A method for directly preparing a polyimide insulating film on a metal aluminum plate

Abstract

The application discloses a method for directly preparing a polyimide insulating film on a metal aluminum plate. A coupling agent is added into a polyamide acid slurry to obtain a coating liquid. The coating liquid is uniformly coated on the surface of a pretreated metal aluminum plate, and a first gradient temperature rising is performed to remove the solvent. Finally, the metal aluminum plate is transferred into a muffle furnace, a second gradient temperature rising is performed, and heat imidization is realized. The metal aluminum plate is naturally cooled to room temperature, and the polyimide insulating film is directly prepared on the metal aluminum plate, and an integrated insulating metal plate is obtained. The method has low process cost, no pollution, low process requirement, simple production equipment requirement, and the formed polyimide insulating film has good low dielectric, low dielectric loss, insulation, high temperature resistance and other performances.

Description

Technical Field

[0001] This invention relates to a method for preparing a polyimide insulating film, specifically a method for directly preparing a polyimide insulating film on a metal aluminum plate. It belongs to the field of film coating technology. Background Technology

[0002] Polyimide is an engineering material with excellent properties. Due to its superior high temperature resistance, heat resistance, insulation, low dielectric constant and dielectric loss, and high mechanical strength, it is widely used in aerospace, electronic communications, insulating films, separation films and other fields.

[0003] Currently, there are many challenges in improving traditional insulating film coating technology in the field of new energy vehicle manufacturing. These include the complexity of the insulating film coating process, its cumbersome procedures, high costs, and demanding industrial production equipment requirements. Furthermore, the precision requirements for insulating film coating on irregular substrates or small devices are high, making the operation difficult. For example, in new energy vehicle motors, with technological advancements, resin impregnation technology has been used in the preparation of insulating devices. The application scenarios of electrical insulation materials require the prepared films to have excellent heat resistance and insulation properties. However, this technology is too expensive and has not yet been widely adopted in China. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for directly preparing a polyimide insulating film on a metal aluminum plate.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for directly preparing a polyimide insulating film on a metallic aluminum plate includes the following steps:

[0007] S1. First, add a coupling agent to the polyamic acid slurry to obtain the coating solution;

[0008] S2. Then, the coating liquid is uniformly applied to the surface of the pretreated aluminum plate, and the first gradient heating is performed to remove the solvent.

[0009] S3. Finally, transfer it to a muffle furnace for a second gradient heating to achieve thermal imidization, and then allow it to cool naturally to room temperature.

[0010] Preferably, in step S1, the coupling agent is γ-glycidoxypropyltrimethoxysilane.

[0011] Preferably, in step S1, the polyamic acid slurry is obtained by stirring and dispersing polyamic acid in N,N-dimethylacetamide, and the mass solid content is 10-20%.

[0012] More preferably, the amount of coupling agent is 1-10% of the mass of polyamic acid; after adding the coupling agent to the polyamic acid slurry, it is stirred vigorously to mix evenly, and then ultrasonically treated at 99W for 10-60 minutes to remove air bubbles (100W ultrasonic machine, using 99% power).

[0013] More preferably, the polyamic acid is obtained by polycondensation reaction of hexafluorodianhydride and a diamine (diamine a, diamine b, or diamine c) having the following structure:

[0014] ;

[0015] Diamine a is 4,4'-diamino-4''(2,3,5,6-tetrafluoro-4-ethylphenoxy)triphenylmethane; diamine b is 4-[bis-(4-amino-3-methylphenyl)-4''-(2,3,5,6-tetrafluoro-4-ethylphenoxy)triphenylmethane; diamine c is 4-[bis-(4-amino-3,5-dimethylphenyl)-4''-(2,3,5,6-tetrafluoro-4-ethylphenoxy)triphenylmethane].

[0016] More preferably, the preparation method of the diamine a is as follows: At room temperature, 0.05 mol of p-hydroxybenzaldehyde, 0.0125 mol of o-toluidine hydrochloride, and 0.125 mol of o-toluidine are weighed and added to a three-necked flask equipped with a spherical condenser and nitrogen inlet and outlet. The reaction is carried out at 120 °C for 3 h. After stopping the reaction, the mixture is cooled, diluted with 20 ml of anhydrous ethanol, and poured into 20 ml of saturated K2CO3 solution. After chloroform extraction, water washing, drying with anhydrous magnesium sulfate, filtration, vacuum distillation, and precipitation with n-hexane, the mixture is purified by column chromatography with a 1:2 volume ratio of ethyl acetate / petroleum ether mixed solvent. After removing the solvent by rotary evaporation, the mixture is dried in a vacuum oven at 60 °C for 24 h to obtain the intermediate product a* of a.

[0017] Weigh out 0.01 mol of a*, 0.02 mol of calcium hydride, 0.001 mol of cesium fluoride, and 0.012 mol of 2,3,4,5,6-pentafluorostyrene and add them to a three-necked flask equipped with a spherical condenser for nitrogen inlet and outlet. Add 30 mL of N,N-dimethylacetamide. React at 80 °C for 18 h under light-protected conditions. After cooling to room temperature, add 10 mL of deionized water, extract with diethyl ether, dry to anhydrous magnesium sulfate, distill under reduced pressure, and purify by column chromatography with a 1:1 (v / v) mixture of ethyl acetate and petroleum ether. Remove the solvent by rotary evaporation and dry in a vacuum oven at 60 °C for 24 h to obtain diamine a.

[0018] Diamine b or diamine c is obtained by referring to the preparation method of diamine a.

[0019] The structural formulas of the polyamic acids (PAA-a, PAA-b, PAA-c) are as follows:

[0020] .

[0021] Preferably, in step S2, the size of the aluminum plate is 21 cm × 30 cm.

[0022] Preferably, in step S2, the specific method of pretreatment is as follows: first, polish the aluminum plate with 1000-grit sandpaper until smooth, then rinse it multiple times with deionized water and isopropanol, and let it air dry naturally at room temperature.

[0023] Preferably, in step S2, the specific method of coating is as follows: place the pretreated aluminum plate on a horizontal platform, uniformly coat the surface of the aluminum plate with the coating liquid, let it stand for 5 minutes, carefully observe the bubble content and uniformity of the liquid film, adjust it with a glass rod and let it stand again, repeat the standing and adjustment operation three times to obtain a uniform liquid film without bubbles coated on the aluminum plate.

[0024] Preferably, in step S2, the process conditions for the first gradient heating are: performing 3 to 4 stages of heat preservation within the range of 40 to 120 °C to evaporate the solvent and obtain a smooth and uniform film. The applicant has screened the temperature range; outside this temperature range, it is difficult to obtain a uniformly coated and smooth film, which can easily cause the film to crack or separate from the metal substrate.

[0025] Further preferred process conditions for the first gradient heating are: heating to 40 ℃ and holding for 30 min; heating to 60 ℃ and holding for 30 min; heating to 80 ℃ and holding for 60 min; heating to 100 ℃ and holding for 60 min.

[0026] Further preferred process conditions for the first gradient heating are: heating to 50 ℃ and holding for 30 min; heating to 70 ℃ and holding for 30 min; heating to 90 ℃ and holding for 60 min; heating to 110 ℃ and holding for 60 min.

[0027] Further preferred process conditions for the first gradient heating are: heating to 80℃ and holding for 30 min; heating to 100℃ and holding for 60 min; heating to 120℃ and holding for 60 min.

[0028] Preferably, in step S2, a dust cover should be applied during the first gradient heating to prevent dust from falling into the liquid film.

[0029] Preferably, in step S3, the process conditions for the second gradient heating are as follows: heating from room temperature to 100–120 °C at a heating rate of 10 °C / min, holding for 120 min; heating to 150 °C at a heating rate of 6 °C / min, holding for 30 min; heating to 200 °C at a heating rate of 6 °C / min, holding for 30 min; and heating to 270 °C at a heating rate of 6 °C / min, holding for 30 min. Preferably, in step S3, thermal imidization generates polyimides (PI-a, PI-b, PI-c), with the following structural formula:

[0030] .

[0031] The integrated insulating metal plate is prepared using the aforementioned method.

[0032] The beneficial effects of this invention are:

[0033] This invention first adds a coupling agent to a polyamic acid slurry to obtain a coating solution; then, the coating solution is uniformly coated on the surface of a pretreated aluminum plate, and a first gradient heating is performed to remove the solvent; finally, it is transferred to a muffle furnace for a second gradient heating to achieve thermal imidization, and then naturally cooled to room temperature, thereby directly preparing a polyimide insulating film on the aluminum plate to obtain an integrated insulating metal plate.

[0034] The process of this invention is low-cost, pollution-free, has low process requirements, and requires simple production equipment. The resulting polyimide insulating film has excellent properties such as low dielectric strength, low dielectric loss, insulation, and high temperature resistance.

[0035] This invention solves the problem of improving the adhesion between the insulating film and the substrate, thereby enhancing adaptability, reducing the difficulty of industrial cutting and coating, providing a new direction for insulating film coating technology, and offering new ideas for detailed coating of insulating films on complex-shaped substrates. The insulating film of this invention exhibits excellent adhesion to the aluminum substrate. Especially after coating on large-area aluminum substrates, it still maintains a complete, smooth, and bubble-free coating surface, while also possessing excellent peel resistance and insulation properties. This invention has promising applications in the field of insulating device fabrication.

[0036] In particular, this invention introduces a novel diamine and a coupling agent, and the film can maintain its structural stability at high temperatures above 500 °C, showing great promise for applications in new energy materials, insulating devices and other fields. Attached Figure Description

[0037] Figure 1 They are different polyamic acid (PAA) and polyimide (PI) molecular structures;

[0038] Figure 2 It is the structural formula of a diamine;

[0039] Figure 3 These are the 1H NMR spectra of the various diamines, where a is the PAA-a precursor diamine, b is the PAA-b precursor diamine, and c is the PAA-c precursor diamine.

[0040] Figure 4 These are the infrared spectra of PI-a, PI-b, and PI-c. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that the following description is only for explaining the present invention and does not limit its content.

[0042] The structural formulas and proton NMR spectra of the corresponding diamines for PAA-a, PAA-b, and PAA-c in the examples are shown below. Figure 2 , Figure 3 The proton NMR data are as follows:

[0043] PAA-a raw material diamine: 1 H NMR(400MHz, DMSO-d6): 4.43 (4H, s), 5.10 (1H, s), 5.84 (1H, d, J = 7.5 Hz), 6.08 (1H, d, J = 4.1 Hz), 6.55 (1H, s), 6.73 – 6.68(2H, m), 6.80 – 6.73 (2H, m), 7.02 – 6.96 (4H, m), 7.06 – 7.02 (4H, m)

[0044] PAA-b raw material diamine: 1 H NMR(400MHz, DMSO-d6): 1.97 (6H, s), 4.75 (4H, s), 5.15 (1H, s), 5.82 (1H, d, J = 7.9 Hz), 6.06 (1H, d, J = 12.0 Hz), 6.51 (2H,d, J = 5.4 Hz), 6.69 – 6.55 (5H, m), 7.00 (2H, d, J = 5.8 Hz), 7.00 (2H, d, J= 5.8 Hz)

[0045] PAA-c raw material diamine: 1H NMR(400MHz, DMSO-d6): 2.07 – 2.00 (12H, m), 4.35(1H, s), 5.08 (1H, s), 5.83 (1H, d, J = 7.5 Hz), 6.05 (1H, dd, J = 11.7, 4.4Hz), 6.55 (1H, s), 6.71 – 6.62 (2H, m), 6.79 – 6.72 (2H, m), 7.04 (4H, dd, J= 8.3, 5.7 Hz).

[0046] Figure 1 They are different polyamic acid (PAA) and polyimide (PI) molecular structures. Figure 4 The infrared spectra are for PI-a, PI-b, and PI-c. Example

[0047] The preparation method of the coating solution is as follows: 3.0 g of N,N-dimethylacetamide solvent is added to 15 g of PAA-a solution with a solid content of 18% to dilute it and obtain PAA-a solution with a solid content of 15%. Then, 0.081 g of γ-glycidoxypropyltrimethoxysilane is added as a coupling agent. After vigorous stirring and homogenization, the solution is ultrasonically treated for 30 min to eliminate the air bubbles in the coating solution.

[0048] The processing method for aluminum plates is as follows: use 1000-grit sandpaper to polish the aluminum plate smooth and flat, remove the oxide layer and small particles attached to the aluminum plate. The size of the aluminum plate is 21 cm × 30 cm. Rinse the aluminum plate with deionized water until no particles are attached to the surface. Then rinse the surface of the aluminum plate with isopropyl alcohol and let it air dry in a clean space.

[0049] The preparation method of the integrated PI-a insulating aluminum plate is as follows: A clean and dry aluminum plate is placed on a horizontal platform. 18 g of PAA-a solution is evenly spread on the aluminum plate. After standing for 5 minutes, the bubble content and uniformity of the liquid film are carefully observed. Adjustments are made promptly using a glass rod, and the plate is allowed to stand again. This standing and adjustment process is repeated three times to obtain a uniformly spread, bubble-free liquid film on the aluminum plate. The aluminum plate coated with the smooth liquid film is placed on a horizontal heated plate. The plate is heated to 40℃, and the presence of bubbles and uneven solution in the liquid film is observed. Intervention is made promptly, and the plate is held at this temperature for 30 minutes. The temperature is then increased to 60℃, and the presence of bubbles and uneven solution in the liquid film is observed again. Intervention is made promptly, and the plate is held at this temperature for 30 minutes. The temperature is then increased to 80℃, and the presence of bubbles and uneven solution in the liquid film is observed again. Intervention is made promptly, and the plate is held at this temperature for 60 minutes. Finally, the temperature is increased to 100℃, and the presence of bubbles and uneven solution in the liquid film is observed again. Intervention is made promptly, and the plate is held at this temperature for 60 minutes. Thermal imidization process: The aluminum plate coated with a smooth liquid film (after the solvent has been removed) is placed smoothly into a muffle furnace. A gradient heating program is set, heating from room temperature to 100 ℃ at a heating rate of 10 ℃ / min and holding for 120 min; heating to 150 ℃ at a heating rate of 6 ℃ / min and holding for 30 min; heating to 200 ℃ at a heating rate of 6 ℃ / min and holding for 30 min; heating to 270 ℃ at a heating rate of 6 ℃ / min and holding for 30 min. After the heating program is completed, allow it to cool naturally to obtain an integrated PI-a insulating aluminum plate. Example

[0050] The casting solution is prepared as follows: 4.0 g of N,N-dimethylacetamide solvent is added to 20 g of PAA-b solution with a solid content of 18% to dilute it and obtain PAA-b solution with a solid content of 15%. Then, 0.108 g of γ-glycidoxypropyltrimethoxysilane is added as a coupling agent. After vigorous stirring and homogenization, the solution is ultrasonically treated for 30 min to eliminate air bubbles in the casting solution.

[0051] The processing method for aluminum plates is as follows: use 1000-grit sandpaper to polish the aluminum plate smooth and flat, remove the oxide layer and small particles attached to the aluminum plate. The size of the aluminum plate is 21 cm × 30 cm. Rinse the aluminum plate with deionized water until no particles are attached to the surface. Then rinse the surface of the aluminum plate with isopropyl alcohol and let it air dry in a clean space.

[0052] The preparation method of integrated PI-b insulating aluminum plate is as follows: A clean and dry aluminum plate is placed on a horizontal platform. 24 g of polyamic acid coating liquid is evenly spread on the aluminum plate. After standing for 5 minutes, the bubble content and uniformity of the liquid film are carefully observed. Adjustments are made promptly using a glass rod, and the plate is allowed to stand again. This standing and adjustment process is repeated three times to obtain a uniformly spread and bubble-free liquid film on the aluminum plate. The aluminum plate coated with the smooth liquid film is placed on a horizontal heated plate. The plate is heated to 50 °C, and the presence of bubbles and uneven solution in the liquid film is observed. Intervention is made promptly, and the plate is held at this temperature for 30 minutes. The temperature is then increased to 70 °C, and the presence of bubbles and uneven solution in the liquid film is observed again. Intervention is made promptly, and the plate is held at this temperature for 30 minutes. The temperature is then increased to 90 °C, and the presence of bubbles and uneven solution in the liquid film is observed again. Intervention is made promptly, and the plate is held at this temperature for 60 minutes. Finally, the temperature is increased to 110 °C, and the presence of bubbles and uneven solution in the liquid film is observed again. Intervention is made promptly, and the plate is held at this temperature for 60 minutes. Thermal imidization process: The aluminum plate coated with a smooth liquid film (after the solvent has been removed) is placed smoothly into a muffle furnace. A gradient heating program is set, heating from room temperature to 110 ℃ at a heating rate of 10 ℃ / min and holding for 120 min; heating to 150 ℃ at a heating rate of 6 ℃ / min and holding for 30 min; heating to 200 ℃ at a heating rate of 6 ℃ / min and holding for 30 min; heating to 270 ℃ at a heating rate of 6 ℃ / min and holding for 30 min. After the heating program is completed, allow it to cool naturally to obtain an integrated PI-b insulating aluminum plate. Example

[0053] The casting solution is prepared as follows: 5.0 g of N,N-dimethylacetamide solvent is added to 25 g of PAA-c solution with a solid content of 18% to dilute it and obtain a PAA-c solution with a solid content of 15%. Then, 0.135 g of γ-glycidoxypropyltrimethoxysilane is added as a coupling agent. After vigorous stirring and homogenization, the solution is ultrasonically treated for 30 min to eliminate air bubbles in the casting solution.

[0054] The processing method for aluminum plates is as follows: use 1000-grit sandpaper to polish the aluminum plate smooth and flat, remove the oxide layer and small particles attached to the aluminum plate. The size of the aluminum plate is 21 cm × 30 cm. Rinse the aluminum plate with deionized water until no particles are attached to the surface. Then rinse the surface of the aluminum plate with isopropyl alcohol and let it air dry in a clean space.

[0055] The preparation method of integrated PI-c insulating aluminum plate is as follows: A clean, dry aluminum plate is placed on a horizontal platform. 30 g of polyamic acid coating solution is evenly spread on the aluminum plate. After standing for 5 minutes, the bubble content and uniformity of the liquid film are carefully observed. Adjustments are made promptly using a glass rod, and the plate is allowed to stand again. This process of standing and adjustment is repeated three times to obtain a uniformly spread, bubble-free liquid film on the aluminum plate. The aluminum plate coated with the smooth liquid film is placed on a horizontal heated plate. The plate is heated to 80℃, and the presence of bubbles and uneven solution in the liquid film is observed. Intervention is made promptly, and the plate is held at this temperature for 30 minutes. The temperature is then increased to 100℃, and the presence of bubbles and uneven solution in the liquid film is observed again. Intervention is made promptly, and the plate is held at this temperature for 60 minutes. The temperature is then increased to 120℃, and the presence of bubbles and uneven solution in the liquid film is observed again. Intervention is made promptly, and the plate is held at this temperature for 60 minutes. Thermal imidization process: The aluminum plate coated with a smooth liquid film (after the solvent has been removed) is placed smoothly into a muffle furnace. A gradient heating program is set, heating from room temperature to 120 ℃ at a heating rate of 10 ℃ / min and holding for 120 min; heating to 150 ℃ at a heating rate of 6 ℃ / min and holding for 30 min; heating to 200 ℃ at a heating rate of 6 ℃ / min and holding for 30 min; heating to 270 ℃ at a heating rate of 6 ℃ / min and holding for 30 min. After the heating program is completed, allow it to cool naturally to obtain an integrated PI-c insulating aluminum plate. Example

[0056] The casting solution is prepared by adding 5.0g of N,N-dimethylacetamide solvent to 25g of PMDA-ODA type polyamic acid solution with a solid content of 18% to dilute it and obtain PMDA-ODA type polyamic acid solution with a solid content of 15%. After vigorous stirring and uniform mixing, the solution is ultrasonically treated for 30 minutes to eliminate air bubbles in the casting solution.

[0057] The processing method for aluminum plates is as follows: use 1000-grit sandpaper to polish the aluminum plate smooth and flat, remove the oxide layer and small particles attached to the aluminum plate. The size of the aluminum plate is 21 cm × 30 cm. Rinse the aluminum plate with deionized water until no particles are attached to the surface. Then rinse the surface of the aluminum plate with isopropyl alcohol and let it air dry in a clean space.

[0058] The preparation method of integrated PI (PMDA-ODA) insulating aluminum plate is as follows: A clean, dry aluminum plate is placed on a horizontal platform. 30 g of polyamic acid coating solution is evenly spread on the aluminum plate. After standing for 5 minutes, the bubble content and uniformity of the liquid film are carefully observed. Adjustments are made promptly using a glass rod, and the plate is allowed to stand again. This process of standing and adjustment is repeated three times to obtain a uniformly spread, bubble-free liquid film on the aluminum plate. The aluminum plate coated with the smooth liquid film is placed on a horizontal heated plate. The plate is heated to 80 °C, and the presence of bubbles and uneven solution in the liquid film is observed. Any interventions are made promptly, and the plate is held at this temperature for 30 minutes. The temperature is then increased to 100 °C, and the presence of bubbles and uneven solution in the liquid film is observed. Any interventions are made promptly, and the plate is held at this temperature for 60 minutes. Finally, the temperature is increased to 120 °C, and the presence of bubbles and uneven solution in the liquid film is observed. Any interventions are made promptly, and the plate is held at this temperature for 60 minutes. Thermal imidization process: The aluminum plate coated with a smooth liquid film (after the solvent has been removed) is placed smoothly into a muffle furnace. A gradient heating program is set, heating from room temperature to 120 ℃ at a heating rate of 10 ℃ / min and holding for 120 min; heating to 150 ℃ at a heating rate of 6 ℃ / min and holding for 30 min; heating to 200 ℃ at a heating rate of 6 ℃ / min and holding for 30 min; heating to 270 ℃ at a heating rate of 6 ℃ / min and holding for 30 min. After the heating program is completed, allow it to cool naturally to obtain an integrated PI (PMDA-ODA) insulating aluminum plate.

[0059] The properties of commercially available polyimide films (PMDA-ODA type) obtained by directly coating a treated aluminum plate (see Example 4 for specific preparation steps) and the properties of the integrated insulating aluminum plate prepared by this invention are shown in Table 1.

[0060] Table 1 Properties of polyimide films

[0061] <![CDATA[Dielectric constant (10 7 Hz)]]> <![CDATA[Dielectric loss (10 7 Hz)]]> <![CDATA[T d5% / ℃]]> Carbon residue percentage (800℃) Adhesion rating Example 1 2.38 0.0033 519 60 5B Example 2 2.33 0.0034 535 64 5B Example 3 2.36 0.0034 544 66 5B Example 4 3.07 0.0066 558 59 3B

[0062] Table 1 shows the dielectric constant and dielectric loss data obtained by testing with an E4990A impedance analyzer at room temperature; the 5% thermal decomposition temperature and char residue were obtained by testing the thermal decomposition data of 30–800 °C with a nitrogen purging rate of 10 °C / min using a Setline STA synchronous thermal analyzer; the adhesion grade is classified according to the cross-cut adhesion test standard, which can be found in the standard test method ASTM D3359-09 and standard ISO 2409.

[0063] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Based on the technical solutions of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A method for directly preparing a polyimide insulating film on a metallic aluminum plate, characterized in that, Includes the following steps: S1. First, add a coupling agent to the polyamic acid slurry to obtain the coating solution; S2. Then, the coating liquid is uniformly applied to the surface of the pretreated aluminum plate, and the first gradient heating is performed to remove the solvent. S3. Finally, transfer it to a muffle furnace for a second gradient heating to achieve thermal imidization, and then let it cool naturally to room temperature. In step S1, the coupling agent is γ-glycidoxypropyltrimethoxysilane; In step S1, the polyamic acid slurry is obtained by dispersing polyamic acid in N,N-dimethylacetamide by stirring, and the solid content is 10-20% by mass. The structural formulas of the polyamic acids PAA-a, PAA-b, and PAA-c are as follows: The polyamic acid is obtained by polycondensation reaction of hexafluorodianhydride and diamines having the following structures: diamine a, diamine b, or diamine c. In step S3, thermal imidization generates polyimides PI-a, PI-b, and PI-c, with the following structural formulas:

2. The method according to claim 1, characterized in that, In step S2, the dimensions of the aluminum plate are 21cm × 30cm.

3. The method according to claim 1, characterized in that, In step S2, the specific pretreatment method is as follows: first, polish the aluminum plate with 1000-grit sandpaper until smooth, then rinse it multiple times with deionized water and isopropanol, and let it air dry naturally at room temperature.

4. The method according to claim 1, characterized in that, In step S2, the specific method of coating is as follows: place the pretreated aluminum plate on a horizontal platform, apply the coating liquid evenly to the surface of the aluminum plate, let it stand for 5 minutes, carefully observe the bubble content and uniformity of the liquid film, adjust it with a glass rod and let it stand again. Repeat the standing and adjustment operation three times to obtain a liquid film that is evenly coated on the aluminum plate without bubbles.

5. The method according to claim 1, characterized in that, In step S2, the process conditions for the first gradient heating are: to perform 3 to 4 stages of heat preservation operation in the range of 40 to 120°C to evaporate the solvent and obtain a smooth and uniform film.

6. The method according to claim 1, characterized in that, In step S2, a dust cover should be placed during the first gradient temperature increase to prevent dust from falling into the liquid film.

7. The method according to claim 1, characterized in that, In step S3, the process conditions for the second gradient heating are as follows: heating from room temperature to 100-120℃ at a heating rate of 10℃ / min and holding for 120 min; heating to 150℃ at a heating rate of 6℃ / min and holding for 30 min; heating to 200℃ at a heating rate of 6℃ / min and holding for 30 min; and heating to 270℃ at a heating rate of 6℃ / min and holding for 30 min.

8. An integrated insulating metal plate, characterized in that, It is prepared using the method described in any one of claims 1 to 7.

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