Hollow coal pitch carbon fiber and preparation method thereof

Abstract

The invention belongs to the technical field of coal pitch carbon fibers, and discloses a hollow coal pitch carbon fiber and a preparation method thereof. Comprising the steps of coal-based pitch preparation, melt spinning, pre-oxidation, carbonization and graphitization. According to a specific spinning process, the coal-based pitch carbon fiber with high strength and a hollow structure can be prepared. The hollow coal-based pitch carbon fiber prepared by the method not only keeps higher mechanical properties, but also has high thermal conductivity, the cost is effectively saved, meanwhile, the comprehensive performance is remarkable, finally, the yield of the coal-based pitch carbon fiber can be improved, and the coal-based pitch carbon fiber has wide application prospects.

Description

Technical Field

[0001] This invention belongs to the field of coal tar pitch carbon fiber technology, and relates to a hollow coal tar pitch carbon fiber and its preparation method. Background Technology

[0002] Melt spinning is a common method for preparing coal-based pitch carbon fibers. By optimizing spinning equipment and process parameters, such as spinning temperature, pressure, spinneret orifice diameter, and take-up roller speed, continuous and uniform pitch fibers can be produced. The pre-oxidation process is used to give the pitch fibers thermal stability and prevent them from melting and deforming during carbonization. Air oxidation is often used, and stable pre-oxidation of the pitch fibers is achieved by precisely controlling parameters such as heating rate, oxidation temperature, and time. The carbonization stage involves heating the pre-oxidized fibers to a high temperature under an inert atmosphere, causing reactions such as carbon cyclization and dehydrogenation to form carbon fibers. To improve carbonization efficiency and carbon fiber quality, graphitization treatment can be used to increase the crystallinity and graphitization degree of the carbon fibers, thereby improving their electrical conductivity and mechanical properties.

[0003] However, coal-based pitch has a wide range of sources, and the composition and properties of coal-based pitch obtained from different origins and production processes vary greatly. This leads to significant fluctuations in the performance of the produced carbon fibers, making it difficult to achieve stable quality control. During melt spinning, the high viscosity of coal-based pitch results in high spinning pressure, placing high demands on spinning equipment and increasing equipment investment and maintenance costs. Furthermore, melt fracture is prone to occur during spinning, affecting fiber uniformity and continuity. During pre-oxidation, oxygen diffuses slowly within the pitch fibers, requiring a long pre-oxidation time to ensure sufficient internal oxidation. This not only reduces production efficiency but also increases energy consumption. In addition, uneven oxidation levels inside and outside the fibers during pre-oxidation can easily lead to defects in the fibers during subsequent carbonization, affecting carbon fiber performance. During carbonization, coal-based pitch fibers undergo volume shrinkage and structural changes, easily generating defects such as internal stress and microcracks. These defects reduce the mechanical properties of the carbon fibers, especially tensile strength and toughness. Simultaneously, impurities in the pitch decompose or volatilize during carbonization, forming pores and other defects, further affecting carbon fiber quality. Graphitization requires a high-temperature, high-pressure environment, resulting in enormous energy consumption.

[0004] Furthermore, existing methods for preparing coal-based pitch carbon fiber cannot simultaneously achieve high mechanical properties and high thermal conductivity while reducing costs, thus failing to meet market demands. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a hollow coal-based pitch carbon fiber and its preparation method. By subjecting coal-based pitch with different softening points to a series of processes including melt spinning, pre-oxidation, carbonization, and graphitization, production costs are reduced while ensuring mechanical strength and thermodynamic properties. The resulting coal-based pitch carbon fiber possesses both high mechanical properties and high thermal conductivity.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution:

[0007] A method for preparing hollow coal-based pitch fiber includes preparing coal-based pitch, melt spinning, pre-oxidation, carbonization, and graphitization.

[0008] The specific steps are as follows:

[0009] S1. Preparation of coal-based pitch: using coal pitch as raw material, coal-based pitch is prepared by aeration at 360-380℃.

[0010] S2. Melt spinning: The coal-based pitch prepared in step S1 is melt spun under the following conditions: temperature 305℃-330℃ and gas pressure 40kPa-120kPa, to obtain monofilament fibers.

[0011] S3. Pre-oxidation treatment: The monofilament fibers prepared in step S2 are pre-oxidized to obtain pre-oxidized monofilament fibers. The pre-oxidation reaction temperature is 340℃-360℃, the air flow rate is 2L / min-3L / min, and the heating rate of the pre-oxidation process is 1-5℃ / min.

[0012] S4. Carbonization treatment: Carbonize the monofilament fibers after the pre-oxidation treatment in step S3 to obtain carbonized monofilament fibers. The carbonization temperature is 1000-1200℃.

[0013] S5. Graphitization treatment: The monofilament fibers carbonized in step S4 are graphitized at a temperature of 2000-2200℃.

[0014] Furthermore, the softening point of the coal-based pitch prepared in step S1 is 280±5℃.

[0015] Furthermore, in step S1, the reaction conditions for the aeration method are: temperature 360℃-380℃, aeration rate 2L / min-3L / min, and time 45min-60min.

[0016] Furthermore, in step S2, the diameter of the obtained monofilament fiber is 27μm-87μm. Preferably, the diameter of the monofilament fiber is 50μm-60μm.

[0017] Furthermore, in step S3, the pre-oxidation temperature is 350℃, and the heating rate of the pre-oxidation process is 3℃ / min.

[0018] Furthermore, in step S4, the carbonization temperature is 1000℃.

[0019] Furthermore, in step S5, the graphitization temperature is 2000℃.

[0020] The advantages of this invention compared to the prior art are:

[0021] This invention provides a method for preparing hollow coal-based pitch carbon fibers. The prepared hollow coal-based pitch carbon fibers maintain high mechanical properties and high thermal conductivity, effectively saving costs while significantly improving overall performance. Ultimately, this method can improve the yield of coal-based pitch carbon fibers and has broad application prospects. Attached Figure Description

[0022] Figure 1 The images are photographs of the wire diameter obtained under a microscope. a is Example 1, b is Example 2, c is Example 3, and d is Example 4.

[0023] Figure 2 The images are photographs of the wire diameter observed under a microscope. a is Example 2, b is Comparative Example 1, c is Comparative Example 2, and d is Comparative Example 3.

[0024] Figure 3 This is a scanning electron microscope (SEM) schematic diagram of the prepared coal-based pitch. a represents magnification x 2000, and b represents magnification x 5000. Detailed Implementation

[0025] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0026] To make the objectives, technical solutions, and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the hollow coal-based pitch carbon fiber prepared by the present invention will now be clearly and completely described.

[0027] The coal tar pitch prepared by this invention introduces oxygen into the pitch through chemical modification by using a thermal polymerization-air oxidation treatment method. During air oxidation, the coal tar pitch undergoes dehydrogenation condensation, aromatization, cross-linking and other reactions to generate larger molecules, finally yielding oxidized cross-linked coal tar pitch. In the prepared oxidized cross-linked coal tar pitch, oxygen exists in the form of COC chemical bonds. Due to the cross-linking effect of oxygen, the molecular sheets of coal tar pitch form a three-dimensional spatial connection structure, improving the amorphous structure of the coating layer.

[0028] Example 1

[0029] A method for preparing coal-based pitch carbon fiber includes the following steps:

[0030] Coal tar pitch was loaded into a reactor and air was introduced at a flow rate of 3 L / min to oxidize and crosslink it at 380 °C to increase its softening point. The aeration time was 1 h. Coal tar pitch was obtained.

[0031] After grinding and drying, 30g of the coal-based pitch obtained through oxidative crosslinking was weighed out and spun. The spinning barrel was heated to 300℃, higher than the softening point of the coal-based pitch, to ensure complete melting of the pitch. Then, under the protection of high-purity nitrogen, monofilament fiber A was prepared through melt spinning. The diameter of monofilament fiber A was controlled by adjusting the material temperature, gas pressure, and take-up roller speed. The material temperature was maintained at 305℃-320℃, the gas pressure at 80kPa-120kPa, and the take-up roller speed at 500rpm.

[0032] Monofilament fiber A obtained from melt spinning was pre-oxidized using a quartz tube furnace. The air flow rate was 2-3 L / min, the pre-oxidation temperature was 350℃, and the reaction time was 6 h. Monofilament fiber B was obtained.

[0033] The pre-oxidized monofilament fiber B was carbonized under nitrogen protection at a gas flow rate of 2-3 L / min, a carbonization temperature of 1000℃, and a heating rate of 3℃ / min. The reaction time was 26 h. Monofilament fiber C was obtained.

[0034] The carbonized monofilament fiber C was graphitized under nitrogen protection at a temperature of 2000℃ for 20 hours to obtain coal-based pitch carbon fiber. Its physical properties were tested, and the results are shown in Table 1.

[0035] Example 2

[0036] A method for preparing coal-based pitch carbon fiber includes the following steps:

[0037] Coal tar pitch was loaded into a reactor and air was introduced at a flow rate of 3 L / min to oxidize and crosslink it at 380℃ to increase its softening point. The aeration time was 2 h. Coal tar pitch was obtained.

[0038] After grinding and drying, 30g of the coal-based pitch obtained through oxidative crosslinking was weighed out and spun. The spinning barrel was heated to 300℃, higher than the softening point of the coal-based pitch, to ensure complete melting of the pitch. Then, under the protection of high-purity nitrogen, monofilament fiber A was prepared through melt spinning. The diameter of monofilament fiber A was controlled by adjusting the material temperature, gas pressure, and take-up roller speed. The material temperature was maintained at 305℃-320℃, the gas pressure at 80kPa-120kPa, and the take-up roller speed at 500rpm.

[0039] Monofilament fiber A obtained from melt spinning was pre-oxidized using a quartz tube furnace. The air flow rate was 2-3 L / min, the pre-oxidation temperature was 350℃, and the reaction time was 6 h. Monofilament fiber B was obtained.

[0040] The pre-oxidized monofilament fiber B was carbonized under nitrogen protection at a gas flow rate of 2-3 L / min, a carbonization temperature of 1000℃, and a heating rate of 3℃ / min. The reaction time was 26 h. Monofilament fiber C was obtained.

[0041] The carbonized monofilament fiber C was graphitized under nitrogen protection at a temperature of 2000℃ for 20 hours to obtain coal-based pitch carbon fiber. Its physical properties were tested, and the results are shown in Table 1.

[0042] Example 3

[0043] A method for preparing coal-based pitch carbon fiber includes the following steps:

[0044] Coal tar pitch was loaded into a reactor and air was introduced at a flow rate of 3 L / min to oxidize and crosslink it at 380 °C to increase its softening point. The aeration time was 3 h. Coal tar pitch was obtained.

[0045] After grinding and drying, 30g of the coal-based pitch obtained through oxidative crosslinking was weighed out and spun. The spinning barrel was heated to 300℃, higher than the softening point of the coal-based pitch, to ensure complete melting of the pitch. Then, under the protection of high-purity nitrogen, monofilament fiber A was prepared through melt spinning. The diameter of monofilament fiber A was controlled by adjusting the material temperature, gas pressure, and take-up roller speed. The material temperature was maintained at 305℃-320℃, the gas pressure at 80kPa-120kPa, and the take-up roller speed at 500rpm.

[0046] Monofilament fiber A obtained from melt spinning was pre-oxidized using a quartz tube furnace. The air flow rate was 2-3 L / min, the pre-oxidation temperature was 350℃, and the reaction time was 6 h. Monofilament fiber B was obtained.

[0047] The pre-oxidized monofilament fiber B was carbonized under nitrogen protection at a gas flow rate of 2-3 L / min, a carbonization temperature of 1000℃, and a heating rate of 3℃ / min. The reaction time was 26 h. Monofilament fiber C was obtained.

[0048] The carbonized monofilament fiber C was graphitized under nitrogen protection at a temperature of 2000℃ for 20 hours to obtain coal-based pitch carbon fiber. Its physical properties were tested, and the results are shown in Table 1.

[0049] Example 4

[0050] A method for preparing coal-based pitch carbon fiber includes the following steps:

[0051] Coal tar pitch was loaded into a reactor and air was introduced at a flow rate of 3 L / min to oxidize and crosslink it at 380℃ to increase its softening point. The aeration time was 4 h. Coal tar pitch was obtained.

[0052] After grinding and drying, 30g of the coal-based pitch obtained through oxidative crosslinking was weighed out and spun. The spinning barrel was heated to 300℃, higher than the softening point of the coal-based pitch, to ensure complete melting of the pitch. Then, under the protection of high-purity nitrogen, monofilament fiber A was prepared through melt spinning. The diameter of monofilament fiber A was controlled by adjusting the material temperature, gas pressure, and take-up roller speed. The material temperature was maintained at 305℃-320℃, the gas pressure at 80kPa-120kPa, and the take-up roller speed at 500rpm.

[0053] Monofilament fiber A obtained from melt spinning was pre-oxidized using a quartz tube furnace. The air flow rate was 2-3 L / min, the pre-oxidation temperature was 350℃, and the reaction time was 6 h. Monofilament fiber B was obtained.

[0054] The pre-oxidized monofilament fiber B was carbonized under nitrogen protection at a gas flow rate of 2-3 L / min, a carbonization temperature of 1000℃, and a heating rate of 3℃ / min. The reaction time was 26 h. Monofilament fiber C was obtained.

[0055] The carbonized monofilament fiber C was graphitized under nitrogen protection at a temperature of 2000℃ for 20 hours to obtain coal-based pitch carbon fiber. Its physical properties were tested, and the results are shown in Table 1.

[0056] Example 5

[0057] A method for preparing coal-based pitch carbon fiber includes the following steps:

[0058] Coal tar pitch was loaded into a reactor and air was introduced at a flow rate of 3 L / min to oxidize and crosslink it at 380℃ to increase its softening point. The aeration time was 4 h. Coal tar pitch was obtained.

[0059] After grinding and drying, 30g of the coal-based pitch obtained through oxidative crosslinking was weighed out and spun. The spinning barrel was heated to 300℃, higher than the softening point of the coal-based pitch, to ensure complete melting of the pitch. Then, under the protection of high-purity nitrogen, monofilament fiber A was prepared through melt spinning. The diameter of monofilament fiber A was controlled by adjusting the material temperature, gas pressure, and take-up roller speed. The material temperature was maintained at 305℃-320℃, the gas pressure at 80kPa-120kPa, and the take-up roller speed at 500rpm.

[0060] Monofilament fiber A obtained from melt spinning was pre-oxidized using a quartz tube furnace. The air flow rate was 2-3 L / min, the pre-oxidation temperature was 350℃, and the reaction time was 6 h. Monofilament fiber B was obtained.

[0061] The pre-oxidized monofilament fiber B was carbonized under nitrogen protection at a gas flow rate of 2-3 L / min, a carbonization temperature of 1000℃, and a heating rate of 1℃ / min. The reaction time was 26 h. Monofilament fiber C was obtained.

[0062] The carbonized monofilament fiber C was graphitized under nitrogen protection at a temperature of 2000℃ for 20 hours to obtain coal-based pitch carbon fiber. Its physical properties were tested, and the results are shown in Table 1.

[0063] Example 6

[0064] A method for preparing coal-based pitch carbon fiber includes the following steps:

[0065] Coal tar pitch was loaded into a reactor and air was introduced at a flow rate of 3 L / min to oxidize and crosslink it at 380℃ to increase its softening point. The aeration time was 4 h. Coal tar pitch was obtained.

[0066] After grinding and drying, 30g of the coal-based pitch obtained through oxidative crosslinking was weighed out and spun. The spinning barrel was heated to 300℃, higher than the softening point of the coal-based pitch, to ensure complete melting of the pitch. Then, under the protection of high-purity nitrogen, monofilament fiber A was prepared through melt spinning. The diameter of monofilament fiber A was controlled by adjusting the material temperature, gas pressure, and take-up roller speed. The material temperature was maintained at 305℃-320℃, the gas pressure at 80kPa-120kPa, and the take-up roller speed at 500rpm.

[0067] Monofilament fiber A obtained from melt spinning was pre-oxidized using a quartz tube furnace. The air flow rate was 2-3 L / min, the pre-oxidation temperature was 350℃, and the reaction time was 6 h. Monofilament fiber B was obtained.

[0068] The pre-oxidized monofilament fiber B was carbonized under nitrogen protection at a gas flow rate of 2-3 L / min, a carbonization temperature of 1000℃, and a heating rate of 5℃ / min. The reaction time was 26 h. Monofilament fiber C was obtained.

[0069] The carbonized monofilament fiber C was graphitized under nitrogen protection at a temperature of 2000℃ for 20 hours to obtain coal-based pitch carbon fiber. Its physical properties were tested, and the results are shown in Table 1.

[0070] Comparative Example 1

[0071] In this comparative example, during melt spinning, the material temperature was 320℃-335℃, the gas pressure was 80kPa-120kPa, and the take-up roller speed was 500rpm. The pre-oxidized monofilament fiber B was carbonized under nitrogen protection at an air flow rate of 2-3L / min, a carbonization temperature of 1000℃, a heating rate of 5℃ / min, and a reaction time of 26h. Other procedures were the same as in Example 4.

[0072] Coal-based pitch carbon fiber was obtained. Its physical properties were tested, and the results are shown in Table 1.

[0073] Comparative Example 2

[0074] In this comparative example, the material temperature during melt spinning was 305℃-320℃, the gas pressure was 40kPa-80kPa, and the take-up roller speed was 500rpm. The pre-oxidized monofilament fiber B was carbonized under nitrogen protection at a gas flow rate of 2-3L / min, a carbonization temperature of 1000℃, a heating rate of 5℃ / min, and a reaction time of 26h. Other procedures were the same as in Example 4. Coal-based pitch carbon fiber was obtained. Its physical properties were tested, and the results are shown in Table 1.

[0075] Comparative Example 3

[0076] In this comparative example, during melt spinning, the material temperature was 305℃-320℃, the gas pressure was 80kPa-120kPa, and the take-up roller speed was 800rpm. The pre-oxidized monofilament fiber B was carbonized under nitrogen protection at an air flow rate of 2-3L / min, a carbonization temperature of 1000℃, a heating rate of 5℃ / min, and a reaction time of 26h. Coal-based pitch carbon fiber was obtained. Its physical properties were tested, and the results are shown in Table 1. Figure 1 , Figure 2 .

[0077] Table 1. Physical properties of coal-based pitch carbon fibers prepared in Examples 1-4 and Comparative Examples 1-3

[0078]

[0079] A comparison of the examples and comparative examples shows that coal-based pitch carbon fibers with high strength and a hollow structure can be obtained by following specific spinning processes and defined preparation methods. The hollow structure is crucial for thermal insulation performance because it reduces solid conduction paths, restricts gas convection, and increases the length of heat conduction paths. Data in the table shows that the fiber diameters in the examples are more stable and uniform, while changes in spinning conditions result in larger deviations in fiber diameter, rendering them unsuitable for normal application. Furthermore, the heating rate during the pre-oxidation process significantly impacts the fiber diameter structure. A lower heating rate, as in Example 5, can lead to excessive volatilization of some low-molecular-weight components in the fiber, resulting in a loose internal structure and affecting its overall performance. A faster heating rate, as in Example 6, can cause significant thermal and structural stresses within the fiber. These stresses can cause microcracks and defects within the fiber, affecting its density and continuity. The results show that a hollow structure appears when the pre-oxidation heating rate is 3°C / min. Figure 3 .

[0080] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing hollow coal-based pitch fibers, characterized in that, The specific steps are as follows: S1. Preparation of coal-based pitch: using coal pitch as raw material, coal-based pitch is prepared by aeration at 360-380℃. S2. Melt spinning: The coal-based pitch prepared in step S1 is melt spun under the following conditions: temperature 305℃-330℃ and gas pressure 40kPa-120kPa, to obtain monofilament fibers. S3. Pre-oxidation treatment: The monofilament fibers prepared in step S2 are pre-oxidized to obtain pre-oxidized monofilament fibers. The pre-oxidation reaction temperature is 340℃-360℃, the air flow rate is 2L / min-3L / min, and the heating rate of the pre-oxidation process is 1-5℃ / min. S4. Carbonization treatment: Carbonize the monofilament fibers after the pre-oxidation treatment in step S3 to obtain carbonized monofilament fibers. The carbonization temperature is 1000-1200℃. S5. Graphitization treatment: The monofilament fibers carbonized in step S4 are graphitized at a temperature of 2000-2200℃.

2. The method for preparing hollow coal-based pitch fiber as described in claim 1, characterized in that, The softening point of the coal-based pitch prepared in step S1 is 280±5℃.

3. The method for preparing hollow coal-based pitch fiber as described in claim 1, characterized in that, In step S1, the reaction conditions for the ventilation method are: temperature 360℃-380℃, ventilation rate 2L / min-3L / min, and time 45min-60min.

4. The method for preparing hollow coal-based pitch fiber as described in claim 1, characterized in that, In step S2, the diameter of the obtained monofilament fibers is 27μm-87μm.

5. The method for preparing hollow coal-based pitch fiber as described in claim 1, characterized in that, In step S2 and step S3, the pre-oxidation temperature is 350℃ and the heating rate of the pre-oxidation process is 3℃ / min.

6. The method for preparing hollow coal-based pitch fiber as described in claim 1, characterized in that, In step S4, the carbonization temperature is 1000℃.

7. The method for preparing hollow coal-based pitch fiber as described in claim 1, characterized in that, In step S5, the graphitization temperature is 2000℃.

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