High-stain-resistance reflective heat-insulation coating applied to steel tile base material and preparation method of high-stain-resistance reflective heat-insulation coating

Abstract

The invention relates to a high-stain-resistance reflective thermal insulation coating applied to a steel tile base material and a preparation method of the high-stain-resistance reflective thermal insulation coating. The high-stain-resistance reflective thermal insulation coating comprises a coating composition and a coating composition, wherein the coating composition comprises cellulose, a pH regulator, a dispersing agent, a wetting agent, a defoaming agent, rutile titanium dioxide, calcined kaolin, aluminum triphosphate, precipitated barium sulfate, dipropylene glycol butyl ether, propylene glycol, a bactericidal preservative, a mildew preventive, epoxy modified acrylic resin and a thickening agent; and pre-mixing slurry and pure water. The preparation method comprises the following steps: firstly, carrying out high-speed grinding treatment on silane modified polyurethane resin, water, sepiolite, a dispersing agent and a defoaming agent to obtain premixed slurry, wherein the premixed slurry is prepared by directly dispersing or grinding and dispersing by using pickaxe beads in the prior art; according to the present invention, the pores in the porous structure of the sepiolite and the aluminum triphosphate material can be furthest utilized by using the prefabricated slurry, and the large particle size of the silane-modified polyurethane resin is used to block the pores of the powder so as to make the porous structure of the paint film more stable and make the thermal insulation performance of the paint film more excellent;

Description

Technical Field

[0001] The invention belongs to the field of water-based building exterior wall paint and topcoat, and particularly relates to a highly stain-resistant reflective heat-insulating paint applied to a steel tile substrate and a preparation method thereof. Background Art

[0002] Global warming and the energy crisis are two major challenges facing the world. Reducing the consumption of traditional energy sources has become a key measure to reduce carbon emissions. With the advancement of science and technology and the implementation of the "dual carbon" roadmap, new materials, technologies, and processes are constantly emerging, and roof covering materials are becoming increasingly diverse.

[0003] Building energy consumption accounts for approximately 20-30% of global energy consumption, and in China, it accounts for 25%, making it the largest energy-consuming industry. With the development of my country's construction industry, energy conservation in buildings is becoming increasingly important. The application of thermal insulation materials is crucial for improving the thermal insulation performance of building envelopes and has become a research hotspot in the field of building energy conservation.

[0004] The use of metal roof coverings is becoming increasingly common. According to statistics, there are approximately 11 billion square meters of metal roofing in China, with approximately 70 million square meters added annually, and over 100 million square meters of metal roofing repaired annually. However, leaks caused by metal roof corrosion and the need for thermal insulation and cooling within factories are a major concern for many metal roofing installers and factory owners.

[0005] Traditional thermal insulation systems mostly utilize insulation panels, which have disadvantages such as complex installation, low insulation efficiency, and short insulation duration. With the development and maturation of coating technology, reflective insulation coatings are becoming a trend in replacing insulation panels. The diverse characteristics of roofing locations and roofing materials require a stain-resistant reflective insulation product that can be used on a variety of substrates to meet market demand.

[0006] Patent application CN201410621587.8 discloses a process for preparing a color-coated steel tile coating. This process utilizes an acrylic polymer resin and incorporates chlorinated rubber to enhance water resistance, chemical resistance, and vapor permeability, making the coating more resistant to atmospheric aging and extending its service life. Unlike the system described in this technical solution, this solvent-based coating incorporates chlorinated rubber to enhance the coating's chemical and aging resistance, but suffers from poor environmental performance.

[0007] Patent application CN201911096812.X discloses a water-based reflective thermal insulation coating and its preparation method. The coating utilizes carbon nanotube-modified epoxy resin, silicone-modified fluorocarbon emulsion, silicon-aluminum-coated modified nano-titanium dioxide, nano-ytterbium oxide, kaolin, and heavy calcium carbonate, among other high-hardness particles, to comprehensively enhance the film's reflective thermal insulation, wear resistance, and scrub resistance. However, the filler's function is overly idealistic; kaolin and heavy calcium carbonate may not necessarily enhance the coating's wear resistance and scrub resistance.

[0008] Patent application document CN201810244810.X discloses a waterproof, anti-corrosion, and thermal insulation coating and its preparation method. Three emulsions are mixed and, under the combined action of a film-forming aid and other additives, can crosslink to form a film. The emulsion has good stability and forms a cross-linked network structure. The resulting coating has excellent waterproofness, heat resistance, low-temperature resistance, and air permeability. This is different from the film-forming material of the present technical solution and is overly idealized. The three film-forming materials may not necessarily form a good and stable cross-linked network structure. The resulting coating is unlikely to combine the advantages of the three resins. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a highly stain-resistant reflective thermal insulation coating for steel tile substrates and a preparation method thereof. The present invention first uses silane-modified polyurethane resin, water, sepiolite, dispersant, and defoamer for high-speed grinding to obtain a premixed slurry. The existing technology is to prepare by direct dispersion or grind and disperse with pick beads; the technical solution of the present invention adopts the method of prefabricated slurry to maximize the use of the pores in the porous structure of sepiolite and aluminum tripolyphosphate materials themselves. The prefabricated slurry uses the large particle size of silane-modified polyurethane resin to block the pores of the powder, which can make the porous structure of the paint film more stable and promote better thermal insulation performance of the paint film.

[0010] To solve the above problems, the present invention is implemented through the following technical solutions:

[0011] The first object of the present invention is:

[0012] Provided is a highly stain-resistant reflective thermal insulation coating for use on a steel tile substrate, comprising the following components in parts by weight:

[0013] Coating composition:

[0014] 0.1-0.3 parts of cellulose, 0.05-0.2 parts of pH regulator, 0.3-0.8 parts of dispersant, 0.1-0.4 parts of wetting agent, 0.2-0.8 parts of defoaming agent, 8-16 parts of rutile titanium dioxide, 5-12 parts of calcined kaolin, 5-10 parts of aluminum tripolyphosphate, 2-10 parts of precipitated barium sulfate, 0.5-1.2 parts of dipropylene glycol butyl ether, 0.3-0.8 parts of propylene glycol, 0.1-0.3 parts of bactericidal preservative, 0.1-0.3 parts of mildewproofing agent, 25-33 parts of epoxy modified acrylic resin, 0.5-1.2 parts of thickener, 10-23 parts of premixed slurry, and the balance of pure water; the total weight ratio is 100 parts;

[0015] The premixed slurry comprises the following components in parts by weight:

[0016] 0.05-0.2 parts of pH regulator, 0.2-1.2 parts of dispersant, 0.2-1 parts of wetting agent, 0.1-0.6 parts of defoaming agent, 20-40 parts of sepiolite, 20-40 parts of silane-modified polyurethane resin, and the balance of pure water; the total weight is 100 parts.

[0017] During the premix slurry preparation process, the porous structure and high reflectivity of sepiolite enhance the coating's reflective and thermal insulation properties. The large particle size of the silane-modified polyurethane resin blocks the porous pores of the powder, creating a stable structure. The silane-modified polyurethane resin preserves the porous structure of fillers like sepiolite within the coating.

[0018] The high-fouling-resistant reflective thermal insulation coating applied to the steel tile substrate of the present invention is further optimized as follows:

[0019] The molecular weight of the silane-modified polyurethane resin is 50,000 to 80,000, and the particle size of the resin is 0.5 to 10 μm.

[0020] The high-fouling-resistant reflective thermal insulation coating applied to the steel tile substrate of the present invention is further optimized as follows:

[0021] The particle size of the sepiolite powder is between 10 and 25 μm.

[0022] The high-fouling-resistant reflective thermal insulation coating applied to the steel tile substrate of the present invention is further optimized as follows:

[0023] The aluminum tripolyphosphate has a mesh size of 800 to 2000.

[0024] The high-fouling-resistant reflective thermal insulation coating applied to the steel tile substrate of the present invention is further optimized as follows:

[0025] The calcined kaolin has a mesh size of 800 to 2000 meshes.

[0026] The high-fouling-resistant reflective thermal insulation coating applied to the steel tile substrate of the present invention is further optimized as follows:

[0027] The precipitated barium sulfate has a mesh size of 600 to 1500.

[0028] The high-fouling-resistant reflective thermal insulation coating applied to the steel tile substrate of the present invention is further optimized as follows:

[0029] It includes one or a combination of the following features:

[0030] The pH regulator is 2-amino-2-methyl-1-propanol;

[0031] The dispersant is one of styrene maleic anhydride copolymers;

[0032] The wetting agent is one of the polyether-modified siloxane polymers;

[0033] The defoaming agent is one or a combination of silicone polyether or mineral oil;

[0034] The cellulose is cellulose 250HBR;

[0035] The bactericidal preservative is one or a combination of an organic bactericidal preservative or a heterocyclic compound;

[0036] The mildew inhibitor is one or a combination of organic copper salt, organic tin salt or inorganic salt copper sulfate;

[0037] The thickener is one or a combination of polyacrylate copolymer emulsion, polyurethane or modified polyurea.

[0038] The second object of the present invention is:

[0039] A method for preparing the aforementioned highly stain-resistant reflective thermal insulation coating for use on a steel tile substrate is provided, comprising the following steps:

[0040] A. Preparation of premixed slurry:

[0041] Add an appropriate amount of pure water to the container, add pH regulator, dispersant, wetting agent, defoamer in sequence at a stirring speed of 300 r / min, and stir for 3 minutes;

[0042] Increase the speed to 750r / min, slowly add a certain amount of sepiolite, and then increase the speed to 2000r / min and disperse at high speed for 15 minutes;

[0043] Then reduce the speed to 750r / min and slowly add silane modified polyurethane resin.

[0044] Evenly disperse for 15 minutes and prepare the slurry for later use;

[0045] B. Preparation of coating composition:

[0046] Add an appropriate amount of pure water to the container, then add cellulose and pH regulator in sequence at 360r / min, disperse evenly for 3 minutes, then add dispersant, wetting agent, part of defoaming agent in sequence and stir for 3 minutes;

[0047] Increase the speed to 750r / min and slowly add rutile titanium dioxide, calcined kaolin, aluminum tripolyphosphate, and precipitated barium sulfate. Then increase the speed to 2000r / min and disperse at high speed for 15 minutes.

[0048] Then reduce the speed to 750r / min and slowly add the remaining pure water, dipropylene glycol butyl ether, propylene glycol, bactericide and preservative, mildew inhibitor, epoxy modified acrylic resin, thickener, remaining defoamer, and premixed slurry. Continue stirring for 15 minutes to obtain the highly stain-resistant reflective thermal insulation coating applied to the steel tile substrate.

[0049] The key points of the technical solution of the present invention are:

[0050] The introduction of aluminum tripolyphosphate enhances the coating's water and chemical resistance, making it more resistant to atmospheric aging and extending its service life. The excellent low thermal conductivity of sepiolite and the pores in the coating reduce the overall thermal conductivity of the coating, giving it a good reflective and heat-insulating effect.

[0051] The use of silane-modified polyurethane resin and aluminum tripolyphosphate meets the requirements of color steel tiles, various woods and wall substrates; the hydrophilic additive and sepiolite filler cooperate with each other, and the hydrophilic additive migrates to the surface of the coating to improve the stain resistance of the coating. The present invention uses silane-modified polyurethane resin, water, sepiolite, aluminum tripolyphosphate, dispersant, and defoamer to perform high-speed grinding to obtain a premixed slurry. The existing technology is direct dispersion preparation or grinding and dispersion with pick beads. The present invention uses prefabricated slurry to maximize the use of pores in the porous structure of sepiolite and aluminum tripolyphosphate materials themselves, allowing the pores to exist stably in the coating so that the coating has good reflective and heat-insulating effects.

[0052] The present invention utilizes a premixed silane-modified polyurethane resin and sepiolite to achieve a good bond between the resin and the sepiolite. Because the silane-modified polyurethane resin particles are large, they cannot enter the pores of the sepiolite, and the resin and sepiolite particles adhere well. Once the premixed slurry is added to the formulation, the sepiolite is firmly encapsulated by the silane-modified polyurethane resin due to steric hindrance and van der Waals forces, preventing small particles of resin or other substances from entering the pores. This effectively preserves the sepiolite's microporous structure within the coating.

[0053] The technical solution of the present invention uses a prefabricated slurry to maximize the use of the pores in the porous structure of sepiolite and aluminum tripolyphosphate materials. The prefabricated slurry uses the large particle size of the silane-modified polyurethane resin to block the pore openings of the powder, making the porous structure of the paint film more stable and promoting better thermal insulation performance of the paint film. Several fillers of different shapes and particle sizes, such as sepiolite, aluminum tripolyphosphate, barium sulfate, calcined kaolin, and rutile titanium dioxide, are arranged in a high-density disordered manner to make the paint film denser; the compounding of the above functional fillers forms a dense, irregular structure that can effectively prevent the pore wall from being damaged by stress, and improves the compressive strength and flexural strength of the coating, thereby achieving an enhanced toughening effect; when the coating is compounded with fillers of different specifications and morphologies for a high-density disordered arrangement and the metal oxide surface of the fillers, the efficient reflectivity of light and heat in the coating is improved.

[0054] The complex of sepiolite, kaolin, and aluminum tripolyphosphate. The numerous bubbles in the sepiolite's microstructure, combined with the loose, porous nature of calcined kaolin, contribute to the paint film's excellent thermal insulation properties. When applied to color-coated steel tiles, aluminum tripolyphosphate reacts with iron ions to form a water-insoluble chelate, forming a dense film on the substrate surface. Aluminum tripolyphosphate generates aluminum ions, which, along with the metal oxides present in the sepiolite, kaolin, and aluminum tripolyphosphate materials, enhance the paint film's reflective, thermally insulating properties.

[0055] The technical solution of this invention utilizes raw materials and a unique preparation process to address the limited application scenarios and short-lasting reflective insulation effects of traditional coatings. The silane-modified polyurethane resin and epoxy-modified acrylic resin in the main formulation ensure excellent adhesion of the coating to various substrates. The combination of functional raw materials such as sepiolite, aluminum tripolyphosphate, and calcined kaolin effectively addresses formulation instability caused by production and the short-lasting reflective insulation properties of the coating due to poor stain resistance.

[0056] There are two main types of reflective thermal insulation architectural coatings on the market. One is a reflective thermal insulation coating that incorporates hollow microspheres. However, this thin-walled, porous structure easily breaks under high shear, losing its thermal insulation effect and resulting in unstable results. The coating is prone to delamination and poor stain resistance. The other is a coating that incorporates high-value metal oxides in combination with materials such as aerogel to produce a coating with excellent radiant heat dissipation effects. However, this has the disadvantages of high material cost and difficulty in coating application.

[0057] The highly stain-resistant reflective thermal insulation coating prepared by the present invention avoids the problems of unstable product performance, poor stain resistance, and high material costs, and also avoids the limitations of application scenarios due to a single formula. The improved product of the present invention solves the problems of unstable product performance, unsustainable performance, and high material costs, and is simple to produce. DETAILED DESCRIPTION

[0058] In order to make the application, technical solutions and advantages of the present invention more clearly understood, the present invention is described in detail with reference to specific embodiments. It should be understood that the embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention. Any simple improvement to the preparation method of the present invention based on the concept of the present invention falls within the scope of protection of the present invention.

[0059] The technical solution of the present invention is a further technical innovation based on the basic performance results of the following materials:

[0060] The effects of different addition ratios of three functional fillers, namely sepiolite, rutile titanium dioxide and barium sulfate, on the thermal insulation performance of the coating were studied, and the following six groups of experiments were conducted respectively.

[0061] Table 1 Addition ratio of raw material powder in six groups of experiments (mass percentage)

[0062] Experiment number Meerschaum Rutile titanium dioxide barium sulfate A 2 13 7 B 0 13 9 C 0 15 7 D 2 18 0 E 7 15 0 F 2 0 20

[0063] Table 2 Test results of reflective thermal insulation performance of six groups of experiments

[0064]

[0065]

[0066] Through the above six groups of experiments, we can conclude that the relatively optimized addition ratio of sepiolite, rutile titanium dioxide and barium sulfate (experiment A) can make the coating have good reflective and heat-insulating effects while also having good stain resistance and storage stability.

[0067] Sepiolite powder can improve the coating's hemispherical emissivity and thermal insulation performance; rutile titanium dioxide powder can significantly increase the coating's reflectance; and precipitated barium sulfate powder can improve the coating's reflectance and hemispherical emissivity. This invention utilizes these commonly used functional fillers through a specific process and incorporation of a novel resin to achieve outstanding technical results. The three functional fillers work together to create a 1+1 greater than 2 effect, enhancing the coating's reflective and thermal insulation properties.

[0068] Example 1

[0069] A method for preparing a highly stain-resistant reflective thermal insulation coating applied to a steel tile substrate comprises the following steps:

[0070] A. Preparation of premixed slurry:

[0071] Add an appropriate amount of pure water to the container, add pH regulator, dispersant, wetting agent, defoamer in sequence at a stirring speed of 300 r / min, and stir for 3 minutes;

[0072] Increase the speed to 750r / min, slowly add a certain amount of sepiolite, and then increase the speed to 2000r / min and disperse at high speed for 15 minutes;

[0073] Then, the speed was reduced to 750 r / min and the silane-modified polyurethane resin was slowly added and uniformly dispersed for 15 minutes. The slurry was then ready for use.

[0074] Preparation of coating composition:

[0075] Add an appropriate amount of pure water to the container, then add cellulose and pH regulator in sequence at 360r / min, disperse evenly for 3 minutes, then add dispersant, wetting agent, part of defoaming agent in sequence and stir for 3 minutes;

[0076] Increase the speed to 750r / min and slowly add rutile titanium dioxide, calcined kaolin, aluminum tripolyphosphate, and precipitated barium sulfate. Then increase the speed to 2000r / min and disperse at high speed for 15 minutes.

[0077] Then reduce the speed to 750r / min and slowly add the remaining pure water, dipropylene glycol butyl ether, propylene glycol, bactericide and preservative, mildew inhibitor, epoxy modified acrylic resin, thickener, remaining defoamer, and premixed slurry. Continue stirring for 15 minutes to obtain the highly stain-resistant reflective thermal insulation coating applied to the steel tile substrate.

[0078] Table 3 Composition of the premixed slurry and coating in each solution of Example 1 (parts by weight)

[0079]

[0080]

[0081] Table 4 Test results of reflective thermal insulation performance of four groups of experiments in Schemes 1-3 and Comparative Example 1 in this Example 1

[0082]

[0083] Comparative Example 1, based on Scheme 1, pre-disperses rutile titanium dioxide and sepiolite. This results in a slight decrease in the reflectance of the coating, while the thermal conductivity of the coating increases significantly, which is detrimental to the thermal insulation of the coating. This is primarily due to the small-particle titanium dioxide entering the microporous structure of the sepiolite during pre-dispersion, significantly improving the thermal conductivity of the coating. Other powders were also tested for their effect on the reflective and thermal insulation properties of the coating during the pre-dispersion stage. The results indicate that the other three powders—precipitated barium sulfate, aluminum tripolyphosphate, and calcined kaolin—all have a certain effect on the reflective insulation and thermal conductivity of the coating. The order of effect is: rutile titanium dioxide > precipitated barium sulfate > aluminum tripolyphosphate > calcined kaolin.

[0084] According to the above four groups of experimental results, it can be clearly concluded that the present invention has a good effect on the pre-dispersion of sepiolite, significantly improves the reflective and heat-insulating effect of the coating, and especially greatly improves the anti-fouling effect of the coating.

[0085] Comparative Examples 2-4 are based on Scheme 1 in Example 1, and different types of resins are used to test the prefabricated slurry: the resins used in Scheme 1 and Comparative Examples 2-4 are: silane-modified polyurethane resin, water-based acrylic resin, water-based epoxy resin, and water-based polyurethane resin, respectively. The test results are shown in Table 5.

[0086] Table 5 Test results of reflective thermal insulation performance of four groups of experiments in Scheme 1 and Comparative Examples 2-4 in Example 1

[0087]

[0088] The results in Table 4 above indicate that the use of a high-molecular-weight, large-particle-size silane-modified polyurethane resin enhances the coating's reflective and thermal-insulating properties. The resin's multi-core structure chemically reacts with the outer polyurethane resin and the inner isocyanate during drying, resulting in a coating with excellent performance. The resin's large particle size allows for excellent adsorption onto the surface of the functional filler, sepiolite, preserving the stone's micropores within the coating. This enhances the coating's reflective and thermal-insulating properties while also strengthening its anti-fouling properties, ultimately maintaining its long-lasting reflective and thermal-insulating properties.

[0089] Conventional reflective thermal insulation coatings have certain difficulties in coating on different substrates: coating on metal substrates easily causes rust or poor adhesion, which limits the application of the product. The aluminum tripolyphosphate prepared by the present invention is hydrolyzed to form tripolyphosphate ions with strong chelating ability, which can bind to Fe or Fe on the metal surface. 3+ Chelates cover the active points on the metal surface, preventing corrosion and providing chemical protection. Tripolyphosphate ions form water-insoluble chelates, which undergo chemical conversion to form a dense orthophosphate film that isolates moisture and oxygen from the metal surface, achieving a rust-proofing effect and improving the product's corrosion resistance.

[0090] We conducted coating tests on Sankeshu reflective thermal insulation coatings and Jimeibang reflective insulation coatings. Both competing products experienced varying degrees of rusting, which compromised the integrity of the coating and shortened the lifespan of the paint film.

[0091] In summary, the above are only preferred embodiments of the present invention and do not limit the present invention in any form. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the scope of the technical solution of the present invention using the disclosed technical content shall be regarded as equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

[0092] The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] The experimental methods in the present invention where specific conditions are not specified are generally based on conventional conditions or conditions recommended by the manufacturer.

[0094] Unless otherwise stated, the various optimization technical solutions in the present invention can be combined with each other.

[0095] Unless otherwise indicated, percentages and parts are by weight.

[0096] Experimental methods without specific conditions specified in the instructions and examples are generally performed under conventional conditions or conditions recommended by the manufacturer.

[0097] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein can be applied to the methods of the present invention.

Claims

1. A highly stain-resistant reflective thermal insulation coating applied to a steel tile substrate, characterized by: It comprises the following components in parts by weight: Coating composition: 0.1-0.3 parts of cellulose, 0.05-0.2 parts of pH regulator, 0.3-0.8 parts of dispersant, 0.1-0.4 parts of wetting agent, 0.2-0.8 parts of defoaming agent, 8-16 parts of rutile titanium dioxide, 5-12 parts of calcined kaolin, 5-10 parts of aluminum tripolyphosphate, 2-10 parts of precipitated barium sulfate, 0.5-1.2 parts of dipropylene glycol butyl ether, 0.3-0.8 parts of propylene glycol, 0.1-0.3 parts of bactericidal preservative, 0.1-0.3 parts of mildewproofing agent, 25-33 parts of epoxy modified acrylic resin, 0.5-1.2 parts of thickener, 10-23 parts of premixed slurry, and the balance of pure water; the total weight ratio is 100 parts; The premixed slurry comprises the following components in parts by weight: 0.05-0.2 parts of pH regulator, 0.2-1.2 parts of dispersant, 0.2-1 parts of wetting agent, 0.1-0.6 parts of defoaming agent, 20-40 parts of sepiolite, 20-40 parts of silane-modified polyurethane resin, and the balance of pure water; The total weight parts is 100 parts.

2. The highly stain-resistant reflective thermal insulation coating for use on a steel tile substrate according to claim 1, characterized in that: The molecular weight of the silane modified polyurethane resin is 50,000 to 80,000, and the particle size of the resin is 0.5 to 10 μm .

3. The highly stain-resistant reflective thermal insulation coating for steel tile substrate according to claim 1, characterized in that: The particle size of the sepiolite powder is between 10 and 25 μm between.

4. The highly stain-resistant reflective thermal insulation coating for use on a steel tile substrate according to claim 1, characterized in that: The aluminum tripolyphosphate has a mesh size of 800 to 2000.

5. The highly stain-resistant reflective thermal insulation coating for use on a steel tile substrate according to claim 1, characterized in that: The calcined kaolin has a mesh size of 800 to 2000 meshes.

6. The highly stain-resistant reflective thermal insulation coating for use on a steel tile substrate according to claim 1, characterized in that: The precipitated barium sulfate has a mesh size of 600 to 1500.

7. The highly stain-resistant reflective thermal insulation coating for steel tile substrate according to claim 1, characterized in that: It includes one or a combination of the following features: The pH regulator is 2-amino-2-methyl-1-propanol; The dispersant is one of styrene maleic anhydride copolymers; The wetting agent is one of the polyether-modified siloxane polymers; The defoaming agent is one or a combination of silicone polyether or mineral oil; The cellulose is cellulose 250HBR; The bactericidal preservative is one or a combination of an organic bactericidal preservative or a heterocyclic compound; The mildew inhibitor is one or a combination of organic copper salt, organic tin salt or inorganic salt copper sulfate; The thickener is one or a combination of polyacrylate copolymer emulsion, polyurethane or modified polyurea.

8. A method for preparing the highly stain-resistant reflective thermal insulation coating for steel tile substrates according to claim 1, characterized in that: It includes the following preparation steps: A. Preparation of premixed slurry: Add an appropriate amount of pure water to the container, add pH regulator, dispersant, wetting agent, defoamer in sequence at a stirring speed of 300 r / min, and stir for 3 minutes; Increase the speed to 750r / min, slowly add a certain amount of sepiolite, and then increase the speed to 2000r / min and disperse at high speed for 15 minutes; Then, the speed was reduced to 750 r / min and the silane-modified polyurethane resin was slowly added and uniformly dispersed for 15 minutes. The slurry was then ready for use. B. Preparation of coating composition: Add an appropriate amount of pure water to the container, then add cellulose and pH regulator in sequence at 360r / min, disperse evenly for 3 minutes, then add dispersant, wetting agent, part of defoaming agent in sequence and stir for 3 minutes; Increase the speed to 750r / min and slowly add rutile titanium dioxide, calcined kaolin, aluminum tripolyphosphate, and precipitated barium sulfate. Then increase the speed to 2000r / min and disperse at high speed for 15 minutes. Then reduce the speed to 750r / min and slowly add the remaining pure water, dipropylene glycol butyl ether, propylene glycol, bactericide and preservative, mildew inhibitor, epoxy modified acrylic resin, thickener, remaining defoamer, and premixed slurry. Continue stirring for 15 minutes to obtain the highly stain-resistant reflective thermal insulation coating applied to the steel tile substrate.

Images