CN113337116B

CN113337116B - High-conductivity flexible polyimide composite film and preparation method thereof

Info

Publication number: CN113337116B
Application number: CN202110664131.XA
Authority: CN
Inventors: 方省众; 姜晗洲; 李嘉欣; 徐禄波; 陈国飞
Original assignee: Ningbo Institute of Material Technology and Engineering of CAS
Current assignee: Ningbo Institute of Material Technology and Engineering of CAS
Priority date: 2021-06-16
Filing date: 2021-06-16
Publication date: 2022-08-05
Anticipated expiration: 2041-06-16
Also published as: CN113337116A

Abstract

The invention relates to the technical field of polymer composite materials, and discloses a flexible polyimide composite film with high conductivity and a preparation method thereof, wherein the preparation method comprises the following steps: preparing PI @ rGO microspheres and polyamic acid salt; adding conductive nano-filler, PI @ rGO microspheres and a dispersing agent into a polyamic acid salt aqueous solution, performing ultrasonic dispersion to obtain a mixed solution, performing tape casting film formation and thermal imidization on the mixed solution to prepare the flexible polyimide composite film, mixing the PI @ rGO microspheres with waterborne PAAS to avoid the damage of a core-shell structure of the PI @ rGO microspheres by an organic solvent, constructing a three-dimensional ordered conductive network structure in the polyimide and the conductive nano-filler, preventing the film from cracking by utilizing the entanglement and bridging action of the waterborne PAAS, and preparing the composite film with regular surface and good toughness.

Description

High-conductivity flexible polyimide composite film and preparation method thereof

Technical Field

The invention relates to the technical field of polymer composite materials, in particular to a flexible polyimide composite film with high conductivity and a preparation method thereof.

Background

Polyimide (PI) is a high-performance engineering plastic with good thermal stability, mechanical property and chemical corrosion resistance, and is widely applied to the fields of microelectronic devices, aerospace, automobile manufacturing, gas separation, adhesives and the like. However, the polyimide resin has low electrical conductivity and poor thermal conductivity, and the defects limit the application of the polyimide in the fields of aviation, microelectronics and the like.

Relevant researches show that conductive nano fillers such as Carbon Nano Tubes (CNT) and Graphene (GNP) are introduced into a PI matrix, so that the conductivity and the heat conductivity of the PI can be greatly improved. At present, home and abroad PI/GNP composite materials are prepared by adopting in-situ compounding and solution compounding methods, a large amount of solvents are needed, the process is complicated, and the environmental protection is not facilitated; moreover, the use of a large amount of conductive filler can introduce defects into the polymer matrix, and the mechanical properties of the polymer are affected. In addition, in order to uniformly disperse the conductive filler in the PI matrix, it is necessary to modify the conductive filler, and the introduction of a functional group may reduce the conductive performance of the conductive filler.

For example, CN112795041A discloses a preparation method of a conductive polyimide film, which is prepared from the following raw materials in parts by mass: 1-5 parts of pyromellitic dianhydride, 1-3 parts of silane coupling agent, 5-9 parts of polymerized polyamide acid resin, 2.5-6 parts of ingredient A, 5-12 parts of diaminodiphenyl ether, 3-4 parts of dimethylacetamide solvent, 17-36 parts of conductive ingredient and 1.9-4 parts of ingredient B; the situation that the polyimide film is replaced more frequently when in use is avoided; the toughness of the polyimide film is greatly reduced due to the mixing of the conductive materials in the wear-resistant performance.

In view of the above disadvantages, new technologies need to be developed to solve them. The conductive network structure of the conductive filler is a major factor affecting polymer composites. The highly three-dimensional ordered conductive network structure can be constructed by compounding the latex particles or the microspheres, and the percolation threshold of the composite material is greatly reduced, so that attention of a plurality of researchers is paid in recent years.

The applicant discloses a polyimide/graphene composite material with high conductivity and a preparation method thereof in CN105273403A, wherein unmodified polyimide microspheres and graphene oxide are used as raw materials to prepare core-shell structure composite microspheres, the core-shell structure composite microspheres are subjected to chemical reduction to obtain polyimide/reduced graphene oxide microspheres, and finally the polyimide/graphene composite material is obtained through hot press molding. However, the method can only be used for preparing a thin plate through hot press molding, and is difficult to prepare a polyimide film, so that the application of the high-conductivity composite material in the field of films is limited.

Disclosure of Invention

Aiming at the defects of the method for improving the conductivity of the polyimide material in the prior art, the invention provides the preparation method of the flexible polyimide composite film with high conductivity, and the method can improve the conductivity of the polyimide film and can ensure that the film keeps flexibility and certain mechanical property.

In order to achieve the purpose, the invention adopts the technical scheme that:

a preparation method of a high-conductivity flexible polyimide composite film comprises the following steps:

(1) adding a graphene oxide aqueous dispersion to a polyimide microsphere aqueous dispersion for coating to obtain a dispersion of PI @ GO microspheres; adding a reducing agent, and carrying out chemical reduction reaction and post-treatment to obtain PI @ rGO microspheres;

(2) diamine and dianhydride react in a solvent to obtain a polyamic acid solution, an organic base is added for reaction, and polyamic acid salt is obtained through post-treatment;

(3) adding conductive nano filler, PI @ rGO microspheres and a dispersing agent into a polyamic acid salt aqueous solution, performing ultrasonic dispersion to obtain a mixed solution, and preparing the flexible polyimide composite film by tape-casting the mixed solution into a film and performing thermal imidization.

The preparation method comprises the steps of firstly preparing Polyimide (PI) microspheres by a precipitation method (CN 105273403A is referred to in the preparation process of the PI microspheres), then preparing the composite microspheres with the PI @ GO core-shell structure by taking water as a dispersion medium, and obtaining the composite microspheres with the PI @ rGO core-shell structure by chemical reduction. On the basis, a polyimide composite film is prepared by taking a polyamic acid salt (PAAS) aqueous solution as a substrate, adding the prepared PI @ rGO microspheres, conductive nano-fillers and a dispersing agent, and mixing.

The PI @ rGO microspheres are mixed with the waterborne PAAS, so that the core-shell structure of the PI @ rGO microspheres is prevented from being damaged by an organic solvent, a three-dimensional ordered conductive network structure is constructed in polyimide and conductive nano-filler, the film is prevented from cracking by utilizing the entanglement and bridging action of the waterborne PAAS, and the composite film with regular surface and good toughness is prepared.

The preparation process of the polyimide microsphere comprises the following specific steps:

the raw material is soluble polyimide, and can be commercialized polyimide, such as HI-P-100 (Gillen Qi polyimide materials Co., Ltd.), Ultem1000P (Saudi basic Industrial Co., Ltd.), YZPI (Nanjing Yue chemical industry Co., Ltd.). The solvent of the polyimide microsphere dispersion liquid is water or ethanol, the polyimide microsphere dispersion liquid is dispersed in a stirring mode, and the concentration is 0.1-10%. Preferably, the average particle size of the polyimide microspheres is 0.1-10 μm, wherein the surfaces of the polyimide microspheres are not modified or modified.

The preparation method of the PI microspheres comprises the following steps:

firstly, adding polyimide into N, N-dimethylacetamide (DMAc) at 90 ℃, stirring and dissolving, then adding polyvinyl alcohol (PVA) with the same content, stirring and dissolving to obtain PI/PVA mixed solution. Then deionized water is used as a solvent to prepare a PVA aqueous solution, and the solid content of the PVA aqueous solution is kept the same as that of the polyimide solution. And (3) dropwise adding the polyvinyl alcohol aqueous solution into the polyimide solution which is vigorously stirred under the reaction condition of 90 ℃ to obtain the polyimide microsphere suspension. And (3) performing centrifugal filtration, cleaning for 3-5 times, and drying at 120 ℃ to obtain the polyimide microspheres. The concentration of the polyimide and the polyvinyl alcohol in DMAc is preferably 0.1-50 mg/ml.

The PI @ GO microspheres comprise 90.0-99.9 wt% of polyimide microspheres and 0.1-10 wt% of graphene oxide.

The graphene oxide is single-layer or multi-layer graphene oxide, the sheet diameter is 0.1-10 mu m, the thickness is 0.5-5 nm, and the mass concentration of the graphene oxide aqueous dispersion is 0.1-10 mg/mL.

The coating temperature in the step (1) is 0-50 ℃, and the coating time is 0.5-6 hours; preferably, the temperature during coating is 10-30 ℃, and the coating time is 1-2 hours. The temperature is controlled to be 10-30 ℃ during coating, the coating time is controlled to be 1-2 hours, and the situation that the microspheres are agglomerated due to the fact that the graphene coats a plurality of microspheres due to overhigh temperature or overlong coating time is avoided.

The reducing agent comprises one or more of ascorbic acid, hydrazine hydrate, dimethylhydrazine, phenylhydrazine, p-methylsulfonyl hydrazine, sodium borohydride, lithium aluminum hydride, ethylenediamine, p-phenylenediamine and hydroiodic acid.

The addition amount of the reducing agent is 1-100 times of the mass of the graphene oxide. Preferably, the addition amount of the reducing agent is 10 to 30 times of the mass of the graphene oxide. The reduction degree of the graphene oxide can be improved, and the redundant reducing agent can be conveniently removed in the post-treatment process.

The temperature of the reduction reaction is 0-50 ℃, and the time of the reduction reaction is 8-24 hours. Preferably, the temperature of the reduction reaction is 10-30 ℃, and the time of the reduction reaction is 12-24 hours. The temperature of the reduction reaction is controlled to be 10-30 ℃, on one hand, the reducing agent is prevented from being heated and decomposed, the reduction degree of the graphene oxide is improved, and on the other hand, the microspheres can be prevented from agglomerating. The reduction efficiency is low at the reaction temperature, and the reaction time should be properly prolonged.

And (2) after the reduction reaction in the step (1) is finished, the post-treatment aims to remove a reducing agent and an aqueous solution, a centrifugal washing method is adopted for 3-5 times, and drying is carried out at 50-80 ℃ after centrifugation, so that the PI @ rGO microspheres are obtained.

The solvent in the step (2) is a polar aprotic solution, and comprises one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, m-cresol, dimethyl sulfoxide and gamma-butyrolactone.

The diamine comprises one or more of p-phenylenediamine, m-phenylenediamine, benzidine, 3 '-diaminodiphenyl ether, 4' -diaminodiphenyl sulfide, 3 '-diaminodiphenyl sulfoxide, 4-diaminodiphenylmethane and 2,2' -bis (trifluoromethyl) benzidine.

The dianhydrides include pyromellitic dianhydride, 3,3',4,4' -biphenyltetracarboxylic dianhydride, 2,3',3,4' -biphenyltetracarboxylic dianhydride, 2',3,3' -biphenyltetracarboxylic dianhydride, 3,3',4,4' -benzophenone tetracarboxylic dianhydride, 3,3',4,4' -diphenyl ether tetracarboxylic dianhydride, 2,3',3,4' -diphenyl ether tetracarboxylic dianhydride, 2,2',3,3' -diphenyl ether tetracarboxylic dianhydride, diphenyl sulfide dianhydride, 2',3,3' -triphenyl diether tetracarboxylic dianhydride, 3,3',4,4' -triphenyl diether tetracarboxylic dianhydride, bisphenol a type diether dianhydride, 3,3',4,4' -diphenyl sulfone tetracarboxylic dianhydride, and 2,2' -bis (3, 4-dicarboxylic acid) hexafluoropropane dianhydride.

The organic base comprises one or more of trimethylamine, triethylamine, dimethylethanolamine, N-methylmorpholine and pyridine.

The molar ratio of the organic base to the dianhydride is 0.1-5, and the reaction is carried out for 1-24 hours after the organic base is added. Preferably, the molar ratio of the organic base to the dianhydride is 1.5-3, and the reaction is carried out for 6-12 hours after the organic base is added. The carboxyl side group of the polyamic acid can be fully reacted with the organic base, the salt forming rate of the polyamic acid is improved, and the solubility of the polyamic acid salt solid in water is improved.

In the step (2), the post-treatment means adding an organic base to react to obtain a polyimide acid salt solution, and precipitating and purifying the polyimide acid salt solution in a poor solvent to obtain the polyimide salt. The poor solvent includes acetone and/or methanol.

The conductive nano filler comprises one or more of carbon black, graphite fiber, carbon nano tube and graphene; preferably, the conductive nanofiller is Carbon Nanotubes (CNTs);

further preferably, the conductive nano filler is prepared by connecting more PI @ rGO microspheres in series by using the CNT with a high length-diameter ratio one-dimensional structure, so that a three-dimensional conductive network structure in the PI composite film is further perfected, and the conductivity of the PI composite film is improved.

The dispersing agent comprises one or more of polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyethylene glycol and polyvinyl pyrrolidone.

In the flexible polyimide composite film, the mass ratio of the conductive nano filler is 0.1-30 wt%; the mass ratio of the PI @ rGO microspheres is 1-50 wt%; the mass ratio of the dispersing agent is 1-10 wt%.

Preferably, in the flexible polyimide composite film, the mass ratio of the conductive nano filler is 5-20 wt%; the mass ratio of the PI @ rGO microspheres is 5-20 wt%.

Further preferably, in the flexible polyimide composite film, the mass ratio of the conductive nano filler is 3-15 wt%; the mass ratio of the PI @ rGO microspheres is 5-20 wt%; the mass percentage of the dispersing agent is 3-6 wt%.

More preferably, in the flexible polyimide composite film, the mass ratio of the conductive nano filler is 5-10 wt%; the mass ratio of the PI @ rGO microspheres is 5-15 wt%; the inventor finds that the conductivity of the composite film is rapidly increased along with the increase of the content of the PI @ rGO microspheres, and the film has good flexibility, can be bent at will and keeps good mechanical properties.

Preferably, the mixed solution in the step (3) is cured in a vacuum oven for 2-6 hours before thermal imidization, and the curing temperature is room temperature. On one hand, the composite film is cured in advance, so that the surface of the composite film can be prevented from being wrinkled due to air blowing of an oven, on the other hand, most of solvent in the mixed solution can be removed in advance, the polyamic acid salt aqueous solution is prevented from forming hydrogel, and the composite film is prevented from foaming or sponginess in the imidization process.

The temperature of the thermal imidization is 80-300 ℃, and the time is 1-12 hours; preferably, the thermal imidization temperature is 100 to 200 ℃ and the time is 3 to 6 hours.

Preferably, the thermal imidization is performed at different temperatures for 0.5 to 1 hour, such as heating at 80 ℃ for 1 hour, heating at 100 ℃ for 1 hour, heating at 150 ℃ for 1 hour, heating at 200 ℃ for 1 hour, and heating at 250 ℃ for 1 hour.

The invention also provides the high-conductivity flexible polyimide composite film prepared by the preparation method. The conductive nanofiller and the PI @ rGO microspheres in the film are connected in series to form a highly ordered conductive three-dimensional network structure, so that the conductivity of the composite film is greatly improved, and the film keeps good flexibility and mechanical properties.

Compared with the prior art, the invention has the following beneficial effects:

(1) the method for preparing the flexible polyimide film can greatly improve the conductivity of the composite film, and the film keeps good flexibility and mechanical property.

(2) According to the flexible polyimide film, the structural design of polyimide is not required, the chemical modification of graphene is also not required, the preparation process is simplified, and the influence of modified graphene on the thermal conductivity is avoided; the composite material is prepared by adopting a thermal imidization process, and is suitable for industrial production of large-area composite films.

(3) According to the invention, the water-based polyimide is adopted as the composite film substrate, so that the damage of the PI @ rGO microsphere core-shell structure by an organic solvent is avoided, and the solvent is deionized water, so that the composite film is environment-friendly and pollution-free.

Drawings

FIG. 1 shows the electrical conductivity of the flexible polyimide composite films obtained in examples 1 to 3.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Those skilled in the art should understand that they can make modifications and equivalents without departing from the spirit and scope of the present invention, and all such modifications and equivalents are intended to be included within the scope of the present invention.

The raw materials used in the following embodiments are all commercially available.

Example 1

(1) Preparing PI microspheres: the polyimide microspheres are self-made microspheres, and are prepared by a precipitation method (the specific preparation method is shown in patent CN105273403A), and the average particle size of the obtained PI microspheres is about 3 mu m.

(2) Preparation of PI @ rGO microspheres: adding 4g of PI microspheres into a 1L beaker, adding 340mL of deionized water, and performing ultrasonic dispersion for 10min to obtain a PI microsphere water dispersion. And slowly adding 60mL of graphene oxide aqueous dispersion with the concentration of 2mg/mL into the PI microsphere aqueous dispersion, and stirring at room temperature for 2 hours to obtain the PI @ GO microsphere aqueous dispersion. And then adding 5mL of 55% hydriodic acid aqueous solution into the dispersion, and stirring and reacting for 16 hours at room temperature to obtain the PI @ rGO microsphere aqueous dispersion. And (3) centrifugally washing with deionized water for 3-5 times, and drying at 80 ℃ to obtain the PI @ rGO microsphere.

(3) Preparation of aqueous PAAS solution: 2.1628g (0.02mol) of m-phenylenediamine and 113.1535g N, N-dimethylacetamide were charged into a 250mL three-necked flask under nitrogen atmosphere, stirred until the solid was completely dissolved, and 10.4098g (0.02mol) of bisphenol A type diether dianhydride was further added and reacted at room temperature for 12 hours. 3.9222g (0.044mol) of N, N-dimethylethanolamine was then added to the polyamic acid solution and reacted at room temperature for 4 hours to obtain a polyamic acid salt solution. Then slowly pouring the polyamic acid salt solution into acetone for precipitation, removing residual solvent after washing for multiple times to obtain polyamic acid salt solid, and dissolving the polyamic acid salt solid in deionized water to prepare PAAS aqueous solution with the concentration of 6.85 wt%.

(4) Preparation of PAAS mixed solution: and (3) adding 2.4464g of carbon nanotube aqueous dispersion with the mass concentration of 14% and 0.2056g of polyethylene glycol into 50g of PAAS aqueous solution, and stirring until the polyethylene glycol is completely dissolved to obtain a PAAS/CNT mixed solution. And then adding 0.0343gPI @ rGO microspheres into 10g of PAAS/CNT mixed solution, and performing ultrasonic dispersion for 3min to obtain the PAAS/CNT/microsphere mixed solution.

(5) Preparing a flexible polyimide composite film: coating 10g of the mixed solution on a clean glass plate, curing the mixed solution in a vacuum oven for 4 hours at room temperature, and then performing thermal imidization in a common oven, wherein the specific temperature rise procedures are heating at 80 ℃ for 1 hour, heating at 100 ℃ for 1 hour, heating at 150 ℃ for 1 hour, heating at 200 ℃ for 1 hour and heating at 250 ℃ for 1 hour.

Example 2

The preparation process is the same as that of example 1, and only in the step (4), the addition amount of the PI @ rGO microspheres is replaced by 0.0685g to obtain a PAAS/CNT/microsphere mixed solution, and then the PAAS/CNT/microsphere mixed solution is subjected to thermal imidization to obtain the flexible polyimide composite film.

Example 3

The preparation process is the same as that of example 1, and 0.1028g of the PI @ rGO microspheres are replaced in the step (4) to obtain a PAAS/CNT/microsphere mixed solution, and then the PAAS/CNT/microsphere mixed solution is subjected to thermal imidization to obtain the flexible polyimide composite film.

Comparative example 1

The preparation process is the same as that of the embodiment 1, only in the step (4), the addition amount of the PI @ rGO microspheres is replaced by 0g to obtain a PAAS/CNT/microsphere mixed solution, and then the PAAS/CNT/microsphere mixed solution is subjected to thermal imidization to obtain the flexible polyimide composite film.

Comparative example 2

The preparation process is the same as that of the example 2, and 1.2232g of PAAS/CNT mixed solution is obtained only by replacing the adding amount of the carbon nano tube aqueous dispersion in the step (4), and then the flexible polyimide composite film is prepared by thermal imidization.

Example 4

The preparation procedures of the steps (1) to (2) are the same as those of the example 1;

(3) preparation of aqueous PAAS solution: 6.4048g (0.02mol) of 2,2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl and 137.6064g N, N-dimethylacetamide were charged into a 250mL three-necked flask under nitrogen atmosphere, and the mixture was stirred until the solid was completely dissolved, and 8.8848g (0.02mol) of 4, 4-hexafluoroisopropylphthalic anhydride was further added and reacted at room temperature for 12 hours. 3.9222g (0.044mol) of N, N-dimethylethanolamine was then added to the polyamic acid solution and reacted at room temperature for 4 hours to obtain a polyamic acid salt solution. Then slowly pouring the polyamic acid salt solution into acetone for precipitation, and removing residual solvent after multiple times of washing to obtain polyamic acid salt solid. The polyamic acid salt solid was then dissolved in deionized water at a concentration of 6.85 wt% to give an aqueous solution of PAAS.

(4) Preparation of PAAS mixed solution: and (3) adding 2.4464g of 14% carbon nanotube aqueous dispersion and 0.2056g of polyethylene glycol into 50g of PAAS aqueous solution, and stirring until the polyethylene glycol is completely dissolved to obtain a PAAS/CNT mixed solution. And then adding 0.0343g of PI @ rGO microspheres into 10g of PAAS/CNT mixed solution, and performing ultrasonic dispersion for 3min to obtain the PAAS/CNT/microsphere mixed solution.

The flexible polyimides prepared in examples 1 to 4 and comparative examples 1 to 2 were tested for their mechanical properties and electrical conductivity. The mechanical property is measured by a universal material testing machine at a stretching speed of 5mm/min, and the conductivity is calculated by resistance, a contact area of a meter pen and film thickness measured by a universal meter. The results are summarized in Table 1, and the electrical conductivities of the films of examples 1-3 are shown in FIG. 1.

TABLE 1 Properties of Flexible polyimide composite films prepared in examples and comparative examples

As can be seen from fig. 1 and table 1, in examples 1 to 3, the conductivity of the flexible polyimide composite film rapidly increases with the increase of the content of the PI @ rGO microspheres, while the tensile modulus and the elongation at break of the film are not significantly reduced, the film maintains good flexibility, can be bent at will, and has slightly reduced tensile strength, but generally maintains good mechanical properties.

In comparison with example 2, the conductive nano filler in the PAAS mixed solution is preferably added in an amount of 5 wt% or more because the conductivity of the film is greatly reduced when the content of the carbon nanotubes is slightly reduced.

Claims

1. A preparation method of a high-conductivity flexible polyimide composite film is characterized by comprising the following steps:

(3) adding conductive nano filler, PI @ rGO microspheres and a dispersing agent into a polyamic acid salt aqueous solution, performing ultrasonic dispersion to obtain a mixed solution, and preparing the flexible polyimide composite film by tape-casting film-forming and thermal imidization of the mixed solution;

in the flexible polyimide composite film, the mass ratio of the conductive nano filler is 5-20 wt%; the mass ratio of the PI @ rGO microspheres is 5-20 wt%; the mass ratio of the dispersing agent is 1-10 wt%;

the PI @ GO microspheres comprise 90.0-99.9 wt% of polyimide microspheres and 0.1-10 wt% of graphene oxide; the conductive nanofiller is carbon nanotubes.

2. The method for preparing a flexible polyimide composite film with high conductivity according to claim 1, wherein the average particle size of the polyimide microspheres is 0.1-10 μm; the graphene oxide is single-layer or multi-layer graphene oxide, the sheet diameter is 0.1-10 mu m, the thickness is 0.5-5 nm, and the mass concentration of the graphene oxide aqueous dispersion is 0.1-10 mg/mL.

3. The method for preparing a flexible polyimide composite film with high conductivity according to claim 1, wherein the temperature for coating in the step (1) is 0-50 ℃ and the time for coating is 0.5-6 hours;

the reducing agent comprises one or more of ascorbic acid, hydrazine hydrate, dimethylhydrazine, phenylhydrazine, p-methylsulfonyl hydrazine, sodium borohydride, lithium aluminum hydride, ethylenediamine, p-phenylenediamine and hydroiodic acid;

the temperature of the reduction reaction is 0-50 ℃, and the time of the reduction reaction is 8-24 hours.

4. The method of preparing a highly conductive flexible polyimide composite film according to claim 1, wherein the diamine comprises one or more of p-phenylenediamine, m-phenylenediamine, benzidine, 3 '-diaminodiphenyl ether, 4' -diaminodiphenyl sulfide, 3 '-diaminodiphenyl sulfoxide, 4-diaminodiphenylmethane, and 2,2' -bis (trifluoromethyl) benzidine;

the dianhydrides include pyromellitic dianhydride, 3,3',4,4' -biphenyltetracarboxylic dianhydride, 2,3',3,4' -biphenyltetracarboxylic dianhydride, 2',3,3' -biphenyltetracarboxylic dianhydride, 3,3',4,4' -benzophenone tetracarboxylic dianhydride, 3,3',4,4' -diphenyl ether tetracarboxylic dianhydride, 2,3',3,4' -diphenyl ether tetracarboxylic dianhydride, one or more of 2,2',3,3' -diphenyl ether tetracarboxylic dianhydride, diphenyl sulfide dianhydride, 2',3,3' -triphendiether tetracarboxylic dianhydride, 3,3',4,4' -triphendiether tetracarboxylic dianhydride, bisphenol a type diether dianhydride, 3,3',4,4' -diphenylsulfone tetracarboxylic dianhydride, and 2,2' -bis (3, 4-dicarboxylic acid) hexafluoropropane dianhydride;

5. The method for preparing the high-conductivity flexible polyimide composite film according to claim 1, wherein the molar ratio of the organic base to the dianhydride is 0.1-5, and the reaction is carried out for 1-24 hours after the organic base is added.

6. The method for preparing a flexible polyimide composite film with high conductivity according to claim 1, wherein the dispersant comprises one or more of polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyethylene glycol and polyvinylpyrrolidone.

7. The method for preparing a flexible polyimide composite film with high conductivity according to claim 1, wherein the thermal imidization is performed at a temperature of 80 to 300 ℃ for 1 to 12 hours.

8. The high-conductivity flexible polyimide composite film obtained by the preparation method according to any one of claims 1 to 7.