A high temperature resistant powder coating and a method for preparing the same

Abstract

The application relates to the field of advanced petrochemical chemical new material technologies, and particularly discloses a high-temperature-resistant powder coating and a preparation method thereof. The preparation raw materials of the high-temperature-resistant powder coating include organic silicon resin, polyester resin, isocyanuric acid triglycidyl ester curing agent, high-temperature-resistant additive, leveling agent and degassing agent. The preparation raw materials of the high-temperature-resistant additive include mixed filler, amino silane and polyethylene glycol intermediate, and the mass ratio of the mixed filler, the amino silane and the polyethylene glycol intermediate is (400-550):(20-30):(100-200). The high-temperature-resistant additive effectively improves the high-temperature resistance and mechanical properties of the powder coating.

Description

A high-temperature resistant powder coating and its preparation method Technical Field

[0001] This invention relates to the field of advanced petrochemical new materials technology, and in particular to a high-temperature resistant powder coating and its preparation method. Background Technology

[0002] Powder coatings, as an environmentally friendly high-performance coating, are widely used in home appliances, automobiles, construction, and industrial equipment due to their advantages such as being solvent-free, having high utilization rates, and exhibiting strong corrosion resistance. Common powder coatings are mainly composed of epoxy resins and polyester resins, exhibiting good adhesion and mechanical properties under normal or medium temperature conditions. However, with the increasing demand for high-temperature environments in industrial applications, such as engine parts, exhaust pipes, and industrial furnaces, the high-temperature resistance of existing powder coatings has become a key challenge for technological development.

[0003] Existing epoxy or polyester resins typically decompose at around 280°C. When the coating is exposed to a sustained high-temperature environment, the resin molecular chains undergo thermal degradation, causing the coating to powder, lose adhesion, and eventually fall off. This limits the application of powder coatings in high-performance industrial equipment and fails to meet the requirements for long-term heat exposure. Summary of the Invention

[0004] To improve the temperature resistance of powder coatings, this application provides a high-temperature resistant powder coating and its preparation method.

[0005] Firstly, this application provides a high-temperature resistant powder coating, which adopts the following technical solution:

[0006] A high-temperature resistant powder coating, by weight, is prepared from the following raw materials:

[0007] 400-500 parts of silicone resin, 20-100 parts of polyester resin, 1.5-7 parts of triglycidyl isocyanate curing agent, 360-520 parts of high-temperature resistant additives, 13-15 parts of leveling agent, and 7-10 parts of degassing agent.

[0008] The raw materials for preparing the high-temperature resistant additive include mixed fillers, aminosilane, and polyethylene glycol intermediate, and the mass ratio of the mixed fillers, aminosilane, and polyethylene glycol intermediate is (400-550):(20-30):(100-200).

[0009] By adopting the above technical solution, this invention uses silicone resin as one of the main film-forming substances. Silicone resin has excellent high-temperature resistance. In high-temperature environments, as the temperature rises, the CH structure in the silicone resin may undergo a thermal oxidation reaction, and the Si atoms connected to CH form Si-O-Si bonds with a higher degree of crosslinking. The Si-O-Si bonds have higher stability and can, to a certain extent, slow down or prevent the polymer backbone from breaking and degrading due to high temperature, thereby maintaining the internal stability of the system. The triglycidyl isocyanate curing agent works together with the polyester resin to increase the adhesion of the coating and improve the crosslinking density. The high-temperature resistance of the powder coating is significantly improved by the high-temperature resistant additives.

[0010] In this process, the surface modification of the mixed filler using aminosilanes and polyethylene glycol intermediates creates a composite interface layer between the inorganic filler particles and the organic resin matrix, combining rigid anchoring and flexible buffering. This promotes uniform dispersion of the mixed filler and improves its compatibility with the resin matrix. The aminosilanes are used for coupling modification of the mixed filler, reducing agglomeration and introducing amino groups onto the surface. These amino groups then replace chlorine atoms in the polyethylene glycol intermediates, grafting the intermediates onto the surface of the mixed filler. During the heating process, the difference in thermal expansion coefficients between the resin and the filler generates significant internal stress. The flexible long chains of polyethylene glycol can deform, effectively absorbing and relaxing thermal stress, reducing stress concentration that leads to the generation and propagation of microcracks, thereby enhancing the high-temperature resistance and thermal shock resistance of the powder coating.

[0011] Preferably, the raw materials for preparing the polyethylene glycol intermediate include monomethoxy polyethylene glycol, cyanuric chloride and dopamine, and the weight ratio of monomethoxy polyethylene glycol, cyanuric chloride and dopamine is (150-250):(180-300):(270-370).

[0012] By employing the above technical solution, cyanuric chloride, as a rigid triazine linker, provides high thermal stability and strong crosslinking ability. The chlorine atom in cyanuric chloride undergoes a substitution reaction with the hydroxyl group in monomethoxy polyethylene glycol, thereby activating the monomethoxy polyethylene glycol and giving it better reactivity. The addition of dopamine allows its amino group to replace one chlorine atom in cyanuric chloride, further participating in the reaction to construct the polyethylene glycol intermediate structure. Furthermore, the hydroxyl group in dopamine can crosslink with the polyester, thereby promoting the dispersibility of the powder coating, enhancing the bonding force between the powder coating and resin molecules, and improving the mechanical properties of the coating.

[0013] Preferably, the preparation method of the high-temperature resistant additive includes the following steps:

[0014] (1) Add the mixed packing material to NaOH solution, ultrasonically disperse for 10-20 min, filter, wash and dry to obtain the pretreated mixed packing material;

[0015] (2) Dissolve aminosilane in a solvent to obtain a coupling agent solution. Disperse the pretreated mixed filler in the solvent, add the coupling agent solution, stir and react for 2-3 hours, filter, wash and dry to obtain the coupling modified mixed filler.

[0016] (3) Dissolve the coupling modified mixed filler and polyethylene glycol intermediate in a solvent, introduce nitrogen gas, add alkaline catalyst, heat to 37-42℃, stir for 3-4 hours, purify and dry to obtain high temperature resistant additive.

[0017] Preferably, the method for preparing the polyethylene glycol intermediate includes the following steps:

[0018] Monomethoxy polyethylene glycol and cyanuric chloride are mixed and added to a solvent. Nitrogen gas is introduced, an alkaline catalyst is added, and the mixture is stirred for 1-2 hours to precipitate the product. The precipitate is then dissolved and the precipitation and dissolution process is repeated 2-3 times to remove unreacted cyanuric chloride. The product is then dried under vacuum to obtain activated polyethylene glycol.

[0019] Activated polyethylene glycol was dissolved in a solvent, nitrogen gas was introduced, dopamine was added, the mixture was heated to 27-35℃, stirred for 3-4 hours, purified, and then freeze-dried to obtain a polyethylene glycol intermediate.

[0020] By adopting the above technical solution, after the mixed filler is modified by aminosilane coupling, the amino group acts as a nucleophile to attack the remaining chlorine atoms on the polyethylene glycol intermediate, and a nucleophilic substitution reaction is carried out to form a stable CN covalent bond, thereby covalently linking the aminosilane with the PEG chain, and grafting the polyethylene glycol intermediate onto the surface of the filler particles, thus realizing the composite modification of the mixed filler.

[0021] Preferably, the aminosilane includes one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, and N-2-aminoethyl-3-aminopropyltriethoxysilane.

[0022] By adopting the above technical solution, coupling modification of the surface of the mixed packing is achieved through aminosilane, which effectively improves the dispersion performance and subsequent reactivity of the mixed packing.

[0023] Preferably, the mixed filler includes mica powder, silica powder and manganese iron black, and the mass ratio of mica powder, silica powder and manganese iron black is (334-430):(54-100):(12-20).

[0024] By adopting the above technical solution, the three fillers, after synergistic modification at a specific mass ratio, significantly improved the high-temperature resistance of the coating, enabling the powder coating to better maintain its structure and performance under high-temperature environments. Specifically, mica powder possesses excellent heat resistance and chemical stability, forming a stable structure at high temperatures; silica powder can fill the voids in the coating, increasing its density and reducing heat transfer; and manganese iron black has high thermal conductivity, effectively dispersing heat and preventing localized overheating.

[0025] Preferably, the polyester resin is a carboxyl-terminated polyester resin, the acid value of the carboxyl-terminated polyester resin is 20-40 mgKOH / g, and the number-average molecular weight of the carboxyl-terminated polyester resin is 8000-12000.

[0026] By adopting the above technical solution and using the above-mentioned carboxyl-terminated polyester resin with acid value and number-average molecular weight as raw material to prepare high-temperature resistant powder coatings, the coating can better crosslink with organosilicon resin, triglycidyl isocyanate curing agent, etc. when the raw materials are mixed in the proportion of each ingredient in the formula, thereby improving the adhesion of the coating.

[0027] Preferably, the leveling agent is a polyacrylate leveling agent; the degassing agent includes one or two of ethylene bis-stearamide and hydrogenated castor oil.

[0028] By adopting the above technical solution, the leveling agent and the degassing agent work together to effectively eliminate pinholes, shrinkage cavities and bubbles generated during the curing process of powder coatings, which is beneficial to improving the surface quality and smoothness of the coating.

[0029] Secondly, the method for preparing a high-temperature resistant powder coating provided in this application adopts the following technical solution:

[0030] A method for preparing a high-temperature resistant powder coating includes the following steps:

[0031] Weigh the raw materials according to the proportions, mix the silicone resin, polyester resin, triglycidyl isocyanate curing agent, high-temperature resistant additive, leveling agent, and degassing agent at high speed for 5-10 minutes, melt and extrude the uniformly mixed material at 110-125℃, cool and press into sheets, grind and sieve the sheets to obtain a high-temperature resistant powder coating.

[0032] Preferably, the average particle size of the high-temperature resistant powder coating is 10-20 μm.

[0033] By adopting the above technical solution, the raw materials are fully mixed and fully fused and reacted at a suitable temperature during the preparation of powder coating. After extrusion and tableting, the powder is ground. By controlling the particle size of the powder coating, the powder coating can have better fluidity and dispersibility during construction, and can adhere more evenly to the surface of the object being coated, improving the smoothness and quality of the coating, and thus helping to enhance the high temperature resistance and protective effect of the coating.

[0034] This application has the following beneficial effects:

[0035] This invention uses silicone resin as one of the main film-forming substances. Silicone resin has excellent high-temperature resistance. In high-temperature environments, as the temperature rises, the CH structure in the silicone resin may undergo a thermal oxidation reaction, and the Si atoms connected to CH form Si-O-Si bonds with a higher degree of crosslinking. The Si-O-Si bonds have higher stability and can, to a certain extent, slow down or prevent the polymer backbone from breaking and degrading due to high temperature, thereby maintaining the internal stability of the system. The triglycidyl isocyanate curing agent works together with the polyester resin to increase the adhesion of the coating and improve the crosslinking density. The high-temperature resistance of the powder coating is significantly improved by high-temperature resistant additives.

[0036] In this process, the surface modification of the mixed filler using aminosilanes and polyethylene glycol intermediates creates a composite interface layer between the inorganic filler particles and the organic resin matrix, combining rigid anchoring and flexible buffering. This promotes uniform dispersion of the mixed filler and improves its compatibility with the resin matrix. The aminosilanes are used for coupling modification of the mixed filler, reducing agglomeration and introducing amino groups onto the surface. These amino groups then replace chlorine atoms in the polyethylene glycol intermediates, grafting the intermediates onto the surface of the mixed filler. During the heating process, the difference in thermal expansion coefficients between the resin and the filler generates significant internal stress. The flexible long chains of polyethylene glycol can deform, effectively absorbing and relaxing thermal stress, reducing stress concentration that leads to the generation and propagation of microcracks, thereby enhancing the high-temperature resistance and thermal shock resistance of the powder coating.

[0037] Cyanuryl chloride, as a rigid triazine atom, provides high thermal stability and strong crosslinking ability. The chlorine atom in cyanuryl chloride undergoes a substitution reaction with the hydroxyl group in monomethoxy polyethylene glycol, thereby activating the monomethoxy polyethylene glycol and giving it better reactivity. The addition of dopamine allows its amino group to replace one chlorine atom in cyanuryl chloride, further participating in the reaction to construct the polyethylene glycol intermediate structure. Furthermore, the hydroxyl group in dopamine can crosslink with the polyester, thereby promoting the dispersibility of the powder coating, enhancing the bonding force between the powder coating and resin molecules, and improving the mechanical properties of the coating. Detailed Implementation

[0038] The present application will be further described in detail below with reference to the embodiments.

[0039] Preparation Example

[0040] Preparation Example 1

[0041] Preparation method of polyethylene glycol intermediate:

[0042] 150g of monomethoxy polyethylene glycol and 180g of cyanuric chloride were mixed and added to 1L of anhydrous benzene. Nitrogen gas was introduced and 5g of triethylamine was added. The mixture was stirred and reacted for 1 hour. The product was precipitated with diethyl ether and then dissolved with anhydrous benzene. The precipitation and dissolution were repeated twice to remove unreacted cyanuric chloride. The product was then dried under vacuum to obtain activated polyethylene glycol.

[0043] Activated polyethylene glycol was dissolved in 1 L of N,N-dimethylformamide, nitrogen gas was introduced, 270 g of dopamine was added, the mixture was heated to 27 °C, stirred for 3 h, purified and freeze-dried to obtain the polyethylene glycol intermediate.

[0044] The monomethoxy polyethylene glycol was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd., with the product number lnb-153.

[0045] Preparation Example 2

[0046] Preparation method of polyethylene glycol intermediate:

[0047] 200g of monomethoxy polyethylene glycol and 240g of cyanuric chloride were mixed and added to 1L of anhydrous benzene. Nitrogen gas was introduced, and 8g of triethylamine was added. The mixture was stirred and reacted for 1.5h. The product was precipitated with diethyl ether and then dissolved with anhydrous benzene. The precipitation and dissolution were repeated 3 times to remove unreacted cyanuric chloride. The product was then dried under vacuum to obtain activated polyethylene glycol.

[0048] Activated polyethylene glycol was dissolved in 1 L of N,N-dimethylformamide, nitrogen gas was introduced, 320 g of dopamine was added, the mixture was heated to 30 °C, stirred for 3.5 h, purified and freeze-dried to obtain the polyethylene glycol intermediate.

[0049] The monomethoxy polyethylene glycol was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd., with the product number lnb-153.

[0050] Preparation Example 3

[0051] Preparation method of polyethylene glycol intermediate:

[0052] 250g of monomethoxy polyethylene glycol and 300g of cyanuric chloride were mixed and added to 1L of anhydrous benzene. Nitrogen gas was introduced and 10g of triethylamine was added. The mixture was stirred and reacted for 2 hours. The product was precipitated with diethyl ether and then dissolved with anhydrous benzene. The precipitation and dissolution were repeated 3 times to remove unreacted cyanuric chloride. The product was then dried under vacuum to obtain activated polyethylene glycol.

[0053] Activated polyethylene glycol was dissolved in 1 L of N,N-dimethylformamide, nitrogen gas was introduced, 370 g of dopamine was added, the mixture was heated to 35 °C, stirred for 4 h, purified and freeze-dried to obtain the polyethylene glycol intermediate.

[0054] The monomethoxy polyethylene glycol was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd., with the product number lnb-153.

[0055] Preparation Example 4

[0056] The difference between this preparation example and preparation example 3 is that dopamine is replaced by aniline by mass.

[0057] Preparation Example 5

[0058] The difference between this preparation example and preparation example 3 is that cyanuric chloride is replaced by cyanuric acid by mass.

[0059] Preparation Example 6

[0060] Preparation method of high temperature resistant additives:

[0061] (1) Mix 334g mica powder, 54g silica powder and 12g manganese iron black evenly and add them to 1L of 30% NaOH solution. Disperse by ultrasonication for 10min, filter, wash and dry to obtain pretreated mixed filler.

[0062] (2) Dissolve 10g of 3-aminopropyltriethoxysilane and 10g of 3-aminopropyltrimethoxysilane in 50mL of anhydrous ethanol to obtain a coupling agent solution. Disperse the pretreated mixed filler in 500mL of anhydrous ethanol, slowly add the coupling agent solution, stir and react for 2h, filter, wash and dry to obtain the coupling modified mixed filler.

[0063] (3) The coupling modified mixed filler and 100g of polyethylene glycol intermediate (prepared in Example 1) were dissolved in 1000mL of N,N-dimethylformamide, nitrogen gas was introduced, 5g of triethylamine was added, the mixture was heated to 37°C, stirred for 3h, purified and dried to obtain the high temperature resistant additive.

[0064] Preparation Example 7

[0065] (1) Mix 382g of mica powder, 80g of silica powder and 18g of manganese iron black evenly and add them to 1L of 30% NaOH solution. Disperse by ultrasonication for 15min, filter, wash and dry to obtain pretreated mixed filler.

[0066] (2) Dissolve 25g of N-2-aminoethyl-3-aminopropyltrimethoxysilane in 50mL of anhydrous ethanol to obtain a coupling agent solution. Disperse the pretreated mixed filler in 550mL of anhydrous ethanol, slowly add the coupling agent solution, stir and react for 2.5h, filter, wash and dry to obtain the coupling modified mixed filler.

[0067] (3) The coupling modified mixed filler and 150g of polyethylene glycol intermediate (prepared in Example 2) were dissolved in 1000mL of N,N-dimethylformamide, nitrogen gas was introduced, 8g of triethylamine was added, the mixture was heated to 40℃, stirred for 3.5h, purified and dried to obtain the high temperature resistant additive.

[0068] Preparation Example 8

[0069] (1) Mix 430g mica powder, 100g silica powder and 20g manganese iron black evenly and add them to 1L of 30% NaOH solution. Disperse by ultrasonication for 20min, filter, wash and dry to obtain pretreated mixed filler.

[0070] (2) Dissolve 30g of N-2-aminoethyl-3-aminopropyltriethoxysilane in 50mL of anhydrous ethanol to obtain a coupling agent solution. Disperse the pretreated mixed filler in 600mL of anhydrous ethanol, slowly add the coupling agent solution, stir and react for 3h, filter, wash and dry to obtain the coupling modified mixed filler.

[0071] (3) The coupling modified mixed filler and 200g of polyethylene glycol intermediate (prepared in Example 3) were dissolved in 1000mL of N,N-dimethylformamide, nitrogen gas was introduced, 10g of triethylamine was added, the mixture was heated to 42℃, stirred and reacted for 4h, purified and dried to obtain the high temperature resistant additive.

[0072] Preparation Example 9

[0073] The difference between this preparation example and preparation example 8 is that the polyethylene glycol intermediate obtained in preparation example 4 is used.

[0074] Preparation Example 10

[0075] The difference between this preparation example and preparation example 8 is that the polyethylene glycol intermediate obtained in preparation example 5 is used.

[0076] Preparation Example 11

[0077] The difference between this preparation example and preparation example 8 is that N-2-aminoethyl-3-aminopropyltriethoxysilane was replaced by an equal mass of the polyethylene glycol intermediate obtained in preparation example 3.

[0078] Preparation Example 12

[0079] The difference between this preparation example and Preparation Example 8 is that the polyethylene glycol intermediate is replaced by an equal mass of N-2-aminoethyl-3-aminopropyltriethoxysilane.

[0080] Preparation Example 13

[0081] The difference between this preparation example and preparation example 8 is that the polyethylene glycol intermediate is replaced by polyethylene glycol in equal mass.

[0082] Example

[0083] Example 1

[0084] A high-temperature resistant powder coating, comprising:

[0085] 400g silicone resin, 20g carboxyl-terminated polyester resin, 1.5g triglycidyl isocyanate curing agent, 360g high-temperature resistant additive (prepared in Example 6), 13g polyacrylate leveling agent, and 7g ethylene bis-stearamide.

[0086] The silicone resin used was a commercially available product purchased from Hubei Longsheng Sihai New Materials Co., Ltd., with the brand name SH-1053.

[0087] The acid value of the carboxyl-terminated polyester resin is 20 mg KOH / g, and the number-average molecular weight is 8000.

[0088] BYK-355 is selected as the polyacrylate leveling agent.

[0089] The preparation method of the high-temperature resistant powder coating is as follows:

[0090] Weigh the raw materials according to the component ratio, and mix the silicone resin, carboxyl-terminated polyester resin, triglycidyl isocyanate curing agent, high-temperature resistant additive, polyacrylate leveling agent, and ethylene bis-stearamide at high speed for 5 minutes. Melt and extrude the uniformly mixed material at 110°C, cool and press into sheets, and grind and sieve the sheets to obtain a high-temperature resistant powder coating with an average particle size of 10μm.

[0091] Example 2

[0092] A high-temperature resistant powder coating comprises: 450g of silicone resin, 60g of carboxyl-terminated polyester resin, 5g of triglycidyl isocyanurate curing agent, 440g of high-temperature resistant additive (prepared in Preparation Example 7), 14g of polyacrylate leveling agent, and 8.5g of hydrogenated castor oil.

[0093] The silicone resin used was a commercially available product purchased from Hubei Longsheng Sihai New Materials Co., Ltd., with the brand name SH-1053.

[0094] The acid value of the carboxyl-terminated polyester resin is 30 mg KOH / g, and the number average molecular weight is 10,000.

[0095] BYK-355 is selected as the polyacrylate leveling agent.

[0096] Hydrogenated castor oil was selected from commercially available products, purchased from Rongsheng New Material Technology (Nantong, Jiangsu) Co., Ltd., CAS No. 8001-78-3.

[0097] The preparation method of the high-temperature resistant powder coating is as follows:

[0098] Weigh the raw materials according to the component ratio, and mix the silicone resin, carboxyl-terminated polyester resin, triglycidyl isocyanate curing agent, high-temperature resistant additive, polyacrylate leveling agent, and hydrogenated castor oil at high speed for 8 minutes. Melt and extrude the uniformly mixed material at 120°C, cool and press into sheets, and then grind and sieve the sheets to obtain a high-temperature resistant powder coating with an average particle size of 15μm.

[0099] Example 3

[0100] A high-temperature resistant powder coating comprises: 500g of silicone resin, 100g of carboxyl-terminated polyester resin, 7g of triglycidyl isocyanurate curing agent, 520g of high-temperature resistant additive (prepared in Preparation Example 8), 15g of polyacrylate leveling agent, and 10g of hydrogenated castor oil.

[0101] The silicone resin used was a commercially available product purchased from Hubei Longsheng Sihai New Materials Co., Ltd., with the brand name SH-1053.

[0102] The acid value of the carboxyl-terminated polyester resin is 40 mg KOH / g, and the number-average molecular weight is 12000.

[0103] BYK-355 is selected as the polyacrylate leveling agent.

[0104] Hydrogenated castor oil was selected from commercially available products, purchased from Rongsheng New Material Technology (Nantong, Jiangsu) Co., Ltd., CAS No. 8001-78-3.

[0105] The preparation method of the high-temperature resistant powder coating is as follows:

[0106] Weigh the raw materials according to the component ratio, and mix the silicone resin, carboxyl-terminated polyester resin, triglycidyl isocyanate curing agent, high-temperature resistant additive, polyacrylate leveling agent, and hydrogenated castor oil at high speed for 10 minutes. Melt and extrude the uniformly mixed material at 125°C, cool and press into sheets, and grind and sieve the sheets to obtain a high-temperature resistant powder coating with an average particle size of 20μm.

[0107] Example 4

[0108] The difference between this embodiment and Example 3 is that the high-temperature resistant additive prepared in Example 9 is used.

[0109] Example 5

[0110] The difference between this embodiment and Example 3 is that the high-temperature resistant additive prepared in Example 10 is used.

[0111] Comparative Example

[0112] Comparative Example 1

[0113] A high-temperature resistant powder coating differs from Example 3 in that it uses the high-temperature resistant additive obtained in Preparation Example 11.

[0114] Comparative Example 2

[0115] A high-temperature resistant powder coating differs from Example 3 in that it uses the high-temperature resistant additive obtained in Preparation Example 12.

[0116] Comparative Example 3

[0117] A high-temperature resistant powder coating differs from Example 3 in that it uses the high-temperature resistant additive obtained in Preparation Example 13.

[0118] Comparative Example 4

[0119] A high-temperature resistant powder coating differs from Example 3 in that 430g of mica powder, 100g of silica powder, and 20g of manganese iron black are used together to replace the high-temperature resistant additives.

[0120] Comparative Example 5

[0121] A high-temperature resistant powder coating differs from Example 3 in that no high-temperature resistant additives are added.

[0122] Comparative Example 6

[0123] A high-temperature resistant powder coating differs from Example 3 in that the polyester resin is replaced by type A epoxy resin E44 by mass.

[0124] Comparative Example 7

[0125] A high-temperature resistant powder coating differs from Example 3 in that the triglycidyl isocyanurate curing agent is replaced by Wanhua IPDI curing agent.

[0126] Performance testing

[0127] Coating preparation: Steel plates with dimensions of 150mm × 75mm × 1mm were selected, and pretreatment was performed on the test plates according to GB / T 9271-2008. Powder coating was uniformly sprayed onto the surface of the steel plate using an electrostatic spray gun and cured at 230℃ for 15 minutes. After curing, the steel plates were removed and allowed to cool naturally at room temperature to complete the coating process. The coating thickness of each test plate was controlled at 50μm.

[0128] Temperature resistance test: Refer to T / CSTM00640-2022 to test the adhesion, appearance, bending performance and resistance to pointer scratches of the coating after baking (450℃ / 1h).

[0129] The adhesion test was conducted according to GB / T 9286-2021 "Paints and Varnishes Cross-cut Test". One hundred small squares were cut on the steel plate with a sharp blade, then special tape was applied and quickly torn off. The coating peeling off inside the squares was observed to evaluate the adhesion. The adhesion level was divided into 0-5, with 0 being the best and 5 being the worst.

[0130] The bending performance was tested according to GB / T 6742-1986 "Bending Test of Paint Film (Cylindrical Shaft)" using a bending diameter of 2mm. After holding the bending position for 15 seconds, the coating was returned to its original position, and the cracking of the coating was observed.

[0131] The resistance to pointer scratch is determined according to the test principle of ASTM D 5178-98 by pushing an arc-shaped (ring or circular) scriber under the steel plate. The scriber is installed at a 45-degree angle and pressed down on the surface of the steel plate, gradually increasing the load on the steel plate until the coating is scratched.

[0132] Table 1

[0133]

[0134] Based on the comparison between Examples 3 and 4-5 and the data in Table 1, it can be seen that: the aniline molecule in Example 4 lacks hydroxyl groups, making it unable to crosslink with the resin system, resulting in weak bonding between the mixed filler and the resin system; the cyanuric acid in Example 5 has weak bonding with monomethoxy polyethylene glycol, leading to a decrease in the yield and quality of the generated activated polyethylene glycol, deteriorating the performance of the polyethylene glycol intermediate, and affecting the mechanical properties of the coating. In contrast, the cyanuric chloride in this invention provides high thermal stability and strong crosslinking ability, enabling better activation of monomethoxy polyethylene glycol and giving it superior reactivity. The amino group in dopamine replaces one chlorine atom in the cyanuric chloride, further participating in the reaction to construct the polyethylene glycol intermediate structure. Furthermore, the hydroxyl groups in dopamine can crosslink with the polyester, thereby promoting the dispersibility of the powder coating and improving the bonding between the powder coating and resin molecules, thus improving the mechanical properties of the coating.

[0135] Based on the comparison between Example 3 and Comparative Examples 1-3, and the data in Table 1, it can be seen that: Comparative Example 1 uses polyethylene glycol intermediates alone to modify the mixed filler, resulting in fewer long-chain polyethylene glycol grafts on the filler surface and the presence of some agglomerates, leading to a poor improvement in the mechanical properties of the coating; Comparative Example 2 uses aminosilanes alone to modify the mixed filler, which can promote the dispersion of the mixed filler to some extent, but stress defects still exist in the filler at high temperatures, causing the coating to become brittle; In Comparative Example 3, the hydroxyl groups in the polyethylene glycol molecule have weak reactivity and cannot bind well with the mixed filler, thus affecting the dispersibility of the mixed filler and the mechanical properties of the coating.

[0136] Based on the comparison between Example 3 and Comparative Examples 4-5 and the data in Table 1, it can be seen that: the mixed filler in Comparative Example 4 was not modified, and its dispersibility in the resin system was poor. The filler agglomerates were prone to forming stress defect points, leading to coating performance failure. No high-temperature resistant additives were added in Comparative Example 5. Although the silicone resin itself has excellent heat resistance, the mechanical properties of the pure silicone resin coating are poor. However, this application can effectively compensate for the defect of poor mechanical properties of the pure silicone resin coating by adding high-temperature resistant additives, and maintain the excellent mechanical properties of the coating at high temperatures.

[0137] Based on the comparison between Example 3 and Comparative Example 6, and the data in Table 1, it can be seen that the epoxy resin in Comparative Example 6 cannot form a good cross-linking structure with the triglycidyl isocyanurate curing agent, resulting in a decrease in the high-temperature resistance of the powder coating.

[0138] Based on the comparison between Example 3 and Comparative Example 7, and the data in Table 1, it can be seen that: Comparative Example 7 uses IPDI curing agent. IPDI molecules do not contain triazine rings, resulting in poor heat resistance. The IPDI curing agent cannot form a stable cross-linking structure with the polyester resin in this application, meaning the degree of cross-linking is low, leading to poor high-temperature resistance of the coating. The triglycidyl isocyanate curing agent in this application is an epoxy-based curing agent. Its own triazine ring structure has good thermal stability, and the triglycidyl isocyanate curing agent works synergistically with the polyester resin to increase the cross-linking density and enhance the adhesion of the coating.

[0139] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-temperature resistant powder coating, characterized in that, The product, by weight, is prepared from the following raw materials: 400-500 parts of silicone resin, 20-100 parts of polyester resin, 1.5-7 parts of triglycidyl isocyanate curing agent, 360-520 parts of high-temperature resistant additive, 13-15 parts of leveling agent, and 7-10 parts of degassing agent; the raw materials for preparing the high-temperature resistant additive include mixed fillers, aminosilane, and polyethylene glycol intermediate, wherein the mass ratio of the mixed fillers, aminosilane, and polyethylene glycol intermediate is... The ratio of the polyethylene glycol intermediate to the total polyethylene glycol content is (400-550):(20-30):(100-200). The raw materials for preparing the polyethylene glycol intermediate include monomethoxy polyethylene glycol, cyanuric chloride, and dopamine, and the weight ratio of the monomethoxy polyethylene glycol, cyanuric chloride, and dopamine is (150-250):(180-300):(270-370). The polyester resin is a carboxyl-terminated polyester resin with an acid value of 20-40 mg KOH / g and a number-average molecular weight of 8000-12000.

2. The high-temperature resistant powder coating according to claim 1, characterized in that, The preparation method of the high-temperature resistant additive includes the following steps: (1) Add the mixed filler to NaOH solution, ultrasonically disperse for 10-20 min, filter, wash and dry to obtain pretreated mixed filler; (2) Dissolve aminosilane in solvent to obtain coupling agent solution, disperse the pretreated mixed filler in solvent, add coupling agent solution, stir reaction for 2-3 h, filter, wash and dry to obtain coupling modified mixed filler; (3) Dissolve coupling modified mixed filler and polyethylene glycol intermediate in solvent, introduce nitrogen gas, add alkaline catalyst, heat to 37-42℃, stir reaction for 3-4 h, purify and dry to obtain high-temperature resistant additive.

3. The high-temperature resistant powder coating according to claim 1, characterized in that, The preparation method of the polyethylene glycol intermediate includes the following steps: Monomethoxy polyethylene glycol and cyanuric chloride are mixed and added to a solvent, nitrogen gas is introduced, an alkaline catalyst is added, and the mixture is stirred for 1-2 hours to precipitate the product. The precipitate is then dissolved, and the precipitation and dissolution process is repeated 2-3 times to remove unreacted cyanuric chloride. The product is then vacuum dried to obtain activated polyethylene glycol. The activated polyethylene glycol is dissolved in a solvent, nitrogen gas is introduced, dopamine is added, and the mixture is heated to 27-35°C and stirred for 3-4 hours. After purification, the product is freeze-dried to obtain the polyethylene glycol intermediate.

4. The high-temperature resistant powder coating according to claim 1, characterized in that, The aminosilane includes one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, and N-2-aminoethyl-3-aminopropyltriethoxysilane.

5. The high-temperature resistant powder coating according to claim 1, characterized in that, The mixed filler includes mica powder, silica powder and manganese iron black, and the mass ratio of mica powder, silica powder and manganese iron black is (334-430): (54-100): (12-20).

6. The high-temperature resistant powder coating according to claim 1, characterized in that, The leveling agent is a polyacrylate leveling agent; the degassing agent includes one or two of ethylene bis-stearamide and hydrogenated castor oil.

7. A method for preparing a high-temperature resistant powder coating according to any one of claims 1-6, characterized in that, The process includes the following steps: weighing raw materials according to the group ratio, mixing silicone resin, polyester resin, triglycidyl isocyanate curing agent, high-temperature resistant additive, leveling agent, and degassing agent at high speed for 5-10 minutes, melting and extruding the uniformly mixed material at 110-125℃, cooling and pressing into sheets, and grinding and sieving the sheets to obtain a high-temperature resistant powder coating.

8. The method for preparing a high-temperature resistant powder coating according to claim 7, characterized in that, The average particle size of the high-temperature resistant powder coating is 10-20 μm.

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