Preparation method and application of high and low temperature cycle resistant powder coating

Abstract

The present application relates to the technical field of powder coating, in particular to a preparation method and application of a high and low temperature cycle resistant powder coating, which is used to solve the problems of the existing powder coating in the aspects of high and low temperature cycle resistance performance and interface bonding force; the temperature resistant polyester resin is used as a framework, the material heat resistance is improved by introducing rigid structure units, the flexible chain segment ratio is controlled to ensure the low temperature toughness, the epoxy resin is added to improve the crosslinking density and chemical resistance of the coating, and the functional groups such as carboxyl provide anchoring points for the reaction with the curing agent and the toughening agent; the epoxy group and the hydroxymethyl on the surface of the toughening agent can chemically react with the carboxyl and the hydroxyl of the resin and the curing agent to form a strong chemical bonding interface, the organic silicon improves the temperature resistance and flexibility, the fluorine-containing chain segment improves the weather resistance and hydrophobicity, the silicon dioxide hybridization improves the wear resistance and thermal stability, and the inorganic filler is added to reduce the thermal expansion coefficient of the material.

Description

Technical Field

[0001] This invention relates to the field of powder coating technology, specifically to a method for preparing and applying a high and low temperature resistant cyclic powder coating. Background Technology

[0002] Powder coatings, as an environmentally friendly coating material, have been widely used in various industrial fields. However, in special application scenarios such as aerospace, automotive engine parts, outdoor communication equipment, and infrastructure in high-altitude and cold regions, coating materials need to withstand drastic temperature changes, such as from extreme low temperatures of -60°C to high temperatures of over 200°C, and need to maintain long-term stability under such high and low temperature cycling conditions.

[0003] Currently, common powder coatings on the market generally suffer from the following problems when subjected to severe temperature cycling: Due to the difference in thermal expansion coefficients between the resin matrix and the metal substrate, thermal stress is generated during drastic temperature changes, leading to the formation and propagation of microcracks in the coating; temperature cycling weakens the interfacial adhesion between the coating and the substrate, especially in humid and hot environments, making the coating prone to peeling; repeated temperature shocks lead to a decline in the physical and mechanical properties of the coating, such as reduced flexibility and changes in hardness; some pigments and additives may undergo color changes or surface gloss loss during temperature cycling; in existing technologies, methods to improve the temperature resistance of powder coatings often fail to simultaneously ensure the stability of the coating at high temperatures and its flexibility at low temperatures, and the interfacial adhesion between the coating and the substrate remains insufficient under long-term temperature cycling conditions.

[0004] Therefore, the preparation method and application of the high and low temperature resistant powder coating of the present invention are of great significance in the field of powder coating technology. Summary of the Invention

[0005] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide a method for preparing and applying a high and low temperature resistant powder coating, which solves the problems of insufficient high and low temperature resistant performance and interfacial bonding strength of existing powder coatings.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] In a first aspect, this application provides a method for preparing a high and low temperature resistant powder coating, comprising the following steps:

[0008] Step 1: Weigh out 40-60 parts of heat-resistant polyester resin, 10-20 parts of epoxy resin, 3-8 parts of curing agent, 2-6 parts of toughening agent, 15-30 parts of inorganic filler, 5-15 parts of pigment, 1-3 parts of functional additives, and 0.5-2 parts of adhesion promoter according to the following weight proportions.

[0009] Step 2: Place the inorganic filler in an oven and dry it at 120-150℃ for 2-4 hours; add the heat-resistant polyester resin, epoxy resin, curing agent, toughening agent, pretreated inorganic filler, pigment, functional additives and adhesion promoter into a high-speed mixer and mix at 25℃ and a speed of 800-1500r / min for 5-10 minutes to obtain the premix.

[0010] Step 3: The premixed material is melt-extruded and compounded through a twin-screw extruder at a temperature of 100-130℃ and a screw speed of 300-500 r / min. The extruded material is then cooled and pressed into 1-2 mm thick sheets by a cooling roller press, and then fed into a crusher for crushing to obtain flaky particles with a particle size of about 3-8 mm.

[0011] Step 4: The crushed flaky particles are fed into an ACM mill for fine grinding, with a particle size distribution D50 of 30-40μm. The powder is then sieved using a vibrating screener to obtain a high and low temperature resistant cyclic powder coating.

[0012] In a preferred embodiment of the present invention, the epoxy resin is one of bisphenol A type epoxy resin CYD-014U and phenolic epoxy resin DEN438-A85; the curing agent is one or more of triglycidyl isocyanate, hydroxyalkylamide SDL-552 and curing agent VT5327; the pigment is a heat-resistant inorganic pigment; the heat-resistant inorganic pigment is one or more of titanium dioxide, iron oxide, cobalt blue and titanium yellow.

[0013] In a preferred embodiment of the present invention, the inorganic filler is a composition of silica powder, mica powder and talc powder in a mass ratio of 5-15g: 5-10g: 3-8g; the silica powder has a particle size of 1-10μm; the mica powder has a flake structure with a diameter-to-thickness ratio >50; and the talc powder has a needle-like structure.

[0014] In a preferred embodiment of the present invention, the functional additive is composed of defoamer T-4201A, leveling agent TEGOGlide450, ultraviolet absorber UV-531 and antioxidant 626 in a dosage ratio of 0.1-0.5g: 0.3-0.8g: 0.2-0.5g: 0.1-0.4g.

[0015] In a preferred embodiment of the present invention, the adhesion promoter is one of the following: silane coupling agent KH-550, titanate coupling agent TCA-44, and phosphate ester adhesion promoter KM2110.

[0016] In a preferred embodiment of the present invention, the heat-resistant polyester resin is prepared by the following steps:

[0017] Step a1: Ethylene glycol, phthalic anhydride, maleic anhydride, catalyst, and toluene are added to a four-necked flask equipped with a thermometer, stirrer, and reflux condenser. The mixture is heated to 120-140℃ and stirred for 0.5-2 hours. The mixture is then cooled to 90-120℃, cyclohexane oxide is added, and the mixture is stirred at a constant temperature for 3-6 hours. The mixture is then distilled under reduced pressure for 0.5-1 hour, and a diluent is added. The mixture is stirred for 30 minutes to obtain intermediate 1.

[0018] Step a2: Add 1,4-naphthalenedicarboxylic acid, terephthalic acid, intermediate 1,2,2-dimethyl-1,3-propanediol, powder additives, and liquid additives to a beaker, transfer to a polymerization reactor, replace the air in the reactor with nitrogen, pressurize with nitrogen to 0.1 MPa, start heating and stirring, raise the temperature to 200℃, raise the temperature to 230-250℃ at a rate of 1℃ / min, release the pressure to 0 MPa, add the catalyst, mix and stir for 10-15 min, turn on the vacuum pump to evacuate to -0.1 MPa, raise the temperature to 260-265℃, hold the temperature for 30-40 min, continue to raise the temperature to 280℃, and carry out the polycondensation reaction for 2-3 h. After water cooling and granulation, obtain the heat-resistant polyester resin.

[0019] In a preferred embodiment of the present invention, the ratio of ethylene glycol, phthalic anhydride, maleic anhydride, catalyst, toluene, cyclohexane oxide, and diluent in step a1 is 65-70 mL: 145-150 g: 95-100 g: 1-3 g: 100-200 mL: 90-95 mL: 100-150 mL; the catalyst is hexadecyltrimethylammonium bromide; and the diluent is styrene.

[0020] In a preferred embodiment of the present invention, the ratio of 1,4-naphthalenedicarboxylic acid, terephthalic acid, intermediate 1,2,2-dimethyl-1,3-propanediol, powder additive, liquid additive, and catalyst in step a2 is 150-195g:16-50g:150-180mL:45-60g:0.5-2g:5-10mL:5-10mL; the powder additive is a mixture of antimony glycolate and anhydrous sodium acetate in a molar ratio of 0.6mol:0.5mol; the liquid additive is triphenyl phosphite; and the catalyst is tetrabutyl titanate.

[0021] In a preferred embodiment of the present invention, the toughening agent is prepared by the following steps:

[0022] Step b1: Perfluorooctanoic acid, p-hydroxyanisole, tetrabutylammonium bromide and glycidyl methacrylate were added to a three-necked flask equipped with a stirrer, reflux condenser and thermometer. Nitrogen gas was introduced for protection, and the mixture was stirred at 100°C for 24 h. The mixture was then distilled under reduced pressure for 1-2 h, extracted with diethyl ether, washed 1-2 times with sodium chloride solution, sodium carbonate solution and deionized water, dried with anhydrous sodium sulfate for 30 min, and evaporated to dryness to obtain the fluorinated monomer.

[0023] Step b2: Nonylphenol polyoxyethylene ether, sodium dodecyl sulfonate, and deionized water are added to a three-necked flask equipped with a stirrer, reflux condenser, and thermometer. The mixture is stirred for 30 minutes and then divided into two equal groups. The first group contains butyl acrylate, a first portion of acrylic acid, and a first portion of N-hydroxymethyl acrylamide. The mixture is stirred at 500 rpm for 30 minutes to obtain a core pre-emulsion. The second group contains isobornyl methacrylate, a second portion of acrylic acid, glycidyl methacrylate, a second portion of N-hydroxymethyl acrylamide, tetrabutylammonium bromide, and a fluorinated monomer. The mixture is stirred at 500 rpm for 30 minutes to obtain a shell pre-emulsion. The first portion of acrylic acid constitutes half of the total amount of acrylic acid. The first portion of N-hydroxymethyl acrylamide constitutes half of the total amount of N-hydroxymethyl acrylamide. The second portion of acrylic acid constitutes half of the total amount of acrylic acid. The second portion of N-hydroxymethyl acrylamide constitutes half of the total amount of N-hydroxymethyl acrylamide.

[0024] Step b3: Add the core preemulsion and the first initiator to a four-necked flask equipped with a stirrer and thermometer. Purge with nitrogen for protection and mix at 60°C and 200 rpm for 1 hour. Add the first shell preemulsion and the second initiator to the reactor and mix for 2-3 hours. Mix the second shell preemulsion, organosilicon, and the third initiator for 1-2 hours and add to the reactor. Heat to 70-72°C, add the fourth initiator, and react at a constant temperature for 2-3 hours. Allow to cool naturally to 25°C, add tetraethyl orthosilicate, and maintain the reaction temperature for 12 hours. Adjust the pH to 7 using a pH adjuster and filter. The material was discharged and added to the four-necked flask mentioned above. Sodium bisulfite solution was added, and the mixture was kept at 65°C for 30 minutes. It was then naturally cooled to 25°C, and the pH was adjusted to 8-9 with ammonia. The gel was filtered off to obtain the toughening agent. The amount of the first shell pre-emulsion accounted for 70% of the total amount of the shell pre-emulsion. The amount of the first initiator accounted for 20% of the total amount of the initiator. The amount of the second initiator accounted for 35% of the total amount of the initiator. The amount of the second shell pre-emulsion accounted for 30% of the total amount of the shell pre-emulsion. The amount of the third initiator accounted for 35% of the total amount of the initiator. The amount of the fourth initiator accounted for 10% of the total amount of the initiator.

[0025] In a preferred embodiment of the present invention, the ratio of perfluorooctanoic acid, p-hydroxyanisole, tetrabutylammonium bromide, glycidyl methacrylate, diethyl ether, and anhydrous sodium sulfate in step b1 is 8-20g:0.05-0.1g:0.04-0.08g:5-8mL:100mL:3-5g; the mass fraction of the sodium chloride solution is 15%; and the mass fraction of the sodium carbonate solution is 5%.

[0026] In a preferred embodiment of the present invention, the ratio of nonylphenol polyoxyethylene ether, sodium dodecyl sulfonate, deionized water, butyl acrylate, total acrylic acid, total N-hydroxymethylacrylamide, isobornyl methacrylate, glycidyl methacrylate, tetrabutylammonium bromide, and fluorinated monomers in step b2 is 1.5-2 mL: 1.5-2 g: 100-120 mL: 40-45 mL: 4-5 mL: 2-3 g: 40-45 mL: 2.5-3 mL: 0.1-0.2 g: 5-6 g.

[0027] In a preferred embodiment of the present invention, the ratio of the total amount of core preemulsion, initiator, shell preemulsion, organosilicon, tetraethyl orthosilicate, and sodium bisulfite solution in step b3 is 10-30 mL: 1-2 g: 50-60 mL: 0.5-1 g: 6-8 mL: 3-5 mL; the initiator is ammonium persulfate; the organosilicon is one of KH-570, A-172, A-151, and Vi-D4; the mass fraction of the sodium bisulfite solution is 20-30%; and the pH adjuster is AM-95.

[0028] Secondly, this application provides the application of the high and low temperature resistant powder coating prepared by the method described in the first aspect in coating materials.

[0029] The beneficial effects of this invention are:

[0030] This invention discloses a method for preparing and applying a high- and low-temperature resistant cyclic powder coating. The method involves drying inorganic fillers to remove moisture; mixing the components according to the formula ratio in a high-speed mixer; passing the premix through a twin-screw extruder, pressing the extrudate through cooling rollers, and then crushing it into flakes after cooling; pulverizing the flakes using an ACM mill to control the particle size distribution; and sieving to remove coarse particles and fine powder to obtain the finished powder coating. The heat-resistant polyester resin is improved by introducing rigid structural units, while controlling the proportion of flexible segments to ensure low-temperature toughness. Epoxy resin is added to improve the crosslinking density and chemical resistance of the coating. The toughening agent is a core-shell structured acrylate polymer that is modified to improve the low-temperature toughness and impact resistance of the coating. Inorganic fillers are added to reduce the coefficient of thermal expansion.

[0031] In the preparation of high and low temperature cycling resistant powder coatings, a heat-resistant polyester resin was first prepared. The hydroxyl groups of ethylene glycol attacked the carbonyl groups of phthalic anhydride and maleic anhydride, undergoing a ring-opening reaction to generate chain segments with carboxyl groups at both ends, introducing a benzene ring. After cooling, cyclohexane oxide was added. The carboxyl groups at the end of the prepolymer attacked the epoxy groups of cyclohexane oxide, undergoing a ring-opening reaction to generate an ester bond and a new secondary hydroxyl group. After ring-opening, the saturated six-membered ring structure of cyclohexane oxide remained intact in the main chain. A diluent was added to reduce the viscosity, yielding a stable liquid intermediate 1. The terminal carboxyl and hydroxyl groups, and the unsaturated double bonds in the chain served as the final... The "active flexible segments" of the continuous polycondensation provide the basis for toughness, adhesion, and crosslinking sites. Under high temperature and catalysis, the carboxyl groups of 1,4-naphthalenedicarboxylic acid and terephthalic acid undergo dehydration condensation with the hydroxyl groups of the intermediate 1,2,2-dimethyl-1,3-propanediol to form ester bonds, resulting in a heat-resistant polyester resin. The naphthalene ring and terephthalic acid benzene ring in the main chain provide high rigidity, giving the coating high hardness and high heat deformation resistance, ensuring high-temperature dimensional stability. The embedded flexible segments can absorb and dissipate stress through small deformations during low temperature or thermal shock, preventing the generation and propagation of microcracks.

[0032] In the preparation of high and low temperature cycling resistant powder coatings, a toughening agent was first prepared. The carboxylic acid of perfluorooctanoic acid (PFOA) undergoes a ring-opening esterification reaction with the epoxy group of glycidyl methacrylate. Tetrabutylammonium bromide acts as a phase transfer catalyst to promote the reaction, and p-hydroxyanisole acts as a polymerization inhibitor to prevent the double bonds in glycidyl methacrylate from undergoing thermal polymerization during heating, yielding a fluorinated monomer. One end of the molecule is a hydrophobic and oleophobic long perfluorocarbon chain, and the other end is an acrylate double bond that can participate in free radical polymerization. The core layer pre-emulsion is mainly composed of flexible monomers. Butyl acrylate provides excellent low-temperature flexibility and high elasticity, while acrylic acid provides hydrophilicity and carboxyl groups. This process helps stabilize the emulsion and provides active sites for subsequent reactions. The shell preemulsion is mainly composed of rigid / functional monomers. Isoborneol methacrylate, with its large rigid alicyclic structure, provides high hardness, high heat resistance, and hydrophobicity. Fluorinated monomers introduce low surface energy fluorocarbon chains, and glycidyl methacrylate provides epoxy groups, which can react with the carboxyl and amino groups of other raw materials in the powder coating to enhance interfacial bonding. Tetrabutylammonium bromide serves as an emulsification aid. A preemulsion with a core-shell structure design is prepared to lay the foundation for subsequent emulsion polymerization. The core preemulsion and part of the initiator are added first to form seed latex particles, and then most of the shell preemulsion is added to react. The first step, shell polymerization, polymerizes on the seed surface to form the main shell layer, introducing functional monomers. The remaining shell pre-emulsion, organosilicon monomers, and initiators are added to initiate the second step of shell polymerization and hybridization. Silane coupling agent monomers participate in the polymerization, introducing polysiloxane segments into the outermost layer of the particles, improving flexibility, temperature resistance, and hydrophobicity. Tetraethyl orthosilicate is added; its surface silanol groups interact with silanoxy groups or other polar groups on the polymer chains to form an organic-inorganic hybrid structure, improving the particle modulus and wear resistance, thus obtaining a toughening agent. Using a multi-component synergistic approach, the organosilicon shell imparts good low-temperature flexibility and high-temperature stability, while the fluorinated segments... The coating surface migrates, forming a low surface energy protective layer, reducing environmental erosion. Silica-hybridized inorganic nanoparticles improve the thermal stability and high-temperature strength retention of the composite material. When the coating is subjected to impact or thermal stress, the soft-core particles dispersed in the rigid resin matrix act as stress concentration points, inducing shear yielding or creasing of the surrounding matrix, thereby absorbing and dissipating a large amount of energy, preventing crack propagation, and improving impact resistance. Fluorine-containing segments and organosilicon segments have extremely strong chemical inertness, effectively resisting the erosion of ultraviolet light, ozone, acids, alkalis, and moisture. The chemically bonded interface reduces the path of water vapor penetration along the interface, improving the coating's lifespan. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to a table comparing the embodiments and comparative examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] Example 1:

[0035] This embodiment describes a method for preparing a high and low temperature resistant powder coating, comprising the following steps:

[0036] Step S1: Add 65 mL of ethylene glycol, 145 g of phthalic anhydride, 95 g of maleic anhydride, 1 g of hexadecyltrimethylammonium bromide, and 100 mL of toluene to a four-necked flask equipped with a thermometer, stirrer, and reflux condenser. Heat to 120 °C, mix and stir for 0.5 h, cool to 90 °C, add 90 mL of cyclohexane oxide, continue stirring at a constant temperature for 3 h, distill under reduced pressure for 0.5 h, add 100 mL of styrene, mix and stir for 30 min to obtain intermediate 1;

[0037] Step S2: Add 150g of 1,4-naphthalenedicarboxylic acid, 16g of terephthalic acid, 150mL of intermediate 1, 45g of 2,2-dimethyl-1,3-propanediol, 0.5g of ethylene glycol antimony and anhydrous sodium acetate in a molar ratio of 0.6mol:0.5mol to a beaker, transfer to a polymerization reactor, replace the air in the reactor with nitrogen, pressurize with nitrogen to 0.1MPa, start heating and stirring, raise the temperature to 200℃, raise the temperature to 230℃ at a rate of 1℃ / min, release the pressure to 0MPa, add 5mL of tetrabutyl titanate, mix and stir for 10min, turn on the vacuum pump to evacuate to -0.1MPa, raise the temperature to 260℃, hold the temperature for 30min, continue to raise the temperature to 280℃, and carry out the polycondensation reaction for 2h. After water cooling and granulation, heat-resistant polyester resin is obtained.

[0038] Step S3: Add 8g of perfluorooctanoic acid, 0.05g of p-hydroxyanisole, 0.04g of tetrabutylammonium bromide and 5mL of glycidyl methacrylate to a three-necked flask equipped with a stirrer, reflux condenser and thermometer. Purge with nitrogen and stir at 100℃ for 24h. Distill under reduced pressure for 1h. Extract with 100mL of diethyl ether. Wash once with 15% sodium chloride solution, 5% sodium carbonate solution and deionized water. Add 3g of anhydrous sodium sulfate and dry for 30min. Rotate to dryness to obtain fluorine-containing monomer.

[0039] Step S4: Add 1.5 mL of nonylphenol polyoxyethylene ether, 1.5 g of sodium dodecyl sulfonate, and 100 mL of deionized water to a three-necked flask equipped with a stirrer, reflux condenser, and thermometer. Mix and stir for 30 min. Divide the mixture into two equal groups. For the first group, add 40 mL of butyl acrylate, 2 mL of acrylic acid, and 1 g of N-hydroxymethylacrylamide. Stir at 500 r / min for 30 min to obtain the core preemulsion. For the second group, add 40 mL of isobornyl methacrylate, 2 mL of acrylic acid, 2.5 mL of glycidyl methacrylate, 1 g of N-hydroxymethylacrylamide, 0.1 g of tetrabutylammonium bromide, and 5 g of fluorinated monomer. Stir at 500 r / min for 30 min to obtain the shell preemulsion.

[0040] Step S5: Add 10 mL of core pre-emulsion and 0.2 g of initiator to a four-necked flask equipped with a stirrer and thermometer, purge with nitrogen for protection, and mix and stir at 200 r / min for 1 h at 60 °C; add 35 mL of shell pre-emulsion and 0.35 g of initiator to a reactor, and mix and stir for 2 h; mix and stir 15 mL of shell pre-emulsion, 0.5 g of organosilicon KH-570 and 0.35 g of initiator for 1 h, add to the above reactor, heat to 70 °C, add 0.1 g of initiator, react at a constant temperature for 2 h, cool naturally to 25 °C, add 6 mL of tetraethyl orthosilicate, keep the reaction at the same temperature for 12 h, adjust the pH to 7 with pH adjuster AM-95, filter out the product, add to the above four-necked flask, add 3 mL of 20% sodium bisulfite solution, keep at 65 °C for 30 min, cool naturally to 25 °C, adjust the pH to 8 with ammonia, filter out the gel, and obtain the toughening agent;

[0041] Step S6: Weigh out 40 parts by weight of heat-resistant polyester resin, 10 parts by weight of bisphenol A type epoxy resin CYD-014U, 3 parts by weight of triglycidyl isocyanate, 2 parts by weight of toughening agent, 15 parts by weight of inorganic filler, 5 parts by weight of titanium dioxide, 1 part by weight of functional additive, and 0.5 parts by weight of silane coupling agent KH-550; the inorganic filler is a composition of silica powder, mica powder and talc powder in a mass ratio of 5g:5g:3g; the silica powder has a particle size of 1μm; the functional additive is a mixture of defoamer T-4201A, leveling agent TEGO Glide450, ultraviolet absorber UV-531 and antioxidant 626 in a dosage ratio of 0.1g:0.3g:0.2g:0.1g.

[0042] Step S7: Place the inorganic filler in an oven and dry it at 120℃ for 2 hours; add the heat-resistant polyester resin, bisphenol A type epoxy resin CYD-014U, triglycidyl isocyanate, toughening agent, pretreated inorganic filler, titanium dioxide, functional additives and silane coupling agent KH-550 into a high-speed mixer and mix at 25℃ and 800 r / min for 5 minutes to obtain a premix.

[0043] Step S8: The premixed material is melt-extruded and compounded through a twin-screw extruder at a temperature of 100℃ and a screw speed of 300r / min. The extruded material is cooled and pressed into 1mm thick sheets through a cooling roller tablet press, and then fed into a crusher for crushing to obtain flaky particles with a particle size of about 3mm.

[0044] Step S9: The crushed flaky particles are fed into an ACM mill for fine grinding, with a particle size distribution D50 of 30μm. The powder is then sieved using a vibrating screener to obtain a high and low temperature resistant cyclic powder coating.

[0045] Example 2:

[0046] This embodiment describes a method for preparing a high and low temperature resistant powder coating, comprising the following steps:

[0047] Step S1: Add 68 mL of ethylene glycol, 148 g of phthalic anhydride, 98 g of maleic anhydride, 2 g of hexadecyltrimethylammonium bromide, and 150 mL of toluene to a four-necked flask equipped with a thermometer, stirrer, and reflux condenser. Heat to 130 °C, mix and stir for 1 h, cool to 105 °C, add 93 mL of cyclohexane oxide, continue stirring at a constant temperature for 4.5 h, distill under reduced pressure for 45 min, add 125 mL of styrene, mix and stir for 30 min to obtain intermediate 1;

[0048] Step S2: 170g of 1,4-naphthalenedicarboxylic acid, 33g of terephthalic acid, 165mL of intermediate 1, 55g of 2,2-dimethyl-1,3-propanediol, 1g of antimony glycol and anhydrous sodium acetate mixed in a molar ratio of 0.6mol:0.5mol, and 8mL of triphenyl phosphite were added to a beaker, transferred to a polymerization reactor, and the air inside the reactor was replaced with nitrogen. The reactor was pressurized to 0.1MPa with nitrogen and the temperature was raised and stirred. When the temperature reached 200℃, it was raised to 240℃ at a rate of 1℃ / min. The pressure was then released to 0MPa, and 8mL of tetrabutyl titanate was added. The mixture was stirred for 13min, and the vacuum pump was turned on to evacuate to -0.1MPa. The temperature was raised to 263℃ and held for 35min. The temperature was then raised to 280℃ and the polycondensation reaction was carried out for 2.5h. After water cooling and granulation, the heat-resistant polyester resin was obtained.

[0049] Step S3: 14g of perfluorooctanoic acid, 0.08g of p-hydroxyanisole, 0.06g of tetrabutylammonium bromide and 7mL of glycidyl methacrylate were added to a three-necked flask equipped with a stirrer, reflux condenser and thermometer. Nitrogen gas was introduced for protection, and the mixture was stirred at 100℃ for 24h. The mixture was then distilled under reduced pressure for 1.5h, extracted with 100mL of diethyl ether, and washed twice with 15% sodium chloride solution, 5% sodium carbonate solution and deionized water, respectively. 4g of anhydrous sodium sulfate was added and dried for 30min. The mixture was then evaporated to dryness to obtain the fluorinated monomer.

[0050] Step S4: Add 1.8 mL of nonylphenol polyoxyethylene ether, 1.8 g of sodium dodecyl sulfonate, and 110 mL of deionized water to a three-necked flask equipped with a stirrer, reflux condenser, and thermometer. Mix and stir for 30 min. Divide the mixture into two groups. For the first group, add 43 mL of butyl acrylate, 2.3 mL of acrylic acid, and 1.3 g of N-hydroxymethylacrylamide. Stir at 500 rpm for 30 min to obtain the core preemulsion. For the second group, add 43 mL of isobornyl methacrylate, 2.3 mL of acrylic acid, 2.8 mL of glycidyl methacrylate, 1.3 g of N-hydroxymethylacrylamide, 0.15 g of tetrabutylammonium bromide, and 5.5 g of fluorinated monomer. Stir at 500 rpm for 30 min to obtain the shell preemulsion.

[0051] Step S5: Add 20 mL of core preemulsion and 0.3 g of initiator to a four-necked flask equipped with a stirrer and thermometer, purge with nitrogen for protection, and mix and stir at 200 r / min for 1 h at 60 °C; add 38 mL of shell preemulsion and 0.5 g of initiator to the reactor, and mix and stir for 2.5 h; mix and stir 17 mL of shell preemulsion, 0.8 g of organosilicon KH-570 and 0.5 g of initiator for 1.5 h, and add to the above reactor. The temperature was raised to 71°C, 0.15g of initiator was added, and the reaction was kept at a constant temperature for 2.5h. The temperature was then naturally cooled to 25°C, 7mL of tetraethyl orthosilicate was added, and the reaction was kept at a constant temperature for 12h. The pH was adjusted to 7 with pH adjuster AM-95, the product was filtered out, and the product was added to the above four-necked flask. 4mL of 25% sodium bisulfite solution was added, and the temperature was kept at 65°C for 30min. The temperature was then naturally cooled to 25°C, the pH was adjusted to 9 with ammonia, and the gel was filtered off to obtain the toughening agent.

[0052] Step S6: Weigh out 50 parts by weight of heat-resistant polyester resin, 15 parts by weight of bisphenol A type epoxy resin CYD-014U, 5 parts by weight of triglycidyl isocyanate, 4 parts by weight of toughening agent, 22 parts by weight of inorganic filler, 10 parts by weight of titanium dioxide, 2 parts by weight of functional additive, and 1 part by weight of silane coupling agent KH-550; the inorganic filler is a composition of silica powder, mica powder and talc powder in a mass ratio of 10g:8g:5g; the silica powder has a particle size of 5μm; the functional additive is a mixture of defoamer T-4201A, leveling agent TEGO Glide450, ultraviolet absorber UV-531 and antioxidant 626 in a dosage ratio of 0.3g:0.5g:0.4g:0.3g.

[0053] Step S7: Place the inorganic filler in an oven and dry it at 135℃ for 3 hours; add the heat-resistant polyester resin, bisphenol A type epoxy resin CYD-014U, triglycidyl isocyanate, toughening agent, pretreated inorganic filler, titanium dioxide, functional additives and silane coupling agent KH-550 into a high-speed mixer and mix at 1150 r / min for 8 minutes at 25℃ to obtain a premix.

[0054] Step S8: The premixed material is melt-extruded and compounded through a twin-screw extruder at a temperature of 115℃ and a screw speed of 400r / min. The extruded material is cooled and pressed into 1.5mm thick sheets through a cooling roller tablet press, and then fed into a crusher for crushing to obtain flaky particles with a particle size of about 5mm.

[0055] Step S9: The crushed flaky particles are fed into an ACM mill for fine grinding, with a particle size distribution D50 of 35μm. The powder is then sieved using a vibrating screener to obtain a high and low temperature resistant cyclic powder coating.

[0056] Example 3:

[0057] This embodiment describes a method for preparing a high and low temperature resistant powder coating, comprising the following steps:

[0058] Step S1: Add 70 mL of ethylene glycol, 150 g of phthalic anhydride, 100 g of maleic anhydride, 3 g of hexadecyltrimethylammonium bromide and 200 mL of toluene to a four-necked flask equipped with a thermometer, stirrer and reflux condenser. Heat to 140 °C and stir for 2 h. Cool to 120 °C and add 95 mL of cyclohexane oxide. Continue stirring at a constant temperature for 6 h. Distill under reduced pressure for 1 h. Add 150 mL of styrene and stir for 30 min to obtain intermediate 1.

[0059] Step S2: Add 195g of 1,4-naphthalenedicarboxylic acid, 50g of terephthalic acid, 180mL of intermediate 1, 60g of 2,2-dimethyl-1,3-propanediol, 2g of antimony glycol and anhydrous sodium acetate in a molar ratio of 0.6mol:0.5mol to a beaker, transfer to a polymerization reactor, replace the air in the reactor with nitrogen, pressurize with nitrogen to 0.1MPa, start heating and stirring, raise the temperature to 200℃, raise the temperature to 250℃ at a rate of 1℃ / min, release the pressure to 0MPa, add 10mL of tetrabutyl titanate, mix and stir for 15min, turn on the vacuum pump to evacuate to -0.1MPa, raise the temperature to 265℃, hold the temperature for 40min, continue to raise the temperature to 280℃, and carry out the polycondensation reaction for 3h. After water cooling and granulation, heat-resistant polyester resin is obtained.

[0060] Step S3: Add 20g of perfluorooctanoic acid, 0.1g of p-hydroxyanisole, 0.08g of tetrabutylammonium bromide and 8mL of glycidyl methacrylate to a three-necked flask equipped with a stirrer, reflux condenser and thermometer. Purge with nitrogen and stir at 100℃ for 24h. Distill under reduced pressure for 2h. Extract with 100mL of diethyl ether. Wash twice with 15% sodium chloride solution, 5% sodium carbonate solution and deionized water. Add 5g of anhydrous sodium sulfate and dry for 30min. Rotate dry to obtain fluorine-containing monomer.

[0061] Step S4: Add 2 mL of nonylphenol polyoxyethylene ether, 2 g of sodium dodecyl sulfonate, and 120 mL of deionized water to a three-necked flask equipped with a stirrer, reflux condenser, and thermometer. Mix and stir for 30 min. Divide the mixture into two groups. For the first group, add 45 mL of butyl acrylate, 2.5 mL of acrylic acid, and 1.5 g of N-hydroxymethylacrylamide. Stir at 500 rpm for 30 min to obtain the core preemulsion. For the second group, add 45 mL of isobornyl methacrylate, 2.5 mL of acrylic acid, 3 mL of glycidyl methacrylate, 1.5 g of N-hydroxymethylacrylamide, 0.2 g of tetrabutylammonium bromide, and 6 g of fluorinated monomer. Stir at 500 rpm for 30 min to obtain the shell preemulsion.

[0062] Step S5: Add 30 mL of core pre-emulsion and 0.4 g of initiator to a four-necked flask equipped with a stirrer and thermometer, purge with nitrogen for protection, and mix and stir at 200 r / min for 1 h at 60 °C; add 42 mL of shell pre-emulsion and 0.7 g of initiator to a reactor, and mix and stir for 3 h; mix and stir 18 mL of shell pre-emulsion, 1 g of organosilicon KH-570 and 0.7 g of initiator for 2 h, add to the above reactor, heat to 72 °C, add 0.2 g of initiator, react at a constant temperature for 3 h, cool naturally to 25 °C, add 8 mL of tetraethyl orthosilicate, keep the reaction at this temperature for 12 h, adjust the pH to 7 with pH adjuster AM-95, filter out the product, add to the above four-necked flask, add 5 mL of sodium bisulfite solution, keep at 65 °C for 30 min, cool naturally to 25 °C, adjust the pH to 9 with ammonia, filter out the gel, and obtain the toughening agent;

[0063] Step S6: Weigh out 60 parts by weight of heat-resistant polyester resin, 20 parts by weight of bisphenol A type epoxy resin CYD-014U, 8 parts by weight of triglycidyl isocyanate, 6 parts by weight of toughening agent, 30 parts by weight of inorganic filler, 15 parts by weight of titanium dioxide, 3 parts by weight of functional additives, and 2 parts by weight of silane coupling agent KH-550; the inorganic filler is a composition of silica powder, mica powder and talc powder in a mass ratio of 15g:10g:8g; the silica powder has a particle size of 10μm; the functional additives are composed of defoamer T-4201A, leveling agent TEGO Glide450, ultraviolet absorber UV-531 and antioxidant 626 in a dosage ratio of 0.5g:0.8g:0.5g:0.4g.

[0064] Step S7: Place the inorganic filler in an oven and dry it at 150℃ for 4 hours; add the heat-resistant polyester resin, bisphenol A type epoxy resin CYD-014U, triglycidyl isocyanate, toughening agent, pretreated inorganic filler, titanium dioxide, functional additives and silane coupling agent KH-550 into a high-speed mixer and mix at 1500 r / min for 10 minutes at 25℃ to obtain a premix.

[0065] Step S8: The premixed material is melt-extruded and compounded through a twin-screw extruder at a temperature of 130°C and a screw speed of 500 r / min. The extruded material is cooled and pressed into 2 mm thick sheets through a cooling roller sheeter and then fed into a crusher for crushing to obtain flaky particles with a particle size of about 8 mm.

[0066] Step S9: The crushed flaky particles are fed into an ACM mill for fine grinding, with a particle size distribution D50 of 40μm. The powder is then sieved using a vibrating screener to obtain a high and low temperature resistant cyclic powder coating.

[0067] Comparative Example 1:

[0068] This comparative example illustrates a method for preparing a high and low temperature resistant powder coating, comprising the following steps:

[0069] Step S1: Weigh out 50 parts by weight of polyester resin FX-450, 15 parts by weight of bisphenol A epoxy resin CYD-014U, 5 parts by weight of triglycidyl isocyanate, 4 parts by weight of toughening agent QS-P24F, 22 parts by weight of inorganic filler, 10 parts by weight of titanium dioxide, 2 parts by weight of functional additives, and 1 part by weight of silane coupling agent KH-550; the inorganic filler is a composition of silica powder, mica powder and talc powder in a mass ratio of 10g:8g:5g; the silica powder has a particle size of 5μm; the functional additives are composed of defoamer T-4201A, leveling agent TEGO Glide450, ultraviolet absorber UV-531 and antioxidant 626 in a dosage ratio of 0.3g:0.5g:0.4g:0.3g.

[0070] Step S2: Place the inorganic filler in an oven and dry it at 135℃ for 3 hours; add polyester resin FX-450, bisphenol A epoxy resin CYD-014U, triglycidyl isocyanate, toughening agent QS-P24F, pretreated inorganic filler, titanium dioxide, functional additives and silane coupling agent KH-550 into a high-speed mixer and mix at 1150 r / min for 8 minutes at 25℃ to obtain a premix.

[0071] Step S3: The premixed material is melt-extruded and compounded through a twin-screw extruder at a temperature of 115℃ and a screw speed of 400r / min. The extruded material is cooled and pressed into 1.5mm thick sheets through a cooling roller sheeter and then fed into a crusher for crushing to obtain flaky particles with a particle size of about 5mm.

[0072] Step S4: The crushed flaky particles are fed into an ACM mill for fine grinding, with a particle size distribution D50 of 35μm. The powder is then sieved using a vibrating screener to obtain a high and low temperature resistant cyclic powder coating.

[0073] Comparative Example 2:

[0074] This comparative example illustrates a method for preparing a high and low temperature resistant powder coating, comprising the following steps:

[0075] Step S1: Add 68 mL of ethylene glycol, 148 g of phthalic anhydride, 98 g of maleic anhydride, 2 g of hexadecyltrimethylammonium bromide, and 150 mL of toluene to a four-necked flask equipped with a thermometer, stirrer, and reflux condenser. Heat to 130 °C, mix and stir for 1 h, cool to 105 °C, add 93 mL of cyclohexane oxide, continue stirring at a constant temperature for 4.5 h, distill under reduced pressure for 45 min, add 125 mL of styrene, mix and stir for 30 min to obtain intermediate 1;

[0076] Step S2: 170g of 1,4-naphthalenedicarboxylic acid, 33g of terephthalic acid, 165mL of intermediate 1, 55g of 2,2-dimethyl-1,3-propanediol, 1g of antimony glycol and anhydrous sodium acetate mixed in a molar ratio of 0.6mol:0.5mol, and 8mL of triphenyl phosphite were added to a beaker, transferred to a polymerization reactor, and the air inside the reactor was replaced with nitrogen. The reactor was pressurized to 0.1MPa with nitrogen and the temperature was raised and stirred. When the temperature reached 200℃, it was raised to 240℃ at a rate of 1℃ / min. The pressure was then released to 0MPa, and 8mL of tetrabutyl titanate was added. The mixture was stirred for 13min, and the vacuum pump was turned on to evacuate to -0.1MPa. The temperature was raised to 263℃ and held for 35min. The temperature was then raised to 280℃ and the polycondensation reaction was carried out for 2.5h. After water cooling and granulation, the heat-resistant polyester resin was obtained.

[0077] Step S3: Weigh out 50 parts by weight of heat-resistant polyester resin, 15 parts by weight of bisphenol A type epoxy resin CYD-014U, 5 parts by weight of triglycidyl isocyanate, 4 parts by weight of toughening agent QS-P24F, 22 parts by weight of inorganic filler, 10 parts by weight of titanium dioxide, 2 parts by weight of functional additives, and 1 part by weight of silane coupling agent KH-550; the inorganic filler is a composition of silica powder, mica powder and talc powder in a mass ratio of 10g:8g:5g; the silica powder has a particle size of 5μm; the functional additives are composed of defoamer T-4201A, leveling agent TEGOGlide450, ultraviolet absorber UV-531 and antioxidant 626 in a dosage ratio of 0.3g:0.5g:0.4g:0.3g.

[0078] Step S4: Place the inorganic filler in an oven and dry it at 135℃ for 3 hours; add the heat-resistant polyester resin, bisphenol A type epoxy resin CYD-014U, triglycidyl isocyanate, toughening agent QS-P24F, pretreated inorganic filler, titanium dioxide, functional additives and silane coupling agent KH-550 into a high-speed mixer and mix at 1150 r / min for 8 minutes at 25℃ to obtain a premix.

[0079] Step S5: The premixed material is melt-extruded and compounded through a twin-screw extruder at a temperature of 115℃ and a screw speed of 400r / min. The extruded material is cooled and pressed into 1.5mm thick sheets through a cooling roller tablet press, and then fed into a crusher for crushing to obtain flaky particles with a particle size of about 5mm.

[0080] Step S6: The crushed flaky particles are fed into an ACM mill for fine grinding, with a particle size distribution D50 of 35μm. The powder is then sieved using a vibrating screener to obtain a high and low temperature resistant cyclic powder coating.

[0081] Comparative Example 3:

[0082] This comparative example illustrates a method for preparing a high and low temperature resistant powder coating, comprising the following steps:

[0083] Step S1: 14g of perfluorooctanoic acid, 0.08g of p-hydroxyanisole, 0.06g of tetrabutylammonium bromide and 7mL of glycidyl methacrylate were added to a three-necked flask equipped with a stirrer, reflux condenser and thermometer. Nitrogen gas was introduced for protection, and the mixture was stirred at 100℃ for 24h. The mixture was then distilled under reduced pressure for 1.5h, extracted with 100mL of diethyl ether, and washed twice with 15% sodium chloride solution, 5% sodium carbonate solution and deionized water. 4g of anhydrous sodium sulfate was added and dried for 30min. The mixture was then evaporated to dryness to obtain the fluorinated monomer.

[0084] Step S2: Add 1.8 mL of nonylphenol polyoxyethylene ether, 1.8 g of sodium dodecyl sulfonate, and 110 mL of deionized water to a three-necked flask equipped with a stirrer, reflux condenser, and thermometer. Mix and stir for 30 min. Divide the mixture into two groups. For the first group, add 43 mL of butyl acrylate, 2.3 mL of acrylic acid, and 1.3 g of N-hydroxymethylacrylamide. Stir at 500 rpm for 30 min to obtain the core preemulsion. For the second group, add 43 mL of isobornyl methacrylate, 2.3 mL of acrylic acid, 2.8 mL of glycidyl methacrylate, 1.3 g of N-hydroxymethylacrylamide, 0.15 g of tetrabutylammonium bromide, and 5.5 g of fluorinated monomer. Stir at 500 rpm for 30 min to obtain the shell preemulsion.

[0085] Step S3: Add 20 mL of core preemulsion and 0.3 g of initiator to a four-necked flask equipped with a stirrer and thermometer, purge with nitrogen for protection, and mix and stir at 200 r / min for 1 h at 60 °C; add 38 mL of shell preemulsion and 0.5 g of initiator to the reactor, and mix and stir for 2.5 h; mix and stir 17 mL of shell preemulsion, 0.8 g of organosilicon KH-570 and 0.5 g of initiator for 1.5 h, and add to the above reactor. The temperature was raised to 71°C, 0.15g of initiator was added, and the reaction was kept at a constant temperature for 2.5h. The temperature was then naturally cooled to 25°C, 7mL of tetraethyl orthosilicate was added, and the reaction was kept at a constant temperature for 12h. The pH was adjusted to 7 with pH adjuster AM-95, the product was filtered out, and the product was added to the above four-necked flask. 4mL of 25% sodium bisulfite solution was added, and the temperature was kept at 65°C for 30min. The temperature was then naturally cooled to 25°C, the pH was adjusted to 9 with ammonia, and the gel was filtered off to obtain the toughening agent.

[0086] Step S4: Weigh out 50 parts by weight of polyester resin FX-450, 15 parts by weight of bisphenol A epoxy resin CYD-014U, 5 parts by weight of triglycidyl isocyanate, 4 parts by weight of toughening agent, 22 parts by weight of inorganic filler, 10 parts by weight of titanium dioxide, 2 parts by weight of functional additive, and 1 part by weight of silane coupling agent KH-550; the inorganic filler is a composition of silica powder, mica powder and talc powder in a mass ratio of 10g:8g:5g; the silica powder has a particle size of 5μm; the functional additive is a mixture of defoamer T-4201A, leveling agent TEGOGlide450, ultraviolet absorber UV-531 and antioxidant 626 in a dosage ratio of 0.3g:0.5g:0.4g:0.3g.

[0087] Step S5: Place the inorganic filler in an oven and dry it at 135℃ for 3 hours; add polyester resin FX-450, bisphenol A epoxy resin CYD-014U, triglycidyl isocyanate, toughening agent, pretreated inorganic filler, titanium dioxide, functional additives and silane coupling agent KH-550 into a high-speed mixer and mix at 1150 r / min for 8 minutes at 25℃ to obtain a premix.

[0088] Step S6: The premixed material is melt-extruded and compounded through a twin-screw extruder at a temperature of 115℃ and a screw speed of 400r / min. The extruded material is cooled and pressed into 1.5mm thick sheets through a cooling roller sheeter and then fed into a crusher for crushing to obtain flaky particles with a particle size of about 5mm.

[0089] Step S7: The crushed flaky particles are fed into an ACM mill for fine grinding, with a particle size distribution D50 of 35μm. The powder is then sieved using a vibrating screener to obtain a high and low temperature resistant cyclic powder coating.

[0090] The powder coatings prepared in Examples 1-3 and Comparative Examples 1-3 were tested according to the cold and heat resistance test method of GB / T 4893.7-2013: The powder coatings were applied to the test specimens and placed in an air-circulated environment at 25°C for 7 days. The adhesion grade (cross-cut test) and flexibility (bending, φ2mm) were tested. The specimens were sealed with sealing material on all four sides and the back, and placed horizontally in a constant temperature and humidity chamber. The first stage was placed at a high temperature of 200°C for 7 days; the second stage was placed at a low temperature of -60°C for 7 days. The high and low temperature transfer time should not exceed 10 minutes. After the test, the specimens were placed at 25°C for 1 day, and the surface was cleaned with a dry cotton cloth. The adhesion grade (cross-cut test), flexibility (bending, φ2mm), gloss retention (60°), and color difference (ΔE) were tested.

[0091] Adhesion rating:

[0092] Grade 1: No peeling;

[0093] Grade 2: Minor peeling, small amount of coating detached;

[0094] Grade 3: Moderate peeling, with significant coating loss;

[0095] Grade 4: Severe peeling, most of the coating has fallen off;

[0096] Level 5: Complete peeling, all coating has come off;

[0097] The test results are shown in the table below:

[0098]

[0099] Comparing Examples 1-3 with Comparative Examples 1-3: Example 1 used lower amounts of resin and filler, and the least amount of toughening agent, resulting in a coating that was more rigid overall, with higher hardness and heat deformation resistance. However, under severe impact at extreme low temperatures, its toughness reserve reached its limit first. Example 3 used the highest amounts of resin, filler, and toughening agent, resulting in a coating that was most tough, with better impact resistance and low-temperature flexibility. However, its hardness and wear resistance decreased due to the excessively high proportion of toughening agent. Example 2 had a balanced amount of resin, filler, and toughening agent, resulting in balanced performance in all aspects. Comparing Example 2 with Comparative Example 1, it can be seen that: Comparative Example 1 used ordinary materials. The molecular structure of ordinary polyester resin lacks a rigid skeleton that is resistant to high temperatures and flexible segments that are resistant to low temperatures. The matrix itself cannot withstand the internal stress generated by extreme temperature alternation. The bonding between ordinary toughening agent and resin matrix relies on intermolecular forces and lacks strong chemical bonds. Under repeated thermal cycling stress... Under these conditions, the interface between the two phases is prone to debonding, becoming the origin and propagation channel for microcracks, leading to decreased adhesion and loss of impact resistance. Comparing Example 2 with Comparative Example 2, it can be seen that Comparative Example 2 uses a self-made heat-resistant polyester resin, which has excellent heat resistance, rigidity-toughness balance, and hydrolysis resistance. However, the ordinary toughening agent used in Comparative Example 2 cannot form a strong chemical bond with the self-made resin. The interface between the two is mainly physically bonded. Under thermal stress, the stress is concentrated at the interface and cannot be effectively transferred and dissipated, ultimately causing interface debonding and microcracks, which manifest as decreased adhesion and reduced impact resistance. Comparing Example 2 with Comparative Example 3, it can be seen that Comparative Example 3 uses an ordinary resin, which has limited heat resistance and mechanical strength, limiting the overall performance of the coating. At high temperatures, the matrix softens or degrades, failing to provide stable support for the toughening agent. At low temperatures, the matrix becomes brittle, and the toughening effect of the toughening agent is difficult to fully exert.

[0100] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0101] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high and low temperature resistant powder coating, characterized in that, Includes the following steps: Step 1: Weigh out 40-60 parts of heat-resistant polyester resin, 10-20 parts of epoxy resin, 3-8 parts of curing agent, 2-6 parts of toughening agent, 15-30 parts of inorganic filler, 5-15 parts of pigment, 1-3 parts of functional additives, and 0.5-2 parts of adhesion promoter according to the following weight proportions. Step 2: Dry the inorganic filler in an oven; add the heat-resistant polyester resin, epoxy resin, curing agent, toughening agent, pretreated inorganic filler, pigment, functional additives and adhesion promoter to a high-speed mixer and mix to obtain a premix. Step 3: The premixed material is melt-extruded and compounded through a twin-screw extruder. The extruded material is cooled and pressed into thin sheets through a cooling roller tablet press, and then fed into a crusher for crushing to obtain flaky granules. Step 4: The crushed flaky particles are fed into an ACM mill for fine grinding, and the powder is sieved using a vibrating screener to obtain a high and low temperature resistant cyclic powder coating. The heat-resistant polyester resin is prepared by the following steps: Step a1: Mix ethylene glycol, phthalic anhydride, maleic anhydride, catalyst and toluene, heat, stir and react, cool, add cyclohexane oxide, stir at constant temperature, distill under reduced pressure, add diluent, mix and stir to obtain intermediate 1; Step a2: Add 1,4-naphthalenedicarboxylic acid, terephthalic acid, intermediate 1,2,2-dimethyl-1,3-propanediol, powder additives and liquid additives to a beaker, heat and stir, depressurize, add catalyst, mix and stir, vacuum, heat, polycondensation reaction, water-cooled granulation, to obtain heat-resistant polyester resin. The toughening agent is prepared by the following steps: Step b1: Mix perfluorooctanoic acid, p-hydroxyanisole, tetrabutylammonium bromide and glycidyl methacrylate, stir and react, distill under reduced pressure, extract with diethyl ether, wash successively with sodium chloride solution, sodium carbonate solution and deionized water, add anhydrous sodium sulfate to dry, and evaporate to dryness to obtain fluorine-containing monomer; Step b2: Nonylphenol polyoxyethylene ether, sodium dodecyl sulfonate, and deionized water are mixed and stirred, and divided into two equal groups. The first group is mixed with butyl acrylate, a first portion of acrylic acid, and a first portion of N-hydroxymethyl acrylamide, and stirred to obtain a core pre-emulsion. The second group is mixed with isobornyl methacrylate, a second portion of acrylic acid, glycidyl methacrylate, a second portion of N-hydroxymethyl acrylamide, tetrabutylammonium bromide, and a fluorinated monomer, and stirred to obtain a shell pre-emulsion. The first portion of acrylic acid accounts for 1 / 2 of the total amount of acrylic acid. The first portion of N-hydroxymethyl acrylamide accounts for 1 / 2 of the total amount of N-hydroxymethyl acrylamide. The second portion of acrylic acid accounts for 1 / 2 of the total amount of acrylic acid. The second portion of N-hydroxymethyl acrylamide accounts for 1 / 2 of the total amount of N-hydroxymethyl acrylamide. Step b3: Add the core preemulsion and the first initiator to a four-necked flask and mix. Add the first shell preemulsion and the second initiator to a reactor and mix. Add the second shell preemulsion, organosilicon, and the third initiator to the reactor, heat, add the fourth initiator, maintain the temperature, cool, add tetraethyl orthosilicate, maintain the temperature, adjust the pH with a pH adjuster, filter, add to the four-necked flask, add sodium bisulfite solution, maintain the temperature, cool, adjust the pH with ammonia, filter to remove the gel, and obtain the toughening agent. The amount of the first shell preemulsion accounts for 70% of the total amount of the shell preemulsion; the amount of the first initiator accounts for 20% of the total amount of the initiator; the amount of the second initiator accounts for 35% of the total amount of the initiator; the amount of the second shell preemulsion accounts for 30% of the total amount of the shell preemulsion; the amount of the third initiator accounts for 35% of the total amount of the initiator; and the amount of the fourth initiator accounts for 10% of the total amount of the initiator.

2. The method for preparing a high and low temperature resistant powder coating according to claim 1, characterized in that, The epoxy resin is one of bisphenol A type epoxy resin CYD-014U and phenolic epoxy resin DEN438-A85; the curing agent is one or more of triglycidyl isocyanate, hydroxyalkylamide SDL-552 and curing agent VT5327; the pigment is a heat-resistant inorganic pigment; the heat-resistant inorganic pigment is one or more of titanium dioxide, iron oxide, cobalt blue and titanium yellow; the inorganic filler is a composition of silica powder, mica powder and talc powder in a mass ratio of 5-15g:5-10g:3-8g; the silica powder has a particle size of 1-10μm; the mica powder has a flake structure with an aspect ratio >50; the talc powder has a needle-like structure; the functional additives are defoamer T-4201A and leveling agent TEGO. Glide450, UV absorber UV-531, and antioxidant 626 are mixed in a ratio of 0.1-0.5g: 0.3-0.8g: 0.2-0.5g: 0.1-0.4g; the adhesion promoter is one of silane coupling agent KH-550, titanate coupling agent TCA-44, and phosphate ester adhesion promoter KM2110.

3. The method for preparing a high and low temperature resistant powder coating according to claim 1, characterized in that, In step a1, the ratio of ethylene glycol, phthalic anhydride, maleic anhydride, catalyst, toluene, cyclohexane oxide, and diluent is 65-70 mL: 145-150 g: 95-100 g: 1-3 g: 100-200 mL: 90-95 mL: 100-150 mL; the catalyst is hexadecyltrimethylammonium bromide; and the diluent is styrene.

4. The method for preparing a high and low temperature resistant powder coating according to claim 1, characterized in that, In step a2, the ratio of 1,4-naphthalenedicarboxylic acid, terephthalic acid, intermediate 1,2,2-dimethyl-1,3-propanediol, powder additive, liquid additive, and catalyst is 150-195g:16-50g:150-180mL:45-60g:0.5-2g:5-10mL:5-10mL; the powder additive is a mixture of antimony glycolate and anhydrous sodium acetate in a molar ratio of 0.6mol:0.5mol; the liquid additive is triphenyl phosphite; and the catalyst is tetrabutyl titanate.

5. The method for preparing a high and low temperature resistant powder coating according to claim 1, characterized in that, In step b1, the ratio of perfluorooctanoic acid, p-hydroxyanisole, tetrabutylammonium bromide, glycidyl methacrylate, diethyl ether, and anhydrous sodium sulfate is 8-20g: 0.05-0.1g: 0.04-0.08g: 5-8mL: 100mL: 3-5g; the mass fraction of the sodium chloride solution is 15%; and the mass fraction of the sodium carbonate solution is 5%.

6. The method for preparing a high and low temperature resistant powder coating according to claim 1, characterized in that, The ratio of the amounts of nonylphenol polyoxyethylene ether, sodium dodecyl sulfonate, deionized water, butyl acrylate, total acrylic acid, total N-hydroxymethylacrylamide, isobornyl methacrylate, glycidyl methacrylate, tetrabutylammonium bromide, and fluorinated monomers in step b2 is 1.5-2 mL: 1.5-2 g: 100-120 mL: 40-45 mL: 4-5 mL: 2-3 g: 40-45 mL: 2.5-3 mL: 0.1-0.2 g: 5-6 g.

7. The method for preparing a high and low temperature resistant powder coating according to claim 1, characterized in that, In step b3, the ratio of the total amount of core preemulsion, initiator, shell preemulsion, organosilicon, tetraethyl orthosilicate, and sodium bisulfite solution is 10-30 mL: 1-2 g: 50-60 mL: 0.5-1 g: 6-8 mL: 3-5 mL; the initiator is ammonium persulfate; the organosilicon is one of KH-570, A-172, A-151, and Vi-D4; the mass fraction of the sodium bisulfite solution is 20-30%; and the pH adjuster is AM-95.

8. The application of a high-low temperature cycling resistant powder coating prepared by the preparation method of any one of claims 1-7 in coating materials.

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