Low temperature cure thin film powder coating and method of making same

Abstract

The application discloses a low-temperature curing thin coating powder paint and a preparation method thereof, and belongs to the field of paint preparation. The powder paint comprises preparation raw materials of resin, accelerant, curing agent, dispersant, benzoin, barium sulfate, leveling agent, gloss enhancer and pigment. The preparation raw materials of the resin comprise neopentyl glycol, ethylene glycol, 1,4-cyclohexane dimethanol, terephthalic acid, adipic acid, isophthalic acid, catalyst and antioxidant. The application effectively improves the branching degree and end carboxyl activity of the resin by optimizing the preparation raw materials and the preparation raw material ratio of the resin, reduces the curing temperature of the powder paint while ensuring the reaction activity of the resin, and also obtains excellent weather resistance and mechanical properties. The catalyst and antioxidant are added in the resin preparation stage, which helps to improve the storage stability, solves the problem of uneven dispersion of the powder paint as a whole, and helps to improve the gloss of the coating and the performance of the coating.

Description

Technical Field

[0001] This invention relates to the field of coating preparation, and more specifically, to a low-temperature curing thin-film powder coating and its preparation method. Background Technology

[0002] Compared to traditional organic solvent coatings, powder coatings are favored for their advantages of being safer, more environmentally friendly, easier to control film thickness, and higher coating efficiency. Powder coatings can be classified into thermoplastic powder coatings and thermosetting powder coatings based on resin properties. Thermoplastic powder coatings do not require a curing agent, and the coating film exhibits excellent chemical resistance, toughness, flexibility, and a certain mechanical strength, making them suitable for thick-film coating. However, their adhesion to metal substrates is poor, generally requiring a primer or modified resin for improvement. Common thermoplastic resins used in powder coatings include polyethylene, polyvinyl chloride, polypropylene, polyamide, and thermoplastic polyester. Thermosetting powder coatings require a curing agent. Thermosetting resins melt under heat, and at a certain temperature, undergo a chemical cross-linking reaction with the curing agent to form a coating film with specific mechanical properties. Thermosetting powder coatings are mainly classified into three types: polyester / epoxy hybrid powder coatings, epoxy powder coatings, and pure polyester powder coatings. Existing technologies increase the activity of powder coatings to achieve low-temperature curing by adding curing accelerators or using more active functional groups in the base material. However, this approach has several drawbacks: low-temperature curing powder coatings exhibit poor physical and mechanical stability and chemical stability, especially when exposed to heat for extended periods. They are prone to melting, fusion, or clumping after prolonged exposure to sunlight. Similarly, if the powder coating contains a curing agent that reacts below 170°C, prolonged exposure to heat can compromise its chemical stability. Curing may occur during storage before the coating film has formed, such as pre-crosslinking, leading to difficulties in leveling or even failure to level during curing. This results in a "orange peel" texture or rough surface appearance during curing. Therefore, deterioration in the physical and mechanical stability of powder coatings leads to significant problems in their performance, application, and appearance, while deterioration in chemical properties results in serious quality issues. Furthermore, the curing temperature of existing powder coatings is mostly between 190℃ and 200℃, which not only leads to: ① higher energy consumption during the curing process compared to liquid coatings, but also ② limits the application of powder coatings on temperature-sensitive materials (materials that are not heat-resistant). Therefore, some powder coating manufacturers have developed low-temperature curing powder coatings, which use low-temperature curing resins with higher reactivity or add reaction catalysts to enable powder coatings to cure at lower temperatures (<170℃). However, low-temperature curing powder coatings also suffer from uneven dispersion, coating gloss, and performance degradation after the addition of accelerators. Moreover, existing technologies rarely modify the performance by improving the particle size of the powder coating, and the particle size of the powder coating also affects the overall flowability and coating quality. Summary of the Invention

[0003] Based on this, in order to solve the problems of poor quality, uneven dispersion, and decreased gloss and performance of low-temperature curing thin-coat powder coatings in the prior art, the present invention provides a low-temperature curing thin-coat powder coating and its preparation method, the specific technical solution of which is as follows:

[0004] A low-temperature curing thin-film powder coating comprises, by weight, the following raw materials: 45-55 parts resin, 1-3 parts accelerator, 3-9 parts curing agent, 0.5-1 part dispersant, 3-7 parts benzoin, 15-20 parts barium sulfate, 1-5 parts leveling agent, 1-7 parts gloss enhancer, and 7-9 parts pigment;

[0005] The resin is prepared from neopentyl glycol, ethylene glycol, 1,4-cyclohexanediethanol, terephthalic acid, adipic acid, isophthalic acid, a catalyst, and an antioxidant. The ratio of neopentyl glycol, ethylene glycol, 1,4-cyclohexanediethanol, terephthalic acid, adipic acid, and isophthalic acid by mass is (1-3):(1-4):(1-5):(3-7):(1-3):(2-5). The catalyst accounts for 0.05% to 1% of the resin by mass, and the antioxidant accounts for 0.1% to 7% of the resin by mass.

[0006] The accelerator is a nanoscale low-temperature accelerator with fumed silica as a carrier.

[0007] Furthermore, the catalyst is monobutyltin oxide.

[0008] Furthermore, the antioxidant is obtained by mixing pentaerythritol dioctadecanyl phosphite and trimellitic anhydride in a mass ratio of (1-3):(2-5).

[0009] Furthermore, the method for preparing the resin is as follows:

[0010] Neopentyl glycol, ethylene glycol and 1,4-cyclohexanediethanol were mixed, water was added, and the mixture was heated to 75℃~85℃ at a speed of 25r / min~50r / min to obtain a mixture.

[0011] Continue adding terephthalic acid, adipic acid, isophthalic acid, and catalyst to the mixture. Adjust the temperature to 100 r / min to 200 r / min, then continue heating to 200°C to 220°C and maintain the temperature for 20 min to 30 min. Add an antioxidant and continue stirring for 10 min to 20 min. Then cool the mixture to 180°C to 200°C and continue refluxing for 40 min to 60 min. Finally, turn on the cooling water. After the reaction is complete, the resin is obtained.

[0012] Furthermore, the acid value of the resin is 25 mg / KOH / g to 70 mg / KOH / g.

[0013] Furthermore, the nanoscale low-temperature accelerator is a mixture of polyester low-temperature accelerator and ultra-low temperature epoxy curing accelerator or a polyester low-temperature curing accelerator.

[0014] Furthermore, the curing agent is a β-hydroxyalkylamide.

[0015] Further, the dispersant is one or a mixture of VOK-DS330 dispersant, VOK-DS360 dispersant, VOK-DS361 dispersant, VOK-DS363 dispersant, VOK-DS6203 dispersant, and VOK-DS6904 dispersant.

[0016] Furthermore, the leveling agent is an acrylate leveling agent.

[0017] In addition, this application also provides a method for preparing a low-temperature curing thin-film powder coating, the preparation method comprising the following steps:

[0018] After the resin, accelerator, curing agent, dispersant, benzoin, barium sulfate, leveling agent, gloss enhancer and pigment are thoroughly mixed and uniformly, the mixture is extruded through a twin-screw extruder, then pressed and pulverized, pulverized in a micro-pulverizer and sieved to obtain a low-temperature curing thin-coat powder coating.

[0019] The above-mentioned scheme effectively improves the branching degree and end carboxyl activity of the resin by optimizing the raw materials and their ratio. While ensuring the reactivity of the resin, it lowers the curing temperature of the powder coating and also achieves excellent weather resistance and mechanical properties. Furthermore, the addition of catalysts and antioxidants during the resin preparation stage helps to improve storage stability. The interaction between the resin, fumed silica as a carrier, nano-scale low-temperature accelerator, and dispersant helps to reduce the problem of uneven dispersion of the powder coating during coating formation and helps to improve the gloss and performance of the coating. In the case of thin coating, it avoids the problems of poor powder coating flowability and coating grit, and overall achieves low-temperature curing thin coating. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] According to one embodiment of the present invention, a low-temperature curing thin-film powder coating comprises the following raw materials in parts by weight: 45-55 parts resin, 1-3 parts accelerator, 3-9 parts curing agent, 0.5-1 part dispersant, 3-7 parts benzoin, 15-20 parts barium sulfate, 1-5 parts leveling agent, 1-7 parts gloss enhancer, and 7-9 parts pigment.

[0023] The resin is prepared from neopentyl glycol, ethylene glycol, 1,4-cyclohexanediethanol, terephthalic acid, adipic acid, isophthalic acid, a catalyst, and an antioxidant. The ratio of neopentyl glycol, ethylene glycol, 1,4-cyclohexanediethanol, terephthalic acid, adipic acid, and isophthalic acid by mass is (1-3):(1-4):(1-5):(3-7):(1-3):(2-5). The catalyst accounts for 0.05% to 1% of the resin by mass, and the antioxidant accounts for 0.1% to 7% of the resin by mass.

[0024] The accelerator is a nanoscale low-temperature accelerator with fumed silica as a carrier.

[0025] In one embodiment, the catalyst is monobutyltin oxide.

[0026] In one embodiment, the antioxidant is a mixture of pentaerythritol dioctadecanyl phosphite and trimellitic anhydride in a mass ratio of (1-3):(2-5).

[0027] In one embodiment, the resin is prepared by:

[0028] Neopentyl glycol, ethylene glycol and 1,4-cyclohexanediethanol were mixed, water was added, and the mixture was heated to 75℃~85℃ at a speed of 25r / min~50r / min to obtain a mixture.

[0029] Continue adding terephthalic acid, adipic acid, isophthalic acid, and catalyst to the mixture. Adjust the temperature to 100 r / min to 200 r / min, then continue heating to 200°C to 220°C and maintain the temperature for 20 min to 30 min. Add an antioxidant and continue stirring for 10 min to 20 min. Then cool the mixture to 180°C to 200°C and continue refluxing for 40 min to 60 min. Finally, turn on the cooling water. After the reaction is complete, the resin is obtained.

[0030] In one embodiment, the acid value of the resin is 25 mg / KOH / g to 70 mg / KOH / g.

[0031] In one embodiment, the molecular weight of the resin is 2000 to 3000.

[0032] In one embodiment, the nanoscale low-temperature accelerator is a mixture of a polyester low-temperature accelerator and an ultra-low-temperature epoxy curing accelerator, or a polyester low-temperature curing accelerator, wherein the polyester low-temperature curing accelerator is preferably TE-230; and the ultra-low-temperature epoxy curing accelerator is preferably JT-6015A.

[0033] In one embodiment, the curing agent is a β-hydroxyalkylamide.

[0034] In one embodiment, the dispersant is one or a mixture of VOK-DS330 dispersant, VOK-DS360 dispersant, VOK-DS361 dispersant, VOK-DS363 dispersant, VOK-DS6203 dispersant, and VOK-DS6904 dispersant.

[0035] In one embodiment, the leveling agent is an acrylate leveling agent.

[0036] In one embodiment, the brightening agent is one of an acrylate copolymer or a 701B brightening agent.

[0037] In one embodiment, the pigment is one or more of titanium dioxide, titanium dioxide, and calcium carbonate.

[0038] In addition, this application also provides a method for preparing a low-temperature curing thin-film powder coating, the preparation method comprising the following steps:

[0039] After the resin, accelerator, curing agent, dispersant, benzoin, barium sulfate, leveling agent, gloss enhancer and pigment are thoroughly mixed and uniformly, the mixture is extruded through a twin-screw extruder, then pressed and pulverized, pulverized in a micro-pulverizer and sieved to obtain a low-temperature curing thin-coat powder coating.

[0040] In one embodiment, the front zone temperature of the twin-screw extruder is set to 115°C to 120°C, the rear zone temperature is set to 100°C to 105°C, and the twin-screw rotation speed is set to 30 r / min to 35 r / min.

[0041] In one embodiment, the average particle size of the low-temperature curing thin-film powder coating is 10 μm to 40 μm.

[0042] In one embodiment, the average particle size of the low-temperature curing thin-film powder coating satisfies the following condition: D 50 <25μm, D 10 >11μm, D 90 <40μm. Narrowing the particle size distribution of powder coatings facilitates thinner coatings and avoids problems such as reduced flowability and surface grit associated with smaller particle sizes. This is achieved by reducing D... 50 It also narrows the particle size distribution of powder coatings, which helps to achieve thin coatings in low-temperature curing powder coatings, reduces the heat absorption of powder coatings, and is conducive to further reducing curing time / lowering curing temperature. In addition, it is also conducive to reducing the amount of powder coating used and reducing the amount of components used.

[0043] The above-mentioned scheme effectively improves the branching degree and end carboxyl activity of the resin by optimizing the raw materials and their ratio. While ensuring the reactivity of the resin, it lowers the curing temperature of the powder coating and also achieves excellent weather resistance and mechanical properties. Furthermore, the addition of catalysts and antioxidants during the resin preparation stage helps to improve storage stability. The interaction between the resin, fumed silica as a carrier, nano-scale low-temperature accelerator, and dispersant helps to reduce the problem of uneven dispersion of the powder coating during coating formation and helps to improve the gloss and performance of the coating. In the case of thin coating, it avoids the problems of poor powder coating flowability and coating grit, and overall achieves low-temperature curing thin coating.

[0044] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0045] Example 1:

[0046] A method for preparing a low-temperature curing thin-film powder coating includes the following steps:

[0047] Neopentyl glycol, ethylene glycol, and 1,4-cyclohexanediethanol were mixed in a mass ratio of 3:4:5, and water was added. The mixture was heated to 75°C at 50 r / min to obtain a final mixture.

[0048] Continue adding terephthalic acid, adipic acid, and isophthalic acid in a mass ratio of 7:3:5 to the mixture, and add monobutyltin oxide at a mass percentage of 1% of the resin. Adjust the temperature to 100 r / min, continue heating to 200°C, maintain for 20 min, and then add an antioxidant at a mass percentage of 3% of the resin. The antioxidant is a mixture of pentaerythritol dioctadecanyl phosphite and trimellitic anhydride in a mass ratio of 3:5. Continue stirring for 20 min, then cool to 180°C, continue reflux for 40 min, and then turn on the cooling water. After the reaction is complete, the resin is obtained.

[0049] By weight ratio, 55 parts resin, 3 parts polyester low-temperature accelerator with fumed silica as carrier, 7 parts β-hydroxyalkylamide, 0.5 parts VOK-DS330 dispersant, 3 parts benzoin, 20 parts barium sulfate, 4 parts acrylate leveling agent, 3 parts acrylate copolymer, and 7 parts calcium carbonate are thoroughly mixed and extruded through a twin-screw extruder. The front zone temperature of the twin-screw extruder is set to 120°C, the rear zone temperature is set to 105°C, and the twin screw speed is set to 35 r / min. Then, the mixture is pressed into tablets, pulverized in a micro-pulverizer, and sieved to obtain a low-temperature curing thin-coat powder coating.

[0050] Example 2:

[0051] A method for preparing a low-temperature curing thin-film powder coating includes the following steps:

[0052] Neopentyl glycol, ethylene glycol, and 1,4-cyclohexanediethanol were mixed in a mass ratio of 3:2:4, and water was added. The mixture was heated to 80°C at 30 r / min to obtain a final mixture.

[0053] Continue adding terephthalic acid, adipic acid, and isophthalic acid in a mass ratio of 7:3:4 to the mixture, and add monobutyltin oxide at a mass percentage of 0.8% of the resin. Adjust the temperature to 120 r / min, continue heating to 210°C, maintain for 25 min, and then add an antioxidant at a mass percentage of 4% of the resin. The antioxidant is a mixture of pentaerythritol diacetyl phosphite and trimellitic anhydride in a mass ratio of 3:4. Continue stirring for 20 min, then cool to 200°C, continue reflux for 45 min, and then turn on the cooling water. After the reaction is complete, the resin is obtained.

[0054] By weight ratio, 53 parts resin, 2 parts polyester low-temperature accelerator with fumed silica as carrier, 8 parts β-hydroxyalkylamide, 0.6 parts VOK-DS330 dispersant, 4 parts benzoin, 17 parts barium sulfate, 5 parts acrylate leveling agent, 4 parts acrylate copolymer, and 8 parts calcium carbonate are thoroughly mixed and extruded through a twin-screw extruder. The front zone temperature of the twin-screw extruder is set to 120°C, the rear zone temperature is set to 105°C, and the twin screw speed is set to 30 r / min. Then, the mixture is pressed and pulverized, pulverized in a micro-pulverizer, and sieved to obtain a low-temperature curing thin-coat powder coating.

[0055] Example 3:

[0056] A method for preparing a low-temperature curing thin-film powder coating includes the following steps:

[0057] Neopentyl glycol, ethylene glycol, and 1,4-cyclohexanediethanol were mixed in a mass ratio of 2:3:5, and water was added. The mixture was heated to 85°C at 35 r / min to obtain a final mixture.

[0058] Continue adding terephthalic acid, adipic acid, and isophthalic acid in a mass ratio of 5:2:4 to the mixture, and add monobutyltin oxide accounting for 1% of the resin mass percentage. Adjust the temperature to 150 r / min, continue heating to 220°C, maintain for 30 min, and then add an antioxidant accounting for 5% of the resin mass percentage. The antioxidant is a mixture of pentaerythritol dioctadecanyl phosphite and trimellitic anhydride in a mass ratio of 3:4. Continue stirring for 18 min, then cool to 185°C, continue reflux for 50 min, and then turn on the cooling water. After the reaction is complete, the resin is obtained.

[0059] By weight ratio, 54 parts resin, 3 parts polyester low-temperature accelerator with fumed silica as carrier, 9 parts β-hydroxyalkylamide, 0.7 parts VOK-DS330 dispersant, 6 parts benzoin, 18 parts barium sulfate, 4 parts acrylate leveling agent, 6 parts acrylate copolymer, and 7 parts calcium carbonate are thoroughly mixed and extruded through a twin-screw extruder. The front zone temperature of the twin-screw extruder is set to 118°C, the rear zone temperature is set to 102°C, and the twin screw speed is set to 35 r / min. Then, the mixture is pressed and pulverized, pulverized in a micro-pulverizer, and sieved to obtain a low-temperature curing thin-coat powder coating.

[0060] Example 4:

[0061] A method for preparing a low-temperature curing thin-film powder coating includes the following steps:

[0062] Neopentyl glycol, ethylene glycol, and 1,4-cyclohexanediethanol were mixed in a mass ratio of 2:3:5, and water was added. The mixture was heated to 82°C at a speed of 40 r / min to obtain a final mixture.

[0063] Continue adding terephthalic acid, adipic acid, and isophthalic acid in a mass ratio of 6:2:5 to the mixture, and add 0.7% monobutyltin oxide, which accounts for 150 r / min of the resin. Adjust the temperature to 220°C and maintain it for 20 min. Then add 5% antioxidant, which is a mixture of pentaerythritol dioctadecanyl phosphite and trimellitic anhydride in a mass ratio of 2:5. Continue stirring for 20 min, then cool to 200°C and reflux for 55 min. Finally, turn on the cooling water. After the reaction is complete, the resin is obtained.

[0064] By weight ratio, 55 parts resin, 3 parts polyester low-temperature accelerator with fumed silica as carrier, 7 parts β-hydroxyalkylamide, 0.5 parts VOK-DS330 dispersant, 5 parts benzoin, 18 parts barium sulfate, 3 parts acrylate leveling agent, 6 parts acrylate copolymer, and 7 parts calcium carbonate are thoroughly mixed and extruded through a twin-screw extruder. The front zone temperature of the twin-screw extruder is set to 115℃, the rear zone temperature is set to 105℃, and the twin screw speed is set to 30 r / min. Then, the mixture is pressed and pulverized, pulverized in a micro-pulverizer, and sieved to obtain a low-temperature curing thin-coat powder coating.

[0065] It should be noted that the particle size distribution of the low-temperature curing thin-film powder coatings in Examples 1-4 meets the following condition: D 50 <25μm, D 10 >11μm, D 90 <40μm.

[0066] Comparative Examples 1-5:

[0067] The difference between Comparative Examples 1-5 and Example 4 is that the raw materials and the ratio of the raw materials used to prepare the resin are different in Comparative Examples 1-5, as shown in Table 1. The other aspects are the same as in Example 4.

[0068] Comparative Example 6:

[0069] The difference between Comparative Example 6 and Example 4 is that no antioxidant was added to the resin in Comparative Example 6, but otherwise it is the same as Example 4.

[0070] Comparative Example 7:

[0071] The difference between Comparative Example 7 and Example 4 is that no polyester low-temperature accelerator with fumed silica as a carrier was added in Comparative Example 7, while the rest is the same as in Example 4.

[0072] Comparative Example 8:

[0073] The difference between Comparative Example 8 and Example 4 is that Comparative Example 8 uses a commercially available accelerator, while the rest is the same as Example 4.

[0074] Table 1:

[0075]

[0076]

[0077] The powder coatings prepared in Examples 1-4 and Comparative Examples 1-8 were tested for appearance, storage stability, impact resistance, and corrosion resistance. The coating thickness was 40 μm. Appearance was observed visually, checking for smoothness, color uniformity, presence of bubbles, cracks, pinholes, and orange peel texture. Storage stability was assessed by sealing and storing the powder coatings at 25°C under ventilated and dry conditions for three months. Impact resistance was tested according to GB1732-79 (50 kg·cm). Weather resistance was tested using the QUVB accelerated aging test for 4000 h. The results of appearance and storage stability are shown in Table 2. The results of leveling, impact resistance, and weather resistance are shown in Table 3.

[0078] Table 2:

[0079]

[0080]

[0081] As can be seen from the data analysis in Table 2, by optimizing the raw materials and the ratio of the raw materials for resin preparation, this application obtains a powder coating that is stable in storage, and the coating surface is smooth and even, without bubbles, shrinkage cavities, pinholes, or orange peel texture, thus obtaining a high-quality coating.

[0082] Table 3:

[0083]

[0084]

[0085] The data analysis in Table 3 shows that by optimizing the raw materials and their proportions, this application can obtain powder coatings with excellent leveling properties, impact resistance, and weather resistance. The difference between Comparative Examples 1-5 and Example 4 lies in the different raw materials and their proportions, resulting in different powder coating performances, which are worse than those of Example 4. This indicates that the raw materials and their proportions significantly contribute to the technical effect of this application. The difference between Comparative Example 6 and Example 4 is that no antioxidant was added in Comparative Example 6. Adding an antioxidant during the resin preparation stage helps improve the weather resistance of the subsequent powder coating. Comparative Example 7 did not add a polyester low-temperature accelerator with fumed silica as a carrier, while Comparative Example 8 added a commercially available accelerator, but the effects were worse than those of Example 4. This indicates that this application uses a nano-scale low-temperature accelerator with fumed silica as a carrier to improve the dispersibility of the reaction accelerator in the raw materials and reduce problems such as gloss reduction and deterioration of coating performance caused by uneven dispersion of reaction accelerators.

[0086] In addition, the following tests were conducted on the particle size distribution of the powder coating. The specific particle size distribution and results are shown in Table 4.

[0087] Table 4:

[0088]

[0089]

[0090] As can be seen from the data analysis in Table 4, this application reduces D 50 It also narrows the particle size distribution, enabling thin coatings and avoiding poor powder flowability and coating grit. Furthermore, it combines the thin-coating process with a low-temperature curing process, further aiding in the low-temperature curing of the coating through thin coating / reduced film thickness.

[0091] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0092] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A low-temperature curing thin-film powder coating, characterized in that, According to the weight ratio, the raw materials include the following: 45-55 parts resin, 1-3 parts accelerator, 3-9 parts curing agent, 0.5-1 part dispersant, 3-7 parts benzoin, 15-20 parts barium sulfate, 1-5 parts leveling agent, 1-7 parts gloss enhancer, and 7-9 parts pigment; The resin is prepared from neopentyl glycol, ethylene glycol, 1,4-cyclohexanediol, terephthalic acid, adipic acid, isophthalic acid, a catalyst, and an antioxidant. The ratio of neopentyl glycol, ethylene glycol, 1,4-cyclohexanediol, terephthalic acid, adipic acid, and isophthalic acid by mass is (1~3):(1~4):(1~5):(3~7):(1~3):(2~5). The catalyst accounts for 0.05%~1% of the resin's mass, and the antioxidant accounts for 0.1%~7% of the resin's mass. The accelerator is a nanoscale low-temperature accelerator with fumed silica as a carrier. The average particle size of the low-temperature curing thin-film powder coating meets the following condition: D 50 <25μm, D 10 >11μm, D 90 <40μm.

2. The low-temperature curing thin-film powder coating according to claim 1, characterized in that, The catalyst is monobutyltin oxide.

3. The low-temperature curing thin-film powder coating according to claim 1, characterized in that, The antioxidant is obtained by mixing pentaerythritol dioctadecanyl phosphite and trimellitic anhydride in a mass ratio of (1~3):(2~5).

4. The low-temperature curing thin-film powder coating according to claim 1, characterized in that, The resin is prepared by: Neopentyl glycol, ethylene glycol and 1,4-cyclohexanediethanol were mixed, water was added, and the mixture was heated to 75℃~85℃ at a speed of 25r / min~50r / min to obtain a mixture. Continue adding terephthalic acid, adipic acid, isophthalic acid, and catalyst to the mixture. Adjust the temperature to 100 r / min to 200 r / min, then continue heating to 200°C to 220°C and maintain the temperature for 20 min to 30 min. Add an antioxidant and continue stirring for 10 min to 20 min. Then cool the mixture to 180°C to 200°C and reflux for 40 min to 60 min. Finally, turn on the cooling water. After the reaction is complete, the resin is obtained.

5. The low-temperature curing thin-film powder coating according to claim 1, characterized in that, The acid value of the resin is 25 mg / KOH / g to 70 mg / KOH / g.

6. The low-temperature curing thin-film powder coating according to claim 1, characterized in that, The nanoscale low-temperature accelerator is a mixture of polyester low-temperature accelerator and ultra-low temperature epoxy curing accelerator or a polyester low-temperature curing accelerator.

7. The low-temperature curing thin-film powder coating according to claim 1, characterized in that, The curing agent is β-hydroxyalkylamide.

8. The low-temperature curing thin-film powder coating according to claim 1, characterized in that, The dispersant is one or a mixture of VOK-DS330 dispersant, VOK-DS360 dispersant, VOK-DS361 dispersant, VOK-DS363 dispersant, VOK-DS6203 dispersant, and VOK-DS6904 dispersant.

9. The low-temperature curing thin-film powder coating according to claim 1, characterized in that, The leveling agent is an acrylate leveling agent.

10. A method for preparing a low-temperature curing thin-film powder coating, characterized in that, The preparation method is used to prepare the low-temperature curing thin-film powder coating as described in any one of claims 1 to 9, and the preparation method includes the following steps: After the resin, accelerator, curing agent, dispersant, benzoin, barium sulfate, leveling agent, gloss enhancer and pigment are thoroughly mixed and uniformly, the mixture is extruded through a twin-screw extruder, then pressed and pulverized, pulverized in a micro-pulverizer and sieved to obtain a low-temperature curing thin-coat powder coating.

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