A method for pre-oxidation of carbon fiber

Abstract

This application relates to a pre-oxidation method for carbon fibers, belonging to the technical field of carbon fiber preparation. A pre-oxidation method for carbon fibers includes: subjecting polyacrylonitrile-based carbon fiber precursor filaments prepared by the dry-jet wet spinning process to pre-oxidation treatment through three consecutive pre-oxidation temperature zones, so that the pre-oxidation degree of the finally obtained pre-oxidized fiber filaments meets the following conditions: the bulk density is 1.33 - 1.35 g / cm 3 , and the cyclization degree is 85 - 92%. The pre-oxidation method provided in this application is used in the pre-oxidation reaction of dry-jet wet precursor filaments. By only performing pre-oxidation treatment through three consecutive pre-oxidation temperature zones, the pre-oxidation can meet the qualified standard. It has the advantages of reducing the reaction time, lowering energy consumption, and improving production efficiency, etc.

Description

Technical Field

[0001] This application relates to the technical field of carbon fiber preparation, and particularly to a pre-oxidation method for carbon fiber. Background Art

[0002] Tow carbon fiber has a series of excellent properties such as high specific strength, high specific modulus, high temperature resistance, corrosion resistance, fatigue resistance, creep resistance, electrical conductivity, heat transfer and small thermal expansion coefficient, and is widely used in sports and leisure products and high-tech industrial fields, especially in the aerospace field with great application prospects. The preparation of dry-jet wet-spun carbon fiber generally includes three major processes: polymerization spinning, pre-oxidation, and carbonization. Among them, the production efficiency of pre-oxidation is one of the main factors controlling the preparation cycle of carbon fiber, and it is also the key directly affecting the quality of carbon fiber. At present, the pre-oxidation time is approximately 60 - 120 minutes, the carbonization time is from a few minutes to more than ten minutes, and the graphitization time is calculated in seconds.

[0003] Pre-oxidation is generally carried out in the temperature range of 180 - 300°C and under the conditions of segmented drawing and introducing clean air. Due to the importance of pre-oxidation in the process of carbon fiber preparation, scientific workers have devoted a lot of energy to this process and obtained a series of improved methods. For example: 1) The tensile strength and Young's modulus of the carbon fiber obtained by using silicone oil to modify the raw fiber can be significantly improved; 2) By pre-treating the polyacrylonitrile raw fiber, such as soaking pretreatment with potassium permanganate or X-ray pre-radiation, etc., the pre-oxidation reaction proceeds more gently and uniformly, reducing the formation of the fiber skin-core structure and achieving the purpose of improving the fiber performance. In the past five years, the main research directions in the field of carbon fiber preparation in various countries in the world have been to improve performance and reduce costs. Although great progress has been made in improving performance, there have been few breakthroughs in reducing costs, resulting in high carbon fiber costs and seriously hindering the in-depth expansion of carbon fiber products in the civilian field. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the embodiments of this application includes providing a pre-oxidation method for carbon fiber to improve the technical problems of too long pre-oxidation time, high energy consumption, and low efficiency in the existing dry-jet wet-spun carbon fiber preparation process.

[0005] In the first aspect, the embodiments of this application provide a pre-oxidation method for carbon fiber, including: pre-oxidizing the polyacrylonitrile-based carbon fiber raw fiber obtained by the dry-jet wet-spinning process through three consecutive pre-oxidation temperature zones, so that the pre-oxidation degree of the finally obtained pre-oxidized fiber satisfies the following conditions: the bulk density is 1.33 - 1.35 g / cm 3, the degree of cyclization is 85-92%; the pre-oxidation temperature zone is divided into the first temperature zone, the second temperature zone and the third temperature zone; wherein, the temperature of the first temperature zone is higher than the temperatures of the second temperature zone and the third temperature zone, and the temperature of the third temperature zone is greater than or equal to the temperature of the second temperature zone; the fiber tension of the carbon fiber in the first temperature zone is greater than the fiber tensions of the carbon fiber in the second temperature zone and the third temperature zone, and the fiber tension of the carbon fiber in the third temperature zone is greater than or equal to the fiber tension of the carbon fiber in the second temperature zone.

[0006] The pre-oxidation method provided by the present application is used in the pre-oxidation reaction of the dry-jet wet spinning precursor. By controlling the temperatures of different temperature zones, the pre-oxidation reaction can proceed more efficiently and rapidly. Combining with the regulation of the fiber tensions of the carbon fiber in different temperature zones, the fiber morphology can be maintained, the reaction efficiency can be improved, the pre-oxidation degree can be further controlled, and the pre-oxidation conditions can be optimized, so that the pre-oxidation process of the dry-jet wet spinning carbon fiber is more efficient and stable, and finally high-quality carbon fiber products that meet the requirements can be obtained. This pre-oxidation method can make the pre-oxidation reach the qualified standard only through pre-oxidation treatment in three consecutive pre-oxidation temperature zones. It has the advantages of reducing the reaction time, lowering the energy consumption and improving the production efficiency.

[0007] In some embodiments of the present application, the temperature of the first temperature zone is defined as T1, the temperature of the second temperature zone is defined as T2, and the temperature of the third temperature zone is defined as T3; then 12°C < T1 - T2 < 26°C, 0°C ≤ T3 - T2 < 15°C. Within this temperature range, the cyclization reaction can proceed more rapidly, and at the same time, the pre-oxidation degree of the fiber in the three temperature zones can be more sufficient.

[0008] In some embodiments of the present application, T1 is 272-276°C; and / or, T2 is 250-260°C; and / or, T3 is 260-265°C. By reasonably controlling such a temperature range, the pre-oxidation reaction can proceed under different temperature conditions, giving full play to the reaction advantages at different temperatures, further optimizing the reaction process, making the bulk density and cyclization degree of the pre-oxidized fiber filaments meet the requirements, while reducing the energy consumption and improving the production efficiency.

[0009] In some embodiments of the present application, the fiber tension of the carbon fiber in the first temperature zone is defined as F1, the fiber tension of the carbon fiber in the second temperature zone is defined as F2, and the fiber tension of the carbon fiber in the third temperature zone is defined as F3; then 500 cN < F1 - F2 < 1300 cN, 0 cN ≤ F3 - F2 < 800 cN. Within this tension range, it is beneficial to regulate the fiber structure, reduce physical shrinkage, and thus better regulate the degree of the reaction.

[0010] In some embodiments of the present application, F1 is 2500 - 3000 cN; and / or, F2 is 1700 - 2000 cN; and / or, F3 is 2000 - 2500 cN. By controlling the tension within the above range, the pre-oxidized fiber filaments can obtain better fiber structures and properties during the pre-oxidation reaction in different temperature zones, while improving the stability and uniformity of the fibers, and finally obtaining carbon fiber products that meet the requirements.

[0011] In some embodiments of the present application, the treatment time in the first temperature zone is less than the treatment times in the second and third temperature zones.

[0012] In some embodiments of the present application, the treatment time in the second temperature zone is the same as the treatment time in the third temperature zone.

[0013] By controlling the treatment time in the first temperature zone to be less than the treatment times in the second and third temperature zones, and the treatment time in the second temperature zone to be the same as the treatment time in the third temperature zone, the pre-oxidation reaction process of carbon fibers can be optimized, energy can be saved, production efficiency can be improved, and the performance and quality of carbon fiber products can be ensured. In addition, setting the treatment times in the second and third temperature zones to be the same can ensure the continuous progress of the pre-oxidation reaction of carbon fibers, further accelerate the progress of pre-oxidation, and make the finally obtained pre-oxidized fiber filaments meet the required bulk density and degree of cyclization.

[0014] In some embodiments of the present application, the treatment time in the first temperature zone is defined as t1, the treatment time in the second temperature zone is defined as t2, and the treatment time in the third temperature zone is defined as t3; then 6 min < t1 - t2 < 10 min.

[0015] In some embodiments of the present application, t1 is 6 - 8 min; and / or, t2 is 14 - 16 min; and / or, t3 is 14 - 16 min. Within this time range, there can be sufficient cyclization reaction and partial oxidation reaction time in the first temperature zone.

[0016] In some embodiments of the present application, the total treatment time of pre-oxidation is 32 - 40 min. By controlling within the above treatment time range, the pre-oxidized fiber filaments can fully undergo cyclization and oxidation reactions in three consecutive pre-oxidation temperature zones, and maintain stable fiber structures and properties. Finally, carbon fiber products that meet the requirements are obtained, while achieving the goals of an efficient production process and resource conservation. Detailed implementation manners

[0017] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0018] The embodiments of this application provide a pre-oxidation method for carbon fibers, including: subjecting the polyacrylonitrile-based carbon fiber precursor filaments prepared by the dry-jet wet spinning process to pre-oxidation treatment through three consecutive pre-oxidation temperature zones, so that the pre-oxidation degree of the finally obtained pre-oxidized fiber filaments meets the following conditions: the bulk density is 1.33-1.35 g / cm 3 , and the cyclization degree is 85-92%. Among them, the pre-oxidation temperature zones are divided into the first temperature zone, the second temperature zone, and the third temperature zone; the following conditions are controlled for the above temperature zones: 1) The temperature of the first temperature zone is higher than the temperatures of the second temperature zone and the third temperature zone; the temperature of the third temperature zone is greater than or equal to the temperature of the second temperature zone. 2) The fiber tension of the carbon fibers in the first temperature zone is greater than the fiber tensions of the carbon fibers in the second temperature zone and the third temperature zone; the fiber tension of the carbon fibers in the third temperature zone is greater than or equal to the fiber tension of the carbon fibers in the second temperature zone. 3) The treatment time of the first temperature zone is less than the treatment times of the second temperature zone and the third temperature zone; the treatment time of the second temperature zone is the same as the treatment time of the third temperature zone.

[0019] In this application, the temperature of the temperature zone is equal to the temperature of the pre-oxidation furnace in the temperature zone, that is, the temperature for pre-oxidation. The entire pre-oxidation process of the dry-jet wet carbon fiber precursor filaments is carried out in a continuous pre-oxidation furnace with three temperature zones, that is, the carbon fiber precursor filaments are sequentially passed through the No. 1, No. 2, and No. 3 pre-oxidation furnaces for pre-oxidation treatment.

[0020] This application enables the pre-oxidation reaction to be completed in a relatively short time by setting different temperature intervals. The high-temperature treatment in the first temperature zone can quickly initiate the pre-oxidation reaction, while the lower-temperature treatments in the second and third temperature zones help to further promote the reaction, thus completing the pre-oxidation process in a relatively short time. Since the pre-oxidation is carried out at a relatively low temperature, controlling the temperature of the first temperature zone to be higher than that of the subsequent temperature zones can reduce the pre-oxidation time and energy consumption. In addition, through reasonable temperature regulation of the temperature zones, the temperature of the first temperature zone is higher than the temperatures of the second temperature zone and the third temperature zone; the temperature of the third temperature zone is greater than or equal to the temperature of the second temperature zone; in this way, energy can be utilized more efficiently, and the energy consumption can be further reduced.

[0021] Furthermore, by controlling the fiber tension in different temperature zones, the morphological stability of the carbon fiber precursor during the pre-oxidation process can be maintained. A higher fiber tension in the first temperature zone helps prevent fiber deformation and distortion, ensuring that the overall morphology of the fiber remains good during the pre-oxidation process. Moreover, by setting different fiber tensions in different temperature zones, on the one hand, the cyclization reaction of the carbon fiber precursor can be completed more quickly in the first temperature zone, thereby improving the reaction efficiency of pre-oxidation. On the other hand, different degrees of reaction can be achieved during the pre-oxidation process, thereby controlling the pre-oxidation degree of the finally obtained pre-oxidized fiber filaments. For example, the bulk density is 1.33 - 1.35 g / cm 3 , and the degree of cyclization is 85 - 92%. In addition, by controlling the fiber tension of the carbon fiber in the first temperature zone to be greater than the fiber tension of the carbon fiber in the second and third temperature zones; and the fiber tension of the carbon fiber in the third temperature zone to be greater than or equal to the fiber tension of the carbon fiber in the second temperature zone; it can enable the fiber to reach a better reaction state at different temperatures during the pre-oxidation process, which helps optimize the pre-oxidation process conditions, make the pre-oxidation reaction more uniform and stable, and thus improve the quality and performance of the carbon fiber.

[0022] Furthermore, by setting different processing times in different temperature zones, the reaction process of carbon fiber pre-oxidation can be optimized. The processing time in the first temperature zone is shorter, which can quickly promote the cyclization reaction of the fiber, enabling the fiber to complete the preliminary pre-oxidation reaction in a shorter time, and is conducive to shortening the processing time of the entire pre-oxidation process. The processing times in the second and third temperature zones are the same, which can keep the fiber undergoing pre-oxidation reaction for a longer time and further improve the degree of pre-oxidation. Such a setting of processing time is conducive to achieving precise control and optimization of the pre-oxidation reaction. Compared with the processing times in the second and third temperature zones, the processing time in the first temperature zone is shorter and the energy consumption required is less. This helps to save energy and reduce the energy consumption cost during the carbon fiber pre-oxidation process. At the same time, the processing times in the second and third temperature zones are the same. Because during the pre-oxidation process in the second temperature zone, the cyclization reaction of the carbon fiber has been initially promoted, maintaining the same processing time in the third temperature zone allows the carbon fiber to further undergo pre-oxidation reaction and further improve the degree of pre-oxidation. When the carbon fiber enters the second temperature zone, it has experienced the processing in the first temperature zone and initially completed the cyclization reaction. At this time, the fiber structure of the carbon fiber has changed and it has partial pre-oxidation properties. Maintaining the same processing time in the second temperature zone allows the carbon fiber to continue to be in a high-temperature environment, enabling the cyclization reaction to proceed further and the degree of pre-oxidation to continue to increase. Since the processing times in the second and third temperature zones are the same, the time experienced by the carbon fiber in these two temperature zones is continuous without interruption. Such continuous processing helps to accelerate the progress of the pre-oxidation reaction and enables the carbon fiber to reach the expected degree of pre-oxidation in a shorter time. Such a setting of processing time helps to improve production efficiency, speed up the preparation speed of carbon fiber, and increase the output.

[0023] In this application, the temperature of the first temperature zone is defined as T1, the temperature of the second temperature zone is defined as T2, and the temperature of the third temperature zone is defined as T3; then T1 is 272 - 276 °C; T2 is 250 - 260 °C; T3 is 260 - 265 °C. Among them, controlling T1 within the range of 272 - 276 °C is to carry out pre-oxidation reaction at a relatively high temperature, thereby promoting the cyclization reaction, so that the cyclization degree of the fiber can reach the required 85 - 92%. The cyclization reaction speed is relatively fast at high temperature, which can accelerate the reaction progress, thereby reducing the pre-oxidation time and energy consumption. Controlling T2 within the range of 250 - 260 °C is to carry out pre-oxidation reaction at a medium temperature, thereby further promoting the cyclization reaction and ensuring that the fiber tension is within an appropriate range. Appropriate tension helps to stabilize the fiber morphology and form the structure, and further improve the fiber performance. Controlling T3 within the range of 260 - 265 °C is to carry out pre-oxidation reaction at a relatively low temperature, thereby balancing the reaction rate and fiber performance. The relatively low temperature can make the pre-oxidation reaction proceed more gently and evenly, reduce the formation of the fiber skin-core structure, and ensure the uniformity and stability of the fiber quality.

[0024] In this application, the fiber tension of carbon fiber in the first temperature zone is defined as F1, the fiber tension of carbon fiber in the second temperature zone is defined as F2, and the fiber tension of carbon fiber in the third temperature zone is defined as F3; then F1 is 2500 - 3000 cN; F2 is 1700 - 2000 cN; F3 is 2000 - 2500 cN. Within such a range of tension control, the carbon fiber can maintain good morphological stability, preventing excessive deformation or fracture of the fiber during the pre-oxidation process. It also helps to promote the cyclization reaction of the carbon fiber, enabling the cyclization degree of the fiber to reach the required 85 - 92%. Moreover, different tension conditions can affect the internal structure formation of the carbon fiber, control the fiber spacing and lattice structure of the fiber, thereby adjusting the properties of the fiber. This helps to improve the tensile strength and anti-tensile properties of the carbon fiber, making the finally obtained carbon fiber filaments have better strength and durability when in use.

[0025] In this application, the treatment time in the first temperature zone is defined as t1, the treatment time in the second temperature zone is defined as t2, and the treatment time in the third temperature zone is defined as t3; then, t1 is 6 - 8 min; t2 is 14 - 16 min; t3 is 14 - 16 min; the total treatment time of the pre-oxidation treatment is 32 - 40 min. Within the above treatment time range, the carbon fiber can fully undergo cyclization and oxidation reactions during the pre-oxidation process, enabling the cyclization degree of the fiber to reach the required 85 - 92%. And controlling within the above time range can make the pre-oxidation reaction proceed efficiently, reducing unnecessary treatment time and energy consumption, thereby reducing production costs. It can also control the internal structure formation of the carbon fiber, adjust the fiber spacing and lattice structure of the fiber, thereby optimizing the properties of the fiber.

[0026] In this application, the process flow of preparing polyacrylonitrile-based carbon fiber by the dry-jet wet spinning process is as follows:

[0027] This application adopts the AN / IA / MA terpolymerization method to obtain a spinning solution through a one-step method. Then, after the solution stream is ejected from the spinneret, it first passes through the nitrogen layer in the dry section and then enters the coagulation bath for phase separation to form a coagulated filament. Then, it undergoes multi-stage stretching, washing, and heat setting to obtain polyacrylonitrile fiber. The obtained PAN fiber is subjected to three-temperature-zone thermal stabilization treatment, and then carbon fiber is obtained through low-temperature carbonization and high-temperature carbonization. Finally, the surface of the carbon fiber is treated to make it have good adhesion with the resin.

[0028] The features and properties of this application are further described in detail below in combination with examples.

[0029] Example 1

[0030] The 12k dry-jet wet spinning precursor yarn is passed through the No. 1, No. 2, and No. 3 pre-oxidation furnaces in sequence. The temperature of the No. 1 pre-oxidation furnace is 272 °C, with vertical air blowing, the wind speed is controlled at 2 m / s, the fiber tension is controlled at 3000 cN, and the constant-temperature heat treatment is carried out for 6 min; the temperature of the No. 2 pre-oxidation furnace is 250 °C respectively, the fiber tension is controlled at 1700 cN, and the heat treatment time is 14 min; the temperature of the No. 3 pre-oxidation furnace is 260 °C, the fiber tension is controlled at 2000 cN, and the heat treatment time is 14 min respectively.

[0031] The pre-oxidation methods of the remaining examples are basically the same as those of Example 1, except that the temperatures, tensions, and treatment times of each pre-oxidation furnace are different. Please refer to Table 1 for details.

[0032] Table 1

[0033]

[0034] Comparative Example 1

[0035] This comparative example is basically the same as Example 2, except that the temperature of the No. 2 oxidation furnace is 265 °C, that is, the temperature gradients of the No. 1, No. 2, and No. 3 pre-oxidation furnaces decrease in sequence.

[0036] Comparative Example 2

[0037] This comparative example is basically the same as Example 2, except that the temperature of the No. 1 oxidation furnace is 234 °C, that is, the temperature gradients of the No. 1, No. 2, and No. 3 pre-oxidation furnaces increase in sequence.

[0038] Comparative Example 3

[0039] This comparative example is basically the same as Example 2, except that the fiber tension of the No. 1 oxidation furnace is 1600 cN, that is, the fiber tensions of the No. 1, No. 2, and No. 3 pre-oxidation furnaces increase in sequence.

[0040] Comparative Example 4

[0041] This comparative example is basically the same as Example 2, except that the fiber tension of the No. 1 oxidation furnace is 1500 cN, that is, the fiber tensions of the No. 1, No. 2, and No. 3 pre-oxidation furnaces decrease in sequence.

[0042] Test Example

[0043] In this test example, the cyclization degree and bulk density of the pre-oxidized fibers in Examples 1-32 are detected, and the detection results are shown in Table 2.

[0044] The cyclization degree detection method is as follows: After cutting the dry fibers into pieces, KBr and the fibers are mixed and ground at a mass ratio of 200:5 to prepare a KBr tablet for infrared analysis. Among them where IC≡N is the characteristic absorption peak intensity of the cyano group, corresponding to the wave number 2240 cm-1; IC=N is the characteristic absorption peak intensity of C=N, corresponding to the wave number 1580 cm-1.

[0045] The method for detecting the bulk density is as follows: GB / T 30019-2013.

[0046] Table 2

[0047]

[0048]

[0049] It can be seen from Table 2 that by comparing Examples 2, 10-15, it can be known that when the temperature of the No. 1 pre-oxidation furnace is greater than or less than 272-276 °C, the temperature of the No. 2 pre-oxidation furnace is greater than or less than 250-260 °C, and the temperature of the No. 3 pre-oxidation furnace is greater than or less than 260-265 °C, the bulk density or degree of cyclization of the pre-oxidized fiber cannot meet the requirements of qualified pre-oxidation. The reason for this may be that the higher the temperature, the more intense the oxidation reaction and the larger the oxygen content. Both too high and too low oxygen content are not conducive to the generation of more defects during the carbonization process and are not conducive to the production of carbon fibers; an appropriate oxygen content will promote the progress of the cyclization reaction. When the oxygen content is too high, intermolecular oxidative cross-linking hinders the progress of the subsequent cyclization reaction. By comparing Example 2 and Examples 16-21, it can be known that at a suitable temperature, when the tension of the No. 1 pre-oxidation furnace is greater than or less than 2500-3000 cN, the tension of the No. 2 pre-oxidation furnace is greater than or less than 1700-2000 cN, and the tension of the No. 3 pre-oxidation furnace is greater than or less than 2000-2500 cN, the bulk density or degree of cyclization of the pre-oxidized fiber cannot meet the requirements of qualified pre-oxidation. The main reason is that appropriate tension inhibits the physical shrinkage of the fiber and is conducive to the progress of the cyclization reaction; when the tension is large, sliding occurs between molecules, which is not conducive to the progress of the cyclization reaction and oxidative cross-linking; when the tension is too small, the fiber grains recrystallize and the grains grow, hindering the diffusion of oxygen and being not conducive to the progress of the oxidation reaction. At the same time, the molecular chains are de-oriented, which is not conducive to the progress of the cyclization reaction.

[0050] By comparing Examples 1-3 and Examples 6-7, it can be known that when the temperature of the first temperature zone is 272-276 °C, the temperature of the second temperature zone is 250-260 °C, and the temperature of the third temperature zone is 260-265 °C, the requirements for qualified pre-oxidation can be met, even if the bulk density is 1.33-1.35 g / cm 3, the degree of cyclization is 85-92%. By comparing Examples 2, 8-9, it can be seen that when the tension in the first temperature zone is 2500-3000 cN, the tension in the second temperature zone is 1700-2000 cN, and the tension in the third temperature zone is 2000-2500 cN, the requirements for qualified pre-oxidation can be met. By comparing Examples 2, 4-5, it can be seen that when the treatment time in the first temperature zone is 6-8 min, the treatment time in the second temperature zone is 14-16 min, and the treatment time in the third temperature zone is 14-16 min, the pre-oxidation process can reach the predetermined qualified standard.

[0051] The embodiments described above are some, but not all, of the embodiments of the present application. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

Claims

1. A pre-oxidation method for carbon fiber, characterized in that, Including: The polyacrylonitrile-based carbon fiber precursor obtained by the dry-jet wet spinning process is pre-oxidized through three consecutive pre-oxidation temperature zones, so that the pre-oxidation degree of the finally obtained pre-oxidized fiber filament meets the following conditions: the bulk density is 1.33-1.35 g / cm 3 , and the cyclization degree is 85-92%; The pre-oxidation temperature zone is divided into a first temperature zone, a second temperature zone and a third temperature zone; wherein, the temperature of the first temperature zone is higher than the temperatures of the second temperature zone and the third temperature zone, and the temperature of the third temperature zone is greater than or equal to the temperature of the second temperature zone; the fiber tension of the carbon fiber in the first temperature zone is greater than the fiber tensions of the carbon fiber in the second temperature zone and the third temperature zone, and the fiber tension of the carbon fiber in the third temperature zone is greater than or equal to the fiber tension of the carbon fiber in the second temperature zone; wherein, the temperature of the first temperature zone is 272 - 276 °C, the temperature of the second temperature zone is 250 - 260 °C, and the temperature of the third temperature zone is 260 - 265 °C; the fiber tension of the carbon fiber in the first temperature zone is 2500 - 3000 cN, the fiber tension of the carbon fiber in the second temperature zone is 1700 - 2000 cN, and the fiber tension of the carbon fiber in the third temperature zone is 2000 - 2500 cN; the treatment time of the first temperature zone is 6 - 8 min, the treatment time of the second temperature zone is 14 - 16 min, and the treatment time of the third temperature zone is 14 - 16 min.

2. The pre-oxidation method according to claim 1, characterized in that The total time of the pre-oxidation treatment is 32 - 40 min.

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