A cathodic electrocoat composition having improved resistance to artificial sweat and weathering and a method for making the same

Abstract

The application discloses a kind of artificial sweat-resistant weather-resistant cathode electrophoretic paint and preparation method thereof.The artificial sweat-resistant weather-resistant cathode electrophoretic paint includes the following components by weight: modified acrylic resin 40-50 parts, curing agent 25~30 parts, artificial sweat-resistant auxiliary agent 5~7 parts, weather-resistant auxiliary agent 3~4 parts, acid 2~3 parts, deionized water 2~4 parts.The working solution prepared by the composition of the application is cathodically electrophoretically coated, and the coating film after heat curing has both artificial sweat-resistant performance and weather-resistant performance, with artificial sweat-resistant performance of 96 hours, achieving high-end glasses frame and other materials requiring high weather resistance, artificial sweat resistance and other properties.

Description

Technical Field

[0001] This invention relates to the field of electrophoretic coating technology, and in particular to a weather-resistant cathodic electrophoretic coating resistant to artificial sweat and its preparation method. Background Technology

[0002] Acrylic cathodic electrophoretic coatings have broad application prospects due to their excellent decorative properties and ability to form a uniform coating on the workpiece surface through electrochemical deposition. However, in certain specific applications, such as electroplated mirror frames, prolonged contact with human skin makes them susceptible to corrosion from sweat secreted by the skin, leading to problems such as plating peeling and rusting, which can affect skin health. Therefore, high sweat resistance is required for electrophoretic coatings. However, existing electrophoretic coatings on the market generally have a sweat resistance time of <72h under simulated sweat environments (such as GB / T 14214—2019 standard), which is still insufficient to meet the needs of some high-durability applications. Summary of the Invention

[0003] The purpose of this invention is to provide a weather-resistant cathodic electrophoretic coating that is resistant to artificial sweat and its preparation method, thereby solving one or more of the problems in the prior art.

[0004] The present invention provides a weather-resistant cathodic electrophoretic coating resistant to artificial sweat, comprising the following raw materials in parts by weight: 40-50 parts of modified acrylic resin, 25-40 parts of hardener 3-4 parts of weather-resistant additives, 5-7 parts of artificial sweat resistant agent, 2-3 parts acid, 2-4 parts deionized water.

[0005] By adopting the above technical solution, the electrophoretic working solution prepared by the above composition is stable, has good leveling effect and fast curing speed after electrophoretic film formation, and also has good weather resistance and artificial sweat resistance.

[0006] In some embodiments, the modified acrylic resin is prepared by the following method: The modified acrylic resin is formed by free radical polymerization of 2-3 parts vinyltrimethoxysilane, 5-10 parts lauryl methacrylate, 7-10 parts hydroxyethyl methacrylate, 20-26 parts methyl methacrylate, 20-26 parts dimethylaminoethyl methacrylate, and 3-5 parts isobornyl methacrylate under the action of an initiator.

[0007] In some embodiments, the initiator is selected from at least one of azobisisobutyronitrile and benzoyl peroxide, and the initiator accounts for 0.5-1.5 parts of the total monomer.

[0008] In some embodiments, the curing agent is prepared by reacting 20-30 parts of isophorone diisocyanate with 10-15 parts of a chain extender and 10-25 parts of a blocking agent under the action of a catalyst; the chain extender is selected from at least one of trimethylolpropane, 1,4-butanediol, and 3,3'-dichloro-4,4'-diaminodiphenylmethane; the blocking agent is selected from at least one of 1-butyl-2,3-dimethylimidazolium bromide, ethylene glycol ethyl ether, and methyl ethyl ketone oxime; and the catalyst is selected from at least one of stannous octoate, N,N-dimethyl-4-nitrobenzylamine, and organobismuth.

[0009] In some embodiments, the curing agent is prepared as follows: Under nitrogen protection, isophorone diisocyanate and solvent are mixed, heated to 60-70°C, and catalyst is added dropwise. The temperature is maintained at 60-70°C for 1-1.5 hours until the addition is complete. The temperature is then raised to 75-82°C and held for 1-1.8 hours. A blocking agent is added, and the temperature is maintained at 50-60°C. The temperature is then raised to 60-70°C and held for 2-2.5 hours. A chain extender is then added, and the temperature is raised to 90-100°C and held for 2-2.5 hours. The NCO content is tested to be ≤0.3% (di-n-butylamine titration method). The temperature is lowered, and solvent is added to adjust the solid content to 80.0-85.0%. The mixture is cooled to room temperature, filtered to remove impurities, and a pale yellow to brown transparent liquid is obtained.

[0010] In some embodiments, the solvent is selected from methyl isobutyl ketone or propylene glycol methyl ether acetate.

[0011] In some embodiments, the artificial sweat-resistant adjuvant is prepared by the following method: Mix 10-15 parts of ethylene glycol butyl ether with 25-40 parts of E128 epoxy resin, add 0.1-0.7 parts of catalyst, and react with 10-15 parts of amine compound to obtain a sweat-resistant additive.

[0012] In some embodiments, the preparation method of the artificial sweat resistant agent is as follows: Diethanolamine is added to a four-necked flask, and nitrogen gas is introduced to replace the air in the flask. The temperature is raised to 75-80°C, and 0.7-1 parts of tetrabutylammonium bisulfate are added. The solvent ethylene glycol butyl ether and E128 epoxy resin are mixed evenly and added dropwise to the four-necked flask over 2-3 hours. The temperature is maintained, and the reaction continues for 1-2 hours to allow the epoxy groups to fully react with the diethanolamine to open the ring. Impurities are removed by filtration to obtain a transparent liquid.

[0013] In some embodiments, the amine compound is selected from at least one of diethanolamine, methylethanolamine, and di-n-propylamine; the molar ratio of the amine compound to the epoxy group of the epoxy resin is 1:1; and the catalyst is selected from at least one of tetrabutylammonium bisulfate, tetrabutylammonium acetate, and tetrabutylammonium bromide.

[0014] In some embodiments, the weather-resistant agent is a mixture of nano-graphene and nano-zinc oxide in a mass ratio of 1-1.6:1.5-2.8.

[0015] In some embodiments, the acid is selected from at least one of lactic acid, acetic acid, oxalic acid, and citric acid.

[0016] On the other hand, the preparation method of the artificial sweat-resistant and weather-resistant cathodic electrophoretic coating provided by the present invention includes the following steps: The modified acrylic resin is heated to 80-90℃, a curing agent is added, and the mixture is kept at this temperature for 1.5-2.5 hours. Then, the temperature is lowered to 40-50℃, and weather-resistant additives, artificial sweat-resistant additives, acid, and deionized water are added and mixed thoroughly to obtain the final product. The following raw materials are included in the specified weight proportions: 40-50 parts of modified acrylic resin, 25-40 parts of hardener 3-4 parts of weather-resistant additives, 5-7 parts of artificial sweat resistant agent, 2-3 parts acid, 2-4 parts deionized water.

[0017] Beneficial Effects: This invention provides a cathodic electrophoretic coating with improved resistance to artificial sweat and weathering. By incorporating a certain proportion of hydrophobic monomers, with lauryl methacrylate as the main hydrophobic functional monomer, the water resistance of the coating film is enhanced within the resin structure. Simultaneously, the addition of hydrophilic monomers such as methyl methacrylate effectively adjusts the hydrophilicity and hydrophobicity of the resin, thereby improving the water resistance of the electrophoretic coating film. Furthermore, the addition of vinyltrimethoxysilane improves the interfacial properties of the coating, thus enhancing the overall mechanical properties of the film. In addition, the addition of an artificial sweat resistance additive introduces a large number of secondary hydroxyl groups into the main resin. These secondary hydroxyl groups enhance the adhesion of the main resin to the substrate, thereby improving the coating's resistance to salt spray and sweat. Furthermore, this artificial sweat resistance additive contains multiple terminal hydroxyl groups. The introduction of these terminal hydroxyl groups increases the number of groups that can react with the curing agent, increasing the crosslinking density and improving not only the hydrophobicity of the coating but also further enhancing its resistance to artificial sweat. Furthermore, the addition of a weather-resistant additive allows for antioxidant effects through the synergistic effect of graphene and nano-zinc oxide, forming a dense barrier and mechanical stability to resist environmental aging. The electrophoretic working solution formulated with the cathodic electrophoretic coating of the present invention, which exhibits resistance to artificial sweat and weathering, shows significantly improved storage stability. The coating film after electrophoretic coating demonstrates excellent leveling properties, superior weather resistance, and good resistance to artificial sweat. Detailed Implementation

[0018] The present invention will be further described in detail below through embodiments.

[0019] The present patent application will be further described below with reference to the embodiments. Unless otherwise stated, the raw materials used in the embodiments and comparative examples are all commercially available industrial products that can be purchased through commercial channels.

[0020] The E128 epoxy resin used in the following embodiments of this application is industrial grade and manufactured by Jiangsu Sanmu Chemical Co., Ltd.

[0021] Example 1 A cathodic electrophoretic coating with resistance to artificial sweat and weathering is prepared by the following method: (1) Preparation of modified acrylic resin The specific preparation method of modified acrylic resin is as follows: 2 parts vinyltrimethoxysilane, 5 parts lauryl methacrylate, 7 parts hydroxyethyl methacrylate, 20 parts methyl methacrylate, 20 parts dimethylaminoethyl methacrylate, 3 parts isobornyl methacrylate, and 2 parts benzoyl peroxide solution are heated at 88℃-95°C for 0.5-1h; the monomer conversion rate reaches more than 99%; thus, the modified acrylic resin is obtained.

[0022] (2) Preparation of curing agent Under nitrogen protection, isophorone diisocyanate and methyl isobutyl ketone are mixed and heated to 60-70°C. The catalyst is then added dropwise, and the temperature is maintained at 60-70°C for 1-1.5 hours until the addition is complete. The temperature is then raised to 75-82°C and held for 1-1.8 hours. A blocking agent is added, and the temperature is maintained at 50-60°C. The temperature is then raised to 60-70°C and held for 2-2.5 hours. A chain extender is then added, and the temperature is raised to 90-100°C and held for 2-2.5 hours. The NCO content is tested to be ≤0.5% (di-n-butylamine titration method). The mixture is cooled and solvent is added to adjust the solid content to 80.0-85.0%. The mixture is cooled to room temperature, filtered to remove impurities, and a pale yellow to brown transparent liquid is obtained.

[0023] (3) Preparation of artificial sweat resistant adjuvants Add diethanolamine to a four-necked flask, purge with nitrogen to displace the air. Heat to 75-80°C, add 0.7-1 parts of tetrabutylammonium bisulfate, mix the solvent ethylene glycol butyl ether with E128 epoxy resin evenly and add dropwise to the four-necked flask over 2-3 hours. Maintain the temperature and continue the reaction for 1-2 hours to allow the epoxy groups to fully react with the diethanolamine and open the ring. Filter to remove impurities and obtain a transparent liquid.

[0024] (4) Preparation of weather-resistant additives A mixture of nano-graphene and nano-zinc oxide in a mass ratio of 1-1.6:1.5-2.8.

[0025] (5) Preparation of a cathodic electrophoretic coating composition resistant to artificial sweat and weathering. Add 100.0g of the modified acrylic resin prepared in step (1) above to a reaction flask, heat to 85°C, add 32.0g of the curing agent prepared in step (2) above, keep warm for 1 hour, cool down to 45°C, add 3.0g of the artificial sweat resistant agent prepared in step (3) above, 2.0g of the weather resistant agent prepared in step (4) above, 2.0g of lactic acid and 10.0g of deionized water to obtain an artificial sweat resistant and weather resistant cathodic electrophoretic coating composition.

[0026] Example 2 A method for preparing an artificial sweat-resistant and weather-resistant cathodic electrophoretic coating differs from Example 1 in that: in step (1), 10 parts of isooctyl acrylate are used instead of 10 parts of n-butyl acrylate used in step (1) of Example 1, while the remaining amounts and specific preparation steps are the same as in Example 1.

[0027] Example 3 A method for preparing an artificial sweat-resistant and weather-resistant cathodic electrophoretic coating differs from Example 1 in that: in step (1), 2 parts of benzoyl peroxide are used instead of 2 parts of azobisisobutyronitrile used in step (1) of Example 1, while the remaining amounts and specific preparation steps are the same as in Example 1.

[0028] Comparative Example 1 A method for preparing a weather-resistant cathodic electrophoretic coating resistant to artificial sweat, which differs from Example 1 in that: the 3.0g artificial sweat resistant additive used in step (3) of Example 1 is not added in step (3), while the remaining dosages and specific preparation steps are the same as in Example 1.

[0029] Comparative Example 2 A method for preparing an artificial sweat-resistant and weather-resistant cathodic electrophoretic coating differs from Example 1 in that: step (4) does not include the 2.0g weather-resistant additive used in step (4) of Example 1, while the remaining dosages and specific preparation steps are the same as in Example 1.

[0030] Performance testing The following performance tests were performed on the products of Examples 1-2 and Comparative Examples 1-2:

[0031] As shown in Table 1, the test results of the artificial sweat-resistant and weather-resistant cathodic electrophoretic coating composition of the present invention, when prepared using existing methods and electrophoretically coated, exhibit significantly better performance in all aspects of the coating film after thermosetting than comparative examples 1 and 2. The artificial sweat-resistant and weather-resistant cathodic electrophoretic coating of the present invention has good storage stability, a smooth and even appearance, good weather resistance, and excellent resistance to artificial sweat (no discoloration or peeling of the coating film after 96 hours). It can be used in high-end applications such as eyeglass frames, meeting the requirements of coating materials in harsh environments.

[0032] In summary, the preparation method of the artificial sweat-resistant and weather-resistant coating of the present invention combines cathodic electrophoretic coating process with artificial sweat-resistant and weather-resistant technology, and is suitable for high-end hardware materials, etc. It has the characteristics of excellent coating performance and maintaining excellent film stability in harsh environments.

[0033] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these should also be considered within the scope of protection of the invention.

Claims

1. A weather-resistant cathodic electrophoretic coating resistant to artificial sweat, characterized in that, The ingredients include the following parts by weight: 40-50 parts of modified acrylic resin, 25-40 parts of hardener 3-4 parts of weather-resistant additives, 5-7 parts of artificial sweat resistant agent, 2-3 parts acid, 2-4 parts deionized water.

2. The artificial sweat-resistant and weather-resistant cathodic electrophoretic coating according to claim 1, characterized in that, The modified acrylic resin is prepared by the following method: The modified acrylic resin is formed by free radical polymerization of 2-3 parts vinyltrimethoxysilane, 5-10 parts lauryl methacrylate, 7-10 parts hydroxyethyl methacrylate, 20-26 parts methyl methacrylate, 20-26 parts dimethylaminoethyl methacrylate, and 3-5 parts isobornyl methacrylate under the action of an initiator.

3. The artificial sweat-resistant and weather-resistant cathodic electrophoretic coating according to claim 2, characterized in that, The initiator is selected from at least one of azobisisobutyronitrile and benzoyl peroxide, and the initiator accounts for 0.5-1.5 parts of the total monomer.

4. The artificial sweat-resistant and weather-resistant cathodic electrophoretic coating according to claim 1, characterized in that, The curing agent is prepared by reacting 20-30 parts of isophorone diisocyanate with 10-15 parts of chain extender and 10-25 parts of blocking agent under the action of a catalyst; the chain extender is selected from at least one of trimethylolpropane, 1,4-butanediol, and 3,3'-dichloro-4,4'-diaminodiphenylmethane; the blocking agent is selected from at least one of 1-butyl-2,3-dimethylimidazolium bromide, ethylene glycol ethyl ether, and methyl ethyl ketone oxime; the catalyst is selected from at least one of stannous octoate, N,N-dimethyl-4-nitrobenzylamine, and organobismuth.

5. The artificial sweat-resistant and weather-resistant cathodic electrophoretic coating according to claim 1, characterized in that, The artificial sweat-resistant additive is prepared by the following method: Mix 10-15 parts of ethylene glycol butyl ether with 25-40 parts of E128 epoxy resin, add 0.1-0.7 parts of catalyst, and react with 10-15 parts of amine compound to prepare a sweat-resistant additive.

6. The artificial sweat-resistant and weather-resistant cathodic electrophoretic coating according to claim 5, characterized in that, The amine compound is selected from at least one of diethanolamine, methylethanolamine, and di-n-propylamine; the molar ratio of the amine compound to the epoxy group of the epoxy resin is 1:1; and the catalyst is selected from at least one of tetrabutylammonium hydrogen sulfate, tetrabutylammonium acetate, and tetrabutylammonium bromide.

7. The artificial sweat-resistant and weather-resistant cathodic electrophoretic coating according to claim 1, characterized in that, The weather-resistant additive is a mixture of nano-graphene and nano-zinc oxide in a mass ratio of 1-1.6:1.5-2.

8.

8. The artificial sweat-resistant and weather-resistant cathodic electrophoretic coating according to claim 1, characterized in that, The acid is selected from at least one of lactic acid, acetic acid, oxalic acid, and citric acid.

9. A method for preparing a cathodic electrophoretic coating resistant to artificial sweat as described in any one of claims 1 to 8, characterized in that, Includes the following steps: The modified acrylic resin is heated to 80-90℃, a curing agent is added, and the mixture is kept at this temperature for 1.5-2.5 hours. Then, the temperature is lowered to 40-50℃, and weather-resistant agents, artificial sweat-resistant agents, acid, and deionized water are added and mixed thoroughly to obtain the final product.

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