Composite fireproof coating based on resin modification and preparation method thereof

Abstract

The invention discloses a composite fireproof coating based on resin modification and a preparation method thereof, and belongs to the technical field of coatings, the coating comprises the following raw materials in parts by weight: a component A: 20-30 parts of water, 10-12 parts of a curing agent, 10-15 parts of modified aerogel powder and 24-30 parts of a flame retardant; the component B comprises 20 parts of water-borne epoxy resin emulsion, 5-10 parts of boric acid ester modified epoxy resin and 1-2 parts of a coalescing agent; the modified aerogel powder is cellulose ether modified carbon nanotube doped silicon dioxide aerogel. In the coating, a tough organic cross-linked network is constructed by boric acid ester modified epoxy resin, and meanwhile, modified aerogel powder is used as a high-performance inorganic filler. And the two components generate a synergistic enhancement effect through an organic-inorganic hybridization technology, so that the impact resistance of the coating is remarkably improved, the coating can bear a harsh physical environment and mechanical stress, and the service life of the coating is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a resin-modified composite fire-retardant coating and its preparation method. Background Technology

[0002] Fire-retardant coatings, also known as flame-retardant coatings, are special coatings applied to the surface of combustible substrates. They significantly reduce the flammability of the coated material, inhibit the rapid spread of fire, and improve its fire resistance. In addition to basic fire-retardant functions, these coatings typically also provide protection, decoration, and corrosion protection. Currently, most fire-retardant coatings on the market are made from various resins or emulsions as base materials, supplemented with pigments, additives, fillers, and other functional additives. They are widely used in steel chimneys, high-temperature pipelines, high-temperature furnace shells, petroleum cracking units, and high-temperature environments such as tanks and artillery. They effectively slow down the thermal oxidation and corrosion process of steel and other metal equipment under high-temperature environments, thereby ensuring the long-term stable operation of the equipment.

[0003] Although fire-retardant coatings are widely used in many fields, and there are numerous technical reports on their heat resistance, existing products, while generally meeting basic fire resistance requirements, still have several significant shortcomings in practical applications. Firstly, driven by environmental trends, while water-based fire-retardant coatings have reduced volatile organic compound (VOC) emissions to some extent, their surface drying time is typically longer. During application and curing, they are susceptible to contamination from environmental dust and other factors, directly affecting the final film's appearance and decorative effect, and potentially slowing down the application process. Secondly, from a deeper environmental and safety perspective, to improve corrosion resistance and inhibition, some traditional solvent-based and even some water-based fire-retardant coatings still frequently use hexavalent chromium and other heavy metal compounds as corrosion inhibitors. These substances can pose significant hazards to the environment and human health during coating production, use, and disposal. In addition, water-based systems themselves bring new technical challenges. Some existing water-based fire retardant coatings are still insufficient in terms of film density, adhesion, and long-term durability under continuous high temperature conditions. Their comprehensive protective performance, especially the synergistic effect between flame retardant properties and temperature resistance and corrosion resistance, is often inferior to that of traditional solvent-based coatings, which limits their long-term application in more demanding environments.

[0004] In summary, existing fire-retardant coatings, especially environmentally friendly water-based systems, still have significant shortcomings in terms of surface drying speed, overall environmental friendliness, and resistance to high and low temperatures. There is an urgent need to develop new fire-retardant coatings to meet the development needs of high-end equipment manufacturing and industrial facilities for long service life, low maintenance, and green environmental protection. Summary of the Invention

[0005] The purpose of this invention is to provide a resin-modified composite fire-retardant coating and its preparation method to solve the problem of poor overall protective performance of water-based fire-retardant coatings.

[0006] The objective of this invention can be achieved through the following technical solutions: The first aspect of this application provides a resin-modified composite fire-retardant coating, comprising the following raw materials in parts by weight: Component A: 20-30 parts water, 10-12 parts curing agent, 10-15 parts modified aerogel powder, and 24-30 parts flame retardant; Component B: 20 ​​parts waterborne epoxy resin emulsion, 5-10 parts borate ester modified epoxy resin, and 1-2 parts film-forming aid; the modified aerogel powder is cellulose ether modified carbon nanotube doped silica aerogel.

[0007] In some possible implementations, borate ester modified epoxy resins are prepared via the following steps: A boron-containing modifier is added to N,N-dimethylformamide and tetrahydrofuran, followed by the addition of an aqueous epoxy resin emulsion. The mixture is stirred at 85-87°C for 4-5 hours, and then dried to remove the remaining solvent, yielding a boron ester-modified epoxy resin. A reflux condenser is used in the above reaction process, allowing the epoxy groups to react with the B-OH groups in the boron-containing modifier, introducing B-O bonds into the structure of the boron ester-modified epoxy resin.

[0008] In some possible implementations, the mass ratio of boron-containing modifier, waterborne epoxy resin emulsion, N,N-dimethylformamide, and tetrahydrofuran is 5-6:30:10:40. The epoxy equivalent of the waterborne epoxy resin emulsion is between 400 and 1100.

[0009] In some possible implementations, the boron-containing modifier is prepared by the following steps: Under nitrogen protection, 4-aldehyde phenylboronic acid and 3,5-diamino-1,2,4-triazole were added to ethanol and stirred at 80℃ for 7-9 h. After the reaction was completed, the mixture was hot-filtered, and the filtrate was evaporated to dryness to obtain the crude product. The crude product was recrystallized from ethanol and dried under vacuum at 60-80℃ to obtain the boron-containing modifier. The boron-containing modifier (an aromatic Schiff base containing diboronic acid and triazole structures) is synthesized by the Schiff base reaction of 4-aldehyde phenylboronic acid with the aldehyde group and the amino group of 3,5-diamino-1,2,4-triazole. Introducing the B-O bond into the molecular structure of epoxy resin can greatly improve the heat resistance of the resin.

[0010] Boron-containing modifiers are reactive crosslinking agents with good char-forming ability and thermal stability, promoting char formation of the coating during combustion. The boric acid structure in the boron-containing modifier and the boron and nitrogen provided by the triazole can form a synergistic flame-retardant effect with the added flame retardant.

[0011] In some possible implementations, the molar ratio of 4-aldehyde phenylboronic acid and 3,5-diamino-1,2,4-triazole is 2:1.

[0012] In some possible implementations, the flame retardant includes ammonium polyphosphate, pentaerythritol, and melamine; wherein the mass ratio of the ammonium polyphosphate, pentaerythritol, and melamine is 3:1:2.

[0013] In some possible implementations, the epoxy equivalent of the waterborne epoxy resin emulsion is between 400 and 1100. The curing agent used is an amine-based curing agent with an active hydrogen equivalent of 300 to 600.

[0014] In some possible implementations, the doping amount of the cellulose ether modified carbon nanotubes is 8% to 12% of the total mass of the modified aerogel powder.

[0015] In some possible implementations, modified silica aerogel powder is prepared by the following steps: Ethanol, water, tetraethyl orthosilicate, and cellulose ether-modified carbon nanotubes were stirred and mixed, ultrasonically dispersed, and then hydrochloric acid was added to adjust the pH to 1.5-2. The mixture was stirred for 2-3 hours, and then ammonia was added to adjust the pH to 7. The mixture was aged at 65℃ for 12-16 hours to obtain a gel. Ethanol was evaporated at room temperature, and then the gel was freeze-dried under vacuum at -70℃ to -50℃. After pulverization, the modified aerogel was obtained.

[0016] In some possible implementations, the mass ratio of ethanol, water, and tetraethyl orthosilicate is 4:1:10.

[0017] In some possible implementations, cellulose ether-modified carbon nanotubes are prepared via the following steps: Multi-walled carbon nanotubes and an acidic solution were mixed and ultrasonically dispersed, stirred at 35-45℃ for 1-2 hours, and then separated, washed with water and dried to obtain oxidized multi-walled carbon nanotubes. Oxidized multi-walled carbon nanotubes and cellulose ether were added to an aqueous ethanol solution and stirred at 35-45℃ for 24-48 hours. After the reaction was completed, the cellulose ether-modified carbon nanotubes were obtained by separation, washing with water and drying.

[0018] In some possible implementations, the acidic solution is at least one of sulfuric acid and nitric acid; the ratio of multi-walled carbon nanotubes to the acidic solution is 0.1 g: 10 mL; the acidic solution is a mixture of 65% nitric acid and 98% sulfuric acid in a volume ratio of 1:1. The mass ratio of oxidized multi-walled carbon nanotubes to cellulose ether is 1:3-4, the volume fraction of the ethanol aqueous solution is 70%-80%, and the volume ratio of cellulose ether to ethanol aqueous solution is 1g:200mL.

[0019] In some possible implementations, the cellulose ether is one of hydroxypropyl methylcellulose or hydroxypropyl cellulose. In this invention, modified aerogel powder is prepared by introducing cellulose ether-modified carbon nanotubes into the aerogel powder preparation process. The cellulose ether-modified carbon nanotubes are formed by physically adsorbing and coating the carbon nanotubes onto their surface. Cellulose ether is hydrophilic, and carbon nanotubes are hydrophobic, creating an amphiphilic material. During the aerogel powder preparation process, the azo carbon nanotubes treated with cellulose ether are fully dispersed in the gel, forming a uniform system and fully utilizing the supporting role of the carbon nanotubes, avoiding insufficient gel strength due to the dispersion of carbon nanotubes. Simultaneously, the hydroxyl groups in the cellulose ether form connections with the silica network, further enhancing the bonding strength between the carbon nanotubes and the silica aerogel network, forming a new network structure, and improving the toughness and crack resistance of the silica aerogel. Cellulose ether itself is a carbon source; in the presence of a charring agent and an acid source, cellulose and carbon nanotubes can act as carbon sources, supporting silica, improving heat resistance, and forming a synergistic flame-retardant effect.

[0020] The second aspect of this application provides a method for preparing a resin-modified composite fire-retardant coating, comprising the following steps: Component A is obtained by mixing water, curing agent, modified aerogel powder and flame retardant; Component B is obtained by mixing waterborne epoxy resin emulsion, borate ester modified epoxy resin and film-forming aid evenly; Component A and Component B are mixed evenly to obtain a resin-modified composite fireproof coating.

[0021] The beneficial effects of this invention are: This invention provides a resin-modified composite fire-retardant coating, in which modified aerogel powder and borate-modified epoxy resin are added. The borate-modified epoxy resin constructs a strong and tough organic cross-linked network, while the modified aerogel powder serves as a high-performance inorganic filler. The two components produce a synergistic reinforcing effect through organic-inorganic hybrid technology, significantly improving the coating's impact resistance, enabling it to withstand harsher physical environments and mechanical stresses, and extending the coating's service life.

[0022] The composite fire-retardant coating provided by this invention incorporates silicon (Si) and boron (B) as key flame-retardant elements in the modified aerogel powder and boron ester modified epoxy resin, respectively. At high temperatures, silicon helps form a stable and continuous silicate glassy protective layer, while boron promotes the formation of a dense, high-strength boronate-carbon composite char layer. Together with other flame retardants in the system, they produce a significant "boron-silicon synergistic flame-retardant effect," effectively delaying flame spread and reducing heat release rate, while greatly improving the strength, density, and thermal stability of the residual char layer, thus achieving more durable and effective thermal insulation protection for the substrate.

[0023] The composite fire-retardant coating provided by this invention successfully introduces BO bonds into the polymer skeleton through borate-modified epoxy resin. These bonds have higher bond energies than traditional C-C and CO bonds, endowing the cured coating with excellent thermal stability and resistance to high and low temperatures. This makes the coating less prone to decomposition and pulverization under long-term alternating high and low temperature environments, while maintaining good toughness even at low temperatures. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] The following is a detailed description of a resin-modified composite fire-retardant coating and its preparation method according to an embodiment of this application.

[0026] In the following examples and comparative examples, the waterborne epoxy resin emulsions have an epoxy resin solid content of 55% and an epoxy equivalent of 500 g / eq; the epoxy emulsion curing agent is an amine-based curing agent. The solid content is 68%, and the active hydrogen equivalent is 300 g / eq; both are commercially available products.

[0027] The following is a detailed description with reference to specific examples.

[0028] Example 1 This embodiment provides a resin-modified composite fire-retardant coating, and the preparation steps are as follows: Component A is obtained by mixing 20 parts water, 10 parts curing agent, 10 parts modified aerogel powder and 24 parts flame retardant according to weight; Component B is obtained by mixing 20 parts waterborne epoxy resin emulsion, 5 parts borate ester modified epoxy resin and 1 part film-forming aid evenly. At 60°C, component A and component B are mixed uniformly to obtain a resin-modified composite fire-retardant coating.

[0029] The flame retardant includes ammonium polyphosphate, pentaerythritol, and melamine; the mass ratio of ammonium polyphosphate, pentaerythritol, and melamine is 3:1:2; the film-forming aid is ethylene glycol butyl ether. The borate ester modified epoxy resin is prepared through the following steps: Under nitrogen protection, 4-aldehyde phenylboronic acid and 3,5-diamino-1,2,4-triazole were added to ethanol and stirred at 80°C for 7 hours. After the reaction was completed, the mixture was hot-filtered, and the filtrate was evaporated to dryness to obtain the crude product. The crude product was recrystallized from ethanol and dried under vacuum at 60°C to obtain the boron-containing modifier. The molar ratio of 4-aldehyde phenylboronic acid to 3,5-diamino-1,2,4-triazole was 2:1.

[0030] A boron-containing modifier was added to N,N-dimethylformamide and tetrahydrofuran, followed by the addition of an aqueous epoxy resin emulsion. The mixture was stirred at 85°C for 4 hours, and the remaining solvent was removed by drying to obtain a borate-modified epoxy resin. The mass ratio of the boron-containing modifier, aqueous epoxy resin emulsion, N,N-dimethylformamide, and tetrahydrofuran was 5:30:10:40.

[0031] The modified silica aerogel powder is prepared through the following steps: Multi-walled carbon nanotubes were mixed and ultrasonically dispersed with an acidic solution, stirred at 35°C for 2 hours, and then separated, washed with water, and dried to obtain oxidized multi-walled carbon nanotubes. Oxidized multi-walled carbon nanotubes and cellulose ether were added to an ethanol-water solution and stirred at 35°C for 48 hours. After the reaction, the mixture was separated, washed with water, and dried to obtain cellulose ether-modified carbon nanotubes. The ratio of multi-walled carbon nanotubes to acidic solution was 0.1 g: 10 mL; the acidic solution was a mixture of 65% nitric acid and 98% sulfuric acid at a volume ratio of 1:1; the mass ratio of oxidized multi-walled carbon nanotubes to cellulose ether was 1:3; the volume fraction of the ethanol-water solution was 70%; and the ratio of cellulose ether to ethanol-water solution was 1 g: 200 mL; the cellulose ether was hydroxypropyl methylcellulose.

[0032] Ethanol, water, tetraethyl orthosilicate, and cellulose ether-modified carbon nanotubes were stirred and mixed, ultrasonically dispersed, and then hydrochloric acid was added to adjust the pH to 1.5. Stirring was continued for 2 hours, and then ammonia was added to adjust the pH to 7. The mixture was aged at 65°C for 12 hours to obtain a gel. Ethanol was evaporated at room temperature, and then the gel was freeze-dried under vacuum at -50°C. After pulverization, the modified aerogel was obtained. The doping amount of the cellulose ether-modified carbon nanotubes was 8% of the total mass of the modified aerogel powder; the mass ratio of ethanol, water, and tetraethyl orthosilicate was 4:1:10.

[0033] Example 2 This embodiment provides a resin-modified composite fire-retardant coating, and the preparation steps are as follows: Component A is obtained by mixing 25 parts water, 11 parts curing agent, 12 parts modified aerogel powder and 28 parts flame retardant according to weight; Component B is obtained by mixing 20 parts waterborne epoxy resin emulsion, 8 parts borate ester modified epoxy resin and 2 parts film-forming aid evenly. At 60°C, component A and component B are mixed uniformly to obtain a resin-modified composite fire-retardant coating.

[0034] The flame retardant, film-forming aid, borate ester modified epoxy resin, and modified silica aerogel powder are the same as in Example 1.

[0035] Example 3 This embodiment provides a resin-modified composite fire-retardant coating, and the preparation steps are as follows: Component A is obtained by mixing 30 parts water, 12 parts curing agent, 15 parts modified aerogel powder and 30 parts flame retardant according to weight; Component B is obtained by mixing 20 parts waterborne epoxy resin emulsion, 10 parts borate ester modified epoxy resin and 2 parts film-forming aid evenly. At 60°C, component A and component B are mixed uniformly to obtain a resin-modified composite fire-retardant coating.

[0036] The flame retardant, film-forming aid, borate ester modified epoxy resin, and modified silica aerogel powder are the same as in Example 1.

[0037] Example 4 This embodiment provides a resin-modified composite fire-retardant coating, and the preparation steps are as follows: Component A is obtained by mixing 20 parts water, 10 parts curing agent, 12 parts modified aerogel powder and 24 parts flame retardant according to weight; Component B is obtained by mixing 20 parts waterborne epoxy resin emulsion, 5 parts borate ester modified epoxy resin and 1 part film-forming aid evenly. At 60°C, component A and component B are mixed uniformly to obtain a resin-modified composite fire-retardant coating.

[0038] The flame retardant, film-forming aid, borate ester modified epoxy resin, and modified silica aerogel powder are the same as in Example 1.

[0039] Example 5 This embodiment provides a resin-modified composite fire-retardant coating, and the preparation steps are as follows: Component A is obtained by mixing 20 parts water, 10 parts curing agent, 15 parts modified aerogel powder and 24 parts flame retardant according to weight; Component B is obtained by mixing 20 parts waterborne epoxy resin emulsion, 5 parts borate ester modified epoxy resin and 1 part film-forming aid evenly. At 60°C, component A and component B are mixed uniformly to obtain a resin-modified composite fire-retardant coating.

[0040] The flame retardant, film-forming aid, borate ester modified epoxy resin, and modified silica aerogel powder are the same as in Example 1.

[0041] Example 6 The difference between this embodiment and Example 1 lies in the preparation conditions of the modified silica aerogel powder: Oxidized multi-walled carbon nanotubes (same as in Example 1) and cellulose ether were added to an ethanol-water solution and stirred at 35°C for 48 hours. After the reaction, the nanotubes were separated, washed with water, and dried to obtain cellulose ether-modified carbon nanotubes. The ratio of multi-walled carbon nanotubes to acidic solution was 0.1 g: 10 mL; the acidic solution was a mixture of 65% nitric acid and 98% sulfuric acid at a volume ratio of 1:1; the mass ratio of oxidized multi-walled carbon nanotubes to cellulose ether was 1:4; the volume fraction of the ethanol-water solution was 70%; and the ratio of cellulose ether to ethanol-water solution was 1 g: 200 mL; the cellulose ether was hydroxypropyl methylcellulose.

[0042] Ethanol, water, tetraethyl orthosilicate, and cellulose ether-modified carbon nanotubes were stirred and mixed, ultrasonically dispersed, and then hydrochloric acid was added to adjust the pH to 1.5. Stirring was continued for 2 hours, and then ammonia was added to adjust the pH to 7. The mixture was aged at 65°C for 12 hours to obtain a gel. Ethanol was evaporated at room temperature, and then the gel was freeze-dried under vacuum at -50°C. After pulverization, the modified aerogel was obtained. The doping amount of the cellulose ether-modified carbon nanotubes was 8% of the total mass of the modified aerogel powder; the mass ratio of ethanol, water, and tetraethyl orthosilicate was 4:1:10.

[0043] The remaining raw materials and preparation process are the same as in Example 1.

[0044] Example 7 The difference between this embodiment and Example 1 lies in the preparation conditions of the modified silica aerogel powder: Oxidized multi-walled carbon nanotubes (same as in Example 1) and cellulose ether were added to an ethanol-water solution and stirred at 35°C for 48 hours. After the reaction, the nanotubes were separated, washed with water, and dried to obtain cellulose ether-modified carbon nanotubes. The ratio of multi-walled carbon nanotubes to acidic solution was 0.1 g: 10 mL; the acidic solution was a mixture of 65% nitric acid and 98% sulfuric acid at a volume ratio of 1:1; the mass ratio of oxidized multi-walled carbon nanotubes to cellulose ether was 1:3, the volume fraction of the ethanol-water solution was 70%, and the ratio of cellulose ether to ethanol-water solution was 1 g: 200 mL; the cellulose ether was hydroxypropyl methylcellulose.

[0045] Ethanol, water, tetraethyl orthosilicate, and cellulose ether-modified carbon nanotubes were stirred and mixed, ultrasonically dispersed, and then hydrochloric acid was added to adjust the pH to 1.5. Stirring was continued for 2 hours, and then ammonia was added to adjust the pH to 7. The mixture was aged at 65°C for 12 hours to obtain a gel. Ethanol was evaporated at room temperature, and then the gel was freeze-dried under vacuum at -50°C. After pulverization, the modified aerogel was obtained. The doping amount of the cellulose ether-modified carbon nanotubes was 12% of the total mass of the modified aerogel powder; the mass ratio of ethanol, water, and tetraethyl orthosilicate was 4:1:10.

[0046] The remaining raw materials and preparation process are the same as in Example 1.

[0047] Example 8 The difference between this embodiment and Example 1 lies in the preparation conditions of the borate ester modified epoxy resin: A boron-containing modifier (same as in Example 1) was added to N,N-dimethylformamide and tetrahydrofuran, followed by the addition of an aqueous epoxy resin emulsion. The mixture was stirred at 85°C for 4 hours, and the remaining solvent was removed by drying to obtain a borate ester modified epoxy resin. The mass ratio of the boron-containing modifier, aqueous epoxy resin emulsion, N,N-dimethylformamide, and tetrahydrofuran was 6:30:10:40.

[0048] The remaining raw materials and preparation process are the same as in Example 1.

[0049] Comparative Example 1 The difference between this comparative example and Example 1 lies in the use of different modified silica aerogel powders, specifically: Ethanol, water, tetraethyl orthosilicate, and oxidized multi-walled carbon nanotubes (same as in Example 1) were stirred and mixed, ultrasonically dispersed, and then hydrochloric acid was added to adjust the pH to 1.5. Stirring was continued for 2 hours, and then ammonia was added to adjust the pH to 7. The mixture was aged at 65°C for 12 hours to obtain a gel. Ethanol was evaporated at room temperature, and then the gel was freeze-dried under vacuum at -50°C. After pulverization, the modified aerogel was obtained. The doping amount of the oxidized multi-walled carbon nanotubes was 12% of the total mass of the modified aerogel powder; the mass ratio of ethanol, water, and tetraethyl orthosilicate was 4:1:10.

[0050] The remaining raw materials and preparation process are the same as in Example 1.

[0051] Comparative Example 2 The difference between this comparative example and Example 1 lies in the use of different modified silica aerogel powders, specifically: Ethanol, water, and tetraethyl orthosilicate were stirred and mixed, then ultrasonically dispersed. Hydrochloric acid was added to adjust the pH to 1.5, and stirring continued for 2 hours. Ammonia was added to adjust the pH to 7, and the mixture was aged at 65°C for 12 hours to obtain a gel. Ethanol was evaporated at room temperature, and the gel was then freeze-dried under vacuum at -50°C. After pulverization, the modified aerogel was obtained. The mass ratio of ethanol, water, and tetraethyl orthosilicate was 4:1:10.

[0052] The remaining raw materials and preparation process are the same as in Example 1.

[0053] Comparative Example 3 The difference between this comparative example and Example 1 lies in the amount of modified aerogel powder used. Specifically, this comparative example provides a resin-modified composite fire-retardant coating, and the preparation steps are as follows: Component A is obtained by mixing 20 parts water, 10 parts curing agent, 5 parts modified aerogel powder and 24 parts flame retardant according to weight; Component B is obtained by mixing 20 parts waterborne epoxy resin emulsion, 5 parts borate ester modified epoxy resin and 1 part film-forming aid evenly. At 60°C, component A and component B are mixed uniformly to obtain a resin-modified composite fire-retardant coating.

[0054] The flame retardant, film-forming aid, borate ester modified epoxy resin, and modified silica aerogel powder are the same as in Example 1.

[0055] The remaining raw materials and preparation process are the same as in Example 1.

[0056] Comparative Example 4 The difference between this comparative example and Example 1 is that borate ester modified epoxy resin is not added. Specifically, this comparative example provides a resin-modified composite fire-retardant coating, and the preparation steps are as follows: Component A is obtained by mixing 20 parts water, 10 parts curing agent, 10 parts modified aerogel powder and 24 parts flame retardant according to weight; Component B is obtained by mixing 25 parts waterborne epoxy resin emulsion and 1 part film-forming aid evenly. At 60°C, component A and component B are mixed uniformly to obtain a resin-modified composite fire-retardant coating.

[0057] The remaining raw materials and preparation process are the same as in Example 1.

[0058] Comparative Example 5 Compared with Example 1, this comparative example does not add borate-modified epoxy resin, and the aerogel powder is replaced with the modified aerogel powder prepared in Comparative Example 2. Specifically, this comparative example provides a resin-modified composite fire-retardant coating, and the preparation steps are as follows: According to the weight, 20 parts of water, 10 parts of curing agent, 10 parts of modified aerogel powder (prepared in Comparative Example 2) and 24 parts of flame retardant are mixed to obtain component A; 25 parts of waterborne epoxy resin emulsion and 1 part of film-forming aid are mixed evenly to obtain component B. At 60°C, component A and component B are mixed uniformly to obtain a resin-modified composite fire-retardant coating.

[0059] The remaining raw materials and preparation process are the same as in Example 1.

[0060] Test case Performance tests were conducted on Examples 1-8 and Comparative Examples 1-5: Impact resistance: Tested according to GB / T1732-2020; Charcoal layer strength: The test was conducted using a compressive bending tester. A 60mm×60mm charcoal layer was cut from the middle of the charcoal layer after the fire resistance test using a utility knife, placed on the compressive bending tester, and tested at a downward pressure speed of 5mm / min. The strength value was recorded. Thermal cycling test: Place the coated test plate at room temperature (23±2℃) for 18 hours, then refrigerate it in a low-temperature chamber for 3 hours (-20±2℃). After that, remove the test piece and store it in a constant temperature chamber for 3 hours (50±2℃). Repeat the above operation 15 times. The coating is considered qualified if there is no cracking or peeling. At least 2 out of 3 test pieces must be qualified.

[0061] The coating thickness was 0.5-0.6 mm. The coating performance was tested, and the test results are shown in Table 1 below: Table 1 According to Table 1, in conjunction with the comparison of Example 1 and Comparative Examples 1-3, it can be seen that the modified aerogel powder in this invention has a significant impact on impact resistance. In Comparative Example 1, modified aerogel was prepared using unmodified carbon nanotubes. Due to the poor dispersibility of carbon nanotubes in the gel system, their supporting role was difficult to achieve, resulting in insufficient impact resistance of the coating and indirectly affecting the strength of the char layer after combustion. In Comparative Example 2, the aerogel powder without added carbon nanotubes was brittle, and the impact resistance of the coating and the strength of the char layer after burning were also poor. In Comparative Example 3, the proportion of modified aerogel powder was too small to fully utilize its function.

[0062] As shown in Example 1 and Comparative Examples 4-5, the borate-modified epoxy resin in this invention mainly affects the high and low temperature resistance of the coating. In Comparative Example 4, replacing the borate-modified epoxy resin with untreated epoxy resin resulted in a decrease in high and low temperature resistance. According to Comparative Example 5, there is a certain synergistic effect between the modified aerogel powder and the borate-modified epoxy resin. This is because the modified aerogel powder and the borate-modified epoxy resin produce a synergistic reinforcement effect through organic-inorganic hybrid technology, which significantly improves the impact resistance of the coating, enabling it to withstand more severe physical environments and mechanical stresses, and extending the service life of the coating. During combustion, the borate-modified epoxy resin can decompose and produce borates (such as B2O3), which melt at high temperatures, flow and cover the silica skeleton and carbon particles, playing a "bonding" and "sealing" role, thus producing a significant "boron-silicon synergistic flame retardant effect". This not only effectively slows down the spread of flame and reduces the heat release rate, but also greatly improves the strength, density and thermal stability of the residual char layer, thereby achieving more durable and effective heat insulation protection for the substrate.

[0063] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A resin-modified composite fire-retardant coating, characterized in that, The raw materials include the following parts by weight: Component A: 20-30 parts water, 10-12 parts curing agent, 10-15 parts modified aerogel powder, and 24-30 parts flame retardant; Component B: 20 ​​parts waterborne epoxy resin emulsion, 5-10 parts borate ester modified epoxy resin, and 1-2 parts film-forming aid; the modified aerogel powder is cellulose ether modified carbon nanotube doped silica aerogel.

2. The resin-modified composite fire-retardant coating according to claim 1, characterized in that, Boronate-modified epoxy resin is prepared by the following steps: Add a boron-containing modifier to the solvent, then add an aqueous epoxy resin emulsion. Stir at 85-87℃ for 4-5 hours, and dry to remove the remaining solvent to obtain a boron ester modified epoxy resin. The mass ratio of boron-containing modifier, aqueous epoxy resin emulsion and solvent is 5-6:30:

50.

3. The resin-modified composite fire-retardant coating according to claim 2, characterized in that, The boron-containing modifier is prepared by the following steps: Under nitrogen protection, 4-aldehyde phenylboronic acid and 3,5-diamino-1,2,4-triazole were added to ethanol and stirred at 80°C for 7-9 hours. After the reaction was completed, the mixture was hot-filtered, and the filtrate was evaporated to dryness to obtain the crude product. The crude product was recrystallized from ethanol and dried under vacuum at 60-80°C to obtain the boron-containing modifier. The molar ratio of 4-aldehyde phenylboronic acid to 3,5-diamino-1,2,4-triazole was 2:

1.

4. The resin-modified composite fire-retardant coating according to claim 1, characterized in that, The flame retardant includes ammonium polyphosphate, pentaerythritol and melamine; the mass ratio of the ammonium polyphosphate, pentaerythritol and melamine is 3:1:

2.

5. The resin-modified composite fire-retardant coating according to claim 1, characterized in that, The amount of cellulose ether modified carbon nanotubes added is 8% to 12% of the total mass of the modified aerogel powder.

6. The resin-modified composite fire-retardant coating according to claim 1, characterized in that, Modified silica aerogel powder is prepared through the following steps: Ethanol, water, tetraethyl orthosilicate, and cellulose ether-modified carbon nanotubes were stirred and mixed, ultrasonically dispersed, and then hydrochloric acid was added to adjust the pH to 1.5-2. The mixture was stirred for 2-3 hours, and then ammonia was added to adjust the pH to 7. The mixture was aged at 65℃ for 12-16 hours to obtain a gel. Ethanol was evaporated at room temperature, and then the gel was freeze-dried under vacuum at -70℃ to -50℃. After pulverization, the modified aerogel was obtained.

7. The resin-modified composite fire-retardant coating according to claim 6, characterized in that, The mass ratio of ethanol, water and tetraethyl orthosilicate is 4:1:

10.

8. The resin-modified composite fire-retardant coating according to claim 6, characterized in that, Cellulose ether-modified carbon nanotubes are prepared through the following steps: Oxidized multi-walled carbon nanotubes and cellulose ether were added to an aqueous ethanol solution and stirred at 35-45℃ for 24-48 hours. After the reaction was completed, the cellulose ether-modified carbon nanotubes were obtained by separation, washing with water and drying.

9. A resin-modified composite fire-retardant coating according to claim 8, characterized in that, The cellulose ether is one of hydroxypropyl methylcellulose and hydroxypropyl cellulose; the mass ratio of oxidized multi-walled carbon nanotubes to cellulose ether is 1:3-4.

10. A method for preparing a resin-modified composite fire-retardant coating, used to prepare the resin-modified composite fire-retardant coating according to any one of claims 1-9, characterized in that, Includes the following steps: Component A is obtained by mixing water, curing agent, modified aerogel powder and flame retardant; Component B is obtained by mixing waterborne epoxy resin emulsion, borate ester modified epoxy resin and film-forming aid evenly; Component A and Component B are mixed evenly to obtain a resin-modified composite fireproof coating.

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