CN111003712A - Preparation method of aerogel composite material - Google Patents
Preparation method of aerogel composite material Download PDFInfo
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- CN111003712A CN111003712A CN201911180448.5A CN201911180448A CN111003712A CN 111003712 A CN111003712 A CN 111003712A CN 201911180448 A CN201911180448 A CN 201911180448A CN 111003712 A CN111003712 A CN 111003712A
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
- C01B33/157—After-treatment of gels
- C01B33/158—Purification; Drying; Dehydrating
- C01B33/1585—Dehydration into aerogels
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
- C01B33/155—Preparation of hydroorganogels or organogels
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/32—Thermal properties
Abstract
The invention discloses a preparation method of an aerogel composite material, which comprises the steps of taking alkoxy silane as a raw material, hydrolyzing the alkoxy silane to form sol, adding a flame retardant, an infrared blocking agent and a base material into the silica sol, and preparing silica wet gel containing the base material; and aging, performing supercritical drying and normal-pressure drying to obtain the silicon dioxide aerogel composite material, and recycling alkoxy alcohol which is a hydrolysis byproduct for preparing alkoxy silane. By adopting the technical scheme of the invention, the preparation method is simple, the overall reaction is stable, the controllability is strong, the investment cost is low, the production period is short, and the process technology can realize continuous production and is environment-friendly; the prepared silicon dioxide aerogel composite material has excellent heat insulation performance and heat resistance and higher processing performance.
Description
Technical Field
The invention belongs to the technical field of preparation of inorganic nano materials, and particularly relates to a preparation method of an aerogel composite material.
Background
The silicon dioxide aerogel is a typical three-dimensional nano porous material, consists of more than 95% of air and less than 5% of Si skeleton, has an average pore diameter of 20-50 nm, and has an extremely high specific surface area of 500-1200 m2A very low density of 0.003 to 0.10g/cm3And an extremely low thermal conductivity of 0.011 to 0.021W/m.K (at room temperature). The high-purity silicon dioxide aerogel is widely applied to Cherenkov detectors, special optical equipment, supercapacitors, sound insulation and silencing materials and drug carriersHowever, because of poor mechanical properties and hydrophilicity of-OH groups on the surface, when the composite material is applied to the heat insulation market, silica aerogel powder and particles need to be prepared, then the coating is doped to exert the heat insulation property, and the application range of the composite material needs to be expanded, the composite material needs to be compounded with rock wool, glass fiber, ceramic fiber and the like to prepare composite materials such as silica aerogel felts, aerogel plates and other aerogel special-shaped members with certain strength and hydrophobicity.
Generally, the preparation process of silica aerogel mainly comprises three processes of gel preparation, gel aging and gel drying, wherein the gel can be prepared by a sol-gel method, generally by catalytic hydrolysis of a silicon-containing solution, the gel aging refers to aging a sol in a mother solution for a period of time to strengthen the network structure of the sol, the shrinkage in the drying process is minimized, and the gel drying refers to removing a solvent of the sol pore structure and ensuring that the pore structure is not changed. The commonly used silica aerogel preparation raw materials comprise silica sol, water glass, ethyl orthosilicate and the like, when the silica sol or the water glass is used as a raw material, the purity and the heat conducting property of a silica aerogel product are limited by the characteristics of the raw material, and meanwhile, a large amount of waste water and waste liquid are generated in the preparation process of the silica aerogel, so that the environment is greatly polluted. When the tetraethoxysilane is used as a raw material, the product performance is good, but the production cost is greatly improved, a large amount of byproduct ethanol generated by hydrolysis of the tetraethoxysilane has a byproduct concentration of about 30-80 percent, and contains some silicon dioxide nanoparticles and modified dopants, and at present, a silicon dioxide aerogel product manufacturer does not have a byproduct ethanol recycling process, and a matched manufacturer is often matched to return to the factory for treatment, so that certain environmental risks and problems exist.
In addition, the drying link of the silicon dioxide aerogel product is very critical, the selection of the drying mode directly determines the quality of the performance of the aerogel product and the production cost, and common drying methods comprise a supercritical drying method and a normal-temperature normal-pressure drying method. The supercritical drying method has high production cost of the silicon dioxide aerogel product due to high equipment investment and high energy consumption, and the normal-temperature and normal-pressure drying method has poor blocking property, incomplete structure and irregular appearance. Therefore, there are problems in the preparation of silica aerogel, regardless of the selection of raw materials or drying methods.
At present, the sol-gel method in the prior art has complex process, extremely high cost and long production period, which causes the preparation of the silica aerogel composite material, and is not satisfactory in the aspects of raw material selection, byproduct utilization and product drying process, so that a new method for preparing the silica aerogel composite material with better physical properties by a simpler process needs to be developed.
Disclosure of Invention
The invention aims to provide a preparation method of an aerogel composite material, which has the advantages of simple process, low production cost, short production period, recyclability of recovery of alkoxy alcohol as a hydrolysis byproduct, realization of continuous and stable production and environmental friendliness; the prepared silicon dioxide aerogel composite material has good hydrophobic property, low heat conductivity coefficient, excellent hydrophobic property and heat resistance, and high processability.
In order to achieve the purpose, the invention adopts the technical scheme that: a method of preparing an aerogel composite, comprising the steps of:
(1) preparing a mixed solution from alkoxy silane, alkoxy alcohol, deionized water and a modifier to obtain silica sol;
(2) preparing silicon dioxide wet gel containing a base material by taking silica sol as a raw material;
(3) aging a silica wet gel containing a substrate;
(4) drying the silica wet gel containing the substrate;
(5) recovering the alkoxyalcohol.
Preferably, in the step (1), the alkoxy silane, the alkoxy alcohol, the deionized water and the modifying agent are mixed according to a molar ratio of 1: (2-40): (4-25): (0.1-10) mixing in a molar ratio to prepare a mixed solution; and (3) gradually adding an acid catalyst into the mixed solution, adjusting the pH value to 2.5-5.5, adjusting the temperature to 20-80 ℃, and continuously stirring for 10-60 min to fully hydrolyze the alkoxy silane to obtain the silica sol.
Preferably, the alkoxysilane, the alkoxy alcohol, the deionized water and the modifier in the step (1) are mixed according to a molar ratio of 1: (6-18): (4-12): (0.5-9) and adjusting the pH value to 3-4.5.
Preferably, the alkoxysilane in step (1) is one or more of trimethoxysilane, triethoxysilane, tripropoxysilane, tetramethoxysilane, tetraethoxysilane or tetrapropoxysilane; the alkoxy alcohol is lower polyhydric alcohol with 1-6 carbon atoms; the modifier is one or more of hexamethyldisiloxane, hexamethyldisilazane, hexamethyldisiloxane, polymethyltriethoxysilane, polymethyltrimethoxysilane, trimethylchlorosilane, trimethylsilanol, dimethyldimethoxysilane and dimethyldiethoxysilane; the acidic catalyst is HCl and H2SO4、H3PO4、HF、HBr、CH3One or more of COOH and HOOC-COOH.
Preferably, in the step (2), the silica sol prepared in the step (1) is kept stand at a constant temperature of 30-80 ℃ for 10-120 min, when the flame retardant and the infrared blocking agent are added into the silica sol, the flame retardant and the infrared blocking agent are added into the silica sol after standing according to the proportion that 1-50 g of the flame retardant and 1-50 g of the infrared blocking agent are doped into each liter of the silica sol, rapidly stirring for 1-10 min, dispersing uniformly to obtain doped modified silica sol, dropwise adding an alkaline catalyst while stirring, adjusting the pH value of the silica sol to 6-8, quickly immersing the base material into the doped silica sol or quickly spraying the doped silica sol onto the base material to ensure that the sol fully permeates into the base material, and standing for 1-60 min at the constant temperature of 30-80 ℃ to gelatinize the silica sol to form the silica wet gel composite material.
Preferably, the flame retardant in the step (2) is one or more of aluminum hydroxide, magnesium hydroxide, molybdenum hydroxide, ammonium polyphosphate, melamine phosphate and N, N-p-phenylenediamine dibenzyl tetraethyl phosphate; the infrared blocking agent is one or more of iron oxide, manganese oxide, nickel oxide, titanium oxide, chromium oxide, indium tin oxide, tin antimony oxide, aluminum zinc oxide, mica powder, talcum powder and titanium dioxide; the alkaline catalyst is selected from one or more of NaF, NaOH, KOH or ammonia water; the base material is one of inorganic fiber base material, porous inorganic plate, inorganic fiber and a special-shaped part prefabricated by the porous inorganic plate.
Preferably, the inorganic fiber substrate is one or more of glass fiber, ceramic fiber, pre-oxidized fiber, aluminum silicate fiber, mullite fiber, basalt fiber, polyester fiber or carbon fiber; the porous inorganic plate is prepared from one or more of aluminum silicate, calcium silicate, mullite, basalt, volcanic rock, bentonite, expanded perlite, foamed high polymer resin and foamed phenolic resin.
Preferably, in the step (3), after the wet gel composite material is formed in the step (2), slowly adding an aging liquid along the wall of the container to soak the wet gel in the aging liquid, sealing and standing for aging for 1-100 hours at the temperature of 30-80 ℃ to obtain an aged silicon dioxide wet gel composite material; and (2) the aging liquid is an aqueous solution of alkoxy alcohol or deionized water, the alkoxy alcohol is consistent with the alkoxy alcohol in the step (1), and a certain amount of modifier is added, wherein the added modifier accounts for 0.1-10% of the volume of the aging liquid.
Preferably, in the step (4), the silica wet gel composite material is transferred into a supercritical drying kettle, dried for 30-90 min under the pressure of 10-20 MPa and at the temperature of 30-80 ℃, transferred into a normal pressure drying kettle, and continuously dried for 20-100 min at the temperature of 80-120 ℃.
Preferably, in the step (5), during supercritical drying, the separated aqueous solution of the alkoxy alcohol enters a rectifying tower for rectification after precipitation and multi-stage filtration, and is treated by a molecular sieve adsorption drying or membrane permeation process.
Compared with the prior art, the invention has the following advantages:
(1) according to the invention, alkoxy silane is adopted as a precursor to generate sol through hydrolysis, the preparation method is simple, the controllability is strong, the investment cost of the whole device is low, the production period is short, and the process technology can realize continuous production and is environment-friendly;
(2) the alkoxy alcohol used in the invention can be recycled and then used for preparing alkoxy silane, and can also be directly used for preparing silicon dioxide aerogel, so that the alkoxy alcohol is recycled, the comprehensive utilization of resources is realized, the solid waste treatment cost is reduced, the problem of high aerogel preparation cost is solved, and the pollution to the environment is avoided;
(3) compared with the method which only adopts the supercritical drying method, the method has the advantages that the drying time of the silicon dioxide aerogel in supercritical equipment can be greatly shortened, the drying efficiency is improved by more than 1 time, the drying effect of the silicon dioxide aerogel composite material is thorough, the forming effect is good, the complete three-dimensional network structure can be preserved, and the large-scale industrial production can be realized;
(4) the silicon dioxide aerogel composite material obtained by the invention has uniform size, good hydrophobic property, low heat conductivity coefficient, excellent hydrophobic and heat-resistant properties and higher processability;
the technical scheme of the invention belongs to a green circulating process route, the consumption of the alkoxy alcohol in the whole preparation process is less, the whole investment cost is low, the process flow for obtaining the target product is shortened, corrosive HCl gas is not generated, and the process also conforms to the chemical principle of green development.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and examples. It should be noted that the scope of the present invention is not limited by these embodiments, and the specific ratios, reaction parameters and material selections involved in the embodiments are included in the embodiments for illustrating the present invention and are not meant to limit the present invention in any way.
A method of preparing an aerogel composite as shown in fig. 1, comprising the steps of:
(1) preparing a mixed solution from alkoxy silane, alkoxy alcohol, deionized water and a modifier to obtain silica sol;
(2) preparing silicon dioxide wet gel containing a base material by taking silica sol as a raw material;
(3) aging a silica wet gel containing a substrate;
(4) drying the silica wet gel containing the substrate;
(5) recovering the alkoxyalcohol.
In the step (1), alkoxy silane, alkoxy alcohol, deionized water and a modifier are mixed according to a molar ratio of 1: (2-40): (4-25): (0.1-10) mixing the components in a molar ratio to prepare a mixed solution, preferably, the alkoxysilane, the alkoxy alcohol, the deionized water and the modifier are mixed according to a molar ratio of 1: (6-18): (4-12): (0.5-9) preparing a mixed solution; and (3) gradually adding an acid catalyst into the mixed solution, adjusting the pH value to 2.5-5.5, preferably adjusting the pH value to 3-4.5, adjusting the temperature to 20-80 ℃, and continuously stirring for 10-60 min to fully hydrolyze the alkoxy silane to obtain the silica sol.
For those skilled in the art, the adjustment and optimization of the molar ratio of the alkoxysilane, the alkoxy alcohol and the water can adjust the pore size, the specific surface area, the density and the like of the silica aerogel; wherein, the addition of the modifier and the optimization of the dosage can improve the hydrophobicity of the final product silicon dioxide aerogel.
Wherein, the alkoxy silane in the step (1) is one or more of trimethoxy silane, triethoxy silane, tripropoxy silane, tetramethoxy silane, tetraethoxy silane or tetrapropoxy silane; the alkoxy alcohol is lower polyhydric alcohol with 1-6 carbon atoms; preferably, the lower alcohol is methanol, ethanol, propanol or butanol; the modifier is one or more of hexamethyldisiloxane, hexamethyldisilazane, hexamethyldisiloxane, polymethyltriethoxysilane, polymethyltrimethoxysilane, trimethylchlorosilane, trimethylsilanol, dimethyldimethoxysilane and dimethyldiethoxysilane; the acidic catalyst is HCl and H2SO4、H3PO4、HF、HBr、CH3COOH, HOOC-COOH and the like.
Wherein in the step (2), the silica sol prepared in the step (1) is kept stand at a constant temperature of 30-80 ℃ for 10-120 min, when the flame retardant and the infrared blocking agent are added into the silica sol, the flame retardant and the infrared blocking agent are added into the silica sol after standing according to the proportion that 1-50 g of the flame retardant and 1-50 g of the infrared blocking agent are doped into each liter of the silica sol, rapidly stirring for 1-10 min, dispersing uniformly to obtain doped modified silica sol, dropwise adding an alkaline catalyst while stirring, adjusting the pH value of the silica sol to 6-8, quickly immersing the base material into the doped silica sol or quickly spraying the doped silica sol onto the base material to ensure that the sol fully permeates into the base material, and standing for 1-60 min at the constant temperature of 30-80 ℃ to gelatinize the silica sol to form the silica wet gel composite material.
Wherein, the flame retardant in the step (2) is one or more of aluminum hydroxide, magnesium hydroxide, molybdenum hydroxide, ammonium polyphosphate, melamine phosphate and N, N-p-phenylenediamine dibenzyl tetraethyl phosphate; the infrared blocking agent is one or more of iron oxide, manganese oxide, nickel oxide, titanium oxide, chromium oxide, indium tin oxide, tin antimony oxide, aluminum zinc oxide, mica powder, talcum powder and titanium dioxide; the alkaline catalyst is selected from one or more of NaF, NaOH, KOH or ammonia water; the base material is one of inorganic fiber base material, porous inorganic plate, inorganic fiber and a special-shaped part prefabricated by the porous inorganic plate.
Wherein the inorganic fiber base material is one or more of glass fiber, ceramic fiber, pre-oxidized fiber, aluminum silicate fiber, mullite fiber, basalt fiber, polyester fiber or carbon fiber; the porous inorganic plate is a plate prepared from one or more of aluminum silicate, calcium silicate, mullite, basalt, volcanic rock, bentonite, expanded perlite, foamed high polymer resin and foamed phenolic resin; the special-shaped part is a special structural part processed according to the requirements of customers.
After the wet gel composite material is formed in the step (2), slowly adding an aging liquid along the wall of the device to soak the wet gel in the wet gel composite material, sealing and standing the wet gel composite material at the temperature of 30-80 ℃ for aging for 1-100 hours to obtain the silicon dioxide wet gel composite material with more excellent performance and more complete structure; and (2) the aging liquid is an aqueous solution of alkoxy alcohol or deionized water, the alkoxy alcohol is consistent with the alkoxy alcohol in the step (1), and a certain amount of modifier is added, wherein the added modifier accounts for 0.1-10% of the volume of the aging liquid.
And (4) transferring the silicon dioxide wet gel composite material into a supercritical drying kettle, drying for 30-90 min at the pressure of 10-20 MPa and the temperature of 30-80 ℃, transferring into a normal-pressure drying kettle, continuously drying for 20-100 min at the temperature of 80-120 ℃, and completely drying to obtain the qualified silicon dioxide aerogel composite material.
In the step (5), the separated aqueous solution of the alkoxyls is subjected to precipitation and multistage filtration during supercritical drying, enters a rectifying tower for rectification to obtain the alkoxyls with the purity of about 95%, and is subjected to molecular sieve adsorption drying or membrane permeation process treatment to obtain the anhydrous alkoxyls with the purity of more than 99.7%.
When transferring out silica aerogel combined material from supercritical drying cauldron, its degree of dryness has reached more than 93 ~ 97%, and it is good, the gel is even to glue even state, and the complete silica aerogel skeleton of structure has formed, continues the drying in transferring to the normal pressure drying cauldron, during the drying, has only increased silica aerogel combined material's degree of dryness, can not lead to the fact other influences to silica aerogel combined material's skeleton, structure etc..
Wherein the temperature of the normal pressure drying kettle is 80-120 ℃, and after normal pressure drying, the dryness of the silicon dioxide aerogel composite material reaches more than 99%. Compared with the supercritical drying method, the process of 'supercritical drying and normal pressure drying' does not affect the product quality, and the drying efficiency is improved by more than 1 time.
In the recovery step of the alkoxy alcohol, the aqueous solution of the alkoxy alcohol separated by supercritical drying enters a rectifying tower for rectification after precipitation, multistage filtration and the like to obtain the alkoxy alcohol with the purity of about 95%, and then the alkoxy alcohol is subjected to molecular sieve adsorption drying or membrane permeation process treatment to obtain the anhydrous alkoxy alcohol with the purity of more than 99.7%.
The obtained anhydrous alkoxy alcohol is used for preparing alkoxy silane, so that the alkoxy alcohol is recycled, green and recyclable, the production cost is reduced, and the environmental pollution is avoided.
The steps form a complete production process technology of the silicon dioxide aerogel product, and the closed-loop type green cycle development is realized.
Example 1
Mixing triethoxysilane, methanol, deionized water and hexamethyldisilazane according to a specific molar ratio to prepare a solution, wherein the molar ratio of the triethoxysilane to the methanol to the deionized water to the hexamethyldisilazane is 1: 2: 25: 0.1, stirring for 15min, uniformly mixing, maintaining stirring, then dropwise adding an acidic catalyst phosphoric acid, adjusting the pH value to 3.5, adjusting the temperature to 40 ℃, continuously stirring for 50min, fully hydrolyzing triethoxysilane to obtain silica sol, keeping the temperature at 30 ℃, standing for 120min, adding a flame retardant and an infrared blocking agent into the silica sol after standing according to the proportion of 1-50 g flame retardant aluminum hydroxide and 1-50 g infrared blocking agent iron oxide per liter of silica sol, rapidly stirring for 1-10 min, uniformly dispersing to obtain a doped modified silica sol, dropwise adding a proper amount of an alkaline catalyst NaF while stirring, adjusting the pH value of the silica sol to 7, rapidly putting a glass fiber mat into the sol for soaking, fully permeating the sol into the glass fiber mat, then standing at 80 ℃ for 30min, compounding and gelling the silica sol and the glass fiber mat, forming a silica wet gel comprising a substrate; after the wet gel composite material is formed, slowly adding aging liquid along the wall of the device to immerse the glass fiber wet gel felt in the aging liquid, sealing and standing the glass fiber wet gel felt for aging for 100 hours at the temperature of 30 ℃ to obtain the silicon dioxide wet gel felt with better quality and more complete structure.
And transferring the silica aerogel wet felt into a supercritical drying kettle, drying for 80min under the pressure of 17MPa and the temperature of 50 ℃, and discharging more than 96% of ethanol, water and the like in the wet gel to obtain the silica aerogel felt which is not dried completely. And taking the silica aerogel felt out of the supercritical drying kettle, transferring the silica aerogel felt into a normal-pressure drying kettle, continuously drying for 100min at the temperature of 80 ℃, and completely drying to obtain the qualified silica aerogel felt, wherein the thermal conductivity coefficient of the qualified silica aerogel felt is 0.015W/(m.K), and the hydrophobicity rate of the qualified silica aerogel felt is 99.1% through detection.
Example 2
Mixing tetraethoxysilane, ethanol, deionized water and trimethylsilanol according to a specific molar ratio to prepare a solution, wherein the molar ratio of tetraethoxysilane to ethanol to deionized water to trimethylsilanol is 1: 40: 6: 0.5, stirring for 20min, uniformly mixing, maintaining stirring, then dropwise adding an acidic catalyst hydrochloric acid, adjusting the pH value to 4, adjusting the temperature to 50 ℃, continuously stirring for 60min, fully hydrolyzing tetraethoxysilane to obtain silica sol, keeping the temperature at 40 ℃, standing for 100min, then dropwise adding a proper amount of alkaline catalyst ammonia water while stirring, adjusting the pH value of the silica sol to 7, then quickly putting the ceramic fiber felt into the sol for soaking, fully permeating the sol into the ceramic fiber felt, then keeping the temperature at 30 ℃ for 60min, compounding the silica sol and the ceramic fiber felt together and gelatinizing to form silica wet gel containing a base material; after the wet gel composite material is formed, slowly adding aging liquid along the wall of the device to immerse the ceramic fiber wet gel felt in the aging liquid, sealing and standing the ceramic fiber wet gel felt for aging for 80 hours at 50 ℃ to obtain the silicon dioxide wet gel felt with better quality and more complete structure.
And transferring the silica aerogel wet felt into a supercritical drying kettle, drying for 90min under the pressure of 18MPa and the temperature of 55 ℃, and discharging more than 97% of ethanol, water and the like in the wet gel to obtain the silica aerogel felt which is not dried completely. And then taking the silica aerogel felt out of the supercritical drying kettle, transferring the silica aerogel felt into a normal-pressure drying kettle, continuously drying for 20min at the temperature of 120 ℃, and completely drying to obtain the qualified silica aerogel felt, wherein the thermal conductivity coefficient of the silica aerogel felt is 0.017W/(m.K) through detection, and the hydrophobicity rate is 99.3%.
Example 3
Mixing tetramethoxysilane, propanol, deionized water and dimethyldimethoxysilane according to a specific molar ratio to prepare a solution, wherein the molar ratio of the tetramethoxysilane to the propanol to the deionized water to the dimethyldimethoxysilane is 1: 30: 25: 5, stirring for 20min, uniformly mixing, maintaining stirring, then dropwise adding an acidic catalyst acetic acid, adjusting the pH value to 5, adjusting the temperature to 80 ℃, continuously stirring for 10min to fully hydrolyze tetraethoxysilane to obtain silica sol, then keeping the temperature at 40 ℃, standing for 80min, adding a flame retardant and an infrared blocking agent into the silica sol after standing according to the proportion of 1-50 g flame retardant melamine phosphate and 1-50 g infrared blocking agent indium tin oxide doped in each liter of silica sol, rapidly stirring for 1-10 min, uniformly dispersing to obtain doped and modified silica sol, dropwise adding a proper amount of an alkaline catalyst NaOH while stirring, adjusting the pH value of the silica sol to 7, then rapidly putting a porous silica aluminum plate into the sol for soaking to enable the sol to fully permeate into the porous silica aluminum plate, then standing for 30min at the constant temperature of 80 ℃, compounding and gelatinizing the silica sol and the porous aluminum silicate plate to form silica wet gel containing a base material; after the wet gel composite material is formed, the aging liquid is slowly added along the wall of the device, so that the aluminum silicate wet gel plate is soaked in the aging liquid, and the silicon dioxide wet gel plate with better quality and more complete structure is obtained after sealing and standing aging for 30 hours at the temperature of 70 ℃.
Transferring the silica aerogel wet plate into a supercritical drying kettle, drying at 50 ℃ under 16MPa for 60min, and discharging more than 95% of ethanol, water and the like in the wet gel to obtain the silica aerogel plate which is not dried completely. And then taking the silicon dioxide aerogel plate out of the supercritical drying kettle, transferring the silicon dioxide aerogel plate into a normal-pressure drying kettle, continuously drying for 60min at the temperature of 100 ℃, and completely drying to obtain the qualified silicon dioxide aerogel plate, wherein the heat conductivity coefficient is 0.021W/(m.K), and the hydrophobicity rate is 99.6% through detection.
Example 4
Mixing trimethoxy silane, butanol, deionized water and trimethyl chlorosilane according to a specific molar ratio to prepare a solution, wherein the molar ratio of the trimethoxy silane to the butanol to the deionized water to the trimethyl chlorosilane is 1: 20: 12: 1, stirring for 40min, uniformly mixing, maintaining stirring, then dropwise adding an acidic catalyst sulfuric acid, adjusting the pH value to 3, adjusting the temperature to 45 ℃, continuously stirring for 50min to fully hydrolyze tetraethoxysilane to obtain silica sol, then keeping the temperature at 40 ℃, standing for 100min, adding a flame retardant N, N-p-phenylenediamine dibenzyl phosphoric acid tetraethyl ester and 1-50 g of infrared blocking agent talcum powder into the silica sol after standing according to the proportion of 1-50 g of flame retardant N, N-p-phenylenediamine dibenzyl phosphoric acid tetraethyl ester and 1-50 g of infrared blocking agent talcum powder per liter of silica sol, rapidly stirring for 1-10 min, uniformly dispersing to obtain doped and modified silica sol, dropwise adding a proper amount of an alkaline catalyst KOH while stirring, adjusting the pH value of the silica sol to 7, rapidly putting a porous aluminum silicate special-shaped piece into the sol for soaking to enable the sol to fully permeate into the porous aluminum silicate special-shaped piece, then standing for 55min at the constant temperature of 50 ℃ to compound and gelatinize the silica sol and the porous aluminum silicate special-shaped piece to form silica wet gel containing a base material; after the wet gel composite material is formed, the aging liquid is slowly added along the wall of the device, so that the aluminum silicate wet gel plate is soaked in the aging liquid, and the aluminum silicate wet gel plate is sealed, kept stand and aged for 90 hours at the temperature of 40 ℃ to obtain the silicon dioxide wet gel special-shaped piece with better quality and more complete structure.
Transferring the silica wet gel special-shaped piece into a supercritical drying kettle, drying for 50min under the pressure of 20MPa and the temperature of 80 ℃, and discharging more than 94% of ethanol, water and the like in the wet gel to obtain the silica aerogel special-shaped piece which is not dried completely. And then taking the silicon dioxide aerogel special-shaped piece out of the supercritical drying kettle, transferring the silicon dioxide aerogel special-shaped piece into a normal-pressure drying kettle, continuously drying for 60min at the temperature of 100 ℃, and completely drying to obtain the qualified silicon dioxide aerogel special-shaped piece, wherein the heat conductivity coefficient of the qualified silicon dioxide aerogel special-shaped piece is 0.020W/(m.K) and the hydrophobic rate of the qualified silicon dioxide aerogel special-shaped piece is 99.4% through detection.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (11)
1. A method for preparing an aerogel composite, comprising the steps of:
(1) preparing a mixed solution from alkoxy silane, alkoxy alcohol, deionized water and a modifier to obtain silica sol;
(2) preparing silicon dioxide wet gel containing a base material by taking silica sol as a raw material;
(3) aging a silica wet gel containing a substrate;
(4) drying the silica wet gel containing the substrate;
(5) recovering the alkoxyalcohol.
2. The method for preparing an aerogel composite material as claimed in claim 1, wherein the alkoxysilane, the alkoxy alcohol, the deionized water and the modifier are added in a molar ratio of 1: (2-40): (4-25): (0.1-10) mixing in a molar ratio to prepare a mixed solution; and (3) gradually adding an acid catalyst into the mixed solution, adjusting the pH value to 2.5-5.5, adjusting the temperature to 20-80 ℃, and continuously stirring for 10-60 min to fully hydrolyze the alkoxy silane to obtain the silica sol.
3. The method for preparing an aerogel composite material as claimed in claim 2, wherein the alkoxysilane, the alkoxy alcohol, the deionized water and the modifier in the step (1) are added in a molar ratio of 1: (6-18): (4-12): (0.5-9) and adjusting the pH value to 3-4.5.
4. The method of claim 2 or 3, wherein the alkoxysilane in step (1) is one or more selected from trimethoxysilane, triethoxysilane, tripropoxysilane, tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane; the alkoxy alcohol is lower polyhydric alcohol with 1-6 carbon atoms; the modifier is hexamethyldisiloxane, hexamethyldisilazane, hexamethyldisiloxane, polymethyltriethoxysilane, polymethyltrimethoxysilane, trimethylchlorosilane, trimethylsilanol, dimethyldimethyldimethyldisiloxaneOne or more of oxysilane and dimethyldiethoxysilane; the acidic catalyst is HCl and H2SO4、H3PO4、HF、HBr、CH3One or more of COOH and HOOC-COOH.
5. The preparation method of the aerogel composite material according to claim 4, wherein in the step (2), the silica sol prepared in the step (1) is kept at a constant temperature of 30-80 ℃ for 10-120 min, when the flame retardant and the infrared blocking agent are added into the silica sol, the flame retardant and the infrared blocking agent are added into the silica sol after the standing according to the proportion of doping 1-50 g of the flame retardant and 1-50 g of the infrared blocking agent into each liter of the silica sol, the mixture is rapidly stirred for 1-10 min and uniformly dispersed to obtain a doped and modified silica sol, an alkaline catalyst is dropwise added while stirring, after the pH value of the silica sol is adjusted to 6-8, the substrate is rapidly immersed into the doped silica sol or the doped silica sol is rapidly sprayed onto the substrate to enable the sol to fully permeate into the substrate, and standing for 1-60 min at the constant temperature of 30-80 ℃ to gelatinize the silica sol to form the silica wet gel composite material.
6. The preparation method of the aerogel composite material according to claim 4, wherein in the step (2), the silica sol prepared in the step (1) is kept at a constant temperature of 30-80 ℃ for 10-120 min, the flame retardant and the infrared blocking agent are added into the silica sol after the silica sol is kept at a constant temperature, the mixture is rapidly stirred for 1-10 min and uniformly dispersed to obtain a doped modified silica sol according to the proportion that 1-50 g of flame retardant and 1-50 g of infrared blocking agent are doped into each liter of silica sol, an alkaline catalyst is dropwise added while the mixture is stirred, after the pH value of the silica sol is adjusted to 6-8, the base material is rapidly immersed into the doped silica sol or the doped silica sol is rapidly sprayed onto the base material, so that the sol is fully infiltrated into the base material, then the mixture is kept at a constant temperature of 30-80 ℃ for 1-60 min to gelatinize the silica sol, forming a silica wet gel composite.
7. The method for preparing an aerogel composite material according to claim 5, wherein the flame retardant in step (2) is one or more of aluminum hydroxide, magnesium hydroxide, molybdenum hydroxide, ammonium polyphosphate, melamine phosphate and tetraethyl N, N-p-phenylenediamine dibenzyl phosphate; the infrared blocking agent is one or more of iron oxide, manganese oxide, nickel oxide, titanium oxide, chromium oxide, indium tin oxide, tin antimony oxide, aluminum zinc oxide, mica powder, talcum powder and titanium dioxide; the alkaline catalyst is selected from one or more of NaF, NaOH, KOH or ammonia water; the base material is one of inorganic fiber base material, porous inorganic plate, inorganic fiber and a special-shaped part prefabricated by the porous inorganic plate.
8. The method of claim 7, wherein the inorganic fiber substrate is one or more of glass fiber, ceramic fiber, pre-oxidized fiber, alumina silicate fiber, mullite fiber, basalt fiber, polyester fiber, carbon fiber, etc.; the porous inorganic plate is prepared from one or more of aluminum silicate, calcium silicate, mullite, basalt, volcanic rock, bentonite, expanded perlite, foamed high polymer resin and foamed phenolic resin.
9. The preparation method of the aerogel composite material as claimed in claim 7 or 8, wherein in the step (3), after the wet gel composite material is formed in the step (2), the aging solution is slowly added along the wall of the container to immerse the wet gel in the aging solution, and the aging solution is sealed and kept stand for aging for 1 to 100 hours at 30 to 80 ℃ to obtain the aged silica wet gel composite material; and (2) the aging liquid is an aqueous solution of alkoxy alcohol or deionized water, the alkoxy alcohol is consistent with the alkoxy alcohol in the step (1), and a certain amount of modifier is added, wherein the added modifier accounts for 0.1-10% of the volume of the aging liquid.
10. The preparation method of the aerogel composite material as claimed in claim 9, wherein in the step (4), the silica wet gel composite material is transferred into a supercritical drying kettle, dried for 30-90 min under the pressure of 10-20 MPa and at the temperature of 30-80 ℃, transferred into a normal pressure drying kettle, and continuously dried for 20-100 min at the temperature of 80-120 ℃.
11. The method for preparing an aerogel composite material as claimed in claim 5, wherein in the step (5), the separated aqueous solution of the alkoxyalcohol is subjected to precipitation, multi-stage filtration, rectification in a rectification tower, and adsorption drying by a molecular sieve or membrane permeation.
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