Modified silica aerogel powder and preparation method thereof, aerogel slurry and preparation method thereof and application thereof

Abstract

The present application belongs to the technical field of thermal insulation material preparation, and discloses modified silica aerogel powder and preparation method, aerogel slurry and preparation method and application. The preparation of modified silica aerogel powder in the present application includes the following steps: (1) using dodecyl methacrylate and pentafluorophenyl methacrylate to modify halloysite nanotubes; (2) preparing silica sol; (3) adding the modified halloysite nanotubes to the silica sol to prepare wet gel; (5) preparing modified silica aerogel powder from the wet gel. The present application also prepares aerogel slurry with the modified silica aerogel powder, and prepares aerogel thermal insulation felt with the aerogel slurry. The aerogel thermal insulation felt prepared in the present application exhibits low thermal conductivity and can effectively block heat transfer; the aerogel thermal insulation felt prepared in the present application has good mechanical properties, and the low powder loss is conducive to transportation, and can adapt to thermal insulation applications in various scenarios.

Description

Technical Field

[0001] The present application relates to the technical field of thermal insulation material preparation, and in particular to modified silica aerogel powder and a preparation method thereof, and aerogel slurry and a preparation method and application thereof. Background Art

[0002] Silica aerogel is a lightweight nano-amorphous solid material. As an emerging super thermal insulation material, its thermal conductivity is extremely low, much lower than the thermal conductivity of static air at room temperature of 0.25W / m·K. It has a thermal insulation effect that other materials cannot match. It has low density, is waterproof and flame retardant, is green and environmentally friendly, anti-corrosion, not easy to age, and has a long service life. It is called a super thermal insulation material.

[0003] The slurry molding method is a new solution for compounding silica aerogel with fiber materials. It is prepared by mixing prefabricated nanopowders and solvents, injecting the slurry into prefabricated fiber fabrics, and then removing the solvent from the fabrics to form fiber-reinforced aerogel composite materials. Benefiting from the low cost of the slurry molding method and the good compatibility between the slurry and the fiber, the slurry can be compounded with various fiber felts (such as glass fiber felt, quartz fiber felt, alumina fiber felt and mullite fiber felt, etc.) to prepare aerogel composite insulation felts with both flexibility and excellent mechanical properties.

[0004] The existing composite thermal insulation felt prepared by the slurry molding method still has the problems of high thermal conductivity, low mechanical strength, and poor high temperature resistance. Therefore, it is of great practical significance to realize the rapid and low-cost preparation of silica aerogel composite thermal insulation felt and make the material have flexibility, good mechanical properties, excellent thermal insulation performance and high temperature resistance. Summary of the invention

[0005] In order to solve the above technical problems, a modified silica aerogel powder with better hydrophobic effect and larger contact angle is developed, and at the same time an aerogel slurry with lower thermal conductivity is developed. The aerogel insulation felt prepared by combining it with fiber felt can meet the requirements of low thermal conductivity, high mechanical strength and better solution to the powder falling problem. The present application provides modified silica aerogel powder and preparation method, aerogel slurry and preparation method and application.

[0006] In a first aspect, the present application provides a method for preparing modified silica aerogel powder, comprising the following steps:

[0007] S1, adding dodecyl methacrylate, pentafluorophenyl methacrylate, an organic solvent and halloysite nanotubes into a reaction container, adding an initiator, controlling the reaction temperature to 70-80° C., reacting for 4-8 hours while stirring, cooling, filtering and collecting the residue, washing, and drying to obtain a copolymer-modified halloysite nanotube, which is then set aside;

[0008] S2, stirring a silicon source, deionized water, anhydrous ethanol, and n-hexane at room temperature to prepare a silicon source precursor solution;

[0009] S3, adding an acid catalyst to the silicon source precursor solution obtained in step S2, adjusting the pH of the solution to 2-3, and performing a hydrolysis reaction while heating in a water bath to obtain a silica sol;

[0010] S4, adding an alkaline catalyst to the silica sol prepared in step S3, adjusting the pH of the solution to 6-7, adding the copolymer-modified halloysite nanotubes prepared in step S1, stirring, ultrasonicating, adding diphenylmethane diisocyanate and an organic tin catalyst, reacting at 50-60° C. for 8-15 hours, and standing to obtain a wet gel;

[0011] S5, aging the wet gel obtained in step S4, the aging time is controlled to be 10-15 hours, adding a hydrophobic modifier for hydrophobic modification, drying, and ball milling to obtain modified silica aerogel powder.

[0012] Optionally, in step S1, the weight ratio of dodecyl methacrylate, pentafluorophenyl methacrylate, initiator and halloysite nanotubes is 5-10:2-3:0.2-0.5:50-80.

[0013] Optionally, in step S1, the halloysite nanotubes are coupled modified halloysite nanotubes, and the preparation process of the coupled modified halloysite nanotubes includes the following steps: mixing the halloysite nanotubes with a urea solution, ultrasonicating, letting stand, then adding sulfuric acid, letting stand, filtering, and drying to obtain pretreated halloysite nanotubes; adding a silane coupling agent, water, and pretreated halloysite nanotubes to a reaction container, adjusting the pH to 9-10, reacting at 60-80°C for 2-3h, adjusting the pH to neutral, cooling, filtering, washing the filter residue, and drying to obtain coupled modified halloysite nanotubes.

[0014] Optionally, in step S1, the preparation process of the pretreated halloysite nanotubes includes the following steps: mixing halloysite nanotubes with a weight ratio of (1:8-10) and 20wt% urea solution, ultrasonicating, standing, then adding 5wt% sulfuric acid solution, standing, filtering, and drying to obtain pretreated halloysite nanotubes; wherein the weight ratio of sulfuric acid solution to halloysite nanotubes is 5:1.

[0015] Optionally, in step S1, the preparation process of the coupled modified halloysite nanotubes includes the following steps: adding a silane coupling agent, water and pretreated halloysite nanotubes to a reaction container, adjusting the pH to 9-10, reacting at 60-80°C for 2-3h, adjusting the pH to neutral, cooling, filtering, washing the filter residue, and drying to obtain coupled modified halloysite nanotubes; wherein the weight ratio of the silane coupling agent, water and pretreated halloysite nanotubes is 1-1.5:100:9-14.

[0016] By adopting the above technical solution, urea, as a polar solvent, can help open the lumen of the halloysite nanotubes. On the one hand, it can enhance the thermal insulation capacity of the halloysite nanotubes, and on the other hand, it can increase its internal surface area. At the same time, it may change the surface properties of the halloysite nanotubes through the insertion of urea molecules, thereby improving its dispersibility and reactivity. After the halloysite nanotubes are treated with acid, although some hydroxyl groups will be removed first, the re-hydroxylation of the surface of the halloysite nanotubes will be promoted, thereby generating more hydroxyl groups on the surface of the halloysite nanotubes, providing more reaction sites for subsequent functionalization.

[0017] Optionally, in step S2, the weight ratio of the silicon source, deionized water, anhydrous ethanol and n-hexane is 1:(5-10):(3-6):(1-2).

[0018] Optionally, in step S2, the silicon source is selected from one or more of methyl orthosilicate, ethyl orthosilicate, sodium silicate, isopropyl orthosilicate, methyltrimethoxysilane, and methyltriethoxysilane.

[0019] Optionally, in step S3, the acid catalyst is one of oxalic acid solution, hydrochloric acid solution, phosphoric acid solution and citric acid solution, and the concentration is 0.3-0.5wt%.

[0020] Optionally, in step S4, the alkaline catalyst is one of an aqueous ammonia solution, a sodium carbonate solution, and a sodium bicarbonate solution, and the concentration is 0.2-0.4 wt%.

[0021] Optionally, in step S4, the weight ratio of silica sol, copolymer-modified halloysite nanotubes, diphenylmethane diisocyanate and organic tin catalyst is (20-30):(1-3):(0.5-1):0.05.

[0022] Optionally, in step S6, the hydrophobic modifier is trimethylchlorosilane.

[0023] Optionally, in step S6, the hydrophobic modifier is a mixed liquid of n-hexane and trimethylchlorosilane in a weight ratio of 7-12:1.

[0024] By adopting the above technical solution, trimethylchlorosilane and n-hexane are mixed for hydrophobic modification, which can prevent the wet gel from reacting too violently during the hydrophobic treatment process and causing the gel to crack, thereby ensuring the surface properties of the prepared aerogel.

[0025] Optionally, in step S5, the drying process adopts freeze vacuum drying, the temperature is (-60)-(-30)°C, the vacuum degree is 50-100Pa, and the drying time is 10-30h.

[0026] By adopting the above technical scheme, the present application grafts the copolymer of dodecyl methacrylate and pentafluorophenyl methacrylate on the surface of halloysite nanotubes through the copolymerization reaction of acrylic acid monomers, so that the surface of the halloysite nanotubes is connected with pentafluorophenyl ester groups and dodecyl ester groups, which contain fluorine elements and benzene rings. Both groups have strong hydrophobicity and stability, and the long-chain alkyl structure in the dodecyl ester group can enhance the hydrophobic interaction between molecules, thereby reducing thermal conductivity; therefore, the halloysite nanotubes are modified by compounding dodecyl methacrylate and pentafluorophenyl methacrylate and performing a copolymerization reaction, so that the corresponding functional groups can be grafted on the surface to obtain copolymer-modified halloysite nanotubes.

[0027] By adopting the above technical scheme, the copolymer-modified halloysite nanotubes are added to the hydrolyzed silica sol, and in the alkaline catalysis process, the copolymer-modified halloysite nanotubes and the silica gel can be connected through Si-O-Si bonding. At the same time, the hydroxyl groups on the surface of the silica gel and the hydroxyl groups on the surface of the modified halloysite nanotubes are cross-linked and cured with the isocyanate groups of diphenylmethane diisocyanate to form a three-dimensional network structure, which can promote the copolymer-modified halloysite nanotubes to be evenly distributed in the silica aerogel on the one hand, and can further improve the mechanical properties, weather resistance and hydrophobicity of the formed composite aerogel on the other hand. In addition, during the cross-linking and curing process of diphenylmethane diisocyanate, water acts as a foaming agent to make the generated composite aerogel have high porosity and high specific surface area. At the same time, diphenylmethane diisocyanate is a curing agent containing multiple benzene rings. Under the hydrophobic effect of the benzene rings, the prepared composite aerogel has strong hydrophobicity. The hydrophobicity of the composite aerogel after hydrophobic modification is further improved, so that the final modified silica aerogel powder has a good hydrophobic effect and a large contact angle.

[0028] Halloysite nanotubes are introduced into the silica aerogel matrix material. Halloysite nanotubes have a high specific surface area. Moving hydrophobic groups onto their surface can greatly improve the hydrophobic effect of the material. Halloysite nanotubes have a nanometer-sized tubular structure and a large aspect ratio, so that the modified silica aerogel powder has good mechanical properties and temperature resistance.

[0029] In a second aspect, the present application provides modified silica aerogel powder prepared by the above-mentioned method for preparing modified silica aerogel powder.

[0030] In a third aspect, the present application provides an aerogel slurry prepared from the above-mentioned modified silica aerogel powder, the aerogel slurry comprising the following raw materials in parts by weight: 15-45 parts of modified silica aerogel powder, 35-60 parts of lightweight microspheres, 250-350 parts of aqueous inorganic resin, 5-10 parts of sodium bentonite, 4-10 parts of wetting agent, 4-8 parts of dispersant, 2-3 parts of defoaming agent, 2-3 parts of antibacterial agent, and 400-550 parts of water.

[0031] Optionally, the lightweight microspheres include one or more of hollow glass microspheres, hollow silica microspheres, hollow ceramic microspheres, and hollow phenolic resin microspheres; the particle size of the lightweight microspheres is 100-350 um, and the density of the lightweight microspheres is 0.1-0.4 g / cm 3 .

[0032] By adopting the above technical scheme, the silicate in the water-based inorganic resin has strong permeability and can react with calcium ions in lightweight microspheres, carbon dioxide in the air, etc. to form a film. The silicate in the water-based inorganic resin can also react with aluminum ions in the aluminum oxide layer in the halloysite nanotubes to form a film, thereby improving the film-forming effect of the aerogel slurry on the surface of the fiber felt, and can reduce the cracking and collapse of the aerogel slurry during drying, thereby reducing the occurrence of powdering and slag falling, so that the prepared aerogel insulation felt has a better thermal insulation effect.

[0033] Sodium-based bentonite can provide suitable viscosity for the construction of aerogel slurry, which is beneficial to the spreading and penetration of aerogel slurry on the surface of fiber felt; secondly, sodium-based bentonite has a good thickening effect on organic resin, which can improve the anti-sagging performance of aerogel slurry, thereby making the coating of aerogel slurry more uniform, and after drying, it can reduce the cracking and collapse of aerogel slurry and reduce the occurrence of powder loss.

[0034] By adopting the above technical scheme, the aerogel slurry is an aqueous slurry. The aerogel slurry is coated on the surface of the fiber felt to form a layer of aqueous film, which has good adhesion and leveling properties to the hydrophilic fiber felt surface, making the coating of the aerogel slurry more uniform and stable and not easy to drip and flow. In the subsequent baking process, the high temperature treatment of 300-500°C allows the water molecules in the coating layer to be quickly evaporated. On the one hand, it is beneficial to maintain the integrity of the overall structure of the coating layer, so that the coating layer can completely cover the surface of the fiber felt to further improve the thermal insulation capacity, and at the same time, it can also reduce the powder loss rate of the aerogel insulation felt. On the other hand, the modified silica aerogel powder on the surface of the coating layer is exposed, and the various hydrophobic groups carried on its surface make the final aerogel insulation felt have a good hydrophobic effect and a large contact angle, so that the aerogel insulation felt has low thermal conductivity and can effectively block heat transfer.

[0035] In a fourth aspect, the present application provides a method for preparing the above-mentioned aerogel slurry, comprising the following steps:

[0036] Add water, dispersant, defoamer and half amount of wetting agent into the reaction container, stir, adjust the pH to 9-9.5, add water-based inorganic resin and modified silica aerogel powder, control the temperature to 45-50°C, stir, add lightweight microspheres and sodium bentonite, stir, add antibacterial agent and the remaining amount of wetting agent, stir to obtain aerogel slurry.

[0037] In a fifth aspect, the present application provides the use of the above-mentioned aerogel slurry in the preparation of aerogel insulation felt.

[0038] Optionally, the method for preparing the aerogel insulation felt comprises the following steps: coating the aerogel slurry onto the surface of the fiber felt, allowing the fiber felt to stand until the aerogel slurry is stably absorbed by the fiber felt, and drying to obtain the aerogel insulation felt.

[0039] Optionally, the fiber felt is selected from one of glass fiber felt, carbon fiber felt, nickel fiber felt, stainless steel fiber felt, aluminum silicate fiber felt, ceramic fiber felt, alumina fiber felt, basalt fiber felt and polyacrylonitrile fiber felt.

[0040] Optionally, the fiber felt has a thickness of 0.5-500 mm.

[0041] Optionally, the method for preparing the aerogel thermal insulation felt comprises the following steps:

[0042] (1) applying the aerogel slurry to the surface of the fiber felt, standing the fiber felt until the aerogel slurry is stably absorbed, and during the drying process, first heat-treating the fiber felt at 100-150° C. for 1-2 hours, and then heat-treating the fiber felt at 300-500° C. for 1-2 hours to obtain a pretreated aerogel insulation felt;

[0043] (2) Standing the pretreated aerogel insulation felt obtained in step (1) upright, spraying a hydrophobic modifier from top to bottom using a spray gun, drying at 200° C., then repeating the spraying once and drying again to obtain an aerogel insulation felt.

[0044] Optionally, the hydrophobic modifier is trimethylchlorosilane.

[0045] Optionally, the adsorption amount of aerogel slurry on the fiber felt surface is 0.5-500kg / m 2 .

[0046] In summary, the present invention includes at least one of the following beneficial technical effects:

[0047] 1. In this application, copolymer-modified halloysite nanotubes are added to hydrolyzed silica sol to prepare composite aerogels, and under the cross-linking action of diphenylmethane diisocyanate, composite aerogels with three-dimensional network structure, high porosity, high specific surface area, and hydrophobic groups such as pentafluorophenyl ester groups grafted on the surface are obtained. The modified silica aerogel powder obtained on this basis has a strong hydrophobic effect. This application also prepares aerogel slurry with the above-mentioned modified silica aerogel powder and coats the aerogel slurry on the surface of fiber felt to prepare aerogel insulation felt. The aerogel insulation felt prepared in this application has low thermal conductivity and can effectively block heat transfer; the aerogel insulation felt prepared in this application has good temperature resistance and good mechanical properties, and can adapt to insulation applications in various scenarios.

[0048] 2. The modified silica aerogel powder, aerogel slurry and aerogel insulation felt prepared in this application have low raw material prices, simple and easy preparation processes, and low production costs, which are conducive to industrial production and application and have important practical significance for the development of related industries. DETAILED DESCRIPTION

[0049] The present application provides a method for preparing modified silica aerogel powder, comprising the following steps:

[0050] S1, adding dodecyl methacrylate, pentafluorophenyl methacrylate, an organic solvent and halloysite nanotubes into a reaction container, adding an initiator, controlling the reaction temperature to 70-80° C., reacting for 4-8 hours while stirring, cooling, filtering and collecting the residue, washing, and drying to obtain a copolymer-modified halloysite nanotube, which is then set aside;

[0051] S2, stirring a silicon source, deionized water, anhydrous ethanol, and n-hexane at room temperature to prepare a silicon source precursor solution;

[0052] S3, adding an acid catalyst to the silicon source precursor solution obtained in step S2, adjusting the pH of the solution to 2-3, and performing a hydrolysis reaction while heating in a water bath to obtain a silica sol;

[0053] S4, adding an alkaline catalyst to the silica sol prepared in step S3, adjusting the pH of the solution to 6-7, adding the copolymer-modified halloysite nanotubes prepared in step S1, stirring, ultrasonicating, adding diphenylmethane diisocyanate and an organic tin catalyst, reacting at 50-60° C. for 8-15 hours, and standing to obtain a wet gel;

[0054] S5, aging the wet gel obtained in step S4, the aging time is controlled to be 10-15 hours, adding a hydrophobic modifier for hydrophobic modification, drying, and ball milling to obtain modified silica aerogel powder.

[0055] The present application designs a modified silica aerogel powder prepared by the above preparation method.

[0056] The present application designs an aerogel slurry, which includes the following raw materials in parts by weight: 15-45 parts of modified silica aerogel powder, 35-60 parts of lightweight microspheres, 250-350 parts of water-based inorganic resin, 5-10 parts of sodium bentonite, 4-10 parts of wetting agent, 4-8 parts of dispersant, 2-3 parts of defoaming agent, 2-3 parts of antibacterial agent, and 400-550 parts of water.

[0057] The aerogel slurry of the present application is prepared by the following method, comprising the following steps:

[0058] Add water, dispersant, defoamer and half amount of wetting agent into the reaction container, stir, adjust the pH to 9-9.5, add water-based inorganic resin and modified silica aerogel powder, control the temperature to 45-50°C, stir, add lightweight microspheres and sodium bentonite, stir, add antibacterial agent and the remaining amount of wetting agent, stir to obtain aerogel slurry.

[0059] The aerogel slurry of the present application can be used in the field of preparing aerogel thermal insulation felt.

[0060] The preparation method of aerogel thermal insulation felt comprises the following steps:

[0061] The aerogel slurry is coated on the surface of the fiber felt, and the fiber felt is allowed to stand until the aerogel slurry is stably absorbed by the fiber felt, and then dried to obtain the aerogel insulation felt.

[0062] The technical problem solved by the present application is that the composite thermal insulation felt prepared by the existing slurry molding method still has the problems of high thermal conductivity, low mechanical strength, and low high temperature resistance. The modified silica aerogel prepared by the present application has a three-dimensional network cross-linked structure and high porosity, high specific surface area, and hydrophobic groups such as pentafluorophenyl ester groups are grafted on the surface. The modified silica aerogel powder prepared on this basis has a strong hydrophobic effect. The present application also prepares aerogel slurry with the above-mentioned modified silica aerogel powder and coats the aerogel slurry on the surface of the fiber felt to prepare an aerogel thermal insulation felt. The aerogel thermal insulation felt prepared by the present application has low thermal conductivity and can effectively block heat transfer; the aerogel thermal insulation felt prepared by the present application has good temperature resistance and good mechanical properties, and can adapt to thermal insulation applications in a variety of scenarios.

[0063] The present application is further described in detail below in conjunction with specific embodiments.

[0064] Preparation Example 1

[0065] The preparation method of the modified silica aerogel powder in Preparation Example 1 comprises the following steps:

[0066] S1, adding 0.6 kg of dodecyl methacrylate, 0.25 kg of pentafluorophenyl methacrylate, 25 kg of organic solvent and 6 kg of halloysite nanotubes into a reaction container, adding 0.03 kg of initiator, controlling the reaction temperature to 80° C., reacting for 6 hours while stirring, cooling, filtering and collecting the residue, washing, and drying to obtain copolymer-modified halloysite nanotubes for later use;

[0067] S2, 1 kg of silicon source, 7 kg of deionized water, 5 kg of anhydrous ethanol, and 1.8 kg of n-hexane were stirred at room temperature to prepare a silicon source precursor solution;

[0068] S3, adding an acid catalyst with a concentration of 0.4 wt% to the silicon source precursor solution until the pH is 2-3, and performing a hydrolysis reaction while heating in a water bath for 5 hours at a water bath temperature of 70° C. to obtain a silica sol;

[0069] S4, take 26kg of silica sol, add 0.4wt% of alkaline catalyst to adjust the pH to 6-7, then add 2kg of copolymer-modified halloysite nanotubes, stir for 30min, ultrasonicate for 10min, add 0.6kg of diphenylmethane diisocyanate and 0.05kg of organotin catalyst, react at 60°C for 12h, let stand for 3h, and obtain wet gel;

[0070] S5. The prepared wet gel is placed in a water / anhydrous ethanol mixture with a volume ratio of 1:4 and aged at constant temperature and pressure at 25°C and one atmosphere for 12 hours; the aged wet gel is immersed in a hydrophobic modifier for hydrophobic modification for 24 hours; then freeze-dried at a temperature of -50°C, a vacuum degree of 100 Pa, and a drying time of 24 hours; the dried modified silica aerogel is ball-milled to a particle size of 800 mesh to obtain modified silica aerogel powder.

[0071] The halloysite nanotubes used in Preparation Example 1 are coupled modified halloysite nanotubes, and the preparation process of the coupled modified halloysite nanotubes includes the following steps:

[0072] (1) 6 kg of halloysite nanotubes were mixed with 60 kg of 20 wt% urea solution, ultrasonicated for 30 min, allowed to stand for 10 h, then 30 kg of 5 wt% sulfuric acid solution was added, allowed to stand for 3 h, filtered, and dried to obtain pretreated halloysite nanotubes; (2) 0.6 kg of silane coupling agent, 50 kg of water and 5 kg of pretreated halloysite nanotubes were added to a reaction container, the pH was adjusted to 9-10, reacted at 80°C for 2 h, the pH was adjusted to neutral, cooled, filtered, washed the filter residue, and dried to obtain coupled modified halloysite nanotubes.

[0073] The silane coupling agent used in Preparation Example 1 is KH-570.

[0074] The dodecyl methacrylate used in Preparation Example 1 was purchased from Sigma-Aldrich Company with a CAS number of 142-90-5.

[0075] Pentafluorophenyl methacrylate used in Preparation Example 1 was purchased from Tokyo Chemical Industry (Shanghai) Co., Ltd. with a product code of P2289 and a CAS number of 13642-97-2.

[0076] The silicon source used in Preparation Example 1 is tetraethyl orthosilicate.

[0077] The acid catalyst used in Preparation Example 1 is oxalic acid solution; the base catalyst used in Preparation Example 1 is ammonia solution.

[0078] The organotin catalyst used in Preparation Example 1 is dibutyltin dilaurate.

[0079] The hydrophobic modifier in Preparation Example 1 is composed of n-hexane and trimethylchlorosilane in a weight ratio of 8:1.

[0080] Preparation Example 2

[0081] The preparation method of the modified silica aerogel powder in Preparation Example 2 comprises the following steps:

[0082] S1, adding 0.5 kg of dodecyl methacrylate, 0.3 kg of pentafluorophenyl methacrylate, 25 kg of organic solvent and 6 kg of halloysite nanotubes into a reaction container, adding 0.03 kg of initiator, controlling the reaction temperature to 80° C., reacting for 6 h while stirring, cooling, filtering and collecting the residue, washing and drying to obtain modified halloysite nanotubes for later use;

[0083] S2, 1 kg of silicon source, 7 kg of deionized water, 5 kg of anhydrous ethanol, and 1.8 kg of n-hexane were stirred at room temperature to prepare a silicon source precursor solution;

[0084] S3. Add 0.4 wt% of an acid catalyst to the silicon source precursor solution to adjust the pH of the solution to 2-3, and perform a hydrolysis reaction while heating in a water bath for 5 hours at a water bath temperature of 70° C. to obtain a silica sol.

[0085] S4, take 26kg silica sol, add 0.4wt% alkaline catalyst to adjust the solution pH to 6-7, add 1kg copolymer modified halloysite nanotubes, stir for 30min, ultrasonicate for 10min, add 0.5kg diphenylmethane diisocyanate and 0.05kg organotin catalyst, react at 60°C for 12h, let stand for 3h, and obtain wet gel;

[0086] S5. The prepared wet gel is placed in a water / anhydrous ethanol mixture with a volume ratio of 1:4 and aged at constant temperature and pressure at 25°C and one atmosphere for 12 hours; the aged wet gel is immersed in a hydrophobic modifier for hydrophobic modification for 24 hours; then freeze-dried at a temperature of -50°C, a vacuum degree of 100 Pa, and a drying time of 24 hours; the dried modified silica aerogel is ball-milled to a particle size of 800 mesh to obtain modified silica aerogel powder.

[0087] The halloysite nanotubes used in Preparation Example 2 are coupled modified halloysite nanotubes, and the preparation process is the same as that of Preparation Example 1.

[0088] The silicon source used in Preparation Example 2 is methyltrimethoxysilane, with CAS No. 1185-55-3.

[0089] The acid catalyst used in Preparation Example 2 is oxalic acid solution; the base catalyst used in Preparation Example 1 is ammonia solution.

[0090] The organotin catalyst used in Preparation Example 2 is dibutyltin dilaurate.

[0091] The hydrophobic modifier in Preparation Example 2 is composed of n-hexane and trimethylchlorosilane in a weight ratio of 12:1.

[0092] Preparation Example 3

[0093] The preparation method of the modified silica aerogel powder in Preparation Example 3 comprises the following steps:

[0094] S1, adding 1 kg of dodecyl methacrylate, 0.2 kg of pentafluorophenyl methacrylate, 25 kg of organic solvent and 6 kg of halloysite nanotubes into a reaction container, adding 0.03 kg of initiator, controlling the reaction temperature to 80° C., reacting for 6 hours while stirring, cooling, filtering and collecting the residue, washing, and drying to obtain copolymer-modified halloysite nanotubes for later use;

[0095] S2, 1 kg of silicon source, 7 kg of deionized water, 5 kg of anhydrous ethanol, and 1.8 kg of n-hexane were stirred at room temperature to prepare a silicon source precursor solution;

[0096] S3, adding an acid catalyst with a concentration of 0.4 wt% to the silicon source precursor solution until the pH is 2-3, and performing a hydrolysis reaction while heating in a water bath for 5 hours at a water bath temperature of 70° C. to obtain a silica sol;

[0097] S4, taking 26 kg of silica sol, adding a base catalyst with a concentration of 0.4 wt% to adjust the pH to 6-7, then adding 3 kg of copolymer-modified halloysite nanotubes, stirring for 30 min, ultrasonicating for 10 min, adding 1 kg of diphenylmethane diisocyanate and 0.05 kg of organic tin catalyst, reacting at 60 ° C for 12 h, standing for 3 h, and obtaining a wet gel;

[0098] S5. The prepared wet gel is placed in a water / anhydrous ethanol mixture with a volume ratio of 1:4 and aged at constant temperature and pressure at 25°C and one atmosphere for 12 hours; the aged wet gel is immersed in a hydrophobic modifier for hydrophobic modification for 24 hours; then freeze-dried at a temperature of -50°C, a vacuum degree of 100 Pa, and a drying time of 24 hours; the dried modified silica aerogel is ball-milled to a particle size of 800 mesh to obtain modified silica aerogel powder.

[0099] The silane coupling agent used in Preparation Example 3 is KH-550.

[0100] The halloysite nanotubes used in Preparation Example 3 are coupled modified halloysite nanotubes, and the preparation process is the same as that of Preparation Example 1.

[0101] The silicon source used in Preparation Example 3 is sodium silicate.

[0102] The acid catalyst used in Preparation Example 3 is oxalic acid solution; the base catalyst used in Preparation Example 1 is ammonia solution.

[0103] The organotin catalyst used in Preparation Example 3 is dibutyltin dilaurate.

[0104] The hydrophobic modifier in Preparation Example 3 is composed of n-hexane and trimethylchlorosilane in a weight ratio of 7:1.

[0105] Preparation Example 4

[0106] Preparation Example 4 is based on Preparation Example 1, except that the coupled modified halloysite nanotubes used in step S2 of Preparation Example 4 are not pretreated with urea solution and sulfuric acid solution before reacting with the coupling agent.

[0107] Preparation Comparative Example 1

[0108] Preparation Comparative Example 1 is based on Preparation Example 1, except that in step S1 of Preparation Comparative Example 1, pentafluorophenyl methacrylate is replaced with an equal amount of tetrafluoroethyl methacrylate.

[0109] In the preparation comparative example 1, step S1 is changed to:

[0110] S1. Add 0.6 kg of dodecyl methacrylate, 0.25 kg of tetrafluoroethyl methacrylate, 25 kg of organic solvent and 6 kg of halloysite nanotubes into a reaction container, add 0.03 kg of initiator, control the reaction temperature to 80°C, react with stirring for 6 hours, cool, filter and obtain the residue, wash and dry to obtain copolymer-modified halloysite nanotubes for later use.

[0111] Preparation Comparative Example 2

[0112] Preparation Comparative Example 2 is based on Preparation Example 1, except that: in step S1 of Preparation Comparative Example 2, pentafluorophenyl methacrylate is not used to modify the halloysite nanotubes.

[0113] In the preparation comparative example 2, step S1 is changed to:

[0114] S1. Add 0.6 kg of dodecyl methacrylate, 25 kg of organic solvent and 6 kg of halloysite nanotubes into a reaction container, add 0.03 kg of initiator, control the reaction temperature to 80°C, react for 6 hours while stirring, cool, filter and obtain the residue, wash and dry to obtain copolymer-modified halloysite nanotubes for later use.

[0115] Preparation Comparative Example 3

[0116] Preparation Example 3 is based on Preparation Example 1, except that in step S1 of Preparation Example 3, dodecyl methacrylate is replaced by an equal amount of n-butyl methacrylate.

[0117] In the preparation comparative example 3, step S1 is changed to:

[0118] S1. Add 0.6 kg of n-butyl methacrylate, 0.25 kg of pentafluorophenyl methacrylate, 25 kg of organic solvent and 6 kg of halloysite nanotubes into a reaction container, add 0.03 kg of initiator, control the reaction temperature to 80°C, react for 6 hours while stirring, cool, filter and obtain the residue, wash and dry to obtain copolymer-modified halloysite nanotubes for later use.

[0119] Preparation Comparative Example 4

[0120] Preparation Comparative Example 4 is based on Preparation Example 1, except that in step S1 of Preparation Comparative Example 4, dodecyl methacrylate is not used to modify the halloysite nanotubes.

[0121] In the preparation comparative example 4, step S1 is changed to:

[0122] S1. Add 0.25 kg of pentafluorophenyl methacrylate, 25 kg of organic solvent and 6 kg of halloysite nanotubes into a reaction container, add 0.03 kg of initiator, control the reaction temperature to 80°C, react for 6 hours while stirring, cool, filter and obtain the residue, wash and dry to obtain copolymer-modified halloysite nanotubes for later use.

[0123] Examples 1-3

[0124] Examples 1-3 are different aerogel slurries prepared, the difference being that the raw material ratios and amounts are different, as follows:

[0125] The aerogel slurry prepared in Example 1 includes the following raw materials in parts by weight:

[0126] 38 parts of modified silica aerogel powder, 45 parts of lightweight microspheres, 280 parts of water-based inorganic resin, 8 parts of sodium bentonite, 6 parts of wetting agent, 6 parts of dispersant, 2.5 parts of defoaming agent, 2.5 parts of antibacterial agent, and 500 parts of water.

[0127] The aerogel slurry prepared in Example 2 includes the following raw materials in parts by weight:

[0128] 15 parts of modified silica aerogel powder, 60 parts of lightweight microspheres, 250 parts of water-based inorganic resin, 5 parts of sodium bentonite, 10 parts of wetting agent, 4 parts of dispersant, 2 parts of defoaming agent, 2 parts of antibacterial agent, and 400 parts of water.

[0129] The aerogel slurry prepared in Example 3 includes the following raw materials in parts by weight:

[0130] 45 parts of modified silica aerogel powder, 35 parts of lightweight microspheres, 350 parts of water-based inorganic resin, 10 parts of sodium bentonite, 4 parts of wetting agent, 8 parts of dispersant, 3 parts of defoaming agent, 3 parts of antibacterial agent, and 550 parts of water.

[0131] The modified silica aerogel powders used in Examples 1-3 were all prepared in Preparation Example 1.

[0132] The lightweight microspheres used in Examples 1-3 are hollow ceramic microspheres with an average particle size of 150 μm and an average density of 0.3 g / cm 3 .

[0133] The aqueous inorganic resin used in Examples 1-3 is lithium silicate resin purchased from Tianjin Bodao New Materials, with a modulus (silicon-alkali ratio) of 4.8±0.1 and SiO 2 The content is 19.0-21.0wt%, Li 2 The O content is 2.0-2.2 wt%. The wetting agent used in Examples 1-3 is from Mingling Chemical of Germany. 514.

[0134] The dispersant used in Examples 1-3 is EDAPLAN 490 produced by German Mingling Chemical.

[0135] The defoamer used in Examples 1-3 is from Germany's Mingling Chemical 299.

[0136] The antibacterial agent used in Examples 1-3 is industrial mildew-proof agent No. 75, namely oxybisphenoxane arsenic.

[0137] The preparation process of Examples 1-3 comprises the following steps:

[0138] Add water, dispersant, defoamer and half amount of wetting agent to the reaction container, stir for 5 minutes, adjust the pH to 9-9.5, add water-based inorganic resin and modified silica aerogel powder, control the temperature to 45°C, stir for 30 minutes, add lightweight microspheres and sodium bentonite, stir for 5 minutes, add antibacterial agent and the remaining amount of wetting agent, stir for 5 minutes, and prepare aerogel slurry.

[0139] Embodiment 4-5

[0140] Example 4 is based on Example 1, except that the amount of modified silica aerogel powder in Example 4 is changed from 38 parts to 15 parts.

[0141] Example 5 is based on Example 1, except that the amount of modified silica aerogel powder in Example 5 is changed from 38 parts to 45 parts.

[0142] Examples 6-8 and Comparative Examples 1-2

[0143] Examples 6-8 and Comparative Examples 1-2 are based on Example 1, with the difference that different modified silica aerogel powders are used in Examples 6-8 and Comparative Examples 1-2, as shown in Table 1 for details.

[0144] Table 1

[0145] Aerogel slurry Modified silica aerogel powder Example 6 Preparation Example 2 Example 7 Preparation Example 3 Example 8 Preparation Example 4 Comparative Example 1 Preparation Comparative Example 1 Comparative Example 2 Preparation Comparative Example 2 Comparative Example 3 Preparation Comparative Example 3 Comparative Example 4 Preparation Comparative Example 4

[0146] Comparative Example 5

[0147] Comparative Example 5 is based on Example 1, except that: in Comparative Example 5, the modified silica aerogel powder in the raw material is replaced with commercially available silica aerogel powder, which is German Wacker H15 fumed silica.

[0148] Application Examples 1-8

[0149] Application Examples 1-8 are aerogel insulation felts prepared using the aerogel slurries prepared in Examples 1-8, respectively. The aerogel slurries used in Application Examples 1-8 correspond to Examples 1-8, respectively.

[0150] The preparation method of the aerogel thermal insulation felt in Application Examples 1-8 comprises the following steps:

[0151] The aerogel slurry was used to scrape the 5 mm thick glass fiber felt, and the fiber felt was allowed to stand for a long time to stably absorb the aerogel slurry. The fiber felt was dried and heat-treated at 150 °C for 1 h and then at 200 °C for 2 h to obtain the aerogel insulation felt. The adsorption amount of the aerogel slurry on the fiber felt surface was controlled to be 4 kg / m 2 .

[0152] The density of the glass fiber mat used in Application Example 1-8 is 0.2 g·cm -3 .

[0153] Application Example 9

[0154] Application Example 9 is based on Application Example 1, except that the preparation method of Application Example 9 includes the following steps:

[0155] (1) Using aerogel slurry to scrape a 5 mm thick glass fiber felt, leaving it to stand until the fiber felt stably absorbs the aerogel slurry, drying it, and then heat-treating it at 150°C for 1 hour and then at 200°C for 2 hours to obtain a pretreated aerogel insulation felt; the adsorption amount of aerogel slurry on the fiber felt surface is controlled to be 4 kg / m 2 .

[0156] (2) The pretreated aerogel insulation felt prepared in step (1) is erected, and a hydrophobic modifier is sprayed from top to bottom using a spray gun, and then dried at 200° C., and then the spraying is repeated once and dried again to obtain an aerogel insulation felt; wherein the hydrophobic modifier is trimethylchlorosilane, and the spraying amount each time is 40 g / m 2 .

[0157] Application Comparative Example 1

[0158] Application Comparative Example 1 is based on Application Example 1, with the difference that the aerogel slurry in Application Comparative Example 1 is the aerogel slurry prepared in Comparative Example 1.

[0159] Application Comparative Example 2

[0160] Application Comparative Example 2 is based on Application Example 1, with the difference that the aerogel slurry in Application Comparative Example 2 is the aerogel slurry prepared in Comparative Example 2.

[0161] Application Comparative Example 3

[0162] Application Example 3 is based on Application Example 1, with the difference that the aerogel slurry in Application Example 3 is the aerogel slurry prepared in Comparative Example 3.

[0163] Application Comparative Example 4

[0164] Application Example 4 is based on Application Example 1, with the difference that the aerogel slurry in Application Example 4 is the aerogel slurry prepared in Comparative Example 4.

[0165] Application Comparative Example 5

[0166] Application Example 5 is based on Application Example 1, with the difference that the aerogel slurry in Application Example 5 is the aerogel slurry prepared in Comparative Example 5.

[0167] Performance Testing

[0168] 1. The thermal conductivity (W / (m·K)) of the aerogel insulation felts prepared in Application Examples 1-9 and Comparative Application Examples 1-5 at 25°C was determined with reference to the standard GB / T 10295-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Insulating Materials - Heat Flow Meter Method".

[0169] 2. Determine the compressive strength (MPa) of the aerogel insulation felts prepared in Application Examples 1-9 and Comparative Application Examples 1-5.

[0170] 3. Referring to the standard GB 34336-2017 "Standard for Nano-aerogel Composite Insulation Products", the powder loss rate (%) of the aerogel insulation felts prepared in Application Examples 1-9 and Comparative Application Examples 1-5 was determined.

[0171] 4. Aerogel insulation blanket burn-through test: NexGen oil burner was used at 1009-1036°C. Two aerogel insulation blankets were taken as samples for each application example. The thickness was controlled to be 10 mm. The same side of the sample was burned for 30 minutes. After burning, it was observed whether it was burned through. The maximum heat flux (W / cm2) at the back of the two aerogel insulation blankets 305 mm from the surface was measured. 2) and occurrence time (s), and the burn-through test was carried out for Example 3, Application Example 5 and Application Example 9 respectively. The test results are shown in Table 3. (The evaluation standard is that the maximum heat flux at the back of the insulation felt 305mm away from the surface cannot exceed 2.27W / cm 2 )The measurement results are shown in Table 2.

[0172] Table 2

[0173] Thermal conductivity W / (m·K) Compressive strength(MPa) Powder loss rate (%) Application Example 1 0.015 3.3 0.37 Application Example 2 0.021 2.8 0.42 Application Example 3 0.019 2.9 0.44 Application Example 4 0.018 3.1 0.39 Application Example 5 0.015 3.3 0.34 Application Example 6 0.024 2.8 0.51 Application Example 7 0.019 2.6 0.47 Application Example 8 0.022 3.0 0.66 Application Example 9 0.014 3.3 0.32 Application Comparative Example 1 0.073 3.1 1.04 Application Comparative Example 2 0.094 3.0 1.22 Application Comparative Example 3 0.048 2.9 0.78 Application Comparative Example 4 0.055 2.3 0.93 Application Comparative Example 5 0.089 2.2 1.50

[0174] Table 3

[0175]

[0176] By analyzing the data in Table 2, it can be obtained that the thermal conductivity of the aerogel insulation felt prepared in the present application is as low as 0.014W / (m·K) at 25°C. It can be seen that the aerogel insulation felt prepared in the present application has extremely low thermal conductivity and can effectively block heat transfer. Comparing Application Example 1 with Application Comparative Examples 1 and 2, it can be seen that the thermal conductivity of the aerogel insulation felt prepared by replacing pentafluorophenyl methacrylate with tetrafluoroethyl methacrylate has increased significantly, the insulation capacity has been significantly weakened, and the powder loss rate has also increased significantly. It can be seen that pentafluorophenyl methacrylate has a significant effect on controlling the hydrophobicity of modified silica aerogel powder and aerogel insulation felt, which is beneficial to improving the insulation capacity of the aerogel insulation felt and the rapid removal of moisture from the aerogel insulation felt coating during baking, maintaining the structural integrity of the aerogel insulation felt coating and reducing the occurrence of powder loss. By comparing Application Example 1 with Application Comparative Examples 3 and 4, it can be found that the use of long-chain alkyl methacrylate improves the hydrophobicity of the modified silica aerogel powder to a certain extent, but the effect of improving the hydrophobicity of the modified silica aerogel powder is lower than that of pentafluorophenyl methacrylate.

[0177] By analyzing the data in Table 3, it can be seen that the aerogel insulation felt prepared in the present application has excellent heat resistance, heat insulation and fire prevention performance, and can be used in various fire prevention facilities, heat insulation facilities or various fire prevention scenes. In addition, the aerogel insulation felt prepared in the present application has high mechanical strength and less powder loss, and can be used in various heat insulation scenes.

[0178] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing modified silica aerogel powder, characterized in that: The following steps are involved: S1. Add dodecyl methacrylate, pentafluorophenyl methacrylate, organic solvent and halloysite nanotubes in a weight ratio of 5-10:2-3:0.2-0.5:50-80 into a reaction container, add an initiator, control the reaction temperature to 70-80°C, react for 4-8 hours while stirring, cool, filter and collect the residue, wash and dry to obtain copolymer-modified halloysite nanotubes for later use; the halloysite nanotubes are coupled modified halloysite nanotubes, and the preparation process of the coupled modified halloysite nanotubes comprises the following steps: mixing the halloysite nanotubes with a urea solution, ultrasonically , let stand, then add sulfuric acid, let stand, filter, and dry to obtain pretreated halloysite nanotubes; add silane coupling agent, water and pretreated halloysite nanotubes to a reaction container, adjust the pH to 9-10, react at 60-80°C for 2-3h, adjust the pH to neutral, cool, filter, wash the filter residue, and dry to obtain coupled modified halloysite nanotubes; the concentration of urea is 20wt%; the concentration of sulfuric acid solution is 5wt%; the weight ratio of halloysite nanotubes to urea is (1:8-10); the weight ratio of sulfuric acid solution to halloysite nanotubes is 5:1; S2, stirring a silicon source, deionized water, anhydrous ethanol, and n-hexane at room temperature to prepare a silicon source precursor solution; S3, adding an acid catalyst to the silicon source precursor solution obtained in step S2, adjusting the pH of the solution to 2-3, and performing a hydrolysis reaction while heating in a water bath to obtain a silica sol; S4, adding an alkaline catalyst to the silica sol prepared in step S3, adjusting the pH of the solution to 6-7, adding the copolymer-modified halloysite nanotubes prepared in step S1, stirring, ultrasonicating, adding diphenylmethane diisocyanate and an organotin catalyst, reacting at 50-60° C. for 8-15 hours, standing to obtain a wet gel; the weight ratio of the silica sol, copolymer-modified halloysite nanotubes, diphenylmethane diisocyanate and organotin catalyst is (20-30): (1-3): (0.5-1): 0.05; S5. Aging the wet gel obtained in step S4 for 10-15 hours, adding a hydrophobic modifier for hydrophobic modification, drying, and ball milling to obtain modified silica aerogel powder; the drying process adopts freeze vacuum drying at a temperature of (-60)-(-30)°C, a vacuum degree of 50-100Pa, and a drying time of 10-30 hours; the ball milling is performed to a particle size of 800 mesh.

2. The method for preparing modified silica aerogel powder according to claim 1, characterized in that: In step S3, the acid catalyst is one of oxalic acid solution, hydrochloric acid solution, phosphoric acid solution and citric acid solution, and the concentration is 0.3-0.5wt%; in step S4, the base catalyst is one of ammonia solution, sodium carbonate solution and sodium bicarbonate solution, and the concentration is 0.2-0.4wt%.

3. The method for preparing modified silica aerogel powder according to claim 1, characterized in that: In the step S5, the hydrophobic modifier is trimethylchlorosilane.

4. A modified silica aerogel powder obtained by the method for preparing the modified silica aerogel powder according to any one of claims 1 to 3.

5. An aerogel slurry prepared from the modified silica aerogel powder according to claim 4, characterized in that: The aerogel slurry comprises the following raw materials in parts by weight: 15-45 parts of modified silica aerogel powder, 35-60 parts of lightweight microspheres, 250-350 parts of water-based inorganic resin, 5-10 parts of sodium bentonite, 4-10 parts of wetting agent, 4-8 parts of dispersant, 2-3 parts of defoaming agent, 2-3 parts of antibacterial agent, and 400-550 parts of water; the water-based inorganic resin is lithium silicate resin.

6. A method for preparing the aerogel slurry according to claim 5, characterized in that: The following steps are involved: Add water, dispersant, defoamer and half amount of wetting agent into the reaction container, stir, adjust the pH to 9-9.5, add water-based inorganic resin and modified silica aerogel powder, control the temperature to 45-50°C, stir, add lightweight microspheres, stir, add antibacterial agent and the remaining amount of wetting agent, stir to obtain aerogel slurry.

7. Use of the aerogel slurry according to claim 6 in preparing aerogel insulation felt, wherein the thermal conductivity of the aerogel insulation felt is 0.014~0.024W / (m·K); the compressive strength is 2.6~3.3Mpa; and the powder loss rate is 0.32~0.66%.

8. The use of the aerogel slurry according to claim 7 in preparing aerogel insulation felt, characterized in that: The preparation method of the aerogel thermal insulation felt comprises the following steps: (1) applying aerogel slurry to the surface of the fiber felt, allowing the fiber felt to stand until the fiber felt stably absorbs the aerogel slurry, and during the drying process, firstly heat-treating the fiber felt at 100-150° C. for 1-2 hours, and then heat-treating the fiber felt at 300-500° C. for 1-2 hours to obtain a pretreated aerogel thermal insulation felt; (2) standing the pretreated aerogel insulation felt obtained in step (1) upright, spraying a hydrophobic modifier from top to bottom using a spray gun, drying at 200° C., then repeating the spraying once and drying again to obtain an aerogel insulation felt; The fiber felt is selected from one of glass fiber felt, carbon fiber felt, nickel fiber felt, stainless steel fiber felt, aluminum silicate fiber felt, ceramic fiber felt, alumina fiber felt, basalt fiber felt and polyacrylonitrile fiber felt; the thickness of the fiber felt is 0.5-500mm; The adsorption amount of the aerogel slurry on the fiber felt surface is 0.5-50kg / m 2 .

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