Hydrophobic SiO2 aerogel preparing process

An airgel and sol technology, applied in chemical instruments and methods, inorganic chemistry, non-metallic elements, etc., can solve the problem of not finding cost-effective preparation methods of hydrophobic SiO aerogels, and the difficulty and unavoidability of increasing bulk aerogels Hydrogen chloride and other problems, to achieve the effect of improved production efficiency, low price, and easy conditions

Inactive Publication Date: 2005-07-13
TONGJI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] The above-mentioned two-step preparation process is quite complicated, and the quality is difficult to guarantee
First of all, the surface silylation reaction of silica gel cannot be guaranteed to be complete; secondly, modification with a chlorosilylating agent will inevitably produce by-products such as hydrogen chloride, which complicates the subsequent purification process; In addition, raw materials such as relatively expensive alkyl siloxanes (such as methyl orthosilicate, ethyl orthosilicate) and titanium tetrachloride are still used in some preparation processes, and supercritical drying processes are required in some preparation methods. , the process requires high equipment, which increases the difficulty of preparing bulk aerogels and makes airgel products extremely expensive
[0007] In short, so far, no hydrophobic SiO with low cost, simple process and high product quality has been found at home and abroad. 2 Airgel preparation method

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0020] First, commercially available neutral silica sol was selected as the silicon source, the pH of the silica sol was about 7.6, and the density was about 1.20 g cm -3 , SiO 2 Content about 30%, Na 2 O content 0.05%, SiO 2 The particle size of the colloidal particles is concentrated between 5 and 25nm, and the particle size distribution is quite uniform. Then, this silica sol is filtered with a filter screen to remove a small amount of suspended impurities in the commercially available silica sol. Select a commercially available density of about 0.899g cm -3 (25°C), colorless and transparent methyltriethoxysilane liquid with content ≥98% (molecular formula is CH 3 Si(OC 2 h 5 ) 3 ) is a silylating agent. At room temperature, under the stirring of an electric mixer, add silica sol, absolute ethanol and deionized water dropwise into a sealable container filled with methyltriethoxysilane (abbreviated as MTES). The typical formula is MTES: no The volume ratio of water ...

Embodiment 2

[0022] Repeat Example 1, but make the following changes: the pH of the selected silica sol is 9.96, and the density is 1.050g cm -3 , SiO 2 Content about 20%, Na 2 O content 0.35%, SiO 2 The particle size of the colloidal particles is concentrated between 12-40nm. Select industrial grade density of about 0.899g cm -3 (25°C), colorless and transparent methyltrimethoxysilane liquid with content ≥98% (molecular formula is CH 3 Si(OCH 3 ) 3 ) is a silylating agent. Methyltrimethoxysilane (abbreviated as MTMS): absolute ethanol: water: silica sol was mixed in a volume ratio of 1.5:2:1:1, and a certain amount of acetic acid was added to adjust the pH value to 6, and stirred at room temperature for 6 hours Then it turns into a slightly milky white transparent liquid, then add concentrated ammonia water to adjust the pH value to 7.0, seal it and place it in an oven at 60°C, and after 42 hours, ≡Si-O-Si≡ and ≡Si-O- Si-CH 3 Interlinked hydrophobic wet gel. After aging the gel ...

Embodiment 3

[0024] Repeat Example 1, but make the following changes: select commercially available alkaline silica sol as silicon source, the pH of this silica sol is about 10.5, and the density is about 1.320g cm -3 , SiO 2 Content about 40%, Na 2 O content 0.5%, SiO 2 The particle size of the colloidal particles is concentrated between 12-40nm. The selected silylating agent has a purity of not less than 98% and a density of 0.950-0.954 g·cm -3 Colorless and transparent methyltrimethoxysilane (molecular formula CH 3 Si(OCH 3 ) 3 )liquid. Methyltrimethoxysilane (abbreviated as MTMS): ethanol: water: silica sol mixed in a volume ratio of 4:16:8:1, adding a certain amount of acetic acid to adjust the pH value to 5, stirring at room temperature for 1 hour and mixing evenly , then add alkali to make the pH value at 10, seal it and place it in a constant temperature box at 30°C for about 20 hours to obtain Si-O-Si≡ and ≡Si-O-Si-CH 3 Interlinked hydrophobic wet gel. After aging for 24 ...

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Abstract

The hydrophobic SiO2 aerogel preparing process is one normal pressure one-step process. The preparation process includes mixing methyl trialkoxyl silane, lower alcohol, water and silicon sol in the volume ratio of 0.5-4 to 2-16 to 1-8 to 1 inside one sealed container; regulating pH value to 4-6, stirring 1-6 hr and letting stand at room temperature for 2-6 hr; regulating pH value to 7-10, sealing, letting stand inside stove at 30-60 deg.c for 4-42 hr to prepare cross-linked SiO2 mixed alcohol gel; ageing for 24 hr, soaking with alcohol or acetone for three times of 4 hr each; and finally stoving inside a stove at 60-80 deg.c for 12-36 hr to prepare the hydrophobic SiO2 aerogel. The prepared hydrophobic SiO2 aerogel has excellent performance: density of 100-600 kg/cu m, specific surface area of 340.06-436.86 sq m/g and water contact angle of 127-141 deg.

Description

technical field [0001] The present invention relates to a kind of hydrophobic SiO 2 The preparation method of airgel, specifically the preparation of hydrophobic SiO 2 Airgel process. Background technique [0002] SiO 2 Airgel is made of SiO 2 Colloidal particles coalesce to form a porous network structure, and a highly dispersed solid material filled with air in the pores of the porous network structure. It has unique properties in thermal, electrical, optical, acoustic and other aspects, so it has a wide range of applications. application prospects. However, many applications of aerogels need to be exposed to water or humid air. Since the usual airgel materials have open pores connecting the surface, high porosity, and the presence of a large number of hydroxyl groups on the surface, it is very easy to absorb air. The water vapor in the air will deteriorate, which weakens the practical value of aerogels in commercial applications. And the ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B33/159
Inventor 甘礼华马晓伟陈根李泽华王京红陈龙武
Owner TONGJI UNIV
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