Capacitor aluminum alloy shell protective coating and preparation method thereof

Abstract

The invention discloses a capacitor aluminum alloy shell protective coating and a preparation method thereof, and belongs to the technical field of coating preparation. The modified epoxy resin is prepared by modifying the epoxy resin through two compounded ultraviolet absorbents, the ultraviolet absorbents are chemically bonded with the epoxy resin, migration resistance is achieved, the anti-ultraviolet and anti-aging performance of a coating is remarkably improved, degradation of the resin is delayed, and the ultraviolet absorbents and the organic silicon modified FEVE tetrafluoro resin have a synergistic effect, so that the anti-ultraviolet and anti-aging performance of the coating is improved, and the anti-ultraviolet and anti-aging performance of the coating is improved. According to the present invention, the coating has characteristics of high weather resistance, high chemical stability and further environmental erosion resistance, the antioxidant modifies the alkyd resin, the chemical bonding effect provides the significant oxidation resistance, the added nanometer anti-rust agent fills the coating microdefects, and the coating defects can be significantly reduced under the interaction with the leveling agent, the defoaming agent and the dispersant, such that the coating quality can be improved; and the service life of the capacitor shell in the outdoor or strong light environment can be prolonged comprehensively.

Description

Technical Field

[0001] The present invention relates to the field of coating preparation, and more particularly, to a protective coating for an aluminum alloy shell of a capacitor and a preparation method thereof. Background Art

[0002] Aluminum alloy is a common alloy material with advantages such as high specific strength, low density, good processing performance, and heat-treatable strengthening, and has good application prospects, such as being used for preparing the shell of a capacitor. However, its low corrosion resistance limits its further development and application. An anti-corrosion and rust-proof coating refers to a coating that can resist the erosion of the external environment and protect the aluminum alloy shell from corrosion and rust. It is usually applied to the surface of aluminum alloy and has characteristics such as weather resistance and chemical corrosion resistance. For example, the raw material components of a coating for a capacitor aluminum shell film disclosed in the Chinese patent application No. CN200810061993.8 are, by weight percentage: 48-56% of polyurethane polyol, 38.6-47% of mixed solvent, 2.7-3.5% of surface lubricant, 0.28-0.34% of leveling agent, 0.18-0.24% of defoaming agent, and 1.44-1.72% of adhesion promoter. The coating for the capacitor aluminum shell film and the coated capacitor aluminum shell prepared by the coating process provided by this invention have an elongation ability of the film layer that allows the maximum aspect ratio of the capacitor shell to reach 3:1. After testing, the air temperature resistance performance of the film layer for 2 minutes is above 260°C. Another example is the Chinese patent application No. CN202210562909.0, which discloses a corrosion-resistant and high-temperature-resistant capacitor coating, which includes the following raw materials in parts by weight: 35-40 parts of organosilicon-modified fluororesin, 25-30 parts of polyamide resin, 8-12 parts of phenolic resin, 20-25 parts of polyvinyl acetate, and 1-3 parts of nano-zirconia; the raw materials of the organosilicon-modified fluororesin include a bis-silicon type silane coupling agent BSC, a boron carbide-organosilicon two-dimensional layered composite material, and a fluorine monomer. The capacitor coating provided by this invention is corrosion-resistant and high-temperature-resistant. Still another example is the Chinese patent No. CN201110329722.8, which discloses a coating for a capacitor aluminum shell film and a preparation method thereof. It mainly mixes and stirs composition A and composition B in the composition raw materials in certain parts by weight. Composition A is composed of polyamide resin, acetone, polymethyl methacrylate, and attapulgite; composition B is composed of phenolic resin, organosiloxane, silicone, and straw ash. It has a good curing effect on the capacitor aluminum shell, effectively protects the capacitor, and the prepared film coating has heat-resistant and wear-resistant properties, increasing the service life of the capacitor. However, in the actual application process of the existing protective coatings for aluminum alloy shells of capacitors, the mechanical properties, corrosion resistance, and aging resistance still need to be improved. Summary of the Invention

[0003] Based on this, in order to solve the problems of poor mechanical properties, corrosion resistance and aging resistance of the existing protective coatings for aluminum alloy casings of capacitors, the present invention provides a protective coating for aluminum alloy casings of capacitors and a preparation method thereof. The specific technical solutions are as follows:

[0004] A protective coating for an aluminum alloy casing of a capacitor, the protective coating for the aluminum alloy casing of the capacitor comprises the following preparation raw materials in parts by weight: 30 parts to 40 parts of organosilicon-modified FEVE tetrafluororesin, 20 parts to 25 parts of modified epoxy resin, 15 parts to 20 parts of modified alkyd resin, 3 parts to 7 parts of curing accelerator, 1 part to 7 parts of nano rust inhibitor, 0 parts to 20 parts of filler, 3 parts to 9 parts of adhesion promoter, 1 part to 5 parts of leveling agent, 1 part to 3 parts of defoaming agent and 1 part to 3 parts of dispersant;

[0005] Among them, the modified epoxy resin is an ultraviolet absorber-modified epoxy resin,

[0006] The modified alkyd resin is an antioxidant-modified alkyd resin.

[0007] Further, the preparation method of the ultraviolet absorber-modified epoxy resin is as follows:

[0008] Under a nitrogen atmosphere, an ultraviolet absorber is added to the epoxy resin, a catalyst is added, the temperature is raised to 100 °C to 130 °C, and the mixture is stirred and reacted at a rotation speed of 300 r / min to 800 r / min for 3 h to 5 h. Then the temperature is lowered to 80 °C to 90 °C, and then triethylenetetramine and benzyldimethylamine are added, and stirring is continued for 20 min to 40 min to obtain the ultraviolet absorber-modified epoxy resin.

[0009] Further, the ultraviolet absorber is obtained by mixing 2-hydroxy-4-(3-triethoxysilylpropoxy) benzophenone and 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole in a mass ratio of (1 to 5):(1 to 7).

[0010] Further, the weight part ratio of the ultraviolet absorber, epoxy resin, catalyst, triethylenetetramine and benzyldimethylamine is (1 to 5):100:(0.1 to 2):(0.1 to 2):(5 to 8).

[0011] Further, the catalyst is dibutyltin dilaurate.

[0012] Further, the preparation method of the antioxidant-modified alkyd resin is as follows: Add the antioxidant to a solvent, ultrasonically disperse for 10 min to 15 min, then slowly add it to the alkyd resin that has been pre-heated to 60°C to 80°C, and then add 3-allyl-cyclooctene and itaconic anhydride, heat to 150°C to 200°C, and stir at a speed of 500 r / min to 1000 r / min for 1 h to 2 h, and perform vacuum defoaming to obtain the antioxidant-modified alkyd resin.

[0013] Further, the antioxidant is obtained by mixing pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite in a mass ratio of (1 to 3):(1 to 7).

[0014] Further, the acid value of the alkyd resin is 50 mg KOH / g to 80 mg KOH / g.

[0015] Further, the weight part ratio of the antioxidant, solvent, alkyd resin, 3-allyl-cyclooctene, and itaconic anhydride is (1 to 3):(1 to 3):(20 to 30):(1 to 5):(1 to 2).

[0016] In addition, the present invention also provides a preparation method of a protective coating for a capacitor aluminum alloy housing, and the preparation method includes the following steps:

[0017] Add the organosilicon-modified FEVE tetrafluororesin, modified epoxy resin, and modified alkyd resin to a mixing kettle, heat to 50°C to 60°C and stir at a speed of 100 r / min to 500 r / min for 30 min to 60 min, then add an adhesion promoter, raise the temperature to 80°C to 100°C, and continue to stir for 1 h to 2 h to obtain mixture A;

[0018] Add a nano-rust inhibitor, filler, leveling agent, defoaming agent, and dispersant to the mixture A, stir at a speed of 1000 r / min to 2000 r / min for 30 min to 60 min to obtain mixture B; cool down to 40°C to 60°C, add a curing promoter, and stir at a speed of 200 r / min to 500 r / min for 10 min to 30 min, and perform vacuum defoaming to obtain the protective coating for the capacitor aluminum alloy housing.

[0019] Compared with the prior art, the present invention also has the following beneficial effects:

[0020] 1. By optimizing the composition of the protective coating for the capacitor aluminum alloy housing, the present invention adds a specific proportion of organosilicon-modified FEVE tetrafluororesin, modified epoxy resin, and modified alkyd resin. The components can crosslink with each other to form a three-dimensional network structure, balance flexibility and hardness, and improve impact resistance and wear resistance.

[0021] 2. The modified epoxy resin of the present invention is prepared by modifying epoxy resin with two ultraviolet absorbers through compounding. The ultraviolet absorbers bond with the epoxy resin through chemical bonding, are resistant to migration, significantly improve the anti-ultraviolet and anti-aging performance of the coating, delay the degradation of the resin, and synergistically act with the organosilicon-modified FEVE tetrafluororesin to endow high weather resistance and chemical stability, further resisting environmental erosion. At the same time, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (primary antioxidant) and tris[2,4-di-tert-butylphenyl] phosphite are used to modify alkyd resin, and through chemical bonding, the significant antioxidant performance of the antioxidant-modified alkyd resin is ensured, effectively blocking the oxidation chain reaction, preventing embrittlement due to high temperature or long-term use, and helping to extend the service life of the capacitor housing in outdoor or strong light environments.

[0022] 3. The present invention adds a nano-rust inhibitor to fill the microscopic defects of the coating, forming a dense barrier to block the penetration of water vapor and corrosive media. Under the interaction with a leveling agent, a defoaming agent, and a dispersing agent, it can significantly reduce coating defects, avoid phenomena such as orange peel and bubbles, and form a uniform and smooth coating, which comprehensively helps to extend the service life of the capacitor housing in outdoor or strong light environments. Detailed implementation manners

[0023] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with its embodiments. It should be understood that the specific implementation manners described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific implementation manners and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0025] A protective coating for an aluminum alloy housing of a capacitor in an embodiment of the present invention, the protective coating for the aluminum alloy housing of the capacitor comprises the following raw materials for preparation in parts by weight: 30 parts to 40 parts of organosilicon-modified FEVE tetrafluororesin, 20 parts to 25 parts of modified epoxy resin, 15 parts to 20 parts of modified alkyd resin, 3 parts to 7 parts of a curing accelerator, 1 part to 7 parts of a nano-rust inhibitor, 0 parts to 20 parts of a filler, 3 parts to 9 parts of an adhesion promoter, 1 part to 5 parts of a leveling agent, 1 part to 3 parts of a defoaming agent, and 1 part to 3 parts of a dispersing agent;

[0026] Among them, the modified epoxy resin is an ultraviolet absorber-modified epoxy resin,

[0027] The modified alkyd resin is an antioxidant-modified alkyd resin.

[0028] In one embodiment, the preparation method of the ultraviolet absorber-modified epoxy resin is as follows:

[0029] Under a nitrogen atmosphere, an ultraviolet absorber is added to the epoxy resin, a catalyst is added, the temperature is raised to 100 °C to 130 °C, and the mixture is stirred and reacted at a rotation speed of 300 r / min to 800 r / min for 3 h to 5 h. Then the temperature is lowered to 80 °C to 90 °C, and then triethylenetetramine and benzyldimethylamine are added, and stirring is continued for 20 min to 40 min to obtain the ultraviolet absorber-modified epoxy resin.

[0030] In one embodiment, the ultraviolet absorber is obtained by mixing 2-hydroxy-4-(3-triethoxysilylpropoxy) benzophenone and 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole in a mass ratio of (1 to 5):(1 to 7).

[0031] In one embodiment, the weight part ratio of the ultraviolet absorber, epoxy resin, catalyst, triethylenetetramine, and benzyldimethylamine is (1 to 5):100:(0.1 to 2):(0.1 to 2):(5 to 8).

[0032] In one embodiment, the catalyst is dibutyltin dilaurate.

[0033] In one embodiment, the preparation method of the antioxidant-modified alkyd resin is as follows: The antioxidant is added to a solvent and ultrasonically dispersed for 10 min to 15 min, and then slowly added to the alkyd resin that has been preheated to 60 °C to 80 °C. Then 3-allyl-cyclooctene and itaconic anhydride are added, and the mixture is heated to 150 °C to 200 °C and stirred at a rotation speed of 500 r / min to 1000 r / min for 1 h to 2 h, and then vacuum degassed to obtain the antioxidant-modified alkyd resin.

[0034] In one embodiment, the antioxidant is obtained by mixing pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite in a mass ratio of (1 to 3):(1 to 7).

[0035] In one embodiment, the acid value of the alkyd resin is 50 mg KOH / g to 80 mg KOH / g. Limiting the acid value of the alkyd resin can ensure that the alkyd resin has sufficient active carboxyl groups for grafting and guarantee the modification effect of the antioxidant.

[0036] In one embodiment, the solvent is one or two of xylene and n-butanol.

[0037] In one embodiment, the weight ratio of the antioxidant, the solvent, the alkyd resin, 3 - allyl - cyclooctene, and itaconic anhydride is (1 - 3):(1 - 3):(20 - 30):(1 - 5):(1 - 2).

[0038] In one embodiment, the curing accelerator is methyldiethanolamine.

[0039] In one embodiment, the nano - rust inhibitor is nano - zinc phosphate.

[0040] In one embodiment, the filler is at least one of attapulgite, diatomite, mica powder, barium sulfate, titanium dioxide, and talc powder.

[0041] In one embodiment, the adhesion promoter is KH - 550 silane coupling agent.

[0042] In one embodiment, the leveling agent is polyether - modified polyorganosiloxane.

[0043] In one embodiment, the defoaming agent is polydimethylsiloxane.

[0044] In one embodiment, the dispersant is polyacrylic acid or polymethacrylic acid.

[0045] In addition, the present invention also provides a preparation method of a protective coating for a capacitor aluminum alloy housing, and the preparation method includes the following steps:

[0046] Add the organosilicon - modified FEVE fluororesin, the modified epoxy resin, and the modified alkyd resin into a mixing kettle, heat to 50°C - 60°C, and stir at a speed of 100 r / min - 500 r / min for 30 min - 60 min, then add the adhesion promoter, raise the temperature to 80°C - 100°C, and continue to stir for 1 h - 2 h to obtain mixture A;

[0047] Add the nano - rust inhibitor, the filler, the leveling agent, the defoaming agent, and the dispersant into the mixture A, and stir at a speed of 1000 r / min - 2000 r / min for 30 min - 60 min to obtain mixture B;

[0048] Cool down to 40°C - 60°C, add the curing accelerator, stir at a speed of 200 r / min - 500 r / min for 10 min - 30 min, and perform vacuum degassing to obtain the protective coating for the capacitor aluminum alloy housing.

[0049] The coating prepared by the above - mentioned scheme has excellent mechanical properties, and has remarkable corrosion resistance and aging resistance. When applied to the surface of the capacitor housing, it has an excellent service life.

[0050] The implementation scheme of the present invention will be described in detail below in conjunction with specific embodiments.

[0051] Example 1:

[0052] A preparation method of a protective coating for an aluminum alloy shell of a capacitor includes the following steps:

[0053] According to the weight ratio, add an ultraviolet absorber obtained by mixing 4 parts of a mixture of 2-hydroxy-4-(3-triethoxysilylpropoxy) benzophenone and 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole with a mass ratio of 2:2 to 100 parts of epoxy resin, add 0.5 part of dibutyltin dilaurate, heat up to 120 °C, and stir and react at a speed of 300 r / min for 4 h. Cool down to 80 °C, then add 0.5 part of triethylenetetramine and 6 parts of benzyldimethylamine, and continue to stir for 25 min to obtain an ultraviolet absorber-modified epoxy resin;

[0054] According to the weight ratio, add an antioxidant obtained by mixing 2 parts of a mixture of pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and tris [2,4-di-tert-butylphenyl] phosphite with a mass ratio of 1:1 to 3 parts of n-butanol, ultrasonically disperse for 10 min, and then slowly add it to 25 parts of alkyd resin that has been preheated to 60 °C. Then add 3 parts of 3-allyl-cyclooctene and 1 part of itaconic anhydride, heat up to 150 °C, and stir at a speed of 500 r / min for 1 h, and perform vacuum defoaming to obtain an antioxidant-modified alkyd resin;

[0055] According to the weight ratio, add 35 parts of organosilicon-modified FEVE fluororesin, 20 parts of modified epoxy resin, and 15 parts of modified alkyd resin to a mixing kettle, heat up to 60 °C and stir at a speed of 200 r / min for 40 min, then add 5 parts of KH-550 silane coupling agent, heat up to 100 °C, and continue to stir for 2 h to obtain mixture A;

[0056] Add 5 parts of nanozinc phosphate, 15 parts of attapulgite, 3 parts of polyether-modified polyorganosiloxane, 2 parts of polydimethylsiloxane, and 2 parts of polymethacrylic acid to the mixture A, and stir at a speed of 1000 r / min for 40 min to obtain mixture B;

[0057] Cool down to 60 °C, add 5 parts of methyldiethanolamine, stir at a speed of 200 r / min for 25 min, and perform vacuum defoaming to obtain a protective coating for an aluminum alloy shell of a capacitor.

[0058] Example 2:

[0059] A preparation method of a protective coating for an aluminum alloy shell of a capacitor includes the following steps:

[0060] By weight ratio, an ultraviolet absorber obtained by mixing 4 parts of a mixture of 2-hydroxy-4-(3-triethoxysilylpropoxy) benzophenone and 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole with a mass ratio of 1:3 is added to 100 parts of epoxy resin. 0.6 part of dibutyltin dilaurate is added, the temperature is raised to 120 °C, and the mixture is stirred at a speed of 300 r / min for 4 h. Then the temperature is lowered to 80 °C, and 0.5 part of triethylenetetramine and 6 parts of benzyldimethylamine are added, and stirring is continued for 25 min to obtain an ultraviolet absorber-modified epoxy resin;

[0061] By weight ratio, an antioxidant obtained by mixing 2 parts of a mixture of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite with a mass ratio of 1:1 is added to 3 parts of n-butanol, ultrasonically dispersed for 10 min, and then slowly added to 30 parts of alkyd resin that has been preheated to 80 °C. Then 4 parts of 3-allyl-cyclooctene and 2 parts of itaconic anhydride are added, the temperature is raised to 150 °C, and the mixture is stirred at a speed of 500 r / min for 1 h, and then degassed under vacuum to obtain an antioxidant-modified alkyd resin;

[0062] By weight ratio, 37 parts of organosilicon-modified FEVE fluororesin, 23 parts of modified epoxy resin, and 17 parts of modified alkyd resin are added to a mixing kettle, heated to 60 °C and stirred at a speed of 300 r / min for 40 min. Then 7 parts of KH-550 silane coupling agent are added, the temperature is raised to 95 °C, and stirring is continued for 2 h to obtain mixture A;

[0063] 6 parts of nano-zinc phosphate, 12 parts of attapulgite, 3 parts of polyether-modified polyorganosiloxane, 3 parts of polydimethylsiloxane, and 2 parts of polymethacrylic acid are added to the mixture A, and the mixture is stirred at a speed of 1000 r / min for 40 min to obtain mixture B;

[0064] The temperature is lowered to 60 °C, 7 parts of methyldiethanolamine are added, and the mixture is stirred at a speed of 200 r / min for 30 min, and then degassed under vacuum to obtain a protective coating for the aluminum alloy shell of the capacitor.

[0065] Example 3:

[0066] A preparation method of a protective coating for the aluminum alloy shell of a capacitor, comprising the following steps:

[0067] According to the weight ratio, an ultraviolet absorber obtained by mixing 5 parts of 2-hydroxy-4-(3-triethoxysilylpropoxy) benzophenone with a mass ratio of 2:3 and 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole is added to 100 parts of epoxy resin. 0.8 part of dibutyltin dilaurate is added, the temperature is raised to 130 °C, and the mixture is stirred at a speed of 500 r / min for 5 h. Then the temperature is lowered to 80 °C, and then 0.5 part of triethylenetetramine and 5 parts of benzyldimethylamine are added, and stirring is continued for 30 min to obtain an ultraviolet absorber-modified epoxy resin;

[0068] According to the weight ratio, an antioxidant obtained by mixing 3 parts of pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] with a mass ratio of 1:2 and tris [2,4-di-tert-butylphenyl] phosphite is added to 3 parts of n-butanol, and ultrasonically dispersed for 15 min. Then it is slowly added to 30 parts of alkyd resin that has been preheated to 80 °C. Then 4 parts of 3-allyl-cyclooctene and 2 parts of itaconic anhydride are added, and the mixture is heated to 180 °C and stirred at a speed of 800 r / min for 2 h, and then vacuum degassed to obtain an antioxidant-modified alkyd resin;

[0069] According to the weight ratio, 38 parts of organosilicon-modified FEVE fluororesin, 25 parts of modified epoxy resin, and 18 parts of modified alkyd resin are added to a mixing kettle, heated to 60 °C and stirred at a speed of 500 r / min for 60 min. Then 9 parts of KH-550 silane coupling agent is added, the temperature is raised to 100 °C, and stirring is continued for 2 h to obtain mixture A;

[0070] 5 parts of nano-zinc phosphate, 15 parts of attapulgite, 4 parts of polyether-modified polyorganosiloxane, 3 parts of polydimethylsiloxane, and 2 parts of polymethacrylic acid are added to the mixture A, and stirred at a speed of 1000 r / min for 50 min to obtain mixture B;

[0071] The temperature is lowered to 60 °C, 5 parts of methyldiethanolamine is added, and stirring is carried out at a speed of 500 r / min for 30 min, and then vacuum degassed to obtain a protective coating for the capacitor aluminum alloy housing.

[0072] Comparative Example 1:

[0073] Compared with Example 3, in Comparative Example 1, organosilicon-modified FEVE fluororesin was not added, and the others were the same as in Example 3.

[0074] Comparative Example 2:

[0075] Compared with Example 3, in Comparative Example 2, modified epoxy resin was not added, and the others were the same as in Example 3.

[0076] Comparative Example 3:

[0077] Comparative Example 3 is compared with Example 3. In Comparative Example 3, the modified alkyd resin is not added, and the others are the same as those in Example 3.

[0078] Comparative Example 4:

[0079] Comparative Example 4 is compared with Example 3. In Comparative Example 4, the epoxy resin is not modified with an ultraviolet absorber, and the others are the same as those in Example 3.

[0080] Comparative Example 5:

[0081] Comparative Example 5 is compared with Example 3. In Comparative Example 5, a single 2-hydroxy-4-(3-triethoxysilylpropoxy) benzophenone (ultraviolet absorber) is added to modify the epoxy resin, and the others are the same as those in Example 3.

[0082] Comparative Example 6:

[0083] Comparative Example 6 is compared with Example 3. In Comparative Example 6, the alkyd resin is not modified, and the others are the same as those in Example 3.

[0084] Comparative Example 7:

[0085] Comparative Example 7 is compared with Example 3. In Comparative Example 7, a single tris[2,4-di-tert-butylphenyl] phosphite (antioxidant) is added, and the others are the same as those in Example 3.

[0086] Comparative Example 8:

[0087] Comparative Example 8 is compared with Example 3. In Comparative Example 8, the ultraviolet absorber and antioxidant are directly added and used, and the others are the same as those in Example 3. The preparation method of Comparative Example 8 is as follows:

[0088] A preparation method of a protective coating for an aluminum alloy housing of a capacitor includes the following steps:

[0089] By weight ratio, add 2 parts of 2-hydroxy-4-(3-triethoxysilylpropoxy) benzophenone, 3 parts of 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 1 part of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2 parts of tris[2,4-di-tert-butylphenyl] phosphite, 38 parts of organosilicon-modified FEVE fluororesin, 25 parts of epoxy resin, and 18 parts of alkyd resin into a mixing kettle, heat to 60 °C and stir at a speed of 500 r / min for 60 min, then add 9 parts of KH-550 silane coupling agent, raise the temperature to 100 °C, and continue to stir for 2 h to obtain mixture A;

[0090] Add 5 parts of nano-zinc phosphate, 15 parts of attapulgite, 4 parts of polyether-modified polyorganosiloxane, 3 parts of polydimethylsiloxane, and 2 parts of polymethacrylic acid to the mixture A, and stir at a speed of 1000 r / min for 50 min to obtain mixture B;

[0091] Cool down to 60 °C, add 5 parts of methyldiethanolamine, stir at a speed of 500 r / min for 30 min, and perform vacuum degassing to obtain the protective coating for the aluminum alloy shell of the capacitor.

[0092] Coat the protective coatings for the aluminum alloy shell of the capacitor prepared in Examples 1 to 3 and the protective coatings for the aluminum alloy shell of the capacitor prepared in Comparative Examples 1 to 8 on the surface of the aluminum plate respectively. After curing, test the performance of the formed coatings.

[0093] Among them, for the mechanical property test: Adhesion: Test according to "GB5210-85 Determination Method for Film Adhesion (Pull-off Method)"; Impact resistance: Test according to "GB / T1732-93 Determination Method for Film Impact Resistance", and record the impact resistance at normal temperature and when heated (40 °C); Abrasion resistance: Test according to "GB / T1768-89 Determination Method for Film Abrasion Resistance", with a load of 500 g and a polishing rotation speed of 500 r; For the weather resistance test: Age in an ultraviolet aging chamber for 7 d, measure the gloss of the coating before and after ultraviolet aging with a WGG-60E4 glossmeter, and record the light retention rate (%), and the ultraviolet aging chamber uses a straight-tube high-pressure mercury lamp GGZ-500 as the ultraviolet light source, with an ultraviolet light intensity of 20 w / m 2 , and the test temperature is 60 °C; For the anti-corrosion property test: Use the acidified brine immersion test to test the anti-corrosion property of the coating. Pre-make scratches on the surface of each group of samples. One test cycle is 24 h, including 18 h of immersion and 6 h of baking, and it is carried out continuously for 240 h. Environmental conditions: The solution is an acidic 5 wt% NaCl solution, pH = 3 - 4, T = 40 °C. When baking, dry the surface moisture of the specimen within 10 min, and the surface temperature of the specimen is below 60 °C. The results are shown in Table 1 below.

[0094] Table 1: Performance test results

[0095]

[0096]

[0097] From the data analysis in Table 1, it can be seen that in the present invention, by chemically bonding the ultraviolet absorber with epoxy resin, the migration resistance is improved, and the anti-ultraviolet and anti-aging performance of the coating is significantly enhanced, delaying the degradation of the resin. At the same time, it synergistically acts with the organosilicon-modified FEVE tetrafluororesin to endow high weather resistance and chemical stability, further resisting environmental erosion. Meanwhile, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (main antioxidant) and triphenyl phosphite modified alkyd resin are used to ensure the significant antioxidant performance of the antioxidant-modified alkyd resin through chemical bonding, effectively blocking the oxidation chain reaction and preventing embrittlement due to aging at high temperature or during long-term use. In summary, after optimizing the components and their ratios of the coating, a coating with excellent mechanical properties, corrosion resistance and weather resistance can be obtained as a whole, which plays a significant protective role for the capacitor housing.

[0098] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0099] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A protective coating for the aluminum alloy shell of a capacitor, characterized in that, The protective coating for the aluminum alloy housing of the capacitor comprises the following raw materials for preparation in parts by weight: 30 to 40 parts of organosilicon-modified FEVE tetrafluoro resin, 20 to 25 parts of modified epoxy resin, 15 to 20 parts of modified alkyd resin, 3 to 7 parts of curing accelerator, 1 to 7 parts of nano rust inhibitor, 0 to 20 parts of filler, 3 to 9 parts of adhesion promoter, 1 to 5 parts of leveling agent, 1 to 3 parts of defoaming agent, and 1 to 3 parts of dispersant; Among them, the modified epoxy resin is an ultraviolet absorber-modified epoxy resin, and the modified alkyd resin is an antioxidant-modified alkyd resin.

2. The protective coating for the aluminum alloy housing of the capacitor according to claim 1, characterized in that, The preparation method of the ultraviolet absorber-modified epoxy resin is as follows: Under a nitrogen atmosphere, an ultraviolet absorber is added to the epoxy resin, a catalyst is added, the temperature is raised to 100°C to 130°C, and the mixture is stirred and reacted at a rotation speed of 300 r / min to 800 r / min for 3 h to 5 h. Then the temperature is lowered to 80°C to 90°C, and then triethylenetetramine and benzyldimethylamine are added, and stirring is continued for 20 min to 40 min to obtain the ultraviolet absorber-modified epoxy resin.

3. The aluminum alloy housing protection coating for a capacitor according to claim 2, characterized in that, The ultraviolet absorber is obtained by mixing 2-hydroxy-4-(3-triethoxysilylpropoxy) benzophenone and 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole in a mass ratio of (1 to 5):(1 to 7).

4. The protective coating for the aluminum alloy housing of the capacitor according to claim 2, characterized in that, The weight part ratio of the ultraviolet absorber, epoxy resin, catalyst, triethylenetetramine, and benzyldimethylamine is (1 to 5):100:(0.1 to 2):(0.1 to 2):(5 to 8).

5. The protective coating for the aluminum alloy housing of the capacitor according to claim 4, wherein The catalyst is dibutyltin dilaurate.

6. The protective coating for the aluminum alloy shell of the capacitor according to claim 1, wherein The preparation method of the antioxidant-modified alkyd resin is as follows: The antioxidant is added to the solvent and ultrasonically dispersed for 10 min to 15 min, and then slowly added to the alkyd resin that has been preheated to 60°C to 80°C. Then 3-allyl-cyclooctene and itaconic anhydride are added, and the temperature is raised to 150°C to 200°C, and the mixture is stirred at a rotation speed of 500 r / min to 1000 r / min for 1 h to 2 h, and then vacuum degassed to obtain the antioxidant-modified alkyd resin.

7. The protective coating for the aluminum alloy housing of the capacitor according to claim 6, characterized in that, The antioxidant is obtained by mixing pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite in a mass ratio of (1 to 3):(1 to 7).

8. The protective coating for the aluminum alloy housing of the capacitor according to claim 6, characterized in that, The acid value of the alkyd resin is 50 mg KOH / g to 80 mg KOH / g.

9. The protective coating for the aluminum alloy shell of the capacitor according to claim 6, wherein The weight part ratio of the antioxidant, solvent, alkyd resin, 3-allyl-cyclooctene, and itaconic anhydride is (1 to 3):(1 to 3):(20 to 30):(1 to 5):(1 to 2).

10. A preparation method of a protective coating for an aluminum alloy shell of a capacitor, characterized in that, The preparation method is used to prepare the protective coating for the aluminum alloy housing of the capacitor as described in any one of claims 1 to 9, and the preparation method comprises the following steps: Add silicone-modified FEVE tetrafluoro resin, modified epoxy resin, and modified alkyd resin to a mixing kettle, heat to 50°C to 60°C and stir at a speed of 100 r / min to 500 r / min for 30 min to 60 min, then add an adhesion promoter, raise the temperature to 80°C to 100°C, and continue stirring for 1 h to 2 h to obtain mixture A; Add a nano-rust inhibitor, filler, leveling agent, defoaming agent, and dispersant to the mixture A, and stir at a speed of 1000 r / min to 2000 r / min for 30 min to 60 min to obtain mixture B; Cool down to 40°C to 60°C, add a curing promoter, stir at a speed of 200 r / min to 500 r / min for 10 min to 30 min, and perform vacuum degassing to obtain a protective coating for the aluminum alloy shell of the capacitor.

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