X-shaped high-thermal-conductivity pitch-based carbon fiber as well as preparation method and production equipment thereof

Abstract

The invention belongs to the technical field of preparation of high-performance pitch-based carbon fibers, and discloses an X-shaped high-thermal-conductivity pitch-based carbon fiber as well as a preparation method and production equipment thereof. The production equipment comprises a spinneret plate and a high-temperature channel, the spinneret plate is formed by connecting an inlet section which converges step by step with a vertical yarn outlet section; the high-temperature channel consists of a channel and a temperature control system; and the channel is positioned at an outlet of the spinneret plate. The X-shaped high-thermal-conductivity pitch-based carbon fiber prepared by the preparation method disclosed by the invention is used as a three-dimensional reinforcement, can provide a rich pore structure, reduces the generation of closed pores, is beneficial to full filling of a matrix material, can form an efficient heat conduction path in a composite material, and improves the energy transmission efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of high-performance pitch-based carbon fibers, and particularly relates to an X-shaped high-thermal-conductivity pitch-based carbon fiber, a preparation method thereof, and a production device therefor. Background Art

[0002] Carbon fiber is a new type of fiber material with a carbon content exceeding 95%. It has the characteristics of low density, corrosion resistance, high chemical stability, high temperature resistance, excellent thermal conductivity and mechanical properties. It also has the spinnability of fibers such as cotton and polyester, and has good application prospects in the fields of aerospace, military, and high-end civil materials. So far, the relatively maturely developed carbon fibers can be divided into three types: polyacrylonitrile (PAN)-based carbon fibers, pitch-based carbon fibers, and viscose-based carbon fibers. Different types of carbon fibers have different structures and properties. For PAN-based carbon fibers, their advantage lies in having a relatively high tensile strength. For example, the tensile strength of the commercial PAN-based carbon fiber with the grade of T1000G can reach 6.37 GPa, but its tensile modulus is only 294 GPa, and the thermal conductivity is only 150 W / (m·K). The raw materials used for viscose-based carbon fibers are mostly natural cellulose substances, which have a wide range of renewable raw material sources and excellent high-temperature resistance. However, its preparation process is complex, and the carbonization yield is relatively low. In addition, it lacks competitiveness in some scenarios with strict mechanical property requirements. In recent years, pitch-based carbon fibers have attracted the attention of many researchers due to their unique performance advantages. Pitch-based carbon fibers are liquid crystal-like material raw materials polymerized from coal tar pitch, petroleum pitch, or aromatic hydrocarbon compounds. After processes such as pitch modulation, melt spinning, pre-oxidation, and heat treatment, they are prepared. Compared with PAN-based carbon fibers, they have more significant advantages in terms of tensile modulus and thermal conductivity. For example, the carbon fiber with the grade of K1100 from Cytec Company in the United States has a tensile strength of 3.1 GPa, a tensile modulus of 931 GPa, and a thermal conductivity as high as 1100 W / (m·K). Therefore, pitch-based carbon fibers are often used as the reinforcement of composite materials, which can potentially improve the thermal conductivity of the composite materials in the device to ensure effective heat diffusion conduction to avoid degradation caused by severe local overheating of the device, and have broad application prospects in the field of device thermal management.

[0003] Continuously improving the comprehensive properties of pitch-based carbon fibers is of great significance for broadening the application scenarios of pitch-based carbon fibers. The preparation process of pitch-based carbon fibers includes the modulation and purification of pitch, melt spinning, pre-oxidation, carbonization, and graphitization. There are numerous influencing factors in each step. The composition and purity of pitch determine its drawability. The structure of the spinneret, spinning temperature, winding speed, etc. during the melt spinning process determine the arrangement state of liquid crystal molecules inside the fiber. The temperature and time during the heat treatment process determine the size of graphite microcrystals. These influencing factors jointly determine the structure and properties of the final carbon fiber. How to regulate relevant parameters to prepare pitch-based carbon fibers with high thermal conductivity has been studied by many researchers.

[0004] The main research directions focus on asphalt type, spinning temperature, winding speed, filter type, and heat treatment temperature during the melt spinning process. Some scholars have taken a different approach. By regulating the structure of the spinneret holes inside the spinneret, they control the shear effect of pitch in the spinneret holes, change the fiber cross-sectional shape, and prepare profiled fibers, thereby achieving the purpose of changing the fiber structure and properties. It is reported that compared with circular fibers, profiled pitch-based fibers have better mechanical and thermal properties. For example, Yuan Guanming et al. found that the thermal conductivity of ribbon fibers graphitized at 2400°C is equivalent to that of circular fibers graphitized at 300°C. The graphite microcrystals inside the ribbon fibers develop better, the degree of graphitization is higher, and to reach the same pre-oxidation degree, the time required for ribbon fibers is shorter than that of circular fibers, which can significantly reduce the fiber production cost. D.D. Edie et al. found that non-circular pitch-based carbon fibers such as trilobal and octagonal fibers have better strength and modulus than circular fibers, and their unique cross-sectional shape is conducive to optimizing the pore structure of the carbon fiber network reinforcement. Profiled fibers also have a more complex surface structure and a larger specific surface area, which can enhance the bonding with the matrix material and further improve the thermal conductivity and mechanical strength of the composite material. For example, Yuan Guanming et al. prepared C / C composites using ribbon fibers. After graphitization at 3100°C, it was found that the thermal conductivity of the ribbon fiber-reinforced C / C composite is 10 times that of copper and 2.5 times that of ordinary circular fibers. In addition, it is found that the range of 3 - 4 mm from the spinneret hole outlet is the drawable area of pitch. In this area, pitch rapidly forms a stable molecular orientation. By extending the length of the drawable area, the draw orientation effect can be strengthened and the fiber thermal conductivity can be improved. Therefore, by combining the regulation of the spinneret structure and the extension of the pitch drawable area, profiled fibers with high thermal conductivity and large specific surface area can be developed. The special structure of profiled carbon fibers gives them a more complex surface state and thermal conductivity superior to that of conventional circular fibers. When used as a reinforcement, profiled fibers can better bond with the matrix material and serve as a high-speed heat transfer channel, comprehensively improving the performance of the composite material. This is of great significance for the wide application of pitch-based carbon fibers in fields such as aerospace, nuclear fusion devices, and 3C electronics.

[0005] Therefore, it is of great significance to study a preparation method and production equipment of X-shaped pitch-based carbon fiber with high thermal conductivity and large specific surface area. Summary of the Invention

[0006] In view of this, the present invention provides an X-shaped high thermal conductivity pitch-based carbon fiber, its preparation method and production equipment, aiming to meet the current needs of the composite material field for high thermal conductivity profiled carbon fiber reinforcements, which can realize the construction of a micron-level pore structure network body, reduce the closed pore rate of the composite material, and form a good three-dimensional heat conduction path inside the composite material.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a production equipment for X-shaped high thermal conductivity pitch-based carbon fiber, and the production equipment includes a spinneret plate and a high-temperature channel;

[0009] The spinneret plate is composed of an inlet section with gradually converging levels connected to a vertical wire outlet section;

[0010] The high-temperature channel is composed of a channel and a temperature control system;

[0011] The channel is located at the outlet of the spinneret plate.

[0012] Preferably, the inlet section with gradually converging levels is composed of conical surfaces with different angles whose angles gradually decrease;

[0013] The number of the conical surfaces with different angles ≥ 4;

[0014] The inner wall of the conical surface of the inlet section with gradually converging levels is provided with a flow channel;

[0015] The width of the flow channel ≤ 0.06 mm, and the depth of the flow channel ≤ 0.07 mm.

[0016] Preferably, the horizontal section of the outlet of the vertical wire outlet section is a rectangle with circular arcs at both ends or a slit with circular arcs at both ends;

[0017] The aspect ratio of the length to the width of the horizontal section is 5 - 20:1.

[0018] Preferably, the length of the channel is 20 - 30 cm;

[0019] The temperature of the temperature control system is 300 - 350 °C.

[0020] The present invention also provides a preparation method for X-shaped high thermal conductivity pitch-based carbon fiber, including the following steps:

[0021] 1) Melting and spinning the mesophase pitch to obtain ribbon-shaped pitch fiber;

[0022] 2) Successively subject the strip-shaped pitch fiber to pre-oxidation, carbonization, and graphitization to obtain X-shaped high thermal conductivity pitch-based carbon fiber;

[0023] The melt spinning is carried out in the above production equipment.

[0024] Preferably, in step 1), the mesophase pitch is oil-based mesophase pitch, coal-based mesophase pitch, or naphthalene-based mesophase pitch, the mesophase content of the mesophase pitch is 100%, and the ash content of the mesophase pitch < 20 ppm;

[0025] The process of the melt spinning is nitrogen pressure type;

[0026] The nitrogen pressure of the melt spinning is 0.4 - 1.6 MPa, the temperature of the spinneret is 314 - 328 °C, and the winding speed is 200 - 1500 rpm.

[0027] Preferably, in step 2), the pre-oxidation is carried out in air or oxygen, and the feeding rate of the air or oxygen is 0.8 - 1.5 L / min;

[0028] The temperature of the pre-oxidation is 150 - 300 °C, and the time of the pre-oxidation is 200 - 400 min.

[0029] Preferably, in step 2), the carbonization is carried out in a protective atmosphere, and the feeding rate of the protective atmosphere is 0.3 - 1 L / min;

[0030] The temperature of the carbonization is 400 - 1300 °C, and the time of the carbonization is 60 - 300 min.

[0031] Preferably, in step 2), the graphitization is carried out in a protective atmosphere, and the feeding rate of the protective atmosphere is 4 - 8 L / min;

[0032] The temperature of the graphitization is ≥2400 °C, and the time of the graphitization is 10 - 60 min.

[0033] The present invention also provides an X-shaped high thermal conductivity pitch-based carbon fiber prepared by the preparation method of the X-shaped high thermal conductivity pitch-based carbon fiber.

[0034] According to the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention provides a special structure spinneret, introducing a gradually converging special slope structure and an extremely small flow channel, synergistically enhancing the shear action of asphalt molecules in the spinneret holes, which is beneficial to obtaining profiled fibers with better orientation and stronger performance.

[0036] The present invention designs a temperature - controllable high - temperature channel at the exit of the spinneret holes. Through appropriate temperature regulation, the stretchable region of asphalt is extended, the stretching and orientation effect of asphalt is strengthened, and the orientation degree of the fiber is further improved.

[0037] The ribbon - shaped carbon fiber prepared by the present invention gradually splits to form an "X" - shaped cross - section structure during heat treatment processes such as pre - oxidation, carbonization, and graphitization. Compared with general circular fibers, the structure is more irregular, and the occurrence of large - area fiber adhesion can be reduced during the stacking process.

[0038] The X - shaped high - thermal - conductivity pitch - based carbon fiber prepared by the present invention, as a three - dimensional reinforcement, can provide a rich pore structure, reduce the generation of closed pores, and is conducive to the full filling of the matrix material. In addition, while having a unique special - shaped cross - section structure, the "X" - shaped pitch - based carbon fiber maintains a high thermal conductivity of 700 - 1200 W / (m·K), can form an efficient heat conduction path in the composite material, and improve the energy transmission efficiency. Brief Description of the Drawings

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0040] Figure 1 Schematic diagram of the spinneret plate described in the present invention;

[0041] Figure 2 Schematic diagram of the flow channel on the inner wall of the conical surface of the gradually converging inlet section of the spinneret plate described in the present invention;

[0042] Figure 3 Schematic diagram of the production equipment described in the present invention;

[0043] Figure 4 Microscopic morphology diagram of the horizontal cross - section of the X - shaped high - thermal - conductivity pitch - based carbon fiber obtained in Example 1;

[0044] Figure 5 Microscopic morphology diagram of the horizontal cross - section of the X - shaped high - thermal - conductivity pitch - based carbon fiber obtained in Example 2;

[0045] Figure 6 Microscopic morphology diagram of the horizontal cross - section of the X - shaped high - thermal - conductivity pitch - based carbon fiber obtained in Example 3. Detailed Embodiments

[0046] The present invention provides a production equipment for X - shaped high - thermal - conductivity pitch - based carbon fiber. The production equipment includes a spinneret plate and a high - temperature channel;

[0047] The spinneret consists of an inlet section with gradually converging steps connected to a vertical filament outlet section;

[0048] The high-temperature duct is composed of a duct and a temperature control system;

[0049] The duct is located at the outlet of the spinneret.

[0050] In the present invention, a high-temperature duct with precisely controllable temperature is designed to fit the outlet of the vertical filament outlet section of the spinneret, which is used to extend the asphalt stretching zone, thereby improving the stretching-induced orientation of asphalt molecules;

[0051] The diameter of the duct is preferably larger than the diameter of the spinneret and fits the filament outlet surface of the spinneret.

[0052] In the present invention, the inlet section with gradually converging steps is composed of conical surfaces with gradually decreasing angles;

[0053] The number of conical surfaces with different angles is preferably ≥4, more preferably ≥5, and even more preferably ≥6; the end of the last conical surface is connected to the vertical filament outlet section, thereby forming a special ramp structure with convergent inner hole angles;

[0054] Flow channels are laid on the inner wall of the conical surface of the inlet section with gradually converging steps;

[0055] The width of the flow channel is preferably ≤0.06 mm, more preferably ≤0.05 mm, and even more preferably ≤0.03 mm; the depth of the flow channel is preferably ≤0.07 mm, more preferably ≤0.06 mm, and even more preferably ≤0.05 mm;

[0056] The existence of the flow channel can increase the shear force exerted on the asphalt in the small flow channels on the inner wall of the conical surface of the inlet section with gradually converging steps, thereby strengthening the liquid crystal orientation arrangement.

[0057] In the present invention, the horizontal cross-section of the outlet of the vertical filament outlet section is a rectangle with rounded ends or a slit with rounded ends;

[0058] The width of the horizontal cross-section is preferably 0.1 - 0.2 mm, more preferably 0.12 - 0.18 mm, and even more preferably 0.15 - 0.17 mm; the aspect ratio of the length to the width of the horizontal cross-section is preferably 5 - 20:1, more preferably 8 - 16:1, and even more preferably 10 - 12:1.

[0059] In the present invention, when asphalt enters the inlet section with gradually converging steps of the spinneret, due to the continuously decreasing conical surface angle of the inlet section, the flow velocity of the asphalt continuously increases, thereby accelerating the shear of the asphalt liquid crystal molecules against the inner wall of the inlet section of the spinneret and guiding the asphalt liquid crystal molecules to align along the direction of the inlet section wall; when the asphalt enters the vertical filament outlet section of the spinneret, the flow shear is further strengthened, and a higher liquid crystal orientation arrangement is obtained.

[0060] In the present invention, the length of the passageway is preferably 20 - 30 cm, more preferably 22 - 28 cm, and still more preferably 24 - 26 cm;

[0061] The temperature of the temperature control system is preferably 300 - 350 °C, more preferably 310 - 340 °C, and still more preferably 320 - 330 °C.

[0062] The present invention also provides a method for preparing X-shaped highly thermally conductive pitch-based carbon fibers, comprising the following steps:

[0063] 1) Melting and spinning mesophase pitch to obtain ribbon-shaped pitch fibers;

[0064] 2) Sequentially subjecting the ribbon-shaped pitch fibers to pre-oxidation, carbonization, and graphitization to obtain X-shaped highly thermally conductive pitch-based carbon fibers;

[0065] The above melting and spinning is carried out in the above production equipment.

[0066] In the present invention, in step 1), the mesophase pitch is preferably oil-based mesophase pitch, coal-based mesophase pitch, or naphthalene-based mesophase pitch. The mesophase content of the mesophase pitch is preferably 100%, and the ash content of the mesophase pitch is preferably < 20 ppm, more preferably < 18 ppm, and still more preferably < 16 ppm;

[0067] The process of the melting and spinning is preferably nitrogen pressure type;

[0068] The nitrogen pressure for the melting and spinning is preferably 0.4 - 1.6 MPa, more preferably 0.6 - 1.4 MPa, and still more preferably 0.8 - 1 MPa. The temperature of the spinneret is preferably 314 - 328 °C, more preferably 316 - 325 °C, and still more preferably 318 - 320 °C. The winding speed is preferably 200 - 1500 rpm, more preferably 400 - 1200 rpm, and still more preferably 500 - 1000 rpm.

[0069] In the present invention, in step 1), after the molten mesophase pitch is sheared and drawn-induced oriented by the spinneret, the liquid crystal molecules at both ends in the fiber length direction are semi-circularly radially oriented, and the liquid crystal molecules in the middle of the fiber are oriented perpendicular to the horizontal center line of the fiber.

[0070] In the present invention, in step 2), the pre-oxidation is preferably carried out in air or oxygen. The feeding rate of the air or oxygen is preferably 0.8 - 1.5 L / min, more preferably 1 - 1.4 L / min, and still more preferably 1.1 - 1.2 L / min;

[0071] The pre-oxidation temperature is preferably 150 - 300 °C, more preferably 180 - 260 °C, and even more preferably 200 - 250 °C. The pre-oxidation time is preferably 200 - 400 min, more preferably 250 - 390 min, and even more preferably 280 - 380 min;

[0072] The pre-oxidation transforms the fiber from thermoplastic to thermosetting.

[0073] In the present invention, in step 2), the carbonization is preferably carried out in a protective atmosphere. The feeding rate of the protective atmosphere is preferably 0.3 - 1 L / min, more preferably 0.4 - 0.8 L / min, and even more preferably 0.5 - 0.7 L / min;

[0074] The carbonization temperature is preferably 400 - 1300 °C, more preferably 600 - 1100 °C, and even more preferably 700 - 1000 °C. The carbonization time is preferably 60 - 300 min, more preferably 70 - 250 min, and even more preferably 90 - 120 min;

[0075] During the carbonization, due to the increase in the carbonization temperature, non-carbon elements inside the fiber are gradually removed, the microcrystals gradually grow, and the interlayer spacing gradually shrinks, resulting in stress concentration at the semi-circular radiating lamellae at both ends of the fiber, and thus splitting phenomenon occurs.

[0076] In the present invention, in step 2), the graphitization is preferably carried out in a protective atmosphere. The feeding rate of the protective atmosphere is preferably 4 - 8 L / min, more preferably 5 - 7 L / min, and even more preferably 6 - 6.5 L / min;

[0077] The graphitization temperature is preferably ≥2400 °C, more preferably ≥2600 °C, and even more preferably ≥2800 °C. The graphitization time is preferably 10 - 60 min, more preferably 20 - 50 min, and even more preferably 30 - 40 min;

[0078] During the graphitization, as the graphitization temperature increases, the graphite microcrystals in the fiber gradually grow, the orientation degree and graphitization degree are correspondingly improved, and the interlayer spacing gradually approaches the ideal graphite interlayer spacing (0.3354 nm). At the same time, the cracks at both ends of the fiber further expand towards the middle, and the splitting angle and depth increase.

[0079] In the present invention, in step 2), the graphitization is preferably intermittent or continuous.

[0080] The present invention also provides an X-shaped high thermal conductivity pitch-based carbon fiber prepared by the preparation method of the X-shaped high thermal conductivity pitch-based carbon fiber.

[0081] The technical solution provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0082] Embodiment 1

[0083] In this embodiment, the production equipment of the X-shaped high thermal conductivity pitch-based carbon fiber consists of a spinneret and a high-temperature tunnel:

[0084] The spinneret consists of an inlet section with gradually converging angles connecting a vertical filament outlet section: The gradually converging inlet section is divided into 4 conical surfaces with different angles. From top to bottom, the conical surface angle of the first stage is 140°, the conical surface angle of the second stage is 110°, the conical surface angle of the third stage is 80°, and the conical surface angle of the fourth stage is 40°. The end of the fourth-stage conical surface is connected to the vertical filament outlet section; A plurality of flow channels are laid on the inner wall of the conical surface of the gradually converging inlet section. The width of the flow channel is 0.02 mm and the depth is 0.03 mm; The horizontal cross-section of the outlet of the vertical filament outlet section is a rectangle with rounded ends at both ends, with a width of 0.15 mm and a length of 1.5 mm;

[0085] The high-temperature tunnel consists of a tunnel and a temperature control system: The tunnel is located at the outlet of the spinneret and is attached to the spinneret. The diameter of the tunnel is 5 cm, the diameter of the spinneret is 4 cm, and the length of the tunnel is 24 cm; The temperature control system is located inside the tunnel, and the temperature is set at 320 °C.

[0086] In this embodiment, the preparation steps of the X-shaped high thermal conductivity pitch-based carbon fiber are as follows:

[0087] The oil-based mesophase pitch with a mesophase content of 100% and an ash content of 15 ppm in a molten state is melt-spun in the production equipment described in this embodiment by nitrogen pressure. During spinning, the temperature of the spinneret is 318 °C, the nitrogen pressure is 1 MPa, and the winding speed is 850 rpm to obtain ribbon-shaped pitch fibers;

[0088] The ribbon-shaped pitch fibers are placed in a pre-oxidation furnace, and air is introduced at a rate of 1.1 L / min and pre-oxidized at a temperature of 250 °C for 300 min to obtain pre-oxidized fibers;

[0089] The pre-oxidized fibers are placed in a carbonization furnace, and nitrogen is introduced at a rate of 0.5 L / min and carbonized at 600 °C for 90 min to obtain carbonized fibers;

[0090] The carbonized fibers are placed in a graphitization furnace, and argon is introduced at a rate of 6 L / min and subjected to intermittent graphitization treatment at 3000 °C for 30 min to obtain X-shaped high thermal conductivity pitch-based carbon fibers. The thermal conductivity of the obtained X-shaped high thermal conductivity pitch-based carbon fibers is 750 W / (m·K).

[0091] The microscopic morphology diagram of the horizontal cross-section of the X-shaped high thermal conductivity pitch-based carbon fibers obtained in this embodiment is asFigure 4 As shown in Figure 4

[0092] Example 2

[0093] In this example, the production equipment of the X-shaped high thermal conductivity pitch-based carbon fiber consists of a spinneret plate and a high-temperature channel:

[0094] The spinneret plate consists of an inlet section with gradually converging angles connected to a vertical wire outlet section: The gradually converging inlet section is divided into 6 conical surfaces with different angles. From top to bottom, the first-stage conical surface angle is 150°, the second-stage conical surface angle is 130°, the third-stage conical surface angle is 110°, the fourth-stage conical surface angle is 90°, the fifth-stage conical surface angle is 70°, and the sixth-stage conical surface angle is 50°. The end of the sixth-stage conical surface is connected to the vertical wire outlet section; A plurality of flow channels are laid on the inner wall of the conical surface of the gradually converging inlet section. The width of the flow channel is 0.02 mm and the depth is 0.04 mm; The horizontal section of the outlet of the vertical wire outlet section is a rectangle with rounded ends at both ends, with a width of 0.17 mm and a length of 1.8 mm;

[0095] The high-temperature channel consists of a channel and a temperature control system: The channel is located at the outlet of the spinneret plate and is attached to the spinneret plate. The diameter of the channel is 7 cm, the diameter of the spinneret plate is 5 cm, and the length of the channel is 24 cm; The temperature control system is located inside the channel and the temperature is 330 °C.

[0096] In this example, the preparation steps of the X-shaped high thermal conductivity pitch-based carbon fiber are as follows:

[0097] The oil-based mesophase pitch with a mesophase content of 100% and an ash content of 15 ppm in the molten state is melt-spun in the production equipment of the present invention by nitrogen pressure. When spinning, the temperature of the spinneret plate is 325 °C, the nitrogen pressure is 0.8 MPa, and the winding speed is 850 pm to obtain strip-shaped pitch fibers;

[0098] The strip-shaped pitch fibers are placed in a pre-oxidation furnace, and air is introduced at a rate of 1.1 L / min and pre-oxidized at a temperature of 250 °C for 300 min to obtain pre-oxidized fibers;

[0099] The pre-oxidized fibers are placed in a carbonization furnace, and nitrogen is introduced at a rate of 0.5 L / min and carbonized at 700 °C for 90 min to obtain carbonized fibers;

[0100] Place the carbonized fibers in a graphitization furnace, introduce argon at a rate of 6 L / min, and perform continuous graphitization treatment at 3000 °C for 30 min to obtain X-shaped high thermal conductivity pitch-based carbon fibers. The thermal conductivity of the obtained X-shaped high thermal conductivity pitch-based carbon fibers is 952 W / (m·K).

[0101] The microscopic morphology diagram of the horizontal cross-section of the X-shaped high thermal conductivity pitch-based carbon fibers obtained in this example is as follows Figure 5 shown. From Figure 5 it can be seen that the arrangement of the graphite lamellae of the obtained carbon fibers is the same as that of the carbon fibers obtained in Example 1, but the splitting angle at both ends of the carbon fibers obtained in Example 2 is significantly smaller, about 45°.

[0102] Example 3

[0103] In this example, the production equipment of the X-shaped high thermal conductivity pitch-based carbon fibers consists of a spinneret and a high-temperature channel

[0104] The spinneret consists of an inlet section with gradually converging angles connected to a vertical wire outlet section: the inlet section with gradually converging angles is divided into 6 conical surfaces with different angles, which are, from top to bottom, the first-stage conical surface angle is 160°, the second-stage conical surface angle is 140°, the third-stage conical surface angle is 120°, the fourth-stage conical surface angle is 100°, the fifth-stage conical surface angle is 80°, and the sixth-stage conical surface angle is 60°. The end of the sixth-stage conical surface is connected to the vertical wire outlet section; multiple flow channels are laid on the inner wall of the conical surface of the inlet section with gradually converging angles, the width of the flow channel is 0.03 mm, and the depth is 0.04 mm; the horizontal cross-section of the outlet of the vertical wire outlet section is a rectangle with circular arcs at both ends, the width is 0.15 mm, and the length is 1.5 mm

[0105] The high-temperature channel consists of a channel and a temperature control system: the channel is located at the outlet of the spinneret and is attached to the spinneret. The diameter of the channel is 5 cm, the diameter of the spinneret is 4 cm, and the length of the channel is 24 cm; the temperature control system is located inside the channel, and the temperature is 330 °C

[0106] In this example, the preparation steps of the X-shaped high thermal conductivity pitch-based carbon fibers are as follows

[0107] Perform melt spinning of the oil-based mesophase pitch with a melting point of 100% and an ash content of 15 ppm in the production equipment of the present invention by nitrogen pressure. When spinning, the temperature of the spinneret is 325 °C, the nitrogen pressure is 1 MPa, and the winding speed is 500 pm to obtain strip-shaped pitch fibers

[0108] Place the strip-shaped pitch fibers in a pre-oxidation furnace, introduce air at a rate of 1.1 L / min, and pre-oxidize at a temperature of 250 °C for 380 min to obtain pre-oxidized fibers

[0109] Place the pre-oxidized fibers in a carbonization furnace, introduce nitrogen at a rate of 0.5 L / min, and carbonize at 700 °C for 100 min to obtain carbonized fibers;

[0110] Place the carbonized fibers in a graphitization furnace, introduce argon at a rate of 6 L / min, and perform continuous graphitization treatment at 3000 °C for 40 min to obtain X-shaped high thermal conductivity pitch-based carbon fibers. The thermal conductivity of the obtained X-shaped high thermal conductivity pitch-based carbon fibers is 1100 W / (m·K).

[0111] From Figure 6 It can be seen that the splitting angle at both ends of the carbon fiber is relatively large, about 85°. By adjusting the relevant parameters in the fiber preparation process, the splitting angle and thermal conductivity of the "X"-shaped carbon fiber can be controlled to meet the requirements of fiber reinforcements in different scenarios.

[0112] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A production device for X-shaped high thermal conductivity pitch-based carbon fiber, characterized in that, The production equipment includes a spinneret plate and a high-temperature duct; The spinneret plate is composed of an inlet section with gradually converging levels connecting a vertical filament outlet section; The high-temperature duct is composed of a duct and a temperature control system; The duct is located at the outlet of the spinneret plate.

2. The production equipment of an X-shaped high thermal conductivity pitch-based carbon fiber according to claim 1, characterized in that, The inlet section with gradually converging levels is composed of conical surfaces with different angles whose angles gradually decrease; The number of conical surfaces with different angles ≥ 4; The inner wall of the conical surface of the inlet section with gradually converging levels is paved with a flow channel; The width of the flow channel ≤ 0.06 mm, and the depth of the flow channel ≤ 0.07 mm.

3. The production equipment of an X-shaped high thermal conductivity pitch-based carbon fiber according to claim 2, characterized in that, The horizontal cross-section of the outlet of the vertical filament outlet section is a rectangle with rounded ends or a slit shape with rounded ends; The aspect ratio of the horizontal cross-section is 5 - 20:

1.

4. The production equipment of an X-shaped high thermal conductivity pitch-based carbon fiber according to claim 2 or 3, characterized in that, The length of the duct is 20 - 30 cm; The temperature of the temperature control system is 300 - 350 °C.

5. A preparation method of X-shaped high thermal conductivity pitch-based carbon fiber, characterized in that, It includes the following steps: 1) Melting and spinning the mesophase pitch to obtain ribbon-shaped pitch fibers; 2) Sequentially subjecting the ribbon-shaped pitch fibers to pre-oxidation, carbonization, and graphitization to obtain X-shaped high thermal conductivity pitch-based carbon fibers; The melting and spinning is carried out in the production equipment according to any one of claims 1 - 4.

6. The preparation method of an X-shaped highly thermally conductive pitch-based carbon fiber according to claim 5, characterized in that, In step 1), the mesophase pitch is oil-based mesophase pitch, coal-based mesophase pitch, or naphthalene-based mesophase pitch, the mesophase content of the mesophase pitch is 100%, and the ash content of the mesophase pitch < 20 ppm; The process of the melting and spinning is nitrogen pressure type; The nitrogen pressure of the melting and spinning is 0.4 - 1.6 MPa, the temperature of the spinneret plate is 314 - 328 °C, and the winding speed is 200 - 1500 rpm.

7. The preparation method of an X-shaped high thermal conductivity pitch-based carbon fiber according to claim 6, wherein, In step 2), the pre-oxidation is carried out in air or oxygen, and the feeding rate of the air or oxygen is 0.8 - 1.5 L / min; The temperature of the pre-oxidation is 150 - 300 °C, and the time of the pre-oxidation is 200 - 400 min.

8. The preparation method of an X-shaped high thermal conductivity pitch-based carbon fiber according to claim 6 or 7, characterized in that In step 2), the carbonization is carried out in a protective atmosphere, and the feeding rate of the protective atmosphere is 0.3 - 1 L / min; The temperature of the carbonization is 400 - 1300 °C, and the time of the carbonization is 60 - 300 min.

9. The preparation method of an X-shaped highly thermally conductive pitch-based carbon fiber according to claim 8, characterized in that, In step 2), the graphitization is carried out in a protective atmosphere, and the feeding rate of the protective atmosphere is 4 - 8 L / min; The temperature of the graphitization is ≥ 2400 °C, and the time of the graphitization is 10 - 60 min.

10. The X-shaped high thermal conductivity pitch-based carbon fiber prepared by the preparation method of the X-shaped high thermal conductivity pitch-based carbon fiber according to any one of claims 5 - 9.

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