Spinnable mesophase pitch and preparation method thereof

Abstract

The invention discloses spinnable mesophase pitch and a preparation method thereof, the method changes a traditional batch-type reaction mode, two single-kettle reactors are connected through a pipeline, and a special kettle is realized. The method comprises the following steps: carrying out pressurized thermal polycondensation reaction on oil slurry serving as a raw material in a reaction kettle A, transferring the reaction material to a reaction kettle B, and sequentially carrying out vacuum thermal polycondensation reaction and secondary heat treatment. The method can synchronously perform heating, cooling, polycondensation and other operations, thereby saving time and improving production efficiency; and the equipment failure frequency is reduced, the process variable is reduced, the equipment condition and the reaction degree can be accurately controlled, the stability between batches of products is improved, and the performance consistency is ensured. In addition, the two-step thermal polycondensation method is subjected to process optimization, the dependence on the vacuum degree is reduced, the vacuum polycondensation product is subjected to secondary heat treatment, the light components are further removed, the polycyclic aromatic hydrocarbon structure is perfected, and the finally prepared mesophase pitch is high in mesophase content, appropriate in softening point, high in carbon residue and good in spinnability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high polymer materials, and relates to a spinnable mesophase pitch and a preparation method thereof. BACKGROUND

[0002] At present, new material technology is developing rapidly in the world. High-performance carbon materials have irreplaceable application value in many high-end fields due to their unique properties, and have become the key force to promote technological progress and industrial upgrading. Among them, mesophase pitch, as a high-quality precursor for the preparation of functional carbon materials such as porous carbon, foam carbon and carbon fiber, has attracted much attention because of its excellent properties such as thermal stability, easy graphitization and spinnability. After the mesophase pitch molecules are oriented and arranged by shearing force in the spinning process, and then subjected to heat treatment such as oxidation, carbonization and graphitization, mesophase pitch-based carbon fibers are prepared, which have the characteristics of high strength, high modulus, low thermal expansion coefficient and excellent electrical and thermal conductivity, and play a crucial role in the fields of aerospace, military technology and other fields with extremely strict requirements on material performance. It is one of the key materials to ensure national strategic security and promote the development of high-end manufacturing industry.

[0003] In recent years, domestic and foreign researchers have carried out a large number of researches on the preparation of mesophase pitch and have made many progress. At present, the preparation methods of mesophase pitch mainly include condensation method, pre-mesophase method and latent mesophase method. The condensation method controls the condensation reaction of heavy aromatic hydrocarbons at high temperature to promote the transformation of molecular structure to mesophase with optical anisotropy. The pre-mesophase method first prepares a pre-polymer with a certain mesophase structure, and then further processes to obtain the target product. The latent mesophase method uses specific additives or reaction conditions to stimulate the latent mesophase formation ability of raw materials.

[0004] In domestic production practice, two-step condensation method is a commonly used method for preparing mesophase pitch, and most of them use batch reaction mode. Although this mode can achieve the preparation of mesophase pitch to a certain extent, there are still many problems that cannot be ignored. On the one hand, during the reaction process, there are inevitable differences in heating conditions and equipment running states of each reaction kettle. Due to the lack of precise real-time monitoring and control means, the actual state of the equipment and the degree of reaction during each batch reaction process are difficult to control accurately, which easily leads to inconsistent product performance and large fluctuations in batch stability. On the other hand, the batch reaction mode has long reaction time and low production efficiency. Long-time reaction not only increases energy consumption, but also prolongs the production cycle, which cannot meet the market demand for large-scale and rapid supply of mesophase pitch. These problems bring high production cost to enterprises and increase uncontrollable risk factors, which restricts the further development of mesophase pitch industry. Therefore, it is urgent to develop efficient, stable and controllable mesophase pitch preparation technology. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a spinnable mesophase pitch and a preparation method thereof, so as to solve the technical problems of inconsistent product batch performance, large stability fluctuation, long reaction time and low production efficiency in the preparation of mesophase pitch by adopting a two-step polycondensation method intermittent reaction in the prior art.

[0006] The present application is realized by the following technical solutions: A preparation method of a spinnable mesophase pitch, comprising the following steps: S1: performing a pressurized thermal polycondensation reaction in a reaction kettle A with oil slurry as raw material; S2: transferring the reaction material in the reaction kettle A to a reaction kettle B; S3: continuing to perform a vacuum thermal polycondensation reaction and a secondary heat treatment in the reaction kettle B in sequence to obtain the spinnable mesophase pitch.

[0007] Preferably, in step S1, the reaction pressure of the pressurized thermal polycondensation reaction is 1-5 MPa.

[0008] Preferably, in step S1, the reaction temperature of the pressurized thermal polycondensation reaction is 400-450℃, and the reaction time is 2-10 h.

[0009] Preferably, in step S2, when the material is transferred, the pressure in the reaction kettle A is 0.1-1 MPa.

[0010] Preferably, in step S2, when the material is transferred, the pressure in the reaction kettle B is-0.01--0.1 MPa.

[0011] Preferably, in step S3, when the vacuum thermal polycondensation reaction is performed, the reaction pressure is-0.05--0.1 MPa, the reaction temperature is 360-430℃, and the reaction time is 2-12 h.

[0012] Preferably, in step S3, when the secondary heat treatment is performed, the pressure in the reaction kettle B is-0.1 MPa-1 MPa, the heat treatment temperature is 250-400℃, and the heat treatment time is 2-10 h.

[0013] Preferably, the reaction kettle A and the reaction kettle B are connected through a pipeline.

[0014] A spinnable mesophase pitch prepared by the above method.

[0015] The above spinnable mesophase pitch has a mesophase content of ≥98%, a softening point of 285±10℃, and a carbon residue content of ≥75%.

[0016] Compared with the prior art, the present application has the following beneficial technical effects: This invention discloses a method for preparing spinnable mesophase pitch. This method changes the traditional batch reaction mode by connecting two single-reactor reactors via pipelines. Reactor A and reactor B are used for pressurized thermal polycondensation and vacuum thermal polycondensation reactions, respectively, achieving dedicated reactors for specific purposes. Simultaneous heating, cooling, and polycondensation reactions can be performed, effectively saving time and improving production efficiency. Furthermore, under the same reaction conditions, the frequency of equipment failure is significantly reduced, process variables are decreased, and equipment and parameter fluctuations are significantly reduced. This solves the problem of inaccurate control over equipment conditions and reaction degree in batch reactions, effectively improving batch-to-batch stability and ensuring consistent product performance. In addition, the two-step thermal polycondensation method is optimized to reduce dependence on and stringent requirements for vacuum levels. The vacuum polycondensation product undergoes secondary heat treatment to further remove light components. Pitch molecules complete the polycyclic aromatic hydrocarbon structure at lower reaction temperatures and longer times, completing the transformation into the mesophase, ensuring that material performance meets standards. The final mesophase pitch has a high mesophase content, suitable softening point, high carbon residue, and good spinnability.

[0017] Furthermore, in step S1, the reaction pressure of the pressurized thermal polycondensation reaction is 1~5MPa. This pressure range provides a suitable environment for the reaction, which helps the oil slurry raw material to better carry out the thermal polycondensation reaction under this pressure, which is conducive to the formation of intermediate products with specific structures, and lays the foundation for subsequent reactions and finally obtaining high-quality spinnable mesophase asphalt.

[0018] Furthermore, in step S1, the reaction temperature of the pressurized thermal polycondensation reaction is 400~450℃, and the reaction time is 2~10h. This temperature range can ensure that the oil slurry undergoes sufficient thermal polycondensation reaction, so that the molecular structure changes in the expected direction; the reasonable time range ensures that the reaction is fully carried out, without over-reacting and wasting energy, and also ensures that the intermediate product reaches a suitable state, which is beneficial for subsequent processing.

[0019] Furthermore, in step S2, during material transfer, the pressure inside reactor A is 0.1~1MPa. This pressure condition facilitates the smooth transfer of materials from reactor A, while avoiding adverse effects on material properties due to excessively high or low pressure, thus ensuring the stability of materials during the transfer process.

[0020] Furthermore, in step S2, during material transfer, the pressure inside reactor B is -0.01 to -0.1 MPa. The negative pressure environment is conducive to receiving materials from reactor A, and this pressure range can prevent external impurities from entering, creating good starting conditions for the subsequent vacuum thermal polycondensation reaction.

[0021] Furthermore, in step S3, during the vacuum thermal polycondensation reaction, the reaction pressure is -0.05~-0.1MPa, the reaction temperature is 360~430℃, and the reaction time is 2~12h. The appropriate combination of negative pressure, temperature, and time can promote further deep reaction of the material, effectively remove light components, improve the molecular structure, and enhance the quality and performance of mesophase asphalt.

[0022] Furthermore, in step S3, during the secondary heat treatment, the pressure inside reactor B is -0.1MPa to 1MPa, the heat treatment temperature is 250 to 400℃, and the heat treatment time is 2 to 10 hours. These conditions allow the asphalt molecules to continue to improve the polycyclic aromatic hydrocarbon structure at a lower reaction temperature and a longer time, further completing the transformation to the mesophase, ensuring that the material performance meets the standards, and improving the spinnability of the product.

[0023] Furthermore, reactor A and reactor B are connected by pipes, which changes the traditional batch reaction mode and allows for simultaneous heating, cooling, polycondensation and other operations, effectively saving time, improving production efficiency, reducing equipment failure frequency, reducing process variables, and improving batch-to-batch stability of products. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The image shows the mesophase asphalt prepared in Example 1 of this invention as observed under a hot-stage microscope. Figure 2 Thermogravimetric curve of the mesophase pitch prepared in Example 1 of this invention; Figure 3 The viscosity-temperature curve of the mesophase pitch prepared in Example 1 of this invention; Figure 4 The precursor fiber prepared by spinning the mesophase pitch prepared in Example 1 of this invention; Figure 5 The image shows the mesophase asphalt prepared in Example 2 of this invention as observed under a hot-stage microscope. Figure 6 Thermogravimetric curve of the mesophase pitch prepared in Example 2 of this invention; Figure 7 The viscosity-temperature curve of the mesophase pitch prepared in Example 2 of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0027] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0028] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0029] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0030] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0031] This invention provides a method for preparing spinnable mesophase pitch, comprising the following steps: S1: Pressurized thermal polycondensation reaction is carried out in reactor A using oil slurry as raw material.

[0032] In this step, the reaction pressure is 1~5MPa, the reaction temperature is 400~450℃, and the reaction time is 2~10h.

[0033] S2: Transfer the reactants from reactor A to reactor B.

[0034] During material transfer, the pressure inside reactor A is 0.1~1 MPa, and the pressure inside reactor B is -0.01~-0.1 MPa. The pressure difference is used to transfer the reactants from reactor A to reactor B. S3: Vacuum thermopolymerization reaction is carried out in reactor B.

[0035] In the vacuum thermal polycondensation reaction carried out in reactor B, the reaction pressure is -0.05 to -0.1 MPa, the reaction temperature is 360 to 430°C, and the reaction time is 2 to 12 hours.

[0036] S4: Secondary heat treatment is carried out in reactor B.

[0037] When secondary heat treatment is carried out in reactor B, the reaction pressure is -0.1MPa~1MPa, the reaction temperature is 250~400℃, and the reaction time is 2~10h.

[0038] The reactors A and B are connected by pipes to facilitate material transfer.

[0039] Furthermore, this invention discloses mesophase pitch prepared by the above method, wherein the mesophase content of the mesophase pitch is ≥98%. The higher mesophase content allows the pitch molecules to form a more ordered structure during heat treatment, which helps improve the performance of the final carbon material, such as strength, modulus, and thermal stability. Simultaneously, the high mesophase content of the pitch enables the formation of a more continuous fiber structure during carbon fiber preparation, thereby improving the mechanical and electrical properties of the carbon fiber. In addition, the softening point of the mesophase pitch in this invention is 285±10℃, which is moderate and has a narrow range, allowing for better temperature control flexibility during processing. This helps optimize subsequent processing steps such as spinning, oxidation, and carbonization, improving production efficiency and product quality. A higher softening point also indicates better thermal stability of the pitch at high temperatures, which is crucial for preparing carbon materials that require high-temperature applications (such as aerospace materials). The carbon residue is ≥75%, indicating a higher carbon content. A high carbon residue value means that the pitch can retain more carbon elements during high-temperature heat treatment, forming a high-density carbonaceous residue. This helps improve the yield and quality of carbon materials. Meanwhile, the high residual carbon value of the pitch forms a more stable carbon structure during carbonization, which helps to improve the mechanical properties and chemical stability of the final carbon material. Furthermore, the mesophase pitch in this invention has good spinnability, allowing it to pass smoothly through spinning equipment to form a continuous fiber structure. This is crucial for the preparation of high-performance carbon fibers, as continuous fibers have higher strength and modulus.

[0040] The "mesophase pitch" described in this invention is a special pitch material derived from the deep processing of coal tar or heavy petroleum components (such as oil slurry). Specifically, it is a substance with optical anisotropy formed by the deep thermal condensation reaction of heavy aromatic hydrocarbons under specific heat treatment conditions. Mesophase pitch exhibits significant optical anisotropy under a polarizing microscope, a key characteristic distinguishing it from other pitch materials. After high-temperature heat treatment, mesophase pitch forms carbonaceous residues with high carbon content, indicating its high carbon content and thermal stability. During spinning, mesophase pitch molecules are oriented and arranged under shear forces, forming a continuous fibrous structure, thus exhibiting good spinnability. Furthermore, mesophase pitch readily graphitizes at high temperatures, forming graphite materials with a layered structure, further expanding its application areas.

[0041] The "pressurized thermal polycondensation reaction" described in this invention is a thermal polycondensation process carried out under conditions higher than atmospheric pressure. Its main purpose is to promote the polycondensation reaction of heavy aromatic feedstocks at high temperatures by increasing pressure, thereby accelerating the formation and growth of the mesophase. Under pressurized conditions, the mobility of feedstock molecules increases, and the collision frequency increases, which is beneficial to the polycondensation reaction. Simultaneously, the high-pressure environment can suppress the occurrence of certain side reactions, improving the yield and quality of mesophase asphalt.

[0042] The "vacuum thermopolymerization reaction" described in this invention is a thermopolymerization process carried out under conditions below atmospheric pressure (i.e., a vacuum environment). Its main purpose is to promote the volatilization and removal of light components by reducing pressure, thereby further improving the structure and properties of mesophase asphalt. Under vacuum conditions, the volatilization and removal rates of light components (such as small molecule compounds and volatile substances) are accelerated, which is beneficial for reducing light components and enriching heavy components in mesophase asphalt. This helps to improve the molecular structure of mesophase asphalt and enhance its thermal stability, spinnability, and other properties.

[0043] This invention employs the needle penetration method to test the softening point of mesophase pitch. The needle penetration method is an experimental method used to measure the softening point of soft materials such as mesophase pitch. Its basic principle is based on the characteristic of material hardness changes during heating. As the temperature increases, mesophase pitch gradually softens, and its hardness gradually decreases. By measuring the depth to which a standard needle penetrates the material under specific conditions, the degree of softening can be assessed, and thus its softening point can be determined.

[0044] Furthermore, the "softening point" mentioned in this invention refers to the temperature at which mesophase asphalt begins to soften significantly during heating. At this temperature, the hardness of the asphalt decreases significantly, exhibiting a certain degree of fluidity.

[0045] In this invention, "mesophase content" refers to the proportion of mesophase (i.e., anisotropic phase) in mesophase asphalt. The mesophase is an ordered structure formed during the heat treatment of asphalt, possessing unique physical and chemical properties. The mesophase content is typically observed using a hot-stage microscope and calculated using image analysis software. Under the microscope, the mesophase region exhibits optical properties different from the isotropic non-mesophase region, and the mesophase content can be calculated through image analysis.

[0046] In this invention, "carbon residue" refers to the proportion of solid carbonaceous material remaining after mesophase asphalt has undergone heat treatment (such as carbonization) at high temperatures. It reflects the degree of carbon enrichment and thermal stability of the asphalt. Carbon residue is typically measured using methods such as thermogravimetric analysis (TGA). In TGA, the sample is heated to a high temperature under a controlled atmosphere, and its mass change with temperature is recorded. The carbon residue is the ratio of the sample's mass at which it no longer changes significantly at high temperatures to its original mass.

[0047] The "oil slurry" mentioned in this invention refers to the heavy residue oil remaining after crude oil has undergone refining processes such as distillation and cracking.

[0048] This invention uses oil slurry as raw material and employs a two-step polycondensation and secondary heat treatment method. Firstly, it connects two single-reactor reactors via pipelines, changing the traditional batch reaction mode where two-step thermal polycondensation is completed within the same reactor. This traditional mode requires completing the entire process of heating, positive pressure reaction, cooling, negative pressure reaction, and cooling again within the same reactor, which is time-consuming and energy-wasting. Furthermore, since positive and negative pressure reactions are performed separately within the same reactor, it easily leads to equipment mechanical failures and affects the production cycle. This invention uses reactor A and reactor B for pressurized thermal polycondensation and vacuum thermal polycondensation reactions respectively, allowing for simultaneous heating, cooling, and polycondensation operations, effectively saving time and improving production efficiency. Simultaneously, reactors A and B are dedicated to their respective functions, significantly reducing the frequency of equipment failures under the same reaction conditions. The process variables during each reactor's production are effectively reduced, and equipment and parameter fluctuations are significantly decreased. This solves the problem of inaccurate control over equipment conditions and reaction degree in batch reactions, effectively improving batch-to-batch stability and ensuring consistent product performance. On the other hand, the two-step thermal polycondensation method was optimized, which changed the high dependence and stringent requirements of the two-step thermal polycondensation method on vacuum degree. By performing secondary heat treatment on the vacuum polycondensation product, light components were further removed, and the asphalt molecules continued to improve the polycyclic aromatic hydrocarbon structure at a lower reaction temperature and a longer reaction time, and further completed the transformation into the meso phase, ensuring that the material performance met the standards. The final meso phase asphalt had a meso phase content of ≥98%, a softening point of 285±10℃, a carbon residue of ≥75%, and good spinnability.

[0049] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0050] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0051] Example 1 This embodiment provides a method for preparing spinnable mesophase pitch, including the following steps: S1: Using oil slurry as raw material, a pressurized thermal polycondensation reaction is carried out in reactor A. The reaction pressure is 2 MPa, the reaction temperature is 410~430℃, and the reaction time is 7 h.

[0052] S2: When the pressure inside reactor A is 0.5 MPa and the pressure inside reactor B is -0.08 MPa, the reactants are transferred from reactor A to reactor B.

[0053] S3: Vacuum thermal polycondensation reaction is carried out in reactor B at a pressure of -0.09 MPa, a temperature of 400~420℃, and a reaction time of 8 hours.

[0054] S4: Secondary heat treatment is carried out in reactor B, with a reaction pressure of 0 MPa, a reaction temperature of 350~400℃, and a reaction time of 8 hours.

[0055] The mesophase pitch prepared in this embodiment has a softening point of 288℃ (needle penetration method), a mesophase content of 99%, and a carbon residue of 76.68%. Its spinnability was simply evaluated using single-hole spinning. It can continuously spin filaments under conditions of ≥6 min. Further melt spinning verification was performed, and stable spinning with a length of ≥1000 m was achieved, proving that it has good spinnability.

[0056] Example 2 This embodiment provides a method for preparing spinnable mesophase pitch, including the following steps: S1: Using oil slurry as raw material, a pressurized thermal polycondensation reaction is carried out in reactor A. The reaction pressure is 2.5 MPa, the reaction temperature is 410~430℃, and the reaction time is 7 h.

[0057] S2: When the pressure inside reactor A is 0.6 MPa and the pressure inside reactor B is -0.04 MPa, the reactants are transferred from reactor A to reactor B.

[0058] S3: Vacuum thermal polycondensation reaction is carried out in reactor B at a pressure of -0.08 MPa, a temperature of 400~420℃, and a reaction time of 8 hours.

[0059] S4: Secondary heat treatment is carried out in reactor B, with a reaction pressure of 0.2 MPa, a reaction temperature of 350~400℃, and a reaction time of 10 h.

[0060] The mesophase pitch prepared in this embodiment has a softening point of 294℃ (needle penetration method), a mesophase content of 98%, a carbon residue of 81.05%, and good spinnability.

[0061] Example 3 This embodiment provides a method for preparing spinnable mesophase pitch, including the following steps: S1: Using oil slurry as raw material, a pressurized thermal polycondensation reaction is carried out in reactor A. The reaction pressure is 1 MPa, the reaction temperature is 400~415℃, and the reaction time is 10 h.

[0062] S2: When the pressure inside reactor A is 0.2 MPa and the pressure inside reactor B is -0.05 MPa, the reactants are transferred from reactor A to reactor B.

[0063] S3: Vacuum thermal polycondensation reaction is carried out in reactor B at a pressure of -0.05 MPa, a temperature of 400~420℃, and a reaction time of 4 hours.

[0064] S4: Secondary heat treatment is carried out in reactor B, with a reaction pressure of 0.4 MPa, a reaction temperature of 310~330℃, and a reaction time of 6 h.

[0065] The mesophase pitch prepared in this embodiment has a content of 98.5%, a softening point of 286℃ (needle penetration method), and a carbon residue of 77.32%. Furthermore, in single-hole spinning tests, this mesophase pitch can be continuously spun into filaments under conditions of ≥5 min. Further melt spinning verification achieved stable spinning of filaments with a length of ≥800 m, demonstrating good spinnability.

[0066] Example 4 This embodiment provides a method for preparing spinnable mesophase pitch, including the following steps: S1: Using oil slurry as raw material, a pressurized thermal polycondensation reaction is carried out in reactor A. The reaction pressure is 3 MPa, the reaction temperature is 415~425℃, and the reaction time is 6 hours.

[0067] S2: When the pressure inside reactor A is 0.5 MPa and the pressure inside reactor B is -0.04 MPa, the reactants are transferred from reactor A to reactor B.

[0068] S3: Vacuum thermal polycondensation reaction is carried out in reactor B at a pressure of -0.06 MPa, a temperature of 390~410℃, and a reaction time of 6 hours.

[0069] S4: Secondary heat treatment is carried out in reactor B, with a reaction pressure of 0.6 MPa, a reaction temperature of 290~310℃, and a reaction time of 4 h.

[0070] The mesophase pitch prepared in this embodiment has a content of 99.2%, a softening point of 292℃ (needle penetration method), and a carbon residue of 79.56%. Furthermore, in single-hole spinning tests, this mesophase pitch can be continuously spun into filaments under conditions of ≥7 min. Further melt spinning verification achieved stable spinning of filaments with a length of ≥1200 m, demonstrating its excellent spinnability.

[0071] Example 5 This embodiment provides a method for preparing spinnable mesophase pitch, including the following steps: S1: Using oil slurry as raw material, a pressurized thermal polycondensation reaction is carried out in reactor A. The reaction pressure is 4 MPa, the reaction temperature is 425~435℃, and the reaction time is 4 h.

[0072] S2: When the pressure inside reactor A is 0.7 MPa and the pressure inside reactor B is -0.03 MPa, the reactants are transferred from reactor A to reactor B.

[0073] S3: Vacuum thermal polycondensation reaction is carried out in reactor B at a pressure of -0.07 MPa, a temperature of 380~400℃, and a reaction time of 10 h.

[0074] S4: Secondary heat treatment is carried out in reactor B, with a reaction pressure of 0.8 MPa, a reaction temperature of 270~290℃, and a reaction time of 2 hours.

[0075] The mesophase pitch prepared in this embodiment has a content of 98.7%, a softening point of 289℃ (needle penetration method), and a carbon residue of 78.15%. Furthermore, in single-hole spinning tests, it can continuously spin filaments within ≥6 minutes. During melt spinning verification, stable spinning with a length ≥900m was achieved, indicating that this mesophase pitch has good spinnability.

[0076] Example 6 This embodiment provides a method for preparing spinnable mesophase pitch, including the following steps: S1: Using oil slurry as raw material, a pressurized thermal polycondensation reaction is carried out in reactor A. The reaction pressure is 5 MPa, the reaction temperature is 430~450℃, and the reaction time is 2 hours.

[0077] S2: When the pressure inside reactor A is 0.8 MPa and the pressure inside reactor B is -0.02 MPa, the reactants are transferred from reactor A to reactor B.

[0078] S3: Vacuum thermal polycondensation reaction is carried out in reactor B at a pressure of -0.07 MPa, a temperature of 360~380℃, and a reaction time of 12h.

[0079] S4: Secondary heat treatment is carried out in reactor B, with a reaction pressure of -0.1MPa, a reaction temperature of 250~270℃, and a reaction time of 5h.

[0080] The mesophase pitch prepared in this embodiment has a content of 98.3%, a softening point of 287℃ (needle penetration method), and a carbon residue of 76.89%. Furthermore, in single-hole spinning tests, this pitch can be continuously spun into filaments under conditions of ≥5.5 min. During melt spinning, stable spinning with a length of ≥850 m was achieved, demonstrating good spinnability.

[0081] Figure 1 The image shows a photograph of the mesophase pitch prepared in Example 1 of this invention under a hot-stage microscope. As can be seen from the image, a large area of ​​continuous mesophase can be observed in the field of view, and almost no black, optically inactive isotropic non-mesophase can be seen. According to image analysis, the mesophase content is 99%, which is a high-content, high-quality spinnable mesophase pitch.

[0082] Figure 2 The thermogravimetric curve (TGA) of the mesophase pitch prepared in Example 1 of this invention is shown in the figure. As can be seen, the curve exhibits a gentle, slight weight loss below approximately 300°C, indicating that the mesophase pitch possesses good thermal stability and a wide spinnable window, which is beneficial for subsequent melt spinning processes. Weight loss occurs between 300-700°C. Compared to conventional isotropic pitch, the weight loss step of this mesophase pitch is steeper, and the thermogravimetric loss is concentrated and occurs within a narrow temperature range, indicating that the mesophase pitch has a uniform composition and reactivity and exhibits high reaction efficiency. When the temperature exceeds 800°C, the weight loss curve tends to flatten, forming a stable plateau at a high residual carbon value of 76.68%, indicating that the pitch has high aromaticity and a high carbon yield.

[0083] Figure 3The viscosity-temperature curve of the mesophase pitch prepared in Example 1 of the present invention is shown in the figure. As can be seen from the figure, the viscosity of the mesophase pitch is relatively high in the low temperature region. When the temperature rises to 340℃, the viscosity drops sharply. It reaches and maintains a relatively wide low viscosity plateau in the range of 350℃-400℃, forming an ideal spinning window plateau. The viscosity changes little in this temperature range, which is beneficial to stable spinning.

[0084] Figure 4 The precursor fiber prepared by melt spinning of the mesophase pitch prepared in Example 1 of this invention is shown in the figure. As can be seen from the figure, the specification of the mesophase pitch-based carbon fiber precursor fiber is 1350m / spool, which proves that the pitch has good spinnability and continuity.

[0085] Figure 5 The image shows a photograph of the mesophase asphalt prepared in Example 2 of this invention under a hot-stage microscope. As can be seen from the image, the anisotropic region of the mesophase asphalt is continuous and well-developed. Image analysis shows that the mesophase content is 98%, which is a high-content, high-quality spinnable mesophase asphalt.

[0086] Figure 6 The thermogravimetric curve of the mesophase pitch prepared in Example 2 of this invention is shown in the figure. As can be seen from the figure, the pitch begins to lose weight significantly at about 350°C, and the weight loss is basically completed at about 750°C. Then the curve enters the flat region, and the final carbon residue value is 81.05%, which indicates that the mesophase pitch has a high carbon residue value, uniform composition, good thermal stability, excellent spinning performance, high raw material conversion rate, and small carbonization shrinkage. It can be used to prepare high modulus and high strength mesophase pitch-based carbon fibers.

[0087] Figure 7 The viscosity-temperature curve of the mesophase pitch prepared in Example 2 of the present invention is shown in the figure. As can be seen from the figure, there is a relatively stable low viscosity plateau in the range of 360℃-420℃. The pitch has stable rheological properties and is less affected by temperature, which is conducive to achieving stable and continuous melt spinning.

[0088] This invention addresses the problems of low product qualification rate, poor stability, and low production efficiency faced by current batch reaction methods in production. It proposes a spinnable mesophase pitch and its preparation method. Using oil slurry as raw material, this invention employs a two-step polycondensation and secondary heat treatment method, sequentially carrying out relevant reactions in different reactors and utilizing pressure difference to achieve material transfer. This produces high-quality mesophase pitch with a mesophase content ≥98%, a softening point of 285±10℃, and a carbon residue ≥75%, exhibiting excellent spinnability. It is a superior precursor for preparing high-performance mesophase pitch-based carbon fibers.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A process for the preparation of spinnable mesophase pitch, characterized in that, The method comprises the following steps: S1: performing a pressurized thermal polycondensation reaction in a reaction kettle A with slurry as raw material; S2: transferring the reaction material in the reaction kettle A to a reaction kettle B; S3: continuing to perform a vacuum thermal polycondensation reaction and a secondary heat treatment in the reaction kettle B in sequence to obtain the indicated spinnable mesophase pitch.

2. The process for preparing a spinnable mesophase pitch according to claim 1, characterized by, In step S1, the reaction pressure of the pressurized thermal polycondensation reaction is 1-5 MPa.

3. The method for preparing spinnable mesophase pitch according to claim 1, characterized in that, In step S1, the reaction temperature of the pressurized thermal polycondensation reaction is 400-450℃, and the reaction time is 2-10 h.

4. The process for preparing a spinnable mesophase pitch according to claim 1, characterized by, In step S2, when the material is transferred, the pressure in the reaction kettle A is 0.1-1 MPa.

5. The method for preparing spinnable mesophase pitch according to claim 1, characterized in that, In step S2, when the material is transferred, the pressure in the reaction kettle B is -0.01--0.1 MPa.

6. The method for preparing spinnable mesophase pitch according to claim 1, characterized in that, In step S3, when the vacuum thermal polycondensation reaction is performed, the reaction pressure is -0.05--0.1 MPa, the reaction temperature is 360-430℃, and the reaction time is 2-12 h.

7. The method for preparing spinnable mesophase pitch according to claim 1, characterized in that, In step S3, when the secondary heat treatment is performed, the pressure in the reaction kettle B is -0.1 MPa-1 MPa, the heat treatment temperature is 250-400℃, and the heat treatment time is 2-10 h.

8. The process for preparing a spinnable mesophase pitch according to claim 1, characterized by, The reaction kettle A and the reaction kettle B are connected by a pipeline.

9. A spinnable mesophase pitch characterized in that, The method is prepared by any one of claims 1-8.

10. A spinnable mesophase pitch according to claim 8, wherein The mesophase pitch has a mesophase content of ≥98%, a softening point of 285±10℃, and a carbon residue content of ≥75%.

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