Insulating coating composition suitable for electrodeposition coating and preparation method therefor

Abstract

An insulating coating composition suitable for electrodeposition coating, comprising the following components in percentage by weight: 20% to 30% of a phenolic epoxy and cyclohexanediamine modified polyphenylene ether multi-branched polymer, 10% to 25% of a blocked isocyanate curing agent, 0.1% 0.5% of an acetylene glycol wetting dispersant, 1% to 5% of methanesulfonic acid, 0% to 50% of a first batch of deionized water, 8% to 20% of a second batch of deionized water, and 1% to 5% of polyvinyl alcohol aqueous solution; and a preparation method for the insulating coating composition. A prepared coating has excellent insulativity, corrosion resistance, and damp-heat resistance.

Description

Insulating coating composition suitable for electrodeposition coating and preparation method thereof Technical Field

[0001] The present invention relates to the technical field of coatings, in particular to an insulating coating composition suitable for electrodeposition coating and a preparation method thereof. Background Art

[0002] Currently, insulating coatings for new energy batteries are primarily powder coatings made from bisphenol A epoxy resin, which offer excellent corrosion resistance and voltage resistance. A typical film thickness of 150 microns can meet the 3800V voltage requirement. However, with the continuous advancement of new energy vehicles and battery technology, traditional powder insulating coatings are no longer fully meeting market demand. For example, some new energy vehicle manufacturers have proposed integrating the power battery with the vehicle chassis, with the battery cell holder and cell housing as one unit, to improve production efficiency, reduce material usage, and further lightweight the vehicle. This results in complex battery system components, and powder coatings, due to their inherent spraying process, cannot effectively spray all of them. Electrodeposition coatings are ideally suited for coating complex structures. These coatings are formed by electrodeposition under the action of a high-voltage electric field. The resulting coatings are more compact than powder coatings and offer superior corrosion resistance, voltage resistance, and production efficiency. However, the film thickness of traditional epoxy resin system electrodeposition coatings is generally only 30-60 microns, which cannot reach a thickness of one hundred to several hundred microns like powder coatings. Therefore, the voltage resistance performance of traditional electrodeposition coatings on the market can generally only reach about 1200V, which cannot meet the high voltage resistance performance requirements of power battery cells.

[0003] Summary of the Invention

[0004] The purpose of the present invention is to provide an insulating coating composition suitable for electrodeposition coating, which has excellent insulation, corrosion resistance and moisture and heat resistance. It can be used for surface coating of power battery cells, replacing PET blue film and insulating powder coating, and providing excellent insulation protection for the battery cells.

[0005] In one aspect, the present invention provides an insulating coating composition suitable for electrodeposition coating, comprising the following components in percentage by weight:

[0006] In certain embodiments, the novolac epoxy and cyclohexanediamine modified polyphenylene ether multi-branched polymer comprises the following preparation method:

[0007] First, a small molecule secondary amine and a modified polyphenylene ether prepolymer are reacted at a temperature of 100-110°C for 30 minutes under nitrogen protection, then the temperature is cooled to below 85°C, cyclohexanediamine is quickly added, the temperature is raised to 120-130°C, and the reaction is carried out for 2.5 hours. After the reaction is completed, ethylene glycol butyl ether is added and the temperature is lowered to 90°C to obtain the product.

[0008] In certain embodiments, the small molecule secondary amine is an organic amine with a molecular weight between 70 and 300, and its molecule contains a secondary amine structure, or contains both a secondary amine structure and a ketimine structure; the organic amine is monoethanolamine, diethanolamine, N-methylethanolamine or methyl isobutyl ketimine;

[0009] The molecular structure of cyclohexanediamine is shown in formula a:

[0010] Wherein: R1 is methylene, R2, R3 are hydrogen, methyl or ethyl.

[0011] In certain embodiments, the small molecule secondary amine is diethanolamine, N-methylethanolamine, or methylisobutylketimine.

[0012] In certain embodiments, the molar ratio of secondary amine to cyclohexanediamine is 1:1 to 3, the molar ratio of active hydrogen contained on the amino group to epoxy group is 1.2 to 2:1, and the molecular chain of the phenolic epoxy and cyclohexanediamine modified polyphenylene ether multi-branched polymer does not contain epoxy groups but contains amino groups.

[0013] Among them: the molecular chains of the polyphenylene ether multi-branched polymers modified with phenolic epoxy and cyclohexanediamine contain a large number of amino groups.

[0014] In certain embodiments, the modified polyphenylene ether prepolymer comprises the following preparation method:

[0015] Phenolic epoxy and hydroxy-terminated polyphenylene ether were reacted under nitrogen protection, with xylene as solvent and a catalyst added, at 160-180°C for 1 hour, then cooled to 125-130°C for 2 hours, and then the catalyst was added and the reaction was continued for 4 hours. The material was obtained and the epoxy equivalent and number average molecular weight distribution were tested.

[0016] In certain embodiments, the molecular structure of the novolac epoxy is as shown in formula b:

[0017] Among them, n is generally 0 to 1, and the average functionality of the epoxy group is 2.0 to 3.0;

[0018] The hydroxyl-terminated polyphenylene ether is a mixture of a polyphenylene ether with two hydroxyl groups at the end and a polyphenylene ether with one hydroxyl group at the end, with a molar ratio of 8 to 10:1 and a number average molecular weight Mn of 900 to 1500;

[0019] The modified polyphenylene ether prepolymer has an epoxy equivalent of 1300-1500, and a number average molecular weight Mn distribution of 5000-7000 accounting for 50-58%, and 3000-5000 accounting for 22-30%.

[0020] In certain embodiments, the molecular structure of the novolac epoxy is as shown in formula b:

[0021] Among them, n is generally 0 to 1, and the average functionality of the epoxy group is 2.3 to 2.6;

[0022] In certain embodiments, the blocked isocyanate curing agent comprises the following preparation method:

[0023] Add a catalyst to polypentaerythritol and diisocyanate under nitrogen protection, and carry out a chain extension reaction at a temperature of 60-70°C. The reaction consumes 50% of the NCO groups. After the NCO value is tested and qualified, add a small molecule alcohol ether, raise the temperature to 80°C, and continue the reaction for 2 hours until the NCO value is less than 1. The material is obtained.

[0024] In certain embodiments, the number of pentaerythritol structures in the polypentaerythritol is ≥2;

[0025] The diisocyanate is an aromatic isocyanate containing two isocyanate groups;

[0026] The small molecule alcohol ether is an alcohol ether containing 4 to 20 carbon atoms and having a molecular weight between 90 and 300.

[0027] In certain embodiments, the polypentaerythritol is any one of pentaerythritol, dipentaerythritol, and tripentaerythritol, or a mixture of two thereof;

[0028] The diisocyanate is toluene diisocyanate or diphenylmethane diisocyanate;

[0029] The small molecule alcohol ether is ethanol, ethylene glycol monobutyl ether, ethylene glycol ethyl ether, ethylene glycol hexyl ether, diethylene glycol monobutyl ether or propylene glycol methyl ether.

[0030] On the other hand, the present invention provides a method for preparing the above-mentioned insulating coating composition, comprising the following steps:

[0031] Phenolic epoxy, cyclohexanediamine-modified polyphenylene ether multi-branched polymer, blocked isocyanate curing agent and acetylene glycol wetting and dispersing agent are mixed, stirred and methylsulfonic acid is added, dispersed at 60-70°C for 1 hour to neutralize and ionize the resin, the first batch of deionized water and the second batch of deionized water are added in sequence, emulsified and dispersed for 30 minutes, then desolventized and desolventized, the solid content is adjusted to 33%, and finally a polyvinyl alcohol aqueous solution is added to obtain the product.

[0032] The beneficial effects of the present invention are:

[0033] The present invention carries out polymerization reaction by phenolic epoxy and specific molecular weight end hydroxyl polyphenylene ether, and prepares the modified polyphenylene ether prepolymer containing epoxy group on the molecular chain, which has suitable epoxide equivalent and molecular weight distribution. The prepolymer further reacts with cyclohexanediamine and small molecule secondary amine to prepare phenolic epoxy, cyclohexanediamine modified polyphenylene ether multi-branched polymer. The modified polyphenylene ether prepolymer should have suitable epoxide equivalent and molecular weight distribution, can further react with cyclohexanediamine, introduce a large amount of polyphenylene ether and cyclohexanediamine structure on the polymer molecule main chain, make the cross-linked coating have good insulation performance, corrosion resistance and wet heat resistance, while the main chain and side chain all contain ionizable amino groups, have good water solubility and electrodeposition stability after acid neutralization. Fully enclosed isocyanate is used as the curing agent of polymer, and when it and polymer undergo cross-linking reaction, isocyanate group can react with amino and hydroxyl in the polymer to generate polyurea and polyurethane, forming a coating with high cross-linking density, and the cured coating has excellent insulation performance, corrosion resistance and wet heat resistance. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is described in detail below in conjunction with various embodiments.

[0035] Example 1

[0036] Preparation of modified polyphenylene ether prepolymer:

[0037] Among them: 1-phenolic epoxy: epoxy equivalent weight is 170-190, functionality is 2.5;

[0038] 2-Hydroxy-terminated polyphenylene ether: The number average molecular weight Mw is about 1200, and the molar ratio of the hydroxyl groups at both ends to the hydroxyl group at one end is about 9:1.

[0039] In a reaction flask equipped with a thermometer, a stirrer and a reflux condenser, the formulated amounts of phenolic epoxy, terminal hydroxy polyphenylene ether and xylene are added in sequence. After the addition is completed, the reaction system is heated to 100°C with stirring and triphenylphosphine is added. After the addition is completed, the temperature is first raised to 160-180°C for reaction for 1 hour, then the temperature is lowered to 125-130°C for reaction for 2 hours, and the reaction is continued for 4 hours after additional triphenylphosphine is added. The tested epoxy equivalent reaches between 1380 and 1430, and the number average molecular weight Mn distribution is between 5000 and 7000, accounting for 50-58%, and between 3000 and 5000, accounting for 22-30%.

[0040] Example 2

[0041] The preparation process is the same as that of Example 1, except that the number average molecular weight Mw of the polyphenylene ether is about 1500.

[0042] Example 3

[0043] The preparation process is the same as that of Example 1, except that the number average molecular weight Mw of the polyphenylene ether is about 2500.

[0044] Example 4

[0045] Preparation of polyphenylene ether multi-branched polymer modified with phenolic epoxy and cyclohexanediamine:

[0046] In a reaction flask equipped with a thermometer, a stirrer and a reflux condenser, nitrogen protection was passed through, and the modified polyphenylene ether prepolymer and diethanolamine in the formula amount were added in sequence. The reaction system was heated to 110°C with stirring and reacted for 30 minutes, then cooled to 85°C, cyclohexanediamine was quickly added, the temperature was raised to 120-130°C, and the reaction was carried out for 2.5 hours. After the reaction, ethylene glycol butyl ether was added and the temperature was lowered to 90°C for discharge.

[0047] Example 5

[0048] The preparation process is the same as that of Example 4, except that the modified polyphenylene ether prepolymer of Example 2 is used instead of the modified polyphenylene ether prepolymer of Example 1.

[0049] Example 6

[0050] The preparation process is the same as that of Example 4, except that the modified polyphenylene ether prepolymer of Example 3 is used instead of the modified polyphenylene ether prepolymer of Example 1.

[0051] Example 7

[0052] The preparation process is the same as that of Example 4, except that polyetheramine D400 is used instead of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane.

[0053] Example 8

[0054] Preparation of blocked isocyanate curing agent:

[0055] In a reaction flask equipped with a thermometer, stirrer, and reflux condenser, add the formulated amounts of diphenylmethane diisocyanate and methyl isobutyl ketone in sequence. Under a nitrogen atmosphere, stir and raise the reaction system temperature to 60-70°C. Mix dipentaerythritol, methyl isobutyl ketone, and dibutyltin dilaurate evenly, then slowly add dropwise to the reaction system containing diphenylmethane diisocyanate and methyl isobutyl ketone. The reaction system temperature should be between 60-70°C during the addition. Add the mixture over a period of approximately 1-2 hours. After the addition is complete, keep the mixture warm for 1 hour. The NCO value should be between 100 and 106. Slowly add ethylene glycol butyl ether dropwise to the reaction system over a period of approximately 1-2 hours. After the addition is complete, raise the temperature to 80°C and keep the mixture warm for 2 hours. The mixture is qualified when the NCO value is less than 1.0.

[0056] Example 9

[0057] Preparation of electrodeposition insulating coating:

[0058] Add phenolic epoxy, cyclohexanediamine-modified polyphenylene ether multi-branched polymer, blocked isocyanate curing agent, and acetylene glycol wetting and dispersing agent to a reactor equipped with a thermometer and a stirrer, add 20% methanesulfonic acid with stirring, disperse at 60-70°C for 1 hour to neutralize and ionize the resin, add the required deionized water in sequence and emulsify and disperse for 30 minutes, then perform decompression and desolventizing, adjust the solid content to about 33%, and finally add 4% polyvinyl alcohol (molecular weight 350,000) aqueous solution.

[0059] Example 10

[0060] The preparation process is the same as that of Example 9, except that the novolac epoxy and cyclohexanediamine modified polyphenylene ether multi-branched polymer of Example 5 replaces the novolac epoxy and cyclohexanediamine modified polyphenylene ether multi-branched polymer of Example 4.

[0061] Example 11

[0062] The preparation process is the same as that of Example 9, except that the novolac epoxy and cyclohexanediamine modified polyphenylene ether multi-branched polymer of Example 6 replaces the novolac epoxy and cyclohexanediamine modified polyphenylene ether multi-branched polymer of Example 4.

[0063] Example 12

[0064] The preparation process is the same as that of Example 9, except that the modified polyphenylene ether multi-branched polymer of Example 7 replaces the novolac epoxy and cyclohexanediamine modified polyphenylene ether multi-branched polymer of Example 4.

[0065] Example 13

[0066] It is a commercially available epoxy electrodeposition coating CR681.

[0067] Example 14

[0068] It is commercially available epoxy insulating powder coating FA-0101.

[0069] Preparation of electrodeposition coating:

[0070] The electrodeposited insulating coatings of Examples 9 to 12 were respectively added with pure water to prepare a coating bath having a solid content of about 13%. The bath temperature was 34 to 35° C. A 3-series aluminum battery cell was immersed in the coating bath. The battery cell was connected to the cathode and coated by electrodeposition at a voltage of 160 to 280 V for 3 to 4 minutes. After the electrodeposition was completed, the product was washed with water and baked to obtain a product having an insulating coating.

[0071] The thickness of the insulating coating corresponding to Example 9 is 60 to 70 microns, and the product is recorded as F9;

[0072] The thickness of the insulating coating corresponding to Example 10 is 60 to 70 microns, and the product is recorded as F10;

[0073] The thickness of the insulating coating corresponding to Example 11 is 60 to 70 μm, and the product is recorded as F11;

[0074] The thickness of the insulating coating corresponding to Example 12 is 60 to 70 microns, and the product is recorded as F12;

[0075] Example 13 corresponds to an insulating coating thickness of 60 to 70 μm, and the product is designated as F13;

[0076] The insulating coating thickness corresponding to Example 14 is 180 to 200 microns, and the product is recorded as F14.

[0077] Performance Testing

[0078] 1. Insulation test (normal temperature layer insulation test):

[0079] The withstand voltage test is conducted in accordance with GB / T 1408.1-2006, "Electrical strength test methods for insulating materials - Part 1: Tests at power frequency." The withstand voltage is tested for 30 seconds at DC currents of 4kV, 6kV, and 8kV, with a leakage current of less than 0.1mA.

[0080] 2. Double 85 aging resistance test:

[0081] Temperature 85°C, humidity 85°, test time 1000 hours, test adhesion level 0-1, meet the withstand voltage 30S under DC current 4KV, 6KV, 8KV, and leakage current less than 0.1mA.

[0082] 3. Corrosion resistance

[0083] According to GB / T 1771-2007 “Paints and varnishes - Determination of resistance to neutral salt spray”, a 1500h salt spray test was conducted on the test sample with a film thickness of 25-30μm. The number of blisters and the width of corrosion expansion in the cut part were evaluated.

[0084] In summary, the flame-retardant insulating electrophoretic coating of the present invention has the following advantages:

[0085] The present invention prepares a modified polyphenylene ether prepolymer containing epoxy groups on the molecular chain by polymerizing phenolic epoxy and a specific molecular weight hydroxyl-terminated polyphenylene ether, which has a suitable epoxy equivalent and molecular weight distribution. The prepolymer is further reacted with cyclohexanediamine and a small molecule secondary amine to prepare a phenolic epoxy-cyclohexanediamine modified polyphenylene ether multi-branched polymer. If the molecular weight of the hydroxyl-terminated polyphenylene ether is too large, it will affect the water solubility and electrodeposition stability of the later polymer ionization, and will also cause the crosslinking density of the coating to decrease, affecting the insulation performance and corrosion resistance. If the molecular weight is too small, the dielectric properties of the polyphenylene ether cannot be reflected, resulting in a decrease in the insulation performance of the crosslinked coating. The modified polyphenylene ether prepolymer should have a suitable epoxy equivalent and molecular weight distribution, and can further react with cyclohexanediamine to introduce a large amount of polyphenylene ether and cyclohexanediamine structures into the main chain of the polymer molecule, so that the crosslinked coating has good insulation performance, corrosion resistance and moisture-heat resistance. At the same time, both the main chain and the side chain contain ionizable amino groups, and after acid neutralization, it has good water solubility and electrodeposition stability. Fully enclosed isocyanate is used as a curing agent for the polymer. When it undergoes a cross-linking reaction with the polymer, the isocyanate group will react with the amino and hydroxyl groups in the polymer to generate polyurea and polyurethane, forming a coating with a high cross-linking density. After curing, the coating has excellent insulation, corrosion resistance, and moisture and heat resistance.

[0086] It will be apparent to those skilled in the art that various modifications to the above embodiments may be made without departing from the overall spirit and concept of the present invention. Such modifications fall within the scope of protection of the present invention. The protection scheme of the present invention shall be subject to the claims appended hereto.

Claims

1. An insulating coating composition suitable for electrodeposition coating, characterized in that: The composition includes the following weight percentages:

2. The insulating coating composition suitable for electrodeposition coating according to claim 1, characterized in that: The phenolic epoxy and cyclohexanediamine modified polyphenylene ether multi-branched polymer comprises the following preparation method: First, the small molecule secondary amine and the modified polyphenylene ether prepolymer are reacted at a temperature of 100-110°C for 30 minutes under nitrogen protection, then the temperature is lowered to below 85°C, cyclohexanediamine is quickly added, the temperature is raised to 120-130°C, and the reaction is carried out for 2.5 hours. After the reaction is completed, ethylene glycol butyl ether is added and the temperature is lowered to 90°C to obtain the material.

3. The insulating coating composition suitable for electrodeposition coating according to claim 2, characterized in that: The small molecule secondary amine is an organic amine with a molecular weight between 70 and 300, and the molecule contains a secondary amine structure, or contains a secondary amine structure and a ketimine structure at the same time; the organic amine is monoethanolamine, diethanolamine, N-methylethanolamine or methyl isobutyl ketimine; The molecular structure of cyclohexanediamine is shown in formula a: Wherein: R1 is methylene, R2, R3 are hydrogen, methyl or ethyl.

4. The insulating coating composition suitable for electrodeposition coating according to claim 2, characterized in that: The molar ratio of secondary amine to cyclohexanediamine is 1:1-3, the molar ratio of active hydrogen on the amino group to epoxy group is 1.2-2:1, and the molecular chain of the phenolic epoxy and cyclohexanediamine modified polyphenylene ether multi-branched polymer does not contain epoxy groups but contains amino groups.

5. The insulating coating composition suitable for electrodeposition coating according to claim 2, characterized in that: The modified polyphenylene ether prepolymer comprises the following preparation method: Phenolic epoxy and terminal hydroxyl polyphenylene ether were reacted at 160-180°C for 1 hour with xylene as solvent and catalyst added under nitrogen protection, then cooled to 125-130°C for 2 hours, and then the catalyst was added to continue the reaction for 4 hours. The material was obtained and the epoxy equivalent and number average molecular weight distribution were tested.

6. The insulating coating composition suitable for electrodeposition coating according to claim 5, characterized in that: The molecular structure of the phenolic epoxy is shown in formula b: Wherein, n is 0 to 1, and the average functionality of the epoxy group is 2.0 to 3.0; The hydroxyl-terminated polyphenylene ether is a mixture of two hydroxyl-terminated polyphenylene ethers and one hydroxyl-terminated polyphenylene ether, and the molar ratio is 8-10:1, number average molecular weight Mn is 900-1500; The modified polyphenylene ether prepolymer has an epoxy equivalent of 1300-1500, and a number average molecular weight Mn distribution of 5000-7000 accounting for 50-58%, and 3000-5000 accounting for 22-30%.

7. The insulating coating composition suitable for electrodeposition coating according to claim 1, characterized in that: The blocked isocyanate curing agent comprises the following preparation method: Add a catalyst to polypentaerythritol and diisocyanate under nitrogen protection, and carry out a chain extension reaction at a temperature of 60-70°C. The reaction consumes 50% of the NCO groups. After the NCO value is tested to be qualified, add a small molecule alcohol ether, raise the temperature to 80°C and continue the reaction for 2 hours until the NCO value is less than 1, and the material is obtained.

8. The insulating coating composition suitable for electrodeposition coating according to claim 7, characterized in that: The number of pentaerythritol structures in the polypentaerythritol is ≥ 2; The diisocyanate is an aromatic isocyanate containing two isocyanate groups; The small molecule alcohol ether is an alcohol ether containing 4 to 20 carbon atoms and having a molecular weight between 90 and 300.

9. The insulating coating composition suitable for electrodeposition coating according to claim 7, characterized in that: The polypentaerythritol is any one of pentaerythritol, dipentaerythritol, tripentaerythritol or a mixture of two thereof; The diisocyanate is toluene diisocyanate or diphenylmethane diisocyanate; The small molecule alcohol ether is ethanol, ethylene glycol monobutyl ether, ethylene glycol ethyl ether, ethylene glycol hexyl ether, diethylene glycol monobutyl ether or propylene glycol methyl ether.

10. A method for preparing the insulating coating composition according to any one of claims 1 to 9, characterized in that: The following steps are involved: Curing of phenolic epoxy, cyclohexanediamine modified polyphenylene ether multi-branched polymer, blocked isocyanate The agent and the acetylene glycol wetting and dispersing agent are mixed, stirred and methyl sulfonic acid is added, dispersed at 60-70°C for 1 hour to neutralize and ionize the resin, the first batch of deionized water and the second batch of deionized water are added in sequence, emulsified and dispersed for 30 minutes, then decompressed and desolventized, the solid content is adjusted to 33%, and finally a polyvinyl alcohol aqueous solution is added to obtain the material.

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