Preparation method of spinnable mesophase pitch

Abstract

The invention belongs to the field of coal chemical industry and novel carbon materials, and discloses a spinnable mesophase pitch preparation method, which comprises: carrying out heat treatment on a raw material to prepare pyrolytic pitch; carrying out solvent extraction separation on the pyrolytic asphalt to obtain insoluble substances; and carrying out hot filtration orientation on the insoluble substance to obtain the mesophase pitch. The heat treatment-solvent extraction process adopted by the invention can significantly improve the anisotropic content of the mesophase pitch, and lays a structural foundation for subsequent spinnability. According to the hot-melting filtering process, high-viscosity impurities can be selectively removed in a molten state, spinning resistance can be reduced, meanwhile, high-orientation components are reserved, the balance of rheological property and molecular orientation is achieved, and pre-orientation is achieved before melt spinning, so that the spinnability of mesophase pitch is improved, and the mechanical property and heat-conducting property of graphite fibers are further improved. The mesophase pitch prepared by the method has good spinnability, and is greatly helpful for improving the mechanical property and heat-conducting property of the graphite fiber.

Description

Technical Field

[0001] The present invention belongs to the fields of coal chemical industry and new carbon materials, and relates to a preparation method of spinnable mesophase pitch. Background Art

[0002] In recent years, with the continuous development of new carbon material preparation technologies, high-performance pitch-based carbon fibers have been widely used in the fields of thermal management materials and C / C composite materials due to their characteristics of high thermal conductivity, high modulus, high temperature resistance, and corrosion resistance, and are one of the important military materials. One of the key technical bottlenecks in the preparation of high-performance pitch-based carbon fibers is the preparation of high-quality spinnable mesophase pitch. This requires that the mesophase pitch has the characteristics of high mesophase content, low softening point, and low heteroatom content, so that continuous spinning can be carried out within a large spinnable temperature range. However, the main key problem existing in the current domestic mesophase pitch preparation technology is the contradiction between the mesophase content and the softening point: pitch with a high mesophase content usually has a relatively high softening point, resulting in poor fluidity during melt spinning, and prone to filament breakage or uneven fiber diameter; while reducing the softening point may introduce too many light components, affecting the orientation degree and mechanical properties of the final carbon fiber.

[0003] To prepare highly spinnable mesophase pitch, researchers have done a lot of research. Chinese Patent with Publication No. CN118087095A discloses "a high thermal conductivity mesophase pitch-based carbon fiber precursor and its preparation method", which uses petroleum resid as raw material, forms mesophase under mild conditions, and improves the mesophase content through the treatment process of N2 purging. However, this method consumes a large amount of N2 and has the disadvantage of low mesophase yield. Chinese Patent with Publication No. CN117512816A discloses "a method for preparing mesophase pitch-based carbon fiber using coal tar pitch", which uses coal tar pitch as raw material, obtains pyrolysis products through an alternating method of polycondensation reaction and hydrogenation reaction, and uses pyridine as a solvent in the subsequent process, extracts and separates insoluble substances, and uses them as raw materials for spinning. This treatment process using pyridine as an extractant faces the disadvantages of large extractant consumption, high cost, and difficult separation, and it is also difficult to ensure a high yield. Chinese Patent with Publication No. CN112048332B discloses "a centrifugal circulation magnetic drive thin film evaporator for preparing mesophase pitch-based carbon fiber". This invention can remove light components in mesophase pitch through a thin film evaporation process and enrich anisotropic components therein. This thin film evaporation equipment has the problem of low production capacity and is difficult to adapt to industrial production. Summary of the Invention

[0004] The present invention provides a method for preparing spinnable mesophase pitch. By adopting a heat treatment-solvent extraction process, mesophase pitch with a high anisotropy content is prepared. Then, through a hot melt filtration process, the high-viscosity components in the mesophase pitch are removed directionally, and at the same time, pre-orientation of the mesophase pitch before melt spinning is achieved, thereby preparing highly spinnable mesophase pitch.

[0005] The technical solution of the present invention:

[0006] A method for preparing spinnable mesophase pitch, comprising the following steps:

[0007] Step 1: Place the raw pitch in a reaction kettle, and subject it to heat treatment at 380 - 460°C and 0.1 - 5 MPa for 1 - 30 h under an inert atmosphere; after the reaction ends, rapidly cool down to obtain pyrolytic pitch.

[0008] Step 2: Crush the pyrolytic pitch obtained in Step 1, and after passing through a 60 - 300 mesh sieve, place the pyrolytic pitch powder in an aromatic solvent for extraction. The mass ratio of the pyrolytic pitch to the extractant is 1:1 - 50, the extraction temperature is controlled at 20 - 80°C, and the extraction time is 1 - 6 h. After the extraction ends, filter the obtained suspension to obtain the insoluble matter.

[0009] Step 3: After vacuum drying the insoluble matter obtained in Step 2, heat it to a molten state 5 - 100°C above the softening point under an inert atmosphere, and process it through a hot melt filtration process at a pressure of 0.1 - 5 Mpa for 5 - 30 min, thereby preparing spinnable mesophase pitch.

[0010] In Step 1, it is preferred that the heat treatment temperature is 420 - 440°C, the heat treatment time is 5 - 13 h, and the pressure is 0.1 - 1.5 Mpa.

[0011] In Step 2, it is preferred to pass through a 60 - 100 mesh sieve after crushing, and the solvent is selected from one or more of benzene, toluene, and xylene. The mass ratio of the pyrolytic pitch to the extractant is preferably 1:5 - 10, the extraction temperature is 20 - 50°C, and the extraction time is 2 - 5 h.

[0012] In Step 3, it is preferred that the hot melt filtration temperature is 20 - 50°C above the softening point, the pressure is 0.5 - 2 Mpa, and the time is 5 - 20 min.

[0013] The material of the filter element used in the hot melt filtration operation in Step 3 includes but is not limited to metal sintered materials, ceramic materials, carbon / graphite materials and their composites. The thickness of the filter element is preferably 1 - 10 mm, and the pore size distribution range is preferably 1 - 150 μm.

[0014] The beneficial effects of the present invention are:

[0015] 1. The heat treatment - solvent extraction process can significantly increase the anisotropic content of mesophase pitch, laying a structural foundation for subsequent spinnability.

[0016] 2. The hot melt filtration process can selectively remove high - viscosity impurities (such as quinoline insoluble matter, macromolecular aggregates) in the molten state, reduce the spinning resistance, while retaining highly oriented components, achieve the balance of rheological properties and molecular orientation, and pre - orient it before melt spinning, thereby improving the spinnability of mesophase pitch and further enhancing the mechanical and thermal conductivity of graphite fibers. Specific Embodiments

[0017] The following further illustrates the specific embodiments of the present invention in combination with the technical solutions.

[0018] Example 1

[0019] Step 1: Place 300 g of coal tar pitch in a reaction kettle, and subject it to heat treatment for 7 h under the conditions of N2 atmosphere, a temperature of 430 °C, and a pressure of 2 MPa. After the reaction is completed, rapidly cool down to obtain pyrolytic pitch.

[0020] Step 2: Crush the pyrolytic pitch obtained in Step 1, pass it through a 100 - mesh sieve, and then place the pyrolytic pitch powder in xylene for extraction. The mass ratio of pyrolytic pitch to the extractant is 1:10, the extraction temperature is controlled at 50 °C, and the extraction time is 3 h. After the extraction is completed, filter the obtained suspension to obtain the insoluble matter.

[0021] Step 3: After vacuum - drying the insoluble matter obtained in Step 2, heat it to 330 °C in an N2 atmosphere and treat it by the hot melt filtration process at a pressure of 1 Mpa for 10 min, passing through a metal sintered filter element with a thickness of 5 mm and a pore diameter of 10 μm, thereby preparing a spinnable mesophase pitch product. Its continuous spinning length is greater than 10000 m, and the tensile strength of the graphite fiber prepared therefrom can reach 2.8 GPa, and the axial thermal conductivity is 650 W / (m·K).

[0022] Comparative Example 1

[0023] Step 1: Place 300 g of coal tar pitch in a reaction kettle, and subject it to heat treatment for 7 h under the conditions of N2 atmosphere, a temperature of 430 °C, and a pressure of 2 MPa. After the reaction is completed, rapidly cool down to obtain pyrolytic pitch.

[0024] Step 2: Crush the pyrolytic pitch obtained in Step 1, pass it through a 100 - mesh sieve, and then place the pyrolytic pitch powder in xylene for extraction. The mass ratio of pyrolytic pitch to the extractant is 1:10, the extraction temperature is controlled at 50 °C, and the extraction time is 3 h. After the extraction is completed, filter the obtained suspension to obtain the insoluble matter.

[0025] Step 3: Vacuum dry the insoluble matter obtained in Step 2 and place it in a reaction kettle. Heat-treat it for 20 min under the conditions of 330 °C and normal pressure in an N2 atmosphere. After the heat treatment, rapidly cool down to obtain mesophase pitch. Its maximum continuous spinning length does not exceed 200 m, and the tensile strength of the graphite fiber prepared therefrom is 1.8 GPa, and the axial thermal conductivity is 320 W / (m·K).

[0026] Compared with Comparative Example 1, after hot melt filtration in Example 1, the spinnability is significantly improved, and the mechanical properties and thermal conductivity of the graphite fiber obtained after graphitization are significantly improved. This is because the hot melt filtration process can effectively intercept the high-viscosity and thermosetting components in the mesophase pitch, avoiding the occurrence of broken filaments during the spinning process. At the same time, during this process, the anisotropic components are directionally rearranged to form a highly ordered microcrystalline structure, which is beneficial to the improvement of the mechanical and thermal conductivity of the graphite fiber.

[0027] Comparative Example 2

[0028] Step 1: Place 300 g of coal tar pitch in a reaction kettle. Heat-treat it for 7 h under the conditions of 430 °C and a pressure of 2 MPa in an N2 atmosphere. After the reaction, rapidly cool down to obtain pyrolytic pitch.

[0029] Step 2: Crush the pyrolytic pitch obtained in Step 1. After passing through a 100-mesh sieve, place the pyrolytic pitch powder in xylene for extraction. The mass ratio of the pyrolytic pitch to the extractant is 1:10. Control the extraction temperature at 50 °C and the extraction time at 3 h. After the extraction, filter the obtained suspension to obtain the insoluble matter.

[0030] Step 3: Vacuum dry the insoluble matter obtained in Step 2, heat it to 330 °C in an N2 atmosphere, and treat it by the hot melt filtration process under a pressure of 1 Mpa for 10 min. Pass through a metal sintered filter element with a thickness of 5 mm and a pore size of 200 μm to prepare a spinnable mesophase pitch product. Its continuous spinning length is greater than 1000 m, and the tensile strength of the graphite fiber prepared therefrom can reach 2.1 GPa, and the axial thermal conductivity is 360 W / (m·K).

[0031] Compared with Example 1 in Comparative Example 2, after passing through a metal sintered filter element with a smaller pore size in the hot melt filtration operation, the selectivity for high-viscosity components is improved, thereby significantly improving the spinnability of the mesophase pitch, and the mechanical properties and thermal conductivity of the graphite fiber obtained after graphitization are improved.

[0032] Example 2

[0033] Step 1: Place 300 g of coal liquefaction pitch in a reaction kettle. Heat-treat it for 13 h under the conditions of 430 °C and a pressure of 1 MPa in an N2 atmosphere. After the reaction, rapidly cool down to obtain pyrolytic pitch.

[0034] Step 2: Crush the pyrolytic pitch obtained in Step 1. After passing through a 100-mesh sieve, place the pyrolytic pitch powder in xylene for extraction. The mass ratio of pyrolytic pitch to the extractant is 1:10. Control the extraction temperature at 30°C and the extraction time at 3 h. After the extraction is completed, filter the obtained suspension to obtain the insoluble matter.

[0035] Step 3: After vacuum-drying the insoluble matter obtained in Step 2, heat it to 350°C under a N2 atmosphere and treat it by a hot-melt filtration process at a pressure of 1 Mpa for 10 min through a metal sintered filter element with a thickness of 5 mm and a pore size of 1 μm, thereby preparing a spinnable mesophase pitch product with a continuous spinning length greater than 5000 m, and the tensile strength of the graphite fiber prepared therefrom can reach 2.5 GPa and the axial thermal conductivity is 490 W / (m·K).

[0036] Example 3

[0037] Step 1: Place 300 g of FCC slurry in a reaction kettle and subject it to heat treatment for 9 h under a N2 atmosphere at a temperature of 440°C and a pressure of 3 Mpa. After the reaction is completed, rapidly cool down to obtain pyrolytic pitch.

[0038] Step 2: Crush the pyrolytic pitch obtained in Step 1. After passing through a 100-mesh sieve, place the pyrolytic pitch powder in xylene for extraction. The mass ratio of pyrolytic pitch to the extractant is 1:20. Control the extraction temperature at 50°C and the extraction time at 3 h. After the extraction is completed, filter the obtained suspension to obtain the insoluble matter.

[0039] Step 3: After vacuum-drying the insoluble matter obtained in Step 2, heat it to 320°C under a N2 atmosphere and treat it by a hot-melt filtration process at a pressure of 1 Mpa for 10 min through a metal sintered filter element with a thickness of 5 mm and a pore size of 1 μm, thereby preparing a spinnable mesophase pitch product with a continuous spinning length greater than 10000 m, and the tensile strength of the graphite fiber prepared therefrom can reach 2.4 GPa and the axial thermal conductivity is 420 W / (m·K).

[0040] Example 4

[0041] Step 1: Place 300 g of ethylene tar in a reaction kettle and subject it to heat treatment for 7 h under a N2 atmosphere at a temperature of 420°C and a pressure of 0.5 Mpa. After the reaction is completed, rapidly cool down to obtain pyrolytic pitch.

[0042] Step 2: Crush the pyrolytic pitch obtained in Step 1. After passing through a 100-mesh sieve, place the pyrolytic pitch powder in xylene for extraction. The mass ratio of pyrolytic pitch to the extractant is 1:30. Control the extraction temperature at 20°C and the extraction time at 3 h. After the extraction is completed, filter the obtained suspension to obtain the insoluble matter.

[0043] Step 3: After vacuum drying the insoluble matter obtained in Step 2, heat it to 350 °C under a N2 atmosphere, and perform a hot melt filtration process treatment for 10 min under a pressure of 2 Mpa, passing through a metal sintered filter element with a thickness of 5 mm and a pore size of 1 μm, thereby preparing a spinnable mesophase pitch product, whose continuous spinning length is greater than 8000 m, and the tensile strength of the graphite fiber prepared therefrom can reach 2.1 GPa, and the axial thermal conductivity is 510 W / (m·K).

Claims

1. A method for preparing a spinnable mesophase pitch, characterized in that: The following steps are involved: Step 1: placing the raw asphalt in a reactor, subjecting it to heat treatment at 380-460°C and 0.1-5MPa for 1-30h under an inert atmosphere; cooling rapidly after the reaction to obtain pyrolysis asphalt; Step 2: crush the pyrolysis asphalt obtained in step 1, pass it through a 60-300 mesh sieve, and then extract the pyrolysis asphalt powder in an aromatic solvent. The mass ratio of pyrolysis asphalt to extractant is 1:1-50, the extraction temperature is controlled at 20-80°C, and the extraction time is 1-6 hours. After the extraction, filter the obtained suspension to obtain insoluble matter. Step 3: After vacuum drying the insoluble matter obtained in step 2, heat it to a molten state of 5 to 100° C. above the softening point under an inert atmosphere, and treat it by hot melt filtration process at a pressure of 0.1 to 5 MPa for 5 to 30 minutes to prepare a spinnable mesophase asphalt.

2. The preparation method according to claim 1, characterized in that: In step 1, the heat treatment temperature is 420-440° C., the heat treatment time is 5-13 h, and the pressure is 0.1-1.5 MPa.

3. The preparation method according to claim 1, characterized in that: In step 2, after crushing, the asphalt is sieved through a 60-100 mesh sieve, and the aromatic solvent is selected from one or a combination of two or more of benzene, toluene, and xylene; the mass ratio of pyrolysis asphalt to aromatic solvent is 1:5-10, the extraction temperature is 20-50°C, and the extraction time is 2-5h.

4. The preparation method according to claim 1, characterized in that: In step 3, the hot melt filtration temperature is 20 to 50° C. above the softening point, the pressure is 0.5 to 2 MPa, and the time is 5 to 20 min.

5. The preparation method according to claim 1, characterized in that: In step 3, the material of the filter element used in the hot melt filtration operation includes but is not limited to metal sintered materials, ceramic materials, carbon / graphite materials and composite materials thereof, the filter element thickness is 1 to 10 mm, and the pore size distribution range is 1 to 150 μm.