US3846537A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process of preparing silica xerogels
Assignee: Monsanto Co
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Filing: 1972-08-21
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Granted: 1974-11-05
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Expires: 1992-08-21
Abstract
Abstract Silica xerogels having improved properties as flatting agents are prepared by the steps of (a) forming a semi-stable silica sol below pH 4 and below 70*C., using a minor portion of the batch silicate charge, (b) shutting off the batch agitator and gelling the sol below 70*C. and pH 4 or higher, (c) allowing the gel to grow in firmness without agitation, (d) dispersing the gel with agitation and continuing silicate and acid charging at about 87*C. and about pH 5.3, and (e) recovering the silica product.
Inventors
- 👤 R Marotta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 23:29
CPC Classifications
C; C01; C01B; C01B33/00; C01B33/113; C01B33/12; C01B33/14; C01B33/152; C01B33/154
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
162 words
A PROCESS OF PREPARING AN AMORPHOUS, PULVERULENT SILICA XEROGEL WHICH COMPRISES THE STEPS OF: A. FORMING A SILICA SOL BY FEEDING, TO AN AGITATED AQUEOUS HEEL, AN ALKALI METAL SILICATE SOLUTION AND A MINERAL ACID OTHER THAN HYDROFLUORIC ACID, WHILE MAINTAINING A BATCH PH OF LESS THAN ABOUT 4 AND A BATCH TEMPERATURE BELOW ABOUT 70*C., THEWEIGHT OF SILICA ADDED DURING THIS STEP (A) BEING FROM ABOUT 10 PERCENT TO ABOUT 45 PERCENT OF THE TOTAL SILICA TO BE ADDED DURING SAID PROCESS; B. GELLING SAID SOL AT A BATCH PH OF ABOUT 4 OR HIGHER AND A BATCH TEMPERATURE OF ABOUT 50*C. TO 70*C., AND INTERRUPTING THE AGITATION FOR AT LEAST ABOUT 30 SECONDS; C. RESUMING SAID AGITATION TO DISPERSE THE GEL; D. INTRODUCING ADDITIONAL ALKALI METAL SILICATE SOLUTION AND ACID WHILE MAINTAINING A BATCH PH OF FROM ABOUT 4 TO ABOUT 6.6 AND A BATCH TEMPERATURE OF FROM ABOUT 75*C. TO ABOUT 100*C.; AND E. RECOVERING THE SILICA XEROGEL PRODUCT.
Claim 2
Dependent Claim
162 words
A PROCESS OF PREPARING AN AMORPHOUS, PULVERULENT SILICA XEROGEL WHICH COMPRISES THE STEPS OF: A. FORMING A SILICA SOL BY FEEDING, TO AN AGITATED AQUEOUS HEEL, AN ALKALI METAL SILICATE SOLUTION AND A MINERAL ACID OTHER THAN HYDROFLUORIC ACID, WHILE MAINTAINING A BATCH PH OF LESS THAN ABOUT 4 AND A BATCH TEMPERATURE BELOW ABOUT 70*C., THEWEIGHT OF SILICA ADDED DURING THIS STEP (A) BEING FROM ABOUT 10 PERCENT TO ABOUT 45 PERCENT OF THE TOTAL SILICA TO BE ADDED DURING SAID PROCESS; B. GELLING SAID SOL AT A BATCH PH OF ABOUT 4 OR HIGHER AND A BATCH TEMPERATURE OF ABOUT 50*C. TO 70*C., AND INTERRUPTING THE AGITATION FOR AT LEAST ABOUT 30 SECONDS; C. RESUMING SAID AGITATION TO DISPERSE THE GEL; D. INTRODUCING ADDITIONAL ALKALI METAL SILICATE SOLUTION AND ACID WHILE MAINTAINING A BATCH PH OF FROM ABOUT 4 TO ABOUT 6.6 AND A BATCH TEMPERATURE OF FROM ABOUT 75*C. TO ABOUT 100*C.; AND E. RECOVERING THE SILICA XEROGEL PRODUCT.
Claim 3
Dependent Claim
33 words
A process of claim 1 wherein the silica sol is gelled at a batch pH of from about 4 to about 6.6 and a batch temperature of from about 58*C. to about 66*C.
Claim 4
Dependent Claim
21 words
A process of claim 1 wherein the gel is dispersed at a batch temperature of from about 82*C. to about 92*C.
Claim 5
Dependent Claim
28 words
A process of claim 1 wherein the major portion of silica introduced during said process is added at a batch temperature of from about 82*C. to about 92*C.
Claim 6
Dependent Claim
13 words
A process oF claim 1 wherein the alkali metal silicate is sodium silicate.
Claim 7
Dependent Claim
12 words
A process of claim 1 wherein the mineral acid is sulfuric acid.
Claim 8
Dependent Claim
28 words
A process of claim 1 wherein the silica introduced in step (a) comprises from about 15 percent to about 32 percent of the silica added during said process.
Claim 9
Dependent Claim
16 words
A process of claim 1 wherein the agitation is interrupted for at least about 6 minutes.
Claim 10
Dependent Claim
25 words
A process of claim 1 wherein the silica concentration in the final batch slurry is from about 6 percent to about 20 percent by weight.
References Cited (Backward Citations)
GB159508A
Cited
US3428425A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-11-04 | 1978-05-06 | 1978-11-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-04 | 1982-05-06 | 1982-11-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-04 | 1986-05-06 | 1986-11-05 | $7700.00 | Window Closed / Lapsed |