Rigid polyimide resin for anode electrophoretic paint and anode electrophoretic paint

Abstract

According to the rigid polyimide resin for the anode electrophoretic paint and the anode electrophoretic paint provided by the invention, the polyimide resin is rigid water-soluble high-molecular-weight resin, has good insulating property, high temperature resistance and electrolyte resistance, and can be used for protecting a shell film of a power battery when being used for protecting the shell film of the power battery. And the interior and / or the exterior of the power battery can have relatively good insulation, temperature resistance and electrolyte resistance protection.

Description

Technical Field

[0001] This invention relates to the field of electrophoretic paint technology, and more particularly to a rigid polyimide resin for anodic electrophoretic paint and an anodic electrophoretic paint. Background Technology

[0002] Electrophoretic paint is a new type of environmentally friendly water-based coating that uses an electrophoretic coating method. The principle is that the object to be coated is placed in an electrophoretic paint solution diluted with water as the anode or cathode. Under the action of an external electric field (direct current), the resin particles in the electrophoretic paint move in a direction and are deposited on the surface of the object to form a uniform, stable and water-insoluble electrophoretic paint film.

[0003] Currently, the most technologically mature and widely used anodic electrophoretic paints include acrylic anodic electrophoretic paints, epoxy ester anodic electrophoretic paints, phenolic anodic electrophoretic paints, and polybutadiene anodic electrophoretic paints. Acrylic anodic electrophoretic paints are widely used due to their good gloss, excellent color retention, and good weather resistance; however, their heat resistance and corrosion resistance need improvement. Polyimide resins, with their good heat resistance, high mechanical properties, and excellent corrosion resistance, would undoubtedly endow anodic electrophoretic paints with superior heat resistance and corrosion resistance if used in their development.

[0004] Typically, polyimides used in electrophoretic coatings are required to be water-soluble. To increase the water solubility of polyimides, a common method is to involve monomers with water-soluble functional groups (carboxyl or sulfonic acid groups) in the polymerization process. This introduces hydrophilic polar groups into the molecular chain of the polyimide resin, resulting in electrostatic repulsion between the polyimide molecules and thus increasing its dispersibility in water. For example, patent CN101715474B discloses an electrophoretic polyimide with siloxane bonds in its molecular backbone and anionic groups in its molecule. Although it can form a highly insulating electrodeposited film with excellent uniformity, the introduction of siloxane structures with flexible segments significantly reduces the electrolyte resistance of the coating film, which is detrimental to providing good insulation protection for the inside and / or outside of the power battery casing. Summary of the Invention

[0005] Based on the technical problems existing in the background art, the present invention proposes a rigid polyimide resin for anodic electrophoretic coating and an anodic electrophoretic coating. The polyimide resin is a rigid water-soluble high molecular weight resin with good insulation properties, high temperature resistance and electrolyte resistance. When used for film protection of power battery casing, it can enable the inside and / or outside of the power battery to have good insulation, temperature resistance and electrolyte resistance protection.

[0006] The present invention proposes a rigid polyimide resin for anodic electrophoretic coating, comprising a block structure of repeating units as shown in the following structural formula (1):

[0007] R1 is an aromatic group.

[0008] In this invention, on the one hand, because the molecular chain structure of polyimide resin contains carboxylic acid groups, it has good water solubility and can be emulsified to form an electrophoretic paint solution; on the other hand, because the molecular chain structure of polyimide resin contains aromatic benzene ring groups, it can avoid the problem of poor electrolyte resistance caused by flexible chain segments.

[0009] Preferably, R1 is a divalent group derived from aromatic dianhydrides; Preferably, the aromatic dianhydride is at least one selected from pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, or 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride.

[0010] Preferably, the rigid polyimide resin further includes a block structure of repeating units as shown in the following structural formula (2):

[0011] In this context, R2 is an aromatic group, and R3 is hydrogen or a C1-C5 alkyl group.

[0012] Preferably, R2 is a divalent group derived from aromatic dianhydrides; Preferably, the aromatic dianhydride is at least one selected from pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, or 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride.

[0013] Preferably, R3 is one or more, and is preferably methyl or ethyl.

[0014] Preferably, the molar ratio of the block structure of the repeating unit shown in structural formulas (1) and (2) is 1:0.6-1.5.

[0015] In this invention, by controlling the molar ratio of the repeating structural units shown in structural formulas (1) and (2), it can be ensured that the polyimide resin is both water-soluble and rigid.

[0016] The present invention also proposes an anodic electrophoretic paint, comprising the above-mentioned rigid polyimide resin, an alkaline compound, a water-soluble organic solvent, an aliphatic alcohol solvent, and water; Preferably, the anodic electrophoretic paint comprises, by weight percentage: 5-25 wt% rigid polyimide, 0.1-5 wt% alkaline compound, 35-70 wt% water-soluble organic solvent, 5-35 wt% aliphatic alcohol solvent, and 1-30 wt% water.

[0017] Preferably, the basic compound is at least one of triethylamine, diethanolamine, triethanolamine, pyrrole, imidazole, oxazole, pyrazole, isoxazole, thiazole, isothiazole, pyridine, pyridazine, pyrimidine, pyrazine, piperidine, or piperazine; the water-soluble organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, or γ-butyrolactone; and the aliphatic alcohol solvent is at least one of diethylene glycol, dipropylene glycol, tripropylene glycol, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, or propylene glycol methyl ether acetate.

[0018] The present invention also proposes a power battery casing, the surface of which has an insulating film formed by electrodeposition of the above-mentioned anodic electrophoretic paint.

[0019] When power battery casings are used, they often face the problem of insufficient resistance to electrolytes. When electrolyte leakage occurs, the casings are easily corroded by the electrolyte, leading to detachment and compromising the original insulation properties, which poses a high risk. This invention proposes a rigid polyimide resin for anodic electrophoretic coating. In addition to improving the water solubility and increasing the penetration of the polyimide resin, it can also effectively improve the electrolyte resistance of the polyimide resin, thereby obtaining a high-quality electrophoretic coating film. Detailed Implementation

[0020] The technical solution of the present invention will be described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0021] Example 1 This embodiment presents a rigid polyimide resin, which is prepared by the following method: Under a nitrogen atmosphere, 0.2 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 0.15 mol of 2,4,6-trimethyl-1,3-phenylenediamine were added to 300 mL of N-methylpyrrolidone. After stirring at room temperature for 0.5 h, 0.05 mol of pyridine and 0.3 mol of acetic anhydride were added. The mixture was heated to 180 °C and stirred for 2 h. After cooling the resulting reactant to room temperature, 0.1 mol of pyromellitic dianhydride, 0.15 mol of 3,5-diaminobenzoic acid and 200 mL of N-methylpyrrolidone were added. The mixture was heated to 180 °C and stirred for 6 h. After cooling to room temperature, the resulting reactant was added dropwise to ethanol to form a precipitate. The precipitate was washed three times at 70 °C to obtain the rigid polyimide resin.

[0022] Example 2 This embodiment presents an anodic electrophoretic paint, which is prepared by the following method: Under a nitrogen atmosphere, the rigid polyimide resin (20g) described in Example 1 was added to N-methylpyrrolidone (150mL), heated to 160°C and stirred until completely dissolved to obtain a polyimide resin solution. After cooling to room temperature, N-methylpyrrolidone (50mL) and piperidine (3g) were added, and the mixture was stirred vigorously. Then, propylene glycol monomethyl ether (80g) and water (60g) were added and stirred until homogeneous to obtain the anodic electrophoretic paint.

[0023] Example 3 This embodiment presents a rigid polyimide resin, which is prepared by the following method: Under a nitrogen atmosphere, 0.2 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 0.15 mol of diethyltoluenediamine were added to 300 mL of N-methylpyrrolidone. After stirring at room temperature for 0.5 h, 0.05 mol of pyridine and 0.3 mol of acetic anhydride were added. The mixture was heated to 180 °C and stirred for 2 h. After cooling the resulting reactant to room temperature, 0.1 mol of pyromellitic dianhydride, 0.15 mol of 3,5-diaminobenzoic acid and 200 mL of N-methylpyrrolidone were added. The mixture was heated to 180 °C and stirred for 6 h. After cooling to room temperature, the resulting reactant was added dropwise to ethanol to form a precipitate. The precipitate was washed three times at 70 °C to obtain the rigid polyimide resin.

[0024] Example 4 This embodiment presents an anodic electrophoretic paint, which is prepared by the following method: Under a nitrogen atmosphere, the rigid polyimide resin (20g) described in Example 3 was added to N-methylpyrrolidone (150mL), heated to 160°C and stirred until completely dissolved to obtain a polyimide resin solution. After cooling to room temperature, N-methylpyrrolidone (50mL) and triethylamine (3g) were added, and the mixture was stirred vigorously. Then, diethylene glycol (50g) and water (80g) were added and stirred until homogeneous to obtain the anodic electrophoretic paint.

[0025] Example 5 This embodiment presents a rigid polyimide resin, which is prepared by the following method: Under a nitrogen atmosphere, pyromellitic anhydride (0.2 mol) and 2,4-dimethyl-1,5-phenylenediamine (0.15 mol) were added to N-methylpyrrolidone (300 mL). After stirring at room temperature for 0.5 h, pyridine (0.05 mol) and acetic anhydride (0.3 mol) were added. The mixture was heated to 180 °C and stirred for 2 h. After cooling the resulting reactant to room temperature, 3,3',4,4'-biphenyltetracarboxylic dianhydride (0.1 mol), 3,5-diaminobenzoic acid (0.15 mol), and N-methylpyrrolidone (200 mL) were added. The mixture was heated to 180 °C and stirred for 6 h. After cooling to room temperature, the resulting reactant was added dropwise to ethanol to form a precipitate. The precipitate was washed three times at 70 °C to obtain the rigid polyimide resin.

[0026] Example 6 This embodiment presents an anodic electrophoretic paint, which is prepared by the following method: Under a nitrogen atmosphere, the rigid polyimide resin (20g) described in Example 5 was added to N,N-dimethylacetamide (120mL), heated to 160°C and stirred until completely dissolved to obtain a polyimide resin solution. After cooling to room temperature, N,N-dimethylacetamide (60mL) and diethanolamine (3.5g) were added, and the mixture was stirred vigorously to obtain a mixture. Then, propylene glycol monomethyl ether (80g) and water (60g) were added, and the mixture was stirred until homogeneous to obtain the anodic electrophoretic paint.

[0027] Example 7 This embodiment presents a rigid polyimide resin, which is prepared by the following method: Under a nitrogen atmosphere, 0.2 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 0.15 mol of 2-methyl-m-phenylenediamine were added to 300 mL of N-methylpyrrolidone. After stirring at room temperature for 0.5 h, 0.05 mol of pyridine and 0.3 mol of acetic anhydride were added. The mixture was heated to 180 °C and stirred for 2 h. After cooling the resulting reactant to room temperature, 0.1 mol of pyromellitic dianhydride, 0.15 mol of 3,4-diaminobenzoic acid and 200 mL of N-methylpyrrolidone were added. The mixture was heated to 180 °C and stirred for 6 h. After cooling to room temperature, the resulting reactant was added dropwise to ethanol to form a precipitate. The precipitate was washed three times at 70 °C to obtain the rigid polyimide resin.

[0028] Example 8 This embodiment presents an anodic electrophoretic paint, which is prepared by the following method: Under a nitrogen atmosphere, the rigid polyimide resin (20g) described in Example 7 was added to N-methylpyrrolidone (150mL), heated to 160°C and stirred until completely dissolved to obtain a polyimide resin solution. After cooling to room temperature, N-methylpyrrolidone (50mL) and piperidine (3g) were added, and the mixture was stirred vigorously to obtain a mixture. Then, ethylene glycol monoethyl ether (100g) and water (60g) were added, and the mixture was stirred until homogeneous to obtain the anodic electrophoretic paint.

[0029] Example 9 This embodiment presents a rigid polyimide resin, which is prepared by the following method: Under a nitrogen atmosphere, 0.2 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 0.12 mol of 2,5-dimethyl-p-phenylenediamine were added to 300 mL of N-methylpyrrolidone. After stirring at room temperature for 0.5 h, 0.05 mol of pyridine and 0.3 mol of acetic anhydride were added. The mixture was heated to 180 °C and stirred for 2 h. After cooling the resulting reactant to room temperature, 0.1 mol of pyromellitic dianhydride, 0.18 mol of 3,5-diaminobenzoic acid and 200 mL of N-methylpyrrolidone were added. The mixture was heated to 180 °C and stirred for 6 h. After cooling to room temperature, the resulting reactant was added dropwise to ethanol to form a precipitate. The precipitate was washed three times at 70 °C to obtain the rigid polyimide resin.

[0030] Example 10 This embodiment presents an anodic electrophoretic paint, which is prepared by the following method: Under a nitrogen atmosphere, the rigid polyimide resin (20g) described in Example 9 was added to N-methylpyrrolidone (150mL), heated to 160°C and stirred until completely dissolved to obtain a polyimide resin solution. After cooling to room temperature, N-methylpyrrolidone (50mL) and piperidine (3g) were added, and the mixture was stirred vigorously. Then, propylene glycol monomethyl ether (80g) and water (60g) were added and stirred until homogeneous to obtain the anodic electrophoretic paint.

[0031] Example 11 This embodiment presents a rigid polyimide resin, which is prepared by the following method: Under a nitrogen atmosphere, 0.2 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 0.18 mol of p-phenylenediamine were added to 300 mL of N-methylpyrrolidone. After stirring at room temperature for 0.5 h, 0.05 mol of pyridine and 0.3 mol of acetic anhydride were added. The mixture was heated to 180 °C and stirred for 2 h. After cooling the resulting reactant to room temperature, 0.1 mol of pyromellitic dianhydride, 0.12 mol of 3,5-diaminobenzoic acid and 200 mL of N-methylpyrrolidone were added. The mixture was heated to 180 °C and stirred for 6 h. After cooling to room temperature, the resulting reactant was added dropwise to ethanol to form a precipitate. The precipitate was washed three times at 70 °C to obtain the rigid polyimide resin.

[0032] Example 12 This embodiment presents an anodic electrophoretic paint, which is prepared by the following method: Under a nitrogen atmosphere, the rigid polyimide resin (20g) described in Example 11 was added to N-methylpyrrolidone (150mL), heated to 160°C and stirred until completely dissolved to obtain a polyimide resin solution. After cooling to room temperature, N-methylpyrrolidone (50mL) and piperidine (3g) were added. After vigorous stirring to obtain a mixture, propylene glycol monomethyl ether (80g) and water (60g) were added. After stirring and mixing, the anodic electrophoretic paint was obtained.

[0033] Comparative Example 1 This comparative example presents a polyimide resin prepared by the following method: Under a nitrogen atmosphere, 3, 3', 4 4'-Biphenyltetracarboxylic dianhydride (0.2 mol) and 2,4,6-trimethyl-1,3-phenylenediamine (0.15 mol) were added to N-methylpyrrolidone (300 mL). After stirring at room temperature for 0.5 h, pyridine (0.05 mol) and acetic anhydride (0.4 mol) were added. The mixture was heated to 180 °C and stirred for 2 h. After cooling the resulting reactant to room temperature, pyromellitic dianhydride (0.2 mol), 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (0.1 mol), 3,5-diaminobenzoic acid (0.15 mol), and N-methylpyrrolidone (200 mL) were added. The mixture was heated to 180 °C and stirred for 6 h. After cooling to room temperature, the resulting reactant was added dropwise to ethanol to form a precipitate. The precipitate was washed three times at 70 °C to obtain the rigid polyimide resin.

[0034] Comparative Example 2 This comparative example presents an anodic electrophoretic paint, which is prepared by the following method: Under a nitrogen atmosphere, the rigid polyimide resin (20g) described in Comparative Example 1 was added to N-methylpyrrolidone (150mL), heated to 160°C and stirred until completely dissolved to obtain a polyimide resin solution. After cooling to room temperature, N-methylpyrrolidone (50mL) and piperidine (3g) were added. After vigorous stirring to obtain a mixture, propylene glycol monomethyl ether (80g) and water (60g) were added. After stirring and mixing, the anodic electrophoretic paint was obtained.

[0035] Comparative Example 3 This comparative example presents a polyimide prepared by the following method: Under a nitrogen atmosphere, 0.2 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 0.15 mol of 4,4'-diaminodiphenyl ether were added to 300 mL of N-methylpyrrolidone. After stirring at room temperature for 0.5 h, 0.05 mol of pyridine and 0.3 mol of acetic anhydride were added. The mixture was heated to 180 °C and stirred for 2 h. After cooling the resulting reactant to room temperature, 0.1 mol of pyromellitic dianhydride, 0.15 mol of 3,5-diaminobenzoic acid and 200 mL of N-methylpyrrolidone were added. The mixture was heated to 180 °C and stirred for 6 h. After cooling to room temperature, the resulting reactant was added dropwise to ethanol to form a precipitate. The precipitate was washed three times at 70 °C to obtain the rigid polyimide resin.

[0036] Comparative Example 4 This comparative example presents an anodic electrophoretic paint, which is prepared by the following method: Under a nitrogen atmosphere, the rigid polyimide resin (20g) described in Comparative Example 3 was added to N-methylpyrrolidone (150mL), heated to 160℃ and stirred until completely dissolved to obtain a polyimide resin solution. After cooling to room temperature, N-methylpyrrolidone (50mL) and piperidine (3g) were added, and the mixture was stirred vigorously. Then, propylene glycol monomethyl ether (80g) and water (60g) were added and stirred until well mixed to obtain the anodic electrophoretic paint.

[0037] Comparative Example 5 This comparative example presents a polyimide resin prepared by the following method: Under a nitrogen atmosphere, 0.2 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 0.15 mol of 2,4,6-trimethyl-1,3-phenylenediamine were added to 300 mL of N-methylpyrrolidone. After stirring at room temperature for 0.5 h, 0.05 mol of pyridine and 0.3 mol of acetic anhydride were added. The mixture was heated to 180 °C and stirred for 2 h. After cooling the resulting reactant to room temperature, 0.1 mol of 1,2,3,4-butanetetracarboxylic dianhydride, 0.15 mol of 3,5-diaminobenzoic acid, and 200 mL of N-methylpyrrolidone were added. The mixture was heated to 180 °C and stirred for 6 h. After cooling to room temperature, the resulting reactant was added dropwise to ethanol to form a precipitate. The precipitate was washed three times at 70 °C to obtain the rigid polyimide resin.

[0038] Comparative Example 6 This comparative example presents an anodic electrophoretic paint, which is prepared by the following method: Under a nitrogen atmosphere, the rigid polyimide resin (20g) described in Comparative Example 5 was added to N-methylpyrrolidone (150mL), heated to 160°C and stirred until completely dissolved to obtain a polyimide resin solution. After cooling to room temperature, N-methylpyrrolidone (50mL) and piperidine (3g) were added. After vigorous stirring to obtain a mixture, propylene glycol monomethyl ether (80g) and water (60g) were added. After stirring and mixing, the anodic electrophoretic paint was obtained.

[0039] Performance testing: Electrophoretic deposition was performed on the anodic electrophoretic paints obtained in the examples and comparative examples. Specifically, a lithium battery with a square aluminum shell was immersed in the above electrophoretic paint as the positive electrode. Electrophoresis was started by applying a DC voltage of 40V. The electrophoresis time was controlled by the current magnitude and the electrophoresis time was 200s (charge amount of 45C). The paint film was allowed to grow slowly on the surface of the shell, and an insulating film layer was obtained on the inner and / or outer surfaces of the shell. The film was dried at 80°C for 1 hour, then heated to 160°C for 1 hour, and then further heated to 240°C for 1 hour.

[0040] Room temperature electrical insulation performance test: The withstand voltage test is carried out in accordance with GB / T1408.1-2006 "Electrical strength test method for insulating materials - Part 1: Test under power frequency"; specifically, the withstand voltage is 60s at DC 3.0KV, and the leakage current is less than 10mA, which is considered as passing. High temperature resistance test: Bake at 500℃ for 10 minutes and observe the appearance changes of the insulating film layer; Electrical insulation performance test after high temperature: The withstand voltage test is carried out according to GB / T1408.1-2006 "Electrical strength test method for insulating materials - Part 1: Test under power frequency"; the insulation film layer after the high temperature withstand voltage test is considered to pass if the leakage current is less than 10mA under DC current of 3.0KV for 60s. Electrolyte resistance test: Drop the commonly used electrolyte for commercially available liquid batteries onto the insulating film layer, let it stand at room temperature for 3 days, and observe the changes in the appearance of the insulating layer.

[0041] Table 1 Performance test results of the anodic electrophoretic coatings prepared in the examples and comparative examples

[0042] As can be seen from the data in Table 1, compared with the comparative insulating electrophoretic coating, the anodic electrophoretic paint provided in this application can form a highly uniform insulating layer on the workpiece surface. The adhesion between the insulating layer and the workpiece, as well as the insulating performance of the insulating layer, are all better. Moreover, the insulating layer can still have an insulating effect after baking at 500℃ for 10 minutes. At the same time, the insulating layer has good electrolyte resistance.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A rigid polyimide resin for anodic electrophoretic coating, characterized in that, The block structure includes repeating units as shown in the following structural formula (1): R1 is an aromatic group.

2. The rigid polyimide resin for anodic electrophoretic coating according to claim 1, characterized in that, R1 is a divalent group derived from aromatic dianhydrides; Preferably, the aromatic dianhydride is at least one of pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, or 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride.

3. The rigid polyimide resin for anodic electrophoretic coating according to claim 1 or 2, characterized in that, It also includes the block structure of repeating units as shown in the following structural formula (2): In this context, R2 is an aromatic group, and R3 is hydrogen or a C1-C5 alkyl group.

4. The rigid polyimide resin for anodic electrophoretic coating according to claim 3, characterized in that, R2 is a divalent group derived from aromatic dianhydrides; Preferably, the aromatic dianhydride is at least one of pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, or 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride.

5. The rigid polyimide resin for anodic electrophoretic coating according to claim 3 or 4, characterized in that, R3 can be one or more, preferably methyl or ethyl.

6. The rigid polyimide resin for anodic electrophoretic coating according to any one of claims 3-5, characterized in that, The molar ratio of the block structure of the repeating unit shown in structural formulas (1) and (2) is 1:0.6-1.

5.

7. An anodic electrophoretic paint, characterized in that, Includes the rigid polyimide resin as described in any one of claims 1-6, an alkaline compound, a water-soluble organic solvent, an aliphatic alcohol solvent, and water.

8. The anodic electrophoretic paint according to claim 7, characterized in that, By mass percentage, it comprises: 5-25 wt% rigid polyimide, 0.1-5 wt% basic compound, 35-70 wt% water-soluble organic solvent, 5-35 wt% aliphatic alcohol solvent, and 1-30 wt% water.

9. The anodic electrophoretic paint according to claim 8, characterized in that, The basic compound is at least one of triethylamine, diethanolamine, pyrrole, imidazole, oxazole, pyrazole, isoxazole, thiazole, isothiazole, pyridine, pyridazine, pyrimidine, pyrazine, piperidine, or piperazine; the water-soluble organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, or γ-butyrolactone; the aliphatic alcohol solvent is at least one of diethylene glycol, dipropylene glycol, tripropylene glycol, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, or propylene glycol methyl ether acetate.

10. A power battery casing, characterized in that, Its surface has an insulating film formed by electrodeposition of the anodic electrophoretic paint as described in any one of claims 7-9.

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