Preparation method of cationic insulation electrophoretic paint

Abstract

The invention discloses a preparation method of a cationic insulation electrophoretic coating, and belongs to the technical field of special coatings. The preparation method comprises the following steps: S1, mixing inorganic siloxane and a first organic solvent, heating, dropwise adding a mixed solution of a functional acrylate monomer and an initiator, heating, carrying out a heat preservation reaction, adding an acidity neutralizer, emulsifying with deionized water, and removing the solvent to prepare the organic-inorganic hybrid cationic resin. S2, mixing the organic-inorganic hybrid cationic resin, polyhedral oligomeric silsesquioxane, carbon black, barium sulfate and deionized water, and grinding to obtain the color paste. S3, mixing and curing the color paste, a second organic solvent and deionized water to prepare the cationic insulation electrophoretic coating. A coating formed by the coating prepared by the method has excellent insulativity, heat resistance and long-acting corrosion resistance and has basic mechanical properties such as good adhesive force and impact resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of special coatings, in particular to a preparation method of a cationic insulating electrophoretic coating. BACKGROUND

[0002] Cathodic electrophoretic coating has been widely used in the coating of metal parts in the automobile, household appliance, hardware and other industries due to its excellent corrosion resistance, high coating efficiency and good coverage of complex workpieces. Among them, the cationic electrophoretic coating with insulation function plays a key role in components that require electrical insulation protection, such as motors and motor cabinets. Its basic working principle is that the positively charged resin particles migrate and deposit towards the cathode (workpiece) under the action of a direct current electric field, and then the resin loses its ionicity and solidifies to form an insulating coating.

[0003] Although the cationic electrophoretic coating technology with insulation function is mature, there are still significant bottlenecks in applications that require higher performance, mainly in the following two core contradictions: Intrinsic heat resistance of the organic skeleton: Currently, the coating system is mainly based on pure acrylic resin or epoxy modified acrylic resin, which has limited glass transition temperature and thermal decomposition temperature. When the working temperature rises, the polymer chain segment movement intensifies, resulting in a significant decrease in the volume resistivity of the coating film and deterioration of the insulation performance. At the same time, the organic resin is more prone to thermal oxidation at high temperatures, affecting the long-term reliability of the coating.

[0004] Conflict between high insulation and good adhesion: In order to improve the insulation, high-resistance inorganic fillers (such as silicon powder, mica powder, etc.) are usually introduced. However, in the electrophoretic system, a high proportion of inorganic fillers can easily cause sedimentation, destroying the stability of the bath, and more critically, it can severely damage the adhesion and flexibility of the coating to the metal substrate, affecting the mechanical properties of the final product.

[0005] Therefore, from the perspective of resin molecular design, it is of great technical significance and market application value to develop a new type of cathodic electrophoretic coating that can balance excellent electrophoretic deposition characteristics, high insulation, high heat resistance and good mechanical adhesion, in order to meet the stringent requirements of new energy vehicle motors, electrical cabinets, high temperature coils and other high performance fields for insulating coating. SUMMARY

[0006] Therefore, the present application provides a preparation method of a cationic insulating electrophoretic coating to overcome the problems of insufficient heat resistance of the resin skeleton, and the difficulty in balancing the insulation performance and comprehensive mechanical properties in the prior art.

[0007] In order to achieve the above purpose, the present application provides the following technical solutions: According to a first aspect of the present application, there is provided a method for preparing a cationic insulating electrocoating paint, comprising the following steps: S1, preparing an organic-inorganic hybrid cationic resin; S2, preparing a color paste according to the organic-inorganic hybrid cationic resin prepared in step S1; S3, mixing and aging the color paste prepared in step S2, a second organic solvent and deionized water to prepare a cationic insulating electrocoating paint.

[0008] Further, the organic-inorganic hybrid cationic resin prepared in step S1 is prepared by the following method: Under inert gas, the inorganic siloxane is mixed with the first organic solvent in proportion, and the system temperature is raised to 78-82℃; a mixed solution composed of functional acrylate monomers and an initiator is added dropwise, and the dropping is completed in 3h; after the dropping is completed, the system temperature is raised to 90℃, and the reaction is kept for 5h; then the system temperature is lowered to 60℃, and an acidity neutralizer is added; the temperature is kept unchanged, deionized water is added for phase inversion emulsification under high-speed dispersion, and finally the solvent is removed by distillation under reduced pressure to obtain the organic-inorganic hybrid cationic resin.

[0009] Further, the inorganic siloxane is added in an amount of 97-103 parts by weight, the first organic solvent is added in an amount of 195-205 parts by weight, the functional acrylate monomer is added in an amount of 62-78 parts by weight, the initiator is added in an amount of 2 parts by weight, the acidity neutralizer is added in an amount of 7-9 parts by weight, and the deionized water is added in an amount of 480-520 parts by weight.

[0010] Further, the inorganic siloxane is hydrogen polydimethylsiloxane (PDMS-H) with a hydrogen value of 1.5%; the first organic solvent is selected from at least one of hydrocarbon organic solvents, heterocyclic organic solvents, amide organic solvents, alcohol organic solvents, alcohol ether organic solvents and ketone organic solvents; the functional acrylate monomer is selected from at least one of acrylate monomers containing epoxy groups, tertiary amine groups and hydroxyl groups; the initiator is selected from at least one of azobisisobutyronitrile (AIBN), azobisisoheptyl nitrile (ABVN) and dimethyl azobis isobutyrate (MAIB); and the acidity neutralizer is selected from at least one of lactic acid, formic acid and glacial acetic acid.

[0011] Further, the functional acrylic monomer is an epoxy group-containing, tertiary amine group-containing and hydroxyl group-containing acrylic monomer, and the additive mass ratio among the three is (28-32):(23-27):(13-17), the epoxy group-containing acrylic monomer includes but is not limited to glycidyl methacrylate (GMA), the tertiary amine group-containing acrylic monomer includes but is not limited to dimethylaminoethyl methacrylate (DMAEMA), and the hydroxyl group-containing acrylic monomer includes but is not limited to hydroxyethyl acrylate (HEA).

[0012] Further, the heterocyclic organic solvent includes but is not limited to 1,4-dioxane; the amide organic solvent includes but is not limited to N,N-dimethylformamide (DMF) or N,N-diethylformamide (DEF); the alcohol organic solvent includes but is not limited to n-butanol (NBA), isooctanol (EHO), ethylene glycol (EG) or propylene glycol (PG); the alcohol ether organic solvent includes but is not limited to ethylene glycol ethyl ether (EE), ethylene glycol butyl ether (EB) or propylene glycol methyl ether (PM); and the ketone organic solvent includes but is not limited to methyl isobutyl ketone (MIBK), cyclohexanone (CYC) or acetylacetone (AcAc).

[0013] Further, the first organic solvent is selected from at least one of toluene, 1,4-dioxane, N,N-dimethylformamide (DMF), N,N-diethylformamide (DEF) and xylene.

[0014] Further, the colorant paste is prepared from the organic-inorganic hybrid cation resin prepared in step S1 in step S2, and the specific method is as follows: The organic-inorganic hybrid cation resin, the cage-like silsesquioxane, the carbon black, the barium sulfate and the deionized water are mixed in proportion and uniformly ground to a fineness of ≤15 μm by a sand mill to prepare the colorant paste.

[0015] Further, the additive amount of the organic-inorganic hybrid cation resin is 100 parts, the additive amount of the cage-like silsesquioxane is 15 parts, the additive amount of the carbon black is 5 parts, the additive amount of the barium sulfate is 29-31 parts, and the additive amount of the deionized water is 96-106 parts by weight.

[0016] Further, the cage-like silsesquioxane (POSS) is selected from at least one of an aminated cage-like silsesquioxane (AM-POSS) and an epoxy group-containing cage-like silsesquioxane (Epoxy-POSS).

[0017] Further, the cage-like silsesquioxane is an aminated cage-like silsesquioxane (AM-POSS) with an amino value of 0.8 mmol / g.

[0018] Further, the mass ratio of the color paste, the second organic solvent and the deionized water in step S3 is 250: (7-11): (200-225), and the second organic solvent is at least one selected from ethylene glycol butyl ether (EGBE), diethylene glycol monobutyl ether (DEGBE), propylene glycol methyl ether (PGME) and dipropylene glycol dimethyl ether (DMMP).

[0019] According to a second aspect of the present application, the cationic insulating electrophoretic paint prepared by the preparation method is provided.

[0020] Further, the process parameters for using the cationic insulating electrophoretic paint are as follows: The bath parameters are as follows: the pH value is 5.4-6.4; the conductivity is 800-1600 μS·cm -1 , and the solid content is 18%; The electrophoretic coating process parameters are as follows: the voltage is 50-300 V, the temperature is 25-30℃, and the time is 2 min (30 s soft start); The baking and curing parameters are as follows: the temperature is 150-210℃, and the time is 20-30 min.

[0021] Compared with the prior art, the present application has the following advantages: The present application is based on the innovation of organic-inorganic hybridization and nano-crosslinking structure, and a cationic insulating electrophoretic paint system is developed. Through molecular design, the system realizes the cathode electrophoretic process performance while having excellent heat resistance, high insulation, excellent adhesion and excellent mechanical properties. The fundamental principle is to construct a main chain of inorganic siloxane (such as PDMS-H, etc.) at the molecular scale and introduce cage-like silsesquioxane (POSS) as a nano-enhancing and crosslinking node, so as to realize the synergistic effect of organic and inorganic phases through chemical bonding. The specific mechanism is as follows: (1) Construction of linear siloxane-acrylic hybrid main chain: The hybrid resin has a linear polysiloxane (-Si-O-Si-) main chain and side chain branched acrylic polymer segments. The polysiloxane main chain provides intrinsic high heat resistance, chain flexibility and excellent dielectric properties. The acrylic side chain has multiple functions: part of the monomers containing tertiary amine groups (such as DMAEMA, etc.) are introduced, and stable cationic centers are formed after neutralization by acidity neutralizer, ensuring the water dispersibility and electrophoretic deposition ability of the resin; another part of the monomers containing hydroxyl groups (such as HEA, etc.) or epoxy groups (such as GMA, etc.) are introduced as active sites for subsequent crosslinking. This structure is complex at the molecular level, overcoming the interface defects of physical blending, and realizing the unity of the intrinsic heat resistance of inorganic phase and the processability and adhesion of organic phase.

[0022] (2) Introduction of cage-like silsesquioxane (POSS) as a nano-crosslinking center: The cage-like silsesquioxane (POSS) with surface modified with reactive groups (such as amino, epoxy) is introduced into the system. Its rigid inorganic siloxane cage ( (SiO 1.5 )8) with a size of 1-3 nm as a nano-enhanced point can effectively limit the thermal motion of polymer segments, greatly improving the thermal decomposition temperature and high-temperature dimensional stability of the coating. More importantly, the reactive groups on the surface of POSS chemically react with the active sites on the hybrid resin during curing to form a three-dimensional nano-crosslinked network with POSS as the node. This structure effectively suppresses the movement of polymer segments at high temperatures, maintaining the dense structure of the coating, thereby significantly improving the volume resistivity and insulation durability of the coating in a high-temperature environment.

[0023] (3) Synergistically ensure process and mechanical properties: Through synergistic effect, good construction process and comprehensive mechanical properties are ensured. The grafted acrylic polymer segment and the organic groups on the periphery of POSS ensure good compatibility and adhesion of the resin to the metal substrate. The cationic properties of the side chain perfectly adapt to the existing cathodic electrophoretic coating process, depositing uniformly and stabilizing the bath. At the same time, the POSS nanoparticles are uniformly dispersed in the crosslinked network, acting as rigid reinforcing points to effectively improve the hardness and long-term corrosion resistance of the coating. Based on the improvement of toughness by inorganic siloxane (such as PDMS-H, etc.), good impact resistance is maintained, avoiding the brittleness problem that may be caused by simply increasing the crosslinking density.

[0024] In summary, the present application, through the synergistic design of "hybrid main chain" and "nano-crosslinking center", constructs a high-performance insulating coating system with a dense structure and balanced performance from the molecular level. DETAILED DESCRIPTION

[0025] The embodiments of the present application will be described in detail by the following specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosure. Obviously, the described embodiments are part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0026] According to a first aspect of the present application, a preparation method of a cationic insulating electrophoretic paint is provided, comprising the following steps: S1, preparing an organic-inorganic hybrid cationic resin; S2, preparing a color paste according to the organic-inorganic hybrid cationic resin prepared in step S1; S3, mixing and aging the color paste prepared in step S2, a second organic solvent and deionized water to prepare a cationic insulating electrophoretic paint.

[0027] Further, the organic-inorganic hybrid cation resin is prepared in step S1, and the specific method is as follows: The inorganic siloxane and the first organic solvent are mixed in proportion under inert gas, the temperature of the system is raised to 78-82°C, a mixed solution composed of the functional acrylate monomer and the initiator is added dropwise, and the dropping is completed in 3h; after the dropping is completed, the temperature of the system is raised to 90°C, and the reaction is kept for 5h; then the temperature of the system is reduced to 60°C, and the acidity neutralizer is added; the temperature is kept unchanged, deionized water is added for phase inversion emulsification under high-speed dispersion, and finally the solvent is removed by distillation under reduced pressure to obtain the organic-inorganic hybrid cation resin.

[0028] Further, the addition amount of the inorganic siloxane is 97-103 parts by weight, the addition amount of the first organic solvent is 195-205 parts by weight, the addition amount of the functional acrylate monomer is 62-78 parts by weight, the addition amount of the initiator is 2 parts by weight, the addition amount of the acidity neutralizer is 7-9 parts by weight, and the addition amount of the deionized water is 480-520 parts by weight.

[0029] Further, the inorganic siloxane is hydrogen polydimethylsiloxane (PDMS-H), and the hydrogen value is 1.5%; the first organic solvent is at least one selected from the group consisting of hydrocarbon organic solvents, heterocyclic organic solvents, amide organic solvents, alcohol organic solvents, alcohol ether organic solvents and ketone organic solvents; the functional acrylate monomer is at least one selected from the group consisting of acrylate monomers containing epoxy groups, tertiary amine groups and hydroxyl groups; the initiator is at least one selected from the group consisting of azobisisobutyronitrile (AIBN), azobisisoheptyl nitrile (ABVN) and dimethyl azobis isobutyrate (MAIB); and the acidity neutralizer is at least one selected from the group consisting of lactic acid, formic acid and glacial acetic acid.

[0030] Further, the functional acrylate monomer is the acrylate monomer containing epoxy groups, tertiary amine groups and hydroxyl groups, and the addition mass ratio among the acrylate monomers containing epoxy groups, tertiary amine groups and hydroxyl groups is (28-32):(23-27):(13-17); the acrylate monomer containing epoxy groups includes but is not limited to glycidyl methacrylate (GMA), the acrylate monomer containing tertiary amine groups includes but is not limited to dimethylaminoethyl methacrylate (DMAEMA), and the acrylate monomer containing hydroxyl groups includes but is not limited to hydroxyethyl acrylate (HEA).

[0031] Further, the heterocyclic organic solvent includes but is not limited to 1,4-dioxane; the amide organic solvent includes but is not limited to N,N-dimethylformamide (DMF) or N,N-diethylformamide (DEF); the alcohol organic solvent includes but is not limited to n-butanol (NBA), isooctanol (EHO), ethylene glycol (EG) or propylene glycol (PG); the alcohol ether organic solvent includes but is not limited to ethylene glycol ethyl ether (EE), ethylene glycol butyl ether (EB) or propylene glycol methyl ether (PM); the ketone organic solvent includes but is not limited to methyl isobutyl ketone (MIBK), cyclohexanone (CYC) or acetylacetone (AcAc).

[0032] Further, the first organic solvent is selected from at least one of toluene, 1,4-dioxane, N,N-dimethylformamide (DMF), N,N-diethylformamide (DEF) and xylene.

[0033] Further, the color paste is prepared from the organic-inorganic hybrid cationic resin prepared in step S1 in step S2, and the specific method is as follows: The organic-inorganic hybrid cationic resin, the cage-like silsesquioxane, the carbon black, the barium sulfate and the deionized water are mixed uniformly in proportion, and are ground to a fineness of ≤15 μm by a sand mill to prepare the color paste.

[0034] Further, the addition amount of the organic-inorganic hybrid cationic resin is 100 parts by weight, the addition amount of the cage-like silsesquioxane is 15 parts, the addition amount of the carbon black is 5 parts, the addition amount of the barium sulfate is 29-31 parts, and the addition amount of the deionized water is 96-106 parts.

[0035] Further, the cage-like silsesquioxane (POSS) is selected from at least one of aminated cage-like silsesquioxane (AM-POSS) and epoxy-containing cage-like silsesquioxane (Epoxy-POSS).

[0036] Further, the cage-like silsesquioxane is aminated cage-like silsesquioxane (AM-POSS) with an amino value of 0.8 mmol / g.

[0037] Further, the addition mass ratio of the color paste, the second organic solvent and the deionized water in step S3 is 250: (7-11): (200-225), and the second organic solvent is selected from at least one of ethylene glycol butyl ether (EGBE), diethylene glycol monobutyl ether (DEGBE), propylene glycol methyl ether (PGME) and dipropylene glycol dimethyl ether (DMMP).

[0038] According to the second aspect of the present application, the cationic insulating electrophoretic paint prepared by the preparation method is provided.

[0039] Further, the process parameters for using the cationic insulating electrophoretic paint are as follows: The bath parameters are as follows: pH value is 5.4-6.4; conductivity is 800-1600 μS·cm -1 , solid content is 18%; The electrophoretic coating process parameters are as follows: voltage is 50-300 V, temperature is 25-30℃, time is 2 min (30 s soft start); The baking and curing parameters are as follows: temperature is 150-210℃, time is 20-30 min. Example 1

[0040] (1) Preparation of organic-inorganic hybrid cationic resin: Under inert gas, 97 g of PDMS-H (hydrogen value 1.5%) and 195 g of DMF were added to a reaction vessel, and the system temperature was raised to 80℃; a mixed solution composed of 28 g of GMA, 23 g of DMAEMA, 13 g of HEA and 2 g of MAIB was added dropwise, and the dropping was controlled for 3 h; after the dropping was completed, the temperature was raised to 90℃, and the reaction was continued for 5 h; then the system temperature was reduced to 60℃, and 7 g of lactic acid was added for neutralization of the tertiary amine group; the temperature was kept unchanged, and 480 g of deionized water was added for phase inversion emulsification under high-speed dispersion; finally, DMF and part of the deionized water were removed by distillation under reduced pressure, and an organic-inorganic hybrid cationic resin with a solid content of 35% was obtained.

[0041] (2) Preparation of color paste: 100 g of the organic-inorganic hybrid cationic resin prepared in step (1), 15 g of AM-POSS (amino value 0.8 mmol / g), 5 g of carbon black, 29 g of barium sulfate and 96 g of deionized water were mixed, and ground to a fineness of ≤15 μm with a sand mill to prepare a color paste.

[0042] (3) Preparation of cationic insulating electrophoretic coating: 250 g of the color paste prepared in step (2), 7 g of DEGBE and 200 g of deionized water were mixed to obtain a cationic insulating electrophoretic coating. Example 2

[0043] (1) Preparation of organic-inorganic hybrid cationic resin: Under inert gas, 100 g of PDMS-H (hydrogen value 1.5%) and 200 g of toluene were added into a reaction vessel, and the temperature of the system was raised to 80°C; a mixed solution composed of 30 g of GMA, 25 g of DMAEMA, 15 g of HEA and 2 g of AIBN was added dropwise thereinto, and the dropping was controlled to be completed in 3 h; after the dropping was completed, the temperature was continuously raised to 90°C, and the reaction was kept for 5 h; then the temperature of the system was lowered to 60°C, 8 g of glacial acetic acid was added for neutralizing the tertiary amine group; while keeping the temperature unchanged, 500 g of deionized water was added for phase inversion emulsification under high-speed dispersion, and finally toluene and part of the deionized water were removed by distillation under reduced pressure to obtain an organic-inorganic hybrid cation resin with a solid content of 35%.

[0044] (2) Preparation of color paste: The organic-inorganic hybrid cation resin prepared in step (1), 15 g of AM-POSS (amino value 0.8 mmol / g), 5 g of carbon black, 30 g of barium sulfate and 100 g of deionized water were mixed, and ground to a fineness of ≤15 μm by using a sand mill to prepare a color paste.

[0045] (3) Preparation of cationic insulating electrophoretic paint: The color paste prepared in step (2), 10 g of EGBE and 212 g of deionized water were mixed to obtain a cationic insulating electrophoretic paint. Example 3

[0046] (1) Preparation of organic-inorganic hybrid cation resin: Under inert gas, 103 g of PDMS-H (hydrogen value 1.5%) and 205 g of 1,4-dioxane were added into a reaction vessel, and the temperature of the system was raised to 80°C; a mixed solution composed of 32 g of GMA, 27 g of DMAEMA, 17 g of HEA and 2 g of ABVN was added dropwise thereinto, and the dropping was controlled to be completed in 3 h; after the dropping was completed, the temperature was continuously raised to 90°C, and the reaction was kept for 5 h; then the temperature of the system was lowered to 60°C, 9 g of formic acid was added for neutralizing the tertiary amine group; while keeping the temperature unchanged, 520 g of deionized water was added for phase inversion emulsification under high-speed dispersion, and finally 1,4-dioxane and part of the deionized water were removed by distillation under reduced pressure to obtain an organic-inorganic hybrid cation resin with a solid content of 35%.

[0047] (2) Preparation of color paste: The organic-inorganic hybrid cation resin prepared in step (1), 15 g of AM-POSS (amino value 0.8 mmol / g), 5 g of carbon black, 31 g of barium sulfate and 106 g of deionized water were mixed, and ground to a fineness of ≤15 μm by using a sand mill to prepare a color paste.

[0048] (3) Preparation of cationic insulating electrophoretic paint: Mix 250 g of the color paste prepared in step (2), 11 g of PGME, and 225 g of deionized water to obtain a cationic insulating electrophoretic paint.

[0049] Comparative Example 1 (1) Preparation of an organic-inorganic hybrid cationic resin: Under inert gas, 100 g of PDMS-H (hydrogen value 1.5%) and 200 g of toluene were added to a reaction vessel, and the temperature of the system was raised to 80°C; a mixed solution composed of 30 g of GMA, 25 g of DMAEMA, 15 g of HEA, and 2 g of AIBN was added dropwise thereto, and the dropping was controlled to be completed in 3 h; after the dropping was completed, the temperature was raised to 90°C, and the reaction was continued for 5 h; then the temperature of the system was lowered to 60°C, and 8 g of glacial acetic acid was added for neutralization of the tertiary amine groups; while maintaining the temperature, 500 g of deionized water was added for phase inversion emulsification under high-speed dispersion, and finally toluene and part of the deionized water were removed by distillation under reduced pressure to obtain an organic-inorganic hybrid cationic resin with a solid content of 35%.

[0050] (2) Preparation of a color paste: 100 g of the organic-inorganic hybrid cationic resin prepared in step (1), 5 g of carbon black, 30 g of barium sulfate, and 105 g of deionized water were mixed, and ground to a fineness of ≤15 μm by using a sand mill to prepare a color paste.

[0051] (3) Preparation of a cationic insulating electrophoretic paint: 240 g of the color paste prepared in step (2), 9.6 g of EGBE, and 203.5 g of deionized water were mixed to obtain a cationic insulating electrophoretic paint.

[0052] Comparative Example 2 (1) Preparation of an acrylic resin: Under inert gas, 30 g of GMA, 25 g of DMAEMA, 15 g of HEA, 200 g of toluene, and 2 g of AIBN were added to a reaction vessel, mixed uniformly, the temperature of the system was raised to 80°C, and the reaction was continued for 8 h; then the temperature of the system was lowered to 60°C, and 9 g of formic acid was added for neutralization of the tertiary amine groups; while maintaining the temperature, 500 g of deionized water was added for phase inversion emulsification under high-speed dispersion, and finally toluene and part of the deionized water were removed by distillation under reduced pressure to obtain an acrylic resin with a solid content of 35%.

[0053] (2) Preparation of a color paste: 100 g of the acrylic resin, 5 g of carbon black, 30 g of barium sulfate, and 105 g of deionized water were mixed, and ground to a fineness of ≤15 μm by using a sand mill to prepare a color paste.

[0054] (3) Preparation of a conventional insulating electrophoretic paint: The 240 g of color paste, 9.6 g of EGBE and 203.5 g of deionized water prepared in step (2) were mixed to obtain a conventional insulating electrophoretic coating.

[0055] Test Example: The coating performance tests were carried out on the cationic insulating coatings prepared in Examples 1-3 and Comparative Examples and the conventional insulating coating prepared in Comparative Example 2, and the specific test steps were as follows: Preparation of coating: the coating was transferred to an electrophoresis tank, the pH of the tank solution was controlled at 5.9, and the conductivity was 1200 μS·cm -1 , deionized water was added to adjust the solid content to 18%, and aging was carried out for 24 h. A phosphating treated cold rolled steel plate was used as the cathode, and electrophoresis was carried out at a voltage of 150 V and a temperature of 25℃ for 2 min according to the conventional method. After electrophoresis, the coating sample was obtained by baking at 180℃ for 30 min after washing with deionized water for 3 times. Ten parallel samples were set for each test group.

[0056] The specific test items were as follows: Film thickness test: refer to GB / T 13452.2-2008 "Paints and varnishes - Determination of film thickness"; Adhesion test: refer to GB / T 9286-2021 "Paints and varnishes - Cross-hatch adhesion test"; Impact resistance test: refer to GB / T 1732-2020 "Determination of impact resistance of paint films"; Hardness test: refer to GB / T 6739-2006 "Paints and varnishes - Determination of film hardness by pencil method"; Volume resistivity test: refer to GB / T 1410-2006 "Determination of volume and surface resistivity of solid insulating materials"; Dielectric strength test: refer to GB / T 1408.1-2016 "Insulating materials - Determination of electrical strength - Part 1: Test at power frequency"; Salt spray resistance test: refer to GB / T 1771-2007 "Paints and varnishes - Determination of resistance to neutral salt spray"; Thermal decomposition temperature test: thermogravimetric analysis (TGA) method was used, and the temperature corresponding to 5% weight loss (Td, 5%) was defined as the thermal decomposition temperature, and the specific method was as follows: under nitrogen atmosphere, the temperature was raised from room temperature to 600℃ at a rate of 10℃ / min, and the temperature (℃) corresponding to 5% weight loss of the sample was recorded; Continuous use temperature evaluation: The insulation stability of the coating under long-term high-temperature working conditions was evaluated by high-temperature accelerated aging test. The specific method is as follows: the coating sample was placed in an accelerated thermal aging environment at different constant high temperatures (120℃, 150℃, 180℃ and 200℃) for 2000h. After aging, the sample was cooled to room temperature and the volume resistivity was measured. According to the fact that the coating can still maintain the volume resistivity ≥ 1 × 10 11 Ω·cm after aging, the highest test temperature was determined as the upper limit of the temperature at which it can work stably for a long time.

[0057] The following table is the performance test results of the cationic insulating coating prepared in Examples 1-3 and Comparative Example 2 and the traditional insulating coating prepared in Comparative Example 2:

[0058] Note: The test results of adhesion, impact resistance, thermal decomposition temperature, volume resistivity (25℃ and 150℃), dielectric strength, and salt spray resistance are the average values of 10 parallel samples.

[0059] As can be seen from the above table, the cationic insulating electrophoretic coating of the present application (Examples 1-3) exhibits excellent and stable performance in each of the above key properties, significantly better than the traditional insulating coating (Comparative Example 2). At the same time, compared with the cationic insulating electrophoretic coating system only introducing PDMS-H (Comparative Example 1), the thermal decomposition temperature, volume resistivity (25℃ and 150℃), dielectric strength, salt spray resistance and continuous use temperature and other core properties are significantly improved. Specifically embodied in the following: (1) Electrical insulation performance: Room temperature volume resistivity: At 25℃, the volume resistivity of the coating formed by the cationic insulating electrophoretic coating in Examples 1-3 (3.8 × 10 15 Ω·cm) is about 81% higher than that of the cationic insulating electrophoretic coating containing only PDMS-H in Comparative Example 1 (2.1 × 10 15 Ω·cm), and about 192% higher than that of the traditional insulating coating in Comparative Example 2 (1.3 × 10 15 Ω·cm), indicating that the introduction of AM-POSS significantly enhances the room temperature insulation capacity of the coating.

[0060] High temperature volume resistivity: At 150℃, the volume resistivity of the coating formed by the cationic insulating electrophoretic coating in Examples 1-3 (2.1 × 10 12 Ω·cm) is nearly 45 times higher than that of the cationic insulating electrophoretic coating containing only PDMS-H in Comparative Example 1 (4.7 × 10 10 Ω·cm), and about 545% higher than that of the traditional insulating coating in Comparative Example 2 (3.3 × 10 8The Ω·cm is nearly 6400 times higher, indicating that AM-POSS can effectively maintain the insulation stability of the coating at high temperatures.

[0061] Dielectric strength: The dielectric strength of the coatings formed by the cationic insulating electrophoretic coatings in Examples 1-3 (42 MV·m) -1 Compared to the cationic insulating electrophoretic coating containing only PDMS-H in Comparative Example 1 (34 MV·m -1 The content is approximately 23.5% higher than that of traditional insulating coatings in Comparison Example 2 (29 MV·m). -1 The percentage is about 44.8% higher, indicating that the cationic insulating electrophoretic coating of the present invention has a significantly enhanced ability to resist high voltage breakdown.

[0062] (2) Thermal stability: Thermal decomposition temperature (Td, 5% weight loss): The thermal decomposition temperature of the coating formed by the cationic insulating electrophoretic coating in Examples 1-3 is as high as 415℃, which is significantly higher than that of the cationic insulating electrophoretic coating containing only PDMS-H in Comparative Example 1 (386℃) and the traditional insulating coating in Comparative Example 2 (318℃). This is mainly due to the excellent thermal stability of the AM-POSS inorganic cage structure.

[0063] Continuous operating temperature: According to the evaluation of the high temperature accelerated aging test, the upper limit of the safe operating temperature of the coating formed by the cationic insulating electrophoretic coating in Examples 1-3 (≤180℃) is much higher than that of the cationic insulating electrophoretic coating containing only PDMS-H in Comparative Example 1 (≤152℃) and the traditional insulating coating in Comparative Example 2 (≤125℃), thus expanding its application range in high temperature environments.

[0064] (3) Mechanical and protective properties: Adhesion: The cationic insulating electrophoretic coatings in Examples 1-3 and Comparative Example 1 all achieved the optimal grade 0 (no peeling), which is better than the grade 1 (slight peeling) of the traditional insulating coating. This shows that the introduction of PDMS-H is the key to improving the adhesion between the coating and the substrate.

[0065] Hardness: The hardness (2H) of the coating formed by the cationic insulating electrophoretic coating in Examples 1-3 is higher than that of the cationic insulating electrophoretic coating containing only PDMS-H in Comparative Example 1 (1H) and the conventional insulating coating in Comparative Example 2 (1H). This indicates that AM-POSS as a nano-reinforcing phase effectively improves the hardness of the coating.

[0066] Impact resistance: The impact resistance (50cm) of the cationic insulating electrophoretic coatings in Examples 1-3 is better than that of the cationic insulating electrophoretic coating containing only PDMS-H in Comparative Example 1 (40cm) and the conventional insulating coating in Comparative Example 2 (40cm), indicating that PDMS-H effectively improves the flexibility and impact resistance of the coating.

[0067] Salt spray resistance: The coatings formed by the cationic insulating electrophoretic coatings in Examples 1-3 have a salt spray resistance time of up to 1000h and minimal corrosion diffusion (<1.5mm), which is significantly better than the cationic insulating electrophoretic coating containing only PDMS-H in Comparative Example 1 (750h, <1.9mm) and the traditional insulating coating in Comparative Example 2 (560h, <2.2mm). This further confirms the synergistic effect of AM-POSS and PDMS-H, which makes the coating system form a denser and more stable coating structure, thereby greatly improving its long-term corrosion resistance.

[0068] In summary, the cationic insulating electrophoretic coating system developed in this invention, based on an organic-inorganic hybrid framework cationic resin (containing PDMS-H) and cage-like silsesquioxane (POSS), exhibits excellent comprehensive performance and is stable and reliable. This coating system demonstrates outstanding insulation and protective properties, particularly under harsh environments such as high temperature, high humidity, high pressure, and corrosive conditions. It is suitable for high-performance insulation protection in high-end electrical equipment, new energy vehicles, and other fields, and has broad application prospects.

[0069] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A process for the preparation of a cationic insulating electrocoat, characterized in that, The method comprises the following steps: S1, preparing an organic-inorganic hybrid cation resin; S2, preparing a color paste according to the organic-inorganic hybrid cation resin prepared in step S1; S3, mixing the color paste prepared in step S2, a second organic solvent and deionized water and aging to prepare a cationic insulating electrophoretic paint.

2. The method of preparing cationic insulating electrophoretic paint according to claim 1, characterized in that, The organic-inorganic hybrid cation resin is prepared in step S1, and the specific method is as follows: Under inert gas, the inorganic siloxane is mixed with the first organic solvent in proportion, and the system temperature is raised to 78-82℃; a mixed solution composed of functional acrylate monomers and an initiator is added dropwise, and the dropping is controlled to be completed in 3h; after the dropping is completed, the system temperature is raised to 90℃, and the reaction is kept for 5h; then the system temperature is lowered to 60℃, and an acidity neutralizer is added; the temperature is kept unchanged, deionized water is added for phase inversion emulsification under high-speed dispersion, and finally the solvent is removed by distillation under reduced pressure to obtain the organic-inorganic hybrid cation resin.

3. The method of preparing cationic insulating electrocoat according to claim 2, characterized in that, The addition amount of the inorganic siloxane is 97-103 parts by weight, the addition amount of the first organic solvent is 195-205 parts by weight, the addition amount of the functional acrylate monomer is 62-78 parts by weight, the addition amount of the initiator is 2 parts by weight, the addition amount of the acidity neutralizer is 7-9 parts by weight, and the addition amount of the deionized water is 480-520 parts by weight.

4. The method of preparing cationic insulating electrophoretic paint according to claim 3, characterized in that, The inorganic siloxane is hydrogen polydimethylsiloxane; the first organic solvent is selected from at least one of hydrocarbon organic solvents, heterocyclic organic solvents, amide organic solvents, alcohol organic solvents, alcohol ether organic solvents and ketone organic solvents; the functional acrylate monomer is selected from at least one of acrylate monomers containing epoxy groups, tertiary amine groups and hydroxyl groups; the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptyl nitrile and dimethyl azobis isobutyrate; and the acidity neutralizer is selected from at least one of lactic acid, formic acid and glacial acetic acid.

5. The method of preparing cationic insulating electrophoretic paint according to claim 4, characterized in that, The functional acrylate monomer is an acrylate monomer containing epoxy groups, tertiary amine groups and hydroxyl groups, and the addition mass ratio among the three is (28-32):(23-27):(13-17).

6. The method of preparing cationic insulating electrophoretic paint according to claim 1, characterized by, The color paste is prepared in step S2 according to the organic-inorganic hybrid cation resin prepared in step S1, and the specific method is as follows: The organic-inorganic hybrid cation resin, cage-type silsesquioxane, carbon black, barium sulfate and deionized water are mixed in proportion and uniformly ground to a fineness of ≤15μm with a sand mill to prepare the color paste.

7. The method of preparing cationic insulating electrophoretic paint according to claim 6, characterized in that, The addition amount of the organic-inorganic hybrid cation resin is 100 parts by weight, the addition amount of the cage-type silsesquioxane is 15 parts by weight, the addition amount of the carbon black is 5 parts by weight, the addition amount of the barium sulfate is 29-31 parts by weight, and the addition amount of the deionized water is 96-106 parts by weight.

8. The method of preparing cationic insulating electrophoretic paint according to claim 7, characterized by, The cage-type silsesquioxane is selected from at least one of aminated cage-type silsesquioxane and cage-type silsesquioxane containing epoxy groups.

9. The method of preparing cationic insulating electrophoretic paint according to claim 8, characterized in that, The color paste, the second organic solvent and the deionized water in step S3 are added in a mass ratio of 250:(7-11):(200-225), and the second organic solvent is at least one selected from ethylene glycol butyl ether, diethylene glycol monobutyl ether, propylene glycol methyl ether and dipropylene glycol dimethyl ether.

10. Cationic, electrophoretic paint prepared according to the process of any one of claims 1 to 9.

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