Preparation method of environment-friendly outdoor matt powder coating

Abstract

The application discloses a preparation method of an environment-friendly outdoor non-gloss powder coating, relates to the technical field of powder coating, and comprises the steps of HAA microcapsule preparation, raw material premixing, melt extrusion, tabletting, crushing and micro-powder grading. First, a HAA microcapsule is prepared from a hydroxyalkyl amide curing agent, epoxidized soybean oil acrylate, silane coupling agent KH570 and the like; then, after premixing the HAA microcapsule with a polyester matrix, a matt resin, functional fillers and functional additives, the mixture is subjected to melt extrusion, crushing and grading to obtain a finished product. The coating prepared by the method has low 60-degree gloss, high corrosion resistance, excellent adhesion and good weather resistance, and is suitable for outdoor scenes.

Description

Technical Field

[0001] This invention relates to the field of powder coating technology, and in particular to a method for preparing an environmentally friendly outdoor matte powder coating. Background Technology

[0002] Powder coatings, as an environmentally friendly coating material, have advantages such as solvent-free pollution, high coating efficiency, and easy film thickness control, and have been widely used in outdoor facilities, building materials, and household appliances. With the increasing aesthetic demand for matte finishes on building exteriors and the ever-increasing requirements for weather resistance in outdoor applications, the development of high-performance outdoor matte powder coatings has become an important research direction in the industry.

[0003] Existing outdoor matte powder coatings suffer from two main problems: First, insufficient environmental friendliness. Some products, in pursuit of matting effects and weather resistance, use raw materials containing heavy metals, harmful additives, or volatile organic compounds, failing to meet modern environmental protection requirements. Furthermore, some matting agents contain cyclopentadiene compounds, which can easily lead to yellowing of the coating and poor baking resistance. Second, it is difficult to balance matting effect with overall performance. Most matte powder coatings achieve matting by adding large amounts of inorganic matting agents (such as ordinary talc and silica). However, excessive addition can significantly reduce the mechanical properties (such as adhesion and impact strength) and weather resistance of the coating, making it prone to cracking and peeling. Resin-modified matting methods often involve complex processes, unstable matting effects, and high production costs, and are difficult to adapt to highly corrosive outdoor environments with strong ultraviolet radiation. Especially in C4 and higher highly corrosive environments, the coating's salt spray resistance is often substandard.

[0004] To address the aforementioned issues, invention patent document CN101787239B discloses a method for preparing an environmentally friendly outdoor matte powder coating resin. This method utilizes a combination of polyester resin and acrylic resin to manufacture outdoor matte powder coatings. This method eliminates the need for additional matting agents and avoids the additional dry-mixing matting step required for two-component powder coatings. Instead, it utilizes the immiscibility of polyester resin and acrylic resin, and the network interpenetration formed between their molecular structures during the curing reaction, to create a microscopically uneven coating film, achieving the matte finish. By mixing resin A with resin B, additives, pigments, and fillers, and then melting and extruding, an outdoor matte powder coating with a gloss level below 10% can be obtained. The powder coating made from the carboxyl-terminated polyester resin A and glycidyl acrylic resin B of this invention exhibits excellent chemical resistance, excellent weather resistance, good powder storage stability, and impact resistance. However, this method still has certain limitations in practical applications. For example, the ratio of polyester resin to acrylic resin needs to be precisely controlled to maintain the stability of the coating performance, and the anti-aging performance and corrosion resistance for long-term use in complex outdoor environments still need to be further improved.

[0005] Therefore, it is particularly important to seek more effective methods to prepare an environmentally friendly outdoor matte powder coating with good weather resistance, excellent corrosion resistance, safe and environmentally friendly use, and significant matting effect. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method for preparing an environmentally friendly outdoor matte powder coating. The outdoor matte powder coating prepared by this method has good weather resistance, excellent corrosion resistance, is safe and environmentally friendly to use, and has a significant matting effect.

[0007] To achieve the above objectives, this invention provides a method for preparing an environmentally friendly outdoor matte powder coating, comprising the following steps: Step S1, Preparation of HAA microcapsules: Place the β-hydroxyalkylamide curing agent in a vacuum drying oven and dry for 2-3 hours at 78-82℃ and a vacuum of -0.08 to -0.09 MPa; place the epoxidized soybean oil acrylate in a constant temperature water bath, heat to 48-52℃, stir at 280-320 rpm, and hold for 28-32 minutes; then mix the β-hydroxyalkylamide curing agent and epoxidized soybean oil acrylate, pour into a high-speed disperser, and adjust the speed to 1000-1300 rpm. The mixture was dispersed at 23-25℃ for 55-65 min; then silane coupling agent KH570 was added, the stirring speed was adjusted to 750-850 rpm, and the constant temperature water bath was heated to 60-70℃ and stirred for 25-35 min; then azobisisobutyronitrile was added, stirred evenly, and the reaction was continued at 60-70℃ for 18-22 min; finally, the mixture was centrifuged and dried at 68-72℃ and vacuum degree -0.08 to -0.09 MPa for 3-5 h to obtain HAA microcapsules. Step S2, Raw material premixing: The polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additives, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate are sequentially added into a high-speed mixer and mixed at 800-1200 r / min for 3-5 min at room temperature to obtain a uniform premixed material. Step S3, 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 250-300 r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S4, Crushing: Feed the flaky material into the crusher, adjust the crusher speed to 1400-1600 rpm, and crush it into coarse powder with a particle size of <5mm. Step S5, Micronization: The coarse powder is fed into an ACM mill for pulverization and classification, and the fine powder with a particle size of 25-45μm is collected by a cyclone separator.

[0008] Preferably, the mass ratio of β-hydroxyalkylamide curing agent, epoxidized soybean oil acrylate, silane coupling agent KH570, and azobisisobutyronitrile in step S1 is 3:1:(0.04-0.08):(0.02-0.04).

[0009] Preferably, the β-hydroxyalkylamide curing agent is grade T105M and is provided by Ningbo Nanhai Chemical Co., Ltd.

[0010] Preferably, the mass ratio of the polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additive, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate in step S2 is (60-65):(8-10):(5-7):(10-15):(3-5):(2-4):0.3:(0.8-1.2).

[0011] Preferably, the polyester matrix in step S2 is a compound of carboxyl-type fluorinated polyester, end-carboxyl hyperbranched long-chain aromatic polyester, and carboxyl polyester resin REAFREE® 6419 in a mass ratio of 1:(0.8-1.2):(3-5).

[0012] Preferably, there are no special requirements for the source of the carboxyl-type fluorinated polyester. In one embodiment of the present invention, the carboxyl-type fluorinated polyester is prepared according to the preparation method of carboxyl-type fluorinated polyester in Example 6 of CN113736350B.

[0013] Preferably, the end-carboxyl hyperbranched long-chain aromatic polyester is of type HyPer C302, provided by Wuhan Hyperbranched Resin Technology Co., Ltd.

[0014] Preferably, the functional filler is a compound of barium sulfate, rutile titanium dioxide, lignin, and shell powder in a mass ratio of 1:(2-3):(0.5-0.8):(0.8-1.2).

[0015] Preferably, the average particle size of the functional filler is 3-8 μm.

[0016] Preferably, the functional additives are light stabilizers, antioxidants, coupling agents, degassing agents, leveling agents, and matting wax powder compounded in a mass ratio of (1-1.2):(0.8-1.2):(3-5):1:(0.8-1.2):(1-2).

[0017] Preferably, the light stabilizer is UV-1577, the antioxidant is antioxidant 1010, the coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570, the degassing agent is benzoin, the leveling agent is leveling agent GLP788, and the matting wax powder is matting wax powder mju:Wax2739.

[0018] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The preparation method of the environmentally friendly outdoor matte powder coating disclosed in this invention achieves a triple breakthrough in environmental protection, matting stability and weather resistance through the synergistic effect of HAA microcapsules and compound polyester matrix, solving the core pain points of "matting and weather resistance cannot be taken into account" and "environmental protection and performance are mutually restrictive" in the prior art. In this solution, HAA microcapsules are modified by epoxidized soybean oil acrylate coating and interface modification with silane coupling agent KH570. This not only completely eliminates harmful matting additives containing heavy metals and cyclopentadiene, achieving all-environmentally friendly raw materials, but also forms a stable network interpenetrating structure with the compound system of carboxyl-type fluorinated polyester, end-carboxyl hyperbranched long-chain aromatic polyester and REAFREE® 6419. The microcapsules slowly release curing agent and react precisely with the carboxyl groups of the polyester matrix. This avoids the problems of complex matting process and unstable effect of traditional resin modification. Furthermore, through the weather resistance of fluorinated groups and the compatibility of hyperbranched structure, the coating's resistance to ultraviolet aging is synergistically improved, breaking through the single-function limitation of traditional microcapsules that can only improve curing uniformity. Microcapsules control the release rate of HAA, creating a curing rate difference between it and the fast-reacting curing system, resulting in microscopic phase separation and achieving internal matting, thus breaking through the technical bottleneck that "matting inevitably reduces weather resistance".

[0019] (2) The preparation method of the environmentally friendly outdoor matte powder coating disclosed in this invention, through the synergistic compounding of functional fillers and functional additives, solves the industry problem of decreased mechanical properties and corrosion resistance caused by excessive addition of inorganic matting agents, and achieves synergistic improvement of matting effect and comprehensive protective performance. This solution employs a compound functional filler consisting of barium sulfate, rutile titanium dioxide, lignin, and shell powder. The UV resistance of rutile titanium dioxide and lignin, combined with the matting effect of lignin, replaces the use of large amounts of traditional inorganic matting agents. Simultaneously, the porous structure of shell powder adsorbs functional additives, forming a synergistic protective system with the light stabilizer UV-1577, antioxidant 1010, and composite silane coupling agent. The coupling agent enhances the interfacial bonding between the filler and the resin matrix, preventing coating cracking and peeling. The light stabilizer and antioxidant synergistically inhibit UV-induced degradation reactions, while the shell powder enhances the coating's breathability and waterproofness. Under the synergistic effect of these three components, the coating's salt spray resistance and impact strength are significantly improved, and adhesion reaches grade 0. This completely solves the industry bottleneck of "matting inevitably reducing performance," resulting in a more significant matting effect and superior corrosion resistance compared to traditional inorganic matting solutions.

[0020] (3) The preparation method of the environmentally friendly outdoor matte powder coating disclosed in this invention is precisely matched with the preparation process of HAA microcapsules and the subsequent melt extrusion and micro powder classification process, which can avoid microcapsule breakage during extrusion. At the same time, the melt viscosity of the compounded polyester matrix is ​​coordinated with the temperature and speed parameters of the twin-screw extrusion, which reduces the extrusion energy consumption and significantly improves the production efficiency compared with the traditional resin-modified matte process. In addition, the synergistic crosslinking effect of BMI-7000, tert-butyl peroxide and triallyl isocyanurate further strengthens the crosslinking density of the coating and forms a multi-component synergistic network with other components. This not only improves the baking resistance of the coating (avoiding yellowing and discoloration) but also enhances the long-term stability of the coating in complex outdoor environments (high temperature, high humidity and high corrosion), filling the application gap of existing outdoor matte powder coatings in highly corrosive environments. Detailed Implementation

[0021] 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

[0022] A method for preparing an environmentally friendly outdoor matte powder coating includes the following steps: Step S1, Preparation of HAA microcapsules: β-hydroxyalkylamide curing agent was placed in a vacuum drying oven and dried at 78℃ and -0.08MPa for 2 hours; epoxidized soybean oil acrylate was placed in a constant temperature water bath, heated to 48℃, stirred at 280 rpm, and kept at this temperature for 28 minutes; then, β-hydroxyalkylamide curing agent and epoxidized soybean oil acrylate were mixed, poured into a high-speed disperser, and dispersed at 23℃ for 55 minutes at 1000 rpm; subsequently, silane coupling agent KH570 was added, the stirring speed was adjusted to 750 rpm, and the constant temperature water bath was heated to 60℃ and stirred for 25 minutes; then, azobisisobutyronitrile was added, stirred evenly, and the reaction was continued at 60℃ for 18 minutes; finally, the mixture was centrifuged and dried at 68℃ and -0.08MPa for 3 hours to obtain HAA microcapsules. Step S2, Raw material premixing: The polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additives, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate are sequentially added to a high-speed mixer and mixed at 800 r / min for 3 min at room temperature to obtain a uniform premixed material. Step S3, 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 250r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S4, Crushing: Feed the flaky material into the crusher, adjust the crusher speed to 1400 rpm, and crush it into coarse powder with a particle size of <5mm. Step S5, Micronization: The coarse powder is fed into an ACM mill for pulverization and classification, and the fine powder with a particle size of 25μm is collected by a cyclone separator.

[0023] In step S1, the mass ratio of β-hydroxyalkylamide curing agent, epoxidized soybean oil acrylate, silane coupling agent KH570, and azobisisobutyronitrile is 3:1:0.04:0.02; the β-hydroxyalkylamide curing agent is of brand T105M and is provided by Ningbo Nanhai Chemical Co., Ltd.; in step S2, the mass ratio of polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additives, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate is 60:8:5:10:3:2:0.3:0.8.

[0024] The polyester matrix in step S2 is a compound of carboxyl-type fluorinated polyester, end-carboxyl hyperbranched long-chain aromatic polyester, and carboxyl polyester resin REAFREE® 6419 in a mass ratio of 1:0.8:3; the carboxyl-type fluorinated polyester is prepared according to the preparation method of carboxyl-type fluorinated polyester in Example 6 of CN113736350B; the end-carboxyl hyperbranched long-chain aromatic polyester is of type HyPer C302 and is provided by Wuhan Hyperbranched Resin Technology Co., Ltd.

[0025] The functional filler is a compound of barium sulfate, rutile titanium dioxide, lignin, and shell powder in a mass ratio of 1:2:0.5:0.8; the average particle size of the functional filler is 3 μm; the functional additives are a compound of light stabilizer, antioxidant, coupling agent, degassing agent, leveling agent, and matting wax powder in a mass ratio of 1:0.8:3:1:0.8:1; the light stabilizer is UV-1577, the antioxidant is antioxidant 1010, the coupling agent is silane coupling agent KH550, the degassing agent is benzoin, the leveling agent is leveling agent GLP788, and the matting wax powder is matting wax powder mju:Wax2739. Example 2

[0026] A method for preparing an environmentally friendly outdoor matte powder coating includes the following steps: Step S1, Preparation of HAA microcapsules: β-hydroxyalkylamide curing agent was placed in a vacuum drying oven and dried at 79℃ and -0.083MPa for 2.3h; epoxidized soybean oil acrylate was placed in a constant temperature water bath, heated to 49℃, stirred at 290rpm, and kept at this temperature for 29min; then, β-hydroxyalkylamide curing agent and epoxidized soybean oil acrylate were mixed and poured into a high-speed disperser, the speed was adjusted to 1100rpm, and dispersed at 23.5℃ for 58min; then, silane coupling agent KH570 was added, the stirring speed was adjusted to 770rpm, and the constant temperature water bath was heated to 63℃ and kept at this temperature for 27min; then, azobisisobutyronitrile was added, stirred evenly, and the reaction was continued at 63℃ for 19min; finally, the mixture was centrifuged and dried at 69℃ and -0.083MPa for 3.5h to obtain HAA microcapsules. Step S2, Raw material premixing: The polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additives, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate are sequentially added to a high-speed mixer and mixed at 900 r / min for 3.5 min at room temperature to obtain a uniform premixed material. Step S3, 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 102℃, the temperature of the third zone is 113℃, and the screw speed is 260r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S4, Crushing: Feed the flaky material into the crusher, adjust the crusher speed to 1450 rpm, and crush it into coarse powder with a particle size of <5mm. Step S5, Micronization: The coarse powder is fed into an ACM mill for pulverization and classification, and the fine powder with a particle size of 30μm is collected by a cyclone separator.

[0027] In step S1, the mass ratio of the β-hydroxyalkylamide curing agent, epoxidized soybean oil acrylate, silane coupling agent KH570, and azobisisobutyronitrile is 3:1:0.05:0.025; the β-hydroxyalkylamide curing agent is brand T105M and is provided by Ningbo Nanhai Chemical Co., Ltd.; in step S2, the polyester matrix, matting curing agent XG665, HAA microcapsules, functional fillers, functional additives, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate... The mass ratio is 62:8.5:5.5:12:3.5:2.5:0.3:0.9; the polyester matrix in step S2 is a compound of carboxyl-type fluorinated polyester, end-carboxyl hyperbranched long-chain aromatic polyester, and carboxyl polyester resin REAFREE® 6419 in a mass ratio of 1:0.9:3.5; the carboxyl-type fluorinated polyester is prepared according to the preparation method of carboxyl-type fluorinated polyester in Example 6 of CN113736350B; the end-carboxyl hyperbranched long-chain aromatic polyester is HyPer C302, provided by Wuhan Hyperbranched Resin Technology Co., Ltd.

[0028] The functional filler is a compound of barium sulfate, rutile titanium dioxide, lignin, and shell powder in a mass ratio of 1:2.3:0.6:0.9; the average particle size of the functional filler is 4 μm; the functional additives are a compound of light stabilizer, antioxidant, coupling agent, degassing agent, leveling agent, and matting wax powder in a mass ratio of 1.1:0.9:3.5:1:0.9:1.2; the light stabilizer is UV-1577, the antioxidant is antioxidant 1010, the coupling agent is silane coupling agent KH560, the degassing agent is benzoin, the leveling agent is leveling agent GLP788, and the matting wax powder is matting wax powder mju:Wax2739. Example 3

[0029] A method for preparing an environmentally friendly outdoor matte powder coating includes the following steps: Step S1, Preparation of HAA microcapsules: β-hydroxyalkylamide curing agent was placed in a vacuum drying oven and dried at 80℃ and -0.085MPa for 2.5h; epoxidized soybean oil acrylate was placed in a constant temperature water bath, heated to 50℃, stirred at 300rpm, and kept at this temperature for 30min; then, β-hydroxyalkylamide curing agent and epoxidized soybean oil acrylate were mixed and poured into a high-speed disperser, the speed was adjusted to 1150rpm, and dispersed at 24℃ for 60min; then, silane coupling agent KH570 was added, the stirring speed was adjusted to 800rpm, and the constant temperature water bath was heated to 65℃ and kept at this temperature for 30min; then, azobisisobutyronitrile was added, stirred evenly, and the reaction was continued at 65℃ for 20min; finally, the mixture was centrifuged and dried at 70℃ and -0.085MPa for 4h to obtain HAA microcapsules. Step S2, Raw material premixing: The polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additives, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate are sequentially added to a high-speed mixer and mixed at 1000 r / min for 4 min at room temperature to obtain a uniform premixed material. Step S3, 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 280r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S4, Crushing: Feed the flaky material into the crusher, adjust the crusher speed to 1500 rpm, and crush it into coarse powder with a particle size of <5mm. Step S5, Micronization: The coarse powder is fed into an ACM mill for pulverization and classification, and the fine powder with a particle size of 35μm is collected by a cyclone separator.

[0030] In step S1, the mass ratio of β-hydroxyalkylamide curing agent, epoxidized soybean oil acrylate, silane coupling agent KH570, and azobisisobutyronitrile is 3:1:0.06:0.03; the β-hydroxyalkylamide curing agent is brand T105M and is provided by Ningbo Nanhai Chemical Co., Ltd.; in step S2, the mass ratio of polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additives, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate is 63:9:6:13:4:3:0.3:1.

[0031] The polyester matrix in step S2 is a compound of carboxyl-type fluorinated polyester, end-carboxyl hyperbranched long-chain aromatic polyester, and carboxyl polyester resin REAFREE® 6419 in a mass ratio of 1:1:4; the carboxyl-type fluorinated polyester is prepared according to the preparation method of carboxyl-type fluorinated polyester in Example 6 of CN113736350B; the end-carboxyl hyperbranched long-chain aromatic polyester is of type HyPer C302 and is provided by Wuhan Hyperbranched Resin Technology Co., Ltd.

[0032] The functional filler is a compound of barium sulfate, rutile titanium dioxide, lignin, and shell powder in a mass ratio of 1:2.5:0.65:1; the average particle size of the functional filler is 5 μm; the functional additives are a compound of light stabilizer, antioxidant, coupling agent, degassing agent, leveling agent, and matting wax powder in a mass ratio of 1.1:1:4:1:1:1.5; the light stabilizer is UV-1577, the antioxidant is antioxidant 1010, the coupling agent is silane coupling agent KH570, the degassing agent is benzoin, the leveling agent is leveling agent GLP788, and the matting wax powder is matting wax powder mju:Wax2739. Example 4

[0033] A method for preparing an environmentally friendly outdoor matte powder coating includes the following steps: Step S1, Preparation of HAA microcapsules: β-hydroxyalkylamide curing agent was placed in a vacuum drying oven and dried at 81℃ and -0.088MPa for 2.8h; epoxidized soybean oil acrylate was placed in a constant temperature water bath, heated to 51℃, stirred at 310rpm, and kept at this temperature for 31min; then, β-hydroxyalkylamide curing agent and epoxidized soybean oil acrylate were mixed and poured into a high-speed disperser, and dispersed at 24.5℃ for 63min at a speed of 1250rpm; subsequently, silane coupling agent KH570 was added, the stirring speed was adjusted to 840rpm, and the constant temperature water bath was heated to 68℃ and kept at this temperature for 33min; then, azobisisobutyronitrile was added, stirred evenly, and the reaction was continued at 68℃ for 21min; finally, the mixture was centrifuged and dried at 71℃ and -0.088MPa for 4.5h to obtain HAA microcapsules. Step S2, Raw material premixing: The polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additives, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate are sequentially added to a high-speed mixer and mixed at 1100 r / min for 4.5 min at room temperature to obtain a uniform premixed material. Step S3, 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 290r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S4, Crushing: Feed the flaky material into the crusher, adjust the crusher speed to 1550 rpm, and crush it into coarse powder with a particle size of <5mm. Step S5, Micronization: The coarse powder is fed into an ACM mill for pulverization and classification, and the fine powder with a particle size of 40μm is collected by a cyclone separator.

[0034] In step S1, the mass ratio of β-hydroxyalkylamide curing agent, epoxidized soybean oil acrylate, silane coupling agent KH570, and azobisisobutyronitrile is 3:1:0.07:0.035; the β-hydroxyalkylamide curing agent is brand T105M and is provided by Ningbo Nanhai Chemical Co., Ltd.; in step S2, the mass ratio of polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additives, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate is 64:9.5:6.5:14:4.5:3.5:0.3:1.1.

[0035] The polyester matrix in step S2 is a compound of carboxyl-type fluorinated polyester, end-carboxyl hyperbranched long-chain aromatic polyester, and carboxyl polyester resin REAFREE® 6419 in a mass ratio of 1:1.1:4.5; the carboxyl-type fluorinated polyester is prepared according to the preparation method of carboxyl-type fluorinated polyester in Example 6 of CN113736350B; the end-carboxyl hyperbranched long-chain aromatic polyester is of type HyPer C302 and is provided by Wuhan Hyperbranched Resin Technology Co., Ltd.

[0036] The functional filler is a compound of barium sulfate, rutile titanium dioxide, lignin, and shell powder in a mass ratio of 1:2.8:0.75:1.1; the average particle size of the functional filler is 7 μm; the functional additives are a compound of light stabilizer, antioxidant, coupling agent, degassing agent, leveling agent, and matting wax powder in a mass ratio of 1.2:1.1:4.5:1:1.1:1.8; the light stabilizer is UV-1577, the antioxidant is antioxidant 1010; the coupling agent is a compound of silane coupling agents KH550, KH560, and KH570 in a mass ratio of 1:2:1; the degassing agent is benzoin; the leveling agent is leveling agent GLP788; and the matting wax powder is matting wax powder mju:Wax2739. Example 5

[0037] A method for preparing an environmentally friendly outdoor matte powder coating includes the following steps: Step S1, Preparation of HAA microcapsules: β-hydroxyalkylamide curing agent was placed in a vacuum drying oven and dried at 82℃ and -0.09MPa for 3 hours; epoxidized soybean oil acrylate was placed in a constant temperature water bath, heated to 52℃, stirred at 320 rpm, and kept at this temperature for 32 minutes; then, β-hydroxyalkylamide curing agent and epoxidized soybean oil acrylate were mixed and poured into a high-speed disperser, and dispersed at 25℃ for 65 minutes at a speed of 1300 rpm; subsequently, silane coupling agent KH570 was added, the stirring speed was adjusted to 850 rpm, and the constant temperature water bath was heated to 70℃ and stirred for 35 minutes; then, azobisisobutyronitrile was added, stirred evenly, and the reaction was continued at 70℃ for 22 minutes; finally, the mixture was centrifuged and dried at 72℃ and -0.09MPa for 5 hours to obtain HAA microcapsules. Step S2, Raw material premixing: The polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additives, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate are sequentially added to a high-speed mixer and mixed at 1200 r / min for 5 min at room temperature to obtain a uniform premixed material. Step S3, 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 300r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S4, Crushing: Feed the flaky material into the crusher, adjust the crusher speed to 1600 rpm, and crush it into coarse powder with a particle size of <5mm. Step S5, Micronization: The coarse powder is fed into an ACM mill for pulverization and classification, and the fine powder with a particle size of 45μm is collected by a cyclone separator.

[0038] In step S1, the mass ratio of β-hydroxyalkylamide curing agent, epoxidized soybean oil acrylate, silane coupling agent KH570, and azobisisobutyronitrile is 3:1:0.08:0.04; the β-hydroxyalkylamide curing agent is of brand T105M and is provided by Ningbo Nanhai Chemical Co., Ltd.; in step S2, the mass ratio of polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additives, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate is 65:10:7:15:5:4:0.3:1.2.

[0039] The polyester matrix in step S2 is a compound of carboxyl-type fluorinated polyester, end-carboxyl hyperbranched long-chain aromatic polyester, and carboxyl polyester resin REAFREE® 6419 in a mass ratio of 1:1.2:5; the carboxyl-type fluorinated polyester is prepared according to the preparation method of carboxyl-type fluorinated polyester in Example 6 of CN113736350B; the end-carboxyl hyperbranched long-chain aromatic polyester is of type HyPer C302 and is provided by Wuhan Hyperbranched Resin Technology Co., Ltd.

[0040] The functional filler is a compound of barium sulfate, rutile titanium dioxide, lignin, and shell powder in a mass ratio of 1:3:0.8:1.2; the average particle size of the functional filler is 8 μm; the functional additives are a compound of light stabilizer, antioxidant, coupling agent, degassing agent, leveling agent, and matting wax powder in a mass ratio of 1.2:1.2:5:1:1.2:2; the light stabilizer is UV-1577, the antioxidant is antioxidant 1010, the coupling agent is silane coupling agent KH550, the degassing agent is benzoin, the leveling agent is leveling agent GLP788, and the matting wax powder is matting wax powder mju:Wax2739.

[0041] Comparative Example 1 A method for preparing an environmentally friendly outdoor matte powder coating is basically the same as in Example 5, except that an equal amount of β-hydroxyalkylamide is used instead of HAA microcapsules.

[0042] Comparative Example 2 A method for preparing an environmentally friendly outdoor matte powder coating is basically the same as that in Example 5, except that an equal amount of epoxidized soybean oil acrylate is used instead of HAA microcapsules.

[0043] Comparative Example 3 A method for preparing an environmentally friendly outdoor matte powder coating is basically the same as that in Example 5, except that an equal amount of triallyl isocyanurate is used instead of BMI-7000.

[0044] Comparative Example 4 A method for preparing an environmentally friendly outdoor matte powder coating is basically the same as that in Example 5, except that an equal amount of BMI-7000 is used instead of triallyl isocyanurate.

[0045] Comparative Example 5 A method for preparing an environmentally friendly outdoor matte powder coating is basically the same as that in Example 5, except that an equal amount of rutile titanium dioxide is used instead of lignin.

[0046] The environmentally friendly outdoor matte powder coatings 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 coatings prepared in each example were electrostatically sprayed using a corona discharge spray gun with the following parameters: voltage 75kV, spray distance 30cm, and powder application rate 95g / m². After spraying, the coatings were placed in a constant temperature oven for step curing. The oven was preheated at 165℃ for 5 minutes, then heated to 185℃ and held for 15 minutes. After curing, the coating was obtained, and the dry film thickness of the coating was controlled at 60μm.

[0047] 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. 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. 3. 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 500h. The gloss retention rate of the coating after aging was tested (60° gloss after aging / 60° gloss before aging × 100%). 4. Corrosion resistance test: Referring to GB / T 1771-2007 "Determination of resistance to neutral salt spray of paints and varnishes", a 5% NaCl solution was used for continuous spraying at 35°C, and the longest time without cracking, blistering, whitening, or peeling of the coating was recorded.

[0048] Table 1 Performance test results of environmentally friendly outdoor matte powder coatings

[0049] As shown in Table 1, the environmentally friendly outdoor matte powder coating prepared in Example 5 is significantly better than the comparative examples in terms of 60° gloss (3.2%), corrosion resistance (2300h), adhesion grade (0 grade), and weather resistance (93.8%). This indicates that the combined use of HAA microcapsules, triallyl isocyanurate, BMI-7000, and lignin can effectively improve the matte effect, corrosion resistance, adhesion, and weather resistance of the coating.

[0050] 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 method for preparing an environmentally friendly outdoor matte powder coating, characterized in that, Includes the following steps: Step S1, Preparation of HAA microcapsules: Place the β-hydroxyalkylamide curing agent in a vacuum drying oven and dry for 2-3 hours at 78-82℃ and a vacuum of -0.08 to -0.09 MPa; place the epoxidized soybean oil acrylate in a constant temperature water bath, heat to 48-52℃, stir at 280-320 rpm, and hold for 28-32 minutes; then mix the β-hydroxyalkylamide curing agent and epoxidized soybean oil acrylate, pour into a high-speed disperser, and adjust the speed to 1000-1300 rpm. The mixture was dispersed at 23-25℃ for 55-65 min; then silane coupling agent KH570 was added, the stirring speed was adjusted to 750-850 rpm, and the constant temperature water bath was heated to 60-70℃ and stirred for 25-35 min; then azobisisobutyronitrile was added, stirred evenly, and the reaction was continued at 60-70℃ for 18-22 min; finally, the mixture was centrifuged and dried at 68-72℃ and vacuum degree -0.08 to -0.09 MPa for 3-5 h to obtain HAA microcapsules. Step S2, Raw material premixing: The polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additives, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate are sequentially added into a high-speed mixer and mixed at 800-1200 r / min for 3-5 min at room temperature to obtain a uniform premixed material. Step S3, 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 250-300 r / min. After the material is melt-mixed and extruded, it is cooled and pressed into sheet to obtain sheet material. Step S4, Crushing: Feed the flaky material into the crusher, adjust the crusher speed to 1400-1600 rpm, and crush it into coarse powder with a particle size of <5mm. Step S5, Micronization: The coarse powder is fed into an ACM mill for pulverization and classification, and the fine powder with a particle size of 25-45μm is collected by a cyclone separator.

2. The preparation method of the environmentally friendly outdoor matte powder coating according to claim 1, characterized in that, The mass ratio of β-hydroxyalkylamide curing agent, epoxidized soybean oil acrylate, silane coupling agent KH570, and azobisisobutyronitrile in step S1 is 3:1:(0.04-0.08):(0.02-0.04).

3. The method for preparing the environmentally friendly outdoor matte powder coating according to claim 1, characterized in that, The grade of the β-hydroxyalkylamide curing agent is T105M.

4. The method for preparing the environmentally friendly outdoor matte powder coating according to claim 1, characterized in that, The mass ratio of the polyester matrix, matting curing agent XG665, HAA microcapsules, functional filler, functional additive, BMI-7000, tert-butyl peroxide, and triallyl isocyanurate in step S2 is (60-65):(8-10):(5-7):(10-15):(3-5):(2-4):0.3:(0.8-1.2).

5. The method for preparing the environmentally friendly outdoor matte powder coating according to claim 1, characterized in that, The polyester matrix mentioned in step S2 is a compound of carboxyl-type fluorinated polyester, end-carboxyl hyperbranched long-chain aromatic polyester, and carboxyl polyester resin REAFREE® 6419 in a mass ratio of 1:(0.8-1.2):(3-5).

6. The method for preparing the environmentally friendly outdoor matte powder coating according to claim 5, characterized in that, The type of the end-carboxyl hyperbranched long-chain aromatic polyester is HyPer C302.

7. The method for preparing the environmentally friendly outdoor matte powder coating according to claim 1, characterized in that, The functional filler is a compound of barium sulfate, rutile titanium dioxide, lignin, and shell powder in a mass ratio of 1:(2-3):(0.5-0.8):(0.8-1.2).

8. The method for preparing the environmentally friendly outdoor matte powder coating according to claim 1, characterized in that, The average particle size of the functional filler is 3-8 μm.

9. The method for preparing the environmentally friendly outdoor matte powder coating according to claim 1, characterized in that, The functional additives are light stabilizers, antioxidants, coupling agents, degassing agents, leveling agents, and matting wax powder compounded in a mass ratio of (1-1.2):(0.8-1.2):(3-5):1:(0.8-1.2):(1-2).

10. The method for preparing the environmentally friendly outdoor matte powder coating according to claim 9, characterized in that, The light stabilizer is UV-1577, the antioxidant is antioxidant 1010, the coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570, the degassing agent is benzoin, the leveling agent is leveling agent GLP788, and the matting wax powder is matting wax powder mju:Wax2739.

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