Boiling-resistant highlight black powder coating

Abstract

The invention discloses a boiling-resistant highlight black powder coating, and relates to the field of powder coatings. The boiling-resistant highlight black powder coating comprises the following raw materials in parts by weight: 30-45 parts of amide modified polyester resin; 25 to 35 parts of epoxy resin; 0.8 to 1.5 parts of a leveling agent; 0.3 to 0.6 part of a degassing agent; 0.8 to 1.2 parts of a brightening agent; 0.4 to 0.9 part of micro powder polyethylene wax; 1-2 parts of carbon black; 1-3 parts of a curing agent; 10-16 parts of stearic acid modified mica powder; and 10-16 parts of hollow glass beads. The boiling resistance and weather resistance of the thermosetting powder coating are improved, and the highlight black powder coating with good boiling resistance is prepared.

Description

Technical Field

[0001] This invention relates to the field of powder coatings, and in particular to a water-resistant high-gloss black powder coating. Background Technology

[0002] Powder coatings are solid powdered synthetic resin coatings composed of solid resins, pigments, fillers, and additives. The dispersion medium for powder coatings is air, so they have the characteristics of no solvent pollution, 100% film formation, and low energy consumption. They are widely used in industries such as pipeline industry, shipbuilding industry, automotive decoration, and coating of wood and plastics.

[0003] Powder coatings can be classified into thermoplastic powder coatings and thermosetting powder coatings. Compared to thermoplastic powder coatings, thermosetting powder coatings have superior leveling and gloss, and also exhibit better adhesion to polar substrates such as metals, resulting in better decorative properties. Thermosetting powder coatings use thermosetting synthetic resins as film-forming substances. During the drying process, the resin first melts and then undergoes chemical cross-linking to solidify into a smooth and hard coating film.

[0004] When traditional thermosetting powder coatings are used as decorative powder coatings, they are prone to various problems such as loss of gloss, coating bubbles, and large color differences when exposed to direct sunlight or rain for a long time. Therefore, it is necessary to improve the formulation of thermosetting powder coatings to enhance their resistance to boiling water and weathering. Summary of the Invention

[0005] In order to improve the water resistance and weather resistance of thermosetting powder coatings, this application provides a water-resistant high-gloss black powder coating.

[0006] The water-resistant, high-gloss black powder coating provided in this application adopts the following technical solution: A water-resistant, high-gloss black powder coating comprises the following raw materials in parts by weight: 30-45 parts of amide-modified polyester resin; 25-35 parts epoxy resin; Leveling agent 0.8-1.5 parts; Degassing agent 0.3-0.6 parts; Brightener 0.8-1.2 parts; 0.4-0.9 parts of micronized polyethylene wax; 1-2 parts carbon black; 1-3 parts of curing agent; 10-16 parts of stearic acid-modified mica powder; 10-16 parts of hollow glass microspheres.

[0007] By adopting the above technical solutions, the powder coating uses amide-modified polyester resin and epoxy resin as the main resins. The complementary nature of the resins improves the decorative and anti-corrosion properties of the epoxy-polyester powder coating. Under the action of the curing agent, the coating exhibits high crosslinking density and good water resistance. The amide-modified polyester resin reduces melt viscosity by introducing amide bonds, resulting in better flowability and smoothness of the powder coating. Simultaneously, the increased steric hindrance lowers surface energy, improving water resistance and enhancing wettability to fillers and substrates, leading to better adhesion. The addition of leveling agents, degassing agents, and brighteners improves the coating performance and high gloss of the powder coating. Carbon black is used as a pigment to obtain a black coating, and the addition of micro-powdered polyethylene wax enhances the hardening and abrasion resistance of the coating. Stearic acid-modified mica powder and hollow glass microspheres are selected as fillers, which, while maintaining good water resistance, further improve the coating's high-temperature resistance and weather resistance, and enhance its hardness and adhesion.

[0008] Optionally, the amide-modified polyester resin comprises the following raw materials in parts by weight: 3-3.5 parts of hexahydrophthalic anhydride; 1.8-2.3 parts of 4,4-diaminodiphenylmethane; 30-45 parts of neopentyl glycol; 55-60 parts of isophthalic acid; 4-9 parts of glycidyl neodecanoate; Catalyst 0.07-0.1 parts.

[0009] By adopting the above technical solution, a diacid with amide bonds is generated by reacting hexahydrophthalic anhydride and 4,4-diaminodiphenylmethane. This diacid then reacts with neopentyl glycol along with isophthalic acid, thereby introducing amide bonds into the polyester resin. This reduces the melt viscosity and improves the flowability of the powder coating during melt curing. The addition of glycidyl neodecanoate reacts with the diacid, and the ring-opening reaction of the epoxy and carboxyl groups results in a polyester with greater steric hindrance, further reducing the surface energy and improving the water resistance.

[0010] Optionally, the amide-modified polyester resin is prepared by the following steps: 4,4-Diaminodiphenylmethane and hexahydrophthalic anhydride were dissolved in acetone to obtain solution a and solution b, respectively. Solution a was slowly added dropwise to solution b over a period of 3.5-4 hours, with constant stirring and the precipitation of a white precipitate. The white precipitate was placed in a refrigerator at 5°C and cooled for 1-1.5 hours. The precipitate was then filtered to obtain a white solid, washed with acetone, filtered again, and dried to obtain a dicarboxylic acid containing an amide bond. Neopentyl glycol, glycidyl neodecanoate, and catalyst are added to a reactor and heated to 60-65°C to melt them. Isophthalic acid and the aforementioned amide-containing dicarboxylic acid are added, and the temperature is raised to 240-243°C to react. After the material becomes transparent, the acid value is tested. When the acid value is 43-47 mgKOH / g, vacuum polycondensation is performed. When the acid value is 31-38 mgKOH / g, the mixture is vented to atmospheric pressure. The temperature is lowered to 220°C, antioxidant 1010 and curing accelerator BETP are added, and the mixture is stirred for 15-30 minutes before being discharged.

[0011] By adopting the above technical solution, an amide-modified polyester resin with high acid value, low melt viscosity and good water boiling resistance was generated.

[0012] Optionally, the stearic acid-modified mica powder is prepared by the following steps: Mix mica powder with stearic acid at a mass fraction of 4-7% of the mica powder, stir for 5-10 minutes, then heat to 76-80℃ and stir for 20-25 minutes to obtain modified mica powder.

[0013] By adopting the above technical solution, mica powder possesses a fine, flaky crystalline structure. When added as a filler, it can improve the density of the powder coating, prevent moisture penetration, and further enhance its resistance to boiling water. Activation modification with stearic acid improves the dispersibility and compatibility of mica powder in the coating system, thereby enhancing the overall performance of the powder coating.

[0014] Optionally, the hollow glass microspheres are modified hollow glass microspheres, prepared through the following steps: Weigh out hollow glass microspheres and place them in 1 mol / L hydrochloric acid and stir for 24 hours. Filter the mixture and wash the hollow glass microspheres several times with deionized water. Dry the mixture in an oven at 110-120℃. Solution A is obtained by adding 5-7% (by mass) of nonafluorohexyltrimethoxysilane to ethanol. Solution B is obtained by weighing the dried hollow glass microspheres and placing them in pure water. Solution A and solution B are mixed and stirred for 24 hours. The modified hollow glass microspheres are then filtered out, washed, and dried.

[0015] By adopting the above technical solution, nonafluorohexyltrimethoxysilane is selected to modify hollow glass microspheres, thereby improving the hydrophobicity of hollow glass microspheres and enhancing their compatibility in the coating system. This results in better smoothness and adhesion of the coating, and the formation of a hydrophobic interface further improves the coating's resistance to boiling water.

[0016] Optionally, the epoxy resin is selected from bisphenol A type epoxy resin with an epoxy equivalent of 700-750 g / eq.

[0017] By adopting the above technical solution, the selected epoxy resin and amide-modified polyester resin have a higher crosslinking density, resulting in a denser and more water-resistant coating.

[0018] Optionally, the leveling agent is an acrylate leveling agent, and the degassing agent is one or more of benzoin and benzoin.

[0019] Optionally, the brightener may be one or more of QR701, R701B and PV88.

[0020] Optionally, the curing agent may be one or more of DDCM, THPA, TGIC and MNA.

[0021] Optionally, the powder coating is prepared by the following method: The raw materials are added to a high-speed mixer, dry-mixed, and then added to an extruder. The mixture is melted, kneaded, cooled, and pressed into sheets at an extrusion temperature of 80-110℃. The sheets are then crushed, graded, sieved, and packaged to obtain a water-resistant, high-gloss black powder coating.

[0022] By adopting the above technical solution, the epoxy polyester powder coating prepared in this application has good leveling properties, good water resistance and mechanical properties, and the cured coating has good decorative properties.

[0023] In summary, this application has the following beneficial effects: 1. The powder coating uses amide-modified polyester resin and epoxy resin as the main resins. The complementary nature of these resins enhances the decorative and anti-corrosion properties of the epoxy-polyester powder coating. Under the action of the curing agent, the coating exhibits high cross-linking density and good water resistance. The amide-modified polyester resin reduces melt viscosity by introducing amide bonds, resulting in better flowability and smoothness of the powder coating. Simultaneously, the increased steric hindrance lowers surface energy, improving water resistance and enhancing wettability to fillers, pigments, and substrates, leading to better adhesion. The addition of leveling agents, degassing agents, and brighteners improves the coating performance and high gloss. Carbon black is used as a pigment to obtain a black coating, and the addition of micro-powdered polyethylene wax enhances the coating's hardening and abrasion resistance. Stearic acid-modified mica powder and hollow glass microspheres are selected as fillers, which, while maintaining good water resistance, further improve the coating's high-temperature resistance and weather resistance, and enhance its hardness and adhesion.

[0024] 2. A diacid with amide bonds is generated by reacting hexahydrophthalic anhydride and 4,4-diaminodiphenylmethane. This diacid, along with isophthalic acid, reacts with neopentyl glycol, thereby introducing amide bonds into the polyester resin. This reduces the melt viscosity and improves the flowability of the powder coating during melt curing. The addition of glycidyl neodecanoate reacts with the diacid, and the ring-opening reaction of the epoxy and carboxyl groups results in a polyester with greater steric hindrance, further reducing the surface energy and improving the water resistance. Detailed Implementation

[0025] The present application will be further described in detail below with reference to Examples 1-5 and Comparative Example 1. Preparation Example

[0026] Preparation Example 1 An amide-modified polyester resin comprises the following raw materials: 3g of hexahydrophthalic anhydride was purchased from Shandong Yuxuan Chemical Products Co., Ltd., CAS No. 1314900-3; 1.8 g of 4,4-diaminodiphenylmethane was purchased from Jiangsu Bost Chemical Technology Co., Ltd., CAS No. 101-77-9; 30g of neopentyl glycol was purchased from Jinan Zhengkang Chemical Co., Ltd., CAS No. 126-30-7; 55g of isophthalic acid was purchased from Jinan Century Tongda Chemical Co., Ltd., under the brand Lotte (Korea), CAS number 121-91-5; 4g of glycidyl neodecanoate was purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd., CAS No. 26761-45-5; The catalyst is 0.07g, specifically monobutyltin catalyst PC4100.

[0027] Amide-modified polyester resin is prepared by the following steps: 4,4-Diaminodiphenylmethane was dissolved in 20 ml of acetone to obtain solution a, and hexahydrophthalic anhydride was dissolved in 50 ml of acetone to obtain solution b. Solution a was slowly added dropwise to solution b over a period of 3.5 h with constant stirring. The process was stopped when no more white precipitate formed in the mixture. The white precipitate was placed in a refrigerator at 5 °C and cooled for 1 h. After filtration, a white solid was obtained. The white solid was washed several times with acetone at 5 °C and filtered again. Finally, the white solid was placed in an oven at 70 °C and dried for 8 h to obtain a dicarboxylic acid containing an amide bond. Neopentyl glycol, glycidyl neodecanoate, and catalyst were added to a reactor and heated to 60°C. Toluenedicarboxylic acid and the aforementioned amide-containing dicarboxylic acid were then added to the reactor. The temperature was raised to 240°C for reaction. After the material became transparent, the acid value was tested. Vacuum polycondensation was performed when the acid value reached 43-47 mgKOH / g, and when it reached 31-38 mgKOH / g, the mixture was vented to atmospheric pressure. The temperature was lowered to 220°C, and antioxidant 1010 and curing accelerator BETP were added. The mixture was stirred for 15 minutes, and the amide-modified polyester resin was obtained by discharging the material.

[0028] Preparation Example 2 An amide-modified polyester resin comprises the following raw materials: 3.5g of hexahydrophthalic anhydride was purchased from Shandong Yuxuan Chemical Products Co., Ltd., CAS No. 13149-00-3; 2.3 g of 4,4-diaminodiphenylmethane was purchased from Jiangsu Bost Chemical Technology Co., Ltd., CAS No. 101-77-9; 45g of neopentyl glycol was purchased from Jinan Zhengkang Chemical Co., Ltd., CAS No. 126-30-7; 60g of isophthalic acid was purchased from Jinan Century Tongda Chemical Co., Ltd., under the brand Lotte (Korea), CAS number 121-91-5. 9g of glycidyl neodecanoate was purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd., CAS No. 26761-45-5; 0.1g of catalyst, specifically monobutyltin catalyst PC4100.

[0029] Amide-modified polyester resin is prepared by the following steps: 4,4-Diaminodiphenylmethane was dissolved in 30 ml of acetone to obtain solution a, and hexahydrophthalic anhydride was dissolved in 70 ml of acetone to obtain solution b. Solution a was slowly added dropwise to solution b over a period of 4 hours with constant stirring. The process was stopped when no more white precipitate formed in the mixture. The white precipitate was then cooled in a refrigerator at 5°C for 1.5 hours and filtered to obtain a white solid. The white solid was washed several times with acetone at 5°C and filtered again. Finally, the white solid was dried in an oven at 72°C for 8 hours to obtain a dicarboxylic acid containing an amide bond. Neopentyl glycol, glycidyl neodecanoate, and catalyst were added to a reactor and heated to 65°C. Toluenedicarboxylic acid and the aforementioned amide-containing dicarboxylic acid were then added to the reactor. The temperature was raised to 243°C for reaction. After the material became transparent, the acid value was tested. Vacuum polycondensation was performed when the acid value reached 43-47 mgKOH / g, and when it reached 31-38 mgKOH / g, the mixture was vented to atmospheric pressure. The temperature was lowered to 220°C, and antioxidant 1010 and curing accelerator BETP were added. The mixture was stirred for 30 minutes, and the amide-modified polyester resin was obtained by discharging the material.

[0030] Preparation Example 3 An amide-modified polyester resin comprises the following raw materials: 3.5g of hexahydrophthalic anhydride was purchased from Shandong Yuxuan Chemical Products Co., Ltd., CAS No. 13149-00-3; 2.3 g of 4,4-diaminodiphenylmethane was purchased from Jiangsu Bost Chemical Technology Co., Ltd., CAS No. 101-77-9; 45g of neopentyl glycol was purchased from Jinan Zhengkang Chemical Co., Ltd., CAS No. 126-30-7; 60g of isophthalic acid was purchased from Jinan Century Tongda Chemical Co., Ltd., under the brand Lotte (Korea), CAS number 121-91-5. 9g of glycidyl neodecanoate was purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd., CAS No. 26761-45-5; 0.1g of catalyst, specifically monobutyltin catalyst PC4100.

[0031] Amide-modified polyester resin is prepared by the following steps: 4,4-Diaminodiphenylmethane was dissolved in 30 ml of acetone to obtain solution a, and hexahydrophthalic anhydride was dissolved in 70 ml of acetone to obtain solution b. Solution a was slowly added dropwise to solution b over a period of 4 hours with constant stirring. The process was stopped when no more white precipitate formed in the mixture. The white precipitate was then cooled in a refrigerator at 5°C for 1.5 hours and filtered to obtain a white solid. The white solid was washed several times with acetone at 5°C and filtered again. Finally, the white solid was dried in an oven at 72°C for 8 hours to obtain a dicarboxylic acid containing an amide bond. Neopentyl glycol, glycidyl neodecanoate, and catalyst were added to a reactor and heated to 65°C. Toluenedicarboxylic acid and the aforementioned amide-containing dicarboxylic acid were then added to the reactor. The temperature was raised to 243°C for reaction. After the material became transparent, the acid value was tested. Vacuum polycondensation was performed when the acid value reached 43-47 mgKOH / g, and when it reached 31-38 mgKOH / g, the mixture was vented to atmospheric pressure. The temperature was lowered to 220°C, and antioxidant 1010 and curing accelerator BETP were added. The mixture was stirred for 30 minutes, and the amide-modified polyester resin was obtained by discharging the material.

[0032] Preparation Example 4 A modified hollow glass microsphere is prepared by the following steps: Weigh 10g of hollow glass microspheres and place them in 100ml of 1mol / L hydrochloric acid. Stir for 24h, filter, and wash several times with deionized water. Then place the hollow glass microspheres in an oven at 110℃ to dry. 0.5g of nonafluorohexyltrimethoxysilane was added to 30ml of ethanol to obtain solution A. 10g of cleaned hollow glass microspheres were weighed and placed in 50ml of pure water to obtain solution B. Solution A and solution B were mixed and stirred for 24h. The modified hollow glass microspheres were filtered out and washed with deionized water. After drying in an oven, the modified hollow glass microspheres were obtained.

[0033] Preparation Example 5 A modified hollow glass microsphere is prepared by the following steps: Weigh 16g of hollow glass microspheres and place them in 160ml of 1mol / L hydrochloric acid. Stir for 24h, filter and wash with deionized water several times. Then place the hollow glass microspheres in an oven at 120℃ to dry. 1.05g of nonafluorohexyltrimethoxysilane was added dropwise to 70ml of ethanol to obtain solution A. 15g of cleaned hollow glass microspheres were weighed and placed in 120ml of pure water to obtain solution B. Solution A and solution B were mixed and stirred for 24h. The modified hollow glass microspheres were filtered out and washed with deionized water. After drying in an oven, the modified hollow glass microspheres were obtained. Example

[0034] Example 1 A water-resistant, high-gloss black powder coating, comprising the following raw materials: 30g of amide-modified polyester resin, the amide-modified polyester resin prepared in Preparation Example 1 was selected; 25g of epoxy resin, bisphenol A type epoxy resin with an epoxy equivalent of 700g / eq, was purchased from Hubei Shiteng Chemical Co., Ltd. 0.8g of leveling agent, specifically acrylate leveling agent ASK-193, purchased from Greenlink (Jining) Chemical Technology Co., Ltd. Degassing agent 0.3g, benzoin is selected; Brightening agent 0.8g, using brightening agent QR701; 0.4g of micronized polyethylene wax; 1g of carbon black; 1g of curing agent, selected as DDCM (4,4'-diaminodicyclohexylmethane). 10g of stearic acid-modified mica powder 10g of hollow glass microspheres.

[0035] Stearic acid-modified mica powder is prepared through the following steps: Mix 10g of mica powder and 0.4g of stearic acid, stir for 5 minutes, heat to 76℃ and continue stirring for 20 minutes to obtain modified mica powder.

[0036] A method for preparing powder coatings includes the following steps: The above-mentioned raw materials are added to a high-speed mixer and dry-mixed for 5 minutes. Then, they are added to an extruder and melt-mixed and extruded at an extrusion temperature of 80-110℃. After passing through a cooling roller, the material is pressed into sheets. The cooled sheets are then crushed by a pulverizer. After coarse crushing and grinding, the material is sieved using a 180-mesh sieve. The sieved material is then naturally cooled and packaged to obtain a water-resistant high-gloss black powder coating.

[0037] Example 2 A water-resistant, high-gloss black powder coating, comprising the following raw materials: 45g of amide-modified polyester resin, the amide-modified polyester resin prepared in Preparation Example 2 was selected; 35g of epoxy resin, bisphenol A type epoxy resin with an epoxy equivalent of 750g / eq, was purchased from Hubei Shiteng Chemical Co., Ltd. 1.5g of leveling agent, specifically acrylate leveling agent SF-6356, purchased from Jining Fangyu Chemical Co., Ltd. Degassing agent 0.6g, benzoin selected; Brightening agent 1.2g, using brightening agent R701B; 0.9g of micronized polyethylene wax; 2g of carbon black; 3g of curing agent, using TGIC (triglycidyl isocyanate). 16g of stearic acid-modified mica powder 16g of hollow glass microspheres.

[0038] Stearic acid-modified mica powder is prepared through the following steps: Mix 16g of mica powder and 1.12g of stearic acid, stir for 10 minutes, heat to 80℃ and continue stirring for 25 minutes to obtain modified mica powder.

[0039] The preparation method of the powder coating is the same as that in Example 1.

[0040] Example 3 A water-resistant, high-gloss black powder coating, comprising the following raw materials: 38g of amide-modified polyester resin, selected from the amide-modified polyester resin prepared in Preparation Example 3; 29g of epoxy resin, bisphenol A type epoxy resin with an epoxy equivalent of 700g / eq, was purchased from Hubei Shiteng Chemical Co., Ltd. 1g of leveling agent, specifically acrylate leveling agent SF-6356, purchased from Jining Fangyu Chemical Co., Ltd.; Degassing agent 0.5g, benzoin is selected; 1g of brightener, 0.5g of brightener R701B and 0.5g of brightener PV88 are selected; 0.7g of micronized polyethylene wax; 1.5g of carbon black; 2g of curing agent, using 1g THPA (tetrahydrophthalic anhydride) and 1g MNA (methylnadic anhydride). 13g of stearic acid-modified mica powder 14g of hollow glass microspheres.

[0041] Stearic acid-modified mica powder is prepared through the following steps: Mix 13g of mica powder and 0.78g of stearic acid, stir for 8 minutes, heat to 80℃ and continue stirring for 20 minutes to obtain modified mica powder.

[0042] The preparation method of the powder coating is the same as that in Example 1.

[0043] Example 4 The difference between this embodiment and Embodiment 1 is that the hollow glass microspheres in the powder coating raw materials are different.

[0044] The hollow glass microspheres used in this embodiment are the modified hollow glass microspheres prepared in Preparation Example 4.

[0045] The other raw materials and preparation methods for powder coatings are the same as in Example 1.

[0046] Example 5 The difference between this embodiment and Embodiment 1 is that the hollow glass microspheres in the powder coating raw materials are different.

[0047] The hollow glass microspheres used in this embodiment are the modified hollow glass microspheres prepared in Preparation Example 5.

[0048] The other raw materials and preparation methods for powder coatings are the same as in Example 1. Comparative Example

[0049] Comparative Example 1 The difference between this comparative example and Example 1 is that the polyester resin in the powder coating raw materials is different.

[0050] In this comparative example, an equal amount of carboxyl-terminated polyester resin was used to replace the amide-modified polyester resin. The acid value of the carboxyl-terminated polyester resin was 35-40 mg KOH / g, and it was purchased from Huangshan Shenjian New Materials Co., Ltd.

[0051] The other raw materials and preparation methods for powder coatings are the same as in Example 1.

[0052] The following performance tests were conducted on the powder coatings prepared in Examples 1-5 and Comparative Example 1, and the test results are recorded in Table 1.

[0053] Preparation of powder coating: An electrostatic spraying process is used. Before coating, the substrate is cleaned with acetone, and then the powder coating is evenly sprayed onto the substrate surface using an electrostatic spray gun. After spraying, the substrate is quickly placed in an oven, which is pre-set to the temperature required for coating curing. After the sample has cured, it is removed and allowed to cool naturally to room temperature to obtain the coating.

[0054] Water resistance: Tested according to GB / T 1733-1993 "Determination of water resistance of paint film".

[0055] Adhesion (cross-cut test): The adhesion is determined according to the method of ISO 2409-2007 "Paints and varnishes - cross-cut test". The adhesion is classified into grades 0-4.

[0056] Impact resistance: Tested according to GB / T 1732-1993 "Test Method for Impact Resistance of Coating Film".

[0057] Table 1 Sample Water boiling resistance Adhesion Impact resistance Example 1 No air bubbles, ΔE = 0.8 Level 1 No damage from forward and reverse strikes Example 2 No air bubbles, ΔE = 0.7 Level 0-1 No damage from forward and reverse strikes Example 3 No air bubbles, ΔE = 1.0 Level 1 No damage from forward and reverse strikes Example 4 No air bubbles, ΔE = 0.5 Level 0 No damage from forward and reverse strikes Example 5 No air bubbles, ΔE = 0.4 Level 0 No damage from forward and reverse strikes Comparative Example 1 Slight bubbles, ΔE = 1.4 Level 2 No damage from forward and reverse strikes According to the data in Table 1, the powder coating prepared in this application by using amide-modified polyester resin and high epoxy value epoxy resin as the main resin, combined with stearic acid-modified mica powder and hollow glass microspheres as fillers, has good adhesion to the substrate, and good water resistance, impact resistance and weather resistance.

[0058] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A water-resistant, high-gloss black powder coating, characterized in that, Including the following parts by weight of raw materials: 30-45 parts of amide-modified polyester resin; 25-35 parts epoxy resin; Leveling agent 0.8-1.5 parts; Degassing agent 0.3-0.6 parts; Brightener 0.8-1.2 parts; 0.4-0.9 parts of micronized polyethylene wax; 1-2 parts carbon black; 1-3 parts of curing agent; 10-16 parts of stearic acid-modified mica powder; 10-16 parts of hollow glass microspheres.

2. The water-resistant high-gloss black powder coating according to claim 1, characterized in that: The amide-modified polyester resin comprises the following raw materials in parts by weight: 3-3.5 parts of hexahydrophthalic anhydride; 1.8-2.3 parts of 4,4-diaminodiphenylmethane; 30-45 parts of neopentyl glycol; 55-60 parts of isophthalic acid; 4-9 parts of glycidyl neodecanoate; Catalyst 0.07-0.1 parts.

3. The water-resistant high-gloss black powder coating according to claim 2, characterized in that: The amide-modified polyester resin is prepared by the following steps: 4,4-Diaminodiphenylmethane and hexahydrophthalic anhydride were dissolved in acetone to obtain solution a and solution b, respectively. Solution a was slowly added dropwise to solution b over a period of 3.5-4 hours, with constant stirring and the precipitation of a white precipitate. The white precipitate was placed in a refrigerator at 5°C and cooled for 1-1.5 hours. The precipitate was then filtered to obtain a white solid, washed with acetone, filtered again, and dried to obtain a dicarboxylic acid containing an amide bond. Neopentyl glycol, glycidyl neodecanoate, and catalyst are added to a reactor and heated to 60-65°C to melt them. Isophthalic acid and the aforementioned amide-containing dicarboxylic acid are added, and the temperature is raised to 240-243°C to react. After the material becomes transparent, the acid value is tested. When the acid value is 43-47 mgKOH / g, vacuum polycondensation is performed. When the acid value is 31-38 mgKOH / g, the mixture is vented to atmospheric pressure. The temperature is lowered to 220°C, antioxidant 1010 and curing accelerator BETP are added, and the mixture is stirred for 15-30 minutes before being discharged.

4. The water-resistant high-gloss black powder coating according to claim 1, characterized in that: The stearic acid-modified mica powder is prepared through the following steps: Mix mica powder with stearic acid at a mass fraction of 4-7% of the mica powder, stir for 5-10 minutes, then heat to 76-80℃ and stir for 20-25 minutes to obtain modified mica powder.

5. The water-resistant high-gloss black powder coating according to claim 1, characterized in that: The hollow glass microspheres are modified hollow glass microspheres, prepared through the following steps: Weigh out hollow glass microspheres and place them in 1 mol / L hydrochloric acid and stir for 24 hours. Filter the mixture and wash the hollow glass microspheres several times with deionized water. Dry the mixture in an oven at 110-120℃. Solution A is obtained by adding 5-7% (by mass) of nonafluorohexyltrimethoxysilane to ethanol. Solution B is obtained by weighing the dried hollow glass microspheres and placing them in pure water. Solution A and solution B are mixed and stirred for 24 hours. The modified hollow glass microspheres are then filtered out, washed, and dried.

6. The water-resistant high-gloss black powder coating according to claim 1, characterized in that: The epoxy resin used is a bisphenol A type epoxy resin with an epoxy equivalent of 700-750 g / eq.

7. The water-resistant high-gloss black powder coating according to claim 1, characterized in that: The leveling agent is an acrylate leveling agent, and the degassing agent is one or more of benzoin and benzoin.

8. The water-resistant high-gloss black powder coating according to claim 1, characterized in that: The brightener is selected from one or more of QR701, R701B and PV88.

9. The water-resistant high-gloss black powder coating according to claim 1, characterized in that: The curing agent is selected from one or more of DDCM, THPA, TGIC and MNA.

10. The water-resistant high-gloss black powder coating according to claim 1, characterized in that: The powder coating is prepared by the following method: The raw materials are added to a high-speed mixer, dry-mixed, and then added to an extruder. The mixture is melted, kneaded, cooled, and pressed into sheets at an extrusion temperature of 80-110℃. The sheets are then crushed, graded, sieved, and packaged to obtain a water-resistant, high-gloss black powder coating.