High temperature resistant powder coating and preparation method thereof

Abstract

The present invention relates to a high-temperature resistant powder coating and a preparation method thereof. The high-temperature resistant powder coating comprises the following raw materials in parts by weight: 100 parts of a phenolic epoxy resin; 20-30 parts of an amino-terminated adduct; 15-25 parts of melamine; 80-90 parts of a high-temperature resistant filler; and 2-5 parts of an aminosiloxane. The amino-terminated adduct is the reaction product of an amino-terminated linear polysiloxane and an epoxy mixture, wherein the epoxy mixture is a mixture of a bisphenol A epoxy resin and an alicyclic epoxy resin. The powder coating has excellent high-temperature resistance and can be used at temperatures above 300°C without damage.

Description

Technical Field

[0001] The present invention relates to the field of powder coatings, and in particular to a high-temperature resistant powder coating and a preparation method thereof. Background Art

[0002] Powder coating is a solid powdered synthetic resin coating that usually does not contain solvents. When used, it is sprayed on the surface of the substrate using air as the medium, and then cured by heating or other methods to form a coating on the surface of the substrate. Therefore, powder coating has the advantages of being non-toxic and environmentally friendly compared to solvent-dispersed coatings.

[0003] With the development of powder coatings, powder coatings have also been used in fireplaces, heaters, barbecue grills, frying pans, exhaust pipes, chimneys and other fields in recent years. These fields often involve high-temperature application scenarios, requiring powder coatings to have better high-temperature resistance. Existing ordinary powder coatings cannot meet the high-temperature resistance requirements and are prone to cracking and peeling when used under high-temperature conditions. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the first object of the present invention is to provide a high temperature resistant powder coating, which has good high temperature resistance and can be used above 300°C without damage.

[0005] The second object of the present invention is to provide a method for preparing the high-temperature resistant powder coating, which has the advantages of simple steps and improved coating performance.

[0006] To achieve the first objective of the present invention, the present invention provides a high-temperature resistant powder coating, which includes the following raw materials in parts by mass: 100 parts of phenolic epoxy resin; 20 to 30 parts of terminal amino adduct; 15 to 25 parts of melamine; 80 to 90 parts of high-temperature resistant filler; and 2 to 5 parts of aminosiloxane; wherein the terminal amino adduct is the reaction product of terminal amino linear polysiloxane and an epoxy mixture, and the epoxy mixture is a mixture of bisphenol A epoxy resin and alicyclic epoxy resin.

[0007] In some embodiments of the present invention, the amino-terminated linear polysiloxane has a number average molecular weight of 1000 to 1500.

[0008] In some embodiments of the present invention, the bisphenol A epoxy resin is selected from at least one of E44 and E51.

[0009] In some embodiments of the present invention, the alicyclic epoxy resin is selected from at least one of 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate, cyclohexane-1,2-dicarboxylic acid diglycidyl ester, and dicyclopentadiene diepoxide.

[0010] In some embodiments of the present invention, the mass ratio of the epoxy mixture to the amino-terminated linear polysiloxane is 1:(3-5).

[0011] In some embodiments of the present invention, the mass ratio of the bisphenol A epoxy resin to the alicyclic epoxy resin is 1:(2-3).

[0012] In some embodiments of the present invention, the phenolic epoxy resin is at least one selected from Epalloy 8240 and Epalloy 8250 produced by CVC.

[0013] In some embodiments of the present invention, the high temperature resistant filler is selected from at least one of ceramics, graphite, alumina, and silica.

[0014] In some embodiments of the present invention, the high temperature resistant powder coating further comprises an additive, and the amount of the additive is 1 to 10 parts by mass relative to 100 parts by mass of the phenolic epoxy resin.

[0015] In some embodiments of the present invention, the additive is selected from at least one of a pigment, a wetting agent, a dispersant, and a curing accelerator.

[0016] To achieve the second purpose of the present invention, the present invention provides a method for preparing a high-temperature resistant powder coating as described in any of the above schemes, which comprises the following steps: Step 1: reacting the epoxy mixture with the amino-terminated linear polysiloxane to obtain an amino-terminated adduct; Step 2: uniformly mixing the amino-terminated adduct, melamine, a high-temperature resistant filler and aminosiloxane to obtain a curing agent composition; Step 3: melt-mixing the curing agent composition and a phenolic epoxy resin to obtain a powder.

[0017] In some embodiments of the present invention, in step 2, the amino-terminated adduct, aminosiloxane and a solvent are mixed to obtain a dispersion, the dispersion is stirred and mixed evenly with melamine and a high-temperature resistant filler, and then dried to obtain a curing agent composition; the solvent is a mixture of water and ethanol.

[0018] In some embodiments of the present invention, in step three, the temperature of the melt mixing is 100-130°C.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0020] The high-temperature resistant powder coating of the present invention uses a phenolic epoxy resin as a base resin and is combined with an amino-terminated adduct and melamine as curing agents. The phenolic epoxy resin contains a phenolic resin segment structure, which has good heat resistance; the melamine has a triazine ring structure, which also improves high-temperature resistance; the amino-terminated adduct is an adduct of amino-terminated linear polysiloxane with bisphenol A epoxy resin and a cycloaliphatic epoxy resin. The linear siloxane segment can withstand high temperatures and improve the flexibility of the coating, preventing the coating from cracking in high-temperature environments. The bisphenol A epoxy resin and alicyclic epoxy resin also have good heat resistance. When mixed, they can react more fully with the amino-terminated linear polysiloxane, improving the fluidity of the resulting amino-terminated adduct coating and the uniformity of the resulting coating, thereby improving the coating's high-temperature resistance. The present invention also improves the dispersion of the filler and the high-temperature resistance of the coating by adding a high-temperature resistant filler and a reactive silane coupling agent. The coating produced by the high-temperature resistant powder coating of the present invention can be used at temperatures above 300°C without damage and has good high-temperature stability. DETAILED DESCRIPTION

[0021] Embodiments of the present invention provide a high-temperature resistant powder coating that can be used at temperatures exceeding 300°C without blistering, cracking, or flaking. This powder coating is suitable for high-temperature applications such as fireplaces, heaters, barbecue grills, griddles, exhaust pipes, and chimneys.

[0022] Specifically, the high-temperature resistant powder coating includes the following raw materials in parts by mass: 100 parts of phenolic epoxy resin; 20-30 parts of terminal amino adduct; 15-25 parts of melamine; 80-90 parts of high-temperature resistant filler; 2-5 parts of aminosiloxane; wherein the terminal amino adduct is the reaction product of terminal amino linear polysiloxane and epoxy mixture, and the epoxy mixture is a mixture of bisphenol A type epoxy resin and alicyclic epoxy resin. Among them, the phenolic epoxy resin has a phenolic resin structure and an epoxy group on its molecular chain. It itself has high heat resistance and can further react and cure to form a three-dimensional cross-linked network to improve the high-temperature resistance of the coating. The terminal amino adduct is obtained by pre-polymerization of terminal amino linear polysiloxane, bisphenol A type epoxy resin and alicyclic epoxy resin. It has amino groups at both ends of its molecular chain. The amino group can participate in the curing reaction of the epoxy resin, so the terminal amino adduct can be used as a curing agent; the linear polysiloxane has S iOS i segment, has high heat resistance, good segment flexibility, can rotate flexibly at high temperature, and avoids coating cracking; the bisphenol A type epoxy resin structure and the alicyclic epoxy resin structure in the terminal amino adduct can improve the compatibility of the terminal amino adduct and the phenolic epoxy resin, and the bisphenol A type epoxy resin is mixed with the alicyclic epoxy resin, both of which have good heat resistance, and the mixture of the two can react more fully with the terminal amino linear polysiloxane, improve the fluidity of the coating of the obtained terminal amino adduct and the uniformity of the obtained coating, and improve the high temperature resistance of the coating; melamine has primary and tertiary amino groups, can participate in epoxy resin curing well, and has a triazine ring on its molecular chain, and has good high temperature resistance; high temperature resistant filler can further improve the heat resistance of the coating, and aminosilicone can improve the dispersibility of high temperature resistant filler in the resin. The present invention obtains a powder coating that can form a coating that can be used for a long time at 300°C through the mutual cooperation of multiple components.

[0023] In some examples, relative to 100 parts by mass of the epoxy novolac resin, the parts by mass of the amino-terminated adduct can be 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, etc.; the parts by mass of melamine can be 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, etc.; the parts by mass of the high-temperature resistant filler can be 80 parts, 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, etc.; the parts by mass of the aminosilicone can be 2 parts, 3 parts, 4 parts, 5 parts, etc. Without departing from the spirit and principles of the present invention, the parts by mass of each raw material can be selected within the above values or within the range therebetween.

[0024] In some examples, the high-temperature resistant powder coating is primarily composed of the following raw materials in parts by weight: 100 parts of a novolac epoxy resin; 20-30 parts of an amino-terminated adduct; 15-25 parts of melamine; 80-90 parts of a high-temperature resistant filler; and 2-5 parts of an aminosilicone. In addition to the novolac epoxy resin, the amino-terminated adduct, melamine, the high-temperature resistant filler, and the aminosilicone, the powder coating may also contain other components, with the amount of the other components not exceeding 10% of the total weight of the novolac epoxy resin, the amino-terminated adduct, melamine, the high-temperature resistant filler, and the aminosilicone.

[0025] In some examples, the high-temperature resistant powder coating is composed of the following raw materials in parts by weight: 100 parts of phenolic epoxy resin; 20-30 parts of amino-terminated adduct; 15-25 parts of melamine; 80-90 parts of high-temperature resistant filler; and 2-5 parts of aminosiloxane. Besides the phenolic epoxy resin, amino-terminated adduct, melamine, high-temperature resistant filler, and aminosiloxane, the powder coating may contain no other components. This allows for a simpler raw material composition and achieves the desired high-temperature resistance.

[0026] In some examples, the amino-terminated linear polysiloxane has a number-average molecular weight of 1,000 to 1,500, providing a longer silane chain and imparting greater heat resistance and flexibility to the coating. The amino-terminated linear polysiloxane can be an aminopropyl-dicapped polydimethylsiloxane, meaning aminopropyl groups are attached to both ends of the polydimethylsiloxane chain. The preparation process for this amino-terminated linear polysiloxane is mature and commercially available.

[0027] In some examples, the bisphenol A epoxy resin is selected from at least one of E44 and E51. The bisphenol A epoxy resin has a high epoxy value and reacts quickly and fully with the amino-terminated linear polysiloxane.

[0028] In some examples, the alicyclic epoxy resin is selected from at least one of 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate, cyclohexane-1,2-dicarboxylic acid diglycidyl ester, and dicyclopentadiene diepoxide. The alicyclic epoxy resin molecules have a six-membered ring and have high heat resistance and chemical stability.

[0029] In some examples, the mass ratio of the epoxy mixture to the amino-terminated linear polysiloxane is 1:(3-5), for example, 1:3, 1:4, 1:5, etc. When the mass ratio of the epoxy mixture to the amino-terminated linear polysiloxane is within the above range, the desired amino-terminated adduct can be obtained, and the molecular weight of the adduct is controlled, thereby improving the fluidity of the powder coating during application.

[0030] In some examples, the mass ratio of the bisphenol A epoxy resin to the alicyclic epoxy resin is 1:(2-3), for example, 1:2, 1:2.5, 1:3, etc. When the mass ratio of the bisphenol A epoxy resin to the alicyclic epoxy resin is within the above range, the resulting amino-terminated linear polysiloxane has moderate viscosity and fluidity, which facilitates dispersion of the amino-terminated linear polysiloxane and its full reaction with the novolac epoxy resin to form a uniform coating film.

[0031] In some examples, the novolac epoxy resin is selected from at least one of Epalloy 8240 and Epalloy 8250 produced by CVC. These novolac epoxy resins are solid or semi-solid at room temperature, which helps to produce a solid powder coating with high storage stability. Furthermore, these novolac epoxy resins have a high epoxy value, which can increase the crosslinking density and compactness of the coating, thereby improving the coating's high-temperature resistance.

[0032] In some examples, the high temperature resistant filler is selected from at least one of ceramics, graphite, alumina, and silica. The above fillers have good stability at high temperatures and can improve the high temperature resistance of the coating.

[0033] In some examples, the high-temperature resistant powder coating further includes an additive. The additive is present in an amount of 1 to 10 parts by mass relative to 100 parts by mass of the phenolic epoxy resin, for example, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc. The additive can be selected from at least one of a pigment, a wetting agent, a dispersant, and a curing accelerator, and is used to color the coating, improve wetting of the coating on the substrate, promote dispersion of the raw materials, and accelerate the curing reaction. In some examples, the high-temperature resistant powder coating comprises a phenolic epoxy resin, an amino-terminated adduct, melamine, a high-temperature resistant filler, an aminosilicone, and the additive.

[0034] In some examples, the method for preparing the high temperature resistant powder coating may include the following steps:

[0035] Step 1: React the epoxy mixture with an amino-terminated linear polysiloxane to obtain an amino-terminated adduct. In step 1, the epoxy mixture and amino-terminated linear polysiloxane can be uniformly mixed in a solvent such as ethyl acetate and reacted at approximately 150-200°C for 16-20 hours. After the reaction, the solvent is recovered by rotary evaporation to obtain an amino-terminated epoxy adduct. The amino-terminated epoxy adduct can contain reaction products of various epoxy mixtures with varying degrees of polymerization and amino-terminated linear polysiloxanes. Unreacted amino-terminated linear polysiloxane may remain in the amino-terminated epoxy adduct and does not need to be removed.

[0036] Step 2: Evenly mix the amino-terminated adduct, melamine, high-temperature resistant filler, and aminosilicone to obtain a curing agent composition. Step 2: First, mix the amino-terminated adduct, melamine and other curing agents, as well as aminosilicone and high-temperature resistant filler to facilitate uniform dispersion of the high-temperature resistant filler.

[0037] Step 3: Melt-mix the curing agent composition and epoxy novolac resin to form a powder. Adding the epoxy novolac resin and melt-mixing after the curing agent composition is evenly mixed prevents excessive crosslinking and curing of the epoxy resin and ensures a more complete and dispersed mixing of the raw materials. In step 3, the curing agent composition and epoxy novolac resin are partially prepolymerized to increase the viscosity of the mixture, thereby producing a powder coating that is stable in a solid state at room temperature.

[0038] As can be seen from the above, the preparation method of the high temperature resistant powder coating of the present invention is simple, and the raw material components are fully and evenly mixed, thereby improving the performance of the powder coating.

[0039] In some examples, in step 2, the amino-terminated adduct and aminosilicone are mixed with a solvent to obtain a dispersion, and the dispersion is stirred and mixed evenly with melamine and a high-temperature resistant filler, followed by drying to obtain a curing agent composition. The above steps allow the amino-terminated adduct and aminosilicone to be dispersed onto the surfaces of the solid melamine and high-temperature resistant filler, making the curing agent composition more evenly mixed and promoting the hydrolysis of the aminosilicone and its binding to the filler surface. The solvent can be a mixture of water and ethanol, which is non-toxic, environmentally friendly, and easily recyclable.

[0040] In some examples, in step three, the melt mixing temperature is 100-130°C. The above melt temperature range allows the curing agent composition and the phenolic epoxy resin to be melt mixed evenly, and the epoxy resin and the curing agent will not be over-cured and cross-linked prematurely.

[0041] In some examples, step three can be performed in an extruder, and the step of forming the powder can include granulation and pulverization.

[0042] The present invention will be further described in detail below by way of specific examples. In the following examples and comparative examples, substances with the same name are substances with the same source and physical properties. The raw materials are all commercially available or obtained according to conventional processes in the prior art.

[0043] Example 1

[0044] The raw materials of the high temperature resistant powder coating of this embodiment are as follows:

[0045] 100 parts of Epoxy Novolac 8240;

[0046] 20 parts of an amino-terminated adduct, obtained by prepolymerizing an aminopropyl-diblocked polydimethylsiloxane having a number average molecular weight of 1000 with an epoxy mixture consisting of E44 epoxy resin and 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate, wherein the mass ratio of the epoxy mixture to the aminopropyl-diblocked polydimethylsiloxane is 1:3, and the mass ratio of the E44 epoxy resin to the 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate is 1:2;

[0047] 15 parts of melamine;

[0048] 90 parts of high temperature resistant filler alumina powder;

[0049] 5 parts of aminopropyltriethoxysilane;

[0050] 3 parts pigment.

[0051] The steps of the preparation method of the high temperature resistant powder coating of this embodiment are as follows:

[0052] Step 1: Mix the epoxy mixture and aminopropyl-dicapped polydimethylsiloxane in ethyl acetate, react at 180°C for 18 hours, and remove the solvent by rotary evaporation after the reaction to obtain an amino-terminated adduct;

[0053] Step 2: uniformly mixing the amino-terminated adduct, aminopropyltriethoxysilane, and a mixture of water and ethanol (volume ratio 1:1) to obtain a dispersion, uniformly mixing the dispersion with melamine, a high-temperature resistant filler, and a pigment, and then heating and drying under vacuum to obtain a curing agent composition;

[0054] Step 3: melt and mix the curing agent composition and the phenolic epoxy resin in an extruder at 130° C., and prepare powder to obtain a powder coating.

[0055] The obtained powder coating was sprayed onto the surface of a stainless steel plate and then baked at 160°C for 1 h to obtain a coating thickness of about 0.5 mm.

[0056] Example 2

[0057] The raw materials of the high temperature resistant powder coating of this embodiment are as follows:

[0058] 100 parts of Epoxy Novolac 8250;

[0059] 30 parts of an amino-terminated adduct, obtained by prepolymerizing an aminopropyl-diblocked polydimethylsiloxane having a number average molecular weight of 1500 with an epoxy mixture consisting of E51 epoxy resin and cyclohexane-1,2-dicarboxylic acid diglycidyl ester, wherein the mass ratio of the epoxy mixture to the aminopropyl-diblocked polydimethylsiloxane is 1:5, and the mass ratio of the E51 epoxy resin to the cyclohexane-1,2-dicarboxylic acid diglycidyl ester is 1:3;

[0060] 25 parts of melamine;

[0061] 80 parts of high temperature resistant filler silica powder;

[0062] 3 parts of aminopropyltriethoxysilane;

[0063] 3 parts pigment.

[0064] The steps of the preparation method of the high temperature resistant powder coating of this embodiment are as follows:

[0065] Step 1: Mix the epoxy mixture and aminopropyl-dicapped polydimethylsiloxane in ethyl acetate, react at 180°C for 18 hours, and remove the solvent by rotary evaporation after the reaction to obtain an amino-terminated adduct;

[0066] Step 2: uniformly mixing the amino-terminated adduct, aminopropyltriethoxysilane, and a mixture of water and ethanol (volume ratio 1:1) to obtain a dispersion, uniformly mixing the dispersion with melamine, a high-temperature resistant filler, and a pigment, and then heating and drying under vacuum to obtain a curing agent composition;

[0067] Step 3: melt and mix the curing agent composition and the phenolic epoxy resin in an extruder at 130° C., and prepare powder to obtain a powder coating.

[0068] The obtained powder coating was sprayed onto the surface of a stainless steel plate and then baked at 160°C for 1 h to obtain a coating thickness of about 0.5 mm.

[0069] Example 3

[0070] The raw materials of the high temperature resistant powder coating of this embodiment are as follows:

[0071] 100 parts of Epoxy Novolac 8240;

[0072] 25 parts of an amino-terminated adduct, obtained by prepolymerizing an aminopropyl-diblocked polydimethylsiloxane having a number average molecular weight of 1300 with an epoxy mixture consisting of E44 epoxy resin and dicyclopentadiene diepoxide, wherein the mass ratio of the epoxy mixture to the aminopropyl-diblocked polydimethylsiloxane is 1:4, and the mass ratio of the E44 epoxy resin to the dicyclopentadiene diepoxide is 1:2.5;

[0073] 20 parts of melamine;

[0074] 85 parts of high temperature resistant filler ceramic powder;

[0075] 2 parts of aminopropyltriethoxysilane;

[0076] 3 parts pigment.

[0077] The steps of the preparation method of the high temperature resistant powder coating of this embodiment are as follows:

[0078] Step 1: Mix the epoxy mixture and aminopropyl-dicapped polydimethylsiloxane in ethyl acetate, react at 180°C for 18 hours, and remove the solvent by rotary evaporation after the reaction to obtain an amino-terminated adduct;

[0079] Step 2: uniformly mixing the amino-terminated adduct, aminopropyltriethoxysilane, and a mixture of water and ethanol (volume ratio 1:1) to obtain a dispersion, uniformly mixing the dispersion with melamine, a high-temperature resistant filler, and a pigment, and then heating and drying under vacuum to obtain a curing agent composition;

[0080] Step 3: melt and mix the curing agent composition and the phenolic epoxy resin in an extruder at 130° C., and prepare powder to obtain a powder coating.

[0081] The obtained powder coating was sprayed onto the surface of a stainless steel plate and then baked at 160°C for 1 h to obtain a coating thickness of about 0.5 mm.

[0082] Example 4

[0083] The raw materials of the high temperature resistant powder coating of this embodiment are as follows:

[0084] 100 parts of Epoxy Novolac 8250;

[0085] 30 parts of an amino-terminated adduct, obtained by prepolymerizing an aminopropyl-diblocked polydimethylsiloxane having a number average molecular weight of 1500 with an epoxy mixture consisting of E51 epoxy resin and cyclohexane-1,2-dicarboxylic acid diglycidyl ester, wherein the mass ratio of the epoxy mixture to the aminopropyl-diblocked polydimethylsiloxane is 1:7, and the mass ratio of the E51 epoxy resin to the cyclohexane-1,2-dicarboxylic acid diglycidyl ester is 1:3;

[0086] 25 parts of melamine;

[0087] 80 parts of high temperature resistant filler alumina powder;

[0088] 3 parts of aminopropyltriethoxysilane;

[0089] 3 parts pigment.

[0090] The steps of the preparation method of the high temperature resistant powder coating of this embodiment are as follows:

[0091] Step 1: Mix the epoxy mixture and aminopropyl-dicapped polydimethylsiloxane in ethyl acetate, react at 180°C for 18 hours, and remove the solvent by rotary evaporation after the reaction to obtain an amino-terminated adduct;

[0092] Step 2: uniformly mixing the amino-terminated adduct, aminopropyltriethoxysilane, and a mixture of water and ethanol (volume ratio 1:1) to obtain a dispersion, uniformly mixing the dispersion with melamine, a high-temperature resistant filler, and a pigment, and then heating and drying under vacuum to obtain a curing agent composition;

[0093] Step 3: melt and mix the curing agent composition and the phenolic epoxy resin in an extruder at 130° C., and prepare powder to obtain a powder coating.

[0094] The obtained powder coating was sprayed onto the surface of a stainless steel plate and then baked at 160°C for 1 h to obtain a coating thickness of about 0.5 mm.

[0095] Example 5

[0096] The raw materials of the high temperature resistant powder coating of this embodiment are as follows:

[0097] 100 parts of Epoxy Novolac 8240;

[0098] 25 parts of an amino-terminated adduct, obtained by prepolymerizing an aminopropyl-diblocked polydimethylsiloxane having a number average molecular weight of 1300 with an epoxy mixture consisting of E44 epoxy resin and dicyclopentadiene diepoxide, wherein the mass ratio of the epoxy mixture to the aminopropyl-diblocked polydimethylsiloxane is 1:4, and the mass ratio of the E44 epoxy resin to the dicyclopentadiene diepoxide is 1:6;

[0099] 20 parts of melamine;

[0100] 85 parts of high temperature resistant filler ceramic powder;

[0101] 2 parts of aminopropyltriethoxysilane;

[0102] 3 parts pigment.

[0103] The steps of the preparation method of the high temperature resistant powder coating of this embodiment are as follows:

[0104] Step 1: Mix the epoxy mixture and aminopropyl-dicapped polydimethylsiloxane in ethyl acetate, react at 180°C for 18 hours, and remove the solvent by rotary evaporation after the reaction to obtain an amino-terminated adduct;

[0105] Step 2: uniformly mixing the amino-terminated adduct, aminopropyltriethoxysilane, and a mixture of water and ethanol (volume ratio 1:1) to obtain a dispersion, uniformly mixing the dispersion with melamine, a high-temperature resistant filler, and a pigment, and then heating and drying under vacuum to obtain a curing agent composition;

[0106] Step 3: melt and mix the curing agent composition and the phenolic epoxy resin in an extruder at 130° C., and prepare powder to obtain a powder coating.

[0107] The obtained powder coating was sprayed onto the surface of a stainless steel plate and then baked at 160°C for 1 h to obtain a coating thickness of about 0.5 mm.

[0108] Comparative Example 1

[0109] The raw materials of the powder coating of this comparative example are as follows:

[0110] 100 parts of Epoxy Novolac 8240;

[0111] 40 parts of an amino-terminated adduct, obtained by prepolymerizing an aminopropyl-diblocked polydimethylsiloxane having a number average molecular weight of 1000 with an epoxy mixture consisting of E44 epoxy resin and 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate, wherein the mass ratio of the epoxy mixture to the aminopropyl-diblocked polydimethylsiloxane is 1:3, and the mass ratio of the E44 epoxy resin to the 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate is 1:2;

[0112] 5 parts of melamine;

[0113] 90 parts of high temperature resistant filler alumina powder;

[0114] 5 parts of aminopropyltriethoxysilane;

[0115] 3 parts pigment.

[0116] The preparation method of the powder coating of this comparative example comprises the following steps:

[0117] Step 1: Mix the epoxy mixture and aminopropyl-dicapped polydimethylsiloxane in ethyl acetate, react at 180°C for 18 hours, and remove the solvent by rotary evaporation after the reaction to obtain an amino-terminated adduct;

[0118] Step 2: uniformly mixing the amino-terminated adduct, aminopropyltriethoxysilane, and a mixture of water and ethanol (volume ratio 1:1) to obtain a dispersion, uniformly mixing the dispersion with melamine, a high-temperature resistant filler, and a pigment, and then heating and drying under vacuum to obtain a curing agent composition;

[0119] Step 3: melt and mix the curing agent composition and the phenolic epoxy resin in an extruder at 130° C., and prepare powder to obtain a powder coating.

[0120] The obtained powder coating was sprayed onto the surface of a stainless steel plate and then baked at 160°C for 1 h to obtain a coating thickness of about 0.5 mm.

[0121] Comparative Example 2

[0122] The raw materials of the powder coating of this comparative example are as follows:

[0123] 100 parts of Epoxy Novolac 8240;

[0124] 20 parts of an amino-terminated adduct, obtained by prepolymerizing an aminopropyl-diblocked polydimethylsiloxane having a number average molecular weight of 1000 and 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate, wherein the mass ratio of 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate to aminopropyl-diblocked polydimethylsiloxane is 1:3;

[0125] 15 parts of melamine;

[0126] 90 parts of high temperature resistant filler alumina powder;

[0127] 5 parts of aminopropyltriethoxysilane;

[0128] 3 parts pigment.

[0129] The steps of the preparation method of the high temperature resistant powder coating of this embodiment are as follows:

[0130] Step 1: 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate and aminopropyl-dicapped polydimethylsiloxane were mixed evenly in ethyl acetate, reacted at 180°C for 18 hours, and after the reaction was completed, the solvent was removed by rotary evaporation to obtain an amino-terminated adduct;

[0131] Step 2: uniformly mixing the amino-terminated adduct, aminopropyltriethoxysilane, and a mixture of water and ethanol (volume ratio 1:1) to obtain a dispersion, uniformly mixing the dispersion with melamine, a high-temperature resistant filler, and a pigment, and then heating and drying under vacuum to obtain a curing agent composition;

[0132] Step 3: melt and mix the curing agent composition and the phenolic epoxy resin in an extruder at 130° C., and prepare powder to obtain a powder coating.

[0133] The obtained powder coating was sprayed onto the surface of a stainless steel plate and then baked at 160°C for 1 h to obtain a coating thickness of about 0.5 mm.

[0134] Comparative Example 3

[0135] The raw materials of the powder coating of this comparative example are as follows:

[0136] 100 parts of Epoxy Novolac 8240;

[0137] 20 parts of an amino-terminated adduct, which is obtained by prepolymerizing an aminopropyl-dicapped polydimethylsiloxane with a number average molecular weight of 1000 and an E44 epoxy resin, wherein the mass ratio of the E44 epoxy resin to the aminopropyl-dicapped polydimethylsiloxane is 1:3;

[0138] 15 parts of melamine;

[0139] 90 parts of high temperature resistant filler alumina powder;

[0140] 5 parts of aminopropyltriethoxysilane;

[0141] 3 parts pigment.

[0142] The steps of the preparation method of the high temperature resistant powder coating of this embodiment are as follows:

[0143] Step 1: E44 epoxy resin and aminopropyl dicapped polydimethylsiloxane were mixed evenly in ethyl acetate, and reacted at 180°C for 18 hours. After the reaction, the solvent was removed by rotary evaporation to obtain an amino-terminated adduct;

[0144] Step 2: uniformly mixing the amino-terminated adduct, aminopropyltriethoxysilane, and a mixture of water and ethanol (volume ratio 1:1) to obtain a dispersion, uniformly mixing the dispersion with melamine, a high-temperature resistant filler, and a pigment, and then heating and drying under vacuum to obtain a curing agent composition;

[0145] Step 3: melt and mix the curing agent composition and the phenolic epoxy resin in an extruder at 130° C., and prepare powder to obtain a powder coating.

[0146] The obtained powder coating was sprayed onto the surface of a stainless steel plate and then baked at 160°C for 1 h to obtain a coating thickness of about 0.5 mm.

[0147] Comparative Example 4

[0148] The raw materials of the high temperature resistant powder coating of this embodiment are as follows:

[0149] 100 parts of Epoxy Novolac 8240;

[0150] 20 parts of an amino-terminated adduct, obtained by prepolymerizing p-phenylenediamine with an epoxy mixture consisting of E44 epoxy resin and 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate, wherein the mass ratio of the epoxy mixture to p-phenylenediamine is 1:1, and the mass ratio of E44 epoxy resin to 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate is 1:2;

[0151] 15 parts of melamine;

[0152] 90 parts of high temperature resistant filler alumina powder;

[0153] 5 parts of aminopropyltriethoxysilane;

[0154] 3 parts pigment.

[0155] The steps of the preparation method of the high temperature resistant powder coating of this embodiment are as follows:

[0156] Step 1: Mix the epoxy mixture and p-phenylenediamine in ethyl acetate, react at 180°C for 18 hours, and remove the solvent by rotary evaporation to obtain an amino-terminated adduct;

[0157] Step 2: uniformly mixing the amino-terminated adduct, aminopropyltriethoxysilane, and a mixture of water and ethanol (volume ratio 1:1) to obtain a dispersion, uniformly mixing the dispersion with melamine, a high-temperature resistant filler, and a pigment, and then heating and drying under vacuum to obtain a curing agent composition;

[0158] Step 3: melt and mix the curing agent composition and the phenolic epoxy resin in an extruder at 130° C., and prepare powder to obtain a powder coating.

[0159] The obtained powder coating was sprayed onto the surface of a stainless steel plate and then baked at 160°C for 1 h to obtain a coating thickness of about 0.5 mm.

[0160] Performance Testing

[0161] The amino-terminated adducts prepared in the above examples and comparative examples were subjected to viscosity testing at 25°C. The coatings prepared in the above examples and comparative examples were tested for adhesion according to GB9286-98. The coatings were subjected to thermogravimetric testing at a heating rate of 10°C / min, and the temperature corresponding to a 10% weight loss of the coating was obtained. The coatings were subjected to a long-term high-temperature resistance test according to GB / T 1735-2009, with a 60-day test period of 300°C for 10 hours each day, and changes in the coatings were observed. After the long-term high-temperature resistance test, the undamaged coatings were removed and tested for adhesion according to GB9286-98.

[0162] The test results are shown in Table 1 below.

[0163] Table 1 Test results of examples and comparative examples

[0164]

[0165]

[0166] The test results of the above examples and comparative examples demonstrate that the amino-terminated adducts of the present invention possess suitable viscosity, and the resulting high-temperature-resistant powder coating exhibits excellent adhesion to substrates and high temperature resistance, with a 10% thermal decomposition temperature exceeding 350°C and the coating capable of being used at temperatures exceeding 300°C without damage. The high-temperature-resistant powder coating of the present invention is suitable for high-temperature applications.

[0167] Finally, it should be emphasized that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A high temperature resistant powder coating, characterized in that Including the following raw materials by weight: 100 parts of phenolic epoxy resin; 20-30 parts of amino-terminated adduct; 15-25 parts of melamine; 80-90 parts of high temperature resistant filler; 2-5 parts of aminosilicone; Wherein, the amino-terminated adduct is the reaction product of amino-dicapped linear polysiloxane and an epoxy mixture, and the epoxy mixture is a mixture of bisphenol A epoxy resin and alicyclic epoxy resin; The number average molecular weight of the amino di-terminated linear polysiloxane is 1000 to 1500; The mass ratio of the epoxy mixture to the amino di-terminated linear polysiloxane is 1:(3-5); The mass ratio of the bisphenol A epoxy resin to the alicyclic epoxy resin is 1:(2-3).

2. The high temperature resistant powder coating according to claim 1, characterized in that: The bisphenol A epoxy resin is selected from at least one of E44 and E51; The alicyclic epoxy resin is selected from at least one of 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate, cyclohexane-1,2-dicarboxylic acid diglycidyl ester, and dicyclopentadiene diepoxide.

3. A high temperature resistant powder coating according to claim 1 or 2, characterized in that: The phenolic epoxy resin is selected from at least one of Epalloy 8240 and Epalloy 8250 produced by CVC.

4. A high temperature resistant powder coating according to claim 1 or 2, characterized in that: The high temperature resistant filler is selected from at least one of ceramics, graphite, alumina and silicon dioxide.

5. A high temperature resistant powder coating according to claim 1 or 2, characterized in that: The high temperature resistant powder coating further comprises an additive, wherein the mass portion of the additive is 1 to 10 parts relative to 100 parts by mass of the phenolic epoxy resin; The additive is selected from at least one of a pigment, a wetting agent, a dispersant, and a curing accelerator.

6. The method for preparing a high temperature resistant powder coating according to claim 1, characterized in that The following steps are involved: Step 1: reacting the epoxy mixture with the amino-dicapped linear polysiloxane to obtain an amino-terminated adduct; Step 2: Evenly mixing the amino-terminated adduct, melamine, high-temperature resistant filler and aminosiloxane to obtain a curing agent composition; Step 3: Melt and mix the curing agent composition and the phenolic epoxy resin uniformly and prepare into powder.

7. The method for preparing a high temperature resistant powder coating according to claim 6, characterized in that: In the step 2, the amino-terminated adduct, aminosiloxane and solvent are mixed to obtain a dispersion, the dispersion is stirred and mixed with melamine and a high-temperature resistant filler, and then dried to obtain a curing agent composition; The solvent is a mixture of water and ethanol.

8. The method for preparing a high temperature resistant powder coating according to claim 6 or 7, characterized in that: In the step 3, the temperature of the melt mixing is 100-130°C.

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