High-temperature-resistant flame-retardant heat-insulating coating as well as preparation method and application thereof

Abstract

The invention discloses a high-temperature-resistant flame-retardant heat-insulating coating as well as a preparation method and application thereof, and relates to the technical field of functional coatings. The invention relates to a high-temperature-resistant flame-retardant heat-insulating coating, which comprises the following components in parts by weight: 30-40 parts of a resin base material system, which comprises bifunctional modified resin, epoxy organic silicon resin and water-based styrene-acrylic emulsion compounded according to a mass ratio of 1: 1.5-2: 1; and 6-10 parts of an interface strengthening and filler treating agent. The technical problems that a high-temperature protective coating is weak in interface bonding, and functions and durability are difficult to cooperate are effectively solved; the prepared coating realizes superstrong and lasting adhesion with a metal substrate, and the long-term high-temperature-resistant stability, efficient heat insulation and flame-retardant safety are remarkably improved; meanwhile, the system successfully integrates multiple protection functions such as corrosion resistance and weather resistance, a compact and reliable composite barrier is constructed, and therefore an excellent integrated long-acting protection solution is provided for high-temperature metal equipment in a harsh and complex environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of functional coating technology, in particular to a high-temperature-resistant flame-retardant thermal-insulation coating, a preparation method and application thereof. BACKGROUND

[0002] Metallic facilities such as heat supply pipelines and outer walls of industrial furnaces are long-term exposed to harsh environments of high temperature, corrosion and severe thermal cycling. An ideal protective coating must meet the following core requirements simultaneously: form extremely firm and durable bonding with the metal substrate to resist thermal stress; maintain physical and chemical stability of the coating itself under long-term high temperature (such as 100-300℃); have high-efficiency flame-retardant and thermal-insulation properties to reduce heat loss and fire risk; and provide reliable protection against corrosion and weathering. However, the existing technical solutions are difficult to achieve these goals synergistically, and have the following key defects: (1) The interface bonding between the coating and the metal substrate is weak and difficult to withstand long-term high temperature and thermal cycling. The metal surface is an inorganic substance with high surface energy, while the traditional organic coating is an organic substance with low surface energy, which are incompatible by nature. Although the initial adhesion can be improved by using traditional methods such as silane coupling agent, the Si-O-Me bond formed thereby is prone to hydrolysis or thermal decomposition under long-term high temperature and dry-wet / cold-hot cycling, leading to coating bubbling, peeling and even large-area peeling, which becomes the weakest link in the protective system.

[0003] (2) The high-temperature resistance of the coating and the synergistic effect of functional fillers are mutually restricted. Many organic resins are prone to degradation under long-term high temperature, limiting the upper limit of the use temperature. In order to improve the temperature resistance or introduce flame-retardant and thermal-insulation functions, a large amount of inorganic fillers need to be added, but due to thermodynamic incompatibility between the fillers and the organic resins, the fillers are prone to agglomeration and uneven dispersion. This not only weakens the mechanical properties of the coating, but also forms defects at the interface between the two phases, which becomes a preferential channel for the penetration of heat and corrosive media, and thus accelerates the overall failure of the coating.

[0004] (3) The protective functions are single and lack systematic integration and synergy. Existing coatings often focus on improving a single performance, such as only improving flame retardancy or only reducing thermal conductivity. However, the protection of high-temperature metal equipment is a system engineering, which requires the coating to simultaneously have multiple functions such as flame retardancy, thermal insulation, corrosion resistance and weather resistance. Simple physical blending of these functional components often cannot achieve effective synergy and addition of performance due to poor interfacial compatibility and potential interference between functional components, and the overall protection effect is limited.

[0005] Therefore, developing a coating that can fundamentally strengthen the interface bonding between the coating and the metal substrate, ensure long-term high-temperature service stability, and effectively integrate multiple protective functions in one, is the key to solving the problem of long-term protection of high-temperature metal equipment.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a high-temperature resistant, flame-retardant, and heat-insulating coating, its preparation method, and its application, thereby resolving the issues raised in the background section.

[0008] I. The technical concept of the high-temperature resistant flame-retardant heat-insulating coating, its preparation method, and its application provided by the present invention is as follows: This invention proposes a systematic solution, the core of which lies in constructing a composite material system that is highly synergistic from the interface to the bulk, specifically achieved through the following three levels of design: First, at the interface strengthening level, this invention innovatively proposes a triple synergistic mechanism to overcome the limitations of traditional single coupling agents. This mechanism includes reactive resin coordination anchoring, chemical bridging by composite coupling agents, and physical interlocking of pre-crosslinked fillers.

[0009] In terms of coordination anchoring, a bifunctional modified resin was specially designed. The strong coordinating groups (such as siloxanes and specific hydroxyl groups) contained in its main chain can react chemically with the active sites (such as hydroxyl groups) on the metal surface to form stable covalent bonds. The bond energy of this chemical bond is high, and its resistance to hydrolysis and thermal decomposition is far superior to weak interactions such as physical adsorption or hydrogen bonding, thereby achieving a durable and high-strength anchoring with the metal substrate at the molecular level.

[0010] Meanwhile, the resin has highly reactive groups such as epoxy and amino groups on its side links. During the coating curing process, these groups can undergo extensive chemical reactions with other active components in the resin matrix and the treatment layer on the surface of the filler to form chemical bond bridges, thereby tightly linking the metal substrate, resin matrix and functional filler into a whole through chemical bonds.

[0011] In terms of chemical bridging, epoxy silane coupling agents and titanate coupling agents are combined. The former further establishes chemical bonding networks such as Si-O-Si and Si-O-Me between the resin, filler and metal substrate, while the latter strongly improves the compatibility between inorganic fillers and organic resins through its unique molecular structure, and enhances the overall crosslinking network density by participating in the hydrolysis and condensation reaction of the system with its alkoxy group.

[0012] In terms of physical interlocking, by pre-crosslinking the surface of all functional fillers, a flexible crosslinking network composed of composite coupling agent and bifunctional modified resin is coated on its surface. When the coating is finally cured, this network can undergo deep molecular entanglement and further secondary crosslinking with the main resin, forming countless mechanical anchor points that strengthen the bond at the microscopic level. This significantly enhances the bonding force between the filler and the organic matrix, preventing interfacial slippage and damage.

[0013] Secondly, at the resin matrix design level, high-temperature resistance and multifunctionality are integrated and optimized. Epoxy silicone resin, with its excellent heat resistance and inorganic silicon-oxygen bonds in its molecular chain segments, serves as the framework, providing the system with basic high-temperature stability and resistance to thermal oxidation. A waterborne styrene-acrylic emulsion with a specific ratio of styrene to butyl acrylate is added, and through the rational combination of its soft and hard monomers, the coating's flexibility, cohesion, and film-forming properties are improved, alleviating internal stress caused by differences in thermal expansion coefficients. Then, the aforementioned bifunctional modified resin, which combines anchoring and bridging functions, is compounded with it, ultimately forming a composite resin matrix system that is structurally interpenetrating and chemically cross-linked. This system possesses excellent long-term high-temperature resistance, high reactivity, and good application adaptability.

[0014] Finally, at the functional filler system level, a gradient composite design is adopted. Inorganic fillers with different particle sizes, morphologies, and core functions are carefully selected and optimized for blending. These mainly include glass powder for enhanced temperature resistance and skeletal support; hollow glass microspheres for efficient heat insulation and reduced thermal conductivity; melamine-coated ammonium polyphosphate and zinc borate for synergistic flame retardancy and smoke suppression in both the gas and condensed phases; and nano-silica for nanofilling and enhanced density. All fillers undergo the aforementioned pre-crosslinking surface treatment to ensure uniform and robust dispersion within the resin matrix, thereby maximizing their respective functional properties and reducing microscopic defects caused by filler-resin interface incompatibility, constructing a dense and reliable physicochemical barrier.

[0015] II. A high-temperature resistant, flame-retardant, and heat-insulating coating, comprising the following components by weight: The resin base system consists of 30-40 parts, which includes a bifunctional modified resin, an epoxy silicone resin and an aqueous styrene-acrylic emulsion compounded in a mass ratio of 1:1.5-2:1. 6-10 parts of interface strengthening and filler treatment agent, which includes epoxy silane coupling agent and titanate coupling agent compounded in a mass ratio of 1:1-1.5; 35-45 parts of pre-crosslinked composite filler, including glass powder, hollow glass microspheres, melamine-coated ammonium polyphosphate, zinc borate and nano silica, and the composite filler is pre-crosslinked surface treated with a composite coupling agent and a bifunctional modified resin. The additive system consists of 21-31 parts, including 5-7 parts of crosslinking agent, 12-18 parts of solvent, 3-5 parts of interface promoter, and 4-6 parts of other additives. The bifunctional modified resin is a polymer prepared by graft copolymerization of glycidyl methacrylate and γ-aminopropyltriethoxysilane with epoxy silicone resin as the matrix.

[0016] Preferably, the preparation method of the bifunctional modified resin includes: dissolving 100 parts by weight of epoxy silicone resin in a solvent, and adding dropwise a mixed monomer consisting of 15-20 parts of glycidyl methacrylate and 10-15 parts of γ-aminopropyltriethoxysilane over 1.5-2 hours at 80-85°C in the presence of an initiator, followed by reacting at 85-90°C for 3-4 hours.

[0017] Preferably, in the resin base system, the mass ratio of styrene to butyl acrylate monomer in the aqueous styrene-acrylic emulsion is 1:1.6-1.8.

[0018] Preferably, in the composite filler, glass powder accounts for 20-30%, hollow glass microspheres account for 25-30%, melamine-coated ammonium polyphosphate accounts for 20-25%, zinc borate accounts for 15-20%, and nano-silica accounts for 5-10%. The pre-crosslinking surface treatment conditions are as follows: at 50-60℃, the filler is blended with 1-2% of its mass of a composite coupling agent and 10-20% of the total amount of bifunctional modified resin in the coating for 3-4 hours.

[0019] Preferably, the crosslinking agent is a compound of aziridine crosslinking agent and hexamethylenediamine in a mass ratio of 1:0.5-0.8; the solvent is a mixture of butyl acetate, anhydrous ethanol and xylene in a mass ratio of 2:1:0.5.

[0020] Preferably, the other additives include leveling agents, defoamers, flash rust inhibitors, and anti-aging agents.

[0021] A method for preparing a high-temperature resistant, flame-retardant, and heat-insulating coating as described above includes the following steps: (1) Preparation of pre-crosslinked modified composite filler: Weigh each filler according to the ratio, add 1-2% of the total mass of the composite coupling agent and 10-20% of the total amount of bifunctional modified resin in the coating formulation, disperse at high speed at 50-60℃ and heat treat for 3-4 hours, and dry for later use. (2) Preparation of resin matrix: Mix the remaining bifunctional modified resin, epoxy silicone resin, waterborne styrene-acrylic emulsion and interface promoter, and stir evenly. (3) Mixing and grinding: Add the pre-crosslinked modified composite filler obtained in step (1) to the resin matrix obtained in step (2), mix initially, and then transfer to a grinding equipment to disperse to a fineness ≤50μm; (4) Curing: Add crosslinking agent, other additives and solvent to the slurry obtained in step (3), stir at low speed at 45-55℃ for 1.5-2 hours, and filter to obtain the finished coating.

[0022] A method for applying the above-described high-temperature resistant, flame-retardant, and heat-insulating coating to the surface of a metal substrate includes the following steps: (a) Substrate treatment: Rust removal, cleaning and drying of the metal surface; (b) Coating application: After stirring the coating evenly, apply it to the surface of the treated substrate, and control the total dry film thickness to be 200-300μm; (c) Curing: After pre-curing at room temperature, heat to cure at 80-120℃ for 2-4 hours.

[0023] The present invention provides a high-temperature resistant, flame-retardant, and heat-insulating coating, its preparation method, and its application, which have the following beneficial effects: (1) It fundamentally solves the problem of weak interfacial bonding between the coating and the metal substrate: By constructing a triple synergistic interfacial strengthening system of "reactive resin coordination anchoring, composite coupling agent chemical bridging, and pre-crosslinked filler physical interlocking", a strong, hydrolysis-resistant, and thermally decomposition-resistant gradient transition interface is formed between the metal substrate and the organic coating. This design essentially overcomes the problems of blistering, peeling, and delamination failure that traditional coatings are prone to under long-term high temperature and severe thermal cycling conditions, and achieves super strong and long-lasting adhesion to the substrate.

[0024] (2) Achieving efficient synergy between high temperature resistance, thermal insulation, and flame retardancy: By integrating the high temperature resistant resin matrix with the pre-crosslinked surface-treated gradient functional filler, not only is the physicochemical stability of the coating ensured under long-term high-temperature service conditions, but it also endows the coating with excellent thermal insulation performance and outstanding flame retardant safety. This system effectively solves the technical contradiction between improving the functionality of the coating and ensuring long-term durability.

[0025] (3) A multifunctional integrated long-lasting composite protection system has been constructed: This invention successfully integrates multiple protective functions such as high-efficiency heat insulation, excellent flame retardancy, corrosion resistance and weather resistance into a single coating system. A reliable physical and chemical barrier is constructed through a dense cross-linked network and a strong filler-resin interface, which significantly improves the comprehensive protective durability of the coating in complex and harsh environments such as high temperature, corrosion, humid heat and thermal cycling, and provides an integrated long-lasting protection solution for high-temperature metal equipment. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] To address the aforementioned technical problems, this invention provides a high-temperature resistant, flame-retardant, and heat-insulating coating, its preparation method, and its application, thereby resolving the issues raised in the background section.

[0028] I. Experimental Materials and Equipment (1) Raw materials: Epoxy silicone resin (epoxy value 0.12 eq / 100g, solid content 70%), glycidyl methacrylate (GMA, industrial grade, purity ≥96%), γ-aminopropyltriethoxysilane (KH-550, industrial grade), benzoyl peroxide (BPO, chemically pure), xylene (industrial grade), anhydrous ethanol (industrial grade).

[0029] Aqueous styrene-acrylic emulsion (Acronal® S 400, styrene-acrylic ratio 1:1.7, solid content 48%).

[0030] Epoxy silane coupling agent (KH-560, industrial grade), monoalkoxy titanate coupling agent (NDZ-201, industrial grade).

[0031] Glass powder (softening point 380℃, D50=8μm), hollow glass microspheres (3M K1, true density 0.25 g / cm³, D50=12μm), melamine-coated ammonium polyphosphate (APP-105, D50=5μm), zinc borate (ZB-2335, D50=3μm), fumed silica nanoparticles (AEROSIL 200, specific surface area 200 m² / g).

[0032] Crosslinking agent (aziridine crosslinking agent CX-100, hexamethylenediamine), mixed solvent (butyl acetate, anhydrous ethanol, xylene), interface promoter (diethylenetriamine, chemically pure), leveling agent (BYK-333), defoamer (BYK-066N), flash rust inhibitor (a mixture of sodium nitrite and sodium benzoate in a 1:1 mass ratio), anti-aging agent (benzotriazole).

[0033] Base material: Q235 steel plate (150mm × 70mm × 5mm).

[0034] (2) Equipment: Reaction apparatus: four-necked flask, constant temperature water bath, mechanical stirrer, condenser, dropping funnel.

[0035] Dispersion and mixing equipment: high-speed disperser, basket mill.

[0036] Coating equipment: Precision coater (scraper).

[0037] Curing and testing environment: forced-air drying oven, constant temperature and humidity chamber.

[0038] Testing equipment: adhesion cross-cut tester, peel strength tester, thermal conductivity tester (transient plane heat source method), limiting oxygen index tester, ultraviolet aging test chamber, etc.

[0039] II. Preparation of Key Components 2.1 Preparation of Bifunctional Modified Resin (denoted as Resin M) In a four-necked flask equipped with a stirring, condensing, temperature measuring, and dropping device, add 100 parts of epoxy silicone resin and 50 parts of xylene, stir, and heat to 83±2℃. Add 0.5 parts of benzoyl peroxide (BPO), and keep warm and stir for 30 minutes to fully dissolve and activate the initiator.

[0040] 18 parts glycidyl methacrylate (GMA) and 12 parts γ-aminopropyltriethoxysilane (KH-550) were premixed and uniformly added to the reaction system over 1.8 hours using a constant-pressure dropping funnel. After the addition was complete, the system was heated to 88±2℃ and the reaction continued for 3.5 hours. After the reaction was completed, the temperature was lowered to 60℃, and 5 parts anhydrous ethanol were added for dilution. After stirring evenly, the product was discharged to obtain a pale yellow viscous liquid, which is the bifunctional modified resin M.

[0041] 2.2 Preparation of pre-crosslinked modified composite filler (denoted as filler P) Weigh out the following fillers according to the following mass percentages: 25% glass powder, 28% hollow glass microspheres, 22% melamine-coated ammonium polyphosphate, 18% zinc borate, and 7% fumed nano silica, totaling 40 parts. Add the mixed fillers to a high-speed dispersion vessel, then add 0.8 parts of the composite coupling agent (KH-560:NDZ-201 = 1:1.2, mass ratio), 8 parts of the resin M prepared in step 2.1 (equivalent to 20% of the total planned amount of resin M), and 10 parts of the mixed solvent (butyl acetate: anhydrous ethanol = 2:1) as a carrier.

[0042] The material was dispersed at 3500 rpm for 40 minutes to ensure uniformity. The slurry was then transferred to a 55℃ oven and allowed to stand for 3.5 hours to allow for complete coupling and pre-crosslinking reactions. After treatment, the material was dried in an 80℃ forced-air drying oven to constant weight, then pulverized and passed through a 200-mesh sieve to obtain a pre-crosslinked modified composite filler P with good flowability.

[0043] III. Preparation of Coatings in Examples and Comparative Cases All coatings are prepared according to the following general steps: (1) Resin matrix preparation: Add various resins (including resin M, epoxy silicone resin, waterborne styrene-acrylic emulsion) and interface promoter diethylenetriamine required for the resin matrix system into the mixing tank, and stir at 1200 rpm for 90 minutes to form a uniform and stable blended resin matrix.

[0044] (2) Filler mixing and wetting: The specified amount of pre-crosslinked modified composite filler P is slowly added to the above resin matrix. First, stir at a low speed of 800 rpm for 40 minutes to ensure that the filler particles are fully wetted and coated by the resin liquid.

[0045] (3) Grinding and dispersion: The preliminarily mixed slurry is transferred to a basket mill (the medium is zirconia beads with a particle size of 1.0-1.2 mm) for grinding and dispersion for a total of 120 minutes. The temperature of the grinding system is controlled to be below 45℃.

[0046] (4) Curing and paint mixing: After grinding to the required standard (fineness ≤50μm), remove the slurry. Add the crosslinking agent (aziridine crosslinking agent CX-100 and hexamethylenediamine in a 1:0.6 ratio), other additives (leveling agent BYK-333, defoamer BYK-066N, anti-flash rust agent, anti-aging agent), and the remaining mixed solvent (butyl acetate, anhydrous ethanol, and xylene in a 2:1:0.5 ratio). Place the paint mixing tank in a 50℃ water bath and cure at a low speed of 700 rpm for 120 minutes.

[0047] (5) Filtration and packaging: The matured coating is filtered through a 250-mesh filter to obtain the finished coating.

[0048] The specific formulations (by weight) of each embodiment and comparative example are shown in Table 1.

[0049] Table 1: Coating Formulations for Examples and Comparative Examples

[0050] Note: Comparative Example 1: No bifunctional modified resin M and composite coupling agent were used; the resin base consisted only of epoxy silicone resin and styrene-acrylic emulsion, but pre-crosslinked filler P was used. Comparative Example 2: The same original mixed filler as in Example 1 was used, but without pre-crosslinking treatment (denoted as P*). Comparative Example 3: No bifunctional modified resin M was used; only the composite coupling agent was used; M in the resin base was replaced by an equal amount of epoxy silicone resin, and pre-crosslinked filler P was used.

[0051] IV. Coating and Curing Process Substrate pretreatment: All Q235 steel plates were sandblasted to a cleanliness level of Sa2.5, with a surface roughness Ra≈4.5μm. They were then wiped clean with acetone and dried at 80℃ for 30 minutes before use.

[0052] Coating application: A precision applicator (scraper) is used to evenly apply the coating to the surface of the steel plate, controlling the wet film thickness.

[0053] Curing and maintenance: After surface drying for 4 hours at 23±2℃ and 50±5% humidity, the sample was transferred to a 100℃ forced-air oven for curing for 3 hours. The final dry film thickness was controlled at 220±20μm.

[0054] V. Performance Testing and Results The coating samples of Examples 1-3 and Comparative Examples 1-3 were tested, and the results are shown in Table 2.

[0055] Table 2: Coating performance test results

[0056] VI. Results Analysis The experimental data in Table 2 fully verify that the present invention systematically solves the problems of weak interfacial bonding and difficulty in synergistically combining heat insulation and flame retardant functions with durability in high-temperature resistant coatings through the design of a three-level synergistic system of "resin base material system - interface strengthening and filler treatment agent - pre-crosslinking functional filler".

[0057] (1) Regarding interfacial bonding strength and durability: Comparative Example 1 (without bifunctional resin M and composite coupling agent) had extremely poor initial adhesion, low wet peel strength, and completely detached after thermal cycling, indicating that the system lacking interfacial reinforcement design was extremely fragile. Comparative Example 3 (using only composite coupling agent, without bifunctional resin M) showed improved performance, but it was far from reaching the level of the examples, proving that the effect of small molecule coupling agents is limited. Examples 1-3, relying on the triple synergistic interfacial reinforcement strategy of "coordination anchoring, chemical bridging, and physical interlocking", maintained the best adhesion and a wet peel strength of over 2.8 N / mm after various stringent tests, demonstrating excellent interfacial durability.

[0058] (2) Regarding thermal insulation and flame retardant performance: The thermal conductivity of Comparative Example 2 (filler without pre-crosslinking treatment) was significantly higher than that of the Example, and the corrosion resistance also decreased, indicating that simple physical mixing led to defects at the filler-resin interface, affecting the performance of thermal insulation and barrier functions. Examples 1-3 constructed a robust "filler-resin" composite structure through pre-crosslinking treatment of the filler, achieving a thermal conductivity as low as 0.029-0.032 W / (m·K) and a limiting oxygen index of over 30%, synergistically achieving efficient thermal insulation and excellent flame retardancy.

[0059] (3) Regarding long-term high temperature resistance and comprehensive protective performance: The coating of the example remained intact after long-term aging at 300℃ and exhibited excellent chemical resistance and UV aging resistance. This is due to the synergistic design of the entire formulation system (high temperature resistant resin, gradient functional filler, dense cross-linked network) and excellent interfacial stability.

[0060] Conclusion: The high-temperature resistant, flame-retardant, and heat-insulating coating provided in this embodiment of the invention achieves superior interfacial bonding, excellent heat insulation and flame-retardant performance, and outstanding long-term protective durability through the synergistic effect of multiple methods, including bifunctional modified resin interface strengthening technology, gradient composite filler pre-crosslinking treatment, and high-temperature resistant resin system compounding. Its comprehensive performance is significantly better than that of existing technical solutions, and it fully meets the stringent protection requirements of high-temperature metal equipment.

[0061] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A high-temperature resistant, flame-retardant, and heat-insulating coating, characterized in that, By weight, it includes the following components: The resin base system consists of 30-40 parts, which includes a bifunctional modified resin, an epoxy silicone resin and an aqueous styrene-acrylic emulsion compounded in a mass ratio of 1:1.5-2:

1. 6-10 parts of interface strengthening and filler treatment agent, which includes epoxy silane coupling agent and titanate coupling agent compounded in a mass ratio of 1:1-1.5; 35-45 parts of pre-crosslinked composite filler, including glass powder, hollow glass microspheres, melamine-coated ammonium polyphosphate, zinc borate and nano silica, and the composite filler is pre-crosslinked surface treated with a composite coupling agent and a bifunctional modified resin. The additive system consists of 21-31 parts, including 5-7 parts of crosslinking agent, 12-18 parts of solvent, 3-5 parts of interface promoter, and 4-6 parts of other additives. The bifunctional modified resin is a polymer prepared by graft copolymerization of glycidyl methacrylate and γ-aminopropyltriethoxysilane with epoxy silicone resin as the matrix.

2. The high-temperature resistant, flame-retardant, and heat-insulating coating according to claim 1, characterized in that, The preparation method of the bifunctional modified resin includes: dissolving 100 parts by weight of epoxy silicone resin in a solvent, and adding a mixed monomer consisting of 15-20 parts of glycidyl methacrylate and 10-15 parts of γ-aminopropyltriethoxysilane dropwise over 1.5-2 hours at 80-85°C in the presence of an initiator, followed by reacting at 85-90°C for 3-4 hours.

3. The high-temperature resistant, flame-retardant, and heat-insulating coating according to claim 1, characterized in that, In the resin base system, the mass ratio of styrene to butyl acrylate monomer in the aqueous styrene-acrylic emulsion is 1:1.6-1.

8.

4. The high-temperature resistant, flame-retardant, and heat-insulating coating according to claim 1, characterized in that, In the composite filler, glass powder accounts for 20-30%, hollow glass microspheres account for 25-30%, melamine-coated ammonium polyphosphate accounts for 20-25%, zinc borate accounts for 15-20%, and nano-silica accounts for 5-10%. The pre-crosslinking surface treatment conditions are as follows: at 50-60℃, the filler is blended with 1-2% of its mass of a composite coupling agent and 10-20% of the total amount of bifunctional modified resin in the coating for 3-4 hours.

5. The high-temperature resistant, flame-retardant, and heat-insulating coating according to claim 1, characterized in that, The crosslinking agent is a compound of aziridine crosslinking agent and hexamethylenediamine in a mass ratio of 1:0.5-0.8; the solvent is a mixture of butyl acetate, anhydrous ethanol and xylene in a mass ratio of 2:1:0.

5.

6. The high-temperature resistant, flame-retardant, and heat-insulating coating according to claim 1, characterized in that, The other additives include leveling agents, defoamers, flash rust inhibitors, and anti-aging agents.

7. A method for preparing a high-temperature resistant, flame-retardant, and heat-insulating coating as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Preparation of pre-crosslinked modified composite filler: Weigh each filler according to the ratio, add 1-2% of the total mass of the composite coupling agent and 10-20% of the total amount of bifunctional modified resin in the coating formulation, disperse at high speed at 50-60℃ and heat treat for 3-4 hours, and dry for later use. (2) Preparation of resin matrix: Mix the remaining bifunctional modified resin, epoxy silicone resin, waterborne styrene-acrylic emulsion and interface promoter, and stir evenly. (3) Mixing and grinding: Add the pre-crosslinked modified composite filler obtained in step (1) to the resin matrix obtained in step (2), mix initially, and then transfer to a grinding equipment to disperse to a fineness ≤50μm; (4) Curing: Add crosslinking agent, other additives and solvent to the slurry obtained in step (3), stir at low speed at 45-55℃ for 1.5-2 hours, and filter to obtain the finished coating.

8. A method for applying the high-temperature resistant, flame-retardant, and heat-insulating coating according to any one of claims 1-6 to the surface protection of a metal substrate, characterized in that, Includes the following steps: (a) Substrate treatment: Rust removal, cleaning and drying of the metal surface; (b) Coating application: After stirring the coating evenly, apply it to the surface of the treated substrate, and control the total dry film thickness to be 200-300μm; (c) Curing: After pre-curing at room temperature, heat to cure at 80-120℃ for 2-4 hours.

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