance from the lower edge of the feed roller 2 to the surface of the bath is 1.0. Specifically, the distance from the lower edge of the guide roller 3 to the surface of the bath is 30mm. The lower edge of the first drawing roller 4 is 125.5mm higher than the surface of the bath in the trough 1, and the lifting angle of the fiber bundle between the guide roller 3 and the first drawing roller 4 along the yarn feeding direction is 11°. Among them, the guide roller 3 is a fixed roller; the diameter of the guide roller 3 is 40mm and the surface roughness is ≤Ra0.8μm.

[0115] After washing, the fibers enter the hot water drawing device, tank 1, for the hot water drawing process. The first water supply line, preheated by preheater 7, has deionized water at a temperature of 64℃. The hot water drawing temperature is 68℃, and the drawing ratio is 2.5. The fiber velocity at the outlet side of tank 1 is 80 m / min, and the liquid level at the outlet side of tank 1 is stable, with no overflow caused by the fibers. The torque of each drawing roller motor is 19-22%.

[0116] After being cooled by cooler 8, the second water supply pipeline contains deionized water at a temperature of 18℃ and a flow rate of 0.5m³ / h. 3 The spray is applied to the fiber bundle at a rate of / h via spray device 6. To further prevent excessive moisture from entering the subsequent oiling process, a pressure roller 5 is placed above the fourth drafting roller. The pressure roller is made of rubber with a Shore hardness of 60-70 and a compression set of 20-30%, and the pressure of roller 5 is 4 bar. After lowering roller 5, the motor torque of the fourth drafting roller increases by 30-33%. During operation, there is minimal fuzz on the drafting roller, and no roller entanglement occurs.

[0117] (5) Oiling and Drying Densification: After hot water stretching, the fibers are oiled once and then dried and densified. The oil concentration is 3%, and the drying and densification temperature is 130-170℃. During the oiling process, the oil does not deteriorate significantly, the oil is replaced every 30 days, and the liquid level in the oil tank is stable.

[0118] (6) Steam drawing and winding: The dried and densified fibers are steam drawn at a pressure of 0.6 MPa and a drawing ratio of 3.5. Polyacrylonitrile precursor fibers are wound at a rate of 280 m / min.

[0119] The polyacrylonitrile precursor fiber prepared in this embodiment has a fineness of 1.1 dtex, a tensile strength of 660 MPa, and a tensile modulus of 14.6 GPa.

[0120] The polyacrylonitrile precursor fiber prepared in this embodiment is then subjected to processes such as pre-oxidation, carbonization, surface treatment, and sizing to obtain polyacrylonitrile-based carbon fiber. The polyacrylonitrile-based carbon fiber has a tensile strength of 5.15 GPa and a tensile modulus of 250 ± 10 GPa.

[0121] Experimental Example 3

[0122] This embodiment provides a method for preparing polyacrylonitrile precursor fibers, the main steps of which are as follows:

[0123] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 12 m / min.

[0124] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The temperature of the coagulation bath is 6℃, the concentration of the coagulation bath is 35%, and the draw ratio is 2.67.

[0125] (3) Washing: The nascent fibers enter the washing process at a rate of 32 m / min, with the water flow direction opposite to the fiber's spinning direction. The washing temperature is 50-55℃, and the residence time is 75 s.

[0126] (4) Hot water stretching:

[0127] See hot water stretching device Figure 1 As shown, the first bottom 11 of the trough 1 is a downward-sloping section with an angle of 3° along the yarn feeding direction; the second bottom 12 is parallel to the surface of the hot water drawing bath. The horizontal distance between the center points of the feed roller 2 and the guide roller 3 along the yarn feeding direction is 3200mm, and the horizontal distance between the center points of the feed roller 2 and the first drawing roller 4 along the yarn feeding direction is 4000mm. The distance from the lower edge of the feed roller 2 to the surface of the bath is 30mm, and the ratio of the distance from the lower edge of the guide roller 3 to the surface of the bath to the distance from the lower edge of the feed roller 2 to the surface of the bath is 1.0. Specifically, the distance from the lower edge of the guide roller 3 to the surface of the bath is 30mm. The lower edge of the first drawing roller 4 is 125.5mm higher than the surface of the bath in the trough 1, and the lifting angle of the fiber bundle between the guide roller 3 and the first drawing roller 4 along the yarn feeding direction is 11°. Among them, the guide roller 3 is a fixed roller; the diameter of the guide roller 3 is 45mm and the surface roughness is ≤Ra0.8μm.

[0128] After washing, the fibers enter the hot water drawing device's tank 1 for hot water drawing. The first water supply line, preheated by preheater 7, has deionized water at a temperature of 64℃. The hot water drawing temperature is 68℃, and the drawing ratio is 2.5. The fiber velocity at the outlet side of tank 1 is 80 m / min, and the liquid level at the outlet side of tank 1 is stable, with no overflow caused by the fibers. The torque of each drawing roller motor is 19-22%.

[0129] After being cooled by cooler 8, the second water supply pipeline contains deionized water at a temperature of 15℃ and a flow rate of 0.5m³ / h. 3 The spray is applied to the fiber bundle at a rate of / h via spray device 6. To further prevent excessive moisture from entering the subsequent oiling process, pressure roller 5 is placed above the fourth drafting roller. Pressure roller 5 is made of rubber with a Shore hardness of 60-70 and a compression set of 20-30%, and the pressure of pressure roller 5 is 4 bar. After pressure roller 5 is placed, the motor torque of the fourth drafting roller increases by 34-37%. During operation, there is minimal fuzz on the drafting roller, and no roller entanglement occurs.

[0130] (5) Oiling and Drying Densification: After hot water stretching, the fibers are oiled once and then dried and densified. The concentration of the oiling agent is 3%, and the drying and densification temperature is 130-170℃. During the oiling process, the oiling agent does not deteriorate significantly, the oiling agent is replaced every 45 days, and the liquid level in the oiling agent tank is stable.

[0131] (6) Steam drawing and yarn taking: The dried and densified fibers are steam drawn at a pressure of 0.6 MPa and a drawing ratio of 3.5. Polyacrylonitrile precursor fibers are taken at a speed of 280 m / min.

[0132] The polyacrylonitrile precursor fiber prepared in this embodiment has a fineness of 1.1 dtex, a tensile strength of 655 MPa, and a tensile modulus of 14.5 GPa.

[0133] Polyacrylonitrile precursor fibers are processed through pre-oxidation, carbonization, surface treatment, and sizing to produce polyacrylonitrile-based carbon fibers. The tensile strength of the polyacrylonitrile-based carbon fibers is 5.15 GPa, and the tensile modulus is 250 ± 10 GPa.

[0134] Experimental Example 4

[0135] This embodiment describes a method for preparing polyacrylonitrile precursor fibers, the main steps of which are as follows:

[0136] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 12 m / min.

[0137] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The temperature of the coagulation bath is 6℃, the concentration of the coagulation bath is 35%, and the draw ratio is 2.67.

[0138] (3) Washing: The nascent fibers enter the washing process at a rate of 32 m / min, with the water flow direction opposite to the fiber's spinning direction. The washing temperature is 50-55℃, and the residence time is 75 s.

[0139] (4) Hot water stretching:

[0140] See hot water stretching device Figure 1 As shown, the first bottom 11 of the trough 1 is a downward-sloping section with an angle of 3° along the yarn feeding direction; the second bottom 12 is parallel to the surface of the hot water drawing bath. The horizontal distance between the center points of the feed roller 2 and the guide roller 3 along the yarn feeding direction is 3200mm, and the horizontal distance between the center points of the feed roller 2 and the first drawing roller 4 along the yarn feeding direction is 4000mm. The distance from the lower edge of the feed roller 2 to the surface of the bath is 30mm, and the ratio of the distance from the lower edge of the guide roller 3 to the surface of the bath to the distance from the lower edge of the feed roller 2 to the surface of the bath is 0.4. Specifically, the distance from the lower edge of the guide roller 3 to the surface of the bath is 12mm. The lower edge of the first drawing roller 4 is 125.5mm higher than the surface of the bath in the trough 1, and the lifting angle of the fiber bundle between the guide roller 3 and the first drawing roller 4 along the yarn feeding direction is 9.75°. Among them, the guide roller 3 is a fixed roller; the diameter of the guide roller 3 is 40mm and the surface roughness is ≤Ra0.8μm.

[0141] After washing, the fibers enter the hot water drawing device, tank 1, for hot water drawing. The first water supply line, after passing through preheater 7, contains deionized water at a temperature of 64℃. The hot water drawing temperature is 68℃, and the drawing ratio is 2.5. The fiber velocity at the outlet side of tank 1 is 80 m / min, and the liquid level at the outlet side of tank 1 is stable, with no overflow caused by the fibers. The torque of each drawing roller motor is 18-21%.

[0142] After being cooled by cooler 8, the second water supply pipeline contains deionized water at a temperature of 15℃ and a flow rate of 0.5m³ / h. 3 The spray is applied to the fiber bundle at a rate of / h via spray device 6. To further prevent excessive moisture from entering the subsequent oiling process, a pressure roller 5 is placed above the fourth drafting roller. Pressure roller 5 is made of rubber with a Shore hardness of 60-70 and a compression set of 20-30%, and its pressure is 4 bar. After lowering pressure roller 5, the motor torque of the fourth drafting roller increases by 33-36%. During operation, there is minimal fuzz on the drafting roller, and no roller entanglement occurs.

[0143] (5) Oiling and Drying Densification: After hot water stretching, the fibers are oiled once and then dried and densified. The concentration of the oiling agent is 3%, and the drying and densification temperature is 130-170℃. During the oiling process, the oiling agent does not deteriorate significantly, the oiling agent is replaced every 45 days, and the liquid level in the oiling agent tank is stable.

[0144] (6) Steam drawing and yarn taking: The dried and densified fibers are steam drawn at a pressure of 0.6 MPa and a drawing ratio of 3.5. Polyacrylonitrile precursor fibers are taken at a speed of 280 m / min.

[0145] The polyacrylonitrile precursor fiber prepared in this embodiment has a fineness of 1.1 dtex, a tensile strength of 640 MPa, and a tensile modulus of 14.5 GPa.

[0146] Polyacrylonitrile precursor fibers are further processed through pre-oxidation, carbonization, surface treatment, and sizing to produce polyacrylonitrile-based carbon fibers. The tensile strength of polyacrylonitrile-based carbon fibers is 4.95 GPa, and the tensile modulus is 250 ± 10 GPa.

[0147] Experimental Example 5

[0148] This embodiment provides a method for preparing polyacrylonitrile precursor fibers, the main steps of which are as follows:

[0149] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 12 m / min.

[0150] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The temperature of the coagulation bath is 6℃, the concentration of the coagulation bath is 35%, and the draw ratio is 3.0.

[0151] (3) Washing: The nascent fibers enter the washing process at a rate of 36 m / min, the washing temperature is 50-55℃, and the residence time is 67 s.

[0152] (4) Hot water stretching:

[0153] See hot water stretching device Figure 1As shown, the first bottom 11 of the trough 1 is a downward-sloping section with an angle of 3° along the yarn feeding direction; the second bottom 12 is parallel to the surface of the hot water drawing bath. The horizontal distance between the center points of the feed roller 2 and the guide roller 3 along the yarn feeding direction is 3200mm, and the horizontal distance between the center points of the feed roller 2 and the first drawing roller 4 along the yarn feeding direction is 4000mm. The distance from the lower edge of the feed roller 2 to the surface of the bath is 30mm, and the ratio of the distance from the lower edge of the guide roller 3 to the surface of the bath to the distance from the lower edge of the feed roller 2 to the surface of the bath is 1.0. Specifically, the distance from the lower edge of the guide roller 3 to the surface of the bath is 30mm. The lower edge of the first drawing roller 4 is 125.5mm higher than the surface of the bath in the trough 1, and the lifting angle of the fiber bundle between the guide roller 3 and the first drawing roller 4 along the yarn feeding direction is 11°. Among them, the guide roller 3 is a fixed roller; the diameter of the guide roller 3 is 40mm and the surface roughness is ≤Ra0.8μm.

[0154] After washing, the fibers enter the hot water drawing device, tank 1, for hot water drawing. The first water supply line, after passing through preheater 7, contains deionized water at a temperature of 70℃. The hot water drawing temperature is 75℃, and the drawing ratio is 2.2. The fiber velocity at the outlet side of tank 1 is 79.2 m / min, and the liquid level at the outlet side of tank 1 is stable, with no overflow caused by the fibers. The torque of each drawing roller motor is 16-19%.

[0155] After being cooled by cooler 8, the second water supply pipeline contains deionized water at a temperature of 15℃ and a flow rate of 0.5m³ / h. 3 The spray is applied to the fiber bundle via spray device 6 at a rate of / h. To further prevent excessive moisture from entering the subsequent oiling process, pressure roller 5 is placed above the fourth drafting roller. Pressure roller 5 is made of rubber with a Shore hardness of 60-70 and a compression set of 20-30%, and the pressure of pressure roller 5 is 4 bar. After pressure roller 5 is placed, the motor torque of the fourth drafting roller increases by 28-31%. During operation, there is minimal fuzz on the drafting roller, and no roller entanglement occurs.

[0156] (5) Oiling and Drying Densification: After hot water stretching, the fibers are oiled once and then dried and densified. The concentration of the oiling agent is 3%, and the drying and densification temperature is 130-170℃. During the oiling process, the oiling agent does not deteriorate significantly, the oiling agent is replaced every 30 days, and the liquid level in the oiling agent tank is stable.

[0157] (6) Steam drawing and winding: The dried and densified fibers are steam drawn at a pressure of 0.6 MPa and a drawing ratio of 3.54. Polyacrylonitrile precursor fibers are wound at a speed of 280 m / min.

[0158] The polyacrylonitrile precursor fiber prepared in this embodiment has a fineness of 1.1 dtex, a tensile strength of 652 MPa, and a tensile modulus of 14.4 GPa.

[0159] Polyacrylonitrile precursor fibers are further processed through pre-oxidation, carbonization, surface treatment, and sizing to produce polyacrylonitrile-based carbon fibers. The tensile strength of polyacrylonitrile-based carbon fibers is 5.10 GPa, and the tensile modulus is 250 ± 10 GPa.

[0160] Experimental Example 6

[0161] This embodiment provides a method for preparing polyacrylonitrile precursor fibers, the main steps of which are as follows:

[0162] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 12 m / min.

[0163] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The temperature of the coagulation bath is 6℃, the concentration of the coagulation bath is 35%, and the draw ratio is 2.67.

[0164] (3) Washing: The nascent fibers enter the washing process at a rate of 32 m / min, with the water flow direction opposite to the fiber's spinning direction. The washing temperature is 50-55℃, and the residence time is 75 s.

[0165] (4) Hot water stretching:

[0166] See hot water stretching device Figure 1 As shown, the first bottom 11 of the trough 1 is a downward-sloping section with an angle of 3° along the yarn feeding direction; the second bottom 12 is parallel to the surface of the hot water drawing bath. The horizontal distance between the center points of the feed roller 2 and the guide roller 3 along the yarn feeding direction is 3200mm, and the horizontal distance between the center points of the feed roller 2 and the first drawing roller 4 along the yarn feeding direction is 4000mm. The distance from the lower edge of the feed roller 2 to the surface of the bath is 35mm, and the ratio of the distance from the lower edge of the guide roller 3 to the surface of the bath is 0.5. Specifically, the distance from the lower edge of the guide roller 3 to the surface of the bath is 17.5mm. The lower edge of the first drawing roller 4 is 125.5mm higher than the surface of the bath in the trough 1, and the lifting angle of the fiber bundle between the guide roller 3 and the first drawing roller 4 along the yarn feeding direction is 6.56°. Among them, the guide roller 3 is a fixed roller; the diameter of the guide roller 3 is 40mm and the surface roughness is ≤Ra0.8μm.

[0167] After washing, the fibers enter the hot water drawing device's tank 1 for hot water drawing. The first water supply line, after passing through preheater 7, contains deionized water at a temperature of 64℃. The hot water drawing temperature is 68℃, and the drawing ratio is 2.5. The fiber bundle's running speed at the outlet side of tank 1 is 80 m / min. The liquid level at the outlet side of tank 1 is stable, with no overflow caused by the fibers. The torque of each drawing roller motor is 18-21%.

[0168] After being cooled by cooler 8, the second water supply pipeline contains deionized water at a temperature of 15℃ and a flow rate of 0.5m³ / h. 3 The fiber bundle is sprayed at a rate of / h through spray device 6. To further prevent excessive moisture from entering the subsequent oiling process, pressure roller 5 is placed above the fourth drafting roller. Pressure roller 5 is made of rubber with a Shore hardness of 60-70 and a compression set of 20-30%, and the pressure of pressure roller 5 is 4 bar. After pressure roller 5 is placed, the motor torque of the fourth drafting roller increases by 32-35%. During operation, there is little fuzz on the drafting roller, and no roller entanglement occurs.

[0169] (5) Oiling and Drying Densification: After hot water stretching, the fibers are oiled once and then dried and densified. The concentration of the oiling agent is 3%, and the drying and densification temperature is 130-170℃. During the oiling process, the oiling agent does not deteriorate significantly, the oiling agent is replaced every 45 days, and the liquid level in the oiling agent tank is stable.

[0170] (6) Steam drawing and winding: The dried and densified fibers are steam drawn at a pressure of 0.6 MPa and a drawing ratio of 3.5. Polyacrylonitrile carbon fiber precursor is obtained at a speed of 280 m / min.

[0171] The polyacrylonitrile precursor fiber prepared in this embodiment has a fineness of 1.1 dtex, a tensile strength of 638 MPa, and a tensile modulus of 14.6 GPa.

[0172] In this embodiment, the polyacrylonitrile precursor fiber is further processed through pre-oxidation, carbonization, surface treatment, and sizing to obtain polyacrylonitrile-based carbon fiber. The tensile strength of the polyacrylonitrile-based carbon fiber is 5.00 GPa, and the tensile modulus is 250 ± 10 GPa.

[0173] Experimental Example 7

[0174] This embodiment describes a method for preparing polyacrylonitrile precursor fibers, the main steps of which are as follows:

[0175] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 10 m / min.

[0176] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The temperature of the coagulation bath is 5℃, the concentration of the coagulation bath is 32%, and the draw ratio is 3.0.

[0177] (3) Washing: The nascent fibers enter the washing process at a rate of 30 m / min, with the water flow direction opposite to the fiber's spinning direction. The washing temperature is 50-55℃, and the residence time is 80 s.

[0178] (4) Hot water stretching:

[0179] See hot water stretching device Figure 1 As shown, the first bottom 11 of the trough 1 is a downward-sloping section with an angle of 3° along the yarn feeding direction; the second bottom 12 is parallel to the surface of the hot water drawing bath. The horizontal distance between the center points of the feed roller 2 and the guide roller 3 along the yarn feeding direction is 3200mm, and the horizontal distance between the center points of the feed roller 2 and the first drawing roller 4 along the yarn feeding direction is 4000mm. The distance from the lower edge of the feed roller 2 to the surface of the bath is 30mm, and the ratio of the distance from the lower edge of the guide roller 3 to the surface of the bath to the distance from the lower edge of the feed roller 2 to the surface of the bath is 1.0. Specifically, the distance from the lower edge of the guide roller 3 to the surface of the bath is 30mm. The lower edge of the first drawing roller 4 is 125.5mm higher than the surface of the bath in the trough 1, and the lifting angle of the fiber bundle between the guide roller 3 and the first drawing roller 4 along the yarn feeding direction is 11°. Among them, the guide roller 3 is a fixed roller; the diameter of the guide roller 3 is 40mm and the surface roughness is ≤Ra0.8μm.

[0180] After washing, the fibers enter the hot water drawing device, tank 1, for hot water drawing. The first water supply line, after passing through preheater 7, contains deionized water at a temperature of 66℃. The hot water drawing temperature is 70℃, and the drawing ratio is 2.8. The fiber velocity at the outlet side of tank 1 is 84 m / min. The liquid level at the outlet side of tank 1 is stable, with no overflow caused by the fibers. The torque of each drawing roller motor is 19-22%.

[0181] After being cooled by cooler 8, the second water supply pipeline contains deionized water at a temperature of 18℃ and a flow rate of 0.5m³ / h. 3 The spray is applied to the fiber bundle at a rate of / h via spray device 6. To further prevent excessive moisture from entering the subsequent oiling process, a pressure roller 5 is placed above the fourth drafting roller. Pressure roller 5 is made of rubber with a Shore hardness of 60-70 and a compression set of 20-30%, and its pressure is 3 bar. After lowering pressure roller 5, the motor torque of the fourth drafting roller increases by 30-33%. During operation, there is minimal fuzz on the drafting roller, and no roller entanglement occurs.

[0182] (5) Oiling and Drying Densification: After hot water stretching, the fibers are oiled once and then dried and densified. The oil concentration is 3%, and the drying and densification temperature is 140-170℃. During the oiling process, the oil does not deteriorate significantly, the oil is replaced every 45 days, and the liquid level in the oil tank is stable.

[0183] (6) Steam drawing and winding: The dried and densified fibers are steam drawn at a pressure of 0.6 MPa and a drawing ratio of 4.0. Polyacrylonitrile carbon fiber precursor is obtained at a speed of 336 m / min.

[0184] The polyacrylonitrile precursor fiber prepared in this embodiment has the following characteristics: fineness of 0.8 dtex, strength of 760 MPa, and modulus of 16.5 GPa.

[0185] Polyacrylonitrile precursor fibers are further processed through pre-oxidation, carbonization, surface treatment, and sizing to produce polyacrylonitrile-based carbon fibers. The tensile strength of these polyacrylonitrile-based carbon fibers is 6.08 GPa, and the tensile modulus is 290 ± 10 GPa.

[0186] The above experimental examples 1-7 are preferred embodiments, encompassing all preferred solutions of the present invention. Furthermore, based on the inventive concept of this application, the present invention provides comparative examples 1-5, which, while based on the main inventive points of the present invention, do not employ certain preferred solutions (these preferred solutions are further conceptualizations based on the main inventive points of the present invention to improve the main inventive points, coordinate the inventive points, or further solve other existing problems, and are not conventional technical means). Specifically, as follows:

[0187] Comparative Example 1

[0188] Comparative Example 1 provides a method for preparing polyacrylonitrile precursor fibers, the main steps of which are as follows:

[0189] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 12 m / min.

[0190] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The temperature of the coagulation bath is 6℃, the concentration of the coagulation bath is 35%, and the draw ratio is 2.67.

[0191] (3) Washing: The nascent fibers enter the washing process at a rate of 32 m / min, with the water flow direction opposite to the fiber's spinning direction. The washing temperature is 50-55℃, and the residence time is 75 s.

[0192] (4) Hot water stretching:

[0193] like Figure 1 As shown, the first bottom 11 of the hot water drawing device is a downward-sloping section with an angle of 3° along the yarn feeding direction; the second bottom 12 is parallel to the surface of the hot water drawing bath. The horizontal distance between the center points of the feed roller and the guide roller along the yarn feeding direction is 3200 mm, and the horizontal distance between the center points of the feed roller 2 and the first drawing roller 4 along the yarn feeding direction is 4000 mm. The distance from the lower edge of the feed roller 2 to the surface of the bath is 30 mm, and the ratio of the distance from the lower edge of the guide roller 3 to the surface of the bath to the distance from the lower edge of the feed roller to the surface of the bath is 1.33. Specifically, the distance from the lower edge of the guide roller to the surface of the bath is 40 mm. The lower edge of the first drawing roller 4 is 125.5 mm higher than the surface of the bath in the hot water drawing tank, and the lifting angle of the fiber bundle between the guide roller 3 and the first drawing roller 4 along the yarn feeding direction is 11.68°.

[0194] After washing, the fibers enter the hot water drawing device for hot water drawing. The first water supply line passes through preheater 7, where the deionized temperature is 64℃. The hot water drawing temperature is 68℃, and the drawing ratio is 2.5. The fiber speed at the outlet of the hot water drawing device is 80 m / min. The liquid level at the outlet of the hot water drawing bath is stable, with no overflow caused by the fibers. The torque of each drawing roller motor is 20-23%.

[0195] After passing through cooler 8, the second water supply pipeline contains deionized water at a temperature of 18℃ and a flow rate of 0.5m³ / h. 3 The spray is applied to the fiber bundle at a rate of / h via a spraying device. To further prevent excessive moisture from entering the subsequent oiling process, a pressure roller 5 is lowered above the fourth drafting roller, with a pressure of 4 bar. The pressure roller 5 is made of rubber with a Shore hardness of 60-70 and a compression set of 20-30%. After lowering the pressure roller 5, the motor torque of the fourth drafting roller increases by 31-34%. During operation, the drafting roller winds once every 3 days.

[0196] (5) Oiling and Drying Densification: After hot water stretching, the fibers are oiled once and then dried and densified. The concentration of the oiling agent is 3%, and the drying and densification temperature is 130-170℃. During the oiling process, the oiling agent does not deteriorate significantly, the oiling agent is replaced every 30 days, and the liquid level in the oiling agent tank is stable.

[0197] (6) Steam drawing and winding: The dried and densified fibers are steam drawn at a pressure of 0.6 MPa and a drawing ratio of 3.5. Polyacrylonitrile carbon fiber precursor is obtained at a speed of 280 m / min.

[0198] The polyacrylonitrile precursor fiber prepared in Comparative Example 1 has a fineness of 1.1 dtex, a tensile strength of 642 MPa, and a tensile modulus of 14.4 GPa.

[0199] Polyacrylonitrile precursor fibers are further processed through pre-oxidation, carbonization, surface treatment, and sizing to produce polyacrylonitrile-based carbon fibers. The tensile strength of these polyacrylonitrile-based carbon fibers is 4.90 GPa, and the tensile modulus is 250 ± 10 GPa.

[0200] Here, since Comparative Example 1 did not control the ratio of the distance from the lower edge of the guide roller to the surface of the bath liquid to the distance from the lower edge of the feed roller to the surface of the bath liquid to be 0.3-1.0, and the lifting angle of the fiber bundle between the guide roller and the first drawing roller along the wire feeding direction was not controlled to be 6-11°, therefore, compared with Examples 1-7, the hot drawing process of Comparative Example 1 has the phenomenon of drawing roller wrapping (the frequency of drawing roller wrapping is 1 time / 3 days), and the performance of the prepared polyacrylonitrile precursor and carbon fiber is not as good as that of Examples 1-7.

[0201] Comparative Example 2

[0202] Comparative Example 2 provides a method for preparing polyacrylonitrile precursor fibers, the main steps of which are as follows:

[0203] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 12 m / min.

[0204] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The temperature of the coagulation bath is 6℃, the concentration of the coagulation bath is 35%, and the draw ratio is 2.67.

[0205] (3) Washing: The nascent fibers enter the washing process at a rate of 32 m / min, with the water flow direction opposite to the fiber's spinning direction. The washing temperature is 50-55℃, and the residence time is 75 s.

[0206] (4) Hot water stretching:

[0207] like Figure 1As shown, the first bottom 1 of the hot water drawing device is a downward-sloping section with an angle of 3° along the yarn feeding direction; the second bottom 2 is parallel to the surface of the hot water drawing bath. The horizontal distance between the center points of the feed roller and the guide roller along the yarn feeding direction is 3200 mm, and the horizontal distance between the center points of the feed roller 2 and the first drawing roller 4 along the yarn feeding direction is 4000 mm. The distance from the lower edge of the feed roller 2 to the surface of the bath is 30 mm, and the ratio of the distance from the lower edge of the guide roller 3 to the surface of the bath to the distance from the lower edge of the feed roller 2 to the surface of the bath is 1.0. Specifically, the distance from the lower edge of the guide roller 3 to the surface of the bath is 30 mm. The lower edge of the first drawing roller 4 is 125.5 mm higher than the surface of the bath in the hot water drawing tank, and the lifting angle of the fiber bundle between the guide roller 3 and the first drawing roller 4 along the yarn feeding direction is 11°.

[0208] After washing, the fibers enter the hot water drawing device for hot water drawing. The first water supply line, after passing through preheater 7, contains deionized water at a temperature of 64℃. The hot water drawing temperature is 68℃, and the drawing ratio is 2.5. The fiber speed at the outlet side of the hot water drawing device is 80 m / min. The liquid level at the outlet side of the hot water drawing bath is stable, with no overflow caused by the fibers. The torque of each drawing roller motor is 19-22%.

[0209] After passing through cooler 9, the second water supply pipeline contains deionized water at a temperature of 10℃ and a flow rate of 0.5m³ / h. 3 / h, the hot water is sprayed onto the fiber bundle through the spray device 6. The temperature of the hot water-drawn fiber bundle (after being sprayed) is too low, resulting in poor elasticity of the pressure roller rubber. This prevents the oil solution from becoming too hot in the subsequent oiling process, thus avoiding oil spoilage. To further prevent the fiber bundle from carrying too much moisture into the subsequent oiling process, a pressure roller is placed above the fourth drawing roller, with a pressure of 3 bar. The pressure roller 5 is made of rubber with a Shore hardness of 60-70 and a compression set of 20-30%. After the pressure roller is placed, the motor torque of the fourth drawing roller increases to 39-42%. The motor torque is close to the upper limit (45%), which can easily cause the motor inverter to overcurrent alarm and stop during operation.

[0210] Here, according to the scheme of Comparative Example 2, it can be seen that after spraying the hot water drawn-out filament bundle with the spraying device 6, if the spraying temperature is too low, below 14-18℃, the rubber elasticity will be poor. As a result, after the pressure roller is pressed down, the motor torque of the fourth drawing roller will approach the upper limit, causing an alarm and shutdown.

[0211] Comparative Example 3

[0212] This embodiment describes a method for preparing polyacrylonitrile precursor fibers, the main steps of which are as follows:

[0213] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 12 m / min.

[0214] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The temperature of the coagulation bath is 6℃, the concentration of the coagulation bath is 35%, and the draw ratio is 2.67.

[0215] (3) Washing: The nascent fibers enter the washing process at a rate of 32 m / min, with the water flow direction opposite to the fiber's spinning direction. The washing temperature is 50-55℃, and the residence time is 75 s.

[0216] (4) Hot water stretching:

[0217] like Figure 1 As shown, the first bottom 11 of the hot water drawing device's tank 1 is a downward-sloping section with an angle of 3° along the yarn feeding direction; the second bottom 12 is parallel to the surface of the hot water drawing bath. The horizontal distance between the center points of the feed roller 2 and the guide roller 3 along the yarn feeding direction is 3200 mm, and the horizontal distance between the center points of the feed roller 2 and the first drawing roller 4 along the yarn feeding direction is 4000 mm. The distance from the lower edge of the feed roller 2 to the surface of the bath is 30 mm, and the ratio of the distance from the lower edge of the guide roller 3 to the surface of the bath to the distance from the lower edge of the feed roller to the surface of the bath is 1.0. Specifically, the distance from the lower edge of the guide roller 3 to the surface of the bath is 30 mm. The lower edge of the first drawing roller 4 is positioned 125.5 mm higher than the surface of the bath in the hot water drawing tank, and the lifting angle of the fiber bundle between the guide roller and the first drawing roller along the yarn feeding direction is 11°.

[0218] After washing, the fibers enter the hot water drawing device for hot water drawing. The first water supply line, after passing through preheater 7, contains deionized water at a temperature of 64℃. The hot water drawing temperature is 68℃, and the drawing ratio is 2.5. The fiber speed at the outlet side of the hot water drawing device is 80 m / min. The liquid level at the outlet side of the hot water drawing bath is stable, with no overflow caused by the fibers. The torque of each drawing roller motor is 19-22%.

[0219] After passing through cooler 8, the second water supply pipeline contains deionized water at a temperature of 18℃ and a flow rate of 0.5m³ / h. 3At a rate of / h, a spray system is used to spray water onto the fiber bundle to lower the temperature of the hot water drawn-out fiber bundle, preventing the oil solution from becoming too hot in the subsequent oiling process and thus avoiding oil spoilage. To further prevent the fiber bundle from carrying excessive moisture into the subsequent oiling process, a pressure roller 5 is lowered above the fourth drawing roller. The pressure roller 5 has a pressure of 1 bar and is made of rubber with a Shore hardness of 60-70 and a compression set of 20-30%. After lowering the pressure roller, the motor torque of the fourth drawing roller increases by 29-32%. During operation, there is minimal fuzz on the drawing roller, and no roller entanglement occurs.

[0220] (5) Oiling and Drying Densification: After hot water stretching, the fibers are oiled once and then dried and densified. The oil concentration is 3%, and the drying and densification temperature is 130-170℃. During operation, the oil tank level gradually rises, and the rising oil solution needs to be pumped out every 3 hours.

[0221] (6) Steam drawing and winding: The dried and densified fibers are steam drawn at a pressure of 0.6 MPa and a drawing ratio of 3.5. Polyacrylonitrile carbon fiber precursor is obtained at a speed of 280 m / min.

[0222] The polyacrylonitrile precursor fiber prepared in Comparative Example 3 has a fineness of 1.1 dtex, a tensile strength of 655 MPa, and a tensile modulus of 14.6 GPa.

[0223] The polyacrylonitrile precursor fiber of Comparative Example 3 was further processed through pre-oxidation, carbonization, surface treatment, and sizing to obtain polyacrylonitrile-based carbon fiber. The tensile strength of the polyacrylonitrile-based carbon fiber was 5.15 GPa, and the tensile modulus was 250 ± 10 GPa.

[0224] Here, in Comparative Example 3, the pressure of the pressure roller was set to 1 bar in the hot stretching process, which is lower than 2-5 bar. After the pressure roller was used, the moisture content of the fiber still exceeded the standard. As a result, the following situation occurred in the oiling process: the liquid level of the oil tank gradually increased, and the rising oil solution needed to be extracted once every 3 hours.

[0225] Comparative Example 4

[0226] Comparative Example 4 provides a method for preparing polyacrylonitrile precursor fibers, the main steps of which are as follows:

[0227] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 12 m / min.

[0228] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The temperature of the coagulation bath is 6℃, the concentration of the coagulation bath is 35%, and the draw ratio is 2.67.

[0229] (3) Washing: The nascent fibers enter the washing process at a rate of 32 m / min, with the water flow direction opposite to the fiber's spinning direction. The washing temperature is 50-55℃, and the residence time is 75 s.

[0230] (4) Hot water stretching:

[0231] like Figure 1 As shown, the first bottom 11 of the hot water drawing device's tank 1 is a downward-sloping section with an angle of 3° along the yarn feeding direction; the second bottom 12 is parallel to the surface of the hot water drawing bath liquid. The horizontal distance between the center points of the feed roller 2 and the guide roller 3 along the yarn feeding direction is 3200 mm, and the horizontal distance between the center points of the feed roller 2 and the first drawing roller 4 along the yarn feeding direction is 4000 mm. The distance from the lower edge of the feed roller 2 to the surface of the bath liquid is 30 mm, and the ratio of the distance from the lower edge of the guide roller 3 to the surface of the bath liquid to the distance from the lower edge of the feed roller 2 to the surface of the bath liquid is 1.0, specifically 30 mm. The lower edge of the first drawing roller 4 is positioned 125.5 mm higher than the surface of the bath liquid in the hot water drawing tank, and the lifting angle of the fiber bundle between the guide roller and the first drawing roller along the yarn feeding direction is 11°.

[0232] After washing, the fibers enter the hot water drawing device for hot water drawing. The first water supply line, after passing through preheater 7, contains deionized water at a temperature of 64℃. The hot water drawing temperature is 68℃, and the drawing ratio is 2.5. The fiber speed at the outlet of the hot water drawing device is 80 m / min. The liquid level at the outlet of the hot water drawing bath is stable, with no overflow caused by the fibers. The torque of each drawing roller motor is 19-22%.

[0233] Turn off the spray device that sprays deionized water onto the fiber bundle. Lower the pressure roller above the fourth drafting roller, setting the pressure roller pressure to 3 bar. The pressure roller 5 is made of rubber with a Shore hardness of 60-70 and a compression deformation of 20-30%. After lowering the pressure roller, the motor torque of the fourth drafting roller increases by 25-28%. During operation, the drafting roller may develop a lot of fuzz (due to pressing the pressure roller directly without turning on the spray, resulting in excessively low moisture content in the fiber bundle at the hot drafting exit, making it prone to fuzzing), posing a risk of roller entanglement. Timely cleaning is necessary.

[0234] (5) Oiling and Drying Densification: After hot water stretching, the fibers are oiled once and then dried and densified. The concentration of the oiling agent is 3%, and the drying and densification temperature is 130-170℃. During the oiling process, the oiling agent shows obvious signs of spoilage. The oiling agent is replaced every 15 days, and the liquid level in the oiling agent tank remains stable overall.

[0235] (6) Steam drawing and winding: The dried and densified fibers are steam drawn at a pressure of 0.6 MPa and a drawing ratio of 3.5. Polyacrylonitrile carbon fiber precursor is obtained at a speed of 280 m / min.

[0236] The polyacrylonitrile precursor fiber prepared in Comparative Example 4 has a fineness of 1.1 dtex, a tensile strength of 642 MPa, and a tensile modulus of 14.4 GPa.

[0237] Polyacrylonitrile precursor fibers are processed through pre-oxidation, carbonization, surface treatment, and sizing to produce polyacrylonitrile-based carbon fibers. The tensile strength of polyacrylonitrile-based carbon fibers is 4.86 GPa, and the tensile modulus is 250 ± 10 GPa.

[0238] In Comparative Example 4, the fiber bundles drawn out by hot water were not sprayed, resulting in a large amount of fuzz on the drawing rollers, posing a risk of roller entanglement, and poor carbon fiber filament and carbon fiber processing performance. Furthermore, the temperature of the fiber bundles on the hot water drawing-out side was not reduced, leading to significant oil contamination.

[0239] Comparative Example 5

[0240] The main difference between Comparative Example 5 and Comparative Example 1 is that Comparative Example 5 does not use a guide roller. Specifically, a method for preparing polyacrylonitrile precursor fiber is provided, the main steps of which are as follows:

[0241] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 12 m / min.

[0242] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The coagulation bath temperature is 6℃, the coagulation bath concentration is 35%, and the draw ratio is 2.67.

[0243] (3) Washing: The nascent fibers enter the washing process at a rate of 32 m / min, the washing temperature is 50-55℃, and the residence time is 75 s.

[0244] (4) Hot water stretching:

[0245] The structure of the hot water stretching device is as follows: Figure 1The guide roller is omitted from the basic design. The first bottom 11 of the trough 1 is a downward-sloping section extending in the wire feeding direction, with a slope angle of 3°; the second bottom 12 is parallel to the surface of the hot water drawing bath. The horizontal distance between the center points of the feed roller 2 and the first drawing roller 4 along the wire feeding direction is 4000mm. The distance from the lower edge of the feed roller 2 to the surface of the bath is 30mm, and the lower edge of the first drawing roller 4 is positioned 125.5mm higher than the surface of the bath in the trough.

[0246] After washing, the fibers enter the hot water drawing device's tank 1 for hot water drawing. The first water supply line, after passing through preheater 7, maintains the temperature of the deionized water at 70℃, while the hot water drawing temperature is 75℃, with a drawing ratio of 2.5. The fiber bundle's running speed at the outlet side of tank 1 is 80 m / min, and the liquid level at the outlet side of tank 1 remains stable, with no overflow caused by the fibers. The motor torque of each drawing roller is 16-19%.

[0247] After being cooled by cooler 8, the second water supply pipeline contains deionized water at a temperature of 15℃ and a flow rate of 0.5m³ / h. 3 / h, by spraying the fiber bundle with the spray device 6. To further prevent the fiber bundle from carrying too much moisture into the subsequent oiling process, a pressure roller 5 is placed above the fourth drafting roller. The pressure roller 5 is made of rubber with a Shore hardness of 60-70 and a compression deformation of 20-30%, and the pressure of the pressure roller 5 is 4 bar. After the pressure roller 5 is placed, the motor torque of the fourth drafting roller increases by 28-31%. During operation, there is a lot of fuzz on the drafting roller (because there is no guide roller, the residence time of the fiber bundle in the hot water environment is short, and it is easy to become fuzzy), which poses a risk of roller entanglement.

[0248] (5) Oiling and Drying Densification: After hot water stretching, the fibers are oiled once and then dried and densified. The concentration of the oiling agent is 3%, and the drying and densification temperature is 130-170℃. During the oiling process, the oiling agent does not deteriorate significantly, the oiling agent is replaced every 30 days, and the liquid level in the oiling agent tank is stable.

[0249] (6) Steam drawing and yarn taking: The dried and densified fibers are steam drawn at a pressure of 0.6 MPa and a drawing ratio of 3.5. Polyacrylonitrile precursor fibers are taken at a speed of 280 m / min.

[0250] The polyacrylonitrile precursor fiber prepared in this embodiment has a fineness of 1.1 dtex, a tensile strength of 632 MPa, and a tensile modulus of 14.2 GPa.

[0251] The polyacrylonitrile precursor fiber prepared in this embodiment is then subjected to processes such as pre-oxidation, carbonization, surface treatment, and sizing to obtain polyacrylonitrile-based carbon fiber. The polyacrylonitrile-based carbon fiber has a tensile strength of 4.82 GPa and a tensile modulus of 250 ± 10 GPa.

[0252] In Comparative Example 5, the absence of guide rollers in the hot water drawing trough resulted in a short residence time of the fiber bundles in the hot water, insufficient drawing treatment, excessive fuzz on the drawing rollers, a risk of roller entanglement, and poor carbon fiber precursor and carbon fiber processing performance.

[0253] Comparative Example 6

[0254] Comparative Example 6 provides a method for preparing polyacrylonitrile precursor fibers. Unlike Experimental Examples 1-7 and Comparative Examples 1-5, Comparative Example 6 uses a conventional process, specifically employing a hot water stretching treatment step... Figure 2 The device shown is used for thermal drawing.

[0255] The preparation method of the polyacrylonitrile precursor fiber of Comparative Example 6 mainly includes the following steps:

[0256] This embodiment provides a method for preparing polyacrylonitrile precursor fibers, the main steps of which are as follows:

[0257] (1) Spinning: The spinning solution with a solid content of 21% and a viscosity of 110 Pa·s is metered by a metering pump and then passed through a spinneret with a specification of 0.12 mm to form a fine stream of the solution. The final spinning speed of the fine stream of the solution is 12 m / min.

[0258] (2) Coagulation and forming: The spinneret is lowered to a position 5 mm away from the surface of the coagulation bath. The raw liquid stream enters the coagulation bath to form nascent fibers. The coagulation bath temperature is 6℃, the coagulation bath concentration is 35%, and the draw ratio is 2.67.

[0259] (3) Washing: The nascent fibers enter the washing process at a rate of 32 m / min, the washing temperature is 50-55℃, and the residence time is 75 s.

[0260] (4) Hot water stretching:

[0261] See the structure of the hot water stretching device. Figure 2 As shown, the bottom of the tank 9 is horizontal. The fiber bundle enters the tank 9 through the feed roller 10 for hot drawing, and then exits through the first drawing roller 13. The lower edge of the feed roller 10 and the lower edge of the first drawing roller 13 are both below the surface of the bath liquid; and the lower edges of the feed roller 10 and the first drawing roller 13 are at the same level.

[0262] After washing, the fibers enter the hot water drawing device (tank 9) for hot water drawing. The temperature of the hot water drawing is 68℃, and the drawing ratio is 2.5. The fiber speed at the outlet side of the hot water drawing device is 80 m / min. During operation, the following phenomena occur: a large amount of hot water is carried out of the bath on the fiber exit side, resulting in large fluctuations in the bath liquid level; the hot water drawing temperature fluctuates greatly; during operation, there are many fuzzy fibers on the drawing roller surface, and the frequency of roller wrapping is 1-3 times / day. The torque of each drawing roller motor is 20-23%.

[0263] To further prevent excessive moisture from entering the subsequent oiling process along with the fiber bundles, a pressure roller 14 is lowered above the fourth drafting roller, with a pressure of 3 bar. After lowering the pressure roller 14, the motor torque of the fourth drafting roller does not increase significantly (here, the torque is greatly affected by the hardness of the pressure roller. In the comparative example, the pressure roller 14 is affected by the incoming fiber bundle, so the torque is not particularly large; however, it may deform under long-term use at high temperatures).

[0264] (5) Oiling and Drying Densification: After hot water stretching, the fibers are oiled once and then dried and densified. The concentration of the oiling agent is 3%, and the drying and densification temperature is 130-170℃. During the oiling process, the oiling agent deteriorates significantly, and the oiling agent is replaced every 7-10 days. The liquid level in the oiling agent tank is stable.

[0265] (6) Steam drawing and winding: The dried and densified fibers are steam drawn at a pressure of 0.6 MPa and a drawing ratio of 3.5. Polyacrylonitrile carbon fiber precursor is obtained at a speed of 280 m / min.

[0266] The polyacrylonitrile precursor fiber prepared in Comparative Example 6 has a fineness of 1.1 dtex, a tensile strength of 627 MPa, and a tensile modulus of 14.0 GPa.

[0267] Polyacrylonitrile precursor fibers are further processed through pre-oxidation, carbonization, surface treatment, and sizing to produce polyacrylonitrile-based carbon fibers. The tensile strength of these polyacrylonitrile-based carbon fibers is 4.70 GPa, and the tensile modulus is 250 ± 10 GPa.

[0268] As can be seen from Experimental Examples 1-7 and Comparative Examples 1-6, the performance of the polyacrylonitrile precursor and polyacrylonitrile-based carbon fiber prepared in Comparative Example 6 is inferior to that of Comparative Examples 1 and 3-5, and even more inferior to that of the polyacrylonitrile precursor and polyacrylonitrile-based carbon fiber prepared in Experimental Examples 1-7.

[0269] In summary, the hot water drafting device and method proposed in this invention for the preparation of dry-jet wet-spun polyacrylonitrile precursor yarn solves the technical problems of existing hot water drafting devices in the dry-jet wet-spun precursor yarn production process, such as "large fluctuations in the bath liquid level, resulting in uneven temperature field and easy filament entanglement on the rollers." Furthermore, by controlling the temperature of the yarn bundle at the hot drafting exit, the temperature of the pressure roller is indirectly controlled. Combined with the pressure roller parameters, this solves the technical problem of high torque on the motor corresponding to the pressure roller during the hot water drafting process of dry-jet wet spinning, which easily causes overcurrent faults in the frequency converter of the drafting roller motor.

[0270] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A hot water drawing device for use in the preparation of dry-jet wet-spinning polyacrylonitrile precursor fibers, characterized in that, The hot water stretching device includes: A tank body for holding bath liquid; wherein the tank body has a first end and a second end disposed opposite to each other; wherein the bottom of the tank body includes a first bottom and a second bottom; wherein the first bottom includes a portion of the bottom located on and near the yarn inlet side, and the second bottom includes a portion of the bottom located on the yarn outlet side; wherein, along the yarn feeding direction, the first bottom has a downwardly extending slope. A fiber feed roller is located at the first end of the trough; wherein the fiber bundle enters the trough through the fiber feed roller; A first drafting roller is located at the second end of the groove; wherein the fiber bundle leaves the groove after passing through the first drafting roller. The lower edge of the feed roller is immersed in the bath liquid in the tank; the lower edge of the first drawing roller is located above the surface of the bath liquid in the tank. The hot water stretching device further includes: The fiber bundle entering the groove first passes through the guide roller and then through the first drawing roller. The lower edge of the guide roller is immersed in the bath liquid inside the tank.

2. The hot water drawing device for preparing dry-jet wet-spinning polyacrylonitrile precursor according to claim 1, characterized in that, The lifting angle α of the fiber bundle between the guide roller and the first drawing roller along the wire feeding direction; wherein α is 6-11°.

3. The hot water drawing device for preparing dry-jet wet-spinning polyacrylonitrile precursor according to claim 1, characterized in that, The guide roller is a fixed roller; wherein the diameter of the guide roller is 35-45mm and the surface roughness is ≤Ra0.8μm.

4. The hot water drawing device for preparing dry-jet wet-spinning polyacrylonitrile precursor according to claim 1, characterized in that, The distance from the lower edge of the guide roller to the surface of the bath liquid is D1; ​​the distance from the lower edge of the feed roller to the surface of the bath liquid is D2; wherein the ratio of D1 to D2 is 0.3-1.0; and / or The distance D2 from the lower edge of the feed roller to the surface of the bath liquid is 25-35mm.

5. The hot water drawing device for preparing polyacrylonitrile precursor yarn in dry-jet wet spinning according to claim 1, characterized in that, The horizontal distance D3 between the center of the feed roller and the center of the first drafting roller along the wire feeding direction is 3800-4200 mm; and / or The horizontal distance D4 between the center of the feed roller and the center of the guide roller along the wire feeding direction is 3000-3400mm.

6. The hot water drawing device for preparing dry-jet wet-spinning polyacrylonitrile precursor according to claim 1, characterized in that, The angle of the slope is 2-5°; The bottom of the second tank is parallel to the surface of the bath liquid.

7. The hot water drawing device for preparing dry-jet wet-spinning polyacrylonitrile precursor according to claim 6, characterized in that, The bottom of the first tank and the bottom of the second tank are connected.

8. The hot water drawing device for preparing dry-jet wet-spinning polyacrylonitrile precursor according to claim 1, characterized in that, The hot water stretching device also includes: The first water supply pipeline passes through the preheater and connects to the tank body; wherein the connection point between the first water supply pipeline and the tank body is located on the bottom of the tank body at the wire outlet side.

9. The hot water drawing device for preparing polyacrylonitrile precursor yarn in dry-jet wet spinning according to claim 1, characterized in that, The hot water stretching device also includes: The second water supply pipeline passes through the cooler and is connected to a spray device; wherein the spray device is used to spray water onto the fiber bundle after passing through the first drafting roller to reduce the temperature of the fiber bundle to a set temperature.

10. The hot water drawing device for preparing polyacrylonitrile precursor by dry-jet wet spinning according to claim 9, characterized in that, The hot water stretching device also includes: A pressure roller is used to compress the fiber bundles after water spraying treatment; wherein the pressure roller is made of rubber material with a Shore hardness of 60-70 and a compression deformation of 20-30%.

11. The hot water drawing device for preparing dry-jet wet-spun polyacrylonitrile precursor according to claim 10, characterized in that, The hot water stretching device also includes: The hot water drawing device includes a drawing roller assembly; wherein the drawing roller assembly includes a first drawing roller, a second drawing roller, a third drawing roller, a fourth drawing roller, and a fifth drawing roller; wherein the fiber bundle passing through the first drawing roller passes sequentially through the second drawing roller, the third drawing roller, the fourth drawing roller, and the fifth drawing roller; wherein the spraying device is located above the third drawing roller; and the pressure roller is located above the fourth drawing roller.

12. A hot water drawing method for preparing dry-jet wet-spun polyacrylonitrile precursor fibers, characterized in that, The fiber bundle is hot-drawn using the hot water drawing device described in any one of claims 1-11 for the preparation of dry-jet wet-spun polyacrylonitrile precursor.

13. The hot water drawing method for preparing dry-jet wet-spun polyacrylonitrile precursor according to claim 12, characterized in that, The temperature for hot water stretching is 65-85℃, and the stretching ratio is 2.0-3.

0.

14. The hot water drawing method for preparing dry-jet wet-spun polyacrylonitrile precursor fibers according to claim 12, characterized in that, When the hot water drawing device used in the preparation of dry-jet wet-spinning polyacrylonitrile precursor includes a spraying device, the spraying device is used to spray cooling water at a temperature of 14-18°C onto the fiber bundle.

15. The hot water drawing method for preparing dry-jet wet-spun polyacrylonitrile precursor fibers according to claim 12, characterized in that, When the hot water drafting device used in the preparation of dry-jet wet-spinning polyacrylonitrile precursor includes a pressure roller, the pressure of the pressure roller is set to 2-5 bar.

16. A method for preparing dry-jet wet-spun polyacrylonitrile precursor, characterized in that, It includes the following steps: 1) The spinning solution is spun and solidified to obtain nascent fibers; 2) The nascent fibers are subjected to water washing, hot water drawing, oiling, drying and densification, steam drawing and winding treatment to obtain polyacrylonitrile precursor fibers; The hot water drawing process is performed using the hot water drawing device described in any one of claims 1-11 for the preparation of dry-jet wet-spinning polyacrylonitrile precursor.

17. The method for preparing dry-jet wet-spun polyacrylonitrile precursor according to claim 16, characterized in that, The temperature for hot water stretching is 65-85℃, and the stretching ratio is 2.0-3.

0.

18. The method for preparing dry-jet wet-spun polyacrylonitrile precursor according to claim 16, characterized in that, When the hot water drawing device used in the preparation of dry-jet wet-spinning polyacrylonitrile precursor includes a spraying device, the spraying device is used to spray cooling water at a temperature of 14-18°C onto the fiber bundle during the hot water drawing process.

19. The method for preparing dry-jet wet-spun polyacrylonitrile precursor according to claim 16, characterized in that, When the hot water drawing device used in the preparation of dry-jet wet-spun polyacrylonitrile precursor includes a pressure roller, the pressure of the pressure roller is set to 2-5 bar during the hot water drawing process.

20. The method for preparing dry-jet wet-spun polyacrylonitrile precursor according to claim 16, characterized in that, The polyacrylonitrile precursor fiber has a fineness of 0.7-1.2 dtex, a tensile strength ≥630 MPa, and a tensile modulus ≥14 GPa.

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