Cationic adjuvant, insulating cathodic electrocoat

Abstract

The application provides a cationic assistant, an insulating cathode electrophoretic paint, and the cationic assistant is a sulfur compound modified phenolic epoxy resin cationic assistant; the sulfur compound modified phenolic epoxy resin cationic assistant is obtained by the reaction of a sulfur compound and a phenolic epoxy resin; the general formula of the sulfur compound is R1-S-R2, wherein R1 and R2 independently include at least one of a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group and a hydroxybutyl group; the structural formula of the phenolic epoxy resin is wherein R3, R4 and R5 are independently selected from at least one of a hydrogen atom, a linear alkylene group with 1-20 carbon atoms, a branched alkylene group with 3-20 carbon atoms, and n is a number from 0 to 20. 1～5 1～5 The coating layer formed by the insulating cathode electrophoretic paint has the advantages of high edge coverage, high insulating breakdown voltage, excellent chemical resistance and the like.​

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coatings, and particularly relates to a cationic additive and an insulating cathodic electrophoretic coating. BACKGROUND

[0002] At present, new energy vehicles are developing rapidly, and power battery packs are the research focus of new energy vehicles, and as the demand for the energy density of power batteries is increasingly high, the demand for the safety performance of power batteries is also increasingly high.

[0003] In order to improve the safety performance of power battery packs in new energy vehicles, the power battery packs are usually protected, and at present, insulating paper, insulating powder coating, solvent-based high-pressure-resistant insulating coating, water-based insulating coating and the like are mainly used. However, there is an air gap between the insulating paper and the battery shell, which is easy to cause partial discharge and affect the service life of the battery, thereby increasing the uncertainty of the new energy electric vehicle during driving; the insulating powder coating cannot be sprayed on the complex parts such as the inner cavity and the gap of the battery pack, thereby affecting the overall insulation; the coating efficiency of the solvent-based high-pressure-resistant insulating coating and the water-based insulating coating is slow, which cannot meet the coating requirements of the power battery packs of new energy vehicles.

[0004] Electrophoretic coating is a new type of coating with energy saving, high efficiency and high corrosion resistance, and the paint film has smooth appearance, excellent water resistance and chemical resistance, and can be automatically coated, and in recent years, it has been widely used in the protection field of power battery packs in new energy vehicles. However, when the current electrophoretic coating is used to protect the power battery pack, due to the electrochemical effect, the coating on the edge part of the power battery pack is thin, the edge coverage of the coating is poor, and the corrosion resistance of the edge part of the power battery pack is poor. Moreover, the current electrophoretic coating has low insulation breakdown voltage, and the coating is easy to be broken down during electrophoresis, and the protection effect of the deteriorated coating on the power battery pack is poor. SUMMARY

[0005] In order to solve the problems and deficiencies in the prior art, the present application provides an insulating cathodic electrophoretic coating, which has high cross-linking density, strong chemical corrosion resistance, high corner coverage, high insulation breakdown voltage, high swimming penetration and the like, and has high coating efficiency, and can meet the production efficiency and performance requirements of the power battery pack of the new energy vehicle.

[0006] According to a first aspect of the present application, a cationic additive is provided, and the cationic additive is a sulfur compound modified phenolic epoxy resin cationic additive; the sulfur compound modified phenolic epoxy resin cationic additive is obtained by reaction of a sulfur compound and a phenolic epoxy resin; the general formula of the sulfur compound is R1-S-R2, wherein R1 and R2 include at least one of hydroxymethyl, hydroxyethyl, hydroxypropyl and hydroxybutyl; and the structural formula of the phenolic epoxy resin is: R3, R4 and R5 are independently selected from at least one of a hydrogen atom, a linear alkylene group of C 1～5 a branched alkylene group of C 1～5 n is a value of 0-20.

[0007] The cationic assistant provided by the application has a multi-functional structure in the molecular structure, and thus forms a cross-linking bond after curing, and has a tight and rigid structure, so that the cured product has excellent thermal stability, mechanical strength, electrical insulation and chemical corrosion resistance. The reason why the cationic assistant has the above excellent performance is as follows: the cationic assistant is prepared from a sulfur compound and a phenolic epoxy resin. First, the phenolic epoxy resin contains multiple rigid benzene ring structures, and the rigid benzene ring structure endows the resin molecule obtained by further curing subsequently with excellent thermal stability and mechanical properties. Second, each benzene ring on the phenolic epoxy resin is connected with an epoxy group, and the epoxy group has high activity and can be combined with the hydroxyl group in the sulfur compound. The addition of the sulfur compound further improves the corrosion resistance and thermal stability of the resin, and enhances the mechanical properties such as elasticity and flexibility of the resin. Therefore, the cationic assistant can further improve the cross-linking strength of the resin formed finally in the subsequent curing process, so that the resin has a more compact three-dimensional network structure, and the comprehensive performance of the coating prepared by using the resin is enhanced.

[0008] The cationic assistant is also beneficial to enhancing the electrophoretic performance of the cathodic electrophoretic coating. When a voltage is applied to the cathodic electrophoretic coating, the cathodic electrophoretic coating prepared by introducing the cationic assistant can quickly and uniformly form a coating on the surface of the object to be protected (such as the surface of a power battery), and since the resin prepared by the cationic assistant has strong stability, a uniform and dense coating with high coverage can be formed even at the edge of the object to be protected, thereby greatly improving the edge coverage of the cathodic electrophoretic material and optimizing the protection effect of the cathodic electrophoretic coating. In addition, the coating of the cathodic electrophoretic coating prepared by the cationic assistant has uniform and dense thickness, and has high coverage at the edge, which makes the cathodic electrophoretic coating have strong stability, and thus has higher withstand voltage performance. Therefore, the coating of the cathodic electrophoretic coating prepared by the cationic assistant can better meet the requirements of high heat resistance, high mechanical strength, high edge coverage, high withstand voltage, and strong chemical corrosion resistance of the new energy automobile power battery pack.

[0009] Preferably, n is a value of 3-10. When the structure of the phenolic epoxy resin is n is within the above range, it is more beneficial to form a resin material with a suitable molecular weight, which can ensure that the resin material after final curing has strong rigidity and also has certain flexibility, so that the resin obtained finally has high flexibility and chemical resistance.

[0010] Preferably, the sulfur compound includes at least one of 2,2'-thiodiethanol, 2-methylthioethanol, 1-(2-thiohydroxyethyl)-2-propanol, 3-[(-2-hydroxyethyl)thio]-1,2-propanediol, 1-(2-hydroxyethylthio)-2-methyl-2-propanol, 1-butoxy-3-[(2-hydroxyethyl)sulfanyl]propan-2-ol. These sulfur compounds have active groups of hydroxyl, which can realize crosslinking of the sulfur compound with the phenolic epoxy resin, while increasing the number of active groups of the obtained cationic adjuvant, which is conducive to increasing the degree of crosslinking of the cationic adjuvant with other resin molecules in the subsequent curing process, and further increasing the crosslinking tightness of the three-dimensional network structure of the final resin system, thereby being conducive to improving the rigidity and other properties of the resin system. The CAS numbers of the above-mentioned sulfur compounds are as follows: 2,2'-thiodiethanol (111-48-8), 2-methylthioethanol (5271-38-5), 1-(2-thiohydroxyethyl)-2-propanol (6713-03-7), 3-[(-2-hydroxyethyl)thio]-1,2-propanediol (1468-40-2), 1-(2-hydroxyethylthio)-2-methyl-2-propanol (26475-41-2), 1-butoxy-3-[(2-hydroxyethyl)sulfanyl]propan-2-ol (20142-76-1).

[0011] Preferably, the sulfur compound includes at least one of 2,2'-thiodiethanol, 2-methylthioethanol, 1-(2-thiohydroxyethyl)-2-propanol, 3-[(-2-hydroxyethyl)thio]-1,2-propanediol.

[0012] Preferably, the mass ratio of the phenolic epoxy resin to the sulfur compound is 1.5-2.5:1. By controlling the ratio of the phenolic resin to the sulfur compound, the phenolic resin and the sulfur compound can be fully reacted, so that the obtained cationic adjuvant can better play its role in the subsequent preparation of the cathodic electrophoretic paint, and the comprehensive performance of the cathodic electrophoretic paint can be effectively enhanced.

[0013] Preferably, the above-mentioned cationic adjuvant is prepared by the following steps:

[0014] A1. The phenolic epoxy resin and the first organic solvent are mixed under inert gas, and heated to 125-135°C to dissolve uniformly to obtain a first mixed system;

[0015] A2. The first mixed system is cooled to 78-83°C, and then the sulfur compound and the first aqueous acidic neutralizer are sequentially added thereto to obtain a second mixed system;

[0016] A3. The second mixed system is continuously cooled to 73-76°C, and incubated to react until the acid value is not more than 5 to obtain a sulfur compound modified phenolic epoxy resin cationic adjuvant.

[0017] The cationic assistant obtained by the preparation method has strong rigidity, high flexibility and many active functional groups, and lays a good foundation for subsequent preparation of a high cross-linking density and strong chemical resistance cathodic electrophoretic paint.

[0018] Preferably, the first organic solvent comprises at least one of a hydrocarbon organic solvent, an alcohol organic solvent, an alcohol ether organic solvent, a ketone organic solvent, and an ester organic solvent.

[0019] Preferably, the hydrocarbon organic solvent comprises at least one of toluene, xylene, and trimethylbenzene; the alcohol organic solvent comprises at least one of methanol, ethanol, n-butanol, isopropyl alcohol, isooctanol, ethylene glycol, and propylene glycol; the alcohol ether organic solvent comprises at least one of ethylene glycol ether, diethylene glycol ether, ethylene glycol butyl ether, diethylene glycol butyl ether, ethylene glycol hexyl ether, diethylene glycol hexyl ether, propylene glycol methyl ether, propylene glycol phenyl ether, and diethylene glycol dibutyl ether; the ketone organic solvent comprises at least one of acetone, butanone, methyl isobutyl ketone, cyclohexanone, isofuroleone, and acetylacetone; and the ester organic solvent comprises at least one of ethylene glycol ethyl ether acetate and ethylene glycol butyl ether acetate.

[0020] Preferably, the first organic solvent comprises at least one of methyl isobutyl ketone, ethylene glycol butyl ether, and xylene.

[0021] According to another aspect of the present application, there is provided an insulating cathodic electrophoretic paint, raw materials of which comprise, by weight fraction, 500-700 parts of bisphenol A type epoxy resin, 200-300 parts of bisphenol A, 150-250 parts of first blocking agent, 35-65 parts of polyimide resin, 300-400 parts of polyamide resin, 750-850 parts of curing agent, and 150-250 parts of cationic assistant; the cationic assistant is a sulfur compound modified phenolic epoxy resin cationic assistant. In the raw materials of the paint provided by the present application, the respective resin components, the curing agent, and the cationic assistant are in a specific ratio, so that the finally formed paint resin molecules have a high cross-linking density and good electrophoretic performance, thereby further enabling the formed paint coating to have high edge coverage, high insulating breakdown voltage, excellent chemical resistance, and the like.

[0022] Preferably, the bisphenol A type epoxy resin has an epoxy equivalent weight of 150-200. The bisphenol A type epoxy resin is ensured to have a certain epoxy equivalent weight, so as to ensure that the resin molecules in the finally formed emulsion have a high cross-linking density.

[0023] Preferably, the first blocking agent comprises diethanolamine.

[0024] Preferably, the preparation method of the paint comprises the following steps:

[0025] B1. Bisphenol A type epoxy resin, bisphenol A are mixed uniformly under inert gas, heated to 130-150°C, then the first catalyst is added, followed by incubation at 140-145°C for 4-6 hours, to obtain a polyepoxy compound;

[0026] B2. The second organic solvent is added to the polyepoxy compound, then cooled to 60-80°C, followed by the addition of the first blocking agent, incubated at 90-120°C for 1.5-2.5 hours to obtain a third mixed system;

[0027] B3. The fourth mixed system is cooled to not more than 80°C, then the polyimide resin, polyamide resin, third organic solvent are added, incubated at 90-120°C for 1.5-2.5 hours to obtain a fourth mixed system;

[0028] B4. The fourth mixed system is cooled to not more than 90°C, then the curing agent, cationic aid are added, incubated at 70-80°C for 20-40 minutes to obtain a fifth mixed system;

[0029] B5. The fifth mixed system is cooled to not more than 60°C, then the second acidic neutralizer aqueous solution is added, reacted for 0.5-1.5 hours to obtain a coating.

[0030] In the above preparation method of the coating, by adding reaction raw materials in multiple stages, on the one hand, it can ensure the full reaction of each raw material, on the other hand, it is conducive to controlling the reaction process and the reaction degree, so that the resin molecules in the finally obtained coating have a suitable molecular weight and molecular weight distribution, so that the coating has a suitable viscosity, which is conducive to forming a coating layer with uniform thickness and density, and improving the comprehensive performance of the coating layer.

[0031] Preferably, the polyepoxy compound has an epoxy equivalent weight of 500-1200.

[0032] Preferably, the solid content of the above-mentioned coating is 30-37%; the pH is 5-7; the conductivity is 2000-4000 μs / cm.

[0033] Preferably, the raw materials of the curing agent include at least one of a polyisocyanate compound; the polyisocyanate compound includes hexamethylene diisocyanate trimer, hexamethylene diisocyanate pentamer, isophorone diisocyanate trimer, isophorone diisocyanate pentamer, cyclohexane dimethylene diisocyanate trimer, methylene diisocyanate pentamer.

[0034] Preferably, the second organic solvent and the third organic solvent independently include ethylene glycol butyl ether.

[0035] Preferably, the above-mentioned curing agent is prepared by the following steps:

[0036] C1. The polyisocyanate structured compound, the fourth organic solvent, the catalyst are mixed uniformly under inert gas, and heated to 70-100°C, then the second blocking agent is added to obtain the sixth mixed system;

[0037] C2. The temperature of the sixth mixed system is kept at 60-90°C, and the reaction is kept until no -NCO group is detected, then cooled to not higher than 60°C, then the fifth organic solvent is added to obtain the curing agent.

[0038] Preferably, the mass ratio of the polyisocyanate structured compound: the first catalyst is 170-210: 0.15-0.25.

[0039] Preferably, the first catalyst, the second catalyst, the third catalyst include at least one of bismuth octoate, stannous octoate, N,N-dimethylbenzylamine, dibutyl bismuth dilaurate, dibutyl tin dilaurate, triethylamine, triethanolamine, tetramethylammonium chloride, N,N-dimethylimidazole, triphenylphosphine.

[0040] Preferably, the fourth organic solvent, the fifth organic solvent independently include at least one of hydrocarbon organic solvents, ketone organic solvents; the hydrocarbon organic solvents include at least one of toluene, xylene, trimethylbenzene; the ketone organic solvents include at least one of acetone, butanone, methyl isobutyl ketone, cyclohexanone, isofuroleone, acetylacetone.

[0041] Preferably, the second blocking agent includes at least one of alcohol ether blocking agent, phenol blocking agent, lactam blocking agent, active methylene compound blocking agent, thiol blocking agent, acid amide blocking agent, amine blocking agent, imidazole blocking agent, urea blocking agent, carbamate blocking agent, imine blocking agent, oxime blocking agent, sulfite blocking agent, hydroxamic acid ester blocking agent.

[0042] Preferably, the second blocking agent independently includes at least one of ethylene glycol butyl ether, trimethylolpropane.

[0043] Preferably, the second acidity neutralizer in the aqueous solution includes acetic acid.

[0044] Preferably, the above-mentioned insulating cathodic electrophoretic paint further includes a paint auxiliary agent, and the paint auxiliary agent includes a color paste.

[0045] Preferably, the above-mentioned insulating cathodic electrophoretic paint has a pH of 5-6.5; an electrical conductivity of 800-2000 μs / cm; an acid neutralization equivalent (MEQA) of 25-40; a coulombic efficiency of >25; an electrophoretic voltage of 80-300 V; an electrophoretic temperature of 26-30°C; an electrophoretic time of 3 min (30 s soft start); and a baking temperature of 150-220°C and a baking time of 20-50 min. Detailed Implementation

[0046] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0047] Example 1

[0048] 1. Preparation of sulfur compound-modified phenolic epoxy resin cationic additives

[0049] A1. In a nitrogen atmosphere, 784.2g of methylphenol type phenolic epoxy resin (model CN703) and 322.3g of ethylene glycol butyl ether organic solvent were added to a flask equipped with a stirrer, cooling pipe, nitrogen inlet pipe and thermometer. Then, the mixture was heated to 130°C in a nitrogen atmosphere to dissolve the materials evenly and obtain the first mixed system.

[0050] A2. Cool the first mixture to 80°C, then add 407g of 1-(2-thiohydroxyethyl)-2-propanol, 89.7g of acetic acid neutralizer, and 215g of pure water to it in sequence, mix well, and obtain the second mixture.

[0051] A3. Continue cooling the second mixture to 75°C and maintain the temperature until the acid value is no greater than 5 to obtain a sulfur compound modified phenolic epoxy resin cationic additive.

[0052] In the preparation of the above-mentioned sulfur compound-modified phenolic epoxy resin cationic additive, the structural formula of the methylphenol type phenolic epoxy resin is:

[0053] n = 3 to 10, R3 is -CH3, R4 is -CH3, and R5 is -CH3.

[0054] Furthermore, the structural formula (in aqueous solution) of the sulfur compound-modified phenolic epoxy resin cationic additive obtained in this embodiment is as follows:

[0055]

[0056] 2. Preparation of Insulating Cathodic Electrophoretic Coating

[0057] B1. In a nitrogen atmosphere, 600g of bisphenol A type epoxy resin with an epoxy equivalent of 188 and 250g of bisphenol A were added to a reactor equipped with a stirrer, reflux condenser, internal thermometer and nitrogen inlet. After stirring and mixing evenly, the mixture was heated to 130-135℃, and then 0.5g of N,N-dimethylbenzylamine was added. The mixture was kept at 140-145℃ for 4-6 hours to obtain a polyepoxy compound with an epoxy equivalent of 800-1000.

[0058] B2. After cooling the second mixed system to 60-80°C, 200 g of diethanolamine is added thereto, and the reaction is maintained at 90-120°C for 2 hours to obtain a third mixed system;

[0059] B3. The fourth mixed system is cooled to 60-80°C or below, and then 50 g of a polyimide resin and 350 g of a polyamide resin and 50 g of ethylene glycol butyl ether are added thereto, and the reaction is maintained at 90-120°C for 2 hours to obtain a fourth mixed system;

[0060] B4. The fourth mixed system is cooled to not higher than 90°C, and 800 g of a curing agent and 200 g of a sulfur compound modified phenol novolac type epoxy resin cationic co-agent are added thereto, and the reaction is maintained at 70-80°C for 30 minutes to obtain a fifth mixed system;

[0061] B5. The fifth mixed system is cooled to not higher than 60°C, and a mixed aqueous solution of 40 g of acetic acid and 400 g of water is added thereto, and the reaction is stirred at high speed for 1 hour, and then 500 g of water is slowly added thereto in two steps at intervals of 30 minutes, and after the addition is completed, 2000 g of water is further slowly added thereto to obtain a polyimide modified polyamide epoxy emulsion; and then the polyimide modified polyamide epoxy emulsion thus obtained is mixed with a paint color paste, water, and the like, in a mass ratio of 1:6-10:7-11 to obtain an insulating cathodic electrophoretic paint.

[0062] In the preparation of the polyimide modified polyamide epoxy emulsion described above, the curing agent used in step B4 is a high cross-linking density curing agent, and the specific preparation method is as follows:

[0063] C1. Under a nitrogen atmosphere, a reactor equipped with a stirrer, a reflux condenser, an internal thermometer, and a nitrogen inlet is charged with 191 g of hexamethylene diisocyanate (HDI) trimer, 95 g of methyl isobutyl ketone (MIBK), and 0.2 g of dibutyl tin dilaurate, and after the mixture is stirred and mixed uniformly, it is heated to 70-100°C, and then 10 g of trimethylolpropane and 80 g of ethylene glycol butyl ether are added thereto to obtain a sixth mixed system;

[0064] C2. The temperature of the sixth mixed system is maintained at 60-90°C, and the reaction is maintained for 2-4 hours until no -NCO group is detected, and then the temperature is cooled to not higher than 60°C, and then 35 g of ethylene glycol butyl ether is added thereto to obtain a curing agent, which is a high cross-linking density curing agent.

[0065] In addition, in the present embodiment, the structural formula of the polyamide used is as follows:

[0066]

[0067] wherein R6 is a polyacid, and R7 is a dimer acid fatty acid;

[0068] The polyimide has the following structure:

[0069]

[0070] The final polyimide-modified polyamide has at least one of the following structures: (1)

[0072] (2)

[0074] (3)

[0076]

[0077] In the above structures (1) to (3), M represents: M1 represents:

[0078]

[0079] M2 represents:

[0080] X1 is the structure of (1); and X2 is the structure of (2).

[0081] Example 2

[0082] 1. Preparation of a sulfur compound-modified phenolic epoxy resin cationic assistant

[0083] In the preparation of the sulfur compound-modified phenolic epoxy resin cationic assistant in this example, the difference from Example 1 is that the phenolic epoxy resin used in A1 is a phenol-type phenolic resin having the following structure:

[0084] n = 3-10, R3 is -H, R4 is -H, and R5 is -H.

[0085] 2. Preparation of an insulating cathodic electrophoretic paint

[0086] In the preparation of the insulating cathodic electrophoretic paint in this example, the preparation is the same as in Example 1.

[0087] Example 3

[0088] 1. Preparation of a sulfur compound-modified phenolic epoxy resin cationic assistant

[0089] The preparation of the sulfur compound-modified phenol novolac epoxy resin cationic adjuvant in this example is different from that in Example 1 in that the 1-(2- thioxyl-hydroxyethyl)-2-propanol added in A2 is replaced by 2,2'-thiodiethanol, and the rest is consistent with Example 1.

[0090] 2. Preparation of an insulating cathodic electrophoretic paint

[0091] The preparation of the insulating cathodic electrophoretic paint in this example is consistent with that in Example 1.

[0092] Example 4

[0093] 1. Preparation of a sulfur compound-modified phenol novolac epoxy resin cationic adjuvant

[0094] The preparation of the sulfur compound-modified phenol novolac epoxy resin cationic adjuvant in this example is different from that in Example 1 in that the 1-(2- thioxyl-hydroxyethyl)-2-propanol added in A2 is replaced by 2-methylthioethanol, and the rest is consistent with Example 1.

[0095] 2. Preparation of an insulating cathodic electrophoretic paint

[0096] The preparation of the insulating cathodic electrophoretic paint in this example is consistent with that in Example 1.

[0097] Example 5

[0098] 1. Preparation of a sulfur compound-modified phenol novolac epoxy resin cationic adjuvant

[0099] The preparation of the sulfur compound-modified phenol novolac epoxy resin cationic adjuvant in this example is different from that in Example 1 in that the 1-(2- thioxyl-hydroxyethyl)-2-propanol added in A2 is replaced by 3-[(-2- hydroxyethyl)thio]-1,2-propanediol, and the rest is consistent with Example 1.

[0100] 2. Preparation of an insulating cathodic electrophoretic paint

[0101] The preparation of the insulating cathodic electrophoretic paint in this example is consistent with that in Example 1.

[0102] Example 6

[0103] 1. Preparation of a sulfur compound-modified phenol novolac epoxy resin cationic adjuvant

[0104] The preparation of the sulfur compound-modified phenol novolac epoxy resin cationic adjuvant in this example is different from that in Example 1 in that the 1-(2- thioxyl-hydroxyethyl)-2-propanol added in A2 is replaced by 1-butoxy-3-[(2- hydroxyethyl)sulfanyl]propan-2-ol, and the rest is consistent with Example 1.

[0105] 2. Preparation of an insulating cathodic electrophoretic paint

[0106] The preparation of the insulating cathodic electrophoretic paint in this example is identical with that of Example 1.

[0107] Example 7

[0108] 1. Preparation of a sulfur compound-modified phenol novolac epoxy resin cationic aid

[0109] The preparation of the sulfur compound-modified phenol novolac epoxy resin cationic aid in this example is identical with that of Example 1, except that the mass of 1-(2- thioxyl-hydroxyethyl)-2-propanol added in A2 is adjusted to 203 g, and the rest is identical with that of Example 1.

[0110] 2. Preparation of an insulating cathodic electrophoretic paint

[0111] The preparation of the insulating cathodic electrophoretic paint in this example is identical with that of Example 1.

[0112] Example 8 (epoxy equivalent of polyepoxy compound is 200-450, too small)

[0113] 1. Preparation of a sulfur compound-modified phenol novolac epoxy resin cationic aid

[0114] The preparation of the sulfur compound-modified phenol novolac epoxy resin cationic aid in this example is identical with that of Example 1.

[0115] 2. Preparation of an insulating cathodic electrophoretic paint

[0116] The preparation of the insulating cathodic electrophoretic paint in this example is identical with that of Example 1, except that the feeding amounts of the bisphenol A type epoxy resin and bisphenol A added in B1 are adjusted to 200 g and 45 g, respectively (the feeding ratio is not identical with that of Example 1), and the epoxy equivalent of the finally obtained polyepoxy compound is 300-450; the rest is identical with that of Example 1.

[0117] Example 9

[0118] 1. Preparation of a sulfur compound-modified phenol novolac epoxy resin cationic aid

[0119] The preparation of the sulfur compound-modified phenol novolac epoxy resin cationic aid in this example is identical with that of Example 1.

[0120] 2. Preparation of an insulating cathodic electrophoretic paint

[0121] The preparation of the insulating cathodic electrophoretic paint in this example is identical with that of Example 1, except that the feeding amounts of the bisphenol A type epoxy resin and bisphenol A added in B1 are adjusted to 200 g and 98 g, respectively (the feeding ratio is not identical with that of Example 1), and the epoxy equivalent of the finally obtained polyepoxy compound is 1300-1600; the rest is identical with that of Example 1.

[0122] Example 10

[0123] 1. Preparation of a sulfur compound-modified phenolic epoxy resin cationic assistant

[0124] The preparation of the sulfur compound-modified phenolic epoxy resin cationic assistant in this example is consistent with that in Example 1.

[0125] 2. Preparation of an insulating cathodic electrophoretic paint

[0126] The preparation of the insulating cathodic electrophoretic paint in this example is different from that in Example 1 in that the high cross-linking density curing agent added in B4 is adjusted to be hexamethylene diisocyanate (HDI) trimer, i.e. the hexamethylene diisocyanate (HDI) trimer does not undergo subsequent reaction steps of C1 and C2; the rest is consistent with Example 1.

[0127] Comparative Example 1

[0128] No sulfur compound-modified phenolic epoxy resin cationic assistant is prepared in this comparative example.

[0129] And in the preparation of the insulating cathodic electrophoretic paint in this comparative example, it is different from Example 1 in that no sulfur compound-modified phenolic epoxy resin cationic assistant is added in B4; the rest is consistent with Example 1.

[0130] Comparative Example 2

[0131] The insulating cathodic electrophoretic paint in this comparative example is a commercially available insulating cathodic electrophoretic paint.

[0132] Comparative Example 3

[0133] The phenolic epoxy resin in this comparative example is not modified by a sulfur compound, i.e. the cationic assistant is only a phenolic epoxy resin, specifically, it is different from Example 1 in that no sulfur compound-modified phenolic epoxy resin cationic assistant is prepared in this comparative example, i.e. the steps of A1, A2 and A3 are omitted, and the methyl phenolic epoxy resin phenolic epoxy resin in A1 is directly used as the cationic assistant.

[0134] And the preparation of the insulating cathodic electrophoretic paint in this comparative example is consistent with that in Example 1.

[0135] Comparative Example 4

[0136] No sulfur compound-modified phenolic epoxy resin cationic assistant is prepared in this comparative example.

[0137] And in the preparation of the insulating cathodic electrophoretic paint in this comparative example, it is different from Example 1 in that in B5, the reactants (methyl phenolic epoxy resin, thiohydroxyethyl propanol) used to prepare the sulfur compound-modified phenolic epoxy resin cationic assistant in Example 1 are directly used to replace the sulfur compound-modified phenolic epoxy resin cationic assistant; the rest is consistent with Example 1.

[0138] Comparative Example 5

[0139] 1. Preparation of a sulfide compound-modified phenolic epoxy resin cationic adjuvant

[0140] In the preparation of the sulfide compound-modified phenolic epoxy resin cationic adjuvant in this comparative example, the addition of the methyl phenol type phenolic epoxy resin in A1 was replaced by a polyphenol type glycidyl ether type epoxy resin, and the rest was consistent with Example 1.

[0141] 2. Preparation of an insulating cathodic electrophoretic paint

[0142] The preparation of the insulating cathodic electrophoretic paint in this example is consistent with Example 1.

[0143] Test Example

[0144] 1. Experimental construction method

[0145] The cathodic electrophoretic paint prepared in Examples 1-10 and Comparative Examples 1-5 was tested for film performance. First, the film was prepared according to the following operation: set the tank temperature to 28±2℃, and apply a conventional method of electrophoresis at 200±50V to a film thickness of 30-40μm. After electrophoresis, wash and bake at 180℃ for 30min to obtain the film; then test the film performance.

[0146] The following film performance tests were mainly performed: appearance, visual inspection; film thickness, tested according to GB / T 13452; gloss, tested according to GB / T 9754; adhesion level, tested according to GB / T 9286; cupping, tested according to GB / T 9753; hardness, tested according to GB / T 6739; flexibility, tested according to GB / T 1731; water resistance, tested according to GB / T 1865; volume resistivity, tested according to GB / T 1410; insulation breakdown voltage, tested according to JIS C 3003 metal foil method; double 85 test, tested according to GB / T 2423.

[0147] 2. Experimental results

[0148] The film performance tests of the cathodic electrophoretic paint prepared in Examples 1-10 and Comparative Examples 1-5 are shown in Table 1.

[0149] Table 1 Film performance test results of the cathodic electrophoretic paint in Examples 1-10 and Comparative Examples 1-5 (including Table 1-1,

[0150] 1-2)

[0151] 1-1

[0152]

[0153] 1-2

[0154]

[0155]

[0156] As can be seen from Table 1, the cationic assistant provided by the present application can be used to prepare an insulating cathode electrophoretic paint with high heat resistance, high mechanical strength, high edge coverage, high insulation breakdown voltage, and strong chemical corrosion resistance. The performance of the insulating cathode electrophoretic coating in Examples 1-5 can be referred to, and these examples all have relatively good comprehensive performance. However, compared with Example 1, Example 2 has high film impedance due to the structure of the coating film, which leads to difficulty in film formation. At the same time, the glass transition temperature of the structure resin is high, which leads to reduced performance such as smoothness, gloss, and cupping of the coating film. In Example 3, the use of a symmetrical structure of the sulfur compound leads to poor appearance and leveling of the coating film. In Example 4, the hydrophilic group (hydroxyl group) of the sulfur compound is insufficient, leading to poor appearance and leveling of the coating film. The performance of Example 5 is similar to that of Example 1.

[0157] Further, the performance of the coating in Example 6 is observed, which has low conversion rate of the sulfur compound, leading to poor water solubility of the assistant and unqualified stability of the product. In Example 7, the amount of the sulfur compound used is too small, resulting in unstable emulsion and failing to form an effective insulating cathode electrophoretic coating, so the corresponding performance cannot be tested. In Example 8, the epoxy equivalent of the polyepoxy compound is too small, and the product cannot be self-emulsified into a stable emulsion with an oil-in-water structure due to the small molecular weight during the emulsification process. In Example 9, the epoxy equivalent of the polyepoxy compound is too large, leading to high glass transition temperature of the coating film, poor leveling appearance, and poor cupping performance. In Example 10, the curing agent is not further modified, so the resulting emulsion is unstable and cannot form an effective insulating cathode electrophoretic coating, and the corresponding performance cannot be tested.

[0158] In Comparative Example 1, the insulating performance of the coating is improved compared with the traditional electrophoretic paint on the market due to the modification of the polyepoxy compound by the polyimide in the absence of the cationic assistant, but the performance in terms of sharp edge insulation is not good enough. In Comparative Example 2, the coating film thickness is not enough, and the cationic assistant is lacking, leading to unsatisfactory performance in terms of insulation. In Comparative Example 3, the phenolic epoxy resin is not modified by the sulfur compound, and in Comparative Example 4, the phenolic epoxy resin is directly mixed with the sulfur compound. These changes in process conditions will affect the stability of the emulsion formed, and an effective insulating cathode electrophoretic coating cannot be formed, and the corresponding performance cannot be tested. In Comparative Example 5, a polyphenol glycidyl ether type linear epoxy is used instead, which improves the saturation and cupping performance of the coating film, but the linear structure leads to a decrease in insulation performance.

[0159] The above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application is described in detail with reference to the above examples, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently, and these modifications or replacements are within the protection scope of the present application.

Claims

1. A cationic builder characterized in that: The cationic assistant is a sulfur compound modified phenolic aldehyde epoxy resin cationic assistant; the sulfur compound modified phenolic aldehyde epoxy resin cationic assistant is obtained by reaction of a sulfur compound and a phenolic aldehyde epoxy resin; The sulfur compound includes at least one of 1-(2-thioxyl-hydroxyethyl)-2-propanol and 3-[(2-hydroxyethyl)thio]-1,2-propanediol; The phenolic epoxy resin has a structural formula of: wherein R3, R4, and R5 are independently selected from at least one of a linear alkylene group of C 1～5 a branched alkylene group of C 1～5 n has a value of 0 to 20; The feeding mass ratio of the phenolic aldehyde epoxy resin to the sulfur compound is 1.5-2.5:

1.

2. The cationic aid of claim 1, wherein, The sulfur compound modified phenolic aldehyde epoxy resin cationic assistant is prepared by the following steps: A1. The phenolic aldehyde epoxy resin and the first organic solvent are mixed under inert gas and heated to 125-135°C to be dissolved uniformly to obtain a first mixed system; A2. The first mixed system is cooled to 78-83°C, then the sulfur compound and the first acidic neutralizer aqueous solution are sequentially added to obtain a second mixed system; A3. The second mixed system is continuously cooled to 73-76°C, and the reaction is kept until the acid value is not more than 5 to obtain the sulfur compound modified phenolic aldehyde epoxy resin cationic assistant.

3. An insulating cathodic electrodeposition coating, characterized in that, The raw materials include, calculated by weight fraction, 500-700 parts of bisphenol A type epoxy resin, 200-300 parts of bisphenol A, 150-250 parts of first blocking agent, 35-65 parts of polyimide resin, 300-400 parts of polyamide resin, 750-850 parts of curing agent, and 150-250 parts of the cationic assistant according to any one of claims 1-2; The preparation method of the insulating cathode electrophoretic paint includes the following steps: B1. Bisphenol A type epoxy resin and bisphenol A are mixed uniformly under inert gas, heated to 130-150°C, then the first catalyst is added, and then the reaction is kept at 140-145°C for 4-6 hours to obtain a polyepoxy compound; B2. The second organic solvent is added to the polyepoxy compound, then cooled to 60-80°C, then the first blocking agent is added, and the reaction is kept at 90-120°C for 1.5-2.5 hours to obtain a third mixed system; B3. The third mixed system is cooled to not higher than 80°C, then the polyimide resin, the polyamide resin, and the third organic solvent are added, and the reaction is kept at 90-120°C for 1.5-2.5 hours to obtain a fourth mixed system; B4. The fourth mixed system is cooled to not higher than 90°C, then the curing agent and the cationic assistant are added, and the reaction is kept at 70-80°C for 20-40 minutes to obtain a fifth mixed system; B5. The fifth mixed system is cooled to not higher than 60°C, then the second acidic neutralizer aqueous solution is added, and the reaction is kept for 0.5-1.5 hours to obtain the paint; In the B1, the epoxy equivalent weight of the polyepoxy compound is 500-1200; In the B4, the raw materials of the curing agent include a polyisocyanate structural compound; the curing agent is prepared by the following steps: C1. The polyisocyanate structural compound, the fourth organic solvent, and the catalyst are mixed uniformly under inert gas and heated to 70-100°C, then the second blocking agent is added to obtain a sixth mixed system; C2. The temperature of the sixth mixed system is maintained at 60-90°C, and after the reaction is kept until no -NCO group is detected, the temperature is cooled to not higher than 60°C, then the fifth organic solvent is added to obtain the curing agent.

4. The insulating cathode electrophoretic paint according to claim 3, characterized in that: The polyisocyanate structural compound includes at least one of hexamethylene diisocyanate trimer, hexamethylene diisocyanate pentamer, isophorone diisocyanate trimer, isophorone diisocyanate pentamer, cyclohexane dimethylene diisocyanate trimer, and methylene diisocyanate pentamer.

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