US3969266A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Microporous membrane process for making concentrated silica sols
Assignee: EIDP Inc
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Filing: 1973-07-02
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Granted: 1976-07-13
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Expires: 1993-07-02
Abstract
Abstract Aqueous silica sols having a pH from 8 to 11 containing 1 to 40% by weight of colloidal silica and soluble salts can be purified and concentrated by filtering the soluble salt from the sol using a microporous membrane filter while maintaining the salt concentration within a range determined by the concentration of silica in the sol. In one embodiment, colloidal silica particles are grown to a larger size by starting with a sol of nuclei, and adding sodium silicate solution and acid.
Inventors
- 👤 Ralph K. Iler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 13:00
CPC Classifications
C; C01; C01B; C01B33/00; C01B33/113; C01B33/12; C01B33/14; C01B33/146; C01B33/148; C01B33/141; C01B33/142; C01B33/143
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
193 words
A process for increasing the size of colloidal silica particles in an aqueous silica sol containing from 1 to 10% by weight silica consisting essentially of mixing with the sol at 80 to 100°C., a feed of sodium silicate solution and a solution of sulfuric acid, hydrochloric acid or carbon dioxide, the concentration of silica in the feed being below 0.6 times the weight ratio of SiO 2 :Na 2 O in the sodium silicate, the molar ratio of sodium silicate to sulfuric acid, hydrochloric acid or carbon dioxide in the feed being such to maintain the pH of the sol from 8 to 10 and the sodium salt concentration of the sol not above 0.2 normal and ultrafiltering the sol using a microporous membrane having pores smaller than the silica particles in the sol to remove sodium salt solution, while maintaining the concentration of sodium in the sol from N = 0.005 to N = 0.26-0.005C-0.002 (T-40) where N is the normality of the sodium in the sol, T is the temperature in degrees centigrade and C is the grams of silica per 100 milliliters of sol by the addition of water.
Claim 2
Dependent Claim
193 words
A process for increasing the size of colloidal silica particles in an aqueous silica sol containing from 1 to 10% by weight silica consisting essentially of mixing with the sol at 80 to 100°C., a feed of sodium silicate solution and a solution of sulfuric acid, hydrochloric acid or carbon dioxide, the concentration of silica in the feed being below 0.6 times the weight ratio of SiO 2 :Na 2 O in the sodium silicate, the molar ratio of sodium silicate to sulfuric acid, hydrochloric acid or carbon dioxide in the feed being such to maintain the pH of the sol from 8 to 10 and the sodium salt concentration of the sol not above 0.2 normal and ultrafiltering the sol using a microporous membrane having pores smaller than the silica particles in the sol to remove sodium salt solution, while maintaining the concentration of sodium in the sol from N = 0.005 to N = 0.26-0.005C-0.002 (T-40) where N is the normality of the sodium in the sol, T is the temperature in degrees centigrade and C is the grams of silica per 100 milliliters of sol by the addition of water.
Claim 3
Dependent Claim
102 words
The process of claim 1 wherein the maximum allowable concentration of sodium ions present during ultrafiltration is defined by the following equations: log.sub.10 C = -2.2 -3.2 log.sub.10 N.sub.80 n.sub.t = n.sub.80 +0.002 (80-t) where N 80 and N T are greater than 0.005; N 80 is the normality of the salt in the sol when ultrafiltering at 80°C.; N t is the normality of the salt in the solution at T °C.; T is the temperature in degrees centigrade at which ultrafiltration is carried out; and C is the concentration of silica expressed in grams of SiO 2 per 100 milliliters.
Claim 4
Dependent Claim
13 words
The process of claim 1 wherein sulfuric acid is employed in the feed.
Claim 5
Dependent Claim
13 words
The process of claim 2 wherein sulfuric acid is employed in the feed.
Claim 6
Dependent Claim
20 words
The process of claim 1 wherein the silica particles are first increased in size, and then the sol is ultrafiltered.
Claim 7
Dependent Claim
18 words
The process of claim 1 wherein the silica particles are increased in size and the sol ultrafiltered simultaneously.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-07-13 | 1980-01-12 | 1980-07-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-07-13 | 1984-01-12 | 1984-07-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-07-13 | 1988-01-12 | 1988-07-13 | $7700.00 | Window Closed / Lapsed |