Polyimide as well as preparation method and application thereof

Abstract

The invention discloses polyimide which contains rich-CF3 and ester groups, the-CF3 provides low polarity and large free volume, the ester groups provide regularity, and due to the fact that the polyimide has low polarity, large free volume and high regularity, the polyimide can have the advantages of low dielectric constant and low dielectric loss at the same time. And moreover, the absorptivity of the polyimide is improved, the original heat resistance and flexibility of the polyimide are ensured, and the polyimide has excellent comprehensive performance. Meanwhile, the invention also discloses a preparation method of the polyimide and application of the polyimide in the field of electronic industry.

Description

Technical Field

[0001] The present invention relates to the field of polyimide materials, and in particular to a high-performance polyimide material with low dielectric constant and low dielectric loss, and a preparation method and application thereof. Background Art

[0002] Polyimide (PI) is a class of high-performance organic polymer materials, whose main chain contains an imide ring (-CO-N-CO-) structure, and is usually prepared by polycondensation of dianhydride and diamine. This structure gives polyimide many excellent properties, such as polyimide is an excellent electrical insulating material with a low dielectric constant and low dielectric loss. This makes it widely used in the electronics industry to manufacture circuit boards, chip packaging materials, etc., which can effectively isolate current, reduce signal interference and energy loss. With the development of the electronics industry, the application of polyimide requires lower dielectric constant and lower dielectric loss, but the current preparation of low dielectric polyimide mainly focuses on the improvement of a single dielectric performance parameter of low dielectric constant or low dielectric loss, or involves cumbersome steps such as blending, copolymerization and composite materials.

[0003] CN117362642A discloses that a heterocyclic group is introduced into the main chain of polyimide to increase the glass transition temperature and tensile strength and reduce the dielectric constant. CN116924927A discloses a diamine monomer containing an ester bond and a fluorene group, a polyimide film and a preparation method thereof, wherein the dielectric constant thereof is reduced by introducing a fluorene ring. CN114616270B discloses a block copolymer with low dielectric loss, wherein the first block is obtained by polymerizing and imidizing benzophenone tetracarboxylic acid dianhydride and biphenyl tetracarboxylic acid dianhydride with p-phenylenediamine, and the second block is obtained by polymerizing and imidizing benzophenone tetracarboxylic acid dianhydride and pyromellitic acid dianhydride with m-toluidine. CN116925405A discloses an intrinsically high thermal conductivity and low dielectric loss crystalline polyimide film, wherein the dielectric loss thereof is reduced by crystallization. CN115466509B discloses a polyimide composite material with a low dielectric constant obtained by using polyimide as a matrix, quartz fiber cloth as a reinforcement, and phenylethynyl-modified thermoplastic polyimide as a modifier. CN116925399A discloses a low dielectric all-organic polyimide composite film for electronic packaging, which uses in-situ polymerization to add hollow polydopamine spheres coated with a silane coupling agent into a polyimide (PI) matrix to reduce the dielectric constant.

[0004] Although molecular structure design can reduce dielectric constant or dielectric loss, it can only reduce one of the parameter indicators, that is, if the dielectric constant is reduced, the dielectric loss will increase, or if the dielectric loss is reduced, the dielectric constant will increase. Or when the dielectric constant or dielectric loss is reduced, its mechanical properties or thermal properties will deteriorate. Reducing the dielectric constant through composite materials often increases dielectric loss, and destroys the insulation and breakdown strength of the PI film, which has an adverse effect on its application in the field of electronics industry. The preparation process is complicated, and methods such as copolymerization and blending may affect the uniformity of the material and thus affect the dielectric properties. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a high-performance polyimide which has both low dielectric constant and low dielectric loss and has high heat resistance and low water absorption properties; at the same time, the present invention also provides a preparation method and application of the high-performance polyimide.

[0006] To achieve the above object, the present invention provides a polyimide having both low dielectric constant and low dielectric loss, wherein the polyimide is prepared by using compound A and compound B; the structural formula of compound A is as follows:

[0007]

[0008] The compound B is at least one of pyromellitic anhydride, 3,3',4,4'-diphenyl ether tetracarboxylic anhydride, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride and tert-butylhydroquinone.

[0009] The compound A contains -CF 3 When the compound A and at least one of pyromellitic anhydride (PMDA), 3,3',4,4'-diphenyl ether tetracarboxylic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), and tert-butyl hydroquinone (TAHQ) are used to prepare a polyimide, the obtained polyimide contains a rich amount of -CF 3 and ester group, -CF 3 It provides low polarity and large free volume, while the ester group provides regularity. Since it has both low polarity and large free volume and high regularity, it has the advantages of low dielectric constant and low dielectric loss at the same time and has excellent comprehensive performance.

[0010] The compound A used in the present invention can be obtained by methods known in the art, for example, it can be purchased on the market, or prepared by conventional methods in the art. Preferably, the compound A of the present invention is prepared by the following method:

[0011] (1) dissolving 4,4'-(hexafluoroisopropylidene)diphenol in a solvent to obtain a solution 1;

[0012] (2) dissolving 4-nitrobenzoyl chloride in a solvent to obtain solution 2;

[0013] (3) placing solution 2 in an ice water bath and stirring, slowly adding solution 1 under the protection of inert gas, removing excess solvent after the reaction is completed, washing, collecting and drying the precipitate to obtain a crude dinitro compound;

[0014] (4) recrystallizing the crude dinitro compound product, collecting and drying the precipitate to obtain a dinitro compound product;

[0015] (5) dispersing the dinitro compound product in a solvent, adding a catalyst, and then stirring and reacting under a pressurized hydrogen atmosphere, removing the catalyst after the reaction, and collecting the filtrate;

[0016] (6) The collected filtrate is poured into deionized water to obtain a white precipitate, which is collected by filtration, recrystallized and dried to obtain the compound.

[0017] In the preparation method of the compound A described above, 4,4'-(hexafluoroisopropylidene)diphenol and 4-nitrobenzoyl chloride are first dissolved in a solvent to obtain solution 1 and solution 2, respectively, and then solution 2 is placed in an ice water bath and stirred, and solution 1 is slowly added dropwise under the protection of an inert gas to allow 4,4'-(hexafluoroisopropylidene)diphenol and 4-nitrobenzoyl chloride to react. After the reaction is completed, the solvent is removed and washed and dried to first obtain a crude dinitro compound product, and then the obtained crude dinitro compound product is recrystallized to obtain a dinitro compound product. Finally, the dinitro compound product is subjected to a pressurized hydrogen reaction under the action of a catalyst, and the filtrate after the reaction is purified to obtain the compound A of the structure described above.

[0018] In the preparation method of the compound A described above, in the step (1), the amount ratio of 4,4'-(hexafluoroisopropylidene)diphenol to the solvent is not strictly limited, and the amount of the solvent added is preferably sufficient to dissolve the 4,4'-(hexafluoroisopropylidene)diphenol; preferably, the mass volume ratio of 4,4'-(hexafluoroisopropylidene)diphenol to the solvent in the step (1) is 1:(5-7) g / ml. For example, the mass volume ratio of the 4,4'-(hexafluoroisopropylidene)diphenol to the solvent is 1:5 g / ml, 1:6 g / ml, 1:6.44 g / ml, 1:7 g / ml, and any ratio between them.

[0019] In the preparation method of compound A described above, in step (2), 4-nitrobenzoyl chloride and the solvent are not strictly limited, and the amount of the solvent added is preferably sufficient to dissolve 4-nitrobenzoyl chloride. Preferably, the mass volume ratio of 4-nitrobenzoyl chloride to the solvent in step (2) is 1: (10-14) g / ml. For example, the mass volume ratio of 4-nitrobenzoyl chloride to the solvent is 1: 10 g / ml, 1: 10.7 g / ml, 1: 11 g / ml, 1: 12 g / ml, 1: 13 g / ml, 1: 14 g / ml, and the ratio between any two of them.

[0020] In view of the structural characteristics of the compound A of the present invention, the molar ratio of the 4,4'-(hexafluoroisopropylidene)diphenol to 4-nitrobenzoyl chloride is generally preferably 1:2, which can fully react to generate the compound of the structure of the present invention and has a high conversion rate.

[0021] In the preparation method of compound A described above, in the step (5), the amount of the catalyst is not strictly limited. Preferably, the mass ratio of the catalyst to the dinitro compound product in the step (5) is 5 to 10%. For example, the mass ratio of the catalyst to the dinitro compound product in the step (5) is 5%, 6%, 7%, 8%, 9%, 10% and any ratio between them, which can fully play a catalytic reaction without causing waste of the catalyst, thereby saving resource costs.

[0022] In the preparation method of compound A described above, the solvents in the steps (1), (2) and (5) are selected so as to be able to dissolve the corresponding substance to be dissolved well without causing adverse effects on the reaction. Preferably, the solvents in the steps (1), (2) and (5) are each independently selected from at least one of THF, pyridine and DMF. More preferably, the solvent used in the step (1) is a mixed solution of THF and pyridine, and the ratio of the two is not strictly limited. For example, the volume ratio of THF to pyridine can be 5:1, 5:1.44, 5:2, etc. More preferably, the solvent used in the step (2) is THF, and the solvent used in the step (5) is DMF.

[0023] Preferably, the catalyst in step (5) is Pd / C.

[0024] Preferably, the polyimide is prepared by using compound A and compound B in a molar ratio of 1:1.

[0025] Preferably, the structural formula of the polyimide is any one of the following:

[0026]

[0027] When the polyimide is prepared from compound A and PMDA, the structural formula of the polyimide is:

[0028]

[0029] When the polyimide is prepared from compound A and ODPA, the structural formula of the polyimide is:

[0030]

[0031] When the polyimide is prepared from compound A and 6FDA, the structural formula of the polyimide is:

[0032]

[0033] When the polyimide is prepared from compound A and TAHQ, the structural formula of the polyimide is:

[0034]

[0035] In a second aspect, the present invention provides a method for preparing the polyimide as described above. To achieve this purpose, the technical solution adopted by the present invention is: a method for preparing the polyimide as described above, comprising the following steps:

[0036] S1. In the presence of sufficient water and oxygen removal and under the protection of an inert gas, compound A is mixed with a solvent and stirred in a cold water bath until dissolved to form a homogeneous solution;

[0037] S2. Compound B is added three times to the homogeneous solution formed in step S1, and the reaction is stirred at room temperature to obtain a polyamic acid solution having a certain viscosity;

[0038] S3. The polyamic acid solution obtained in step S2 is degassed and evenly coated on a dry and clean glass plate, and an imidization reaction is carried out by a thermal imidization method to obtain polyimide.

[0039] The preparation method of the polyimide of the present invention comprises the following steps: firstly dissolving compound A to form a homogeneous solution, then adding at least one of PMDA, ODPA, 6FDA and TAHQ dropwise thereto three times, reacting at room temperature to obtain a polyamic acid solution with a certain viscosity, then coating the solution on a glass plate, and performing an imidization reaction by a thermal imidization method to obtain a polyimide material.

[0040] Preferably, the molar ratio of compound A to compound B is 1:1.

[0041] The solvent for dissolving compound A is not particularly limited, as long as it can fully dissolve compound A to form a homogeneous solution and can carry out subsequent reactions. Preferably, the solvent in step S1 is N-methyl-2-pyrrolidone.

[0042] The amount ratio of the compound A to the solvent is not particularly limited, and the amount of the solvent added can be sufficient to dissolve the compound A to form a homogeneous solution. Preferably, the molar volume ratio of the compound A to the solvent in step S1 is 1:1 mmol / ml.

[0043] Preferably, after adding compound B three times in step S2, the solvent is replenished in the reaction system in time. After compound B is added three times, if the solvent in the reaction system is insufficient, the solvent needs to be replenished in time. Compound B is added three times, which can make the reaction more complete and improve the conversion rate of the raw material. The amount ratio of the three additions is not particularly limited. For example, compound B can be added three times in any ratio of 1:1:1, 2:1:1, 2:2:1, etc.

[0044] The reaction time in step S2 is not particularly limited, but considering the sufficiency of the reaction, preferably, the stirring reaction time in step S2 is 10 to 18 hours.

[0045] The thermal imidization method in step S3 is a conventional method in the art, and its temperature rise curing procedure is not particularly limited. Preferably, the temperature rise curing procedure in the thermal imidization method in step S3 is: 80°C / 3h, 250°C / 1h, 300°C / 1h, 330°C / 1h.

[0046] Finally, the present invention also provides the application of the polyimide in the electronic industry. The polyimide of the present invention has the advantages of low dielectric constant and low dielectric loss, has excellent comprehensive performance, and can be widely used in the electronic industry such as the preparation of circuit boards and chip packaging materials.

[0047] The present invention is realized by studying the raw material structure for preparing polyimide, using the compound A of the specific structure and at least one of pyromellitic dianhydride (PMDA), 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA), 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), and tert-butyl hydroquinone (TAHQ), and finding that the polyimide synthesized by them contains rich -CF 3 and ester group, -CF 3The ester group provides low polarity and large free volume, while the ester group provides regularity. Since the ester group has both low polarity and large free volume and high regularity, the polyimide can have the advantages of low dielectric constant and low dielectric loss at the same time, and the absorbency of the polyimide is improved, and the original heat resistance and flexibility of the polyimide are guaranteed, and the polyimide has excellent comprehensive performance. The preparation method of the polyimide of the present invention has simple process steps, does not need to adopt copolymerization, blending and other methods, and the prepared polyimide can have the advantages of low dielectric constant and low dielectric loss at the same time, and the preparation method has broad industrial application value. The application of the polyimide of the present invention in the field of electronic industry provides a polyimide selection with better comprehensive performance for electronic industries such as circuit boards and chip packaging materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A schematic diagram of the reaction process for preparing a polyimide compound according to the present invention;

[0049] Figure 2 is a nuclear magnetic resonance spectrum of the polyimide compound used for preparing the present invention;

[0050] Figure 3 This is the infrared spectrum of the polyimide prepared in Examples 1-4 of the present invention;

[0051] Figure 4 The XRD test diagram of the polyimide prepared in Examples 1-4 of the present invention;

[0052] Figure 5 This is a POM test diagram of the polyimide prepared in Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0053] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0054] The substances used in the following examples are all common substances in the art and can be prepared by known methods or directly purchased from the market.

[0055] Example 1

[0056] An embodiment of the polyimide having both low dielectric constant and low dielectric loss according to the present invention, the preparation method of the polyimide according to this embodiment comprises the following steps:

[0057] (I) Preparation of target compound

[0058] (1) 10 g of 4,4'-(hexafluoroisopropylidene)diphenol was dissolved in a mixed solvent of 50 ml of THF and 14.4 ml of pyridine to obtain a solution 1;

[0059] (2) 12.1 g of 4-nitrobenzoyl chloride was added to 130 ml of THF and dissolved to obtain solution 2;

[0060] (3) placing solution 2 in an ice water bath and stirring, slowly adding solution 1 under the protection of nitrogen atmosphere, after the reaction is completed, filtering with a Buchner funnel to remove excess solution 2 and solvent, washing with THF and deionized water, collecting the precipitate, and drying in a forced air oven at 80° C. for 24 h to obtain a white crude dinitro compound;

[0061] (4) recrystallizing the crude dinitro compound product, collecting the precipitate and drying it in a forced air oven at 80° C. for 24 h to obtain a dinitro compound product;

[0062] (5) 10 g of the dinitro compound product was dispersed in 350 ml of DMF, and 0.5 g of Pd / C (10 wt.%) was used as a catalyst. The mixture was stirred for 24 h under a pressurized hydrogen atmosphere. After the reaction was complete, the catalyst was filtered out from the black solution and the filtrate was collected;

[0063] (6) The collected filtrate is poured into a large amount of deionized water to obtain a white precipitate, which is collected by filtration, recrystallized in ethanol / water, and dried in a vacuum oven to obtain the target compound.

[0064] The structural formula of the target compound is shown below:

[0065]

[0066] The reaction process diagram of the target compound is shown in the attached figure Figure 1 As shown, the target compound has a nuclear magnetic (H) of: (600 MHz, DMSO-d 6 , δ (ppm)): δ7.80 (d, J = 8.4Hz, 4H), 7.42 (d, J = 9.0Hz, 4H), 7.38 (d, J = 9.0Hz, 4H), 6.64 (d, J = 9.0Hz, 4H), 6.23 (s, 4H), as detailed in the appendix Figure 2 shown.

[0067] (II) Preparation of polyimide

[0068] S1. In a 100mL three-necked round-bottom flask equipped with a nitrogen inlet, a mechanical stirrer and a cold water bath, 5mmol of the target compound prepared above and 5ml of NMP were added and stirred until dissolved to form a homogeneous solution;

[0069] S2. A total of 5 mmol PMDA was added three times to the homogeneous solution formed in step S1, the molar ratio of the three additions was 2:2:1, and NMP was added in time, and the reaction was stirred at room temperature for 14 hours to obtain a polyamic acid solution having a certain viscosity;

[0070] S3. After degassing the polyamic acid solution obtained in step S2, it is evenly coated on a dry and clean glass plate by an automatic coating machine, and imidization reaction is carried out by thermal imidization method. The temperature curing program is: 80℃ / 3h, 250℃ / 1h, 300℃ / 1h, 330℃ / 1h, to obtain the polyimide of this embodiment.

[0071] The polyimide prepared in this example is named A2E6F-PMDA, and its structural formula is as follows:

[0072]

[0073] Example 2

[0074] This embodiment describes an embodiment of a polyimide having both low dielectric constant and low dielectric loss. Compared with Example 1, the only difference between this embodiment and Example 1 is that an equal amount of ODPA is used to replace PMDA in Example 1 during the preparation of the polyimide, and the rest is the same as Example 1.

[0075] The polyimide prepared in this example is named A2E6F-ODPA, and its structural formula is as follows:

[0076]

[0077] Example 3

[0078] This embodiment describes an embodiment of a polyimide having both low dielectric constant and low dielectric loss. Compared with Example 1, the only difference between this embodiment and Example 1 is that an equal amount of 6FDA is used to replace PMDA in Example 1 during the preparation of the polyimide, and the rest is the same as Example 1.

[0079] The polyimide prepared in this example is named A2E6F-6FDA, and its structural formula is as follows:

[0080]

[0081] Example 4

[0082] This embodiment describes an embodiment of a polyimide having both low dielectric constant and low dielectric loss. Compared with Example 1, the only difference between this embodiment and Example 1 is that an equal amount of TAHQ is used to replace PMDA in Example 1 during the preparation of the polyimide, and the rest is the same as Example 1.

[0083] The polyimide prepared in this example is named A2E6F-TAHQ, and its structural formula is as follows:

[0084]

[0085] Effect Example 1

[0086] Test of structural characteristics of the polyimide of the present invention

[0087] The polyimide prepared in the above examples 1-4 was subjected to infrared spectrum test, XRD test and POM test, and the test results are shown in the attached figures. Figures 3 to 5 shown.

[0088] By the attached Figure 3 It can be seen that the polyimide films prepared in Examples 1-4 are all completely imidized. Figure 4 and attached Figure 5 It can be seen that the polyimides prepared in Examples 1-4 all have certain orientation and crystallinity, among which Example 4 has the highest ester content and the best crystallinity. 3 The ester group provides low polarity and large free volume, while the ester group provides regularity. Since the polyimide films in Examples 1-4 of the present invention have both low polarity and large free volume and high regularity, they all have the advantages of low dielectric constant and low dielectric loss.

[0089] Effect Example 2

[0090] Performance test of the polyimide of the present invention

[0091] The dielectric properties, water absorption rate and thermal properties of the polyimide prepared in Examples 1-4 were tested respectively. At the same time, the polyimide film material (trade name KAPTON) produced by DuPont of the United States, 4-(4-aminobenzoyl)oxyphenyl 4-aminobenzoate and p-phenylene-diphenyltrimethylol dianhydride synthesized according to the conventional method in the field (abbreviated as ABHQ-TAHQ) were used as controls. The specific test method is:

[0092] Dielectric performance test method: Use vector network analyzer E5080B (USA, KEYSIGHT TECHNOLOGIES) to test, test frequency 10GHz, test temperature 25℃, humidity 40% RH, sample area 3×3cm 2 , respectively test the dielectric constant of each group of polyimide (D k ) and dielectric loss factor (D f ).

[0093] Water absorption test method: Use ME54 electronic analytical balance (METTLER TOLEDO) to measure the mass. First, place the sample film in a vacuum oven at 110℃ for 24h and weigh its mass as m 0 , respectively, soak the sample film in water for 72 hours, take it out and wipe it dry to reveal the water stains, and weigh its mass as m 100 , using the formula W A =(m 100 -m 0 ) / m 0 ×100% to calculate the water absorption of the sample.

[0094] Thermal performance test method: Dynamic mechanical analysis (DMA) was used to test the prepared black polyimide film in a dynamic mechanical analyzer (TA Company, USA, Q800 series) with a heating rate of 5°C / min and a frequency of 1Hz. The glass transition temperature (T g ), thermal decomposition temperature (T d ), maximum stress (σ max ) and tensile fracture strain (ε b ).

[0095] The test results of each group are shown in Table 1 below.

[0096] Table 1 Performance test results of each group of polyimide

[0097]

[0098] It can be seen from the results in Table 1 that, compared with KAPTON and ABHQ-TAHQ, the polyimide prepared in Examples 1-4 of the present invention has the advantages of low dielectric constant and low dielectric loss, and improves the water absorption of the polyimide, while ensuring the original heat resistance and flexibility of the polyimide.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A polyimide, characterized in that: The polyimide is prepared by using compound A and compound B; the structural formula of compound A is as follows: The compound B is at least one of pyromellitic anhydride, 3,3',4,4'-diphenyl ether tetracarboxylic anhydride, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride and tert-butylhydroquinone.

2. The polyimide according to claim 1, characterized in that The compound A is prepared by the following method: (1) dissolving 4,4'-(hexafluoroisopropylidene)diphenol in a solvent to obtain a solution 1; (2) dissolving 4-nitrobenzoyl chloride in a solvent to obtain solution 2; (3) placing solution 2 in an ice water bath and stirring, slowly adding solution 1 under the protection of inert gas, removing excess solvent after the reaction is completed, washing, collecting and drying the precipitate to obtain a crude dinitro compound; (4) recrystallizing the crude dinitro compound product, collecting and drying the precipitate to obtain a dinitro compound product; (5) dispersing the dinitro compound product in a solvent, adding a catalyst, and then stirring and reacting under a pressurized hydrogen atmosphere, removing the catalyst after the reaction, and collecting the filtrate; (6) The collected filtrate is poured into deionized water to obtain a white precipitate, which is collected by filtration, recrystallized and dried to obtain the compound A.

3. The polyimide according to claim 2, characterized in that In the preparation method of the compound A, the mass volume ratio of 4,4'-(hexafluoroisopropylidene)diphenol to the solvent in step (1) is 1:(5-7) g / ml; And / or, in step (2), the mass volume ratio of 4-nitrobenzoyl chloride to the solvent is 1:(10-14) g / ml; and / or, the molar ratio of the 4,4'-(hexafluoroisopropylidene)diphenol to 4-nitrobenzoyl chloride is 1:2; And / or, in step (5), the mass ratio of the catalyst to the dinitro compound product is 5-10%.

4. The polyimide according to claim 2, characterized in that In the preparation method of compound A, the solvents in step (1), step (2) and step (5) are each independently selected from at least one of THF, pyridine and DMF; And / or, the catalyst in step (5) is Pd / C.

5. The polyimide according to claim 1, characterized in that The molar ratio of compound A to compound B is 1:

1.

6. The polyimide according to claim 1, wherein The structural formula of the polyimide is any one of the following:

7. The method for preparing a polyimide according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: S1. In the presence of sufficient water and oxygen removal and under the protection of an inert gas, compound A is mixed with a solvent and stirred in a cold water bath until dissolved to form a homogeneous solution; S2. Compound B is added three times to the homogeneous solution formed in step S1, and the reaction is stirred at room temperature to obtain a polyamic acid solution having a certain viscosity; S3. The polyamic acid solution obtained in step S2 is degassed and evenly coated on a dry and clean glass plate, and an imidization reaction is carried out by a thermal imidization method to obtain polyimide.

8. The method for preparing a polyimide according to claim 7, characterized in that: The molar ratio of compound A to compound B is 1:1; And / or, the solvent in step S1 is N-methyl-2-pyrrolidone; And / or, in step S1, the molar volume ratio of compound A to the solvent is 1:1 mmol / ml; And / or, and / or, after adding compound B three times in step S2, the solvent is added to the reaction system in a timely manner.

9. The method for preparing a polyimide according to claim 7, characterized in that: The stirring reaction time in step S2 is 10 to 18 hours; And / or, the temperature rising curing procedure in the thermal imidization method in step S3 is: 80°C / 3h, 250°C / 1h, 300°C / 1h, 330°C / 1h.

10. Use of the polyimide according to any one of claims 1 to 6 in the field of electronics industry.

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