US3574648A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for the production of synthetic calcium sulfate hemihydrate
Assignee: Knauf Gips KG
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Filing: 1967-12-18
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Granted: 1971-04-13
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Expires: 1987-12-18
Abstract
Abstract BY-PRODUCT GYPSUM ARISING IN THE EXTRACTION OF PHOSPHORUS-CONTAINING MINERALS AND CONTAMINATED WITH PHOSPHORIC ACID AND ITS WATER-SOLUBLE SALTS IS CALCINED, THE CALCINE IS TREATED WITH WATER AND A NEUTRALISING AGENT TO FORM CALCIUM SULFATE DIHYDRATE AND WATER-INSOLUBLE COMPOUNDS OF THE CONTAMINANTS AND THE DIHYDRATE IS SUBJECTED TO A SECOND CALCINATION TO PRODUCE A SYNTHETIC CALCIUM SULFATE HEMIHYDRATE WHICH HAS PROPERTIES COMPARABLE TO OR BETTER THAN THOSE OF PLASTER OF PARIS DERIVED FROM NATURAL GYPSUM.
Inventors
- 👤 Franz Wirsching
- 👤 Bruno Wandser
- 👤 Karl Knauf
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 11:24
CPC Classifications
C; C04; C04B; C04B11/00; C04B11/26
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-04-12 | 1974-10-12 | 1975-04-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-04-12 | 1978-10-12 | 1979-04-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-04-12 | 1982-10-12 | 1983-04-13 | $7700.00 | Window Closed / Lapsed |