Production process of isostatic graphite, isostatic graphite and its application

Abstract

The present invention provides a production process of isostatic graphite, isostatic graphite and application, and specifically relates to the field of graphite production technology. The production process comprises the following steps: A. mixing calcined petroleum coke and fluorinated pitch, kneading and coarsely crushing to obtain a coarse crushed material; B. crushing the coarse crushed material and cold isostatic pressing to obtain a raw product; C. subjecting the raw product to a roasting and impregnation cycle and a final roasting to obtain an isostatic graphite semi-finished product; D. graphitizing the isostatic graphite semi-finished product at 2300°C to 2500°C for 60h to 70h to obtain the isostatic graphite. The production process uses fluorinated pitch to release fluorine gas during the roasting process, which reacts with metal impurities in the roasted product to generate metal fluoride to escape, and further graphitizes to obtain ultra-high purity and uniform isostatic graphite.

Description

Technical Field

[0001] The invention relates to the technical field of graphite production, in particular to a production process of isostatically pressed graphite, isostatically pressed graphite and applications. Background Art

[0002] The graphite materials used in the semiconductor industry are required to be as pure as possible, especially graphite devices that are in direct contact with semiconductor materials, such as crucibles and sintering molds. High impurity content will contaminate the semiconductor materials.

[0003] The semiconductor industry requires that the graphite material used must have fine particle size. Graphite with fine particle size is not only easy to achieve processing accuracy but also has high high temperature strength and low loss. In particular, molds used for sintering require very high processing accuracy.

[0004] At present, the research on graphite purification is mainly focused on the purification of graphite powder. The more effective purification methods include alkali fusion, acid leaching combined chemical method, hydrofluoric acid method, high temperature method, chlorine roasting method and Freon method. For graphite powder, the hydrofluoric acid method can achieve 99.9%, and the high temperature method can achieve 99.99%.

[0005] There is currently no good purification solution for graphite block purification, especially the semiconductor field's requirements for ultrapure and ultrafine graphite blocks, which further increases the difficulty of purification: ultrafine graphite has low porosity, which is not conducive to the diffusion of reaction gases and the escape of impurities generated after the reaction during gas refining, making it difficult to achieve the goal of ultrapurity. In actual production, chlorine and other halogen gases are often used to purify graphite blocks, but there are problems such as different sampling depths of graphite blocks and large differences in impurity content. The purity of the surface of the graphite block is significantly higher than that of the inside of the block, and the difference is even 4-5 times.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] One of the purposes of the present invention is to provide a production process for isostatic graphite to alleviate the technical problem of uneven purity in the preparation process of isostatic graphite in the prior art.

[0008] In order to solve the above-mentioned technical problems, the present invention particularly adopts the following technical solutions:

[0009] A first aspect of the present invention provides a process for producing isostatic graphite, comprising the following steps:

[0010] A. mixing calcined petroleum coke and fluorinated asphalt, kneading and coarsely crushing to obtain a coarse crushed material;

[0011] B. crushing the coarsely crushed material and then performing cold isostatic pressing to obtain a raw product;

[0012] C. subjecting the raw product to a roasting and impregnation cycle and then to a final roasting to obtain an isostatic graphite semi-finished product;

[0013] D. Graphitizing the isostatic graphite semi-finished product at 2300° C. to 2500° C. for 60 h to 70 h to obtain the isostatic graphite.

[0014] Optionally, the roasting and impregnation cycles are performed twice.

[0015] Preferably, the roasting and impregnation cycle comprises a first roasting, a first impregnation, a second roasting and a second impregnation performed in sequence.

[0016] Optionally, the first calcination time is 500 h to 800 h.

[0017] Preferably, the time of the second calcination and the final calcination are independently 120 h to 170 h.

[0018] Preferably, the temperatures of the first calcination, the second calcination and the final calcination are independently 800°C to 1300°C.

[0019] Preferably, the temperatures of the first impregnation and the second impregnation are independently 150°C to 250°C.

[0020] Preferably, the pressure of the first impregnation and the second impregnation are independently 4 MPa to 4.5 MPa.

[0021] Optionally, the fluorinated asphalt has an ash content of ≤0.1%, a softening point of ≥120° C., quinoline insoluble matter of ≤1%, and a fluorine content of 6% to 20%.

[0022] Preferably, the first impregnation and the second impregnation use a first impregnation fluorinated asphalt and a second impregnation fluorinated asphalt respectively.

[0023] Preferably, the first impregnated fluorinated asphalt has an ash content of ≤0.05%, a softening point of 80°C to 95°C, quinoline insolubles of ≤0.5% and a fluorine content of 3% to 5%.

[0024] Preferably, the second impregnated fluorinated asphalt has an ash content of ≤0.05%, a softening point of 80°C to 95°C, quinoline insolubles of ≤0.01% and a fluorine content of 0.5% to 2%.

[0025] Optionally, the mass ratio of the calcined petroleum coke to the fluorinated asphalt is 3 to 4:1.

[0026] Preferably, the ash content of the calcined petroleum coke is ≤0.7%, and the degree of graphitization is ≥80%.

[0027] Preferably, the particle size of the calcined petroleum coke is 5 μm to 10 μm.

[0028] Optionally, in step A, the particle size of the coarsely crushed material is less than 1 mm.

[0029] Preferably, in step B, the coarsely crushed material is crushed to obtain a finely crushed material, and the particle size of the finely crushed material is 3 μm to 5 μm.

[0030] Optionally, the method further includes a vacuuming process after the first calcination, the second calcination and the final calcination are completed.

[0031] Preferably, the vacuum degree after evacuation is -95 kPa to -98 kPa.

[0032] Optionally, the cold isostatic pressing pressure is 280 MPa to 320 MPa.

[0033] Preferably, the cold isostatic pressing time is 30 min to 80 min.

[0034] The second aspect of the present invention provides isostatic graphite produced by the production process.

[0035] The third aspect of the present invention provides the application of the isostatically pressed graphite in the semiconductor field.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] The production process provided by the present invention utilizes ultrafine grinding and uniform kneading technology to fully mix fluorinated coal tar pitch with calcined petroleum coke, which is beneficial to the reaction between metal impurities and fluorine gas released by decomposition; fluorinated tar pitch releases fluorine gas during the roasting process, which reacts with metal impurities in the calcined petroleum coke to generate metal fluoride that escapes from the roasted product, so that impurities in the calcined petroleum coke are removed; the products after the fluorinated tar pitch is decomposed are fluorine gas and compounds containing elements such as C / H, and no impurities are introduced; in the raw product, the uniformly mixed calcined petroleum coke and fluorinated tar pitch are in full contact, so that sufficient fluorine gas inside the raw product reacts with the calcined petroleum coke, so as to obtain isostatic graphite with uniform purity; the roasting and impregnation cycle can further remove impurities, so as to obtain isostatic graphite with high purity.

[0038] The purity of the isostatically pressed graphite provided by the invention can reach 99.9999%, thus expanding its industrial application.

[0039] The application of the isostatically pressed graphite provided by the present invention provides graphite with higher purity for the semiconductor field, thus promoting the development of the semiconductor industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 The production process flow chart provided for Example 1. DETAILED DESCRIPTION

[0042] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in combination with the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, but not all of the embodiments. The components of the embodiment of the present invention can be arranged and designed in various different configurations.

[0043] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0044] At present, the purification of isostatic graphite is usually carried out at high temperature using gases such as chlorine, fluorine, and Freon. Impurities are halogenated into low-boiling halides and then volatilized and removed. The impurities in the graphite block obtained by this purification method are easily unevenly distributed, and the purity inside the block is difficult to meet the requirements of semiconductor applications. In addition, some processes increase the purity of the final graphite products by adding steps to control impurities during the preparation of isostatic graphite, such as adding raw material or roasted product purification steps, but this method increases the complexity of the process and it is still difficult to meet the requirements of ultra-high purity semiconductor graphite ash content <5ppm.

[0045] According to a first aspect of the present invention, a production process for isostatic graphite is provided, comprising the following steps:

[0046] A. mixing calcined petroleum coke and fluorinated asphalt, kneading and coarsely crushing to obtain a coarse crushed material;

[0047] B. crushing the coarsely crushed material and then performing cold isostatic pressing to obtain a raw product;

[0048] C. subjecting the raw product to a roasting and impregnation cycle and then to a final roasting to obtain an isostatic graphite semi-finished product;

[0049] D. Graphitizing the isostatic graphite semi-finished product at 2300° C. to 2500° C. for 60 h to 70 h to obtain the isostatic graphite.

[0050] The production process provided by the present invention comprises the following steps: during the roasting process, fluorinated pitch releases fluorine gas, which reacts with metal impurities in calcined petroleum coke to generate metal fluoride that escapes from the roasted product, thereby removing impurities in the calcined petroleum coke; after the fluorinated pitch is decomposed, the products are fluorine gas and compounds containing elements such as C / H, without introducing impurities; in the raw product, the evenly mixed calcined petroleum coke and the fluorinated pitch are in full contact, so that there is also sufficient fluorine gas in the raw product to react with the calcined petroleum coke, thereby obtaining isostatic graphite with uniform purity; and the roasting and impregnation cycle can further remove impurities, thereby obtaining isostatic graphite with high purity.

[0051] Calcined petroleum coke is the product of high-temperature calcination of petroleum coke. After calcination in an airtight environment, most of the moisture, ash and volatile matter in the petroleum coke are removed. At this time, the structure and elemental composition of the carbonaceous raw materials undergo a series of profound changes, and the physical and chemical properties are stable, thus obtaining calcined petroleum coke.

[0052] Fluorinated asphalt is a light yellow or black substance. Depending on the raw materials, it can be powdery, liquid, or transparent. It has a high refractive index. It has similar softening and solubility to asphalt and can be dissolved in certain organic fluorine solvents. When heated, it will undergo a softening and melting process similar to asphalt. Fluorinated asphalt has good thermal and chemical stability, extremely low surface energy, and good processability. It is easy to make objects of various geometric shapes and apply, making it easy to use.

[0053] Optionally, the roasting and impregnation cycles are performed twice.

[0054] Preferably, the roasting and impregnation cycle comprises a first roasting, a first impregnation, a second roasting and a second impregnation performed in sequence.

[0055] Optionally, the first calcination time is 500 h to 800 h.

[0056] Preferably, the time of the second calcination and the final calcination are independently 120 h to 170 h.

[0057] Preferably, the temperatures of the first calcination, the second calcination and the final calcination are independently 800°C to 1300°C.

[0058] In some embodiments of the present invention, during the first calcination process, the temperature is raised to 500°C to 700°C in the 120h to 160h, raised to 900°C to 1100°C in the 180h to 220h, and raised to a maximum of 1300°C in the 350h to 450h, maintained at this temperature for 20h, then vacuumed at this temperature, and the pressure is gradually changed from a slight positive pressure to -95kPa within 10h, and maintained at this pressure and temperature for 3h to 8h. In the range of 500h to 800h, the temperature is lowered to 150°C before being taken out of the furnace.

[0059] In some embodiments of the present invention, the second calcination and final calcination process is to increase the temperature to 1300°C in 60h-84h, gradually change the pressure from slightly positive pressure to -0.095Mpa in 90h-104h, and maintain this pressure and temperature for 3h-10h. In the range of 120-170 hours, reduce the temperature to 150°C and take out of the furnace.

[0060] Preferably, the first calcination, the second calcination and the final calcination are all performed under the protection of an inert gas.

[0061] Optionally, the method further includes a vacuuming process after the first calcination, the second calcination and the final calcination are completed.

[0062] Preferably, the vacuum degree after evacuation is -95 kPa to -98 kPa.

[0063] Preferably, the temperatures of the first impregnation and the second impregnation are independently 150°C to 250°C.

[0064] Preferably, the pressure of the first impregnation and the second impregnation are independently 4 MPa to 4.5 MPa.

[0065] Preferably, the time of the first impregnation and the second impregnation are independently 24h-32h.

[0066] In some embodiments of the present invention, the calcined product obtained by the first calcination is placed in a container and evacuated to -0.99 MPa, a first impregnation fluorinated asphalt at 150°C to 250°C is added, the vacuum system is turned off, and the impregnation tank is continuously pressurized to 4MPa to 4.5MPa by liquid pressure for 24h-32h.

[0067] Optionally, the fluorinated asphalt has an ash content of ≤0.1%, a softening point of ≥120° C., quinoline insoluble matter of ≤1%, and a fluorine content of 6% to 20%.

[0068] Preferably, the first impregnation and the second impregnation use a first impregnation fluorinated asphalt and a second impregnation fluorinated asphalt respectively.

[0069] Preferably, the first impregnated fluorinated asphalt has an ash content of ≤0.05%, a softening point of 80°C to 95°C, quinoline insolubles of ≤0.5% and a fluorine content of 3% to 5%.

[0070] Preferably, the second impregnated fluorinated asphalt has an ash content of ≤0.05%, a softening point of 80°C to 95°C, quinoline insolubles of ≤0.01% and a fluorine content of 0.5% to 2%.

[0071] In some embodiments of the present invention, the second impregnated fluorinated asphalt is obtained by purifying and fluorinating the impregnated asphalt, wherein the ash content of the impregnated asphalt is ≤0.05%, the softening point is 80°C to 95°C, and the quinoline insoluble matter is ≤0.5%. The purification method is typically but not limited to the solvent sedimentation method, and the specific operation is to use a mixed solvent and impregnated asphalt with a mass ratio of 1:1 for sedimentation, the sedimentation temperature is 165°C, the sedimentation time is 1h, and after the sedimentation is completed, the upper liquid is distilled and desolventized to obtain the second impregnated fluorinated asphalt. The mixed solvent is a mixture of kerosene and solvent oil with a mass ratio of 3:1.

[0072] Optionally, the mass ratio of the calcined petroleum coke to the fluorinated asphalt is 3 to 4:1.

[0073] When the mass ratio of calcined petroleum coke to fluorinated pitch is less than 3:1, there is too much volatile matter, resulting in cracking of the calcined product. In addition, the excess fluorine will react with the calcined body to cause graphite defects. When the mass ratio of calcined petroleum coke to fluorinated pitch is greater than 4:1, the purification effect is not ideal. In some embodiments of the present invention, the mass ratio of calcined petroleum coke to fluorinated pitch is typically but not limited to 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1 or 4:1.

[0074] Preferably, the ash content of the calcined petroleum coke is ≤0.7%, and the degree of graphitization is ≥80%.

[0075] The ash content of calcined petroleum coke refers to the mineral impurities in the petroleum coke. The graphitization degree of calcined petroleum coke is a measure of the degree to which the crystals of calcined petroleum coke approach perfect graphite through structural rearrangement from amorphous carbon.

[0076] Preferably, the particle size of the calcined petroleum coke is 5 μm to 10 μm. In some embodiments of the present invention, the calcined petroleum coke is air flow crushed at room temperature to a particle size of 5 μm to 10 μm.

[0077] Optionally, in step A, the particle size of the coarsely crushed material is less than 1 mm.

[0078] Preferably, in step B, the coarsely crushed material is crushed to obtain a finely crushed material, and the particle size of the finely crushed material is 3 μm to 5 μm.

[0079] Optionally, the cold isostatic pressing pressure is 280 MPa to 320 MPa.

[0080] Preferably, the cold isostatic pressing time is 30 min to 80 min.

[0081] In some embodiments of the present invention, the isostatic pressing pressure is typically but not limited to 280 MPa, 290 MPa, 300 MPa, 310 MPa or 320 MPa; the cold isostatic pressing time is typically but not limited to 30 min, 40 min, 50 min, 60 min, 70 min or 80 min.

[0082] The second aspect of the present invention provides isostatic graphite produced by the production process.

[0083] The purity of the isostatically pressed graphite provided by the invention can reach 99.9999%, thus expanding its industrial application.

[0084] The third aspect of the present invention provides the application of the isostatically pressed graphite in the semiconductor field.

[0085] The application of the isostatically pressed graphite provided by the present invention provides graphite with higher purity for the semiconductor field, thus promoting the development of the semiconductor industry.

[0086] In the following, some embodiments of the present invention are described in detail in conjunction with the examples. In the absence of conflict, the following examples and features in the examples can be combined with each other. The raw materials in the examples and comparative examples can be obtained by commercial purchase if not specifically stated.

[0087] Example 1

[0088] This embodiment provides an isostatic graphite, the production process is as follows Figure 1 As shown, the details are as follows:

[0089] 1. Calcined petroleum coke with an ash content of 0.7% and a graphitization degree of 81% is pulverized by air flow at room temperature to an average particle size of 8 μm.

[0090] 2. Put 78 kg of crushed calcined petroleum coke into a kneader, preheat to 150°C, and then add 22 kg of fluorinated pitch, the ash content of the fluorinated pitch is 0.1%, the softening point is 125°C, the quinoline insoluble matter is 1% and the fluorine content is 10%. Heat the raw materials to 200°C and knead for 45 minutes, cool to 150°C, cool the material, and coarsely crush it to obtain a coarse material with a particle size of less than 1 mm.

[0091] 3. After the coarse crushed material is pulverized by air flow, the particle size is reduced to 3μm-5μm, and the fine crushed material is loaded into the mold sleeve of the compression mold, evacuated to -98kPa, and sent to the cold isostatic press for pressure molding, the molding pressure is 300MPa, and the molding time is 60min. A raw product with a length×width×height of 500×500×800mm is obtained.

[0092] 4. The first calcination is to load the raw product into a vacuum resistance heating furnace, under nitrogen protection, and heat it to 600℃ in the 150th hour, 1000℃ in the 200th hour, and 1300℃ in the 400th hour. Maintain it at this temperature for 20 hours, then evacuate it at this temperature, and gradually change the pressure from a slight positive pressure to -0.095Mpa within 10 hours, and maintain it at this pressure and temperature for 5 hours. Within the 600th hour, cool it to 150℃ and take it out of the furnace to obtain the first calcined product.

[0093] 5. Place the first roasted product into an impregnation tank, evacuate to -0.99 MPa, and pump in a first impregnation fluorinated asphalt at 200°C, wherein the ash content of the first impregnation fluorinated asphalt is 0.05%, the softening point is 85°C, the quinoline insoluble matter is 0.5%, and the fluorine content is 4%. When the impregnation tank is full, turn off the vacuum system, and continue to pressurize the impregnation tank to 4.2 MPa by liquid pressure for 30 hours.

[0094] 6. After the first impregnation, the second roasting was continued. Under nitrogen protection, the temperature was raised to 1300°C at the 72nd hour, and the pressure was gradually changed from slightly positive pressure to -0.095Mpa within 10 hours. This pressure and temperature was maintained for 6 hours. Within the 130th hour, the temperature was lowered to 150°C and the product was taken out of the furnace.

[0095] 7. Place the second roasted product into the impregnation tank, evacuate to -0.99 MPa, and pump in the second impregnation fluorinated asphalt at 200°C. The second impregnation fluorinated asphalt has an ash content of 0.05%, a softening point of 85°C, a quinoline insoluble matter of 0.009%, and a fluorine content of 1%. When the impregnation tank is full, turn off the vacuum system, and continue to increase the pressure of the impregnation tank to 4.2 MPa by liquid pressure for 30 hours.

[0096] 8. After the second impregnation, the final calcination is carried out. Under nitrogen protection, the temperature is raised to 1300°C at the 72nd hour, and the pressure is gradually changed from slightly positive pressure to -0.095Mpa within 10 hours. This pressure and temperature is maintained for 6 hours. Within the 130th hour, the temperature is reduced to 150°C and the isostatic graphite semi-finished product is obtained.

[0097] 9. Place the isostatic graphite semi-finished product into an internal string graphitization furnace for graphitization at a graphitization temperature of 2400°C and a power supply time of 65 hours. After cooling, isostatic graphite can be obtained.

[0098] Example 2

[0099] This embodiment provides an isostatically pressed graphite, which is different from that in Embodiment 1 in that the ash content of the calcined petroleum coke used is 0.5%, and the degree of graphitization is 85%; the ash content of the fluorinated pitch is 0.05%, the softening point is 125°C, the quinoline insoluble matter is 0.5%, and the fluorine content is 20%; the ash content of the fluorinated pitch for the first impregnation is 0.04%, the softening point is 80°C, the quinoline insoluble matter is 0.4%, and the fluorine content is 5%; the ash content of the fluorinated pitch for the second impregnation is 0.04%, the softening point is 80°C, the quinoline insoluble matter is 0.008%, and the fluorine content is 2%. The remaining processes and methods are the same as those in Embodiment 1 and are not repeated here.

[0100] Example 3

[0101] This embodiment provides an isostatically pressed graphite. The difference from Embodiment 1 is that in Step 2, the calcined petroleum coke is 80 kg and the fluorinated asphalt is 20 kg. The remaining methods and steps are the same as those in Embodiment 1 and will not be described again.

[0102] Example 4

[0103] This embodiment provides an isostatically pressed graphite. The difference from Embodiment 1 is that in Step 2, the calcined petroleum coke is 75 kg and the fluorinated asphalt is 25 kg. The remaining methods and steps are the same as those in Embodiment 1 and will not be described again.

[0104] Example 5

[0105] This embodiment provides an isostatically pressed graphite. The difference from Embodiment 1 is that in Step 2, the calcined petroleum coke is 60 kg and the fluorinated asphalt is 40 kg. The remaining methods and steps are the same as those in Embodiment 1 and will not be described again.

[0106] Example 6

[0107] This embodiment provides an isostatically pressed graphite. The difference from Embodiment 1 is that in Step 2, the calcined petroleum coke is 90 kg and the fluorinated asphalt is 10 kg. The remaining methods and steps are the same as those in Embodiment 1 and will not be described again.

[0108] Comparative Example 1

[0109] This comparative example provides an isostatically pressed graphite. The difference from Example 1 is that ordinary asphalt is used as a binder and impregnating agent instead of fluorinated asphalt. The remaining raw materials and methods are the same as those in Example 1 and will not be repeated here.

[0110] Comparative Example 2

[0111] This comparative example provides an isostatically pressed graphite. Different from Example 1, general fluorinated asphalt is used as a binder and an impregnating agent, and the quinoline insoluble content in the fluorinated asphalt as an impregnating agent is no longer controlled. The remaining raw materials and methods are the same as those in Example 1 and are not described again.

[0112] Comparative Example 3

[0113] This comparative example provides an isostatically pressed graphite. The difference from Example 1 is that the vacuuming process in steps 3-8 is omitted and the process is directly carried out under normal pressure. The remaining raw materials and methods are the same as those in Example 1 and will not be described again.

[0114] Test Example 1

[0115] The isostatic graphite obtained in Examples 1-6 and Comparative Examples 1-2 was sampled by drilling holes at a depth of 100 mm and 200 mm, and the detection was performed according to the JC / T2571-2020 method for determining trace elements in high-purity graphite. The detection instrument was an inductively coupled plasma atomic emission spectrometer ICP-AES (model: 710-ES). It can be seen from the test results that the test results of different sampling depths are basically the same. The present invention records the test results of 200 mm deep drilling sampling in Table 1.

[0116] Table 1

[0117]

[0118] As can be seen from Table 1, the use of fluorinated asphalt as a binder and impregnating agent has a very obvious purification effect on graphite products. As the fluorine content increases, the purification effect improves. However, when it increases to a certain level, it will cause cracking of the calcined product (Example 5). Too little fluorine content cannot achieve the purification target (Example 6). According to the invention, 99.9999% ultra-high purity graphite can be produced to meet the needs of ultra-high purity semiconductors.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A production process for isostatic graphite, It is characterized in that The following steps are involved: A. Mix calcined petroleum coke and fluorinated asphalt in a mass ratio of 3 to 4:1, knead and coarsely crush to obtain a coarse crushed material with a particle size of less than 1 mm; B. crushing the coarsely crushed material to obtain finely crushed material with a particle size of 3 μm to 5 μm; and cold isostatically pressing the finely crushed material to obtain a raw product; C. subjecting the raw product to first calcination, first impregnation, second calcination and second impregnation in sequence, and then final calcination to obtain an isostatic graphite semi-finished product; D. graphitizing the isostatic graphite semi-finished product at 2300° C. to 2500° C. for 60 h to 70 h to obtain the isostatic graphite; The calcined petroleum coke has an ash content of ≤0.7%, a graphitization degree of ≥80%, and a particle size of 5 μm to 10 μm; The fluorinated asphalt has an ash content of ≤0.1%, a softening point of ≥120°C, quinoline insoluble matter of ≤1% and a fluorine content of 6% to 20%; The first impregnation and the second impregnation use a first impregnation fluorinated asphalt and a second impregnation fluorinated asphalt respectively; The first impregnated fluorinated asphalt has an ash content of ≤0.05%, a softening point of 80°C to 95°C, quinoline insoluble matter of ≤0.5% and a fluorine content of 3% to 5%; The second impregnated fluorinated asphalt has an ash content of ≤0.05%, a softening point of 80°C to 95°C, quinoline insolubles of ≤0.01% and a fluorine content of 0.5% to 2%; The first calcination time is 500h~800h; The time of the second calcination and the final calcination is independently 120h~170h; The temperatures of the first calcination, the second calcination and the final calcination are independently 800° C. to 1300° C.; The temperatures of the first impregnation and the second impregnation are independently 150° C. to 250° C.; The pressures of the first impregnation and the second impregnation are independently 4 MPa to 4.5 MPa.

2. The production process according to claim 1, It is characterized in that The method further includes a vacuuming process after the first calcination, the second calcination and the final calcination are completed.

3. The production process according to claim 2, It is characterized in that The vacuuming process is to evacuate the roasted product to remove impurities after roasting, so that the vacuum degree in the roasting chamber is -95kPa~-98kPa.

4. The production process according to claim 1, It is characterized in that The process of the first impregnation and / or the second impregnation is to add the first impregnation fluorinated asphalt and the second impregnation fluorinated asphalt into the vacuumed impregnation container to impregnate the roasted product obtained after roasting.

5. The production process according to claim 1, It is characterized in that The pressure of the cold isostatic pressing is 280MPa~320MPa.

6. The production process according to claim 1, It is characterized in that The cold isostatic pressing time is 30 min to 80 min.

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