US4774068A
Expired / Lapsed
US
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Method for production of mullite of high purity
Assignee: Resonac Holdings Corp
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Filing: 1986-07-11
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Granted: 1988-09-27
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Expires: 2006-07-11
Abstract
Abstract Mullite of high purity is obtained by neutralizing an aqueous solution containing a basic aluminum salt and colloidal silica thereby causing formation of a precipitate in the aqueous solution, and subsequently heating the precipitate.
Inventors
- 👤 Tadashi Hiraiwa
- 👤 Eizi Ando
- 👤 Kunihiro Miyazaki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 07:55
CPC Classifications
C; C01; C01B; C01B33/00; C01B33/20; C01B33/26; C04; C04B; C04B35/00; C04B35/01; C04B35/16; C04B35/18
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
186 words
A method for the production of high purity mullite which has a particle size diameter ranging from 200 to 500 Å, a specific area ranging from 20 to 60 m 2 /g, a combined Al 2 O 3 and SiO 2 content of not less than 99 wt. % and having an ability to sinter easily, which comprises: neutralizing an aqueous solution containing colloidal silica and from 7.5-20% by weight, as Al, of a basic aluminum salt prepared by the reaction of metallic aluminum and at least one salt selected from the group consisting of the nitrate, sulfate, hydrochloride and acetate salts of aluminum at a temperature within the range of 50° to 100° C., thereby inducing formation of a precipitate from said aqueous solution; separating said precipitate from said aqueous solution; mixing said precipitated material still containing water with an organic solvent; distilling the resulting mixture to expel water from the precipitate together with the organic solvent; drying the precipitate obtained; and heating the separated precipitate to form the mullite product, said mullite not exhibiting thermal shrinkage as a result of said organic solvent treatment.
Claim 2
Independent Claim
186 words
A method for the production of high purity mullite which has a particle size diameter ranging from 200 to 500 Å, a specific area ranging from 20 to 60 m 2 /g, a combined Al 2 O 3 and SiO 2 content of not less than 99 wt. % and having an ability to sinter easily, which comprises: neutralizing an aqueous solution containing colloidal silica and from 7.5-20% by weight, as Al, of a basic aluminum salt prepared by the reaction of metallic aluminum and at least one salt selected from the group consisting of the nitrate, sulfate, hydrochloride and acetate salts of aluminum at a temperature within the range of 50° to 100° C., thereby inducing formation of a precipitate from said aqueous solution; separating said precipitate from said aqueous solution; mixing said precipitated material still containing water with an organic solvent; distilling the resulting mixture to expel water from the precipitate together with the organic solvent; drying the precipitate obtained; and heating the separated precipitate to form the mullite product, said mullite not exhibiting thermal shrinkage as a result of said organic solvent treatment.
Claim 3
Dependent Claim
42 words
The method of claim 1, wherein the concentration of said colliodial silica in said aqueous solution is such that the aluminum of said basic aluminum salt and silicon in said colloidal silica will for a composition corresponding to the composition of mullite.
Claim 4
Dependent Claim
22 words
The method of claim 1, wherein said separated precipitate is heated to a temperature within the range of 950° to 1300° C.
Claim 5
Dependent Claim
16 words
The method of claim 1, wherein said organic solvent is an alcohol, acetone, benzene or xylene.
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) | 1991-09-27 | 1992-03-28 | 1992-09-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-09-27 | 1996-03-28 | 1996-09-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-09-27 | 2000-03-28 | 2000-09-27 | $7700.00 | Window Closed / Lapsed |