A kind of supercritical drying preparation method of silica airgel thermal insulation material

Abstract

The invention relates to a supercritical drying preparation method for a silicon dioxide aerogel heat-insulation material. The method comprises the following steps: 1) diluting a water glass solution by using a certain amount of deionized water; 2) slowly adding the diluted water glass solution into a concentrated hydrochloric acid solution, and performing uniform mixing under continuous stirring, so as to obtain a highly-acidic silica sol; 3) performing rotary evaporation on the acidic silica sol solution to evaporate off partial water, taking out the processed sol, adding a water-soluble polar solvent with a low surface tension, performing uniform mixing with stirring, and then adding the diluted water glass solution to adjust the pH of the formed solution, so as to form a gel; and 4) adding a water-soluble polar solvent into the gel for aging and gelation, then putting the obtained wet gel in an extraction kettle, enabling the kettle to have a high-pressure internal environment and to be sealed, introducing supercritical CO2, contacting CO2 with the wet gel, and performing extraction and drying. The preparation method has the beneficial effects that the technology can be finished within a half day.

Description

technical field [0001] The invention belongs to the technical field of macromolecules, and in particular relates to a method for preparing a silica airgel thermal insulation material by supercritical drying. Background technique [0002] Silica airgel is a lightweight nanoporous material with controllable structure, which has many excellent properties, such as high porosity, high specific surface area, low density, low thermal conductivity, etc. The preparation of silica airgel at home and abroad usually uses methyl orthosilicate, ethyl orthosilicate or "water glass" as raw materials, adopts sol-gel method, and is often pressed and dried, such as Chinese patents 200810042222.4, 200910042159.5 , 201210123519.X, CN201210121968.0, CN201210114691.9, etc. all prepared mesoporous silica airgel materials using organic or inorganic silicon sources as precursors. The ubiquitous problems are that the preparation cycle is long, the hydrophilic material cannot be prepared, and the cont...

AI Technical Summary

Problems solved by technology

The ubiquitous problems are that the preparation cycle is long, the hydrophilic materials cannot be prepared, and the continuous production capacity is weak, which is not conducive to large-scale operation.

However, the temperature of this supercritical drying method is as high as 250 ° C and the pressure is 22 MPa, which consumes a lot of energy and is dangerous to operate. Tetraethyl orthosilicate is used as the silicon source, which greatly increases the cost of airgel and is not conducive to large-scale production. Production; similarly, the Chinese patent (application number 201510911661.4) adopts the supercritical drying method of solvent, the pressure and temperature are relatively high, and the silicon source also uses expensive organic silicon source, which will lead to the production cost of airgel Increase

[0004] To sum up, at present, the supercritical drying technology for preparing silica aerogels uses organosilicon sources as precursors, and the preparation cost is relatively high, which leads to the high price of silica aerogels currently on the market.