Extrusion type corona-resistant polyimide resin and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to extrusion type corona-resistant polyimide resin and a preparation method thereof. The extrusion type corona-resistant polyimide resin is prepared from the following raw materials: a diamine monomer and a dianhydride monomer, the diamine monomer has a structural formula as shown in a formula I, and the dianhydride monomer is selected from at least one of bisphenol A type diether dianhydride and 3, 3 ', 4, 4'-diphenylsulfonyltetracarboxylic dianhydride. A diamine monomer with a specific structure and a diamine monomer with specific components are polymerized, and a fluorine element and sulfuryl are introduced into molecules, so that the corona resistance and mechanical strength of the resin are improved; meanwhile, the dielectric constant of the extruded polyimide can also be reduced.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of high polymer materials, in particular to an extrusion type corona-resistant polyimide resin and a preparation method thereof. BACKGROUND

[0002] Polyimide thermoplastic resin is widely used in electronic and electrical, aerospace, automobile, medical equipment and other industries due to its good melt flowability, extrusion injection molding process, high production efficiency, excellent mechanical properties, electrical insulation properties and wear resistance. With the development of power technology towards high voltage and high frequency, pulse width modulation variable frequency motors are widely used. Under the action of factors such as electricity and heat caused by long-term repetitive overvoltage, the insulation material is easily aged and broken down, thereby causing the motor to fail. Therefore, it is urgent to improve the insulation properties and corona resistance of the insulation material to meet the development of high voltage technology. In particular, the development of new energy vehicles is further accelerated, and the technology of new energy vehicle motors and charging piles is gradually developing towards high frequency and high voltage. High-voltage, high-temperature and especially corona-resistant insulation wires will become a new market growth point.

[0003] Currently, there are three types of insulation wires, namely, enameled wire, wrapped wire and extruded wire. The enameled wire has a complex process and the performance of the paint film is prone to decline during multiple baking processes. The thickness of the paint film is not easy to control. The wrapped wire needs to use adhesive and polyimide film, and needs to be bonded in multiple layers, which puts higher requirements on the adhesive and the film. The extruded wire has been widely used due to its simple process, one-time extrusion molding and easy thickness control.

[0004] Currently, the improvement of the corona resistance of the insulation material is mainly achieved by adding inorganic substances and fluorides. For example, in patent CN109749082A, the synergistic interaction of nanoparticles and nanosheets forms a multi-level structure with good dispersity, thereby improving the corona resistance and breakdown strength of the composite material. In patent CN114989466A, a surface modifier and ultrasonic dispersion method are used to disperse nano-inorganic materials and layered inorganic materials, thereby improving the dispersity of the inorganic fillers and enabling the corona resistance of the corona-resistant film to reach 130 min. Patent CN103832033A discloses a composite polyimide film having A-B two-layer structure and B-A-B three-layer structure. The A layer is a PI (polyimide) layer filled with inorganic nanoparticles, and the B layer is a polytetrafluoroethylene resin filled with inorganic nanoparticles. The composite film has excellent performance of both materials.

[0005] Currently, the improvement of the corona resistance of the polyimide resin is mainly achieved by adding a modifier. However, the addition of the modifier has the problems of uneven dispersion in the base resin and poor combination, which easily leads to the failure of the material to meet the requirements of corona resistance and the decrease of the mechanical properties in terms of impact resistance.

[0006] In addition, the preparation methods of the extruded polyimide mainly include a screw high-temperature extrusion method and a solution polymerization method. The screw high-temperature extrusion method has simple preparation process and high efficiency; the solution polymerization method mainly includes a chemical imidization method and a thermal imidization method, and the common problem of the extruded polyimides prepared by the chemical imidization method and the thermal imidization method is that a large amount of solvent needs to be used for precipitation and washing, resulting in difficult solvent recovery and high cost. SUMMARY

[0007] Therefore, the purpose of the present application is to overcome the deficiencies of the prior art, provide an extruded corona-resistant polyimide resin to solve the technical problem of low corona resistance and decreased impact strength caused by adding a modifier in the prior art, and provide a preparation method of the extruded corona-resistant polyimide resin to solve the technical problem of difficult solvent recovery and high cost caused by the use of a large amount of solvent for precipitation and washing in the prior preparation method.

[0008] To achieve the above purpose, the present application adopts the following technical solutions:

[0009] Firstly, the present application provides an extruded corona-resistant polyimide resin, and the preparation raw materials thereof include diamine monomers and dianhydride monomers, the diamine monomers have a structural formula as shown in Formula I, and the dianhydride monomers are selected from at least one of bisphenol A type diether dianhydride and 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride.

[0010] .

[0011] Preferably, the molar ratio of the dianhydride monomers to the diamine monomers is (1-1.1):1.

[0012] Preferably, the corona resistance time of the extruded corona-resistant polyimide resin is 360-370 h.

[0013] Preferably, the impact strength of the extruded corona-resistant polyimide resin is 155-160 kJ / m 2 .

[0014] Preferably, the dielectric constant of the extruded corona-resistant polyimide resin is 2.5-2.7 MHz.

[0015] Based on one general inventive concept, the present application further provides a preparation method of an extruded corona-resistant polyimide resin, including the following steps:

[0016] S1, dissolving diamine monomers in a composite solvent, adding dianhydride monomers in batches, and then performing a polymerization reaction to obtain a polyamic acid solution, and then adding an end-capping agent to perform an end-capping reaction; the composite solvent includes a polar aprotic solvent and an aromatic hydrocarbon solvent, and the mass ratio of the polar aprotic solvent to the aromatic hydrocarbon solvent is 1:(4-5);

[0017] S2, after the end-capping reaction is completed, performing vacuum distillation to remove part of the aromatic hydrocarbon solvent until the mass ratio of the polar aprotic solvent to the aromatic hydrocarbon solvent in the remaining composite solvent reaches 1: (0.5-1), and then cooling to precipitate the resin, and filtering and drying to obtain a polyimide resin;

[0018] S3, melting and extruding the polyimide resin through an extruder to obtain extruded corona-resistant polyimide resin particles.

[0019] Preferably, the polar aprotic solvent is selected from at least one of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and N-methyl pyrrolidone (NMP).

[0020] Preferably, the aromatic hydrocarbon solvent is selected from at least one of toluene and xylene.

[0021] Preferably, in step S1, the mass of the composite solvent is 2-5 times the total mass of the diamine monomer and the dianhydride monomer.

[0022] Preferably, in step S1, the dianhydride monomer is added in three batches, with an interval of 15 minutes between each batch.

[0023] Preferably, the temperature of the polymerization reaction is 60-80°C, and the polymerization reaction time is 2-3h.

[0024] Preferably, the end-capping agent is phthalic anhydride (PA), and the amount of the end-capping agent is 10-30% of the molar mass of the diamine monomer.

[0025] Preferably, the end-capping reaction time is 30-40min.

[0026] Preferably, in step S2, the temperature of the vacuum distillation is 80-120°C.

[0027] Preferably, in step S2, the cooling is to 5-10°C.

[0028] Preferably, in step S2, the drying step includes: first drying at 100°C for 1h, then drying at 150°C for 1h, and finally drying at 180°C for 1h.

[0029] Preferably, in step S3, the process conditions for the extrusion granulation include: a feeding speed of 1-1.5kg / h; the rotation speed of the extruder is set to 75-80rpm; the temperature of the feeding section is set to 120-180°C, the temperature of the cylinder is set to 250-320°C, and the temperature of the discharging section is set to 330°C.

[0030] Compared with the prior art, the application has the following beneficial effects:

[0031] 1. In the preparation method of the application, a diamine monomer with a specific structure is selected to be polymerized with a specific component of a dianhydride monomer to introduce fluorine elements and sulfone groups into the polyimide bulk resin, which can improve the insulation and temperature resistance, and avoid the mixing unevenness and separation caused by the conventional additive method, thereby improving the corona resistance and mechanical properties of the polyimide resin. At the same time, through the polymerization of the diamine monomer with the specific structure and the specific component of the dianhydride monomer, the fluorine atoms are introduced into the molecules, the C-F bond energy is high, the polarizability is reduced, the fluorine-containing group volume is large, the free volume is increased, and the polar group density is reduced, thereby reducing the dielectric constant.

[0032] 2. In the preparation method of the application, a composite solvent with a specific composition ratio is designed to make the diamine and dianhydride monomers polymerize smoothly, and the polyamide acid can be imidized to form the polyimide resin in the process of reduced pressure distillation. At the same time, by controlling the composition ratio of the composite solvent after distillation, the system after reaction can smoothly precipitate the polyimide resin in the cooling process, without adding additional precipitation solvents and washing solvents; the recovery steps and costs of the precipitation solvents and washing solvents are reduced. DETAILED DESCRIPTION

[0033] The embodiments described in the specification are only for the purpose of explaining the application, and are not intended to limit the application.

[0034] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, as can any upper limit with any other upper limit to form a range not explicitly recited. Furthermore, although not explicitly recited, every point or individual number between the range end points is included in the range. Thus, every point or individual number can serve as its own lower limit or upper limit to combine with another point or individual number or to combine with other lower limits or upper limits to form a range not explicitly recited.

[0035] Those skilled in the art can understand that in the method of each embodiment or example, the writing order of each step does not mean a strict execution order and does not constitute any limitation on the implementation process, and the detailed execution order of each step should be determined by its function and possible internal logic. If not specifically stated, all steps of the application can be sequentially performed or randomly performed, and preferably sequentially performed.

[0036] The present application will be further described in conjunction with the following examples. It should be understood that these examples are only for illustrative purposes, and various modifications and variations within the scope of the present application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further purification, and the instruments used in the examples are commercially available.

[0037] The diamine monomer D containing fluorine element and sulfone group used in the examples and comparative examples of the present application is prepared according to the method disclosed in CN115449076 A.

[0038] Preparation Example 1

[0039] Into 2400 g of DMAc, 269 g of bisphenol AF, 64 g of sodium hydroxide, 230 g of 4,4'-dichlorodiphenyl sulfone and 87.3 g of m-aminophenol were added, stirred at room temperature for 3 hours, then 472 g of xylene was added, and the temperature was raised to 150°C to reflux and dehydrate, after completion, the xylene was removed by evaporation, vacuum was opened, and the solvent was distilled off under reduced pressure, and the temperature was gradually raised to 175°C, the solvent was completely evaporated, then ethanol was added, stirred and cooled to room temperature, and then filtered and dried to obtain diamine monomer D, which was used as prepared.

[0040] The following examples and comparative examples are examples of the preparation of polyimides.

[0041] Example 1

[0042] Into 1203.6 g of DMAc and 4814.4 g of xylene mixed solution, 984 g of diamine monomer D was dissolved at 60°C, and then 520.49 g of BPADA (bisphenol A type diether dianhydride) was added in three equal portions under stirring, with an interval of 15 min between each portion, after the addition was completed, the reaction was maintained for 3 h, then 14.8 g of PA was added and reacted for 30 min, vacuum distillation was started, and the temperature was raised to 100°C, while 3610.8 g of xylene was distilled off, the system was vented, and the temperature was lowered to 10°C, then the filter cake was dried at 100°C, 150°C and 180°C for 1 h respectively, and a yellowish powder resin was obtained.

[0043] Example 2

[0044] 984g of diamine monomer D was dissolved in 1203.6g of DMSO and 4814.4g of xylene at 60°C, and nitrogen was bubbled while stirring until the raw material was dissolved. Then, 520.49g of BPADA was added to the solution in three equal portions with an interval of 15 minutes, and after the addition was completed, the reaction was allowed to proceed for 3 hours. Then, 29.6g of PA was added, and the reaction was allowed to proceed for 30 minutes. After that, the vacuum distillation was started, and the temperature was increased to 100°C. While distilling 3610.8g of xylene, the vacuum was released, and the temperature was decreased to 10°C. Then, the filter cake was dried at 100°C, 150°C and 180°C for 1 hour, respectively, to obtain a yellowish powder resin.

[0045] Example 3

[0046] 984g of diamine monomer D was dissolved in 1203.6g of DMSO and 4814.4g of xylene at 60°C, and nitrogen was bubbled while stirring until the raw material was dissolved. Then, 520.49g of BPADA was added to the solution in three equal portions with an interval of 15 minutes, and after the addition was completed, the reaction was allowed to proceed for 3 hours. Then, 29.6g of PA was added, and the reaction was allowed to proceed for 30 minutes. After that, the vacuum distillation was started, and the temperature was increased to 100°C. While distilling 3610.8g of xylene, the vacuum was released, and the temperature was decreased to 10°C. Then, the filter cake was dried at 100°C, 150°C and 180°C for 1 hour, respectively, to obtain a yellowish powder resin.

[0047] Example 4

[0048] 984g of diamine monomer D was dissolved in 1203.6g of DMSO and 4814.4g of xylene at 60°C, and nitrogen was bubbled while stirring until the raw material was dissolved. Then, 520.49g of BPADA was added to the solution in three equal portions with an interval of 15 minutes, and after the addition was completed, the reaction was allowed to proceed for 3 hours. Then, 29.6g of PA was added, and the reaction was allowed to proceed for 30 minutes. After that, the vacuum distillation was started, and the temperature was increased to 100°C. While distilling 3610.8g of xylene, the vacuum was released, and the temperature was decreased to 10°C. Then, the filter cake was dried at 100°C, 150°C and 180°C for 1 hour, respectively, to obtain a yellowish powder resin.

[0049] Example 5

[0050] Dissolve 984 g of diamine monomer D in 1073.8 g of DMAc and 4295.2 g of xylene at 60°C, and stir under nitrogen until the raw materials are dissolved. Then, add 358.28 g of DSDA (3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride) in three equal portions to the solution at intervals of 15 min under stirring, and allow to react for 3 h after the addition is completed. Then, add 14.8 g of PA, and allow to react for 30 min. Open the reduced-pressure distillation, and raise the temperature to 100°C while distilling 3221.4 g of xylene. Then, vent, and lower the temperature to 10°C. Filter, and dry the filter cake at 100°C, 150°C, and 180°C for 1 h each to obtain a yellowish powder resin.

[0051] Comparative Example 1

[0052] Dissolve 320.23 g of 2,2'-bis(trifluoromethyl)-(1,1'-biphenyl)-4,4'-diamine (TFMB) in 672.4 g of DMAc and 2689.9 g of xylene at 60°C, and stir under nitrogen until the raw materials are dissolved. Then, add 520.49 g of BPADA in three equal portions to the solution at intervals of 15 min under stirring, and allow to react for 3 h after the addition is completed. Then, add 14.8 g of PA, and allow to react for 30 min. Open the reduced-pressure distillation, and raise the temperature to 100°C while distilling 2017.2 g of toluene. Then, vent, and lower the temperature to 10°C. Filter, and dry the filter cake at 100°C, 150°C, and 180°C for 1 h each to obtain a yellow powder resin.

[0053] Comparative Example 2

[0054] Dissolve 984 g of diamine monomer D in 6018 g of DMF at room temperature, and stir under nitrogen until the raw materials are dissolved. Then, add 520.49 g of BPADA in three equal portions to the solution at intervals of 15 min under stirring, and allow to react for 3 h after the addition is completed. Then, add 22.2 g of PA, and allow to react for 30 min. Add 1203.6 g of acetic anhydride and 300.9 g of triethylamine, raise the temperature to 150°C, and allow to react for 3 h. Lower the temperature to 50°C, and at this time, the solution is slightly turbid. Pour the solution into 12036 g of ethanol to precipitate, filter, wash the filter cake with 12036 g of ethanol, filter, dry at 100°C and 150°C for 1 h each, and obtain a yellowish powder resin.

[0055] Comparative Example 3

[0056] Dissolve 984 g of diamine monomer D in a mixed solution of 4814.4 g of DMSO and 1203.6 g of xylene at room temperature, and stir under nitrogen until the raw material is dissolved. Then, add 520.49 g of BPADA to the solution in three equal portions with an interval of 15 min under stirring, and allow to react for 3 h after the addition is completed. Then, add 29.6 g of PA, and allow to react for 30 min. After that, raise the temperature to 150°C, and distill off the xylene. Then, lower the temperature to 50°C, and at this time, the solution is slightly turbid, so the solution is poured into 12036 g of ethanol to precipitate, and then filtered. The filter cake is washed with 12036 g of ethanol, filtered, and dried at 100°C and 150°C for 1 h each, to obtain a yellowish powder resin.

[0057] Comparative Example 4

[0058] Dissolve 432.5 g of 4,4'-bis(3-aminophenoxy)diphenyl sulfone (m-BAPS) in a mixed solution of 762.4 g of NMP and 3049.6 g of toluene at 60°C, and stir under nitrogen until the raw material is dissolved. Then, add 520.49 g of BPADA to the solution in three equal portions with an interval of 15 min under stirring, and allow to react for 3 h after the addition is completed. Then, add 44.4 g of PA, and allow to react for 30 min. After that, open the distillation under reduced pressure, and raise the temperature to 100°C. While distilling off 2287.2 g of toluene, vent, and lower the temperature to 10°C. Then, filter, and dry the filter cake at 100°C, 150°C, and 180°C for 1 h each, to obtain a light yellow powder resin. Then, add 90 g of alumina powder to the resin, and mix well, to obtain a modified mixed resin.

[0059] Comparative Example 5

[0060] Dissolve 984 g of diamine monomer D in a mixed solution of 1203.6 g of DMAc and 7221.6 g of toluene at 60°C, and stir under nitrogen until the raw material is dissolved. Then, add 520.49 g of BPADA to the solution in three equal portions with an interval of 15 min under stirring, and allow to react for 3 h after the addition is completed. Then, add 14.8 g of PA, and allow to react for 30 min. After that, open the distillation under reduced pressure, and raise the temperature to 100°C. While distilling off 6018 g of toluene, vent, and lower the temperature to 10°C. Then, filter, and dry the filter cake at 100°C, 150°C, and 180°C for 1 h each, to obtain a yellowish powder resin.

[0061] Comparative Example 6

[0062] 60℃, 984g of diamine monomer D was dissolved in 1035.4g of DMAc and 4141.6g of xylene mixed solution, nitrogen was passed, and stirring was dissolved, then 310.21g of 4, 4'-diphenyl ether dianhydride (ODPA) was added to the solution in three equal parts, each batch interval was 15min, after the addition was completed, the reaction was kept for 3h, then 14.8g of PA was added and the reaction was kept for 30min, the vacuum distillation was started and the temperature was raised to 100℃, 3106.2g of xylene was distilled out, the vacuum was released, the temperature was lowered to 10℃, and the filter cake was dried at 100℃, 150℃ and 180℃ for 1h respectively, and a yellow powder resin was obtained.

[0063] Experimental Example 1

[0064] The resins of the above examples and comparative examples were extruded and molded according to the following process. The extrusion granulation process was: the feeding speed was 1kg / h; the rotation speed of the extruder was set to 75rpm; the feeding section temperature was set to 120℃, 180℃, the barrel temperature was set to 250℃, 270℃, 300℃, 320℃, and the discharge section temperature was set to 330℃; after the material was extruded from the extruder, it was cooled by air, cut into particles, and then thermoplastic polyimide particles were obtained. The obtained particles were brown transparent particles.

[0065] The molding process was: the molding temperature was 320℃, the molding time was 30min, and the molding pressure was 10-15MPa, which was added to the flat vulcanizing machine for molding. The obtained polyimide plate was tested for dielectric constant, corona resistance and impact strength; among them, the dielectric constant was tested according to the method specified in GB / T1408-2006, the corona resistance was tested according to the method specified in GB / T21707-2018, and the impact strength was tested according to the method specified in GB / T1043.1-2008. The specific test results are shown in Table 1.

[0066] Table 1: Polyimide performance test data statistics table

[0067]

[0068] In the table, components A and B in the composite solvent represent non-polar protic solvents and aromatic hydrocarbon solvents, respectively. For example, in Example 1, component A is DMAc and component B is xylene.

[0069] From the performance test data of Table 1, it can be seen that, by using specific diamine monomers and dianhydride under the condition of composite solvent, the polyimide resin is prepared by reaction, and then the extruded polyimide is obtained by extrusion. Among them, the fluorine element and the sulfone group are introduced into the molecular structure by the diamine monomer, the fluorine element can improve the corona resistance of the resin, and the introduction of the flexible group sulfone group can improve the impact strength, solving the problem of poor corona resistance and mechanical strength of conventional polyimide. Further, by controlling the ratio of composite reaction solvents A and B, and removing part of the solvent B by vacuum distillation after the completion of the polymerization reaction, the polyamide imine can be successfully precipitated without adding additional solvent to precipitate the resin; in this way, the amount of precipitated solvent can be reduced, the problem of difficult recovery of additional precipitated solvent can be solved, and it has good industrialization prospect.

[0070] In the preparation of polyimide, Comparative Example 1 and Comparative Example 4 respectively use 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl)-4,4'-diamine and 4,4'-bis(3-aminophenoxy) diphenyl sulfone as diamine monomers. Both of them contain fluorine element or sulfone group in the diamine monomers they use; they cannot introduce fluorine element and sulfone group at the same time, so that the impact strength and corona resistance of the prepared extruded polyimide are not as good as the examples.

[0071] In the preparation of polyimide, Comparative Example 2 uses a single solvent, although the prepared extruded polyimide has high impact strength and long corona resistance, but it still needs to precipitate polyimide by ethanol, and needs to add a large amount of precipitated solvent.

[0072] Although Comparative Example 3 is under the condition of composite solvent, the mass ratio of DMSO and dimethylbenzene in the composite solvent is 1:0.25, and after vacuum distillation, the dimethylbenzene is completely distilled out, and the remaining DMSO is a good solvent, so that the polymer resin in the remaining mixture is dissolved in the solvent, and needs to be poured into ethanol to precipitate.

[0073] Although Comparative Example 5 is under the condition of composite solvent, the mass ratio of DMAc and dimethylbenzene in the composite solvent is 1:6. Under the condition of the composite solvent in this ratio, the solubility of the diamine monomer is reduced at 60°C, and part of the diamine monomer cannot be dissolved and cannot participate in the polymerization reaction; the molar ratio of the diamine monomer and the dianhydride monomer actually participating in the reaction does not reach the preset requirement, and the performance of the obtained polyimide is also reduced.

[0074] It can be seen from the examples and comparative examples that the dielectric property and corona resistance of the resin can be greatly improved by adding the fluorine-containing compound. The essence is that the fluorine atom is introduced into the molecule. The C-F bond has high bond energy, which reduces the polarization rate. At the same time, the fluorine-containing group has large volume, which increases the free volume and reduces the density of the polarization group, thereby reducing the dielectric constant. The C-F bond has high bond energy, which improves the chemical stability and can significantly reduce the surface energy, has hydrophobic function, reduces surface leakage and partial discharge, and delays the occurrence of corona.

[0075] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An extruded corona-resistant polyimide resin, characterized in that, The raw materials for its preparation include diamine monomers and dianhydride monomers. The diamine monomers have the structural formula shown in Formula I, and the dianhydride monomers are selected from at least one of bisphenol A type diether dianhydride and 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride. 。 2. The extruded corona-resistant polyimide resin according to claim 1, characterized in that, The molar ratio of the dianhydride monomer to the diamine monomer is (1~1.1):

1.

3. The method for preparing the extruded corona-resistant polyimide resin according to any one of claims 1 to 2, characterized in that, Includes the following steps: S1. The diamine monomer is dissolved in a composite solvent, and the dianhydride monomer is added in batches. Then, a polymerization reaction is carried out to obtain a polyamic acid solution. Subsequently, a capping agent is added to carry out a capping reaction. The composite solvent includes a polar aprotic solvent and an aromatic hydrocarbon solvent, and the mass ratio of the polar aprotic solvent to the aromatic hydrocarbon solvent is 1:(4~5). S2. After the end-capping reaction is completed, vacuum distillation is performed to remove part of the aromatic hydrocarbon solvent until the mass ratio of the polar aprotic solvent to the aromatic hydrocarbon solvent in the remaining composite solvent reaches 1:(0.5~1). Then, the temperature is lowered to precipitate the resin, which is then filtered and dried to obtain polyimide resin. S3. The polyimide resin is melt-extruded and granulated using an extruder to obtain extruded corona-resistant polyimide resin particles.

4. The preparation method according to claim 3, characterized in that, The polar aprotic solvent is selected from at least one of N,N-dimethylacetyl, N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone; The aromatic hydrocarbon solvent is selected from at least one of toluene and xylene.

5. The preparation method according to claim 3, characterized in that, In step S1, the capping agent is phthalic anhydride, and its amount is 10-30% of the mass of the diamine monomer.

6. The preparation method according to claim 3, characterized in that, In step S1, the mass of the composite solvent is 2 to 5 times the total mass of the diamine monomer and the dianhydride monomer.

7. The preparation method according to claim 3, characterized in that, The polymerization reaction is carried out at a temperature of 60-80°C for 2-3 hours.

8. The preparation method according to claim 3, characterized in that, In step S2, the temperature of the vacuum distillation is 80~120℃.

9. The preparation method according to claim 3, characterized in that, In step S2, the cooling is to reduce the temperature to 5~10℃.

10. The preparation method according to claim 3, characterized in that, In step S3, the extrusion granulation process conditions include: feeding speed of 1~1.5 kg / h; extruder speed of 75~80 rpm; feeding section temperature of 120~180℃; barrel temperature of 250~320℃; and discharge section temperature of 330℃.

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