A kind of purple sand non-stick ceramic coating and preparation method thereof

Abstract

The invention discloses a purple sand non-stick ceramic coating and a preparation method thereof; the coating is a single-coat four-component coating composition; based on 100%, the percentage content of each component is as follows: component A is filler slurry: 50-52%, component B contains silane and hydroxy silicone oil: 20-22%, component C is 20-25% formic acid: 0.6-0.8%, and component D is purple sand slurry: the balance. The present invention prepares a single-coat purple sand ceramic coating through the sol-gel reaction of the ceramic coating and the addition of purple sand through low-temperature curing molding technology, so that the coating has both the texture and advantages of purple sand and the non-stickiness of the ceramic coating, and perfectly combines the advantages of purple sand in releasing trace elements required by the human body and the advantages of the non-stickiness of the ceramic coating.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic coatings, and in particular relates to a purple sand non-stick ceramic coating and a preparation method thereof. Background Art

[0002] Zisha is a clay siltstone with multiple minerals, acid and alkali resistance and iron. It contains hydromica, kaolin, quartz, mica chips, iron and other ingredients. It does not contain any harmful metal substances and is rich in iron, silicon, manganese, calcium, magnesium, sodium, potassium and other trace elements required by the human body. Zisha has been used for cooking and drinking utensils for more than 1,000 years. Zisha utensils are heated evenly during the cooking process of food, which can decompose the fat in food, so the soup is not so greasy and can lower cholesterol. Zisha pots do not contain any chemical coatings and are rich in multiple mineral trace elements. Whether it is soup or cooking, it is very fragrant. It can not only preserve the nutrients of food, but also avoid the intake of harmful metal elements, and is deeply loved by consumers. However, purple clay pots also have some shortcomings, such as: (1) purple clay pots are usually made by high-temperature sintering (800-1200℃), which has high energy consumption and low yield; (2) purple clay pots have a porous structure and may have odor transfer after long-term use; (3) since there is no coating on the surface, it is not non-stick. Purple clay pots are only suitable for slow cooking of food by stewing, simmering, boiling, braising, etc., and are not suitable for stir-frying and frying. In addition, the blackened surface and residual stains are difficult to clean, which limits the scope of use.

[0003] Ceramic coatings have the advantages of being healthy, safe, and environmentally friendly. As a non-stick coating, they are increasingly being used on the inner surface of non-stick pans. Ceramic coatings are formed by low-temperature curing, with low energy consumption and high yield rate. With the continuous innovation of ceramic coating non-stick durability technology, the non-stick properties of ceramic coatings have also been significantly improved.

[0004] As people's pursuit of quality of life continues to improve, the research and development of cooking utensils that are easy to use and more beneficial to health is a development trend. How to combine the advantages of purple clay pots in releasing trace elements needed by the human body and the advantages of non-stick ceramic coatings to prepare a non-stick purple clay ceramic coating is the direction scientists are working towards. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a purple sand non-stick ceramic coating and a preparation method thereof. Specifically, the advantages of purple sand pots in releasing trace elements required by the human body and the advantages of ceramic coatings in non-stick properties are combined to prepare a purple sand ceramic coating for the surface of a non-stick pan, which has the appearance of purple sand and good non-stick properties.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] In the first aspect, the present invention relates to a purple sand ceramic coating, which is a single-coat four-component coating composition; based on 100%, the percentage content of each component is as follows:

[0008]

[0009] As an embodiment, in terms of mass percentage of the total weight of component A, component A comprises:

[0010]

[0011] As an embodiment, the silica sol is a mixture of acidic silica sol with a particle size of 20-25 nm and a particle size of 7-10 nm.

[0012] As an embodiment, the mass ratio of the acidic silica sol with a particle size of 20-25nm and the particle size of 7-10nm is 3:2-1:1. In the system of the present invention, the above two silica sols with different particle sizes are mixed and used to form a denser coating structure. Since purple clay has a microporous structure with a porosity of about 4-12%, it is easy to cause the residue of food odor. When cooking food for a long time, the problem of cross-flavor will occur. The formation of a denser coating structure and the control of the coating porosity at 2-4% can reduce the problem of food cross-flavor, and does not affect the release of trace elements in purple clay, and improves the wear resistance and non-stick durability of the coating.

[0013] As an embodiment, the acidic silica sol with a particle size of 20-25 nm is selected from Bindzil2034DI of Akzo Nobel, ST-O-40 of Nissan Chemical, At least one of CL-P.

[0014] As an embodiment, the acidic silica sol with a particle size of 7-10 nm is selected from ST-OS of Nissan Chemical and the like.

[0015] As an embodiment, the pH value of component A is 9.5-10.5.

[0016] As an embodiment, the filler is selected from at least one of mica powder, silica powder, silicon whisker, kaolin, alumina powder, and fumed silica.

[0017] As an embodiment, the B component comprises, in terms of mass percentage of the total weight of the B component:

[0018]

[0019] As an embodiment, the molecular formula of the silane is (CH3) n Si(OCH3) 4-n(n=1-2). The silane of the above molecular formula selected by the present invention has the shortest molecular chain group (methyl / methoxy). When mixed in a certain proportion, the ceramic coating structure formed is dense, and has excellent wear resistance and non-stick properties. If the silane selected has different molecular chain groups, the density of the ceramic coating structure formed will also be different due to the large difference in hydrolysis and polymerization speed, so the wear resistance and non-stick properties of the final coating will also have a large difference.

[0020] As an implementation example, the silane is preferably a mixture of methyltrimethoxysilane and dimethyldimethoxysilane.

[0021] Furthermore, the mass ratio of methyltrimethoxysilane to dimethyldimethoxysilane is 3:1-4:1. When mixed according to this ratio, the ceramic coating formed has a dense structure, excellent wear resistance and wear resistance and non-stick properties.

[0022] As an embodiment, the hydroxy silicone oil has the structural formula HO[(CH3)2SiO] n H, n=7-9.

[0023] As an embodiment, the solvent is selected from methanol or isopropanol.

[0024] The 20-25% formic acid in the above-mentioned component C acts as a catalyst. The prior art also adds methyl formate, ethyl acetoacetate, and maleic anhydride as catalysts in ceramic coatings. However, the present invention has confirmed through experiments that they are not suitable for the system of the present invention. As for other acids, such as acetic acid, hydrochloric acid, citric acid, etc.; however, the acidity difference is large. When the addition ratio is 0.3-1 parts, the pH value of the final coating will be large. The pH value is a key technical parameter that needs to be controlled in ceramic coatings. Ceramic coatings can only be used normally within the widest range of 3.8-5.5. If it exceeds this range, the ceramic coating will cause gelation and cannot be used. Therefore, only 20-25% formic acid is suitable for the system of the present invention.

[0025] As an embodiment, the D component comprises, in terms of mass percentage of the total weight of the D component:

[0026] Zisha powder: 60-65%

[0027] Dispersant: 6-6.5%

[0028] Deionized water: balance.

[0029] As an embodiment, the dispersant is selected from at least one of BYK180, BYK190 and Dow Corning DC-57.

[0030] The present invention also relates to a method for preparing purple sand ceramic coating, which comprises the following steps:

[0031] S1. Preparation of component A: Silica sols of different particle sizes are mixed, 1%-1.5% NaOH solution is added to a pH value of 9.5-10.5, fillers and deionized water are added and mixed; the obtained slurry is ground under ultrasonic conditions to a fineness of ≤10 μm to obtain component A;

[0032] S2. Preparation of component B: Mix silane, hydroxy silicone oil, leveling agent and solvent to obtain component B;

[0033] S3. Preparation of component D: Mix purple sand powder, deionized water and dispersant, and grind them under ultrasonic conditions to a fineness of ≤10 μm to obtain component D.

[0034] As an embodiment, the ultrasonic conditions in steps S1 and S3 are: 40 Hz frequency and 500-800 W power.

[0035] As an embodiment, the grinding in steps S1 and S3 is performed in a basket grinder at a grinding speed of 1200-1800 rpm.

[0036] The present invention also relates to a method for preparing a single coating of purple sand ceramic paint, the method comprising the following steps:

[0037] A1. Substrate pretreatment: sandblast or shot blast the surface of the substrate to make the surface roughness reach 2.5-5μm (then use an air gun to blow off the dust on the surface of the substrate), and put it in a 60-80℃ preheated oven for use;

[0038] A2. Spraying: Filter the cured paint with a 300-mesh filter cloth into the spray gun and spray when the substrate temperature is 45-55°C;

[0039] A3. Curing: Put the sprayed substrate into the oven for low temperature curing at 80-100℃×(5-10)min, then high temperature curing at (180-230)℃×(15-20)min, and then cool naturally.

[0040] Among them, step A1 can remove stains and oil stains on the surface of the substrate, so that the coating and the substrate have good adhesion; if the pretreatment is not good, the adhesion between the coating and the substrate will be poor.

[0041] Ripening process:

[0042] Add component C to component B, mix well, then add component A, mix well (put on a roller rack and react at 120-180 rpm for 4-5 hours), then add component D, continue to mature (0.5-1 hour), remove and set aside. The pH value is between 4.0-5.5. In the above-mentioned maturation, components A and B cannot be mixed first and then added to C, because the silane of component B needs to be hydrolyzed under acidic conditions to obtain colorless and transparent silanol, and then react with component A to obtain a uniform coating; if A and B are mixed directly, because component A is alkaline, the alkaline hydrolysis of siloxane after mixing will produce a white precipitate, and a uniform coating cannot be obtained. Component D is purple sand mortar, which provides color for the coating, does not participate in the sol-gel reaction, and only needs to be mixed evenly at the end.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) Through the sol-gel reaction of ceramic coating and the addition of purple sand, a single-coat purple sand ceramic coating is prepared by low-temperature curing molding technology, so that the coating has both the texture and advantages of purple sand and the non-stickiness of ceramic coating, perfectly combining the advantages of purple sand in releasing trace elements needed by the human body and the advantages of ceramic coating in non-stickiness;

[0045] (2) By using two silica sols with different particle sizes, a coating with a dense structure is obtained, and the porosity is controlled at 2-4%, which not only avoids the problem of food odor caused by the pore structure of purple sand, but also does not affect the release of trace elements in purple sand;

[0046] (3) During the slurry grinding process, the superposition of ultrasonic technology and the denser structure of the coating make the coating have excellent wear resistance and non-stick durability, thus preparing a purple clay ceramic coating with excellent non-stick durability, which expands the application range of purple clay cookware. DETAILED DESCRIPTION

[0047] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0048] Unless otherwise specified, all experimental materials and biological supplies described in the present invention are conventional commercial products, and the biological methods used are commonly used by those skilled in the art.

[0049] The purple sand ceramic coating of the present invention is a single coating, and the percentages of the components are as follows based on 100%:

[0050]

[0051] Ceramic coatings are prepared by sol-gel reaction. Since the reaction is in a continuous and unstable state, ceramic coatings can only be used for 2-3 days after aging. Once 3 days have passed, the unused coatings will become gelled due to excessive reaction and cannot be used, resulting in waste. The present invention stores ceramic coatings in groups and separately, which can be stored for about 1 year, which is conducive to mass production. It can be used after aging as needed to avoid waste.

[0052] Conventional commercially available ceramic coatings are composed of 2-3 components. When adjusting the color, each pigment needs to be ground into a color paste, and then the color is mixed, which is time-consuming and labor-intensive, and also easily causes waste. The purple sand ceramic coating of the present invention is provided with four components, that is, the D component (purple sand pigment paste component) is provided separately, which can facilitate the adjustment of the color and the addition of other functional additives to the coating. For example, the D component can be mixed with pigment pastes of other colors in different proportions to adjust the color of the purple sand; or an antibacterial agent can be added to the purple sand paste to prepare a purple sand coating with antibacterial function, etc.

[0053] The coating is a single coating, which is conducive to the slow release of trace elements in purple sand during the cooking process. If the topcoat is added, the trace elements in purple sand cannot be released due to the obstruction of the topcoat layer, and the advantages of purple sand cannot be brought into play.

[0054] The formula requires component A: component B>2:1, the coating has a matte appearance, has the texture of purple sand and has excellent wear resistance and non-stick properties. If A:B≤2, the coating gloss is too high, which is very different from the matte appearance of purple sand, and the coating has slightly poor wear resistance and non-stick properties.

[0055] in:

[0056] Component A is 100%, and the formula is as follows:

[0057]

[0058] Silica sol: The main film-forming substance of ceramic coatings, which is a mixture of two acidic silica sols with different particle sizes, particle size 20-25nm: particle size 7-10nm = 3:2-1:1. Acidic silica sol has a wide range of applications and low production costs. It is a commercially available product. Silica sols with particle sizes of 20-25nm include: Bindzil 2034DI from Akzo Nobel, ST-O-40 from Nissan Chemical, and Grace CL-P, etc., silica sol with particle size of 7-10nm, such as Nissan Chemical's ST-OS, etc.

[0059] By mixing two silica sols with different particle sizes, a denser coating structure can be formed. Since purple clay has a microporous structure with a porosity of about 4-12%, it is easy to cause food odor to remain, and the problem of odor contamination will occur when cooking food for a long time. Forming a denser coating structure and controlling the porosity at 2-4% can reduce the problem of food odor contamination, and does not affect the release of trace elements in purple clay, and improves the wear resistance and non-stick durability of the coating.

[0060] 1% NaOH solution: pH value regulator for filler slurry, adjust the pH value of the filler slurry to 9.5-10.5. After the filler slurry is ground by silica sol, the pH value will decrease during storage. When the pH value drops below 8.5 and approaches neutral, the silica sol will gel and cause the filler slurry to deteriorate. Therefore, it is necessary to adjust the pH value of the filler slurry with an alkaline solution before grinding to ensure that the filler slurry will not deteriorate after grinding and during storage.

[0061] Filler: It plays a role in reducing the cost of coatings and increasing the solid content of coatings. Common fillers are selected, such as mica powder, silica powder, whisker silicon, kaolin, alumina powder, fumed silica, etc.

[0062] Component B is 100%, and the formula is as follows:

[0063]

[0064] Silane: The film-forming substance of ceramic coating, methyltrimethoxysilane: dimethyldimethoxysilane = 3:1-4:1.

[0065] Hydroxyl silicone oil: non-stick additive, providing non-stick properties for coatings. Because it contains hydroxyl groups, it can form chemical bonds with -OH on the molecular chain of ceramic coatings, and during use, the non-stick properties are long-lasting. The structural formula of hydroxyl silicone oil is HO[(CH3)2SiO] n H, n = 7-9, when n < 7, the molecular weight of the silicone oil is too small, and the non-stick durability of the coating is poor; when n > 9, the molecular weight is too large, and floating oil will appear on the coating surface.

[0066] Leveling agent: It is a commonly used coating additive, which can help the coating form a flat, smooth and uniform coating film during the drying process. Commercially available products include BYK333.

[0067] Solvent: It can increase the compatibility of silicone oil with water-based coating system. One of methanol and isopropanol can be selected.

[0068] Component C is 25% formic acid, a catalyst for the sol-gel reaction of ceramic coatings. Silane is hydrolyzed under acidic conditions and then undergoes a polycondensation reaction with silica sol to form ceramic coatings. 25% formic acid is used to reduce addition errors. If pure formic acid is used, a small amount of addition error can cause a large pH change, resulting in a large difference in the use time and final performance of the ceramic coating.

[0069] Component D is purple sand mortar

[0070] Zisha powder: 60-65%

[0071] Dispersant: 6-6.5%

[0072] Deionized water: balance.

[0073] Zisha powder: It is equivalent to the pigment component of Zisha ceramic coating, contains a variety of trace elements that are beneficial to the human body. It can provide the coating with the color texture of Zisha, and can also release trace elements that are beneficial to the human body during the cooking process. Commercially available products.

[0074] Dispersant: used to improve the wetting of pigments, reduce grinding time and stabilize pigment dispersion. Commonly used commercially available products include BYK180, BYK190, Dow Corning DC-57, etc.

[0075] The preparation steps of purple sand ceramic coating are as follows:

[0076] (1) Preparation of filler slurry of component A: First, silica sols of different particle sizes are mixed evenly, and then 1% NaOH solution is added. After mixing evenly, the pH value is tested to be between 9.5 and 10.5. Then, fillers and deionized water are added and mixed evenly. The slurry is poured into a grinding cylinder, and the grinding cylinder is placed in an ultrasonic cleaning machine. At a frequency of 40 Hz and a power of 500 W, the slurry is ground at 1200-1800 rpm using a basket grinder, that is, the slurry is ground under the dual effects of ultrasound and basket grinder. After 1-1.5 hours, the fineness is tested to be ≤10 μm and the material is discharged. The pH value of the filler slurry is tested. If it is less than 9.0, it is adjusted to above 9.0 with 1% NaOH solution and set aside.

[0077] (2) Preparation of component B: Silane, hydroxy silicone oil, leveling agent and solvent are mixed evenly to obtain component B for standby use.

[0078] (3) Preparation of purple sand mortar of component D: purple sand powder, deionized water and dispersant were mixed evenly, and the slurry was poured into a grinding cylinder, which was placed in an ultrasonic cleaning machine. The slurry was ground at 1200-1800 rpm using a basket grinder at a frequency of 40 Hz and a power of 500 W. That is, the slurry was ground under the dual effects of ultrasound and basket grinder. After 1-1.5 hours, when the fineness was tested to be ≤10 μm, the slurry was discharged and set aside.

[0079] Test data show that the filler slurry and purple sand slurry are dispersed and ground under the dual effects of ultrasound and basket grinder, and the final coating has excellent wear-resistant, non-stick and long-lasting properties.

[0080] The compositions involved in the following examples and comparative examples are as follows:

[0081] Table 1

[0082]

[0083]

[0084] Table 2

[0085]

[0086] C1 is 25% formic acid; D1 is 60% purple sand powder + 6% BYK180 + the balance is deionized water; D2 is 65% purple sand powder + 6% BYK180 + the balance is deionized water.

[0087] Example 1

[0088] This embodiment provides a purple sand non-stick ceramic coating; the composition and dosage thereof are shown in Table 3.

[0089] The preparation steps of the purple sand non-stick ceramic coating of this embodiment are as follows:

[0090] (1) Preparation of filler slurry of component A: First, silica sols of different particle sizes are mixed evenly, and then 1% NaOH solution is added. After mixing evenly, the pH value is tested to be between 9.5 and 10.5. Then, fillers and deionized water are added and mixed evenly. The slurry is poured into a grinding cylinder, and the grinding cylinder is placed in an ultrasonic cleaning machine. At a frequency of 40 Hz and a power of 500 W, the slurry is ground at 1200-1800 rpm using a basket grinder, that is, the slurry is ground under the dual effects of ultrasound and basket grinder. After 1-1.5 hours, the fineness is tested to be ≤15 μm and the material is discharged. The pH value of the filler slurry is tested. If it is less than 9.0, it is adjusted to above 9.0 with 1% NaOH solution and set aside.

[0091] (2) Preparation of component B: Silane, hydroxy silicone oil, leveling agent and solvent are mixed evenly to obtain component B for standby use.

[0092] (3) Preparation of component D purple sand mortar: purple sand powder, deionized water and dispersant were mixed evenly, and the slurry was poured into a grinding cylinder. The grinding cylinder was placed in an ultrasonic cleaning machine, and ground with a basket grinder at 1200-1800 rpm at a frequency of 40 Hz and a power of 500 W. That is, the slurry was ground under the dual action of ultrasound and basket grinder. After 1-1.5 hours, when the fineness was tested to be ≤25 μm, the material was discharged and set aside.

[0093] The steps for preparing a single coating of the purple sand non-stick ceramic coating of this embodiment are as follows:

[0094] (1) Substrate pretreatment: sandblast or shot blast the substrate surface to make the substrate surface roughness reach 3 μm, then blow off the dust on the substrate surface with an air gun and place it in a 60°C preheated oven for standby use;

[0095] (2) Spraying: The cured coating (component C is added to component B, mixed evenly, then component A is added, mixed evenly, placed on a roller stand for reaction at 150 rpm for 4 hours, then component D is added, and continued to mature for 1 hour, and removed for use) is filtered through a 300-mesh filter cloth into a spray gun, and sprayed at a substrate temperature of 50°C;

[0096] (3) Curing: The sprayed substrate is first placed in an oven for low-temperature curing at 90°C for 8 min, then high-temperature curing at 200°C for 18 min, and then naturally cooled.

[0097] Embodiment 2-4

[0098] Example 2-4 provides a purple sand non-stick ceramic coating; its composition and amount are shown in Table 3. Its preparation is the same as that of Example 1.

[0099] Comparative Examples 1-5

[0100] Comparative Examples 1-5 provide a purple sand ceramic coating, the composition and dosage of which are shown in Table 3. The preparation thereof is the same as that of Example 1.

[0101] Comparative Example 6

[0102] This comparative example provides a purple sand ceramic coating; its composition and dosage are basically the same as those in Example 1, except that hydrochloric acid is used instead of 25% formic acid. Since hydrochloric acid is too acidic, the pH value after aging is between 2.0-3.0, and the coating quickly gels and cannot be used.

[0103] Comparative Example 7

[0104] (1) Preparation of liquid A: Weigh liquid A, 10.75 g polysiloxane, 10.5 g silicon dioxide, 17.75 g aluminum oxide, 5.25 g zinc oxide, 125.5 g water, 17.75 g methanol, 16 g methylcellulose, 15 g iron oxide, 5 g zirconium dioxide, and 26.5 g titanium dioxide according to the amount, mix thoroughly with water as solvent, and then stir in a stirrer at 180 rpm for 120 minutes;

[0105] (2) Preparation of Solution B: Weigh Solution B, 57.3 g of silica, and 42.7 g of methanol according to the amount, mix thoroughly with methanol as solvent, and then stir in a stirrer at 180 rpm for 120 minutes;

[0106] (3) Mix liquid A and liquid B, pour liquid A into liquid B under heating conditions and stir in a stirrer for 5 hours at a temperature of 35°C and a speed of 100 times / min (weight ratio 2.5:1)

[0107] (4) Stop rolling and leave for 3 hours.

[0108] Table 3 Composition and dosage (wt.%)

[0109]

[0110] The main performance test methods of the coatings obtained in the above embodiments and comparative examples are shown in Table 4 below; the test results are shown in Table 5, Table 6 and Table 7.

[0111] Table 4

[0112]

[0113]

[0114] Table 5

[0115]

[0116] Table 6

[0117]

[0118] Table 7

[0119]

[0120]

[0121] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A purple sand ceramic coating, which is a single-coat four-component coating composition; based on 100%, the mass percentage content of each component is as follows: Component A, filler slurry: 50-52%, Component B, containing silane and hydroxy silicone oil: 20-22%, C component, 20-25% formic acid: 0.6-0.8%, Component D is purple sand mortar: balance; in, Measured by mass percentage of the total weight of component A, component A includes: Silica sol: 62-64%, 1-1.5% NaOH solution: 6-8%, Filler: 20-22%, Deionized water: balance; The silica sol is a mixture of an acidic silica sol with a particle size of 20-25 nm and a particle size of 7-10 nm in a mass ratio of 3:2-1:1; Measured by mass percentage of the total weight of component B, component B includes: Silane: 78-80% Hydroxyl silicone oil: 6-8% Leveling agent: 4-6% Solvent: balance; The hydroxy silicone oil structural formula is HO[(CH3)2SiO] n H, n=7-9; the silane is selected from a mixture of methyltrimethoxysilane and dimethyldimethoxysilane in a mass ratio of 3:1-4:1; Measured by mass percentage of the total weight of component D, component D includes: Purple sand powder: 60-65% Dispersant: 6-6.5% Deionized water: balance.

2. The purple sand ceramic coating according to claim 1, characterized in that: The acidic silica sol with a particle size of 20-25 nm is selected from at least one of Bindzil 2034DI of Akzo Nobel, ST-O-40 of Nissan Chemical, and Grace LUDOX® CL-P; the acidic silica sol with a particle size of 7-10 nm is selected from ST-OS of Nissan Chemical.

3. A method for preparing the purple sand ceramic coating according to claim 1, characterized in that: The method comprises the following steps: S1. Preparation of component A: Silica sols of different particle sizes are mixed, 1-1.5% NaOH solution is added to a pH value of 9.5-10.5, fillers and deionized water are added and mixed; the obtained slurry is ground under ultrasonic conditions to a fineness of ≤10 μm to obtain component A; S2. Preparation of component B: Mix silane, hydroxy silicone oil, leveling agent and solvent to obtain component B; S3. Preparation of component D: Mix purple sand powder, deionized water and dispersant, and grind them under ultrasonic conditions to a fineness of ≤10 μm to obtain component D.

4. A method for preparing a single coating of purple sand ceramic coating according to claim 1, characterized in that: The method comprises the following steps: A1. Substrate pretreatment: sandblast or shot blast the surface of the substrate to make the surface roughness reach 2.5-5μm, and put it in a 60-80 ℃ preheated oven for use; A2. Spraying: Filter the cured paint with a 300-mesh filter cloth into the spray gun and spray when the substrate temperature is 45-55°C; A3. Curing: Put the sprayed substrate into the oven for low-temperature curing at 80-100℃ for 5-10min, then high-temperature curing at 180-230℃ for 15-20min, and then cool naturally.

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