General-purpose carbon fiber using waste heat conducting oil as raw material and preparation method thereof

Abstract

The present application relates to the technical field of general grade pitch-based carbon fiber preparation, and discloses a general grade carbon fiber prepared from waste heat-conducting oil and a preparation method thereof.The preparation method of the general grade carbon fiber comprises the following steps: preheating and filtering the waste heat-conducting oil, transferring the waste heat-conducting oil to a reaction kettle, pressurizing polymerization, and cooling to obtain polymerized pitch; adding a crosslinking agent, a catalyst and the polymerized pitch into the reaction kettle, microwave heating, and cooling to obtain isotropic pitch; then performing thin layer evaporation, keeping constant temperature after heating to obtain spinning pitch; continuously melt spinning the spinning pitch, hot air drafting, circulating hot air blowing to the spinning outlet, and collecting through a mesh chain, transferring, and then performing pre-oxidation and carbonization treatment to obtain the general grade carbon fiber.The present application solves the problems of high cost and environmental pollution in the utilization of waste heat-conducting oil, realizes effective utilization of waste resources, and simultaneously prepares general grade carbon fiber with excellent spinnability and high performance.

Description

Technical Field

[0001] This invention relates to the field of general-purpose pitch-based carbon fiber preparation technology, and in particular to a general-purpose carbon fiber made from waste heat transfer oil and its preparation method. Background Technology

[0002] Dibenzyltoluene (DMT) heat transfer oil is a high-temperature liquid-phase heat transfer oil with an operating temperature up to 350℃. It is used as a heat transfer medium in some high-temperature equipment due to its high thermal stability, high boiling point, excellent low-temperature fluidity, and safe operation. It is currently widely used as a high-temperature heat transfer oil both domestically and internationally. Statistics show that my country's annual production of DMT heat transfer oil has reached over 3 million tons, but approximately 900,000 tons of waste heat transfer oil (referring to waste DMT heat transfer oil) are generated annually. This is because DMT heat transfer oil oxidizes and deteriorates over time, leading to decreased fluidity and thermal conductivity, thus requiring regular replacement, generally every 1-3 years. Currently, waste heat transfer oil disposal methods include recycling, pyrolysis, and waste treatment. Recycling is costly and can only be used when the heat transfer oil pollution is relatively low. Pyrolysis, when used as fuel, has low economic efficiency and easily generates large amounts of harmful gases. Therefore, how to achieve efficient, rational, and high-value utilization of waste heat transfer oil is a key issue that urgently needs to be addressed by those skilled in the art.

[0003] On the other hand, with the deepening research on the molecular structure of general-purpose spinning pitch and its influence on the mechanical properties of carbon fibers in recent years, the academic community generally believes that regulating the molecular structure of general-purpose spinning pitch to form a linear chain molecular structure with aromatic structural units connected by methylene bridges is an effective way to prepare high-performance general-purpose pitch carbon fibers. From the perspective of molecular structure, dibenzyltoluene heat transfer oil not only has a high carbon content, but also has abundant methyl branches and a good linear molecular structure. Therefore, a method for preparing general-purpose carbon fibers using waste heat transfer oil as raw material is proposed, which can not only realize the effective utilization of waste resources, but also effectively reduce the large amount of CO2 emissions generated during the current waste heat transfer oil incineration process.

[0004] Currently, the main raw materials for preparing general-purpose carbon fiber include coal tar pitch, ethylene tar pitch, and bio-pitch, and the main methods include thermal polycondensation, atmospheric and vacuum distillation, and air oxidation. However, the difference in precursor preparation processes directly determines the mechanical properties of general-purpose pitch-based carbon fiber. Among them, Chinese invention patent application number CN202010468692.8, "A method for preparing general-purpose pitch-based fiber from coal liquefaction residue," discloses a method for preparing general-purpose carbon fiber using coal liquefaction residue as raw material. This method involves sedimentation separation, vacuum filtration, and oxidative polycondensation to obtain a pitch precursor with a softening point of 240–340℃, which is then processed through melt spinning, non-melting treatment, and carbonization to obtain carbon fiber. Chinese invention patent application number CN202010496675.5, "A method for producing spinning pitch for coal tar pitch-based general-purpose carbon fiber raw materials," obtains pitch with a high softening point through distillation, vacuum distillation, component adjustment, and oxidation. The two patents mentioned above both involve air oxidation, a method commonly used in industry. However, air oxidation has low oxidation efficiency, takes too long, and the heat transfer oil has good oxidation resistance, making it unsuitable for this application. Therefore, there is an urgent need to propose a general-purpose carbon fiber and its preparation method using waste heat transfer oil as raw material, which also possesses the characteristics of rapid reaction and being environmentally friendly and clean. Summary of the Invention

[0005] Based on the above, the purpose of this invention is to provide a general-purpose carbon fiber made from waste heat transfer oil and its preparation method, which solves the problems of high cost and environmental pollution in the current utilization of waste heat transfer oil, realizes the effective utilization of waste resources, and at the same time prepares general-purpose carbon fiber with excellent spinnability and high performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material includes the following steps:

[0008] Waste heat transfer oil is preheated and filtered to obtain desolidified waste heat transfer oil; the desolidified waste heat transfer oil is transferred to a reactor, pressurized and polymerized, cooled and discharged to obtain polymerized asphalt;

[0009] Add 5-25% by mass of crosslinking agent, 2-10% by mass of catalyst and 65-93% by mass of polymerized asphalt to a reactor, introduce inert gas, microwave heat, stir reaction, cool down and take out material to obtain isotropic asphalt.

[0010] The isotropic pitch was subjected to thin-layer evaporation, and then heated and kept at a constant temperature under vacuum to obtain spinning pitch.

[0011] The spinning pitch is continuously melt-spun. The pitch melt is ejected from the spinneret and then drawn by hot air. The hot air is then blown to the fiber outlet and collected by a mesh chain. The collected pitch fibers are transferred together with the mesh chain and subjected to pre-oxidation and carbonization treatments in an inert environment to obtain general-purpose carbon fibers.

[0012] As a preferred embodiment of a method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material, the waste heat transfer oil has a molecular weight distribution of 180-400, an H / C molar ratio of 0.7-1.10, and an ash content of 50-200 ppm; when the waste heat transfer oil is preheated and filtered, the pressure is not greater than 1 MPa under an inert environment.

[0013] As a preferred embodiment of a method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material, the deconsolidated waste heat transfer oil is transferred to a reactor, and then subjected to a pressurized polymerization reaction at a temperature of 360–450°C. The pressure is increased to 1–2 MPa, and the holding time is 4–6 h. The temperature is then reduced to 360–400°C, and inert gas is introduced for purging for 2–4 h.

[0014] In a preferred embodiment of a method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material, the crosslinking agent includes one or more of terephthalic acid, benzaldehyde, and terephthaloyl chloride; the catalyst includes one or more of boric acid, nitric acid, sulfuric acid, and hydrochloric acid.

[0015] In a preferred embodiment of a method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material, the microwave heating process involves raising the temperature to 200℃~280℃ and reacting for 3~6 hours.

[0016] As a preferred embodiment of a method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material, the vacuum degree during the thin-layer evaporation process is no greater than -0.09 MPa, and the temperature is increased from room temperature to 320-350℃ at a heating rate of 2-5℃ / min.

[0017] In a preferred embodiment of a method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material, during the melt-blown spinning process, the melt-blown spinning temperature is 280℃~350℃. The spinning pressure and spinning speed are controlled by controlling the screw feed rate and the metering pump speed. The screw feed rate is 0.1~5Kg / min, the metering pump speed is 5~300r / min, the spinning pressure is 0.05~5MPa, the spinneret flow rate is 0.1~4Kg / min, the average diameter of the pitch fiber is 8~30μm, the circulating hot air temperature is 280~350℃, and the hot air fan frequency is 5~50Hz.

[0018] As a preferred embodiment of a method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material, the pre-oxidation treatment is carried out at a temperature of 280℃~320℃ and a chain moving speed of 0.1~5m / s; the carbonization treatment is carried out at a carbonization temperature of 800~1200℃ and a carbonization heating rate of 1~20℃ / min.

[0019] In a preferred embodiment of a method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material, the polymerized pitch has a softening point of 20–50°C and an H / C molar ratio of 0.6–1.0; the isotropic pitch has a softening point of 230–260°C; and the spinning pitch has a softening point of 260–290°C and an H / C molar ratio of 0.45–0.75.

[0020] A general-purpose carbon fiber made from waste heat transfer oil is prepared by any one of the preparation methods described above.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention provides a general-purpose carbon fiber made from waste heat transfer oil and its preparation method. This method utilizes a microwave crosslinking reaction, which is highly efficient, rapid, and reduces production costs. Furthermore, due to the high carbon content of waste heat transfer oil, along with its abundant methyl branches and favorable linear molecular structure, high-performance general-purpose carbon fibers with excellent mechanical properties are obtained. This invention also achieves the effective utilization of waste heat transfer oil. Compared to existing waste heat transfer oil treatment technologies, this invention effectively solves environmental pollution problems, reduces the large CO2 emissions during the current waste heat transfer oil incineration process, and the cost of preparing general-purpose carbon fibers from waste heat transfer oil is low, resulting in higher economic benefits. Detailed Implementation

[0023] To facilitate understanding of the present invention, a more comprehensive description will be provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention. Unless otherwise defined, all technical and scientific terms used in this invention pertain to the technical field of the invention.

[0024] This invention provides a general-purpose carbon fiber made from waste heat transfer oil and a method for preparing the same, comprising the following steps:

[0025] S100: Preheat and filter the waste heat transfer oil to obtain desolidified waste heat transfer oil; transfer the desolidified waste heat transfer oil to a reactor, pressurize and polymerize it, and discharge it after cooling to obtain polymerized asphalt;

[0026] Furthermore, the waste heat transfer oil has a molecular weight distribution of 180–400, an H / C molar ratio of 0.7–1.10, and an ash content of 50–200 ppm; the polymerized asphalt has a softening point of 20–50℃ and an H / C molar ratio of 0.6–1.0.

[0027] Specifically, during the preheating and filtration of waste heat transfer oil, the pressure is no more than 1 MPa in an inert environment, and the filtration process is mainly used to remove particulate impurities.

[0028] Specifically, after the solidified waste heat transfer oil is transferred to the reactor, the pressure polymerization reaction temperature is 360-450℃, the pressure is increased to 1-2MPa, the holding time is 4-6h, and the temperature is reduced to 360-400℃ and inert gas is introduced for 2-4h purging.

[0029] S200: Add 5-25% by mass of crosslinking agent, 2-10% by mass of catalyst and 65-93% by mass of polymerized asphalt into a reactor, introduce inert gas, microwave heat, stir and react, cool and take out the material to obtain isotropic asphalt.

[0030] Furthermore, the softening point of isotropic asphalt is 230–260℃.

[0031] Specifically, the crosslinking agent includes one or more of terephthalic acid, benzaldehyde, and terephthaloyl chloride; the catalyst includes one or more of boric acid, nitric acid, sulfuric acid, and hydrochloric acid.

[0032] Specifically, during microwave heating, the temperature is raised to 200℃~280℃, and the reaction time is 3~6h.

[0033] S300: Thin-layer evaporation of isotropic pitch, followed by heating and constant temperature under vacuum to obtain spinning pitch;

[0034] Furthermore, the softening point of the spinning pitch is 260–290℃, and the H / C molar ratio is 0.45–0.75.

[0035] Specifically, during the thin-layer evaporation process, the vacuum degree is no greater than -0.09 MPa, and the temperature is increased from room temperature to 320-350°C at a rate of 2-5°C / min. The purpose of thin-layer evaporation is to adjust the softening point of the isotropic asphalt. After the above reaction, maintaining a constant temperature can remove the light components in the isotropic asphalt, thus obtaining spinning asphalt.

[0036] S400: The spinning pitch is continuously melt-spun. The pitch melt is sprayed from the spinneret and then drawn by hot air. The circulating hot air is blown to the fiber outlet and collected by a mesh chain. The collected pitch fibers are transferred together with the mesh chain and subjected to pre-oxidation and carbonization treatments in an inert environment to obtain general-purpose carbon fibers.

[0037] Specifically, during the meltblown spinning process, the meltblown spinning temperature is 280℃~350℃. The spinning pressure and spinning speed are controlled by controlling the screw feed rate and the metering pump speed. The screw feed rate is 0.1~5Kg / min, the metering pump speed is 5~300r / min, the spinning pressure is 0.05~5MPa, the spinneret flow rate is 0.1~4Kg / min, the average diameter of the pitch fiber is 8~30μm, the circulating hot air temperature is 280~350℃, and the hot air fan frequency is 5~50Hz.

[0038] Specifically, during the pre-oxidation treatment, the temperature is 280℃~320℃ and the mesh chain moving speed is 0.1~5m / s; during the carbonization treatment, the carbonization temperature is 800~1200℃ and the carbonization heating rate is 1~20℃ / min.

[0039] Specifically, nitrogen is preferred in all of the above-mentioned inert gas environments.

[0040] The present invention will be further described below through specific embodiments.

[0041] Example 1

[0042] After filtering the waste heat transfer oil, under nitrogen atmosphere and pressure not exceeding 1MPa, the solidified waste heat transfer oil is obtained. The solidified waste heat transfer oil is then placed in a reaction vessel and heated to 420℃ and pressurized to 2MPa. It is kept at this temperature for 4 hours, then cooled to 380℃ and purged with N2 for 2 hours at a flow rate of 3L / min to obtain polymerized asphalt.

[0043] Polymerized asphalt (85% by mass), terephthalic acid (5% by mass), and concentrated sulfuric acid (10% by mass) were microwave-heated in a closed system under nitrogen protection. The temperature was raised to 260°C and stirring was started. The reaction time was 4 hours. After the reaction was completed, isotropic asphalt was obtained.

[0044] The softening point of isotropic pitch was increased by thin-layer evaporation method with a vacuum degree of -0.09 MPa and room temperature was heated to 320℃ at a heating rate of 2℃ / min to obtain spinning pitch with a softening point of 265℃.

[0045] Spinning bitumen is fed from a hopper to the spinning box of a meltblown spinning machine via a feeding screw for continuous meltblown spinning. The meltblown spinning temperature is 280℃. During the spinning process, the spinning pressure and speed are controlled by the screw feed rate and the metering pump speed. The screw feed rate is 1 kg / min, the metering pump speed is 200 r / min, the spinning pressure is 0.5 MPa, and the spinneret flow rate is 1 kg / min. After the bitumen melt is ejected from the spinneret and drawn by hot air, the average diameter of the bitumen fibers is 11.52 μm. The spun bitumen fibers are then recycled... After being blown to the filament outlet by hot air, the fibers are collected by a mesh chain. The temperature of the circulating hot air is 280℃, and the frequency of the hot air fan is 20Hz. The pitch precursor fibers collected by the mesh chain are transferred to a continuous pre-oxidation furnace for pre-oxidation treatment in an air atmosphere. The operating temperature of the continuous pre-oxidation furnace is 280℃, and the mesh chain moving speed is 1m / s. After the pre-oxidation is completed, the fibers are further transferred to a carbonization furnace for carbonization treatment in a nitrogen atmosphere. The carbonization temperature is 1000℃, and the carbonization heating rate is 5℃ / min, to obtain general-purpose carbon fiber.

[0046] The general-purpose carbon fiber prepared in Example 1 was subjected to performance testing. The cross-sectional area of ​​each filament was independently measured according to the method specified in GB / T29762. When using optical microscopy or laser diffraction, the selected single fiber sample was used for both cross-sectional area and tensile property testing. The tensile property testing standard was GB / T 31290-2022. A bundle of filaments approximately 10 cm long was cut from the example sample and roughly divided into four equal parts according to the number of fibers. The same number of filaments were taken from each part to prepare a sample, ensuring at least 20 valid test results. Finally, the average diameter of the general-purpose carbon fiber was measured to be 10.64 μm, and the tensile strength of the general-purpose carbon fiber filament was 960.05 MPa.

[0047] Example 2

[0048] After filtering the waste heat transfer oil, under nitrogen atmosphere and pressure not exceeding 1MPa, solidified waste heat transfer oil is obtained. The solidified waste heat transfer oil is then placed in a reaction vessel and heated to 360℃ and pressurized to 2MPa. It is kept at this temperature for 4 hours, then cooled to 380℃ and purged with N2 for 2 hours at a flow rate of 3L / min to obtain polymerized asphalt.

[0049] The polymerized asphalt, benzaldehyde, and concentrated hydrochloric acid, with a mass fraction of 80%, 15%, and 5% respectively, were microwave-heated in a closed system under nitrogen protection. The temperature was raised to 240°C and stirring was started. The reaction time was 5 hours. After the reaction was completed, isotropic asphalt was obtained.

[0050] The softening point of isotropic pitch was increased by thin-layer evaporation method with a vacuum degree of -0.09 MPa and room temperature was heated to 350℃ at a heating rate of 3℃ / min to obtain spinning pitch with a softening point of 278℃.

[0051] Spinning bitumen is fed from a hopper to the spinning box of a meltblown spinning machine via a feeding screw for continuous meltblown spinning. The meltblown spinning temperature is 330℃. During the spinning process, the spinning pressure and speed are controlled by the screw feed rate and the metering pump speed. The screw feed rate is 0.5 kg / min, the metering pump speed is 100 r / min, the spinning pressure is 1.0 MPa, and the spinneret flow rate is 0.5 kg / min. After the bitumen melt is ejected from the spinneret and drawn by hot air, the average diameter of the bitumen fibers is 12.53 μm. The spun bitumen fibers... After being blown to the filament outlet by circulating hot air, the fibers are collected by a mesh chain. The temperature of the circulating hot air is 310℃, and the frequency of the hot air fan is 5Hz. The pitch precursor fibers collected by the mesh chain are transferred to a continuous pre-oxidation furnace for pre-oxidation treatment in an air atmosphere. The operating temperature of the continuous pre-oxidation furnace is 300℃, and the mesh chain moving speed is 2m / s. After the pre-oxidation is completed, the fibers are further transferred to a carbonization furnace for carbonization treatment in a nitrogen atmosphere. The carbonization temperature is 800℃, and the carbonization heating rate is 1℃ / min, to obtain general-purpose carbon fiber.

[0052] The general-purpose carbon fiber prepared in Example 2 was subjected to performance testing. The cross-sectional area of ​​each filament was independently measured according to the method specified in GB / T29762. When using optical microscopy or laser diffraction, the selected single fiber sample was used for both cross-sectional area and tensile property testing. The tensile property testing standard was GB / T 31290-2022. A bundle of filaments approximately 10 cm long was cut from the example sample and roughly divided into four equal parts according to the number of fibers. The same number of filaments were taken from each part to prepare a sample, ensuring at least 20 valid test results. Finally, the average diameter of the general-purpose carbon fiber was measured to be 11.63 μm, and the tensile strength of the general-purpose carbon fiber filament was 1390.51 MPa.

[0053] Example 3

[0054] After filtering the waste heat transfer oil, under nitrogen atmosphere and pressure not exceeding 1MPa, solidified waste heat transfer oil is obtained. The solidified waste heat transfer oil is then placed in a reactor and heated to 390℃ and pressurized to 1.5MPa. It is kept at this temperature for 5 hours, then cooled to 380℃ and purged with N2 for 3 hours at a flow rate of 3L / min to obtain polymerized asphalt.

[0055] Polymerized asphalt, 20% terephthaloyl chloride, and 5% boric acid were microwave-heated in a closed system under nitrogen protection. The temperature was raised to 280°C and stirring was started. The reaction time was 3 hours. After the reaction was completed, isotropic asphalt was obtained.

[0056] The softening point of isotropic pitch was increased by thin-layer evaporation method. The vacuum degree was -0.09MPa, and the temperature was increased from room temperature to 340℃ at a heating rate of 4℃ / min to obtain spinning pitch with a softening point of 288℃.

[0057] Spinning bitumen is fed from the hopper to the spinning box of a meltblown spinning machine via a feeding screw for continuous meltblown spinning. The meltblown spinning temperature is 310℃. During the spinning process, the spinning pressure and speed are controlled by the screw feed rate and the metering pump speed. The screw feed rate is 0.1 kg / min, the metering pump speed is 5 r / min, the spinning pressure is 0.05 MPa, and the spinneret flow rate is 0.1 kg / min. After the bitumen melt is ejected from the spinneret and drawn by hot air, the average diameter of the bitumen fibers is 13.53 μm. The spun bitumen fibers are then... After being blown to the filament outlet by circulating hot air, the fibers are collected by a mesh chain. The temperature of the circulating hot air is 350℃ and the frequency of the hot air fan is 50Hz. The pitch precursor fibers collected by the mesh chain are transferred to a continuous pre-oxidation furnace for pre-oxidation treatment in an air atmosphere. The operating temperature of the continuous pre-oxidation furnace is 320℃ and the mesh chain moving speed is 5m / s. After the pre-oxidation is completed, the fibers are further transferred to a carbonization furnace for carbonization treatment in a nitrogen atmosphere. The carbonization temperature is 1200℃ and the carbonization heating rate is 15℃ / min, resulting in general-purpose carbon fiber.

[0058] The general-purpose carbon fiber prepared in Example 3 was subjected to performance testing. The cross-sectional area of ​​each filament was independently measured according to the method specified in GB / T29762. When using optical microscopy or laser diffraction, the selected single fiber sample was used for both cross-sectional area and tensile property testing. The tensile property testing standard was GB / T 31290-2022. A bundle of filaments approximately 10 cm long was cut from the example sample and roughly divided into four equal parts according to the number of fibers. The same number of filaments were taken from each part to prepare a sample, ensuring at least 20 valid test results. Finally, the average diameter of the general-purpose carbon fiber was measured to be 12.72 μm, and the tensile strength of the general-purpose carbon fiber filament was 1125.20 MPa.

[0059] Example 4

[0060] After filtering the waste heat transfer oil, under nitrogen atmosphere and pressure not exceeding 1MPa, solidified waste heat transfer oil is obtained. The solidified waste heat transfer oil is then placed in a reaction vessel and heated to 450℃ and pressurized to 1MPa. It is kept at this temperature for 6 hours, then cooled to 380℃ and purged with N2 for 4 hours at a flow rate of 3L / min to obtain polymerized asphalt.

[0061] The polymerized asphalt, benzaldehyde, and concentrated hydrochloric acid, with a mass fraction of 73%, 25%, and 2% respectively, were microwave-heated in a closed system under nitrogen protection. The temperature was raised to 200°C and stirring was started. The reaction time was 6 hours. After the reaction was completed, isotropic asphalt was obtained.

[0062] The softening point of isotropic pitch was increased by thin-layer evaporation method with a vacuum degree of -0.09 MPa and room temperature was heated to 350℃ at a heating rate of 5℃ / min to obtain spinning pitch with a softening point of 293℃.

[0063] Spinning bitumen is fed from the hopper to the spinning box of the meltblown spinning machine via a feeding screw for continuous meltblown spinning. The meltblown spinning temperature is 350℃. During the spinning process, the spinning pressure and speed are controlled by the screw feed rate and the metering pump speed. The screw feed rate is 5.0 kg / min, the metering pump speed is 300 r / min, the spinning pressure is 5.0 MPa, and the spinneret flow rate is 4 kg / min. After the bitumen melt is ejected from the spinneret and drawn by hot air, the average diameter of the bitumen fibers is 11.82 μm. The spun bitumen fibers are then recycled. Hot air is blown to the filament outlet and collected by a mesh chain. The circulating hot air temperature is 325℃ and the hot air fan frequency is 40Hz. The pitch precursor fibers collected by the mesh chain are transferred to a continuous pre-oxidation furnace for pre-oxidation treatment in an air atmosphere. The operating temperature of the continuous pre-oxidation furnace is 280℃ and the mesh chain moving speed is 0.1m / s. After pre-oxidation, the fibers are further transferred to a carbonization furnace for carbonization treatment in a nitrogen atmosphere. The carbonization temperature is 1000℃ and the carbonization heating rate is 20℃ / min, resulting in general-purpose carbon fiber.

[0064] The general-purpose carbon fiber prepared in Example 4 was subjected to performance testing. The cross-sectional area of ​​each filament was independently measured according to the method specified in GB / T29762. When using optical microscopy or laser diffraction, the selected single fiber sample was used for both cross-sectional area and tensile property testing. The tensile property testing standard was GB / T 31290-2022. A bundle of filaments approximately 10 cm long was cut from the example sample and roughly divided into four equal parts according to the number of fibers. The same number of filaments were taken from each part to prepare a sample, ensuring at least 20 valid test results. Finally, the average diameter of the general-purpose carbon fiber was measured to be 11.03 μm, and the tensile strength of the general-purpose carbon fiber filament was 980.20 MPa.

[0065] The above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. More other equivalent embodiments may be included without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material, characterized in that, Includes the following steps: Waste heat transfer oil is preheated and filtered to obtain desolidified waste heat transfer oil; the desolidified waste heat transfer oil is transferred to a reactor, pressurized and polymerized, cooled and discharged to obtain polymerized asphalt; Add 5-25% by mass of crosslinking agent, 2-10% by mass of catalyst and 65-93% by mass of polymerized asphalt to a reactor, introduce inert gas, microwave heat, stir reaction, cool down and take out material to obtain isotropic asphalt. The isotropic pitch was subjected to thin-layer evaporation, and then heated and kept at a constant temperature under vacuum to obtain spinning pitch. The spinning pitch is continuously melt-spun. The pitch melt is ejected from the spinneret and then drawn by hot air. The hot air is then blown to the fiber outlet and collected by a mesh chain. The collected pitch fibers are transferred together with the mesh chain and subjected to pre-oxidation and carbonization treatments in an inert environment to obtain general-purpose carbon fibers. The waste heat transfer oil has a molecular weight distribution of 180–400, an H / C molar ratio of 0.7–1.10, and an ash content of 50–200 ppm; when the waste heat transfer oil is preheated and filtered, the pressure is not greater than 1 MPa under an inert environment.

2. The method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material according to claim 1, characterized in that, After the waste heat transfer oil is transferred to the reactor, the pressure polymerization reaction temperature is 360-450℃, the pressure is increased to 1-2MPa, the holding time is 4-6h, and the temperature is reduced to 360-400℃ and then purged with inert gas for 2-4h.

3. The method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material according to claim 1, characterized in that, The crosslinking agent includes one or more of terephthalic acid, benzaldehyde, and terephthaloyl chloride; the catalyst includes one or more of boric acid, nitric acid, sulfuric acid, and hydrochloric acid.

4. The method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material according to claim 1, characterized in that, During the microwave heating process, the temperature is raised to 200℃~280℃, and the reaction time is 3~6h.

5. The method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material according to claim 1, characterized in that, During the thin-layer evaporation process, the vacuum degree is no greater than -0.09 MPa, and the temperature is increased from room temperature to 320-350℃ at a heating rate of 2-5℃ / min.

6. The method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material according to claim 1, characterized in that, During the meltblown spinning process, the meltblown spinning temperature is 280℃~350℃. The spinning pressure and spinning speed are controlled by controlling the screw feed rate and the metering pump speed. The screw feed rate is 0.1~5Kg / min, the metering pump speed is 5~300r / min, the spinning pressure is 0.05~5MPa, the spinneret flow rate is 0.1~4Kg / min, the average diameter of the pitch fiber is 8~30μm, the circulating hot air temperature is 280~350℃, and the hot air fan frequency is 5~50Hz.

7. The method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material according to claim 1, characterized in that, During the pre-oxidation treatment, the temperature is 280℃~320℃ and the mesh chain moving speed is 0.1~5m / s; during the carbonization treatment, the carbonization temperature is 800~1200℃ and the carbonization heating rate is 1~20℃ / min.

8. The method for preparing general-purpose carbon fiber using waste heat transfer oil as raw material according to claim 1, characterized in that, The polymerized asphalt has a softening point of 20–50°C and an H / C molar ratio of 0.6–1.0; the isotropic asphalt has a softening point of 230–260°C; and the spinning asphalt has a softening point of 260–290°C and an H / C molar ratio of 0.45–0.

75.

9. A general-purpose carbon fiber made from waste heat transfer oil, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.