Flame-retardant powder coating and preparation method thereof

Abstract

The invention discloses a flame-retardant powder coating and a preparation method thereof in the technical field of coatings. The flame-retardant powder coating is prepared from the following components in parts by weight: 50-80 parts of hydroxyl-terminated polyester resin, 5-10 parts of a curing agent, 11-13 parts of a flame retardant, 2-6 parts of a flatting agent and 2-4 parts of a defoaming agent. The flame retardant is a modified Ni-MOF / graphite phase carbon nitride composite material; the flame retardant is prepared from the following components: phenyl phosphoryl dichloride, 2-aminoterephthalic acid, nickel nitrate hexahydrate and melamine. The 2-aminoterephthalic acid is modified through phenylphosphoryl dichloride, the modified Ni-MOF is prepared in cooperation with nickel nitrate hexahydrate, the modified Ni-MOF is loaded to graphite phase carbon nitride to prepare the flame retardant, and the flame retardant property of the powder coating is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a flame retardant powder coating and a preparation method thereof. Background Art

[0002] Powder coatings are generally composed of base resins, curing agents, additives, and pigments. Polyester resin is the main base material with the widest application field and the largest consumption in powder coatings. The polyester and curing agent in polyester powder coatings are high molecular polymers, and their flame retardant properties are generally poor. Under the continuous heating of external heat sources, the polymer first undergoes a free radical chain degradation reaction with oxygen in the air to produce volatile combustibles. When the substance reaches a certain concentration and temperature, it will catch fire and burn. Part of the heat released by the combustion is supplied to the degrading polymer, further aggravating its degradation, producing more combustible gases, and causing the fire to intensify.

[0003] In the prior art, the flame retardant used in powder coatings has low flame retardant efficiency, and adding a large amount will cause the performance of the coating to deteriorate. Summary of the invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a flame retardant powder coating and a preparation method thereof. In order to solve the problem of poor flame retardant effect of polyester powder coating, the present invention modifies 2-aminoterephthalic acid by phenylphosphoryl dichloride, prepares modified Ni-MOF with nickel nitrate hexahydrate, and loads the modified Ni-MOF on graphite phase carbon nitride to prepare a flame retardant, thereby improving the flame retardant properties of the powder coating.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: The invention provides a flame retardant powder coating, which is prepared by comprising the following components in parts by weight: 50-80 parts of a terminal hydroxyl polyester resin, 5-10 parts of a curing agent, 11-13 parts of a flame retardant, 2-6 parts of a leveling agent, and 2-4 parts of a defoaming agent; the flame retardant is a modified Ni-MOF / graphite phase carbon nitride composite material; the flame retardant is prepared by comprising the following components: phenylphosphoryl dichloride, 2-aminoterephthalic acid, nickel nitrate hexahydrate, and melamine.

[0006] The present invention also proposes a method for preparing a flame retardant powder coating, which specifically comprises the following steps: Weigh the terminal hydroxyl polyester resin, curing agent, flame retardant, leveling agent and defoaming agent, mix them evenly, melt-blend and extrude them at 90-100° C., press them into sheets, cool them, crush them, grade them and sieve them to obtain a flame retardant powder coating.

[0007] Furthermore, the preparation method of the flame retardant specifically comprises the following steps: S1. Weigh phenylphosphoryl dichloride and add it to 1,4-dioxane to obtain a phenylphosphoryl dichloride solution. Take 2-aminoterephthalic acid and add it to 100-150 times the weight of deionized water, then add it to the phenylphosphoryl dichloride solution. Under a nitrogen atmosphere, react at 80-110° C. for 5-10 hours. Collect the product, wash it, and dry it to obtain a modified organic ligand. S2, weigh melamine and place it in a crucible, move it to a tube furnace, heat it at 550° C. for 4-5 hours, collect the product, grind it, and obtain graphite phase carbon nitride; S3. Weigh the modified organic ligand prepared in step S1 and add it to methanol to obtain solution A. Weigh nickel nitrate hexahydrate and add it to methanol to obtain solution B. Weigh the graphite phase carbon nitride prepared in step S2 and add it to solution B. After stirring, ultrasonic treatment is performed to obtain a mixed solution C. Solution A and mixed solution C are mixed, placed in a reactor, and kept warm at 100-120° C. for 10-12 h. The product is collected, washed, and dried to obtain a flame retardant.

[0008] Further, in step S1, the molar ratio of the phenylphosphoryl dichloride to the 2-aminoterephthalic acid is 1:1.8-2.4.

[0009] Furthermore, in step S1, the concentration of phenylphosphoryl dichloride in the phenylphosphoryl dichloride solution is 0.5 mol / L.

[0010] Furthermore, in step S3, the power of the ultrasonic treatment is 300-400 W, and the time is 30-40 min.

[0011] Furthermore, in step S3, the amount of the modified organic ligand added to methanol is 8-10 g / L.

[0012] Furthermore, in step S3, the amount of nickel nitrate hexahydrate added to methanol is 12-14 g / L.

[0013] Further, in step S3, the mass ratio of the graphite phase carbon nitride to the nickel nitrate hexahydrate is 1:2-3.

[0014] Furthermore, in step S3, the volume ratio of the solution A to the mixed solution C is 2-3:1.

[0015] The beneficial effects achieved by the present invention are as follows: 2-aminoterephthalic acid was modified by phenylphosphinoyl dichloride, and modified Ni-MOF was prepared by combining with nickel nitrate hexahydrate. The modified Ni-MOF was loaded on graphite phase carbon nitride to prepare a flame retardant to improve the flame retardant properties of powder coatings. 2-aminoterephthalic acid in the modified Ni-MOF has good compatibility with the hydroxyl-terminated polyester resin. After modification by phenylphosphinoyl dichloride, the modified organic ligand decomposes during combustion to produce CO2 and NH 3 The non-combustible gases such as carbonized nitrogen and graphite can act as a gas source for the expanding flame retardant, promoting the formation of an expanding carbon layer, which can better insulate heat and oxygen, thereby playing a flame retardant role. At the same time, the nickel oxide formed during the combustion process has a catalytic carbonization effect, which can reduce the emission of decomposition products and improve the heat resistance of the carbon layer. The graphite phase carbonized nitrogen can increase the density of the carbon layer, and the dense carbon layer plays a good role in heat insulation and oxygen isolation. External oxygen also requires a complex path to penetrate into the interior of the substrate, avoiding the diffusion of combustion to the inside, and playing a role in protecting the substrate. In addition, by loading the modified Ni-MOF onto the graphite phase carbonized nitrogen, the compatibility of the modified graphite phase carbonized nitrogen with the terminal hydroxyl polyester resin can be improved, thereby improving the performance of the powder coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The impact resistance test results of Examples 1-3 and Comparative Examples 1-3 of the present invention are shown in FIG. Figure 2 This is a scanning electron microscope image of the flame retardant prepared in Example 1 of the present invention.

[0017] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0019] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein may be applied to the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only and are not intended to limit the content of this application.

[0020] In view of the deficiencies in the prior art mentioned in the background technology, the first aspect of the present invention provides a flame retardant powder coating, comprising: 50-80 parts of a terminal hydroxyl polyester resin, 5-10 parts of a curing agent, 11-13 parts of a flame retardant, 2-6 parts of a leveling agent, and 2-4 parts of a defoaming agent; the flame retardant is a modified Ni-MOF / graphite phase carbon nitride composite material; the flame retardant comprises the following components: phenylphosphoryl dichloride, 2-aminoterephthalic acid, nickel nitrate hexahydrate, and melamine.

[0021] Among them, the hydroxyl value of the terminal hydroxyl polyester resin can be 35 to 45, with a shorter curing time and better hardness after curing. The curing agent can induce a cross-linking reaction between the terminal hydroxyl polyester resin molecules, thereby greatly improving the mechanical strength, heat resistance, wear resistance, corrosion resistance and other properties of the resin. The leveling agent can improve the leveling performance of the terminal hydroxyl polyester resin and improve the appearance performance of the coating. The defoaming agent can reduce the surface tension of the terminal hydroxyl polyester resin, thereby destroying the stable structure of the bubbles, causing the bubbles to burst quickly and release gas, thereby improving the processing performance of the terminal hydroxyl polyester resin.

[0022] In addition, the 2-aminoterephthalic acid in the modified Ni-MOF has good compatibility with the hydroxyl-terminated polyester resin. After modification with phenylphosphinoyl dichloride, the modified organic ligand can decompose during combustion to produce CO. 2 and NH 3 The non-combustible gases such as carbonized nitrogen and graphite can act as a gas source for the expanding flame retardant, promoting the formation of an expanding carbon layer, which can better insulate heat and oxygen, thereby playing a flame retardant role. At the same time, the nickel oxide formed during the combustion process has a catalytic carbonization effect, which can reduce the emission of decomposition products and improve the heat resistance of the carbon layer. The graphite phase carbonized nitrogen can increase the density of the carbon layer, and the dense carbon layer plays a good role in heat insulation and oxygen isolation. External oxygen also requires a complex path to penetrate into the interior of the substrate, avoiding the diffusion of combustion to the inside, and playing a role in protecting the substrate. In addition, by loading the modified Ni-MOF onto the graphite phase carbonized nitrogen, the compatibility of the modified graphite phase carbonized nitrogen with the terminal hydroxyl polyester resin can be improved, thereby improving the mechanical properties of the powder coating.

[0023] A second aspect of the present invention provides a method for preparing a flame retardant powder coating, which specifically comprises the following steps: The hydroxy-terminated polyester resin, curing agent, flame retardant, leveling agent and defoaming agent are weighed in parts by weight, mixed evenly, melt-blended and extruded at 90-100° C., pressed into sheets and cooled, crushed, graded and sieved to obtain a flame-retardant powder coating.

[0024] In some embodiments, the method for preparing a flame retardant specifically comprises the following steps: S1. Weigh phenylphosphoryl dichloride and add it to 1,4-dioxane to obtain a phenylphosphoryl dichloride solution. Take 2-aminoterephthalic acid and add it to 100-150 times the weight of deionized water, then add it to the phenylphosphoryl dichloride solution. Under a nitrogen atmosphere, react at 80-110° C. for 5-10 hours. Collect the product, wash it, and dry it to obtain a modified organic ligand. S2, weigh melamine and place it in a crucible, move it to a tube furnace, heat it at 550° C. for 4-5 hours, collect the product, grind it, and obtain graphite phase carbon nitride; S3. Weigh the modified organic ligand prepared in step S1 and add it to methanol to obtain solution A. Weigh nickel nitrate hexahydrate and add it to methanol to obtain solution B. Weigh the graphite phase carbon nitride prepared in step S2 and add it to solution B. After stirring, ultrasonic treatment is performed to obtain a mixed solution C. Solution A and mixed solution C are mixed, placed in a reactor, and kept warm at 100-120° C. for 10-12 h. The product is collected, washed, and dried to obtain a flame retardant.

[0025] In some embodiments, in step S1, the molar ratio of phenylphosphoryl dichloride to 2-aminoterephthalic acid is 1:1.8-2.4.

[0026] In some embodiments, in step S1, the concentration of phenylphosphoryl dichloride in the phenylphosphoryl dichloride solution is 0.5 mol / L.

[0027] In some embodiments, in step S3, the power of ultrasonic treatment is 300-400 W, and the time is 30-40 min.

[0028] In some embodiments, in step S3, the amount of modified organic ligand added to methanol is 8-10 g / L.

[0029] In some embodiments, in step S3, the amount of nickel nitrate hexahydrate added to methanol is 12-14 g / L.

[0030] In some embodiments, in step S3, the mass ratio of graphite phase carbon nitride to nickel nitrate hexahydrate is 1:2-3.

[0031] In some embodiments, in step S3, the volume ratio of solution A to mixed solution C is 2-3:1.

[0032] The present invention will be further described below by way of specific embodiments.

[0033] The experimental methods in the following examples are conventional methods unless otherwise specified; the experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0034] The sources of some materials in the examples are as follows: Hydroxyl-terminated polyester resin, brand: DN-22, was purchased from Shandong Dengnuo New Material Technology Co., Ltd.

[0035] The curing agent is hydroxyalkylamide curing agent, CAS number: 6334-25-4, purchased from Kunshan Aichao Biotechnology Co., Ltd.

[0036] The leveling agent is an organic silicon leveling agent, brand: BYK-378, purchased from Shanghai Mengdihu Industrial Co., Ltd.

[0037] The defoaming agent is an organosilicon defoaming agent, brand: MY-240, purchased from Shandong Meiyu Chemical Co., Ltd.

[0038] Phenylphosphoryl dichloride, CAS number: 824-72-6, was purchased from Jiangsu Runfeng Synthetic Technology Co., Ltd.

[0039] 2-Aminoterephthalic acid, CAS No. 10312-55-7, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0040] Nickel nitrate hexahydrate, CAS number: 13478-00-7, was purchased from Hubei Longxin Chemical Industry Co., Ltd.

[0041] Melamine, CAS No.: 108-78-1, was purchased from Guangzhou Haoyu International Trade Co., Ltd.

[0042] Example 1 A flame retardant powder coating is prepared by comprising the following components: 50 parts of hydroxyl-terminated polyester resin, 5 parts of curing agent, 11 parts of flame retardant, 2 parts of leveling agent, and 2 parts of defoaming agent; the flame retardant is prepared by comprising the following components: phenylphosphoryl dichloride, 2-aminoterephthalic acid, nickel nitrate hexahydrate, and melamine.

[0043] A method for preparing a flame retardant powder coating comprises the following steps: The hydroxy-terminated polyester resin, curing agent, flame retardant, leveling agent and defoaming agent are weighed in parts by weight, mixed evenly, melt-blended and extruded at 90° C., pressed into sheets and cooled, crushed, graded and sieved to obtain a flame-retardant powder coating.

[0044] The preparation method of the flame retardant specifically comprises the following steps: S1. Weigh 0.05 mol of phenylphosphoryl dichloride and add it to 100 mL of 1,4-dioxane to obtain a phenylphosphoryl dichloride solution. Take 0.09 mol of 2-aminoterephthalic acid and add it to 100 times the weight of deionized water. Then add it to the phenylphosphoryl dichloride solution. React at 80° C. for 5 h under a nitrogen atmosphere. Collect the product, wash it, and dry it to obtain a modified organic ligand. S2, weigh 20g of melamine and place it in a crucible, move it to a tube furnace, heat it at 550°C for 4h, collect the product, grind it, and obtain graphite phase carbon nitride; S3. Weigh 0.8 g of the modified organic ligand prepared in step S1 and add it to 100 mL of methanol to obtain solution A. Weigh 0.36 g of nickel nitrate hexahydrate and add it to 30 mL of methanol to obtain solution B. Weigh 0.18 g of graphite phase carbon nitride prepared in step S2 and add it to solution B. After stirring, ultrasonic treatment is performed at a power of 300 W for 30 min to obtain a mixed solution C. 60 mL of solution A and 30 mL of mixed solution C are mixed, placed in a reactor, and kept warm at 100° C. for 10 h. The product is collected, washed, and dried to obtain a flame retardant.

[0045] Example 2 A flame retardant powder coating is prepared by comprising the following components: 80 parts of hydroxyl-terminated polyester resin, 10 parts of curing agent, 13 parts of flame retardant, 6 parts of leveling agent, and 4 parts of defoaming agent; the flame retardant is prepared by comprising the following components: phenylphosphoryl dichloride, 2-aminoterephthalic acid, nickel nitrate hexahydrate, and melamine.

[0046] A method for preparing a flame retardant powder coating comprises the following steps: The hydroxy-terminated polyester resin, curing agent, flame retardant, leveling agent and defoaming agent are weighed in parts by weight, mixed evenly, melt-blended and extruded at 100° C., pressed into sheets and cooled, crushed, graded and sieved to obtain a flame-retardant powder coating.

[0047] The preparation method of the flame retardant specifically comprises the following steps: S1. Weigh 0.05 mol of phenylphosphoryl dichloride and add it to 100 mL of 1,4-dioxane to obtain a phenylphosphoryl dichloride solution. Take 0.12 mol of 2-aminoterephthalic acid and add it to 150 times the weight of deionized water. Then add it to the phenylphosphoryl dichloride solution. Under a nitrogen atmosphere, react at 110° C. for 10 h. Collect the product, wash it, and dry it to obtain a modified organic ligand. S2, weigh 20g of melamine and place it in a crucible, move it to a tube furnace, heat it at 550°C for 5h, collect the product, grind it, and obtain graphite phase carbon nitride; S3. Weigh 1 g of the modified organic ligand prepared in step S1 and add it to 100 mL of methanol to obtain solution A. Weigh 0.42 g of nickel nitrate hexahydrate and add it to 30 mL of methanol to obtain solution B. Weigh 0.14 g of graphite phase carbon nitride prepared in step S2 and add it to solution B. After stirring, ultrasonic treatment is performed at a power of 400 W for 40 min to obtain a mixed solution C. Mix 90 mL of solution A and 30 mL of mixed solution C, place in a reactor, and keep warm at 120° C. for 12 h. Collect the product, wash it, and dry it to obtain a flame retardant.

[0048] Example 3 A flame retardant powder coating is prepared by comprising the following components: 65 parts of hydroxyl-terminated polyester resin, 8 parts of curing agent, 12 parts of flame retardant, 4 parts of leveling agent, and 3 parts of defoaming agent; the flame retardant is prepared by comprising the following components: phenylphosphoryl dichloride, 2-aminoterephthalic acid, nickel nitrate hexahydrate, and melamine.

[0049] A method for preparing a flame retardant powder coating comprises the following steps: The hydroxy-terminated polyester resin, curing agent, flame retardant, leveling agent and defoaming agent are weighed in parts by weight, mixed evenly, melt-blended and extruded at 95° C., pressed into sheets and cooled, crushed, graded and sieved to obtain a flame-retardant powder coating.

[0050] The preparation method of the flame retardant specifically comprises the following steps: S1. Weigh 0.05 mol of phenylphosphoryl dichloride and add it to 100 mL of 1,4-dioxane to obtain a phenylphosphoryl dichloride solution. Take 0.11 mol of 2-aminoterephthalic acid and add it to 120 times the weight of deionized water. Then add it to the phenylphosphoryl dichloride solution. Under a nitrogen atmosphere, react at 100° C. for 8 h. Collect the product, wash it, and dry it to obtain a modified organic ligand. S2, weigh 20g of melamine and place it in a crucible, move it to a tube furnace, heat it at 550°C for 4.5h, collect the product, grind it, and obtain graphite phase carbon nitride; S3. Weigh 0.9 g of the modified organic ligand prepared in step S1 and add it to 100 mL of methanol to obtain solution A. Weigh 0.39 g of nickel nitrate hexahydrate and add it to 30 mL of methanol to obtain solution B. Weigh 0.13 g of graphite phase carbon nitride prepared in step S2 and add it to solution B. After stirring, ultrasonic treatment is performed at a power of 350 W for 35 min to obtain a mixed solution C. Mix 75 mL of solution A and 30 mL of mixed solution C, place in a reactor, and keep warm at 110° C. for 11 h. Collect the product, wash it, and dry it to obtain a flame retardant.

[0051] Comparative Example 1 This comparative example provides a flame retardant powder coating, which differs from Example 1 only in that phenylphosphoryl dichloride is not included in the preparation components of the flame retardant, 2-aminoterephthalic acid is used as the organic ligand, and the remaining components and component contents are the same as those in Example 1.

[0052] Comparative Example 2 This comparative example provides a flame retardant powder coating, which differs from Example 1 only in that the preparation components of the flame retardant do not include melamine, the flame retardant only includes modified Ni-MOF, and the remaining components and component contents are the same as those in Example 1.

[0053] Comparative Example 3 This comparative example provides a flame retardant powder coating, which differs from Example 1 only in that no flame retardant is added, and the remaining components and component contents are the same as those in Example 1.

[0054] Experimental Example 1 The powder coatings of Examples 1-3 of the present invention and Comparative Examples 1-3 were subjected to flame retardancy tests, and the specific method was as follows: (1) Sample preparation: Put the powder coating into the standard workpiece to make UL94 combustion test specimens. The curing conditions are 200℃, 30min. The specimens are (125±5)mm×(13.0±0.5)mm×(3.0±0.5)mm. The quantity is 2 sets×5 pieces. (2) Sample pretreatment: place at (23+2)℃, relative humidity (50±5)% for 48h, place in an air exchange oven at (70±1)℃, place in a desiccator after 168h, and cool at room temperature for at least 4h.

[0055] (3) Sample test: Fix the sample on the sample clamp with its free end 300 mm from the ground and ensure that the sample is perpendicular to the ground. Burn the center of the lower edge of the test piece with a blue 20 mm high flame for 10 seconds and then remove it. If the test piece stops burning within 30 seconds, the Bunsen burner flame will burn the lower edge of the test piece again for 10 seconds. If the test piece melts, the dripping flame molecules will fall on the cotton layer 300 mm away from the lower end of the test piece.

[0056] (4) Record data: Record the first afterflame time t 1 , the second afterflame time t 2 , the second afterburning time t 3 , whether the sample is burned out, whether the dripping particles during the test ignite the cotton, and determine the flame retardant performance level according to Table 1.

[0057] Table 1 Grade determination criteria

[0058] Table 2 shows the flame retardant test results. It can be seen from Example 1 and Comparative Example 1 that the modified organic ligand can increase the flame retardant effect. It can be seen from Example 1 and Comparative Example 2 that the addition of graphite phase carbon nitride can increase the flame retardant effect.

[0059] Table 2 Flame retardant grade

[0060] Experimental Example 2 The impact resistance of the powder coatings of Examples 1-3 of the present invention and Comparative Examples 2 and 3 was tested. The specific method is as follows: referring to GB / T 1732-2020, the powder coating is sprayed on a metal substrate. The curing conditions are 200°C and 15 min to obtain a test sample. A heavy hammer is dropped from a certain height to impact the punch. The height of the heavy hammer drop is increased by 5 cm each time to test the value of damage to the paint film.

[0061] Figure 1 The test results of impact resistance are shown in the figure. The test results of Examples 1-3 are 70 cm, 70 cm, and 70 cm, the test result of Comparative Example 2 is 55 cm, and the test result of Comparative Example 3 is 50 cm. Example 1 has better impact resistance than Comparative Example 2, indicating that the impact resistance of the powder coating can be improved after the addition of graphite phase carbon nitride loaded by the modified Ni-MOF. Comparative Example 2 has better impact resistance than Comparative Example 3, indicating that the modified Ni-MOF has good compatibility with the terminal hydroxyl polyester resin, and the impact resistance of the powder coating can be improved after addition.

[0062] Experimental Example 3 The morphology of the flame retardant of Example 1 of the present invention was observed using a scanning electron microscope.

[0063] Figure 2 This is a scanning electron microscope image of the flame retardant. As shown in the figure, the modified Ni-MOF has a good combination with graphite phase carbon nitride.

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A flame retardant powder coating, characterized in that: The invention comprises the following components in parts by weight: 50-80 parts of terminal hydroxyl polyester resin, 5-10 parts of curing agent, 11-13 parts of flame retardant, 2-6 parts of leveling agent and 2-4 parts of defoaming agent; the flame retardant is a modified Ni-MOF / graphite phase carbon nitride composite material; the flame retardant comprises the following components: phenylphosphoryl dichloride, 2-aminoterephthalic acid, nickel nitrate hexahydrate and melamine.

2. A method for preparing a flame retardant powder coating according to claim 1, characterized in that: The specific steps include: Weigh the terminal hydroxyl polyester resin, curing agent, flame retardant, leveling agent and defoaming agent, mix them evenly, melt-blend and extrude them at 90-100° C., press them into sheets, cool them, crush them, grade them and sieve them to obtain a flame retardant powder coating.

3. The method for preparing a flame retardant powder coating according to claim 2, characterized in that: The preparation method of the flame retardant specifically comprises the following steps: S1. Weigh phenylphosphoryl dichloride and add it to 1,4-dioxane to obtain a phenylphosphoryl dichloride solution. Take 2-aminoterephthalic acid and add it to 100-150 times the weight of deionized water, then add it to the phenylphosphoryl dichloride solution. Under a nitrogen atmosphere, react at 80-110° C. for 5-10 hours. Collect the product, wash it, and dry it to obtain a modified organic ligand. S2, weigh melamine and place it in a crucible, move it to a tube furnace, heat it at 550° C. for 4-5 hours, collect the product, grind it, and obtain graphite phase carbon nitride; S3. Weigh the modified organic ligand prepared in step S1 and add it to methanol to obtain solution A. Weigh nickel nitrate hexahydrate and add it to methanol to obtain solution B. Weigh the graphite phase carbon nitride prepared in step S2 and add it to solution B. After stirring, ultrasonic treatment is performed to obtain a mixed solution C. Solution A and mixed solution C are mixed, placed in a reactor, and kept warm at 100-120° C. for 10-12 h. The product is collected, washed, and dried to obtain a flame retardant.

4. The method for preparing a flame retardant powder coating according to claim 3, characterized in that: In step S1, the molar ratio of the phenylphosphoryl dichloride to the 2-aminoterephthalic acid is 1:1.8-2.

4.

5. The method for preparing a flame retardant powder coating according to claim 3, characterized in that: In step S1, the concentration of phenylphosphoryl dichloride in the phenylphosphoryl dichloride solution is 0.5 mol / L.

6. The method for preparing a flame retardant powder coating according to claim 3, characterized in that: In step S3, the power of the ultrasonic treatment is 300-400 W, and the time is 30-40 min.

7. The method for preparing a flame retardant powder coating according to claim 3, characterized in that: In step S3, the amount of the modified organic ligand added to methanol is 8-10 g / L.

8. The method for preparing a flame retardant powder coating according to claim 3, characterized in that: In step S3, the amount of nickel nitrate hexahydrate added to methanol is 12-14 g / L.

9. The method for preparing a flame retardant powder coating according to claim 3, characterized in that: In step S3, the mass ratio of the graphite phase carbon nitride to the nickel nitrate hexahydrate is 1:2-3.

10. The method for preparing a flame retardant powder coating according to claim 3, characterized in that: In step S3, the volume ratio of the solution A to the mixed solution C is 2-3:1.

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