US4678652A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for producing silica in fine powder form
Assignee: Nippon Sheet Glass Co Ltd
•
Filing: 1985-10-09
•
Granted: 1987-07-07
•
Expires: 2005-10-09
Abstract
Abstract A process for producing silica in fine powder form, which comprises (a) adding at least one water-miscible alcohol selected from water-miscible monohydric and dihydric alcohols to an aqueous solution of an alkali metal silicate having an SiO 2 concentration of 9 to 20% by weight until a solid precipitate forms and the solution begins, or is about, to become turbid, (b) adding a mineral acid to the resulting mixture in an amount 35 to 80% of the stoichiometrical amount required to neutralize the alkali metal silicate to precipitate silica as a fine powder, and (c) thereafter bringing the resulting slurry into contact with a mineral acid under an acidity of at least 1N.
Inventors
- 👤 Hiroyuki Tamenori
- 👤 Akihiko Hattori
- 👤 Mitsugi Yoshiyagawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 21:41
CPC Classifications
C; C01; C01B; C01B33/00; C01B33/113; C01B33/12; C01B33/18; C01B33/187; C01P; C01P2006/00; C01P2006/80
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
112 words
A process for producing silica in powder form, which comprises (a) adding at least one water-miscible alcohol selected from water-miscible monohydric and dihydric alcohols to an aqueous solution of an alkali metal silicate having an SiO 2 concentration of 9 to 20% by weight until a solid precipitate forms and the solution begins, or is about, to become turbid, (b) adding a mineral acid to the resulting mixture in an amount 35 to 80% of the stoichiometrical amount required to neutralize the alkali metal silicate to precipitate silica as a fine powder, and (c) thereafter bringing the resulting slurry into contact with a mineral acid under an acidity of at least 1N.
Claim 2
Dependent Claim
112 words
A process for producing silica in powder form, which comprises (a) adding at least one water-miscible alcohol selected from water-miscible monohydric and dihydric alcohols to an aqueous solution of an alkali metal silicate having an SiO 2 concentration of 9 to 20% by weight until a solid precipitate forms and the solution begins, or is about, to become turbid, (b) adding a mineral acid to the resulting mixture in an amount 35 to 80% of the stoichiometrical amount required to neutralize the alkali metal silicate to precipitate silica as a fine powder, and (c) thereafter bringing the resulting slurry into contact with a mineral acid under an acidity of at least 1N.
Claim 3
Dependent Claim
13 words
The process of claim 1 wherein the alkali metal silicate is sodium silicate.
Claim 4
Dependent Claim
23 words
The process of claim 1 wherein the SiO 2 concentration of the aqueous alkali metal silicate solution is 11 to 17% by weight.
Claim 5
Dependent Claim
26 words
The process of claim 1 wherein the water-miscible alcohol is added in an amount within the range of not more than ±30% of its turbidity point.
Claim 6
Dependent Claim
19 words
The process of claim 1 wherein the water-miscible monohydric alcohol is an alkanol having 1 to 4 carbon atoms.
Claim 7
Dependent Claim
33 words
The process of claim 1 wherein the water-miscible dihydric alcohol is selected from alkylene diols having 2 to 4 carbon atoms and polyalkylene oxides having an average molecular weight of 200 to 600.
Claim 8
Dependent Claim
21 words
The process of claim 1 wherein the water-miscible alcohol is polyethylene oxide having an average molecular weight of 200 to 400.
Claim 9
Dependent Claim
15 words
The process of claim 1 wherein the mineral acid is sulfuric acid or nitric acid.
Claim 10
Dependent Claim
33 words
The process of claim 1 wherein in step (b) the mineral acid is added in an amount corresponding to 50 to 70% of the stoichiometrical amount required to neutralize the alkali metal silicate.
Claim 11
Dependent Claim
26 words
The process of claim 1 wherein the addition of the mineral acid in step (b) is carried out slowly while inhibiting the formation of a gel.
Claim 12
Dependent Claim
41 words
The process of claim 10 wherein in step (b), the addition of the mineral acid in an amount reaching 35% of the stoichiometrical amount required to neutralize the alkali metal silicate is effected over the course of at least 5 minutes.
Claim 13
Dependent Claim
34 words
The process of claim 10 wherein in step (b), the addition of the mineral acid is effected while stirring the mixture so that the pH of the resulting slurry is not lower than 10.
Claim 14
Dependent Claim
23 words
The process of claim 1 wherein the step (b) is carried out at a temperature in the range of 15° to 50° C.
Claim 15
Dependent Claim
19 words
The process of claim 1 wherein the acidity in step (c) is in the range of 1.5 to 4N.
Claim 16
Dependent Claim
20 words
The process of claim 1 wherein the step (c) is carried out at a temperatrue of at least 70° C.
Claim 17
Dependent Claim
26 words
The process of claim 1 wherein following step (c), the resulting slurry is filtered, and the filtration cake is washed with a mineral acid and/or water.
Claim 18
Dependent Claim
15 words
The process of claim 16 wherein the mineral acid is hydrochloric acid or nitric acid.
References Cited (Backward Citations)
EP0044236A1
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-07-06 | 1991-01-05 | 1991-07-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-07-06 | 1995-01-05 | 1995-07-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-07-06 | 1999-01-05 | 1999-07-07 | $7700.00 | Window Closed / Lapsed |