CN110902690A - Method for rapidly preparing hydrophobic silica aerogel by repeatedly increasing and decreasing pressure - Google Patents
Method for rapidly preparing hydrophobic silica aerogel by repeatedly increasing and decreasing pressure Download PDFInfo
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 58
- 238000000034 method Methods 0.000 title claims abstract description 36
- 230000002209 hydrophobic effect Effects 0.000 title claims abstract description 31
- 239000004965 Silica aerogel Substances 0.000 title claims abstract description 27
- 230000003247 decreasing effect Effects 0.000 title claims abstract description 17
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 35
- 238000000352 supercritical drying Methods 0.000 claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 20
- 238000001035 drying Methods 0.000 claims abstract description 17
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 15
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 15
- 230000000630 rising effect Effects 0.000 claims abstract description 13
- 230000032683 aging Effects 0.000 claims abstract description 10
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 9
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 9
- 238000002156 mixing Methods 0.000 claims abstract description 9
- 238000003756 stirring Methods 0.000 claims abstract description 9
- -1 orthosilicate ester Chemical class 0.000 claims abstract description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 22
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 13
- 239000000835 fiber Substances 0.000 claims description 12
- 239000003153 chemical reaction reagent Substances 0.000 claims description 11
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims description 10
- 238000002791 soaking Methods 0.000 claims description 9
- 229910021529 ammonia Inorganic materials 0.000 claims description 8
- LDDQLRUQCUTJBB-UHFFFAOYSA-N ammonium fluoride Chemical compound [NH4+].[F-] LDDQLRUQCUTJBB-UHFFFAOYSA-N 0.000 claims description 8
- 229910000069 nitrogen hydride Inorganic materials 0.000 claims description 8
- LFQCEHFDDXELDD-UHFFFAOYSA-N tetramethyl orthosilicate Chemical compound CO[Si](OC)(OC)OC LFQCEHFDDXELDD-UHFFFAOYSA-N 0.000 claims description 6
- JJQZDUKDJDQPMQ-UHFFFAOYSA-N dimethoxy(dimethyl)silane Chemical compound CO[Si](C)(C)OC JJQZDUKDJDQPMQ-UHFFFAOYSA-N 0.000 claims description 4
- YYLGKUPAFFKGRQ-UHFFFAOYSA-N dimethyldiethoxysilane Chemical compound CCO[Si](C)(C)OCC YYLGKUPAFFKGRQ-UHFFFAOYSA-N 0.000 claims description 4
- 235000019441 ethanol Nutrition 0.000 claims description 4
- UQEAIHBTYFGYIE-UHFFFAOYSA-N hexamethyldisiloxane Chemical compound C[Si](C)(C)O[Si](C)(C)C UQEAIHBTYFGYIE-UHFFFAOYSA-N 0.000 claims description 4
- SWGZAKPJNWCPRY-UHFFFAOYSA-N methyl-bis(trimethylsilyloxy)silicon Chemical compound C[Si](C)(C)O[Si](C)O[Si](C)(C)C SWGZAKPJNWCPRY-UHFFFAOYSA-N 0.000 claims description 4
- BFXIKLCIZHOAAZ-UHFFFAOYSA-N methyltrimethoxysilane Chemical compound CO[Si](C)(OC)OC BFXIKLCIZHOAAZ-UHFFFAOYSA-N 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims description 2
- VSYLGGHSEIWGJV-UHFFFAOYSA-N diethyl(dimethoxy)silane Chemical compound CC[Si](CC)(OC)OC VSYLGGHSEIWGJV-UHFFFAOYSA-N 0.000 claims description 2
- RSIHJDGMBDPTIM-UHFFFAOYSA-N ethoxy(trimethyl)silane Chemical compound CCO[Si](C)(C)C RSIHJDGMBDPTIM-UHFFFAOYSA-N 0.000 claims description 2
- MDLRQEHNDJOFQN-UHFFFAOYSA-N methoxy(dimethyl)silicon Chemical compound CO[Si](C)C MDLRQEHNDJOFQN-UHFFFAOYSA-N 0.000 claims description 2
- POPACFLNWGUDSR-UHFFFAOYSA-N methoxy(trimethyl)silane Chemical compound CO[Si](C)(C)C POPACFLNWGUDSR-UHFFFAOYSA-N 0.000 claims description 2
- MSRJTTSHWYDFIU-UHFFFAOYSA-N octyltriethoxysilane Chemical compound CCCCCCCC[Si](OCC)(OCC)OCC MSRJTTSHWYDFIU-UHFFFAOYSA-N 0.000 claims description 2
- 229960003493 octyltriethoxysilane Drugs 0.000 claims description 2
- UQMOLLPKNHFRAC-UHFFFAOYSA-N tetrabutyl silicate Chemical compound CCCCO[Si](OCCCC)(OCCCC)OCCCC UQMOLLPKNHFRAC-UHFFFAOYSA-N 0.000 claims description 2
- CPUDPFPXCZDNGI-UHFFFAOYSA-N triethoxy(methyl)silane Chemical compound CCO[Si](C)(OCC)OCC CPUDPFPXCZDNGI-UHFFFAOYSA-N 0.000 claims description 2
- IWICDTXLJDCAMR-UHFFFAOYSA-N trihydroxy(propan-2-yloxy)silane Chemical compound CC(C)O[Si](O)(O)O IWICDTXLJDCAMR-UHFFFAOYSA-N 0.000 claims description 2
- 102100029469 WD repeat and HMG-box DNA-binding protein 1 Human genes 0.000 claims 1
- 101710097421 WD repeat and HMG-box DNA-binding protein 1 Proteins 0.000 claims 1
- 239000004964 aerogel Substances 0.000 abstract description 21
- 238000002360 preparation method Methods 0.000 abstract description 3
- 239000007788 liquid Substances 0.000 description 15
- 239000000243 solution Substances 0.000 description 15
- 239000000499 gel Substances 0.000 description 11
- 125000004108 n-butyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 8
- 230000003068 static effect Effects 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 6
- 239000011259 mixed solution Substances 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- 125000001449 isopropyl group Chemical group [H]C([H])([H])C([H])(*)C([H])([H])[H] 0.000 description 4
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 208000035404 Autolysis Diseases 0.000 description 1
- 206010057248 Cell death Diseases 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000003889 chemical engineering Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 239000002612 dispersion medium Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000001879 gelation Methods 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000028043 self proteolysis Effects 0.000 description 1
- 239000000741 silica gel Substances 0.000 description 1
- 229910002027 silica gel Inorganic materials 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000011240 wet gel Substances 0.000 description 1
Classifications
-
- 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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- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Silicon Compounds (AREA)
Abstract
The invention discloses a method for rapidly preparing hydrophobic silica aerogel by repeatedly increasing and decreasing pressure, which comprises the following steps of ① taking orthosilicate ester, ethanol and water, mixing uniformly, and sequentially adding NH4The preparation method comprises the steps of uniformly stirring the solution F and ammonia water to obtain silicon dioxide sol, ② immersing a fibrofelt in the silicon dioxide sol, standing and aging for 8-24 h at 30-60 ℃, ③ carrying out repeated pressure rising and falling supercritical drying treatment on the fibrofelt, rising the pressure from 6-12 MPa to 18-20 MPa in short time, continuing for 0.5-2 h, then quickly lowering the pressure from 18-20 MPa to 6-12 MPa, continuing for 0.5-1 h, repeating the steps for many times, introducing a hydrophobizing agent during each pressure rising in the supercritical drying process to carry out hydrophobization treatment, and obtaining the hydrophobic silicon dioxide aerogel felt after drying.
Description
Technical Field
The invention relates to the technical field of aerogel preparation, in particular to a method for quickly preparing hydrophobic silica aerogel by repeatedly increasing and decreasing pressure.
Background
The aerogel is a gel material taking a dispersion medium as gas, has a highly-crosslinked continuous three-dimensional network nano hollow structure inside, and has a large specific surface area (500-2G) low density (30-150 Kg/m)3) High porosity (85-99 percent), small average pore diameter (2-50 nm), lower thermal conductivity (0.01-0.02W/m.K) than room temperature air and the like, and is a solid material with the lowest thermal conductivity which is generally accepted at present. The silicon dioxide aerogel realizes wide research and application in the aspects of aerospace, chemical engineering, energy-saving buildings, heat insulation, catalyst carriers, optics, acoustics and the like by using the unique physical and chemical characteristics.
The existing preparation technology of silicon dioxide aerogel mainly comprises two parts, namely: preparing gel and drying the gel. Silicon source, solvent and catalyst are adopted to prepare silica gel to be dried through hydrolysis, gelation, aging and hydrophobization treatment, and then the aerogel is obtained through drying the gel. The hydrophobization method that is commonly used at present is to place the gel in a prepared hydrophobization solution after the completion of the gel reaction, and take out the hydrophobization-treated gel to perform a drying treatment. Although this method can produce a hydrophobized silica aerogel, it involves many solvent replacements in actual production, has a long reaction period, and increases production costs, and since the hydrophobization modification treatment of the gel is performed by autolysis, the degree of hydrophobization of the gel is not uniform, and the efficiency is low.
In order to obtain aerogel with good structural performance, the conventional drying method of the gel is mainly supercritical drying, and the conversion from wet gel to aerogel is completed on the premise of maintaining the original skeleton structure because the solvent has no obvious surface tension in the supercritical drying process. However, the conventional supercritical drying process needs a relatively long experimental period and high production cost, and the drying is completed in a sealing manner at proper pressure and temperature, so that the supercritical drying can be more efficiently improved on the basis of ensuring the good performance of the aerogel structure, and the hydrophobization treatment is performed in the drying process, so that the hydrophobization reagent is uniformly diffused under a high-pressure state, and the homogenization treatment is realized.
Disclosure of Invention
The invention aims to provide a method for rapidly preparing hydrophobic silica aerogel by repeatedly increasing and decreasing pressure.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for rapidly preparing hydrophobic silica aerogel by repeatedly increasing and decreasing pressure comprises the following steps:
① mixing n-silicate, ethanol and water, and sequentially adding NH4Uniformly stirring the solution F and ammonia water to obtain silicon dioxide sol; wherein, in terms of molar ratio, the orthosilicate ester, the ethanol and the water are = 1: (4-12): (2-4); NH (NH)4The amount of solution F added is in terms of mole ratio, NH4F, orthosilicate ester = (0.002-0.01): 1; the amount of ammonia added is in terms of molar ratio, NH3Orthosilicate = (0.005-0.015) 1;
②, soaking the fibrofelt in the silica sol obtained in the step ①, and then statically aging for 8-24 hours at the temperature of 30-60 ℃;
③, repeatedly performing pressure rising and falling supercritical drying treatment on the fibrofelt obtained in the step ②, wherein the pressure is raised from 6-12 MPa to 18-20 MPa for 0.5-2 h in a short time, then quickly lowered from 18-20 MPa to 6-12 MPa for 0.5-1 h, repeating the steps for multiple times, introducing a hydrophobizing reagent into supercritical equipment while raising the pressure each time in the supercritical drying process, performing hydrophobizing treatment, and drying to obtain the hydrophobic silica aerogel felt.
In step ①, the orthosilicate is one of methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate, or isopropyl orthosilicate.
In step ②, the time for dipping the fiber felt into the silica sol is 12-24 hours.
In step ③, the number of times of repeatedly raising and lowering the pressure in the supercritical drying is 4 to 6 times.
In step ③, the hydrophobizing agent is a mixture of a hydrophobizing agent and absolute ethyl alcohol in a molar ratio of 1: 2-5.
The hydrophobic agent is one or more of methyltrimethoxysilane, methyltriethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethylmethoxysilane, diethyldimethoxysilane, tetraethoxysilane, hexamethyldisiloxane, heptamethyltrisiloxane and octyltriethoxysilane.
The invention provides a method for rapidly preparing hydrophobic silica aerogel by repeatedly increasing and decreasing pressure, wherein the pressure is increased from 6-12 MPa to 18-20 MPa for 0.5-2 h in a short time, then is rapidly decreased from 18-20 MPa to 6-12 MPa for 0.5-1 h, and the process is repeated for many times, so that the supercritical drying pressure is changed by repeatedly increasing and decreasing the pressure, the drying speed is accelerated, the gas is promoted to be forcibly diffused into the aerogel at high pressure, the gas is promoted to bring the liquid out of gel holes at low pressure, the drying time of the aerogel is shortened, the product quality is ensured, and the production cost is reduced.
According to the invention, in the supercritical drying process, the pressure is increased each time, the hydrophobization reagent is introduced, the hydrophobization reagent is carried by the supercritical carbon dioxide and enters the supercritical equipment for hydrophobization treatment, the hydrophobization reagent can be forcibly diffused in the supercritical state, so that the hydrophobization reagent is uniformly distributed in an aerogel network, the conventional hydrophobization reaction time is shortened, and the hydrophobization reaction rate is improved by repeatedly increasing and decreasing the pressure. Meanwhile, the method avoids the replacement of a large amount of solvent after the traditional hydrophobization reaction is finished, so that the on-site solvent storage amount can be reduced, and the production efficiency is improved. The unreacted hydrophobizing agent of the invention can also be reacted via CO2The extraction is separated out for continuous use, and the production cost is reduced.
The hydrophobic silica aerogel felt prepared and produced by the method adopts a protractor to measure the contact angle of the static liquid drop (water drop) on the surface of the aerogel felt, and the included angle between the liquid drop and the surface is 120-135 degrees.
Detailed Description
The invention will be further explained and illustrated with reference to specific examples:
example 1
A method for rapidly preparing hydrophobic silica aerogel by repeatedly increasing and decreasing pressure comprises the following steps:
① mixing ethyl orthosilicate, absolute ethyl alcohol and water evenly, then adding 2mol/L NH in turn4Uniformly stirring the solution F and 0.2moL/L ammonia water to obtain silicon dioxide sol; wherein, in terms of molar ratio, ethyl orthosilicate: anhydrous ethanol: water = 1: 12: 4; NH (NH)4The amount of solution F added is in terms of mole ratio, NH4F: ethyl orthosilicate = 0.008: 1; the amount of ammonia added is in terms of molar ratio, NH3: ethyl orthosilicate = 0.01: 1;
② soaking the fiber felt in the silica sol obtained in the step ① for 20h, and then statically aging the fiber felt for 24h at 40 ℃;
③, repeatedly performing pressure rising and falling supercritical drying treatment on the fibrofelt obtained in the step ②, wherein the pressure rises from 10MPa to 20MPa in a short time and lasts for 2 hours, then quickly falls from 20MPa to 10MPa and lasts for 0.5 hour, repeating the steps for 5 times, introducing a hydrophobizing agent into a supercritical device while rising the pressure each time in the supercritical drying process, performing hydrophobizing treatment, and obtaining the hydrophobic silica aerogel felt after drying.
Wherein the hydrophobization reagent is methyl trimethoxy silane and absolute ethyl alcohol, and the molar ratio of the methyl trimethoxy silane to the absolute ethyl alcohol is 1:2, and (c) a mixed solution.
The contact angle of the static liquid drop (water drop) on the surface of the aerogel felt is measured by using a protractor, and the included angle between the liquid drop and the surface is 132 degrees.
Example 2
A method for rapidly preparing hydrophobic silica aerogel by repeatedly increasing and decreasing pressure comprises the following steps:
① mixing methyl orthosilicate, absolute ethyl alcohol and water evenly, then adding 2mol/L NH in turn4Solution FUniformly stirring the solution and 0.2moL/L ammonia water to obtain silicon dioxide sol; wherein, in terms of mole ratio, methyl orthosilicate: anhydrous ethanol: water = 1: 10: 3; NH (NH)4The amount of solution F added is in terms of mole ratio, NH4F: methyl orthosilicate = 0.01: 1; the amount of ammonia added is in terms of molar ratio, NH3: methyl orthosilicate = 0.008: 1;
② soaking the fiber felt in the silica sol obtained in the step ① for 16h, and then statically aging the fiber felt for 15h at 60 ℃;
③, repeatedly performing pressure rising and falling supercritical drying treatment on the fibrofelt obtained in the step ②, wherein the pressure rises from 8MPa to 18MPa in a short time and lasts for 1.5h, then the pressure quickly falls from 18MPa to 8MPa and lasts for 1h, repeating the steps for 6 times, introducing a hydrophobizing agent into a supercritical device while rising the pressure each time in the supercritical drying process, performing hydrophobizing treatment, and obtaining the hydrophobic silica aerogel felt after drying.
Wherein the hydrophobization reagent is a mixed solution of tetraethoxysilane and absolute ethyl alcohol according to the molar ratio of 1: 3.
The contact angle of the static liquid drop (water drop) on the surface of the aerogel felt is measured by using a protractor, and the included angle between the liquid drop and the surface is 125 degrees.
Example 3
A method for rapidly preparing hydrophobic silica aerogel by repeatedly increasing and decreasing pressure comprises the following steps:
① taking n-butyl silicate, absolute ethyl alcohol and water, mixing evenly, and then adding 2mol/L NH in sequence4Uniformly stirring the solution F and 0.2moL/L ammonia water to obtain silicon dioxide sol; wherein, in terms of mole ratio, n-butyl silicate: anhydrous ethanol: water = 1: 8: 3; NH (NH)4The amount of solution F added is in terms of mole ratio, NH4F: n-butyl silicate = 0.006: 1; the amount of ammonia added is in terms of molar ratio, NH3: n-butyl silicate = 0.012: 1;
② soaking the fiber felt in the silica sol obtained in the step ① for 24h, and then statically aging at 50 ℃ for 20 h;
③, repeatedly performing pressure rising and falling supercritical drying treatment on the fibrofelt obtained in the step ②, wherein the pressure is raised from 12MPa to 19MPa in a short time and lasts for 0.5 hour, then the pressure is rapidly lowered from 19MPa to 12MPa and lasts for 0.8 hour, repeating the steps for 4 times, introducing a hydrophobizing agent into a supercritical device while raising the pressure in the supercritical drying process each time, performing hydrophobizing treatment, and obtaining the hydrophobic silica aerogel felt after drying.
Wherein the hydrophobization reagent is a mixed solution of dimethyl diethoxy silane and absolute ethyl alcohol according to the molar ratio of 1: 5.
The contact angle of the static liquid drop (water drop) on the surface of the aerogel felt is measured by using a protractor, and the included angle between the liquid drop and the surface is 128 degrees.
Example 4
A method for rapidly preparing hydrophobized silicon dioxide aerogel by repeatedly increasing and decreasing pressure comprises the following steps:
① mixing isopropyl n-silicate, anhydrous ethanol and water, and sequentially adding 2mol/L NH4Uniformly stirring the solution F and 0.2moL/L ammonia water to obtain silicon dioxide sol; wherein, in terms of mole ratio, isopropyl n-silicate: anhydrous ethanol: water = 1: 6: 2; NH (NH)4The amount of solution F added is in terms of mole ratio, NH4F: isopropyl n-silicate = 0.003: 1; the amount of ammonia added is in terms of molar ratio, NH3: isopropyl n-silicate = 0.006: 1;
② soaking the fiber felt in the silica sol obtained in the step ① for 15h, and then statically aging the fiber felt for 20h at 50 ℃;
③, repeatedly performing pressure rising and falling supercritical drying treatment on the fibrofelt obtained in the step ②, wherein the pressure is raised from 6MPa to 18MPa in a short time and lasts for 0.8 hour, then the pressure is rapidly lowered from 18MPa to 6MPa and lasts for 0.5 hour, and repeating for 4 times, a hydrophobizing agent is introduced into a supercritical device while the pressure is raised each time in the supercritical drying process, so that the hydrophobizing treatment is performed, and the hydrophobic silica aerogel felt is obtained after the drying is completed.
Wherein the hydrophobization reagent is a mixed solution of dimethyl dimethoxysilane and absolute ethyl alcohol according to the molar ratio of 1: 5.
The contact angle of the static liquid drop (water drop) on the surface of the aerogel felt is measured by using a protractor, and the included angle between the liquid drop and the surface is 124 degrees.
Example 5
A method for rapidly preparing hydrophobic silica aerogel by repeatedly increasing and decreasing pressure comprises the following steps:
① mixing ethyl orthosilicate, absolute ethyl alcohol and water evenly, then adding 2mol/L NH in turn4Uniformly stirring the solution F and 0.2moL/L ammonia water to obtain silicon dioxide sol; wherein, in terms of molar ratio, ethyl orthosilicate: anhydrous ethanol: water = 1: 6: 3; NH (NH)4The amount of solution F added is in terms of mole ratio, NH4F: ethyl orthosilicate = 0.005: 1; the amount of ammonia added is in terms of molar ratio, NH3: ethyl orthosilicate = 0.009: 1;
② soaking the fiber felt in the silica sol obtained in the step ① for 15h, and then statically aging the fiber felt for 18h at 50 ℃;
③, repeatedly performing pressure rising and falling supercritical drying treatment on the fibrofelt obtained in the step ②, wherein the pressure is raised from 9MPa to 16MPa in a short time and lasts for 1.2h, then the pressure is rapidly lowered from 16MPa to 9MPa and lasts for 0.8h, the steps are repeated for 5 times, a hydrophobizing agent is introduced into a supercritical device while the pressure is raised each time in the supercritical drying process, the hydrophobizing treatment is performed, and the hydrophobic silica aerogel felt is obtained after the drying is completed.
Wherein the hydrophobizing agent is a mixed solution of a hydrophobizing agent and absolute ethyl alcohol according to the molar ratio of 1: 4, the hydrophobizing agent is a mixture of dimethyldiethoxysilane and dimethyldimethoxysilane, and the molar ratio of the two is 1: 1.
The contact angle of the static liquid drop (water drop) on the surface of the aerogel felt is measured by using a protractor, and the included angle between the liquid drop and the surface is 130 degrees.
Example 6
A method for rapidly preparing hydrophobized silicon dioxide aerogel by repeatedly increasing and decreasing pressure comprises the following steps:
① taking n-butyl silicate, absolute ethyl alcohol and water, mixing evenly, and then adding 2mol/L NH in sequence4Uniformly stirring the solution F and 0.2moL/L ammonia water to obtain silicon dioxide sol; wherein, in terms of mole ratio, n-butyl silicate: anhydrous ethanol: water = 1: 10: 4; NH (NH)4Addition of F solutionIn terms of mole ratio, NH4F: n-butyl silicate = 0.007: 1; the amount of ammonia added is in terms of molar ratio, NH3: n-butyl silicate = 0.012: 1;
② soaking the fiber felt in the silica sol obtained in the step ① for 22h, and then statically aging at 60 ℃ for 10 h;
③, repeatedly performing pressure rising and falling supercritical drying treatment on the fibrofelt obtained in the step ②, wherein the pressure is raised from 8MPa to 16MPa in a short time and lasts for 1.8h, then the pressure is rapidly lowered from 16MPa to 8MPa and lasts for 0.6h, the steps are repeated for 5 times, a hydrophobizing agent is introduced into a supercritical device while the pressure is raised each time in the supercritical drying process, the hydrophobizing treatment is performed, and the hydrophobic silica aerogel felt is obtained after the drying is completed.
Wherein the hydrophobizing agent is a mixed solution of a hydrophobizing agent and absolute ethyl alcohol according to the molar ratio of 1: 3, the hydrophobizing agent is a mixture of heptamethyltrisiloxane and hexamethyldisiloxane, and the molar ratio of the heptamethyltrisiloxane to the hexamethyldisiloxane is 1: 2.
The contact angle of the static liquid drop (water drop) on the surface of the aerogel felt is measured by using a protractor, and the included angle between the liquid drop and the surface is 132 degrees.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A method for rapidly preparing hydrophobic silica aerogel by repeatedly increasing and decreasing pressure comprises the following steps:
① mixing n-silicate, ethanol and water, and sequentially adding NH4Uniformly stirring the solution F and ammonia water to obtain silicon dioxide sol; wherein, in terms of mole ratio, orthosilicate: ethanol: water = 1: 4-12: 2-4; NH (NH)4The amount of solution F added is in terms of mole ratio, NH4F, orthosilicate ester = (0.002-0.01): 1; the amount of ammonia added is in terms of molar ratio, NH3Orthosilicate (0.005-0.015) and1；
②, soaking the fibrofelt in the silica sol obtained in the step ①, and then statically aging for 8-24 hours at the temperature of 30-60 ℃;
③, repeatedly performing pressure rising and falling supercritical drying treatment on the fibrofelt obtained in the step ②, wherein the pressure is raised from 6-12 MPa to 18-20 MPa for 0.5-2 h in a short time, then quickly lowered from 18-20 MPa to 6-12 MPa for 0.5-1 h, repeating the steps for multiple times, introducing a hydrophobizing reagent into supercritical equipment while raising the pressure each time in the supercritical drying process, performing hydrophobizing treatment, and drying to obtain the hydrophobic silica aerogel felt.
2. The method for rapidly preparing hydrophobic silica aerogel by using repeated pressure and pressure drop as claimed in claim 1, wherein in step ①, the n-silicate is one of methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate and isopropyl orthosilicate.
3. The method for rapidly preparing the hydrophobic silica aerogel by using repeated pressure and pressure drop as claimed in claim 1, wherein in the step ②, the time for soaking the fiber mat in the silica sol is 12-24 hours.
4. The method for rapidly preparing hydrophobic silica aerogel by using repeated pressure increase and decrease according to claim 1, wherein in the step ③, the number of times of repeated pressure increase and decrease in the supercritical drying is 4-6.
5. The method for rapidly preparing hydrophobic silica aerogel by using repeated pressure increase and decrease according to claim 1, wherein in step ③, the hydrophobic agent is a mixture of a hydrophobic agent and absolute ethyl alcohol in a molar ratio of 1: 2-5.
6. The method for rapidly preparing the hydrophobic silica aerogel by using repeated pressure and pressure reduction as claimed in claim 5, wherein the pressure reduction step comprises the following steps: the hydrophobic agent is one or more of methyltrimethoxysilane, methyltriethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethylmethoxysilane, diethyldimethoxysilane, tetraethoxysilane, hexamethyldisiloxane, heptamethyltrisiloxane and octyltriethoxysilane.
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| CN114773027A (en) * | 2022-06-16 | 2022-07-22 | 巩义市泛锐熠辉复合材料有限公司 | Aerogel felt prepared at low cost and preparation method thereof |
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