Aging-resistant matting powder coating and a preparation method thereof

Abstract

The application discloses an anti-aging matt powder coating and a preparation method thereof, and belongs to the technical field of coatings. The specific modified polyester resin A and the modified polyester resin B are compounded, so that the matt effect of the coating is ensured, and the weather resistance and the mechanical properties of the coating are obviously improved. In addition, the optimized compounded matt system is added, so that the coating has stable matt effect. The compounded anti-aging system is further added, so that the aging degradation of the coating is inhibited from multiple action mechanisms of free radical capture, ultraviolet shielding and peroxide decomposition, and long-acting weather protection is realized. Overall, the components of the powder coating are scientifically compounded, the powder coating is sprayed on a metal surface, the coating with the matt effect, excellent anti-aging and mechanical properties is obtained, and the powder coating has high application value and is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of powder coating technology, and more specifically, to an aging-resistant matte powder coating and its preparation method. Background Technology

[0002] Powder coatings, with their advantages of energy saving, environmental protection, and solvent-free evaporation, have been widely used in building materials, outdoor furniture, transportation facilities, and home appliances. Among them, matte / superficial powder coatings are particularly favored due to their soft optical effects and excellent decorative properties. With the continuous expansion of outdoor applications, the market is placing increasingly higher demands on the aging resistance of matte powder coatings. Especially under harsh climatic conditions such as high UV intensity, high temperature, and high humidity, coatings are prone to problems such as decreased gloss, yellowing, cracking, and chalking, which not only damage the aesthetic appearance but also shorten the service life of the substrate.

[0003] Currently, the mainstream methods for preparing matte powder coatings include the addition of matting agents and the dry-mixing method. The addition of matting agents involves adding physical or chemical matting agents to conventional high-gloss powder coatings to achieve a matte effect. However, because matting agents significantly affect the weather resistance of the coating, they often fail to meet the high weather resistance requirements of outdoor applications. The dry-mixing method involves physically mixing two or more resins with different reactivity. Utilizing the differences in reaction rates during the curing process, a microscopic uneven structure is formed on the coating surface to scatter light, thereby achieving a matte effect. While the dry-mixing method can balance matte finish and weather resistance to some extent, matte powder coatings prepared using existing technologies still suffer from the problem of poor balance between matte gloss and weather resistance.

[0004] To address the aforementioned technical problems, existing technologies offer several improvements. For example, Chinese invention patent CN110922856B discloses a powder coating with ultra-high weather resistance and matting effect. Its raw materials include powder coating component A and powder coating component B, which are dry-mixed and have different curing speeds. Component A contains a first polyester resin and a corresponding curing agent. This solution achieves the matting effect through dry mixing of components with different curing speeds; however, further improvements in its matting effect and aging resistance are still limited by the structural design of the resin system itself. Another example is Chinese invention patent CN119463146B, which discloses a method for preparing an ultra-weather-resistant HAA-curable matting polyester resin. This method involves reacting neopentyl glycol, triazine phenylimide diol monomer, diacid, esterification catalyst, and onium salt curing accelerator. The phenylimide ring and triazine ring structure in the triazine phenylimide diol monomer improve the resin's heat resistance and mechanical strength, and the steric hindrance and shielding effect of the dialkyl side chain inhibits ester hydrolysis. This solution mainly improves weather resistance and gloss retention at the molecular structure level of polyester resin, but does not address the synergistic matting and aging resistance mechanisms of the resin compound system.

[0005] It can be seen that the existing aging-resistant matting powder coatings still have the following shortcomings: (1) It is difficult for a single resin system to simultaneously achieve excellent matting effect and high aging resistance; (2) The compatibility and reactivity of each resin component in the dry mixing method are not well matched, resulting in unstable mechanical properties and weather resistance of the coating; (3) It is difficult to systematically solve the problems of coating aging resistance and matting.

[0006] Therefore, developing a powder coating with both excellent matting effect and high aging resistance, and its preparation method, has important practical significance and application value. Summary of the Invention

[0007] In view of this, in order to solve one of the above-mentioned technical problems, the present invention provides an aging-resistant matte powder coating and its preparation method, the specific technical solution of which is as follows: An aging-resistant matte powder coating, wherein the aging-resistant matte powder coating comprises the following raw materials in parts by weight: Modified polyester resin A 40-50 parts, modified polyester resin B 25-30 parts, curing agent 5-15 parts, curing accelerator 1-2 parts, compound matting system 3-10 parts, modified filler 9-15 parts, compound aging resistant system 0.5-5 parts, matting agent 0.1-0.5 parts, leveling agent 0.5-3 parts, and stearamide 0.2-1 parts; The compound matting system is obtained by mixing fluorinated hydroxyl acrylic resin, nano hollow silica microspheres and anhydride-functionalized polyacrylic resin in a mass ratio of (10~20):(3~7):(1~3). The compound anti-aging system is obtained by mixing terminal amino hyperbranched polyamide, nano titanium dioxide, antioxidant, light stabilizer and anti-ultraviolet absorber in a mass ratio of (5~10):(1~3):(0.1~1):(0.1~1):(0.1~0.5).

[0008] Furthermore, the modified polyester resin A is prepared by: Neopentyl glycol, triazine phenylimide diol monomer, and diacid were added to the reactor at a molar ratio of (2~4):(0.5~1.5):(3~5). An esterification catalyst was added, nitrogen gas was introduced, and the temperature was raised to 160~180℃ and kept at that temperature for 1~3 hours. Then the temperature was raised to 240~250℃ and kept at that temperature for 3~5 hours. When the acid value of the reaction system reached 5~20 mg KOH / g, an acid hydrolysate was added, and the reaction continued for 1~3 hours. When the acid value reached 50~70 mg KOH / g, a vacuum was applied for polycondensation reaction for 2~4 hours, and the material was discharged after cooling to obtain modified polyester resin A.

[0009] Furthermore, the modified polyester resin B is prepared by: Diol, diacid and organosilicon intermediate were added to the reactor at a molar ratio of (2~5):(3~5):(0.5~1), a catalyst was added, nitrogen gas was introduced, the temperature was raised to 160~180℃ and kept at the temperature for 1~3h; then the temperature was raised to 230~250℃ and kept at the temperature for 2~5h. When the acid value reached 10~30 mg KOH / g, an acid hydrolysate was added, and the reaction was continued for 2~4h. The product was then cooled and discharged to obtain modified polyester resin B.

[0010] Furthermore, the organosilicon intermediate is at least one of hydroxyl-terminated polydimethylsiloxane and hydroxyl-terminated polymethylphenylsiloxane.

[0011] Furthermore, the curing agent is at least one of triglycidyl isocyanurate and β-hydroxyalkylamide.

[0012] Furthermore, the fluorinated hydroxyl acrylic resin has a fluorine content of 5-15 wt%, a hydroxyl value of 30-60 mg KOH / g, and a number-average molecular weight of 5000-20000.

[0013] Furthermore, the particle size of the nano-hollow silica microspheres is 50~200nm, and the wall thickness is 5~20nm.

[0014] Furthermore, the anhydride-functionalized polyacrylic acid resin has an acid value of 50-120 mg KOH / g and a weight-average molecular weight of 1000-8000.

[0015] Furthermore, the modified filler is a silane coupling agent modified filler, and the filler is at least one of magnesium aluminum hydrotalcite, titanium dioxide, silicon dioxide, quartz powder, mica powder, and aluminum hydroxide.

[0016] In addition, the present invention also provides a method for preparing an aging-resistant matte powder coating, the method comprising the following steps: S1. Add modified polyester resin A, modified polyester resin B, curing agent, curing accelerator, compound matting system, modified filler, compound aging resistant system, matting aid, leveling agent and stearamide to a mixer and premix for 5 to 10 minutes at a speed of 500 to 1000 r / min to obtain a mixture. S2. Add the mixture to a twin-screw extruder, control the temperature of zone 1 of the extruder to be 80~100℃, the temperature of zone 2 to be 90~120℃, the temperature of zone 3 to be 100~130℃, and the screw speed to be 200~500rpm, melt extrusion to obtain the extruded material; S3. After cooling the extruded material, it is pressed, crushed, pulverized and graded and sieved to obtain an aging-resistant matte powder coating.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes a specific blend of modified polyester resin A and modified polyester resin B to achieve a matte finish while significantly improving the coating's weather resistance and mechanical properties. Specifically, modified polyester resin A incorporates a triazine phenylimide diol monomer into its molecular structure. This monomer contains heat-resistant and structurally stable phenylimide and triazine rings, which enhance the coating's high-temperature resistance and mechanical strength, resulting in higher impact resistance. Simultaneously, the dialkyl side chains introduced into the polyester molecular chain create steric hindrance and shielding effects, inhibiting the contact between water molecules and ester bonds in the polyester molecular chain, reducing ester group hydrolysis, and thus significantly improving the coating's hydrolysis resistance and weather resistance. The introduction of organosilicon into modified polyester resin B significantly improves the coating's heat resistance.

[0018] 2. This invention incorporates an optimized compound matting system. The introduction of fluorine significantly improves the outdoor weather resistance of the coating, and the hydroxyl groups it contains can participate in the curing and cross-linking reaction. By interacting with the hollow silica microspheres, it helps to improve the interfacial bonding with the resin matrix, forming a micro-rough structure on the coating surface to scatter light and achieve a physical matting effect. Furthermore, it works synergistically with polyacrylic resin containing anhydride functional groups to achieve a stable matting effect, overcoming the problems of unstable matting effect and poor compatibility with the resin matrix in traditional powder coatings.

[0019] 3. This invention incorporates a compounded anti-aging system into powder coatings. The hyperbranched molecular structure of amino-based hyperbranched polyamides provides a large number of active terminal amino groups, improving the wettability of the coating and substrate and enhancing adhesion. Simultaneously, its nanoscale molecular size effectively fills micro-defects in the coating, improving its density. Nano-titanium dioxide acts as an anti-UV aging additive, effectively absorbing and scattering ultraviolet rays, significantly improving the photoaging resistance of powder coatings. The synergistic use of antioxidants, light stabilizers, and UV absorbers inhibits coating aging and degradation through multiple mechanisms, including free radical capture, UV shielding, and peroxide decomposition, achieving long-lasting weather protection.

[0020] 4. This invention, through the scientific compounding of powder coating components, can obtain a coating that combines matte finish, excellent aging resistance, and mechanical properties when sprayed onto a metal surface. It has high application value and is suitable for large-scale production. Detailed Implementation

[0021] 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.

[0022] 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.

[0023] An embodiment of the present invention provides an aging-resistant matte powder coating, wherein the aging-resistant matte powder coating comprises the following raw materials in parts by weight: Modified polyester resin A 40-50 parts, modified polyester resin B 25-30 parts, curing agent 5-15 parts, curing accelerator 1-2 parts, compound matting system 3-10 parts, modified filler 9-15 parts, compound aging resistant system 0.5-5 parts, matting agent 0.1-0.5 parts, leveling agent 0.5-3 parts, and stearamide 0.2-1 parts; The compound matting system is obtained by mixing fluorinated hydroxyl acrylic resin, nano hollow silica microspheres and anhydride-functionalized polyacrylic resin in a mass ratio of (10~20):(3~7):(1~3). The compound anti-aging system is obtained by mixing terminal amino hyperbranched polyamide, nano titanium dioxide, antioxidant, light stabilizer and anti-ultraviolet absorber in a mass ratio of (5~10):(1~3):(0.1~1):(0.1~1):(0.1~0.5).

[0024] In one embodiment, the antioxidant is a mixture of hindered phenolic antioxidants and phosphite antioxidants in a mass ratio of (1~3):1.

[0025] In one embodiment, the light stabilizer is an amine-based light stabilizer.

[0026] In one embodiment, the UV absorber is at least one of benzotriazoles and benzophenones.

[0027] In one embodiment, the terminal amino hyperbranched polyamide has a branching degree of 0.4 to 0.8, a number-average molecular weight of 2000 to 8000, and an amino content of 5 to 15 mmol / g.

[0028] In one embodiment, the modified polyester resin A is prepared by: Neopentyl glycol, triazine phenylimide diol monomer, and diacid were added to the reactor at a molar ratio of (2~4):(0.5~1.5):(3~5). An esterification catalyst was added, nitrogen gas was introduced, and the temperature was raised to 160~180℃ and kept at that temperature for 1~3 hours. Then the temperature was raised to 240~250℃ and kept at that temperature for 3~5 hours. When the acid value of the reaction system reached 5~20 mg KOH / g, an acid hydrolysate was added, and the reaction continued for 1~3 hours. When the acid value reached 50~70 mg KOH / g, a vacuum was applied for polycondensation reaction for 2~4 hours, and the material was discharged after cooling to obtain modified polyester resin A.

[0029] In one embodiment, the dicarboxylic acid is obtained by mixing isophthalic acid and terephthalic acid in a molar ratio of (1~2):(1~3).

[0030] In one embodiment, the esterification catalyst is monobutyltin oxide.

[0031] In one embodiment, the amount of the esterification catalyst added accounts for 0.05% to 0.1% of the total feed amount.

[0032] In one embodiment, in the preparation of modified polyester resin A, the acid hydrolysant is at least one of isophthalic acid, 1,4-cyclohexanedicarboxylic acid, dodecanoic acid, and adipic acid.

[0033] In one embodiment, the amount of acid hydrolysate added accounts for 5% to 10% of the total feed amount.

[0034] In one embodiment, the modified polyester resin A has an acid value of 50~70 mg KOH / g, a hydroxyl value of ≤5 mg KOH / g, and a melt viscosity of 6000~10000 mPa·s at 200℃.

[0035] In one embodiment, the modified polyester resin B is prepared by: Diol, diacid and organosilicon intermediate were added to the reactor at a molar ratio of (2~5):(3~5):(0.5~1), a catalyst was added, nitrogen gas was introduced, the temperature was raised to 160~180℃ and kept at the temperature for 1~3h; then the temperature was raised to 230~250℃ and kept at the temperature for 2~5h. When the acid value reached 10~30 mg KOH / g, an acid hydrolysate was added, and the reaction was continued for 2~4h. The product was then cooled and discharged to obtain modified polyester resin B.

[0036] In one embodiment, the diol is neopentyl glycol.

[0037] In one embodiment, the dicarboxylic acid is isophthalic acid.

[0038] In one embodiment, the catalyst is at least one of tetrabutyl titanate and monobutyltin oxide.

[0039] In one embodiment, the amount of catalyst added accounts for 0.01% to 0.4% of the total feed amount.

[0040] In one embodiment, in the preparation of modified polyester resin B, the acid hydrolysant is at least one selected from isophthalic acid, 1,4-cyclohexanedicarboxylic acid, dodecanoic acid, and adipic acid.

[0041] In one embodiment, the amount of acid hydrolysate added accounts for 5% to 10% of the total feed amount.

[0042] In one embodiment, the modified polyester resin B has an acid value of 15~30 mg KOH / g, a hydroxyl value of ≤8 mg KOH / g, and a melt viscosity of 2000~5000 mPa·s at 200℃.

[0043] In one embodiment, the organosilicon intermediate is at least one of hydroxyl-terminated polydimethylsiloxane and hydroxyl-terminated polymethylphenylsiloxane.

[0044] In one embodiment, the curing agent is at least one of triglycidyl isocyanurate and β-hydroxyalkylamide.

[0045] In one embodiment, the curing accelerator is at least one of dimethylimidazole, heptadecanylimidazole, and isopropylimidazole.

[0046] In one embodiment, the fluorinated hydroxyl acrylic resin has a fluorine content of 5-15 wt%, a hydroxyl value of 30-60 mg KOH / g, and a number-average molecular weight of 5000-20000.

[0047] In one embodiment, the nano-hollow silica microspheres have a particle size of 50-200 nm and a wall thickness of 5-20 nm.

[0048] In one embodiment, the anhydride-functionalized polyacrylic acid resin has an acid value of 50-120 mg KOH / g and a weight-average molecular weight of 1000-8000.

[0049] In one embodiment, the modified filler is a silane coupling agent modified filler, wherein the filler is at least one selected from magnesium aluminum hydrotalcite, titanium dioxide, silica, quartz powder, mica powder, and aluminum hydroxide. The modified filler of the present invention provides interfacial bonding with the resin matrix, exhibits excellent dispersibility and stability, and contributes to improving the mechanical properties and durability of the coating.

[0050] In one embodiment, the silane coupling agent is at least one of γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)ethoxydiethoxyphosphate.

[0051] In one embodiment, the matting agent is at least one of polyethylene wax powder and polytetrafluoroethylene powder. The addition of a matting agent in this invention further assists in matting.

[0052] In one embodiment, the leveling agent is a polyacrylate leveling agent.

[0053] In addition, the present invention also provides a method for preparing an aging-resistant matte powder coating, the method comprising the following steps: S1. Add modified polyester resin A, modified polyester resin B, curing agent, curing accelerator, compound matting system, modified filler, compound aging resistant system, matting aid, leveling agent and stearamide to a mixer and premix for 5 to 10 minutes at a speed of 500 to 1000 r / min to obtain a mixture. S2. Add the mixture to a twin-screw extruder, control the temperature of zone 1 of the extruder to be 80~100℃, the temperature of zone 2 to be 90~120℃, the temperature of zone 3 to be 100~130℃, and the screw speed to be 200~500rpm, melt extrusion to obtain the extruded material; S3. After cooling the extruded material, it is pressed, crushed, pulverized and graded and sieved to obtain an aging-resistant matte powder coating.

[0054] This invention achieves a stable and controllable matting effect through the synergistic compounding of modified polyester resin A and modified polyester resin B, combined with a ternary compound matting system consisting of fluorinated hydroxyl acrylic resin / nano hollow silica microspheres / anhydride-based polyacrylic acid resin. Furthermore, it utilizes a multi-protective aging-resistant system constructed from terminal amino hyperbranched polyamide, nano titanium dioxide, and various anti-aging additives. This systematically solves the technical challenge of powder coatings in simultaneously achieving matting performance and aging resistance from three levels: molecular structure design, microscopic physical matting, and multi-layered chemical protection. The result is a high-performance powder coating that combines low gloss, high weather resistance, excellent mechanical properties, and good application adaptability.

[0055] The embodiments of the present invention will be described in detail below with reference to specific examples. Any methods not described in detail below are considered conventional techniques.

[0056] Example 1: A method for preparing an aging-resistant matte powder coating includes the following steps: S1. By weight, add 45 parts of modified polyester resin A, 25 parts of modified polyester resin B, 12 parts of triglycidyl isocyanurate, 1 part of dimethylimidazole, 5 parts of compound matting system, 12 parts of γ-aminopropyltriethoxysilane modified quartz powder, 3 parts of compound aging resistant system, 0.3 parts of polyethylene wax micro powder, 1 part of polyacrylate leveling agent and 0.8 parts of stearamide to a mixer, and premix at 800 r / min for 10 min to obtain a mixture. The modified polyester resin A is prepared as follows: Neopentyl glycol, triazine phenylimide diol monomer, and a diacid (isophthalic acid and terephthalic acid in a molar ratio of 2:3) are added to a reaction vessel at a molar ratio of 3:0.8:4. Monobutyltin oxide (0.06% of the total feed weight) is added, nitrogen gas is introduced, and the temperature is raised to 165°C and maintained for 1 hour. The temperature is then raised to 250°C and maintained for 3 hours. When the acid value of the reaction system reaches 20 mg KOH / g, isophthalic acid (7% of the total feed weight) is added, and the reaction continues for 1 hour. When the acid value reaches 60 mg KOH / g, a vacuum polycondensation reaction is carried out for 2 hours, followed by cooling and discharge to obtain modified polyester resin A. The modified polyester resin B is prepared as follows: neopentyl glycol, isophthalic acid, and hydroxyl-terminated polydimethylsiloxane are added to a reaction vessel in a molar ratio of 3:3:0.6. Monobutyltin oxide (0.03% of the total feed amount) is added, nitrogen gas is introduced, the temperature is raised to 165°C and kept at that temperature for 1 hour; then the temperature is raised to 240°C and kept at that temperature for 3 hours. When the acid value reaches 20 mg KOH / g, isophthalic acid (6% of the total feed amount) is added, and the reaction is continued for 2 hours. The mixture is then cooled and discharged to obtain modified polyester resin B. The compound matting system is obtained by mixing fluorinated hydroxyl acrylic resin, nano-hollow silica microspheres, and anhydride-functionalized polyacrylic resin in a mass ratio of 10:4:1; wherein the fluorinated hydroxyl acrylic resin has a fluorine content of 5wt%, a hydroxyl value of 45 mg KOH / g, and a number-average molecular weight of 8000; the nano-hollow silica microspheres have a particle size of 80 nm and a wall thickness of 10 nm; and the anhydride-functionalized polyacrylic resin has an acid value of 80 mg KOH / g and a weight-average molecular weight of 6000. The compound anti-aging system is obtained by mixing amino-terminated hyperbranched polyamide, nano-titanium dioxide, antioxidants (hindered phenolic antioxidants and phosphite antioxidants in a mass ratio of 1:1), amine-resistant light stabilizers, and benzotriazole UV absorbers in a mass ratio of 10:2:0.5:0.3:0.2; and the amino-terminated hyperbranched polyamide has a branching degree of 0.6, a number-average molecular weight of 6000, and an amino content of 12 mmol / g; S2. Add the mixture to a twin-screw extruder, control the temperature of zone one of the extruder to 90°C, the temperature of zone two to 110°C, the temperature of zone three to 125°C, and the screw speed to 200 rpm, melt extrusion to obtain the extruded material; S3. After cooling the extruded material, it is pressed, crushed, pulverized and graded and sieved to obtain an aging-resistant matte powder coating.

[0057] Example 2: A method for preparing an aging-resistant matte powder coating includes the following steps: S1. By weight, add 44 parts of modified polyester resin A, 26 parts of modified polyester resin B, 11 parts of triglycidyl isocyanate, 2 parts of dimethylimidazole, 6 parts of compound matting system, 13 parts of γ-aminopropyltriethoxysilane modified quartz powder, 4 parts of compound aging resistant system, 0.4 parts of polyethylene wax micro powder, 1 part of polyacrylate leveling agent and 0.8 parts of stearamide to a mixer, and premix at 800 r / min for 10 min to obtain a mixture. The modified polyester resin A is prepared as follows: Neopentyl glycol, triazine phenylimide diol monomer, and a diacid (isophthalic acid and terephthalic acid in a molar ratio of 2:3) are added to a reactor at a molar ratio of 3:1.0:4. Monobutyltin oxide (0.06% of the total feed weight) is added, nitrogen gas is introduced, and the temperature is raised to 165°C and maintained for 1 hour. The temperature is then raised to 250°C and maintained for 3 hours. When the acid value of the reaction system reaches 20 mg KOH / g, isophthalic acid (7% of the total feed weight) is added, and the reaction continues for 1 hour. When the acid value reaches 60 mg KOH / g, a vacuum polycondensation reaction is carried out for 2 hours, followed by cooling and discharge to obtain modified polyester resin A. The modified polyester resin B is prepared as follows: neopentyl glycol, isophthalic acid, and hydroxyl-terminated polydimethylsiloxane are added to a reaction vessel in a molar ratio of 3:3:0.6. Monobutyltin oxide (0.04% of the total feed amount) is added, nitrogen gas is introduced, the temperature is raised to 170°C and kept at that temperature for 1 hour; then the temperature is raised to 235°C and kept at that temperature for 3 hours. When the acid value reaches 25 mg KOH / g, isophthalic acid (5% of the total feed amount) is added, and the reaction is continued for 2 hours. The mixture is then cooled and discharged to obtain modified polyester resin B. The compound matting system is obtained by mixing fluorinated hydroxyl acrylic resin, nano-hollow silica microspheres, and anhydride-functionalized polyacrylic resin in a mass ratio of 10:5:1; wherein the fluorinated hydroxyl acrylic resin has a fluorine content of 5wt%, a hydroxyl value of 45 mg KOH / g, and a number-average molecular weight of 8000; the nano-hollow silica microspheres have a particle size of 80 nm and a wall thickness of 10 nm; and the anhydride-functionalized polyacrylic resin has an acid value of 80 mg KOH / g and a weight-average molecular weight of 6000. The compound anti-aging system is obtained by mixing amino-terminated hyperbranched polyamide, nano-titanium dioxide, antioxidants (hindered phenolic antioxidants and phosphite antioxidants in a mass ratio of 1:1), amine-type light stabilizers, and benzotriazole-type UV absorbers in a mass ratio of 10:3:0.5:0.3:0.2; and the amino-terminated hyperbranched polyamide has a branching degree of 0.6, a number-average molecular weight of 6000, and an amino content of 12 mmol / g; S2. Add the mixture to a twin-screw extruder, control the temperature of zone one of the extruder to be 100°C, the temperature of zone two to be 115°C, the temperature of zone three to be 125°C, and the screw speed to be 200 rpm, melt extrusion to obtain the extruded material; S3. After cooling the extruded material, it is pressed, crushed, pulverized and graded and sieved to obtain an aging-resistant matte powder coating.

[0058] Example 3: A method for preparing an aging-resistant matte powder coating includes the following steps: S1. By weight, add 43 parts of modified polyester resin A, 27 parts of modified polyester resin B, 12 parts of triglycidyl isocyanate, 2 parts of dimethylimidazole, 7 parts of compound matting system, 12 parts of γ-aminopropyltriethoxysilane modified quartz powder, 5 parts of compound aging resistant system, 0.5 parts of polyethylene wax micro powder, 1.2 parts of polyacrylate leveling agent and 0.8 parts of stearamide to a mixer, and premix at 800 r / min for 10 min to obtain a mixture. The modified polyester resin A is prepared as follows: Neopentyl glycol, triazine phenylimide diol monomer, and a diacid (isophthalic acid and terephthalic acid in a molar ratio of 2:3) are added to a reaction vessel at a molar ratio of 3:1.1:4. Monobutyltin oxide (0.06% of the total feed weight) is added, nitrogen gas is introduced, and the temperature is raised to 165°C and maintained for 1 hour. The temperature is then raised to 250°C and maintained for 3 hours. When the acid value of the reaction system reaches 20 mg KOH / g, isophthalic acid (7% of the total feed weight) is added, and the reaction continues for 1 hour. When the acid value reaches 60 mg KOH / g, a vacuum polycondensation reaction is carried out for 2 hours, followed by cooling and discharge to obtain modified polyester resin A. The modified polyester resin B is prepared as follows: neopentyl glycol, isophthalic acid, and hydroxyl-terminated polydimethylsiloxane are added to a reaction vessel in a molar ratio of 3:3:0.7. Monobutyltin oxide (0.05% of the total feed amount) is added, nitrogen gas is introduced, the temperature is raised to 175°C and kept at that temperature for 1 hour; then the temperature is raised to 250°C and kept at that temperature for 2 hours. When the acid value reaches 30 mg KOH / g, isophthalic acid (7% of the total feed amount) is added, and the reaction is continued for 2 hours. The mixture is then cooled and discharged to obtain modified polyester resin B. The compound matting system is obtained by mixing fluorinated hydroxyl acrylic resin, nano-hollow silica microspheres, and anhydride-functionalized polyacrylic resin in a mass ratio of 10:7:1; wherein the fluorinated hydroxyl acrylic resin has a fluorine content of 5wt%, a hydroxyl value of 45 mg KOH / g, and a number-average molecular weight of 8000; the nano-hollow silica microspheres have a particle size of 80 nm and a wall thickness of 10 nm; and the anhydride-functionalized polyacrylic resin has an acid value of 80 mg KOH / g and a weight-average molecular weight of 6000. The compound anti-aging system is obtained by mixing amino-terminated hyperbranched polyamide, nano-titanium dioxide, antioxidants (hindered phenolic antioxidants and phosphite antioxidants in a mass ratio of 1:1), amine-type light stabilizers, and benzotriazole-type UV absorbers in a mass ratio of 10:3:0.5:0.3:0.2; and the amino-terminated hyperbranched polyamide has a branching degree of 0.6, a number-average molecular weight of 6000, and an amino content of 12 mmol / g; S2. Add the mixture to a twin-screw extruder, control the temperature of zone one of the extruder to be 100°C, the temperature of zone two to be 115°C, the temperature of zone three to be 125°C, and the screw speed to be 200 rpm, melt extrusion to obtain the extruded material; S3. After cooling the extruded material, it is pressed, crushed, pulverized and graded and sieved to obtain an aging-resistant matte powder coating.

[0059] Comparative Example 1: The difference between Comparative Example 1 and Example 3 is that ordinary polyester resin was used to replace modified polyester resin A in Comparative Example 1, while the rest is the same as in Example 3.

[0060] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that ordinary polyester resin was used to replace modified polyester resin B in Comparative Example 2, while the rest is the same as in Example 3.

[0061] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that Comparative Example 3 added a single 70 parts of modified polyester resin A, that is, no modified polyester resin B was added, otherwise it was the same as Example 3.

[0062] Comparative Example 4: Compared with Example 3, Comparative Example 4 differs in that ordinary hydroxyl acrylic resin is used instead of fluorinated hydroxyl acrylic resin in the compound matting system of Comparative Example 4, while the rest is the same as Example 3.

[0063] Comparative Example 5: The difference between Comparative Example 5 and Example 3 is that no compound matting system was added in Comparative Example 5, but otherwise it is the same as Example 3.

[0064] Comparative Example 6: The difference between Comparative Example 6 and Example 3 is that no compound anti-aging system was added in Comparative Example 6, but otherwise it is the same as Example 3.

[0065] The powder coating samples prepared in Examples 1-3 and Comparative Examples 1-6 were electrostatically sprayed onto the surface of phosphated cold-rolled steel sheets and cured at 200°C for 15 min to obtain coated samples. Performance tests were then performed, and the results are shown in Table 1 below.

[0066] The adhesion test follows GB / T 9286-2021, using the cross-cut test, with a rating of 0-5 (0 being the best). The gloss test follows GB / T 9754-2025. The impact resistance test follows GB / T 1732-2020. The accelerated aging test follows GB / T1865-2009, involving 1000 hours of xenon lamp aging to evaluate gloss retention and color difference.

[0067]

[0068] Analysis of the data in Table 1 shows that the present invention, by optimizing the formulation of powder coatings, produces coatings with excellent low gloss, high adhesion, high impact resistance, and superior aging resistance. Compared with Example 3, Comparative Example 1, which replaced modified polyester resin A with ordinary polyester resin, resulted in coating adhesion, impact resistance, and aging resistance all being inferior to Example 3. This indicates that the triazine phenylimide diol monomer introduced into modified polyester resin A significantly improves the mechanical strength and aging resistance of the resin due to its phenylimide ring and triazine ring structure. Simultaneously, the steric hindrance shielding effect of the dialkyl side chain effectively inhibits ester hydrolysis, further enhancing the coating's impact resistance and weather resistance. In Comparative Example 2, replacing modified polyester resin B with ordinary polyester resin resulted in a coating with higher gloss, but its impact resistance and aging resistance were inferior to those in Example 3. This indicates that the organosilicon segments (hydroxyl-terminated polydimethylsiloxane) introduced by modified polyester resin B can form a reactive gradient with modified polyester resin A, promoting the formation of a micro-rough structure and thus synergistically reducing gloss. Simultaneously, the hydrophobic and oleophobic properties of organosilicon enhance the weather resistance of the coating. In Comparative Example 3, only modified polyester resin A was added (without modified polyester resin B), resulting in adhesion, impact resistance, and aging resistance all inferior to those in Example 3. This indicates that a single resin system cannot create a difference in curing rate, the coating surface lacks an effective micro-uneven structure, the matting effect is unstable, and the lack of synergistic protection from organosilicon components significantly deteriorates aging resistance and mechanical properties. In Comparative Example 4, the compound matting system replaced the fluorinated hydroxyl acrylic resin with ordinary hydroxyl acrylic resin. Although the adhesion remained at grade 0, other properties were worse than in Example 3. This indicates that the fluorine in the fluorinated hydroxyl acrylic resin can significantly reduce the surface energy of the coating, reducing the penetration of ultraviolet rays and moisture. Simultaneously, its hydroxyl groups can participate in cross-linking and form a strong interfacial bond with the nano-hollow silica microspheres, helping to maintain a stable matting structure and improve the coating's weather resistance. In Comparative Example 5, no compound matting system was added. The coating had a high gloss, and although the impact resistance and adhesion did not decrease significantly, the aging resistance was worse than in Example 3. This indicates that the compound matting system can significantly promote the formation of a matting coating. It achieves a stable matting effect through the physical scattering of the nano-hollow microspheres and the chemical compatibility adjustment of the fluorinated / anhydride resins. Since the compound matting system also contains nano-hollow silica microspheres, it also has a certain promoting effect on aging resistance. In Comparative Example 6, without the addition of the compound anti-aging system, the coating's anti-aging performance was significantly reduced. This indicates that the nano-size filling effect of the terminal amino hyperbranched polyamide, the ultraviolet shielding effect of nano titanium dioxide, and the multiple free radical capture and peroxide decomposition mechanisms of antioxidants, light stabilizers, and ultraviolet absorbers in the compound anti-aging system jointly construct a long-term protective network. Its absence will lead to rapid aging and failure of the coating.

[0069] In summary, this invention systematically solves the technical problem of powder coatings being unable to simultaneously achieve matte finish and weather resistance through resin molecular structure design, multi-component matte system construction, and the synergistic effect of an all-round aging-resistant protective layer. The synergistic effect of each component together endows the coating with excellent comprehensive performance.

[0070] 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.

[0071] 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. An aging-resistant matte powder coating, characterized in that, The aging-resistant matte powder coating comprises the following raw materials in parts by weight: Modified polyester resin A 40-50 parts, modified polyester resin B 25-30 parts, curing agent 5-15 parts, curing accelerator 1-2 parts, compound matting system 3-10 parts, modified filler 9-15 parts, compound aging resistant system 0.5-5 parts, matting agent 0.1-0.5 parts, leveling agent 0.5-3 parts, and stearamide 0.2-1 parts; The compound matting system is obtained by mixing fluorinated hydroxyl acrylic resin, nano hollow silica microspheres and anhydride-functionalized polyacrylic resin in a mass ratio of (10~20):(3~7):(1~3). The compound anti-aging system is obtained by mixing terminal amino hyperbranched polyamide, nano titanium dioxide, antioxidant, light stabilizer and anti-ultraviolet absorber in a mass ratio of (5~10):(1~3):(0.1~1):(0.1~1):(0.1~0.5).

2. The aging-resistant matte powder coating according to claim 1, characterized in that, The modified polyester resin A is prepared by: Neopentyl glycol, triazine phenylimide diol monomer, and diacid were added to the reactor at a molar ratio of (2~4):(0.5~1.5):(3~5). An esterification catalyst was added, nitrogen gas was introduced, and the temperature was raised to 160~180℃ and kept at that temperature for 1~3 hours. Then the temperature was raised to 240~250℃ and kept at that temperature for 3~5 hours. When the acid value of the reaction system reached 5~20 mg KOH / g, an acid hydrolysate was added, and the reaction continued for 1~3 hours. When the acid value reached 50~70 mg KOH / g, a vacuum was applied for polycondensation reaction for 2~4 hours, and the material was discharged after cooling to obtain modified polyester resin A.

3. The aging-resistant matte powder coating according to claim 1, characterized in that, The modified polyester resin B is prepared by: Diol, diacid and organosilicon intermediate were added to the reactor at a molar ratio of (2~5):(3~5):(0.5~1), a catalyst was added, nitrogen gas was introduced, the temperature was raised to 160~180℃ and kept at the temperature for 1~3h; then the temperature was raised to 230~250℃ and kept at the temperature for 2~5h. When the acid value reached 10~30 mg KOH / g, an acid hydrolysate was added, and the reaction was continued for 2~4h. The product was then cooled and discharged to obtain modified polyester resin B.

4. The aging-resistant matte powder coating according to claim 3, characterized in that, The organosilicon intermediate is at least one of hydroxyl-terminated polydimethylsiloxane and hydroxyl-terminated polymethylphenylsiloxane.

5. The aging-resistant matte powder coating according to claim 1, characterized in that, The curing agent is at least one of triglycidyl isocyanurate and β-hydroxyalkylamide.

6. The aging-resistant matte powder coating according to claim 1, characterized in that, The fluorinated hydroxyl acrylic resin has a fluorine content of 5-15 wt%, a hydroxyl value of 30-60 mg KOH / g, and a number-average molecular weight of 5000-20000.

7. The aging-resistant matte powder coating according to claim 1, characterized in that, The particle size of the nano-hollow silica microspheres is 50~200nm, and the wall thickness is 5~20nm.

8. The aging-resistant matte powder coating according to claim 1, characterized in that, The polyacrylic acid resin containing anhydride functional group has an acid value of 50~120 mg KOH / g and a weight-average molecular weight of 1000~8000.

9. The aging-resistant matte powder coating according to claim 1, characterized in that, The modified filler is a silane coupling agent modified filler, and the filler is at least one of magnesium aluminum hydrotalcite, titanium dioxide, silicon dioxide, quartz powder, mica powder, and aluminum hydroxide.

10. A method for preparing an aging-resistant matte powder coating, characterized in that, The preparation method is used to prepare the aging-resistant matte powder coating as described in any one of claims 1 to 9, and the preparation method includes the following steps: S1. Add modified polyester resin A, modified polyester resin B, curing agent, curing accelerator, compound matting system, modified filler, compound aging resistant system, matting aid, leveling agent and stearamide to a mixer and premix for 5 to 10 minutes at a speed of 500 to 1000 r / min to obtain a mixture. S2. Add the mixture to a twin-screw extruder, control the temperature of zone 1 of the extruder to be 80~100℃, the temperature of zone 2 to be 90~120℃, the temperature of zone 3 to be 100~130℃, and the screw speed to be 200~500rpm, melt extrusion to obtain the extruded material; S3. After cooling the extruded material, it is pressed, crushed, pulverized and graded and sieved to obtain an aging-resistant matte powder coating.

Images