Powder coating for automobile lifting tailboard as well as preparation method and application of powder coating

Abstract

The invention discloses a powder coating for an automobile lifting tail plate as well as a preparation method and application of the powder coating, and belongs to the technical field of powder coatings. According to the invention, a double-layer coating is formed by combining the base powder and the flour, so that the corner covering is stronger, and the corrosion resistance is ensured. Besides, the epoxy resin A and the epoxy resin B with different epoxy equivalents are adopted, so that excellent shielding performance and chemical medium resistance are achieved, a more excellent anti-corrosion barrier is provided for a bottom layer, and self-repairing corrosion inhibition protection can be provided by combining the anti-rust pigment and achieving a synergistic effect; the carboxyl-terminated polyester resin A and the carboxyl-terminated polyester resin B with different acid values are adopted, so that the coating is endowed with better flexibility, the coating is prevented from being damaged due to deformation or impact, meanwhile, the flexibilizer is added into the bottom powder and the flour, impact energy can be effectively absorbed and dispersed, and the impact resistance of the coating is remarkably improved; the silica powder and the feldspar powder are added into the flour and interact with each other, so that the wear resistance of the coating can be obviously improved.

Description

Technical Field

[0001] This invention relates to the field of powder coating technology, and more specifically, to a powder coating for automobile tailgate lifters, its preparation method, and its application. Background Technology

[0002] As a crucial loading and unloading device for logistics vehicles, vehicle tailgates are constantly exposed to a complex and ever-changing external environment, making them susceptible to corrosion from moisture, salt spray, chemicals, and mechanical impacts. This leads to problems such as coating corrosion, peeling, and wear, severely impacting their service life and safety. Currently, most common vehicle tailgate coatings employ a single-layer spray structure. While this provides some protection, it still falls short in terms of corrosion resistance, wear resistance, adhesion, and impact resistance. Especially at edges and welds, uneven coating coverage easily becomes a starting point for corrosion. Furthermore, traditional coatings perform poorly in terms of friction, easily causing slippage during loading and unloading, posing a safety hazard.

[0003] Existing technologies include numerous powder coatings developed and applied for metal protection. Powder coatings possess superior environmental performance and excellent physicochemical properties. Compared to traditional liquid coatings, powder coatings produce virtually no volatile organic compounds during application, thus offering significant advantages in reducing environmental pollution and improving workplace safety. Furthermore, powder coatings exhibit better adhesion and abrasion resistance, forming a robust and uniform coating that provides higher surface quality and a longer service life. However, current powder coating technologies primarily rely on simple resin systems and curing agents, and this single formulation often fails to meet the requirements for highly corrosion-resistant coatings. Over time, especially in harsh outdoor environments, these coatings are prone to fading, peeling, and surface degradation, leading to a decline in their performance. Therefore, as market demands for coating applications continue to increase, the corrosion resistance, impact resistance, and abrasion resistance of traditional powder coatings still require improvement.

[0004] In addition, there are few existing powder coatings specifically developed for automobile tailgates. Developing a coating that can improve corrosion resistance while ensuring other application performance, so as to meet the requirements for automobile tailgate use, is of great significance. Summary of the Invention

[0005] In view of this, in order to solve one of the above-mentioned technical problems, the present invention provides a powder coating for automobile tailgates, its preparation method and application, the specific technical solution of which is as follows: A powder coating for a car lift tailgate, the powder coating comprising base powder and flour; The base powder comprises the following raw materials in parts by weight: epoxy resin A: 30-40 parts; epoxy resin B: 20-30 parts; micronized dicyandiamide: 1.6-1.8 parts; silica powder: 5-15 parts; leveling agent: 0.5-2 parts; brightener: 0.5-2 parts; adhesion promoter: 0.5-1 part; benzoin: 0.2-0.5 parts; defoamer: 0.5-2 parts; antioxidant: 0.5-2 parts; rust-preventive pigment: 3-10 parts; desiccant: 0.1-0.2 parts; toughening agent: 0.5-1.5 parts; mica powder: 5-10 parts; catalyst: 0.1-0.5 parts. The flour comprises the following raw materials in parts by weight: carboxyl-terminated polyester resin A: 15-30 parts; carboxyl-terminated polyester resin B: 30-45 parts; triglycidyl isocyanate: 3-5 parts; feldspar powder: 5-10 parts; wollastonite: 5-15 parts; leveling agent: 0.5-2 parts; gloss agent: 0.5-2 parts; anti-scratch agent: 0.2-0.3 parts; benzoin: 0.2-0.5 parts; antioxidant: 0.5-2 parts; pigment: 1-3.0 parts; desiccant: 0.1-0.2 parts; toughening agent: 0.5-1.5 parts.

[0006] Furthermore, in the base powder, the epoxy resin A has an epoxy equivalent of 840-900, an ICI viscosity of 70.0-100.0℃, and a softening point of 99.0-110.0 Pa·s; the epoxy resin B has an epoxy equivalent of 740-800, an ICI viscosity of 35.0-45.0 Pa·s, and a softening point of 89.0-97.0℃.

[0007] Furthermore, in the base powder, the micronized dicyandiamide has a particle size D50 of 5 μm and a solid content of 99.5%.

[0008] Furthermore, in the base powder, the median particle size of the silicon micropowder is 8nm-12μm.

[0009] Furthermore, in the base powder, the anti-rust pigment includes at least one of zinc phosphate, modified aluminum tripolyphosphate, and aluminum dihydrogen tripolyphosphate.

[0010] Furthermore, in the flour, the carboxyl-terminated polyester resin A has an acid value of 27 mgKOH / g-33 mgKOH / g, a viscosity at 200℃ (mPa.s) of 4500-6500, and a glass transition temperature of 65-68℃. The carboxyl-terminated polyester resin B has an acid value of 31 mgKOH / g-37 mgKOH / g, a viscosity of 5500-6500 at 200℃ (mPa.s), and a glass transition temperature of 67-70℃.

[0011] Furthermore, in the flour, the feldspar powder is silica alumina and oxides of potassium, sodium, and calcium.

[0012] Furthermore, in the flour, the drying agent is aluminum oxide C with a specific surface area of ​​100±10 m². 2 / g, with an average particle size of 10-13nm and an AL2O3 content ≥99.7%.

[0013] In addition, the present invention also provides a method for preparing a powder coating for an automobile tailgate, the method comprising the following steps: Preparation of foundation powder: Weigh each component of the base powder according to the specified ratio and put them into a mixing tank for premixing to obtain mixture A; The mixture A is melt-extruded, cooled, and ground with AMC to obtain the base powder; The conditions for melt extrusion are as follows: screw speed is 35-40 Hz, melting zone temperature is 90-100℃, and mixing zone temperature is 110-120℃. The conditions for AMC grinding are: main mill frequency of 38-42 Hz, auxiliary mill frequency of 20-30 Hz, and feeding frequency of 18-25 Hz. Flour preparation: After weighing each component of the flour according to the specified ratio, put them into a mixing tank for premixing to obtain mixture B; Mixture B is melt-extruded, cooled, and ground with AMC to obtain flour; The conditions for melt extrusion are as follows: screw speed is 45-50 Hz, melting zone temperature is 100-110℃, and mixing zone temperature is 120-135℃. The conditions for AMC grinding are: main grinding frequency of 42-47 Hz, auxiliary grinding frequency of 20-30 Hz, and feeding frequency of 18-25 Hz.

[0014] In addition, the present invention also provides an application of powder coating for automobile tailgate lifting panels, wherein the application method is as follows: Preheat the substrate, then spray on the base powder and cure at 180-185℃ for 10-15 minutes; then spray on the flour and cure at 200-220℃ for 20-25 minutes.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a combination of base powder and flour to form a double-layer coating, resulting in superior corrosion resistance and stronger edge coverage, preventing corrosion pitting from sharp locations and further ensuring its anti-corrosion performance. Furthermore, in terms of formulation, this invention employs epoxy resins A and B with different epoxy equivalents, fully leveraging the excellent shielding and chemical resistance of epoxy resins to provide a superior anti-corrosion barrier for the underlying layer. Combined with anti-rust pigments, this synergistic effect effectively passivates the metal substrate and provides self-healing corrosion inhibition protection at scratches. The use of carboxyl-terminated polyester resins A and B with different acid values ​​effectively protects the base powder from UV aging. Their combined effect enhances corrosion resistance while also giving the coating superior flexibility, preventing damage from deformation or impact. 2. Both the base powder and flour of this invention contain toughening agents, which not only have good compatibility in the system, but also effectively absorb and disperse impact energy. Furthermore, the carboxyl-terminated polyester resin A and carboxyl-terminated polyester resin B in the flour also have excellent flexibility properties, which significantly increases the impact resistance of the coating and prevents the coating from peeling off during the use of the car tailgate.

[0016] 3. In this invention, silica powder is added to the base powder, and silica powder and feldspar powder are added to the flour. While ensuring the hardness of the coating, the interaction of the components can also significantly improve the wear resistance of the coating.

[0017] 4. By optimizing the flour formula, the silica powder and wollastonite can disrupt the microscopic smoothness of the powder coating, forming an uneven surface that provides better friction. When applied to a car tailgate, the contact surface has better friction performance, effectively increasing friction with other materials, preventing slippage, and improving safety. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] A powder coating for a car lift tailgate according to one embodiment of the present invention, the powder coating comprising base powder and flour; The base powder comprises the following raw materials in parts by weight: epoxy resin A: 30-40 parts; epoxy resin B: 20-30 parts; micronized dicyandiamide: 1.6-1.8 parts; silica powder: 5-15 parts; leveling agent: 0.5-2 parts; brightener: 0.5-2 parts; adhesion promoter: 0.5-1 part; benzoin: 0.2-0.5 parts; defoamer: 0.5-2 parts; antioxidant: 0.5-2 parts; rust-preventive pigment: 3-10 parts; desiccant: 0.1-0.2 parts; toughening agent: 0.5-1.5 parts; mica powder: 5-10 parts; catalyst: 0.1-0.5 parts. The flour comprises the following raw materials in parts by weight: carboxyl-terminated polyester resin A: 15-30 parts; carboxyl-terminated polyester resin B: 30-45 parts; triglycidyl isocyanate: 3-5 parts; feldspar powder: 5-10 parts; wollastonite: 5-15 parts; leveling agent: 0.5-2 parts; gloss agent: 0.5-2 parts; scratch-resistant agent: 0.2-0.3 parts; benzoin: 0.2-0.5 parts; antioxidant: 0.5-2 parts; pigment: 1-3.0 parts; desiccant: 0.1-0.2 parts; toughening agent: 0.5-1.5 parts.

[0021] In one embodiment, the epoxy resin A in the base powder has an epoxy equivalent of 840-900, an ICI viscosity of 70.0-100.0 Pa·s, and a softening point of 99.0-110.0℃; the epoxy resin B has an epoxy equivalent of 740-800, an ICI viscosity of 35.0-45.0 Pa·s, and a softening point of 89.0-97.0℃.

[0022] In one embodiment, the micronized dicyandiamide in the base powder has a particle size D50 of 5 μm and a solid content of 99.5%.

[0023] In one embodiment, the leveling agent in the base powder is a polyester-modified silicone leveling agent.

[0024] In one embodiment, the brightening agent in the base powder is an acrylate copolymer.

[0025] In one embodiment, the benzoin in the base powder is an ethanol ketone, also known as benzoin, with a melting temperature of 130-135°C and a solid content of ≥99%.

[0026] In one embodiment, the antioxidant in the base powder is AT626-hindered phenolic antioxidant.

[0027] In one embodiment, the adhesion promoter in the base powder is adhesion promoter MC001.

[0028] In one embodiment, the defoamer in the base powder is a polyether defoamer with a softening point of 105-110°C.

[0029] In one embodiment, the drying agent in the base powder is aluminum oxide C with a specific surface area of ​​100±10m². 2 / g, with an average particle size of 10-13nm and an AL2O3 content ≥99.7%.

[0030] In one embodiment, the toughening agent in the base powder is polyetherimide.

[0031] In one embodiment, the anti-rust pigment in the base powder includes at least one of zinc phosphate, modified aluminum tripolyphosphate, and aluminum dihydrogen tripolyphosphate.

[0032] In one embodiment, the mica powder in the base powder has a D50 of 12 μm.

[0033] In one embodiment, the catalyst in the base powder is dimethylimidazole with a melting point of 145-150°C.

[0034] In one embodiment, the flour contains a carboxyl-terminated polyester resin A with an acid value of 27 mgKOH / g-33 mgKOH / g, a viscosity at 200℃ (mPa.s) of 4500-6500, and a glass transition temperature of 65-68℃. The carboxyl-terminated polyester resin B has an acid value of 31 mgKOH / g-37 mgKOH / g, a viscosity of 5500-6500 at 200℃ (mPa.s), and a glass transition temperature of 67-70℃.

[0035] In one embodiment, the feldspar powder in the flour is silica alumina and oxides of potassium, sodium, and calcium.

[0036] In one embodiment, the flour contains wollastonite with a D97 ≤ 10 μm and an oil absorption value of 25-30 g / 100g.

[0037] In one embodiment, the median particle size of the silicon microparticles in the flour is 8 nm to 12 μm.

[0038] In one embodiment, the leveling agent in the flour is a polyester-modified silicone leveling agent.

[0039] In one embodiment, the brightening agent in the flour is an acrylate copolymer.

[0040] In one embodiment, the anti-scratch agent in the flour is micronized polypropylene wax.

[0041] In one embodiment, the benzoin in the flour is an ethanol ketone, also known as benzoin, with a melting temperature of 130-135°C and a solid content of ≥99%.

[0042] In one embodiment, the antioxidant in the flour is AT626-hindered phenolic antioxidant.

[0043] In one embodiment, the drying agent in the flour is aluminum oxide C, with a specific surface area of ​​100 ± 10 m². 2 / g, with an average particle size of 10-13nm and an AL2O3 content ≥99.7%.

[0044] In one embodiment, the toughening agent in the flour is a polyvinyl butyral toughening agent.

[0045] In one embodiment, the defoamer in the flour is a modified amide compound.

[0046] In addition, the present invention also provides a method for preparing a powder coating for an automobile tailgate, the method comprising the following steps: Preparation of foundation powder: Weigh each component of the base powder according to the specified ratio and put them into a mixing tank for premixing to obtain mixture A; The mixture A is melt-extruded, cooled, and ground with AMC to obtain the base powder; The conditions for melt extrusion are as follows: screw speed is 35-40 Hz, melting zone temperature is 90-100℃, and mixing zone temperature is 110-120℃. The conditions for AMC grinding are: main mill frequency of 38-42 Hz, auxiliary mill frequency of 20-30 Hz, and feeding frequency of 18-25 Hz. Flour preparation: After weighing each component of the flour according to the specified ratio, put them into a mixing tank for premixing to obtain mixture B; Mixture B is melt-extruded, cooled, and ground with AMC to obtain flour; The conditions for melt extrusion are as follows: screw speed is 45-50 Hz, melting zone temperature is 100-110℃, and mixing zone temperature is 120-135℃. The conditions for AMC grinding are: main grinding frequency of 42-47 Hz, auxiliary grinding frequency of 20-30 Hz, and feeding frequency of 18-25 Hz.

[0047] In addition, the present invention also provides an application of powder coating for automobile tailgate lifting panels, wherein the application method is as follows: Preheat the substrate, then spray on the base powder and cure at 180-185℃ for 10-15 minutes; then spray on the flour and cure at 200-220℃ for 20-25 minutes.

[0048] In one embodiment, the substrate is a car tailgate.

[0049] The above solution optimizes the formulation of the base powder and flour, resulting in excellent component compatibility and the formation of a double-layer coating, which provides significant anti-corrosion, anti-slip, and impact-resistant properties.

[0050] The implementation scheme of the present invention will be described in detail below with reference to specific embodiments. The unspecified ingredients can be purchased from commercially available products, and the unspecified process can be understood as conventional technology, which will not be elaborated here.

[0051] Example 1: A method for preparing a powder coating for an automobile tailgate, the method comprising the following steps: Preparation of foundation powder: By weight, 35 parts of epoxy resin A with an epoxy equivalent of 850, 25 parts of epoxy resin B with an epoxy equivalent of 780, 1.6 parts of micronized dicyandiamide, 12 parts of silica powder, 1 part of polyester-modified silicone leveling agent, 0.5 parts of acrylate copolymer brightener, 0.6 parts of adhesion promoter MC001, 0.3 parts of benzoin, 1 part of polyether defoamer, 1 part of AT626-hindered phenolic antioxidant, 8 parts of rust-preventive pigment (obtained by mixing zinc phosphate and modified aluminum tripolyphosphate in a mass ratio of 3:5), 0.2 parts of alumina C, 0.8 parts of polyether imide, 6 parts of mica powder, and 0.3 parts of dimethylimidazole are added to a mixing tank for premixing to obtain mixture A; The mixture A is melt-extruded, cooled, and ground with AMC to obtain the base powder; The melt extrusion conditions were: screw speed 40 Hz, melt zone temperature 95℃, and mixing zone temperature 120℃; the AMC grinding conditions were: main mill frequency 40 Hz, auxiliary mill frequency 25 Hz, and feeding frequency 22 Hz. Flour preparation: By weight, 25 parts of carboxyl-terminated polyester resin A with an acid value of 30 mgKOH / g, 40 parts of carboxyl-terminated polyester resin B with an acid value of 35 mgKOH / g, 4 parts of triglycidyl isocyanate, 6 parts of feldspar powder, 15 parts of wollastonite, 1 part of polyester-modified silicone leveling agent, 2 parts of acrylate copolymer, 0.3 parts of micronized polypropylene wax, 0.4 parts of benzoin, 1 part of AT626-hindered phenolic antioxidant, 1 part of pigment, 0.2 parts of alumina C, and 1 part of polyvinyl butyral toughening agent were added to a mixing tank for premixing to obtain mixture B; Mixture B is melt-extruded, cooled, and ground with AMC to obtain flour; The conditions for melt extrusion are: screw speed of 45 Hz, melting zone temperature of 110℃, and mixing zone temperature of 125℃; the conditions for AMC grinding are: main mill frequency of 45 Hz, auxiliary mill frequency of 25 Hz, and feeding frequency of 22 Hz.

[0052] Preheat the car tailgate to 65°C, then spray on the base powder and cure at 180°C for 10 minutes to form a 60μm thick coating; then spray on the flour and cure at 200°C for 20 minutes to form an 80μm thick coating.

[0053] Example 2: A method for preparing a powder coating for an automobile tailgate, the method comprising the following steps: Preparation of foundation powder: By weight, 37 parts of epoxy resin A with an epoxy equivalent of 850, 23 parts of epoxy resin B with an epoxy equivalent of 780, 1.8 parts of micronized dicyandiamide, 13 parts of silica powder, 1 part of polyester-modified silicone leveling agent, 0.6 parts of acrylate copolymer brightener, 0.7 parts of adhesion promoter MC001, 0.2 parts of benzoin, 1 part of polyether defoamer, 1 part of AT626-hindered phenolic antioxidant, 8 parts of rust-preventive pigment (obtained by mixing zinc phosphate and modified aluminum tripolyphosphate in a mass ratio of 3:5), 0.2 parts of alumina C, 1 part of polyether imide, 7 parts of mica powder, and 0.4 parts of dimethylimidazole were added to a mixing tank for premixing to obtain mixture A; The mixture A is melt-extruded, cooled, and ground with AMC to obtain the base powder; The melt extrusion conditions were: screw speed 40 Hz, melt zone temperature 95℃, and mixing zone temperature 120℃; the AMC grinding conditions were: main mill frequency 40 Hz, auxiliary mill frequency 25 Hz, and feeding frequency 22 Hz. Flour preparation: By weight, 27 parts of carboxyl-terminated polyester resin A with an acid value of 30 mgKOH / g, 38 parts of carboxyl-terminated polyester resin B with an acid value of 35 mgKOH / g, 5 parts of triglycidyl isocyanate, 5 parts of feldspar powder, 15 parts of wollastonite, 2 parts of polyester-modified silicone leveling agent, 1 part of acrylate copolymer, 0.3 parts of micronized polypropylene wax, 0.5 parts of benzoin, 1 part of AT626-hindered phenolic antioxidant, 1 part of pigment, 0.2 parts of alumina C, and 1 part of polyvinyl butyral toughening agent were added to a mixing tank for premixing to obtain mixture B; Mixture B is melt-extruded, cooled, and ground with AMC to obtain flour; The conditions for melt extrusion are: screw speed of 45 Hz, melting zone temperature of 110℃, and mixing zone temperature of 125℃; the conditions for AMC grinding are: main mill frequency of 45 Hz, auxiliary mill frequency of 25 Hz, and feeding frequency of 22 Hz.

[0054] Preheat the car tailgate to 65°C, then spray on the base powder and cure at 180°C for 10 minutes to form a 60μm thick coating; then spray on the flour and cure at 200°C for 20 minutes to form an 80μm thick coating.

[0055] Example 3: A method for preparing a powder coating for an automobile tailgate, the method comprising the following steps: Preparation of foundation powder: By weight, 40 parts of epoxy resin A with an epoxy equivalent of 850, 20 parts of epoxy resin B with an epoxy equivalent of 780, 1.7 parts of micronized dicyandiamide, 14 parts of silica powder, 2 parts of polyester-modified silicone leveling agent, 1 part of acrylate copolymer brightener, 0.7 parts of adhesion promoter MC001, 0.3 parts of benzoin, 1 part of polyether defoamer, 1 part of AT626-hindered phenolic antioxidant, 8 parts of rust-preventive pigment (obtained by mixing zinc phosphate and modified aluminum tripolyphosphate in a mass ratio of 3:5), 0.2 parts of alumina C, 1 part of polyether imide, 7 parts of mica powder, and 0.5 parts of dimethylimidazole are added to a mixing tank for premixing to obtain mixture A; The mixture A is melt-extruded, cooled, and ground with AMC to obtain the base powder; The melt extrusion conditions were: screw speed 40 Hz, melt zone temperature 95℃, and mixing zone temperature 120℃; the AMC grinding conditions were: main mill frequency 40 Hz, auxiliary mill frequency 25 Hz, and feeding frequency 22 Hz. Flour preparation: By weight, 30 parts of carboxyl-terminated polyester resin A with an acid value of 30 mgKOH / g, 35 parts of carboxyl-terminated polyester resin B with an acid value of 35 mgKOH / g, 4 parts of triglycidyl isocyanate, 5 parts of feldspar powder, 16 parts of wollastonite, 2 parts of polyester-modified silicone leveling agent, 1 part of acrylate copolymer, 0.3 parts of micronized polypropylene wax, 0.5 parts of benzoin, 1 part of AT626-hindered phenolic antioxidant, 1 part of pigment, 0.2 parts of alumina C, and 1 part of polyvinyl butyral toughening agent were added to a mixing tank for premixing to obtain mixture B; Mixture B is melt-extruded, cooled, and ground with AMC to obtain flour; The conditions for melt extrusion are: screw speed of 45 Hz, melting zone temperature of 110℃, and mixing zone temperature of 125℃; the conditions for AMC grinding are: main mill frequency of 45 Hz, auxiliary mill frequency of 25 Hz, and feeding frequency of 22 Hz.

[0056] Preheat the car tailgate to 65°C, then spray on the base powder and cure at 180°C for 10 minutes to form a 60μm thick coating; then spray on the flour and cure at 200°C for 20 minutes to form an 80μm thick coating.

[0057] Comparative Example 1: The difference between Comparative Example 1 and Example 3 is that 60 parts of epoxy resin A with an epoxy equivalent of 850 were added to the base powder in Comparative Example 1, that is, epoxy resin B was not added. Otherwise, it was the same as Example 3.

[0058] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that no silicon micropowder was added to the base powder in Comparative Example 2, while the rest is the same as in Example 3.

[0059] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that no anti-rust pigment was added to the base powder in Comparative Example 3, but otherwise it is the same as Example 3.

[0060] Comparative Example 4: The difference between Comparative Example 4 and Example 3 is that no polyetherimide was added to the base powder in Comparative Example 4, but otherwise it was the same as Example 3.

[0061] Comparative Example 5: Compared with Example 3, Comparative Example 5 differs in that 65 parts of epoxy resin A with an epoxy equivalent of 850 were used to replace the carboxyl-terminated polyester resin A and carboxyl-terminated polyester resin B in the flour. Otherwise, they are the same as in Example 3.

[0062] Comparative Example 6: The difference between Comparative Example 6 and Example 3 is that no feldspar powder was added to the flour in Comparative Example 6, but otherwise it is the same as Example 3.

[0063] Comparative Example 7: The difference between Comparative Example 7 and Example 3 is that no wollastonite was added to the flour in Comparative Example 7, but otherwise it is the same as Example 3.

[0064] Comparative Example 8: The difference between Comparative Example 8 and Example 3 is that no polyvinyl butyral toughening agent was added to the flour in Comparative Example 8, but otherwise it was the same as Example 3.

[0065] The samples prepared in Examples 1-3 and the samples prepared in Comparative Examples 1-8 were subjected to performance tests. The adhesion was tested according to GB / T9286-2021; the salt spray resistance was tested according to GB / T1771; the impact resistance was tested according to GB / T1732-2020; and the abrasion resistance was tested according to GB / T1768-2006. The test conditions were 1 kg / 1000 r and CS-17 wheel. The abrasion resistance was judged by the total mass loss (mg). The average value was recorded after 5 parallel tests. The results are shown in Table 1 below.

[0066] Table 1: Performance Test Results

[0067] Analysis of the data in Table 1 shows that, through optimized composition, the components of this invention work synergistically, resulting in an overall double-layer coating structure that achieves excellent corrosion resistance, impact resistance, and wear resistance. Compared to Example 3, Comparative Example 1, which did not add epoxy resin B, showed decreased adhesion, poorer salt spray resistance, and significantly worse impact resistance than Example 3. This indicates that the present invention, by compounding epoxy resin B (epoxy equivalent 740-800), which has lower viscosity and softening point, can improve the flexibility and compatibility of the base powder. The lack of epoxy resin B leads to increased internal stress in the coating, decreased adhesion, weakened shielding, and reduced corrosion resistance and impact resistance. Comparative Example 2's base powder did not contain silica fume. Silica fume primarily improves coating hardness and wear resistance, indicating that even changes in the base powder composition can negatively impact the overall wear resistance of the coating. Comparative Example 3's base powder did not contain rust-inhibiting pigments. Although the amount of rust-inhibiting pigments in the base powder of this invention is small, they can passivate the metal substrate and provide self-healing corrosion inhibition protection. The lack of this component results in the coating being unable to effectively inhibit corrosion diffusion, especially at scratches, where salt spray resistance is significantly worse than in Example 3. Comparative Example 4's base powder did not contain toughening agents. The toughening agent in the base powder is polyetherimide, which can absorb and disperse impact energy and improve coating toughness. Without toughening agents, the coating formed by the base powder is more brittle than the coating in Example 3, and its impact resistance is reduced. Comparative Example 5's flour uses epoxy resin A. Replacing the polyester resin with carboxyl-terminated polyester resins A and B provides flexibility and weather resistance, while epoxy resin A is more brittle and has poorer weather resistance. After replacement, the coating flexibility decreased significantly, resulting in poorer adhesion, corrosion resistance, and impact resistance compared to Example 3. Feldspar powder was not added to the flour in Comparative Example 6. Feldspar powder can increase the surface roughness of the coating, improving friction and wear resistance. The lack of feldspar powder in Comparative Example 6 resulted in significantly worse wear resistance compared to Example 3. Wollastonite was not added to the flour in Comparative Example 7. Wollastonite can disrupt the microscopic smoothness of the coating, improving wear resistance and friction. It works synergistically with feldspar powder to improve the wear resistance of the coating. However, the lack of this component in Comparative Example 7 resulted in significantly worse wear resistance compared to Example 3. No toughening agent was added to the flour in Comparative Example 8. The toughening agent in Comparative Example 8 was polyvinyl butyral, which improves impact resistance in flour. Without it, the coating toughness decreased, and the impact resistance was reduced.

[0068] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A powder coating for a car liftgate, characterized in that, The powder coating includes base powder and flour; The base powder comprises the following raw materials in parts by weight: epoxy resin A: 30-40 parts; epoxy resin B: 20-30 parts; micronized dicyandiamide: 1.6-1.8 parts; silica powder: 5-15 parts; leveling modifier: 0.5-2 parts; brightener: 0.5-2 parts; adhesion promoter: 0.5-1 part; benzoin: 0.2-0.5 parts; defoamer: 0.5-2 parts; antioxidant: 0.5-2 parts; rust-preventive pigment: 3-10 parts; desiccant: 0.1-0.2 parts; toughening agent: 0.5-1.5 parts; mica powder: 5-10 parts; catalyst: 0.1-0.5 parts. The flour comprises the following raw materials in parts by weight: carboxyl-terminated polyester resin A: 15-30 parts; carboxyl-terminated polyester resin B: 30-45 parts; triglycidyl isocyanate: 3-5 parts; feldspar powder: 5-10 parts; wollastonite: 5-15 parts; leveling agent: 0.5-2 parts; gloss agent: 0.5-2 parts; scratch-resistant agent: 0.2-0.3 parts; benzoin: 0.2-0.5 parts; antioxidant: 0.5-2 parts; pigment: 1-3.0 parts; desiccant: 0.1-0.2 parts; toughening agent: 0.5-1.5 parts.

2. The powder coating according to claim 1, characterized in that, In the base powder, the epoxy resin A has an epoxy equivalent of 840-900, an ICI viscosity of 70.0-100.0 Pa·s, and a softening point of 99.0-110.0℃; the epoxy resin B has an epoxy equivalent of 740-800, an ICI viscosity of 35.0-45.0 Pa·s, and a softening point of 89.0-97.0℃.

3. The powder coating according to claim 1, characterized in that, In the base powder, the micronized dicyandiamide has a particle size D50 of 5 μm and a solid content of 99.5%.

4. The powder coating according to claim 1, characterized in that, In the base powder, the median particle size of the silicon micropowder is 8nm-12μm.

5. The powder coating according to claim 1, characterized in that, The base powder contains at least one of zinc phosphate, modified aluminum tripolyphosphate, and aluminum dihydrogen tripolyphosphate.

6. The powder coating according to claim 1, characterized in that, In the flour, the acid value of the carboxyl-terminated polyester resin A is 27 mgKOH / g-33 mgKOH / g, the viscosity at 200℃ (mPa.s) is 4500-6500, and the glass transition temperature is 65-68℃. The carboxyl-terminated polyester resin B has an acid value of 31 mgKOH / g-37 mgKOH / g, a viscosity of 5500-6500 at 200℃ (mPa.s), and a glass transition temperature of 67-70℃.

7. The powder coating according to claim 1, characterized in that, In the flour, the feldspar powder is composed of silicon dioxide, aluminum oxide, and oxides of potassium, sodium, and calcium.

8. The powder coating according to claim 1, characterized in that, In the flour, the drying agent is aluminum oxide C with a specific surface area of ​​100±10m². 2 / g, with an average particle size of 10-13nm and an Al2O3 content ≥99.7%.

9. A method for preparing a powder coating for an automobile tailgate, characterized in that, The preparation method is used to prepare the powder coating as described in any one of claims 1-8, and the preparation method includes the following steps: Preparation of foundation powder: Weigh each component of the base powder according to the specified ratio and put them into a mixing tank for premixing to obtain mixture A; The mixture A is melt-extruded, cooled, and ground with AMC to obtain the base powder; The conditions for melt extrusion are as follows: screw speed is 35-40 Hz, melting zone temperature is 90-100℃, and mixing zone temperature is 110-120℃. The conditions for AMC grinding are: main mill frequency of 38-42 Hz, auxiliary mill frequency of 20-30 Hz, and feeding frequency of 18-25 Hz. Flour preparation: After weighing each component of the flour according to the specified ratio, put them into a mixing tank for premixing to obtain mixture B; Mixture B is melt-extruded, cooled, and ground with AMC to obtain flour; The conditions for melt extrusion are as follows: screw speed is 45-50 Hz, melting zone temperature is 100-110℃, and mixing zone temperature is 120-135℃. The conditions for AMC grinding are: main grinding frequency of 42-47 Hz, auxiliary grinding frequency of 20-30 Hz, and feeding frequency of 18-25 Hz.

10. The application of a powder coating for an automobile tailgate, characterized in that, The application is the application of the powder coating according to any one of claims 1-8, and the method is as follows: Preheat the substrate, then spray on the base powder and cure at 180-185℃ for 10-15 minutes; then spray on the flour and cure at 200-220℃ for 20-25 minutes.

Images