Waterproof flame-retardant aerogel thermal insulation paste and preparation method thereof

Abstract

The invention relates to the field of aerogel, and particularly discloses waterproof flame-retardant aerogel thermal insulation paste and a preparation method thereof.The aerogel thermal insulation paste is prepared from, by weight, 90-110 parts of heat-resistant and aging-resistant styrene-acrylic emulsion, 60-80 parts of thermal insulation filler, 20-40 parts of flame retardant, 0.5-1.5 parts of dispersing agent, 0.5-2 parts of thickening agent and 20-40 parts of deionized water. The aerogel thermal insulation paste is prepared by the following steps: carrying out flame-retardant hydrophobic modification on silicon dioxide aerogel; by optimizing a core-shell structure, a cross-linked network and organic silicon of the styrene-acrylic emulsion, the effects of water resistance, flame retardance, heat preservation and the like are efficiently achieved.

Description

Technical Field

[0001] This invention belongs to the field of aerogels, specifically relating to a waterproof and flame-retardant aerogel insulation paste and its preparation method. Background Technology

[0002] Aerogels, as ultralight solid materials with nanoporous structures, are widely used in building energy conservation, aerospace, new energy battery insulation, and industrial pipeline insulation due to their low density, high porosity, and excellent thermal insulation properties. However, traditional aerogel materials face multiple challenges in practical applications: First, the easy aggregation and poor dispersibility of nanoparticles lead to insufficient material uniformity and reduced overall performance; second, the inherent brittleness of the aerogel skeleton results in insufficient mechanical properties, making it prone to breakage under stress; third, hydrophilic aerogels are susceptible to humidity, leading to structural collapse and decreased thermal insulation performance.

[0003] To address the aforementioned limitations, researchers have focused on developing composite aerogel materials. For example, patent CN104556969B proposes a method for preparing a hydrophobic silica aerogel thermal insulation composite material: using siloxane as a precursor, silica sol is prepared via a sol-gel method, then combined with inorganic fibers, and finally, a block composite material is obtained through solvent displacement and drying. The resulting material maintains a low thermal conductivity while possessing overall waterproofness (contact angle >150°). However, this technology is limited to pre-formed components, and its application is very difficult for complex structures with irregular shapes, dense pipelines, or requiring seamless filling. Considering the issue of construction flexibility, patent CN103589258B improves construction flexibility by mixing aerogel particles and binders into a flowable form that can be applied or sprayed. However, the added organic binder has problems such as poor heat resistance and easy aging, which limits the application of aerogel materials.

[0004] Based on the advancements in composite aerogel materials mentioned in the aforementioned patents, this invention aims to provide a composite aerogel material that can simultaneously achieve waterproof, flame-retardant, and heat-insulating functions. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention modifies silica aerogel to be flame-retardant and hydrophobic; simultaneously, it optimizes the core-shell structure, cross-linking network, and organosilicon of styrene-acrylic emulsion to make the emulsion heat-resistant and aging-resistant. The combination of these two methods yields an insulating paste that uses silica aerogel as the core insulating filler and a heat-resistant and aging-resistant styrene-acrylic emulsion as a binder, effectively achieving waterproofing, flame retardancy, and thermal insulation functions.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides a waterproof and flame-retardant gel insulation paste, which, by weight, comprises the following raw materials: 90-110 parts of heat-resistant and aging-resistant styrene-acrylic emulsion, 60-80 parts of insulation filler, 20-40 parts of flame retardant, 0.5-1.5 parts of dispersant, 0.5-2 parts of thickener, and 20-40 parts of deionized water.

[0007] This invention selects silica aerogel powder with a nanoporous structure as the core insulation filler to provide a low thermal conductivity insulation body, and uses an aqueous polymer emulsion as a binder to improve the environmental friendliness and weather resistance of the aerogel. Regarding waterproofing, the aqueous polymer emulsion provides excellent water resistance after film formation, and the silane coupling agent surface treatment of the aerogel powder also imparts excellent surface hydrophobic properties.

[0008] In some embodiments, the preparation steps of the thermal insulation filler are as follows: Pour a mixture of water and ethanol into the vacuum-dried silica aerogel powder, then add polyethyleneimine and stir for 4-6 hours at 200-300 rpm. Filter to obtain wet powder. Heat-treat the wet powder in air at 120-150℃ for 2-3 hours, then soak, stir, and wash. Filter, transfer to n-hexane, add hexamethyldisilazane, and reflux at 40-60℃ for 6-8 hours. Filter, wash, and vacuum dry to obtain the thermal insulation filler.

[0009] In some embodiments, the particle size of the silica aerogel powder is <50 μm.

[0010] This invention utilizes the high porosity and adsorption properties of aerogels to impregnate polyethyleneimine into its nanopores, introduce nitrogen-based flame-retardant elements, and then react them with silanol groups through heat treatment to achieve chemical bonding and prevent the loss of flame retardants. After flame-retardant modification, a silanization reaction is used to graft hydrophobic groups onto the aerogel surface, achieving superhydrophobicity.

[0011] In some embodiments, the preparation steps of the heat-resistant and aging-resistant styrene-acrylic emulsion are as follows: S1. Deionized water, reactive emulsifier, high glass transition temperature reactive monomer, and acrylonitrile are stirred at 1500-2000 rpm for 15-20 min to obtain a core phase pre-emulsion. S2. Stir deionized water, reactive emulsifier, low glass transition temperature reactive monomer, acrylic acid, and functional monomer at 1500-2000 rpm for 15-20 min to obtain shell phase preemulsion. S3. At 78-85℃, deionized water, reactive emulsifier, and sodium bicarbonate are stirred at 200-300 rpm for 10-20 min. Then, 3-8% of the total mass of the core phase preemulsion and initiator solution are added, and the mixture is stirred for 20-30 min. The remaining core phase preemulsion and initiator solution are then added simultaneously over 2.5-3 h. After the addition is complete, the shell phase preemulsion and initiator solution obtained in S2 are added simultaneously over 1.5-2.5 h. After all materials have been added, the temperature is raised to 80-90℃ and maintained for 0.5-1.5 h to obtain a crude emulsion. S4. Cool the crude emulsion to below 60°C, add tert-butyl hydrogen peroxide aqueous solution and ascorbic acid aqueous solution in sequence, stir for 10-20 minutes, then cool to room temperature, adjust the pH value to 7.5-8.5, and then add defoamer to obtain heat-resistant and aging-resistant styrene-acrylic emulsion.

[0012] In some embodiments, in step S1, the high glass transition temperature reactive monomer comprises styrene and methyl methacrylate.

[0013] In some embodiments, in step S2, the low glass transition temperature reactive monomer is butyl acrylate.

[0014] In some embodiments, in step S2, the functional monomer comprises N-hydroxymethylacrylamide and vinyltriethoxysilane.

[0015] This heat- and aging-resistant styrene-acrylic emulsion achieves a performance balance through a soft-shell, hard-core structure. Styrene and methyl methacrylate serve as the core layer, imparting high initial hardness, strength, and heat resistance to the emulsion particles. Butyl acrylate acts as the shell layer, encapsulating the hard core and providing flexibility and film-forming properties, improving coating and adhesion with aerogel solid fillers. The introduction of the crosslinking monomer N-hydroxymethylacrylamide during synthesis allows it to form a three-dimensional network structure during film formation and post-curing, enhancing the material's heat resistance and mechanical strength.

[0016] In terms of aging resistance systems, methyl methacrylate, which is more resistant to ultraviolet light, is selected to replace part of the styrene, thus slowing down yellowing; at the same time, cyano groups, which have excellent heat resistance, oil resistance, and aging resistance, are introduced. In addition, the silicon-oxygen bond energy of the functional monomer vinyltriethoxysilane is much higher than that of the carbon-carbon bond, and it has excellent heat resistance, ultraviolet resistance, and hydrophobicity. It can also play a role in internal crosslinking and surface modification in emulsion polymerization.

[0017] In some embodiments, the reactive emulsifier contains double bonds.

[0018] Preferably, the reactive emulsifier is allyloxynonylphenol polyoxyethylene ether ammonium sulfate.

[0019] Reactive emulsifiers permanently bond to the surface of latex particles through polymerizable double bonds, improving the mechanical, chemical, and freeze-thaw stability of the emulsion and reducing performance degradation caused by the migration of small molecule emulsifiers.

[0020] In some embodiments, the flame retardant comprises expanded graphite and aluminum hydroxide.

[0021] In some embodiments, the mass ratio of expanded graphite to aluminum hydroxide is 1:(0.8-1.5).

[0022] This invention employs a synergistic flame-retardant system. Expanded graphite can foam to form a dense carbon layer when heated, which isolates heat and oxygen. The inorganic flame-retardant filler aluminum hydroxide absorbs heat and releases water vapor when decomposed, which plays a role in cooling and diluting flammable gases. At the same time, silica aerogel itself is a non-flammable inorganic material, which also contributes to the flame retardancy.

[0023] Another aspect of the present invention provides a method for preparing the above-mentioned aerogel heat-insulating paste, the specific steps of which are as follows: (1) Dry the insulation filler and flame retardant for later use; (2) Mix deionized water and dispersant evenly under stirring at 200-400 rpm to obtain a liquid matrix; (3) Adjust the stirring speed to 300-500 rpm, add flame retardant to the liquid matrix in 3-4 batches, and after adding, increase the speed to 600-800 rpm and stir until the powder is completely dispersed; then reduce the speed back to 300-400 rpm, add the heat insulation filler, stir for 30-40 minutes to form a paste. (4) Keep stirring, add heat-resistant and aging-resistant styrene-acrylic emulsion to the paste and stir for 20-30 minutes, then add thickener and stir for 10-30 minutes; discharge, seal and package, and age at room temperature for more than 24 hours to obtain aerogel heat preservation paste.

[0024] The preparation process of this aerogel insulation paste follows the principle of "premixing first, then integrating, and slow stirring at low speed to prevent damage" in order to protect the nanoporous structure of the aerogel.

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1. This thermal insulation paste uses silica aerogel as the core insulating filler, supplemented by heat-resistant and aging-resistant styrene-acrylic emulsion, achieving efficient waterproofing, flame retardancy, and thermal insulation functions. Regarding flame retardancy: It achieves environmentally friendly and high flame retardancy efficiency through the synergistic combination of expanded graphite insulating against heat and oxygen, aluminum hydroxide cooling and dilution, and nitrogen-based flame-retardant elements introduced by the silica aerogel. Regarding waterproofing: It achieves hydrophobicity through silane coupling agent surface treatment of the aerogel powder, while the silicon-oxygen bonds introduced by the styrene-acrylic emulsion also contribute to hydrophobicity; the synergistic hydrophobicity of these two components achieves durable hydrophobicity from the inside out. Regarding thermal insulation performance: It uses nanoporous silica aerogel powder as the low thermal conductivity insulating material.

[0026] 2. Addressing the issues of poor heat resistance and easy aging inherent in conventional organic adhesives, this invention utilizes a core-shell structure, a cross-linking network, and the introduction of organosilicon to enable the styrene-acrylic emulsion to withstand higher temperatures, preventing it from becoming sticky, softening, or degrading due to high temperatures. The combination of acrylic acid, acrylonitrile, and methyl methacrylate enhances the insulation paste's resistance to UV aging, preventing powdering, yellowing, and cracking with long-term use, thus extending the lifespan of the insulation system. Simultaneously, the soft shell in the core-shell structure better encapsulates and bonds aerogel particles, enhancing adhesion and compatibility. Furthermore, the ethoxy group of vinyltriethoxysilane can react with the silanol groups on the aerogel surface to form strong chemical bonds, significantly improving the coating's cohesive strength and water resistance.

[0027] 3. The use of reactive emulsifiers containing double bonds gives the emulsion excellent mechanical and storage stability, making it less prone to demulsification when mixed with high-powder materials such as aerogels. Furthermore, the reactive emulsifier can be permanently bonded to the surface of latex particles through double bonds, reducing performance degradation caused by the migration of small molecule emulsifiers. Detailed Implementation

[0028] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0029] It is worth noting that, unless otherwise specified, the raw materials used in the following preparation examples and embodiments are all from any commercially available manufacturer: polyethyleneimine (PEI), Mw=800; allyloxynonylphenol polyoxyethylene ether ammonium sulfate, model DNS-86.

[0030] Preparation Example 1 The preparation steps of heat-resistant and aging-resistant styrene-acrylic emulsion A are as follows: S1. Stir 40g deionized water, 1.6g reactive emulsifier DNS-86, 70g styrene, 30g methyl methacrylate, and 10g acrylonitrile at 1800±100rpm for 18±2min to obtain a core phase preemulsion. S2. Stir 30g deionized water, 1.2g reactive emulsifier, 60g butyl acrylate, 4g acrylic acid, 4g N-hydroxymethylacrylamide, and 6g vinyltriethoxysilane at 1800±100rpm for 18±2min to obtain a shell-phase preemulsion. S3. At 80±2℃, 40g of deionized water, 0.4g of reactive emulsifier, and 0.2g of sodium bicarbonate were stirred at 250±20rpm for 15±2min. Then, 5% of the total mass of the core phase preemulsion and 6.8g of ammonium persulfate solution (concentration 2wt%) were added, and the mixture was stirred for 25±2min. Then, within 2.7±0.3h, the remaining core phase preemulsion and 9.6g of ammonium persulfate solution (concentration 2wt%) were added simultaneously. After the addition was complete, within 2±0.2h, the shell phase preemulsion obtained in S2 and 4g of ammonium persulfate solution (concentration 2wt%) were added simultaneously. After all materials were added, the temperature was raised to 85±2℃ and kept at this temperature for 1±0.2h to obtain a crude emulsion. S4. Cool the crude emulsion to below 60℃, add 10g of tert-butyl hydrogen peroxide aqueous solution (concentration of 2wt%) and 10g of ascorbic acid aqueous solution (concentration of 2wt%) in sequence, stir for 15±2min, then cool to room temperature, adjust the pH value to 8±0.2 with ammonia water, and then add 0.4g of defoamer BYK-024 to obtain heat-resistant and aging-resistant styrene-acrylic emulsion A.

[0031] Preparation Example 2 The preparation steps of the heat-resistant and aging-resistant styrene-acrylic emulsion B differ from those in Preparation Example 2 in that step S2 is adjusted as follows: S2. Stir 30g deionized water, 1.2g reactive emulsifier DNS-86, 60g butyl acrylate, 8g acrylic acid, and 6g vinyltriethoxysilane at 1800±100rpm for 18±2min to obtain a shell-phase pre-emulsion.

[0032] Preparation Example 3 The preparation steps of the heat-resistant and aging-resistant styrene-acrylic emulsion C differ from those in Preparation Example 2 in that step S2 is adjusted as follows: S2. Stir 30g deionized water, 1.2g reactive emulsifier DNS-86, 60g butyl acrylate, 10g acrylic acid, and 4g N-hydroxymethylacrylamide at 1800±100rpm for 18±2min to obtain a shell phase preemulsion.

[0033] Preparation Example 4 The preparation steps of heat-resistant and aging-resistant styrene-acrylic emulsion D are as follows: S1. Stir 70g deionized water, 2.8g reactive emulsifier DNS-86, 100g styrene, 20g methyl methacrylate, 10g acrylonitrile, 14g acrylic acid, 4g N-hydroxymethylacrylamide, and 6g vinyltriethoxysilane at 1800±100rpm for 18±2min to obtain a pre-emulsion. S2. At 80±2℃, 40g of deionized water, 0.4g of reactive emulsifier, and 0.2g of sodium bicarbonate were stirred at 250±20rpm for 15±2min. Then, 5% of the total mass of pre-emulsion and 6.8g of ammonium persulfate solution (concentration of 2wt%) were added, and the mixture was stirred for 25±2min. Then, the remaining pre-emulsion and 13.6g of ammonium persulfate solution (concentration of 2wt%) were added simultaneously over 4±0.3h. After all materials were added, the temperature was raised to 85±2℃ and kept at that temperature for 1±0.2h to obtain crude emulsion. S3. Cool the crude emulsion to below 60℃, add 10g of tert-butyl hydrogen peroxide aqueous solution (concentration of 2wt%) and 10g of ascorbic acid aqueous solution (concentration of 2wt%) in sequence, stir for 15±2min, then cool to room temperature, adjust the pH value to 8±0.2 with ammonia water, and then add 0.4g of defoamer BYK-024 to obtain heat-resistant and aging-resistant styrene-acrylic emulsion D.

[0034] Preparation Example 5 The preparation steps for thermal insulation filler A are as follows: 100g of vacuum-dried silica aerogel powder (particle size 40-50μm) was poured into 500mL of a 1:1 mixture of water and ethanol, and then 20g of polyethyleneimine was added. The mixture was stirred at 250±20rpm for 5±0.5h, filtered, and wet powder was obtained. The wet powder was heat-treated in air at 130±10℃ for 2.5±0.2h, cooled, and then immersed in anhydrous ethanol. The powder was stirred and washed three times, 1h each time. The powder was filtered, transferred to 400mL of n-hexane, and 30mL of hexamethyldisilazane was added. The mixture was refluxed at 50±5℃ for 7±0.2h, filtered, washed, and vacuum dried to obtain thermal insulation filler A.

[0035] Preparation Example 6 The preparation steps for thermal insulation filler B are as follows: 100g of vacuum-dried silica aerogel powder (particle size 40-50μm) was poured into 500mL of a 1:1 mixture of water and ethanol, and then 20g of polyethyleneimine was added. The mixture was stirred at 250±20rpm for 5±0.5h, filtered, and wet powder was obtained. The wet powder was heat-treated in air at 130±10℃ for 2.5±0.2h, cooled, and then immersed in anhydrous ethanol. The powder was stirred and washed three times, 1h each time. The powder was then filtered, washed, and vacuum-dried to obtain thermal insulation filler B.

[0036] Preparation Example 7 The preparation steps for thermal insulation filler C are as follows: 400 mL of n-hexane was poured into 100 g of vacuum-dried silica aerogel powder (particle size 40-50 μm), and 30 mL of hexamethyldisilazane was added. The mixture was refluxed at 50±5 °C for 7±0.2 hours. After filtration, washing, and vacuum drying, the thermal insulation filler C was obtained.

[0037] Example 1 A waterproof and flame-retardant gel insulation paste, by weight, comprises the following raw materials: 100 parts of heat-resistant and aging-resistant styrene-acrylic emulsion A, 70 parts of insulation filler A, 30 parts of flame retardant (15 parts of expanded graphite and 15 parts of aluminum hydroxide), 1 part of dispersant - BASFDISPEX® Ultra PX 4575, 1.2 parts of thickener - Dow Chemical ASE-60, and 30 parts of deionized water.

[0038] The preparation method of the waterproof and flame-retardant gel insulation paste in this embodiment specifically includes the following steps: (1) Dry the thermal insulation filler A and flame retardant for later use; (2) Under stirring at 300 rpm, deionized water and dispersant were mixed evenly to obtain a liquid matrix; (3) Adjust the stirring speed to 400 rpm, add flame retardant to the liquid matrix in three equal batches, and after adding, increase the speed to 700 rpm and stir until the powder is completely dispersed; then reduce the speed back to 350 rpm, add the heat insulation filler, stir for 35 minutes to form a paste. (4) Keep stirring, add heat-resistant and aging-resistant styrene-acrylic emulsion A to the paste and stir for 25 minutes, then add thickener and stir for 20 minutes; discharge, seal and package, and age at room temperature for more than 24 hours to obtain aerogel heat preservation paste.

[0039] Example 2 A waterproof and flame-retardant gel insulation paste, by weight, comprises the following raw materials: 90 parts of heat-resistant and aging-resistant styrene-acrylic emulsion A, 60 parts of insulation filler A, 20 parts of flame retardant (12 parts of expanded graphite and 8 parts of aluminum hydroxide), 0.5 parts of dispersant - BASF DISPEX® Ultra PX 4575, 0.5 parts of thickener - Dow Chemical ASE-60, and 20 parts of deionized water.

[0040] The preparation method of the waterproof and flame-retardant gel insulation paste in this embodiment specifically includes the following steps: (1) Dry the thermal insulation filler A and flame retardant for later use; (2) Under stirring at 200 rpm, deionized water and dispersant were mixed evenly to obtain a liquid matrix; (3) Adjust the stirring speed to 300 rpm, add flame retardant to the liquid matrix in three equal batches, and after adding, increase the speed to 600 rpm and stir until the powder is completely dispersed; then reduce the speed back to 300 rpm, add the heat insulation filler, stir for 40 minutes to form a paste. (4) Keep stirring, add heat-resistant and aging-resistant styrene-acrylic emulsion A to the paste and stir for 20 minutes, then add thickener and stir for 10 minutes; discharge, seal and package, and age at room temperature for more than 24 hours to obtain aerogel heat preservation paste.

[0041] Example 3 A waterproof and flame-retardant gel insulation paste, by weight, comprises the following raw materials: 110 parts of heat-resistant and aging-resistant styrene-acrylic emulsion A, 80 parts of insulation filler A, 40 parts of flame retardant (18 parts of expanded graphite and 22 parts of aluminum hydroxide), 1.5 parts of dispersant - BASFDISPEX® Ultra PX 4575, 2 parts of thickener - Dow Chemical ASE-60, and 40 parts of deionized water.

[0042] The preparation method of the waterproof and flame-retardant gel insulation paste in this embodiment specifically includes the following steps: (1) Dry the thermal insulation filler A and flame retardant for later use; (2) Under stirring at 400 rpm, deionized water and dispersant were mixed evenly to obtain a liquid matrix; (3) Adjust the stirring speed to 500 rpm, add the flame retardant to the liquid matrix in four equal batches, and after adding the flame retardant, increase the stirring speed to 800 rpm and stir until the powder is completely dispersed; then reduce the stirring speed back to 400 rpm, add the heat insulation filler, stir for 30 minutes to form a paste. (4) Keep stirring, add heat-resistant and aging-resistant styrene-acrylic emulsion A to the paste and stir for 30 minutes, then add thickener and stir for 30 minutes; discharge, seal and package, and age at room temperature for more than 24 hours to obtain aerogel heat preservation paste.

[0043] Example 4 This embodiment provides a waterproof and flame-retardant gel thermal insulation paste and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that the heat-resistant and aging-resistant styrene-acrylic emulsion A is replaced by an equal part of heat-resistant and aging-resistant styrene-acrylic emulsion B.

[0044] Example 5 This embodiment provides a waterproof and flame-retardant gel thermal insulation paste and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that the heat-resistant and aging-resistant styrene-acrylic emulsion A is replaced by an equal part of heat-resistant and aging-resistant styrene-acrylic emulsion C.

[0045] Example 6 This embodiment provides a waterproof and flame-retardant gel thermal insulation paste and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that the heat-resistant and aging-resistant styrene-acrylic emulsion A is replaced by an equal part of heat-resistant and aging-resistant styrene-acrylic emulsion D.

[0046] Example 7 This embodiment provides a waterproof and flame-retardant gel insulation paste and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that the insulation filler A is replaced by an equal amount of insulation filler B.

[0047] Example 8 This embodiment provides a waterproof and flame-retardant gel insulation paste and its preparation method. The specific implementation method is the same as that in Embodiment 1, except that the insulation filler A is replaced by an equal amount of insulation filler C.

[0048] Performance testing: 1. Flame retardant performance test: Refer to GB 8624-2012 "Classification of Combustion Performance of Building Materials and Products", the combustion performance levels from high to low are A1, A2, B1, B2, B3.

[0049] 2. Water absorption rate test: Make the thermal insulation paste into a 300mm×300mm×300mm test block, soak it in water for 24 hours, and measure the percentage of water absorbed to dry weight. The lower the value, the better the waterproof performance.

[0050] 3. Water contact angle test: Use a contact angle measuring instrument to measure the angle formed between the droplet and the solid surface.

[0051] 4. Thermal insulation performance test: Prepare two flat plate-shaped specimens of thermal insulation paste, each 300mm×300mm×100mm, and measure their thermal conductivity. The lower the thermal conductivity, the better the thermal insulation performance.

[0052] 5. Heat resistance and aging resistance test: Place the test plate coated with heat-insulating paste in a xenon lamp aging test chamber (irradiance 0.51W / m²). 2 @340nm, light exposure time 102min, chamber temperature 38±3℃, relative humidity 50±5%), after taking it out, check whether the coating has cracked, chalked, discolored or other phenomena. The grades from best to worst are 0, 1, 2, 3, 4, 5.

[0053] The results are shown in Table 1.

[0054] Table 1 In Table 1, the thermal insulation pastes of Examples 1-3 have a flame retardant rating of A1 (non-combustible); a water absorption rate of less than 3% and a water contact angle of >120° (high hydrophobicity), demonstrating excellent waterproof performance; a thermal conductivity of 0.025-0.030 W / (m·K), which is better than most traditional thermal insulation materials; and a cracking, chalking, and discoloration rating of 0, with no cracking, chalking, or discoloration, indicating that the polymer emulsion exhibits excellent heat resistance and aging resistance.

[0055] Compared to Example 1, the styrene-acrylic emulsions used in Examples 4-5 had N-hydroxymethylacrylamide and vinyltriethoxysilane removed during preparation. The former weakened the three-dimensional cross-linked network, resulting in reduced heat and aging resistance. Although no cracking or powdering occurred, slight discoloration was observed. The latter, with its missing siloxane groups, led to a decrease in the emulsion's heat and aging resistance. Simultaneously, the water absorption rate of the thermal insulation paste changed to <5%, and the water contact angle was >90° (hydrophobic). Although slightly reduced, it still maintained a waterproof effect. Compared to Example 1, the core-shell structure of the latex particles in the styrene-acrylic emulsion of Example 6 had a smaller impact on the flame retardant effect and heat and aging resistance of the aerogel thermal insulation paste; however, the water absorption rate increased, possibly because the absence of the soft shell in the core-shell structure led to a decrease in the adhesion and compatibility between the binder and the aerogel particles.

[0056] Compared to Example 1, Example 7 only modified the aerogel powder with flame retardancy, resulting in a decrease in waterproofing effect and slight cracking and powdering under high humidity. Example 8 only modified the powder with waterproofing, resulting in a decrease in flammability.

[0057] The embodiments described above do not limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A waterproof and flame-retardant gel insulation paste, characterized in that, By weight, it contains the following raw materials: 90-110 parts of heat-resistant and aging-resistant styrene-acrylic emulsion, 60-80 parts of thermal insulation filler, 20-40 parts of flame retardant, 0.5-1.5 parts of dispersant, 0.5-2 parts of thickener, and 20-40 parts of deionized water.

2. The waterproof and flame-retardant gel insulation paste according to claim 1, characterized in that, The preparation steps of the thermal insulation filler are as follows: Pour a mixture of water and ethanol into the vacuum-dried silica aerogel powder, then add polyethyleneimine and stir for 4-6 hours at 200-300 rpm. Filter to obtain wet powder. Heat-treat the wet powder in air at 120-150℃ for 2-3 hours, then soak, stir, and wash. Filter, transfer to n-hexane, add hexamethyldisilazane, and reflux at 40-60℃ for 6-8 hours. Filter, wash, and vacuum dry to obtain the thermal insulation filler.

3. The waterproof and flame-retardant gel insulation paste according to claim 2, characterized in that, The particle size of the silica aerogel powder is <50μm.

4. The waterproof and flame-retardant gel insulation paste according to claim 1, characterized in that, The preparation steps of the heat-resistant and aging-resistant styrene-acrylic emulsion are as follows: S1. Stir deionized water, reactive emulsifier, high glass transition temperature reactive monomer, and acrylonitrile at 1500-2000 rpm for 15-20 min to obtain a core phase preemulsion; S2. Stir deionized water, reactive emulsifier, low glass transition temperature reactive monomer, acrylic acid, and functional monomer at 1500-2000 rpm for 15-20 min to obtain shell phase preemulsion. S3. At 78-85℃, deionized water, reactive emulsifier, and sodium bicarbonate are stirred at 200-300 rpm for 10-20 min. Then, 3-8% of the total mass of the core phase preemulsion and initiator solution are added, and the mixture is stirred for 20-30 min. The remaining core phase preemulsion and initiator solution are then added simultaneously over 2.5-3 h. After the addition is complete, the shell phase preemulsion and initiator solution obtained in S2 are added simultaneously over 1.5-2.5 h. After all materials have been added, the temperature is raised to 80-90℃ and maintained for 0.5-1.5 h to obtain a crude emulsion. S4. Cool the crude emulsion to below 60°C, add tert-butyl hydrogen peroxide aqueous solution and ascorbic acid aqueous solution in sequence, stir for 10-20 minutes, then cool to room temperature, adjust the pH value to 7.5-8.5, and then add defoamer to obtain heat-resistant and aging-resistant styrene-acrylic emulsion.

5. The waterproof and flame-retardant gel insulation paste according to claim 4, characterized in that, In step S1, the high glass transition temperature reactive monomer includes styrene and methyl methacrylate.

6. The waterproof and flame-retardant gel insulation paste according to claim 4, characterized in that, In step S2, the low glass transition temperature reactive monomer is butyl acrylate.

7. The waterproof and flame-retardant gel insulation paste according to claim 4, characterized in that, In step S2, the functional monomer comprises N-hydroxymethylacrylamide and vinyltriethoxysilane.

8. The waterproof and flame-retardant gel insulation paste according to claim 1, characterized in that, The reactive emulsifier contains double bonds.

9. The waterproof and flame-retardant gel insulation paste according to claim 1, characterized in that, The flame retardant comprises expanded graphite and aluminum hydroxide.

10. A method for preparing the waterproof and flame-retardant gel thermal insulation paste according to any one of claims 1-9, characterized in that, The specific steps are as follows: (1) Dry the insulation filler and flame retardant for later use; (2) Mix deionized water and dispersant evenly under stirring at 200-400 rpm to obtain a liquid matrix; (3) Adjust the stirring speed to 300-500 rpm, add flame retardant to the liquid matrix in 3-4 batches, and after adding, increase the speed to 600-800 rpm and stir until the powder is completely dispersed; then reduce the speed back to 300-400 rpm, add the heat insulation filler, stir for 30-40 minutes to form a paste. (4) Keep stirring, add heat-resistant and aging-resistant styrene-acrylic emulsion to the paste and stir for 20-30 minutes, then add thickener and stir for 10-30 minutes; discharge, seal and package, and age at room temperature for more than 24 hours to obtain aerogel heat preservation paste.

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