A highly weather-resistant powder coating and its preparation method

Abstract

The present invention provides a highly weather-resistant powder coating and a preparation method thereof. The highly weather-resistant powder coating comprises the following raw materials in parts by weight: 40-70 parts of modified polyester, 5-20 parts of curing agent, 10-30 parts of pigment and filler, 0.1-3 parts of leveling agent, and 1-3 parts of antioxidant. The preparation method of the highly weather-resistant powder coating comprises the following steps: adding the modified polyester, pigment and filler, curing agent, leveling agent, and antioxidant into a high-speed mixer and mixing evenly, extruding with a twin-screw extruder, then pressing into sheets and crushing to form uniform powder, which is the highly weather-resistant powder coating. This highly weather-resistant powder coating has good weather resistance and adhesion, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and particularly relates to a highly weather-resistant powder coating and a preparation method thereof. Background Art

[0002] A coating is a solid film that can be coated on the surface of an object to be coated and has a certain strength, and can play a decorative and protective role. Since early coatings contained vegetable oils, in China, coatings are also called paints. According to historical records, as early as about 7,000 years ago, our country began to use paints, and the use of paints has a long history in our country. Since the 18th century, the development and utilization of zinc oxide and linseed oil have enabled coatings to be widely used worldwide. Now, synthetic resins have long replaced vegetable oils as the main components of coatings, but the vast majority of coatings still use organic solvents as the blending agents and dispersants for each component. With the progress of technology and society, the disadvantages of solvent-based coatings have become more and more recognized by people. For example, they are prone to catching fire, bringing great inconvenience to transportation, storage and use; they are toxic, posing a great threat to human health; they are volatile, causing waste of resources and environmental pollution at the same time. The existence of these disadvantages has promoted the emergence of new coatings that can solve the above problems, mainly including water-based coatings and powder coatings. Among them, powder coatings are the most environmentally friendly and most promising coating varieties.

[0003] Since the 1950s of the last century, powder coatings have developed rapidly. Compared with traditional solvent-based coatings, powder coatings have the following advantages: (1) There is no emission of volatile organic compounds (VOCs), and the utilization rate can reach more than 98%, meeting the requirements of building a resource-saving and environment-friendly society; (2) It reduces the harm of organic solvents to human health and also avoids dangers such as fire and explosion during the transportation of organic solvents; (3) When using powder coatings, the film thickness is easy to control, and the process is relatively simple, making it easy to realize automated operation; (4) Since high-molecular-weight organic resins can be used, the mechanical properties of the coatings obtained by using powder coatings are higher. Currently, powder coatings have shifted from thermoplastic powder coatings to thermosetting powder coatings with better coating properties. In terms of functions, it has developed from the initial anti-corrosion protection function to the direction of equal emphasis on decoration, protection and functionalization, and more and more functional powder coating varieties have received attention, such as antibacterial coatings, hydrophobic coatings, high-temperature resistant coatings, weather-resistant coatings, heavy-duty anti-corrosion coatings, etc. Powder coatings are playing an increasingly important role in various industrial fields and people's daily lives.

[0004] Patent CN105062321A discloses a coating for surface treatment of aluminum materials, which is prepared from raw materials such as brominated bisphenol A epoxy resin, acrylic modified alkyd resin, amino resin, etc. The overall performance is balanced, but the mixing between isophorone diamine and brominated bisphenol A epoxy resin causes a slow curing reaction, low crosslinking degree, and is prone to problems such as poor weather resistance and corrosion resistance. Patent CN102134424B discloses a waterborne styrene-acrylic exterior wall coating with ultraviolet resistance. This coating uses a composite powder of nano-TiO2 and Mg-Al hydrotalcite as an ultraviolet absorber, and is prepared by adding pigments, fillers and additives, etc. Although it has a good ultraviolet resistance effect, the effect of adding the ultraviolet absorber by blending is not durable enough and needs to be further improved. Patent CN116102952A discloses a salt spray resistant powder coating and its preparation method. The salt spray resistant powder coating is prepared from raw materials such as epoxy resin, polyester resin and additives. Although this salt spray resistant powder coating has good salt spray resistance and flame retardancy, its adhesion needs to be improved and there are certain deficiencies in practical applications.

[0005] Therefore, it is necessary to provide a powder coating with good weather resistance and strong adhesion to meet the needs of practical applications. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a high weather resistance powder coating.

[0007] To achieve this purpose, the technical solution of the present invention is as follows:

[0008] The present invention provides a high weather resistance powder coating, and the high weather resistance powder coating comprises the following raw materials in parts by weight: 40-70 parts of modified polyester, 5-20 parts of curing agent, 10-30 parts of pigment and filler, 0.1-3 parts of leveling agent, and 1-3 parts of antioxidant.

[0009] In some embodiments of the present invention, the pigment and filler is selected from one or more combinations of nano calcium carbonate, talcum powder, kaolin, silica powder, carbon black.

[0010] In some embodiments of the present invention, the leveling agent is selected from one or more combinations of polyacrylic acid, carboxymethyl cellulose, polydimethylsiloxane.

[0011] In some embodiments of the present invention, the antioxidant is selected from one or more combinations of antioxidant 1076, antioxidant 330, antioxidant 3114.

[0012] In some embodiments of the present invention, the preparation method of the curing agent comprises the following steps:

[0013] Under nitrogen protection, the curing agent monomer is added to a reactor, heated with stirring to 70 - 90 °C, a catalyst is added, and the reaction is carried out at a constant temperature for 1 - 6 h. After thin-film evaporation, the product is the curing agent.

[0014] Among them, the curing agent monomer has a structure as shown in formula A:

[0015] R'-N=C=S A,

[0016] Among them, R' is an aromatic group, and the aromatic group is selected from any one of phenyl, naphthyl, anthracenyl, and biphenyl.

[0017] In the preparation method of the curing agent of the present invention, the catalyst is selected from tetraethylammonium hydroxide or epoxy accelerator DMP-30.

[0018] In some embodiments of the present invention, the preparation method of the curing agent monomer is as follows: An aromatic hydrocarbon and triethylenediamine are added to tetrahydrofuran, carbon disulfide is added, and the mixture is stirred for 3 - 5 h, filtered by suction, and the filter cake is washed with a small amount of tetrahydrofuran. After drying, the filter cake is dissolved in tetrahydrofuran, cooled to 5 - 10 °C, triphosgene is added while maintaining 5 - 10 °C, reacted at room temperature for 1 - 2 h, and then refluxed for 1 - 2 h. After the reaction is completed, the solvent tetrahydrofuran is distilled off, separated and purified, and the product is the curing agent monomer.

[0019] In the preparation method of the curing agent monomer of the present invention, the molar ratio of the aromatic hydrocarbon, triethylenediamine, carbon disulfide, and triphosgene is 1:5 - 15:5 - 15:1 - 3; the aromatic hydrocarbon is selected from any one of benzene, naphthalene, anthracene, and biphenyl.

[0020] In some embodiments of the present invention, the preparation method of the ultraviolet-resistant polyester resin includes the following steps:

[0021] (1) The ultraviolet-resistant monomer, diol, and dibasic acid are put into a reaction kettle, nitrogen is introduced, and after heating to melt the raw materials, they are stirred evenly;

[0022] (2) A catalyst is added, and the temperature is raised to 95 - 105 °C for reaction for 2 - 6 hours to remove the water generated during the reaction;

[0023] (3) The vacuum pump is turned on, the temperature is raised to 140 - 145 °C for reaction for 1.5 - 2.5 h, then the temperature is raised to 160 - 165 °C for reaction for 1.5 - 2.5 h, then the temperature is raised to 180 - 185 °C for reaction for 1.5 - 2.5 h, then the temperature is raised to 200 - 205 °C for reaction for 1.5 - 2.5 h, and finally the temperature is raised to 220 - 225 °C for reaction for 1.5 - 2.5 h. After the reaction is completed, the product is discharged at a high temperature to obtain the ultraviolet-resistant polyester resin.

[0024] In the preparation method of the ultraviolet-resistant polyester resin of the present invention, in step (1), the mass ratio of the ultraviolet-resistant monomer, diol, and diacid is 1:5-10:5-10; the temperature increase is 70-80 °C.

[0025] In the preparation method of the ultraviolet-resistant polyester resin of the present invention, in step (1), the diol is selected from one or more combinations of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol.

[0026] In the preparation method of the ultraviolet-resistant polyester resin of the present invention, in step (1), the diacid is selected from one or more combinations of oxalic acid, 1,3-propanedioic acid, 1,4-butanedioic acid, 1,5-pentanedioic acid, 1,6-hexanedioic acid, 1,7-heptanedioic acid, 1,8-octanedioic acid, 1,9-nonanedioic acid, and 1,10-decanedioic acid.

[0027] In the preparation method of the ultraviolet-resistant polyester resin of the present invention, in step (2), the catalyst is selected from dibutyltin oxide or methylphenyltin oxide.

[0028] In the preparation method of the ultraviolet-resistant polyester resin of the present invention, in step (3), the vacuum degree is -0.1 to -0.08 MPa.

[0029] In the preparation method of the ultraviolet-resistant polyester resin of the present invention, the structure of the ultraviolet-resistant monomer in step (1) is as shown in formula B:

[0030]

[0031] Wherein, R is any one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and tert-butyl; n is an integer from 2 to 6.

[0032] In some embodiments of the present invention, the preparation method of the ultraviolet-resistant monomer comprises the following steps:

[0033] 1) Mix the benzotriazole derivative, sodium hydroxide, and bis(di-n-propylamino)methane evenly, heat to 115 - 125 °C to melt all the materials, then raise the reaction temperature to 135 - 145 °C and react for 1 - 2 h. Distill off n-propylamine under reduced pressure, then raise the reaction temperature to 155 - 165 °C and react under vacuum for 2 - 3 h. Stop heating and remove the vacuum, cool the temperature to 105 - 115 °C, add toluene to completely dissolve the materials, cool the temperature to 85 - 95 °C, add a hydrochloric acid solution with a concentration of 10 - 15%, stir to make the materials completely neutral, crystallize and cool with ice water for 4 - 5 h, filter to collect the precipitated substance, wash the filter cake with deionized water 2 - 3 times and then with methanol 2 - 3 times, and dry to obtain the intermediate; the structural formula of the benzotriazole derivative is as shown in Formula C:

[0034] wherein R is any one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and tert-butyl,

[0035] The structural formula of the intermediate is as shown in Formula D:

[0036]

[0037] 2) Add the intermediate, sodium carbonate, and the hydroxyl-containing bromohydrocarbon to N,N-dimethylformamide, stir and react at 20 - 40 °C for 18 - 24 hours. After the reaction is completed, distill off the unreacted hydroxyl-containing bromohydrocarbon and distill off most of the N,N-dimethylformamide, add water, filter to collect the precipitated substance, wash it with n-heptane 2 - 3 times, and dry to obtain the anti-ultraviolet monomer.

[0038] In the preparation method of the anti-ultraviolet monomer of the present invention, in step (1), the molar ratio of 2-(2H-benzotriazol-2-yl)-phenol to bis(di-n-propylamino)methane is 1:1 - 2; the mass of sodium hydroxide is 0.5 - 1.5% of the total mass of 2-(2H-benzotriazol-2-yl)-phenol and bis(di-n-propylamino)methane; the vacuum degree is -0.1 to -0.05 MPa.

[0039] In the preparation method of the anti-ultraviolet monomer of the present invention, in step (2), the molar ratio of the intermediate to the hydroxyl-containing bromohydrocarbon is 1:1 - 2; the hydroxyl-containing bromohydrocarbon is selected from any one of bromoethanol, bromopropanol, bromobutanol, bromopentanol, and bromohexanol.

[0040] A preparation method of a highly weather-resistant powder coating, the preparation method of the highly weather-resistant powder coating includes the following steps:

[0041] The modified polyester, pigment and filler, curing agent, leveling agent, and antioxidant are added to a high-speed mixer and mixed evenly. After extrusion using a twin-screw extruder, it is pressed into tablets and crushed to form uniform powder, which is the high-weather resistance powder coating.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The high-weather resistance powder coating provided by the present invention is prepared from substances such as modified polyester, curing agent, pigment and filler, etc. By adding modified polyester, the prepared powder coating can have excellent weather resistance. The modified polyester connects the benzotriazole group to the main chain of the polyester, which can more effectively improve the weather resistance of the material compared with the method of mixing anti-ultraviolet additives in the coating. By adding the curing agent of the present invention, the performance of the modified polyester can be further improved. The curing agent and the modified polyester are used in combination, and the two can play a synergistic role. The N-(C=S)-O bond formed after the curing agent of the present invention is cured has good stability. When used together with the modified polyester, it can effectively improve the weather resistance of the coating, and at the same time, the prepared coating can also have good adhesion. Specific embodiments

[0044] The following will illustrate the present invention in combination with specific implementation schemes. It should be noted that the following examples are examples of the present invention, only for illustrating the present invention, and not for limiting the present invention. Other combinations and various improvements within the concept of the present invention can be made without departing from the main idea or scope of the present invention. The raw material reagents used in the examples can be purchased on the market. Among them, triphosgene is purchased from Shanghai Xinfan Biotechnology Co., Ltd., talcum powder is purchased from Anhui Xuanlang New Materials Technology Co., Ltd., 2-(2H-benzotriazol-2-yl)-phenol is purchased from Anhui Zesheng Technology Co., Ltd., bis(di-n-propylamino)methane is purchased from Tianjin Li'anlong New Materials Co., Ltd., and antioxidant 1076 is purchased from Changzhou Youfeng Chemical Co., Ltd.

[0045] Preparation of modified polyester I

[0046] A modified polyester, and the preparation method of the modified polyester includes the following steps:

[0047] (1) 0.1 mol of anti-ultraviolet monomer, 0.9 mol of 1,5-pentanediol, and 0.9 mol of oxalic acid are put into a reaction kettle, nitrogen is introduced, and the temperature is raised to 80 °C. After the raw materials are melted, they are stirred evenly;

[0048] (2) 0.3 g of dibutyltin oxide is added, and the temperature is raised to 100 °C and reacted for 6 hours to remove the water generated in the reaction;

[0049] (3) Turn on the vacuum pump, control the vacuum degree to -0.1 MPa, heat up to 140 °C and react for 2 h, then heat up to 160 °C and react for 2 h, then heat up to 180 °C and react for 2 h, then heat up to 200 °C and react for 2 h, and finally heat up to 220 °C and react for 2 h. After the reaction is completed, discharge the material at high temperature to obtain the modified polyester.

[0050] Among them, the preparation method of the anti-ultraviolet monomer includes the following steps:

[0051] 1) Mix 1 mol of 2-(2H-benzotriazol-2-yl)-phenol, 3 g of sodium hydroxide and 1 mol of bis(di-n-propylamino)methane evenly, heat to 120 °C to melt all the materials, then raise the reaction temperature to 140 °C and react for 2 h. Distill off n-propylamine under reduced pressure, then raise the reaction temperature to 160 °C and react under vacuum (vacuum degree: -0.1 MPa) for 3 h. Stop heating and remove the vacuum, lower the temperature to 110 °C, add 500 g of toluene to completely dissolve the materials, lower the temperature to 90 °C, add a 10% hydrochloric acid solution, stir to make the materials completely neutral, crystallize and cool with ice water for 5 h, filter to collect the precipitate, wash the filter cake with deionized water twice and then with methanol twice, and dry to obtain the intermediate.

[0052] 2) Add 1 mol of the intermediate, 3 mol of sodium carbonate and 1 mol of bromoethanol to 2000 ml of N,N-dimethylformamide, stir and react at 40 °C for 24 hours. After the reaction is completed, distill off the unreacted bromoethanol and most of the N,N-dimethylformamide, add 1000 ml of water, filter to collect the precipitate, wash it twice with n-heptane, and dry to obtain the anti-ultraviolet monomer.

[0053] Preparation of polyester polyol II

[0054] A modified polyester, the preparation method of the modified polyester includes the following steps:

[0055] (1) Put 0.2 mol of the anti-ultraviolet monomer, 1.5 mol of 1,5-pentanediol and 1.5 mol of oxalic acid into the reaction kettle, introduce nitrogen, heat up to 80 °C, and after the raw materials are melted, stir evenly;

[0056] (2) Add 0.3 g of dibutyltin oxide, heat up to 100 °C and react for 6 hours to remove the water generated during the reaction;

[0057] (3) Turn on the vacuum pump, control the vacuum degree to -0.1 MPa, heat up to 140 °C and react for 2 h, then heat up to 160 °C and react for 2 h, then heat up to 180 °C and react for 2 h, then heat up to 200 °C and react for 2 h, and finally heat up to 220 °C and react for 2 h. After the reaction is completed, discharge the material at high temperature to obtain the modified polyester.

[0058] Among them, the preparation method of the ultraviolet-resistant monomer includes the following steps:

[0059] 1) Mix 1 mol of 2-(2H-benzotriazol-2-yl)-phenol, 3 g of sodium hydroxide, and 1 mol of bis(di-n-propylamino)methane evenly, heat to 120 °C to melt all the materials, then raise the reaction temperature to 140 °C, react for 2 h, distill off n-propylamine under reduced pressure, then raise the reaction temperature to 160 °C, react under vacuum (vacuum degree is -0.1 MPa) for 3 h, stop heating and remove the vacuum, lower the temperature to 110 °C, add 500 g of toluene to completely dissolve the materials, lower the temperature to 90 °C, add a hydrochloric acid solution with a concentration of 10%, stir to make the materials completely neutral, crystallize and cool with ice water for 5 h, filter to collect the precipitate, wash the filter cake twice with deionized water and then twice with methanol, and dry to obtain the intermediate;

[0060] 2) Add 1 mol of the intermediate, 3 mol of sodium carbonate, and 1 mol of bromohexanol to 2000 ml of N,N-dimethylformamide, stir and react at 40 °C for 24 hours. After the reaction is completed, distill off the unreacted bromohexanol and distill off most of the N,N-dimethylformamide, add 1000 ml of water, filter to collect the precipitate, wash twice with n-heptane, and dry to obtain the ultraviolet-resistant monomer.

[0061] Curing agent Ⅰ

[0062] A curing agent, the preparation method of the curing agent includes the following steps:

[0063] Under nitrogen protection, add 1000 g of the curing agent monomer to the reactor, heat up to 90 °C with stirring, add 3 g of tetraethylammonium hydroxide, react at a constant temperature for 4 h, and through thin-film evaporation, the product is curing agent Ⅰ, wherein the mass fraction of the trimer is 77.3%.

[0064] The curing agent monomer (purchased from Shanghai Jiuqing International Trade Co., Ltd.) has the structure shown in Formula E:

[0065]

[0066] Curing agent Ⅱ

[0067] A curing agent, the preparation method of the curing agent includes the following steps:

[0068] Under nitrogen protection, add 1000 g of the curing agent monomer to the reactor, heat up to 90 °C with stirring, add 2.5 g of tetraethylammonium hydroxide, react at a constant temperature for 4 h, and through thin-film evaporation, the product is curing agent Ⅱ, wherein the mass fraction of the trimer is 76.5%.

[0069] The curing agent monomer (purchased from Shanghai Jiuqing International Trade Co., Ltd.) has the structure shown in Formula F:

[0070]

[0071] Curing agent III

[0072] A curing agent, and the preparation method of the curing agent includes the following steps:

[0073] Under nitrogen protection, 1000 g of the curing agent monomer is added to a reactor, heated to 90 °C with stirring, 2.5 g of tetraethylammonium hydroxide is added, and the reaction is carried out at a constant temperature for 6 h. After thin-film evaporation, the product is Curing agent III, wherein the mass fraction of the trimer is 75.4%.

[0074] The curing agent monomer (purchased from Shanghai Jiuqing International Trade Co., Ltd.) has the structure shown in Formula G:

[0075]

[0076] Example 1

[0077] A highly weather-resistant powder coating, and the highly weather-resistant powder coating comprises the following raw materials in parts by weight: 70 parts of modified polyester I, 20 parts of curing agent I, 30 parts of talcum powder, 3 parts of polyacrylic acid, and 3 parts of antioxidant 1076.

[0078] The preparation method of the highly weather-resistant powder coating is as follows: Modified polyester I, talcum powder, curing agent I, polyacrylic acid, and antioxidant 1076 are added to a high-speed mixer and mixed evenly, then extruded using a twin-screw extruder, and after extrusion, tablet pressing and crushing are carried out to form a uniform powder, which is the highly weather-resistant powder coating.

[0079] Example 2

[0080] A highly weather-resistant powder coating, and the highly weather-resistant powder coating comprises the following raw materials in parts by weight: 70 parts of modified polyester I, 20 parts of curing agent II, 30 parts of talcum powder, 3 parts of polyacrylic acid, and 3 parts of antioxidant 1076.

[0081] The preparation method is the same as that of Example 1.

[0082] Example 3

[0083] A highly weather-resistant powder coating, and the highly weather-resistant powder coating comprises the following raw materials in parts by weight: 70 parts of modified polyester II, 20 parts of curing agent III, 30 parts of talcum powder, 3 parts of polyacrylic acid, and 3 parts of antioxidant 1076.

[0084] The preparation method is the same as that of Example 1.

[0085] Example 4

[0086] A highly weather-resistant powder coating, the highly weather-resistant powder coating comprising the following raw materials in parts by weight: 40 parts of modified polyester II, 5 parts of curing agent III, 10 parts of talcum powder, 0.1 part of polyacrylic acid, and 1 part of antioxidant 1076.

[0087] The preparation method is the same as that of Example 1.

[0088] Comparative Example 1

[0089] The difference from Example 1 is that no modified polyester is added.

[0090] Comparative Example 2

[0091] The difference from Example 1 is that no curing agent is added.

[0092] Comparative Example 3

[0093] The difference from Example 1 is that the modified polyester is replaced with 800# polyester (purchased from Shanghai Xinhua Resin Factory).

[0094] Comparative Example 4

[0095] The difference from Example 1 is that the curing agent is replaced with dicyandiamide curing agent (purchased from Lu'an Jietongda New Materials Co., Ltd., model SA2830).

[0096] Comparative Example 5

[0097] The difference from Example 1 is that no modified polyester and curing agent are added.

[0098] Performance tests were carried out on the highly weather-resistant powder coatings prepared in each example and comparative example, and the test methods are as follows:

[0099] 1. Weather resistance: Test the gloss retention rate of xenon lamp aging (1500 h);

[0100] 2. Adhesion: Test according to the standard HG / T2006-2022.

[0101] The measurement results are shown in Table 1:

[0102] Table 1

[0103] Number Weather resistance (%) Adhesion (grade) Example 1 91 0 Example 2 90 0 Example 3 90 0 Example 4 87 0 Comparative Example 1 78 2 Comparative Example 2 76 2 Comparative Example 3 82 1 Comparative Example 4 85 1 Comparative Example 5 63 6

[0104] From the comparison of the test results of each example and comparative example in Table 1, it can be seen that in the preparation process of the high weather-resistant powder coating provided by the present invention, by adding a modified polyester, the used modified polyester connects the benzotriazole group with ultraviolet resistance function to the main chain of the polyester, effectively improving its ultraviolet resistance performance and making the coating have good weather resistance; by adding a curing agent, the formed N-(C=S)-O bond has good stability. When used in combination with the modified polyester, it further improves the weather resistance of the coating, and at the same time has good adhesion, with broad application prospects.

[0105] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it. It cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A highly weather-resistant powder coating, characterized in that, The high weather-resistant powder coating comprises the following raw materials in parts by weight: 40-70 parts of modified polyester, 5-20 parts of curing agent, 10-30 parts of pigment and filler, 0.1-3 parts of leveling agent, and 1-3 parts of antioxidant; the modified polyester has a benzotriazole structure; The preparation method of the curing agent comprises the following steps: Under nitrogen protection, add the curing agent monomer into a reactor, heat up to 70-90 °C with stirring, add a catalyst, and react at a constant temperature for 1-6 h. After thin-film evaporation, the product is the curing agent; The structure of the curing agent monomer is selected from one of E, F or G: E， F， G； The preparation method of the modified polyester comprises the following steps: (1) Put the ultraviolet-resistant monomer, diol, and dibasic acid into a reaction kettle, introduce nitrogen, heat up to melt the raw materials, and stir evenly; (2) Add a catalyst, heat up to 95-105 °C and react for 2-6 hours to remove the water generated during the reaction; (3) Turn on the vacuum pump, heat up to 140-145 °C and react for 1.5-2.5 h, then heat up to 160-165 °C and react for 1.5-2.5 h, then heat up to 180-185 °C and react for 1.5-2.5 h, then heat up to 200-205 °C and react for 1.5-2.5 h, and finally heat up to 220-225 °C and react for 1.5-2.5 h. After the reaction is completed, discharge the material at high temperature to obtain the modified polyester; The structure of the ultraviolet-resistant monomer in the step (1) is shown as formula B: B Wherein, R is any one of hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl; n is an integer from 2 to 6; The preparation method of the ultraviolet-resistant monomer comprises the following steps: 1) Mix the benzotriazole derivative, sodium hydroxide, and bis(di-n-propylamino)methane evenly, heat up to 115-125 °C to melt all the materials, then raise the reaction temperature to 135-145 °C and react for 1-2 h. Distill off n-propylamine under reduced pressure, then raise the reaction temperature to 155-165 °C and react under vacuum for 2-3 h. Stop heating and remove the vacuum, lower the temperature to 105-115 °C, add toluene to completely dissolve the materials, lower the temperature to 85-95 °C, add a hydrochloric acid solution with a concentration of 10-15%, stir to make the materials completely neutral, crystallize and cool with ice water for 4-5 h, filter to collect the precipitate, wash the filter cake with deionized water 2-3 times, then wash with methanol 2-3 times, and dry to obtain the intermediate; the structural formula of the benzotriazole derivative is shown as formula C: C, wherein R is any one of hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl, The structural formula of the intermediate is shown as formula D: D； 2) Add the intermediate, sodium carbonate, and hydroxyl-containing bromohydrocarbon into N,N-dimethylformamide, stir and react at 20-40 °C for 18-24 hours. After the reaction is completed, distill off the unreacted hydroxyl-containing bromohydrocarbon and most of the N,N-dimethylformamide, add water, filter to collect the precipitate, wash with n-heptane 2-3 times, and dry to obtain the ultraviolet-resistant monomer.

2. The high weather-resistant powder coating according to claim 1, characterized in that, The pigment and filler are selected from one or a combination of nano calcium carbonate, talcum powder, kaolin, silica powder, carbon black, etc.

3. The high weather-resistant powder coating according to claim 1, characterized in that, The leveling agent is polyacrylic acid.

4. The high weather-resistant powder coating according to claim 1, wherein The antioxidant is selected from one or a combination of antioxidants 1076, 330, and 3114.

5. The high weather-resistant powder coating according to claim 1, wherein In the method for preparing the modified polyester, in step (1), the mass ratio of the ultraviolet light-absorbing monomer, diol, and dicarboxylic acid is 1:5-10:5-10; the temperature increase is 70-80 °C.

6. The high weather-resistant powder coating according to claim 1, characterized in that, In the method for preparing the modified polyester, in step (1), the diol is selected from one or a combination of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol.

7. A preparation method of the highly weather-resistant powder coating according to any one of claims 1-6, characterized in that, The method for preparing the high weather resistance powder coating is as follows: The modified polyester, pigment filler, curing agent, leveling agent, and antioxidant are added to a high-speed mixer and mixed evenly. After extrusion using a twin-screw extruder, it is pressed into tablets and crushed to form uniform powder, which is the high weather resistance powder coating.

Images