Method for preparing hydrophobic silica aerogel

Patent metadata

Field	Value
Publication number	US-9834446-B2
Application number	US-201514653189-A
Country	US
Kind code	B2
Filing date	Feb 4, 2015
Priority date	Feb 6, 2014
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

Provided are a method for preparing a hydrophobic silica aerogel by the combined use of a first surface modifier and a second surface modifier, and a hydrophobic silica aerogel prepared by using the method. A hydrophobic silica aerogel having excellent physical properties and pore characteristics as well as a high degree of hydrophobicity may be prepared with high efficiency by the preparation method according to the present invention.

First claim

The invention claimed is:

1. A method for preparing a hydrophobic silica aerogel, the method comprising:
preparing a hydrated second surface modifier by mixing a second surface modifier with water in a weight ratio of from 1:0.5 to 1:2 and stirring for 20 to 30 hours;
preparing a hydrophobic silica wet gel by adding a first surface modifier, the hydrated second surface modifier, a non-polar organic solvent, and an inorganic acid to a water glass solution and performing a reaction; and
washing and drying the hydrophobic silica wet gel, wherein:
the first surface modifier comprises two or more hydrophobic groups in one molecule, and
the hydrated second surface modifier comprises two or more reactive groups reactable with a hydrophilic group on a surface of silica.

2. The method of claim 1 , wherein the water glass solution comprises silica in an amount of 0.1 wt % to 30 wt %.

3. The method of claim 1 , wherein the water glass solution and the first surface modifier are added in a volume ratio of 1:0.03 to 1:0.15.

4. The method of claim 1 , wherein the water glass solution and the hydrated second surface modifier are added in a volume ratio of 1:0.001 to 1:0.05.

5. The method of claim 1 , wherein
the water glass solution comprises silica in an amount of 3 wt % to 30 wt %.

6. The method of claim 1 , wherein the first surface modifier and the hydrated second surface modifier are added in a volume ratio of 1:0.01 to 1:0.9.

7. The method of claim 1 , wherein the first surface modifier comprises any one selected from the group consisting of an alkyldisilazane-based compound and a hydrate thereof, or a mixture of two or more thereof.

8. The method of claim 1 , wherein the first surface modifier comprises any one selected from the group consisting of an alkyldisilazane-based compound of Chemical Formula 1 and a hydrate thereof, or a mixture of two or more thereof:

wherein each R 1 independently is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, each R 2 independently is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms and, in R 1 and R 2 , at least two functional groups are alkyl groups.

9. The method of claim 1 , wherein the first surface modifier comprises any one selected from the group consisting of hexaalkyldisilazane, tetraalkyldisilazane, and a hydrate thereof, or a mixture of two or more thereof.

10. The method of claim 1 , wherein the first surface modifier comprises any one selected from the group consisting of hexamethyldisilazane and hydrated hexamethyldisilazane, or a mixture thereof.

11. The method of claim 1 , wherein the second surface modifier comprises an alkoxysilane-based compound including two or more alkoxy groups in one molecule, or a mixture of two or more thereof.

12. The method of claim 1 , wherein the second surface modifier comprises an alkoxysilane-based compound of Chemical Formula 2, or a mixture of two or more thereof:

wherein R 21 to R 24 each independently is an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, and at least two of R 21 to R 24 are alkoxy groups.

13. The method of claim 1 , wherein the second surface modifier comprises an alkyltrialkoxysilane, a dialkyldialkoxysilane, or a mixture of two or more thereof.

14. The method of claim 1 , wherein the second surface modifier comprises methyltrimethoxysilane, dimethyldimethoxysilane, or a mixture thereof.

15. The method of claim 1 , wherein the non-polar organic solvent comprises any one selected from the group consisting of hexane, heptane, toluene, and xylene, or a mixture of two or more thereof.

16. The method of claim 1 , wherein the water glass solution and the non-polar organic solvent are added in a volume ratio of 1:1 to 1:2.

17. The method of claim 1 , wherein the inorganic acid comprises any one selected from the group consisting of nitric acid, hydrochloric acid, sulfuric acid, acetic acid, and hydrofluoric acid, or a mixture of two or more thereof.

18. The method of claim 1 , wherein the preparing of the hydrophobic silica wet gel is performed in a temperature range of 40° C. to 60° C.

19. The method of claim 1 , wherein solvent substitution, surface modification, and gelation are simultaneously performed during the preparation of the hydrophobic silica wet gel.

20. The method of claim 1 , wherein the hydrophobic silica wet gel is prepared by adding the non-polar organic solvent to the water glass solution to prepare a water glass-non-polar organic solvent layer separation composition which includes a water glass solution layer and a non-polar organic solvent layer; and adding the first surface modifier, the hydrated second surface modifier, and the inorganic acid to the water glass-non-polar organic solvent layer separation composition and performing a reaction.

21. The method of claim 20 , wherein the first surface modifier, the hydrated second surface modifier, and the inorganic acid are simultaneously added or sequentially added to the water glass-non-polar organic solvent layer separation composition.

22. The method of claim 20 , wherein the inorganic acid is added in two divided portions to the water glass-non-polar organic solvent layer separation composition.

23. The method of claim 1 , wherein the hydrophobic silica wet gel is prepared by adding the non-polar organic solvent to the water glass solution to prepare a water glass-non-polar organic solvent layer separation composition which includes a water glass solution layer and a non-polar organic solvent layer; adding the first surface modifier and an inorganic acid to the water glass-non-polar organic solvent layer separation composition and reacting to prepare a first surface-modified silica wet gel; and adding an inorganic acid and the hydrated second surface modifier to the first surface-modified silica wet gel and performing a reaction.

24. The method of claim 1 , wherein the hydrophobic silica wet gel is prepared by passing the water glass solution through an ion exchange resin to prepare a silica sol; and adding the inorganic acid, the first surface modifier, the hydrated second surface modifier, and the non-polar organic solvent to the silica sol and performing a reaction.

25. The method of claim 24 , wherein the inorganic acid, the first surface modifier, the hydrated second surface modifier, and the non-polar organic solvent are simultaneously added or sequentially added to the silica sol.

26. The method of claim 24 , wherein the ion exchange resin is selected from the group consisting of a cation exchange resin, an anion exchange resin, or an amphoteric ion exchange resin.

27. The method of claim 24 , wherein the ion exchange resin is a strong acidic cation exchange resin.

28. The method of claim 1 , wherein the hydrophobic silica wet gel is prepared by passing the water glass solution through an ion exchange resin to prepare a silica sol; adding the inorganic acid, the first surface modifier, and the non-polar organic solvent to the silica sol and reacting to prepare a first surface-modified silica wet gel; and adding the hydrated second surface modifier to the first surface-modified silica wet gel and perform

Assignees

• Lg Chemical Ltd

Inventors

• Kim Mi Ri
• Oh Kyoung Shil
• Kim Ye Hon
• Cho Dong Hyun
• Kim Young Sam
• Yu Sung Min
• Oh Jin Hee
• Lee Je Kyun

Classifications

• C01P2006/12

  Surface area · CPC title

• C01P2006/17

  Pore diameter distribution · CPC title

• C01P2006/14

  Pore volume · CPC title

• C01B33/1585 Primary

  Dehydration into aerogels · CPC title

• C01B33/16 Primary

  Preparation of silica xerogels · CPC title