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Process for the preparation of alkali-poor α-alumina for ceramic purposes
Assignee: Magyar Aluminiumipari Troeszt
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Filing: 1982-11-09
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Granted: 1984-10-16
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Expires: 2002-11-09
Abstract
Abstract Process for the preparation of alkali-poor alpha -alumina for ceramic purposes. Technical grade aluminum hydroxide is activated and calcinated in the presence of a mineralizing mixture comprising halides and boron compounds. The process further comprises activating aluminum hydroxide at a temperature of 500-600 degrees C., washing the activated product with alkali-free water containing calcium ions and having a conductivity not exceeding 70 mu S/cm until the alkali content expressed in Na2O becomes lower than 0.15% by weight, adding 0.4-0.7% by weight of a mineralizing mixture to the washed product, and calcinating the same at a temperature of 1200-1350 degrees C.
Inventors
- 👤 Jozsef Matyasi
- 👤 Gyorgy Kaptay
- 👤 Laszlo Zsembery
- 👤 Bela Kokeny
- 👤 Jozsef T. Toth
- 👤 Maria Toth Nee Homostrei
- 👤 Imre Penzes
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 04:01
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/01; C04B35/10; C04B35/111; C01; C01F; C01F7/00; C01F7/02; C01F7/44; C01F7/441; C01F7/442
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
77 words
Process for the preparation of alkali-poor α-alumina for ceramic purposes, comprising (a) activating technical grade aluminum hydroxide by heating it to a temperature of 500°-600° C., (b) washing the activated product with alkali-free water containing calcium ions and having a conductivity not exceeding 70 μs/cm until the alkali content expressed in Na 2 O becomes lower than 0.15% by weight, and (c) calcinating the same in the presence of a mineralizing mixture comprising halides and boron compounds.
Claim 2
Dependent Claim
77 words
Process for the preparation of alkali-poor α-alumina for ceramic purposes, comprising (a) activating technical grade aluminum hydroxide by heating it to a temperature of 500°-600° C., (b) washing the activated product with alkali-free water containing calcium ions and having a conductivity not exceeding 70 μs/cm until the alkali content expressed in Na 2 O becomes lower than 0.15% by weight, and (c) calcinating the same in the presence of a mineralizing mixture comprising halides and boron compounds.
Claim 3
Dependent Claim
13 words
Process according to claim 1, which comprises activating aluminum hydroxide for 10-30 minutes.
Claim 4
Dependent Claim
33 words
Process according to claim 1, which comprises adding to the washed product as mineralizing mixture 0.3-0.45% by weight of boric acid and 0.1-0.15% by weight of aluminum fluoride, based on the total weight.
Claim 5
Dependent Claim
15 words
Process according to claim 1, which comprises using a mineralizing additive, containing a calcium salt.
Claim 6
Dependent Claim
39 words
Process according to claim 4, which comprises adding to the washed product as mineralizing mixture 0.3-0.45% by weight of boric acid, 0.1-0.15% by weight of aluminum fluoride and 0.1-0.15% by weight of calcium fluoride, based on the total weight.
Claim 7
Dependent Claim
13 words
Process according to claim 1, which comprises carrying out calcination for 20-30 minutes.
References Cited (Backward Citations)
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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) | 1987-10-16 | 1988-04-16 | 1988-10-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-10-16 | 1992-04-16 | 1992-10-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-10-16 | 1996-04-16 | 1996-10-16 | $7700.00 | Window Closed / Lapsed |