A matt scratch-resistant powder coating composition and a process for the preparation thereof

Abstract

The application discloses a kind of matt scratch-resistant powder coating compositions and preparation method thereof, it is related to powder coating technical field.The composition is made of composite matrix resin, composite curing agent, functional matt filler, matt auxiliary agent, silane coupling agent, pigment filling, synergistic component and functional auxiliary agent;The composite matrix resin is hydroxyl-terminated hyperbranched polyurethane, acrylic matt resin G600-3, carboxyl-terminated hyperbranched polyester resin is compounded according to mass ratio 0.3:1:(3-5);The composite curing agent is 1,3,5-triglycidyl-S-triazine triketone, beta-hydroxyalkylamide, 9,9-di [(2,3-epoxypropoxy) phenyl] fluorene is compounded according to mass ratio (2-3):1:(0.8-1.2).The composition is significantly matt, and has excellent scratch resistance and weather resistance, suitable for coating scene with high performance requirements for coating layer.

Description

Technical Field

[0001] This invention relates to the field of powder coating technology, and in particular to a matte, scratch-resistant powder coating composition and its preparation method. Background Technology

[0002] Powder coatings, as solvent-free and environmentally friendly coatings, are widely used in various industrial fields due to their convenient application, high utilization rate, zero VOC emissions, and excellent coating performance. With the upgrading of market demands, consumers are not only focusing on the environmental friendliness and basic protective performance of powder coatings, but also placing higher demands on the appearance, texture, and durability of the coatings. Among them, matte coatings, with their low-key and elegant matte effect, can effectively cover up surface defects of the substrate and are increasingly widely used in high-end furniture, home appliances, automotive interiors, and other fields.

[0003] Existing matting technologies mainly include physical matting and chemical matting. Physical matting typically achieves matting by adding fillers or incompatible substances to create a slightly rough surface, but this often affects the smoothness and mechanical properties of the coating. Chemical matting is achieved through the difference in reaction rates or phase separation between the resin and the curing agent. Although it has good impact and bending resistance, there is still room for improvement in hardness and scratch resistance. Therefore, achieving excellent matting while ensuring other physical and mechanical properties of the coating, especially scratch resistance, remains a challenge in the current technological field.

[0004] To address the aforementioned issues, invention patent document CN112745740B discloses a matte, scratch-resistant powder coating composition, the raw materials of which include at least a thermosetting resin and a styrene-maleic anhydride polymer, wherein the styrene-maleic anhydride polymer and the thermosetting resin can undergo a cross-linking curing reaction. This invention also discloses a method for preparing the aforementioned matte, scratch-resistant powder coating composition, wherein the raw materials are obtained through mixing, melt extrusion, and crushing. Furthermore, this invention discloses a matte, scratch-resistant coating, which is formed by spraying the aforementioned matte, scratch-resistant powder coating composition onto a substrate and then curing it. The cured coating film obtained by this invention can simultaneously achieve surprisingly excellent matte and scratch-resistant effects. However, this technology still suffers from problems such as easy yellowing during high-temperature curing, insufficient weather resistance, and poor gloss stability during thin-coat application, making it difficult to meet the stringent requirements of high-end outdoor and precision coating scenarios. Summary of the Invention

[0005] To address the technical problems of unstable matting effect, poor scratch resistance, and easy defects in existing matting powder coatings, which make it difficult to balance matting, scratch resistance, and other protective properties, this invention provides a matting and scratch-resistant powder coating composition and its preparation method. Through reasonable component ratio and process optimization, the matting effect and scratch resistance are synergistically improved, while ensuring that the coating has excellent leveling, adhesion, weather resistance, and chemical resistance. Moreover, the preparation process is simple, energy-efficient, and cost-controllable, meeting the needs of industrial production and satisfying the application requirements of high-end fields.

[0006] To achieve the above objectives, the present invention provides a matte scratch-resistant powder coating composition, prepared from the following components in parts by weight: 50-65 parts of composite matrix resin, 3-6 parts of composite curing agent, 15-25 parts of functional matte filler, 2-4 parts of matte additive, 1-2 parts of silane coupling agent, 3-8 parts of pigments and fillers, 0.3-0.5 parts of synergistic components, and 2-5 parts of functional additives; wherein the composite matrix resin is a compound of hydroxyl-terminated hyperbranched polyurethane, acrylic matte resin G600-3, and carboxyl-terminated hyperbranched polyester resin in a mass ratio of 0.3:1:(3-5); wherein the composite curing agent is a compound of 1,3,5-triglycidyl-S-triazinetrione, β-hydroxyalkylamide, and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene in a mass ratio of (2-3):1:(0.8-1.2).

[0007] Preferably, the hydroxyl-terminated hyperbranched polyurethane is grade 2499, catalog number HXKJ2025, brand name Huaxiang Kejie, and is provided by Wuhan Huaxiang Kejie Biotechnology Co., Ltd.; the β-hydroxyalkylamide is grade T105M and is provided by Ningbo Nanhai Chemical Co., Ltd.

[0008] Preferably, the acrylic matte resin G600-3 is provided by Wuhan Yincai Technology Co., Ltd.; the carboxyl-terminated hyperbranched polyester resin is a compound of carboxyl-terminated hyperbranched polyester resin HyPer C204 and carboxyl-terminated hyperbranched polyester resin HyPer C404 in a mass ratio of 1:(0.8-1.2).

[0009] Preferably, the functional matting filler is a mixture of nano-silicon nitride, nano-titanium dioxide and ultrafine barium sulfate, with a mass ratio of (1-2):(1-2):(6-8).

[0010] Preferably, the average particle size of the nano-silicon nitride is 10-70 nm; the average particle size of the nano-titanium dioxide is 10-70 nm; and the average particle size of the ultrafine barium sulfate is 0.8-2 μm.

[0011] Preferably, the matting agent is matting wax powder mju:Wax2739.

[0012] Preferably, the silane coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570.

[0013] Preferably, the pigment / filler is rutile titanium dioxide with an average particle size of 0.2-0.5 μm.

[0014] Preferably, the synergistic component is boron nitride nanosheets with a diameter of 1-2 μm and a thickness of 10 nm.

[0015] Preferably, the functional additive is a compound of leveling agent, degassing agent, antioxidant and light stabilizer in a mass ratio of (0.8-1.5):(0.3-0.8):(0.3-0.7):(0.5-0.8).

[0016] Preferably, the leveling agent is leveling agent GLP788; the degassing agent is benzoin; the antioxidant is antioxidant 1010; and the light stabilizer is BASF Tinuvin 770.

[0017] Another object of the present invention is to provide a method for preparing the aforementioned matte scratch-resistant powder coating composition, comprising the following steps: Step S1: Raw material premixing: Weigh the composite matrix resin, composite curing agent, functional matting filler, matting agent, silane coupling agent, pigments and fillers, synergistic components and functional additives according to the weight parts, put them into a high-speed mixer, and mix them at a speed of 800-1200 r / min for 5-10 min at room temperature to obtain a uniform premixed material.

[0018] Step S2, Melt Extrusion: The premixed material is fed into a twin-screw extruder for melt extrusion. The temperature of the first zone of the extruder is controlled at 90-100℃, the temperature of the second zone is 100-110℃, and the temperature of the third zone is 110-120℃. The screw speed is 200-400 r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S3, coarse crushing and fine grinding: The cooled flaky material is crushed into granules by a coarse crusher, and then the granules are fed into an ultra-fine pulverizer for fine grinding. The pulverizing speed is controlled at 3000-5000 r / min. After pulverization, the material is passed through a 180-220 mesh standard sieve to obtain a semi-finished powder coating.

[0019] Step S4, Grading and Finished Product Collection: The semi-finished powder coating is fed into an air classifier for grading to remove excessively large particles and ultrafine dust. Powder with uniform particle size distribution is collected to obtain the matte scratch-resistant powder coating composition.

[0020] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The matte and scratch-resistant powder coating composition disclosed in this invention breaks through the industry technical bottleneck of "mutual restriction between matte performance and scratch resistance performance" compared with existing matte powder coatings, and achieves synergistic improvement of both. In the prior art, matte coatings often achieve matte by adding a large amount of inert filler or reducing the resin crosslinking density, which often leads to a decrease in film hardness and a deterioration in scratch resistance. However, this solution ensures excellent matte effect and significantly improves the scratch resistance of the film by precisely compounding the composite matrix resin and the composite curing agent. In this composite matrix resin, hydroxyl-terminated hyperbranched polyurethane, acrylic matting resin G600-3, and carboxyl-terminated hyperbranched polyester resin are blended in a specific ratio. The carboxyl-terminated hyperbranched polyester resin provides good film-forming properties and basic hardness for the coating, while the acrylic matting resin G600-3 imparts stable basic matting properties to the coating. The hydroxyl-terminated hyperbranched polyurethane effectively improves the compatibility between the three resins. The synergistic effect of the three successfully solves the technical problem that a single resin cannot simultaneously achieve both matting effect and scratch resistance. This results in a coating with uniform matting and significantly improved surface hardness, overcoming the defect in existing technologies where matting and scratch resistance cannot be simultaneously achieved.

[0021] (2) The matte scratch-resistant powder coating composition disclosed in this invention, with its precise proportions and synergistic effects, further enhances the overall performance of the coating. The composite curing agent is made by compounding 1,3,5-triglycidyl-S-triazine trione, β-hydroxyalkylamide and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene in a specific ratio. Among them, 1,3,5-triglycidyl-S-triazine trione can significantly increase the resin crosslinking density, β-hydroxyalkylamide can improve the coating curing efficiency and shorten the curing cycle, and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene can effectively enhance the toughness of the coating film. The synergistic effect of the three makes the resin crosslinking reaction more complete and uniform, which not only further improves the scratch resistance of the coating film, but also simultaneously improves the chemical resistance, matte performance and adhesion of the coating film. Compared with the existing single curing agent system, the composite curing agent of this scheme can make the coating cure faster and effectively reduce defects such as pinholes and edge shrinkage in the coating film. In this functional matting filler, nano-silicon nitride, nano-titanium dioxide, and ultrafine barium sulfate are mixed in a specific ratio. Nano-silicon nitride and nano-titanium dioxide have both reinforcing and matting effects, while ultrafine barium sulfate can further optimize the uniformity of matting of the coating. The synergistic effect of the three not only avoids the problems of rough coating surface and reduced adhesion that are easily caused by single matting fillers, but also synergistically improves the wear resistance of the coating, achieving multiple technical effects of "matting + scratch resistance + reinforcement". This effect cannot be achieved by existing single matting filler systems.

[0022] (3) The matte and scratch-resistant powder coating composition disclosed in this invention, with the reasonable addition of silane coupling agent, synergistic components and functional additives, further amplifies the synergistic effect between the components, bringing unexpected additional technical advantages to the coating. The silane coupling agent can effectively improve the compatibility between inorganic fillers and organic resins, reduce defects at the interface between the two, and thus improve the adhesion and water resistance of the coating film. At the same time, it can promote the uniform dispersion of functional matte fillers in the resin system, avoiding problems such as uneven matting and reduced scratch resistance caused by filler agglomeration. The synergistic component boron nitride nanosheets, with their unique layered structure, can form a dense protective layer on the coating film surface, which can not only further enhance the scratch resistance of the coating film, but also improve the high temperature resistance and insulation of the coating film. In synergy with the functional matte fillers, it can further optimize the mechanical properties and matting effect of the coating film. The functional additives, including leveling agents, degassing agents, antioxidants, and light stabilizers, are compounded in specific proportions. The leveling agent ensures good leveling during the coating application process, the degassing agent effectively reduces bubble defects in the coating film, and the antioxidant and light stabilizer work together to improve the anti-aging performance of the coating film. This avoids problems such as the decay of matte effect, yellowing, and cracking of the coating film after long-term use, effectively solving the industry pain point of performance degradation of existing matte coatings after long-term use, and significantly extending the service life and stability of the coating's performance.

[0023] (4) The matte and scratch-resistant powder coating composition disclosed in this invention, through the scientific compounding and synergistic effect of each component, not only effectively solves the technical problems of existing matte powder coatings such as "the inability to achieve both matte finish and scratch resistance", "performance degradation after long-term use", and "many coating defects", but also simultaneously improves the coating in key performance indicators such as matte uniformity, scratch resistance, adhesion, chemical resistance, and aging resistance, with comprehensive performance far exceeding the level of existing technologies. Its technical effect is not a simple superposition of the individual effects of each component, but a comprehensive effect produced by the mutual cooperation and synergistic effect between each component. It can be widely used in various scenarios with high requirements for matte effect and scratch resistance, and has good industrial application value. Detailed Implementation

[0024] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. Example 1

[0025] A matte, scratch-resistant powder coating composition is prepared from the following components in parts by weight: 50 parts of composite matrix resin, 3 parts of composite curing agent, 15 parts of functional matte filler, 2 parts of matte additive, 1 part of silane coupling agent, 3 parts of pigments and fillers, 0.3 parts of synergistic components, and 2 parts of functional additives; wherein the composite matrix resin is a compound of hydroxyl-terminated hyperbranched polyurethane, acrylic matte resin G600-3, and carboxyl-terminated hyperbranched polyester resin in a mass ratio of 0.3:1:3; wherein the composite curing agent is a compound of 1,3,5-triglycidyl-S-triazinetrione, β-hydroxyalkylamide, and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene in a mass ratio of 2:1:0.8.

[0026] The hydroxyl-terminated hyperbranched polyurethane is grade 2499, catalog number HXKJ2025, brand name Huaxiang Kejie, and is provided by Wuhan Huaxiang Kejie Biotechnology Co., Ltd.; the acrylic matting resin G600-3 is provided by Wuhan Yincai Technology Co., Ltd.; the β-hydroxyalkylamide is grade T105M and is provided by Ningbo Nanhai Chemical Co., Ltd.; the carboxyl-terminated hyperbranched polyester resin is a compound of carboxyl-terminated hyperbranched polyester resin HyPer C204 and carboxyl-terminated hyperbranched polyester resin HyPer C404 in a mass ratio of 1:0.8; the functional matting filler is a mixture of nano-silicon nitride, nano-titanium dioxide, and ultrafine barium sulfate in a mass ratio of 1:1:6; the average particle size of the nano-silicon nitride is 10 nm; the average particle size of the nano-titanium dioxide is 10 nm; and the average particle size of the ultrafine barium sulfate is 0.8 μm.

[0027] The matting agent is matting wax powder mju:Wax2739; the silane coupling agent is silane coupling agent KH550; the pigment and filler is rutile titanium dioxide with an average particle size of 0.2 μm; the synergistic component is boron nitride nanosheets with a sheet diameter of 1-2 μm and a sheet thickness of 10 nm; the functional additives are leveling agent, degassing agent, antioxidant, and light stabilizer compounded in a mass ratio of 0.8:0.3:0.3:0.5; the leveling agent is leveling agent GLP788; the degassing agent is benzoin; the antioxidant is antioxidant 1010; and the light stabilizer is BASF Tinuvin 770.

[0028] A method for preparing the aforementioned matte scratch-resistant powder coating composition includes the following steps: Step S1: Raw material premixing: Weigh the composite matrix resin, composite curing agent, functional matting filler, matting agent, silane coupling agent, pigments and fillers, synergistic components and functional additives according to the weight parts, put them into a high-speed mixer, and mix them at 800 r / min for 5 min at room temperature to obtain a uniform premixed material.

[0029] Step S2, Melt Extrusion: The premixed material is fed into a twin-screw extruder for melt extrusion. The temperature of the first zone of the extruder is controlled at 90℃, the temperature of the second zone is 100℃, the temperature of the third zone is 110℃, and the screw speed is 200r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S3, coarse crushing and fine grinding: The cooled flaky material is crushed into granules by a coarse crusher, and then the granules are fed into an ultra-fine pulverizer for fine grinding. The pulverizing speed is controlled at 3000 r / min. After pulverization, the material is passed through a 180-mesh standard sieve to obtain a semi-finished powder coating.

[0030] Step S4, Grading and Finished Product Collection: The semi-finished powder coating is fed into an air classifier for grading to remove excessively large particles and ultrafine dust. Powder with uniform particle size distribution is collected to obtain the matte scratch-resistant powder coating composition. Example 2

[0031] A matte, scratch-resistant powder coating composition is prepared from the following components in parts by weight: 55 parts of composite matrix resin, 4 parts of composite curing agent, 17 parts of functional matte filler, 2.5 parts of matte additive, 1.2 parts of silane coupling agent, 4 parts of pigments and fillers, 0.35 parts of synergistic components, and 3 parts of functional additives; wherein the composite matrix resin is a compound of hydroxyl-terminated hyperbranched polyurethane, acrylic matte resin G600-3, and carboxyl-terminated hyperbranched polyester resin in a mass ratio of 0.3:1:3.5; wherein the composite curing agent is a compound of 1,3,5-triglycidyl-S-triazinetrione, β-hydroxyalkylamide, and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene in a mass ratio of 2.3:1:0.9.

[0032] The hydroxyl-terminated hyperbranched polyurethane is grade 2499, catalog number HXKJ2025, brand name Huaxiang Kejie, and provided by Wuhan Huaxiang Kejie Biotechnology Co., Ltd.; the β-hydroxyalkylamide is grade T105M and provided by Ningbo Nanhai Chemical Co., Ltd.; the acrylic matting resin G600-3 is provided by Wuhan Yincai Technology Co., Ltd.; the carboxyl-terminated hyperbranched polyester resin is a compound of carboxyl-terminated hyperbranched polyester resin HyPer C204 and carboxyl-terminated hyperbranched polyester resin HyPer C404 in a mass ratio of 1:0.9; the functional matting filler is a mixture of nano-silicon nitride, nano-titanium dioxide, and ultrafine barium sulfate in a mass ratio of 1.3:1.3:6.5; the average particle size of the nano-silicon nitride is 30 nm; the average particle size of the nano-titanium dioxide is 30 nm; and the average particle size of the ultrafine barium sulfate is 1 μm.

[0033] The matting agent is matting wax powder mju:Wax2739; the silane coupling agent is silane coupling agent KH560; the pigment and filler is rutile titanium dioxide with an average particle size of 0.3 μm; the synergistic component is boron nitride nanosheets with a sheet diameter of 1-2 μm and a sheet thickness of 10 nm; the functional additives are leveling agent, degassing agent, antioxidant, and light stabilizer compounded in a mass ratio of 1:0.4:0.4:0.6; the leveling agent is leveling agent GLP788; the degassing agent is benzoin; the antioxidant is antioxidant 1010; and the light stabilizer is BASF Tinuvin 770.

[0034] A method for preparing the aforementioned matte scratch-resistant powder coating composition includes the following steps: Step S1, Raw material premixing: Weigh the composite matrix resin, composite curing agent, functional matting filler, matting aid, silane coupling agent, pigments and fillers, synergistic components and functional additives according to the weight parts, put them into a high-speed mixer, and mix them at 900 r / min for 6 minutes at room temperature to obtain a uniform premixed material.

[0035] Step S2, Melt Extrusion: The premixed material is fed into a twin-screw extruder for melt extrusion. The temperature of the first zone of the extruder is controlled at 93℃, the temperature of the second zone is 103℃, the temperature of the third zone is 113℃, and the screw speed is 250r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S3, coarse crushing and fine grinding: The cooled flaky material is crushed into granules by a coarse crusher, and then the granules are fed into an ultra-fine pulverizer for fine grinding. The pulverizing speed is controlled at 3500 r / min. After pulverization, the material is passed through a 190-mesh standard sieve to obtain a semi-finished powder coating.

[0036] Step S4, Grading and Finished Product Collection: The semi-finished powder coating is fed into an air classifier for grading to remove excessively large particles and ultrafine dust. Powder with uniform particle size distribution is collected to obtain the matte scratch-resistant powder coating composition. Example 3

[0037] A matte, scratch-resistant powder coating composition is prepared from the following components in parts by weight: 58 parts of composite matrix resin, 4.5 parts of composite curing agent, 20 parts of functional matte filler, 3 parts of matte additive, 1.5 parts of silane coupling agent, 6 parts of pigments and fillers, 0.4 parts of synergistic components, and 3.5 parts of functional additives; wherein the composite matrix resin is a compound of hydroxyl-terminated hyperbranched polyurethane, acrylic matte resin G600-3, and carboxyl-terminated hyperbranched polyester resin in a mass ratio of 0.3:1:4; wherein the composite curing agent is a compound of 1,3,5-triglycidyl-S-triazinetrione, β-hydroxyalkylamide, and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene in a mass ratio of 2.5:1:1.

[0038] The hydroxyl-terminated hyperbranched polyurethane is grade 2499, catalog number HXKJ2025, brand name Huaxiang Kejie, and provided by Wuhan Huaxiang Kejie Biotechnology Co., Ltd.; the β-hydroxyalkylamide is grade T105M and provided by Ningbo Nanhai Chemical Co., Ltd.; the acrylic matting resin G600-3 is provided by Wuhan Yincai Technology Co., Ltd.; the carboxyl-terminated hyperbranched polyester resin is a compound of carboxyl-terminated hyperbranched polyester resin HyPer C204 and carboxyl-terminated hyperbranched polyester resin HyPer C404 in a mass ratio of 1:1; the functional matting filler is a mixture of nano-silicon nitride, nano-titanium dioxide, and ultrafine barium sulfate in a mass ratio of 1.5:1.5:7; the average particle size of the nano-silicon nitride is 50 nm; the average particle size of the nano-titanium dioxide is 50 nm; and the average particle size of the ultrafine barium sulfate is 1.5 μm.

[0039] The matting agent is matting wax powder mju:Wax2739; the silane coupling agent is silane coupling agent KH570; the pigment and filler is rutile titanium dioxide with an average particle size of 0.35 μm; the synergistic component is boron nitride nanosheets with a sheet diameter of 1-2 μm and a sheet thickness of 10 nm; the functional additives are leveling agents, degassing agents, antioxidants, and light stabilizers compounded in a mass ratio of 1.2:0.6:0.5:0.65; the leveling agent is leveling agent GLP788; the degassing agent is benzoin; the antioxidant is antioxidant 1010; and the light stabilizer is BASF Tinuvin 770.

[0040] A method for preparing the aforementioned matte scratch-resistant powder coating composition includes the following steps: Step S1, Raw material premixing: Weigh the composite matrix resin, composite curing agent, functional matting filler, matting agent, silane coupling agent, pigments and fillers, synergistic components and functional additives according to the weight parts, put them into a high-speed mixer, and mix at 1000 r / min for 8 min at room temperature to obtain a uniform premixed material.

[0041] Step S2, Melt Extrusion: The premixed material is fed into a twin-screw extruder for melt extrusion. The temperature of the first zone of the extruder is controlled at 95℃, the temperature of the second zone is 105℃, the temperature of the third zone is 115℃, and the screw speed is 300r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S3, coarse crushing and fine grinding: The cooled flaky material is crushed into granules by a coarse crusher, and then the granules are fed into an ultra-fine pulverizer for fine grinding. The pulverizing speed is controlled at 4000 r / min. After pulverization, the material is passed through a 200-mesh standard sieve to obtain a semi-finished powder coating.

[0042] Step S4, Grading and Finished Product Collection: The semi-finished powder coating is fed into an air classifier for grading to remove excessively large particles and ultrafine dust. Powder with uniform particle size distribution is collected to obtain the matte scratch-resistant powder coating composition. Example 4

[0043] A matte, scratch-resistant powder coating composition is prepared from the following components in parts by weight: 62 parts of composite matrix resin, 5.5 parts of composite curing agent, 23 parts of functional matte filler, 3.5 parts of matte additive, 1.8 parts of silane coupling agent, 7 parts of pigments and fillers, 0.45 parts of synergistic components, and 4.5 parts of functional additives; wherein the composite matrix resin is a compound of hydroxyl-terminated hyperbranched polyurethane, acrylic matte resin G600-3, and carboxyl-terminated hyperbranched polyester resin in a mass ratio of 0.3:1:4.5; wherein the composite curing agent is a compound of 1,3,5-triglycidyl-S-triazinetrione, β-hydroxyalkylamide, and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene in a mass ratio of 2.8:1:1.1.

[0044] The hydroxyl-terminated hyperbranched polyurethane is grade 2499, catalog number HXKJ2025, brand name Huaxiang Kejie, and is provided by Wuhan Huaxiang Kejie Biotechnology Co., Ltd.; the β-hydroxyalkylamide is grade T105M and is provided by Ningbo Nanhai Chemical Co., Ltd.; the acrylic matting resin G600-3 is provided by Wuhan Yincai Technology Co., Ltd.; the carboxyl-terminated hyperbranched polyester resin is a compound of carboxyl-terminated hyperbranched polyester resin HyPer C204 and carboxyl-terminated hyperbranched polyester resin HyPer C404 in a mass ratio of 1:1.1; the functional matting filler is a mixture of nano-silicon nitride, nano-titanium dioxide, and ultrafine barium sulfate in a mass ratio of 1.8:2:7.5; the average particle size of the nano-silicon nitride is 60 nm; the average particle size of the nano-titanium dioxide is 60 nm; and the average particle size of the ultrafine barium sulfate is 1.8 μm.

[0045] The matting agent is matting wax powder mju:Wax2739; the silane coupling agent is a mixture of silane coupling agents KH550, KH560, and KH570 in a mass ratio of 1:1:2; the pigment / filler is rutile titanium dioxide with an average particle size of 0.45 μm; the synergistic component is boron nitride nanosheets with a diameter of 1-2 μm and a thickness of 10 nm; the functional additives are a mixture of leveling agent, degassing agent, antioxidant, and light stabilizer in a mass ratio of 1.3:0.7:0.6:0.75; the leveling agent is leveling agent GLP788; the degassing agent is benzoin; the antioxidant is antioxidant 1010; and the light stabilizer is BASF Tinuvin 770.

[0046] A method for preparing the aforementioned matte scratch-resistant powder coating composition includes the following steps: Step S1: Raw material premixing: Weigh the composite matrix resin, composite curing agent, functional matting filler, matting agent, silane coupling agent, pigments and fillers, synergistic components and functional additives according to the weight parts, put them into a high-speed mixer, and mix them at 1100 r / min for 9 min at room temperature to obtain a uniform premixed material.

[0047] Step S2, Melt Extrusion: The premixed material is fed into a twin-screw extruder for melt extrusion. The temperature of the first zone of the extruder is controlled at 98℃, the temperature of the second zone is 108℃, the temperature of the third zone is 118℃, and the screw speed is 350r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S3, coarse crushing and fine grinding: The cooled flaky material is crushed into granules by a coarse crusher, and then the granules are fed into an ultra-fine pulverizer for fine grinding. The pulverizing speed is controlled at 4500 r / min. After pulverization, the material is passed through a 210-mesh standard sieve to obtain a semi-finished powder coating.

[0048] Step S4, Grading and Finished Product Collection: The semi-finished powder coating is fed into an air classifier for grading to remove excessively large particles and ultrafine dust. Powder with uniform particle size distribution is collected to obtain the matte scratch-resistant powder coating composition. Example 5

[0049] A matte, scratch-resistant powder coating composition is prepared from the following components in parts by weight: 65 parts of composite matrix resin, 6 parts of composite curing agent, 25 parts of functional matte filler, 4 parts of matte additive, 2 parts of silane coupling agent, 8 parts of pigments and fillers, 0.5 parts of synergistic components, and 5 parts of functional additives; wherein the composite matrix resin is a compound of hydroxyl-terminated hyperbranched polyurethane, acrylic matte resin G600-3, and carboxyl-terminated hyperbranched polyester resin in a mass ratio of 0.3:1:5; wherein the composite curing agent is a compound of 1,3,5-triglycidyl-S-triazinetrione, β-hydroxyalkylamide, and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene in a mass ratio of 3:1:1.2.

[0050] The hydroxyl-terminated hyperbranched polyurethane is grade 2499, catalog number HXKJ2025, brand name Huaxiang Kejie, and provided by Wuhan Huaxiang Kejie Biotechnology Co., Ltd.; the β-hydroxyalkylamide is grade T105M and provided by Ningbo Nanhai Chemical Co., Ltd.; the acrylic matting resin G600-3 is provided by Wuhan Yincai Technology Co., Ltd.; the carboxyl-terminated hyperbranched polyester resin is a compound of carboxyl-terminated hyperbranched polyester resin HyPer C204 and carboxyl-terminated hyperbranched polyester resin HyPer C404 in a mass ratio of 1:1.2; the functional matting filler is a mixture of nano-silicon nitride, nano-titanium dioxide, and ultrafine barium sulfate in a mass ratio of 2:2:8; the average particle size of the nano-silicon nitride is 70 nm; the average particle size of the nano-titanium dioxide is 70 nm; and the average particle size of the ultrafine barium sulfate is 2 μm.

[0051] The matting agent is matting wax powder mju:Wax2739; the silane coupling agent is silane coupling agent KH550; the pigment and filler is rutile titanium dioxide with an average particle size of 0.5 μm; the synergistic component is boron nitride nanosheets with a sheet diameter of 1-2 μm and a sheet thickness of 10 nm; the functional additives are leveling agents, degassing agents, antioxidants, and light stabilizers compounded in a mass ratio of 1.5:0.8:0.7:0.8; the leveling agent is leveling agent GLP788; the degassing agent is benzoin; the antioxidant is antioxidant 1010; and the light stabilizer is BASF Tinuvin 770.

[0052] A method for preparing the aforementioned matte scratch-resistant powder coating composition includes the following steps: Step S1: Raw material premixing: Weigh the composite matrix resin, composite curing agent, functional matting filler, matting agent, silane coupling agent, pigments and fillers, synergistic components and functional additives according to the weight parts, put them into a high-speed mixer, and mix them at 1200 r / min for 10 min at room temperature to obtain a uniform premixed material.

[0053] Step S2, Melt Extrusion: The premixed material is fed into a twin-screw extruder for melt extrusion. The temperature of the first zone of the extruder is controlled at 100℃, the temperature of the second zone is 110℃, the temperature of the third zone is 120℃, and the screw speed is 400r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S3, coarse crushing and fine grinding: The cooled flaky material is crushed into granules by a coarse crusher, and then the granules are fed into an ultra-fine pulverizer for fine grinding. The pulverizing speed is controlled at 5000 r / min. After pulverization, the material is passed through a 220-mesh standard sieve to obtain a semi-finished powder coating.

[0054] Step S4, Grading and Finished Product Collection: The semi-finished powder coating is fed into an air classifier for grading to remove excessively large particles and ultrafine dust. Powder with uniform particle size distribution is collected to obtain the matte scratch-resistant powder coating composition.

[0055] Comparative Example 1 A matte, scratch-resistant powder coating composition and its preparation method are basically the same as those in Example 5, except that an equal amount of 1,3,5-triglycidyl-S-triazine trione is used instead of 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene.

[0056] Comparative Example 2 A matte, scratch-resistant powder coating composition and its preparation method are basically the same as those in Example 5, except that an equal amount of 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene is used instead of 1,3,5-triglycidyl-S-triazinetrione.

[0057] Comparative Example 3 A matte scratch-resistant powder coating composition and its preparation method are basically the same as those in Example 5, except that an equal amount of terminal hydroxyl hyperbranched polyurethane is used instead of terminal carboxyl hyperbranched polyester resin.

[0058] Comparative Example 4 A matte scratch-resistant powder coating composition and its preparation method are basically the same as those in Example 5, except that an equal amount of end-carboxyl hyperbranched polyester resin is used instead of end-hydroxyl hyperbranched polyurethane.

[0059] Comparative Example 5 A matte scratch-resistant powder coating composition and its preparation method are basically the same as those in Example 5, except that an equal amount of functional matte filler is used to replace the synergistic components.

[0060] The matte scratch-resistant powder coating compositions prepared in Example 5 and Comparative Examples 1-5 were subjected to performance testing. The test results are shown in Table 1. The test methods are as follows: The powder coating compositions of each example were electrostatically sprayed using a corona discharge spray gun with the following parameters: voltage 70kV, spray distance 25cm, and powder application rate 90g / m². After spraying, the coating was placed in a constant temperature oven for step curing. The oven was preheated at 160℃ for 3 minutes, then heated to 180℃ and held for 12 minutes. After curing, the coating was obtained, and the dry film thickness of the coating was controlled at 60μm.

[0061] The cured coating was subjected to the following performance tests, and the test methods and reference national standards are as follows: 1. Gloss (60°): The test was conducted in accordance with GB / T 9754-2017 "Determination of 20°, 60° and 85° specular gloss of paint films without metallic pigments". The test temperature was 25°C and the humidity was 50%RH. Five points were tested for each sample and the average value was taken. The lower the gloss, the better the matting effect. 2. Scratch resistance: Tested according to GB / T 31591-2015 "Determination of scratch resistance of paints and varnishes", using steel wool (#0000), load 500g, 50 reciprocating rubs, rubbing speed 100mm / min, rubbing distance 50mm; test the gloss change rate at the scratch (gloss at 60° after scratch / gloss at 60° before scratch × 100%). 3. Adhesion (cross-cut test): The test is conducted in accordance with GB / T 9286-2021 "Paints and Varnishes Cross-cut Test". A 1mm×1mm grid is used. After the grid is drawn, 3M tape is applied and then the coating is peeled off to observe the coating peeling.

[0062] 4. Weather resistance (UVB-313 aging test): The test was conducted in accordance with GB / T 16422.3-2014 "Plastics Laboratory Light Source Exposure Test Part 3: Fluorescent Ultraviolet Lamp", with an aging time of 350h. The gloss retention rate of the coating after aging was tested (60° gloss after aging / 60° gloss before aging × 100%).

[0063] Table 1. Performance test results of matte scratch-resistant powder coating compositions unit % % class % Example 5 10.5 96.2 0 92.4 Comparative Example 1 25.8 86.8 1 84.9 Comparative Example 2 22.0 90.0 1 88.2 Comparative Example 3 30.3 82.8 2 79.9 Comparative Example 4 19.1 91.1 1 88.0 Comparative Example 5 16.4 81.7 1 84.1 As shown in Table 1, the matte scratch-resistant powder coating composition of Example 5 exhibits the best overall performance, with the lowest 60° gloss (10.5%), the highest scratch resistance (96.2%) and weather resistance (92.4%), and the best adhesion grade (0). Comparative Examples 1-5, due to the replacement of key components in Example 5, all showed decreased matte effect, reduced scratch resistance or weather resistance, and lower adhesion grade, resulting in overall performance inferior to Example 5. Therefore, the combined use of 1,3,5-triglycidyl-S-triazinetrione, 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene, hydroxyl-terminated hyperbranched polyurethane, carboxyl-terminated hyperbranched polyester resin, and synergistic components is beneficial for improving the aforementioned performance.

[0064] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A matte, scratch-resistant powder coating composition, characterized in that, It is prepared from the following components in parts by weight: 50-65 parts of composite matrix resin, 3-6 parts of composite curing agent, 15-25 parts of functional matting filler, 2-4 parts of matting aid, 1-2 parts of silane coupling agent, 3-8 parts of pigments and fillers, 0.3-0.5 parts of synergistic components, and 2-5 parts of functional aids; the composite matrix resin is a compound of hydroxyl-terminated hyperbranched polyurethane, acrylic matting resin G600-3, and carboxyl-terminated hyperbranched polyester resin in a mass ratio of 0.3:1:(3-5); the composite curing agent is a compound of 1,3,5-triglycidyl-S-triazinetrione, β-hydroxyalkylamide, and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene in a mass ratio of (2-3):1:(0.8-1.2).

2. The matte, scratch-resistant powder coating composition according to claim 1, characterized in that, The end-carboxyl hyperbranched polyester resin is a compound of end-carboxyl hyperbranched polyester resin HyPer C204 and end-carboxyl hyperbranched polyester resin HyPer C404 in a mass ratio of 1:(0.8-1.2); the β-hydroxyalkylamide is designated as T105M.

3. The matte, scratch-resistant powder coating composition according to claim 1, characterized in that, The functional matting filler is a mixture of nano silicon nitride, nano titanium dioxide and ultrafine barium sulfate, with a mass ratio of (1-2):(1-2):(6-8).

4. The matte, scratch-resistant powder coating composition according to claim 3, characterized in that, The average particle size of the nano-silicon nitride is 10-70 nm; the average particle size of the nano-titanium dioxide is 10-70 nm; and the average particle size of the ultrafine barium sulfate is 0.8-2 μm.

5. The matte, scratch-resistant powder coating composition according to claim 1, characterized in that, The matting agent is matting wax powder mju:Wax2739; the silane coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570.

6. The matte scratch-resistant powder coating composition according to claim 1, characterized in that, The pigment / filler is rutile titanium dioxide with an average particle size of 0.2-0.5 μm.

7. The matte, scratch-resistant powder coating composition according to claim 1, characterized in that, The synergistic component is boron nitride nanosheets with a diameter of 1-2 μm and a thickness of 10 nm.

8. The matte scratch-resistant powder coating composition according to claim 1, characterized in that, The functional additives are leveling agents, degassing agents, antioxidants, and light stabilizers compounded in a mass ratio of (0.8-1.5):(0.3-0.8):(0.3-0.7):(0.5-0.8).

9. The matte, scratch-resistant powder coating composition according to claim 8, characterized in that, The leveling agent is leveling agent GLP788; the degassing agent is benzoin; the antioxidant is antioxidant 1010; and the light stabilizer is BASF Tinuvin 770.

10. A method for preparing a matte, scratch-resistant powder coating composition according to any one of claims 1-9, characterized in that, The steps include the following: Step S1, Raw material premixing: Weigh the composite matrix resin, composite curing agent, functional matting filler, matting agent, silane coupling agent, pigments and fillers, synergistic components and functional additives according to the weight parts, put them into a high-speed mixer, and mix at a speed of 800-1200 r / min for 5-10 min at room temperature to obtain a uniform premixed material. Step S2, Melt Extrusion: The premixed material is fed into a twin-screw extruder for melt extrusion. The temperature of the first zone of the extruder is controlled at 90-100℃, the temperature of the second zone is 100-110℃, and the temperature of the third zone is 110-120℃. The screw speed is 200-400 r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S3, coarse crushing and fine grinding: The cooled flaky material is crushed into granules by a coarse crusher, and then the granules are fed into an ultra-fine pulverizer for fine grinding. The pulverizing speed is controlled at 3000-5000 r / min. After pulverization, the material is passed through a 180-220 mesh standard sieve to obtain a semi-finished powder coating product. Step S4, Grading and Finished Product Collection: The semi-finished powder coating is fed into an air classifier for grading to remove excessively large particles and ultrafine dust. Powder with uniform particle size distribution is collected to obtain the matte scratch-resistant powder coating composition.