Sweat-resistant cathode electrophoretic coating and preparation method thereof

Abstract

The invention discloses a sweat-resistant cathode electrophoretic coating and a preparation method thereof. The sweat-resistant cathode electrophoretic coating comprises the following components in parts by weight: 50-60 parts of modified acrylic resin, 30-42 parts of a curing agent, 5-7 parts of a sweat-resistant additive, 1-2 parts of an adhesion promoter, 1-2 parts of nano microspheres, 3-4 parts of acid and 2-4 parts of deionized water. A working solution prepared from the composition is used for cathode electrophoretic coating, a thermocured coating film has the effects of corrosion resistance and artificial perspiration resistance, the artificial perspiration resistance can reach 96 hours, and the requirements of high protection, high artificial perspiration resistance and high decoration performance can be met through one-time electrophoretic coating.

Description

Technical Field

[0001] The invention relates to the field of cathode electrophoretic coatings, and in particular to a sweat-resistant cathode electrophoretic coating and a preparation method thereof. Background Art

[0002] Acrylic cathodic electrophoretic coatings have broad application prospects due to their excellent corrosion resistance, weather resistance, and decorative properties, as well as their ability to form a uniform coating on the surface of workpieces through electrochemical deposition. In recent years, with the rapid development of industries such as glasses and watches, acrylic decorative cathodic electrophoretic coatings have been required to exhibit higher artificial sweat resistance. However, existing high-artificial sweat-resistant acrylic cathodic electrophoretic coating compositions, when formed by electrophoresis, exhibit only moderate leveling effects and exhibit certain deficiencies in artificial sweat resistance, particularly in high-temperature and high-humidity environments. Artificial sweat contains corrosive components such as lactic acid, urea, and sodium chloride (pH approximately 4.5), which can easily cause the resin to swell, hydrolyze, or discolor. The ester structure of traditional acrylic resins is easily attacked and destroyed by the acidic components of sweat, thereby reducing the mechanical strength and adhesion of the coating. Summary of the Invention

[0003] To address the above technical issues, the present invention provides a sweat-resistant cathodic electrophoretic coating and a preparation method thereof. By employing a modified acrylic resin with a specific structure, a bio-based curing agent, and a compounding system containing special functional additives, the present invention significantly improves the coating's artificial sweat resistance, storage stability, and film-forming properties.

[0004] In a first aspect, the present invention provides a sweat-resistant cathodic electrophoretic coating, which is achieved by adopting the following technical solutions.

[0005] A sweat-resistant cathode electrophoretic coating comprises the following components in parts by weight: 50-60 parts of modified acrylic resin, 30-42 parts of curing agent, 5-7 parts of sweat-resistant auxiliary agent, 1-2 parts of adhesion promoter, 1-2 parts of nano-microspheres, 3-4 parts of acid and 2-4 parts of deionized water.

[0006] By adopting the above technical solution, the electrophoretic working fluid prepared from the above composition has excellent storage stability. After cathode electrophoresis film formation, the resulting coating has good leveling effect, high cross-linking density, fast curing speed and excellent salt spray resistance and artificial sweat resistance.

[0007] Furthermore, the modified acrylic resin is prepared by free radical polymerization of 2-3 wt% of vinyltrimethoxysilane, 10-15 wt% of lauryl methacrylate, 10-15 wt% of glycidyl methacrylate or glycidyl acrylate, 20-26 wt% of versatate vinyl carbonate, 20-26 wt% of 2-hydroxypropyl methacrylate and 15-20 wt% of other ethylenically unsaturated monomers under the action of an initiator, and then reacting with an organic secondary amine compound; wherein the mass ratio of versatate vinyl carbonate to 2-hydroxypropyl methacrylate is 1:1.

[0008] Furthermore, the other vinyl unsaturated monomers are selected from acrylates, and the acrylates are selected from at least one of isooctyl methacrylate, isooctyl acrylate, tert-butyl acrylate, dodecafluoroheptyl acrylate, and cyclohexyl acrylate; the initiator is selected from at least one of azobisisobutyronitrile and benzoyl peroxide, and the initiator accounts for 1.5 to 2.2 wt% of the total monomer amount; the organic secondary amine compound is selected from at least one of N-methylethylamine, diethylamine, dibutylamine, N-methylaniline, and diphenylamine, and the molar ratio of the organic secondary amine compound to the epoxy group of the epoxy group-containing acrylic resin is 1:1.

[0009] Specifically, the preparation method of the modified acrylic resin is as follows: 8-12% isopropyl alcohol and 30-40% propylene glycol methyl ether (based on the total weight of the monomers) are mixed, the temperature is raised to 88-90° C., and the monomers (vinyl trimethoxysilane, lauryl methacrylate, glycidyl methacrylate or glycidyl acrylate, vinyl esters, 2-hydroxypropyl methacrylate and other vinyl unsaturated monomers) that have been mixed well and 1.3-1.8% of the total weight of the monomers by initiator are added dropwise at a uniform rate. The solution is added dropwise over 2 to 3 hours and kept warm at 85 to 90° C. for 1 to 1.2 hours; the remaining uniformly mixed mixture of 0.2 to 0.4% of the total weight of the monomers, 5 to 10% of isopropyl alcohol and 1 to 3% of propylene glycol methyl ether is added dropwise over 0.5 to 0.8 hours and kept warm at 88 to 90° C. for 3 to 3.5 hours until the monomer conversion rate reaches more than 99%; the prepared acrylic resin and the organic secondary amine compound are reacted at 80 to 90° C. for 3 to 3.5 hours to prepare the modified acrylic resin.

[0010] Furthermore, the curing agent is prepared by reacting 50-75wt% of bio-based pentamethylene diisocyanate (bio-based PDI) with 6-15wt% of a chain extender and 10-25wt% of a blocking agent in the presence of 0.1-0.3wt% of a catalyst; the chain extender is selected from at least one of trimethylolpropane, 1,4-butanediol, and hydroquinone dihydroxyethyl ether; the blocking agent is selected from at least one of 3,5-dimethylimidazole, ethylene glycol ethyl ether, and methyl ethyl ketoxime; and the catalyst is selected from at least one of stannous octoate, N,N-dimethylbenzylamine, and organic bismuth.

[0011] Furthermore, the preparation method of the curing agent is as follows: under nitrogen protection, bio-based pentamethylene diisocyanate and a solvent are mixed, the temperature is raised to 40-50°C, and a chain extender and a catalyst are started to be added dropwise, and the temperature is maintained at 40-60°C for 1-1.5 hours. The temperature is raised to 75-80°C and kept warm for 1.5-2 hours. A sealing agent is added, the temperature is maintained at 40-50°C, and the temperature is raised to 55-60°C and kept warm for 2-2.5 hours. The NCO content is tested to be ≤0.5% (di-n-butylamine titration method), the temperature is lowered and a solvent is added to adjust the solid content to 82.0-84.0%, the mixture is cooled to room temperature, and impurities are removed by filtration to obtain a light yellow to brown transparent liquid.

[0012] Specifically, the solvent is methyl isobutyl ketone or propylene glycol methyl ether acetate.

[0013] Furthermore, the preparation method of the sweat-resistant auxiliary agent is as follows: 100 parts by weight of phenolic epoxy resin and 0.1 to 0.3 parts by weight of catalyst are mixed, and the temperature is raised to 85 to 90° C. under N2 protection; 10 to 30 parts by weight of isopropyl alcoholamine is added dropwise over 1 to 1.5 hours, and the temperature is raised to 105 to 110° C. for reaction for 3 to 3.5 hours; the temperature is lowered to below 80° C., and a long-chain carboxylic acid is added to neutralize the mixture to a pH of 7.0 to 8.5 to obtain the anti-perspiration auxiliary agent.

[0014] Furthermore, the phenolic epoxy resin is selected from at least one of epoxy resins F-44, F-51, and F-46; the catalyst is selected from at least one of tetrabutylammonium hydrogen sulfate, tetrabutylammonium acetate, and tetrabutylammonium bromide; and the long-chain carboxylic acid is selected from at least one of capric acid, stearic acid, and lauric acid.

[0015] Furthermore, the adhesion promoter is selected from at least one of polyether modified siloxane (AC-8333), silane compound (KH550), and phosphate compound (AKN-6105).

[0016] Furthermore, the preparation method of the nanospheres is as follows: disperse nano-SiO2 in a solvent, stir and ultrasonicate for more than 50 minutes; add 3-5wt% of a silane compound (KH550), add acid to adjust the pH to 4-5; stir at 70-80°C for 2-2.5 hours, cool, wash and dry to obtain the product.

[0017] Furthermore, the particle size of nano-SiO2 is 20-50nm; the solvent is a mixed solution of water and ethanol, and the volume ratio of water to ethanol is 8:2; the acid is lactic acid or glacial acetic acid.

[0018] Furthermore, the acid is selected from acetic acid, formic acid, lactic acid, methanesulfonic acid, phosphoric acid, oxalic acid or citric acid.

[0019] In the second aspect, the application provides a preparation method of a sweat-resistant cathodic electrophoretic paint.

[0020] The preparation method of the sweat-resistant cathodic electrophoretic paint comprises the following steps:

[0021] The modified acrylic resin is heated to 70-80 DEG C, and then a specified amount of curing agent, sweat-resistant additive and adhesion promoter is added and kept for 1-1.5 hours, and then the temperature is lowered to 40-50 DEG C, and then the nano microspheres, acid and deionized water are added and mixed uniformly to obtain the sweat-resistant cathodic electrophoretic paint.

[0022] The application has the following beneficial effects.

[0023] The sweat-resistant cathodic electrophoretic paint of the application uses a certain proportion of hydrophobic monomers in the formula, and uses lauryl methacrylate and vinyl versatate as the main hydrophobic functional monomers. The multi-alkyl structure of the vinyl versatate interweaves to form a large steric hindrance, and due to the hydrophobic property of the alkyl structure itself, the introduction of the vinyl versatate into the resin structure can effectively improve the water resistance of the coating film. The mass ratio of the vinyl versatate and 2-hydroxypropyl methacrylate is 1:1, and this specific ratio plays a key role in effectively adjusting the balance between the hydrophobicity and the hydrophilicity of the main resin, thereby significantly improving the water resistance and sweat resistance of the obtained paint film. Further, the composition of the application introduces vinyl trimethoxysilane, and the addition of this component can significantly improve the interfacial properties of the coating, thereby improving the comprehensive mechanical properties, water resistance and moisture resistance of the paint. The ratio of each monomer is optimized and designed, and the amount is scientific and reasonable. In terms of the curing agent system, the application uses bio-based isocyanate as the raw material for the full blocking reaction of the NCO group, thereby replacing the traditional petrochemical raw material isocyanate. This scheme effectively reduces the dependence on fossil fuels and significantly reduces the environmental cost. In addition, the composition also introduces a quaternary ammonium salt sweat-resistant additive with a rigid structure and a hydrophobic segment. The rigid aromatic ring structure of the phenolic epoxy in the additive resists the penetration of sweat, the beta-methyl of the isopropyl alcohol amine inhibits the attack of salt ions on the quaternary ammonium group, and the long-chain carboxylic acid enhances the hydrophobic barrier. At the same time, it synergistically acts on the nano-modified microspheres contained in the composition. The microspheres can significantly inhibit the penetration of corrosive media (such as water, oxygen, ions, etc.) to the substrate material through their efficient physical barrier mechanism. Based on the synergistic effect of the above components and ratios, the storage stability of the electrophoretic working solution prepared by using the sweat-resistant cathodic electrophoretic paint of the application is significantly improved. The coating film obtained through the cathodic electrophoretic coating process exhibits excellent leveling effect, high crosslinking density, good mechanical properties, excellent salt spray resistance and outstanding artificial sweat resistance. DETAILED DESCRIPTION

[0024] The present patent application is further illustrated below in conjunction with examples. The raw materials used in the examples and comparative examples are all commercially available industrial products, which can be purchased through commercial channels, unless otherwise specified.

[0025] The polyether-modified siloxane AC-8333 used in the following examples of the present application was purchased from Guangdong Fangzhou Chemical Industry Co., Ltd.

[0026] The silane compound KH550 used in the following examples of the present application was purchased from Nanjing Chemical Reagent Co., Ltd.

[0027] The phosphate compound AKN-6105 used in the following examples of the present application was purchased from Guangzhou Zhihui Fine Chemical Co., Ltd.

[0028] The organic bismuth catalyst CATWS075 used in the following examples of the present application was purchased from Hangzhou Fuyang Jiehui Chemical Co., Ltd.

[0029] The bio-based pentamethylene diisocyanate PDI used in the following examples of the present application was purchased from Gansu Yinguang Poly-silver Chemical Co., Ltd.

[0030] Example 1

[0031] A method for preparing a sweat-resistant cathodic electrophoretic paint, comprising the following steps:

[0032] (1) Preparation of modified acrylic resin

[0033] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and a burette, solvent components (8.0 g of isopropyl alcohol, 36.0 g of propylene glycol methyl ether) were added, and the temperature was raised to 90°C. A mixture of monomers and initiators was added at a constant speed, including a mixture of 54.2 g of acrylate monomers (including 14.0 g of glycidyl methacrylate, 24.0 g of vinyl versatate, 14.2 g of lauryl methacrylate, and 2.0 g of vinyl trimethoxysilane), 24.0 g of 2-hydroxypropyl methacrylate, 21.8 g of isooctyl acrylate, and 1.8 wt% of the total amount of monomers of initiator benzoyl peroxide 1.8 g. The addition was completed in 3 hours, and the temperature was maintained at 88°C for 1 hour. The remaining solvent and initiator mixture components (9.0 g of isopropyl alcohol, 3.0 g of propylene glycol methyl ether, and 0.3 g of benzoyl peroxide) were added dropwise for 0.5 hours, and the reaction was carried out at 88°C for 3 hours to obtain the acrylic resin. The resin was reacted with 12.7 g of di-n-butylamine at 85°C for 3 hours to obtain the modified acrylic resin.

[0034] (2) Preparation of curing agent

[0035] 195.6 g of bio-based pentamethylene diisocyanate PDI and 30.0 g of methyl isobutyl ketone solvent were added to the reaction flask, nitrogen was passed through, the temperature was raised to 45°C, 33.0 g of 1,4-butanediol and 0.3 g of catalyst organic bismuth were added dropwise, the temperature was maintained at 55°C for 1 hour, the temperature was raised to 80°C and kept warm for 2 hours, 28.8 g of 3,5-dimethylimidazole was added, the temperature was maintained at 48°C, the temperature was raised to 55°C and kept warm for 2 hours, the temperature was lowered and 26.5 g of methyl isobutyl ketone was added to adjust the solid content to 82.0%, and a curing agent was prepared, which was stored for later use.

[0036] (3) Preparation of anti-perspiration auxiliary agent

[0037] Add 100.0g of phenolic epoxy resin F-51 to the reaction flask, heat to 90°C under N2 protection, add 0.3g of catalyst tetrabutylammonium bromide, add 24.2g of isopropanolamine dropwise (drip over 1 hour), heat to 108°C and react for 3 hours; cool to below 80°C, add 16.8g of lauric acid and neutralize to pH 7.6 to obtain an anti-sweat additive, which is stored for later use.

[0038] (4) Preparation of nanospheres

[0039] 10.0 g of nano-SiO2 (particle size 20-50 nm) was dispersed in 1000.0 g of a mixed solvent of water and ethanol (water:ethanol = 8:2), and subjected to strong mechanical stirring and ultrasonic treatment for 50 minutes; 0.5 g of KH550 was added, and the pH was adjusted to 4.7 with glacial acetic acid; the mixture was stirred at 80°C for 2.5 hours, washed several times with ethanol, and then vacuum dried at 60°C for 3.5 hours.

[0040] (5) Preparation of sweat-resistant cathode electrophoretic coating composition

[0041] 56.0 g of the modified acrylic resin prepared in the above step (1) was added to a reaction flask, heated to 75° C., 35.0 g of the curing agent prepared in the above step (2), 5.2 g of the anti-perspiration auxiliary agent prepared in the above step (3), and 1.2 g of the silane compound KH550 were added, and the mixture was kept warm for 1 hour, then cooled to 45° C., 1.8 g of the nanospheres prepared in the above step (4), 1.9 g of formic acid, and 4.0 g of deionized water were added to obtain a sweat-resistant cathodic electrophoretic coating composition.

[0042] Example 2

[0043] A method for preparing a sweat-resistant cathodic electrophoretic coating is different from that of Example 1 in that: 21.8 g of dodecafluoroheptyl acrylate is used in step (1) instead of 21.8 g of isooctyl acrylate used in step (1) of Example 1, and the remaining amounts and specific preparation steps are the same as those of Example 1.

[0044] Example 3

[0045] A method for preparing a sweat-resistant cathodic electrophoretic coating, which differs from Example 1 in that: 128.0 g of phenolic epoxy resin F-44 is used in step (4) instead of 100.0 g of phenolic epoxy resin F-51 used in step (4) of Example 1, and the remaining amounts and specific preparation steps are the same as those in Example 1.

[0046] Example 4

[0047] A method for preparing a sweat-resistant cathodic electrophoretic coating, which differs from Example 1 in that: 1.2 g of polyether-modified siloxane AC-8333 is used in step (5) instead of 1.2 g of the silane compound KH550 used in step (5) of Example 1; the remaining amounts and specific preparation steps are the same as those in Example 1.

[0048] Comparative Example 1

[0049] A method for preparing a cathode electrophoretic coating is different from that of Example 1 in that: 5.2 g of anti-perspiration auxiliary agent used in step (5) of Example 1 is not added in step (5), and the remaining amounts and specific preparation steps are the same as those of Example 1.

[0050] Comparative Example 2

[0051] A method for preparing a cathode electrophoretic coating is different from that of Example 1 in that: 1.2 g of the silane compound KH550 used in step (5) of Example 1 is not added in step (5), and the remaining amounts and specific preparation steps are the same as those of Example 1.

[0052] Comparative Example 3

[0053] A method for preparing a cathode electrophoretic coating, which differs from Example 1 in that: 5.2g of sweat-resistant additive, 1.2g of silane compound KH550 and 1.8g of nanospheres used in step (5) of Example 1 are not added in step (5); the remaining amounts and specific preparation steps are the same as those in Example 1.

[0054] Comparative Example 4

[0055] A method for preparing a cathode electrophoretic coating is disclosed, which differs from Example 1 in that: 22.0 g of versatate vinyl carbonate and 26.0 g of 2-hydroxypropyl methacrylate are used in step (1) instead of 24.0 g of versatate vinyl carbonate and 24.0 g of 2-hydroxypropyl methacrylate; the remaining amounts and specific preparation steps are the same as those in Example 1.

[0056] Testing coating performance

[0057] ①Prepare sample

[0058] The coating compositions prepared in Examples 1-4 and Comparative Examples 1-4 were used to prepare an electrophoretic coating working solution with a mass ratio of 1:5 between the coating composition and deionized water. The working solution had a solid content of 12 wt %. An electrophoretic coating film was formed on a sample plate using an existing electrophoretic coating method to prepare a test sample plate, which was then stored for future use.

[0059] ②Test method

[0060] Appearance of the paint film: Observe with the naked eye to see if there is orange peel or smoothness. The evaluation criteria are: 4 is very good, 3 is good, 2 is poor, and 1 is very poor.

[0061] Paint film gloss: The paint film gloss at 60° is measured according to GB / T9754-2007. The evaluation criteria are: 4 is very good (gloss > 80); 3 is good (gloss 65 < ≤ 80); 2 is poor (gloss 40 < ≤ 65); 1 is very poor (gloss ≤ 40).

[0062] Paint film hardness: The paint film hardness is tested according to GB / T 6739-2022 to examine the paint film hardness grade. The evaluation criteria are: 4H is very good; 3H is good; 2H is poor; 1H is very poor.

[0063] Paint film adhesion: Paint film adhesion is tested according to GB / T 9286-2021 to assess the film adhesion grade. The evaluation criteria are: Grade 0: Very good; Grade 1: Good; Grade 2: Poor; Grade 3: Very poor.

[0064] Working fluid stability: Place the electrophoretic coating working fluid in a 50°C oven and observe whether there is any precipitation. The evaluation criteria are: 4 is very good, with precipitation time ≥6 months; 3 is good, with precipitation time >3 months; 2 is poor, with precipitation time ≤1 month ≤3 months; 1 is very poor, with precipitation time <1 month.

[0065] Neutral salt spray resistance of paint films: The neutral salt spray resistance of paint films was tested according to GB / T 1771-2007 to examine the neutral salt spray resistance of the paint films. The evaluation criteria are: 250 hours is very good; 220 hours is good; 200 hours is poor; 180 hours is very poor.

[0066] Artificial perspiration resistance of the paint film: The artificial perspiration resistance of the eyeglass frame paint film was tested according to GB / T 14214-2019 to examine the paint film's artificial perspiration resistance. The evaluation criteria are: 96 hours is very good; 72 hours is good; 48 hours is poor; and 24 hours is very poor.

[0067] The experimental results are shown in Table 1.

[0068] Table 1

[0069]

[0070]

[0071] As can be seen from the test results in Table 1, the sweat-resistant cathodic electrophoretic coating composition of the present invention (Examples 1 to 4) was prepared by preparing the working fluid according to the existing method and then subjected to cathodic electrophoretic coating to prepare the sample. The various properties of the coating after thermal curing were significantly better than those of Comparative Examples 1 to 4. The electrophoretic working fluid prepared using the sweat-resistant cathodic electrophoretic coating of the present invention has good storage stability. After electrophoretic coating, the coating has a smooth appearance, high hardness, good adhesion, good salt spray resistance, and excellent artificial sweat resistance. There is no discoloration or shedding of the paint film for 96 hours. It can be applied in high-end fields such as eyeglass frames, luggage hardware, biomedical equipment, flexible electronic devices, and precision instruments, meeting the dual requirements of long-term stability and surface decorativeness of the coating material in extreme sweat environments.

[0072] The embodiments of this specific implementation method are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sweat-resistant cathodic electrophoretic coating, characterized in that: The invention comprises the following components in parts by weight: 50-60 parts of modified acrylic resin, 30-42 parts of curing agent, 5-7 parts of sweat-resistant auxiliary agent, 1-2 parts of adhesion promoter, 1-2 parts of nano-microspheres, 3-4 parts of acid and 2-4 parts of deionized water.

2. The sweat-resistant cathodic electrophoretic coating according to claim 1, wherein: The modified acrylic resin is prepared by free radical polymerization of 2-3 wt% of vinyltrimethoxysilane, 10-15 wt% of lauryl methacrylate, 10-15 wt% of glycidyl methacrylate or glycidyl acrylate, 20-26 wt% of versatate vinyl carbonate, 20-26 wt% of 2-hydroxypropyl methacrylate, and 15-20 wt% of other ethylenically unsaturated monomers under the action of an initiator, and then reacting with an organic secondary amine compound; wherein the mass ratio of versatate vinyl carbonate to 2-hydroxypropyl methacrylate is 1:

1.

3. The sweat-resistant cathodic electrophoretic coating according to claim 2, wherein: The other vinyl unsaturated monomers are selected from acrylates, and the acrylates are selected from at least one of isooctyl methacrylate, isooctyl acrylate, tert-butyl acrylate, dodecafluoroheptyl acrylate, and cyclohexyl acrylate; the initiator is selected from at least one of azobisisobutyronitrile and benzoyl peroxide, and the initiator accounts for 1.5 to 2.2 wt% of the total monomer amount; the organic secondary amine compound is selected from at least one of N-methylethylamine, diethylamine, dibutylamine, N-methylaniline, and diphenylamine, and the molar ratio of the organic secondary amine compound to the epoxy group of the epoxy group-containing acrylic resin is 1:

1.

4. The sweat-resistant cathodic electrophoretic coating according to claim 1, wherein: The curing agent is prepared by reacting 50-75 wt% of bio-based pentamethylene diisocyanate with 6-15 wt% of a chain extender and 10-25 wt% of a blocking agent in the presence of a catalyst; the chain extender is selected from at least one of trimethylolpropane, 1,4-butanediol, and hydroquinone dihydroxyethyl ether; the blocking agent is selected from at least one of 3,5-dimethylimidazole, ethylene glycol ethyl ether, and methyl ethyl ketoxime; and the catalyst is selected from at least one of stannous octoate, N,N-dimethylbenzylamine, and organic bismuth.

5. The sweat-resistant cathodic electrophoretic coating according to claim 1, characterized in that: The preparation method of the anti-perspiration auxiliary agent is as follows: 100 parts by weight of phenolic epoxy resin and a catalyst are mixed, and the temperature is raised to 85-90° C. under N2 protection; 10-30 parts by weight of isopropyl alcoholamine is added dropwise, and the temperature is raised to 105-110° C. for reaction for 3-3.5 hours; the temperature is lowered to below 80° C., and a long-chain carboxylic acid is added to neutralize the mixture to a pH of 7.0-8.5 to obtain the anti-perspiration auxiliary agent.

6. The sweat-resistant cathodic electrophoretic coating according to claim 5, characterized in that: The phenolic epoxy resin is selected from at least one of epoxy resins F-44, F-51, and F-46; the catalyst is selected from at least one of tetrabutylammonium hydrogen sulfate, tetrabutylammonium acetate, and tetrabutylammonium bromide; and the long-chain carboxylic acid is selected from at least one of capric acid, stearic acid, and lauric acid.

7. The sweat-resistant cathodic electrophoretic coating according to claim 1, characterized in that: The adhesion promoter is selected from at least one of polyether modified siloxane, silane compound and phosphate compound.

8. The sweat-resistant cathodic electrophoretic coating according to claim 1, characterized in that: The preparation method of the nanospheres is as follows: disperse nano-SiO2 in a solvent, stir and ultrasonicate for more than 50 minutes; add 3-5wt% of a silane compound, add acid to adjust the pH to 4-5; stir at 70-80°C for 2-2.5 hours, cool, wash and dry to obtain the nanospheres.

9. The sweat-resistant cathodic electrophoretic coating according to claim 1, characterized in that: The acid is selected from acetic acid, formic acid, lactic acid, methanesulfonic acid, phosphoric acid, oxalic acid or citric acid.

10. A method for preparing the sweat-resistant cathodic electrophoretic coating according to any one of claims 1 to 9, characterized in that: The following steps are involved: Heat the modified acrylic resin to 70-80°C, add the specified amount of curing agent, sweat-resistant additive, and adhesion promoter, keep warm for 1-1.5 hours, cool to 40-50°C, add nano-microspheres, acid and deionized water, and mix thoroughly to obtain the product.

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