US4474824A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Methods of preparing hydrous silica gels
Assignee: WR Grace and Co Conn
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Filing: 1980-02-15
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Granted: 1984-10-02
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Expires: 2000-02-15
Abstract
Abstract Dentifrice compositions containing a hydrous silica gel having a water content of from about 20 to about 60 weight percent are disclosed. The abrasiveness of the gel is increased by contacting the gel with an alkaline medium to provide a gel pH of about 6 to about 10 and/or preparing the gel by drying and grinding a silica hydrogel that has been washed with an aqueous acidic solution having a temperature of from about 80 DEG to about 100 DEG F.
Inventors
- 👤 II Robert B. DeWolf
- 👤 Rimantas Glemza
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:13
CPC Classifications
A; A61; A61K; A61K8/00; A61K8/02; A61K8/04; A61K8/042; A61K8/18; A61K8/19; A61K8/25; A61Q; A61Q11/00; A61K2800/00; A61K2800/40; A61K2800/41; A61K2800/412
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
113 words
A method of preparing a hydrous silica gel which comprises setting a silica hydrosol having a pH of less than about 5 to an acid-set silica hydrogel, washing the acid-set silica hydrogel with an aqueous acidic solution to provide a silica hydrogel having a pH of from about 2.5 to about 5, drying the washed hydrogel to a water content of from about 20 to about 60 weight percent, grinding the washed hydrogel to an average particle size of from about 1 to about 40 microns, and contacting the dried gel with an alkaline medium in an amount sufficient to provide a gel having a pH of from about 6 to about 10.
Claim 2
Independent Claim
113 words
A method of preparing a hydrous silica gel which comprises setting a silica hydrosol having a pH of less than about 5 to an acid-set silica hydrogel, washing the acid-set silica hydrogel with an aqueous acidic solution to provide a silica hydrogel having a pH of from about 2.5 to about 5, drying the washed hydrogel to a water content of from about 20 to about 60 weight percent, grinding the washed hydrogel to an average particle size of from about 1 to about 40 microns, and contacting the dried gel with an alkaline medium in an amount sufficient to provide a gel having a pH of from about 6 to about 10.
Claim 3
Dependent Claim
24 words
The method of claim 1 in which the hydrogel is dried to a water content of from about 35 to about 60 weight percent.
Claim 4
Dependent Claim
33 words
The method of claim 1 in which the gel is contacted with an alkaline medium in an amount sufficient to provide a gel having a pH of from about 8 to about 9.5.
Claim 5
Dependent Claim
15 words
The method of claim 1 in which the gel is contacted with an ammoniacal medium.
Claim 6
Dependent Claim
14 words
The method of claim 1 in which the gel is contacted with gaseous ammonia.
Claim 7
Dependent Claim
20 words
The method of claim 1 in which the gel is contacted with an alkaline medium comprising an alkali metal hydroxide.
Claim 8
Dependent Claim
27 words
The method of claim 1 in which the hydrogel is washed with an aqueous acidic solution having a temperature of from about 80° to about 200° F.
Claim 9
Dependent Claim
27 words
The method of claim 7 in which the hydrogel is washed with an aqueous acidic solution having a temperature of from about 80° to about 100° F.
Claim 10
Dependent Claim
21 words
The method of claim 7 in which the aqueous acidic solution has a pH of from about 2.0 to about 5.0.
Claim 11
Dependent Claim
21 words
The method of claim 7 in which the aqueous acidic solution has a pH of from about 2.5 to about 4.5.
Claim 12
Dependent Claim
32 words
The method of claim 7 which the hydrogel is washed for a period of time sufficient to reduce the total salts content of the hydrogel to less than about 5 weight percent.
Claim 13
Dependent Claim
18 words
The method of claim 7 in which the hydrogel is washed for about 6 to about 15 hours.
Claim 14
Dependent Claim
18 words
The method of claim 7 in which the hydrogel is washed for about 6 to about 12 hours.
Claim 15
Dependent Claim
28 words
The method of claim 1 in which the hydrogel is simultaneously dried and ground in an impact mill into which a moving stream of heated air is introduced.
Claim 16
Dependent Claim
43 words
The method of claim 14 in which the mill is an air classifying hammer mill and the heated air has an inlet temperature of from about 200° to about 500° F. and an outlet temperature of from about 80° to about 150° F.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-10-02 | 1988-04-02 | 1988-10-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-10-02 | 1992-04-02 | 1992-10-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-10-02 | 1996-04-02 | 1996-10-02 | $7700.00 | Window Closed / Lapsed |