US5565142A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Preparation of high porosity xerogels by chemical surface modification.
Assignee: UNM Rainforest Innovations
•
Filing: 1993-04-28
•
Granted: 1996-10-15
•
Expires: 2013-04-28
Abstract
Abstract This invention provides an extremely porous xerogel dried at vacuum-to-below supercritical pressures but having the properties of aerogels which are typically dried at supercritical pressures. This is done by reacting the internal pore surface of the wet gel with organic substances in order to change the contact angle of the fluid meniscus in the pores during drying. Shrinkage of the gel (which is normally prevented by use of high autoclave pressures, such that the pore fluid is at temperature and pressure above its critical values) is avoided even at vacuum or ambient pressures.
Inventors
- 👤 Ravindra Deshpande
- 👤 Douglas M. Smith
- 👤 C. Jeffrey Brinker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 21:27
CPC Classifications
B; B01; B01J; B01J13/00; B01J13/0091; C; C01; C01B; C01B33/00; C01B33/113; C01B33/12; C01B33/16; C01B33/163; Y; Y02; Y02P; Y02P20/00; Y02P20/50; Y02P20/54; Y10; Y10T; Y10T428/00; Y10T428/29; Y10T428/2982; Y10T428/2991; Y10T428/2993; Y10T428/2995
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
167 words
The method of producing a xerogel of porosity greater than about 0.6 comprising the steps of: a) preparing a wet gel containing water, said gel having a pore fluid contact angle Θ and a substantial number of its atoms which are surface species, by at least one process selected from the group of hydrolysis and condensation of metal alkoxides, gelling of particulate metal oxides, and gelation of organic precursors; b) exchanging substantially all of the water contained in said wet gel with a protic or aprotic solvent; c) reacting said wet gel with a surface modification agent R x MX y , wherein R is an organic group, M is selected from the group consisting of Si and Al, and X is halogen, to cause replacement of a substantial number of surface species with a different species which substantially increases the pore fluid contact angle Θ; and d) drying said wet gel at one or more pressures selected to be within the range from vacuum to sub-critical.
Claim 2
Independent Claim
167 words
The method of producing a xerogel of porosity greater than about 0.6 comprising the steps of: a) preparing a wet gel containing water, said gel having a pore fluid contact angle Θ and a substantial number of its atoms which are surface species, by at least one process selected from the group of hydrolysis and condensation of metal alkoxides, gelling of particulate metal oxides, and gelation of organic precursors; b) exchanging substantially all of the water contained in said wet gel with a protic or aprotic solvent; c) reacting said wet gel with a surface modification agent R x MX y , wherein R is an organic group, M is selected from the group consisting of Si and Al, and X is halogen, to cause replacement of a substantial number of surface species with a different species which substantially increases the pore fluid contact angle Θ; and d) drying said wet gel at one or more pressures selected to be within the range from vacuum to sub-critical.
Claim 3
Dependent Claim
32 words
The method of claim 1 further including the step of aging the wet gel at an elevated temperature for a predetermined period of up to 46 hours before said step of exchanging.
Claim 4
Dependent Claim
27 words
The method of claim 2 wherein the elevated temperature is within the range of ambient to about the boiling point of the water in the wet gel.
Claim 5
Dependent Claim
29 words
The method of claim 1 further including, after said step of exchanging, the step of aging the gel at a temperature up to the boiling point of the solvent.
Claim 6
Dependent Claim
22 words
The method of claim 1 wherein in said step c) the wet gel is reacted with an organosilane in a selected solvent.
Claim 7
Dependent Claim
13 words
The method of claim 5 wherein the selected solvent is an organic solvent.
Claim 8
Dependent Claim
26 words
The method of claim 5 wherein said step c) further includes the step of removing unreacted surface modification agent with a protic or an aprotic solvent.
Claim 9
Dependent Claim
27 words
The method of claim 1 wherein said step a) includes the step of preparing the gel as a metal oxide gel from a solution of tetraethylorthosilicate (TEOS).
Claim 10
Dependent Claim
27 words
The method of claim 1 wherein said step a) includes the step of preparing the gel as a metal oxide gel from a colloidal or particulate silica.
Claim 11
Dependent Claim
33 words
The method of claim 1 wherein said step a) includes the step of preparing the gel as a metal oxide gel from an alkoxide or a particulate gel or a combination of both.
Claim 12
Dependent Claim
49 words
The method of claim 1 wherein the step of drying is in a range of pressures between vacuum and sub-critical and in a range of temperatures between ambient and the boiling point of the solvent in the wet gel, until the gel does not undergo any further weight loss.
References Cited (Backward Citations)
US2765242A
Cited
US2978298A
Cited
US2993809A
Cited
US3210273A
Cited
US3346507A
Cited
US3963627A
Cited
US3803046A
Cited
US4017528A
Cited
US4316807A
Cited
US4447345A
Cited
US5110784A
Cited
US4950635A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-10-15 | 2000-04-15 | 2000-10-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-10-15 | 2004-04-15 | 2004-10-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-10-15 | 2008-04-15 | 2008-10-15 | $7700.00 | Window Closed / Lapsed |