A high temperature resistant protective layer and its preparation method and application

Abstract

The present invention relates to a high-temperature resistant protective layer, its preparation method, and application. The high-temperature resistant protective layer is made of the following components by weight: 100 parts of monomer A; 7-19 parts of filler; 2-8 parts of catalyst; 5-11 parts of acid; and 48-77 parts of water. The structural formula of monomer A is: The high-temperature resistant protective layer is screen-printed onto the surface of a carbon-containing electric heating material, then baked at 50-70°C to form the layer. After cooling, a high-temperature resistant protective layer is obtained on the surface of the carbon-containing electric heating material. Compared with the prior art, the high-temperature resistant protective layer of the present invention can effectively isolate the carbon-containing electric heating material from air, preventing the carbon-containing components in the electric heating material from being oxidized by air, and allowing the protected carbon-containing electric heating material to operate stably at an operating temperature of 500°C.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, and in particular relates to a high-temperature resistant protective layer, its preparation method and application. Background Technology

[0002] With the development of electrothermal technology, carbon-containing electrothermal materials, including graphene and carbon ceramic materials, have gradually replaced traditional resistance wire heating elements and ceramic PTC heating elements in low-temperature heating fields due to their large heating area and uniform temperature. However, in high-temperature heating fields, carbon-containing electrothermal materials still need to address the issue of isolating themselves from oxygen. Unlike resistance wire heating elements and ceramic PTC heating elements, prolonged contact with air causes the carbon atoms inside the carbon-containing electrothermal materials to oxidize, reducing the power of these heating elements and ultimately causing them to lose their heating function.

[0003] In the field of low-temperature heating, encapsulating carbon-containing heating materials with films such as PET or PI is a mature technical solution. This method protects the heating material by isolating it from air; and because the heating temperature is low, the oxidation rate of carbon atoms is extremely slow, so the oxidation problem is not significant. However, when carbon-containing heating materials are heated above 150°C, films such as PET or PI soften and become unsuitable. If the heating material is directly exposed to air, the oxidation rate of its carbon components will increase geometrically with increasing temperature, and such heating materials will quickly lose their heating function; when the temperature exceeds 450°C, the carbon components in the heating material may even burn out.

[0004] Patents CN 216491110 U, CN 213342723 U, and CN 113973406 use hot melt adhesive or silicone as a protective layer to isolate the carbon-containing heating material from the air. However, none of the above-mentioned prior art mentions the maximum operating temperature of its heating element; on the other hand, the stable operating temperature of hot melt adhesive and silicone is less than 300°C. Above this temperature, these two types of adhesives will melt or even carbonize, so it can be reasonably inferred that their operating temperature cannot exceed 300°C. Patent CN114891389 A uses a commercially available coating as a protective layer, but this application also does not mention the maximum operating temperature of the heating element.

[0005] To protect carbon-containing electrothermal materials under high-temperature heating conditions, isolate them from air, and ensure stable operation, the protective layer material needs to possess the following four characteristics simultaneously: high temperature resistance, maintaining stability under high-temperature conditions; temperature change resistance, withstanding drastic temperature changes; good insulation effect, effectively isolating air in high-temperature environments; and sufficient mechanical strength, especially in long-term high-temperature environments.

[0006] However, there is currently no suitable material to serve as a protective layer for carbon-containing electric heating materials under high-temperature heating conditions exceeding 300°C. Therefore, there is an urgent need to develop a high-temperature resistant protective layer suitable for use as a carbon-containing electric heating material under high-temperature heating conditions. Summary of the Invention

[0007] The purpose of this invention is to provide a high-temperature resistant protective layer, its preparation method, and its application in order to enable carbon-containing electrothermal materials to operate under high-temperature conditions.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] The present invention provides a high-temperature resistant protective layer, which is made of the following components in parts by weight: 100 parts monomer A, 7-19 parts filler, 2-8 parts catalyst, 5-11 parts acid, and 48-77 parts water.

[0010] The monomer A is 1-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxylic acid, and its structural formula is as follows:

[0011]

[0012] The high-temperature resistant protective layer has a network polymer structure, and its structural formula is as follows:

[0013]

[0014] In the formula, R is -COOH.

[0015] The structure of monomer A and the high-temperature resistant protective layer of the polymer in this invention has the following characteristics:

[0016] (1) Each monomer A molecule has a benzyl group. The carbon atom on the benzyl group will form a carbon atom free radical under the oxidation of the catalyst. The free radical will attack the carbon atom at the β position of the carbonyl group and the carbon atom at the N atom of the phenyl group, eventually forming a spatial network structure.

[0017] (2) Monomer A contains a hydrophilic carboxyl group, so monomer A has good solubility in water, which makes it easy to adjust the viscosity of the protective layer precursor and facilitates screen printing.

[0018] (3) The polymer molecules formed contain a large number of carboxyl groups. The H and O atoms on these groups can form hydrogen bonds with the carbon-containing electrothermal materials and the substrate, increasing adhesion.

[0019] (4) The pore structure of the polymer contains non-polar phenyl groups and polar carboxyl and carbonyl groups, which allows the filler molecules to be uniformly dispersed in its pores, so no additional dispersant is needed.

[0020] (5) The polymer formed has large pores that can accommodate fillers, thus it has good high temperature resistance and is easy to apply to various scenarios.

[0021] Furthermore, the filler comprises any one or more of alumina, magnesium oxide, or mica powder. In this invention, the filler is used to improve the high-temperature resistance of the protective layer after drying.

[0022] Furthermore, the catalyst is 9-thioxanthone. Thioxanthone catalysts are common photocatalysts that can catalyze a variety of photochemical reactions. In this invention, 9-thioxanthone forms hydrogen bonds with acids and enters an excited state after being irradiated by natural light or artificial light, generating an excited-state intermediate. The excited-state catalyst has strong oxidizing properties and can abstract electrons from the benzyl carbon atom in monomer A to form a benzyl radical intermediate. The benzyl radical intermediate then attacks the carbon atom at the β-position of the carbonyl group. In a heating environment, this process is greatly accelerated, ultimately generating a polymer with a stereostructure.

[0023] Furthermore, the acid is trifluoromethanesulfonic acid. A trace amount of acid can provide an acidic environment, increasing the reaction rate.

[0024] This invention also provides a method for preparing a high-temperature resistant protective layer, comprising the following steps:

[0025] S1: Add monomer A to water and disperse it evenly;

[0026] S2: Add the filler to the solution of S1 and disperse it evenly;

[0027] S3: When there are no particulate matter, add the catalyst and acid in sequence, and stir in the dark to obtain the high-temperature resistant protective layer precursor.

[0028] S4: Heat-treat the high-temperature resistant protective layer precursor to obtain the high-temperature resistant protective layer.

[0029] Furthermore, in step S1, the dispersion is carried out by a disperser at a rotation speed of 450-700 rpm.

[0030] Furthermore, in step S2, the dispersion rotation speed is 500-900 rpm.

[0031] Furthermore, in step S3, the stirring speed is 1000-1500 rpm.

[0032] Furthermore, in step S4, the temperature of the heat treatment is 50-70°C.

[0033] The present invention also provides an application of a high-temperature resistant protective layer in protecting carbon-containing electrothermal materials. The high-temperature resistant protective layer is obtained by screen printing the high-temperature resistant protective layer precursor onto the surface of the carbon-containing electrothermal material, followed by baking at 50-70°C, and after cooling, a high-temperature resistant protective layer is obtained on the surface of the carbon-containing electrothermal material.

[0034] Furthermore, the screen used for the screen printing is a 60-mesh screen.

[0035] Furthermore, the thickness of the carbon-containing electrothermal material does not exceed 0.3 mm.

[0036] Furthermore, the baking time is 0.5-1 hour.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The present invention prints the high temperature resistant protective layer precursor on the surface of the carbon-containing electric heating material by screen printing. After drying, it can effectively isolate the carbon-containing electric heating material from the air, prevent the carbon-containing components in the electric heating material from being oxidized by the air, extend the service life of the electric heating material, and enable the carbon-containing electric heating material protected by it to operate stably at a working temperature of 500℃.

[0039] (2) The high-temperature resistant protective layer monomer A of the present invention has hydrophilic carboxyl groups, which makes it more soluble in water, making it easier to adjust the viscosity of the protective layer precursor and easier to screen print; the polymer molecule obtained by final polymerization contains a large number of carboxyl groups, and the H and O atoms on the group can form hydrogen bonds with the carbon-containing electrothermal material and the substrate, increasing the adhesion.

[0040] (3) The high-temperature resistant protective layer of the present invention has a spatial network structure with a large pore structure. The pore structure contains non-polar phenyl groups and polar carboxyl and carbonyl groups, which allows the filler to be uniformly dispersed in its pores. Therefore, no additional dispersant is needed, and it has good high-temperature resistance, making it easy to apply in various carbon-containing electric heating materials.

[0041] (4) The high-temperature protective layer precursor slurry of the present invention is easy to prepare and can be printed on the surface of carbon-containing electrothermal material by screen printing. The operation is simple and convenient for large-scale industrial preparation. Attached Figure Description

[0042] Figure 1 This is a photograph of the high-temperature resistant protective layer of Embodiment 1 of the present invention after a high-temperature test.

[0043] Figure 2 This is an infrared photograph of the high-temperature resistant protective layer of Embodiment 3 of the present invention.

[0044] Figure 3This is a photograph of the protective layer of Comparative Example 1 of the present invention after a high-temperature test. Detailed Implementation

[0045] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0046] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0047] The carbon-containing electrothermal materials of this invention include, but are not limited to, graphite, graphene, carbon fiber, carbon nanotubes, carbon black, and carbon ceramic electrothermal materials. In the following embodiments and comparative examples, WJ-1103GF graphene heating oil from Hefei Microcrystalline Materials Technology Co., Ltd., with a thickness of approximately 0.2 mm, can be specifically selected.

[0048] In the following examples and comparative examples, each part by weight of each raw material is 10 grams.

[0049] In the following examples and comparative examples, the synthesis method and NMR data of monomer A are as follows:

[0050]

[0051] Synthesis of S1: Dimethyl 2-((phenylamino)methylene)malonate (3):

[0052] Aniline (30.0 mmol) and dimethyl 2-methylenemalonate (35.0 mmol) were added to THF (200 mL) and stirred for 5 minutes under an oxygen atmosphere. Then, palladium acetate (1.5 mmol) and lithium bromide (10.0 mmol) were added to the mixture. The mixture was heated and stirred at 80 °C for 5 hours under an oxygen atmosphere. After cooling, the mixture was extracted three times with water and ethyl acetate. The combined organic phases were evaporated to dryness to give crude product 3.

[0053] Synthesis of S2: Dimethyl 2-((benzyl(phenyl)amino)methylene)malonate (4):

[0054] Crude product 3 (10.0 mmol), benzyl bromide (10.0 mmol), K₂CO₃ (12.0 mmol), and acetonitrile (50.0 mL) were mixed. The mixture was stirred at 65 °C for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and rotary evaporated under reduced pressure to obtain crude product 4.

[0055] Synthesis of S3: 2-((phenyl(phenyl)amino)methylene)malonic acid (5):

[0056] The crude product 4 (8.0 mmol), NaOH (0.5 mmol), water (6 mL), and tetrahydrofuran (18 mL) were mixed. The mixture was heated under reflux at 70 °C for 10 hours. After the reaction was complete, the mixture was cooled to room temperature and extracted three times with water and ethyl acetate. The organic phases were combined. The combined organic phases were evaporated to dryness to give crude product 5.

[0057] Synthesis of S4: 3-(benzyl(phenyl)amino)-2-(chlorocarbonyl)acrylic acid (6):

[0058] Crude product 5 (7.5 mmol) was mixed with tetrahydrofuran (15 mL), and the mixture was stirred in an ice bath for 10 minutes. Oxaloyl chloride (1.9 mmol) was slowly added to the mixture, and stirring was continued in an ice bath for 2 hours. After the reaction was complete, the mixture was rotary evaporated under reduced pressure to give crude product 6.

[0059] S5: Synthesis of 1-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (A):

[0060] Crude product 6 (5.0 mmol), acetonitrile (15 mL), and tetrahydrofuran (15 mL) were mixed and stirred at 0 °C for 5 minutes. Ferric chloride (0.05 mmol) was added to the mixture, and the mixture was stirred at room temperature for 24 hours. After the reaction was complete, the mixture was rotary evaporated under reduced pressure, and then the crude product (PE / EtOAc = 2:1) was purified by silica gel column chromatography to obtain monomer A.

[0061] 1 H NMR (400MHz, DMSO-d6): δ15.12(s,1H),9.28(s,1H),8.39(d,J=8.0Hz,1H),7.97-7.86(m,2H),7.65(t,J=7.9Hz,1H),7.40-7.22(m,5H),5.87(s,2H); 13 CNMR (100MHz, DMSO-d6): δ177.9,166.1,150.3,139.5,134.1,129.0,128.8,128.1,126.7,126.0,118.6,110.3,56.4.

[0062] In the following examples, the chemical reaction equations for monomer A after heat treatment are as follows:

[0063]

[0064] The final network polymer molecular structure obtained on the surface of the carbon-containing electrothermal material is as follows:

[0065]

[0066] In the formula, R is -COOH.

[0067] Example 1:

[0068] This embodiment provides a high-temperature resistant protective layer and its specific application in carbon-containing electrothermal materials. The high-temperature resistant protective layer of this embodiment comprises the following raw materials by weight ratio: 100 parts of monomer A, 12 parts of alumina, 5.1 parts of 9-thioxanone, 7.2 parts of trifluoromethanesulfonic acid, and 61 parts of water.

[0069] In a room temperature environment, monomer A was added to water and stirred for 20 minutes at a disperser speed of 500 rpm. Alumina was added to the solution in batches and dispersed at a disperser speed of 750 rpm. After all the alumina was added, the disperser speed was increased to 1250 rpm and stirred for 1 hour until the slurry surface was uniform and free of particulate matter. The catalyst and acid were added and stirred for 5 minutes in the dark. The resulting viscous slurry was the precursor of the protective layer material in Example 1.

[0070] The application steps are as follows: Before printing, the protective layer material precursor needs to be stirred evenly in the dark. Then, it is printed onto the surface of the carbon-containing electric heating material by screen printing (the printing equipment is a TX-5080SF-P screen printing machine from Hangzhou Taoxing Printing Equipment Co., Ltd.), using a 60-mesh screen. After printing, it is baked in a forced-air oven at 55℃ for 0.8 hours, then removed and cooled to room temperature to obtain a carbon-containing electric heating material with a high-temperature resistant protective layer.

[0071] Example 2:

[0072] This embodiment provides a high-temperature resistant protective layer and its specific application in carbon-containing electrothermal materials. The high-temperature resistant protective layer of this embodiment comprises the following raw materials by weight ratio: 100 parts of monomer A, 9 parts of alumina, 6.3 parts of 9-thioxanone, 8.7 parts of trifluoromethanesulfonic acid, and 58 parts of water.

[0073] In a room temperature environment, monomer A was added to water and stirred for 20 minutes at a disperser speed of 680 rpm. Alumina was added to the solution in batches and dispersed at a disperser speed of 660 rpm. After all the alumina was added, the disperser speed was increased to 1190 rpm and stirred for 1 hour until the slurry surface was uniform and free of particulate matter. The catalyst and acid were added and stirred for 5 minutes in the dark. The resulting viscous slurry was the precursor of the protective layer material in Example 2.

[0074] The application steps are as follows: Before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed onto the surface of the carbon-containing electric heating material by screen printing with a 60-mesh screen. After printing, it is baked in a forced-air oven at 55°C for 0.7 hours, then removed and cooled to room temperature to obtain a carbon-containing electric heating material with a high-temperature resistant protective layer.

[0075] Example 3:

[0076] This embodiment provides a high-temperature resistant protective layer and its specific application in carbon-containing electrothermal materials. The high-temperature resistant protective layer of this embodiment comprises the following raw materials by weight ratio: 100 parts of monomer A, 19 parts of mica powder, 3.5 parts of 9-thioxanone, 6.7 parts of trifluoromethanesulfonic acid, and 70 parts of water.

[0077] In a room temperature environment, monomer A was added to water and stirred for 20 minutes at a disperser speed of 500 rpm. Alumina was added to the solution in batches and dispersed at a disperser speed of 760 rpm. After all the alumina was added, the disperser speed was increased to 1250 rpm and stirred for 1 hour until the slurry surface was uniform and free of particulate matter. The catalyst and acid were added and stirred for 5 minutes in the dark. The resulting viscous slurry was the precursor of the protective layer material in Example 3.

[0078] The application steps are as follows: Before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed onto the surface of the carbon-containing electric heating material by screen printing with a 60-mesh screen. After printing, it is baked in a forced-air oven at 55°C for 0.9 hours, then removed and cooled to room temperature to obtain a carbon-containing electric heating material with a high-temperature resistant protective layer.

[0079] Example 4:

[0080] This embodiment provides a high-temperature resistant protective layer and its specific application in carbon-containing electrothermal materials. The high-temperature resistant protective layer of this embodiment comprises the following raw materials by weight ratio: 100 parts of monomer A, 11 parts of mica powder, 7.5 parts of 9-thioxanone, 6 parts of trifluoromethanesulfonic acid, and 59 parts of water.

[0081] In a room temperature environment, monomer A was added to water and stirred for 20 minutes at a disperser speed of 640 rpm. Alumina was added to the solution in batches and dispersed at a disperser speed of 880 rpm. After all the alumina was added, the disperser speed was increased to 1370 rpm and stirred for 1 hour until the slurry surface was uniform and free of particulate matter. The catalyst and acid were added and stirred for 5 minutes in the dark. The resulting viscous slurry was the precursor of the protective layer material in Example 4.

[0082] The application steps are as follows: Before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed onto the surface of the carbon-containing electric heating material by screen printing with a 60-mesh screen. After printing, it is baked in a forced-air oven at 55°C for 0.5 hours, then removed and cooled to room temperature to obtain a carbon-containing electric heating material with a high-temperature resistant protective layer.

[0083] Example 5:

[0084] This embodiment provides a high-temperature resistant protective layer and its specific application in carbon-containing electrothermal materials. The high-temperature resistant protective layer of this embodiment comprises the following raw materials by weight ratio: 100 parts of monomer A, 17 parts of magnesium oxide, 6.8 parts of 9-thioxanone, 8.4 parts of trifluoromethanesulfonic acid, and 57 parts of water.

[0085] In a room temperature environment, monomer A was added to water and stirred for 20 minutes at a disperser speed of 490 rpm. Alumina was added to the solution in batches and dispersed at a disperser speed of 660 rpm. After all the alumina was added, the disperser speed was increased to 1400 rpm and stirred for 1 hour until the slurry surface was uniform and free of particulate matter. The catalyst and acid were added and stirred for 5 minutes in the dark. The resulting viscous slurry was the precursor of the protective layer material in Example 5.

[0086] The application steps are as follows: Before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed onto the surface of the carbon-containing electric heating material by screen printing with a 60-mesh screen. After printing, it is baked in a forced-air oven at 55°C for 0.8 hours, then removed and cooled to room temperature to obtain a carbon-containing electric heating material with a high-temperature resistant protective layer.

[0087] Comparative Example 1:

[0088] The raw material formula and preparation steps of the protective layer in this comparative example are the same as those in Example 1, except that acid is not added.

[0089] The application steps are as follows: Before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed on the surface of the carbon-containing electrothermal material by screen printing. After printing, it is baked in a forced-air oven at 55°C for 0.8 hours, then taken out and cooled to room temperature to obtain Comparative Example 1.

[0090] Comparative Example 2:

[0091] The raw material formula and preparation steps of the protective layer in this comparative example are the same as those in Example 2, except that the amount of alumina used is 30 parts.

[0092] The application steps are as follows: Before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed on the surface of the carbon-containing electrothermal material by screen printing. After printing, it is baked in a forced-air oven at 55°C for 0.7 hours, then taken out and cooled to room temperature to obtain Comparative Example 2.

[0093] The amounts of ingredients used in the above embodiments and comparative examples are shown in Table 1. Each portion of each ingredient weighs 10 grams.

[0094] Table 1 Summary of feed amounts for each embodiment and comparative example

[0095]

[0096] The present invention conducted appearance and high temperature resistance tests on the above embodiments and comparative examples. The test contents and methods are shown in Table 2, and the test results are shown in Table 3.

[0097] Table 2 Test Content and Test Methods

[0098] project Performance indicators Test methods Appearance The surface color is uniform and there is no peeling. Visual inspection High temperature resistance No cracking at 500℃ Keep at 500℃ for 24 hours

[0099] Table 3 Summary of test results for each embodiment and comparative example

[0100]

[0101] The results above show that Examples 1-5 can meet the requirements for appearance and resistance to high temperatures of 500°C. Figure 1 The image shows the actual product of the high-temperature resistant protective layer of Example 1 after being kept at 500°C for 24 hours. It can be seen that the surface of the protective layer is uniform and free of fine lines and cracks. Figure 2 The image shows the high-temperature resistant protective layer of Example 3 under infrared light. It can be seen that Example 3 can remain stable at 500℃ and has uniform heat transfer without obvious low-temperature zones.

[0102] In Comparative Example 1, due to the lack of acid, the reaction was incomplete, failing to form polymer molecules with sufficiently large molecular weights. The filler could not be uniformly dispersed within the pores of the polymer molecules. The protective layer precursor exhibited high fluidity, resulting in uneven filler distribution on the surface. After a period of time in a high-temperature environment, the protective layer cracked (e.g., ...). Figure 3 (As shown).

[0103] In contrast, Comparative Example 2 contained excessive filler, exceeding the pore capacity, causing the excess filler to agglomerate on the surface of the cured protective layer. Furthermore, in a high-temperature environment, the agglomerated portion had a different coefficient of thermal expansion than other parts, ultimately leading to rapid cracking of the protective layer.

[0104] In summary, this invention develops a high-temperature resistant protective layer material to protect carbon-containing electric heating materials in high-temperature environments, isolate them from air, and prevent the carbon-containing components in the heating materials from being oxidized by air. This high-temperature resistant protective layer enables the protected carbon-containing electric heating materials to operate stably at a working temperature of 500°C. By screen printing this protective layer precursor onto the surface of the carbon-containing electric heating material and then drying it, the material effectively isolates the carbon-containing electric heating material from air, preventing the carbon-containing components in the heating material from being oxidized by air and extending the service life of the heating material. Furthermore, this protective layer material exhibits excellent resistance to high temperatures and drastic temperature changes, making it highly suitable as a high-temperature resistant protective layer for a class of carbon-containing electric heating materials.

[0105] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A high-temperature resistant protective layer, characterized in that, The high-temperature resistant protective layer is made of the following components in parts by weight: 100 parts monomer A, 7-19 parts filler, 2-8 parts catalyst, 5-11 parts acid, and 48-77 parts water. The structural formula of monomer A is: ； The catalyst is 9-thioxanone; The acid is trifluoromethanesulfonic acid; The method for preparing the high-temperature resistant protective layer includes the following steps: S1: Add monomer A to water and disperse it evenly; S2: Add the filler to the solution of S1 and disperse it evenly; S3: When there are no particulate matter, add the catalyst and acid in sequence, and stir in the dark to obtain the high-temperature resistant protective layer precursor. S4: Heat-treat the high-temperature resistant protective layer precursor to obtain the high-temperature resistant protective layer; the heat treatment temperature is 50-70℃ and the heat treatment time is 0.5-1 h.

2. The high-temperature resistant protective layer according to claim 1, characterized in that, The high-temperature resistant protective layer has a network polymer structure, and its structural formula is as follows: ； In the formula, R is -COOH.

3. The high-temperature resistant protective layer according to claim 1, characterized in that, The filler includes any one or more of alumina, magnesium oxide, or mica powder.

4. The high-temperature resistant protective layer according to claim 1, characterized in that, In step S1, the dispersion is carried out by a disperser at a speed of 450-700 rpm. In step S2, the dispersion rotation speed is 500-900 rpm; In step S3, the stirring speed is 1000-1500 rpm.

5. The application of the high-temperature resistant protective layer according to any one of claims 1-4 in protecting carbon-containing electrothermal materials, characterized in that, The high-temperature resistant protective layer is formed by screen printing the high-temperature resistant protective layer precursor onto the surface of the carbon-containing electrothermal material, followed by baking at 50-70℃, and then cooling to obtain the high-temperature resistant protective layer on the surface of the carbon-containing electrothermal material.

6. The application of the high-temperature resistant protective layer according to claim 5 in protecting carbon-containing electrothermal materials, characterized in that, The screen used for the screen printing is 60 mesh, and the thickness of the carbon-containing heating material does not exceed 0.3 mm.

7. The application of the high-temperature resistant protective layer according to claim 6 in protecting carbon-containing electrothermal materials, characterized in that, The baking time is 0.5-1 hour.

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