Composite curing agent, method of preparation and use thereof in the production of electrically insulating powder coatings

Abstract

The application discloses a kind of composite curing agent, by modified imidazole curing agent and triethylene tetramine are prepared;The preparation method of the modified imidazole curing agent includes the following steps: S1: 2-methyl imidazole is mixed with methyl acrylate, solvent and polymerization inhibitor are added, heating, stirring and reflux are carried out, until color becomes dark;S2: stop heating, after cooling to room temperature, remove solvent and excess methyl acrylate by distillation under reduced pressure, and then cool to room temperature;The application of the composite curing agent in electrically insulating powder coating includes the following raw materials: epoxy resin, composite curing agent, modified red mud, polyacrylate, silicon dioxide, electric enhancer, leveling agent, degassing agent, flatting agent, dispersing agent.The coating of the application has good insulation performance and mechanical properties, low cost, and can be widely used in the field of insulation coating for new energy vehicle batteries.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to composite curing agents, preparation methods, and their application in the production of electrically insulating powder coatings. Background Technology

[0002] In recent years, my country's electronics and electrical engineering industries have been developing rapidly at a double-digit growth rate annually. In this rapidly developing industry, the quality of insulating materials directly affects the quality and lifespan of electrical products. The electronics and electrical engineering industry uses a large amount of insulating materials, typically solvent-based insulating varnishes. Insulating varnishes are convenient to use and inexpensive, and can meet the insulation requirements of some electrical materials. However, they produce waste gas emissions, most solvents are toxic, and the coating utilization efficiency is relatively low. Insulating powder coatings are a specialized type of powder coating used in the electronics industry. In addition to the protective and decorative properties of general powder coatings, insulating powder coatings also have excellent electrical insulation properties. Compared with traditional insulating varnishes, insulating powder coatings have similar costs, produce no solvent emissions, and after curing, they have high density, a smooth surface, and strong adhesion. These characteristics perfectly compensate for the disadvantages of traditional solvent-based insulating varnishes.

[0003] Epoxy resin powder coatings are the most commonly used insulating powder coatings, mainly used for insulating products such as motor rotors, electromagnetic wires, and enameled wires. Epoxy resin powder coatings have low melt viscosity, produce no substances during curing, and exhibit excellent leveling and gloss properties, without pinholes or depressions. The hydroxyl groups in the resin give the coating excellent adhesion, while the presence of the bisphenol A backbone and ether bonds contributes to good mechanical properties. Epoxy powder coatings offer a wide range of curing agents, good color matching and powder mixing capabilities, and a broad range of applications.

[0004] Chinese invention patent (publication number: CN110698950A) discloses an insulating powder coating comprising the following raw material components in parts by weight: 60-80 parts epoxy resin; 20-30 parts silicate powder; 5-10 parts calcium silicate; 3-5 parts ammonium polyphosphate; 1-3 parts benzoin; 20-40 parts curing agent; 1-5 parts accelerator; and 1-5 parts leveling agent. The insulating powder coating described in this invention has excellent insulating properties. However, the use of phenolic curing agents results in poor reactivity, a relatively high curing temperature, insufficient insulating properties, and poor mechanical properties.

[0005] Chinese invention patent application (publication number: CN112898871A) discloses an insulating powder coating and its application. The insulating powder coating includes an insulating agent, a flame retardant, a thermal conductive agent, a curing agent, and a leveling agent. The thermal conductive agent includes any one or a combination of at least two of titanium dioxide, silicon dioxide, boron carbide, or silicon nitride. The leveling agent includes a polymer of phenol, formaldehyde, and glycidyl ether and / or polyacrylic acid. The various substances in the insulating powder coating work together to give the insulating layer formed by the coating good insulation, flame retardant, and heat dissipation properties. Furthermore, the insulating powder adheres well to the battery casing and can withstand long-term high temperature and high humidity environments, solving the problem of unreliable adhesion between the insulating film and the battery casing in existing technologies. However, it uses phenolic resin as a curing agent, which has high irritant and toxicity.

[0006] Chinese invention patent application (publication number: CN113416470A) discloses an electronic insulating powder coating and its preparation method. The raw materials and their weight percentages of the electronic insulating powder coating are: epoxy resin 50-60%, modified silicate 5-16%, curing agent 5-6%, leveling agent 0.8-1.2%, gloss enhancer 0.8-1.0%, defoamer 2-4%, titanium dioxide pigment 20-28%, and barium sulfate filler 0.5-20%. The modified silicate is obtained by modifying silicate with a silane coupling agent. This powder coating has excellent chemical resistance and high resistivity, which makes the powder coating of this invention have a good protective effect on medical electronic components, thus extending the service life of the equipment. However, it uses a traditional dicyandiamide curing agent, which has a high curing temperature and low stability. Summary of the Invention

[0007] The purpose of this invention is to provide a composite curing agent, a preparation method, and its application in the production of electrically insulating powder coatings. This invention can solve the technical problems of low insulation performance and poor mechanical properties in existing insulating powder coatings. The resulting coating has good insulation and mechanical properties, low irritation, and low cost.

[0008] A composite curing agent is prepared by mixing a modified imidazole curing agent and triethylenetetramine in a mass ratio of 1.2-2.5:0.8-1.4.

[0009] Furthermore, the modified imidazole curing agent is made from methyl acrylate modified 2-methylimidazole.

[0010] The preparation method of the modified imidazole curing agent includes the following steps:

[0011] S1: Mix 2-methylimidazole with methyl acrylate, add solvent and polymerization inhibitor, heat to 90-100℃, stir and reflux until the color darkens;

[0012] S2: Stop heating, cool to room temperature, then distill under reduced pressure to remove the solvent and excess methyl acrylate, and then cool to room temperature.

[0013] Furthermore, the solvent is toluene, and the polymerization inhibitor is hydroquinone.

[0014] An application of a composite curing agent in the production of electrically insulating powder coatings comprises the following raw materials: 80-120 parts epoxy resin, 20-40 parts composite curing agent, 60-90 parts modified red mud, 8-10 parts polyacrylate, 5-20 parts silica, 1-3 parts thermal conductive agent, 1-4 parts leveling agent, 1-2 parts degassing agent, 2-4 parts matting agent, and 0.6-2 parts dispersant.

[0015] Furthermore, the method for preparing the modified red mud includes the following steps:

[0016] (1) The red mud waste generated during the alumina production process is washed away by water washing to remove water-soluble substances such as Na2O. After the pH value of the washed red mud is tested to be 8.9, it is filtered to obtain clean red mud. The clean red mud is then dried to a moisture content of 5%.

[0017] (2) The clean red mud obtained in step (1) is subjected to ultrafine grinding and sieved to obtain clean red mud powder with a mesh size greater than 300.

[0018] (3) Add modifier I to the clean red mud powder obtained in step (2). Modifier I is composed of diethanolamide stearate monoester and sodium ethylene-bis(N-ethanesulfonic acid-dodecanoate). The amount of modifier I added is 4.2% of the mass of the clean red mud powder. The mass ratio of diethanolamide stearate monoester and sodium ethylene-bis(N-ethanesulfonic acid-dodecanoate) is 9.2:5.8. The temperature is controlled at 56-60℃ and stirred at 1000r / min for 26min to obtain mixture I.

[0019] (4) Add the mixture I obtained in step (3) and the modifier II to a mixer. The modifier II is composed of aminopyramidized dimethylsiloxane, hexabromocyclotriphosphazene, and N-propyl-perfluorooctylsulfonylglutamate sodium. The amount of modifier II added is 2% of the mass of the clean red mud powder. The mass ratio of aminopyramidized dimethylsiloxane, hexabromocyclotriphosphazene, and N-propyl-perfluorooctylsulfonylglutamate sodium is 5.3:1.8:3.5. The temperature is controlled at 80-84℃ and the mixture is stirred at 1200r / min for 40min to obtain mixture II.

[0020] (5) The mixture II obtained in step (4) is dried at a temperature of 42-45℃ until the water content is 0.9%, then ultra-fine grinding is performed, and after sieving, modified red mud for coating with a mesh size greater than 300 is obtained.

[0021] Furthermore, the thermal conductive agent includes one or more of boron carbide and silicon nitride.

[0022] Furthermore, the leveling agent includes one or more of ethyl polyacrylate, butyl polyacrylate, and lauryl polyacrylate.

[0023] Furthermore, the degassing agent includes one or more of benzoin, polyethylene wax, and polyamide wax.

[0024] Furthermore, the dispersant is TiO2.

[0025] Furthermore, the matting agent is one or more of B68 matting agent and B55 matting agent.

[0026] The advantages of this invention compared to the prior art are as follows:

[0027] 1. The curing agent of the present invention is prepared by using modified imidazole curing agent and triethylenetetramine. After modification with methyl acrylate, the nitrogen atom on the imidazole ring of 2-methylimidazole has good reactivity and can react with the double bond in methyl acrylate that has an adjacent electron-withdrawing group, thereby improving the reactivity and stability of imidazole and the curing performance of the imidazole curing agent. Triethylenetetramine can undergo an addition reaction with the epoxy group of epoxy resin, improving the curing performance, while imidazole can catalyze the ring-opening polymerization reaction of the epoxy group in the resin, promoting the reaction process of triethylenetetramine. At the same time, imidazole can also catalyze the polymerization reaction between triethylenetetramine and epoxy resin, acting as an accelerator. The two react synergistically to improve the performance of the coating.

[0028] 2. The filler used in this invention is modified red mud prepared using the technology of the Chinese invention patent "Modified Red Mud for Coatings and its Preparation Method (Patent No.: ZL201910453010.3)" obtained by the applicant. After modifying the surface of the red mud, the agglomeration effect in the red mud matrix can be effectively reduced, and the adhesion, compatibility and wettability between epoxy resin and modified red mud in the production of electrical insulating powder coatings can be effectively improved, thereby greatly improving the performance of the produced electrical insulating powder coatings. Furthermore, the raw materials for the produced electrical insulation powder coating contain a high proportion of modified red mud, which not only makes great use of waste red mud as a filler but also effectively reduces the amount of epoxy resin used as the matrix resin. Compared with the conventional filler barium sulfate, the cost of the electrical insulation powder coating produced by this invention is reduced by more than 1,000 yuan / ton. This not only effectively reduces the cost of producing electrical insulation powder coating but also greatly reduces the environmental damage caused by the accumulation of waste red mud, reduces radiation, and increases added value, thus achieving the goal of "turning waste red mud into treasure." At the same time, the modifier used in the modified red mud can coat the surface of the clean red mud powder, thereby significantly improving the mechanical properties of the coating without damaging its insulation performance.

[0029] 3. This invention utilizes the technical achievement of the applicant's Chinese invention patent "Modified Red Mud for Coatings and its Preparation Method (Patent No.: ZL201910453010.3)" to prepare modified red mud, which is then applied to the production of electrically insulating powder coatings. This powder coating is an epoxy resin system, using bisphenol A type epoxy resin, combined with the curing agent, filler, and additives of this invention. The resulting powder coating exhibits excellent insulation properties, high mechanical strength, and good thermal conductivity. It can be widely applied in coating technology fields requiring high insulation performance, such as motor rotors, stators, transformers, electromagnetic wires, and new energy vehicles. In particular, it can be widely used for insulating coatings of new energy vehicle batteries. Therefore, this invention achieves the transformation of patented technology achievements, greatly improving the applicant's economic benefits. Attached Figure Description

[0030] Figure 1 This is a product image of the electrically insulating powder coating of Embodiment 3 of the present invention;

[0031] Figure 2 This is a graph showing the test results of the electrical insulation performance of the powder coating sprayed in Embodiment 3 of the present invention. Detailed Implementation

[0032] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention.

[0033] A composite curing agent is prepared by mixing a modified imidazole curing agent made of methyl acrylate-modified 2-methylimidazole with triethylenetetramine at a mass ratio of 1.2-2.5:0.8-1.4.

[0034] The preparation method of the modified imidazole curing agent includes the following steps:

[0035] S1: Mix 2-methylimidazole with methyl acrylate, add toluene solvent and hydroquinone polymerization inhibitor, heat to 90-100℃, stir and reflux until the color darkens;

[0036] S2: Stop heating, cool to room temperature, then distill under reduced pressure to remove the solvent and excess methyl acrylate, and then cool to room temperature.

[0037] An application of a composite curing agent in the production of electrically insulating powder coatings comprises the following raw materials: 80-120 parts epoxy resin, 20-40 parts composite curing agent, 60-90 parts modified red mud, 8-10 parts polyacrylate, 5-20 parts silica, 1-3 parts thermal conductive agent, 1-4 parts leveling agent, 1-2 parts degassing agent, 2-4 parts matting agent, and 0.6-2 parts TiO2.

[0038] The method for preparing the modified red mud includes the following steps:

[0039] (1) The red mud waste generated during the alumina production process is washed away by water washing to remove water-soluble substances such as Na2O. After the pH value of the washed red mud is tested to be 8.9, it is filtered to obtain clean red mud. The clean red mud is then dried to a moisture content of 5%.

[0040] (2) The clean red mud obtained in step (1) is subjected to ultrafine grinding and sieved to obtain clean red mud powder with a mesh size greater than 300.

[0041] (3) Add modifier I to the clean red mud powder obtained in step (2). Modifier I is composed of diethanolamide stearate monoester and sodium ethylene-bis(N-ethanesulfonic acid-dodecanoate). The amount of modifier I added is 4.2% of the mass of the clean red mud powder. The mass ratio of diethanolamide stearate monoester and sodium ethylene-bis(N-ethanesulfonic acid-dodecanoate) is 9.2:5.8. The temperature is controlled at 56-60℃ and stirred at 1000r / min for 26min to obtain mixture I.

[0042] (4) Add the mixture I obtained in step (3) and the modifier II to a mixer. The modifier II is composed of aminopyramidized dimethylsiloxane, hexabromocyclotriphosphazene, and N-propyl-perfluorooctylsulfonylglutamate sodium. The amount of modifier II added is 2% of the mass of the clean red mud powder. The mass ratio of aminopyramidized dimethylsiloxane, hexabromocyclotriphosphazene, and N-propyl-perfluorooctylsulfonylglutamate sodium is 5.3:1.8:3.5. The temperature is controlled at 80-84℃ and the mixture is stirred at 1200r / min for 40min to obtain mixture II.

[0043] (5) The mixture II obtained in step (4) is dried at a temperature of 42-45℃ until the water content is 0.9%, then ultra-fine grinding is performed, and after sieving, modified red mud for coating with a mesh size greater than 300 is obtained.

[0044] The thermally conductive agent includes one or more of boron carbide and silicon nitride.

[0045] The leveling agent includes one or more of ethyl polyacrylate, butyl polyacrylate, and lauryl polyacrylate.

[0046] The degassing agent includes one or more of benzoin, polyethylene wax, and polyamide wax.

[0047] The matting agent is one or more of B68 matting agent and B55 matting agent.

[0048] The following describes the process through more specific embodiments.

[0049] Example 1

[0050] A composite curing agent is prepared by mixing a modified imidazole curing agent made of methyl acrylate-modified 2-methylimidazole with triethylenetetramine at a mass ratio of 1:1.2.

[0051] The preparation method of the modified imidazole curing agent includes the following steps:

[0052] S1: Mix 2-methylimidazole with methyl acrylate, add toluene solvent and hydroquinone polymerization inhibitor, heat to 90°C, stir and reflux until the color darkens;

[0053] S2: Stop heating, cool to room temperature, then distill under reduced pressure to remove toluene solvent and excess methyl acrylate, and then cool to room temperature.

[0054] An application of a composite curing agent in the production of electrically insulating powder coatings comprises the following raw materials: 90 parts of bisphenol A type epoxy resin, 40 parts of composite curing agent, 70 parts of modified red mud, 10 parts of polyacrylate, 5 parts of silica, 2 parts of boron carbide, 4 parts of polybutyl acrylate, 2 parts of benzoin, 4 parts of B68 matting agent, and 1 part of TiO2.

[0055] The modified red mud is prepared using the method described in Example 1 of the Chinese invention patent "Modified Red Mud for Coatings and its Preparation Method (Patent No.: ZL201910453010.3)" obtained by the applicant. The preparation method of the modified red mud includes the following steps:

[0056] (1) The red mud waste generated during the alumina production process is washed away by water washing to remove water-soluble substances such as Na2O. After the pH value of the washed red mud is tested to be 8.9, it is filtered to obtain clean red mud. The clean red mud is then dried to a moisture content of 5%.

[0057] (2) The clean red mud obtained in step (1) is subjected to ultrafine grinding and sieved to obtain clean red mud powder with a mesh size greater than 300.

[0058] (3) Add modifier I to the clean red mud powder obtained in step (2). Modifier I is composed of diethanolamide stearate monoester and sodium ethylene-bis(N-ethanesulfonic acid-dodecanoate). The amount of modifier I added is 4.2% of the mass of the clean red mud powder. The mass ratio of diethanolamide stearate monoester and sodium ethylene-bis(N-ethanesulfonic acid-dodecanoate) is 9.2:5.8. The temperature is controlled at 56-60℃ and stirred at 1000r / min for 26min to obtain mixture I.

[0059] (4) Add the mixture I obtained in step (3) and the modifier II to a mixer. The modifier II is composed of aminopyramidized dimethylsiloxane, hexabromocyclotriphosphazene, and N-propyl-perfluorooctylsulfonylglutamate sodium. The amount of modifier II added is 2% of the mass of the clean red mud powder. The mass ratio of aminopyramidized dimethylsiloxane, hexabromocyclotriphosphazene, and N-propyl-perfluorooctylsulfonylglutamate sodium is 5.3:1.8:3.5. The temperature is controlled at 80-84℃ and the mixture is stirred at 1200r / min for 40min to obtain mixture II.

[0060] (5) The mixture II obtained in step (4) is dried at a temperature of 42-45℃ until the water content is 0.9%, then ultra-fine grinding is performed, and after sieving, modified red mud for coating with a mesh size greater than 300 is obtained.

[0061] Example 2

[0062] A composite curing agent is prepared by mixing a modified imidazole curing agent made of methyl acrylate-modified 2-methylimidazole with triethylenetetramine at a mass ratio of 2.5:0.8.

[0063] The preparation method of the modified imidazole curing agent includes the following steps:

[0064] S1: Mix 2-methylimidazole with methyl acrylate, add toluene solvent and hydroquinone polymerization inhibitor, heat to 90°C, stir and reflux until the color darkens;

[0065] S2: Stop heating, cool to room temperature, then distill under reduced pressure to remove toluene solvent and excess methyl acrylate, and then cool to room temperature.

[0066] An application of a composite curing agent in the production of electrically insulating powder coatings comprises the following raw materials: 120 parts of bisphenol A type epoxy resin, 25 parts of composite curing agent, 60 parts of modified red mud, 8 parts of polyacrylate, 15 parts of silica, 1 part of silicon nitride, 2 parts of ethyl polyacrylate, 1 part of polyamide wax, 3 parts of B55 matting agent, and 0.8 parts of TiO2.

[0067] The modified red mud described herein is the same as the modified red mud in Example 1, and is also prepared using the method of Example 1 disclosed in the Chinese invention patent "Modified Red Mud for Coatings and its Preparation Method (Patent No.: ZL201910453010.3)" obtained by the applicant.

[0068] Example 3

[0069] A composite curing agent is prepared by mixing a modified imidazole curing agent made of methyl acrylate-modified 2-methylimidazole with triethylenetetramine at a mass ratio of 1.2:1.4.

[0070] The preparation method of the modified imidazole curing agent includes the following steps:

[0071] S1: Mix 2-methylimidazole with methyl acrylate, add toluene solvent and hydroquinone polymerization inhibitor, heat to 100°C, stir and reflux until the color darkens;

[0072] S2: Stop heating, cool to room temperature, then distill under reduced pressure to remove toluene solvent and excess methyl acrylate, and then cool to room temperature.

[0073] An application of a composite curing agent in the production of electrically insulating powder coatings comprises the following raw materials: 80 parts bisphenol A type epoxy resin, 20 parts composite curing agent, 80 parts modified red mud, 8 parts polyacrylate, 10 parts silica, 1 part silicon nitride, 2 parts ethyl polyacrylate, 2 parts benzoin, 4 parts B68 matting agent, and 2 parts TiO2. The resulting electrically insulating powder coating product is as follows: Figure 1 As shown.

[0074] The modified red mud described herein is the same as the modified red mud in Example 1, and is also prepared using the method of Example 1 disclosed in the Chinese invention patent "Modified Red Mud for Coatings and its Preparation Method (Patent No.: ZL201910453010.3)" obtained by the applicant.

[0075] Example 4

[0076] A composite curing agent is prepared by mixing a modified imidazole curing agent made of methyl acrylate-modified 2-methylimidazole with triethylenetetramine at a mass ratio of 2:1.4.

[0077] The preparation method of the modified imidazole curing agent includes the following steps:

[0078] S1: Mix 2-methylimidazole with methyl acrylate, add toluene solvent and hydroquinone polymerization inhibitor, heat to 100°C, stir and reflux until the color darkens;

[0079] S2: Stop heating, cool to room temperature, then distill under reduced pressure to remove toluene solvent and excess methyl acrylate, and then cool to room temperature.

[0080] An application of a composite curing agent in the production of electrically insulating powder coatings comprises the following raw materials: 100 parts of bisphenol A type epoxy resin, 30 parts of composite curing agent, 90 parts of modified red mud, 9 parts of polyacrylate, 20 parts of silica, 3 parts of silicon nitride, 3 parts of polylauryl acrylate, 2 parts of polyethylene wax, 2 parts of B68 matting agent, and 0.6 parts of TiO2.

[0081] The modified red mud described herein is the same as the modified red mud in Example 1, and is also prepared using the method of Example 1 disclosed in the Chinese invention patent "Modified Red Mud for Coatings and its Preparation Method (Patent No.: ZL201910453010.3)" obtained by the applicant.

[0082] Example 5

[0083] A composite curing agent is prepared by mixing a modified imidazole curing agent made of methyl acrylate-modified 2-methylimidazole with triethylenetetramine at a mass ratio of 2.5:1.

[0084] The preparation method of the modified imidazole curing agent includes the following steps:

[0085] S1: Mix 2-methylimidazole with methyl acrylate, add toluene solvent and hydroquinone polymerization inhibitor, heat to 90°C, stir and reflux until the color darkens;

[0086] S2: Stop heating, cool to room temperature, then distill under reduced pressure to remove toluene solvent and excess methyl acrylate, and then cool to room temperature.

[0087] An application of a composite curing agent in the production of electrically insulating powder coatings comprises the following raw materials: 110 parts of bisphenol A type epoxy resin, 35 parts of composite curing agent, 60 parts of modified red mud, 10 parts of polyacrylate, 18 parts of silica, 2 parts of boron carbide, 1 part of polybutylene acrylate, 1 part of polyamide wax, 3 parts of B55 matting agent, and 1 part of TiO2.

[0088] The modified red mud described herein is the same as the modified red mud in Example 1, and is also prepared using the method of Example 1 disclosed in the Chinese invention patent "Modified Red Mud for Coatings and its Preparation Method (Patent No.: ZL201910453010.3)" obtained by the applicant.

[0089] Example 6

[0090] A composite curing agent is prepared by mixing a modified imidazole curing agent made of methyl acrylate-modified 2-methylimidazole with triethylenetetramine at a mass ratio of 2:1.

[0091] The preparation method of the modified imidazole curing agent includes the following steps:

[0092] S1: Mix 2-methylimidazole with methyl acrylate, add toluene solvent and hydroquinone polymerization inhibitor, heat to 100°C, stir and reflux until the color darkens;

[0093] S2: Stop heating, cool to room temperature, then distill under reduced pressure to remove toluene solvent and excess methyl acrylate, and then cool to room temperature.

[0094] An application of a composite curing agent in the production of electrically insulating powder coatings comprises the following raw materials: 85 parts of bisphenol A type epoxy resin, 40 parts of composite curing agent, 80 parts of modified red mud, 10 parts of polyacrylate, 20 parts of silica, 3 parts of boron carbide, 1 part of ethyl polyacrylate, 2 parts of benzoin, 2 parts of B68 matting agent, and 2 parts of TiO2.

[0095] The modified red mud described herein is the same as the modified red mud in Example 1, and is also prepared using the method of Example 1 disclosed in the Chinese invention patent "Modified Red Mud for Coatings and its Preparation Method (Patent No.: ZL201910453010.3)" obtained by the applicant.

[0096] Comparative Example 1

[0097] It is basically the same as Example 3, except that a composite curing agent was not used, but an equal amount of dicyandiamide curing agent was used.

[0098] Comparative Example 2

[0099] It is basically the same as Example 3, except that no modified imidazole is added to the composite curing agent.

[0100] Comparative Example 3

[0101] It is basically the same as Example 3, except that triethylenetetramine is not added to the composite curing agent.

[0102] Comparative Example 4

[0103] It is basically the same as Example 3, except that the imidazole in the composite curing agent was not modified.

[0104] 1. Coating performance test

[0105] The insulating powder coating products obtained in Examples 1-6 and Comparative Examples 1-4 were subjected to volume resistivity, breakdown strength, and impact resistance tests. The volume resistivity was tested according to the method of national standard GB / T1410-2006, the breakdown strength was tested according to the method of national standard GB / T6554-2003, and the impact resistance was tested according to the method of national standard GB / T1732-1993.

[0106]

[0107] As shown in Table 1:

[0108] (1) Examples 1-6, which used the composite curing agent of the present invention, all had a volume resistivity of 5.8 × 10⁻⁶. 15 The resistance to Ω·cm is above 78 kV / mm, the breakdown strength is above 78 kV / mm, and the impact resistance is above 57 kg / cm. These are all higher than those of Comparative Examples 1-4, which did not use the composite curing agent of this invention or did not fully use the components of the composite curing agent of this invention. Moreover, the volume resistivity of Example 3 reached 6.4 × 10⁻⁶. 15 The breakdown strength reached 88 kV / mm and the impact resistance reached 67 kg / cm, indicating that the modified imidazole and triethylenetetramine in the composite curing agent of this invention have a synergistic effect, which jointly improves the performance of the coating.

[0109] (2) In Comparative Example 4, all experimental data were lower than those in Examples 1-6 of the present invention, indicating that the modification of 2-methylimidazole in the present invention can improve the performance of the coating.

[0110] This is because:

[0111] The curing agent of this invention is prepared by using a modified imidazole curing agent and triethylenetetramine. After modification with methyl acrylate, the nitrogen atom on the imidazole ring of the 2-methylimidazole has good reactivity and can react with the double bond in methyl acrylate that has an adjacent electron-withdrawing group, thereby improving the reactivity and stability of imidazole and enhancing the curing performance of the imidazole curing agent. Triethylenetetramine can undergo an addition reaction with the epoxy groups of epoxy resin, improving the curing performance, while imidazole can catalyze the ring-opening polymerization reaction of the epoxy groups in the resin, promoting the reaction process of triethylenetetramine. At the same time, imidazole can also catalyze the polymerization reaction between triethylenetetramine and epoxy resin, acting as an accelerator. The two react synergistically to jointly improve the performance of the coating.

[0112] 2. Insulation performance testing of spray paint

[0113] The electrical insulating powder coating prepared in Example 3 was subjected to spray painting insulation performance testing, and the results are as follows: Figure 2 As shown.

[0114] from Figure 2 As can be seen from the above, the electrical insulating powder coating prepared in Example 3 of the present invention has a leakage current of <0.1mA, which meets the relevant standards, indicating that the electrical insulating powder coating of the present invention has good insulation performance.

[0115] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. The application of a composite curing agent in the production of electrically insulating powder coatings, characterized in that, The product comprises the following raw materials: 80-120 parts epoxy resin, 20-40 parts composite curing agent, 60-90 parts modified red mud, 8-10 parts polyacrylate, 5-20 parts silica, 1-3 parts thermal conductive agent, 1-4 parts leveling agent, 1-2 parts degassing agent, 2-4 parts matting agent, and 0.6-2 parts dispersant; the composite curing agent is prepared by mixing modified imidazole curing agent and triethylenetetramine at a mass ratio of 1.2-2.5:0.8-1.4; the modified imidazole curing agent is made by modifying 2-methylimidazolium with methyl acrylate; the preparation method of the modified imidazole curing agent includes the following steps: S1: Mix 2-methylimidazole with methyl acrylate, add toluene solvent and hydroquinone polymerization inhibitor, heat to 90-100℃, stir and reflux until the color darkens; S2: Stop heating, cool to room temperature, then distill under reduced pressure to remove the solvent and excess methyl acrylate, and then cool to room temperature. The method for preparing the modified red mud includes the following steps: (1) The red mud waste generated during the alumina production process is washed away by water washing to remove water-soluble substances such as Na2O. After the pH value of the washed red mud is tested to be 8.9, it is filtered to obtain clean red mud. The clean red mud is then dried to a moisture content of 5%. (2) The clean red mud obtained in step (1) is subjected to ultrafine grinding and sieved to obtain clean red mud powder with a mesh size greater than 300. (3) Add modifier I to the clean red mud powder obtained in step (2). Modifier I is composed of diethanolamide stearate monoester and sodium ethylene-bis(N-ethanesulfonic acid-dodecanoate). The amount of modifier I added is 4.2% of the mass of the clean red mud powder. The mass ratio of diethanolamide stearate monoester and sodium ethylene-bis(N-ethanesulfonic acid-dodecanoate) is 9.2:5.

8. The temperature is controlled at 56-60℃ and stirred at 1000r / min for 26min to obtain mixture I. (4) Add the mixture I obtained in step (3) and the modifier II to a mixer. The modifier II is composed of aminopyramidized dimethylsiloxane, hexabromocyclotriphosphazene, and N-propyl-perfluorooctylsulfonylglutamate sodium. The amount of modifier II added is 2% of the mass of the clean red mud powder. The mass ratio of aminopyramidized dimethylsiloxane, hexabromocyclotriphosphazene, and N-propyl-perfluorooctylsulfonylglutamate sodium is 5.3:1.8:3.

5. The temperature is controlled at 80-84℃ and the mixture is stirred at 1200r / min for 40min to obtain mixture II. (5) The mixture II obtained in step (4) is dried at a temperature of 42-45℃ until the water content is 0.9%, then ultra-fine grinding is performed, and after sieving, modified red mud for coating with a mesh size greater than 300 is obtained.

2. The application of the composite curing agent according to claim 1 in the production of electrically insulating powder coatings, characterized in that: The thermally conductive agent includes one or more of boron carbide and silicon nitride.

3. The application of the composite curing agent according to claim 1 in the production of electrically insulating powder coatings, characterized in that: The leveling agent includes one or more of ethyl polyacrylate, butyl polyacrylate, and lauryl polyacrylate.

4. The application of the composite curing agent according to claim 1 in the production of electrically insulating powder coatings, characterized in that: The degassing agent is one or more of benzoin, polyethylene wax, and polyamide wax.

5. The application of the composite curing agent according to claim 1 in the production of electrically insulating powder coatings, characterized in that: The matting agent is one or more of B68 matting agent and B55 matting agent.

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