Recoatable ceramic coatings, their preparation methods, and their application in honeycomb nonstick cookware

Abstract

This invention discloses a recoatable ceramic coating, its preparation method, and its application in honeycomb non-stick cookware. The primer, calculated at 100%, contains: 20-22% silica sol, 3-4% 1% NaOH solution, 10-12% pigment, 8-10% filler, 1-1.5% dispersant, 18-20% methyltrimethoxysilane, 2-4% KH560, 8-10% PAI, 3-5% isopropanol, 3-5% acetic acid, and 1-2% leveling agent. The topcoat, calculated at 100%, contains: 30-35% silica sol, 25-30% methyltrimethoxysilane, 3-5% KH560, 8-10% PAI, 3-5% isopropanol, 3-5% acetic acid, 2-4% leveling agent, and 2-4% non-stick additive; the balance is water. This invention solves the problems of recoating the cured ceramic coating, interlayer adhesion, and adhesion strength between the coating and raised metal parts while maintaining the honeycomb non-stick cookware manufacturing process.

Description

Technical Field

[0001] This invention belongs to the field of ceramic coating technology, specifically relating to a recoatable ceramic coating, its preparation method, and its application in honeycomb non-stick pans. Background Technology

[0002] In recent years, a type of non-stick cookware with a textured inner surface has appeared on the market. Because its texture resembles a honeycomb shape, it is called a honeycomb non-stick pan. These pans typically use stainless steel, composite steel, or titanium alloy for the body. First, the inner surface undergoes chemical etching to create a pre-set textured pattern resembling a honeycomb or other shapes. Then, a non-stick coating is sprayed onto the surface. After firing, the non-stick coating on the raised parts is removed by grinding, leaving the coating on the recessed areas, thus creating the textured pattern. When cooking, the spatula generally only contacts the raised stainless steel parts and doesn't easily come into contact with the coating on the recessed areas. Because this caters to consumers' habit of using metal spatulas, it has become popular. However, since the raised parts lack a non-stick coating, food can still stick to these areas during cooking, significantly impacting the user experience.

[0003] The non-stick coating on honeycomb cookware typically uses PTFE, or polytetrafluoroethylene. On one hand, PTFE coating has a high viscosity and doesn't fully penetrate the recessed areas of the cookware during baking, leaving some air residue. During use, due to the thermal expansion and contraction of this residual air, the non-stick coating in the recessed areas is prone to peeling off, reducing its non-stick properties and failing to meet user requirements. On the other hand, PTFE coating contains PFAS (phosphoalkanoates), which decompose at temperatures above 250°C, releasing toxic substances that seriously endanger consumer health. Therefore, countries like the United States and the European Union have implemented restrictions on PFAS, making the search for a healthy and safer alternative to PTFE coatings an inevitable trend.

[0004] Ceramic coatings belong to the water-based inorganic non-stick coating category. They are a safe, healthy, and environmentally friendly coating, and their application in cookware has increased significantly in recent years. Ceramic coatings for cookware are generally a single layer or a two-layer structure of primer and topcoat. For two-layer ceramic coatings, a wet-on-wet spraying method is typically used, followed by a single curing. If a two-coat, two-bake application method is used—first spraying and curing the primer, then spraying and curing the topcoat—the adhesion between the primer and topcoat layers is insufficient due to the low surface tension of the primer layer, leading to easy coating peeling and failure to meet normal usage requirements. To achieve ceramic coating application on honeycomb pots, and to apply a non-stick coating to the raised areas of the pot's inner surface, it is necessary to solve the problem of the bonding strength between the primer and topcoat to meet practical usage requirements.

[0005] CN115322598A discloses a high-temperature resistant, long-lasting, non-stick ceramic coating and its preparation method. The coating includes a primer and a topcoat. Based on 100% of the total weight of the primer, the primer includes: silica sol: 26-28%, 1% NaOH solution: 4-5%, pigment: 10-12%, filler: 8-10%, dispersant: 1-1.5%, silane: 28-30%, isopropanol: 3-3.5%, silicone oil microcapsules: 3-4%, 25% formic acid: 0.7-1%, and deionized water: balance. Based on 100% of the total weight of the topcoat, the topcoat includes: silica sol + silane: 82-85%, silicone oil microcapsules: 6-8%, leveling agent: 1-1.5%, 25% formic acid: added until the pH value of the topcoat is the same as that of the primer, and isopropanol: balance. The long-lasting non-stick ceramic coating of this invention has an inorganic main molecular chain. Besides its long-lasting non-stick properties, it also features high temperature resistance, high hardness, and good wear resistance. However, this patent only allows for a wet-on-wet application method, i.e., spraying a primer followed directly by the topcoat, and then allowing it to cure. If the manufacturing process of honeycomb non-stick pans is followed—spraying a primer, curing it first, sanding, and then spraying a clear topcoat—the adhesion between the primer and topcoat will be poor, causing the topcoat coating to peel off during use. In other words, this patent cannot achieve recoating of the ceramic coating. Summary of the Invention

[0006] The purpose of this invention is to provide a recoatable ceramic coating, its preparation method, and its application in honeycomb non-stick pans. This invention solves the following technical problems: (1) Polytetrafluoroethylene coatings belong to PFAS substances, which decompose and release toxic substances at temperatures above 250°C, posing a health hazard. Countries such as the United States and the European Union have proposed restricting the use of PFAS substances. Ceramic coatings are a healthy, safe, and environmentally friendly water-based inorganic non-stick coating, belonging to PFAS-FREE substances, and can replace commonly used polytetrafluoroethylene coatings for the inner surface of honeycomb pans; (2) The raised parts on the inner surface of honeycomb non-stick pans are not protected by a non-stick coating, and the pan will stick during cooking. This invention applies a non-stick coating to the raised parts on the inner surface of the pan to solve the sticking problem; (3) While keeping the manufacturing process of honeycomb non-stick pans unchanged, this invention solves the problems of recoating the ceramic coating after curing, interlayer adhesion, and adhesion strength between the coating and the raised metal parts, thus meeting the requirements for practical use.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention relates to a recoatable non-stick ceramic coating, comprising a primer and a topcoat.

[0009] The primer is a colored paint, and its composition, based on 100%, is as follows: silica sol: 20-22%, 1% NaOH solution: 3-4%, pigment: 10-12%, filler: 8-10%, dispersant: 1-1.5%, methyltrimethoxysilane: 18-20%, KH560: 2-4%, waterborne polyamide-imide resin (PAI): 8-10%, isopropanol: 3-5%, acetic acid: 3-5%, leveling agent: 1-2%, deionized water: balance;

[0010] The topcoat is colorless and transparent, and its composition, based on 100%, is as follows: silica sol: 30-35%, methyltrimethoxysilane: 25-30%, KH560: 3-5%, waterborne polyamide-imide resin (PAI): 8-10%, isopropanol: 3-5%, acetic acid: 3-5%, leveling agent: 2-4%, non-sticking agent: 2-4%, deionized water: balance.

[0011] As one embodiment of the present invention, the silica sol includes: AkzoNobel's Bindzil 2034DI, Nissan Chemical's ST-O-40, and Grace. HS-40, etc.

[0012] As one embodiment of the present invention, the 1% NaOH solution is used to adjust the pH value of the pigment paste to between 9.5 and 10.5 during grinding, and to adjust the pH value of the pigment paste to above 9.5 after grinding.

[0013] As one embodiment of the present invention, the pigments include: titanium dioxide, manganese iron black, iron oxide yellow, iron oxide red, cobalt blue, etc.

[0014] As one embodiment of the present invention, the filler includes: mica powder, silicon micro powder, silicon carbide, alumina powder, talc powder, etc.

[0015] As one embodiment of the present invention, the dispersant includes BYK180, BYK190, BYK2010, BYK2001, etc.

[0016] As one embodiment of the present invention, the leveling agent includes: BYK-333 and Dow Corning DC-57.

[0017] In one embodiment of the present invention, the non-stick additive is selected from those with hydroxyl groups at the ends of their molecular chains. The non-stick additives include: 3600 from Guangzhou Hanju Polymer Materials Co., Ltd., and K-766 from Guangdong Biaomei Fluorosilicone New Materials Co., Ltd.

[0018] Secondly, the present invention also relates to a method for preparing a ceramic coating, the method comprising:

[0019] Preparation of primer:

[0020] A1. Preparation of color paste: Mix silica sol, 1% NaOH solution, pigment, filler and dispersant evenly, grind to a fineness of less than 20μm, test the pH value of the color paste, if it is less than 9.5, adjust it to above 9.5 with 1% NaOH solution, and set aside for use;

[0021] A2. Mix methyltrimethoxysilane, KH560, waterborne PAI resin, isopropanol, acetic acid, leveling agent, and deionized water evenly, then add the color paste from step A1, and roll at 120-150 rpm for 6-8 hours to obtain ceramic primer.

[0022] In one embodiment of the present invention, step A2 further includes testing the viscosity of the coating using a Forecast-4 cup and controlling the viscosity to be within 16 seconds. If the Forecast-4 cup viscosity exceeds 16 seconds, isopropanol is added to adjust it to within 16 seconds.

[0023] Preparation of transparent topcoat:

[0024] Mix methyltrimethoxysilane, KH560, waterborne PAI resin, isopropanol, acetic acid, leveling agent, non-sticking agent, and deionized water evenly, then add silica sol, and roll at 120-150 rpm for 6-8 hours to obtain ceramic topcoat.

[0025] Thirdly, the present invention also relates to the application of the recoatable ceramic coating obtained by the aforementioned method on honeycomb nonstick pans.

[0026] The application includes: spraying a ceramic coating primer onto a predetermined area on the inner surface of the pot, removing the ceramic primer from the honeycomb protrusions after curing; and continuing to spray a ceramic topcoat onto the predetermined area on the inner surface of the pot.

[0027] As a specific embodiment of the present invention, the application of ceramic coating on a honeycomb non-stick pan is as follows:

[0028] (1) Forming etching patterns: The inner surface of a stainless steel, composite steel or titanium alloy pot body is formed with a predetermined pattern of raised and recessed patterns by chemical etching.

[0029] (2) Sandblasting: A rough surface is formed on the inner surface of the pot body by sandblasting at the pre-set pattern. Ra = 2.0-3.5μm. The rough surface increases the contact area between the coating and the substrate, which can improve the adhesion between the pot body and the coating.

[0030] (3) Spraying primer: Spray ceramic coating primer on the preset area on the inner surface of the pot, and cure at 80-100℃ for 8-10 minutes until the coating reaches the surface dry state.

[0031] (4) Polishing: Use sandpaper to mechanically polish the ceramic coating on the inner surface of the pot, completely remove the ceramic base paint on the raised surface of the textured surface of the inner surface of the pot, reveal the texture of the preset pattern, and retain the ceramic base paint on the recessed surface.

[0032] (5) Spraying ceramic topcoat: Spray ceramic topcoat on the preset area on the inner surface of the pot, and then cure it at 320-350℃ for 10-15 minutes. After cooling, a honeycomb non-stick pot with preset texture and ceramic coating is obtained.

[0033] Fourthly, the present invention also relates to a honeycomb non-stick pan, wherein the raised and recessed parts of the inner surface of the pan are coated with a ceramic coating, wherein the raised parts are coated with the transparent topcoat of the aforementioned ceramic coating, and the recessed parts are coated with the ceramic primer and transparent topcoat of the aforementioned ceramic coating.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) Aqueous PAI resin was added to the ceramic coating formulation. During the high-temperature cooling and curing process, the good bonding performance of PAI resin and the characteristics of thermoplastic materials were utilized to improve the overall coating adhesion strength, thus solving the problem of recoating when used on honeycomb pots. Coupling agent KH560 has good compatibility with aqueous PAI resin, thereby improving the compatibility between PAI resin and ceramic coating, and preparing a homogeneous and stable coating.

[0036] (2) The honeycomb non-stick pan utilizes a two-layer design: a colored ceramic base coat and a transparent top coat. This ensures that both the raised and recessed areas on the inner surface of the pan are coated with a ceramic coating, improving its non-stick performance. Furthermore, the textured surface of the inner surface is clearly visible, satisfying consumers' preference for the appearance of honeycomb non-stick pans. The PAI resin added to the formula, with its benzene rings in the molecular chain, enhances the coating's wear resistance and alkali resistance. Adjusting the viscosity of the ceramic base coat ensures that it fills the recessed areas within the pan, effectively preventing coating peeling and significantly extending the lifespan of the non-stick coating.

[0037] (3) Use ceramic non-stick coating instead of the commonly used polytetrafluoroethylene coating for honeycomb non-stick pans. Since ceramic coating is a water-based inorganic coating that does not contain PFAS substances, it will not decompose and release toxic substances at high temperatures. It is a truly safe, healthy and environmentally friendly non-stick coating. Detailed Implementation

[0038] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0039] This invention provides a ceramic coating, which consists of a primer and a topcoat. The primer is a colored paint and, based on 100%, has the following composition: silica sol: 20-22%, 1% NaOH solution: 3-4%, pigment: 10-12%, filler: 8-10%, dispersant: 1-1.5%, methyltrimethoxysilane: 18-20%, KH560: 2-4%, waterborne polyamide-imide resin (PAI): 8-10%, isopropanol: 3-5%, acetic acid: 3-5%, leveling agent: 1-2%, and deionized water: balance.

[0040] Silica sol: a major film-forming substance in ceramic coatings, including AkzoNobel's Bindzil 2034DI, Nissan Chemical's ST-O-40, and Grace. HS-40, etc.

[0041] 1% NaOH solution: pH adjuster for color pastes. The pH of color pastes may decrease slightly during grinding and storage. When the pH drops below 8.5 and approaches neutral, the silica sol will gel, causing the color paste to deteriorate. Therefore, before grinding, the pH of the color paste needs to be adjusted to between 9.5 and 10.5 with an alkaline solution, and after grinding, the pH should be adjusted to above 9.5 to ensure that the color paste does not deteriorate due to pH decrease during storage.

[0042] Pigments: Give coatings different colors. Common inorganic pigments are selected because they have good temperature resistance and safety. Inorganic pigments are suitable for coatings used in food contact, such as titanium dioxide, manganese iron black, iron oxide yellow, iron oxide red, cobalt blue, etc.

[0043] Fillers: They play a role in reducing the cost of coatings and increasing the solid content of coatings. Commonly used fillers are selected, such as mica powder, silicon micro powder, silicon carbide, alumina powder, talc powder, etc.

[0044] Dispersants: They reduce the dispersion time of pigments and fillers, stabilize pigment dispersions, and improve the tinting strength and hiding power of pigments. Examples include BYK180, BYK190, BYK2010, and BYK2001.

[0045] Methyltrimethoxysilane: A film-forming aid. On the one hand, methyltrimethoxysilane has a fast hydrolysis and polymerization rate, which can shorten the reaction time of ceramic coatings and improve the curing efficiency of ceramic coatings. On the other hand, Si is connected to three -OCH3 groups, and after hydrolysis, it forms three silanol groups (Si-OH). After polymerization with silica sol, it can form a coating with a three-dimensional cross-linked structure. The coating has a dense structure and is not easy to crack.

[0046] KH560: A silane coupling agent. The methoxy group (Si-OCH3) at one end of the molecular chain hydrolyzes to form silanol (Si-OH), which can undergo condensation reaction with the products of silica sol and methyltrimethoxysilane hydrolysis. The epoxy group at the other end of the molecular chain has good compatibility with waterborne PAI resin, improving the compatibility between PAI resin and ceramic coatings, and forming a homogeneous and stable coating. Moreover, the longer flexible molecular chain can improve the toughness of the coating and effectively prevent the coating from cracking.

[0047] Waterborne polyamide-imide resin (PAI): A thermoplastic material, meaning it softens upon heating and hardens upon cooling. It possesses excellent mechanical properties, high tensile strength, and good adhesion to metals and other materials, improving the overall bonding strength of the coating. It exhibits good compatibility with KH560 and can form a homogeneous system with ceramic coatings. The benzene rings on the molecular chain enhance the coating's wear resistance and alkali resistance. Examples include PSY225 from Nantong Bolian Materials Technology Co., Ltd., and RI-925 from Wuxi Xiano New Materials Technology Co., Ltd.

[0048] Acetic acid: a catalyst for the sol-gel reaction of ceramic coatings. Methyltrimethoxysilane undergoes hydrolysis under acidic conditions and then condenses with silica sol to form ceramic coatings. Acetic acid has a milder catalytic effect than formic acid, and small addition errors will not affect the pH value of the sol-gel reaction, which is beneficial for controlling the rate of the sol-gel reaction and the structure of the film-forming material.

[0049] Leveling agents: These promote the formation of a smooth, even, and uniform coating film during the drying process. Examples include BYK-333 and Dow Corning DC-57.

[0050] The topcoat of the present invention is colorless and transparent, and its composition, based on 100%, is as follows: silica sol: 30-35%, methyltrimethoxysilane: 25-30%, KH560: 3-5%, waterborne polyamide-imide resin (PAI): 8-10%, isopropanol: 3-5%, acetic acid: 3-5%, leveling agent: 2-4%, non-sticking agent: 2-4%, deionized water: balance.

[0051] Non-stick additives: Improve the feel and non-stick properties of the coating. Non-stick additives with hydroxyl groups at the ends of their molecular chains are preferred. These additives can participate in the reaction during the curing process of the ceramic coating, chemically bonding to the molecular chain and providing a more durable non-stick effect. Examples include: 3600 from Guangzhou Hanju Polymer Materials Co., Ltd., and K-766 from Guangdong Biaomei Fluorosilicone New Materials Co., Ltd.

[0052] This invention also provides a method for preparing a ceramic coating, the method comprising preparing a primer:

[0053] (1) Preparation of color paste: Mix silica sol, 1% NaOH solution, pigment, filler and dispersant evenly, grind to a fineness of less than 20μm on a basket mill, test the pH value of the color paste, if it is less than 9.5, adjust it to above 9.5 with 1% NaOH solution, and set aside for use.

[0054] During grinding and storage, the pH value of ceramic coating pigments will decrease slightly. The degree of pH decrease will vary depending on the color of the pigment. When the pH value of the pigment drops below 8.5 and approaches neutral, the silica sol will gel and cause the pigment to deteriorate. Therefore, it is necessary to use an alkaline solution to adjust the pH value of the ground pigment to above 9.5 to ensure that the pigment does not deteriorate due to the decrease in pH value during storage.

[0055] (2) Mix methyltrimethoxysilane, KH560, waterborne PAI resin, isopropanol, acetic acid, leveling agent, and deionized water evenly, then add the color paste from step (1), and roll at 120-150 rpm for 6-8 hours to obtain ceramic primer; test the viscosity of the coating with a Ford cup 4 and control it within 16s. If the Ford cup viscosity exceeds 16s, add isopropanol to adjust it to within 16s.

[0056] The viscosity of a standard ceramic coating (Coating 4 cup) is typically 12-14s. The PAI resin added to the primer can increase the viscosity of the ceramic coating. Because the inner surface of the pot is etched with small recesses, if the viscosity of the ceramic coating primer is too high, it will not level well and will not be able to fully penetrate and fill these recesses, leaving air trapped inside. During later use, the thermal expansion and contraction of this trapped air can cause the coating to crack and peel off. Therefore, the viscosity of the ceramic coating primer needs to be adjusted to below 16s to ensure that the coating completely penetrates into the recesses on the inner surface of the pot, effectively preventing cracking and peeling.

[0057] The preparation steps for the transparent topcoat are as follows:

[0058] Mix methyltrimethoxysilane, KH560, waterborne PAI resin, isopropanol, acetic acid, leveling agent, non-sticking agent, and deionized water evenly, then add silica sol, and roll at 120-150 rpm for 6-8 hours to obtain ceramic topcoat.

[0059] The application of the ceramic coating provided by this invention on honeycomb non-stick pans is as follows:

[0060] (1) Forming etching patterns: The inner surface of a stainless steel, composite steel or titanium alloy pot body is formed with a predetermined pattern of raised and recessed patterns by chemical etching.

[0061] (2) Sandblasting: A rough surface is formed on the inner surface of the pot body by sandblasting at the pre-set pattern. Ra = 2.0-3.5μm. The rough surface increases the contact area between the coating and the substrate, which can improve the adhesion between the pot body and the coating.

[0062] (3) Spraying primer: Spray ceramic coating primer on the preset area on the inner surface of the pot, and cure at 80-100℃ for 8-10 minutes until the coating reaches the surface dry state.

[0063] (4) Polishing: Use sandpaper to mechanically polish the ceramic coating on the inner surface of the pot, completely remove the ceramic base paint on the raised surface of the textured surface of the inner surface of the pot, reveal the texture of the preset pattern, and retain the ceramic base paint on the recessed surface.

[0064] (5) Spraying ceramic paint: Spray ceramic paint on the preset area on the inner surface of the pot, then cure it at 320-350℃ for 10-15 minutes. After cooling, a honeycomb non-stick pot with preset texture and ceramic coating is obtained.

[0065] Because PAI resin in primers and topcoats is a thermoplastic material, it softens when heated to high temperatures, exhibiting excellent adhesion to metals and other materials. Upon cooling, it becomes solid, enabling it to bond coatings together and to the substrate. Furthermore, PAI resin has a glass transition temperature above 270°C, requiring heating temperatures higher than its glass transition temperature to utilize its thermoplastic properties.

[0066] After the above process, both the raised and recessed areas of the inner surface of the pot are coated with a ceramic coating. Specifically, the raised areas are coated with a transparent topcoat, while the recessed areas are coated with a ceramic primer and a transparent topcoat. This significantly improves the non-stick properties of the pot. Because the topcoat is colorless and transparent, the textured surface of the inner surface of the pot is clearly visible, satisfying consumers' preference for the honeycomb non-stick appearance. Furthermore, the benzene rings in the PAI resin molecular chain enhance the coating's wear resistance and alkali resistance, resulting in excellent and long-lasting non-stick performance and a long service life in actual use.

[0067] See the following examples for specific examples:

[0068] Examples 1-6

[0069] Examples 1-6 provide a recoatable non-stick ceramic coating, the composition of which is shown in Table 1. This coating is suitable for honeycomb non-stick pans, and is especially suitable for a two-coat, two-bake application process.

[0070] The preparation steps for ceramic coating primer are as follows:

[0071] (1) Preparation of color paste: Mix silica sol, 1% NaOH solution, pigment, filler and dispersant evenly, grind to a fineness of less than 20μm on a basket mill, test the pH value of the color paste, if it is less than 9.5, adjust it to above 9.5 with 1% NaOH solution, and set aside for use.

[0072] (2) Mix methyltrimethoxysilane, KH560, waterborne PAI resin, isopropanol, acetic acid, leveling agent, and deionized water evenly, then add the color paste from step (1), and roll at 150 rpm for 7 hours to obtain ceramic primer; test the viscosity of the coating with a Ford cup 4 and control it within 16s. If the viscosity of the Ford cup 4 exceeds 16s, add isopropanol to adjust it to within 16s.

[0073] The preparation steps for ceramic coating topcoat are as follows:

[0074] Methyltrimethoxysilane, KH560, waterborne PAI resin, isopropanol, acetic acid, leveling agent, non-sticking agent, and deionized water are mixed evenly, and then silica sol is added. After rolling at 150 rpm for 7 hours, a ceramic topcoat is obtained.

[0075] Comparative Examples 1-6

[0076] Comparative Examples 1-6 provide a ceramic coating with the composition shown in Table 1; the preparation is the same as in Example 1.

[0077] Comparative Example 7

[0078] Following the preparation steps of the ceramic coating primer in Example 1, the primer was prepared with a Coating-4 cup viscosity of 18s and was ready for direct use.

[0079] Table 1. Coating composition and dosage (wt.%) of the examples and comparative examples

[0080]

[0081]

[0082] Main performance tests

[0083] The coatings prepared in the above embodiments and comparative examples were applied using the following methods, and their main performance was tested. The test items and methods are shown in Table 2, and the test results are shown in Table 3.

[0084] The application of ceramic coating on honeycomb non-stick pans is as follows:

[0085] (1) Forming etching patterns: The inner surface of a stainless steel, composite steel or titanium alloy pot body is formed with a predetermined pattern of raised and recessed patterns by chemical etching.

[0086] (2) Sandblasting: A rough surface is formed on the inner surface of the pot body by sandblasting at the pre-set pattern. Ra = 3.0 μm. The rough surface increases the contact area between the coating and the substrate, which can improve the adhesion between the pot body and the coating.

[0087] (3) Spraying primer: Spray ceramic coating primer on the preset area on the inner surface of the pot, cure at 100℃ for 8 minutes, and the coating reaches the surface dry state.

[0088] (4) Polishing: Use sandpaper to mechanically polish the ceramic coating on the inner surface of the pot, completely remove the ceramic base paint on the raised surface of the textured surface of the inner surface of the pot, reveal the texture of the preset pattern, and retain the ceramic base paint on the recessed surface.

[0089] (5) Spraying ceramic paint: Spray ceramic paint on the preset area on the inner surface of the pot, then cure at 320℃ for 15 minutes, and after cooling, a honeycomb non-stick pot with preset texture and ceramic coating is obtained.

[0090] Table 2. Test methods for main performance of coatings

[0091]

[0092]

[0093] Table 3. Key performance test results of the examples and comparative examples.

[0094]

[0095] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A recoatable non-stick ceramic coating suitable for a two-coat, two-bake application method, comprising a primer and a topcoat, characterized in that, The primer is a colored paint, and its composition, based on 100%, is as follows: silica sol: 20-22%, 1% NaOH solution: 3-4%, pigment: 10-12%, filler: 8-10%, dispersant: 1-1.5%, methyltrimethoxysilane: 18-20%, KH560: 2-4%, waterborne polyamide-imide resin: 8-10%, isopropanol: 3-5%, acetic acid: 3-5%, leveling agent: 1-2%, deionized water: balance; The topcoat is colorless and transparent, and its composition, based on 100%, is as follows: silica sol: 30-35%, methyltrimethoxysilane: 25-30%, KH560: 3-5%, waterborne polyamide-imide resin: 8-10%, isopropanol: 3-5%, acetic acid: 3-5%, leveling agent: 2-4%, non-sticking agent: 2-4%, deionized water: balance; The recoatable non-stick ceramic coating is applied to a honeycomb non-stick pan; specifically, the primer of the ceramic coating is sprayed onto a preset area on the inner surface of the pan, and the ceramic primer is removed from the honeycomb raised surface after curing. Continue spraying the topcoat of the ceramic coating onto the predetermined area on the inner surface of the pot.

2. The recoatable non-stick ceramic coating according to claim 1, characterized in that, The silica sols include: AkzoNobel's Bindzil 2034DI, Nissan Chemical's ST-O-40, and Grace LUDOX® HS-40.

3. The recoatable non-stick ceramic coating according to claim 1, characterized in that, The 1% NaOH solution is used to adjust the pH value of the pigment paste to between 9.5 and 10.5 during grinding, and to adjust the pH value of the pigment paste to above 9.5 after grinding.

4. The recoatable non-stick ceramic coating according to claim 1, characterized in that, The pigments include: titanium dioxide, manganese iron black, iron oxide yellow, iron oxide red, and cobalt blue; the fillers include: mica powder, silica powder, silicon carbide, alumina powder, and talc; the dispersants include: BYK180, BYK190, BYK2010, and BYK2001; and the leveling agents include: BYK-333 and Dow Corning DC-57.

5. The recoatable non-stick ceramic coating according to claim 1, characterized in that, The non-stick additives are selected from those with hydroxyl groups at the ends of their molecular chains; including: 3600 from Guangzhou Hanju Polymer Materials Co., Ltd., and K-766 from Guangdong Biaomei Fluorosilicone New Materials Co., Ltd.

6. A method for preparing a recoatable non-stick ceramic coating according to claim 1, characterized in that, The method includes: Preparation of primer: A1. Preparation of color paste: Mix silica sol, 1% NaOH solution, pigment, filler and dispersant evenly, grind to a fineness of less than 20μm, test the pH value of the color paste, if it is less than 9.5, adjust it to above 9.5 with 1% NaOH solution, and set aside for use; A2. Mix methyltrimethoxysilane, KH560, waterborne PAI resin, isopropanol, acetic acid, leveling agent, and deionized water evenly, then add the color paste from step A1, and roll at 120-150 rpm for 6-8 hours to obtain ceramic primer. Preparation of transparent topcoat: B1: Mix methyltrimethoxysilane, KH560, waterborne PAI resin, isopropanol, acetic acid, leveling agent, non-sticking agent, and deionized water evenly, then add silica sol, and roll at 120-150 rpm for 6-8 hours to obtain ceramic topcoat.

7. The method for preparing the recoatable non-stick ceramic coating according to claim 6, characterized in that, Step A2 also includes testing the viscosity of the coating with a Forecast 4 cup and controlling the viscosity to be within 16s; if the Forecast 4 cup viscosity exceeds 16s, isopropanol is added to adjust it to within 16s.

8. A honeycomb non-stick pan, wherein the raised and recessed surfaces of the pan's inner surface are coated with a ceramic coating, characterized in that... The raised portion is coated with a transparent topcoat of the recoatable non-stick ceramic coating as described in claim 1, and the recessed portion is coated with a ceramic primer and a transparent topcoat of the recoatable non-stick ceramic coating as described in claim 1.

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